JPH0428518A - Non-return ring for resin mold screw - Google Patents

Abstract

PURPOSE:To increase the flow resistance of a molten resin on injection, and to prevent a back flow owing to the quick retreat of a non-return ring completely by partially reducing the path area or the communication path or the molten resin mounted between the inner circumferential surface of the non-return ring and the peripheral surface of an assembling shaft in a non-return ring front region on the screw head side. CONSTITUTION:A communication path 7 for flowing and moving a molten resin from the screw body 2 side to the front of a screw head 3 on weighing and retreating is formed between the inner circumferential surface of a non- return ring 5 and the peripheral surface of an assembling shaft 4. On the contrary, a projecting section 20 is formed to the inner circumferential surface of the non-return ring 5 or the path area of the communication path is reduced only in a non-return ring 5 front region on the screw head 3 side in order to leave only the non-return ring 5, close a rear communicating port 13 and easily prevent the back flow of the resin though a screw body 2 and the screw head 3 are unified and moved forward on injection.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The object of the present invention is to quickly and reliably perform a check operation of a check mechanism at the start of an injection operation.

[Prior Art] FIG. 4 shows a vertical sectional view of the main part of the most common conventional check ring.

In FIG. 4, the check ring is attached to the shaft 4 in a small diameter assembly with the screw head 3 fixed to the front end of the screw body 2.
A cylindrical check ring 5 is fitted loosely into the heating cylinder 1 with an outer diameter that can prevent leakage of molten resin between the heating cylinder 1 and the heating cylinder 1, and is fitted so as to be slidable in the front and rear directions. When assembled, a direct communication path 7 is provided between the inner circumferential surface of the retaining ring 5 and the circumferential surface of the shaft 4, so that the molten resin can flow from the screw body 2 side to the front of the screw head 3. ing.

Further, on the front end surface 9 of the non-return link 5, protrusions 1 are provided at predetermined intervals.
Several zeros are provided so that even if the check ring 5 is pressed against the screw head 3, the communication path 7 will not be blocked.

The opening of the communication path 7 in the rear end surface 11 of the check ring 5 is arranged so that its entire area faces the screw front surface 12 of the screw body 2, so that the rear end surface 11 of the check ring 5 is in contact with the screw front surface 12. In some cases, it becomes completely occluded.

When the molten resin is plasticized and metered backwards (hereinafter referred to simply as metering backwards), the check ring 5 is pressed forward by the flow resistance of the molten resin, and the rear communication port 13, the communication path 7, and the front communication port are 14 and is pushed out to the front of the screw head 3.

At the time of injection, the screw body 2 and the screw head 3 move forward together, while only the check ring 5 remains to close the rear communication port 13 and prevent the molten resin from flowing back.

[Problems to be Solved by the Invention] However, in reality, when the viscosity of the molten resin is low or the injection speed is slow, the degree of backflow of the molten resin increases until the rear communication port 13 is closed. This will cause variations in the injection amount.

For this reason, if measurements were made taking into account incompleteness and back flow of molten resin, overfilling would result in defective products, and this would cause mold damage due to the generation of flakes, a serious drawback.

As a means to eliminate these inconveniences, check ring 5
There are measures such as reducing the fitting gap between the outer circumferential surface of the heating cylinder 1 and the inner circumferential surface of the heating cylinder 1, or reducing the operating stroke of the check ring 5, but the former is due to the occurrence of burrs 9, and the latter is The narrowing of the resin flow path results in an increase in flow resistance, which increases the measuring time, which has a limit and cannot be used as a substantial solution.

[Means for Solving the Problems] In order to solve these problems, small-diameter assemblies are installed on the front end of the screw body, which is rotatably installed in the heating cylinder and can move forward and backward. In a check ring that is slidably fitted in the front-rear direction between the rear surface of the screw head and the front surface of the screw body that are attached to the screw head, the inner peripheral surface of the check ring and the assembly are connected to the shaft. The passage area of the molten resin communication path provided between the circumferential surfaces of the screw head is locally reduced in the front area of the check ring on the screw head side.

[Function] The small-diameter assembly that connects the inner peripheral surface of the check ring, the front end of the screw body, and the screw head reduces the passing area of the communication passage formed between the shafts to a local area in the front area of the check ring on the screw head side. I made it smaller. As a result, during injection, flow resistance increases when the molten resin flows backward through the communication path, and the check ring quickly retreats to press the check ring against the screw body, thereby preventing the backward flow of the molten resin.

