GB2236768A

GB2236768A - Conveying packages from a false twisting machine

Info

Publication number: GB2236768A
Application number: GB9020381A
Authority: GB
Inventors: Kazuyasu Hirai; Kazuyoshi Suzuki
Original assignee: Murata Machinery Ltd
Current assignee: Murata Machinery Ltd
Priority date: 1989-09-18
Filing date: 1990-09-18
Publication date: 1991-04-17
Anticipated expiration: 2010-09-18
Also published as: DE4029464C2; KR910006530A; DE4029464A1; IT1247721B; IT9048283A0; GB2236768B; GB9020381D0; IT9048283A1; KR930006089B1

Abstract

In a yarn package conveyance method the packages (60) are doffed out of the body of the false twisting machine (23) by an automatic doffer which moves between the machine body (23) and primary heaters (56). The packages are transferred onto pegs coupled to an endless drive device (1) which traverses around the primary heaters (56). The dive device (1) is then revolved to convey the packages, and pushers (15) push out the packages onto an out-of-the-machine conveying device (30) having trays or pegs. <IMAGE>

Description

-7 G, ES METHOD AND APPARATUS FOR CONVEYING PACKAGES FROM A FALSE TWISTING

MACHINE The present invention relates to a method of and apparatus for conveying a package of a textured yarn produced by a false twisting machine automatically to an out-of -the-machine conveying device extending to an inspection and packing room or the like.

There is known a conventional method of conveying a package from a draw false twisting machine.

In this known method, the package is doffed from the body of the machine by an automatic doffer movable is between a primary heater and the body, is transferred onto a peg stand secured along the primary heater, and is then conveyed to an inspection and packing chamber by a person using a handcart or the like. This known method is now described with reference to Figs. 10 and 11 of the drawings. The whole structure of the draw false twisting machine for producing the package is first described. As shown in Fig. 10, a yarn 52 fed from a yarn supply package 51 in a creel stand 50 is kept at such a tension by a first feed roller 53 and a second feed roller 54 that the yarn can be drawn. A false twisting unit 55. such as a nip twister, is provided between the feed rollers 53 and 54 near the feed roller 54 located downstream from the other feed roller 53, and tentatively twists the yarn 52 upstream of the twisting unit. A primary heater 56 for thermally fixing the yarn is provided between the feed rollers 53 and 54 near the feed roller 53 located upstream from the other feed roller 54. and heats the tentatively twisted yarn 52 to a drawing temperature.

A third feed roller 57 is provided downstream from the second feed roller 54. A secondary heater 58 is provided between the feed rollers 54 and 57, and reheats the yarn 52. The reheated yarn 52 is finished as the package 60 by a take-up winder 59. Since the primary heater 56 of the draw false twisting machine is tall, the primary heater 56 is disposed separately from the body 61 of the machine, which includes the f alse twisting unit 55 and the other downstream portions of the machine. The primary heater 56 faces the machine body 61. A pathway 62 is provided between the primary heater 56 and the machine body 61 so as to make it easy to engage the yarn and perform maintenance work. The method itself is now described with reference to Fig.

11. An automatic doffer 63 is provided as a package conveyor in the pathway 62 so that the doffer is movable along the machine body 61. A peg stand 64 is secured to the ground so that the peg stand faces the pathway side of the primary heater 56. Three pegs 65 project from the peg stand 64 into the pathway 62. The automatic doffer 63 transfers the package 60 out of the machine body 61 onto the pegs 65. To do that, the doffer 63 holds the package 60 on a bobbin, picks up the package from the take-up winder, changes the direction of the package by an angle of 90 degrees, moves the package to a position opposed to a peg 65.

and pushes out the package towards the peg. In other words, in this method, the automatic doffer movable between the primary heater and the machine body doffs the package 60 out of the machine body and transfers the package onto a peg 65 of the peg stand 64 so that the operator can then manually pick up the package from the peg and carry the package on a handcart or the like to the inspection and packing room.

