Fixtures for CNC machining

Abstract

The present invention discloses a clamping fixture for CNC machining, including a base plate, a carrier plate and a cover plate, wherein the carrier plate is fixedly mounted on the upper surface of the base plate, the upper surface of the carrier plate is in contact with and connected to the lower surface of a workpiece to be machined, the cover plate is arranged above the workpiece, and the lower surface of the cover plate is pressed and connected to the workpiece, a plurality of pressure head mechanisms are installed at the edges of the base plate, and the pressure head mechanisms are pressed and connected to the top surface of the cover plate, a fixed block is connected to the upper end of the push-pull rod, a strip through hole is opened on the fixed block, the third rotating shaft is embedded in the strip through hole, and the two ends of the third rotating shaft extend from the strip through hole respectively, and the first strip portions of the two connecting rotating plates are respectively rotatably connected to the two ends of the third rotating shaft. The present invention can clamp a cover plate at a distance with stable and constant pressure, thereby reducing the size of the cover plate, providing more space for the machining of the workpiece, and can perform multiple processes on the workpiece at one time, thereby improving the machining effect and efficiency of the workpiece.

Description

Technical Field

[0001] The invention relates to a clamping fixture for CNC processing, and belongs to the field of mechanical processing. Background Art

[0002] Computerized Numerical Control (CNC) is an automated machine tool equipped with a program control system that can logically process control codes or other symbolic instructions and decode them to enable the machine tool to move and process parts. Therefore, compared with traditional manufacturing, CNC has higher processing accuracy and automation, saves a lot of manual operation links, improves productivity, and is widely used in the modernization process of manufacturing.

[0003] Fixtures are very common parts in the industrial manufacturing industry that assist in production and processing. They fix the workpiece to be processed to facilitate transportation or related processing. Especially when performing CNC processing (CNC, Computerized Numerical Control Machine, computer numerical control machine tools, referred to as CNC machine tools), it is often necessary to clamp the workpiece to be processed with fixtures. Summary of the invention

[0004] The purpose of the present invention is to provide a clamping fixture for CNC machining, which can clamp a cover plate at a distance with stable and constant pressure, thereby reducing the size of the cover plate, providing more space for the machining of the workpiece, and can perform multiple processes on the workpiece at one time, thereby improving the machining effect and efficiency of the workpiece.

[0005] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a clamping fixture for CNC machining, comprising a base plate, a carrier plate and a cover plate, wherein the carrier plate is fixedly mounted on the upper surface of the base plate, the upper surface of the carrier plate is in contact with and connected to the lower surface of a workpiece to be machined, the cover plate is arranged above the workpiece, and the lower surface of the cover plate is press-fitted with the workpiece, and a plurality of pressing head mechanisms are installed at the edges of the base plate, and the pressing head mechanisms are press-fitted with the top surface of the cover plate;

[0006] The pressure head mechanism further includes a fixed plate, a fixed seat, a push-pull rod, a tilting plate, a pressure head and two connecting rotating plates symmetrically arranged on both sides of the fixed seat, one end of the fixed plate is mounted on the base plate, and a through hole for the push-pull rod to pass through is opened on the other end of the fixed plate away from the base plate, the upper end of the push-pull rod is rotatably connected to the connecting rotating plate, and the lower end of the push-pull rod passes through the fixed plate and is connected to a driving assembly;

[0007] The base portion at the lower end of the fixed seat is fixedly installed on the upper surface of the fixed plate, and the base portion is connected to a connecting portion inclined toward one side of the push-pull rod, and a first rotating shaft penetrating the connecting portion is installed at the lower end of the connecting portion, and a second rotating shaft penetrating the connecting portion is installed at the upper end of the connecting portion, and the two ends of the first rotating shaft extend from the two sides of the connecting portion respectively, and are respectively connected to the connecting rotating plate, and the second rotating shaft is rotatably connected to the end of the tilting plate;

[0008] The connecting rotating plate comprises a first strip portion and a second strip portion, one end of each of the first strip portion and the second strip portion is connected, so that an acute angle is formed between the first strip portion and the second strip portion, and a corner portion is formed at the connection between the first strip portion and the second strip portion, and the corner portions of the two connecting rotating plates are respectively rotatably connected to the two ends of the first rotating shaft;

