Support tubes for cross-wound coils and cross-windings

A support tube for cross-wound coils and cross-wound windings for the bleaching and dyeing of shrinking yarns consisting of a strip, closed in itself, of a porous, elastic two-layer nonwoven fabric of synthetic fibers and/or endless fibers which are joined to each other, where the lower layer has a corrugation oriented parallel to the longitudinal direction, and the upper layer covers the folds formed by the corrugation on the outside and is connected firmly to the lower layer in the region of the largest diameter of the folds.

BACKGROUND OF THE INVENTION 
The present invention relates to a support tube for cross-wound coils and 
cross-windings for bleaching and dyeing shrinking yarns, consisting of a 
strip, closed in itself, of a porous, elastic nonwoven fabric of synthetic 
fibers and/or endless fibers which are connected to each other. 
A support tube of the type mentioned above is known from DE-OS 22 47 751. 
The support tube consists of a thickwalled hollow cylinder or hollow cone 
of an elastic nonwoven fabric, the wall thickness of which is made so that 
the yarn winding taken-up is securely held from the start without adverse 
effect from the diameter reduction resulting from the shrinkage. Because 
of the large fiber volume, the cost of the materials for such a support 
tube is relatively high. In addition, the compression of the wall 
thickness of the support tube due to the shrinkage of the yarn thereon can 
result in a reduction of the pore volume and, in particular, of the pore 
radii, of the nonwoven fabric, which has an adverse effect on the 
permeability of the fabric and, therefore, on the uniformity with which 
the individual layers of the yarn winding are acted on by the subsequent 
treatment (i.e., dyeing or bleaching) liquor. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to develop a support tube of the 
type mentioned at the outset such that the mentioned disadvantages no 
longer occur in production and the cost of the materials is reduced. 
According to the present invention, this and other objects are achieved by 
the provision of a support tube which comprises two distinct layers bonded 
to each other. The so-called lower layer of the support tube is a 
cylindrical layer of a porous elastic nonwoven fabric of synthetic fibers 
(and/or endless fibers) which are cemented together. The lower layer is 
corrugated in the longitudinal direction along the length of the cylinder. 
The so-called "upper layer", against which the yarn is taken up, covers or 
surrounds the lower layer and itself consists of a cylindrical layer of a 
porous elastic nonwoven fabric of synthetic fibers and/or endless fibers 
cemented together to form a continuous surface. The upper layer is 
attached to the lower layer, e.g., at the points of the lower layers where 
the corrugation folds are of their largest area. 
The nonwoven fabric of the support tube of the present invention is 
constructed of two layers and consists of an upper and lower layer, where 
the lower layer has a plisse (corrugation) oriented parallel to the 
longitudinal direction, and the upper layer covers the folds formed by the 
corrugation on the outside, and is firmly connected to the lower layer in 
the region of the largest diameter of the folds. The wound-up yarn rests 
on the continuous outside, closed in itself, of the upper layer which 
consists of a soft light-weight nonwoven fabric with particularly high 
permeability for liquids. The flexibility is fixed so that a good fit to 
the innermost yarn layers of the accepted winding is obtained. This 
winding is thereby secured in an excellent manner and sliding-off in the 
axial direction at an undesirable time can thereby largely be precluded. 
Through the corrugation of the lower layer, which is firmly connected to 
the upper layer, a pressure exerted on the innermost yarn layers is 
achieved which is largely constant over the course of the entire shrinking 
of the yarn winding which takes place during the treatment. Undesirable 
deformations, for example, flattening of the innermost yarn layers, are 
thereby reliably prevented. The treatment liquor can at the same time act 
with the same intensity on all the layers of the wound-up yarn, 
independently of the shrinkage that has already occurred. This is of great 
practical importance with respect to ensuring uniform treatment, for 
example, uniform dyeing. 
Special savings in material can be obtained if the fibers of the upper 
and/or lower layer are oriented predominantly in the circumferential 
direction. In such a case, the amount of fibers required in the 
longitudinal direction is only that required to ensure good internal 
ability. 
The permeability of the nonwoven fabrics employed is favored by small 
thickness of the upper and lower layers. The thickness of these layers 
should not exceed the range of about 0.2 to 2 mm and preferably 0.2 to 0.8 
mm. 
The bending stiffness of the lower layer should exceed that of the upper 
layer, preferably by three to six times. This design ensures, on the one 
hand, good conformity of the upper layer to the innermost wound up yarn 
layers and, on the other hand, an especially well equalized pressure over 
the range of the shrinkage occurring in typically employed yarns. 
In order to prevent displacement of the innermost yarn layers during the 
starting-up of the winding and later handling, it has been found to be 
advantageous if the upper layer has a roughened outside. The roughening 
may consist of fibers which stand off from the surface of the upper layer, 
such as can be obtained, for example, by a needling operation performed 
from the inside. The roughening also can be achieved by sprinkling or 
printing sinterable powders on the outside surface of the upper layer. 
Preferably, a polyamide powder with a diameter of 100 to 400 m, referred 
to the largest cross section, is used for this purpose. 
The corrugation of the lower layer can be shaped differently and may be 
carried out, for example, either with sharp edges or rounded in the region 
of the inner and/or outer circumference. A design with sharp edges ensures 
more precise securing of the accepted yarn winding; the rounded design, on 
the other hand, allows the attainment of uniform pressures for larger 
shrinkage distances. Through a combination, in which, for example, the 
inner edges of the fold are made with sharp corners and the outer edges of 
the folds are rounded, both advantages can be combined. A reverse design, 
in which the inner fold edges are rounded and the outer fold edges are 
made with sharp corners, also is directly advantageous, depending on the 
circumstances of the individual case. 
The upper and the lower layers preferably are joined together by welding or 
cementing zones. By comparison, sewing the layers together has been found 
to be technically more expensive and has the further disadvantage that the 
fibers of the upper and/or lower layer, which preferably extend in the 
circumferential direction, are not bound sufficiently stiffly at the ends. 
The welding or cementing zones can be made continuous without difficulty. 
The ratio of the mutual spacing of the welding or cementing zones and the 
depth of the corrugation, as measured in the radial direction, should 
preferably be 0.2 to 4.0 and preferably 1.5 to 2.5. The ratio 
predominantly determines the forces active in the force triangle which is 
formed of each individual fold open toward the outside, and the portion of 
the upper layer bridging the former. The surfaces of the fold are 
subjected in this force triangle to a compression load acting parallel to 
its direction, on which a bending stress may be superimposed, depending on 
the design of the edges of the fold. Within the range given, good 
stability is achieved with advantageous material consumption.

