5781 5785.output

* GB786189 (A)
Description: GB786189 (A) ? 1957-11-13
Improvements in or relating to attenuators
Description of GB786189 (A)
COMPLETE SPECIFICATION mpoenenita in or relating to Attenuatzors
We, MUIRSEAD & COMPANY LIMITED, of
Croydon Road, Elmer's End, Kent, a British
Company, do hereby declare this 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 relates to adjustable attenuators.
It is a known practice to provide measuring instruments with
switcbable shunt networks for the purpose of adjusting the sensitivity
of the instrument and also for maintaining the input impedance
constant irrespective of the sensitivity adjustment. Alternatively, in
some cases, an adjustable shunt has been provided with multi-range
instruments such that, when the range is changed by adjusting the
shunt, the impedance presented to the instrument is held constant so
as to maintain the damping of the instrument constant. The present
invention relates to adjustable attenuators which may be used in
combination with a measuring instrument for similar purposes and it is
an object of the invention to provide an adjustable attenuator which
provides advantages additional to those obtainable heretofore from
adjustable shunts for measuring instruments.
Suitable forms of network for use in the adjustable attenuator may be
modified forms of bridged-T networks.
According to the invention an adjustable attentuator comprises a four
terminal constant impedance network of the bridged-T type having a
first branch connecting one input terminal to one output terminal, a
second branch connecting the second input terminal to the second
output terminal and containing in series two equal fixed impedances, a
third branch also connecting the second input terminal to the second
output terminal and containing a variable series impedance, and a

variable shunt impedance connected between said first branch and the
junction of the fixed impedances in said second branch, in which the
attenuation ratio may be varied without changing the input impedance
of the network provided that the dimensions of the variable series and
shunt impedances are always such that RRb=Ro2 where Ra is the series
impedance, Rt is the shunt impedance and R0 is the desired input
impedance in the network, characterized in that the variable series
impedance consists of a plurality of sets of variable impedances and
the variable shunt impedance consists of a like number of sets of
variable impedances, the attenuator including a plurality of pairs of
switches equal to the number of sets of series and shunt impedances,
one switch of each pair controlling one set of series impedances and
the other switch of each pair controlling a related set of shunt
impedances, the two switches of each pair being mechanically linked so
that a series and a shunt impedance are varied together, each pair of
switches having a numerically indexed scale, and the series and shunt
impedances are so dimensioned that for all settings of the switches
the product of the series and shunt impedances in circuit is constant,
whereby the sum of the scale indices is equal to the numerical ratio
of attenuation between the input and output terminals. By this
arrangement the various switches may be adjusted to provide the
required attenuation and then the ratio of the input to output may be
read directly from the indices on the switches. This arrangement is
particularly useful with an indicating instrument for indicating when
the attenuator output is at some predetermined level of voltage or
current, as with this arrangement, the attenuator can be adjusted to
give the required output voltage or current and the magnitude of the
input can then be read directly from the indices on the selector
switches. The attenuator can also be used, however, with instruments
for mesuring the output voltage or current, the attenuator enabling
the range of measurement of the instrument to be increased.
Furthermore, when used with a measuring instrument, the attenuator
permits the measuring instrument to be used at very nearly full scale
deflection where the reading accuracy is a maximum.
It will be understood that the network will have to be terminated in a
load of suitable impedance since the output to input current ratio
will depend on the load.
In a simple form of bridged-T network having two input terminals and
two output terminals and arranged as a constant resistant attenuator,
there is provided a first branch comprising a direct connection
between one input terminal and one output terminal, a second branch
comprising two fixed resistors each of a magnitude equal to the
required impedance of the network, connecting the second input
terminal to second output terminal, a third branch bridging the two

fixed resistors and containing a variable resistance and a shunt
branch also containing a variable resistance and connecting the
junction between the fixed resistors to the direct connection between
the first input terminal and the first output terminal. This network
is either fed from a source of impedance equal to the required
impedance of the network or is terminated in a load of this impedance.
Then, if the shunt resistance is varied so that its magnitude, when
multiplied by the magnitude of the resistance in the bridging circuit,
is equal to the square of the required impedance of the network, then
simultaneous adjustment of the two variable resistances will not alter
the input impedance of the network but will vary the attenuation
between the input and output terminals. The ratio, however, of the
input to the output current will depend on the load and, in general,
this network would be terminated in a load of impedance equal to that
of the network. Various modifications of this form of network are
posssible and in particular the connection between the first input
terminal and the first output terminal may be made similar to that
between the second input terminal and the second output terminal and
provided with a variable bridging resistance.
In applying the principles of the bridged-T constant resistance
attenuator to the present invention, there may be provided an
adjustable attenuator having two input and two output terminals and
comprising a network having a first branch connecting one input
terminal to one output terminal, a second branch connecting the second
input terminal to the second output terminal, which second branch
includes in series two equal fixed impedances, a third branch also
connecting the second input terminal to the second output terminal and
including in series two or more adjustably stepped impedances, said
network further including a number of sets of shunt impedances equal
to the number of said adjustablystepped impedances, and a selector
switch for each of said sets of shunt impedances arranged for
selectively connecting any one or more of the set as a shunt between
said first branch and said second branch, the connection to the latter
being made between the two fixed impedances, each of said switches
being operaitvely associated with an adjustably-stepped impedance in
the third branch so that, by operation of each switch, a shunt
impedance and a series impedance are varied together, the magnitudes
of the impedances being arranged so that the product of the shunt and
series impedance remains constant. The aforementioned second branch
preferably comprises two equal fixed impedances each of a magnitudes
equal to the required impedance of the network. As indicated above,
this network would, in general, be terminated in a load of impedance
equal to that of the network. If, however, the iimpedance of the
source is equal to the impedance of the network, then, no matter what

the load impedance, the attenuation would be varied without altering
the network impedance although the actual input to output ratios would
depend on the magnitude of the load impedance.
It is well known that if a bridged-T attenuator of the type described
is terminated in a load equal to the required impedance of the network
then the current in the fixed impedance in the second branch which is
adjacent to the load is zero and there is no potential difference
between its ends. Accordingly, this fixed impedance may be made
infinitely high or infinitely low without affecting the functioning of
the network. Alternatively, if the source impedance is equal to the
required impedance of the network then the fixed impedance in the
second branch which is adjacent to the source may be made infinitely
high or infinitely low.
In its simplest form the aforementioned first branch comprises a
direct connection of negligible impedance between said one input
terminal and said one input terminal. In this case, the adjustable
shunt and series impedances are so proportioned that the product of
each shunt impedance with its associated series impedance is equal to
the square of the input impedance of the network. Alternatively,
however, said first branch may be included in series two fixed equal
impedances and there may be provided a branch connecting said one
input terminal to said one output terminal and including in series a
number of adjustable stepped impedances, which are similar to and
associated respectively with the adjustable stepped impedances in the
third branch and arranged so that the impedance in the third and
fourth branches are varied together by said switch means, the
magnitudes of the impedances being such that the separate products of
each shunt impedance with each of its associated series impedances in
the third and fourth branches remain constant. In this case the fixed
impedances are all preferably made equal to the required input
impedance of the network and the adjustable shunt and series
impedances are so proportioned that the product of each shunt
impedance with the sum of its associated series impedances is equal to
the square of the input impedance of the network.
In general a purely resistive attenuator will be preferred and in this
case all the impedances would be made resistive non-reactive
impedances.
Preferably, for convenience of reading and calculation, the selector
switches are arranged and the impedances proportioned to provide two
or more decade ranges of input to output ratio.
It is most generally convenient that the aforementioned series
impedance or the aforementioned adjustably-stepped impedances comprise
a plurality of adjustably-stepped impeaance units divided into steps
of equal magnitude, the total impedance of each unit after the first

