Clamping device for prebaked anode carbon block production

Abstract

The utility model relates to the technical field of prebaked anode carbon block production equipment, and discloses a clamping device for prebaked anode carbon block production, which comprises a transverse plate and clamping plates, the front side and the rear side of the bottom of the transverse plate are fixedly connected with guide rods, and the two clamping plates are in sliding connection with the two guide rods. A bidirectional threaded rod is rotationally connected to the middle of the bottom end of the transverse plate, a transmission assembly is arranged at the top of the transverse plate, grooves are formed in the adjacent sides of the two clamping plates, protection pads are arranged on the inner walls of the two grooves, and clamping mechanisms are arranged on the outer walls of the two grooves. According to the device, the first motor is matched with the gear and the two-way threaded rod, the clamping plate can flexibly move and accurately adapt to carbon blocks with different widths, the second motor drives the supporting plate and the sliding plate to rotate, after the sliding plate is in magnetic connection with the electromagnet, the carbon blocks can be supported from the bottom of the device, the carbon blocks are prevented from falling off, and the production reliability is greatly improved.

Description

Technical Field

[0001] This utility model relates to the technical field of prebaked anode carbon block production equipment, and in particular to a clamping device for prebaked anode carbon block production. Background Technology

[0002] Prebaked anode carbon blocks are a key consumable material in aluminum electrolysis production and play an extremely important role in aluminum electrolysis cells. During the production process of prebaked anode carbon blocks, it is often necessary to handle, transfer, and position the carbon blocks during processing. Therefore, a clamping device for the production of prebaked anode carbon blocks is required.

[0003] Traditional clamping devices for prebaked anode carbon block production mainly consist of cylinders and clamping plates. The cylinder extends to push the clamping plates closer to the anode carbon block, thereby clamping it. However, due to the limited extension length of the cylinder, it can only clamp anode carbon blocks of a single specification. Existing technology uses a lead screw in conjunction with the clamping plates, which allows for flexible adjustment of the distance between the two clamping plates to clamp anode carbon blocks of different specifications. However, during the process, after the clamping plates clamp the anode carbon blocks, they need to be transferred to a designated area. During the transfer, since the bottom of the anode carbon blocks is not supported, they may fall during the transfer, causing production losses and reducing the practicality of the device. Utility Model Content

[0004] To overcome the above shortcomings, this utility model provides a clamping device for the production of prebaked anode carbon blocks, which aims to improve the problem in the prior art where the anode carbon blocks fall off during transportation due to the lack of support at the bottom, causing production losses and reducing the practicality of the device.

[0005] To achieve the above objectives, this utility model adopts the following technical solution: a clamping device for producing prebaked anode carbon blocks, comprising a horizontal plate and clamping plates. Guide rods are fixedly connected to the front and rear sides of the bottom of the horizontal plate. The two clamping plates are slidably connected to the two guide rods. A bidirectional threaded rod is rotatably connected to the center of the bottom end of the horizontal plate. A transmission assembly is provided at the top of the horizontal plate. Grooves are formed on adjacent sides of the two clamping plates. Protective pads are provided on the inner walls of the two grooves. A locking mechanism is provided on the outer walls of the two grooves. The locking mechanism is used to quickly connect the protective pads to the grooves. The right side... A fixing plate is fixedly connected to the right side of the outer wall of the clamping plate. A support plate is rotatably connected between two adjacent fixing plates. A sliding plate is slidably connected to the inner wall of the two support plates. Bolts are threadedly connected to the front and rear sides of the outer wall of the two support plates. A second motor is fixedly connected to the front side of the outer wall of the front fixing plate. The output end of the second motor passes through the front fixing plate and is fixedly connected to the support plate. An electromagnet is fixedly connected to the bottom of the left clamping plate. A telescopic rod is fixedly connected to the top of the horizontal plate. A mounting plate is fixedly connected to the top of the telescopic rod. Two reserved slots are opened on the front and rear sides of the inner wall of the multiple grooves.

