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* GB785208 (A)
Description: GB785208 (A) ? 1957-10-23
Sound-insulating boards
Description of GB785208 (A)
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The EPO does not accept any responsibility for the accuracy of data
and information originating from other authorities than the EPO; in
particular, the EPO does not guarantee that they are complete,
up-to-date or fit for specific purposes.
PATENT SPECIFICATION
Inventor: ANDERS EINAR ANDERLIND 785208 Date of Application and filing
Complete Specification: June 11, I 1956.
? E No18022/56 Patent of Addition to No 736755 dated Oct 6, 1953.
Complete Specification Published: Oct 23, 1957.
Index at acceptance:-Class 96, B( 1: 2 A: 15: 19: 20).
International Classification:-D 21.
COMPLETE SPECIFICATION
Sound-Insulating Boards We, AKTIEBOLAGET SCHAWNS SONER, a Swedish
Joint-Stock Company, of Klemensnis, Sweden, 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 present invention relates to sound insulating boards which are
formed from fibrous or like material and are provided with a plurality
of holes in the face surface thereof In these boards the holes are
usually placed symmetrically over the complete surface and spaced
evenly from each other whereby an overall, uniform pattern is obtained
when a number of boards are placed adjacent to each other, on a wall
or ceiling of a room Sometimes the holes are placed at random over the
surface of the boards whereby an irregular overall pattern is
obtained.

There is described and claimed in Specification No 736,755 a sound
insulating board which comprises at least two groups of holes arranged
in such a manner that a decorative pattern is formed when several
boards are placed adjacent to each other.
According to the present invention a sound insulating board is
provided with a face surface in part of which is formed one group of
holes the other part or parts of said surface being plain, whereby a
decorative pattern is formed when several boards are placed adjacent
to each other The holes of the group lPrice 3 s 6 d l may be all of
the same or of different dia 35 meter, evenly spaced from each other
or spaced at random.
The group of holes may have any desired outline and may be positioned
in any part of the face surface of the board, for example 40 the
groups may define a circle or square in the centre of the board, a
square or triangle in one corner of the board, or a stripe extending
across the board diagonally or otherwise It will be appreciated that
innumer 45 able ornamental and decorative overall patterns may be
obtained by placing a number of boards adjacent to each other The
individual boards which compositely make up an overall pattern may be
identical with or 50 different from each other and furthermore the
boards of the present invention may be used in conjunction with the
boards as described in Specification No 736,755 to give a desired
pattern 55
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* GB785209 (A)
Description: GB785209 (A) ? 1957-10-23
Manufacture of 1:1-difluoro-1-chlorethane

A high quality text as facsimile in your desired language may be available
amongst the following family members:
DE1002303 (B) FR1151291 (A)
DE1002303 (B) FR1151291 (A) less
COMPLETE SPECIFICATION.
Manuacture sf: Difluoro-l-Chlorethane.
We, FARBWERKE HOECHST AKTIEN
GESELLSCHAFT vormals Meister Lucius &
Bruning, a body corporate recognised under
German law, of Frankfurt (M)-Hoechst,
Germany, 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:
It is known to chlorinate l:l-difluorethane at about 80" C. to about
120 C. in the gaseous phase with exposure to light.
A yield of somewhat more than 70 per cent of 1: 1-difluoro-
l-chlorethane is obtained under the most favourable conditions. A
little more than 20 per cent of the starting material remains
unchanged and about 5 per cent of the starting material is converted
into more highly chlorinated products. It has also been proposed to
react 1: lidifluor- ethane in the gaseous phase with chlorine at a
temperature ranging from room temperature up to 300 C. with exposure
to light, to form 1: l-difluoro-l-chlorethane, which is then further
chlorinated at a temperature above 300" C. In the first stage of this
process, 1: l-difluoroXl-chlorethane is obtained in a total yield of
about 60 per cent.
However, about 15 to about 20 per cent of the reacted product is
converted into more highly chlorinated products. In this reaction the
yield is therefore about 70 per cent. Accordingly, this process as
compared with that referred to above has the further disadvantage that
a considerably larger amount of by-products is formed and an even
smaller yield is obtained.

