False tooth impression scanning clamp
By designing a clamp that combines strip and curved grooves, using sliders, screw transmission and positioning mechanisms, the problem of poor versatility of existing denture scanner clamps is solved, and the stable clamping and operation of impressions of different sizes is achieved. simplify.
Patent Information
- Application Number
- CN202420490891.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-03-13
- Publication Date
- 2025-01-07
- Estimated Expiration
- 2034-03-13
AI Technical Summary
Existing denture scanner fixtures are poorly versatile and require multiple models of fixtures to fix models of different sizes, resulting in cumbersome operation and increased costs.
A denture impression scanning fixture is designed, including a combination fixture of strip grooves and arc grooves. The flexible movement and adjustment of the clamp arm can be achieved through sliders, screw transmission and positioning mechanisms, so that the impressions of different sizes can be stabilized.
Stable clamping of impressions of different sizes is achieved, which improves the versatility of the fixture, simplifies the operation process and reduces costs.
Smart Images
Figure CN222304062U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the field of fixtures, in particular to a scanning fixture for fixing a denture which is used when a three-dimensional scanning operation is performed on the denture. Background Art
[0002] Existing denture 3D scanners all have an automatically rotating platform and a curved scanning probe, and have the advantages of simple and quick operation. They can obtain data on single teeth, full teeth, plaster (tooth) models and 3D printed dentures, and are widely used in tooth filling, tooth restoration, tooth correction and denture replacement treatment.
[0003] The general operation process is to first fix the model on the rotating platform with a fixture, then adjust the curved surface scanning probe to align it with one side of the model, and finally start the platform rotation drive unit. As the platform carries the model to rotate, the curved surface scanning probe can quickly obtain the three-dimensional data of the model. However, the problem with existing denture scanners is that the versatility of the fixture is poor. In order to scan and obtain the model data of single teeth, multiple teeth, and full teeth, multiple types of fixtures are required to fix models / impressions of different sizes on the rotating platform. Not only does it require repeated disassembly and installation of different types of molds on the rotating platform, making the operation cumbersome, but it also increases the cost of fixture investment. Utility Model Content
[0004] The denture impression scanning fixture provided by the utility model can firmly and reliably clamp impressions of different sizes and has good versatility.
[0005] The technical solution adopted by the utility model to solve the technical problem is: a denture impression scanning fixture, comprising:
[0006] The main body has a pair of strip grooves opposite to each other on the front end and a pair of arc grooves opposite to each other on the rear end. The strip grooves extend straightly along the front-back direction. The arc grooves extend from the outside to the inside and gradually approach the front side.
[0007] The four clamp arms form a pair of two each, and the lower ends are respectively inserted into the two strip grooves and the two arc grooves, and the upper ends of the four clamp arms extend upward relative to the upper end surface of the body.
[0008] The slider is fixed on the front side of the lower end face of the body through a linear slide rail structure, is opposite to the two strip grooves up and down, and the lower ends of the two clamping arms are fixed on the slider.
[0009] The driving mechanism matches the slider and can drive the slider to move back and forth relative to the body along the front and rear directions, thereby achieving the purpose of the slider carrying the two clamping arms to move back and forth in the strip groove.
[0010] The assembly block is fixed on the rear side of the lower end surface of the body.
[0011] A pair of swing arms, one end of which matches the assembly block through a pivot structure, and the other end of which can correspond to the bottom of the two arc-shaped slots and make the lower ends of the other two clamping arms correspondingly fixed to the free ends of the two swing arms. The two swing arms can rotate around the pivot relative to the assembly block respectively, so as to achieve the purpose of the swing arm carrying the clamping arm to move back and forth in the arc-shaped slot.
[0012] and a pair of positioning mechanisms, which are matched with the swing arms in a one-to-one correspondence. The positioning mechanisms are associated with the pivot structure at one end of the swing arms and can selectively switch the swing arms between a state in which they can rotate freely relative to the assembly block and a state in which they are blocked from rotating relative to the assembly block.
[0013] Optionally, the left-right vertical distance between the two clamping arms at the rear side can be adjusted to be greater than, equal to, or less than the left-right vertical distance between the two clamping arms at the front side.
