Hydraulically driven multi-cylinder double-acting variable displacement piston diaphragm pump

Abstract

The application discloses a hydraulic driving multi-cylinder double-acting variable piston diaphragm pump. The pump comprises a pump base body, a power end, a liquid cylinder body, a diaphragm tank and a buffer tank which are installed on the pump base body, the power end is connected with the liquid cylinder body, the diaphragm tank is connected with the liquid cylinder body through connecting pipes respectively, flanges at two ends of the diaphragm tank are connected with suction valves and discharge valves respectively, wherein, the lower end suction valves are connected with suction pipes respectively, the upper end discharge valves are connected with discharge pipes respectively, and the discharge pipes are connected with the buffer tank. The application adopts a swash plate mechanism to realize the reciprocating motion of the multi-cylinder piston, drives the fluid medium in the working cavities on both sides of the piston to make the diaphragm in the diaphragm tank periodically concave-convex deformation, and realizes the self-suction of the pump feeding pulp from the suction pipe and the output of the discharge buffer tank. The diaphragm pump has the advantages of compact structure, small size, reduced output flow pulsation and reduced pulsation load impact of the filter press feeding on the filter plate.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of solid-liquid separation and relates to a liquid-driven multi-cylinder double-acting variable piston diaphragm pump. BACKGROUND

[0002] The filter press has become a general device widely used in the field of solid-liquid separation due to its simple process, high filtration efficiency and low operation cost. However, the filter press is a process device, and a feeding pump is needed to pump the feed slurry to realize the filter pressing operation. In the initial stage of the filter pressing operation, the feed flow is large and the pressure is low. In the later stage of the filter pressing operation, the feed flow gradually becomes small and the feed pressure gradually increases until the constant pressure is maintained, that is, the filter pressing operation is a constant-speed-constant-pressure filtration process.

[0003] For a long time, the centrifugal pump has been used as the filter press feeding pump. The flow and pressure of the centrifugal pump are related to the rotating speed of the centrifugal pump impeller, and it is difficult to simultaneously meet the requirements of the constant-speed-constant-pressure filter pressing operation. Only the excess flow can be discharged back to the slurry tank in the later constant-pressure filtration stage, resulting in unnecessary energy consumption. In recent years, based on the characteristics that the output flow and pressure of the reciprocating pump are not related and can be controlled respectively, a vertical or horizontal reciprocating feeding pump has been developed. Both of them directly introduce the pumped slurry into the working chamber of the reciprocating pump, and then discharge it at a certain pressure by the plunger or piston. Due to the wide application of the filter press, the slurry usually has corrosive, abrasive or high-temperature properties, which makes the working chamber, plunger and piston of the reciprocating pump easily corroded or worn, especially the sealing ring of the plunger or piston becomes a vulnerable part, which directly affects the performance, reliability and service life of the reciprocating pump. Moreover, the working cylinders of the reciprocating pump need to be arranged side by side, and it is not suitable to make multiple cylinders, which increases the pulsation rate of the slurry entering the filter press, makes the filter press filter plate bear asymmetric pulsating impact load, reduces the service life of the filter plate or damages the filter plate. In addition, the existing vertical or horizontal reciprocating feeding pump uses a hydraulic oil cylinder to drive the working plunger or piston to reciprocate, and the frequent reciprocating of the working oil cylinder will cause a certain energy loss. Furthermore, the reciprocating pump with large flow has a relatively large size. SUMMARY

[0004] To solve the above problems, the present application provides a liquid-driven multi-cylinder double-acting variable piston diaphragm pump to solve the problems of the existing reciprocating pump, and provides a new filter press feeding pump technology for the field of solid-liquid separation with energy-saving and high-reliability technical characteristics. The specific technical scheme of the present application is as follows:

