Nozzle contact force control and pressure relief hydraulic circuit for an injection molding machine

Abstract

The utility model provides an injection molding machine's nozzle contact force control and pressure relief hydraulic circuit belongs to injection molding machine technical field, include: reversing valve, one end of first oil circuit is connected with the one work oil port of reversing valve and is configured to be connected with one of the rod cavity and the rodless cavity of actuating mechanism, first node is located between second check valve and actuating mechanism, second node is located between first check valve and second check valve, one end of second oil circuit is connected with the other work oil port of reversing valve, the oil inlet of pilot type pressure reducing valve is connected with second node, the oil outlet of pilot type pressure reducing valve is connected with first node, the utility model's beneficial effect is: pilot type pressure reducing valve can not only control the contact force size between nozzle and mould, eliminate the influence that oil circuit pressure fluctuation caused, can also realize the function of contact force pressure relief before opening mould, protect mould and nozzle not be damaged.

Description

Technical Field

[0001] This utility model belongs to the field of injection molding machine technology, and relates to a nozzle contact force control and pressure relief hydraulic circuit for an injection molding machine. Background Technology

[0002] The injection unit's overall movement (referred to as "injection port movement") function pushes the barrel-nozzle assembly towards the mold, ensuring a tight seal between the nozzle end face and the mold gate. This provides a closed flow path for subsequent melt filling and holding pressure processes. After the injection port movement is completed, a contact force is formed between the nozzle and the mold. The magnitude and stability of this force directly affect the process reliability during injection and holding pressure stages, the repeatability of the product, and the service life of the nozzle and mold itself.

[0003] Existing hydraulic circuits for mold alignment typically employ a three-position four-way valve combined with a check valve, allowing only forward clamping and backward release. This lack of control over the contact force after clamping is insufficient. Specifically, during the injection and holding pressure stages, the system relies on the alignment cylinder to maintain nozzle sealing. Traditional solutions directly lock the high-pressure oil source within the rodless chamber of the cylinder, resulting in the contact force passively following the oil supply pressure and lacking dynamic adjustment capabilities. After the molding cycle, traditional circuits directly switch and close the oil path via a reversing valve, leaving a high residual pressure between the nozzle and the mold. This residual pressure is suddenly released upon mold opening, potentially impacting vulnerable areas like the mold cavity and increasing the risk of mold damage. Furthermore, existing solutions typically only passively reduce the alignment pressure after a malfunction, failing to proactively and quantitatively release the contact force before each molding cycle's mold opening, thus hindering further improvements in process stability and equipment lifespan.

[0004] In summary, with the increasing demands for pressure stability during injection and holding processes, it has become an urgent need to independently set up pressure reduction and stabilization functions and pre-mold release functions in the hydraulic system for the transfer, and to achieve closed-loop adjustable contact force and automatic cycle zeroing. Utility Model Content

[0005] The purpose of this invention is to address the aforementioned problems in the existing technology by proposing a nozzle contact force control and pressure relief hydraulic circuit for an injection molding machine.

[0006] The objective of this utility model can be achieved through the following technical solution: a nozzle contact force control and pressure relief hydraulic circuit for an injection molding machine, comprising:

[0007] Reversing valve;

[0008] The first oil circuit has one end connected to a working port of the directional valve, and the other end of the first oil circuit is configured to be connected to one of the rod chamber and the rodless chamber of the actuator. The first oil circuit is provided with a first check valve, a second check valve, a first node, and a second node.

[0009] The first check valve and the second check valve are arranged sequentially along the direction from the reversing valve to the actuator. The first node is located between the second check valve and the actuator, and the second node is located between the first check valve and the second check valve. When the first check valve is in a unidirectional flow state, it is configured to allow oil to flow from the reversing valve to the second node, and the second check valve is configured to allow oil to flow from the first node to the second node.

[0010] The second oil passage has one end connected to the other working port of the reversing valve, and the other end of the second oil passage is configured to be connected to the other of the rod chamber and rodless chamber of the actuator.

[0011] A pilot-operated pressure reducing valve, wherein the oil inlet of the pilot-operated pressure reducing valve is connected to the second node, and the oil outlet of the pilot-operated pressure reducing valve is connected to the first node.

