GB1574532A - Open-end spinning - Google Patents

Description

PATENT SPECIFICATION 1574532

q ( 21) Application No 30910/79 ( 22) Filed 25 March 1977 f ( 62) Divided out of No 1 574 531 ( 31) Convention Application No 2 613 263 ( 32) Filed 27 March 1976 in a ( 33) Fed Rep of Germany (DE) < ( 44) Complete Specification published 10 Sept 1980 ( 51) INT CL 3 DO 1 H 1/12 ( 52) Index at acceptance D 1 D AEX ( 54) OPEN-END SPINNING ( 71) We, BARMAG BARMER MASCHINENFABRIK AKTIENGESELLSCHAFT, a body corporate organised under the laws of the Federal Republic of Germany, of Remscheid-Lennep, Federal Republic of 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 5

described in and by the following statement:-

This invention relates to a method of open-end spinning.

According to the invention there is provided an apparatus for spinning fibres to form a yarn, comprising two air permeable bodies of rotation moving in opposite directions, between which bodies the fibres fed in are twisted together to form a 10 yarn; air suction devices in the interior of the bodies of rotation, the suction devices each having an opening bounded by a straight line of yarn formation; and a fibre feed device arranged in front of the narrowest gap which is formed between the bodies of rotation and bounded by a straight line, the fibre feed device comprising a housing with cylindrical chamber in which a rotatably driven carding roller is 15 mounted, a channel for introducing a card sliver which channel opens into the chamber, a fibre feed channel extending substantially from the carding roller to the narrowest gap between the bodies of rotation and having a fibre inlet slot which connects the chamber with the fibre feed channel, the said fibre feed channel having an opening the width of which is substantially equal to the width of the 20 narrowest gap and the length of which is at least one third of the axial length of the air permeable wall of the bodies of rotation and the opening plane of which is inclined to the narrowest gap at an angle of between O and 20 towards the yarn outlet and means for producing an air current from the fibre inlet slot to the mouth, the surface area of the cross section of the fibre feed channel diminishing between 25 the fibre inlet slot and the mouth.

The forces acting on the fibres preferably also have components in the direction of feed of the yarn This can be achieved particularly advantageously by means of sieve drums having the form of hyperboloids since such drums both 3 orientate the individual fibres in the direction of the sliver which is to be formed 30 and transport the fibres and the sliver This is especially so if the sliver is clamped between the end plates of the hyperboloids The distance between the sieve drums in the region of the yarn outlet is preferably not smaller than the diameter of sliver which is to be formed The distance is limited upwardly by the speeds of rotation obtainable since a large distance between the drum surfaces 35 and the axis of the yarn and high -yarn draw-off rates necessitate very high circumferential velocities of the sieve drums.

The invention can be used very advantageously for producing a yarn from fibres of different origins, for example natural fibres and synthetic fibres obtained from different raw material or synthetic fibres differing in their properties may be 40 mixed.

This combined mixing and spinning process may be used to produce core/sheath yarns with core fibres differing from the external fibres if the core fibres are carried to the line of yarn formation in front of the external fibres.

The moments of torsion exerted on the fibres or sliver by the apparatus of the 45 invention should preferably be relatively small and the apparatus should not be used in all cases of very thick yarns or high twists for producing the entire moment of torsion required for twisting the yarn In the case of such yarns additional twisting devices are therefore advantageously employed.

The invention will now be described with reference to the accompanying drawings, in which:

Fig I is a sectional view of one embodiment of the invention but without details of the fibre feed device; Fig la is a similar view of another embodiment, again without details of the 5 fibre feed device; Fig 2 and Fig 2 a are representations of yet another embodiment, again without details of the fibre feed device; Fig 3 is a perspective view of an apparatus according to the invention, including a fibre feed device; 10 Fig 3 a is a section through the spinning apparatus of Fig 3 and Fig 3 b shows a modified fibre feed device.

The apparatus shown in Fig 1 comprises cylindrical sieve drums 1 and 2 which rotate in the same sense so that their surfaces move in opposite directions in the region of the line of yarn formation 9 On both sides of this line, suction devices 13 15 and 14 are arranged in their interior of the drums 1 and 2 respectively Each of these suction devices produces an air current 3 or 4 penetrating the respective sieve drum.

