JP3157966B2 - Screw for injection molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw for an injection molding machine used for a plasticizing device of an injection molding machine.

[0002]

Conventional injection molding machine screw, as shown in FIG. 3, for implementing the anti-galling with enhanced effective extrusion amount per one rotation, the screw flight width F ₀ flights 22 of the screw 21 It is set to 0.2 times the diameter D ₀ of 21, and a sequentially supplying section 24, compression section 25 and metering unit 26 from the rear end side.

The supply section 24 is a section which plays a role of conveying the supplied molding material forward while preheating it. The depth of the screw groove 23 is deeper than other parts, and is perpendicular to the groove direction. the cross-sectional area of a cross-section has been slightly reduced as it goes forward.

The compressing section 25 is a section which plays a role of transmitting and melting heat from a heating cylinder (not shown) while giving a shearing action to the molding material, and has a cross section perpendicular to the depth of the screw groove 23 and its groove direction. Has a relatively sharp decrease in cross section.

[0005] The measuring section 26 is a section which plays a role of kneading and homogenizing the molten molding material.
Is shallow, and the cross-sectional area perpendicular to the groove direction is hardly changed.

[0006]

In the above prior art,
Since the volume of the entire recess formed by the screw groove of the screw (hereinafter, referred to as “total volume of the screw groove”) is large, the amount of the molding material retained in the heating cylinder is also large.
Therefore, during injection molding of a thick molded product in which the cycle per shot is long, a large amount of molding material may stay in the heating cylinder for a long time, causing discoloration or decomposition. In addition, when an injection molding machine designed to injection-mold a large-volume molded product is used for injection-molding a small-volume molded product, the injection amount per shot is small. There is a problem that the molding material stays for a long time to cause discoloration and decomposition.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has been made to reduce the effective extrusion amount per rotation and the residence time of a molding material in a heating cylinder without impairing the galling prevention function. An object of the present invention is to realize a screw for an injection molding machine that can be shortened.

[0008]

In order to achieve the above object, a screw for an injection molding machine according to the present invention has a substantially same pitch.
The screw width of the screw flight is 0.3 mm of the screw diameter.
It is characterized in that it is within the range of times to 0.5 times.

[0009]

[Function] A screw having screw grooves of almost the same pitch
In the above, by setting the flight width of the flight of the screw within the range of 0.3 to 0.5 times the diameter of the screw, the pitch of the flight of the screw is increased or the groove depth of the screw groove is increased. The residence time of the molding material in the heating cylinder can be reduced without making it shallow.

[0010]

An embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic plan view showing a screw for an injection molding machine according to a first embodiment of the present invention. The screw 1 has screw grooves 3 having substantially the same pitch P, and the groove depth is gradually reduced from the supply section to the measuring section as in the conventional screw, but the flight width F of the flight 2 is Is set in the range of 0.3 to 0.5 times the diameter D of For this reason, despite the fact that the depth of the screw groove 3 is the same as that of the conventional screw, the total volume of the screw groove 3 is reduced in the entire screw, so that the molding material stays in the heating cylinder. The amount is reduced and the residence time is shortened, so that it becomes difficult to receive the heat history, and the discoloration and decomposition of the molding material are prevented and the generation of contamination is reduced.

Here, if the flight width F of the flight 2 is smaller than 0.3 times the diameter D of the screw 1, the total volume of the screw groove becomes large and the residence time becomes longer, and the flight width F becomes smaller than that of the screw 1. If it is larger than 0.5 times the diameter D, 1
The effective extrusion rate per revolution becomes too small and galling occurs.

FIG. 2 is a schematic sectional view of a main part of a plasticizing apparatus using a screw for an injection molding machine according to a second embodiment of the present invention.

The screw 11 of this embodiment differs from that of the first embodiment only in that a flight 12a having a small flight width is provided in a so-called supply section near an inlet 15a of a hopper 15 of a heating cylinder 14. Are the same, and a description thereof will be omitted.

[0015] In the present embodiment, the solid state molding material in the supply section is well absorbed.

[0016]

Since the present invention is configured as described above, the following effects can be obtained.

Since the flight width of the flight of the screw is in the range of 0.3 to 0.5 times the diameter of the screw,
Compared to the above-described conventional screw for an injection molding machine, the amount of stagnation of the molding material in the heating cylinder is reduced, and thus the stagnation time is shortened. The occurrence of contamination is reduced. In addition, since sufficient shearing force and cylinder heat can be received, the degree of kneading of the molding material is improved, and the dispersibility of pigments and the like is improved.

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing a screw for an injection molding machine according to a first embodiment of the present invention.

FIG. 2 is a schematic partial sectional view of a main part of a plasticizing apparatus using a screw for an injection molding machine according to a second embodiment of the present invention.

FIG. 3 is a schematic plan view showing a conventional screw for an injection molding machine.

[Explanation of symbols]

 1,11 screw 2,12 flight 3,13 screw groove D screw diameter F flight width P pitch

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) B29C 45/00-45/84 B29C 47/00-47/96

Claims (1)

(57) [Claims] 1. Screw grooves having substantially the same pitch (P)
In the screw (1) having (3), the flight width (F) of the flight (2) of the screw (1) is in the range of 0.3 to 0.5 times the diameter (D) of the screw (1). A screw for an injection molding machine, characterized in that: