JPH0716419Y2 - Metering-stabilized fluid pressure circuit in injection molding machine - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to an injection molding machine, and more specifically, to measurement of a molten molding material that is stored in a tip of a heating cylinder of the injection molding machine and is injected by advancing a screw. The present invention relates to a metering-stabilized fluid pressure circuit in an injection molding machine that accurately and stably performs the process.

"Prior Art" Conventionally, a screw type injection molding machine has an electromagnetic switching valve connected to a backward side port 6b of an injection cylinder 6 of an injection molding machine 1 ', as shown in Fig. 2, in a weighing process prior to an injection process.
17 is at the left side switching position shown in the figure, that is, at the position where the retreat side port 6b communicates with the tank, and the electromagnetic switching valve 8 connected to the forward side port 6a of the injection cylinder 6 is switched to the right side switching position, that is, the metering position, The pressure oil from the pump P is supplied to the hydraulic motor 7 to rotate the hydraulic motor 7, and the forward port 6a of the injection cylinder 6 is connected to the tank via the relief valve 9.

In such a situation, the hopper 4'of the injection molding machine 1 '
The molding material such as a synthetic resin supplied from the above falls into the heating cylinder 2 due to its own weight and is kneaded along with the rotation of the screw 5 rotated by the hydraulic motor 7, and along the spiral groove of the screw 5. It is sent to the tip of the heating cylinder 2.

At that time, the molding material is heated by a heater arranged on the outer periphery of the heating cylinder 2 and also generates heat from inside due to frictional heat generated by the kneading action, resulting in a relatively uniform plasticized state at the front end. It is sent to the heating cylinder 2 to which the nozzle 3'is mounted and the tip end portion.

Then, as the molten molding material is stored at the tip of the heating cylinder 2, the screw 5 is pushed back by the reaction force due to the back pressure of the material in balance with the hydraulic motor 7 and the like to the set pressure of the relief valve 9. Therefore, the retreat amount is regulated by the limit switch, the excitation of the right solenoid 8a of the electromagnetic switching valve 8 is cut off, the electromagnetic switching valve 8 is switched to its central position, that is, the metering stop position, and the rotation of the screw 5 by the hydraulic motor 7 is kept constant. The injection amount is determined or measured by stopping at the position.

[Problems to be Solved by the Invention] According to the above-described metering method, the open nozzle which is most commonly used as the nozzle 3'is used to supply the molding material from the hopper 4'by its own weight as described above. In such a case, the back pressure of the molten material stored in the tip portion of the heating cylinder 2 during measurement does not become too high,
Although the metering is performed substantially accurately, the shut-off nozzle having excellent shutoff and operability is used as the nozzle, and the molding material is forced into the heating cylinder 2 by using the material pushing cylinder capable of accurately supplying the material. In the case of supplying to the heating cylinder 2, since the back pressure of the molten material stored in the tip of the heating cylinder 2 becomes considerably high, the set pressure of the relief valve 9 is increased to balance the back pressure, and the above-described measurement is performed. In that case, when the metering is completed, the hydraulic pressure in the forward-side port 6a of the injection cylinder 6 is correspondingly increased, which makes it easier for pressure oil to leak from the electromagnetic switching valve 8, and therefore the pressure in the forward-side port 6a decreases. As a result, the screw 5, which has once been weighed, retreats to a new balance position, and the molten material is replenished to the tip of the heating cylinder 2 again. There is a problem that the measurement is not uniform.

Therefore, an object of the present invention is to provide a metering-stabilizing fluid pressure circuit in an injection molding machine, which is capable of forcibly preventing the screw from retreating after the completion of metering and thus solving the above-mentioned problems.