The compound 1:1-difluoro-1-chlorethane is useful as a refrigerant,
but is especially valuable as an intermediate. Thus, it can be
dehydrochlorinated, usually by pyrolysis, to produce vinylidene
fluoride, which can be polymerized alone or copolymerized, for
example, with trifluorochlorethylene to produce a variety of valuable
products.
The present invention is based on the observation that the
chlorination of 1:1difluorethane with exposure to light, for example,
ultra-violet light, can be carried out in the liquid phase. In this
case practically no undesired side reactions occur. Favourable factors
are the lower reaction temperatures which can be attained, and the
diluting action of the components of the reaction.
It is immaterial in what manner the liquid phase is obtained. If it is
obtained by cooling the 1: 1-difluorethane below its boiling point (24
C.), it is unnecessary to work under pressure, and the chlorination
can be carried out at correspondingly higher temperature but below the
critical temperature.
Finally, the chlorination may be carried out in a suitable solvent
which forms the liquid phase, and the pressure and temperature can be
varied within a wide range. As solvents there are suitable halogenated
hydrocarbons which are not chlorinated under the reaction conditions,
such as carbon tetrachloride or 1: l-difluoro-l-chlorethane. In each
of these cases, the chlorination can be carried out in a continuous
manner. When the chlorine tion is carried out in accordance with the
invention under these conditions, the reaction almost ceases when the
quantity of chlorine calculated for the formation of 1:
1-diftuoro-l-chlorethane has been consumed, and very pure 1:
1-difluoro-1-chlorethane boiling at -23 to --23.70 C. is obtained in
a yield exceeding 90 per cent.
As compared with the known processes which are carried out in the
gaseous phase, the process of this invention which is conducted in the
liquid phase has the advantage of producing a considerably larger
yield coupled with a considerably smaller quantity of more highly
chlorinated products.
Furthermore, chlorination in the liquid
phase, as compared with chlorination in the
gaseous phase, has the further advantage
that the yield per unit of volume and time
is greater. Furthermore, the removal of the
hydrogen chloride formed is considerably
simpler than in the known processes, since - in the process of this
invention the hydrogen
chloride escapes in gaseous form and can
be removed to a great extent by distillation.

In contradistinction thereto, in the known
processes which are conducted in the gaseous
phase the hydrogen chloride is removed by
washing with water and thereby lost.
Although it is known to carry out the
photochemical chlorination of normally
gaseous halogenated hydrocarbons other
than 1: 1-difluorethane in the liquid phase,
it could not be expected that it would be
possible to chlorinate 1: 1-difluorethane in
the liquid phase to form almost exclusively
1: l-difluoro-l-chlorethane, especially as it
is known that the chlorination of the analog
ous 1: 1-dichlorethane in the liquid phase
a mixture of 1:1:1- and 1: 1: 2-trichlor-
ethane is formed, whereas in the gaseous
phase practically only 1:1: l-trichlorethane
is obtained. It would, therefore, have been
expected that in the chlorination of 1:1
difluorethane in the liquid phase, i.e. at a
temperature lower than that used in the
known processes, a mixture of 1: l-difluoro-
2-chlorethane and 1: l-difluoro-l-chlor
ethane would be obtained.
The following Examples illustrate the
invention
EXAMPLE 1.
1660 grams of 1: 1-difluorethane were
condensed in a chlorination vessel provided
with an irradiation lamp, using reflux con
densation with dry ice/butanol. Chlorine
was introduced while irradiating the mixture
and the hydrogen chloride escaped at the
top. When 1790 grams of chlorine had
been absorbed the chlorination practically
ceased. The produce was washed, dried,
and fractionally distilled. There were
obtained 145 grams of 1: 1-difluorethane,
2200 grams 1:1- difluoro -1- chlorethane
(which, after deducting the quantity of
starting product, corresponds to a yield of
96%) and 175 grams of over-chlorinated
higher boiling constituents. By introducing
the chlorine and the 1: l-difluorethane at

