Abstract:
According to the present invention, a temperature controlled therapy device is provided which maintains a desired temperature in a fluid. The temperature controlled therapy device includes a fluid reservoir, a temperature controlled fluid, a watertight blanket having an internal space located therewith, a conduit connected between an exit port of the reservoir and an entry port of the blanket and between an exit port of the blanket and an entry port of the reservoir for defining a fluid circuit within which the temperature controlled fluid may circulate, a pump for circulating the temperature controlled fluid through the fluid circuit, a differential temperature sensor for generating an output signal proportional to a difference in fluid temperature in the blanket and a temperature at a remote location, an absolute temperature sensor for generating an output signal proportional to the temperature at the remote location, a control circuit having as inputs the outputs of the differential temperature sensor and the absolute temperature sensor for generating a control signal for operating the pump in order to maintain a defined temperature range in the fluid in the blanket, and a power supply for supplying power to the device.

Description:
TECHNICAL FIELD 
     This invention relates to the field of therapeutic medical devices. More particularly, this invention relates to a temperature controlled fluid therapy system utilizing sensors to provide signals to a continuously variable pump which cycles fluid therapy to an individual. 
     BACKGROUND OF THE INVENTION 
     Hot and cold therapies have been used for many years to treat physiological maladies. Ice, one of the more traditional cold therapy methods has the advantage of minimal cost and is easily manufactured. However, traditional ice application methods are not perfect, many patients complaining about leaky ice bags and the inconvenience of refilling the ice bag as the ice melts. Furthermore, traditional ice application methods are not very precise in applying a uniform temperature throughout the injured area. Likewise, the applicator temperature is not easily regulated. 
     Various mechanical cold and hot therapy systems have been developed to surmount some of the problems associated with the more traditional therapeutic techniques. Continuous flow cold therapy devices utilize a pump to force temperature regulated fluid through a “blanket” or applicator which, in turn, is applied to a patient. However, not all of these mechanical fluid therapy systems give a constant temperature regulation which may be deleterious to patient recovery. Additionally, current temperature sensors are susceptible to the presence of a liquid, resulting in operational fluctuations, unrelated to temperature. These fluctuations make it impossible to control the system temperature precisely. 
     There is a need for an improved fluid therapy system including improved temperature sensor systems that are inexpensive and not amenable to fluid contamination. 
     SUMMARY OF THE INVENTION 
     The foregoing and other needs are met by a temperature controlled therapy device according to the present invention. The temperature controlled therapy device is designed to maintain a desired temperature in a fluid, depending on a user&#39;s preference of a hot or a cold therapy treatment. The device includes a fluid reservoir, preferably containing a temperature controlled fluid. The reservoir has an entry and an exit port allowing the fluid to circulate from the reservoir to a watertight blanket. The blanket has an internal space for circulating the fluid therethrough and an entry and an exit port in fluid communication with the reservoir entry and exit ports, respectively. A conduit is connected between the exit port of the reservoir and the entry port of the blanket and between the exit port of the blanket and the entry port of the reservoir. The conduit defines a fluid circuit wherein the temperature controlled fluid circulates from the reservoir to the blanket and from the blanket to the reservoir. The device utilizes a pump to circulate the temperature controlled fluid through the fluid circuit. The device also utilizes a differential temperature sensor to generate an output signal which is proportional to a difference in fluid temperature in the blanket and a temperature at a remote location. An absolute temperature sensor generates an output signal that is proportional to the temperature at the remote location. The outputs from the differential temperature sensor and the absolute temperature sensor are input to a control circuit. The control circuit uses these inputs to generate a control signal which controls the operation of the pump and thereby maintains a defined temperature range within the fluid in the blanket. A power supply supplies power to the device. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further advantages of the invention will become apparent by reference to the detailed description when considered in conjunction with the figures, not drawn to scale, wherein like reference numbers indicate like elements through the several views, and wherein: 
     FIG. 1 is a front perspective view of a temperature controlled fluid therapy device in accordance with the invention; 
     FIG. 2 is a cross-sectional side view of components of the temperature controlled fluid therapy device in accordance with the invention; 
     FIG. 3 is another cross-sectional side view of components of the temperature controlled fluid therapy device in accordance with the invention; 
     FIG. 4 is a perspective view of a component of the temperature controlled fluid therapy device of FIGS. 2 and 3; 
     FIG. 5 is a block diagram illustrating the operation of the temperature controlled fluid therapy device; 
     FIG. 6 is a circuit diagram illustrating the temperature sensors and associated output voltage input into the pulse width modulator; 
     FIG. 7 is another cross-sectional side view of components of the temperature controlled fluid therapy device in accordance with the invention; 
     FIG. 8 is a front perspective view of an alternative embodiment of a temperature controlled fluid therapy device in accordance with the invention; 
     FIG. 9 is a circuit diagram illustrating the reservoir fluid sensor and associated output voltage input into the fill indicator means; and, 
     FIG. 10 is a circuit diagram illustrating the reservoir fluid sensor and associated output voltage input into the fill indicator means and the temperature sensors and associated output voltage input into the pulse width modulator. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With initial reference to FIG. 1 the invention relates to a temperature controlled fluid therapy device  10  for providing hot and cold therapies to an ailing area of a patient for rehabilitation of the patient. In a preferred embodiment of the invention, the temperature controlled fluid therapy device  10  includes a fluid reservoir  12 , a circuit board  14  including a control circuit  129  (FIGS.  5  and  6 ), a fluid conduit  16 , a submersible continuously variable pump  17 , a temperature controlled fluid blanket  18  and sensors  20  and  22 . 
     Fluid reservoir  12  is preferably constructed of a thermoplastic material, plastic or rubber, and has a fluid handling capacity of between about 4 liters and about 6 liters. Preferably, fluid reservoir  12  includes an interior wall  24  which forms a cavity  26  between the interior wall  24  and outer wall  28 . It is preferred that the cavity  26  be filled with an insulating material such as a gas under vacuum conditions, or styrofoam, Alternatively, the interior wall may be constructed of an insulating material such as foam or plastic, formed adjacent to the outer wall  28 . Fluid reservoir  12  includes a fill port  30  which is generally circular in shape having a diameter of between about 3.75 inches and about 4.75 inches. The filler port  30  includes a threaded neck  32  extending outward from the outer wall  28  of the fluid reservoir  12  for threadably engaging a complimentary threaded enclosure  34 . It is preferred that the enclosure  34  be constructed so as to insulate the fluid reservoir  12 , substantially preventing the evaporation of fluid contained therein. As will be discussed in more detail below, the fluid reservoir  12  preferably includes an entry port  36  and an exit port  38  for admitting and expelling fluid into and out of fluid reservoir  12 , respectively. 
     A submersible continuously variable pump  17  is housed within the fluid reservoir  12 . The pump  17  preferably has a throughput of between about ¼ gallons/hour and about 10 gallons/hour. The pump  17  is connected to the printed circuit board  14  via wires  40  providing a continuously variable power supply to the pump  17  by utilizing power source  42 , to be described more fully below. The submersible pump  17  includes an intake  44  port and an output port  46 . When the pump  17  is operating, fluid within reservoir  12  is drawn into the intake port  44  of pump  17  and forced out through the output port  46  of pump  17  and into the connector  48 . In an alternative embodiment of the invention, a hand pump  19  (FIG. 8) may also be included, operable to provide an alternative pump means for the device  10 . The hand pump  19  is preferably disposed adjacent the fluid conduit  16 , and includes two one-way check valves for pumping fluid through the fluid circuit. If a pump  17  is not included in device  10 , or if the pump  17  is inoperable or malfunctioning, the hand pump  19  is effective to pump fluid between the reservoir  12  and the watertight blanket  18 . The connector  48  is preferably a flexible plastic or rubber hose having a diameter of between about ¼ inches and about ⅜ inches. As shown in FIG. 1, the connector  48  fluidly connects the output port  46  of the pump  17  with the exit port  38  of the fluid reservoir  12 . A strap  160  may also be attached via fasteners  162  to the reservoir  12  for ready portability of the fluid therapy device  10  (FIG. 8) 
     The fluid conduit  16  preferably comprises two elongate tubes, intake conduit  50  and output conduit  52 , each having first ends  132  and  134 , and second ends  136  and  138 , respectively. It is preferred that the intake conduit  50  and the output conduit  52  are enclosed with an insulating layer  53  of material such as foam rubber or foam plastic (FIG.  7 ). The insulating layer  53  of material tends to keep the fluid circulating within the intake and output conduits  50  and  52 , respectively, at a relatively constant temperature with little heat transfer into or out of the insulating layer  53 . Preferably the elongate tubes, intake conduit  50  and output conduit  52  are composed of similar material as the connector  48 , having diameters of between about 0.25 inches and about 0.75 inches and lengths of between about 4 feet and about 8 feet. 
     The first ends  132  and  134  of elongate tubes  50  and  52  are preferably fixedly secured within the fluid reservoir  12 . The first end  132  of the intake conduit  50  is secured within reservoir  12  so that the end  132  is in fluid communication with the interior of the fluid reservoir  12 . The first end  134  of the output conduit  52  is preferably secured to the connector  48 , forming a fluid path between the output port  46  of the pump  17  and the output conduit  52 . As shown in FIGS. 2 and 3, identical female spring actuated quick-release snap fit couplers  54  are attached to the second ends  136  and  138  of the intake conduit  50  and output conduit  52 , respectively, and are formed to accept complimentary male snap fit couplers  56  located adjacent to the first ends  140  and  142  of an inflow conduit  58  and outflow conduit  60 , respectively, being in fluid communication with the temperature controlled fluid blanket  18 . In a preferred embodiment of the invention, the second ends  144  and  146  of the inflow conduit  58  and outflow conduit  60  are fixedly attached to the blanket  18 . Preferably, the inflow and outflow conduits  58  and  60  have a length of between about 4 inches and about 8 inches, and a diameter of between about 0.25 inches and about 0.75 inches. It is also preferred that the inflow and outflow conduits  58  and  60  are enclosed by a similar layer of insulating material as described above for the intake and output conduits  50  and  52 . 