[0005] The application relates to a hydraulic driving multi-cylinder double-acting variable piston diaphragm pump which is used as a filter press feeding pump and comprises a pump base body, a power end, a liquid cylinder body, a diaphragm tank, a buffer tank, a suction valve, a discharge valve, a suction pipe, a discharge pipe, a connecting pipe and a fluid medium tank. The power end, the liquid cylinder body, the diaphragm tank and the buffer tank are arranged on the pump base body, the power end is connected with the liquid cylinder body, the diaphragm tank is connected with the liquid cylinder body through the connecting pipe, the suction valve and the discharge valve are respectively connected with the upper and lower flanges of the diaphragm tank, the lower end suction valve is connected with the suction pipe, the upper end discharge valve is connected with the discharge pipe, and the discharge pipe is connected with the buffer tank. The inclined disc mechanism is adopted to realize the reciprocating motion of the multi-cylinder piston and drive the fluid medium in the working cavities on both sides of the piston to make the diaphragm in the diaphragm tank periodically deform, then the suction valve and the discharge valve are alternately opened and closed to realize the suction of the pump feeding slurry from the suction pipe and the output of the discharge buffer tank, the hydraulic system oil motor is adopted to input power, the output pressure feedback is adopted to adjust the input flow and the output rotating speed of the hydraulic oil of the oil motor, the output flow of the feeding pump is adjusted to meet the constant speed and constant pressure operation requirement of the filter press. The combined valve which integrates the working fluid medium supplement, exhaust and safety protection is arranged in the piston cavity considering the sealing of each link. The working fluid medium can be emulsion or hydraulic oil, and the diaphragm material can be selected from nitrile rubber, chloroprene rubber, polyurethane rubber, fluorine rubber or polytetrafluoroethylene according to the corrosion, abrasion or high temperature of the transported slurry.

[0006] The technical scheme of the application is specifically introduced as follows.

[0007] The application relates to a hydraulic driving multi-cylinder double-acting variable piston diaphragm pump which comprises a pump base body, a power end, a liquid cylinder body, a diaphragm tank and a buffer tank, the power end is connected with the liquid cylinder body to drive the reciprocating motion of the piston of the liquid cylinder body, the diaphragm tank is connected with the liquid cylinder body through the connecting pipe, the lower and upper ends of the diaphragm tank are respectively flange-connected with the suction valve and the discharge valve, the suction valve is connected with the suction pipe, the discharge valve is connected with the discharge pipe, and the output end of the discharge pipe is connected with the buffer tank.

[0008] The power end comprises a transmission box body, an end cover, an inclined disc mechanism and a connecting rod, the inclined disc mechanism is the transmission part of the power end and comprises a three-jaw inclined disc and a crankshaft, the three-jaw inclined disc is connected with the crankshaft through a second rolling bearing, the two ends of the crankshaft are respectively supported on the transmission box body and the end cover of the power end through first rolling bearings, the number of the connecting rods is the same as that of the claws of the three-jaw inclined disc and is uniformly distributed, a hinged sliding block is arranged in the cross head hole of the connecting rod, each claw of the three-jaw inclined disc is connected with the hinged sliding block arranged in the cross head hole of the connecting rod, and the second rolling bearing arranged at the center of the three-jaw inclined disc is moved to realize the space swing of the three-jaw inclined disc when the crankshaft rotates, and then the connecting rod is horizontally reciprocated along the slide hole of the transmission box body.

[0009] The liquid cylinder body comprises a cylinder body and a piston mechanism, the front end of the cylinder body is connected with the end cover of the power end through a flange, the power end is coaxially connected with the liquid cylinder body as a whole, cylinder barrels which are coaxial with the upper and lower connecting rods and have the same number as the three-jaw swash plate claws in the swash plate mechanism are arranged in the cylinder body, each cylinder barrel is provided with a cylinder barrel cover and a sealing groove; the piston mechanism comprises a piston ring and a piston rod, the piston rod is coaxial with the upper and lower connecting rods and drives the piston to reciprocate in the cylinder barrel.

[0010] During operation, the power end drives the piston rod in the cylinder barrel of the liquid cylinder body to reciprocate, and the fluid medium in the working cavities on both sides of the piston makes the diaphragm in the diaphragm tank periodically deform concave-convex, thereby driving the suction valve and the discharge valve to alternately open and close, realizing that the pump feeding slurry is sucked through the suction pipe and output through the outlet of the buffer tank.

[0011] In the application, the power end further comprises a hydraulic station, an electric control cabinet and an oil motor, the output shaft of the oil motor is connected with the crankshaft in the swash plate mechanism; during operation, the electric control cabinet controls the hydraulic station to drive the output shaft of the oil motor to rotate and drive the crankshaft to rotate, so that the swash plate swings and drives the connecting rod to horizontally reciprocate along the slide hole of the transmission box body.

