GB2447287A - Cooling sheet with internal fluid flow conduits - Google Patents

Abstract

A flexible sheet 1 contains flexible fluid-carrying conduits 2 which connect to a temperature regulation device 7 and a pump. Preferably the conduits are surrounded by a gel 4 containing glycol or glycerine which conducts heat to or from the conduits and cushions them. A watertight outer casing 5 holds the gel in place. The conduits may be plastic tubing which extends through the interior of the casing arranged in a series of loops 3 and is connected by inflow and outflow tubes 6 to a regulation device containing two thermoelectric Peltier devices having their faces in opposition. A water-based heat transfer fluid is cooled or heated by the devices and pumped through the tubing. The sheet may be used as a cooling (or warming) blanket for a bed (figure 4), to cool a car seat (figure 5), to cool a pet animal's bed (figure 6) and to wrap round all or part of a patient requiring local or general control of body temperature.

Description

PERSONAL TEMPERATURE CONTROL DEVICE

The present invention relates to a device for cooling, warming or generally controlling the temperature of a human or animal body. More particularly but not exclusively, it relates to a flexible laminar device adapted to cool or warm the body or parts thereof.

While the primary purpose of the temperature control device is for cooling, as will be more particularly described, it may also be used for warming or for maintaining a controlled constant temperature for the body, whatever variations in ambient conditions may occur.

There are many situations in which one might wish to cool all or part of one's person. This may be for reasons of comfort, or may be necessary for reasons of health.

In the British summer, or for much of the year in warmer climates, ambient temperatures may be too high for comfort. While fans, air conditioning and the like may bring some benefits, they will not help the discomfort of sitting in an overheated seat for prolonged periods (e.g. in an office or in a motor vehicle), nor of lying in an overheated bed (whether sleeping or confined to bed by sickness, etc).

Pet animals, particularly those such as dogs which can only pant and not sweat, suffer similar or even greater discomfort.

Many people, particularly women above a certain age, experience variations in body temperature (so-called "hot flushes"), and so may feel uncomfortably warm even at relatively low ambient temperatures.

A common palliative for minor ailments such as muscle strains, neck ache, inflammations, headaches, sinus problems, hay fever and so forth is the topical application of a pad or bag of pre-cooled material (for example, a pouch of gel having high thermal inertia, or even in exiremis a bag of frozen peas). For this, one must have a refrigerator in which to cool the pad, etc, before use; one must have started to pre-cool the pad well beforehand; and one must provide replacement cooled pads for when the original has warmed up to room temperature.

One has little control over cooling rates or how far cooling proceeds. This form of treatment is not particularly convenient, therefore, particularly when required for prolonged periods.

In more life-threatening situations, it may also be important to keep body temperature from rising too high over a prolonged period. Sunstroke victims, and persons running a high fever, may have their body temperature lowered in the short term by immersion in ice baths, for example, but these are hardly practical over longer periods.

Babies and toddlers are particularly at risk, whether from high body temperature or high ambient temperatures, as they may suffer high temperature convulsions, which are potentially life-threatening.

As a general rule, normal human body temperature is around 37 C, while skin temperature is around 32 C. Sweating sets in as the skin temperature reaches normal body temperature. At a body temperature of 40 C or more, disorientation sets in, followed by symptoms such as fainting, weakness and breathlessness. Convulsions set in at a body temperature of 42 C or more, and a body temperature of over 44 C is frequently fatal. The body's own thermoregulatory mechanisms will begin to fail above about 4 1 C, leaving it unable to reduce body temperature without external help. The thermoregulatory systems of babies are believed to be less effective than those of adults, hence their increased susceptibility to heat- induced convulsions.

Where there is a need for cooling, however, there may be risks involved with excessive cooling, particularly where thermoregulatory mechanisms are impaired. In such situations, the ability to cool and to warm, so as to maintain a desired temperature, would be desirable.

Burns victims are another class of patient who may suffer from extreme sensitivity to heat, particularly through direct contact with the skin.

In opposite circumstances, where only heating is necessary, conventional electric blankets or the like are convenient, controllable, easily transportable, simple to use and rapidly effective.

However, there has until now been nothing as good where cooling is required.

