A brake wedge assembly

Abstract

The invention relates to the field of brakes, and discloses a wedge assembly of a brake, wherein the free stroke is integrated into a spiral piston at the top of a housing, avoiding the method of controlling the free stroke of a traditional wedge-type expander through the gap between a piston and a piston sleeve, and integrating the self-adjusting functions at both ends at the upper end of the housing. When there is an excessive gap between the brake and the brake drum, the automatic adjustment mechanism at the upper end detects it, and then drives the adjustment pairs at both ends to adjust simultaneously through the transmission of a rectangular spline and a bevel gear, so that the adjustment amount generated by the leading shoe and the following shoe is consistent, thereby avoiding the occurrence of eccentric wear. The method of controlling the free stroke by vertical axial displacement controls the gap between the brake drum and the brake shoe in a more stable manner, effectively reduces eccentric wear, and also reduces the occurrence of locking caused by eccentric wear.

Description

Technical Field

[0001] The present invention relates to the technical field of brakes, and more particularly to a wedge assembly of a brake. Background Art

[0002] The wedge expander of the traditional brake is prone to eccentric wear and locking during use. The eccentric wear of the wedge expander is mainly because the wedge brake is an unbalanced brake. When the driver steps on the pedal, the air chamber is inflated for braking. According to theoretical calculations, during the braking process of the wedge brake, the efficiency factor of the leading shoe is about 2.6 times that of the trailing shoe. When it is assumed that the wear of the friction plate is proportional to the force condition of the brake shoe, the wear degree of the friction plate of the leading shoe is about 2.6 times that of the trailing shoe. In addition, because the adjustment mechanism of the wedge brake (wedge expander) is unilaterally controlled at the leading shoe and the trailing shoe end, the self-adjusting mechanism at the leading shoe end is always in effect due to the high wear of the leading shoe end. Due to the above reasons, the wedge brake is prone to eccentric wear during use. Since the push rod of the wedge expander has no limit, when braking occurs, the push rod is prone to swing, which is easy to interfere with the components and cause jamming.

[0003] Therefore, how to provide a wedge assembly for a brake is a problem that those skilled in the art need to solve urgently. Summary of the invention

[0004] Therefore, the purpose of the present invention is to provide a wedge assembly of a brake, which solves the problem that the traditional wedge expander is prone to eccentric wear and locking.

[0005] The present invention provides a brake wedge assembly, comprising:

[0006] A housing, wherein a vertical channel and a horizontal channel interpenetrating each other are vertically arranged in the housing; a first channel is formed at the top of the vertical channel, and a spiral piston sleeve is fixed in the first channel;

[0007] A rotary piston mechanism, comprising a spiral piston, a rectangular spring and a rectangular spline shaft; the outer wall of the spiral piston is threadedly connected to the spiral piston sleeve, and a push-up space is defined at the top thereof; the rectangular spring is located in a space formed by the bottom of the spiral piston and the top of the rectangular spline shaft, and the rectangular spring and the spiral piston rotate in reverse or forward direction, and the reverse state realizes synchronous rotation of the spiral piston and the rectangular spline shaft; the bottom of the rectangular spline shaft is connected with an active bevel gear;

[0008] A push rod, the push rod comprises a bottom push rod and a top push rod, the top end of the bottom push rod is connected to the top push rod and can move in a second channel formed by the spiral piston, the rectangular spring and the middle part of the rectangular spline shaft, the bottom of the top push rod and the push space have a free stroke S; a wedge block is formed at the bottom of the bottom push rod, a bracket with a roller is sleeved on the wedge block, and the bracket moves with the bottom push rod in the through area of ​​the horizontal channel and the vertical channel;

[0009] Auxiliary bevel gears, two of which are symmetrically arranged on both sides of the active bevel gears, and are both meshed with the active bevel gears and rotate in the horizontal channel;

[0010] Adjustment pairs, the adjustment pairs are in two groups, located below the auxiliary bevel gear and gear-transmitted with the auxiliary bevel gear; the two groups of adjustment pairs are located on both sides of the bracket and contact with one group of rollers in a one-to-one correspondence;

[0011] A limit screw is inserted into the housing and connected to the adjustment pair to limit its rotation.

