JP3182708B2 - Hydraulic circuit of booster ram type clamping device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit of an injection molding machine having a booster ram type mold clamping device, and more particularly to a rapid mold opening by providing a back pressure in a booster ram cylinder chamber when a depressurizing mold is opened. The present invention relates to a hydraulic circuit of a booster ram type mold clamping device, which eliminates the problem and does not adversely affect molded products.

[0002]

2. Description of the Related Art When a thermosetting resin or rubber is injection-molded, air existing in a mold (cavity) or gas generated from an injection molding material (resin or rubber) during injection molding is confined in the mold. . If this gas is cooled and solidified while being confined in a mold, product defects due to this gas appear. In order to prevent the occurrence of this defect, at present, the mold is slightly opened during or after injection molding to degas.

A hydraulic circuit of a conventional booster ram type clamping device will be described with reference to FIG. A booster ram cylinder chamber 4 is provided at the center of the main ram 2 moving in the main cylinder chamber 1,
The booster ram 3 is slidably inserted into the booster ram cylinder chamber 4. A surge valve 5 that forms an oil path with a gap provided between the booster ram 3 and the outer periphery of the booster ram 3 is provided in the cylinder 7. The surge valve 5 is closed by a spring 6 so that the main cylinder chamber 1 is closed by a spring 6. It is constantly pressed against the room 1. A movable plate 8 is fixed to the main ram 2, and a movable mold (not shown) attached to the movable plate 8 is moved with respect to a fixed mold (not shown) by moving the main ram 2 forward and backward. They are closed and opened.

Next, a hydraulic circuit for moving the main ram 2 will be described. Main ram 2 inserted into main cylinder chamber 1
The oil chamber 102 and the booster ram oil passage 301 formed at the center of the booster ram 3 are connected to the secondary side of the first switching valve device 11 by oil pipes 9 and 10, respectively. An oil pump 12 and an oil return pipe 13 are connected to the primary side of the first switching valve device 11.
14 is an oil tank. Reference numeral 15 denotes a sequence valve which is branched from the oil pipe 10 and connected to the cylinder 7 so as to communicate with the cylinder chamber 1 through a gap between the inner peripheral surface of the surge valve 5 and the outer peripheral surface of the booster ram 3. 16 is a throttle valve, 17 is a check valve, and 18 is a surge valve opening / closing valve.

In this hydraulic circuit, when closing the mold, the solenoid C on the close side of the first switching valve device 11 in the neutral state (the state shown in the figure) is excited, and the solenoid Z of the surge valve opening / closing valve 18 is demagnetized. Then, the surge valve 5 is opened against the elastic force of the spring 6. As a result, the oil pressurized by the hydraulic pump 12 flows through the oil pipe 10 and the booster ram oil passage 301 and is supplied into the booster ram cylinder chamber 4 to move the main ram 2 forward. The oil chamber 101 on the main ram forward side of 1 has a negative pressure and sucks oil from the pipe 19 to cause the main ram 2 to move forward at high speed and push the movable platen 8 to clamp the mold. On the other hand, the oil in the oil chamber 102 on the retreat side is returned to the tank 14 through the pipes 9 and 13.

Next, when the mold is opened, the solenoid O on the open side of the first switching valve device 11 in the neutral state (the state shown in the figure) is excited, and the solenoid Z of the surge valve opening / closing valve 18 is excited. The surge valve 5 is closed by the elastic force of the spring 6. As a result, the oil pressurized by the hydraulic pump 12 flows through the oil pipe 9 and the oil chamber 10 on the retreat side of the main ram.
2, the main ram 2 is retracted, and the oil in the booster ram cylinder chamber 4 is supplied to the booster ram oil passage 301,
The gas flows through the pipes 10 and 13 and is returned to the tank 14. The oil in the oil chamber 101 on the forward side of the main cylinder chamber 1 flows through the throttle valve 16 and the check valve 17 and returns to the tank 14. At this time oil chamber 1
A back pressure is applied to 01 by the throttle valve 16 to prevent sudden opening of the mold.