being equal to the impedance of one step of the preceding unit.
The invention also includes within its scope an adjustable attenuator
comprising a network with a pair of input terminals and a pair of
output terminals and including a first branch connecting one input
terminal to one output terminal, a second branch connecting the second
input terminal to the second output terminal, which second branch
contains in series two fixed resistances each equal to the desired
input impedance of the network a third branch containing a plurality
of adjustably-stepped resistances connected in series between said
second input terminal and said second output terminal, a plurality of
sets of shunt resistances the number of sets being equal to the number
of said adjustablystepped resistances, a separate selector switch for
each set of shunt resistances, which switches are arranged to connect
a shunt resistance from each set in parallel between said first branch
and the junction of said fixed resistances in said second branch, the
said switches also each being associated with one of the
adjustably-stepped resistances so that operation of a switch selects a
shunt resistance and alters the associated adjustably-stepped
resistance, the switches being arranged and the resistances so
proportioned that operation of each switch maintains the product of
the magnitude of the shunt resistance controlled by the switch and the
magnitude of the associated adjustably-stepped resistance constant. As
previously indicated said adjustably-stepped resistances preferably
comprise decade units divided into equal steps and, in this
arrangement, the third branch may also contain in series a
continuously adjustable resistance of maximum magnitude equal to one
step of the decade unit of lowest resistance and there may be provided
an adjustable shunt resistance in parallel with the other selected
shunt resistances, the operation of which adjustable shunt resistance
is mechanically linked to said continuously adjustable resistance,
which adjustable shunt resistance comprises one or more steps of
infinite resistance together with a further range of adjustment formed
by a continuously adjustable resistance. It will be appreciated that
the shunt resistances associated with the lowest values of series
resistance must be very high in order to maintain the magnitude of the
product of the shunt and series resistances constant. The shunt
resistance associated with the low resistance step of the series
resistance will be very high and, as will be explained in further
detail later, it is generally adequate within the required limits of
accuracy to make the resistance infinite for the lowest index values.
In such an arrangement, the shunt resistance (apart from the lowest
index values) may comprise a continuously adjustable resistance which
would have a maximum value within practical limits.
It is generally found also that sufficient accuracy can be obtained

even if both the continuously adjustable resistances are linearly
variable although it would be appreciated that if the series
resistance is linearly variable the shunt resistance should ideally
follow a reciprocal function.
The sets of shunt impedances need not necessarily contain an
individual impedance for each switch position since some of the
required values of impedance can be formed by combining two or more
impedance units which are individually associated with other switch
positions. Similarly it is not necessary to provide a separate
impedance unit for each step of the adjustably stepped impedance since
some of the steps may be provided by combining impedance units used
for other steps.
As indicated above the form of attenuator described finds particular
application for use in measuring instruments. By providing a large
number of range settings, preferably with decade calibrated switches,
the attenuator may readily be used with an indicator for indicating
one particular value of voltage or current
In addition to its use with an indicator for indicating one particular
value of voltage or current, the attenuator also finds application for
increasing the range of measurement of other types of measuring
instruments. It i particularly of value with sensitive galvanometers
since, with such instruments, it is important to keep the damping
constant and hence the resistance presented to the galvanometer must
remain constant. The form of attenuator described above not only has
constant input impedance but also presents constant impedance to the
output terminals and hence can be used for increasing the range of the
galvanometer without affecting the damping of the instrument.
In the following description, reference will be made to the
accompanying drawings in which:
Figure 1 is a diagram of a known form of bridged-T attenuator;
Figure 2 is a diagram of an alternative known form of attenuator
network;
Figure 3 is a diagram of one form of attenuator in accordance with the
present invention;
Figure 4 is an explanatory diagram;
Figures 5 and 6 illustrate how a number of resistance units may be
used together as an adjustable series impedance for the attenuator of
Figure 3, and
Figures 7 and 8 are diagrams illustrating how a number of resistance
units may be combined together as an adjustable shunt impedance in the
attenuator of Figure 3.
Figure 1 illustrates a bridged-T type of attenuator having two input
terminals 10, 11 and two output terminals 12, 13. Between the
terminals 11 and 13 there is provided a direct connection 14 forming a

first branch of the network. Between the terminals 10 and 12 there are
connected two resistance 15, 16 in series each having a resistance R0
where R0 is to be the required input impedance of the attenuator
which, it is assumed, is to be connected to a load also of resistance
R0. Connected in shunt across the two resistors 15, 16 is a variable
resistor 17 of impedance resistance R.
Between the junction of the resistors 15 and 16 and the conductor 14
there is connected a shunt circuit comprising a variable resistor 18
of resistance Rb. If the resistors 17 and 18 are varied simultaneously
in such a manner that a product of their magnitudes R, and Rb iS equal
to the square of W,, then the input impedance of the attenuator and
the impedance presented to the load both remain constant and equal to
lElo. The voltage loss ratio L through the K R0 network is equal to
1+N where N=-=-.
R0 Rb
If a measuring instrument is used as the load, the network becomes, in
effect, a universal shunt of " range factor " L.
It may readily be shown that the input impedance looking into the
terminals 10, 11 is always Ro and also that the impedance looking back
into the network from the load at terminals 12, 13 is also always K if
the input is suitably matched.
In the special case where the source is of impedance K, then the input
impedance of the network of Figure 1 will remain constant as the
attenuation is varied no matter what the load impedance is. The actual
ratios of input to output current will depend, however, on the
magnitude of the load impedance.
Figure 2 illustrates a modified form of bridged-T network having input
terminals 10, 11 and output terminals 12, 13 and also variable
resistors 17, 18 of magnitudes R, and
Rb respectively as in Figure 1. Instead, however, of having series
fixed resistors 15, 16, there is provided in the arrangement of Figure
2 a single fixed resistor 20 of magnitude K connected in the shunt
circuit in series with resistor 18. In effect, the network Gl Figure 2
is the same as that of Figure 1 with the resistance 16 made infinite.
With this arrangement also, ir may be shown that provided R,B.= R,2,
then the input impedance remains K although the output impedance is
not constant in this case.
The attenuator shown in Figure 3 is based on the form of bridged-T
network shown in
Figure 1. In Figure 3 there are provided input terminals 21, 22 and
output terminals 23, 24.
A direct connection 25 is made between the terminals 22 and 24 and
forms the first branch of the network. Between the terminals 21 and 23
there are connected in series two resistors 26, 27 each having a

magnitude equal to the required input and output impedance of the
attenuator, which, for simplicity in the following description, will
be assumed to be 1,000 ohms. Also connected between the terminals 21
and 23 are a number of adjustable resistors 28, 29, 30, 31, which
together corre-pond to the resistance Ra of Figure l.
The resistance 28 is adjustable in steps and comprises nine resistance
elements each of 1,000 ohms. connected in series. The position of an
adjustable tap 32, which Jetermines the number of resistance elements
in circuit, is controlled by means of a control knob (not shown)
having a dial marked with indices 110 (corresponding to the
tapping-point markings shown in Figure 3).
The tap 32 is connected to one end of the resistance 29 which is also
an ad,ustably- stepped resistance having ten resistance elements each
of 100 ohms. The control knob for controlling a tap 33 on the
resistance 29 thus has eleven positions corresponding to the tapping
points marked 0-10 in Fire 3 and is adjusted by means of a control
knob provided with indices correspondingly marked from 0-10. The tap
33 is connected to one end of the resistance 30 which likewise has ten
resistance elements which, in this case, are each of 10 ohms.
resistance. An adjustable tap 34 may be set on any of the tapping
points marked 0-10 of resistance 30 and is adjusted by means of a
control knob provided with corresponding indices. The tap 34 is
connected to one end of a continuously variable resistance 31 which is
linearly variable by movement of an adjustable tap 35 which is
connected to the terminal 32. The total impedance of the resistance 31
is 10 ohms.
Between the junction of the resistors 26 and 27 and the connector 25
there are provided a number of sets of adjustable shunt impedances.
The first set 40 is associated with the resistance 28 and the
magnitude of the shunt impedance introduced into the circuit is
controlled by means of an adjustable tap 41 which is operated by the
same control knob as operates the tap 32 on resistance 28. In the
first position corresponding to zero impedance on resistance 28 there
is an infinite shunt impedance introduced into the network. In each of
the other positions of the tap 41 there is introduced a resistive
impedance, the magnitude of which is such that the product of the
shunt resistance and the series resistance 28 provided by the
corresponding position of the tap 32 is equal to 1,0002. Thus, the
resistance 42 in the second position or tap 41 would have an impedance
of 1,000 ohms, the resistance 43 in the third position would have a
resistance of 500 ohms and so on to the impedance 44 in the tenth
position which would be 1000
ohms.
9