It is hence one object of the present invention to provide a means of cooling the human or animal body that obviates the above disadvantages, is simple to set up and use, is rapidly effective yet suitable for use over prolonged periods if necessary, and which ideally does not require expensive, large and power-hungry equipment to make it work. It is a further object to provide such a means that is also capable of warming andlor maintaining a body temperature.

According to the present invention, there is provided a personal temperature control device comprising a laminar body adapted to contact a portion of a human or animal body to be cooled or warmed, one or more substantially flexible conduit means passing therethrough or adjacent thereto, means to alter a temperature of heat transfer fluid and pump means to pass said heat transfer fluid through said conduit means.

Preferably, the laminar body is flexible.

The flexible laminar body may comprise sheet means, blanket means, wrap means or the like.

The laminar body preferably comprises a cushioning medium surrounding the conduit means.

Advantageously, said cushioning medium is adapted to conduct heat to or from the conduit means.

Said cushioning medium may comprise a gel medium, for example an aqueous gel medium.

Said gel medium may comprise a polyol, optionally glycerol or propylene glycol.

Said gel medium may comprise a water-soluble polymer, such as a poly(ethylene glycol) compound.

The laminar body may be provided with watertight envelope means surrounding the cushioning means.

Said envelope means may comprise a flexible plastics material, optionally a hypoallergenic plastics material, for example surgical grade poly(vinyl chloride).

Said envelope means may comprise a woven textile material, coated or impregnated with a flexible plastics material.

The envelope means may be provided with removable cover means.

The cover means may comprise a textile material.

The cover means may be washable.

Optionally, the envelope means may comprise at least a surface layer of a material adapted for contact with damaged skin, for example for use in contact with the body of a burns victim.

Preferably, the heat transfer fluid comprises water.

The heat transfer fluid may comprise an additive to depress its freezing point, such as an alcohol.

Preferably, the means to alter the temperature of the fluid comprises solid-state cooling means.

Advantageously, the solid-state cooling means comprises at least one Peltier device.

The solid-state cooling means may comprise at least one pair of Peltier devices, so disposed that respective coolable faces of the or each pair of Peltier devices are in spaced opposition.

The or each conduit means may then pass between the opposed coolable faces of the or each pair of Peltier devices.

Each Peltier device is preferably provided with heat sink means.

The heat sink means may comprise an array of planar heat conducting elements extending outwardly from a face of the Peltier device opposite to the coolable face thereof.

Optionally, a direction of current flow through the Peltier device or devices may be reversible so that the coolable face(s) thereof become warmed, warming the fluid in the conduit means.

The personal temperature control device may be selectably operable as a personal warming device.

The personal temperature control device may be adapted so to switch between a cooling action and a warming action as to maintain substantially a selected temperature.

The personal temperature control device is preferably provided with a temperature adjustment unit comprising the cooling means, the pump means and control means for the personal cooling device.

The device may be provided with temperature sensing means, optionally thermostat means.

The device may be provided with a mains electrical power supply, optionally operatively linked to transformer means of the device.

Alternatively or additionally, it may be provided with electrical battery means, optionally rechargeable battery means.

The personal temperature control device may be dimensioned to be wrappable around a portion of the body.

Alternatively, it may be configured to be mountable to a body contact area of a bed, seat or the like.

Embodiments of the present invention will now be more particularly described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a schematic partial cutaway perspective view of a first cooling sheet embodying the present invention; Figure 2 is a scrap cross-section of a Peltier device cooling arrangement as used in embodiments of the present invention; Figure 3 is a partially sectioned perspective view of a cooling unit of the cooling sheet shown in Figure 1; Figure 4 is a perspective view of the cooling sheet shown in Figure 1, in position on a bed; Figure 5 is a perspective view of a second cooling sheet embodying the present invention in position on a car seat; Figure 6 is a perspective view of a third cooling sheet embodying the present invention, on a dog bed; Figure 7 is a schematic perspective view of a fourth cooling sheet embodying the present invention; and Figure 8 is a scrap cross-section of part of the cooling sheet shown in Figure 7.

