4461 4465.output

* GB784868 (A)
Description: GB784868 (A) ? 1957-10-16
Improvements in and relating to apparatus for the measurement of the
workability of concrete
Description of GB784868 (A)
COMPLETE SPECIFICATION.
Improvements in and relating to Apparatus ior the iMeasurmement oX the
Workability of Concrete.
We, NATIONAL RESEARCHDEVELOPMENT
CORPORATION, a British Corporation, of 1
Tilney Street, London, W.1, 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 relates to apparatus for the measurement of the
workability of concrete, comprising a cylinder into which a charge of
concrete is introduced under pre
scribed conditions by the aid of two hoppers fitted with trap doors in
their bottoms and arranged vertically one above the other and above
the cylinder so that the charge can be dropped from one hopper to the
other and thence to the cylinder. The weight of concrete retained in
the cylinder in relation to the weight of fully compacted concrete of
the same mix which the cylinder would contain is known as the
compacting factor and is a measure of the workability. The weight is
usually ascertained by direct weighing of the cylinder and contents.
One way of introducing the charge is to fill the top hopper level with
its brim with the concrete, open a trap door in the bottom of the
hopper and allow the concrete to fall into a lower hopper. Immediately
it has come to rest a trap door in the bottom of the lower hopper is
opened and the concrete allowed to fall into the cylinder. Further
details of one such apparatus and method may be found in British
Standard Specification No. 1881 of 1952.
An object of the present invention is to
provide apparatus which can be operated quickly and by unskilled

labour on site, so that adjustments to the water content of the
concrete can be made without delay.
In the apparatus according to the present invention, the cylinder is
supported by counterbalancing means arranged to indicate the weight
and preferably the indication is calibrated directly in terms of the
compacting factor.
The instrument is further preferably provided with adjusting means
whereby the zero position can be set when the cylinder received a
concrete charge having the desired compacting factor.
Convenient constructions of apparatus according to the invention are
illustrated by way of example in the accompanying drawings:
Fig. 1 is a front view; and
Fig. 2 is a side view of one construction of apparatus;
Fig. 3 is a detail side elevation in section on an enlarged scale of
the same construction;
Fig. 4 is a detail front view, partly in section, of a modified
construction.
The main framework of the apparatus shown in Figs. 1 to 3 is built up
around a hollow vertical standard 11, the lower end of which can rest
on the ground. A baseplate 12 is secured, e.g. welded, to the standard
and carries a pair of wheels 13 enabling the apparatus to be moved
easily, and supported by the baseplate and wheels are two short
pillars 14 braced to the standard 11 by a tubular brace 15. This brace
protects the parts within it from accidental damage.
To the standard 11 are secured, e.g.
welded, brackets 16, 17, carrying the respective upper and lower
hoppers 18, 19, each having its bottom closed by a hinged trap door 21
controlled by a hand lever 22.
The receiving cylinder 23 is carried by a platform or ring 24
supported as described below. The sizes and positions of the hoppers
and cylinder will be in accordance with the desired conditions of the
test, for example those prescribed in British
Standard Specification No. 1881 of 1952.
The platform or ring 24 is supported at three points, two fixed and
one vertically movable over a small distance, by any convenient means
such as ball races, knife edges cones or the like which adequately
define the load distribution on the movable point and which minimise
friction, the two fixed points being at the upper ends of the pillars
14 and the moving point just in front of the column 11. In the
illustrated example the supporting means comprise cones 25 on the
Dillars 14, and a cone 26 on a bracket 27 at the lower end of a rod 28
passing upwardly within the standard 11.
By providing suitable seatings on the platform or ring 24 which engage
the cones 25, 26, the lateral position of the platform or ring and

hence of the lower end of the rod 28 is completely defined. If
desired, these seatings can be on the well-known "kinematic"
principle, that engaging the cone 26 being a conical or spherical
depression, the second a V section groove and the third plane.
Near its upper end the rod 28 has a shoulder 29 which through a washer
31 rests on the upper end of a compression spring 32. The lower end of
the spring rests on a support 33 movable within the standard 11 but
having a pin 34 projecting through a slot in the standard and resting
on a nut 35 which can be screwed up or down on the column, this
determining the position of the support 33. As will be explained this
serves as a zero adjustment.
On the upper end of the standard is secured a head member 36 which
supports a conventional dial gauge 37. To the stem 38 of the dial
gauge is secured an extension piece 39 which incorporates a screw
adjustment for length and is provided with a lock nut 41. The lower
end of the extension bears against the upper end of the rod 28.
The verticaI movements of the rod are limited by any convenient means.
As shown stops are constituted by the washer 31 and a shoulder 42
formed on the rod 28
which co-operate with a flange 43 which is held in place by the head
36. The extension 39 is adjusted so that the indications of the dial
gauges are substantially equally on opposite sides of a mid zero
position when the washer 31 and the shoulder 42 respectively abut the
flange 43.
The nut 35 is adjusted so that when the cylinder 23 has been charged
in the prescribed manner with concrete of the desired compacting
factor, the dial indicator gives its zero reading. The compression of
the spring 32 will vary according to the weight of concrete in the
cylinder and the rate of the spring is chosen so that the range of
movement determined by the stops 31, 42 covers the range of variation
it is desirable to provide for. It will be understood that this
movement is within the movement which the dial indicator can deal with
and the indicator is thus protected from damage for instance when the
cylinder is empty, or under the impact of the concrete falling into
the cylinder.
The indicator or a separate dial surrounding it may be calibrated in
terms of compacting factor, and for specific conditions, that is to
say, a known composition of concrete and a particular size of concrete
mixer the dial can instead or in addition be calibrated in terms of
the change in water required to give a concrete of the desired
compacting factor.
The rate of the spring and the pitch of the threads of the nut 35
being known it is possible to calibrate the instrument by providing a
load scale consisting of horizontal divisions on the standard or on a

