GB2564852A

GB2564852A - Garments, heating systems and methods

Info

Publication number: GB2564852A
Application number: GB1711641.9A
Authority: GB
Inventors: Caird Robin; Nakhal Solset Rana
Original assignee: Emel&aris Ltd
Current assignee: Emel&aris Ltd
Priority date: 2017-07-19
Filing date: 2017-07-19
Publication date: 2019-01-30
Also published as: GB201711641D0; WO2019016524A1

Abstract

A garment (10, figure 2a) comprises an integrated heating system 1. The heating system comprises a resistive heating element 2 formed from a material with an electrical sheet resistance of less than 23 ohms per square, and preferably between 15 and 16 ohms per square. The heating element may include first and second electrodes 3, 4, each running along a length of the heating element with a separation 5 such that, in use, an electric current flows between the electrodes. The garment may also include a closed-loop system controllable by a radio frequency interface to maintain a predetermined surface temperature of the heating element. A garment having a resistive heating element and a closed loop system, a garment having a resistive heating element and a flat-braided electrical conductor and a method of manufacturing an active heating garment is also disclosed.

Description

GARMENTS, HEATING SYSTEMS AND METHODS

Technical Field

The present invention relates to garments, heating systems and methods.

Background

Garments, such as coats, with integrated heating systems are known. The integrated heating system has a heating element formed from an electrically conductive material. The heating element is connected to a battery by an electrode. Passage of an electric current from the battery via the electrode and through the heating element produces heat energy in the heating element (known as resistive, ohmic or joule heating). The heat energy from the heating element is transferred to a wearer of the garment. An example garment with an integrated heating system is the Smart Coat™ produced by Emel&Aris Ltd.

Summary

According to a first aspect of the present invention, there is provided a garment with an integrated heating system including a resistive heating element comprising a material having an electrical sheet resistance of less than 23 ohms per square.

According to a second aspect of the present invention, there is provided a garment comprising a heating system, the heating system having a resistive heating element and a closed-loop system for controlling a surface temperature of the resistive heating element.

According to a third aspect of the present invention, there is provided a garment comprising a heating system, the heating system including a resistive heating element and a flat-braided electrical conductor coupled to the resistive heating element.

According to a fourth aspect of the present invention, there is provided a garment comprising a heating system, the heating system including and a resistive heating element and a plurality of electrodes coupled to the resistive heating element, wherein the resistive heating element material has a lower electrical resistivity in a direction of separation between the first and second electrodes than in a direction in which the first and second electrodes run along the length of the resistive heating element.

According to a fifth aspect of the present invention, there is provided a method of making an active heating garment, the method comprising:

providing a garment;

providing a resistive heating element comprising a material having an electrical sheet resistance of less than 23 ohms per square;

coupling first and second electrodes to the resistive heating element; and integrating the resistive heating element and the first and second electrodes into the garment.

According to a sixth aspect of the present invention, there is provided a heating system for integrating into a garment, the heating system including a resistive heating element comprising a material having an electrical sheet resistance of less than 23 ohms per square.

Further features and advantages will become apparent from the following description of preferred embodiments, given by way of example only, which is made with reference to the accompanying drawings.

Brief Description of the Drawings

Figure 1 shows a schematic diagram of an example heating system for integrating into a garment.

Figures 2a and 2b show schematic diagrams of an example garment with an integrated heating system.

Figure 3 shows a flow diagram depicting an example of a method of making an active heating garment.

Detailed Description

The heating power generated by a resistive heating element, connected to an electrical power source (for example, a battery) is dependent on (at least) a voltage of the electrical power source, a geometry of the resistive heating element, and an electrical resistivity of the heating element. With the resistive heating element in the form of a panel or sheet, the electrical resistivity can be reformulated as an electrical sheet resistance, as discussed further below.

Known garments with an integrated heating system include a resistive heating element made of a material having an electrical sheet resistance of 25 ohms per square (Ω/sq.) or greater. In reality, a material having a stated electrical sheet resistance of 25 Ω/sq. may have an electrical sheet resistance down to 23 Ω/sq., for example due to manufacturing tolerances. The resistive heating element is typically connected to a 7.4 volt (V) battery.