Referring now to the Figures, and to Figure 1 in particular, a first cooling sheet I contains a Continuous length of semi-flexible plastics tubing 2, arranged in a series of generally parallel loops 3 extending generally from end to end of the sheet 1. The tubing 2 is embedded within a layer 4 of an aqueous gel material, here shown partially cut away for clarity. The layer 4 of gel material acts as padding, so that someone resting on the sheet 1 cannot feel the loops 3 of the tubing 2, and so that their weight does not compress the tubing 2 closed, It also helps to keep the loops 3 in position, neatly spaced apart across the sheet 1. The gel layer 4 is sealed within a watertight casing 5 of a flexible, soft allergen free plastics material, here surgical grade poly(vinyl chloride). (The casing 5 is also shown partially cut away, for clarity).

The first sheet I thus has an appearance of a fairly thick plastics sheet, which, as shown, is sufficiently flexible to conform generally to a desired shape. A removable, washable textile cover, for example of cotton, may be provided if desired.

The tubing 2 within the cooling sheet I continues as an inflow and an outflow tube 6, each extending from an edge of the sheet 1 to a cooling unit 7. The cooling unit 7 is connected by a cable 8 to a mains electrical power supply (other embodiments may be battery powered).

En operation, the cooling unit 7 (an internal mechanism of which is shown below) cools a working fluid, usually water or water containing a polyol such as glycerol or propylene glycol or other additive to lower its freezing point, and pumps it along an inflow tube 6 to the tubing of the sheet 1. Here, the cooled fluid picks up heat from the gel layer 4 as it passes along the array of loops 3. The gel layer 4 significantly improves thermal contact and transmission between the cooled loops 3 and a surface of the sheet 1. (The composition of the gel 4 is selected both for this and for safety in case of leaks. A gel based on water and propylene glycol and/or glycerol, optionally thickened and/or gelled with high molecular weight poly(ethylene glycol) additives, is believed to be suitable). The sheet I as a whole is thus cooled over substantially its whole area to a temperature significantly below ambient.

The working fluid then passes back along the outflow tube 6 to the cooling unit 7.

The cooling unit 7 is provided with controls 9, with associated operation indicator lights 1 0, which allow a desired temperature, or a desired temperature drop, to be selected. The cooling unit 7 is also provided with thermistor temperature sensors to monitor the temperature of the working fluid, linked to an automatic cut-out, which operates if the temperature falls so low as to risk discomfort or harm to someone using the cooling sheet 1.

The preferred method of cooling the working fluid within the cooling unit 7 is to employ a pair of Peltier devices II, as shown in Figure 2. Each Peltier device 11 comprises a first 12 and a second 13 ceramic plate, holding between them an array of bismuth telluride (Bi2Te3) cuboids 14. These cuboids 14, or "couples", have the property that when a direct electrical current is passed across them, one side of the cuboid 14 heats up and the other cools. Thus, when a direct current is passed in the appropriate direction between the ceramic plates 12, 13, through the cuboids 14, the first plate 12 is cooled and the second plate 13 heats up.

Thus, if two Peltier devices 11 are arranged with opposing respective first plates 12, a zone between the Peltier devices 11 will also be cooled significantly. The inflow and outflow tubes 6 each extend through this region 15, ensuring that the working fluid within them is cooled on its way into and out of the cooling unit 7. In practice, the region 15 may be filled with a heat conductive block (e.g. of aluminium) provided with bores to receive the tubes 6, or another heat conducting medium, although this is not shown in the Figures for clarity.

To prevent heat building up in the second ceramic plate 13 of each Peltier device 11, a heat sink comprising an array of parallelly-extending metal vanes 16 is mounted thereto. This allows excess heat to be dissipated away from the Peltier devices 11.

Peltier devices 11 have several advantages over conventional refrigeration systems, such as those used in domestic refrigerators. They have no moving parts, correctly-sized heat sink vanes 1 6 obviating the need for a fan or the like to dissipate heat extracted from the working fluid. Unlike conventional refrigeration systems, they are very quiet on start-up and when they cycle on and off, and there is no vibration during operation. No chiorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), ammonia or other such conventional refrigerant is required. Peltier devices can be made very compact, are robust and have long operating lives. The temperature produced can be regulated precisely by adjusting the current passed between the plates 12, 13, (e.g. using feedback from a thermistor), and the cooling effect starts very rapidly. Indeed, an achievable rate of temperature drop may limited merely by the need to avoid sudden thermal contraction effects within the Peltier device 11.

