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Patent Searching and Data


Title:
SLIDE FASTENER
Document Type and Number:
WIPO Patent Application WO/2021/058649
Kind Code:
A1
Abstract:
The slider comprises an upper portion, a lower portion, and a guide post disposed between said upper and lower portions. The upper portion, lower portion and guide post co-operate to define a Y-shaped channel. The Y-shaped channel has a first arm separated from a second arm by the guide post and a third arm which extends along a longitudinal axis of the slider and which adjoins the first and second arms. The first and second arms are configured to carry uncoupled coupling elements of a first stringer and second stringer of the slide fastener respectively. The third arm is configured to carry coupling elements of the first stringer and second stringer, when coupled. The coupling elements of each of the first stringer and second stringer are located along the respective stringer at a pitch distance. The third arm has a third arm length defined, parallel to the longitudinal axis of the slider, between a tip of the guide post proximal the third arm and an end of the third arm distal to the guide post. The third arm length is at least 8 times the pitch distance.

Inventors:
ANNAKA SHIGEKI (GB)
Application Number:
PCT/EP2020/076731
Publication Date:
April 01, 2021
Filing Date:
September 24, 2020
Export Citation:
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Assignee:
YKK EUROPE LTD (GB)
International Classes:
A44B19/26; A44B19/12
Foreign References:
US4099302A1978-07-11
US20050132541A12005-06-23
US20070204439A12007-09-06
Attorney, Agent or Firm:
MARKS & CLERK LLP (GB)
Download PDF:
Claims:
CLAIMS:

1. A slider (11) for a slide fastener (10), the slider comprising: an upper portion (20), a lower portion (21), and a guide post (23) disposed between said upper (20) and lower (21) portions, wherein: the upper portion (20), lower portion (21) and guide post (23) co operate to define a Y-shaped channel (36), the Y-shaped channel (36) having a first arm (36a) separated from a second arm (36b) by the guide post (23), and a third arm (36c) which extends along a longitudinal axis (A) of the slider and which adjoins the first and second arms (36a, 36b); the first (36a) and second (36b) arms are configured to carry uncoupled coupling elements (14a, 14b) of a first stringer (12a) and second stringer (12b) of the slide fastener (10) respectively; the third arm (36c) is configured to carry coupling elements (14a, 14b) of the first stringer (12a) and second stringer (12b), when coupled, wherein the coupling elements (14a, 14b) of each of the first stringer (12a) and second stringer (12b) are located along the respective stringer (12a, 12b) at a pitch distance (P); the third arm (36c) has a third arm length (27) defined, parallel to the longitudinal axis (A) of the slider, between a tip (22) of the guide post (23) proximal the third arm (36c) and an end of the third arm (36c) distal to the guide post (23); and the third arm length (27) is at least 8 times the pitch distance (P).

2. The slider (11) of claim 1 wherein the third arm (36c) is defined, at least in part, by first and second opposing side flanges (24a, 24b, 25a, 25b) which each extend from the upper (20) or lower portion (21) of the slider, wherein: said first (24a, 25a) and second (24b, 25b) side flanges are spaced from one another, in a direction perpendicular to the longitudinal axis (A) of the slider, by a third arm width (W’); said third arm width (W’) is configured to be greater than or equal to a width (Wc) of coupling elements (14a, 14b) of the first stringer (12a) and second stringer (12b), when coupled; the third arm (36c) has a first portion (16) and a second portion (17), wherein: the second portion (17) is provided between the first portion (16) and a tip (22) of the guide post (23) proximal the first portion (16); and, a first portion of the first side flange (24a, 25a) and a first portion of the second side flange (24b, 25b) are substantially parallel and define the first portion (16) of the third arm (36c).

3. The slider (11) of claim 1 or 2 wherein the third arm length (27) is less than 12 times the pitch distance (P).

4. A slider (11) according to claim 2 or 3, wherein: the third arm length (27) provides a first portion length (27a) and a second portion length (27b), wherein: the first portion length (27a) is defined as the length of the first portion (16), parallel to the longitudinal axis (A) of the slider; the second portion length (27b) is defined, parallel to the longitudinal axis (A) of the slider, between a tip (22) of the guide post (23) proximal the third arm and an end of the first portion (17) of the third arm (36c) proximal the guide post (23); and the first portion length (27a) is at least 6 times the pitch distance (P).

5. A slider (11) for a slide fastener (10), the slider comprising: an upper portion (20), a lower portion (21), and a guide post (23) disposed between said upper (20) and lower (21) portions, wherein: the upper portion (20), lower portion (21) and guide post (23) co operate to define a Y-shaped channel (36), the Y-shaped channel (36) having a first arm (36a) separated from a second arm (36b) by the guide post (23), and a third arm (36c) which extends along a longitudinal axis (A) of the slider and which adjoins the first and second arms; the first (36a) and second (36b) arms are configured to carry uncoupled coupling elements (14a, 14b) of a first stringer (12a) and second stringer (12b) of the slide fastener (10) respectively; the third arm (36c) is configured to carry coupling elements (14a, 14b) of the first stringer (12a) and second stringer (12b), when coupled, wherein the coupling elements (14a, 14b) of each of the first stringer (12a) and second stringer (12b) are located along the respective stringer (12a, 12b) at a pitch distance (P); the third arm (36c) is defined, at least in part, by first and second opposing side flanges (24a, 24b, 25a, 25b) which each extend from the upper (20) and/or lower portion (21) of the slider, wherein: said first (24a, 25a) and second (24b, 25b) side flanges are spaced from one another, in a direction perpendicular to the longitudinal axis (A) of the slider, by a third arm width (W’); said third arm width (W’) is configured to be greater than or equal to a width (Wc) of coupling elements (14a, 14b) of the first stringer (12a) and second stringer (12b), when coupled; the third arm (36c) has a first portion (16) and a second portion (17), wherein: the second portion (17) is provided between the first portion (16) and a tip (22) of the guide post (23) proximal the first portion (16); and, a first portion of the first side flange (24a, 25a) and a first portion of the second side flange (24b, 25b) are substantially parallel and configured so as to define the first portion of the third arm (36c); the third arm (36c) has a third arm length (27) defined, parallel to the longitudinal axis (A) of the slider, between a tip (22) of the guide post (23) proximal the third arm (36c) and an end of the third arm (36c) distal to the guide post (23); the third arm length (27) provides a first portion length (27a) and a second portion length (27b), wherein: the first portion length (27a) is defined as the length of the first portion (16) parallel to the longitudinal axis (A) of the slider; the second portion length (27b) is defined, parallel to the longitudinal axis (A) of the slider, between a tip (22) of the guide post (23) proximal the third arm and an end of the first portion proximal the guide post (23); and the first portion length (27a) is at least 6 times the pitch distance (P). 6. The slider (11 ) of claim 5 wherein the first portion length (27a) is less than 10 times the pitch distance (P).