[0014] Optionally, the driving mechanism is a screw transmission rod mechanism, wherein a screw lever of the screw transmission rod mechanism matches the slider, and a front end of the screw lever relatively extends outside the body and is matched with a knob.
[0015] By turning the wire lever with a knob, the slider can be driven to move linearly along the front-rear direction relative to the body, thereby adjusting the front-rear positions of the two clamping arms located at the front side.
[0016] Optionally, the positioning mechanism includes a threaded rod and a handle rod.
[0017] The upper part of the rod body of the threaded rod is formed as a pivot structure for the swing arm to match the assembly block, and the lower part of the rod body of the threaded rod matches the threaded hole formed on the assembly block.
[0018] One end of the handle rod matches the upper end of the threaded rod, and the other end extends out of the body. By moving the end of the handle rod extending out of the body, the handle rod can drive the threaded rod to rotate.
[0019] Counterbores are formed at the lower end of the pivot hole of the swing arm and the upper end of the threaded hole of the assembly block. Two ends of the spring sleeved on the rod body of the threaded rod are respectively inserted into the two counterbores.
[0020] A shoulder is formed on the upper portion of the rod body of the threaded rod, and the lower end surface of the shoulder is opposite to the upper end surface of the swing arm.
[0021] By adjusting the length of the lower end of the threaded rod screwed into the threaded hole through the handle rod, the compression amount of the spring can be changed, thereby achieving the adjustment of the vertical distance between the opposite surfaces of the swing arm and the assembly block.
[0022] The matching between the handle rod and the upper end of the threaded rod can be a fixed connection relationship, an integral molding relationship, or a surface matching relationship formed by one end of the handle rod and the upper end of the threaded rod, etc., as long as the other end of the handle rod can achieve the purpose of rotating the threaded rod relative to the threaded hole (in the clockwise direction and in the counterclockwise direction).
[0023] When the spring is compressed to a certain extent, the spring can push the swing arm upward, so that the upper end surface of the swing arm contacts the lower end surface of the shoulder on the threaded rod. In this way, when the threaded rod is screwed downward to increase the length of the lower end extending into the threaded hole, the shoulder can press the swing arm downward to move the lower end surface of the swing arm gradually approaching the upper end surface of the assembly block.
[0024] By adjusting the vertical spacing between the opposing surfaces of the swing arm and the assembly block, the rotation state of the swing arm relative to the assembly block can be switched. For example, when a vertical spacing is maintained between the lower end surface of the swing arm and the upper end surface of the assembly block, the swing arm is in a state where it can rotate freely relative to the assembly block; when the lower end surface of the swing arm is in pressure contact with the upper end surface of the assembly block, the swing arm is in a state where its rotation relative to the assembly block is blocked.
[0025] Optionally, a pair of left-right opposite grooves are formed on the upper end surface of the assembly block.
[0026] One end of the two swing arms extends into the two grooves respectively to establish a pivot matching relationship with the assembly block.
[0027] The upper end surface of the swing arm is relatively located below the notch of the profile groove.
[0028] The upper end surface of the assembly block contacts the lower end surface of the body, and preferably an elastic anti-skid pad is provided between the contacting surfaces of the two to improve the firmness, stability and reliability of the connection between the two.
[0029] Optionally, the groove is through-through from front to back. One end of the handle rod is inserted into the groove and matches with the swing arm through the threaded rod. The upper end surface of the handle rod is relatively located below the notch of the groove.
[0030] The front end port of the groove can limit the angle of rotation of the swing arm to the left and right, and the rear end port of the groove can limit the angle of swing of the handle rod to the left and right.
[0031] Optionally, an elastic ring is provided on the upper end surface of the assembly block, and the elastic ring protrudes upward relative to the upper end surface of the assembly block.
[0032] On the lower end surface of the swing arm, a plurality of convex points or an annular flange are formed around the periphery of the countersunk hole at the lower end of the pivot hole. The convex points can be point-shaped or strip-shaped.
[0033] The convex point or the annular flange formed on the lower end surface of the swing arm corresponds to the position directly above the elastic ring.
[0034] As the swing arm moves up and down relative to the assembly block, the convex point or the annular flange can gradually approach the elastic ring and can be pressed into contact with the elastic ring, and the convex point or the annular flange can be partially sunken into the elastic ring.
