A special hydraulic system for a foam plastic forming machine

Abstract

The application relates to a hydraulic system special for a foam plastic forming machine, belonging to the foam plastic mechanical field. The hydraulic system comprises an oil tank, a main oil cylinder, an auxiliary oil cylinder, a main oil cylinder control part and an auxiliary oil cylinder control part. The main oil cylinder control part comprises a main pump, a main oil inlet path, a main oil return path, a main control valve, an oil path 1 and an oil path 2. The main oil inlet path is connected between the oil tank and the main control valve. The main pump is arranged on the main oil inlet path. The main oil return path is connected between the main control valve and the oil tank. The oil path 1 is connected between a rodless cavity of the main oil cylinder and the main control valve. The oil path 2 is connected between a rod cavity of the main oil cylinder and the main control valve. The auxiliary oil cylinder control part comprises an auxiliary oil path and a liquid filling valve. The auxiliary oil path is connected between the oil tank and a rodless cavity of the auxiliary oil cylinder. The liquid filling valve is arranged on the auxiliary oil path. The hydraulic system has the advantages of low cost, high pressure, high speed and large flow.

Description

Technical Field

[0001] This application relates to the field of foam plastic machinery, and in particular to a hydraulic system specifically for foam molding machines. Background Technology

[0002] Foam molding machines are common types of machinery used to manufacture polystyrene foam boards. Most existing foam molding machines use hydraulic cylinder systems to control the mold movement, performing operations such as mold opening and closing. Currently, there are many foam molding machine manufacturers in China, but their hydraulic systems cannot meet the market's demands for high pressure and high speed. Summary of the Invention

[0003] To address the issue that existing hydraulic systems cannot meet the market's demand for high pressure and high speed, this application provides a dedicated hydraulic system for foam molding machines.

[0004] The hydraulic system for a foam molding machine provided in this application adopts the following technical solution:

[0005] A hydraulic system for a foam molding machine includes an oil tank, a main oil cylinder, an auxiliary oil cylinder, a main oil cylinder control section, and an auxiliary oil cylinder control section. The main oil cylinder control section includes a main pump, a main oil inlet circuit, a main oil return circuit, a main control valve, an oil circuit one, and an oil circuit two. The main oil inlet circuit connects the oil tank and the main control valve. The main pump is located on the main oil inlet circuit. The main oil return circuit connects the main control valve and the oil tank. Oil circuit one connects the rodless chamber of the main oil cylinder and the main control valve. Oil circuit two connects the rod chamber of the main oil cylinder and the main control valve. The auxiliary oil cylinder control section includes an auxiliary oil circuit and a filling valve. The auxiliary oil circuit connects the oil tank and the rodless chamber of the auxiliary oil cylinder. The filling valve is located on the auxiliary oil circuit.

[0006] By adopting the above technical solution, when the piston rod of the main cylinder is rapidly extended, the piston rod of the auxiliary cylinder is passively extended through a mechanical connection, opening the filling valve. Due to the vacuum, the rodless chamber of the auxiliary cylinder draws a large amount of oil from the oil tank. At this time, the auxiliary cylinder and the main cylinder extend together to perform the corresponding work. During retraction, the main cylinder retracts first, and through a mechanical connection, the auxiliary cylinder is passively retracted. At this time, the filling valve is opened, and the oil in the rodless chamber of the auxiliary cylinder flows back to the oil tank quickly through the auxiliary channel. This dedicated hydraulic system for foam molding machines requires only one main pump for the main cylinder, while the auxiliary cylinder does not require an oil pump, thus saving the cost of oil pumps. By configuring the filling valve, a hydraulic pump with a relatively small displacement can be selected for the main pump to meet the system's large flow requirements.

[0007] Optionally, it also includes a pressure relief circuit, wherein the oil circuit one and the rodless chamber of the auxiliary oil cylinder are both connected to one end of the pressure relief circuit, the other end of the pressure relief circuit is connected to the oil tank, and a pressure relief switch valve is provided on the pressure relief circuit.

