A hydraulic control system for self-loading and unloading of push plates

Abstract

This invention discloses a hydraulic control system for push-plate self-loading and unloading in the field of horizontal self-unloading transport vehicles and fixed equipment. The system includes a hydraulic oil tank, a dual pump, a valve assembly, and a push-plate cylinder. The valve assembly integrates a directional valve, a filling valve, a back pressure valve, two safety valves, and four solenoid valves. Externally, the valve assembly has working ports A1 and B1, inlet ports P1 and P2, and return ports T1 and T2. The inlet of the dual pump is connected to the hydraulic oil tank, and the front and rear pump outlets of the dual pump are connected to the valve assembly's inlet ports P1 and P2, respectively. The working ports A1 and B1 of the valve assembly are connected to the rodless and rod-side chambers of the push-plate cylinder, respectively. The return ports T1 and T2 of the valve assembly are both connected to the inlet of a return filter, and the outlet of the return filter is connected to the hydraulic oil tank. The valve assembly has multiple internal channels connecting the valve bodies and the valve assembly ports. This invention can conveniently, safely, and reliably achieve the various requirements of pushing and pulling the push plate.

Description

Technical Field

[0001] This invention belongs to the field of horizontal self-unloading transport vehicles and fixed equipment, and particularly relates to a hydraulic control system for push-plate type horizontal self-unloading vehicles and fixed equipment. Background Technology

[0002] In the prior art, horizontal self-unloading transport vehicles or fixed equipment include push-plate type, which works by a hydraulic system controlling a double-acting multi-stage hydraulic cylinder. The hydraulic cylinder pushes the structural components, thereby moving the structural components and unloading the materials loaded inside the vehicle or fixed equipment box.

[0003] The structural principle of the push plate self-unloading mechanism is as follows: Figure 1 As shown, it includes a box assembly, a push plate cylinder, a push plate, and a rear door. The push plate can move horizontally inside the box. The push plate cylinder is installed between the box and the push plate. When the push plate cylinder extends, the push plate moves backward, thereby pushing the material inside the box and even pushing it out of the box to achieve unloading. After unloading is completed, the push plate cylinder extends, and the push plate moves to its final position. At this point, simply retracting the push plate cylinder will pull the push plate back to its foremost position for the next loading. Therefore, the horizontal self-unloading action is controlled solely by the cylinder; good control of the cylinder's extension and retraction allows for good control of the push plate system.

[0004] like Figure 1 Furthermore, since the space where the hydraulic cylinder is installed at the front of the housing is an ineffective space, the smaller this space is, the larger the loading space of the housing will be, and the higher the space utilization rate will be, provided that the housing volume remains unchanged. Therefore, if we want to minimize the installation space of the hydraulic cylinder, the hydraulic cylinder must be designed as a double-acting multi-stage cylinder.

[0005] like Figure 1 As shown, the area difference between the rod-side and rodless chambers of a double-acting multistage hydraulic cylinder is very large, typically reaching 1:10 to 1:15. Such a large area difference results in significant flow rate and pressure differences. The flow rate formulas for the rodless and rod-side chambers of the hydraulic cylinder are as follows:

[0006] Q=V*S

[0007] Q – Flow rate at the oil inlet;

[0008] V—the speed of movement of the hydraulic cylinder piston rod;

[0009] S – Working area of ​​the hydraulic cylinder.

[0010] As can be seen from the above formula, the flow rate of the hydraulic cylinder's working port is directly proportional to its effective working area. Because the area difference between the rod chamber and the rodless chamber of a multi-stage hydraulic cylinder is very large, the flow rate difference between the rod chamber and the rodless chamber ports will be very large under a certain working condition (when the hydraulic cylinder extends or retracts).

[0011] In this situation, when the cylinder extends, oil enters the rodless chamber and returns oil to the rod chamber. At this time, the movement speed of the cylinder will be determined by the amount of oil entering the rodless chamber. Due to the aforementioned area difference, the flow rate of the rod chamber will not be very large. This is the normal operating condition.

