Hollow structure for wafer rotary film expansion

Abstract

The utility model provides a wafer rotation film expansion hollow structure, which comprises a turntable piece and at least three limiting transmission units, and is characterized in that the turntable piece is provided with an annular edge; the at least three limiting transmission units are arranged at intervals in the circumferential direction of the rotary disc part, each limiting transmission unit comprises a limiting cylinder and a mounting shaft, grooves are formed in the side walls of the limiting cylinders in the circumferential direction in an extending mode, and the grooves form a closed annular structure; the mounting shaft is arranged in the limiting cylinder in a penetrating mode along the central axis of the limiting cylinder, and the limiting cylinder can pivot around the central axis relative to the mounting shaft; wherein the annular edge of the rotating disc piece is embedded in the inner wall of the groove in a rolling mode, and when the limiting cylinder pivots around the central axis, the rotating disc piece can be driven to rotate through friction force between the groove and the annular edge. According to the utility model, the problems of easy vibration, large noise and easy structure shaking in the aspect of rotary support of a wafer rotary film expansion hollow structure in the prior art are solved.

Description

TECHNICAL FIELD

[0001] The utility model relates to belong to wafer processing technical field, especially related to a wafer rotation expansion film hollow structure. BACKGROUND

[0002] In the related field such as semiconductor manufacturing, wafer rotation expansion film hollow structure is a kind of key equipment, and its performance directly influences the quality and efficiency of wafer processing.The existing wafer rotation expansion film hollow structure has obvious deficiency in rotation support aspect.

[0003] At present, the structure generally adopts large bearing as rotating support component.However, the material of large bearing is usually steel, which makes the load of moving part greatly increase.In the process of long-term high-frequency operation of equipment, this larger load is prone to cause vibration and noise problem.Vibration not only causes the equipment to appear loose phenomenon, but also makes the stability of structure gradually deteriorate, and then influences the processing precision of wafer and the service life of equipment.

[0004] In order to improve the rotation support performance, the prior art attempts to adopt the way of placing roller bearing in multiple directions to design a structure similar to bearing.As shown in Figure 1 , the end face in the circumferential direction of rotary disc part is provided with groove structure, and the central axis of rotary disc part is parallel to vertical direction. Figure 1 The bottom view of a kind of wafer rotation expansion film hollow structure in prior art is shown in Figure 1 , and vertical direction is The direction perpendicular to the plane of paper in

[0005] . Figure 1 Specifically, a plurality of first roller bearings 100 are provided along the circumferential direction of rotary disc part 1 in The central axis of first roller bearing 100 is parallel to vertical direction, and at least part of first roller bearing 100 is radially deepened into groove structure, and the position of rotary disc part 1 in horizontal direction can be defined by a plurality of first roller bearings 100.When first roller bearing 100 is driven to rotate, rotary disc part can also be driven to rotate by the friction force generated by first roller bearing 100 and groove structure;And the central axis of second roller bearing 200 is usually arranged along horizontal direction, and second roller bearing 200 can limit rotary disc part 1 in vertical direction, and can roll on the side wall of groove structure.

[0006] However, this design has many disadvantages. On the one hand, the processing difficulty is extremely great, and high-precision processing technology and equipment are required, which not only increases the production cost, but also puts forward very high requirements for processing technology. On the other hand, processing gaps are easily generated in the processing process. These gaps can cause the structure to shake during operation, seriously affecting the stability and reliability of the structure. Once the structure shakes, the position accuracy of the wafer during the rotating film expansion process cannot be guaranteed, thereby reducing the quality of wafer processing, and even causing the wafer to be scrapped.

[0007] In summary, the existing wafer rotating film expansion hollow structure has the problems of easy vibration, large noise and easy shaking of the structure in the aspect of rotating support. Practical new type content

[0008] The utility model discloses a wafer rotating film expansion hollow structure to solve the problems of easy vibration, large noise and easy shaking of the structure in the aspect of rotating support in the prior art.

[0009] In order to realize the above-mentioned purpose of the utility model, an embodiment of the utility model provides a wafer rotating film expansion hollow structure, comprising:

[0010] The disc part has an annular edge.

