JPS6032979Y2 - Hydraulic circuit for ejector of injection molding machine - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a hydraulic circuit for a hydraulic ejector (a device for ejecting a molded product using a hydraulic cylinder) of an injection molding machine.

In a hydraulic ejector type injection molding machine, a molded product is released from a mold by an ejector pin of a hydraulic ejector.

The ejection of the molded product includes a first step in which the ejector pin advances from the return position to the ejected position, and a second step in which the ejector pin is held at the ejected position until removal of the molded product is completed. The third step is to move the ejector pin back to its return position to close the mold.

The present invention particularly relates to an improvement in the hydraulic circuit for holding the second stage ejector pin in the ejected position.

First, regarding the conventional hydraulic circuit, Part 1-1 shows an example of the conventional hydraulic circuit.
This will be explained based on FIG.

A movable platen 3 is guided on the tie bar 1 so as to face a fixed platen 2 fixed to the tie bar 1.

A fixed mold 4 and a movable mold 5 are attached to the fixed platen 2 and the movable platen 3, respectively.

The movable platen 3 is provided with a hydraulic cylinder 6, and a piston rod 8 coupled to the piston 7 passes through the movable platen 3, and a protruding pin 9 that can protrude from the movable mold 5 is provided at the tip of the piston rod 8. are combined.

Note that the protruding pin 9 is always subjected to a force in the direction of the return position by the spring 10.

When the fixed die 4 and the movable die 5 are closed, the ejector pin 9 remains protruded. If the ejector pin 9 is closed, the ejector pin 9 will damage the stationary die 4, so the spring 10 always moves the ejector pin 9 to the return position. It is meant to make you retreat.

Chambers 11 and 12 separated by the piston rod 7 of the hydraulic cylinder 6 are connected to the A port and B port of the solenoid valve 13, respectively, and a flow control valve is provided between the chamber 6 and the A port. .

This hydraulic circuit operates as follows.

When the molding is finished, the movable mold 5 moves back, and then the solenoid a of the solenoid valve 13 is energized, and pressure oil is supplied to the solenoid valve 1.
3 flows from the P port to the A port, and is sent to the chamber 11 via the flow control valve 14.

As a result, the piston 7 is pushed to the right, and the ejector pin 9 is also moved to the right via the piston rod 8, thereby performing an ejecting operation.

Next, the solenoid a of the solenoid valve 13 is deenergized, and the spool enters a neutral state, leading to a second stage in which the ejecting pin 9 is held in the ejecting position.

At this time, since the piston rod 8 is pushed to the left by the spring 10, the oil in the chamber 11 escapes from the A port to the T port of the solenoid valve 13, and the protruding pin 9, which moves the piston rod 8 to the left, It is gradually pulled back to the return position.

For this reason, the conventional hydraulic circuit has the disadvantage that the operation of separating the molded product 15 from the mold 5 cannot be performed smoothly.

An object of the present invention is to provide a hydraulic circuit that prevents the piston of a hydraulic cylinder from being pushed back by the return spring of the ejecting pin, so that the mold release operation can be performed smoothly.

Hereinafter, the present invention will be explained based on FIG. 2 of the accompanying drawings showing an embodiment thereof.

Note that the same reference numerals are used in FIG. 2 for the same members as in FIG. 1-1.

The difference from the conventional hydraulic circuit is that a pilot check valve 16 is arranged between the A port of the solenoid valve 13 and the flow control valve 14 in a direction that blocks the flow from the flow control valve 14 to the A port. The point is that the pressure at the B port is guided through the flow path 17 as the pilot pressure.

The other configurations are basically the same as the conventional hydraulic circuit shown in FIG. 1-1.

Next, the operation of this hydraulic circuit will be explained.

The operation until the ejecting pin 9 is ejected is not particularly different from that of a conventional hydraulic circuit.

That is, when the molding is finished, the movable mold 5 retreats, and then the solenoid a of the solenoid valve 13 is energized, and pressure oil flows from the P port to the A port of the solenoid valve 13, and the pilot check valve 16 and the flow control valve 14 are activated. is sent to chamber 11 via.

