Conventional heating apparatus employing heat generating elastomers in the form of flexible sheets are known in the art. Such apparatus is required to be fixedly attached by means to a garment of clothing.

Unfortunately, the attachment means may break due to constant flexing of the garment causing the apparatus to be detached from said garment, and failure of the apparatus.

Previously proposed heating apparatus comprises a power circuit coupled to a network of heat generating wires embedded into, or attached to, a garment of clothing.

Unfortunately, since the wires have to be malleable to allow movement of the garment, the wires are

susceptible to breakage due to constant flexing of the garment.

According to a first aspect of the present invention there is provided a heating element comprising a substrate yarn, a heat generating yarn and an electrically conductive yarn, said substrate yarn, heat generating yarn and conductive yarn being knitted together to form the heating element.

Preferably the substrate yarn is made of a knittable material suitable for knitting a desired article.

Preferably the heat generating yarn is a heat generating conductive elastomer material.

Preferably the heat generating yarn is a heat generating conductive thermoplastic material.

Preferably the electrically conductive yarn is a knittable metallic conductive yarn.

Preferably the electrically conductive yarn is a knittable non-metallic conductive yarn.

Preferably the electrically conductive yarn is an electrically conductive knittable thermoplastic material.

Preferably the electrically conductive yarn is an electrically conductive knittable elastomer material.

Preferably a portion made of said heat generating yarn is disposed or knitted between two portions made of electrically conductive yarn, wherein one electrically conductive yarn portion acts in use as a positive conductor and the other electrically conductive yarn portion acts in use as a negative conductor, such as to allow a current to flow through the portion of heat generating yarn, causing the generation of heat.

According to a second aspect of the present invention, there is provided a method of manufacturing a heating element comprising the steps of: providing a substrate yarn, a heat generating yarn and an electrically conductive yarn; and knitting the substrate yarn, the heat generating yarn and the electrically conductive yarn together to form the heating element.

Preferably, the method includes the step of knitting a portion made of said heat generating yarn between two portions made of electrically conductive yarn, wherein one electrically conductive yarn portion acts in use as a positive conductor and the other electrically conductive yarn portion acts in use as a negative conductor, such as to allow a current to flow through the portion of heat generating yarn, causing the generation of heat.

According to a third aspect of the present invention, there is provided an article to be heated including a

heating element according to the first aspect of the present invention.

According to a fourth aspect of the present invention, there is provided a method of making an article to be heated comprising knitting a heating element according to the method of the second aspect of the present invention while simultaneously knitting an inner layer and/or an outer layer of said article to be heated.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:- Fig. 1 is a top plan view of a heating element made in accordance with the present invention; and Fig. 2 is a top plan schematic view of the heating element of Fig. 1 of the form of a glove.

With reference to Fig. 1, there is shown a heating element 10 comprising a substrate yarn 14, a heat generating yarn 16 and electrically conductive yarns 18, 20, which are knitted together.

The substrate material 14 is made of a known material for a desired article, to which the heating element 10 is to be applied, the desired article may be an article of clothing, headgear, or footwear, in which case the substrate yarn 14 may be made of wool, nylon, polyester, lycra@, etc.; and as will be appreciated, may be of other materials for other applications.

The heat generating yarn 16 is made of a heat generating material that generates heat when an electrical current is passed therethrough, for example, a conductive elastomer or conductive thermoplastic material such as, silicon rubber, styrene-butadiene rubber (SBR), linear low density polyethylene (LLDPE), polyurethane (PU), styrenic thermoplastic elastomer (TES), olefinic thermoplastic elastomer (TEO), etc.

The heat generating yarn 16 is obtained by extruding the heat generating material with an approximate yarn diameter preferably between 100 microns and 600 microns and preferably has an elongation at break of at least 80%.

Varying the diameter of the extruded heat generating yarn 16 will alter its internal resistance and therefore the power dissipated, as well as the heat radiated therefrom.

The electrically conductive yarns 18,20 are of the form of metallic or non-metallic conductive yarns that are knittable.

Alternatively, the electrically conductive yarns 18,20 may be of the form of an electrically conductive elastomer doped with a conductive particulate filler, for example, silver, that similarly is extruded into a knittable yarn. One such elastomer is x-static @, which has a natural layer of silver.

In fabrication, the substrate yarn 14, the heat generating yarn 16 and the conductive yarns 18,20 are

knitted together, preferably simultaneously, to form the heating element 10. The conductive yarns 18,20 serve as a positive and negative conductor, whereby a current from a power circuit (not shown), passes through one of the conductive yarns 18,20, through the heat generating yarn 16 disposed or knitted between the conductive yarns 18,20, through the other conductive yarn 20,18, thereby causing the heat generating yarn 16 to generate heat. It is important to note that the heat generating yarn 16 must be disposed or knitted between a positive and negative conductor yarn 18,20 in order for the disposed heat generating yarn 16 therebetween to generate heat.

In use, a power circuit, including at least one power supply, a switch, and a thermostat if needed, is electrically coupled to the electrically conductive yarns 18,20 of the heating element 10, and switched "ON".

A current from the power circuit, passes through one of the conductive yarns 18, 20, through the heat generating yarn 16, to the other electrically conductive yarn 18,20. As the current passes through the heat generating yarn 16, heat is generated and radiates therefrom.

By way of example only, the following describes the heating element above in the form of a glove.

