A differential clamping pressure relief oil circuit for a two-platen injection molding machine

Abstract

The invention discloses a differential mold locking pressure relief oil circuit for a two-plate injection molding machine, which comprises a cartridge valve, two two-position two-way electromagnetic reversing valves and an oil tank; the bottom working oil port of the cartridge valve is connected with the mold locking cavity, and the side working oil port is connected with the mold breaking cavity to form a main channel oil circuit; during the mold locking pressure relief action, when the electromagnet of the second two-position two-way electromagnetic reversing valve is energized, the pilot port of the cartridge valve reaches the side working oil port of the cartridge valve through the first damping, the third damping, the fourth damping and the fifth damping, and the bottom working oil port of the cartridge valve reaches the side working oil port of the cartridge valve through the second damping, the fourth damping and the fifth damping, so that the cartridge valve is slowly opened to realize differential mold locking pressure relief; during the mold breaking action, when the electromagnet of the first two-position two-way electromagnetic reversing valve is energized, the pilot port of the cartridge valve reaches the oil tank through the first damping, so that the cartridge valve is quickly opened to realize differential mold breaking; the advantages are that the mold locking pressure relief process is stable, the mold breaking action is taken into consideration, and the oil cleanliness is good.

Description

Technical Field

[0001] The invention relates to a mold locking pressure relief technology for an injection molding machine, in particular to a differential mold locking pressure relief oil circuit for a two-platen injection molding machine. Background Art

[0002] In a two-platen injection molding machine, the basic actions are as follows: mold closing - brake - high-pressure mold locking - injection table forward - injection - pressure holding - pre-plasticization - injection back - cooling - mold locking pressure relief - mold breaking - brake opening - mold opening - part removal. The mold locking pressure relief action is the process of releasing the oil in the mold locking cavity of the mold locking cylinder from high pressure to low pressure. It is a key action of the two-platen injection molding machine. Since the instantaneous release of pressure will generate huge energy, it will impact the oil return area, which will cause vibration and then generate oil return noise.

[0003] In order to solve the above problems, industry insiders proposed a clamping mold pressure relief oil circuit. Figure 1An existing clamping pressure relief oil circuit is provided, which connects a small-flow channel back to the oil tank separately in the clamping cavity 11 of the clamping cylinder 1 by installing a two-position two-way electromagnetic reversing valve V51, a damping joint Z1, and a small-diameter steel pipe (with a diameter of 8 mm). The clamping pressure is first slowly reduced to a set pressure (the set pressure is less than the clamping pressure) by using the channel, and then the remaining clamping pressure is directly returned to the oil tank through a large-flow return oil cartridge valve V59 to realize a two-stage clamping pressure relief of the clamping pressure. When the two-platen injection molding machine is in full automatic production, the mold cavity pressure has been reduced before the cooling is completed. The two-platen injection molding machine does not need too much clamping pressure to ensure that the mold does not expand and the normal production of the product is guaranteed. According to actual on-site production experience, half of the clamping pressure after the product pressure holding is completed is sufficient to ensure the normal production of the product. Therefore, during the cooling process after the product pressure holding is completed, the two-position two-way solenoid reversing valve V51 is energized, and the oil in the clamping cavity 11 returns to the oil tank through the two-position two-way solenoid reversing valve V51, and the pressure begins to drop. Because the flow rate of the two-position two-way solenoid reversing valve V51 is small and the two-position two-way is energized The steel pipes connected at both ends of the magnetic reversing valve V51 have a small diameter, and with the damping joint Z1, the oil flow rate of the entire channel is very small, and the pressure drop is controllable; when the oil pressure in the clamping cavity 11 slowly drops, the clamping pressure sensor F10 detects in real time. When it is detected that the clamping pressure reaches the set pressure (the set pressure is generally set to half of the clamping pressure), the two-position two-way electromagnetic reversing valve V51 loses power. At this time, the clamping cavity 11 has only half of the current machine's clamping pressure. This process is also called early pressure relief. The pressure drops slowly during this pressure relief process, the action impact is small, the sound is light, but the pressure relief time is long. When cooling is completed and the mold locking pressure relief action is performed, the electromagnetic reversing valve V62 and the two-position two-way electromagnetic reversing valve V58 acting as the switch valve are energized. When the electromagnetic reversing valve V62 acting as the switch valve is energized, the oil circuits of the B port and the C port of the return oil cartridge valve V59 are cut off. When the two-position two-way electromagnetic reversing valve V58 is energized, the C port of the return oil cartridge valve V59 is directly connected to the oil tank. There is no pressure at the C port of the return oil cartridge valve V59. The return oil cartridge valve V59 is opened, and the remaining oil in the clamping cavity 11 is released through the B port of the return oil cartridge valve V59 to the A port of the return oil cartridge valve to return to the oil tank, thereby completing the entire clamping pressure relief action.

