JPH0140614Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a hydraulic system for opening and closing a mold of a molding machine and strongly clamping the mold.

In this type of hydraulic system, a reduction in mold clamping force due to hydraulic pressure leakage during strong mold clamping is prevented by using a pressure compensating device such as a pressure retention pump or an accumulator.

However, the use of a pressure holding pump in combination complicates the hydraulic circuit and control circuit, and increases costs. In the case of an accumulator, not only is the cost high, but also it takes time to increase the pressure, and in both the case of a pressure holding pump and an accumulator, high pressure oil corresponding to the discharge flow rate is lost.

In addition, in a hydraulic system that moves oil between the mold clamping oil chamber and the auxiliary oil tank connected to the mold clamping oil chamber via a pre-fill valve when opening and closing the mold, when pressure oil flows in and out, It had the disadvantage of producing loud noise and vibration.

This invention attempts to eliminate the above-mentioned conventional drawbacks using extremely simple means. Leakage of pressure oil during strong mold clamping occurs at the sliding seal surface of the switching valve and piston.The switching valve can be prevented by a pilot check valve circuit, but leakage at the sealing surface of the piston can be prevented by special packing. It is said that it is difficult to improve even if Therefore, as mentioned above, a pressure compensating device is used, but this idea does not use a pressure compensating device such as an accumulator, and instead uses two oil chambers separated by a piston in the mold opening/closing cylinder. By communicating with each other via a hydraulic path, leakage of pressure oil during strong mold clamping can be prevented, and the pre-fill valve can be pushed into the mold clamping oil chamber under high pressure to open it, allowing the mold clamping oil chamber to be opened all at once. This is intended to prevent noise and vibration caused by sudden pressure fluctuations when pressure is released.

The feature of this invention for the above purpose is that the inside of the mold opening/closing cylinder is divided into a mold clamping oil chamber and a mold opening oil chamber by a piston integrated with the mold clamping ram, and an auxiliary oil tank is connected to the mold clamping oil chamber via a prefill valve. At the same time, the booster ram is inserted from the rear of the mold opening/closing cylinder into the mold closing cylinder in the mold clamping ram, and the above oil chambers, cylinders, and prefill valves are connected to the hydraulic source and tank by a hydraulic path equipped with a directional control valve. In the mold opening/closing hydraulic system, which is switchably connected to either of the above, a check valve is installed in the mold clamping hydraulic path, and a pilot circuit is installed in the mold opening hydraulic chamber, which is smaller in size and has a lower operating pressure than the prefill valve mentioned above. A pilot check valve connected to the hydraulic path of the pre-fill valve is provided, and a mold clamping hydraulic path and a mold opening hydraulic path are connected from the mold clamping hydraulic path to the mold opening/closing cylinder between both check valves and the mold opening/closing cylinder. It communicates with a hydraulic path provided with a check valve that allows oil to flow into the hydraulic path, and is also provided with means for controlling the discharge of oil from the mold oil opening chamber.

This invention will be explained in detail below using illustrated examples.

In the figure, 1 is a mold opening/closing cylinder, and the inside is partitioned into a mold clamping oil chamber A and a mold opening oil chamber B by a piston 3 integrated with a mold clamping ram 2.
An auxiliary oil tank C equipped with a pre-fill valve 10 is disposed in the tank.

Further, since the opening/closing force may be much smaller than the mold clamping force, the piston pressure receiving area of the mold opening oil chamber B is formed to be much smaller than the piston pressure receiving area of the mold clamping oil chamber A.

A cylinder 4 for high-speed mold closing is formed inside the mold clamping ram 2, and a booster ram 5 is inserted into the cylinder from the rear of the mold opening/closing cylinder 1. Further, a movable platen 7 is connected to the mold clamping ram 2 and moves while being guided by a tie bar 6 provided between the mold opening/closing cylinder 1 and the fixed platen 8. Mold 9 is installed separately.

11 is a directional switching valve for hydraulic path a for mold clamping, hydraulic path d for high-speed mold closing, and hydraulic path b for mold opening, 12 is a directional switching valve for the hydraulic path a, and 13 is a hydraulic pressure for the prefill valve 10. This is a directional valve for road C.

A check valve 14 and a pilot check valve 15 are provided in the hydraulic paths a and b, and the pilot circuit of the pilot check valve 15 is connected to the hydraulic path c of the prefill valve.
It is connected to the circuit and is activated by the circuit pressure.

