A fixture for printing a mobile phone shell

Abstract

This utility model discloses a fixture for printing mobile phone cases, comprising: a base; a pair of first positioning members movably disposed on the base and configured to move synchronously towards or in opposite directions along a first direction; a pair of second positioning members movably disposed on the base and configured to move synchronously towards or in opposite directions along a second direction; the first and second positioning members are respectively provided with a first hook and a second hook for hooking the side edge of the mobile phone case; an elastic lifting mechanism disposed on the base and located within the area enclosed by the first and second positioning members, the elastic lifting mechanism including a lifting platform and an elastic structure that drives the lifting platform to generate an upward movement tendency, the lifting platform being configured to elastically support the printing surface of the mobile phone case so that the printing surface of the mobile phone case remains flat during the printing process. This solves the problem that traditional fixtures easily cause deformation of the printing surface of the mobile phone case.

Description

Technical Field

[0001] This utility model relates to the field of fixture technology, and in particular to a fixture for printing mobile phone cases. Background Technology

[0002] In existing technologies, mechanical fixtures are commonly used for surface printing or spraying of thin-walled workpieces such as mobile phone cases. These fixtures have significant drawbacks: First, to provide sufficient clamping force, the fixture typically applies large concentrated stress to the sides of the phone case, easily causing elastic deformation of the printed surface, affecting the flatness of the printed plane, and consequently reducing print quality. Second, the clamping process may cause scratches on the workpiece surface, and the fixture itself can easily obstruct the area to be processed or interfere with the processing equipment. Furthermore, traditional fixture clamping operations are cumbersome, and positioning accuracy and repeatability are difficult to guarantee, failing to meet the demands of high-efficiency, high-quality production. Utility Model Content

[0003] To address the shortcomings of the existing technology, this utility model provides a fixture for printing mobile phone cases, which solves the problem that traditional fixtures easily cause deformation of the printing surface of mobile phone cases.

[0004] This utility model is achieved using the following technical solution:

[0005] A fixture for printing mobile phone cases includes:

[0006] Base;

[0007] A pair of first positioning members are movably disposed on the base and configured to move synchronously toward or in opposite directions along a first direction;

[0008] A pair of second positioning members are movably disposed on the base and configured to move synchronously toward or in opposite directions along a second direction;

[0009] The first positioning component and the second positioning component are respectively provided with a first hook and a second hook for hooking the side edge of the phone case.

[0010] An elastic lifting mechanism is disposed on a base and located within the area enclosed by a first positioning member and a second positioning member. The elastic lifting mechanism includes a lifting platform and an elastic structure that drives the lifting platform to generate an upward movement tendency. The lifting platform is configured to elastically support the printing surface of the mobile phone case so that the printing surface of the mobile phone case remains flat during the printing process.

[0011] Furthermore, the elastic lifting mechanism also includes a support base, and the elastic structure is disposed between the support base and the lifting platform.

[0012] Furthermore, the elastic structure includes a spring and a guide post. The spring is sleeved on the guide post, the guide post is located at the bottom of the lifting platform, and the top of the support base is provided with a guide hole that cooperates with the guide post.

[0013] Furthermore, both the first hook and the second hook are retaining steps that extend outward from the top of the first positioning member or the second positioning member.

[0014] Furthermore, the base is provided with a positioning pin at its bottom, which is configured to be inserted into the positioning slot of the printing platform.

[0015] Furthermore, the upper surface of the base is provided with a first guide groove for guiding a pair of first positioning components to move synchronously toward or in opposite directions; the upper surface of the base is provided with a second guide groove for guiding a pair of second positioning components to move synchronously toward or in opposite directions.

[0016] Furthermore, a pair of first positioning components move synchronously through a first gear and rack mechanism, and a pair of second positioning components move synchronously through a second gear and rack mechanism. The base is also provided with an isolation plate, which is disposed between the first gear and rack mechanism and the second gear and rack mechanism to isolate the movement space of the two.

