Serum pipettor

Abstract

The invention relates to the field of medical apparatus and instruments, and particularly discloses a serum pipettor which comprises a pipette and a grip, a pipetting exhaust tube communicated with the grip is fixed on the periphery of the grip, the pipetting exhaust tube is connected with the pipette through a pipetting connecting tube, a suction component capable of forming negative pressure in the pipetting exhaust tube is arranged in the grip, and the suction component is connected with the pipette through a pipetting connecting tube. When the handle is held, a pressing rod on the fixing assembly is pressed at the same time, a first piston in a piston barrel slides, negative pressure is generated in the piston barrel, negative pressure is generated on an adsorption head through a ventilation pipe to adsorb and fix a pipette, and therefore the handle and the pipette can be rapidly disassembled and assembled; meanwhile, the relative position between the grip and the transfer pipette can be freely adjusted, and when the transfer pipette is fixed on the adsorption head, the transfer pipette is positioned on one side of the grip, and the axes of the transfer pipette and the grip are parallel, so that the relative position between the transfer pipette and the grip is reduced, and an operator can conveniently insert the transfer pipette into a test tube and suck serum by holding the grip.

Description

Technical Field

[0001] This invention relates to the field of medical devices, specifically a serum pipette. Background Technology

[0002] Serum pipettes are generally used in conjunction with serum pipettes, primarily for transferring serum. The pipette is usually attached to the serum pipette. By holding the serum pipette and pressing the button, negative pressure is created in the pipette, allowing serum to be drawn. Because serum pipettes are relatively long, the distance between the operator's hand and the serum storage tube is relatively large when holding the pipette, and the tube opening is relatively small. If the hand holding the serum pipette shakes even slightly, the shaking at the end of the pipette used to draw serum is amplified by the length of the pipette, making it difficult to insert the pipette end into the tube and affecting the normal operation of serum transfer. Summary of the Invention

[0003] The purpose of this invention is to provide a serum pipette that overcomes the aforementioned deficiencies in the prior art.

[0004] According to a serum pipette of the present invention, a pipette and a handle are provided. A pipette aspiration tube communicating with the handle is fixed on the outer periphery of the handle. The pipette aspiration tube is connected to the pipette through a pipette connecting tube. An aspiration assembly that can create negative pressure in the pipette aspiration tube is provided inside the handle. The pipette is located on one side of the handle and the axes of the two are parallel to each other. A fixing assembly that fixes the pipette by adsorption through negative pressure is provided on the outer side of the handle. The fixing assembly includes two piston cylinders and two adsorption heads for adsorbing pipettes. A first piston is slidably disposed inside the piston cylinder. A pressure rod is fixed between the two first pistons, penetrating the outer peripheral wall of the piston cylinder. The first piston slides inside the piston cylinder as the pressure rod moves. The ends of the two piston cylinders are connected by a vent pipe. The two adsorption heads are fixed on the vent pipe and connected to the vent pipe. The adsorption head includes an adsorption tube and a suction cup fixed to one end of the adsorption tube. The suction cup is connected to the adsorption tube. The other end of the adsorption tube is fixed to and connected to the venting tube. A sealing gasket is fixed on the side of the suction cup near the pipette.

[0005] With the above technical solution, pressing the lever on the fixing component while holding the handle causes the first piston inside the piston cylinder to slide, creating a negative pressure inside the piston cylinder. This negative pressure, generated through the vent tube, causes the adsorption head to adsorb and fix the pipette, thus enabling quick assembly and disassembly of the handle and the pipette. Furthermore, the relative position between the handle and the pipette is freely adjustable. When the pipette is fixed to the adsorption head, it is located on one side of the handle, and their axes are parallel, thereby reducing the relative position between the pipette and the handle. This facilitates the operator inserting the pipette into the test tube and drawing serum by holding the handle.

[0006] Furthermore, the side of the suction cup near the pipette is an arc surface, and a cavity is formed on the side of the suction cup near the pipette that is recessed towards the adsorption tube, and the cavity is connected to the adsorption tube.

[0007] The above technical solution helps to increase the contact area between the sealing gasket and the outer periphery of the pipette, ensuring the sealing effect of the sealing gasket, and at the same time increasing the suction force of the suction cup to fix the pipette.

