Cold end of liquid nitrogen pump with unloading device

Abstract

The present application relates to the technical field of liquid nitrogen pump for oilfield special equipment, and particularly relates to a liquid nitrogen pump cold end with unloading device, a suction valve cavity is formed around the end of the cylinder sleeve in the cold end close to the suction valve head, a suction valve piece is installed in the suction valve cavity, an axial through hole extending to a liquid passing ring groove is formed in one end of the suction valve head, axial stepped round holes are formed through the two ends of the suction valve head, a through hole connected with the liquid passing ring groove is formed in the large diameter end of the stepped round hole, a resilient unloading plunger is installed in the stepped round hole, the unloading plungers are symmetrically distributed around the axis of the suction valve head, the through holes are uniformly distributed between adjacent stepped round holes, an unloading pipeline is installed at the unloading outlet, and an unloading valve is installed on the unloading pipeline; by opening or closing the unloading valve, the unloading and loading of the liquid nitrogen pump cold end are effectively controlled without changing the original equipment structure, normal operation of various displacement conditions is met, repeated disassembly of the liquid nitrogen pump cold end is avoided, and operation efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of liquid nitrogen pump for oilfield special equipment, and particularly relates to a liquid nitrogen pump cold end with unloading device. BACKGROUND

[0002] The liquid nitrogen (oxygen, LNG, hydrogen) cold end is a core component of the liquid nitrogen (oxygen, LNG, hydrogen) pump, which can be extended into the ultra-low temperature environment to realize high-pressure pumping of the liquid nitrogen (liquid oxygen, LNG, liquid hydrogen), and can be used for nitrogen gas lifting, nitrogen replacement, nitrogen fracturing, mixed gas acidification and other special operations for exploration and development. The reciprocating liquid nitrogen pump is usually of three-cylinder or five-cylinder structure, and the cold end with a fixed cylinder diameter is installed and fixed, so the displacement is fixed. Since the working conditions of oilfield operations are complex and the displacement range is required to be large, only the speed adjustment by the driving device cannot meet the operation requirements of small displacement. How to realize the quick switching between the small displacement and the large displacement of the liquid nitrogen pump and make the displacement adjustment more convenient and fast is a technical problem to be solved urgently. SUMMARY

[0003] The technical problem to be solved by the present application is to provide a liquid nitrogen pump cold end with unloading device, which can effectively control the unloading and loading of the liquid nitrogen pump cold end without changing the original equipment structure, meet the normal operation of various displacement conditions, avoid repeated disassembly of the cold end, improve the operation efficiency, and at the same time, does not affect the internal lubrication of the cold end and will not cause abnormal wear of the cold end.

[0004] To solve the above technical problems, the technical scheme of the present application is: the cold end of the liquid nitrogen pump with unloading device, comprising a cylindrical cold end outer cylinder sleeve, a cold end inner cylinder sleeve, a suction valve head and a high-pressure liquid discharge head are sequentially sleeved in the cold end outer cylinder sleeve, a cold end piston is movably installed in the cold end inner cylinder sleeve, a liquid nitrogen inlet and an unloading outlet are formed on the cold end outer cylinder sleeve, a suction valve cavity is formed around the end of the cold end inner cylinder sleeve close to the suction valve head, a suction valve plate is installed in the suction valve cavity, a liquid passing ring groove is formed in the middle of the suction valve head, a liquid passing through hole extending axially to the liquid passing ring groove is formed at one end of the suction valve head, a stepped circular hole axially extending through both ends of the suction valve head is formed, a guide hole communicating with the liquid passing ring groove is formed at the large diameter end of the stepped circular hole, a resilient unloading plunger is installed in the stepped circular hole, the unloading plungers are symmetrically distributed around the axis of the suction valve head, the liquid passing through holes are uniformly distributed between adjacent stepped circular holes, the opening positions of the suction valve plate, the liquid passing through hole and the stepped circular hole correspond to each other, a one-way valve cavity is formed at the center of the suction valve head, a liquid discharge one-way valve is installed in the one-way valve cavity, a liquid discharge through hole communicating with the liquid discharge one-way valve is formed at the center of the high-pressure liquid discharge head, an unloading channel communicating the stepped circular hole with the unloading outlet is also formed on the high-pressure liquid discharge head, an unloading pipeline is installed at the unloading outlet, and an unloading valve is installed on the unloading pipeline; when the cold end piston works, the suction valve plate freely slides in the suction valve cavity under the open state of the unloading valve, and the liquid nitrogen is normally discharged; under the closed state of the unloading valve, when the cold end piston works, the suction valve plate is pushed by the unloading plunger and cannot freely slide in the suction valve cavity, so that the liquid nitrogen is not discharged and flows back to the original place, thereby achieving the unloading of the liquid nitrogen cold end.

