A cryogenic end piston of a cryogenic pump

Abstract

The present invention discloses a low-temperature end piston of a low-temperature pump, comprising a cylindrical piston body, wherein a plurality of sealing grooves are arranged on the outer circumference of the piston body; a first sealing structure and / or a second sealing structure are respectively arranged in the sealing grooves; the first sealing structure comprises a spring, a stepped elastic column and a first sealing ring; the second sealing structure comprises a second sealing ring, an elastic sheet and an opening structure; the first sealing structure and the second sealing structure are alternately arranged; or the first sealing structure and the second sealing structure are sequentially arranged along the piston body; under the cooperation of the first sealing structure and the second sealing structure, the low-temperature end piston of the low-temperature pump can better offset the thermal expansion and contraction effects caused by changes in ambient temperature, always maintain a good sealing state, and can make up for the gap caused by wear, thereby improving the service life and service life of the piston.

Description

Technical Field

[0001] The invention relates to the technical field of cryogenic pistons, and in particular to a low-temperature end piston of a cryogenic pump. Background Art

[0002] Some pumps transfer fluids at high pressures, while others produce fluids at low temperatures, processes that require the use of piston mechanisms.

[0003] The piston mechanism can generate reciprocating motion through external mechanical force or gas or liquid pressure to convert other energy into the required mechanical energy for use by mechanical equipment; the piston mechanism is mainly composed of a piston cylinder, a piston sleeved and fitted in the piston cylinder, and related sealing and fixing structures. For some piston mechanisms used in low-temperature and high-pressure environments, such as cryogenic liquid pumps, it is necessary to transport high-pressure and low-temperature liquid gas through a cryogenic pump; when the cryogenic pump pumps liquid, there will be a low-temperature cold end and a normally warm end. The piston structure near the cold end is easily affected by the external low temperature. The corresponding changes in temperature will cause certain thermal expansion and contraction of each structure. Especially for sealing structures, frequent thermal expansion and contraction will inevitably test the sealing performance. Therefore, it can be seen that how to perform better sealing is a problem that needs to be solved.

[0004] For example, a Chinese utility model patent (publication number: CN202719131U) disclosed a piston elastic sealing ring and a piston mechanism in 2013. The piston mechanism includes a piston, and one or more piston elastic sealing rings are installed on the outer periphery of the piston end. The piston elastic sealing ring includes an elastic metal sheet wound into a ring shape, and the metal sheet is covered with a carbon fiber sealing ring. The sealing ring has at least one Z-shaped staggered opening. The sealing ring can adapt to the changes caused by thermal expansion and contraction, and still has good sealing performance under the condition of hot and cold deformation of the piston cylinder; however, the Z-shaped staggered opening cannot ensure that the opening of the sealing ring can be aligned and connected during long-term movement; there is also a risk of misalignment between the elastic metal sheet and the sealing ring, which affects the sealing effect; and the material cost of carbon fiber is high, the processing difficulty is large, and the stress is not well controlled, which is not suitable for large-scale use.

[0005] In addition, during the frequent reciprocating motion of the piston, the sealing structure will wear, and the wear will reduce the sealing effect and affect the service life of the piston. Setting a single sealing structure on the piston cannot effectively resist this risk and cannot improve the life of the piston sealing assembly to increase the use or maintenance cycle of the piston. Summary of the invention

[0006] The purpose of the present invention is to provide a low temperature end piston of a cryogenic pump in view of the problems existing in the prior art.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] A low temperature end piston of a cryogenic pump comprises a cylindrical piston body, wherein a plurality of sealing grooves are arranged on the outer circumference of the piston body; a first sealing structure and / or a second sealing structure are respectively arranged in the sealing grooves;

[0009] The first sealing structure comprises a spring, a stepped elastic column and a first sealing ring; a plurality of circular holes are evenly distributed along the radial direction of the piston body in the sealing groove corresponding to the first sealing structure; the spring and the stepped elastic column are arranged in the circular holes, and one end of the stepped elastic column is sleeved in the spring; the first sealing ring is arranged in the sealing groove, and its inner circumferential surface is tightly fitted to the other end of the stepped elastic column;

[0010] The second sealing structure includes a second sealing ring and an elastic sheet; the second sealing ring has an opening structure, and the opening structure includes a first groove arranged at one end of the second sealing ring, and a protrusion arranged at the other end of the second sealing ring; the first groove is connected to and cooperates with the protrusion; a second groove is also arranged on the inner circumferential surface of the second sealing ring, and the elastic sheet is arranged in the second groove.