[0007]

In particular, after the injection molding of the thermosetting resin or rubber, the cavity of the mold is filled with the resin or rubber and is in close contact with the cavity.
When the mold is closed and the mold is opened in the minute gap to release gas, it is necessary to overcome the adhesive force of the resin or rubber and apply a force necessary for opening the mold.

Therefore, when the first switching valve device 11 is switched to open the mold in the above-described conventional example and the gas is released during the process of opening the mold, the back pressure in the booster ram cylinder chamber 4 becomes zero. At the moment when the filled resin or rubber comes off the mold, its adhesive strength becomes zero, and the balance between the mold opening force and the back pressure in the oil chamber 101 is lost. The mold opening force with respect to the back pressure in the chamber 101 becomes excessive, the mold is opened rapidly, and the mold opening amount also varies according to the variation in the adhesive force. As a result, the molded product is cracked, the weight of the molded product varies,
There is a problem that the dimensions of the molded product also vary.

An object of the present invention is to provide a mold degassing hydraulic circuit which solves the above-mentioned problem by eliminating abrupt mold opening and keeping the mold opening amount constant.

[0010]

Means for solving the above-mentioned problems according to the present invention are as follows. A main ram for moving a movable plate forward and backward is inserted into a main cylinder chamber of a main cylinder, and the main ram is inserted into the main ram. A booster ram provided with a booster ram cylinder chamber, and a booster ram provided with an oil passage communicating with the booster ram cylinder chamber is inserted into the booster ram cylinder chamber, and an oil chamber and a hydraulic pressure on the side for retracting the main ram inserted into the main cylinder chamber are provided. A source is in communication with the oil passage of the booster ram and the tank is in communication with the oil chamber on the side for retracting the main ram inserted into the main cylinder chamber and the tank is in communication with the oil in the booster ram. In a hydraulic circuit of a booster ram type mold clamping device having a first switching valve device capable of selectively switching a state in which a passage and a hydraulic source communicate with each other from a neutral state, the booster ram oil A second switching valve device for selectively opening and closing the oil piping is provided in the middle of an oil pipe connecting the passage and the first switching valve device, and the second switching valve device is connected in parallel. A sequence valve is provided such that the primary side is detoured to the oil passage side of the booster ram.

[0011]

According to the present invention, the following operations are provided. That is, a second switching valve device for selectively opening and closing the oil piping is provided in the middle of the oil piping connecting the booster ram oil passage of the booster ram type mold clamping device and the first switching valve device. Since the sequence valve was provided so that the primary side was on the oil passage side of the booster ram bypassing the second switching valve device in parallel, the first switching valve device and the second switching valve device were switched and the mold was opened. Sometimes, a predetermined back pressure can be maintained in the booster ram cylinder chamber by a sequence valve, thereby making it possible to eliminate abrupt mold opening and to keep the mold opening amount constant.

[0012]

An embodiment of the present invention will be described below with reference to the drawings. The booster ram type clamping device shown in FIG. 1 illustrates the same device as that shown in FIG. That is, a booster ram cylinder chamber 4 is provided at the center of the main ram 2 moving in the main cylinder chamber 1, and the booster ram 3 is slidably inserted into the booster ram cylinder chamber 4. A surge valve 5 for forming an oil passage with a gap provided between the booster ram 3 and the outer periphery of the booster ram 3 is provided in the cylinder 7. It is constantly pressed against the room 1.
A movable plate 8 is fixed to the main ram 2, and a movable mold (not shown) attached to the movable plate 8 is moved with respect to a fixed mold (not shown) by moving the main ram 2 forward and backward. They are closed and opened.

Next, a hydraulic circuit for moving the main ram 2 will be described. Main ram 2 inserted into main cylinder chamber 1
The oil chamber 102 and the booster ram oil passage 301 formed at the center of the booster ram 3 are connected to the secondary side of the first switching valve device 11 by oil pipes 9 and 10, respectively. An oil pump 12 and an oil return pipe 13 are connected to the primary side of the first switching valve device 11. 14 is an oil tank. Reference numeral 15 denotes a main cylinder chamber sequence valve which is branched from the oil pipe 10 and connected to the cylinder 7 so as to communicate with the cylinder chamber 1 through a gap between the inner peripheral surface of the surge valve 5 and the outer peripheral surface of the booster ram 3. ing. 16 is a throttle valve, 17 is a check valve, and 18 is a surge valve opening / closing valve.