[0008] By adopting the above technical solution, when depressurizing, the pressure relief switch valve is opened, and the oil in the rodless chamber of the main cylinder reaches the pressure relief circuit through the oil circuit and flows into the oil tank. At the same time, the oil in the rodless chamber of the auxiliary cylinder enters the pressure relief circuit and flows into the oil tank. After reaching the set pressure or time, the pressure relief switch valve is closed. The function of the pressure relief circuit is to release the oil in the rodless chamber before the main cylinder and auxiliary cylinder retract. After the piston rods of the main cylinder and auxiliary cylinder extend, the system maintains pressure. After the pressure maintenance is completed, each cylinder must be depressurized before returning to avoid the cylinder being unable to open or causing impact.

[0009] Optionally, a cartridge valve for controlling the speed of the main oil cylinder is provided on the main oil inlet line, and the cartridge valve is located on the outlet side of the main pump.

[0010] By adopting the above technical solution, in order to meet the user's high speed requirements and the system needs a large flow rate, this hydraulic system adopts a cartridge valve structure. Under the same large flow rate, the entire equipment structure is more compact than that of ordinary directional valves.

[0011] Optionally, the direction of the internal oil passage of the control cover of the cartridge valve is controlled by a three-way solenoid directional valve.

[0012] By adopting the above technical solution, when the cartridge valve needs to be opened, the pressurized oil is diverted through the three-way solenoid directional valve, and the oil in the F port of the cartridge valve spring chamber is depressurized through the Y port inside the cover plate, thus opening the cartridge valve. When the three-way solenoid directional valve is not working, the high-pressure oil enters the F port of the cartridge valve spring chamber through the X port, forming a closed chamber that presses down on the cartridge valve, which is the pressure-holding state of the entire system. This cartridge valve is an independently designed design with low internal resistance, suitable for high-flow-rate operation, and has the advantages of being safer, more reliable, and significantly improving the system pressure-holding effect.

[0013] Optionally, it also includes a pressure selection circuit, one end of which is connected to the main oil inlet circuit and the other end is connected to the oil tank. The connection point between the pressure selection circuit and the main oil inlet circuit is located on the outlet side of the main pump. The pressure selection circuit is equipped with a pressure control valve group that controls the pressure according to the load of the main oil cylinder.

[0014] By adopting the above technical solution, the pressure selection circuit adjusts the pressure according to the load of the main oil cylinder. When the load of the main oil cylinder increases, the pressure selection circuit opens, and the oil in the main oil inlet is diverted to the pressure selection circuit and flows back to the oil tank. By setting up the pressure selection circuit, users can achieve two system pressures by purchasing one set of equipment, thereby greatly reducing manufacturing costs and creating greater economic benefits for users.

[0015] Optionally, the pressure control valve assembly includes a pressure control valve block, a primary pressure solenoid directional valve, a secondary pressure solenoid directional valve, and a pressure reducing valve, wherein the primary pressure solenoid directional valve, the secondary pressure solenoid directional valve, and the pressure reducing valve are mounted on the pressure control valve block.

[0016] By adopting the above technical solution, the pressure control valve group has two states: when the first-stage pressure solenoid directional valve switches, the system pressure oil enters port P through port P1, which serves as the first pressure; when the second-stage pressure solenoid directional valve switches, the system pressure oil enters port P through port P1 and the pressure reducing valve, which serves as the second pressure. The pressure control valve group can select different pressures on different equipment, thus having expandability.

[0017] Optionally, the filling valve is connected to the oil tank via a reverse control circuit, and the reverse control circuit is equipped with a reverse switching valve.

[0018] By adopting the above technical solution, the filling valve is a hydraulically controlled one-way valve. With the setting of the filling valve, the oil in the oil tank can directly enter the rodless chamber of the auxiliary cylinder, but cannot flow back on its own, thereby improving the pressure holding effect of the auxiliary cylinder. When returning oil, the filling valve is opened by the reverse flow of oil, so that the oil in the rodless chamber of the auxiliary cylinder can return to the oil tank.