[0011] The low-temperature end piston is sealed by a multi-channel first sealing structure and a second sealing structure, and the sealing effect is good; when the low-temperature fluid is extracted from the low-temperature container through the low-temperature pump, the ambient temperature of the cold end of the low-temperature pump will be significantly reduced, and the temperature of the corresponding piston assembly will also be reduced; the thermal expansion and contraction effect of the piston and the seal is obvious;

[0012] With the cooperation of the spring and the stepped elastic column, the contact tightness between the first sealing ring and the piston and the piston cylinder can be adaptively adjusted according to environmental changes, and the first sealing ring can be automatically retracted and tightened after being worn during long-term reciprocating motion, thereby playing a role in supplementing and offsetting wear, and extending the service life of the first sealing structure as a whole; the radially uniformly distributed elastic columns are more uniform when providing elastic force, and the uniformly distributed circular holes are set to avoid opening too much internal accommodation space on the piston body, so as not to reduce the strength of the piston body. Even if the first sealing structure closest to one end of the hydraulic oil leaks during movement, a small amount of leaked oil can still be accommodated in the area where the spring is located, reducing the speed of further leakage to the next sealing structure.

[0013] Similarly, the elastic sheet and the second sealing ring in the second sealing structure can both expand and contract adaptively according to the stress conditions, always closely fit the piston body and the piston cylinder, and maintain a good sealing effect. There is also a good synergistic effect between the two. The second sealing ring with higher strength protects the elastic sheet to prevent frequent friction during reciprocating motion, which affects the service life and elastic deformation ability of the elastic sheet; at the same time, the elastic force of the elastic sheet can make up for the gap caused by the wear of the outer circumference of the second sealing ring during long-term friction.

[0014] The setting of the opening structure facilitates opening the second sealing ring to install the elastic sheet, and is also conducive to installation in the sealing groove of the piston body; after installation, the opening structure is always connected together, and at least one pair of parallel surfaces among the multiple matching surfaces are in contact with or overlapped with each other, which can withstand the axial or circumferential force of the second sealing structure, ensuring that the second sealing structure is always in a benign sealing state.

[0015] Furthermore, the first sealing structure and the second sealing structure are arranged alternately; or the first sealing structure and the second sealing structure are arranged sequentially along the piston body.

[0016] Furthermore, the circular holes in the same sealing groove are symmetrically arranged around the central axis of the piston body; the diameter of the circular hole is smaller than the axial width of the sealing groove; and the connection between the circular hole and the sealing groove is chamfered.

[0017] The circular holes arranged symmetrically in the center are conducive to each spring providing a balanced force; the corner arrangement avoids stress concentration at right angles and acute angles, and avoids the debris generated by damaged sealing grooves affecting the sealing effect.

[0018] Furthermore, the stepped elastic column has an integrally formed first cylinder and a second cylinder; the diameter of the first cylinder is smaller than the diameter of the second cylinder; the first cylinder is sleeved in the spring; the second cylinder and the inner wall of the circular hole confine the spring in the circular hole; the outer diameter of the second cylinder is smaller than or equal to the diameter of the circular hole.

[0019] The end surface of the second column that contacts the inner circumference of the first sealing ring is arc-shaped, and its contour and curvature are matched with the inner circumference of the first sealing ring.

[0020] Furthermore, the first groove is arranged along the circumference of the second sealing ring and penetrates the inner circumferential surface and the outer circumferential surface of the second sealing ring in the radial direction; the corresponding protrusion is also arranged along the circumference of the second sealing ring.

[0021] Furthermore, the first groove is arranged along the axial direction of the second sealing ring and penetrates the second sealing ring in the axial direction; and the corresponding protrusion is also arranged along the axial direction of the second sealing ring.

[0022] During the long-term reciprocating motion, the cooperation of the first groove, the protrusion and the elastic sheets arranged in a staggered manner prevents the opening of the second sealing structure from being misaligned.

[0023] Furthermore, the elastic sheet has an elastic sheet opening, and the elastic sheet opening is staggered from the opening structure by 90° to 180°; one end of the elastic sheet is closely attached to the inner wall of the second groove, and the other end radially leaks out of the second groove.

[0024] Leaking part of the elastic sheet inside is conducive to one end of the elastic sheet tightly fitting the sealing groove and the other end tightly fitting in the second groove, avoiding a gap between the second groove and the corresponding sealing groove to affect the sealing effect.

