CN112589481A

CN112589481A - Clamp for milling inclined surface of tooth claw body

Info

Publication number: CN112589481A
Application number: CN202011553121.0A
Authority: CN
Inventors: 杨日平; 孙升; 杨湘龙
Original assignee: Changsha Heijingang Industrial Co Ltd
Current assignee: Changsha Heijingang Industrial Co Ltd
Priority date: 2020-12-24
Filing date: 2020-12-24
Publication date: 2021-04-02
Anticipated expiration: 2040-12-24
Also published as: CN112589481B

Abstract

The invention relates to a fixture for milling inclined planes of a jaw body, which comprises a base and a clamping device arranged on the base, wherein the clamping device is used for clamping a cone unit, so that the inclined plane on the cone unit faces upwards, the correcting device is used for correcting the cone unit and comprises a first support seat positioned on one side of the cone unit in the width direction, a second support seat positioned on the other side of the cone unit in the width direction, and V-shaped blocks detachably connected with the second support seat and the first support seat respectively, and the included angle on each V-shaped block is the same as the included angle between the two inclined planes on the jaw body. The application provides a gripper body mills inclined plane anchor clamps can guarantee in the gripper body course of working, and two inclined planes are symmetrical for the gear wheel unit central line, and the machining allowance distribution on two inclined planes is even, avoids one of them inclined plane machining allowance too little gear wheel unit that causes to scrap.

Description

Clamp for milling inclined surface of tooth claw body

Technical Field

The invention relates to the technical field of roller bit manufacturing, in particular to a fixture for milling an inclined plane on a tooth claw body.

Background

Drilling is an important technical means in geological exploration work. Roller cone drill bits are also most used in oil and geological drilling. The roller bit has the functions of impacting, crushing and shearing broken stratum rocks when rotating, and can be divided into a milling tooth (steel tooth) roller bit and an insert (hard alloy teeth are inserted on a roller) roller bit according to tooth types; it can be divided into single cone bit, tri-cone bit and assembled multi-cone bit according to the number of cones. The tricone bit is most used and most common at home and abroad. Under the action of bit weight and rotation of the drill string, the teeth crush and bite into the rock, and certain sliding is generated to shear the rock. When the roller cone rolls at the bottom of the well, teeth on the roller cone impact and are pressed into the stratum in sequence, the action can crush one part of rock at the bottom of the well, and meanwhile, the other part of rock remained among the teeth is cut off by the shearing action brought by the sliding of the roller cone, so that the rock at the bottom of the well is crushed completely, and a well hole is extended.

The three-jaw roller bit mainly comprises three roller cone units, and in order to ensure that the cutting load borne by each roller cone unit is the same in the drilling process and therefore the structure of each roller cone unit is the same, the three-jaw roller bit mainly comprises a roller cone body, a roller leg arranged on the roller cone body and a roller cone arranged on the roller leg. In the process of assembling the three-jaw roller bit into the lathe, three jaw bodies are required to be welded and assembled into a revolving body, and then connecting threads are lathed on the outer wall of the revolving body.

Thus, the angle between the two contact surfaces on each jaw body is 120 °, whereas in order to balance the load experienced by the individual jaw bodies during operation, the two contact surfaces are symmetrical with respect to the centre line of the jaw body itself, i.e. the angle between the two contact surfaces and the centre line is 60 °. The roller cone unit blank is usually a forged piece, the allowance on the included angle of two contact surfaces is uneven, if the machining allowances on the two contact surfaces cannot be uniformly distributed, the machining allowance of one contact surface is too much, the machining allowance of one contact surface is too little in the machining process of the contact surface, and the milling inclined surface of the roller cone unit is scrapped.

Disclosure of Invention

The invention aims to provide a fixture for milling inclined planes of a tooth claw body, which can ensure that two inclined planes are symmetrical relative to the central line of a cone unit and the processing allowance on the two inclined planes is uniformly distributed in the processing process of the tooth claw body, and avoid the cone unit from being scrapped due to too little processing allowance on one inclined plane.

