JP3311999B2 - Check mechanism of pre-plastic injection molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a check mechanism in a plasticizing resin filling device of a pre-plastic injection molding machine.

[0002]

2. Description of the Related Art Conventionally, an injection cylinder for shaping a small precision product, and a plasticizing cylinder which is connected to a plunger chamber of the injection cylinder through a communication passage and weighs and charges a plasticized resin into the plunger chamber. Equipped with a pre-plastic injection molding machine. In this pre-plastic injection molding machine, a check mechanism is provided to prevent the plasticized resin from returning to the plasticizing cylinder side due to the injection pressure during injection.

[0003] As a conventionally known check mechanism, FIG.
As shown in Fig. 5, a check mechanism is provided at the front end of the screw of the plasticizing cylinder to close the entrance of the communication passage by a slight back and forth movement of the screw. And those provided with a ball-type check mechanism are known.

However, in these systems, the molten resin stays in the communication path for each shot. In particular, if the weight of the molded article is small, the weight of the molded article will be covered by the retained resin. Since the injection pressure is applied to the retained resin during injection, the resin is compressed, which causes thermal deterioration and leads to deterioration of the physical properties of the resin. In the case of the rotary type or the ball type, the injection pressure may be applied to the rotary portion or the ball portion to damage the portion, or the movement of the ball may be jerky, so that the check function may not be sufficiently exhibited.

[0005] Japanese Patent Publication No. 4-70969 (FIG. 6) discloses a plunger having a gap formed by cutting an outer peripheral portion in a longitudinal direction so that the plunger can advance and retreat to a heating cylinder. It is provided rotatably. According to this configuration, it is possible to form a gap that guides the molten resin supplied from the plasticizing cylinder from the communication path to the injection chamber in front of the plunger at the time of metering. Can be shielded from

[0006] However, when the plunger moves forward during injection, the front face of the plunger is not uniform around the axis, so that the pressurized surface receives an uneven load. That is, the injection pressure is also applied to the gap, and the plunger is pressed from the gap side, so that the plunger does not go straight and there is a disadvantage that galling occurs with the cylinder. As described above, in each of the methods, some inconvenience is pointed out.

[0007]

SUMMARY OF THE INVENTION According to the present invention, the communication path of the plasticized resin can be blocked by the rotation of the plunger, and the pressure surface of the plunger is made uniform around the axis so that the plunger moves forward. It is an object of the present invention to obtain a check mechanism of a pre-plastic injection molding machine which is not subjected to a bias load.

[0008]

According to the present invention, a plunger having a front surface having a uniform shape about an axis is provided on a heating cylinder so as to be fitted forward and backward and rotatably, and the axial center of the plunger is provided. A groove is provided on the upper side, and the groove is bent to open on the side of the plunger, so that the opening on the side of the plunger can face the opening on the plunger side of the communication passage with the plasticizing cylinder.

[0009]

Embodiments of the present invention will be described below. FIG. 1 is a sectional view showing an embodiment of a check mechanism according to the present invention, FIG. 2 is a plan view of a plunger taken along the arrow A in FIG. 1, and FIG. 3 is a sectional view showing another embodiment of the present invention. FIG. In the figure, 1 is a heating cylinder, 2 is a plunger, the front surface of which is formed in a uniform shape around the axis, and a rod portion thereof is connected to a pressing machine (not shown);
The heating cylinder 1 is fitted in the heating cylinder 1 so as to be able to advance and retreat and to be rotatable.

A groove 3 is formed in the head of the plunger 2 on the axis thereof.
An opening 4 is provided on the side surface of the. In the configuration of FIG.
Is formed as an elongated hole in the axial direction of the plunger 2.
5 is a plunger room. Reference numeral 6 denotes a plasticizing cylinder mounted on the heating cylinder 1, the screw tip side of which is open to the communication passage 7, and the plunger chamber 5 of the heating cylinder 1 is rotated by the plunger 2 via the groove 3. Is communicated to.

