Slide Fastener

Abstract

A slide fastener serves to connect mutually overlapping edge portions of flexible sheet elements. Two stringers are provided, each of which is adapted to be secured to one of the edge portions by a sewing thread, which extends generally longitudinally of the stringer. Two rows of engaging elements are provided. The engaging elements of each row are secured to one of the stringers and spaced in the longitudinal direction of the stringer to define spaces of substantial length in which the stringer is exposed between adjacent engaging elements carried by it. Each of the engaging elements comprises two engaging knobs and a bridge portion, which is disposed between the knobs. The knobs and bridge portion of each engaging element protrude from and are aligned transversely to the stringer carrying them. The knobs of each row are adapted to interengage with the knobs of the other row. The bridge portions of each row are designed to support the thread so that the same has uncontacted portions which in the spaces extend generally longitudinally of and are spaced from the associated stringer and are disposed between and laterally engageable by the knobs of the other row when the knobs of both rows are thus interengaged.

Description

This invention relates to a slide fastener for connecting overlapping edge portions of garments.

Known slide fasteners for connecting overlapping edge portions of garments or the like comprise two identical rows of engaging elements and two stringers, each of which carries one of two identical rows of engaging elements, which are made of plastics material. Each of the engaging elements comprises two engaging knobs, which are aligned transversely to the stringer, and a bridge portion, which enter fills the space between the knobs of the adjacent engaging elements of the other row as the fastener is closed (French Pat. specification 1,275,030).

An improvement of that known slide fastener has been disclosed in the U.S. Pat. No. 3,600,766. That improvement resides in that the bridge portion and the engaging hooks which protrude beyond the bridge portion and interengage with the engaging knobs of the other row of engaging elements are arranged one beside the other and protrude from the plane of the stringer.

A fixing thread crosses the edges of the bridge portions in grooves formed in the bridge portions so that the thread does not protrude into the space between the engaging hooks.

It is an object of the invention to provide a slide fastener which is of the same general type as the slide fastener described last hereinbefore and in which the engaging elements have a simpler three-dimensional shape. Specifically, the engaging elements should have a smaller width transversely to the stringer without loss of interengaging surface area, and the slide fastener should have a higher flexibility. Besides, the sewing of the slide fastener to a garment should be facilitated.

In the slide fastener according to the invention, this object is accomplished in that the bridge portions are defined only by smooth surfaces and transversely to the stringer are flush with the stems of the engaging knobs. The fixing thread crosses the edges of the smooth-surfaced bridge portions and does not lie in grooves of the bridge portions but protrudes into the space between two engaging elements. As a result, the thread alone performs a function which in the known slide fastener is performed by the bridge portions and which resides in holding the interengaged series of engaging elements against a lateral displacement.

The performance of this function by the fixing thread will be promoted if the thread enters the stringer at a point which is remote from the bridge portion. For this reason, the thread suitably enters the stringer at a point which is approximately midway of the space between two engaging elements. Because the bridge portion is approximately flush with the stems of the engaging knobs, and does not protrude into the space between adjacent engaging elements, as it does in the known slide fastener, the flexibility of the slide fastener is much improved. The bridge portion serves only as a support for the fixing thread and actually defines only the bottom of a recess between the two engaging knobs. The width of said recess need not exceed the thickness of the thread. For this reason, the slide fastener according to the invention may be much narrower than the known fastener without a loss in interengaging surface area.

Whereas the sewing needle often breaks when used to fasten the apertured bridge portions of the known fastener, such needle break need not be feared in connection with the slide fastener according to the invention, particularly because the latter can be fastened with the aid of a much thicker sewing needle and the latter does not contact hard parts.

In the fastening process proposed by the invention, a synchronized fastening of the slide fastener according to the invention will be ensured if a conical pilot pin is secured to the needle bar and is lowered into the space between adjacent engaging elements with a phase displacement relative to the piercing of the stringer by the needle, and the feed is corrected in dependence on the motion of said index pin. This correction is restricted to a displacement of the needle by an order of 0.1 millimeter in the hole which has been pierced by the needle.

The drawing shows diagrammatically and partly in section a preferred embodiment of a slide fastener according to the invention and apparatus for carrying out the process accordqng to the invention.

In the drawing,

FIG. 1 is a top plan view showing a stringer provided with a row of engaging elements.

FIG. 2 is a side elevation showing the stringer and row of engaging elements of FIG. 1 and the second stringer and the second row of engaging elements during the fastening operation.

FIG. 3 is a perspective view of the slide fastener in accordance with the invention.

The drawing shows engaging elements 2, which are carried by a stringer 2, and engaging elements 3', which are carried by a stringer 3'. Each engaging element 2 or 2' comprises two engaging knobs 4, 4', which are aligned transversely to the stringer 3 or 3', and a smooth narrow bridge portion 5, from which the engaging knobs 4, 4' protrude and which transversely to the stringer is flush with the stems 13, 13' of the engaging knobs 4, 4'.

The needle 6 is used to extend the thread 7 or 7' over the bridge portions and to pierce the stringer in the spaces 8 between adjacent engaging elements 2 or 2' so that the stringer 3 or 3' is secured to the garment 10. That surface 14 of the bridge portion 5 which is engaged by the thread 7 or 7' is rounded. The width of the bridge portion 5 exceeds only slightly the thickness of the thread 7 or 7'. For this reason, the slide fastener can be narrower than a slide fastener according to the above-mentioned U.S. patent without a loss in interengaging surface area. Because the spaces 8 are entirely free of rigid parts, the slide fastener has a much higher flexibility. When the slide fastener is closed, the inclined portions of each of the threads 7 and 7' extend in part between the engaging knobs 4, 4' of the other row and prevent a lateral displacement of the two rows of engaging elements relative to each other.

A conical pilot pin 13 is secured with arms 12 to the needle bar 11 and together with the needle 6 is lowered into each space 8 so that the position of the stitch 14 in the longitudinal direction of the stringer is corrected by a suitable enlargement of the hole pierced by the needle.

Claims

What is claimed is:

1. A slide fastener assembly which comprises two mutually overlapping edge portions of flexible sheet elements, two stringers, two rows of engaging elements, the engaging elements of each row being secured to one of said stringers and spaced in the longitudinal direction of said stringers to define spaces of substantial length in which said stringer is exposed between adjacent engaging elements carried by it, each of said engaging elements comprises two engaging knobs and a bridge portion, which is disposed between said knobs and recessed from the outer ends thereof, said knobs and bridge portion of each engaging element protruding from and being aligned transversely to the stringer carrying them, said knobs having enlarged heads spaced from said stringer and stems connecting said heads to said stringer, each of said bridge portions having a rounded surface and being substantially flush with the associated stems transversely of said stringer, the two knobs and the bridge portion of each of said engaging elements defining a channel of given width, said knobs of each row being adapted to interengage with the knobs of the other row, and two sewing threads, each of which securing one of said stringers to one of said edge portions and being supported by the channels defined by the knobs and bridge portions of the associated row and extending through the exposed portions of said stringer and having uncontacted portions which in said spaces extend generally longitudinally of and are spaced from the associated stringer and are disposed between and laterally engageable by said knobs of the other row when said knobs of both rows are thus interengaged to connect said edge portions and said bridge portion having transversely of said stringer a dimension which is approximately twice the diameter of said thread.

2. A slide fastener assembly as set forth in claim 1, in which said engaging elements consist of plastics material.

3. A slide fastener as set forth in claim 1, in which each of said bridge portions has a height which is at least one-half of the height of said hooks.