Concealed slide fastener

Abstract

In a concealed slide fastener in which coupling elements 11, 13, 15 are injection moulded on the edge 25, 27 of a tape 17, 19, a coupling portion 53 of a coupling element is provided on one side of the tape 17, 19 and a shelf 47 of the coupling element on the other side of the tape 17, 19. A coupling portion 53 bears on the shelf 47 of the opposed coupling element with the respective tape 17, 19 sandwiched between them, to limit out of plane separation of the coupling elements. The coupling portion 53 can be made the full thickness of the coupling portion on one side of the tape without the need to provide any recess or undercut in the coupling head 43 and the coupling element can be moulded using a two part mould.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

The entire disclosures of British Patent Application 0604599.1 filed on Mar. 7, 2006 are incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a concealed slide fastener and in particular to a concealed slide fastener having moulded elements.

Examples of concealed slide fasteners having moulded elements are described in U.S. Pat. No. 4,078,278, JP-A-2000-201708, JP-U-2598345 and U.S. Pat. No. 3, 124,871. FIG. 10 shows a coupling element illustrated in U.S. Pat. No. 4,078,278. A stringer of a concealed slide fastener having moulded elements 101 is provided by moulding the fastener elements 101 on to an edge of a tape (not shown) so that the tape exits the element from a slot 103 formed in a front surface 105 of the element body 107. The coupling part 109 of the coupling element 101 is formed on the front surface 105 of the body, to one side of the tape. The tape is then folded around the upper body portion 107a, away from the coupling part 109 to cover the upper surface 111 of the body. When the stringer is coupled with a like stringer, the tapes abut, between the facing front surfaces 105 of the coupling elements 101, thus concealing the elements 101 when viewed from above. A similar technique can be used for providing waterproof fasteners and the present invention includes such fasteners.

A drawback of the prior art arrangement is that the coupling part 109 is formed completely to one side of the tape. Because the element body 107 must be of sufficient thickness in the region 107a above the tape, to prevent it fracturing, the body portion 107b below the tape must be kept relatively thin to avoid the element body 107 being too thick overall. Thus, the coupling part 109 formed is on only about one half the overall thickness of the body. The coupling part 109 serves two main functions. Firstly, heads 117 of the coupling parts on opposed elements engage behind each other to prevent separation in the plane of the fastener. Secondly, shelves 113 are formed on the heads 117 to bear on shelves 115 provided on the opposed elements to limit out of plane bending of the fastener and prevent separation of the coupling elements by out of plane movement. This shelf 113 forms an undercut on the head 117 facing the tape and so it is necessary to use a sliding core mould for moulding the coupling elements 101 on the tape. If the coupling part 109 is too thin, particularly at the region of a shelf, it is likely to break when the fastener is flexed roughly or even in normal use. Also, the thin coupling element head 117 itself contributes less resistance to out of plane bending of the fastener. However, the overall thickness of the element 101 must be kept small for aesthetic reasons, and also to reduce the amount and cost of materials.

SUMMARY

In one aspect of our invention we provide a concealed slide fastener comprising a pair of stringers in which moulded coupling elements are provided on the edge of a respective tape, the coupling element including a body straddling the edge of the tape, a coupling portion extending from the body on one side of the tape and a shelf projecting from the body on the other side of the tape; when the coupling elements of the opposed stringers are engaged, the coupling portions of the coupling elements of one stringer bearing on the shelves of the opposed elements of the other stringer through the respective tape. By forming the shelves on the other side of the tape, the coupling head can be the full thickness of the body on the one side of the tape. Preferably there is no undercut facing the tape, and so the coupling elements can be moulded without a sliding core: a two-part mould can be used.

Preferably, the tape portion within the body is positioned substantially at a mid plane of the body.

The coupling element head is formed on a neck which extends from the front face of the body. A coupling element head engages behind the heads of two opposed coupling elements on the other stringer and lays between their respective necks. A shoulder is provided each side of the neck, to provide an abutment surface for the head of an opposed element.