band attached to the standard at 44 with which the lower edge of the
nut 35 co-operates and sub-divisions on the skirt of the nut.
For the case of a test in accordance with the above mentioned British
Standard Specification the parts may be proportioned so that the band
44 bears 1 lb. divisions and the skirt of the nut ounce divisions and
the parts are set so that when there is a load of 30 lb. in the
cylinder the dial gauge is at zero when the nut indicates 30 lb. on
the band 44 with the ounce divisions at zero.
To set the instrument for use instead of filling the cylinder with
concrete in the prescribed manner with concrete of a prescribed
compacting factor, the value to which the nut 35 must be set can be
calculated by multiplying the weight of fully compacted concrete the
cylinder will hold, based upon the density of the materials used, by
the desired compacting factor.
For the case of a cylinder 23 which will hold about 30 lb. of
concrete, a convenient range of movement of the rod 28 which will give
a close degree of accuracy is about th of an inch. The angular
movement of the platform or ring 24 involved is obviously negligible.
Fig. 4 shows a modification in which the counterbalancing means
consists not of a spring but of a weighted lever. Those parts in Fig.
4 which correspond with the parts in
Figs. 1 to 3 bear the same references. Adjacent the upper end of the
rod 28 an angle lever 51 is fulcrummed in the head 36.
One end of the lever is pivoted to the upper end of the rod 28, while
the other end carries a weight 52. To enable the apparatus to be
adjusted according to the appropriate weight in the cylinder the
weight 52 can be screwed along the arm of the lever 51 and it has an
index mark 53 which cooperates with a scale 54 carried by the head. In
all other respects the mode of adjustment and operation of the
apparatus is the same as above described with reference to Figs. i to
3.
Other modifications are also possible within the scope of the appended
claims.
Thus for any other prescribed method of charging the cylinder
appropriate provision could be made and it would even be possible to
provide the hoppers 18, 19, or other equivalent devices for effecting
the prescribed method of charging with a separate mounting and bring
the cylinder into position beneath them by the aid of the wheels 13.
Some means of positively locating the cylinder in the correct position
would be provided, for instance notches to engage the standard 11.
What we claim is : -
1. Apparatus for the measurement of the workability of concrete
comprising a cylinder into which a charge of concrete is introduced
under prescribed conditions by

the aid of two hoppers fitted with trap doors in their bottoms and
arranged vertic
ally one above the other and above the cylinder so that the charge can
be dropped from one hopper to the other and thence to the cylinder, in
which the cylinder is supported by counterbalancing means arranged to
indicate the weight of the concrete.
2. Apparatus according to Claim 1 pro
vided with adjusting means whereby the zero position can be set to
correspond with a concrete charge having a desired compacting factor.
3. Apparatus according to Claim 1 or 2 in which the counterbalancing
means comprises a preloaded system the deflection of which is measured
by a dial gauge, means being provided to keep the displacement within
the permissible range of movement of the dial gauge.
4. Apparatus according to Claim 3 in which the counterbalancing system
comprises a preloaded spring.
5. Apparatus according to Claim 4 in which an abutment for the spring
is movable in relation to the dial gauge thereby to provide a zero
adjustment.
6. Apparatus according to Claim 3 in which the counterbalancing means
comprises a weighted lever.
7. Apparatus according to Claim 6 in which the weight is adjustable
along the lever arm to provide a zero adjustment.
S. Apparatus according to any preceding claim in which the cylinder is
carried by a platform or ring supported at three points, two fixed and
one coupled to the counterbalancing means.
9. Apparatus according to Claim 8 in which the movable point is
carried by a vertical rod the upper end of which is supported by the
counterbalancing means and engages the stem of a dial gauge.
10. Apparatus according to Claim 9 in which the rod passes upwardly
within a hollow standard at the upper end of which the dial gauge is
carried.
11. Apparatus according to Claim 10 in which the movements of the rod
are limited by shoulders co-operating with a flange at the upper end
of the standard.
12. Apparatus according to Claim 10 or 11 as limited to Claim 6 in
which a nut screwed on the outside of the column serves as a support
for the spring abutment which is provided with a pin projecting
through a slot in the standard and resting on the nut.
13. Apparatus according to Claim 10, 11 or 12, in which the standard
is provided with a baseplate and wheels enabling the apparatus to be
moved easily, the lower end of the standard resting on the ground when
the apparatus is in use,
14. Apparatus according to any of
Claims PO to 13 in which the standard supports a pair of hoppers, one

above the other, and each with a trap door in the bottom whereby a
sample of concrete can be allowed to fall from the upper hopper into
the lower hopper and from the lower hopper into the cylinder.
15. Apparatus according to any of
Claims 9 to 14 in which a length adjustment is provided between the
dial gauge stem and the upper end of the rod.
16. Apparatus for the measurement of the workability of concrete
substantially as described with reference to Figs. 1 to 3 of the
accompanying drawings.
* GB784869 (A)
Description: GB784869 (A) ? 1957-10-16
Improvements relating to the production of glass containing tellurium
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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 SPECIFICATON
Inventor: -PETER LEWIS BAYNTON.
Date of filing Complete Specification: Jan 25, 1956.
Application Date: Jan 26, 1955 No 2384 155.
(Patent of Addition to No 736,073, dated Sept 30, 1952).
Complete Specification Published: Oct 16, 1957.

784,869 Index at Acceptance:-Class 56, Mli Bl.
International Classification:-C 03 c.
COMPLETE SPECIFICATION.
Improvements relating to the Production of Glass Containing Tellurium.
We, THE BRITISH THOMSON-HOUSTON COMPANY Ll MITED, a British Company,
having its registered office at Crown House, Aldwych, London, W C 2,
do hereby dedare 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 relates to the production of glasses having tellurium
dioxide as an essential constituent, and is an improvement in or
modification of the invention described and claimed in Patent
Specification No.
736,073.
In that prior Patent Specification we have disclosed glasses
containing less than 10 % silica, at least 15 % by weight of tellurium
dioxide, and at least 5 % of one or more of the following oxides,
namely, barium oxide, lead oxide, boric oxide, selenium dioxide and
vanadium pentoxide, given by way of example These glasses have been
found to possess unusual characteristics which render them suitable
for various purposes, and in particular, many of the glasses possess
high refractive indices which permit them to be used in the production
of glasses for optical systems For this purpose, however, they suffer
from the disadvantage of possessing a yellow/green colour which
restricts their possible application as optical components.
We have now found that the undesirable colouration is only shown by
tellurite glasses melted from materials of commercial purity and does
not occur if pure tellurium dioxide is employed in their production.
Accordingly the present invention involves the preparation of glasses
containing tellurium dioxide as claimed in the above-mentioned
Specification in which the tellurium dioxide is substantially free
from impurities, i e it lPrice 3 s 6 d l should contain less than 0
001 % by weight of impurities Care should also be taken that
impurities prevented from being present in the tellurium dioxide are
not introduced into the glass by way of the remaining ingredients of
the batch used for its production The total impurities in the batch
should not exceed 0 001 % by weight.
In order to obtain the pure tellurium dioxide necessary for the
production of substantially colour free tellurite glass, tellurium
metal of commercial purity is distilled under reduced atmospheric
pressure and the distillate, consisting of pure tellurium metal is
converted to the dioxide under conditions which inhibit the
introduction of impurities.
In carrying out the process, tellurium metal of commercial purity is

