Double-pump hydraulic system of crown block

Abstract

The double-pump hydraulic system of the crown block comprises a servo motor, a variable pump, a hydraulic pump, a first oil return pipe and a second oil return pipe, the servo motor respectively drives the variable pump and the hydraulic pump to operate through a driving shaft, and an oil inlet of the variable pump and an oil inlet of the hydraulic pump are respectively communicated with hydraulic oil in an oil tank; and an oil outlet of the hydraulic pump is communicated with the normal-pressure pipeline. The rotating speed of the servo motor (controlling the flow of the pump) is automatically controlled through the hydraulic pressure sensor and the servo motor so as to realize precise control of pressure and flow; servo motor control response is fast and accurate, and the rotating speed can be well controlled; and the low oil temperature can be well controlled, and oil is saved. In addition, the output flow at the electromagnetic reversing position can be controlled through the first hydraulic control reversing valve and the second hydraulic control reversing valve, and therefore dynamic flow control is achieved to ensure stable operation of the system.

Description

TECHNICAL FIELD

[0001] The utility model relates to the hydraulic technology of crown block, in particular to a double pump hydraulic system of crown block. BACKGROUND

[0002] At present, the crown block generally adopts proportional (PQ) double pump hydraulic system, which adopts the crown block system powered by the constant-displacement pump and ordinary variable frequency motor or the variable-displacement pump and ordinary asynchronous motor, P controls the pressure through the proportional pressure valve, and Q controls the flow of the pump through the proportional flow valve; the ordinary motor power is constant through PQ, which not only has low efficiency, low control precision, poor stability, high noise and large heat generation, but also has high energy consumption (high oil temperature, high oil consumption and short service life).

[0003] Therefore, how to reduce the energy consumption, control the heat generation, improve the stability and control precision is the technical problem to be solved at present. UTILITY MODEL CONTENT

[0004] In view of the above defects of the prior art, the technical problem to be solved by the utility model is to provide a double pump hydraulic system of crown block, which has low energy consumption, low heat generation and high stability.

[0005] In order to achieve the above purpose, the utility model provides a double pump hydraulic system of crown block, which comprises a servo motor, a variable pump, a hydraulic pump, a first oil return pipe and a second oil return pipe, the servo motor drives the variable pump and the hydraulic pump to run through a driving shaft, and the oil inlet of the variable pump and the hydraulic pump is communicated with the hydraulic oil in the oil tank; the oil outlet of the hydraulic pump is communicated with a normal pressure pipeline;

[0006] The oil outlet of the variable pump is communicated with a first pipeline, the first pipeline is communicated with a first liquid control pipe and a first liquid supply pipe, a second liquid control pipe and a second liquid supply pipe through a second pipeline, and is communicated with the second oil return pipe;

[0007] The first pipeline is also communicated with the P port of a four-way valve and a first branch pipe, the first branch pipe is communicated with a second branch pipe and the oil outlet of a first one-way joint MA respectively, the second branch pipe is communicated with a third branch pipe, the third branch pipe is communicated with the oil inlet of a hydraulic pressure sensor, and the hydraulic pressure sensor is used for detecting the hydraulic pressure in the third branch pipe and then inputting an industrial computer;

[0008] The third branch pipe is communicated with the A port of the four-way valve, the A port of the four-way valve is communicated with the T port, the P port is communicated with the B port, the B port of the four-way valve is communicated with a first oil pipe through a fourth branch pipe, and the fourth branch pipe is communicated with the T port of the four-way valve through a fifth branch pipe;

[0009] The first oil pipe is in communication with the P port of the electromagnetic reversing valve directly or indirectly, the T port of the electromagnetic reversing valve is in communication with the first oil return pipe through a third oil pipe, A and B ports are further arranged on the electromagnetic reversing valve, and the electromagnetic reversing valve is used for controlling the P port to deliver hydraulic oil to the A port, the B port or the T port.

[0010] As a further improvement of the utility model, a first throttling hole and a second throttling hole are connected in sequence on the first oil pipe, and the first oil pipe is in communication with the P port of the electromagnetic reversing valve.

