CN217345367U - Firing pin locking structure of nailing gun - Google Patents

Abstract

The utility model provides a firing pin locking structure of nailing gun belongs to nailing gun technical field. It has solved how to improve the life of nailing gun. This nailing gun's firing pin locking structure, the nailing gun includes interior casing and the firing pin that can move and be used for the nailing of casing relatively, still be equipped with the locking piece that is used for indirect or direct pinning the firing pin on the interior casing, still be equipped with actuating mechanism on the interior casing and can follow the apical axis of the vertical direction motion of interior casing under actuating mechanism drives, the apical axis is connected with the locking piece, during the firing pin unblock, apical axis and locking piece can be followed the vertical direction of interior casing and kept away from the firing pin and remove. The locking piece of the scheme has high disengaging speed, reduces the contact of the locking piece with the firing pin or the locking piece, the firing pin and other parts, slows down the abrasion of the locking piece with the firing pin or the locking piece, the firing pin and other parts, and prolongs the service life of the nailing gun.

Description

Firing pin locking structure of nailing gun

Technical Field

The utility model belongs to the technical field of the nailing gun, a nailing gun is related to, in particular to firing pin locking structure of nailing gun.

Background

The nailing gun is a modern nail shooting fastening technology product, can shoot nails, and belongs to a direct consolidation technology. Is a necessary manual tool for carpentry, building construction and the like. The products of the nailing gun in the market at present mainly use a pneumatic nailing gun as a main part, the working principle of the pneumatic nailing gun uses high-pressure gas generated by an air pump (an air compressor) as a power source, when the pneumatic gas is generated, a firing pin is in a locking state, and when the firing pin is unlocked, the high-pressure gas drives the firing pin in a cylinder of the nailing gun to do hammering motion, so that nails in a nail outlet groove are driven into an object or nails in rows are ejected out. Since the striker is subjected to high-pressure gas, the striker is subjected to large frictional force for unlocking and locking, and the striker is worn during use, which may eventually lead to failure of the striker locking.

The applicant provides a design scheme for a locking structure of a firing pin, and the design scheme is shown in Chinese patents (application number: 201910099968.7 discloses a nailing gun, comprising a housing and a striker reciprocally movable with respect to the housing, wherein the housing is provided with a locking member and an intermediate member movable with respect to the housing, the intermediate member is located between the locking member and the striker, and the intermediate member is respectively provided with a first locking portion and a second locking portion capable of being locked on the striker; the locking piece can abut against the first locking part and block the middle piece from moving relative to the shell to enable the second locking part to be clamped with the firing pin, or the locking piece can be unblocked to enable the second locking part to move and disengage the firing pin.

In the structure, when the hinged rod rotates to the position of the shifting block, the hinged rod can trigger the shifting block to drive the locking piece to rotate, and then the locking piece can release the blocking of the middle piece, so that the middle piece rotates relative to the shell under the pushing of the firing pin and overcomes the elasticity of the torsion spring to disengage the firing pin until the blocking surface II on the locking piece contacts and abuts against the backstop surface on the middle piece. In the structure, the middle part is unlocked through rotation, the middle part still contacts with the groove of the firing pin for a long time in the unlocking process to generate large friction, meanwhile, the contact time between the middle part and the locking part is also long, the abrasion of the firing pin, the middle part and the locking part is accelerated, and the service life of the nailing gun is shortened.

Disclosure of Invention

The utility model aims at solving the problems of the prior art and providing a striker locking structure of a nailing gun, which aims to solve the technical problems that: how to improve the service life of the nailing gun.

The purpose of the utility model can be realized by the following technical proposal: the utility model provides a firing pin locking structure of nailing machine, the nailing machine includes interior casing and the firing pin that can move and be used for the nailing of casing relatively, still be equipped with the locking piece that is used for indirect or direct pinning the firing pin on the interior casing, its characterized in that, still be equipped with actuating mechanism on the interior casing and can follow the apical axis of the vertical direction motion of interior casing under actuating mechanism drives, the apical axis is connected with the locking piece, during the firing pin unblock, apical axis and locking piece can be followed the vertical direction of interior casing and kept away from the firing pin and remove.

