Stacking gripper and battery piece feeding system

Abstract

The utility model provides a stacking gripper and a battery piece feeding system, and relates to the technical field of battery piece machining, the stacking gripper provided by the utility model comprises a support, a first clamping mechanism and a second clamping mechanism, the first clamping mechanism and the second clamping mechanism are both connected with the support and are driven independently, and the first clamping mechanism and the second clamping mechanism are connected with the support. The first clamping mechanism is used for clamping the two ends of a battery piece in the first direction and provided with a bearing part used for bearing the bottom end of the battery piece, the second clamping mechanism is provided with a clamping face used for clamping the two end faces of the battery piece in the second direction, and the first direction is perpendicular to the second direction. And the first direction and the second direction are parallel to the plane of the battery piece. According to the stacking gripper, the stability of the battery pieces in the transferring process can be guaranteed, meanwhile, it is guaranteed that the battery pieces can lean down as much as possible when the battery pieces are thoroughly released, large clamping force does not need to be continuously given to the battery pieces in the whole transferring and stacking process, and the phenomena that workpieces fall off and fragments are generated are effectively relieved or even eradicated.

Description

Technical Field

[0001] The utility model relates to the technical field of battery cell processing, in particular to a stacking gripper and a battery cell feeding system. Background Art

[0002] During the production and processing of battery cells, the battery cells need to be transported and stacked. In the existing stacking grippers, multiple grippers are designed around, one end of each gripper is connected to the same driving member, and the other end of each gripper is used to clamp the workpiece. When the driving member is activated, it can drive each gripper to open or close together. In order to allow the workpiece to be as low as possible when released and reduce the impact generated when the workpiece is released, the gripper is usually not designed with a supporting part to support the bottom of the workpiece. This means that when clamping the workpiece, the gripper needs to continuously apply a large clamping force to the side end face of the workpiece, otherwise the workpiece is likely to fall off, and if the clamping force is too large, it is easy to damage the workpiece and produce fragments. Utility Model Content

[0003] The purpose of the utility model is to provide a stacking gripper and a battery cell feeding system, which does not require continuous application of a large clamping force to the battery cells during the entire transfer and stacking process, thereby effectively alleviating or even preventing the phenomenon of workpieces falling and generating fragments.

[0004] In order to achieve the above purpose, the utility model provides the following technical solutions:

[0005] The utility model provides a stacking gripper, comprising a support, a first clamping mechanism and a second clamping mechanism, wherein the first clamping mechanism and the second clamping mechanism are both connected to the support and are independently driven, the first clamping mechanism is used to clamp the two ends of a battery cell along a first direction, the first clamping mechanism has a supporting portion for supporting the bottom end of the battery cell, the second clamping mechanism has a clamping surface, the clamping surface is used to clamp the two end surfaces of the battery cell along a second direction, the first direction is perpendicular to the second direction, and the first direction and the second direction are parallel to the plane where the battery cell is located.

[0006] Further, the first clamping mechanism comprises a first supporting claw group and a second supporting claw group which are arranged opposite to each other along the first direction;

[0007] The first supporting claw group and the second supporting claw group both include a driving member and a supporting claw. The driving member is connected between the support and the supporting claw. The driving member is used to drive the supporting claw to move along the first direction. The supporting claw includes the supporting portion.

[0008] Furthermore, the supporting claw also includes a matching portion for abutting against the top of the battery cell, and the matching portion is arranged opposite to the supporting portion along a third direction, and the third direction is perpendicular to the plane where the battery cell is located.

[0009] Furthermore, the number of the first clamping mechanisms is two, the two first clamping mechanisms are spaced apart along the second direction, and the two first clamping mechanisms are independently driven.

[0010] Further, the second clamping mechanism comprises a first clamping jaw group and a second clamping jaw group which are arranged opposite to each other along the second direction;

[0011] The first jaw group and the second jaw group both include flexible jaws, which are connected to the support and have the clamping surface. The flexible jaws are used to communicate with an external air source and deform under the drive of the external air source, and the deformation has a deformation amount along the second direction.

[0012] Furthermore, the number of the second clamping mechanisms is three, the three second clamping mechanisms are spaced apart along the first direction, and the three second clamping mechanisms are driven synchronously.

[0013] In a second aspect, the utility model also provides a battery cell feeding system, including the stacking gripper described in the above solution.

[0014] Furthermore, it also includes a deviation correction and transportation mechanism, which is located on the side of the battery cell stacking station. The deviation correction and transportation mechanism is used to correct the position of the battery cell after the stacking gripper is released and push the stacked battery cells to the next station.

[0015] Furthermore, the deviation-correcting transport mechanism includes a first telescopic member, a second telescopic member, a first push plate, and a second push plate;

[0016] The first telescopic member is connected to the first push plate, the second telescopic member is connected to the second push plate, and the second push plate is located on a side of the first push plate facing the battery cell stacking station;

[0017] The first telescopic member is used to drive the first push plate to push the second push plate to correct the position of the battery cell released by the stacking gripper, and the second telescopic member is used to drive the second push plate to push the stacked battery cells to the next station.

[0018] Furthermore, the first telescopic member is located above the second telescopic member, and a notch for the second telescopic member to pass through is provided at the bottom end of the first push plate.

[0019] The stacking gripper and battery cell feeding system provided by the utility model can produce the following beneficial effects:

[0020] When the stacking gripper is working, the first clamping mechanism clamps the two ends of the battery cell along the first direction, and the supporting part thereon can support the bottom end of the battery cell. The second clamping mechanism clamps the two end surfaces of the battery cell along the second direction. The first clamping mechanism and the second clamping mechanism cooperate to clamp the battery cell. When the battery cell needs to be put down, the first clamping mechanism opens and releases the battery cell first. Under the clamping of the second clamping mechanism, the battery cell continues to approach the topmost battery cell. Finally, the second clamping mechanism releases the battery cell to achieve stacking of the battery cells.

[0021] Compared with the prior art, the stacking gripper provided in the first aspect of the utility model not only has a first clamping mechanism capable of supporting the bottom of the battery cell, but also has a second clamping mechanism that only clamps the end face of the battery cell, and the first clamping mechanism and the second clamping mechanism are driven independently. While ensuring the stability of the battery cell during the transportation process, it is ensured that the battery cell can be as low as possible when the battery cell is completely released. During the entire transportation and stacking process, it is not necessary to continuously apply a large clamping force to the battery cell, which effectively alleviates or even eliminates the phenomenon of workpiece falling and the generation of fragments.

[0022] The battery cell loading system provided in the second aspect of the utility model has the stacking gripper provided in the first aspect of the utility model, and thus has all the beneficial effects of the stacking gripper provided in the first aspect of the utility model. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the specific implementation methods of the utility model or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 A front view of a stacking gripper provided in an embodiment of the utility model;

[0025] Figure 2 A side view of a stacking gripper provided by an embodiment of the utility model;

[0026] Figure 3 A front view of a deviation-correcting and transporting mechanism provided in an embodiment of the utility model;

[0027] Figure 4 A schematic diagram of the three-dimensional structure of a first push plate provided in an embodiment of the utility model.

[0028] Icons: 1-support; 2-first clamping mechanism; 21-first supporting claw group; 211-driving member; 212-supporting claw; 2121-supporting part; 2122-matching part; 22-second supporting claw group; 3-second clamping mechanism; 31-first clamping claw group; 311-flexible clamping claw; 3111-clamping surface; 32-second clamping claw group; 4-correcting and transporting mechanism; 41-first telescopic member; 42-second telescopic member; 43-first push plate; 431-notch; 44-second push plate. DETAILED DESCRIPTION