The individual fibres are fed to the apparatus by a fibre feed device 6 or a fibre feed device 7 or both The fibre feed devices 6 and 7 are shown only 20 diagrammatically, and for further details reference should be made to Figs 3, 3 a and 3 b 1 and 2 Transport of the individual fibres in the fibre feed devices can be effected by an injector 15.

The individual fibres which have been transferred to the sieve drums 1 and 2 in the region of the air currents 3 and 4 by the fibre feed devices 6 and 7 are pressed 25 against the drum surfaces by the air currents and carried into the zone of the line of yarn formation 9 The open ends of the suction devices overlap only slightly in the region of this line 9.

The directions of the vectors of movement of the drums indicated in Fig 1 and the directions of the air currents combine to convert the individual fibres into a 30 sliver along the line of yarn formation 9 The sliver formed along the line 9 is removed from the spinning zone, for example by means of a winding device, and may subsequently be subjected to further twisting by means of a suitable twisting device, optionally after the spinning device, to impart the desired twist The twisting device may, for example, comprise three shafts rotating in the same sense 35 and arranged at the corners of an isosceles triangle Friction discs are mounted in the sequence of their sense of rotation on these shafts, the discs overlapping at the centre of the isosceles triangle The sliver is passed through the centre of this triangle and the friction discs both twist the sliver and transport the sliver or the resulting yarn 40 The narrowest gap between the sieve drums 1 and 2, which lies in the plane containing the axes of the sieve drums, is approximately equal to the diameter of the yarn which is to be formed, but at the yarn outlet it is preferably slightly smaller and in the region of the fibre inlet it is about 2 to 3 times greater than the diameter of the yarn to be formed For the manufacture of cotton yarn Nm 10, the preferred 45 measurements of the narrowest gap are 0 1 mm in the region of the yarn outlet and 0.5 mm in the region of the fibre inlet For a cotton yarn Nm 20, the distance between the sieve rollers is preferably between 0 2 mm and 0 8 mm.

Fig la shows an apparatus similar to that of Fig 1 but in Fig la fibres are supplied only through the fibre feed device 6 It should be noted, however, that a 50 second feed device could also be provided in this case, as in Fig 1 A particular feature of the apparatus shown in Fig I a is that the opening of a suction device 13 is arranged in front of the plane connecting the axes of the two rollers 1 and 2 An edge 16 of the opening, which determines the position of the line of yarn formation, is situated in front of the said plane, based on the direction of movement of the 55 roller 1 which carries the fibres into the nip, by a distance equal to up to 10 times the diameter of the yarn Another feature of the arrangement of Fig la is that the area defined by the opening of a suction device 14 in the roller 2 slightly overlaps the area defined by the opening of the suction device 13 The distance between the 60: edge 16 of the opening of the suction device 13 and an edge 17 of the opening of the 60 suction device 14 in the region of overlap is equal to up to 10 yarn diameters This arrangement of the openings of the suction devices ensures that the line of yarn formation will be situated before the narrowest part of the nip This is Advantageous, not only for stabilizing the line of yarn formation but also for increasing the moment of torsion to be introduced tis 1,574,532 The principle of combined twisting and transport of the slivers is illustrated in Fig 2 The suction devices 13 and 14 are arranged on the two sides of the line of yarn formation 9, optionally with slight overlapping of their openings The maximum width of the overlap is 10 times the diameter of the yarn The diameter refer, as before, to the completely twisted yarn, and is calculated according to the 5 following formula:

d(mm) = 1 12838 V/ y(g/cm 3) x Nm\ Im wherein y is the specific gravity and Nm (metric number) the fineness of the yarn, measured in metres per gram The individual fibres 5 are fed on to the belt 2 and may in addition be fed on to the belt 1, and they are forced against the belts by the 10 suction devices The slivers are then twisted on the principle already described above.

The apparatus of Fig 2 comprises sieve drums which are formed as hyperboloids 31 and 32 These hyperboloids are so arranged that their axes lie in parallel planes or that each of them has a generating straight line parallel to the line 15 of yarn formation 9 This means that if the two axes are projected on a plane, the angle between them is twice the angle a at which each of the generating straight lines intersects its hyperboloid axis The vectors of movement 11 and 12 of the surface velocities of the circumferential surfaces of the hyperboloids in the narrowest gap formed between the two parallel generating straight lines intersect at 20 an angle 2 a, which has already been defined.