[0011] At least three limiting transmission units are arranged along the circumference of the disc part, and each limiting transmission unit comprises:

[0012] A limiting cylinder is provided with a groove extending along the circumference on the side wall, and the groove forms a closed annular structure.

[0013] An installation shaft is arranged in the limiting cylinder along the central axis of the limiting cylinder, and the limiting cylinder can pivot relative to the installation shaft around the central axis.

[0014] The annular edge of the disc part is rollingly embedded on the inner wall of the groove, and when the limiting cylinder pivots around the central axis, the disc part can be driven to rotate by the friction force between the groove and the annular edge.

[0015] As a further improvement of the embodiment of the utility model, the groove is provided as a V-shaped groove.

[0016] As a further improvement of the embodiment of the utility model, the slope of the groove side wall of the V-shaped groove is between 50° and 70°.

[0017] As a further improvement of the embodiment of the utility model, the limiting cylinder is of stainless steel structure.

[0018] As a further improvement of an embodiment of the utility model, four limit transmission units are arranged along the circumference of the rotating disc part.

[0019] As a further improvement of an embodiment of the utility model, the limit transmission unit comprises a mounting part arranged on the mounting base, and the mounting part comprises a bottom plate, and the mounting shaft is arranged on the bottom plate and fixedly connected with the bottom plate.

[0020] As a further improvement of an embodiment of the utility model, the first synchronous belt transmission unit and the first driving part are arranged on the mounting base, the first driving part is in transmission cooperation with the side wall of the limit cylinder through the first synchronous belt transmission unit to drive the limit cylinder to pivot around the middle axis.

[0021] As a further improvement of an embodiment of the utility model, the side wall of the limit cylinder has a large-diameter section and a small-diameter section arranged along the axial direction of the limit cylinder in sequence, the small-diameter section is arranged close to the bottom plate, the groove is arranged on the large-diameter section, and the first driving part is in transmission cooperation with the small-diameter section through the first synchronous belt transmission unit.

[0022] As a further improvement of an embodiment of the utility model, the mounting base is connected with the rack through a lead screw, the lead screw is threadedly connected with the mounting base and can pivot relative to the rack, the second driving part and the second synchronous belt transmission unit are arranged on the rack, the second driving part is in transmission cooperation with the lead screw through the second synchronous belt transmission unit to drive the lead screw to pivot around the middle axis of the lead screw and drive the mounting base to move in the axial direction of the lead screw.

[0023] As a further improvement of an embodiment of the utility model, the number of the lead screws is four, the four lead screws are arranged along the circumference of the rotating disc part in uniform intervals and are arranged on the mounting base, the second synchronous belt transmission unit comprises a driving synchronous belt unit and a transmission synchronous belt unit, the second driving part is in transmission cooperation with one of the four lead screws through the driving synchronous belt unit, and the lead screw is in transmission cooperation with the other three lead screws through the transmission synchronous belt unit.

[0024] Compared with the prior art, the utility model has the beneficial effects that:

[0025] By utilizing the grooves on the sidewalls of the limiting cylinder, the position of the turntable component in the axial and radial directions of the limiting cylinder can be limited. Furthermore, the friction between the grooves and the annular edge can be used to drive the turntable component to rotate. This design effectively overcomes problems such as vibration, significant noise, and structural instability that easily occur during the rotational support of hollow wafer rotary expansion structures. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of a wafer rotational expansion hollow structure in the prior art.

[0027] Figure 2 A top view of a wafer rotational expansion hollow structure provided in an embodiment of this utility model;

[0028] Figure 3 for Figure 2 A bottom view;

[0029] Figure 4 for Figure 2 Cross-sectional view along the AA direction;

[0030] Figure 5 for Figure 3 Enlarged view at point M;

[0031] Figure 6 for Figure 3 A schematic diagram of the middle limit transmission unit.

