Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Patent
1994-04-04
1996-11-26
Walberg, Teresa J.
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
219469, 392417, 57282, F27B 928, D01H 1326
Patent
active
055782310
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a heater for heating an advancing, thermoplastic yarn.
Such a heater is known from EP 412 429 and corresponding U.S. Pat. No. 5,148,666. It has the disadvantage that the curvature of the yarn path is invariably predetermined, and it simultaneously determines the distance of the yarn from the heated surface.
Such a heater is used, for example, in a false twist crimping machine.
However, also different applications are taken into consideration.
Heaters for heating advancing, thermoplastic yarns (synthetic filament yarns) false twist crimping machines include, in general, elongated rails which are heated to a certain temperature, and over which the yarn is advanced.
For the drawing and heat setting of a synthetic filament yarn, a heated tube is described in DE-AS 13 03 384 which is looped by the yarn in a steep helix. At the yarn outlet end, the tube is provided with a bead to prevent a movement in circumferential direction.
A thermoplastic material for the yarn includes in particular polyamide (PA6, PA6.6) or polyethylene terephthalate, but is not limited to these materials.
It is the object of the present invention to provide a yarn heating apparatus which is simple to assemble, and which makes it possible to vary the curvature of the yarn path within wide ranges and to ensure for each yarn path and in all points of the yarn path a distance from the surface, which is independent of the selected curvature.
SUMMARY OF THE INVENTION
The above and other objects and advantages of the present invention are achieved by the provision of a heater for heating a thermoplastic yarn which is advanced along and spaced-apart from a heating surface over ridge portions arranged on the heating surface. The heating surface is the curvilinear outer surface normal to the longitudinal axis of a heating tube. The ridge portions are ring segments which are mounted on the heating surface and extend at least partially around the circumference of the heating tube. Yarn guides at each end of the tube are offset in the direction of the circumference of the tube, and cooperate to guide the yarn helically along the tube such that the yarn contacts the ring segments without contacting the heating surface of the tube.
Moreover, a further development of the invention is to make it possible to influence the heat transfer for the respective case of application.
This heater allows to select by adjusting the yarn guides provided at the inlet and the outlet end of the yarn path, the slope of the helix in circumferential direction, at which the yarn passes over the rings of the tube, and thus the curvature of the yarn path. While, however, the curvature of the yarn path has a decisive influence on the heat transfer in the described and otherwise known heaters, this is not the case in the present invention. Here, the heat transfer is based exclusively on the temperature of the tube and the height of the rings above the tube. The slope of the helix, however, i.e., the curvature and the looping angle of the yarn path, can be selected without influencing the heat transfer such that the yarn advances in a smooth and stable manner, and that, moreover, in false twist crimping machines the twist imparted to the yarn is allowed to propagate unimpeded in the region of the yarn length which is exposed to the heater.
Thus however, also a clear adjustment of the temperature is made possible. Since the curvature of the yarn path is without an influence on the heat transfer, the yarn temperature is, besides the height of the rings (see above), dependent only on the temperature and length of the tube. The length and the looping angle are not dependent on each other. Consequently, the length may be selected such that it is possible to operate the tube in a temperature range which corresponds to the selfcleaning temperature of the heated surface, i.e., it is above 300.degree. C.
One yarn guide respectively precedes and follows the heating tube of the present invention. Both yarn guides are offset from one an
REFERENCES:
patent: 3420983 (1969-01-01), McCard
patent: 3559965 (1971-02-01), Kinyu
patent: 4027467 (1977-06-01), Smith
patent: 4567721 (1986-02-01), Kuroda
patent: 5148666 (1992-09-01), Bauer et al.
patent: 5193293 (1993-03-01), Gabalda et al.
patent: 5332882 (1994-07-01), Gabalda et al.
International Search Report dated May 13, 1993 of corresponding PCT Application, WO93/25738.
Bauer Karl
Bruske Johannes
Dedeken Ralf
Fischer Martin
Frank Benno
Barmag AG
Pelham J.
Walberg Teresa J.
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