A servo motor brake device

Abstract

The present invention discloses a servo motor brake device, which relates to the field of electromechanical control technology, and comprises: a connecting shell, which is fixed on a shell at one end of the output shaft of the servo motor; a protective shell, which is fixedly connected to the connecting shell, and the center of the protective shell is rotatably connected to the output shaft; a sleeve, which is arranged between the connecting shell and the protective shell, and is fixed on the output shaft; a brake pad, which is arranged at one end of the sleeve close to the connecting shell, and the brake pad is slidably connected to the sleeve; a secondary brake assembly, which is arranged on the outside of the sleeve and fits with the brake pad; a primary brake assembly, which is arranged on the outside of the secondary brake assembly and connected to the inner wall of the protective shell; the present invention stops the output shaft instantly by gradually reducing the speed, and under the gradually reducing the speed, effectively reduces the shear force on the brake assembly during the braking process, thereby reducing equipment loss.

Description

Technical Field

[0001] The present invention relates to the field of electromechanical control technology, and more specifically, to a servo motor brake device. Background Art

[0002] The rotor speed of the servo motor is controlled by the input signal and can respond quickly. In the automatic control system, it is used as an actuator and has the characteristics of small electromechanical time constant and high linearity. It can convert the received electrical signal into angular displacement or angular velocity output on the motor shaft. When used in high-precision fields, the servo motor needs to have a fast braking capability so that the equipment driven by the servo motor can stop quickly and accurately. Although the servo motor performs well in the automatic control system, there are still some problems with the existing servo motor brake device. When the servo motor stops, its reciprocating fine-tuning motion time is too long, which will affect the rapid response rate of other equipment connected to the servo motor. In addition, some brake devices are complex in structure and difficult to install, and may generate large shear forces during use, resulting in equipment damage or performance degradation. Therefore, it is necessary to provide a servo motor brake device to solve the problems raised in the above background technology. Summary of the invention

[0003] To achieve the above object, the present invention provides the following technical solution: a servo motor brake device, comprising:

[0004] A connecting housing is fixed to the housing at one end where the output shaft of the servo motor is located;

[0005] A protective shell is fixedly connected to the connecting shell, and the center of the protective shell is rotatably connected to the output shaft;

[0006] A shaft sleeve, arranged between the connecting housing and the protective housing, and fixedly connected to the output shaft through a wedge block, and the wedge block is fixed on the output shaft;

[0007] A brake pad is arranged at one end of the shaft sleeve close to the connecting housing, and the brake pad is fixedly connected to the shaft sleeve;

[0008] A secondary brake assembly is arranged on the outside of the sleeve and fits the brake pad;

[0009] A primary brake assembly is arranged outside the secondary brake assembly and connected to the inner wall of the protective shell;

[0010] The secondary brake assembly comprises:

[0011] The secondary brake pad is annular and arranged on the outside of the sleeve, fitting into the annular groove on the brake pad;

[0012] A first rotation adjustment mechanism is fixedly connected to a side of the secondary brake pad away from the brake pad;

[0013] A plurality of first locking mechanisms are provided in an annular distribution and fixed inside the first rotation adjustment mechanism, and the first locking mechanisms correspond to the shaft sleeve;

[0014] A plurality of connecting bayonet holes are provided in an annular distribution and are fixed on the outside of the first rotation adjustment mechanism, and the positions of the connecting bayonet holes and the first locking mechanism do not overlap;

[0015] The primary brake assembly comprises:

[0016] The primary brake pad is annular and is arranged on the side of the brake pad away from the connection housing;

[0017] A second rotation adjustment mechanism is fixedly connected to a side of the primary brake pad away from the brake pad;

[0018] A plurality of second locking mechanisms are provided in an annular distribution and fixed in the second rotation adjustment mechanism, corresponding to the connection bayonet on the secondary brake assembly;

[0019] The telescopic shaft body is composed of a fixed shaft and an extension shaft. The fixed shaft is fixed on the inner wall of the protective shell, and the extension shaft is slidably arranged in the fixed shaft and fixedly connected with the second rotation adjustment mechanism.

