CN220322991U - Test tool and test machine - Google Patents

Abstract

The application relates to a test fixture and a test machine. The device comprises an upward pressing mechanism, a plurality of clamping pieces which are abutted to a pressing head, and a downward pressing mechanism, wherein the upward pressing mechanism can move towards the downward pressing mechanism, and the downward pressing mechanism comprises a pressing seat which is used for placing a sample. According to the clamping device, the clamping pieces are respectively arranged on the two sides of the pressure head, the pair of clamping pieces are clamped on the pressure head jointly, the clamping pieces play a supporting role on the pressure head, and therefore stability of the pressure head in a cold bending test is improved, and the test is carried out smoothly.

Description

Test tool and test machine

Technical Field

The application relates to the technical field of cold bending tests, in particular to a test tool and a test machine.

Background

With the development of the light weight requirements of automobiles, the high-strength steel used by automobiles is gradually increased.

In the related art, before the high-strength steel is formally put into use, cold bending performance test is required to be carried out on the high-strength steel, namely, a press bending method or folding bending is adopted, and under the condition that the arc surface radius R of a male die is gradually reduced, the minimum bending radius Rmin when no crack is generated on the high-strength steel is measured, and the ratio of the minimum bending radius Rmin to the thickness T of the high-strength steel, namely, the minimum relative bending radius Rmin/T0 is used as a bending forming performance index.

However, when cold bending performance tests are performed on high-strength steel, the male die often suffers from buckling instability.

Disclosure of Invention

Based on the above, it is necessary to provide a test tool and a test machine for the problem that the male die is easy to bend and unstably during the cold bending test.

In a first aspect, the present application provides a test fixture, which adopts the following technical scheme:

the utility model provides a test fixture, includes upward press mechanism, butt in a plurality of holders of pressure head, and pushing down the mechanism, upward press the mechanism can be faced pushing down the mechanism and removing, pushing down the mechanism and including pressing the seat, it is used for placing the sample to press the seat.

In one embodiment, the press seat is provided with a bending groove, the bending groove penetrates through the press seat to face the side wall of the press head, the sample can cover the bending groove, and the press head can be inserted into the bending groove along the height direction.

In one embodiment, an insertion opening is formed in a surface, facing the pressure head, of the pressure seat, the bending groove is communicated with the insertion opening, a guide surface is arranged on the pressure seat at the insertion opening, and the guide surface is connected with the edge of the insertion opening and the surface, facing the pressure head, of the pressure seat.

In one embodiment, the pressing mechanism further comprises a positioning component, wherein the positioning component is arranged on the pressing seat and is abutted against the side wall of the sample so as to prevent the sample from moving in the plane direction of the sample, and the sample always covers the bending groove.

In one embodiment, the positioning assembly comprises a plurality of positioning stop pins, wherein the positioning stop pins are arranged on the surface of the pressing seat facing the pressing head, a part of the positioning stop pins are arranged at one end of the sample, the rest positioning stop pins are respectively arranged at two sides of the sample, and all the positioning stop pins are in butt joint with the side wall of the sample.

In one embodiment, the pressing mechanism further comprises a fastener, and the fastener passes through the clamping pieces to enable the clamping pieces to be clamped on the pressing head.

In one embodiment, the clamping member is provided with a relief groove, and the relief groove penetrates through one side wall of the clamping member.

In a second aspect, the present application provides a testing machine, which adopts the following technical scheme:

the testing machine comprises the testing tool, an upper machine base and a lower machine base, and the testing tool is arranged between the upper machine base and the lower machine base.

In one embodiment, the testing machine further comprises a first connecting assembly and a second connecting assembly, the pressing head and the clamping pieces are connected to the upper machine base through the first connecting assembly, and the pressing base is connected to the lower machine base through the second connecting assembly.