[0032] The above description of the figures includes the following reference numerals:

[0033] 100. First roller bearing;

[0034] 200. Second roller bearing;

[0035] 1. Turntable component;

[0036] 2. Limit transmission unit;

[0037] 21. Limiting cylinder;

[0038] 211. Large diameter section;

[0039] 2111, Groove;

[0040] 212. Small path section;

[0041] 22. Install the shaft;

[0042] 23. Installation components;

[0043] 231. Base plate;

[0044] 3. Install the base;

[0045] 4. First synchronous belt drive unit;

[0046] 5. First driving component;

[0047] 6. Rack;

[0048] 61. Lead screw;

[0049] 7. Second synchronous belt drive unit;

[0050] 71. Drive synchronous belt unit;

[0051] 72. Transmission synchronous belt unit;

[0052] 8. Second drive unit. Detailed Implementation

[0053] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0054] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0055] In this utility model, unless otherwise stated, directional terms such as "upper," "lower," "top," and "bottom" are generally used in relation to the direction shown in the accompanying drawings, or in relation to the vertical, perpendicular, or gravitational direction of the component itself; similarly, for ease of understanding and description, "inner" and "outer" refer to the inner and outer contours of each component itself, but the above directional terms are not used to limit this utility model.

[0056] Figure 1 This illustrates a prior art wafer spin-expanded hollow structure. Figure 1 In this design, the turntable component 1 is provided with multiple first roller bearings 100 with vertical central axes and second roller bearings 200 with horizontal central axes. The former limits the horizontal position of the turntable component and drives its rotation by friction, while the latter limits its vertical position and can roll on the sidewall of the groove. However, this design has drawbacks: it is difficult to manufacture, costly, and requires advanced technology. It is also prone to manufacturing gaps, which can cause structural wobbling, affect stability and reliability, reduce wafer processing quality, and even lead to wafer scrap.

[0057] To address the problems of vibration, high noise, and structural wobbling in existing wafer rotational expansion hollow structures, this invention provides a novel wafer rotational expansion hollow structure.

[0058] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Example

[0059] like Figures 2-6 As shown, this embodiment provides a wafer rotation expansion hollow structure including a turntable 1 and at least three limiting transmission units 2.

[0060] The turntable component 1 has an annular edge; at least three limiting transmission units 2 are arranged at intervals along the circumference of the turntable component, each limiting transmission unit 2 includes a limiting cylinder 21 and a mounting shaft 22, and a groove 2111 is provided on the side wall of the limiting cylinder 21 along the circumference, the groove 2111 forming a closed annular structure.

[0061] The mounting shaft 22 passes through the limiting cylinder 21 along the central axis of the limiting cylinder 21, and the limiting cylinder 21 can pivot about the central axis relative to the mounting shaft 22.

[0062] The annular edge of the turntable 1 is rolled and embedded in the inner wall of the groove 2111, and when the limiting cylinder 21 pivots around the central axis, the turntable 1 can be driven to rotate by the friction between the groove 2111 and the annular edge.

[0063] With this configuration, the groove 2111 on the side wall of the limiting cylinder 21 can limit the position of the turntable 1 in the axial and radial directions of the limiting cylinder 21; on the other hand, the friction between the groove 2111 and the annular edge can drive the turntable 1 to rotate, effectively solving the problems of easy vibration, high noise and easy swaying of the hollow structure in the wafer rotation expansion film in terms of rotation support.

[0064] Preferably, the groove 2111 is configured as a V-groove. Designing the groove 2111 as a V-groove offers several advantages. From a positioning perspective, the inclined surfaces on both sides of the V-groove better fit the annular edge of the turntable 1, providing a more stable and precise positioning effect when limiting the axial and radial positions of the turntable 1 to the positioning cylinder 21, reducing the possibility of the turntable 1 wobbling. Regarding driving the turntable 1 to rotate, the inclined surface structure of the V-groove makes the frictional force distribution between the groove 2111 and the annular edge more uniform and reasonable. When the positioning cylinder 21 pivots around the central axis, it can more effectively transmit power to the turntable 1, further reducing vibration and noise generated during equipment operation, thus more comprehensively solving the problems existing in the rotational support of current wafer rotary expansion hollow structures.

