Patent Publication Number: US-2006001727-A1

Title: Controllable thermal warming device

Description:
RELATED APPLICATIONS  
      This application is a continuation-in-part of application Ser. No. 10/910,443 filed Aug. 3, 2004, which is a continuation-in-part of Ser. No. 10/854,838 filed May 27, 2004, which claims benefit to U.S. provisional application 60/473,349 filed on May 27, 2003 and is a continuation-in-part of Ser. No. 10/15,846 filed Apr. 3, 2002, which has issued to U.S. Pat. No. 6,770,848 on Aug. 3, 2004 and claims benefit to provisional application Ser. No. 60/284,837 filed Apr. 19, 2001. Application Ser. No. 10/910,443 also claims benefit to provisional patent application Ser. No. 60/494,023 filed on Aug. 11, 2003 and provisional patent application Ser. No. 60/578,100 filed on Jun. 8, 2004. The disclosures set forth in the referenced applications are incorporated herein by reference in their entirety. 
    
    
     FIELD  
      This disclosure relates generally to controllable thermal warming devices, and more particularly to controllable thermal warming devices.  
     BACKGROUND  
      Heating elements of various constructions and configurations are heretofore known. Additionally, heating elements have been used in many different applications. An example of a heating element construction is disclosed in U.S. Pat. No. 6,189,487 to Owen.  
     SUMMARY  
      The present disclosure comprises one or more of the following features or combinations thereof disclosed herein or in the Detailed Description below.  
      The present disclosure relates to a controllable thermal warming device including a heating element, a power source, and a controller. The heating element may be removably or otherwise securable to any suitable structures, including, for example, blankets, clothing, consumer products, farming products, apparel, restaurant products, HVAC products, building construction products, hospital and other medical products, vehicles, to name a few. The heating element may comprise a conductive ink disposed on a substrate. The controllable thermal warming device may be used in any suitable manner as part of a heating system. 
    
    
     DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a functional block diagram of a controllable thermal warming device including a radio frequency link in accordance with an embodiment of the disclosure;  
       FIG. 2  is a functional block diagram of another controllable thermal warming device in accordance with an other embodiment of the disclosure;  
       FIG. 3  is a top view of a thermal ink heating element in accordance with an embodiment of the disclosure;  
       FIG. 4  is a top view of another thermal ink heating element including a sensor in accordance with an embodiment of the disclosure;  
       FIG. 5  is a top plan view of the thermal ink heating element of  FIG. 4  in a pouch, the pouch being shown in broken view;  
       FIG. 6  is a top plan view of the thermal ink heating element of  FIG. 3  in the pouch, the pouch being shown in broken view;  
       FIG. 7  is a section view taken along the line  7 - 7  in  FIG. 6 ;  
       FIG. 8  is a section view taken along lines  8 - 8  in  FIG. 5 ;  
       FIG. 9  is a plan view of an exemplary vest garment that includes the thermal ink heating element of  FIG. 3 ;  
       FIG. 10  is a plan view of an exemplary pants garment that includes the thermal ink heating element of  FIG. 3 ;  
       FIG. 111  is a plan view of another exemplary pants garment that includes the thermal ink heating element of  FIG. 3 ;  
       FIG. 12  is a top plan view of another controllable thermal warming device in accordance with another embodiment of the disclosure;  
       FIG. 13  is a top plan view of yet another controllable thermal warming device similar to the controllable thermal warming device of  FIG. 6 ;  
       FIG. 14  is a front view of an exemplary glass panel assembly that includes the thermal ink heating element of  FIG. 3 ;  
       FIG. 15  is a section view taken along lines  15 - 15  in  FIG. 14 ;  
       FIG. 16  is a front view of another exemplary glass panel assembly that includes a thermal ink heating element utilizing an invisible conductive ink;  
       FIG. 17  is a section view taken along lines  17 - 17  in  FIG. 16 ;  
       FIG. 18  is a side view of an exemplary building structure duct assembly that includes the thermal ink heating element of  FIG. 3 ;  
       FIG. 19  is a front view of the exemplary building structure duct assembly of  FIG. 18 ; and  
       FIG. 20  is a top plan view of a thermal ink heating element and a release layer removably affixed to the film in accordance with another embodiment of the disclosure, the thermal ink heating element shown in broken view to illustrate the release layer. 
    
    
     DETAILED DESCRIPTION  
      While the present disclosure may be susceptible to embodiment in different forms, there is shown in the drawings, and will be described herein in detail, one or more embodiments with the understanding that the present description is to be considered an exemplification of the principles of the disclosure and is not intended to be exhaustive or to limit the disclosure to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings.  
