This invention relates to ejector pins for ejecting molded articles from a mold cavity of an injection molding machine utilizing an ejector plate having knock out pins for engaging the ejector pins in the mold after opening of the mold and for pulling the ejector pins to retracted positions during closing of the mold and at the same time provide an increased stroke of the ejector pins.
An injection molding machine such as that shown in U.S. Pat. No. 3,726,625 has ejector pins which are actuated by a knock out pin engageable with a stop which moves the retracted ejector pins into the mold cavity. This action takes place after a first mold half containing the ejector pins has been moved away from the opposite second mold half carrying the molded article to a spaced apart position where the ejector pins then force the article out of the first mold half. As shown in the patent, the movement of the actuating rods is limited by the spring of the ejector pins which is not desirable because the space required by the spring limits the stroke of the ejector pins.
The present invention is directed to an ejector pin assembly for a split mold in which each ejector pin is actuated by a knock out pin which is engageable with the pin for returning it to the retracted position without requiring a spring.
In accordance with one aspect of the invention, there is provided a method of injection molding a molded article in a split mold having an upper mold half providing a mold cavity and an ejector plate having knock out pins for engagement with ejector pins in the upper mold half comprising:
a. injecting a moldable material into the mold cavity;
b. separating the lower mold half from the upper mold half whereby the molded article is pulled away from the lower mold half;
c. depressing the ejector plate carrying the knock out pins into engagement with the ejector pins and movement of the ejector pins into the mold cavity to eject the molded article into the space between the upper mold half and the lower mold half;
d. removing the moldable article from the space; characterized by,
e. lifting the ejector plate and the ejector pins into a retractable position by the engagement of the knock out pins with the ejector pins; and,
f. disengaging the knock out pins from the ejector pins in the retracted position during additional lifting movement of the ejector plate.
In accordance with another aspect of the invention, there is provided apparatus for injection molding a molded article in a mold cavity comprising:
a. an upper mold half;
b. a lower mold half;
c. ejector pins mounted on the upper mold half;
d. an ejector plate positioned over the upper mold half having knock out pins for engaging the ejector pins;
e. means for raising the lower mold half to provide the mold cavity;
f. means for injecting moldable material into the mold cavity to form the molded article;
g. means for lowering the lower mold half with the molded article attached to the upper mold half;
h. means for lowering the ejector plate to engage the knock out pins with the ejector pins for extending the ejector pins to eject the molded article from the upper mold half;
i. means for raising the ejector plate to retract the knock out pins and the ejector pins which are in engagement with the knock out pins; characterized by,
j. means to grip the ejector pins in the retracted position; and,
k. means for disengaging the knock out pins from the ejector pins in the retracted position of the ejector pins.