The shelf may extend the full width of the body, in the elongate direction of the tape. Preferably two shelves are provided, at opposite ends of the body surface, and respective protrusions forming the shelves form a recess between the protrusions. The recess may partially accommodate the shelves of opposed elements.

The protrusions of opposed coupling element are spaced from each other by the thickness of the intervening tapes. Depending on the desired appearance, a greater spacing may be provided. Particularly for a waterproof fastener, the protrusions may be arranged to pinch the tapes together.

As well known, as the fastener is flexed, a coupling element head bears on the adjacent necks and heads of the opposed coupling elements and the opposed shoulders. By maximising the height of the element heads, to the thickness of the body on one side of the tape, the coupling elements are better able to resist flexing of the fastener. Preferably the element heads and the necks are shaped so that a coupling head abuts the shoulders on the opposed elements and also abuts the side surface of the adjacent coupling heads at a region which transitions from the head to the neck. Preferably the side surfaces abut one another at a region midway between the opposed tapes. The heads also bear on the shelves of the opposed elements through the respective tape to prevent separation by out of plane movement.

Other features and advantages of the invention will be apparent from the accompanying description and claims.

DESCRIPTION OF THE DRAWINGS

The invention will be further described by way of example with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view from above of three coupling elements of a slide fastener which forms an embodiment of the invention, with the respective tapes removed for clarity;

FIG. 2 is an underneath perspective view of the elements of FIG. 1;

FIG. 3 is a cross-section along line III-III of FIG. 1, and showing the slide fastener tapes;

FIG. 4 is a plan view of a slide fastener coupling element of FIG. 1;

FIG. 5 is an underneath view of the element of FIG. 4;

FIG. 6 is a side view of the element of FIG. 4;

FIG. 7 is a plan view of a modification of the slide fastener, with one tape removed;

FIG. 8 is a cross-section through the slide fastener, showing a part of a slider;

FIG. 9 is an underneath plan view of the coupling elements of FIG. 1 showing the contact surfaces of the elements, and

FIG. 10 shows a prior art coupling element.

DETAILED DESCRIPTION OF THE INVENTION

Description is now made in accordance with some preferred embodiments in conjunction with the drawings appended hereto.

A slide fastener according to the present invention has a pair or fastener tapes, two rows of coupling elements injection-moulded onto the respective inner longitudinal edges of the fastener tapes and a slider movable along the coupling element rows in order to couple or decouple the coupling elements.

FIG. 1 is a perspective view from above of three coupling elements of a slide fastener which forms an embodiment of the invention.

Referring to FIG. 1, this shows three coupling elements 11, 13, 15 which are parts of coupling elements of thermoplastic material which are moulded directly onto respective tapes 17, 19 (shown in FIG. 3) by injection moulding. The tapes have cords 21, 23 at their edges 25, 27. As seen in FIG. 3, the element bodies 29 of the coupling elements 11, 13, 15 straddle both the front and rear surfaces of the respective tape edge in U-cross-sectional shape. The coupling elements 11, 13, 15 has a coupling portion 53 formed on one end thereof and the side of the coupling elements 11, 13, 15 whereon the coupling portion 53 is formed is greater in length than the other side. Specifically, the body 29 has two sides across the plane of the fastener tape 17, 19, that is, one side whereon the coupling portion 53 is formed and the other side whereon the below-described projections 33 is formed. The body 29 is moulded astraddle the edges of the tapes 17, 19 or so as to enclose them in substantially U-cross-sectional shape. The surface of the body 29 on which the element portion 53 is formed is referred to as a front face 31. The coupling elements 11, 13, 15 are moulded to the fastener tapes 17, 19 with the tapes 17 19 inserted in substantially the middle of the front face 31 of the body 29. The part of the body 29 into which the tapes 17, 19 are inserted is called “slot” here. In other words, the tape 17, 19 exits the body at a slot 30 in the front face 31, approximately mid way of the face. The tape edge portion 25, 27 is shown in FIG. 3 to be substantially at a mid plane of the body 29. The edge portion of the tape 17, 19 attached to the coupling element 11, 13, 15 is folded around the front face 31 of the body 29 at the slot 30, and the coupling portion 53 projects beyond the folded part of the fastener tapes 17, 19. However, the tape edge portion could be angled to the mid plane of the body 29. The tape edge portion 25, 27 is positioned to ensure that there is sufficient thickness of material of the body 29 around the tape edge to avoid any weakness in the body 29.