[0035] Optionally, a multi-step through hole is formed at the lower end of the threaded hole on the assembly block. The lower end of the threaded rod can extend into the upper end hole of the multi-step through hole, and a curved groove is formed on the lower end surface of the threaded rod.
[0036] A threaded block is fixedly installed in the multi-step through hole with internal threads. A boss with a protruding curved top surface is formed at the upper end of the threaded block, and an elastic layer is embedded on the surface of the boss. The curved groove on the lower end surface of the threaded rod can be pressed on the top surface of the boss on the threaded block, and the elastic layer will exert an upward elastic force on the end of the threaded rod.
[0037] The above design scheme can promote the threaded rod to rotate downward and move to the state where the opposite surfaces of the swing arm and the assembly block are in contact. The stability of the threaded rod's positioning position will not be loosened by external vibration, and has a relaxation function.
[0038] The beneficial effect of the utility model is that the denture impression scanning fixture provided by the patent can firmly and reliably clamp impressions of different sizes and has good versatility. BRIEF DESCRIPTION OF THE DRAWINGS
[0039] Figure 1 This is a schematic diagram of the top view of the structure of the implementation scheme of this patent.
[0040] Figure 2 It is a schematic diagram of the assembly structure of the first embodiment of the positioning mechanism, swing arm, and assembly block related structures.
[0041] Figure 3 It is a schematic diagram of the top view of the matching structure of the assembly block and the swing arm.
[0042] Figure 4 It is a schematic diagram of the assembly structure of the second embodiment of the positioning mechanism, swing arm, and assembly block related structure.
[0043] In the figure: 10 body, 11 strip groove, 12 arc groove, 20 clamping arm, 30 slider, 40 screw transmission mechanism, 50 assembly block, 51 groove, 52 threaded hole, 53 countersunk hole, 54 elastic ring, 55 multi-step through hole, 60 swing arm, 61 convex point, 70 positioning mechanism, 71 threaded rod, 72 handle rod, 73 curved groove, 80 spring, 90 threaded block. DETAILED DESCRIPTION
[0044] The structures, proportions, sizes, etc. illustrated in the drawings of the specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the utility model, so they have no substantial technical significance. Any modification of the structure, change of the proportion relationship or adjustment of the size, without affecting the effect and purpose that can be achieved by the utility model, should still fall within the scope of the technical content disclosed by the utility model. At the same time, the terms such as "upper", "lower", "front", "back", "middle" and so on quoted in this specification are only for the convenience of description, and are not used to limit the scope of the implementation of the utility model. The change or adjustment of their relative relationship should also be regarded as the scope of the implementation of the utility model without substantial change of the technical content.
[0045] like Figures 1 to 3 A denture impression scanning fixture is shown, comprising:
[0046] The main body 10 has a pair of strip grooves 11 formed at the front end and a pair of arc grooves 12 formed at the rear end. The strip grooves 11 extend straight along the front-back direction. The arc grooves 12 extend from the outside to the inside and gradually approach the front side.
[0047] The four clamp arms 20 form a pair of two, and the lower ends are respectively inserted into the two strip grooves 11 and the two arc grooves 12 , and the upper ends of the four clamp arms 20 extend upward relative to the upper end surface of the body 10 .
[0048] The slider 30 is fixed to the front side of the lower end face of the body 10 through a linear slide rail structure, and is vertically opposite to the two strip grooves 11 , and the lower ends of the two clamping arms 20 are fixed to the slider 30 .
[0049] The lead screw transmission rod mechanism 40 matches the slider 30 and can drive the slider 30 to move back and forth relative to the body 10 in the front-to-back direction, thereby achieving the purpose of the slider 30 carrying the two clamping arms 20 to move back and forth in the strip groove 11. As shown in the figure, the lead screw lever of the lead screw transmission rod mechanism 40 matches the slider 30, and the front end of the lead screw lever relatively extends outside the body 10 and is matched with a knob. By turning the knob to turn the lead screw lever, the slider 30 can be driven to move linearly in the front-to-back direction relative to the body 10, thereby adjusting the front-to-back positions of the two clamping arms 20 located at the front side.
[0050] The assembly block 50 is fixed to the rear side of the lower end surface of the body 10 .