Described herein are examples of a garment with an integrated heating system that includes a resistive heating element. The heating system is integrated into the garment in that at least part of the heating system is attached, fastened, secured or joined to the garment. For example the heating system may be integrated into the garment such that a resistive heating element, as part of the heating system, is attached, fastened, secured or joined to the garment. In some examples, the heating system, or a part thereof, is integrated into the garment such that it is concealed within the garment. This may give an extra layer of protection to the concealed parts of the heating system, for example by a layer of textile material that acts as a barrier to direct contact with those parts of the heating system. In some cases, at least part of the heating system is removably attached to the garment, such that in normal use the at least part of the heating system remains attached to the garment, but may be detached or removed from the garment, for example by a human with their hands and without any tools. In other cases, the at least part of the heating system is not detachable from the garment, such that detaching the at least part of the heating system from the garment involves use of a tool and/or significant force.

The resistive heating element in these examples comprises a material having an electrical sheet resistance of less than 23 Ω/sq. Compared to known systems, this allows the present heating system to heat a larger surface area to the same predetermined heating element surface temperature, using the same voltage supply. For example, compared to known systems, the present heating system is able to actively heat a larger surface area of a resistive heating element to the same surface temperature (for example, between 40 and 45 degrees Celsius) using a battery with the same voltage (for example,

7.4 V) and capacity (for example, 2000 mAh), and drawing electrical energy from the battery at the same rate, such that a run-time of the battery is the same. The run-time is a measure of the length of time that the battery, and therefore the garment, will be able to operate for before the battery runs out of charge.

An alternative to reducing the electrical sheet resistance of the resistive heating element, in order to increase the active heating area, is to alter the geometry of the resistive heating element such that the size of the resistive heating element increases but the same amount of material is used. However, making the overall heating area of the resistive heating element larger while using the same amount of material reduces the heating intensity (for example, heat energy per unit area) in the enlarged area. Therefore, at a set battery power, the average surface temperature of the resistive heating element would decrease. Or, for a set average surface temperature of the resistive heating element, the electrical power drain would increase and so the run-time of the battery would decrease.

Reducing the electrical sheet resistance of the resistive heating element material to less than 23 Ω/sq. allows the active heating area of the resistive heating element to be increased without reducing the heat intensity in the enlarged heating area. For example, the active heating area may be increased by 25% to 35% compared to some known systems, with the same electric power supply and run-time. Therefore, compared to a heating system with a resistive heating element having a higher electrical sheet resistance and a smaller active heating area, the same surface temperature of the resistive heating element can be maintained with the same battery capacity and runtime. Alternatively, reducing the electrical sheet resistance of the resistive heating element material to less than 23 Ω/sq. allows the same active heating area of resistive heating material to be used to maintain the same surface temperature, but with a lower battery voltage. This may allow the battery to be smaller in physical dimensions so that it is easier to conceal in the garment and/or lighter in weight so that it is easier and/or less obtrusive for the wearer to carry.

There would, however, be a prejudice in the art against decreasing electrical sheet resistance for a heating element to be used in a garment since decreasing electrical sheet resistance generally leads to increased rigidity of the heating element which may be considered not to be appropriate in the context of heating systems for garments. Furthermore, decreasing the electrical sheet resistance of a composite material generally involves increasing the amount of one or more electrically conductive components per unit volume of the composite material, which can increase the cost per unit of the composite material. This would likely deter a designer of a heating system to be used in a garment against decreasing the electrical sheet resistance of the heating element material.

The applicant has realised, against these prejudices in the art, that the electrical sheet resistance of the heating element may be reduced to a specific range that improves the heating performance of the heating element, while maintaining a suitable amount of flexibility and cost per unit for the heating element to be suitable for its application as part of a heating system for a garment.

Referring to Figure 1, there is shown schematically an example of a heating system 1 for integrating into a garment. The heating system 1 includes a resistive heating element 2 made of a material having an electrical sheet resistance of less than 23 Ω/sq. The material may be a composite formed from electrically conductive members dispersed in a polymer matrix. The electrically conductive members may comprise electrically conductive particles or fibres. The electrically conductive members may allow an electric current to flow through the material when a voltage (or ‘electric potential difference’) is applied to the material. The polymer matrix may be electrically non-conductive, and serve to support the electrically conductive members. Such a resistive heating material is obtainable from Primasil Silicones Limited, Kington Road, Weobley, Herefordshire, HR4 8QU, United Kingdom.

In some examples, the material of the heating element 2 comprises carbon particles dispersed in a silicone matrix. In some examples, the resistive heating element 2 is formed from the material coated on a sheet of textile material. The resistive heating element 2 may be a flexible panel or sheet. Compared to metal wire based heating systems, the polymer based system may be more tolerant of small breaks in the conducting material, as the area of conduction is large. In addition, metals may suffer from fatigue related breakage when subjected to repetitive deformation cycles, whereas silicone polymer may not.