the bottom of the vessel in the ratio 1:1,
the 1: l-difluoro-l-chlorethane can be con
tinuously withdrawn by means of an over
flow pipe.
EXAMPLE 2.
2.5 kilograms of 1: 1-difluorethane were
condensed in a lead-lined pressure vessel
provided with a reflux condenser and an
irradiation lamp. The temperature was maintained at 05 C. to 10 C. by
cooling with brine. While irradiating with ultraviolet light chlorine
was forced in under pressure at the rate at which decolorisation
occurs. When 2.7 kilograms of chlorine had been absorbed the
chlorination was practically finished. The pressure rose to 18
atmospheres at --5" C. The gaseous mixture was washed, dried and
distilled. There were obtained 3.28 kilograms of l:l-difluoro-
l-chlorethane in addition to 217 grams of the starting material and
260 grams of overchlorinated constituents. The yield, after deducting
quantity of starting material, was 98%. If, after termination of the
above operation, additional quantities of chlorine and 1:
1-difluorethane are introduced in the ratio of 1:1 under pressure into
the 1:1difluoro-l-chlorethane formed, and the reaction product is
removed from the liquid phase by means of a valve and the hydrogen
chloride is separately removed from the gaseous phase by releasing the
pressure, the process becomes continuous.
EXAMPLE 3.
Two litres of carbon tetrachloride were charged into a chlorination
vessel provided with a water cooling coil and an irradiation lamp. 1:
1-difluorethane and chlorine in a molar ratio of 1:1 were introduced
separately, while irradiating and cooling the mixture to 10 C. In this
manner, 850 grams of l:l-difluorethane and 912 grams of chlorine were
introduced in the course of eight hours. The escaping reaction gases,
and the carbon tetrachloride entrained in proportion to its vapour
pressure, were washed with water, dried over calcium chloride, and
distilled. There were obtained 110 grams of starting material and 1045
grams of 1: l-difluoro-l-chlorethane, corresponding to a yield of
gf0O. The residue consisted of the entrained carbon tetrachloride and
over-chlorinated constituents.
What we claim is : -
1. A process for the manufacture of 1: l-difluoro-l-chlorethane,
wherein 1:1difluorethane is reacted in liquid phase with chlorine with
exposure to light.
2. A process as claimed in Claim 1, wherein the 1:1 -difluorethane is
maintained in the liquid phase by cooling.
3. A process as claimed in Claim 1 or 2, wherein the reaction is

carried out at a temperature below about --34" C. and under
atmospheric pressure.
4. A process as claimed in Claim 1 or 2, wherein the reaction is
carried out under a pressure sufficient to maintain the 1: l-di-
fluorethane in the liquid phase.
5. A process as claimed in any one of
Claims 1 to 4 wherein the liquid phase is formed by an inert solvent.
6. A process as claimed in Claim 5,
* GB785210 (A)
Description: GB785210 (A) ? 1957-10-23
Combustion chambers
We, POWER JETS (RESEARCHAND
DEVELOPMENT) LIMITED, a British Company, of 25 Green 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 fol-
lowing statement: -
In a combustion system for continuously burning fuel in a stream of
air, such as for example, that of a continuous combustion turbine
plant, or that of some form of aircraft jet-propulsion plant employing
a gas turbine or a ram jet system, the incoming air is often divided
into two or more separate main streams, at least one of which is for
initiating and supporting combustion while at least one other may for
example be for diluting the hot combustion products with cooler air In
such combustion systems where the air flow is divided into two or more
main streams, it may be desirable to have means operable, on occasion,
to vary the distribution of air between these streams There are
difficulties in designing valves for this purpose which will operate
satisfactorily and consistently at the high temperatures prevailing in
the neighbourhood of the combustion zone.
According to the invention, the distribution of air between streams in
a combustion chamber is varied by injecting into a main stream a

supply of controlling air under pressure in a sense tending to divert
the main flow from one stream to the other.
The invention is illustrated by the drawing accompanying the
Provisional Specification, showing a combustion chamber partly in
axial section.
The combustion system and burner arrangement indicated in the drawing
is of the common form comprising a combustion chamber 1 and, inside
the combustion chamlPrice 7 W 55210 ber, a flame tube 2 which encloses
the actual combustion space Compressed air flows into the space within
the chamber 1 and around the outside of the flame tube 2:
however, a stream of some of this air, as combustion air, enters the
upstream end of the flame tube 2 The liquid fuel injector 4, and its
supply pipe 5, which is connected to the source of fuel, are located
within the tube 2 at or adjacent to this up-stream end.
Slightly downstream of this is the igniting means 6 The chamber is a
cylinder 1 reduced at one end at which it is open to admit a stream of
air, and closed at the other The flame tube 2 is cylindrical and
mounted coaxially within the combustion chamber 1 but spaced apart
from the inner wall of the chamber, it is open at each end for the
passage of the air stream, and has its inlet end adjacent to but
somewhat downstream of the inlet end of the chamber 1 The tube 2 at
its downstream end extends through the closure wall of the closed end
of the chamber 1 The open inlet end of the combustion chamber is
connected to receive the supply of air under pressure-i e the air from
the compressor in a gas turbine plant or the ram air in a ram jet
plant Usually the air will be flowing at a flame-extinguishing
velocity and accordingly some means are provided for maintaining a
stable zone of combustion inside the tube 2, into which zone the fuel
is injected and ignited This is shown as a closure 3 extending across
the flame tube 2 but admitting air through swirl ports to set up a
helical vortex, the stable zone of combustion being within the core of
this vortex, in well-known manner The injector 4 is located to inject
the fuel into the stable zone Downstream of the closure 3 the flame
tube wall is pierced by a succession of further rings of ports 2 a,
for admitting the rest of the air as further combustion r 7 PATENT
SPECFICATION Inventor: -PETER MARTIN.
Date of filing Complete Specification: March 22, 1955.
Application Date: April 1, 1954 No 9563154.
Index at Acceptance:-Class 51 ( 1), Al B 1 A.
International Classification:-F 23 d.
Combustion Chambers.
785,210 air or as dilution air mixing with the combustion products.

The invention is concerned with providing means-operable at will and
possibly partly automatically controlled according to ambient
atmospheric pressure-for varying the distribution of the incoming air
by reducing the proportion of the air which enters the upstream end of
the flame tube 2 as combustion air, relatively to that which flows
between the tube 2 and the walls of the chamber 1, to enter the tube
by the ports 2 a.
These are operable to supply a small auxiliary control jet of
compressed air to the neighbourhood of the upstream inlet to the flame
tube 2 in a sense tending to oppose the entry of combustion air and
accordingly to divert some of this air to the down-stream entry ports
2 a The control jet issues as an annular sheet of air from an annular
slit.
The control-air line enters the flame tube transversely through a
streamlined tubular member 8 similar to fuel-tube 5, and which
connects through a right-angled bend with the hollow body 7 lying
along the axis of the flame tube 2 and chamber 1; this body 7 has an
open end terminating in substantially the same plane as the inlet end
of the flame tube 2, and a closed end nearer to the closure 3 Screwed
into the wall of the closed end and extending along the axis of the
body 7 with annular space around is a stem 9 terminating in a head 9 a
outside the body 7 and close to the end of the wall of the body so
that between them they form a shallow annular slit 7 b Air can issue
from this slit as an annular sheet either radially in the plane of the
inlet edge of the flame tube or preferably, as shown, partly in this
plane btfff with a component directed upstream relatively to the main
stream of air The end of the body 7 and the underside of the head 9 a
are both conical but of different angles so that the issuing air has
an upstream component and the gap between head and body decreases
radially outwardly so that the air passage is either of constant area
or convergent.
In operation, the main stream of air, at} which may be supplied by a
main compressor (driven, for example, by a gas turbine operated by the
combustion products issuing from the flame tube), enters the
combustion chamber 1, travels a short distance up to the -56 inlet end
of the flame tube 2 and then divides, as shown by the arrows One
branch of the stream enters the flame tube as combustion air; the
second branch flows along 'the chamber, outside the flame tube, C)C
which it eventually enters through the ports 2 a as additional or
diluent air Control air can be supplied to the interior of tube 8 and
body 7 from, for example, an auxiliary compressor or from the main
compressor S.3 and a booster compressor, by opening a control valve,
whereupon a small annular air jet issues from body 7, crossing the
first main air stream branch transversely where this stream is

entering the flame tube; accordingly part of this branch of the stream
70 is diverted into the second branch and flows around the outside of
the flame tube 2 to the downstream ports 2 a The flow of control air
required for this action is small The supply of this air may be
controlled by a 75 barometric device so as to effect diversion at high
altitudes, or the control may be in accordance with the temperature in
some part of the combustion chamber or may be by the turbine speed
governor or by some 80 other means, according to the purpose for which
the distribution of air streams within the combustion chamber is being
varied.
Thus in Patent No 662,434 one stream of air is preheated by flowing
between the flame 85 tube and an enveloping jacket, fuel being
introduced into the air in this space for vaporisation before the
air-fuel mixture enters the flame tube, and a valve, which may be
thermostatically controlled, can W vary the air distribution, the
present invention can be applied to such an arrangement, the supply of
air for effecting diversion being possibly thermostatically
controlled.
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* GB785211 (A)
Description: GB785211 (A) ? 1957-10-23
A method of extracting cellulose from cellulosic raw material
A high quality text as facsimile in your desired language may be available
amongst the following family members:
CH317139 (A) DE1039351 (B) FR1086213 (A) NL182089 (C)
CH317139 (A) DE1039351 (B) FR1086213 (A) NL182089 (C) less

