Pre-pressing steady-flow pumping method and pre-pressing steady-flow delivery pump

Abstract

The invention discloses a pre-pressing steady-flow pumping method and a pre-pressing steady-flow delivery pump. According to the method, a double-cylinder conveying pump is adopted for pumping, the double-cylinder conveying pump comprises two pumping units, when pumping work is conducted, each pumping unit sequentially conducts pumping material pushing, retreating material sucking and material pre-pressing, the two pumping units alternately conduct the process, and therefore material pumping is conducted, the retreating speed of the pumping piston in the retreating material sucking process is higher than the advancing speed of the pumping piston in the pumping material pushing stroke; before one pumping unit completes the pumping and pushing process, the other pumping unit completes the retreating and sucking process and starts the material pre-pressing process, and for the pumping unit in the material pre-pressing process, the pressure of materials contained in the pumping unit is increased due to the fact that the materials are pressed, but the materials cannot be discharged out of the pumping unit; when one pumping unit completes material pumping and pushing, the other pumping unit completes material pre-pressing and prepares to be switched to material pumping and pushing.

Description

Technical Field

[0001] The present invention relates to the field of pipeline pumping equipment, and in particular to a pre-pressure steady-flow pumping method and a pre-pressure steady-flow transfer pump for pumping materials such as liquids, slurries, pastes, and paste-like materials. Background Art

[0002] In projects such as paste pipeline transportation for mine filling and cement mortar pipeline transportation in construction projects, an S-valve transfer pump is usually used for transportation, which has disadvantages such as low transportation efficiency and large fluctuations in transportation flow rate.

[0003] For this reason, the patent document CN 106014903 A discloses a double-cylinder steady-flow transfer pump (patent number: 2016103078026). The prior art in this patent document eliminates the interruption of pumping and maintains the stability of the pumping flow rate by adding a common pumping process during the alternating pumping conversion between two pumping cylinders.

[0004] However, since the pressure of the material in the pumping cylinder waiting to be pumped is much lower than the pressure of the material in the conveying pipeline, when the two pumping cylinders are simultaneously connected to the conveying pipeline, it is necessary to pressurize the material in the pumping cylinder to a pressure equal to the pressure of the material in the conveying pipeline.

[0005] During the pressurization process, due to the elastic deformation of the cylinder body, pumping piston, and feed valve body of the pumping cylinder waiting to be pumped, as well as the mixing of some gas in the pumped material and the intake of air by the feed valve, on the one hand, the volume of the material being pressurized will shrink, and on the other hand, the volume of the cavity being pressurized will increase, resulting in the backflow of the high-pressure material in the conveying pipeline and entering the cavity being pressurized until its pressure increases to be equal to the pressure of the material in the conveying pipeline. Inevitably, this causes fluctuations in the pressure in the conveying pipeline and interruptions and / or fluctuations in the conveying flow rate.

[0006] Therefore, the double-cylinder steady-flow transfer pump in the above patent document can only reduce the fluctuations in pressure and flow rate when pumping low-pressure fluids without compressible gases, but there are still situations of material backflow and pressure fluctuations when pumping high-pressure fluids, pastes, and paste-like materials containing compressible gases. Moreover, the greater the conveying pressure, the greater the fluctuations in the conveying pressure and the conveying flow rate, and the conveying pressure is related to the conveying distance, conveying flow rate, concentration, viscosity, etc. of the conveyed material. The longer the conveying distance, the greater the conveying flow rate, the higher the concentration of the conveyed material, and the greater the viscosity, the greater the fluctuations in the conveying pressure and the conveying flow rate. When the conveying pressure is relatively high, even violent pulse pressure will be generated. This leads to the following disadvantages and deficiencies:

[0007] 1. The fluctuation of the flow rate causes the material in the conveying pipeline to move back and forth. Under the action of reciprocating impact, the aggregate in the material will precipitate, aggregate and accumulate, resulting in an increase in the pipe blockage rate. Especially in the conveying pipeline during upward or downward movement, the influence of reciprocating impact is stronger, and pipe blockage is more likely to occur, greatly affecting the reliability of pipeline transportation. Once the pipeline is blocked, not only is it difficult to determine the blockage point, but also the difficulty, workload and cost of dredging the pipeline are very large.

[0008] 2. The fluctuation of pressure and pulse pressure will cause fatigue damage and impact brittle fracture to the pumping equipment, conveying pipeline and pipeline valves, etc., seriously affecting the service life of the pumping equipment, conveying pipeline and pipeline valves, and further affecting their reliability, and bringing serious potential safety hazards.

[0009] 3. Since the greater the conveying flow rate and the farther the conveying distance, the greater the fluctuation of the flow rate and the pulse pressure, the higher the pipe blockage rate and the shorter the fatigue life. Therefore, the conveying flow rate and conveying distance of the conveying project are severely restricted and it is difficult to meet the needs of large-flow and long-distance conveying projects.

[0010] 4. In some application fields, it is required to have a relatively stable pressure or flow rate when conveying materials through pipelines. For example, when conveying water-coal slurry fuel to a water-coal slurry boiler, if flow pulsation occurs, when the flow rate decreases or interrupts, it will lead to the interruption of combustion due to insufficient fuel supply, resulting in a boiler shutdown failure.

[0011] Therefore, it is desirable to have a technical solution to overcome or at least mitigate at least one of the above-mentioned defects of the prior art. Summary of the Invention

[0012] The purpose of the present invention is to provide a pre-pressure and stable flow pumping method and a pre-pressure and stable flow conveying pump to overcome or at least mitigate at least one of the above-mentioned defects of the prior art.

[0013] To achieve the above object, the present invention provides a pre-pressure and stable flow pumping method, which uses a double-cylinder conveying pump for pumping. The double-cylinder conveying pump includes two pumping units. When performing pumping work, each pumping unit sequentially performs pumping and pushing materials, retreating and sucking materials, and material pre-pressure. The two pumping units alternately perform the above processes to pump materials.

[0014] Wherein, during the process of retreating and sucking materials, the speed at which the pumping piston or pumping plunger of the pumping unit retreats is greater than the speed at which the pumping piston or pumping plunger of the pumping unit advances during the pumping and pushing material stroke.

[0015] Before one pumping unit completes the process of pumping and pushing materials, the other pumping unit has completed the process of retreating and sucking materials and the enclosure of the sucked materials, and starts the pre-pressure process of the sucked materials. The enclosed materials increase in pressure due to being pressurized.

[0016] When a pumping unit completes the pumping and pushing process, another pumping unit has completed the material pre-pressing process and is ready to switch to the pumping and pushing process.

[0017] Preferably, after the pumping piston or pumping plunger of a pumping unit retracts to the end point, its pumping piston or pumping plunger advances to push the material, pre-pressing the material inside it to make the pressure of the material equal to or close to the pressure of the material in another pumping unit, and then switches to the pumping and pushing process to perform pumping relay with another pumping unit.

[0018] Preferably, the double-cylinder transfer pump includes: a first pumping unit, a second pumping unit, a material reversing valve group, a pumping hydraulic subsystem, a pre-pressing hydraulic subsystem, and a quick-retreat hydraulic subsystem.

[0019] Both the first pumping unit and the second pumping unit are connected to the material reversing valve group. The material reversing valve group includes a first material suction channel, a first material discharge channel, a second material suction channel, and a second material discharge channel, and controls their on-off. Among them, the first material suction channel and the first material discharge channel are both communicated with the first pumping unit for the suction and discharge of the first pumping unit, and the second material suction channel and the second material discharge channel are both communicated with the second pumping unit for the suction and discharge of the second pumping unit.

[0020] The first pumping unit includes a first pumping oil cylinder, the second pumping unit includes a second pumping oil cylinder, the inner cavities of the first pumping oil cylinder and the second pumping oil cylinder are divided into a front cavity and a rear cavity by a piston. The front cavities of the first pumping oil cylinder and the second pumping oil cylinder are communicated through an oil circuit. The pumping hydraulic subsystem and the pre-pressing hydraulic subsystem are connected to the rear cavities of the first pumping oil cylinder and the second pumping oil cylinder, and the quick-retreat hydraulic subsystem is connected to the front cavities of the first pumping oil cylinder and the second pumping oil cylinder.

[0021] The double-cylinder transfer pump continuously pumps in a cycle according to the following processes 1 to 4:

[0022] Process 1, the first pumping unit pumps, and the second pumping unit quickly retreats to suck materials:

[0023] The first material suction channel is closed, the first material discharge channel is opened, the second material suction channel is opened, the second material discharge channel is closed. The pumping hydraulic subsystem injects hydraulic oil into the rear cavity of the first pumping oil cylinder to make its pumping piston or pumping plunger advance and push the material into the discharge pipe. At the same time, the hydraulic oil output by the quick-retreat hydraulic subsystem and the hydraulic oil discharged from the front cavity of the first pumping oil cylinder enter the front cavity of the second pumping oil cylinder at the same time, so that the pumping piston or pumping plunger of the second pumping oil cylinder quickly retreats at a speed faster than the advancing speed of the pumping piston or pumping plunger of the first pumping oil cylinder and sucks materials.

