Abstract:
This invention is a flexible heater or cooler which includes a flexible, conformal, thermally conductive container filled with thermally conductive material. A thermal element within the container or in contact with the outside of the container provides heat to the container or removes heat from the container. The thermal element is powered by a low voltage direct current electrical source. A sensor for determining the temperature of the thermally conductive material is also included. The thermal element, electrical source, and sensor are in communication by connectors with a solid state continuous temperature controller. In operation, the electrical source provides power to the thermal element, thereby heating or cooling the thermally conductive material within the container. The temperature in the container is determined by the sensor and the controller controls the power delivery to the thermal element in response to the setting on the controller and the temperature in the container.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    Not Applicable.  
         STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
         [0002]    Not Applicable.  
         REFERENCE TO A MICROFICHE APPENDIX  
         [0003]    Not Applicable.  
         BACKGROUND OF THE INVENTION.  
         [0004]    2. Field of the Invention  
           [0005]    This invention relates to flexible heating and cooling devices in which an electric current provides the power for heating and cooling.  
           [0006]    2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.  
           [0007]    U.S. Pat. No. 4,388,607 discloses conductive polymer compositions made of carbon black dispersed in a crystalline copolymer. The use of such compositions in self-regulating heaters was disclosed.  
           [0008]    U.S. Pat. No. 4,764,664 discloses a process for reducing the contact resistance between an electrode and a conductive polymer composition, thereby increasing the stability of a heating device constructed of such a polymer and electrodes. In the process, the electrode is heated to a temperature above the melting point of the composition before contacting the composition.  
           [0009]    U.S. Pat. No. 4,777,346 discloses a liquid or gel filled pillow containing a resistance heater which is activated when a person compresses a switch formed of a layer of non-conductive foam located between two conductive layers.  
           [0010]    U.S. Pat. No. 4,907,340 discloses a method for increasing the stability of a conductive polymer composition, which consists of cross-linking the composition using irradiation.  
           [0011]    U.S. Pat. No. 5,111,032 discloses a self-regulating strip heater made of conductive polymer with embedded electrodes surrounded by a strengthening braid. The thermal efficiency of the heater is increased by impregnating the interstices of the braid with an outer insulating layer.  
           [0012]    U.S. Pat. No. 5,653,741 discloses a flexible pad for heating or cooling a body part which has thermoelectric devices attached to a thermal conductive material. The thermoelectric devices heat or cool depending on the polarity of the current which power them. An enclosure surrounds the thermoelectric devices and fans are used to cool the heat sink portion of the thermoelectric devices when used to cool the body part.  
           [0013]    The KA SMARTEST heating pad has an electronic control connected by a wire to the pad which provides four temperatures settings and automatic shutoff after 30 minutes. The heating pad has a cloth cover with a strap to secure the pad in place and a moistening sponge pad. KA SMARTEST is a trademark for a heating pad obtainable from Comfort House, Newark, N.J.  
           [0014]    The prior art does not disclose the heater or cooler of this invention in which a flexible conformal container loaded with thermally conductive material is heated by a PTC heater or cooled by a thermoelectric device mounted on the outside of the container. The heater or thermoelectric device is powered by low voltage direct current which is controlled by a controller in response to the temperature of the thermally conductive material in the container as sensed by a thermoelectric device sensor.  
         BRIEF SUMMARY OF THE INVENTION  
         [0015]    This invention is a flexible heater or cooler which includes a flexible, conformal, thermally conductive container filled with thermally conductive material. A thermal element within the container or in contact with the outside of the container provides heat to the container or removes heat from the container. The thermal element is powered by a low voltage direct current electrical source. A sensor for determining the temperature of the thermally conductive material is also included. The thermal element, electrical source, and sensor are in communication by connectors with a solid state continuous temperature controller. In operation, the electrical source provides power to the thermal element, thereby heating or cooling the thermally conductive material within the container. The temperature in the container is determined by the sensor and the controller controls the power delivery to the thermal element in response to the setting on the controller and the temperature in the container.  
           [0016]    The objective of this invention is to provide a flexible, conformal heater or cooler for application to sore or distressed areas of the body.  
           [0017]    Another objective is to provide a heater for regulated industrial heating or cooling applications.  
           [0018]    Another objective is to provide a heater with provisions to prevent overheating.  