[0012] However, when the hydraulic cylinder retracts, it is not in a working state but is unloaded. Therefore, to improve working efficiency, the retraction time needs to be shortened as much as possible. Shortening the retraction time means increasing the flow rate in the rod chamber of the hydraulic cylinder. Due to the significant area difference between the rod chamber and the rodless chamber in the multi-stage hydraulic cylinder mentioned above, increasing the flow rate in the rod chamber will greatly increase the flow rate in the rodless chamber. Preliminary calculations show that if the retraction time is controlled within 20 seconds, the flow rate in the rodless chamber will reach 500 L / min. This requires a significant increase in the flow rate in the rodless chamber. When the cylinder retracts, the valve assembly has a large flow diameter. Furthermore, according to the force balance condition, the pressure in the rod-side and rodless-side chambers of the cylinder is inversely proportional to their working area. Therefore, if the main valve's flow diameter is not large enough, the large flow rate generated in the rodless-side chamber during cylinder retraction will cause significant throttling through the main valve, resulting in very high back pressure. Due to the large area difference between the rodless and rod-side chambers, this significant back pressure will translate into even higher pressure in the rod-side chamber, with a pressure difference of tens of times. Such high rod-side chamber pressure can damage the cylinder. Therefore, it is necessary to keep the pressure in the rodless-side chamber as low as possible during cylinder retraction. The current main method is to make the main valve controlling the cylinder have a very large flow diameter. However, the problem is that large-diameter valves are very expensive, and such a large flow diameter is completely unnecessary for cylinder extension operations. Therefore, simply increasing the valve's flow diameter is very uneconomical. Summary of the Invention

[0013] The purpose of this invention is to provide a hydraulic control system for self-loading and unloading pushers, which can meet the various action requirements of the pushers of self-unloading vehicles or fixed equipment to extend outward and retract inward, and can conveniently, safely and reliably realize the various requirements of pushing and pulling the pushers.

[0014] The objective of this invention is achieved as follows: A hydraulic control system for self-loading and unloading push plate includes a hydraulic oil tank, a dual pump, a valve group, and a push plate cylinder. The valve group integrates a directional valve, a filling valve, a back pressure valve, two safety valves, and four solenoid valves. Externally, the valve group has working ports A1 and B1, inlet ports P1 and P2, and return ports T1 and T2. The inlet of the dual pump is connected to the hydraulic oil tank. The front and rear pump outlets of the dual pump are connected to the inlet ports P1 and P2 of the valve group, respectively. The working ports A1 and B1 of the valve group are connected to the rodless and rod-side chambers of the push plate cylinder, respectively. The return ports T1 and T2 of the valve group are both connected to the inlet of a return oil filter, and the outlet of the return oil filter is connected to the hydraulic oil tank. The valve group has multiple internal channels connecting the valve bodies and the valve group ports.

[0015] The push plate cylinder of this invention is a double-acting cylinder, having a rod chamber and a rodless chamber. A dual pump pumps oil from the hydraulic oil tank into the inlet ports P1 and P2 of the valve assembly. The working ports A1 and B1 of the valve assembly are respectively connected to the rodless chamber and the rod chamber of the push plate cylinder. Oil in the valve assembly returns to the hydraulic oil tank through return ports T1 and T2. The filling valve opens only when pilot hydraulic oil enters the hydraulic control port S of the filling valve, allowing oil to flow from port P to port T. When no hydraulic oil enters the hydraulic control port S of the filling valve, the filling valve closes. When the low-pressure hydraulic oil in the rod chamber of the push plate cylinder enters the P port of the back pressure valve, the back pressure valve acts as a buffer and damper. Only when the low-pressure hydraulic oil in the rod chamber of the push plate cylinder exceeds the pressure limit of the back pressure valve can it come out from the T port of the back pressure valve. When high-pressure oil enters from the T port of the back pressure valve, the hydraulic oil passes through the main circuit and the one-way valve branch of the back pressure valve and comes out directly from the P port of the back pressure valve.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This hydraulic control system does not require a large main valve diameter for controlling the push plate cylinder, only needing to meet the flow requirements when the piston rod of the push plate cylinder extends. When the piston rod of the push plate cylinder retracts, the flow in the rodless chamber of the push plate cylinder allows it to flow back to the hydraulic oil tank through the bypass (filling valve), and the diameter of the bypass (filling valve) is set to be relatively large. In this way, even if the flow rate is large during return oil, a very small back pressure can still be generated. At the same time, this hydraulic control system is equipped with a dual pump. The front pump is a large displacement pump, which only needs to meet the flow requirements when the piston rod of the push plate cylinder extends, and the rear pump is a small displacement pump, which only needs to meet the flow requirements when the piston rod of the push plate cylinder retracts.

