Novel clamping device

Abstract

The utility model relates to a novel clamping device which comprises a bearing seat, a cylinder barrel, a piston and a clamping assembly, the cylinder barrel is arranged on the bearing seat and detachably connected with the bearing seat, and the bearing seat is used for bearing the cylinder barrel; the cylinder barrel is hollow, and the piston is slidably arranged in the cylinder barrel. A communicating hole is formed in the cylinder barrel in a penetrating mode from the top end of the interior of the cylinder barrel to the exterior of the cylinder barrel, the clamping assembly comprises a chuck and a tightening pipe, the fixed end of the chuck is arranged in the cylinder barrel, the clamping end of the chuck penetrates through the communicating hole and extends to the exterior of the cylinder barrel, and the tightening pipe is fixedly connected with the piston and is in sliding fit with the communicating hole; a containing cavity matched with the chuck in shape is formed in the tightening pipe in the length direction of the tightening pipe in a penetrating mode, and the tightening pipe and the chuck are in sliding fit along the containing cavity. The inner wall of the tightening pipe is gradually expanded from the position close to the upper end of the cylinder barrel to the end face of the tightening pipe, and the outer side wall of the chuck is gradually expanded from the position close to the upper end of the cylinder barrel to the end face of the chuck.

Description

Technical Field

[0001] The present application relates to the technical field of manipulators, and in particular to a novel clamping device. Background Art

[0002] The gripper cylinder is highly controllable and precise, enabling it to stably grasp and accurately position the workpiece. The gripper cylinder has a fast response speed and is suitable for various automated production tasks such as assembly, packaging, and handling, playing a positive guiding role in improving production efficiency.

[0003] In the prior art, the gripper cylinder is a pneumatic component that usually works continuously at high speed. As the use time increases, the piston, chuck and other components will be affected by friction and cause irreversible mechanical damage, and the working efficiency and accuracy of the gripper cylinder will also change accordingly. When the parts of the gripper cylinder are damaged, the corresponding parts can be replaced, but the composition structure of the gripper cylinder is relatively complex, which is not easy to disassemble or assemble. When reassembling, if it is not installed accurately, it will affect the accuracy of the gripper cylinder.

[0004] Therefore, further improvement is needed. Utility Model Content

[0005] In order to improve the convenience of assembling the clamping cylinder, the present application provides a new clamping device.

[0006] A novel clamping device provided in this application adopts the following technical solution:

[0007] The cam is configured to move the piston rod and the piston rod toward the outside of the cam, and the piston rod and the piston rod are connected in a detachable manner to the cam, and the cam is configured to move the piston rod toward the outside of the cam, so that the cam can move relative to the piston rod.

[0008] By adopting the above technical scheme, the cylinder and the bearing seat are detachably connected. When the piston, tightening tube or chuck needs to be maintained or replaced, the piston and the tightening tube can be taken out along the cylinder. Since the inner wall of the tightening tube is gradually expanded along the area near the upper end of the cylinder to the end face of the tightening tube, and the outer wall of the chuck is gradually expanded along the area near the upper end of the cylinder to the end face of the chuck, when the piston carries the tightening tube to move, the tightening tube squeezes the chuck, thereby contracting the chuck to complete the clamping operation of the workpiece. Similarly, when the chuck needs to be maintained or replaced, the chuck can be pulled in the opposite direction of the tightening tube to tighten the chuck until the chuck can be taken out along the tightening tube. The superposition of the above processes realizes the replacement or maintenance of the jaw cylinder components.

[0009] Preferably, a bushing is provided in the communicating hole, the bushing is overfitted with the communicating hole, and the tightening tube is slidably connected with the bushing.

[0010] By adopting the above technical solution, since the clamping cylinder is usually in a high-speed, sustainable operation state, if the tightening tube moves directly along the connecting hole, it will cause irreversible mechanical damage to the cylinder as the use time increases. The bushing has a lower friction coefficient, which reduces the friction force on the tightening tube when it moves, thereby slowing down the wear rate of the tightening tube; the bushing and the connecting hole are over-fitted, so that the bushing can be stably installed in the connecting hole. At the same time, when the bushing needs to be replaced, it only needs to be taken out along the connecting hole.

[0011] Preferably, the bearing seat includes an extension portion and a base, the cylinder is detachably connected to the upper end of the extension portion, and the lower end of the extension portion is detachably connected to the base.

