Textiles: cloth finishing – Expanding device for textile webs – Spreader
Patent
1996-11-20
1998-04-14
Vanatta, Amy B.
Textiles: cloth finishing
Expanding device for textile webs
Spreader
26 72, 26 93, D06C 304
Patent
active
057378126
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a transport device for material webs, in particular a stretching system for plastic film webs, in accordance with the precharacterizing clause of claim 1, 3 or 4.
Devices for stretching a moving material web are employed in particular in the production of plastic films.
In the production of plastic films, both transverse stretching systems, longitudinal stretching systems and also simultaneous stretching systems are known, in which the material web, that is to say the plastic film web, is simultaneously subjected to a longitudinal and transverse stretching.
For this purpose, so-called tenters or tenter carriages are used, which are moved along a guide device, generally a guide rail.
A device for the simultaneous biaxial stretching of a moving material web, in particular a plastic web, has been disclosed, for example, by DE 37 41 582 C2. In this case, a multiplicity of tenters or tenter carriages run around along guide rails on both sides of the material web to be treated, and are connected to one another by means of chain scissor-jacks. By means of the specific separate guidance of the chain jacks, in this case the spacing of the individual tenter carriages can be deliberately increased in the stretching zone, so that the longitudinal and transverse stretch ratio can be adjusted thereby. As is known, there are provided on the tenter carriages clamping devices by means of which the edge of the material web to be treated can be gripped and moved on.
A device for the transverse stretching and fixing of film webs has been disclosed, for example, by DE 40 06 440 C2, in which device the individual chain carriages or tenter carriages are moved on by means of a circulating transport chain, the spacing between the individual tenter carriages remaining essentially unchanged.
Even though it is known from DE 33 33 938 to support the tenter element, for example, via three sliding guides which are stationary and located offset with respect to one another, in practice corresponding transport devices with tenter carriages have become widespread, said carriages being guided via a plurality of rollers which are seated at intervals in the longitudinal direction of the guide web on the tenter carriage and support the tenter carriage in the vertical and horizontal direction.
In order to increase the production capacity, web speeds are also continuously increasing. Web speeds of more than 300 m/min are not infrequent. In particular also in relation to the non-negligible mass of the individual tenter carriages, the loading on the rollers and bearings and on the guide rails is also naturally increasing.
Thus, for example for simultaneous stretching systems according to U.S. Pat. No. 5,072,493, inter alia also to increase the web speeds and to minimize the susceptibility to faults, it is proposed to drive a tenter carriage, which can likewise be moved along a guide rail by means of running rollers, by means of a linear motor. This opens up the possibility that in principle the tenter carriages can be driven and accelerated individually and that, for example, differing from the simultaneous stretching system according to DE 37 41 582 C2, the chain jacks connecting the individual tenter carriages can be dispensed with.
Nevertheless, with the increasing transport and web speeds of the advancing web and hence of the tenter carriages, the forces arising on the tenter carriages are increasing in such a way that, on account of the loadings occurring, and in particular also the bearing loadings, the lifetime of the overall transport system is restricted and repairs are frequently necessary because of failures.
It is therefore an object of the present invention to provide an improved transport device for material webs, in particular a stretching system for stretching plastic film webs, which, by contrast, is less susceptible to faults and makes longer operating times possible.
It must be considered entirely surprising that a distinct improvement over the prior art is possible, in the sense of the invention, using c
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Database WPI Section Ch, Derwent Publications Ltd., London, GB; Class A32, AN 73-72307U XP002005726 & JP,B,48 038 779 (Japan Steel Work Ltd).
Breil Jurgen
Steffl Manfred
Bruckner Maschinenbau GmbH
Vanatta Amy B.
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