Anti-falling screw-in crown for a mechanical watch

Abstract

This invention discloses a screw-in crown for a mechanical watch that prevents it from falling off. The crown is located in the middle of one side of the outer wall of the watch. The top end of the crown inside the watch is connected to the inner mechanical transmission. A wedge-shaped push mechanism is located on the outer side of the crown inside the watch, and this mechanism is connected to the crown's push drive. The output end of the wedge-shaped push mechanism is sealed to the outer surface of the crown. A stabilizing ring is located on the side of the crown inside the watch, near the wedge-shaped push mechanism. The inner wall of the stabilizing ring is fitted to the outer surface of the crown, and the outer wall is fitted to the inner wall of the watch. Two stabilizing rings are provided, with a gap between them. This invention utilizes the pushing force when the crown is screwed into the watch's thread to form a double seal at the connection point, improving the sealing strength of the gap at the crown position.

Description

Technical Field

[0001] This invention relates to the field of mechanical watch crown technology, specifically to a screw-down crown for a mechanical watch that prevents it from falling off. Background Technology

[0002] A mechanical watch is a timekeeping device that uses a mainspring as a power source and a series of mechanical structures to keep time. Unlike electronic or quartz watches, mechanical watches, with their unique mechanical operation and aesthetic craftsmanship, have become works of art in the eyes of watch enthusiasts. The time adjustment of a mechanical watch requires the use of the crown at its edge to drive the internal mechanical structure and adjust the hour hand, minute hand, and date.

[0003] Mechanical watches are further categorized based on the crown's connection method: screw-down crowns, crown guards, bridge crowns, and concealed crowns. Among these, screw-down crowns offer the best water resistance and are favored by swimming and diving enthusiasts. However, ordinary screw-down crowns rely on a threaded connection to seal the crown to the inside of the watch. This method can loosen as the watch moves, allowing sweat, rain, or high-pressure water from swimming or diving to enter and damage the watch's internal components. Therefore, there is a pressing need to design a screw-down crown for mechanical watches that prevents it from falling out, thus addressing these issues. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides a screw-in crown for a mechanical watch that prevents it from falling off. A wedge-shaped reverse-push mechanism is provided at the position where the crown connects to the inside of the mechanical watch. During the screwing process between the crown and the threads of the mechanical watch, the wedge-shaped reverse-push mechanism is driven, thereby causing the rubber sealing ring at the output end of the wedge-shaped reverse-push mechanism to move towards the outer surface of the crown. This completes the sealing fit between the front of the crown and the outer surface of the mechanical watch, improves the sealing strength at the crown of the mechanical watch, and achieves a double seal at the connection between the crown and the mechanical watch. This invention provides a screw-in crown for a mechanical watch that prevents it from falling off. The crown is located in the middle of one side of the outer wall of the watch. The top end of the crown inside the watch is connected to the inner mechanical transmission. A wedge-shaped push mechanism is located on the outer side of the crown inside the watch, and this mechanism is connected to the crown's push-drive mechanism. The output end of the wedge-shaped push mechanism is sealed to the outer surface of the crown. A stabilizing ring is located on the side of the crown inside the watch, near the wedge-shaped push mechanism. The inner wall of the stabilizing ring is fitted to the outer surface of the crown, and the outer wall of the stabilizing ring is fitted to the inner wall of the watch. Two stabilizing rings are provided, with a gap between them.

[0005] Preferably, the crown is positioned inside the mechanical watch as the watch crown, and the wedge-shaped thrust mechanism and the stabilizing ring are connected to the outside of the watch crown. The position where the watch crown connects to the stabilizing ring has longitudinal and transverse stabilizing holes. A drive push plate is located at the position where the watch crown connects to the wedge-shaped thrust mechanism, inside the center of the wedge-shaped thrust mechanism. A concave arc-shaped ring is fixed to the outer side of the crown near the mechanical watch, and the concave arc-shaped ring elastically fits the wedge-shaped thrust mechanism. A threaded rod is provided at the end of the watch crown connected to the watch crown, and the threaded rod is threaded onto the inner side of the outer wall end of the mechanical watch. The drive push plate is located inside the wedge-shaped thrust mechanism and can transmit the thrust of the crown to the inside of the wedge-shaped thrust mechanism, providing power to the wedge-shaped thrust mechanism.