A similar set of shunt impedances 45 are associated with the
resistance 29. In this case, a tap 46 (which is controlled by the same
control knob as tap 33) can be adjusted to insert a shunt impedance of
infinity in the position corresponding to zero on the indices of the
control knob. The shunt impedances are arranged so that the product of
the shunt resistance introduced by the tap 46 and the series
resistance introduced by the tap 33 is equal to 1,0002 and the shunt
resistors are proportioned accordingly. Thus the tap 46 inserts a
shunt resistance 47 of 10,000 ohms. in the position marked 1 of the
control knob. In the position marked 2, a shunt resistance 48 of 5,000
ohms would be inserted and so on until, in the position marked 10, the
shunt resistance would be 1,000 ohms.
A similar set of shunt impedances 50 are provided in association with
the series resistance 30, an adjustable tap 51 being controlled by the
same control knob as controls the tap 34. The shunt resistance for a
zero position will be infinity. The resistances for positions 1-10 are
arranged so that the product of their resistance and that introduced
by the tap 34 in a corresponding position on resistance 30 is equal to
1,0002 as before and thus, for example, the shunt resistance 52 for
the position marked 1 would be 100,000 ohms.
The resistance 31 is continuously variable. It would not be
practicable to introduce a continuously variable shunt resistance in
this case since the shunt resistance would have to be adjustable
between 100,000 ohms. and infinity following a reciprocal law. For
practical purposes it is sufficiently accurate to introduce infinite
resistance in the first and second position of an adjustable tap 55
which controls the shunt impedance and which is operated by the same
control knob as controls the tap 35 on resistance 31. Hence there will
be an infinite shunt impedance until the tap 35 has been moved one
fifth of the way from resistance 31 from the zero end. For the
remaining part of the shunt impedance, there is provided a linearly
variable resistance 56 of 200,000 ohms connected in series with a
fixed resistance 57 of 100,000 ohms so that when the tap 55 has been
moved to the lower end of the resistance 56 in the diagram, that is
corresponding to maximum impedance of the resistance 31, then there is
100,000 ohms. in the shunt impedance.
The shunt impedance is thus 300,000 ohms. when the series impedance of
resistance 31 is two ohms. and the shunt impedance decreases linearly
to 100,000 ohms. as the series impedance increases to ten ohms.
The use of two continuously variable resistors 31 and 56 may be more
clearly understood by reference to Figure 4 which is a graph having
the index positions of taps 35 and 55 as abscissa. The straight line
60 shows, on the right hand ordinate scale, the magnitude of the
series resistance 31. The dotted curve 61 shows the desired value of

total shunt resistance such that the product of the shunt and series
impedances should be 1,0002. The straight line 62 shows the value of
shunt resistance obtained using a variable resistor 56 of 200,000
ohms. together with a fixed resistor 57 of P00,000 ohms. The
chain-dotted line 63 represents the shunt impedance obtained with an
alternative arrangement in which the resistor 56 is 350,000 ohms. and
the resistor 57 is 50,000 ohms.
It may be shown that such an arrangement introduces almost negligible
error compared with the use of correctly proportioned shunt
resistances. The effect of the infinite resistance in the first two
positions is to alter the input impedance of the network and the
effect is dependent upon the value of the impedance from which the
network draws its input. In a typical application, as described later,
this is a cathode follower of an amplifier stage and in such a case
the impedance may be as low as 10 ohms. If the ratio of the source
impedance to the characteristic impedance K of the network is K it can
be shown that the error is a(q+2KK)
1+1l
t+2Ro) where m is the magnitude of the resistance 31.
If we assume that the steps represented by taps 32, 41 are unity, then
the index markings for taps 35, 55 are steps of 0.001. For these to be
reliable to one tenth of a division, the quantity e above must not
exceed 0.0001. For an attenuator setting of 1.002, which is the
setting known to yield the largest error, the
ar value of -- is only 0.002. Thus a is negligible
Ro in comparison with K whilst KRo is small and thus it may be shown
that, for this required accuracy, K can reach a value of one quarter.
With a characteristic impedance of 1,000 ohms, the source resistance
must therefore not exceed 250 ohms, if the 0.001 dial is to be relied
upon to one tenth of a division.
If it is not possible to use a low impedance source, the final shunt
and series resistances may be made in decade steps like the others.
If the attenuator is used, as described below, with a null indicator,
interpolation between steps may be made by reading the "offbalance"
indications on the indicator.
Another method of obtaining the required accuracy if the attenuator is
to be used with a source not of sufflciently low impedance would be to
use a shunt resistor arranged such that movement of the tap 55 gives a
non-linear variation of resistance.
It may be noted that the precision of the resistors 30, 50 may be
substantially less than those of the earlier stages of the attenutator
and in a typical case may be of the order of 1% as against 0.1% for
the earlier stages. The precision of the last stage may be still less,
for example, of the order of 10%, whilst still maintaining the

required overall accuracy of the attenuator.
To revert to consideration of the attenuator as a whole, if the first
taps 3Z, 41 are set to index marks 3, the second taps 33, 46 are set
to index mark 2 and remaining taps are set to zero, then the series
impedance is 2,200 ohms. and the shunt impedance, which it will be
noted are in parallel, will be 1,000x0.5 in parallel with 1,000X5
mating an effective
1,000 shunt impedance of - ohms. Thus the
2.2 product of the shunt and series impedances is 1,0002. The value of
N, as defined above, is 2.2 and the loss ratio L is 3.2 which is equal
to the sum o together so as to be movable simultaneously along two
steps of tapping points 130, 131 respectively. By connecting the
various tapping points together as shown in Figure 8, the required 10
steps of the shunt impedance are provided together with the infinite
impedance in the zero index position.
It will readily be apparent that other arrangements for combining
units of resistance may be used in order to reduce the number of fixed
resistors employed in the attenuator.
What we claim is :
1. An adjustable attenuator comprising a four terminal constant
impedance network of the bridged-T type having a first branch
connecting one input terminal to one output terminal, a second branch
containing in series two equal fixed impedances, a third branch also
containing a variable series impedance, and a variable shunt impedance
connected between said first branch and the junction of the fixed
impedances in said second branch, in which the attenuation ratio may
be varied without changing the input impedance of the network provided
that the dimensions of the variable series and shunt impedances are
always such that RaRb=K', where Ra is the series impedance, Rb is the
shunt impedance and K is the desired input impedance in the network,
characterized in that the variable series impedance consists of a
plurality of sets of variable impedances and the variable shunt
impedance consists of a like number of sets of variable impedances,
the attenuator including a plurality of pairs of switches equal to the
number of sets of series and shunt impedances, one switch of each pair
controlling one set of series impedances and the other switch of each
pair controlling a related set of shunt impedances, the two switches
of each pair being mechanically linked so that a series and a shunt
impedance are varied together, each pair of switches having a
numerically indexed scale, and the series and shunt impedances are so
dimensioned that for all settings of the switches the product of the
series and shunt impedances in circuit is constant, whereby the sum of

