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US 5,288,225 AGranted
Pressure balanced valve stem
AssigneeHusky Injection Molding Systems Ltd.
InventorsHarald Schmidt, Bruce Catoen, Michael Dybka
Life of this patent
Estimating the term…
Abstract
Apparatus includes a mold cavity and a molten plastic inlet channel for communication with the mold cavity for transmission of molten plastic to the mold cavity. A valve stem is provided with substantially no net resulting forces on the valve stem due to melt pressure acting on the projecting area of its upstream and downstream faces.
Claims10
Injection molding apparatus comprising:
- a mold cavity;
- a molten plastic inlet channel defining an outer end for communication with a source of molten plastic and an inner end for communication with said mold cavity for transporting molten plastic from the outer end to the mold cavity;
- a valve gate between the mold cavity and inlet channel inner end and a reciprocable valve stem movable from a first position closing the valve gate to a second position opening the valve gate;
- wherein said stem has an upstream end region adjacent the inlet channel outer end exposed to upstream pressure of said molten plastic and a downstream end region adjacent the inlet channel inner end exposed to downstream pressure of said molten plastic, wherein the upstream and downstream pressures are substantially equal and opposite due to said end regions being of substantially equal surface area;
- and
- means for moving the valve stem from closed to open position and from open to closed position.
3 more elements
Dependencies are inferred from the claim text.