Series plunger pump

Abstract

The utility model provides a series plunger pump. The series plunger pump comprises a low-pressure pump and a high-pressure pump which communicate in series. A water suction cavity and a pressure relief structure are arranged on the low-pressure pump, and the water suction cavity is communicated with the high-pressure pump through the pressure relief structure; the pressure relief structure comprises a first valve, a second valve and a pressure relief opening, the first valve is used for conducting pressure relief on liquid flowing from the high-pressure pump to the low-pressure pump, and the second valve is used for conducting pressure relief on liquid flowing from the water suction cavity to the pressure relief opening; the pressure relief opening is provided with a limiting piece, and the limiting piece is used for limiting movement of the first valve towards the pressure relief opening. The first valve and the second valve are matched to realize dual pressure relief, so that the protectiveness of the low-pressure pump and the integral plunger pump is improved; the limiting piece can limit the displacement of the second valve towards the pressure relief opening, normal use of first-stage pressure relief of the second valve is guaranteed, if the pressure of liquid is too high, the liquid can push the second valve to move towards the pressure relief opening and break through the limiting piece, the liquid can be sprayed outwards from the pressure relief opening, and therefore second-stage pressure relief of the second valve is achieved; and the overall pressure relief capacity of the plunger pump is improved.

Description

Technical Field

[0001] This application relates to the field of plunger pump technology, and more specifically to a tandem plunger pump. Background Technology

[0002] A tandem plunger pump includes a low-pressure pump and a high-pressure pump, which are connected in series to output low-pressure liquid and high-pressure liquid, respectively. The low-pressure pump has a main inlet, and the high-pressure pump has a main outlet. Liquid flows from the low-pressure pump to the high-pressure pump. If high-pressure liquid needs to be output, the high-pressure pump will pressurize the liquid and release it from the main outlet. If low-pressure liquid needs to be output, the high-pressure pump will not work, and the low-pressure liquid will still be output from the main outlet.

[0003] However, when outputting high-pressure water, if the outlet pipe is closed or the liquid output is reduced, the water pressure inside the pump body will increase and backflow will occur. Therefore, most plunger pumps in modern technology are equipped with a pressure relief flow path inside the pump body to guide the high-pressure liquid back to the corresponding high-pressure suction chamber or low-pressure suction chamber for pressure relief, so as to avoid the pump body from bursting due to excessive liquid pressure, which would endanger the workers.

[0004] However, in existing plunger pumps, the pressure relief structure is only set in the corresponding suction chamber. The pressure relief capacity in the suction chamber is limited. When the pressure sensing device in the plunger pump malfunctions or the pressure is too high, it cannot effectively relieve pressure, which will still cause the hydraulic pressure in the pump body to be too high and burst.

[0005] Therefore, there is room for further improvement in the existing plunger pump technology. Utility Model Content

[0006] In view of this, and in response to the technical problem that the pressure relief structure in the existing plunger pump cannot meet the large pressure relief requirements, this application provides a series plunger pump, which has a pressure relief structure on the low-pressure pump and has a dual pressure relief function. It can relieve pressure on both the low-pressure pump and the high-pressure pump, thereby preventing the plunger pump from bursting due to excessive pressure and improving the safety of the plunger pump.

[0007] This application provides a series plunger pump, including a low-pressure pump and a high-pressure pump connected in series;

[0008] The low-pressure pump is provided with a water suction chamber and a pressure relief structure, and the water suction chamber is connected to the high-pressure pump through the pressure relief structure.

[0009] The pressure relief structure includes a first valve, a second valve, and a pressure relief port. The first valve is used to relieve pressure on the liquid flowing from the high-pressure pump to the low-pressure pump, and the second valve is used to relieve pressure on the liquid flowing from the suction chamber to the pressure relief port.

[0010] The pressure relief port is equipped with a limiting member, which is used to restrict the movement of the first valve toward the pressure relief port.

[0011] Compared with the prior art, the tandem plunger pump provided in this application has a first valve and a second valve in the pressure relief structure. The first valve is used to relieve the high pressure liquid returning from the high pressure pump, and the second valve is used to relieve the high pressure liquid in the suction chamber of the low pressure pump itself, thereby achieving dual pressure relief and improving the protection of the low pressure pump and the integral plunger pump.