For a uniform three-dimensional sample of an electrical conductor, the electrical resistivity of the conductor material may be given by:

A P = ^R _T where p is the resistivity of the conductor having a SI unit of ohm meter (Ω-m), R is the electrical resistance of the sample in ohms (Ω), A is the cross-sectional area of the sample, for example in metres squared (m²), and I is the length of the sample for example in metres (m).

For a sheet or panel of an electrical conductor, the cross-sectional area of the sheet (relative to a direction of current flow) may be given by the product of a width w of the sheet and a thickness t of the sheet: A = w t. The above equation for a resistivity of a conductor may then be reformulated to give a sheet resistance R_s:

w p

R_s = R~r = ~ ^s I t where the sheet resistance Rs may be given in units of ohms per square (Ω/sq. or Ω/Π), which are dimensionally equivalent to ohms but denote that an aspect ratio of the sheet or panel is incorporated therein. For a square sheet of a conductor, the sheet resistance R_s is equal to the bulk resistance R (as w = I in the equation above), for any size of the square sheet.

As shown in the above equation, the bulk resistivity p of the sheet may be determined if the sheet resistance Rs and the thickness t of the sheet is known. The sheet resistance Rs may alternatively be termed a sheet resistivity or surface resistivity p_s due to its close relationship to the bulk resistivity p.

References herein to a sheet resistance of a material are suitable given a construction of a resistive heating element 2 with a plurality of electrical contacts at a surface of the resistive heating element 2. With such a construction, an electric current flowing between the electrical contacts may be approximated as a surface current conducted at the (two-dimensional) surface of the resistive heating element 2. Therefore, a surface resistance Rs may be used as a pseudo-intrinsic property of the resistive heating element 2 material in such a construction, for example in comparing electrical conductivity properties between sheets of different materials (with arbitrary thicknesses).

In constructions where an electric current flows between a plurality of electrical contacts through a cross sectional area of a three-dimensional sample of material (as described above) the bulk resistivity p of the material may be determined from the sheet resistance R_s using the thickness t (or equivalent height h) of the sample. Therefore, in such constructions (where, for example, one or more electric contacts are embedded in the resistive heating element 2) the resistive heating element 2 is made of a material having an electrical resistivity corresponding to an electrical sheet resistance of less than 23 Ω/sq. For example, the resistive heating element 2 may be made of a material having an electrical resistivity p equal to the electrical sheet resistance of the material R_s multiplied by the thickness t of the resistive heating element 2.

Decreasing the electrical sheet resistance of the heating element 2 allows the heating element 2 to cover a larger active heating area with the same temperature, voltage, and power consumption constraints, as previously described. In examples where the material comprises electrically conductive particles or fibres, such as carbon, dispersed in a polymer matrix, such as silicone rubber, decreasing the electrical sheet resistance may be achieved by increasing the density of the electrically conductive particles or fibres dispersed in the polymer matrix. However this can compromise the pliability of the composite material and therefore the resistive heating element 2. As the resistive heating element 2, as part of the heating system 1, is for integrating into a garment, having a degree of pliability may enable the resistive heating element 2, and in some examples the heating system 1 as a whole, to cope with movement of the garment when worn by a person, and to contour to the person’s body. In some examples, the resistive heating element 2 material has an electrical sheet resistance of at least 10 Ω/sq. so that the resistive heating element 2 is not too rigid, while providing a lower electrical sheet resistance than that in use in known heating systems for garments.

In some examples, the resistive heating element 2 material has an electrical sheet resistance of between 15 and 16 Ω/sq. which balances between the effects, described above, of making the resistive heating element 2 more conductive but maintaining a desired degree of pliability.

The electrical resistivity or sheet resistance of the resistive heating element 2 material may increase with temperature; a property which may be referred to as a positive temperature coefficient (PTC). The material of the resistive heating element 2 having a PTC may help in establishing a uniform temperature in the presence of an uneven or non-uniform mixing of the electrically conductive particles or fibres with the polymer matrix. For example, a high concentration of electrically conductive particles or fibres in an area of the material will lower the electrical resistance in that area, causing a ‘hot-spot’. As the hot-spot heats up, the PTC may cause the electrical resistance of the higher temperature area to increase, so that the energy going into the higher temperature area decreases. A PTC may be considered a useful property when dealing with real material samples, which may vary in homogeneity of particle or fibre density within sheets and between batches.