[0024] Process 2, the first pumping unit pumps, and the second pumping unit pre-presses:

[0025] The first material suction channel remains closed, the first material discharge channel remains open, and the first pumping unit continues to pump; the second material suction channel is closed, the second material discharge channel remains closed, and the preloading hydraulic subsystem injects hydraulic oil into the rear cavity of the second pumping cylinder to make its pumping piston or pumping plunger advance, pressurize the material in the second pumping unit until its pressure is close to or equal to the pressure of the material in the first pumping unit. The hydraulic oil discharged from the front cavity of the first pumping cylinder and the front cavity of the second pumping cylinder and the hydraulic oil discharged from the fast return hydraulic subsystem flow back to the oil tank;

[0026] Process 3, the first pumping unit fast returns to suck material, and the second pumping unit pumps:

[0027] The first material suction channel is opened, the first material discharge channel remains closed, the second material suction channel remains closed, the second material discharge channel is opened, and the pumping hydraulic subsystem injects hydraulic oil into the rear cavity of the second pumping cylinder to make its pumping piston or pumping plunger advance and push the material into the discharge pipe. The hydraulic oil discharged from the fast return hydraulic oil circuit and the hydraulic oil discharged from the front cavity of the second pumping cylinder enter the front cavity of the first pumping cylinder at the same time, so that the pumping piston or pumping plunger of the first pumping cylinder retreats at a speed faster than the advancing speed of the pumping piston or pumping plunger of the second pumping cylinder and sucks the material;

[0028] Process 4, the first pumping unit preloads, and the second pumping unit pumps:

[0029] The second material suction channel remains closed, the second material discharge channel remains open, and the second pumping unit continues to pump; the first material suction channel is closed, the first material discharge channel remains closed, and the preloading hydraulic subsystem injects hydraulic oil into the rear cavity of the first pumping cylinder to make its pumping piston or pumping plunger advance, pressurize the material in the first pumping unit until its pressure is close to or the same as the pressure of the material in the second pumping unit. The hydraulic oil discharged from the front cavity of the first pumping cylinder and the front cavity of the second pumping cylinder and the hydraulic oil discharged from the fast return hydraulic subsystem flow back to the oil tank.

[0030] Preferably, Process 2 and Process 3 are switched in the following manner:

[0031] The first pumping unit and the second pumping unit pump in relay:

[0032] After the pumping piston or plunger of the first pumping cylinder advances to the set position, the pumping hydraulic subsystem simultaneously injects hydraulic oil into the rear chambers of the first pumping cylinder and the second pumping cylinder. The pumping pistons or plungers of the two pumping units simultaneously apply the same pumping pressure to the materials therein. At the same time, the first suction channel remains closed, the second suction channel remains closed, the first discharge channel and the second discharge channel switch between open and closed states, the first pumping cylinder and the second pumping cylinder switch between pumping and stopping states, and the hydraulic oil discharged from the front chambers of the first pumping cylinder and the second pumping cylinder and the hydraulic oil discharged from the quick return hydraulic subsystem flow back to the fuel tank;

[0033] Or

[0034] Process 4 and Process 1 are switched in the following manner:

[0035] After the pumping piston or plunger of the second pumping cylinder advances to the set position, the pumping hydraulic subsystem simultaneously injects hydraulic oil into the rear chambers of the first pumping cylinder and the second pumping cylinder. The pumping pistons or plungers of the two pumping units simultaneously apply the same pumping pressure to the materials therein. At the same time, the first suction channel remains closed, the second suction channel remains closed, the first discharge channel and the second discharge channel switch between open and closed states, the first pumping cylinder and the second pumping cylinder switch between pumping and stopping states, and the hydraulic oil discharged from the front chambers of the first pumping cylinder and the second pumping cylinder and the hydraulic oil discharged from the quick return hydraulic subsystem flow back to the fuel tank.

[0036] The present invention also provides a pre-pressure steady-flow conveying pump, and the pre-pressure steady-flow conveying pump is a double-cylinder conveying pump,

[0037] The double-cylinder conveying pump includes two pumping units. When performing pumping work, each pumping unit sequentially performs pumping and pushing materials, retreating and sucking materials, and pre-pressing the materials. The two pumping units alternately perform the above processes to pump the materials,

[0038] Wherein, during the process of retreating and sucking materials, the speed at which the pumping piston or plunger of the pumping unit retreats is greater than the speed at which the pumping piston or plunger of the pumping unit advances during the pumping and pushing material stroke;

[0039] Before one pumping unit completes the process of pumping and pushing materials, the other pumping unit has completed the process of retreating and sucking materials and the enclosure of the sucked materials, and starts the process of pre-pressing the sucked materials. For the pumping unit in the process of pre-pressing the materials, the enclosed materials are pressurized due to the pressure;

[0040] When one pumping unit completes the process of pumping and pushing materials, the other pumping unit has completed the process of pre-pressing the materials and is ready to switch to the process of pumping and pushing materials.

[0041] Preferably, after the pumping piston or pumping plunger of a pumping unit retracts to the end point, its pumping piston or pumping plunger advances to push the material, pre-presses the material inside it, and then switches to the pumping and pushing process to perform pumping relay with another pumping unit.

[0042] Preferably, the pre-pressure and steady-flow conveying pump includes a first pumping unit, a second pumping unit, a material commutation valve group, a pumping hydraulic subsystem, a pre-pressure hydraulic subsystem, and a quick-retreat hydraulic subsystem. The first pumping unit and the second pumping unit are both connected to the material commutation valve group.

[0043] The material commutation valve group includes a first material suction channel, a first material discharge channel, a second material suction channel, and a second material discharge channel, and controls their on-off.

[0044] The first material suction channel and the first material discharge channel are both communicated with the first pumping unit, and the second material suction channel and the second material discharge channel are both communicated with the second pumping unit.

[0045] The first pumping unit includes a first pumping oil cylinder and a first pumping material cylinder, and the second pumping unit includes a second pumping oil cylinder and a second pumping material cylinder. The inner cavities of the first pumping oil cylinder and the second pumping oil cylinder are divided into a rear cavity and a front cavity by pistons. The front cavities of the first pumping oil cylinder and the second pumping oil cylinder are connected by an oil circuit.

[0046] The pumping hydraulic subsystem includes a first pumping valve group, a first oil return valve group, a second pumping valve group, a second oil return valve group, and a pumping hydraulic pump group.

[0047] The rear cavity of the first pumping oil cylinder is simultaneously connected to the first pumping valve group and the first oil return valve group by an oil circuit. The first pumping valve group is further connected to the pumping hydraulic pump group by an oil circuit, and the first oil return valve group is further connected to the oil return oil circuit. The first pumping valve group is used to control the on-off of the oil circuit between the rear cavity of the first pumping oil cylinder and the pumping hydraulic pump group, and the first oil return valve group is used to control the on-off of the oil return oil circuit of the rear cavity of the first pumping oil cylinder.

[0048] The rear cavity of the second pumping oil cylinder is simultaneously connected to the second pumping valve group and the second oil return valve group by an oil circuit. The second pumping valve group is further connected to the pumping hydraulic pump group by an oil circuit, and the second oil return valve group is further connected to the oil return oil circuit. The second pumping valve group is used to control the on-off of the oil circuit between the rear cavity of the second pumping oil cylinder and the pumping hydraulic pump group, and the second oil return valve group is used to control the on-off of the oil return oil circuit of the rear cavity of the second pumping oil cylinder.

[0049] The preloading hydraulic subsystem is respectively connected to the rear chambers of the first pumping cylinder and the second pumping cylinder through oil circuits. The preloading hydraulic subsystem further includes a preloading valve group, which is located on the oil circuit for supplying oil to the first pumping cylinder and the second pumping cylinder in the preloading hydraulic subsystem, and is used to control the on-off of the oil circuit for the preloading hydraulic subsystem to supply oil to the first pumping cylinder and the second pumping cylinder. When the first pumping cylinder or the second pumping cylinder retreats to the end point to complete material suction, the preloading valve group can connect the oil circuit for the preloading hydraulic subsystem to supply oil to the first pumping cylinder or the oil circuit for the preloading hydraulic subsystem to supply oil to the second pumping cylinder, so that hydraulic oil can enter the rear chamber of the first pumping cylinder or the rear chamber of the second pumping cylinder, driving the first pumping cylinder or the second pumping cylinder to advance to pre-press the material; The quick-retreat hydraulic subsystem further includes a quick-retreat hydraulic pump and a quick-retreat valve group. The quick-retreat hydraulic pump is simultaneously connected to the front chambers of the first pumping cylinder and the second pumping cylinder through oil circuits. The front chambers of the first pumping cylinder and the second pumping cylinder are also connected to the oil return circuit. The quick-retreat valve group is connected to the oil return circuit of the front chambers of the first pumping cylinder and the second pumping cylinder, and is used to control the on-off of this oil return circuit; When the first pumping cylinder or the second pumping cylinder retreats, the quick-retreat valve group cuts off the oil return circuit of the front chambers of the first pumping cylinder and the second pumping cylinder. The hydraulic oil discharged from the front chamber of the second pumping cylinder or the hydraulic oil discharged from the front chamber of the first pumping cylinder and the hydraulic oil discharged from the quick-retreat hydraulic pump simultaneously enter the front chamber of the first pumping cylinder or the front chamber of the second pumping cylinder, making it retreat at a speed faster than the advancing speed of the second pumping cylinder or the first pumping cylinder; When the first pumping cylinder or the second pumping cylinder retreats to the end point, the quick-retreat valve group connects the oil return circuit of the front chambers of the first pumping cylinder and the second pumping cylinder, and all the hydraulic oil discharged from the front chamber of the second pumping cylinder or the hydraulic oil discharged from the front chamber of the first pumping cylinder and the hydraulic oil discharged from the quick-retreat hydraulic pump flow back to the fuel tank.

