Woven sailcloth

Abstract

A woven sailcloth has groups of load-bearing yarns which extend in straight lines through tunnels without being woven. The tunnels are bordered front and back by woven layers and at the sides by crossing-over yarns. Because the load-bearing yarns extend along the tunnels there is no crimp in their longitudinal direction. The load-bearing yarns may include components for resistance to displacement along the tunnels, such as resin adhesives or wrapped-around filament.

Claims

1. A sailcloth comprising: a first woven layer, a second woven layer, wherein said first and second woven layers are interconnected and form parallel tunnels in the warp direction, and load-bearing yarns, each extending through and parallel to a tunnel, in which there is at least one load-bearing yarn per tunnel for a plurality of said tunnels.

2. The sailcloth as claimed in claim 1, wherein there is a plurality of load-bearing yarns in each tunnel.

3. The sailcloth as claimed in claim 1, wherein the first woven layer has yarn which crosses over and is woven in the adjoining second woven layer at intervals.

4. The sailcloth as claimed in claim 1, wherein the first woven layer has yarn which crosses over and is woven in the adjoining second woven layer at intervals; and wherein said yarn crosses over to form sides of said tunnels.

5. The sailcloth as claimed in claim 1, wherein the first woven layer has yarn which crosses over and is woven in the adjoining second woven layer at intervals; and wherein the second woven layer has yarn which crosses over and is woven in the first woven layer at intervals.

6. The sailcloth as claimed in claim 1, wherein the first woven layer has yarn which crosses over and is woven in the adjoining second woven layer at intervals; and wherein said yarn crosses over to form sides of said tunnels; and wherein said yarn crosses over to form sides of said tunnels.

7. The sailcloth as claimed in claim 1, wherein said first and second woven layers are interconnected by stitching.

8. The sailcloth as claimed in claim 1, wherein said first and second woven layers are interconnected by stitching; and wherein said stitching is by a yarn in one or both of adjoining layers between said tunnels.

9. The sailcloth as claimed in claim 1, wherein said first and second woven layers are interconnected by stitching; and wherein said stitching is by a yarn in one or both of adjoining layers between said tunnels; and wherein there are at least two intermediate stitches formed between each tunnel.

10. The sailcloth as claimed in claim 1, wherein tenacity of the load bearing yarns is greater than that of the parallel yarns in the first and second layers.

11. The sailcloth as claimed in claim 1, wherein strength characteristic tenacity of the load-bearing yarns are greater than 6 grams per Denier.

12. The sailcloth as claimed in claim 1, wherein strength characteristic tenacity of the load-bearing yarns are greater than 6 grams per Denier; and wherein the tenacity is greater than 8.5 grams per Denier.

13. The sailcloth as claimed in claim 1, wherein there are greater than 50 tunnels per metre, and preferably greater than 80 tunnels per metre in a direction across the tunnels.

14. The sailcloth as claimed in claim 1, wherein there are at least five load-bearing yarns in at least some tunnels; and wherein the load-bearing yarns are in a multi-layer structure with a plurality of layers between the first and second layers.

15. The sailcloth as claimed in claim 1, wherein the sailcloth further comprises a component to assist resistance to displacement of load-bearing yarns along the tunnels; and wherein said components include an adhesive compound in said tunnels.

16. The sailcloth as claimed in claim 1, wherein the sailcloth further comprises a component to assist resistance to displacement of load-bearing yarns along the tunnels; and wherein said components include an adhesive compound in said tunnels; and wherein at least some of the load-bearing yarns are exposed at parts of their length and said anti-slippage component engages the load-bearing yarns at said exposed locations.

17. The sailcloth as claimed in claim 1, wherein at least some load-bearing yarns each include one or more filament wrapped around the load-bearing yarn.

18. A method of manufacturing a sailcloth comprising: a first woven layer, a second woven layer, in which said first and second woven layers are interconnected to form parallel tunnels, and load-bearing yarns extending through the tunnels, the method comprising weaving the yarns according to one or more of the following parameters to achieve desired cloth strength characteristics: number of tunnels per unit length, number of load-bearing yarns per tunnel, number of yarns per tunnel, yarn strength per unit length in said first and second layers, and tenacity of the load bearing yarns.