[0011] As a further improvement of the utility model, a part of the first oil pipe between the first throttling hole and the second throttling hole is in communication with the second oil outlet of the second hydraulic control reversing valve through a second oil pipe; a hydraulic control oil port of the second hydraulic control reversing valve is in communication with a second hydraulic control pipe, a first oil inlet is in communication with a second oil supply pipe, a first oil outlet is in communication with a fourth pipeline, and a second oil inlet is in communication with a second connecting pipe; the fourth pipeline is in communication with a second oil return pipe;

[0012] The second connecting pipe is in communication with a first oil outlet of a first hydraulic control reversing valve and a third connecting pipe; a first oil inlet of the first hydraulic control reversing valve is in communication with a second oil supply pipe, a second oil inlet is in communication with a third pipeline, a hydraulic control oil port is in communication with a first hydraulic control pipe, and a second oil outlet is in communication with the fourth pipeline through a first connecting pipe; the third pipeline is in communication with the fourth pipeline through a fourth connecting pipe; a third throttling hole and a fourth throttling hole are connected in sequence on the fourth connecting pipe; a part of the fourth connecting pipe between the third throttling hole and the fourth throttling hole is in communication with the third connecting pipe; and the third connecting pipe is further in communication with a rodless cavity of a second oil cylinder.

[0013] As a further improvement of the utility model, a first stop valve and a second stop valve are connected in sequence on the first oil return pipe and the second oil return pipe respectively, and the first stop valve and the second stop valve are used for controlling the opening and closing of the first oil return pipe and the second oil return pipe respectively.

[0014] As a further improvement of the utility model, the first pipeline is in communication with the rodless cavity of the first oil cylinder through a fifth pipeline; the first pipeline is in communication with an oil inlet of a pressure relief valve; and an oil outlet of the pressure relief valve is in communication with the first oil return pipe.

[0015] As a further improvement of the utility model, the first oil pipe is in communication with an oil outlet of a second one-way joint MB; the second one-way joint MB is in communication with an oil inlet of a hydraulic pressure gauge; and the hydraulic pressure gauge is used for observing the oil pressure in the first oil pipe.

[0016] As a further improvement of the utility model, the utility model further comprises a pressure valve and a fluctuation detector; the pressure valve is input into the fluctuation detector and a hydraulic pressure sensor after being opened by hydraulic pressure in a third branch pipe.

[0017] The pressure valve comprises a valve body, a valve cavity is arranged in the valve body, a first outlet and a second outlet are further arranged on the valve body, the third branch pipe is communicated with the valve cavity, and the first outlet and the second outlet are communicated with the valve cavity; a valve core is sealingly and slidingly arranged in the valve cavity, and the valve core and the inner wall of the valve cavity away from the first outlet are respectively pressed or assembled with the two ends of a valve core spring.

[0018] As a further improvement of the utility model, the fluctuation detector comprises a detection shell, a piston and a potentiometer, the detection shell is provided with a piston cavity, the piston is clamped and slidingly arranged in the piston cavity, one end of the piston is assembled with a piston rod, the other end of the piston rod is sleeved with a piston spring and then passes through the detection shell and is assembled with a connecting plate, and the connecting plate is assembled with an extension shaft of the potentiometer; one side of the piston cavity away from the piston is communicated with the second outlet, and the other side is communicated with the energy accumulator through a first energy storage pipe; the first energy storage pipe is communicated with the valve cavity away from one end of the third branch pipe through a second energy storage pipe.

[0019] The utility model has the advantages of:

[0020] The utility model solves the shortcomings of traditional proportional (PQ) double pumps, especially in energy saving, and gradually becomes the mainstream of the headgear system, and can well control the low oil temperature and save oil (low oil: long service life). Through the hydraulic pressure sensor (set pressure), the servo motor automatically controls the servo motor speed (controls the flow of the pump) to realize precise pressure and flow control; the servo motor control is fast and accurate (it starts when it starts and stops when it stops) and can well control the speed; and the low oil temperature and oil saving (low oil: long service life) can be well controlled. In addition, the ordinary asynchronous motor can be replaced with a servo motor and the PQ proportional valve can be replaced with a common directional valve and a through-flow cover plate, and the pipeline can be optimized and the corresponding valve body can be added, which can greatly save the transformation cost and time.