In this example, the heating system 1 includes an electrode 3 coupled to the resistive heating element 2. For example, the electrode 3 may be attached to the resistive heating element 2 such that electricity may be conducted between them. In some examples, the electrode 3 comprises a braided electrical conductor. An example of a braided electrical conductor is braided nickel plated copper. Copper is often used as an electrical conductor because of its high electrical conductivity, but is a comparatively reactive metal, and the braided electrical conductor may be subject to a variety of corrosion and degradation effects in normal use. Coating the copper with a less reactive metal, such as tin or nickel, may reduce the overall rate of damage to the braid due to these corrosion and degradation effects. Tin can become more brittle than nickel after heating and cooling cycles, and exposure to oxygen. The nickel plating may therefore reduce the overall rate of damage to the copper braid, while being less prone to brittling compared to other example plating such as tin. This may be beneficial when the heating system 1 is integrated into a garment. For example, accessing the resistive heating element and braided electrical conductor may involve tools, which may make repairing a damaged electrode more difficult.

In some examples, the braided electrical conductor is flat-braided. A flatbraided electrode may provide a more reliable coupling between the electrode 3 and the resistive heating element 2 than rounded conductors, for example by increasing a contact area between the electrode 3 and the heating element 2 which may in turn decrease the likelihood of the electrode 3 and resistive heating element 2 becoming decoupled. A more reliable coupling between the electrode 3 and the resistive heating element 2 is additionally effective when the heating system 1 is integrated into a garment. In these cases, the wearer of the garment may not have direct access to the heating element 2, which may not be visible on the garment, and so a decoupling of the electrode 3 and the resistive heating element 2 may negatively affect the performance of the heating system 1 while going undetected.

The electrode 3 may be coupled to the resistive heating element 2 by stitching, for example a row of stitches passing through the electrode 3, illustrated schematically in Figure 1 by the dashing of electrode 3. The stitching may be a zigzag stitch.

In some examples, the electrode 3 is a first electrode 3, and the heating system includes a second electrode 4 coupled to the resistive heating element 2. The first and second electrodes 3, 4 may each run along a length of the heating element 2 with a separation 5 between the first and second electrodes 3, 4 such that an electric current can flow between the first and second electrodes 3, 4. For example, the first and second electrodes 3, 4, or respective portions thereof, may run along a length of the heating element in substantially parallel directions 6a, 6b. Substantially parallel may be considered to mean that the first and second electrodes 3, 4, or respective portions thereof, do not meet or cross on the resistive heating element 2. In examples where the first and second electrodes 3, 4, or respective portions thereof, are parallel, with the separation 5 consistent along the length of the heating element 2, a direction of the separation 5 may be perpendicular to the directions 6a, 6b that the first and second electrodes 3, 4, run in.

In some examples, the separation 5 between the first and second electrodes 3, 4 is between 60 millimetres (mm) and 100 mm. In some specific examples, the separation 5 is 80 mm. The separation 5 between the first and second electrodes 3, 4 may be constant, within acceptable manufacturing tolerances, along the length of the heating element 2. Alternatively, the separation 5 may vary along the length of the heating element 2 but may have an average of between 60 mm and 100 mm, or in some specific examples 80 mm. In some examples, the first and second electrodes 3,4 are not straight, as shown in Figure 1, but may have a kinked or curved profile on the resistive heating element 2. In such examples, the separation 5 between corresponding points of the first and second electrodes 3, 4 along the length of the heating element 2 may be constant.

The first and second electrodes 3, 4 may be connected to an electrical power source 7. The electrical power source 7 may be a battery. The battery may be a lithiumion polymer (LiPo) battery. The battery may have a voltage of between 3.7 and 14.8 V, for example 3.7 V, 7.4 V, 11.1 V or 14.8 V. In some examples, the battery has a capacity of between 2000 and 8000 milliampere hours (mAh). The battery may supply a direct current (DC).

When connected to the electrical power source 7, the first and second electrodes 3, 4 are of opposite polarity. Therefore, electrical paths across or through the resistive heating element 2 material are formed between the electrodes 3, 4. The distance of separation 5 between parallel electrodes 3, 4 of different polarity determines the resistance of electrical paths between the electrodes.

In some examples, the resistive heating element 2 material has a lower electrical resistivity in one direction than in another direction. In this specific example, the resistive heating element 2 material has a lower electrical resistivity a direction of separation 5 between the first and second electrodes 3, 4 than in a direction 6a, 6b in which the first and second electrodes 3, 4 run along the length of the heating element 2. Such a directional resistivity, or conversely conductivity, of the resistive heating element 2 material may be referred to as a “grain” of the material from which the resistive heating element 2 is made. The grain may be such that the resistive heating element 2 material is more conductive in the direction of separation 5 between the first and second electrodes 3, 4 than in some or all other directions.

