A cold end structure of an ultra-low temperature and ultra-high pressure pump

Abstract

The present invention relates to a cold end structure of an ultra-low temperature and ultra-high pressure pump, and relates to the field of ultra-low temperature pumping. The cold end structure comprises an outer cylinder sleeve capable of inhaling liquid nitrogen, liquid oxygen, liquid hydrogen or LNG, a piston rod slidably connected to the outer cylinder sleeve, an inner cylinder sleeve sleeved between the piston rod and the outer cylinder sleeve, an inner core fixedly connected to one end of the outer cylinder sleeve, a discharge one-way valve slidably connected to the inner core, a discharge joint fixedly connected to one end of the outer cylinder sleeve, a cover fixedly connected to the other end of the outer cylinder sleeve, and a slip connected to a driving component; the slip is a semi-cylindrical shell structure, and the two ends of the two slips in the axial direction are buckled to the outside of the driving shaft of the driving component at one end of the piston rod extending out of the outer cylinder sleeve, and the two slips do not contact and are connected by a bolt pair. The present invention has the advantage of being able to well perform ultra-high pressure compression pumping of ultra-low temperature media.

Description

Technical Field

[0001] The present invention relates to the technical field of ultra-low temperature pumping, and in particular to a cold end structure of an ultra-low temperature and ultra-high pressure pump. Background Art

[0002] The liquid nitrogen (oxygen, LNG, hydrogen) cold end is a core component of a liquid nitrogen (oxygen, LNG, hydrogen) pump. It can penetrate ultra-low temperature environments, enabling high-pressure pumping of liquid nitrogen (liquid oxygen, LNG, liquid hydrogen). This allows for specialized exploration and development operations such as nitrogen gas lift, nitrogen displacement, nitrogen fracturing, and mixed gas acidizing. Because liquid nitrogen (oxygen, LNG, hydrogen) pumps are specialized equipment, the media they transport are characterized by high pressure and low temperatures. Therefore, triplex pumps used in oilfields, such as water injection pumps and fracturing pumps, are not suitable for transporting cryogenic liquids. Furthermore, the inlet and outlet valve blocks used in existing motorized reciprocating pumps are complex in structure, have numerous vulnerable parts, and exhibit low reliability.

[0003] Therefore, in view of the above shortcomings, it is necessary to provide a cold end structure of an ultra-low temperature and ultra-high pressure pump. Summary of the Invention

[0004] (1) Technical issues to be resolved

[0005] The technical problem to be solved by the present invention is how to improve the reliability of the ultra-low temperature cold end.

[0006] (2) Technical solution

[0007] In order to solve the above technical problems, the present invention provides a cold end structure of an ultra-low temperature and ultra-high pressure pump, including an outer cylinder sleeve that can inhale liquid nitrogen, liquid oxygen, liquid hydrogen or LNG, a piston rod slidably connected to the outer cylinder sleeve, an inner cylinder sleeve sleeved between the piston rod and the outer cylinder sleeve, an inner core fixedly connected to one end of the outer cylinder sleeve, a discharge one-way valve slidably connected to the inner core, a discharge joint fixedly connected to one end of the outer cylinder sleeve, a cover fixedly connected to the other end of the outer cylinder sleeve and a slip connected to the driving component; the slip is a semi-cylindrical shell structure, and the two ends of the two slips in the axial direction are buckled to the end of the piston rod extending out of the outer cylinder sleeve and the outside of the driving shaft of the driving component. The two slips do not contact and are connected by a bolt pair.

[0008] As a further illustration of the present invention, preferably, a bolt hole is opened in the middle of the slip, and the bolt pair is inserted into the bolt hole and is located between the drive shaft and the piston rod so that the drive shaft does not contact the piston rod.

[0009] As a further explanation of the present invention, preferably, the diameter of the part of the piston rod extending into the outer cylinder sleeve is reduced, and the inner cylinder sleeve is sleeved on the outside of the end of the piston rod with reduced diameter. A plurality of overflow grooves are provided at intervals on the outer wall of the inner cylinder sleeve. The length direction of the overflow groove is the same as the length direction of the inner cylinder sleeve. One end of the overflow groove close to the inner core is closed and the other end is open. An overflow port is provided on the outer cylinder sleeve at the closed end of the overflow groove, and the overflow port is connected to the overflow groove.