[0012] In addition, the pressure relief structure is equipped with a pressure relief port, which has a limiting component. The limiting component restricts the displacement of the second valve toward the pressure relief port, thereby ensuring the normal operation of the first-stage pressure relief of the second valve. However, if the liquid pressure is too high, the liquid can push the second valve toward the pressure relief port, breaking through the limiting component, allowing the liquid to spray outward from the pressure relief port, thereby achieving the second-stage pressure relief of the second valve. This improves the overall pressure relief capacity of the plunger pump, prevents the plunger pump from bursting due to excessive pressure, and improves the safety of the plunger pump.

[0013] Preferably, the pressure relief structure includes a first pressure relief channel and a second pressure relief channel, wherein the axis of the first pressure relief channel is parallel to a first direction, the axis of the second pressure relief channel is parallel to a second direction, and the first direction is perpendicular to the second direction;

[0014] The first valve is located in the first pressure relief channel, the second valve is located in the second pressure relief channel, and the pressure relief port is located on the first pressure relief channel.

[0015] Preferably, along the first direction, one end of the first pressure relief channel is provided with a first water inlet connected to the high-pressure pump, and the other end of the first pressure relief channel is a pressure relief outlet;

[0016] The first valve moves toward the pressure relief port to connect the first pressure relief channel.

[0017] Preferably, the first pressure relief channel is provided with a first connecting channel at its side end, and the second pressure relief channel is connected to the first pressure relief channel through the first connecting channel;

[0018] Along the first direction, the first connecting channel is located between the first water inlet and the pressure relief port.

[0019] Preferably, the first pressure relief channel includes a first inner cavity and a second inner cavity, wherein the first inner cavity is normally connected to the first outer cavity;

[0020] The first connecting channel is normally open to the first outer cavity; the first valve is used to control the connection between the first inner cavity and the high-pressure pump.

[0021] Preferably, the first outer cavity is an annular structure, and the axial direction of the first connecting channel is parallel to the tangential direction of the first outer cavity.

[0022] Preferably, the second pressure relief channel includes a second inner cavity and a second outer cavity;

[0023] One end of the second outer cavity is normally connected to the water absorption cavity, and the other end is normally connected to the first pressure relief channel;

[0024] The second inner cavity is normally connected to the water absorption cavity, wherein the second valve is used to control the connection between the second inner cavity and the second outer cavity.

[0025] Preferably, the pressure relief structure includes a second connecting channel, and the second outer cavity is connected to the water absorption cavity through the second connecting channel;

[0026] The second outer cavity is provided with a second water inlet, and the second outer cavity is connected to the first pressure relief channel through the second water inlet;

[0027] Along the first direction, the second inlet is located above the second connecting channel.

[0028] Preferably, the second connecting channel includes a first opening and a second opening, the second connecting channel communicates with the second outer cavity through the first opening, and the second connecting channel communicates with the water absorption cavity through the second opening;

[0029] Along the axis of the second pressure relief channel, the projections of the first opening and the second opening do not overlap.

[0030] Preferably, the second outer cavity is an annular structure, the second inner cavity is a cylindrical structure, and the axes of the second inner cavity and the second outer cavity are on the same straight line;

[0031] Parallel to the first direction, the second valve moves toward the second opening direction to connect the second inner cavity and the second outer cavity.

[0032] The tandem piston pump disclosed in this application has at least the following technical advantages:

[0033] 1. By setting a first valve to depressurize the liquid flowing back from the high-pressure pump to the low-pressure pump, and setting a second valve to depressurize the liquid in the suction chamber of the low-pressure pump, dual depressurization can be achieved, thereby improving the depressurization effect of the plunger pump.

[0034] 2. By setting a limiting device at the pressure relief port, the first-stage pressure relief function of the first valve can be ensured to work normally. However, when the liquid pressure is greater than a certain level, the limiting device can be broken, allowing the liquid to break through the first valve and the limiting device and rush out from the pressure relief port, thus achieving second-stage pressure relief. This improves the pressure relief adjustment range of the plunger pump and increases the safety of the plunger pump.

[0035] 3. By setting the first pressure relief channel and the second pressure relief channel to be constantly connected, and the second pressure relief channel to be constantly connected to the suction chamber of the low-pressure pump, the high-pressure liquid can enter the suction chamber by opening the first valve, thereby achieving pressure relief regulation.