[0012] By adopting the above technical solution, the cylinder can be connected to the extension part or the cylinder can be directly connected to the base, so that it can meet the clamping requirements of two different heights and has high practicality.

[0013] Preferably, a limit seat is provided in the cylinder, the fixed end of the chuck movably passes through the piston and is fixedly connected to the limit seat, and when the piston is in an initial state, the piston abuts against the upper surface of the limit seat, and the lower surface of the limit seat abuts against the upper surface of the extension part.

[0014] By adopting the above technical solution, the movement path of the piston along the cylinder is limited by the limit seat, that is, the piston can only move between the top end of the cylinder and the upper surface of the limit seat, thereby indirectly limiting the amplitude of the tightening tube and the tightening chuck, which to a certain extent solves the problem of damage to the tightening tube and / or chuck caused by excessive tightening of the tightening tube and the chuck.

[0015] Preferably, a first sealing rubber component is disposed in the piston, one end of the first sealing rubber component is closed, and the other end of the first sealing rubber component is open, and the first sealing rubber component 31 has an open end facing the bearing seat.

[0016] By adopting the above technical solution, when the piston carries the tightening tube to move and tighten the chuck, gas is filled between the piston and the bearing seat, so that the two ends of the opening of the first sealing rubber component are quickly propped up. At this time, one end of the opening of the first sealing rubber component abuts against the inner wall of the piston, and the other end abuts against the outer wall of the chuck, thereby reducing the gap between the piston and the chuck, thereby reducing the amount of gas leakage, and to a certain extent solves the problem that the piston carrying the tightening tube to tighten the chuck due to excessive gas leakage is insufficient, resulting in the chuck being unable to clamp the workpiece.

[0017] Preferably, the limiting seat is provided with a flange along the circumferential direction, and the cylinder barrel is provided with a receiving groove expanding outward along the circumferential direction of the inner wall, and the shape of the receiving groove is adapted to the flange.

[0018] By adopting the above technical solution, the limiting seat is stably arranged in the cylinder barrel through the cooperation of the accommodating groove and the flange, thereby reducing the shaking of the limiting seat along the cylinder barrel when the clamping claw cylinder is working.

[0019] Preferably, a positioning pin is provided on the limit seat, a pin hole is provided on the extension portion, and the positioning pin is plug-fitted into the pin hole.

[0020] By adopting the above technical solution, when the cylinder is disassembled along the extension part and needs to be reinstalled, the limit seat can be quickly and relatively accurately installed on the extension part through the guiding cooperation of the pin hole and the positioning pin.

[0021] Preferably, the piston divides the interior of the cylinder into a first chamber and a second chamber, the first chamber is located between the piston and the limit seat, the second chamber is located between the piston and the top end of the cylinder, and the cylinder is provided with a first air duct and a second air duct, the first air duct is connected to the first chamber, and the second air duct is connected to the second chamber.

[0022] By adopting the above technical solution, when the gas enters the first chamber along the first air channel, the gas pushes the piston to move toward the top end of the cylinder, and through the cooperation between the piston and the tightening tube, the chuck is driven to tighten, thereby clamping the workpiece; when the gas enters the second chamber along the second air channel, the gas pushes the piston to move toward the limit seat, and the chuck is in a relaxed state at this time, thereby realizing the release operation of the clamped workpiece.

[0023] In summary, the present application includes at least one of the following beneficial technical effects:

[0024] 1. The cylinder barrel is detachably connected to the bearing seat. When the piston, tightening tube or chuck needs to be maintained or replaced, the piston and tightening tube can be taken out along the cylinder barrel. When the chuck needs to be maintained or replaced, the chuck can be pulled in the opposite direction of the tightening tube to tighten the chuck until the chuck can be taken out along the tightening tube. The superposition of the above processes realizes the replacement or maintenance of the jaw cylinder parts;

[0025] 2. The cylinder can be connected to the extension part or directly connected to the base, so that it can meet the clamping requirements of two different heights and is highly practical;

[0026] 3. The path of the piston moving along the cylinder is limited by the limit seat, thereby indirectly limiting the amplitude of the tightening tube and the clamp, reducing the probability of damage to the tightening tube and / or the clamp due to excessive amplitude when the tightening tube tightens the clamp. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the overall structure of a new type of clamping device in an embodiment of the present application.

