Title of Invention

A HEATING APPARATUS FOR HEATING AN ADVANCING YARN

Abstract

ABSTRACT An apparatus for heating an advancing yarn is provided which has an elongate heater with a U-shaped groove accommodating a plurality of yarn guides. The yarn advancing through the heating apparatus is deflected on each yarn guide The arrangement of the yarn guides is configured such that at least two yarn guides each of a number of n yarn guides extend side by side in the direction of the advancing yarn and are arranged such that the number of changes in sign of the direction gradient of the curve corresponding to the yarn travel is smaller than the number of (n-1) yarn guides.

Full Text

APPARATUS FOR HEATING AN ADVANCING YARN The invention relates to an apparatus for heating an advancing yarn as defined in the preamble of claim 1. Such heating apparatus are known. EP 0 412 429 Bl describes a heating apparatus of the described type in which the yarn is guided by means of a plurality of yarn guides along a heater in the general direction of the advancing yarn. The yarn guides are arranged in a groove of the heater so that the heating surfaces of the heater facing the groove contribute to the heating of the yarn. The yarn guides of the known heating apparatus extend along a curved line, which is spaced from the heating surfaces. This curved line forms a zigzag line, which extends in a surface, which is spaced from the heating surfaces over the entire length of the heating apparatus. While, when related to the length of the heating apparatus, the zigzag line increases the yarn length, which is subjected to heating in the heating apparatus, it also increases the friction of the yarn on the yarn guides. An increase of the friction on the yarn guides is disadvantageous to the yarn tension. On the one hand, having in mind an effective heating, the yarn is to remain in a guided state in the heating apparatus as long as possible and yet under little friction. On the other hand, this requirement is confronted with increased yarn speeds. It is therefore the object of the present invention to provide a heating apparatus for heating an advancing yarn, in which the friction of the yarn on the yarn guides is reduced while maintaining a high yarn speed and a substantially unchanged heat transfer. This object is achieved with a heating apparatus having the characteristics of claim 1. Accordingly, the apparatus for heating the advancing yarn is designed and constructed as an elongate heater with heating surfaces in the form of a groove, in which several yarn guides are arranged, one following the other, in the direction of the advancing yarn. On each yarn guide, the yarn undergoes a deflection, so that the curve Corresponding to the yarn travel exhibits changes in sign of the direction gradient. In accordance with the invention, the yarn guides are arranged such that of a number of n yarn guides at least two yarn guides each are arranged side by side in the direction of the advancing yarn, so that number of changes in the direction gradient of the yarn travel curve is smaller than the number of n-1 yarn guides. In a preferred embodiment, two yarn guides each axially adjacent in the direction of the advancing yarn extend along a straight-line substantially parallel to the heating surfaces, and they are arranged such that the yarn, when passing over the yarn guides, assizes a distance from the groove, which alternately varies in pairs. Each line segment of the advancing yarn that is formed by the two side-by-side yarn guides, faces a respective one of the heating surfaces in an off-center relationship, when related to the center of the groove in the heating apparatus. In this manner, the yarn alternately contacting two side-by-side yarn guides successively faces the one heating surface of the groove, so as to merge, after leaving this segment, into a line segment of yarn advance, which extends likewise substantially parallel to the opposite heating surface of the groove in the heating apparatus. Arranged in the groove of the heating apparatus are several of these pairs of yarn guides. Such a double arrangement of two yarn guides each which alternate with one another on each of the heating surfaces, means that the direction gradient changes its sign after every second yarn guide. In a preferred embodiment, the yarn guides are constructed as slide-in plates or disks, which have yarn guide slots extending into the groove of the heating apparatus, the slots extending likewise parallel to the heating surfaces. In a further preferred embodiment, the yarn guides are constructed as rod-shaped elements, which are arranged on the heating surfaces, and contacted by the yarn. The rod-shaped elements are arranged such that the yarn advances always along the side of the yarn guides facing away from the heating surfaces, the yarn path along the side-by-side yarn guides