[0019] Optionally, a two-way suction filter is provided between the inlet of the main oil inlet and the oil tank; a two-way suction filter is provided between the auxiliary oil inlet and the oil tank.

[0020] By adopting the above technical solution, the oil coming out of the tank and the oil entering the tank can be filtered, thereby improving the cleanliness of the oil.

[0021] Optionally, the main pump is a load-sensitive pump capable of sensing system pressure and flow demands and responding correctly to changes in flow and pressure demands.

[0022] By adopting the above technical solution, the load-sensitive pump can simultaneously sense the system's pressure and flow requirements, and can respond correctly to changes in flow and pressure requirements, thereby saving motor power and achieving energy saving.

[0023] In summary, this application includes at least one of the following beneficial technical effects:

[0024] 1. The dedicated hydraulic system for this foam molding machine requires only one main pump for the main cylinder, while the auxiliary cylinder 3 does not require a pump, thus saving on pump costs. By configuring a filling valve, the main pump can be a hydraulic pump with a relatively small displacement, which can meet the system's large flow requirements. This gives the hydraulic system the advantages of high pressure and high speed, with a maximum pressure of 400T and a maximum mold closing speed of 260mm / s.

[0025] 2. The special hydraulic system of this foam molding machine is equipped with a pressure relief circuit, which releases the oil in the rodless chamber before the main cylinder and auxiliary cylinder retract. After the system finishes holding pressure, the pressure is released before each cylinder returns, thereby avoiding the cylinder from failing to open or causing impact.

[0026] 3. The special hydraulic system of this foam molding machine is equipped with a pressure selection circuit, which allows users to achieve two system pressures with one set of equipment, thereby greatly reducing manufacturing costs and creating greater economic benefits for users. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the hydraulic system for a foam molding machine in the embodiments of this application.

[0028] Figure 2 This is a front view of the cartridge valve in an embodiment of this application.

[0029] Figure 3 This is a bottom view of the cartridge valve in an embodiment of this application.

[0030] Figure 4 This is a front view of the pressure control valve assembly in the embodiments of this application.

[0031] Figure 5 This is a left view of the pressure control valve assembly in an embodiment of this application.

[0032] Explanation of reference numerals in the attached diagram: 1. Oil tank; 2. Main oil cylinder; 3. Auxiliary oil cylinder; 4. Main pump; 5. Main oil inlet circuit; 6. Main oil return circuit; 7. Main control valve; 8. Oil circuit one; 9. Oil circuit two; 10. Auxiliary oil circuit; 11. Filling valve; 12. Pressure relief circuit; 13. Pressure relief switch valve; 14. Cartridge valve; 141. Cover plate; 142. Three-way solenoid directional valve; 15. Pressure selection circuit; 16. Pressure control valve assembly; 161. Pressure control valve block; 162. First-stage pressure solenoid directional valve; 163. Second-stage pressure solenoid directional valve; 164. Pressure reducing valve; 17. Reverse control circuit; 18. Reverse switch valve; 19. Main oil circuit; 20. Two-way suction filter. Detailed Implementation

[0033] The following is in conjunction with the appendix Figure 1-5 This application will be described in further detail.

[0034] This application discloses a dedicated hydraulic system for a foam molding machine. (Refer to...) Figure 1This dedicated hydraulic system for foam molding machines includes an oil tank 1, main cylinders 2, auxiliary cylinders 3, a main cylinder control unit, and an auxiliary cylinder control unit. In this embodiment, two main cylinders 2 and four auxiliary cylinders 3 are provided, together constituting the actuators of the hydraulic system. The extension and retraction of the two main cylinders 2 are controlled by the main cylinder control unit. To meet the user's cost-saving requirements, the four auxiliary cylinders 3 adopt passive hydraulic replenishment, that is, the extension and retraction of the auxiliary cylinders 3 are linked and controlled by the main cylinders 2, and the retraction is controlled by the auxiliary cylinder control unit, thus saving a pump motor unit.