If the direction of the current across the Peltier device 11 is reversed, the first plate 12 will heat up and the second plate 13 cool down. It can thus potentially be used to warm the working fluid, allowing the cooling sheet I to be used instead as a warming sheet, if desired.

It is thus possible to operate the sheet I to produce a controlled temperature, using data from a temperature sensor to operate the Peltier device 11 in a warming or a cooling mode as necessary to achieve a preselected temperature adjacent the sheet 1. Thus, one could cool a body part to a therapeutic degree without risk of over-chilling or even frostbite. One could also maintain a bed at a comfortable temperature in varying ambient conditions.

Although other cooling systems may be used in place of the Peltier devices 11 shown, if preferred, it is believed that in most applications they will be the most effective option.

The cooling unit 7 is shown in more detail in Figure 3, with its casing 17 shown sectioned to reveal its internal structure. The inflow and outflow tubes 6 pass between the two Peltier devices II to an electric circulating pump 18, so that the working fluid returning from the sheet I is cooled both on entry into the cooling unit 7 and as it is pumped back towards the sheet 1.

Since Peltier devices 11 operate on direct current, a transformer may be provided within the cooling unit 7 to convert an alternating current mains supply. An external transformer may be used instead, for example one integral to a mains plug.

To permit heat dissipated from the Peltier devices 11 by their heat sinks 16 to leave the casing 1 7, it is provided with a series of vents 19 (shown in Figure 1 but omitted from Figure 3 for simplicity). A fan (not shown) may be provided to pass air over the heat sinks 16, to speed heat dissipation.

Figure 4 shows a particularly useful application for the cooling sheet 1. Here, a bed 20 has been fitted with a cooling sheet 1, located between a mattress 21 and conventional bed linen 22 (here shown partially turned back to display the cooling sheet I). Thus, someone sleeping in the bed 20 can not only dispense with some or all of the bed linen 22 to keep an upper surface of her or his body cool on hot nights, but also maintain a lower surface of her or his body at a comfortable temperature. Conversely. on cooler nights, the same sheet I may be operarated to take the chill off the bed 20 or to keep it warm through the night. Also, as mentioned above, with data from appropriate temperature sensors, one may set a desired temperature and allow the sheet 1 to warm or cool as necessary in order to maintain that temperature.

Note: while the inflow and outflow tubes 6 are shown as extending a considerable distance beneath the bed 20, this is to demonstrate the principle of operation. In practice, these tubes 6 would probably be shorter, and may also be provided with an insulating sleeve to prevent the working fluid warming up appreciably before it reaches the sheet 1.

The cooling sheet I mounted to a bed 20 will be of particular benefit for those confined to bed for long periods by health problems, and to those with particular sensitivity to heat (e.g. sufferers from sunburn or other mild or partially healed burns, toddlers, babies, or those with variable body temperature). A cooling sheet with a surface adapted or treated to prevent adhesion may be of use to cool recently burnt tissue.

A second cooling sheet 23 is shown in Figure 5, in position on a car seat 24. The second cooling sheet 23 is constructed so that it can be mounted to both a back portion 25 and a seat portion 26 of the car seat 24. (The cooling unit 7 and inflow/outflow tubes 6 of the second cooling sheet 23 are not shown for simplicity). The cooling unit 7 may be hard-wired into an electrical system of the car, may have a power plug insertable into a "cigar-lighter" socket on a dashboard of the car, or may be battery powered. Various conventional attachment arrangements (e.g. straps, poppers, or hook and loop fastening fabric) may be used to mount the second sheet 23 to the seat 24, or it may be incorporated into the seat 24 during manufacture. Similar arrangements may be used for office or domestic chairs.

Figure 6 shows a bed 27 for a dog or other pet animal, provided with an appropriately-sized third cooling sheet 28 lining its floor. Thus, an animal may sit or lie in the bed 27 in hot weather to keep cool, rather than having to pant profusely.

Smaller versions of the cooling sheets shown may be used to cool a particular part of the body, for example an inflamed area or an area in pain. For example, they could be wrapped round an aching neck or feet, applied to the face of a sufferer from hay fever or sinus problems, or to the forehead of a migraine sufferer.

In each case, they would be superior to existing treatments using gel pouches and the like, pre-cooled in a refrigerator. Little or no preparation is needed, and the cooling sheets will work for as long as is needed, whereas the gel pouches will warm up in use and need to be replaced, with fresh cooled pouches. With such gel pouches, one has little or no control over the rate of cooling or how cold one becomes.