[0012] It can be seen from the above technical solutions that compared with the prior art, the present invention discloses a wedge assembly of a brake, the free stroke is integrated into the spiral piston at the top of the shell, avoiding the method of controlling the free stroke of the traditional wedge expander through the gap between the piston and the piston sleeve, and integrating the self-adjusting function at both ends at the upper end of the shell. When there is an excessive gap between the brake and the brake drum, the automatic adjustment mechanism at the upper end detects it, and then drives the adjustment pairs at both ends to adjust at the same time through the transmission of the rectangular spline and the bevel gear, so that the adjustment amount generated by the leading shoe and the following shoe is consistent, thereby avoiding the occurrence of eccentric wear. The method of controlling the free stroke by vertical axial displacement is more stable to control the gap between the brake drum and the brake shoe, effectively reducing eccentric wear, and also reducing the occurrence of locking caused by eccentric wear.

[0013] Furthermore, the top of the top push rod is a columnar rod, and the bottom is a push block with a diameter larger than the columnar rod, and the middle of the push block has a threaded groove connected to the bottom push rod.

[0014] Furthermore, a top spring is sleeved on the top push rod, and the top of the top push rod is connected to a butterfly gasket through a shaft retaining spring. One end of the top spring abuts against the butterfly gasket, and the other end enters the first channel and stops at the top of the spiral piston sleeve T.

[0015] Furthermore, a downward-opening stepped groove is formed at the bottom of the spiral piston, the first stepped groove is used to install the rectangular spring, and a first clamping groove is provided on the inner wall of the second stepped groove; an upward mating groove is formed at the top of the rectangular spline shaft, and the mating groove cooperates with the first stepped groove to install the rectangular spring, and the outside of the groove wall of the mating groove has a second clamping groove that engages with the first clamping groove, and a square retaining ring is installed between the first clamping groove and the second clamping groove.

[0016] Furthermore, a bottom spring is sleeved on the rectangular spline shaft, one end of the bottom spring abuts against the bottom of the matching ring groove, and the other end abuts against the top of the active bevel gear.

[0017] Furthermore, each of the auxiliary bevel gears includes a wheel axle, a auxiliary bevel gear body, and a first spur gear; the wheel axle is horizontally arranged in the horizontal channel, and is provided with the auxiliary bevel gear body at one end close to the active bevel gear, and is formed with a hexagonal adjustment rod at one end away from the active bevel gear, and the hexagonal adjustment rod extends out of the horizontal channel and then blocks the horizontal channel through a screw cover; the first spur gear is located in the middle of the wheel axle and is transmitted to the adjustment auxiliary gear.

[0018] Furthermore, each of the adjustment pairs includes an adjusting screw, a piston, a slider, a square retaining ring and a fixing card; a second spur gear meshing with the first spur gear is provided on the outer wall of the piston, and the tooth width of the second spur gear is greater than the tooth width of the first spur gear; a horizontal thread groove threadedly connected to the adjusting screw is provided inside the piston, and one end of the adjusting screw extends out of the horizontal channel and is fixed by a fixing card, and the end of the horizontal channel is blocked by a dust cover; the piston is connected to the slider via a square retaining ring in the direction corresponding to the other end of the adjusting screw; the slider abuts against the roller, and the bottom of the limit screw is connected to the slider. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0020] Figure 1 The accompanying drawing is a schematic structural diagram of a wedge assembly of a brake provided by the present invention (in a state where there is a free stroke S);

[0021] Figure 2 The accompanying drawing is a schematic structural diagram of a wedge assembly of a brake provided by the present invention (a state in which the free travel S is eliminated);