[0017] Furthermore, the first gear and rack mechanism includes a first directional gear and two first directional racks. The two first directional racks are respectively connected to a pair of first positioning members and mesh with the first directional gear. The second gear and rack mechanism includes a track seat, a second directional gear disposed in the track seat, and two second directional racks. The two second directional racks are respectively connected to a pair of second positioning members and mesh with the second directional gear. A gear shaft is provided on the base. The gear shaft passes through the isolation plate and is connected to the track seat. The first directional gear and the second directional gear are both sleeved on the gear shaft and separated by the isolation plate.

[0018] Furthermore, each of the two second-direction racks extending from the end of the base is provided with a pressing part.

[0019] Furthermore, each of the first directional racks is provided with a first receiving space, and a first directional elastic preload is provided in the first receiving space; the base is provided with a first placement groove that communicates with the first receiving space; the two ends of the first directional elastic preload act on the end of the first receiving space and the end of the first placement groove respectively, so that the first directional rack and the first positioning member connected thereto are always subjected to a preload force away from the center.

[0020] Each second-direction rack has a second accommodating space inside, and a second-direction elastic preload member is provided therein. The base has a limiting protrusion extending to the second accommodating space. The two ends of the second-direction elastic preload member act on the end of the second accommodating space and the limiting protrusion, respectively, so that the second-direction rack and the second positioning member connected thereto are always subjected to a preload force away from the center.

[0021] Compared with the prior art, the beneficial effects of this utility model include at least the following:

[0022] This invention achieves omnidirectional fixation of the phone case by hooking the side edge of the phone case in the width direction with the first hook and the side edge of the phone case in the length direction with the second hook. The elastic lifting mechanism is located in the enclosed area, and its elastic structure drives the lifting platform to elastically support the printing surface upward, thereby dynamically supporting the printing surface of the phone case. This continuously counteracts external pressure during the printing process, keeping the printing surface flat, ensuring printing quality, and preventing the printing surface of the phone case from deforming due to lack of support. It ensures that the printing surface remains flat throughout the processing, thus improving printing quality. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of a fixture for printing mobile phone cases according to an embodiment of this utility model;

[0024] Figure 2 yes Figure 1 Front view of the structure;

[0025] Figure 3 yes Figure 1 Top view of the structure;

[0026] Figure 4 This is a schematic diagram of the internal structure of the base according to an embodiment of the present utility model;

[0027] Figure 5 yes Figure 4 Top view of the structure;

[0028] Figure 6 This is a schematic diagram of the isolation sheet according to an embodiment of the present utility model;

[0029] Figure 7 This is a schematic diagram of the first gear and rack mechanism according to an embodiment of the present utility model;

[0030] Figure 8 This is a schematic diagram of the first direction rack of this utility model embodiment;

[0031] Figure 9 This is a schematic diagram of the track seat according to an embodiment of the present utility model;

[0032] Figure 10This is a schematic diagram of the second gear and rack mechanism according to an embodiment of the present utility model;

[0033] Figure 11 This is a schematic diagram of the second-direction rack according to an embodiment of the present invention;

[0034] Figure 12 This is a schematic diagram of the bottom of the base according to an embodiment of the present invention;

[0035] Figure 13 This is a schematic diagram of the printing platform according to an embodiment of the present utility model;

[0036] In the diagram: 1. Base; 11. Positioning pin; 12. Isolation plate; 13. First guide groove; 14. Second guide groove; 15. Limiting protrusion; 16. Gear shaft; 17. First placement groove; 2. First positioning component; 21. First hook; 3. Second positioning component; 31. Second hook; 4. Elastic lifting mechanism; 41. Lifting platform; 42. Support seat; 43. Spring; 44. Guide post; 5. Printing platform; 51. Positioning groove; 61. First direction gear; 62. First direction rack; 621. First accommodating space; 63. First direction elastic preload; 70. Track seat; 71. Second direction gear; 72. Second direction rack; 721. Second accommodating space; 73. Second direction elastic preload; 74. Pressing part. Detailed Implementation

[0037] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided to make the present invention more comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and therefore repeated descriptions of them will be omitted.

[0038] The terms used to describe position and direction in this utility model are illustrated with the accompanying drawings, but changes can be made as needed, and all such changes are included within the scope of protection of this utility model.

