Automatic cutting and die forming integrated machine for coiled material

Abstract

The present application relates to the technical field of coil processing equipment, and discloses a kind of automatic cutting and punching forming integrated machine of coil, including the unwinding structure of being arranged in the one side of machine body, and the binding mechanism and the stamping mechanism connected with machine body are sequentially arranged in the rear of unwinding mechanism operation line, and the driving roller group a along horizontal plane mirror image is arranged between the stamping mechanism and the binding mechanism, and the driving roller group b along horizontal plane mirror image is also arranged in the discharge side of stamping mechanism, and the driving roller group a and the driving roller group b are synchronous operation between them, for providing forward driving force for the flattened coil at the same time.The present application makes the driving roller group of two groups synchronous operation, so that the coil keeps constant speed, flat conveying state between binding and stamping, effectively avoids the tensile deformation and position deviation of coil, improves the precision and product consistency of binding and stamping forming, realizes the integrated continuous automatic production of coil, significantly improves production efficiency and product quality.

Description

Technical Field

[0001] This invention relates to the field of **, and in particular to an integrated machine for automatic slitting, snapping and forming of rolled materials. Background Technology

[0002] In the field of coil processing, especially in production processes that require coils to be fastened (attached) before slitting and stamping, traditional processing methods typically involve multiple independent machines operating sequentially. After unwinding, the fasteners are first fastened by a fastening machine, and then the coil is transferred to a stamping machine for slitting. This decentralized production model not only involves numerous processes, a large floor space, and significant manual intervention, but also requires repeated repositioning and threading of the coil during transfer between different machines, resulting in low production efficiency. More importantly, during the process of conveying the coil from the fastening stage to the stamping stage, due to the lack of effective synchronous traction and flattening methods, the coil is prone to slackness, folding, or overstretching due to gravity, tension fluctuations, or speed mismatch. This causes the fasteners to shift, and the length and profile of the stamping and slitting are difficult to control precisely, ultimately resulting in a large number of scraps. Therefore, this invention proposes an integrated automatic coil slitting, fastening, and forming machine to solve the above problems. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides an integrated machine for automatic slitting, snapping, and forming of rolled materials.

[0004] The automatic roll material slitting, buttoning, and forming integrated machine provided by this invention adopts the following technical solution:

[0005] An automatic roll material slitting and buttoning forming integrated machine includes an unwinding structure disposed on one side of the machine body. Behind the unwinding mechanism's operating line, an attachment mechanism and a stamping mechanism connected to the machine body are arranged in sequence. A drive roller group a is arranged in a horizontal plane mirror image between the stamping mechanism and the attachment mechanism. A drive roller group b is also arranged in a horizontal plane mirror image on the discharge side of the stamping mechanism. The drive roller group a and drive roller group b operate synchronously to flatten the roll material while providing it with forward driving force.

[0006] Preferably, each roller in drive roller group a and drive roller group b has an inward groove at its centerline, and one of drive roller group a and drive roller group b is connected to each other by a transmission belt.

[0007] Preferably, the stamping mechanism includes a stamping machine mounted on the machine body and a die support platform that cooperates with the stamping machine, and a material feeding channel is fixedly connected below the die support platform.

[0008] Preferably, the binding mechanism includes a binding machine mounted on the machine body, and a feeding bracket fixedly connected to the machine body below the binding machine. A feeding channel for conveying raw materials is also provided on one side of the binding machine, and the output end of the feeding channel extends to the position below the binding part of the binding machine.

[0009] Preferably, the unwinding structure includes a mounting shaft fixedly connected to one side of the machine body, and a steering shaft a fixedly connected to the machine body support leg. The machine body is also provided with a drive shaft assembly mirror-mounted along the horizontal plane behind the steering shaft a. The bottom of the machine body is also fixedly connected with an upwardly extending elastic rod, and the top of the machine body is also rotatably connected with a steering shaft b.

[0010] Preferably, the roll material is conveyed to the binding machine in sequence through the steering shaft a, the drive shaft assembly, the elastic rod and the steering shaft b, and the roll material is always in a flat state.