       FIG. 1  is a functional block diagram of a controllable thermal warming device  10  in accordance with an embodiment of the invention. In accordance with the embodiment of  FIG. 1 , the controllable thermal warming device  10  includes a heating element in the form of a thermal ink heating element  12  configured to generate or otherwise radiate heat, a power source  14  coupled to the thermal ink heating element  12  and adapted to provide a voltage to the thermal ink heating element  12 , and a controller  16  coupled to the power source  14  and the thermal ink heating element  12 . The heating element  12 , the power source  14  and the controller  16  may have any suitable construction and include any suitable features. The controller  16  may, for example, include a memory and a processor coupled to the memory, or elements associated with an electromechanical controller. Among other things, as described below, the controller  16  may be adapted to control the voltage delivered to the thermal ink heating element  12  and to detect an operating characteristic (e.g., a current, a resistance, a temperature, etc.) of the thermal ink heating element  12  and, in response to the characteristic, adjust the voltage delivered to the thermal ink heating element  12 .  
      The controllable thermal warming device  10  is configured to be activated or otherwise controllable by radio frequency signal in any suitable manner, and in this regard may include one or more radio frequency (RF) link(s) to enable remote monitoring and control of the thermal ink heating element  12  during operation. The controller  16  may be activated or otherwise controlled by radio frequency signal.  FIG. 1  provides an example of the controllable thermal warming device  10  in accordance with an embodiment of the disclosure, which is adapted to control the controller  16  from a location remote to the thermal ink heating element  12 , to (1) cause, or otherwise control, the delivery of voltage to the thermal ink heating element  12 , (2) to detect an operating characteristic of the thermal ink heating element  12  and, (3) in response to the characteristic, to adjust the voltage delivered to the thermal ink heating element  12 .  
      The controllable thermal warming device  10  of  FIG. 1  includes the thermal ink heating element  12 , the power source  14  coupled to the thermal ink heating element  12 , and a first transceiver  32  operatively coupled to the power source  14  and the thermal ink heating element  12 . An optional sensor/microcontroller  34  may also be included to detect a characteristic(s) of the thermal ink heating element  12  and/or control operation of the first transceiver  32 . The controller  16 , remotely located from the thermal ink heating element  12  and the power source  14 , is coupled to a second transceiver  38 . The controller  16  is therefore operatively coupled to the power source  14  via the first and second transceivers  32 ,  36  communicating via an RF link  38 .  
      The first and second transceivers  32 ,  36  may be one of any number of types of suitable transceivers configured to communicate using one of any number of radio frequency, or wireless link protocols. For example, for short range applications up to 10 yards, the first and second transceiver  32 ,  36  may be Bluetooth™ transceivers capable of transmitting and receiving over the RF link  38  using one of a number of versions of the Institute of Electrical and Electronic Engineers, Inc. (IEEE) 802.15 protocols. Using the current version (version 1.2) of IEEE 802.15, the controller  16  can remotely monitor and control up to eight separate thermal ink heating elements  12  via the second transceiver  36  (without additional power amplification). In that case, the second transceiver  36  establishes a Bluetooth™ “piconet” with the first transceiver  32  and possibly seven other like transceivers. The individual RF link  38  between each first transceiver  32  and the second transceiver  36  allows each first transceiver  32  to transmit operation characteristic data about its thermal ink heating element  12  to the second transceiver  36  and allows the second transceiver  36  to transmit operation characteristic adjustment data to each of the first transceivers  32  for use by the power source  14 . Thus, the controller  16  and second transceiver  36  located in a nurses station may concurrently monitor and control the temperature of thermal ink heated blankets of eight patients located in a recovery room. Such a Bluetooth™ piconet may be further linked together with other Bluetooth™ piconets to form a large wireless monitoring and control network.  
      When using a Bluetooth™ protocol, the microcontroller of the sensor/microcontroller  34  is configured with a Bluetooth™ microcontroller and suitable Bluetooth™ control logic, optionally formed as a single chipset. Although not separately illustrated, the second transceiver  36  is similarly configured with a Bluetooth™ microcontroller and suitable Bluetooth™ control logic, formed as a single chipset. If any wireless link protocol requiring digital signal transmission is utilized, signals representing operating characteristics of the thermal ink heating element  12  may be converted to digital signals suitable for transmission via an analog-to-digital (A/D) converter in the 1 st  transceiver  32 , and vice versa.  
      For low power applications requiring monitoring and control of tens, hundreds or even thousands of thermal ink heating elements  12  per second transceiver  36 , the first and second transceiver  32 ,  36  may be configured as Zigbee transceivers capable of transmitting and receiving over an RF link using IEEE 802.15.4 protocol. In that case, the first transceiver  32  and the sensor/microcontroller  34  are combined to form a “ZigBee sensor”  35  that performs the sensor and transmit function and includes a Zigbee specific microcontroller. Similarly, the second transceiver  36  also includes a ZigBee specific microcontroller (not separately illustrated) to form a second ZigBee sensor. A single Z-link ZigBee chipset available from Atmel® Corporation may be utilized for this purpose.  