[0065] More preferably, refer to Figure 5 As shown, the slope of the sidewall of the V-shaped groove is between 50° and 70°, that is... Figure 5The mid-angle 'a' ranges from 50° to 70°. This slope range is the optimal range determined through extensive practice and research. When the slope of the groove sidewall is within this range, the fit between the V-groove and the annular edge of the turntable is optimal. If the slope is too small, the V-groove will not provide sufficient restraint for the turntable, and the turntable may easily shift radially or axially during equipment operation, affecting the stability of the structure. If the slope is too large, the friction between the groove and the annular edge will be too high, increasing the operating resistance of the equipment, leading to increased energy consumption, and may even cause overheating. Controlling the slope between 50° and 70° ensures both good restraint and appropriate friction, effectively reducing vibration and noise, and improving the overall performance of the equipment.

[0066] Optionally, the limiting cylinder 21 can be made of stainless steel. Using stainless steel to make the limiting cylinder 21 has significant advantages. Stainless steel possesses excellent strength and hardness, capable of withstanding various forces and loads generated during the operation of the hollow structure in the wafer rotation expansion process, ensuring that the limiting cylinder 21 is not easily deformed or damaged during long-term high-frequency use, thereby ensuring the stability and reliability of the structure. Simultaneously, stainless steel has good corrosion resistance, adapting to different working environments and avoiding material degradation caused by environmental factors. Furthermore, the smooth surface of stainless steel effectively reduces frictional resistance when in contact with the annular edge of the turntable, reducing wear and extending the equipment's service life. This material selection is one of the important foundations for ensuring the stable and reliable performance of this structure.

[0067] Furthermore, in this embodiment, reference is made to... Figure 2 and Figure 3 As shown, the number of limiting transmission units 2 is set to four, and the four limiting transmission units 2 are evenly spaced along the circumference of the turntable 1. This number and layout arrangement is reasonable. The even distribution of the four limiting transmission units 2 can provide a more balanced and stable support force for the turntable 1, effectively avoiding the phenomenon of uneven load on the turntable 1 during rotation, and further enhancing the stability of the structure. At the same time, the even spacing can make the load borne by each limiting transmission unit 2 relatively uniform, reduce the force concentration of a single unit, and reduce the risk of structural damage due to local overload. This arrangement can also make the turntable 1 more evenly stressed and rotate more smoothly during rotation, thereby better solving the problems existing in the rotation support of the prior art.

[0068] Furthermore, such as Figure 6As shown, the wafer rotating and film expanding hollow structure provided by the embodiment further comprises a mounting base 3, the limiting transmission unit 2 comprises a mounting piece 23, the mounting piece 23 is arranged on the mounting base 3, the mounting piece 23 comprises a bottom plate 231, and the mounting shaft 22 penetrates through the bottom plate 231 and is fixedly connected with the bottom plate 231. The mounting base 3 provides a stable basic support for the whole structure, ensuring the stability of the equipment during operation. The bottom plate 231 of the mounting piece 23 serves as a fixed carrier of the mounting shaft 22, and the structural design enables the mounting shaft 22 to be firmly mounted on the mounting base 3. This fixed connection mode not only ensures the connection strength between the limiting transmission unit 2 and the mounting base 3, but also effectively reduces the connection loosening problem caused by equipment vibration, thereby ensuring the normal operation of the limiting transmission unit 2 and improving the reliability and stability of the whole wafer rotating and film expanding hollow structure.

[0069] As Figure 2 As shown, the wafer rotating and film expanding hollow structure provided by the embodiment further comprises a first synchronous belt transmission unit 4 and a first driving piece 5 arranged on the mounting base 3, and the first driving piece 5 is in transmission cooperation with the side wall of the limiting cylinder 21 through the first synchronous belt transmission unit 4 to drive the limiting cylinder 21 to pivot around the central axis. The first driving piece 5 serves as a power source to provide power for the pivoting of the limiting cylinder 21. The first synchronous belt transmission unit 4 plays a key role in power transmission, which accurately transmits the power output by the first driving piece 5 to the limiting cylinder 21. This transmission mode has the advantages of stable transmission and high efficiency, which can effectively ensure the stable pivoting of the limiting cylinder 21 around the central axis. Through this power transmission and transmission cooperation, the rotating disc piece 1 can stably rotate under the drive of the limiting transmission unit, further improving the operation stability and reliability of the wafer rotating and film expanding hollow structure. The first synchronous belt transmission unit 4 is usually composed of a synchronous belt and a synchronous wheel, and those skilled in the art should be able to understand the specific structure of the first synchronous belt transmission unit 4, which will not be described here.