[0021] The utility model can also control the output flow of the electromagnetic reversing through the first hydraulic control reversing valve and the second hydraulic control reversing valve, so as to realize dynamic flow control and ensure stable operation of the system. In addition, the utility model can use the reference pressure of the hydraulic pressure sensor and the fluctuation detector to input the oil pressure, and use the fluctuation detector to detect the oil pressure fluctuation and compare it with the hydraulic pressure sensor to timely return the system failure. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 It is the hydraulic principle diagram of the utility model;

[0023] Figure 2 It is Figure 1 The first hydraulic control reversing valve 450 and the second hydraulic control reversing valve 460 are enlarged views;

[0024] Figure 3It is the structural schematic diagram after the utility model increases pressure valve and fluctuation detector. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the utility model will be clearly and completely described in combination with the drawings in the embodiments of the utility model.

[0026] Referring to Figures 1-2 The double-pump hydraulic system of the embodiment comprises a servo motor 310, a variable pump 322, a hydraulic pump 321, a first oil return pipe 110 and a second oil return pipe 120. The servo motor 310 drives the variable pump 322 and the hydraulic pump 321 to operate through a driving shaft 330. The oil inlets of the variable pump 322 and the hydraulic pump 321 are communicated with hydraulic oil in an oil tank 340. The oil outlet of the hydraulic pump 321 is communicated with a normal-pressure pipeline 180, so that the hydraulic oil is delivered to the normal-pressure pipeline 180 for some low-pressure and control oil circuits. The first oil return pipe 110 and the second oil return pipe 120 are respectively provided with a first stop valve 211 and a second stop valve 212 in series. The first stop valve 211 and the second stop valve 212 are respectively used for controlling the opening and closing of the first oil return pipe 110 and the second oil return pipe 120. The servo motor 310 is controlled to operate by an industrial computer.

[0027] The oil outlet of the variable pump 322 is communicated with a first pipeline 131. The first pipeline 131 is communicated with a rodless cavity of a first oil cylinder 640 through a fifth pipeline 135, communicated with a first hydraulic control pipe 161 and a first liquid supply pipe 162 as well as a second hydraulic control pipe 171 and a second liquid supply pipe 172 through a second pipeline 132, and communicated with the second oil return pipe 120. The first pipeline 131 is communicated with an oil inlet of a pressure relief valve 410. An oil outlet of the pressure relief valve 410 is communicated with the first oil return pipe 110.

[0028] The first pipeline 131 is also communicated with a P port of a four-way valve 420 and a first branch pipe 141. The first branch pipe 141 is communicated with a second branch pipe 142 and an oil outlet of a first one-way joint MA respectively. The second branch pipe 142 is communicated with a third branch pipe 143. The third branch pipe 143 is communicated with an oil inlet of a hydraulic pressure sensor 510. The hydraulic pressure sensor 510 is used for detecting the hydraulic pressure in the third branch pipe 143 and then inputting the industrial computer.

[0029] The third branch pipe 143 is communicated with an A port of the four-way valve 420. The A port of the four-way valve 420 is communicated with a T port and the P port is communicated with a B port. The B port of the four-way valve 420 is communicated with a first oil pipe 151 through a fourth branch pipe 144. The fourth branch pipe 144 is communicated with the T port of the four-way valve 420 through a fifth branch pipe 145. The first oil pipe 151 is communicated with an oil outlet of a second one-way joint MB. The second one-way joint MB is communicated with an oil inlet of a hydraulic gauge 520. The hydraulic gauge 520 is used for observing the oil pressure in the first oil pipe 151.

