Abstract:
A steam generator for use with a steam bath has a storage tank for holding a quantity of water from which steam is to be made, means for permitting the ingress of water and the egress of steam from the tank, first heating means for controllably maintaining the water at a temperature that is elevated from the ambient temperature but below its boiling point, and second heating means for selectively heating the water from its elevated temperature to produce steam upon demand.

Description:
This application is a continuation of co-pending U.S. patent application Ser. No. 11/015,814 filed Dec. 16, 2004 now abandoned, the priority of which is claimed. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to steam bath systems and, more specifically, to steam bath systems having electric heaters for generating the steam. 
     BACKGROUND OF THE INVENTION 
     Steam baths have long been a popular method for relaxing and renewing one&#39;s energy level. Many people also believe that steam baths have a number of health benefits. Typical steam baths require a mist to be permanently present, requiring energy-intensive components and methods for generating steam. 
     In practice, those who take steam baths typically do so for 15–20 minutes, sometimes followed by a shower to cool down the body and a second steam bath. Moreover, this can be repeated as many as two to three times for a single session. Steam baths accordingly require a sufficient quantity of water to be heated to its boiling point of 100° C. to produce the requisite amount of steam. This can be quite energy intensive. 
     In addition, it can take considerable time to heat the required quantity of water to its boiling point; typically, as long as four to six minutes. This is inconvenient, particularly given the fact that the steam bath is taken for 15–20 minutes, as described above. The proportion of total time thereby devoted to waiting for steam is significant. Although one can theoretically utilize the heated water from a home&#39;s hot water heater to reduce the waiting time by reducing the temperature gradient that must be transversed to produce steam, the water from a hot water heater typically contains impurities that can harm the steam bath system, shorten its life, and detract from the beneficial health effects attributable to steam baths. Thus, one has typically had to wait a considerably lengthy time before one could engage in a desired steam bath 
     SUMMARY OF THE INVENTION 
     The invention herein is directed to a steam generator for use with a steam bath having a storage tank for holding a quantity of water from which steam is to be made, means for permitting the ingress of water and the egress of steam from the tank, first heating means for controllably maintaining the water at a temperature that is elevated from the ambient temperature but below its boiling point, and second heating means for selectively heating the water from its elevated temperature to produce steam. 
     Further details concerning the invention will be appreciated from the following detailed description of the invention, of which the drawing is a part. 
    
    
     
       THE DRAWING 
       In the drawing, 
         FIG. 1  is an isometric view in explosion of a steam-bath heating unit constructed in accordance; and 
         FIG. 2  is a top plan view of the preheater element used in accordance with the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is an isometric view in explosion of a steam-bath heating unit constructed in accordance with the invention. The system comprises a stainless steel boiler tank  10  which can be of any convenient size and shape. The system we have constructed utilizes a square 2 gallon tank having dimensions of approximately 9 inches in height, 10 inches in depth, and 10 inches in width. 
     The tank  10  has a steam outlet port  12 , which is typically ½″ in diameter, as well as a water inlet port  16  through which a water enters the tank via an external inlet nipple from an inlet pipe  22 . A float  18 , inserted into the tank through the inlet port, extends within the tank from a stem  20  is operatively connected to a flapper valve at the inlet port  14  to close the flapper when the water level in the tank reaches the maximum desired level, and to open the flapper when the water level is lower than the maximum desired level to permit the ingress of more water. 
     A heater coil  26  is inserted into the tank through a coil-receiving port  28  to heat the water to its boiling point and thereby create the steam that emerges from the steam outlet port. The heater coil  26  is an electrically resistive element that is responsive to the flow of electricity within the coil to sufficiently heat the water in which it is immersed to raise the water temperature to the boiling point. Preferably, the heating coil is a 220 volt, 6 KW heater. The heating coil  26  is electrically coupled through a circuit board  34  to a source of household current, which is fed through a port  30  in a junction box  32  to an electric circuit board  34 . 
     Those skilled in the art will recognize that is the heating element  26  need not the coil shaped, and that any desirable configuration for the heating element can be used. In addition, a source of heat other than an electrically heated element can be used. For example, steam maybe generated using natural gas and a gas burner. Similarly, other fuels and energy sources can be utilized, and it should be understood that this invention is not limited to the use of electrically heated coils or similar electrically heated elements. 
     The heating coil  26  can preferably be disabled by a water level sensing switch  22  that is inserted in to the tank via a port  14 . The level sensing switch  22  operates to electrically decouple the heating element  26  from its current source if the water level in the tank  10  falls below a desired minimum level. The switch  22  thereby acts as a safety device to ensure that the heat generated by the element  26  is sufficiently dissipated within the water, and will not continue to operate when there is an insufficient amount of water for this purpose. 
     The tank  10  is located within a housing comprising a lower section  36 , a front panel  38 , and a top panel  40 . The tank  10  is nested within a layer of thermal insulation  42  disposed within the lower section  36  of the housing. A preheater  48  is affixed to the portion of one wall of the tank  10  with a suitable adhesive to transfer heat through the tank wall and into the water, as explained below. 
       FIG. 2  is a top plan view of the preheater  48  used in accordance with the invention. The preheater is preferably a Kapton™ heater. Heaters of this type typically comprise an external layer of magnesium powder, which conducts heat but not electricity, together with a more interior layer of electrically conductive, but suitably resistive, material. The preferred preheater comprises a thin, substantially flat, 1.5 inch×4.5 inch external strip  49  having an internal foil-like resistive heating element disposed within the illustrated dotted line  50 . The resistive heating element is preferably characterized by 750 ohm of resistance to produce a suitable amount of heat in response to the application of electric current. 
     The preheater  48  is electrically coupled to household current through a thermostatic switch  52  positioned on the strip for thermal coupling to the tank&#39;s surface when the preheater  48  is affixed to the tank. The switch  52  is preferably affixed to the preheater  48  with a suitable epoxy or other adhesive. The current source is electrically coupled to the thermostat switch and resistive heating element via leads  50   a ,  50   b.    
     The preheater  48  is affixed to the tank with the thermostat switch  52  thermally coupled to the water inside the tank via the tank&#39;s wall. When the water in the tank is below the desired temperature range, the thermostat closes, completing the circuit and activating the preheater. When the water in the tank reaches the upper end of the desired temperature range, the thermostat switch opens, breaking the circuit and deactivating the preheater  48 . Preferably, the water is maintained just 20–50° F. below the water&#39;s boiling point. 
     In operation, the preferred preheater utilizes approximately 80 watts of power when activated by the thermostat to maintain the water within the desired temperature range. When steam is desired, the heating coil  26  is energized by the user, and steam is produced from the preheated water within approximately 3–4 minutes. Thus, the relatively energy-intensive heating coil  26  is used minimally, with minimal power being consumed at other times in maintaining the water at an elevated temperature below its boiling point. Energy savings is achieved, and the inconvenience of waiting for a substantial period of time for steam production is avoided. 
     The steam emanating from the tank  10  exits from the housing through the steam discharge port  12 , and is conducted towards the steam bath enclosure by a steam outlet conduit  54  that is typically screwed into the port or sealingly fastened to it by other appropriate means. 
     Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.