[0006] Preferably, a crown hole is provided at the mechanical watch position corresponding to the crown, a threaded hole is provided at the end of the crown hole where the crown is connected, a wedge drive groove is provided at the position where the crown hole is connected to the wedge push mechanism, the wedge push mechanism slides on the inner wall of the wedge drive groove, and a ring sliding groove is provided at the position where the crown hole is connected to the stabilizing ring, the stabilizing ring slides in close contact with the inner side of the ring sliding groove.

[0007] Preferably, the inclined wedge counter-pushing mechanism includes a driven stop plate, which abuts against and fits against the driving push plate. An inner hook ring is fixed on the side of the driven stop plate connected to the driving push plate. An inclined sliding push block is provided on the inner side of the end of the inner hook ring. The inner hook ring and the side of the inclined sliding push block are obliquely fitted and slidably connected. A top ring is provided on the inner side of the inclined sliding push block. The top ring and the inner side of the inclined sliding push block are obliquely fitted and slidably connected. A rubber sealing ring is connected to the other end of the top ring. One end of the rubber sealing ring is located on the outside of the mechanical watch and abuts against the concave arc ring on the outer surface of the crown.

[0008] Preferably, the stabilizing ring includes a first horizontal ring, a first horizontal bar passing through the center of the first horizontal ring, the first horizontal ring fitting around the outside of the watch crown, the first horizontal bar passing through the inside of the horizontal loop, a second vertical ring on one side of the first horizontal ring, a second vertical bar passing through the middle of the second vertical ring, the second vertical ring fitting around the outer surface of the watch crown on one side of the first horizontal ring, the second vertical bar passing through the inside of the first horizontal bar, and equidistant and annularly arranged position limiting blocks on the inner wall of the ring sliding groove between the first horizontal ring and the second vertical ring, the position limiting blocks abutting against the outer wall ends of the first horizontal ring and the first horizontal bar, and a miniature spring on the side of the position limiting block connected to the ring sliding groove, the two ends of the miniature spring being connected to the outer surface of the position limiting block and the inner wall of the ring sliding groove, respectively.

[0009] The first horizontal ring allows the crown to fit snugly against the inner wall of the mechanical watch. Meanwhile, the spaced-out second vertical ring works in conjunction with the first horizontal ring to provide horizontal stability to the center of the crown. This completely isolates the crown from the rear of the first horizontal ring and the second vertical ring, preventing the oblique force generated during crown operation from affecting the mechanical structure connected to the crown's end. This improves the safety and stability of the crown's operation of the mechanical watch. Furthermore, the first horizontal and second vertical rings increase the contact area between the crown and the first and second horizontal rings, enhancing the connection seal. The first horizontal and second vertical rings also limit the crown's movement, preventing it from detaching from the mechanical watch.

[0010] Preferably, the inner side of the inclined wedge drive groove is provided with inclined wedge drive sliding grooves, which are connected to the inclined wedge drive groove. A limit sliding groove is provided on the side of the inclined wedge drive sliding groove away from the inclined wedge drive groove. A sealing pressure pushing groove is provided on the side of the limit sliding groove away from the inclined wedge drive groove. The driven baffle and the inner hook ring slide on the inner side of the inclined wedge drive groove. The end of the inner hook ring away from the driven baffle slides on the inner side of the inclined wedge drive sliding groove. The bottom surface of the inclined sliding pushing block slides against the inner wall of the inclined wedge drive sliding groove. The top ring... One end of the inclined sliding propulsion block slides inside the inclined wedge drive groove, and the other end of the top ring slides on the inner wall of the limiting groove and the sealing pressure propulsion groove. The rubber sealing ring slides and seals against the inner wall of the sealing pressure propulsion groove, and the bottom surface of the rubber sealing ring is in contact with the end of the top ring. A gear limiting block groove is provided at the position where the gear limiting block is connected inside the ring sliding groove. The gear limiting block slides in a limited manner on the inner wall of the gear limiting block groove. The end of the micro spring away from the gear limiting block is fixed to the bottom surface of the gear limiting block groove.