distilled under a pressure of 20 mm of mercury in a quartz tube, the
middle fraction of the distillate is collected at a temperature of
approximately 650 C, and the distillate is re-distilled preferably
three times to obtain pure tellurium metal The pure tellurium metal is
then first converted to tellurium basic nitrate by reaction with
nitric acid, and the tellurium nitrate is then converted to tellurium
dioxide by any known process which will not involve the introduction
of impurities into the dioxide.
Pure tellurium metal may be converted into pure tellurium dioxide as
follows:The pure tellurium metal is powdered and dissolved in diluted
nitric acid The solution is evaporated until crystals of tellurium
basic nitrate separate These are collected on a glass filter, washed
with water, and air-dried.
The tellurium basic nitrate is then converted into tellurium dioxide
by heating for several hours at a temperature of 400 '-430 ' C.
As an example of the production of a substantially colour-free
tellurite glass from the W _ rp, 0 _,,784,869 pure tellurium dioxide
so obtained, we may mix with the tellurium dioxide barium carbonate of
"Analar" (Registered Trade Mark) purity and melt the mixture in a gold
crucible, the proportions of the mixture obtained being such that the
resultant glass possesses a composition of 90 % by weight tellurium
dioxide and 10 % by weight barium oxide.
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* GB784870 (A)
Description: GB784870 (A) ? 1957-10-16
Method and apparatus for regulating the rate of supply of additives to
materials being conveyed

PATENT SPECIFICATION
Inventor: VAINO JUHANI OSOLA Date of filing Complete Specification Dec
15, 1955.
l I f Application Date Jan27, 1955 No 250 Complete Specifcation
Published Oct 16, 1957.
Index at Acceptance: -Class 40 ( 1), NI (A 3 B: D 3), N 357 H.
International Classification: -G Oc.
COMPLETE SPECIFICATION
Method and Apparatus for Regulating the Rate of Supply of Additives to
Materials being Conveyed We, THOMAS HEDLEY & CO LIMITED, a British
company, of Phoenix Buildings, Collingwood Street, Ne-wvcast 1
e-upon-Tyne, 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: -
During the manufacture of certain synthetic detergent powders the
powder is conveyed e g by a belt conveyor and while it is being
conveyed there is added thereto a persalt It is necessary that the
persalt be added in fixed proportion by weight of the detergent which
is being conveyed and due to manufacturing considerations it is found
that the weight of the detergent is not uniformly spread along the
belt It is therefore required that the rate of addition shall vary
depending on the weight of the detergent which passes a fixed station
at any particular instant To meet this requirement it has been
proposed hitherto to weigh the amount of the detergent passing the
station and to vary the rate of addition of the persalt so as to
accord with the weight of the detergent passing the station, the
control being effected electrically The present invention is concerned
with an apparatus of this kind and relates to an improved construction
thereof whereby more sensitive control of the quantity of persalt may
be obtained Although reference is made to the addition of a persalt to
a synthetic detergent powder it is to be understood that the present
invention is not so limited and broadly is concerned with regulating
the rate of supply of an additive to a material as the latter is being
conveyed, the additive being a solid, liquid or a gas.
According to this invention a method of regulating the rate of supply
of an additive to a material being conveyed so that the volume or
weight of the additive which is added at any instant is determined by
the weight of the material passing a station at said instant comprises
weighing the amount of material passing said station, utilising the
measure of the weight to actuate an electrical transducer, regulating
the output of an alternating current rectifier unit by adjustment of
the transducer, and applying the output of the rectifier unit to

control said rate of supply.
The material may be a powder or granular substance and the additive
may be a solid (e g.
another powder or granular substance) or a liquid or a gas.
According to a feature of the invention the output of the rectifier
unit is applied to control the rate of supply of two or more additives
and it may be, according to another feature of the invention, that the
supply of different kinds of additives (solids, liquids, gases) may be
regulated For instance, the supply of a solid and a liquid may be
simultaneously regulated as additives to a powder or granular
material.
Thus, during manufacture of a synthetic detergent powder the detergent
powder is conveyed on a belt conveyor and, in accordance with the
weight of powder passing a station, there is added to the powder
another powder (e g a persalt) and a liquid perfume, the quantity of
the persalt and of the perfume being maintained as a preselected
proportion of the weight of detergent powder Of course liquids other
than perfume may be used and the solid additive need not be persalt.
The invention also includes within its scope apparatus for carrying
into practice the method set forth above.
A practical application of the present invention will now be
described, by way of example only, with reference to the drawings
accompanying the provisional specification in which:Fig 1 is a
schematic view of an apparatus in accordance with the present
invention; and Figs 2, 3 and 4 are diagrammatic views showing
different ways in which the quantity of the additive may be regulated
in the apparatus of Fig 1.
The apparatus shown in Fig 1 is intended 6/s 55.
54,870 for regulating the supply of persalt to a powder detergent The
powder detergent is conveyed by a belt conveyor 5 which passes over a
pulleyr 6 which is suitably driven At a convenient station the
conveyor passes over an arm 7 so that the weight of the material on
the conveyor at the station displaces the arm In this way the vertical
movement of the arm is a measure of the weight of the material passing
the station at any instant The arm 7 is connected by a lever 8 to a
link 9 which carries the core 10 of an electric transducer, generally
indicated by the reference numeral 11.
The coil 12 of the transducer is connected with an alternating current
rectifier generally indicated at 13, thei latter being supplied
through the mains 14 Vertical adjustment of the core 10 within the
coil 12 regulates the output of thile unit 13 and it will be
appreciated that the instantaneous value of the output of the unit 13
is a measure of the weight of the powder passing the arm 7 The output
of the rectifier is applied by leads 15 to a control 16 for a motor 17