[0005] As a preferred technical scheme, the unloading plunger is a stepped cylinder, the small diameter end of the unloading plunger is equal in diameter to the small diameter end of the stepped circular hole, the length of the small diameter end of the unloading plunger is greater than the length of the small diameter end of the stepped circular hole, the length of the large diameter end of the unloading plunger is less than the length of the large diameter end of the stepped circular hole, and a plunger spring cavity is formed at the center of the large diameter end of the unloading plunger, and an unloading plunger spring is installed in the plunger spring cavity.

[0006] As a preferred technical scheme, a stepped groove is formed around the outer periphery of the suction valve plate, a valve spring is sleeved on the stepped groove, one end of the valve spring abuts against the cold end inner cylinder sleeve, and the other end of the valve spring abuts against the stepped groove.

[0007] As a preferred technical scheme, a one-way valve spring groove is formed at one end of the liquid discharge one-way valve close to the high-pressure liquid discharge head, a one-way valve reset spring is installed in the one-way valve spring groove, and the length of the liquid discharge one-way valve is less than the length of the one-way valve cavity.

[0008] As a preferred technical scheme, the cold end outer cylinder sleeve is sequentially provided with an inner cylinder sleeve cavity, a valve head cavity and a liquid discharge head cavity, the cold end inner cylinder sleeve is interference fitted in the inner cylinder sleeve cavity, the suction valve head is installed in the valve head cavity, the liquid containing space is formed between the liquid passing ring groove and the cavity wall of the valve head cavity, and the high-pressure liquid discharge head is installed in the liquid discharge head cavity.

[0009] As a preferred technical scheme, the unloading channel is an axial circular hole opened at one end of the high-pressure liquid discharge head close to the stepped circular hole, a radial circular hole is vertically communicated with the axial circular hole, and the radial circular hole extends through the outer wall of the high-pressure liquid discharge head to the liquid discharge head cavity.

[0010] As a preferred technical scheme, the liquid discharge head screw plug for plugging the high-pressure liquid discharge head is threadedly installed in the liquid discharge head cavity, the wedge-shaped sealing ring is installed between the high-pressure liquid discharge head and the cold end outer cylinder sleeve, and the compression ring for compressing the wedge-shaped sealing ring is installed between the liquid discharge head screw plug and the high-pressure liquid discharge head.

[0011] As a preferred technical scheme, the unloading outlet is a radial circular channel extending from the outer wall of the cold end outer cylinder sleeve to the axis, an axial circular channel is opened in the radial circular channel extending into the liquid discharge head cavity, and the outlet of the axial circular channel is communicated with the radial circular hole.

[0012] As a preferred technical scheme, a plurality of axial threaded holes are opened in the liquid discharge head screw plug, the axial threaded holes are used for installing compression bolts, and the compression bolts are used for fixing the compression ring on the high-pressure liquid discharge head.

[0013] As a preferred technical scheme, the stepped circular holes are uniformly distributed in three, and the corresponding unloading plungers are installed in three.