     The components of the female and male couplers  54  and  56  operate together to provide fluid communication between the intake and output conduits  50  and  52  and inflow and outflow conduits  58  and  60 , respectively, providing a fluid circuit between the reservoir  12  and the blanket  18 . As shown in FIGS. 2 and 4, the female coupler  54  includes a flange  61 , throat  62 , stem  64 , locking member  66 , locking member spring  68 , pin actuator  70 , pin actuator spring  72 , receiving end  74 , throat actuator  76 , throat actuator spring  78 , o-ring  80 , rear wall  81 , apertures  83 , and body  85 . The male coupler  56  includes a throat  82 , stem  84 , throat actuator  86 , throat actuator spring  88 , throat actuator orifices  90 , o-ring  92 , bore  94 , recess  96 , flange  98 , body  100 , actuator o-ring  102 , and rear wall  104 . 
     The stem  64  of each female coupler  54  is inserted into the second ends  136  and  138  of the intake conduit  50  and output conduit  52 . The female coupler  54  is fully seated when the flange  61  lies substantially adjacent to the second ends  136  and  138  of the intake conduit  50  and output conduit  52 , respectively. Likewise, the stem  84  of each male coupler  56  is inserted into the first ends  140  and  142  of the inflow conduit  58  and outflow conduit  60 . The male couplers  56  are fully seated when the flange  98  lies substantially adjacent to the first ends  140  and  142  of the inflow conduit  58  and outflow conduit  60 , respectively. As shown in FIG. 2, when the male and female couplers  54  and  56  are uncoupled, the throat actuators  76  and  86  are not actuated, meaning that the throats  62  and  82  of the female and male couplers  54  and  56  are blocked by the throat actuators  76  and  86 . As will be described below, coupling the female coupler  54  with the male coupler  56  actuates both throat actuators  76  and  86 , providing fluid communication between the intake conduit  50  and output conduit  52  and the inflow conduit  58  and outflow conduit  60 . 
     As shown in FIG. 2, when the male coupler  56  is uncoupled from the female actuator  54 , the spring  88  urges the throat actuator  86  away from the throat  82  so that the throat actuator orifices  90  of the male throat actuator  86  are occluded by the body  100  and the actuator o-ring  102  secured to a rear wall  104  of throat actuator  86  ensures that no fluid may be transported between the inflow and outflow conduits  58  and  60  and the bore  94  of the male throat actuator  86 . Similarly, when the female coupler  54  is uncoupled, the spring  78  urges the female throat actuator  76  away from the throat  62  so that the receiving end  74  is occluded by the rear wall  81  and o-ring  80  of the female throat actuator  76  and the apertures  83  are occluded by the body  85  of the female coupler  54 , thereby preventing fluid from being transported between the intake and output conduits  50  and  52  and the female coupler  54 . 
     The intake conduit  50  and output conduit  52  and the inflow conduit  58  and outflow conduit  60  are coupled together by releasably connecting each male coupler  56  of the inflow conduit  58  and outflow conduit  60  into each female coupler  54  of the intake conduit  50  and output conduit  52 . As best shown in FIG. 3, when the male coupler  56  is inserted into the receiving end  74  of the female coupler  54 , the throat actuator  86  and body  100  of the male coupler  56  impinges on the throat actuator  76  of the female coupler  54 , thereby compressing throat actuation springs  78  and  88 , allowing the female throat actuators  76  to actuate towards the second ends  136  and  138  of the intake conduit  50  and output conduit  52  and the male throat actuator  86  to actuate towards the first ends  140  and  142  of the inflow conduit  58  and outflow conduit  60 . As the body  100  of each male coupler  56  impinges on the female throat actuator  76 , the female actuators  76  are urged towards the second ends  136  and  138 , the rear wall  81  and o-ring  80  gravitating away from the receiving end  74  and into the wider portion of the throat  62 . Additionally, the apertures  83  located on the throat actuator  76  also move into the wider throat  62  creating a fluid pathway between the receiving end  74  and throat  62  of the female coupler  54 . As the male throat actuator  86  impinges on the female throat actuator  76 , the actuator spring  88  compresses and the rear wall  104  and associated actuator o-ring  102  are urged away from the recess  96  allowing the throat actuator orifices  90  to enter into the throat  82  of the male coupler  56 , thereby creating a fluid pathway between the bore  94  of the male throat actuator  86  and the throat  82  of the male coupler  56 . 
