Apparatus improvements for controlling parison length

Claim 1

In blow molding apparatus which includes: a downwardly directed extrusion head having a vertically disposed annular orifice for shaping a freely pendant hollow thermoplastic parison therein; a carrier supporting a plurality of molds generally adjacent said head; drive means to move the carrier to consecutively position such molds beneath the head to receive portions of such parison for blow molding therein; means responsive to a control signal for regulating the length of a parison section protruding beyond the cavity of successively presented molds; and means for severing the parison from the orifice; the improvement in said apparatus whereby the amount of said length is varied without causing a related change in the rheological properties of the thermoplastic forming the parison, which improvement comprises, in combination: variable speed means for said drive means responsive to said control signal for changing the speed of said carrier to vary the rate at which consecutive molds are presented beneath the head.