5181 5185.output

* GB785588 (A)
Description: GB785588 (A) ? 1957-10-30
A cathode-ray tube with deflection control
Description of GB785588 (A)
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The EPO does not accept any responsibility for the accuracy of data
and information originating from other authorities than the EPO; in
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up-to-date or fit for specific purposes.
PATENT SPECIFICATION
Date of Application and filing Complete Specification Feb 4 1,53.
&, No 8363/55.
Application made in Germany on Feb 5, 1952.
Application made in Germany on March 31, 1952.
(Divided out of No 785,587).
Complete Specification Published Oct 30, 1957.
Index at Acceptance:-Class 39 ( 1), D 4 (A 1: A 7 1 Di 102: El: E 41 F
613: FWI: GCA K 1 A 4), D 10 i Al A 2), D 15 (A: 3), D 3 (I 9 C: 34 45
A).
International Classificatin: -H Olj.
COMPLETE SPECIFICATION
A Cathlode-R Ray Tube with De 1 electi 6 N Con Ltrol To GUENTHER
HERMANN KRAWINIKEL, of 54, Haeberlinstrasse, Frankfurt/Main,
Eschersheim, Germany, a German citizen, do hereby declare the
invention for which I pray that a patent may be granted to me, and the

method by which it is to be performed to be particularly described in
and by the following statement:The present invention relates to
cathode ray tubes wherein the electron beam is deflected from its
normal direction by means of an electrostatic or electromagnetic
deflecting field set up by a signal voltage transversely with respect
to the direction of flow of electrons, so that the point where the
deflected electron beam impinges upon a target electrode is displaced
from the point where the target electrode is struck by the undetected
beam The distance between the two points is proportional to the
magnitude of the signal voltage and can be used therefore as a measure
of the signal voltage The displacement of the point where the beam
strikes the target electrode may be indicated directly by this
electrode However, there are cases where an indirect indication is
preferred, and it is the object of the invention to devise an improved
target electrode which produces in an associated output circuit a
current or a voltage indicating the occurrence or the magnitude of the
electron beam's deflection.
To this end, a cathode ray tube which comprises an electron gun to
produce an electron beam, deflecting means for the deflection of the
electron beam in dependence on the magnitude of an input signal, and
target means for producing in an output circuit a current of which the
magnitude is dependent on the 'magnitude of the beam deflection, is
characterised according to the invention in that the target means
comprise a target electrode capable of emitting secondary electrons
when struck by the electron beam and a collecting electrode arranged
within the output circuit so as to attract the secondarv electrons
emitted from the said target electrode, and that the target electrode
comprises means which absorb the lPrice 3 s 6 d l emitted secondary
electrons or prevent their emission in such a manner that the quantity
of electrons which reach the collecting electrode gradually increases
or decreases with increasing distances from a line of the target
electrode which line extends transversely to a direction in which the
beam's deflection is proportional to the input signal.
According to one embodiment of the invention, the target electrode
comprises a number of parallel strips which consist of a conductive
material capable of emitting secondary electrons when struck by the
electron beam and which extend at right angles with respect to the
said line, and between each two of the said strips a strip is disposed
which consists, of highresistance conductive material, and the strips
of high-resistance conductive material are connected in parallel to a
voltage source so that a current is caused to flow from one end to the
other producing a varying potential along the said strips, so that the
secondary electrons, liberated by the electron beam, are attracted by
the strips of resistance material with correspondingly varying force

The strips which are capable of emitting secondary electrons are
preferably connected to the negative pole of the current source to
which the high resistance conductive strips are connected.
According to another embodiment of the invention, the target
electrode, comprises a number of parallel strips which extend at right
angles to the said line and which consist of a high-resistance
conductive material capable of emitting secondary electrons when
struck by the electron beam, and all odd numbered strips are connected
in parallel to form a group, of stips and all even numbered strips are
connected in parallel to form another group, and both groups of strips
are connected to a direct current source in an opposite sense so that
currents are caused to flow in opposite directions through the strips
of each group.
According to a still further embodiment, the target electrode
comprises a number of parallel strips which are disposed parallel to s
O 785,588 the said line and consisting of conductive material capable
of emitting secondary electrons, and each of the odd numbered strips
is connected to a point on a resistor which is connected to a direct
current source, the individual connecting points being distributed
along the resistor so that the individual strips have different
potential, and wherein the even numbered strips are similarly
connected to another resistor connected to a direct current source,
but the connection of these strips being such that their potential
varies in an opposite sense over the width of the target electrode at
right angles to the said line.
These and other features of the invention will now be described in
more detail with reference to the accompanying dra 7 wings In order
that the invention may be clearly understood and readily carries into
practice, first a deflection system of a cathode-ray tube will be
described by way of example, followed by the description of three
embodiments of target electrodes according to the invention In the
drawings:Fig 1 shows schematically a longitudinal section of a cathode
ray tube which comprises means for an amplification of the beam's
original signal deflection as described and claimed in U K
Specification No (Application No.
3137/53) (Serial No 785,587).
Fig 2 is a perspective representation on an enlarged scale of one
member of the tube shown in Fig 1 together with the associated circuit
connections; Fig 3 serves for explaining the function of the
arrangements according to Fig 2; Fig 4 shows in more detail a target
electrode according to the invention; Figs 5 and 6 serve for the
explanation of the function of the electrode shown in Fig 4.
Figs 7 and 8 represent some modified target of constructions; Figs 9
and 10 serve for the explanation of the function of the targets

according to Fig.
8.
As shown in Fig 1, within an evacuated vessel G an electron beam St is
produced by means of an electron gun K,-AI-A,, which may be of any
conventional design The electron beam passes in succession through
electrode systems P,-P, El-E 11, E 2-EW, and the beam then strikes a
target electrode S.
The electrode system P,-P is constituted by deflecting plates to which
the voltage is applied which is to be ascertained and measured, but
which may also be magnified, rectified, or modulated The electrode
system E,-E,' serves as a deflection amplifier and is shown in more
detail in Fig 2 Both plates E, and E 11, between which the electron
beam passes, consist of a resistance material which may be either self
supporting or may be applied to a carrier by evaporation, by chemical
deposition or in a mechanical manner As shown in Fig.
6 o 2, the terminals of each plate E, and E,' are connected to a
direct voltage source K through resistances R,, R, and R,', R,,
respectively in such a manner that at both plates E, and E,' voltage
drops are set up in opposite directions These voltage conditions are
indicated 70 in Fig 3 in respect of the axis z which extends at right
angles to the undeflected beam and is parallel with and at the same
distance from each of the plates E, and E,' It will be appreciated
that in the z-direction there will be a 75 point z,, depending upon
the magnitude of the resistances R,, R,, R,' and R ' (Fig 2), where
there will be no resulting deflecting field between E, and E,' for an
electron beam at right angles to the plane of the drawing 80 Although
the undeflected electron beam need not pass through the point z,
between the plates E, and E,' in order to obtain the desired effect,
it will be assumed for the explanation of the deflection magnification
that the un 85 deflected electron beam passes through the point z,
between the plates E, and E,' (Figs.
2 and 3) Now, if the electron beam St is deflected the distance ds in
the direction indicated by the arrow z of Figs 2 and 3 due to 90 a
deflecting field set up at the control plates
P,-P, then the beam is subjected, as indicated in Fig 3, to a
deflecting field KW between the plates E, and E,' By a suitable choice
of the magnitude of the voltage K applied to the 95 plates E, and E,'
(Fig 2), it is obviously possible to obtain by the influence of the
resulting field K' in Fig 3 a deflection of the beam
St in a direction perpendicular to ds, which is substantially larger
than, but proportional to, 100 the deflection ds The beam,
additionally deflected in the direction of the field K', now enters
the space between the two plates E and E' as shown in Fig 1, which are
constructed in a similar manner as the plates E, and E,', 105 i.e that

they form resistances and are connected to voltage sources as
described with reference to Fig 2 However, the position of the plates
E and E' is at right angles with respect to the direction of the
plates E, and 110 E,', but also transverse with respect to the
longitudinal axis of the tube The beam which, due to its original
deflection ds, has been deflected in the system E,, El' under the
influence of the field K' (Fig 3) through a 115 distance ds' in a
direction perpendicular to ds, now enters the space between the plates
E and E ' and it is there subjected to a further deflection
amplification in a similar manner as described with reference to Fig 3
In view 120 of the cross-wise disposition of the plates E, and E,'
with respect to the plates E and E,1, the deflection ds&" of the beam
which occurs between the plates E and E,1, has the same direction as
the deflection ds produced bv the 22 plates P, and P 2 As a result of
the voltage drop at the plates E and E,1, the beam is subjected to a
deflection between these plates which is proportional to ds' but
perpendicular to the direction of ds', whereby the beam is 130 N
785,588 again deflected in the direction of the orginal deflection ds
Naturally, any number of such plate systems may be used for a
deflection amplification, the individual systems being arranged in
succession with alternately crosswise arranged plates A
correspondingly amplified deflection of the electron beam will result
which is proportional to the deflection control at the plates PI, P,.
The electron beam, which has been subjected to a deflection control
and the deflection of which has been amplified as described, now
impinges upon a target electrode S adapted to ascertain the beam
deflection, as shown in Fig.
1 This electrode is basically an electrode adapted to emit secondary
electrons, and its characteristic feature is to be seen in that the
emission of these secondary electrons, liberated by the electron beam
St, is dependent upon the location of the point where the electron
beam strikes the electrode S This function will now be described in
more detail with reference to the arrangement shown by way of example
in Fig 4 The plate S may be made of insulating material and is
equipped with two systems of strips The strip system V, which is
connected to a collecting bar V, represents the secondary electron
emitting electrode proper.
Adjacent to each strip V, at the right as well as at the left of it, a
strip W is disposed The strips W, which are insulated from their
strips V, consist of resistance material and their ends are connected
to two collecting bars W, and W 2 To the collecting bars W, and W 2 is
applied, for instance through a series resistance R,, a direct current
voltage M Thus a voltage drop -M/2 to +M/2 is set up along the strips
W (Fig 5) The collecting bar V, of the strip system V may be connected

