Plunger pump for improving alternating pressure sealing

Abstract

The plunger pump comprises a pump head and a valve assembly, the valve assembly is arranged in the pump head, a main cavity is formed in the pump head, a plunger is arranged in the main cavity, one end of the plunger is connected with a power source, the power source drives the plunger to axially move in the length direction of the plunger, and the power source drives the plunger to axially move in the length direction of the plunger. The end, away from the power source, of the main cavity is provided with a plug assembly used for sealing the main cavity. The chock plug assembly comprises an outer chock plug and an inner chock plug, the outer chock plug and the inner chock plug are both connected to the end, close to the main cavity, of the pump head, and a self-balancing cavity is formed between the outer chock plug and the inner chock plug; a one-way valve is arranged on the inner chock plug and allows a medium to enter the self-balancing cavity from the main cavity. The plunger pump has the advantage that the service life of the plunger pump for improving alternating pressure sealing is prolonged.

Description

Technical Field

[0001] The present application belongs to the technical field of plunger pumps, and in particular relates to a plunger pump with improved alternating pressure sealing. Background Art

[0002] As a common reciprocating positive displacement pump in the industrial field, the plunger pump is widely used in various fields such as water injection, hydraulic pressure, and boosting and delivery. The plunger pump is mainly divided into the power end and the hydraulic end. The power end converts the rotary motion into reciprocating linear motion through the crank-connecting rod mechanism, thereby driving the plunger to reciprocate in the hydraulic end, realizing the volume change inside the hydraulic end, thereby realizing the boosting function.

[0003] When the plunger is pushed toward the hydraulic end, the volume of the hydraulic end cavity decreases, and the internal medium pressure increases. At this time, the inlet valve is closed, and the outlet valve is opened due to the pressure difference to achieve pressurized liquid injection. When the plunger moves in the opposite direction, the volume of the hydraulic end cavity increases, and the internal medium pressure decreases. At this time, the outlet valve is closed, and the inlet valve is opened to achieve liquid inlet. During the operation of the plunger pump, the medium pressure in the internal cavity of the hydraulic end changes periodically, which is an alternating pressure, and the pressure value fluctuates repeatedly between the inlet pressure and the discharge pressure, and the fluctuation value is very large. For such medium seals with alternating pressure, their elastic sealing materials (such as O-rings) will deform repeatedly with pressure fluctuations, and are more prone to fatigue damage. In addition, the related components used to fix the sealing materials are also subjected to periodic forces from the medium, thereby generating alternating stresses in fixed parts such as threads, causing the threads to loosen easily, thereby causing the seal to fail, or the threads to bite and become unable to be disassembled, and at the same time, the stress-bearing parts are more prone to fatigue damage.

[0004] Especially for large-flow and high-pressure plunger pumps, the cavity and seal dimensions are large. For cavity medium sealing with alternating pressure, the axial seal is easy to loosen due to the alternating stress on the fixed parts. Once axial displacement occurs, the axial seal will fail quickly. Therefore, radial sealing is generally adopted, which will not fail immediately even if the fixed parts are slightly displaced. However, for large-flow and high-pressure plunger pumps, the cavity and seal dimensions are large, and the radial seal installation requirements are high. Especially under high pressure conditions, radial seals need to be equipped with sealing retaining rings; large-diameter sealing retaining rings are very easy to deform, and they are easily squeezed out of the sealing groove during installation and stuck on the sealing surface, resulting in seal failure; at the same time, the radial sealing ring has a reduced life due to repeated deformation under alternating pressure medium conditions.

[0005] Patent 202211653810.8 provides a pressure balancing chamber method to improve the sealing problem of alternating pressure media. A self-balancing chamber is set inside the plug head, and a one-way valve is used to separate the main chamber from the self-balancing chamber. During the operation of the plunger pump, the medium inside the self-balancing chamber is always kept at high pressure, thereby reducing the alternating pressure range and its influence. However, the limitations of this method are: first, the self-balancing chamber is excavated on the plug head, and the left and right side walls that constitute the self-balancing chamber belong to the plug head. Therefore, the forces of the high-pressure medium in the self-balancing chamber on the left and right sides will offset each other. The overall result is that the combined force of the high-pressure medium on the plug head is very small, and its effective action area is only the difference between the area of ​​the axial sealing ring of the plug head and the area of ​​the radial sealing ring; and the front end of the plug head is still in direct contact with the medium in the main chamber, and is affected by the alternating pressure of the main chamber medium, so the fluctuation range of the alternating force on the plug head is still very large. In addition, the rear end of the one-way valve on the plug is directly connected to the external atmosphere, thus adding a leakage point. Once the one-way valve seal fails and leakage occurs, shutdown maintenance is also required. Summary of the invention

[0006] The purpose of the present application is to provide a plunger pump with improved alternating pressure sealing, so as to solve the above-mentioned problems existing in the prior art.

