JPS6343059Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a vacuum evacuation device for a vacuum forming machine that performs injection molding by evacuating the cavity of a mold in the injection molding machine.

Recently, high-speed molding has been attracting attention in the injection molding industry. This is because by injecting the molten resin into the mold in a short period of time, it is possible to prevent defects such as warpage and uneven orientation in the molded product.

However, when injecting at high speed, if the air inside the mold does not escape properly, the air is adiabatically compressed by the resin pressure and becomes high temperature, which burns the resin and causes defects in the molded product.

To prevent this, there is a so-called vacuum forming machine that evacuates the cavity of the mold before injection molding.

This is the mold clamping cylinder 3 as shown in FIG.
Pressure oil is introduced into the interior, and the movable platen 2 is moved toward the fixed platen 1 by the piston 4. When the fixed side mold 5 and the movable side mold 6 are in close contact, the switching valve 9 is opened and the motor 12 is moved. , the mold cavity 21 is evacuated from the vacuum tank 10 evacuated by the vacuum pump 11, and at the same time the mold clamping cylinder 3 is
Injection molding is performed by introducing high-pressure oil into the mold to generate a predetermined mold clamping force.

Therefore, this requires expensive equipment such as a vacuum tank 10, a vacuum pump 11, and a motor 12, and it is also necessary to constantly rotate the motor 12 to maintain the vacuum level of the vacuum tank 10. This causes a problem of power loss.

In order to eliminate these drawbacks of conventional devices, the present invention provides a pneumatic cylinder with a piston that moves along with the movable platen of the vacuum forming machine as a power source to open and close the mold. By evacuating the cavity, the vacuum evacuation device is extremely simplified and the evacuation can be performed rationally.

Its configuration will be explained with reference to FIG.

By the operation of the piston 4 of the mold clamping cylinder 3, the bracket 16 is attached to the movable platen 2 that moves along the tie bar 7.
This bracket 16 and the end of the piston rod 17 of the piston 18 are pivotally connected with a pin 20.

19 is a pneumatic cylinder equipped with a piston 18, and the pneumatic cylinder 19 is appropriately fixed to a fixed part of the device.

A vacuum passage 13 drawn from the cavity 21 of the mold formed between the stationary mold 5 and the movable mold 6 is attached to the cylinder chamber 19' of the pneumatic cylinder 19 via the electromagnetic switching valve 15. It is connected to the vacuum passage 14.

A and b indicate solenoids that perform switching operations of the electromagnetic switching valve 15, and S indicates the stroke of the piston 18.

The effect will be explained.

Pressure oil is introduced into the mold clamping cylinder 3, and the piston 4
The movable platen 2 is moved to bring the movable mold 6 into close contact with the fixed mold 5.

At this time, the electromagnetic switching valve 15 is de-energized and closed.

Then, as the movable platen 2 moves, the piston 18 moves from the dotted line position to the solid line position in the figure.
It moves by a stroke S, and the inside of the cylinder chamber 19' and the inside of the vacuum passage 14 reach a predetermined degree of vacuum.

Then, the solenoid a is energized and the electromagnetic switching valve 15 is
By switching between the two vacuum passages 13 and 14 to communicate with each other, the air inside the cavity 21 of the mold is sucked and a predetermined degree of vacuum is obtained.

At the same time, high pressure oil is introduced into the mold clamping cylinder 3 to generate a predetermined mold clamping force to perform injection molding.

When injection molding is completed, the electromagnetic switching valve 15 is returned to the neutral position.

Once the molded product has been cooled, the solenoid b is energized to open the vacuum passage 14 to the atmosphere and open the mold.

In the above, the degree of vacuum within the mold cavity 21 can be arbitrarily set by appropriately selecting the inner diameter size of the cylinder chamber 19' of the pneumatic cylinder 19.

Note that this device can of course also be used in a toggle type mold clamping device.

The present invention has an extremely simple structure, does not require expensive vacuum tanks, vacuum pumps, or motors, and uses the movement of the movable plate as the power source, and uses commercially available pneumatic cylinders. A predetermined vacuum can be rationally drawn using this pneumatic cylinder as the movable platen is moved. Therefore, the device is inexpensive and has low maintenance and operation costs, which in turn makes it possible to lower the unit price of the molded product.

[Brief explanation of drawings]

FIG. 1 is a vertical side view of a conventional device, and FIG. 2 is a vertical side view of the device of the present invention. 1...Fixed plate, 2...Movable plate, 5...Fixed side mold, 6...Movable side mold, 13...Vacuum passage,
14... Vacuum passage, 15... Solenoid switching valve, 1
6...Bracket, 17...Piston rod, 1
8...Piston, 19...Pneumatic cylinder, 1
9'...Cylinder chamber, 20...Pin.

Claims (1)

[Scope of utility model registration request] A bracket 16 is fixed to the movable platen 2, and the piston 1 of the pneumatic cylinder 19 is connected to the bracket 16.
Piston rod 17 end of 8 is pivotally connected to movable platen 2.
The mold cavity 2 is formed between the movable mold 6 provided on the fixed plate 1 and the fixed mold 5 provided on the fixed platen 1.
In this vacuum forming machine vacuum forming machine, a vacuum passage 13 drawn from 1 and a vacuum passage 14 attached to a cylinder chamber 19' of a pneumatic cylinder 19 are connected via an electromagnetic switching valve 15.