A piston assembly and a method for increasing the service life of the piston assembly

Abstract

The present invention provides a piston assembly and a method for improving the service life of the piston assembly. The piston assembly includes a piston rod, a tensioning force providing body, a Teflon sleeve and a piston tube. The tensioning force providing body is connected to the head end of the piston rod, the tail end of the Teflon sleeve is connected to the piston rod, the tensioning force providing body applies a tensioning force along the circumference to the Teflon sleeve, and the outer circumference of the Teflon sleeve is in contact with the inner tube wall of the piston tube. By adopting the technical solution of the present invention, the Teflon sleeve fits and slides along the inner wall of the piston tube, the Teflon sleeve has a low friction coefficient, good self-lubrication, good wear resistance, and improved service life; a split structure is adopted between the Teflon sleeve and the tensioning force providing body, and when encountering a position where the roundness and straightness of the inner cavity of the piston tube are not good, the Teflon sleeve can adaptively keep in contact with the inner wall of the piston tube to ensure sealing and improve the pipetting accuracy. Since the precision requirements for the roundness and straightness of the inner cavity of the piston tube are reduced, the manufacturing cost is reduced, and the demand for automated pipetting can be met.

Description

Technical Field

[0001] The invention relates to the technical field of liquid transfer, in particular to a piston assembly and a method for prolonging the service life of the piston assembly. Background Art

[0002] In biochemical experiments, quantitative pipetting is a basic step of the experiment, and the accuracy of pipetting is an important factor affecting the experimental results. For manual pipettes, since manual operation is slow and the pipetting stroke is not large, the piston can generally be a rubber piston.

[0003] However, for some automated biochemical detection equipment or special automatic pipetting workstations, their pipetting mechanisms are required to have long service life, fast pipetting speed, high pipetting accuracy and other performance. Ordinary rubber pistons are not suitable due to their poor wear resistance and short service life. In the prior art, there are also rubber pistons with a layer of Teflon wear-resistant coating on the surface, which can improve the wear resistance of the piston, but the piston tube on the automated pipetting device is relatively slender, and the roundness and straightness of the inner cavity of the slender piston tube are difficult to achieve high precision, which will cause the piston to be unable to be fully and tightly combined with the piston tube throughout the entire circumference, affecting the sealing between the piston and the piston tube, and thus resulting in low pipetting accuracy. Summary of the invention

[0004] In order to overcome the above-mentioned deficiencies in the prior art, an object of the present invention is to provide a piston assembly and a method for increasing the service life of the piston assembly.

[0005] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention to solve its technical problem is: a piston assembly, including a piston rod, a tensioning force providing body, a Teflon sleeve and a piston tube, the tensioning force providing body is connected to the head end of the piston rod, the tail end of the Teflon sleeve is connected to the piston rod, the tensioning force providing body is located in the inner hole of the Teflon sleeve, and applies a tensioning force along the circumference outward to the Teflon sleeve, and the outer periphery of the Teflon sleeve is in contact with the inner tube wall of the piston tube.

[0006] By adopting the technical solution of the present invention, the Teflon sleeve fits and slides along the inner wall of the piston tube, the Teflon sleeve has a low friction coefficient, good self-lubrication, good wear resistance, and improved service life; a split structure is adopted between the Teflon sleeve and the tensioning force provider, and when encountering a position where the roundness and straightness of the inner cavity of the piston tube are not good, the Teflon sleeve can adaptively keep in contact with the inner wall of the piston tube to ensure sealing and improve pipetting accuracy. Since the accuracy requirements on the roundness and straightness of the inner cavity of the piston tube are reduced, the manufacturing cost is reduced and the needs of automated pipetting can be met.

[0007] Furthermore, the tensioning force providing body is an annular elastic member, an annular groove is provided on the piston rod, and the annular elastic member is installed in the annular groove.

[0008] The above preferred solution is adopted to facilitate installation and maintain the position stability of the annular elastic member.

[0009] Furthermore, there are multiple annular elastic members, and the multiple annular elastic members are distributed at intervals on the head end of the piston rod.

[0010] By adopting the above preferred solution, the Teflon sleeve and the piston tube are driven to form multiple tight-fitting seals in the length direction.

[0011] Furthermore, the tensioning force provider is a conical plastic part, the head end of the conical plastic part includes a conical outer wall surface and an inner conical hole, the head end outer diameter of the conical outer wall surface is larger than the tail end outer diameter, and the head end aperture of the inner conical hole is larger than the tail end aperture.