[0007] In order to achieve the above-mentioned purpose, the present application adopts the following technical scheme: a plunger pump for improving alternating pressure sealing, comprising a pump head and a valve assembly, wherein the valve assembly is arranged in the pump head, a main cavity is provided in the pump head, a plunger is arranged in the main cavity, one end of the plunger is connected to a power source, the power source drives the plunger to make axial movement along the length direction of the plunger, and a plug assembly for sealing the main cavity is arranged at one end of the main cavity away from the power source; The plug assembly comprises an external plug and an internal plug, both of which are connected to the end of the pump head close to the main cavity, and a self-balancing cavity is provided between the external plug and the internal plug; A one-way valve is arranged on the inner plug head, and the one-way valve allows the medium to enter the self-balancing cavity from the main cavity.

[0008] Preferably, the one-way valve includes a one-way valve fastening screw plug, a valve sleeve, a one-way valve spring, a valve core and a valve seat, the valve seat is arranged in an inner plug head, the valve sleeve is fixed to the end of the valve seat, a flow channel 1 is opened in the valve seat, the valve core is connected to the valve sleeve through a one-way valve spring, and the one-way valve spring is in a compressed state, the valve core seals flow channel 1, and the valve sleeve is opened with flow channel 2. When the pressure of the main cavity is greater than that of the self-balancing cavity, the valve core is separated from the valve seat, and the medium of the main cavity enters the self-balancing cavity through flow channel 1 and flow channel 2 respectively.

[0009] Preferably, the one-way valve further comprises a one-way valve radial sealing ring, and the one-way valve radial sealing ring is installed on the outer diameter of the valve seat.

[0010] Preferably, an inner plug end face sealing ring is provided on the inner plug, and an outer plug end face sealing ring is provided on the outer plug.

[0011] Preferably, a fixing structure for fixing the external plug is provided on the external plug.

[0012] Preferably, the fixing structure is a fastening screw plug, the fastening screw plug is fixed on the pump head, and the fastening screw plug is pressed against the external plug head.

[0013] Preferably, the fixing structure is an external plug pressing plate, the external plug pressing plate is fixed on the pump head at the end close to the main cavity, and the external plug pressing plate is pressed against the external plug.

[0014] Preferably, an inner plug head radial sealing ring is arranged on the outside of the inner plug head close to the left side, and a connecting spring is arranged between the outer plug head and the inner plug head, and the connecting spring is in a compressed state.

[0015] Preferably, an annular buffer pad is provided between the left step surface of the inner plug head and the step surface of the pump head, and the material of the annular buffer pad is preferably a soft copper alloy.

[0016] Preferably, the one-way valve is installed at a middle position of the inner plug head.

[0017] Beneficial effect: The present application sets up a self-balancing cavity with completely independent left and right walls, which is connected to the main cavity through a one-way valve. The external plug has no contact with the medium of the main cavity, and is only subjected to the pressure from the high-pressure medium inside the self-balancing cavity, thereby minimizing the fluctuation range of the alternating stress on the external plug and the fastening screw plug; at the same time, the one-way valve is arranged in the inner plug and has no connection with the external atmosphere. Therefore, even if the one-way valve is damaged, the system does not need to be shut down. At this time, it is equivalent to the traditional sealing method and can still operate normally; the influence of alternating pressure on the seal is solved, thereby increasing the service life of the one-way valve. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the structure of the first embodiment of the present application.

[0019] Figure 2 for Figure 1 Enlarged schematic diagram of part A in the middle.

[0020] Figure 3 This is a structural diagram of the second embodiment of the present application.

[0021] Figure 4 This is a structural diagram of Example 3 of the present application.

[0022] Figure 5 This is a structural diagram of embodiment 4 of the present application.

[0023] Figure 6 This is a schematic diagram of the area of ​​action of the high-pressure medium on the plug in this application.