to the minus pole of the direct voltage M Between the electrode S and
another electrode s, (Fig.
1), to which a positive potential B with respect to the electrode S is
applied, a suction field in the direction towards s is established.
The electron beam St liberates, when impinging upon the electrode S,
secondary electrons.
These secondary electrons are subjected to the influence of two
fields; firstly, to the field between the strip systems V and W, the
intensity of which increases in the direction x (Fig.
4), and secondly, to the suction field which is directed from S
towards s, The effect of these two fields upon the liberated secondary
electrons is easily understood In the direction x (Fig 4) of the
deflection of the electron beam at the electrode S, the released
secondary electrons are under the influence of a field between the
strips W and V the intensity of which decreases from the lower to the
upper end of the electrode Superposed on this varying field between W
and V is the suction field established by the voltage source B between
S and s, The field between W and V, which decreases in the direction
x, is determined by the direct current voltage M (Fig 4) It will be
appreciated that by a suitable choice of the magnitude of M in
relation to the voltage B applied to S 1, which determines the suction
field (Fig 1), it can be reached that all secondary electrons released
in the lower part of the 70 strips V as shown in Fig 4 will travel to
the strips W under the influence of the field between V and W However,
if the point where the electron beam St strikes the electrode is
shifted upwards in the direction x (Fig 4), 75 then first the
electrons with high velocity and later, as the said point moves
upward's, also the electrons of lower velocity will move towards the
electrode s, under the influence of the suction field (Fig 1) The
variations, of the 80 voltage from +M/2 to -M/2 along the resistance
strips W is indicated in Fig 5 by the dotted straight line I, and the
constant voltage of the strips V at -M/2 is represented by the
straight line II over the direction x As indi 85 cated the secondary
electrons, released by the electron beam St, are under the influence
of a varying counter field D, which is different in respect of each
magnitude x (Fig 5) Fig 6 indicates the proportion of the stream J of
90 secondary electrons moving from the electrode S towards the
collecting electrode s, (Fig 1), which is dependent upon the
displacement in the direction x of the point where the electron beam
impinges upon the electrode S 95 The stream J of secondary electrons,
the intensity of which has been controlled as described, can now be
utilised directly at the electrode sl, or as an amplified stream after
it has been subjected to a multiplication of the secon 100 dary
emission in a manner known per se Fig.

1 represents schematically a one-stage multiplication of the secondary
electrons without limiting the application of the invention to the
shown arrangement Thus, the electrode s, 105 may form an electrode
adapted to emit secondary electrons instead of being a collecting
electrode only With a one-stage multiplication of the secondary
emission, the electrode S 2 then represents the collecting electrode
To the 110 latter a resistance r may be connected from which the
amplified signal may be derived.
The described target electrode is adapted to avoid the usual
difficulties of adjusting cathode ray tubes with deflection control
For 115 instance the described deflection amplification is equally
effective at each point of the deflection amplifiers (E-systems)
through which the electron beam passes, and only an additional
constant deflection has to be taken into con 120 sideration if the
electron beam does not pass through the point z O of one of the
E-systems.
Such a constant deflection does not affect the function of the
apparatus, in view of the fact that the secondary electron stream
produced by 125 the target electrode will be always proportional to
the deflection without regard to the initial position of the point of
incidence of the undeflected beam.
In view of the fact that the characteristic of 130 785,588 the current
J starts with a bend (Fig 6), it is possible to use the tube, when
adjusted to work at this point of the characteristic, for
rectification or modulation purposes.
A shifting of the working point along the characteristic can be
effected for instance by an additional direct-current voltage applied
to the system E of the arrangement represented as an example in Fig 1,
or by application of an additional direct-current voltage to the
control plates P, and P A modulation with a different oscillation may
be obtained for instance by superposing an auxiliary oscillation on
the direct current voltage K applied to one of the deflection
amplifiers, or alternatively by modulating the intensity of the beam
in the beam generating system K 1, AI, A with the auxiliary
Oscillations.
The target electrode system according to Figs 4 to 6 has the property
that the movement of the secondary electrons towards the suction
electrode s, is influenced by means c 4 electric fields in such a
manner that at least one of these fields causes a locally varying
emission of secondary electrons, i e varying over the whole surface of
the secondary-emission electrode S In order to prevent with such an
arrangement that the electron beam; wvzhich has been subjected to the
deflection control, when it approached the electrode S is itself
influenced at different points of this indicating arrangement by

different fields, it is advisable to design the deflecticn-indicating
device symmetric 2 lly with respect to the electrodes which produce
the locally varving field influencing the emission of secondary
electrons.
Such a symmetrically designed electrode arrangement for the deflection
indication of a defection controlled cathode-ray tube is shown by way
of example in Fig 7 Two strip systems V and W are arranged upon an
insulating plate S, and the individual strips, which consisi of a
suitable resistance material, alternate like two combs shifted one
into the other The system of strips V is arranged between collecting
bars V, and V whilst the system of strips W is connected to collecting
bars W, and W_.
The collecting bars W 1, W 2, and V 1, V respectively are connected in
an opposite sense to the voltage source M Thus, along the resistance
strips V a voltage drop is set up having at the top the highest
positive value and at the bottom the lowest negative voltage value,
whilst at the system of strips W a voltage drop from the top towards
the-bottom from negative to positive voltage values is established If
now the strip systems Vand W respectively comprise a great number of
individual strips, then the voltage values at the individual strips
cancel one another in respect of the approaching deflection controlled
electron beam up to a point directly in front of the
deflection-indicating device, whilst the secondary electrons released
at the electrodes V and W when the latter are struck by the deflection
controlled electron beam, are subiected to the influence of the field
between the electrodes V and W.
At the upper end of the strips this field is directed from the
W-electrodes to the V-electrodes At the lower end of the plate this
field 70 is directed from the V 7-electrodes towards the W-eletrodes
In the centre of the plate a zone subsists where there is no field
between the Velectrodes and the W-electrodes If the number of strips
of which the systems of V-electrodes 75 and W-electrodes are formed is
suficiently large, it is obvious that the same conditions between the
V-electrodes and W-electrodes prevail above and below the field-free
central zone in respect of the secondary electrons 80 released by t
Cce defiectien controlled electron beam This is due to the fact that
the liberated secondary electrons Yrll travel above and below the
field-free zone to the positively biased electredes, whilst they are
free to travel from the 85 field-free central zone to a suction
electrode under the influence of a suction field established in front
of the whole deflection indicating system, and the suction electrode
may be constituted for instance by an input electrode 90 of a
secondary-emission multiplier as hereinbefore described with reference
to Fig 1 In order to avoid undesired charges to be set up upon the

insulating surfaces between the individual V-electrodes and
W-electrodes caused 95 by the arrival of the p-imarv electron beam, it
may be convenient to make the carrier plate S or at least its surface
of a semi-conductive rmaterials, such as for instance glass of a
suitable composition 100 The stream of secondary electrons leaving the
deflection-iildicating device and designated J in Figs 1 to 6, has a
rising characz-ristic if the beam approaches the field-free central
zone as a result of the movemient of the primary 105 electron beam in
the direction: 'Fig 7) under the in'iuence of the hereinbefore
described deflecting Ifields, and the characteristic has a dropping
course -wvhen the beamt move S away from fhee central zone 110 Fig 8
indicates an arranemen which, it is true, results in a stemped voltage
characteristic between the two electrode systems in the direction of
the beam's deflection, out in this case, it is no longer ne Cesrary to
male the electrode 115 systems proper of resistance material Wit-h
regard to the desized higl secondary emission ratio of the whole
arrangemnt this may be even an advantage compared with the arrangement
shown in Fig 7 A, shown, unon a plate 120 S, made of a resistance
material or of a semicondluctive nmateria 1, the two comb-like
disposed electrode systems T, and T are arranged which are connected
alternately to resistances U, and r J Across the resistances 125 M M
U, and U 2 the voltages + and ±are 2 2 connected so that also in this
case at the upper edge of the plate a voltage M subsists between known
difficulties in connection with the adjustment of the electron beam.
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* 5.8.23.4; 93p
* GB785589 (A)
Description: GB785589 (A) ? 1957-10-30
Improvements in or relating to machines for manipulating cut tobacco

We, DESMOND WALTER MOLINS, a British
Subject, GORDON FRANCIS WELLINGTON POWELL, a British Subject, and
MOLINS MACHINE COMPANY LIMITED, a British Company, all of 2 Evelyn
Street, Deptford, London, S E 8, England, do hereby declare the
invention, for which we pray that a patent may be granted to us, and
the method by which it is to be performed, to be particularly
described in and by the following
statement: -
This invention concerns improvements in or relating to machines for
manipulating cut tobacco, that is, machines in which cut tobacco is
fed and subsequently issues from the machine in separated portions
namely, cigarettes in a cigarette making machine, or packages in a
tobacco packaging machine.
Some machines of this kind are provided with apparatus in which the
mass of a length of moving tobacco filler is measured by a detector in
which electric currents are produced, said currents varying with
variations in the mass of the filler passing the detector, and also
have means for applying the current due to the variations to regulate
at some stage in the machine the rate at which tobacco is being fed at
that stage for the formation of the final product Such a ma-30 chine
is hereinafter called a "machine as specified".
An example of such a machine is described in British Patent
Application No.
19271/51 (Serial No 781,042) and in that case regulation is effected
by altering the speed of a conveyor which carries the tobacco filler
This kind of regulation is referred to herein as 'conveyor speed
control".
While the regulation as carried out by the apparatus described in said
Specification is verv good it is desired further to improve lPrice 3 s
6 d l the uniformity of the finished product, in the example
described, cigarettes.
For brevity the term "ray device" will be used hereafter to mean "a
radio-active source of penetrative radiation" and the term
"source-gap-chamber" will mean a ray box and its associated parts, for
adjustment, screening and shielding; the space between ray source and
ionisation chamber; and the ionisation chamber and its associated
parts for mounting and adjusting it The three words source, gap, and
chamber, will be used to refer to any separate item of the triple
combination.
As will be seen later measuring and regulation can be effected at two
positions, or stages, in the machine The idea of the two-stage method
in the embodiment described is briefly, to keep the conveyor speed