[0011] Preferably, a support plate assembly is also vertically fixedly connected to the top of the machine body. The support plate assembly includes a support plate a disposed between the steering shaft b and the stitching machine, a support plate b disposed between the stitching machine and the drive roller assembly a, and a support plate c disposed between the drive roller assembly a and the stamping machine.

[0012] Preferably, the upper surfaces of the support plate a, support plate b and support plate c are all tangent to the steering shaft b and the drive roller group a.

[0013] In summary, the present invention has at least one of the following beneficial technical effects:

[0014] By installing synchronously operating drive roller sets between the binding machine and the stamping machine, as well as on the stamping machine's output side, the coil material maintains a constant conveying speed and balanced flattening tension throughout the two key stations of binding and stamping, and during the output process after stamping. This completely solves the problems of coil material stretching deformation, loosening and wrinkling, as well as binding position misalignment and inaccurate stamping dimensions caused by speed differences between processes in traditional split-type equipment. The synchronous and coordinated action of the two sets of drive roller sets ensures that the coil material enters the stamping die in a flat state and ensures precise consistency in the stamping and cutting length, significantly improving product qualification rate and production continuity, and realizing integrated high-precision automated production of coil material from unwinding to finished product. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the material conveying structure according to an embodiment of the invention.

[0016] Figure 2 This is an isometric structural schematic diagram of an embodiment of the invention.

[0017] Figure 3 This is a schematic diagram of the drive mechanism structure of an embodiment of the invention.

[0018] Explanation of reference numerals in the attached drawings: 1. Machine body; 2. Mounting shaft; 3. Steering shaft a; 4. Drive shaft assembly; 5. Elastic rod; 6. Steering shaft b; 7. Support plate assembly; 71. Support plate a; 72. Support plate b; 73. Support plate c; 8. Stitching machine; 9. Feeding bracket; 10. Feeding channel; 11. Drive roller assembly a; 12. Drive roller assembly b; 13. Transmission belt; 14. Stamping machine; 15. Die support platform; 16. Unloading channel; 17. Groove. Detailed Implementation

[0019] The following is in conjunction with the appendix Figure 1 - Appendix Figure 3 The present invention will be described in further detail below.

[0020] Example 1: Refer to Figure 1 - Figure 3 An automatic slitting, buckling, and forming machine for rolled materials includes a machine body 1, which serves as the mounting base for the entire machine. The machine body 1 is constructed from high-strength cast iron or welded steel plates, providing sufficient rigidity and stability. An unwinding structure is located on one side of the machine body 1 to support and release the rolled strip material. Following the direction of the rolled material's travel (i.e., the direction of the work line), a binding machine 8 and a stamping machine 14 are sequentially located behind the unwinding structure. Both the binding machine 8 and the stamping machine 14 are fixedly connected to the machine body 1. The binding machine 8 is used to buckle the rolled material (i.e., attach connecting buckles), and the stamping machine 14 is used to slitting and stamping the rolled material.

[0021] A drive roller group a11, arranged in a mirror image along the horizontal plane, is provided between the stamping machine 14 and the binding machine 8. A drive roller group b12, also arranged in a mirror image along the horizontal plane, is also provided on the discharge side of the stamping machine 14. The drive roller groups a11 and b12 operate synchronously via a synchronous transmission mechanism, working together to flatten the coiled material while providing a continuous forward driving force. Drive roller group a11, located between the binding machine 8 and the stamping machine 14, serves to flatten and pull the bound coiled material; drive roller group b12, located on the discharge side of the stamping machine 14, serves to pull and output the finished coiled material after stamping. The synchronous operation of the two drive roller groups ensures that the coiled material maintains a constant tension and speed between the binding and stamping stations, preventing stretching deformation or wrinkling of the coiled material due to asynchronous speeds.

[0022] In a preferred embodiment of the present invention, both drive roller group a11 and drive roller group b12 employ upper pressure rollers and lower support rollers arranged in pairs. The upper pressure rollers can be adjusted in position by a cylinder or a manual screw, thereby adjusting the clamping force on the coiled material to accommodate coiled materials of different thicknesses. Each roller in drive roller group a11 and drive roller group b12 is made of high-quality carbon steel with a chrome-plated surface, possessing high hardness and wear resistance, and capable of long-term stable operation.

