CN116812528A - Self-tightening connecting device suitable for iron chain - Google Patents

Abstract

The application discloses a self-tightening connecting device suitable for an iron chain, which comprises a binding assembly, a fastening assembly, a transmission assembly and a connecting assembly, wherein the binding assembly comprises a fixed binding block, a movable binding block, a nut and a tightening screw block, the fastening assembly is arranged inside the binding assembly and comprises a vertical moving block, a large spring, a positioning limiting block and the transmission assembly is arranged inside the fastening assembly and comprises a transmission cross column, a small spring, a transmission cross cylinder and a transmission vertical column. According to the device, under the cooperation of the attaching assembly, the fastening assembly and the transmission assembly, the iron chain can be tightly clamped for a long time, and the device can be self-tightened when loosening, so that the problem that a common bolt can loosen when being used for a long time is solved.

Description

Self-tightening connecting device suitable for iron chain

Technical Field

The application relates to the field of material transportation, in particular to a self-tightening connecting device suitable for an iron chain.

Background

The mechanical components of the chain are usually bolts, for example, when the bucket is used, the mechanical components are often required to be combined with the loop chain, the bucket and the chain are usually fastened by bolts by using the connecting piece, however, the bucket and the chain are usually in a vibrating state, the general bolt connecting structure is often subjected to vibration, load change, impact and other dynamic loads or working temperature to change greatly, and the clamping force and the loosening-resisting friction force of the bolt connecting structure are gradually reduced or even eliminated after repeated times, so that the bolt connecting structure is finally loosened and loses efficacy, the reliability of the bucket and the chain is affected, and therefore, a connecting mode capable of self tightening is required.

Disclosure of Invention

This section is intended to outline some aspects of embodiments of the application and to briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section as well as in the description of the application and in the title of the application, which may not be used to limit the scope of the application.

The present application has been made in view of the above and/or problems occurring in the prior art devices for connecting chains and buckets.

Therefore, the problem to be solved by the present application is how to solve the problem that when an iron chain is used as a connected object, the connecting device can be kept stable for a long time and can be self-tightened when loosened.

In order to solve the technical problems, the application provides the following technical scheme: a self-tightening connecting device suitable for an iron chain comprises a fitting assembly, a fastening assembly and a transmission assembly.

As a preferred embodiment of the self-tightening connection device according to the application for an iron chain, wherein: the laminating assembly comprises a fixed laminating block, a movable laminating block, a nut and a tightening screw block, wherein the movable laminating block is arranged on one side of the fixed laminating block, the nut is matched with the movable laminating block, and the tightening screw block is sleeved outside the nut;

the fastening assembly is arranged inside the attaching assembly and comprises a vertical moving block, a large spring and positioning limiting blocks, wherein the vertical moving block is arranged on one side of the attaching assembly and penetrates through the two moving blocks, the number of the vertical moving blocks is two, the large spring is arranged between the two vertical moving blocks, and the positioning limiting blocks are arranged on two sides of the inner wall of the vertical moving block; the method comprises the steps of,

the transmission assembly is arranged inside the fastening assembly and comprises a transmission cross column, a small spring, a transmission cross cylinder and a transmission vertical column, wherein the transmission cross column is arranged on one side of the positioning block, the transmission cross column is provided with two pieces, the small spring is arranged between the transmission cross columns, the transmission cross cylinder is sleeved on the transmission cross column, the small spring is arranged outside the transmission cross cylinder, and the transmission vertical column is arranged at the bottom of the transmission cross cylinder.

As a preferred embodiment of the self-tightening connection device according to the application for an iron chain, wherein: the utility model discloses a piece is decided to paste piece, decide to paste piece both ends and be equipped with semicircle recess and round hole respectively, semicircle recess has two, round hole has one, round hole sets up in two between the semicircle recess.

As a preferred embodiment of the self-tightening connection device according to the application for an iron chain, wherein: the movable attaching block comprises a movable block and a stud, the stud is arranged at one end of the movable block, the stud penetrates through the first round hole, two semicircular grooves, two circular holes and three slotted holes are formed in the movable block, two semicircular grooves are formed in the two sides of the stud and are correspondingly matched with the first semicircular grooves, the second round hole penetrates through the stud and the movable block, and the three slotted holes penetrate through the movable block and are perpendicular to the second round hole.