the scale indices is equal to the numerical ratio of attenuation
between the the input and output terminals.
2. An adjustable attenuator, as claimed in
Claim 1, in which one of the fixed impedances in the second branch is
made infinitely high.
3. An adjustable attenuator, as claimed in
Claim 1, in which one of the fixed impedances is made infinitely low.
4. An adjustable attenuator, as claimed in any of the preceding claims
wherein each of the fixed impedances has a magnitude equal to the
required input impedance of the network.
5. An adjustable attenuator as claimed in any of the preceding claims
wherein said first branch comprises a direct connection of negligible
impedance between said one input terminal and said one output
terminal.
6. An adjustable attenuator as claimed in either Claim 2 or Claim 3
wherein said first branch includes in series two equal fixed
impedances and wherein there is provided a fourth branch also
connecting said one input terminal to said one output terminal and
including in series a number of adjustablystepped impedances which are
similar to and associated respectively with the adjustablystepped
impedances in the third branch and arranged so that the impedances in
the third and fourth branches are varied together by said switch
means, the magnitudes of the impedances being such that the separate
products of each shunt impedance with each of its associated series
impedances in the third and fourth branches remains constant.
7. An adjustable attenuator as claimed in
Claim 1, wherein the adjustable shunt and series impedances are so
proportioned that for any setting of the switches the product of the
shunt impedance and the series impedance in circuit is equal to the
square of the input impedance of the network.
8. An adjustable attenuator as claimed in any one of the preceding
claims wherein the impedances are all resistive non-reactive
impedances.
9. An adjustable attenuator comprising a network with a pair of input
terminals and a pair of output terminals and including a first branch
connecting one input terminal to one output terminal, a second branch
connecting the second input terminal to the second output terminal,
which second branch contains in series two fixed resistances each
equal to the input impedance of the network, a third branch containing
a plurality of adjustably-stepped resistances connected in series
between said second input terminal and said second output terminal, a
plurality of sets of shunt resistances the number of sets being equal
to the number of said adjustably-stepped resistances, a separate
selector switch for each set of shunt resistances, which switches are

arranged to connect a shunt resistance from each set in parallel
between said first branch and the junction of said fixed resistances
in said second branch, the said switches also each being associated
with one of the adjustably-stepped resistances so that operation of a
switch selects a shunt resistance and alters the associated adjustable
stepped resistance, the switches being arranged and the resistances so
proportioned that operation of each switch maintains the product of
the magnitude of the shunt resistance contrilled by the switch and the
magnitude of the associated adjustably-stepped resistance constant.
10. An adjustable attenuator as claimed in
Claim 9 wherein said adjustably-stepped resist
* GB786190 (A)
Description: GB786190 (A) ? 1957-11-13
Improvements in and relating to water plastic paint
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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.
COMPLETE SPECIFICATION.
Improvements in and relating to Water Plastic Paint.
I, AUGUSTUS GORDONELLIOTT, 28 Irish
Avenue, Bexley, Kent, British Subject, 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 :
This invention relates to water paints of the kind known as water
plastic paints which have a consistency similar to wet mixes of
plaster and can be applied in relief. Such paints have a base

consisting of carbonate of lime or oxides of certain metals such as
zinc or iron or Lithopone, and a binder which is usually casein but
can be an animal glue, dextrine or starch.
All such water plastic paints are easily affected by water and when
rendered damp by condensed water or by splashing they can easily be
rubbed off the surface to which they have been applied.
The object of the present invention is to enable a surface of water
plastic paint to be created which cannot be rubbed off when rendered
damp by condensation or by wetting with water. Such is hereafter
referred to as a surface of the kind specified.
It is known in the preparation of washable wall paper to coat the same
with an aqueous composition containing a protein such as glue or
casein and a protein hardening agent such as paraformaldehyde.
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* GB786191 (A)
Description: GB786191 (A) ? 1957-11-13
Improvements in or relating to liquid dispensing valves
PATENT SPECIFICATION
Date of filing Complete Specification: Jan 28, 1955.
Application Date: Feb 2, 1954 No 3118154.
Complete Specification Published&: Nov 13, 1957.
Index at Acceptance:-Class 135, VE( 1 G 4: 5 B), VM 6 F.
International Classification:-FO 6 k.
COMPLETE SPECIFICATION.
Improvements in or relating to Liquid Dispensing Valves.
LIMITED, a British Company, of Chertsey Road, Woking, Surrey, and

LESLIE ATHERTON, a British Subject, of 7 Orchard Gardens, Aldershot,
Hampshire, 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 comprises improvements in or relating to liquid
dispensing valves, and an object is to provide an improved valve for
dispensing two different beverages or liquid beverage ingredients, in
particular, a beverage such as tea or coffee, and milk.
According to the present invention, there is provided in beverage
dispensing apparatus, a valve for dispensing two different beverages
or liquid beverage ingredients simultaneously, comprising a valve body
having a tapered valve bore, a correspondingly tapered valve plug
rotatable in said bore, two separate inlet ports in the valve body
spaced longitudinally thereof and communicating with the valve bore,
with corresponding longitudinally spaced outlet ports, and separate
ducts in the valve plug for connecting each inlet port with the
corresponding outlet port as the plug is rotated in the bore, the
arrangement being such that as the valve plug is turned to dispense
both liquids together the flow rates of both increase simultaneously.
Preferably, the arrangement of the ports in the valve body and the
ducts in the valve plug is such that the valve is closed, or dispenses
liquid supplied at either inlet, or both inlets simultaneously,
according as to which of four different angular settings the valve
plug is rotated.
According to a preferred form, in beverage lPrice 3 s 6 d 1 P Ice 2 t
D dispensing apparatus, a valve for dispensing two different beverages
or liquid beverage ingredients (such as tea or coffee, with milk)
simultaneously, comprises a valve body having a tapered valve bore
with its axis horizontal, a correspondingly tapered valve plug
rotatable in said bore, an inlet at the top of the valve body
communicating with the valve bore and adapted to receive a container
for milk or like liquid, a corresponding milk outlet underneath the
valve body opposite the inlet, a side inlet in the valve body spaced
along the valve axis from the first inlet and adapted for connection
to a tea urn or the like, a corresponding tea outlet underneath the
valve body, a straightthrough duct across the valve plug for
connecting the milk inlet and outlet, a separate angled, for example
right angled, duct in said plug for connecting the tea inlet and
outlet, and means for varying at will the flow passage in said duct
for milk, whereby when the corresponding valve inlets and outlets are
put in communication by rotation of the valve plug tea and milk are
dispensed simultaneously in predetermined proportions.
This construction of valve makes for easy and thorough cleaning, which

is an essential consideration if beverages are to be dispensed under
hygienic conditions.
Other features of the invention will be apparent from the following
description, given by way of example, of one construction in
accordance with the invention, reference being had to the accompanying
drawings, in which:Figure 1 is a side elevation, in section, of a
dispensing valve; and Figure 2 is an end elevation of the valve.
The valve to be described has a tapered plug 11 fitting into a
correspondingly tapered 786,191 65.
786,191 horizontal bore 12 in the valve body 14, with two inlets and
two outlets for handling two different liquids The valve is designed
to permit the flow of either or both liquids, as determined by the
rotation of the valve plug 11 in the bore 12 The valve body 14 has,
for the first liquid, an inlet 13 through its side and a downwardly
directed outlet at right angles to the inlet For the second liquid the
valve body has an inlet 16 at the top of the valve spaced horizontally
along the bore from the inlet for the first liquid, the outlet 17 for
said second liquid being also downward and directly opposite to the
corresponding inlet.
Opposite the inlet 13 and outlet 15 for the first liquid, the
rotatable valve plug 11 has a duct 18 straight through it along a
diameter and a further duct 19 communicating therewith and extending
radially from the centre of the plug to the exterior thereof at right
angles to the first duct, so that the two ducts form a T Opposite the
inlet 16 and outlet 17 for the second liquid, the valve plug has a
straight-through duct 20 extending along a diameter and at right
angles to the straight-through duct 18 for the first liquid, that is,
parallel to the duct 19 forming the stem of the T.
At its end of larger diameter, the valve plug is provided with an
axially-extending valve rod 21 projecting outwardly from the end of
the valve body 14, with a lever handle 22 on said rod for operating
the valve This end of the valve body is closed by a cap 23 around the
valve rod and screw-threadedly received on the end of the valve body,
and a spring 24 surrounding the valve rod 14 between the cap 23 and
the valve plug 11 serves to keep the valve plug pressed in against the
surface of the tapered valve bore 12.
The inlet 16 and outlet 17 for the second liquid are near to the
smaller diameter end of the valve, and the valve plug 11 has at that
end a relatively large diameter axial bore 25 in which is screwed a
metal bushing 26 having at its inner end a rubber bush 27.
An adjusting screw 28 passes through a bore so 29 in the bushing 26,
and through the bush 27; it projects into the duct 20 by way of a port
30 in the inner end wall 31 of the bore 25 The screw 28 is in
screw-threaded engagement with the bushing 26, whereby adjustment of