[0011] Preferably, the position where the inner hook ring connects to the inclined sliding propulsion block is provided with an inner hook inclined surface, and the side of the inclined sliding propulsion block connected to the inner hook ring is provided with an outer inclined surface. The inner hook inclined surface and the outer inclined surface are in close sliding connection. The position where the inclined sliding propulsion block connects to the top ring is provided with an inner inclined surface, and the position where the top ring connects to the inclined sliding propulsion block is provided with a top ring outer inclined surface. The inner inclined surface and the top ring outer inclined surface are in close sliding connection.

[0012] The inner hook ring can transmit the thrust from the driven plate to the inclined sliding push block through the inner hook bevel, thereby allowing the inclined sliding push block to transmit the thrust to the top ring using the inner bevel, so that the top ring can have thrust, thus completing the seal between the crown and the inside of the mechanical watch.

[0013] Compared with related technologies, the anti-fall-out screw-in crown of a mechanical watch provided by the present invention has the following beneficial effects: 1. The present invention adds a wedge-shaped reverse thrust mechanism at the entrance of the watch crown to the mechanical watch. It can use the pushing force when the crown is screwed into the mechanical watch thread to drive the wedge-shaped reverse thrust mechanism to push towards the outer surface of the mechanical watch, so that the rubber sealing ring is attached to the side of the crown that is attached to the mechanical watch, forming a double seal at the connection between the crown and the mechanical watch, thereby improving the sealing strength of the gap at the crown position of the mechanical watch.

[0014] 2. The wedge-shaped push mechanism pushes the rubber sealing ring to fit against the side of the watch crown that connects to the mechanical watch. When the crown is screwed onto the mechanical watch thread, the inward thrust of the wedge-shaped push mechanism applies an outward thrust to the crown, ensuring a high degree of tightness in the connection between the crown and the watch case. This enhances the stability of the connection between the crown and the watch case, preventing loosening even under high pressure. At the same time, the rubber sealing ring, through its compression of the crown and its own elasticity, continuously applies pressure to the crown, ensuring the sealing and fixing strength of the connection between the crown and the mechanical watch.

[0015] 3. The smoothing ring located inside the wedge-driven structure on the inner side of the crown enhances the smoothness of the crown's operation during use by binding it with the double rings. This prevents the crown from tilting and causing pressure or transmission problems to the internal gear transmission mechanism, thus improving the stability of the crown's operation. At the same time, there are equidistantly arranged stop blocks in the sliding area of ​​the smoothing ring, which can stably enter the fixed position when the crown is pulled to adjust the mechanical watch, improving the convenience and safety of operation. Attached Figure Description

[0016] Figure 1 This is a diagram showing the crown of the present invention in use; Figure 2 for Figure 1 An exploded and enlarged sectional view of the structure at the crown location shown; Figure 3 for Figure 2 A schematic diagram showing the exploded and enlarged side view of the structure; Figure 4 for Figure 3 An exploded cross-sectional view of the structure at the location of the wedge thrust mechanism; Figure 5 for Figure 4 The diagram shown is an exploded cross-sectional view of the inclined wedge thrust mechanism. Figure 6 for Figure 2 The diagram shows an exploded cross-sectional view of the structure at the location of the stable bead loop.

[0017] Labels in the diagram: 1. Mechanical watch; 3. Crown; 4. Crown hole; 5. Wedge reverse thrust mechanism; 6. Smooth retaining ring; 31. Watch crown; 32. Longitudinal retaining hole; 33. Lateral retaining hole; 34. Drive push plate; 35. Concave arc surface ring; 36. Threaded rod; 41. Wedge drive groove; 42. Retaining ring sliding groove; 51. Driven stop plate; 52. Inner hook ring; 53. Inclined sliding push block; 54. Top ring; 55. 61. Rubber sealing ring; 62. First transverse ring; 63. First transverse bar; 64. Second longitudinal ring; 65. Second longitudinal bar; 66. Gear limit block; 67. Miniature spring; 411. Wedge drive groove; 412. Limiting groove; 413. Sealing pressure pushing groove; 421. Gear limit block groove; 521. Inner hook inclined surface; 531. Outer inclined surface; 532. Inner inclined surface; 541. Top ring outer inclined surface. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0019] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0020] Please see the appendix Figures 1-6 The present invention provides a screw-in crown for a mechanical watch that prevents it from falling off. The crown is located in the middle of one side of the outer wall of the mechanical watch 1. The end of the crown 3 connected to the mechanical watch 1 is provided with a stem 31. The stem 31 passes through the inner side of the mechanical watch 1 and is connected to the internal gear structure of the mechanical watch 1 for transmission.