[0022] Figure 3 The accompanying drawing is a three-dimensional diagram of a wedge block assembly of a brake provided by the present invention;

[0023] Figure 4 The accompanying drawing is a three-dimensional partial cross-sectional view of a wedge assembly of a brake provided by the present invention;

[0024] Figure 5 The accompanying drawing shows a schematic diagram of the connection state of the bottom push rod, the bracket and the roller;

[0025] Figure 6 The accompanying drawing is an exploded view of the rotary piston mechanism;

[0026] Figure 7 The accompanying drawing is a cross-sectional view of the rotary piston mechanism;

[0027] Figure 8 The accompanying drawing shows a schematic diagram of the connection state of the auxiliary bevel gear, the adjustment pair and the active bevel gear;

[0028] In the figure: 100-housing, 200-bottom push rod, 201-wedge block, 202-roller, 203-bracket, 300-top push rod, 301-top spring, 302-shaft retaining ring, 303-butterfly washer, 400-rotary piston mechanism, 401-spiral piston, 402-rectangular spring, 403-rectangular spline shaft, 404-active bevel gear, 405-square retaining ring, 406-bottom spring, 5 00-secondary bevel gear, 501-axle, 502-secondary bevel gear body, 503-first spur gear, 504-hexagonal adjusting rod, 600-adjusting pair, 601-adjusting screw, 602-piston, 603-slider, 604-square retaining ring, 605-fixing card, 606-second spur gear, 700-dust cover, 800-screw cover, 900-limit screw, T-spiral piston sleeve, S-free travel. DETAILED DESCRIPTION

[0029] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0030] In the description of the present invention, it is necessary to understand that the terms "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0031] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0032] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] See attached Figure 1-8The embodiment of the present invention discloses a wedge assembly of a brake, comprising: a housing 100, wherein a vertical channel and a horizontal channel which are interconnected are vertically arranged in the housing 100; a first channel formed at the top of the vertical channel, wherein a spiral piston sleeve T is fixed in the first channel; a rotary piston mechanism 400, wherein the rotary piston mechanism 400 comprises a spiral piston 401, a rectangular spring 402 and a rectangular spline shaft 403; the outer wall of the spiral piston 401 is threadedly connected to the spiral piston sleeve T, and a push space is defined at the top thereof; the rectangular spring 402 is located in a space formed by the bottom of the spiral piston 401 and the top of the rectangular spline shaft 403, and the rectangular spring 402 and the spiral piston 401 are reversed or forwardly rotated, and the reverse state realizes the synchronous rotation of the spiral piston 401 and the rectangular spline shaft 403; an active bevel gear 404 is connected to the bottom of the rectangular spline shaft 403; a push rod, wherein the push rod comprises a bottom push rod 200 and a top push rod 300, and the top of the bottom push rod 200 is connected to the top push rod 300. Rod 300, and can move in the second channel formed by the spiral piston 401, the rectangular spring 402 and the middle part of the rectangular spline shaft 403, the bottom of the top push rod 300 and the push space have a free stroke S; a wedge block 201 is formed at the bottom of the bottom push rod 200, and a bracket 203 with a roller 202 is sleeved on the wedge block 201, and the bracket 203 follows the bottom push rod 200 to move in the horizontal channel and the vertical channel penetration area; auxiliary bevel gear 500, two auxiliary bevel gears 500 are symmetrically arranged on both sides of the active bevel gear 404, and both are engaged with the active bevel gear 404 and rotate in the horizontal channel; adjustment pair 600, the adjustment pair 600 is divided into two groups, located below the auxiliary bevel gear 500, and is gear-driven with the auxiliary bevel gear 500; the two groups of adjustment pairs 600 are located on both sides of the bracket 203, and contact one group of rollers 202 one by one; limit screw 900, the limit screw 900 is connected to the adjustment pair 600 after being inserted into the housing 100 to limit its rotation.