[0008] Furthermore, a first suction chamber is provided inside the piston cylinder, the first piston is slidably connected to the first suction chamber, the vent pipe is connected to the first suction chamber, a through groove is provided on the outer peripheral wall of the piston cylinder that communicates with the first suction chamber, and the two ends of the pressure rod pass through the two through grooves respectively and are fixed to the outer periphery of the two piston rods.

[0009] With the above technical solution, when the pressure bar is pressed towards the grip, the movement of the pressure bar drives the two first pistons to move towards the grip through the piston rod, which creates a negative pressure in the space between the first piston and the side wall of the first suction chamber away from the grip. This negative pressure is then generated at the adsorption head through the vent pipe, thereby achieving adsorption and fixing of the pipette.

[0010] Furthermore, a guide plate is fixedly provided in the first suction chamber, and a circular hole with the same cross-section as the piston rod is opened in the guide plate. A plurality of vent holes are evenly distributed circumferentially around the piston rod in the guide plate. The vent holes are connected to the circular hole. A plurality of guide strips are fixedly provided on the outer periphery of the piston rod. The plurality of guide strips are slidably connected to the plurality of vent holes respectively. A gap is formed between the side wall of the vent hole away from the piston rod and the end of the guide strip away from the piston rod.

[0011] Through the above technical solution, the piston rod slides through the circular hole in the guide plate, which provides guidance for the sliding of the piston rod and ensures the stability of the first piston when sliding. The setting of the vent hole is conducive to the air flow between the first piston and the guide plate, reducing the resistance encountered by the first piston when sliding.

[0012] Furthermore, a spring seat is fixed to the end of the piston rod away from the first piston, and a first return spring is fixed between the spring seat and the side wall of the first suction chamber near the handle.

[0013] The above technical solution utilizes the elastic force of the first return spring to facilitate the reset of the first piston.

[0014] Furthermore, the venting tube includes a first connecting tube and two second connecting tubes. The first connecting tube includes a vertical portion and two horizontal portions, and the two horizontal portions are connected to the vertical portion to form a "C" shape. The two adsorption tubes are fixed on the outer periphery of the vertical portion of the first connecting tube. The horizontal portion of the first connecting tube is parallel to the piston cylinder. The two ends of the first connecting tube are fixedly connected to the ends of the two piston cylinders away from the handle through the two second connecting tubes. The two second connecting tubes are respectively connected to the two first suction chambers.

[0015] Through the above technical solution, the negative pressure formed in the first suction chamber can create negative pressure in the two adsorption tubes through the first connecting pipe and the second connecting pipe, thereby creating negative pressure in the suction cup to achieve adsorption pipetting.

[0016] Furthermore, a connecting rod is fixedly connected between the horizontal portion of the first connecting pipe and the outer periphery of the piston cylinder.

[0017] The above technical solution helps to increase the stability of the first connecting tube, thereby ensuring the stability of the adsorption head when adsorbing liquid into the pipette.

[0018] Furthermore, the handle is hollow inside, and a fixing plate is fixedly provided on the inner side wall of the handle. The fixing plate divides the internal space of the handle into a second suction chamber located on the lower side of the fixing plate. One end of the pipetting suction tube extends into the handle and is fixed to the fixing plate and communicates with the second suction chamber. A screw that extends through the thickness of the fixing plate is slidably connected inside the fixing plate. The upper end of the screw extends upward and passes through the upper end of the handle. A second piston is fixed at the lower end of the handle. The second piston is slidably connected to the second suction chamber. A second return spring is fixed between the second piston and the fixing plate.

[0019] By pressing the screw, a negative pressure is created in the space between the second piston and the fixed plate. This negative pressure is then created in the pipette via the pipetting tube and the pipetting connection tube, thereby enabling the aspiration of serum.

[0020] Furthermore, a button is fixedly provided at the upper end of the screw, an internal thread is provided on the outer circumference of the screw, an adjusting nut is threadedly connected to the outer circumference of the screw, a rotating ring is rotatably connected to the lower end face of the adjusting nut, an indicator rod is fixedly provided on the lower end face of the rotating ring and extends downward through the upper end of the handle, and a scale is provided on the end face of the indicator rod away from the screw.

