Patent Publication Number: US-6335517-B1

Title: Humidifier having induction heating system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based on and claims priority to U.S. Provisional Patent Application Ser. No. 60/136,500, which was filed on May 28, 1999, the disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The field of the invention relates to humidifiers including induction heating systems for generating steam, a method of providing humidity and to various components of induction type humidifiers. 
     2. Brief Description of the Related Art 
     Induction heating involves the heating of a metal target or workpiece by an induced current. Such heating has been used for various purposes, including the heating of water. U.S. Pat. Nos. 4,013,742; 4,341,936 and 5,286,942 disclose systems for producing steam through the use of inductor coils and metal targets. 
     SUMMARY OF THE INVENTION 
     A portable humidifier is provided for use in the home, office or other suitable location. The humidifier includes an inductor coil for heating a heating element. It accordingly requires no direct electrical connection between the power source and heating element. 
     A humidifier in accordance with the invention includes a tray defining a chamber for holding water, and a metal target movably positioned within the chamber. A float is coupled to the metal target, and provides buoyancy when the tray is filled with water. An inductor coil is provided for heating the target. The inductor coil is separated from the target by a wall. 
     The invention is further directed to a humidifier which includes a removable tray for holding water, a metal target movably positioned in the tray, an inductor coil for heating the metal target with an induced current, and a wall separating the inductor coil and metal target. The metal target is engageable with the wall. Channels are preferably provided between the wall and the target to allow water to flow therebetween. 
     The invention further provides a humidifier including a tray for holding water, a metal target movably positioned within the tray, an inductor coil for heating the metal target, a wall separating the inductor coil and metal target, and means for deenergizing the coil when the water level in the tray drops below a predetermined level. The deenergizing means may include an inductor sensor which senses a decrease in the induction current should the target move away from the inductor coil. Such a sensor may cause a switch between the power source and the inductor coil to open upon sufficient displacement of the target, whether due to a low water level or separation of the tray and inductor coil. 
     A portable humidifier is also provided which includes a tray for holding water, a metal target within the tray, a wall separating the metal target and the inductor coil, the target positioned beneath and engaging the wall, and a plurality of channels between the metal target and the wall for allowing the passage of water therein. 
     A method for providing humidity is further provided by the invention. The method includes the steps of providing a tray, a metal target within the tray, an inductor coil and a wall separating the inductor coil and the target, providing water to the tray, maintaining the target at a position corresponding to the water level in the tray, and supplying power to the induction coil, thereby causing the target to heat the water sufficiently to produce steam. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top perspective view of a humidifier according to the invention; 
     FIG. 2 is a top plan view thereof; 
     FIG. 3 is a front perspective view of the base of the humidifier and components within the base; 
     FIG. 4 is a sectional, elevation view of a humidifier in accordance with the invention; 
     FIG. 5A is a top plan view of a float and target assembly for the humidifier; 
     FIG. 5B is a side elevation view thereof; 
     FIG. 6 is a partially sectional, elevation view of an inductor coil for the humidifier; 
     FIG. 7 is an enlarged sectional view showing a corrugated wall separating the inductor coil and target; 
     FIG. 8A is a sectional view showing an alternative embodiment of the portion of the humidifier used for making steam; 
     FIG. 8B is a top perspective view of the target and float assembly for this alternative embodiment; 
     FIG. 9A is a sectional elevation view showing a second alternative embodiment of the portion of the humidifier used for making steam; 
     FIG. 9B is a top perspective view of the target and float assembly for the second alternative embodiment; 
     FIG. 10A is a sectional elevation view of a third alternative embodiment of the portion of the humidifier used for making steam, and 
     FIG. 10B is a top perspective view of the target and float assembly for the third alternative embodiment. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A portable humidifier  10  is provided for use in the home, the office, or other suitable location. The humidifier includes a water tank  12 , a tray  14  or other suitable receptacle for receiving water from the tank, a target  16  positioned within the tray, and an inductor coil  18  for heating the target. The water tank  12  is preferably removable to facilitate refilling and/or cleaning. A handle  20  is accordingly provided near the top of the tank, and may be integral with a tank cover  22 . The tank cover  22  is mounted to the tank to protect the contents thereof. The cover is preferably bonded to the tank, but can be removable if desired. While the tank is preferably cleanable and reusable, a disposable tank could alternatively be employed. 
     A conventional tank valve  24  or other suitable means are provided for releasing water from the tank in a controlled manner. Tank valves are well known to the art, and are employed in commercially available humidifiers of various types. While more sophisticated water delivery means, such as a pump, could be employed, tank valves are economic and reliable for use in the consumer market. 