[0012] Preferably, the first check valve has a unidirectional flow state and a bidirectional flow state, and the state of the first check valve is determined by the oil flow direction of the second oil circuit; wherein, when the oil in the second oil circuit flows to the reversing valve, the first check valve is in a unidirectional flow state that allows the oil to flow from the reversing valve to the second node; when the oil in the second oil circuit flows to the actuator, the first check valve is in a bidirectional flow state that allows the oil to flow in both directions.

[0013] Preferably, the first check valve is configured as a hydraulically controlled check valve, and the control port of the first check valve is connected to the second oil circuit.

[0014] Preferably, the first node and the second node are arranged sequentially along the direction from the actuator to the reversing valve.

[0015] Preferably, the pressure at the first node is equal to the pressure in either the rod-side chamber or the rodless chamber of the actuator, and the pressure at the second node is equal to the pressure at one working port of the directional valve.

[0016] Preferably, the return port of the pilot-operated pressure reducing valve is connected to the oil tank.

[0017] Preferably, the pilot-operated pressure reducing valve has a control unit configured to set the pilot control pressure of the pilot-operated pressure reducing valve based on a received electrical signal.

[0018] Preferably, the directional valve is a three-position four-way solenoid directional valve.

[0019] Preferably, the directional valve has a neutral position, a left-side working position, and a right-side working position.

[0020] Preferably, when the directional valve is in the neutral position, the actuator is in the contact force relief state; when the directional valve is in the left position, the actuator is in the injection and pressure holding state; and when the directional valve is in the right position, the actuator is in the retraction and retraction state.

[0021] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0022] 1. The pilot-operated pressure reducing valve can not only control the contact force between the nozzle and the mold and eliminate the influence of oil pressure fluctuations, but also release the contact force before mold opening to protect the mold and nozzle from damage.

[0023] 2. It can ensure the accuracy and repeatability of injection molding. The pilot-operated pressure reducing valve can ensure that the contact force during the injection and holding process is controllable and stable, and is not affected by the fluctuation of the oil supply pressure, thus ensuring the stability of the injection and holding process.

[0024] 3. The pilot port pressure of the pilot-operated pressure reducing valve can control and ensure that the accumulated pressure generated after the oil pressure overshoots is reduced to the contact force required for injection, preventing the nozzle and mold from generating plastic indentations and damaging the mold structure due to excessive contact force. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the nozzle contact force control and pressure relief hydraulic circuit of this utility model.

[0026] In the diagram, 100 is the directional valve; 200 is the first oil circuit; 210 is the first check valve; 220 is the second check valve; 230 is the first node; 240 is the second node; 300 is the second oil circuit; 400 is the pilot-operated pressure reducing valve; and 500 is the actuator. Detailed Implementation

[0027] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0028] like Figure 1 As shown, a nozzle contact force control and pressure relief hydraulic circuit for an injection molding machine includes:

[0029] Reversing valve 100;

[0030] The first oil passage 200 has one end connected to a working port of the reversing valve 100, and the other end of the first oil passage 200 is configured to be connected to one of the rod chamber and the rodless chamber of the actuator 500. The first oil passage 200 is provided with a first check valve 210, a second check valve 220, a first node 230 and a second node 240.

[0031] The first check valve 210 and the second check valve 220 are arranged sequentially along the direction from the reversing valve 100 to the actuator 500. The first node 230 is located between the second check valve 220 and the actuator 500, and the second node 240 is located between the first check valve 210 and the second check valve 220. When the first check valve 210 is in a one-way flow state, it is configured to allow oil to flow from the reversing valve 100 to the second node 240, and the second check valve 220 is configured to allow oil to flow from the first node 230 to the second node 240.

[0032] The second oil passage 300 has one end connected to the other working port of the directional valve 100, and the other end of the second oil passage 300 is configured to be connected to the other of the rod chamber and rodless chamber of the actuator 500.

[0033] The pilot-operated pressure reducing valve 400 has its inlet connected to the second node 240 and its outlet connected to the first node 230.