(see Figs 2, 3 and 4) The motor 17 drives a rotary valve 18 through a
shaft 19, the rotary valve being adapted to deliver the persalt for
mixing with the paolder detergent being carried along by the conveyor
5 it will be appreciated that if the speed of the rotary valve 18 is
increased the quantity of persalt added to the detergent will
correspondingly increase.
In Figs 2, 3 and 4 there is illustrated arrangements whereby the speed
of the shaft 19 may be varied in accordance with the weight of the
detergent on the conveyor 5, i e.
in accordance with the output of the rectifier unit 13.
In Fig 2 the motor 17 has its armature connected to the leads 15, the
field-winding 20 being separately energised In kn Ia-ow-n manner
variations in the current supply to the armature vary the speed of the
armature and thence of the rotary valve 18 In Fig 3 the motor 17 has
its field coil 20 energised by the unit 13 the armature being
separately energised In Fig 4 an alternating current motor 17 drives
the shaft 19 through a variable slip magnetic coupling 21, the
coupling being energised by the unit 13.
The rotary valve 18 may be replaced by a conveyor such as a screw
conveyor or a belt conveyor when the additive of a pulverulent or
granular solid Instead of the rotary valve 18 there may be provided a
reciprocating or rotary pump when the additive is a liquid e g.
a perfume to be added to the detergent.
Finally, instead of the rotary valve 18 there may be provided a fan or
pump or a valve if the additive is a gas.
If the additive is a pulverulent cr granular solid whose bulk density
is liable to alter, the rotary valve 18 may be replaced by a constant
weight feeder which ensures that the weight per unit time of additive
supplied bears a constant weight ratio to the weight per unit time of
the material on the conveyor 5 passing the said station.
Where two or more additives are simultaneously to be regulated it may
be arranged that 70 the unit 13 supplies two or more controls 16 for
adjusting a conveyor, pump, valve or the like regulating each additive
separately Alternatively, if convenient, a single control 16 may be
utilised to adjust a number of different ele 75 ments, one for each
additive, such as a pump, conveyor or valve.
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* GB784871 (A)
Description: GB784871 (A) ? 1957-10-16
Improvements in or relating to the production of artificial sausage casings
Inventors: BERNARD VICTOR F 1 OX and GEOFFREY DOWNING PEARCE Date of
filing Complete Specification Jan 31, 1956.
Application Date Feb 3, 1955.
,a Complete Specification Published Oct 16, 1957.
Index at Acceptance: -Class 2 ( 2), B 2 C 5.
International Classification: -D 01 f.
Improvements in or relating to the Production of Artificial Sausage
Casings We, BRITISH GCELLOPHANE LIMITED, a British Company, of Bath
Road, Bridgwater, Somerset, do hereby declare the invention, for which
following statement:-
This invention is for improvements in or relating to the production of
artificial sausage casings.
A method of producing artificial sausage casings has already been
proposed which comprises forming a viscous aqueous solution of an
alginate, passing said solution through an annular nozzle into a
coagulating bath, and allowing the formed tubular structure to set in
said coagulating bath The coagulating bath consists preferably of 10 %

to 15 % weakly acid calcium chloride solution In cdhe-.
known procedures for the manufacture of thraeds, filaments films and
the like from alginates, coagulating baths consisting of more dilute
aqueous calcium chloride solutions, containing for example calcium
chloride in proportions down to 5 0 %, have been proposed.
It has now been found, however, that artificial sausage casings,
produced by these known procedures, are liable to show a serious
defect, in that the inside surface of the wall of the casing, instead
of being smooth usually assumes a ribbed or serrated appearance when
viewed in cross-section, whereby a relatively weak casing is formed
This defect shows itself with particular disadvantage during the
operation of filling such casihgs with sausage-meat, inasmuch as,
owing to the aforementioned irregularities in the crosssection of the
casing, longitudinal splits are liable to be formed therein Thus,
althouguhe known procedures represent lFr; a considerable advance,
there is still room for improvement.
Investigations have shown that this defect in artificial sausage
casings produced by these known procedures is caused, at least in
part, by excessively rapid setting of the tubular structure, formed by
passing the viscous solution of an alginate through an annular hozzle
into the coagulating bath.
Our copending British Patent Application No 2118155 (Serial No
783,235) is concerned with a process for the production of an improved
alginate sausage casing in which the inside wall-surfaces are
substantially free from ribs and serrations, by forming a viscous
aqueous solution of a water-soluble alginate, passing said solution
through an anhular nozzle into a coagulating bath, whereby a tubular
structure is formed, and allowing the formed tubular structure to set
in said coagulating bath, in which process the coagulating bath is
constituted by an aqueous solution comp ising a watersoluble calcium
salt in a proportion lying within the range between 0 1 % and 4 9 % by
weight, based on the weight of the bath.
In the present specification, artificial sausage casings consisting of
a waterinsoluble calcium alginate with or without a proportion of
alginic acid, are hereinafter referred to as alginate sausage casings.
One of the objects of the present invention is to provide a process
for the production of improved alginate sausage casings, having inside
wall-surfaces substantially free from ribs and serrations, whereby the
defect referred to above is minimised, overcome and avoided.
Accordingly, the present invention provides a process for the
productiobn of an, 784587 1 No 3260/55.
improved alginate sausage casing, by forming a viscous aqueous
solution of a water-soluble alginate, passing said solution through an
annular nozzle into a coagulating bath, ahd allowing the formed

