Door hinges

Abstract

This utility model relates to the technical field of door hardware equipment, specifically, to a door hinge, comprising: a fixed body; a moving body, which has a sliding block that can slide along the depth direction of the moving body, wherein one side of the sliding block has a trajectory surface, a first trajectory surface, a second trajectory surface, and a third trajectory surface in sequence, the angle between the starting end of the first trajectory surface and the trajectory surface is α1, the angle between the starting end of the second trajectory surface and the trajectory surface is α2, and the angle between the starting end of the third trajectory surface and the trajectory surface is α3, α1<α2<α3; a linkage assembly, including multiple linkage blocks, the two ends of which are respectively connected to the fixed body and the moving body, and one linkage block is hinged to the sliding block; and a self-closing mechanism, which is disposed in the moving body near the trajectory surface and can extend and retract along the length of the moving body. When the end of the self-closing mechanism abuts against the trajectory surface and extends, it drives the sliding block to slide into the moving body. This door hinge can still achieve automatic closing even when closed to a small angle.

Description

Technical Field

[0001] This utility model relates to the technical field of door hardware equipment, specifically to a door hinge. Background Technology

[0002] Currently, most doors in buildings such as shopping malls, residential communities, office buildings, and conference rooms are self-closing doors. One method to achieve this is by using door hinges with self-closing functions. Chinese patent CN112922476B discloses a door hinge capable of automatically closing at a preset angle. This hinge mainly includes a stationary body, an active body, and a connecting assembly linking the two. A self-closing mechanism and a sliding block are installed in the active body. The sliding block slides along the depth direction of the active body and is connected to a fourth connecting block in the connecting assembly. The side of the sliding block has a trajectory surface and a trajectory plane. When the end of the self-closing mechanism abuts against the trajectory plane, it drives the sliding block to slide, thereby driving the connecting assembly to operate, closing the active body and the stationary body together. However, the angle between the trajectory plane and the trajectory surface in this patent is small, resulting in insufficient depth-direction force of the force exerted by the self-closing mechanism on the active body. Especially when the hinge is closed to a small angle, the spring force in the self-closing mechanism has decreased compared to when it started closing, making it difficult to continue pushing the sliding block to achieve automatic closing of the door hinge. Utility Model Content

[0003] This invention was made to solve the above-mentioned technical problems. Its purpose is to provide a door hinge that can continue to close automatically even when closed to a small angle.

[0004] According to one embodiment of the present invention, a door hinge is provided, comprising: a fixed body, which is a hollow shell; a moving body, which is a hollow shell, having a sliding block inside which can slide along the depth direction of the moving body, wherein a track surface, a first track surface, a second track surface, and a third track surface are sequentially provided on one side of the sliding block, wherein the angle between the starting end of the first track surface and the track surface is α1, the angle between the starting end of the second track surface and the track surface is α2, and the angle between the starting end of the third track surface and the track surface is α3, and α1<α2<α3; a linkage assembly, comprising multiple linkage blocks, both ends of which are respectively connected to the fixed body and the moving body, and one linkage block is hinged to the sliding block; and a self-closing mechanism, disposed in the moving body near the track surface, which is a telescopic structure and can extend and retract along the length of the moving body, one end of which abuts against the side of the sliding block, and when the end of the self-closing mechanism abuts against the track surface and extends, it drives the sliding block to slide into the moving body.

[0005] As one implementation, 8°≤α1≤15°, 16°≤α2≤44°, 45°≤α3≤50°.

[0006] In one implementation, α1 = 10°, α2 = 18°, and α3 = 47°.

[0007] In one embodiment, the self-closing mechanism includes: a spring slider with a bearing hinged at one end, the bearing abutting against the side of the slider; and a storage spring disposed in the motor body, one end of which is connected to the spring slider and applies a force to the spring slider, causing the bearing to press tightly against the side of the slider.

[0008] As one implementation, the opening angle of the door hinge is β; when 86° < β ≤ 180°, the bearing abuts against the straight surface of the track; when 30° < β ≤ 86°, the bearing abuts against the first track surface; when 4° < β ≤ 30°, the bearing abuts against the second track surface; when 0° ≤ β ≤ 4°, the bearing abuts against the third track surface.

