WATERCRAFT LEASH CONSTRUCTION

Abstract

A watercraft leash assembly has a leash cord construction comprising an elongate, elastomeric cord body having a reinforcing element embedded therein. The reinforcing element may comprise a co-extruded filament which is helical or other non-linear shape when the leash cord is in a non-extended condition, and which straightens as the leash cord extends.

Claims

1. A watercraft leash comprising: a first end having a first end connector portion for securing to a watercraft, a second end having a second end connector portion for securing to a watercraft user, a leash cord extending generally from the first end to the second end of the leash, the leash cord comprising an elongate, elastomeric cord body having a non-linear filament embedded therein, the filament being non-linear when the leash cord is in a non-extended condition, and straightening as the leash cord extends.

2. A watercraft leash according to claim 1 wherein the non-linear filament acts as a reinforcing element for the leash cord.

3. A watercraft leash according to claim 1 wherein the non-linear filament straightens with extension of the cord body under tensile force.

4. A watercraft leash according to claim 1 wherein the leash cord has a first stress-strain characteristic during initial stretching from the non-extended condition when the non-linear filament is substantially non-linear, and a second stress-strain characteristic when the leash cord is in an extended condition whereby the non-linear filament approaches the linear.

5. A watercraft leash according to claim 4 wherein the first stress-strain characteristic is predominantly determined by the stress-strain properties of the cord body up to approximately breaking point of the cord body.

6. A watercraft leash according to claim 1 wherein the non-linear filament when the leash cord is in its non-extended condition has a regular repeating shape.

7. A watercraft leash according to claim 6 wherein the regular repeating shape is selected from one of helical, sinuous, and zig-zag.

8. A watercraft leash according to claim 7 wherein the regular repeating shape is helical.

9. A watercraft leash according to claim 8 wherein the helical shape has a helix diameter greater than 50% of an outer diameter of the cord body

10. A watercraft leash according to claim 7, wherein the regular repeating shape has a pitch selected from the range from one of 6 to 30 mm, 6-20 mm, 8-16 mm, 10-14 mm, 11-13 mm, or about 10, 11, 12, 13, or 14 mm.

11. A watercraft leash according to claim 10 wherein the pitch is from 11 to 13 mm.

12. A watercraft leash according to claim 1 wherein the cord body has an outer diameter selected from one of 4-11 mm, or 5-10 mm, or about 5, 5.5, 6, 7, 8, 9 or 10 mm diameter.

13. A watercraft leash according to claim 1 wherein the non-linear filament is a single strand helical filament, which is co-extruded with the elastomeric cord body.

14. A watercraft leash according to claim 13 wherein the single strand helical filament has a filament diameter of 1 to 2 mm.

15. A watercraft leash according to claim 1 wherein the material of the reinforcing element has a higher elastic modulus than the cord body material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The description is made with reference to the accompanying drawings, of which:

[0035] FIG. 1 is a schematic isometric view of a surf leash assembly with a leash cord including a non-linear reinforcing element, according to an example embodiment.

[0036] FIG. 2 is a side view of the leash assembly of FIG. 1.

[0037] FIG. 3 is a side view detail of an end portion of the leash cord and its end piece, showing the reinforcing element embedded in the leash cord in greater detail.

[0038] FIG. 4 is a schematic of an example force-elongation (stress-strain) graph of an example stress-strain profile of a leash cord assembly according to an embodiment of the invention, compared to a typical prior art TPU leash cord.

DETAILED DESCRIPTION

[0039] An example surfboard or other watercraft leash assembly is described with reference to FIGS. 1 to 3.

[0040] FIG. 1 is a schematic isometric view of a surf or other watercraft leash assembly 110 with an ankle cuff assembly 112 with hook and loop fabric/textile fastening for securing about a limb of the surfer or other watercraft user.

[0041] The ankle cuff assembly 112 may have a slip-reducing print or pattern (not shown) on the inside surface 114 of the cuff facing the limb of the watercraft user in use. The cuff 112 may also feature a hydrodynamically shaped pull tab 116 to facilitate fastening and unfastening of the cuff by the user. The pull tab 116 may be used by the watercraft user to undo the cuff by pulling upon the pull tab with a finger inserted into the pull tab aperture 118 or by grasping the erect loop with two fingers.

[0042] The ankle cuff assembly 112 has attached to it or includes an outwardly projecting moulded horn 120 extending from a base 122, which is suitably attached to the cuff 116, for example by stitching, adhesives and/or moulding. The base 122 extends circumferentially about the cuff and limb of the watercraft user.

[0043] A swivel assembly is inset into the end of the horn and projecting therefrom to form a swivel connection for an enlarged end piece 124 of the leash cord 126.

[0044] The swivel assembly is obscured in FIGS. 1 and 2, however the swivel assembly and construction and configuration of the cuff may be similar to that described and shown in FIG. 8 of WO2017181225.

[0045] The contents of WO2017181225 are incorporated herein by reference.