tubular structure to set in said coagulating bath, in which process
the coagulating bath is prepared by dissolving and mixing in aqueous
solution a water-soluble calcium salt and, in a proportion of at least
O 5 % by weight, based oh the weight of the bath, a water-soluble
alkali metal salt or a water-soluble ammonium salt, which salt does
not react in aqueous solution with the water-soluble calcium salt
present in the bath, to yield, by double decomposition, a calcium salt
insoluble in the aqueous solution of the bath.
The invention includes alginate sausage casing, whenever produced by
the process in accordance with the invention.
Preferably the coagulating bath also comprises in aqueous solution a
watersoluble acidic substance of such a nature and present in such a
proportion as to provide a bath having a p H value of 6 or less.
The acidic substance present in the coagulating bath may be, for
example, hydrochloric acid or acetic acid When hydrochloric acid is
employed, its preferred range of concentration in the bath lies
between 0 01 % and O 15 % (inclusive? by weight, based on the weight
of the bath, though concentrations as high as 5 0 % by weight,
reckoned on the same basis, may be employed if desired The acidic
substance chosen should not, of course, be such as to react in aqueous
solution with the water-soluble calcium salt present, to yield a
calcium salt which is insoluble in the bath For this reason, sulphuric
acid, sodium hydrogen sulphate, and orthophosphoric acid except at
high dilutions, are unsuitable for this purpose.
The preferred water-soluble calcium salt is calcium chloride Calcium
nitrate, calcium chlorate, or calcium acetate may alternatively be
employed if desired Other water-soluble calcium salts will readily
suggest themselves to those skilled in the art Mixtures of
water-soluble calcium salts may be employed, if desired The
coagulating bath, when prepared, may contain in aqueous solution the
water-soluble calcium salt in a proportion lying within the range
between 0 1 % and 30.0 % by weight, based on the weight of the bath,
with a preferred proportion lying within the range between 0 5 % and 1
5 % by weight, reckoned on the same basis.
The preferred water-soluble alkali metal salt is sodium chloride Other
watersoluble alkali metal salts or water-soluble ammonium salts that
may be employed include sodium acetate, sodium bronmide, or sodium
nitrate; potassium chloride, potassium acetate, potassium bromide;
ammonium chloride, ammonium acetate, 70 ammnonium bromide or ammonium
nitrate.
The water-soluble alkali metal salt or water-soluble ammonium salt
chosen should not, of course, be such as to react in aqueous solution
with the water-soluble 75 calcium salt present, to yield, by double
decomposition, a calcium salt which is insoluble in the bath, nor

should it be such as to react with the acidic substance that may be
present to yield a water 80 insoluble salt fhus amminonium sulphate,
potassium carbonate, and sodium bicarbonate, are typical examples of
watersoluble alkali metal salts and ammonium salts which should not be
employed for the 85 present purpose.
The coagulating bath, when prepared, may contain in aqueous solution
tle watersoluble alkali metal salt or water soluble ammnonium salt in
any proportion lying 90 within the range between 0 5 % by weight,
based on the weight of the bath, and saturation, and preferably within
the range between 2 % and 10 O (inclusive) by weight, based on the
weight of the bath 95 Miixtures of water-soluble alkali metals salts
and/or ammonium salts may be employed, if desired.
The coagulating bath, in which the tubular structure is formed may be
used 100 at room temperature ( 15 to 25 C), since no advantage appears
to be gained by using the bath at a higher or lower temperature.
The formed tubular structure sets in the 105 coagulating bath quickly,
exposure of the formed tubular structure to the action of the
coagulating bath for a period of from to 10 seconds normally being
sufficient to yield a solidified tubular structure 110 possessing
sufficient strength to permit gentle handling Howe er, the reactioi
between the water-soluble alginate of the tubular structure, formed by
passing the viscous aqueous alginate solution through 115 the annular
nozzle, with the water-soluble calcium salt of the coagulating bath,
to form insoluble calcium alginate, is incomplete at this stage In the
preferred procedures, therefore the solidified tubular 120 structure
is next passed into a bath of aqueous solution, at room temperature (
15 to 25 C j) containing a water-soluble calcium salt, for example
calciunt chloride, preferably in a proportion lying 125 within the
range between 10 % and 25 % by weight, based on the weight of the
bath, to complete the conversion of the tubular structure by double
decomposition of the sodium alginate with, for example, 130 784,871
Throughout the present specification, parts and' proportions are parts
and proportions by weight, unless otherwise stated.
EXAMPLE 70
An improved alginate sausage casing, having an inside wall-surface
substantially free from ribs and serrations, was produced in the
following way:A viscous aqueous solution of sodium 75 alginate was
prepared by stirring 40, lbs.
of granular sodium alginate, of the kind sold by Algitate Industries
Limited under the designation W 1018, into 860 lbs of water at 20 ' C,
and continuing agitation 80 until solution was complete The solution
was de-aerated by standing for 24 hours in a closed vessel under an
absolute pressure of 8 inches of mercury, and the de-aerated solution
was filtered through 85 mesh metal gauze The filtered viscous aqueous

solution of sodium alginate was passed under pressure to an extrusion
machine, where it was passed through a metering pump, and then 90
extruded through an annular orifice into a coagulating bath having a
temperature of 20 ' C, and constituted by an aqueous solution
containing 10 % calcium chloride by weight, 5 % sodium chloride by
weight, 95 and 0 1 % hydrochloric acid by weight, based on the weight
of the bath The viscous aqueous sodium alignate solution extruded
through the annular orifice was coagulated on entering the bath,
whereby 100 a continuous solidified tubular structure was formed The
continuous solidified tubular structure formed was then immersed for 2
hours in a bath having a temperature of 20 ' C, and consisting of an
105 aqueous solution containing 22 % of calcium chloride by weight,
based on the weight of the bath, to complete the conversiaon of the
tubular structure by double decomposition of the sodium alginate 110
with the calcium chloride, with the formation of calcium alginate and
sodium chloride The fully coagulated alginate sausage casing thus
obtained was then purified by washing thoroughly with 115 water,
having a temperature of 20 ' C, until the easing, thus treated, was
substantially free from water-soluble impurities.
The purified alginate sausage casing, 120 substantially free from
water-soluble impurities, was thereupon subjected to a drying
treatment by fiattenibg the casing and passing the flattened casing
over, and in contact with, drying rollers heated to 125 C, whereby the
water-content of the easing was reduced from its initial value to a
value of 5 % by weight, based on the weight of alginae plus water
contained in the partially dried casing Thereafter 130 the calcium
chloride, with the formation of water-insoluble calcium alginate and
water-soluble sodium chloride Watersoluble calcium salts other than
calcium chloride may be used, however, if desired, and these
water-soluble calcium salts may be used, in some cases, ih proportions
higher than 25 % by weight or lower than 10 % by weight, based on the
weight of the bath, though in general a bath of an aqueous solution,
at room temperature ( 150 to 25 C), containing calcium chloride in a
proportion lying within the range between 10 % and 25 % by weight,
based on the weight of the bath, appears to give the best results The
content of water-soluble sodium salt or salts in this bath should be
kept as low as possible, and for best results should normally be below
3 % by weight, eased on the weight of the bath The fully coagulated
alginate sausage casing may subsequently be purified by washing with
water until the casing, thus treated, is substantially free from
water-soluble impurities The water-wet alginate casing, in the
water-swollen state and substantialy free from water-soluble
impurities is then subjected to a drying treatment, preferaby by
evaporation of the water by heat at a temperatue or temperatures lying

