JP2000135725A - Hopper hole structure of injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect a plurality of pellets from being bitten in even when a pellet-shaped resin is bitten between a screw flight and a hopper hole and reduce the fluctuation of slide resistance between a screw and a cylinder. SOLUTION: Out of corners whereon formed the inner periphery of a hopper hole 4 and a screw opening 1b crossing each other, the angle β of a corner in the screw end direction is formed as 5 deg.-40 deg. in the direction reverse to the screw angle of a flight 3 of a screw 2 to increase the angle formed by the flight 3 of the screw 2 and the hopper hole 4, and even when a pellet-shaped resin 5 is bitten therein, the resin is slid along the flight 3 of the screw 2 and can be moved. Also it is desirable that the above angle β is so defined as to set the angle (α+β) formed by adding the helix angle α and the angle β as 20 deg.-55 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the shape of a hopper hole of an injection molding machine.

[0002]

2. Description of the Related Art Conventionally, in an injection molding machine, the shape of a hopper hole for supplying pellet-shaped resin to a screw has been a cylindrical shape or a rectangular tube shape.

[0003]

In the case of an in-line screw type injection molding machine, a screw having a flight is
Since the screw slides below the cylindrical or rectangular cylindrical hopper hole provided in the direction perpendicular to the screw hole, when the screw advances in the injection step and the pressure holding step, the flight between the screw flight and the hopper hole It is inevitable that the resin in the form of pellets is caught between them. Moreover, a plurality of pellets may be bitten.

In the pressure-holding step, since the screw is generally not rotated, when the pellet-shaped resin is caught in the hopper hole, if the screw advances, the pellet-shaped resin is crushed. Is required, and this force becomes the sliding resistance between the screw and the cylinder.

Further, in order to stabilize the substantial resin pressure in the pressure-holding step every shot, the hydraulic pressure from the back of the screw or the mechanical pressure is controlled to be constant, and the molten resin at the screw tip is caused to act on the molten resin. ing. However, no matter how much the holding pressure from the back of the screw is controlled, if the pellet-shaped resin is caught in the hopper hole, the above-mentioned sliding resistance occurs, and the substantial holding pressure acting on the molten resin decreases. .

As a result of the fact that the holding pressure fluctuates depending on the presence or absence of the pellet-shaped resin, the weight and quality of the molded product fluctuate. This phenomenon is, for example, as shown in FIG.
Since there is a position where the angle of the flight 3 of the screw 2 and the angle of the hopper hole 4 are substantially parallel to each other, when the screw 2 advances, the pellet-shaped resin 5 is easily bitten, and moreover, a plurality of pellets can be bitten. It is possible, especially in this case, that the resin pressure at the time of holding pressure is greatly reduced, which results in large variations in molded article weight and quality.

The present invention prevents a plurality of pellets from being caught even if the resin in the form of pellets is caught between the flight of the screw and the hopper hole, thereby reducing the fluctuation of the sliding resistance between the screw and the cylinder. It is an object to reduce it.

[0008]

The present invention has solved the above-mentioned problems as follows. That is, of the corners where the inner periphery of the hopper hole and the screw hole intersect, the angle of the corner in the screw tip direction is set to 5 in the direction opposite to the twist angle of the flight of the screw.
The angle between the screw flight and the hopper hole was increased by setting the angle to 40 °, so that even if the pellet-shaped resin was bitten into the hopper hole, the screw could slide and move along the flight of the screw. This prevents a plurality of pellet-shaped resins from being caught and eliminates or reduces the variation in the resin pressure in the pressure holding step, thereby reducing the variation in the weight and quality of the molded product.

[0009]

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

FIG. 1 is a longitudinal sectional view of a hopper hole of an injection molding machine according to the present invention. As shown in the figure, a hopper cylinder 1a is attached to the rear outer peripheral portion of the screw cylinder 1. A hopper hole 4 penetrating both cylinders 1 and 1a and communicating with the screw hole 1b of the screw cylinder 1 is provided. In the screw hole 1b, a screw 2 having a flight 3 is provided rotatably and movable back and forth. A hopper (not shown) is attached to an upper part of the hopper cylinder 1a.

FIG. 2 is an enlarged view showing one embodiment of the present invention, taken along line AA of FIG. As shown in the figure, a pocket portion 4 having an angle β opposite to the twist angle α of the flight 3 of the screw 2 is formed in the cylindrical hopper hole 4.
a is provided in communication with the screw hole 1b.