[0034] The present invention discloses a wedge assembly of a brake, wherein the free stroke is integrated into the spiral piston at the top of the housing, avoiding the method of controlling the free stroke of a traditional wedge expander through the gap between the piston and the piston sleeve, and integrating the self-adjusting functions at both ends at the upper end of the housing. When there is an excessive gap between the brake and the brake drum, the automatic adjustment mechanism at the upper end detects it, and then drives the adjustment pairs at both ends to adjust simultaneously through the transmission of the rectangular spline and the bevel gear, so that the adjustment amount generated by the leading shoe and the following shoe is consistent, thereby avoiding the occurrence of eccentric wear. The method of controlling the free stroke by vertical axial displacement is more stable to control the gap between the brake drum and the brake shoe, effectively reducing eccentric wear, and also reducing the occurrence of locking caused by eccentric wear.

[0035] Advantageously, see Appendix Figure 1 The top of the top push rod 300 is a columnar rod with a smooth transition at the top, and the bottom is a push block with a diameter larger than the columnar rod, and the middle of the push block has a thread groove connected to the bottom push rod 200. The thickness of the push block is less than the height value of the top push space.

[0036] In the above embodiment, a top spring 301 is sleeved on the top push rod 300, and the top of the top push rod 300 is connected to the butterfly gasket 303 through the shaft retaining ring 302. One end of the top spring 301 abuts against the butterfly gasket 303, and the other end enters the first channel and stops at the top of the spiral piston sleeve T.

[0037] Advantageously, see Appendix Figure 4 , 6 and 7, a stepped groove opening downward is formed at the bottom of the spiral piston 401, the first stepped groove is used to install the rectangular spring 402, and a first clamping groove is formed on the inner wall of the second stepped groove; an upward matching groove is formed on the top of the rectangular spline shaft 403, and the matching groove cooperates with the first stepped groove to install the rectangular spring 402, and the outer part of the groove wall of the matching groove has a second clamping groove that is engaged with the first clamping groove, and a square retaining ring 405 is installed between the first clamping groove and the second clamping groove, and a bottom spring 406 is sleeved on the rectangular spline shaft 403, one end of the bottom spring 406 abuts against the bottom of the matching ring groove, and the other end abuts against the top of the active bevel gear 404.

[0038] Assembly grooves for square retaining rings are designed in the spiral piston and the rectangular spline shaft. During assembly, the square retaining ring is inserted into the first groove of the spiral piston, and then the rectangular spline shaft with a rectangular spring is screwed into the spiral piston. After assembly, the square retaining ring will be inserted into the second groove of the rectangular spline shaft, which can prevent the spiral piston and the rectangular spline shaft from being dragged apart.

[0039] See attached Figure 8 Each auxiliary bevel gear 500 includes a wheel shaft 501, an auxiliary bevel gear body 502, and a first spur gear 503; the wheel shaft 501 is horizontally arranged in the horizontal channel, and a auxiliary bevel gear body 502 is provided at one end thereof close to the active bevel gear 404, and a hexagonal adjustment rod 504 is formed at one end thereof away from the active bevel gear 404. After the hexagonal adjustment rod 504 extends out of the horizontal channel, the horizontal channel is blocked by a screw cover 800; the first spur gear 503 is located in the middle of the wheel shaft 501, and is geared with the adjustment pair 600.

[0040] A hexagonal adjusting rod is designed on the head of the secondary bevel gear. When the brake is locked, the excess clearance can be recovered by adjusting the hexagonal adjusting rod, thereby avoiding the problem of being unable to disassemble when the brake is locked.

