Hydrostatic mold gate

A gate for a mold which comprises, a molding compound inlet conduit defining an outer end for communication with a source of molding compound and an inner end for communication with a second mold cavity, a plunger member slidably mounted adjacent said molding compound inlet conduit and adapted to prevent flow through said conduit in a first sliding position, and to permit flow through said conduit in a second sliding position, said plunger defining a shaft slidably positioned in a receptacle and an enlarged end proportioned to prevent said flow through the conduit in the first position, said plunger defining a second mold cavity-facing surface which is of larger cross-sectional area than the surface of the plunger opposed to said mold chamber, and subject to contact with pressurized molding compound in said conduit, whereby relatively pressurized molding compound in the conduit causes said plunger to spontaneously advance to open into a second sliding position by the action of pressure on said opposed surface, and essential equalization of the pressures in the second mold cavity and the conduit causes the plunger to spontaneously retract to close to its first sliding position, said plunger member defining a second end opposed to said enlarged end, said second end being also proportioned to prevent flow through said molding compound inlet conduit in the first position of the plunger, and further capable of permitting flow through the conduit in the second position of the plunger, a first mold cavity positioned in communication with said molding compound inlet conduit at a position upstream from said second end, whereby molding compound fills said first cavity until rising pressure against said second end of the plunger causes said plunger to move toward the second position, so that molding compound can pass further through the molding compound inlet conduit and about said enlarged end into the second mold cavity after substantial filling of the first mold cavity.