preferably within the range between 70 C and 90 C', whereby the
water-content is reduced to less than 50 % by weight, and preferably
to a value lying within the range between 10 % and 2 % (inclusive) by
weight, based on the weight of the partially dried casing, in order to
improve the physical properties of the casing The casing may then be
re-wetted with water, or with an aqueous solution of a softening
agent, e g with a % (by weight) aqueous solution of glycerol As an
alternative procedure, the water-wet alginate casing, in the
waterswollen state and substantially free from water-soluble
impurities, may be impregnated with such a softening agent before
being subjected to the drying operation.
The alginate casing may be dried, or partially dried, by passing the
flattened casing over and in contact with the drying rollers, heated
for example to a temperature of 90 C, in a drying atmosphere, other
methods of drying the alginate casing will readily suggest themselves
themselves to those skilled in the art The finished alginate sausage
casing may finally be reeled or shirred or collected in any other form
suitable for storage or despatch.
A specific method of carrying the invention into effect will now be
described by way of illustration with reference to the following
example.
784,871 784,871 the partially dried flattened casing was rehumidified
to water-saturation, by passing it through a bath of water having a
temperature of 18 C, and the water-wet flattened casing was finally
wound in the form of a reel.
The wall-thickness of the finished wet alginate sausage casing was
about 0 002 inch.
It has been found that by allowing the formed tubular structure to set
in a coagulating bath prepared by dissolving and mixing in aqueous
solution a-watersoluble calcium salt and, in a proportion of at least
O 5 % by weight, a water-soluble alkali metal or a water-soluble
ammonium salt of the type hereinabove described, the rate at which
coagulation takes place is retarded, compared with that at which
coagulation occurs in a coagulation bath prepared by dissolving in
aqueous solution the water-soluble calcium salt in like proportion,
but omitting the water-soluble alkali metal salt or water-soluble
ammonium salt as aforesaid It has been found, moreover, that the
water-soluble alkali metal salt or the water-soluble ammonium salt of
the type hereinabove described has a marked effect even when it is
present in a proportion as low as 10 5 % by weight, based on the
weight of the bath This slower rate at which coagulation takes place
results in greater ease in performing the casting operation,
especially during the early stages of the operation.
Thus the process of the present iavention is of special advantage in

the initial stages of the manufacture, even in those cases where the
coagulating bath, at first free from water-soluble alkali metal salt
or water-soluble ammonium salt, is used unchanged for long periods, so
that the water-soluble alkali metal salt or watersoluble ammonium
salt, formed by, double decomposition, gradually accumulates in
aqueous solution in the coagulating bath.
A further advantage lies in a reduction in {he incidence of so-called
" split tubes" caused by the formation of particles of calcium
alginate adhering to the outside edge of the annular nozzle.
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* 5.8.23.4; 93p
* GB784872 (A)
Description: GB784872 (A) ? 1957-10-16
Improvements in transducers for magnetic reproducing and/or recording
apparatus
A high quality text as facsimile in your desired language may be available
amongst the following family members:
CH338623 (A) FR1141866 (A) NL101509 (C)
CH338623 (A) FR1141866 (A) NL101509 (C) less

784,872 Date of Application and Filing Complete Specification: Feb4,
1955 No 3341/55.
Application mode in United States of America on Feb 9, 19-54.
Complete Specification Published: Oct 16, 1957.
Index at Acceptance:-Class 40 ( 2), M.
International Classification;-G ij.
Improvements in Transducers for Magnetic Reproducing and/or Recording
Apparatus.
We, INTERNATIONAL BUSINESS MACHINES CORPORATION, a corporation
organized and existing under the laws of the State of New York, United
States of America, of 590 Madison Avenue, New York 22, New York,
United States of America, do hereby declare the invention, for which
following statement: -
This invention relates to magnetic reproducing and/or recording
apparatus, having a magnetic transducer whereby intelligence signals
are derived from magnetized spots or areas upon a magnetizable surface
or layer, or whereby spots or areas upon a magnetizable surface are
magnetized in response to intelligence signals.
More particularly, although not necessarily exclusively, this
invention is concerned with magnetic recording and reproducing
apparatus whereby magnetized spots are recorded upon and reproduced
from a magnetizable surface of a so-called "magnetic drum" of the type
wherein a cylinder of non-magnetic material is coated or plated with a
magnetizable peripheral surface.
Normally the magnetic coating of these cylinders is a few thousandths
of an inch or less in thickness in order to keep the saturating
recording current to a value low enough to be supplied direct from the
output circuits of low powered electron discharge tubes It is
customary also in magnetic drum apparatus of this type -to space the
transducer from the drum so that transducer core parts between which a
transducing gap is formed do not contact the magnetizable surface with
which they co-operate to record and reproduce intelligence signals, in
contradistinction with the well known direct contact arrangement of
Poulsen This non-contacting arrangement is made to avoid scratching or
penetrating the thin magnetizable drum surface which obviously would
result in damaging the magnetic recording properties of the drum.
Two problems which arise in apparatus of this type are: (I) spacing
the recording and 50 reproducing transducer a suitable distance from

the drum surface to obtain effective S magnetization of the surface
and also to enable effective reproduction of the intelligence signals,
and ( 2) providing an arrange 55 ment whereby an expansion of the
drum.
e.g, due to temperature rise, wherein the radius of the drum is
increased by an amount equal to or greater than the spacing of the
transducer from the drum, does not 60 result in damage to the
magnetizable surface or to the transducer.
It is an object of the present invention to provide improved magnetic
recording and/or reproducing apparatus and an im 65 proved magnetic
transducer therefor.
According to the invention we provide a magnetic recording andlor
reproducing transducer comprising a mounting, a winding secured to
said mounting, a magnetic 70 core so pivotally attached to said
mounting as to allow a limited range of movement of said core through
said winding, resilient means arranged to urge said core in one
direction relative to said mounting, and 75 means for adjusting the
position of said core relative to that of its mounting by moving it in
the opposite direction against the urging of said resilient means or
permitting movement by the resilient means in the one 80 direction.
We further provide magnetic recording and/or reproducing apparatus
comprising a magnetic -transducer as set out above and arranged to
co-act with a magnetic record 85 carrier to record and reproduce
intelligence signals, in which coating surfaces of the said transducer
and of the said magnetic record carrier are of complementary form.
Such apparatus may be adjusted when 90 (Price 316) 784,872 assembled
in a variety of ways, but we prefer to employ a method comprising the
steps of bringing the transducer into contact with the drum, revolving
the drum with the transducer in contact therewith for a predetermined
period of time, and thereafter increasing the spacing between the
transducer and the drum.
When performing the above method of adjustment it is convenient for
the transducer to be arranged so that the resilient means biases the
core towards the record carrier In this way the effect of slight
irregularities in the surface of the record carrier will be absorbed
by the resilient means Such an arrangement is described hereinafter.
In order that the invention may be fully understood an embodiment
thereof will now be described with reference to the accompanying
drawings, in which:
Fig 1 is a front elevation view of a transducer according to the
invention with certain parts broken away to illustrate its
functioning.
Fig 2 is a sectional view of Fig 1, along the line 2-2.
Fig 3 is another sectional view of Fig 1.