[0009] As one implementation, the tail end of the third trajectory surface is connected to a concave limiting arc surface.

[0010] In one implementation, the first trajectory surface, the second trajectory surface, and the third trajectory surface are curved surfaces or inclined planes.

[0011] As one implementation, an arc-shaped guide surface is provided between the trajectory plane, the first trajectory plane, the second trajectory plane, and the third trajectory plane.

[0012] As one embodiment, a buffer mechanism is also provided in the engine body. The buffer mechanism includes: a top plate, which is detachably connected to the side wall of the engine body; a damper, one end of which is fixedly connected to the top plate and the other end is a telescopic end; and a damping slider, which is slidably assembled in the engine body and can slide along the depth direction of the engine body. One end of the slider abuts against the telescopic end of the damper, and the other end is provided with an outwardly protruding top block.

[0013] In one embodiment, the fixed body is provided with a first connecting shaft and a second connecting shaft along its length; the linkage assembly includes a first linkage block, a second linkage block, a third linkage block, and a fourth linkage block; one end of the first linkage block and the second linkage block are hinged to the first connecting shaft, and the other end of the first linkage block and the second linkage block are hinged to one end of the third linkage block; the other end of the third linkage block is hinged to the engine body, and the middle part of the third linkage block is provided with a notch for the fourth linkage block to pass through; one end of the fourth linkage block is hinged to the second connecting shaft, the middle part of the fourth linkage block is hinged in the notch of the third linkage block, and the other end of the fourth linkage block is hinged to the sliding block.

[0014] Based on the above description and practice, the door hinge of this utility model has three trajectory surfaces—a first trajectory surface, a second trajectory surface, and a third trajectory surface—sequentially arranged on the sliding block, with the angles between these three trajectory surfaces and the trajectory planes increasing progressively. When the door hinge is closed, after the opening angle of the door hinge reaches a preset angle range, one end of the self-closing mechanism first abuts against the first trajectory surface, pushing the sliding block to slide inward into the motor body, thereby automatically closing the door hinge. Subsequently, one end of the self-closing mechanism gradually abuts against the second and third trajectory surfaces. During this process, as one end of the self-closing mechanism extends forward, the force exerted by the self-closing mechanism on the sliding block gradually decreases. However, because the angles between the first, second, and third trajectory surfaces and the trajectory planes increase progressively, the component of the force exerted by the self-closing mechanism on the sliding block along the depth direction of the motor body does not decrease, and may even increase, ensuring that the door hinge can be fully closed. Therefore, when the angle between the moving body and the stationary body is small during the closing process of the door hinge, the self-closing mechanism can still drive the sliding block to move, so that the door hinge can continue to close automatically. Attached Figure Description

[0015] Figure 1 This is a three-dimensional structural diagram of a door hinge involved in one embodiment of the present invention.

[0016] Figure 2 This is a cross-sectional structural diagram of the motor body of the door hinge in the fully open state in one embodiment of the present invention.

[0017] Figure 3 This is a cross-sectional structural diagram of the motor body of the door hinge when it begins to automatically close, according to one embodiment of the present invention.

[0018] Figure 4 This is a schematic diagram of the internal structure of a door hinge in one embodiment of the present invention from a first-view perspective. To clearly show each component, the adjustment mechanism is shown in a disassembled state.

[0019] Figure 5 This is a schematic diagram of the internal structure of a door hinge in one embodiment of the present invention from a second perspective. To clearly show each component, the adjustment mechanism is shown in a disassembled state.

[0020] Figure 6 This is a three-dimensional structural diagram of the sliding block in a door hinge according to one embodiment of the present invention.

[0021] Figure 7 This is a cross-sectional structural diagram of the sliding block in a door hinge according to one embodiment of the present invention.