The technical scheme of the invention is as follows:

a gripper body inclined plane milling clamp comprises a base;

the clamping device is arranged on the base and is used for clamping the cone unit, so that the inclined surface on the cone unit faces upwards;

the correcting device is used for correcting the roller cone unit and comprises a first support seat positioned on one side of the roller cone unit in the width direction;

the second support is positioned on the other side of the cone unit in the width direction;

the V-shaped block is detachably connected with the second support and the first support respectively, and an included angle formed by the V-shaped block is the same as an included angle formed by two inclined planes on the jaw body.

Preferably, the clamping device comprises a tail clamping assembly for clamping the tail portion of the cone unit;

a head clamp assembly for clamping a head location adjacent the cone unit.

Preferably, the clamping device comprises a supporting component for supporting the bit leg on the cone unit from bottom to top.

Preferably, the supporting component comprises a third support which is detachably connected with the base, and a supporting surface for supporting the back of the dental claw body is arranged on the third support;

a rotating pin is arranged in the third support, the rotating pin is arranged obliquely, and the central line of the rotating pin is parallel to the tangent line of the supporting surface;

the head pressing plate is connected with the rotating pin through a connecting structure, so that the head pressing plate can rotate around the rotating pin, and the head pressing plate has a first state of pressing the bit leg and a second state of being far away from the bit leg.

Preferably, the connecting structure includes a first rotating member having one end rotating about the rotating pin;

and the head pressing plate rotates around the first fastening piece.

Preferably, the head pressing plate is provided with an accommodating groove;

and an avoidance groove communicated with the accommodating groove;

the first fastener passes through the holding tank, the other end of the first rotating piece passes through the holding tank and the avoidance groove, and can move along the length direction of the avoidance groove.

Preferably, the first fastener is in threaded connection with the third support;

and a locking piece is arranged at the back of the head pressing plate and is in threaded connection with the other end of the rotating pin.

Preferably, the nose clamping assembly is arranged on one side of the supporting assembly close to the tail direction of the cone unit, and the nose clamping assembly is located between the correcting device and the supporting assembly;

the head clamping assembly comprises a fourth support arranged on the base;

the first clamping jaw and the second clamping jaw are hinged with the fourth support and used for clamping the width direction of the roller cone unit;

and the control structure is used for controlling the first clamping jaw and the second clamping jaw to open and close.

Preferably, the control structure comprises a first nut and a second nut arranged in the fourth support;

the screw rod is in threaded connection with the first nut and the second nut;

an acting member connected to an end of the screw to rotate the screw.

Preferably, the tail clamp assembly includes a fifth seat provided on the base,

and the pressing block is connected with the fifth support through a lifting structure, so that the pressing block can move up and down.

The invention provides a fixture for milling inclined planes of a tooth claw body, which comprises a base and a clamping device arranged on the base, wherein the clamping device is used for clamping a cone unit, so that the inclined plane on the cone unit faces upwards, and a correcting device is used for correcting the cone unit and comprises a first support arranged on one side of the cone unit in the width direction, a second support arranged on the other side of the cone unit in the width direction, and V-shaped blocks which are detachably connected with the second support and the first support respectively, wherein the included angle on each V-shaped block is the same as the included angle between the two inclined planes on the tooth claw body. The three tooth claw units can be assembled and welded into a three-claw roller bit, each roller unit comprises a tooth claw body and a tooth leg arranged on the tooth claw body, and a roller is arranged on the tooth leg in the welding and assembling process. The fixture for milling the inclined surface of the dental claw body is suitable for processing two inclined surfaces with an included angle of 120 degrees on the dental claw body. But is not limited to, beveling of this included angle. And the cone unit is generally a forged piece, and compared with the prior art, when the inclined planes on the cone unit need to be machined, a correcting device is firstly adopted for correcting, so that the intersection line between the two inclined planes on the cone unit is parallel to the horizontal line. Specifically, the V-shaped blocks with the same included angle between the included angle and the two inclined planes are attached to the two inclined planes to adjust the posture of the cone unit, when the intersection line between the two inclined planes on the cone unit is parallel to a horizontal line, the cone unit is clamped by a clamping device, so that the inclined planes on the cone unit face upwards, the V-shaped blocks are removed, and the two inclined planes are machined by a milling machine. Therefore, the same machining allowance on the two inclined planes can be ensured, and the phenomenon that the machining allowances on the two inclined planes are different due to the fact that the initial clamping posture of the cone unit is incorrect and further the distribution of the machining allowances is uneven is avoided. Therefore, the fixture for milling the inclined surface of the tooth claw body can ensure that the two inclined surfaces are symmetrical relative to the central line of the cone unit in the machining process of the tooth claw body, the machining allowance on the two inclined surfaces is uniformly distributed, and the cone unit scrapping caused by too little machining allowance of one inclined surface is avoided.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present application, and other drawings can be obtained by those skilled in the art without creative efforts.