[0021] With the above technical solution, rotating the adjusting nut can adjust the distance between the adjusting nut and the upper end of the handle. The scale on the indicator rod indicates the amount of serum that can be drawn from the pipette when the button is pressed until the adjusting nut is in contact with the upper end of the adjusting nut. The scale on the indicator rod allows you to intuitively know how much serum can be drawn from the pipette after pressing the button once.

[0022] The beneficial effects of this invention are as follows: When the handle is held and the pressure rod on the fixing component is pressed, the first piston inside the piston cylinder slides, creating a negative pressure inside the piston cylinder. This negative pressure is then generated on the adsorption head through the vent tube, adsorbing and fixing the pipette. This allows for quick assembly and disassembly of the handle and the pipette. At the same time, the relative position between the handle and the pipette can be freely adjusted. Furthermore, when the pipette is fixed on the adsorption head, the pipette is located on one side of the handle and the axes of the two are parallel, thereby reducing the relative position between the pipette and the handle. This makes it easier for the operator to insert the pipette into the test tube and aspirate serum by holding the handle. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a cross-sectional schematic diagram of the grip in this invention; Figure 3 This is the present invention. Figure 2 Enlarged view of point A in the middle; Figure 4 This is the present invention. Figure 2 Enlarged view of point B in the middle; Figure 5 This is a cross-sectional schematic diagram of the piston cylinder in this invention; Figure 6 This is the present invention. Figure 5 Enlarged view of point C in the middle; Figure 7 This is a cross-sectional schematic diagram of the guide plate in this invention; Figure 8 This is a cross-sectional schematic diagram of the adsorption tube in this invention; Figure 9 This is the present invention. Figure 8 Enlarged diagram of point D in the middle.

[0024] In the picture: 10. Pipette; 20. Handle; 201. Second suction chamber; 21. Pipette suction tube; 22. Adjusting nut; 23. Button; 24. Screw; 25. Indicator rod; 26. Rotating ring; 27. Fixing plate; 28. Second piston; 29. ​​Second return spring; 30. Adsorption tube; 31. Suction cup; 32. Sealing washer; 40. First connecting tube; 41. Second connecting tube; 50. Piston cylinder; 501. First suction chamber; 502. Through groove; 51. Pressure rod; 52. First piston; 53. Guide plate; 531. Vent hole; 54. First return spring; 55. Spring seat; 56. Piston rod; 561. Guide bar; 60. Connecting rod; 70. Pipette connecting tube; 71. Connecting sleeve. Detailed Implementation

[0025] In the description of this invention, it should be understood that the terms "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the appendix. Figure 1 The orientations or positional relationships shown are merely for the purpose of simplifying the description of the present invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0026] To make the objectives and advantages of this invention clearer, the invention will be specifically described below with reference to embodiments. It should be understood that the following text is only used to describe one or more specific embodiments of the invention and does not strictly limit the scope of protection specifically claimed by the invention. As used herein, the terms up and down and left and right are not limited to their strict geometric definitions, but include tolerances for reasonable and inconsistent machining or human errors. The specific features of this serum pipette are described in detail below: An embodiment of the present invention: Reference Figures 1-9This invention provides a serum pipette, including a pipette 10 and a handle 20. A pipetting aspiration tube 21, communicating with the handle 20, is fixed to the outer periphery of the handle 20. The pipetting aspiration tube 21 and the pipette 10 are connected by a pipetting connecting tube 70. A connecting sleeve 71 is fixed to one end of the pipetting connecting tube 70 near the pipette 10 and is fitted onto the upper end of the pipette 10. The other end of the pipetting connecting tube 70 is fitted onto the pipetting aspiration tube 21, and the two are bonded together with an adhesive. A suction assembly is provided inside the handle 20 to create negative pressure in the pipetting aspiration tube 21. The pipette 10 is located on one side of the handle 20, and their axes are parallel to each other. A fixing assembly is provided on the outside of the handle 20 to fix the pipette 10 by negative pressure adsorption. The assembly includes two piston cylinders 50 and two adsorption heads for adsorbing the pipette 10. A first piston 52 is slidably disposed inside the piston cylinder 50. A pressure rod 51 is fixed between the two first pistons 52, penetrating the outer peripheral wall of the piston cylinder 50. The first pistons 52 slide inside the piston cylinder 50 as the pressure rod 51 moves. The ends of the two piston cylinders 50 are connected by a vent pipe. The two adsorption heads are fixed on the vent pipe and communicate with the vent pipe. Each adsorption head includes an adsorption tube 30 and a suction cup 31 fixed to one end of the adsorption tube 30. The suction cup 31 communicates with the adsorption tube 30. The other end of the adsorption tube 30 is fixed on the vent pipe and communicates with the vent pipe. A sealing gasket 32 ​​is fixed on the side of the suction cup 31 near the pipette 10.