[0022] The attached figures are labeled as follows: 1. Fixed body; 11. Fixed base; 12. Fixed base fixing block; 13. First connecting shaft; 14. Second connecting shaft; 2. Linkage assembly; 21. First linkage block; 22. Second linkage block; 23. Third linkage block; 24. Fourth linkage block; 3. Engine body; 31. First fixing block of engine base; 32. Second fixing block of engine base; 33. Engine base; 34. Sliding block; 341. Track surface; 342. First track surface; 343. Second track surface; 344. Third track surface; 345. Guide surface; 346. Limiting arc surface; 4. Self-closing mechanism; 41. Storage spring; 42. Spring slider; 43. Bearing; 5. Buffer mechanism; 51. Damping slider; 52. Damper; 53. Top plate; 54. Top block. Detailed Implementation

[0023] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be more comprehensive and complete, and will fully convey the concept of exemplary embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0024] Furthermore, the accompanying drawings are merely illustrative of this disclosure and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted. It should be noted that in this disclosure, the terms "comprising," "configured with," and "set in" are used to indicate an open-ended inclusion, meaning that additional elements / components / etc. may exist besides those listed; the terms "first," "second," etc., are used only as labels and are not intended to limit the number or order of objects; the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0025] Unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0026] According to one embodiment of this utility model, a door hinge is provided. Please refer to [reference needed]. Figures 1 to 7 The door hinge in this embodiment has the function of automatically closing within a preset angle range. Specifically, the door hinge mainly includes the following structure: a fixed body 1, a linkage component 2, a moving body 3, and a self-closing mechanism 4.

[0027] The fixed body 1 consists of a fixed base 11 and a fixed base fixing block 12. The fixed base 11 has a hollow cavity in the middle and connecting plates at both ends for connection with the door frame. The fixed base fixing block 12 is detachably installed in the cavity in the middle of the fixed base 11 by bolts. The fixed base fixing block 12 has a U-shaped structure and has a cavity between it and the fixed base 11 to accommodate part of the linkage assembly 2. In addition, a first connecting shaft 13 and a second connecting shaft 14 are sequentially arranged in the fixed base fixing block 12 along the depth direction of the fixed base 11, with the first connecting shaft 13 closer to the inner side of the fixed base 11.

[0028] The aforementioned fixed body 1 adopts a structure assembled from a fixed base 11 and a fixed base fixing block 12. The purpose is to facilitate the assembly of the door hinge. In other embodiments, the fixed base 11 and the fixed base fixing block 12 can also be set as an integral structure, which can also achieve the automatic closing function.

[0029] Please combine Figure 4 and Figure 5 The linkage assembly 2 includes a first linkage block 21, a second linkage block 22, a third linkage block 23, and a fourth linkage block 24. All of the linkage blocks are curved plates, each with through holes at both ends for a connecting shaft to pass through. Furthermore, the third linkage block 23 has a notch in its middle for the fourth linkage block 24 to pass through, and both the notch and the middle of the fourth linkage block 24 have through holes for a connecting shaft to pass through. The middle portions of the third linkage block 23 and the fourth linkage block 24 are hinged together by the connecting shaft.

[0030] One end of the first linkage block 21 and the second linkage block 22 are hinged to the first connecting shaft 13, and the other ends of the first linkage block 21 and the second linkage block 22 are hinged to one end of the third linkage block 23 through the connecting shaft. The end of the fourth linkage block 24 near the stationary body 1 is hinged to the second connecting shaft 14.

[0031] The motor body 3 consists of a motor base 33, a first fixing block 31, and a second fixing block 32. The motor base 33 has a hollow cavity in the middle and connecting plates at both ends for connection to the door leaf. The first fixing block 31 and the second fixing block 32 are detachably fixed to the motor base 33 by rivets, dividing the cavity within the motor base 33 into three accommodating chambers for accommodating the sliding block 34, the self-closing mechanism 4, and the buffer mechanism 5. The first fixing block 31 has opposing through holes for a connecting shaft to pass through. Similarly, through holes for a connecting shaft to pass through are also provided on the adjacent side walls of the first fixing block 31 and the second fixing block 32. These two through holes are used to hinge the third linkage block 23. The end of the third linkage block 23 closest to the motor body 3 has two support arms, which are hinged to the first fixing block 31 and the second fixing block 32 of the motor base via connecting shafts.