[0029] The technical solution of the utility model will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0030] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0031] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0033] The first aspect of the present invention provides a stacking gripper. Figure 1 and Figure 2As shown, it includes a support 1, a first clamping mechanism 2 and a second clamping mechanism 3. The first clamping mechanism 2 and the second clamping mechanism 3 are both connected to the support 1 and are independently driven. The first clamping mechanism 2 is used to clamp the two ends of the battery cell along a first direction. The first clamping mechanism 2 has a supporting portion 2121 for supporting the bottom end of the battery cell. The second clamping mechanism 3 has a clamping surface 3111. The clamping surface 3111 is used to clamp the two end surfaces of the battery cell along a second direction. The first direction is perpendicular to the second direction, and the first direction and the second direction are parallel to the plane where the battery cell is located.

[0034] like Figure 1 and Figure 2 As shown, when the above-mentioned stacking gripper is working, the first clamping mechanism 2 clamps the two ends of the battery cell along the first direction, and the supporting portion 2121 thereon can support the bottom end of the battery cell to prevent the battery cell from falling during transportation. At the same time, the second clamping mechanism 3 clamps the two end surfaces of the battery cell along the second direction, and the first clamping mechanism 2 and the second clamping mechanism 3 cooperate to realize the clamping of the battery cell.

[0035] When the clamped battery cell needs to be placed above other stacked battery cells, the first clamping mechanism 2 opens first to release the battery cell, and under the clamping of the second clamping mechanism 3, the battery cell clamped by the second clamping mechanism 3 continues to approach the topmost battery cell, and finally the second clamping mechanism 3 releases the battery cell to achieve stacking of the battery cells.

[0036] In the above process, the first clamping mechanism 2 can support the bottom of the battery cell to prevent the battery cell from falling during transportation. The second clamping mechanism 3 does not need to have a large holding force. After the battery cell is initially in place, the first clamping mechanism 2 opens, and only the end face of the battery cell is clamped by the second clamping mechanism 3, so that the battery cell is as close as possible to the required stacking position, and finally the battery cell is released. In summary, the stacking gripper provided in the above embodiment does not need to continuously apply a large clamping force to the battery cell during the entire transportation and stacking process, which effectively alleviates or even eliminates the phenomenon of workpiece falling and the generation of fragments.

[0037] In an optional embodiment, the first clamping mechanism 2 includes a first supporting claw group 21 and a second supporting claw group 22 arranged opposite to each other along a first direction, wherein the first supporting claw group 21 and the second supporting claw group 22 both include a driving member 211 and a supporting claw 212. The first supporting claw group 21 is taken as an example for specific description:

[0038] like Figure 1 As shown, the driving member 211 is connected between the support 1 and the supporting claw 212 . The driving member 211 is used to drive the supporting claw 212 to move along the first direction to grasp and release the battery cell. The supporting claw 212 includes a supporting portion 2121 .

[0039] When it is necessary to grab the battery cell, the driving member 211 drives the supporting claw 212 to approach the battery cell along the first direction, and the supporting portion 2121 extends into the bottom of the battery cell to support the battery cell. When it is necessary to release the battery cell, the driving member 211 drives the supporting claw 212 to move away from the battery cell along the first direction.

[0040] The first clamping mechanism 2 has a simple structure, and the supporting claws 212 support and release the battery cell through the driving of the driving member 211 , without the need to set up other transmission structures, and thus the cost is lower.

[0041] It should be noted that any structure that can drive the supporting claw 212 to move along the first direction can be the driving member 211 mentioned in the above embodiment. For example, the driving member 211 can be a pneumatic cylinder, a hydraulic cylinder, a linear motor, etc.

[0042] In a preferred embodiment, the driving member 211 is a pneumatic cylinder, a cylinder body of which is fixed on the support 1 , and a piston rod of which is connected to the supporting claw 212 .

[0043] In an optional embodiment, if Figure 1 As shown, in order to enable the supporting claw 212 to clamp the battery cell, the supporting claw 212 also includes a matching portion 2122 for abutting against the top of the battery cell. The matching portion 2122 is arranged opposite to the supporting portion 2121 along a third direction, and the third direction is perpendicular to the plane where the battery cell is located.