[Example 1] Figures 1 to 3 show one embodiment of the check ring according to the present invention. FIG. 3 is a longitudinal cross-sectional view of a main part showing still another embodiment of the invention.

The present invention provides a screw head 3 attached to the front end of a straight bar-shaped screw body 2 which is rotatably assembled in a heating cylinder 1 and movable forward and backward, and has a screw flight on its circumferential surface. between the screw head 3 and the screw body 2.
A check ring 5 is provided which operates according to the sliding movement in the front-rear direction.

The present invention has a configuration having three major features.

(1) First, as shown in the illustrated embodiment (front communication port 1
4 (the difference between the outer circumferential surface of the base 3b of the screw head and the circumferential surface of the assembled shaft 4) is higher than that of the conventional example.

(2) In addition, the inner circumferential surface of the check ring 5 and the circumferential surface of the shaft 4 are installed so that the molten resin flows from the screw body 2 side to the front of the screw head 3 during metering retraction. A communication path 7 is formed. On the other hand, during injection, the screw body 2 and the screw head 3 move forward together, but only the reverse ring 5 remains and the rear communication port 13
In order to make it easier to close the check ring 5 and prevent backflow of resin, a protrusion 20 is formed on the inner peripheral surface of the check ring 5 only in the front area of the check ring 5 on the screw head 3 side, or a protrusion 20 is formed on the inner circumferential surface of the check ring 5, or This reduces the passage area.

(3) Furthermore, due to the difference between the pressure acting on the projected area of the screw head base 3b in the axial direction of the screw body 2 and the pressure acting on the projected area of the check ring 5, the check ring 5 In response to the pressing force in the direction of the screw front surface 12, the rear end surface 11 of the check ring 5 comes into contact with the screw front surface 12, and the rear communication port 13 is completely closed.

By using a non-return mechanism having the configuration (1) or 3) described above, the molten resin can flow through the front communication hole 1 during injection.
4. Since there is a large flow resistance when the flow flows backward from the screw head 3 side to the screw body 2 side through the communication passage 7 and the rear communication port 13, the screw head 3 is pressed against the screw body 2 by the injection pressure to quickly check the flow. becomes achievable.

Note that even if the check ring 5 is pressed against the head rear surface 3a due to the flow resistance of the molten resin and the retreat of the screw body 2, the protrusions 10 are provided at predetermined intervals on the front end surface 9 of the check ring 5. Since several of them are provided, there is no possibility that the forward extrusion of the molten resin will be blocked.

In the present invention, the protruding portion 20 is formed on the inner peripheral surface of the check ring 5 only in the front area of the check ring 5 described in (2) above, so that the passage area between the check ring 5 and the shaft 4 is reduced during assembly. Regarding this, when the screw rotates to retreat and extrude the molten resin in front of the screw head 3, it is necessary to smoothly pass the molten resin in front of the screw head 3. Care has been taken to completely prevent resin backflow.

The embodiments described above are illustrated in FIGS. 1 to 3, but
Similar results were obtained.

[Effects of the Invention] As is clear from the above embodiments, in the check ring of the present invention, a convex step is formed on the inner peripheral surface of the front area of the check ring to reduce the passage area of the communication path. Since the size is locally reduced, the flow resistance of the molten resin increases during injection, and the check ring quickly retreats, making it possible to completely prevent backflow.

In addition, the structure is simple and the entire screw configuration can be simplified.

[Brief explanation of drawings]

1 to 3 show one embodiment of the check ring according to the present invention, FIG. 1 is a vertical cross-sectional view of the main part showing the basic structure of the present invention, and FIG. FIG. 3 is a vertical cross-sectional view of the main part showing another embodiment of the present invention, and FIG. 4 is a main part of the most common conventional check ring. A vertical cross-sectional view is shown. 1... Heating tube, 2... Screw body,
3... Screw head, 4... Shaft for assembly, 5...
...Check ring, 7...Communication path, 13...Rear communication port, 14...Front communication port, 20...Protrusion portion. Patent applicant Ube Industries Co., Ltd. Figure 2

Claims (1)

[Claims] The screw head is attached to the front end of the screw body, which is rotatably attached to the heating cylinder so that it can move forward and backward, and the screw head is attached to the front end of the screw head via a small diameter assembly shaft, and the screw front side of the screw body. In a check ring that is slidably fitted in the front-rear direction, the passage area of the molten resin communication passage provided between the inner circumferential surface of the check ring and the circumferential surface of the assembly shaft is A check ring for resin molded screws that is characterized by being locally smaller in the front area of the lock ring.