CN221474792U

CN221474792U - Turnover device

Info

Publication number: CN221474792U
Application number: CN202420090961.5U
Authority: CN
Inventors: 李文坚
Original assignee: Langxin Suzhou Precision Optics Co ltd
Current assignee: Langxin Suzhou Precision Optics Co ltd
Priority date: 2024-01-15
Filing date: 2024-01-15
Publication date: 2024-08-06
Anticipated expiration: 2034-01-15

Abstract

The utility model provides a turnover device which is used for turning a workpiece, wherein the workpiece at least comprises a first surface; the turnover device comprises a first turnover mechanism and a second turnover mechanism which is arranged opposite to the first turnover mechanism; the first turnover mechanism is used for receiving the workpiece with the first surface facing downwards and turning over the workpiece; the second turnover mechanism is used for receiving the workpiece turned over by the first turnover mechanism and turning over the workpiece so that the first surface of the workpiece faces upwards. Compared with the prior art, the turnover device provided by the utility model can enable the turnover of the workpiece to be more stable, can obviously reduce the manual operation strength and the turnover difficulty, improves the working efficiency, and can reduce the safety accidents caused by manual misoperation.

Description

Turnover device

Technical Field

The utility model relates to the technical field of ion beam polishing, in particular to a turnover device.

Background

The ion beam polishing machine is a device for removing materials with atomic-level resolution by bombarding the surface of a workpiece to be processed with rare gas ions, and is one of processing devices with highest processing precision so far. The polishing device has the technical advantages that non-contact polishing is adopted, defects cannot be caused, pollution such as metal ions and the like remained on the surface of a workpiece to be processed can be effectively removed, and the surface shape of the workpiece can be accurately modified.

The principle of the ion beam polishing machine is that an ion source device mounted on a multi-axis motion system generates a focused ion beam to bombard the surface of a workpiece, and complex cascade collision occurs between ions and atoms of the workpiece and between the atoms of the workpiece, so that the deterministic removal of the material on the surface of the workpiece is realized, and the purpose of correcting positive errors is achieved.

Currently, ion beam polishing machines mainly have two structural forms: the horizontal structure is a mode that a workpiece to be processed is clamped on a workbench in a side-to-side mode, the surface to be processed faces to the horizontal direction, and an ion source device is carried on a moving shaft system of the ion beam polishing machine and is oppositely arranged with the workpiece; the other is of a vertical structure, namely, a workpiece to be processed is hung on a workbench at the top upside down, the processing surface of the workpiece to be processed faces downwards, and an ion source device carried by a moving shaft system of the ion beam polishing machine is vertically upwards aligned with the surface to be processed of the workpiece.

When the plasma polishing machine with the vertical structure is used for processing the optical lens, the surface to be processed of the workpiece to be processed faces downwards, and the surface to be processed of the workpiece to be processed is generally upwards before clamping and is protected, so that the workpiece to be processed needs to be overturned. In addition, when the workpiece enters the next measuring procedure after being processed, the measuring surface of the workpiece is required to be detected accurately upwards, so that the workpiece is required to be overturned.

At present, when a workpiece is turned over, the workpiece is turned over by means of the aerial crane of a workshop and a special tool, the turning over mode has great potential safety hazard, the workpiece is easy to damage, the operation experience of operators is high, and especially when the workpiece with a large caliber is turned over, the turning over operation is more difficult to control due to the fact that the size and the weight of the workpiece are large.

Therefore, how to provide a turnover device to reduce the turnover difficulty of the workpiece to be processed and the potential safety hazard is a technical problem to be solved in the field.

Disclosure of utility model

Aiming at the technical problems. The utility model provides a turnover device which is provided with a first turnover mechanism and a second turnover mechanism which are opposite, the workpiece can be taken in and turned over through the cooperation between the first turnover mechanism and the second turnover mechanism, the workpiece is not required to be turned over in a hoisting mode, the workpiece can be turned over more stably, the manual operation strength and the turnover difficulty can be remarkably reduced, the working efficiency is improved, and the safety accidents caused by manual operation errors can be reduced.