control substantially as described in the Specification referred to as
a second-stage control to take care of the "longer-term
irregularities" in mass (as hereafter defined) and, most particularly,
to keep a very accurate control of the mean weight, and to have, in
addition, a very quick-acting first-stage control to smooth out the
unevenness of the hopper output or shower, that is to take care of
"shorter-term irregularities", which term is also defined later As
explained later the two controlling operations need not be in this
sequence but longer-term irregularities could be dealt with first and
the shorter-term irregularities later.
According to the invention there is provided a machine as specified
comprising an endless conveyor which receives a filler at one end and
discharges it from the other and whose speed at the delivery end is
constant, means for feeding the filler to said conveyor, and means
controlled bv the detector, which detector is responsive to 7 7 $
59589 PATENT SPECIFICATION
Date of filing Comnplete Specification: June 16, 1954.
Application Date: March 16, 1953 No 7201/53.
Complete Speciflication Published: Oct 30, 1957.
Index at Acceptance:-Classes 38 ( 4), R( 4: 37 62: 69); and 130, Cl
Al.
International Classilication:-A 24 c G 05 d.
COMPLETE SPECIFICATION.
Improvements in or relating to Machines for Manipulating Cut Tobacco.
,'c 111 785,589 variations in the mass of the filler being fed to said
conveyor, to spread the filler as it is being delivered on to the
endless conveyor, substantially in accordance with the detector
responses, whereby irregularities in the filler are, at least partly,
corrected.
Further according to the invention there is provided a machine as set
forth in the preceding paragraph comprising an endless conveyor
supported on and geared to two driving pulleys, the pulley at the
delivery end of the conveyor rotating at a uniform speed and the
pulley at the receiving end rotating at a speed controlled by the
detector responsive to variations in the mass of a filler delivered to
said receiving end; said conveyor being elastic to accommodate changes
in the speed of the pulley at the receiving end and the filler being
delivered thereto on an unstretched part on which it is spread in
accordance with the speed of said part and later discharged from said
part as it passes over the uniformly rotating pulley at the delivery
end of the conveyor.
The term "unstretched" means that no change is made in the normal
tension existing in the belt, for naturally the belt is stretched to
some extent when it is mounted on the pulleys as is usual with belts

The filler may be delivered to said elastic conveyor from a hopper
tape which collects a shower from a tobacco feed in the known manner.
The arrangements recited in the two preceding paragraphs are of a
particular value for smoothing-out short-term (or high frequency)
variations in a filler and further according to the invention the
filler may be discharged from the elastic conveyor to a further
conveyor having a detector associated therewith and regulating
mechanism controlled thereby to effect conveyor speed control as
herein defined.
Conveyor speed control is of particular 4.5 value for correcting
long-term irregularities in the filler.
The machine may comprise means for detecting shorter-term
irregularities in a filler and manipulating the filler to at least ao
partly, correct them and means for detecting longer-term
irregularities in the manipulated filler and further manipulating the
filler (e g.
by conveyor speed control) to, at least partly, correct them.
ad The detector may be a source-gap-chamber device as herein defined,
or where a ray source is employed a scintillation counter with
necessary auxiliary equipment may be used.
The invention will be more fully described with reference to the
accompanying drawings, in which:Figure 1 is a diagram of a continuous
rod cigarette makina machine showinz the application of the invention
thereto.
Figure 2 shows to a larger scale details of a pulley and conveyor
shown in Figure 1.
Figure 3 is a longitudinal section of a source-gap-chamber device
shown in Figure 1, and drawn to a larger scale 70 Figure 4 is a
circuit diagram.
Figure 5 is a diagrammatic chart or graph for the purpose of
explaining certain terms used in the Specification.
Figure 6 is a diagram of a modified way 75 of carrying out the
invention.
Before proceeding with the detailed description of the drawings the
meanings of the terms "longer-term irregularities" and "shorter-term
irregularities" will be ex 80 plained in some detail.
In machines for manipulating cut tobacco, tobacco is fed from a mass
in a hopper by carded rollers and other contrivances and in view of
the nature of the material and 85 the available feeding devices there
are inevitable variations and irregularities in the quantity of
tobacco fed out of the hopper in a given time The variations or
fluctuations appear to be generally random How 90 ever, it appears
that while over extremely long periods the total output may be roughly
constant, there are in any such long period, times when the output is

above a desired rate and times when it is below such rate 95
Similarly, if a shorter period is considered there are still times
within this period when the rate is higher or lower than the desired
rate Further, however short the period considered may be, there seems
to be com 100 paratively sharp and relatively short-term deviations
from what may be regarded as the general rate of output at any time It
will be seen then that if the output of, say several seconds is
considered, there may be 105 a general change in output over such a
period which can be called a longer-term variation while more rapid
deviations within the period may be called shorter-term variations
and, more generally stated, 110 changes in any given period may be
separated into "longer-term irregularities" and "shorter-term
irregularities" respectively These terms are used in the Specification
and claims and are to be considered 115 as having these meanings.
The terms can be understood more easily from the diagram shown in
Figure 5 in which a is representative of the sort of "curve" obtained
when a succession of equal 120 lengths of cigarette rod as made by a
machine, are weighed individually and recorded consecutively as
ordinates on a chart The horizontal line shows the actual weight
desired and each angle point in the "curve" 125 a shows how far the
particular length differs from the desired weight The curve b is drawn
by hand as near as may be, to show the trend of the weight deviation
alone the succession of weighings Thus the curve a 130 As will appear
later the speed of the rear pulley 7, at any instant, is determined by
reactions from the source-gap-chamber device 5.
The tobacco filler on the elastic belt 6 is 70 passed down a sloping
passage 11, constructed and operating as described in British Patent
Specification No 646,746 and delivered to the cigarette paper web 12
which is moved by a garniture tape 13 75 driven by a tape drum 14, in
the usual manner of continuous rod cigarette machines The tape drum is
driven from a differential gear 23 controlled by an oil unit 19
Another source-gap-chamber device is 80 disposed at 15 and is of
normal construction.
Referring particularly to Figure 1 of the drawing, it will be seen
that conditions to the left of the vertical line A-B are the same as
those described in British Patent 85 Application No 19271/51 (Serial
No.
781,042) referred to earlier, except that the output from the
amplifier and feed-back filter at 16 is taken to a long-time-constant
circuit at 17 to control (through a speed 90 control device 20, which
itself is controlled by a relay unit 21, explained more fully later) a
variable speed pulley drive 18 to the hopper 1, in addition to going
to the variable speed oil unit 19 This scheme has 95 already been
proposed in the Specification mentioned and it is necessary because

the existing differential gear in that Specification can only change
the speed of the machinery it drives by 10 % so that if the 100 mean
hopper output changes by, say, 10 % heavy, then no shorter-term
correction can be applied on the heavy side, as the limit of control
will have been reached A further consideration is that with the
feed-back 105 amplifier described in said Specification any deviation
from the mean is not completely brought back to the zero line but the
devia1 tion is reduced by a factor of where K 1 +K is the gain of the
feed-back used; in that 110 case about 25 is convenient, so that for a
persistent mean error of the hopper of % the output mean error would
be % = 0.38 % On the other hand the speed 26 control device 20 will
continue to correct 115 until the mean weight is returned to within
preset limits and this ensures that the feedback amplifier will deal
with smaller variations from the mean, say 2 % maximum, so the mean
error would not exceed 120 2 % = 0.0770/% Further by this means the 26
output in cigarettes per minute is kept very nearly constant The
time-constant of this overriding correction is long compared with
shows "shorter-term irregularities" while the curve b shows
"longer-term irregularities".
It must be understood that the curves have been drawn solely for the
purpose of explaining the above terms and have no other significance.
Referring now to the remaining Figures of the drawings 1, Figure 1, is
the Hopper of the machine, from which tobacco is showered in the usual
way on to a hopper tape 2, which is arranged to run in the opposite
direction to that usually employed The tape 2 passes round a pulley 3
and delivers the collected shower or loose filler to a belt 1,5
conveyor 4 which conveys the tobacco downwards as shown At the lower
end of the conveyor 4 is a source-gap-chamber device which is of a
special construction and will be described in detail later, with
reference 0 to Figure 3 It will be noted that the tobacco is received
on a conveyor belt 6 at a position where the belt is supported by a
pulley 7.
The belt 6 is of elastic material and is driven at the front end by a
toothed pulley 8 running at constant speed and at the rear end by the
toothed pulley 7 These two pulleys ensure that while the belt is in
full engagement with the teeth, the linear speed of the belt is
controlled, while the elastic belt itself allows of a variation
(practically instantaneous variation) in the speed of the rear pulley
7 relatively to the front pulley 8.
The pulley 7 and belt 6 are shown in detail in Figure 2 The belt has
teeth (e g metal teeth bonded to the belt) arranged on its inner side
The teeth are pointed and have involute flanks The pulley is provided
with correspondingly shaped grooves and it will be seen that the part
of the belt which receives the filler is held on the pulley and is