In some examples, the resistive heating element 2 includes apertures 8 forming one or more strips 9. For example, the resistive heating element 2 may include a grating with a set of elongated elements or strips 9 separated by apertures 8. The apertures 8 may be cut out from a sheet or panel of the resistive heating element 2 material. Figure shows an example of the resistive heating element 2 having a plurality of strips 9 with lengths along the direction of separation 5 between the first and second electrodes 3, 4. In some examples, the strips 9 are regularly spaced along a length of the resistive heating element 2. In other examples, as shown in Figure 1, one or more larger apertures 8 (in this example the central aperture) increases the spacing between some adjacent strips 9. A larger aperture 8 may be used to alter where produced heat energy from the resistive heating element 2 is concentrated. For example, the resistive heating element shown in Figure 1 may be used as a kidney panel to heat the back of a wearer, specifically the kidney area, of a wearer of a garment that the heating system 1 is integrated into. The central larger aperture 8 may be positioned over the spine of the wearer, such that heat energy is not actively produced by the resistive heating element over the spine, but is instead concentrated either side of the large aperture 8, where the strips 9 are positioned. The areas either side of the large aperture 8 that include strips 9 may, for example, concentrate the heat energy produced by the resistive heating element 2 in areas where a muscle of the wearer is positioned. In other examples, the strips 9 and apertures 8 may be arranged to concentrate the heat energy produced in particular areas or locations on the wearer of a garment that the heating system 1 is integrated into.

In some examples, heating elements 2 are positioned at regions of high blood flow on the wearer’s body. This may give a more efficient heating effect on the core temperature of the wearer. These high blood flow regions may include the kidneys and the stomach. Regions with little blood flow may be avoided for heating element 2 placement, for example bony regions such as the shoulders, as the effect of increasing the core temperature of the wearer by heating these regions may be lower and/or heating of such areas may cause pain or discomfort to a wearer.

The apertures 8 may allow space for sweat evaporation from the wearer in examples where the heating system 1 is integrated into a garment. In the example resistive heating element 2 shown in Figure 1, the strips 9 are each 5 mm wide and 70 mm long, and the apertures 8 are each 70 mm long and 20 mm wide, except for the larger middle aperture 8 which is 40 mm wide. The density and sizing of the strips 9 and apertures 8 may be chosen to allow for a predetermined level of structural rigidity of the resistive heating elements 2 to be achieved.

In some examples, the resistive heating element 2 material has a lower electrical resistivity in a direction along a length of each strip 9 than in a direction along a width of each strip 9. For example, in the heating element 2 shown in Figure 1, the strips 9 are perpendicular to the first and second electrodes 3, 4, which run parallel to each other. In these examples, the material of the resistive heating element 2 may have a lower electrical resistivity, or a higher electrical conductivity, in a direction parallel to the length of the strips 9. This may lower the resistance of electrical paths between the electrodes 3, 4 via the strips 9. By having a lower resistance along the electrical paths, one or more other parameters of the heating system 1 may be altered. For example a run-time may be increased, an active heating area may be increased and/or a battery size may be decreased.

Referring now to Figures 2a and 2b, there is shown schematically an example of a garment with an integrated heating system 1. In this example, the garment is a coat

10. Figure 2a shows a back-view of the coat 10, while Figure 2b shows a front-view. The integrated heating system 1 may be an implementation of any example integrated heating system described herein, for example the example integrated heating system described above with reference to Figure 1.

In some examples, the heating system 1 integrated into the coat 10 includes a plurality of resistive heating elements 2, which may each be an implementation of any example resistive heating element 2 described herein. The example coat 10 with integrated heating system 1 shown in Figures 2a and 2b includes three resistive heating elements 2: two at the front of the coat 10 for heating a wearer’s chest; and one at the back of the coat 10 for heating the wearer’s back, specifically kidney area. The two heating elements 2 at the front of the coat 10 may each be referred to as a chest panel, while the heating element 2 at the back of the coat 10 may be referred to as a kidney panel. The resistive heating elements 2 may be integrated into the inside of the coat 10 to heat the skin of the wearer. For example, each resistive heating element 2 may be attached to a respective panel 11 and, in examples where there is a plurality of resistive heating elements 2, the plurality of panels 11 may be part of a harness 12 attached to the inside of the coat 10. The example harness 12 shown in Figures 2a and 2b comprises chest backing material for each of the front heating elements 2, kidney backing material for the back heating element 2, and shoulder backing material that forms straps for passing over the wearer’s shoulders when integrated into the coat 10.