[0020] Preferably, the inner wall of the connecting shell is provided with a plurality of annularly distributed limit blocks and a lifting platform slidably arranged on the inner side of the limit blocks, and the limit blocks are fitted with the outer ring of the brake pad; the lifting platform is fitted with a side of the brake pad close to the connecting shell.

[0021] Preferably, a rotating assembly is further provided on the inner wall of the connecting shell, and the rotating assembly includes a rotating motor fixed on the inner wall of the connecting shell, and a rotating gear fixedly connected to the rotating motor, and the rotating gear corresponds to the brake pad.

[0022] Preferably, a plurality of annularly distributed locking bayonet holes are provided on the outer side of the sleeve, and the locking bayonet holes correspond to the secondary brake assemblies.

[0023] Preferably, the outer ring of the brake pad is provided with a connecting gear ring, the connecting gear ring corresponds to the rotating gear, and an annular groove is provided at a position of the brake pad corresponding to the secondary brake assembly.

[0024] Preferably, the first rotation adjustment mechanism and the second rotation adjustment mechanism have the same structure, and the first rotation adjustment mechanism comprises:

[0025] A rotating ring is fixedly connected to the side of the brake pad away from the brake pad;

[0026] A plurality of arc-shaped tracks are provided in an annular distribution and are arranged on the rotating ring, corresponding to the locking mechanism;

[0027] An adjusting member is slidably arranged in the arc track and fixedly connected to the locking mechanism;

[0028] The positioning ring body is fixed on a side of the rotating ring away from the brake pad, and the locking mechanism is fixed in the positioning ring body.

[0029] Preferably, the locking mechanism comprises:

[0030] A fixed track is fixed in the positioning ring body;

[0031] A moving part is slidably arranged in the fixed track and fixedly connected to the adjusting part;

[0032] The locking block is slidably arranged in the fixed track and fixedly connected with the moving part.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The present invention fixes the brake device and maintains the normal operation and braking operation of the servo motor by setting a connecting shell and a protective shell; the output shaft is extremely decelerated by setting a primary brake assembly, and is further decelerated under the action of a secondary brake assembly, and the output shaft is instantly stopped by the joint action of the sleeve and the secondary brake assembly; under the joint action of the multi-stage brake assembly and the brake pad, the shear force on the brake assembly during the braking process is effectively reduced, thereby reducing equipment loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the overall structure of a servo motor brake device;

[0036] Figure 2 It is a schematic diagram of the internal structure of the connecting shell in the present invention;

[0037] Figure 3 It is a structural schematic diagram of the secondary brake assembly in the present invention;

[0038] Figure 4 It is a structural schematic diagram of the primary brake assembly in the present invention;

[0039] Figure 5 It is a structural schematic diagram of the first rotation adjustment mechanism and the locking mechanism in the present invention;

[0040] In the figure: 1. connecting shell; 2. protective shell; 3. bushing; 4. brake pad; 5. secondary brake assembly; 6. primary brake assembly; 11. limit block; 12. lifting platform; 13. rotating assembly; 31. locking bayonet; 41. connecting gear ring; 51. secondary brake pad; 52. first rotation adjustment mechanism; 53. first locking mechanism; 54. connecting bayonet; 61. primary brake pad; 62. second rotation adjustment mechanism; 63. second locking mechanism; 64. telescopic shaft; 131. rotating motor; 132. rotating gear; 521. rotating ring; 522. arc track; 523. adjusting member; 524. positioning ring; 551. fixed track; 552. moving member; 553. locking block. DETAILED DESCRIPTION

[0041] See also Figure 1 to Figure 5 In an embodiment of the present invention, a servo motor brake device includes:

[0042] Connecting housing 1, fixed on the housing at one end where the output shaft of the servo motor is located;

[0043] The protective housing 2 is fixedly connected to the connecting housing 1, and the center of the protective housing 2 is rotatably connected to the output shaft;

[0044] A shaft sleeve 3 is arranged between the connecting housing 1 and the protective housing 2 and is fixedly connected to the output shaft via a wedge block, and the wedge block is fixed on the output shaft;

[0045] A brake pad 4 is arranged at one end of the shaft sleeve 3 close to the connection housing 1, and the brake pad 4 is fixedly connected to the shaft sleeve 3;

[0046] A secondary brake assembly 5 is arranged on the outer side of the sleeve 3 and fits with the brake pad 4;

[0047] The primary brake assembly 6 is arranged on the outer side of the secondary brake assembly 5 and connected to the inner wall of the protective shell 2 .

