Automatic rubber demolding mechanism

Abstract

The utility model discloses an automatic rubber demoulding mechanism which comprises a truss platform and a demoulding mechanism, the truss platform comprises a supporting frame, an X-axis ball screw, a Y-axis ball screw and a Z-axis ball screw, the X-axis ball screw is fixedly installed on the supporting frame, the Z-axis ball screw is fixedly installed on a sliding seat of the X-axis ball screw, and the Y-axis ball screw is fixedly installed on a sliding seat of the Z-axis ball screw. The Y-axis ball screw is fixedly mounted on a sliding seat of the Z-axis ball screw; the demolding mechanism comprises a truss connecting block, a first air cylinder and a hinge piece, the truss connecting block is fixedly installed on a sliding seat of the Y-axis ball screw, an installation frame is fixedly installed at the bottom of the truss connecting block, a clamping jaw disc is installed at the output end of the first air cylinder through a connecting piece, and the truss connecting block is hinged to the clamping jaw disc through the hinge piece; clamping jaws are installed at the bottom of the clamping jaw disc and used for clamping the rubber foot pad. According to the utility model, the manual operation can be effectively reduced, the labor intensity of workers can be reduced, and dangerous situations occurring when the workers directly demould can be reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of rubber product production, in particular to an automatic rubber demoulding mechanism. Background Art

[0002] After the production of rubber products is completed, the ambient temperature of the molds used to produce rubber products is 60-70℃. The weights of different types of rubber pads vary greatly. The rubber pads for agricultural machinery are relatively heavy, and the rubber and mold have high adsorption forces, so single-person operation is very difficult. Usually, two people are required to operate the pads, and the physical exertion of the operators is quite high, so the operators have a very hard time. Utility Model Content

[0003] The purpose of the utility model is to provide an automatic rubber demoulding mechanism to solve the problems raised in the above background technology.

[0004] To achieve the above purpose, the utility model provides the following technical solutions: an automated rubber demoulding mechanism, comprising a rack platform and a demoulding mechanism,

[0005] The travel platform comprises a support frame, an X-axis ball screw, a Y-axis ball screw and a Z-axis ball screw, wherein the X-axis ball screw is fixedly mounted on the support frame, the Z-axis ball screw is fixedly mounted on a sliding seat of the X-axis ball screw, and the Y-axis ball screw is fixedly mounted on a sliding seat of the Z-axis ball screw;

[0006] The demoulding mechanism comprises a rack connection block, a first cylinder and a hinge, wherein the rack connection block is fixedly mounted on the sliding seat of the Y-axis ball screw, a mounting frame is fixedly mounted on the bottom of the rack connection block, a mounting plate is fixedly mounted on the mounting frame, the first cylinder is fixedly mounted on the bottom of the mounting plate, a clamping plate is mounted on the output end of the first cylinder through a connecting member, and the rack connection block is hinged to the clamping plate through a hinge;

[0007] The bottom of the clamping claw plate is provided with a clamping claw, and the clamping claw is used to clamp the rubber foot pad.

[0008] In one embodiment of the utility model, the articulated component includes a guide rail, a slider plate slidably mounted on the guide rail, and an upper hinge fixedly mounted on the bottom of the slider plate, a lower hinge is fixedly mounted on the clamping jaw plate, the upper hinge is hinged to the lower hinge through a first rotating shaft, and the guide rail is fixedly mounted on the bottom of the mounting frame.

[0009] In an embodiment of the present utility model, the connecting member includes a second rotating shaft and a pin seat, the second rotating shaft is rotatably installed in a pin hole of the pin seat, and the second rotating shaft is rotatably connected to the output end of the first cylinder.

[0010] In one embodiment of the utility model, the clamp includes a second cylinder, a clamp body and a cylinder seat, the cylinder seat can be detachably mounted on the bottom of the clamp plate, the second cylinder can be detachably mounted on the clamp body, a driving block is fixedly mounted on the output end of the second cylinder, a strip hole is provided on the side of the driving block, a follower is installed in the clamp body, the driving block can drive the follower to move, and the follower is used to clamp the rubber foot pad.