[0004] The two-stage clamping pressure relief of the above clamping pressure relief oil circuit has the following problems:

[0005] 1) In order to slow down the speed of opening the valve core of the oil return cartridge valve V59, a damper Z2 is installed at the C port of the oil return cartridge valve V59, and the oil return cartridge valve V59 is equipped with a buffer type valve core. Since the damper Z2 needs to take into account the mold breaking speed at the same time (the smaller the damper Z2 is, the better when the mold is locked and the pressure is released, and the larger the damper Z2 is, the better when the mold is broken), the damper Z2 should not be too small. If the damper Z2 is too small, the hole of the damper Z2 is easy to be blocked when the weather is cold and the oil is viscous, which will cause the oil to flow difficultly, resulting in slow mold breaking speed or even mold breaking failure; in addition, the actual measured effect of the buffer type valve core is also very limited. Therefore, although the mold locking pressure has dropped during this process, due to the large flow rate, the valve core of the oil return cartridge valve V59 is still opening fast, and the oil impact during this pressure relief process is still large;

[0006] 2) Since the two-stage clamping pressure relief is based on the product process, there are many uncertainties. For example, some product processes require constant pressure maintenance, some products end cooling after injection pressure maintenance, and some products should not have too much clamping pressure drop after pressure maintenance. These situations make the early pressure relief function unusable, or occupy the production cycle after use, or the secondary pressure relief sound is still very loud after use, resulting in the inability of the two-stage pressure relief to fully cover the application;

[0007] 3) The final large-flow pressure relief in the two-stage clamping pressure relief still returns directly to the oil tank. There is a lack of energy absorption, the vibration caused by the impact is still relatively obvious, the oil return noise is still relatively obvious, and the cleanliness of the oil in the oil tank is also poor. Summary of the invention

[0008] The technical problem to be solved by the present invention is to provide a differential mold locking pressure relief oil circuit for a two-platen injection molding machine, which makes the mold locking pressure relief process smooth, the oil impact is small, and the oil return noise is low. It takes into account the mold breaking action and can quickly open the cartridge valve during the mold breaking action. It has no impact on the oil tank, so that the oil cleanliness is better. Its mold locking pressure relief has no effect on other actions and can cover comprehensive applications.

[0009] The technical solution adopted by the present invention to solve the above technical problems is: a differential locking mold pressure relief oil circuit for a two-plate injection molding machine, characterized in that: it includes a cartridge valve with a valve core of 1:1, a first two-position two-way electromagnetic reversing valve, a second two-position two-way electromagnetic reversing valve and an oil tank; the bottom working oil port of the cartridge valve is connected to the locking cavity of the locking cylinder and the side working oil port of the cartridge valve is connected to the mold breaking cavity of the locking cylinder to form a main channel oil circuit; when the electromagnet of the second two-position two-way electromagnetic reversing valve is energized, the pilot port of the cartridge valve passes through the first damping, the third damping, the fourth damping, the channel from the oil inlet to the oil return port of the second two-position two-way electromagnetic reversing valve, and the fifth damping to reach the side working oil port of the cartridge valve to form a first pilot control oil circuit, and the bottom working oil port of the cartridge valve passes through the second damping, the fourth damping, the first damping, the second two-position two-way electromagnetic reversing valve, and the second two-position two-way electromagnetic reversing valve. The passage from the oil inlet of the second two-position two-way electromagnetic reversing valve to the oil return port and the fifth damper to the side working oil port of the cartridge valve constitute the second pilot control oil circuit; when the electromagnet of the first two-position two-way electromagnetic reversing valve is energized, the pilot port of the cartridge valve sequentially passes through the first damper and the passage from the oil inlet of the first two-position two-way electromagnetic reversing valve to the oil return port to reach the oil tank to constitute the third pilot control oil circuit; during the mold locking pressure relief action, the first pilot control oil circuit and the second pilot control oil circuit are used to slowly open the cartridge valve, and the oil flows from the mold locking cavity of the mold locking cylinder to the mold breaking cavity of the mold locking cylinder to realize the differential mold locking pressure relief of the two cavities of the mold locking cylinder; during the mold breaking action, the third pilot control oil circuit is used to quickly open the cartridge valve, and the oil flows from the mold locking cavity of the mold locking cylinder to the mold breaking cavity of the mold locking cylinder to realize differential mold breaking.