[0009] One end of the two first strip portions opposite to the corner portion is rotatably connected to the upper end of the push-pull rod through a third rotating shaft, and a fourth rotating shaft is connected between one end of the two second strip portions opposite to the corner portion, and the fourth rotating shaft is rotatably connected to the rear end of the pressure head, and the rear end of the pressure head has a downwardly extending adapter, and the adapter is rotatably connected to the middle and rear part of the tilting plate through a fifth rotating shaft, and the front end lower surface of the pressure head can be pressed and contacted with the upper surface of the tilting plate;

[0010] The upper end of the push-pull rod is connected to a fixed block, which has a strip through hole. The third rotating shaft is embedded in the strip through hole, and the two ends of the third rotating shaft extend out from the strip through hole respectively. The first strip parts of the two connecting rotating plates are respectively rotatably connected to the two ends of the third rotating shaft.

[0011] The further improved scheme in the above technical scheme is as follows:

[0012] 1. In the above solution, the driving component is a cylinder.

[0013] 2. In the above scheme, limit cards are installed at both ends of the first rotating shaft, the third rotating shaft and the fourth rotating shaft. The limit cards are embedded in the grooves at both ends of the first rotating shaft, the third rotating shaft or the fourth rotating shaft, and the inner surface of the limit card is in contact with the outer surface of the connecting rotating plate.

[0014] 3. In the above scheme, the number of the pressing head mechanisms is 8, and they are installed in groups of two at the four edges of the substrate respectively.

[0015] 4. In the above solution, a handle is respectively installed on the two opposite side surfaces of the cover.

[0016] 5. In the above solution, the handle is installed on the side surface of the short side of the cover.

[0017] 6. In the above solution, the cover plate is an iron cover plate or a plastic cover plate.

[0018] 7. In the above scheme, a bottom plate is arranged directly below the base plate, and the bottom plate is connected to the cover plate through a plurality of support columns.

[0019] 8. In the above solution, the base plate and the cover plate are connected by four support columns, and the four support columns are respectively located at the four corners of the base plate.

[0020] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0021] The clamping fixture for CNC processing of the present invention has an ingenious design of the pressure head mechanism structure. Through the linkage of multiple components, the tilting plate and the pressure head provide double pressure, which not only enhances the pressure and stability of the tilting plate on the cover plate, but also avoids shaking, knife vibration, knife marks and the like due to insufficient clamping force when processing the workpiece, thereby improving the stability and quality of workpiece processing; it can also increase the pressure of the tilting plate when the driving force provided by the driving component is the same. Further, when the length of the tilting plate is relatively long, the second pressure is provided in the middle of the tilting plate by the pressure head, so that the tilting plate can clamp the cover plate at a distance with a stable and constant pressure, thereby providing more space for the processing of the workpiece, and can process the workpiece in multiple processes at one time, thereby improving the processing effect and efficiency of the workpiece; in addition, through the coordinated arrangement of the push rod and each structure, the tilting plate can be opened to a maximum angle greater than 90°, which is convenient for clamping the workpiece without damaging the clamped object, thereby further improving the stability and quality of workpiece processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Attached Figure 1 It is a structural front view of the clamping fixture used for CNC machining of the present invention;

[0023] Attached Figure 2 It is a front view of the structure of the pressing head mechanism of the clamping fixture for CNC machining of the present invention;

[0024] Attached Figure 3 The schematic diagram of the pressure head mechanism structure of the clamping fixture for CNC machining of the present invention is as follows Figure 1 ;

[0025] Attached Figure 4 The schematic diagram of the pressure head mechanism structure of the clamping fixture for CNC machining of the present invention is as follows Figure 2 ;

[0026] Attached Figure 5 For attachment Figure 4 A magnified view of the local structure;

[0027] Attached Figure 6This is a schematic diagram of the structure of the connecting rotating plate of the clamping fixture for CNC machining of the present invention;

[0028] Attached Figure 7 It is a schematic diagram of the structure of the fixing seat of the clamping fixture used for CNC machining of the present invention;

[0029] Attached Figure 8 A schematic structural diagram of a clamping fixture for CNC machining according to the present invention.