The hyperboloids are so arranged that the narrowest gap between the adjacent generating straight line is substantially rectangular The hyperboloid 31 is displaceable on the support 22 by means of a mounting 21 and is pivotal about an axis 24 It is therefore possible to adjust the width of the gap and/or to set the 25 hyperboloid 31 at such an angle of inclination that the narrowest gap tapers towards the yarn outlet The frictional forces exerted by the sieve drums on the sliver which is in the process of being compressed to a yarn consequently increase with progressive compression of the sliver Excessive moments of torsion and forces of tension liable to tear the sliver are thereby prevented from acting on the 30 sliver At the same time, the tapering of the gap towards the yarn outlet ensures that sufficient torsion can be exerted to produce the required twist on the yarn leaving the spinning device The dimensions of the narrowest gap are adjusted so that in the region where the fibres 20 are introduced the gap is twice as great whilst in the region of the yarn outlet it is smaller than the yarn diameter 35 The drums 31 and 32 are driven in the directions 11 and 12 by drive motors 18 and 19 The suction devices 13 and 14 are situated on the insides of these drums, and the openings of the suction devices extend over part of the internal circumference of the drums 31 and 32 and end shortly before, on or behind the line of yarn formation 9 The area of overlap between the devices 13 and 14 is situated 40 before the narrowest gap, on the fibre feed side The fibre feed device (not shown in Fig 2) extends into the narrowest gap between the drums 31 an 32 and having an opening in the form of a slit which extends over at least part of the length of the gap The conipletely formed yarn is drawn off by winding devices 23 at a draw-off rate of Va, optionally via a delivery mechanism 45 In operation, the surface velocity of-the drums is carefully adjusted to the required twist and to the required yarn draw-off rate, and at the same time a compromise must be reached to allow for the amount of yarn tension which can be tolerated The draw-off rate is particularly limited by the fact that the yarn must not be exposed to excessive tension but at the same time it must not become slack 50 The desired value am depends on the envisaged use of the yarn.

Experiments carried out with an apparatus according to the invention having two slightly overlapping suction devices provided the following results:

1,574,532 1,574,532 4 Two hyperboloids maximum diameter: 85 mm Width of gap: 0 3 mm Overlap of suction devices 0 9 mm Angle of intersection of the vectors 5 of movement 2 a 1400 Yarn: Cotton, nominal staple 28 mm p= 1 54 g cm 3 Nm 24 m gr a metric = metric twist multiplier = 120 (am is mainly a practical coefficient 10 specific to the particular application of the yarn, used for calculating the twist T if the yarn according to the formula T = a V Nm) am is obtained from the particular use of the yarn Experience has shown a suitable value to be between 100 and 150.

Draw-off rate V = 300 m/min 15 The factor varied in the experiment was the speed of rotation of the hyperboloids (u in m/min) This was done in such a manner that both hyperboloids had the same peripheral velocity at the point of yarn outlet The properties measured were the yarn tension (P, measured in Ponds) at which the yarn was drawn from the apparatus, the twist per meter value (T/m) actually achieved in the 20 finished yarn, and the breaking length (km), and they were calculated within the optimum ranges determined by the following formulae:

4.25 Xl O-3 xam X Va <u < 0 95 Va V 7 x sin a cos a as the wider range and 4.25 xl O-3 xam x V xsina +Va xcosa<u< O 85 X Va a 30 VT cos a as the narrower range.

It was found that advantageous surface velocities u could be obtained within the following ranges:

132 m/min < 220 m/min <u < 746 m/min < 833 m/min.

The experimental results are shown in the following Table; 35 u (mrmin) 100 200 400 600 800 900 P (p) 55 32 28 22 19 15 7 T (I/m) 375 505 630 680 730 795 BREAKING LENGTH 5 7 9 2 11 8 11 2 10 2 8 4 (km) a (metric) 76 5 103 128 6 138 149 162 1 574 532 5 The experimental results show that excessively high circumferential velocities and excessively high twist reduce the strength of the yarn Both these factors are deleterious for further processing In the region of the lower limit, on the other hand, the twists produced were so low that sufficient strength could not be obtained 5 The circumferential surfaces of the hyperboloids could, for example, be cut off in the normal planes along the lines 36 and 37 to produce an asymmetric structure.

