GB2085348A - Stretching of fastener stock - Google Patents

Abstract

A method and apparatus is described for the stretching of fastener stock comprising two side members (10a, 10b) joined by transverse filaments (12) which are to be stretched. The stock is engaged by wheels (18, 20) which are spaced apart and are inclined to one another. The wheels, which have projections (22) (24) on their peripheries spaced apart by the same distances as the filaments, rotate at substantially the same peripheral speed in different planes to stretch the filaments that extend between the wheels. <IMAGE>

Description

SPECIFICATION Method and apparatus for the stretching of fastener stock This invention relates to a method and apparatus for the stretching of fastener stock. Stretched fasteners have gained wide industrial and commercial acceptance. A shown, for example, in British Patent Specification (G.B.P.) 1 474242 the fasteners can be formed by a thin flexible filament, typically of plastics, with an enlarged head at each end. Such fasteners are used to attach buttons to garments, tags to merchandise, in matching pairs of shoes and socks, and generally for the temporary or permanent joinder of items.

The fasteners typically are provided in an assemblage, and individual fasteners are secured, as needed, from the assemblage. There are two basic types of fastener assemblage. In the first type, as disclosed in United States patent 3,103,666 and G.B.P. 151 750 and 1 156 290, the individual fasteners have filaments that extend to cross bars which are in turn joined to a support rod by severable necks. The filaments of the fasteners are stretched to decrease their diameters and to strengthen their joinder to the cross bars. The filaments can be stretched within the mould by which the fasteners are formed, as illustrated in G.B.P. 151 750 or they can be stretched independently of the mould as illustrated by G.B.P. 1 225 841.The resulting fasteners can be applied by the dispensers illustrated in United States patent 3,103,666 and G.B.P. 162 978,1 401 501,1 401 502 and 1 474 242.

In the second type of assemblage, as shown in G.B.P. 1 474 242, two opposed longitudinally extending side members are joined together by regularly spaced and transversely extending filaments. Individual fasteners are severed from the side members between adjoining filaments. The latter are stretched either outside the mould or preferably in the mould in which they are formed.

The foregoing procedures and apparatus for the stretching of fasteners are relatively slow and expensive.

According to one aspect of the present invention, apparatus for stretching fastener stock formed by longitudinally joined side members that are coupled at predetermined intervals by transversely extending and stretchable connectors, comprises means for divergingly engaging the fastener stock at spaced apart positions of the connectors to stretch them.

Another aspect of the present invention consists in apparatus for stretching the filaments of plastics fastener stock, the stock comprising two opposed, longitudinally extending side members joined together along their lengths by transverselyextending filaments, the filaments being spaced apart along the side members at a substantially constant interval, the apparatus comprising:: (a) a pair of wheels each of which has a plurality of upstanding projections about its periphery, the leading edges of the projections on each wheel being spaced apart at the said constant interval; (b) means for mounting the wheels to rotate at substantially the same peripheral speed but in different planes, the planes and extensions thereof converging to define an acute angle, the wheels being spaced apart to define an angled gap therebetween, the wheels having points of maximum and minimum spacing at points 1800 apart about the periphery of the wheels; (c) meansforfeeeding successive filaments of fastener stock into driving engagement with successive opposed pairs of the projections at a first peripheral position; and (d) means for removing stretched fastener stock from the wheels at a second peripheral position at which the spacing between the wheels is greater than at the first peripheral position.

According to the third aspect of the present invention a method of stretching fastener stock formed by longitudinally joined side members that are cross coupled at predetermined intervals by transversely extending stretchable connectors, comprises divergingly engaging the fastener stock at spaced apart positions of the connectors to stretch them into flexible filaments.

According to a fourth aspect a method of stretching fastener stock according to the third aspect is effected by apparatus according to either the first or the second aspect of the invention.

The invention may be carried into practice in various ways but one apparatus embodying the invention and a method of stretching stock in accordance with the invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a view of unstretched fastener stock of the construction described in G.B.P. 1 474 242; Figure2 is a section on the line 2-2 in Figure 1; Figure 3 is a view of the stock of Figure 1 after stretching; Figure 4 is a view of the stretching apparatus; Figure 5 is a side view of the apparatus of Figure 4 showing the stretching of fastener stock; Figure 6 is a perspective view of the rearward engagement portion of the apparatus of Figure 4; Figure 7 is a perspective view of the diverging frontal portion of the apparatus of Figure 4;; Figure 8 is an enlarged fragmentary plan view of the apparatus illustrating the stretching of fastener stock; and Figure 9 is a view of alternative stock which may be stretched on the apparatus.

As shown in Figures 1 and 2, one form of fastener stock 11 which may be stretched is formed by longitudinally extending side members 10a and 10b which are joined together at regular intervals by a succession of unstretched, transversely extending cross connectors 12.

The fastener stock 11 can be made in any suitable fashion, for example, by injection moulding, extrusion, butt welding, and as described in G.B.P. 1 474 242. The fastener stock typically is a unitized plastics structure manufactured, for example, of nylon, polyethylene, polypropylene, polyurethane, or other similar material.

After being stretched, the stock 11 of Figure 1 has a configuration similar to that of the stock 15 in Figure 3, with each cross connector or filament 12s stretched by an amount which typically is two to five times the original unstretched length of the cross connector 12 in Figure 1.The only limitation on the stretching is that it not exceed the tensile limit of the material. Individual fasteners are provided from the stretched stock 15 by severing the side members 10a and 10b between adjoining filaments 12s to provide a fastener with cross bars 14 and 16 on the opposite ends of a filament 12s.