      Operating much like a Bluetooth™ piconet, the second transceiver  36  (and its associated ZigBee microcontroller) acts as a “network coordinator” to link the first transceiver(s)  32  to the second transceiver  36  to form a “ZigBee monitoring network”. A large number of ZigBee sensors (i.e., the first transceiver  32  and associated microcontroller and sensor) communicating with each other and the network coordinator (i.e., the second transceiver  36  and associated microcontroller) may be formed, with one ZigBee sensor per thermal ink heating element  12 . Monitored operating characteristics of the thermal ink heating element(s)  12  can then be transmitted from the first ZigBee sensor  35  directly to the second transceiver  36  (network coordinator), or from the first ZigBee sensor  35  to one of any number of other ZigBee sensors in the ZigBee monitoring network, in a relay fashion, to the second transceiver  36  (network coordinator), and then to the controller  16 . In this way, the controller  16  can monitor the selected operating characteristic(s) of the thermal ink heating element  12 , and if necessary, cause associated adjustments to the voltage delivered by the power source  14  to the thermal ink heating element  12 .  
      Although not separately illustrated, it is contemplated that future generations of one or more “micro” ZigBee sensors may be embedded directly into the piece of clothing, the pouch, the blanket, the mirror, the hospital cover, etc. housing the thermal ink heating element  12 .  
      For even longer range applications requiring monitoring and control of many thermal ink heating elements  12  per second transceiver  36 , the first and second transceiver  32 ,  36  may be configured as WiFi transceivers capable of transmitting and receiving over the RF link  38  using IEEE 802.11a, 802.11b, or 802.11g protocols, depending on the frequency selected (e.g., 2.4 GHz range, 5 GHz range). Like the Bluetooth and ZigBee examples described above, the microcontroller of the sensor/microcontroller  34  is configured with a WiFi specific microcontroller. Additionally, however, each of the individual WiFi microcontrollers (and therefore each of the thermal ink heating elements  12 ) is operatively coupled to a computer having a WiFi specific transceiver installed therein (i.e., the first transceiver  32 ). The individual WiFi microcontrollers may be operatively coupled to the computer/WiFi transceiver via a wire line, another RF link such as, for example, an Infrared (IR) link or a cellular mobile station link (e.g., GSM, CDMA, TDMA), or a combination thereof. Thus, using such a WiFi “mesh network”, and an Internet capable controller  16  (e.g., personal computer), monitoring may be accomplished from any location having access to the Internet. For example, a manufacturer of polymeric-based landfill liners desiring to maintain a relatively constant warm temperature during the curing process of a 700 square foot liner during the curing process, may utilize hundreds of thermal ink heating elements  12  arranged in a WiFi mesh network to monitor temperatures via a remotely located personal computer.  
      Although not separately illustrated, each of the first and second transceivers  32 ,  36  configured in one of any number of suitable wireless communication protocols, may further include one or more power or control buttons, and/or one or more visual or audible indicators to assist an individual. For example, if the first and second transceivers  32 ,  36  are configured using a Bluetooth protocol, the second transceiver  36  may include an Acquire button and a light emitting diode (LED) where the actuation of the Acquire button initiates formation of the piconet and where the LED indicates successful acquisition of the first transceiver  32  into the piconet.  
      Generally, during operation, the thermal ink heating element  12  radiates heat in response to a current generated in the thermal ink heating element  12  by application of the voltage from the power source  14 . As the voltage is increased, the current increases. As the current increases, the resistance increases, and resulting heat is generated. With increased resistance, more voltage is needed to maintain the same current (and therefore temperature). Accordingly, using one or more of the operating characteristics of the thermal ink heating element  12  such as, for example, resistance, temperature, current, etc., the controller  16  makes adjustments to the voltage delivered by the power source  14 . Thus, the feedback arrangement of the thermal ink heating element  12 , the controller  16 , and the power source  14  enables the temperature of the heat radiating from the thermal ink heating element  12  to be maintained at a relatively steady temperature; in this case, about 100 degrees Fahrenheit.  
       FIG. 2  is a functional block diagram of another controllable thermal warming device  19  that includes a sensor  33  in accordance with an embodiment of the invention. As illustrated in  FIG. 2 , the controllable thermal warming device  19  includes the thermal ink heating element  12  configured to generate heat, the power source  14  coupled to the thermal ink heating element  12  and adapted to provide a voltage to the thermal ink heating element  12 , the controller  16  coupled to the power source  14 , and the sensor  33  coupled between the thermal ink heating element  12  and the controller  16 . In this feedback arrangement, the sensor  33  is adapted to detect an operating characteristic of the thermal ink heating element  12  (e.g., a temperature) and transmit the operating characteristic to the controller  16 . In response to receiving the operating characteristic, the controller  16  causes an adjustment to the voltage delivered to the thermal ink heating element  12 . The controllable thermal warming device  19  may include any suitable means for activating or otherwise controlling the controller  16  by radio frequency.  
