US-12623384-B2 - Screw for direct molding, injection molding apparatus, and kneading piece

US12623384B2US 12623384 B2US12623384 B2US 12623384B2US-12623384-B2

Abstract

A screw for direct molding that transports, toward a downstream side, thermoplastic resin supplied from the upstream side, while melting the thermoplastic resin, and that kneads the molten resin which has been transported thereto, together with an additive material introduced at an intermediate point, includes a screw main body and a kneading piece main body. The screw main body includes a first stage and a second stage. A main flight in a spiral form is provided on an outer circumferential surface of the first stage. A plurality of flights in a spiral form are provided on an outer circumferential surface of the second stage. A plurality of flights in a spiral form are provided on an outer circumferential surface of the kneading piece main body. At least one cutout part is formed at an intermediate point of the flights provided on the kneading piece.

Inventors

Daisuke KUNIHIRO
Mitsuhide Umeda
Hideki Chiba

Assignees

THE JAPAN STEEL WORKS, LTD.

Dates

Publication Date: 20260512
Application Date: 20221014
Priority Date: 20220317

Claims (11)

1 . A screw for direct molding that transports, toward a downstream side, thermoplastic resin supplied from an upstream side, while melting the thermoplastic resin, and that kneads molten resin which has been transported thereto, together with an additive material introduced at an intermediate point, the screw for direct molding comprising: a screw main body; and a kneading piece main body detachably attached to an end part of the screw main body on the downstream side, wherein the screw main body includes a first stage positioned on the upstream side and a second stage positioned on the downstream side, a main flight in a spiral form is provided on an outer circumferential surface of the first stage, a plurality of flights in a spiral form are provided on an outer circumferential surface of the second stage, a plurality of flights in a spiral form are provided on an outer circumferential surface of the kneading piece main body, at least one cutout part is formed at an intermediate point of the flights provided on the kneading piece, and a step part into which the molten resin enters is formed at an apex part of the main flight, by cutting out a section of the apex part of the main flight on the downstream side.
2 . The screw for direct molding according to claim 1 , wherein the cutout part is arranged in a ring form in a circumferential direction.
3 . The screw for direct molding according to claim 1 , wherein a sub flight in a spiral form is further provided on the outer circumferential surface of the first stage, and the sub flight branches from the main flight at a boundary part between the compression part and the measurement part and merges with the main flight again at an end part of the first stage on the downstream side.
4 . The screw for direct molding according to claim 1 , wherein a length of the kneading piece main body in an axial direction is shorter than a length of the screw main body in an axial direction.
5 . The screw for direct molding according to claim 1 , wherein the number of flights provided on the kneading piece main body is larger than the number of flights provided in the second stage.
6 . The screw for direct molding according to claim 1 , wherein a lead angle of the flights provided on the kneading piece main body is larger than a lead angle of the flights provided in the second stage.
7 . The screw for direct molding according to claim 1 , wherein a groove depth of a flight groove defined by the flights provided on the kneading piece main body is shallower than a groove depth of a flight groove defined by the flights provided in the second stage.
8 . An injection molding apparatus comprising the screw for direct molding according to claim 1 .
9 . A kneading piece comprising: a kneading piece main body detachably attached to an end part, on a downstream side, of a screw for direct molding that transports, toward the downstream side, thermoplastic resin supplied from an upstream side, while melting the thermoplastic resin, and that kneads molten resin which has been transported thereto, together with an additive material introduced at an intermediate point, wherein a plurality of flights in a spiral form are provided on an outer circumferential surface of the kneading piece main body, at least one cutout part is formed at an intermediate point of the flights provided on the kneading piece, and a step part into which the molten resin enters is formed at an apex part of the main flight, by cutting out a section of the apex part of the main flight on the downstream side.
10 . The kneading piece according to claim 9 , further comprising a threaded part to be engaged, by a thread, with a threaded bore formed in an end part of the screw main body on the downstream side.
11 . An injection molding apparatus comprising a screw for direct molding to which, in an end part thereof on the downstream side, the kneading piece according to claim 9 is detachably attached.