[0050] Preferably, the preloading hydraulic subsystem includes an accumulator, which is connected to the hydraulic oil source through an oil circuit and is connected to the rear chambers of the first pumping cylinder and the second pumping cylinder through the preloading valve group, and is used to store high-pressure hydraulic oil and provide preloading hydraulic oil for the rear chambers of the first pumping cylinder and the second pumping cylinder.

[0051] Preferably, the preloading valve group includes a pressure control valve, which is connected to the oil circuit between the accumulator and the hydraulic oil source and is used to control the filling pressure of the accumulator. The set pressure of the pressure control valve is equal to or close to the pressure of the hydraulic oil injected by the pumping hydraulic subsystem into the rear chambers of the first pumping cylinder and the second pumping cylinder.

[0052] Preferably, the preloading hydraulic subsystem further includes a pressure reducing valve, which is connected to the oil paths between the preloading hydraulic subsystem and the rear chambers of the first pumping cylinder and between the preloading hydraulic subsystem and the rear chamber of the second pumping cylinder, and is used to control the pressure of the hydraulic oil injected into the rear chambers of the first pumping cylinder and the second pumping cylinder. The set pressure of the pressure reducing valve is equal to or close to the pressure of the hydraulic oil injected into the rear chambers of the first pumping cylinder and the second pumping cylinder by the pumping hydraulic subsystem.

[0053] Preferably, the preloading valve group includes check valves, which are connected to the oil paths between the preloading hydraulic subsystem and the rear chamber of the first pumping cylinder and between the preloading hydraulic subsystem and the rear chamber of the second pumping cylinder, and are used to prevent the hydraulic oil in the rear chamber of the first pumping cylinder and the hydraulic oil in the rear chamber of the first pumping cylinder from flowing back to the preloading hydraulic subsystem.

[0054] Preferably, the preloading valve group includes a first preloading valve and a second preloading valve. The first preloading valve is located on the oil path between the accumulator and the rear chamber of the first pumping cylinder and is used to control the on-off of the oil path between the accumulator and the rear chamber of the first pumping cylinder. The second preloading valve is located on the oil path between the accumulator and the rear chamber of the second pumping cylinder and is used to control the on-off of the oil path between the accumulator and the rear chamber of the second pumping cylinder. Both the first preloading valve and the second preloading valve are two-way cartridge valves with adjustable openings, and the hydraulic oil injected into the rear chambers of the first pumping cylinder and the second pumping cylinder can be throttled by adjusting the openings of the two-way cartridge valves.

[0055] Compared with the prior art, the method and pump of the present invention can achieve the following beneficial effects:

[0056] 1. Before pumping, the material to be pumped in the corresponding pumping cylinder is pre-pressurized so that the pressure of the material therein rises to be equal (or close) to the pressure of the material in the conveying pipeline. In this way, when starting to be pumped, the material in the waiting-to-be-pumped material cylinder will no longer be compressed, and the volumes of the waiting-to-be-pumped material cylinder and the feeding valve will no longer elastically expand. The material in the conveying pipeline will not flow back, and during the relay transition and switching process of the first pumping cylinder and the second pumping cylinder during subsequent pumping, the pressure and flow rate of the conveyed material will not fluctuate (or only have extremely low fluctuations), thereby achieving non-fluctuating (or low-fluctuating) conveying pressure and conveying flow rate.

[0057] 2. Since the material can be output at a stable flow rate, the material in the conveying pipeline no longer repeatedly undergoes forward and reverse flow conversions. The material flows uniformly in the conveying pipeline, and the relative positions of its various particles are basically unchanged, eliminating the precipitation, aggregation, and accumulation of aggregates caused by the sharp reversal and impact of the material flow, reducing the pipe blockage rate, improving the reliability of conveying, and reducing the operation and maintenance costs of pipeline conveying.

[0058] 3. Since the material can be output with a stable pressure and there is no pulsed pressure, components such as the pumping equipment, conveying pipelines, and valves hardly bear the action of alternating stress and impact force, greatly extending the fatigue life and eliminating the impact brittle fracture damage to the components.

[0059] 4. Since the material always moves forward during the conveying process and there is no material backflow, the conveying efficiency is not affected by the conveying distance, and it will not reduce the conveying efficiency as the conveying distance increases like the S-tube valve conveying pump, and it can meet the needs of long-distance pipeline conveying projects.

[0060] 5. Since the conveying flow rate is stable, the applicable range is wider, and it can meet the engineering projects with stable requirements for the conveying flow rate and conveying pressure in some special fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 is a simplified process flow diagram of the pre-pressure steady-flow pumping method according to an embodiment of the present invention.

[0062] Figure 2 is a schematic diagram of the principle of the pre-pressure steady-flow conveyor pump according to an embodiment of the present invention.

[0063] Figure 3 is a schematic diagram of the principle of the pre-pressure steady-flow conveyor pump according to another embodiment of the present invention.

[0064] Figure 4 is a schematic diagram of the principle of the pre-pressure steady-flow conveyor pump according to still another embodiment of the present invention.

[0065] Reference Signs:

[0066] 1 First pumping unit 41 First pumping valve group 2 Second pumping unit 42 First oil return valve group 3 Material commutation valve group 43 Second pumping valve group 4 Pumping hydraulic subsystem 44 Second oil return valve group 5 Preloading hydraulic subsystem 45 Pumping hydraulic pump group 6 Quick return hydraulic subsystem 51 Preloading valve group 7 Pumping piston 52 Accumulator 11 First pumping oil cylinder 53 Preloading hydraulic pump 12 First pumping material cylinder 54 Pressure reducing valve 21 Second pumping oil cylinder 61 Quick return hydraulic pump 22 Second pumping material cylinder 62 Quick return valve group 31 First material suction channel 511 First preloading valve 32 First material discharge channel 512 Second preloading valve 33 Second material suction channel 513 Pressure control valve 34 Second material discharge channel 514 Check valve DETAILED DESCRIPTION OF THE EMBODIMENTS

[0067] In the drawings, the same or similar reference numerals are used to denote the same or similar elements or elements having the same or similar functions. The embodiments of the present invention will be described in detail below with reference to the drawings.

[0068] In the description of the present invention, the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the protection scope of the present invention.

[0069] In the present invention, the forward or backward movement of the pumping unit, pumping cylinder, pumping oil cylinder, and pumping material cylinder refers to the forward or backward movement of the piston rod of the pumping oil cylinder or the pumping piston, rather than the forward or backward movement of the entire pumping unit, pumping cylinder, pumping oil cylinder, and pumping material cylinder.

[0070] In the present invention, the valve group includes at least one hydraulic valve, and the pumping hydraulic pump group includes at least one hydraulic pump.

[0071] The pumping unit (with the main body being the pumping cylinder) includes a pumping oil cylinder and a pumping material cylinder. The pumping oil cylinder is divided into a rear chamber and a front chamber by a hydraulic piston arranged therein. The hydraulic piston moves back and forth under the drive of hydraulic oil from drive sources such as the pumping hydraulic subsystem, pre-pressure hydraulic subsystem, and fast-retreat hydraulic subsystem.

[0072] A pumping piston or a pumping plunger is arranged in the pumping material cylinder. The pumping piston or the pumping plunger is connected to the hydraulic piston through structures such as a connecting rod and a piston rod, and moves integrally in the forward and backward directions. The front end of the pumping piston or the pumping plunger directly contacts the material.

[0073] In the present invention, the chamber referred to as the "rear chamber" is the chamber that, after being injected with hydraulic oil, can drive the pumping piston or the pumping plunger forward, so that the material chamber of the corresponding material cylinder is pressurized and the material is discharged. Correspondingly, the chamber referred to as the "front chamber" is the chamber that, after being injected with hydraulic oil, can drive the pumping piston or the pumping plunger backward, so that the material chamber of the corresponding material cylinder expands and sucks in the material.

[0074] In the present invention, "forward" refers to the direction in which the "pumping piston or the pumping plunger" moves to discharge the material from the corresponding material cylinder, and "backward" refers to the direction in which the "pumping piston or the pumping plunger" moves to suck in the material into the corresponding material cylinder.

[0075] In the present invention, the pressure control valve can adopt any suitable form such as a unloading valve, a relief valve, or a pressure reducing valve to control the pressure at the corresponding oil circuit or chamber within the required pressure or the required pressure range.

[0076] In the present invention, "associated" or "connected" includes direct connection by contact and non-contact indirect connection or connection through other components.

[0077] Embodiment 1

[0078] Figure 1 The schematic diagram shows the working process of the pre-pressure steady-flow pumping method according to an embodiment of the present invention. As shown in the figure, the pressure steady-flow pumping method includes the following six steps that are continuously cycled and repeated:

[0079] Step 1) The first pumping unit pumps, and the second pumping unit fast-retreats. This step can be called process 1.

[0080] Step 2) The first pumping unit pumps, and the second pumping unit pre-presses. This step can be called Process 2.

[0081] Step 3) The first pumping unit and the second pumping unit perform pumping in relay.

[0082] In Process 1 and Process 2, generally, the first pumping unit pumps the material, while the second pumping unit simultaneously retreats to suck the material and pre-presses the sucked material.

[0083] And in Step 3), the working modes of the first pumping unit and the second pumping unit are switched.

[0084] Step 4) The second pumping unit pumps, and the first pumping unit quickly retreats. This step can be called Process 3.

[0085] Step 5) The second pumping unit pumps, and the first pumping unit pre-presses. This step can be called Process 4.

[0086] Step 6) The second pumping unit and the first pumping unit perform pumping in relay.

[0087] In Process 3 and Process 4, generally, the second pumping unit pumps the material, while the first pumping unit simultaneously retreats to suck the material and pre-presses the sucked material.