      Referring to  FIGS. 1 and 2 , the thermal ink heating element  12  may have any suitable configuration and structure. For example,  FIG. 3  is a top view of an exemplary thermal ink heating element  12 . In the illustrated example, the thermal ink heating element  12  includes a conductive ink  20  fixedly disposed on a substrate  22 . The conductive ink  20  includes a first conductive ink pad  21  and a second conductive ink pad  23 . The conductive ink  20  may be an ultra violet (UV) ink, for example, FD 3500 CL UV ink made by Allied PhotoChemical of Kimball, Mich., or any other suitable conductive ink. The substrate  22  may be one of any number of materials, such as, for example, acetate, Mylar, Liquiflex, paper or cloth and may have any suitable construction and configuration.  
      In accordance with other embodiments, the thermal ink heating element  12  may be releasably or otherwise removably securable to an other structure so that the thermal ink heating element may be used on a wider variety of items, such as, for example, disposable or reusable items. The thermal ink heating  12  element may, for example, be removably secured to disposable hospital gowns or on other clothing, any consumer products or building structure, or any other suitable structure. The manner of removably securing the thermal heating element to such other structure may be accomplished in any suitable manner. Referring to  FIG. 20 , for example, the substrate  22 A of the thermal ink heating element  12  may be constructed of a material that includes a film  302  comprising mylar or other suitable material. An adhesive is affixed to a backside of the film  302  and a removable release layer  306  is affixed to the film for removably securing the film to other structure. The thermal ink heating element  12  may be releasably secured to the structure with the adhesive after removal of the release layer  306 . The substrate  22 A may, for example, be a pressure sensitive film commercially available from FLEXCON of Spencer, Mass. or any similar product. In accordance with other embodiments, any suitable strip for adhering or other suitable material such as any suitable two-sided tape, tape adhesive, adhesive backing, glue, hook and loop fastening means or other suitable material, utilized with or without a release layer, may be applied to the thermal ink heating element  12  to facilitate removable securement of the thermal ink heating element to the structure.  
      The conductive ink  20  is fixedly disposed on the substrate  22  using any suitable manner such as, for example, affixing the conductive ink  20  onto the substrate  22  via a conventional printing press or via a screen printing press. The process of affixing the conductive ink  20  to the substrate  22  may begin by creating a pattern. The pattern may include a series of lines and be created with the aid of a computer and a computer aided drawing program. Once created, the pattern may be used to generate a film positive which is then translated into a screen, stencil, printing plate, or the like. Utilizing, for example, the stencil, the conductive ink  20  may be applied to the substrate  22  either by hand or automatically via a printing press. After application to the substrate  22 , the conductive ink  20  is cured and set via application of a UV light, thereby forming the thermal ink heating element  12 .  
       FIG. 4  is a top view of another exemplary thermal ink heating element fixedly coupled to, inter alia, a sensor in accordance with an embodiment of the invention. In the illustrated example, the sensor is configured as a thermally sensitive resistor. Additional details of the thermally sensitive resistor are discussed below in connection to  FIG. 5 .  
      Referring again to  FIG. 3 , once formed, the thermal ink heating element  12 , with or without the sensor  33 , may be used in a wide variety of heating system applications. For example, the thermal ink heating element  12  may be inserted into a piece of clothing, a pouch, a blanket, a mirror, a hospital cover, etc. A wide variety of applications for the thermal ink heating element  12  are described hereinafter and in U.S. patent application Ser. No. 10/115,846 filed Apr. 3, 2002, and in an associated United States continuation-in-part patent application Ser. No. 10/854,838 filed May 27, 2004, both naming Haas et al. as inventors, and herein incorporated by reference in their entirety.  
      In the controllable thermal warming devices  10 ,  19  illustrated by the functional block diagrams of  FIGS. 1 and 2 , elements such as the power source  14 , the thermal ink heating element  12 , the controller  16  and the sensor  33  may be connected via a wire line scheme.  
      As mentioned above, the controllable thermal warming devices  10  and  19  include the thermal ink heating element  12 , the controller  16  and the power source  14  in a feedback control arrangement. When enabled, it is contemplated that the controllable thermal warming device  10  may include additional components such as sensors, transceivers, connectors, plugs, buttons, etc.  
      For example,  FIG. 5  is a top plan view of a controllable thermal warming device  100  having a sensor in accordance with an embodiment of the invention. The controllable thermal warming device  100  includes the thermal ink heating element  12  configured to generate heat, the power source  14  operatively coupled to the thermal ink heating element  12  via a wire link  105 , and the controller  16  operatively coupled to the thermal ink heating element  12  and the power source  14 . In the illustrated example, the wire link  105  includes a temperature controller connector  102  coupled to the thermal ink heating element  12  and terminating in a first socket  104 . The wire link  105  also includes a temperature cable  106  coupled to the controller  16  and the power source  14  and terminating in a second socket  108 . The first and second sockets  104 ,  108  are mated to provide a continuous electrical path between the power source  14  and the thermal ink heating element  12 , and to provide a continuous signal path from the sensor coupled to the thermal ink heating element  12  to the controller  16 . Although illustrated as an individual block, it is contemplated that the power supply  14  and the controller  16  may be illustrated as separate blocks configured to maintain the feedback control path.  