In one embodiment, the first connecting assembly includes a first fixing seat, a first connecting piece and a pair of fixing pieces, the first connecting piece is disposed on a side of the first fixing seat opposite to the pressure head, the first connecting piece is used for connecting the first fixing seat and the upper stand, the pair of fixing pieces are disposed on a surface of the first fixing seat opposite to the first connecting piece, a plugging slot is defined between the first fixing seat and the pair of fixing pieces, and one ends of the pressure head and the pair of clamping pieces can be plugged into the plugging slot, so that the pair of fixing pieces are clamped on the pair of clamping pieces;

the second connecting assembly comprises a second fixing seat, a second connecting piece and a connecting piece, wherein the second connecting piece is arranged on one side, opposite to the pressing seat, of the second fixing seat, the second connecting piece is used for connecting the second fixing seat with the lower machine seat, and the connecting piece is used for connecting the second fixing seat with the pressing seat.

In one embodiment, the portion of the pressing head and the pair of clamping pieces inserted into the insertion groove is an insertion portion, the insertion portion is configured such that the cross-sectional width gradually decreases from one end close to the first fixing seat to one end far away from the first fixing seat, and the insertion portion is inserted into the insertion groove in a width direction of the first fixing seat.

In one embodiment, the first connecting component further comprises a limiting piece penetrating through the first fixing seat, and the limiting piece is arranged along the height direction of the pressure head and abuts against the surface, facing the first fixing seat, of the inserting portion.

According to the test tool and the test machine, the clamping piece is arranged on the side edge of the pressure head and is abutted to the pressure head and plays a supporting role on the pressure head, so that the instability phenomenon of the pressure head due to the fact that the thickness of the pressure head is thin in the cold bending test process is reduced, and the stability of the pressure head in the cold bending test is improved.

Drawings

Fig. 1 is a schematic perspective view of a test tool according to an embodiment of the present application.

Fig. 2 is a schematic diagram of an upward pressing mechanism according to an embodiment of the present application.

Fig. 3 is an enlarged view of a portion a in fig. 2.

Fig. 4 is a schematic view of a pressing mechanism according to an embodiment of the present application.

Fig. 5 is a schematic view of a first connection component according to an embodiment of the present application.

Fig. 6 is a schematic perspective view of the pressing mechanism and the first connecting component in an embodiment of the present application.

Fig. 7 is a cross-sectional view of a hold-down mechanism in an embodiment of the present application.

The drawings are marked with the following description:

1. an upward pressing mechanism; 11. a pressure head; 12. a clamping member; 121. a relief groove; 13. a fastener; 2. a pressing mechanism; 21. pressing a base; 211. a bending groove; 212. an insertion port; 213. a guide surface; 22. a positioning assembly; 221. positioning a stop pin; 3. a first connection assembly; 31. a first fixing seat; 32. a first connector; 33. a fixing member; 34. a limiting piece; 4. a second connection assembly; 41. the second fixing seat; 411. a first through hole; 412. a second through hole; 42. a second connector; 43. a connecting piece; 431. a connecting pin; 432. a connecting bolt; 433. a nut; 5. a plug-in part; 6. a plug-in groove; 7. and (3) a sample.

Detailed Description

In order to make the above objects, features and advantages of the present application more comprehensible, embodiments accompanied with figures are described in detail below. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. This application is, however, susceptible of embodiment in many other forms than those described herein and similar modifications can be made by those skilled in the art without departing from the spirit of the application, and therefore the application is not to be limited to the specific embodiments disclosed below.

In the description of the present application, it should be understood that, if there are terms such as "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., these terms refer to the orientation or positional relationship based on the drawings, which are merely for convenience of description and simplification of description, and do not indicate or imply that the apparatus or element referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the present application.

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

In this application, unless explicitly stated and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly. For example, the two parts can be fixedly connected, detachably connected or integrated; can be mechanically or electrically connected; either directly or indirectly, through intermediaries, or both, may be in communication with each other or in interaction with each other, unless expressly defined otherwise. The specific meaning of the terms in this application will be understood by those of ordinary skill in the art as the case may be.

In this application, unless expressly stated or limited otherwise, the meaning of a first feature being "on" or "off" a second feature, and the like, is that the first and second features are either in direct contact or in indirect contact through an intervening medium. Moreover, a first feature being "above," "over" and "on" a second feature may be a first feature being directly above or obliquely above the second feature, or simply indicating that the first feature is level higher than the second feature. The first feature being "under", "below" and "beneath" the second feature may be the first feature being directly under or obliquely below the second feature, or simply indicating that the first feature is less level than the second feature.