There is formed on the side free of the coupling portion 53 on the front face 31 of the body 29 at each outer end 35 thereof, projections 33 projecting from the front face 31. A recess 37 is formed between the projections 33. As shown in FIG. 4, the front surface of the recess 37 are recessed from the front surface of the two projections 33 toward the connecting portion of the body 29. Thus, the folded tapes 17, 19 contact the front ends of the projections 33 but not the front surface of the recess 37. The projections 33 extend down to the tape 17, 19 perpendicularly of the plane of the fastener tape 17, 19 to form shelves 47 facing the tape. As seen in FIG. 3, the tapes 17, 19 are folded in the direction opposite to the coupling portion53 around the projections 33, passing over the recess 37 and covering the upper surface 41 of the respective coupling elements 11, 13, 15.

A coupling portion 53 extends out from the front surface 31 of the body 29 and is formed by a coupling element head 43 on a neck 45. There are formed shoulders 46 on the lateral opposed sides of the neck 45 on the front face 31 of the body 29. From FIG. 2 it can be seen that in the coupled fastener, the head 43 of coupling element 15 (the middle coupling element as viewed in FIG. 1) engages behind the heads 43 of the opposed elements 11, 13 (beside the neck 45) to prevent separation of the coupling elements in the horizontal plane of the fastener, as well known in the art. In order to limit out of plane movement or twisting of the elements relative to one another; when the coupling elements 11, 13, 15 is about to move or twist, the head 43 pressingly contacts the necks 45, heads 43 and shoulders 46 of the adjacent elements 11, 13, thereby limiting out of plane movement or twisting of the elements relative to one another. The head 43 also bears on the shelf 47 (FIG. 5) formed by the underside of the projections 33, to limit relative out of plane movement of the adjacent coupling elements. It will be appreciated that the respective tape (in this case tape 17) is interposed between the head 43 of element 15 and the shelves 47 of elements 11, 13.

Thus it can be seen that the upper faces 49 of the coupling element heads 43, that is, the faces close to the projection 33 are adjacent the underneath surface of the tape 17, 19 where it exits the coupling body 29 and the shelves 47 are adjacent the upper surface of the tape 17, 19, generally in line with the upper and lower walls of the slots 30. The projections 33 are formed for the purpose of forming the shelves 47. As shown in FIG. 5, the shelves 47 extend beyond the shoulder 46 formed on the front face 31 toward the coupling head 43 and are formed on the lateral opposed sides of the neck 45. The shelves 47 can bear upon the upper face 49 of the coupling head 43 through the respective tapes 17, 19 and are formed large enough to ensure that the shelves 47 can accomplish the shelves 47 bearing upon the upper face 49 of the coupling head 43. In other words, the projections 33 project so as to bear upon the coupling heads 43 of the other stringer. Since the coupling elements 11, 13, 15 are provided by injection moulding process, the shelves 47 are moulded upon the tapes 17, 19. Usually, the shelves 47 will not be peeled off the tapes 17, 19. Even if the shelves 47 is peeled off the tape 17, 19 due to repeated severe use, the shelves 47 can bear upon the coupling heads 43 of the coupling elements 11, 13, 15 through the tapes 17, 19.

Referring to FIG. 3, the tapes 17, 19 are nipped between the projections 33 of the opposed elements 11, 13, 15. The degree of compression of the tapes will depend on the distance between the projections 33 (the shelves 47). As shown in FIG. 3, the distance between the opposed projections 33 is made greater than the thickness of the tapes 17, 19 interposed therebetween, therefore, the tapes 17, 19 are not compressed thereby, however, some compression is desirable for a waterproof fastener. For a fabric, relatively less compression is desirable to avoid puckering of the fabric. Referring to FIG. 6, it can be seen that the elements 11, 13, 15 can be injection moulded on to the respective tape which is captured in a mould which splits into two parts approximately along the horizontal plane of the tapes 17, 19 indicated by the line X-X, because there are no undercuts facing the tape 17, 19. As known in the art, several coupling elements can be moulded at a time on to the tape 17, 19. Metal elements could be stamped or crimped onto the tape edge.