Fig. 1 is a schematic structural diagram of a claw body milling fixture for calibration according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of a claw body milling fixture for calibration according to an embodiment of the present invention;

fig. 3 is a schematic structural view of the gripper body inclined surface milling fixture according to the embodiment of the present invention, when a V-shaped block is removed and an inclined surface is to be processed;

FIG. 4 is a schematic structural view of a head clamp assembly according to an embodiment of the present invention;

FIG. 5 is a cross-sectional view of a head clamp assembly provided by an embodiment of the present invention;

FIG. 6 is a schematic structural diagram of a V-shaped block and a centralizer provided by an embodiment of the invention;

FIG. 7 is a schematic view of a support assembly according to an embodiment of the present invention;

FIG. 8 is a schematic view of a support assembly according to an embodiment of the present invention;

figure 9 is a cross-sectional view of a support assembly according to an embodiment of the present invention;

figure 10 is an exploded view of a support assembly according to an embodiment of the present invention;

figure 11 is an exploded view of a support assembly according to an embodiment of the present invention.

Reference numbers in the drawings illustrate: 1. a base; 2. a cone unit; 3. a first support; 4. a second support; 5. a V-shaped block; 6. a third support; 7. a support surface; 8. a rotation pin; 9. a head pressure plate; 10. a bit leg; 11. a first rotating member; 12. a first fastener; 13. accommodating grooves; 14. an avoidance groove; 15. a locking member; 16. a fourth support; 17. a first jaw; 18. a second jaw; 19. a first nut; 20. a second nut; 21. a screw; 22. an acting element; 23. a fifth support; 24. briquetting; 25. a centralizer.

Detailed Description

In order to make those skilled in the art better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

In the description of the present invention, it is to be understood that the terms "upper", "lower", and the like, indicate an orientation or positional relationship only for convenience of description and simplicity of description, but do not indicate or imply that the referenced components or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention.

As shown in fig. 1 to 11, the present invention provides a gripper body slope milling fixture, which includes a base 1, and a clamping device disposed on the base 1, wherein the clamping device is used to clamp a cone unit 2, so that a slope on the cone unit 2 faces upward, and a correcting device used to correct the cone unit 2, the correcting device includes a first support 3 located on one side of the cone unit 2 in a width direction, a second support 4 located on the other side of the cone unit 2 in the width direction, and a V-shaped block 5 detachably connected to the second support 4 and the first support 3, and an included angle between the two slopes on the gripper body is the same as an included angle between the two slopes on the gripper body and the V. Three jaw units may be assembled and welded to form a three-jaw roller bit, and each of the cone units 2 includes a jaw body, a bit leg 10 provided on the jaw body, and a cone is mounted on the bit leg 10 during the welding assembly. The fixture for milling the inclined surface of the dental claw body is suitable for processing two inclined surfaces with an included angle of 120 degrees on the dental claw body. But is not limited to, beveling of this included angle. And the cone unit 2 is generally a forged piece, compared with the prior art, when the inclined surfaces on the cone unit 2 need to be machined, firstly, a correcting device is adopted for correcting, so that the intersection line between the two inclined surfaces on the cone unit 2 is parallel to the horizontal line. Specifically, the V-shaped blocks 5 with the same included angle between the two inclined planes are attached to the two inclined planes to adjust the posture of the cone unit 2, when the intersection line between the two inclined planes on the cone unit 2 is parallel to a horizontal line, the cone unit 2 is clamped by a clamping device, so that the inclined planes on the cone unit 2 face upwards, the V-shaped blocks 5 are removed, and the two inclined planes are machined by a milling machine. Therefore, the same machining allowance on the two inclined planes can be ensured, and the phenomenon that the machining allowances on the two inclined planes are different due to the fact that the initial clamping posture of the cone unit 2 is incorrect and further the distribution of the machining allowances is uneven is avoided. Therefore, the fixture for milling the inclined surface of the tooth claw body can ensure that the two inclined surfaces are symmetrical relative to the central line of the gear unit 2 in the machining process of the tooth claw body, the machining allowance on the two inclined surfaces is uniformly distributed, and the gear unit 2 which is caused by too little machining allowance of one inclined surface is prevented from being scrapped.