FIG. 3 shows another embodiment of the present invention.
FIG. 3 is an enlarged view taken along line AA of FIG. In this embodiment,
Instead of the cylindrical hopper hole 4, a square tubular hopper hole 4 is used. A pocket portion 4a having an angle β opposite to the twist angle α of the flight 3 of the screw 2 is provided in the rectangular cylindrical hopper hole 4 so as to communicate with the screw hole 1b.

In both of the above embodiments, of the corners where the inner periphery of the hopper hole 4 and the screw hole 1b intersect, β, which is the angle of the corner in the direction of the screw tip, is determined by the twist angle α of the flight 3 of the screw 2. It is desirable that the angle is 5 ° to 40 ° in the opposite direction.

Preferably, the angle β is determined so that an angle (α + β) obtained by adding the torsion angle α and the angle β is 20 ° to 55 °.

Next, the pellet-shaped resin 5 stored in the hopper for explaining the operation is supplied to the screw 2 through the hopper hole 4. The resin is transported to the front of the screw by the rotation of the screw 2, and is melted by the heat of the heater arranged in the screw cylinder 1 and the heat generated by shearing in the screw 2 and stored at the tip of the screw. The molten resin stored at the tip of the screw is filled into a mold by an injection step of moving the screw 2 toward the tip of the screw, and then cooled through a pressure-holding step of pressing the screw 2 at a predetermined pressure for a predetermined time. Is molded.

During the pressure-holding step, as shown in FIG. 2 or FIG. 3, the screw 2 moves forward, and the flight 3 of the screw 2 comes to a position where it crosses the pocket portion 4a. In the state of being bitten, the crossing angle (α + β) between the flight 3 of the screw 2 and the pocket portion 4a of the hopper hole 4 is large, so that the resin 5 in the form of pellets moves downward along the screw flight 3 in the figure. As a result, they will not be bitten. Alternatively, the frequency of biting is significantly reduced as compared with the related art. If it is bitten, it will not be bitten.

[0017]

EXAMPLE When the pellet-shaped resin was caught between the flight of the screw and the hopper hole, the angle (α + β) at which the pellet-shaped resin began to slide along the flight of the screw was investigated. (Α + β) greatly differs depending on the resin material, and was 10 ° to 40 °.

The torsion angle α of the screw is 17 ° when the general screw pitch is the same as the screw outer diameter, and the maximum angle β of the hopper hole sliding along the flight of the screw is 23 °. The larger β is, the more difficult it is for the pellet-shaped resin to be caught. However, if β is large, there is a problem that the length of the screw hole required for kneading the resin is shortened. In the experimental results in which β was set to 15 °, the variation in the weight of the molded product was reduced to half as compared with the conventional cylindrical hopper hole. The optimal value of β differs depending on the screw shape, resin material, resin shape, and the like, and the optimal value including the adverse effect of being too large is 5 to 40 °.

[0019]

According to the present invention, as described above, since a plurality of pellet-shaped resins are not caught, the hydraulic pressure or mechanical pressure from the back of the screw during the pressure-holding process is accurate. Is transmitted to the molten resin at the screw tip, so that the weight and quality of the molded product are stabilized.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a hopper hole of an injection molding machine according to the present invention.

FIG. 2 is an enlarged view showing one embodiment of the present invention, taken along line AA of FIG. 1;

FIG. 3 is an enlarged view showing another embodiment of the present invention, taken along line AA of FIG. 1;

FIG. 4 is a view showing a relationship between a conventional hopper hole and a flight angle of a screw.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 screw cylinder 1 a hopper cylinder 1 b screw hole 2 screw 3 flight 4 hopper hole 4 a pocket 5 pellet resin

Claims (4)

[Claims] In a hopper hole (4) of a screw cylinder (1) of an injection molding machine, a corner in the direction of the screw tip, of a corner portion where an inner periphery of the hopper hole (4) intersects with the screw hole (1b). A hopper hole structure for an injection molding machine, characterized in that the angle (β) of the section is 5 ° to 40 ° in a direction opposite to the twist angle (α) of the flight (3) of the screw (2). 2. The angle (β) is determined so that an angle (α + β) obtained by adding the torsion angle (α) and the angle (β) is 20 ° to 55 °.
The hopper hole structure of the injection molding machine described in the above. 3. The hopper hole structure of an injection molding machine according to claim 1, wherein said hopper hole (4) is cylindrical. 4. The hopper hole structure of an injection molding machine according to claim 1, wherein said hopper hole (4) has a rectangular cylindrical shape.