1. Field of the Invention
This invention relates to molding machines, more particularly, to ejector mechanisms commonly used in molding machines. The invention is directed particularly to electrically operated ejector devices having apparatus for selectably increased ejection force.
2. Description of Related Art
In molding machines, plastically deformable material to be molded is formed in cavities defined by mating mold sections and allowed to cure to a state wherein the material will not unacceptably deform upon removal from the mold cavity. The cured material defines molded articles that are removed from the machine upon separation of the mating mold sections. However, as it is common that articles will adhere to one of the mold sections, it is typical to provide ejector pins communicating with the mold cavity and linked to movable ejector members in the mold assembly comprising the mating mold sections. Motion of the ejector pins is effective to dislodge molded articles from the mold section, assuring their complete removal. The movable members are typically translatable and include links to the ejector pins to move the ejector pins between retracted positions whereat the free ends of the ejector pins are flush with mold cavity surfaces and forward positions whereat the free ends protrude into the mold cavity.
It is known to use electrically operated actuators to operate ejection devices of molding machines. In particular, it is known to use rotating electrical machines with motion converters to effect linear motion of ejector members. It is known that ejection of articles that have relatively high ratios of internal depth to overall cross sectional area or surface features such as threads can require unusually high ejection force to separate molded articles from so-called mold cores. However, to increase the maximum force exerted by an electrically driven ejection device to accommodate ejection of such articles can result in substantial increases of cost, either as a result of sizing of electrical components and motion converters or to interpose force multipliers between the motor and ejector members. In light of such limitations, there is a need to enable an increase of force exerted on ejector members without the prohibitive attendant costs of known constructions.