19. The method as claimed in claim 18, wherein the load-bearing yarns are pre-treated for enhanced resistance to displacement.

20. The method as claimed in claim 18, wherein said pre-treatment includes heat or chemical-induced shrinking.

21. The method as claimed in claim 18, wherein said pre-treatment includes wrapping a filament around each load-bearing yarn.

22. A boat sail comprising a sailcloth of claim 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

Brief Description of the Drawings

(1) The invention will be more clearly understood from the following description of some embodiments thereof, given by way of example only with reference to the accompanying drawings in which:

(2) FIG. 1 is a diagrammatic cross-sectional view across the warp of portion of a sailcloth of the invention; and

(3) FIG. 2 is a cross-sectional view in the weft direction of part of an alternative woven cloth.

DESCRIPTION OF THE EMBODIMENTS

(4) We describe a cloth comprising at least two woven layers including a first woven layer and a second woven layer which are interconnected and form parallel tunnels which are preferably in the warp direction. Load-bearing or “reinforcing” yarns extend through at least some of the tunnels. At least some tunnels each have more than one load-bearing yarn.

(5) The cloth may include means to retain or hold the load bearing yarns in position to prevent or minimise slippage displacement.

(6) A first woven layer has weft yarn which crosses over and is woven in an adjoining second woven layer at intervals, in which weft yarn crosses over to form upper and lower sides of the tunnels. Also, the second woven layer has weft yarn which crosses and is woven in the first woven layer at intervals. In other examples it is the warp yarn which crosses over, terms “weft” and “warp” meaning being defined as the yarns which extend across and along respectively.

(7) The woven layers are interconnected by stitching laterally between the tunnels by a yarn in one or both of the adjoining layers. Preferably, there are at least two intermediate stitches formed between each tunnel.

(8) Tenacity of the load bearing yarns is greater than that of the parallel yarns, in one example warp yarns, and in one case the tenacity of the load-bearing yarns are greater than 6 grams per Denier. Preferably, the load bearing yarns have greater tenacity than 8.5 grams per Denier.

(9) In more detail, referring to FIG. 1 a sailcloth 1 comprises woven layers 3 and 4 between which are load-bearing yarns 2. The load-bearing yarns 2 are in groups of five large-diameter yarns, the groups being equally spaced at intervals across the weft direction. In this case the direction across the page is defined as the weft direction and the direction out of the plane of the page is defined as the warp direction. The load-bearing yarns 2 are independent of the weaving of the various other yarns—being trained without bends in the load-bearing direction (out of the plane of the page).

(10) Each group of five load-bearing yarns may be regarded as being in a “tunnel” 20 between the woven layers 3 and 4 at the front and rear, and sides being formed in the weft direction by crossing-over weft yarns.

(11) The top layer 3 comprises parallel warp yarns 5 and two sets of opposed inter-woven weft yarns 10 and 11. Although not shown in the drawing, as is well known in the field the warp yarns 5 also cross over the weft yarns 10 and 11 out of the plane of the page. For clarity, the weft yarn 10 is shown thicker than the weft yarn 11, however this is merely to illustrate them so that they can be distinguished. They are preferably the same thickness.

(12) Equally, the layer 4 has parallel warp yarns 5 and inter-woven weft yarns 15 and 16.

(13) The weft yarns 10 and 15 also cross over to the other layer to encompass the load-bearing yarns 2. The weft yarns 11 and 16 also cross over to the opposite layer, but only for intermediate stitching at periodic intervals.

