JPH0339223Y2 - - Google Patents

Description

[Detailed explanation of the idea] [Technical field to which the invention belongs] The present invention relates to a mold protection device for an injection molding machine.

[Prior art]

Conventionally, the hydraulic circuit is configured to switch to low speed and low pressure slightly before the movable mold advances at high speed and comes into contact with the stationary mold, so that if there is a foreign object between the two molds, the two molds will not contact each other. There is a mold protection device that sounds a buzzer after a certain period of time to notify the operator of an abnormality and prevent damage to the mold. This method is an excellent device in that it can detect the cause of damage to the mold before the mold clamping pressure is increased.However, in today's precision molding world, the inventor found that there were problems that could not be solved with such a protection device alone. Ta.

That is, when both the fixed and movable mold clamps are held by high-pressure mold clamping and then high-pressure molten resin is injected into the cavities of both molds by injection operation, the parting of both molds is performed after filling is completed and the pressure holding process begins. The surfaces always open slightly and separate, and then the parting surface closes as the resin contracts. If the amount of resin injected at this time is too large or the mold clamping force is weak, the resin will flow out from the parting surface and foreign matter in the form of burrs will be generated, and this burr will be removed when the molds try to close again after injection is completed. This may be caught by high mold clamping force on the parting surface, damaging the cavity end. This is a particularly serious problem when using molds for forming precision molded parts that are expensive and cannot be modified.

[Purpose of invention]

The present invention was developed from this point of view, and its purpose is to fill the cavities of fixed and movable molds with molten resin after mold clamping, then monitor for burrs during the pressure holding process, and when burrs are found, remove the mold. It is an object of the present invention to provide a mold protection device for an injection molding machine that reduces or eliminates the hydraulic pressure for tightening.

[Key points of the idea]

The mold protection device of the injection molding machine in this invention is as follows:
A detection means for detecting the amount of mold opening that is opened by the injection force when a cavity formed by a fixed mold and a movable mold is injected and filled with molten resin, and a permissible mold opening amount of the mold opening amount is set. The setting device and the value detected by the mold opening amount detection means and the set value set in the setting device are used as a signal from the comparator to switch the solenoid valve to zero the mold clamping force of the mold clamping cylinder or to reduce the mold clamping force. It is characterized by consisting of an electromagnetic pressure reducing valve.

[Example of idea]

FIG. 1, which shows an embodiment of the present invention, will be described below. Movable mold 12 fixed to mounting plate 11
moves forward and backward with respect to the fixed mold 16 fixed to the mounting plate 15 by the piston 14 moving within the mold clamping cylinder 13, and when both the molds 12 and 16 are in close contact with each other as shown in the figure, the A cavity 17 is formed on the opposing surface. The mold clamping cylinder 13 is selectively connected to a hydraulic source 18 such as a pump and a tank 19 via an electromagnetic switching valve 20, and the discharge side of the hydraulic source 18 is controlled to a set pressure by a pressure control valve 21 and is connected to an electromagnetic switching valve. It is designed to be connected to the tank 19 via a valve 22 when necessary.

A mounting rod 26 is fixed to the mounting plate 15 on the fixed mold 16 side along the forward and backward direction of the movable mold.
A linear scale 27 for detecting the opening amount of the mold is attached to the tip of 6. A detection head 28 for reading the linear scale 27 is fixed to the mounting plate 11 of the movable mold 12, and the output signal of the detection head 28 is sent to a counter 29.

A pressure sensor 30 is provided in the pressure chamber 13A to detect when the movable mold 12 advances and comes into close contact with the fixed mold 16 and the hydraulic pressure in the pressure chamber 13A of the mold clamping cylinder 13 reaches a constant value. When the detection signal is sent to the counter 29, the counter 29 clears the previous count and continues counting thereafter.
The output signal of the counter 29 is sent to a comparator 31, where it is compared with the setting value of the allowable opening amount setter 32 of the mold parting surface, and when the two match, the matching signal is amplified by the amplifier 33, and then Solenoid switching valve 22
is switched from the illustrated state to the right chamber, and the discharge side of the hydraulic power source 18, that is, the pressure chamber 13A, is connected to the tank 19.