     As the body  100  of the male coupler  56  enters the receiving end  74  of the female coupler, the o-ring  92  seals against the body  85  of the female coupler  84 , preventing leakage between the coupled male and female couplers  56  and  54 , respectively. As the male coupler  56  is inserted into the female coupler  54 , the body  100  of the male coupler  56  continues to impel the female throat actuator  76  as the facing surface  106  of the male coupler  56  moves the pin actuator  70  against the force of the pin actuator spring  72  until the notch  108  of the pin actuator  70  is aligned with the slot  110  of the locking member  66 . Once the notch  108  of the pin actuator  70  is aligned with slot  110 , the locking member spring  68  expands, releasing locking member  66  from its unlocked position to releasably engage the recess  96  of the male coupler  56 , securing the male coupler  56  to the female coupler  54 , thereby providing fluid communication between the fluid reservoir  12  and blanket  18 . The male coupler and female coupler  56  and  54  are disengaged by depressing the actuating surface  112  of the locking member  66  which compresses the locking member spring  68 , allowing a wide portion of the slot  110  to move towards the pin actuator  70 . The wide portion of the slot  110  is wider than the notch  108  diameter of the actuator pin  70  (FIG.  4 ). As the pin actuator spring  72  expands, the actuator pin  70  is impelled outward so that a wider portion of the actuator pin  70  engages the wider portion of the slot  110  maintaining the locking member  66  away from the recess  96  of the male coupler, so that the female and male couplers  54  and  56  may now be disengaged. 
     As shown in FIG. 1, the blanket  18  is preferably secured to the second ends  144  and  146  of the inflow and outflow conduits  58  and  60 , respectively. However, alternatively, it may be preferred to utilize a releasable coupler between the inflow and outflow conduits  58  and  60  and the blanket  18 . The shape of the blanket  18  can be designed to accommodate a variety of rehabilitation area configurations. For example, a different shape can be used to treat a head rehabilitation area compared to the shape used to treat a shoulder or knee rehabilitation area. A plurality of elastic straps  114 , including fastening means  116  are used to releasably maintain the blanket  18  adjacent to the area to be rehabilitated. The fastening means  116  are preferably velcro, but male and female snap members are also available. Furthermore, according to the present invention, the releasable snap-fit male and female couplers  56  and  54  allow for quick interchangeability of a specific blanket  18  directed to rehabilitating specific areas of a patient. The blanket  18  includes an interior space  118  for circulating hot or cold fluid pumped from the reservoir  12  by the submersible continuously variable pump  17  through the fluid circuit defined by the output conduit  52 , inflow conduit  58 , outflow conduit  60 , intake conduit  50 , pump  17 , reservoir  12  and blanket  18 . It is preferred that the interior space  118  of the blanket  18  forms a plurality of channels  120  for cycling the fluid through the blanket at a rate of between about ¼ gallons/hour and about 10 gallons/hour. Blanket  18  is preferably formed of plastic, rubber, and non-woven material. 
     As shown in FIG. 1, the printed circuit board  14  is attached to outer wall  28  of the fluid reservoir  12 . Preferably, the circuit board  14  is enclosed by a faceplate  122 , including a reservoir  12  fill indicator means  124 , and a power source connection port  126 . The power source connection port  126  is configured for connecting an alternating current (AC) to direct current (DC) adapter to an AC power source  42  or, alternatively, a DC power source  42  may be directly connected to the power source connection port  126  via electrical connector  43 . 
     The fill indicator means  124  indicates a fluid fill condition to an operator or user. The fill indicator means  124  may be a dual-mode light, a green signal indicating a no-fill condition and a red signal indicating a fluid fill alert. Preferably, the fill indicator means is electrically connected to the control circuit  129  and also to a reservoir sensor  128  located in the interior space of the reservoir  12  (FIG.  9 ). The sensor  128  may be capable of sensing a plurality of fluid conditions within reservoir  12 , such as the fluid temperature and quantity. In one embodiment, the sensor  128  is a thermistor which is operable to provide a voltage signal to the control circuit  129  proportional to the temperature of the fluid within the reservoir  12 . 
     For a cold therapy application the voltage signal V 00  provided by the sensor  128  is compared to a voltage V REFR  corresponding to the preferred optimal fluid temperature of between about 35° F. and about 55° F. within the fluid reservoir  12 . If the sensed temperature is about 55° F. or less, the fill indicator means  124  will indicate a no-fill condition. However, if the sensed temperature is greater than about 55° F., the fill indicator means  124  will indicate a fill condition, alerting a user or operator to add more ice or cold fluid to the reservoir  12 . 
     For a hot therapy application the voltage signal V o  provided by the sensor  128  is compared to a voltage V REFR  corresponding to the preferred optimal fluid temperature of between about 95° F. and about 110° F. within the fluid reservoir  12 . If the sensed temperature is between about 95° F. to about 110° F., the fill indicator means will indicate a no-fill condition. However, if the sensed temperature is less than 95° F., the fill indicator means will indicate a fill condition, alerting a user or operator to add more hot fluid to the reservoir  12 . For a device  10 , having an internal refrigeration or heating means within the reservoir  12 , the signal provided by the sensor  128  operates as a control signal, enabling or disabling the refrigeration or heating means. Table 1 lists preferred values for the components of FIG.  9 . 
     
