JPH0460807B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) This invention relates to a feed screw of a raw material supply device for supplying a fixed amount of raw material to an injection molding machine.

(Prior Art) In an injection molding machine, a raw material supply device is attached to feed a resin raw material such as raw material pellets into a heating cylinder of the molding machine. This raw material supply device guides the raw material in the hopper to the input port through a feed screw, and from there continuously inputs and supplies the raw material into the rotating heating cylinder of the main screw.

In this way, the amount of raw material supplied to the heating cylinder of a molding machine is determined by the amount of raw material fed into the input port by the feed screw, but in conventional feeding devices, this amount of feed is often constant. It has been pointed out that there is no such thing.

In other words, as shown in Fig. 4, in conventional feed screws, the screw pitches P are formed at equal pitches, but if this pitch is too wide, the screws will not fall continuously at the inlet as the screw rotates. However, there was a problem in that the feed rate of raw materials varied, with some falling at the same time or not falling all at once. On the other hand, if the pitch of the feed screw is too narrow, a so-called bridging phenomenon occurs in which the raw material gets stuck in the ridges of the screw, making it impossible to feed the raw material reliably and causing the problem that the predetermined amount of extrusion cannot be obtained at the input port. It was hot.

If the amount of raw material supplied into the heating cylinder is not constant in this way, it not only has an unexpected effect on the injection molding material being plasticized, but also affects the rotation of the main screw, causing the retracted position of the screw to vary. ,
Alternatively, it may cause idle rotation, leading to deterioration of melting conditions due to overheating or the like.

(Problems to be Solved by the Invention) Therefore, it is an object of the present invention to provide a feed screw for a raw material supply device that can reliably obtain a uniform feed amount.

(Means for Solving the Problems) That is, the feed screw of the raw material supply device in the injection molding machine of the present invention is characterized in that the pitch of the feed screw is configured to gradually become narrower toward the tip of the screw.

Furthermore, the feed screw according to claim 2 is constructed such that the pitch of the feed screw becomes gradually narrower toward the tip of the screw, and the depth of the screw groove becomes gradually deeper. The range described in item 3 relates to the item described in item 2 above, in which the volumes between the pitches are approximately the same.

(Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 of the attached drawings is an overall sectional view of a raw material supply device equipped with a feed screw according to an embodiment of the present invention, and FIG. FIG. 3 is a side view of the main part of the feed screw, and FIG. 3 is a side view of the feed screw showing an embodiment in which the depth of the screw groove is changed.

The raw material supply device 10 shown in FIG. 1 is attached to the rear part of the heating cylinder 31 of an injection molding machine, and the resin raw material M in the hopper 12 is conveyed to the input port 13 by the feed screw 11 and molded from the input port 13. It is supplied into the heating cylinder 31 of the machine. In the figure, reference numeral 14 represents the casing of the feeding device, 19 represents the drive section of the feed screw, and 32 represents the main screw.

The feed screw 11 according to the present invention has a second
As shown in the figure, the pitch of the screw becomes gradually narrower toward the tip of the screw. In the example, the pitch Pr at the rear end (closer to the hopper) is formed to a width of 25 mm, and gradually narrows by about 1 mm as it goes toward the tip (closer to the input port), and the pitch Pf at the tip has a width of about 15 mm. is formed.

When compared with the conventional feed screw 51 shown in FIG. 4 for reference, the pitches P of the conventional feed screw 51 of the same type are approximately 25 mm wide and are formed at equal intervals.

The feed screw 21 shown in FIG. 3 is constructed so that the pitch becomes gradually narrower toward the tip of the screw, and correspondingly, the depth of the screw groove becomes gradually deeper toward the tip of the screw. .

In this example, as above, the rear end pitch Pr near the hopper is 25 mm, the tip pitch Pf is 15 mm wide, and the depth of the screw groove is 8 mm at the rear end Dr near the hopper. The depth gradually increases by 0.5 mm toward the tip, and the depth is 13 mm at the tip Df.

As shown above, in the case where the pitch is gradually narrowed toward the tip of the screw and the depth of the screw groove is also gradually deepened, the relationship between the pitch and the groove depth should be adjusted so that the volume between each pitch is the same. can be designed.

(Action/Effect) Regarding the feed screw according to this invention,
The pitch of the screw near the hopper is wide and gradually narrows toward the tip of the screw near the input port. With this configuration, the raw material from the hopper can reliably enter the pitch groove due to the wide pitch portion. In addition, the pitch of the screw gradually narrows as it goes toward the tip, so the raw material is gradually fed in a dense state, and the area near the input port at the tip is in a highly dense state, which means that the pitch of the screw gradually narrows as it goes toward the tip. This makes it possible to feed out raw materials uniformly.

In addition, in the case where the pitches are gradually narrowed and the groove depth of each pitch is gradually deepened, a certain amount of raw material chips is reliably and constantly held in the grooves at the front and rear of the screw. This makes it possible to supply the necessary amount of raw material uniformly and continuously, and to obtain an accurate amount of raw material extrusion. In this case, it is preferable that the spacing between the pitches and the groove depth be set in such a relationship that the volumes between the screws are approximately the same.

As described above, in the present invention, the conventional problem of variations in feed rate of raw materials is solved at once, and the molding conditions of injection molding can be significantly improved.

[Brief explanation of the drawing]

Fig. 1 is an overall sectional view of a raw material supply device equipped with a feed screw according to an embodiment of the present invention, Fig. 2 is a side view of the main part of the feed screw, and Fig. 3 is an embodiment in which the depth of the screw groove is changed. FIG. 4 is a side view of a conventional feed screw. 10... Raw material supply device, 11, 21... Feed screw, 13... Inlet, M... Resin material,
P, Pr, Pf...Pitch, Dr, Df...Depth of the screw groove.

Claims (1)

[Scope of Claims] 1. A feed screw for a raw material supply device in an injection molding machine, characterized in that the pitch of the feed screw is configured to gradually become narrower toward the tip of the screw. 2. A feed screw of a raw material supply device in an injection molding machine according to claim 1, wherein the depth of the screw groove of the feed screw becomes gradually deeper toward the tip of the screw. 3. A feed screw of a raw material supply device in an injection molding machine according to claim 2, wherein the pitches of the feed screw and the depths of the screw grooves are configured so that the volumes between the pitches are approximately equal.