      The power source  14  of  FIG. 5  is may, for example, be either a single or dual Ni-MH battery pack, made by AVT, Inc., and integrated with the controller  16 . Each individual pack may consist of twelve +1.2 volt cells in series to yield an overall voltage of +14.4 VDC rated at 6.8 amp-hour. Typically, if a single Ni-MH battery pack is used in conjunction with the thermal ink heating element  12 , 8-10 hours of voltage delivery time is yielded. If a dual Ni-MH battery pack is used conjunction with the thermal ink heating element  12 , 14-16 hours can be yielded. Although described above in terms of providing a DC voltage output, it is contemplated that the power source  14  may be one of any number of suitable power sources. For example, the power source  14  may be a DC power source, an AC power source, a solar power source, or one of any number of other power sources that may be able to provide a direct current flow in the thermal ink heating element  12 .  
      The power source  14  of  FIG. 5  may be also configured using battery packs requiring use of a battery charger, such as, for example, a Model DV2005S1 Series battery charger manufactured by Texas Instruments, Inc. The battery charger is adapted to receive its power from a boost converter that steps up the voltage output of the internal power supply. The higher voltage output is required to properly charge a twelve cell battery pack. The battery charger also incorporates safety features that cause the charge cycle to be terminated in the event a maximum charge time and/or a maximum voltage exceeds a pre-set limit.  
      During operation, the power source  14 , optionally integrated with the controller  16 , is regulated by the controller  16  to deliver the appropriate voltage to the thermal ink heating element  12  in order to maintain a current that causes heat to be radiated at a temperature of approximately +100+/−4 degrees Fahrenheit. As described above in connection with  FIG. 1 , current flow in the thermal ink results when the free electrons of the thermal ink are repelled by the negative battery terminal of the power source  14 . Heat is generated by the associated resistance of the flowing electrons in the conductive ink  20 . The controller  16 , electrically connected to the thermal ink heating element  12  via the temperature cable  106  and the temperature controller connector  102 , receives temperature characteristics of the thermal ink heating element  12 . Based on those temperature characteristics, the controller  16  regulates the voltage delivered by the power source  14  to the thermal ink heating element  12  to maintain the desired approximate +100 degrees Fahrenheit temperature.  
      In some cases, it may be useful to determine the capacity of the power source  14 . The capacity of the power source  14  may be determined by measuring the voltage of the power source  14  and then displaying the results visually through use of a capacity meter. One example of such a capacity meter is a capacity meter having Part. No. 58-90001000-000, manufactured by WJH Engineering, and utilizing a National Semiconductor device (LM3419) designed to drive a series of five LEDs. The five LEDs indicate a FULL battery condition, a ¾ battery condition, a ½ battery condition, a ¼ battery condition or an EMPTY battery condition. When coupled to the capacity meter, a drop in the capacity of the power source  14  below a minimum set threshold will cause an alarm to sound on the capacity meter. It should be noted that during operation, the capacity meter is electrically disconnected from the power source  14  when the controller  16  turns off the power source  14 . This ensures that the battery packs do not inadvertently self-discharge.  
      As previously mentioned, the power source  14  may be configured using an AC power source. In that case, the controller  16  may contain a switching power supply that is capable of operating from 85 to 250 VAC at a rated output of 15 VDC @ 7 amps. The switching power supply also provides the power to charge the internal battery pack(s). It is further contemplated that the power source  14  may also be configured using another type of power source  14  such as a +12 to +16 VDC source from a vehicle cigarette lighter or from a DC source within an emergency vehicle.  
      For ease of use, the thermal ink heating element  12  is fixedly coupled to the temperature controller connector  102  and placed in a pouch  110 . For example,  FIG. 6  is a top plan view of the thermal ink heating element of  FIG. 3  in a pouch, the pouch being shown in broken view, and  FIG. 8  is a section view taken along the line  8 - 8  in  FIG. 6 . The pouch  110  may then be hermetically sealed and the pouch/thermal ink heating element combination placed in a blanket  50 , garment, or the like. For example,  FIG. 8  is a section view taken along lines  9 - 9  in  FIG. 5  showing the thermal ink heating element  12  inside the pouch  110  inside the blanket  50 .  FIGS. 10-12 , are views of exemplary garments that include the controllable thermal warming device of  FIG. 6 .  
      After use, the pouch/thermal ink heating element combination can be removed from the blanket and then the thermal ink heating element  12  and its associated the temperature controller connector  102  can be removed from the pouch  110  for reuse in a new pouch. The spent pouch  110  and/or blanket  50  may then be disposed of.  
      Also as previously mentioned, the controller  16  preferably causes the thermal ink heating element  12  to maintain its heat output at +100 degrees Fahrenheit, +/−4 degrees. Alternatively, the controller  16  may be configured to causes the thermal ink heating element  12  to maintain the heat output of its associated blanket or garment at +100 degrees Fahrenheit, +/−4 degrees.  