       
         
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
             
             
               
                 V 1   
                 ˜5.0 
                 V 
               
               
                 V 2   
                 ˜2.5 
                 V 
               
               
                 V REFR   
                 ˜3.38 
                 V 
               
               
                 R 1   
                 ˜100 
                 ohms 
               
               
                 R 2   
                 ˜100 
                 ohms 
               
               
                 R 3   
                 ˜69.8 
                 kohms 
               
               
                 R 4   
                 ˜69.8 
                 kohms 
               
               
                 R 5   
                 ˜1.74 
                 kohms 
               
               
                   
               
             
          
         
       
     
     In an alternative embodiment of the invention, a thermocouple may be used in place of the thermistor as the sensor  128  which is also operable to provide a temperature of the fluid within the reservoir  12 . As described below, the output voltage signal from the thermocouple sensor is proportional to the temperature difference between two wire junctions,  164  and  166 . Since the output voltage signal of the thermocouple sensor is proportional to the temperature difference between the two junctions  164  and  166 , the thermocouple sensor cannot provide an absolute temperature indication at the junctions. Therefore, by utilizing a cold junction compensation circuit such as thermistor  20 , the signal provided by the thermistor sensor  20  located adjacent to the circuit board  14  changes with and compensates for the changes in the ambient temperature to determine an absolute temperature and output voltage V 00  at junction  164  of the thermocouple (FIG.  9 ). Since the thermocouple is inherently insensitive to water permeation, the thermocouple sensor is operable to provide a reservoir temperature indication signal and/or control signal V 00  which is used as described above without erroneous indications due to fluid permeation. 
     Furthermore, an audible signaling device may be used to indicate a fluid fill alert, audibly signaling a fluid fill condition to an operator or user. Similarly, a fluid level indicator and temperature indicator may be used to alert the operator to the fluid conditions within the reservoir  12 . 
     Preferably, the circuit board  14  is disposed between the outer wall  28  and interior wall  24  of the fluid reservoir  12  so that the fluid within reservoir  12  does not come into contact with the circuit board  14 . That is, it is preferred that the circuit board  14  is maintained in a dry state, ensuring the operability of the electrical connections of the board  14 . The wires  40  connecting the circuit board to the pump  17  pass through an aperture formed in the interior wall  24  of the reservoir  12 , and a sealant or gasket is used around the wires  40  at the point where they pass through the aperture for preventing fluid from entering the space between the interior wall  24  and exterior wall  28 , where the circuit board  14  is located. 
     According to a preferred embodiment of the invention, two sensors  20  and  22  are utilized to determine a control signal, which controls the operation of the submersible pump  17 . Preferably, when a DC or AC power source  42  is connected to the power source connector port  126  a voltage is always applied to the submersible pump  17  via the conducting wires  40 . The power provided to the submersible pump  17  is based on the control signal determined from the output of sensors  20  and  22 . Preferably, sensor  20  is a thermistor type sensor having a variable resistance of between about 1,000 ohms and 10,000 ohms. The resistance of a thermistor type sensor varies exponentially according to the surrounding temperature and is operable to output an absolute temperature reading. As shown in FIG. 1, the thermistor sensor  20  is adjacently located to the circuit board  14 , and similarly protected between the interior wall  24  and exterior wall  28  as the circuit board  14  from potential fluid permeation. It is preferable to maintain the thermistor sensor  20  in a “dry” state since fluid permeation impinging on the thermistor sensor  20  may tend to cause the thermistor sensor  20  to provide an erroneous absolute temperature signal. 
     For a cold fluid therapy device, it is preferable to maintain the fluid within a desired temperature range so that maximal beneficial results are seen at the treatment area of a user or patient. According to the invention, to obtain an accurate blanket  18  temperature reading, it is preferable to sense the temperature of the fluid circulating through the blanket  18  as close as possible to the blanket  18 . Preferably, the fluid temperature is sensed at a location adjacent to the second end  136  of the intake conduit  50  which when connected to the outflow conduit  60  tends to give a close approximation of the temperature of the fluid circulating through the blanket  18 . 