[0012] Furthermore, in a free state, the outer diameter of the head end of the tapered outer wall surface is larger than the inner tube diameter of the piston tube.

[0013] By adopting the above preferred scheme, the conical structure can be used to enable plastic parts with weaker elasticity to generate reliable radial external tension; since the conical plastic parts have almost no elastic deformation in the axial direction, this effectively avoids the negative impact of the deformation of the elastomer on the accuracy of pipetting when using the elastomer.

[0014] Furthermore, the cone angle of the tapered outer wall surface is smaller than the cone angle of the inner tapered hole, and the cone angle of the inner tapered hole is 10-30°.

[0015] The above preferred solution is adopted to ensure that the conical plastic part has a tough structure capable of generating stable external tension.

[0016] Furthermore, the wall thickness of the Teflon sleeve is less than 1 mm.

[0017] Furthermore, the wall thickness of the Teflon sleeve is 0.1-0.4 mm.

[0018] The above preferred solution is adopted to ensure that the Teflon sleeve has appropriate flexibility so as to maintain a stable fit with the inner wall of the piston tube.

[0019] Furthermore, the tail end of the Teflon sleeve is connected to the piston rod via a hoop.

[0020] The above preferred solution is adopted to ensure the reliability of the connection between the Teflon sleeve and the piston rod.

[0021] Furthermore, the piston rod includes a core rod and a rod sleeve, the core rod is inserted into the rod sleeve, the head end of the core rod protrudes from the head end of the rod sleeve, the tensioning force providing body is connected to the head end of the core rod, and the tail end of the Teflon sleeve is connected to the head end of the rod sleeve; and also includes a displacement adjustment mechanism for driving the rod sleeve to move axially relative to the core rod.

[0022] When the piston assembly is working, the position where the peripheral wear of the Teflon sleeve occurs mainly corresponds to the position of the tensioning force providing body. Through the above-mentioned preferred scheme, after a period of use, the relative position of the tensioning force providing body in the length direction of the Teflon sleeve can be changed to seal the unworn outer surface of the Teflon sleeve with the piston tube, so as to ensure a reliable sealing effect and thereby increase the service life of the piston assembly.

[0023] A method for increasing the service life of a piston assembly: after the piston assembly has been used a set number of times, a displacement adjustment mechanism is used to move the rod sleeve toward the tail end relative to the core rod, driving the Teflon sleeve to move backward relative to the tensioning force providing body, so as to change the axial position where the tensioning force providing body contacts the inner wall of the Teflon sleeve. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 It is a structural schematic diagram of the piston assembly of the present invention;

[0026] Figure 2 is a cross-sectional view of an embodiment of a piston assembly of the present invention;

[0027] Figure 3 yes Figure 2 A partial enlarged view of the middle part;

[0028] Figure 4 It is a schematic diagram of the structure in which the piston rod head adopts an annular elastic member;

[0029] Figure 5 is a cross-sectional view of another embodiment of the piston assembly of the present invention;

[0030] Figure 6 yes Figure 5 A partial enlarged view of point B in the middle;

[0031] Figure 7 It is a schematic diagram of the structure in which the piston rod head adopts a conical plastic part;

[0032] Figure 8 is a cross-sectional view of another embodiment of the piston assembly of the present invention;

[0033] Fig. 9 yes Figure 8 A partial enlarged view of point C in the middle;

[0034] Fig.10 yes Figure 8 A partial enlarged view of point D in the middle.

[0035] The numbers and letters in the figure represent the names of the corresponding parts:

[0036] 10-piston rod; 101-core rod; 102-rod sleeve; 11-ring groove; 12-card slot; 20-tensioning force provider; 21-annular elastic member; 22-conical plastic member; 221-conical outer wall surface; 222-inner conical hole; 30-Teflon sleeve; 40-piston tube; 50-hoop; 51-elastic washer; 60-displacement adjustment mechanism; 61-adjusting nut sleeve. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] like Figure 1-7 As shown, a piston assembly includes a piston rod 10, a tensioning force providing body 20, a Teflon sleeve 30 and a piston tube 40. The tensioning force providing body 20 is connected to the head end of the piston rod 10, and the tail end of the Teflon sleeve 30 is connected to the piston rod 10. The tensioning force providing body 20 is located in the sleeve of the Teflon sleeve 30 and applies a circumferential outward tensioning force to the Teflon sleeve 30. The outer periphery of the Teflon sleeve 30 is in contact with the inner tube wall of the piston tube 40.