This would be advantageous in cases where no tension was to be exerted on the resulting yarn.

Fig 2 a shows a spinning apparatus similar to that of Fig 2 In Fig 2 a beadings 10 34 and 35 are placed on the end faces of the hyperboloid sieve drums on the outlet sides These beadings serve to grip the sliver which is already fully twisted at this stage In the region of the line of yarn formation, the hyperboloid sieve drums have a component of movement which causes twisting and another component of movement which transports the resulting sliver and the individual fibres The 15 transporting action is assisted by the beadings 34 and 35.

Such additional increase in the torque may be advantageous when a high torque is required to produce the necessary twist, as in the case of coarse fibres or a very high twist In these cases, an additional false twister 33 may also be provided downstream of the spinning device 20 It should also be mentioned with reference to Fig 1 that the fibres may be supplied either from the fibre feed device 6 or from the fibre feed device 7 or from both By supplying fibres from both feed devices 6 and 7 it is possible to produce mixed fibre yarns if fibres from one source are supplied through the fibre feed device 6 and fibres from another source are supplied through the fibre feed device 25 7 The spinning apparatus represented in Fig 1 can therefore be used for both mixing and spinning individual fibres The fibre feed devices 6 and 7 may be staggered in relation to the line of yarn formation or additional fibre feed devices may be provided behind the devices 6 and 7 In this way, it is possible to spin yarn in which the core differs from the external fibres in the origin of the individual fibres 30 and the structure In this way it is possible, for example, to produce fancy yarns with a core and sheath effect, (e g yarns having a core of man-made fibres for high strength and a sheath of natural fibres to improve other properties such as the appearance, handle, and moisture absorption).

As can be seen from Fig 2 for example, the core of the yarn may be formed 35 from a continuous filament for example a continuous synthetic filament supplied from above on the line of yarn formation 9 and passing between the surfaces This method can be used to produce a spun yarn in which the core is made up of continuous filaments and the sheath is of staple fibres The continuous filament is advantageously a textured filament with a three-dimensional crimp of the kind 40 obtained, for example, by false twist texturing or air jet texturing.

In applying the invention to thick yarns and particularly thick yarns which are to be highly twisted, it has been found that the twist is not uniform over the crosssection of the yarn It has been found that the more internally situated filaments of the sliver have a smaller number of twists per metre than the more externally 45 situated filaments To achieve uniform twisting across the section of the fibre even in the case of thick yarns, an additional torque may be introduced into the sliver by means of a rotating needle The needle may be rotatably mounted in bearings and driven by a motor via a belt and a pulley in the direction in which the vectors of movement of the surfaces 1 and 2 and of the air current and encircle the line of 50 yarn formation The needle can be shifted axially (this is not shown in the figure) so that is can dip to varying extents into the region in which the fibres 5 are brought to the line of yarn formation 9 Experiments have shown that is is most effective to dip the needle into the sliver to a depth of about 30 mm In these experiments, the diameter of the needle was 1 5 mm and the needle tapered to a cone at its outer and 55 end over a length of about 10 mm The speed of rotation of the needle was 60,000 revs/min A twist of 600 turns per metre could be achieved under these conditions.

The yarn draw-off rate was 100 m/min.

It should be noted that the needle may also advantageously be mounted in two pairs of rotatable support rollers at least one of which is driven, the needle being 60 held in the nip of each pair of support rollers by magnetic forces.

The needle may be hollow A core yarn can then be supplied through the needle By being supplied inside the needle, this yarn forms the core of the complete yarn to be formed, and as such has a major influence in the textile 0,1 properties, particularly the strength and elongation of the completed yarn It should be mentioned here that the needle could be used with all the embodiments of the invention described in this specification.

Figs 3 and 3 a illustrate a spinning apparatus having a fibre feed device 45 The spinning apparatus comprises cylindrical rollers 41 and 42 The circumferential surfaces of the cylindrical rollers are perforated The rollers are both driven to 5 rotate in the same sense The rollers contain air suction devices, of which the suction pipe connections 43 and 44 are shown in Fig 3 The fibre feed device comprises a housing which, in the representation in Fig 3 has been cut in a tangential plane This housing is placed against the roller 41 in the narrowest gap between the rollers 41 and 42 A delivery roller 47 and a carding roller 48 are 10 rotatably mounted in the housing of the fibre feed device and driven by motors and transmissions not shown in the drawing.