[0030] In the above drawings: 1. substrate; 2. carrier plate; 3. workpiece; 5. cover plate; 6. pressure head mechanism; 601. fixed plate; 602. fixed seat; 6021. base part; 6022. connecting part; 603. push-pull rod; 604. tilting plate; 605. pressure head; 6051. adapter part; 606. through hole; 607. driving assembly; 608. first rotating shaft; 609. second rotating shaft; 610. third rotating shaft; 611. fourth rotating shaft; 612. fifth rotating shaft; 613. fixed block; 6131. ​​strip through hole; 614. connecting rotating plate; 6141. first strip part; 6142. second strip part; 6143. corner part; 7. handle; 8. bottom plate; 9. support column. DETAILED DESCRIPTION

[0031] In the description of this patent, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply 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 a limitation on the present invention; the terms "first", "second", and "third" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance; in addition, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" 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 an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in this patent can be understood according to specific circumstances.

[0032] Embodiment 1: A clamping fixture for CNC machining, comprising a base plate 1, a carrier plate 2 and a cover plate 5, wherein the carrier plate 2 is fixedly mounted on the upper surface of the base plate 1, the upper surface of the carrier plate 2 is in contact with and connected to the lower surface of a workpiece 3 to be machined, the cover plate 5 is disposed above the workpiece 3, and the lower surface of the cover plate 5 is pressed and connected to the workpiece 3, and a plurality of pressing head mechanisms 6 are mounted on the edges of the base plate 1, and the pressing head mechanisms 6 are pressed and connected to the top surface of the cover plate 5;

[0033] The pressure head mechanism 6 further includes a fixed plate 601, a fixed seat 602, a push-pull rod 603, a tilting plate 604, a pressure head 605 and two connecting rotating plates 614 symmetrically arranged on both sides of the fixed seat 602. One end of the fixed plate 601 is mounted on the base plate 1. The other end of the fixed plate 601 away from the base plate 1 is provided with a through hole 606 for the push-pull rod 603 to pass through. The upper end of the push-pull rod 603 is rotatably connected to the connecting rotating plate 614. The lower end of the push-pull rod 603 passes through the fixed plate 601 and is connected to a driving component 607.

[0034] The base portion 6021 at the lower end of the fixed seat 602 is fixedly installed on the upper surface of the fixed plate 601, and the base portion 6021 is connected to a connecting portion 6022 inclined to one side of the push-pull rod 603, and a first rotating shaft 608 penetrating the connecting portion 6022 is installed at the lower end of the connecting portion 6022, and a second rotating shaft 609 penetrating the connecting portion 6022 is installed at the upper end of the connecting portion 6022, and two ends of the first rotating shaft 608 extend from both sides of the connecting portion 6022 respectively, and are respectively connected to the connecting rotating plate 614, and the second rotating shaft 609 is rotatably connected to the end of the tilting plate 604;

[0035] The connecting rotating plate 614 includes a first strip portion 6141 and a second strip portion 6142, and one end of each of the first strip portion 6141 and the second strip portion 6142 is connected, so that an acute angle is formed between the first strip portion 6141 and the second strip portion 6142, and a corner portion 6143 is formed at the connection between the first strip portion 6141 and the second strip portion 6142, and the corner portions 6143 of the two connecting rotating plates 614 are respectively rotatably connected to the two ends of the first rotating shaft 608;

[0036] One end of the two first strip portions 6141 opposite to the corner portion 6143 is rotatably connected to the upper end of the push-pull rod 603 via a third rotating shaft 610, and one end of the two second strip portions 6142 opposite to the corner portion 6143 is connected with a fourth rotating shaft 611, and the fourth rotating shaft 611 is rotatably connected to the rear end of the pressing head 605, and the rear end of the pressing head 605 has a downwardly extending adapter portion 6051, and the adapter portion 6051 is rotatably connected to the middle and rear part of the tilting plate 604 via a fifth rotating shaft 612, and the lower surface of the front end of the pressing head 605 can be pressed and contacted with the upper surface of the tilting plate 604;

[0037] The upper end of the push-pull rod 603 is connected to a fixed block 613, and a strip through hole 6131 is opened on the fixed block 613. The third rotating shaft 610 is embedded in the strip through hole 6131, and the two ends of the third rotating shaft 610 extend out from the strip through hole 6131 respectively. The first strip portions 6141 of the two connecting rotating plates 614 are respectively rotatably connected to the two ends of the third rotating shaft 610.