therefore unstretched for the distance shown by the double-headed
arrow The upper and lower runs of the belt will frequently be
stretched during operation, as explained more fully later, but as the
stretch is not excessive, the points of the teeth will enter the
grooves in the pulley, even when somewhat out of pitch, and so the
belt readily mates with the pulley although the lower run may be
stretched.
In the lower part of Figure 2 the stretch is somewhat exaggerated to
illustrate the point.
The spaces between the grooves on the pulley are, in effect, teeth and
the pulleys have been referred to as toothed pulleys.
The action is as follows:The rear pulley 7 is driven from the front
pulley 8 (or any other similar constant speed point) through a small
differential gear 9 and by varying the speed of the input shaft (that
is, the planet control shaft) of the gear from zero in a positive or
negative direction, the speed of the rear pulley 7 relatively to the
front pulley 8 can be varied.
785,589 the "Integral" time constant of the feedback amplifier and the
rate of correction small to ensure that they do not conflict with one
another.
The machine is driven by a motor 22 which is shown as coupled to the
differential gear 23 by chain gearing and to the hopper tape pulley by
toothed gears and directly to the pulley 8, but, as previously stated,
the Figure is a diagram and the couplings are only schematic to show
the necessary mechanical connections between the parts.
Referring to the right-hand side of the vertical line A-B the
measurement in the source-gap-chamber 5 is effected on a very short
length of filler and the measurement of ionisation current is
performed in a simple manner, as explained later when the circuits are
described as compared with the use of the vibrating reed electrometer
for the second stage and as in British Patent Application No 19271/51
(Serial No.
781,042).
Only the irregular components of this measurement are used, that is,
that no attempt is made to control the mean output at this point but
measurement is used only to reduce the shorter-term irregularities in
the tobacco stream The filter networks of the two stages are so chosen
that at the frequencies where the usefulness of the first measurement
diminishes, the effect of the second measurement is appreciable and
the speed control device 20 controlling the hopper speed deals only
with the persistent mean drifts The device 20 is a solenoid operated
ratchet-device similar to that described in British Patent Application
No.
19270/51 (Serial No 781,041) and the solenoid operation is controlled

from the relay unit 21 consisting of a limit relay switch with close
limits, the unit itself being under control of the time-constant
device 17.
The whole system is intended to cover variations from zero frequency
to a high frequency, limited mainly by random source emission,
variation in the packing of the filler, and the length of the first
source-gapchamber combination.
The remaining items in Figure 1 will be described together with
Figures 3 and 4 because some items of the circuit are subject to
mechanical control and are indicated both in Figures 1 and 3 and some
electrical items operate on mechanical contrivances and are therefore
shown in both Figures.
In Figure 1 the box marked 24 contains the circuit elements shown in
the top part of Figure 4, where the box is shown in chain lines The
enclosed apparatus is termed the pre-amplifier The lower box 25 in
botil Figures contains the circuit elements for the speed control
stage.
For the source-gap-chambor device 5 the source 26 is located as close
as possible to the delivery point of the tobacco on to the belt 6 and
is very short, and the ionisation chamrber of the combination, which
chamber is generally represented by 27 is constructed in pulley form
with a rim of approximately 70) 0.010 " thickness for the width of the
tobacco stream The chamber section can be seen in Figure 3, where it
will also be seen that the outer part 28 of the chamber is fixed to a
long hollow hub 29 running 75 in ball races in housing 30 and 31 A
sprocket wheel 32 is fixed to the hub, whereby the chamber is rotated
at the required speed An insulating ring 33, fixed at one end of the
hub, carries a slip ring 34 con SOJ tacted by a brush 35 to apply the
polarising voltage to the outer part 28 of the chamber.
The inner part 36 of the chamber is clamped to the part 28 by a nut 37
with a sealing rinu 38 between the parts Contact is made 55 to the
rotating part 36 by a contact 39 at the end of the signal cable 40,
the contact engaging a spring-pressed stud 41 The end of the hub is
shaped to form the guard ring 43 of the chamber and is thus grounded
90 i) through the hub, bearings, and housings.
Side guides 42 for the tobacco filler are also shown.
Referring now to the upper part of Figure 4 the polarising voltage for
the rotary 9 i chamber is fed from a battery 44 through a current
limiting resistor 46 and this same potential is applied to the source
mounting plate 47 and the adjacent guides 42, Figure 3, to prevent a
potential difference across 100 O the tobacco stream In the following
description "tube" means a therimionic valve.
The ionisation chamber collector electrode 36 is connected to the
upper end of an input resistor 48, and to the grid of the 103

electrometer tube 49 shown operating as a triodeconnected cathode
follower supplied with 1 H T from a battery 50, the tube circuit being
completed by a cathode resistor 51.
The output from the tube 49, is applied to 1 o 1 the series-connected
triodes 52 and 53 provided with cathode resistors 54 and 55 and
forming a stable and linear amplification stage with a gain of
approximately half the amplification factor of the individual tubes
115 The output of this stage is taken from the anode of the tube 53
and applied to the upper end of a resistor 56 and the positive
terminal of a battery 57 The upper slider of the resistor 56 provides
a voltage which 124 is negative relative to the anode of the tube 53
and which is applied to the lower end of the input resistor 48, the
whole circuit from the upper end of resistor 48, through 49 series
amplifier 5 53 and through 12 a 5 resistor 56 forming a loop with
considerable gain connected so as to degenerate the capacitance across
the input signal cable ane to provide the shortest possible measuring
time-constant compatible with the source 134 t 785,589 is arranged so
that with the anode currents of the tubes 62 and 63 substantially the
same, the hydraulic motor output shaft 10 (which is naturally the
input shaft of the differential gear 9) is stationary When, 70
however, the balance of the currents is upset by an input signal, the
output shaft 10 rotates at a speed proportional to the input signal
and in a direction depending on the polarity of the signal 75 The
conveyor belt 6 is, as previously mentioned, of an elastic nature,
thus permitting relative peripheral speed changes of the pulleys 7 and
8 The permissible total of relative movement, while ample for the 80
purpose is, however, limited and it is essential that the output shaft
10 of the hydraulic motor, irrespective of its instantaneous velocity,
does not make more than a limited number of revolutions from a mean
datum 85 Such an event might occur if there were a small change in the
output sensitive valve position-characteristic, or a change in the
characteristics of tubes 62 and 63.
To ensure that this excessive movement 90 cannot happen, the output
shaft of the hydraulic motor is coupled, as shown in Figure 1, to the
arm 70 of a rotary potentiometer 71, the ends of which are connected
to a source 72 of medium voltage In the 95 circuit diagram, Figure 4,
the potentiometer and its arm are shown only diagrammatically, that
is, not as a rotary device Connections are taken from the centre tap
of the source 72 of E M F and from the arm 100 of the potentiometer 71
The voltage appearing across these leads will be dependent within
desired limits for magnitude and polarity on the amount of rotation of
the output shaft 10 from its desired mean posi 105.
tion These leads are taken to an integrating circuit formed by a
resistor 73 and a capacitor 74 and from the output of this circuit to

the control grid of the tube 63.
Consider now the action of the device 110 Variations from the desired
mass, of the tobacco stream, cause variations in the ionisation
current in resistor 48 and variations in the grid potential of the
tube 49.
The presence of the amplifier loop formed 115 by the connection from
the slider of the resistor 56 to the lower end of resistor 48 causes
less variation in the grid potential of 49 for a given ionisation
current than would otherwise be the case, and as previ 120 ously
stated, effectively reduces the timeconstant of the measuring circuit
The resulting output signal is fed through the tube 58 to the C R
coupling 60-61, which due to the smallness of the capacitor react 125
ance relatively to that of the resistor passes to the control grid of
the tube 62 all the oscillating components of the deviation signal
with which we are concerned but attentuates and modifies the lower fre
130 stochastic emission and the arrangement of the loose tobacco in
the tobacco stream The upper sliding contact on resistor 56 is so
adjusted that with an ionisation current resuiting from the desired
mean weight of tobacco stream, flowing in the high value resistor 48,
the resultant potential applied to the grid of the electrometer tube
49 is sufficiently negative for optimum conditions.
The lower slider of the resistor 56 is connected to the grid of a tube
58 which, with a resistor 59, forms a cathode-follower stage to give
an output which is a faithful copy of the input, but with a low
impedance, for connection to the circuit elements in the speed control
stage box 25, which may be located some distance away.
The output signal from the tube 58 is connected through a C R coupling
provided by a capacitor 60 and a resistor 61 to the grid of a tube 62
which, with a tube 63, forms a common cathode amplifier with a cathode
resistor 64.
In the anode circuit of the tubes 62 and 63, which are supplied with H
T from a battery 45, are coils 65-66 which form the moving elements of
a positioning device 67, see also Figure 1 These coils are connected
in a differential linear-movement solenoid device of known kind
provided with a permanent magnet field and arranged so that with equal
current in both coils and with both coils mechanically coupled there
is no resultant force on the coil assembly.
The coil assembly itself is provided with a positioning spring spider,
not shown, with linear deflection/force characteristics, which
accurately positions the moving member at all times.
When the current through the tube 62 increases, the current through
the tube 63 decreases, and the resultant out-of-balance force between
the two coils 65-66 causes an axial movement of the assembly which
continues until the spring spider exerts an equal and opposite force.

When the current through the tube 62 decreases, the current through
the tube 63 increases, and an axial movement is obtained in the
opposite direction.
The differential solenoid device has its moving member coupled to a
valve contained in a casing 68, Figure 1 and constituting the
sensitive valve of a hydraulic unit 69 This unit is generally similar
to the oil unit 19, previously referred to but is called a hydraulic
unit to avoid confusion It contains a rotary pump and hydraulic motor
and the pump is driven by an external motor 80 The output speed, and
direction of the unit are controlled by the sensitive valve.
This hydraulic unit is a standard commercial unit of exceedingly quick
response and high torque-inertia ratio The coupling between the
solenoid device and the sensitive valve I-_ 785,589 quencies due to
any changes in the mean mass of the tobacco stream, these changes
being substantially corrected later in the second stage corrector In
other words the devices just described do not respond effectively to a
change in the mean.
Consider for the moment that the grid of the tube 63 is at earth
potential, then the variation signals arriving at the grid of the tube
62 cause variations in the anode current and approximately equal but
opposite variations in the anode current of tube 63 These
out-of-balance currents flowing through the moving coils 65-66 of the
solenoid positioning device 67 cause a change in the position of the
sensitive valve in the casing 68 with a resulting rotation of the
hydraulic motor with a velocity proportional to amplitude of the
deviation signal.
The output shaft of the hydraulic motor is as aforesaid coupled to the
differential gear 9 and increases or decreases the peripheral velocity
of the belt pulley 7, on to which the tobacco stream is fed The
connections and proportions are made so that should the tobacco stream
for a short time become, say, % heavy then the peripheral speed of the
pulley 7 is increased by 10 % so that the spreading of the tobacco on
the unstretched piece of belt on top of the pulley remains as near as
practicable to the desired uniformity; and vice versa.
Returning now to the grid circuit of tube 63, any movement of the
hydraulic motor shaft from its desired neutral position causes a
voltage to be applied to the integrator circuit 73-74, but this is
arranged with a long time-constant so that the voltage applied to the
grid of the tube 63 from the upper end of capacitor 74, and which is
arranged to return the output shaft of the hydraulic motor towards its
neutral position, rises so slowly that it does not interfere with the
excursions of the hydraulic motor output shaft but ensures that should
the output shaft tend to remain away from its neutral position for
longer periods than are desirable then it is urged to return towards