[0014] The cold end of the liquid nitrogen pump with the unloading device comprises a cylindrical cold end outer cylinder sleeve, a cold end inner cylinder sleeve, a suction valve head and a high-pressure liquid discharge head which are sequentially sleeved in the cold end outer cylinder sleeve, a cold end piston which is movably installed in the cold end inner cylinder sleeve, a liquid nitrogen inlet and an unloading outlet which are formed in the cold end outer cylinder sleeve, a suction valve cavity which is formed around an end of the cold end inner cylinder sleeve close to the suction valve head, a suction valve piece which is installed in the suction valve cavity, a liquid passing ring groove which is formed in the middle of the suction valve head, a liquid passing through hole which is formed in one end of the suction valve head and extends to the liquid passing ring groove, a stepped circular hole which penetrates through both ends of the suction valve head, a through hole which is formed in the large-diameter end of the stepped circular hole and connects the liquid passing ring groove, a plurality of elastic unloading plungers which are symmetrically distributed around the axis of the suction valve head, the liquid passing through holes are uniformly distributed between the adjacent stepped circular holes, the suction valve piece corresponds to the opening positions of the liquid passing through holes and the stepped circular holes, a one-way valve cavity which is formed in the center of the suction valve head, a liquid discharge one-way valve which is installed in the one-way valve cavity, a liquid discharge through hole which is formed in the center of the high-pressure liquid discharge head and is in communication with the liquid discharge one-way valve, an unloading channel which is formed in the high-pressure liquid discharge head and is in communication with the stepped circular hole and the unloading outlet, an unloading pipeline which is installed at the unloading outlet, and an unloading valve which is installed on the unloading pipeline. When the unloading valve is opened, liquid nitrogen enters the liquid containing space in the cold end through the suction valve head, at this time, the suction pressure should be greater than the pressure in the storage tank at the other end of the unloading plunger, at this time, the suction pressure keeps the unloading plunger at a certain position, overcomes the elastic force of the unloading plunger spring, and makes the suction valve piece freely move in the suction valve cavity, so that the liquid nitrogen cold end works normally; when the unloading valve is closed, liquid nitrogen enters the internal cavity of the cold end through the suction valve head, at this time, the suction pressure acts on both ends of the unloading plunger through the through hole above the suction valve head, so that the suction pressure at both ends of the unloading plunger is equal, so that the unloading plunger spring pushes the unloading plunger to the direction of the suction valve piece, the suction valve piece is pushed by the unloading plunger, so that the suction valve piece and the suction valve head are not allowed to contact, in this state, low-temperature liquid nitrogen can still be normally sucked into the cold end inner cylinder sleeve, but liquid nitrogen is not discharged, but is backflowed to the original place, low-temperature cooling and lubrication are performed on the whole cold end, although the cold end piston can still freely move, but it cannot be pressurized in the pump chamber, the unloading of the liquid nitrogen cold end is realized; the beneficial effects of the present application are that the cold end inner cylinder sleeve is installed in the cold end outer cylinder sleeve, the cold end piston reciprocatingly moves in the cold end inner cylinder sleeve, is used for compression and pressurization of liquid nitrogen, the liquid passing through hole in the suction valve head is used for discharging the cold end, the liquid discharge one-way valve makes the high-pressure liquid discharged from the cold end not backflow in the reverse direction; according to the use requirement, the unloading valve is opened or closed, the original equipment structure is not changed, the unloading and loading of the liquid nitrogen pump cold end are effectively controlled, normal operation of various displacement conditions is met, repeated disassembly of the cold end is avoided, operation efficiency is improved, meanwhile, internal lubrication of the cold end is not affected, and abnormal wear of the cold end is not caused. BRIEF DESCRIPTION OF DRAWINGS

[0015] The following drawings are merely intended to schematically illustrate and explain the present application, and do not limit the scope of the present application. Among them:

[0016] Figure 1 is a structural schematic view of the cold end of the liquid nitrogen pump with unloading device of the present application;

[0017] Figure 2 is a structural schematic view of the cold end of the liquid nitrogen pump with unloading device of the present application;

[0018] Figure 3 is a partial structural sectional view of the present application when the cold end piston is pushed in the open state of the unloading valve;

[0019] Figure 4 is Figure 3 is a partial enlarged view of I in FIG. 4;

[0020] Figure 5 is a partial structural sectional view of the present application when the cold end piston is pulled in the open state of the unloading valve;

[0021] Figure 6 is Figure 5 is a partial enlarged view of II in FIG. 5;

[0022] Figure 7 is a partial structural sectional view of the present application when the cold end piston is pushed in the closed state of the unloading valve;

[0023] Figure 8 is Figure 7 is a partial enlarged view of III in FIG. 6;

[0024] Figure 9 is a partial structural sectional view of the present application when the cold end piston is pulled in the closed state of the unloading valve;

[0025] Figure 10 is Figure 9 is a partial enlarged view of IV in FIG. 7;

[0026] Figure 11 is a structural schematic view of the suction valve head of the present application;

[0027] Figure 12 is a structural schematic view of the suction valve head of the present application;

[0028] Figure 13 is Figure 12 is a sectional view of A-A in FIG. 8;

[0029] Figure 14 is a sectional view of the outer cylinder sleeve of the cold end of the present application;

[0030] Figure 15 is a structural schematic view of the unloading plunger of the present application;

[0031] Figure 16 is a structural schematic diagram of the suction valve piece of the present application;

[0032] Figure 17 is a structural schematic diagram of the present application after installing the upper compression bolt;

[0033] Figure 18 is a partial sectional view of the present application after installing the upper compression bolt.