Further, in the hydraulic paths a and b, a hydraulic path e that communicates the mold clamping oil chamber A and the mold opening oil chamber B is connected to the check valve 1.
4. Disposed between the pilot check valve 15 and the mold clamping cylinder 1. Also, in this hydraulic path e,
Equipped with a check valve 16 that allows oil to flow from the mold clamping hydraulic path A to the mold opening hydraulic path B, and a means for controlling the outflow of pressure oil from the mold opening hydraulic path B to the mold clamping hydraulic path a when the mold is opened. do.

The control means of the embodiment shown in FIG.
The check valve 16 prevents pressure oil from flowing from the hydraulic path b side to the hydraulic path a side, but a small amount of pressure oil always flows through the small passage 17. It's like this.

This small passage 17 is to prevent the pressure in the mold opening oil chamber from increasing during strong mold clamping and to balance the pressure in both chambers, and is preferably formed in the shape of an orifice. By doing so, the amount of oil escaping changes less due to oil temperature, and the amount can be determined by calculation. Further, the cross-sectional area of the small passage 17 varies depending on the inner diameter of the hydraulic cylinder 1.
If the cross-sectional area of the small passage 17 is too large compared to the inner diameter, the amount of oil escaping from the hydraulic path b side during mold opening will increase, making it difficult to increase the mold opening speed. On the other hand, if it is too small, the amount of oil escaping from the hydraulic path b side during strong mold clamping will be restricted, resulting in excessive pressure being generated in the mold opening oil chamber B.

Furthermore, when the mold is opened, a part of the pressure oil in the hydraulic passage b flows into the hydraulic passage a through the small passage 17, but the amount of oil depends on the cross-sectional area of the small passage 17 and the pressure difference between the two chambers. It is decided. Further, at the initial stage of mold opening, there is a large pressure difference due to the resistance of the mold 9, but at this time, a high mold opening speed is not required, so even if some pressure oil escapes, it does not pose a particular problem. Also, the highest speed is required during the middle stage of mold opening, and although it is not desirable for pressure oil to escape, at this time,
Since only a pressure difference sufficient to overcome the sliding resistance in the piston 3, movable platen 7, etc. is generated, the amount of oil escaping is small.

The amount of oil passing through the small passage can be calculated using the following formula.

However, α: flow coefficient F: cross-sectional area of the small passage g: gravitational acceleration γ: specific weight of oil q: flow rate passing through the small passage △P: differential pressure before and after the small passage Next, the operation will be explained. First, directional control valve 1
1 and 13 are operated to open the prefill valve 10 and supply pressure oil to the high-speed closing cylinder 4. Further, the pilot check valve 15 in the hydraulic path b is opened by the hydraulic pressure in the hydraulic path c of the prefill valve 10, and the pressure oil in the mold opening oil chamber B flows out into the tank. As a result, the piston 3 moves together with the mold clamping ram 2 to close the mold 9 at high speed.

When mold closing is completed, the directional control valve 13 is operated to the illustrated state to reduce the pressure in the hydraulic path c and close the prefill valve 10 and pilot check valve 15. Following this operation, the directional switching valve 12 is operated, and pressure oil is supplied from the hydraulic path a to the mold clamping oil chamber A to perform strong mold clamping. Oil chamber A for mold clamping and oil chamber B for mold opening
Since the chambers are in communication with each other through the small passage 17, the pressure in both chambers is balanced and increased, and the mold clamping force is not affected by the leakage of pressure oil from the sealing surface of the piston 3. By closing 14, the mold clamping force is maintained as it is even if the supply of pressure oil from the hydraulic source is cut off.

After the pressure retention is completed, first, the directional switching valve 13 is operated to send pressure oil to the hydraulic path c. As a result, the pilot check valve 15 is first opened, the pressure in the mold opening oil chamber B is released, the check valve 16 is opened due to the differential pressure, and the pressure in the mold clamping oil chamber A is released, and then the prefill valve 10 is opened. be opened. Therefore, it is possible to prevent noise and vibration from occurring when the prefill valve 10 is opened when the mold clamping oil chamber A is in a high pressure state.

Note that the pilot check valve 15 is the prefill valve 1.
The pilot check valve 1 opens before 0.
This is because the valve 5 is smaller than the prefill valve 10, has a lower operating pressure, and has good response performance.

Next, operate the directional control valve 11 to open the hydraulic path d for high-speed mold closing, and connect the hydraulic path b to the oil chamber B for mold opening.
Send pressure oil to open the mold. As a result, the oil in the mold clamping oil chamber A flows out into the auxiliary oil tank C. At this time, a part of the pressure oil in the hydraulic path b flows into the hydraulic path a through the small passage 17, but the cross-sectional area of the small passage 17 is small and does not interfere with the mold opening function as described above.