[0036] 4. By setting a second valve, the second inner cavity and the second outer cavity can be opened, and the second outer cavity is always connected to the first pressure relief channel. If the liquid pressure in the low-pressure pump is abnormally high, it can also break through the pressure relief port and rush out, which improves the pressure relief adjustment range of the low-pressure pump and further improves the safety and service life. Attached Figure Description

[0037] Figure 1 This is a three-dimensional structural schematic diagram of a tandem plunger pump provided in an embodiment of this application;

[0038] Figure 2 This is a schematic diagram of a partially exploded structure of a tandem plunger pump provided in an embodiment of this application. Figure 1 ;

[0039] Figure 3 This is a schematic diagram of a partially exploded structure of a tandem plunger pump provided in an embodiment of this application. Figure 2 ;

[0040] Figure 4 This is a schematic diagram of a partially exploded structure of a tandem plunger pump provided in an embodiment of this application. Figure 3 ;

[0041] Figure 5 This is a schematic diagram of a partial explosion structure of a low-pressure pump body provided in an embodiment of this application;

[0042] Figure 6 yes Figure 1 A magnified view of part A;

[0043] Figure 7 yes Figure 2 A magnified schematic diagram of part B.

[0044] Reference numerals: 1. Low-pressure pump; 2. High-pressure pump;

[0045] 11. Suction chamber; 12. First valve; 13. Second valve; 14. Pressure relief port; 15. First pressure relief channel; 16. Second pressure relief channel; 17. First connecting channel; 18. Second connecting channel; 19. Limiting component;

[0046] 151. First water inlet; 152. First inner cavity; 153. First outer cavity;

[0047] 161. Second inner cavity; 162. Second outer cavity;

[0048] 171. Second water inlet;

[0049] 181. First opening; 182. Second opening. Detailed Implementation

[0050] To enable those skilled in the art to better understand the technical solutions of this disclosure, the following detailed, clear, and complete description of this disclosure is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this disclosure and are not intended to limit it.

[0051] In the description of this application, the use of "first" and "second" is for the purpose of distinguishing technical features only, and should not be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated or the order of the technical features indicated.

[0052] Those skilled in the art should understand that in the disclosure of this application, the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "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 application 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, the above terms should not be construed as limitations on this application.

[0053] The present application will now be described in further detail with reference to the accompanying drawings, see below. Figures 1 to 7 illustrate.

[0054] This application provides a tandem piston pump, such as Figure 1 As shown, it includes a low-pressure pump 1 and a high-pressure pump 2 connected in series. The low-pressure pump 1 is provided with a total liquid inlet, and the high-pressure pump 2 is provided with a total liquid outlet. The low-pressure pump 1 and the high-pressure pump 2 are connected. Liquid enters the low-pressure pump 1 through the total liquid inlet, then enters the high-pressure pump 2, and flows out from the total liquid outlet.

[0055] The low-pressure pump 1 is equipped with a suction chamber 11 and a pressure relief structure. The main inlet is connected to the suction chamber 11, and the suction chamber 11 is connected to the high-pressure pump 2 through the pressure relief structure. Figures 2 to 5 As shown, the pressure relief structure includes a first pressure relief channel 15, a second pressure relief channel 16, a first valve 12, a second valve 13, and a pressure relief port 14. The first pressure relief channel 15 and the second pressure relief channel 16 are connected in series.

[0056] Specifically, such as Figure 7As shown, the first valve 12 is installed in the first pressure relief channel 15. The first valve 12 is used to relieve the pressure of the liquid flowing from the high-pressure pump 2 to the low-pressure pump 1. That is, when the liquid flowing back from the high-pressure pump 2 to the low-pressure pump 1, it will enter the first pressure relief channel 15 by opening the first valve 12, and then enter the second pressure relief channel 16 and the suction chamber 11 in sequence, thereby relieving the pressure of the high-pressure liquid flowing back from the high-pressure pump 2.

[0057] like Figure 3 , Figure 4 As shown, the second valve 13 is disposed in the second pressure relief channel 16. The second valve 13 is used to relieve the pressure of the liquid flowing from the suction chamber 11 to the pressure relief port 14. When the liquid in the suction chamber 11 of the low-pressure pump 1 is under high pressure, it can move toward the second pressure relief channel 16 to open the second valve 13, so that the liquid of the low-pressure pump 1 flows into the first pressure relief channel 15 through the second pressure relief channel 16, thereby realizing the pressure relief of the liquid in the suction chamber 11 of the low-pressure pump 1.

