Method for heating plastics materials

Claim 1

A method of heating an essentially tubular thermoplastic parison, comprising the steps of placing the parison at a first temperature in a thermal conditioning zone in simultaneous heat exchange relation to both an elongated array of infra-red heating elements and a source of a gaseous coolant, displacing the parison transversely along the array of heating elements (a) while simultaneously subjecting the parison to both heat from the infra-red heating elements and a stream of gaseous coolant issuing from said source, and (b) while rotating the parison about its longitudinal axis so that the exterior surface of said parison is both heated and cooled to avoid localized overheating and consequent heat degradation of the parison surface, and then displacing the parison from the thermal conditioning zone at a second temperature greater than the first temperature, wherein the parison at the second temperature is deformable and workable.

Claim 2

A method of heating an essentially tubular thermoplastic parison, comprising the steps of placing the parison at a first temperature in a thermal conditioning zone in simultaneous heat exchange relation to both an elongated array of infra-red heating elements and a source of a gaseous coolant, displacing the parison transversely along the array of heating elements (a) while simultaneously subjecting the parison to both heat from the infra-red heating elements and a stream of gaseous coolant issuing from said source, and (b) while rotating the parison about its longitudinal axis so that the exterior surface of said parison is both heated and cooled to avoid localized overheating and consequent heat degradation of the parison surface, and then displacing the parison from the thermal conditioning zone at a second temperature greater than the first temperature, wherein the parison at the second temperature is deformable and workable.

Claim 3

A method of heating an essentially tubular parison formed of a heat degradable thermoplastic material from a temperature at which the parison is essentially non-deformable and non-workable to a temperature at which the parison is deformable and workable, comprising the steps of placing a tubular parison at a non-deformable temperature onto a laterally displaceable and rotatable carrier, laterally displacing the carrier and conveying the parison past a bank of infra-red heaters while (a) simultaneously rotating the carrier and the parison about a common longitudinal axis and (b) directing a stream of gaseous coolant onto the surface of the rotating parison to prevent overheating of the surface of the parison while facilitating heating the interior of the parison, and displacing the tubular parison from adjacent the radiant heaters at a deformable, workable temperature.

Claim 4

A method of heating an essentially tubular parison formed of a heat degradable thermoplastic material from a temperature at which the parison is essentially non-deformable and non-workable to a temperature at which the parison is deformable and workable, comprising the steps of placing a tubular parison at a non-deformable temperature onto a laterally displaceable and rotatable carrier, laterally displacing the carrier and conveying the parison past a bank of infra-red heaters while (a) simultaneously rotating the carrier and the parison about a common longitudinal axis and (b) directing a stream of gaseous coolant onto the surface of the rotating parison to prevent overheating of the surface of the parison while facilitating heating the interior of the parison, and displacing the tubular parison from adjacent the radiant heaters at a deformable, workable temperature.

Claim 5

A method for heating an essentially tubular parison of heat degradable thermoplastic material to a deformable, workable temperature preparatory to blowing the parison to shape in a blow mold, comprising the steps of laterally conveying the preform parison in a predetermined path in heating proximity to a battery of infra-red heating elements, rotating the parison about its own axis while the preform is so being laterally conveyed, laterally conveying a source of gaseous coolant along with said preform, and directing a stream of gaseous coolant from said source against the exterior surface of the parison to prevent overheating of the parison periphery by virtue of its heating proximity to said elements, and heating the parison to a deformable, workable temperature while the parison is in heating proximity to the infra-red elements and while directing the stream of gaseous coolant onto the exterior surface of the parison.

Claim 6

A method for heating an essentially tubular parison of heat degradable thermoplastic material to a deformable, workable temperature preparatory to blowing the parison to shape in a blow mold, comprising the steps of laterally conveying the preform parison in a predetermined path in heating proximity to a battery of infra-red heating elements, rotating the parison about its own axis while the preform is so being laterally conveyed, laterally conveying a source of gaseous coolant along with said preform, and directing a stream of gaseous coolant from said source against the exterior surface of the parison to prevent overheating of the parison periphery by virtue of its heating proximity to said elements, and heating the parison to a deformable, workable temperature while the parison is in heating proximity to the infra-red elements and while directing the stream of gaseous coolant onto the exterior surface of the parison.

Claim 7

A method of heating an essentially tubular parison formed of poly (ethylene terephthalate) and of appreciable wall thickness, comprising the steps of interposing the parison between an elongated array of infra-red heating elements and a tubular conduit connected to a source of gaseous coolant, the parison axis and the conduit axis being parallel, heating one side of the parison by said heating elements, directing a flow of gaseous coolant from the conduit against the opposite side of the parison, and simultaneously (1) rotating the parison about its own axis and (2) moving both the parison and the conduit longitudinally along the array of heating elements, so that the periphery of said parison is alternately subjected to heating from said elements and cooling by the flow of gaseous coolant from the conduit, whereby the exterior of the parison is cooled to prevent crystallization thereof while the remainder of the parison interiorly of the exterior thereof is heated by penetration of the infra-red thereinto.

Claim 8

A method of heating an essentially tubular parison formed of poly (ethylene terephthalate) and of appreciable wall thickness, comprising the steps of interposing the parison between an elongated array of infra-red heating elements and a tubular conduit connected to a source of gaseous coolant, the parison axis and the conduit axis being parallel, heating one side of the parison by said heating elements, directing a flow of gaseous coolant from the conduit against the opposite side of the parison, and simultaneously (1) rotating the parison about its own axis and (2) moving both the parison and the conduit longitudinally along the array of heating elements, so that the periphery of said parison is alternately subjected to heating from said elements and cooling by the flow of gaseous coolant from the conduit, whereby the exterior of the parison is cooled to prevent crystallization thereof while the remainder of the parison interiorly of the exterior thereof is heated by penetration of the infra-red thereinto.