JPS582054B2 - plastic snail - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In the spinneret of the set of spiders shown in FIG. 1, which is generally used as the die of a conventional thermoplastic resin extrusion molding machine or blow molding machine, the resin flow is symmetrical. Therefore, there is less uneven flow or accumulation of resin, but there is a disadvantage that the strength of spider e is limited and the weld line is only visible by the number of spiders, which affects the strength of the molded product and impairs its appearance. .

In addition, the crosshead type shown in Figure 2 does not have obstacles such as spiders, but since the flow is asymmetrical, it tends to cause uneven flow or stagnation, which may affect the accuracy of the product's wall thickness.
In order to eliminate this effect on the appearance quality, special measures are required for the structure, and when the structure is constructed as shown in the figure, precise machining accuracy by hand finishing is required.

In addition, the flow characteristics of these conventional nozzles change when the type of resin, extrusion pressure, temperature, melt viscosity, etc. change, so if the same nozzle is not adjusted accordingly, it will no longer be possible to use it. However, the technology for this adjustment is very difficult, and at present there is no one that can be adjusted to completely adapt to these various conditions.

The present invention has been devised to eliminate all of these conventional drawbacks, and there is no uneven flow or stagnation of the resin, and the product has excellent wall thickness accuracy and strength. The present invention relates to a plastic extrusion die which is excellent, does not require any special technology to manufacture, and can be adjusted according to the flow characteristics of the resin.

Next, drawings showing embodiments of the present invention will be explained.

In FIG. 3, 1 is a die body, 2 is a die ring, and 3 is an eccentric core metal, and the die ring 2 and the core metal 3 form a resin flow path 6.

4 is a resin pressure inlet, and 5 is an annular manifold following the resin pressure inlet 4.

The center of the manifold 5 is designated m.

The center of the core bar 3 to be eccentric is indicated by m'.

That is, the core metal 3 is eccentrically provided by α with respect to the center of the manifold 5 on the side far from the resin injection port 4.

7 is a discharge port of the resin flow path 6.

An adjustment lip 8 is provided on the discharge port 7, and the adjustment lip 8 adjusts the gap between the discharge port 7 of the resin flow path 6 using an adjustment bolt 9.

The molten resin is press-fitted into the resin injection port 4 from an extruder (not shown), goes around the manifold 5, and exits from the resin flow path 6 through the discharge port 7, but on the side of the resin flow path 6 farther from the injection port 4. Since the manifold flow path is that long, the flow of resin becomes uneven, but since the core bar 3 is installed eccentrically with respect to the center of the manifold 5, the resin entering from the resin injection port 4 reaches the point shown in Figure 3. It flows through an eccentric adjustment flow path p as shown in the figure.

In other words, the flow path from the manifold 5 to the discharge port 7 becomes longer due to this adjustment flow path p, and the flow resistance of the resin becomes larger as the side is closer to the resin injection port 4. The resistance due to the long manifold flow path on the side is exactly balanced and the amount of resin flowing out from the entire circumference of the resin flow path 6 is made uniform.

The one shown in FIG. 4 is another embodiment in which the center m' of the core bar 3 is eccentric to the side far from the resin injection port 4 with respect to the center m of the manifold 5, and is appropriately fixed to the die body 1 with fixing bolts 10. be done.

This amount of eccentricity can be arbitrarily selected when assembling the die.

In this case, the adjustment flow path p is formed in two stages above and below the choke ring 8'.

In other words, the amount of eccentricity of the core metal 3 to be eccentrically determined takes into account the flow characteristics of the resin, and the core metal 3 is placed in the best position so that the upper and lower two stages of adjustment channels p, p are most suitable. 3'
It is fixed to the die body 1 with a fixing bolt 10.

And even with this, the fine adjustment that is difficult to adjust is the choke ring 8'.
By adjusting , it is possible to obtain molded products such as films and sheets with even better thickness accuracy.

In FIG. 5, the discharge ports 7 of the two-layer resin channels 6, 6'
An example of a die used as a flow path adjustment mechanism in a multilayer die for extruding two layers of film from 7' is shown.

The base of the present invention is mainly a crosshead type base that is equipped with a flow path adjustment mechanism for precisely adjusting the flow and wall thickness of resin, and as described above, has a simple structure and is easy to handle. There is no accumulation of resin in the flow path, and a product with extremely high thickness accuracy can be obtained.

Furthermore, the same die can be used for resins with different flow characteristics.

In other words, the present invention balances the flow resistance of the resin in the flow path by adjusting the resin flow path on the side closer to the injection port and the resin flow path on the side farther from the injection port by providing an eccentric core metal, thereby reducing the tendency for uneven distribution. This completely eliminates the buildup of certain resins, making it possible to obtain products with good thickness accuracy.
The amount of eccentricity of the core metal to be eccentric can be arbitrarily selected so as to match the properties of the resin at the time of installation.

[Brief explanation of drawings]

1 and 2 show a conventional cap. Fig. 3A is a longitudinal sectional side view of a plastic extrusion die embodying the present invention, a plan view taken across the mark in Fig. 3 and the line A-A in Fig. 3A, and Fig. 4A is a cross-sectional side view of a plastic extrusion die embodying the present invention. FIG. 4 is a vertical sectional side view of the cap as an example; FIG. 4 is a plan view of the mouth taken across the line A-A in FIG. 4 A; FIG. . DESCRIPTION OF SYMBOLS 1...Die body, 2...Die ring, 4...Resin pressure inlet, 3...Eccentric core bar, 5...Manifold, 6...Resin flow path, 7...Discharge port .

Claims (1)

[Claims] 1. A resin flow path is formed by a die ring and a core bar provided within the die ring, and a ring-shaped manifold is provided at the bottom of the flow channel extending from the resin injection port. It is characterized by being eccentric to the side far from the resin pressure inlet with respect to the center of the manifold, so that the length from the manifold to the discharge port of the flow path is longer on the side closer to the resin pressure inlet than on the side farther from the resin pressure inlet. Plastic extrusion die.