In this scheme, among the firing pin unblock process, apical axis and locking piece can be followed the vertical direction of interior casing and keep away from the firing pin removal and locking piece and apical axis move towards the top or the below of interior casing promptly, the disengagement speed of locking piece is fast, the contact of locking piece with firing pin or locking piece, firing pin and other parts has been reduced, the wearing and tearing of locking piece with firing pin or locking piece, firing pin and other parts have been slowed down, the life of nailing gun has been improved. The technical scheme with different technical concepts is provided, and the level of the prior art can be achieved.

In the striker locking structure of the nailing gun, the driving mechanism comprises a rotary disc arranged in the inner shell, at least one boss is arranged on the rotary disc, one end of the top shaft is connected with the locking piece, and the other end of the top shaft is provided with a propping block capable of propping against the boss. After supporting the kicking block and contacting the boss, apical axis and locking piece all move along the vertical direction of interior casing toward interior casing top, and the firing pin unblock this moment, when supporting kicking block and boss separation, the firing pin can relock or continue to move, continue to move the in-process firing pin at the firing pin and do not take place the contact with other objects among the locking structure, the removal of locking piece in this scheme with reset by apical axis control, simple structure guarantees going on smoothly of firing pin locking and unblock.

In the striker locking structure of the nailing gun, the top shaft is provided with a return spring for returning the top shaft, one end of the return spring is abutted against or fixed on the top shaft, and the other end of the return spring is abutted against the inner shell. The return spring is used for returning in the vertical direction of the top shaft.

In the striker locking structure of the nailing gun, the locking piece directly locks the striker, the striker is further provided with a groove, the locking piece comprises a locking part, and when the striker is locked, the locking part is positioned in the groove and directly locks the striker; when the striker is unlocked, the lock portion is located above or below the groove.

In the striker locking structure of the nailing gun, the inner shell is further provided with a fixed block close to the locking member, the fixed block and the locking member are positioned on the same side of the striker, the fixed block is far away from the striker compared with the locking member, and when the striker is locked, partial structures of the fixed block, the locking member and the striker are positioned on the same horizontal plane. The fixed block is used for preventing the locking piece from moving in the horizontal direction, and the locking effect of the locking piece on the firing pin is improved.

In the striker locking structure of the nailing gun, the parts of the fixed block, which are in contact with the locking piece, are inclined planes and are matched with each other; or the fixing block or the locking piece has a slope. Be equipped with the inclined plane on the fixed block, the higher authority on inclined plane is compared and is kept away from or is close to the locking piece in the lower level. Above-mentioned structure is favorable to the locking piece vertical when the casing motion that moves towards, and the locking piece is difficult to appear blocking, provides certain guide effect for the motion of locking piece.

In foretell nailing gun's firing pin locking structure, the locking piece indirectly pins the firing pin, be equipped with the recess on the firing pin, be equipped with the intermediate member between locking piece and the firing pin, have locking portion one on the intermediate member respectively and can block locking portion two on the firing pin, the locking piece can support and lean on locking portion one and stop the relative inner casing of intermediate member and remove the recess that makes locking portion two and firing pin and keep the joint, it is connected with the axis of rotation to rotate on the inner casing, the cover is equipped with one end and can supports the torsional spring on the inner casing in the axis of rotation, the other end of torsional spring links firmly in the axis of rotation, the intermediate member is connected in the axis of rotation, during the firing pin unblock, the locking piece is located the top or the below of intermediate member. When the firing pin unlocks, drive the intermediate member rotatory, at firing pin unblock in-process, the intermediate member no longer contacts in the locking piece, has slowed down the wearing and tearing of intermediate member and locking piece, has improved nailing gun's life.

In the striker locking structure of the nailing gun, the inner shell is further connected with a limiting shaft, the locking piece is provided with a limiting hole matched with the limiting shaft, and the limiting shaft is positioned in the limiting hole. Spacing axle and spacing hole combined action prevent that the locking piece from taking place to rotate on the horizontal direction, when the firing pin locking, the locking piece supports and leans on the middleware, has improved the locking effect of middleware to the firing pin.

In the firing pin locking structure of the nailing gun, a turntable connected with the output shaft of the motor is further arranged in the inner shell, a boss is arranged on the turntable, the ejector shaft is fixedly connected with the locking piece, a reset device is arranged on the ejector shaft, one end of the reset device can abut against the inner shell, the other end of the reset device abuts against a limiting table of the ejector shaft, the locking piece is further connected with an abutting shaft, an ejection block is arranged at one end of the abutting shaft, and the ejection block can abut against the boss.

