Textiles: manufacturing – Thread finishing – Surface modification of running length
Patent
1998-02-18
1999-10-26
Vanatta, Amy
Textiles: manufacturing
Thread finishing
Surface modification of running length
219619, 219671, 219469, D02J 122, H05B 614
Patent
active
059705922
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a godet for heating an advancing filament yarn.
U.S. Pat. No. 3,508,024 describes a godet for heating an advancing yarn wherein the godet has more than two axially adjacent stationary primary windings and a magnetically conductive godet jacket. The jacket is supported for rotation in concentric relationship with the primary windings, and is inductively connected with the primary windings via a narrow radial clearance for generating secondary currents. The carrier of the primary windings is built up from several laminated transformer sheets, which are arranged perpendicular to the axis of a coil support. A trigger circuit operates each of the primary windings with an alternating current of adjustable frequency, the primary windings being included in an oscillation circuit, which is adapted to the adjusted frequency. Via corresponding power switches in cooperation with associated temperature controllers, the oscillation circuit can be connected or disconnected as a function of the temperature measured on the godet jacket.
A similar godet is described in GB 989,349, wherein a primary winding is mounted on a circular carrier arranged in concentric relationship with a hollow cylindrical godet jacket. In the same manner as in U.S. Pat. No. 3,508,024, all flat transformer sheets of the carrier accommodating the primary windings are laminated on a coil support in axial direction. With respect to the inner surface of the godet jacket, the laminated iron sheets are arranged such as to form annular air gaps radially concentric with the axis of rotation of the godet.
In general with such heated godets, the problem arises that the loss of the magnetic flux toward the outside, in particular toward the coil support is relatively great, since all flat transformer sheets of the carrier of the primary windings are laminated on the coil support in the axial direction. Likewise, the magnetic flux in the thus-constructed carrier is not optimal, since axially adjacent transformer sheets form boundary layers. To overcome these boundary layers, a certain energy is required, which causes a loss of power. In particular, in a high-frequency application at, for example, 2 kHz and higher, the power loss increases significantly because of thicker boundary layers.
It is therefore the object of the invention to provide a heatable godet of the above-outlined kind, which permits an optimal magnetic flux in the godet by preventing a leakage field within the godet jacket, in particular in the region of the channel bottoms of the carrier, and by reducing the power loss caused by the boundary layers.
SUMMARY OF THE INVENTION
The above and other objects and advantages are achieved by the provision of a godet which has a plurality of annular U-shaped carriers mounted in an axially adjacent arrangement along a fixed tubular coil support so that the carriers lie between the coil support and the tubular wall of the yarn engaging jacket of the godet. The carriers comprise a bottom wall and opposite side walls, and the bottom wall of each carrier comprises a plurality of axially extending transformer sheets which radially overlie each other. Preferably, the side walls of each of the carriers comprise a plurality of transformer sheets which extend radially and overlie each other in the axial direction. An induction coil is mounted coaxially within each of the annular carriers, such that when an alternating current is delivered to the induction coils a secondary current is induced in the tubular wall of the jacket to thereby heat the jacket.
Since the magnetic flux, in particular toward the coil support is shielded, a leakage field is prevented from escaping outward. This permits obtaining in addition an optimal magnetic flux, which need not overcome boundary layers, and which effectively shields sections not being heated.
The special construction and arrangement of the transformer sheets ensure an improved heating of the godet jacket, since the leakage field within the godet is considerably redu
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Feldhoff Ralf
Tietmeyer Stefan
Voss Rainald
Barmag AG
Vanatta Amy
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