     As shown in FIGS. 3 and 4, the tray  14  is positioned within a base  26 . (FIG. 4 is a schematical illustration of the invention, and is not intended to correlate precisely with the humidifier shown in FIGS. 1-3. The same reference numerals are used in FIGS. 1-7 to designate similar parts.) The base includes bottom and side walls which together define an enclosure for the tray and other elements. An elongate, tortuous channel  28  is provided within the base. One end  28 A of the channel is positioned beneath the tank valve  24 . The other end  28 B of the channel is in fluid communication with the tray  14 , which has an opening in a side wall thereof for admitting water into the tray from the channel. The use of a tortuous channel is preferred in order to substantially confine the hot water within the tray. Backflow through the tortuous path is very limited. The tray  14  and channel  28  are both preferably removable from the base  26  to facilitate washing. 
     The tray  14  includes a support  30  for a float and target assembly  32 , as shown in FIGS. 3 and 4. The support is preferably, but not necessarily, integral with the tray. It includes a fitting  34  for receiving a pivot pin. 
     As best shown in FIGS. 5A and 5B, the float and target assembly  32  is comprised of an arm portion  36  having a pivot pin  38  at one end and the metal target  16  in the form of a flat, stainless steel ring at the other end. The pivot pin, which is preferably integral with the arm, is used for pivotally securing the assembly to the support  30 . There should be sufficient play between the pin and fitting that pivotal movement of the assembly is substantially unimpeded. The particular manner in which the assembly is coupled to the support is not considered to be critical so long as the target is capable of moving towards and away from the inductor coil  18 . A living hinge may, for example, be used to couple the assembly to the support or another portion of the tray  14 . The target and inductor coil are preferably substantially parallel to each other as well as in close proximity when the humidifier is operated. 
     The float and target assembly  32  further includes a float  40  either integral with or coupled to the arm. In the embodiment shown in FIG. 5B, the float is in the form of an air-tight compartment including a chamber filled with air. The float provides sufficient buoyancy that the target will be maintained at or just below the water level in the tray  14 . As discussed below, the target is positioned in close proximity to a wall separating it from the inductor coil, and preferably in engagement with the wall. Buoyancy may alternatively be provided by employing an appropriate foam material integral with, coupled to or comprising the arm. 
     One of the advantages of induction heating is that no direct coupling is required between the heating element and power source. The lack of such coupling obviates the need for seals and electrical connections, which are potential problem areas in prior art warm mist humidifiers. The heating element, i. e., the target  16 , is separated from the inductor coil  18  and other electrical components by a bottom wall  42  of a housing  44 . The housing  44  is removably coupled to the base  26 . The bottom wall  42  is preferably corrugated on both surfaces, as shown in FIG.  7 . As the target preferably engages and makes substantially flush contact with the bottom wall during operation of the humidifier, the corrugations or other irregularities in the wall surface allow water to move in channels  42 A formed between the target and the inductor coil, and be converted to steam. They also increase the surface area of the target in contact with the water. The air spaces  42 B between the upper surface of the bottom wall and the lower surface of the inductor coil permit air circulation between these elements. A fan  46  is provided within the housing  44  to provide air circulation throughout the chamber defined by the housing. It will be appreciated that the inductor coil could alternatively be positioned in a water-tight portion of the base  26  such that the bottom wall of the tray separates the inductor coil and target. The target would instead move towards the bottom of the tray as the tray filled with water, as opposed to moving upwardly in the preferred embodiment of the invention. Such movement could be effected by a float connected to the target, but positioned on the opposite side of a pivotable support. 
     As shown in FIG. 4, the bottom of the housing includes an extension  48  which is positionable within the tray  14 . The extension includes a side wall defining an enclosure having an open bottom end and a top wall defined in part by the corrugated wall  42 . An opening  50  is provided in the bottom wall of the housing  44 . This opening is in fluid communication with the tray  14 , and allows the escape of steam. The outer wall of the housing  44  includes one or more vent openings  52  which allow the steam to exit the humidifier. The vent openings  52  may be connected to the wall opening  50  by a chute  53 . Movement of the steam from the humidifier may be facilitated by the internal pressure in the housing caused by the fan, or by an additional fan (not shown). The temperature of the steam/air mixture emitted from the humidifier can be reduced in such a manner. 
     In addition to containing the fan  46 , the housing  44  contains the electronic assembly  54  for providing power to the inductor coil  18  and fan, and for controlling their operation. The manner in which the humidifier is controlled in accordance with the preferred embodiment is described later below. 
     Referring now to FIG. 6, the inductor coil  18  is shown as comprising a flat ring  56  comprised of two wire spirals, one spiral being positioned directly on top of the other. The two spirals are formed from a single wire, each of which extends clockwise. The preferred material for the inductor coil is Litz wise, but a solid wire could instead be used, albeit with lower efficiency. An insulation varnish or the like is used to maintain the spirals in position. The wire ends extending from the inductor coil are protected by a high temperature sleeve, and are coupled to appropriate terminals. Four ferrite blocks  58  are glued to the top surface of the flat ring. The inductor coil (and resonant circuit) is fed by a rectified alternating current. The current is switched at a frequency around 30 HZ by a switching transistor. The particular type of inductor coil is not considered critical so long as it is capable of heating the metal target  16  sufficiently to create steam in an efficient manner. Likewise, the composition of the target is not critical provided it can be heated safely and reliably by the inductor coil. 