A turnover device for turning over a workpiece, wherein the workpiece at least comprises a first surface;

the turnover device comprises a first turnover mechanism and a second turnover mechanism which is arranged opposite to the first turnover mechanism;

the first turnover mechanism comprises a first frame body, a first turnover frame and a first turnover unit;

The first roll-over stand is used for receiving the workpiece with the first face facing downwards, and the first roll-over stand can be arranged on the first stand body in a roll-over manner;

The first overturning unit is connected with the first overturning frame and used for driving the first overturning frame to overturn;

The second turnover mechanism comprises a second frame body, a second turnover frame and a second turnover unit;

The second roll-over stand is used for receiving the workpiece which is turned over by the first roll-over stand, and the second roll-over stand can be turned over and arranged on the second stand body so as to turn over the workpiece, so that the first surface of the workpiece faces upwards;

The second overturning unit is connected with the second overturning frame and used for driving the second overturning frame to overturn.

Preferably, the device further comprises a base;

The first frame body and the second frame body are arranged on the base, and at least one of the first frame body and the second frame body is arranged on the base in a sliding way.

Preferably, the base is provided with a guide rail, and at least one of the first frame body and the second frame body is slidably arranged on the guide rail.

Preferably, the guide rail is disposed along a length direction of the base.

Preferably, a first supporting member is arranged at one end of the first turnover frame, which is close to the second turnover mechanism;

The second turnover frame is close to one end of the first turnover mechanism and is provided with a second supporting piece, and the second supporting piece and the first supporting piece are arranged in a staggered mode.

Preferably, the bearing parts of the first bearing part and the second bearing part are respectively provided with an anti-slip part.

Preferably, a first bearing seat is arranged at one end of the first frame body, which is close to the second turnover mechanism, and one end of the first turnover frame is connected to the first bearing seat in a turnover manner through a first pin shaft.

Preferably, a second bearing seat is arranged at one end of the second frame body, which is close to the first turnover mechanism, and one end of the second turnover frame is connected to the second bearing seat in a turnover way through a second pin shaft.

Preferably, the first overturning unit is a linear telescopic unit, two ends of the first overturning unit are respectively and rotatably connected with the first frame body and the first overturning frame, and the first overturning unit is used for driving the first overturning frame to overturn in a range of 0-95 degrees.

Preferably, the second overturning unit is a linear telescopic unit, two ends of the second overturning unit are respectively and rotatably connected with the second frame body and the second overturning frame, and the second overturning unit is used for driving the second overturning frame to overturn in a range of 0-90 degrees.

Compared with the prior art, the turnover device provided by the utility model is used for turnover of the workpiece, and the workpiece at least comprises a first surface; the turnover device comprises a first turnover mechanism and a second turnover mechanism which is arranged opposite to the first turnover mechanism; the first turnover mechanism comprises a first frame body, a first turnover frame and a first turnover unit; the first roll-over stand is used for receiving the workpiece with the first face facing downwards, and the first roll-over stand can be arranged on the first stand body in a roll-over manner; the first overturning unit is connected with the first overturning frame and used for driving the first overturning frame to overturn; the second turnover mechanism comprises a second frame body, a second turnover frame and a second turnover unit; the second roll-over stand is used for receiving the workpiece which is turned over by the first roll-over stand, and the second roll-over stand can be turned over and arranged on the second stand body so as to turn over the workpiece, so that the first surface of the workpiece faces upwards; the second overturning unit is connected with the second overturning frame and used for driving the second overturning frame to overturn. The turnover device is provided with the first turnover mechanism and the second turnover mechanism, and the turnover cooperation between the first turnover mechanism and the second turnover mechanism is realized, so that the workpiece is turned over without adopting a hoisting mode, the workpiece can be turned over more stably, the manual operation strength and the turnover difficulty can be remarkably reduced, the working efficiency is improved, and the safety accidents caused by manual operation errors can be reduced.