Referring to Figure 4, an apparatus for stretching the stock 11 is formed by a pair of rotatable wheels 18 and 20 with projections 22 and 24 spaced around their peripheries for engaging side members 10a and 10b between successive cross connectors of the stock at intervals substantially equal to their distances of separation. The wheels 18 and 20 are rotated by synchronous motors 26 and 28 at substantially the same speed, and are regularly mounted with respect to one another such that extensions 30 and 32 of their planes of rotation converge in an acute angle. As a result, the wheels have a position of maximum convergency 34 and a position of maximum divergence 36 at an angular displacement of 180 .

The motors 26 and 28 are pivotally mounted to permit variation of the angle between the wheels as indicated by the arrows 38 and 40. This can be accomplished by using clamping bolts in an arcuate track (not shown). A change in the angle between the wheels 18 and 20 and the accompanying variation in the divergence 36, permits different lengths of stretched filaments to be made from a single length of cross bar.

As indicated in Figure 5 the unstretched fastener stock 11 is fed mechanically or manually under a feed bar 42 and over projections of the two wheels, such as the projections 24 of the wheel 20, at a point where the wheels converge with a distance between them no greater than the length of the unstretched cross connector 12. Opposed pairs of projections, such as the projections 22 and 24 as shown in Figure 6 engage side members 10a and 10b adjacent opposite ends of each cross connector to advance and simultaneously stretch the connectorgas the wheels diverge, the cross connectors fitting into notches defined between adjacent projections.

Stretching continues until the wheels 18 and 20 reach their position of maximum divergence 36, after which, as indicated in Figure 7, pairs of projections converge and release the stretched filaments. The stretched stock is then removed at a bar 44, as illustrated in Figures 6 and 7.

The point of maximum convergency 34 of the wheels 18 and 20 is illustratively less than the length of any unstretched cross connector 12, and the point of maximum divergency 36 is equal to the length of the stretched filament. If desired, however, the gap 34 may equal the length of the unstretched connector and the maximum divergency 36 may be somewhat greater than the desired length of the stretched filament, especially where the plastics material possesses resilience. It has been found, for example, that the stretching of fastener stock by the method described is beneficial even where the material stock is so resilient that it returns to nearly its original length after stretching.

While the unstretched fastener stock 11 is shown being fed onto the projections at the peripheries of the wheels near the position 34 of maximum convergence, the stock may be fed at any other position where the wheels are spaced apart a distance no greater than the length of the unstretched cross connectors 12. Similarly, it is preferred that the stretched stock be advanced beyond the position of maximum stretching 36 to facilitate removal.

However, the stretched stock may be forcibly withdrawn at an earlier position, particularly if the maximum divergence 36 exceeds the desired length of the fastener.

Fixed peripheral projections are preferred and shown for retaining the fastener stock on the engagement wheels. Any other suitable retainer, however, may be employed. For example, the peripheries of the wheels 18,20 may be grooved to receive the end members 10a and 10b with clamps that retain the end members in the grooves during stretching.

It will also be appreciated that the stock 11 of Figure 1 is merely illustrative and that alternative types of stock may be employed. One such example is the stock 61 of Figure 9 in which the rail 10a of Figure 1 is substituted by successive heads 60a which are joined by thin webs 60c and the rail 1 0b is substituted by cross bars 60b joined by thin webs 60d. Each head is joined to a cross bar by a cross connector 62. Another example is a modification of the stock 61 in which the webs 60c or 60dare omitted and the successive head 60a, and successive cross bars 60b, are integrally joined.

Claims (10)

1. Apparatus for stretching fastener stock formed by longitudinally joined side members that are coupled at predetermined intervals by transversely extending and stretchable connectors, the apparatus comprising means for divergingly engaging the fastener stock at spaced apart positions of the connectors to stretch them.

2. Apparatus as claimed in Claim 1 in which the engaging means comprises a pair of members mounted for rotation at substantially the same peripheral speed in different planes which define an acute angle when extended.

3. Apparatus as claimed in Claim 2 in which the members are wheels which are spaced apart to define an angled gap between them.

4. Apparatus as claimed in Claim 1 or Claim 2 or Claim 3 which includes means for removing successive increments of stretched fastener stock from the engaging means after a prescribed rotation thereof.

5. Apparatus as claimed in any of the preceding claims in which the engaging means are adjustable to vary the divergency thereof.

6. Apparatus for stretching the filaments of plastics fastener stock, the stock comprising two opposed longitudinally extending side members joined together along their lengths by transverselyextending filaments, the filaments being spaced apart along the side members at a substantially constant interval, the apparatus comprising:: (a) a pair of wheels each of which has a plurality of upstanding projections about its periphery, the leading edges of the projections on each wheel being spaced apart at the said constant interval; (b) means for mounting the wheels to rotate at substantially the same peripheral speed but in different planes, the planes and extensions thereof converging to define an acute angle, the wheels being spaced apart to define an angled gap therebetween, the wheels having points of maximum and minimum spacing at points 1800 apart aboutthe periphery of the wheels; (c) means for feeding successive filaments of fastener stock into driving engagement with successive opposed pairs of the projections at a first peripheral position; and (d) means for removing stretched fastener stock from the wheels at a second peripheral position at which the spacing between the wheels is greater than at the first peripheral position.

7. Apparatus for stretching fastener stock substantially as described herein with reference to the accompanying drawings.

8. A method of stretching fastener stock formed by longidutinally joined side members that are cross coupled at predetermined intervals by transversely extending stretchable connectors, comprising divergingly engaging the fastener stock at spaced apart positions of the connectors to stretch them into flexible filaments.

9. A method of stretching fastener stock as claimed in Claim 8 in which the stretching is effected by apparatus as claimed in any of Claims 1 to 7.

10. A method of stretching fastener stock substantially as described herein with reference to Figures 1 to 8 or with reference to Figures 1 to 8 modified as described with reference to Figure 9 of the accompanying drawings.