[0041] See attached Figure 1-4and 8, each adjustment pair 600 includes an adjusting screw 601, a piston 602, a slider 603, a square retaining ring 604 and a fixing card 605; a second spur gear 606 meshing with the first spur gear 503 is provided on the outer wall of the piston 602, and the tooth width of the second spur gear 606 is greater than the tooth width of the first spur gear 503; a horizontal thread groove threadedly connected to the adjusting screw 601 is provided inside the piston 602, and one end of the adjusting screw 601 extends out of the horizontal channel and is fixed by the fixing card 605, and the end of the horizontal channel is blocked by the dust cover 700; the piston 602 is connected to the slider 603 in the direction corresponding to the other end of the adjusting screw 601 through the square retaining ring 604; the slider 603 is in contact with the roller 202, the bracket is sleeved on the bottom push rod, the roller is installed on the bracket, the bottom push rod moves downward, and the roller opens to both sides; and the bottom of the limit screw 900 is connected to the slider 603 to limit the rotation of the slider.

[0042] The transmission angle of the bevel gear is 90°. When there is an excessive gap, the spiral piston rotates under the action of the piston sleeve, and the spiral piston mechanism is in a reverse gear relationship, so the spiral piston drives the rectangular spline to rotate, and then drives the main bevel gear to rotate, and then drives the secondary bevel gear to rotate, and the secondary bevel gear drives the piston to rotate. Since the adjustment bolt does not rotate under the action of the card, L increases in this case, thereby eliminating the excessive gap. The tail of the adjustment bolt has a fixed disk, and a plurality of protrusions are arranged on the fixed disk. The fixed card has a plurality of notches that match the protrusions of the fixed disk.

[0043] See attached Figure 1 , eliminate the set free travel S: There is a certain gap between the top push rod and the inside of the spiral piston (i.e. free travel S). When the driver steps on the pedal, the brake air chamber is inflated to push the top push rod downward to eliminate the above gap. See attached Figure 2 .

[0044] Eliminate excess clearance: When there is excess clearance between the brake drum and the brake, the brake air chamber pushes the top push rod to continue to move downward. Since the internal clearance between the top push rod and the spiral piston has been eliminated, the spiral piston will continue to move downward. During the downward movement, the spiral piston rotates due to the action of the spiral piston sleeve. At this time, the spiral piston and the rectangular spline are in the reverse tooth direction (forward tooth relationship: when the spiral piston and the rectangular spring rotate in the same direction, the rectangular spring begins to contract. Since there is no obstruction to the rotation of the spiral piston at this time, it is in the forward tooth direction at this time. Reverse tooth relationship: when the spiral piston and the rectangular spring rotate in opposite directions, the rectangular spring begins to expand and contacts the inner wall of the spiral piston. At this time, the spiral piston is blocked and cannot rotate, so it is in the reverse tooth direction at this time). The spiral piston will drive the rectangular spline to rotate, and then drive the main bevel teeth to rotate, and then drive the secondary bevel teeth to rotate, and the secondary bevel teeth drive the bottom piston to rotate, thereby eliminating excess clearance.

[0045] Push rod reset: When the brake is released, the brake air chamber is deflated, and the top push rod returns to its original position under the action of the spring. Since the spiral piston and the piston sleeve are in the tooth direction at this time, the gears do not rotate during the return process.

[0046] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification.