7. A slider (11) for a slide fastener (10), the slider comprising: an upper portion (20), a lower portion (21), and a guide post (23) disposed between said upper (20) and lower (21) portions, wherein: the upper portion (20), lower portion (21) and guide post (23) co operate to define a Y-shaped channel (36), the Y-shaped channel (36) having a first arm (36a) separated from a second arm (36b) by the guide post (23) and a third arm (36c) which extends along a longitudinal axis (A) of the slider and which adjoins the first (36a) and second (36b) arms; the first (36a) and second (36b) arms are configured to carry uncoupled coupling elements (14a, 14b) of a first stringer (12a) and second stringer (12b) of the slide fastener (10) respectively; the third arm (36c) is configured to carry coupling elements (14a, 14b) of the first stringer (12a) and second stringer (12b), when coupled, wherein the coupling elements (14a, 14b) of each of the first stringer (12a) and second stringer (12b) are located along the respective stringer (12a, 12b) at a pitch distance (P); the third arm (36c) is defined, at least in part, by first and second opposing side flanges (24a, 25a, 24b, 25b) which each extend from the upper (20) and/or lower portion (21) of the slider, wherein: said first (24a, 25a) and second (24b, 25b) side flanges are spaced from one another, in a direction perpendicular to the longitudinal axis (A) of the slider, by a third arm width (W’); said third arm width (W’) is configured to be greater than or equal to a width (Wc) of coupling elements (14a, 14b) of the first stringer (12a) and second stringer (12b), when coupled; the third arm (36c) has a first portion (16) and a second portion (17), wherein: the second portion (17) is provided between a tip (22) of the guide post (23) and the first portion (17); and a first portion of the first side flange (24a, 25a) and a first portion of the second side flange (24b, 25b) being substantially parallel and defining the first portion of the third arm; the third arm (36c) has a third arm length (27), parallel to the longitudinal axis (A) of the slider; the third arm length (27) provides a first portion length (27a) and a second portion length (27b), wherein: the first portion length (27a) is defined as the length of the first portion, parallel to the longitudinal axis (A) of the slider; the second portion length (27b) is defined, parallel to the longitudinal axis (A) of the slider, between a tip (22) of the guide post (23) proximal the third arm and an end of the first portion proximal the guide post (23); and the first portion length (27a) is greater than or equal to 2 times the second portion length (27b).

8. The slider (11) of claim 7, wherein the first portion length (27a) is less than 3.5 times the second portion length (27b).

9. A slide fastener (10) comprising a slider (11) according to any preceding claim, wherein: the slider is mounted to a first stringer (12a) and a second stringer (12b), the first stringer (12a) comprising coupling elements (14a) which are couplable with coupling elements (14b) of the second stringer (12b), and the second stringer (12b) comprising coupling elements (14b) which are couplable with coupling elements (14a) of the first stringer (12a); the coupling elements (14a, 14b) of each of the first stringer (12a) and second stringer (12b) are located along a longitudinal axis (A) of the respective stringer (12a, 12b) at a pitch distance (P); the first (36a) and second arms (36b) carry uncoupled coupling elements (14a, 14b) of the first stringer (12a) and the second stringer (12b) of the slide fastener (10) respectively; and the third arm (36c) carries coupling elements (14a, 14b) of the first stringer (12a) and second stringer (12b), when coupled.

10. A slide fastener (10) according to claim 9, wherein a first coil comprises the coupling elements (14a) of the first stringer (12a) and a second coil comprises the coupling elements (14b) of the second stringer (12b).

11 . A slide fastener (10) according to claim 9 or claim 10, wherein: the first and second stringers (12a, 12b) comprise a woven or knitted material; the coupling elements (14a) of the first stringer (12a) are woven or knitted into the woven or knitted material of the first stringer (12a); and the coupling elements (14b) of the second stringer (12b) are woven or knitted into the woven or knitted material of the second stringer (12b).

12. A slide fastener (10) according to any of claims 9 to 11 , wherein the slide fastener

(10) is a fluid-tight slide fastener.

13. A slide fastener (10) according to claim 12, wherein each of the first and second stringers (12a, 12b) comprise respective sealing lips (15a, 15b), said sealing lips (15a, 15b) comprising a fluid-tight material and contacting one another when coupling elements (14a, 14b) of the first and second stringers (12a, 12b) are coupled.

14. A slide fastener (10) according to claim 13, wherein the first (36a) and second (36b) arms of the slider (11 ) carry the sealing lip (15a, 15b) of the first stringer (12a) and second stringer (12b) respectively; and the third arm (36c) of the slider carries the sealing lips (15a, 15b) of the first stringer (12a) and second stringer (12b).

15. A slide fastener (10) according to claim 14, wherein the third arm (36c) of the slider

(11 ) is sized such that a first cavity (42) is formed between a portion of the upper portion (20) defining the third arm (36c) and the sealing lip (15a) of the first stringer (12a), and a second cavity (44) is formed between said portion of the upper portion (20) defining the third arm (36c) and the sealing lip (15b) of the second stringer (12b).

16. An article comprising a slide fastener (10) according to any of claims 9 to 15.

Description:
Slide Fastener

The present invention relates to a slider for a slide fastener and a slide fastener including such a slider. The invention also relates to an article including such a slide fastener.

Conventional slide fasteners comprise a pair of stringers and an opening and closing means commonly referred to as a slider. Each stringer comprises a tape and a plurality of coupling elements. The coupling elements extend along a first edge of each tape and when the slider of the slide fastener has been moved to a closed position, corresponding coupling elements of the stringers interdigitate, couple or interlock. When each tape of the slide fastener is attached to separate portions of an article, the separate portions of the article may be releasably joined by closing the slide fastener by moving the slider to the closed position, and thereby bringing the coupling elements into said interdigitating relationship.

Slide fasteners are therefore both useful and versatile and are employed in a range of applications including garments, furnishings and luggage.

Known slide fasteners (also referred to as zip fasteners) are generally constructed as follows.

A coupling portion, usually in the form of a plurality of coupling elements (also referred to as teeth) is attached to a first edge of a tape to form a stringer. The tape is usually woven or knitted and may be formed from, for example, polyester. The coupling elements may be attached to the tape by, for example, crimping or moulding the coupling elements onto a reinforced edge of the tape, which may be referred to as a cord. Alternatively, the coupling elements may be formed as a continuous coil. In this case the coupling elements are most commonly stitched to a surface of the tape at the edge of the tape or, alternatively, are woven or knitted into the tape.

The invention discussed in more detail below is of most use in combination with a slide fastener of the type in which each stringer includes a plurality of coupling elements formed as a continuous coil. Two stringers are brought together, such that the coupling elements of each stringer can attach to one another, for example, by interdigitating, to form a chain. The chain is generally planar, and the chain (and the coupling elements which form part of the chain) extends along a longitudinal axis of the chain. A slider is mounted to the chain onto coupling elements of each respective stringer such that it can move along the chain between the two stringers.

The slider commonly includes a main body through which the coupling elements of each stringer pass and a pull tab or pull cord attached to the main body which may be grasped by a user in order to effect movement of the slider along the chain. The main body includes a guide post (sometimes referred to as a diamond) which, in part, defines a Y- shaped channel which is configured to carry coupling elements of the first and second stringers.

