WO2014155160A1

WO2014155160A1 - Supply cable handling mechanism and scraper chain conveyor channel for mining thin seams

Info

Publication number: WO2014155160A1
Application number: PCT/IB2013/054431
Authority: WO
Inventors: Stanisław TYTKO; Zdzisław WALCZAK; Andrzej SKRZYPIEC; Jan Pilch; Jan DZIURA
Original assignee: Kopex Machinery Spółka Akcyjna
Priority date: 2013-03-29
Filing date: 2013-05-29
Publication date: 2014-10-02
Also published as: PL222661B1; UA118347C2; CN105209717A; CN105209717B; EA201600658A1; CZ2015752A3; CZ307148B6; PL403357A1

Abstract

The present invention relates to a feeder cable laying mechanism and a face conveyor gate of a mining machine for thin seams used especially for cutting thin coal seams. The cable laying mechanism /6/ of the mining machine /1/ for low faces has a lower branch /6b/ of the cable laying mechanism /6/ arranged in the upper section /8a/ of gates /5/ of the face conveyor /2/ guided on guide inserts /27,28/ of a drive strand /10/ of a tensioning trolley /9/ of said cable laying mechanism /6/, wherein the return pulley /12/ of the drive strand /10/ is slidably mounted by means of a tensioner /17/ arranged in the upper section /8a/ of the gates /5/ of the face conveyor /2/. The pulling strand /11/ and the return strand /13/ of the drive strand /10/ are arranged horizontally in the guide inserts /27,28/. Tensioning of the drive strand /10/ is performed by means of the tensioning trolley /9/ and the tensioner /17/. The gate according to the invention preferably has an insert /26/ located in the upper section /8a/ of the gates /5/ which is equipped with the properly made and mounted guide inserts /27,28/.

Description

SUPPLY CABLE HANDLING MECHANISM AND SCRAPER CHAIN CONVEYOR CHANNEL FOR MINING THIN SEAMS

This invention relates to a feeder cable laying mechanism and a face 5 conveyor gate of a mining machine for thin seams, used especially in longwall mining for coal extraction from thin seams.

For example, Polish patent application P.392762 discloses a cutting-loading machine for thin seams comprising two extreme segments equipped with cutting drums and a middle member located

10 between them in which drives of the cutting drums are located.

The cutting-loading machine has not its own drive for hauling said machine along the conveyor, therefore it is hauled with a driving chain, a system used for driving ploughs. However, the cutting- loading machine, unlike ploughs must have adequate power supply

15 to drive both cutting drums as well as a water supply to control dust levels during the mining process. That in turn requires the proper guiding of the feeder cables along the face conveyor. The cutting- loading machine has a cable system member located in superstructures of the face conveyor which is wound through

20 a movable carriage moved along the conveyor in line with working travel of the machine by means of a hoist, which leads to operational problems. Laying feeder cables for a mining machine in the form of a bunch of cables is disclosed in numerous patent descriptions, for example CN 202 390 033 U, CN 201 874 572 U, or GB 1 189 667.

25 In general terms it consists in that in a coal face section longer than half the length of the coal face a cable bunch loop is formed and the upper branch thereof is led to the mining machine, whereas the lower branch thereof is passively laid in the gates of the face conveyor. The formed loop is continuously being tensed either by

30 means of a rope hoist or a rope hoist with an additional two-block tensioning unit as is disclosed in the invention CN 201 874 572U. For example, Polish patent description PL 191589 Bl also discloses a system for laying feeder cables especially for mobile mining machines where cables mounted to the mining machine by means of a holder and a cable grip form a bunch of cables without a cable laying modular mechanism. The bunch of cables is arranged in the gate channel of a face conveyor and has a loop of cables directed in one side, wound into a block and tensed by means of a pulling device. It is attached to the mining machine with an upper holder located on the edge towards the wall plate of the gate channel and a free vertically and horizontally of said holder the loop is fed into a closed gate channel in such a manner that cables are arranged along the whole working travel of the mining machine and they are tightly covered by plates of the channel at least from the side of the roof and the side wall. The other end of the loop is fed into said channel and mounted on the bottom by means of the lower holder. However, such an arrangement of feeder cables requires conveyor gates of adequate height. Furthermore, on low walls arranging cables not covered by a cable laying mechanism is highly risky as in the case of catching or damaging the cables within the operational range of the face conveyor, there is practically no chance to fix the damage by methods commonly applied on medium and high walls.