[0034] In the figure: 1 - cold end outer cylinder sleeve; 11 - inner cylinder sleeve cavity; 12 - valve head cavity; 13 - liquid discharge head cavity; 14 - liquid nitrogen inlet; 15 - radial circular channel; 16 - axial circular channel; 2 - cold end inner cylinder sleeve; 21 - suction valve cavity; 22 - suction valve piece; 221 - stepped groove; 23 - valve piece spring; 3 - suction valve head; 31 - liquid passing ring groove; 32 - liquid passing through hole; 33 - stepped circular hole; 34 - guide through hole; 35 - one-way valve cavity; 36 - wedge-shaped sealing ring; 37 - compression ring; 4 - high-pressure liquid discharge head; 41 - liquid discharge through hole; 42 - axial circular hole; 43 - radial circular hole; 5 - cold end piston; 6 - unloading plunger; 61 - plunger spring cavity; 62 - unloading plunger spring; 7 - liquid discharge one-way valve; 71 - one-way valve spring groove; 72 - one-way valve return spring; 8 - unloading pipeline; 9 - unloading valve; 10 - liquid discharge head screw plug; 101 - axial threaded hole; 102 - compression bolt. DETAILED DESCRIPTION

[0035] The present application will be further described below in conjunction with the accompanying drawings and examples. In the following detailed description, certain exemplary embodiments of the present application are described by way of illustration only. It goes without saying that those skilled in the art can recognize that the described embodiments can be modified in various ways without departing from the spirit and scope of the present application. Therefore, the accompanying drawings and description are essentially illustrative, and are not intended to limit the scope of protection of the claims.

[0036] As Figures 1 to 18As shown, the cold end of the liquid nitrogen pump with unloading device comprises a cylindrical outer cylinder 1, an inner cylinder 2, a suction valve head 3 and a high-pressure discharge head 4 are sequentially sleeved in the outer cylinder 1, a cold end piston 5 is movably installed in the inner cylinder 2, and the cold end piston 5 is used for extracting and discharging liquid nitrogen by pushing and pulling in the inner cylinder 2. A liquid nitrogen inlet 14 and an unloading outlet are formed on the outer cylinder 1, the liquid nitrogen inlet 14 is used for liquid nitrogen to enter the liquid space of the cold end, the unloading outlet is used for connecting an unloading pipeline 8, and then connecting an external tank, a suction valve cavity 21 is formed around the end of the inner cylinder 2 close to the suction valve head 3, a suction valve plate 22 is installed in the suction valve cavity 21, the suction valve plate 22 can slide left and right in the suction valve cavity 21, a liquid passing ring groove 31 is formed in the middle of the suction valve head 3, a liquid passing through hole 32 extending to the liquid passing ring groove 31 is formed at one end of the suction valve head 3, a stepped circular hole 33 is formed at both ends of the suction valve head 3, a through hole 34 is formed in the large-diameter end of the stepped circular hole 33, so that the suction liquid pressure can act on both ends of the unloading plunger 6 when the unloading device works, and the force acting on both ends of the unloading plunger 6 is balanced; the unloading plunger 6 is installed in the stepped circular hole 33 and is elastic, the unloading plunger 6 is symmetrically distributed around the axis of the suction valve head 3, the liquid passing through hole 32 is uniformly distributed between adjacent stepped circular holes 33, the suction valve plate 22 corresponds to the opening positions of the liquid passing through hole 32 and the stepped circular hole 33, a one-way valve cavity 35 is formed at the axis of the suction valve head 3, a discharge one-way valve 7 is installed in the one-way valve cavity 35, a discharge through hole 41 is formed at the axis of the high-pressure discharge head 4 and is connected with the discharge one-way valve 7, an unloading passage is formed on the high-pressure discharge head 4 and is connected with the stepped circular hole 33 and the unloading outlet, the unloading pipeline 8 is installed at the unloading outlet, an unloading valve 9 is installed on the unloading pipeline 8, the unloading valve 9 is a prior art and is used for controlling the unloading or normal working of the cold end.When the unloading valve 9 is open, liquid nitrogen enters the liquid space inside the cold end through the suction valve head 3. At this time, the suction pressure should be greater than the external tank pressure at the other end of the unloading plunger 6. At this time, the suction pressure keeps the unloading plunger 6 at a certain position, overcoming the elastic force of the unloading plunger spring 62, so that the suction valve plate 22 can move freely in the suction valve cavity 21, thereby enabling the liquid nitrogen cold end to work normally. When the unloading valve 9 is closed, liquid nitrogen enters the internal cavity of the cold end through the suction valve head 3. At this time, the suction pressure acts on both ends of the unloading plunger 6 through the through hole 34 above the suction valve head 3, so that the suction pressure on both ends of the unloading plunger 6 is equal. In this way, the unloading plunger spring 62 pushes the unloading plunger 6 towards the direction of the suction valve plate 22, and the suction valve plate 22 is pushed by the unloading plunger 6, so that the suction valve plate 22 and the suction valve head 3 are not allowed to contact. In this state, low-temperature liquid nitrogen can still be normally sucked into the cold end cylinder 2, but the liquid nitrogen is not discharged, but is backflowed into the original place, thereby cooling and lubricating the entire cold end. Although the cold end piston 5 can still move freely, it cannot pressurize in the pump chamber, thereby achieving unloading of the liquid nitrogen cold end. The cold end cylinder 2 is installed inside the cold end outer cylinder 1, and the cold end piston 5 moves reciprocally in the cold end cylinder 2 to compress and pressurize the liquid nitrogen, which is discharged through the liquid passage hole 32 in the suction valve head 3. The discharge one-way valve 7 prevents the high-pressure liquid discharged from the cold end from backflowing in the reverse direction. According to the use requirements, the unloading of the liquid nitrogen pump cold end and the loading can be effectively controlled by opening or closing the unloading valve 9 without changing the original equipment structure, thereby meeting the normal operation of various displacement conditions, avoiding repeated disassembly of the cold end, improving the operation efficiency, and not affecting the internal lubrication of the cold end, thereby avoiding abnormal wear of the cold end.