Wherein the clamping means comprises a tail clamping assembly for clamping the tail of the cone unit 2 and a nose clamping assembly for clamping a location adjacent the nose of the cone unit 2. The clamping assembly comprises a tail clamping assembly and a head clamping assembly, the tail clamping assembly is used for clamping the tail of the cone unit 2, the head clamping assembly is used for clamping the head position close to the cone unit 2, when the cone unit 2 is machined, firstly, the cone unit 2 is corrected by using a correcting device, after an intersection line between two inclined planes on the cone unit 2 is parallel to a horizontal line, the tail and the head of the cone unit 2 are simultaneously clamped, after the cone unit 2 is clamped, a V-shaped block 5 of the correcting device is removed, and a milling machine processes the two inclined planes.

Furthermore, a centralizer 25 can be arranged at the top of the V-shaped block 5, the overall structure of the centralizer 25 is symmetrical in the width direction of the cone unit 2, the V-shaped block 5 can be taken conveniently, and meanwhile the V-shaped block 5 can quickly correct the position of the cone unit 2.

Preferably, the clamping means comprises a bearing assembly that holds the bit leg 10 of the cone unit 2 from below upwards. Because the bit leg 10 is arranged at the head part, the weight is concentrated at the head part, the structural characteristic of the cone unit 2 is heavy at the head part and light at the tail part, and a bearing assembly for supporting the bit leg 10 on the cone unit 2 from bottom to top is arranged in order to avoid that the corrected posture of the cone unit 2 is destroyed when the cone unit 2 is clamped and processed after a correcting device is used.

In the embodiment provided by the invention, the supporting component comprises a third support 6 which is detachably connected with the base 1, and a supporting surface 7 for supporting the back of the dental paw body is arranged on the third support 6; a rotating pin 8 is arranged in the third support 6, the rotating pin 8 is arranged obliquely, the central line of the rotating pin 8 is parallel to the tangent line of the supporting surface 7, and a head pressing plate 9 connected with the rotating pin 8 through a connecting structure enables the head pressing plate 9 to rotate around the rotating pin 8, and the head pressing plate 9 has a first state of pressing the palm of teeth 10 and a second state of being far away from the palm of teeth 10. The supporting surface 7 is contacted with the side surface on the back of the gripper body to provide auxiliary supporting force for the gripper body, on the other hand, the central line of the rotating pin 8 is parallel to the tangent line of the supporting surface 7 through the inclined arrangement of the rotating pin 8, and then the head pressing plate 9 presses the bit leg 10. The arrangement that the central line of the rotating pin 8 is parallel to the tangent line of the supporting surface 7 enables the pressing point of the head pressing plate 9 to be consistent with the supporting point of the supporting surface 7 in position, so that the head of the whole cone unit 2 is stressed uniformly, and the phenomenon of cutter shaking caused by unbalanced stress of a clamping force is avoided.