[0024] Figure 7 This is a comparison chart of the force exerted by the cavity medium on the plug under different methods of this application.

[0025] In the figure: 1. pump head; 2. fastening screw plug; 3. external plug; 4. one-way valve; 41. one-way valve fastening screw plug; 42. valve sleeve; 43. one-way valve spring; 44. valve core; 45. valve seat; 46. one-way valve radial sealing ring; 5. self-balancing chamber; 6. inner plug; 7. inner plug end face sealing ring; 8. outer plug end face sealing ring; 9. main chamber; 10. packing; 11. pressing sleeve; 12. packing fastening screw plug; 13. plunger; 14. valve assembly; 15. valve pressing sleeve; 16. valve pressure plate; 17. external plug pressure plate; 18. inner plug radial sealing ring; 19. buffer pad; 20. connecting spring. DETAILED DESCRIPTION

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the present application will be briefly introduced below in combination with the drawings and the description of the embodiments or the prior art. Obviously, the following description of the structure of the drawings is only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. It should be noted that the description of these embodiments is used to help understand the present application, but does not constitute a limitation of the present application.

[0027] Example 1: Reference Figure 1 and Figure 2 The present embodiment provides a plunger pump for improving alternating pressure sealing, including a pump head 1 and a valve assembly 14. The valve assembly 14 is arranged in the pump head 1. A main cavity 9 is opened in the pump head 1. A plunger 13 is arranged in the main cavity 9. One end of the plunger 13 is connected to a power source. The power source drives the plunger 13 to make axial movement along the length direction of the plunger 13, changes the volume of the main cavity 9, thereby realizing the pressurization of the internal medium and the liquid inlet and discharge. After the liquid medium enters the inlet valve in the valve assembly 14 through the liquid inlet pipe, it enters the main cavity 9, and then enters the liquid discharge pipe through the liquid discharge valve in the valve assembly 14 for discharge.

[0028] A plurality of turns of packing 10 are arranged on one side of the pump head 1 close to the plunger 13, and a pressing sleeve 11 is provided at the front end of the packing 10 for flattening the packing 10. A packing fastening screw plug 12 is threadedly connected to the pump head 1, and the end face of the packing fastening screw plug 12 is in contact with the pressing sleeve 11. By adjusting the packing fastening screw plug 12, the tightness of the packing 10 is controlled, thereby achieving sealing of the main cavity 9 close to the plunger 13 side.

[0029] A plug assembly for sealing the main cavity 9 is provided on the end of the main cavity 9 away from the power source; the plug assembly includes an inner plug 6, which is connected to the end of the pump head 1 close to the main cavity 9, and the inner plug 6 is fastened to the pump head 1 through a thread. A step surface is provided on the inner plug 6, and an inner plug end face sealing ring 7 for sealing the end face of the inner plug 6 is provided on the step surface. The step surface contacts and cooperates with the step surface on the pump head 1 to achieve sealing. A polygonal slot is provided on the right end face of the inner plug 6 to facilitate the installation of the inner plug 6 on the pump head 1.

[0030] The plug assembly also includes an external plug 3, which is installed on the side of the pump head 1 away from the plunger 13. The right end face of the internal plug 6, the inner surface of the external plug 3 and the step surface of the pump head 1 constitute a self-balancing cavity 5. The left end face of the external plug 3 is in direct contact with the step surface of the pump head 1, and an external plug end face sealing ring 8 for sealing the end face of the external plug 3 is provided on the left end face of the external plug 3, so as to achieve sealing between the self-balancing cavity 5 and the external environment.

[0031] The external plug 3 is provided with a fixing structure for fixing the external plug 3. The fixing structure is a tightening screw 2, which is fixed on the pump head 1 and is pressed against the external plug 3. The left end surface of the tightening screw 2 is in direct contact with the right end surface of the external plug 3, and the tightening screw 2 is tightened and connected to the pump head 1 through a thread. The external plug 3 is tightly pressed against the pump head 1 by adjusting the tightening screw 2, thereby achieving the fixing and sealing of the external plug 3.