[0027] Reference Figure 9 The side of the suction cup 31 near the pipette 10 is an arc surface. A cavity is formed on the side of the suction cup 31 near the pipette 10 that is recessed towards the adsorption tube 30. The cavity is connected to the adsorption tube 30.

[0028] Reference Figure 6 , Figure 7The piston cylinder 50 has a first suction chamber 501, and the first piston 52 is slidably connected to the first suction chamber 501. A rubber sealing ring is wrapped around the outer periphery of the first piston 52 to ensure the sealing between the first piston 52 and the first suction chamber 501. The vent pipe is connected to the first suction chamber 501. The outer peripheral wall of the piston cylinder 50 has a through groove 502 that communicates with the first suction chamber 501. The two ends of the pressure rod 51 pass through two through grooves 502 respectively and are fixed to the outer periphery of the two piston rods 56. The pressing part of the pressure rod 51 is designed as four arc-shaped depressions towards the handle 20. The piston rod 56 has a section for easy operation by pressing the lever 51 with the operator's fingers. A guide plate 53 is fixedly installed in the first suction chamber 501. A circular hole with the same cross-section as the piston rod 56 is opened in the guide plate 53. Several vent holes 531 are evenly distributed around the piston rod 56. The vent holes 531 are connected to the circular hole. Several guide strips 561 are fixedly installed on the outer periphery of the piston rod 56. The guide strips 561 are slidably connected to the several vent holes 531. A gap is formed between the side wall of the vent hole 531 away from the piston rod 56 and the end of the guide strip 561 away from the piston rod 56.

[0029] Reference Figure 6 A spring seat 55 is fixed to the end of the piston rod 56 away from the first piston 52, and a first return spring 54 is fixed between the spring seat 55 and the side wall of the first suction chamber 501 near the handle 20.

[0030] Reference Figure 1 , Figure 6 The ventilation tube includes a first connecting tube 40 and two second connecting tubes 41. The first connecting tube 40 includes a vertical part and two horizontal parts, and the two horizontal parts are connected to the vertical part to form a "C" shape. Two adsorption tubes 30 are fixed on the outer periphery of the vertical part of the first connecting tube 40. The horizontal part of the first connecting tube 40 is parallel to the piston cylinder 50. The two ends of the first connecting tube 40 are fixedly connected to the ends of the two piston cylinders 50 away from the handle 20 through the two second connecting tubes 41. The two second connecting tubes 41 are respectively connected to the two first suction chambers 501.

[0031] Reference Figure 1 A connecting rod 60 is fixedly connected between the horizontal part of the first connecting pipe 40 and the outer periphery of the piston cylinder 50.

[0032] Reference Figure 2 , Figure 4The handle 20 is hollow inside. A fixing plate 27 is fixed on the inner wall of the handle 20. The fixing plate 27 divides the internal space of the handle 20 into a second suction chamber 201 located on the lower side of the fixing plate 27. One end of the pipetting suction tube 21 extends into the handle 20 and is fixed on the fixing plate 27 and communicates with the second suction chamber 201. A screw 24 is slidably connected inside the fixing plate 27 and passes through its thickness. The upper end of the screw 24 extends upward and passes through the upper end of the handle 20. A second piston 28 is fixed at the lower end of the handle 20. The second piston 28 is slidably connected to the second suction chamber 201. A second return spring 29 is fixed between the second piston 28 and the fixing plate 27.

[0033] Reference Figure 2 , Figure 3 , Figure 4 A button 23 is fixedly installed at the upper end of the screw 24. An internal thread is provided on the outer circumference of the screw 24. An adjusting nut 22 is threadedly connected to the outer circumference of the screw 24. A rotating ring 26 is rotatably connected to the lower end face of the adjusting nut 22. An indicator rod 25 is fixed on the lower end face of the rotating ring 26, extending downward through the upper end of the handle 20. A scale (not shown) is provided on the end face of the indicator rod 25 away from the screw 24. The scale on the indicator rod 25 indicates the amount of serum that can be drawn from the pipette 10 when the button 23 is pressed until the adjusting nut 22 touches the upper end of the adjusting nut 22.