Since the peg stand 64 is fixedly secured in the above-mentioned method of conveying the package from the draw false twisting machine, the operator moves about in the pathway 62 while pushing the handcart or the like to pick up the package 60 from the peg stand 64. For that reason, there is a problem that it is time-consuming and inefficient to pick up the package 60 from the peg stand 64. The operator is not allowed to hold the package 60 on its surface, in order to protect the yarn layer thereof, but holds the package on the bobbin to pick up the package from the peg 65 and then puts the package on the handcart or the like in such a manner that the bobbin is located on the downside of the package. Such troublesome work is repeated. Therefore, it takes a great deal of time for the operator to perform the work. The work has also is become more inefficient, particularly because the packages more recently have tended to increase in size and weight. Since the yarn is engaged after the package is picked up from the peg, the production efficiency of the machine is lowered if picking up the package is delayed.

Accordingly, it is an object of the present invention to provide a method of and apparatus for efficiently and automatically conveying out packages from a false twisting machine.

In accordance with the present invention there is provided a method of conveying packages from a false twisting machine, in which said packages are doffed out of the body of said machine by an automatic doffer which is moved between said body and primary heaters; said packages are transferred onto pegs coupled to an endless drive means which travels around said heaters; said drive means is then revolved so that said packages are conveyed; and pushers push said packages onto an out- of -the -machine conveying device having trays or pegs.

The step in which the packages are conveyed with the pegs coupled to the endless drive means, which is revolved around the primary heaters, and the step in which the packages are pushed out onto the conveying device are kinematically connected with each other.

For that reason, the packages are efficiently delivered onto the out-of-the-machine conveying device.

Also in accordance with the invention there is provided a package conveying apparatus for a false twisting machine in which primary heaters are disposed so as to face the body of said machine across a pathway and an automatic doffer is movably disposed in said pathway, wherein a plurality of pegs for bearing said packages delivered from said doffer are coupled around is about half the periphery or less of an endless drive means which travels around said heaters.

In the accompanying drawings:

Fig. 1 is a plan view for describing a method of conveying a package from a draw false twisting machine.

Fig. 2 is a side view of a peg circulator.

Fig. 3 is a perspective view of the peg circulator.

Figs. 4,5 and 6 are perspective views of an out-of-the-machine conveying device.

Fig. 7 is a plan view for describing a method in which a package is conveyed from an elongation false twisting machine and showing another embodiment.

Fig. 8 is a perspective view of a peg circulator shown in Fig. 7.

Fig. 9 is a plan view for describing yet another embodiment of the present invention.

Fig. 10 is a side view of a conventional draw false twisting machine.

Fig. 11 is a side view for describing a package conveyance method for the conventional draw false twisting machine.

Components shown in Figs. 1,2,3,4,5 and 6 which are equivalent to those shown in Figs. 10 and 11 are denoted by the same reference symbols as the latter and are not described in detail hereinafter.

The package conveyance method includes a step in which the package is transferred onto a peg by an automatic doffer 63 shown in Fig. 1, a step in which the package is conveyed to an end section by the peg circulator 1, and a step in which the package is pushed out from the peg onto the out-of-the-machine conveying device 30 by a pusher 15. Fig. 1 also shows primary heater blocks 20, each of which is for twelve packages, is body blocks 21, each of which is for twelve packages, control end sections 22, and drive end sections 23.

The steps of the method are described along with the construction and operation of the equipment.

The function of the automatic doffer 63 for the transfer step is the same as that described above for the conventional method. The automatic doffer 63 performs doffing for every block, and transfers the packages 60 onto pegs 5 sequentially, as shown at 1 in the upper half of Fig. 1, and moves in a pathway 62, as shown at 2. When all the packages 60 are transferred onto the pegs 5, the transfer step is complete. The difference in the transfer step from that of the conventional method is that the package 60 is transferred not onto the peg of the peg stand but onto the peg 5 of the peg circulator 1.

The conveyance step of the method is now described. The peg circulator 1 is intermittently revolved clockwise as shown as 3 in the lower half of Fig. 1, so that the package 60 is conveyed to the end section 1A of the peg circulator. The peg circulator 1, which is revolved around the primary heaters 56 shown in Fig. 2, is provided for the conveyance step.