[0070] Further, the side wall of the limiting cylinder 21 has a large-diameter section 211 and a small-diameter section 212 arranged in sequence along the axial direction of the limiting cylinder 21, wherein the small-diameter section 212 is arranged close to the bottom plate 231, the groove 2111 is arranged on the large-diameter section 211, and the first driving piece 5 is in transmission cooperation with the small-diameter section 212 through the first synchronous belt transmission unit 4. Such structural design is reasonable, the large-diameter section 211 is provided with the groove 2111 for cooperation with the rotating disc piece to realize limiting and driving thereof, and the small-diameter section 212 is arranged close to the bottom plate 231 to facilitate cooperation with the first synchronous belt transmission unit 4 to transmit power.

[0071] Preferably, some anti-skid protrusions can also be arranged on the small-diameter section 212. These anti-skid protrusions can increase the friction between the small-diameter section 212 and the synchronous belt, prevent slipping during transmission, ensure that power can be stably and efficiently transmitted to the limiting cylinder 21, and thus ensure the smooth rotation of the turntable 1 and improve the operation accuracy and reliability of the wafer rotary membrane expansion hollow structure.

[0072] As a preferred embodiment, the wafer rotary membrane expansion hollow structure in the embodiment further comprises a rack 6, a second synchronous belt transmission unit 7, and a second driving member 8. The mounting base 3 is connected to the rack 6 through a lead screw 61, which is threadedly connected to the mounting base 3 and can pivot relative to the rack 6. This connection allows the mounting base 3 to move axially under the action of the lead screw 61. The second driving member 8 and the second synchronous belt transmission unit 7 are arranged on the rack 6. The second driving member 8 is in transmission cooperation with the lead screw 61 through the second synchronous belt transmission unit 7 to make the lead screw 61 pivot around its own central axis. When the second driving member 8 is started, power is transmitted to the lead screw 61 through the second synchronous belt transmission unit 7. When the lead screw 61 pivots, it moves the mounting base 3 in the axial direction of the lead screw 61 due to the threaded connection between the lead screw 61 and the mounting base 3. This design can conveniently adjust the position of the mounting base 3, and thus adjust the height or position of the entire wafer rotary membrane expansion hollow structure to adapt to different processing requirements, improving the versatility and flexibility of the equipment.

[0073] Further, the number of lead screws 61 is four, and the four lead screws 61 are uniformly spaced around the circumference of the turntable 1 and are arranged on the mounting base 3. Such a layout can make the mounting base 3 stable when moving, avoiding tilting or shaking, and improving the stability of the entire structure.

[0074] The second synchronous belt transmission unit 7 comprises a driving synchronous belt unit 71 and a transmission synchronous belt unit 72. The driving synchronous belt unit 71 is mainly responsible for receiving external power and converting it into the movement driving force of the synchronous belt. The transmission synchronous belt unit 72 is responsible for transmitting driving force to subsequent working components, so as to realize power transmission and work execution of the entire transmission unit. This clear division of labor design makes power transmission more efficient and orderly.

[0075] The second driving member 8 is in transmission cooperation with one of the four lead screws 61 through the driving synchronous belt unit 71, and power is transmitted to the lead screw. Further, the lead screw 61 is in transmission cooperation with the other three lead screws 61 through the transmission synchronous belt unit 72, so that the four lead screws 61 can rotate synchronously. When one of the lead screws 61 rotates under the driving of the driving synchronous belt unit 71, the other three lead screws 61 also rotate synchronously through the transmission action of the transmission synchronous belt unit 72, thereby driving the mounting base 3 to move stably in the axial direction of the lead screw 61. This transmission mode ensures the synchronization of the movement of the four lead screws 61, further improves the stability and accuracy of the movement of the mounting base 3, and makes the wafer rotary film expansion hollow structure better adapt to different working requirements.