along the line 3-3.
Fig 4 is a third sectional view of Fig 1.
along the line 4-4.
Fig 5 is a diagrammatic view of the transducer of Fig 1 embodied in an
arrangement for spacing a magnetic transducer from a magnetic drum.
Fie 6 is a diagrammatic view of a known transducer-drum arrangement.
Fig 7 is a diagrammatic view of a feature of the novel arrangement for
spacing a magnetic transducer and a magnetic drum accordinq to the
teaching of the invention.
In Fig I there is shown a mounting 10 of a suitable material such as a
plastics material to which is secured a winding 20.
which may consist of a single winding or of multiple windings, having
terminals 22 (see also Figs 2 and 3) to which leads 21 are carried
through the mounting 10 A laminated magnetic core structure including
the legs 14 and 15 is pivotally sunnorted by a pin 13 in the mounting
10 and an air gar 16 is provided between the extremities of the legs
14 and 15 the air gap being filled with a non-magnetic material such
as silver solder, and the leg 15 passing loosely through the winding
20 so as to be capable of movement therethrough Normally the core
structure is urged in a counterclockwise direction by a compression
spring 19 A stud 17 is carried by the core structure and co-operating
therewith is a screw threaded cam rod 18 threaded in the mounting 10.
When the rod 18 is rotated in such a direction as to translate the rod
downward (as viewed in Fig 1), a tip 18 a on the rod 18 co-acts with
the stud 17 to cam the core structure in a clockwise direction against
the resilience of the spring 19 Any upward thrust of the core
structure is also resisted by the resilience of the spring 19 70 The
mounting 10 is preferably molded and may comprise two halves, as
indicated by the cross-hatching of Figs 2, 3, 4, fastened together by
rivets 23 The mounting is also provided with ears 11, which are 75
slotted parallel with the mounting face seen in Fig 1, and therefore
not shown, from the ear tips to the body line 12 of the mounting 10 to
permit the mounting to be adjustably fastened to a pair of bars 25 and
80 24 by mounting bolts 12 a and 12 b and spring clips 11 a and 1 lb
for co-acting with a magnetic drum 27 (as in Fig 5) which rotates
about a shaft 26.
The construction of the magnetic trans-85 ducer is best understood
from the foregoing description in connection with Figs 1-4 inclusive
Application of a magnetic transducer of this type is best understood
from the drawing of Fig 5 where, as also pre-90 viously described, the
transducer is mounted upon a pair of bars 24 and 25 in proximity to a
magnetic recording drum 27, which in operation c ontinuolsly rotates
at a predetermined speed about its axis (shaft 26} 95 For purposes of
explanation let it be assumed that the transducer shown in Fig 5 is

provided with two windings: ( 1 i a first winding for recording
discrete magnetic spots or bits" upon the surface of tile drum 100 27,
and ( 2) a second winding or reproducing signals frorl discrete
m-agnet;pots recorded on tihe drunm by the first wining.
Referring again to Fig 5 the arrangment provides for a power supply 29
including 105 a conventional source of timed electrical pulses
selectively controlled by a switch S for energizing the first
mentioned (recordinc; winding of the transducer and an amplifier and
indicating device 30, preferably of the 110 cathode ray tube type, for
measuring the amplitudes of voltage pulses (appearing across a
resistor R 28) induced in the second mentioned (reproducing) winding
of the transducer when the recorded magnetized 115 spots are "read
back", the lines to 31 32 and 33 connecting the transducer windings to
the power supply 29 and the amplifier and indicating device 30.
Conventionally, as shown in Fig 5 the 120 transducer is arranged to be
spaced awav from the peripheral surface of the drum 27 so that a
distance "d" separates the core legs 14-15 (at the air gap 16) from
the drum surface The distance "d" is hereinafter 125 referred to as
"transducer-drum space".
such space being necessary to prevent contact between the transducer
core and the drum which would result in excessive wear and damage to
one or the other (or both) 130 784,872 Heretofore -transducer-drum
space" has l been adjusted when the magnetic drum is stationary, by
means of a shim or similar spacing facility placed between the drum
and the transducer core However, it has been determined that such
adjustment frequently results in non-uniform and unsatisfactory
recordings and reproductions when the transducer-drum space" is set in
that manner Also where many transducers have to be adjusted to a
single magnetic drum.
as is the case with most magnetic drum storage apparatus, a great
amount of time is consumed in adjustment of "transducerdrum space" in
repeated tedious adjustments.
By the arrangement in Fig 5 it is possible to adjust the
"transducer-drum space" by mounting the transducer upon the bars 25
and 24 via bolts 12 a and 12 b and spring clips Ha and l Ib so that
the core (legs 14 and 15) rests upon the surface of drum 27 at the air
gap 16, the core being urged against the drum by spring 19 (see Fig 1
f.
By means of the rod 18 the core is then spaced from the drum to permit
a thin shim to pass therebetween The drum is then rotated in the
conventional manner, e g by an alternating current synchronous motor,
to revolve at a constant speed and the switch S is operated on power
supply 29 thereby energizing the recording winding of the transducer
and recording a discrete spot on the drum The reproducing winding of

