The use of control units such as shooting pots to introduce thermoplastic resin into single cavity molds is well known. In such arrangements a primary resin source feeds the reservoir of a shooting pot and the shooting pot, in turn, is operated to feed a measured or metered quantity of compound into a single cavity mold to form large items such as buckets, trash containers and like receptacles.
In contrast, the present invention is directed to the concept of supplying thermoplastic molding compound to a multi-cavity mold there the cavities of the mold are fed by a hot runner system where the hot runner system includes hooting pots (metering means or control units) which are individual to each cavity. That is, conduits that lead from the hot runner system to feed the respective mold cavities each contain a shooting pot or metering means for controlling precisely the introduction of a single shot of compound to a mating cavity on an individual or cavity by cavity basis.
The hot runner system is supplied or fed with thermoplastic material from a primary source usually in the form of an extruder or similar device in well known fashion.
For purposes of claiming the present invention, the shooting pots are referred to as metering means or as secondary compound advancing units.
It is a primary feature of the present invention to provide a hot runner system cooperating with a multi-cavity mold where the hot runner system includes metering means individual to each mold cavity.
It is a further feature of the invention to provide metering means in the hot runner system which are operable to feed precisely measured quantities of compound to each cavity.
It is a further feature of the invention to provide metering means individual to each cavity where the metering means are adjustable to change volume, for example, on a cavity by cavity basis. That is, each metering means may be adjusted individually without disabling the setting, function and operation of the other metering means in the hot runner system.
A further feature of the invention is the treatment of a multi-cavity mold and a hot runner system as a unitary assembly.
A still further feature of the invention is the provision of a novel process for feeding, metering and adjusting the introduction of thermoplastic compound into individual cavities of a multi-cavity mold by incorporating the feeding, metering and adjusting steps into a hot runner system.
An arrangement embracing certain features of the present invention may comprise, in combination, a multi-cavity mold and a hot runner system, supply means incorporated in the hot runner system for feeding measured quantities of thermoplastic compound to each said mold cavity on an individual cavity basis.
A method embracing certain other features of the present invention may comprise the steps of providing a mold having a plurality of cavities, providing a hot runner system for feeding said cavities, connecting the hot runner system to each cavity by means of compound conduits individual to each cavity and placing metering means in each said cavity conduit for controlling the introduction of compound to each cavity on an individual cavity basis.
Other feature and advantages of the present invention will become more apparent from an examination of the succeeding specification when read in conjunction with the a pended drawings in which;