[0030] The first oil pipe 151 is in series with the first throttle hole 611 and the second throttle hole 612 in sequence, and the first oil pipe 151 is communicated with the P port of the electromagnetic reversing valve 440, the T port of the electromagnetic reversing valve 440 is communicated with the first return oil pipe 110 through the third oil pipe 153, the electromagnetic reversing valve 440 is further provided with the A port and the B port respectively, the electromagnetic reversing valve 440 is used for controlling the P port to transport hydraulic oil to the A port, the B port and the T port alternatively, and the A port and the B port are communicated with two oil ports of an executing element (such as the rod cavity and the rodless cavity of an oil cylinder) respectively. By switching the P port to be communicated with the A port and the B port alternatively, the flow direction of the hydraulic oil transported outward by the A port and the B port can be realized.

[0031] The part of the first oil pipe 151 between the first throttle hole 611 and the second throttle hole 612 is communicated with the second oil outlet of the second hydraulic control reversing valve 460 through the second oil pipe 152; the hydraulic control oil port of the second hydraulic control reversing valve 460 is communicated with the second hydraulic control pipe 171, the first oil inlet is communicated with the second oil supply pipe 172, the first oil outlet is communicated with the fourth pipeline 134, and the second oil inlet is communicated with the second connecting pipe 164, and the fourth pipeline 134 is communicated with the second return oil pipe 120.

[0032] The second connecting pipe 164 is communicated with the first oil outlet of the first hydraulic control reversing valve 450 and the third connecting pipe 165 respectively, the first oil inlet of the first hydraulic control reversing valve 450 is communicated with the second oil supply pipe 162, the second oil inlet is communicated with the third pipeline 133, the hydraulic control oil port is communicated with the first hydraulic control pipe 161, and the second oil outlet is communicated with the fourth pipeline 134 through the first connecting pipe 163; the third pipeline 133 is communicated with the fourth pipeline 134 through the fourth connecting pipe 166, the fourth connecting pipe 166 is in series with the third throttle hole 621 and the fourth throttle hole 622 in sequence, the part of the fourth connecting pipe 166 between the third throttle hole 621 and the fourth throttle hole 622 is communicated with the third connecting pipe 165, and the third pipeline 133 is further communicated with the rodless cavity of the second oil cylinder 630.

[0033] As a preferred scheme, the variable pump 322 can be associated with the in-pump servo variable mechanism in the first oil cylinder 640 and the second oil cylinder 630, so that the operation of the feedback control servo motor 310 is realized through the first oil cylinder 640 and the second oil cylinder 630 to realize the on-demand delivery of hydraulic oil and the on-demand delivery of hydraulic oil with sufficient pressure. Of course, in the design, the hydraulic servo mechanism can be replaced by an electric executing unit, and the fast and non-overshoot adjustment of the swash plate inclination angle is realized through the DSP controller, which is suitable for high-precision hydraulic systems. Of course, these are prior art, and existing products can be directly used in actual implementation. In actual implementation, this scheme can be selected as needed, and this scheme is not necessary.

[0034] Referring to Figure 3In order to detect the hydraulic fluctuation of the system, prevent the leakage of one side of the hydraulic pressure sensor from being found in time or the damage of the hydraulic pressure sensor from being found in time, the pressure valve and the fluctuation detector are additionally arranged in the embodiment, and the hydraulic pressure in the third branch pipe 143 is used to open the pressure valve and then input the fluctuation detector and the hydraulic pressure sensor 510.

[0035] The pressure valve comprises a valve body 710, a valve cavity 711 arranged in the valve body 710, and a first outlet 722 and a second outlet 723 arranged on the valve body respectively, wherein the third branch pipe 143 is communicated with the valve cavity 711, and the first outlet 722 and the second outlet 723 are communicated with the valve cavity 711; a valve core 720 is sealingly and slidably arranged in the valve cavity 711, and the valve core 720 and the inner wall of the valve cavity 711 away from the first outlet 722 are respectively pressed or assembled with two ends of a valve core spring 730, and the valve core spring 730 applies an elastic force to the valve core to push the valve core to the first outlet 722. When the hydraulic oil is input into the third branch pipe 143, the hydraulic oil enters the valve cavity, and under the action of the oil pressure, the valve core is pushed to move downward to make the first outlet 722 and the second outlet 723 communicated with the valve core, at this time, the third branch pipe is communicated with the first outlet 722 and the second outlet 723. In the initial state, the valve core seals and divides the first outlet 722 and the second outlet 723 from the valve cavity.

