Lead screw clearance eliminating mechanism

Abstract

The utility model discloses a lead screw clearance eliminating mechanism, and belongs to the field of spectrometers. The lead screw anti-backlash mechanism is used for a lead screw motor in a spectrograph, the lead screw anti-backlash mechanism comprises a split nut, a bearing platform and a pressurization bolt assembly, the split nut comprises a first half nut and a second half nut which are detachably connected, and when the first half nut and the second half nut are spliced, an inner threaded hole matched with an outer thread of a lead screw is formed; the lead screw penetrates through a first penetrating through hole in the bearing platform, the direction of the first penetrating through hole is the same as that of the axis of the lead screw, the first half nut and the second half nut are detachably connected with the second face of the bearing platform, the lead screw penetrates through a center through hole of the fixing plate, and the first face of the bearing platform is connected with the fixing plate through four pressurizing bolts. The pressure adjusting nut transmits the pre-tightening force to the split nut through the bearing platform. The effects of improving the transmission precision and stability of the lead screw clearance eliminating mechanism and the disassembly and assembly convenience are achieved.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of spectrometer, especially a screw rod gap elimination mechanism. BACKGROUND

[0002] The driving mechanism in the spectrometer is usually a screw rod motor, a transmission nut is arranged on the screw rod of the screw rod motor, the internal thread of the transmission nut is matched with the external thread of the screw rod, the transmission nut is connected with a bearing platform, and the rotation of the screw rod can drive the transmission nut to move linearly, thereby driving the bearing platform on the transmission nut to move. However, during the thread transmission process, there is a small space between the thread of the screw rod and the thread of the transmission nut when they are matched, and a thread gap is formed. The existence of the gap makes the transmission nut not immediately move synchronously at the initial stage of the rotation of the screw rod, thereby causing transmission error. When the optical components of the spectrometer are positioned, the positioning deviation is caused, and the light path accuracy of the optical system is affected. The transmission error can be avoided by arranging the screw rod gap elimination mechanism on the screw rod.

[0003] A screw rod gap elimination mechanism is provided in the prior art, which comprises a transmission nut, a bearing platform, a pressurizing bolt, and a pressurizing nut. The pressurizing nut is connected to the transmission nut by a plurality of pressurizing bolts parallel to the screw rod. One end of the pressurizing bolt is fixed to the transmission nut, and the other end of the pressurizing bolt is threaded out of the flange of the pressurizing nut to form a pressure regulating end. The bearing platform is fixed to the side wall on the side of the transmission nut away from the pressurizing nut. When the transmission nut drives the bearing platform, the transmission nut will be pressed by the pressurizing nut to eliminate the gap between the transmission nut and the thread of the screw rod.

[0004] In the process of implementing the utility model, the inventor found that the screw rod gap elimination mechanism in the prior art has at least the following problems: in the screw rod gap elimination mechanism in the prior art, the transmission nut needs to be sleeved on the screw rod before the screw rod motor is packaged. Similarly, when the screw rod gap elimination mechanism is repaired and replaced, the packaging part at one end of the screw rod needs to be disassembled to take out the transmission nut. Therefore, the screw rod gap elimination mechanism in the prior art is not convenient to disassemble and assemble. UTILITY MODEL CONTENTS

[0005] The utility model embodiment provides a screw rod gap elimination mechanism, which can solve the problem of inconvenient disassembly and assembly of the screw rod gap elimination mechanism in the related art. The technical solution is as follows:

[0006] According to the first aspect of the utility model, a screw rod gap elimination mechanism is provided for a screw rod motor in a spectrometer. The screw rod motor comprises a driving part, a supporting part, and a screw rod. One end of the screw rod is connected to the driving part, and the other end is connected to the supporting part. The screw rod gap elimination mechanism comprises a split nut, a bearing platform, and a pressurizing bolt assembly.

[0007] The split nut comprises a first half nut and a second half nut, the first half nut and the second half nut are detachably connected, and when the first half nut and the second half nut are spliced, an inner threaded hole matched with the outer thread of the lead screw is formed.

[0008] The bearing platform has a first through hole in the same direction as the axis of the lead screw, the lead screw passes through the first through hole, the bearing platform has a first face and a second face opposite along the axis of the lead screw, and the first half nut and the second half nut are respectively detachably connected with the second face of the bearing platform.