[0058] Among them, such as Figure 1 , Figure 6 As shown, the pressure relief port 14 is located on the first pressure relief channel 15. The pressure relief port 14 is equipped with a limiting member 19, which restricts the movement of the second valve 13 toward the pressure relief port 14. This allows the first pressure relief channel 15 to have a two-stage pressure relief function with the cooperation of the limiting member 19 and the first valve 12. Specifically, the limiting member 19 can restrict the displacement of the second valve 13 toward the pressure relief port 14, thereby ensuring the normal operation of the first-stage pressure relief of the second valve 13. That is, it ensures that the return liquid from the high-pressure pump 2 can open the first valve 12 and enter the suction chamber 11 through the first pressure relief channel 15. However, if the liquid is too high-pressure, the high-pressure thrust of the liquid can push the second valve 13 toward the pressure relief port 14, breaking through the limiting member 19 and allowing the liquid to spray outward from the pressure relief port 14, thereby achieving the second-stage pressure relief of the second valve 13. This improves the overall pressure relief capacity of the plunger pump, prevents the plunger pump from bursting due to excessive pressure, and improves the safety of the plunger pump.

[0059] like Figure 6 As shown, the limiting member 19 is a rod-shaped member that is inserted into the pressure relief port 14 of the first pressure relief channel 15 and is located at the upper end of the first valve 12 to limit the upward displacement of the first valve 12. It has a certain strength, but if it reaches the critical value, it can be broken by the liquid, thereby opening the pressure relief port 14 to allow the high-pressure liquid to be released.

[0060] It should be noted that, as Figure 5As shown, the axis of the first pressure relief channel 15 is parallel to the first direction, the axis of the second pressure relief channel 16 is parallel to the second direction, and the first direction is perpendicular to the second direction; wherein, the first direction is parallel to the X-axis, the second direction is parallel to the Y-axis, the third direction is parallel to the Z-axis, and the third direction is perpendicular to both the first and second directions, so as to establish an X, Y, Z three-axis coordinate system.

[0061] Specifically, the first pressure relief channel 15 will be further described; such as Figure 5 , Figure 7 As shown, along the first direction, the bottom of the first pressure relief channel 15 is provided with a first inlet 151, the pressure relief port 14 is located above the first pressure relief channel 15, and the first valve 12 is disposed between the first inlet 151 and the pressure relief port 14. The first valve 12 is used to control the opening and closing of the first inlet 151. The first valve 12 is a one-way valve. The high-pressure liquid impacts the first valve 12 upward, opens the first valve 12 and enters into the first pressure relief channel 15, thereby being able to enter the second pressure relief channel 16.

[0062] Among them, such as Figure 4 , Figure 7 As shown, the pressure relief structure also includes a first connecting channel 17, which is located at the side end of the first pressure relief channel 15. The first connecting channel 17 is connected to the second pressure relief channel 16, that is, one end of the first connecting channel 17 is connected to the first pressure relief channel 15 and the other end is connected to the second pressure relief channel 16, so that the liquid in the first pressure relief channel 15 can enter the second pressure relief channel 16 through the first connecting channel 17. In the first direction, the first connecting channel 17 is located between the first inlet 151 and the pressure relief port 14, that is, the first valve 12 needs to be opened before the liquid can enter the first pressure relief channel 15 and then the second pressure relief channel 16.

[0063] Specifically, such as Figure 4 As shown, the axis of the first connecting channel 17 and the first pressure relief channel 15 form an angle, which is an acute angle, so that the axial direction of the first connecting channel 17 is basically parallel to the tangent direction of the first outer cavity 153. In the second direction, the first connecting channel 17 is connected to the rear end of the first pressure relief channel 15. The first connecting channel 17 extends obliquely forward along the circular tangent of the first pressure relief channel 15 to connect with the second pressure relief channel 16. This allows the liquid flowing into the first pressure relief channel 15 to quickly enter the second pressure relief channel 16 after rotating along the inner wall of the first pressure relief channel 15 and flowing out in the tangential direction, reducing the resistance of the liquid flowing from the first pressure relief channel 15 into the second pressure relief channel 16 and accelerating the pressure relief effect.