[0006] As a further description of the above technical solution:

[0007] The card and mechanism include multiple card blocks, which are slidably connected to the inner wall of the corresponding reserved slots. A spring is fixedly connected to the far end of each card block, and both ends of the spring are fixedly connected to the corresponding card block. A connecting rod is fixedly connected to the far end of each card block, and the far end of the connecting rod passes through the corresponding clamp and is rotatably connected to a pull ring. Card slots are provided on the front and rear sides of the outer walls of the two protective pads, and the multiple card blocks are respectively engaged with the corresponding card slots.

[0008] As a further description of the above technical solution:

[0009] The transmission assembly includes a motor, which is fixedly connected to the top right side of the horizontal plate. The output end of the motor and the right end of the bidirectional threaded rod are both fixedly connected with gears, and the two gears are meshed together.

[0010] As a further description of the above technical solution:

[0011] A rubber pad is fixedly connected to the top of the mounting plate, and screws are threaded around the bottom of the mounting plate, with the tips of the screws penetrating the rubber pad.

[0012] As a further description of the above technical solution:

[0013] A mounting box is fixedly connected to the top left side of the horizontal plate, and an alarm is fixedly connected to the inner wall of the mounting box.

[0014] As a further description of the above technical solution:

[0015] An information board is provided on the front side of the outer wall of the horizontal plate. Two screws are threadedly connected to the left and right sides of the outer wall of the information board, and the rear ends of the two screws are threadedly connected to the horizontal plate.

[0016] As a further description of the above technical solution:

[0017] A controller is fixedly connected to the left side of the outer wall of the left-side clamping plate, and the controller is electrically connected to the first motor and the second motor.

[0018] As a further description of the above technical solution:

[0019] The bolt has a cross groove at its front end, and the surface of the bolt is smoothed.

[0020] This utility model has the following beneficial effects:

[0021] In this invention, motor one, in conjunction with gears and a bidirectional threaded rod, allows the clamping plate to move flexibly and precisely adapt to carbon blocks of different widths. Motor two drives the support plate and sliding plate to rotate, so that after the sliding plate is magnetically connected to the electromagnet, it can support the carbon block from the bottom of the device, effectively preventing the carbon block from falling. This comprehensively ensures the safety and stability of the carbon block during the clamping process and greatly improves the reliability of production.

[0022] In this invention, the protective pad is quickly and securely fixed by simply aligning and pushing the spring, without the need for complicated tools, ensuring the protection of the carbon block surface. When replacing, pulling the pull ring separates the card from the card slot, making it easy to remove. This convenient and quick solution can meet the need for replacement of the protective pad due to wear and tear, improving the ease of use and the continuity of protection of the device. Attached Figure Description

[0023] Figure 1 This is a perspective view of a clamping device for producing prebaked anode carbon blocks according to the present invention;

[0024] Figure 2 This is a partial structural schematic diagram of a clamping device for producing prebaked anode carbon blocks according to the present invention;

[0025] Figure 3 This is a schematic diagram of the clamping device and mechanism for producing prebaked anode carbon blocks according to this utility model;

[0026] Figure 4This is a front view of a clamping device for producing prebaked anode carbon blocks according to the present invention;

[0027] Figure 5 This is a side view of a clamping device for producing prebaked anode carbon blocks according to the present invention.

[0028] Legend:

[0029] 1. Horizontal plate; 2. Clip and mechanism; 201. Clip block; 202. Spring; 203. Connecting rod; 204. Pull ring; 205. Slot; 3. Clamping plate; 4. Guide rod; 5. Two-way threaded rod; 6. Gear; 7. Motor 1; 8. Reserved slot; 9. Groove; 10. Protective pad; 11. Fixing plate; 12. Support plate; 13. Slide plate; 14. Bolt; 15. Motor 2; 16. Electromagnet; 17. Telescopic rod; 18. Mounting plate; 19. Rubber pad; 20. Screw 1; 21. Mounting box; 22. Alarm; 23. Information board; 24. Screw 2; 25. Controller; 26. Cross slot. Detailed Implementation