the screw serves to vary the extent to which its end blocks the duct
20 and hence the flow of the second liquid when the valve is open The
rubber bush 27 serves to prevent liquid leaking from the port 30 along
the stem of the screw The end of the adjusting screw may be shaped so
that when in the fully closed position a known proportion of the
second liquid to the first may flow.
To pour both liquids simultaneously, the valve is set, as shown in the
drawings, with the duct 20 in the valve plug for the second liquid
vertical and the T stem 19 of the T-form ducts 18, 19 for the first
liquid downward 'If the valve plug 11 is turned 70 through 1800 from
this position the second liquid only is poured, while if the valve
plug is turned through 90 ' so that the T stem is horizontal and
registers with the inlet for the first liquid the first liquid only is
poured 75 To locate the valve plug 11 in the fully open position with
both liquids being poured, a spring-pressed ball 32 accommodated in a
transverse bore 33 in the plug is arranged to snap into a co-operating
80 recess or groove 34 in the inner wall of the valve body 14, when
this setting of the valve plug is reached.
The valve is intended primarily for use when the two liquids concerned
are tea (or 85 coffee) as the first liquid and milk as the second In
this case, the valve is connected, by means of a union nut 35, to a
tea urn so that the tea is delivered into the first liquid inlet 13,
and a milk container deliver 90 ing into the second inlet 16 is
mounted directly over the valve in a readily detachable manner for
easy cleaning The proportion of milk to tea can be set as required by
means of the screw-threaded rod or 95 spindle control 28 as previously
described.
Other means for operating the valve may be incorporated, as, for
example, the arrangement shown in broken lines in Figure 1 and
comprising depending levers 36 fixed to 100 rotate the plug 11, and a
bar 37 connecting the lower ends of said levers When a cup is pushed
under the outlets 15, 17 it engages the bar 37 and causes the levers
36 to open the valve; as soon as the cup is removed, 105 the valve is
closed and the levers returned automatically by springs (not shown)
The valve may be arranged so that when operated in this manner, there
is no position where milk only or tea only is dispensed 110 It will be
understood that the valve as above constructed can be quickly and
easily cleaned by flushing through with boiling water Previous designs
of dispensing valves for this purpose have failed through diffi 115
culties in cleaning the second liquid (milk) container and valve
parts.
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* GB786192 (A)
Description: GB786192 (A) ? 1957-11-13
Improvements relating to gathering and binding apparatus for mown crop
COMPLET SPECIFICATION
Improvements relating to Gathering and Bindmg Apparatus
for Mown Crop
We, BREVETTI A. L. I. T., of Corso Vittorio
Emanuele II No. 123, Turin, Italy, a body corporate organised and
existing under the laws of Italy, do hereby declare the invention, for
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 relates to gathering and binding apparatus for mown
crops.
The mowing-binding machines for wheat and like crops, in use up till
now, are of considerable dimensions, weight and cost, and present
difficulties in carriage and handling, which renders them inefflcient
and useless for mowing on sloping, uneven or confined land.
On such land light mowing machines are used, the gathering or
formation into sheaves of the wheat or such like being effected by
hand.
The present invention has for its principal object to provide
apparatus capable of mechanically effecting the operations of mowing,
gathering and shaping into sheaves.
The invention is an apparatus for collecting and binding standing
vegetable stems adapted to be detachably coupled with a mowing
machine, and comprising in combination, a frame provided with means
for detachable connection to a mowing bar, two devices adapted to act

as rakes and performing an elliptic orbital movement in a horizontal
plane, said devices being adapted to grip the cut stalks before said
stalks fall and convey said stalks towards the back portion of the
frame, and a binding device adapted to receive the said stalks in
bundles, bind and discharge said stalks to the rear of the device.
Preferably such apparatus is characterised by means for catching the
mown crop while it is standing, and for driving the crop, pressed into
swaths, to binding means which form the crop into sheaves and leave
the sheaves on the ground ready for stacking.
The present invention also provides for a driving connection for
universally coupling said gathering-binding apparatus in driving
relationship with the various kinds of mowing machine.
The invention may be advantageously applied also to agricultural
machines other than harvesting or mowing machine, provided that they
are able to receive in combination a mowing bar of a known knd as is
the case with certain tractors for agricultural purposes.
An embodiment of the invention will now be described, by way of
example, with reference to the accompanying drawings, in which :-
Fig. 1 is a plan view of the gathering and binding apparatus.
Fig. 2 is a rear view in elevation.
Fig. 3 is a detail view to an enlarged scale of the rear of the
apparatus.
Fig. 4 is a side view in perspective of the apparatus attached to a
mowing machine of a known type.
Fig. 5 is a rear perspective view of Fig. 4.
Fig. 6 is a top perspective view of Fig. 4.
Figs. 7 and 8 show the drive to the agricultural vehicle e. g. a
tractor.
Referring to the drawings : u
The apparatus frame consists of iron tubes 4090 401401l interconnected
by soldered junction pipes, and made preferably of malleable cast-iron
or of stamped plates, or of hollow elements made of malleable
cast-iron or some other metal, united one to another.
Said frame comprises a main tie beam 40 at the outer end of which is
secured a bracket bearing the supporting wheel 36 the position of
which can be regulated by means of the adjustment device 37.
The other end 401 of the tie beam carries a fastening bar 7 which with
two others 71 and 711 constitute the connection means between the
apparatus frame and that of the mowing machine; to effect the
connection, the same bolts 34 may be used so as to fix the combs 35 on
the arm 31 of the mowing machine.
The power drive from the mower is eidected through an assembly
comprising a toothed crown wheel 87 and a grooved pulley wheel 88
coupled to the mower's rear wheel 83 by means of three bolts 89 which

are hooked on to the wheel spokes and are tightened by means of nuts
891.
A reel 50 adjustably secured to a post 51 is driven from the mower
through the intermediary of the grooved pulley wheel 88. Wheel 88 is
coupled to a secondary pulley wheel 8oui by means of an extensible
transmission belt 52.
Between the pulley wheel 88 and the toothed crown wheel 87 a loose
collar 43 in disposez carrying an extension 42 constituting a bear-
ing block for a shaft 44 with a hinge joint element 41 adapted to be
coupled with a universally jointed extensible coupling shaft 1.
The hooked bolts 89 interlock with the wheel 87 and pulley 88 and also
with an interpose disc 871, so that the collar 43 of the extension 42
is loose and prevented to rotate by the drawbar 47, which may be
anchored to any fixed portion of the machine.
A pinion 45 meshing with the crown wheel 87 transmits motion to the
shaft 44 to which it is secured. By the side of the pinion 45 is fixed
a second bracket 48 supporte on the inner periphery of the toothed
crown wheel 87 by rollers 49.
A tie rod 47 connected at one end to a fixed part of the mower in the
example to the beam 32, has its other end connected to the collar
extension 42 with the driving means mounted on same, so that the
driving means are locked against rotation with crown wheel 37.
This arrangement provides for an operative coupling, making use of
toothed wheels, without regard to the axial dimensions or to the exact
centering relative to the wheel of the mowing machine ; it also allows
swinging of the apparatus and the adaptation of the mowing machine
comb to the sloping ground.
A driving shaft 1 is provided with two universal joints 2 which permit
certain displacements between the chassis of the vehicle and the
mowing arm, so that the latter can move upwards and downwards
according to the configuration of the ground. At the end of the main
driving shaft 1 a bevel gear 3 is keyed, which engages with the bevel
gear 4, this being operatively connected with the crank 5. The pin 6
of the crank lever 5 (Fig.
3) has on its lower portion a bevel gearing 97, 98, which drives the
shaft 9. At the end of the shaft 9, the bevel gearing 971, 981 trans-
mits the movement to the shaft 6'of the crank 51.
The cranks 5,51 are articulated with their pins 10, 101 at the rods
11, 11'of which the front ends are coupled with the pushing elements
12, 121 shaped as a rake, and the back ends are coupled with the
levers 13,13'.
The pushing elements 12,121 are also connected through rods 14,141
with the levers 13, 131, so that a quadrilateral-like guide is bulk up
for the pushing elements 12,121 with the fixed points 13A, 13B of said

