Plastic article or earthenware shaping or treating: apparatus – Female mold and charger to supply fluent stock under... – With product ejector
Reexamination Certificate
2001-11-02
2004-11-02
Walker, W. L. (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Female mold and charger to supply fluent stock under...
With product ejector
C425S444000
Reexamination Certificate
active
06811391
ABSTRACT:
TECHNICAL FIELD
The present invention relates to injection molding machines for molding plastics articles and, more particularly, to a mold clamp system for an injection molding machine, wherein the clamp system includes an electrically-operated ejector mechanism for separating the molded part from a molding surface and for ejecting the part from the mold.
BACKGROUND ART
Injection molding machines are utilized for molding plastic parts that range from simple to quite complex configurations. In the course of injection molding a part, two cooperating mold halves that define a mold cavity corresponding to the part to be molded are brought together in contacting relationship. The molds halves are held together under pressure so that when molten plastic material is injected into the mold cavity, a molded part conforming to the shape of the mold cavity Is produced. Often the molded part will adhere to a surface of the mold cavity, and it must be physically separated from the surface so that the mold can be employed during subsequent molding cycles to form additional parts.
Typically, one or more ejector pins assist removal of molded parts from an injection mold cavity. The ejector pins are slidably carried in one of the mold halves, usually the movable mold half, and they are movable into and out of the mold cavity so that they can be brought into contact with a molded part and thereby push the molded part away from the molding surface. In the past, when most injection molding machines were hydraulically-operated, the ejector pins were actuated by an hydraulic linear actuator that caused the pins to extend into the mold cavity during a ejection operation, and to retract from the mold cavity after a part had been separated from the molding surface and ejected from the mold half.
With the advent of completely electrically-powered injection molding machines, electric motors and mechanical drive systems replace hydraulically-operated systems, including hydraulic pumps, hydraulic cylinders, and the like. Such motors and drive systems provide or for the necessary rotary and linear movements of the operative parts of the injection molding machine. Thus, in an all-electric machine a different mechanism must be employed to actuate the ejector pins. In that regard, one way to actuate the ejector pins electrically is to provide a screw and nut arrangement to convert the rotary output of an electric motor to linear movement, thereby causing Me ejector pins to extend into and to retract from the mold cavity. Providing the power for the ejection function in that manner, however, requires that a separate electric motor be provided to operate the screw mechanism that moves the ejector pins. Such a drive arrangement requires that the motor (a) accelerate to rotate in a first direction, causing the ejector pins to extend into the mold cavity, (b) decelerate and stop after part ejection has occurred, (c) accelerate to rotate in a reverse direction to cause the ejector pins to retract into the mold member after part ejection has been accomplished, then (d) decelerate and stop so that the pins are properly retracted. Given the need to accelerate, decelerate, stop and reverse the direction of rotation of the ejection drive motor for this type of eject system, its operation includes “dead” (unproductive) time that unnecessarily extends the time during which the ejection drive motor must be active. It is therefore desirable to minimize such dead time.
Additionally, because the ejection phase of an injection molding cycle is such a brief period of time relative to the machine cycle, it is also desirable to provide an ejector pin actuation mechanism that does not require a separate, dedicated electric motor, thereby simplifying the overall injection molding machine drive system and lowering its cost.
It is therefore an object of the present invention to provide an ejector pin actuation mechanism that does not require stopping and reversal of an ejection system drive motor during part ejection.
It is another object of the present invention to provide an ejector pin actuation mechanism that operates a molded part ejection system by means of an electric motor that can also be employed to perform additional functions during a molding cycle at those times when the part ejection system is not in operation.
DISCLOSURE OF INVENTION
Briefly stated, in accordance with one aspect of the present invention, part ejection apparatus is provided for separating a molded part from a molding surface and for ejecting the molded part from a mold cavity defined by a pair of mold members. The apparatus includes an ejector pin actuator configured to engage at least one ejector pin that is slidably carried in a mold member for movement into and out of the mold cavity. In particular, the ejector pin is operable for separating a molded part from the molding surface and for ejecting the molded part from a cavity by moving axially from a retracted position within the mold member, to an extended position in which part of the ejector pin extends outwardly beyond the molding surface and into the mold cavity.
The apparatus further includes an electrically-powered ejector pin drive system for moving the ejector pin actuator along a guide surface. The ejector pin drive system includes an electric motor having a rotatable output shaft, and a cam-and-follower connected with the motor output shaft and with the ejector pin actuator for converting motor drive shaft rotary motion to linear movement for moving the ejector pin actuator linearly relative to the mold member, into and out of the mold cavity, while the motor is rotated in only one direction of rotation to operate the ejector pin actuator. The cam member is configured to allow the position of its geometric center to be varied with respect to the motor output shaft, thereby enabling adjustment of the length of the ejector stroke. In addition, if desired, the motion imparted to the follower by the cam member can be customized to pulsate the ejector pins during a single revolution of the cam member.
REFERENCES:
patent: 3680998 (1972-08-01), Sharman
patent: 3726625 (1973-04-01), Rees
patent: 4552525 (1985-11-01), Stehr
patent: 4735080 (1988-04-01), Stehr
patent: 5067892 (1991-11-01), Rahn et al.
patent: 5736079 (1998-04-01), Kamiguchi et al.
Bernardi David S.
Brown Todd W.
Klaus M. Barr
Friskney Stephen H.
Gregg John W.
Luk Emmanuel
Milacron Inc.
Walker W. L.
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