its neutral position.
The elastic belt 6 may be of any suitable material If rubber is
objectionable to any users a suitable plastic may be used A woven belt
of canvas and rubber, in which the weft is canvas and the warp
includes a proportion of rubber threads is also suitable.
It will be appreciated that the expressions longer-term and
shorter-term irregularities are to be considered as limited to
irregularities occurring over periods of time which can both be
measured and dealt with by the machine For instance, in the specific
example the longer-term irregularity is corrected by altering the
speed of the paper web.
In dealing with these errors they are treated as if they were
sinusoidal, irrespective of their actual nature Every effort is made
to reduce the measurement lags and time-constants of the measuring
devices but in the particular apparatus described no improvement is
really noticeable until the 70longer-term error has a period of the
order of three seconds.
The purpose of the first stage measuring and correcting device
described is to improve the uniformity of the filler in respect 75 of
shorter-term errors, without materially interfering with the
functioning of the second stage measurement control and no attempt is
made in the first stage to deal with variations in the mean hopper
errors so or the longer-term errors which are dealt with later by the
second stage.
The construction described in the example for dealing with the
shorter-term irregularities is capable of effecting an improvement so
for periods down to less than one second.
The period, as has been stated above, depends upon the measuring
time-constant distance velocity lags and characteristics of the
control loop including the response of 90 the hydraulic unit, and
accordingly any apparatus made according to the principles outlined
above will depend upon the equipment which is available for obtaining
higher speeds of response and, of course, the ran 95 dom emission of
the source itself and the packing of the tobacco.
However, it will be appreciated that the invention is not limited to
periods shown in the specific example, but to any longer 100 and
shorter periods which can be handled by a machine Thus the corrections
are made in two stages, one stage in which a detection is made in one
kind of error alone, independently of any other error upon which 105
it is superimposed (that is to say a longerterm irregularity or error)
and in a second stage a device is used to measure the filler or the
tobacco stream after it has been detected by the first detector and
suitably 110 modified, and irregularities over a longer period are
then measured and an adjustment made in the machine to attempt to

correct longer-term errors so measured.
Although the Specification has been con 115 cerned only with first
correcting "shorterterm" errors and then correcting the resulting
filler for "longer-term" errors it will be appreciated that although
this is a convenient way of improving the consistency it 120 is not
essential that the corrections should be made in this order and
longer-term irregularities could be dealt with first and then the
resulting filler could be subjected to further treatment for the
correction of 125 shorter-term irregularities.
An alternative arrangement to avoid the use of an elastic tape will
now be described with reference to Figure 6 In this case the tobacco
is showered from the hopper 1 130 785,589 tions in the mass of a
filler delivered to said receiving end; said conveyor being elastic to
accommodate changes in the speed of the pulley at the receiving end
and the filler being delivered thereto on an unstretched 70 part on
which it is spread in accordance with the speed of said part and later
discharged from said part as it passes over the uniformly rotating
pulley at the delivery end of the conveyor 75
* Sitemap
* Accessibility
* Legal notice
* Terms of use
* 5.8.23.4; 93p
* GB785590 (A)
Description: GB785590 (A) ? 1957-10-30
Improvements in or relating to machines for manipulating cut tobacco
Subject, GORDON FRANCIS WELLINGTON POWELL, a British Subject, and MO
Li NS MACHINE COMPANY LIMITED, a British Company, all of 2 Evelyn
Street, Deptford, London, S E 8, England, do hereby declare the

invention, for which we pray that a patent may be granted to us, and
the method by which it is to be performed, to be particularly
described in and
by the following statement:-
manipulating cut tobacco, that is, machines in which cut tobacco is
fed and subsequently issues from the machine in separated portions
namely, cigarettes in a cigarette-making machine, or packages in a
tobacco packaging machine Some machines of this kind are provided with
apparatus in which the mass of a length of moving tobacco filler is
measured by a detector in which electric currents are produced, said
currents varying with variations in the mass of the filler passing the
detector, and also have means for applying the current due to the
variations to regulate at some stage in the machine the rate at which
tobacco is being fed at that stage for the formation of the final
product Such a machine is hereinafter called a "machine as specified "
An example of such a machine is described in British Patent
Application No.
19271/51 (Serial No 781,042) and in that case regulation is effected
by altering the speed of a conveyor which carries the tobbacco filler
This kind of regulation is referred to herein as "conveyor speed
control " While the regulation as carried out by the apparatus
described in said Specification is very good it is desired further to
lPrice '-s 6 d l improve the uniformity of the finished product, in
the example described, cigarettes.
For brevity the term "ray device" will be used hereafter to mean "a
radio-active source of penetrative radiation" and the term
"source-gap-chamber" will mean a ray box and its associated parts, for
adjustment, screening and shielding, the space between ray source and
ionisation chamber; and the ionisation chamber and its associated
parts for mounting and adjusting it.
The three words source, gap, and chamber, will be used to refer to any
separate item of the triple combination.
As will appear later variations in the mass of the filler may be
classed as longer-term irregularities and shorter-term irregularities.
It will be understood that the term "filler" when used herein is
intended to refer to the moving tobacco filler mentioned above whether
before or after detection, but before being enclosed in a paper tube.
According to the invention there is provided a machine as specified
comprising means for effecting separate detection of shorter-term and
longer-term irregularities in a filler and means for manipulating the
filler to, at least partly, correct for such errors The means for
detecting the shorterterm and longer-term irregularities may be
separate detectors at different stages along the path of the filler In

this case the filler may be manipulated to correct for shorterterm
irregularities at a position in advance the position at which the
longer-term irregularities are corrected and then the filler is
manipulated for longer-term irregularities (e.g by conveyor speed
control) subsequently by the longer-term irregularity detector.
Alternatively there may be means for detecting longer-term
irregularities in a filler 7859590 PATENT SPECIFICATION
Date of filing Complete Specification: June 16, 1954.
Application Date: March 16, 1953 No 5535156.
(Divided out of No 785,589).
Complete Specification Published: Oct 30, 1957,
Index at Acceptance -Classes 38 ( 4), ( 4: 37: 62: 69); and 130, Cl
Al.
International Classification -A 21 c 005 d.
Improvements in or relating to Machines for Manipulating Cut Tobacco.
785,590 and manipulating the filler to at least partly correct them
and means for detecting shorter-term irregularities in the manipulated
filler, and further manipulating the filler to at least partly correct
them.
The machine may have a tobacco hopper and means for feeding tobacco
therefrom and showering it on to a hopper tape which collects the
shower to form said filler, with means for regulating the speed of the
hopper when the output thereof varies above or below a given tolerance
exceeding the capacity of the manipulating means to correct.
The detector may be a source-gap-chamber device as herein defined, or
where a ray source is employed a scintillation counter with necessary
auxiliary equipment may be used.
accompanying drawings in which: Figure 1 is a diagram of a continuous
rod cigarette-making machine, showing the application of the invention
thereto.
Figure 2 shows to a larger scale details of a pulley and conveyor
shown in Figure 1.
Figure 3 is a longitudinal section of a source-gap-chamber device
shown in Figure 1, and drawn to a larger scale.
Figure 4 is a circuit diagram.
Figure 5 is a diagrammatic chart or graph for the purpose of
explaining certain terms used in the Specification.
Figure 6 is a diagram of a modified way of carrying out the invention.
Before proceeding with the detailed description of the drawings the
meanings of the terms "longer-term irregularities" and "shorter-term
irregularities" will be explained in some detail.
In machines for manipulating cut tobacco, tobacco is fed from a mass

in a hopper by carded rollers and other contrivances and in view of
the nature of the material and the available feeding devices there are
inevitable variations and irregularities in the quantity of tobacco
fed out of the hopper in a given time The variations so or
fluctuations appear to be generally random However, it appears that
while over extremely long periods the total output may be roughly
constant, there are in any such long period, times when the output is
above a desired rate and times when it is below such rate Similarly,
if a shorter period is considered there are still times within this
period when the rate is higher or lower than the desired rate Further,
however short the period considered may be, there seems to be
comparatively sharp and relatively short-term deviations from what may
be regarded as the general rate of output at any time It will be seen
then that if the output of, say several seconds is considered, there
may be a general change in output over such a period which can be
called a longer-term variation while more rapid deviations within the
period may be called shorter-term variations and, more 70 generally
stated, changes in any given period may be separated into "longer-term
irregularities" and shorter-term irregularities" respectively These
terms are used in the Specification and claims and are to be con 75
sidered as having these meanings.
The terms can be understood more easily from the diagram shown in
Figure 5 in which a is representative of the sort of "curve" obtained
when a succession of equal 80 lengths of cigarette rod as made by a
machine, are weighed individually and recorded consecutively or
ordinates on a chart The horizontal line shows the actual weight
desired and each angle point 55 in the "curve" a shows how far the
particular length differs from the desired weight.
The curve b is drawn by hand as near as may be, to show the trend of
the weight deviation along the succession of weighings,wg O Thus the
curve a shows "shorter-term irregularities" while the curve b shows
"longer-term irregularities " It must be understood that the curves
have been drawn solely for the purpose of explaining the 95 above
terms and have no other significance.
Referring now to the remaining Figures of the drawings 1 Figure 1, is
the hopper of the machine, from which tobacco is showered in the usual
way on to a hopper 100 tape 2, which is arranged to run in the
opposite direction to that usually employed.
The tape 2 passes round a pulley 3 and delivers the collected shower
or loose filler to a belt conveyor 4 which conveys the 10)5 tobacco
downwards as shown At the lower end of the conveyor 4 is a source-gap
chamber device 5 which is of special construction and will be
described in detail later, with reference to Figure 3 It will be 11 D
noted that the tobacco is received on a conveyor belt 6 at a position