[0009] The pressurizing bolt assembly comprises a fixed plate and four pressurizing bolts, each of the pressurizing bolts comprises a screw rod, a spring and a pressure regulating nut, the fixed plate has a central through hole and four bolt through holes, the lead screw passes through the central through hole, the first face of the bearing platform has four first threaded holes, one end of each of the screw rods is threadedly connected with one of the first threaded holes of the first face of the bearing platform through one of the bolt through holes, the other end of each of the screw rods is threadedly connected with the pressure regulating nut, the spring is sleeved on the screw rod, and the two ends of the spring are respectively abutted with the pressure regulating nut and the fixed plate, and the four pressurizing bolts are symmetrically arranged with the lead screw as the symmetric axis.

[0010] Optionally, the split nut further comprises a connecting screw, the first half nut has a first through hole, the second half nut has a first threaded through hole, and the connecting screw is threadedly connected with the first threaded through hole through the first through hole.

[0011] Optionally, the bearing platform further comprises four first screws, the split nut further has four second through holes, the second face of the bearing platform further has four second threaded holes, each of the first screws is threadedly connected with one of the second threaded holes through one of the second through holes, and the four first screws are symmetrically arranged with the lead screw as the symmetric axis.

[0012] Optionally, the bearing platform further comprises two connecting plates and four second screws, each of the connecting plates has two through holes, the bearing platform further has a third face and a fourth face perpendicular to the axis of the lead screw, the third face and the fourth face are two opposite faces, the third face and the fourth face respectively have a threaded hole on the side close to the split nut, the split nut respectively has a threaded hole on the side close to the third face and the fourth face, and each of the second screws is threadedly connected with the threaded holes on the third face and the fourth face through the through holes on each of the connecting plates.

[0013] Optionally, the lead screw motor further comprises a slide rail, one end of the slide rail is connected with the driving part, the other end is connected with the supporting part, the slide rail is located directly below the lead screw and is parallel to the lead screw.

[0014] The bearing platform further comprises a guide rail slider, the guide rail slider is detachably connected with the bearing platform, the guide rail slider is located directly below the bearing platform, the guide rail slider is assembled on the slide rail, and the guide rail slider can move along the length direction of the slide rail on the slide rail.

[0015] Optionally, the bearing platform further comprises four third screws, the bearing platform is provided with four third through holes, the guide rail slider is provided with four threaded holes, the four third screws are respectively screwed through the third through holes on the bearing platform and the threaded holes on the guide rail slider, and the four third screws are symmetrically arranged with the lead screw as the symmetric axis.

[0016] Optionally, the bearing platform comprises a first bearing platform and a second bearing platform which are detachably connected, the first bearing platform and the second bearing platform are symmetrically arranged with the lead screw as the symmetric axis, the first bearing platform and the second bearing platform respectively have semicircular grooves with the same diameter, and the two semicircular grooves are spliced to form the first through hole.

[0017] Optionally, the fixing plate comprises two sub-fixing plates, the two sub-fixing plates are symmetrically arranged with the lead screw as the symmetric axis, the two sub-fixing plates respectively have semicircular grooves with the same diameter, and the two semicircular grooves are spliced to form the central through hole on the fixing plate.

[0018] The technical scheme provided by the embodiment of the utility model has at least the following beneficial effects:

[0019] The screw rod gap elimination mechanism is used for a screw rod motor in a spectrometer, and the screw rod gap elimination mechanism comprises a split nut, a bearing platform and a pressurizing bolt assembly. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0021] Figure 1 is a structural schematic view of the screw rod gap elimination mechanism shown in the present application;

[0022] Figure 2 is another angle structural schematic view of the screw rod gap elimination mechanism shown in the present application; Figure 1

[0023] Figure 3 is a partial structural schematic view of the optical screw rod gap elimination mechanism shown in the present application; Figure 1

[0024] Figure 4 is another partial structural schematic view of the screw rod gap elimination mechanism shown in the present application;

[0025] BRIEF DESCRIPTION OF DRAWINGS ​​

[0026] 1-Lead screw motor, 11-Drive unit, 12-Support unit, 13-Lead screw, 14-Slide rail;

