Abstract: Device for extruding hollow strands from thermoplastic material, with an extruder head, having a mandrel, and a calibrating device, for making a dimensional change while production is in progress, and with a radially adjustable inlet, at least one Ranque vortex chamber being formed in the mandrel, the cooling air outlet of which chamber leads into a cooling tube, which extends as an axial extension of the mandrel through the inlet of the calibrating device and has a cooling air outlet opening out into the calibrating device. This device achieves the object of providing a device with which effective interior cooling is achieved in calibrating devices designed for making a dimensional change while operation is in progress.

Abstract: Device for extruding hollow strands from thermoplastic material, with an extruder head, having a mandrel, and a calibrating device, for making a dimensional change while production is in progress, and with a radially adjustable inlet, at least one Ranque vortex chamber being formed in the mandrel, the cooling air outlet of which chamber leads into a cooling tube, which extends as an axial extension of the mandrel through the inlet of the calibrating device and has a cooling air outlet opening out into the calibrating device. This device achieves the object of providing a device with which effective interior cooling is achieved in calibrating devices designed for making a dimensional change while operation is in progress.

Abstract: Device for extruding hollow strands from thermoplastic material, with an extrusion die and a calibrating device, arranged between which is a mold chamber with an outer mold body for influencing the diameter of a hot, still moldable hollow strand emerging from an annular die of the extrusion die. The device is configured for extruding hollow strands of thermoplastic material and with which changing the wall thickness of the hollow strand emerging from the annular die is also possible. This is achieved by the mold chamber having an inner mold body, the inner and outer mold bodies being arranged coaxially in relation to the annular die and, by axial and/or radial adjustment in relation to each other, forming an annular gap between them for changing the cross section and/or the wall thickness of the hollow strand emerging from the annular die.

Abstract: Calibration sleeve for extruded plastic pipes with a first layer of flexible straps that run diagonal to the longitudinal axis of the calibration device and a second layer of flexible straps, the first and second layers of straps intercross in the manner of an extendable lattice grate in which the intercrossing points are connected in an articulated manner. The first or second layers of straps are fastened in an articulated manner on an axially adjustable rigid retaining ring at the end of a calibration sleeve, and the straps of the other layer end at an axial distance from the retaining ring. Such a calibration sleeve has an inside diameter which can be adjusted precisely while taking the contraction behavior of the extruded pipe into account. The straps of the first and second layer are fastened in a stationary and in an articulated manner at the intake of the calibration sleeve.