[0037] As shown in Figure 15 , the unloading plunger 6 is a stepped cylinder. The small-diameter end of the unloading plunger 6 has a diameter equal to that of the small-diameter end of the stepped hole 33, and the length of the small-diameter end of the unloading plunger 6 is greater than that of the small-diameter end of the stepped hole 33. The diameter of the large-diameter end of the unloading plunger 6 is slightly smaller than that of the large-diameter end of the stepped hole 33, which allows liquid nitrogen to flow. The length of the large-diameter end of the unloading plunger 6 is less than that of the large-diameter end of the stepped hole 33. A plunger spring cavity 61 is formed at the axis of the large-diameter end of the unloading plunger 6, and the unloading plunger spring 62 is installed in the plunger spring cavity 61. A sealing groove is also formed on the outer periphery of the large-diameter end of the unloading plunger 6 for installing a sealing ring.

[0038] As shown in Figure 16As shown, the outer periphery of the suction valve plate 22 is provided with a stepped groove 221, and the valve plate spring 23 is sleeved on the stepped groove 221. One end of the valve plate spring 23 abuts against the cold end inner cylinder sleeve 2, and the other end of the valve plate spring 23 abuts against the stepped groove 221. When the unloading valve 9 is in the open state and the unloading plunger 6 does not protrude out of the stepped circular hole 33, the valve plate spring 23 is used to ensure that the suction valve plate 22 stably reciprocates in the suction valve chamber 21 during normal operation of the cold end.

[0039] As shown in Figure 4 , the one-way valve spring groove 71 is provided in the one end of the liquid discharge one-way valve 7 close to the high-pressure liquid discharge head 4, the one-way valve reset spring 72 is installed in the one-way valve spring groove 71, and the length of the liquid discharge one-way valve 7 is less than the length of the one-way valve chamber 35. The one-way valve reset spring 72 is used to reset the liquid discharge one-way valve 7, and the length of the liquid discharge one-way valve 7 is less than the length of the one-way valve chamber 35, so that the liquid discharge one-way valve 7 can generate a gap between the liquid discharge one-way valve 7 and the suction valve head 3 when pushing the cold end piston 5, and the gap is used for liquid nitrogen to pass through.