In the embodiment shown in FIG. 3, the groove 3 perforated on the axis of the heating cylinder 1 is bent to the side with the same cross-sectional shape, forming an opening 4 'having a round hole on the side surface of the plunger 2. Reference numeral 8 denotes an opening on the plunger side of the communication path 7 formed in a long hole shape on the wall surface of the heating cylinder 1. Also in this case, similarly, by rotating the plunger 2, the screw tip side of the plasticizing cylinder 6 and the heating cylinder 1 through the communication passage 7 and the groove 3.
Plunger chamber 5 is communicated. In the drawing, reference numeral 9 denotes an injection nozzle attached to the heating cylinder 1, which is connected to a molding die (not shown) to inject molten resin.

The configuration of the present invention is as described above, and the operation thereof will be described below. First, the resin resin is supplied to the plasticizing cylinder 6, measured, melted, and communicated from the screw tip to the communication path 7. At this time, if the plunger 2 is rotated so that the opening 4 on the side of the plunger of the groove 3 faces the opening of the communication path 7 on the plunger side, the molten resin is supplied to the plunger chamber 5 through the groove 3.

The plunger chamber 5 is expanded or contracted in advance depending on the weight of the molded product. In other words, the position of the plunger 2 moves forward and backward. Either of them is a long hole, so any positioning can be handled.

When the plunger chamber 5 is filled with a predetermined amount of molten resin, the plunger 2 is rotated to block the communication between the opening 4 of the groove 3 and the communication path 7. Then, the plunger 2 is pressed and advanced (to the left in the figure), and the molten resin in the plunger chamber 5 is injected from the nozzle 9 into the molding die.

When the plunger 2 moves forward in the heating cylinder 1 in this injection step, an even pressure is applied to the front surface of the plunger 2, and the plunger 2 advances straight without imbalanced load. In addition, since the communication path 7 is shielded by the rotation of the plunger 2, the injection pressure is not applied to the staying resin staying in the communication path 7 for each shot, so that the resin is not thermally degraded.

[0016]

According to the present invention, the plunger has a uniform front surface, and the molten resin is supplied to the plunger chamber through a groove provided on the axis of the plunger. And the plunger can be smoothly moved forward. In addition, since the communication path with the plasticizing cylinder is shielded by the rotation of the plunger, it is possible to prevent thermal deterioration of the accumulated resin accumulated in the communication path.

[Brief description of the drawings]

FIG. 1 is a sectional view of a check mechanism according to the present invention.

FIG. 2 is a plan view of the plunger along the arrow A in FIG.

FIG. 3 is a cross-sectional view of a check mechanism according to another embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a conventional check mechanism that seals at a screw front end.

FIG. 5 is a sectional view showing a conventional ball type check mechanism.

FIG. 6 is a cross-sectional view showing a conventional check mechanism in which a gap is provided at an end of a plunger.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating cylinder 2 Plunger 3 Groove 4, 4 'Groove opening 5 Plunger chamber 6 Plasticizing cylinder 7 Communication passage 8 Communication passage opening 9 Nozzle

Claims (3)

(57) [Claims] In a pre-plastic injection molding machine having a heating cylinder and a plasticizing cylinder mounted on the heating cylinder and capable of communicating with a plunger chamber of the heating cylinder through a communication passage, the front surface is even around an axis. A plunger having a shape is provided so as to be fitted to the heating cylinder so as to be able to advance and retreat and to be rotatable, and a groove is provided on the axis of the plunger. A non-return mechanism of a pre-plastic injection molding machine, wherein an opening on a side surface can be made to face an opening on a plunger side of a communication passage by rotation of a plunger. 2. The non-return mechanism according to claim 1, wherein the opening of the groove on the side of the plunger is formed as an elongated hole in the axial direction of the plunger. 3. A check mechanism according to claim 1, wherein the opening of the communication passage on the plunger side is formed as an elongated hole in the axial direction of the plunger.