[0010] As a further illustration of the present invention, preferably, a plurality of piston rings are inserted into the interface between the piston rod and the inner cylinder sleeve, and the piston rings are fitted in pairs and the outer walls thereof are in contact with the inner cylinder sleeve.

[0011] As a further illustration of the present invention, preferably, an expansion ring is inserted between the inner wall surface of the piston ring and the piston rod, and the outer wall surface of the expansion ring abuts against the inner wall surface of the piston ring to push the piston ring toward the inner cylinder sleeve.

[0012] As a further illustration of the present invention, preferably, a guide ring is inserted into the piston rod between the piston ring and the inner core, and the guide ring is interference fit with the inner cylinder sleeve at room temperature.

[0013] As a further explanation of the present invention, preferably, multiple layers of packing are arranged along the axial direction between the piston rod and the outer cylinder sleeve. The packing is conical and the end with a smaller outer diameter is facing the inner core. A pressure ring with a conical groove is inserted between adjacent packings, and the pressure ring abuts against the conical surface of the packing and the outer cylinder sleeve.

[0014] As a further illustration of the present invention, preferably, a ring is provided at the end of the packing with a larger outer diameter, the outer diameter of the ring is equal to the inner diameter of the outer cylinder sleeve, and the side surface of the pressure ring abuts against the ring.

[0015] As a further illustration of the present invention, preferably, a waterline seal is provided at the junction of the inner cylinder sleeve and the inner core, a waterline seal is adopted on the inner side of the junction surface between the inner core and the drain joint, and a non-metallic wedge seal is adopted on the outer side.

[0016] (3) Beneficial effects

[0017] The above technical solution of the present invention has the following advantages:

[0018] 1. The cold end designed in the present invention has high assembly adaptability. Since the connection end adopts a slip connection compensator structure design, the coaxiality requirement between the cold end and the drive device is reduced, and the piston can be automatically compensated in the radial direction, thereby achieving higher stroke requirements. The stroke rate of an ordinary cold end is usually 200 to 300 strokes / min. However, due to the use of a replaceable special material inner cylinder liner, the cold end of the present invention can reach a maximum stroke rate of 1000 strokes / min, which is three times that of an ordinary cold end.

[0019] 2. The present invention achieves a larger cold end displacement through the linkage of various components. Under the condition of the same cylinder diameter, the displacement of a single cold end is 3 to 4 times that of an ordinary cold end.

[0020] 3. The present invention achieves a stronger pressure resistance of the cold end structure through the coordinated coordination of various components. The normal pressure resistance of a common cold end of the same cylinder diameter is 35-40 MPa, while the maximum pressure resistance of the cold end of the present invention can reach 140 MPa, which is 3-4 times the pressure resistance limit of the common cold end.

[0021] 4. The present invention extends the service life of the cold end as a whole through the linkage of various components. Under normal operating conditions, the internal wear-resistant steel sleeve and piston ring can be replaced to extend the service life of the entire cold end, greatly reducing the customer's cost of use.

[0022] 5. The cold end volumetric efficiency of the present invention can reach more than 90%. The piston ring and the inner cylinder liner are made of highly wear-resistant materials and adopt an interference fit sealing method, so that the piston ring and the inner cylinder liner are in full contact and thus bear pressure together, resulting in lower leakage and stronger pressure resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a cross-sectional view of the general assembly of the present invention;

[0024] Figure 2 It is a diagram of the slip structure of the present invention;

[0025] Figure 3 yes Figure 1 A magnified view of middle A;

[0026] Figure 4 It is a diagram of the packing structure of the present invention;

[0027] Figure 5 yes Figure 1 Enlarged view of middle B;

[0028] Figure 6 It is a structural diagram of the inner cylinder sleeve of the present invention.

[0029] In the figure: 1. Outer cylinder sleeve; 11. Liquid inlet; 12. Overflow port; 2. Piston rod; 21. Pressure ring; 22. Packing; 23. Piston ring; 24. Expansion ring; 25. Guide ring; 3. Inner cylinder sleeve; 31. Overflow groove; 4. Inner core; 41. Flow channel; 5. Discharge check valve; 6. Discharge joint; 7. Sealing cover; 8. Slip; 9. Drive shaft. DETAILED DESCRIPTION

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are 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 making creative efforts shall fall within the scope of protection of the present invention.