           [0019]    Another objective is to provide a heater or cooler which is powered by low voltage direct current electricity.  
           [0020]    Another objective is to provide a heater or cooler which does not emit EMF radiation  
           [0021]    Another objective is to provide a heater which inherently limits the maximum temperature attainable.  
           [0022]    Another objective is to provide a heater which avoids the hazards of accidental electrical shock.  
           [0023]    Another objective is to provide a heater or cooler with user control of the temperature.  
           [0024]    A final objective is to provide a flexible conformal heater or cooler which is constructed easily and inexpensively of common materials and whose manufacture and use is without adverse effects on the environment. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0025]    [0025]FIG. 1 is a schemetic diagram of a first embodiment heater with an internal resistance heater element.  
         [0026]    [0026]FIG. 2 is a schematic diagram of a second embodiment heater with a PTC heater element.  
         [0027]    [0027]FIG. 3 is a schematic diagram of a first embodiment heater and cooler with an external heater and cooler element.  
         [0028]    [0028]FIG. 4 is a schematic diagram of a second embodiment heater and cool with an external heater and cooler element attached to two containers.  
         [0029]    [0029]FIG. 5A is a cross section of a two layer container.  
         [0030]    [0030]FIG. 5B is a cross section of a four layer container.  
         [0031]    [0031]FIG. 5C is a cross section of a two layer container.  
         [0032]    [0032]FIG. 5D is a cross section of a two layer container.  
         [0033]    [0033]FIG. 5E is a cross section of a two layer container.  
         [0034]    [0034]FIG. 5F is a cross section of a four layer container.  
         [0035]    [0035]FIG. 6 is a schematic diagram of the controller.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0036]    The invention has several components, a container which contains thermally conductive material, a heating or cooling element located within the container or attached to the outside, a temperature sensor located inside the container, and a controller and power source.  
         [0037]    [0037]FIG. 1 is a diagrammatic representation of the first embodiment heater  100 . The container or bag  10  holds the thermally and electrically conducting gel  20 . A thermocouple safety sensor  60  is immersed in the gel  20 . A resistance heater  30  is also immersed in gel  20 . A controller  50  controls the operation of the heater. Power supply  40  converts AC line voltage to 12 volt DC current to power the heater  30  and sensor  60 . The sensor is connected to the controller by connector  70 . The controller is connected to the power supply by connector  72 . The power supply is connected to the resistance heater  30  by connector  78 . The power supply  40  is connected to the line voltage supply by connector  74 . The controller  50  and power supply  40  may be combined in a single housing.  
         [0038]    [0038]FIG. 2 is a diagrammatic representation of the second embodiment heater  200 . The second embodiment heater is identical to the first embodiment heater  100  shown in FIG. 1 except there is no resistance heater  30 . The heat is provided by a PTC heater which comprises thermally and electrically conducting gel  24  into which are immersed two strip-like electrodes  31  and  32 . Electrical current at 12 volt DC is passed through the gel  24  between the electrodes  31  and  32 , thereby heating the gel  24 . Electrode  31  is connected by connector  77  to power supply  40 . Electrode  32  is connected by connector  75  to power supply  40 .  
         [0039]    [0039]FIG. 3 is a diagrammatic representation of the first embodiment heater and cooler  300 . The second embodiment heater and cooler is identical to the first embodiment heater  100  shown in FIG. 1 except there is no resistance heater  30 . A thermoelectric cooling and heating unit  34  based on the Peltier effect is mounted on the outside of the container  10 . The cooling and heating unit  34  is connected to the power supply  40  by connector  76 . The unit  34  has side  35  in thermal contact with the container  10  and a side  35  in thermal contact with ambient air. In operation as a cooler side  35  is cooled and cools the container  10 . Side  36  is heated and the heat is dissipated into the air. When the polarity of current to the thermoelectric cooling and heating unit  34  is reversed, side  35  becomes heated, as does container  10 , and side  36  becomes cooled.  
         [0040]    [0040]FIG. 4 is a diagrammatic representation of the second embodiment heater and cooler  400 . The second embodiment heater and cooler is identical to the first embodiment heater and cooler  300  shown in FIG. 3 except that a second container  11  containing thermally and electrically conducting gel  22  and a sensor  62  is in thermal contact with the thermoelectric cooling and heating unit  34  on the side  36 . In operation, if container  10  is cooled, container  11  is heated. Reversal of the polarity to unit  34  causes container  10  to be heated and container  11  to be cooled. This is particularly useful for alternative heating and cooling of affected body parts.  
