Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Patent
1995-03-09
1998-06-02
Hoang, Tu B.
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
392417, 57284, F27D 1102, F27B 914, D02J 1300, D01H 746
Patent
active
057603740
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a heating apparatus, in particular an elongate body, such as a tubular heater for heating an advancing yarn.
Such a heating apparatus is used, for example in a false twist crimping machine.
Apparatus for heating synthetic yarns in false twist crimping machines are known. In general, they comprise heating rails arranged in elongate heating chambers, which are heatable to a certain temperature, and over which the yarn can be guided in that it advances over yarn carriers, so-called ridges, so as to be heated.
For drawing and thermosetting synthetic yarns, tubular yarn guide members are known. For example, DE-AS 13 03 384 describes a guide member, which is looped by the yarn. This yarn guide member has a rotationally symmetric configuration and is provided with a bead at its yarn contact end. It can be heated from its yarn contact end toward its yarn runoff end to temperatures increasing continuously from a yarn drawing temperature to a yarn setting temperature, and be configured and arranged such that it can be looped by the yarn in a steep coil. This yarn guide member is complicated in its structure, and requires for its manufacture a plurality of costly operations. In addition, it is expected not to operate with the reliability to be met by high-speed processes.
In modern false twist crimping processes, the yarns advance at a considerable speed. The temperatures prevailing in the heating chambers are therefore accordingly high, which may result in damage to the yarn, when it contacts the heated surfaces of the heater. Furthermore, it is difficult to provide a uniform level of the yarn path over the heated surface, especially in curved heating chambers, in a simple manner, which ensures that the advancing yarn is heated without damage. Moreover, the known heating devices do not permit a modification of the predetermined curvature or length of a yarn path without great expenditure.
Since such heating apparatus are also used in the treatment and processing of film tapes and filaments, the latter will always be included, when in the following reference is made to a yarn.
A thermoplastic material for the yarn includes in particular polyamide or polyethylene therephthalate (PA 6, PA 6.6), but is not limited thereto.
It is the object of the invention to provide a heating apparatus, which allows to operate all structural components at high temperatures, and to make effective use in particular of the selfcleaning effects.
SUMMARY OF THE INVENTION
The above and other objects and advantages of the present invention are achieved by the provision of a yarn heating apparatus which comprises an elongate heating surface, means for heating the heating surface, and yarn guide means comprising a plurality of yarn carriers mounted in a longitudinally spaced apart arrangement along the length of the heating surface. The yarn carriers define relatively short axial ranges which directly contact the yarn and thereby directly heat the yarn, and axial ranges between the yarn carriers which are not in contact with the yarn and wherein the yarn is heated by radiation. Also, the yarn carriers are thermally connected to the heating surface and constructed so that in operation they assume approximately the same temperature as that of the heating surface.
By the described configuration of the yarn carriers and a close thermal bonding of the yarn carriers to the heating surface, it has been found that the heating surface and the yarn carriers may be maintained at a relatively high temperature during operation, preferably at a temperature above that necessary for self cleaning, without damaging the yarn.
As a surprise, it has been found that a danger of burning does not exist for the yarn at high temperatures and thin yarns, even when, as is further proposed to be advantageous, the height of the yarn carriers is selected from about 0.1 mm to 5 mm, preferably from 0.5 mm to 3 mm. The lower limit is predetermined by the curvature of the heating surface and the slope of the helix, along
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Bauer Karl
Bruske Johannes
Dedeken Ralf
Fischer Martin
Frank Benno
Barmag AG
Hoang Tu B.
Pelham J.
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