[0032] A one-way valve 4 is arranged on the inner plug head 6, and the one-way valve 4 allows the medium to enter the self-balancing cavity 5 from the main cavity 9. The one-way valve 4 includes a one-way valve fastening screw plug 41, a valve sleeve 42, a one-way valve spring 43, a valve core 44 and a valve seat 45. The one-way valve 4 is placed in the groove of the inner plug head 6, and the left end face of the valve seat 45 is in direct contact with the inner plug head 6. A one-way valve radial sealing ring 46 is arranged on the periphery of the valve seat 45, and the sealing is achieved by the valve seat 45 and the inner surface of the groove. A flow channel 1 is provided in the middle of the valve seat 45. The valve core 44 and the valve seat 45 are sealed by the conical surface. One end of the one-way valve spring 43 presses against the end face of the valve core 44, and the other end of the one-way valve spring 43 is located in the groove on the valve sleeve 42, so that the valve core 44 is pressed against the valve seat 45 to achieve sealing. The valve sleeve 42 is fastened to the valve seat 45 by threads, and a flow channel 2 is also provided on the valve sleeve 42. A flow channel 3 is provided in the middle of the one-way valve fastening screw plug 41, and the one-way valve fastening screw plug 41 is fastened and connected by an external thread and an inner plug head 6. The left end surface of the one-way valve fastening screw plug 41 contacts the right end surface of the valve sleeve 42, thereby fixing the valve sleeve 42 and the valve seat 45. When the pressure of the main cavity 9 is greater than that of the self-balancing cavity 5, the valve core 44 separates from the valve seat 45, and the medium of the main cavity 9 enters the self-balancing cavity 5 through the flow channel 1, the flow channel 2 and the flow channel 3 respectively.

[0033] When the plunger 13 moves toward the hydraulic end, the volume of the main chamber 9 decreases, the internal medium is compressed, and the pressure increases. At this time, the one-way valve 4 opens, and the high-pressure medium inside the main chamber 9 enters the self-balancing chamber 5. When the plunger moves in the opposite direction, the volume of the main chamber 9 increases, and the internal medium pressure decreases. At this time, the one-way valve 4 is closed. During the closing process of the one-way valve 4, a small amount of high-pressure medium will leak back to the main chamber 9 from the self-balancing chamber 5, but the medium inside the self-balancing chamber 5 still maintains a very high pressure, and the fluctuation range is very small. Therefore, during the entire reciprocating operation process, the medium inside the self-balancing chamber 5 always maintains a high pressure. The external plug 3 is always subjected to the outward pressure given by the high-pressure medium, and the pressure fluctuation range is very small. Therefore, the thread stress value of the fastening screw 2 fluctuates little, which effectively improves the thread stress condition, increases the service life, and effectively prevents the fastening screw 2 from loosening due to alternating stress. At the same time, the pressure from the medium on the external plug 3 is relatively stable, so the reliability of the end face seal between the external plug 3 and the pump head is effectively guaranteed.

[0034] As for the stress on the inner plug head 6, when the plunger 13 moves toward the hydraulic end, the one-way valve 4 is open, and the medium pressures on both sides of the main cavity 9 and the self-balancing cavity 5 are balanced. Therefore, the force on the threads on the inner plug head 6 and the step surface of the inner plug head 6 is the preload force of the inner plug head 6 during installation. When the plunger 13 moves in the opposite direction, the one-way valve 4 is closed, the main cavity 9 is at low pressure, and the self-balancing cavity 5 is at high pressure. At this time, the inner plug head 6 is subjected to the pressure from the high-pressure medium in the balancing cavity 5 to the left, pressing the inner plug head 6 against the step surface of the pump head 1. At this time, the threads of the inner plug head 6 are basically not subjected to stress. Therefore, the fluctuation range of the alternating force on the threads of the inner plug head 6 is only the size of the preload force, which is much smaller than the force of the high-pressure medium on the inner plug head 6.

[0035] Example 2: Reference Figure 3 , which is different from the first embodiment in that the fixing structure is an external plug pressing plate 17, and the external plug 3 is fixed by the external plug pressing plate 17. The right end face of the external plug 3 protrudes outward by a certain size compared with the right end face of the pump head 1, and the right end face of the external plug 3 is in direct contact with the left end of the external plug pressing plate 17, and the external plug 3 is pressed by the external plug pressing plate 17. The external plug pressing plate 17 is fixed to the pump head 1 by multiple bolts. The middle part of the external plug pressing plate 17 is hollow, which is convenient for installing the external plug 3.