[0028] Figure 2 It is a cross-sectional schematic diagram of a novel clamping device in an embodiment of the present application.

[0029] Figure 3 yes Figure 2 Enlarged schematic diagram of part A.

[0030] Explanation of the reference numerals: 1. bearing seat; 11. extension portion; 111. pin hole; 112. boss; 12. base; 121. mounting hole; 2. cylinder barrel; 21. limit seat; 211. flange; 212. positioning pin; 213. first mounting groove; 22. accommodating groove; 3. piston; 31. first sealing rubber component; 4. clamping assembly; 41. chuck; 42. tightening tube; 5. accommodating cavity; 6. bushing; 7. first chamber; 8. second chamber; 9. first air duct; 10. second air duct; 101. first clamping groove; 102. second clamping groove; 103. sealing ring; 104. second sealing rubber component. DETAILED DESCRIPTION

[0031] The following is combined with Figure 1-3 This application is described in further detail.

[0032] The present application embodiment discloses a novel clamping device. Figure 1 and Figure 2A new type of clamping device includes a bearing seat 1, a cylinder 2, a piston 3 and a clamping assembly 4. The cylinder 2 is arranged on the bearing seat 1, and the cylinder 2 and the bearing seat 1 are detachably connected to facilitate the maintenance of the clamping cylinder. The bearing seat 1 is used to support the cylinder 2. The cylinder 2 is hollow inside, and the piston 3 is slidably arranged in the cylinder 2. The cylinder 2 is provided with a connecting hole from the top end thereof to the outside of the cylinder 2. The clamping assembly 4 includes a chuck 41 and a tightening tube 42, wherein the chuck 41 is a conventional clamping component, usually made of metal material, and the chuck 41 is composed of a plurality of clamping plates. When pressure is applied to the clamping plates, the plurality of clamping plates are deformed so that they come into contact with the workpiece to achieve clamping of the workpiece. The specific composition and principle thereof are not described in detail here; the fixed end of the chuck 41 is arranged in the cylinder 2, the clamping end of the chuck 41 is penetrated in the connecting hole and extends to the outside of the cylinder 2, the tightening tube 42 is fixedly connected to the piston 3, and the tightening tube 42 is slidably matched with the connecting hole, and the tightening tube 42 is penetrated along its length direction and is opened with a 1, the tightening tube 42 and the chuck 41 are slidably matched along the accommodating cavity 5, and the inner wall of the tightening tube 42 is gradually expanded along the position close to the upper end of the cylinder 2 to the end face of the tightening tube 42, and the outer wall of the chuck 41 is gradually expanded along the position close to the upper end of the cylinder 2 to the end face of the chuck 41. Therefore, when the piston 3 carries the tightening tube 42 to move toward the top end of the cylinder 2, the tightening tube 42 drives the chuck 41 to tighten, and the workpiece is clamped. When the piston 3 carries the tightening tube 42 to move toward the bearing seat 1, the tightening tube 42 is separated from the chuck 41, and the chuck 41 is in a relaxed state when not subjected to external force, thereby realizing the release of the clamped workpiece.

[0033] Similarly, when the chuck 41 needs to be maintained or replaced, the chuck 41 and the tightening tube 42 can be pulled in opposite directions respectively, so that the chuck 41 is tightened until the chuck 41 can be removed along the tightening tube 42, which is convenient for replacing or maintaining the jaw cylinder parts.

[0034] Reference Figure 1 The bearing seat 1 includes an extension portion 11 and a base 12 , the cylinder 2 is detachably connected to the upper end of the extension portion 11 , and the lower end of the extension portion 11 is detachably connected to the base 12 .

[0035] Specifically, the cylinder 2, the extension portion 11 and the base 12 are connected in sequence by bolts, and the base 12 has four mounting holes 121 arranged in a matrix. The base 12 can be installed on the production equipment through the four mounting holes 121 by using bolts. At the same time, in this embodiment, the extension portion 11 can be removed or installed to meet the clamping requirements of two different heights.

[0036] That is, when the workpiece is relatively low, the two ends of the extension portion 11 can be fixed to the cylinder 2 and the base 12 respectively, thereby reducing the distance between the clamping end of the chuck 41 and the workpiece; when the workpiece is relatively high, the extension portion 11 can be disassembled along between the cylinder 2 and the base 12. At this time, the cylinder 2 and the base 12 are fixedly connected, so that the chuck 41 can be initially positioned above the workpiece without the need to equip two different sizes of jaw cylinders, which is more practical.

