JPH07214616A - Check ring opening/closing device in injection molding machine - Google Patents

Abstract

PURPOSE:To prevent a counterflow of a molten resin to stabilize an injection stage by a method wherein for forcibly opening/closing a check ring, a piston firmly fixed to a screw head is engaged with a recessed part of a top of a screw shaft, the screw head can be moved forward and backwiard, and a hydraulic pressure for moving a screw forward can be applied on the head-side of the piston. CONSTITUTION:A check ring 2 can move forward and backward between a top of a screw shaft 1 and a rear end of a screw head 27. A piston 23 firmly fixed to the rear end of the screw head 27 is engaged with a recessed part of a top of the screw shaft 1. The screw head 27 can be moved forward and backward. A spring capable of moving the screw head 27 backward is resiliently provided on the rod-side of the piston 23. A hydraulic pressure for moving a screw forward can be applied on the head-side of the piston 23. In this manner, the check ring 2 can be forcibly opened and closed between the top of the screw shaft 1 and the rear end of the screw head 27.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention opens and closes a check ring in an injection molding machine for preventing backflow of molten resin by forcibly opening and closing a check ring inserted between a screw and a screw head so as to be movable back and forth. It relates to the device.

[0002]

2. Description of the Related Art In an injection molding machine for molding a plastic product, an inline screw type machine melts a resin and injects it into a mold cavity with only one screw mounted in a heating cylinder.

In the measuring step of melting the pellet resin and storing the molten resin in the front part of the screw head,
It is necessary to secure a resin flow path for the resin melted in the screw groove portion to flow forward.

Further, in the injection step of injecting and filling the molten resin stored in the front portion of the screw head into the mold cavity, it is necessary to block the resin flow passage so that the molten resin does not flow back to the rear portion of the screw.

For this reason, a part called a check sheet is fixed to the front portion of the screw, and a check ring that is freely movable between the screw head and the check sheet is provided.

During the measuring process, the check ring is pushed and moved toward the screw head side by the molten resin flowing from the rear of the screw to the front so that a resin flow path is secured between the check sheet and the check ring. Become.

During the injection process, the check ring is left behind as the screw advances, and the check ring moves to the check sheet side and comes into close contact therewith, thereby blocking the resin flow passage and preventing backflow. There is.

[0008]

By the way, when the screw starts to move forward in the injection process, the check ring moves forward to some extent due to the resin pressure generated between the check ring and the check sheet and the high viscosity of the molten resin. Therefore, the blocking of the resin flow path by the check ring is delayed,
During that time, a backflow phenomenon of the resin occurs.

As a result, there is a discrepancy between the screw advancing start time and the time when the resin begins to flow into the mold, and theoretically, the actual filling completion time and the injection stroke of the screw necessary for injection filling are different. It will be different.

The variations in the filling completion time and the injection stroke cause variations in the pressure-holding process start time, which will be described later, resulting in variations in the quality of the molded product.

In particular, even if the optimum injection conditions are rigorously calculated using CAE (Computer Assisted Technology) calculation, if the initial state at the start of injection filling is not theoretically the same as the initial state, the subsequent state will also change and the desired state will be obtained. In addition to obtaining good quality molded products, advanced CAE calculations are also useless.

The present invention has been made in view of the above problems, and provides an opening / closing device for a check ring in an injection molding machine, in which the check ring is forcibly closed before the injection is started to prevent the reverse flow of the molten resin. It is intended to be provided.

[0013]

In order to achieve the above object, according to the present invention, there is provided a check ring which can be moved forward and backward between a tip end portion of a screw shaft and a rear end portion of the screw head. A piston fixed to the rear end of the screw head is engaged in the screw head so as to be movable back and forth, and a spring for retracting the screw head is mounted on the rod side of the piston, and the head side of the piston is mounted. An oil pressure for advancing the screw is provided so that the screw can be loaded so that the check ring can be forcibly opened and closed between the front end of the screw shaft and the rear end of the screw head.

[0014]

In the present invention, the check ring is forcibly opened and closed by moving the screw head forward and backward by utilizing the hydraulic pressure and the extension force of the spring to pinch or open the check ring. Since the backflow of the molten resin due to the delay in closing the check ring at the start of the injection process is prevented, an ideal injection operation can be performed.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of a check ring opening / closing device in an injection molding machine according to the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic diagram showing a simplified configuration of essential parts of an injection apparatus according to one embodiment of the present invention, FIG. 2 is a detailed sectional view of a rear portion of an injection cylinder, FIG. 3 is a detailed sectional view of a front portion of a screw, and FIG. 4 is a check. Explanatory drawing showing the opened state of the ring, FIG.
FIG. 4 is an explanatory diagram showing a forced closed state of a check ring.

In FIG. 1, a screw 1 is inserted into a heating cylinder 3 which constitutes an injection device 30 so as to be able to move forward and backward with respect to rotation, a nozzle 4 is attached to the tip of the heating cylinder 3, and a rear end thereof. An injection cylinder 20 having a piston 23 in which the screw 1 is movable in the axial direction and is rotatably attached is attached thereto.

The hydraulic chamber 9 of the injection cylinder 20 is composed of a rod-side hydraulic chamber 9a and a head-side hydraulic chamber 9b. The hydraulic chamber 9 is supplied with hydraulic oil from a hydraulic pump 10 (not shown) and is hydraulically actuated by a hydraulic valve 11. Controlled by. The hydraulically operated valve 11 is composed of a rod side hydraulically operated valve 11a communicating with the rod side hydraulic chamber 9a and a head side hydraulically operated valve 11b communicating with the head side hydraulic chamber 9b.

