Venting construction for molds for forming plastic foam parts

Claim 1

A MOLD FOR FORMING FOAMED PLASTIC PARTS COMPRISING, A BASE AND A TOP COVER THEREON, SAID BASE AND COVER EACH HAVING HORIZONTALLY EXTENDING PLANAR SURFACES AROUND THE PERIPHERY THEREOF WHICH, WHEN THE COVER IS LOCATED ON SAID BASE, DEFINE A PARTING FACE THEREBETWEEN, SAID BASE AND COVER COOPERATING TO DEFINE A FOAM MOLDING CHAMBER THEREBETWEEN IN WHICH A WORK-PIECE IS ADAPTED TO BE MOLDED, SAID PARTING FACE EXTENDING HORIZONTALLY AROUNG THE PERIPHERY OF SAID FOAM MOLDING CHAMBER, SAID COVER BEING SEPARABLE FROM SAID BASE AT SAID PARTING FACE TO PROVIDE ACCESS TO SAID CHAMBER, SAID COVER HAVING A CIRCULAR CYLINDRICAL OPENING THEREIN EXTENDING VERTICALLY DOWNWARDLY FROM THE TOP OUTER SURFACE OF THE COVER TO SAID MOLDING CHAMBER, AN INSERT HAVING A CIRCULAR CYLINDRICAL OUTER SURFACE SIZED TO FIT SAID OPENING, SAID INSERT COMPRISING AN INTEGRAL ONEPIECE MEMBER FORMED OF A PLASTIC MATERIAL SELECTED FROM THE GROUP CONSISTING OF ACETAL, POLYETHYLENE AND POLYPROPYLENE, SAID INSERT FILLING SAID OPENING AND EXTENDING UPWARDLY FROM SUBSTANTIALLY FLUSH WITH THE COVER SURFACE FORMING THE UPPER PORTION OF SAID MOLDING CHAMBER TO THE TOP OUTER SURFACE OF THE COVER, SAID INSERT HAVING A SINGLE VERTICAL PASSAGEWAY OF CIRCULAR CROSS SECTION EXTENDING AXIALLY THERETHROUGH AND CONCENTRIC WITH THE VERTICAL AXIS OF THE OPENING IN THE COVER SO THAT DURING THE FOAM MOLDING OF THE ARTICLE THE AIR IN SAID CHAMBER IS VENTED VERTICALLY UPWARDLY THROUGH SAID PASSAGEWAY AND THE PLASTIC FOAM MATERIAL IN THE CHAMBER IS PERMITTED TO EXPAND INTO ABUTTING RELATION WITH THE INNER END OF SAID INSERT AND INTO SAID PASSAGEWAY TO FORM A PLUG WHICH RISES THROUGH SAID PASSAGEWAY TO THE TOP SURFACE OF THE COVER WHEREBY TO FACILITATE SEPARATION OF SAID PLUG FROM FOAM MOLDED ARTICLE AND TO FACILITATE REMOVAL OF SAID PLUG FROM WITHIN SAID INSERT.