[0027] 2-Screw backlash elimination mechanism, 21-Split nut, 211-First half nut, 2111-First through hole, 212-Second half nut, 213-Second through hole, 2121-First threaded through hole, 22-Bearing platform, 221-First screw, 222-Connecting plate, 223-Second screw, 224-Guide rail slider, 225-Third screw, 226-Third through hole, 227-First bearing platform, 228-Second bearing platform, 23-Pressure bolt assembly, 231-Fixing plate, 231a-Sub-fixing plate, 232-Pressure bolt, 2321 Screw, 2322-Spring, 2323-Adjusting nut, 224-Guide rail slider.

[0028] The accompanying drawings have illustrated specific embodiments of the present invention, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the present invention in any way, but rather to illustrate the concept of the present invention to those skilled in the art through reference to specific embodiments. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this utility model clearer, the embodiments of this utility model will be described in further detail below with reference to the accompanying drawings.

[0030] Figure 1 This is a schematic diagram of a lead screw backlash elimination mechanism according to an embodiment of the present invention. Figure 2 for Figure 1 The diagram shows another angle of the lead screw backlash elimination mechanism, in which... Figure 2 for Figure 1 The side view of the lead screw backlash elimination mechanism shown is combined with... Figure 1 and Figure 2 As shown, the lead screw backlash elimination mechanism is used in the lead screw motor of a spectrometer. The lead screw motor 1 includes a drive unit 11, a support unit 12, and a lead screw 13. One end of the lead screw 13 is connected to the drive unit 11, and the other end is connected to the support unit 12. The lead screw backlash elimination mechanism 2 includes a split nut 21, a bearing platform 22, and a pressure bolt assembly 23.

[0031] The split nut 21 includes a first half nut 211 and a second half nut 212, which are detachably connected. When the first half nut 211 and the second half nut 212 are spliced ​​together, they form an internal thread hole that matches the external thread of the lead screw 13. Figure 1 , Figure 2 (Not shown in the image).

[0032] The bearing platform 22 has a first through hole in the same direction as the axis of the lead screw 13. Figure 1 , Figure 2 (Not shown in the image) The lead screw 13 passes through the first through hole, and the bearing platform 22 has a first surface and a second surface opposite to each other along the axial direction of the lead screw. The first half nut 211 and the second half nut 212 are detachably connected to the second surface of the bearing platform, respectively.

[0033] The pressure bolt assembly 23 includes a fixing plate 231 and four pressure bolts 232. Each pressure bolt 232 includes a screw 2321, a spring 2322, and an adjusting nut 2323. The fixing plate 231 has a central through hole and four bolt through holes. Figure 1 , Figure 2 (Not shown in the image) The lead screw passes through the central through hole. The first surface of the bearing platform 22 has four first threaded holes. One end of each lead screw 2321 passes through a bolt through hole and is threadedly connected to one of the first threaded holes on the first surface of the bearing platform 22. The other end of each lead screw 2321 is threadedly connected to the pressure adjusting nut 2323. A spring 2322 is sleeved on the lead screw 2321, and the two ends of the spring 2322 abut against the pressure adjusting nut 2323 and the fixing plate 231, respectively. The four pressure bolts 232 are symmetrically arranged about the lead screw 13 as the axis of symmetry.

[0034] In this system, by adjusting the pressure adjusting nut 2323, the spring 2322 extends and retracts, providing axial preload. This axial preload is transmitted to the split nut 21 through the bearing platform 22. The axial preload is converted into a clamping force on the thread side of the lead screw through the threaded inclined surface of the internal thread of the split nut 21. When the split nut 21 moves under the drive of the lead screw, the bearing platform 22 and the pressure bolt assembly 23 move synchronously and in the same direction, thereby keeping the preload stable. That is, the friction between the bearing platform 22, the split nut 21 and the lead screw 13 remains relatively stable.