[0035] The main hydraulic cylinder control section mainly includes a main pump 4, a main oil inlet circuit 5, a main oil return circuit 6, a main control valve 7, an oil circuit 1 8, and an oil circuit 2 9. The main oil inlet circuit 5 connects the oil tank 1 and the main control valve 7. The main pump 4 is located on the main oil inlet circuit 5 and is used to draw oil from the oil tank 1 to supply the main hydraulic cylinder 2. The oil circuit 1 8 connects the rodless chamber of the main hydraulic cylinder 2 and the main control valve 7. The oil circuit 2 9 connects the rod chamber of the main hydraulic cylinder 2 and the main control valve 7. The oil circuit 1 8 enables the main hydraulic cylinder 2 to extend, and the oil circuit 2 9 enables the main hydraulic cylinder 2 to retract. The main oil return circuit 6 connects the main control valve 7 and the oil tank 1 to enable the main hydraulic cylinder 2 to return oil. The main control valve 7 enables the main oil inlet circuit 5 to connect with the oil circuit 1 8, or the main oil inlet circuit 5 to connect with the oil circuit 2 9, thereby controlling the oil inlet direction and the oil return direction of the main hydraulic cylinder 2.

[0036] The auxiliary cylinder control section includes auxiliary oil circuits 10 and filling valves 11. The filling valve 11 is located on the auxiliary oil circuits 10. The four auxiliary cylinders 3 have four auxiliary oil circuits 10, each equipped with a filling valve 11. The four auxiliary oil circuits 10 are connected in parallel to form two converging oil circuits 19, which are connected to the oil tank. The end of an auxiliary oil circuit 10 furthest from the converging oil circuit 19 is connected to the rodless chamber of the auxiliary cylinder 3. The auxiliary cylinder 3 is a single-chamber cylinder with oil entering only the rodless chamber; the rod chamber is empty. The piston rods of the four auxiliary cylinders 3 act on a pusher. When the piston rod of the main cylinder 2 is rapidly extended, the piston rod of the auxiliary cylinder 3 is passively extended via a mechanical connection (the thrust of the main cylinder 2 drives the extension of the auxiliary cylinder 3). Due to the vacuum in the rodless chamber of the auxiliary cylinder 3, the filling valve 11 opens, drawing a large amount of oil from the oil tank 1. At this time, the auxiliary cylinder 3 and the main cylinder 2 extend together to perform the corresponding operation. During retraction, the main cylinder 2 retracts first, and through mechanical connection, the auxiliary cylinder 3 is passively retracted. The oil in the rodless chamber of the auxiliary cylinder 3 flows back to the oil tank 1 quickly through the auxiliary oil circuit 10.

[0037] This dedicated hydraulic system for foam molding machines requires only one main pump 4 for the main cylinder 2, while the auxiliary cylinder 3 does not require a pump, thus saving on pump costs. Furthermore, by configuring a filling valve 11, the main pump 4 can be selected with a relatively small displacement hydraulic pump to meet the system's high flow requirements, thereby giving the hydraulic system the advantages of high pressure and high speed. The maximum pressure can reach 400T, and the fastest mold closing speed can reach 260mm / s.

[0038] It should be noted that, since the rodless chamber space of the auxiliary cylinder 3 is larger than the rod chamber space, the auxiliary oil circuit 10 is connected to the rodless chamber of the auxiliary cylinder 3, allowing the oil to enter the rodless chamber, which can ensure a larger output pressure under the same conditions.