[0039] like Figures 1 to 13 As shown, the present invention provides a fixture for printing mobile phone cases, comprising:

[0040] Base 1;

[0041] A pair of first positioning members 2 are movably disposed on the base 1 and configured to move synchronously toward or in opposite directions along a first direction;

[0042] A pair of second positioning members 3 are movably disposed on the base 1 and configured to move synchronously toward or in opposite directions along a second direction;

[0043] The first positioning member 2 and the second positioning member 3 are respectively provided with a first hook 21 and a second hook 31 for hooking the side edge of the mobile phone case.

[0044] The elastic lifting mechanism 4 is disposed on the base 1 and located in the area enclosed by the first positioning member 2 and the second positioning member 3. The elastic lifting mechanism 4 includes a lifting platform 41 and an elastic structure that drives the lifting platform 41 to generate an upward movement tendency. The lifting platform 41 is configured to elastically support the printing surface of the mobile phone case so that the printing surface of the mobile phone case always remains flat during the printing process.

[0045] In this embodiment, the phone case is placed upside down on the first positioning member 2 and the second positioning member 3, and the first hook 21 hooks the side edge of the phone case in the width direction, and the second hook 31 hooks the side edge of the phone case in the length direction, so as to achieve all-round fixation of the phone case; the elastic lifting mechanism 4 is located in the enclosed area, and the second positioning member 3 limits the elastic lifting mechanism 4 from the side. Its elastic structure drives the lifting platform 41 to elastically support the printing surface upward, so as to dynamically support the printing surface of the phone case, so as to continuously offset the external pressure during the printing process, keep the printing surface flat, ensure the printing quality, avoid the problem of deformation of the printing surface of the phone case due to lack of support, ensure that the printing surface remains flat during processing, and improve the printing quality.

[0046] In a preferred embodiment, the elastic lifting mechanism 4 further includes a support base 42, and the elastic structure is disposed between the support base 42 and the lifting platform 41.

[0047] In this embodiment, the support base 42, as an independent support component, is disposed between the base 1 and the elastic structure. It can isolate potential unevenness or external vibration interference of the base 1, preventing these factors from being directly transmitted to the lifting platform 41, thereby ensuring that the lifting platform 41 maintains a stable trajectory during movement. The elastic structure, located between the support base 42 and the lifting platform 41, makes the transmission path of elastic force shorter and more concentrated. It can dynamically adjust the support force according to the real-time stress state of the lifting platform 41, evenly distributing the pressure on the printed surface of the phone case, avoiding the risk of deformation caused by local stress concentration, and thus reliably maintaining the flatness of the printed surface.

[0048] In a preferred embodiment, the elastic structure includes a spring 43 and a guide post 44. The spring 43 is sleeved on the guide post 44, the guide post 44 is disposed at the bottom of the lifting platform 41, and the top of the support base 42 is provided with a guide hole that cooperates with the guide post 44.

[0049] In this embodiment, by sleeved spring 43 on guide post 44, the axial constraint of guide post 44 on spring 43 is used to prevent lateral bending deformation of spring 43 during compression or extension, thereby ensuring that elastic force is transmitted only in the vertical direction and avoiding uneven support caused by spring 43 instability. By setting guide post 44 at the bottom of lifting platform 41, the movement of lifting platform 41 is directly associated with guide post 44, forming a rigid guide path, allowing lifting platform 41 to move only in the vertical direction, thereby eliminating the risk of skew and ensuring that lifting platform 41 always maintains stable vertical displacement during elastic support, providing uniform and continuous flat support for the printed surface of the mobile phone case.

[0050] In a preferred embodiment, the first hook 21 and the second hook 31 are both retaining steps that extend outward from the top of the first positioning member 2 or the second positioning member 3.

[0051] In this embodiment, both the first hook 21 and the second hook 31 are clamping steps extending outward from the top of the first positioning member 2 or the second positioning member 3, forming a continuous support platform. This extension ensures that when the phone case is placed, its side edges can naturally engage with the horizontal surface of the clamping step, transforming potential point or line contact into surface contact and significantly increasing the distribution area of ​​the clamping force. Simultaneously, the smooth transition surface of the clamping step eliminates sharp edges, preventing scratches on the side edges of the phone case during clamping. Furthermore, the top-extending design fully utilizes the structural height of the positioning member, enabling rapid alignment and stable clamping of the phone case without additional adjustments during clamping operations. This improves clamping efficiency and ensures the printed surface remains flat throughout the processing, providing a reliable foundation for high-quality printing.