[0031] A cold end structure of an ultra-low temperature and ultra-high pressure pump, such as Figure 1 As shown, it includes an outer cylinder sleeve 1, a piston rod 2, an inner cylinder sleeve 3, an inner core 4, a discharge one-way valve 5, a discharge joint 6, a cover 7 and a slip 8; one end of the piston rod 2 is slidably connected to the outer cylinder sleeve 1, and the other end extends out of the outer cylinder sleeve 1, the inner cylinder sleeve 3 is fixedly connected between the outer cylinder sleeve 1 and the piston rod 2, the inner core 4 is fixedly connected to the outer cylinder sleeve 1, the discharge one-way valve 5 is slidably connected to the inner core 4, the discharge joint 6 is fixedly connected to the side of the outer cylinder sleeve 1 close to the inner core 4, the cover 7 is fixedly connected to the side of the outer cylinder sleeve 1 away from the discharge joint 6, and the slip 8 is sleeved on the piston rod 2 and the outside of the driving component.

[0032] like Figure 1 As shown, the outer cylinder sleeve 1 is a cylindrical structure with a liquid inlet 11 at one side. The inner core 4 is located within the outer cylinder sleeve 1 at the liquid inlet 11. Several flow channels 41 are defined on the outer wall of the inner core 4. The liquid inlet 11 communicates with the flow channels 41, which in turn connect to the inner space of the outer cylinder sleeve 1 between the piston rod 2 and the inner core 4 through the inner core 4. The outer cylinder sleeve 1 has threads on its outer wall near the protruding end of the piston rod 2, which are threaded with a nut. The outer cylinder sleeve 1 is installed by inserting the threaded portion of the outer cylinder sleeve 1 into the fixed end of the drive component and tightening the nut. The output end of the drive component is connected to the piston rod 2 via slips 8, which push and pull the piston rod 2. When the piston rod 2 is pulled outward, a negative pressure environment is created within the inner cylinder sleeve 3. At this time, atmospheric pressure forces the ultra-cold liquid nitrogen, liquid oxygen, liquid hydrogen, or LNG in the container through the liquid inlet 11 and into the inner cylinder sleeve 3 via the flow channels 41, achieving the extraction effect.

[0033] like Figure 1As shown, the inner core 4 has a stepped hole in the middle, with the smaller end communicating with the active space of the piston rod 2. A drain check valve 5 is slidably connected to the larger end, and a drain connector 6 abuts the larger end of the inner core 4. A spring abuts between the drain check valve 5 and the connector, pushing the valve toward the smaller end to seal the hole. When the drive assembly pushes the piston rod 2 inward, the piston rod 2 pushes ultra-cold (-196°C) liquid nitrogen, liquid oxygen, liquid hydrogen, or LNG toward the drain check valve 5. The drain check valve 5 compresses the spring, connecting the active space of the piston rod 2 with the space within the drain connector 6, allowing the ultra-cold liquid nitrogen, liquid oxygen, liquid hydrogen, or LNG to be pumped out, achieving pumping operation. The end face of the drain connector 6 features an autoclave design with a 60° tapered surface, capable of withstanding a maximum pressure of 700 MPa. In addition, a waterline seal is provided at the connecting end between the inner cylinder sleeve 3 and the inner core 4. A waterline seal is adopted on the inner side of the connecting surface between the inner core 4 and the drain joint 6, and a non-metallic wedge seal is adopted on the outer side to ensure that the compressed high-pressure medium will not leak during the process of discharging the outer cylinder sleeve 1.