[0064] Furthermore, such as Figure 4 , Figure 7As shown, the first pressure relief channel 15 includes a first inner cavity 152 and a second inner cavity 161. The first inner cavity 152 is normally connected to the first outer cavity 153. The first outer cavity 153 is located on the outer periphery of the first inner cavity 152 and has an annular structure. The first connecting channel 17 is normally connected to the first outer cavity 153, meaning that the first connecting channel 17 and the first outer cavity 153 are always in a connected state. Under normal pressure, the first valve 12 blocks the first inlet 151 to prevent the liquid in the first pressure relief channel 15 from flowing from the first inlet 151 to the high-pressure pump 2. However, when the high-pressure liquid of the high-pressure pump 2 flows back, it will push the valve ball of the first valve 12 to move upward, thereby opening the first inlet 151. The high-pressure backflow liquid then flows into the first inner cavity 152 through the first inlet 151 and then into the first outer cavity 153.

[0065] In another optional embodiment of this application, such as Figures 3 to 5 As shown, the pressure relief structure includes a second connecting channel 18. The second pressure relief channel 16 includes a second inner cavity 161 and a second outer cavity 162. Along the first direction, the second connecting channel 18 is located at the bottom of the second outer cavity 162. One end of the second outer cavity 162 is always connected to the water absorption cavity 11 through the second connecting channel 18. The first connecting channel 17 is located at the side end of the second outer cavity 162. The first connecting channel 17 opens on the second outer cavity 162 to form a second water inlet 171. The second outer cavity 162 is connected to the first pressure relief channel 15 through the second water inlet 171. The second outer cavity 162 is always connected to the first pressure relief channel 15 through the first connecting channel 17. The second water inlet 171 is higher than the connection point between the second connecting channel 18 and the second outer cavity 162. That is, the second water inlet 171 is located entirely above the second connecting channel 18, so that after the liquid in the first pressure relief channel enters the second outer cavity 162, it can quickly enter the water absorption cavity 11 through the second connecting channel 18.

[0066] In this embodiment, as Figure 7 As shown, the second inlet 171 and the second connecting channel 18 are distributed along the third direction; wherein, along the third direction, the second pressure relief channel 16 is located to the side of the first pressure relief channel 15.

[0067] like Figure 3 As shown, the second inner cavity 161 is normally connected to the water suction cavity 11. The second valve 13 is used to control the connection between the second inner cavity 161 and the second outer cavity 162. That is, under normal conditions, the second inner cavity 161 and the second outer cavity 162 are blocked. However, if the high-pressure liquid in the water suction cavity 11 applies a force along the second direction to the second valve 13, the second valve 13 can be pushed open, so that the second inner cavity 161 and the second outer cavity 162 are connected. The liquid in the water suction cavity 11 can enter the second outer cavity 162 through the second inner cavity 161, and then enter the first pressure relief channel 15 to achieve pressure relief.

[0068] In this embodiment, if the liquid pressure inside the low-pressure pump 1 is too high, secondary pressure relief can also be achieved by breaking through the limiting member 19.

[0069] Furthermore, such as Figure 3 As shown, the second connecting channel 18 includes a first opening 181 and a second opening 182. The second connecting channel 18 communicates with the second outer cavity 162 through the first opening 181 and with the water absorption cavity 11 through the second opening 182. Along the axis of the second pressure relief channel 16, the projections of the first opening 181 and the second opening 182 do not overlap. Figure 3 As shown, the second connecting channel 18 extends obliquely downward to accelerate the speed at which liquid enters the suction chamber 11 from the second connecting channel 18, which helps the first valve 12 to quickly depressurize the high-pressure return liquid of the high-pressure pump 2.

[0070] Among them, such as Figures 3 to 4 , Figure 7 As shown, the second outer cavity 162 is an annular structure, and the second inner cavity 161 is a cylindrical structure. The axes of the second inner cavity 161 and the second outer cavity 162 are on the same straight line, and the second outer cavity 162 is arranged around the outside of the second inner cavity 161. Similarly, the second valve 13 is a one-way valve, parallel to the first direction. The second valve 13 moves toward the second opening 182 to connect the second inner cavity 161 and the second outer cavity 162, so that the liquid in the suction chamber 11 can enter the second outer cavity 162 through the second inner cavity 161, and then enter the first pressure relief channel 15 through the first connecting channel 17 to realize the pressure relief of the high pressure liquid of the low pressure pump 1.

[0071] It should be noted that the various embodiments of this application can be arbitrarily combined into new embodiments, provided that the solutions do not conflict and the technical solutions can coexist.

