JPH08150647A - Mold clamping device in injection molding machine - Google Patents

Abstract

PURPOSE: To depressurize the oil chamber of a mold clamping cylinder at the stop time of an oil pressure pump by providing a shut-off valve to the branch pipe between an opening and closing valve for confining pressure in the mold clamping cylinder and the pilot opening and closing valve for controlling the opening and closing thereof. CONSTITUTION: The branch circuit 18 communicating with an oil tank 7 from the pilot circuit connecting an opening and closing valve 12 holding a state confining pressure in a mold clamping cylinder 2 and a pilot opening and closing valve 13 is provided. A shut-off valve 17 becoming an excited/non-excited state in connection with the ON/OFF operation of an oil pressure pump and closing the branch circuit 18 at the time of non-excitation is provided to the branch circuit 18. In this oil pressure circuit, the shut-off valve 17 becomes a non-excited state when a power supply is cut off during molding operation and the oil pressure pump is turned OFF and the branch circuit 18 communicates with the oil tank 7. Therefore, the pressure oil in the oil chamber 6 of the mold clamping cylinder is returned to the oil tank 7 from the pipeline 9 connecting a solenoid changeover valve 10 and the mold clamping cylinder 2 through the branch circuit 18 and the unnecessary pressure in the oil chamber 6 of the mold clamping cylinder can be released and the life of the apparatus can be extended.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit for controlling a mold clamping cylinder of an injection molding machine, and more particularly to a mold for an injection molding machine provided with a hydraulic circuit for keeping pressure in the mold clamping cylinder. Regarding improvement of fastening device.

[0002]

2. Description of the Related Art A conventional apparatus will be described with reference to FIG. 2. Reference numeral 1 is a mold clamping device, and a mold clamping ram 5 having a movable platen 4 having a movable mold 3 attached to one end thereof is fixed to a mold clamping cylinder 2 so as to be movable back and forth. It is worn. A pre-fill valve 8 is provided between the oil chamber 6 of the mold clamping cylinder 2 and the oil tank 7, so that communication and cutoff of the oil chamber 6 and the oil tank 7 are controlled by a hydraulic circuit (not shown). Has become.

A pipe line 9 is provided in the oil chamber 6, and the other end can be selectively switched to a hydraulic pressure source 11 and an oil tank 7 via an electromagnetic switching valve 10. A logic valve 12, which is an opening / closing valve for maintaining pressure in the mold clamping cylinder, is provided between the mold clamping cylinder 2 and the electromagnetic switching valve 10 for boosting and depressurizing the pipe line 9. This logic valve 12 is opened and closed by the pilot circuit 1 which branches from the pipe line 9.
4 and the pilot check valve 13 communicating with the pilot circuit 14. The pilot circuit 15 of the pilot check valve 13 uses the logic valve 1
It branches from the upstream of 2. Reference numeral 16 is a pressure sensor for detecting the oil pressure in the oil chamber 6.

The above-mentioned structure is described below. Next, the operation and operation will be described. When the electromagnetic switching valve 10 is set to the a position during mold clamping, the pressure oil from the hydraulic pressure source 11 is supplied to the pilot circuit 15.
Since the check valve 13 is actuated via the check valve 13 and is in the "open" state, the pilot circuit 14 of the logic valve 12 is connected to the oil tank 7 through the check valve 13 in the "open" state, Pressure oil from source 11 is logic valve 12
Is pushed open to allow the pressure oil to flow into the oil chamber 6 from the pipe line 9, and the movable platen 4 is moved forward in the right direction in the drawing by the die opening / closing cylinder attached to the fixed platen (not shown). When the movable platen 4 moves forward, the inside of the oil chamber 6 becomes a negative pressure state, and a large amount of pressure oil is introduced into the oil chamber 6 from the pre-fill valve 8 in the “open” state.

When the movable platen 4 moves forward and comes into contact with a fixed mold (not shown), the prefill valve 8 which has been open until now is closed by a signal from a mold closing completion switch (not shown) and the hydraulic power source 11 Since the pressure oil from 1 continues to act in the oil chamber 6, the pressure increase in the oil chamber 6 is started. When the pressure sensor 16 detects a preset pressure in the oil chamber 6, the electromagnetic switching valve 1
Since 0 is in the neutral position and the other end of the pipeline 9 is connected to the oil tank 7, there is no pressure oil acting on the pilot circuit 15 of the check valve 13 and the check valve 13 is in the "closed" state, so the logic valve The oil pressure in the oil chamber 6 acts on the pilot circuit 14 of 12 through the pipe line 9, the logic valve 12 is in the “closed” state, and the pressure oil from the oil pressure source 11 into the oil chamber 6 is in the oil chamber 6. The internal pressure of the oil chamber 6 becomes closed.

The molten resin is injected into the mold by the injection step following this mold clamping pressure increase, and after the molten resin is cooled and cured,
When the product is taken out from the mold, the pre-fill valve 8 is opened by the control hydraulic circuit of the pre-fill valve 8 (not shown), the pressure in the closed state is released into the oil chamber 6, and then the solenoid switching valve is opened. 10 is at the b position, and the movable platen 4 is retracted (moved to the left in the drawing) by a mold opening / closing cylinder (not shown) to open the mold.