[0046] The base 122 and horn 120 of the cuff, and the end piece 124 of the cord 126 may be constructed of a suitable elastomer/plastics material, for example of TPU, which may be of similar material properties to the cord body material. The swivel assembly may typically be metal, for example a stainless steel with sufficient corrosion resistance to withstand the harsh conditions to which the leash may typically be exposed in use.

[0047] The enlarged diameter end piece 124 is attached for example by overmoulding or adhesive to the end of the cord 126, and may include cut out portions 128 to facilitate stretching of the end portion with the section of the cord within the end portion in use, to help prevent breakage. The end piece may also be formed of TPU, for example of similar properties to the cord body

[0048] The end piece includes a hole 130 receiving a grub screw 132 or similar projecting into the centre cavity of the end piece to engage within a groove in the portion of the swivel which projects from the end of the horn, to provide the swivel connection, this reducing tangling of the leash in use.

[0049] At the other end of the leash cord, a further similar end piece 124b connects to a further swivel assembly 134 connected to a webbing strap, rail saver or securing strap 136 which includes a rope loop 138 for threading through and connecting to a surfboard leash plug. In this way, the leash is attached to the surfboard or other watercraft (not shown) at one end, and to the user at the other end.

[0050] The rail saver arrangement and the connection between the cord and the rail saver may be generally similar to that described in WO2017181225.

[0051] The construction of the cord 126 is shown in FIGS. 1 to 3, but seen in more detail in FIG. 3.

[0052] The cord 126 construction comprises a generally cylindrical, elongate, elastomeric cord body matrix 140 forming the matrix of the cord, with a sinuous reinforcing filament 142 extending throughout the length of the cord. In the illustrated embodiment, the reinforcing filament is helical.

[0053] The cord body may be formed of extruded elastomer, for example a thermoplastic polyurethane (TPU), Thermoplastic Elastomers (TPEs) such as Thermoplastic Polyester Elastomers (TPC-ETs), or artificial rubber such as Nitrile Rubber and Natural Rubber with similar properties could conceivably be used (but not preferable). However, TPU is preferred.

[0054] Where TPU is used for the extruded cord body matrix and for other moulded portions of the leash, the TPU may contain a percentage of TPU derived from natural/renewable sources such as corn starch and/or castor oil.

[0055] A TPU material containing up to about 47% natural material raw material, a tensile strength of about 46 MPa, and density of about 1.2 g/cm.sup.3 has been found in initial prototyping to be an appropriate material for the cord body matrix material.

[0056] The reinforcing filament 142 formed within and running along the length the cord body may also be formed from TPU, and preferably has a higher elastic modulus and break strength than the TPU of the cord body.

[0057] For example, the reinforcing filament may have an elastic modulus and/or break strength approximately 10 to 20% higher than that of the cord body.

[0058] In an example embodiment, the filament diameter may be about 1-2 mm, for example about 1.3 mm.

[0059] The reinforcing filament may be formed within the cord body by co-extrusion, so that the cord body and reinforcing filament form a composite, with the cord body forming a continuous matrix about filament.

[0060] The co-extrusion of the helical TPU reinforcing element within the cylindrical TPU cord body may be formed by means of a spinning machine which houses a rotary internal die for the reinforcing filament which sits within the outer, circular profile extrusion die for the cylindrical cord body matrix. Rotation of the spinning machine as the leash cord is being extruded results in co-extrusion of a helical strand of TPU within the generally cylindrical cord body matrix.

[0061] Whilst the cord body is described here as being generally cylindrical, the co-extrusion of the cylindrical cord body matrix with the helical reinforcing filament may result in a slightly raised contour variation in outside diameter of the cord following the helical pattern of the embedded reinforcing element. For example, the outside diameter of the cord may have a regular variation in outside diameter of from 0.2-1.5 mm, more preferably about 0.5-1 mm. Without wishing to be bound by theory, it is believed that having this slight variation from perfect cylindrical shape may in fact provide an improvement in hydrodynamics and reduced drag as the cord trails through the water during use.

[0062] The pitch P of the reinforcing filament helix may vary for example from about 6 mm to about 30 mm, for example about 10-15 mm, and may be for example about 12 mm for a 6 mm diameter cord as shown. As shown, the diameter of the helix is less than the diameter of the cord body, so that the filament is not exposed at the surface of the cord and is thus protected against abrasion or damage in the harsh conditions to which the leash will be subjected in use.

[0063] As an alternative to co-extrusion, the non-linear reinforcing element may first be manufactured, for example by extrusion or moulding, then forming the cord body matrix to encompass the reinforcing element, for example by over-extruding or overmoulding. However, forming the composite cord by the co-extrusion as described above is preferred.