[Means for Solving the Problems] In order to achieve the above-mentioned object, a metering-stabilizing fluid pressure circuit in an injection molding machine according to the present invention includes a switching valve having a metering position, a metering stop position, and an injection position in an injection cylinder. In the injection molding machine connected to the forward port of the injection cylinder, between the forward port of the injection cylinder and the switching valve, a backflow is allowed at the time of metering, and a backflow is prevented at the time of metering stop and injection. It is characterized in that a pilot operated check valve connected to an electromagnetic switching valve for supplying pilot pressure that operates in synchronization with the switching valve is provided.

"Operation" With the above configuration, the switching valve is
Also, because the pilot operated check valve allows backflow, the injection cylinder connected to the screw by the back pressure of the molten material stored at the tip of the heating cylinder is connected to the screw through the pilot operated check valve and the switching valve from its forward port. Pressure oil is discharged to the tank via the relief valve and pushed back.

When, for example, a limit switch is operated at a position where the screw is retracted by a predetermined distance, the output of the limit switch switches the switching valve to the metering stop position, and the pilot operated check valve stops the pilot operation so as to prevent backflow. It

As a result, the flow of pressure oil from the advancing port of the injection cylinder is completely blocked, and the backward movement of the screw is forcibly prevented via the injection cylinder, and the metering is stabilized.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example in which the fluid pressure circuit of the present invention is applied to a horizontal screw type injection molding machine.

The same parts as those of the conventional example shown in FIG. 2 are designated by the same reference numerals.

The injection molding machine 1 has a heating cylinder 2 as shown in FIG.
And a shut-off nozzle 3 is attached to the front end thereof, and a material pushing cylinder 4 is connected to the upper portion near the rear end thereof.

Then, the screw 5 having a spiral groove formed on the outer periphery is fitted into the heating cylinder 2 so as to be able to move forward and backward,
Rear end portion of the screw 5 protruding from the heating cylinder 2
5a is connected to the injection cylinder 6.6 via an appropriate member, and is also connected to the hydraulic motor 7 via an appropriate mechanism.

And, to the retract side port 6b.6b of the injection cylinder 6.6, the port B is connected to the port 6b.6b, and the solenoid 17a
Is a 4-port / 2-position solenoid switching valve 7 that takes the switching position with PA / BT connection on the left side when is not excited and takes the switching position with AT / PB connection on the right side when the solenoid 17a is excited.
Is connected to the forward side ports 6a.6a of the injection cylinder 6.6, the port A is connected to the ports 6a.6a through a pilot operated check valve 10 described later, and the solenoids 8a.8b are excited together. When the solenoid 8a is energized, the center position is AT connected, and when the solenoid 8a is energized, the PB / AT connected weighing position is on the right side. A 4-port / 3-position solenoid directional control valve 8 having a position is connected. The B port of the directional control valve 8 is connected to the hydraulic motor 7 and the T port is connected to a tank via a relief valve 9. There is.

A pilot operated check valve 10 is arranged between the forward-moving ports 6a.6a of the injection cylinder 6.6 and the port A of the electromagnetic switching valve 8, and the check valve 10 is provided.
The pilot port 10a takes the switching position connected to the PA / BT on the right side when the solenoid 11a is not excited,
When the solenoid 11a is energized, a 4-port / 2-position type pilot pressure supply electromagnetic switching valve 11 that takes a switching position connected to the PB / AT on the left side is connected, and the solenoid 11a is energized by the switching valve 8. It is designed to be synchronized with the energization of the solenoid 8a.

Since the present embodiment is configured as described above, during metering, the solenoid 8a is energized to switch the switching valve 8 to the right metering position, the pressure oil from the pump P is supplied to the hydraulic motor 7, and The forward side ports 6a.6a of the injection cylinder 6.6 are connected to the tank via the pilot operated check valve 10, the switching valve 8 and the relief valve 9.

Further, the solenoid 11a is also energized at the same time, the switching valve 11 is switched to the left position in the figure, and the pilot operet check valve 10
The pilot pressure is applied to the pilot port 10a of the check valve 10, and the check valve 10 is in a state in which the backflow is allowed.