The present invention aims to devise a feeder cable mechanism and a face conveyor gate of a mining machine for thin seams which will allow for lowest possible working height in feeder cable laying for a mining machine with totally automated activities connected with laying and tensioning feeder cables for a mining machine.

The essence of the mechanism according to the invention consists in that the lower branch of a cable laying mechanism including the mining machine feeder cables within is arranged in the upper section of a face conveyor gates on guide inserts of a drive strand of a tensioning trolley for cable laying mechanism, wherein the drive strand of the tensioning trolley is wound into a return pulley located in relation to the discharge drive of the face conveyor at a distance longer than half the length of said face conveyor and attached to the face conveyor gate in such a manner that the longitudinal position and tensioning are adjustable.

Most preferably the pulling strand and the return strand of the drive strand of the tensioning trolley are horizontally oriented, mutually parallel in the upper section of the face conveyor gates, below the lower surface of the cable laying mechanism. In a preferred embodiment the cable tensioning trolley has a rigid box body, open on top and on the front facing the drive of the drive strand within which there is a rotary roll whose rotation axle is perpendicular to said drive strand, and has fixing protrusions rigidly fixed to the lower plate thereof and which fixing protrusions resemble L-shaped angle bars in front view, used for connecting the tensioning trolley with the pulling strand of the drive strand.

It is preferable that a drive strand should be a link chain and then the ends of the fixing protrusions of the tensioning trolley go through respective clearances of the links of the pulling strand of said link chain.

The fixing protrusions constructed in this manner have separably mounted locking bars at their ends, which prevents undesirable disconnection of the tensioning trolley.

The rotary roll of the tensioning trolley has side flanges which guide the covers of the cable laying mechanism, wherein the height of the flanges is smaller than the height of the members, and the spacing of the flanges exceeds the width of the members of the cable laying mechanism.

It is also preferable that the mechanism be made in such a manner that the return pulley of the drive strand of the tensioning trolley of the cable laying mechanism is fixed with the axle thereof to the holder of the tensioner separably rigidly mounted to the gate of the face conveyor in the upper section of said gate.

In order to make it possible to adjust the longitudinal position of the return end and tensioning of the drive strand the tensioner has a form of a battery of springs fixed by means of the holder to the return pulley on one side, and on the other side with a tensioning screw attached to the fixed resistance holder in the upper section of the face conveyor gate. A hydraulic cylinder may be used instead of the tensioning screw.

In yet another embodiment of the invention the tensioner may be a hydraulic cylinder on one end fixed to the return pulley by means of a holder, and on the other end attached to the fixed resistance holder of the face conveyor gate and then the drive strand is tensioned exclusively by the cylinder, without the use of springs.

In order to prevent the cables from being pulled into the gates towards the tensioning trolley, the end of the lower branch is attached to an attachable trough of the discharge drive of the face conveyor by means of a screwed-down holder having through holes for seating feeder cables for the mining machine.

In a preferred embodiment said holder comprises a vertical support screwed to the attachable trough and a clamping ring rotably mounted in the horizontal plane to said support, wherein a fixing head for the feeder cables of the mining machine is seated inside the clamping ring by means of a horizontal bolt, and said head also comprises a connecting unit for connecting the members of the cable laying mechanism.

It is most preferable that the head of said holder should have a central cylindrical hole and two longitudinally cut half-bushings mounted therein, and said half-bushings have a stepped inside diameter, and said half-bushings are made in such a way that they can clamp the electric resistance cable and said half-bushings are protected against rotating around the hole axis and two cylindrical side holes equipped with pin seats on both sides thereof for positive fixing of water supply conduits.

The essence of the invention which relates to a face conveyor gate is that it in the upper section of said gate it has two guide inserts separably rigidly mounted on the sides of said upper section, wherein a pulling strand and a return strand of a drive strand of a tensioning trolley of the cable laying mechanism is located, and there is a longitudinal through clearance between said inserts in the middle section, whereas the guide insert for the pulling strand of the drive strand from the side of said longitudinal clearance has a longitudinal through slit through which fixing protrusions of the tensioning trolley body go alongside the pulling strand of the drive strand.

It is most preferable that the upper surfaces of both guide inserts of the assembled gate lie in one horizontal plane.

