Bushing seal for valve-gated injection mold

Abstract

This invention relates to a bushing seal for a heater of a valve-gated injection mold. In a single cavity application, the heater is advantageously located directly between the molding machine and the cavity and a valve pin is reciprocated in a cylindrical bore through the bushing seal seated in the upper surface of the heater. The hot runner passage also extends through the bushing seal and joins the heater bore directly beneath the bushing seal. The cylindrical wall of the bore through the bushing seal is interrupted by a circumferential opening vented to atmosphere through a vent passage which relieves the build up of pressure between the valve pin and the wall of the bore and vents corrosive gases to substantially reduce corrosion and wear of the valve pin. A circular valve seat on the bottom face of the bushing seal receives an inclined shoulder on the valve pin to seal the bore of the bushing seal from the molten plastic material in the hot runner passage when the valve pin is in its uppermost position. This reduction in corrosion and wear reduces malfunctioning of the mechanism due to seizure of the valve pin in the bushing seal.

Dependencies are inferred from the claim text.