[0034] Combine Figure 1 、 Figure 6 The piston rod 2 is a solid cylindrical rod. The diameter of the part of the piston rod 2 that extends into the outer cylinder sleeve 1 is reduced. The inner cylinder sleeve 3 is a T-shaped cylindrical structure made of highly wear-resistant stainless steel. The part of the inner cylinder sleeve 3 with a smaller outer diameter is sleeved on the outside of the end of the piston rod 2 with a reduced diameter, and the end of the inner cylinder sleeve 3 with a larger outer diameter is clamped between the outer cylinder sleeve 1 and the inner core 4. A plurality of overflow grooves 31 are spaced apart on the outer wall surface of the inner cylinder sleeve 3 with a smaller outer diameter. The length direction of the overflow groove 31 is the same as that of the inner cylinder sleeve 3. The overflow groove 31 extends from the end close to the inner core 4 to the end with a larger outer diameter of the inner cylinder sleeve 3 and is then grooved radially so that the end close to the inner core 4 of the overflow groove 31 is closed. The other end of the overflow groove 31 extends out of the inner cylinder sleeve 3 to be open. An overflow port 12 is provided on the outer cylinder sleeve 1 at the closed end of the overflow groove 31. The overflow port 12 is connected to the overflow groove 31. Compressed liquid leaking from the inner cylinder liner 3 is discharged to the cold end through the overflow groove 31 and the overflow port 12 on the outer cylinder liner 1, thus preventing damage to the cold end caused by cavitation. Furthermore, the interference fit sealing between the inner cylinder liner 3 and the piston rod 2 ensures full contact between the piston ring 23 and the inner cylinder liner 3, allowing them to share pressure without being affected by shrinkage in ultra-low temperature environments. This reduces leakage and improves pressure resistance. Through reasonable design, the inner cylinder liner 3 can withstand pressures of up to 140 MPa.

[0035] Combine Figure 1 、 Figure 3 and Figure 4The sealing cap 7 is located at the end of the piston rod 2 extending out of the outer cylinder sleeve 1. Multiple layers of packing 22 are arranged along the axial direction between the piston rod 2 and the outer cylinder sleeve 1. The packing 22 is made of composite low-temperature resistant PTFE material. The packing 22 is conical and the end with a smaller outer diameter faces the inner core 4. A pressure ring 21 with a tapered groove is inserted between adjacent packings 22. The pressure ring 21 is made of metal and abuts against the conical surface of the packing 22 and the outer cylinder sleeve 1. A circular ring is provided at the end with a larger outer diameter of the packing 22. The outer diameter of the circular ring is equal to the inner diameter of the outer cylinder sleeve 1. The side of the pressure ring 21 abuts against the circular ring. The circular ring on the outermost layer of packing 22 abuts against the sealing cap 7 to ensure that the packing 22 is always located inside the outer cylinder sleeve 1.

[0036] Through the above arrangement, the packing 22 is compressed by the preload of the pressure ring 21 to form a conical seal. When the piston rod 2 is moving inward, the high-pressure pumped liquid will overflow to the packing 22 through the gap of the inner cylinder sleeve 3. At this time, the overflow liquid pressure will act on the inverted conical sealing cone surface. Under the dual effects of the preload pressure of the pressure ring 21 and the auxiliary pressure of the overflow liquid, the inverted conical packing 22 is in close contact with the piston rod 2, thereby ensuring that the piston rod 2 has an excellent sealing effect at the packing 22 when the liquid is compressed. At the same time, when the piston rod 2 is in the outward state, the inverted conical packing 22 can also scrape off the low-temperature liquid on the surface of the piston rod 2, ensuring that the low-temperature liquid is not carried out of the outer cylinder sleeve 1 with the piston rod 2, killing two birds with one stone.

[0037] Combine Figure 1 、 Figure 5 Several sets of piston rings 23 are inserted into the interface between the piston rod 2 and the inner cylinder liner 3. Each set of piston rings 23 contains two piston rings 23, each tightly fitting together. The outer surfaces of the piston rings 23 abut against the inner cylinder liner. An expansion ring 24 is inserted between the inner surfaces of the piston rings 23 and the piston rod 2. Its outer surface abuts the inner surface of the piston ring 23. When in its free state, the outer diameter of the expansion ring 24 is larger than the inner diameter of the piston ring 23. After installation, the tension of the expansion ring 24 maintains constant pressure contact with the inner cylinder liner 3. Furthermore, as the piston rod 2 moves, ultra-low temperature liquid nitrogen, liquid oxygen, LNG, or liquid hydrogen lubricates the contact surface, significantly improving the cold end's pumping efficiency under high pressure. Furthermore, as the piston rings 23 wear, their thickness decreases. The expansion of the expansion ring 24 provides radial compensation, ensuring maximum utilization of the piston ring 23 and significantly extending the service life of the cold end.