Movement of the slider along the chain in a first sliding direction causes the coupling elements of the first stringer to attach to the coupling elements of the second stringer. When the slider is no longer able to couple elements any further in the first sliding direction i.e. substantially all the coupling elements of the first stringer are attached to substantially all the coupling elements of the second stringer, the slide fastener may be said to be in a fully closed configuration. Movement of the slider along the chain in a second sliding direction, opposite to the first sliding direction, causes the coupling elements of the first stringer to detach from the coupling elements of the second stringer. When the slider is no longer able to uncouple elements any further in the second sliding direction i.e. substantially all the coupling elements of the first stringer are detached from the coupling elements of the second stringer, the slide fastener may be said to be in a fully open configuration.

The chain is cut to a desired length to form a desired length of slide fastener. Stops (often referred to as top stops and bottom stops) may be attached to either or both ends of the chain. The stops limit the extent of movement that the slider can undertake along the chain. It is usually the case that a top stop limits movement of the slider in the first sliding direction, and a bottom stop limits movement of the slider in the second sliding direction. Typically, stops may be used in order to limit the movement of the slider along the chain. Typically, the slider is no longer able to couple or uncouple elements, or move, when the slider abuts a stop of some variety, such as a bottom stop or a top stop. Some slide fasteners may have a single bottom stop which is attached to both the first and second stringers. Other slide fasteners, which may be referred to as separating slide fasteners, may have two separate bottom stops each attached to a corresponding one of the stringers. The two bottom stops may take the respective forms of a retainer box and an insertion pin. The insertion pin can be inserted into the retainer box in order to interlink the first and second stringers with one another. Conversely, the insertion pin can be removed from the retainer box when the slider is located adjacent the retainer box in order to pass through the slider and separate the first and second stringers from one another.

Some slide fasteners may have two separate top stops, each being attached to a corresponding one of the stringers. Other slide fasteners may have a single top stop attached to one or both of the stringers.

Some slide fasteners may be fluid-tight. A common type of fluid-tight slide fastener is a water-tight slide fastener. A known example of such a water-tight slide fastener includes coupling elements formed by continuous coils woven into an edge on one surface of the tape of each stringer. The other surface of each tape is coated with a water-proof layer which extends beyond the edge of the tape to form a bulbous sealing lip. When the coupling elements of the tapes are coupled together the sealing lips of the water-proof layer of each stringer abut to form a seal. Such fasteners can provide a reasonably effective seal against liquids (or gasses), depending on various factors such as the design of the sealing lips, of the fluid-proof layers, the extent to which the sealing lips are urged together by the coupled elements and the extent of flexing of the slide fastener in use.

In some applications of this type of slide fastener, the bulbous sealing lip may be difficult to transport through the slider. In particular, the bulbous nature of the sealing lip as well as the polymeric composition of the coating may mean that there is a high degree of friction between the slider and the stringers. This may make the slider difficult to operate and/or cause excessive force to be applied to the slider, which in turn makes it more likely that the slide fastener is twisted. In particular, if sufficient space is provided between an inner wall of the slider and the chain in order to make the slider easier to operate, the potential for the slider to twist is increased. It has been found that, in certain applications, if a slide fastener is twisted, the longitudinal axis is no longer straight but may become curved or twisted (either in the plane of the fastener or out of said plane). In this situation, whilst the slider slides in the first sliding (or closing) direction, the coupling elements may mis-mesh. Such mis-mesh (or engagement fault) occurs when more than one coupling element of one stringer is received between adjacent coupling elements of the other stringer. This leads to inadequate coupling of the first and second stringers. Such inadequate coupling of the first and second stringers may be particularly problematic in the case of a fluid-tight slide fastener of the type discussed above - inadequate coupling of the first and second stringers may prevent abutment between the sealing lips and hence reduce the efficacy of the seal.

Sliders on slide fasteners frequently have a pull cord that may be grasped by a user in order to effect movement of the slider along the chain. The pull cord allows easier movement of the slider, but also allows for forces to be applied at an angle to the axis of operation. Off-axis forces may permit movement of the slider along the chain, but may also increase the chance of engagement faults of the type discussed above.

Slide fasteners with continuous coil coupling elements are particularly susceptible to engagement faults as the coupling members have a smaller area of engagement between opposing coupling elements compared to other types of coupling member arrangements. This reduced area of engagement makes coupling members more susceptible to being rotated or translated from their natural on-axis position, also known as tilting. As such, off-axis slider movement may cause coupling elements to be tilted, which can further encourage engagement faults. In addition, when sufficient space is provided between an inner wall of the slider and the chain in order to ease operation of the slider, off-axis movement may cause coupling elements to be tilted within the slider (e.g. be rotated) which can further encourage engagement faults.

The present invention overcomes one or more of the disadvantages associated with existing sliders and slide fasteners, whether mentioned above or otherwise. The present invention also provides an alternative design of slider and slide fastener.

Summary of invention According to a first aspect of the invention there is provided a slider for a slide fastener, the slider comprising: an upper portion, a lower portion, and a guide post disposed between said upper and lower portions; the upper portion, lower portion and guide post co-operating to define a Y-shaped channel, the Y-shaped channel having a first arm separated from a second arm by the guide post and a third arm which extends along a longitudinal axis of the slider and which adjoins the first and second arms; the first and second arms being configured to carry uncoupled coupling elements of a first stringer and second stringer of the slide fastener respectively; and the third arm being configured to carry coupling elements of the first stringer and second stringer, when coupled, wherein the coupling elements of each of the first stringer and second stringer are located along the respective stringer at a pitch distance; the third arm having a third arm length, parallel to the longitudinal axis of the slider, between a tip of the guide post proximal the third arm and an end of the third arm distal to the guide post; and wherein the third arm length is at least 8 times the pitch distance.

A slider according to the present invention reduces engagement faults such as chain mis-meshing. This includes mis-meshing in high force situations such as when the slider is pulled in an off-axis direction and/or whilst the slide fastener is twisted.

A slider according to the present invention achieves this because it has an elongated main body portion in the third arm where engaged coupling elements are carried. This elongated portion enables more pairs of engaged coupling elements to be located inside the slider body at any given time. This improves alignment of coupling elements, reduces the forces acting on coupling elements in off-axis directions and hence reduces the chance of an engagement fault.

Due to the general Y-shape of the slider channel, coupling elements undergo an angular change in direction when moving from the first arm to the third arm, and from the second arm to the third arm. This, in addition to off-axis forces applied to the slider, can induce additional angular stress on the coupling elements and cause mis-meshing. The present invention is concerned with alleviating these off-axis forces during engagement of coupling elements, i.e. the forces arising in the time and/or distance shortly before and after engagement and disengagement. The third arm may allow for coupling and uncoupling of elements. That is, while the third arm is configured to carry coupling elements, when coupled, it may also carry coupling elements that are uncoupled or in the process of coupling or uncoupling.

According to the invention, the third arm length is large enough to retain a substantial number of engaged coupling elements. This helps to reduce the extent of angular change in direction when moving from the first arm to the third arm, and from the second arm to the third arm; and allows the travel of coupling elements (relative to the slider) in a direction substantially parallel to the axis of operation during and after the process of engagement. This may reduce the off-axis forces exerted on coupling elements during engagement and hence reduce the chance of engagement faults.

It has been found through extensive testing that the effect of the elongated third arm only produces a significant effect when the third arm length is at least 8 times the pitch distance.

