Extruder with a shaping device

DETAILED DESCRIPTION The object underlying the present invention is to achieve, even at high throughputs, a perfect and constant surface quality of the extrudates produced, particularly of window profiles or pipes or the like, without increasing the outlay on machinery.
This object of the invention is achieved by providing a shaping device for an extrusion system comprising an extrusion tool and a calibrating device having a plurality of calibrating tools arranged one after another along an extrusion direction in which an extruded article from the extrusion tool travels through the calibrating device, wherein a seal device is disposed between an end face of the extrusion tool and an upstream end face of the first calibrating tool, and between the downstream end face of each calibrating tool and the upstream end face of an immediately succeeding calibrating tool, the seal devices being structured and arranged to surround the outer surface of the extruded article and to maintain a space in the extrusion direction between the respective end faces between which the seal device is disposed so as to create a cavity surrounding the extruded article that is closed off from environmental pressure outside the calibrating device, whereby the cavity can be evacuated to a reduced pressure relative to the environmental pressure.
The surprising advantage of this solution resides in the fact that, simultaneously with a reduction in the outlay for construction and servicing the calibrating tools, the surface quality can be considerably increased, avoiding air passages or cavities for application of vacuum to the profile in the calibrating tools.
In a way which could not be foreseen and was totally surprising to the person skilled in the art, in this way however higher dimensional exactitude of the extrudate could be achieved, as the extrudate, after emerging from the nozzle lip of the extruder tool, is no longer exposed to environmental conditions.
By means of the direct transfer of the extrudate from the extruder tool into the calibrating tools, sinking of the outer peripheral surfaces by means of a web located there under or within the profile, is avoided, as the external air pressure cannot become directly effective on the outer surface