Stack mold

Details Stack mold Stack mold

1999-08-16

2001-06-26

Mackey, James P. (Department: 1722)

Plastic article or earthenware shaping or treating: apparatus

With apparatus assembly or dismantling means or with idle part

For extrusion or injection type shaping means

C425S451300, C425S588000, C425S589000

Reexamination Certificate

active

06250906

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to injection molding machines and, in particular, to stack molds employed therein.
BACKGROUND TO THE INVENTION
In the molding of plastic parts by injection molding, mold parts are brought together to define a mold cavity, polymeric material is injected into the mold cavity and, after allowing time for the polymer to solidify, the mold parts are drawn apart and the molded part removed.
The moveable elements or plattens of the molding machine are arranged to move in a horizontal direction and slide on stationary bars to transport the moveable mold parts into and out of mating relationship with a stationary mold part.
Such molds may be single face, with a single moveable mold part and a stationary mold part or may be a stack mold where two or more moveable mold parts move towards and away from a stationary mold part.
In the latter molding machines, a rack-and-pinion structure often is used to achieve synthronized self-positioning of the moveable mold parts. In such devices, rack elements are attached to the stationary mold part and the outer moveable mold part, while a pinion is mounted to the inner moveable mold part. Depending on the size of the stack mold, one or more such rack-and-pinion structures may be provided on each side of the stack mold.
In general, the rack-and-pinion structure is custom-made for a specific stack mold and it is necessary to precisely position the device on the mold parts of the stack mold to ensure correct mold operation in the molding machine. When access to the mold parts is required for removal from the molding machine and replacement by another stack mold, the rack-and-pinion structure often needs to be first removed and then subsequently reassembled, a time consuming operation.
SUMMARY OF INVENTION
The present invention represents an improvement on the prior art, permitting a degree of flexibility and ease of operation which has not previously been achieved. The present invention provides a universal rack-and-pinion structure for use with stack molds, which is readily and rapidly demounted and mounted and permits rapid adjustment for proper proportioning of movement of the moveable mold parts in a stack mold in a molding machine.
Accordingly, in one aspect of the present invention, there is provided in a stack mold of the type wherein at least a pair of moveable molding parts move into and away from mold-cavity forming relationship with each other and a stationary mold part, the improvement comprising rack-and-pinion structure mounting plates affixed one to each of the moveable mold parts and stationary mold part; a pinion housing structure containing a pinion mountable to and demountable from the mounting plate affixed to the inner moveable mold part; a rack mounting element mountable to and demountable from the mounting plate affixed to the outer moveable mold part and to the stationary mold part; a first rack element extending between one said rack mounting elements and into gear-meshing relationship with the pinion in the pinion housing when said molding parts are out of mold cavity forming relationship; a second rack element extending between the other of said rack mounting element and into gear-meshing relationship with the pinion in the pinion housing when said molding parts are out of mold cavity forming relationship; and adjustment means associated with each of the rack mounting elements and the respective end of the rack element to adjust the distance between the moveable mold part from each other and from the stationary mold part to ensure that a mold cavity is formed between the outer and inner moveable mold parts at the same time as a mold cavity is formed between the inner moveable mold part and the stationary mold parts.


REFERENCES:
patent: 4154566 (1979-05-01), Ward
patent: 4260358 (1981-04-01), Mehnert
patent: 5395232 (1995-03-01), Hori
patent: 5908597 (1999-06-01), Boudreau et al.

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