It is known to warp knit a support tape for a slide-fastener stringer half. This tape has a pair of parallel longitudinal edges and a pair of opposite faces. A monofilamentary coupling element having a succession of like turns is laid on one face at one edge thereof and stitched to the tape. The stitching is typically a multithread double chain stitch or double-lock stitch of class 400 (Federal Standard 751a).
Such stringer halves have shown themselves to give long service. They have relatively good transverse and longitudinal dimensional stability and are relatively wear resistant. Nonetheless in most of these arrangements the warp yarns, that is the filaments running mainly longitudinally, form chains into which a group of weft yarns, that is filaments running mainly transversely, are laid. These weft filaments are invariably laid in over at least four chains (see German open application DT-OS 2,016,141 and U.S. Pat. No. 3,708,836), so as to give maximum transverse dimensional stability.
More particularly, in this arrangement, the wales are of the single-bar type formed as warp chains which are bridged only by the filler or weft. As indicated the sole connecting threads or yarns between the warp chains are the laid-in weft filaments or yarns which extend over four warp chains each so that four such weft inlays fill each warp loop to provide the transverse stability of the tape (stability in the plans of the tape perpendicular to the warp chains) and, in addition, prevent longitudinal extension and contraction (change of dimension in the plane of the tape parallel to the warp chains). The dimensional stability is most pronounced if the tapes are composed of synthetic-resin yarn. which has been thermofixed, i.e. subjected to a heating or ultrasonic treatment which relaxes internal stresses within the yarn.
The advantage of single-bar warp chains, i.e. individual spaced apart wales of loops interconnected only by the weft, is that channels are formed between wales so that the row of stitching for attaching the coupling element can lay along one of these channels or valleys.
While such an arrangement has proven itself relatively desirable it has been found to be advantageous to operate the sewing machine which secures the coupling element to the tape edge at still higher rates of speed. Furthermore, such a knit does not fully utilize the capacities of the industrially normally used warp-knit machine, so that capacity is lost.