Plastic article or earthenware shaping or treating: apparatus – Female mold and charger to supply fluent stock under... – Plural mold cavities
Reexamination Certificate
1999-04-26
2001-07-17
Mackey, James P. (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Female mold and charger to supply fluent stock under...
Plural mold cavities
C338S245000, C338S245000
Reexamination Certificate
active
06261085
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to presses. In particular, this invention relates to a press particularly suitable for use with an injection or extrusion molding apparatus, and a molding apparatus utilizing the press.
BACKGROUND OF THE INVENTION
Presses have many uses, one of the most popular being to clamp mold parts together in an injection molding apparatus. In a conventional injection molding apparatus a press section is disposed behind a plastic injection section. The press includes a moving platen which is forced toward a stationary platen by at least one actuator, usually a hydraulic cylinder mounted at the rear of the apparatus. The actuator bears against a stationary rear frame or “spider”, which supports upper and lower pairs of guide bars that maintain the moving and stationary platens (and thus the mold parts) in precise alignment as the actuator forces the moving platen toward the stationary platen and into the clamping position.
Typically a hydraulic press is used in an injection molding apparatus, due to the very high forces required to properly clamp the mold parts together. In a conventional hydraulic actuator the hydraulic cylinder must be longer than the length of a full stroke of the piston and must be oriented in the direction of the stroke. Since the injection molding apparatus occupies the space in front of the press, the hydraulic cylinder is conventionally mounted to the rear of the press and thus a large clearance is required behind the operative clamping portion of the press in order to accommodate the cylinder.
Moreover, in a conventional hydraulic press the hydraulic cylinder serves the sole purpose of actuating the moving platen, and separate guide bars are used to maintain the moving and stationary platens in precise alignment. The use of separate structures for these purposes results in an expensive and heavy apparatus which makes poor use of available space.
It would accordingly be advantageous to provide a hydraulic press in which the actuating cylinders can be reduced in length and contained within the operative clamping section of the press, to significantly reduce the space requirements of the overall apparatus and thus allow plastics fabricators to utilize production facilities more efficiently.
It would also be advantageous to provide a press which combines the actuating and platen alignment functions of the press into the same structure, to reduce the weight and cost of the apparatus.
It would also be advantageous to provide a press that operates in two directions, taking advantage of the reciprocating motion of the actuator, to provide two injection molding cycles within a single press cycle.
SUMMARY OF THE INVENTION
The present invention overcomes these disadvantages and provides an economical, lightweight and compact press and injection molding apparatus utilizing the press. The press of the invention may be used in virtually any application in which a conventional hydraulic press may be used, the press of the invention being particularly advantageously used with injection molding units in an injection molding apparatus.
The invention accomplishes this by providing a tandem press having a moving frame comprising a moving platen moving in a reciprocating motion between stationary outer platens. The moving platen moves on a track between a first clamping position in which the moving platen clamps a first mold mounted on one side of the press, and a second clamping position in which the moving platen clamps a second mold on the other side of the press. Because of the tandem design, as one mold is moved to a clamping position the other mold is being separated to remove a molded article. The tandem press of the invention thus provides two complete clamping cycles within one press cycle.
In the preferred embodiment the hydraulic pistons actuating the moving platen also serve as guide bars for maintaining the moving platen in alignment with the stationary platens. The tandem press of the invention thus avoids the need for separate guide bars by providing hydraulic actuating cylinders mounted on the stationary platens, the pistons for which serve both as guide bars to maintain alignment between the platens and as actuators to move the moving platen between clamping positions. In the preferred embodiment the actuating cylinders operate at a relatively low pressure and high speed, and the moving platen is provided with hydraulic clamping cylinders operating at relatively high pressure to apply the required clamping force to the mold after the actuating cylinders have moved the moving platen to the clamping position.
The present invention thus provides press, comprising a stationary frame comprising a first stationary platen having a working face and a second stationary platen having a working face, disposed in opposition to the first stationary platen, and a moving frame comprising a moving platen disposed between the first and second stationary platens and in alignment therewith, having a first working face in opposition to the working face of the first stationary platen and a second working face in opposition to the working face of the second stationary platen, movable between the first and second stationary platens so as to alternately apply a clamping force to the working face of the first stationary platen and to the working face of the second stationary platen, and an actuator for moving the moving platen between the first and second stationary platens.
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Meidan Daniel
Steger Rudy
Dimock Stratton Clarizio
Eisen Mark B.
Mackey James P.
Reena Corporation
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