This invention relates to the application of heat activated substances, such as dyes or the like, to fibres and textiles in general, and in particular, to ropes.

A recent invention relates to a rope, cable, webbing or the like which comprises an indicator means for providing information in relation to the extent of wear or stress the textile or fibre has undergone. The indicator is preferably a heat activated dye.

Heat activated dyes are appropriate for use as indicators for this purpose as it has been found that rope fibres or the like tend to increase in temperature in relation to the extent of stress or wear which has been imparted to them. It has been found in the present invention that many nylon dynamic ropes may reach, say, 95 - 100°C as a result of undergoing a level of stress which renders the rope unreliable for future use.

A difficulty which has been encountered in relation to the application of heat activated dyes, with an activation temperature within the suggested range given above of 95 - 100°C is that in the manufacture of the ropes, webbing or the like for dynamic applications, the fibres may be required to be heated to temperatures in excess of 100°C. For example, in the production of seat belts or climbing ropes which are desired to stretch under load, heat setting is employed which may cause the fibres or yarn to be raised to a temperature above the activation temperature of the dye. Thus, it is impractical to apply the heat activated dye or substance to the rope fibres, prior to the fibres having been heat set.

Furthermore, in the case of ropes, cables, webbing or the like used for static applications, while heat setting may not be employed to the same extent, other physical, abrasive or otherwise rugged processes may be imposed upon the fibres which would be detrimental to the heat activated substance if applied too early in the production process, or by an unsuitable means.

According to the invention there is provided a method of applying a heat activated substance to a textile made of fibre construction, wherein said method includes;

a) producing the fibres to an appropriate tenacity, b) constructing the fibres into a yarn, c) optionally dying the yarn with an appropriate colour and heat setting the yarn at a predetermined temperature, d) ensuring the yarn is a temperature below the activation temperature of the heat activated

substance, and e) passing the yarn through a solution in which the heat activated substance is suspended in particle form, such that said particles adhere to said yarn.

Preferably, said yarn is thereafter coated with a protective layer, such as a varnish, lacquer or the like.

Optionally, said yarn is thereafter braided to form a cover, said cover encapsulating an inner core.

According to the present invention, there is provided a method of applying a heat activated substance to a yarn which has been heat set and allowed to cool to a temperature below the activation temperature of the substance, comprising suspending the substance in the form of particles in a solution, immersing the yarn in the solution and subsequently air drying the yarn.

Preferably, said solution comprises chemicals which are adapted to be air dried such as, and by way of example only, ethyl and alcohol based chemicals.

Preferably, said textile is coated with a protective covering after said solution has dried, in order to protect the particles of the heat activated substance from abrasion or other attack.

Preferably, said protective covering is a clear or transparent varnish.

A method in accordance with the invention will now be described, by way of example only, in order to provide

a better understanding of the invention herein intended.

A common application for the use of heat activated substances to indicate wear in textiles is found in respect of climbing ropes. Climbing ropes generally comprise an inner core and a cover. It is not necessary to apply the heat activated substance to the inner core as the core is not visible, in use. Thus, generally in ropes of this construction, that is kermantle ropes, the heat activated substance is only required to be applied to the cover.

Manufacture of the cover may be performed by the following method. Fibre is prepared in the factory and brought to the required tenacity for its intended application. This may involve the gathering of, say, some 240 filaments together, applying a holding twist to the filaments and then stretching same with the use of appropriate machinery or apparatus, including, for example, a series of hot rollers rotating at consecutively increasing speeds.

A flat yarn is thereby produced which may be heat set at an appropriate temperature. Heat setting temperatures are dependent on the desired characteristics of the textile, and typical temperatures may range between 100 and 130°C.

This is followed by constructing the fibres by twisting or other conventional methods. For example, in the case of cabling a 3-strand twist is commonly applied, which will be well known to persons skilled in the art. The constructed fibres are then, typically, twisted to form a yarn. In this form the constructed fibres may

be supplied to a rope manufacturer who may use them to produce a cover for a climbing rope. Such covers are generally coloured for aesthetic reasons and thus the constructed fibres are dyed with an appropriate colour dye and simultaneously heat set, typically at a temperature between 100 and 130°C.

This step may be followed, in the invention, by applying the heat activated substance to the cover yarn. The heat activated substance is supplied in the form of a powder which is added to a chemical bath or solution. The content of the chemical solution may largely depend on the activation temperature of the substance, but is adapted to suspend the particles of the substance in a manner which allows them to be readily adhered to the cover yarn passed through the solution.

It is important that the chemical solution is also adapted to be air dried. That is, the solution should be adapted to dry quickly, preferably by relatively immediate evaporation, to facilitate the application of the protective layer instantly thereafter in the production process. If this was not the case, it is likely that drying the yarn by mechanical or forced means would cause abrasion of the heat activated particles resulting in their loss or failure. Similarly, drying by application of heat is not appropriate as the heat may activate the substance.

It is important also to protect the particles as much as possible. This is because, once bathed in the chemical solution, the particles are egg like in that they comprise an inner yoke which is covered by a shell like layer. In use, the heat which results from

applied stress to the rope fibres causes a chemical reaction within the shell like layer giving rise to the colour change.

Accordingly, a protective layer may be applied to the yarn, which would protect the particles from abrasion or other external attack. The layer may be a clear varnish. As the stress resultant heat is generated from within the rope fibre, the application of the varnish to the exterior of the rope is not inclined to adversely effect the working of the heat activated substance.

The yarn may then be braided to provide a suitable cover for an inner core.

Similar methods may be employed for a wide variety of textiles. Not all ropes demand stringent controls in relation to heat setting which are applicable to climbing ropes. Thus, in some cases, one particular strand of a multi-strand rope or cable may have the heat activated substance applied, and this strand may be exempted from heat setting at temperatures above the activation temperature. Versatility in when to apply the substance is thereby provided.

Further modifications and improvements may be incorporated without departing from the spirit or scope of the invention herein intended.