[0039] In this embodiment, the filling valve 11 is connected to the oil tank 1 via a reverse control circuit 17, and a reverse switching valve 18 is provided on the reverse control circuit 17. The filling valve 11 is a hydraulically controlled check valve. When the piston rod of the auxiliary cylinder 3 extends, the oil in the oil tank 1 can directly enter the rodless chamber of the auxiliary cylinder 3 through the filling valve; when the piston rod of the auxiliary cylinder 3 retracts, the oil in the oil tank reverse control circuit 17 opens the filling valve 11, and the oil in the rodless chamber of the auxiliary cylinder 3 flows back into the oil tank 1. The reverse switching valve 18 controls the opening and closing of the reverse control circuit 17.

[0040] In this embodiment, since the auxiliary oil circuit 10 and the oil tank 1 are bidirectional oil circuits, a bidirectional suction oil filter 20 is provided so that the oil in the oil tank 1 is filtered before entering the auxiliary oil cylinder 3, and the oil in the auxiliary oil cylinder 3 is filtered before entering the oil tank 1. The bidirectional suction oil filter 20 is located on the main oil circuit 19. Similarly, a bidirectional suction oil filter 20 is provided between the inlet of the main oil circuit 5 and the oil tank 1.

[0041] In this embodiment, the main pump 4 is preferably a load-sensitive pump, which is a pressure-flow compensated variable displacement piston hydraulic pump that can simultaneously sense the system pressure and flow demand and respond correctly to changes in flow and pressure demand, thereby saving motor power and achieving energy saving.

[0042] In this embodiment, the hydraulic system is also equipped with a pressure relief circuit 12. The function of the pressure relief circuit 12 is to release the oil in the rodless chamber before the main cylinder 2 and the auxiliary cylinder 3 retract. The oil circuit 8 and the rodless chamber of the auxiliary cylinder 3 are both connected to one end of the pressure relief circuit 12, and the other end of the pressure relief circuit 12 is connected to the oil tank 1. A pressure relief switch valve 13 is provided on the pressure relief circuit 12. After the piston rods of the main cylinder 2 and the auxiliary cylinder 3 extend, the system maintains pressure. After the pressure maintenance is completed, the pressure must be released before each cylinder returns to its original position; otherwise, the cylinders may fail to open or cause impact. When depressurization occurs, the depressurization switch valve 13 is opened. The oil in the rodless chamber of the main cylinder 2 flows through oil circuit 8 to the depressurization circuit 12 and into the oil tank 1. At the same time, the oil in the rodless chamber of the auxiliary cylinder 3 enters the depressurization circuit 12 and flows into the oil tank 1. After the set pressure or time is reached, the depressurization switch valve 13 is closed, and both the main cylinder 2 and the auxiliary cylinder 3 enter normal oil return. At this time, when the main cylinder 2 retracts rapidly, the auxiliary cylinder 3 is passively retracted through mechanical connection. That is, the oil in the rodless chamber of the main cylinder 2 enters the oil tank 1 through oil circuit 8, the main control valve 7 and the main return oil circuit 6, and the oil in the rodless chamber of the auxiliary cylinder 3 enters the oil tank 1 through the auxiliary oil circuit 10.

[0043] In this embodiment, to meet the user's high-speed requirements, the system needs a large flow rate. Therefore, this hydraulic system adopts a cartridge valve structure. Compared to a conventional directional valve, this structure is more compact for the same large flow rate. The cartridge valve 14 is located on the main inlet circuit 5 and is used to control the speed of the main cylinder 2. The cartridge valve 14 is located on the outlet side of the main pump 4. The oil in the main inlet circuit 5 passes through the load-sensitive pump, then through the cartridge valve 14, and finally reaches the main control valve 7. (Refer to...) Figure 2 and Figure 3 The cartridge valve 14 controls the direction of the oil passage inside the cover plate 141 of the cartridge valve 14 via a three-way solenoid directional valve 142. When the cartridge valve 14 needs to be opened, the pressurized oil is diverted through the three-way solenoid directional valve 142, and the oil in the spring chamber F port of the cartridge valve 14 is depressurized through the Y port inside the cover plate 141, thus opening the cartridge valve 14. When the three-way solenoid directional valve is not working, the high-pressure oil enters the spring chamber F port of the cartridge valve 14 through the X port, forming a closed chamber that presses down on the cartridge valve 14, which is the pressure-holding state of the entire system. The cartridge valve 14 is an independently designed product with low internal resistance, suitable for high-flow operation, and has the advantages of being safer, more reliable, and significantly improving the system pressure-holding effect.