[0036] The fluctuation detector comprises a detection shell 810, a piston 820, and a potentiometer 530, wherein the detection shell 810 is provided with a piston cavity 811, the piston 820 is clamped and slidably arranged in the piston cavity 811, the piston 820 is assembled with one end of a piston rod 830, the other end of the piston rod 830 is sleeved with a piston spring 840, and then the piston rod 830 penetrates through the detection shell 810 and is assembled with a connecting plate 850, the connecting plate 850 is assembled with an extension shaft 531 of the potentiometer 530, the piston rod can drive the extension shaft 531 to move when the piston rod moves, so that the hydraulic fluctuation is detected by the potentiometer 530, and the data detected by the hydraulic pressure sensor is compared to determine whether the potentiometer 530 and the hydraulic pressure sensor are faulty. One side of the piston cavity 811 where the piston 820 is arranged is communicated with the second outlet 723, and the other side is communicated with the accumulator 900 through a first energy storage pipe 910, and the first energy storage pipe 910 is communicated with the valve cavity 711 away from one end of the third branch pipe 143 through a second energy storage pipe 920, so that the accumulator provides hydraulic damping for the movement of the piston and the valve core.

[0037] The use process of the embodiment is as follows:

[0038] S100, the servo motor 310 is started, and the hydraulic pump 321 and the variable pump 322 are driven to pump the hydraulic oil in the oil tank to the normal pressure pipeline 180 and the first pipeline 131 respectively. The pressure data detected by the hydraulic pressure sensor is transmitted to the industrial computer. The industrial computer controls the running state of the servo motor 310 according to the preset program to ensure that the hydraulic oil in the system has sufficient pressure but is in an energy-saving state.

[0039] S200, the hydraulic oil enters the P port of the four-way valve 420 through the first pipeline 131, then enters the B port of the four-way valve, and then enters the first oil pipe 151 and the fifth branch pipe 145 through the fourth branch pipe 144. The hydraulic oil entering the fifth branch pipe 145 enters the T port of the four-way valve and then inputs the hydraulic oil in the third branch pipe 143 and the second branch pipe 142, so as to facilitate the detection of the hydraulic pressure by the hydraulic pressure sensor and the input of the industrial computer. The design of the four-way valve 420 is mainly to facilitate the control of the flow direction of the hydraulic oil and the detection of the pressure of the hydraulic oil in the system.

[0040] S300, the hydraulic oil entering the first oil pipe 151 passes through the first throttle valve 611 and then part of it passes through the second throttle valve 612 and inputs the P port of the electromagnetic reversing valve 440. The electromagnetic reversing valve 440 can control the P port to be connected to the A port, the B port or the T port.

[0041] S400, part of the hydraulic oil output by the variable pump enters the second pipeline 132, and when the pressure is small, such as between 2.5 Mpa and 18 Mpa, the second hydraulic control reversing valve 460 is opened, so that the second liquid supply pipe 172 is connected with the second connecting pipe 164 and the second oil pipe 152, thereby inputting part of the hydraulic oil from the second oil pipe 152 into the first oil pipe 151, then passing through the second throttle valve 612 and then inputting the P port of the electromagnetic reversing valve to fine-tune the flow rate or flow of the hydraulic oil input to the P port. The hydraulic oil entering the second connecting pipe 164 passes through the third connecting pipe 163 and inputs the fourth connecting pipe 166, thereby entering the second oil cylinder 630 or the second oil return pipe 120 through the fourth connecting pipe 166.