Next, the operation of the embodiment described above will be explained. Since the electromagnetic switching valve 20 is switched to the right chamber during mold clamping, the hydraulic pressure from the hydraulic power source 118 acts on the pressure chamber 13A of the mold clamping cylinder 13, so that both molds 12 and 16 are in close contact with each other. In this state, when the oil pressure in the pressure chamber 13 reaches the mold clamping pressure, the pressure sensor 30 issues a detection signal, and the counter 29 clears the previous count and continues counting thereafter.

Injection is started by the operation of the pressure sensor 30, and the cavity 17 is filled with molten resin (not shown). Then, when the pressure holding process begins, the movable mold 12 opens slightly and the mounting plate 11 retreats (left side). )
The partying surface opens. The opening amount of the parting surface is counted by a counter 29 by a linear scale 27 and a detection head 28, and the count value and the setting value of the allowable opening amount setting device 32, that is, the opening amount that causes burrs, are determined by a comparator 31. When the two values are compared, the comparator 31 issues a one-value signal, which is amplified by the amplifier 33 to switch the electromagnetic switching valve 22 from the illustrated state to the right ventricle. As a result, the pressure chamber 13A of the mold clamping cylinder 13 is connected to the tank 19, and the mold clamping force becomes zero.

In the above explanation, the mold clamping force of the mold clamping cylinder 13 was made zero by the electromagnetic switching valve 22, but an electromagnetic pressure reducing valve (not shown) is provided in place of the electromagnetic switching valve 22 to reduce the pressure in the pressure chamber 13A. You can also do this.

FIG. 2 shows another version of the present invention. Whereas in the first embodiment described above, the opening amount of the parting surface was detected using a linear scale and a detection head, in this embodiment, a fixed body 51 is fixed to the movable mold 12 and an electric micrometer 52 is attached to the fixed mold 16. The tip of the electric micrometer is compressed to some extent when both molds 12 and 16 are clamped. The output of the electric micrometer 52 is added to the counter 29, and the counter 29 is applied to the pressure sensor 3.
It is cleared by a detection signal of 0. The operation is the same except that the linear scale and detection head shown in FIG. 1 are replaced with a fixed body 51 and an electric micrometer 52, so a description thereof will be omitted.

[Effect of idea]

As explained above, the mold protection device for an injection molding machine according to the present invention includes a means for detecting the mold opening amount between the fixed mold and the movable mold, and compares this detection signal with the allowable mold opening amount. When the two match, the mold clamping pressure of the mold clamping cylinder is set to zero or reduced by the matching signal, so there is no burr generation and there is no risk of damaging the mold.

[Brief explanation of the drawing]

FIG. 1 is a partially sectional view of the mechanism of one embodiment of the present invention, and FIG. 2 is a partially sectional view of the mechanism of another embodiment of the present invention. 12...Moving mold, 13...Mold clamping cylinder, 1
6...Fixed mold, 27...Linear scale, 28
...Detection head, 22...Solenoid switching valve, 31...
Comparator, 32... Permissible opening setting device, 52... Electric micrometer.

Claims (1)

[Scope of utility model registration request] A detection means for detecting the amount of mold opening that is opened by the injection force when a cavity formed by a fixed mold and a movable mold is injected and filled with molten resin, and a permissible mold opening amount of the mold opening amount is set. a setter that compares the value detected by the mold opening amount detection means with a set value set in the setter, and a comparator that issues a signal when the two match; A mold protection device for an injection molding machine comprising an electromagnetic switching valve that reduces the mold clamping force to zero or an electromagnetic pressure reducing valve that reduces the mold clamping force.