[0032] A sliding block 34 is slidably mounted inside the engine body 3 at a position opposite to the fourth linkage block 24. A limiting groove is provided on the inner wall of the engine body 3 to allow the sliding block 34 to slide along the depth direction of the engine body 3. Please refer to... Figure 6 The sliding block 34 has a U-shaped notch in the middle, and the two side walls of the U-shaped notch have opposing through holes for hinged connection with the end of the fourth linkage block 24 via a connecting shaft. When the door hinge is opened or closed, the fourth linkage block 24 drives the sliding block 34 to slide along the depth direction of the motor body 3.

[0033] One side of the sliding block 34 is a straight surface and abuts against the side wall of the second fixing block 32 of the motor seat. A straight bearing is also provided between the side wall of the second fixing block 32 of the motor seat and the sliding block 34 to improve the sliding efficiency of the sliding block 34. On the other side of the sliding block 34, that is, the side near the first fixing block 31 of the motor seat, there are sequentially arranged track straight surface 341, first track surface 342, second track surface 343, and third track surface 344, which are connected end to end. The first track surface 342, second track surface 343, and third track surface 344 are used to cooperate with the self-closing mechanism 4 to drive the sliding block 34 to slide towards the inside of the motor body 3, thereby driving the door hinge to close. The angle between the starting end of the first trajectory surface 342 and the trajectory plane 341 is α1, the angle between the starting end of the second trajectory surface 343 and the trajectory plane 341 is α2, and the angle between the starting end of the third trajectory surface 344 and the trajectory plane 341 is α3, and α1<α2<α3.

[0034] The self-closing mechanism 4 is located inside the motor body 3 on one side near the track surface 341. It is a telescopic structure that can extend and retract along the length of the motor body 3. One end of the mechanism abuts against the side of the sliding block 34. When the end of the self-closing mechanism 4 abuts against the first track surface 342, the second track surface 343, or the third track surface 344, its own elasticity drives the sliding block 34 to slide into the motor body 3, thereby causing the door hinge to close.

[0035] In this embodiment, the door hinge has three trajectory surfaces sequentially arranged on the sliding block 34: a first trajectory surface 342, a second trajectory surface 343, and a third trajectory surface 344. The angles between these three trajectory surfaces and the trajectory plane 341 increase progressively. When the door hinge is closed, after the opening angle of the door hinge reaches a preset angle range, one end of the self-closing mechanism 4 first abuts against the first trajectory surface 342, pushing the sliding block 34 to slide into the motor body 3, thereby automatically closing the door hinge. Subsequently, one end of the self-closing mechanism 4 gradually abuts against the second trajectory surface 343 and the third trajectory surface 344.

[0036] During this process, as one end of the self-closing mechanism 4 extends forward, the force exerted by the self-closing mechanism 4 on the sliding block 34 gradually decreases. However, because the angles between the first track surface 342, the second track surface 343, and the third track surface 344 and the track plane 341 increase, the component of the force exerted by the self-closing mechanism 4 on the sliding block along the depth direction of the motor body 3 does not decrease, and may even increase, ensuring that the door hinge can be fully closed. Therefore, when the angle between the motor body 3 and the stationary body 1 is small during the closing process of the door hinge, the self-closing mechanism 4 can still drive the sliding block 34 to move, allowing the door hinge to continue to close automatically.

[0037] The first track surface 342, the second track surface 343, and the third track surface 344 can be inclined planes or curved surfaces. When one end of the self-closing mechanism 4 abuts against them, it generates a component force toward the interior of the motor body 3, which in turn pushes the sliding block 34 to move, causing the door hinge to close. Among these values, 8°≤α1≤15°, 16°≤α2≤44°, and 45°≤α3≤50° ensure that the door hinge can achieve smooth automatic closing.