[0044] When in use, the matching portion 2122 and the supporting portion 2121 can cooperate with each other to clamp the upper and lower ends of the battery cell, thereby achieving the clamping effect on the battery cell.

[0045] It can be understood that for the convenience of description, the thickness of the battery cell is regarded as infinitely small in the plane where the battery cell is located. Of course, when the top and bottom surfaces of the battery cell are parallel to each other and are both planes, it can also be understood that the third direction is perpendicular to the top or bottom surface of the battery cell.

[0046] In a preferred embodiment, the matching portion 2122 and the supporting portion 2121 are both made of elastic materials, such as rubber, silicone, etc., so as not to cause damage to the battery cell during the clamping process.

[0047] In an optional embodiment, the first clamping mechanism 2 may be configured as a plurality of first clamping mechanisms 2, and the plurality of first clamping mechanisms 2 are distributed at intervals along the second direction.

[0048] In a preferred embodiment, Figure 2 As shown, there are two first clamping mechanisms 2, the two first clamping mechanisms 2 are spaced apart along the second direction, and the two first clamping mechanisms 2 are driven independently.

[0049] In the above embodiment, the first clamping mechanism 2 is configured as two that can generate four supporting points or supporting surfaces on the bottom surface of the battery cell, thereby being able to support the battery cell more stably without significantly increasing the cost.

[0050] The two first clamping mechanisms 2 are driven independently so that the two first clamping mechanisms 2 do not release the battery cells at the same time. The following is a detailed description of a complete transport stacking process:

[0051] First, a sensor is used to detect whether the open position of the stacking gripper is at the origin; then the stacking gripper directly clamps the first stack of battery cells and places it on the carrying tray; then the stacking gripper takes the next stack of battery cells from the assembly line again and drives the battery cells to be initially in place, then releases one of the first clamping mechanisms 2, and then the robot arm drives the support 1 to be tilted so that one end of the battery cell along the second direction close to the released first clamping mechanism 2 contacts the corresponding end of the first stack of battery cells; after the root of the battery cell contacts, release the other first clamping mechanism 2, and then the robot drives the support 1 to rotate and lower it, with the rotation axis parallel to the first direction, until the other end of the placed battery cell along the second direction is 1 mm away from the first stack of battery cells, the second clamping mechanism 3 is opened, and the battery cells are lowered and stacked in a simulated manner; the remaining stacks of battery cells are arranged in the same way, and 3 stacks of battery cells are sorted out.

[0052] The above-mentioned implementation method helps to realize the gradual release of the battery cells, simulating the release method of human hands, and the whole process is gentler.

[0053] In an optional embodiment, if Figure 2 As shown, the second clamping mechanism 3 includes a first clamping jaw group 31 and a second clamping jaw group 32 which are arranged opposite to each other along the second direction, wherein the first clamping jaw group 31 and the second clamping jaw group 32 both include a flexible clamping jaw 311. The first clamping jaw group 31 is taken as an example for specific description:

[0054] like Figure 2 As shown, the flexible clamping jaw 311 is connected to the support 1 and has a clamping surface 3111. The flexible clamping jaw 311 is used to communicate with an external air source and deform under the drive of the external air source. The deformation has a deformation amount along the second direction.

[0055] When it is necessary to grab a battery cell, the external air source enters the flexible clamp 311, and the flexible clamp 311 is in a positive pressure state, causing the flexible clamp 311 to deform and clamp the end face of the battery cell. When it is necessary to release the battery cell, the external air source does not inflate the flexible clamp 311 or extracts the air in the flexible clamp 311, causing the flexible clamp 311 to deform in the opposite direction and release the end face of the battery cell.

[0056] The first clamping mechanism 2 has a simple structure, and the flexible clamping claws 311 clamp and release the battery sheet through pneumatic drive, without the need to set up other transmission structures, and the cost is lower.