The peg circulator 1 is now described in detail with reference to Fig. 3. An endless chain 2 constituting an endless drive means, an upper guide rail 3 and a lower guide rail 4 are provided around the primary heaters 56. Vertical plates 6. from each of which three pegs 5 project. are attached to the chain 2 at joints 6A so that the pegs are coupled to the chain through the vertical plates. The vertical plates 6 are attached to the endless chain 2 over not more than about a half of the length of the chain and are not attached thereto elsewhere along its length (refer to the upper half of Fig. 3). The endless chain 2 is performs a revolutionary orbit around sprockets 7 and 8, and is driven by a drive motor 9. Roller followers 10 and 11, which are moved on the upper guide rail 3, and roller followers 12, which are moved on the lower guide rail 4 in such a manner that the lower guide rail is interposed between the roller followers 12 and the vertical plates 6, are secured to the vertical plates 6. In the peg circulator 1 having the above-described construction, the pegs 5 travel around the primary heaters 56 by the power of the drive motors 9 as the pegs remain with a horizontal pitch spacing P1 between them, so that the packages 60 are sequentially conveyed to the end section 1A. When the step of the conveyance of the packages 60 is completed, the pegs 5 of the peg circulator 1 are all located between the primary heater blocks 20 and creel stands 50. In that state, the yarn engagement work is performed. Only the guide rails 3 and 4 and the chain 2, which are shown in Fig. 3, are left in the pathway 62 with the peg circulator 1 in that state, so that there is an opening at the guide rails and the chain. For that reason, the yarn engagement work to first feed the rollers 53 shown in Fig. 8 or the like can be efficiently performed. The pegs 5 should be coupled to the chain 2 over not more than about half the length of the chain so that the pegs are not located in the pathway 62 at the end of the above-mentioned revolution of the chain. After the yarn engagement work is performed, the pegs 5 are moved back to the original state shown in the upper half of Fig. 1. Although the peg circulator 1 has the endless drive means constituted by the chain, the circulator may alternatively have the endless drive means constituted by a rope or the like. Also, various conventional coupling and driving means may be adopted as means for coupling the pegs to the endless drive means, and as the guide rails.

The push-out step of the method is now described. When the package 60 is moved to the end section 1A as shown in the lower half of Fig. 1, the pusher 15 is brought into action to push out the package to the out-of-the-machine conveying device 30 as shown at 4 in Fig. 1. After the conveying device is thus filled with the packages 60, the conveyor is moved, as shown at 5 in Fig. 1. to an inspection and packing room or the like, which is not shown in the drawings, and a following empty out-of-the-machine conveying device 30 is located at the end section 1A.

The pushers 15 comprise pneumatic cylinders constituting a vertical threesome. When a vertical plate 6 holding packages 60 is located at the end section 1A, the piston rods 16 of the cylinders protrude through holes 6B in the vertical plate to push against the ends of the bobbins of the packages engaged on the pegs 5.

The out-of-the-machine conveying device 30, which receives the packages 60 from the peg circulator 1, has pegs or trays, and is described in detail with reference to the drawings. Fig. 4 shows a conveying device 30 which has pegs and is of the truck type. In the conveying device 30 shown in Fig. 4, the pegs 33 constitute a vertical threesome and project from a truck 34 which can perf orm controlled movements on a guide rail 35. The truck 34 is stopped in a position wherein the empty pegs 33 are opposed to the end section 1A and receive the packages 60 pushed out by the pushers 15. The truck 34 is thereafter moved by a pitch distance P2 so that the next empty pegs 33 are opposed to the end section 1A. After the truck 34 is filled with packages 60, the truck is moved away from the end section 1A and another. empty truck is stopped at the end section.

Fig. 5 shows an out-of -the-machine conveying device 31 which has pegs and is of the overhead type.

The conveying device 31 may be provided instead of the conveying device 30. In the conveying device 31, a hanger 37 having a vertical array of three pegs 36 can perform controlled movements while being guided by an overhead rail 38. The empty hanger 37 is stopped in a position wherein it is opposed to the end section 1A and is positioned by guides 39 and receives the packages 60 pushed out by the pushers 15. The hanger 37 filled with the packages 60 is moved away from the position, and the next, empty hanger 37 -4s stopped in that position.

Fig. 6 shows an out-of -the-machine conveying device 32 which has trays and is of the tray type. The conveying device 32 may be provided instead of the conveying device 30. The conveying device 32 includes a first conveyance unit 41 for conveying empty trays 40, a second conveyance unit 42 for conveying trays bearing the packages, a turning conveyance unit 43, and a tilting conveyance unit 44. The empty trays 40 are conveyed from the first conveyance unit 41 onto the tilting conveyance unit 44 by way of the turning conveyance unit 43 as shown at 11 in Fig. 6. The trays on the tilting conveyance unit are secured in prescribed positions by positioning holders, not shown in Fig. 6. The tilting conveyance unit 44 is then tilted through an angle of 90 degrees as shown at 12 in Fig. 6, so that the shafts 40A of the trays are opposed to the packages in the end section 1A. The tilting conveyance unit 44 then receives the packages pushed out by the pushers 15, as shown at 13 in Fig. 6, and is thereafter returned to the original horizontal position thereof as shown at 14 in Fig. 6.