(14) Yarn Sizes and Materials

(15) The yarn compositions (materials) are in this specific embodiment: load-bearing yarns 2: 2500 Denier polyester tenacity of 8.5 grams per Denier, warp yarns 5: 150 Denier polyester tenacity of 7 grams per Denier, weft yarn 10: 250 Denier polyester tenacity of 7 grams per Denier, weft yarn 11: 250 Denier polyester tenacity of 7 grams per Denier, weft yarn 15: 250 Denier polyester tenacity of 7 grams per Denier, and weft yarn 16: 250 Denier polyester tenacity of 7 grams per Denier,

(16) In other embodiments the yarn compositions (materials) may include but are not confined to UHMWPE, (Ultra High Molecular Weight Polyethene) polyolefin, aramid, LCP (Liquid Crystal Polymer). These are often marketed under registered trades such Vectran®, Kevlar®, Dyneema®, Spectra®.

(17) The strength characteristics (tenacity) of the load-bearing yarns 2 are greater than 6 grams per Denier. The sum total of the Denier of all load bearing yarns contained within a single tunnel may be calculated and expressed as total denier per centimetre (Den/cm). The same calculation should be done for the combined ground and tunnel warp yarns. The results should then be compared to ensure the Den/cm of the load bearing yarns is greater than the Den/cm of the ground and tunnel yarns. The magnitude of the difference can be adjusted by varying the following items: number of tunnels per cm, number, denier and yarn type in each tunnel, the number of yarns per cm. and denier. The preferred tenacity of the load bearing yarns is greater than 8.5 grams per denier. If high modulus yarns are used for the load bearing yarns the Den/cm may be reduced.

(18) The cover factor (CF) for ground and tunnel warp yarns, can be calculated by the formula:
(yarns per centimetre/10)×square root(denier/9).
The result for ground and tunnel warp yarns should be added together to give a total warp CF. The weft CF is calculated by using the same formula. The weft CF may be up to 10% lower than the CF of the combined ground and tunnel yarns.

(19) The range of tunnels per metre across the width (the weft direction) is preferably in the range of 50 to 175, and more preferably 80 to 125 per metre. However the actual number of tunnels per metre may be varied outside of this range according to the requirements of a particular end use, for example sail type or position of use in a sail. Different sections of the woven cloth may have different tunnel densities.

(20) There are several ways to indicate the yarn strength. a) Breaking load—directly related to the Denier, the higher the Denier, (increased cross sectional area) the greater the load required to break the yarn. However the result is only valid for that particular Denier. b) Elongation at break is not a direct indicator of strength but a yarn with high extension might take 20 kgs to break but if it extends more than 20% before breaking it is not suitable, again this only relates to a particular Denier. c) Tenacity uses the Denier in the calculation by using the formula load at break/Denier. The result provides a relationship between yarns of different Denier and across all yarn types as it allows for the different cross section area. The results provide a simple basis for comparison. For example 1000 Denier break load 8 kg has a tenacity of 8 grams per Denier. If one needs to match a higher Denier yarn of say 1400 and a break load of say 7 kgs the tenacity is 5 gm/den so is not suitable. It is common practice to segregate yarns into divisions of tenacity. NT=Normal Tenacity or MT=Medium Tenacity, HT=High Tenacity. Unfortunately there is no consensus as to the boundaries of each type by chemical composition and tenacity. The most common is NT (MT less than 7 grams per Denier, and HT is greater than 6 grams per Denier).

(21) The load bearing yarns 2 are included in the cloth in a predetermined number and sequence according to the intended application.

(22) The setup and programming of the weaving machine is such that the sequence of interlacing and interchanging of the yarn sets form tubes or tunnels in the cloth. Each “tunnel” includes a group of load-bearing yarns 2. The warp yarns 5 adjacent the load-bearing yarns are referred to as “tunnel warp yarns” and those in-between are referred to as “ground warp yarns”. Each tunnel has an upper surface and lower surface. The extremities of each tunnel are connected to the body of the cloth which avoids excessive flexing between tunnels.

(23) The preferred sequence of ground and tunnel weave interlacing is plain weave and double plain, which is well known to those experienced in the art.

(24) The ground and tunnel warp yarns 5 can be of any type, size or tenacity. Preference is polyester or nylon, size range from 20 Denier to 500 Denier or the equivalent in other yarn numbering systems and a tenacity of greater than 7 grams per Denier.