[0076] In summary, the embodiments of the utility model realize the following technical effects:

[0077] With the help of the groove 2111 on the side wall of the limiting cylinder 21, on the one hand, the position of the rotating disc part 1 in the axial and radial directions of the limiting cylinder 21 can be limited, and on the other hand, the rotating disc part 1 can be driven to rotate by using the friction force between the groove 2111 and the annular edge. This design effectively overcomes the problems of vibration, large noise and unstable shaking of the wafer rotary film expansion hollow structure during the rotating support process.

[0078] Obviously, the above-described embodiments are only a part of the embodiments of the utility model, rather than all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by those skilled in the art without creative labor should belong to the protection scope of the utility model.

[0079] It should be noted that the terms used herein are only intended to describe specific embodiments, and are not intended to limit the exemplary embodiments according to the present application. As used herein, the singular form is intended to include the plural form unless the context clearly indicates otherwise, and it should be understood that when the terms "comprise" and / or "include" are used in the specification, there is a feature, step, work, device, component and / or combination thereof.

[0080] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above-described drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein.

[0081] The above merely describes preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A wafer rotational expansion hollow structure, characterized in that, include: Turntable component with a ring-shaped edge; At least three limiting transmission units are arranged at intervals along the circumference of the turntable component, and each limiting transmission unit includes: A limiting cylinder has a groove extending circumferentially on its side wall, the groove forming a closed annular structure; The mounting shaft passes through the limiting cylinder along the central axis of the limiting cylinder, and the limiting cylinder can pivot about the central axis relative to the mounting shaft. The annular edge of the turntable is rolled and embedded in the inner wall of the groove, and when the limiting cylinder pivots around the central axis, the turntable can be driven to rotate by the friction between the groove and the annular edge.

2. The wafer rotational expansion hollow structure according to claim 1, characterized in that, The groove is configured as a V-shaped groove.

3. The wafer rotational expansion hollow structure according to claim 2, characterized in that, The slope of the sidewall of the V-shaped groove is between 50° and 70°.

4. The wafer rotational expansion hollow structure according to claim 1, characterized in that, The limiting cylinder is made of stainless steel.

5. The wafer rotational expansion hollow structure according to claim 1, characterized in that, The number of the limiting transmission units is set to four, and the four limiting transmission units are evenly spaced along the circumference of the turntable.

6. The wafer rotational expansion hollow structure according to claim 1, characterized in that, It also includes a mounting base, and the limiting transmission unit includes a mounting component, which is disposed on the mounting base. The mounting component includes a base plate, and the mounting shaft passes through the base plate and is fixedly connected to the base plate.

7. The wafer rotational expansion hollow structure according to claim 6, characterized in that, It also includes a first synchronous belt drive unit and a first drive component mounted on the mounting base. The first drive component engages with the side wall of the limiting cylinder through the first synchronous belt drive unit to drive the limiting cylinder to pivot around the central axis.

8. The wafer rotational expansion hollow structure according to claim 7, characterized in that, The side wall of the limiting cylinder has a large diameter section and a small diameter section arranged sequentially along the axial direction of the limiting cylinder. The small diameter section is located close to the base plate. The groove is located on the large diameter section. The first driving member is driven by the small diameter section through a first synchronous belt transmission unit.

9. The wafer rotational expansion hollow structure according to claim 6, characterized in that, It also includes a frame, a second synchronous belt drive unit, and a second drive component. The mounting base is connected to the frame via a lead screw. The lead screw is threadedly connected to the mounting base and can pivot relative to the frame. The second drive component and the second synchronous belt drive unit are mounted on the frame. The second drive component is driven by the lead screw through the second synchronous belt drive unit to make the lead screw pivot about its own central axis and to make the mounting base move in the axial direction of the lead screw.

10. The wafer rotational expansion hollow structure according to claim 9, characterized in that, The number of lead screws is set to four. The four lead screws are evenly spaced around the circumference of the turntable and pass through the mounting base. The second synchronous belt drive unit includes a drive synchronous belt unit and a transmission synchronous belt unit. The second drive unit is driven by one of the four lead screws through the drive synchronous belt unit. The lead screw is driven by the other three lead screws through the transmission synchronous belt unit.

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