It is preferable that the gate should be constructed in such a manner that the upper section thereof has a replaceable insert in the form of a U-shaped tray whose length corresponds with the length of the scale of the troughs of the face conveyor, wherein two guide inserts are separably rigidly fixed, and the insert is separably fixed at least with one vertical wall thereof to the body of the guide of the drive chain of the mining machine.

In a preferred embodiment the guide insert for the pulling strand of the drive strand has a shape resembling a T-bar whose roof on one side is adjacent to the edge along the full length thereof to the vertical wall finished on top with a pipe guide and said roof is folded and screwed to the vertical wall, and on the other side said roof is folded downwards and there is a through slit between the bottom of the insert, or possibly the upper section, and the horizontal edge of the roof folded downwards, wherein between the foot of said guide insert and the surface of the vertical wall there is a slidably vertically fixed lock with a holder going through the vertical wall in the longitudinal recess thereof, and said lock is used for connecting and mutual fixing of adjacent gates of the face conveyor.

In a preferred embodiment of the invention the guide insert of the return strand also resembles an angle bar in shape whose upper horizontally located shelf is positively connected with a corresponding vertical wall of the insert, or possibly the upper section, whereas the vertical shelf has lower protrusions at the ends thereof which protrusions go through corresponding horizontal recesses in the bottom of the insert, or possibly the upper section, going out through the vertical wall finished on top with the pipe guide, whereto horizontal locking plates are put and said locking plates are below the lock of the guide insert, wherein the pulling strand of the drive strand is located.

The main advantage of the invention both in relation to the cable laying mechanism and to the face conveyor gate is that feeder cables for the mining machine run very low, and said feeder cables are fully protected and mechanically covered, which eliminates the need for the mining staff to work in the low face while cutting the solid coal. Using a typical, modular cable laying mechanism in a stable tensioning unit of the cable laying mechanism ensures that the cable laying mechanism will properly follow the mining machine. Both the cable laying mechanism and the drive strand of the tensioning trolley for the cable laying mechanism are separated and cannot directly affect the work of the other mechanism, and the horizontal position of the pulling strand and the return strand of the drive strand of the tensioning trolley, located below the cable laying mechanism, makes it possible to locate the cable laying mechanism as low as possible. All elements of the cable laying mechanism and of the gate according to the invention have a compact structure, and therefore they are resistant to accidental mechanical damage, which minimizes maintenance along the length of the face conveyor, which is of utmost importance at thin seams whose height approaches or is even lower than 1.0 m. Repairs or maintenance activities are carried out in the area of galleries after a mining machine is appropriately transported to those areas.

The invention is presented in more detail in the embodiment in a drawing where fig. 1 shows a simplified representation of a face conveyor with a mining machine and a cable laying mechanism in view from the side of the goafs, fig. 2 is a simplified cross section of a part of the face conveyor with a gate and a tensioning trolley for the cable laying mechanism, fig. 3 shows the tensioning mechanism of the drive strand of the tensioning trolley in a simplified top view of a part of the face conveyor, fig. 4 is a spatial view of the tensioning trolley of the cable laying mechanism, fig. 5 is a cross section of the tensioning trolley of the cable laying mechanism, fig. 6 is a replaceable insert of the upper section of the face conveyor gate, and fig. 7 is an assembly for fixing feeder cables for the mining machine to an attachable trough.