The connecting structure comprises a first rotating part 11 with one end rotating around the rotating pin 8, a first fastening part 12 connected with the other end of the first rotating part 11, and the head pressing plate 9 rotates around the first fastening part 12. Because the rotating pin 8 is arranged on the third support 6, the head pressing plate 9 needs to change the posture continuously in the rotating process, if the head pressing plate 9 is directly hinged with the transmission pin, the head pressing plate 9 can be extruded continuously in the third support 6, firstly, the rotating pin 8 can be extruded and deformed, and secondly, the stress borne by the third support 6 is larger. Therefore, in this embodiment, one end of the first rotating member 11 rotates around the rotating pin 8, the other end is connected to the first fastening member 12, and the head pressing plate 9 is connected to the first fastening member 12, so that the head pressing plate 9 is prevented from being pressed in the third seat 6. On the other hand, the rotatable angle of the head pressing plate 9 is increased, the cone unit 2 is prevented from interfering with the cone unit 2 in the correction process, and when the inclined surface of the cone unit 2 is machined and the cone unit 2 needs to be detached from the clamp, the head pressing plate 9 can provide a large avoiding position, so that the head pressing plate 9 and the bit leg 10 cannot interfere.

Preferably, the head pressing plate 9 is provided with an accommodating groove 13 and an avoiding groove 14 communicated with the accommodating groove 13, the first fastening member 12 passes through the accommodating groove 13, and the other end of the first rotating member 11 passes through the accommodating groove 13 and the avoiding groove 14 and can move along the length direction of the avoiding groove 14. The receiving groove 13 is used for receiving the first rotating member 11, and the avoiding groove 14 is provided to avoid the first rotating member 11 and the head pressing plate 9 from generating pressing interference during the rotation of the head pressing plate 9.

In the embodiment provided by the invention, the first fastening piece 12 is connected with the third support 6 in a screw mode, the back of the head pressing plate 9 is provided with a locking piece 15, and the locking piece 15 is connected with the other end of the rotating pin 8 in a screw mode. In order to avoid that the movement amplitude of the first fastening piece 12 is too large, so that the rotation angle of the head pressing plate 9 is too large, and the pressing force provided by the head pressing plate 9 to the bit leg 10 is not well adjusted, the first fastening piece 12 is connected with the third support 6 in a threaded manner, so that the rotation of the first fastening piece 12 is converted into the linear movement of the first fastening piece 12, and the rotation amplitude of the head pressing plate 9 is further controlled. Preferably, a rotatable wrench is provided at the end of the first fastener 12 to facilitate rotational adjustment of the first fastener 12. The back of the head pressing plate 9 is provided with a locking piece 15, the locking piece 15 is connected with the other end of the rotating pin 8 in a screw-in mode, when the head pressing plate 9 rotates to be in contact with the outer wall of the bit leg 10, the locking piece 15 can be locked, and the head pressing plate 9 applies pressing force to the bit leg 10.

The head clamping assembly is arranged on one side, close to the tail direction of the cone unit 2, of the bearing assembly, is located between the correcting device and the bearing assembly, and comprises a fourth support 16 arranged on the base 1, a first clamping jaw 17 and a second clamping jaw 18 hinged to the fourth support 16, the second clamping jaw 18 and the first clamping jaw 17 are used for clamping the width direction of the cone unit 2, and a control structure is used for controlling the first clamping jaw 17 and the second clamping jaw 18 to be opened and closed. The location of the head clamp assembly is closer to the position where the cone unit 2 is easily leaped, so that the clamping of the cone unit 2 in the width direction is more reliable. On the other hand, the first jaw 17, the second jaw 18 are arranged inside the fourth seat 16, avoiding the fall of foreign bodies in the hinged position of the first jaw 17, the second jaw 18.

Preferably, the control structure includes a first nut 19 and a second nut 20 provided in the fourth seat 16, a screw 21 screw-coupled to the first nut 19 and the second nut 20, and an acting member 22 coupled to an end of the screw 21 to rotate the screw 21. The screw 21 rotates, and the first clamping jaw 17 and the second clamping jaw 18 are driven to rotate by the first nut 19 and the second nut 20, so that the opening and closing degree of the first clamping jaw 17 and the second clamping jaw 18 is realized. The transmission is more accurate due to the threaded connection mode, the opening and closing amplitude of the first clamping jaw 17 and the second clamping jaw 18 is more finely controlled, the first clamping jaw 17 and the second clamping jaw 18 are prevented from being conveniently clamped and adjusted, and the impact load on the cone unit 2 caused by the first clamping jaw 17 and the second clamping jaw 18 in the clamping process can be further avoided.