guide at the end of the levers 13,131, the guide itself being set in
motion by the pins 10,10'of the crank' 5,5'. The pushing elements
12,121 describe therefore an elliptical path, of which the shorter
diameter lies in the direction of the forward motion of the machine ;
this, with the teeth 15,151 turned ahead.
The teeth 16, 16'of the pushing elements 12,12', directe towards the
passage (hereinafter called"a canal") in which the vegetable stems are
bound convey, by virtue of their arrangement, the cut stems to the
rear of the machine into the canal during the movement of the pushing
elements 12, 121 aLhrough the aforesaid elliptical path. The stalks
collected in the"canal"are pushed against the cross member 17, which
is lixed at the upper end of the shaft 18. This shaft transmits
downwards, to the cross rod 19, the motion wi the cross member 17,
which motion begins when a determined position is reached. The rod 19,
in moving, releases the stop 20 (Figs. 2 and 3). The bevel gear 21
(Fig. 1), which meshes with the bevel gear 22, is then caused to
couple with the main driving shaft 1 and set it in rotation. With the
bevel gear 22 is eccentrically coupled one end of the transmission rod
23, while the other end is rotatably fixed to the lever 24 that guides
the binding needle 26 on the shaft 25. During the binding operation,
the binding needle 26 swings with its point up to a knotting hook 27
of known construction. While the binding needle 26 prevents, during
the knotting operation, the outlet of the stalks, the action of the
baling tooth 161 con- tinues. However since the binding needle 26
crosses its path of movement of the tooth 16, the latter must be
stopped. For this purpose there is provided a stop 28 that is acted by
the binding needle 26 through the intermediary of a lever 29 to
release the rigid connection between the pushing element 12 and the
tooth 16, so that the tooth 16 can now apply to the stalks only the
pressure exerted upon it by a spring connected at the point 30, the
spring serving also to release the stop 28 after the binding needle 26
becomes inoperative.
The toothed wheel 22, carrying the eccentric 31, permits, by means of
the toggle lever 32, the release of the transmission rod 33. This rod
operates therefore the opening of the binding"canal"by means of the
cross member 17 which on rotation of the driving wheel 34 of the
knotting device is swung at the same time as the expeller 85, and so
leave the bound sheaf free so that the expeller 85 can grip it.
The cross member 17 closes immediately again after the described
motion, as soon as the sheaf has gone out. The supporting wheel 36 of
the device is displaceable with respect to the stopping sector 37 for
adjustment of the cutting height. By means of the arms 7,71,711 the
device is connected at three points with the mowing arm.
What we claim is :-

1. An apparatus for collecting and binding standing vegetable stems,
adapted to be detachably coupled with a mowing machine, and
comprising, in combination, a frame provided with means for detachable
connection to mowing bar, two devices adapted to act as rakes and
performing an elliptic orbital movement in a horizontal plane, said
devices being adapted to grip the cut stalks before said stalks fall
and convey said stalks towards the back portion of the frame, and a
binding device adapted to receive the said stalks in bundles, bind and
discharge said stalks to the rear of the device.
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* GB786193 (A)
Description: GB786193 (A) ? 1957-11-13
Device for the surface treatment of metallic or non-metallic objects in one
or more fluid baths
COMPLETE SPECIFICATION
Device for the Surface Treatment of Metallic or Non-metallic Objects
in one or more Fluid Baths
We, N.V. METALLIC INDUSTRY, a Corporation organised under the laws of
Holland, of Loosdrechtse Rading, Loosdrecht, Holland, 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:
The invention relates to a device for the surface treatment of
metallic or non-metallic objects in one or more fluid baths whereby
the supporting members for the objects are moved in a predetermined
cycle over a guide path. It is usual in such devices, such as, for

example, galvanizing devices, to interconnect the supporting members
for the workpieces with a cable, chain or the like.
by means of which said workpieces are simultaneously driven with a
speed which necessarily depends on the longest time during which a
workpiece should be at a certain treating station. This method,
consequently, comprises a rigid control. In said known method the
guide path further has reciprocal portions in a vertical direction in
order to lower into a treating bath a supporting member present on
such a portion together with the workpieces mounted or hung thereon or
to lift the same therefrom again. A device is also known in which
various treating stations are combined in groups, each group having a
separate guide path adapted to the optimum operating speed for the
driving chain. The described known devices are all complicated due to
the drive of the movable parts, whilst in the device of the last
mentioned kind separate means are still required for the transport of
the workpieces from the one group to the other. Also a galvanizing
device is known in which the supporting members for the workpieces are
provided with levers which are rotatable in a vertical plane, which
levers are simultaneously guided in a closed path along the treating
stations so that the workpieces may be brought into or out of the
treating baths by a swinging movement of the levers. The constructions
of such a device is naturally complicated and possesses the drawback
of the simultaneous drive.
The present invention provides a device of the general type described
above, in which the drawbacks of the known devices are eliminated and
which nevertheless has a relatively simple construction.
According to the present invention a device for the surface treatment
of metallic or non-metallic objects in one or more treating baths
comprises members for supporting and moving said objects in a
predetermined cycle over a guide means, said members comprising a
number of carriages each being provided with a separate electric
driving motor, a suspension rack for supporting said objects to be
treated, and means co-operating with said guide means adapted to move
said carriages in respect of said guide means, said guide means
comprising a fixed endless guide path being arranged at different
levels adjacent a series of containers provided with said treating
baths.
As each of the supporting members has a separate driving motor it is
possible to obtain for said members a different speed at different
stations along the guide path, but care should be taken that the
mutual distance between adjacent supporting members should not fall
below a certain minimum distance.
The movement of the separate supporting members may then be such that
a workpiece should remain the correct time in the correct treating

place for a special treatment without any influence on the treating
time of another worlxpiece.
As the guide path is fixed its support may be carried out in a simple
manner since the presence of level differences in the guide path
renders it possible to arrange a portion of the guide path, e.g., on
another floor of the work- shop or the factory which may particularly
be adapted to special treatments.
The electric motors are fed with the aid of current collectors and
current conducting contact strips present along the guide path,
whereby the contact strips may have different voltages at different
locations along said path.
In this manner the device may be operated entirely automatically, for
instance, according to a predetermined time scheme.
The device according to the invention is further characterized in that
the guide path has a raised portion located over the vertical
partitions between the treating stations.
By a suitable choice of the difference in level in the guide path at
the location of such a partition, e.g., a wall of a liquid container,
it will be possible to dip the workpieces on a supporting member into
the corresponding liquid bath or to lift it therefrom without making
use of separate means. Here the path as well as the part of a
supporting member co-operating therewith remains out of contact with
the liquid bath.
In an embodiment of the device according to the invention the endless
guide path is generally located in a straight cylinder and the guide
path has horizontal portions lying at at least two levels with
intermediate vertical portions, the portions of the path which are
arranged at an angle being interconnected by curved portions. By a
"straight cylinder" should be understood a surface, the generatrices
of which are parallel to each other and in which the section
perpendicular to a generatrix has the shape of a curved line, circle
or rectangle. Furthermore by "horizontal" parts of the guide path
should also be understood those parts of the guide path which have
only small dimension in in horizontal direction, e.g., where the
treating time of the workpiece is very short and consequently the
longitudinal dimension of the bath is small.
In another embodiment the endless guide path is generally arranged in
a straight cylinder and the guide path has horizontal portions lying
at at least two levels with intermediate vertical portions, the
adjacent portions of the path which are arranged at an angle, being
interconnected in such a manner by a rotatable portion of the path
that a supporting member may pass from one portion of the path to an
adjacent portion of the path. In this manner bends in the guide path
may be avoided, which consequently need consist only of straight

