Plastic article or earthenware shaping or treating: apparatus – Female mold and charger to supply fluent stock under... – With means to close mold
Patent
1989-04-18
1990-03-06
Woo, Jay H.
Plastic article or earthenware shaping or treating: apparatus
Female mold and charger to supply fluent stock under...
With means to close mold
4254501, 4254514, B29C 4566
Patent
active
049061739
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an injection-compression molding machine for compressing molten resin injected into molds and molding the resin, and more particularly, to a compressor unit thereof.
BACKGROUND ART
In molding a special resin which lacks fluidity at a normal injection temperature, or in precision molding of products, such as lenses or optical disk substrates, which require dimensional accuracy in microns or higher, injection-compression molding is effected whereby resin injected into molds is compressed, in order to attain improvement in dimensional accuracy and uniformity in material density.
Usually, the injection-compression molding is effected by pushing out a compression pin, at a clamp mechanism section of an injection-molding machine, from a movable platen toward the molds by means of a hydraulic mechanism, thereby thrusting a pressure block toward a cavity of the movable-side mold, at a point in time corresponding to a pressure hold process after the end of the injecting operation. In injection-compression molding of this type, it is essential to control the operation timing, thrusting force, or position of the compression pin. However, in high-accuracy molding, use of a hydraulic compressor unit, as in a conventional arrangement, causes a change of the properties of the hydraulic operating fluid depending on the temperature and the like, thereby changing the follow-up performance and reproducibility of the operation of the compressor unit. Thus, it is difficult to accurately control the compression pin. Since the hydraulic compressor unit is liable to be contaminated by the hydraulic operating fluid, and is under high pressure. Moreover, it must be strictly maintained, and the unit itself is expensive.
DISCLOSURE OF THE INVENTION
The object of the present invention is to provide a compressor unit for an injection-compression molding machine having high control performance, including follow-up performance, reproducibility, etc., and which is capable of high-accuracy molding.
In order to achieve the above object, according to the present invention, there is provided a compressor unit of an injection-compression molding machine in which a pin is projected from a movable platen toward a mold mounted on the platen, thereby compressing molten resin filling the mold. The compressor unit comprises a servomotor disposed on the movable platen, a ball nut operatively coupled to the servomotor for rotation, and a ball screw adapted to be threadedly engaged with the ball nut and movable in an axial direction upon rotation of the ball nut, and which is operatively coupled to the pin.
Thus, in the compressor unit of the present invention, the compression pin is driven by means of the servomotor with the aid of the ball screw and the ball nut, so that variation factors in control related to the compression pin can be eliminated, and high-quality precision moldings can be repeatedly obtained. Moreover, the compressor unit can be relatively easily maintained without soiling its surroundings, and can be constructed at a relatively low cost.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a front view, partially in section, showing the principal part of a compressor unit according to one embodiment of the present invention;
FIG. 2 is a schematic front view, partially in section, showing a clamp mechanism of an injection-compression molding machine furnished with the compressor unit of FIG. 1; and
FIG. 3 is a sectional view taken along line III--III of FIG. 2.
BEST MODE OF CARRYING OUT THE INVENTION
A injection-compression molding machine according to one embodiment of the present invention is provided with a direct-acting clamp mechanism 1 shown in FIG. 2. In this clamp mechanism, a movable platen 3 is disposed for reciprocation along four tie bars 5 which connect a stationary platen 2 and a rear platen 4 with each other. Dies (not shown) are mounted individually on the platens 2 and 3.
Rear platen 4 is fitted with a clamping servomotor 8 and a clamping ball screw 7 which, havi
REFERENCES:
patent: 3156014 (1964-11-01), Wenger
patent: 4696632 (1987-09-01), Inaba
Inaba Yoshiharu
Iwatsuki Masayuki
Naito Hideo
Watanabe Kikuo
Fanuc Ltd.
Heitbrink Timothy W.
Woo Jay H.
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