The object of the present invention is a method of manufacturing wide/narrow webbing, the width of which varies within desired dimensions and at desired intervals according to intended use.

Webbing is generally known as a product of even width in which form it is usually appropriate for its eventual uses. There are, however, numerous uses in which it is and would be sensible to use webbing the width of which varies at certain intervals as desired. The function of the wider part in the webbing is to reduce the surface pressure caused by the webbing in, for example, carrying something on a shoulder and the advantage of the narrower part of the webbing is that it can be more easily fastened to small buckles or to places where there is little space, for example, to radiophones, cameras etc.

Until now wide/narrow webbing has been manufactured, for example, in the following ways:

1. webbings of different widths are joined together at their ends

2. a separate widening part is used with narrow webbing

3. webbing of even width is narrowed at intervals by splitting, folding or turning

4. the webbing is woven directly into wide/narrow form (DE-B 1217289) .

The manufacturing methods relating to 1-3 require separate slow work stages and are thus uneconomic. The manufacturing method put forth in 4 can only be carried out with the old so-called unautomatic shuttle machines which are in the process of being withdrawn entirely from webbing-producing weaving mills.

It is also known to weave webbing of even width using weft yarn types differing from each other in their elasticity properties, the said yarns shrinking differently in the treatment following weaving which results in the narrowing of the webbing. The

differences in weft yarn elasticity cause the width of the webbing to change already during the weaving stage which means that it cannot be woven with a needle weaving machine. Further¬ more, the shrinking of elastic yarns is difficult to control.

The aim of the invention is to establish a method by which webbing of varying width can be manufactured according to conventional methods with the widely used automatic needle weaving machines. According to the present invention this is achieved in such a way that at least a part or several parts of the webbing are woven with weft yarn the fibre material of which is thermoshrinking and that the webbing woven in this manner is heat-treated to shrink the yarns and to solidify the final form of the webbing.

The advantage of the invention is that the width of the wide/ narrow webbing can be kept virtually constant during the weaving process which means that the webbing can be woven with standard- structure automatic so-called needle weaving machines, which are almost exclusively the type used in webbing-producing weaving mills nowadays and which are in the process of being adopted completely. If the width of the webbing varies during the weaving process (DE 1217289), weaving cannot be carried out with needle weaving machines. Weaving the webbing is and will in practice be possible only with the said automatic needle weaving machines considering the economy of weaving, the question of capacity and the fact that leading webbing weaving machine manufacturers have ceased making so-called unautomatic shuttle machines.

The other characteristics of the invention appear from claims 2-6 below.

In the method relating to the present invention, the thermoshrink¬ ing property of the weft yarn and an appropriate finishing tech¬ nique for each particular use are taken advantage of. These are the primary factors with which the wide/narrow form of the web¬ bing is accomplished. Already known filling properties of

different weaves are also utilized.

The present invention is explained in greater detail in the following examples which illustrate some applications of the invention.

Example 1

In this manufacturing method, which is presented in diagrammatic form in figure 1, two different types of weft yarns are used - thermoshrinking and thermally unshrinkable - which are woven into the webbing at certain intervals as required by the intended use. The thermally unshrinkable weft is woven into that part of the webbing which is intended to be wide and the thermoshrinking weft into the part intended to be narrow and into the border area where the width changes. The weave structure can thus be selected according to use in the part of the webbing intended to be wide. The filling properties of the border area weave should change gradually in a desired manner from 100% filling, which begins from the wider part of the webbing and decreases gradually towards the narrower part of the webbing. In that part of the webbing which is intended to be narrow, either the filling of the weave determines the width of the webbing or the filling is so incomplete that the shrinkage of the weft yarn determines the minimum width of the webbing. In the former case the filling of the narrower part becomes 100% due to the shrinkage of the weft yarn which means that once the webbing has been filled as said above and has reached the said width, it can no longer shrink during heat-treatment. If the complete 100% filling is not achieved at the narrower part during heat-treatment, the minimum width of the webbing is determined by the thermoshrinking proper¬ ty of the weft yarn selected and the temperature prevailing during the heat-treatment and time. In this manufacturing method the webbing is heat-treated by the so-called continuous i.e. continu-method. The webbing is fed into a warming cupboard, the temperature and feeding speed of which can be regulated. These warming cupboards are also used for the finishing of the webbing

and thus the webbing can be given the usual resin treatment in connection with the heat-treatment if necessary as regards the use. When the webbing comes out of the warming cupboard, the thermoshrinking parts of the weft have shrunk to be the narrow part of the webbing and the thermally unshrinkable parts have not shrunk and the finished product is wide/narrow webbing.