where the belt is supported by a pulley 7.
The belt 6 is of elastic material and is driven at the front end by a
toothed pulley 115 8 running at constant speed and at the rear end by
the toothed pulley 7 These two pulleys ensure that while the belt is
in full engagement with the teeth, the linear speed of the belt is
controlled, while the elastic 120 belt itself allows of a variation
(practically instantaneous variation) in the speed of the rear pulley
7 relatively to the front pulley 8 The pulley 7 and belt 6 are shown
in detail in Figure 2 The belt has teeth (e g 125 metal teeth bonded
to the belt) arranged on its inner side The teeth are pointed and have
involute flanks The pulley is provided with correspondingly shaped
grooves and it will be seen that the part of the belt 193 cribed in
said Specification any deviation from the mean is not completely
brought back to the zero line but the deviation is 1 reduced by a
factor of where K is 1 + K the gain of the feed-back used; in that
case about 25 is convenient, so that for a persistent mean error of
the hopper of 10 % the % output mean error would be = 0 38 %.
26 On the other hand the speed control device will continue to correct
until the mean weight is returned to within preset limits and this
ensures that the feed-back amplifier will deal with smaller variations
from the mean, say 2 %' maximum, so the mean error 2 % would not
exceed = 0 077 % Further which receives the filler is held on the
pulley and is therefore unstretched for the distance shown by the
double-headed arrow.
The upper and lower runs of the belt will a frequently be stretched
during operation, as explained more fully later, but as the stretch is
not excessive, the points of the teeth will enter the grooves in the
pulley, even when somewhat out of pitch, and so the belt readily mates
with the pulley although the lower run may be stretched In the lower
part of Figure 2 the stretch is somewhat exaggerated to illustrate the
point The spaces between the grooves on the pulley are, in effect,
teeth and the pulleys have been referred to as toothed pulleys.
The action is as follows:The rear pulley 7 is driven from the front
pulley 8 (or any other similar con20) stant speed point) through a
small differential gear 9 and by varying the speed of the input shaft
10 (that is, the planet control shaft) of the gear from zero in a
positive or negative direction, the speed of the rear pulley 7
relatively to the front pulley 8 can be varied As will appear later
the speed of the rear pulley 7, at any instant, is determined by
reactions from the source-gapchamber device 5.
3 OI The tobacco filler on the elastic belt 6 is passed down a sloping
passage 11, constructed and operating as described in British Patent
Specification No 646,746 and delivered to the cigarette paper web 12
which is moved by a garniture tape 13 driven by a tape drum 14, in the

usual manner of continuous rod cigarette machines The tape drum is
driven from a differential gear 23 controlled by an oil unit 19
Another source-gap chamber device is disposed at and is of normal
construction.
Referring particularly to Figure 1 of the drawing, it will be seen
that conditions to the left of the vertical line A-B are the same as
those described in British Patent Application No 19271/51 (Serial No.
781,042) referred to earlier, except that the output from the
amplifier and feed-back filter at 16 is taken to a long-time-constant
circuit at 17 to control (through a speed control device 20, which
itself is controlled by a relay unit 21, explained more fully later) a
variable speed pulley drive 18 to the hopper 1, in addition to going
to the variable speed oil unit 19 This scheme has already been
proposed in the Specification mentioned and it is necessary because
the existing differential gear in that Specification can only change
the speed of the machinery it drives by 10 % so that if the mean
hopper output changes by, say, 10 % heavy, then no shorter-term
correction can be a Dplied on the heavy side, as the limit of control
will have been reached A further consideration is that with the
feed-back amplifier desby this means the output in cigarettes per
minute is kept very nearly constant The time-constant of this
over-riding correction is long compared with the "Integral" time
constant of the feed-back amplifier and the 85 rate of correction
small to ensure that they do not conflict with one another.
The machine is driven by a motor 22 which is shown as coupled to the
differential gear 23 by chain gearing and to the 90 hopper tape pulley
by toothed gears and directly to the pulley 8, but, as previously
stated, the Figure is a diagram and the couplings are only schematic
to show the necessary mechanical connections between 95 the parts.
Referring to the right-hand side of the vertical line A-B the
measurement in the source-gap-chamber 5 is effected on a very short
length of filler and the measurement 100 of ionisation current is
performed in a simple manner, as explained later when the circuits are
described as compared with the use of the vibrating reed electrometer
for the second stage and as in British Patent Appli 105 cation No
19271/51 (Serial No 781,042).
Only the irregular components of this measurement are used, that is,
that no attempt is made to control the mean output at this point but
measurement is used only 110 to reduce the shorter-term irregularities
in the tobacco stream The filter networks of the two stages are so
chosen that at the frequencies where the usefulness of the first
measurement diminishes, the effect of the 115 second measurement is
appreciable and the speed control device 20 controlling the hopper
speed deals only with the persistent mean drifts The device 20 is a

solenoid operated ratchet-device similar to that des 120 cribed in
British Patent Application No.
19270/51 (Serial No 781,041) and the solenoid operation is controlled
from the relay unit 21 consisting of a limit relay 785,590 switch with
close limits, the unit itself being under control of the time-constant
device 17.
The whole system is intended to cover variations from zero frequency
to a high frequency, limited mainly by random source emission,
variation in the packing of the filler, and the length of the first
source-gapchamber combination.
The remaining items in Figure 1 will be described together with
Figures 3 and 4 because some items of the circuit are subject to
mechanical control and are indicated both in Figures 1 and 3 and some
electrical items operate on mechanical contrivances and are therefore
shown in both Figures In Figure 1 the box marked 24 contains the
circuit elements shown in the top part of Figure 4, where the box is
shown in chain lines The enclosed apparatus is termed the
pre-amplifier The lower box 25 in both Figures contains the circuit
elements for the speed control stage.
For the source-gap-chamber device 5 the source 26 is located as close
as possible to the delivery point of the tobacco on to the belt 6 and
is very short, and the ionisation chamber of the combination, which
chamber is generally represented by 27 is constructed in pulley form
with a rim of approximately 0 010 " thickness for the width of the
tobacco stream The chamber section can be seen in Figure 3, where it
will also be seen that the outer part 28 of the chamber is fixed to a
long hollow hub 29 running in ball races in housings 30 and 31 A
sprocket wheel 32 is fixed to the hub, whereby the chamber is rotated
at the required speed An insulating ring 33, fixed at one end of the
hub, carries a slip ring 34 contacted by a brush 35 to apply the
polarising voltage to the outer part 28 of the chamber.
Tlhe inner part 36 of the chamber is clamped to the part 28 by a nut
37 with a sealing ring 38 between the parts Contact is made to the
rotating part 36 by a contact 39 at the end of the signal cable 40,
the contact engaging a spring-pressed stud 41 The end of the hub is
shaped to form the guard ring 43 of the chamber and is thus grounded
through the hub, bearings, and housings.
Side guides 42 for the tobacco filler are also shown.
Referring now to the upper part of Figure 4 the polarising voltage for
the rotary chamber is fed from the battery 44 through a current
limiting resistor 46 and this same potential is applied to the source
mounting plate 47 and the adjacent guides 42, Figure 3, to prevent a
potential difference across the tobacco stream In the following
description "tube" means a thermionic valve.

The ionisation chamber collector electrode 36 is connected to the
upper end of an input resistor 48, and to the grid of the electrometer
tube 49 shown operating as a triode-connected cathode follower
supplied with H T.
from a battery 50, the tub 2 circuit being completed by a cathode
resistor 51 The output from the tube 49, is applied to the
series-connected triodes 52 and 53 provided 7 a 1 with cathode
resistors 54 and 55 and forming a stable and linear amplification
stage with a gain of approximately half the amplification factor of
the individual tubes The output of the stage is taken from the anode 7
i 5 of the tube 53 and applied to the upper end of a resistor 56 and
the positive terminal of a battery 57 The upper slider of the resistor
57 provides a voltage which is negative relative to the anode of the
tube 53 and 80 which is applied to the lower end of the input resistor
48, the whole circuit from the upper end of resistor 48, through 49,
series amplifier 52-53 and through resistor 56 forming a loop with
considerable gain, con 85 nected so as to degenerate the capacitance
across the input signal cable and to provide the shortest possible
measuring time-constant compatible with the source stochastic emission
and the arrangement of the loose 90 tobacco in the tobacco stream The
upper sliding contact on resistor 56 is so adjusted that with an
ionisation current resulting from the desired mean weight of tobacco
stream, flowing in the high voltage resistor 95 48, the resultant
potential applied to the grid of the electrometer tube 49 is
suffiiently negative for optimum conditions The lower slider of the
resistor 56 is connected to the grid of a tube 58 which, with a 100
resistor 59, forms a cathode-follower stage to give an output which is
a faithful copy of the input, but with a low impedence, for connection
to the circuit elements in the speed control stage box 25, which may
be 105 located some distance away.
The output signal from the tube 58 is connected through a C R coupling
provided by a capacitor 60 and a resistor 61 to the grip of a tube 62
which, with a tube 63, 11 forms a common cathode amplifier with a
cathode resistor 64.
In the anode circuit of the tubes 62 and 63, which are supplied with H
T from a battery 45, are coils 65-66 which form the 115 moving
elements of a positioning device 67, see also Figure 1 These coils are
connected in a differential linear-movement solenoid device of known
kind provided with a permanent magnet field and arranged so that with
12) equal current in both coils and with both coils mechanically
coupled there is nc resultant force on the coil assembly The coil
assembly itself is provided with a positioning spring spider, not
shown, with linear 1 '23 deflection force characteristics, which
accurately positions the moving member at all times.