[0021] The crown 3 is provided with a crown hole 4 at the mechanical position of the watch 1. A wedge drive groove 41 is provided inside the crown hole 4. A ring sliding groove 42 is provided on one side of the wedge drive groove 41. The crown 31 passes through the inside of the crown hole 4.

[0022] An inclined wedge reverse thrust mechanism 5 is provided inside the inclined wedge transmission groove 41. The watch crown 31 passes through the center of the inclined wedge reverse thrust mechanism 5, and a drive push plate 34 is provided at the position where the watch crown 31 connects to the inclined wedge reverse thrust mechanism 5. The drive push plate 34 can provide a driving force to the inclined wedge reverse thrust mechanism 5. The inclined wedge reverse thrust mechanism 5 includes a driven baffle 51, which is in contact with the drive push plate 34 and is used to transmit the driving force of the drive push plate 34. An inner hook ring 52 is connected to the outer wall of the side of the driven baffle 51 that is in contact with the drive push plate 34. The inner hook ring 52 can transmit the thrust received by the drive baffle to the inclined sliding push block.

[0023] The pulling force received from the driven plate 51 is used to pull the inclined sliding push block 53 to slide inside the inclined wedge drive groove 411. Then, the sliding inclined sliding push block 53 will apply an upward thrust to the top ring 54, so that the top ring 54 can push the rubber sealing ring 55 to slide inside the sealing pressure push groove 413, so that the rubber sealing ring 55 is pushed to the outside of the mechanical watch 1 and elastically abuts against the concave arc surface ring 35 on the outer surface of the crown 3, thus completing the sealing between the crown 3 and the inside of the crown hole 4 of the mechanical watch 1.

[0024] It should be noted that the rubber sealing ring 55 inside the sealing pressure propulsion groove 413 is sealed and slides on the inside, completely sealing the inside of the propulsion groove, which can completely prevent the entry of water.

[0025] When the rubber sealing ring 55 contacts the crown 3, the rubber sealing ring 55 will form a thrust with the crown 3 while sealing, so that the crown 3, which moves towards the inside of the mechanical watch 1, is subjected to a reverse thrust, which improves the tightness of the screw connection and enhances the sealing performance.

[0026] A symmetrical stabilizing ring 6 is provided inside the ring sliding groove 42. The crown 31 passes through the inner side of the stabilizing ring 6 and is in contact with the inner wall of the stabilizing ring 6. The outer surface of the stabilizing ring 6 is in contact with the inner wall of the ring sliding groove 42. The setting of the stabilizing ring 6 allows the suspended crown 31 to have two support points in the middle to form support with the inner wall of the mechanical watch 1. This allows the torsional oblique pressure generated when the crown 3 is driven to be completely canceled at the position of the stabilizing ring 6, thereby avoiding the impact of the position of the crown 31 connecting with the internal transmission of the mechanical watch 1 on the transmission of the internal mechanical mechanism of the mechanical watch 1.

[0027] The stabilizing ring 6 adopts the design of a first horizontal ring 61 and a second vertical ring 63. The design of the horizontal and vertical bars can limit the connection position of the crown 31, while preventing the crown 31 from falling off the mechanical watch 1 when the adjustment position is pulled, thus improving the durability of the crown 3.

[0028] The inner wall of the ring sliding groove 42 is provided with annularly distributed gear limit blocks 65 at the position where the smooth ring 6 is connected. The gear limit blocks 65 can limit the movement position of the smooth ring 6, so that the crown 3 can move accurately to the gear center when shifting gears, thereby improving the gear shifting accuracy and adjustment convenience inside the mechanical watch 1.