[0057] The material of the flexible clamping claw 311 may be, but is not limited to, rubber, silicone, etc.

[0058] In an optional embodiment, the second clamping mechanism 3 may be configured as a plurality of second clamping mechanisms 3 , and the plurality of second clamping mechanisms 3 are distributed at intervals along the first direction.

[0059] In a preferred embodiment, Figure 1 As shown, the second clamping mechanisms 3 are configured in three, the three second clamping mechanisms 3 are distributed at intervals along the first direction, and the three second clamping mechanisms 3 are driven synchronously.

[0060] The above arrangement can increase the contact area between the second clamping mechanism 3 and the battery cell, thereby ensuring that after the first clamping mechanism 2 releases the battery cell, the second clamping mechanism 3 can still stably clamp the battery cell.

[0061] The embodiment of the second aspect of the present invention provides a battery cell loading system. The battery cell loading system provided by the embodiment of the second aspect of the present invention includes the above-mentioned stacking gripper.

[0062] The battery cell loading system provided in the second aspect of the utility model has the stacking gripper provided in the embodiment of the first aspect of the utility model, and thus has all the beneficial effects of the stacking gripper provided in the embodiment of the first aspect of the utility model.

[0063] In an optional embodiment, if Figure 3 As shown, the battery cell loading system also includes a deviation correction and transfer mechanism 4, which is located on the side of the battery cell stacking station. The deviation correction and transfer mechanism 4 is used to correct the position of the battery cell after the stacking gripper is released and push the stacked battery cells to the next station.

[0064] When the stacking gripper completely releases the battery cell, there will be a certain horizontal position deviation between the released battery cell and the battery cell below. The setting of the deviation correction and transfer mechanism 4 can correct the position of the released battery cell as much as possible, so that the battery cells can be stacked more orderly.

[0065] In an optional embodiment, if Figure 3 As shown, the deviation-correcting transport mechanism 4 includes a first telescopic member 41, a second telescopic member 42, a first push plate 43 and a second push plate 44, wherein:

[0066] The first telescopic member 41 is connected to the first push plate 43, and the first telescopic member 41 drives the first push plate 43 to perform telescopic movement. The second telescopic member 42 is connected to the second push plate 44, and the second telescopic member 42 drives the second push plate 44 to perform telescopic movement. The second push plate 44 is located on the side of the first push plate 43 facing the battery cell stacking station.

[0067] During use, after the last stack of battery cells is released, the first telescopic member 41 first drives the first push plate 43 to push the second push plate 44 to the left, so that the second push plate 44 corrects the position of the last stack of battery cells released by the stacking gripper, and then the second telescopic member 42 drives the second push plate 44 to push the stacked battery cells to the next workstation.

[0068] It should be noted that after the battery cells other than the last stack are released, the first telescopic member 41 drives the first push plate 43 to push the second push plate 44 to the left, so that the second push plate 44 corrects the position of the stack of battery cells released by the stacking gripper, and then the first telescopic member 41 and the second telescopic member 42 synchronously drive the first push plate 43 and the second push plate 44 to retreat.

[0069] The above arrangement can ensure the stacking accuracy of the battery cells and can also realize the centralized transfer of the stacked battery cells to the next workstation.

[0070] It should be noted that any structure that can drive the first push plate 43 to perform telescopic movement can be the first telescopic member 41 mentioned in the above embodiment, and any structure that can drive the second push plate 44 to perform telescopic movement can be the second telescopic member 42 mentioned in the above embodiment. For example, the first telescopic member 41 and the second telescopic member 42 can be pneumatic cylinders, hydraulic cylinders, linear motors, etc.

[0071] In an optional embodiment, if Figure 4 As shown, the first telescopic member 41 is located above the second telescopic member 42 , and a notch 431 for the second telescopic member 42 to pass through is provided at the bottom end of the first push plate 43 .