As a result, the piston 7 is pushed to the right, and the ejector pin 9 is also moved to the right via the piston rod 8, thereby performing an ejecting operation.

Next, the solenoid a of the solenoid valve 13 is deenergized, and the spool enters a neutral state, leading to a second stage in which the ejecting pin 9 is held in the ejecting position.

This second stage differs from the conventional hydraulic circuit as follows.

That is, although the piston rod 8 is pushed leftward by the spring 10, the oil in the chamber 11 is
You cannot escape from port to T port.

This is because the oil in the chamber 11 is blocked by the pilot check valve 16.

Therefore, the piston rod 8 and the ejector pin 9 cannot be moved.

Next, when the second stage of holding the ejector pin 9 in the ejected position is completed, the solenoid b of the solenoid valve 13 is energized.
Hydraulic pressure flows from the P port to the B boat and is sent to the chamber 12 of the hydraulic cylinder 6.

At the same time, pressure acts on the pilot pressure acting portion of the pilot check valve 16 from the B port via the flow path 17, and the pilot check valve 16 opens.

Therefore, the pressure in the chamber 12 pushes the piston 7 to the left, and the oil in the other chamber 11 flows through the flow control valve 14 and the pilot check valve 16 to the solenoid valve 13.
is discharged from the T port into the tank.

Therefore, the piston 7 moves to the left, and the ejector pin 9 is pulled back to its return position.

In the conventional hydraulic circuit, the solenoid valve 13 is of a closed center type (Fig. 1-2), but when the spool is in the neutral position, the
A small amount of oil pressure leaks to the port, and the same pressure acts on chambers 11 and 12 of the hydraulic cylinder 6 at the same time, creating a so-called differential pressure circuit, causing the piston 8 to move forward during idle operation.
A problem sometimes occurred in which the ejector pin 9 was ejected.

Furthermore, if the solenoid 13 is a spring-off cellar 12-position valve (Fig. 1-3), the protrusion can only be maintained at the maximum stroke position of the piston 7, so the protrusion stroke may be adjusted depending on the molded product. Can not.

As described above, according to the present invention, even if the ejector pin is constantly receiving a returning force from the spring, the ejector pin is not pulled back during the ejector pin ρ holding stage.

Therefore, the molded product can be reliably and smoothly released from the mold.

Moreover, the only part required for this purpose is a pie-nine check valve, making it extremely economical.

[Brief explanation of the drawing]

1-1.1-2.1-3 is a circuit diagram showing a conventional hydraulic circuit, and FIG. 2 is a circuit diagram showing a hydraulic circuit according to the present invention. 1...Tie bar, 2...Fixed plate, 3.
...Movable plate, 4...Fixed mold, 5...
...Movable mold, 6...Hydraulic cylinder: lda, 7.
... Zeston, 8... Zeston rod, 9.
...Eject pin, 10...Spring, 11.
...Room, 12...Room, 13...
Solenoid valve, 14...flow control valve, 15...molded product, 16...pilot check valve, 17...flow path.

Claims (1)

[Claims for Utility Model Registration] The ejecting pin 9, which is always pushed toward the return position by a spring 10, is moved between the return position and the ejecting position by a hydraulic cylinder 6 whose operating direction is switched by a solenoid valve 13. In a hydraulic circuit for an ejector of an injection molding machine that ejects a molded product, one port A of a solenoid valve 13 is connected to a chamber 11 of a hydraulic cylinder that introduces hydraulic pressure to move an ejector pin 9 to an ejecting position. A pilot check valve 16 is provided in the flow path to prevent the flow from the chamber 11 to the solenoid valve 13, and the pilot pressure acting part of the pilot check valve 16 is operated to extend hydraulic pressure in order to move the bus 9 to the return position. A hydraulic circuit characterized in that the hydraulic circuit is connected to a flow path that connects the chamber 12 of the hydraulic cylinder into which the oil is introduced and the other port B of the solenoid valve 13.