As a preferred embodiment of the self-tightening connection device according to the application for an iron chain, wherein: the screw tightening block comprises a screw tightening groove block and a screw tightening bolt, a hexagonal groove is formed in the screw tightening groove block and matched with the nut, the screw tightening bolt is arranged at the bottom of the hexagonal groove, the screw tightening bolt penetrates through the second round hole, and one end of the screw tightening bolt is provided with a circle of transmission groove.

As a preferred embodiment of the self-tightening connection device according to the application for an iron chain, wherein: the vertical moving block comprises a large block and a small block, wherein the small block is arranged on two sides of one end of the large block, a convex groove is formed in the large block, an annular groove is formed in the inner wall of one wider side of the convex groove, the positioning limiting blocks are arranged in the annular groove, the two vertical moving blocks are distributed in a central symmetry mode, one end of the transmission component is arranged on one vertical moving block in one wider side of the convex groove, and the other end of the transmission component is arranged on the other vertical moving block in one narrower side of the convex groove.

As a preferred embodiment of the self-tightening connection device according to the application for an iron chain, wherein: the two ends of the large spring are fixedly connected with the opposite surfaces of the vertical moving block, and the large spring is always in a compressed state.

As a preferred embodiment of the self-tightening connection device according to the application for an iron chain, wherein: the positioning blocks are arranged in the annular groove, and each positioning block is low at one end and high at the other end.

As a preferred embodiment of the self-tightening connection device according to the application for an iron chain, wherein: the transmission cross column is matched with the ring groove; and two ends of the small spring are respectively and fixedly connected with the opposite surfaces of the two transmission transverse columns.

As a preferred embodiment of the self-tightening connection device according to the application for an iron chain, wherein: the transmission transverse cylinder is sleeved outside the transmission transverse column and the small spring, and two ends of the transmission transverse cylinder are matched with the inner wall of the wider side of the convex groove;

a tooth slot is arranged on one side of the transmission vertical column, the tooth slot is matched with a transmission groove at one end of the tight stud, and a limiting groove is arranged at the bottom of the transmission vertical column.

As a preferred embodiment of the self-tightening connection device according to the application for an iron chain, wherein: the transmission assembly further comprises a middle spring and a movable limiting block, wherein the two ends of the middle spring are connected with the movable limiting block and the transmission vertical column, a limiting column is arranged at the top of one side of the movable limiting block, and the limiting column is matched with the limiting groove of the transmission vertical column.

The application has the beneficial effects that: the device can tightly clamp the iron chain for a long time under the cooperation of the attaching assembly, the fastening assembly and the transmission assembly, and can self-tighten when loosening, so that the problem that a common bolt can loosen after being used for a long time is avoided.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the description of the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art. Wherein:

fig. 1 is a schematic working view of a self-tightening connection device suitable for an iron chain.

Fig. 2 is a block diagram of a fitting assembly and fastening assembly of a self-tightening attachment device for an iron chain.

Fig. 3 is an exploded view of the overall structure of the self-tightening connection device suitable for the iron chain.

Fig. 4 is a cross-sectional view showing the whole structure of the self-tightening connecting device suitable for the iron chain.

Fig. 5 is a partial transmission assembly block diagram of a self-tightening connection device suitable for use with an iron chain.

Detailed Description

In order that the above-recited objects, features and advantages of the present application will become more readily apparent, a more particular description of the application will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings.

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application, but the present application may be practiced in other ways other than those described herein, and persons skilled in the art will readily appreciate that the present application is not limited to the specific embodiments disclosed below.

Further, reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic can be included in at least one implementation of the application. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.

Example 1

Referring to fig. 1 to 5, for a first embodiment of the present application, there is provided a self-tightening connection device suitable for an iron chain,

specifically, the laminating assembly 100 comprises a fixed laminating block 101, a movable laminating block 102, a nut 103 and a tightening screw block 104, wherein the movable laminating block 102 is arranged on one side of the fixed laminating block 101, the nut 103 is matched with the movable laminating block 102, and the tightening screw block 104 is sleeved outside the nut 103.