Figure 7 shows a fourth cooling sheet 29, designed as a "proof of concept" model. This cooling sheet 29 has an outer casing 30 of a woven cotton textile material coated with a flexible plastics composition, such as plasticised poly(vinyl chloride) or rubber, rendering it liquid-and gas-tight. Such casing materials are ready available, for example being used in air beds and the like. The upper and lower faces of the casing 30 are sealed together around their respective margins using a conventional quick-drying contact adhesive, such as that sold by Bostik Limited under the rcgistered trade mark "Evo-Stik Impact", which is spread along a peripheral strip of each face about thirty millimetres wide. The particular cooling sheet 29 illustrated measures roughly 0.6 metres by 0. 6 metres, and is approximately twelve millimetres thick. This would be a suitable size for cooling just a part of the human body, or to line a pet bed. Tests on the "proof of concept" model show that this could easily be scaled up to dimensions of 0.7 metres by 1.5 metres, which is an appropriate size for a "whole body" cooling sheet.

The casing 30 contains approximately ten metres of flexible poly(vinyl chloride) tubing 31, arranged in a series of generally parallelly-extending loops. Only a few representative loops are shown; in all, eighteen loops of tubing 31 are present in the particular cooling sheet 29 illustrated. The loops of tubing 31 are held in place by being secured at each bend 32 to an interior face of the casing 30 using strips of adhesive tape. The remote ends of the tubing 31 are each connected to a respective supply tube 33 leading to a Peltier cooling device (not shown). The internal tubing 31 and the supply tubes 32 are linked by push-in connectors 34 of known form, which have been inserted through the casing 30 and sealed thereto with a conventional silicone sealant. The internal tubing 31 in this case has an external diameter of nine millimetres and an internal diameter of six millimetres. The supply tubes 33 have an external diameter of fourteen millimetres and an internal diameter of eight millimetres; they are preferably insulated and kept as short as practicable to avoid undesirable warming. An interior of the casing 30 is filled with about three litres of a glycerine (alias glycerol, glycerin or propan-l,2,3-triol) based composition 35.

A scrap cross-section of part of the cooling sheet 29 thus appears as shown in Figure 8, The glycerine composition 35 surrounds each loop of tubing 31, not only ensuring good thermal contact but also cushioning the tubing 3 1 so that someone resting on the cooling sheet 29 is unlikely to feel the loops.

The fourth cooling sheet 29 operates in substantially the same manner as those described above. The Peltier cooling device cools a supply of water, which is passed along one supply tube 33 into the tubing 31 within the cooling sheet 29. The cooled water 36 then flows along the tubing 31, cooling the glycerine composition 35 by absorbing heat therefrom. The total heat capacity of the glycerine composition 35 is five or six times that of the tubing 31 and the water 36 therein, added together, and once it has been brought down to a desired temperature, it has significant thermal inertia. Once the water has passed through each loop of the tubing 31, it flows out along the other supply tube 33 and back to the Peltier cooling device, to be cooled once more.

The cooling sheet 29 shown has been tested with a Peltier cooling device based on a Thermoelectric Liquid Chiller Model LC-200, supplied by TE Technology, Inc of Missouri, USA. This device operates on a 24V DC electrical current, and a suitable transformer was provided to convert a mains 230-240V AC supply to DC at the required voltage. The Peltier device has a cooling capacity of 200W, which turns out to be in excess of that needed for a cooling sheet 29 of the dimensions described. The heat output from a person with a typical skin temperature of 32 C, over an area covered by the cooling sheet 29 shown, is only about 110W. The 200W unit would hence be suitable for the 0.7 metres by 1.5 metre cooling sheet referred to above. This unit appears to be capable of reducing the temperature of a glycerine-filled sheet twelve millimetres thick to substantially its output water temperature in about ten minutes, and then it has cooling capacity in reserve to maintain the sheet at that temperature.

It is about 50% efficient, so only consumes about 400W of electrical power in normal use.

(NB: this particular off-the-shelf chiller unit uses evaporative cooling to supplement its Peltier cooling unit, which has the dual benefits of removing condensation from the heat-dissipating vanes, and providing additional cooling from the latent heat of evaporation of such condensation. Excess condensation might lead to a drip tray or the like being required.