[0034] When in use, the connecting sleeve 71 is attached to the upper end of the pipette 10. According to the length of the serum storage test tube, a sufficient length is reserved on the pipette 10 so that the reserved length of the pipette 10 can be fully inserted into the test tube.

[0035] At this point, depending on the amount of serum to be drawn each time, rotate the adjusting nut 22. This will cause the adjusting nut 22 to move along the screw 24 towards the handle 20, thereby causing the indicator rod 25 to move downward. Observe the scale on the indicator rod 25 aligned with the upper end face of the adjusting nut 22. When the aligned scale is the same as the amount of serum to be drawn each time, stop rotating the adjusting nut 22. This means that when the button 23 is pressed once until the adjusting nut 22 abuts against the upper end of the handle 20, the amount of serum drawn into the pipette 10 is the scale value on the indicator rod 25 indicated by the upper end face of the adjusting nut 22.

[0036] Then, place the two suction cups 31 on the upper side of the reserved length of the pipette 10, with the sealing gasket 32 ​​abutting against the outer periphery of the pipette 10. Then, place the handle 20 in the palm of the hand near the thumb, and then press the lever 51 with all four fingers at the same time. This causes the piston rod 56 to move towards the handle 20, compressing the first return spring 54, which in turn drives the first piston 52 to move towards the handle 20. This creates a negative pressure in the space between the first piston 52 and the side wall of the first suction chamber 501 away from the handle 20. Through the first connecting pipe 40, the second connecting pipe 41, and the suction tube 30, a negative pressure is created in the suction cup 31, thereby adsorbing and fixing the pipette 10 onto the suction cup 31, while simultaneously holding the handle 20 in the palm of the hand.

[0037] By holding the handle 20, the lower end of the pipette 10 is inserted into the test tube. Since the handle 20 is close to the lower end of the pipette 10 at this time, it is easier for the lower end of the pipette 10 to be aligned with the test tube and inserted into it.

[0038] When the lower end of pipette 10 is submerged in serum, pressing button 23 causes screw 24 to move downward, thereby driving second piston 28 to move downward. Second return spring 29 extends, and the downward movement of second piston 28 creates negative pressure in the space between second piston 28 and fixed plate 27. This negative pressure is then created in pipette 10 through pipette suction tube 21 and pipette connecting tube 70, thus allowing serum in the test tube to be drawn into pipette 10.

[0039] When the pipette 10 is transferred to the test tube into which the serum needs to be injected, the button 23 is released. The second piston 28 moves upward under the pulling force of the second return spring 29. The pressure between the second piston 28 and the fixed plate 27 is restored, which causes the serum in the pipette 10 to be discharged.

[0040] After the serum transfer is completed, by releasing the lever 51, the spring seat 55 moves away from the handle 20 under the elastic force of the first return spring 54 and resets, which in turn causes the first piston 52 to move away from the handle 20, so that the air pressure in the suction cup 31 is restored, and the pipette 10 is separated from the sealing gasket 32.

[0041] Those skilled in the art will appreciate that various modifications to the above embodiments can be made without departing from the overall spirit and concept of the present invention. All such modifications fall within the protection scope of the present invention. The protection scheme of the present invention is defined by the appended claims.

Claims

1. A serum pipette, comprising a pipette (10) and a handle (20), characterized in that: The grip (20) is fixed with a pipetting aspiration tube (21) connected to it. The pipetting aspiration tube (21) and the pipetting tube (10) are connected by a pipetting connection tube (70). The grip (20) is provided with a suction assembly that can make the pipetting aspiration tube (21) form a negative pressure. The pipetting tube (10) is located on one side of the grip (20) and the axes of the two are parallel to each other. The grip (20) is provided with a fixing assembly that fixes the pipetting tube (10) by adsorption through negative pressure on the outside. The fixing assembly includes two piston cylinders (50) and two adsorption heads for adsorbing the pipette (10). A first piston (52) is slidably disposed inside the piston cylinder (50). A pressure rod (51) is fixed between the two first pistons (52) and penetrates the outer peripheral wall of the piston cylinder (50). The first piston (52) slides inside the piston cylinder (50) as the pressure rod (51) moves. The ends of the two piston cylinders (50) are connected by a vent pipe. The two adsorption heads are fixed on the vent pipe and connected to the vent pipe. The adsorption head includes an adsorption tube (30) and a suction cup (31) fixed at one end of the adsorption tube (30). The suction cup (31) is connected to the adsorption tube (30). The other end of the adsorption tube (30) is fixed to the venting tube and connected to the venting tube. A sealing gasket (32) is fixed on the side of the suction cup (31) near the pipette (10).