[0088] And in Step 6), the working modes of the second pumping unit and the first pumping unit are switched.

[0089] It should be noted that the durations of Step 3) and Step 6) are very short and account for a very small proportion of the time in a cycle. This is also the main reason why they are not called processes in the present invention. Additionally, the durations of Step 1) and Step 4) are generally longer than those of Step 2) and Step 5).

[0090] Figure 1 The illustrated pre-press and stable-flow pumping method uses a double-cylinder transfer pump for pumping. The double-cylinder transfer pump includes two pumping units. When performing the pumping work, each pumping unit sequentially performs pumping and pushing the material, retreating to suck the material, and pre-pressing the material. The two pumping units alternate in the above processes to pump the material.

[0091] During the process of retreating to suck the material, the speed at which the pumping piston or the pumping plunger of the pumping unit retreats is greater than the speed at which the pumping piston or the pumping plunger of the pumping unit advances during the pumping and pushing stroke. Before one pumping unit completes the pumping and pushing process, the other pumping unit has completed the process of retreating to suck the material and closing the sucked material (for example, closing the corresponding material suction channel and discharge channel), and starts the process of pre-pressing the material. The enclosed material is pressurized and the pressure increases, that is, it is pre-pressed. The pre-pressed material will not be discharged from the transfer pump. When one pumping unit completes the pumping and pushing process, the other pumping unit has completed the process of pre-pressing the material and is ready to switch to the pumping and pushing process.

[0092] In an alternative embodiment of the present invention, after the pumping piston or pumping plunger of a pumping unit retracts to the end point, the pumping piston or pumping plunger advances to push the material under the drive of hydraulic oil (the advancing distance is usually very small, depending on the compressibility of the material and the expansibility of the cavity), pre-presses the material therein, so that the pressure of the material is equal to or close to the pressure of the material being pushed forward in another pumping unit, and then switches to the pumping and pushing process to perform pumping relay with another pumping unit.

[0093] When the pre-pressing pressure is exactly equal to the pressure of the material being pushed forward in the pumping unit, theoretically, the pressure and flow rate of the conveyed material have no fluctuations, which is an ideal state. However, in actual applications, due to the influence of some factors such as the sensitivity of the pressure control valve and pressure reducing valve, and the viscosity of the hydraulic oil, the pre-pressing pressure itself may have small fluctuations, and the pressure of the material being pushed forward may also have small fluctuations. Therefore, it is difficult to make the two exactly the same. Therefore, in the present invention, the equality of the pre-pressing pressure and the pressure of the material being pushed forward in the pumping unit does not mean that the two are absolutely equal, but means that the deviation between the two is less than or equal to 3%.

[0094] In addition, when the pre-pressing pressure and the pressure of the material being pushed forward in the pumping unit are close to each other, an obvious pressure stabilizing effect can also be achieved. For example, it has been experimentally verified that when the deviation between the two is within 25%, a good effect can be achieved. That is to say, the closeness of the two pressures in the present invention means that the deviation between the two is within 25%. The absolute value of the pre-pressing pressure minus the pressure of the material being pushed forward, divided by the ratio of the pressure of the material being pushed forward, is less than or equal to 25%.

[0095] The double-cylinder transport pump may be, for example Figure 2 the pre-pressing and flow-stabilizing transport pump shown.

[0096] The double-cylinder transport pump includes: a first pumping unit 1, a second pumping unit 2, a material commutation valve group 3, a pumping hydraulic subsystem 4, a pre-pressing hydraulic subsystem 5, and a quick-retreat hydraulic subsystem 6. The pumping hydraulic subsystem 4, the pre-pressing hydraulic subsystem 5, and the quick-retreat hydraulic subsystem 6 are used as hydraulic power sources to provide driving forces for pumping, pre-pressing, and quick-retreating respectively.

[0097] Both the first pumping unit 1 and the second pumping unit 2 are connected to the material commutation valve group 3, or are logically controlled according to the working state of the material commutation valve group 3. Or rather, the material commutation valve group 3 enables the first pumping unit 1 and the second pumping unit 2 to be in different working states.

[0098] The material commutation valve group 3 includes a first material suction channel 31, a first material discharge channel 32, a second material suction channel 33 and a second material discharge channel 34 and controls their on-off states. Among them, both the first material suction channel 31 and the first material discharge channel 32 are connected to the first pumping unit 1 for the suction and discharge of materials by the first pumping unit 1. Both the second material suction channel 33 and the second material discharge channel 34 are connected to the second pumping unit 2 for the suction and discharge of materials by the second pumping unit 2.

[0099] The first pumping unit 1 includes a first pumping oil cylinder 11, and the second pumping unit includes a second pumping oil cylinder 21. The inner cavities of the first pumping oil cylinder 11 and the second pumping oil cylinder 21 are divided into a front chamber and a rear chamber by pistons. The front chambers of the first pumping oil cylinder 11 and the second pumping oil cylinder 21 are connected through an oil circuit. The pumping hydraulic subsystem 4 and the pre-pressure hydraulic subsystem 5 are connected to the rear chambers of the first pumping oil cylinder 11 and the second pumping oil cylinder 21, and the quick return hydraulic subsystem 6 is connected to the front chambers of the first pumping oil cylinder 11 and the second pumping oil cylinder 21.

[0100] The double-cylinder transfer pump continuously pumps in a cycle according to the following processes 1 to 4:

[0101] Process 1, the first pumping unit pumps, and the second pumping unit quickly returns to suck materials:

[0102] The first material suction channel 31 is closed, the first material discharge channel 32 is opened, the second material suction channel 33 is opened, and the second material discharge channel 34 is closed. The pumping hydraulic subsystem 4 injects hydraulic oil into the rear chamber of the first pumping oil cylinder 11 to make its pumping piston 7 or pumping plunger advance and push the material into the discharge pipe. At the same time, the hydraulic oil output by the quick return hydraulic subsystem 6 and the hydraulic oil discharged from the front chamber of the first pumping oil cylinder 11 enter the front chamber of the second pumping oil cylinder 21 at the same time, so that the pumping piston 7 or pumping plunger of the second pumping oil cylinder 21 quickly retreats at a speed faster than the advancing speed of the pumping piston 7 or pumping plunger of the first pumping oil cylinder 11 and sucks materials.

[0103] Process 2, the first pumping unit pumps, and the second pumping unit pre-presses:

[0104] The first material suction channel 31 continues to be closed, the first material discharge channel 32 continues to be opened, and the first pumping unit continues to pump; the second material suction channel 33 is closed, the second material discharge channel 34 continues to be closed, the materials sucked by the second pump unit 2 are sealed, and the pre-pressure hydraulic subsystem 5 injects hydraulic oil into the rear chamber of the second pumping oil cylinder 21 to make its pumping piston 7 or pumping plunger advance, and pressurizes the sealed materials to increase their pressure until the pressure is close to or equal to the pressure of the materials in the first pumping unit 1.

[0105] Process 3, the first pumping unit quickly returns to suck materials, and the second pumping unit pumps:

[0106] The first material suction channel 31 is opened, the first material discharge channel 32 remains closed, the second material suction channel 33 remains closed, the second material discharge channel 34 is opened, the pumping hydraulic subsystem 4 injects hydraulic oil into the rear chamber of the second pumping cylinder 21 to make its pumping piston 7 or pumping plunger advance and push the material into the discharge pipe. The hydraulic oil discharged from the quick return hydraulic oil circuit 6 and the hydraulic oil discharged from the front chamber of the second pumping cylinder 21 enter the front chamber of the first pumping cylinder 11 at the same time, so that the pumping piston 7 or pumping plunger of the first pumping cylinder 11 retreats at a speed faster than the advancing speed of the pumping piston 7 or pumping plunger of the second pumping cylinder 21 and sucks in the material;

[0107] Process 4, preloading of the first pumping unit and pumping of the second pumping unit:

[0108] The second material suction channel 33 remains closed, the second material discharge channel 34 remains open, and the second pumping unit continues to pump; the first material suction channel 31 is closed, the first material discharge channel 32 remains closed, the material sucked by the first pumping unit 1 is sealed, and the preloading hydraulic subsystem 5 injects hydraulic oil into the rear chamber of the first pumping cylinder 11 to make its pumping piston 7 or pumping plunger advance, and pressurizes the sealed material to increase its pressure until its pressure is close to or equal to the pressure of the material in the second pumping unit 2.

[0109] Specifically, Process 2 and Process 3 are switched in the following manner:

[0110] Pumping relay of the first pumping unit and the second pumping unit:

[0111] When the pumping piston 7 or pumping plunger of the first pumping cylinder 11 advances to the set position, the pumping hydraulic subsystem 4 injects hydraulic oil into the rear chamber of the first pumping cylinder 11 and the rear chamber of the second pumping cylinder 21 at the same time. The pumping pistons 7 or pumping plungers of the two pumping units apply the same pumping pressure to the material therein. At the same time, the first material suction channel 31 remains closed, the second material suction channel 33 remains closed, the first material discharge channel 32 and the second material discharge channel 34 switch between open and closed states, and the first pumping cylinder 11 and the second pumping cylinder 21 switch between pumping and stopping states to complete the pumping relay.

[0112] Process 4 and Process 1 are switched in the following manner:

[0113] After the second pumping oil cylinder 21 advances to the set position, the pumping hydraulic subsystem 4 simultaneously injects hydraulic oil into the rear chambers of the first pumping oil cylinder 11 and the second pumping oil cylinder 21. The pumping pistons 7 or pumping plungers of the two pumping units simultaneously apply the same pumping pressure to the materials therein. At the same time, the first suction channel (31) remains closed, the second suction channel (33) remains closed, the first discharge channel and the second discharge channel switch between open and closed states, and the first pumping oil cylinder 11 and the second pumping oil cylinder 21 switch between pumping and stopping states to complete the pumping relay.