[0038] The cover plate 5 is an iron cover plate; the driving assembly 607 is a cylinder; both ends of the first rotating shaft 608, the third rotating shaft 610 and the fourth rotating shaft 611 are equipped with limit cards 615, which are embedded in the grooves at both ends of the first rotating shaft 608, the third rotating shaft 610 or the fourth rotating shaft 611, and the inner surface of the limit card 615 is in contact with the outer surface of the connecting rotating plate 614;

[0039] The upper end of the connection portion 6022 of the fixing seat 602 has a groove for the rear end of the tilting plate 604 to be embedded in. The rear end of the tilting plate 604 is embedded in the groove on the connection portion 6022 and is rotatably connected to the fixing seat 602 via the second rotating shaft 609 .

[0040] Embodiment 2: A clamping fixture for CNC machining, comprising a base plate 1, a carrier plate 2 and a cover plate 5, wherein the carrier plate 2 is fixedly mounted on the upper surface of the base plate 1, the upper surface of the carrier plate 2 is in contact with and connected to the lower surface of a workpiece 3 to be machined, the cover plate 5 is disposed above the workpiece 3, and the lower surface of the cover plate 5 is press-fitted with the workpiece 3, and a plurality of pressing head mechanisms 6 are mounted on the edges of the base plate 1, and the pressing head mechanisms 6 are press-fitted with the top surface of the cover plate 5;

[0041] The pressure head mechanism 6 further includes a fixed plate 601, a fixed seat 602, a push-pull rod 603, a tilting plate 604, a pressure head 605 and two connecting rotating plates 614 symmetrically arranged on both sides of the fixed seat 602. One end of the fixed plate 601 is mounted on the base plate 1. The other end of the fixed plate 601 away from the base plate 1 is provided with a through hole 606 for the push-pull rod 603 to pass through. The upper end of the push-pull rod 603 is rotatably connected to the connecting rotating plate 614. The lower end of the push-pull rod 603 passes through the fixed plate 601 and is connected to a driving component 607.

[0042] The base portion 6021 at the lower end of the fixed seat 602 is fixedly installed on the upper surface of the fixed plate 601, and the base portion 6021 is connected to a connecting portion 6022 inclined to one side of the push-pull rod 603, and a first rotating shaft 608 penetrating the connecting portion 6022 is installed at the lower end of the connecting portion 6022, and a second rotating shaft 609 penetrating the connecting portion 6022 is installed at the upper end of the connecting portion 6022, and two ends of the first rotating shaft 608 extend from both sides of the connecting portion 6022 respectively, and are respectively connected to the connecting rotating plate 614, and the second rotating shaft 609 is rotatably connected to the end of the tilting plate 604;

[0043] The connecting rotating plate 614 includes a first strip portion 6141 and a second strip portion 6142, and one end of each of the first strip portion 6141 and the second strip portion 6142 is connected, so that an acute angle is formed between the first strip portion 6141 and the second strip portion 6142, and a corner portion 6143 is formed at the connection between the first strip portion 6141 and the second strip portion 6142, and the corner portions 6143 of the two connecting rotating plates 614 are respectively rotatably connected to the two ends of the first rotating shaft 608;