A mining machine 1 is mounted on a face conveyor 2 slidably along the operational range thereof by means of a hauling chain 3 located in a body of a guide bar 4 of a gate 5 of the face conveyor 2 (fig. 1, fig. 2). The mining machine 1 is powered by electricity and water supplied by cables mounted in a cable laying mechanism 6 spread on the gates 5 of the face conveyor 2, whose one end is fixed to an attachable trough 7 of a discharge drive 2a of the face conveyor 2 and the second end of said mechanism is fixed to the mining machine 1. In order to achieve the proper tracking of the cable laying mechanism 6, said mechanism is located in the upper section 8a of the gate 5 and in the middle section of the face conveyor 2 said mechanism is wound into a tensioning trolley 9 which is bidirectional along a part of the operational range of the face conveyor 2 from the side of the discharge drive 2a which is approximately half the operational range of the face conveyor 2. The hauling of the tensioning trolley 9 is achieved by means of a drive strand 10 in the form of a link chain whose driving stand 11 is connected to a drive not shown in the drawing located beyond the face wound into a return pulley 12 and returning on a return strand 13. A drive chain 10 is located in the upper section 8a of the gates 5 in such a manner that the pulling strand 11 and the return strand 13 are mutually parallel and located below the covers of the cable laying mechanism 6. The return pulley 12 (fig. 3) is mounted so that it is movable to a limited extent of the axle 15 towards a holder 16 of a tensioner 17 in the form of a battery of springs fixed with the second end thereof with a tensioning screw 18 mounted to a fixed resistance holder 19 of the gate 5 of the face conveyor 2. The tensioning screw 18 may be replaced by a hydraulic cylinder. Owing to that the tension of cable laying mechanism 6 is virtually stable regardless of the place of operation of the mining machine 1 and the resulting position of the tensioning trolley 9 within the operational range of the face conveyor 2. The tensioning trolley 9 assembly is so constructed that the body thereof 20 which is a box (fig. 4, fig. 5) open on top and from the side of the drive of the drive chain 10, and has side fixing protrusions 22, resembling an L-shaped angle bar in front view, fixed to the bottom 21 in the lower part thereof. The fixing protrusions 22 go through the vertical clearances of the pulling strand 11 of the drive chain 10 links and are protected by locking bars 23, which allows for connected movement of the tensioning trolley 9 and the drive chain 10. A rotary roll 24 of the tensioning trolley 9 has side flanges 25 whose height h is smaller than the height of the members of the cable laying mechanism 6 and the spacing b of said side flanges 25 exceeds the width of the members of the cable laying mechanism 6. The upper section 8a comprises a replaceable U-shaped insert 26 (fig. 2, fig. 6) in the form of a rigid tray of length b_x corresponding with the length of the scale of the troughs of the face conveyor 2 inside which there are rigidly separably mounted guide inserts 27 and 28, and which insert 26 is screwed with its one vertical wall 29 to the body 30 of the guide bar 4 of the hauling chain 3 moving the mining machine along the route of the face conveyor 2. The guide insert 27 for the pulling strand 11 of the drive chain 10 resembles a T- bar whose roof 31 on one side is adjacent to the gate 5 along its full length with an edge 32 to the other vertical wall 33 of the insert 26, and is finished on top with a pipe guide 34 and is fixed thereto with screws 35, and on the other side said roof 31 is folded downwards with a longitudinal slit 36 between the bottom 37 and the edge 38 of the downward folding of the roof 31. Between a foot 39 and the surface of the vertical wall 33 there is a slidably longitudinally mounted lock 40 with a holder 41 going through the vertical wall 33 in the longitudinal recess 42 of said wall 33. The guide insert 28 for the return strand 13 of the drive chain 10 is shaped like an angle bar whose upper horizontal shelf 43 is positively connected by means of edge protrusions going into corresponding holes of one vertical wall 29 of the insert 26, whereas the vertical shelf 44 has lower protrusions 45 going through corresponding horizontal recesses 46 of the bottom 47 of the insert 26 going outside through the vertical wall 33. Horizontal locking plates 48 located directly under the lock 40, which lock the guide insert 28 for the return stand 13 of the drive chain 10 go through horizontal recesses 46. Between the guide inserts 27, 28 in the middle section of the insert 26 there is a longitudinal clearance 49 through which go the fixing protrusions 22 of the tensioning trolley 9 connected with the pulling strand 11 of the drive chain 10. As can be seen in the drawing the upper shelf 43 and the roof 31 are on the same level, which ensures a smooth movement of the tensioning trolley 9 in the upper section 8a of the gate 5 and horizontal arrangement of the lower branch 6b below the upper branch 6a of the cable laying mechanism 6.

To ensure proper functioning of the cable laying mechanism 6 it is important to attach the end thereof to the attachable trough 7 of the discharge drive 2a of the face conveyor 2. A holder 50 (fig. 7) used for this purpose comprises a vertical support 51 attached to the body of the attachable trough 7 by means of screws 52 and a clamping ring 53 rotably mounted to said support 31 in the horizontal plane and a horizontal bolt 54 of a head 55 wherein are arranged cables which are further arranged in the cable laying mechanism 6. The head 55 has a central hole 56 into which go two half-bushings 57 with a stepped inside diameter, mechanically prevented from turning in the seat after fixing the flexible cable within, for example by means of a locking screw. Furthermore, the head 55 has two cylindrical side holes 58 for water supply cables equipped with pin seats 59 on both ends for rotable mounting of the ends of the water supply cables. The head 55 is also equipped with a connector 60 for fixing it to the members of the cable laying mechanism 6.