[0042] When the hydraulic pressure in the second pipeline 132 increases to open the first hydraulic control reversing valve, the hydraulic pressure in the second pipeline 132 continues to open the second hydraulic control reversing valve 450, so that the first liquid supply pipe 162 inputs the hydraulic oil into the third pipeline 133, part of the hydraulic oil enters the second oil cylinder, part of the hydraulic oil enters the fourth connecting pipe 166, part of the hydraulic oil enters the second oil return pipe 120, part of the hydraulic oil enters the third connecting pipe 165 and then inputs the second oil pipe 152 and finally enters the electromagnetic reversing valve. The design of the first hydraulic control reversing valve and the second hydraulic control reversing valve is mainly to adjust the output hydraulic pressure of the electromagnetic reversing valve by using the system pressure, thereby realizing the adjustment of the output hydraulic pressure, and also driving the second hydraulic cylinder 630 to run and feedback controlling the servo motor to run. The first oil cylinder 640 and the second oil cylinder 630 can have a linkage relationship, thereby facilitating the control of the running state of the servo motor.

[0043] S500, once the variable pump output oil pressure is too large, part of the overflow valve 410 will open into the first return pipe 110, part of the overflow will directly into the second return pipe 120, and finally into the oil tank.

[0044] S600, the hydraulic oil in the third branch pipe 143 has a certain oil pressure to open the valve core to make the hydraulic oil enter the hydraulic pressure sensor and the piston cavity respectively. The signal detected by the hydraulic pressure sensor is input to the industrial computer to control the operation of the servo motor. If the hydraulic pressure in the piston cavity overcomes the accumulator hydraulic pressure, the piston will move, thereby detecting the hydraulic pressure fluctuation by the potentiometer and inputting the industrial computer.

[0045] S700, the industrial computer judges the system pressure fluctuation and whether there is a leak through the signal of the potentiometer and the signal of the hydraulic pressure sensor, so as to facilitate subsequent maintenance.

[0046] The embodiment realizes precise control of pressure and flow by hydraulic pressure sensor (set pressure), servo motor automatically controlling the speed of servo motor (controlling the flow of pump) to realize precise control of pressure and flow; the servo motor control is fast and accurate (it can start and stop as required) and can well control the speed; and it can well control the low oil temperature and save oil (low oil: long service life).

[0047] It should be noted that, unless otherwise specified, the technical terms or scientific terms used in the present application should be the usual meaning understood by the skilled person in the field to which the present application belongs.

[0048] The above is only the preferred specific implementation of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of changes or replacements within the technical range disclosed in the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A double pump hydraulic system for a crown block, characterized by: The hydraulic system comprises a servo motor, a variable pump, a hydraulic pump, a first oil return pipe and a second oil return pipe, the servo motor drives the variable pump and the hydraulic pump to operate through a driving shaft, and the oil inlets of the variable pump and the hydraulic pump are communicated with the hydraulic oil in an oil tank; the oil outlet of the hydraulic pump is communicated with a normal pressure pipeline; The oil outlet of the variable pump is communicated with a first pipeline, the first pipeline is communicated with a first liquid control pipe and a first liquid supply pipe, a second liquid control pipe and a second liquid supply pipe through a second pipeline, and the first pipeline is communicated with the second oil return pipe; The first pipeline is further communicated with a P port of a four-way valve and a first branch pipe, the first branch pipe is communicated with a second branch pipe and an oil outlet of a first one-way joint MA, the second branch pipe is communicated with a third branch pipe, the third branch pipe is communicated with an oil inlet of a hydraulic pressure sensor, and the hydraulic pressure sensor is used for detecting the hydraulic pressure in the third branch pipe and then inputting an industrial computer; The third branch pipe is communicated with an A port of the four-way valve, the A port of the four-way valve is communicated with a T port, the P port is communicated with a B port, the B port of the four-way valve is communicated with a first oil pipe through a fourth branch pipe, and the fourth branch pipe is communicated with the T port of the four-way valve through a fifth branch pipe; The first oil pipe is directly or indirectly communicated with a P port of an electromagnetic reversing valve through the first oil pipe, a T port of the electromagnetic reversing valve is communicated with the first oil return pipe through a third oil pipe, the electromagnetic reversing valve is further provided with an A port and a B port, and the electromagnetic reversing valve is used for controlling the P port to deliver hydraulic oil to the A port, the B port and the T port alternatively, and the A port and the B port are communicated with two oil ports of an executing element.