Drawings

In order to more clearly illustrate the embodiments of the application or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic perspective view of a turnover device according to an embodiment in a state;

FIG. 2 is a schematic view of a perspective view of the turnover device shown in FIG. 1 at another angle;

FIG. 3 is a schematic view of a perspective view of the turnover device shown in FIG. 1 at another angle;

FIG. 4 is a schematic perspective view of the turnover device shown in FIG. 1 when not receiving a workpiece;

FIG. 5 is a schematic perspective view of the base shown in FIG. 1;

FIG. 6 is a schematic perspective view of the first tilting mechanism shown in FIG. 1;

fig. 7 is a schematic perspective view of the second tilting mechanism shown in fig. 1.

Detailed Description

In order to enable those skilled in the art to better understand the technical solutions of the present application, the technical solutions of the embodiments of the present application will be clearly and completely described below, and it is obvious that the described embodiments are only some embodiments of the present application, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

It is noted that when an element is referred to as being "fixed," "mounted," or "disposed" on another element, it can be directly on the other element or be indirectly disposed on the other element; when an element is "connected" or "connected" to another element, it can be directly connected or indirectly connected to the other element.

It is to be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are merely for convenience in describing and simplifying the description based on the orientation or positional relationship shown in the drawings, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus are not to be construed as limiting the application.

Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present application, the meaning of "a plurality" or "a number" means two or more, unless specifically defined otherwise.

It should be understood that the structures, proportions, sizes, etc. shown in the drawings are for illustration purposes only and should not be construed as limiting the application to the extent that it can be practiced, since modifications, changes in the proportions, or adjustments of the sizes, which are otherwise, used in the practice of the application, are included in the spirit and scope of the application which is otherwise, without departing from the spirit or scope thereof.

The utility model provides a turnover device which is used for turning a workpiece, wherein the workpiece at least comprises a first surface; the turnover device comprises a first turnover mechanism and a second turnover mechanism which is arranged opposite to the first turnover mechanism; the first turnover mechanism comprises a first frame body, a first turnover frame and a first turnover unit; the first roll-over stand is used for receiving the workpiece with the first face facing downwards, and the first roll-over stand can be arranged on the first stand body in a roll-over manner; the first overturning unit is connected with the first overturning frame and used for driving the first overturning frame to overturn; the second turnover mechanism comprises a second frame body, a second turnover frame and a second turnover unit; the second roll-over stand is used for receiving the workpiece which is turned over by the first roll-over stand, and the second roll-over stand can be turned over and arranged on the second stand body so as to turn over the workpiece, so that the first surface of the workpiece faces upwards; the second overturning unit is connected with the second overturning frame and used for driving the second overturning frame to overturn. The turnover device is provided with the first turnover mechanism and the second turnover mechanism, and the turnover cooperation between the first turnover mechanism and the second turnover mechanism is realized, so that the workpiece is turned over without adopting a hoisting mode, the workpiece can be turned over more stably, the manual operation strength and the turnover difficulty can be remarkably reduced, the working efficiency is improved, and the safety accidents caused by manual operation errors can be reduced.

Please refer to fig. 1 to 7 in combination. The present embodiment provides a turnover device 100, and in a specific embodiment, the turnover device 100 is applied to an ion beam polisher, and the turnover device 100 may be used during loading or the turnover device 100 may be used during discharging.

The turning device 100 is configured to turn the workpiece 200, where the workpiece 200 includes at least a first surface 210. The turning device 100 includes a first turning mechanism 10 and a second turning mechanism 20 disposed opposite to the first turning mechanism 10.

The first turnover mechanism 10 includes a first frame 11, a first turnover frame 12, and a first turnover unit 13, where the first turnover frame 12 is configured to receive the workpiece 200 with the first surface 210 facing downward, and the first turnover frame 12 is configured to be turned over on the first frame 11. The first turnover unit 13 is connected to the first turnover frame 12, and is used for driving the first turnover frame 12 to turn over. Namely, the turnover power source of the first turnover frame 12 is the first turnover unit 13, and the first turnover frame 12 can be driven to turn over relative to the first frame body 11 through the first turnover unit 13. Because the first roll-over stand 12 is used for receiving the workpiece 200, when the workpiece 200 is received on the first roll-over stand 12, the first roll-over stand 12 is turned over again, so that the workpiece 200 can be synchronously driven to finish turning over.

