Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Patent
1995-05-24
1997-02-25
Walberg, Teresa J.
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
57284, F27B 928, F27D 1102, D01H 1328
Patent
active
056056443
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to an elongate yarn heater for use in a false twist crimping machine.
U.S. Pat. No. 5,148,166 discloses a heating apparatus subjecting a synthetic filament yarn to advance along a zigzagged path. This known heating apparatus allows to select during construction the looping angle on the yarn guides and the total sum of looping angles on all yarn guides, without thereby affecting simultaneously the distance of the yarn path from the heated surface.
The yarn guides of the known heating apparatus contact the yarn with a curved contact surface, with the yarn guides having not only the task of smoothing the yarn path and of establishing it at a defined distance from the groove bottom. Rather, the yarn guides are also very important for the heat transfer.
It is the object of this invention to optimize in a false twist crimping machine the heat transfer of the yarn heating apparatus by a special configuration of the yarn guides.
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, in the preferred embodiment, comprises an elongate rail which includes at least one axial groove extending along the length thereof, with the axial groove defining a base wall, opposite side walls, and a central plane which is parallel to the side walls and equally spaced therebetween. A heater is mounted in the rail, and a plurality of recesses are formed in each of the opposite side walls, with the axially adjacent recesses being arranged in alternate ones of the side walls. Also, a cylindrical yarn guide is disposed in each of the recesses, with the axes of the cylindrical yarn guides being disposed substantially perpendicular to the base wall. The peripheries of the yarn guides thus define curved contact surfaces which extend beyond the central plane, such that a yarn advancing along the groove assumes a zigzagged path in contact with the curved contact surfaces of the yarn guides.
It is customary in the art to differentiate between so-called "contact heaters" and "noncontacting heaters."
The invention is based on the recognition that in a false twist crimping machine for crimping a synthetic filament yarn, a heater with a plurality of yarn guides is, with a suitable configuration of the yarn guides, a contact heater and has its properties. In the false twist crimping machine, the yarn heating apparatus is arranged directly upstream of the false twist unit in a zone of the yarn path, in which the synthetic yarn rotates in addition very rapidly, thereby imparting twist to the yarn, which is withdrawn in the false twist unit. As a result of this rotation, the yarn is surrounded by a layer of air, which impedes the heat transfer. The invention is therefore based on the fact that the yarn guides in the known heating apparatus, when they are used in a false twist crimping machine, result in that the yarn heating apparatus is a contact heater, and that a special importance for the heat transfer is attributed to the configuration of the contact surfaces. On the one hand, the present invention avoids that the extension of the twist in the direction opposed to the yarn advance is hindered. On the other hand, however, this invention effects an adequately close contact of an adequate yarn length with the contact surface of the yarn guide. The formation of an air jacket hindering the heat transfer is prevented, and an air jacket already formed is effectively stripped. In this connection, the yarn guides are designed such that the yarn heating apparatus has adequately good properties for all yarn deniers to be processed by false twist crimping, and that it is ideally designed for the lower denier range of about 20 dtex. Of importance for the specified dimension is the formula:
D=0.0355.times.A/U.times..sqroot.T, wherein
D=diameter of contact surfaces or average diameter of two successive contact surfaces;
U=overlap of successive yarn guides or amplitude of the zigzag line;
A=spacing
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Barmag AG
Pelham J.
Walberg Teresa J.
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