      The controller  16  of  FIG. 5  includes a proportional integral derivative (PID) controller, a control sensor such as a thermistor coupled to the thermal ink heating element  12 , and one or more safety devices. For example, the controller  16  of  FIG. 5  may include a PID controller having Part. No. 5C7-362, manufactured by Oven Industries, Inc., and capable of operating in P, PI, PD or PID control. Such a PID controller is adapted to enable the thermal ink heating element  12  to initially heat to +100 degrees Fahrenheit within 2 minutes, with subsequent heatings likely occurring in less time.  
      Such a PID controller is programmable via an RS232 communication port adapted for direct interface to a compatible PC and can therefore be coupled to a PC via a variety of communication cables having lengths commensurate with RS232 interface specifications. The RS 232 communications interface includes a 1500 VAC isolation from other electronic circuitry to minimize possible interferences due to noise or errant signals caused by common ground loops. When coupled to the PC, parameters of the PID controller may be set to desired values via the PC. Upon establishment of the parameters, the PC may be disconnected and the desired parameter settings retained in non-volatile memory of the PID controller.  
      During operation utilizing the aforementioned PID controller, the output signal from the controller  16  (i.e., the PID controller) to the thermal ink heating element  12  is Pulse Width Modulated (PCM) and is PC selectable for either 675 Hz or 2700 Hz operation. Such a PCM scheme averages the amount of energy provided to the thermal ink heating element  12  and reduces extreme temperature excursions possible in an “on/off” system. As a result, the life and reliability of the power source  14  may be extended. In addition, such a PWM control scheme may afford control accuracy to within +/−0.05 degrees Celsius at the control sensor.  
      The controller  16  of  FIG. 5  may utilize information provided by a sensor such as, for example, a thermally sensitive resistor or a thermistor  122 , to cause the controller  16  to make subsequent adjustments to the voltage supplied to the thermal ink heating element. The thermistor  122 , or control sensor is may be a Negative Temperature Coefficient (NTC) thermistor, rated at 15,000 ohms at +25 degrees Celsius, manufactured by Panasonic, Inc. and having part number ERT-D2FHL153S. For optimum accuracy of temperature control, the thermistor  122  is affixed directly to the thermal ink heating element  12 . Alternatively, the thermistor  122  may be attached to a covering, for example, the pouch  110 .  
      The controllable thermal warming device  100  may incorporate several safety devices and indications to protect the patient from potential injury. For example, if the temperature of the thermal ink heating element  12  climbs above +104 degree Fahrenheit, the controller  16  may automatically shut off the power to thermal ink heating element  12  and cause an alarm to sound. Such an alarm, for example an alarm having Part Number BRP2212L-12-C and manufactured by International Component, can be programmed to any upper limit and can be reset by the temperature controller  130 . Similarly, the controller  16  can also cause a visual indication when the temperature of the thermal ink heating element  12  falls below +98 degree Fahrenheit or when the temperature of the thermal ink heating element  12  is within a programmable target window. The controller  16  may also be configured to cause an alarm to sound if the temperature cable  106  becomes disconnected from the temperature controller connector  102  or if the thermistor  122  is at fault and becomes shorted or opened.  
      The controller  16  may be coupled to the thermal ink heating element  12  using one of any number of methods, depending on the application selected for the thermal ink heating element  12 . For example, in various medical applications, the temperature of the thermal ink heating element  12  should be automatically regulated to remain within +100 +/−4 degree Fahrenheit. In other applications, an individual user may desire to manually control the temperature of the thermal ink heating element  12  to vary the temperature between +100 and +110 degree F. In this case, the controller  16  may be configured in an alternate fashion to enable manual adjustment by a user (described below).  
      Referring again to automatic temperature control of the thermal ink heating element  12  by the controller  16  of  FIG. 5 , the temperature controller connector  102  attaches to the thermal ink heating element  12 , and includes heater element wires  126 , the thermistor  122 , a thermistor wire(s)  123 , a first heater element contact pad  124 , a second heater element contact pad  125 , and the first socket  104 . Each of the heater element wires  126  is an 18 gauge wire. As illustrated, one of the heater element wires  126  contacts the first heater element contact pad  124  and the other heater element wire  126  contacts the second heater element contact pad  125 . The first and second heater element contact pads  124  and  125  are constructed of copper squares. Alternatively, the first and second heater element contact pads  124  and  125  may be constructed of another suitable conductive material. Also as illustrated, each of the first and second heater element contact pads  124  and  125  contacts the first and second conductive inks pads  21  and  23 , respectively. Alternatively, each of the first and second heater element contact pads  124  and  125  may contact the conductive ink  20  at another location. It is contemplated that tape, copper rivets, conductive epoxy or any other suitable structure may be used to affix the heater element contact pads  124 ,  125  to the thermal ink heating element  12 .  