being however likewise off-center. Preferably, the rod-shaped elements have a circular cross section, other rounded cross sections being possible, such as, for example, oval cross sections, slightly flattened cross sections, and the like. In a yet further, preferred embodiment, the yarn guides are constructed as corrugated elements which are attached to the heating surfaces of the heating apparatus. Preferably, the corrugated elements have a substantially semicylindrical cross section. Preferably, the corrugated elements may likewise have a cross section in the shape of a sine wave. It is preferred to space the yarn guides equally from one another, so that the curve segments of the yarn path, which are formed each by the two side-by-side yarn guides and extend substantially parallel to the heating surfaces, have each the same length, so as to ensure an as uniform as possible heating of the yarn during its passage through the heating apparatus. Li a yet further, preferred embodiment, three yarn guides each are arranged off-centered with respect to the groove, so that the direction gradient of the curve corresponding to the yam travel changes its sign only after every third of the three yam guides, the curve of the advancing yarn assuming preferably a substantially sinusoidal course. Accordingly, the present invention provides an heating apparatus for heating an advancing yarn, the apparatus comprising an elongate heater with heating surfaces in the form of a groove, the groove accommodating a plurality of yam guides, which are positioned along a line with zigzag changes in direction, the line extending over a surface, which is spaced apart from the heating surfaces over the entire length of the heating apparatus, characterized in that the number of direction changes of curvature is smaller than the number of yam guides. Further advantages and possible applications of the present invention are now described in more detail with reference to the attached drawings, in which Figure l is a cross sectional view of a heater in accordance with the invention; Figure 2 is a top view of the groove cross section of the heating apparatus; Figure 3 is a front view of a heating apparatus; Figure 4 is a top view of the groove in the heating apparatus with carriers and yarn guides; Figure 5 is a cross sectional view of the heating apparatus in accordance with a further embodiment of the invention; and Figure 6 is a top view of the groove cross section of a heating apparatus with yarn guide elements arranged therein in the form of corrugations. Figure 1 is a cross sectional view of a heater in its basic arrangement. A heating apparatus 1 which has a U-shaped groove 6, is constructed such that the heating elements arranged in the U-shaped block deliver their heating energy above groove bottom 15 as well as heating surfaces 5. Arranged in the groove are yarn guides 2 that are provided in disk-shaped carriers 10. These yarn guides 2 are machined in the form of yarn guide slots out of the carriers 10, the slots extending substantially parallel to the heating surfaces 5 and in direction toward the groove bottom 15. Depending on the yarn speed and existing heating energy, as well as the yarn material, the yarn guide slots may be arranged closer to the heating surfaces or be further removed therefrom. However, in accordance with the invention, these yarn guide slots are always arranged in the region between the center line of groove 6 and heating surfaces 5. Since a yarn, not shown in Figure 1, which advances in the yarn guide slots, undergoes a deflection on each yarn guide, the deflection surfaces are made round across the thickness of carrier 10, so as to exert a least possible influence on the yarn tension, when the yarn enters into the yarn guide slot. The disk-shaped carriers 10 which are substantially equally spaced in the direction of the advancing yarn, have on their side facing away from heating apparatus 1 a funnel-shaped inlet, so as to facilitate the entry of the yarn into the yarn guide slot. Figure 2 is a top view of the groove cross section of the heating apparatus. For reasons of clarity, covers which enclose the heating apparatus are not shown. The substantially evenly spaced yarn guides 2 are shown each with their yarn guide slots, through which a yarn 7 advances. The first two yarn guides, as shown on the left in Figure 2, are provided with yarn guide slots which have a same distance from heating surface 5, so that between these two yarn guides, a substantially parallel advance of the yarn results, i.e., parallel to the heating surface 5. The yarn guide slots are rounded in accordance with the deflection of the yarn, as it enters into the first yarn guide and as it leaves the second yarn guide. The yarn advances through the slots of the next two yarn guides, the slots of which are arranged such that the path of yarn 7, which is