It will be understood that if an element is referred to as being "fixed" or "disposed" on another element, it can be directly on the other element or intervening elements may also be present. If an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like as used herein, if any, are for descriptive purposes only and do not represent a unique embodiment.

Embodiments of the present application are described in further detail below in conjunction with figures 1-7.

Referring to fig. 1, an embodiment of the present application provides a test fixture for performing a cold bending test on a sample 7 with a thickness set to t. The test fixture comprises an upward pressing mechanism 1 and a downward pressing mechanism 2 which are sequentially arranged from top to bottom along the vertical direction. In the cold bending test process, an operator places the sample 7 on the pressing mechanism 2, and then controls the pressing mechanism 1 to move towards the pressing mechanism 2 along the vertical direction, so as to perform the cold bending test on the sample 7.

Sample 7 used in the examples of the present application was a cemented carbide steel plate 150mm long and 35mm wide.

Referring to fig. 2, specifically, the pressing mechanism 1 includes a pair of clamping members 12 disposed in a vertical direction and a pressing head 11 disposed between the pair of clamping members 12, wherein the pair of clamping members 12 are fixed to the pressing head 11 by fastening members 13, and the fastening members 13 in this application are common bolts and nuts.

After the fastener 13 passes through the pair of clamping pieces 12, the opposite end surfaces of the pair of clamping pieces 12 are abutted against the end surface of the pressing head 11 together, so that the pressing head 11 is supported, and the instability phenomenon of the pressing head 11 due to the thin thickness of the pressing head 11 in the cold bending test process is reduced.

Referring to fig. 2 and 3, the indenter 11 in the embodiment of the present application has the same thickness as the sample 7 to be tested, and is constructed in a rectangular plate-like structure cut from a cemented carbide steel plate. The end of the ram 11 near the pressing mechanism 2 is configured with a rounded corner, and the rounded corner of the ram 11 has a size of the thickness of the sample 7, i.e., r=t (sample 7 thickness).

Referring to fig. 1 and 4, the pressing mechanism 2 includes a pressing seat 21 for placing the sample 7, and the pressing seat 21 is disposed right under the pressing head 11 and is arranged concentrically with the pressing head 11 in the vertical direction.

Specifically, the pressing seat 21 in the embodiment of the present application adopts a cuboid structure, and the pressing seat 21 and the pressing head 11 are mutually perpendicular. In addition, the press seat 21 is provided with a press bending groove 211 in a penetrating manner along the width direction, the press bending groove 211 in the present application is provided with a structure with an inverted T-shaped cross section, and the press head 11 can be inserted into the press bending groove 211 along the vertical direction in the test process.

The groove width of the press bending groove 211 in the present application was set according to the thickness of the sample 7 and the test, the groove width of the press bending groove 211 in the present application was set to 2t+1.0mm, and the depth was set to 75mm or more.

In the cold bending test process, the clamping piece 12 is clamped on the pressure head 11 to provide supporting force for the pressure head 11. Along with the movement of the pressure head 11, the sample 7 is pressed into the bending groove 211, and under the co-extrusion action of the inner wall of the bending groove 211 and the pressure head 11, the test of the extreme cold bending fillet of the sample 7 at 0-180 degrees can be realized, and the phenomenon of instability of the pressure head 11 is not easy to occur in the test process.

Referring to fig. 1 and 4, the bending groove 211 penetrates the top surface of the pressing base 21 to form an insertion opening 212 through which the pressing head 11 and the sample 7 pass. The clamping piece 12 is provided with a relief groove 121 in a penetrating way at the longitudinal central axis of the clamping piece 12, and the relief groove 121 penetrates through the bottom surface of the clamping piece 12.

The groove width of the abdication groove 121 is larger than or equal to the width of the pressing seat 21 in the application, so that the clamping piece 12 can only pass through the pressing seat 21 and can not enter the press bending groove 211 when moving along the vertical direction, the condition that the thickness of the pressing head 11 is increased due to the clamping piece 12 is avoided, and the precision of a cold bending test is ensured.