[0023] Specific implementation of the unwinding structure

[0024] like Figure 2 As shown, the unwinding structure includes a mounting shaft 2 fixedly connected to one side of the machine body 1. The mounting shaft 2 extends horizontally outward and is used to mount the wound material. The wound material can rotate freely on the mounting shaft 2 to achieve passive unwinding. A detachable limiting baffle is provided at the end of the mounting shaft 2 to prevent the wound material from moving axially or falling off during the unwinding process.

[0025] A steering shaft a3 is fixedly installed on the support leg of the machine body 1. The steering shaft a3 is located below and behind the mounting shaft 2 and is used to change the direction of the coil from horizontal unwinding to upward conveying. Behind the steering shaft a3, the machine body 1 is also provided with a drive shaft assembly 4 that is mirror-aligned along the horizontal plane. The drive shaft assembly 4 consists of two parallel and relatively rotating drive shafts, with the gap between the two drive shafts adapted to the thickness of the coil. One drive shaft in the drive shaft assembly 4 is driven to rotate by a motor and a reducer, while the other drive shaft is a driven roller. The two work together to apply a certain clamping force to the coil passing through and provide auxiliary traction, so that the coil can be smoothly conveyed from the unwinding end to the subsequent station.

[0026] The bottom of the machine body 1 is also fixedly connected to an upwardly extending elastic rod 5. The elastic rod 5 is an arc-shaped elastic metal rod, the lower end of which is fixed to the bottom crossbeam of the machine body 1, and the upper end is a free end, which can elastically swing back and forth along the direction of the coil travel. The top of the machine body 1 is rotatably connected to a steering shaft b6, which is located at the upper front end of the machine body 1.

[0027] During unwinding, the coiled material is drawn out from the mounting shaft 2 and passes sequentially through the steering shaft a3, drive shaft assembly 4, elastic rod 5, and steering shaft b6 before being conveyed to the binding machine 8. As the coiled material passes through the aforementioned steering shafts and drive shaft assemblies, it maintains a flat, strip-like state without twisting or folding. The elastic rod 5 serves to store material and automatically adjust tension: when the speed of a subsequent station (such as the binding machine 8 or the stamping machine 14) changes instantaneously or stops briefly, the elastic rod 5 can absorb or release a certain length of coiled material through elastic deformation, thereby preventing the coiled material from breaking or loosening due to sudden tension changes, ensuring the continuity and stability of the entire machine's operation.

[0028] Specific implementation method of the ordering machine mechanism

[0029] like Figure 2As shown, the fastening machine 8 mechanism includes a fastening machine 8 mounted on the machine body 1. The fastening machine 8 uses a commercially available standard fastening head or a custom fastening head customized according to the fastener specifications. It is driven by a cylinder or hydraulic cylinder to reciprocate up and down, pressing and fastening the fastener onto the coil material. A feeding bracket 9 is provided below the fastening machine 8. The feeding bracket 9 is fixedly connected to the machine body 1. The upper end surface of the feeding bracket 9 is a flat horizontal support surface, used to support the coil material from below during the fastening operation, ensuring the accuracy of the fastening position and preventing the coil material from denting and deforming downwards during the stamping and fastening process.

[0030] A feeding channel 10 for conveying raw materials (i.e., fasteners) is also provided on one side of the fastening machine 8. The output end of the feeding channel 10 extends to the position below the fastening section of the fastening machine 8. The feeding channel 10 is an inclined chute or vibrating conveyor track used to sequentially convey fasteners to the fastening station. Under the action of gravity or vibration, the fasteners slide down along the feeding channel 10 and enter the output end directly below the punch of the fastening machine 8. Then, the fastening machine 8 punches and fixes the fasteners onto the coil. The input end of the feeding channel 10 is connected to a vibratory feeder or fastener hopper to realize automatic sorting and continuous feeding of fasteners.

[0031] During the binding process, the coil material is laid flat on the upper surface of the feeding bracket 9. The punch of the binding machine 8 moves downward, pressing the fastener located above the coil material onto the coil material, thus fixing the fastener to the coil material. The upper surface of the feeding bracket 9 has a clearance hole at a position corresponding to the punch of the binding machine 8 to accommodate the end of the punch's stroke and prevent the punch from colliding with the feeding bracket 9.