[0035] In summary, the lead screw backlash elimination mechanism provided in this utility model embodiment is used in the lead screw motor of a spectrometer. The lead screw backlash elimination mechanism includes a split nut, a bearing platform and a pressure bolt assembly. The split nut includes a first half nut and a second half nut, which are detachably connected. When the first half nut and the second half nut are spliced ​​together, they form an internal thread hole that matches the external thread of the lead screw. The lead screw passes through a first through hole in the bearing platform, aligned with its axis. The first and second half-nuts are detachably connected to the second surface of the bearing platform. A fixing plate is located on the first surface of the bearing platform, having a central through hole and four bolt through holes. The lead screw passes through the central through hole. The first surface of the bearing platform has four first threaded holes. One end of each lead screw passes through a bolt through hole and is threaded into a first threaded hole on the first surface of the bearing platform. The other end of each lead screw is threaded into an adjusting nut. A spring is fitted onto the lead screw, with both ends abutting against the adjusting nut and the fixing plate, respectively. When adjusting the pressure bolt, the adjusting nut transmits the preload to the split nut via the bearing platform. The bearing platform provides a stable support base and precise positioning for the split nut and pressure bolt assembly. The split nut is detachable, allowing for disassembly and replacement without disassembling the lead screw motor. This solves the problems of poor transmission accuracy and stability, and inconvenient disassembly / reassembly, in related technologies for lead screw backlash elimination mechanisms. It achieves the effect of improving the transmission accuracy and stability of the lead screw backlash elimination mechanism, as well as the ease of disassembly / reassembly.

[0036] Figure 3 for Figure 1 The diagram shows a partial structural schematic of the optical wire rod gap elimination mechanism. Figure 3 A schematic diagram of the first half-nut is shown, combined with... Figure 1 and Figure 3 As shown, the split nut also includes a connecting screw ( Figure 1 , Figure 3 (Not shown in the diagram), the first half-nut 211 has a first through hole 2111, and the second half-nut 212 has a first threaded through hole 2121. A connecting screw passes through the first through hole 2111 and is threadedly connected to the first threaded through hole 2121. Alternatively, the first half-nut may also have a first threaded hole, and the second half-nut may also have a first through hole. The connecting screw passes through the first through hole of the second half-nut and is threadedly connected to the first threaded hole of the first half-nut. That is, the specific location of the first through hole and the first threaded hole in which half-nut of the split nut is not limited in this embodiment of the invention.

[0037] like Figure 3As shown, the first half-nut 211 may also have two first through holes 2111, located directly above and below the internal threaded hole, respectively. Similarly, the second half-nut may have two first threaded holes corresponding to the two first through holes. The split nut includes two screws, which pass through the first through holes and are threadedly connected to the first threaded holes. By placing screws directly above and below the internal threaded hole of the split nut to connect the first half-nut and the second half-nut, the connection of the split nut can be made more stable, thereby further improving the transmission accuracy and stability of the lead screw backlash elimination mechanism.

[0038] like Figure 1 As shown, the support platform also includes four first screws 221, and the split nut also has four second through holes 213. The second side of the support platform also has four second threaded holes. Figure 1 (Not shown in the diagram), each first screw 221 passes through a second through hole 213 and is threaded into a second threaded hole. The four first screws 221 are symmetrically arranged about the lead screw 13 as an axis of symmetry. Connecting the split nut 21 to the bearing platform 22 using the four first screws 221 further improves the stability of the connection between the split nut and the bearing platform, thereby making the preload transmitted from the bearing platform to the split nut more uniform and stable. The number of first screws 221 can also be two, symmetrically arranged about the lead screw 13 as an axis of symmetry; this embodiment of the invention is not limited thereto.

[0039] like Figure 1 As shown, the support platform 22 also includes two connecting plates 222 and four second screws 223. Each connecting plate has two through holes. The support platform 22 also has a third surface and a fourth surface perpendicular to the axis of the lead screw 13. The third surface and the fourth surface are two opposing surfaces. Each of the third surface and the fourth surface has a threaded hole on the side near the split nut 21. The split nut 21 also has a threaded hole on the side near the third surface and the fourth surface. Each second screw 223 passes through the through hole on each connecting plate 222 and is threadedly connected to the third surface, the fourth surface, and the threaded hole on the side of the split nut near the third surface and the fourth surface. The connecting plates and the second screws further make the connection between the split nut and the support platform more secure. In addition, the connecting plates can also be connected to other surfaces of the split nut and the support platform, which is not limited in this embodiment of the present invention.