portions with intermediate point-like passages. Due thereto the
construction of the guide path becomes economically attractive and the
reali- zation of the supporting member portions cooperating with the
guide path may be made more simply.
The invention will be elucidated with the aid of some embodiments of
The device according to the invention represented in the drawings.
Fig. 1 is a cross-section along the line I--I of the device according
to the invention, shown in Fig. 2, in which the guide path has mainly
a hexagonal section and in which the straight horizontal and vertical
portions of the path are interconnected by bends.
In Fig. 1A is shown a supporting member in detail and on an enlarged
scale;
Fig. 2 is a top view of the device shown in Fig. 1;
Fig. 3 is a cross-section along the line III -III of the device shown
in Fig. 2;
Fig. 4 is a timing control system for an automatically operating
device;
Fig. 5 is a diagrammatic view of another embodiment of the device
according to the invention in which the guide path has a mainly
C-shaped section and consists of straight horizontal and vertical
portions and in which the said portions are interconnected by
point-like shaped passages;
Fig. 6 represents a side view of a supporting member applied with the
embodiment according to Fig. 5, with the guide path displayed in
section;
Fig. 7 is a side view of the supporting member, the guide path being
turned about 90 in respect of the representation in Fig.
6, in which the lower part of the driving electric motor is cut away;
Fig. 8 is a cross-section of a turntable-like transfer passage between
a horizontally and vertically arranged portion of the path; and
Fig. 9 is a longitudinal section of the passage of Fig. 8.
In the Figs. 1, 1A, 2 and 3 is shown a device for the galvanization of
workpieces which are suspended from or are attached to supporting
members 1 which via a discharge and loading station 2 move along a
number of treating stations, such as, e.g., successively a purifying,
rinsing, galvanizing, rinsing, polishing, rinsing bath and finally a
drying furnace, indicated by 3 to 9 respectively. Due to the fact that
each of the supporting members has its own driving mechanism in the
shape of an electric motor 10, each of said members is movable with a
speed which may be different at different locations along the guide
path 11. For that purpose the motor 10 drives a driving roller 13 nia
a transmission, which roller together with a set of guide rollers 14
keep the guide path 11 clamped between them with the aid of strong
springs (not represented).

The guide path 11 (Figs. 2, 3) is fixed and has portions 1 lea, which
are at a lower level than portions 1 lb, which portions are connected
by vertical portions llc. The portions interconnecting the vertical
and the horizontal portions of the guide path have been maintained as
short as possible consistent with the requirement that the resiliently
arranged rollers 13, 14 shall not be thereby hindered from turning. As
appears from
Figs. 2 and 3, the position of a liquid bath, e.g., the purifying bath
3 corresponds with a portion 1 la of the guide path lying at a lower
level whereby the dimension of the said portion 1 la seen in
longitudinal direction of the guide path is smaller than that cf the
bath 3. In the embodiment the difference in height between the parts 1
Ia and 11b has been chosen such that during the movement of a
supporting member along the guide path a workpiece suspended from or
attached to said member is lifted from a bath, is passed over the edge
of the bath and is dipped, if desired, into a subsequent bath. In this
manner the provision of complicated and heavy supports requiring
lifting devices, with which either the entire guide path or a part
thereof is movable in vertical direction, is avoided.
Of course, in order to obtain a special treatment for the workpiece
both appertaining portions 1 lc may be longer than indicated above
for raising a workpiece, e.g., so as to arrange a certain part of the
path on another floor of the work space which has been adapted to said
special treatment.
The section of the guide path may have the shape of a regular hexagon,
as represented in Fig. 1A. The flat sides of the guide path then may
serve various purposes. To prevent rotation of a supporting member in
respect of the axis 15 of the guide path, the planes 16, 17 may be
chosen as runing surfaces for the rollers 13, 14, whilst the guide
path may be supported, e.g., at the plane 18.
The conduits for the supply of current to the electric motors 10 are
attached to the plane l5a of the guide path and are insulated
therefrom and are arranged parallel to each other and to the direction
of the axis 15. In the embodiment three conduits 19 are shown which
are supported by insulation.
By the arrangement of suitably chosen interruptions of the conduits,
and a correct choice of the various points of supply on those
conduits, the required control of the separately driven supporting
members may be realized. Furthermore the conduits are arranged in such
a manner that when they interconnect separate sections of the guide
path, they are joined in a correct manner.
In this way it is possible to alter the course of the guide path at
will in a rather simple way, either for applying various treating
baths, or for arranging other differences in level.

A suitable arrangement of the conduits 20 for the galvanizing current
may be obtained by supporting these conduits insulated from the guide
path, approximately at the same level as the edge 21 of the
galvanizing bath 5 (Fig. 1). The conduits may have a vertical part 20a
(Fig. 3) adjacent to an end wall of said bath. In this manner it will
be possible to have the workpiece on the supporting member under
electrical potential before immersion thereof into the liquid bath.
When a supporting member is moving along the said bath, a second
brushholder 22 attached to the supporting member 1 is in electric
contact with the conduits 20 via its brushes, so that the galvanizing
current may be fed to the workpieces via flexible cables 23 and
suspension racks 24. The racks 24 are attached to a horizontal arm 26
of the supporting member 1 via insulating hinges 25, so that on
movement of the supporting member during which movement the arm 26
always remains in a horizontal position, the racks with the workpieces
may maintain a vertical position. The racks are unhooked from the arm
together with the treated workpieces in the discharge and loading
station 2 and are replaced by new racks provided with workpieces to be
treated.
In Fig. 4 a predetermined scheme is represented with the aid of which
the speed of any supporting member 1 may be controlled.
The electric motor 10 consists of a direct current motor chosen on
account of its favourable work characteristic and the presence of
direct current. The current conduit comprises two stator rails 117,
118 and two rotor rails 119, 120. From a 220 volt alternating current
network 121, 122 the rails 117, 118 and the parts 119, 120 of the
rotor rails are supplied with a 42 volts direct current supply via a
control transformer 123 and a rectifying circuit 124. The parts 125,
126 of the rotor rails are supplied with a 6 volt direct current
supply from the said alternating current network via a control
transformer 127 and a rectifying circuit 128. The rotor rails are
further subdivided into sections 129 to 143 which sections may be
brought by intermediate connections 144 to 158 into connection with
each other and/or with the stator rails 117, 118 with the aid of a
time switch 159, which is adjusted to have a period of approximately 1
minute, a polarity reversing switch. 160 and a switch 161 switching in
the latter as soon as the section 130 is positive in respect of the
voltage at the section 140.
The reversing switch 160 is mechanically operated in such a manner
that the guide rails 140 and 130 are negative and positive for a
longer time than positive and negative respectively so that a movement
to the right and to the left will be obtained, wherein the movement to
the right exceeds that to the left. The switch 161 is electrically
coupled to the reversing switch 160, in such a manner that the switch