[0036] The advantage of this solution is that it can reduce the size of the pump head 1, reduce weight and cost. For the solution of embodiment one, the external plug 3 is fixed by a fastening screw 2, and the fastening screw 2 is embedded in the pump head 1 through a thread, so the axial dimension of the pump head 1 will be thicker. Secondly, every time the wearing parts such as the inner plug end face seal 7, the external plug end face seal 8 and the plunger 13 are replaced, the fastening screw 2 needs to be disassembled, and the disassembly and fastening process is relatively laborious; and once the thread of the pump head 1 is damaged during repeated disassembly or installation, the entire pump head needs to be returned to the factory for repair or even replacement. The external plug pressure plate 17 is used for fastening, which is convenient for repeated disassembly and installation, and even if the thread of the external plug pressure plate 17 fails, it is only necessary to replace the bolts and the external plug pressure plate 17, which is simple and reliable.

[0037] Example 3: Reference Figure 4, which is different from the second embodiment in that: the inner plug head 6 adopts radial sealing to achieve the sealing between the main cavity 9 and the self-balancing cavity 5, and the sealing is achieved by setting an inner plug head radial sealing ring 18 on the outside of the inner plug head 6 near the left side. An annular buffer pad 19 is set between the left step surface of the inner plug head 6 and the step surface of the pump head 1. A relatively soft material such as copper alloy can be selected to buffer the alternating impact force between the contact surface of the inner plug head 6 and the pump head 1. By adopting the radial sealing method, the outer diameter of the inner plug head 6 can be reduced, and even if the inner plug head 6 is displaced in the axial direction, the seal will not fail. In addition, in the methods of the first and second embodiments, due to the existence of the end face seal, the step surface of the inner plug head 6 and the step surface of the pump head 1 are in direct contact, and are subjected to alternating forces during operation, so they are prone to deformation or fatigue damage. The solution of this embodiment can effectively solve this problem through the buffer pad 19.

[0038] Example 4: Reference Figure 5 , which is different from the first, second and third embodiments in that the inner plug 6 is no longer fastened to the pump head 1 by threads. An inner plug radial sealing ring 18 is provided on the inner plug 6 to achieve the sealing between the main cavity 9 and the self-balancing cavity 5. A groove is provided at the right end of the inner plug 6 for placing the connecting spring 20. The other end of the connecting spring 20 is against the left end face of the external plug 3. The fixing of the inner plug 6 is achieved by pressing the connecting spring 20 by the external plug 3. The area near the part of the external plug 3 in contact with the connecting spring 20 is flattened and polished to ensure flatness and smoothness. Lubricating oil can be applied during installation. In this way, during the installation process, even if the external plug 3 and the inner plug 6 are not strictly coaxially aligned, the connecting spring 20 can slide freely on the left end face of the external plug 3 to avoid the deflection of the connecting spring 20, thereby ensuring that the connecting spring 20 force on the inner plug 6 maintains the axial direction, which can effectively ensure the radial sealing reliability on the inner plug 6 and avoid the seal from failing easily due to force deflection. Compared with the first three solutions, the one-way valve 4 is located in the middle of the inner plug 6, which can avoid uneven force on the inner plug 6 due to the flow of the medium during the opening and closing process. A guide step is set at the place where the pump head 1 contacts the left end face of the external plug 3 to ensure that the external plug 3 can be installed concentrically with the inner plug 6. An annular buffer pad 19 is set between the left step surface of the inner plug 6 and the pump head 1. A relatively soft material such as copper alloy can be used to buffer the alternating impact force between the contact surface of the inner plug 6 and the pump head 1.

[0039] During operation, the self-balancing chamber 5 always maintains high pressure. Therefore, when the plunger 13 moves toward the hydraulic end, when the pressure of the medium in the main chamber 9 is higher than the pressure in the self-balancing chamber 5, the force of the medium in the main chamber 9 on the inner plug 6 is greater than the force in the self-balancing chamber 5, but at this time, the one-way valve 4 will open immediately, and the pressures in the main chamber 9 and the self-balancing chamber 5 will be quickly balanced. Since the liquid medium is not easy to compress, the flow of the medium is very small. At the same time, due to the preload force of the connecting spring 20, the inner plug 6 will not move axially, but will be pressed on the annular buffer pad 19 and the pump head 1. At this time, since the pressure of the media on both sides is basically balanced, the force of the inner plug 6 on the annular buffer pad 19 and the pump head 1 is small, close to the preload force of the connecting spring 20.