[0012] In the application, the power end comprises a lubricating system, the lubricating system comprises a pump body, a lubricating oil pool, an oil inlet pipe, an oil pipe and an oil injection hole, the oil inlet pipe is connected with the pump body and the lubricating oil pool in communication, the pump body is sealingly connected with the extended section of the lower connecting rod, the oil injection hole is arranged at the top of the transmission box body, when the extended section reciprocates with the connecting rod, the steel ball in the pump body rises or falls on the conical ball seat, and the oil suction of the oil inlet pipe and the oil discharge of the oil pipe are periodically completed, and the discharged oil is sprayed downward through the oil injection hole to lubricate the articulated sliding block and the rolling bearing.

[0013] In the application, the diaphragm tank comprises a tank body, a double-layer diaphragm and a range-limiting mesh plate, the double-layer diaphragm is fixed to the tank body through circumferentially distributed studs, the reciprocating movement of the piston drives the positive and negative pressure in the cylinder barrel to alternately change, and the fluid medium in the driving cavity drives the diaphragm to periodically deform concave-convex between the tank cover and the range-limiting mesh plate. In the application, the diaphragm material can be selected as nitrile rubber, chloroprene rubber, polyurethane rubber, fluorine rubber or polytetrafluoroethylene according to the corrosion, abrasion or high temperature of the transported slurry.

[0014] In the application, the diaphragm tank further comprises a combination valve, the combination valve is arranged in the fluid medium tank and connected with the diaphragm tank through the oil inlet pipe and the oil outlet pipe.

[0015] Tank flange connection; wherein: the combination valve includes top plate, lever mechanism, top rod, compensation spring, compensation valve plate, compensation valve ball, filter, safety spring and safety valve plate; when the piston working cavity of the liquid cylinder body is negative pressure, the diaphragm concave deformation presses the top plate, drives the lever mechanism to push the top rod, overcomes the pressure of the compensation spring to open the compensation valve plate, replaces the gas in the piston working cavity with fluid medium, and the compensation valve ball rises at the same time, and the fluid medium is supplemented into the combination valve through the filter from the fluid medium box; when the piston working cavity is positive pressure, the diaphragm convex deformation stops the compensation of new fluid medium; when the piston working cavity is overpressure, the compensation valve plate and the safety valve plate are opened to unload the overpressure fluid medium into the fluid medium box.

[0016] In the application, the working fluid medium in the fluid medium box is emulsion or hydraulic oil.

[0017] In the application, a pressure transmitter is arranged on the output pipeline of the buffer tank, a pressure signal is fed back to the power end, and the output rotating speed of the driving power end is adjusted.

[0018] The hydraulic drive multi-cylinder double-acting variable piston diaphragm pump is used as a filter press feeding pump, and compared with the prior art, the application has the beneficial effects that:

[0019] The power end is driven by a hydraulic system oil motor to realize separate control of the output flow and pressure of the reciprocating pump, meets the constant speed-constant pressure working characteristics required by the operation of the filter press, simultaneously, the one-way rotating motion of the oil motor avoids the working loss caused by the frequent reversing of the traditional oil cylinder driven reciprocating pump, and the energy-saving effect is remarkable.

[0020] The power end transmission part adopts a swash plate mechanism, which not only has compact structure and small size, but also can change the rotating motion into multi-cylinder reciprocating linear motion, simultaneously drive multiple working cylinders, reduce the output flow pulsation, and reduce the pulsation load impact of the filter press feeding on the filter plate;

[0021] The pumped slurry does not enter the piston working cavity, but is sucked and output by the periodic convex-concave deformation of the diaphragm of the diaphragm tank driven by the reciprocating double-acting fluid medium, effectively solves the problem that the existing reciprocating pump transports the slurry into the working cavity, causes low performance and reliability of the pump, and can be suitable for pumping special slurry materials with corrosion, abrasion or high temperature for the filter press. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The present application is a piston diaphragm pump front view.

[0023] Figure 2 The present application is a piston diaphragm pump side view.

[0024] Figure 3 The present application is a piston diaphragm pump top view.

[0025] Figure 4 The piston diaphragm pump power end front view of the present application.

[0026] Figure 5 The piston diaphragm pump power end side view of the present application.

[0027] Figure 6 The piston diaphragm pump transmission case front view of the present application.

[0028] Figure 7 The piston diaphragm pump transmission case side view of the present application.

[0029] Figure 8 The piston diaphragm pump diaphragm tank, suction valve and discharge valve front view of the present application.