A booster ram cylinder chamber sequence valve 20 is provided in the middle of the oil pipe 10, and a second switching valve 21 is provided in parallel with the booster ram cylinder chamber sequence valve 20. I have.

The operation of the embodiment constructed as described above will now be described. First, mold closing will be described. When closing the mold, the solenoid C on the close side of the first switching valve device 11 in the neutral state (the state shown in the figure) is excited, and the solenoid Y of the second switching valve device 20 is demagnetized to boost the oil pipe 10. Communicates with the ram cylinder chamber 4, and
The solenoid Z of the surge valve opening / closing valve 18 is demagnetized, and the surge valve 5 is opened against the elastic force of the spring 6.

As described above, since the second switching valve device 20 is provided, it is possible to form the mold closing hydraulic circuit as described above, and the oil pressurized by the hydraulic pump 12 is supplied to the oil pipe 10. The second switching valve device 20 flows through the booster ram oil passage 301 and is supplied into the booster ram cylinder chamber 4 to move the main ram 2 forward. When the oil chamber 101 becomes negative pressure and sucks oil from the pipe 19, the main ram 2 moves forward at high speed and pushes the movable plate 8 to clamp the mold. On the other hand, the oil in the oil chamber 102 on the retreat side is returned to the tank 14 through the pipes 9 and 13.

Although not shown, the discharge rate of the hydraulic pump 12 is reduced immediately before the mold is closed to reduce the mold closing speed in order to prevent the mold from being damaged or shock. . Next, when the mold is closed, the solenoid Z of the surge valve opening / closing valve 18 is excited, and the surge valve 5 is closed.
Is closed by the elastic force of the spring 6, the oil pressure of the booster line including the oil pipe 10, the second switching valve device 20, the booster ram oil passage 301, and the booster ram cylinder chamber 4 rises, and the oil pressure is used for the main cylinder chamber. When the pressure exceeds the set pressure of the sequence valve 15 (for example, 70 kg / cm ² ), the main cylinder chamber sequence valve 15 opens and the oil chamber on the forward side is opened.
Oil is supplied to 101, the mold closing force is increased, and the mold closing is completed.

When the completion of the closing of the mold is confirmed by an electric means (not shown) (for example, a limit switch or an encoder), the discharge amount of the hydraulic pump 12 is switched to a large capacity again, and the booster ram cylinder chamber 4 and the main cylinder chamber are returned. The pressure of both the oil chambers 101 in the forward side is increased to maintain a predetermined mold closing pressure in a short time.

Next, when the mold is opened, if the mold is suddenly opened, a shock will occur in the mold and the product will be adversely affected. In this pressure release, the solenoids O and C of the first switching valve device 11 are switched over for a short time. Since the booster ram cylinder chamber sequence valve 20 and the second switching valve device 21 are provided in parallel with the sequence valve 20, the solenoid Y of the second switching valve device 21 is excited to perform the second switching. The hydraulic circuit of the valve device 21 is cut off, and the hydraulic circuit of the booster ram cylinder chamber sequence valve 20 operates, and the back pressure of the booster ram cylinder chamber 4 is reduced by the set pressure of the booster ram cylinder chamber sequence valve 20 (for example, 30
kg / cmm2). The depressurization time for switching the solenoids O and C of the first switching valve device 11 in a short time is usually about 0.3 to 0.4 seconds.

After this pressure release, a back pressure mold opening is performed for gas release or mold opening. In opening the back pressure mold, since the second switching valve device 21 is provided in the oil pipe 10 in parallel with the sequence valve 20, the open-side solenoid O of the first switching valve device 11 is excited,
By switching the first switching valve device 11, the oil chamber 102 on the retreat side of the main ram 2 and the hydraulic pump 12 are communicated, and the solenoid Y of the second switching valve device 21 is switched by being excited. An oil circuit extending from the booster ram oil passage 301 to the tank 14 via the booster ram cylinder chamber sequence valve 20 can be formed.