[0064] The performance of the elastic cord body matrix with respect to strength and shock dampening may also be selected by considering an appropriate hardness, described on the Shore A scale, for the material of elastic cord body. TPU may be used as an appropriate elastomer for the cord body matrix material described herein due to the elongation properties and performance within the prescribed or described environment. The environmental factors may include: robustness in salt water, UV resistance, etc. and the like for the use of watercraft. A Shore A hardness range of 80 to 100 is considered appropriate for the leash cord body matrix, providing sufficient shock dampening properties for the performance of the invention. The preferred value of Shore A 95 provided above may be considered an optimum for the illustrated example cord construction. A lower Shore A hardness range elastomer, for example a Shore A hardness range of 20 to 70 which is common in natural rubber bungee cords, is not appropriate because the elongation at lower forces would be too high, providing insufficient shock-dampening and dangerous recoil. Likewise, an elastomer harder than the preferred useful range of approximately Shore A 80 to 100 may not provide enough shock-absorbing elongation, such that the recoil or contraction of the cord transfers too much force directly to the surfer, providing an uncomfortable and potentially dangerous interaction between the returning watercraft and the watercraft user. For example, a hardness greater than Shore D 60 for the cord body matrix may be unsuitable for use. It will be readily appreciated that other elasticity related properties to hardness may also be used to define and specify the desired performance and selection of the elastic core material.

[0065] FIG. 4 is a schematic diagram of a tensile force versus elongation graph for a prior art, TPU leash cord, and a TPU leash cord incorporating a non-linear reinforcing filament according to the invention described herein. The origin of the graph corresponds to zero force and the original length of the leash. The elongation has been normalised to the original length of each leash cord, accordingly the 5 elongation on the x axis corresponds to a leash cord which has been elongated to five times its original length.

[0066] Each of the two leash cords were tested to the fracture point of the cord. FIG. 4 contrasts typical results for a prior art TPU leash cord and the composite reinforced cord of the invention.

[0067] The results for a traditional TPU leash cord are labelled as A. The results for the leash cord with the helical reinforcing filament core are labelled B.

[0068] As apparent from FIG. 4, the initial response of both cords to application of elongation force is similar, as the force is taken up initially by elastic stretching of the cord body matrix. The reinforcing filament, being initially helical or other non-linear shape, begins to straighten out by mechanical elongation of the helix shape as the cord body stretches but does not greatly contribute to the force-elongation properties of the leash cord at that part of the curve. Thus the desirable force-dampening properties of the leash cord body are substantially retained as the leash stretches, at least initially, in a first behaviour without an abrupt force on the user as the board is swept away and reached the end of the leash length.

[0069] However, as the leash stretches further and cord body approaches and reaches its breaking point, it can be seen from FIG. 4 that the reinforcing filament becomes the dominant factor in performance of the leash beyond that point in a second behaviour, providing a substantial increase in break strength of the leash and reducing the occurrence of leash cord breakage.

[0070] As the cord body reached breaking/plastic deformation pointcorresponding to the extremity of line Ait is seen that there is initially an inflection in curve B believed to correspond to the remaining straightening of the helical reinforcing filament, then an upwards inflection as the straightened filament acts in substantially elastic mode with high elastic modulus.

[0071] Thus it is believed that the described leash cord construction may provide an improved combination of force-dampening and break strength compared to traditional TPU leash cords.

[0072] It will be readily appreciated that most if not all the geometries and dimensions of the components of the watercraft leash assembly invention described herein may be scaled up or down to better cater for the intended end user, the size and weight of the watercraft and/or specific surf conditions. For example, the components may be scaled down to further reduce the weight of the leash assembly for conditions that may withstand a reduction in strength such as small waves or surf competition. Conversely, the components may be scaled up or otherwise adjusted for greater strength in big wave conditions. Also, the components may be slightly modified in geometry to produce better sizing and fit for particular target markets such as male adult, women, children and athletes of watercraft users.

[0073] In this specification, terms denoting direction, such as vertical, up, down, left, right etc. or rotation, should be taken to refer to the directions or rotations relative to the corresponding drawing rather than to absolute directions or rotations unless the context require otherwise.

[0074] Although the invention has been herein shown and described in what is conceived to be the most practical and preferred embodiments, it is recognized that departures can be made within the scope of the invention, which are not to be limited to the details described herein but are to be accorded the full scope of the appended claims so as to embrace any and all equivalent assemblies, devices, apparatus, articles, compositions, methods, processes and techniques.

[0075] In this specification, the word comprising is to be understood in its open sense, that is, in the sense of including, and thus not limited to its closed sense, that is the sense of consisting only of. A corresponding meaning is to be attributed to the corresponding words comprise, comprised and comprises where they appear.

TABLE-US-00001 REFERENCE SIGNS LIST Reference Item Description 110 Leash Assembly 112 Ankle cuff assembly 114 Inside surface of the cuff 116 Pull tab 118 Pull tab aperture 120 Horn 122 Base 124a, 124b Cord end piece 126 Leash cord 128 Cut out portions 130 Hole in end piece 132 Grub screw 134 Further swivel assembly 136 Rail saver 138 Rope loop 140 Leash cord body matrix 142 Helical reinforcing filament