Abstract:
A freeze control system for a spa for maintaining the temperature of the water inside the spa and the spa&#39;s associated piping above the freezing level. Elements include: 1) a heating element for heating the water, 2) at least one pump for pumping the heated water, 3) a first sensor for detecting the temperature of the water in the spa tub, 4) a second sensor for detecting the temperature of the ambient air around the spa, and 5) a computer programmed to process signals generated by the first sensor and the second sensor, wherein the computer selectively activates and deactivates the heating element and the at least one pump.

Description:
[0001]    This invention relates to spas, and, in particular to spas used in climates where water tends to freeze when the temperature gets cold. This application claims priority of provisional application Ser. No. 60/106,229 filed Oct. 30, 1998. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    A spa (also commonly known as a “hot tub”) is a therapeutic bath in which all or part of the body is exposed to forceful whirling currents of hot water. Spas are popular throughout the world but are especially popular in areas of cold climate, such as at ski resorts and other extremely cold locations. Spa users tend to find it especially pleasurable to move from an area of extreme cold to the comfort of a nice, hot spa. However, there is an unfortunate problem associated with operating and maintaining a spa in a cold location. If a spa is operated in a climate where water tends to freeze, unless appropriate measures are taken, water inside the plumbing of the spa may also freeze and cause damage to the plumbing. Conventionally, the water in the tub itself is maintained in its liquid state by the temperature control system of the spa which keeps the water in the tub at a temperature that is high enough to prevent freezing of the water in the tub. The problem with which the industry is faced, however, is that the water in the plumbing system of the spas will cool down much faster than the water in the tub itself. Therefore, the water in the plumbing may freeze while the water in the tub is still in its liquid state.  
           [0003]    U.S. Pat. Nos. 5,361,215, 5,550,753, and 5,559,720 disclose a solution to the problem of water freezing in spa plumbing. These patents teach that the problem can be solved through the installation of temperature sensors that sense the temperature of the water in the plumbing and the tub and will circulate the water through the plumbing if the water in the plumbing gets too cold.  
           [0004]    A prior art spa  1  is shown in FIG. 1. The prior art spa has temperature sensor  3  which measures the water temperature inside tub  7  and temperature sensor  5  which measures the water temperature inside water heater  9 . In the prior art, sensor  5  is used not only to protect the user from excessive temperature, but also for freeze protection. To protect the user for excessive temperature, sensor  5  will send an electrical signal to spa controller  11  if it senses a temperature greater than approximately 119 deg. F. If this temperature is detected by sensor  5 , spa controller  11  will then shut-off water heater  9 .  
           [0005]    As a freeze protection system, the prior art works as follows. While spa users are using the spa, they can manually set the temperature of the spa by entering the desired temperature into spa controller  11  via keypad  15 . When the spa is no longer in use, and the users have left the spa, spa controller  11  continues to automatically control the temperature of the spa. In the prior art, when the temperature in spa tub  7  falls below a preset temperature (as detected by sensor  3 ), sensor  3  sends a signal to spa controller  11 . Spa controller  11  turns on heater  9  and water pump  13 . Hot water is then pumped into spa tub  7 . Heater  9  and water pump  13  will remain on until sensor  3  reports a temperature above the preset temperature. Likewise, in the prior art, when sensor  5  senses a plumbing temperature less than a preset temperature (for example, 40 deg. F.), it will cause spa controller  11  to turn on heater  9  and water pump  13 . Hot water is then pumped back into spa tub  7 . Heater  9  and water pump  13  will remain on until sensor  5  reports a temperature greater than the preset temperature (i.e., 40 deg. F.).  
           [0006]    Unfortunately, the solution offered by the prior art has serious problems. If there is more than one plumbing circuit in a spa, more than one temperature sensor will be needed. In other words, each plumbing circuit will require its own temperature sensor that provides information to spa controller  11 . Because of the extra expense involved, Applicants know of no system that currently offers separate sensors for each plumbing circuit. Also, there is no accommodation in the prior art for protection of the air blower and its associated piping. Although, the air blower functions to blow air into the spa, it is a common occurrence for water to leak back through air injector valves  4  into air blower piping  6  (FIG. 1). Consequently, water inside air blower piping  6  can also expand upon freezing causing severe, costly damage. Another disadvantage is that the plumbing temperature sensor disclosed in the prior art is located at the water heater which causes the sensor to return a value for plumbing water temperature that is actually warmer than the true water temperature in most of the plumbing. This means that water in certain parts of the plumbing may freeze while the water near sensor  5  is still in a liquid state.  