The pitch distance may be the longitudinal distance between a first end of a first coupling element and the equivalent end of a second coupling element which forms part of the same stringer as the first coupling element and which is adjacent the first coupling element.

The third arm may be defined, at least in part, by first and second opposing side flanges which each vertically extend from the upper or lower portion of the slider. The first and second side flanges may be spaced from one another, in a direction perpendicular to the longitudinal axis of the slider, by a third arm width. Said third arm width may be configured to be greater than or equal to a width of coupling elements of the first stringer and second stringer, when coupled. The third arm may have a first portion and a second portion. The second portion may be provided between the first portion and a tip of the guide post proximal the first portion. A first portion of the first side flange and a first portion of the second side flange may be substantially parallel and define the first portion of the third arm.

The third arm length may be less than 12 times the pitch distance. The third arm length may provide a first portion length and a second portion length. The first portion length may be defined as the length of the first portion, parallel to the longitudinal axis of the slider. The second portion length may be defined, parallel to the longitudinal axis of the slider, between a tip of the guide post proximal the third arm and an end of the first portion of the third arm proximal the guide post. The first portion length may be at least 6 times the pitch distance.

According to a second aspect of the invention there is provided a slider for a slide fastener, the slider comprising: an upper portion, a lower portion, and a guide post disposed between said upper and lower portions, wherein: the upper portion, lower portion and guide post co-operate to define a Y-shaped channel, the Y-shaped channel having a first arm separated from a second arm by the guide post, and a third arm which extends along a longitudinal axis of the slider and which adjoins the first and second arms; the first and second arms are configured to carry uncoupled coupling elements of a first stringer and second stringer of the slide fastener respectively; the third arm is configured to carry coupling elements of the first stringer and second stringer, when coupled, wherein the coupling elements of each of the first stringer and second stringer are located along the respective stringer at a pitch distance; the third arm is defined, at least in part, by first and second opposing side flanges which each extend from the upper or lower portion of the slider, wherein: said first and second side flanges are spaced from one another, in a direction perpendicular to the longitudinal axis of the slider, by a third arm width; said third arm width is configured to be greater than or equal to a width of coupling elements of the first stringer and second stringer, when coupled; the third arm has a first portion and a second portion, wherein: the second portion is provided between the first portion and a tip of the guide post proximal the first portion; and, a first portion of the first side flange and a first portion of the second side flange are substantially parallel and define the first portion of the third arm; the third arm has a third arm length, defined, parallel to the longitudinal axis of the slider, between a tip of the guide post proximal the third arm and an end of the third arm distal to the guide post; the third arm length provides a first portion length and a second portion length, wherein: the first portion length is defined as the length of the first portion parallel to the longitudinal axis of the slider; the second portion length is defined, parallel to the longitudinal axis of the slider, between a tip of the guide post proximal the third arm and an end of the first portion proximal the guide post; and the first portion length is at least 6 times the pitch distance. The first portion length may be less than 10 times the pitch distance.

The first and second aspects of the invention above and the third aspect of the invention below provide alternative solutions to the same problem. More specifically, they both relate to an invention whereby the third arm is elongated as compared to a standard slider, the first, second and third aspects of the invention claiming this same feature in alternative ways.

According to a third aspect of the invention there is provided a slider for a slide fastener, the slider comprising: an upper portion, a lower portion, and a guide post disposed between said upper and lower portions; the upper portion, lower portion and guide post co-operating to define a Y-shaped channel, the Y-shaped channel having a first arm separated from a second arm by the guide post and a third arm which extends along a longitudinal axis of the slider and which adjoins the first and second arms; the first and second arms being configured to carry uncoupled coupling elements of a first stringer and second stringer of the slide fastener respectively; and the third arm being configured to carry coupling elements of the first stringer and second stringer, when coupled, wherein the coupling elements of each of the first stringer and second stringer are located along the respective stringer at a pitch distance; the third arm being defined, at least in part, by first and second opposing side flanges which each extend from the upper or lower portion of the slider, wherein: said first and second side flanges are spaced from one another, in a direction perpendicular to the longitudinal axis of the slider, by a third arm width; said third arm width is configured to be greater than or equal to a width of coupling elements of the first stringer and second stringer when coupled; the third arm having a first portion and a second portion, the second portion being provided between a tip of the guide post and the first portion, and a first portion of the first side flange and a first portion of the second side flange are substantially parallel and define the first portion of the third arm, the third arm having a third arm length, parallel to the longitudinal axis of the slider, the third arm providing a first portion length and a second portion length, the first portion length being defined as the length of the first portion, parallel to the longitudinal axis of the slider, and the second portion length being defined, parallel to the longitudinal axis of the slider, between a tip of the guide post proximal the third arm and an end of the first portion proximal to the guide post, wherein the first portion length is greater than or equal to 2 times the second portion length. The first portion length may be less than 3.5 times the second portion length.

According to a fourth aspect of the invention there is provided a slide fastener comprising a slider according to either the first, second or third aspect of the invention. The slider may be mounted to a first stringer and a second stringer, the first stringer comprising coupling elements which are couplable with coupling elements of the second stringer, and the second stringer comprising coupling elements which are couplable with coupling elements of the first stringer. The coupling elements of each of the first stringer and second stringer may be located along a longitudinal axis of the respective stringer at a pitch distance. The first and second arms may carry uncoupled coupling elements of the first stringer and the second stringer of the slide fastener respectively. The third arm may carry coupling elements of the first stringer and second stringer, when coupled.

A first coil may comprise the coupling elements of the first stringer and a second coil may comprise the coupling elements of the second stringer. It has been found that problems associated with mis-mesh are more prevalent in relation to slide fasteners which include coupling elements of this type. This is because, where the coupling elements form part of the coil, each coupling element of a particular stringer is interlinked to the other coupling elements of that stringer by the coil itself. As such, any axial displacement of one coupling element of the coil has the potential to affect the other coupling elements of the coil. It follows that the present invention is particularly advantageous in relation to slide fasteners including coil-type coupling elements.

The first and second stringers may comprise a woven or knitted material. The coupling elements of the first stringer may be woven or knitted into the woven or knitted material of the first stringer. The coupling elements of the second stringer may be woven or knitted into the woven or knitted material of the second stringer. That is, the coil is combined with the tape as part of the weaving or knitting process rather than attached separately by, for example, sewing. Although there are some benefits of using stringers in which the coupling elements are woven or knitted into (as compared to sewn to) the tape of the stringer, it has been found that problems associated with mis-mesh are more prevalent in relation to slide fasteners which include stringers of this type. It follows that the present invention is particularly advantageous in relation to slide fasteners of the woven-in or knitted-in type. The slide fastener may be a fluid-tight slide fastener. In some fluid-tight slide fasteners, in order to give the slide fastener its fluid-tight properties, the tapes of the slide fastener are impregnated with or have an upper surface prepared to receive a fluid-tight material (e.g. a polymeric material). To help with this process an axial force may be applied to the tapes during manufacturing whilst the polymeric material is pressurised and applied to one side of each tape. The stretching of the tapes by application of such an axial force may affect the spacing (or pitch) of the coupling elements. This may in turn make it more likely that mis-mesh occurs within the produced slide fastener. It follows that the present invention may be of particular benefit to these types of slide fastener.