In the striker locking structure of the nailing gun, the peripheries of the boss and the abutting block are arc-shaped, the jacking shaft is provided with a limiting table or a fixing hole, and the return spring abuts against the limiting table or is fixed in the fixing hole. The periphery of the boss and the abutting block is of an arc-shaped structure, so that the abutting block and the boss can be moved to play a certain guiding and buffering role, and the locking piece can be moved more smoothly.

Compared with the prior art, the utility model has the advantages of it is following:

1. in the process of unlocking the firing pin, the top shaft and the locking piece can move towards the upper side of the inner shell along the vertical direction of the inner shell and far away from the firing pin, namely the locking piece and the top shaft move towards the upper side of the inner shell, the separation speed of the locking piece is high, the contact between the locking piece and the firing pin or the locking piece, the firing pin and other parts is reduced, the abrasion between the locking piece and the firing pin or the locking piece, the firing pin and other parts is reduced, and the service life of the nailing gun is prolonged. The scheme provides a technical scheme with different technical concepts, and can reach the level of the prior art.

2. The periphery of the boss and the abutting block is of an arc-shaped structure, so that the abutting block and the ejecting block can be moved to the boss to play a certain guiding and buffering role, and the locking piece can be moved more smoothly.

Drawings

Fig. 1 is a schematic perspective view of the present invention;

fig. 2 is a schematic sectional structure of the present invention;

fig. 3 is a schematic partial structure diagram according to a first embodiment of the present invention;

fig. 4 is a schematic partial structure diagram according to a first embodiment of the present invention;

fig. 5 is a schematic view of a part of the structure in the first embodiment of the present invention;

fig. 6 is a schematic view of a part of the structure in the second embodiment of the present invention;

fig. 7 is a schematic partial structural view of a second embodiment of the present invention;

fig. 8 is a schematic sectional view of a second embodiment of the present invention;

fig. 9 is a schematic view of a part of the structure in the second embodiment of the present invention.

In the figure, 1a, an inner housing; 1b, an outer shell; 2. a striker; 21. a groove; 3. a locking member; 31. a lock portion; 32. a latch hook portion; 321. a first blocking surface; 322. a second blocking surface; 33. a limiting hole; 4. a top shaft; 41. a propping block; 42. a limiting table; 5. a turntable; 51. a boss; 511. a first boss; 512. a second boss; 6. a middleware; 61. a first locking part; 611. a backstop surface; 612. an abutting surface; 62. a second locking part; 7. a rotating shaft; 8. a limiting shaft; 9. a fixed block; 10. a return spring; 11. a torsion spring; 12. a blocking sheet; 13. a motor; 14. a gear reducer; 15. a crank; 16. a piston rod; 17. a first piston; 18. a first cylinder; 18a, a first air chamber; 19. a second cylinder; 19a, a second air chamber; 20. a second piston; 30. and (5) a nail box.

Detailed Description

The following are specific embodiments of the present invention and the accompanying drawings are used to further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

Example one

As shown in fig. 1, 2, 3 and 4, the nailing gun includes an inner case 1a, an outer case 1b and a striker 2 movable relative to the inner case 1a for nailing, a first cylinder 18 and a second cylinder 19 are further provided in the inner case 1a, a first piston 17 capable of performing a compression stroke and a return stroke is provided in the first cylinder 18, the first piston 17 defines a first chamber 18a capable of storing gas in the first cylinder 18, a piston rod 16 is connected to the first piston 17, a crank 15 is connected to the piston rod 16, and a drive mechanism includes a motor 13, a gear reducer 14, a dial 5 and the crank 15. The motor 13, which is provided in the inner housing 1a, of the motor 13 is connected to a gear reducer 14, an output shaft of the gear reducer 14 is connected to a crank 15, and the piston rod 16 and the crank 15 form a crank link structure, so that the rotational power of the motor is changed into power for driving the first piston to linearly reciprocate. The second piston 20 is arranged in the second cylinder 19, the firing pin 2 is fixedly connected to the second piston 20, the second piston 20 divides a second air chamber 19a in the second cylinder 19, and the first air chamber 18a and the second air chamber 19a are communicated with each other through a fully-closed ventilation channel. The motor 13 drives the first piston 17 to perform a compression stroke and a recovery stroke. A staple magazine 30 is provided at the front end of the inner housing 1a, and staples in the staple magazine 30 are automatically lifted to the front of the striker 2 by the spring. After the first piston 17 completes the compression stroke, the striker locking structure is unlocked, so that the striker 2 and the second piston 20 are both in an unlocked state, and the second piston 20 moves at a high speed under the action of high pressure to drive the striker 2 to strike a nail in front of the striker 2, thereby completing one nailing action. And then the first piston 17 performs a return stroke, the second piston 20 is pulled back to the position of the striker locking from the position of the striker after the striker is shot by the negative pressure, the striker 2 is locked again, and the operation is repeated in this way, so that continuous nailing is realized.