However, in many cases a purely Peltier unit could be used instead without problems).

Glycerine has a normal melting point of 1 8 C. The glycerine composition thus should either be a very viscous liquid, a soft solid or a part-solidified gel at the working temperatures of the cooling sheet 29. This ensures that the glycerine composition 35 remains encasing the tubing 31, as shown in Figure 8, and is not squeezed out of the way by the pressure of a user's body resting on the cooling sheet 29. The cooling sheet 29 thus should not feel "lumpy" in use.

Also, the latent heat associated with the freezing of the glycerine composition 35 increases its effective thermal inertia, once it is down to a desired temperature. Glycerine is also colourless, odourless and non-toxic. (A similar gellable glycerine composition may also be used in place of the aqueous gel material 4 described in the first cooling sheet I, above).

The performance described is achieved with a relatively moderate flow of water through the cooling sheet 29, amounting to around 300 millilitres per minute; coincidentally, this roughly equates to one complete exchange of water within the tubing 31 every minute. In terms of linear flow rates, this comes to roughly 170 millimetres per second, which is brisk, but wholly practical for six millimetre internal diameter tubing. Many pumps are available that can achieve such volume flow rates.

The fourth cooling sheet 29 thus demonstrates the feasibility of the invention, and should easily be able to keep a user cool or to reduce an excessive body temperature, using a relatively simple, compact and efficient apparatus.

Claims (19)

1. A personal temperature control device comprising a laminar body adapted to contact a portion of a human or animal body to be cooled or warmed, one or more substantially flexible conduit means passing therethrough or adjacent thereto, means to alter a temperature of a heat transfer fluid and pump means to pass said heat transfer fluid through said conduit means.

2. A personal temperature control device as claimed in claim I, wherein the laminar body is flexible.

3. A device as claimed in claim 2, wherein the flexible laminar body comprises sheet means, blanket means, wrap means or the like.

4. A device as claimed in any one of the preceding claims, wherein the laminar body omprises a cushioning medium surrounding the conduit means, optionally adapted to conduct heat to and/or from the conduit means.

5. A device as claimed in claim 4, wherein said cushioning medium comprises a gel medium, for example comprising water and/or a polyol, optionally glycerolor propylene glycol.

6. A device as claimed in any one of the preceding claims, wherein the laminar body is provided with watertight envelope means surrounding the cushioning means.

7. A device as claimed in claim 6, wherein said envelope means comprises a flexible plastics material, optionally a hypoallergenic plastics material, for example surgical grade poly(vinyl chloride).

8. A device as claimed in either claim 6 or claim 7, wherein said envelope means comprises a woven textile material, coated or impregnated with a flexible plastics material.

9. A device as claimed in any one of claims 6 to 8, wherein the envelope means comprises at least a surface layer of a material adapted for contact with damaged skin, for example for use in contact with the body of a burns victim.

10. A device as claimed in any one of the preceding claims, wherein the heat transfer fluid comprises water.

11. A personal temperature control device as claimed in any one of the preceding claims, wherein the means to alter the temperature of the fluid comprises solid-state cooling means.

12. A device as claimed in claim 11, wherein the solid-state cooling means comprises at least one Peltier device.

13. A device as claimed in claim 12, wherein the solid-state cooling means comprises at least one pair of Peltier devices, so disposed that respective coolable faces of the or each pair of Peltier devices are in spaced opposition, with the or each conduit means passing therebetween.

14. A device as claimed in either claim 12 or claim 13, wherein a direction of current flow through the Peltier device or devices is reversible so that the coolable face(s) thereof become warmed, warming the fluid in the conduit means.

15. A personal temperature control device as claimed in any one of the preceding claims, selectably operable as a personal warming device.

16. A personal temperature control device as claimed in any one of the preceding claims, adapted so to switch between a cooling and a warming action as to maintain substantially a selected temperature.

1 7. A personal temperature control device as claimed in any one of the preceding claims, adapted to be wrappable around a portion of the body.

18. A device as claimed in any one of claims I to 15, configured to be mountable to a body contact area of a bed, seat or the like.

19. A personal temperature control device substantially as described herein with reference to the Figures of the accompanying drawings.