[0034] Based on the above embodiments, the first check valve 210 has a unidirectional flow state and a bidirectional flow state. The state of the first check valve 210 is determined by the direction of oil flow in the second oil passage 300. When the oil in the second oil passage 300 flows to the reversing valve 100, the first check valve 210 is in a unidirectional flow state that allows the oil to flow from the reversing valve 100 to the second node 240. When the oil in the second oil passage 300 flows to the actuator 500, the first check valve 210 is in a bidirectional flow state that allows the oil to flow in both directions.

[0035] Preferably, the first check valve 210 is configured as a hydraulically controlled check valve, and the control port of the first check valve 210 is connected to the second oil circuit 300.

[0036] Structurally, the reversing valve 100 is used to control the movement direction of the translating cylinder. Its two working ports are connected to the first oil circuit 200 and the second oil circuit 300, respectively. By switching the valve position, the communication path between the hydraulic oil and the rod chamber and rodless chamber of the translating cylinder is opened or closed, thereby realizing the forward and backward movement of the injection seat.

[0037] The first check valve 210 is located in the first oil circuit 200 and close to the directional valve 100. During the forward movement of the injection seat, the first check valve 210 is in a one-way flow state, allowing hydraulic oil to be supplied unidirectionally from the directional valve 100 through the second node 240 (K2) of the first oil circuit 200 to the rod chamber of the transfer cylinder. During the pressure holding phase, it prevents reverse flow of the oil, thus reliably maintaining the pressure in the rod chamber. It should be noted that when the second oil circuit 300 establishes pressure, the first check valve 210 is in a two-way flow state, allowing bidirectional flow of the oil to ensure smooth return of oil from the rod chamber when the injection seat moves backward. The second check valve 220 is located in the first oil circuit 200 and between the first node 230 (K1) and the second node 240. Its conduction direction is from the actuator 500 (transfer cylinder) side to the directional valve 100 side, allowing oil from the rod chamber to flow back from the first node 230 to the second node 240.

[0038] The inlet of the pilot-operated pressure reducing valve 400 is connected to the second node 240 in the first oil circuit 200, and its outlet is connected to the first node 230 in the first oil circuit 200. The pilot-operated pressure reducing valve 400 is used to precisely control the effective pressure acting on the rod chamber of the transfer cylinder by adjusting its set pressure during the injection and holding stages, so as to achieve a constant contact force between the nozzle and the mold sprue sleeve; and before mold opening, it actively reduces the set pressure to achieve smooth pressure relief of the nozzle contact force and avoid mold opening impact.

[0039] Based on the above implementation method, the first node 230 and the second node 240 are arranged sequentially along the direction from the actuator 500 to the reversing valve 100.

[0040] Based on the above implementation method, the pressure of the first node 230 is equal to the pressure of one of the rod chamber and the rodless chamber of the actuator 500, and the pressure of the second node 240 is equal to the pressure of a working port of the reversing valve 100.

[0041] Based on the above implementation method, the return port of the pilot-operated pressure reducing valve 400 is connected to the oil tank.

[0042] Based on the above embodiments, the pilot-operated pressure reducing valve 400 has a control unit, which is configured to set the pilot control pressure of the pilot-operated pressure reducing valve 400 according to the received electrical signal.

[0043] Based on the above implementation method, the reversing valve 100 is a three-position four-way solenoid reversing valve 100.

[0044] Based on the above implementation, the reversing valve 100 has a neutral position, a left position working position, and a right position working position.

[0045] Based on the above implementation method, when the directional valve 100 is in the neutral position, the actuator 500 is in the contact force relief state; when the directional valve 100 is in the left position, the actuator 500 is in the injection and pressure holding state; when the directional valve 100 is in the right position, the actuator 500 is in the retraction and retraction state.