Each of the first and second stringers may comprise respective sealing lips. Said sealing lips may comprise a fluid-tight material and contact one another when coupling elements of the first and second stringers are coupled. The sealing lips increase the overall thickness of the chain. In order to minimise the effect of this, it may be beneficial for the coupling elements to be woven or knitted into the tapes (as opposed to sewn onto the tapes).

The first and second arms may carry the sealing lip of the first stringer and second stringer respectively. The third arm may carry the sealing lips of the first stringer and second stringer. It follows from the above that the third arm of the slider may carry not only the engaged coupling elements of both the first and second stringers, but also both sealing lips (i.e. the one of the first stringer and the one of the second stringer). Due to the ‘crowding’ of the third arm in this way and/or the material from which the sealing lip / fluid-tight coating of the stringers is formed of, significant friction may be experienced between the slider and the stringers in the third arm of the slider. Some aspects of the present invention discussed in the subsequent paragraph may be particularly advantageous in relation to this type of slide fastener.

The third arm may be sized such that a first cavity is formed between a portion of the upper portion defining the third arm and the sealing lip of the first stringer, and a second cavity is formed between said portion of the upper portion defining the third arm and the sealing lip of the second stringer. The cavities may also be defined, in part, by a portion of one or more of the side walls. The presence of the cavities minimises the amount of contact between the stringers and the slider in the third arm of the slider. This in turn minimises the amount of friction between the slider and stringers in the third arm of the slider, thereby reducing the force required to move the slider relative to the stringers.

According to a fifth aspect of the invention there is provided an article comprising a slide fastener according to the fourth aspect of the invention.

It will be appreciated that any of the above-discussed aspects of the invention may, where appropriate, be combined with one or more other aspects of the invention. Furthermore, an optional feature described in relation to one of the aspects of the invention may, where appropriate be an optional feature of one of the other aspects of the invention.

The invention will now by described by way of example, with reference to the accompanying figures in which:

Figure 1 shows a portion of a slide fastener, including a slider, according to an embodiment of the present invention.

Figure 2 shows a schematic cross-section of a slider according to an embodiment of the present invention;

Figure 3A shows a side view of a slider according to an embodiment of the present invention;

Figure 3B shows a cross-sectional view of a slider according to an embodiment of the present invention taken along the longitudinal axis A;

Figures 4A and 4B show a cross-sectional view of a slider according to an embodiment of the present invention viewed in direction E; in Figure 4a the slider is shown in isolation, whereas in Figure 4B the slider is shown mounted to stringers of a slide fastener.

Figure 1 shows a portion of a slide fastener 10 according to an embodiment of the present invention. The slide fastener comprises a slider 11 and a pair of stringers 12a, 12b. Each stringer comprises a coupling portion in the form of coupling elements 14a, 14b which are attached an edge of a tape (not shown - although, shown in relation to the invention in Figure 4B by reference numerals 13a and 13b) of each stringer. The tape may be woven or knitted and may be formed from, for example, synthetic fibres such as polyester, vinylon or polyurethane and/or natural fibres such as cotton. The coupling elements 14a, 14b may be formed as a continuous coil with coil elements forming the coupling elements. In this case the coupling elements are most commonly woven or knitted into the tape, but alternatively can be stitched to a surface of the tape at the edge of the tape.

The two stringers 12a, 12b are brought together, such that the coupling elements 14a, 14b of each stringer 12a, 12b can attach to one another, by interdigitating, to form a chain 18. The chain 18 is generally planar, and the chain 18 (and the engaged coupling portions 14a, 14b which form part of the chain 18) extends along a longitudinal axis A of the chain 18. This axis is also known as the axis of operation.

The slider 11 is attached to the chain 18 such that it can move along the chain 18 between the two stringers 12a, 12b. Movement of the slider 11 along the chain 18 in a first sliding direction E causes the coupling elements 14a of the first stringer 12a to attach to the coupling elements 14b of the second stringer 12b. Movement of the slider along the chain in a second sliding direction D, opposite to the first sliding direction E, causes the coupling elements 14a of the first stringer 12a to detach from the coupling elements 14b of the second stringer 12b. Attached coupling elements are also known as coupled coupling elements, engaged coupling elements or paired coupling elements. The process of attaching coupling elements is also known as coupling, engaging or pairing.

The slider may further include a bridge portion 19 through which a pull tab (not shown) may be attached. This pull tab may be grasped by a user in order to effect movement of the slider 11 along the chain 18.

Referring now to Figure 2, which shows a slider in accordance with an embodiment of the present invention, the slider 11 comprises an upper portion (sometimes referred to as an upper blade or upper plate) connected to a lower portion 21 (sometimes referred to as a lower blade or lower plate) by a guide post 23 (sometimes referred to as a diamond or connection post) extending between the upper portion and the lower portion 21 . Figure 2 shows a cross-section taken between the upper and lower portions, so the upper portion is not shown here. The upper portion 20 and lower portion 21 may be best seen in Figure 3A.

The slider has a head end 38 and a tail end 40. The head end 38 is taken to be the end of the slider such that movement of the slider relative to the stringers in the direction of the head end 38 (i.e. movement in the sliding direction E) leads to coupling of coupling elements. The tail end 40 is taken to be distal to the head end 38, and to be the end of the slider such that movement of the slider relative to the stringers in the direction of the tail end 40 (i.e. movement in the direction D) leads to uncoupling of coupling elements.

The slider 11 also comprises upper side walls (or flanges) and lower side walls (or flanges). The lower side walls 25a, 25b may be seen in Figure 2. The upper and lower side walls 24a, 25a on a first side SL of the slider 11 may be best seen in Figure 3A. The upper and lower side walls 24b, 25b on a second side SR of the slider 11 may be best seen in Figure 3B. The upper and lower side walls 24a, 24b, 25a, 25b may also be seen in Figure 4.

The upper side walls 24a, 24b extend from the edges of the upper portion 20 in a direction towards the lower portion 21. The lower side walls 25a, 25b extend from the edges of the lower portion 21 in a direction towards the upper portion 20. The side walls 24a, 24b, 25a, 25b extend generally between the head end 38 of the slider 11 to the tail end 40 of the slider 11 . The side walls extend from the first side SL of the slider 11 and the second side SR of the slider 11 , where the second side is opposed to the first side. By ‘opposed to’, it may be said that the first and second sides SL, SR are symmetrically located on opposite sides of the axis A in the plane of the slider. These sides may be referred to as the left side SL and right side SR respectively, and hence the left side walls 24a, 25a and right side walls 24b, 25b. It will be appreciated that the terms left and right are used for ease of reference and relate to the orientation of the slider as shown in the figures. This language is of course not limiting should the slider be orientated in a different manner to that shown in the figures.