[0039] The beneficial effects of adopting the above technical solution are: the Teflon sleeve fits and slides along the inner wall of the piston tube, the Teflon sleeve has a low friction coefficient, good self-lubrication, good wear resistance, and improved service life; a split structure is adopted between the Teflon sleeve and the tensioning force provider, and when encountering a position where the roundness and straightness of the inner cavity of the piston tube are not good, the Teflon sleeve can adaptively fit the inner wall of the piston tube to ensure sealing and improve pipetting accuracy. Since the accuracy requirements for the roundness and straightness of the inner cavity of the piston tube are reduced, the manufacturing cost is reduced.

[0040] In the present invention, the Teflon sleeve 30 is a thin-walled sleeve body formed of Teflon (PTFE). In other embodiments of the present invention, the length of the Teflon sleeve 30 is significantly greater than the width of the tensioning force providing body 20, that is, the Teflon sleeve 30 is only subjected to tension in a partial length section.

[0041] like Figure 2-4As shown, in other embodiments of the present invention, the tensioning force providing body 20 is an annular elastic member 21, the piston rod 10 is provided with an annular groove 11, and the annular elastic member 21 is installed in the annular groove 11. The beneficial effect of adopting the above technical solution is: convenient installation and maintaining the position stability of the annular elastic member.

[0042] In some other embodiments of the present invention, the annular elastic member 21 is made of elastic materials such as rubber or silicone.

[0043] In other embodiments of the present invention, there are multiple annular elastic members 21, and the multiple annular elastic members 21 are spaced apart and distributed at the head end of the piston rod 10. The beneficial effect of the above technical solution is that the Teflon sleeve and the piston tube are driven to form multiple tight seals in the length direction.

[0044] like Figure 5-7 As shown, in other embodiments of the present invention, the tensioning force providing body 20 is a conical plastic part 22, and the head end of the conical plastic part 22 includes a conical outer wall surface 221 and an inner conical hole 222, the outer diameter of the head end of the conical outer wall surface 221 is larger than the outer diameter of the tail end, and the aperture of the head end of the inner conical hole 222 is larger than the aperture of the tail end. In a free state, the outer diameter of the head end of the conical outer wall surface 221 is slightly larger than the inner tube diameter of the piston tube 40. The beneficial effects of adopting the above technical solution are: with the help of the conical structure, plastic parts with weak elasticity can also generate reliable radial external tension; because the conical plastic part has almost no elastic deformation in the axial direction, this effectively avoids the negative impact of the deformation of the elastomer on the accuracy of the pipetting volume when the elastomer is adopted.

[0045] In other embodiments of the present invention, the conical plastic part 22 may be made of PE plastic material, which is integrally injection molded at the head end of the piston rod 10. In order to enhance the bonding force between the conical plastic part and the piston rod, a process groove is pre-processed at the head end of the piston rod.

[0046] In other embodiments of the present invention, the cone angle of the conical outer wall surface 221 is smaller than the cone angle of the inner conical hole 222, and the cone angle of the inner conical hole 222 is 10-30 degrees. The beneficial effect of adopting the above technical solution is to ensure that the conical plastic part has a tough structure that can generate stable external tension.

[0047] In other embodiments of the present invention, the wall thickness of the Teflon sleeve 30 is less than 1 mm. Preferably, the wall thickness of the Teflon sleeve 30 is 0.1-0.4 mm. The beneficial effect of adopting the above technical solution is to ensure that the Teflon sleeve has appropriate flexibility to maintain a stable fit with the inner wall of the piston tube.

[0048] like Figure 3As shown, in other embodiments of the present invention, a slot 12 is provided on the piston rod 10, and the tail end of the Teflon sleeve 30 is connected to the slot 12 of the piston rod via a hoop 50. An elastic washer 51 can also be provided in the slot 12, and the tail end of the Teflon sleeve 30 is clamped on the elastic washer 51 via the hoop 50, so as to prevent it from loosening after long-term use. The beneficial effect of adopting the above technical solution is: ensuring the reliability of the connection between the Teflon sleeve and the piston rod.