DETAILED DESCRIPTION OF THE INVENTION 
An example of an embodiment of the support tube of the invention is shown 
in the attached drawing. 
FIG. 1 shows the support tube 4 with the wound-up yarn winding 3. The 
support tube 4 consists of the corrugated lower layer 1, which is welded 
undetachably to the upper layer 2 in the region of the largest diameter of 
the edges of the fold. A plastic powder 5 is sprinkled on the outside of 
the upper layer and is sintered-on by a thermal treatment. The inside 
diameter of the corrugated layer 1 is carried on a metallic centering 
sleeve, not shown. 
The starting material for making a support tube according to FIG. 1 is 
shown in FIG. 2. It consists of the corrugated lower layer 1 which is 
joined to the upper layer 2 in the region of welding zones which are 
parallel to the folding edges. The material is rolled up in such a manner 
that the corrugations 1 form the inside, and is welded, cemented or sewed 
to a cylindrical support tube in the region of the outside circumference. 
A conical design with correspondingly shaped folding edges is possible 
without difficulty. 
EXAMPLE 
The support tube consists of a corrugated lower layer of a stiff first 
nonwoven fabric and an upper layer, connected thereto, of a second 
nonwoven fabric which has a soft flexible feel and high surface roughness. 
The first nonwoven fabric is a spun polyester fabric with an area weight of 
200 g/m.sup.2 and a titer between 10 and 12 dtex. The individual elements 
are endless and random-oriented which results in the physical properties 
being equivalent in any direction, particularly tear strength and 
elasticity. The thickness of the fabric is 0.5 mm. 
The second nonwoven fabric is a soft flexible carded fabric with high 
surface roughness, which ensures optimum yarn adhesion when the yarn is 
wound up. Thirty percent (30%) of the second nonwoven fabric consists of 
viscose fibers with a titer of 1.3 and a length of 40 mm, 10% consists of 
polyester fibers which have a titer of 3.3 dtex and a length of 60 mm, and 
60% consists of nylon fibers which have a titer of 3.3 dtex and a length 
of 51 mm. The net fiber content is 35.8 g/m.sup.2. The fibers are oriented 
predominantly in the circumferential direction and are cemented together 
by a bonding agent of 19.2 g/m.sup.2 applied in the form of foam. The 
thickness of the layer is 0.4 mm. The fabric was needled-through from 
below for improving the surface roughness, and was sprinkled on the 
outside with 24 g/m.sup.2 of a polyamide powder which was sintered-on by a 
thermal post-treatment. 
The first nonwoven fabric is conducted at a temperature of 120.degree. C. 
through a serrated pair of pressure rolls and is corrugated in the 
process, whereby a corrugation depth of 4.2 mm is obtained with a mutual 
distance of the individual folds of 8 mm. The profile of the folded edges 
is rounded on both sides. 
The flat second nonwoven fabric is applied to the so-obtained corrugated 
material. The thermal welding along the fold edges is accomplished in the 
manner shown in FIG. 2, i.e., without appreciable change of shape of the 
two nonwoven fabrics. 
Depending on the dimensions of the tube desired, the material obtained is 
cut to a given size, is rolled up to form a hollow cylinder with inward 
pointing folds which extend parallel to the axis according to FIG. 1 and 
is welded in the region of the outside circumference in the axial 
direction. The tube obtained can be used immediately.