JPH0439412B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention relates to a check valve device for an in-line screw type injection molding machine.

<Prior art> To explain the conventional check valve with reference to FIGS. 4 and 5, the valve body 10 is attached to the small diameter portion 12 of the screw head 12 attached to the tip of the screw 11.
It has a cylindrical shape with an inner diameter surface such that a sufficient gap 13 is formed between the screw head 12 and the spacer 14 attached to the distal end surface of the screw 11. The heating cylinder 15 is fitted into the inner diameter surface of the heating cylinder 15 so as to be movable forward and backward in the direction. Further, a pawl 16 provided at the front end of the check valve 10 is engaged with a recess 17 provided in the conical portion 12b of the screw head, so that the screw 11 and the valve body 10 rotate together. A plurality of projections 10a are provided on the screw head, and when the top surface A of the projections 10a comes into contact with the conical portion 12b of the screw head, the screw head is sandwiched between the conical portion 12b of the screw head and the plurality of projections 10a. A gap 18 is formed, and the gap 13 formed between the screw head small diameter portion 12a, the gap 18, and the gap S formed between the rear end surface B of the valve body 10 and the spacer 14 are connected to each other, and the resin It is designed to serve as a distribution channel.

With the above structure, when the screw 11 rotates during the plasticizing process, the resin material that has been melted and transferred from upstream of the screw 11 is pushed toward the front of the valve body 10 (towards the left in the figure) and is pushed to the cone of the screw head. As a result of contact with the shaped portion 12b, the resin material flows through the resin flow path as indicated by arrow a and is accumulated in front of the screw head 12. Next, when a predetermined accumulation amount is measured, the plasticizing process is completed, and the screw 11, which is at the retraction limit, moves forward (moves to the left in the figure) to inject the measured amount of resin material, and the valve body 10
is pushed by the resin accumulated in front of the screw head 12 and retreats to close the gap S formed between the rear end surface B and the surface of the spacer 14, thereby closing the resin passage.

The concave portion 17 provided in the screw head 12 has a side wall surface c on the opposite side to the screw rotation direction b, which has a claw 16.
As it goes further back from the insertion opening, it becomes an inclined surface at an angle θ with respect to the axis line so as to become a grip, and when the screw rotates in the direction of arrow b, the claw 16 hits the side wall surface c of the recess 17 and rotates. The force F ₁ gives a component force F ₂ , and the valve body 10 is pushed backwards (toward the spacer) by the force F ² due to the rotation of the screw, or if the rotational speed is large and the discharged resin pressure is high, this force F ² The valve body 10 is pushed forward by overcoming this. However, when the discharge pressure decreases by decreasing the rotational speed, the component force _F2 becomes larger, the balance that has been maintained up to now is lost, and the valve body 10 closes the gap S or retreats to the point where it is about to close. When the next step, the injection step, moves forward, the gap S is zero or very narrow, so the resin passage is quickly closed, and the dispersion caused by the closing operation is eliminated, resulting in defective molded products. Not.

<Problems to be Solved by the Invention> However, in the conventional device, the pawl 16 and the side wall surface c of the recess 17 of the screw head come into contact with each other at the edges, so the surface pressure under load increases, resulting in the possibility of chipping or jamming of the contact portion. In addition, as a result of the force applied to the tip of the nail, the base of the nail received a large bending moment, causing the nail to break. Furthermore, since there was only one claw, it was disadvantageous in terms of strength.

<Means for solving the problems> In order to eliminate the above-mentioned drawbacks, in the present invention,
Provided between the screw tip and the screw head,
A valve body for preventing backflow that opens the molten resin path during the plasticization process and allows the molten resin to pass toward the screw head side, but moves toward the screw side and closes the resin path during injection. A valve body is provided with a protrusion that engages with a plurality of recesses provided in a plurality of screw heads at the screw head side end of the body, and the side surface of the protrusion that receives torque from the screw head when the screw rotates is sloped so as to become narrower from the base to the tip. and a backflow prevention device comprising a screw head in which the wall surface of the recess of the mating screw head facing the slope of the projection is inclined so as to become narrower toward the back from the insertion opening of the projection so that the wall surface of the recess is the same as the slope of the projection. It was used as a valve device.