In the lower section 8b of the gate of the face conveyor 2 there are high-pressure hydraulic feeder cables for powering roof support and control cables.

The embodiment of the invention presented above does not exhaust the various possibilities of the invention both with regard to the cable laying mechanism and the construction of the face conveyor gate. For example, the upper section of the gate may not be a replaceable insert, but as a whole, like the insert of compact structure. This also refers to the mechanism of the tension member of the tensioning trolley where various elements may perform the functions of a battery of springs, or possibly tensioners of pawl structure.

Claims

1. A feeder cable laying mechanism for a mining machine for thin seams, said mechanism comprises jointedly connected members, located in gates of a face conveyor, feeder cables for the mining machine, a terminal for the feeder cables for the mining machine and a terminal for the face conveyor, as well as a tensioning assembly of the feeder cable laying mechanism having a tensioning trolley slidably mounted along half the length of the face conveyor, into which an upper branch of said feeder cable laying mechanism connected to the mining machine is wound, characterised in that a lower branch /6b/ of the feeder cable laying mechanism /6/ including said cables is arranged in the upper section /8a/ of the gates /5/ of the face conveyor /2/ on guide inserts /27,28/ of a drive strand /10/ of the tensioning trolley /9/, into which the upper branch /6a/ of the feeder cable laying mechanism /6/ is wound, wherein the drive strand /10/ of the tensioning trolley /9/ of the feeder cable laying mechanism /6/ is wound into a corresponding return pulley /12/ located at a distance in relation to a discharge drive /2a/ which exceeds half the length of the face conveyor /2/ and mounted in the upper section /8a/ of the gates /5/ of the face conveyor /2/ with the possibility to adjust the longitudinal position and tension.

2. The mechanism according to claim 1 characterised in that a pulling strand /ll/ and a return strand /13/ of the drive strand /10/ of the tensioning trolley /9/ are mutually parallel and horizontally oriented in the upper sections /8a/ of the gates /5/ of the face conveyor /2/ below the lower surface of the cable laying mechanism /6/.

3. The mechanism according to claim 1 or 2 characterised in that the tensioning trolley /9/ of the cable laying mechanism /6/ has a rigid box body /20/ open on top and from the front facing the drive of the drive strand /10/ where a rotary roll /24/ is located and has in the lower section thereof rigidly mounted to the bottom /24/ fixing protrusions /22/, resembling an L-shaped angle bar in front view, for connecting with the pulling strand /ll/ of the drive strand /10/.

4. The mechanism according to claim 3 characterised in that the drive strand /10/ is a link chain, and the ends of the fixing protrusions /22/ go through the corresponding clearances of the pulling strand /ll/ links of said link chain.

5. The mechanism according to claim 3 or 4 characterised in that the fixing protrusions /22/ are equipped with separably mounted locking bars /23/.

6. The mechanism according to claim 3 characterised in that side flanges /25/ of the roll /24/ of the tensioning trolley /9/ have a height /h/ which is smaller than the height of the members /6a, 6b/ of the feeder cable laying mechanism /6/ and the spacing /b/ thereof is larger than the width of the members /6a, 6b/ of the feeder cable laying mechanism /6/.

7. The mechanism according to claim 1 characterised in that the return pulley /12/ of the drive strand /10/ of the tensioning trolley /9/ of the feeder cable laying mechanism /6/ is fixed with the axle thereof /15/ to a holder /16/ of a tensioner /17/ separably rigidly connected to the gate /5/ of the face conveyor/2/.

8. The mechanism according to claim 7 characterised in that the tensioner /17/ has a form of a battery of springs connected by means of the holder /16/ with the return pulley /12/ on one side and on the other side with a tensioning screw /18/ attached to a fixed resistance holder /19/ of the gate /5/ of the face conveyor /2/.

9. The mechanism according to claim 8 characterised in that it has a hydraulic cylinder instead of the tensioning screw /18/.