      The thermistor wire(s)  123  is soldered to the thermistor  122  and adhesive tape used to affix the thermistor  122  to the thermal ink heating element  12 . After connecting the temperature controller connector  102  to the thermal ink heating element  12 , the first and second sockets  104 ,  108 , respectively, may be mated, thereby coupling temperature cable  106  to the temperature controller connector  102 . In the illustrated example of  FIG. 5 , the temperature cable  106  includes the second socket  134  and four wires; two of the wires comprise the heater element wires  126  and two of the wires comprise the thermistor wire(s)  123 . Thus, the power source  14  is electrically connected to the conductive ink  20  and voltage is supplied from the power source  14  to the conductive ink  20  via the heating element wires  126 . In addition, the controller  16  is coupled to the thermistor  122  via the thermistor wire(s)  123 , thereby proving a feedback path to the controller  16 . Utilizing operating information from the thermistor  122  (e.g., electrical resistance indicative of a temperature), the controller  16  controls the power source  14  via regulating the amount of voltage supplied to the conductive ink  20 .  
      In an alternate embodiment, the thermistor  122  and associated thermistor wire(s)  123  may be deleted and the 18 gauge heating element wires  126  replaced by 22 gauge heating element wires  126 . In that case, the PID controller may be replaced by an alternate controller allowing manual control of the temperature. For example,  FIG. 12  is a top plan view of another controllable thermal warming device  150 , in accordance with an embodiment of the invention. In the illustrated example of  FIG. 12 , the controller  16  has been replaced by an alternate controller  116 , or a potentiometer assembly, having a solid state switch (MOSFET), a stable timer (NE555), a voltage comparator (LM393), a battery connector, a heating element connector and a control potentiometer with a built in On/Off switch.  
      During operation and after tactilely sensing the warmth of the thermal ink heating element  12 , a user may cause the temperature of the thermal ink heating element  12  to be adjusted to a desired comfort level by manually adjusting a control knob within the alternate controller  116 . The alternate controller  116  thereby enables the individual to regulate the amount of voltage supplied by the power source  14  to the conductive ink  20 .  
      In summary, the basic design principle of the alternate controller  116  is to turn the solid state switch on and off very quickly and vary the voltage supplied to the conductive ink  20  by changing the ratio of the “On” time to “Off” time. The ratio is adjustable from 0% (completely turned off) to 100% (completely turned on) via the control potentiometer which can be adjusted to vary the input to the voltage comparator. The variable input voltage is then compared against the output voltage of the timer. Each time the voltage output of the timer crosses the threshold of the comparator, the output of the controller turns on and then back off. The frequency of this On/Off cycle is preferably selected to be approximately 300 Hz.  
      The alternate controller  116  is configured to control the power source  14 , that may be a battery such as, for example, a lithium ion battery or a nickel metal hydride type rechargeable battery, made by AVT, Inc. A battery charger, such as for example, a TM. Model MHTX-7 Series manufactured by XENOTRONIX, Inc., may be used to recharge the battery of  FIG. 9 . Alternatively, the power source  14  of the controllable thermal warming device  150  may be configured as a DC source when it is available. In addition, the alternate temperature controller  116  is capable of operating via a +12 to +16 VDC source provided by a vehicle cigarette lighter or via a DC source within an emergency vehicle.  
      The controller  16  or controller  116  may be eliminated in accordance with other embodiments. For example, there may not be a need to utilize a controller if the temperature of the thermal ink heating element  12  does not need to be closely controlled. Moreover, the heat dissipated by the thermal ink heating element  12  may be held constant by controlling the resistance of the thermal ink heating element  12  in accordance with such embodiments. The resistance of the thermal ink heating element  12  may be controlled in any suitable manner such as, for example, by adjusting the amount of conductive ink that is applied during the manufacturing process. With such an embodiment, the amount of heat developed through the element will be proportional to the voltage applied and the current drawn from the battery source as shown below: 
          Power (Heat dissipated)=Battery Voltage×Current Drawn     where: Current Drawn−Battery Voltage/Heating Element Resistance.        

      The higher the resistance of the thermal ink heating element  12  the lower the operating temperature will be. As the resistance is decreased, the temperature of the thermal ink heating element  12  can be increased in a controlled manner. The temperature of the thermal ink heating element  12  may be controllable within certain ranges by maintaining a constant thermal ink heating element resistance.  
      Like the controllable thermal warming device  100  described in connection with  FIG. 5 , the controllable thermal warming device  150  may be placed in a pouch  40 . For example,  FIG. 13  is a top plan view of the controllable thermal warming device  150  placed the blanket  50 . The thermal ink heating element  12 , with the temperature controller connector  102  attached, is first placed within the pouch  40 , hermetically sealed, and the pouch/thermal ink heating element combination placed in a blanket  50  or the like.  