[0038] like Figure 1As shown, a non-metallic guide ring 25 is inserted into the piston rod 2 between the piston ring 23 and the inner core 4. A guide ring 25 is also provided on the other side of the piston ring 23. The guide ring 25 has an interference fit with the inner cylinder liner 3 at room temperature. The provision of the guide ring 25 ensures that the piston rod 2 remains concentric with the inner cylinder liner 3 during high-speed reciprocating motion within the inner cylinder liner 3, reducing the possibility of metal contact between the piston rod 2 and the inner cylinder liner 3, thereby protecting the inner cylinder liner 3 and the piston rod 2. In addition, in ultra-low temperature environments, because the linear expansion coefficient of the guide ring 25 is smaller than that of the inner cylinder liner 3, the fit between the guide ring 25 and the inner cylinder liner 3 changes from an interference fit at room temperature to a close to clearance fit. At the same time, the ultra-low temperature liquid nitrogen, liquid oxygen, LNG or liquid hydrogen acts as a lubricant in the gap, greatly improving the service life of the cold end and the pumping efficiency under high-pressure conditions.

[0039] like Figure 1 As shown, the slip 8 is a semi-cylindrical shell structure with a bolt hole in the middle of the slip. The two slips 8 are axially connected at both ends to the end of the piston rod 2 extending from the outer cylinder sleeve 1 and the drive shaft 9 of the drive component. The two slips 8 do not touch each other and are connected by a bolt pair. The bolt pair is inserted into the bolt hole and located between the drive shaft 9 and the piston rod 2 to prevent the drive shaft 9 from contacting the piston rod 2. The annular groove at the connection between the upper and lower slips 8 and the piston rod 2 adopts a gap structure design. The traditional threaded connection between the cold end and the drive end cannot ensure the coaxiality of the piston rod 2 and the inner cylinder sleeve 3 due to the action of the preload of the ordinary connector, which can easily cause wear of the piston rod 2 and the inner cylinder sleeve 3. The present invention adopts two-petal slips 8 as compensators, and the upper and lower slips 8 are designed with a gap of a certain width at the connection. When the power end crosshead pushes the piston rod 2, even if there is a coaxiality deviation between the two, due to the compensation gap of the compensator, the piston rod 2 is straightened under the action of the guide ring 25 inside the piston rod 2, avoiding the wear of the piston rod 2 and the inner cylinder sleeve 3 caused by the inability to ensure the coaxiality of the piston rod 2 and the inner cylinder sleeve 3.