[0051] A pair of swing arms 60, one end of which matches the assembly block 50 through a pivot structure, and the other end of which can correspond to the lower part of the two arc-shaped slots 12 and make the lower ends of the other two clamping arms 20 correspondingly fixed to the free ends of the two swing arms 60. The two swing arms 60 can rotate around the pivot relative to the assembly block 50, so as to achieve the purpose of reciprocating movement of the clamping arms 20 carried by the swing arms 60 in the arc-shaped slot 12.
[0052] A pair of positioning mechanisms 70 are matched one by one with the swing arm 60. The positioning mechanism 70 is associated with the pivot structure at one end of the swing arm 60 and can selectively switch the swing arm 60 between a state in which it can rotate freely relative to the assembly block 50 and a state in which it is blocked from rotating relative to the assembly block 50.
[0053] The left-right vertical distance between the two clamping arms 20 at the rear side can be variably adjusted to a state greater than, equal to, or smaller than the left-right vertical distance between the two clamping arms 20 at the front side.
[0054] The positioning mechanism 70 specifically includes a threaded rod 71 and a handle rod 72. The upper portion of the rod body of the threaded rod 71 is formed as a pivot structure for the swing arm 60 to match the assembly block 50, and the lower portion of the rod body of the threaded rod 71 matches the threaded hole 51 formed on the assembly block 50. One end of the handle rod 72 matches the upper end of the threaded rod 71, and the other end extends out of the body 10. By moving the end of the handle rod 72 extending out of the body 10, the handle rod 72 can drive the threaded rod 71 to rotate.
[0055] Counterbores 53 are formed at the lower end of the pivot hole of the swing arm 60 and the upper end of the threaded hole 52 of the assembly block 50. The two ends of the spring 80 sleeved on the rod body of the threaded rod 71 are respectively inserted into the two counterbores 53.
[0056] A shoulder is formed on the upper portion of the rod body of the threaded rod 71 , and a lower end surface of the shoulder is opposite to an upper end surface of the swing arm 60 .
[0057] By adjusting the length of the lower end of the threaded rod 71 screwed into the threaded hole 52 through the handle rod 72, the compression amount of the spring 80 can be changed, thereby adjusting the vertical distance between the opposite surfaces of the swing arm 60 and the assembly block 50.
[0058] The matching between the handle rod 72 and the upper end of the threaded rod 71 can be a fixed connection relationship, an integral molding relationship, or a surface matching relationship formed by one end of the handle rod and the upper end of the threaded rod, etc., as long as the other end of the handle rod can achieve the purpose of rotating the threaded rod relative to the threaded hole (in the clockwise direction and in the counterclockwise direction).
[0059] When the spring 80 is compressed to a certain extent, the spring 80 can push the swing arm 60 upward, so that the upper end surface of the swing arm 60 contacts the lower end surface of the shoulder on the threaded rod 71. In this way, when the threaded rod 71 is screwed downward to increase the length of the lower end extending into the threaded hole 52, the shoulder can press the swing arm 60 downward to move the lower end surface of the swing arm 60 gradually approaching the upper end surface of the assembly block 50.
[0060] By adjusting the vertical distance between the opposing surfaces of the swing arm 60 and the assembly block 50 , the rotation state of the swing arm 60 relative to the assembly block 50 can be switched.
[0061] For example, when a vertical spacing is maintained between the lower end surface of the swing arm 60 and the upper end surface of the assembly block 50, the swing arm 60 is in a state of free rotation relative to the assembly block 50; when the lower end surface of the swing arm 60 is in pressure contact with the upper end surface of the assembly block 50, the swing arm 60 is in a state of obstructed rotation relative to the assembly block 50.
[0062] like Figures 1 to 3 As shown, a pair of left and right opposite grooves 51 may be formed on the upper end surface of the assembly block 50 .
[0063] One end of the two swing arms 60 extends into the two grooves 51 respectively to establish a pivot matching relationship with the assembly block 50 .
[0064] The upper end surface of the swing arm 60 is relatively located below the notch of the profile groove 51 .
[0065] The upper end surface of the assembly block 50 contacts the lower end surface of the body 10, and preferably an elastic anti-skid pad is provided between the contacting surfaces of the two to improve the firmness, stability and reliability of the connection between the two.
[0066] The groove 51 is through-connected from front to back. One end of the handle rod 72 is inserted into the groove 51 and matches with the swing arm 60 through the threaded rod 71. The upper end surface of the handle rod 72 is relatively located below the notch of the groove 51.