[0072] The present application has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present application. The descriptions of the embodiments above are only for the purpose of helping to understand the present application and its core ideas. It should be noted that those skilled in the art can make several improvements and modifications to the present application without departing from the principles of the present application, and these improvements and modifications also fall within the protection scope of the claims of the present application.

Claims

1. A tandem plunger pump, characterized in that, It includes a low-pressure pump (1) and a high-pressure pump (2) connected in series; The low-pressure pump (1) is provided with a water suction chamber (11) and a pressure relief structure. The water suction chamber (11) is connected to the high-pressure pump (2) through the pressure relief structure. The pressure relief structure includes a first valve (12), a second valve (13), and a pressure relief port (14). The first valve (12) is used to relieve pressure on the liquid flowing from the high-pressure pump (2) to the low-pressure pump (1), and the second valve (13) is used to relieve pressure on the liquid flowing from the suction chamber (11) to the pressure relief port (14). The pressure relief port (14) is provided with a limiting member (19), which is used to restrict the movement of the first valve (12) toward the pressure relief port (14).

2. The tandem plunger pump according to claim 1, characterized in that, The pressure relief structure includes a first pressure relief channel (15) and a second pressure relief channel (16). The axis of the first pressure relief channel (15) is parallel to a first direction, and the axis of the second pressure relief channel (16) is parallel to a second direction. The first direction is perpendicular to the second direction. The first valve (12) is located in the first pressure relief channel (15), the second valve (13) is located in the second pressure relief channel (16), and the pressure relief port (14) is located on the first pressure relief channel (15).

3. The tandem plunger pump according to claim 2, characterized in that, Along the first direction, one end of the first pressure relief channel (15) is provided with a first water inlet (151) connected to the high pressure pump (2), and the other end of the first pressure relief channel (15) is a pressure relief port (14); The first valve (12) moves toward the pressure relief port (14) to connect the first pressure relief channel (15).

4. The tandem plunger pump according to claim 3, characterized in that, The first pressure relief channel (15) is provided with a first connecting channel (17) at its side end, and the second pressure relief channel (16) is connected to the first pressure relief channel (15) through the first connecting channel (17); Along the first direction, the first connecting channel (17) is located between the first water inlet (151) and the pressure relief port (14).

5. The tandem plunger pump according to claim 4, characterized in that, The first pressure relief channel (15) includes a first inner cavity (152) and a second inner cavity (161), and the first inner cavity (152) is normally connected to the first outer cavity (153); The first connecting channel (17) is normally connected to the first outer cavity (153); the first valve (12) is used to control the connection between the first inner cavity (152) and the high-pressure pump (2).

6. The tandem plunger pump according to claim 5, characterized in that, The first outer cavity (153) is a ring structure, and the axial direction of the first connecting channel (17) is parallel to the tangential direction of the first outer cavity (153).

7. The tandem plunger pump according to claim 2, characterized in that, The second pressure relief channel (16) includes a second inner cavity (161) and a second outer cavity (162); One end of the second outer cavity (162) is normally connected to the water absorption cavity (11), and the other end is normally connected to the first pressure relief channel (15); The second inner cavity (161) is normally connected to the water absorption cavity (11), wherein the second valve (13) is used to control the connection between the second inner cavity (161) and the second outer cavity (162).

8. The tandem plunger pump according to claim 7, characterized in that, The pressure relief structure includes a second connecting channel (18), and the second outer cavity (162) is connected to the water absorption cavity (11) through the second connecting channel (18); The second outer cavity (162) is provided with a second water inlet (171), and the second outer cavity (162) is connected to the first pressure relief channel (15) through the second water inlet (171); Along the first direction, the second inlet (171) is located above the second connecting channel (18).

9. The tandem plunger pump according to claim 8, characterized in that, The second connecting channel (18) includes a first opening (181) and a second opening (182). The second connecting channel (18) communicates with the second outer cavity (162) through the first opening (181) and with the water absorption cavity (11) through the second opening (182). Along the axis of the second pressure relief channel (16), the projections of the first opening (181) and the second opening (182) do not overlap.

10. The tandem plunger pump according to claim 9, characterized in that, The second outer cavity (162) is an annular structure, and the second inner cavity (161) is a cylindrical structure. The axes of the second inner cavity (161) and the second outer cavity (162) are on the same straight line. Parallel to the first direction, the second valve (13) moves toward the second opening (182) to connect the second inner cavity (161) and the second outer cavity (162).

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