     Therefore, it is preferred to use a sensor which tends to be impervious to fluid permeation, such as a thermocouple sensor  22 . The thermocouple sensor  22  is preferably a T-type thermocouple (constantan member  148  and copper member  150  (FIG.  6 )), but a K-type thermocouple consisting of a chromell member and alumel member, or other types of temperature sensors, are also viable sensors. Accordingly, the thermocouple sensor  22  includes a cold junction  152  and a hot junction  154 , and the output signal from the thermocouple sensor  22  is proportional to the temperature difference between the cold and hot junctions  152  and  154 , respectively. Since the output signal of the thermocouple sensor  22  is proportional to the temperature difference between the cold and hot junctions  152  and  154 , the thermocouple sensor  22  cannot provide an absolute temperature indication at junctions  152  or  154 . By utilizing the absolute (compensating) temperature signal provided by the thermistor sensor  20 , it is possible to determine the absolute temperature at junction  154  of the thermocouple sensor  22 . 
     According to a preferred embodiment of the invention, the cold junction  152  of the thermocouple sensor  22  is adjacently located to the thermistor sensor  20  on the circuit board  14 . An approximate temperature of the cold junction  152  of the thermocouple sensor  22  may be determined by locating the cold junction  152  of the thermocouple sensor  22  adjacent to the thermistor sensor  20  since the thermistor sensor  20  is providing an absolute temperature signal. As described above, the thermocouple sensor  22  provides a signal proportional to the temperature difference between the cold and hot junctions  152  and  154 . Therefore, by utilizing the sensed thermistor sensor  20  signal to determine approximately the cold junction  152  temperature, the hot junction  154  temperature is determined by subtracting the cold junction  152  temperature from the sensed temperature difference of the thermocouple sensor  22 , providing a temperature of the hot junction  154 . 
     FIG. 7 depicts a preferred embodiment for the location of the hot junction  154  of the thermocouple sensor  22 . As shown, the thermocouple  22  is preferably located between the insulating layer  53  and the fluid conduit  16 . The thermocouple  22  extends from the cold junction  152  adjacently located to the circuit board  14  to the hot junction  154 , which preferably penetrates through an orifice  160  into the intake conduit  50 . Preferably, the aperture  160  and hot junction  154  are located adjacent to the second end  136  of the intake conduit  50 . It is preferred that the orifice  160  is sealed around the sensor  22  by using epoxy, or sealant. Accordingly, by locating the hot junction  154  of the thermocouple sensor  22  adjacent to the second end  136  of the intake conduit  50  and thereby adjacent to the first end  142  of the outflow conduit  60  of the blanket  18 , an approximate temperature of the fluid within the blanket  18  may be determined due to the proximity of the hot junction  154  with respect to the fluid exiting the blanket  18 . Correspondingly, the device  10  provides hot or cold fluid therapies to a user without the concern of erroneous temperature readings due to water permeation of the thermocouple sensor  22 , since the thermocouple  22  is substantially insensitive to water permeation. 
     In another embodiment of the invention, the hot junction  154  of thermocouple sensor  22  does not penetrate the intake conduit  50 , but is instead located between the fluid conduit  16  and the insulating layer  53 . Accordingly, it is still possible to obtain an accurate approximation of the fluid temperature within the blanket  16 , however, there may be a slight delay in sensing the actual fluid temperature due to the material properties of the fluid conduit  16 . Therefore, for this latter sensor configuration, a ‘warm-up’ time may be necessary to achieve an appropriate fluid temperature determination. 
     Since the temperature of the fluid flowing throughout the temperature controlled fluid therapy device  10  is in constant flux, the hot junction  154  temperature will vary correspondingly. Therefore, it is possible to regulate the temperature of the fluid within device  10  by using the varying hot junction temperature as an input to a control circuit  129 . Referring to FIG. 5, the control circuit  129  utilizes the thermistor sensor  20  and thermocouple sensor  22  signals to generate a control signal which is input to a calibrated pulse width modulator  130 . More particularly, and with additional reference to FIG. 6, the control circuit  129  generates an output voltage V 0  which varies according to the fluctuating fluid temperature. Table 2 lists preferred values for the circuit components of the control circuit  129  for a cold therapy device  10 . 
     