[0017] As a further improvement of the present invention, the directional valve is provided with oil ports A, B, C, D, P and T respectively; the first solenoid valve, the second solenoid valve and the fourth solenoid valve are all two-position four-way solenoid valves, and each of the first solenoid valve, the second solenoid valve and the fourth solenoid valve is provided with oil ports A, B, P and T; the third solenoid valve is a two-position three-way solenoid valve, and the third solenoid valve is provided with oil ports A, B and P.

[0018] As a further improvement of the present invention, the P port of the reversing valve is connected to the inlet port P1 of the valve group via an inner channel one, the A port of the reversing valve is connected to the working port A1 of the valve group via an inner channel two, the B port of the first solenoid valve is connected to the hydraulic control port S of the filling valve via an inner channel, the P port of the filling valve is connected to the side of the inner channel two, the T port of the filling valve is connected to the return port T2 of the valve group via an inner channel, the A port of the first solenoid valve is blocked by a plug, and the P port of the first solenoid valve... The first solenoid valve's T port is connected to the fourth solenoid valve's A port via inner channel three. The back pressure valve's T port is connected to the side of inner channel three. The back pressure valve's P port is connected to the valve group's working port B1 via inner channel four. The first solenoid valve's T port is connected to the valve group's return port T1 via inner channel four. Inner channel five is connected to the side of inner channel four. The directional control valve's T port is connected to the side of inner channel five via inner channel six. The directional control valve's B port is connected to the side of inner channel three via inner channel six. The C and D ports of the directional valve are connected to the B and A ports of the second solenoid valve, respectively. The P and T ports of the second solenoid valve are connected to the sides of inner channel one and inner channel six via an inner channel, respectively. The B port of the fourth solenoid valve is blocked by a plug. The T port of the fourth solenoid valve is connected to the side of inner channel five via an inner channel. The P port of the fourth solenoid valve is connected to the B port of the third solenoid valve via an inner channel. The A port of the third solenoid valve is connected to the side of inner channel one via a first check valve. The P port of the third solenoid valve is connected to the inlet P2 of the valve group via inner channel seven. An inner channel eight is provided between the sides of inner channel seven and inner channel five. A second safety valve is provided on inner channel eight. An inner channel nine is provided between the sides of inner channel five and inner channel one. A first safety valve is provided on inner channel nine. A second check valve is provided on inner channel one. The second check valve is located between the connection point of inner channel nine and inner channel one and the connection point of the first check valve and inner channel one.

[0019] As a further improvement of the present invention, when the piston rod of the push plate cylinder is in the initial state, none of the solenoid valves are energized. The first solenoid valve is in the right position, and its B port and T port are connected. The second solenoid valve is in the left position, and its P port and A port, as well as its B port and T port, are connected. The third solenoid valve is in the left position, and its P port and A port are connected. The fourth solenoid valve is in the right position, and its P port and T port are connected. The directional valve is in the initial neutral position, and its P port and T port, as well as its D port and C port, are connected.

[0020] As a further improvement of the present invention, when the piston rod of the push plate cylinder is in the extended state, the second solenoid valve is energized, while the first, third, and fourth solenoid valves are not energized. The second solenoid valve operates in the right position, with its P port and B port connected, and its A port and T port connected. Hydraulic oil enters the directional control valve from the B port of the second solenoid valve to the C port of the directional control valve, causing the directional control valve to switch directions. The C port and D port of the directional control valve are connected, as are the P port and A port, and the B port and T port.

[0021] As a further improvement of the present invention, when the piston rod of the push plate cylinder is in the retracted state, the first, third, and fourth solenoid valves are all energized, while the second solenoid valve is not energized; the first solenoid valve operates in the left position, with its P port and B port connected; the third solenoid valve operates in the right position, with its P port and B port connected; the fourth solenoid valve operates in the left position, with its P port and A port connected; hydraulic oil enters the directional control valve from the A port of the second solenoid valve to the D port of the directional control valve, which is in its initial neutral position, with its D port and C port connected, and its P port and T port connected; hydraulic oil enters the filling valve from the B port of the first solenoid valve to the hydraulic control port S of the filling valve, which opens, with its P port and T port connected.