Unlike the side walls 24a, 24b, 25a, 25b shown in relation to the present embodiment, the side walls need not be continuous from the head end 38 to the tail end 40 but may instead be formed from a plurality of discontinuous portions. Furthermore, the slider may have only upper side walls, only lower side walls, or both upper and lower side walls (as described in relation to the present embodiment which relates to a slide fastener with coil elements). The construction of the slider may be modified for the each type of fastener element. For instance, when the coupling elements are attached in contact with both the upper surface and the lower surface of the tape, (in which the lower surface is opposite the upper surface of the tape when the tape is flat), the slider may be provided with both upper and lower side walls. In another example, when the coupling elements are a continuous coil, they may be attached to only one side of the tape, and the slider may be provided with only a pair or upper side walls or a pair of lower side walls.

The upper portion 20, lower portion 21 , guide post 23 and side walls 24a, 24b, 25a, 25b co-operate to define a Y-shaped channel 36. The Y-shaped channel 36 has a first arm 36a separated from a second arm 36b by the guide post 23. The first arm 36a is defined between the left side walls 24a, 25a and the guide post 23. The second arm 36b is defined between the guide post 23 and the right side walls 24b, 25b. The Y-shaped channel 36 also includes a third arm 36c which extends along the longitudinal axis A of the slider towards the tail end 40 and adjoins the first and second arms 36a, 36b.

A space is provided between the upper and lower right sidewalls 24b, 25b (and a respective space is provided between the upper and lower left sidewalls 24a, 25a). The spaces allow the stringer to pass between the walls such that a part of each respective stringer 12a, 12b (and hence the attached coupling elements 14a, 14b on the edges of the stringers 12a, 12b) may be within the slider 11 .

The third arm 36c has a first portion 16 where the left side walls 24a, 25a and right side walls 24b, 25b are generally parallel to one another and to the longitudinal axis A of the slider 11 and/or slide fastener 10. The first portion 16 of the third arm 36c is generally disposed towards the tail end 40 of the slider 11. A width W c of coupled coupling elements 14a, 14b is defined as the extent of the combined coupling elements 14a, 14b when coupled, in a direction transverse to the longitudinal axis A. The first portion 16 of the third arm 36c is such that an inner face of the left side walls 24a, 25a and an inner face of the right side walls 24b, 25b are spaced by a width W’ slightly greater than or equal to the width W c of coupled coupling elements 14a, 14b. This may result in a ‘third gap’, equal to the difference between the width W c of coupled coupling elements and the width W’ of the third arm 36c. The third gap may also be referred to as a relief or horizontal relief. Movement of the slider 11 in a direction E encourages coupling elements 14a of the first stringer 12a to travel from the first arm 36a to the third arm 36c, and coupling elements 14b of the second stringer 12b to travel from the second arm 36b to the third arm 36c. In light of the first portion 16 of the third arm 36c having a width W’ slightly greater than or equal to the width W c of coupled coupling elements 14a, 14b, as the coupling elements 14a, 14b pass into the first portion 16 of the third arm 36c, the side walls 24a, 24b, 25a, 25b urge the coupling elements 14a, 14b to couple.

Movement of the slider 11 in the direction D encourages coupling elements 14a of the first stringer 12a to travel from the third arm 36c to the first arm 36a, and coupling elements 14b of the second stringer 12b to travel from the third arm 36c to the second arm 36b. In this way, the guide post 23 acts to separate or de-couple the coupling elements 14a, 14b.

The third arm 36c has a second portion 17 where the left side walls 24a, 25a and right side walls 24b, 25b diverge from each other (in the direction from the tail end 40 to head end 38). The second portion 17 of the third arm 36c is generally disposed further towards the head end 38 of the slider 11 compared to the first portion 16 of the third arm 36c.

The third arm 36c has a third arm length 27. The third arm length 27 is defined, along the longitudinal axis A of the slider, between a tip 22 of the guide post 23 proximal the third arm 36c and an end of the third arm 36c distal to the guide post 23. In some instances, the side walls 24a, 24b, 25a, 25b, upper portion 20 and lower portion 21 may be of comparable (i.e. substantially the same) longitudinal (i.e. along axis A) extent at the tail end 40 of the slider. In this instance, the third arm length 27 may be defined between the tip 22 of the guide post 23 closest to the tail end 40 (or furthest from the head end 38) and the tail end 40 (e.g. the edge or limit of the tail end which is located the greatest axial distance from said tip 22 of the guide post 23).

Alternatively, although not shown in the figures, at the tail end of the slider, the lower portion 21 (including side walls 25a, 25b) may extend in a longitudinal direction for a greater or lesser distance than the upper portion 20 (including side walls 24a, 24b). Alternatively or additionally, at the tail end of the slider, the upper portion 20 or lower portion 21 may extend longitudinally for a different distance than their corresponding side walls (24a, 24b, 25a, 25b). In these cases, the third arm length 27 may be defined from the tip 22 of the guide post 23 proximal to the third arm 36c, to the end of the shortest of either the side walls 24a, 24b, 25a, 25b or the upper or lower portion 20, 21 , wherein said end is located towards the tail end 40 of the slider 11. For example, if the lower portion 21 extends for a greater distance towards the tail end 40 than the lower side walls 25a, 25b, the third arm length 27 is measured from the tip 22 of the guide post 23 proximal to the third arm 36c, to the end of the lower side walls 25a, 25b proximal to the tail end 40 of the slider 11 rather than to the end of the lower portion 21 proximal to the tail end 40 of the slider 11 .

As mentioned previously, in another example (e.g. when the coupling elements are a continuous coil attached to only one side of the tape), and the slider may be provided with only a pair or upper side walls or a pair of lower side walls. In this instance, the third arm length may be defined (along axis A) from the tip 22 of the guide post 23 proximal to the third arm 36c, to the end of either the lower side walls 25a, 25b and lower portion 21 or to the end of the upper side walls 24a, 24b and upper portion 20. In some instances, whether the third arm length is defined relative to the lower side walls/portion or the upper side walls/portion may depend on whether the coupling elements are mainly contained in the lower or upper portion of the slider, respectively.

That is, in all cases, the third arm length 27 may be defined from the tip 22 of the guide post 23 proximal to the third arm 36c, to the tail-most point at which the coupling elements are substantially surrounded on at least three sides (e.g. by two side walls and an upper or lower portion).

Comparing the third arm length 27 of a known slider with the third arm length 27 of the slider according to the present invention, the third arm length 27 is substantially longer in the present invention compared to the prior art. This elongated portion aids alignment of coupling elements following engagement, reduces off-axis forces on engaged coupling elements at the second portion 17 of the third arm 36c, and reduces the chance of engagement faults on coupling. The applicant has realised that, by housing a greater number of coupling elements 14a, 14b in the third arm 36c of the slider, these elements are kept parallel to the axis of operation A for a greater distance and/or time (during sliding of the slider), which helps to reduce the chance of mis-meshing and other engagement faults.

In addition or alternatively, the third arm length 27 may be defined in terms of the pitch distance of the coupling elements. As shown in Figure 2, the coupling elements of each of the first stringer and second stringer are located along the respective stringer at a pitch distance P. The pitch distance P is the longitudinal distance (i.e. in a direction parallel to the longitudinal axis A) between a first edge of a first coupling element and the equivalent edge of a second coupling element adjacent the first coupling element and attached to the same tape to which the first coupling element is attached. In the embodiment shown in Figure 2 the third arm 36c has a third arm length 27, parallel to the longitudinal axis A of the slider 11 , which is about 10 times the pitch distance P.