Referring to fig. 1 and 4, further, the guide surface 213 is provided on the press seat 21 at the insertion port 212, and the guide surface 213 adopts a rounded design, so that the top surface of the press seat 21 and the groove wall of the buckling groove 211 smoothly transition. The guide surface 213 serves to guide the sample 7 during the test into the bending groove 211.

In addition, in order to keep the sample 7 centered on the top surface of the pressing seat 21 at all times, the pressing seat 21 in the embodiment of the present application further includes a positioning assembly 22 for achieving the centering function of the sample 7. The positioning assembly 22 in this application includes three positioning dowels 221.

The height of the locating stop pin 221 is 20mm, a pin hole for inserting the bottom end part of the locating stop pin 221 is formed in the pressing seat 21 corresponding to the locating stop pin 221, the diameter of the pin hole is 5mm, and the bottom end part of the locating stop pin 221 is abutted against the side wall of the sample 7 after being inserted into the pin hole.

Specifically, one of the positioning stop pins 221 is disposed on one side of the insertion port 212 and abuts against a side wall of one end of the sample 7 to prevent the movement of the sample 7 in the length direction thereof; the remaining two positioning stoppers 221 are provided on the other side of the insertion port 212 and respectively abut against the side walls on both sides of the sample 7 to prevent the movement of the sample 7 in the width direction thereof. The three positioning stop pins 221 are mutually matched to realize the centering function of the sample 7, so that the sample 7 is always placed on the top surface of the pressing seat 21 in the middle in the test process, and abnormal movement is not easy to occur, and the possibility of instability of the pressing head 11 in the test process is reduced.

Referring to fig. 1 to 4, in the test, an operator firstly centers a sample 7 on the top surface of a pressing seat 21, then controls an upward pressing mechanism 1 to move towards a downward pressing mechanism 2, a pressing head 11 of the upward pressing mechanism 1 abuts against the upper end surface of the sample 7 and applies pressure to the sample 7, the sample 7 is extruded into a bending groove 211, the sample 7 is bent upwards under the combined action of the pressure of the pressing head 11 and the supporting force provided by the pressing seat 21, and finally, the minimum bending radius rmin of high-strength steel when no crack is generated is measured, and the ratio of the minimum bending radius rmin/t0 to the thickness t of the high-strength steel is obtained, so that the performance index of bending formation of the sample 7 is obtained.

Referring to fig. 1 to 4, the test fixture may be combined with an upper frame (not shown) and a lower frame (not shown) to form a test machine (not shown) for performing a cold bending test on the sample 7, and the test fixture is installed between the upper frame and the lower frame. Wherein the press head 11 and the pair of clamping members 12 are mounted on the upper frame through the first connecting assembly 3, and the press seat 21 is mounted on the lower frame through the second connecting assembly 4. The testing machine in the embodiment of the application can be a universal testing machine or a pressing machine.

Referring to fig. 5, the first connecting assembly 3 includes a first fixing base 31, a limiting member 34 penetrating through the first fixing base 31 along a vertical direction, a first connecting member 32 disposed on a top surface of the first fixing base 31, and a pair of fixing members 33 disposed on a bottom surface of the first fixing base 31. Wherein, a pair of fixing members 33 and a first connecting member 32 are integrally formed with the first fixing base 31.

Referring to fig. 2, fig. 5 and fig. 6, specifically, the fixing member 33 in the present application adopts a wedge structure, a plugging slot 6 is defined between the opposite end surfaces of the pair of fixing members 33 and the bottom surface of the first fixing seat 31, and the portion of the pressing head 11 and the pair of clamping members 12, which are close to the first fixing seat 31, together form a plugging portion 5, where the plugging portion 5 in the present application adopts a wedge structure adapted to the fixing member 33.