substantially parallel to heating surface S, extends closer to the heating surface 5 that is opposite to the heating surface facing the yarn 7 between the first and the second yarn guide. In comparison with a zigzag line of the yarn path or yarn travel curve, as is known from the prior art, the yarn guidance of the present invention has the advantage that the yarn loops less about the yarn guide and, thus, its friction is reduced. This advantage is achieved in that the yarn is deflected, for example on every second or third yarn guide by the amount of overlap of the yarn guides with respect to the center plane of the groove. As a result of the fact that, when arranged in pairs, always two adjacent yarn guides extend along a line parallel to the groove, the zigzag course of the yarn, as known from the prior art, is interrupted respectively by straight partial line segments. The looping angle on the yarn guide is only half as much, when compared with the looping angle of the prior art arrangement (one third in an arrangement of three, etc.). The overlap of the yarn guides beyond the center plane of the groove is dependent on process parameters, or yarn materials, or the heat output installed. In a double arrangement, the contact zone between yarn and yarn guide, which is reduced by about 50% results in a positive influence on the advancing yarn, in particular with small overlaps and narrow tolerances. The length of the heating apparatus, i.e., the length of the yarn, which is exposed to the heating apparatus for purposes of heating, is determined in accordance with the process parameters, in particular in accordance with the type of yarn. Yarn thickness, yarn speed, temperature of the heater, dimensioning of the heating apparatus, etc. are relevant parameters to this end. Assuming, for example, that the overall length is to be one meter, a length of 500 mm will result for each individual heater. of which several may be arranged, one after the other, in the entire installation. It has been found useful to arrange four yarn guides in the first heater or first heating apparatus, when, viewed in the direction of the yarn advance through the equipment, and five yarn guides in the second heating apparatus. With such a configuration, the spacing of the individual yarn guides is in a range of about 125 mm, this value being naturally dependent on process and material parameters. Figure 3 is a sectioned front view of the heating apparatus. The heating apparatus 1 is constructed as a U-shaped rail and defines in its interior a groove with heating surfaces 5 and groove bottom 15. The actual heating apparatus 1 accommodates a resistance heater 14, which provides a supply of heat energy into the interior of the groove. Provided in axial groove 6 is a structural unit, which is secured preferably by clamps. This structural unit consists of a strip-shaped carrier 10 and yarn guides 3 laterally arranged thereon. The yarn guides are arranged offset from one another on both sides, namely in equally-spaced pairs. The carrier 10 is deformed by the clamping of the structural unit, so that it is in contact respectively with two opposite, successive pairs of yarn guides. In this manner, the structural unit is fitted in the groove by the action of elastic clamping forces. The yarn guides 3 are held in groove 6 by caps 17. These caps 17 are C-shaped and cover the upper edge of each side wall of groove 6, while engaging themselves into small axial grooves, which are provided on both sides of the upper edges in the side walls of the groove, i.e., the heating surfaces 5. Figure 4 is a top view of the groove 6 in heating apparatus 1 with carriers and yarn guides. Inserted into the elongate, U-shaped groove 6 is the carrier 10 with the yarn guides 9. When inserting the carrier 10 with the yarn guides 9, which are rod-shaped elements with a circular cross section, the carrier 10 is forced to assume a linear extension corresponding to that shown in Figure 4. This means that the carrier contacts respectively two adjacent yarn guides, which are arranged in the direction of the advancing yarn, one after the other, alternating in pairs on opposite sides of the heating surfaces 5 of groove 6. The individual yarn guides rest against the side walls, i.e., the heating surfaces of the groove. With respect to the selection of the material, it is important that the strip, which forms carrier 10, be elastic and remain elastic even during the expected heating to more than 400"'C. Shown in Figure 5 is a cross sectional view of a further embodiment of a heating apparatus in accordance with the invention. The heating apparatus 1 is constructed again as an elongate, U-shaped body, which accommodates in its interior resistance heaters 14 that are inserted in corresponding bores of the heating apparatus 1, and serve to heat the groove 6 formed in the U-shaped heater. In groove 6, two