[0048] In this embodiment, a plurality of annularly distributed limit blocks 11 and a lifting platform 12 slidably arranged on the inner wall of the connecting shell 1 are provided, and the limit blocks 11 are fitted with the outer ring of the brake pad 4; the lifting platform 12 is fitted with the side of the brake pad 4 close to the connecting shell 1.

[0049] That is to say, under the pushing action of the lifting platform 12, the brake pad 4 and the sleeve 3 move to the position of the wedge block on the output shaft, so that the sleeve 3 and the output shaft are fixedly connected through the wedge block. At this time, the output shaft can drive the sleeve 3 and the brake pad 4 to rotate synchronously during rotation. When the servo motor stops, the output shaft can be quickly decelerated by the friction between the primary brake assembly 6 and the secondary brake assembly 5 and the brake pad 4, and the sleeve 3 can be locked by the secondary brake assembly 5 to achieve the purpose of immediate stopping of the output shaft; when the lifting platform 12 shrinks, the brake pad 4 and the sleeve 3 are separated from the wedge block on the output shaft under the push of the primary brake assembly 6, and then the brake pad 4 and the sleeve 3 are in a rotatable state. The primary brake assembly 6 and the secondary brake assembly 5 can be reset by rotating the brake pad 4 and the sleeve 3 to release the sleeve 3. After the lifting platform 12 pushes the sleeve 3 to reset, the brake assembly can perform braking work when the servo motor stops again.

[0050] In this embodiment, a rotating assembly 13 is further provided on the inner wall of the connecting shell 1. The rotating assembly 13 includes a rotating motor 131 fixed on the inner wall of the connecting shell 1, and a rotating gear 132 fixedly connected to the rotating motor 131. The rotating gear 132 corresponds to the brake pad 4.

[0051] That is to say, when the brake assembly locks and stops the output shaft, the lifting platform 12 shrinks, and the brake pad 4 and the sleeve 3 are separated from the wedge block on the output shaft under the push of the primary brake assembly 6, and then the brake pad 4 and the sleeve 3 are in a rotating state, and the brake pad 4 is connected to the rotating gear 132. Driven by the rotating motor 131, the rotating gear 132 drives the brake pad 4 to rotate, reset the primary brake assembly 6 and the secondary brake assembly 5, and release the sleeve 3 to facilitate the next braking work of the servo motor.

[0052] In this embodiment, a plurality of annularly distributed locking bayonet holes 31 are provided on the outer side of the shaft sleeve 3 , and the locking bayonet holes 31 correspond to the secondary brake assembly 5 .

[0053] That is to say, when the servo motor stops, the primary brake assembly 6 fits against the brake pad 4, and with the help of the friction between the brake pad 4 and the primary brake assembly 6, the primary brake assembly 6 fixes the secondary brake assembly 5, and then through the friction between the secondary brake assembly 5 and the brake pad 4, the secondary brake assembly 5 is driven to connect with the locking bayonet 31 on the shaft sleeve 3, and the shaft sleeve 3 is locked and fixed, that is, the output shaft is locked and fixed, and after multiple stages of deceleration, the output shaft stops immediately.

[0054] In this embodiment, the outer ring of the brake pad 4 is provided with a connecting toothed ring 41 , the connecting toothed ring 41 corresponds to the rotating gear 132 , and an annular groove is provided at a position of the brake pad 4 corresponding to the secondary brake assembly 5 .

[0055] That is to say, under the action of the connecting gear ring 41, the rotating gear 132 can drive the brake pad 4 to rotate through the connecting gear ring 41 to reset the brake assembly, and under the action of the annular groove on the brake pad 4, the secondary brake assembly 5 is always kept in contact with the brake pad 4. Under the condition of no restriction, the secondary brake assembly 5 follows the brake pad 4 to rotate. Under the restriction of the primary brake assembly 6, the secondary brake assembly 5 reduces the speed of the output shaft again through the friction between the secondary brake assembly 5 and the brake pad 4.