[0025] Furthermore, an internal threaded hole is opened in the middle of one end of the piston body, and the internal threaded hole is used to fix the piston rod; a piston head is provided at the other end of the piston body, and a torsion zone is provided at the end surface of the piston head close to the piston body, and the torsion zone is strengthened; the end surface of the piston body close to the piston head is an inclined surface, which gradually bulges toward the middle.

[0026] Since the piston body needs to be threadedly connected to the piston rod, an area for installing a caliper or a clamp needs to be set on the piston body. Since the outer circumferential surface of the piston body is a very important matching surface, directly clamping the caliper on the outer circumferential surface will damage the piston body and affect the sealing effect; setting a torsion zone near the end face of the piston head can allow the caliper to have a suitable position to clamp the piston body, which is convenient for the threaded twisting of the piston rod and the piston body; the outer circumferential surface of the torsion zone is made into a polygonal plane and reinforced to increase the strength.

[0027] The setting of the torsion zone and the end face slope is beneficial to reducing the dead volume between the piston body and the end of the piston cylinder after the piston head is pushed into the end of the piston cylinder, reducing the accumulation of oil in this area. During the reciprocating motion, less foam is generated by the liquid in the dead volume, which is conducive to reflux.

[0028] Furthermore, there are four sealing grooves which are equidistantly and parallelly arranged in the outer circumferential surface of the piston body; the piston body is also provided with sliding rings on both sides of the sealing grooves.

[0029] A cryogenic pump comprises any one of the cryogenic end pistons described above.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The low-temperature end piston of the cryogenic pump can better offset the thermal expansion and contraction effect caused by the change of ambient temperature under the cooperation of the first sealing structure and the second sealing structure, always maintain a good sealing state, and have a long service life; 2. The cooperation of the spring and the elastic column can adaptively adjust the contact tightness between the first sealing ring and the piston and the piston cylinder according to environmental changes, and play a role in supplementing and offsetting wear in long-term reciprocating motion, thereby extending the service life of the first sealing structure as a whole; 3. The second sealing ring with higher strength protects the elastic sheet to avoid frequent friction during reciprocating motion; at the same time, the elastic force of the elastic sheet can make up for the gap caused by wear of the second sealing ring during long-term friction; 4. The torsion zone allows the caliper to have a suitable position to clamp the piston body, which is convenient for the threaded twisting of the piston rod and the piston body; 5. The dead volume between the piston body and the end of the piston cylinder is small, which reduces the accumulation of oil and the generation of foam in this area, and is conducive to reflux. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a structural schematic diagram of a low-temperature end piston of a cryogenic pump of the present invention;

[0032] Figure 2 It is a schematic diagram of the structure of the low-temperature end piston of a cryogenic pump in the A direction of the present invention;

[0033] Figure 3 It is a schematic diagram of the BB structure of a low-temperature end piston of a cryogenic pump of the present invention;

[0034] Figure 4 It is a schematic diagram of a second sealing structure of a low-temperature end piston of a cryogenic pump of the present invention;

[0035] Figure 5 It is a C-direction enlarged schematic diagram of a second sealing structure of a low-temperature end piston of a cryogenic pump of the present invention;

[0036] Figure 6 It is an enlarged schematic diagram in the DD direction of the second sealing structure of the low-temperature end piston of a cryogenic pump of the present invention;

[0037] Figure 7 It is a structural schematic diagram of a low-temperature end piston of another cryogenic pump of the present invention;

[0038] In the figure: 1. piston body; 2. first sealing structure; 201. spring; 202. stepped elastic column; 203. first sealing ring; 204. circular hole; 3. second sealing structure; 301. second sealing ring; 302. elastic sheet; 303. opening structure; 304. elastic sheet opening; 4. internal threaded hole; 5. piston head; 6. torque zone; 7. sliding ring; 8. first groove; 801. horizontal side one of groove; 802. horizontal side two of groove; 9. protrusion; 901. horizontal side one of protrusion; 902. horizontal side two of protrusion; 10. second groove. DETAILED DESCRIPTION

[0039] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings 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.