the transducer immediately senses the recorded spot and develops a
potential across the resistor R 28 which is reflected by the amplitude
of the pulse appearing upon the cathode ray tube indicator 30 The rod
18 is thereupon further adjusted to vary the "transducer-drum space"
until a predetermined amplitude is obtained in the indicator and all
transducers of a particular multiple transducer magnetic storage drum
apparatus are thus uniformly adjusted In the event of drum expansion,
since the cores of the transducers are spring urged toward the drum
damage will not result through contact of the cores with the drum
surface.
While this method of adjustment can be made with the drum revolving
optimum recording and reproducing efficiency is not obtained due to
the excessive "transducerdrum space" setting required to obtain
uniform signals from all of a plurality of transducers Careful and
accurate design of both transducers and magnetic drum tends to improve
the recording and reproducing efficiency; however, this procedure is
both costly and time consuming, frequently resulting in undesirable
production requirements.
In order to obtain the optimum efficiency of recording and reproducing
in an arrange-65 ment as shown in Fig 5 the following novel method
eliminates the disadvantages noted immediately above Again referring
to Fig.
5, each transducer is mounted by the ears 11 to the fixed bars 25 and
24 via the bolts 12 a and 12 b and the corresponding spring 70 clips
11 a and 111 b, the rod 18 being withdrawn so that no camming action
occurs between the tip 18 a and the stud 17, and the bolts 12 a and 12
b being not fully drawn up A single pulse is then recorded upon 75 the
drum 27 and the amplitude of its corresponding signal, as reproduced,
is observed on the indicator 30 One of the bolts 12 a or 12 b is then
drawn up further and a second single pulse is recorded on the drum 80
and its corresponding signal amplitude is observed on indicator 30 A
succession of single pulses is recorded in this manner with an
observation being made of the amplitude of each corresponding signal
either bolt 12 a 85 or bolt 12 b being drawn up between each
successive recording As a result of this procedure a succession of
signals will be reproduced and indicated at 30 with each successive
signal having a greater amplitude 90 since the "transducer-drum snace"
"d" is decreased after each such adjustment thereby reducing the air
gap between the drum and the transducer Finally when the
"transducer-drum space" becomes zero as 95 the core of the transducer
actually contacts the drum surface no further increase in signal
amplitude will be observed as successive single pulses are recorded on
the drum A further indication that the core has con 100 tacted the
drum surface is observed in the indicator 30 by the presence of a

ripple voltage or background interference in addition to the signals
from the recorded pulses.
All of the adjustment noted in the pre 105 ceding paragraph is made
with the drum 27 rotating at its full operating speed, and the
transducer core is permitted to contact the drum, while the latter
continues to rotate at full speed, for a short period of time (this
110 time was one minute for a particular design used) As a result of
this "run in" period a honing action is obtained between each
transducer core and the drum so that the curvature of the core portion
in contact 115 with the drum coincides with the curvature of the drum.
Furthermore, the drum surface is cleaned of any film in the recording
track of each transducer and minute eccentricities of the 120 drum
surface are worn awav further improving efficiency Most of the honing,
however, occurs on the core since the soft ferromagnetic laminations
normally of which transducer cores are constructed are con 125
siderably softer than the magnetic surface of the drum, the surfaces
of many magnetic drums being of a nickel-cobalt composition.
After the honing or "run-in" period the rod 18 of each transducer is
turned to cause 130 784,872 its core to be carnmed free from the drum
surface, i e to give the "transducer-drum space" a value greater than
zero The transducer-drum space" may be set thereafter to obtain a
predetermined signal value (the actual "transducer-drum space" may he
varied from zero to several thousandths inches) with substantial
uniformity for all transducers co-acting with the magnetic drum By
this method optimum recording and reproducing efficiency is obtained
without resorting to shims or other spacing devices for adjusting
"transducer-drum space" and without introducing prolonged adjusting
operations, which previously required several days for one magnetic
drum apparatus having approximately 200 transducers.
It is obvious that the "run in" or honing operation for a plurality of
transducers coacting with the same drum can be accomplished
simultaneously.
The improved method for obtaining optimum recording and rerroducing
efficiency can produce stronger signals (greater amplitude of
reproduced sienals) than with any other method known to the applicants
for setting of "transducer-drum space" in magnetic drum recording
apparatus For example if "d" is kept in a range between 30.00001
inches and 0005 inches depending on the particular head design used,
it has been found that better recording and reproducing efficiency is
obtained than when recording and reproducing are effected with the
head in contact with the drum.
With reference to Fig 6 a conventional transducer-drum arrangement is
shown, while Fig 7 shows a feature of the arrangement according to the
invention In both Figs 6 and 7 a rotating magnetic drum D is arranged

to co-act with a transducer having a core t provided with a winding c
and an air gap with a "transducer-drum space" "-d" It is obvious that
in each instance (either in the arrangement of Fig 6 or in the
arrangement of Fig 7) there is a spread of the recorded magnetic spot
or "bit" defined by "a" For an eoual value of "d" in each arrangement,
all other factors being equal (viz recording current permeability,
drum surface, etc) it is obvious that the amount of recording flux
being driven across the "transducer-drum space" in the spread area "a"
in the arrangement of Fig 6 where the transducer core has not been
"run in is less than in the arrangement of Fig 7 where the transducer
core has been "run in", as heretofore described, since the "transducer
drum space" above "a" is greater in the arrangement of Fig 6 than in
the arrangement of Fig 7 A similar condition exists when reading the
recorded signal, Consequently, the arrangement shown in Fig 7 will be
more efficient.
A further unique advantage of the transducer arrangement shown in Fi 5
is in thability of the transducer of Fig I to be shifted about its
vertical centerline by 18 (C degrees whereby a recording and/or
reproducing time shift is obtained since the gap 70 16 of Fig I is
"off center " This construction provides a convenient way to effect a
time shift of data in any magnetic drum path or track merely by
reversing the mounting position of the transducer with respect 75 to
the fixed bars 24 and 25 of the arrangement of Fig 5 This provides an
additiona' flexibility not obtainable where the air gap.
which defines the center of the recorded sopt or "bit" is on the
centerline of the trans-80 ducer with respect to its mounting.
In addition to the time shift achieved by the above method of shifting
the transducer about its vertical centreline by 180 degrees.
a vernier time shift may be achieved by the 85 following method After
the transducer core has been placed in contact with th:
drum surface as described above with reference to Fig 5 bolt 12 a may
be adiusted in one direction and bolt 12 b in the oppo 90 site
direction to cause the air gap to mow along the drum surface thereby
azhievina time shift If a starting point has beer established by a
signal from another transducer on the same drum then by observing 95
the time shift on indicator 30 a predetermined time shift may be
accurately obtainer within the limits of the adjustment.
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