Fig. 2 shows a heating element 100 of the form of a glove 112 comprising a substrate yarn 114, heat generating yarns 116a, 116b, 116c, 116d, 116e, and

electrically conductive yarns 118a, 118b, 118c, 118d, 118e and 120a, 120b, 120c, 120d, 120e.

The substrate yarn 114 is made of a typical glove material, for example, wool, nylon, lycra, polyester, etc.

The heat generating yarns 116a, 116b, 116c, 116d, 116e are similar to the previously described heat generating yarn 16 and are knitted to form a heating area in finger portions 124a, 124b, 124c, 124d, 124e disposed or knitted between conductive yarn pairs 118a-120a, 118b-120b, 118c-120c, 118d-120d, 118e-120e.

Further heat generating yarns and conductive yarns may be knitted to form a heating area elsewhere on the glove 112.

The electrically conductive yarns 118a, 118b, 118c, 118d, 118e and 120a, 120b, 120c, 120d, 120e are similar to the previously described electrically conductive yarns 18,20.

The electrically conductive yarns 118a, 118b, 118c, 118d, 118e extend along the back of the glove from a positive conductor base rail yarn 126 which is knitted to a wrist portion 122 of the glove 112, to the finger portions 124a, 124b, 124c, 124d, 124e of the glove 112.

It is to be appreciated that the positive pole of the power supply will be connected to the base rail yarn 126.

The remaining electrically conductive elements 120a, 120b, 120c, 120d, 120e extend along the palm side of the glove 112 from a negative conductor base rail yarn (not shown) which is knitted to the wrist portion of the glove 112, on the opposite side from the positive rail yarn 126, to the finger portions 124a, 124b, 124c, 124d, 124e of the glove 112. The negative pole of the power supply will be attached to the negative conductor base rail yarn.

The electrically conductive yarn pairs 118a-120a, 118b- 120b, 118c-120c, 118d-120d, 118e-120e located on the respective finger portions 124a, 124b, 124c, 124d, 124e, are positioned substantially parallel to one another, separated by the heating areas formed of the heat generating yarns 116a, 116b, 116c, 116d, 116e.

In fabrication, the substrate element 114, the heat generating yarns 116,116b, 116c, 116d, 116e, the electrically conductive yarns 118a-120a, 118b-120b, 118c-120c, 118d-120d, 118e-120e, and the positive and negative conductor base rail yarns 126 (and not shown), are knitted together to form the glove 112.

In use, a power circuit (not shown), including at least one power supply, a switch, and a thermostat if needed, is electrically coupled to the positive and negative conductor base rail yarns 126 (and not shown) of the glove 112, and switched"ON".

The electrically conductive yarn pairs 118a-120a, 118b- 120b, 118c-120c, 118d-120d, 118e-120e serve as positive and negative conductors or electrodes, whereby a

current from the conductive base yarns 126 (and not shown), passes from one set of conductive yarns 118a, 118b, 118c, 118d, 118e, or 120a, 120b, 120c, 120d, 120e, through the heat generating yarns 116a, 116b, 116c, 116d, 116e, to the other set of electrically conductive yarns 120a, 120b, 120c, 120d, 120e, or 118a, 118b, 118c, 118d, 118e.

As the current passes through the heat generating yarns 116a, 116b, 116c, 116d, 116e, heat is generated and radiates therefrom.

The heating element as described above can be used to construct a composite glove comprising an inner layer, a heating layer and an outer layer, said inner layer, heating layer and outer layer being knitted together simultaneously to form the composite glove.

The inner layer is knitted from a skin contactable yarn which, in use is in direct contact with the skin of a wearer of the composite glove, for example, wool, polyester, nylon, lycra@, etc.

The heating layer is a heating element in the form of the glove shown for example in Fig 2.

The outer layer is knitted from a protective yarn to protect the outer surface of the composite glove 112 from the environment and to offer insulation.

In fabrication, the inner layer, heating layer and outer layer are knitted together in a single knitting process to form the composite glove.

Although the previous examples specifically describe a glove, the desired article to be heated can be any article of clothing or apparel, for example, a jacket, socks, trousers, underwear, footwear, headgear, or may be non articles of clothing, for example, blankets, medical blankets to provide warmth to cold patients, upholstery, seat covers, car seats, or other suitable applications. The present invention may also be applied to housing insulation, pipe insulation, and any arrangement where protection is needed against cold conditions.

The heating element of the present invention will be intrinsically safe due to the heat generating yarns 16, 116a, 116b, 116c, 116d, 116e being chemically inert and having a positive temperature coefficient.

It is to be appreciated that conductive yarns made from different materials will have a different conductance, which will have an effect on the amount of current applied to the heat generating yarn, which in turn will have an effect on the heat generated. Furthermore, the smaller the heating areas between the conductive yarns, the more heat is generated for a given current, as there is more energy per unit area, since the area is less.

Modifications and improvements may be made to the above without departing from the scope of the present invention, for example, although there are only two substantially parallel conductive yarns on the finger portions of Fig. 2, there may be more than one conductive yarn pair located on each finger.

Alternating positive and negative conductive yarns may be knitted on each finger portion, or other areas susceptible to the cold. Having more alternating conductive yarn pairs between smaller heating areas i. e. dividing a large area between two conductors, into a number of smaller areas between more than two conductors, allows for more heat to be generated for a given current.