[0046] like Figure 1 As shown, the working principle of the nozzle contact force control and pressure relief circuit is as follows:

[0047] 1. Injection and Holding Pressure Stage: When the injection molding machine performs injection and holding pressure actions, the solenoid terminal D2 of the reversing valve 100 is energized, and the reversing valve 100 switches to the left-hand working state. Hydraulic oil enters the reversing valve 100 from port P and is output to the first oil circuit 200 through port A. The high-pressure oil passes through the first check valve 210 (at this time, the first check valve 210 is in a one-way flow state) to the second node 240 (K2) in the first oil circuit 200. Since the conduction direction of the second check valve 220 is from the first node 230 (K1) to the second node 240 (K2), the hydraulic oil is in a one-way flow state. Node 240 is reverse-cut off, so the oil cannot directly enter the first node 230 through the second check valve 220. It must enter the main valve port of the pilot-operated pressure reducing valve 400 through the inlet. Under the pilot stage control of the pilot-operated pressure reducing valve 400, the outlet pressure is reduced and stabilized at the set pressure value corresponding to the nozzle contact force. The hydraulic oil is output from the outlet of the pilot-operated pressure reducing valve 400 to the first node 230, and then enters the rod chamber of the actuator 500, driving the piston rod to push the injection seat forward, realizing the overall forward movement.

[0048] If the pressure at the first node 230 is momentarily higher than the set pressure due to system overshoot or pressure fluctuation, the high-pressure oil at the first node 230 will flow in the opposite direction through the second check valve 220 to the second node 240 under the action of pressure difference, and return to the oil tank through the pilot pressure relief circuit of the pilot pressure reducing valve 400, thereby dynamically adjusting the pressure to the set value and realizing closed-loop pressure stability control of the nozzle contact force.

[0049] 2. Pre-mold opening contact force relief stage: When the injection molding pressure holding is completed and the mold opening preparation stage begins, both D1 and D2 of the reversing valve 100 are de-energized and switched to the neutral position, cutting off the inlet and outlet oil passages of the first oil circuit 200 and the second oil circuit 300, so that the oil in the rodless chamber of the transfer cylinder is sealed and pressure-held. At this time, the pilot control pressure corresponding to the contact force relief target value is input to the control unit (DP1 point) of the pilot-operated pressure reducing valve 400 through the external control signal. Under the action of this pilot pressure, the main valve port of the pilot-operated pressure reducing valve 400 opens, and the hydraulic oil of the first node 230 (rod chamber side) is released to the return oil tank through the internal channel of the pilot-operated pressure reducing valve 400, realizing the controllable release of the rod chamber pressure. This completes the active pressure relief of the contact force between the nozzle and the mold, avoiding gate damage or mold surface scratches caused by the nozzle still pressing against the mold at the moment of mold opening.

[0050] 3. Retraction and Retraction (Injection Seat Retraction) Stage: When the injection molding machine performs the retraction and retraction action, the solenoid terminal D1 of the directional valve 100 is energized and switched to the right-hand working state. The hydraulic oil is output from port P through port B to the second oil circuit 300 and enters the rodless chamber of the retraction cylinder, pushing the piston to retract. The low-pressure return oil in the rod chamber flows out from the first node 230 and flows to the second node 240 through the second check valve 220. Since the directional valve 100 is in the right-hand working state, the oil circuit at the second node 240 is connected to the return oil port (T port) of the directional valve 100. The return oil is reversed through the hydraulic control first check valve 210 (at this time, the first check valve 210 is opened under the pressure control of the second oil circuit 300 to achieve bidirectional flow), flows back to the directional valve 100 and returns to the oil tank.

[0051] The above solution ensures injection molding accuracy and repeatability. The pilot-operated pressure reducing valve 400 guarantees controllable and stable contact force during the injection holding process, unaffected by fluctuations in oil supply pressure, thus ensuring a stable injection holding process. Furthermore, it extends mold life. Before mold opening, the oil is depressurized through the pilot port of the pilot-operated pressure reducing valve 400, reducing the contact force between the injection nozzle and weak points in the mold cavity, thereby preventing mold damage. Using the pilot-operated pressure reducing valve 400 for pressure control while also providing pressure relief reduces the number of pressure relief valves and corresponding circuits compared to traditional pressure reducing circuits, resulting in a simpler structure and smaller footprint. The pilot port pressure of the pilot-operated pressure reducing valve 400 can control and ensure that the accumulated pressure after oil pressure overshoot is reduced to the contact force required for injection, preventing excessive contact force between the nozzle and mold from causing plastic indentations and damaging the mold structure.

