JPS61222707A - Screw for plastic molding - Google Patents

Abstract

PURPOSE:To realize the smooth flow of resin and consequently enhance the kneading property of the titled screw by a structure wherein an auxiliary flight, which is parallel to a main flight and at the same time the height of which is lower than that of the main flight and is gradually decreased from its starting end in the upstream direction, is provided. CONSTITUTION:An auxiliary flight 6 is formed between a main flight 1 in the vicinity of the starting point M1 of a metering zone M. The auxiliary flight 6 has the same lead angle as that of the main flight 1. The main flight 1 and the auxiliary flight 6 run in parallel to each other. The height of the auxiliary flight 6 is made a little lower than that of the main flight 1. The height of the auxiliary flight 6 is gradually decreased from its starting end 61 in the upstream direction of a screw 5 so as to form a slant surface. In addition, the terminal end of the auxiliary flight 6 is made to be coincide with the bottom of the groove of the screw, resulting in realizing no stagnation of resin.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a screw for plastic molding used in molding methods such as extrusion, injection, and blowing.

[Technical background of the invention and its problems]

In screws used in plastic extrusion molding, injection molding, blow molding, etc., and machines, there are screws that have sub-flights in addition to the main flight to improve the kneading performance of the resin and uniform plasticization performance. be.

However, conventional screws with sub-flights are as shown in Fig. 4 (A) (Utility Model Application Publication No. 53-96070) and Fig. 4 (
B) As shown in (Japanese Utility Model Application No. 58-17122), since the sub-flight 3 intersects with the screw shaft 2 formed by the main flight 1, the sub-flight 3 is cut by a screw flight grinder or an NG Automatic machining using a thread cutting machine is no longer possible, and manual feeding machining is required using cutters, milling end mills, etc., and the number of man-hours required for machining is significantly increased compared to full-flag or straight screws, making the cost significantly higher. It had become.

In addition, in the case of hardened screws, since a thread grinder cannot be used, processing must be performed before hardening, and since the hardening is done afterwards, the accuracy decreases, and as a result, it takes a lot of man-hours to correct the accuracy. This resulted in a significant increase in production costs.

[Purpose of the invention]

The present invention has been made with the aim of improving the above drawbacks of the prior art, and makes it possible to automatically process screws with sub-flights using an NC thread cutting lathe or automatic flight grinder. , and gives the sub-flight a dumb flight function to improve the uniform crosstalk of resin and uniform plasticization performance, as well as eliminate the retention of resin at the starting end of the sub-flight, and improve color dispersion, resin change, and color change performance. The object of the present invention is to provide a plastic molding screw that can be used for plastic molding.

(Summary of the Invention) In order to achieve the above object, the present invention has a sub-flight which is parallel to the main flight and has a lower ^ than the main flight in the screw groove constituted by the main flight. is characterized in that the height of the starting end of the secondary flight gradually decreases toward the upstream side of the screw.

[Embodiments of the Invention] The present invention will be described below with reference to embodiments shown in FIGS. 1 to 3, using the same reference numerals for parts common to those in FIG. 4.

FIG. 1 shows the main parts of the screw 5 for plastic molding according to the present invention, in which the main flight extends from near the starting point C1 of the compression zone C following the feed zone F of the screw 5 to near the starting point M1 of the metering zone M. A sub-flight 6 is formed between the two.

This sub-flight 6 is formed with the same lead angle as the main flight 1, and the main flight 1 and the sub-flight 6
The height of the sub-flight 6 is slightly lower than that of the main flight 1. Melt boule grooves 7 are formed by being divided by the sub-flights 6.
has a width narrower than that of the solid bed groove 8 formed on the opposite side of the sub-flight 6.

The starting end 61 of the secondary flight 6 has a height that gradually decreases toward the upstream side of the screw 5, and forms an inclined surface 61. It is said that

In this embodiment, the height of the end end 6° of the sub-flight 6 is also gradually reduced toward the downstream side of the screw 5, forming an inclined surface 62a.

The groove bottom 8a of the solid bed groove 8, as shown in FIG. The end of the inclined surface 628 is aligned with the groove bottom of the screw 5.

Therefore, in the present invention, as described above, the sub-flight 6 is provided in parallel to the main flight 1 over the entire area,
In addition, the height of the starting point 61 of the sub-flight 6 is gradually reduced toward the upstream side of the screw 5, forming an inclined surface 61a. There is no stagnation, and the height of the terminal end 62 of the sub-flight 6 is gradually reduced toward the downstream side of the screw 5, so that the resin flows smoothly in the core part.
These can significantly improve the crosstalk performance, and if the groove depth of the solid bed groove 8 is gradually reduced in the downstream direction of the screw 5, the efficiency of heat transfer to the solid layer within the groove of the screw 5 can be increased. At the same time, the kneading effect is enhanced, and uniform plasticization performance can be improved.

Since the sub-flight 6 having the above-mentioned performance is formed with the same lead angle so as to be parallel to the main flight 1 over its entire area, automatic processing using a conventional flight automatic grinder or NC thread cutting lathe is possible. The production of the screw 5 can be made extremely easy.

(Effects of the Invention) As explained above, the present invention has a sub-flight parallel to the main flight and lower in height than the main flight in the screw groove constituted by the main flight. The height of the secondary flight is such that the starting end of the secondary flight gradually decreases toward the upstream side of the screw, so there is no accumulation of resin at the starting point of the secondary flight, and the secondary flight can be processed by automatic machinery. This has the excellent effect of making it easy to manufacture the screw and providing a high-performance screw with sub-flights at a low cost.

[Brief explanation of drawings]

Fig. 1 is a front view of the main parts showing an embodiment of the screw for plastic molding according to the present invention, Fig. 2 is a developed plan view of the main parts, and Fig. 3 is a cross-sectional view taken along the line ■-■ in Fig. 2. Figure 4 (A>
, (B) are explanatory diagrams showing a conventional example. 1... Main flight, 5... Screw, 6... Sub-flight, 7... Melt pool groove, 8... Solid bed groove.

Claims (1)

[Claims] 1. In the screw groove formed by the main flight, there is a sub-flight that is parallel to the main flight and has a lower height than the main flight, and the height of the sub-flight is lower than that of the sub-flight. A screw for plastic molding, characterized in that a starting end thereof gradually decreases toward the upstream side of the screw. 2. The screw for plastic molding according to claim 1, wherein the height of the terminal end of the sub-flight gradually decreases toward the downstream side of the screw.