During installation, first connecting piece 32 is clamped on the clamping head of the upper machine seat to play a role in centering, then plug-in portion 5 is inserted into plug-in groove 6 along the width direction of first fixing seat 31, and then the position of limiting piece 34 is adjusted according to the actual thickness of currently selected pressure head 11, and limiting piece 34 is abutted against the surface of plug-in portion 5 facing first fixing seat 31, so that the side wall of plug-in portion 5 is matched and attached with the groove wall of plug-in groove 6, and the installation stability of plug-in portion 5 is improved. In this embodiment, the pressing head 11 and the pair of clamping members 12 are fixed on the first fixing seat 31, so as to complete the fixing operation of the pressing head 11 and the pair of fixing members 33, so that the pressing head 11 can be driven by the upper machine base to synchronously lift and move.

Specifically, in the examples of the present application, the cases where the thickness of the sample 7 is 1.0mm and 1.5mm are taken as examples. When the thickness t of the sample 7 is 1.0mm, a test is carried out by selecting a pressing head 11 with the thickness of 1.0mm (namely, the distance between a pair of clamping pieces 12 is 1.0 mm), the round angle r of the pressing head 11 is set to be 1.0mm, the groove width of the bending groove 211 is set to be 3.0mm, and the length of the part of the limiting piece 34 extending into the inserting groove 6 is 2mm;

when the thickness t of the sample 7 is 1.5mm, the test is performed by selecting the indenter 11 having a thickness of 1.5mm (i.e., the distance between the pair of clamping members 12 is 1.5 mm), the rounded corner r of the indenter 11 is set to 1.5mm, the groove width of the buckling groove 211 is set to 4mm, and at this time, since the distance between the pair of clamping members 12 is larger than that of the sample 7 when the thickness t is 1.0mm, the plugging portion 5 moves upward when t=1.5 mm than when t=1.0 mm, and the length of the portion of the stopper 34 extending into the plugging groove 6 is changed to 1.5mm.

Therefore, the wedge-shaped structure is formed by the inserting groove 6 and the inserting part 5, so that the pressure heads 11 with different thicknesses can be conveniently and rapidly replaced in the test process to be suitable for samples 7 with different thicknesses, and the application range of the test tool can be enlarged.

Referring to fig. 4 and 7, the second connecting assembly 4 includes a second fixing base 41, a connecting piece 43 for connecting the second fixing base 41 and the pressing base 21, and a second connecting piece 42 disposed on a side of the second fixing base 41 opposite to the pressing base 21. The second connecting piece 42 is integrally formed with the second fixing seat 41, and when the second connecting piece 42 is installed, the second connecting piece 42 is clamped on the chuck of the lower machine seat, so that the second fixing seat 41 is installed, and a centering effect is achieved.

Referring to fig. 6 and 7, it is emphasized that the first connector 32 and the second connector 42 in the embodiment of the present application each have a rectangular parallelepiped structure with a square cross section, which plays a role in centering.

Other members connected to the first connecting member 32 or the second connecting member 42 are disposed concentrically with the first connecting member 32 or the second connecting member 42 in the vertical direction to ensure accuracy of the finally obtained performance index of the bending formation of the sample 7.

Referring to fig. 4 and 7, specifically, the connecting member 43 includes a connecting pin 431 and a connecting bolt 432, where the connecting pin 431 and the connecting bolt 432 are disposed as a pair and are symmetrically distributed about the longitudinal axis of the pressing seat 21. The connection pins 431 and the connection bolts 432 are each arranged along the vertical direction.

Wherein, the top end of the connection pin 431 is integrally formed on the pressing seat 21, a first through hole 411 through which the bottom end of the connection pin 431 passes is provided on the second fixing seat 41 along the vertical direction, and the connection pin 431 is inserted into the first through hole 411 to complete the limitation of the pressing seat 21 in the horizontal direction.

In addition, the top end integrated into one piece of connecting bolt 432 is on the bottom surface of pressing seat 21, the second through-hole 412 that supplies connecting bolt 432 bottom to pass is run through equally along vertical direction on the second fixing base 41, threaded connection has nut 433 behind the bottom of connecting bolt 432 passed second fixing base 41 through second through-hole 412, nut 433 supports tightly on the bottom surface of second fixing base 41 for pressing seat 21 is fixed on second fixing base 41, thereby is fixed pressing seat 21 to the lower frame, promotes the stability of pressing seat 21 in the test process, reduces the possibility that abnormal movement appears when pressing seat 21 receives the pressure from pressure head 11.