Reference numeral 8 is a screw position sensor for measuring the forward / backward travel distance of the screw 1. A screw head 27 is screwed onto the tip of the screw 1 with a check sheet 1a placed in the screw head 27. The screw head 27 has a substantially conical shape toward the tip, and the rear side (right side in the figure) of the conical shape is stepped. The check ring 2 which is slidable in the axial direction is inserted in the small diameter portion 27a.

A piston 24 is fixedly attached to the rear end of the small diameter portion 27a of the screw head 27, and is engaged with a cylindrical space 22 at the front end of the screw 1 as shown in FIG. 24 are slidably arranged.

An elastic spring 26 is elastically mounted on the side of the small diameter portion 27a of the piston 24. Further, a through hole 28 is bored in the head side 24a of the piston 24 in the central portion of the screw 1 along the axis to reach the rear portion of the injection cylinder 20 so that hydraulic pressure from a pump (not shown) can be loaded. Has been done.

This through hole 28 is L at the rear as shown in FIG.
An annular passage 29 is arranged in the rear of the injection cylinder 20 so that pressure oil can be supplied to the piston head 24a side from the hydraulic pump 10 via the conduit 11 under the rotating state of the screw 1 through the conduit 11. It is set up.

Reference numeral 15 is a hopper, 15a is a resin pellet, 18 is a screw head front portion, and 25 is a molding machine controller.

Next, the operation of the check ring opening / closing device in the injection molding machine of the present invention will be described. First, in order to store a certain amount of molten resin while rotating the screw 1 from the rear of the screw 1 to the front portion 18 of the screw head while reversing the screw 1 before starting the measuring process and storing the molten resin, By applying pressure oil to the side, the screw head 27 is moved in the direction away from the check sheet 1a by overcoming the extension force of the spring 26 as shown in FIG. When the screw 1 is rotated and retracted in this state, the check ring 2 is pushed by the flow of the molten resin from the rear side to the front side of the screw 1 and is pushed against the rear portion of the screw head 27 to secure the resin passage.

At the start of the measuring process, the screw 1 is located to the left of the position shown in FIG.
When the screw 1 is rotated while a slight back pressure is applied by 1, the pellets 15a are removed from the hopper 15 by the screw 1
Is supplied to the right end side of the
Thus, while being sent to the left, it becomes molten resin and is stored in the screw head front portion 18.

The screw 1 retracts as it is stored in the front portion 18 of the screw head. For example, when a limit switch (not shown) detects this, the rotation of the screw 1 stops and the measurement of the molten resin ends.

When the measuring process is completed, the piston head 2
When the load of pressure oil on the side of 4a is stopped and released, the screw head 27 moves the check sheet 1 by the extension force of the spring 26.
Move to the side a in the proximity direction. Therefore, the check ring 2 is sandwiched between the rear portion of the screw head 27 and the check sheet 1a to close the resin passage. (Fig. 5)

When a so-called injection process is started in which the screw 1 is advanced without rotating in this state, the resin stored in the screw front portion 18 by the measuring process is injected into the mold cavity portion (not shown) through the nozzle 4. Is filled.

Thereafter, when the mold is cooled, the molten resin injected and filled in the mold cavity is solidified, the product is taken out after the mold is opened, and one cycle is completed.

[0029]

As is apparent from the above description, according to the present invention, the check ring is provided so as to be able to move forward and backward between the tip end portion of the screw shaft and the rear end portion of the screw head. A piston fixed to the rear end of the screw head is engaged in the recess so that the screw head is movable back and forth, and a spring for retracting the screw head is mounted on the rod side of the piston, and the piston head is mounted. The hydraulic pressure for advancing the screw to the side is loadable so that the check ring is forcibly opened and closed between the tip of the screw shaft and the rear end of the screw head. Since backflow can be prevented, an ideal injection process can be realized.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a simplified configuration of a main part of an injection device according to a first embodiment of the present invention.

FIG. 2 is a detailed sectional view of a rear portion of an injection cylinder.

FIG. 3 is a detailed sectional view of a front portion of a screw.

FIG. 4 is an explanatory diagram showing an open state of a check ring.

FIG. 5 is an explanatory diagram showing a forcibly closed state of the check ring.

[Explanation of symbols]

 1 screw 1a check sheet 2 check ring 3 heating cylinder 4 nozzle 8 screw position sensor 9 hydraulic chamber 9a rod side hydraulic chamber 9b head side hydraulic chamber 10 hydraulic pump 11 hydraulically actuated valve 15 hopper 18 screw head front 20 injection cylinder 22 cylindrical Space 23, 24 Piston 26 Spring 27 Screw head 28 Through hole 29 Annular path 30 Injection device

Claims (1)

[Claims] 1. A check ring provided so as to be able to move forward and backward between a tip end portion of a screw shaft and a rear end portion of a screw head, wherein a piston fixed to the rear end portion of the screw head is engaged in a recessed portion of the tip end of the screw shaft. A screw head is provided so as to be movable back and forth together, a spring capable of retracting the screw head is mounted on the rod side of the piston, and an oil pressure for advancing the screw is provided on the head side of the piston so as to be loadable. An opening / closing device for a check ring in an injection molding machine, which allows a check ring to be forcibly opened / closed between the front end of a screw shaft and the rear end of a screw head.