[0072] The above arrangement can make the first telescopic member 41 and the second telescopic member 42 more compact in the height direction. Specifically, the above notch 431 can be used for the power output end of the second telescopic member 42 to pass through.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model, rather than to limit it. Although the utility model has been described in detail with reference to the aforementioned embodiments, ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solution of the embodiments of the utility model.

Claims

1. A stacking gripper, characterized in that: The invention comprises a support (1), a first clamping mechanism (2) and a second clamping mechanism (3), wherein the first clamping mechanism (2) and the second clamping mechanism (3) are both connected to the support (1) and are independently driven, the first clamping mechanism (2) is used to clamp the two ends of a battery cell along a first direction, the first clamping mechanism (2) has a supporting portion (2121) for supporting the bottom end of the battery cell, the second clamping mechanism (3) has a clamping surface (3111), the clamping surface (3111) is used to clamp the two end surfaces of the battery cell along a second direction, the first direction is perpendicular to the second direction, and the first direction and the second direction are parallel to the plane where the battery cell is located.

2. The stacking gripper according to claim 1, characterized in that: The first clamping mechanism (2) comprises a first supporting claw group (21) and a second supporting claw group (22) which are arranged opposite to each other along the first direction; The first supporting claw group (21) and the second supporting claw group (22) both comprise a driving member (211) and a supporting claw (212); the driving member (211) is connected between the support (1) and the supporting claw (212); the driving member (211) is used to drive the supporting claw (212) to move along the first direction; the supporting claw (212) comprises the supporting portion (2121).

3. The stacking gripper according to claim 2, characterized in that: The supporting claw (212) also includes a matching portion (2122) for abutting against the top of the battery sheet, and the matching portion (2122) is arranged opposite to the supporting portion (2121) along a third direction, and the third direction is perpendicular to the plane where the battery sheet is located.

4. The stacking gripper according to claim 1, characterized in that: The first clamping mechanisms (2) are configured in two, the two first clamping mechanisms (2) are spaced apart along the second direction, and the two first clamping mechanisms (2) are independently driven.

5. The stacking gripper according to claim 1, characterized in that: The second clamping mechanism (3) comprises a first clamping jaw group (31) and a second clamping jaw group (32) which are arranged opposite to each other along the second direction; The first clamping jaw group (31) and the second clamping jaw group (32) both comprise a flexible clamping jaw (311), wherein the flexible clamping jaw (311) is connected to the support (1) and has a clamping surface (3111), and the flexible clamping jaw (311) is used to communicate with an external air source and deform under the drive of the external air source, and the deformation has a deformation amount along the second direction.

6. The stacking gripper according to claim 1, characterized in that: The second clamping mechanisms (3) are configured in number of three, the three second clamping mechanisms (3) are distributed at intervals along the first direction, and the three second clamping mechanisms (3) are driven synchronously.

7. A battery cell feeding system, characterized in that: It comprises a stacking gripper as claimed in any one of claims 1 to 6.

8. The battery cell feeding system according to claim 7, characterized in that: It also includes a deviation correction and transportation mechanism (4), which is located on the side of the battery cell stacking station, and is used to correct the position of the battery cell after the stacking gripper is released and push the stacked battery cells to the next station.

9. The battery cell feeding system according to claim 8, characterized in that: The deviation-correcting transport mechanism (4) comprises a first telescopic member (41), a second telescopic member (42), a first push plate (43) and a second push plate (44); The first telescopic member (41) is connected to the first push plate (43), the second telescopic member (42) is connected to the second push plate (44), and the second push plate (44) is located on a side of the first push plate (43) facing the battery cell stacking station; The first telescopic member (41) is used to drive the first push plate (43) to push the second push plate (44) to correct the position of the battery cell released by the stacking gripper, and the second telescopic member (42) is used to drive the second push plate (44) to push the stacked battery cells to the next workstation.

10. The battery cell feeding system according to claim 9, characterized in that: The first telescopic member (41) is located above the second telescopic member (42), and a notch (431) for the second telescopic member (42) to pass through is provided at the bottom end of the first push plate (43).

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