Plastic and nonmetallic article shaping or treating: processes – With measuring – testing – or inspecting – Controlling fluid pressure in direct contact with molding...
Reexamination Certificate
2000-12-22
2003-06-03
Tentoni, Leo B. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
With measuring, testing, or inspecting
Controlling fluid pressure in direct contact with molding...
C264S101000, C264S103000, C264S211120, C264S211140, C264S237000, C425S072200, C425S135000, C425S143000, C425S377000, C425S378200, C425S379100, C425S382200, C425S464000
Reexamination Certificate
active
06572798
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus and method for spinning a synthetic multifilament yarn of the type disclosed in WO 95/15409 and corresponding U.S. Pat. No. 5,976,431.
In the apparatus and process of the above referenced publications, an air stream assists freshly extruded filaments in their advance. With that, it is accomplished that the solidification point of the filaments moves away from the spinneret. This leads to a delayed crystallization that favorably influences the physical properties of the yarn. Thus, for example, in the production of a POY yarn, it was possible to increase the withdrawal speed and thus, the draw ratio, without changing the elongation values of the yarn necessary for further processing.
The known spinning apparatus comprises a cooling tube and an air stream generator downstream of the spinneret. Between the spinneret and the cooling tube, an inlet cylinder extends with a gas-permeable wall. By the interaction of the inlet cylinder and the air stream generator, a quantity of air is caused to enter the cooling shaft, and to advance within the cooling shaft as an accelerated air stream in the direction of the advancing yarn. The inlet cylinder consists of a perforated, gas-permeable material. Therefore, the radially inflowing air quantity is proportional to the applied pressure difference that becomes greater as the yarn speed increases. Thus, the quantity of air entering the inlet cylinder becomes greater with an increasing distance from the spinneret.
However, it has shown that besides assisting the advance, it is necessary that the filaments uniformly firm up in their surface layers. While advancing through the inlet cylinder, the filaments are precooled in such a manner that the surface layer has firmed up before entering the cooling tube. In their core, the filaments are still molten when they enter the cooling tube, so that the final solidification occurs only in the cooling tube. Consequently, it is also necessary that all filaments be uniformly precooled. Furthermore, it is desirable to have a uniform quantity of air present over the entire cross section of the inlet cylinder, so that each filament in the cooling tube is uniformly assisted in its advance.
In the production of a yarn, the quality of the yarn is determined by the interaction of the filament properties. It is therefore known that for producing a high-quality yarn, each filament within a bundle of filaments must undergo an equal treatment. In the known method and apparatus, the solidification point is deliberately removed from the spinneret, so that the filaments solidify only after passing through a precooling zone in the cooling zone formed by the cooling tube. Thus, the filaments cover a relatively long distance, over which they are exposed to different air streams.
U.S. Pat. No. 5,034,182 discloses a spinning apparatus, wherein the inlet cylinder is arranged in a pressure chamber. The inlet cylinder has a screen-like wall, so that based on the overpressure prevailing outside of the inlet cylinder, a greater pressure difference is obtained and, thus, a larger quantity of inflowing air. However, this leads to the problem that the filaments are already exposed to a considerable cooling effect within the inlet zone.
It is therefore an object of the invention to further develop a spinning apparatus of the initially described type such that it is possible to make available an air quantity adjusted to the uniform precooling of the filaments and an air quantity necessary for assisting the movement of the filaments.
Another further object of the invention is to further develop the method and the spinning apparatus such that all filaments of the filament bundle undergo a substantially uniform treatment until their solidification.
SUMMARY OF THE INVENTION
The above and other objects and advantages of the present invention are achieved by the provision of a melt spinning apparatus and method wherein the inlet cylinder is subdivided into several zones in the direction of the advancing yarn, each with a different permeability to gas for controlling the air quantity entering the inlet cylinder.
The invention would not have been suggested either by the spinning apparatus known from EP 0 580 977 or the spinning apparatus disclosed in DE 195 35 143. In the known spinning apparatus, the inlet cylinder downstream of the spinneret is constructed with its air permeability varying in the direction of the advancing yarn, so as to realize a cooling the filaments as a function of the yarn advance speed. The purpose of the known spinning apparatus is a complete cooling of the filaments within the inlet cylinder, and they are thus totally unsuited to generate an air stream that assists in the movement of the filaments in the case of only precooled filaments.
The invention has the advantage that, irrespective of the filament speed and irrespective of the differential pressure between the spin shaft and the surroundings, it is possible to influence the air quantity flowing into the spin shaft. This makes it possible to exert a purposeful influence on the properties of the filaments that originate from different zones of the spinneret. On the one hand, the influence may lie in that all filaments undergo a precooling for firming up the surface zones, if possible under the same cooling conditions. Furthermore, it is possible to influence the entry of the filaments into the cooling tube, as well as the development of the air stream in the cooling tube, in particular by the air quantity entering into the lower region of the inlet cylinder. The air quantity entering through the wall of the inlet cylinder is proportionately dependent on the gas permeability or the porosity of the wall. In the case of a high gas permeability, a larger quantity of air per unit time is introduced into the spin shaft under otherwise constant conditions. Conversely, in the case of a low gas permeability of the wall, a proportionately smaller air quantity enters the spin shaft.
The upper zone may have a greater gas permeability in the wall than the lower zone. This has the advantage that a relatively large quantity of air is available for cooling the filaments. A further advantage lies in that a substantially uniform distribution of the air quantity adjusts itself inside the spin shaft. Since in the upper zone the filament speed is low, and since furthermore the filaments are spaced from each other relatively wide due to the small distance from the spinneret, the air quantity is able to distribute itself in the upper zone of the inlet cylinder substantially unimpeded over the entire cross section of the spin shaft. With that, it is accomplished that within the filament bundle, a uniform air stream is able to develop in the cooling tube.
Alternatively, the upper zone may have a smaller gas permeability than the lower zone. This is especially suited to treat the filaments in a relatively weak precooling. From this follows the advantage of a particularly gentle cooling, which means a further improvement in spinning reliability. Spinning reliability means in this instance the quantity of filament breaks.
In the lower zone facing the cooling tube, however, a relatively large quantity of air enters the spin shaft, which facilitates the entry of the filament bundle into the cooling tube. This advantageously prevents the filaments from striking the tube wall in the region of the narrowest cross section.
It is also possible to decrease the gas permeability in the upper zone such that the upper zone becomes impermeable to gas. Thus, a quiet zone develops directly downstream of the spinneret. This quiet zone ensures a stable spinning of the filaments, and thus favors the formation of a uniform filament structure.
An intermediate zone may be positioned between the upper and lower zones, and the intermediate zone may have a smaller gas permeability than the lower zone and/or the upper zone. This has the advantage that both a uniform distribution of the air quantity is realized inside the spin shaft, and thu
Enders Ulrich
Hutter Hans-Gerhard
Meise Hansjörg
Nitschke Roland
Schulz Detlev
Alston & Bird LLP
Barmag AG
Tentoni Leo B.
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