As previously described, each resistive heating element 2 may be coupled to first and second electrodes 3, 4 which are connected to an electrical power source (not shown). In some examples, the integrated heating system 1 comprises first and second electrodes 3, 4 which are coupled to each resistive heating element 2, as shown in Figures 2a and 2b. One of the electrodes 3, 4 may have a positive electric potential, with the other electrode 3, 4 having a negative electric potential. In some examples, one of the electrodes 3, 4 may have a ground electric potential.

The connection from the battery (not shown) to the electrodes 3, 4 may be via respective tubular crimps 13, 14, each of which may accept a corresponding end of an electrode 3, 4 and may be closed by a crimping tool to form the electrical connection. The crimps 13,14 may be deformed and not cut when the connection is made.

A length of the heating element 2 may be a dimension of the heating element 2 in a direction along which the first and second electrodes 3, 4 may each run. A width of the heating element 2 may be a dimension of the heating element 2 in a direction of separation 5 between the first and second electrodes 3, 4. In some examples, each resistive heating element 2 has a length of between 50 mm and 300 mm, and a width of between 75 mm and 165 mm.

In a specific example, the resistive heating element 2 at the back of the coat 10 has a length of 250 mm, and a width of 120 mm. In the specific example the element 2 includes ten strips along the length of the element 2, each strip being 70 mm long and 5 mm wide. In the specific example, the apertures 8 between the strips 9 are each 70 mm long and 20 mm wide, except for a central larger aperture 8 which is 40 mm wide. In this specific example, the resistive heating elements 2 at the front of the coat 10, namely the chest panels, each have a length of 120 mm and a width of 105 mm. In other examples, the chest panels have a length of 105 mm and a width of 120 mm.

In some examples, the coat 10 comprises a closed-loop system configured to control a surface temperature of the resistive heating element(s) 2. For example, the closed-loop system may include one or more temperature sensors attached to the resistive heating element(s) 2. The temperature sensors may detect a surface temperature of the resistive heating element(s) 2 and feed this information to a controller. In some examples, the controller comprises one or more hardware and/or software components, for example a processor to execute computer-readable instructions stored on a memory. The controller may compare the detected surface temperature to a predetermined surface temperature value and adjust the amount of electrical power drawn from the electrical power source (e.g. the battery) based on the comparison. For example, if the detected surface temperature were lower than the predetermined surface temperature value, the electrical power input to the integrated heating system 1 may be increased so as to increase the surface temperature of the resistive heating element(s) 2. Conversely, where the detected surface temperature is determined to be higher than the predetermined surface temperature value, the electrical power input to the integrated heating system 1 may be decreased so as to decrease the surface temperature of the resistive heating element(s) 2.

In this way, the closed-loop system may be controllable to maintain a predetermined surface temperature of the resistive heating element(s) 2. For example, a user can set a desired temperature rather than a power input level, which may have little intrinsic meaning to the user. Such a closed-loop system would be sensitive to ambient temperature changes, allowing the user to set a comfortable temperature and rely on the closed-loop system. In some examples, the closed-loop system implements a cut-out temperature value feature, such that if the detected surface temperature of the resistive heating element 2 is above the cut-out temperature, the electrical power source is turned off. This may improve safety for the wearer in that he or she is not subject to surface temperatures above the cut-out temperature which can be set based on health and safety information. In some examples, the cut-out temperature is between 45 and 50 degrees Celsius. Heating the element 2 to a temperature hotter than 45 degrees Celsius may cause discomfort for the wearer, and can leave temporary marks on the wearer’s skin.

In some examples, the closed-loop system may be controllable by a radio frequency (RF) interface. The RF interface may include a Wi-Fi® or Bluetooth® interface. In some examples, the wearer can set a predetermined surface temperature value for one or more of the resistive heating elements 2 using a Wi-Fi® or Bluetooth® enabled device, such as a smart phone, which wirelessly communicates the value to the closed-loop system via the RF interface.

Referring to Figure 3, there is shown schematically an example of a method 30 of making an active heating garment. An active heating garment is a garment that has an integrated, active heating system.

At item 31, a garment is provided. For example, the garment may be a conventional coat.