Description

TECHNICAL FIELD The present invention is related to a screw for direct molding, an injection molding apparatus, and a kneading piece. BACKGROUND ART An apparatus is known (see Patent Literature 1, for example) that produces a molded product (performs direct molding), by transporting, toward the downstream side, thermoplastic resin (a plurality of resin pellets) supplied from the upstream side (a hopper), while melting the thermoplastic resin with heat transferred from a heating cylinder and shear heating generated from rotation of a screw, kneading molten resin which has been transported thereto, together with reinforcement fibers serving as an additive material introduced at an intermediate point (through a fiber introduction port formed in the heating cylinder), and injecting the molten resin in which the reinforcement fibers have been kneaded, into a mold. CITATION LIST Patent Literature Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2016-64607 SUMMARY OF INVENTION Technical Problem Patent Literature 1 has no mention at all of uniformly dispersing the additive material in the process of kneading the molten resin which has been transported from the upstream side, together with the additive material introduced at the intermediate point. Thus, there is room for improvement in this aspect. Other problems and novel features will become apparent from the description and the accompanying drawings of the present application. Solution to Problem A screw for direct molding according to an embodiment is a screw for direct molding that transports, toward a downstream side, thermoplastic resin supplied from an upstream side, while melting the thermoplastic resin, and that kneads molten resin which has been transported thereto, together with an additive material introduced at an intermediate point. The screw for direct molding includes a screw main body and a kneading piece main body detachably attached to an end part of the screw main body on the downstream side. The screw main body includes a first stage positioned on the upstream side and a second stage positioned on the downstream side. A main flight in a spiral form is provided on an outer circumferential surface of the first stage. A plurality of flights in a spiral form are provided on an outer circumferential surface of the second stage. A plurality of flights in a spiral form are provided on an outer circumferential surface of the kneading piece main body. At least one cutout part is formed at an intermediate point of the flights provided on the kneading piece. Advantageous Effects of Invention According to the embodiment described above, it is possible to provide the screw for direct molding capable of kneading the molten resin which has been transported from the upstream side, together with the additive material introduced at the intermediate point and dispersing the additive material more uniformly. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a diagram showing an overall configuration of an injection molding apparatus 1 according to an embodiment; FIG. 2 is a perspective view of a heating cylinder 17; FIG. 3 is a side view of a screw 18; FIG. 4 is an enlarged view of a first stage S1; FIG. 5 is a drawing showing (as viewed in the direction of the arrow AR1 in FIG. 4) a manner in which solid resin gradually decreases as the solid resin in a flight groove 62 is melted; FIG. 6 is a drawing showing (as viewed in the direction of the arrow AR1 in FIG. 4) a manner in which, due to an action of a sub flight 63, solid resin between the sub flight 63 and a main flight 61 is pressed toward the main flight 61 and increased in height; FIG. 7 is an enlarged view of a second stage S2; FIG. 8 is a graph showing a measuring period in an example (the embodiment) where two flights 65 and 66 are provided and a measuring period in another example (a comparison example) where only one flight is provided; FIG. 9 is an enlarged view of a kneading piece 70; FIG. 10 is an enlarged view of the kneading piece 70 (a modification example); and FIG. 11 is a perspective view of the screw 18. DESCRIPTION OF EMBODIMENTS The following will describe specific embodiments in detail with reference to the drawings; however, possible embodiments are not limited to the embodiments described below. Further, to keep the explanations clear, the following description and the drawings are simplified as appropriate. <An Overall Configuration of an Injection Molding Apparatus> To begin with, an overall configuration of an injection molding apparatus 1 (an injection molding machine) according to an embodiment will be explained, with reference to FIG. 1. FIG. 1 is a diagram showing the overall configuration of the injection molding apparatus 1 according to the embodiment. The injection molding apparatus 1 is an apparatus that produces (performs direct molding) a molded product (a molded product in which an additive material has uniformly been dispersed), by transporting, toward th