[0038] Specifically, in this embodiment, the angle α1 between the starting end of the first track surface 342 and the track surface 341 is 10°, the angle α2 between the starting end of the second track surface 343 and the track surface 341 is 18°, and the angle α3 between the starting end of the third track surface 344 and the track surface 341 is 47°. This ensures that the door hinge can automatically close when the opening angle is within a preset range, even if the opening angle is small.

[0039] In this embodiment, an arc-shaped guide surface 345 is provided between the trajectory surface 341, the first trajectory surface 342, the second trajectory surface 343, and the third trajectory surface 344, so that one end of the self-closing mechanism 4 can move smoothly between adjacent trajectory surfaces, thereby improving the self-closing effect of the door hinge.

[0040] The aforementioned fixed base fixing block 12, first linkage block 21, second linkage block 22, third linkage block 23, fourth linkage block 24, sliding block 34, first fixed block 31 of the motor seat and second fixed block 32 of the motor seat are hinged by a connecting shaft. In order to avoid friction between adjacent structures, a bushing is also provided on the connecting shaft at the hinge.

[0041] Please combine Figure 4 and Figure 5 In this embodiment, the self-closing mechanism 4 includes a storage spring 41, a spring slider 42, and a bearing 43. The storage spring 41 is arranged along the length of the motor body 3, with one end connected to the inner wall of the motor body 3 via an adjustment mechanism, and the other end equipped with a spring slider 42. As shown in the figure, the spring slider 42 has a U-shaped structure, and two storage springs 41 are arranged inside it. The end of the spring slider 42 away from the storage springs 41 is hinged to a bearing 43, which abuts against the side of the sliding block 34.

[0042] When the door hinge is fully open, the sliding block 34 is located near the outer end of the motor body 3. At this time, the bearing 43 abuts against the track surface 341. When the door hinge is closed, the sliding block 34 gradually slides into the motor body. When the bearing 43 abuts against the first track surface 342, the force applied by the self-closing mechanism 4 to the sliding block 34 has a component force along the depth direction, which can drive the sliding block 34 to continue sliding into the motor body 3, thereby causing the door hinge to close automatically. At this time, the opening angle of the door hinge is the angle at which the door hinge can close automatically. The size of this angle can be adjusted by adjusting the starting position of the first track surface 342.

[0043] Specifically, in this embodiment, the opening angle of the door hinge is β; when 86° < β ≤ 180°, the bearing 43 abuts against the track surface 341; when 30° < β ≤ 86°, the bearing 43 abuts against the first track surface 342; when 4° < β ≤ 30°, the bearing 43 abuts against the second track surface 343; and when 0° ≤ β ≤ 4°, the bearing 43 abuts against the third track surface 344.

[0044] In addition, such as Figure 6 and Figure 7As shown, the tail end of the third track surface 344 is connected to a concave limiting arc surface 346. When the door hinge is fully closed, the bearing 43 will abut against the limiting arc surface 346, which can prevent the self-closing mechanism 4 and the sliding block 34 from continuing to move relative to each other after the door hinge is closed, thereby improving the stability of the door hinge and extending its service life.

[0045] Please combine Figures 2 to 3 A buffer mechanism 5 for controlling the closing speed of the door hinge is also provided inside the engine body 3. The buffer mechanism 5 includes a top plate 53, a damper 52, and a damping slider 51. The top plate 53 is a rectangular plate, which is used to detachably connect the buffer mechanism 5 to the engine base 33. The damper 52 can be a hydraulic damper or other existing dampers, with one end fixedly connected to the top plate 53 and the other end being a free end. The damping slider 51 has a U-shaped structure, with its grooved end fitted onto the free end of the damper 52, and a limiting groove is provided in the engine base 33 for the damping slider 51 to slide along the depth direction. The end of the damping slider 51 near the stationary body 1 has an outwardly protruding top block 54, which is located outside the engine body 3 under the elastic force of the damper 52. At the same time, a protrusion is provided on the stationary base fixing block 12 of the stationary body 1 at a position opposite to the top block 54. During the closing process of the door hinge, the top block 54 first abuts against the protrusion, at which point the damper 52 is subjected to force, delaying the closing speed of the door hinge. Preferably, the top block 54 abuts against the protrusion just as the bearing 43 abuts against the third track surface 344. Since the angle between the third track surface 344 and the track plane 341 becomes larger, the force exerted by the self-closing mechanism 4 on the sliding block 34 in the depth direction becomes larger, that is, the closing force becomes larger, ensuring that while the buffer mechanism 5 delays the closing speed of the door hinge, the door hinge has sufficient closing force.