[0037] Reference Figure 2 and Figure 3 A limit seat 21 is provided in the cylinder 2, and the fixed end of the chuck 41 movably passes through the piston 3 and is fixedly connected to the limit seat 21. When the piston 3 is in the initial state, the piston 3 abuts against the upper surface of the limit seat 21, and the lower surface of the limit seat 21 abuts against the upper surface of the extension portion 11.

[0038] Specifically, a boss 112 is provided on the upper surface of the extension portion 11, a flange 211 is provided along the circumferential direction of the limit seat 21, and a receiving groove 22 is provided along the circumferential direction of the inner wall of the cylinder 2 to expand outwardly. The shape of the receiving groove 22 is adapted to the flange 211 and the boss 112, so that the limit seat 21 can be easily taken out from the receiving groove 22. When the operator places the limit seat 21 on the boss 112 of the cylinder 2 and fixes the cylinder 2 to the extension portion 11, the boss 112 can abut against the lower surface of the limit seat 21, so that the limit seat 21 is in a restrained state, so that the limit seat 21 can be stably installed in the cylinder 2, and the shaking of the limit seat 21 along the cylinder 2 when the clamping cylinder is working is reduced.

[0039] Furthermore, the movement path of the piston 3 along the cylinder 2 is limited by the limit seat 21, that is, the piston 3 can only move between the top end of the cylinder 2 and the upper surface of the limit seat 21, thereby indirectly limiting the tightening amplitude of the tightening tube 42 and the clamp 41, which to a certain extent solves the problem of damage to the tightening tube 42 and / or the clamp 41 due to excessive tightening amplitude of the tightening tube 42 and the clamp 41.

[0040] Correspondingly, a positioning pin 212 is provided on the limit seat 21. There are two positioning pins 212. The two positioning pins 212 are arranged on both sides of the geometric center of the limit seat 21 along the same axis. A pin hole 111 is provided on the extension portion 11. The positioning pin 212 is plugged into the pin hole 111. Therefore, when the clamp cylinder needs to be assembled, the position of the limit seat 21 is relatively accurately placed on the boss 112 through the guiding cooperation of the positioning pin 212 and the pin hole 111. Since the boss 112 is compatible with the shape of the accommodating groove 22, the operator can cover the cylinder barrel 2 on the extension portion 11 through the guiding effect of the boss 112, thereby reducing the time required for adjustment due to the misalignment of the position of the limit seat 21 or the cylinder barrel 2 and the extension portion 11.

[0041] Reference Figure 2 and Figure 3The piston 3 separates the interior of the cylinder 2 into a first chamber 7 and a second chamber 8. The first chamber 7 is located between the piston 3 and the limit seat 21, and the second chamber 8 is located between the piston 3 and the top of the cylinder 2. The cylinder 2 is provided with a first air passage 9 and a second air passage 10. The first air passage 9 and the second air passage 10 can be provided with threads. The first air passage 9 is connected to the first chamber 7, and the second air passage 10 is connected to the second chamber 8. The first air passage 9 and the second air passage 10 can be connected to the air compressor using a threaded joint, so that the air compressor can 9 and the second air channel 10 input compressed air. When the compressed air enters the first chamber 7, the second air channel 10 is in an exhaust state, and the gas pushes the piston 3 to carry the tightening tube 42 to move toward the top end of the cylinder 2, thereby realizing the operation of the tightening tube 42 tightening the chuck 41; on the other hand, when the compressed air enters the second chamber 8, the first air channel 9 is in an exhaust state, so that the piston 3 carries the tightening tube 42 to move toward the limit seat 21, and the tightening tube 42 is separated from the chuck 41, thereby realizing the operation of the chuck 41 releasing the clamped workpiece.