At item 32, a resistive heating element comprising a material having an electrical sheet resistance of less than 23 Ω/sq. is provided. In some examples, the resistive heating element provided at item 32 comprises a material having an electrical sheet resistance of at least 10 Ω/sq., for example of between 15 and 16 Ω/sq.

At item 33, first and second electrodes are coupled to the resistive heating element. In some examples, item 33 comprises stitching the first and/or second electrode to the resistive heating element. The first and/or second electrode may comprise a flat-braided electrode, and item 33 may therefore include stitching the flatbraided electrode(s) to the resistive heating element.

At item 34, the resistive heating element, and the first and second electrodes are integrated into the garment. In some examples, this comprises attaching the resistive heating element to a panel, for example a textile blank, and sewing or otherwise attaching the panel to the interior or lining of the coat. In such examples, the resistive heating element is be secured between the panel and the coat. In examples where a plurality of resistive heating elements are provided for integrating into the coat, the resistive heating elements may each be attached to a respective panel, with the panels joined together to form a harness, which can be sewn or attached into the coat interior or lining. In these examples employing a harness, material for joining the panels may be used to integrate the electrodes into the coat by sewing at least part of the joining material to the inside of the coat and trapping the electrode(s) between the material and the coat interior. In other examples, item 34 may comprise integrating the resistive heating element into an internal pocket of the coat.

In some examples, the method 30 includes electrically connecting the first and second electrodes to an electric battery, for example via the electrodes and/or a tubular crimp, as described above. The electric battery may also be integrated into the coat, for example by mounting onto a textile panel or blank, and attaching the panel or blank the interior or lining of the coat. In other examples, the battery is integrated into the coat by placing it in a pocket of the coat. This may allow the battery to be more easily accessed by the wearer, which may allow the user to access the power supply of the battery (for example to replace it).

The items 31 to 33 of method 30 may occur in any order. For example, the garment and resistive heating element may be manufactured at different locations and provided separately prior to integrating them at item 34. The electrodes may be coupled to the resistive heating element (item 33) prior to, or after, the garment is provided (item 31).

Various measures (for example apparatuses and methods) are provided in which a garment with an integrated heating system includes a resistive heating element comprising a material having an electrical sheet resistance of less than 23 ohms per square. As described above, this allows operation of the heating system to be improved. For example, one or more operating parameters can be adjusted as a result of using a relatively low electrical sheet resistance value.

In some examples, the material of the resistive heating element has an electrical sheet resistance of at least 10 ohms per square. This may allow the resistive heating element to not be too rigid, for example due to a higher density of electrically conducting members in the material, while providing heating effects associated with a lower electrical sheet resistance. The material of the resistive heating element may have an electrical sheet resistance of between 15 and 16 ohms per square as a balance between the effects, on the heating performance and the rigidity of the material, of making the material more conductive.

In some examples, the garment comprises a braided nickel plated copper electrode coupled to the resistive heating element. The nickel plating may reduce the overall rate of damage to the copper braid, while being less prone to rusting compared to other plating materials such as tin.

The braided nickel plated copper electrode may be flat-braided. This may provide a more reliable coupling between the electrode and the resistive heating element than using a rounded electrode, for example by increasing a contact area between the electrode and the resistive heating element. This can decrease the likelihood of the electrode and resistive heating element becoming decoupled.

In some examples, the heating system comprises first and second electrodes coupled to the heating element. The first and second electrodes each run along a length of the heating element with a separation between them such that an electric current can flow between them. This allows electricity to be conducted through the resistive heating element between the electrodes, so that the resistive heating element heats up via resistive heating.

In some examples, the resistive heating element material has a lower electrical resistivity in a direction of separation between the first and second electrodes than in a direction that the first and second electrodes run along the length of the resistive heating element. This may improve the efficiency of the resistive heating element, as electricity is conducted more easily between the electrodes (due to a lower resistance in the direction of separation between the electrodes).

In some examples, the garment comprises a closed-loop system configured to control a surface temperature of the resistive heating element. This may allow the wearer to set a desired surface temperature, or electric power level, for the heating system to reach or operate at. For example, the closed-loop system may be controllable to maintain a predetermined surface temperature of the resistive heating element. The closed-loop system may also be sensitive to ambient temperature changes, which may allow the wearer to set a desired temperature, and for the heating system to require no further attention to its operation. The closed-loop system may be controllable by a radio frequency interface, so that the wearer can control temperature or power settings wirelessly. This may allow the heating system to be more concealed within the garment and/or attached more securely therein to reduce the chances of electrical disconnections, as adjustment of the heating system may not involve physical adjustment thereof by the wearer, for example to adjust the temperature of power settings.