The trays 40 bearing the packages 60 are then released and conveyed from the tilting conveyance unit 44 onto the second conveyance unit 42 by way of the turning conveyance unit 43 as shown at 15 in Fig. 6. These actions shown at 11, 12 13, 14 and 15 are repeated to receive and convey groups of three packages 60. Since a conveyance procedure using such trays is convenient for conveyance, securing and so forth in inspection and packing, the procedure is a preferred one.

In a package conveyance method provided in accordance with the present invention, an automatic doffer movable between the machine body and primary heaters of an elongation false twisting machine doffs packages from the machine body and transfers the packages onto pegs coupled to an endless drive means revolvable around the primary heaters. The endless drive means is then revolved so that the packages are conveyed to an end section. Pushers provided at the end section push out the packages to an out-of-the machine conveying device having trays or pegs. The step of the conveyance of the packages by the pegs coupled to the endless drive means revolvable around the primary heaters and the step of the pushing-out of the packages at the end section are kinematically connected with each other so that the packages are efficiently delivered to the out-of-the-machine conveying device. For that reason, the time which it takes to convey the packages from the machine is much shortened, and the production efficiency of the machine is enhanced. Since the endless drive means provided around the primary heaters ensures a maintenance space and the pushers provided at the end section are used in the method, the method can be practised similarly to the conventional method with regard to the size of the entire installation space needed for the machine.

Another embodiment of the present invention is hereinafter described with reference to Figs. 7 and 8. Fig. 7 is a plan view for describing a method which is the embodiment and in which a package is conveyed from an elongation false twisting machine. Fig. 8 is a perspective view of a peg circulator.

The package conveyance method includes a step in which the package is transferred onto a peg by an automatic doffer 163 shown in Fig. 7, a step in which the package is conveyed to an end section by a peg circulator 101, and a step in which the package is pushed out onto an out-of-the-machine conveying device by a pusher 115. Fig. 7 also shows primary heater blocks 120, each of which is for twelve packages, body blocks 121, each of which is for twelve packages, control end sections 122, and drive end sections 123.

The function of the automatic doffer 163 for the transfer step is the same as that described above for -li- the conventional method. The automatic doffer 163 doffs the packages 160 from each block and sequentially transfers the packages onto the pegs 105 as shown at 1 in the upper half of Fig. 7. The automatic doffer 163 is moved in a pathway 162 as shown at 2 in the upper half of Fig. 7. When the packages 160 are all transferred onto the pegs 105, the transfer step has been completed.

The conveyance step of the method is now described. The peg circulator 101 is intermittently driven so that the circulator is revolved anti clockwise as shown at 3 in the upper half of Fig. 7.

The packages 160 are thus conveyed to the end section 101A of the peg circulator 101. As shown in Fig. 8, an endless chain 102 constituting an endless drive means, an upper guide rail 103 and a lower guide rail 104 are provided around the primary heater blocks 120.

Vertical plates 106, from each of which three pegs 105 project, are attached by joints 106A to the chain 102.

The pegs 105 are thus coupled with the vertical plates 106 to the endless chain 102 constituting the endless drive means. The vertical plates 106 are attached to the endless chain 102 over not more than about a half of the length of the chain, and are not attached thereto over any other part of its length. The endless chain 102 performs a revolutionary orbit around sprockets 107 and 108, and is driven by a drive motor 109. Roller followers 110, which are moved on the upper guide rail 103, and roller followers 112, which are moved in such a manner that the lower guide rail 104 is interposed between the roller followers 112 and the vertical plates 106, are secured to the vertical plates. In the peg circulator 101 having the above described construction, the pegs 105 travel around the primary heater blocks 120 driven by the motor 109 with the pegs remaining with a pitch spacing P1 between them, so that the packages are sequentially conveyed to the end section 101A. When the conveyance step has been completed, the pegs 105 of the peg circulator 101 are all located between the primary heater blocks 120 and creel stands 150. In that state, yarn engagement work is performed. Only the guide rails 103 and 104 and the chain 102, which are shown in Fig. 8, are left in the pathway 162 with regard to the peg circulator 101 so that there is an opening at the guide rails and the chain.