[0040] In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "middle", "upper", "lower", "left", "right", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0041] Embodiment 1:

[0042] like Figure 1 to Figure 6 As shown, a low temperature end piston of a cryogenic pump comprises a cylindrical piston body 1, wherein four sealing grooves are arranged on the outer circumference of the piston body 1; and first sealing structures 2 and second sealing structures 3 are alternately arranged in the sealing grooves;

[0043] The first sealing structure 2 includes a spring 201, a stepped elastic column 202 and a first sealing ring 203; Figure 3 As shown, each of the sealing grooves corresponding to the first sealing structure 2 has eight circular holes 204 evenly distributed along the radial direction of the piston body 1; the spring 201 and the stepped elastic column 202 are arranged in the circular holes 204, and one end of the stepped elastic column 202 is sleeved in the spring 201; the first sealing ring 203 is arranged in the sealing groove, and its inner circumferential surface is tightly fitted to the other end of the stepped elastic column 202;

[0044] like Figure 4As shown, the second sealing structure 3 includes a second sealing ring 301 and an elastic sheet 302; the second sealing ring 301 has an opening structure 303, and the opening structure 303 includes a first groove 8 arranged at one end of the second sealing ring 301, and a protrusion 9 arranged at the other end of the second sealing ring 301; the first groove 8 is connected to and cooperates with the protrusion 9; the second sealing ring 301 is also provided with a second groove 10 on the inner circumferential surface, and the elastic sheet 302 is arranged in the second groove 10.

[0045] The low-temperature end piston of the present invention is sealed by a multi-channel first sealing structure 2 and a second sealing structure 3, and the sealing effect is good; when the low-temperature fluid is extracted from the low-temperature container through the low-temperature pump, the ambient temperature of the cold end of the low-temperature pump will be significantly reduced, and the temperature of the corresponding piston assembly will also be reduced; the thermal expansion and contraction effect of the piston and the sealing component is obvious;

[0046] With the cooperation of the spring 201 and the stepped elastic column 202, the contact tightness between the first sealing ring 203 and the piston and the piston cylinder can be adaptively adjusted according to environmental changes, and the first sealing ring 203 can be automatically retracted and tightened after being worn during long-term reciprocating motion, thereby playing a role in supplementing and offsetting wear, and extending the service life of the first sealing structure as a whole; the radially uniformly distributed elastic columns are more uniform when providing elastic force, and the uniformly distributed circular holes are set to avoid opening too much internal accommodation space on the piston body, so as not to reduce the strength of the piston body. Even if the first sealing structure 2 closest to one end of the hydraulic oil leaks during movement, a small amount of leaked oil can still be accommodated in the area where the spring is located, reducing the speed of further leakage to the next sealing structure.

[0047] Similarly, the elastic sheet 302 and the second sealing ring 301 in the second sealing structure 3 can both expand and contract adaptively according to the stress conditions, always closely fit the piston body and the piston cylinder, and maintain a good sealing effect. There is also a good synergistic effect between the two. The second sealing ring 301 with higher strength protects the elastic sheet 302, preventing it from frequent friction during reciprocating motion, which affects the life and elastic deformation ability of the elastic sheet 302; at the same time, the elastic force of the elastic sheet 302 can make up for the gap caused by the wear of the outer circumference of the second sealing ring 301 during long-term friction.

[0048] The setting of the opening structure 303 facilitates opening the second sealing ring 301 to install the elastic sheet 302, and is also convenient for installation in the sealing groove of the piston body 1; after installation, the opening structure 303 is always connected together, and at least one pair of parallel surfaces among the multiple matching surfaces are in contact with or overlapped with each other, which can withstand the axial or circumferential force of the second sealing structure 3, ensuring that the second sealing structure 3 is always in a benign sealing state.

[0049] Furthermore, the diameter of the circular hole 204 is smaller than the axial width of the sealing groove; and the connection between the circular hole 204 and the sealing groove is chamfered.

[0050] The circular holes 204 arranged symmetrically in the center are conducive to each spring providing a balanced force; the corner arrangement avoids stress concentration at right angles and acute angles, and avoids debris generated by damaged sealing grooves affecting the sealing effect.

[0051] Furthermore, the stepped elastic column 202 has an integrally formed first column and a second column; the diameter of the first column is smaller than the diameter of the second column; the first column is sleeved in the spring; the second column and the inner wall of the circular hole 204 restrict the spring 201 in the circular hole 204; the outer diameter of the second column is smaller than or equal to the diameter of the circular hole 204.

[0052] The end surface of the stepped elastic column 202 that contacts the inner circumference of the first sealing ring 203 is arc-shaped, and its contour and curvature are adapted to the inner circumference of the first sealing ring 203 .

[0053] Further, such as Figure 5 As shown, the first groove 8 is arranged along the circumference of the second sealing ring 301 and radially penetrates the inner circumferential surface and the outer circumferential surface of the second sealing ring 301 ; the corresponding protrusion 9 is also arranged along the circumferential direction of the second sealing ring 301 .