The delivery roller 47 pulls a sliver 46 into the fibre feed device and into the region of the circumference of the carding roller 48 The carding roller 48 is provided with teeth 53 on its circumferential surface The teeth 53 serve to separate 15 the individual fibres of the sliver 46 and carry them over the circumference of the carding roller to a channel inlet slot 51 The individual fibres are thrown into the inlet slot 51 by the centrifugal force and by the air current from an injector 49 which produces a vacuum in the channel inlet slot 51 Inside the inlet slot 51, these individual fibres are aligned substantially parallel to the axis of the carding roller 20 The fibre feed channel becomes narrower both in the direction parallel to the axis of the carding roller and in its cross-section The mouth 52 of the fibre feed channel is therefore situated parallel to the gap between the two rollers 41 and 42 and has length which is adjusted depending on the staple length The length of the mouth 52 is at least one third of the air permeable length of the rollers 41 and 42 The mouth 25 52 is only a few millimetres ( 1 to 5 mm) wide Due to the fact that the cross-section changes its form from the inlet slot 51 to the mouth 52 and diminishes in crosssectional area and due to the effect of the air currents from the injector 49, the individual fibres are turned and accelerated so that they are orientated to lie substantially in the same plane as the line of yarn formation and encounter this line, 30 spaced apart from each other, at an angle of less than 300 The fibres are then twisted together to produce the finished yarn 10 It should be mentioned that additional air channels may open into the fibre feed channel between the inlet slot 51 and the mouth 52 These air channels are so arranged that they reinforce the vacuum in the inlet slot 51, and favour the acceleration separation, turning and 35 orientation of the fibres in the manner described above.

Fig 3 a also shows that the fibre feed channel has ribs 54 fanning out from the channel inlet slot 51 The ribs merge with the wall in gentle transitions, (see section) and low enough not to touch the opposite wall or opposite ribs The ribs have the effect of causing the fibres to lie in a plane parallel to the line of yarn formation In 40 the end region 55 of the mouth 52, the plane in which the mouth lies is not parallel to the plane of the narrowest gap between the rollers 41 and 42 but at an angle thereto of 200 This enables the air current produced in the fibre feed channel to escape against the directions of movement of the yarn 10 at the narrowest gap The individual fibres are thereby stretched and orientated If it is desired to use 45 apparatus of Fig 3 a to spin a core/sheath yarn, this can be done by adding an additional fibre feed device (indicated in dashed lines in Fig 3 a) to feed the sheath fibres, the core fibres being fed by the feed device indicated in solid lines.

Fig 3 b shows another embodiment of the fibre feed device, which has the advantage of promoting the orientation of the individual fibres parallel to each 50 other and to the line of yarn formation and of promoting the stretching of the fibres The structure of the fibre feed device is similar to that shown in Fig 3 a except that the mouth 52 of the channel is shifted by a considerable distance from the inlet slot 51 in the direction of yarn formation The rear boundary 56 of the feed channel should make an angle E of less than 600 with the line of yarn formation 55 while the front boundary 55 makes an angle a of less than 450 with the line of yarn formation.

Attention is drawn to our co-pending application No 12695/77 (Serial No.

1,574,531) from which this application is divided and to our co-pending applications Nos 7911911 (Serial No 1,574,533) and 7911912 (Serial No 1, 574,534) 60 which are divided from application 12695/77 (Serial No 1,574,531) which include in their specifications material common to this application.

Claims (1)

1. WHAT WE CLAIM IS:-

   1 An apparatus for spinning fibres to form a yarn, comprising two air 1,574,532 permeable bodies of rotation moving in opposite directions, between which bodies the fibres fed in are twisted together to form a yarn; air suction devices in the interior of the bodies of rotation, the suction devices each having an opening bounded by a straight line of yarn formation; and a fibre feed device arranged in front of the narrowest gap which is formed between the bodies of rotation and 5 bounded by a straight line, the fibre feed device comprising a housing with cylindrical chamber in which a rotatably driven carding roller is mounted, a channel for introducing a card sliver which channel opens into the chamber, a fibre feed channel extending substantially from the carding roller to the narrowest gap between the bodies of rotation and having a fibre inlet slot which connects the 10 chamber with the fibre feed channel, the said fibre feed channel having an opening the width of which is substantially equal to the width of the narrowest gap and the length of which is at least one third of the axial length of the air permeable wall of the bodies of rotation and the opening plane of which is inclined to the narrowest gap at an angle of between 0 and 200 towards the yarn outlet and means for 15 producing an air current from the fibre inlet slot to the mouth, the surface area of the cross-section of the slot feed channel diminishing between the fibre inlet slot and the mouth.

