Abstract: A parison tube former utilizes a radial compression heater to heat a very specific portion of a preform tube for stretching. The heater has a plurality of compression dies that form a central cavity for receiving the preform tube. The working surfaces of the compression dies close down onto the outer surface of the preform tube to heat the tube via conduction, which more accurately and precisely heats the preform tube. A first stretched portion of the preform tube is produced by stretching the preform tube after heating. A second portion of the preform tube is then located within the central cavity and is also heated by the radial compression heater and stretched to produce a second stretched portion of the preform tube and an unexpanded portion of the preform tube, or balloon portion of the parison tube.

Abstract: A parison tube former utilizes a radial compression heater to heat a very specific portion of a preform tube for stretching. The heater has a plurality of compression dies that form a central cavity for receiving the preform tube. The working surfaces of the compression dies close down onto the outer surface of the preform tube to heat the tube via conduction, which more accurately and precisely heats the preform tube. A first stretched portion of the preform tube is produced by stretching the preform tube after heating. A second portion of the preform tube is then located within the central cavity and is also heated by the radial compression heater and stretched to produce a second stretched portion of the preform tube and an unexpanded portion of the preform tube, or balloon portion of the parison tube.

Abstract: A parison tube former utilizes a radial compression heater to heat a very specific portion of a preform tube for stretching. The heater has a plurality of compression dies that form a central cavity for receiving the preform tube. The working surfaces of the compression dies close down onto the outer surface of the preform tube to heat the tube via conduction, which more accurately and precisely heats the preform tube. A first stretched portion of the preform tube is produced by stretching the preform tube after heating. A second portion of the preform tube is then located within the central cavity and is also heated by the radial compression heater and stretched to produce a second stretched portion of the preform tube and an unexpanded portion of the preform tube, or balloon portion of the parison tube.

Abstract: A radial compression mechanism incorporates a plurality of compression die assemblies arranged radially about and forming a central cylindrical cavity. The die assemblies are coupled to a cam plate by a cam bearing retained in cam guide slots in the cam plate. The cam plate is configured to rotate about the central axis of the central cylindrical cavity and thereby rotate the plurality of compression dies about the central axis. The plurality of dies are constrained by a stationary guide slot configured in the housing of the radial compression mechanism and this stationary guide slot forces the compression dies to move radially inward to close the cylindrical cavity. Therefore, the compression dies both rotate about the central cylindrical cavity and move radially inward to close the cylindrical cavity. This arrangement and die displacement mechanism reduces the size or area required by the dies. Therefore the mechanism can be made smaller.