When the current through the tube 62 increases, the current through
the tube 63 o 130 785,590 grating circuit formed by a resistor 73 and
a capacitor 74 and from the output of this circuit to the control grid
of the tube 63.
Consider now the action of the device.
Variations from the desired mass, of the 70 tobacco stream, cause
variations in the ionisation current in resistor 48 and variations in
the grid potential of the tube 49 The presence of the amplifier loop
formed by the connection from the slider of the resistor 75 56 to the
lower end of resistor 48 causes less variation in the grid potential
of 49 for a given ionisation current than would otherwise be the case,
and as previously stated, effectively reduces the time-constant of the
So measuring circuit The resulting output signal is fed through the
tube 58 to the C R.
coupling 60-61, which due to the smallness of the capacitor reactance
relatively to that of the resistor passes to the control grid of 85
the tube 62 all the oscillating components of the deviation signal
with which we are concerned but attentuates and modifies the lower
frequencies due to any changes in the mean mass of the tobacco stream,
these 90 changes being substantially corrected later in the second
stage corrector In other words the devices just described do not
respond effectively to a change in the mean.
Consider for a moment that the grid of 95 the tube 63 is at earth
potential, then the variation signals arriving at the grid of the tube
62 cause variations in the anode current and approximately equal but
opposite variations in the anode current of tube 100 63 These out-of
balance currents flowing through the moving coils 65-66 of the
solenoid positioning device 67 cause a change in the position of the
sensitive valve in the casing 68 with a resulting rotation 105 of the
hydraulic motor with a velocity proportional to amplitude of the
deviation signal The output shaft of the hydraulic motor is as
aforesaid coupled to the differential gear 9 and increases or
decreases the 110 peripheral velocity of the belt pulley 7, on to
which the tobacco stream is fed The connections and proportions are
made so that should the tobacco stream for a short time become, say,
10 % heavy then the 115 peripheral speed of the pulley 7 is increased
by 10 % so that the spreading of the tobacco on the unstretched piece
of belt on top of the pulley remains as near as practicable to the
desired uniformity; and vice versa 120 Returning now to the grid
circuit of tube 63, any movement of the hydraulic motor shaft from its
desired neutral position causes a voltage to be applied to the
integrator circuit 73-74, but this is arranged with a 125 long
time-constant so that the voltage to the grid of the tube 63 from the
upper end of capacitor 74, and which is arranged to return the output

shaft of the hydraulic motor towards its neutral position, rises so
130 decreases, and the resultant out-of-balance force between the two
coils 65-66 causes an axial movement of the assembly which continues
until the spring spider exerts an equal and opposite force.
When the current through the tube 62 decreases, the current through
the tube 63 increases, and an axial movement is obtained in the
opposite direction.
The differential solenoid device has its moving member coupled to a
valve contained in a casing 68, Figure 1, and constituting the
sensitive valve of a hydraulic unit 69 This unit is generally similar
to the oil unit 19, previously referred to but is called a hydraulic
unit to avoid confusion.
It contains a rotary pump and hydraulic motor and the pump is driven
by an external motor 80 The output speed, and direction of the unit
are controlled by the sensitive valve This hydraulic unit is a
standard commercial unit of exceedingly quick response and high
torque-inertia ratio The coupling between the solenoid device and the
sensitive valve is arranged so that with the anode currents of the
tubes 62 and 63 substantially the same, the hydraulic motor output
shaft 10, (which is naturally the input shaft of the differential gear
9) is stationary.
When, however, the balance of the currents is upset by an input
signal, the output shaft rotates at a speed proportional to the input
signal and in a direction depending on the polarity of the signal.
The conveyor belt 6 is, as previously mentioned, of an elastic nature,
thus permitting relative peripheral speed changes of the pulleys 7 and
8 The permissible total of relative movement, while ample for the
purpose is, however, limited and it is essential that the output shaft
10 of the hydraulic motor, irrespective of its instantaneous velocity,
does not make more than a limited number of revolutions from a mean
datum.
Such an event might occur if there were a small change in the output
sensitive valve position-characteristic, or a change in the
characteristics of tubes 62 and 63.
To ensure that this excessive movement cannot happen, the output shaft
of the hydraulic motor is coupled, as shown in Figure 1, to the arm 70
of a rotary potentiometer 71, the ends of which are connected to a
source 72 of medium voltage In the circuit diagram, Figure 4, the
potentiometer and its arm are shown only diagrammatically, that is,
not as a rotary device.
Connections are taken from the centre tap of the source 72 of E M F
and from the arm 70 of the potentiometer 71 The voltage appearing
across these leads will be dependent within desired limits for
magnitude and polarity on the amount of rotation of the output shaft

10 from its desired mean position These leads are taken to an
inte785,590 slowly that it does not interfere with the excursions of
the hydraulic motor output shaft but ensures that should the output
shaft tend to remain away from its neutral posia tion for longer
periods than are desirable then it is urged to return towards its
neutral position.
The elastic belt 6 may be of any suitable material If rubber is
objectionable to any users a suitable plastic may be used A woven belt
of canvas and rubber, in which the weft is canvas and the warp
includes a proportion of rubber threads is also suitable.
It will be appreciated that the expressions longer-term and
shorter-term irregularities are to be considered as limited to
irregularities occurring over periods of time which can both be
measured and dealt with by the machine For instance, in the specific
example the longer-term irregularity is corrected by altering the
speed of the paper web.
In dealing with these errors they are treated as if they were
sinusoidal, irrespective of their actual nature Every effort is made
to reduce the measurement lags and time-constants of the measuring
devices but in the particular apparatus described no improvement is
really noticeable until the longer-term error has a period of the
order of three seconds.
The purpose of the first stage measuring and correcting device
described is to improve the uniformity of the filler in respect of
shorter-term errors, without materially interfering with functioning
of the second stage measurement control and no attempt is made in the
first stage to deal with variations in the mean hopper errors or the
longer-term errors which are dealt with later by the second stage.
The construction described in the example for dealing with the
shorter-term irregularities is capable of effecting an improvement for
periods down to less than one second.
The period, as has been stated above, depends upon the measuring
time-constant distance velocity lags and characteristics of the
control loop including the response of the hydraulic unit, and
accordingly any apparatus made according to the principles outlined
above will depend upon the equipment which is available for obtaining
higher speeds of response and, of course, the random emission of the
source itself and the packing of the tobacco.
However, it will be appreciated that the invention is not limited to
periods shown in the specific example, but to any longer and shorter
periods which can be handled by a machine Thus the corrections are
made in two stages, one stage in which a detection is made in one kind
of error alone, independently of any other error upon which it is
superimposed (that is to say a longerterm irregularity or error) and

in a second stage a device is used to measure the filler or the
tobacco stream after it has been detected by the first detector and
suitably modified, and irregularities over a longer 70 period are then
measured and an adjust-ment made in the machine to attempt to correct
longer-term errors so measured.
Although the Specification has been concerned only with first
correcting "shorter 7 a term" errors and then correcting the resulting
filler for "longer-term" errors it will be appreciated that although
this is a convenient way of improving the consistency it is not
essential that the corrections should So be made in this order and
longer-term irregularities could be dealt with first and then the
resulting filler could be subjected to further treatment for the
correction of shorter-term irregularities 85 An alternative
arrangement to avoid the use of an elastic tape will now be described
with reference to Figure 6 In this case the tobacco is showered from
the hopper 1 on to a hopper tape marked 80 A S') source-gap-chamber
device 81 scans the tobacco travelling with the tape 80, the tobacco
being confined by a guide 82 The whole device 81 is pivoted at 83 From
an amplifier 84 there is a connection to a rever 9 { sible electric
motor 85 whose shaft has a screw attached to it A nut 86 runs on the
screw and is connected by a link 87 to the device 81 As the motor
moves either way, the device is swung to and fro about the 100 pivot
83 and lengthwise of a tape 88, so that the position of discharge on
to this tape, which runs at a constant speed, is varied according to
the output from the hopper, as determined by the measurement 105 and
positioning device shown The remainder of the machine is constructed
substantially as in the first example.
With a ray source as above described an ionisation chamber is a
convenient and 11 ' suitable device for measuring the absorption but
as an alternative a scintillation counter may be used as this has
advantages of small size and rapid response and can be used with a
very small ray 115 source These points are valuable for some purposes
The counter comprises the usual phosphor, light cell and electron
multiplier, that is a multiplier photo cell, and the circuit shown in
Figure 4 is replaced by 120 one appropriate to the new ray responsive
device.
In Specification No 7201/53, (Serial No.
785,589) of which the present case is a division, claim is made to a
tobacco mani 125 pulating machine having novel constructional features
as recited in the claims of
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* 5.8.23.4; 93p
* GB785591 (A)
Description: GB785591 (A) ? 1957-10-30
Improvements in or relating to ionisation chambers of radiation gauges
Improvements in or relating to Ionization ChamLbers of Radiation
Gauges.
Subject, GORDONFRANCIS WELLINGTON
POWELL, a British Subject, and MOLINS MACHINE COMPANY LIMITED, a
British Com- pany, all of 2 Evelyn Street, Deptford,
London, S.E.8, England, do hereby declare the invention for which we
pray that a patent may be granted to us, and the method by which it is
to be performed, to be particularly described in and by t'ne following
statement:
This invention concerns improvements in or relating to ionisation
chambers of radiation gauges used in machines for manipulating cut
tobacco, that is, machines in which cut tobacco is fed to form a
moving filler and subsequently issues from the machine in separated
portions, namely, cigarettes in a cigarette making machine, or
packages in a tobacco packaging machine, and is a division from our
co-pending Application No.
7201/53 (Serial No. 785,589). Some tobacco manipulating machines
comprise apparatus wherein the mass of a length of moving tobacco
filler is measured by a detector by subjecting the length to rays from
a radioactive source of penetrative radiation, the ionisation powers
of which are absorbed by the material in known proportion to its mass,
and changes in the absorption with variations in the tobacco mass are
determined by an ionisation chamber, the current due to the ionisation
being applied to regulate at some stage in the machine the rate at