10. The mechanism according to claim 7 characterised in that the tensioner /17/ is a hydraulic cylinder fixed to the return pulley /12/ by means of the holder /16/ on the first end and on the second end attached to the fixed resistance holder /19/ of the gate /5/ of the face conveyor /2/.

11. The mechanism according to claim 1 characterised in that the feeder cable laying mechanism /6/ is fixed with the end of the lower branch /6a/ thereof to an attachable trough /7/ of the discharge drive /2a/ of the face conveyor /2/ by means of a screwed down holder /50/ having through holes /56,58/ for feeder cables for the mining machine /l/.

12. The mechanism according to claim 1 or 11 characterised in that the holder /50/ consists of a vertical support /51/ attached to the body of the attachable trough /7/ by means of screws /52/ and a clamping ring /53/ rotably attached to said support /51/ in the horizontal plane, wherein a head /55/ is seated by means of a horizontal bolt /54/ for fixing the feeder cables for the mining machine /l/, equipped with a connector /60/ for connecting the members of the feeder cable laying mechanism /6/.

13. The mechanism according to claim 12 characterised in that the head /55/ of the holder /50/ has a central cylindrical hole /56/ and there are two longitudinally cut half-bushings /57/ mounted within which have a stepped inside diameter and are mechanically protected against rotating around the axis of the hole, used for fixing the flexible electric cable and has two side cylindrical holes /58/ equipped with pin seats /59/ on both ends, for mounting the water supply cables.

14. A face conveyor gate of a mining machine for thin seams, mounted to the face conveyor from the side of the goafs, equipped with channels for tracking the hauling chain of the mining machine, an upper section and a lower section for guiding a mechanism for laying electric, water and hydraulic pressure cables and a terminal for a hauling unit with a support to correct the alignment of the face conveyor characterised in that the upper section /8a/ of said gate has two guide inserts /27,28/ separably rigidly mounted on the sides of said upper section /8a/, inside which there is a pulling strand /ll/ and a return strand /13/ of a drive strand /10/ of a tensioning trolley /9/ of the feeder cable laying mechanism /6/, wherein between the guide inserts /27_;28/ in the middle section thereof there is a longitudinal clearance /49/ and the guide insert /27/ of the pulling strand /ll/ of the drive strand /10/ from the side of the longitudinal clearance /49/ has a through longitudinal slit /36/ through which go the fixing protrusions /22/ of the body /20/ of the tensioning trolley /9/ used for connecting with the pulling strand /ll/ of the drive strand /10/.

15. The gate according to claim 14 characterised in that the upper surfaces of both guide inserts /27,28/ in an assembled state are in one horizontal plane.

16. The gate according to claim 14 or 15 characterised in that the upper section /8a/ thereof has a replaceable insert /26/ in the form of a rigid U-shaped tray of the length / b corresponding to the scale of the trough of the face conveyor /2/, inside which there are separably rigidly mounted two guide inserts /27,28/, wherein the insert /26/ is separably mounted with at least one of its vertical walls /29/ to the body of the guide bar /4/ of the hauling chain /3/.

17. The guide according to claim 16 characterised in that the guide insert /27/ for the pulling strand /ll/ of the drive strand /10/ has a profile resembling a T-bar whose roof /31/ on one side is adjacent along the full length thereof with an edge /32/ to a vertical wall /33/ finished on top with a pipe guide /34/ and said roof is connected to said vertical wall /33/ with a fold by means of screws /35/, and on the other side said roof is folded downwards with a through longitudinal slit /36/ between the bottom /37/ of the insert /26/ or the upper section /8a/ and the edge /38/ of the downward folded roof /31/, wherein between the foot /39/ and the surface of the vertical wall /33/ there is a slidably mounted lock /40/ with a holder /41/ which goes through the vertical wall /33/ in the longitudinal recess /42/ thereof.

18. The gate according to claim 16 characterised in that the guide insert /28/ for the return strand /13/ of the drive strand /10/ has a profile resembling an angle bar whose upper shelf /43/ is positively connected with a vertical wall /29/, whereas the vertical wall /44/ thereof has lower protrusions /45/ at the ends which go through corresponding horizontal recesses /46/ in the bottom /47/ of the insert /26/ and go outside through the vertical wall /33/ finished on top with the pipe guide /34/, through which go horizontal locking plates /48/ located below the lock /40/ of the guide insert /27/ for the pulling strand /ll/ of the drive strand /10/.