[0011] In one embodiment of the utility model, the follower includes a first chain plate, a second chain plate, a clamping claw head for clamping a rubber foot pad, and a strip hole opened on the side of the driving block, the first chain plate and the second chain plate are rotatably installed in the clamping claw body through a first pin, the first chain plate is rotatably installed with a second pin at one end away from the first pin, the second pin is slidably installed in the strip hole, and the two ends of the second pin are pin-connected to the clamping claw head, the second chain plate is rotatably installed with a third pin at one end away from the first pin, and the two ends of the third pin are pin-connected to the clamping claw head.

[0012] In one embodiment of the utility model, a plurality of guide holes are formed on the clamping jaw plate, a guide block slidingly matched with the guide holes is fixedly connected to the upper portion of the cylinder seat, and a bolt for fixing the cylinder seat is threadedly mounted on the guide block.

[0013] In an embodiment of the utility model, scale lines are provided on the clamping jaw disk.

[0014] In an embodiment of the present invention, the width of the strip-shaped holes is set to 4-5 mm.

[0015] In an embodiment of the utility model, the clamping portion of the clamping jaw head is provided with convex teeth.

[0016] In summary, due to the adoption of the above technology, the beneficial effects of the utility model are:

[0017] 1. Through the cooperation of the first cylinder with the upper hinge, the lower hinge, the guide rail, the slider plate and the clamping claw, when the clamping claw clamps the rubber foot pad, the output end of the first cylinder contracts to drive the clamping claw to flip, and first lift up the two ends of the rubber foot pad to let air enter, destroying the vacuum when the rubber foot pad and the lower mold are tightly adsorbed. The first cylinder continues to drive the clamping claw plate to flip, and continues to pull the two ends of the rubber foot pad from the outside to the inside, thereby gradually separating the rubber foot pad from the lower mold. Finally, the center section that has not been detached uses the sliding block of the Z-axis ball screw to move upward to drive the clamping claw plate to rise, thereby completely lifting the rubber foot pad, which can effectively reduce manual operation, reduce the labor intensity of workers, and reduce the occurrence of dangerous situations when workers directly demould.

[0018] 2. When clamping the rubber foot pad, open the second cylinder, retract the output end of the second cylinder, drive the driving block to rise, pull the second pin, make the first chain plate and the second chain plate rotate around the first pin, make the two clamping claws approach, drive the clamping claws to perform a closed clamping action, and clamp the mesh ribs on the back of the rubber foot pad;

[0019] After demoulding is completed, the support frame is moved from above the lower mold to above the assembly line through the robotic arm, and the output end of the second cylinder extends out, driving the second pin to move in the strip hole in the direction away from the center of the driving block, so that the first chain plate and the second chain plate rotate downward with the first pin as the axis, so that the two clamping claws move away from each other, thereby loosening the rubber foot pad, and the rubber foot pad falls onto the assembly line and flows out, which can reduce manual operation, automatically separate the rubber foot pad from the clamping claw, effectively reduce manual physical expenditure, and can automatically perform demoulding operations, which can effectively improve work efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of the utility model;

[0021] Figure 2 This is an axonometric schematic diagram of the mounting frame of the utility model;

[0022] Figure 3 This is an axonometric diagram of a rack connection block of the utility model;

[0023] Figure 4 This is a schematic diagram of the axonometric measurement of the guide rail of the utility model;

[0024] Figure 5 This is an axonometric schematic diagram of the cylinder seat of the utility model;

[0025] Figure 6 This is an axonometric schematic diagram of the first chain plate of the utility model;

[0026] Figure 7 It is an axonometric schematic diagram of the clamping jaw head of the present utility model.