The applicant has found that the chance of mis-meshing is reduced when the third arm length 27 is at least 8 times the pitch distance P.

Furthermore, it is preferable that third arm length 27 is at least 9 times the pitch distance P. Preferably the third arm length 27 is less than 12 times the pitch distance P. A third arm length 27 greater than 12 times the pitch distance may cause the weight of the slider and/or material cost and/or sliding friction (caused by the movement of the slider) to increase. An increase in the weight of the slider and/or material cost and/or sliding friction may begin to outweigh the benefits of the invention.

In addition or alternatively, the third arm length 27 may be defined in terms of a first portion length 27a and a second portion length 27b, corresponding to the lengths of the first portion 16 and second portion 17 of the third arm 36c as described above.

The first portion 16 of the third arm 36c extends for a first portion length 27a, substantially equal to the distance for which the side walls 24a, 24b, 25a, 25b proximal to the tail end 40 are generally parallel to each other. In the case of the embodiment shown in Figure 2, the first portion length 27a is defined as 8 times the pitch distance P.

The applicant has found that the chance of mis-meshing is reduced when the first portion length 27a is at least 6 times the pitch distance P. Furthermore, it is preferable the first portion length 27a is at least 7 times the pitch distance P. Preferably the third arm length 27 is less than 10 times the pitch distance P. A third arm length 27 greater than 10 times the pitch distance may cause the weight of the slider and/or material cost and/or sliding friction (caused by the movement of the slider) to increase. An increase in the weight of the slider and/or material cost and/or sliding friction may begin to outweigh the benefits of the invention.

The second portion 17 of the third arm 36c has a second portion length 27b, defined between a tip 22 of the guide post 23 proximal the third arm 36c and an end of the first portion 16 of the third arm 36c proximal the guide post 23.

That is to say, a boundary line between the first portion 16 (with respective first length 27a) and the second portion 17 (with respective second length 27b) is the point at which the respective inner side walls 24a, 24b, 25a, 25b start to diverge from a path parallel to each other. That is to say, the first length 27a comprises a region wherein the width W’ between an inner face of the left walls 24a, 25a (also referred to as the left inner walls) and an inner face of the right walls 24b, 25b (also referred to as the right inner walls) does not change and the second length 27b comprises a region wherein the width W’ between the left inner walls 24a, 25a and the right inner walls 24b, 25b does change.

The length of the second portion of the third arm 36c, as shown in the present embodiment, is approximately equal to 2 pairs of coupling elements, that is substantially 2 times the pitch distance P. This length may comprise both engaged pairs and disengaged pairs of coupling elements.

It is preferable but not a requirement that the second portion length is between 2 to 3 times the pitch distance P in order to reduce the chance of mis-meshing.

In accordance with the invention, the first portion length 27a is greater than or equal to the second portion length 27b. In the particular embodiment shown, the first portion length 27a is approximately 2.5 times the second portion length 27b. This may also be known as the portion-portion ratio. The applicant has found that the chance of mis- meshing is reduced when the first portion length 27a is greater than or equal to 2 times the second portion length 27b, i.e. when the portion-portion ratio is greater than or equal to 2. Alternatively a portion-portion ratio greater than or equal to 2.5 may be used. It is preferable that the first portion length 27a is shorter than 3.5 times the second portion length 27b. A portion-portion ratio greater than 3.5 may increase the weight of the slider and/or the material cost and/or sliding friction (caused by the movement of the slider) to increase. An increase in the weight of the slider and/or material cost and/or sliding friction may begin to outweigh the benefits of the invention.

As mentioned previously, the Y-shaped channel 36 has the first arm 36a separated from the second arm 36b by the guide post 23. The first and second arms 36a, 36b are generally parallel to each other and to the longitudinal axis A, although there is a portion where the arms converge proximal to the tip 22 of the guide post 23. Correspondingly, the left side walls 24a, 25a and right side walls 24b, 25b (which, in part, define the first and second arms 36a, 36b) are generally parallel to one another and to the longitudinal axis A for a length, although there is another length proximal to the tip 22 of the guide post 23 where the walls 24a, 24b, 25a, 25b converge. The length over which the arms and walls converge may vary. For example, Figure 2 depicts the walls 24a, 24b, 25a, 25b converging for a distance approximately equal to 30% of the length of the guide post 23. Flowever, they may converge for a different length, for example they may converge until a point half-way along the guide post 23, or they may converge for a negligible distance, or any other distance. After this converging portion, the side walls 24a, 25a, 24b, 25b, and correspondingly the first and second arm 36a, 36b, are generally parallel to each other extending towards the head 38 of the slider 11 . The side walls 24a, 24b, 25a, 25b may extend fully to the head 38 of the slider 11 , or they may extend to a point proximal to the head end 38. In Figure 2, the side walls 24a, 24b, 25a, 25b are depicted as extending to a point proximal to the head end 38 (i.e. they do not extend fully to a distal end of the slider 11).

The first arm 36a has a first arm length 29. The second arm 36b has a second arm length which is equivalent to the first arm length 29. The first arm length 29 is defined along the longitudinal axis A of the slider between the tip 22 of the guide post 23 proximal the third arm 36c and the end of the side walls 24a, 24b, 25a, 25b proximal the head end 38 of the slider.

The first portion length 27a may be longer than the first arm length 29 or they may be substantially equal. It is preferable that the first arm length 29 is at least 6 times the pitch distance P. The first arm length 29 may preferentially be 7 times the pitch distance P. It is preferable that the second arm length 29 is less than 10 times the pitch distance P.

The first arm length 29 is greater than or equal to the second portion length 27b. In Figure 2, the first arm length 29 is approximately 2.5 times the second portion length 27b. This may also be known as the arm-portion ratio. The applicant has found that the chance of mis-meshing is reduced when the first arm length 29 is greater than or equal to 2 times the second portion length 27b, i.e. when the arm-portion ratio is greater than or equal to 2.

It is preferable that the first arm length 29 is less than 3.5 times the second portion length 27b.

In addition, the left side walls 24a, 25a are arranged such that their inner faces are spaced from the guide post 23 by a first arm width W”. Correspondingly, the right side walls 24b, 25b are spaced from the guide post 23 such that their inner faces are spaced from the guide post 23 by a second arm width equal to the first arm width W”. The first arm width W” is greater than or equal to a width W u of an un-coupled coupling element 14a, 14b.

By providing a first arm width W” that is greater than the width W uc of an un-coupled coupling element 14a, 14b, a first gap is provided between a coupling element 14a and a left side wall 24a, 25a and a second gap is provided between a coupling element 14b and a right side wall 24b, 25b. The first and second gaps are equal to the difference between the first arm width W” and the width W uc of an un-coupled coupling element 14a, 14b. The first and second gaps may be referred to as a relief or horizontal relief, but are different in magnitude to the third gap as described above.

As previously mentioned, a third gap may be provided in the third arm 36c. In order to aid the travelling of coupling elements 14a, 14b through the slider 11 , the first arm width W” is configured such that the sum of the first and second gaps is greater than the third gap. The presence of first and second gaps in the first and second arms 36a, 36b minimises the amount of contact between the stringers 12a, 12b and the slider 11 in the first and second arms 36a, 36b of the slider. This in turn minimises the amount of friction between the slider 11 and stringers 12a, 12b in the first and second arms 36a, 36b of the slider, thereby reducing the force required to move the slider 11 relative to the stringers 12a, 12b.

