JPH0257494B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to screws for extrusion molding machines, injection molding machines, blow molding machines, etc., and particularly to a screw for plastic molding equipped with subflights.

[Prior art]

An example of a conventional screw having sub-flights will be described with reference to FIG. Skrill 11 consists of a main flight 12 and a sub-flight 13 in between.
A melt pool groove 14 is formed on the right side (upstream side) of the subflight 13, and a solid bed groove 15 is formed on the left side, and the interval between the solid bed grooves 15 becomes narrower from upstream to downstream on the right side of the figure, resulting in a dam flight. It has a function. However, since the lead angles of both flights 12 and 13 are different, automatic machining using an NC thread cutting lathe is not possible, and manual feeding machining is required using a milling end mill, etc., so the manufacturing cost is significantly higher than that of a full-flight screw. It was. Furthermore, in the case of hardened screws, automatic thread grinding machines cannot be used, so pre-hardening processing has to be performed, resulting in a decrease in precision due to hardening, which also results in a significant increase in cost.

[Object of the Invention] The present invention eliminates these drawbacks, and its purpose is to provide an NC
To provide a screw for plastic molding equipped with sub-flights that can be used with a thread cutting lathe, an automatic thread grinder, etc., and can reduce costs.

[Key points of the invention]

The plastic molding screw with sub-flights according to the present invention has three zones from the base of the screw to the tip: a feed zone, a compression zone, and a metalling zone. In screws equipped with sub-flights that have the same lead angle as the flights and a slightly lower height than the main flights, the slope of the solid bed groove bottom formed by the sub-flights provided in the compression zone is similar to that of the melt pool groove bottom. The slope is increased toward the downstream side of the resin, and the end of the solid bed groove bottom touches the metering zone groove bottom at the opposite slope from the point where it is higher than the metaling zone groove bottom, while the end of the melt pool groove bottom touches the metalling zone groove bottom. The ring zone is characterized by being in contact with the bottom of the groove.

[Embodiments of the invention]

The present invention will be explained below with reference to FIGS. 1 to 3 showing one embodiment. Figure 1 Skrill 21
It consists of a metering zone 22, a compression zone 23, and a feed zone 24 from the left (tip). The screw 21 includes a main flight 25 and a sub-flight 26 provided in the middle.The sub-flight 26 starts from the start point of the compression zone 23 and ends slightly before the end point of the compression zone 23, and both flights 25 and 26 have the same lead angle, and the flight height of the sub-flight 26 is slightly lower than that of the main flight 25. The width of the melt pool groove 27 on the right side of the sub-flight 26 is narrower than that of the solid bed groove 28 on the left side, and the groove depth of the melt pool groove 27 is smaller than that of the full-flight screw in the feed zone 24 and melt zone 22 that are not equipped with the sub-flight 26. This corresponds to the groove depth of the section.

As shown in FIG. 2, the taper angle of the bottom of the solid bed groove 28 is larger than that of the melt pool groove 27, so the resin is strongly compressed, and the melted resin that has undergone kneading and dispersion forms a solid bed as shown in FIG. The melt flows from the groove 28 over the sub-flights 26 into the melt pool groove 27, where the bottom surface becomes gradually shallower so that it is kneaded. The groove depth of the solid bed groove 28 gradually increases downstream from the end point of the subflight, as shown in FIG. The groove depth is made to match the groove depth of the full-flight screw portion of the metering zone 22 which is not provided, or this position is made to match the end point of the compression zone 23. Even in the portion where the groove depth of the solid bed groove 28 gradually increases, the groove depth is shallower than that of the melt pool groove 27, so that the kneading and dispersion of the resin and the promotion of plasticization are carried out. Further, the groove depth of the solid bed groove 28 at the end point of the sub-flight 26 is preferably 1/2 to 1/5 of the groove depth of the solid bed groove 28 at the start point of the sub-flight 26, and further, the groove depth of the solid bed groove 28 in the screw axis direction is preferably The width is preferably 1/2 to 7/8 of the total groove width.

〔Effect of the invention〕

As explained above, the plastic molding screw with sub-flights according to the present invention has the same lead angle between the main flights and the sub-flights, so it is possible to use NC thread cutting lathes, automatic thread grinding machines, etc. Cost is low. Furthermore, the groove depth of the solid bed groove divided by the subflights gradually decreases from the start point of the subflight toward the end point of the subflight toward the resin downstream, so it has a dam flight function, and this function allows the resin to melt evenly. It has the advantage of obtaining even better dispersion properties when kneaded.

[Brief explanation of the drawing]

Figures 1 to 3 show an embodiment of the present invention; Figure 1 is a side view, Figure 2 is a developed view of the melt pool groove and solid bed groove, Figure 3 is a developed view of the sub-flight, and Figure 4 is a developed view of the sub-flight. is a side view of a conventional example. 21... Skrill, 22... Metering zone, 23... Compression zone, 24...
Feed zone, 25... Main flight, 26...
Subflight, 27... Melt pool groove, 28...
...Solid bed groove.

Claims (1)

[Scope of Claims] 1. It has three zones: a feed zone, a compression zone, and a metering zone, and has the same lead angle as the main flight in the screw groove formed by the main flight, and its height is the same as that of the main flight. In a screw having sub-flights slightly lower than the main flights, the slope of the solid bed groove bottom formed by the sub-flights provided in the compression zone is directed toward the downstream side of the resin relative to the slope of the melt pool groove bottom. so that the end of the solid bed groove bottom touches the metering zone groove bottom at a reverse slope from a point higher than the metering zone groove bottom, while the end of the melt pool groove bottom touches the metering zone groove bottom. Plastic molding screw with sub-flights.