[0040] When the plunger 13 moves in the opposite direction, the medium pressure in the main chamber 9 decreases, and the one-way valve 4 is closed at this time. During the closing process, a small amount of high-pressure medium will leak back to the main chamber 9 from the self-balancing chamber 5, but the medium inside the self-balancing chamber 5 still maintains a very high pressure. At this time, the medium in the main chamber 9 is low pressure (the suction pressure of the pump), so the inner plug head 6 will be pressed against the annular buffer pad 19 and the pump head 1 by the high-pressure medium of the self-balancing chamber 5. At this time, the force of the inner plug head 6 on the annular buffer pad 19 and the pump head 1 is very large. The annular buffer pad 19 can effectively protect the pump head 1 and the inner plug head 6 from deformation and damage caused by direct contact under alternating stress. In summary, compared with the previous schemes, during operation, there is no longer a threaded component that is subjected to large alternating stress in this application, and the inner plug head 6 does not need to be installed by rotation, and the installation process has less impact on the seal.

[0041] Comparative ratio: Reference Figure 6 and Figure 7 , where BC is the inner surface of the main cavity 9 in the pump head 1, and AC is the step surface of the pump head 1, which is in direct contact with the end face of the plug and realizes the end face sealing. The position A corresponds to the position of the axial sealing ring (first sealing ring) of the plug in the patent 202211653810.8 scheme. The position B corresponds to the position of its radial sealing ring (second sealing ring). Under the same size, point A corresponds to the inner plug end face sealing ring ( Figure 1 , Figure 3 ), point E is the position of the external plug end face sealing ring (the third sealing ring).

[0042] The annular area of ​​line segments AC, CD, AD, and ED relative to the central axis is recorded as SAC, SCD, SAD, and SED. The pressure value of the medium inside the main cavity at high pressure is recorded as P1, and the corresponding self-balancing cavity pressure is also P1. The pressure value of the medium inside the main cavity at low pressure is recorded as P2, and the corresponding self-balancing cavity pressure is P10; due to the delay in opening and closing of the one-way valve, a small amount of self-balancing cavity medium will flow back to the main cavity, so P10 will be slightly lower than P1.

[0043] For conventional solutions that do not use a self-balancing cavity, when the medium inside the main cavity is low pressure P2, the total force of the medium acting on the plug is P2×SAD, and when the medium in the main cavity is high pressure P1, the total force of the medium acting on the plug is P1×SAD. Therefore, the fluctuation range of the force on the plug and the rear fastening screw plug (front screw plug) from the medium is (P1-P2)×SAD.

[0044] For the patent 202211653810.8 solution, the high-pressure medium inside the self-balancing cavity will exert forces on both sides of the plug and offset each other, so the effective action area of ​​the high-pressure medium on the plug is SAC. Because the left end of the plug is in direct contact with the medium in the main cavity, when the medium inside the main cavity is low pressure P2, the total force of the medium acting on the plug is P2×SCD+P10×SAC; when the medium in the main cavity is high pressure P1, the total force of the medium acting on the plug is P1×SAD. Therefore, the fluctuation range of the force acting on the plug and the rear end fastening screw (front screw) from the medium is (P1-P2)×SCD+(P1-P10)×SAC.

[0045] For several schemes of the present invention, when the medium in the main cavity is at a high pressure P1, the medium force on the plug (external plug) is P1×SED; when the medium in the main cavity is at a low pressure P2, the corresponding self-balancing cavity pressure is P10, and the medium force on the plug (external plug) is P10×SED. Therefore, the fluctuation range of the force on the plug (external plug) and the rear end fastening screw plug (front screw plug) from the medium is (P1-P10)×SED.

[0046] Take the main cavity inner diameter as 300mm, the first sealing ring (point A) diameter as 330mm, the third sealing ring (point E) diameter as 360mm, the main cavity medium high pressure P1 as 17MPa, the main cavity medium low pressure P2 as 0.3MPa, and the self-balancing cavity pressure P10 as 16Mpa as an example for calculation. Figure 7 The calculation results of the force exerted by the medium on the (external) plug corresponding to different methods. Among them, the "conventional method" corresponds to the conventional scheme without a self-balancing chamber, and the fluctuation rate of the medium force exerted on the plug (the difference between the maximum value and the minimum value divided by the maximum value) is 98.24%. The "existing patent method" is the patent 202211653810.8 scheme, and the fluctuation rate of the medium force exerted on the plug is 82.21%. The "present invention" corresponds to the scheme of the present invention, and the fluctuation rate of the medium force exerted on the plug is 5.88%. It can be seen that the present invention can effectively improve the fluctuation range of the alternating stress exerted on the plug and the fastening screw plug, the sealing is more reliable, and the equipment maintenance cycle is longer.

[0047] Finally, it should be noted that the above is only a preferred embodiment of the present application and is not intended to limit the scope of protection of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the scope of protection of the present application.

Claims

1. A plunger pump for improving alternating pressure sealing, comprising a pump head (1) and a valve assembly (14), wherein the valve assembly (14) is arranged in the pump head (1), wherein a main cavity (9) is provided in the pump head (1), wherein a plunger (13) is arranged in the main cavity (9), wherein one end of the plunger (13) is connected to a power source, wherein the power source drives the plunger (13) to make axial movement along the length direction of the plunger (13), wherein the plunger (13) is provided with a power source. A plug assembly for sealing the main cavity (9) is provided at one end of the main cavity (9) away from the power source; The plug assembly comprises an external plug (3) and an internal plug (6), wherein the external plug (3) and the internal plug (6) are both connected to the end of the pump head (1) close to the main cavity (9), and a self-balancing cavity (5) is provided between the external plug (3) and the internal plug (6); The inner plug head (6) is provided with a one-way valve (4), and the one-way valve (4) allows the medium to enter the self-balancing cavity (5) from the main cavity (9).

2. A plunger pump with improved alternating pressure sealing according to claim 1, characterized in that: The one-way valve (4) comprises a one-way valve fastening screw plug (41), a valve sleeve (42), a one-way valve spring (43), a valve core (44) and a valve seat (45). The valve seat (45) is arranged in an inner plug head (6). The valve sleeve (42) is fixed to the end of the valve seat (45). A flow channel 1 is provided in the valve seat (45). The valve core (44) is connected to the valve sleeve (42) via the one-way valve spring (43). The one-way valve spring (43) is in a compressed state. The valve core (44) seals the flow channel 1. The valve sleeve (42) is provided with a flow channel 2. When the pressure of the main cavity (9) is greater than that of the self-balancing cavity (5), the valve core (44) is separated from the valve seat (45). The medium of the main cavity (9) enters the self-balancing cavity (5) through the flow channel 1 and the flow channel 2 respectively.

3. A plunger pump with improved alternating pressure sealing according to claim 2, characterized in that: The one-way valve (4) further comprises a one-way valve radial sealing ring (46), wherein the one-way valve radial sealing ring (46) is mounted on the outer diameter of the valve seat (45).

4. A plunger pump with improved alternating pressure sealing according to claim 3, characterized in that: The inner plug head (6) is provided with an inner plug head end face sealing ring (7), and the outer plug head (3) is provided with an outer plug head end face sealing ring (8).

5. A plunger pump with improved alternating pressure sealing according to claim 1 or 4, characterized in that: The external plug (3) is provided with a fixing structure for fixing the external plug (3).

6. A plunger pump with improved alternating pressure sealing according to claim 5, characterized in that: The fixing structure is a fastening screw plug (2), the fastening screw plug (2) is fixed on the pump head (1), and the fastening screw plug (2) is pressed against the external plug head (3).

7. A plunger pump with improved alternating pressure sealing according to claim 5, characterized in that: The fixing structure is an external plug pressing plate (17), which is fixed on the pump head (1) at an end close to the main cavity (9), and the external plug pressing plate (17) is pressed tightly against the external plug (3).

8. A plunger pump with improved alternating pressure sealing according to claim 7, characterized in that: An inner plug head radial sealing ring (18) is arranged outside the inner plug head (6) close to the left side, and a connecting spring (20) is arranged between the outer plug head (3) and the inner plug head (6), and the connecting spring (20) is in a compressed state.

9. A plunger pump with improved alternating pressure sealing according to claim 8, characterized in that: An annular buffer pad (19) is provided between the left step surface of the inner plug head (6) and the step surface of the pump head (1), and the material of the annular buffer pad (19) is preferably a soft copper alloy.

10. A plunger pump with improved alternating pressure sealing according to claim 1, characterized in that: The one-way valve (4) is installed in the middle position of the inner plug head (6).

Images