[0056] In this embodiment, the secondary brake assembly 5 includes:

[0057] The secondary brake pad 51 is annular and arranged on the outer side of the sleeve 3 and fits in the annular groove on the brake pad 4;

[0058] A first rotation adjustment mechanism 52 is fixedly connected to a side of the secondary brake pad 51 away from the brake pad 4;

[0059] A plurality of first locking mechanisms 53 are provided in an annular distribution and fixed inside the first rotation adjustment mechanism 52, and the first locking mechanisms 53 correspond to the shaft sleeve 3;

[0060] A plurality of connecting bayonet holes 54 are provided in an annular arrangement and are fixed on the outside of the first rotation adjustment mechanism 52 , and the positions of the connecting bayonet holes 54 and the first locking mechanism 53 do not overlap.

[0061] When the secondary brake assembly 5 is not restricted by external force, the secondary brake pad 51 fits with the brake pad 4, and under the drive of the output shaft, the brake pad 4 drives the secondary brake assembly 5 to rotate synchronously; when the secondary brake assembly 5 is fixed by the connecting bayonet 54 under the restriction of the primary brake assembly 6, the secondary brake pad 51 is rotationally connected with the brake pad 4, and under the action of the friction force between the secondary brake pad 51 and the brake pad 4, the secondary brake pad 51 slows down the output shaft while driving the secondary brake pad 51 to rotate, adjust the first rotation adjustment mechanism 52, and then lock the shaft sleeve 3 through the first locking mechanism 53 to stop the output shaft.

[0062] In this embodiment, the primary brake assembly 6 includes:

[0063] The primary brake pad 61 is annular and is arranged on the side of the brake pad 4 away from the connection housing 1;

[0064] The second rotation adjustment mechanism 62 is fixedly connected to the side of the primary brake pad 61 away from the brake pad 4;

[0065] A plurality of second locking mechanisms 63 are provided in an annular distribution and fixed in the second rotation adjustment mechanism 62, corresponding to the connection bayonet 54 on the secondary brake assembly 5;

[0066] The telescopic shaft body 64 is composed of a fixed shaft and an extension shaft. The fixed shaft is fixed on the inner wall of the protective shell 2 , and the extension shaft is slidably arranged in the fixed shaft and fixedly connected to the second rotation adjustment mechanism 62 .

[0067] That is to say, when the servo motor stops, the telescopic shaft 64 controls the second rotation adjustment mechanism 62 to drive the primary brake pad 61 to fit toward the brake pad 4, and the output shaft is decelerated by the friction between the primary brake pad 61 and the brake pad 4, and under the action of the friction force, the primary brake pad 61 rotates on the second rotation adjustment mechanism 62, and the second rotation adjustment mechanism 62 is rotationally adjusted, thereby driving the second locking mechanism 63 to lock the secondary brake assembly 5, and then the secondary brake assembly 5 is kept fixed under the restriction of the primary brake assembly 6. At this time, the secondary brake pad 51 is rotationally connected with the brake pad 4, and under the action of the friction between the secondary brake pad 51 and the brake pad 4, the secondary brake pad 51 slows down the output shaft while driving the secondary brake pad 51 to rotate, adjusting the first rotation adjustment mechanism 52, and then locking the shaft sleeve 3 through the first locking mechanism 53 to stop the output shaft.

[0068] In this embodiment, the first rotation adjustment mechanism 52 and the second rotation adjustment mechanism 62 have the same structure, and the first rotation adjustment mechanism 52 includes:

[0069] The rotating ring 521 is fixedly connected to the side of the secondary brake pad 51 away from the brake pad 4;

[0070] A plurality of arc-shaped tracks 522 are provided in an annular distribution and are arranged on the rotating ring 521, corresponding to the locking mechanism;

[0071] The adjusting member 523 is slidably disposed in the arc track 522 and fixedly connected to the locking mechanism;

[0072] The positioning ring body 524 is fixed on a side of the rotating ring 521 away from the brake pad 4 , and the locking mechanism is fixed inside the positioning ring body 524 .

[0073] That is to say, under the action of the friction force between the brake pad and the brake pad 4, the rotating ring 521 rotates, and then under the joint restriction of the arc track 522 and the locking mechanism, the adjusting member 523 moves on the locking mechanism, and then the secondary brake assembly 5 and the shaft sleeve 3 are locked in turn through the locking mechanism, and then under the action of the primary brake assembly 6, the output shaft is stopped, and under the action of the positioning ring body 524, the locking mechanism is fixed, and then the adjusting member 523 is restricted, so that the adjusting member 523 moves on the locking mechanism and the arc track 522, and the locking mechanism is adjusted.