[0010] The differential clamping pressure relief oil circuit also includes a small flow overflow valve, the pilot port of the cartridge valve is connected to the oil inlet of the first two-position two-way electromagnetic reversing valve, and the first damping is arranged near the pilot port of the cartridge valve on the connecting pipeline, the oil return port of the first two-position two-way electromagnetic reversing valve is connected to the oil tank, the oil inlet of the overflow valve is connected to the clamping cavity of the clamping cylinder, the oil outlet of the overflow valve is connected to the oil inlet of the second two-position two-way electromagnetic reversing valve, the oil return port of the second two-position two-way electromagnetic reversing valve is connected to the mold breaking cavity of the clamping cylinder, and the connecting pipeline is close to the first damping. The fifth damper is arranged at the oil return port of the second two-position two-way solenoid reversing valve, the bottom working oil port of the cartridge valve is connected with the oil outlet of the overflow valve, and the second damper and the fourth damper are arranged in sequence on the connecting pipeline, the bottom working oil port of the cartridge valve is connected with the pilot port of the cartridge valve, and the third damper is arranged on the connecting pipeline, one end of the third damper is located between the first damper and the oil inlet of the first two-position two-way solenoid reversing valve, and the other end of the third damper is located between the second damper and the fourth damper.

[0011] The pressure of the overflow valve is set to 30 bar.

[0012] The clamping piston in the clamping cylinder and the hose channels of the clamping cavity and the mold breaking cavity of the clamping cylinder are all flexible devices. When the clamping pressure relief is in action, the high-pressure oil in the clamping cavity is released to the mold breaking cavity through the cartridge valve, and is buffered and vibration-absorbed by the clamping piston and the hose channel, thereby reducing the impact and noise during the clamping pressure relief, and realizing flexible clamping pressure relief.

[0013] The pressure difference at both ends of the first damper is controlled within 30 bar. The pressure difference at both ends of the first damper (i.e. the pilot port of the cartridge valve, i.e., port C, and the pressure difference at both ends of the first damper) can be obtained by the relationship between the pressure difference at both ends of the damper and the cross-sectional area through the liquid resistance calculation formula. Figure 2 The pressure difference between the middle point D) is selected for the first damping, the second damping, the third damping, the fourth damping and the fifth damping, so that the two ends of the first damping can always maintain a lower pressure difference. In order to take into account the speed of clamping pressure relief, the pressure difference at both ends of the first damping is preferably controlled within 30bar.

[0014] Compared with the prior art, the advantages of the present invention are:

[0015] 1) Regardless of whether the electromagnet of the second two-position two-way solenoid reversing valve is energized or the electromagnet of the first two-position two-way solenoid reversing valve is energized, or the electromagnet of the first two-position two-way solenoid reversing valve and the electromagnet of the second two-position two-way solenoid reversing valve are energized at the same time, the oil flows from the clamping cavity to the mold breaking cavity, and does not directly return to the oil tank, which greatly reduces the pressure difference between the two cavities of the clamping cylinder.

[0016] 2) When the mold locking pressure relief action is in action, the electromagnet of the second two-position two-way solenoid reversing valve is energized, and the pilot port of the cartridge valve, namely port C, always maintains a low pressure difference at both ends of the first damping. When the pressure difference at both ends of the first damping is low, the flow rate is small, and the opening speed of the valve core of the cartridge valve is relatively slow. The high-pressure oil in the mold locking cavity will not flow out of control when it flows to the mold breaking cavity, thereby making the entire mold locking pressure relief process smooth, with small oil impact and low oil return noise.