[0067] The front end port of the groove 51 can limit the angle of rotation of the swing arm 60 to the left and right, and the rear end port of the groove 51 can limit the angle of swing of the handle rod 72 to the left and right.
[0068] To increase the obstacles / resistance to the swing arm 60 rotating relative to the assembly block 50, the following design may be made:
[0069] like Figures 2 to 4 As shown, an elastic ring 54 is provided on the upper end surface of the assembly block 50 .
[0070] The elastic ring 54 may protrude upward relative to the upper end surface of the assembly block 50 , or may be flush with or concave downward.
[0071] On the lower end surface of the swing arm 60, a plurality of convex points 61 (or annular flanges in other embodiments) distributed alternately around the circumference are formed on the periphery of the countersunk hole at the lower end of the pivot hole. The convex points 61 may be point-shaped or strip-shaped.
[0072] The protrusion 61 (or an annular flange) formed on the lower end surface of the swing arm 60 corresponds to the position directly above the elastic ring 54 .
[0073] As the swing arm 60 moves up and down relative to the assembly block 50, the protrusion 61 (or the annular flange) can gradually approach the elastic ring 54 and can be pressed into contact with the elastic ring 54. The protrusion 61 (or the annular flange) can be partially sunken into the elastic ring 54 to increase the resistance to relative rotation.
[0074] After the convex point 61 or the annular flange is designed, the upper end surface of the elastic ring 54 can be convex, flush or concave relative to the upper end surface of the groove 51 (or the assembly block 50). If the convex point 61 or the like is not provided, the upper end surface of the elastic ring 54 should be convex relative to the upper end surface of the groove 51 (or the assembly block 50).
[0075] like Figure 4 As shown, on the assembly block 50 , a multi-step through hole 55 is formed at the lower end of the threaded hole 52 .
[0076] The lower end of the threaded rod 71 can extend into the upper end hole of the multi-step through hole 55 , and a curved groove 73 is formed on the lower end surface of the threaded rod 71 .
[0077] A thread block 90 is fixedly installed in the multi-step through hole 55 by internal thread. A boss with a protruding curved surface is formed on the upper end of the thread block 90, and an elastic layer is embedded on the surface of the boss.
[0078] The curved groove 73 on the lower end surface of the threaded rod 71 can be pressed against the top surface of the boss on the threaded block 90 , and the elastic layer will exert an upward elastic force on the end of the threaded rod 71 .
[0079] The above design scheme can cause the threaded rod 71 to rotate downward and move to a state where the opposite surfaces of the swing arm 60 and the assembly block 50 are in contact. The stability of the positioning position of the threaded rod 71 will not be loosened by external vibration, and has a relaxation function.
[0080] It should be noted that the “upper end face of the assembly block” should be understood as, on the one hand, the actual end face of the assembly block 50 ; on the other hand, it can also be understood as the (inner) bottom face of the groove 51 when the groove 51 is provided on the assembly block 50 .
[0081] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. The present invention can be improved in many aspects without violating the overall concept, and those familiar with the technology can modify or change the above embodiments without violating the spirit and scope of the present invention. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the relevant technical field without departing from the spirit and technical concept disclosed by the present invention should still be covered by the claims of the present invention.
Claims
1. A denture impression scanning fixture, characterized in that: include: The main body has a pair of strip grooves opposite to each other formed at its front end and a pair of arc grooves opposite to each other formed at its rear end; the strip grooves extend straightly in the front-back direction; the arc grooves extend from the outside to the inside and gradually approach the front side; Four clamp arms are formed into a pair, and the lower ends thereof are respectively passed through the lower parts of the two strip-shaped grooves and the lower parts of the two arc-shaped grooves, and the upper ends of the four clamp arms are all extended upward relative to the upper end surface of the body; A slider is fixed to the front side of the lower end face of the body through a linear slide rail structure, and is vertically opposite to the two strip grooves and has the lower ends of the two clamping arms fixed to the slider; A driving mechanism, matched with the slider, drives the slider to move in the front-rear direction relative to the body, so that the clamp arm can move in the corresponding strip groove; An assembly block, fixed to the rear side of the lower end surface of the body; A pair of swing arms, one end of which matches the assembly block through a pivot structure, and the other end corresponds to the lower part of the arc groove and the lower ends of the other two clamping arms are correspondingly fixed to the free ends of the two swing arms; when the two swing arms rotate around the pivot relative to the assembly block respectively, the two clamping arms can move in the corresponding arc grooves respectively; And a pair of positioning mechanisms, which are matched with the swing arms one by one and are associated with the pivot structure at one end of the swing arms, and can selectively switch the swing arms between a state in which they can rotate freely relative to the assembly block and a state in which they are blocked from rotating relative to the assembly block.