FIG. 7 is a plan view of a slide fastener of the invention. This has coupling elements 11′ similar to those of FIG. 1. One of the tapes has been removed and it can be seen that the projections 33′ are positioned to each side of the neck 45 so as to bear on the adjacent heads 43 of the opposed elements, with the tape sandwiched in between. The projections 33′ help to limit out of plane bending of the fastener by co-operating with the opposed projections 33′ if the fastener is twisted. The positioning and width of the projections will depend on the desired effect and in particular how important it is to avoid any puckering of the material of the tapes on the upper surface of the fastener.

FIG. 8 shows a cross section through a fastener with a part of a slider 51 which carries a pull tab, embraces the coupling elements and is slid along the fastener to close or open the fastener as known in the art.

FIG. 9 shows the contact between coupling elements 11, 13, 15. The coupling element head 43 of element 15 abuts the shoulders 46 on the opposed pair of elements 11, 13. Additionally the coupling portion 53 touches the adjacent coupling portions 53 in the widthways direction at a transition region 55 where the coupling head 43 transitions into the neck 45. There is a gap 57 in the region between where the head 43 abuts the shoulder 46 and the transition region, bridging the centreline A-A of the fastener. Contact at the transition region 55 and the shoulders 46 provides for greater stability of the fastener. However, if adjacent teeth contact completely along their facing surfaces, the fastener will be difficult to operate.

CONCLUSION, RAMIFICATIONS, AND SCOPE

Since the shelves are formed on the other side of the tape, the coupling head can be the full thickness of the body on the one side of the tape. Thus, there is no undercut facing the tape, and so the coupling elements can be moulded without a sliding core: a two part mould can be used.

Since the height of the element heads has been maximised to the thickness of the body on one side of the tape, the coupling elements are better able to resist flexing of the fastener.

While the above descriptions contain many specificities, these shall not be construed as limitations on the scope of the invention, but rather as exemplifications of embodiments thereof. Many other variations are possible. Accordingly, the scope of the invention should be determined not by the embodiments illustrated, but by appended claims and the legal equivalents.

Claims

1. A concealed slide fastener comprising a pair of stringers in which moulded coupling elements are provided on the edge of a respective tape, the coupling element including a body straddling the edge of the tape, a coupling portion extending from the body on one side of the tape and a shelf projecting from the body on the other side of the tape; when the coupling elements of the opposed stringers are engaged, the coupling portions of the coupling elements of one stringer bearing on the shelves of the opposed elements of the other stringer through the respective tape.

2. A concealed slide fastener as claimed in claim 1, the coupling element further including projections formed so as to project from the body at each outer end on the side of the tape opposite to the side whereon the coupling portion extends from the body, the shelves being formed on the side of the projections which face the tapes.

3. A concealed slide fastener as claimed in claim 1 or 2, wherein the coupling elements can be moulded only with a mould which can split into two mould parts substantially along the plane of the tapes.

4. A concealed slide fastener as claimed in claim 1, wherein the tape is positioned at a mid plane of the body.

5. A concealed fastener as claimed in claim 1, wherein two shelves are provided on a coupling element and a recess is formed between the shelves.

6. A concealed slide fastener as claimed in any of claims 1 or 2, wherein the shelves of opposed coupling element are spaced from each other at such a distance as to allow the respective tapes to be interposed therebetween.

7. A slide fastener as claimed in claim 1 or 2, wherein the coupling portion comprises a neck extending from the front face of the body and a head formed on the neck, and shoulders are formed on the body adjacent the neck, wherein the coupling portion abuts the adjacent opposed coupling portions at the shoulders and at the transition regions between the head and the neck.