2. A serum pipette according to claim 1, characterized in that: The suction cup (31) has an arc-shaped side near the pipette (10). A cavity is formed on the side of the suction cup (31) near the pipette (10) that is recessed towards the adsorption tube (30). The cavity is connected to the adsorption tube (30).

3. A serum pipette according to claim 1, characterized in that: The piston cylinder (50) has a first suction chamber (501) inside, the first piston (52) is slidably connected to the first suction chamber (501), the vent pipe is connected to the first suction chamber (501), the piston cylinder (50) has a through groove (502) on its outer peripheral wall that is connected to the first suction chamber (501), and the two ends of the pressure rod (51) pass through the two through grooves (502) respectively and are fixed to the outer periphery of the two piston rods (56).

4. A serum pipette according to claim 3, characterized in that: A guide plate (53) is fixedly provided in the first suction chamber (501). A circular hole with the same cross-section as the piston rod (56) is opened in the guide plate (53). A number of ventilation holes (531) are evenly distributed around the piston rod (56) in the circumferential direction. The ventilation holes (531) are connected to the circular hole. A number of guide strips (561) are fixedly provided on the outer periphery of the piston rod (56). The guide strips (561) are slidably connected in the ventilation holes (531). A gap is formed between the side wall of the ventilation hole (531) away from the piston rod (56) and the end of the guide strip (561) away from the piston rod (56).

5. A serum pipette according to claim 4, characterized in that: A spring seat (55) is fixed at the end of the piston rod (56) away from the first piston (52), and a first return spring (54) is fixed between the spring seat (55) and the side wall of the first suction chamber (501) near the handle (20).

6. A serum pipette according to claim 3, characterized in that: The ventilation tube includes a first connecting tube (40) and two second connecting tubes (41). The first connecting tube (40) includes a vertical part and two horizontal parts, and the two horizontal parts are connected to the vertical part to form a "C" shape. The two adsorption tubes (30) are fixed on the outer periphery of the vertical part of the first connecting tube (40). The horizontal part of the first connecting tube (40) is parallel to the piston cylinder (50). The two ends of the first connecting tube (40) are fixedly connected to the ends of the two piston cylinders (50) away from the handle (20) through the two second connecting tubes (41). The two second connecting tubes (41) are respectively connected to the two first suction chambers (501).

7. A serum pipette according to claim 6, characterized in that: A connecting rod (60) is fixedly connected between the horizontal portion of the first connecting pipe (40) and the outer periphery of the piston cylinder (50).

8. A serum pipette according to claim 1, characterized in that: The handle (20) is hollow inside. A fixing plate (27) is fixed on the inner side wall of the handle (20). The fixing plate (27) divides the internal space of the handle (20) into a second suction chamber (201) located on the lower side of the fixing plate (27). One end of the pipetting suction tube (21) extends into the handle (20) and is fixed on the fixing plate (27) and communicates with the second suction chamber (201). A screw (24) is slidably connected inside the fixing plate (27) and extends through its thickness. The upper end of the screw (24) extends upward and passes through the upper end of the handle (20). A second piston (28) is fixed at the lower end of the handle (20). The second piston (28) is slidably connected to the second suction chamber (201). A second return spring (29) is fixed between the second piston (28) and the fixing plate (27).

9. A serum pipette according to claim 8, characterized in that: A button (23) is fixedly provided at the upper end of the screw (24). An internal thread is provided on the outer periphery of the screw (24). An adjusting nut (22) is threadedly connected to the outer periphery of the screw (24). A rotating ring (26) is rotatably connected to the lower end face of the adjusting nut (22). An indicator rod (25) is fixed on the lower end face of the rotating ring (26) and extends downward through the upper end of the handle (20). A scale is provided on the end face of the indicator rod (25) away from the screw (24).

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