      Referring to  FIGS. 13 and 14 , the controllable thermal warming device  150  may be placed in a bore defined by the pouch  40  which, in turn, is placed in the blanket  50  or a covering  158  of a garment such as the vest or pants of  FIGS. 10-12 , as follows. A flap  152  in the blanket  50  is moved to an open position and the pouch  40 , containing the controllable thermal warming device  150 , is inserted through the pocket opening  152  and into a pocket cavity  154 . The controllable thermal warming device  150  is then secured to the power source  14  with the cables extending from within the pocket cavity  154  to outside the pocket cavity  154 . Activation of the power source  14  causes the controllable thermal warming device  150  to generate heat and warm all or portions of the blanket  50  or the garment. After the initial use, depending upon the construction of the controllable thermal warming device  150  and the extent of the initial use, the controllable thermal warming device  150  individually or in conjunction with the pouch  40  can be reused.  
      The covering  158  may be in one of any number of suitable forms, including, for example, in the form of apparel or clothing such as a vest (see, covering  158   a  of  FIG. 9 ) or a pair of pants (see, covering  158   b  of  FIG. 10  and covering  158   c  of  FIG. 11 ). The clothing may have any suitable outdoor or other use including, for example, clothing to be worn hunting, fishing, sporting, spectating, construction, or any other outdoor use, such as, for example, any use in connection with emergency, police, military, medical, traffic or similar uses. The size, location and number of pocket cavities  154  of the clothing figured to house the one or more controllable thermal warming devices  100  or  150  may vary. One or more controllable thermal warming devices may be included in any suitable garment and may used to heat any part of the body, including the torso, legs, arms, feet, hands, derriere or head.  
      As mentioned above, thermal ink heating element  12  may be configured in one of any number of suitable patterns for use in one of any number of applications. For example,  FIG. 14  is a front view of an exemplary glass panel  200  assembly utilizing a strip-shaped thermal ink heating element. The glass panel assembly  200  includes a glass plate  202  (e.g., a window, door, etc.) having an outer perimeter encased in a strip-shaped thermal ink heating element, or thermal ink heating strip  204 . The thermal ink heating strip  204  utilizes the conductive ink  20  disposed on the substrate in a strip-shaped pattern. In addition, the power source  14  is coupled to the thermal ink heating strip  204  via a suitable power connection  206 .  FIG. 15  is a section view taken along lines  16 - 16  in  FIG. 15 .  
       FIG. 16  is a front view of another exemplary glass panel assembly  220  that includes a sheet-shaped thermal ink heating element  224  sandwiched between two glass plates  222 . In the illustrated example, the glass panel assembly  220  is configured in a window arrangement on a window sill  230 , however, other arrangements are contemplated. The sheet-shaped thermal ink heating element  224  utilizes an invisible conductive ink, and may be placed directly against one of the two glass plates  222 , or may be placed in a space between the two glass plates  222 . The glass panel assembly  220  also includes the power source  14  coupled to the invisible conductive ink of the sheet-shaped thermal ink heating element  222  via a suitable power connection  228 .  FIG. 17  is a section view taken along lines  18 - 18  in  FIG. 16 .  
      The thermal ink heating element  12  may also be adapted to warm ambient air temperature. For example,  FIG. 18  is a side view of an exemplary duct assembly  240  that includes a thermal ink heating element, for example, the thermal ink heating element  12 . The thermal ink heating element may be contained inside of a pouch, for example the pouch  110  (see,  FIGS. 5-7 ), and may be coupled to the power source  14  via a power connection  244 . As illustrated by  FIG. 18 , the heating element  12  is positioned between the duct work  246  of a building structure. A partial front view of the duct assembly  240  is shown in  FIG. 19 . A similar configuration may be utilized to warm floors and walls.  
      In addition to wearing apparel, blankets, glass windows, floors, and walls, the thermal ink heating element  12  may be configured to provide heat to any number of consumer products such as baby bottles, baby carriages, pet water bowls, pet accessories, ceiling fans, mirrors, beverage coolers offering heat, pool coverings, vehicle portions and accessories such as a vehicle battery, a vehicle window, a vehicle seat or a vehicle electronic element (e.g., a vehicle sensor, a vehicle micro-controller). The thermal ink heating element  12  may also be configured to provide heat to farming products or tools such as livestock water troughs, restaurant products and food, military troop gear such as sleeping bags, hospital and patient products, and vehicles such as law enforcement and fire/rescue vehicles. The thermal ink heating element  12  may also be utilized to melt snow on, for example, a sidewalk or driveway. Additional examples, too numerous to mention, are also contemplated.  
      As is apparent in the above discussion, each of the controllable thermal warming devices described herein may provide a lightweight, flexible, portable, reusable, and/or disposable controllable heating device for use in blankets, wearing apparel and the like.  
      While the concepts of the present disclosure have been illustrated and described in detail in the drawings and foregoing description, such an illustration and description is to be considered as exemplary and not restrictive in character, it being understood that only the illustrative embodiment has been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected by the claims set forth below.