metal strips 13 are inserted, which rest against the opposite side walls, i.e., the heating surfaces 5 of the axial groove. Elevations in the shape of corrugations serve as yarn guides and face again, in pairs, the opposite side walls. The two metal strips 13 are interconnected, via cross members 8 in the region of the groove bottom 15, so as to secure on the one hand the metal strips 13 in their position relative to one another, and to prevent on the other hand the yarn from contacting the wall of groove 6, i.e. the groove bottom 15. For this reason, the cross members 8 are arranged preferably at a distance from the groove bottom IS. The corrugations are shaped such as to form on the open side of the U-shaped groove 5, by means of a bevel 18, a V-shaped notch, which likewise facilitates the insertion of the yarn. Shown in Figure 6 is a top view of the groove cross section of a further embodiment of the invention. Elevations in the shape of corrugations are used as yarn guides 11, which are arranged, in pairs, one after the other, each on opposite sides of groove 6, so that between two corrugated elevations, the yarn extends substantially parallel to the heating surfaces 5, the corrugations having such a height as to extend beyond the center plane of groove 6. In the region of the groove bottom 15, cross members 12 are provided for mounting the yarn guides 11 on each of the heating surfaces 5. 1 Heating apparatus 2 Yarn guides 3 Yarn guides 4 Yarn guides 5 Heating surfaces 6 Groove 7 Yarn 8 Cross member 9 Yarn guide 10 Carrier 11 Yarn guides 12 Cross member 13 Metal strip 14 Resistance heater 15 Groove bottom 16 Deflection surfaces 17 Caps 18 Bevel WE CLAIM; 1. A heating apparatus (1) for heating an advancing yam (7), the apparatus comprising an elongate heater with heating surfaces (5) in the form of a groove (6), the groove accommodating a purity of yam guides (3), which are positioned along a (theoretical) line with zigzag changes in direction, the line extending over a surface which is spaced apart from the heating surfaces (5) over the entire length of the heating apparatus, characterized in that the yam guides are positioned such that the number of direction changes of curvature of said line is smaller than the number of yam guides (3). 2. The heating apparatus as claimed in claim 1, wherein the said line along which the yam guides are positioned undergoes a direction change of curvature respectively before or after at least two yam guides (3) one following directly the other. 3. The heating apparatus as claimed in claim 1 or 2, wherein two yams guides (3) each positioned side by side in the direction of the advancing yam are arranged along a line substantially parallel to the heating surfaces (5) and such that the yam (7), as it passes over the yam guides (3) assumes a distance from the groove that ultimately varies in pairs. 4. The heating apparatus as claimed in claim 1, 2, or 3, wherein the yam guides (3) are mounted in the groove (6) and have yam insertion slots (2) extending parallel to the heating surfaces (5). 5. The heating apparatus as claimed in claim 1,2, or 3, wherein the yarn guides (3) are designed and constructed as rod-shaped elements (9, 10) mounted on the heating surfaces (5). 6. The heating apparatus as claimed in claim 5, wherein the rod-shaped elements (9,10) have a circular cross section. 7. The heating apparatus as claimed in claim 1,2, or 3, wherein the yam guides (3) are designed and contacted as corrugated elements (11, 12) mounted on the heating surfaces (5). 8. The heating apparatus as claimed in claim 7, wherein the corm gated elements (11,12) have a substantially semicylindrical cross section. 9. The heating apparatus as claimed in any one of claims 1-8, wherein the parallel distance of the yam (7) being guided by the yarn guides (3) that extend in pairs along a straight-line is always smaller than half the groove width. 10. The heating apparatus as claimed in claim 1, wherein the yarn guides are arranged such that the curve of the advancing yam is substantially sinusoidal, and that they are further arranged such that the direction gradient of the curve formed by the advancing yam changes signs each time after a constant number of yarn guides successively arranged in the direction of the advancing yam. 11. The heating apparatus as claimed in any one of claims 1-10, wherein the yam guides are arranged e qui distantly. 12. A heating apparatus for heating an advancing yam substantially as herein described with reference to the accompanying drawings.

Documents:

1078-mas-1996 abstract.pdf

1078-mas-1996 claims.pdf

1078-mas-1996 correspondence others.pdf

1078-mas-1996 correspondence po.pdf

1078-mas-1996 description (complete).pdf

1078-mas-1996 drawings.pdf

1078-mas-1996 form-2.pdf

1078-mas-1996 form-26.pdf

1078-mas-1996 form-4.pdf

1078-mas-1996 others.pdf

1078-mas-1996 petition.pdf