[0032] Detailed implementation of the support plate assembly

[0033] like Figure 2 As shown, a support plate assembly 7 is also vertically fixedly connected to the top of the body 1. The support plate assembly 7 includes support plate a71, support plate b72 and support plate c73.

[0034] A support plate a71 is positioned between the steering shaft b6 and the binding machine 8, with its two ends close to the feed sides of both the steering shaft b6 and the binding machine 8. The upper surface of the support plate a71 is simultaneously tangent to the upper tangent of the steering shaft b6 and the upper tangent of the drive roller assembly a11, ensuring that the coil material, after being output from the steering shaft b6, transitions horizontally and smoothly onto the worktable of the binding machine 8. The support plate a71 provides intermediate support for the coil material, preventing it from sagging due to its own weight between the steering shaft b6 and the binding machine 8, and ensuring that the coil material enters the binding station in a flat state.

[0035] Support plate b72 is positioned between the binding machine 8 and the drive roller group a11, with its two ends close to the discharge side of the binding machine 8 and the feed side of the drive roller group a11, respectively. The upper surface of support plate b72 is also tangent to the upper tangent of the steering shaft b6 and the drive roller group a11. Support plate b72 is used to receive the bound rolls output from the binding machine 8, smoothly guiding them to the feed inlet of the drive roller group a11, preventing the bound portion from bending due to suspension or scratching against the machine body 1.

[0036] A support plate c73 is positioned between the drive roller assembly a11 and the press 14, with its two ends close to the discharge side of the drive roller assembly a11 and the feed side of the press 14, respectively. The upper surface of the support plate c73 is also tangent to the upper tangent of the steering shaft b6 and the drive roller assembly a11. The support plate c73 is used to smoothly feed the coiled material, after being leveled and pulled by the drive roller assembly a11, into the die area of ​​the press 14.

[0037] Support plates a71, b72, and c73 are all made of stainless steel or galvanized steel with a thickness of 2-5mm. Their upper surfaces are ground to achieve a high degree of flatness. Each support plate is vertically fixed to the bracket at the top of the machine body 1 by bolts. The height position can be adjusted according to actual needs to ensure that the upper surface of each support plate is simultaneously tangent to the upper tangent of the steering shaft b6 and the drive roller group a11. By setting the upper surfaces of support plates a71, b72, and c73 to be simultaneously tangent to the steering shaft b6 and the drive roller group a11, it is ensured that all support points are at the same horizontal height throughout the entire conveying path of the coil from the steering shaft b6 through the mounting machine 8 to the drive roller group a11. The coil is always conveyed in a flat, straight state, avoiding bending, folding, or wrinkling of the coil due to height differences, thereby ensuring the product quality and mounting position accuracy of the subsequent stamping.

[0038] Detailed implementation of drive roller assembly

[0039] like Figure 1 As shown, drive roller group a11 and drive roller group b12 each consist of two rollers mirror-arranged along a horizontal plane, i.e., each drive roller group includes an upper roller and a lower roller, and the gap between the upper roller and the lower roller is used for the winding material to pass through. Each roller is rotatably mounted on the machine body 1 via bearing seats, and the bearing seats are fixedly connected to the machine body 1 by bolts.

[0040] Each roller in drive roller group a11 and drive roller group b12 has an inwardly facing groove 17 at its centerline. The groove 17 is circumferentially oriented and has a width of 5–15 mm and a depth of 2–8 mm, with the specific dimensions determined by the size of the fasteners already attached to the coil. When the coil passes through the gap between the rollers, the fasteners are precisely accommodated within the groove 17, allowing the cylindrical surface of the roller to directly press against the strip-shaped body of the coil without pressing on the protruding fasteners. This structural design ensures both the flattening and traction functions of the drive roller group on the coil and avoids damaging or crushing the fasteners, making it particularly suitable for the smooth transport of coils with fasteners already attached in subsequent workstations.

