Textiles: cloth finishing – Expanding device for textile webs – Spreader
Patent
1996-12-11
1999-07-20
Vanatta, Amy
Textiles: cloth finishing
Expanding device for textile webs
Spreader
26 93, 26 72, D06C 304
Patent
active
059241802
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a transport device, in particular for a moving material web, preferably a stretching system and to an associated guide rail.
Both transverse stretching systems, longitudinal stretching systems and also simultaneous stretching systems are known, in particular, in the production of plastic films. In the case of the latter simultaneous stretching systems, the plastic film web is stretched simultaneously in the longitudinal and transverse directions. The material web is in this case grasped on the opposite outer edges by a multiplicity of so-called tenters or tenter elements, which can be moved in a circulating manner along two rails arrangements provided at the side of the material web, by means of which arrangements the plastic film web is stretched.
A device for the simultaneous biaxial stretching of a moving material web has been disclosed, for example, by DE-C2-37 41 582. A device for the transverse stretching and fixing of film webs is disclosed, on the other hand, by WO 91/12952, for example.
In transport devices of this kind, a rail arrangement is used having at least one guide rail on which the individual tenters or tenter carriages are as a rule guided over a plurality of running rollers, such that the individual tenter carriages cannot lift off from the one or more guide rails. In other words, the individual tenters or tenter carriages are guided on all sides, or at least on three sides, on at least one guide rail such that they are protected by the running rollers mounted on the tenter element. As an alternative to the use of running rollers, it is also known in principle from DE-A1-33 33 938 to support a tenter chain by means of, for example, three slideway which are fixed in terms of position and are offset with respect to one another.
The guide surfaces which are each aligned with an oppositely directed component, i.e. which are formed on opposite sides of the guide rails, essentially correspond to the clear spacing between the running rollers or sliding pieces which can be moved thereon. However, it must be ensured that there is always sufficient play between the running rollers or sliding pieces, also referred to generally below as guide elements, and the running or sliding surfaces interacting therewith of the rails, since only in this way are manufacturing tolerances and unavoidable changes in geometry in curved pieces accommodated without distortion of the guide elements.
During a circulating movement of a tenter, owing to its nature, changing external loads (dynamic forces, film forces in the longitudinal and transverse directions, propulsion forces, etc.) occur, which loads alternately press the various guide elements (i.e., for example, running rollers or sliding pieces) onto the guide rail. The dynamic forces, in particular, rise with the ever increasing speed of the system.
At relatively high speeds, for example from 200 m/min upwards, the guide elements, in particular the running rollers, are subject to high impact stress, since even with the slightest play they repeatedly alternately come into contact with and lift off from the running surfaces on the rails. Running rollers which are temporarily not loaded come to a standstill and, when the situation changes over, that is to say when they come into contact again with the associated running surface, the unloaded running rollers are subjected to high acceleration in an extremely short time. This interaction and the associated impact stress considerably reduces the service life of the guide elements, i.e. in particular of the running rollers. At the same time, the guide rails at these points are subject to considerable wear.
Due to these facts, attempts are continuously being made to keep the necessarily required play between guide elements and rail guide sections as small as possible. However, it has to be borne in mind that particles, e.g. small pieces of film (in particular if the plastic film web tears) may penetrate into this guide rail system at any time, and thus will inevitably have to be passed over. Ho
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Lindner Paul
Ruhlemann Ulrich
Bruckner Maschinenbau GmbH
Vanatta Amy
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