[0044] In this embodiment, the hydraulic system also includes a pressure selection circuit 15. One end of the pressure selection circuit 15 is connected to the main oil inlet circuit 5, and the other end is connected to the oil tank 1. The connection point between the pressure selection circuit 15 and the main oil inlet circuit 5 is located on the outlet side of the main pump 4, extending to the outlet of the cartridge valve 14. A pressure control valve assembly 16 is provided on the pressure selection circuit 15. The pressure control valve assembly 16 adjusts the pressure according to the load of the main cylinder 2. When the load of the main cylinder 2 increases, the pressure selection circuit 15 opens, and the oil in the main oil inlet circuit 5 is diverted to the pressure selection circuit 15 and flows back to the oil tank 1.

[0045] Reference Figure 4 and Figure 5 Specifically, the pressure control valve assembly 16 includes a pressure control valve block 161, a primary pressure solenoid directional valve 162, a secondary pressure solenoid directional valve 163, and a pressure reducing valve 164. The primary pressure solenoid directional valve 162, the secondary pressure solenoid directional valve 163, and the pressure reducing valve 164 are mounted on the pressure control valve block 161. The pressure control valve assembly 16 has two states: when the primary pressure solenoid directional valve 162 switches, system pressure oil enters port P through port P1, serving as the first pressure; when the secondary pressure solenoid directional valve 163 switches, system pressure oil enters port P through port P1 and pressure reducing valve 164, serving as the second pressure. The pressure control valve assembly 16 can select different pressures on different equipment, providing scalability. By setting up the pressure selection loop 15, users can purchase one set of equipment to achieve two system pressures, namely EP and EPS models, thereby significantly reducing manufacturing costs and creating greater economic benefits for users.

[0046] The implementation principle of a special hydraulic system for a foam molding machine according to an embodiment of this application is as follows:

[0047] Cylinder extension: Oil from tank 1 enters the rodless chamber of main cylinder 2 through main inlet 5, main pump 4, cartridge valve 14, main control valve 7, and oil line 8, pushing the piston rod of main cylinder 2 out. At the same time, main cylinder 2 and auxiliary cylinder 3 are connected by a mechanical structure. The piston rod of auxiliary cylinder 3 is passively pushed out. Due to the vacuum in the rodless chamber of auxiliary cylinder 3, filling valve 11 is opened, drawing a large amount of oil from tank 1. At this time, auxiliary cylinder 3 and main cylinder 2 are pushed out together to perform the corresponding work.

[0048] Pressure relief before retraction: Open the pressure relief switch valve 13. The oil in the rodless chamber of the main cylinder 2 passes through oil circuit 8 to reach the pressure relief circuit 12 and flows into the oil tank 1. The oil in the rodless chamber of the auxiliary cylinder 3 enters the pressure relief circuit 12 and flows into the oil tank 1. After reaching the set pressure or time, the pressure relief switch valve 13 closes.

[0049] Cylinder retraction: When the main cylinder 2 retracts rapidly, the oil in the main inlet circuit 5 enters the rod chamber of the main cylinder 2 through the main control valve 7 and the second oil circuit 9, pushing the piston rod of the main cylinder 2 to retract. The oil in the rodless chamber of the main cylinder 2 enters the oil tank 1 through the first oil circuit 8, the main control valve 7 and the main return oil circuit 6. As the main cylinder 2 retracts rapidly, the auxiliary cylinder 3 is passively retracted through the mechanical connection. At this time, the reverse switch valve 18 is opened, the filling valve 11 reverses the flow of fluid, and the oil in the rodless chamber of the auxiliary cylinder 3 enters the oil tank 1 through the auxiliary oil circuit 10.