[0030] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0031] Reference Figure 1 , Figure 2 and Figure 4This utility model provides an embodiment of a clamping device for producing prebaked anode carbon blocks, comprising a horizontal plate 1 and clamping plates 3. The horizontal plate 1 serves as a basic support structure, stably supporting other components. The clamping plates 3 are directly responsible for clamping the prebaked anode carbon blocks. The two clamping plates 3 are slidably connected to two guide rods 4. This connection method gives the clamping plates 3 good mobility and can effectively adapt to the clamping requirements of prebaked anode carbon blocks of different widths. A bidirectional threaded rod 5 is provided at the bottom center of the horizontal plate 1 in a rotatable connection. During rotation, the bidirectional threaded rod 5, through its unique thread structure, cooperates with the clamping plates 3 to precisely drive the clamping plates 3 to move in opposite directions, thereby flexibly controlling the clamping or loosening force on the carbon blocks. The top of the horizontal plate 1 is equipped with a transmission assembly. Grooves 9 are provided on opposite sides of the two clamping plates 3, providing installation space for the protective pads 10. Protective pads 10 are installed on the inner walls of the two grooves 9 to buffer the pressure between the clamping plates 3 and the carbon block, ensuring the quality of the carbon block. Clips and mechanisms 2 are provided on the outer walls of the two grooves 9, used for quick and secure connection between the protective pads 10 and the grooves 9. A fixing plate 11 is fixedly connected to the right side of the outer wall of the right clamping plate 3, providing a stable installation base for the subsequently connected support plate 12, ensuring that the support plate 12 can rotate stably. The support plate 12 is rotatably connected between the opposite sides of the two fixing plates 11, rotating under the drive of motor 15, providing a driving force for the slide plate 13. The system includes a motion track and a support platform. The inner walls of two support plates 12 are slidably connected to a sliding plate 13, allowing the sliding plate 13 to slide flexibly on the inner walls of the support plates 12 to adjust its position and effectively support the bottom of the charcoal block. Bolts 14 are threaded onto the front and rear sides of the outer walls of the two support plates 12. The bolts 14 can be used to adjust the sliding position of the sliding plate 13 within the support plates 12. By tightening or loosening the bolts 14, the position of the sliding plate 13 can be precisely controlled to adapt to the bottom support requirements of charcoal blocks of different sizes. A second motor 15 is fixedly connected to the front side of the outer wall of the front fixed plate 11. The second motor 15 serves as a power source, providing driving force for the rotation of the support plates 12 to ensure that the support plates 12 can rotate according to predetermined requirements. The output end of the second motor 15... The front fixed plate 11 is fixedly connected to the support plate 12. This connection method ensures that the power of the motor 15 can be efficiently transmitted to the support plate 12, so as to realize the stable rotation of the support plate 12. The bottom of the left clamping plate 3 is fixedly connected to the electromagnet 16, which is magnetically connected to the slide plate 13. When the slide plate 13 rotates to a specific position, the two attract each other, thereby providing stable support for the carbon block from the bottom. The top of the horizontal plate 1 is fixedly connected to the telescopic rod 17, and the top of the telescopic rod 17 is fixedly connected to the mounting plate 18. Two reserved slots 8 are opened on the front and rear sides of the inner wall of the multiple grooves 9. The reserved slots 8 cooperate with the card and mechanism 2 to facilitate the quick installation and removal of the protective pad 10, making the replacement operation of the protective pad 10 simpler and faster.The transmission assembly includes a motor 7, which is fixedly connected to the top right side of the horizontal plate 1. The output end of the motor 7 and the right end of the bidirectional threaded rod 5 are both fixedly connected to gears 6, and the two gears 6 are meshed together.

[0032] Specifically, starting motor 7 causes the output of motor 7 to drive the right gear 6 to rotate. Since the two gears 6 mesh with each other, the right gear 6 drives the left gear 6 to rotate, which in turn causes the bidirectional threaded rod 5 to rotate. The bidirectional threaded rod 5 is rotatably connected to the horizontal plate 1. During its rotation, because the two clamping plates 3 are slidably connected to the guide rod 4 and threadedly engaged with the bidirectional threaded rod 5, the two clamping plates 3 will move towards or away from each other along the guide rod 4, achieving the clamping and releasing action of prebaked anode carbon blocks of different widths. When the clamping plates 3 approach the carbon block, the groove 9... The protective pad 10 first contacts the carbon block. The protective pad 10 is quickly connected to the inner wall of the groove 9 through the clip and mechanism 2, which can prevent the surface of the carbon block from being damaged. Then, the second motor 15 is started. The output end of the second motor 15 drives the support plate 12 to rotate. During the rotation of the support plate 12, the slide plate 13, which is slidably connected to its inner wall, rotates accordingly. When the slide plate 13 rotates to the position corresponding to the electromagnet 16, the slide plate 13 is magnetically connected to the electromagnet 16. At this time, the slide plate 13 supports the anode carbon block between the clamping plates 3 from the bottom of the device, effectively preventing the carbon block from falling.