-PATENT SPECIFICATION
Date of Application and filing Complete Specification:
Nov 5, 1953 No 30683-13.
Application made in Belgium on Nov 5, 1952.
Index at Acceptance -Class 2 ( 2), W( 1: 2: X).
International Classification:-D 2 lc.
A Method of Extracting Cellulose from Cellulosic Raw Material.
I, THEOPHILE ISIDORE SOPHIE VERMEIREN, of 48 Avenue Joseph Verboven,
DeurneAnvers, Belgium, of Belgium nationality, do hereby declare the
invention, for which I pray that a patent may be granted to me, and
described in and by the following statement:-
The invention relates to a method of exlo tracting cellulose from
cellulosic raw material, in which an extracting liquid is utilised for
the removal from the cellulosic raw material of the resin and like
extractible substances.
In known processes of this kind extracting liquids in the form of an
acid, calcium, magnesium or ammonium bisulphite solution or solution
of an alkali, may be used.
The invention has among its objects to improve known processes so as
to provide a higher efficiency as well as to improve the quality of
the resultant product.
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* 5.8.23.4; 93p

* GB785212 (A)
Description: GB785212 (A) ? 1957-10-23
Improvements relating to electromagnetic field-controlling devices
COMPLETE SPECIFICATION
Improvements relating to Electromagnetic Field-Controlling
Devices
We, FERRANTI LIMITED, a Company registered under the Laws of Great
Britain, of
Hollinwood, in the County of Lancaster, do hereby declare the
invention, for which we pray that a patent may be granted to us, and
described in and by the following statement:
This invention relates to electromagnetic accelerometers, an object
being to provide an accelerometer of improved sensitivity.
In accordance with the invention an accelerometer comprises two
magnetic circuits having a common airgap, means for setting up an
alternating field in each of said circuits, a short-circuited coil
weighted so as to have substantial mechanical inertia and supported so
that a part only of the coil is adapted to move against spring action
across the common field in the airgap in such manner as to vary the
relative effective reluctances of said magnetic circuits, and response
means for deriving a signal dependent on the relative value of said
reluctances.
Said coil may be mounted at one end of an elastically flexible support
which supplies said spring action, the other end, of the support being
fixed relative to the magnetic circuits.
Said response means may include two windings located respectively on
parts of said magnetic circuits that are not in common, means being
provided for deriving said signal from the difference between the
voltages across said windings.
The accompanying drawing is a simplified and partly diagrammatic view
in perspective of one embodiment of the invention.
In carrying out the invention according to one form by way of example,
an accelerometer consists of a stack 10 of E stampings 11 of suitable
magnetic material. The free ends 121 of the outer limbs 12 are bridged

by a yoke 13 of straight stampings 14 which lies within the same pair
of parallel planes that contains the E stampings 11. The inner limb 15
is shorter thall the outer limbs, thereby providing an airgap 16
between the end face 15' of the inner limb and a central portion of
the bridging yoke 13. Two magnetic circuits are thus formed. Each
includes an outer limb 12 and a part of the yoke 13, the inner limb 15
and the airgap 16 being common to both.
Inner limb 15 carries a primary winding 17 arranged to be energised by
alternating current over leads 171 from a source not shown. Each outer
limb carries a secondary winding 18; these two windings are connected
in series opposition to provide an output at 18l; this is applied to a
suitable instrument 24 which is arranged to respond, to the sense as
well as to the extent of the applied signal.
Loosely surrounding the bridging yoke 13 is a short-circuited coil 19
of one or more turns-conveniently, a single turn of copper.
The turn is weighted in any convenient manner (not shown) so as to
possess appreciable mechanical inertia. The turn is mounted at one end
of an elastically flexible support in the form of a resilient rod 22
the other end 23 of which is fixed relative to the magnetic circuits
so that the rod can flex in a plane parallel to the planes of the
stampings. The turn 19 is thus able to move in the slightly curved
directions indicated by the arrows, thereby causing a part ofthe turn
to cross the common field in the airgap 16.
In operation, the accelerometer is so located in the craft whose
acceleration is to be indicated that the direction of motion of the
craft is aligned with yoke 13, which thus lies in a fore-and-aft
position. The primary winding 17 is energised, thereby setting up an
alternating field in each magnetic circuit.
The copper turn 19 behaves like shortcircuited secondary winding and
so sets up a counteracting field in that portion of bridging yoke 13
embraced by it; the effective reluctance of this portion of the yoke
is thereby so much increased that it forms in effect a boundary
between the two magnetic circuits, the yoke being in effect divided at
this portion into two parts (one on each side of the turn) which form
parts of the respective magnetic circuits. When the turn is at the
centre of the bridging yoke, and therefore in line with the centre of
the gap 16, the flux from the end face inner limb 15 divides equally
between the two parts of the yoke on either side of its centre; the
effective reluctances of the two magnetic circuits are therefore
equal, the output voltages of the two secondary windings 18 are equal,
no signal is developed at 18l, and instrument 24 gives a zero
indication.
Any displacement of the turn 19 from the centre of the yoke 13
correspondingly displaces the effective boundary between the two

