| 摘要 |
A gate for a mold comprises a plunger member mounted in the molding compound inlet conduit and adapted to prevent flow through the conduit in a first longitudinal position and to permit flow through the conduit in second longitudinal positions. The plunger defines an enlarged sealing end which is proportioned to prevent flow through the conduit on the first position. The sealing end defines a mold cavity-facing surface which is of larger cross-sectional area than the surface of the plunger opposed to the mold chamber and subject to contact with pressurized molding compound in the compound. The plunger member is longitudinally expansible and contractible so that even though one end may be rigidly mounted in the conduit, the enlarged sealing end is longitudinally movable to open and close the mold gate in a manner purely responsive to pressures therein. Thus, spontaneous gating of a mold may be provided. The expansible and contractible plunger member may be sealed to prevent seepage of molding compound into its interior.
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