[0052] In a preferred embodiment, the base 1 is provided with a positioning pin 11 at its bottom, the positioning pin 11 being configured to be inserted into the positioning groove 51 of the printing platform 5.

[0053] In this embodiment, by setting the positioning pin 11, the reference relationship between the fixture and the printing platform 5 can be quickly established, simplifying the clamping operation and improving the accuracy of the initial positioning, thereby reducing the tedious steps of manual adjustment. The cooperation between the positioning pin 11 and the positioning groove 51 can reliably constrain the displacement of the fixture during the printing process, prevent positional deviation caused by equipment vibration or external force interference, maintain the precise position of the printed surface of the mobile phone case, ensure the accuracy and consistency of the printed pattern, and improve the repeatability of clamping to meet the needs of high-efficiency production.

[0054] In a preferred embodiment, the upper surface of the base 1 is provided with a first guide groove 13 that guides a pair of first positioning members 2 to move synchronously toward or in opposite directions; the upper surface of the base 1 is provided with a second guide groove 14 that guides a pair of second positioning members 3 to move synchronously toward or in opposite directions.

[0055] In this embodiment, the first guide groove 13 and the second guide groove 14 constrain the lateral offset of the first positioning member 2 and the second positioning member 3 during synchronous movement, so that the movement trajectory strictly follows the design direction. In particular, the cooperative design of the guide groove and the positioning member eliminates the shaking during the movement, ensures the repeatability of each clamping, greatly reduces the clamping difficulty, and maintains the flatness of the printing surface of the mobile phone case, laying the foundation for high-quality printing.

[0056] In a preferred embodiment, a pair of first positioning components 2 move synchronously through a first gear and rack mechanism, and a pair of second positioning components 3 move synchronously through a second gear and rack mechanism. The base 1 is also provided with an isolation plate 12, which is disposed between the first gear and rack mechanism and the second gear and rack mechanism to isolate the movement space of the two.

[0057] In this embodiment, a first gear and rack mechanism drives a pair of first positioning components 2 to move synchronously. This utilizes the rigid meshing characteristics of gears and racks to ensure that the two components maintain strict consistency in opposite directions during movement, avoiding gap errors and elastic deformation caused by manual operation or simple linkage mechanisms, thereby significantly improving the reliability and response speed of synchronous movement. In particular, the gear and rack mechanism directly transmits motion, reducing energy loss in intermediate links and making the clamping force distribution more uniform. Similarly, the second gear and rack mechanism is applied to the synchronous movement of the second positioning component 3, forming an orthogonal cooperation with the first direction mechanism, realizing precise clamping of the phone case in the two-dimensional plane and ensuring balanced force on the printed surface. The isolation plate 12 is located between the two gear and rack mechanisms, effectively preventing gear interference or rack collision between the first and second direction mechanisms during operation by physically separating the movement space, ensuring the independence and continuity of their respective movements, and avoiding sudden positioning changes or jamming caused by mutual interference.

[0058] In a preferred embodiment, the first gear and rack mechanism includes a first directional gear 61 and two first directional racks 62. The two first directional racks 62 are respectively connected to a pair of first positioning members 2 and mesh with the first directional gear 61. The second gear and rack mechanism includes a track seat 70, a second directional gear 71 disposed in the track seat 70, and two second directional racks 72. The two second directional racks 72 are respectively connected to a pair of second positioning members 3 and mesh with the second directional gear 71. A gear shaft 16 is provided on the base 1. The gear shaft 16 passes through the isolation plate 12 and is connected to the track seat 70. The first directional gear 61 and the second directional gear 71 are both sleeved on the gear shaft 16 and separated by the isolation plate 12.