[0033] Reference Figure 1 , Figure 2 and Figure 5 The card and mechanism 2 includes multiple card blocks 201. Each card block 201 is a component that directly engages with the card slot 205 of the protective pad 10. The multiple card blocks 201 are slidably connected to the inner wall of their respective reserved slots 8. The reserved slots 8 provide a sliding track for the card blocks 201, ensuring that the card blocks 201 can move in a specific direction. Springs 202 are fixedly connected to the opposite ends of each of the multiple card blocks 201. The springs 202 provide elastic restoring force to the card blocks 201, allowing them to return to their initial position after being subjected to external force. Both ends of the multiple springs 202 are fixedly connected to the corresponding card blocks 201. Each is fixedly connected with a connecting rod 203, which is used to connect the locking block 201 to the pull ring 204, so that the operator can operate the locking block 201 through the pull ring 204. The far ends of the multiple connecting rods 203 all pass through the corresponding clamping plate 3 and are rotatably connected to the pull ring 204. The pull ring 204 is easy for the operator to pull by hand. By pulling the pull ring 204, the locking block 201 can be moved to slide in the reserved groove 8, so as to separate or engage the locking block 201 with the groove 205. The outer walls of the two protective pads 10 are provided with grooves 205 on the front and back sides, and the multiple locking blocks 201 engage with the corresponding grooves 205 respectively.

[0034] Specifically, when the protective pad 10 needs to be installed, first align the protective pad 10 with the groove 9 and push the protective pad 10 into the groove 9. When the protective pad 10 is pushed into the groove 9, the protective pad 10 will first squeeze the locking block 201, causing the locking block 201 to squeeze the spring 202 and enter the reserved slot 8. When the slot 205 moves to coincide with the locking block 201, the locking block 201 is pushed into the slot 205 under the force of the spring 202, thereby fixing the protective pad 10. This connection method is simple to operate and can quickly realize the installation of the protective pad 10. If the protective pad 10 needs to be replaced, pull the pull ring 204 again to separate the locking block 201 from the slot 205, and the protective pad 10 can be easily removed.

[0035] Reference Figure 1 , Figure 3 and Figure 4 A rubber pad 19 is fixedly connected to the top of the mounting plate 18, and screws 20 are threaded around the bottom of the mounting plate 18. The tops of the screws 20 all penetrate the rubber pad 19. The rubber pad 19 can buffer external vibration and prevent the equipment connected to the mounting plate 18 from being damaged by impact. A mounting box 21 is fixedly connected to the top left side of the horizontal plate 1, and an alarm 22 is fixedly connected to the inner wall of the mounting box 21. When the clamping device malfunctions, the alarm 22 receives a signal and activates to sound an alarm to remind the operator, ensuring production safety and normal equipment operation.

[0036] Specifically, the rubber pad 19 on the top of the mounting plate 18 is fixed by screws 20 around the bottom. The rubber pad 19 can buffer external vibrations and prevent the mounting plate 18 from being damaged by impact when connected to the equipment. The mounting box 21 is fixed on the top left side of the horizontal plate 1. The internal alarm 22 is used to monitor abnormalities. When the clamping device malfunctions, the alarm 22 receives a signal and activates to alert the operator, ensuring production safety and normal equipment operation.