The firing pin 2 is provided with a groove 21, the inner shell 1a is also provided with a blocking piece 12, a top shaft 4 and a locking piece 3, the blocking piece 12 and the locking piece 3 are both fixed on the top shaft 4, and the blocking piece 12 is positioned above the locking piece 3. The locking piece 3 is provided with a locking part 31, the firing pin 2 is provided with a locking part 31 matched with the shape of the groove 21, and the locking piece 3 locks the firing pin 2 by clamping the locking part 31 in the groove 21. Still be equipped with the fixed block 9 that is close to locking piece 3 on the inner casing 1a, fixed block 9 and locking piece 3 lie in the same one side of firing pin 2, and fixed block 9 is compared in locking piece 3 and is kept away from firing pin 2, and the part that fixed block 9 and locking piece 3 contacted can set up to be the inclined plane and the phase-match, and the higher authority on the inclined plane of fixed block 9 is compared in the lower limit and is kept away from locking piece 3. Locking member 3 when striker 2 is locked, the partial structure of mounting block 9, locking member 3 and striker 2 are in the same horizontal plane. The fixing block 9 serves to prevent the locking member 3 from moving in the horizontal direction, improving the locking effect of the locking member 3 to the striker 2. The fixing block 9 may be replaced by a structure in which a positioning shaft is further provided on the inner case 1a and a positioning hole is provided on the locking member 3. The positioning shaft is inserted into the positioning hole, and the locking member 3 and the striker 2 are partially constructed in the same horizontal plane. The positioning shaft is used for preventing the locking piece 3 from rotating in the horizontal direction, and the structure of the positioning hole and the positioning shaft can save the space of the locking structure of the firing pin 2.

As shown in fig. 5, the inner housing body 1a is further provided with a turntable 5 connected with a crank link mechanism, the turntable 5 is provided with a boss 51, the top shaft 4 is fixedly connected with the locking member 3, the other end of the top shaft 4 is provided with a top block 41 capable of abutting against the boss 51, the periphery of the boss 51 and the top block 41 is arc-shaped, the top shaft 4 is provided with a return spring 10, one end of the return spring 10 can abut against the inner housing body 1a, and the other end of the return spring 10 abuts against a limit table 42 of the top shaft 4.

The working principle of the embodiment is that when the striker 2 is locked, the abutting block 41 of the top shaft 4 is in contact with the rotary disc 5, the return spring 10 is in a compressed state, and under the action of the return spring 10, the top shaft 4 and the locking member 3 are subjected to downward force along the inner shell 1a, so that the locking portion 31 is positioned in the groove 21 of the striker 2 to lock the striker 2; when the striker 2 is unlocked, the abutting block 41 of the top shaft 4 abuts on the boss 51, and the top shaft 4 drives the locking member 3 to move upward of the inner housing 1a, so that the lock portion 31 is separated from the groove 21 and finally above the striker 2. Alternatively, when the striker 2 is unlocked, the locking portion 31 is disengaged from the recess 21 and finally under the striker 2, and the corresponding drive mechanism is adjusted accordingly.

Example two

As shown in fig. 6, the structure of the present embodiment is substantially the same as that of the first embodiment, in the present embodiment, a mode of locking the striker 2 by connecting the locking member 3 to the striker 2 is adopted, an intermediate member 6 is disposed between the locking member 3 and the striker 2, the inner housing 1a is rotatably connected with a rotating shaft 7, the intermediate member 6 is fixed on the rotating shaft 7, the rotating shaft 7 is further provided with a blocking piece 12, the blocking piece 12 is located above the intermediate member 6, the inner housing 1a is further connected with a limiting shaft 8, the locking member 3 is provided with a limiting hole 33 matched with the limiting shaft 8, and the limiting shaft 8 is located in the limiting hole 33.