[0054] During the long-term reciprocating motion, the cooperation of the first groove, the protrusion and the elastic sheets arranged in a staggered manner prevents the opening of the second sealing structure from being misaligned.

[0055] Specifically, the opening structure 303 is always connected together, and at least one pair of parallel surfaces among the five matching surfaces are in contact with or overlapped with each other, such as the groove horizontal edge 801 and the protruding horizontal edge 901 remain parallel and in contact, and the groove horizontal edge 802 and the protruding horizontal edge 902 remain parallel and in contact; it can withstand the axial force of the sealing component; and ensure that the sealing component is always in a sealed state.

[0056] Furthermore, the elastic sheet 302 has an elastic sheet opening 304 , and the elastic sheet opening 304 is staggered from the opening structure by 90°; one end of the elastic sheet 302 is closely attached to the inner wall of the second groove 10 , and the other end radially leaks out of the second groove 10 .

[0057] Part of the elastic sheet 302 leaking out from the inside is conducive to one end of the elastic sheet 302 tightly fitting the sealing groove and the other end tightly fitting in the second groove 10, thereby reducing the gap between the second groove 10 and the corresponding sealing groove and affecting the sealing effect.

[0058] Furthermore, an internal threaded hole 4 is opened in the middle of one end of the piston body 1, and the internal threaded hole 4 is used to fix the piston rod; the other end of the piston body 1 is provided with a piston head 5, and the part of the piston head 5 close to the end surface of the piston body 1 is provided with a torsion zone 6, and the torsion zone 6 is strengthened; the end surface of the piston body 1 close to the piston head 5 is an inclined surface, which gradually bulges toward the middle.

[0059] The setting of the torsion zone 6 enables the caliper to have a suitable position to clamp the piston body 1, so as to facilitate the threaded twisting of the piston rod and the piston body 1; the outer contour surface of the torsion zone 6 is a hexagonal surface and is reinforced to increase the strength.

[0060] The setting of the torsion zone 6 and the end face slope is also beneficial to reducing the dead volume between the piston body 1 and the end of the piston cylinder after the piston head is pushed into the end of the piston cylinder, reducing the accumulation of oil in this area. During the reciprocating motion, less foam is generated by the liquid in the dead volume, which is conducive to reflux.

[0061] Furthermore, the sealing grooves are arranged in parallel and equidistantly in the outer circumferential surface of the piston body 1 ; the piston body 1 is also provided with a sliding ring 7 on a side close to the piston head 5 .

[0062] Embodiment 2:

[0063] The difference between this embodiment and the first embodiment is that the first sealing structure and the second sealing structure are arranged at different positions.

[0064] Specifically, Figure 7 As shown, the second sealing structure 3 and the first sealing structure 2 are sequentially arranged from left to right along the piston body 1. With this arrangement, the thickness of the internal solid part of the piston body 1 is basically consistent, thereby enhancing the strength and stability of the piston body. In particular, the solid thickness of the piston body corresponding to the internal threaded hole 4 is increased, thereby enhancing the connection strength at this location.

[0065] Embodiment three:

[0066] The difference between this embodiment and the first embodiment is that the arrangement of the opening structure is different.

[0067] The first groove 8 is arranged along the axial direction of the second sealing ring 301 , and penetrates the upper and lower end surfaces of the second sealing ring 301 in the axial direction; the corresponding protrusion 9 is also arranged along the axial direction of the second sealing ring 301 .

[0068] With the opening structure of the present structure, the grooving direction of the first groove is consistent with the direction of the reciprocating motion of the piston. When the pump piston assembly is arranged in the sealing groove of the piston, the inner side of the sealing groove can just cover the first groove and can press the protrusion, thereby preventing the protrusion from axially moving in the first groove and preventing its misalignment. At the same time, there is only one axial interface seam on the outer circumferential surface of the second sealing ring 301. After being squeezed and deformed, the interface seam will become very small, thereby reducing the possibility of fluid leakage and improving the sealing performance.