As seen in figure 3A, the upper portion 20 and lower portion 21 (including side walls 24a, 24b, 25a, 25b), may be of comparable (i.e. substantially the same) longitudinal (i.e. along axis A) extent at the tail end of the slider. Alternatively, although not shown in the figures, at the tail end of the slider, the lower portion 21 (including side walls 25a, 25b) may extend in a longitudinal direction for a greater distance than the upper portion 20 (including side walls 24a, 24b). Alternatively or additionally, at the tail end of the slider, the upper portion 20 or lower portion 21 may extend longitudinally for a different distance than their corresponding side walls (24a, 24b, 25a, 25b).

As previously discussed, the present invention may be particularly advantageous when applied to a fluid-tight slide fastener. Such a slide fastener is shown in Figures 3A, 3B, 4A and 4B (where Figure 4A and 4B depict cross-sections of Figure 3A and 3B in the direction X). A fluid-tight slide fastener has first and second stringers 12a, 12b comprising respective sealing lips 15a, 15b. Said sealing lips 15a, 15b comprise a fluid-tight material and contact one another to form a seal when coupling elements 14a, 14b of the first and second stringers 12a, 12b are coupled (as shown in the figures).

The slider 11 further comprises a guide plate 28 which separates water-tight sealing members (or sealing lips) 15a, 15b during the decoupling process. The guide plate 28 substantially surrounds the guide post 23. In addition the guide plate 28 is located generally towards the upper portion 21 of the slider, which corresponds with the location of the sealing lips 15a, 15b on an upper side of each of the stringers 12a, 12b. The guide plate is generally wedge shaped, with an edge or blade traversing the portion distal to the guide post, a tip or apex of which is located on the axis A.

In use, when the slider is moved in the second sliding direction D, the apex of the guide plate 28 moves between the sealing lips 15a, 15b and, together with the rest of the guide plate 28, separates the sealing lips 15a, 15b whilst the guide post 23 separates the coupling elements of the stringers as already discussed. The sealing lips 15a, 15b pass over the upper side of the guide plate 28 in the Y-shaped channel 36. That is, the sealing lips 15a, 15b travel through a channel generally defined by the upper portion 20 and the upper side walls 24a, 24b. The coupling elements 14a, 14b pass below the lower side of the guide plate 28 in the Y-shaped channel 36. That is, the coupling elements 14a, 14b travel through a channel generally defined by the lower portion 21 and the lower side walls 25a, 25b. The guide plate 28 acts to separate the sealing lips 15a, 15b and the coupling elements 14a, 14b during uncoupling, in order to aid uncoupling of the coupling elements 14a, 14b and separation of the sealing lips 15a, 15b.

When the slider is moved in the first sliding direction E, the upper side walls 24a, 24b of the third arm 36c of the slider assist in urging the sealing lips 15a, 15b into contact with one another. The sealing lips 15a, 15b are held in contact with one another at a given position by the coupling of the coupling elements beneath the sealing lips 15a, 15b at said given position.

In such a type of fluid-tight slide fastener the first and second arms 36a, 36b carry the sealing lip 15a, 15b of the first stringer 12a and second stringer 12b respectively; and the third arm 36c carries the sealing lips of the first stringer and second stringer 12a, 12b.

In a fluid type fastener of the type described herein, wherein the coupling elements 14a, 14b travel through a channel generally defined by the lower portion 21 and the lower side walls 25a, 25b, the length of the upper portion 20 and upper side walls 24a, 24b may be less important to the reduction of mis-meshing. In this instance, the third arm length 27 is measured from the tip 22 of the guide post 23 proximal to the third arm 36c, to the end of the shortest of either the lower side walls 25a, 25b or the lower portion 21 (if the lower portion 21 extends for a shorter distance than the lower side walls 25a, 25b), wherein said end is located towards the tail end 40 of the slider 11 ,

According to an embodiment of the present invention, as shown in Figure 4B, the sealing lips 15a, 15b have a bulbous cross-sectional shape. That is, the sealing lips 15a, 15b are disposed on the upper surface of each tape 12a 12b, and generally gradually increase in thickness toward the edge of the tape 15a, 15b (and may then taper back inwards), and extend beyond the edge of the tapes 15a, 15b to form a bulbous sealing lip. The sealing lips 15a, 15b comprise a waterproof material and, as such, act like a beading. When the sealing lips 15a, 15b are in abutment (e.g. when the coupling elements 14a, 14b are engaged), the sealing lips 15a, 15b form a continuous curved surface over the upper surface of the tapes 12a, 12b. Said continuous curved surface is a waterproof surface covering the coupling elements and at least a portion of the tapes 12a, 12b.

According to an embodiment of the present invention, as shown in figure 4B, the third arm 36c is sized such that a first cavity 42 is formed between a portion of the upper portion 20 defining the third arm 36c and the sealing lip 15a of the first stringer 12a, and a second cavity 44 is formed between said portion of the upper portion 20 defining the third arm 36c and the sealing lip 15b of the second stringer 12b. The first cavity 42 is created by the abutment of the curved upper surface of the sealing lip 15a with each of a respective inner side wall 24a and the lower surface of the upper portion 20 of the slider 11 . Correspondingly, the second cavity 44 is created by the abutment of the curved upper surface of the sealing lip 15b with each of a respective inner side wall 24b and the lower surface of the upper portion 20 of the slider 11 .

The presence of the cavities 42, 44 minimises the amount of contact between the stringers 12a, 12b and the slider 11 in the third arm 36c of the slider. This in turn minimises the amount of friction between the slider 11 and stringers 12a, 12b in the third arm 36c of the slider, thereby reducing the force required to move the slider relative to the stringers 12a, 12b. This may result in an improved user experience and/or in a reduction in the likelihood that an excessive force may be applied to the slider, which, as discussed above, may result in mis-meshing.

Within the present description reference is made to coupling elements being able to ‘travel’ within the slider from one portion of the slider to another. It will be appreciated that when such ‘travel’ happens it results from the slider being moved relative to (or along) the stringers of the slide fastener. As the slider is moved along the stringers, from the frame of reference of the slider being stationary and the stringers (and hence coupling elements) moving relative to the slider, it may be said that the coupling elements ‘travel’ within the slider.

Within the present description reference is made to a first value being greater than or equal to another value. This statement is intended to be construed in that the first value may be larger than the second value or the first value may be equal to the second value. That is, the term ‘greater than or equal to’ it is intended to mean ‘at least’. The described and illustrated embodiments are to be considered as illustrative and not restrictive in character, it being understood that only preferred embodiments have been shown and described and that all changes and modifications that fall within the scope of the inventions as defined in the claims are desired to be protected.

Optional and/or preferred features as set out herein may be used either individually or in combination with each other where appropriate and particularly in the combinations as set out in the accompanying claims. The optional and/or preferred features for each aspect of the invention set out herein are also applicable to any other aspects of the invention, where appropriate.