[0027] In the figure: 1, the platform; 2, the demoulding mechanism; 3, the support frame; 4, the X-axis ball screw; 5, the Y-axis ball screw; 6, the Z-axis ball screw; 7, the connecting block of the frame; 8, the first cylinder; 9, the mounting frame; 10, the mounting plate; 11, the clamping plate; 12, the clamping jaw; 13, the guide rail; 14, the slider plate; 15, the upper hinge; 16, the lower hinge; 17, the first rotating shaft; 18, the second rotating shaft; 19 , pin seat; 20, second cylinder; 21, jaw body; 22, cylinder seat; 23, drive block; 24, strip hole; 25, follower; 26, first chain plate; 27, second chain plate; 28, first pin; 29, second pin; 30, jaw head; 31, third pin; 32, guide hole; 33, guide block; 34, bolt; 35, scale line; 36, convex tooth; 37, rubber foot pad. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the embodiments of the utility model clearer, the technical scheme in the embodiments of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiments of the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the utility model. Therefore, the following detailed description of the embodiments of the utility model provided in the drawings is not intended to limit the scope of the utility model for which protection is sought, but merely represents the selected embodiments of the utility model. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the utility model.

[0029] In the description of the present invention, it is necessary to understand that the terms indicating orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0030] In the present invention, unless otherwise clearly specified and limited, the terms "install", "connect", "connect", "fix" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances of the specification.

[0031] Example 1

[0032] See also Figure 1-Figure 7 The utility model provides an automatic rubber demoulding mechanism, comprising a rack platform 1 and a demoulding mechanism 2.

[0033] The traveling platform 1 includes a support frame 3, an X-axis ball screw 4, a Y-axis ball screw 5 and a Z-axis ball screw 6, wherein the X-axis ball screw 4 is fixedly mounted on the support frame 3, the Z-axis ball screw 6 is fixedly mounted on the sliding seat of the X-axis ball screw 4, and the Y-axis ball screw 5 is fixedly mounted on the sliding seat of the Z-axis ball screw 6;

[0034] The demoulding mechanism 2 includes a rack connection block 7, a first cylinder 8 and a hinge. The rack connection block 7 is fixedly mounted on the sliding seat of the Y-axis ball screw 5. A mounting frame 9 is fixedly mounted on the bottom of the rack connection block 7. A mounting plate 10 is fixedly mounted on the mounting frame 9. The first cylinder 8 is fixedly mounted on the bottom of the mounting plate 10. A clamping plate 11 is mounted on the output end of the first cylinder 8 through a connecting piece. The rack connection block 7 is hinged to the clamping plate 11 through a hinge.

[0035] A clamping claw 12 is installed at the bottom of the clamping claw plate 11, and the clamping claw 12 is used to clamp the rubber foot pad;

[0036] The hinged member includes a guide rail 13, a slider plate 14 slidably mounted on the guide rail 13, and an upper hinge 15 fixedly mounted on the bottom of the slider plate 14. A lower hinge 16 is fixedly mounted on the clamping claw plate 11. The upper hinge 15 is hinged to the lower hinge 16 via a first rotating shaft 17. The guide rail 13 is fixedly mounted on the bottom of the mounting frame 9.

[0037] The connecting member includes a second rotating shaft 18 and a pin seat 19 . The second rotating shaft 18 is rotatably mounted in a pin hole of the pin seat 19 . The second rotating shaft 18 is rotatably connected to the output end of the first cylinder 8 .

[0038] It should be noted that the support frame 3 is used to provide support for the X-axis ball screw 4, the Y-axis ball screw 5 and the Z-axis ball screw 6, and is mounted on the mold body of the lower mold when the rubber foot pad is demoulded.

[0039] By adopting the above scheme, through the cooperation of the first cylinder 8 with the upper hinge 15, the lower hinge 16, the guide rail 13, the slider plate 14 and the clamping jaw 12, when the clamping jaw 12 clamps the rubber foot pad, the output end of the first cylinder 8 contracts to drive the clamping jaw 12 to flip, and first lift up the two ends of the rubber foot pad to allow air to enter, thereby destroying the vacuum when the rubber foot pad and the lower mold are tightly adsorbed. The first cylinder 8 continues to drive the clamping jaw plate 11 to flip, and continues to pull the two ends of the rubber foot pad from the outside to the inside, thereby gradually separating the rubber foot pad from the lower mold, and finally the center section that has not been detached uses the sliding block of the Z-axis ball screw 6 to move upward to drive the clamping jaw plate 11 to rise, thereby completely lifting the rubber foot pad, which can effectively reduce manual operation, reduce the labor intensity of workers, and reduce the occurrence of dangerous situations when workers directly demold.