[0041] Drive roller group a11 and drive roller group b12 are connected by a transmission belt 13. Specifically, one roller in drive roller group a11 (such as the active upper roller) is connected to the corresponding roller in drive roller group b12 (such as the active upper roller) via the transmission belt 13, which is a synchronous toothed belt or a V-belt. The active roller of drive roller group a11 is driven to rotate by a motor, reducer and coupling, and the power is transmitted to the corresponding roller in drive roller group b12 via the transmission belt 13, realizing the synchronous operation of the two drive roller groups. Synchronous operation ensures that the conveying speed of the coil material between the binding machine 8 and the stamping machine 14 and on the discharge side of the stamping machine 14 is completely consistent, avoiding the stretching or accumulation of the coil material caused by the speed difference between the front and rear, and ensuring the accuracy of the stamping and cutting length.

[0042] In a preferred embodiment of the present invention, each roller in drive roller group a11 and drive roller group b12 is mounted on the machine body 1 via an independent bearing seat. An adjusting shim is provided between the bearing seat and the machine body 1 to adjust the gap between the upper and lower rollers to accommodate rolls of different thicknesses. The drive rollers of drive roller group a11 and drive roller group b12 are driven by the same servo motor. The servo motor is connected to an encoder, which can precisely control the rotation angle and speed of the rollers, thereby achieving precise quantitative feeding of the rolls. This, combined with the stamping frequency of the stamping press 14, enables equal-interval slitting.

[0043] Specific implementation methods of stamping mechanism

[0044] like Figure 3 As shown, the stamping machine 14 includes a stamping machine 14 mounted on the machine body 1 and a die support platform 15 that cooperates with the stamping machine 14. The stamping machine 14 is a pneumatic or hydraulic stamping machine, fixedly installed above the machine body 1, with its punch vertically downward. The die support platform 15 is fixedly installed on the machine body 1, located directly below the punch of the stamping machine 14, and is used to install the lower die. An upper die is installed on the punch of the stamping machine 14, and the upper die cooperates with the lower die to jointly realize the slitting and stamping operations of the rolled material.

[0045] A material discharge channel 16 is fixedly connected to the lower part of the mold support platform 15. The material discharge channel 16 is an inclined chute or pipe, with its upper end opening connected to the lower mold discharge hole on the mold support platform 15, and its lower end extending to the outside of the machine body 1 or to the collection container below. After the stamping machine 14 completes one stamping and cutting cycle, the formed product (i.e., the cut fastener or component) falls from the lower mold discharge hole into the material discharge channel 16 under the action of gravity, slides out of the machine body 1 along the material discharge channel 16, and enters the collection container, realizing the automatic collection of finished products.

[0046] When the stamping press 14 is working, the coil material is pushed into the die area of ​​the stamping press 14 by the drive roller group a11 at a set step length. The length of each entry is equal to the unfolded length of one product. The punch of the stamping press 14 moves downward, the upper and lower dies close, and the coil material is cut and stamped into individual products. After stamping is completed, the punch returns to its original position, and the drive roller group a11 and drive roller group b12 rotate synchronously by one step length, conveying the stamped portion of the coil material forward and simultaneously pulling the new coil material into the die area to enter the next stamping cycle.

[0047] Overall working principle and workflow

[0048] The complete workflow of the automatic roll material slitting and snapping forming integrated machine of the present invention is as follows:

[0049] First, the operator places the rolled material onto the mounting shaft 2, and then sequentially passes the starting end of the material around the bottom of the steering shaft a3, through the gap between the rollers of the drive shaft assembly 4, around the top of the elastic rod 5, and above the steering shaft b6. It is then laid flat on the support plate a71 and passes through the mounting section of the mounting machine 8, then flat on the support plate b72 and through the gap between the rollers of the drive roller assembly a11, then flat on the support plate c73 and through the die area of ​​the stamping machine 14, finally passing through the gap between the rollers of the drive roller assembly b12 and extending out of the machine body 1. Throughout the entire feeding process, the rolled material remains flat and does not twist.

