Injection mechanism of an injection molding machine

Plastic article or earthenware shaping or treating: apparatus – Control means responsive to or actuated by means sensing or... – Feed control of material en route to shaping area

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Details

425149, 425593, B29C 4577

Patent

active

059551178

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to an improvement of an injection mechanism of an injection molding machine.


BACKGROUND ART

In general, the construction of motor-driven injection molding machine broadly comprises a mold clamping mechanism A and an injection mechanism B, as shown in FIG. 6.
The mold clamping mechanism A is composed of a movable platen 95 having a movable mold half MM fixed thereto, a stationary platen 96 having a stationary mold half SM fixed thereto, a rear platen 97, a toggle mechanism 98 for moving the movable platen 95 toward or away from the stationary platen 96 to effect mold clamping or opening, a mold clamping motor 99 for actuating the toggle mechanism 98, etc.
The injection mechanism B is composed of an injection screw 5 and an injection cylinder 2 for injecting a molten resin into a cavity of a mold, which is formed of the movable mold half MM and the stationary mold half SM clamped together, and metering it, a motor 36 for injection as a drive source for advancing the injection screw 5 with respect to the injection cylinder 2 to effect injection, a motor 35 for screw rotation as a drive source for rotating the injection screw 5 in the injection cylinder 2 to effect metering and kneading, etc. The rotation of the motor 36 for injection is transmitted to a ball screw 10 through a pulley 13, and the rotation of this ball screw 10 is converted into a force to press a pusher plate 6 by means of a ball nut 9. Thereupon, the pusher plate 6, guided by guide rods 4, moves straight, so that the screw 5 is actuated for translation. On the other hand, the rotation of the motor 35 for screw rotation is transmitted to the screw 5 through a pulley 20, to drive the screw.
In FIG. 6, symbol BS designates a base. While the mold clamping mechanism A is fixed to the base BS, the whole injection mechanism B is allowed to move toward or away from the mold clamping mechanism A so that the distal end (nozzle) of the injection cylinder 2 can be made either to come into contact or move away from the mold.
Referring now to FIG. 5, the injection mechanism B will be described in detail. A front plate 1 and a rear plate 3 are fixed integrally to each other by means of the guide rods 4, which serve also as tie rods. The injection cylinder 2 is fixed to the front plate 1. The injection screw 5 is attached to the pusher plate 6 so as to be rotatable and immovable in the axial direction. This pusher plate 6 is slidably mounted on the guide rods 4 through bushings 7.
The ball nut 9 is fixed to the side face of the pusher plate 6 which faces the rear plate 3 through a load cell 8, which detects detecting a resin reaction force, so as to be rotatable with respect to the pusher plate 6 but immovable in the injection-axis direction (i.e., axial direction of the injection screw). The ball nut 9 mates with the ball screw 10 that is attached to the side of the rear plate 3 so as to be rotatable and immovable in the axial direction. The ball screw 10 is supported by means of three angular bearings 11, 11 and 12 so as to be rotatable with respect to the rear plate 3 and immovable in the axial direction. Inner and outer rings of each of the bearings 11, 11 and 12 are fixed, respectively, to the outer periphery of the ball screw 10 and the inner periphery of a through hole that is formed in the center of the rear plate 3. Among these bearings, each of the two angular bearings 11 includes an inner ring and an outer ring for supporting a resin reaction force that acts on the inner ring from forward. Also, the angular bearing 12 includes an inner ring and an outer ring for supporting a force that acts on the inner ring from behind.
The axis of the ball screw 10 is in line with the axis of the injection screw 5. In the description to follow, therefore, this common axis will be referred to as an "injection axis."
The pulley 13 for injection is fixed to the end portion of the ball screw 10 which projects rearward from the rear plate 3. When the rotatory force of the motor for injection (not shown), which is fixe

REFERENCES:
patent: 4938682 (1990-07-01), Kadoriku et al.
patent: 5129808 (1992-07-01), Watanabe et al.
patent: 5206034 (1993-04-01), Yamazaki
patent: 5209936 (1993-05-01), Ihara et al.
patent: 5380181 (1995-01-01), Hiraoka et al.
patent: 5421712 (1995-06-01), Laing et al.

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