magnetic circuits, with the result that the bridging yoke and hence
the field in the gap 16 become unequally divided between the two parts
of the yoke and hence between the two magnetic circuits. The magnetic
circuit which now includes the longer part of the yoke consequently
receives more of the flux in the gap and hence has a less effective
reluctance than the other magnetic circuit The output voltages
accordingly cease to be equal and the difference between them provides
a signal at 181 to be displayed by instrument 24.
By thus controlling the distribution of the airgap field between the
two magnetic circuit, the movement of the short-circuited turn or coil
19 controls their relative effective reluctances and hence the value
of the indicated signal.
When the craft is moving at a steady speed or is stationary, the
spring force of the rod 22 maintains turn 19 in the central position.
The reluctances of the magnetic circuits are thus equal, the output
voltages from windings 18 balance one another, and instrument 24 gives
a zero indication.
As soon as the craft starts to accelerate, the inertia of turn 19
causes it to be displaced, against the spring action of rod 22, from
the central position in a direction away from that of the craft's
movement, the extent of displacement of the coil being dependent on
the extent of the acceleration. An out-of-balance signal is thus
developed at 181 and the acceleration is indicated by instrument 24
against a calibrated scale.
When acceleration ceases, the elasticity of rod 22 restores the turn
to the central position.
Retardation of the craft causes the turn to be displaced in the other
direction-i.e. in the direction of the craft's movement. The
out-ofbalance is thus of the opposite sense and instrument 24 gives an
appropriate indication.
Conveniently, instrument 24 is of the centrezero kind, indicating
accelerations on one side and retardations on the other side of the
centre zero.
The alternating field in the magnetic circuits may alternatively be
provided by suitably energising the windings 18 in series, the primary
winding 17 being dispensed with. A bridge circuit including windings
18 in two adjacent arms and fixed resistors in the other arms, may be
used for this purpose.
An accelerometer in accordance with the invention is found to be
sensitive in operation, with particularly good linearity in the zero
region, as well as being robust mechanically.
What we claim is: -
1. An accelerometer comprising two magnetic circuits having a common
airgap, means for setting up an alternating field in each of said

circuits, a short-circuited coil weighted so as to have substantial
mechanical inertia and supported so that a part only of the coil is
adapted to move against spring action across the common field in the
airgap in such manner as to vary the relative effective reluctances of
said magnetic circuits, and response means for deriving a signal
dependent on the relative value of said reluctances.
2. An accelerometer as claimed in claim 1 wherein said coil is mounted
at one end of an elastically flexible support which supplies said
spring action, the other end of the support being fixed relative to
the magnetic circuits.
3. An accelerometer as claimed in either of preceding claims wherein
said response means includes two windings located respectively on
parts of said magnetic circuits that are not in common, means being
provided for deriving said signal from the difference between the
voltages across said windings.
4. An accelerometer as claimed in any of the preceding claims wherein
said means for setting up an alternating field includes means for
energising by alternating current a primary winding carried by a part
of said magnetic circuits which is in common.
5 An accelerometer as claimed in claim 3 wherein said means for
setting up an alternating field includes means for energising by
alternating current said two winding in series.
6. An accelerometer substantially as hereinbefore described with
reference to the accompanying drawing.

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