The fixed block 101 is fixed on a device to be connected with the iron chain, such as a bucket, the movable block 102 is matched with a certain ring of the iron chain, the nut 103 is used for connecting the fixed block 101 and the movable block 102, and the tightening screw block 104 is used for automatically tightening the nut 103.

The doubler assembly 100 is used to connect buckets and chains.

The fastening assembly 200 is arranged inside the attaching assembly 100 and comprises a vertical moving block 201, a large spring 202 and a positioning block 203, wherein the vertical moving block 201 is arranged on one side of the attaching assembly 100 and penetrates through the matching moving attaching block 102, the vertical moving block 201 is provided with two pieces, the large spring 202 is arranged between the two vertical moving blocks 201, and the positioning block 203 is arranged on two sides of the inner wall of the vertical moving block 201.

The vertical moving blocks 201 are used for bearing force on one end when the connection is loosened and the fitting assembly 100 slides on the connected ring, the two vertical moving blocks 201 are close, the large springs 202 are compressed, and the positioning block 203 limits the movement of the transmission assembly 300.

The fastener assembly 200 is used to passively change its state and transfer motion to the transmission assembly 300 as the conformable assembly 100 slides over the attached ring.

The transmission assembly 300 is arranged inside the fastening assembly 200 and comprises a transmission cross column 301, a small spring 302, a transmission cross cylinder 303 and a transmission vertical column 304, wherein the transmission cross column 301 is arranged on one side of the positioning block 203, the transmission cross column 301 is provided with two pieces, the small spring 302 is arranged between the two transmission cross columns 301, the transmission cross cylinder 303 is sleeved outside the transmission cross column 301 and the small spring 302, and the transmission vertical column 304 is arranged at the bottom of the transmission cross cylinder 303.

The drive cross-post 301 of the drive assembly 300 is restrained from movement by the positioning block 203.

The transmission assembly 300 is used for applying the power transmitted by the fastening assembly 200 to the tightening screw 104, so as to tighten the nut 103 for self-tightening.

Specifically, the two ends of the fixing and attaching block 101 are respectively provided with a first semicircular groove K1 and a first circular hole H1, the number of the first semicircular grooves K1 is two, the number of the first circular hole H1 is one, and the number of the first circular hole H1 is arranged between the two number of the first semicircular grooves K1.

The first semicircular groove K1 is matched with one side of a ring on the iron chain, and the first circular hole H1 is opposite to the center of the ring.

Specifically, the movable adhesion block 102 includes a movable block 102a and a stud 102b, the stud 102b is disposed at one end of the movable block 102a, the stud 102b penetrates through a first round hole H1, two semicircular grooves K2, two round holes H2 and three slotted holes H3 are disposed on the movable block 102a, two semicircular grooves K2 are disposed at two sides of the stud 102b and are correspondingly matched with the first semicircular grooves K1, the second round hole H2 penetrates through the stud 102b and the movable block 102a, and the three slotted holes H3 penetrate through the movable block 102a and are perpendicular to the second round hole H2.

The second semicircular groove K2 is matched with the other side of the ring on the iron chain, the stud 102b passes through the center of the ring and is matched with the first round hole H1, the nut 103 is matched with one end of the stud 102b, and the third slotted hole H3 is internally provided with the transmission assembly 300.

Specifically, the tightening screw block 104 includes a tightening screw groove block 104a and a tightening screw 104b, the tightening screw groove block 104a is provided with a hexagonal groove K3 and is matched with the nut 103, the tightening screw 104b is arranged at the bottom of the hexagonal groove K3, the tightening screw 104b penetrates through the second round hole H2, and one end of the tightening screw 104b is provided with a circle of transmission groove K4.

The tightening screw groove block 104a is sleeved on the nut 103, the tightening screw bolt 104b passes through the center of the nut 103 and the second round hole H2, and when the tightening screw bolt 104b is forced to rotate, the tightening screw groove block 104a is driven to rotate, and the tightening screw groove block 104a rotates to drive the nut 103 to tighten.

