Plastic article or earthenware shaping or treating: apparatus – Including means advancing continuous length work through...
Reexamination Certificate
1998-12-22
2001-06-12
Heitbrink, Tim (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Including means advancing continuous length work through...
C425S186000, C425S326100, C425S384000, C425S388000, C425S392000
Reexamination Certificate
active
06244847
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for the cooling and calibration of extruded plastic profiles with a trough which is provided downstream of a dry calibrating device and comprises a water bath through which the profile is guided, with apertures being arranged in the trough between the face walls for calibrating the profile.
An installation for the production of plastic profiles as are used for the production of windows or doors usually currently comprises the following arrangement: An extruder produces a profile of doughy consistency made of plastic granulate. One or several dry calibrating devices will cool the profile to a certain extent, so that a somewhat stable form is achieved. Dry calibration substantially consists of a steel block with an opening through which the profile is guided and with a plurality of vacuum slots in order to suck the profile under pressure against the walls of the opening. In this way the collapse of the still soft profile is prevented. Furthermore, several cooling ducts are provided. One or several wet calibrating apparatuses will ensure the final cooling and shaping of the profile. Wet calibrating apparatuses according to the so-called swirl bath principle have proven to be particularly beneficial in the past few years. In such apparatuses the trough is subdivided by calibration plates into several chambers and a turbulent flow of the cooling medium in the trough is caused by openings in the plates. A negative pressure present in the trough will press the profile against the calibration plates. This allows for a precise calibration and rapid cooling of the profile with a lower water consumption. A caterpillar pull-off will draw the profile through the upstream calibrating devices.
The technical progress of extruders and the recipes for profile extrusion has led to continuously rising demands placed on the work speed of extrusion lines. In order to meet these demands it is currently common practice to arrange several dry calibrations behind one another and, downstream of the same, to provide one or several water baths. Dry calibrations are very costly, however, so that for cost reasons a reduction in their number would be desirable.
Calibration systems can be used for slow working extrusion lines which make do with only one single dry calibration with the common length of approx. 300 mm. If in such a system the work speed is increased over a relatively moderate value, high-quality profiles can no longer be produced.
DESCRIPTION OF THE PRIOR ART
From DE 27 40 989 A, a calibration device for plastic profiles is known in which a profile is calibrated and cooled under vacuum in a water bath. A pipe element is attached to the entry-sided face wall of the calibrating trough in order to guide and calibrate the profile after the entry over a certain distance. However, there are unclear pressure situations in the interior of this pipe, so that a close fit of the profile on the tube is not ensured. In particular, the wetting with the cooling water in the space between the profile and the sleeve is not ensured.
Moreover, from DE 27 34 831 A, an extrusion apparatus for pipes is known in which a water bath is provided immediately downstream of a dry calibration apparatus, which water bath is arranged as in the aforementioned specification. It substantially also has the same disadvantages.
SUMMARY OF THE INVENTION
It is the object of the present invention to avoid such disadvantages and, on the one hand, to achieve high production speeds by achieving, on the other hand, a reduction of the required expenditure. In particular, the present invention is to allow making do with only one single dry calibration of the usual length.
These objects are achieved in accordance with the invention that at least one sleeve encompassing the profile is provided in a section of the trough, which sleeve guides at least one zone of the main body of the profile and, that a gap between the profile and the sleeve is in connection with the water bath on either side. Preferably, the sleeve is provided in the longitudinal direction with a distance to the face walls.
It was established that a main cause of the inadequate profile quality in the case of reducing the number of dry calibration apparatuses is that the profiles enter the water bath in a still very hot and therefore soft state. As a result of the negative pressure which prevails by the system in such a wet calibration, the profile is pulled apart in the zones between the calibration apertures, as a result of which inner bridges of the profiles are expanded in an uncontrolled manner. Although the outer contour of the profile is finally brought back again to the desired shape by the calibration apertures, the inner bridges of the profiles are beyond repair. Such profiles can no longer be used in practice.
In the present invention the profile is protected in a first section of the water bath from the attack of the vacuum by the sleeve. As the forces by the vacuum are proportional to the surface area on which they act, a guidance of the profile is mainly required in the zone of the main body.
The relevant aspect in the invention is that the sleeve is in connection with the cooling water at least at either end. This is achieved most easily in such a way that the sleeve is provided at its face sides with a distance to adjacent components such as the face wall of the trough. Apertures in the sleeve can also be provided which secure a continual wetting of the gap between profile and sleeve.
It is particularly favourable if the length of the sleeve is between 100 and 400 mm, preferably between 250 and 320 mm. Particularly in the case when the sleeve is provided with a thin-walled arrangement a further rapid cooling of the profile is achieved by the cooling medium flowing in the outer zone of the sleeve, so that downstream of the sleeve the shape has already stabilised to such an extent that there is no danger of any over-extension of the inner bridges of the profile.
In a particularly favourable embodiment of the invention, a guidance is provided in particular in the zones of the connection of the inner bridges with the outer shape of the profile. In this way the particularly critical parts of the profile are reliably protected.
Preferably, the sleeve is arranged in an upstream area of the trough. Several sleeves can also be provided behind one another. A particularly reliable cooling without endangering the shape of the profile can be achieved in this way with simple means.
It is particularly favourable if the sleeve is held by several plates and if the plates subdivide the trough into chambers in the axial direction of the profile, with apertures being provided in the zone of the sleeves to allow cooling medium to flow through. It can be provided in particular that at one end of the trough there is provided an inlet opening for a cooling medium and at the other end of the trough an outlet opening for a cooling medium, so that the trough is substantially flowed through by a cooling medium in the longitudinal direction. An outstanding cooling effect can be achieved by this solution with a low water consumption.
A particularly simple arrangement of the apparatus in accordance with the invention can be achieved that preferably the sleeve and/or the calibration plates are held movable in a limited manner in one direction transversally to the axial direction of the profile. A complex adjustment of the sleeve and the calibration plates transversally to the axial direction of the profile can thus be omitted. Tensions and a clamping effect, owing to an insufficient adjustment, can thus be securely prevented.
The present invention further relates to a system for the cooling and calibration of extruded plastic profiles with a dry calibration in which the extruded profile is cooled and calibrated by the application of vacuum. In this process one or several troughs are optionally used in which calibration plates are arranged in a water bath.
A particularly precise adjustability and fine-tuning capacity of
Dorninger Frank
Gugenberger Walter
Wegmaier Rudolf
Dykema Gossett PLLC
Heckenberg Donald
Heitbrink Tim
Technoplast Kunststofftechnik GmbH
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