GB2414910A - Integrated heat generating membrane - Google Patents

Abstract

A heated membrane comprises a random dispersal of waste carbon fibre ends that are well coated with carbon over the entire surface of a PVC base eg polyester which forms the heated membrane element. The element, an insulating seal and weather shield may be incorporated into a laminated structure which may additionally include a conductive earth shield. The laminated membrane may be slotted to for a zig-zag conductive path and conductive strips form busbars for the element. Uses include underfloor heating, heated garments, flash water heating and deicing roads, runways tanks, ship's rigging etc.

Description

Sheet No 1

INTERGRATED HEAT GENERATING MEMBRANE

The invention relates to a heated membrane, or more accurately an integrated heater.

Heated membranes are well known in aerospace and use conventional trace wires enclosed in a suitable outer skin. Typical applications are tracers along pipes, anti icing Heaters on aircraft wings, gate valve heated cover and the most popular of all the electric blanket. Homes are getting smaller the walls are covered with pictures, mirrors, cupboards and shelves. We then need to site radiators and furniture, a headache for anybody and everybody.

But say the heating was under your feet or hidden in the wall the flexibility it releases is surprising. Coverings are no longer cold to touch. Up to the time of the present invention under floor heating or wall has been mainly water filled or ribbon element fitted below the floorboards or within the cavity through which the heat must permeate before you can receive the benefit.

There is a serious drawback to this technique and that is the delay caused by the temperature change in the heat source and that of the room can be so slow that an oscillation condition can and does occur. This is where the room is neither warm enough nor cool with the ideal point being a momentary condition as it passes from one state to the other.

According to the present invention there is provided a continuous veil type membrane that conducts over the entire surface. The invention offers a very short thermal path, giving high energy efficiencies and tight thermal control. The walls can also be configured as radiators using the same process where carpeted floors are to the taste of the occupants, or a combination of the two. The shape of the membrane is rectangular with carefully measured sides, as in all rectangles there are two equal short sides and two equal long sides. Across the edges of the two shorter sides there is a Bus Bar that provides a means of connection across the width of the membrane. (Note that there are two Bus Bars one each end). This principle of carefully measured shapes will change the configuration and the Bus Bars will remain at each end but the rectangle shapes will Zig Zag.

The make up of the membrane is of waste carbon fiber ends that are well coated in carbon and randomly dispersed over the entire surface of the PVA base. The weight of the carbon fiber is the indicator that is directly related to the resistivity and conductivity of the material. The formation of the membrane is Carbonized PAN non woven multidirectional. The flow direction of manufacture provides two distinct levels of resistance the higher resistance being across the direction of flow, both directions are used in the manufacture of the heated membrane with the across direction allowing the manufacture of smaller panels. The ratio of resistivity between 'with' flow and 'across' flow is an overall increase of 50% measured in ohms across flow. i

Sheet No 2 The BUS Bars are generally copper and of good conductivity coated with conductive glue to ensure a good electrical connection between the BUS bars and the surface of the membrane.

The specific embodiment of the invention is described both in text and drawings, the conductive part described above is then encapsulated within two other membrane with suitable electrical connectors attached to one end of each of the Bus bars that feed the electrical energy into the membrane. The electrical supply can be A.C or D.C with the supply voltage depending on the overall dimensions of the membrane. The overall surface area also dictates the heat distribution across the membrane.

The drawing fig. 1 (not to scale) illustrates the membrane size, suitable supply voltage that will allow the membrane to heat up to a maximum temperature of 70 degrees C. The membrane temperature is however controlled to peak at 37 degrees C. This 2.7meter by I meter heated membrane provides a 3.5 by 3.0 by 2.8 high room with an ambient temperature of 21 degrees C when installed as an under floor heating device. When used in floors the surface temperature can be adjusted between 27 degrees C and 37 degrees C depending on the floor surface material. A ceramic tile floor would be best at 37 degrees C whilst a vinyl floor would be best at 27 degrees C. For ease of description the unit length dictates voltage and the unit width dictates amperage. It should be fully understood that this invention is not limited to of rice and home applications, it can be extended to de icing important roads, runways, rigging on ships, fuel oil tanks, industrial drying, in fact anywhere a tight thermal temperature source is required over a large surface area.

Producing a heat source of this kind is not the total solution unless the heat is directional; having a high percentage of the valuable energy lost in the structure of the floor or wall is

not acceptable.

To this end a thermal barrier applied to the back of the element ensures the heat source has only one direction to go. This exhibits very little undesirable losses reflecting all the heat forward from the thermal surface, transferring by contact to the finishes applied to these heated surfaces. The result is a very efficient heating solution in relation to cost, control, and application.

Due to the ability to shape and sculpture complicated shapes it allows the product to be used in garments such as gloves, bibs, coats as well as many applications in both medical and vet nary. Sometimes more complicated shapes are required for the construction industry in bathrooms, toilets and kitchen applications.

Sheet No3 According to the present invention the power supply can be AC or DC. The AC version derives the power from the 230/240 mains. Depending on unit area the voltage is 48 volts up to 250 volts. The unit is safe and can be used under a range of floor finishes. It can be subjected to, nails through the membrane with minimal effect on the performance. The basic element used for the development and that described thus far is a monolithic resistive unit that requires the connection of the correct number of elements arranged in series. Although inventive and simple it is to some extent restrictive. That is to say that the basic product design precludes the application of this invention to small areas. It is seen as important to be able to manufacture a mat A4 size working off 230/240 AC mains supply.

A further part of the invention is to achieve the small size A4 by profiling the individual elements, so as to achieve a single "tile", which is able to operate at up to 70 degrees C. This allows the invention to be used for a limitless number of configurations of heated areas exceeding that of a single tile just by expanding the formula..