[0040] In this embodiment of the present invention, the connection method between the split nut and the bearing platform may include only the connection method of the four first screws, or only the connection method of the connecting plate and the second screw, or both of the above connection methods. The specific connection method between the split nut and the bearing platform is not limited in this embodiment of the present invention.

[0041] like Figure 1As shown, the lead screw motor also includes a slide rail 14. One end of the slide rail 14 is connected to the drive unit 11, and the other end is connected to the support unit 12. The slide rail 14 is located directly below the lead screw 13 and is parallel to the lead screw 13. The support platform 22 also includes a guide rail slider 224, which is detachably connected to the support platform 22. The guide rail slider 224 is located directly below the support platform 22 and is mounted on the slide rail 14. The guide rail slider 224 can move along the length of the slide rail 14. The support platform moves along the length of the lead screw along with the split nut. After the support platform is connected to the guide rail slider, the guide rail slider moves with the support platform when it moves, providing stable support to the support platform during movement, thereby further improving the stability of the support platform, that is, further improving the stable support of the support platform for the split nut and the pressure bolt assembly.

[0042] like Figure 1 As shown, the support platform also includes four third screws 225, the support platform 22 has four third through holes 226, and the guide rail slider has four threaded holes. Figure 1 (not shown in the image) Four third screws 225 pass through the third through hole 226 on the bearing platform 22 and are threadedly connected to the threaded hole on the guide rail slider. The four third screws 225 are symmetrically arranged with the lead screw 13 as the axis of symmetry.

[0043] Optionally, in another embodiment where the support platform and the guide rail slider are connected, the support platform further includes four third screws, and may also have four third threaded holes. The guide rail slider may have four through holes, and the four third screws can pass through the through holes on the guide rail slider and be threadedly connected to the threaded holes on the support platform. The support platform and the guide rail slider can also be detachably connected by other connection methods, which are not limited to this embodiment.

[0044] Figure 4 This is a partial structural schematic diagram of another lead screw backlash elimination mechanism shown in an embodiment of this utility model. Figure 4 A schematic diagram of the supporting platform and the pressure bolt assembly is shown. The supporting platform 22 includes a detachably connected first supporting platform 227 and a second supporting platform 228. The first supporting platform 227 and the second supporting platform 228 are symmetrically arranged about a lead screw as an axis of symmetry. The first supporting platform 227 and the second supporting platform 228 each have a semi-circular groove of the same diameter. The two semi-circular grooves are joined together to form a first through hole. The lead screw passes through this first through hole. After the lead screw motor is assembled, the first supporting platform 227 and the second supporting platform 228 can be connected to the guide rail slider, and then connected to the split nut and the pressure bolt assembly. In addition, the first supporting platform and the second supporting platform can also be connected by screws and bolts to further improve the stability of the first supporting platform and the second supporting platform.

[0045] As Figure 4 The fixed plate 231 includes two sub-fixed plates 231a, which are symmetrically arranged with the screw rod as the symmetric axis, and each of the two sub-fixed plates 231a has a semicircular groove with the same diameter, and the two semicircular grooves are spliced to form a central through hole on the fixed plate. By arranging the first bearing platform 227, the second bearing platform 228 and the sub-fixed plate 231a, all the components in the screw rod gap elimination mechanism provided in the embodiment of the utility model are detachably connected, that is, after the screw rod motor is assembled, the components in the screw rod gap elimination mechanism of the utility model can be connected and then mounted on the screw rod motor, and when the screw rod gap elimination mechanism is disassembled, the screw rod motor does not need to be disassembled, so that the screw rod gap elimination mechanism provided in the embodiment of the utility model is more convenient to disassemble and assemble, and the application scenarios are more extensive.

[0046] In the present utility model, the terms "first", "second", "third" and "fourth" are only for the purpose of description, and cannot be understood as indicating or implying relative importance. The term "a plurality of" means two or more than two, unless otherwise explicitly limited.

[0047] Those skilled in the art can understand that all or part of the steps of the above-mentioned embodiments can be completed by hardware, or by program to instruct related hardware to complete, and the program can be stored in a computer readable storage medium, and the storage medium mentioned above can be a read-only memory, a magnetic disk or an optical disk.

[0048] The above is only the preferred embodiment of the present utility model, and is not used to limit the present utility model, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present utility model shall be included in the protection scope of the present utility model.