[0074] In this embodiment, the locking mechanism includes:

[0075] The fixed track 551 is fixed in the positioning ring body 524;

[0076] The moving member 552 is slidably disposed in the fixed track 551 and fixedly connected to the adjusting member 523;

[0077] The locking block 553 is slidably disposed in the fixed track 551 and is fixedly connected to the moving member 552 .

[0078] That is to say, when the rotating ring 521 rotates driven by the brake pad, under the restriction of the arc track 522, the adjusting member 523 drives the moving member 552 to slide on the fixed track 551, and then drives the locking block 553 to slide on the fixed track 551, and the secondary brake assembly 5 and the sleeve 3 are fixed or released by driving the locking block 553 to extend and retract, so as to complete the locking stop or release of the normal operation of the output shaft.

[0079] In the specific implementation, first the servo motor operates normally. Figure 5For example, the output shaft rotates clockwise, and then the output shaft drives the brake pad 4 and the secondary brake assembly 5 to rotate synchronously through the shaft sleeve 3. When the servo motor stops, the telescopic shaft 64 extends to push the primary brake assembly 6 to fit the brake pad 4, so that the primary brake pad 61 fits the brake pad 4. Through the friction between the primary brake pad 61 and the brake pad 4, the output shaft is initially decelerated. At the same time, driven by the brake pad 4, the primary brake pad 61 drives the corresponding rotating ring 521 to rotate clockwise, and then under the restriction of the arc track 522 and the fixed track 551, the adjusting member 523 drives the movable ring 521 to rotate clockwise. The moving member 552 moves toward the center of the output shaft in the fixed track 551, and at the same time drives the corresponding locking block 553 to move toward the position of the secondary brake assembly 5. When the secondary brake assembly 5 continues to rotate, the locking block 553 is inserted into the connecting bayonet 54 to fix the secondary brake assembly 5, so that the secondary brake pad 51 and the brake pad 4 become in a rotationally connected state. Under the rotation of the brake pad 4, the friction between the secondary brake pad 51 and the brake pad 4 reduces the speed of the output shaft again. At the same time, driven by the brake pad 4, the secondary brake pad 51 drives the corresponding rotating ring 5 21 rotates clockwise, and then under the restriction of the arc track 522 and the fixed track 551, the adjusting member 523 drives the moving member 552 to move toward the center of the output shaft in the fixed track 551, and at the same time drives the corresponding locking block 553 to move toward the position of the sleeve 3. Under the continuous rotation of the sleeve 3, the locking block 553 is inserted into the locking bayonet 31 to lock and stop the output shaft. In addition, due to the length restriction of the arc track 522, multi-stage speed reduction and sleeve 3 locking can be carried out quickly, and the servo motor can be braked immediately. After the output shaft stops, it can be moved by the lifting platform 12 and the telescopic shaft body 6 4 cooperates with each other to push the brake pad 4 and the sleeve 3 to separate from the wedge block on the output shaft, and then the brake pad 4 and the sleeve 3 are in a rotating state, the brake pad 4 is connected to the rotating gear 132, and driven by the rotating motor 131, the rotating gear 132 drives the brake pad 4 to rotate counterclockwise, resets the primary brake assembly 6 and the secondary brake assembly 5, and releases the sleeve 3 and the secondary brake assembly 5 in turn, and then drives the brake pad 4 and the sleeve 3 to reset through the lifting platform 12 and the telescopic shaft 64, and at the same time resets the primary brake assembly 6, so as to brake the servo motor again.