2. The denture impression scanning fixture according to claim 1, characterized in that: The left-right vertical distance between the two clamping arms at the rear side can be adjusted to be greater than, equal to, or less than the left-right vertical distance between the two clamping arms at the front side.
3. The denture impression scanning fixture according to claim 1, characterized in that: The driving mechanism is a screw transmission rod mechanism; the screw lever of the screw transmission rod mechanism matches the sliding block, and the front end of the screw lever relatively extends outside the body and is matched with a knob.
4. The denture impression scanning fixture according to any one of claims 1 to 3, characterized in that: The positioning mechanism includes a threaded rod and a handle rod; The upper part of the rod body of the threaded rod is formed as a pivot structure for the swing arm to match the assembly block, and the lower part of the rod body of the threaded rod matches the threaded hole formed on the assembly block; One end of the handle rod matches the upper end of the threaded rod, and the other end extends out of the body; Countersunk holes are formed at the lower end of the pivot hole of the swing arm and the upper end of the threaded hole of the assembly block; the two ends of the spring sleeved on the rod body of the threaded rod are respectively inserted into the two countersunk holes; A shoulder is formed on the upper portion of the rod body of the threaded rod, and the lower end surface of the shoulder is opposite to the upper end surface of the swing arm; When the length of the lower end of the threaded rod screwed into the threaded hole is regulated by the handle rod, the compression amount of the spring can be changed, thereby achieving the regulation of the vertical distance between the swing arm and the opposite surface of the assembly block.
5. The denture impression scanning fixture according to claim 4, characterized in that: A pair of left and right opposite grooves are formed on the upper end surface of the assembly block; one end of the two swing arms extends into the two grooves respectively to establish a pivot matching relationship with the assembly block; the upper end surface of the swing arm is relatively located below the notch of the groove; the upper end surface of the assembly block contacts the lower end surface of the body.
6. The denture impression scanning fixture according to claim 5, characterized in that: The groove is through-through from front to back; One end of the handle rod extends into the groove and matches with the swing arm through the threaded rod; the upper end surface of the handle rod is relatively located below the notch of the groove.
7. The denture impression scanning fixture according to claim 4, characterized in that: An elastic ring is arranged on the upper end surface of the assembly block, and the elastic ring protrudes upward relative to the upper end surface of the assembly block.
8. The denture impression scanning fixture according to claim 4, characterized in that: An elastic ring is provided on the upper end surface of the assembly block; On the lower end surface of the swing arm, a plurality of convex points or an annular flange are formed around the circumference of the countersunk hole at the lower end of the pivot hole, and the convex points or the annular flange correspond to the upper part of the elastic ring; The convex point or the annular flange can gradually approach the elastic ring and can be in pressure contact with the elastic ring.
9. The denture impression scanning fixture according to claim 4, characterized in that: On the assembly block, a multi-step through hole is formed at the lower end of the threaded hole; the lower end of the threaded rod can extend into the upper end hole of the multi-step through hole, and a curved groove is formed on the lower end surface of the threaded rod; A threaded block is fixedly installed in the multi-step through hole with internal threads; a boss with a protruding curved top surface is formed at the upper end of the threaded block, and an elastic layer is embedded on the surface of the boss; the curved groove on the lower end surface of the threaded rod can be pressed on the top surface of the boss on the threaded block.
10. The denture impression scanning fixture according to any one of claims 1 to 3, characterized in that: A pair of left and right opposite grooves are formed on the upper end surface of the assembly block; one end of the two swing arms extends into the two grooves respectively to establish a pivot matching relationship with the assembly block; the upper end surface of the swing arm is relatively located below the notch of the groove; the upper end surface of the assembly block contacts the lower end surface of the body.