       
         
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
             
             
               
                 V 1   
                 ˜5.0 
                 V 
               
               
                 V 2   
                 ˜2.5 
                 V 
               
               
                 V REF   
                 ˜3.08 
                 V 
               
               
                 R 1   
                 ˜100 
                 ohms 
               
               
                 R 2   
                 ˜100 
                 ohms 
               
               
                 R 3   
                 ˜69.8 
                 kohms 
               
               
                 R 4   
                 ˜69.8 
                 kohms 
               
               
                 R 5   
                 ˜1.74 
                 kohms 
               
               
                   
               
             
          
         
       
     
     According to the invention, the varying voltage V o  is compared to the reference voltage V REF  and the result is used to control the pulsewidth of a pulse output from the voltage controlled pulse width modulator  130 . For a cold therapy device the reference voltage V REF  corresponds to a set-point temperature of between 35° F. and about 55° F. The voltage V o  is proportional to a function of the cold junction temperature (thermistor signal) plus another function of the temperature difference between the hot and the cold junctions  154  and  152  (thermocouple signal), respectively. Additionally, for a hot fluid therapy application, the control circuit  129  utilizes a set point temperature of the fluid of between about 95° F. and about 110° F., essentially comparing the hot junction  154  temperature with the set point temperature to generate a control signal which is input to the pulse width modulator  130 . 
     Accordingly, the pulse width modulator  130  utilizes the control signal output from the control circuit  129  to modulate the width of a pulse which is used to control the operation of the pump  17 . More specifically, the duty cycle of the pulse width modulated signal is continuously varying according to the varying temperature of the fluid at the hot junction  154  of the thermocouple sensor  22 . The varying pulse duty cycle output from the calibrated pulse width modulator  130  controls the average power delivered to the submersible pump  17  via power source  42 , therefore controlling the speed of the continuously variable submersible pump  17 . The pulse width modulator  130  is calibrated to vary the duty cycle of the pulse based on the control signal output from the control circuit  129 . For example, when the control circuit  129  determines that the hot junction  154  temperature of the thermocouple is about equal to the set point temperature, the control circuit  129  sends a corresponding control signal to the pulse width modulator  130 . In response, the pulse width modulator  130  modulates the pulse width modulated signal such that pump  17  is operating at about the mid-range of between about ¼ gallons/hour and about 10 gallons/hour. 
     Depending on the application of the temperature controlled fluid therapy device  10 , that is, cold or hot fluid therapy applications, the control signal output from the control circuit  129  is controlled accordingly. For a cold fluid therapy application, as the hot junction  154  temperature increases, the control signal output from the control circuit  129  will vary correspondingly and the duty cycle of the pulse output from the pulse width modulator  130  will increase, causing the pump rate to increase which correspondingly increases the flow of cool fluid flowing from within reservoir  12  to the blanket  18 . If the temperature at the hot junction  154  decreases below the set point temperature, the duty cycle of the pulse will correspondingly decrease, to a point where the pump  17  is nearly stopped. However, as described above, preferably there is always power applied to the pump  17 , the duty cycle of the pulse output from the pulse width modulator varying the supplied power according to the hot junction temperature  154 . On the other hand, for a hot fluid therapy application, as the hot junction  154  temperature decreases, the control signal output from the control circuit  129  will vary correspondingly and the duty cycle of the pulse output from the pulse width modulator  130  will increase, causing the pump rate to increase which correspondingly increases the flow of hot fluid flowing from within reservoir  12  to the blanket  18 . 