[0114] It should be noted that the material commutation valve group 3 includes multiple valves (each valve can be a one-way valve, gate valve, lift valve, shear valve, etc., or a composite valve), which are used to control the on / off or direction of the corresponding channels or oil circuits, so that the first pumping unit 1 and the second pumping unit 2 are in an appropriate working state. The hydraulic system supplies hydraulic oil to the first pumping unit 1, the second pumping unit 2, the commutation valve group, etc., serving as the source of driving force.

[0115] The specific form of the valves included in the material commutation valve group 3 can be set according to needs. For example, it can be an electric control valve, a hydraulic control valve, or a combination of an electric control valve and a hydraulic control valve. In appropriate cases, it can even be a manually controlled valve.

[0116] As shown in the figure, the first pumping unit 1 includes a first pumping oil cylinder 11, a first pumping cylinder 12, and a pumping piston 7. The first pumping oil cylinder 11 is connected to the first pumping cylinder 12. The piston rod of the first pumping oil cylinder 11 is connected to the pumping piston 7 and can drive the pumping piston 7 to reciprocate in the first pumping cylinder 12 to suck in and discharge materials such as liquids, slurries, pastes, and paste-like materials. The second pumping unit 2 further includes a second pumping oil cylinder 21, a second pumping cylinder 22, and a pumping piston 7. The second pumping oil cylinder 21 is connected to the second pumping cylinder 22. The piston rod of the second pumping oil cylinder 21 is connected to the pumping piston 7 and can drive the pumping piston 7 to reciprocate in the second pumping cylinder 22 to suck in and discharge materials such as liquids, slurries, pastes, and paste-like materials.

[0117] Both the first pumping unit 1 and the second pumping unit 2 are connected to the material commutation valve group 3. The material commutation valve group 3 includes a first suction channel 31, a first discharge channel 32, a second suction channel 33, and a second discharge channel 34, and controls their on / off. Both the first suction channel 31 and the first discharge channel 32 communicate with the first pumping cylinder 12, and both the second suction channel 33 and the second discharge channel 34 communicate with the second pumping cylinder 22. The material commutation valve group 3 can control the on / off of the first suction channel 31, the first discharge channel 32, the second suction channel 33, and the second discharge channel 34.

[0118] The inner cavities of the first pumping oil cylinder 11 and the second pumping oil cylinder 21 are further divided into a rear chamber and a front chamber by pistons. The front chambers of the first pumping oil cylinder 11 and the second pumping oil cylinder 21 are connected by an oil circuit.

[0119] The hydraulic system includes, for example, a pumping hydraulic subsystem 4, a preloading hydraulic subsystem 5, and a quick return hydraulic subsystem 6. The pumping hydraulic subsystem 4 includes a first pumping valve group 41, a first oil return valve group 42, a second pumping valve group 43, a second oil return valve group 44, and a pumping hydraulic pump group 45. The rear chamber of the first pumping oil cylinder 11 is simultaneously connected to the first pumping valve group 41 and the first oil return valve group 42 by an oil circuit. The first pumping valve group 41 is further connected to the pumping hydraulic pump group 45 by an oil circuit. The first oil return valve group 42 is further connected to the oil return oil circuit. The first pumping valve group 41 is used to control the on-off of the oil circuit between the rear chamber of the first pumping oil cylinder 11 and the pumping hydraulic pump group 45. The first oil return valve group 42 is used to control the on-off of the oil return oil circuit of the rear chamber of the first pumping oil cylinder 11. The rear chamber of the second pumping oil cylinder 21 is simultaneously connected to the second pumping valve group 43 and the second oil return valve group 44 by an oil circuit. The second pumping valve group 43 is further connected to the pumping hydraulic pump group 45 by an oil circuit. The second oil return valve group 44 is further connected to the oil return oil circuit. The second pumping valve group 43 is used to control the on-off of the oil circuit between the rear chamber of the second pumping oil cylinder 21 and the pumping hydraulic pump group 45. The second oil return valve group 44 is used to control the on-off of the oil return oil circuit of the rear chamber of the second pumping oil cylinder 21.

[0120] The preloading hydraulic subsystem 5 includes a preloading valve group 51, an accumulator 52, and a preloading hydraulic pump 53. The preloading valve group 51 further includes a first preloading valve 511, a second preloading valve 512, and a pressure control valve 513. The accumulator 52 is connected to the preloading hydraulic pump 53, the rear chamber of the first pumping oil cylinder 11, and the rear chamber of the second pumping oil cylinder 21 by an oil circuit, and is used to store the high-pressure hydraulic oil output by the preloading hydraulic pump 53 and provide preloading hydraulic oil for the first pumping oil cylinder 11 and the second pumping oil cylinder 21. The preloading valve group 51 is connected to the oil circuit between the accumulator 52 and the rear chamber of the first pumping oil cylinder 11 and the rear chamber of the second pumping oil cylinder 21, and is used to control the on-off of the oil circuit between the accumulator 52 and the rear chamber of the first pumping oil cylinder 11 and the oil circuit between the accumulator 52 and the rear chamber of the second pumping oil cylinder 21. Among them, the first preloading valve 511 is located on the oil circuit between the accumulator 52 and the rear chamber of the first pumping oil cylinder 11 and is used to control the on-off of the oil circuit between the accumulator 52 and the rear chamber of the first pumping oil cylinder 11. The second preloading valve 512 is located on the oil circuit between the accumulator 52 and the rear chamber of the second pumping oil cylinder 21 and is used to control the on-off of the oil circuit between the accumulator 52 and the rear chamber of the second pumping oil cylinder 21.

[0121] The first pre-pressure valve 511 and the second pre-pressure valve 512 are both two-way cartridge valves with shuttle valve control covers and adjustable openings. By adjusting the openings of the two-way cartridge valves, the hydraulic oil injected into the rear chambers of the first pumping cylinder 11 and the second pumping cylinder 21 can be throttled. The shuttle valve control covers can prevent the reverse flow of hydraulic oil.

[0122] When the first pumping cylinder 11 or the second pumping cylinder 21 retracts to the end to complete material suction, the pre-pressure valve group 51 connects the oil circuit between the accumulator 52 and the rear chamber of the first pumping cylinder 11 or the oil circuit between the accumulator 52 and the rear chamber of the second pumping cylinder 21, so that the hydraulic oil discharged by the pre-pressure hydraulic pump 53 and the hydraulic oil in the accumulator 52 can enter the rear chamber of the first pumping cylinder 11 or the rear chamber of the second pumping cylinder 21, and drive the pumping piston 7 to advance through the first pumping cylinder 11 or the second pumping cylinder 21 to pre-pressurize the material in the first pumping cylinder 12 or the second pumping cylinder 22.

[0123] The pressure control valve 513 is connected to the oil circuit between the accumulator 52 and the pre-pressure hydraulic pump 53, and is used to control the pressure of the hydraulic oil injected by the pre-pressure hydraulic pump 53 into the accumulator 52 to make its pressure equal to or close to the pressure of the hydraulic oil injected by the pumping hydraulic subsystem 3 into the rear chambers of the first pumping cylinder 11 and the second pumping cylinder 21. In the present invention, equal pressure means that the pressure difference between the two is less than or equal to 3%. Close pressure means that the pressure difference between the two is less than or equal to a set smaller percentage, for example, 25%. Specifically, for example, the absolute value of the pressure difference is less than or equal to 25% of the pressure value of the hydraulic oil injected by the pumping hydraulic subsystem 3.

[0124] The quick-return hydraulic subsystem 6 further includes a quick-return hydraulic pump 61 and a quick-return valve group 62. The quick-return hydraulic pump 61 is simultaneously connected to the front chambers of the first pumping cylinder 11 and the second pumping cylinder 21. The quick-return valve group 62 is connected to the oil return circuit of the front chambers of the first pumping cylinder 11 and the second pumping cylinder 21, and is used to control the on-off of this oil return circuit. When the first pumping cylinder 11 or the second pumping cylinder 21 performs a quick backward movement, the quick-return valve group 61 cuts off the oil return circuit of the front chambers of the first pumping cylinder 11 and the second pumping cylinder 21. The hydraulic oil discharged from the front chamber of the second pumping cylinder 21 or the hydraulic oil discharged from the front chamber of the first pumping cylinder 11 and the hydraulic oil discharged from the quick-return hydraulic pump 61 simultaneously enter the front chamber of the first pumping cylinder 11 or the front chamber of the second pumping cylinder 21, enabling it to move backward at a speed faster than the forward speed of the second pumping cylinder 21 or the first pumping cylinder 11. When the first pumping cylinder 11 or the second pumping cylinder 21 retreats to the end point, the quick-return valve group 62 connects the oil return circuit of the front chambers of the first pumping cylinder 11 and the second pumping cylinder 2. The hydraulic oil discharged from the front chamber of the second pumping cylinder 21 or the hydraulic oil discharged from the front chamber of the first pumping cylinder 11 and the hydraulic oil discharged from the quick-return hydraulic pump 61 can all flow back to the fuel tank through the quick-return valve group 62. When both the first pumping cylinder 11 and the second pumping cylinder 21 perform a backward movement, the quick-return valve group 61 cuts off the oil return circuit of the front chambers of the first pumping cylinder 11 and the second pumping cylinder 21, and the hydraulic oil discharged from the quick-return hydraulic pump 61 enters the front chambers of the first pumping cylinder 11 and the second pumping cylinder 21.