           [0007]    What is needed is a better freeze control system for spas.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention provides a freeze control system for a spa for maintaining the temperature of the water inside the spa and the spa&#39;s associated piping above the freezing level. Elements include: 1) a heating element for heating the water, 2) at least one pump for pumping the heated water, 3) a first sensor for detecting the temperature of the water in the spa tub, 4) a second sensor for detecting the temperature of the ambient air around the spa, and 5) a computer programmed to process signals generated by the first sensor and the second sensor, wherein the computer selectively activates and deactivates the heating element and the at least one pump. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 shows a prior art spa.  
         [0010]    [0010]FIG. 2 shows a first preferred embodiment of the present invention.  
         [0011]    [0011]FIG. 3 shows a second preferred embodiment of the present invention.  
         [0012]    [0012]FIG. 4 shows a perspective view of the second preferred embodiment of the present invention.  
         [0013]    [0013]FIG. 5 shows a detailed view of the spa controller.  
         [0014]    [0014]FIG. 6 shows a perspective view of the first preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0015]    A detailed description of a preferred embodiment of the present invention is seen by reference to FIGS.  2 - 6 .  
         [0016]    First Preferred Embodiment  
         [0017]    As seen in FIG. 2, spa  2  contains sensor  17 . In a first preferred embodiment sensor  17  is mounted to mounting board  22  underneath spa skirt  20  near spa  2 &#39;s piping, as shown in FIG. 6. This location is chosen so that sensor  17  is exposed to the air that is near the piping system of spa  2 . In a preferred embodiment, spa controller  12  contains a CPU that is programmed to maintain the temperature of the water in spa tub  7  and the water in spa  2 &#39;s piping in an optimum operating range (i.e., below a level that is too hot for a user, but above the level which would cause freezing of the water in spa  2 &#39;s piping). As in the prior art, sensor  3  senses the temperature of the water in spa tub  7 . Sensor  5  senses the temperature of water near water heater  9 .  
         [0018]    In the present invention, sensor  3  is still part of the freeze control system in that when the temperature in spa tub  7  drops below a first predetermined value, sensor  3  sends a signal to spa controller  11 . This first predetermined value can be high (i.e., 104 deg. F.) for spas that get fairly regular use, or low (i.e., 59 deg. F) for example, for a homeowner who did not plan on using his spa for an extended period of time. In the first preferred embodiment, Spa controller  11  is model number SSPA, manufactured by Gecko Electronique with offices in Quebec City, Quebec, Canada. Spa controller  11  turns on heater  9  and water pump  13  when the temperature in spa tub  7  drops below the first predetermined value. Hot water is then pumped back into spa tub  7 . Heater  9  and water pump  13  will remain on until sensor  3  reports a second predetermined temperature slightly above the first predetermined temperature. However, in the preferred embodiment of the present invention, sensor  5  is no longer part of the freeze control system. Instead, sensor  5  is used only to shut off heater  9  when the temperature at heater  9  gets too hot (approximately 119 deg. F.).  
         [0019]    In the present invention, sensor  17  has been added to the system and senses the temperature of ambient air around spa  2 &#39;s piping. In the preferred embodiment of the present invention, sensor  17  is a HT Thermistor sensor (part no. Gecko: 530SB0016) manufactured by Ishicuka Electronic with offices in Japan.  
         [0020]    In this first preferred embodiment, sensor  17  detects the true value of ambient air near the piping of spa  2 . The programming of spa controller  12  has been modified from spa controller  11  (FIG. 1) to include the ability to be able to utilize information reported by sensor  17  to better regulate the water temperature of spa  2  to prevent freezing of its associated piping.  
         [0021]    Applicants call this programming “Smart Winter Mode” and its functionality is illustrated by reference to Table 1 below.  