[0059] In this embodiment, the first gear and rack mechanism uses a first direction gear 61 to drive two first direction racks 62. This single-gear double-rack structure ensures that the pair of first positioning members 2 maintain strict synchronization during movement, avoiding deviations caused by independent driving. The connection and meshing relationship between the two first direction racks 62 and the first positioning members 2 allows for uniform power transmission during gear rotation, achieving precise control of opposite or reversible movement. The second gear and rack mechanism incorporates a track seat 70 to enclose the second direction gear 71. The enclosed structure of the track seat 70 provides a stable environment for gear operation, reducing the impact of external vibrations. The connection and meshing between the two second direction racks 72 and the second positioning members 3 also ensure the synchronicity of second-direction movement. The gear shaft 16 on the base 1 serves as the core support. After passing through the isolation plate 12, the gear shaft 16 connects to the track seat 70. This design allows the isolation plate 12 to physically separate the two mechanisms, while the rigid connection of the gear shaft 16 ensures the stable installation of the track seat 70, preventing displacement during movement. The first directional gear 61 and the second directional gear 71 share the same gear shaft 16 but are separated by the isolation plate 12. This layout simplifies the structure by utilizing a single shaft. The blocking effect of the isolation plate 12 completely eliminates the potential collision risk of the two gears during rotation, maintains the independence of their respective movements, and effectively solves the motion interference problem of the two directional gear mechanisms.

[0060] In a preferred embodiment, each of the two second-direction racks 72 extending beyond the base 1 is provided with a pressing part 74. This allows the operator to directly apply external force for fine-tuning, enabling quick adjustment of the position of the second positioning member 3 without the need for tools, significantly improving clamping efficiency and repeatability.

[0061] In a preferred embodiment, each of the first directional racks 62 is provided with a first accommodating space 621, and a first directional elastic preload member 63 is provided in the first accommodating space 621; the base 1 is provided with a first placement groove 17 communicating with the first accommodating space 621; the two ends of the first directional elastic preload member 63 act on the ends of the first accommodating space 621 and the ends of the first placement groove 17 respectively, so that the first directional racks 62 and the first positioning member 2 connected thereto are always subjected to a preload force away from the center;

[0062] Each second-direction rack 72 has a second accommodating space 721 inside, and a second-direction elastic preload member 73 is provided therein. The base 1 has a limiting protrusion 15 extending to the second accommodating space 721. The two ends of the second-direction elastic preload member 73 act on the end of the second accommodating space 721 and the limiting protrusion, respectively, so that the second-direction rack 72 and the second positioning member 3 connected thereto are always subjected to a preload force away from the center.

[0063] In this embodiment, a first accommodating space 621 is provided inside the first direction rack 62, allowing the first direction elastic preload member 63 to be directly embedded inside the first direction rack 62. This avoids the complexity of external additional structures and ensures that the preload force is synchronized with the rack movement in real time, preventing force transmission lag caused by component separation. The base 1 is provided with a first placement groove 17 communicating with the first accommodating space 621, providing a rigid support point for the first direction elastic preload member 63. The fixing characteristics of the base 1 ensure stable output of the preload force, avoiding the impact of base 1 deformation on clamping accuracy. The two ends of the first direction elastic preload member 63 act on the ends of the first accommodating space 621 and the first placement groove 17, forming a preload force away from the center (e.g., Figure 7 (The direction the arrow points), which causes the first positioning member 2 to expand outward during clamping (i.e., move away from the center); similarly, according to the second accommodating space 721 provided inside the second direction rack 72, the second direction elastic preload member 73 can be tightly integrated inside the second direction rack 72, reducing the impact of external interference on the preload effect; the limiting protrusion 15 constrains the installation position of the second direction elastic preload member 73, ensuring that the preload force is accurately applied to the movement direction of the second direction rack 72, avoiding uneven force distribution caused by installation deviation, the limiting protrusion 15 can be a screw; the two ends of the second direction elastic preload member 73 act on the ends of the second accommodating space 721 and the limiting protrusion, maintaining the preload force of the second positioning member 3 always away from the center (such as... Figure 10 (In the direction indicated by the arrow), the second positioning member 3 expands outward during clamping. Through the cooperation of the accommodating space and the elastic preload, the elastic force is built into the motion mechanism, causing the positioning member to automatically expand outward during clamping, which significantly improves clamping efficiency and positioning repeatability.

[0064] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and alterations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention, and all such changes should fall within the protection scope of the claims of the present invention.