In some examples, the garment is a coat. The garment being a coat may allow an overall larger area of the wearer to be heated, compared to other garment types. Furthermore, compared to other garment types, coats may be made of a material that has a relatively high level of thermal insulation meaning that heat applied to the wearer by the heating system is more effectively trapped by the coat material, thereby increasing the efficiency and effectiveness of the active heating system.

Various measures (for example apparatuses and methods) are provided in which a heating system, for integrating into a garment, includes a resistive heating element comprising a material having an electrical sheet resistance of less than 23 ohms per square.

Various measures (for example apparatuses and methods) are provided in which a garment comprises a heating system, the heating system having a resistive heating element and a closed-loop system configured to control a surface temperature of the resistive heating element.

Various measures (for example apparatuses and methods) are provided in which a garment comprises a heating system, the heating system including a resistive heating element and a flat-braided electrical conductor coupled to the resistive heating element. The flat-braided electrical conductor may be formed of nickel plated copper.

In some examples described above, the material of the resistive heating element has a surface resistance of less than 23 ohms per square. In accordance with some examples described herein, for example a garment comprising a heating system including a closed-loop system, a flat-braided electrical conductor, and/or a resistive heating element with a lower electrical resistivity in a direction of separation between first and second electrodes than in another direction, the material of the resistive heating element may have a surface resistance of greater than or equal to 23 ohms per square.

The above embodiments are to be understood as illustrative examples. Further embodiments are envisaged.

In examples described above, the garment with an integrated heating system is a coat. However, in other examples, the garment is another type of outer garment such as a jacket, fleece, blazer, gilet, waistcoat, shirt, trousers, or shorts, or another type of garment such as a pyjama top and/or trousers, gown, dressing gown, bathrobe, underwear, sleeve, scarf, hat, gloves, footwear, shoes, or a garment for an animal.

Although in examples above, the heating system is for integration into a garment, in other examples the heating systems described herein may be integrated into other types of object, for example furniture, car seats, blankets, and duvets.

It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.

Claims

1. A garment with an integrated heating system including a resistive heating element comprising a material having an electrical sheet resistance of less than 23 ohms per square.

2. A garment according to claim 1, the material having an electrical sheet resistance of at least 10 ohms per square.

3. A garment according to claim 1 or 2, the material having an electrical sheet resistance of between 15 and 16 ohms per square.

4. A garment according to any preceding claim comprising an electrode coupled to the resistive heating element.

5. A garment according to claim 4, wherein the electrode comprises a nickel-plated copper electrode.

6. A garment according to claim 4 or 5, wherein the electrode comprises a flatbraided electrode.

7. A garment according to any of claims 4 to 6, wherein the electrode is a first electrode, the heating system comprising a second electrode coupled to the heating element, wherein the first and second electrodes each run along a length of the heating element with a separation between the first and second electrodes such that, in use, an electric current flows between the first and second electrodes.

8. A garment according to claim 7, wherein the resistive heating element material has a lower electrical resistivity in a direction of separation between the first and second electrodes than in a direction in which the first and second electrodes run along the length of the resistive heating element.

9. A garment according to any previous claim, comprising a closed-loop system configured to control a surface temperature of the resistive heating element.

10. A garment according to claim 9, wherein the closed-loop system is controllable to maintain a predetermined surface temperature of the resistive heating element.

11. A garment according to claim 9 or 10, wherein the closed-loop system is controllable by a radio frequency interface.

12. A garment according to any previous claim, the garment being a coat.

13. A garment comprising a heating system, the heating system having a resistive heating element and a closed-loop system configured to control a surface temperature of the resistive heating element.

14. A garment comprising a heating system, the heating system including a resistive heating element and a flat-braided electrical conductor coupled to the resistive heating element.

15. A garment according to claim 14, wherein the flat-braided electrical conductor is formed of nickel-plated copper.

16. A garment comprising a heating system, the heating system including a resistive heating element and a plurality of electrodes coupled to the resistive heating element, wherein the resistive heating element material has a lower electrical resistivity in a direction of separation between the first and second electrodes than in a direction in which the first and second electrodes run along the length of the resistive heating element.

17. A method of making an active heating garment, the method comprising: providing a garment;

coupling first and second electrodes to the resistive heating element; and integrating the resistive heating element and the first and second electrodes into 5 the garment.

18. A heating system for integrating into a garment, the heating system including a resistive heating element comprising a material having an electrical sheet resistance of less than 23 ohms per square.