     In an alternative embodiment of the invention, it is preferable to control the fluid temperature within the blanket  18  based on the skin temperature of the individual using the device  10 . Research has determined the point at which neurons in the skin begin reactivating. Therefore, it would be preferable to measure the skin temperature to control the neuron firing. Accordingly, a thermistor sensor  156  is adjacently located to the blanket  18  (FIG.  8 ). The thermistor sensor  156  is connected to the circuit board  14  via electrical connector  158 . The electrical connector  158  is preferable an insulated conductor, such as insulated copper wire, and may be contained between the insulating layer  53  and the conduit  16 , or alternatively, the connector  158  may be externally located with respect to the insulating layer  53 . The electrical connector  158  preferably includes a coupling  159 , which allows the connector  158  to be disconnected when it is desired to disconnect the blanket  18  from the fluid conduit  16 . In this embodiment of the invention, the thermocouple sensor  22  is not a necessary component of device  10  for measuring the temperature of the blanket  10 . Depending on the particular blanket  18 , the thermistor  156  is preferably located directly adjacent to the rehabilitation area, obtaining the most accurate skin temperature when the blanket  18  and fluid are applied to the individual. In this embodiment, since the thermistor  156  is at a location where there is no potential water contamination, an absolute temperature indication of the skin is available without the possibility of erroneous measurements due to fluid permeation of the thermistor  156 . The control circuit  129  compares the thermistor  156  signal to a reference voltage V REF , inputting the result to the pulse width modulator  130 . The pulse width modulator  130  varies the duty cycle of the pulses according to the result, controlling the operation of the pump  17 , as discussed previously. 
     According to the invention, since the pump  17  speed varies based on the duty cycle of the pulse output from the pulse width modulator  130 , the frequency of the pulses is not a controlling factor. However, the armature of the pump  17  tends to vibrate at the frequency of the pulse width modulated signal, and signal frequencies in the audible range (&lt;20 kHz) tend to make for a noisy pump. According to a preferred embodiment of the invention, the frequency of the pulses output from the pulse width modulator  130  is adjusted by modulation above the audible range (&gt;20 kHz), tending to provide a quieter temperature controlled fluid therapy device  10 . 
     Once the intake conduit  50  and output conduit  52  and the inflow conduit  58  and outflow conduit  60  are connected, a patient may now utilize the temperature controlled fluid therapy device  10  to treat an injured or sore area by applying the blanket  18  thereto. Depending on the application, hot or cold fluid therapy, the fluid reservoir is filled with hot or cold fluid via fill port  30 . The user can place the blanket over the treatment area before or after a DC or an AC power source is plugged into the power source connection port  126 , immediately providing power to the pump  17 . As described above, the control circuit  129  utilizing sensors  20  and  22  automatically regulates the amount of hot or cold fluid flowing to the blanket  18 . If the hot or cold fluid within reservoir  18  drops below or above a preferred fluid temperature, the fill indicator means  124  will communicate the condition to the user or operator, who may then add hot or cold fluid to the reservoir  12  (FIG.  10 ). 
     It is contemplated, and will be apparent to skilled in the art from the preceding description and the accompanying drawings, that modifications and changes may be made in the embodiments of the invention. For example, the intake and output conduits  50  and  52  and inflow and outflow conduits  58  and  60  can be one continuous piece, that is, not including the male and female couplers  54  and  56 . Also, the pump can be externally located from the reservoir  12  controlling the flow of fluid from the reservoir  12  to the blanket  18 . Additionally, reservoir  12  can contain refrigeration and/or heating capability and related circuitry for automatically regulating the temperature of the fluid within reservoir  12 . Moreover, a fluid fill line and drain line can be attached to a fluid fill port and drain port on reservoir  12  which automatically fills reservoir  12  with hot or cold fluid upon a sensed level/temperature condition of reservoir  12 , draining fluid as new fluid is added to reservoir  12 . Accordingly, it is expressly intended that the foregoing description and the accompanying drawings are illustrative of preferred embodiments only, not limiting thereto, and that the true spirit and scope of the present invention be determined by reference to the appended claims.