In this method comprising two different weft yarns, two different weft yarn thicknesses can also be used. For example, if the end product is required to be a firm and unfolding wide webbing part, in this part can be used weft yarn thicker by number which will give the webbing body.

On the other hand, if a thin and light narrow webbing part is desired, weft yarn thinner by number than the thermally unshrink¬ able weft in the wide part can be used. The filling of the webbing structure is thus also reduced which facilitates thermal shrinking.

Example 2

In this manufacturing method shown in figure 2, only one type of weft yarn is used and it is thermoshrinking. The webbing is heat- treated at intervals in a desired manner, whereupon the heat- treated part of the webbing shrinks to a width determined either by the filling of the weave or the thermal shrinkage of the weft and thus becomes the narrower part of the webbing. In the border areas where the shrinkage increases or decreases, the area affect¬ ed by heat-treatment may be restricted in such a way that the shrinking takes place gradually. In this method, wherein the webbing is heat-treated only partially and at intervals are used heat-treatment methods appropriate for the purpose such as e.g. heating drums or plates, the surfaces of which are designed so that the webbing will come into contact with heat only in a particular desired and restricted area.

In this method the filling property of the webbing weave may be

constant along the entire length of the webbing. The basic assumption is, however, that the filling of the weave may not be 100% since then the weft yarn cannot shrink and the webbing will not take a wide/narrow form.

If the weave filling is, for example, 50% this allows for a shrinkage of 50% and thus the webbing can shrink to a half of its original width. The filling of the narrower part of the webbing manufactured in this way is always greater than the filling of the wider part. Due to the foregoing, the narrower part will always feel harder than the wider part. This need not, however, be a negative property as regards the eventual use.

Example 3

Also in this method, which is depicted in figure 3, only one type of thermoshrinking weft yarn is used. In this case the filling property of the weave does not, however, remain constant along the entire length of the webbing but instead to the part of the webbing intended to be wider is woven a 100% filling which prevents the shrinking of the weft yarn during heat- treatment. To the part of the webbing intended to be narrow is woven a e.g. 50% filling which makes possible for the weft to shrink the webbing to a half of its original width. In border areas the filling of the weave should change gradually in the desired manner. As in the method of examle 1, in this method the webbing can also be subjected to continuous heat-treatment, based on the fact that the filling of the weave regulates the shrinkage of the weft yarn during heat-treatment. The 100% filling of the wide part prevents shrinkage and the incomplete filling of the narrow part allows the product to shrink. In this case the finished webbing always feels stiff, which is often a property required by eventual uses. If it is essential from the point of view of the eventual use that the wide part remains soft, the webbing woven according to this method can be heat-treated at intervals as in method 2. In that case it should, however, be noted that the heat-treatment must be synchronized according to

the weave structure, that is, the degree of filling of the webbing.

The yarns used as raw materials

The eventual ^' use of the webbing^is- a-determining factor in selecting the yarns. As regards the warp yarns, the requirements determined by the use concerning raw materials and thicknesses of yarns can be followed as far as is on the whole possible with woven products. The only technical restriction is that the warp yarns should withstand with as small a shrinkage as possible the temperature at which the actual thermoshrinking weft yarn is heat-treated and the webbing acquires its final wide/narrow form. Should the warp yarns also shrink, this would also change the filling properties of the structure, thus preventing the shrink¬ ing of the weft and would be a negative factor. In practice the temperature will be between 80-200 C during the heat-treatment depending on the types of the thermoshrinking yarn. Several known textile fibres can withstand this temperature without shrinking, which means that there is a wide choice of different raw materials for the warp. The same above-mentioned selecting principle also applies to selecting the thermally unshrinkable weft yarn of example 1.

In synthetic textile raw materials, that is, yarns can be found several alternatives with a considerable thermal shrinkage and from which can be selected a thermoshrinking weft yarn type according to use as regards both shrinking and other properties. As an example can be mentioned polyvinylchloride fibres which shrink 55-60% already at a temperature of 100%, which means that with this weft yarn type it is possible to shrink the webbing by heat-treatment to below 50% of its original width. Such a differ¬ ence in width, wherein the ratio is 1:2 is already sufficient in practice.