[0007]

[Problems to be Solved by the Invention]
There is no problem in sequence operation of repeating depressurization and then mold opening.However, for example, when stopping the machine operation during lunch break etc., if the driver stops the machine with the mold open, the mold cavity Since the surface is scratched, turn off the power after closing the mold (hence turning off the hydraulic pump).
I am trying. However, in this case, since a signal such as a limit switch for completion of mold closing is transmitted, the machine is stopped while the pressure inside the oil chamber 6 is increased, and if the machine is stopped for a long time, the mold Alternatively, the machine itself is always subjected to a strong mold clamping force, which has the drawback of reducing its life.

The object of the present invention is to eliminate the above-mentioned drawbacks and to provide a hydraulic circuit in which the pressure is not confined in the oil chamber of the mold clamping cylinder even if the hydraulic pump is stopped by turning off the power during the molding operation. An object is to provide a mold clamping device for an injection molding machine.

[0009]

In order to achieve the above-mentioned object, a switching valve for switching between mold clamping pressure increasing and pressure releasing operations is provided in a control hydraulic circuit of a mold clamping cylinder of an injection molding machine. An on-off valve for keeping pressure in the mold clamping cylinder in a pipeline connecting the mold clamping cylinder and a pilot circuit branched from the pipeline for controlling opening and closing of the on-off valve, and the pilot circuit In a mold clamping device of an injection molding machine provided with a hydraulic circuit having a pilot opening / closing valve communicating with a branch opening communicating with an oil tank branching from a pipeline connecting between the opening opening valve of the hydraulic circuit and the pilot opening opening valve. A shut-off valve that is provided with a circuit and is energized / de-energized in conjunction with ON / OFF of the hydraulic pump for generating the mold clamping force of the injection molding machine in the same branch circuit and opens the circuit when de-energized. By providing the mold clamping device of an injection molding machine according to claim.

[0010]

According to the present invention, when the power is turned off, that is, when the hydraulic pump is turned off, the shut-off valve is de-excited so that the shut-off valve is not connected to the pilot on-off valve. Since the branch circuit that branches is connected to the oil tank,
The pressure oil in the mold clamping cylinder can return to the oil tank from the pipe connecting the switching valve and the mold clamping cylinder to the oil tank via the branch circuit, and the pressure in the oil chamber of the mold clamping cylinder can be released. You can

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, one embodiment of the present invention will be described with reference to FIG. In the description, members that are the same as those in the conventional device are denoted by the same reference numerals, the description thereof will be omitted, and only newly added members will be denoted by new numbers. The configuration of the present invention is provided with a branch circuit 18 connecting from the pilot circuit connecting the on-off valve 12 and the pilot on-off valve 13 of FIG. 2 to the oil tank 7, and the branch circuit 18 is excited / excited in conjunction with ON / OFF of the hydraulic pump. The hydraulic circuit is provided with a shut-off valve 17 that is de-energized and opens the circuit when de-energized.

Since the mold clamping device of the injection molding machine having the hydraulic circuit as described above is used, the shutoff valve 17 is provided when the power is turned off during the molding operation, that is, when the hydraulic pump is turned off. Since the branch circuit 18 that is de-excited and branches from the pilot circuit 14 that connects between the on-off valve 10 and the on-off valve with a pilot circuit 13 communicates with the oil tank 7, the pressure oil in the mold clamping cylinder oil chamber 6 is Solenoid switching valve 10
The branch circuit 1 from the pipe line 9 that connects the mold clamping cylinder 2 and
After returning to the oil tank 7 via 8, the pressure in the mold clamping cylinder oil chamber 6 can be released.

[0013]

As described above, according to the present invention, the hydraulic circuit is provided so that the pressure is not closed in the oil chamber of the mold clamping cylinder even when the hydraulic pump is turned off during the molding operation. The listed drawbacks are removed.

[Brief description of drawings]

FIG. 1 is a diagram of a mold clamping device showing an embodiment of the present invention.

FIG. 2 is a view showing a conventional mold clamping device.

[Explanation of symbols]

 1 mold clamping device 2 mold clamping cylinder 3 moving mold 4 moving plate 5 mold clamping ram 6 mold clamping cylinder oil chamber 7 oil tank 8 prefill valve 9 conduit 10 electromagnetic switching valve 11 hydraulic power source 12 logic valve (open / close valve) 13 Pilot check valve (pilot opening / closing valve) 14 Pilot circuit 16 Pressure detector 17 Shut-off valve 18 Branch circuit

Claims (1)

[Claims] 1. A switching valve for switching between mold clamping pressure increasing and pressure releasing operations is provided in a hydraulic circuit for controlling a mold clamping cylinder of an injection molding machine, and mold clamping is performed in a pipe line connecting the switching valve and the mold clamping cylinder. Hydraulic pressure having an on-off valve for keeping the pressure in the cylinder closed and a pilot circuit branching from the pipeline controlling the opening and closing of the on-off valve, and a pilot on-off valve communicating with the pilot circuit In a mold clamping device of an injection molding machine provided with a circuit, a branch circuit communicating with an oil tank branched from a pipe line connecting the opening / closing valve of the hydraulic circuit and the pilot opening / closing valve is provided, and the injection molding machine is provided in the branch circuit. ON / OFF of hydraulic pump to generate mold clamping force
A mold-clamping device for an injection molding machine, which is provided with a shut-off valve that opens / closes the circuit when excited / de-energized in conjunction with turning off.