The pushing-out step of the method is now described. When the package 160 is moved to the end section 101A as shown in Fig. 7, the pusher 115 is is brought into action so that the package is pushed out onto an unmanned conveyance vehicle 130 as shown at 4 in Fig. 7. After the vehicle 130 is filled with the packages, the vehicle is moved, as shown at 5 in Fig.

7, to an inspection and packing room or the like, which is not shown in the drawings. As shown in Figs. 7 and 8, the pushers 115 comprise pneumatic cylinders in a six horizontal by three vertical array. When the vertical plates 106 bearing the packages 160 are located at the end section 101A, piston rods 116 of the pneumatic cylinders are pushed through the holes 106B of the vertical plates 106 so that the ends of the bobbins of the packages are pushed. Since the pegs 105 on the vertical plates 106 correspond to pegs 133 on the unmanned conveyance vehicle 130, the packages 160 are simultaneously transferred onto the pegs 133 on the vehicle when the piston rods of the pneumatic cylinders constituting the six by three array are simultaneously extended. After that, the peg circulator 101 is revolved through a distance six times larger than the pitch P1 to deliver other packages 160 to a place in front of the unmanned conveyance vehicle 130 to transfer those packages onto the vehicle by the pushers 115.

Such a transfer is performed a number of times to fill the vehicle with the packages. The vehicle 130 is then moved to the inspection and packing room or the like, in which the packages are subjected to further processing.

The unmanned conveyance vehicle 130 is provided with the pegs 133 projecting from the vehicle and constituting a six by three array and can perform controlled movements along a guide line 135. In a position wherein the empty pegs 133 are opposed to the end section 101A, the conveyance vehicle 130 is stopped by a positioning means such as a positioning cylinder is and receives the packages 160 pushed out by the pushers 115.

It will be understood from the above description that in a package conveyance method in accordance with the present invention, the time which it takes to convey out packages is much shortened, and the production efficiency of the machine is enhanced, as compared with the conventional machine.

Yet another embodiment of the present invention will now be described with reference to Fig.

9. Fig. 9 is a plan view for describing a method in which a package is conveyed from a draw false twisting machine. The method is the same as the preceding one except for an unmanned conveyance vehicle 130. The pitch between pegs 105 on vertical plates 106 differs from that between the pegs 133 of the vehicle 130. The packages 160 are transferred onto the vehicle 130 by actions dependent on the difference and now to be described. The difference is for enhancing the efficiency of loading the vehicle 130 when the diameter of the package is small.To transfer the packages onto the unmanned conveyance vehicle 130, the pushers 115A, which are some of pushers 115 and nearest a creel stand 150, and the pegs 133A of the vehicle are positioned opposite to each other. The packages 160 constituting a vertical threesome are then transferred onto the vehicle 130. After that, the package circulator 101 is revolved by a pitch spacing P1 to transfer the other packages onto the vehicle 130. When such operation is repeated a number of times. the pegs 133A of the vehicle are all filled with the packages. After thatt the other pushers 115B and the other pegs 113B are positioned opposite to each other and the operation is repeated. After all the pegs 133 of the vehicle 130 are filled with the packages by the transfer, the is vehicle is moved to an inspection and packing room or the like, in which the packages are subjected to further processing.

The unmanned conveyance vehicle 130 shown in Fig. 9 is provided with the pegs 133 projecting from the vehicle and constituting a six by three array, and can perform controlled movements along a guide line 135. In the position wherein the empty pegs 133 are opposed to an end section 101A, the vehicle 130 is stopped by a positioning means such as a positioning cylinder and receives the packages 160 pushed out by the pushers 115.

Although the pushers 115A. 115B,... and the pegs 133A, 133B,... of the unmanned conveyance vehicle are positioned opposite to each other by moving the package circulator 101, the same effect can be produced by moving the vehicle.

Since the packages 160 can be efficiently loaded on the unmanned conveyance vehicle 130, the vehicle can be made compact.

It will be understood from the above description that in a package conveyance method provided in accordance with the present invention, the time which it takes to convey out packages is much shortened. and the production efficiency of the machine is enhanced.