         [0041]    Further details on the component elements of the first and second embodiment heaters and first and second embodiment cooler and heaters are described below.  
         [0042]    Container.  
         [0043]    Any strong, impervious to fluids, conformable, flexible container or bag may be used to contain the gel. If the bag is multilayered, the inner layer should be heat sealable. Suitable bags are disclosed in U.S. Pat. No. RE34,929, incorporated herein by reference. The layers of a multilayered bag can be made of different materials, for example, the inner layer may be of polyethylene or polypropylene, or polyvinyl chloride, and the outer layer of polyester or nylon or MYLAR brand of polyester film, obtainable from Dupont, Wilmington, Del. Additional layers may be present, for example, an intermediate layer of high density polyethylene, or closed cell polyethylene foam. A preferred 3-ply VACLOCK brand multilayer bag is obtained from Tilia, Inc., San Francisco, Calif. It is not necessary that the container be constructed of gas impermeable material, although the container must be impervious to fluids. Polystyrene; as well as MYLAR brand of polyester film, obtainable from DuPont, Wilmington, Del.; KAPTON brand of polyimide film, obtainable from Circleville, Ohio; SARAN brand of thermoplastic film obtainable from Johnson and Sons, Inc., Racine, Wisconsin; or silicone films may be used. Each layer in a bag is about 0.5 to 3.0 mil thick Metal foils, such al aluminum foil, may be included in a multilayer container.  
         [0044]    FIGS.  5 A- 5 F are diagrammatic representations of the cross-sections of preferred containers.  
         [0045]    [0045]FIG. 5A shows a two-layer container comprised of MYLAR film  11  and polyethylene 12 lm.  
         [0046]    [0046]FIG. 5B shows a four-layer container comprised of MYLAR film  11  attached to polyethylene film  12 , which is in turn attached to one side of aluminum foil  12 . A polyethylene film  12  is attached to the other side of the aluminum foil  12 .  
         [0047]    [0047]FIG. 5C shows a two-layer container comprised of MYLAR film  11  attached to closed cell polyethylene foam  14 .  
         [0048]    [0048]FIG. 5D shows a two-layer container comprised of MYLAR film  11  attached to SARAN film.  
         [0049]    [0049]FIG. 5E shows a two-layer container comprised of MYLAR film  11  coated with an adhesive film  16 .  
         [0050]    [0050]FIG. 5F shows a four-layer container comprised of MYLAR film  11  attached on one side to adhesive film  16 , which is in turn attached to aluminum foil  13 , and the aluminum foil  13  is coated with an adhesive film  16 .  
         [0051]    PTC Heating.  
         [0052]    Heating is achieved by the passage of  12  volt direct current electrical current between two electrodes immersed in the thermally and electrically conductive material referred to as “PTC” materials. PTC is an acronym for positive temperature coefficient of resistance. Such PTC materials have the desirable property increasing electrical resistance with increase in temperature, and therefore automatically limit the temperature achieved by the heater. This provides an additional safety factor for the user of the pad in the heating mode. The electrodes may be parallel columns of wires immersed in the thermally and electrically conductive material or laminal electrodes in the shape of metal foil or mesh. Any suitable highly electrically conductive material may be used for the electrodes, such as copper, nickel, aluminum, or silver. A preferred material is nickel or copper  
         [0053]    Thermally and Electrically Conductive Material.  
         [0054]    The container is filled with a thermally and electrically conducting material which preferably is a thermally conductive gel. The containers are flexible and conform to the portion of the body which is being heated. A gel is constituted of two components, a liquid phase, and a solid phase. The liquid phase may be water based, or based on non-aqueous liquid polymers, such a silicone oil, mineral oil or another petrochemical-origin oil, polyvinylidene fluoride, and a crystalline copolymer consisting essentially of units derived from at least one olefin and at least 10% by weight, based on the copolymer, of units derived from at least one olefinically unsaturated comonomer containing a polar group. The solid phase or particulate conductive filler of the gel is particles of silica, alumina, titania, iron oxide, zinc oxide, aluminum oxide, carbon black, graphite, or ceramics. When non-aqueous liquid phase is used, ionic salts such as sodium chloride, magnesium sulfate, copper sulfate may be used as the solid phase.  