[0052] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in this utility model embodiment are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0053] Furthermore, in this utility model, the use of terms such as "first," "second," and "a" is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this utility model, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0054] In this utility model, unless otherwise explicitly specified and limited, the terms "connection," "fixing," etc., should be interpreted broadly. For example, "fixing" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0055] Furthermore, the technical solutions of the various embodiments of this utility model can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this utility model.

Claims

1. A nozzle contact force control and pressure relief hydraulic circuit for an injection molding machine, characterized in that, include: Reversing valve (100); A first oil passage (200) is provided, one end of which is connected to a working port of the directional valve (100), and the other end of which is configured to be connected to one of the rod chamber and the rodless chamber of the actuator (500). A first check valve (210), a second check valve (220), a first node (230), and a second node (240) are provided on the first oil passage (200). The first check valve (210) and the second check valve (220) are arranged sequentially along the direction from the reversing valve (100) to the actuator (500). The first node (230) is located between the second check valve (220) and the actuator (500), and the second node (240) is located between the first check valve (210) and the second check valve (220). When the first check valve (210) is in a unidirectional flow state, it is configured to allow oil to flow from the reversing valve (100) to the second node (240), and the second check valve (220) is configured to allow oil to flow from the first node (230) to the second node (240). The second oil passage (300) has one end connected to the other working port of the directional valve (100), and the other end of the second oil passage (300) is configured to be connected to the other of the rod chamber and rodless chamber of the actuator (500). A pilot-operated pressure reducing valve (400) is provided, wherein the inlet of the pilot-operated pressure reducing valve (400) is connected to the second node (240), and the outlet of the pilot-operated pressure reducing valve (400) is connected to the first node (230).

2. The nozzle contact force control and pressure relief hydraulic circuit of an injection molding machine as described in claim 1, characterized in that: The first check valve (210) has a unidirectional flow state and a bidirectional flow state. The state of the first check valve (210) is determined by the oil flow direction of the second oil passage (300). When the oil in the second oil passage (300) flows to the reversing valve (100), the first check valve (210) is in a unidirectional flow state that allows the oil to flow from the reversing valve (100) to the second node (240). When the oil in the second oil passage (300) flows to the actuator (500), the first check valve (210) is in a bidirectional flow state that allows the oil to flow in both directions.

3. The nozzle contact force control and pressure relief hydraulic circuit of an injection molding machine as described in claim 2, characterized in that: The first check valve (210) is configured as a hydraulic check valve, and the control port of the first check valve (210) is connected to the second oil circuit (300).

4. The nozzle contact force control and pressure relief hydraulic circuit of an injection molding machine as described in claim 1, characterized in that: The first node (230) and the second node (240) are arranged sequentially along the direction from the actuator (500) to the reversing valve (100).

5. The nozzle contact force control and pressure relief hydraulic circuit of an injection molding machine as described in claim 1 or 4, characterized in that: The pressure at the first node (230) is equal to the pressure in either the rod chamber or the rodless chamber of the actuator (500), and the pressure at the second node (240) is equal to the pressure at one working port of the directional valve (100).

6. The nozzle contact force control and pressure relief hydraulic circuit of an injection molding machine as described in claim 1, characterized in that: The return port of the pilot-operated pressure reducing valve (400) is connected to the oil tank.

7. The nozzle contact force control and pressure relief hydraulic circuit of an injection molding machine as described in claim 1, characterized in that: The pilot-operated pressure reducing valve (400) has a control unit configured to set the pilot control pressure of the pilot-operated pressure reducing valve (400) based on a received electrical signal.

8. The nozzle contact force control and pressure relief hydraulic circuit of an injection molding machine as described in claim 1, characterized in that: The reversing valve (100) is a three-position four-way solenoid reversing valve (100).

9. The nozzle contact force control and pressure relief hydraulic circuit of an injection molding machine as described in claim 8, characterized in that: The reversing valve (100) has a neutral position, a left position working position, and a right position working position.

10. The nozzle contact force control and pressure relief hydraulic circuit of an injection molding machine as described in claim 9, characterized in that: When the directional valve (100) is in the neutral position, the actuator (500) is in the contact force relief state; when the directional valve (100) is in the left position, the actuator (500) is in the injection and pressure holding state; when the directional valve (100) is in the right position, the actuator (500) is in the retraction and retraction state.

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