Claims

1. A fixture for printing mobile phone cases, characterized in that, include: Base (1); A pair of first positioning members (2) are movably disposed on the base (1) and configured to move synchronously toward or in opposite directions along a first direction; A pair of second positioning members (3) are movably disposed on the base (1) and configured to move synchronously toward or in opposite directions along a second direction; The first positioning member (2) and the second positioning member are respectively provided with a first hook (21) and a second hook (31) for hooking the side edge of the mobile phone case. An elastic lifting mechanism (4) is disposed on a base (1) and located in the area enclosed by a first positioning member (2) and a second positioning member (3). The elastic lifting mechanism (4) includes a lifting platform (41) and an elastic structure that drives the lifting platform (41) to generate an upward movement tendency. The lifting platform (41) is configured to elastically support the printing surface of the mobile phone case so that the printing surface of the mobile phone case always remains flat during the printing process.

2. The fixture for printing mobile phone cases according to claim 1, characterized in that, The elastic lifting mechanism (4) also includes a support base (42), and the elastic structure is disposed between the support base (42) and the lifting platform (41).

3. The fixture for printing mobile phone cases according to claim 2, characterized in that, The elastic structure includes a spring (43) and a guide post (44). The spring (43) is sleeved on the guide post (44). The guide post (44) is located at the bottom of the lifting platform (41). The top of the support base (42) is provided with a guide hole that cooperates with the guide post (44).

4. The fixture for printing mobile phone cases according to claim 1, characterized in that, The first hook (21) and the second hook (31) are both holding steps that extend outward from the top of the first positioning member (2) or the second positioning member (3).

5. The fixture for printing mobile phone cases according to claim 1, characterized in that, The base (1) is provided with a positioning pin (11) at its bottom, which is configured to be inserted into the positioning groove (51) of the printing platform (5).

6. The fixture for printing mobile phone cases according to claim 1, characterized in that, The upper surface of the base (1) is provided with a first guide groove (13) that guides a pair of first positioning members (2) to move synchronously toward each other or in opposite directions; the upper surface of the base (1) is provided with a second guide groove (14) that guides a pair of second positioning members (3) to move synchronously toward each other or in opposite directions.

7. The fixture for printing mobile phone cases according to any one of claims 1-6, characterized in that, A pair of first positioning components (2) move synchronously through a first gear and rack mechanism, and a pair of second positioning components (3) move synchronously through a second gear and rack mechanism. The base (1) is also provided with an isolation plate (12), which is disposed between the first gear and rack mechanism and the second gear and rack mechanism to isolate the movement space of the two.

8. The fixture for printing mobile phone cases according to claim 7, characterized in that, The first gear and rack mechanism includes a first directional gear (61) and two first directional racks (62). The two first directional racks (62) are respectively connected to a pair of first positioning members (2) and mesh with the first directional gear (61). The second gear and rack mechanism includes a track seat (70), a second directional gear (71) disposed in the track seat (70), and two second directional racks (72). The two second directional racks (72) are respectively connected to a pair of second positioning members (3) and mesh with the second directional gear (71). A gear shaft (16) is provided on the base (1). The gear shaft (16) passes through the isolation plate (12) and is connected to the track seat (70). The first directional gear (61) and the second directional gear (71) are both sleeved on the gear shaft (16) and separated by the isolation plate (12).

9. The fixture for printing mobile phone cases according to claim 8, characterized in that, Both of the two second-direction racks (72) extending out of the base (1) are provided with pressing parts (74).

10. The fixture for printing mobile phone cases according to claim 8, characterized in that, Each of the first directional racks (62) is provided with a first accommodating space (621), and a first directional elastic preload member (63) is provided in the first accommodating space (621); the base (1) is provided with a first placement groove (17) communicating with the first accommodating space (621); the two ends of the first directional elastic preload member (63) act on the end of the first accommodating space (621) and the end of the first placement groove (17) respectively, so that the first directional rack (62) and the first positioning member (2) connected thereto are always subjected to a preload force away from the center; Each second direction rack (72) has a second accommodating space (721) inside, and a second direction elastic preload member (73) is provided therein. The base (1) has a limiting protrusion (15) extending to the second accommodating space (721). The two ends of the second direction elastic preload member (73) act on the end of the second accommodating space (721) and the limiting protrusion respectively, so that the second direction rack (72) and the second positioning member (3) connected thereto are always subjected to a preload force away from the center.

Images