[0040] In this embodiment, the clamping jaw 12 includes a second cylinder 20, a clamping jaw body 21 and a cylinder seat 22. The cylinder seat 22 can be detachably mounted on the bottom of the clamping jaw plate 11. The second cylinder 20 can be detachably mounted on the clamping jaw body 21. A driving block 23 is fixedly mounted on the output end of the second cylinder 20. A strip hole 24 is opened on the side of the driving block 23. A follower 25 is installed in the clamping jaw body 21. The driving block 23 can drive the follower 25 to move. The follower 25 is used to clamp the rubber foot pad.

[0041] The follower 25 includes a first chain plate 26, a second chain plate 27, a clamping claw head 30 for clamping a rubber foot pad, and a strip hole 24 opened on the side of the driving block 23. The first chain plate 26 and the second chain plate 27 are rotatably installed in the clamping claw body 21 through a first pin 28. The end of the first chain plate 26 away from the first pin 28 is rotatably installed with a second pin 29, and the second pin 29 is slidably installed in the strip hole 24. The width of the strip hole 24 is set to 4-5mm, and the two ends of the second pin 29 are pin-connected to the clamping claw head 30. The end of the second chain plate 27 away from the first pin 28 is rotatably installed with a third pin 31, and the two ends of the third pin 31 are pin-connected to the clamping claw head 30.

[0042] By adopting the above scheme, when performing the clamping operation of the rubber foot pad, the second cylinder 20 is opened, the output end of the second cylinder 20 is retracted, the driving block 23 is driven to rise, the second pin 29 is pulled up, the first chain plate 26 and the second chain plate 27 are rotated around the first pin 28 as the axis, the two clamping claw heads 30 are brought close, and the clamping claw heads 30 are driven to perform a closed clamping action, and the mesh ribs on the back of the rubber foot pad are clamped;

[0043] After demoulding is completed, the support frame 3 is moved from above the lower mold to above the assembly line through the robotic arm, and the output end of the second cylinder 20 extends out, driving the second pin 29 to move in the strip hole in the direction away from the center of the driving block 23, so that the first chain plate 26 and the second chain plate 27 rotate downward with the first pin 28 as the axis, so that the two clamping claw heads 30 are separated, thereby loosening the rubber foot pad, and the rubber foot pad falls onto the assembly line and flows out, which can reduce manual operation and automatically separate the rubber foot pad from the clamping claw 12, effectively reducing manual physical expenditure, and can automatically perform demoulding operations, which can effectively improve work efficiency.

[0044] In this embodiment, a plurality of guide holes 32 are formed on the clamping jaw plate 11, and a guide block 33 that slidably cooperates with the guide holes 32 is fixedly connected to the upper portion of the cylinder seat 22, and a bolt 34 for fixing the cylinder seat 22 is threadedly mounted on the guide block 33.

[0045] It should be noted that there are no less than eight guide holes.

[0046] By adopting the above scheme, through the coordinated use of the guide block 33 and the guide hole 32, when demolding rubber pads of different sizes, the guide block 33 can be slid in the guide block 32 according to the size of the rubber pad, and the position of the cylinder seat 22 can be adjusted, thereby adjusting the position of the clamping jaw 12, so as to meet the demolding operation of rubber pads of various sizes, and can effectively improve the applicability of the equipment.

[0047] In this embodiment, scale lines 35 are provided on the clamping jaw plate 11 .

[0048] It should be noted that when demolding rubber foot pads of various sizes, the installation position of the guide block can be adjusted according to the scale line, so that the staff can quickly determine it.