In the embodiment shown in FIG. 2, the control means for the hydraulic path e and the control means for the oil discharged from the mold opening oil chamber B are configured with a pilot check valve 18. Pilot check valve 18 installed in e.
A pilot circuit is connected to the hydraulic path a side of the hydraulic path e, and when the hydraulic pressure in the hydraulic path a increases, the pilot check valve 18 is opened, and the mold clamping oil chamber A is opened.
and the mold opening oil chamber B are connected via a hydraulic path e.

Therefore, when pressure oil is supplied to the hydraulic path a for mold clamping to increase the pressure in the mold clamping oil chamber A, the opening of the pilot check valve 18 depends on the pressure balance between the two chambers. Pilot check valve 18
By opening the valve, strong mold clamping is performed in a state where pressure increase in the mold opening oil chamber B is prevented, and the mold clamping holding force is not affected by leakage of pressure oil from the sealing surface of the piston 3. Also, when depressurizing the mold clamping oil chamber A, use the hydraulic path a.
Since the pilot check valve 18 is open while the pressure is present, the same operation as in the previous embodiment can be performed by opening the pilot check valve 15. When opening the mold, the pilot check valve 18 closes the hydraulic path b.
The hydraulic path a is cut off, and pressurized oil is supplied from the hydraulic path b to the mold opening oil chamber B to open the mold.

As described above, this device connects the pilot circuit of the pilot check valve 15 of the mold opening hydraulic path b to the hydraulic path c of the prefill valve 10, and also connects the mold opening oil chamber A and the mold opening oil chamber. A check valve 16 is provided in the hydraulic path e that connects both chambers of B, and a mold opening oil chamber B
By controlling the small passage 17 or the check valve 16 that controls the oil discharged from the mold as a pilot check valve 18, the mold clamping force is prevented from being reduced during strong mold clamping, and the prefill valve 10 is opened. Since it reduces the large noise and vibration that occur when the pump is operated, auxiliary devices such as a pressure-holding pump and an accumulator, as well as their hydraulic circuits and control circuits, etc., are not required, and costs can be reduced. In addition, since a pilot check valve, a small passage, a check valve, etc. are used as control means, the structure is simple, there are fewer failures, and mold opening and closing can be performed more quietly than conventional devices.

[Brief explanation of the drawing]

The drawings show a mold opening/closing hydraulic system for a molding machine according to this invention, and FIG. 1 is a circuit diagram of the system, and FIG. 2 is a partial circuit diagram showing another embodiment of the control means. 1... Mold opening/closing cylinder, 2... Mold clamping ram, 3...
...Mold clamping piston, 4...Cylinder for high-speed mold closing,
5... Booster ram, 9... Mold, 10... Prefill valve, 11, 12, 13... Directional switching valve, 1
4, 16... Check valve, 15, 18... Pilot check valve, 17... Small passage, A... Oil chamber for mold clamping, B
...Mold opening oil chamber, C...Auxiliary oil tank, a, b, c,
d, e...Hydraulic path.

Claims (1)

[Scope of utility model registration request] The inside of the mold opening/closing cylinder is divided into a mold clamping oil chamber and a mold opening oil chamber by a piston integrated with the mold clamping ram, and an auxiliary oil tank is connected to the mold clamping oil chamber via a pre-fill valve. Insert the booster ram from the rear into the mold-closing cylinder in the mold clamping ram, and connect the above oil chambers, cylinders, and pre-fill valves so that they can be switched to either the hydraulic power source or the tank using hydraulic paths equipped with directional switching valves. In the mold opening/closing hydraulic system, a check valve is installed in the mold clamping hydraulic path, a pilot circuit is installed in the mold opening hydraulic path, which is smaller in size and has a lower operating pressure than the prefill valve, and a pilot circuit is connected to the hydraulic path of the prefill valve. Each has a check valve,
Between both check valves and the mold opening/closing cylinder, a check valve is provided between the mold clamping hydraulic path and the mold opening hydraulic path, and a check valve that allows oil to flow from the mold clamping hydraulic path to the mold opening hydraulic path. 1. A mold opening/closing hydraulic system for a molding machine, which is connected to the mold opening/closing hydraulic system by a passageway and is provided with means for controlling oil discharge from a mold opening oil chamber.