[0049] like Figure 8-10 As shown, in other embodiments of the present invention, the piston rod 10 includes a core rod 101 and a rod sleeve 102, the core rod 101 is inserted into the rod sleeve 102, the head end of the core rod 101 protrudes from the head end of the rod sleeve 102, the tensioning force providing body 20 is connected to the head end of the core rod 101, and the tail end of the Teflon sleeve 30 is connected to the head end of the rod sleeve 102; and also includes a displacement adjustment mechanism 60 for driving the rod sleeve 102 to move axially relative to the core rod 101. After the piston assembly is used for a set number of times, the rod sleeve 102 is moved toward the tail end relative to the core rod 101 by the displacement adjustment mechanism 60, driving the Teflon sleeve 30 to move backward relative to the tensioning force providing body 20, so as to change the axial position where the tensioning force providing body 20 contacts the inner wall of the Teflon sleeve 30. When the piston assembly is working, the position where the peripheral wear of the Teflon sleeve occurs mainly corresponds to the position of the tensioning force providing body. Through the above-mentioned preferred technical scheme and method, after a period of use, the relative position of the tensioning force providing body in the length direction of the Teflon sleeve can be changed to seal the unworn outer surface of the Teflon sleeve with the piston tube, so as to ensure a reliable sealing effect, thereby significantly improving the service life of the piston assembly.

[0050] In other embodiments of the present invention, the specific form of the displacement adjustment mechanism is not limited and can be selected from the prior art, such as Fig. 9 As shown, the displacement adjustment mechanism 60 includes a positioning nut sleeve 61, which has an internal thread, and the tail end of the core rod 101 is provided with an external thread. The positioning nut sleeve 61 is screwed into the external thread of the core rod 101, and the end of the positioning nut sleeve 61 is also connected to the tail end of the rod sleeve 102 and has a relative rotational freedom. The axial movement of the rod sleeve 102 relative to the core rod 101 can be achieved by rotating the positioning nut sleeve 61. Furthermore, in order to achieve the purpose of automatic adjustment, the positioning nut sleeve can be driven to rotate by a motor. In order to make the structure compact, the motor can be a shaftless brushless motor with a mounting hole in the middle. The motor stator is connected to the rod sleeve, and the motor rotor is connected to the positioning nut sleeve. A displacement detection sensor for measuring the relative position of the rod sleeve and the core rod is installed.

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

Claims

1. A piston assembly, characterized in that: It comprises a piston rod, a tensioning force providing body, a Teflon sleeve and a piston tube, wherein the tensioning force providing body is connected to the head end of the piston rod, the tail end of the Teflon sleeve is connected to the piston rod, the tensioning force providing body is located in the sleeve of the Teflon sleeve and applies a circumferential outward tensioning force to the Teflon sleeve, and the outer periphery of the Teflon sleeve is in contact with the inner tube wall of the piston tube; The tension force providing body is a conical plastic part, the head end of the conical plastic part comprises a conical outer wall surface and an inner conical hole, the outer diameter of the head end of the conical outer wall surface is larger than the outer diameter of the tail end, and the hole diameter of the head end of the inner conical hole is larger than the hole diameter of the tail end; In a free state, the outer diameter of the head end of the tapered outer wall surface is larger than the inner diameter of the piston tube; The cone angle of the tapered outer wall surface is smaller than the cone angle of the inner tapered hole, and the cone angle of the inner tapered hole is 10-30°; The wall thickness of the Teflon sleeve is less than 1 mm.

2. The piston assembly according to claim 1, characterized in that The tail end of the Teflon sleeve is connected to the piston rod via a hoop.

3. The piston assembly according to claim 1, characterized in that The piston rod includes a core rod and a rod sleeve, the core rod is inserted into the rod sleeve, the head end of the core rod protrudes from the head end of the rod sleeve, the tensioning force providing body is connected to the head end of the core rod, and the tail end of the Teflon sleeve is connected to the head end of the rod sleeve; it also includes a displacement adjustment mechanism for driving the rod sleeve to move axially relative to the core rod.

4. A method for increasing the service life of a piston assembly, characterized in that: Using the piston assembly as described in claim 3, after the piston assembly has been used a set number of times, the rod sleeve is moved toward the tail end relative to the core rod through the displacement adjustment mechanism, driving the Teflon sleeve to move backward relative to the tensioning force providing body, so as to change the axial position of the tensioning force providing body in contact with the inner wall of the Teflon sleeve.

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