[0029] It should be noted that: the inner hook ring 52 is connected to the inclined sliding push block on one side with an inner hook inclined surface 521. The inner hook inclined surface 521 will push the outer inclined surface 531 of the inclined sliding push block 53, thereby pushing the inclined sliding push block 53 to slide horizontally. At this time, as the inclined sliding push block 53 slides, the position of the inner inclined surface 532 of the inner wall of the top ring 54 connected to the inclined sliding push block 53 will be pushed by the inner inclined surface 532 and slide towards the outside of the mechanical watch 1, completing the outward movement of the rubber sealing ring 55.

[0030] Usage process: When internal adjustments to the mechanical watch 1 are required, rotate the crown 3 to separate the threaded rod 36 of the crown 31 from the crown hole 4. During the separation process, the wedge-pushing mechanism 5 will lose its thrust, and the rubber sealing ring 55 will separate from the crown 3. After the crown 31 is separated from the crown hole 4, pull the crown 3. The first horizontal ring 61 and the second vertical ring 63 on the outer side of the crown 31 will automatically jump to the first adjustment position. Continuing to pull the crown 3 will press the position limit block 65 and jump to the second position again. When the adjustment is complete, push the crown 3 to make the threaded rod 36 of the crown 31 contact the crown hole 4. After closing, rotate the crown 3 to screw the threaded rod 36 into the crown hole 4, thus fixing the crown 3. During this process, the drive push plate 34 will push the driven stop plate 51 to drive the wedge reverse push mechanism 5 to push the rubber sealing ring 55 outward, so that the rubber sealing ring 55 abuts against the concave arc ring 35 on the outer surface of the crown 3, forming a seal and a reverse elastic thrust. This allows the crown 3 to achieve a high-strength seal and a firm connection with the mechanical watch 1, and always maintains sufficient elastic thrust to push the crown 3, ensuring the fixing of the crown 3.

[0031] The circuits and controls involved in this invention are all existing technologies and will not be described in detail here.

[0032] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A screw-down crown for a mechanical watch that prevents it from falling off, characterized in that, Located in the middle of one side of the outer wall of the mechanical watch (1), the crown (3) is located inside the mechanical watch (1) and its top end is mechanically connected to the inner side of the mechanical watch (1). The crown (3) is located on the outer side of the inner side of the mechanical watch (1) and is provided with a wedge-shaped reverse push mechanism (5). The wedge-shaped reverse push mechanism (5) is driven by the crown (3). The output end of the wedge-shaped reverse push mechanism (5) is sealed and fitted to the outer surface of the crown (3). The crown (3) is located inside the mechanical watch (1) near the wedge-shaped reverse push mechanism (5) and is provided with a smoothing ring (6). The inner wall of the smoothing ring (6) is fitted to the outer surface of the crown (3). The outer wall of the smoothing ring (6) is fitted to the inner wall of the mechanical watch (1). At the same time, there are two smoothing rings (6) with a gap between them. The crown (3) is located inside the mechanical watch (1) and is designated as the watch stem (31). The wedge-shaped reverse thrust mechanism (5) and the smoothing ring (6) are connected to the outside of the watch stem (31). The position where the watch stem (31) is connected to the smoothing ring (6) is provided with a longitudinal and transverse binding hole (32) and a transverse binding hole (33). The position where the watch stem (31) is connected to the wedge-shaped reverse thrust mechanism (5) is provided with a drive push plate (34). The drive push plate (34) is located inside the center of the wedge-shaped reverse thrust mechanism (5). The outer side of the crown (3) near the mechanical watch (1) is fixed with an inner concave arc surface ring (35). The inner concave arc surface ring (35) is elastically fitted with the wedge-shaped reverse thrust mechanism (5). The end where the watch stem (31) is connected to the crown (3) is provided with a threaded rod (36). The threaded rod (36) is threadedly screwed into the inner side of the outer wall end of the mechanical watch (1). The crown (3) is provided with a crown hole (4) at the position of the mechanical watch (1). The crown hole (4) is provided with a threaded hole at the end of the position where it connects to the crown (3). The crown hole (4) is provided with a wedge drive groove (41) at the position where it connects to the wedge push mechanism (5). The wedge push mechanism (5) slides on the inner wall of the wedge drive groove (41). The crown hole (4) is provided with a ring sliding groove (42) at the position where it connects to the stabilizing ring (6). The stabilizing ring (6) slides against the inner side of the ring sliding groove (42). The inclined wedge reverse thrust mechanism (5) includes a driven baffle (51), which abuts against the drive push plate (34). An inner hook ring (52) is fixed on one side of the driven baffle (51) connected to the drive push plate (34). An inclined sliding push block (53) is provided on the inner side of the end of the inner hook ring (52). The inner hook ring (52) and the side of the inclined sliding push block (53) are obliquely fitted and slidably connected. A top ring (54) is provided on the inner side of the inclined sliding push block (53). The top ring (54) and the inner side of the inclined sliding push block (53) are obliquely fitted and slidably connected. A rubber sealing ring (55) is connected to the other end of the top ring (54). One end of the rubber sealing ring (55) is located on the outside of the mechanical watch (1) and abuts against the concave arc ring (35) on the outer surface of the crown (3). The inner hook ring (52) is provided with an inner hook inclined surface (521) at the position where it connects to the inclined sliding propulsion block (53). An outer inclined surface (531) is provided on one side of the inclined sliding propulsion block (53) where it connects to the inner hook ring (52). The inner hook inclined surface (521) and the outer inclined surface (531) are in close contact and slidably connected. The inclined sliding propulsion block (53) is provided with an inner inclined surface (532) at the position where it connects to the top ring (54). The top ring (54) is provided with an outer inclined surface (541) at the position where it connects to the inclined sliding propulsion block (53). The inner inclined surface (532) and the outer inclined surface (541) of the top ring are in close contact and slidably connected.

