SLIDE FASTENER

Abstract: A slide fastener (10) includes a row of coupling elements (13, 14) secured by sewing stitches (21) to one longitudinal edge of a support tape (11, 12) made of a fabric material free of threads woven or knitted together. The sewing stitches (21) are formed of at least one thread (23) having loops passing through the support tape (11, 12). The thread (23) is made of a monofilamentary material which is free from thermal defor­ mation. The slide fastener (10) can retain, after heat-set treat­ ment, sufficient mechanical strength at the connection bet­ ween the sewing stitches (21) and the row of coupling ele­ ments (13, 14).

Description: This invention relates to slide fasteners and has particular reference to a slide fastener having a support tape made of a fabric material free of threads woven or knitted. There are known slide fasteners which comprise a support tape carrying along its one longitudinal edge a row of coupling elements, the support tape being made of a film of synthetic resin, a non-woven fabric or a thread-free material similar to a material used for the marginal edges of an opening in an article such as a bag to which the slide fastener is attached. It has thus been desired to use physicochemically similar or compatible materials for slide fastener tapes and for at least portions of an article to which the slide fastener is attached. Heretofore, rows of coupling elements were secured to the support tapes by means of sewn seams consisting of multifilamentary threads as such multifilament would yield itself to the contour of the coupling element and thus give rise to positional stability of the coupling element. It was however necessary subsequently to heat-set a finished slide fastener chain in order to cause this chain to become thermally contracted thereby stabilizing the attachment of the coupling elements to the support tapes. It has been found that during heat-setting of the fastener chain, the multifilament threads 7 undergo considerable deformation as observed in Figures 5 and 6; that is, the multifilament threads 7 having substantially round cross-section (Figure 5) prior to application of heat grow flattened (Figure 6) after heat-set, with sharp edges extending transversely across the support tape 8 and forcing the perforated seam 9 of the tape 8 to deform in conformity with such sharp edges of the multifilament threads 7. When transverse pull is applied to such slide fastener, the web of the tape 8 tends to become ruptured at and along the perforated seam 9 that has been deformed, loosening up the connection between the multifilament threads and the coupling elements (not shown) and finally rendering the fastener useless. GB-A-2.044.841 discloses a slide fastener where a series of fastener elements are sewn to the stringer tapes along its one longitudinal edge by means of double locked stitches composed of at least one needle thread made of a thermoplastic monofilament yarn and a looper thread including a spun or multifilament yarn. Each row of fastener elements is made of an helical coil mounted on one side of the stringer tape. Consequently, the friction between the fastener elements and the stringer tape is rather small and it is necessary to provide specific means to avoid displacement of the cut end portion of the coil. Constricted portions are provided on the monofilamentary needle thread to keep the looper thread from becoming loose. The present invention seeks to overcome the foregoing drawbacks of the prior art slide fasteners. The present invention further seeks to provide an improved slide fastener having a support tape made of a thread-free material such as plastics and non-woven webs, which fastener can retain, after heat-set treatment, sufficient mechanical strength at the connection between sewing stitches and a row of coupling elements secured thereby to the support tape. As claimed, the slide fastener of the present invention comprises a pair of support tapes, each support tape carrying on its one longitudinal edge a row of coupling elements, each coupling element having a coupling head portion and a pair of upper and lower leg portions, a series of sewing stitches securing said row of coupling elements to each support tape. The sewing stitches are formed of one or several threads having a plurality of loops passing through said support tape, said threads being made of a monofilamentary material. According to the invention, each of said support tapes is made of a film of plastic material, a non-woven fabric or a thread-free material, and the row of coupling elements is formed in a continuous meander or zig-zag shape and mounted astride the longitudinal edge of the tape. The invention will be better understood from the following description taken in conjunction with a preferred embodiment shown in the accompanying drawings. Figure 1 is a fragmentary plan view of a slide fastener provided in accordance with the present invention; Figure 2 is a plan view on enlarged scale of a portion of the slide fastener of Figure 1; Figure 3 is a cross-sectional view takes along the line III-III of Figure 2; Figure 4 is a cross-sectional view on enlarged scale of the sewing threads accommodated in the seam aperture after the fastener has undergone heat-set treatment; Figure 5 is a view similar to Figure 4 but showing the conventional multifilamentary sewing threads prior to heat-set; and Figure 6 is a view showing the conventional sewing threads deformed after heat-set. Referring now to the drawings and Figure 1 in particular, there is shown a slide fastener 10 which comprises a pair of support tapes 11, 12, a pair of opposed rows of coupling elements 13, 14 secured to and along the longitudinal edges of the respective tapes 11, 12, and a slider 15 reciprocal between two remotely disposed end stops 16, 17 to take the rows of elements 13, 14 into and out of engagement with each other as is well known in the art. The support tape 11, (12) may be made of a film of plastics material, a non-woven fabric or a web of other materials which are free of yarns woven or knitted. In the illustrated embodiment, the tape is formed from a plastics film. The rows of coupling elements 13, 14 are of a continuous meander or zig-zag formation and each of the coupling elements has a coupling head portion 18 and a pair of upper and lower leg portions 19 extending from the coupling head portion 18 in common direction and mounted astride the longitudinal edge of the tape as better shown in Figure 3. To increase positional stability of the coupling element 13, 14 on the support tapes 11, 12, there is used an elongate reinforcing strip 20 such as of taffeta which underlies the longitudinal edge of each tape as indicated by dotted line in Figures 1 and 2 and as better shown in Figure 3. Instead of using such reinforcing strip 20, the longitudinal edge portion of the tape 11, (12) may be folded to strengthen this tape portion for mounting the coupling elements 13, (14). Each of the rows of coupling elements 13, 14 is secured to a corresponding one of the support tapes 11, 12 by means of a series of double locked stitches 21 which are formed of two threads, i.e. a looper or locking thread 22 and a needle thread 23. The looper thread 22 overlies the upper legs 19 of the row of coupling elements 13 (14), while the needle thread 23 overlies the lower legs 19 of the coupling elements 13 (14). The needle thread 23, as shown in Figure 3, has a plurality of loops passing through respective perforations 24 in the tape 11, (12) and interlaced with the looper thread 22 in the manner well known in the art. In the illustrated embodiment, the looper thread 22 is made of a multifilamentary material and the needle thread 23 of a monofilamentary material. Both threads 22, 23 however may be monofilamentary for the purpose of the invention. Importantly, the particular thread; i.e. needle thread 23, which passes through the web of the tape 11, (12) should be monofilamentary in order to ensure freedom of deformation when slide fastener 10 is subjected to heat-set treatment. It has now been found that two adjacent portions of the needle thread 23 retain substantially original form and posture with round cross-section even after finished slide fastener 10 has undergone thermal treatment as illustrated in Figure 4. The perforation 24 through which the two adjacent portions of the needle thread 23 pass likewise remains unchanged and conforming peripherally with such portions and is therefore free from rupture which would otherwise occur when lateral pull is exerted to the fastener 10. With the needle threads 23 and the perforations 24 thus held substantially undeformed after heat-set treatment of the fastener 10, the coupling elements 13, 14 can be maintained stably in proper position with respect to the respective support tapes 11, 12.