[0022] As a further improvement of the present invention, the inlet of the first safety valve is connected to inner channel one, and the outlet of the first safety valve is connected to inner channel five; the inlet of the second safety valve is connected to inner channel seven, and the outlet of the second safety valve is connected to inner channel five; when hydraulic oil flows from the valve group inlet P1 to the P port of the directional valve, the second check valve is activated; when hydraulic oil flows from the A port of the third solenoid valve to inner channel one, the first check valve is activated. The first and second safety valves serve a protective function. When the pressure of the hydraulic oil pumped into the valve group inlets P1 and P2 by the dual pump exceeds the specified pressure of the corresponding safety valve, the corresponding first or second safety valve will open to provide pressure relief protection. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the self-unloading pusher plate structure of the present invention.

[0024] Figure 2 This is a schematic diagram of the hydraulic control system of the present invention.

[0025] Figure 3 This is a schematic diagram of the valve assembly.

[0026] Figure 4 This is a flow direction diagram of hydraulic oil in the hydraulic control system when the piston rod of the push plate cylinder of the present invention is in the initial state.

[0027] Figure 5This is a flow direction diagram of hydraulic oil in the hydraulic control system when the piston rod of the push plate cylinder of the present invention is in the extended state.

[0028] Figure 6 This is a diagram showing the flow direction of hydraulic oil in the hydraulic control system when the piston rod of the push plate cylinder of the present invention is in the retracted state.

[0029] The components include: 1. Material, 2. Box assembly, 3. Push plate, 4. Push plate cylinder, 5. Rear door, 6. Hydraulic oil tank, 7. Dual pump, 7a. Front pump, 7b. Rear pump, 8. Valve group, 9. First check valve, 10. First solenoid valve, 11. Second solenoid valve, 12. Third solenoid valve, 13. Fourth solenoid valve, 14. Filling valve, 15. Back pressure valve, 16. Reversing valve, 17. Second check valve, 18. First safety valve, 19. Second safety valve, 20. Return oil filter, 21. Inner channel one, 22. Inner channel two, 23. Inner channel three, 24. Inner channel four, 25. Inner channel five, 26. Inner channel six, 27. Inner channel seven, 28. Inner channel eight, 29. Inner channel nine. Implementation

[0030] like Figure 1 As shown, the push-plate self-unloading structure includes a box assembly 2, a push-plate cylinder 4, a push plate 3, a rear door 5, and material 1. The push plate 3 can move horizontally inside the box. The push-plate cylinder 4 is installed between the box and the push plate 3. When the push-plate cylinder 4 extends, the push plate 3 moves backward, thereby pushing the material 1 inside the box and even pushing it out of the box to achieve unloading. After unloading is completed, the push-plate cylinder 4 extends, and the push plate 3 moves to its final position. At this point, simply retracting the push-plate cylinder 4 pulls the push plate 3 back to its foremost position for the next loading.

[0031] like Figure 2-3 As shown, a hydraulic control system for a push plate self-loading and unloading device includes a hydraulic oil tank 6, a double pump 7, a valve group 8, and a push plate cylinder 4. The valve group 8 integrates a directional valve 16, a filling valve 14, a back pressure valve 15, two safety valves, and four solenoid valves. The valve group 8 is externally equipped with working ports A1 and B1, inlet ports P1 and P2, and return ports T1 and T2. The inlet of the double pump 7 is connected to the hydraulic oil tank 6. The outlet of the front pump 7a and the outlet of the rear pump 7b of the double pump 7 are connected to the inlet ports P1 and P2 of the valve group 8, respectively. The working ports A1 and B1 of the valve group 8 are connected to the rodless chamber and the rod chamber of the push plate cylinder 4, respectively. The return ports T1 and T2 of the valve group 8 are both connected to the inlet of the return oil filter 20, and the outlet of the return oil filter 20 is connected to the hydraulic oil tank 6. The valve group 8 has multiple internal channels connecting the valve bodies and the ports of the valve group 8.