[0049] In this embodiment, the clamping portion of the clamping jaw head 30 is provided with protruding teeth 36 .

[0050] By adopting the above solution, through the use of the convex teeth 36, when the two clamping jaws 30 are closed, the convex teeth 36 can stably clamp the rubber foot pad, which can effectively prevent the rubber foot pad from loosening during the demoulding process.

[0051] Working principle:

[0052] After the mold is opened, the robot moves the platform 1 to the top of the mold. At this time, the gripper heads 30 are all in the open state. The X-axis ball screw 4, the Y-axis ball screw 5 and the Z-axis ball screw 6 are operated to adjust the position of the gripper plate 11 so that the gripper 12 is located above the rubber foot pad. The Z-axis ball screw 6 lowers the gripper plate 11 to the height at which the gripper grabs. The second cylinder 20 is opened to retract the output end of the second cylinder 20, drive the drive block 23 to rise, and pull up the second pin 29 to make the first chain plate The first pin 28 is used as the axis of rotation of the first and second chain plates 26 and 27, so that the two clamping claw heads 30 are close to each other, driving the clamping claw heads 30 to perform a closed clamping action, clamping the mesh ribs on the back of the rubber foot pad, and then controlling the output end of the first cylinder 8 to be retracted, driving the entire clamping claw plate to rotate around the first rotating shaft 17 as the axis. At the same time, the upper hinge 15 is connected to the slider and moves inward along the guide rail 13. The clamping claws tightly grasp the rubber foot pad and lift it upward. During this action, the two ends of the rubber foot pad are first lifted to allow air to enter. The rubber pad is pushed into the mold, destroying the vacuum when the rubber pad and the lower mold are tightly adsorbed. The first cylinder 8 continues to drive the clamping claw plate 11 to flip, and continues to pull the two ends of the rubber pad from the outside to the inside, thereby gradually separating the rubber pad from the lower mold. Finally, the center section that has not been detached uses the sliding block of the Z-axis ball screw 6 to move upward to drive the clamping claw plate 11 to rise, thereby completely lifting the rubber pad and making the entire rubber pad separate from the mold. After lifting to a certain distance, the output end of the first cylinder 8 extends again, and the rubber pad follows the clamping claw plate to flatten. The support frame 3 moves from the top of the lower mold to the top of the assembly line through the robotic arm. The output end of the second cylinder 20 extends, driving the second pin 29 to move in the strip hole in the direction away from the center of the driving block 23, so that the first chain plate 26 and the second chain plate 27 rotate downward with the first pin 28 as the axis, so that the two clamping claw heads 30 are separated, thereby loosening the rubber pad, and the rubber pad falls on the assembly line and flows out. The robotic arm drives the rack platform 1 to move to the edge of the press again, ready for the next mold to grab.

[0053] It should be noted that when the output end of the first cylinder has contracted to the right position, the position sensor installed on the side of the first cylinder senses it and transmits the signal to the PLC controller. The PLC controller controls the robotic arm to lift the rack platform upward to complete the separation of the middle section of the product from the mold, so that the entire rubber foot pad is separated from the mold. After lifting to a certain distance, the output end of the first cylinder extends again to flatten the entire demoulding mechanism 2. When the position sensor installed on the side of the first cylinder detects the signal, the output end of the first cylinder has been pushed to the bottom. The position sensor transmits the signal to the PLC controller again, and the PLC controller gives an instruction to the robotic arm to move the rack platform 1 away from the top of the lower mold.

[0054] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes within the technical scope disclosed by the present invention according to the technical scheme and the utility model concept of the present invention, which should be covered by the protection scope of the present invention.