[0030] Figure label: 1-pump base body, 2-power end, 3-liquid cylinder body, 4-diaphragm tank, 5-buffer tank, 6-suction valve, 7-discharge valve, 8-suction pipe, 9-discharge pipe, 10-connection pipe, 11-transmission case body, 12-end cover, 13-hydraulic station, 14-electric control cabinet, 15-oil motor, 16-inclined disc mechanism, 17-lubrication system, 18-fluid medium tank, 19, 20-flange, 21-spline connection, 22-crankshaft, 23-first rolling bearing, 24-second rolling bearing, 25-three-jaw inclined disc, 26-hinged sliding block, 27-connecting rod, 28-extended section of connecting rod, 29, 31-oil pipe, 30-pump body, 32-sealing ring, 33-steel ball, 34-oil injection hole, 35-cylinder body, 36-piston mechanism, 37-flange, 38-cylinder barrel, 39-cylinder barrel cover, 40-sealing groove, 41-piston ring, 42-piston rod, 43-sealing ring, 44-sealing groove, 45-connection ring, 46, 52-flange, 47-tank body, 48-tank body cover, 49-diaphragm, 50-range limiting screen, 51-combined valve, 53-valve body, 54-valve cover, 55-valve ball, 56-valve seat, 57-range limiting frame, 58-top plate, 59-lever mechanism, 61-compensation spring, 62-compensation valve plate, 63-compensation valve ball, 64-filter, 65-safety spring, 66-safety valve plate, 67-pressure transmitter. DETAILED DESCRIPTION

[0031] The technical solutions of the present application will be described in detail below in combination with the drawings and examples.

[0032] As Figure 1 , Figure 2 and Figure 3As shown, this invention provides a hydraulically driven multi-cylinder double-acting variable piston diaphragm pump, which includes a pump base 1, a power end 2, a hydraulic cylinder 3, a diaphragm tank 4, a buffer tank 5, a suction valve 6, a discharge valve 7, a suction pipe 8, a discharge pipe 9, a connecting pipe 10, and a fluid medium tank 18. The power end 2, the hydraulic cylinder 3, the diaphragm tank 4, and the buffer tank 5 are placed on the pump base 1. The power end 2 is connected to the hydraulic cylinder 3. The diaphragm tank 4 is connected to the hydraulic cylinder 3 through the connecting pipe 10. The suction valve 6 and the discharge valve 7 are connected to the upper and lower flanges 19 of the diaphragm tank 4, respectively. The lower suction valve 6 is connected to the suction pipe 8, and the upper discharge valve 7 is connected to the discharge pipe 9. The discharge pipe 9 is connected to the buffer tank 5.

[0033] like Figure 4 , Figure 5 The power end 2 includes a transmission housing 11, an end cover 12, a hydraulic station 13, an electrical control cabinet 14, an oil motor 15, a swashplate mechanism 16, and a lubrication system 17.

[0034] The electrical control cabinet 14 controls the hydraulic station 13, driving the output shaft of the power end 2 oil motor 15 to rotate. This rotation, via spline connection 21, drives the crankshaft 22 of the swashplate mechanism 16 to rotate. The first rolling bearing 23 supporting the crankshaft 22 is coaxially fixed to the transmission housing 11 and the end cover 12. The rotation of the crankshaft 22, through the second rolling bearing 24 mounted thereon, enables the spatial swing of the three-jaw swashplate 25. Each jaw of the three-jaw swashplate 25 is connected to a circular hinged slider 26. The hinged slider 26 is placed in the crosshead hole of the connecting rod 27, driving the connecting rod 27 to reciprocate horizontally along the slide hole of the transmission housing 11. One of the bottom connecting rod 27 extensions 28, together with the transmission housing 11, forms a reciprocating lubricating oil pump. Figure 5 As shown in the cross-sectional view CC, the reciprocating lubricating oil pump inlet pipe 29 is connected to the pump body 30 and the bottom lubricating oil pool of the power end 2 respectively. A sealing ring 32 is provided between the connecting rod extension section 28 and the pump body 30. When the connecting rod extension section 28 reciprocates with the connecting rod 27, it drives the steel ball 33 to rise or fall on the conical ball seat of the pump body 30, periodically completing the oil suction from the inlet pipe 29 and the oil discharge through the oil pipe 31. The discharged oil is sprayed downward through the oil injection hole 34 at the top of the power end 2 to lubricate the hinged slider 26 and bearing 24 of the high-position connecting rod 27 reciprocating.