The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The above examples only represent a few embodiments of the present application, which are described in more detail and are not to be construed as limiting the scope of the claims. It should be noted that it would be apparent to those skilled in the art that various modifications and improvements could be made without departing from the spirit of the present application, which would be within the scope of the present application. Accordingly, the scope of protection of the present application is to be determined by the claims appended hereto.

Claims (12)

1. The utility model provides a test fixture which characterized in that includes:

the pressing mechanism comprises a pressing head and a plurality of clamping pieces which are abutted against the pressing head; and

the pushing mechanism can move towards the pushing mechanism, and the pushing mechanism comprises a pressing seat used for placing a sample.

2. The test fixture of claim 1, wherein the press seat is provided with a press bending groove, the press bending groove penetrates through the press seat towards the side wall of the press head, the sample can cover the press bending groove, and the press head can be inserted into the press bending groove along the height direction.

3. The test fixture of claim 2, wherein the surface of the pressing seat facing the pressing head is provided with an insertion port, the bending groove is communicated with the insertion port, the pressing seat is provided with a guide surface at the insertion port, and the guide surface is connected with the edge of the insertion port and the surface of the pressing seat facing the pressing head.

4. The test fixture of claim 2, wherein the hold-down mechanism further comprises a positioning assembly disposed on the press seat and abutting against a side wall of the sample to prevent movement of the sample in a direction of a plane of the sample such that the sample always covers the press bending groove.

5. The test fixture of claim 4, wherein the positioning assembly comprises a plurality of positioning stop pins, the positioning stop pins are arranged on the surface of the pressing seat facing the pressing head, a part of the positioning stop pins are arranged at one end of the sample, the rest of the positioning stop pins are respectively arranged at two sides of the sample, and all the positioning stop pins are in butt joint with the side wall of the sample.

6. The test fixture of claim 1, wherein the pressing mechanism further comprises a fastener that passes through the plurality of clamps to clamp the plurality of clamps to the press head.

7. The test fixture of claim 1, wherein the clamping member is provided with a relief groove extending through a side wall of the clamping member.

8. A testing machine comprising a testing tool according to any one of claims 1-7, said testing machine further comprising an upper housing and a lower housing, said testing tool being disposed between said upper housing and said lower housing.

9. The machine of claim 8, further comprising a first connection assembly and a second connection assembly, wherein the ram and the plurality of clamps are connected to the upper housing by the first connection assembly, and wherein the press housing is connected to the lower housing by the second connection assembly.

10. The testing machine of claim 9, wherein the first connecting assembly comprises a first fixing seat, a first connecting piece and a pair of fixing pieces, the first connecting piece is arranged on one side of the first fixing seat, which faces away from the pressure head, the first connecting piece is used for connecting the first fixing seat and the upper machine seat, the pair of fixing pieces are arranged on the surface of the first fixing seat, which faces away from the first connecting piece, a plugging groove is defined between the first fixing seat and the pair of fixing pieces, and one ends of the pressure head and the pair of clamping pieces can be plugged into the plugging groove, so that the pair of fixing pieces are clamped on the pair of clamping pieces;

the second connecting assembly comprises a second fixing seat, a second connecting piece and a connecting piece, wherein the second connecting piece is arranged on one side, opposite to the pressing seat, of the second fixing seat, the second connecting piece is used for connecting the second fixing seat with the lower machine seat, and the connecting piece is used for connecting the second fixing seat with the pressing seat.

11. The testing machine of claim 10, wherein the portion of the ram and the pair of the holding members inserted into the insertion groove is an insertion portion configured such that a cross-sectional width gradually decreases from an end near the first fixing base toward an end far from the first fixing base, and the insertion portion is adapted to be inserted into the insertion groove in a width direction of the first fixing base.

12. The testing machine of claim 11, wherein the first connecting assembly further comprises a limiting member penetrating through the first fixing seat, and the limiting member is disposed along the height direction of the pressure head and abuts against the surface of the plugging portion facing the first fixing seat.