When the set pressure of the booster ram cylinder chamber sequence valve 20 is set to, for example, 30 kg / cm ² and oil is supplied to the oil chamber 102 by the hydraulic pump 12, the back pressure of the booster ram cylinder chamber 4 is reduced by 30 kg. / cm ² to hold the oil chamber
Main ram 2 is retracted to allow back pressure opening while maintaining the back pressure in 101 at the resistive pressure of throttle valve 16. In this way, by opening the back pressure mold while maintaining the back pressure in the booster ram cylinder chamber 4, even if it is adhered to the mold like a thermosetting resin and peeled off when the mold is opened, the booster ram can be opened. Due to the back pressure in the cylinder chamber 4, the rapid retreat of the main ram 2 is suppressed, and the mold can be opened gently.

When degassing is performed, although it depends on the type of molded article, the back pressure mold is opened to about 0.2 to 2.0 mm and stopped, and after counting for 2 to 3 seconds by a timer, the first switching valve device 11 is opened. , And the solenoid Y of the second switching valve device 21 is demagnetized and pressurized again. Further, if the present invention is applied to a mold having a built-in spring, the mold can be opened without damaging the molded product. In this case, for example, a back pressure is provided during the conventional mold opening low speed section. It goes without saying that the back pressure mold can be opened even with a mold that does not incorporate a spring.

As described above, the mold is opened after the back pressure mold is opened. That is, the solenoid O of the first switching valve device 11 is excited, and the solenoid Y of the second switching valve device 21 is excited.
, The solenoid Z of the surge valve switching valve 18 is demagnetized to open the surge valve 5, and the hydraulic pump 12 supplies oil to the oil chamber 102, whereby the main ram 2 is retracted, and the oil chamber 101 and the booster ram are retracted. Oil in cylinder chamber 4 is tank
It is discharged to 14 and the mold is opened.

[0024]

As described above in detail, according to the present invention, the oil passage for selectively opening and closing the oil passage in the middle of the oil passage connecting the booster ram oil passage and the switching valve device of the booster ram type mold clamping device. Since the second switching valve device is provided, and the second switching valve device is bypassed in parallel and the sequence valve is provided so that the primary side is on the oil passage side of the booster ram, the switching valve device and the second switching valve are provided. When the valve device is switched to open the mold, a predetermined back pressure can be maintained in the booster ram cylinder chamber by the sequence valve, so that rapid mold opening can be eliminated and the mold opening amount can be kept constant. As a result, cracking of the molded product is prevented, the productivity is improved, and variations in the weight of the molded product and variations in the dimensions of the molded product are eliminated, so that a highly accurate molded product can be obtained.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram showing one embodiment of the present invention.

FIG. 2 is a conventional hydraulic circuit diagram.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main cylinder chamber 2 Main ram 3 Booster ram 301 Booster ram oil passage 4 Booster ram cylinder chamber 5 Surge valve 8 Movable platen 11 First switching valve device 12 Hydraulic pump 20 Boost ram cylinder chamber sequence valve 21 Second switching valve device

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B29C 45/64-45/68 B29C 45/76-45/84 B29C 33/20-33/28

Claims (1)

(57) [Claims] 1. A main ram for moving a movable plate forward and backward is inserted into a main cylinder chamber of a main cylinder, a booster ram cylinder chamber is provided in the main ram, and an oil passage communicating with the booster ram cylinder chamber is provided. The provided booster ram is inserted into the booster ram cylinder chamber, the oil chamber on the side for retracting the main ram inserted into the main cylinder chamber communicates with the hydraulic pressure source, and the oil passage of the booster ram communicates with the tank. The state and the state in which the oil chamber and the tank on the side for retracting the main ram inserted into the main cylinder chamber communicate with each other, and the state in which the oil passage of the booster ram communicates with the hydraulic pressure source are selectively selected from the neutral state. In a hydraulic circuit of a booster ram type mold clamping device having a switchable first switching valve device, in the middle of an oil pipe connecting the oil passage of the booster ram and the first switching valve device, A second switching valve device for selectively opening and closing the oil pipe was provided, and a sequence valve was provided so that the second switching valve device was bypassed in parallel and the primary side was on the oil passage side of the booster ram. A hydraulic circuit of a booster ram type mold clamping device.