Patent Publication Number: US-6220579-B1

Title: Warm mist humidifier

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention generally relates to humidifiers or vaporizers. More specifically, this invention is directed to a warm mist humidifier for use in domestic applications. 
     2. Description of the Prior Art 
     Various types of humidifier devices are used to provide moisture to indoor air. Included among such humidifiers are ultrasonic humidifiers, steam humidifiers or vaporizers, warm mist humidifiers and evaporative humidifiers. The beneficial effects of these humidifiers are numerous and include: protection to the respiratory system of the user, reducing dryness and irritation in the user&#39;s nose and throat, reduction in static electricity, and protection of wood furniture, paneling and fabrics. 
     The warm mist type humidifiers have been effectively used to achieve very high humidification levels. Conventional humidifiers of the warm mist type usually produce a warm mist (rather than steam produced by the steam vaporization type humidifiers) into the environment to be humidified. Typical warm mist humidifiers employ an electric heater coil, which is in direct contact with water, for converting water contained in a reservoir into vapor. Additionally, the humidifiers may employ a float switch for activating or deactivating the heating coil based on the water level sensed by the float switch. The vapor in the humidifiers will rise through a vapor passage and mix with air drawn from an electric blower. Alternatively, the vapor can be produced in combination with a vaporized medicament for the treatment of colds, coughs, or other disorders of the respiratory system. 
     The conventional warm mist humidifier constructed as described above has many disadvantages. For example, minerals in the water are easily deposited on the surface of the heating coil which is made of a metal such as stainless steel or graphite. As a result, the electrical conductivity of the surface of the coil can deteriorate and it is often difficult to clean the stain on the surface of the coil. A float switch typically found in the conventional warm mist humidifier for activating or deactivating the heating coil according to the sensed water can easily deteriorate since it floats on water and is in direct contact with water. Additionally, moist on the heating coil or the float switch can attract potentially harmful microorganisms, thereby creating a higher amount of bacteria count in the mist. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing disadvantages with the prior art device, it is the object of the present invention to provide a warm mist humidifier which has the same advantages as the aforementioned prior art humidifier, yet allows the humidifier to have a durable heating assembly that is easy to maintain. 
     It is still another object of the invention to provide a warm mist humidifier which automatically shuts off the heating assembly when the water level in a water tank is low without having to come in contact with water or to remove the water tank. 
     It is yet another object of the invention to provide a warm mist humidifier that eliminates the potentially harmful microorganisms in the water. 
     The above objects are achieved by a warm mist humidifier with an air blower comprising: a base unit having an energizing circuit; a water tank having a pressure sensor and disposed on the base unit for supplying water to said base unit; a reservoir in the base unit for receiving water from the water tank; a heating assembly disposed in the base unit for vaporizing water received from the reservoir when the heating assembly is activated by the energizing circuit; and a tank switch for activating or deactivating the energizing circuit, wherein the tank switch is responsive to a change of position of the water tank relative to the base unit in response to the water in the water tank. In particular, the heating assembly in the humidifier consists of a boiler cavity, a heating coil fixedly mounted underneath the boiler cavity, an insulative outer housing mounted on the boiler cavity, and a removable cover covering the insulative outer housing. 