In use, the fixed attachment block 101 is fixed on a device to be connected with an iron chain, such as a bucket, or a bucket is directly perforated to form the fixed attachment block 101, then the second semicircular groove K2 of the movable attachment block 102 is matched with one ring side surface on the iron chain, the first semicircular groove K1 of the fixed attachment block 101 is matched with the other ring side surface on the iron chain, at the moment, the stud 102b passes through the center of the ring on the iron chain, then passes through the first round hole H1 of the fixed attachment block 101, the nut 103 is matched with the part of the stud 102b protruding out of the first round hole H1, the fastening stud 104b of the fastening screw block 104 passes through the center of the nut 103, and passes through the second round hole H2, and the fastening screw block 104a is sleeved on the nut 103.

The internal tightening assembly 200 and transmission assembly 300 thus move to drive the tightening stud 104b and thereby tighten the nut 103.

Example 2

Referring to fig. 1 to 5, a second embodiment of the present application is based on the previous embodiment.

Specifically, the vertical moving block 201 includes a large block 201a and a small block 201b, the small block 201b is disposed on two sides of one end of the large block 201a, a convex groove K5 is disposed on the large block 201a, a ring groove K6 is disposed on an inner wall of a wider side of the convex groove K5, the positioning block 203 is disposed in the ring groove K6, two vertical moving blocks 201 are distributed in a central symmetry manner, one end of the transmission assembly 300 is disposed in a wider side of the convex groove K5 of one vertical moving block 201, and the other end is disposed in a narrower side of the convex groove K5 of the other vertical moving block 201.

The small block 201b protrudes from one end of the movable block 102 and is inserted into the center of the ring of the iron chain so that when the fitting assembly 100 is no longer fitted, an adjacent ring of the iron chain to which the ring of the fitting assembly 100 is secured contacts the small block 201b, thereby allowing the vertical movable block 201 to move.

Specifically, two opposite ends of the large spring 202 are fixedly connected with the opposite surfaces of the two vertical moving blocks 201, and the large spring 202 is always in a compressed state.

The vertical movement of the block 201 drives the large spring 202 to compress to a shorter length.

Specifically, there are a plurality of positioning blocks 203 disposed in the ring groove K6, and each positioning block 203 has a lower end and a higher end.

The positioning block 203 allows the transmission cross-post 301 to move in only one direction within the ring groove K6.

Specifically, the transmission cross column 301 is matched with the ring groove K6; two ends of the small spring 302 are respectively and fixedly connected with the opposite surfaces of the two transmission transverse columns 301.

The transmission cross posts 301 move along the axial direction when passing through the positioning block 203, and a small spring 302 is clamped between the two transmission cross posts 301 to ensure that the transmission cross posts 301 are always clung to the bottom of the ring groove K6.

Specifically, the transmission transverse cylinder 303 is sleeved outside the transmission transverse column 301 and the small spring 302, and two ends of the transmission transverse cylinder 303 are matched with the inner wall of the wider side of the convex groove K5;

the movement of the drive cross post 301 is transferred to the drive cross cylinder 303.

A tooth slot K7 is arranged on one side of the transmission vertical column 304, the tooth slot K7 is matched with a transmission slot K4 at one end of the fastening stud 104b, and a limit slot K8 is arranged at the bottom of the transmission vertical column 304.

The transmission transverse cylinder 303 moves to drive the transmission vertical column 304 to move, and tooth grooves K7 on the transmission vertical column 304 move along with the transmission transverse cylinder.

The motion track of the transmission cross column 301 is in the shape of a ring groove K6, the transmission groove K4 is matched with the tooth groove K7 only when the transmission cross column is close to the transmission groove K4, and meanwhile, the transmission cross column 301 can only rotate unidirectionally, that is to say, the transmission cross column 301 can only do work in the same direction on the tooth groove K7,

specifically, the transmission assembly 300 further includes a middle spring 305 and a movable limiting block 306, two ends of the middle spring 305 are connected with the movable limiting block 306 and the transmission vertical column 304, a limiting column 306a is arranged at the top of one side of the movable limiting block 306, and the limiting column 306a is matched with a limiting groove K8 of the transmission vertical column 304.

The limit post 306a of the movable limit block 306 is inserted into the limit groove K8 of the transmission vertical post 304, so that the movable limit block 306 and the transmission vertical post 304 are kept consistent in the horizontal direction, and only the middle spring 305 does not influence the expansion and contraction.