     FIG. 8A shows an alternative embodiment of the invention. (The embodiment of FIGS. 1-7 is the preferred embodiment.) The water supply and electronic assembly as discussed above are usable with this and other embodiments of the invention described hereafter. FIG. 8B shows a target assembly  132  usable with this or one of the other disclosed embodiments. 
     Referring to FIG. 8A, a tray  114  is provided for holding the water to be converted to steam. A cover or housing extension  148  is mounted to the tray, which together define a boiling chamber. The target assembly  132  in this embodiment is pivotally coupled to a support  130  mounted to the cover  148 . It is comprised of an arm portion  136  having lateral extensions  138  formed at one end and a pair of concentric metal rings  116 A,  116 B secured to the opposite end. A float  140  is coupled to the bottom portion of the arm portion  136 . The target rings  116 A,  116 B each include a fusible section  116 A′,  116 B′. These sections are designed to melt should the temperatures of the rings exceed a predetermined level. 
     The inductor coil  118  rests upon an upper wall  142  of the cover  148 , and includes a ferrite core  158 . As shown in the previous embodiment, water should be able to enter into spaces or channels between the target and wall  142 , while air should be able to circulate between the inductor coil and the wall. 
     FIG. 9A shows another alternative embodiment of the invention for generating steam. It includes a tray  214  and a cover  248  which define a boiling chamber. A vent  252  is provided in the cover for releasing steam. The cover includes a recessed portion  280  having a bottom wall  242  for supporting an inductor coil  218 . As shown in FIG. 9B, a metal target  216  in the form of a pair of concentric rings  216 A,  216 B is positioned in proximity to the bottom surface of the bottom wall  242  when the water in the tray reaches a desired level. Each ring preferably includes a fusible section  216 A′,  216 B′ having a lower melting point than the remainder of the ring. The target is coupled to the bottom wall of a cup  236  which includes a recess conforming to the configuration of the recessed portion  280  of the cover. The recessed portion  280  is nestable in the cup, allowing the target  216  to be aligned with the inductor coil  218 . A ferrite block  258  supports the coil. The cup displaces a sufficient amount of water in the tray such that it floats to the position shown in FIG. 9A when the tray is filled with water. 
     FIG. 10A shows an alternative embodiment of the invention, while FIG. 10B shows a target assembly  332  for use in this embodiment. The humidifying apparatus shown in FIG. 10A includes a tray  314  and a cover  348  which together define a boiling chamber. The cover includes a vent  352  for releasing steam therefrom. It further includes a recessed portion  380  having a bottom wall  342  for supporting an inductor coil  318  and ferrite support  358 . 
     The target assembly  332  includes a pair of concentric metal rings  316 A,  316 B made from stainless steel or other suitable material. Each ring includes a fusible section  316 A′,  316 B′. The rings are secured to a support  336 . Floats  340  are mounted to the support, and provide sufficient buoyancy for allowing the target rings  316 A,  316 B to engage the bottom wall  342 . Guides (not shown) may be provided to ensure that the target assembly is maintained beneath the recessed portion  380  of the cover and that the target rings are in alignment with the inductor coil. Such guides may also be employed in the embodiment of the invention shown in FIG.  9 A. 
     The humidifier may be equipped with a microprocessor or other electronics for controlling its operation. The options of manual and automatic operation are preferably, though not necessarily, provided. Displays showing power on, high and/or low modes or operation, and humidity are also preferred. Use of a humidity detector allows automatic operation of the humidifier. In the automatic mode, the user would set the desired humidity. If the room humidity is less than the desired humidity level, the inductor coil would be powered until the humidity reaches the set level. Whether used manually or automatically, power to the inductor coil is shut off when the water tank is below a preselected level or empty, and/or when the target assembly drops a sufficient amount such that the distance between the inductor coil and metal target exceeds a certain threshold. The latter can be accomplished by means of an induction sensor  60 , shown in FIG.  4 . Additionally or alternatively, a water gauge or separate float in the tank and/or tray may be provided in conjunction with a switch for the purpose of shutting off power to the inductor coil under low water level conditions. Such float/switch assemblies have been used in prior art warn mist humidifiers. The fan can continue to run either until an on/off switch is actuated, or for a preselected time, upon shutting off power to the inductor coil. It should run at least as long as power is supplied to the inductor coil. Power to the inductor coil may be cut off if the fan either fails to operate or discontinues functioning. Power to the inductor coil is also preferably terminated upon disconnection of the housing for the electrical components and the base  26 . This can be accomplished by a switch between the power supply and the inductor coil which is opened upon separation of these components. 
     While there have been described what are presently believed to be the preferred embodiments of the invention, those skilled in the art will realize that various changes and modifications may be made to the invention without departing from the spirit of the invention.