   2 An apparatus according to claim 1, wherein the axis of the cylindrical chamber, as viewed in normal projection, is perpendicular to the axis of the bodies 20 of rotation.

   3 An apparatus according to claim 1 or 2, wherein ribs are arranged in a fan formation in the fibre feed channel on at least one of the boundary surfaces which extend from the broad side of the fibre inlet slot to the long side of the mouth, the height of the said ribs being less than the width of the mouth 25 4 An apparatus according to claims 1, 2 or 3, wherein the front boundary of the fibre feed channel makes an angle of less than 450, and the rear boundary makes an angle less than 600, with the line of yarn formation.

   An apparatus according to preceding claim, wherein the bodies of rotation have perforated surfaces 30 6 An apparatus according to any preceding claim, when in use, wherein the mouths of the suction devices overlap by a width of up to ten times the yarn diameter.

   7 An apparatus according to claim 6, when in use, wherein the area of overlap, viewed in the direction of fibre feed, is arranged in front of the narrowest gap 35 8 An apparatus according to claim 7, when in use, wherein the area overlap is arranged in front of the narrowest gap by an amount equal to ten times the yarn diameter.

   9 An apparatus according to any preceding claim wherein the axial distance and/or the position of the axes of the bodies of rotation is adjustable 40 An apparatus according to any preceding claim wherein the axes of the bodies of rotation are arranged to cross each other in such a manner that the narrowest gap diminishes towards the yarn outlet.

   11 An apparatus according to any preceding claim wherein the diameter of the bodies of rotation continuously decreases towards the yarn outlet 45 12 An apparatus according to any preceding claim, wherein a respective fibre feed device is arranged on each side of a plane perpendicular to the surfaces of bodies of rotation or the line of yarn formation.

   13 An apparatus according to claim 12, when in use, wherein the feed devices are arranged to supply fibres which differ from one another in at least one property 50 14 An apparatus according to any preceding claim, wherein a plurality of fibre feed devices is arranged along the line of yarn formation.

   An apparatus according to any preceding claim comprising a needle which is driven in the sense of yarn twisting by a motor, the needle being mounted in such a manner that its axis lies on the line of yarn formation and its tip extends into the 55 region of the fibre feed.

   16 An apparatus according to claim 15, wherein the needle is hollow and means are provided for supplying a core fibre through the needle.

   17 An apparatus according to any preceding claim, with a twister arranged downstream of the apparatus 60 18 An apparatus according to claim 17, wherein the twister is adapted to impart a component of movement in the direction of yarn delivery.

   19 An apparatus according to any preceding claims, wherein the bodies of rotation are cylindrical.

   20 An apparatus according to any preceding claim, wherein the distance 65 1,574,532 between the bodies of rotation diminishes towards the yarn outlet along the line of yarn formation.

   21 An apparatus according to any preceding claim, when in use, wherein in the region of fibre feed, the distance between the bodies of rotation at the line of yarn formation is not smaller than the thickness of the fibre bundle which is to be 5 formed.

   22 An apparatus according to any preceding claim, when in use wherein the distance between the bodies of rotation at the yarn outlet is smaller than the diameter of the yarn being produced.

   23 An apparatus according to any preceding claim, when in use wherein the 10 distance between the bodies of rotation in the region of the fibre feed is more than twice the yarn diameter.

   24 An apparatus according to any preceding claim, when in use, wherein the spinning of the fibres imparts to the yarn a component of movement in the direction of delivery of the yarn 15 An apparatus according to any preceding claim, wherein the fibre inlet slot is a rectangular slot the long side of which extends along the axial length of the carding roller.

   ELKINGTON AND FIFE, Chartered Patent Agents, High Holborn House, 52/54 High Holborn, London, WC 1 V 65 H.

   Agents for the Applicants.

   Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1980.

   Published by the Patent Office, 25 Southampton Buildings, London, WC 2 A l AY, from which copies may be obtained.

   c L 1,574,532