[0050] The above are all preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A hydraulic system specifically designed for foam molding machines, characterized in that: It includes an oil tank (1), a main oil cylinder (2), an auxiliary oil cylinder (3), a main oil cylinder control section, and an auxiliary oil cylinder control section. The main oil cylinder control section includes a main pump (4), a main oil inlet circuit (5), a main oil return circuit (6), a main control valve (7), an oil circuit one (8), and an oil circuit two (9). The main oil inlet circuit (5) connects the oil tank (1) and the main control valve (7). The main pump (4) is located on the main oil inlet circuit (5). The main oil return circuit (6) connects the main control valve (7) and the oil tank (1). 1) The first oil circuit (8) connects the rodless chamber of the main cylinder (2) to the main control valve (7), and the second oil circuit (9) connects the rod chamber of the main cylinder (2) to the main control valve (7); the auxiliary cylinder control part includes an auxiliary oil circuit (10) and a filling valve (11). The auxiliary oil circuit (10) connects the oil tank (1) to the rodless chamber of the auxiliary cylinder (3). The filling valve (11) is located on the auxiliary oil circuit (10) and also includes a pressure selection circuit (15). One end of the circuit (15) is connected to the main oil inlet circuit (5) and the other end is connected to the oil tank (1). The connection point between the pressure selection circuit (15) and the main oil inlet circuit (5) is located on the outlet side of the main pump (4). The pressure selection circuit (15) is equipped with a pressure control valve group (16) for pressure control according to the load of the main cylinder (2). The pressure control valve group (16) includes a pressure control valve block (161), a first-stage pressure solenoid directional valve (162), and a second-stage pressure solenoid directional valve. Valve (163) and pressure reducing valve (164), the first-stage pressure solenoid directional valve (162), the second-stage pressure solenoid directional valve (163) and the pressure reducing valve (164) are installed on the pressure control valve block (161). When the first-stage pressure solenoid directional valve (162) switches, the system pressure oil enters the P port through the P1 port as the first pressure; when the second-stage pressure solenoid directional valve (163) switches, the system pressure oil enters the P port through the P1 port and the pressure reducing valve (164) as the second pressure.

2. The hydraulic system for foam molding machines according to claim 1, characterized in that: It also includes a pressure relief circuit (12), the rodless chambers of the first oil circuit (8) and the auxiliary oil cylinder (3) are connected to one end of the pressure relief circuit (12), the other end of the pressure relief circuit (12) is connected to the oil tank (1), and a pressure relief switch valve (13) is provided on the pressure relief circuit (12).

3. The hydraulic system for foam molding machines according to claim 1, characterized in that: The main oil inlet (5) is equipped with a cartridge valve (14) that can control the speed of the main oil cylinder (2), and the cartridge valve (14) is located on the outlet side of the main pump (4).

4. The hydraulic system for foam molding machines according to claim 3, characterized in that: The direction of the internal oil passage of the control cover (141) of the cartridge valve (14) is controlled by a three-way solenoid directional valve (142).

5. The hydraulic system for foam molding machines according to any one of claims 1 to 4, characterized in that: The filling valve (11) is connected to the oil tank (1) through a reverse control circuit (17), and a reverse switching valve (18) is provided on the reverse control circuit (17).

6. The hydraulic system for foam molding machines according to any one of claims 1 to 4, characterized in that: A bidirectional oil suction filter (20) is provided between the inlet of the main oil inlet (5) and the oil tank (1); a bidirectional oil suction filter (20) is provided between the auxiliary oil inlet (10) and the oil tank (1).

7. The hydraulic system for foam molding machines according to any one of claims 1 to 4, characterized in that: The main pump (4) is a load-sensitive pump that can sense the system pressure and flow demand and respond correctly to changes in flow and pressure demand.

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