[0040] As shown in Figure 14 , the cold end outer cylinder sleeve 1 is sequentially provided with an inner cylinder sleeve cavity 11, a valve head cavity 12 and a liquid discharge head cavity 13. The cold end inner cylinder sleeve 2 is installed in the inner cylinder sleeve cavity 11 in an interference fit, the suction valve head 3 is installed in the valve head cavity 12, the liquid passage ring groove 31 and the cavity wall of the valve head cavity 12 form a liquid containing space, and the high-pressure liquid discharge head 4 is installed in the liquid discharge head cavity 13. The inner diameters of the inner cylinder sleeve cavity 11, the valve head cavity 12 and the liquid discharge head cavity 13 are different, and are matched with the sizes of the components installed therein, respectively.

[0041] As shown in Figure 6 , the unloading channel is an axial circular hole 42 provided in the high-pressure liquid discharge head 4 close to the stepped circular hole 33, a radial circular hole 43 is vertically communicated with the axial circular hole 42, and the radial circular hole 43 extends through the outer wall of the high-pressure liquid discharge head 4 to the liquid discharge head cavity 13. The unloading channel is used to communicate with the external tank and perform pressure relief.

[0042] As shown in Figure 14 , the unloading outlet is a radial circular channel 15 extending from the outer wall of the cold end outer cylinder sleeve 1 to the shaft center, the radial circular channel 15 extends into the liquid discharge head cavity 13 to form an axial circular channel 16, and the outlet of the axial circular channel 16 is communicated with the radial circular hole 43. The unloading outlet is used to communicate with the external tank and perform pressure relief.

[0043] As shown in Figure 3 , Figure 5 , Figure 7 and Figure 9As shown in the drawings, the drain head cavity 13 is threaded with a drain head plug 10 for plugging the high-pressure drain head 4, and a wedge-shaped sealing ring 36 is installed between the high-pressure drain head 4 and the cold-end outer cylinder sleeve 1, which is used to seal the gap between the high-pressure drain head 4 and the cold-end outer cylinder sleeve 1 to prevent liquid leakage. A compression ring 37 is installed between the drain head plug 10 and the high-pressure drain head 4 for compressing the wedge-shaped sealing ring 36, which is used to compress and fix the wedge-shaped sealing ring 36 on the high-pressure drain head 4 so that it does not fall off.

[0044] As shown in the drawings, Figure 17 and Figure 18 As shown in the drawings, a plurality of axial threaded holes 101 are formed in the drain head plug 10, which are used to install compression bolts 102 for compressing the compression ring 37 on the high-pressure drain head 4 to strengthen the compression force on the compression ring 37. The end face of the compression bolt 102 close to the compression ring 37 is a flat surface, and the length of the compression bolt 102 is greater than the length of the axial threaded hole 101.

[0045] As shown in the drawings, Figure 11 and Figure 12 As shown in the drawings, the stepped circular holes 33 are evenly distributed in three, and the corresponding unloading plungers 6 are installed in three. One cold end is installed with three unloading plungers 6, which is the optimal technical scheme, and other number of stepped circular holes 33 can be designed according to the demand to install unloading plungers 6, as long as they are evenly distributed in the circumferential direction to ensure the balance of liquid nitrogen flow.

[0046] The working process of the present application is as follows:

[0047] (1) Normal working mode, unloading valve 9 is opened.

[0048] As shown in the drawings, Figure 5 and Figure 6 As shown in the drawings, when the cold-end piston 5 is pulled outward, liquid nitrogen enters the liquid passage ring groove 31 and the cavity wall of the valve head cavity 12 to form a liquid space, at this time the suction valve piece 22 overcomes the elastic force of the valve piece spring 23 and moves to the left in the suction valve cavity 21, at this time, since the unloading valve 9 is in the open state, the pressure P1 on the left side of the unloading plunger 6 is greater than the pressure P2 on the right side, a part of the liquid nitrogen enters the large diameter end of the stepped circular hole 33 through the through hole 34, and then passes through the axial circular hole 42, the radial circular hole 43, the axial circular channel 16, the radial circular channel 15, and finally enters the external storage tank through the unloading pipeline 8.