By taking small pieces of the material each reduced in length by a particular amount with equal reductions from one to the next the current is forced to take a zig zag path from one element connection to the other, the whole resistance adding up to the same resistance as the larger mat described earlier, now we have a tile of A4 dimension dissipating the same amount as a measured area as the 8 sq meter mat. This is a way of building a multiple layer path resistive element that can take many forms, but the cost effective solution is the cheapest engineering process rather than the best process as an aesthetic form.

Method one is to stack a large number of potential elements on top of each other and take a very fine router and cut slots in predetermined positions through all of them. Cutting being made easier by placing the stack under compression to ensure a clean cut, the powder created by the cut would need to be vacuumed away safely from the workface.

(Carbon fiber ends can be potentially dangerous).

Method two a punch could be used to punch out the sheets in singles or multiples, this method is less likely to generate dust.

Method three is by roller cutting, this works well for small runs but the hardness of the fibers calls for high pressure and the cutter wear could become troublesome.

The end result is that a new element profile has been created that when coupled to a sensor control system heats up. That gives the operator the ability to control the temperature of the actual element to within one degree (Centigrade) from ambient to say degrees C; this part of the invention is for clothes and incubators where accurate temperature control is paramount. All this is achieved via just two wires connected to the elements, the control electronics doing the rest.

Sheet No 4 A further embodiment of the invention is a tightly wound membrane that is inserted into a suitable tube and arrange such that water can pass through. The water temperature being under critical control and dispensed at a pre determined temperature at a suitable rate for the application, it is in fact a Flash Heater The same unit can be powered from 120 volt AC supply as in the USA and will function in the same way.

The unit is not limited to use under floors it can also be used in walls providing heat around rooms without the need for radiators that take up wall space.

Installation is simple and can just be placed under a carpet or just under the floors finished surface obviating the need for digging up concrete or lifting floor boards.

Sheet No 5

MAKEUP

The make of the membrane is as previously described but the carbon waste fibers of approximately 8 to 10 mm in length and.001 mm in diameter are dispersed evenly and monitored for overall thickness by an electronic sensor, the polyester carrier is used to arrest the fibers. The width determines the current that determines the watts output for a given surface area. The length determines the voltage. Having made the part that will be fed the power the next stage is to ensure that both sides of the membrane are further protected by adding two further membranes top and bottom. Before laminating the two copper Bus Bars are secured at each end to ensure even distribution of power across the entire membrane. Suitable connectors with appropriate size wires carry the power into the membrane. Attached to the surface of the membrane is a thermo sensor that feeds temperature information back to the controller.

With the heated membrane laminated and either glued or heat sealed the unit that produces the heat is finished. This is the first and most simple version.

The other important part is the controller. This has a number of functions; l. Temperature of the membrane surface is pre programmed.

2. Clock timer controls off/on function and can be programmed for three off and on functions 3. Room temperature stat 4. Internet access providing remote control (Note that the control unit for domestic applications has been adapted for use with the invention and no claims are made or intended that this is part of the invention) The controllers for Industrial and commercial applications are the subject of other patent and copy write claims. The choice of Power Supplies includes switched mode isolated power supply that provides from 48v up to 1 1 Ov DC, alternatively an I 1 Ov centre tapped transformer AC supply. The elements can be designed to work off any 12 volt to 48 volt DC supply as found in a vehicle or flying machine. A very simple version can run direct off any AC power supply, the later having screen protection and isolator earth trip. The final version power control is three phase with cross phasing for lengths exceeding 40 meters in 1 meter widths.

The second and more sophisticated version employs new Zig-Zag Technology that in turn employs profiling programs and coding technology. Zig-Zag element profiling allows a monolithic element to support a higher voltage; the current takes a longer route by the introduction of slots and holes in the element material. Current in the element acts, as water in a collection of runners and the voltage is analogous to the slope between inflow and outflow points. If the current is too high then the element will get excessively hot. So the art of element profiling is in getting the current through the element to be low enough not to thermally run away when the voltage is applied over a long period.

Sheet No 6 Makeup continued.

To achieve this it is important to take account of the current density in the working installations and implement the same density per square centimeter in the profiled element.

The uniqueness of this technology is that it uses the elements themselves as sensors; this makes it possible to control a number of thermal sources, in fact a whole new spectrum of applications utilizing an almost zero cost control solution to achieve a new value added product range.

Claims (8)

Sheet No7 Claims.

1. A heated membrane that is the centre laminate of a composite consisting of 2 numbers of additional layers of non woven, a conductive top a composite of 2 numbers of additional layers of non woven with a conductive surface shield layer and a breather layer resulting in a total of 5 layers all glued or heat sealed to form the composite.

2. A heated membrane as in claim 1 that is the centre laminate of top surface shield layer resulting in a total of 4 layers all glued or heat sealed to form the composite.

3. A heated membrane as in claim I that is itself a thermal sensor.

4. A heated membrane as in claim 1 that is the centre laminate of a composite consisting of 2 numbers additional layers of non woven with a conductive top surface layer with additional waterproof layers top and bottom resulting in a total of 6 layers all glued or heat sealed to form the composite.

5. A heated membrane as in claims 1 through to 4 that can be sculptured to enable infinite sizing of the product. (We refer to this as Zig-Zag technology in the text)

6. A heated membrane that when rolled up tightly and inserted into a suitable alkathene pipe will act as a flash heater for water passing through the pipe..

7. A method claim in respect to the methods used to obtain the mathematical relationship that provides the sculpture or cut out requirements to match shape and size to supply voltage and current draw.

8. A conductive material manufactured from carbon fiber short end waste product using the manufacturing system PAN non woven multi- directional with a PVA binder and referred to as the heated membrane in claims 1 through to 7.