[0125] It continuously pumps in a cycle by repeating the following steps 1 to 6:

[0126] 1) The first pumping unit pumps, and the second pumping unit performs a quick return:

[0127] The first suction channel 31 is closed, the first discharge channel 32 is opened, the first pumping valve group 41 opens the oil circuit between the pumping hydraulic pump group 45 and the rear chamber of the first pumping cylinder 11. The hydraulic oil discharged from the pumping hydraulic pump group 45 enters the rear chamber of the first pumping cylinder 11. The first pumping cylinder 11 drives the pumping piston 7 to move forward in the first pumping cylinder 12 and pushes the material in the first pumping cylinder 12 to be discharged through the first discharge channel 32. At the same time, the second suction channel 33 is opened, the second discharge channel 34 is closed, the quick-return valve group 62 is closed, and the hydraulic oil discharged from the quick-return hydraulic pump 61 and the hydraulic oil discharged from the front chamber of the first pumping cylinder 11 enter the front chamber of the second pumping cylinder 21, enabling the second pumping cylinder 21 to quickly retreat at a speed faster than the forward speed of the first pumping cylinder 11 and suck in the material;

[0128] 2) The first pumping unit pumps, and the second pumping unit performs preloading:

[0129] When the second pumping oil cylinder 21 retracts to the end point, the second material suction channel 33 closes, the second material discharge channel 34 remains closed, the first material suction channel 31 remains closed, the first material discharge channel 32 remains open, the pre-pressure valve group 51 opens the oil circuit between the accumulator 52 and the rear cavity of the second pumping oil cylinder 21, and the hydraulic oil discharged from the accumulator 52 and the pre-pressure hydraulic pump (53) enters the rear cavity of the second pumping oil cylinder 21. The second pumping oil cylinder 21 pushes the pumping piston 7 to advance in the second pumping cylinder 22. The quick-retreat valve group 62 opens, and the hydraulic oil discharged from the quick-retreat hydraulic pump 61, the hydraulic oil discharged from the front cavity of the first pumping oil cylinder 11, and the hydraulic oil discharged from the front cavity of the second pumping oil cylinder 21 flow back to the fuel tank. Since the second material suction channel 33 and the second material discharge channel 34 are in the closed state, the material sucked by the second pumping unit 2 is enclosed in the second pumping unit 2 and the material commutation valve group 3 and is pressurized to increase the pressure until it is equal to or close to the pressure of the material in the first pumping cylinder that is being pumped. This pre-pressure is set by the pressure control valve 513. During this process, the first pumping unit 1 continues to advance and pump;

[0130] 3) Pumping relay of the first pumping unit and the second pumping unit:

[0131] When the first pumping oil cylinder 11 advances to the set position (there is still a certain distance from the end point of the advance stroke of the first pumping oil cylinder 11), the pre-pressure valve group 51 closes the oil circuit between the accumulator 52 and the rear cavity of the second pumping oil cylinder 21, the second pumping valve group 43 opens the oil circuit between the pumping hydraulic pump group 45 and the rear cavity of the second pumping oil cylinder 21, the quick-retreat valve group 62 opens, and the hydraulic oil discharged from the quick-retreat hydraulic pump 61, the hydraulic oil discharged from the front cavity of the first pumping oil cylinder 11, and the hydraulic oil discharged from the front cavity of the second pumping oil cylinder 21 flow back to the fuel tank. The first material suction channel 31 continues to remain closed, the second material suction channel 33 continues to remain closed, and the first material discharge channel 32 and the second material discharge channel 34 switch between the open and closed states. The first pumping unit and the second pumping unit switch between the pumping and stopping pumping states until the first material discharge channel 32 closes and the second material discharge channel 34 opens. The first pumping unit 1 stops pumping, and the second pumping unit 2 pumps.

[0132] 4) Quick retreat of the first pumping unit and pumping of the second pumping unit:

[0133] The first material suction channel 31 opens, the first material discharge channel 32 remains closed, the second material suction channel 33 closes, the second material discharge channel 34 remains open, the second pumping unit 2 continues to pump, the quick-retreat valve group 62 closes, and the hydraulic oil discharged from the quick-retreat hydraulic pump 61 and the hydraulic oil discharged from the front cavity of the second pumping oil cylinder 21 enter the front cavity of the first pumping oil cylinder 11, causing the first pumping oil cylinder 11 to drag the pumping piston 7 to quickly retreat and suck the material at a speed faster than the advancing speed of the piston rod of the second pumping oil cylinder 21;

[0134] 5) Pre-pressurization of the first pumping unit and pumping of the second pumping unit:

[0135] When the first pumping oil cylinder 11 retracts to the end point, the first material suction channel 31 is closed, the first material discharge channel 32 remains closed, the second material suction channel 33 remains closed, the second material discharge channel 34 remains open, the pre-pressure valve group 51 opens the oil circuit between the accumulator 52 and the rear chamber of the first pumping oil cylinder 11, and the hydraulic oil discharged from the accumulator 52 and the pre-pressure hydraulic pump 53 enters the rear chamber of the first pumping oil cylinder 11. The first pumping oil cylinder 11 pushes the pumping piston 7 to advance in the first pumping cylinder 12. The quick return valve group 62 is opened, and the hydraulic oil discharged from the quick return hydraulic pump 61, the hydraulic oil discharged from the front chamber of the first pumping oil cylinder 11, and the hydraulic oil discharged from the front chamber of the second pumping oil cylinder 21 flow back to the fuel tank. Since the first material suction channel 31 and the first material discharge channel 32 are in the closed state, the material sucked by the first pumping unit 1 is enclosed in the second pumping unit 2 and the material commutation valve group 3 and is pressurized to increase the pressure until it is equal to or close to the pressure of the material in the second pumping cylinder that is being pumped. This pre-pressure is set by the pressure control valve 513 or the pressure reducing valve 54. During this process, the first pumping unit 1 continues to advance for pumping;

[0136] 6) Pumping relay of the first pumping unit and the second pumping unit: When the second pumping oil cylinder 21 advances to the set position (this position is still a certain distance from the end point of the advancing stroke of the second pumping oil cylinder 21), the pre-pressure valve group 51 closes the oil circuit between the accumulator 52 and the rear chamber of the second pumping oil cylinder 11, the first pumping valve group 41 opens the oil circuit between the pumping hydraulic pump group 45 and the rear chamber of the first pumping oil cylinder 11, the quick return valve group 62 is opened, and the hydraulic oil discharged from the quick return hydraulic pump 61, the hydraulic oil discharged from the front chamber of the first pumping oil cylinder 11, and the hydraulic oil discharged from the front chamber of the second pumping oil cylinder 21 flow back to the fuel tank. The first material suction channel 31 continues to remain closed, the second material suction channel 33 continues to remain closed, the first material discharge channel 32 and the second material discharge channel 34 switch between the open and closed states, and the first pumping unit and the second pumping unit switch between the pumping and stopping states until the first material discharge channel 32 is opened and the second material discharge channel 34 is closed, the first pumping unit pumps, and the second pumping unit stops.

[0137] Embodiment 2

[0138] See Figure 3 , which shows a schematic diagram of the pre-pressure and steady-flow conveying pump of the preferred embodiment of the present invention. The main differences between this embodiment and Embodiment 1 are as follows:

[0139] 1. Two one-way valves 514 are added to the preloading valve group 51, which are respectively connected to the oil paths between the preloading hydraulic subsystem 5 and the rear chambers of the first pumping cylinder 11 and between the preloading hydraulic subsystem 5 and the rear chambers of the second pumping cylinder 21, and are used to prevent the hydraulic oil in the rear chamber of the first pumping cylinder 11 and the hydraulic oil in the rear chamber of the second pumping cylinder 21 from flowing into the preloading hydraulic subsystem 5.

[0140] 2. There is no shuttle valve on the control covers of the first preloading valve 511 and the second preloading valve 512.

[0141] Embodiment III

[0142] See Figure 3 , which shows a schematic diagram of a preloading and steady-flow conveying pump according to another preferred embodiment of the present invention.

[0143] The main differences between this embodiment and Embodiment I are as follows:

[0144] 1. A deceleration pressure valve 54 is added to the preloading hydraulic subsystem 5, which is connected to the oil paths between the accumulator 52 and the rear chamber of the first pumping cylinder 11 and between the accumulator 52 and the rear chamber of the second pumping cylinder 21, and is used to control the pressure of the hydraulic oil injected into the rear chambers of the first pumping cylinder 11 and the second pumping cylinder 21, so that the pressure is equal to or close to the pressure of the hydraulic oil injected into the rear chambers of the first pumping cylinder 11 and the second pumping cylinder 21 by the pumping hydraulic subsystem 3.

[0145] 2. Two one-way valves 514 are added to the preloading valve group 51. They are respectively connected to the oil paths between the preloading hydraulic subsystem 5 and the rear chamber of the first pumping cylinder 11 and between the preloading hydraulic subsystem 5 and the rear chamber of the second pumping cylinder 21, and are used to prevent the hydraulic oil in the rear chamber of the first pumping cylinder 11 and the hydraulic oil in the rear chamber of the second pumping cylinder 21 from flowing into the preloading hydraulic subsystem 5.

[0146] 3. There is no shuttle valve on the control covers of the first preloading valve 511 and the second preloading valve 512.