The second turnover mechanism 20 includes a second frame 21, a second turnover frame 22, and a second turnover unit 23, where the second turnover frame 22 is configured to receive the workpiece 200 turned by the first turnover frame 12, and the second turnover frame 22 is configured to be turned over on the second frame 21, so as to turn over the workpiece 200, so that the first surface 210 of the workpiece 200 faces upward. That is, after the first roll-over stand 12 turns the workpiece 200, the second roll-over stand 22 receives the workpiece 200, and then the second roll-over stand 22 turns the workpiece 200, so as to further turn the workpiece 200, and finally the first surface 210 of the workpiece 200 faces upwards, so as to finish turning the workpiece 200 by 180 °. The second flipping unit 23 is connected to the second flipping frame 22, and is configured to drive the second flipping frame 22 to flip. That is, the second turnover frame 22 is turned over by the second turnover unit 23, and the second turnover frame 22 can be turned over relative to the second frame 21 by the second turnover unit 23.

It can be understood that in the prior art, when the workpiece is turned over, the workpiece is turned over by means of the aerial crane of a workshop and a special tool, the turning over mode has great potential safety hazard, the workpiece is easy to damage, and the operation experience of operators is required to be high, especially when the workpiece with a large caliber (such as a workpiece with a caliber of 2000mm and a thickness of 300mm and the weight of the workpiece exceeds 2 t) is turned over, the turning over operation is more difficult to control due to the large size and the large weight of the workpiece.

In the turning device 100 provided in this embodiment, the first turning mechanism 100 turns the workpiece 200 at a certain angle, and then the second turning mechanism 200 receives the workpiece 200 and turns the workpiece 200 further, so that the turning of the workpiece 200 is completed, the workpiece is not required to be turned in a hoisting manner, the turning of the workpiece can be more stable, the manual operation strength and the turning difficulty can be remarkably reduced, the working efficiency is improved, and the safety accidents caused by manual operation errors can be reduced. The turnover device 100 has a simple and compact overall structure, and the turnover process is more stable through the cooperation of the two turnover mechanisms.

Specifically, in one embodiment, the workpiece 200 includes a workpiece body 220 and a carrying frame 230, the workpiece body 220 is located in the carrying frame 230, and the first tilting mechanism 10 and the second tilting mechanism 20 are both used for docking with the carrying frame 230, so that damage to the workpiece body 220 in the transferring process can be avoided.

Preferably, in one embodiment, the flipping unit 100 further comprises a base 30. The first frame 11 and the second frame 21 are both disposed on the base 30, and at least one of the first frame 11 and the second frame 21 is slidably disposed on the base 30. That is, at least one of the first frame 11 and the second frame 21 may slide with respect to the base 30. Through the sliding arrangement of the first frame 11 and/or the second frame 21, the workpiece 200 can be more accurately and stably conveyed when being transferred between the first turnover mechanism 10 and the second turnover mechanism 20, and meanwhile, the workpiece 200 can be more smoothly conveyed from the first turnover mechanism 10 to the second turnover mechanism 20.

Specifically, in one embodiment, the first frame 11 is fixed on the base 30, and the second frame 21 is slidably disposed on the base 30.

Preferably, in one embodiment, the base 30 is provided with a guide rail 31, and at least one of the first frame 11 and the second frame 21 is slidably disposed on the guide rail 31. Specifically, the first frame 11 and/or the second frame 21 slidably mounted on the base 30 are slidably mounted on the guide rail 31 of the base 30, and the sliding direction of the first frame 11 and/or the second frame 21 can be guided more accurately by the guide rail 31.

Specifically, in one embodiment, the plurality of guide rails 31 are provided, and each of the guide rails 31 is disposed at intervals along the width direction of the base 30.

Specifically, in one embodiment, the first frame 11 is fixed on the base 30, and the second frame 21 is slidably disposed on the guide rail 31. More specifically, in one embodiment, a slider is disposed at the bottom of the second frame 21, and the second frame 21 is slidably disposed on the guide rail 31 through the slider.

Preferably, in one embodiment, the guide rail 31 is disposed along the length of the base 30. So that the first frame 11 and/or the second frame 21 can slide in a direction approaching or moving away from the other when sliding on the guide rail 31.