[0017] 3) The mold breaking action is taken into consideration at the same time. When the mold breaking action occurs, the electromagnet of the first two-position two-way electromagnetic reversing valve is energized, and the pilot port of the cartridge valve, namely port C, returns to the oil tank through the first damping. Because it only passes through one damping, namely the first damping, and the first damping reduces its flow rate by reducing the pressure difference by the damping combination during the mold locking pressure relief action, the first damping selection does not need to be very small, so the flow rate of the pilot control oil circuit of the cartridge valve is relatively large, the cartridge valve can be opened quickly, and the oil flows from the mold locking cavity to the mold breaking cavity. And because the mold breaking cavity is a rodless cavity, its area is larger than the mold locking cavity, thereby realizing differential mold breaking.

[0018] 4) The two-chamber differential pressure relief of the clamping cylinder has no impact on the oil tank, making the oil cleanliness better.

[0019] 5) The principle of two-chamber differential pressure relief of the clamping cylinder is more reasonable, has no effect on other actions, and can cover all applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the existing clamping pressure relief oil circuit;

[0021] Figure 2 It is a schematic diagram of the differential clamping pressure relief oil circuit of the present invention;

[0022] Figure 3 It is a simplified schematic diagram of the hydraulic principle of the first pilot control oil circuit and the second pilot control oil circuit in the differential clamping pressure relief oil circuit of the present invention. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below with reference to the accompanying drawings.

[0024] The present invention proposes a differential clamping pressure relief oil circuit for a two-platen injection molding machine, such as Figure 2As shown, it includes a cartridge valve V1 with a valve core of 1:1, a first two-position two-way electromagnetic reversing valve V2, a second two-position two-way electromagnetic reversing valve V3 and an oil tank 20; the bottom working oil port of the cartridge valve V1, namely the port A, is connected to the clamping cavity 211 of the clamping cylinder 21, and the side working oil port of the cartridge valve V1, namely the port B, is connected to the mold breaking cavity 212 of the clamping cylinder 21 to form a main channel oil circuit; when the electromagnet of the second two-position two-way electromagnetic reversing valve V3 is energized, the cartridge valve V1 The pilot port, i.e., port C, passes through the first damper ZN1, the third damper ZN3, the fourth damper ZN4, the oil inlet port of the second two-position two-way solenoid reversing valve V3, i.e., port P, to the oil return port, i.e., port T, and the fifth damper ZN5 to the side working oil port, i.e., port B, of the cartridge valve V1 to form the first pilot control oil circuit. The bottom working oil port, i.e., port A, of the cartridge valve V1 passes through the second damper ZN2, the fourth damper ZN4, the oil inlet port of the second two-position two-way solenoid reversing valve V3, i.e., port T, and the fifth damper ZN5 to form the first pilot control oil circuit. The passage from the oil port, i.e., the P port, to the oil return port, i.e., the T port, and the fifth damper ZN5 to the side working oil port, i.e., the B port, of the cartridge valve V1 constitutes the second pilot control oil circuit; when the electromagnet of the first two-position two-way solenoid reversing valve V2 is energized, the pilot port, i.e., the C port, of the cartridge valve V1 passes through the first damper ZN1 and the oil inlet, i.e., the P port, of the first two-position two-way solenoid reversing valve V2 to the oil return port, i.e., the T port, in turn, to the oil tank 20 to constitute the third pilot control oil circuit; clamping pressure relief action During mold breaking, the third pilot control oil circuit is used to open the cartridge valve V1 quickly, and the oil flows from the mold locking cavity 211 of the mold locking cylinder 21 to the mold breaking cavity 212 of the mold locking cylinder 21 to realize differential mold breaking.