In use, the fixed attachment block 101 is fixed on a device to be connected with an iron chain, such as a bucket, or a bucket is slotted and perforated directly to serve as the fixed attachment block 101, then the second semicircular groove K2 of the movable attachment block 102 is matched with one ring side surface on the iron chain, the first semicircular groove K1 of the fixed attachment block 101 is matched with the other ring side surface on the iron chain, at the moment, the stud 102b passes through the center of the ring on the iron chain, then passes through the first round hole H1 of the fixed attachment block 101, the nut 103 is matched with the part of the stud 102b protruding out of the first round hole H1, the fastening stud 104b of the fastening screw block 104 passes through the center of the nut 103, and passes through the second round hole H2, and the fastening screw slot block 104a is sleeved on the nut 103.

The chain drives the bucket to generally perform a rotary motion, and the bucket tends to cyclically and repeatedly approach the rings on both sides of the ring of the iron chain.

When the nut 103 of the attaching assembly 100 is loosened, the attaching assembly 100 does not attach to the ring of the iron chain any more, the attaching assembly 100 moves, the small block 201b of the vertical moving block 201 in the direction contacts with the adjacent ring of the iron chain, the small block 201b moves under force to drive the vertical moving block 201 to move, and the internal limiting block 203 in the vertical moving block 201 drives the transmission transverse column 301 to move.

When the transmission cross column 301 is close to the side of the tight stud 104b in the ring groove K6, the transmission groove K4 is matched with the tooth groove K7, the positioning block 203 drives the transmission cross column 301 to move, and the tight stud 104b is driven by the transmission vertical column 304, the middle spring 305 and the movable limiting block 306 to tighten the nut 103;

then the chain turns a half turn, the bucket reverses 180 degrees, the fitting assembly 100 moves towards the adjacent ring on the other side of the ring of the iron chain, during the process, the large spring 202 between the two vertical moving blocks 201 is reduced to 0 under pressure and then is reversely increased, the distance between the two vertical moving blocks 201 is increased and reduced, the middle spring 305 is matched with the moving limiting block 306 and the driving vertical post 304 to pull the driving transverse post 301, so that the driving transverse post 301 moves to the side of the ring groove K6 far away from the tight stud 104b along the ring groove K6 along the positioning limiting block 203, and the section of driving transverse post 301 does not do work on the tight stud 104 b.

Then the chain is rotated a half turn and the bucket is rotated 180 degrees again, the drive cross 301 moves along the groove K6 along the positioning block 203 to the side of the groove K6 adjacent to the tightening stud 104 b.

The fastener assembly 200 and drive assembly 300 on one side then only perform one work on the tightening stud 104b per revolution of the chain. Thus, when the chain drives the bucket turns, the nut 103 is tightened twice each time there is evidence of loosening by one turn of the chain.

It should be noted that the above embodiments are only for illustrating the technical solution of the present application and not for limiting the same, and although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present application may be modified or substituted without departing from the spirit and scope of the technical solution of the present application, which is intended to be covered in the scope of the claims of the present application.

Claims (10)

1. A connecting device suitable for self-tightening of iron chain, its characterized in that: comprising the steps of (a) a step of,

the laminating assembly (100) comprises a fixed laminating block (101), a movable laminating block (102), a nut (103) and a tightening screw block (104), wherein the movable laminating block (102) is arranged on one side of the fixed laminating block (101), the nut (103) is matched with the movable laminating block (102), and the tightening screw block (104) is sleeved outside the nut (103);

the fastening assembly (200) is arranged inside the attaching assembly (100) and comprises a vertical moving block (201), a large spring (202) and positioning limiting blocks (203), wherein the vertical moving block (201) is arranged on one side of the attaching assembly (100) and penetrates through the movable attaching block (102), the number of the vertical moving blocks (201) is two, the large spring (202) is arranged between the two vertical moving blocks (201), and the positioning limiting blocks (203) are arranged on two sides of the inner wall of the vertical moving block (201); the method comprises the steps of,

the transmission assembly (300) is arranged inside the fastening assembly (200), and comprises a transmission cross column (301), a small spring (302), a transmission cross cylinder (303) and a transmission vertical column (304), wherein the transmission cross column (301) is arranged on one side of the positioning block (203), the transmission cross column (301) is provided with two pieces, the small spring (302) is arranged between the two transmission cross columns (301), the transmission cross cylinder (303) is sleeved on the transmission cross column (301) and is arranged outside the small spring (302), and the transmission vertical column (304) is arranged at the bottom of the transmission cross cylinder (303).