[0042] Correspondingly, when the limit seat 21 is installed in the cylinder 2, there is a gap between the limit seat 21 and the cylinder 2. When air enters the first chamber 7, the gas escapes along the gap, reducing the air pressure in the second chamber 8. At this time, the piston 3 will be underpowered, so that the tightening tube 42 drives the chuck 41 to clamp the workpiece with insufficient clamping force, and there is a risk of the workpiece falling during the clamping process. Therefore, the limit seat 21 is provided with a first mounting groove 213 along the circumference of its outer wall, and a sealing ring 103 is installed in the first mounting groove 213. The sealing ring 103 can be made of polyurethane (PU) material, which has good wear resistance and high pressure resistance. When the limit seat 21 is installed in the cylinder 2, the sealing ring 103 is deformed, thereby filling part of the gap between the limit seat 21 and the cylinder 2, thereby reducing the amount of gas leakage, and playing a positive guiding role in maintaining the pressure of the gas entering the first chamber 7.

[0043] Meanwhile, continue to refer to Figure 2 and Figure 3 A first sealing rubber member 31 is disposed in the piston 3 , one end of the first sealing rubber member 31 is closed, and the other end of the first sealing rubber member 31 is open. The first sealing rubber member 31 has an open end facing the limit seat 21 .

[0044] Specifically, the piston 3 is provided with a first engaging groove 101 in an annular shape along the inner wall that slides with the chuck 41. The first engaging groove 101 is formed by the inner wall of the piston 3 being circumferentially recessed outward. The first sealing rubber member 31 is installed in the first engaging groove 101, and the inner diameter of the piston 3 located below the first engaging groove 101 is larger than the outer diameter of the chuck 41, forming a flow channel for gas to enter the first engaging groove 101. When the gas enters the first chamber 7 along the first gas channel 9, the piston 3 is affected by the gas pressure and will slide along the inner wall of the cylinder 2 toward the top of the cylinder 2. At the moment when the piston 3 is separated from the limit seat 21, the gas enters the first engaging groove 101 along the flow channel. One section of the opening of the first sealing member 31 faces the limit seat 21. The first sealing member 31 is affected by the gas pressure, and both ends of its opening are quickly propped up. One end of the opening of the first sealing member 31 abuts against the inner wall of the first clamping groove 101, and the other end abuts against the outside of the chuck 41, thereby filling the gap when the piston 3 slides along the chuck 41, thereby reducing gas leakage, and to a certain extent solves the problem that the gap between the piston 3 and the chuck 41 is too large, resulting in excessive gas leakage, causing insufficient gas pressure in the first chamber 7, and the resulting slow response or insufficient clamping force when the piston 3 carries the tightening tube 42 to drive the chuck 41 to tighten.

[0045] Reference Figure 1 and Figure 2 A bushing 6 is provided in the communicating hole, the bushing 6 is excessively matched with the communicating hole, and the tightening tube 42 is slidably connected with the bushing 6.

[0046] Specifically, when the clamp cylinder works normally, the piston 3 carries the tightening tube 42 to make fast and sustainable reciprocating motion along the cylinder 2, but there is mutual friction between the tightening tube 42 and the cylinder 2. As the use time increases, irreversible mechanical damage will be caused to the tightening tube 42 and / or the cylinder 2. Therefore, the above problem can be effectively solved by the bushing 6. The cross-section of the bushing 6 is arranged in a circular ring shape. The bushing 6 is made of copper material, which has wear-resistant properties. Because the bushing 6 and the connecting hole are over-matched, the bushing 6 can be stably installed in the connecting hole, reducing the probability of the bushing 6 falling off along the connecting hole; when the bushing 6 is installed in the connecting hole, the tightening tube 42 is slidably connected with the bushing 6, thereby reducing the friction on the tightening tube 42, and playing a positive guiding role in slowing down the wear speed of the tightening tube 42; at the same time, when the bushing 6 is worn, it is only necessary to take out the bushing 6 along the connecting hole and replace it.

[0047] Furthermore, due to the gap between the tightening tube 42 and the bushing 6, when the piston 3 carries the tightening tube 42 to move toward the limit seat 21, part of the gas that enters the second chamber 8 along the second air channel 10 will escape along the gap between the tightening tube 42 and the bushing 6, thereby reducing the gas pressure in the second chamber 8, causing the piston 3 to carry the tightening tube 42 to move toward the limit seat 21. The time increases, affecting the production efficiency. Therefore, the connecting hole below the bushing 6 is circumferentially provided with a second snap-in groove 102, and a second sealing rubber component 104 is installed in the second snap-in groove 102. Its working principle is the same as that of the first sealing rubber component 31, and no further details are given here.

