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A vent, system and method for controlling flow of fluid into and out of a mold cavity. The vent has a plurality of passages that each have narrow oblong slot-shaped openings in the mold cavity and which each expand in size in a direction leading away from its opening. The vent preferably is an inser

A vent, system and method for controlling flow of fluid into and out of a mold cavity. The vent has a plurality of passages that each have narrow oblong slot-shaped openings in the mold cavity and which each expand in size in a direction leading away from its opening. The vent preferably is an insert that comprises a grate with at least a plurality of vent slots. The grate preferably is formed of two halves with fingers that interleave to form the slots when assembled. The grate preferably is discharge machined from disc-shaped blanks cut from elongate stock made a material that preferably is non-porous and smooth. The grate can be mounted in a pocket in the mold cavity or carried by a movable pin. A system uses valving and a source of fluid and, if needed, a source of vacuum to help facilitate venting by drawing atmosphere out of the cavity during molding. The system can also be used to introduce fluid through a vent such as for foaming moldable material in the cavity. The system can also be used to introduce a heat transfer medium into the mold cavity. The system can also be used to accelerate venting during one part of a mold cycle and then introduce fluid into the cavity during the same cycle.

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1. A mold for molding a hardenable material comprising:a recessed mold surface that defines a mold cavity that receives the hardenable material; a passageway having an opening in gas flow communication with the mold cavity; and a vent disposed in the passageway that is constructed and arranged to pe

1. A mold for molding a hardenable material comprising:a recessed mold surface that defines a mold cavity that receives the hardenable material; a passageway having an opening in gas flow communication with the mold cavity; and a vent disposed in the passageway that is constructed and arranged to permit gas or vapor to flow through the vent but oppose flow of hardenable material through the vent, wherein the vent comprises a perforate vent insert that is disposed in the passage, the insert having a plurality of vent passages and the vent insert comprised of a first grate portion that engages with a second grate portion, wherein each vent passage is constructed and arranged to permit gas or vapor flow through the vent insert but opposing flow of hardenable material through the vent insert, and wherein the vent insert is comprised of a plurality of spaced apart slots that each communicate with one of the vent passages in the vent insert, with at least one of the vent passages including a chamber that is disposed adjacent the passageway and a plurality of vent passage sidewalls that taper away from each other from adjacent the slot associated with the vent passage toward the passageway.