2. The anti-fall-off screw-in crown of a mechanical watch according to claim 1, characterized in that, The stabilizing ring (6) includes a first horizontal ring (61), a first horizontal bar (62) passing through the center of the first horizontal ring (61), the first horizontal ring (61) fitting around the outside of the crown (31), the first horizontal bar (62) passing through the inside of the transverse bezel (33), a second vertical ring (63) on one side of the first horizontal ring (61), a second vertical bar (64) passing through the middle of the second vertical ring (63), the second vertical ring (63) fitting around the outer surface of the crown (31) on one side of the first horizontal ring (61), and the second vertical bar (64)... Inside the first crossbar (62), the inner wall of the ring sliding groove (42) is provided with equidistant and annularly arranged position limiting blocks (65) between the first horizontal ring (61) and the second vertical ring (63). The position limiting blocks (65) abut against the outer wall ends of the first horizontal ring (61) and the first crossbar (62). A miniature spring (66) is provided on the side of the position limiting block (65) connected to the ring sliding groove (42). The two ends of the miniature spring (66) are respectively connected to the outer surface of the position limiting block (65) and the inner wall of the ring sliding groove (42).

3. The anti-fall-off screw-in crown of a mechanical watch according to claim 2, characterized in that, The inclined wedge drive groove (41) is provided with inclined wedge drive slide grooves (411) on its inner side. The inclined wedge drive slide grooves (411) are connected to the inclined wedge drive groove (41). A limiting slide groove (412) is provided on the side of the inclined wedge drive slide groove (411) away from the inclined wedge drive groove (411). A sealing pressure pushing groove (413) is provided on the side of the limiting slide groove (412) away from the inclined wedge drive slide groove (411). The driven baffle (51) and the inner hook ring (52) slide on the inner side of the inclined wedge drive groove (411). The end of the inner hook ring (52) away from the driven baffle (51) slides on the inner side of the inclined wedge drive slide groove (411). The bottom surface of the inclined sliding pushing block (53) slides against the inner wall of the inclined wedge drive slide groove (411). The top ring ( 54) One end of the inclined sliding propulsion block (53) slides inside the inclined wedge drive groove (411), and the other end of the top ring (54) slides on the inner wall of the limiting groove (412) and the sealing pressure propulsion groove (413). The rubber sealing ring (55) slides and seals against the inner wall of the sealing pressure propulsion groove (413). The bottom surface of the rubber sealing ring (55) is in contact with the end of the top ring (54). A gear limiting block groove (421) is provided at the position where the gear limiting block (65) is connected to the inner side of the ring sliding groove (42). The gear limiting block (65) slides in a limiting manner on the inner wall of the gear limiting block groove (421). The end of the miniature spring (66) away from the gear limiting block (65) is fixed to the bottom surface of the gear limiting block groove (421).

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