[0046] It will be apparent to those skilled in the art that this invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of this invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within this invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A door hinge, characterized in that include: The body is a hollow shell; The engine body is a hollow shell, and a sliding block that can slide along the depth direction of the engine body is provided inside. On one side of the sliding block, there are sequentially arranged a trajectory straight surface, a first trajectory surface, a second trajectory surface, and a third trajectory surface. The angle between the starting end of the first trajectory surface and the trajectory straight surface is α1, the angle between the starting end of the second trajectory surface and the trajectory straight surface is α2, and the angle between the starting end of the third trajectory surface and the trajectory straight surface is α3, and α1 < α2 < α3; The linkage assembly includes multiple linkage blocks, with both ends connected to the stationary body and the moving body respectively, and one of the linkage blocks is hinged to the sliding block; The self-closing mechanism is located on the side of the motor body near the track surface. It is a telescopic structure that can extend and retract along the length of the motor body. One end of the self-closing mechanism abuts against the side of the sliding block. When the end of the self-closing mechanism abuts against the track surface and extends, it drives the sliding block to slide into the interior of the motor body.

2. The door hinge as described in claim 1, characterized in that, 8°≤α1≤15°，16°≤α2≤44°，45°≤α3≤50°。 3. The door hinge as described in claim 2, characterized in that, α1=10°，α2=18°，α3=47°。 4. The door hinge of claim 1, wherein The self-closing mechanism includes: A spring slider, with a bearing hinged at one end, the bearing abutting against the side of the slider; A storage spring is installed inside the motor body, with one end connected to the spring slider, and applies a force to the spring slider to make the bearing press tightly against the side of the sliding block.

5. The door hinge as described in claim 4, characterized in that, The opening angle of the door hinge is β; When 86°<β≤180°, the bearing abuts against the straight surface of the trajectory; When 30°<β≤86°, the bearing rests against the first trajectory surface; When 4°<β≤30°, the bearing rests against the second trajectory surface; When 0°≤β≤4°, the bearing abuts against the third trajectory surface.

6. The door hinge as described in claim 4, characterized in that, The tail end of the third trajectory surface is connected to a concave limiting arc surface.

7. The door hinge as described in claim 1, characterized in that, The first trajectory surface, the second trajectory surface, and the third trajectory surface are curved surfaces or inclined planes.

8. The door hinge as described in claim 1, characterized in that, An arc-shaped guide surface is provided between the trajectory plane, the first trajectory plane, the second trajectory plane, and the third trajectory plane.

9. The door hinge as described in claim 1, characterized in that, The engine body is also provided with a buffer mechanism, which includes: The top plate is detachably connected to the side wall of the engine body; The damper is fixedly connected to the top plate at one end and has a telescopic end at the other end. The damping slider is slidably assembled in the motor body and can slide along the depth direction of the motor body. One end of the slider abuts against the telescopic end of the damper, and the other end is provided with an outwardly protruding top block.

10. The door hinge as described in claim 1, characterized in that, The fixed body is provided with a first connecting shaft and a second connecting shaft along its length. The linkage assembly includes a first linkage block, a second linkage block, a third linkage block, and a fourth linkage block; One end of the first and second linkage blocks is hinged to the first connecting shaft, and the other end of the first and second linkage blocks is hinged to one end of the third linkage block. The other end of the third linkage block is hinged to the motor body, and the middle of the third linkage block is provided with a notch for the fourth linkage block to pass through. One end of the fourth linkage block is hinged to the second connecting shaft, the middle part of the fourth linkage block is hinged to the notch of the third linkage block, and the other end of the fourth linkage block is hinged to the sliding block.

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