JPH07214618A - Check ring opening/closing device in injection molding machine - Google Patents

Abstract

PURPOSE:To forcibly close a check ring to prevent a counterflow of a molten resin by a method wherein a piston firmly fixed to a rear end of a screw head is engaged with a recessed part of a top of a screw shaft, a spring for moving the screw head forward is resiliently provided in the recessed part of the top of the screw shaft, and an electromagnet is provided rearward of the recessed part. 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 24 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 26 for moving the screw head 27 forward is resiliently provided between the piston 24 and the recessed part of the top of the screw shaft 1. An electromagnet 23 is provided rearward of the recessed part of the top of the screw shaft 1. The screw head 27 is provided so as to move backward by exciting the electromagnet 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.

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 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 screw head is mounted in the rear end of the screw head so as to be movable back and forth, and a spring capable of advancing the screw head is mounted between the piston and the recessed end of the screw shaft. An electromagnet is disposed behind the recess of the tip of the screw shaft, and the screw head is provided so as to be retractable by the excitation of the electromagnet so that the check ring can be forcibly opened and closed between the tip 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 excitation force of the electromagnet and the extension force of the spring to sandwich 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, the 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 view showing a simplified configuration of a main part of an injection apparatus according to an embodiment of the present invention, FIG. 2 is a detailed sectional view of a rear portion of an injection cylinder, and FIG. 3 is a more detailed partially enlarged sectional view of FIG. FIG. 4 is a detailed cross-sectional view of the contact terminal portion for energizing the electromagnet, FIG. 5 is an explanatory view showing the open state of the check ring, and FIG. 6 is an explanatory view showing the forced closed state of the 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 into which a piston 19 in which the screw 1 is movable in the axial direction and is rotatably attached is inserted is attached.

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 operated by a hydraulic valve 11. Controlled. 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. Becomes smaller in diameter, and this small diameter portion 27a is located at the front small diameter portion 27b.
And a rear small diameter portion 27c.
A check ring 2 which is slidable in the axial direction is inserted in b.

A piston 24 is fixed in the middle of the small diameter portion 27a of the screw head 27, and is engaged with a cylindrical space portion 22 at the front end portion of the screw 1 as shown in FIG.
The piston 24 is slidably arranged here.

An elastic spring 26 is elastically mounted on the outer periphery of the rear small diameter portion 27c. Further, an electromagnet 23 is disposed behind the cylindrical space portion 22, and as shown in FIG. 2, the length from the electromagnet 23 to the rear portion of the injection cylinder 20 along the axial center of the central portion of the screw 1. Through hole 28
Has been drilled.

This through hole 28 is L at the rear as shown in FIG.
The electromagnet 23 is bent under a rotating state of the screw 1 through a conductor 25 connected to the molding machine control device 32.
An annular passage 12 is provided at the rear of the injection cylinder 20 so as to be constantly energized, and a contact terminal 29 is arranged along the annular passage 12. On the other hand, a brush 21 is arranged at the end of the conducting wire 25, and when the screw 1 rotates, the brush 21 also simultaneously rotates while rubbing against the contact terminal 29, and can be energized even while the screw 1 is rotating.

Reference numeral 15 is a hopper, 15a is a resin pellet, 18 is a screw head front portion, and 32 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. Before the measurement process is started, the electromagnet 23 is demagnetized in order to store a certain amount of molten resin while rotating the screw 1 and moving it backward while moving the molten resin from the rear side of the screw 1 to the screw head front portion 18. As shown in FIG. 5, the screw head 27 overcomes the extension force of the spring 26 and is moved in the direction away from the check sheet 1a. 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 step is completed, when the conducting wire 25 is energized to excite the electromagnet 23, the extension force of the spring 26 is overcome and the screw head 27 is moved closer to the check sheet 1a side. 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. 6)

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 head front portion 18 by the measuring process is passed through the nozzle 4 to a mold cavity (not shown). Injection 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 can be moved back and forth, and a spring that can advance the screw head between the piston and the tip recess of the screw shaft is mounted. An electromagnet is arranged behind the tip concave portion of the screw shaft, and a screw head is provided so as to be retractable by excitation of the electromagnet so that the check ring can be forcibly opened and closed between the tip end of the screw shaft and the rear end of the screw head. Due to
Since the backflow of the molten resin in the check ring due to the delay in closing can be prevented, an ideal injection process can be realized.

[Brief description of drawings]

FIG. 1 is a schematic view showing a simplified configuration of a main part of an injection device according to an 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 cross-sectional view of a contact terminal portion that energizes an electromagnet.

FIG. 4 is a detailed sectional view of a front portion of a screw.

FIG. 5 is an explanatory diagram showing an open state of the check ring.

FIG. 6 is an explanatory diagram showing a forced 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 12 Annular Road 15 Hopper 18 Screw Head Front 19 Piston 20 Injection Cylinder 21 Brush 22 Cylinder-shaped space 23 Electromagnet 24 Piston 25 Conductor 26 Spring 27 Screw head 27a Small diameter part 27b Front small diameter part 27c Rear small diameter part 28 Through hole 29 Contact terminal 30 Injection device 31 Screw head rear end 32 Molding machine control 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. The screw head is provided so as to be movable back and forth, and a spring for advancing the screw head is mounted between the piston and the tip recess of the screw shaft, and an electromagnet is arranged behind the tip recess of the screw shaft. The check ring opening / closing device in an injection molding machine, wherein the screw head is provided so as to be retractable by excitation of the check ring so that the check ring can be forcibly opened / closed between the front end of the screw shaft and the rear end of the screw head.