[0040] In summary, the cold end assembly design of the present invention has high adaptability. Since the connection end adopts the slip 8 connection compensator structure design, the coaxiality requirement of the cold end and the drive device is reduced, and the piston can automatically achieve radial movement compensation, thereby achieving higher stroke requirements. The stroke rate of an ordinary cold end is usually 200 to 300 strokes / min. Due to the use of a replaceable special material inner cylinder liner 3, the cold end stroke rate of the present invention can reach up to 1000 strokes / min, which is three times that of an ordinary cold end. The interference fit with the piston rod 2 is approximately equal to being combined into one part, and the pressure resistance is far greater than that of a single part. In addition, under the action of the packing 22, piston ring 23 and guide ring 25, the cold end structure has a stronger pressure resistance. Specifically, the normal pressure resistance of an ordinary cold end of the same cylinder diameter is 35 to 40 MPa, while the maximum pressure resistance of the cold end of the present invention can reach 104 MPa in actual operation and 140 MPa in theory, which is 3 to 4 times the pressure resistance limit of an ordinary cold end. Even if overflow occurs, the fluid can flow back into the container filled with ultra-low temperature medium through the overflow port 12, thereby avoiding waste and not significantly reducing the structural strength of the inner cylinder sleeve 3 itself.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A cold end structure of an ultra-low temperature and ultra-high pressure pump, characterized by: The invention comprises an outer cylinder sleeve (1) capable of absorbing liquid nitrogen, liquid oxygen, liquid hydrogen or LNG, a piston rod (2) slidably connected to the outer cylinder sleeve (1), an inner cylinder sleeve (3) sleeved between the piston rod (2) and the outer cylinder sleeve (1), an inner core (4) fixedly connected to one end of the outer cylinder sleeve (1), a discharge check valve (5) slidably connected to the inner core (4), a discharge joint (6) fixedly connected to one end of the outer cylinder sleeve (1), a cover (7) fixedly connected to the other end of the outer cylinder sleeve (1) and a slip (8) connected to a driving component; the diameter of the piston rod (2) extending into the outer cylinder sleeve (1) is reduced, the inner cylinder sleeve (3) is a T-shaped cylindrical structure, a waterline seal is provided at the end where the inner cylinder sleeve (3) and the inner core (4) meet, the inner cylinder sleeve (3) is sleeved outside the end of the piston rod (2) with a reduced diameter, the inner cylinder sleeve (3) and the piston rod (2) wall are interference fit, and the piston rod (2) and the inner cylinder sleeve (3) are both ) are inserted into the connecting surface, and the piston rings (23) are fitted in pairs and the outer wall surface is in contact with the inner cylinder sleeve (3), so that the maximum pressure resistance of the cold end reaches 140MPa; a plurality of overflow grooves (31) are provided at intervals on the outer wall surface of the inner cylinder sleeve (3), and a single overflow groove (31) includes three connected parts. The first overflow groove (31) is located at the end with the smaller outer diameter of the inner cylinder sleeve (3) and has a length direction that is radial to the inner cylinder sleeve (3) and passes through the inner cylinder sleeve (3); the second overflow groove (31) has a length direction that is the same as the length direction of the inner cylinder sleeve (3); the third overflow groove (31) is located at the T-shaped right-angle end of the inner cylinder sleeve (3) and is grooved in the radial direction so as not to be connected with the inner core (4); an overflow port (12) is provided on the outer cylinder sleeve (1) at the closed end of the overflow groove (31), and the overflow port (12) is connected to the third overflow groove (31).

2. The cold end structure of the ultra-low temperature and ultra-high pressure pump according to claim 1, characterized in that: A bolt hole is provided in the middle of the slip (8), and the bolt pair is inserted into the bolt hole and is located between the drive shaft (9) and the piston rod (2) so that the drive shaft (9) does not contact the piston rod (2).

3. The cold end structure of the ultra-low temperature and ultra-high pressure pump according to claim 1, characterized in that: The slips (8) are semi-cylindrical shell structures. The two slips (8) are buckled at both ends in the axial direction to one end of the piston rod (2) extending out of the outer cylinder sleeve (1) and the outside of the drive shaft (9) of the drive component. The two slips (8) do not contact each other and are connected by a bolt pair.

4. The cold end structure of the ultra-low temperature and ultra-high pressure pump according to claim 1, characterized in that: An expansion ring (24) is inserted between the inner wall surface of the piston ring (23) and the piston rod (2), and the outer wall surface of the expansion ring (24) abuts against the inner wall surface of the piston ring (23) to push the piston ring (23) toward the inner cylinder sleeve (3).

5. The cold end structure of the ultra-low temperature and ultra-high pressure pump according to claim 1, characterized in that: A guide ring (25) is inserted on the piston rod (2) between the piston ring (23) and the inner core (4), and the guide ring (25) is interference-fitted with the inner cylinder sleeve (3) at room temperature.

6. The cold end structure of the ultra-low temperature and ultra-high pressure pump according to claim 1, characterized in that: Multiple layers of packing (22) are arranged along the axial direction between the piston rod (2) and the outer cylinder sleeve (1). The packing (22) is conical and the end with a smaller outer diameter faces the inner core (4). A pressure ring (21) with a tapered groove is inserted between adjacent packings (22). The pressure ring (21) abuts against the conical surface of the packing (22) and the outer cylinder sleeve (1).

7. The cold end structure of the ultra-low temperature and ultra-high pressure pump according to claim 6, characterized in that: A circular ring is provided at the end of the packing (22) with a larger outer diameter, the outer diameter of the circular ring being equal to the inner diameter of the outer cylinder sleeve (1), and the side surface of the pressure ring (21) is in contact with the circular ring.

8. The cold end structure of the ultra-low temperature and ultra-high pressure pump according to claim 7, characterized in that: The inner side of the interface between the inner core (4) and the drainage joint (6) adopts a waterline seal, and the outer side adopts a non-metallic wedge seal.

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