Claims: A slide fastener comprising : a pair of support tapes (11,12), each support tape carrying on its one longitudinal edge a row of coupling elements (13,14), each coupling element having a coupling head portion (18) and a pair of upper and lower leg portions (19), a series of sewing stitches (21) securing said row of coupling elements (13,14) to each support tape (11,12), said sewing stitches (21) being formed of one or several threads (23) having a plurality of loops passing through said support tape (11,12), said threads (23) being made of a monofilamentary material, characterized in that each of said support tapes is made of a film of plastics material, a non-woven fabric or a thread-free material, and in that the row of coupling elements (13,14) is formed in a continuous meander or zig-zag shape and mounted astride the longitudinal edge of the tape. A slide fastener according to claim 1, said sewing stitches (21) comprising double locked stitches formed of a looper thread (22) and a monofilamentary needle thread (23) having a plurality of loops passing through said support tape (11, 12) and interlaced with said looper thread (22). A slide fastener according to claim 2, said looper thread (22) being made of a multifilamentary material. A slide fastener according to claim 2, said looper thread (22) being made of a monofilamentary material.

Inventors: TSUBOKAWA, YOSHITOKI
Applicants: YOSHIDA KOGYO K.K.
Application year: 1985
Main classification: A44B19
IPC codes: A44B19