161 is only " on " in case the reversing switch 160 has brought a
positive polarity to the section 130 and a negative polarity to the
section 140. This is to avoid a short circuit between the sections 129
and 138 in the moment that a supporting mem ber passes from said
sections to the sections 130 and 140, in case the latter happen to
have a polarity which is contrary to that of the sections 129 and 138.
This results in that a supporting member will stand still on the
section 139 if the polarity of sections 129, 138 is contrary to that
of sections 130, 140, till the said sections have obtained the same
polarity.
In the manner described a supporting member 1 moving from the left to
the right in Fig. 4 will have a speed of 10 cm/sec along the part 120,
along the part 126 a speed of 1 cm/sec, along the part 132 a speed of
10 cm/sec, will stand still on the part 133, have a speed of 10 cm/sec
along the part 134, will stand still on the part 135, have a speed of
10 cmlsec on the part 136, stand still on the part 137, will have a
speed of 10 cm/sec on the part 138, will reciprocate with a speed of
10 cm/sec along the path 140, will have again a speed of 10 cml sec on
the part 141, will stand still on the part 142 and will finally have a
speed of 10 cmlsec on the part 143 connected to the part 120 (as is
part 131 to part 119).
The scheme described applies to a certain series of treatments and may
be varied in a simple way. Once adjusted, each supporting member 1,
its suspension rack 24 and its associated workpieces will be guided
automatically in the correct way along the treating stations 3-8, the
only manipulation carried out by a workman being required at the
discharge and loading stations 2, 9.
In Fig. 5 is diagrammatically shown a further embodiment of the device
according to the invention, wherein the portions corresponding to the
device already described are indicated with the same characters but
with dashed indices. The endless guide path 11' has been cut at a
certain point and is shown in diagrammatic form for the sake of
clarity.
Thus the points I and II of the guide path correspond to each other.
The racks connected to the supporting members carrying the woripieces
are indicated by the characters A-K. The guide path 11' has a C-shaped
cross-section (Fig. 6) and comprises merely straight horizontal
portions 1 la'. llb' and straight vertical portions 1 lie'. Two
adjacent portions lla' or llb' and llc' are interconnected by means of
a turntable section lie. such as shown in detail in Figs. 8 and 9. It
is apparent from the drawing that the device has a lower horizontal
portion Ila' having such a length that several supporting members may
be at the same time on said portion. so that the corresponding racks
and v-'oripieces C. D and E are at the same time in a bath. The

workpiece E happens to be on a turntable section 1 le, as is the case
with the viorkpieces B and J. The guide path has also a lower
horizontal portion llat having a shorter length. on which is only a
single supporting member carrying the workpiece
F. The guide path further has portions having a minimum length in
the direction of movement of the supporting members for a very short
treating time of the workpieces, i.e., at those locations where are
the workpieces G, H, I and K. The supporting members merely move
upwardly and downwardly along the vertical straight portion llc'.
A device as just has been described has the advantage that the
longitudinal dimension of the device may be shorter than the device
described before while the manufacture is as simple as possible since
only straight portions of the guide path have to be constructed.
Both devices described above may be extended at will in a simple
manner by adding a further guide path portion and thus may be adapted
to other treating methods for the workpieces. It is also possible to
adapt the device according to the invention to a treating method which
differs substantially from the treating method as has been described
in accordance with the Figs. 1-3 of the drawings. For instance the
treating times for the workpieces in the various baths may be varied
independently from each other and different coating deposits may be
obtained on the workpieces.
In the Figs. 6 and 7 is shown a supporting member 1' which may be used
with a guide path 11' having a C-shaped cross-section. In this case
four conduits 19' are present for feeding an electric current to the
drive motor 10'. Said motor drives a toothed gear 62 which co-operates
with a toothed rack 63 provided along the guide path 11'. The end
portion 26' of a supporting rack has been connected to the motor
frame. In order to withstand the forces acting on the guide path due
to the supporting racks being loaded by the workpieces the supporting
member has been provided with four guide rollers 13' and four guide
rollers 14'.
In the Figs. 8 and 9 is shown a turntable section 1 le,
interconneefing two upper horizontal path portions llb' and a
vertical path portion llc'. for instance, the passage indicated by
reference numeral 84 on Fig. 5.
The toothed gear 62. driven by the motor 10' is adapted to ce-operate
with a toothed gear 64 which has been provided at an interrupted
portion of a toothed rack 65 which is adapted to be brought into line
with the toothed rack 63 provided on the horizontal and vertical
portions 1 lea' or llb' and llc' respectively. of the guide path 11'.
said gear 64 being supported by a bearing 66. Said toothed rack 65 and
said bearing 66 are provided on a path portion 67, which has been
fixed to a shaft 68 which has been positioned into line with the motor

shaft 69 and which is rotatably supported in a fixed sleeve 70.
Rotation of the path portion 67 is ob, tained by means of the toothed
gears 62, 64, 71 (which is fixed to the toothed gear 64) and 72. The
latter is fixed to the fixed sleeve 70. The edge portions of the path
portion 67 and also the edge portions of the vertical and horizontal
path - portions 1 la, tIc' and llb' facing the shaft 68 are circular.
If the supporting member 1' passes from the left guide path portion
llb' to the portion 67, one of the guide rollers 14' will abut against
a stud 73, which stud may be withdrawn on energizing of a winding 74.
Since movement of the supporting member 1' is prevented by the stud 73
and the motor 10' maintains the drive of the toothed gear 62, the
movable portion 67 will be rotated by rotation of its shaft 68 in the
sleeve 70, due to the gear transmission 64, 71, 72, until the toothed
rack 65 and the flanges of the portion 67 correspond to the toothed
rack 63 and the flanges of the path portion 1 1c' for instance, by
abutment of portion 67 against a stud (not shown).
At this moment, by means of an electrical circuit not shown, the
windings 74 are energized so that the stud 73 is withdrawn and the
supporting member caused to continue its movement in a downward
direction along the vertical portion 1 1c'.
After a certain time has passed, said time corresponding to the
treating time of the workpieces K suspended from the supporting
member, and by the action of the circuit not shown the latter moves
upwardly along the portion llc' and again one of its guide rollers
abuts against the stud 73. The portion 67 will then be rotated by
means of the gear transmission 64, 71, 72 which is driven by the motor
gear 62. till the toothed rack 65 again corresponds to the rack 63 on
the right guide path portion llb', which may be obtained by abutment
of said portion 67 against a stud (not shown). At the same time the
stud 73 will be withdrawn by energizing the windings 74 so that the
supporting member may resume its horizontal movement, however along
the right guide path portion ilk'.
What we claim is : -
1. Device for the surface-treatment of metallic or non-metallic
objects in one or more treating baths, comprising members for
supporting and moving said objects in a predetermined cycle over a
guide means, said members comprising a number of carriages each being
provided with a separate electric driving motor, a suspension rack for
supporting said objects to be treated, and means co-operating with.
said guide means adapted to move said carriages in respect of said
guide means, said guide means comprising a fixed endless guide path
being arranged at different levels adjacent a series of containers
provided with said treating baths.
2. Device according to Claim 1 wherein said means co-operating with

said guide means comprises separate conduits supported on said guide
path and connected to sources of electric potential and current
collectors attached to said carriages, for supplying an electric
current to said electric motors on said carriages, the electric
potential of said sources being different at different stations along
said guide path.
3. Device according to Claim 1 or 2 wherein said guide path comprises
a raised portion located over each of the vertical partitions between
the treating baths.
4. Device according to Claim 1, 2 or 3 wherein said guide path is
located substantially in a straight cylinder and comprises
substantially horizontal portions which are arranged at at least two
different levels, and intermediate substantially vertical portions,
whereby adjacent portions of said guide path which are arranged at an
angle in respect of another are interconnected by means of bent
portions.
5. Device according to Claim 1, 2 or 3 wherein said guide path being
located substantially in a straight cylinder and comprising
substantially horizontal portions whereby adjacent portions of said
guide path which are arranged at an angle to one another, are
interconnected by means of rotatably supported portions in such a
manner that a supporting member may pass from one portion of the guide
path to an adjacent portion of the guide path.
6. Device for the surface treatment of metallic or non-metallic
objects in one or more treating baths substantially as described and
shown in the accompanying drawings.

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