         [0055]    The composition of the thermally and electrically conductive material determines the resistivity and therefore the heating characteristics of the heating pad. Higher resistivity material results in higher temperature generation by the heater. Resistivity is increased by lowering the proportion of conductive filler in the gel; resistivity is decreased by increasing the proportion of conductive filler in the gel. A suitable formulation comprises 10%-90% by weight petroleum jelly as the sol phase and 10%-90% by weight zinc oxide particles as the solid phase. A preferred formulation comprises 25% by weight petroleum jelly and 75% by weight zinc oxide particles.  
         [0056]    Resistance Heating  
         [0057]    In a second embodiment heater, resistance wire heaters are used to provide the heat to thermally conductive material. In this embodiment, gel is used as the thermally conductive material, although it is not necessary that the material be electrically conductive. The resistance heater elements are made of any suitable resistance heating material, a preferred material is Nichrome. Resistance wire elements are immersed in the thermally conductive material, and may be straight or coiled in form. Preferably the resistance elements are laminated between layers of flexible films, such as between layers of MYLAR, KAPTON, or silicon film. A preferred resistance wire tape is an insulated tape suitable for use in an electrically conductive environment, such as Dw-Tape, AWH, manufactured by Amptek Company, Stafford, Tex. Another preferred heater is Model PR 735A07053003 manufactured by American Thermal Products, St. Marys, Pa.  
         [0058]    Cooling Element  
         [0059]    The heating and cooling pad is cooled using a thermoelectric cooling unit based on the Peltier Effect mounted on the outside of the container. Such a cooler is based on the cooling at one junction of a thermoelectric device circuit associated by the passage of a current through the circuit. The cooler has no moving parts. It is mounted on the outside of the container to permit heat produced at the other junction of the thermoelectric device circuit to be dissipated into the air. An electric fan aids in removing the heat from the cooling element. Reversal of the polarity of the electricity supplied to the thermoelectric cooling unit reverses the effect from cooling to heating the container. This may be used when alternative heating and cooling of affected body parts is desired.  
         [0060]    In another embodiment, the thermoelectric cooling agent is mounted between two containers. One container is heated while the other one is cooled.  
         [0061]    A suitable cooling element is the SCTB NORD 300 watt unit obtainable from Advanced Thermoelectric Products, Nashua, N.H.  
         [0062]    Sensor.  
         [0063]    A thermoelectric device or thermistor safety sensor is immersed in the conductive material of the heater and cooler. This sensor turns off the heater if the temperature in the container exceeds a preset level. In addition, the heater is turned off if the sensor fails. A suitable sensor is a type T thermoelectric device with copper and constantan junctions which has a range of measurement of 330 to 660° F. Such sensors can be obtained from Instrument Service &amp; Equipment, Inc., Cleveland, Ohio.  
         [0064]    Controller.  
         [0065]    The controller controls flow of 12 volt DC current to the heater or cooler elements in response to signals from the thermoelectric device sensor which indicate the temperature inside the container. In addition, the controller has an on/off switch and a continually variable temperature setting dial (not shown in the FIGS.).  
         [0066]    [0066]FIG. 6 is a schematic diagram of the controller elements. A current source  51  and regulator  50  are shown, along with resistors  53 ,  54 ,  55 , and  56  with indicated resistances, and resistance heater  57 . A preferred current source is a 3-terminal adjustable current source Model LM 334, manufactured by National Semiconductor Corporation, Santa Clara, Calif. It has a 10,000 to 1 range in operation current and a voltage range of 1 V to 40 V. A preferred regulator is a 5-amp adjustable regulator, a 3-terminal positive voltage regulator capable of supplying over 5 A over a 1.2 V to 32 V output range, Model LM 338, manufactured by National Semiconductor Corporation, Santa Clara, Calif. A preferred resistance heater is Model PR 735A0705300B, manufactured by Advanced Thermal Products, St. Marys, Pa.  
         [0067]    It will be apparent to those skilled in the art that the examples given here are illustrative only, and that this invention is limited only by the appended claims.