2. The self-tightening connection device for an iron chain according to claim 1, wherein:

the utility model discloses a piece is decided to paste piece (101) both ends and is equipped with semicircle recess (K1) and round hole (H1) respectively, semicircle recess (K1) has two, round hole (H1) has one, round hole (H1) set up two between semicircle recess (K1).

3. The self-tightening connection device for iron chains according to claim 2, characterized in that:

the movable attaching block (102) comprises a movable block (102 a) and a stud (102 b), the stud (102 b) is arranged at one end of the movable block (102 a), the stud (102 b) penetrates through the first round hole (H1), a second semicircular groove (K2), a second round hole (H2) and a third groove hole (H3) are formed in the movable block (102 a), the second semicircular groove (K2) is two, the two sides of the stud (102 b) are correspondingly matched with the first semicircular groove (K1), the second round hole (H2) penetrates through the stud (102 b) and the movable block (102 a), and the third groove hole (H3) penetrates through the movable block (102 a) and is perpendicular to the second round hole (H2).

4. A self-tightening connection device for an iron chain as set forth in claim 3, wherein:

the screw tightening block (104) comprises a screw tightening groove block (104 a) and a screw tightening bolt (104 b), a hexagonal groove (K3) is formed in the screw tightening groove block (104 a) and is matched with the nut (103), the screw tightening bolt (104 b) is arranged at the bottom of the hexagonal groove (K3), the screw tightening bolt (104 b) penetrates through the second round hole (H2), and a circle of transmission groove (K4) is formed in one end of the screw tightening bolt (104 b).

5. The self-tightening connection device for iron chains according to claim 4, wherein:

the vertical moving block (201) comprises a large block (201 a) and a small block (201 b), the small block (201 b) is arranged on two sides of one end of the large block (201 a), a convex groove (K5) is formed in the large block (201 a), an annular groove (K6) is formed in the inner wall of one wider side of the convex groove (K5), the positioning block (203) is arranged in the annular groove (K6), two vertical moving blocks (201) are distributed in a central symmetry mode, one end of the transmission assembly (300) is arranged in one side of the vertical moving block (201) which is wider than the convex groove (K5), and the other end of the transmission assembly is arranged in the other side of the vertical moving block (201) which is narrower than the convex groove (K5).

6. The self-tightening connection device for iron chains according to claim 5, wherein:

two ends of the large spring (202) are fixedly connected with two opposite faces of the vertical moving block (201), and the large spring (202) is always in a compressed state.

7. The self-tightening connection device for iron chains according to claim 6, wherein:

the positioning blocks (203) are arranged in the annular groove (K6), and each positioning block (203) is low at one end and high at the other end.

8. The self-tightening connection device for iron chains according to claim 7, wherein:

the transmission cross column (301) is matched with the annular groove (K6); two ends of the small spring (302) are respectively and fixedly connected with the opposite surfaces of the two transmission transverse columns (301).

9. A self-tightening connection device for iron chains according to claim 7 or 8, characterized in that:

the transmission transverse cylinder (303) is sleeved outside the transmission transverse column (301) and the small spring (302), and two ends of the transmission transverse cylinder (303) are matched with the inner wall of the wider side of the convex groove (K5);

one side of the transmission vertical column (304) is provided with a tooth groove (K7), the tooth groove (K7) is matched with a transmission groove (K4) at one end of the tight stud (104 b), and the bottom of the transmission vertical column (304) is provided with a limit groove (K8).

10. The self-tightening connection device for iron chains according to claim 9, characterized in that:

the transmission assembly (300) further comprises a middle spring (305) and a movable limiting block (306), wherein the two ends of the middle spring (305) are connected with the movable limiting block (306) and the transmission vertical column (304), a limiting column (306 a) is arranged at the top of one side of the movable limiting block (306), and the limiting column (306 a) is matched with the limiting groove (K8) of the transmission vertical column (304).