(25) The load bearing yarn used can be of any type, size or tenacity and is determined by reference to the application. The preferred range of a single load-bearing yarn is in the range from 200 to 6000 Denier or the equivalent in other yarn numbering systems. Preference is for the tenacity of the load bearing yarns to be greater than the ground and tunnel warp yarns.

(26) In the direction of the load bearing yarns the ground and tunnel yarns have a similar amount of thermal or chemical shrinkage.

(27) In the direction 90° to the load bearing yarns the parallel yarns have similar tenacities to those of the yarns in the ground and tunnel yarns and preferably have a higher amount of thermal or chemical shrinkage.

(28) The weaving machine is programmed so that the load bearing yarns are totally encased within the tunnels. They are not woven into the structure and do not have any woven crimp.

(29) The load bearing yarns encased within each tunnel can vary in number, size and type within the same tunnel if desired.

(30) After weaving is complete the cloth is processed in such a manner to allow the yarns with a higher amount of potential shrinkage to fully shrink and tighten upon the load bearing yarns.

(31) The size of the tunnels is determined by the final design requirement, the size and number of the load bearing yarns. For example, as shown in FIG. 2 a woven cloth 50 has yarns 5, 10, 11, 15, and 16 as for the cloth 1 of FIG. 1. However, in this case there are tunnels 51 formed between layers 53 and 54, each tunnel having seven load-bearing yarns 52. Within each tunnel the load-bearing yarns are arranged in a multi-layer structure namely a bottom layer of two yarns, a middle layer of three yarns, and a top layer of two yarns.

(32) Further stabilisation or treatment such as coating with resin and/or with a water repellent composition may be performed. In some embodiments additional yarns or other components may be included in the tunnels together with the load bearing yarns for purpose of positional control to prevent slippage displacement. These components may include hot melt yarns, either 100% type or bi-component type, these can be incorporated as individual yarns or pre-wrapped around the load bearing yarns before weaving. The load bearing yarns can be treated before weaving with single or multi-part resin or adhesive and activated after weaving. After weaving, processing with resin, activators or other coating materials which penetrate the tunnel may be performed. Alternatively or additionally, the load bearing yarns may be exposed at intervals on either or both sides of the cloth for contact with an anti-slippage component such as a bonding resin. The amount of exposure and anti-slippage component is determined by the final performance requirements. In one embodiment, consecutive machine revolutions provide such exposures by the programming of the warp lifting sequence and moving the woven cloth forward at a constant preset speed according to the desired length of exposure.

(33) During manufacture, the weaving machine may have a fixed speed, inserting one weft every machine revolution. The space occupied by one weft depends on the denier and the setting on the machine to move the cloth forward prior to the next weft insertion. The thicker the weft the more the machine will advance the cloth before the next insertion.

(34) It will be appreciated that the present invention provides an improved woven cloth which allows load bearing yarns to be incorporated into a woven structure. The incorporation is without any interlacing with other yarns in the structure, thereby ensuring the load bearing yarns have no woven crimp.

(35) Also, it eliminates the cross-over between layers, which we believe reduces chances of premature fatigue.

(36) There is no crimp in the load bearing yarns in the warp direction. Also, the load bearing yarns have no woven crimp and are totally encased in the body of the cloth, thereby protecting them from abrasion.

(37) The tight weaving of traditional woven sailcloth is utilised to full advantage and thereby provides stability in the 45° direction, especially as there is no crimp transfer to the weft.

(38) The securing and positioning of the load bearing yarns may be enhanced by weaving techniques and post weaving operations. These include shrinking the yarns by heat or chemicals, activation of pre-weaving processes applied to yarns, such as hot melt yarns, and/or use of adhesives of one or multi part system types.

(39) For example, it is possible to fix the position of at least some load-bearing yarns by a fine mono-filament stitching weft yarn.

(40) The invention is not limited to the embodiments described but may be varied in construction and detail. For example, the cloth of the invention may be for applications other than sailing.