[0025] Figure 3 The simplified schematic diagram of the hydraulic principle of the first pilot control oil circuit and the second pilot control oil circuit is given. The first pilot control oil circuit: the pilot port of the cartridge valve V1, i.e., port C, passes through the first damper ZN1 to Figure 2 The middle point D is reached after passing through the third damper ZN3 Figure 2 The middle point E, through the fourth damper ZN4, reaches Figure 2 The oil path of the second pilot control oil circuit is from the bottom working oil port of the cartridge valve V1, i.e., port A, through the second damper ZN2 to the side working oil port of the cartridge valve V1. Figure 2 The middle point E, through the fourth damper ZN4, reaches Figure 2At point F, it passes through the fifth damper ZN5 and reaches the side working oil port of the cartridge valve V1, namely port B. When the mold locking pressure relief action starts, the pressure of the bottom working oil port of the cartridge valve V1, namely port A, is the mold locking pressure, and because the valve core of the cartridge valve V1 is a 1:1 valve core, the pressure of the pilot port of the cartridge valve V1, namely port C, is also the mold locking pressure. The side working oil port of the cartridge valve V1, namely port B, is connected to the mold breaking cavity 212, and the pressure is zero.

[0026] In this embodiment, the differential clamping pressure relief oil circuit also includes a small flow relief valve V4, the pressure of the relief valve V4 is set to 30 bar, the pilot port of the cartridge valve V1, namely the C port, is connected to the oil inlet port of the first two-position two-way electromagnetic reversing valve V2, namely the P port, and the first damping ZN1 is set near the pilot port of the cartridge valve V1, namely the C port, on the connecting pipeline, the oil return port of the first two-position two-way electromagnetic reversing valve V2, namely the T port, is connected to the oil tank 20, the oil inlet of the relief valve V4 is connected to the clamping cavity 211 of the clamping cylinder 21, the oil outlet of the relief valve V4 is connected to the oil inlet port of the second two-position two-way electromagnetic reversing valve V3, namely the P port, and the oil return port of the second two-position two-way electromagnetic reversing valve V3, namely the T port, is connected to the clamping oil The mold breaking cavity 212 of the cylinder 21 is connected and a fifth damper ZN5 is arranged on the connecting pipeline near the return oil port of the second two-position two-way electromagnetic reversing valve V3, namely, the T port. The bottom working oil port of the cartridge valve V1, namely, the A port, is connected with the oil outlet of the overflow valve V4, and a second damper ZN2 and a fourth damper ZN4 are arranged in sequence on the connecting pipeline. The bottom working oil port of the cartridge valve V1, namely, the A port, is connected with the pilot port of the cartridge valve V1, namely, the C port, and a third damper ZN3 is arranged on the connecting pipeline. One end of the third damper ZN3 is located between the first damper ZN1 and the oil inlet port of the first two-position two-way electromagnetic reversing valve V2, namely, the P port, and the other end of the third damper ZN3 is located between the second damper ZN2 and the fourth damper ZN4.

[0027] In this embodiment, the mold locking piston (not shown in the figure) in the mold locking cylinder 21 and the hose channels (not shown in the figure) of the mold locking cavity 211 and the mold breaking cavity 212 of the mold locking cylinder 21 are flexible devices. When the mold locking pressure relief action is performed, the high-pressure oil in the mold locking cavity 211 is released to the mold breaking cavity 212 through the cartridge valve V1, and is buffered and vibration-absorbed by the mold locking piston and the hose channel, thereby reducing the impact and noise during the mold locking pressure relief, and realizing flexible mold locking pressure relief.

[0028] In this embodiment, the pressure difference at both ends of the first damper ZN1 is controlled within 30 bar. Based on the relationship between the pressure difference at both ends of the damper and the cross-sectional area, the pressure difference at both ends of the first damper ZN1 (i.e., the pressure difference between the pilot port C of the cartridge valve V1 and the Figure 2The pressure difference between the middle point D) is determined by selecting appropriate sizes for the first damping ZN1, the second damping ZN2, the third damping ZN3, the fourth damping ZN4 and the fifth damping ZN5, so that the two ends of the first damping ZN1 are always maintained at a relatively low pressure difference. In order to take into account the speed of clamping pressure relief, the pressure difference at both ends of the first damping ZN1 is preferably controlled within 30 bar.

[0029] In this embodiment, the first two-position two-way electromagnetic reversing valve V2 acts as a switch valve, and the second two-position two-way electromagnetic reversing valve V3 acts as a pressure relief valve; the damping hole sizes of the first damping ZN1, the second damping ZN2, the third damping ZN3, the fourth damping ZN4, and the fifth damping ZN5 can be determined by combined adjustment so that the pressure difference at both ends of the first damping ZN1 can be controlled within 30 bar.