In such a state, the molding material supplied from the material pushing cylinder 4 is forcibly filled in the heating cylinder 2 and kneaded as the screw 5 rotated by the hydraulic motor 7 is kneaded. A molten state is sent along the spiral groove 5 and is fed to the tip of the heating cylinder 2.

Then, as the molten molding material is stored in the tip of the heating cylinder 2, the back pressure causes the screw 5 to flow backward from the forward-side port 6a of the injection cylinder 6 connected to the screw 5 and the check valve 10 and the switching valve 8. Then, based on the fact that the pressure oil is discharged to the tank through the relief valve 9,
Be retreated.

Then, when the screw 5 is retracted by a predetermined distance from the previous injection completion position, that is, when the measurement of the amount of the molten molding material set at the tip of the heating cylinder 2 is completed, it is detected by a limit switch or the like. Due to the output, the solenoid 8a is de-energized, the switching valve 8 is switched to the central position, that is, the metering stop position, the rotation of the hydraulic motor 7 is stopped, and the solenoid 11a of the switching valve 11 is de-energized. The pilot operated check valve 10 is an injection cylinder.
The state in which the backflow from the forward-side ports 6a and 6a of 6.6 is blocked is set, and thereafter, the backward movement of the screw 5 is completely blocked.

Thus, when the solenoid 8b of the electromagnetic switching valve 8 is energized after the metering is completed, the switching valve 8 is switched to the left position, that is, the injection position, and the pressure oil from the pump P passes through the check valve 10 in the forward direction. Is supplied to the forward-side ports 6a.6a of the injection cylinder 6.6, and the molten molding material measured at the tip of the heating cylinder 2 by the pushing action of the screw 5 accompanying it is opened from the shut-off nozzle 3 (not shown). The mold cavity is filled and injection molding is performed.

In the above embodiment, each switching valve 7.8.11 has been described as an electromagnetic pilot type, but it goes without saying that a fluid pressure pilot type or a mechanical pilot type may be used if necessary.

Further, the hydraulic circuit described above can be similarly applied to the plunger type injection molding machine.

[Advantages of the Invention] As described above, according to the present invention, in an injection molding machine in which a switching valve having a metering position, a metering stop position, and an injection position is connected to a forward side port of the injection cylinder, Between the forward port and the switching valve,
Injection molding is performed by connecting a pilot operated check valve that allows backflow during metering and prevents backflow during metering stop and injection to a pilot pressure supply solenoid switching valve that operates in synchronization with the switching valve. Since the metering stabilization fluid pressure circuit in the machine is configured, the pilot pressure acts on the pilot port of the check valve together with the operation of the switching valve to smooth the flow in the direction permitting the reverse flow of the check valve. Further, after the completion of the metering, the pilot pressure disappears with the switching of the switching valve, and the operation of the check valve completely prevents the backward movement of the screw after the completion of the metering, and the metering is always consistent. Stable and accurate.

In addition, the pilot operated check valve is simply arranged between the injection cylinder and the switching valve, and it is not necessary to use a switching valve that is manufactured with high precision to minimize leakage and the like. , It is possible to achieve the intended purpose at an extremely low cost.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an example in which the fluid pressure circuit of the present invention is applied to a horizontal injection molding machine, and FIG. 2 is a schematic configuration diagram showing a horizontal injection molding machine having a conventional fluid pressure circuit. Explanation of code 1: Injection molding machine 6: Injection cylinder 6a: Forward port 8: Switching valve 10: Pilot operated check valve

Claims (1)

[Scope of utility model registration request] 1. An injection molding machine in which a switching valve having a metering position, a metering stop position, and an injection position is connected to a forward port of an injection cylinder, and between the forward port of the injection cylinder and the switching valve. A pilot operated check valve connected to a pilot pressure supply electromagnetic switching valve that is operated in synchronism with the switching valve so as to allow backflow during metering and prevent backflow during metering stop and injection must be installed. Characteristic stabilizing fluid circuit in injection molding machine.