     Other features and advantages of the invention will become apparent upon reference to the following Description of the Preferred Embodiment when read in light of the attached drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be more clearly understood from the following description in conjunction with the accompanying drawings, where: 
     FIGS. 1 and 1A are partly exploded, perspective view of a preferred embodiment of a warm mist humidifier in accordance with the invention; 
     FIG. 2 is a front elevation view of FIG. 1; 
     FIG. 3 is top view of FIG. 1; 
     FIG. 4 is a bottom view of FIG. 1; 
     FIG. 5 is a side elevation view of FIG. 1; 
     FIG. 6 is a rear elevation view of FIG. 1; 
     FIG. 7 is a top view of a base unit of the warm mist humidifier in accordance with the invention; 
     FIG. 8 is a bottom view of a water tank of the warm mist humidifier in accordance with the invention; 
     FIG. 9 is a bottom view of a top cover of the base unit of the warm mist humidifier in accordance with the invention; and 
     FIG. 10 is a top view of a base cover of the base unit of the warm mist humidifier in accordance with the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIGS. 1-10, in which similar or corresponding parts are identified with the same reference numeral, and more particularly to FIGS. 1 and 1A, a preferred embodiment of the invention is illustrated showing a warm mist humidifier  10  that includes a refillable water tank  14  and a base unit  18  for receiving the water tank  14 . The water tank  14  contains a vapor passage duct  22  therein to facilitate the dispersion of water vapor from the base unit  18 . The discharge opening  24  of the vapor passage duct  22  is fitted with a medication cup  26  with a mist outlet grill  28  for holding liquid medication. The receiving end of the vapor passage duct  22  is surrounded by a receiving channel  30  for communicating with the base unit  18 . 
     The top wall portion of the tank  14  as shown in FIGS. 2-5 has a cavity  32  which is fitted with a tank handle  34  for facilitating the removal the water tank  14  from the base unit  18 . The bottom wall portion of the water tank  14  as shown in FIGS. 1,  1 A,  2  and  8  includes an opening  36  for filling the water, which is removably sealed by a threaded tank cap  38 . A valve assembly  42  is also retained by the bottom wall portion of the water tank  14  for allowing water to flow from the water tank  14  into the base unit  18 . The valve assembly  42  includes a valve stem  44  having a spring (not shown) coupled at one end and a valve  46  coupled at the other end. The valve assembly  42  is mounted on an open-ended tubular housing  50  which extends through a discharge opening in the bottom wall portion of the water tank  14 . The valve  46  is normally biased into a seated position for closing the discharge opening. 
     Additionally, the bottom wall portion of the water tank  14  as shown in FIG. 1A and 8 has a biased, e.g., spring-loaded, weight sensor  54  mounted on a close-ended tubular housing  56  which projects upwardly from the bottom wall portion of the water tank  14  and prevents the water tank  14  from being fully seated in the base unit  18  unless the threshold water limit is reached. Adjacent to the weight sensor  54  is a cylindrical actuating tab  60  which projects downwardly from the bottom wall of the water tank  14  to contact the tank switch  92  when the water tank  14  is fully seated in the base unit  18 . 
     The base unit  18  of the humidifier as shown in FIGS. 1,  1 A and  4  includes a top cover  64  covering the top end of the base unit  18  and a bottom cover  68  covering the bottom end of the base unit  18 . A peripheral rim portion  70  projects upwardly from the top cover  64  to define a tank enclosure for removably receiving the water tank  14 . 
     As shown in FIGS. 4 and 10, the bottom covers  68  of the base unit  18 , which has a plurality of feet  70  extending therefrom, holds a UV germicidal bulb  72  and an air blower  76 . The bulb  72 , preferably a 3.5 watt bulb capable of operating at maximum output for approximately 2,000 hours (typically 1 to 2 years of normal operation) but may operate longer than 2,000 hours at a reduced output, is capable of eliminating microorganisms in the water. The air blower  76 , preferably in the form of an electric motor driven blower contained in a shape housing (not shown) on the bottom cover  68  of the base unit  18 , enhances the vapor discharge through the vapor passage duct  22 . 
     The front of the top cover  64  of the base unit  18  as shown in FIG. 7 has an opening for receiving a heating assembly  84 , a reservoir  88  for receiving water from the water tank  14 , and an opening for a tank switch  92  which is capable of activating or deactivating an energizing circuitry  96  connected to the heating assembly  84 . The energizing circuit  96  as shown in FIGS. 1 and 9 includes an AC electrical cord  97  with an AC plug connector  98  for mating with a conventional electrical receptacle (e.g., wall outlet). 