[0032] The directional valve 16 is provided with oil ports A, B, C, D, P and T respectively. The first solenoid valve 10, the second solenoid valve 11 and the fourth solenoid valve 13 are all two-position four-way solenoid valves, and each of them is provided with oil ports A, B, P and T. The third solenoid valve 12 is a two-position three-way solenoid valve, and it is provided with oil ports A, B and P.

[0033] The P port of the reversing valve 16 is connected to the inlet P1 of the valve group 8 via inner channel 1 21. The A port of the reversing valve 16 is connected to the working port A1 of the valve group 8 via inner channel 2 22. The B port of the first solenoid valve 10 is connected to the hydraulic control port S of the filling valve 14 via an inner channel. The P port of the filling valve 14 is connected to the side of inner channel 2 22. The T port of the filling valve 14 is connected to the return port T2 of the valve group 8 via an inner channel. The A port of the first solenoid valve 10 is blocked by a plug. The P port of the first solenoid valve 10 is connected to the fourth solenoid valve via inner channel 3 23. The A port of valve 13 is connected; the T port of back pressure valve 15 is connected to the side of inner channel 3 23; the P port of back pressure valve 15 is connected to the working port B1 of valve group 8 via the inner channel; the T port of first solenoid valve 10 is connected to the return port T1 of valve group 8 via inner channel 4 24; inner channel 5 25 is connected to the side of inner channel 4 24; the T port of directional valve 16 is connected to the side of inner channel 5 25 via inner channel 6 26; the B port of directional valve 16 is connected to the side of inner channel 3 23 via the inner channel; the C port and D port of directional valve 16... The ports are respectively connected to the B port and A port of the second solenoid valve 11. The P port and T port of the second solenoid valve 11 are respectively connected to the sides of the inner channel 1 21 and the inner channel 6 26 via an inner channel. The B port of the fourth solenoid valve 13 is blocked by a plug. The T port of the fourth solenoid valve 13 is connected to the side of the inner channel 5 25 via an inner channel. The P port of the fourth solenoid valve 13 is connected to the B port of the third solenoid valve 12 via an inner channel. The A port of the third solenoid valve 12 is connected to the side of the inner channel 1 21 via the first check valve 9. The P port of valve 12 is connected to the inlet P2 of valve group 8 via inner channel 7 27. Inner channel 8 28 is provided between inner channel 7 27 and the side of inner channel 5 25. A second safety valve 19 is provided on inner channel 8 28. Inner channel 9 29 is provided between inner channel 5 25 and the side of inner channel 1 21. A first safety valve 18 is provided on inner channel 9 29. A second check valve 17 is provided on inner channel 1 21. The second check valve 17 is located between the connection point of inner channel 9 29 and inner channel 1 21 and the connection point of the first check valve 9 and inner channel 1 21.

[0034] The inlet of the first safety valve 18 is connected to inner channel 21, and the outlet of the first safety valve 18 is connected to inner channel 25. The inlet of the second safety valve 19 is connected to inner channel 27, and the outlet of the second safety valve 19 is connected to inner channel 25. When hydraulic oil flows from the inlet P1 of valve group 8 to the P port of directional valve 16, the second check valve 17 is activated. When hydraulic oil flows from the A port of the third solenoid valve 12 to inner channel 21, the first check valve 9 is activated. The first safety valve 18 and the second safety valve 19 provide protection. When the pressure of the hydraulic oil pumped into the inlets P1 and P2 of valve group 8 by the dual pump 7 exceeds the specified pressure of the corresponding safety valve, the corresponding first safety valve 18 or second safety valve 19 will open to provide pressure relief protection.

[0035] like Figure 4 , Figure 4 The thick solid line represents the high-pressure oil circuit. The thick solid line high-pressure oil circuit includes two thicknesses: the thicker high-pressure oil circuit is the main circuit, and the thinner high-pressure oil circuit is the branch circuit. The dashed line represents the low-pressure oil circuit. The dashed line low-pressure oil circuit includes thick dashed lines and thin dashed lines.