[0035] like Figure 6 and Figure 7The liquid cylinder body 3 comprises a cylinder body 35 and a piston mechanism 36. The flange 37 at the front end of the cylinder body 35 is bolted to the end cover 12 of the power end 2, so that the power end 2 and the liquid cylinder body 3 are coaxially connected as a whole. The cylinder body 35 is provided with cylinder barrels 38 which are the same in number as the claws of the swash plate mechanism 16 and coaxial with the connecting rods 27. Each cylinder barrel is provided with a cylinder barrel cover 39 and a sealing groove 40. The piston ring 41 of the piston mechanism 36 is fixed to the piston rod 42. The circumference of the piston ring 41 is provided with a sealing ring 43 which cooperates with the cylinder barrel 38. The sealing groove 40 is provided with a sealing ring 44 which cooperates with the piston rod 42. The other end of the piston rod 42 is connected to the connecting rod 27 of the power end 2 through a connecting ring 45, so as to drive the piston of the piston mechanism 36 to reciprocate in the cylinder barrel 38. The two ends of the piston reciprocating in the cylinder barrel 38 are provided with connecting flanges 46.

[0036] As Figure 8 The diaphragm tank 4 comprises a tank body 47, a tank body cover 48, a diaphragm 49, a range-limiting screen plate 50 and a combination valve 51. The diaphragm 49 is fixed to the tank body 47 through circumferentially distributed studs. The tank body 47 is provided with a flange 52. The connecting pipe 10 is connected to the flanges 46 and 52, so as to connect each diaphragm tank to the cavity at the two ends of the piston reciprocating in the cylinder barrel 38. The reciprocating movement of the piston ring 41 causes the positive and negative pressure in the cavities at the two sides of the piston ring 41 in the cylinder barrel 38 to change alternately, so as to drive the fluid medium in the cavities to cause the diaphragm 49 to periodically deform concave-convex between the tank body cover 48 and the range-limiting screen plate 50.

[0037] The suction valve 6 and the discharge valve 7 each comprise a valve body 53. The suction valve 6 and the discharge valve 7 are respectively installed at the upper and lower ends of the diaphragm tank 4 through flanges.

[0038] When the diaphragm 49 deforms concave to the right, the valve ball 55 of the discharge valve 7 falls on the valve seat 56, and the valve ball 55 of the suction valve 6 rises below the range-limiting frame 57. The cavity between the tank body cover 48 and the diaphragm 49 of the diaphragm tank 4 is under negative pressure, and the slurry material from the suction pipe 8 is sucked in. When the diaphragm 49 deforms convex to the left, the valve ball 55 of the suction valve 6 falls on the valve seat 56, and the valve ball 55 of the discharge valve 7 rises below the range-limiting frame 57. The cavity between the tank body cover 48 and the diaphragm 49 of the diaphragm tank 4 is under positive pressure, and the sucked slurry is discharged and flows into the buffer tank 5 through the discharge pipe 9, and then is output from the outlet of the buffer tank 5.

[0039] During the actual operation of the reciprocating pump, due to the fact that absolute sealing cannot be achieved, when the positive and negative pressure in the cavities at the two ends of the reciprocating piston ring 41 changes alternately, fluid medium leakage or air suction may occur, which causes the working volume of the medium to decrease, the concave-convex deformation amount of the diaphragm 49 to decrease, and thus the volumetric efficiency and the flow of the pump to decrease. Therefore, the combination valve 51 is arranged at each end of the reciprocating piston ring 41, so as to combine the fluid medium supplement, air discharge and overpressure safety protection into one.

[0040] The combination valve 51 includes a top plate 58, a lever mechanism 59, a top rod, a compensation spring 61, a compensation valve plate 62, a compensation valve ball 63, a filter 64, a safety spring 65, a safety valve plate 66, a combination valve body and a combination valve support. The combination valve 51 is placed in the fluid medium tank 18 through the combination valve body and the combination valve support, and is in sealed connection with the flange 20 of the tank body 47 of the diaphragm tank 4.