[0049] As shown in the drawings, Figure 3 and Figure 4As shown, when the cold end piston 5 is pushed inward, the suction valve plate 22 is pressed tightly against the suction valve head 3 under pressure, completely blocking the small diameter end of the liquid passage 32 and the stepped circular hole 33. The pressure P1 on the left side of the unloading plunger 6 is greater than the pressure P2 on the right side. Under pressure, the discharge check valve 7 overcomes the elastic force of the check valve return spring 72 and moves to the right, creating a gap between the discharge check valve 7 and the suction valve head 3. Liquid nitrogen enters the hole of the discharge check valve 7 through the gap, and then enters the discharge passage 41 and is discharged from the high pressure discharge head 4.

[0050] (2) Unloading mode, unloading valve 9 is closed.

[0051] like Figure 9 and Figure 10 As shown, when the cold end piston 5 is pulled outward, liquid nitrogen enters from the liquid nitrogen inlet 14 into the liquid space formed by the liquid ring groove 31 and the cavity wall of the valve head cavity 12. At this time, since the unloading valve 9 is in the closed state, the pressure P1 on the left side of the unloading plunger 6 is equal to the pressure P2 on the right side. At this time, the unloading plunger 6 moves to the left under the elastic force of the unloading plunger spring 62, and pushes the suction valve plate 22 against the left side, so that the suction valve plate 22 always maintains a certain gap with the suction valve head 3. A part of the liquid nitrogen passes through the guide hole 34 and enters the large diameter end of the stepped circular hole 33 and no longer flows.

[0052] like Figure 7 and Figure 8 As shown, when the cold end piston 5 is pushed inward, the pressure P1 on the left side of the unloading plunger 6 is equal to the pressure P2 on the right side because the unloading valve 9 is closed. At this time, the unloading plunger 6 moves to the left under the elastic force of the unloading plunger spring 62, and the suction valve plate 22 is pressed against the left side, so that the suction valve plate 22 always maintains a certain gap with the suction valve head 3. At this time, the drain check valve 7 is in a blocked state under the elastic force of the check valve reset spring 72. Liquid nitrogen enters the liquid space formed between the liquid ring groove 31 and the cavity wall of the valve head cavity 12 from the liquid through hole 32, and then returns from the liquid nitrogen inlet 14 to achieve unloading.

[0053] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0054] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above-mentioned embodiments, and the above-mentioned embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A cold end of a liquid nitrogen pump with an unloading device, characterized in that: The application relates to a liquid nitrogen cold end unloading device, which comprises a cylindrical cold end outer cylinder (1), a cold end inner cylinder (2), a suction valve head (3) and a high-pressure liquid discharge head (4) are sequentially sleeved in the cold end outer cylinder (1), a cold end piston (5) is movably arranged in the cold end inner cylinder (2), a liquid nitrogen inlet (14) and an unloading outlet are formed in the cold end outer cylinder (1), a suction valve cavity (21) is formed around one end of the cold end inner cylinder (2) close to the suction valve head (3), a suction valve piece (22) is arranged in the suction valve cavity (21), a liquid passing ring groove (31) is formed in the middle of the suction valve head (3), a liquid passing through hole (32) extending to the liquid passing ring groove (31) is formed in one end of the suction valve head (3), a stepped circular hole (33) extending in the axial direction is formed through both ends of the suction valve head (3), a lead-through hole (34) communicating with the liquid passing ring groove (31) is formed in the large-diameter end of the stepped circular hole (33), a plurality of elastic unloading plungers (6) are symmetrically arranged around the axis of the suction valve head (3), the liquid passing through holes (32) are uniformly distributed between adjacent stepped circular holes (33), the suction valve piece (22) corresponds to the opening positions of the liquid passing through holes (32) and the stepped circular holes (33), a one-way valve cavity (35) is formed in the axial center of the suction valve head (3), a liquid discharging one-way valve (7) is arranged in the one-way valve cavity (35), a liquid discharging through hole (41) communicating with the liquid discharging one-way valve (7) is formed in the axial center of the high-pressure liquid discharge head (4), an unloading channel communicating between the stepped circular hole (33) and the unloading outlet is formed in the high-pressure liquid discharge head (4), an unloading pipeline (8) is arranged at the unloading outlet, and an unloading valve (9) is arranged on the unloading pipeline (8). When the unloading valve (9) is in the open state and the cold end piston (5) works, the suction valve piece (22) freely slides in the suction valve cavity (21), and liquid nitrogen is normally discharged. When the unloading valve (9) is in the closed state and the cold end piston (5) works, the suction valve piece (22) is pressed by the unloading plunger (6) and cannot freely slide in the suction valve cavity (21), liquid nitrogen is not discharged and flows back to the original position, thereby realizing unloading of the liquid nitrogen cold end.