[0036] When the piston rod of the push plate cylinder 4 is in the initial state, none of the solenoid valves are energized. The first solenoid valve 10 is in the right position, with its B port and T port connected. The second solenoid valve 11 is in the left position, with its P port and A port connected, and its B port and T port connected. The third solenoid valve 12 is in the left position, with its P port and A port connected. The fourth solenoid valve 13 is in the right position, with its P port and T port connected. The directional valve 16 is in the initial neutral position, with its P port and T port connected, and its D port and C port connected.

[0037] When the push plate cylinder 4 does not need to move, all the solenoid valves are not energized. Therefore, the hydraulic oil output from the front pump 7a and the rear pump 7b of the dual pump 7 will converge into the reversing valve 16. The reversing valve 16 is in the initial neutral position. Therefore, the hydraulic oil passing through the reversing valve 16 returns to the oil tank through the return oil filter 20.

[0038] like Figure 5 , Figure 5 The thick solid line represents the high-pressure oil circuit. The thick solid line high-pressure oil circuit includes two thicknesses: the thicker high-pressure oil circuit is the main circuit, and the thinner high-pressure oil circuit is the branch circuit. The dashed line represents the low-pressure oil circuit. The dashed line low-pressure oil circuit includes thick dashed lines and thin dashed lines.

[0039] When the piston rod of the push plate cylinder 4 is in the extended state, the second solenoid valve 11 is energized, while the first solenoid valve 10, the third solenoid valve 12, and the fourth solenoid valve 13 are not energized. The second solenoid valve 11 is in the right position, with its P port and B port connected, and its A port and T port connected. Hydraulic oil enters the directional valve 16 from the B port of the second solenoid valve 11 to the C port of the directional valve 16. The directional valve 16 reverses direction, and its C port and D port become connected. Its P port and A port become connected, and its B port and T port become connected.

[0040] When the push plate cylinder 4 needs to extend, only the second solenoid valve 11 needs to be energized. The second solenoid valve 11 then reverses, controlling the pilot hydraulic oil to reverse, which in turn pushes the reversing valve 16 to reverse. In this way, the hydraulic oil output from the front pump 7a and the rear pump 7b of the dual pump 7 will also converge into the reversing valve 16 and enter the rodless chamber of the push plate cylinder 4. The hydraulic oil in the rod chamber of the push plate cylinder 4 will enter the reversing valve 16 through the back pressure valve 15, and then return to the hydraulic oil tank 6 through the return oil filter 20. At this time, the function of the back pressure valve 15 is to generate a certain pressure in the rod chamber of the push plate cylinder 4, so that the piston rod of the cylinder extends more smoothly and reliably.

[0041] like Figure 6 , Figure 6 The thick solid line represents the high-pressure oil circuit. The thick solid line high-pressure oil circuit includes two thicknesses: the thicker high-pressure oil circuit is the main circuit, and the thinner high-pressure oil circuit is the branch circuit. The dashed line represents the low-pressure oil circuit. The dashed line low-pressure oil circuit includes thick dashed lines and thin dashed lines.

[0042] When the piston rod of the push plate cylinder 4 is in the retracted state, the first solenoid valve 10, the third solenoid valve 12, and the fourth solenoid valve 13 are all energized, while the second solenoid valve 11 is not energized. The first solenoid valve 10 is in the left position, and its P port and B port are connected. The third solenoid valve 12 is in the right position, and its P port and B port are connected. The fourth solenoid valve 13 is in the left position, and its P port and A port are connected. Hydraulic oil enters the directional valve 16 from the A port of the second solenoid valve 11 to the D port of the directional valve 16. The directional valve 16 is in the initial neutral position, and its D port and C port are connected. Its P port and T port are also connected. Hydraulic oil enters the hydraulic control port S of the filling valve 14 from the B port of the first solenoid valve 10. The filling valve 14 is open, and its P port and T port are connected.

[0043] When the push plate cylinder 4 needs to retract, the first solenoid valve 10, the third solenoid valve 12, and the fourth solenoid valve 13 must be energized simultaneously. At this time, the hydraulic oil output from the front pump 7a of the tandem pump 7 enters the reversing valve 16. Since the reversing valve 16 is in the neutral position, the hydraulic oil returns to the hydraulic oil tank 6 through the return oil filter 20. The hydraulic oil output from the rear pump 7b of the tandem pump 7 passes through the third solenoid valve 12 and then enters the fourth solenoid valve 13 before entering the rod chamber of the push plate cylinder 4. At the same time, since the first solenoid valve 10 is energized, the pilot hydraulic oil can enter the filling valve 14 through the first solenoid valve 10. The filling valve 14 opens, and the hydraulic oil in the rodless chamber of the push plate cylinder 4 will directly enter the filling valve 14 and return to the hydraulic oil tank 6 through the return oil filter 20.