[0050] After the equipment is started, the drive rollers of drive shaft assembly 4 and drive roller assembly a11 begin to rotate under the drive of the motor. Drive roller assembly b12 rotates synchronously with drive roller assembly a11 via transmission belt 13. The coil material is passively unwound from the mounting shaft 2 under the traction of drive shaft assembly 4, turned by steering shaft a3 and conveyed upward, then clamped and pulled by drive shaft assembly 4, passing over elastic rod 5 and steering shaft b6 before entering the mounting station. Mounting machine 8 operates at a set frequency, mounting the fasteners conveyed from feeding channel 10 onto the coil material in sequence. The mounted coil material enters drive roller assembly a11 via support plate b72, and under the flattening traction of drive roller assembly a11, enters stamping machine 14 via support plate c73. Stamping machine 14 operates at a set step length and frequency to cut and stamp the coil material. The finished product falls into the unloading channel 16 via mold support table 15 and is automatically discharged and collected. The remaining edge material of the coil material is pulled out of the machine body 1 by drive roller assembly b12.

[0051] During the above process, the elastic rod 5 automatically oscillates according to the changes in the coil tension, serving as a storage and buffer. The synchronous operation of drive roller group a11 and drive roller group b12 ensures constant speed conveying of the coil between the mounting and stamping processes, avoiding quality defects caused by speed mismatch. The grooves 17 on each roller of the drive roller group effectively avoid the fasteners already mounted on the coil, ensuring flattening and traction effects without damaging the fasteners. Support plates a71, b72, and c73 together ensure the flatness of the coil throughout the entire conveying path, eliminating positioning deviations caused by the coil drooping.

[0052] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0053] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An integrated automatic roll material slitting, buttoning, and forming machine, characterized in that: The unwinding structure is located on one side of the machine body (1). Behind the unwinding mechanism operation line, there are a binding machine (8) and a stamping machine (14) connected to the machine body (1). A drive roller group a (11) is set between the stamping machine (14) and the binding machine (8) in a mirror image along the horizontal plane. A drive roller group b (12) is also set on the discharge side of the stamping machine (14) in a mirror image along the horizontal plane. The drive roller group a (11) and the drive roller group b (12) operate synchronously to flatten the rolled material and provide it with forward driving force.

2. The automatic roll material slitting and buttoning integrated machine according to claim 1, characterized in that: Each roller in the drive roller group a (11) and drive roller group b (12) has an inward groove (17) at the center line position, and one of the drive roller group a (11) and drive roller group b (12) is connected by a transmission belt (13).

3. The automatic roll material slitting and buttoning integrated machine according to claim 1, characterized in that: The press (14) includes a press (14) mounted on the machine body (1) and a mold support platform (15) that cooperates with the press (14). A material feeding channel (16) is also fixedly connected below the mold support platform (15).

4. The automatic roll material slitting and buttoning integrated machine according to claim 3, characterized in that: The binding machine (8) includes a binding machine (8) mounted on the machine body (1) and a feeding bracket (9) fixedly connected to the machine body (1) below the binding machine (8). A feeding channel (10) for conveying raw materials is also provided on one side of the binding machine (8). The output end of the feeding channel (10) extends to the position below the binding part of the binding machine (8).

5. The automatic roll material slitting and buttoning forming integrated machine according to claim 4, characterized in that: The unwinding structure includes a mounting shaft (2) fixedly connected to one side of the machine body (1) and a steering shaft a (3) fixedly on the support leg of the machine body (1). The machine body (1) is also provided with a drive shaft group (4) mirror-mounted along the horizontal plane behind the steering shaft a (3). The bottom of the machine body (1) is also fixedly connected with an upwardly extending elastic rod (5). The top of the machine body (1) is also rotatably connected with a steering shaft b (6).

6. The automatic roll material slitting and buttoning integrated machine according to claim 5, characterized in that: The roll material is sequentially conveyed to the binding machine (8) after passing through the steering shaft a (3), drive shaft group (4), elastic rod (5) and steering shaft b (6), and the roll material is always in a flat state.

7. The automatic roll cutting and buttoning forming integrated machine according to claim 5, characterized in that: The top of the machine body (1) is also vertically fixedly connected to a support plate group (7). The support plate group (7) includes a support plate a (71) disposed between the steering shaft b (6) and the stitching machine (8), a support plate b (72) disposed between the stitching machine (8) and the drive roller group a (11), and a support plate c (73) disposed between the drive roller group a (11) and the stamping machine (14).

8. The automatic roll material slitting and buttoning integrated machine according to claim 7, characterized in that: The upper surfaces of the support plates a (71), b (72) and c (73) are all tangent to the steering shaft b (6) and the drive roller group a (11) at the same time.

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