[0044] One end of the two first strip portions 6141 opposite to the corner portion 6143 is rotatably connected to the upper end of the push-pull rod 603 via a third rotating shaft 610, and one end of the two second strip portions 6142 opposite to the corner portion 6143 is connected with a fourth rotating shaft 611, and the fourth rotating shaft 611 is rotatably connected to the rear end of the pressing head 605, and the rear end of the pressing head 605 has a downwardly extending adapter portion 6051, and the adapter portion 6051 is rotatably connected to the middle and rear part of the tilting plate 604 via a fifth rotating shaft 612, and the lower surface of the front end of the pressing head 605 can be pressed and contacted with the upper surface of the tilting plate 604;

[0045] The upper end of the push-pull rod 603 is connected to a fixed block 613, and a strip through hole 6131 is opened on the fixed block 613. The third rotating shaft 610 is embedded in the strip through hole 6131, and the two ends of the third rotating shaft 610 extend out from the strip through hole 6131 respectively. The first strip portions 6141 of the two connecting rotating plates 614 are respectively rotatably connected to the two ends of the third rotating shaft 610.

[0046] The number of the above-mentioned pressing head mechanisms 6 is 8, and two are installed in a group at the four edges of the base plate 1; a handle 7 is installed on the two opposite side surfaces of the above-mentioned cover plate 5 respectively; the above-mentioned handle 7 is installed on the side surface of the short side of the cover plate 5;

[0047] The cover plate 5 is a plastic cover plate; a bottom plate 8 is disposed directly below the substrate 1, and the bottom plate 8 is connected to the cover plate 5 via four support columns 9, and the four support columns 9 are respectively located at the four corners of the bottom plate 8;

[0048] The adapter part 6051 at the rear end of the pressure head 605 is two symmetrically arranged adapter plates. The tilting pressure plate 604 is embedded between the two adapter plates and is rotatably connected to the two adapter plates via the fifth rotating shaft 612 .

[0049] When the above-mentioned clamping fixture for CNC processing is used, the structure design of the pressure head mechanism is ingenious. Through the linkage of multiple components, the tilting plate and the pressure head provide double pressure, which not only enhances the strength and stability of the tilting plate pressing the cover plate, but also avoids shaking, vibration, knife marks and the like due to insufficient clamping force when processing the workpiece, thereby improving the stability and quality of workpiece processing; it can also increase the pressing force of the tilting plate when the driving force provided by the drive component is the same. Furthermore, when the length of the tilting plate is relatively long, the pressure head provides a second pressure in the middle of the tilting plate so that the tilting plate can clamp the cover plate at a distance with a stable and constant pressure, thereby providing more space for the processing of the workpiece, and can process the workpiece in multiple processes at one time, thereby improving the processing effect and efficiency of the workpiece; in addition, through the coordinated setting of the push rod and each structure, the maximum angle that the tilting plate can open is greater than 90°, which is convenient for clamping the workpiece without damaging the clamped objects, further improving the stability and quality of workpiece processing.

[0050] When in use, the push-pull rod is pushed upward by the driving assembly, and the force is transmitted so that the tilting plate moves downward to press the cover plate. Then the driving assembly continues to drive the push-pull rod upward, and then the force is further transmitted so that the front end of the pressure head presses the tilting plate downward, providing a second pressure for the tilting plate, further enhancing the size and stability of the pressure of the tilting plate on the cover plate.