As shown in fig. 7, the intermediate member 6 has a first locking portion 61 and a second locking portion 62, respectively, the second locking portion 62 can be clamped in the groove 21 of the striker 2, the inner side of the first locking portion 61 has a stop surface 621, the outer side of the first locking portion 61 has an abutting surface 622, the locking member 3 has a hook-shaped locking hook portion 32, the inner side of the locking hook portion 32 has a first blocking surface 321, and the outer side of the locking hook portion 32 has a second blocking surface 322. Still be connected with spacing axle 8 on the interior casing 1a, be equipped with on the locking piece 3 with spacing axle 8 assorted spacing hole 33, spacing axle 8 is located spacing hole 33.

As shown in fig. 8 and 9, the boss 51 of the present embodiment includes a first boss 511 and a first boss 511, a torsion spring 11 having one end abutting on the inner housing 1a is sleeved on the rotating shaft 7, and the other end of the torsion spring 11 is fixedly connected to the rotating shaft 7.

The working principle of the embodiment is that when the striker 2 is locked, the first blocking surface 321 can abut against the abutting surface 622 and the second locking portion 62 is kept fixed in the groove 21 of the striker 2; when the striker 2 needs to be unlocked, the abutting block 41 of the top shaft 4 abuts against the first boss 511, at this time, the top shaft 4 drives the locking member 3 to vertically move upwards along the inner housing 1a, the locking member 3 is located above the intermediate member 6, the intermediate member 6 is in a free rotation state in the horizontal direction, the striker 2 is driven by high-pressure gas to move towards the front end of the inner housing 1a, the striker 2 enables the second locking portion 62 to rotate and be completely separated from the groove 21, at this time, the torsion spring 11 of the rotating shaft 7 is in a compression state, and one end of the torsion spring 11 abuts against the inner housing 1 a; in order to keep the second locking part 62 spaced from the striker 2, the motor 13 drives the rotary disc 5 to rotate, the abutting block 41 is separated from the first boss 511, the return spring 10 drives the top shaft 4 and the locking piece to move downwards along the vertical direction of the inner housing 1a, and the second blocking surface 322 can abut against the stopping surface 621 and keep a gap between the middle piece 6 and the striker 2 all the time; after the firing of the firing pin 2 is completed, the abutting block 41 passes through the second boss 512 on the rotary table again, and finally the locking part two 62 is kept fixed in the firing pin 2 again. Alternatively, when the striker 2 is unlocked, the locking member 3 is located below the intermediate member 6 and the corresponding drive mechanism is adjusted accordingly.

EXAMPLE III

The third embodiment is basically the same as the first embodiment except that an abutting shaft including an ejecting block is further provided on the inner housing 1a, the ejecting block is connected with the locking member 3, the abutting block 41 is not provided on the top shaft 4, and the movement of the locking member 3 is realized by the ejecting block and the boss 51. In this embodiment, the abutment shaft serves to move the locking member vertically upward, and the return spring 10 on the top shaft 4 returns the locking member.

The specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications, additions and substitutions may be made by those skilled in the art to the specific embodiments described without departing from the spirit of the invention or exceeding the scope of the invention as defined in the accompanying claims.

Although used more herein, 1, housing; 2. a striker; 21. a groove; 3. a locking member; 31. a lock portion; 32. a latch hook portion; 321. a first blocking surface; 322. a second blocking surface; 33. a limiting hole; 4. a top shaft; 41. a propping block; 42. a limiting table; 5. a turntable; 51. a boss; 511. a first boss; 512. a second boss; 6. a middleware; 61. a first locking part; 611. a backstop surface; 612. an abutting surface; 62. a second locking part; 7. a rotating shaft; 8. a limiting shaft; 9. a fixed block; 10. a return spring; 11. a torsion spring; 12. a blocking sheet; 13. motors, etc., but does not exclude the possibility of using other terms. These terms are used merely to more conveniently describe and explain the nature of the present invention; they are to be construed in a manner that is inconsistent with the spirit of the invention.