For example, in one embodiment, when the second frame 21 is slidably disposed on the guide rail 31, the second frame 21 may slide along the guide rail 31 toward and away from the first tilting mechanism 10. When the workpiece 200 conveyed by the first tilting mechanism 10 needs to be picked up, the second frame 21 can slide towards the position close to the first tilting mechanism 10, so that the second tilting frame 22 can be ensured to be picked up smoothly to the workpiece 200.

Preferably, in one embodiment, a first support 121 (taking the first roll-over stand 12 in a horizontal state as a reference) is disposed at an end of the first roll-over stand 12 near the second roll-over mechanism 20. The second roll-over stand 22 is provided with a second supporting member 221 (taking the second roll-over stand 22 as a reference in a horizontal state) at one end of the second roll-over stand 22 near the first roll-over mechanism 10, and the second supporting member 221 and the first supporting member 121 are arranged in a staggered manner. During the overturning process of the first overturning frame 12, the workpiece 200 can be well supported by the first supporting member 121, so that the workpiece 200 is prevented from sliding down. Similarly, during the process of taking the workpiece 200 and turning the workpiece by the second roll-over stand 22, the workpiece 200 can be well supported by the second support 221, so that the workpiece 200 is prevented from sliding down. And the second supporting member 221 and the first supporting member 121 are arranged in a staggered manner, so that interference between the second roll-over stand 22 and the first roll-over stand 12 does not occur during the process of taking the workpiece 200 by the second roll-over stand 22, and the workpiece 200 can be more smoothly transferred to the second roll-over stand 22.

Specifically, in one embodiment, a plurality of first supporting members 121 are provided, and the first supporting members 121 are spaced apart from each other along the width direction of the first roll-over stand 12. The second supporting members 221 are provided in plurality, and the second supporting members 221 are spaced apart from each other along the width direction of the second roll-over stand 22. When the second roll-over stand 22 is docked with the first roll-over stand 12, the second support members 221 are inserted into the gaps between two adjacent first support members 121.

Preferably, in one embodiment, the bearing portions of the first bearing member 121 and the second bearing member 221 are provided with anti-slip members, so that the workpiece 200 can be better supported, and accidental sliding of the workpiece 200 is avoided. In particular, in one embodiment, the anti-slip element may employ an anti-slip rubber pad. Of course, in other embodiments, the anti-slip member may be made of any other structural material, which is only required to implement the anti-slip function.

Preferably, in one embodiment, a first bearing seat 111 is disposed at an end of the first frame 11 near the second turning mechanism 20, and an end of the first turning frame 12 is connected to the first bearing seat 111 in a reversible manner through a first pin. The first turnover frame 12 can turn over from the end with the first pin shaft as a turnover point under the driving of the first turnover unit 13, so that the workpiece 200 can be conveyed more smoothly.

Preferably, in one embodiment, a second bearing seat 211 is disposed at an end of the second frame 21 near the first tilting mechanism 10, and an end of the second tilting frame 22 is connected to the second bearing seat 211 in a tiltable manner through a second pin. The second turnover frame 22 can turn over from the end with the second pin shaft as a turnover point, and can more smoothly pick up and convey the workpiece 200, driven by the second turnover unit 23.

Preferably, in one embodiment, the first turning unit 13 is a linear telescopic unit, and two ends of the first turning unit 13 are rotatably connected to the first frame 11 and the first turning frame 12, respectively. That is, in this embodiment, the first roll-over stand 12 is driven to roll over by linear expansion and contraction of the first roll-over unit 13. In one embodiment, the first flipping unit 13 is a cylinder. Of course, in other embodiments, the first flipping unit 13 may also have other structures that can implement linear expansion and contraction, such as a cylinder, an oil cylinder, and the like. The first turning unit 13 is used for driving the first turning frame 12 to turn over in the range of 0-95 degrees. Namely, the telescopic travel of the piston rod of the first turning unit 13 can realize the turning of the first turning frame 12 around the first frame 11 within the range of 0-95 degrees. By tilting the first tilting frame 12 to 95 °, it is better to ensure that the workpiece 200 is fed into the second tilting mechanism 20, avoiding that the workpiece 200 remains on the first tilting frame 12.