<Function> With this structure, the convex part makes surface contact with the side wall surface of the concave part at multiple places, so the contact pressure is lowered and the strength is sufficient compared to the case of conventional line contact with only one place. We can give you a guarantee.

<Embodiments of the Invention> Next, one embodiment of the present invention will be described with reference to FIGS. 1 to 3. In explaining the conventional equipment and configuration,
Since the operations are the same, only the members that are different from the conventional device are given different numbers and will be explained, and the same members as the conventional device are given the same numbers and the explanation will be omitted.

20 is a valve body, and like the conventional device, the screw 11
It can move forward and backward in the axial direction between the screw head 21 and the screw head 21, and when it moves forward and comes into contact with the screw head 21, it opens the resin passage, and when it moves back and comes into contact with the spacer 14 attached to the tip of the screw 11. At this time, the resin passage is closed.
A plurality of protrusions 22 (four in this embodiment) are provided at the end of the valve body 20 on the screw head side, and recesses 23 corresponding to the number of protrusions 22 are provided in the screw head 21. 22 is adapted to engage with the recess 23. Each of the protrusions 22 rotates the screw 11 in the direction b, and the screw head 21
The side surface that receives torque from the base is a sloped surface that tapers from the base to the tip. Also, the recess 23
Each of the concave portions 2 that also come into contact with the inclined surface of the convex portion 22
The side wall surface c of No. 3 has the same slope as the slope of the convex portion 22 .

<Effects of the Invention> With the configuration as explained above, when the convex part contacts the concave part as in the conventional device, surface contact is made between the same inclined surfaces at multiple locations, so the contact pressure is small. This results in a check valve with sufficient strength.If this check valve is operated in the same manner as the conventional device as described above, the resin passage can be quickly closed and a highly accurate product can be molded.

[Brief explanation of drawings]

FIG. 1 is a diagram showing one embodiment of the present invention. FIG. 2 is a cross-sectional view of FIG. 1. FIG. 3 is a detailed diagram of the engaging portion of the concave and convex portion. 4 and 5 are diagrams of a conventional device, and FIG. 4 is a side view thereof. FIG. 5 is an axial cross-sectional view. 10, 20... valve body, 11... screw, 1
2, 21...Screw head, 15...Heating cylinder, 16...Claw, 17, 23...Recess, 22...
...Protrusion.

Claims (1)

[Claims] 1. It is provided between the screw tip and the screw head, and during the plasticizing process, the molten resin path is opened and the molten resin passes to the screw head side. However, during injection, the resin path is moved toward the screw side and the resin path is opened. A backflow prevention valve body configured to close, the valve body having a convex portion that engages with a plurality of concave portions provided in a plurality of screw heads at the screw head side end of the valve body, and when the screw rotates, the convex portion engages with the concave portions provided in the screw head. The protrusion is inserted so that the side surface that receives the torque is inclined so that it becomes narrower from the base to the tip, and the wall surface of the recess of the mating screw head that faces the inclined surface of the protrusion is the same as the slope of the protrusion. A backflow prevention valve device consisting of a screw head that tapers toward the back from the mouth. 2 It is provided between the screw tip and the screw head, and during the plasticization process, the molten resin path is opened and the molten resin passes to the screw head side, but during injection, it moves toward the screw side and closes the resin path. This is a valve body for preventing backflow, and the screw head side end of the valve body is provided with a convex portion that engages with the concave portions provided in a plurality of screw heads, and the side surface of the convex portion that receives torque from the screw head when the screw rotates is the base. The valve body is inclined to become narrower from the tip to the tip, and the recessed wall surface of the mating screw head facing the inclined surface of the convex portion is aligned with the inclination of the convex portion toward the back from the insertion opening of the convex portion. A non-return valve device consisting of a screw head that is inclined to become narrower is used to reduce the screw rotation speed at any time immediately before the completion of the plasticizing process or when the screw is in the retracted position, thereby preventing the discharge of molten resin during plasticization. Backflow characterized in that the pressure is reduced and the valve body is moved toward the screw to close the resin passage or to a position on the verge of closing in advance by the force in the screw axis direction applied to the valve body by the screw rotation torque. How to operate the prevention valve device. 3. The method of operating a check valve device according to claim 2, wherein the operating method is performed by decreasing the screw rotation speed and increasing the screw back pressure.