[0044] The push plate cylinder 4 of this invention is a double-acting cylinder, having a rod chamber and a rodless chamber. A dual pump 7 pumps oil from the hydraulic oil tank 6 into the inlets P1 and P2 of the valve assembly 8. The working ports A1 and B1 of the valve assembly 8 are respectively connected to the rodless chamber and rod chamber of the push plate cylinder 4. Oil from the valve assembly 8 returns to the hydraulic oil tank 6 through return ports T1 and T2. The filling valve 14 opens only when pilot hydraulic oil enters the hydraulic control port S of the filling valve 14, allowing oil to flow from port P to port T. The filling valve 14 closes when no hydraulic oil enters the hydraulic control port S. When the low-pressure hydraulic oil in the rod chamber of the push plate cylinder 4 enters the P port of the back pressure valve 15, the back pressure valve 15 acts as a buffer and damping mechanism. Only when the low-pressure hydraulic oil in the rod chamber of the push plate cylinder 4 exceeds the pressure limit of the back pressure valve 15 can it exit from the T port of the back pressure valve 15. When high-pressure oil enters from the T port of the back pressure valve 15, the hydraulic oil passes through the main circuit and the one-way valve branch of the back pressure valve 15 and exits directly from the P port of the back pressure valve 15.

[0045] This hydraulic control system does not require a very large main valve diameter for controlling the push plate cylinder 4. It only needs to meet the flow requirements when the piston rod of the push plate cylinder 4 extends. When the piston rod of the push plate cylinder 4 retracts, the flow in the rodless chamber of the push plate cylinder 4 allows it to flow back to the hydraulic oil tank 6 through the bypass (filling valve 14). The bypass (filling valve 14) has a relatively large diameter, so even if the return flow is large, it can still generate very small back pressure. At the same time, this hydraulic control system is equipped with a dual pump 7. The front pump 7a is a large displacement pump, which only needs to meet the flow requirements when the piston rod of the push plate cylinder 4 extends, and the rear pump 7b is a small displacement pump, which only needs to meet the flow requirements when the piston rod of the push plate cylinder 4 retracts.

[0046] This invention is not limited to the above embodiments. Based on the technical solutions disclosed in this invention, those skilled in the art can make some substitutions and modifications to some of the technical features without creative effort, and all such substitutions and modifications are within the protection scope of this invention.

Claims

1. A hydraulic control system for self-loading and unloading pusher plates, characterized in that, The system includes a hydraulic oil tank, a tandem pump, a valve assembly, and a push plate cylinder. The valve assembly integrates a directional valve, a filling valve, a back pressure valve, two safety valves, and four solenoid valves. Externally, the valve assembly has working ports A1 and B1, inlet ports P1 and P2, and return ports T1 and T2. The inlet of the tandem pump is connected to the hydraulic oil tank. The front and rear pump outlets of the tandem pump are connected to the valve assembly's inlet ports P1 and P2, respectively. The working ports A1 and B1 of the valve assembly are connected to the rodless and rod-side chambers of the push plate cylinder, respectively. The return ports T1 and T2 of the valve assembly are both connected to the inlet of a return filter, and the outlet of the return filter is connected to the hydraulic oil tank. The valve assembly has multiple internal channels connecting the valve bodies and valve assembly ports. The directional valve has A, B, and C ports respectively. The four solenoid valves are designated as the first, second, third, and fourth solenoid valves, respectively, with ports A, B, P, and T. The first, second, and fourth solenoid valves are all two-position four-way solenoid valves, each with ports A, B, P, and T. The third solenoid valve is a two-position three-way solenoid valve, with ports A, B, and P. The P port of the directional control valve is connected to the valve group's inlet P1 via an inner channel one, and the A port of the directional control valve is connected to the valve group's working port A1 via an inner channel two. The B port of the first solenoid valve is connected to the hydraulic control port S of the filling valve via an inner channel, the P port of the filling valve is connected to the side of the inner channel two, and the T port of the filling valve is connected to the valve group's return port T via an inner channel.