[0051] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A clamping fixture for CNC machining, characterized in that: The invention comprises a base plate (1), a carrier plate (2) and a cover plate (5), wherein the carrier plate (2) is fixedly mounted on the upper surface of the base plate (1), the upper surface of the carrier plate (2) is in contact with and connected to the lower surface of a workpiece (3) to be processed, the cover plate (5) is arranged above the workpiece (3), and the lower surface of the cover plate (5) is pressed and connected to the workpiece (3), and a plurality of pressing head mechanisms (6) are mounted on the edges of the base plate (1), and the pressing head mechanisms (6) are pressed and connected to the top surface of the cover plate (5); The pressure head mechanism (6) further comprises a fixed plate (601), a fixed seat (602), a push-pull rod (603), a tilting plate (604), a pressure head (605) and two connecting rotating plates (614) symmetrically arranged on both sides of the fixed seat (602), one end of the fixed plate (601) is mounted on the base plate (1), and the other end of the fixed plate (601) away from the base plate (1) is provided with a through hole (606) for the push-pull rod (603) to pass through, the upper end of the push-pull rod (603) is rotatably connected to the connecting rotating plate (614), and the lower end of the push-pull rod (603) passes through the fixed plate (601) and is connected to a driving component (607); The base portion (6021) at the lower end of the fixed seat (602) is fixedly mounted on the upper surface of the fixed plate (601), and the base portion (6021) is connected to a connecting portion (6022) inclined toward one side of the push-pull rod (603), and a first rotating shaft (608) penetrating the connecting portion (6022) is installed at the lower end of the connecting portion (6022), and a second rotating shaft (609) penetrating the connecting portion (6022) is installed at the upper end of the connecting portion (6022), and two ends of the first rotating shaft (608) extend from two sides of the connecting portion (6022) and are respectively connected to the connecting rotating plate (614), and the second rotating shaft (609) is rotatably connected to the end of the tilting and pressing plate (604); The connecting rotating plate (614) comprises a first strip portion (6141) and a second strip portion (6142), wherein one end of each of the first strip portion (6141) and the second strip portion (6142) are connected, thereby forming an acute angle between the first strip portion (6141) and the second strip portion (6142), and a corner portion (6143) is formed at the connection between the first strip portion (6141) and the second strip portion (6142), and the corner portions (6143) of the two connecting rotating plates (614) are respectively connected to the two ends of the first rotating shaft (608) for rotation; One end of the two first strip portions (6141) opposite to the corner portion (6143) is rotatably connected to the upper end of the push-pull rod (603) via a third rotating shaft (610); a fourth rotating shaft (611) is connected between one end of the two second strip portions (6142) opposite to the corner portion (6143); the fourth rotating shaft (611) is rotatably connected to the rear end of the pressing head (605); the rear end of the pressing head (605) has a connecting portion (6051) extending downward; the connecting portion (6051) is rotatably connected to the middle and rear part of the tilting plate (604) via a fifth rotating shaft (612); the lower surface of the front end of the pressing head (605) can be in compression contact with the upper surface of the tilting plate (604); The upper end of the push-pull rod (603) is connected to a fixed block (613), and a strip through hole (6131) is formed on the fixed block (613). The third rotating shaft (610) is embedded in the strip through hole (6131), and the two ends of the third rotating shaft (610) extend out from the strip through hole (6131) respectively. The first strip portions (6141) of the two connecting rotating plates (614) are rotatably connected to the two ends of the third rotating shaft (610) respectively.

2. The clamping fixture for CNC machining according to claim 1, characterized in that: The driving component (607) is a cylinder.

3. The clamping fixture for CNC machining according to claim 1, characterized in that: Limiting cards (615) are installed at both ends of the first rotating shaft (608), the third rotating shaft (610) and the fourth rotating shaft (611). The limiting cards (615) are embedded in grooves at both ends of the first rotating shaft (608), the third rotating shaft (610) or the fourth rotating shaft (611), and the inner surface of the limiting card (615) is in contact with the outer surface of the connecting rotating plate (614).

4. The clamping fixture for CNC machining according to claim 1, characterized in that: The number of the pressing head mechanisms (6) is eight, and they are installed in groups of two at the four edges of the base plate (1).

5. The clamping fixture for CNC machining according to claim 1, characterized in that: A handle (7) is respectively mounted on two opposite side surfaces of the cover plate (5).

6. The clamping fixture for CNC machining according to claim 5, characterized in that: The handle (7) is mounted on the side surface of the short side of the cover plate (5).

7. The clamping fixture for CNC machining according to claim 1, characterized in that: The cover plate (5) is an iron cover plate or a plastic cover plate.

8. The clamping fixture for CNC machining according to claim 1, characterized in that: A bottom plate (8) is arranged directly below the base plate (1), and the bottom plate (8) and the base plate (1) are connected via a plurality of support columns (9).

9. The clamping fixture for CNC machining according to claim 8, characterized in that: The bottom plate (8) and the base plate (1) are connected via four support columns (9), and the four support columns (9) are respectively located at the four corners of the bottom plate (8).

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