In a package conveyor provided in accordance with the present invention, for an elongation false twisting machine in which primary heaters are disposed to face the body of the machine across a pathway and an automatic doffer is movably disposed in the pathway, a large number of pegs for bearing packages delivered from the automatic doffer are coupled over about half the periphery or less of an endless drive means, which is revolved around the primary heaters. The endless is drive means receives the packages from the automatic doffer so that the packages are borne by the pegs. The pegs travel around a path so that the packages are conveyed out of the elongation false twisting machine.

After the packages are conveyed out of the machine, the pegs are located opposite the pathway so that the pegs are not present in the pathway when yarn engagement work is performed. For that reason. one enhances the efficiency of the yarn engagement work as well as the automatic conveying-out of the packages.

Claims

CLAIMS:

1. A method of conveying packages from a false twisting machine, in which said packages are doffed out of the body of said machine by an automatic doffer which is moved between said body and primary heaters; said packages are transferred onto pegs coupled to an endless drive means which travels around said heaters; said drive means is then revolved so that said packages are conveyed; and pushers push said packages onto an out-of -the-machine conveying device having trays or pegs.

2. A method of conveying packages as claimed in claim 1, wherein said endless drive means is is revolved so that the packages are conveyed to an end section thereof, and the pushers, provided at the end section, push out the packages onto the out-of-the machine conveying device.

3. A method of conveying packages as claimed in claim 1, wherein said endless drive means is revolved so that said packages are conveyed to an end section; and a plurality of pushers, provided at said end section, push said packages simultaneously in upper, lower, right and left positions onto an unmanned conveyance vehicle having pegs.

4. A method of conveying packages as claimed in claim 1, wherein said endless drive means is revolved so that said packages are conveyed to an end section; and pushers provided at said end section push said packages onto an unmanned conveyance vehicle having pegs, the spacing between which pegs is smaller than the spacing between the pegs coupled to said drive means.

5. A package conveying apparatus for a false twisting machine in which primary heaters are disposed so as to face the body of said machine across a pathway and an automatic doffer is movably disposed in said pathway, wherein a plurality of pegs for bearing said packages delivered from said doffer are coupled around about half the periphery or less of an endless drive means which travels around said heaters.

6. A package conveying apparatus as claimed in claim 5, wherein said endless drive means comprises an endless chain, an upper guide rail. a lower guide rail and vertical plates from each of which a plurality of pegs project, said vertical plates being attached to the endless chain at joints so that the pegs are coupled to the chain through the vertical plates. and wherein the vertical plates are attached to the endless chain over not more than about a half of the length of the chain.

7. A package conveying apparatus as claimed in claim 6, wherein first roller followers which are moved on the upper guide rail and second roller followers which are moved on the lower guide rail are secured to the vertical plates.

8. A package conveying apparatus as claimed in claim 6 or 7, wherein an out- of -the -machine conveying device which provides a plurality of trays or pegs is located opposite the endless drive means, and a pusher is located at a certain position of the endless drive means to push out the package to the out-of-the machine conveying device.

9. A package conveying apparatus as claimed in claim 8, wherein said pusher comprises a pneumatic cylinder having a piston rod, said piston rod of the cylinder being extended through a hole in the vertical plate to push the end of the bobbin of the package engaged on the peg.

10. A package conveying apparatus as claimed in claim 8 or 9, wherein said out-of-the-machine conveying device is of the truck type which travels along a guide rail and has a plurality of pegs projecting from the truck.

11. A package conveying apparatus as claimed in claim 8 or 9, wherein said out-of-the-machine conveying device is of the overhead conveyor type in which a hanger having vertically arrayed pegs performs controlled movements while being guided by an overhead rail.

12. A package conveying apparatus as claimed in claim 8 or 9, wherein said out-of-the-machine conveying device is of the tray type which includes a first conveyance unit for conveying empty trays. a second conveyance unit for conveying trays bearing the packages, a turning conveyance unit, and a tilting conveyance unit.

13. A method of conveying packages substantially as hereinbefore described with reference to the accompanying drawings.

14. A package conveying apparatus substantially as hereinbefore described with reference to the accompanying drawings.

Published 1991 at 7be Patent Office. State House. 66171 High Holborn. London WC1R47P. Further copies may be obtained from Sales Branch. Unit 6, Nine Mile point. Cw7nfelinfach. Cross Keys. NmporL NPI 7HZ. Printed by Multiplex techniques lid. St Mary Cray, Kent.