2. The A port of the first solenoid valve is plugged by a plug. The P port of the first solenoid valve is connected to the A port of the fourth solenoid valve through inner channel three. The T port of the back pressure valve is connected to the side of inner channel three. The P port of the back pressure valve is connected to the working port B1 of the valve group through an inner channel. The T port of the first solenoid valve is connected to the return port T1 of the valve group through inner channel four. Inner channel five is connected to the side of inner channel four. The T port of the directional valve is connected to the side of inner channel five through inner channel six. The B port of the directional valve is connected to the side of inner channel three through an inner channel. The C and D ports of the directional valve are connected to the B and A ports of the second solenoid valve, respectively. The P and T ports of the second solenoid valve are connected to the sides of inner channel one and inner channel six, respectively, through an inner channel. The fourth solenoid valve's B port is plugged by a plug. The fourth solenoid valve's T port is connected to the side of the inner channel five via an inner channel. The fourth solenoid valve's P port is connected to the B port of the third solenoid valve via an inner channel. The third solenoid valve's A port is connected to the side of the inner channel one via a first check valve. The third solenoid valve's P port is connected to the valve group's inlet P2 via an inner channel seven. An inner channel eight is provided between the side of the inner channel seven and the inner channel five. A second safety valve is provided on the inner channel eight. An inner channel nine is provided between the side of the inner channel five and the inner channel one. A first safety valve is provided on the inner channel nine. A second check valve is provided on the inner channel one. The second check valve is located between the connection point of the inner channel nine and the inner channel one and the connection point of the first check valve and the inner channel one.

2. The hydraulic control system for self-loading and unloading of a pusher plate according to claim 1, characterized in that, When the piston rod of the push plate cylinder is in the initial state, none of the solenoid valves are energized. The first solenoid valve is in the right position, with its B and T ports connected. The second solenoid valve is in the left position, with its P and A ports connected, and its B and T ports connected. The third solenoid valve is in the left position, with its P and A ports connected. The fourth solenoid valve is in the right position, with its P and T ports connected. The directional valve is in the initial neutral position, with its P and T ports connected, and its D and C ports connected.

3. A hydraulic control system for self-loading and unloading pusher plates according to claim 1 or 2, characterized in that, When the piston rod of the push plate cylinder is in the extended state, the second solenoid valve is energized, while the first, third, and fourth solenoid valves are de-energized. The second solenoid valve operates in the right position, with its P port and B port connected, and its A port and T port connected. Hydraulic oil enters the directional control valve from the B port of the second solenoid valve to the C port of the directional control valve, causing the directional control valve to switch directions. The C port and D port of the directional control valve are connected, as are the P port and A port, and the B port and T port.

4. A hydraulic control system for self-loading and unloading of a pusher plate according to claim 1 or 2, characterized in that, When the piston rod of the push plate cylinder is in the retracted state, the first, third, and fourth solenoid valves are all energized, while the second solenoid valve is not energized. The first solenoid valve operates in the left position, with its P port and B port connected. The third solenoid valve operates in the right position, with its P port and B port connected. The fourth solenoid valve operates in the left position, with its P port and A port connected. Hydraulic oil enters the directional control valve's D port from the second solenoid valve's A port. The directional control valve is in its initial neutral position, with its D port and C port connected, and its P port and T port connected. Hydraulic oil enters the filling valve's hydraulic control port S from the first solenoid valve's B port. The filling valve opens, and its P port and T port are connected.

5. A hydraulic control system for self-loading and unloading of a pusher plate according to claim 1 or 2, characterized in that, The inlet of the first safety valve is connected to inner channel one, and the outlet of the first safety valve is connected to inner channel five; the inlet of the second safety valve is connected to inner channel seven, and the outlet of the second safety valve is connected to inner channel five; when hydraulic oil flows from the valve group inlet P1 to the directional valve P port, the second check valve is activated; when hydraulic oil flows from the third solenoid valve A port to inner channel one, the first check valve is activated.

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