[0069] Embodiment 4:

[0070] A cryopump, wherein a piston assembly is provided at a cold end of the cryopump, wherein the piston assembly comprises the piston described in the first embodiment, wherein the piston comprises a cylindrical piston body, wherein a plurality of sealing grooves are provided on the outer circumference of the piston body; wherein a first sealing structure and / or a second sealing structure are respectively provided in the sealing grooves;

[0071] The first sealing structure comprises a spring, a stepped elastic column and a first sealing ring; a plurality of circular holes are evenly distributed along the radial direction of the piston body in the sealing groove corresponding to the first sealing structure; the spring and the stepped elastic column are arranged in the circular holes, and one end of the stepped elastic column is sleeved in the spring; the first sealing ring is arranged in the sealing groove, and its inner circumferential surface is tightly fitted to the other end of the stepped elastic column;

[0072] The second sealing structure includes a second sealing ring and an elastic sheet; the second sealing ring has an opening structure, and the opening structure includes a first groove arranged at one end of the second sealing ring, and a protrusion arranged at the other end of the second sealing ring; the first groove is connected to and cooperates with the protrusion; a second groove is also arranged on the inner circumferential surface of the second sealing ring, and the elastic sheet is arranged in the second groove.

[0073] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A low temperature end piston of a cryogenic pump, comprising a cylindrical piston body, wherein a plurality of sealing grooves are provided on the outer circumference of the piston body; characterized in that: The sealing groove is provided with a first sealing structure and a second sealing structure respectively; the first sealing structure and the second sealing structure are arranged alternately; or the first sealing structure and the second sealing structure are arranged sequentially along the piston body; The first sealing structure comprises a spring, a stepped elastic column and a first sealing ring; a plurality of circular holes are evenly distributed along the radial direction of the piston body in the sealing groove corresponding to the first sealing structure; the spring and the stepped elastic column are arranged in the circular hole, and one end of the stepped elastic column is sleeved in the spring; the first sealing ring is arranged in the sealing groove, and its inner circumferential surface is tightly fitted to the other end of the stepped elastic column; the stepped elastic column has an integrally formed first column and a second column; the diameter of the first column is smaller than the diameter of the second column; the first column is sleeved in the spring; the second column and the inner wall of the circular hole restrict the spring in the circular hole; the outer diameter of the second column is smaller than or equal to the diameter of the circular hole; The second sealing structure includes a second sealing ring and an elastic sheet; the second sealing ring has an opening structure, and the opening structure includes a first groove arranged at one end of the second sealing ring, and a protrusion arranged at the other end of the second sealing ring; the first groove is connected to and matched with the protrusion; a second groove is also arranged on the inner circumferential surface of the second sealing ring, and the elastic sheet is arranged in the second groove; the opening structure is always connected together, and at least one pair of parallel surfaces among the five matching surfaces of the opening structure are in contact with each other or overlapped.

2. The low temperature end piston of a cryogenic pump according to claim 1, characterized in that: The circular holes in the same sealing groove are symmetrically arranged around the central axis of the piston body; the diameter of the circular hole is smaller than the axial width of the sealing groove; and the connection between the circular hole and the sealing groove is chamfered.

3. The low temperature end piston of a cryogenic pump according to claim 1, characterized in that: The first groove is arranged along the circumference of the second sealing ring and penetrates the inner circumferential surface and the outer circumferential surface of the second sealing ring in the radial direction; the corresponding protrusion is also arranged along the circumferential direction of the second sealing ring.

4. The low temperature end piston of a cryogenic pump according to claim 1, characterized in that: The first groove is arranged along the axial direction of the second sealing ring and penetrates the second sealing ring in the axial direction; the corresponding protrusion is also arranged along the axial direction of the second sealing ring.

5. The low temperature end piston of a cryogenic pump according to claim 1, characterized in that: The elastic sheet has an elastic sheet opening, and the elastic sheet opening is staggered from the opening structure by 90° to 180°; one end of the elastic sheet is closely attached to the inner wall of the second groove, and the other end radially leaks out of the second groove.

6. The low temperature end piston of a cryogenic pump according to claim 1, characterized in that: An internal threaded hole is opened in the middle of one end of the piston body, and the internal threaded hole is used to fix the piston rod; a piston head is provided at the other end of the piston body, and a torsion zone is provided at the end surface of the piston head close to the piston body, and the torsion zone is strengthened; the end surface of the piston body close to the piston head is an inclined surface, which gradually bulges toward the middle.

7. The low temperature end piston of a cryogenic pump according to claim 1, characterized in that: There are four sealing grooves which are arranged in parallel and at equal distances in the outer circumferential surface of the piston body; the piston body is also provided with sliding rings on both sides of the sealing grooves.

8. A cryopump, characterized in that: The cryogenic pump comprises the low-temperature end piston according to any one of claims 1 to 7.

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