[0041] When the negative pressure of the piston working cavity side, the diaphragm 49 is concave and contacts the top plate 58, drives the lever mechanism 59 to push the top rod, overcomes the pressure of the compensation spring 61 to open the compensation valve plate 62, so that the fluid medium replaces the gas in the piston cavity, and the compensation valve ball 63 rises at the same time, and the fluid medium is supplemented into the combination valve body from the fluid medium tank 18 through the filter 64; when the positive pressure of the piston working cavity side, the diaphragm 49 is convex, the compensation valve ball 63 falls, and the new fluid medium is stopped; when the overpressure of the piston working cavity side, the compensation spring 61 and the safety spring 65 are overcome, the compensation valve plate 62 and the safety valve plate 66 are opened, and the overpressure fluid medium is discharged into the fluid medium tank 18.

[0042] The working fluid medium can be emulsion or hydraulic oil, and the diaphragm material can be selected from neoprene rubber, chloroprene rubber, polyurethane rubber, fluorine rubber or polytetrafluoroethylene according to the corrosion, abrasion or high temperature of the transported slurry.

[0043] The pressure transmitter 67 assembly is arranged on the output pipeline of the buffer tank 5, feeds back the pressure signal to the electric control cabinet 14, controls the hydraulic station 13, adjusts the output rotating speed of the driving oil motor, and matches the corresponding demand flow.

[0044] According to the working principle and structure of the present application, the swash plate mechanism with different claw numbers can be used to design more than three-cylinder double-acting piston diaphragm pumps.

Claims

1. A hydraulically driven multi-cylinder double-acting variable piston diaphragm pump, characterized in that, It is used as a feed pump for a filter press; it includes a pump base (1), and a power end (2), a liquid cylinder (3), a diaphragm tank (4), and a buffer tank (5) mounted on the pump base (1); the power end (2) is connected to the liquid cylinder (3) to drive the piston of the liquid cylinder (3) to reciprocate; the diaphragm tank (4) is connected to the liquid cylinder (3) through connecting pipes (10); the lower and upper ends of the diaphragm tank (4) are respectively flanged to a suction valve (6) and a discharge valve (7); the suction valve (6) is connected to a suction pipe (8); the discharge valve (7) is connected to a discharge pipe (9); and the output end of the discharge pipe (9) is connected to the buffer tank (5); wherein: The power end (2) includes a transmission housing (11), an end cover (12), a swashplate mechanism (16), and connecting rods (27). The swashplate mechanism is the transmission part of the power end, which includes a three-jaw swashplate (25) and a crankshaft (22). The three-jaw swashplate (25) and the crankshaft (22) are connected by a second rolling bearing (24). The two ends of the crankshaft (22) are supported on the transmission housing (11) and the end cover (12) of the power end (2) by first rolling bearings (23), respectively. The number of connecting rods (27) is the same as that of the three-jaw swashplate. The number of claws on the disc (25) is the same and they are evenly distributed. The hinged slider (26) is installed in the crosshead hole of the connecting rod (27). Each claw of the three-jaw swashplate (25) is connected to the hinged slider (26) installed in the crosshead hole of the connecting rod (27). When the crankshaft (22) rotates, it drives the second rolling bearing (24) installed in the center of the three-jaw swashplate (25) to move, thereby realizing the spatial swing of the three-jaw swashplate (25), which in turn drives the connecting rod (27) to move horizontally back and forth along the slide hole of the transmission box (11). The hydraulic cylinder (3) includes a cylinder body (35) and a piston mechanism (36). The front end of the cylinder body (35) is connected to the end cap (12) of the power end (2) by a flange, so that the power end (2) and the hydraulic cylinder body (3) are coaxially connected as one unit. The cylinder body (35) is provided with cylinder barrels (38) with the same number of claws as the three-jaw swashplate (25) in the swashplate mechanism (16) and coaxial with the connecting rod (27). Each cylinder barrel (38) is equipped with a cylinder barrel cover (39) and a sealing groove (40). The piston mechanism (36) includes a piston ring (41) and a piston rod (42). The piston rod (42) is coaxially connected with the connecting rod (27) to drive the piston to reciprocate in the cylinder barrel (38). The diaphragm tank (4) includes a tank body (47), a double-layer diaphragm (49) and a pressure limiting mesh plate (50). The double-layer diaphragm (49) is fixed to the tank body (47) by circumferentially distributed studs. The reciprocating motion of the piston causes the positive and negative pressures inside the cylinder (38) to change alternately, driving the fluid medium inside the cavity to cause the diaphragm (49) to periodically deform between the tank cover (48) and the pressure limiting mesh plate (50). The diaphragm tank (4) also includes a combination valve (51), which is placed inside the fluid medium tank (18) and connected to the flange of the tank body (47) of the diaphragm tank (4); wherein: the combination valve (51) includes a top plate (58), a lever mechanism (59), a push rod, a compensating spring (61), a compensating valve plate (62), a compensating valve ball (63), a filter (64), a safety spring (65), and a safety valve plate (66); when there is negative pressure on one side of the piston working chamber in the cylinder body (3), the concave pressure of the diaphragm (49) contacts the top plate (58), driving the lever mechanism (59) to push the push rod, overcoming the pressure. The pressure of the compensating spring (61) opens the compensating valve plate (62), replacing the gas in the piston working chamber with fluid medium. At the same time, the compensating valve ball (63) rises, and the fluid medium is replenished from the fluid medium tank (18) through the filter (64) into the combination valve (51). When there is positive pressure on one side of the piston working chamber, the diaphragm (49) deforms convexly, the compensating valve ball (63) falls, and the replenishment of new fluid medium stops. When there is overpressure on one side of the piston working chamber, the compensating spring (61) and the safety spring (65) are overcome, and the compensating valve plate (62) and the safety valve plate (66) are opened, and the overpressure fluid medium is unloaded into the fluid medium tank (18). During operation, the power end (2) drives the piston rod (42) in the cylinder (38) of the hydraulic cylinder body (3) to reciprocate, and the fluid medium in the working chambers on both sides of the piston causes the diaphragm in the diaphragm tank (4) to periodically deform, thereby driving the suction valve (6) and the discharge valve (7) to alternately open and close, so as to realize the pumped slurry is sucked in from the suction pipe (8) and output from the outlet of the buffer tank (5).