which tobacco is being fed at that stage for the formation of the
final product. Machines of this kind are hereafter called "machines of
the kind referred to". The combination of a radio-active source and an
ionisation chamber is commonly termed a radiation gauge.
The ionisation chamber hereinafter desbribed is specially suitable for
such machines since in addition to its normal function it is
constructed to act as a guide for the moving filler.
According to the invention there is provided a rotary ionisation
chamber comprising an outer electrode formed as a hollow member having
a circular periphery, a hollow hub fixed to said outer member and
coaxial therewith, said hub being journalled for rotation and provided
with driving means, an inner electrode of the ionisation chamber fixed
to said hub for rotation therewith and contact brush devices for
connecting the outer and inner rotary electrodes to a circuit. The hub
may be connected to the outer member by a flange insulated from said
member and constituting the guard ring of the chamber.
The invention further comprises, subject to certain disclaimers
recited in the appended claims, the combination of a machine of the
kind referred to with a rotary ionisation chamber as set forth in the
preceding paragraph.
accompanying drawings in which:
Figure 1 is a diagram of part of a cigarette machine, showing the
location of the ionisation chamber, and associated devices for feeding
a filler past it.
Figure 2 is a section on the line Il-Il of
Figure 1 drawn to a larger scale.
As is well-known, the radio-active source is separated from the
ionisation chamber by a space or gap in which the material being
measured is placed. For convenience the whole arrangement is termed
herein a "source-gap-chamber detecting device",
Referring to the drawings an ionisation chamber according to the
invention is particularly suitable for use in an arrangment such as
that shown in Figure 1, where a tobacco filler F, supported on a
sloping belt 4 and bounded by the chain line shown, is to be
transferred to another belt 6 carried on a pulley 7 and detection is
to take place at the point of transfer. Tobacco to form the aforesaid
filler is supplied from a belt 2 running round a pulley 3. At the
position of transfer is a source-gap-chamber detecting device
constructed and arranged as follows.
The source 26 is located as close as possible to the delivery point of
the tobacco on to the belt 6 and is very short. It is supported on a
plate 47. The ionisation chamber of the combination, which chamber is
generally represented in Figure 1 by the reference 27, is constructed

in pulley form. An ionisation chamber consists of three main parts,
namely, an outer member constructed as a chamber and constituting one
electrode, with an inner member, usually of hollow construction,
constituting another electrode, these parts being connected
respectively to appropriate terminals of an amplifier or like with
which the ionisation chamber is to be used, and a guard ring which is
grounded.
The construction of such an ionisation chamber when made in pulley
form will now be detailed. The chamber section can be seen in Figure
2, where it will also be seen that the outer part 28 of the chamber is
fixed by insulated screws to a long hollow hub 29 running in ball
races in housings 30 and 31.
At the part where the chamber 28 engages the filler the thickness of
its rim is approximately 0.010". A sprocket wheel 32 is fixed to the
hub, whereby the chamber is rotated at the required speed. An
insulating ring 33, fixed at one end of the hub, carries a slip ring
34 contacted by a brush 35 to apply the polarising voltage to the
outer part 28 of the chamber. The inner part 36 of the chamber is
clamped to the part 28 by a nut 37 with a sealing ring 38 between the
parts.
Contact is made to the rotating part 36 by a contact 39 at the end of
a signal cable 40, the contact engaging a spring pressed stud 41. The
end of the hub is shaped to form the guard ring 43 of the chamber and
is thus grounded through the hub, bearings and housings. Side guides
42 for the tobacco filler F are also shown.
It will be understood that a rotary ionisation chamber as above
described is suitable for use at any place where a filler changes its
direction, the diameter of the chamber varying with the angle made by
the filler at the point where it changes direction.
In Specification Nos. 7201/53 and 5535/56 (Serial No. 785,589 and
785,590) which is also a division from No. 7201/53 (Serial No.
785,589) claims are made to tobacco manipulating machines of novel
construction and no claim is made herein to such machines.
What we claim is : -
1. A rotary ionisation chamber comprising an outer electrode formed as
a hollow member having a circular periphery, a hollow hub fixed to
said outer member and coaxial therewith, said hub being journalled for
rotation and provided with driving means, an inner electrode of the
ionisation chamber fixed to said hub for rotation therewith and
contact brush devices for connecting the outer and inner rotary
electrodes to a circuit.
2. A rotary ionisation chamber as claimed in Claim 1 wherein said hub
is connected to the outer member by a flange insulated from said
member, said flange constituting the guard ring of the ionisation

chamber.
3. In combination, a rotary ionisation chamber as claimed in Claim 1
or Claim 2 and a machine of the kind referred to other than the
machines described and claimed in
Specifications Nos. 7201/53 and 5535/56 (Serial Nos. 785,589 and
785,590).
4. A rotary ionisation chamber substantially as herein described with
reference to the accompanying drawings.
PROVISIONAL SPECIFICATION.
Improvements in or relating to Ionization Chambers of Radiation
Gauges.
Subject, CORDONFRANCIS WELLINGTON
POWELL, a British Subject, and MOLINS
MACHINE COMPANY LIMITED, a British Company, all of 2 Evelyn Street,
Deptford,
London, S.E.8, England, do hereby declare this invention to be
described in the followinn statement:
manipulating cut tobacco, for example, cigarette making machines, and
refers more particularly to tlie kind of machine wherein the mass of a
length of moving tobacco filler is measured by subjecting the length
to rays from a radioactive source of penetrative radiation, for
example Beta rays, the ionisation powers of which are absorbed by the
material -n
* GB785592 (A)
Description: GB785592 (A) ? 1957-10-30
Process for the manufacture of composite sheets or shaped members having
covering layers impregnated with synthetic resin
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The EPO does not accept any responsibility for the accuracy of data
and information originating from other authorities than the EPO; in
particular, the EPO does not guarantee that they are complete,
up-to-date or fit for specific purposes.
PATENT SPECIFICATION
78959592 & Date of Application and filing Complete Specification: May
7, 1953.
No 12814/53.
Complete Specification Published: Oct 30, 1957.
Index at acceptance:-Classes 93, D( 1 C: 2 D); and 140, A 2 (C: G: H:
KIC: X), ASG( 1 A: 1 B: 4), A( 11 C: 1 IF: 16 83: 18).
International Classification:-B 29 d.
WCOMPLETE SPECI'FITCATION Processl for the Manufacture of Composite
Sheets or Shaped Members' having Covering Layers Impregnated with
Synthetic Resin I, EUGEN JOHANN RITTER, a German citizen, of P 61 zer
Strasse, Mainleus, Upper Franconia, Germany, trading as GESELLSCHAFT
FUR WERKSTOFF-FORMUt NG E J.
RITTER K G, do hereby declare the invention, for which I pray that a
Patent may be granted to me, and the method by which it is to be
performed, to be particularly described in land by the following
statement: -
It is known 'to produce by a pressing operation composite sheets or
shaped members which consist internally of fibres or shavings so which
are united on one or both sides covering layers which are impregnated
with synthetic resin The fibres or shavings consist of wood or other
vegetable or even mineral substances, which are preferably mixed with
a synthetic resin as, a binding agent, and form the core layer of the
composite sheet or shaped member after the pressing operation, The
outer covering layers are usually preformed coherent layers, such as
webs of paper, asbestos, textile or glass fabric, wood veneers, metal
or other foils, which are impregnated or coated with a thermoplastic
or hardenable synthetic resin before or during the pressing.
The core layer may either be separately produced and subsequently
united with the covering layers, during which a hardenable resin in
the latter is hardened, for example, a phenol-aldehyde resin, urea
aldehyde resin or melamine-aldehyde resin, or the mixture of fibres
land/or shavings and binding agent may be formed into the core layer
during its union with the covering layers, in which case the fibres
and/or shavings may be previously subjected to a preliminary pressing
operation to form an initial moulding, that is to say, without
previous hardening of the resin that is to serve as binding agent.
According to the present invention there is provided a process for the
manufacture of composite sheets or shaped members of the lPrice 3 s 6

d l , kind in which a core layer of fibres and/ot shavings and a
binding agent is united with preformed coherent covering layers
impregnated with synthetic resin under a moulding pressure
sufficiently high to cause the tore layer to undergo consolidation
with simultaneous heat treatment of the synthetic resin of the
covering layers, wherein at least one of the preformed 'coherent
covering layers used is of locally varying thickness, density or
structure.
A covering layer of locally varying thickness may be fonned from a
single layer of material of locally varying thickness, or may be built
up from a plurality of superposed layers having different areas and,
if desired, having different thickesses The individual layers that are
to form the covering layer may be assembled and pressed in the cold to
form an initial pressing before or after their impregnation with
synthetic resin, but before they are united with the core layer and
the subsequent heat treatment of the synthetic resin contained therein
The individual layers will generally be impregnated with resin before
they are united by cold pressing to form the covering layer If the
individual layers are such as to cohere sufficiently iby cold pressing
without impregnation with resin, they may be impregnated with resin
after the cold pressing.
In this manner the individual, layers are fixed relatively ito one
another in their appropriate positions and can therefore be handled
more easily.
Similarly, a covering layer of locally varying density or structure
may be formed of a single layer of which the density or structure
varies locally, or the covering layer may be built up of a' plurality
of superposed layers of different areas to produce the locally varying
density or structure.
The covering layers of locally varying thickness, density or structure
can be utilised to impart to the final product locally varying moments
of resistance to the stresses to which the final product is to be
subjected in use.
Thus, for example, a sheet or plate which is to be supported at its
edges and unsupported between its edges may be strengthened at the
centre, where the greatest stress occurs, by making the covering
layers thickest at the centre and gradually reducing their thickness
towards the edges, on the principle of a beamn which is supported at
its ends and is gradually thickened towards the centre where the
tendency for bending to occur is greatest, The locally different
thickness, density or structure of the covering layer, especially in
the case of a covering layer built up of separate layers having
different areas, may also be used to enhance the appearance of the
surface of the product.

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