[0037] Reference Figure 1 , Figure 2 and Figure 3 An information board 23 is installed on the front side of the outer wall of the horizontal plate 1. The information board 23 is threaded to the horizontal plate 1 by screws 24 on the left and right sides, which facilitates the recording of device parameters and makes it convenient for operators to view. Screws 24 are threaded on both the left and right sides of the outer wall of the information board 23, and the rear ends of the two screws 24 are threaded to the horizontal plate 1. A controller 25 is fixedly connected to the left side of the outer wall of the left clamping plate 3. The controller 25 is electrically connected to motor 7 and motor 15. The controller 25 can accurately control the operation of motor 7 and motor 15 to control the opening and closing of the clamping plate 3 and the supporting action of the slide plate 13. The front end of the bolt 14 has a cross groove 26. The surface of the bolt 14 is smoothed. The cross groove 26 at the front end of the bolt 14 is adapted to a Phillips screwdriver for easy tightening or loosening. The smooth surface treatment reduces frictional resistance during operation and improves adjustment efficiency.

[0038] Specifically, the information board 23 on the front of the outer wall of the horizontal plate 1 is threaded to the horizontal plate 1 via screws 24 on the left and right sides, which facilitates the recording of device parameters and makes it easy for operators to view. It is also easy to install and disassemble. The controller 25 on the outer wall of the left clamping plate 3 is electrically connected to motor 7 and motor 15, which can precisely control the operation of motor 7 and motor 15 to control the opening and closing of the clamping plate 3 and the supporting action of the slide plate 13. The cross groove 26 at the front end of the bolt 14 is adapted to a Phillips screwdriver for easy tightening or loosening. The smooth surface treatment reduces frictional resistance during operation and improves adjustment efficiency.

[0039] Working principle: Motor 7 is started, and its output drives the right gear 6 to rotate. Since the two gears 6 mesh, the right gear 6 drives the left gear 6 to rotate, which in turn causes the bidirectional threaded rod 5 to rotate. The bidirectional threaded rod 5 is rotatably connected to the horizontal plate 1. During rotation, because the two clamping plates 3 are slidably connected to the guide rod 4 and threadedly engaged with the bidirectional threaded rod 5, the two clamping plates 3 will move towards or away from each other along the guide rod 4, achieving the clamping and releasing action of prebaked anode carbon blocks of different widths. When the clamping plate 3 approaches the carbon block, the protective pad 10 in the groove 9 first contacts the carbon block. The protective pad 10 is quickly connected to the inner wall of the groove 9 through the clip and mechanism 2, preventing damage to the surface of the carbon block. Then, motor 15 is started, and its output... The support plate 12 rotates, and the slide plate 13, which is slidably connected to its inner wall, rotates accordingly. When the slide plate 13 rotates to correspond with the position of the electromagnet 16, the slide plate 13 and the electromagnet 16 are magnetically connected. At this time, the slide plate 13 supports the anode carbon block between the clamping plates 3 from the bottom of the device, effectively preventing the carbon block from falling. In the whole operation process, the motor 17 acts as the driving source and precisely controls the movement of the clamping plate 3 to achieve the adaptive clamping of carbon blocks of different sizes. The protective pad 10, together with the card and mechanism 2, effectively protects the surface of the carbon block. The motor 215, together with the support plate 12, the slide plate 13 and the electromagnet 16, provides stable support for the carbon block from the bottom, ensuring the safety and stability of the prebaked anode carbon block in the clamping process in all aspects.

[0040] Furthermore, when the protective pad 10 needs to be installed, first align the protective pad 10 with the groove 9. This alignment operation ensures the accuracy of subsequent installation. Then, push the protective pad 10 into the groove 9. During this process, the protective pad 10 will first compress the locking block 201. The locking block 201 is slidably connected to the reserved groove 8. After being compressed, the locking block 201 will compress the spring 202 connected to it, causing the locking block 201 to retract into the reserved groove 8. As the protective pad 10 continues to advance, when the locking groove 205 on the outer wall of the protective pad 10 moves to coincide with the locking block 201, the compressed spring 202, due to its elastic restoring force, will push the locking block 201 out again, making it... The protective pad 10 is precisely pushed into the slot 205, thus firmly fixing it in the groove 9. This connection method utilizes the elastic properties of the spring 202 and the engaging structure between the locking block 201 and the slot 205. It requires no complicated tools, is easy to operate, and can quickly install the protective pad 10. If the protective pad 10 needs to be replaced, simply pull the pull ring 204 connected to the locking block 201 again. The pull ring 204 drives the locking block 201 to overcome the elastic force of the spring 202 and disengage from the slot 205, thus separating the locking block 201 from the slot 205. The protective pad 10 can then be easily removed, conveniently and quickly meeting the need to replace the protective pad 10 due to wear or other reasons.