Preferably, in one embodiment, the second overturning unit 23 is a linear telescopic unit, and two ends of the second overturning unit 23 are rotatably connected with the second frame 21 and the second overturning frame 22 respectively. That is, in this embodiment, the second roll-over stand 22 is turned over by linear expansion and contraction of the second roll-over unit 23. In one embodiment, the second flipping unit 23 is an electric cylinder. Of course, in other embodiments, the second flipping unit 23 may also have other structures that can implement linear expansion and contraction, such as a cylinder, an oil cylinder, etc. The second flipping unit 23 is configured to drive the second flipping frame 22 to flip over between 0 ° and 90 °. Namely, the telescopic travel of the piston rod of the second overturning unit 23 can realize overturning of the second overturning frame 22 around the second frame body 21 within the range of 0-90 degrees.

In one embodiment, the working procedure of the flipping device 100 is as follows: the workpiece 200 is transported to the first roll-over stand 12, and the second roll-over mechanism 20 is at the right limit. The first overturning unit 13 drives the first overturning frame 12 to start overturning, and overturns the first overturning frame 12 and the workpiece 200 to about 80 degrees; meanwhile, in the second tilting mechanism 20, the second tilting unit 23 tilts the second tilting frame 22 to 90 ° and slowly approaches the first tilting mechanism 10. After the second turning mechanism 20 moves to a certain position, the second turning frame 22 is basically close to the workpiece 200, and then the first turning frame 12 continues to slowly turn to 90 °, at this time, the second turning frame 22 starts to slowly turn down, and at the same time, the first turning frame 12 cooperates with the second turning frame 22 to continue to synchronously turn. When the second roll-over stand 22 is turned from 90 ° to about 85 °, the first roll-over stand 12 is turned synchronously to about 95 ° at this time, and the workpiece 200 on the first roll-over stand 12 falls onto the second roll-over stand 22. Subsequently, the second tilting mechanism 20 moves rightward along the rail 31 while the second tilting frame 22 continues to tilt downward until the second tilting frame 22 is tilted to 0 ° with the mounted work 200, at which time the 180 ° tilting of the work 200 is completed.

The power source for driving the second turnover mechanism 20 to move on the guide rail 31 may be in a structure of a motor matching with a speed reducer and a rack and pinion, and the position states of the components on the turnover device 100 may be provided with photoelectric switches for signal feedback.

While the utility model has been described with respect to the above embodiments, it should be noted that modifications can be made by those skilled in the art without departing from the inventive concept, and these are all within the scope of the utility model.

Claims

1. The turnover device is characterized by being used for turning over a workpiece, wherein the workpiece at least comprises a first surface;

2. The flipping unit of claim 1, further comprising a base;

3. The turnover device of claim 2, wherein a guide rail is provided on the base, and at least one of the first frame body and the second frame body is slidably disposed on the guide rail.

4. A turning device according to claim 3, wherein the guide rail is disposed along the length of the base.

5. The turning device according to any one of claims 1 to 4, wherein a first support is provided at an end of the first turning frame adjacent to the second turning mechanism;

6. The turnover device of claim 5, wherein the bearing parts of the first bearing and the second bearing are respectively provided with an anti-slip piece.

7. The turnover device of claim 5, wherein a first bearing seat is arranged at one end of the first frame body close to the second turnover mechanism, and one end of the first turnover frame is connected to the first bearing seat in a turnover manner through a first pin shaft.

8. The turnover device of claim 5, wherein a second bearing seat is arranged at one end of the second frame body, which is close to the first turnover mechanism, and one end of the second turnover frame is connected to the second bearing seat in a turnover manner through a second pin shaft.

9. The turnover device of claim 5, wherein the first turnover unit is a linear telescopic unit, two ends of the first turnover unit are respectively rotatably connected with the first frame body and the first turnover frame, and the first turnover unit is used for driving the first turnover frame to turn over in a range of 0 ° -95 °.

10. The turnover device of claim 5, wherein the second turnover unit is a linear telescopic unit, two ends of the second turnover unit are respectively and rotatably connected with the second frame body and the second turnover frame, and the second turnover unit is used for driving the second turnover frame to turn over in a range of 0-90 degrees.