In the embodiment provided by the invention, the tail clamping assembly comprises a fifth support 23 arranged on the base 1, and a pressing block 24 connected with the fifth support 23 through a lifting structure, so that the pressing block 24 can move up and down, and the tail is clamped and disassembled.

The embodiments in the present specification are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same or similar parts in the embodiments are referred to each other.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. The fixture for milling the inclined plane of the jaw body is characterized by comprising a base (1);

the clamping device is arranged on the base (1) and is used for clamping the cone unit (2) so that the inclined surface on the cone unit (2) faces upwards;

a correcting device for correcting the roller cone unit (2), the correcting device comprises a first support seat (3) positioned on one side of the roller cone unit (2) in the width direction;

a second seat (4) located on the other side of the cone unit (2) in the width direction;

respectively with second support (4) with V type piece (5) of connection can be dismantled in first support (3), contained angle on V type piece (5) is the same with the contained angle between two inclined planes on the claw body.

2. The jaw body beveling clamp according to claim 1, wherein the clamping means comprises a tail clamping assembly for clamping a tail portion of the cone unit (2);

a head clamp assembly for clamping a head position adjacent the cone unit (2).

3. The jaw body beveling fixture according to claim 2, wherein the clamping device comprises a bearing assembly that holds up a bit leg (10) of the cone unit (2) from below upwards.

4. The dental jaw body beveling fixture according to claim 3, wherein the supporting member comprises a third support (6) detachably connected to the base (1), the third support (6) being provided with a supporting surface (7) for supporting the back of the dental jaw body;

a rotating pin (8) is arranged in the third support (6), the rotating pin (8) is obliquely arranged, and the central line of the rotating pin (8) is parallel to the tangent line of the supporting surface (7);

the head pressing plate (9) is connected with the rotating pin (8) through a connecting structure, so that the head pressing plate (9) can rotate around the rotating pin (8), and the head pressing plate (9) has a first state of pressing the bit leg (10) and a second state of being far away from the bit leg (10).

5. The jaw body beveling fixture according to claim 4, wherein the coupling structure comprises a first rotating member (11) having one end rotating about the rotating pin (8);

and the head pressure plate (9) rotates around the first fastening piece (12).

6. The jaw body milling fixture as claimed in claim 5, wherein the head pressure plate (9) is provided with a receiving groove (13);

and an avoidance groove (14) communicated with the accommodating groove (13);

the first fastening piece (12) penetrates through the accommodating groove (13), the other end of the first rotating piece (11) penetrates through the accommodating groove (13) and the avoiding groove (14), and the first fastening piece can move along the length direction of the avoiding groove (14).

7. The jaw body beveling fixture according to claim 6, wherein the first fastener (12) is threadedly connected to the third mount (6);

a locking piece (15) is arranged on the back of the head pressing plate (9), and the locking piece (15) is connected with the other end of the rotating pin (8) in a screw-mounting mode.

8. The jaw body beveling clamp according to claim 3, wherein the nose gripping assembly is provided on a side of the bolster assembly in a direction towards a rear of the cone unit (2), the nose gripping assembly being located between the correcting device and the bolster assembly;

the head clamping assembly comprises a fourth support (16) arranged on the base (1);

and a first clamping jaw (17) and a second clamping jaw (18) hinged with the fourth support (16), wherein the second clamping jaw (18) and the first clamping jaw (17) are used for clamping the width direction of the roller cone unit (2);

and the control structure is used for controlling the first clamping jaw (17) and the second clamping jaw (18) to open and close.

9. The jaw body beveling fixture according to claim 8, wherein the control structure comprises a first nut (19) and a second nut (20) provided in the fourth seat (16);

a screw (21) which is connected with the first nut (19) and the second nut (20) in a threaded manner;

an acting member (22) connected to an end of the screw (21) to rotate the screw (21).

10. The jaw body beveling fixture according to claim 2, wherein the tail clamp assembly comprises a fifth abutment (23) provided on the base (1),

a pressing block (24) connected with the fifth support (23) through a lifting structure, so that the pressing block (24) can move up and down.