2. The dual pump hydraulic system of claim 1, wherein: The first oil pipe is sequentially connected with a first throttle hole and a second throttle hole, and the first oil pipe is communicated with the P port of the electromagnetic reversing valve.

3. The dual pump hydraulic system of claim 2, wherein: The part of the first oil pipe between the first throttle hole and the second throttle hole is communicated with a second oil outlet of a second liquid control reversing valve through a second oil pipe, a liquid control oil port of the second liquid control reversing valve is communicated with a second liquid control pipe, a first oil inlet is communicated with a second liquid supply pipe, a first oil outlet is communicated with a fourth pipeline, and a second oil inlet is communicated with a second connecting pipe, and the fourth pipeline is communicated with the second oil return pipe; The second connecting pipe is communicated with a first oil outlet of a first liquid control reversing valve and a third connecting pipe, a first oil inlet of the first liquid control reversing valve is communicated with a second liquid supply pipe, a second oil inlet is communicated with a third pipeline, a liquid control oil port is communicated with a first liquid control pipe, a second oil outlet is communicated with the fourth pipeline through a first connecting pipe, the third pipeline is communicated with the fourth pipeline through a fourth connecting pipe, the fourth connecting pipe is sequentially connected with a third throttle hole and a fourth throttle hole, the part of the fourth connecting pipe between the third throttle hole and the fourth throttle hole is communicated with the third connecting pipe, and the third connecting pipe is further communicated with a rodless cavity of a second oil cylinder.

4. The dual pump hydraulic system of claim 1, wherein: First and second stop valves are connected in series on the first and second oil return pipes respectively, and the first and second stop valves are used for controlling the opening and closing of the first and second oil return pipes respectively.

5. The dual pump hydraulic system of claim 1, wherein: The first pipeline is communicated with a rodless cavity of a first oil cylinder through a fifth pipeline, the first pipeline is communicated with an oil inlet of a pressure relief valve, and an oil outlet of the pressure relief valve is communicated with the first oil return pipe.

6. The dual pump hydraulic system of any of claims 1-5, characterized by: The first oil pipe is communicated with an oil outlet of a second one-way joint MB, the second one-way joint MB is communicated with an oil inlet of a hydraulic gauge, and the hydraulic gauge is used for observing the oil pressure in the first oil pipe.

7. The dual pump hydraulic system of any of claims 1-5, characterized by: Further comprising a pressure valve, a fluctuation detector, and a hydraulic pressure sensor, the pressure valve is opened by the hydraulic pressure in the third branch pipe and then inputs the fluctuation detector; The pressure valve comprises a valve body, a valve cavity is arranged in the valve body, a first outlet and a second outlet are further arranged on the valve body, the third branch pipe is communicated with the valve cavity, and the first outlet and the second outlet are communicated with the valve cavity; a valve core is sealingly and slidably arranged in the valve cavity, and the valve core and the inner wall of the valve cavity away from the first outlet are respectively pressed or assembled with two ends of a valve spring.

8. The dual pump hydraulic system of claim 7, wherein: The fluctuation detector comprises a detection shell, a piston, and a potentiometer, a piston cavity is arranged in the detection shell, the piston is clamped and slidably arranged in the piston cavity, one end of the piston is assembled with a piston rod, the other end of the piston rod is sleeved with a piston spring, then penetrates out of the detection shell and is assembled with a connecting plate, and the connecting plate is assembled with an extension shaft of the potentiometer; one side of the piston cavity away from the piston is communicated with the second outlet, and the other side is communicated with an energy accumulator through a first energy storage pipe, and the first energy storage pipe is communicated with the valve cavity away from one end of the third branch pipe through a second energy storage pipe.

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