[0048] The implementation principle of a new type of clamping device in the embodiment of the present application is: when the jaw cylinder needs to be maintained or parts need to be replaced, the cylinder 2 can be disassembled along the extension part 11. At this time, the cylinder 2 is separated from the extension part 11, and the clamping end of the chuck 41 is knocked. The tightening tube 42 will move along the bushing 6 to the bottom of the cylinder 2, thereby separating the cylinder 2 from the piston 3, the tightening tube 42, the chuck 41 and the limit seat 21, and then the piston 3 and the limit seat 21 are pulled in opposite directions. Since the tightening tube 42 is fixedly connected to the piston 3, the tightening tube 42 drives the clamping end of the chuck 41 to shrink until the chuck 41 is separated from the tightening tube 42, which is convenient for assembling and disassembling the jaw cylinder.

[0049] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A new type of clamping device, characterized in that: The invention comprises a bearing seat (1), a cylinder (2), a piston (3) and a clamping assembly (4); the cylinder (2) is arranged on the bearing seat (1), and the cylinder (2) and the bearing seat (1) are detachably connected; the bearing seat (1) is used to support the cylinder (2); the cylinder (2) is hollow inside, and the piston (3) is slidably arranged in the cylinder (2); a connecting hole is opened from the top end of the cylinder (2) to the outside of the cylinder (2); the clamping assembly (4) comprises a clamp (41) and a tightening tube (42); the fixed end of the clamp (41) is arranged in the cylinder (2), and the clamping end of the clamp (41) is The holding end is passed through the connecting hole and extends to the outside of the cylinder (2); the tightening tube (42) is fixedly connected to the piston (3), and the tightening tube (42) is slidably matched with the connecting hole; the tightening tube (42) passes through a cavity (5) that matches the shape of the chuck (41) along its length direction, and the tightening tube (42) and the chuck (41) are slidably matched along the cavity (5); the inner wall of the tightening tube (42) is gradually expanded from the upper end of the cylinder (2) to the end face of the tightening tube (42), and the outer wall of the chuck (41) is gradually expanded from the upper end of the cylinder (2) to the end face of the chuck (41).

2. A novel clamping device according to claim 1, characterized in that: A bushing (6) is arranged in the communicating hole, the bushing (6) is excessively matched with the communicating hole, and the tightening tube (42) is slidably connected with the bushing (6).

3. A novel clamping device according to claim 1, characterized in that: The bearing seat (1) comprises an extension portion (11) and a base (12); the cylinder (2) is detachably connected to the upper end of the extension portion (11), and the lower end of the extension portion (11) is detachably connected to the base (12).

4. A novel clamping device according to claim 3, characterized in that: A limit seat (21) is arranged in the cylinder (2); the fixed end of the chuck (41) movably passes through the piston (3) and is fixedly connected to the limit seat (21); when the piston (3) is in an initial state, the piston (3) abuts against the upper surface of the limit seat (21), and the lower surface of the limit seat (21) abuts against the upper surface of the extension portion (11).

5. A novel clamping device according to claim 4, characterized in that: A first sealing rubber component (31) is arranged inside the piston (3), one end of the first sealing rubber component (31) is arranged in a closed manner, and the other end of the first sealing rubber component (31) is arranged in an open manner, and the first sealing rubber component 31 has an open end facing the limit seat (21).

6. A novel clamping device according to claim 5, characterized in that: The limiting seat (21) is provided with a flange (211) along the circumferential direction, and the cylinder barrel (2) is provided with a receiving groove (22) extending outward along the circumferential direction of the inner wall, and the shape of the receiving groove (22) is adapted to the flange (211).

7. A novel clamping device according to claim 4, characterized in that: The limiting seat (21) is provided with a positioning pin (212), the extending portion (11) is provided with a pin hole (111), and the positioning pin (212) is plug-fitted with the pin hole (111).

8. A novel clamping device according to claim 4, characterized in that: The piston (3) divides the interior of the cylinder (2) into a first chamber (7) and a second chamber (8); the first chamber (7) is located between the piston (3) and the limit seat (21); the second chamber (8) is located between the piston (3) and the top end of the cylinder (2); a first air channel (9) and a second air channel (10) are provided on the cylinder (2); the first air channel (9) is connected to the first chamber (7); and the second air channel (10) is connected to the second chamber (8).

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