2. The hydraulically driven multi-cylinder double-acting variable piston diaphragm pump according to claim 1, characterized in that, The power end also includes a hydraulic station (13), an electrical control cabinet (14) and an oil motor (15). The output shaft of the oil motor (15) is connected to the crankshaft (22) in the swashplate mechanism (16). During operation, the electrical control cabinet (14) controls the hydraulic station (13), drives the output shaft of the oil motor (15) to rotate, drives the swashplate mechanism (16), and then drives the connecting rod (27) to move horizontally back and forth along the slide hole of the transmission box (11).

3. The hydraulically driven multi-cylinder double-acting variable piston diaphragm pump according to claim 1, characterized in that, The power end includes a lubrication system (17), which includes a pump body (30), a lubricating oil sump, an oil inlet pipe (29), an oil pipe (31), and an oil injection hole (34). The oil inlet pipe (29) is connected to the pump body (30) and the lubricating oil sump respectively. The pump body (30) and the connecting rod extension section (28) of the lower connecting rod (27) are sealed together. The oil injection hole (34) is located at the top of the transmission box (11). When the connecting rod extension section (28) moves back and forth with the connecting rod (27), the steel ball (33) in the pump body (30) rises or falls in the conical ball seat, periodically completing the oil suction of the oil inlet pipe (29) and the oil discharge of the oil pipe (31). The discharged oil is sprayed downward through the oil injection hole (34) to lubricate the hinge slider (26) and the second rolling bearing (24).

4. The hydraulically driven multi-cylinder double-acting variable piston diaphragm pump according to claim 1, characterized in that, The diaphragm material is any one of nitrile rubber, neoprene rubber, polyurethane rubber, fluororubber, or polytetrafluoroethylene.

5. The hydraulically driven multi-cylinder double-acting variable piston diaphragm pump according to claim 1, characterized in that, The working fluid medium contained in the fluid medium tank (18) is emulsion or hydraulic oil.

6. The hydraulically driven multi-cylinder double-acting variable piston diaphragm pump according to claim 1, characterized in that, A pressure transmitter (67) is installed on the output pipeline of the buffer tank (5) to feed back the pressure signal to the power end (2) and adjust the output speed of the drive power end (2).

7. The hydraulically driven multi-cylinder double-acting variable piston diaphragm pump according to claim 1, characterized in that, The three-jaw swashplate (25) can be replaced by a four-jaw swashplate, a five-jaw swashplate or a six-jaw swashplate to obtain a double-acting piston diaphragm pump with more than three cylinders.

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