Claims

1. A differential clamping pressure relief oil circuit for a two-platen injection molding machine, characterized in that: It includes a cartridge valve with a valve core of 1:1, a first two-position two-way electromagnetic reversing valve, a second two-position two-way electromagnetic reversing valve and an oil tank; the bottom working oil port of the cartridge valve is connected to the locking cavity of the locking cylinder, and the side working oil port of the cartridge valve is connected to the mold breaking cavity of the locking cylinder to form a main channel oil circuit; when the electromagnet of the second two-position two-way electromagnetic reversing valve is energized, the pilot port of the cartridge valve passes through the first damping, the third damping, the fourth damping, the channel from the oil inlet to the oil return port of the second two-position two-way electromagnetic reversing valve, and the fifth damping to reach the side working oil port of the cartridge valve to form a first pilot control oil circuit, and the bottom working oil port of the cartridge valve passes through the second damping, the fourth damping, the channel from the oil inlet to the oil return port of the second two-position two-way electromagnetic reversing valve, the fifth damping to reach the side working oil port of the cartridge valve in sequence. The damping reaches the side working oil port of the cartridge valve to form a second pilot control oil circuit; when the electromagnet of the first two-position two-way electromagnetic reversing valve is energized, the pilot port of the cartridge valve sequentially passes through the first damping, the oil inlet of the first two-position two-way electromagnetic reversing valve to the oil return port to reach the oil tank to form a third pilot control oil circuit; when the mold locking pressure relief action is performed, the first pilot control oil circuit and the second pilot control oil circuit are used to slowly open the cartridge valve, and the oil flows from the mold locking cavity of the mold locking cylinder to the mold breaking cavity of the mold locking cylinder to realize the differential mold locking pressure relief of the two cavities of the mold locking cylinder; when the mold breaking action is performed, the third pilot control oil circuit is used to quickly open the cartridge valve, and the oil flows from the mold locking cavity of the mold locking cylinder to the mold breaking cavity of the mold locking cylinder to realize differential mold breaking.

2. The differential clamping pressure relief oil circuit for a two-platen injection molding machine according to claim 1, characterized in that: The differential clamping pressure relief oil circuit also includes a small flow overflow valve, the pilot port of the cartridge valve is connected to the oil inlet of the first two-position two-way electromagnetic reversing valve, and the first damping is arranged near the pilot port of the cartridge valve on the connecting pipeline, the oil return port of the first two-position two-way electromagnetic reversing valve is connected to the oil tank, the oil inlet of the overflow valve is connected to the clamping cavity of the clamping cylinder, the oil outlet of the overflow valve is connected to the oil inlet of the second two-position two-way electromagnetic reversing valve, the oil return port of the second two-position two-way electromagnetic reversing valve is connected to the mold breaking cavity of the clamping cylinder, and the connecting pipeline is close to the first damping. The fifth damper is arranged at the oil return port of the second two-position two-way solenoid reversing valve, the bottom working oil port of the cartridge valve is connected with the oil outlet of the overflow valve, and the second damper and the fourth damper are arranged in sequence on the connecting pipeline, the bottom working oil port of the cartridge valve is connected with the pilot port of the cartridge valve, and the third damper is arranged on the connecting pipeline, one end of the third damper is located between the first damper and the oil inlet of the first two-position two-way solenoid reversing valve, and the other end of the third damper is located between the second damper and the fourth damper.

3. The differential clamping pressure relief oil circuit for a two-platen injection molding machine according to claim 2, characterized in that: The pressure of the relief valve is set to 30 bar.

4. A differential clamping pressure relief oil circuit for a two-platen injection molding machine according to any one of claims 1 to 3, characterized in that: The clamping piston in the clamping oil cylinder and the hose passages of the clamping cavity and the demolding cavity of the clamping oil cylinder adopt flexible devices.

5. The differential clamping pressure relief oil circuit for a two-platen injection molding machine according to claim 4, characterized in that: The pressure difference between the two ends of the first damper is controlled within 30 bar.

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