[0047] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A brake wedge assembly, characterized in that: include: A housing (100), wherein a vertical channel and a horizontal channel interpenetrating each other are vertically arranged in the housing (100); a first channel is formed at the top of the vertical channel, and a spiral piston sleeve (T) is fixed in the first channel; A rotary piston mechanism (400), the rotary piston mechanism (400) comprising a spiral piston (401), a rectangular spring (402) and a rectangular spline shaft (403); the outer wall of the spiral piston (401) is threadedly connected to the spiral piston sleeve (T), and the top of the spiral piston sleeve defines a push-up space; the rectangular spring (402) is located in a space formed by the bottom of the spiral piston (401) and the top of the rectangular spline shaft (403); the rectangular spring (402) and the spiral piston (401) rotate in reverse or forward direction, and the reverse state enables the spiral piston (401) and the rectangular spline shaft (403) to rotate synchronously; the bottom of the rectangular spline shaft (403) is connected to an active bevel gear (404); A push rod, the push rod comprising a bottom push rod (200) and a top push rod (300), the top end of the bottom push rod (200) being connected to the top push rod (300) and being movable in a second channel formed by the spiral piston (401), the rectangular spring (402) and the middle of the rectangular spline shaft (403), the bottom of the top push rod (300) and the pushing space having a free stroke S; a wedge block (201) being formed at the bottom of the bottom push rod (200), a bracket (203) having a roller (202) being sleeved on the wedge block (201), the bracket (203) following the bottom push rod (200) to move in the through-region of the horizontal channel and the vertical channel; Auxiliary bevel gears (500), two of the auxiliary bevel gears (500) are symmetrically arranged on both sides of the active bevel gear (404), and both mesh with the active bevel gear (404) and rotate in the horizontal channel; Adjustment pairs (600), the adjustment pairs (600) being two groups, located below the auxiliary bevel gear (500) and gear-driven with the auxiliary bevel gear (500); the two groups of adjustment pairs (600) are located on both sides of the bracket (203) and contact one group of the rollers (202) in a one-to-one correspondence; A limit screw (900), wherein the limit screw (900) is inserted into the housing (100) and then connected to the adjustment pair (600) to limit its rotation; A top spring (301) is sleeved on the top push rod (300), and the top of the top push rod (300) is connected to a butterfly gasket (303) via a shaft retaining ring (302). One end of the top spring (301) abuts against the butterfly gasket (303), and the other end enters the first channel and abuts against the top of the spiral piston sleeve (T); A stepped groove opening downward is formed at the bottom of the spiral piston (401), the first stepped groove is used to install the rectangular spring (402), and a first clamping groove is formed on the inner wall of the second stepped groove; an upward matching groove is formed at the top of the rectangular spline shaft (403), the matching groove cooperates with the first stepped groove to install the rectangular spring (402), the groove wall of the matching groove has a second clamping groove that is engaged with the first clamping groove, and a square retaining ring (405) is installed between the first clamping groove and the second clamping groove; A bottom spring (406) is sleeved on the rectangular spline shaft (403), one end of the bottom spring (406) abuts against the bottom of the matching ring groove, and the other end abuts against the top of the active bevel gear (404).

2. A brake wedge assembly according to claim 1, characterized in that: The top of the top push rod (300) is a columnar rod, and the bottom is a push block with a diameter larger than the columnar rod. The middle of the push block has a threaded groove connected to the bottom push rod (200).

3. The brake wedge assembly according to claim 1, characterized in that: Each of the auxiliary bevel gears (500) comprises a wheel shaft (501), an auxiliary bevel gear body (502), and a first spur gear (503); the wheel shaft (501) is horizontally arranged in the horizontal channel, and the auxiliary bevel gear body (502) is provided at one end of the wheel shaft (501) close to the active bevel gear (404), and a hexagonal adjustment rod (504) is formed at one end away from the active bevel gear (404); the hexagonal adjustment rod (504) extends out of the horizontal channel and blocks the horizontal channel through a screw cover (800); the first spur gear (503) is located in the middle of the wheel shaft (501) and is geared with the adjustment pair (600).

4. A brake wedge assembly according to claim 3, characterized in that: Each of the adjustment pairs (600) comprises an adjustment screw (601), a piston (602), a slider (603), a square retaining ring (604) and a fixing card (605); a second spur gear (606) meshing with the first spur gear (503) is provided on the outer wall of the piston (602), and the tooth width of the second spur gear (606) is greater than the tooth width of the first spur gear (503); a horizontal thread groove threadedly connected to the adjustment screw (601) is provided inside the piston (602), and one end of the adjustment screw (601) extends out of the horizontal channel and is fixed by the fixing card (605), and the end of the horizontal channel is blocked by a dust cover (700); the piston (602) is connected to the slider (603) in a direction corresponding to the other end of the adjustment screw (601) through a square retaining ring (604); the slider (603) abuts against the roller (202), and the bottom of the limit screw (900) is connected to the slider (603).

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