2. The cold end of a liquid nitrogen pump with unloading device according to claim 1, characterized in that: The unloading plunger (6) is a stepped cylinder, the small-diameter end of the unloading plunger (6) has the same diameter as the small-diameter end of the stepped circular hole (33), the length of the small-diameter end of the unloading plunger (6) is greater than the length of the small-diameter end of the stepped circular hole (33), the length of the large-diameter end of the unloading plunger (6) is smaller than the length of the large-diameter end of the stepped circular hole (33), a plunger spring cavity (61) is formed in the axial center of the large-diameter end of the unloading plunger (6), and an unloading plunger spring (62) is arranged in the plunger spring cavity (61).

3. The cold end of a liquid nitrogen pump with unloading device according to claim 1, characterized in that: The outer periphery of the suction valve plate (22) is provided with a stepped groove (221), and a valve plate spring (23) is sleeved on the stepped groove (221), one end of the valve plate spring (23) abuts against the cold end inner cylinder sleeve (2), and the other end of the valve plate spring (23) abuts against the stepped groove (221).

4. The cold end of a liquid nitrogen pump with unloading device according to claim 1, characterized in that: The one-way valve (7) is provided with a one-way valve spring groove (71) at one end close to the high-pressure liquid discharge head (4), a one-way valve return spring (72) is installed in the one-way valve spring groove (71), and the length of the one-way valve (7) is less than the length of the one-way valve cavity (35).

5. The cold end of a liquid nitrogen pump with unloading device according to claim 1, characterized in that: The cold end outer cylinder sleeve (1) is sequentially provided with an inner cylinder sleeve cavity (11), a valve head cavity (12) and a liquid discharge head cavity (13), the cold end inner cylinder sleeve (2) is installed in the inner cylinder sleeve cavity (11) in an interference fit, the suction valve head (3) is installed in the valve head cavity (12), the liquid containing space is formed between the over-liquid ring groove (31) and the cavity wall of the valve head cavity (12), and the high-pressure liquid discharge head (4) is installed in the liquid discharge head cavity (13).

6. The cold end of a liquid nitrogen pump with unloading device according to claim 5, characterized in that: The unloading channel is an axial circular hole (42) provided at one end of the high-pressure liquid discharge head (4) close to the stepped circular hole (33), a radial circular hole (43) is vertically connected and communicated with the axial circular hole (42), and the radial circular hole (43) extends through the outer wall of the high-pressure liquid discharge head (4) to the liquid discharge head cavity (13).

7. The cold end of a liquid nitrogen pump according to claim 6, characterized in that: A liquid discharge head screw plug (10) for plugging the high-pressure liquid discharge head (4) is threadedly installed in the liquid discharge head cavity (13), a wedge-shaped sealing ring (36) is installed between the high-pressure liquid discharge head (4) and the cold end outer cylinder sleeve (1), and a pressing ring (37) for pressing the wedge-shaped sealing ring (36) is installed between the liquid discharge head screw plug (10) and the high-pressure liquid discharge head (4).

8. The cold end of a liquid nitrogen pump with unloading device according to claim 7, characterized in that: The unloading outlet is a radial circular channel (15) extending from the outer wall of the cold end outer cylinder sleeve (1) to the shaft center, an axial circular channel (16) is provided in the radial circular channel (15) extending to the liquid discharge head cavity (13), and the outlet of the axial circular channel (16) is communicated with the radial circular hole (43).

9. The cold end of a liquid nitrogen pump according to claim 8, characterized in that: A plurality of axial threaded holes (101) are provided on the liquid discharge head screw plug (10), the axial threaded holes (101) are used for installing pressing bolts (102), and the pressing bolts (102) are used for fixing the pressing ring (37) on the high-pressure liquid discharge head (4).

10. The cold end of a liquid nitrogen pump with unloading device according to any of claims 1 to 9, characterized in that: The stepped circular holes (33) are uniformly distributed in three, and the corresponding unloading plungers (6) are installed in three.

Images