[0055] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

Claims

1. An automated rubber demoulding mechanism, comprising a rack platform (1) and a demoulding mechanism (2), characterized in that: The traveling platform (1) comprises a support frame (3), an X-axis ball screw (4), a Y-axis ball screw (5) and a Z-axis ball screw (6), wherein the X-axis ball screw (4) is fixedly mounted on the support frame (3), the Z-axis ball screw (6) is fixedly mounted on a sliding seat of the X-axis ball screw (4), and the Y-axis ball screw (5) is fixedly mounted on a sliding seat of the Z-axis ball screw (6); The demoulding mechanism (2) comprises a rack connection block (7), a first cylinder (8) and a hinge, wherein the rack connection block (7) is fixedly mounted on the sliding seat of the Y-axis ball screw (5), a mounting frame (9) is fixedly mounted on the bottom of the rack connection block (7), a mounting plate (10) is fixedly mounted on the mounting frame (9), the first cylinder (8) is fixedly mounted on the bottom of the mounting plate (10), a clamping plate (11) is mounted on the output end of the first cylinder (8) via a connecting member, and the rack connection block (7) is hinged to the clamping plate (11) via a hinge; A clamping claw (12) is installed at the bottom of the clamping claw plate (11), and the clamping claw (12) is used to clamp the rubber foot pad.

2. The automatic rubber demoulding mechanism according to claim 1, characterized in that: The hinged member comprises a guide rail (13), a slider plate (14) slidably mounted on the guide rail (13), and an upper hinge (15) fixedly mounted on the bottom of the slider plate (14); a lower hinge (16) is fixedly mounted on the clamping claw plate (11); the upper hinge (15) is hingedly connected to the lower hinge (16) via a first rotating shaft (17); and the guide rail (13) is fixedly mounted on the bottom of the mounting frame (9).

3. The automatic rubber demoulding mechanism according to claim 1, characterized in that: The connecting member comprises a second rotating shaft (18) and a pin seat (19); the second rotating shaft (18) is rotatably mounted in a pin hole of the pin seat (19); and the second rotating shaft (18) is rotatably connected to an output end of the first cylinder (8).

4. The automatic rubber demoulding mechanism according to claim 1, characterized in that: The clamping jaw (12) comprises a second cylinder (20), a clamping jaw body (21) and a cylinder seat (22); the cylinder seat (22) can be detachably mounted on the bottom of the clamping jaw plate (11); the second cylinder (20) can be detachably mounted on the clamping jaw body (21); a driving block (23) is fixedly mounted on the output end of the second cylinder (20); a strip hole (24) is provided on the side of the driving block (23); a follower (25) is installed in the clamping jaw body (21); the driving block (23) can drive the follower (25) to move; and the follower (25) is used to clamp the rubber foot pad.

5. The automatic rubber demoulding mechanism according to claim 4, characterized in that: The driven member (25) comprises a first chain plate (26), a second chain plate (27), a clamping claw head (30) for clamping a rubber foot pad, and a strip hole (24) provided on the side of the driving block (23); the first chain plate (26) and the second chain plate (27) are rotatably mounted in the clamping claw body (21) through a first pin (28); a second pin (29) is rotatably mounted on one end of the first chain plate (26) away from the first pin (28); the second pin (29) is slidably mounted in the strip hole (24), and both ends of the second pin (29) are pin-connected to the clamping claw head (30); a third pin (31) is rotatably mounted on one end of the second chain plate (27) away from the first pin (28); and both ends of the third pin (31) are pin-connected to the clamping claw head (30).

6. The automatic rubber demoulding mechanism according to claim 4, characterized in that: The clamping jaw plate (11) is provided with a plurality of guide holes (32); the upper portion of the cylinder seat (22) is fixedly connected with a guide block (33) that is slidably matched with the guide holes (32); and the guide block (33) is threadedly mounted with bolts (34) for fixing the cylinder seat (22).

7. The automatic rubber demoulding mechanism according to claim 1, characterized in that: The clamping jaw plate (11) is provided with scale lines (35).

8. The automatic rubber demoulding mechanism according to claim 4, characterized in that: The width of the strip-shaped holes (24) is set to 4-5 mm.

9. The automatic rubber demoulding mechanism according to claim 5, characterized in that: The clamping portion of the clamping claw head (30) is provided with convex teeth (36).

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