[0147] In the above embodiments, since the displacement of the pressure oil output by the pumping hydraulic pump group 45 is relatively constant, the piston areas of the first pumping cylinder 11 and the second pumping cylinder 21 are the same, the diameters of the pumping pistons 7 of the two cylinders are also the same, and all the pressure oil output by the pumping hydraulic pump group 45 enters the rear chambers of the first pumping cylinder 11 and / or the second pumping cylinder 21. Therefore, the flow rate output by a single cylinder during pumping and the flow rate output by the two cylinders during simultaneous pumping are the same. And during the simultaneous pumping of the two cylinders and the process of pumping commutation, the forward speeds of the first pumping cylinder 11 and the second pumping cylinder 21 offset each other, so that the pumping commutation can be smoothly transitioned, and the flow rate and pressure of the pumped material can be kept stable.

[0148] Finally, it should be pointed out that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Those of ordinary skill in the art should understand that the technical solutions described in the foregoing embodiments may be modified, or some of the technical features may be equivalently replaced; these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A preloading and steady-flow pumping method, which uses a double-cylinder transfer pump for pumping. It is characterized in that the double-cylinder transfer pump includes two pumping units. During the pumping operation, each pumping unit sequentially performs pumping and pushing materials, retreating and sucking materials, and material preloading. The two pumping units alternate in the above processes to pump the materials. wherein, during the process of retreating and sucking materials, the speed at which the pumping piston (7) or the pumping plunger of the pumping unit retreats is greater than the speed at which the pumping piston (7) or the pumping plunger of the pumping unit advances during the pumping and pushing material stroke. Before one pumping unit completes the pumping and pushing material process, the other pumping unit has completed the retreating and sucking material process and the enclosure of the sucked materials, and starts the preloading process of the sucked materials. The enclosed materials increase in pressure due to being pressed. When one pumping unit completes the pumping and pushing material process, the other pumping unit has completed the material preloading process and is ready to switch to the pumping and pushing material process.

2. The preloading and steady-flow pumping method according to claim 1, wherein After the pumping piston (7) or the pumping plunger of one pumping unit retreats to the end point, its pumping piston (7) or pumping plunger advances to push the material, preloading the material inside it to make the pressure of the material equal to or close to the pressure of the material in the other pumping unit, and then switches to the pumping and pushing material process to perform the pumping relay with the other pumping unit.

3. The preloading and steady-flow pumping method according to claim 1, characterized in that the double-cylinder transfer pump includes: a first pumping unit (1), a second pumping unit (2), a material commutation valve group (3), a pumping hydraulic subsystem (4), a preloading hydraulic subsystem (5), and a quick-retreat hydraulic subsystem (6). The first pumping unit (1) and the second pumping unit (2) are both connected to the material commutation valve group (3). The material commutation valve group (3) includes a first suction channel (31), a first discharge channel (32), a second suction channel (33), and a second discharge channel (34) and controls their on / off. Among them, the first suction channel (31) and the first discharge channel (32) are both communicated with the first pumping unit (1) for the suction and discharge of the first pumping unit (1). The second suction channel (33) and the second discharge channel (34) are both communicated with the second pumping unit (2) for the suction and discharge of the second pumping unit (2). The first pumping unit (1) includes a first pumping oil cylinder (11), and the second pumping unit includes a second pumping oil cylinder (21). The inner cavities of the first pumping oil cylinder (11) and the second pumping oil cylinder (21) are divided into a front chamber and a rear chamber by a piston. The front chambers of the first pumping oil cylinder (11) and the second pumping oil cylinder (21) are connected by an oil circuit. The pumping hydraulic subsystem (4) and the preloading hydraulic subsystem (5) are connected to the rear chambers of the first pumping oil cylinder (11) and the second pumping oil cylinder (21), and the quick-retreat hydraulic subsystem (6) is connected to the front chambers of the first pumping oil cylinder (11) and the second pumping oil cylinder (21). The double-cylinder transfer pump continuously pumps in a cycle according to the following processes 1 to 4: Process 1, the first pumping unit pumps, and the second pumping unit quickly retreats to suck materials: The first material suction channel (31) is closed, the first material discharge channel (32) is opened, the second material suction channel (33) is opened, the second material discharge channel (34) is closed, the pumping hydraulic subsystem (4) injects hydraulic oil into the rear chamber of the first pumping oil cylinder (11) to make its pumping piston (7) or pumping plunger advance and push the material into the discharge pipe. At the same time, the hydraulic oil output by the quick return hydraulic subsystem (6) and the hydraulic oil discharged from the front chamber of the first pumping oil cylinder (11) enter the front chamber of the second pumping oil cylinder (21) simultaneously, so that the pumping piston (7) or pumping plunger of the second pumping oil cylinder (21) quickly retreats at a speed faster than the advancing speed of the pumping piston (7) or pumping plunger of the first pumping oil cylinder (11) and sucks in the material; Process 2, the first pumping unit pumps, and the second pumping unit pre-presses: The first material suction channel (31) continues to be closed, the first material discharge channel (32) continues to be opened, and the first pumping unit continues to pump; the second material suction channel (33) is closed, the second material discharge channel (34) continues to be closed, and the pre-pressing hydraulic subsystem (5) injects hydraulic oil into the rear chamber of the second pumping oil cylinder (21) to make its pumping piston (7) or pumping plunger advance and pressurize the material in the second pumping unit (2) until its pressure is close to or equal to the pressure of the material in the first pumping unit (1). The hydraulic oil discharged from the front chambers of the first pumping oil cylinder (11) and the second pumping oil cylinder (21) and the hydraulic oil discharged from the quick return hydraulic subsystem (6) flow back to the fuel tank; Process 3, the first pumping unit quickly retreats to suck in material, and the second pumping unit pumps: The first material suction channel (31) is opened, the first material discharge channel (32) continues to be closed, the second material suction channel (33) continues to be closed, the second material discharge channel (34) is opened, the pumping hydraulic subsystem (4) injects hydraulic oil into the rear chamber of the second pumping oil cylinder (21) to make its pumping piston (7) or pumping plunger advance and push the material into the discharge pipe. The hydraulic oil discharged from the quick return hydraulic oil circuit (6) and the hydraulic oil discharged from the front chamber of the second pumping oil cylinder (21) enter the front chamber of the first pumping oil cylinder (11) simultaneously, so that the pumping piston (7) or pumping plunger of the first pumping oil cylinder (11) retreats at a speed faster than the advancing speed of the pumping piston (7) or pumping plunger of the second pumping oil cylinder (21) and sucks in the material; Process 4, the first pumping unit pre-presses, and the second pumping unit pumps: The second material suction channel (33) continues to be closed, the second material discharge channel (34) continues to be opened, and the second pumping unit continues to pump; the first material suction channel (31) is closed, the first material discharge channel (32) continues to be closed, and the pre-pressing hydraulic subsystem (5) injects hydraulic oil into the rear chamber of the first pumping oil cylinder (11) to make its pumping piston (7) or pumping plunger advance and pressurize the material in the first pumping unit (1) until its pressure is close to or equal to the pressure of the material in the second pumping unit (2). The hydraulic oil discharged from the front chambers of the first pumping oil cylinder (11) and the second pumping oil cylinder (21) and the hydraulic oil discharged from the quick return hydraulic subsystem (6) flow back to the fuel tank.

4. The method for eliminating the flow rate fluctuation of double-cylinder pumping according to claim 3, characterized in that Process 2 and Process 3 are switched in the following manner: The first pumping unit and the second pumping unit perform pumping relay: After the pumping piston (7) or the pumping plunger of the first pumping cylinder (11) advances to the set position, the pumping hydraulic subsystem (4) simultaneously injects hydraulic oil into the rear cavity of the first pumping cylinder (11) and the rear cavity of the second pumping cylinder (21). The pumping pistons (7) or the pumping plungers of the two pumping units simultaneously apply the same pumping pressure to the materials therein. At the same time, the first suction channel (31) remains closed, the second suction channel (33) remains closed, the first discharge channel (32) and the second discharge channel (34) switch between the open and closed states, the first pumping cylinder (11) and the second pumping cylinder (21) switch between the pumping and stopping states, and the hydraulic oil discharged from the front cavities of the first pumping cylinder (11) and the second pumping cylinder (21) and the hydraulic oil discharged from the quick-return hydraulic subsystem (6) flow back to the fuel tank; Or Process 4 and Process 1 are switched in the following manner: After the pumping piston (7) or the pumping plunger of the second pumping cylinder (21) advances to the set position, the pumping hydraulic subsystem (4) simultaneously injects hydraulic oil into the rear cavity of the first pumping cylinder (11) and the rear cavity of the second pumping cylinder (21). The pumping pistons (7) or the pumping plungers of the two pumping units simultaneously apply the same pumping pressure to the materials therein. At the same time, the first suction channel (31) remains closed, the second suction channel (33) remains closed, the first discharge channel and the second discharge channel switch between the open and closed states, the first pumping cylinder (11) and the second pumping cylinder (21) switch between the pumping and stopping states, and the hydraulic oil discharged from the front cavities of the first pumping cylinder (11) and the second pumping cylinder (21) and the hydraulic oil discharged from the quick-return hydraulic subsystem (6) flow back to the fuel tank.