[0041] Finally, it should be noted that the above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A clamping device for the production of prebaked anode blocks, comprising a crosspiece (1) and a clamping plate (3), characterized in that: Guide rods (4) are fixedly connected to the bottom front and rear sides of the horizontal plate (1). The two clamping plates (3) are slidably connected to the two guide rods (4). A bidirectional threaded rod (5) is rotatably connected to the bottom center of the horizontal plate (1). A transmission assembly is provided on the top of the horizontal plate (1). A groove (9) is provided on the adjacent side of the two clamping plates (3). A protective pad (10) is provided on the inner wall of the two grooves (9). A locking mechanism (2) is provided on the outer wall of the two grooves (9). The locking mechanism (2) is used to quickly connect the protective pad (10) and the groove (9). A fixing plate (11) is fixedly connected to the right side of the outer wall of the right clamping plate (3). The two fixing plates (11) are adjacent to each other. A support plate (12) is rotatably connected between the two support plates (12), and a sliding plate (13) is slidably connected to the inner wall of the two support plates (12). Bolts (14) are threadedly connected to the front and rear sides of the outer wall of the two support plates (12). A motor (15) is fixedly connected to the front side of the outer wall of the front fixed plate (11). The output end of the motor (15) passes through the front fixed plate (11) and is fixedly connected to the support plate (12). An electromagnet (16) is fixedly connected to the bottom of the left clamping plate (3). A telescopic rod (17) is fixedly connected to the top of the horizontal plate (1). An installation plate (18) is fixedly connected to the top of the telescopic rod (17). Two reserved slots (8) are opened on the front and rear sides of the inner wall of the multiple grooves (9).

2. A clamping device for the production of prebaked anode carbon blocks according to claim 1, characterized in that The card and mechanism (2) includes multiple card blocks (201), which are slidably connected to the inner wall of the corresponding reserved slot (8). A spring (202) is fixedly connected to the far end of each of the multiple card blocks (201), and both ends of the multiple springs (202) are fixedly connected to the corresponding card blocks (201). A connecting rod (203) is fixedly connected to the far end of each of the multiple card blocks (201), and the far end of each of the multiple connecting rods (203) passes through the corresponding clamp (3) and is rotatably connected to a pull ring (204). Card slots (205) are provided on the front and rear sides of the outer walls of the two protective pads (10), and the multiple card blocks (201) are respectively engaged with the corresponding card slots (205).

3. The gripping device for producing a prebaked anode carbon block according to claim 1, characterized in that: The transmission assembly includes a motor (7), which is fixedly connected to the top right side of the horizontal plate (1). The output end of the motor (7) and the right end of the bidirectional threaded rod (5) are both fixedly connected to gears (6), and the two gears (6) are meshed together.

4. The gripping device for producing a prebaked anode carbon block according to claim 1, characterized in that: A rubber pad (19) is fixedly connected to the top of the mounting plate (18), and screws (20) are threaded around the bottom of the mounting plate (18). The tops of the screws (20) penetrate the rubber pad (19).

5. A clamping device for producing a prebaked anode carbon block according to claim 1, characterized in that: An installation box (21) is fixedly connected to the top left side of the horizontal plate (1), and an alarm (22) is fixedly connected to the inner wall of the installation box (21).

6. A clamping device for producing a prebaked anode carbon block according to claim 1, characterized in that: An information board (23) is provided on the front side of the outer wall of the horizontal plate (1). Screws (24) are threadedly connected to the left and right sides of the outer wall of the information board (23). The rear ends of the two screws (24) are threadedly connected to the horizontal plate (1).

7. A clamping device for producing a prebaked anode carbon block according to claim 3, characterized in that: A controller (25) is fixedly connected to the left side of the outer wall of the clamp (3) on the left side. The controller (25) is electrically connected to the first motor (7) and the second motor (15).

8. The clamping device for producing prebaked anode carbon blocks according to claim 1, characterized in that: The bolt (14) has a cross groove (26) at its front end, and the surface of the bolt (14) is smoothed.

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