Means for forming voids in concrete products

Claim 1

A RETRACTABLE MOLD FOR FORMING VOIDS IN CONCRETE PRODUCTS SAID MOLD COMPRISING A PLURALITY OF LONGITUDINAL MOLD SECTIONS, EACH OF SAID MOLD SECTIONS HAVING LONGITUDINAL EDGE PORTIONS POSITIONED ADJACENT THE LONGITUDINAL EDGE PORTIONS OF TWO ADJACENT MOLD SECTIONS, AN EXPANSIBLE MEMBER POSITIONED ADJACENT THE LONGITUDINAL EDGE PORTIONS OF EACH MOLD SECTION, COOPERATING MEANS ON THE LONGITUDINAL EDGE PORTIONS OF ADJACENT MOLD SECTIONS ENGAGING EACH OF SAID EXPANSIBLE MEMBERS AND HOLDING THEM AGAINST ACCIDENTAL DISPLACEMENT, MEANS FOR SELECTIVELY EXPANDING SAID EXPANSIBLE MEMBERS, SAID EXPANSIBLE MEMBERS SPREADING THE COOPERATING MEANS IN ENGAGEMENT THEREWITH AS THEY ARE BEING EXPANDED, SOME OF SAID COOPERATING MEANS BEING SO CONNECTED TO SAID MOLD SECTION AS TO MOVE SAID MOLD SECTIONS INTO VOID-FORMING POSITION AS THEY ARE SPREAD APART, SAID OTHER COOPERATING MEANS BEING SO CONNECTED TO SAID MOLD SECTIONS AS TO RETRACT SAID MOLD SECTIONS AS THEY ARE SPREAD APART.