[0080] What is described above is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A servo motor brake device, characterized in that: include: A connecting housing (1) is fixed to the housing at one end where the output shaft of the servo motor is located; A protective shell (2) is fixedly connected to the connecting shell (1), and the center of the protective shell (2) is rotatably connected to the output shaft; A shaft sleeve (3) is arranged between the connecting housing (1) and the protective housing (2), and is fixedly connected to the output shaft via a wedge block, wherein the wedge block is fixed on the output shaft; A brake pad (4) is arranged on one end of the shaft sleeve (3) close to the connection housing (1), and the brake pad (4) is fixedly connected to the shaft sleeve (3); A secondary brake assembly (5) is arranged on the outside of the shaft sleeve (3) and is in contact with the brake pad (4); A primary brake assembly (6) is arranged on the outside of the secondary brake assembly (5) and connected to the inner wall of the protective shell (2); The secondary brake assembly (5) comprises: The secondary brake pad (51) is annular and is arranged on the outer side of the shaft sleeve (3) and fits in the annular groove on the brake pad (4); A first rotation adjustment mechanism (52) is fixedly connected to a side of the secondary brake pad (51) away from the brake pad (4); A plurality of first locking mechanisms (53) are provided in an annular arrangement and are fixed inside the first rotation adjustment mechanism (52), and the first locking mechanisms (53) correspond to the shaft sleeve (3); A plurality of connecting bayonet holes (54) are provided in an annular distribution and are fixed on the outside of the first rotation adjustment mechanism (52), and the positions of the connecting bayonet holes (54) and the first locking mechanism (53) do not overlap; The primary brake assembly (6) comprises: A primary brake pad (61) is annular and is arranged on a side of the brake pad (4) away from the connection housing (1); A second rotation adjustment mechanism (62) is fixedly connected to a side of the primary brake pad (61) away from the brake pad (4); A plurality of second locking mechanisms (63) are provided in an annular arrangement and are fixed in the second rotation adjustment mechanism (62) and correspond to the connecting bayonet (54) on the secondary brake assembly (5); The telescopic shaft body (64) is composed of a fixed shaft and an extension shaft, wherein the fixed shaft is fixed on the inner wall of the protective shell (2), and the extension shaft is slidably arranged inside the fixed shaft and is fixedly connected to the second rotation adjustment mechanism (62).

2. A servo motor brake device according to claim 1, characterized in that: The inner wall of the connecting shell (1) is provided with a plurality of annularly distributed limiting blocks (11) and a lifting platform (12) slidably arranged inside the limiting blocks (11); the limiting blocks (11) are in contact with the outer ring of the brake pad (4); and the lifting platform (12) is in contact with a side of the brake pad (4) close to the connecting shell (1).

3. A servo motor brake device according to claim 2, characterized in that: A rotating assembly (13) is also provided on the inner wall of the connecting shell (1), and the rotating assembly (13) comprises a rotating motor (131) fixed on the inner wall of the connecting shell (1), and a rotating gear (132) fixedly connected to the rotating motor (131), and the rotating gear (132) corresponds to the brake pad (4).

4. A servo motor brake device according to claim 1, characterized in that: The outer side of the shaft sleeve (3) is provided with a plurality of annularly distributed locking bayonet openings (31), and the locking bayonet openings (31) correspond to the secondary brake assembly (5).

5. A servo motor brake device according to claim 3, characterized in that: The outer ring of the brake pad (4) is provided with a connecting toothed ring (41), the connecting toothed ring (41) corresponds to the rotating gear (132), and an annular groove is provided at a position of the brake pad (4) corresponding to the secondary brake assembly (5).

6. A servo motor brake device according to claim 1, characterized in that: The first rotation adjustment mechanism (52) and the second rotation adjustment mechanism (62) have the same structure, and the first rotation adjustment mechanism (52) comprises: A rotating ring (521) is fixedly connected to a side of the secondary brake pad (51) away from the brake pad (4); A plurality of arc-shaped tracks (522) are provided in an annular arrangement and are arranged on the rotating ring (521) and correspond to the locking mechanism; An adjusting member (523) is slidably disposed in the arc-shaped track (522) and is fixedly connected to the locking mechanism; The positioning ring body (524) is fixed to a side of the rotating ring (521) away from the brake pad (4), and the locking mechanism is fixed inside the positioning ring body (524).

7. A servo motor brake device according to claim 6, characterized in that: The locking mechanism comprises: A fixed track (551) fixed in the positioning ring body (524); A moving member (552) is slidably disposed in the fixed track (551) and fixedly connected to the adjusting member (523); The locking block (553) is slidably disposed in the fixed track (551) and is fixedly connected to the moving member (552).

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