                           TABLE 1                                   Ambient Air Temp   Conduct a 1 minute purge every:                           40 deg. F.   2 hours           28 deg. F.   1 hour           14 deg. F.   30 minutes            5 deg. F.   15 minutes                      
 
         [0022]    In the first preferred embodiment, as the temperature at sensor  17  decreases to 40 deg. F sensor  17  will send an electrical signal to spa controller  12 . Spa controller  12  will then start water pumps  13  and  14  and air blower  16 . They will each run for 1 minute every two hours. As shown in Table 1, if the temperature drops to 28 deg. F at sensor  17 , water pumps  13  and  14  and air blower  16  will conduct a 1-minute purge every hour. Likewise, when sensor  17  reports a temperature of 14 deg. F, the system will purge every 30 minutes and at 5 deg. F. the system will purge every 15 minutes. In the first preferred embodiment, as an extra added measure of protection, after the ambient has risen above 40 deg. F., spa controller  12  will continue to run water pumps  13  and  14  and air blower  16  for one minute every 2 hours for the next 24 hours.  
         [0023]    Second Preferred Embodiment  
         [0024]    A second preferred embodiment is seen by reference to FIGS. 3, 4 and  5 . In the second preferred embodiment, sensor  17  is attached directly to printed circuit board (PCB)  12 A inside spa controller  12 , as shown in FIGS. 4 and 5. In the second preferred embodiment, Spa controller  12  is model number SSPA, manufactured by Gecko Electronique with offices in Quebec City, Quebec, Canada. By attaching sensor  17  directly to PCB  12 A, a substantial cost savings is realized in that the expense of mounting sensor  17  at another location near spa  2 &#39;s piping (as was shown in the first preferred embodiment) is avoided. In other words, when sensor  17  is mounted on PCB  12 A, funds that would be spent on cabling, housing and connectors are saved. However, it should be noted that when sensor  17  is mounted to PCB  12 A, sensor  17  is exposed not only to ambient air temperature, but also to the temperature of the area around PCB  12 A which is heated by the other components also attached to PCB  12 A. Hence, a correction factor needs to be programmed into spa controller  12  account for the heat generated by spa controller  12 &#39;s components. Through experimentation for spa controller  12  model number SSPA, Applicants have determined the following correlation shown in Table 2:  
                       TABLE 2                               Conduct a       Temp at Sensor 17   Ambient Air Temp.   1 minute purge every:                   68 deg. F.   40 deg. F.   2 hours       59 deg. F.   28 deg. F.   1 hour       54 deg. F.   14 deg. F.   30 minutes       50 deg. F.    5 deg. F.   15 minutes                  
 
         [0025]    In the second preferred embodiment, as the temperature at sensor  17  decreases to 68 deg. F (ambient air temp.=40 deg. F), sensor  17  will send an electrical signal to spa controller  12 . Spa controller  12  will then start water pumps  13  and  14  and air blower  16 . They will each run for 1 minute every two hours. As shown in Table 1, if the temperature drops to 59 deg. F at sensor  17 , water pumps  13  and  14  and air blower  16  will conduct a 1-minute purge every hour. Likewise, when sensor  17  reports a temperature of 54 deg. F, the system will purge every 30 minutes and at 50 deg. F. the system will purge every  15  minutes. As an extra added measure of protection, after the ambient has risen above 40 deg. F. (i.e., sensor  17  reports a Temp =68 deg. F), spa controller  12  will continue to run water pumps  13  and  14  and air blower  16  for one minute every 2 hours for the next 24 hours.  
         [0026]    The above-described invention is an improvement over the prior art in that it provides a much more reliable and effective manner of preventing freezing while at the same time minimizing costs.  
         [0027]    While the above description contains many specifications, the reader should not construe these as limitations on the scope of the invention, but merely as exemplifications of preferred embodiments thereof. Those skilled in the art will envision many other possible variations are within its scope. For example, although the above embodiments described a spa that has an air blower, there are many spas that do not have air blowers. The above invention would work equally well for spas without air blowers. For example, spa controller  12  would be programmed to start the water pumps when sensor  17  detected a low temperature. Also, although the above embodiments discuss using model number SSPA for spa controller  12 , those of ordinary skill in the art will recognize that it would be possible to substitute a different spa controller for spa controller  12 . For the second preferred embodiment, if a different spa controller  12  is used, a new correction factor would have to be calculated to determine a correlation table appropriate for the different spa controller. Accordingly the reader is requested to determine the scope of the invention by the appended claims and their legal equivalents, and not by the examples which have been given.