Claims

1. A lead screw gap elimination mechanism, characterized by, A screw motor used in a spectrometer, the screw motor comprising a driving part, a supporting part and a screw rod, one end of the screw rod is connected with the driving part, the other end is connected with the supporting part, the screw rod gap elimination mechanism comprises: a split nut, a bearing platform and a pressurizing bolt assembly; The split nut comprises a first half nut and a second half nut, the first half nut and the second half nut are detachably connected, and when the first half nut and the second half nut are spliced, an internal threaded hole matched with the external thread of the screw rod is formed; The bearing platform has a first through hole in the same direction as the axis of the screw rod, the screw rod passes through the first through hole, the bearing platform has a first face and a second face opposite along the axis of the screw rod, and the first half nut and the second half nut are respectively detachably connected with the second face of the bearing platform; The pressurizing bolt assembly comprises a fixed plate and four pressurizing bolts, each of the pressurizing bolts comprises a screw rod, a spring and a pressure regulating nut, the fixed plate has a center through hole and four bolt through holes, the screw rod passes through the center through hole, the first face of the bearing platform has four first threaded holes, one end of each of the screw rods is threadedly connected with one of the first threaded holes of the first face of the bearing platform through one of the bolt through holes, the other end of each of the screw rods is threadedly connected with the pressure regulating nut, the spring is sleeved on the screw rod, and the two ends of the spring are respectively abutted with the pressure regulating nut and the fixed plate, and the four pressurizing bolts are symmetrically arranged with the screw rod as the symmetric axis.

2. The lead screw backlash elimination mechanism of claim 1, wherein, The split nut further comprises a connecting screw, the first half nut has a first through hole, the second half nut has a first threaded through hole, and the connecting screw is threadedly connected with the first threaded through hole through the first through hole.

3. The lead screw backlash elimination mechanism of claim 1, wherein, The bearing platform further comprises four first screws, the split nut further has four second through holes, the second face of the bearing platform further has four second threaded holes, each of the first screws is threadedly connected with one of the second threaded holes through one of the second through holes, and the four first screws are symmetrically arranged with the screw rod as the symmetric axis.

4. The lead screw backlash elimination mechanism of claim 1, wherein, The bearing platform further comprises two connecting plates and four second screws, each of the connecting plates has two through holes, the bearing platform further has a third face and a fourth face perpendicular to the axis of the screw rod, the third face and the fourth face are two opposite faces, the third face and the fourth face respectively have a threaded hole on the side close to the split nut, the split nut respectively has a threaded hole on the side close to the third face and the fourth face, and each of the second screws is threadedly connected with the threaded holes on the third face and the fourth face through the through holes on each of the connecting plates.

5. The anti-backlash mechanism for a lead screw as set forth in claim 1, wherein, The screw motor further comprises a sliding rail, one end of the sliding rail is connected with the driving part, the other end is connected with the supporting part, the sliding rail is located directly below the screw rod and is parallel to the screw rod. The bearing platform further comprises a guide rail slider, which is detachably connected with the bearing platform, is located directly below the bearing platform, is assembled on the slide rail, and can move along the length direction of the slide rail.

6. The lead screw backlash elimination mechanism of claim 5, wherein, The bearing platform further comprises four third screws, four third through holes on the bearing platform, and four threaded holes on the guide rail slider, the four third screws are respectively screwed through the third through holes on the bearing platform and the threaded holes on the guide rail slider, and the four third screws are symmetrically arranged with the screw rod as the axis of symmetry.

7. The anti-backlash mechanism for a lead screw as set forth in claim 1, wherein The bearing platform comprises a first bearing platform and a second bearing platform which are detachably connected and symmetrically arranged with the screw rod as the axis of symmetry, the first bearing platform and the second bearing platform respectively have semicircular grooves with the same diameter, and the two semicircular grooves form the first through hole after splicing.

8. The lead screw backlash elimination mechanism of claim 1, wherein, The fixed plate comprises two sub-fixed plates which are symmetrically arranged with the screw rod as the axis of symmetry, the two sub-fixed plates respectively have semicircular grooves with the same diameter, and the two semicircular grooves form the center through hole on the fixed plate after splicing.

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