Claims (10)

1. The utility model provides a firing pin locking structure of nailing machine, the nailing machine includes interior casing (1) and can move and be used for firing pin (2) of nailing relatively interior casing (1), still be equipped with locking piece (3) that are used for indirect or direct pinning firing pin (2) on interior casing (1), its characterized in that, still be equipped with actuating mechanism on interior casing (1) and can follow apical axis (4) of interior casing (1) vertical direction motion under actuating mechanism drives, apical axis (4) are connected with locking piece (3), during firing pin (2) unblock, apical axis (4) and locking piece (3) can be followed interior casing (1) vertical direction and keep away from firing pin (2) and remove.

2. The striker locking structure for a nailing machine according to claim 1, wherein said driving mechanism comprises a rotary table (5) provided in said inner case (1), wherein at least one boss (51) is provided on said rotary table (5), one end of said top shaft (4) is connected to said locking member (3), and the other end of said top shaft (4) is provided with an abutting block (41) capable of abutting against said boss (51).

3. The striker locking structure for a nailing gun according to claim 2 wherein a return spring (10) for returning the top shaft (4) is provided on the top shaft (4), one end of the return spring (10) abuts against or is fixed to the top shaft (4), and the other end of the return spring (10) abuts against the inside of the inner case (1).

4. A striker locking structure for a nailing gun according to claim 1, wherein said locking member (3) directly locks the striker (2), and wherein a recess (21) is provided in said striker (2), and wherein said locking member (3) comprises a lock portion (31), and wherein when the striker (2) is locked, said lock portion (31) is located in the recess (21) and directly locks the striker (2); when the striker (2) is unlocked, the lock portion (31) is positioned above or below the groove (21).

5. The firing pin locking structure of a nailing gun according to claim 4, wherein a fixing block (9) is further provided on the inner case (1) near the locking member (3), the fixing block (9) and the locking member (3) are located on the same side of the firing pin (2), the fixing block (9) is located farther from the firing pin (2) than the locking member (3), and when the firing pin (2) is locked, the fixing block (9), the locking member (3) and the firing pin (2) are partially configured to be on the same horizontal plane.

6. The striker locking structure for a nailing gun according to claim 5 wherein the portions of the fixed block (9) in contact with the locking member (3) are inclined and matched; or the fixing block (9) or the locking piece (3) is provided with an inclined surface.

7. The striker locking structure for a nailing gun according to claim 1, wherein the locking member (3) indirectly locks the striker (2), the striker (2) is provided with a groove (21), an intermediate member (6) is provided between the locking member (3) and the striker (2), the intermediate member (6) is provided with a first locking portion (61) and a second locking portion (62) which can be clamped on the striker (2), the locking member (3) can abut against the first locking portion (61) and block the intermediate member (6) from moving relative to the inner housing (1) so that the second locking portion (62) can be clamped in the groove (21) of the striker (2), the inner housing (1) is rotatably connected with a rotating shaft (7), the rotating shaft (7) is sleeved with a torsion spring (11) having one end which can abut against the inner housing (1), and the other end of the torsion spring (11) is fixedly connected to the rotating shaft (7), the middle piece (6) is connected to the rotating shaft (7), and when the firing pin (2) is unlocked, the locking piece (3) is positioned above or below the middle piece (6).

8. The striker locking structure for a nailing gun according to claim 4 or 7 wherein a limit shaft (8) is further connected to the inner case (1), a limit hole (33) matching with the limit shaft (8) is provided in the locking member (3), and the limit shaft (8) is located in the limit hole (33).

9. The firing pin locking structure of a nailing gun according to claim 1 wherein a rotary table (5) connected to an output shaft of a motor (13) is further provided in the inner case (1), a boss (51) is provided on the rotary table (5), the top shaft (4) is fixedly connected to the locking member (3), a return spring (10) is provided on the top shaft (4) and one end of the return spring can abut against the inner case (1), the other end of the return spring (10) abuts against a limit table (42) of the top shaft (4), the locking member (3) is further connected to an abutting shaft, one end of the abutting shaft is provided with an ejection block, and the ejection block can abut against the boss (51).

10. The striker locking structure for a nailing gun according to claim 3 wherein the peripheries of the boss (51) and the abutting block (41) are arc-shaped, and the top shaft is provided with a stopper (42) or a fixing hole (43), and the return spring (10) abuts against the stopper (42) or is fixed in the fixing hole (43).

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