     The reservoir  88 , which is formed directly below the vapor passage duct  22  of the water tank  14 , includes an exhaust opening  100  for directing air from the air blower  76  into the heating assembly  84 , a cylindrical valve tab  104  projected from the bottom portion of the reservoir  88  for engaging the valve stem  44 , and an outlet  106  for leading water through a water passage tube  108 , which is mounted underneath the reservoir  88  and preferably made from glass or other light admitting material, to the heating assembly  84 . The water passage tube  108  includes a drain passage  109 , which is covered by a threaded drain cap  110  as shown in FIGS. 4 and 9. 
     The heating assembly  84  as shown in FIGS. 1,  7  and  9  includes four main parts, namely a boiler cavity  112  for vaporizing water, a heating coil  116  fixedly mounted underneath the boiler cavity  112  for inducing heat to the boiler cavity  112 , an insulative outer housing  120  mounted on the boiler cavity  112 , and a removable vapor diffuser  124  covering the insulative outer housing. The vapor diffuser  124  has a plurality of inlet slots  128  for receiving air from the exhaust opening and a plurality of outlet slots  132  for directing the mix of air and warm mist towards the vapor passage duct  22 . The boiler cavity  112  has an opening  134  for receiving water from the water passage tube  108 . When the heating coil is energized, warm mists are generated in the boiler cavity  112 , and these warm mists rise and escapes through the vapor passage duct  22 . 
     The tank switch  92 , which is adjacent to the reservoir  88 , controls the heating coil  116  based on the weight of the water tank  14 . More specifically, the condition of the tank switch  92  is controlled by the movement of the water tank  14  between activating and inactivating positions in response to a decrease in the water level (i.e., decrease in the weight of the water within the water tank  14 ), or removal of the water tank  14  from the base unit  18 . The front of the base unit  18  as shown in FIG. 1 includes a control panel  136  having an ON/OFF switch knob  140 , a refill indicator  144 , a reset button  148 , and a UV bulb indicator  152 . The humidifier is activated when the ON/OFF control knob  140  is turned to the “ON” setting while the humidifier is supplied with electrical energy in the form of electrical current from an AC supply such as a household outlet. The illumination of the refill indicator  144  and/or the UV bulb indicator  152  indicates the need to refill the water tank  14  and/or replace the UV bulb. 
     OPERATION 
     To prepare the humidifier  10  for use, the water tank  14  is removed from the base unit  18  using the tank handle  34 , and then the water tank  14  is filled with water through the opening  36  created by the removal of the tank cap  38 . When the water tank  14  is removed from the base unit  18 , the tank switch  92  stops engaging the weight sensor  54 , thereby shutting off the heating coil  116 . 
     With the tank cap  38  secured, the water tank  14  is inverted and positioned on the base unit  18  so that (1) the spring-loaded valve  42  is pushed into an open position, (2) the spring-loaded weight sensor  54  is depressed, and (3) the actuating tab  60  from the water tank operatively engages the tank switch  92 , thereby activating the tank switch  92  to energize the heating coil  116 , which induces heat to the boiler cavity  112 . 
     When the water level in the water tank  14  falls to a predetermined level or the combined weight of the water tank  14  and water contained therein decreases below a threshold level, the biased weight sensor  54  at least partially dislodges the water tank  14  from the base unit  18  as to cause the actuating tab  60  to disengage the tank switch  92 , thereby deactivating the tank switch  92  and de-energizing the heating coil  116  without having to remove the water tank  14  from the base unit  18 . When the water tank  14  is removed from the base unit  18 , actuating tab  60  is also disengaged from the tank switch  92 , thereby deactivating and de-energizing the heating coil  116 . 
     The humidifier  10  eliminates the potentially harmful microorganisms in the water by using the UV germicidal bulb  72 , located inside the base unit  18 , to shine on the water through a glass tube as it passes from the reservoir  88  to the boiler cavity  112 . 
     To facilitate the dispersion of water vapor from the boiler cavity  112  into air by way of vapor passage duct  22  through the water tank  14 , an electric fan  76  is disposed in the base unit  18  to draw air into the boiler cavity by way of an air duct. 
     While a particular embodiment of the present invention have been shown and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit or scope of the invention. Accordingly, it is intended that the appended claims cover such changes and modifications that come within the spirit and scope of the invention.