5. A preloading and steady-flow conveying pump, characterized in that, The pre-pressure steady-flow transfer pump is a double-cylinder transfer pump, The double-cylinder transfer pump includes two pumping units. When performing pumping work, each pumping unit sequentially performs pumping and pushing materials, retreating and sucking materials, and pre-pressing the materials. The two pumping units alternately perform the above processes to pump the materials, wherein, during the process of retreating and sucking materials, the speed at which the pumping piston (7) or the pumping plunger retreats is greater than the speed at which the pumping piston (7) or the pumping plunger advances during the pumping and pushing material stroke of the pumping unit; Before a pumping unit completes the process of pumping and pushing materials, another pumping unit has completed the process of retreating and sucking materials and the enclosure of the sucked materials, and starts the process of pre-pressing the sucked materials. For the pumping unit in the process of pre-pressing the materials, the enclosed materials are pressurized due to the pressure; When a pumping unit completes the process of pumping and pushing materials, another pumping unit has completed the process of pre-pressing the materials and is ready to switch to the process of pumping and pushing materials.

6. The preloading and steady-flow conveying pump according to claim 5, wherein, After the pumping piston (7) or the pumping plunger of a pumping unit retracts to the end point, its pumping piston (7) or the pumping plunger advances to push the material, pre-presses the material inside it, and then switches to the pumping and pushing process to perform the pumping relay with another pumping unit.

7. The pre-pressure and steady-flow conveying pump according to claim 6, characterized in that the pre-pressure and steady-flow conveying pump includes a first pumping unit (1), a second pumping unit (2), a material commutation valve group (3), a pumping hydraulic subsystem (4), a pre-pressure hydraulic subsystem (5) and a quick-retreat hydraulic subsystem (6). The first pumping unit (1) and the second pumping unit (2) are both connected to the material commutation valve group (3). The material commutation valve group (3) includes a first material suction channel (31), a first material discharge channel (32), a second material suction channel (33) and a second material discharge channel (34) and controls their on-off. The first material suction channel (31) and the first material discharge channel (32) are both communicated with the first pumping unit (1), and the second material suction channel (33) and the second material discharge channel (34) are both communicated with the second pumping unit (2). The first pumping unit (1) includes a first pumping oil cylinder (11) and a first pumping material cylinder (12). The second pumping unit (2) includes a second pumping oil cylinder (21) and a second pumping material cylinder (22). The inner cavities of the first pumping oil cylinder (11) and the second pumping oil cylinder (21) are divided into a rear cavity and a front cavity by pistons. The front cavities of the first pumping oil cylinder (11) and the second pumping oil cylinder (21) are connected by an oil circuit. The pumping hydraulic subsystem (4) includes a first pumping valve group (41), a first oil return valve group (42), a second pumping valve group (43), a second oil return valve group (44) and a pumping hydraulic pump group (45). The rear cavity of the first pumping oil cylinder (11) is simultaneously connected to the first pumping valve group (41) and the first oil return valve group (42) by an oil circuit. The first pumping valve group (41) is also connected to the pumping hydraulic pump group (45) by an oil circuit. The first oil return valve group (42) is also connected to the oil return oil circuit. The first pumping valve group (41) is used to control the on-off of the oil circuit between the rear cavity of the first pumping oil cylinder (11) and the pumping hydraulic pump group (45). The first oil return valve group (42) is used to control the on-off of the oil return oil circuit of the rear cavity of the first pumping oil cylinder (11). The rear cavity of the second pumping oil cylinder (21) is simultaneously connected to the second pumping valve group (43) and the second oil return valve group (44) by an oil circuit. The second pumping valve group (43) is also connected to the pumping hydraulic pump group (45) by an oil circuit. The second oil return valve group (44) is also connected to the oil return oil circuit. The second pumping valve group (43) is used to control the on-off of the oil circuit between the rear cavity of the second pumping oil cylinder (21) and the pumping hydraulic pump group (45). The second oil return valve group (44) is used to control the on-off of the oil return oil circuit of the rear cavity of the second pumping oil cylinder (21). The preloading hydraulic subsystem (5) is respectively connected to the rear chambers of the first pumping cylinder (11) and the second pumping cylinder (21) through oil circuits. The preloading hydraulic subsystem (5) further includes a preloading valve group (51), which is located on the oil circuit that supplies oil to the first pumping cylinder (11) and the second pumping cylinder (21) in the preloading hydraulic subsystem (5) and is used to control the on-off of the oil circuit for the preloading hydraulic subsystem (5) to supply oil to the first pumping cylinder (11) and the second pumping cylinder (21). When the first pumping cylinder (11) or the second pumping cylinder (21) retreats to the end to complete material suction, the preloading valve group (51) can connect the oil circuit for the preloading hydraulic subsystem (5) to supply oil to the first pumping cylinder (11) or the oil circuit for the preloading hydraulic subsystem (5) to supply oil to the second pumping cylinder (21), enabling hydraulic oil to enter the rear chamber of the first pumping cylinder (1) or the rear chamber of the second pumping cylinder (2), driving the first pumping cylinder (1) or the second pumping cylinder (2) to advance to pre-pressurize the material. The fast-retreat hydraulic subsystem (6) further includes a fast-retreat hydraulic pump (61) and a fast-retreat valve group (62). The fast-retreat hydraulic pump (61) is simultaneously connected to the front chambers of the first pumping cylinder (11) and the second pumping cylinder (21) through oil circuits. The front chambers of the first pumping cylinder (11) and the second pumping cylinder (21) are also connected to the oil return circuit. The fast-retreat valve group (62) is connected to the oil return circuit of the front chambers of the first pumping cylinder (11) and the second pumping cylinder (21) and is used to control the on-off of this oil return circuit. When the first pumping cylinder (11) or the second pumping cylinder (21) retreats, the fast-retreat valve group (61) cuts off the oil return circuit of the front chambers of the first pumping cylinder (11) and the second pumping cylinder (21). The hydraulic oil discharged from the front chamber of the second pumping cylinder (21) or the hydraulic oil discharged from the front chamber of the first pumping cylinder (11) and the hydraulic oil discharged from the fast-retreat hydraulic pump (61) simultaneously enter the front chamber of the first pumping cylinder (11) or the front chamber of the second pumping cylinder (21), causing it to retreat at a speed faster than the advancing speed of the second pumping cylinder (21) or the first pumping cylinder (11). When the first pumping cylinder (11) or the second pumping cylinder (21) retreats to the end, the fast-retreat valve group (62) connects the oil return circuit of the front chambers of the first pumping cylinder (11) and the second pumping cylinder (2), and all the hydraulic oil discharged from the front chamber of the second pumping cylinder (21) or the hydraulic oil discharged from the front chamber of the first pumping cylinder (11) and the hydraulic oil discharged from the fast-retreat hydraulic pump (61) flows back to the fuel tank.

8. The pre-pressure steady-flow conveying pump according to claim 7, characterized in that, The described preloading hydraulic subsystem (5) includes an accumulator (52), which is connected to the hydraulic oil source through an oil circuit and is connected to the rear chambers of the first pumping cylinder (11) and the second pumping cylinder (2) through the preloading valve group (51). It is used to store high-pressure hydraulic oil and provide preloading hydraulic oil for the rear chamber of the first pumping cylinder (11) and the rear chamber of the second pumping cylinder (21).

9. The preloading and stable flow conveying pump according to claim 8, wherein, The preloading valve group (51) includes a pressure control valve (513) which is connected to the oil path between the accumulator (52) and the hydraulic oil source and is used to control the liquid filling pressure of the accumulator. The set pressure of the pressure control valve is equal to or close to the pressure of the hydraulic oil injected by the pumping hydraulic subsystem (3) into the rear chambers of the first pumping cylinder (11) and the second pumping cylinder (21).

10. The preloading and steady-flow conveying pump according to claim 7 or 8, characterized in that, The preloading hydraulic subsystem (5) further includes a pressure reducing valve (54) which is connected to the oil paths between the preloading hydraulic subsystem (5) and the rear chamber of the first pumping cylinder (11) and between the preloading hydraulic subsystem (5) and the rear chamber of the second pumping cylinder (21) and is used to control the pressure of the hydraulic oil injected into the rear chambers of the first pumping cylinder (11) and the second pumping cylinder (21). The set pressure of the pressure reducing valve (54) is equal to or close to the pressure of the hydraulic oil injected by the pumping hydraulic subsystem (3) into the rear chambers of the first pumping cylinder (11) and the second pumping cylinder (21).

11. The preloading and steady flow conveying pump according to any one of claims 7 to 10, characterized in that, The described preloading valve group (51) further includes check valves (514) which are connected to the oil paths between the preloading hydraulic subsystem (5) and the rear chamber of the first pumping cylinder (11) and between the preloading hydraulic subsystem (5) and the rear chamber of the second pumping cylinder (21) and are used to prevent the hydraulic oil in the rear chamber of the first pumping cylinder (11) and the hydraulic oil in the rear chamber of the second pumping cylinder (21) from flowing back to the preloading hydraulic subsystem (5).

12. The preloading and steady-flow conveying pump according to any one of claims 7 to 11, characterized in that The described preloading valve group (51) further includes a first preloading valve (511) and a second preloading valve (512). The first preloading valve (511) is located on the oil path between the accumulator (52) and the rear chamber of the first pumping cylinder (11) and is used to control the opening and closing of the oil path between the accumulator (52) and the rear chamber of the first pumping cylinder (11). The second preloading valve (512) is located on the oil path between the accumulator (52) and the rear chamber of the second pumping cylinder (21) and is used to control the opening and closing of the oil path between the accumulator (52) and the rear chamber of the second pumping cylinder (21). The first preloading valve (511) and the second preloading valve (512) are both two-way cartridge valves with adjustable openings. By adjusting the openings of the two-way cartridge valves, the hydraulic oil injected into the rear chambers of the first pumping cylinder (11) and the second pumping cylinder (21) can be throttled.

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