Abstract:
An electrically operated scented wax holder that forms a receptacle for receiving unmelted blocks of wax which are heated to the melting point and thereafter maintained at a safe temperature by a temperature-regulated electrical heating element. The wax receptacle is removable mounted on a base section that houses a positive temperature coefficient (PTC) thermistor which has a transition temperature substantially higher than the melting point of the wax to insure that the wax is rapidly melted, but substantially below the temperature that would constitute a danger to a human who might touch the exterior surface of the warmer, or constitute a fire hazard. The heating element is preferably placed in thermal contact with a contact pad having high thermal conductivity that is in turn placed closely adjacent to the wax receptacle, thereby efficiently transferring heat from the electrically operated temperature regulated heating element to the wax in the receptacle. A switch is positioned to de-energize the heating element whenever the wax receptacle is removed from the base section, and a visible pilot light is illuminated whenever the heating element is energized.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a Non-Provisional of, and claims the benefit of the filing date of, U.S. Provisional Patent Application Ser. No. 60/466,967 filed on May 1, 2003, the disclosure of which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates electrically heated warmers for use with scented wax or aromatic oils.  
       BACKGROUND OF THE INVENTION  
       [0003]     Scented wax is commonly heated in decorative holders which form a retaining receptacle positioned at the top of a vented enclosure. A small candle is positioned within the enclosure below the receptacle. A small block of scented wax, commonly called a “scent block” or “tart,” is placed in the cavity. The heat from the burning candle melts the scented wax in the cavity to release the scent into the surrounding area.  
         [0004]     Tart warmers heated by candles have several notable disadvantages. Different candles produce widely varying amounts of heat. If the candle burns poorly, the wax may be slow to melt or may not melt at all, or may not reach the temperature needed to produce the desired scent. If the candle burns too well, too much heat may be produced, creating a safety hazard. As a result, users of candle-heated tart warmers are cautioned never to leave a burning candle in the warmer unattended. In addition, the heating candles must be frequently replaced and the candle holding enclosure needs to be periodically cleaned to remove residual wax.  
         [0005]     To eliminate some of the problems found in candle-heated scent warmers, electrically heated, lantern-like tart warmers have become popular. In these units, the candle is replaced by an incandescent electrical light bulb that heats a scented wax tart placed in a receptacle formed at the top of the lantern. In order to provide adequate heat to melt the scented wax, these lantern units must be large enough to contain a large conventional light bulb and are hence quite bulky. Moreover, the light bulb must be periodically replaced with a new bulb having the proper power rating. Using an available replacement bulb having a power rating that is too low fails to adequately heat the scented wax, and using a bulb with a power rating that is too high overheats the wax and creates a potential fire hazard.  
         [0006]     It is therefore an object of the present invention to provide an improved electrically-operated scented wax warmer that can be much smaller, requires less maintenance, and provides a precisely regulated temperature for heating the scented wax for enhanced safety and performance.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention takes the form of a scented wax holder that forms a receptacle for receiving unmelted scented wax and a temperature-regulated electrical heating element in thermal contact with the receptacle for melting the wax and thereafter maintaining the wax at a regulated temperature.  
         [0008]     In its preferred form, the present invention comprises a wax receptacle is removable mounted on a base section that incorporates a temperature-regulated electrical heating element. The heating element preferably consists of a positive temperature coefficient (PTC) thermistor which has a transition temperature substantially higher than the melting point of the wax to insure that the wax is rapidly melted, but substantially below the temperature that would constitute a danger to a human who might touch the exterior surface of the warmer, or constitute a fire hazard. The heating element is preferably placed in thermal contact with a contact pad having high thermal conductivity that is in turn placed closely adjacent to the wax receptacle, thereby efficiently transferring heat from the electrically operated temperature regulated heating element to the wax in the receptacle.  
         [0009]     Both the wax receptacle and the base section which houses the electrical heating element are preferably formed from a material such as slip cast stoneware that exhibits a low thermal conductivity such that the heat from heating element and the heated wax does not flow to the those portions of the warmer which are most likely to be come in contact with a person using the warmer or with surrounding objects.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     In the detailed description which follows, frequent reference will be made to the attached drawings, in which:  
         [0011]      FIG. 1  is a perspective view of the wax holder;  
         [0012]      FIG. 2  is a perspective view of the contact pad with the heating element positioned as shown by the phantom lines;  
         [0013]      FIG. 3  is a perspective view of the base section that houses the heating element and contact pad;  
         [0014]      FIG. 4  is a cross-sectional view of the wax vessel, base section and heating element;  
         [0015]      FIG. 5  is an exploded view of the components which form the base section heating element;  
         [0016]      FIG. 6  is an exploded view of a further embodiment of the invention which includes a holder for a candle and a translucent covering dome; and  
         [0017]      FIG. 7  is a cross-sectional view of a further embodiment of the invention incorporating a switch for disconnecting the heating element when the wax receptacle is removed and a pilot light for indicating when the heating element is energized. 
     
    
     DETAILED DESCRIPTION  
       [0018]     A preferred embodiment of the invention consists of a wax vessel shown in  FIG. 1  and a base section shown in  FIGS. 2 and 3 . The wax vessel  101  forms a receptacle for receiving a block of scented wax which is dropped into the wax holding receptacle indicated at  103 . The wax vessel  101  and the base section are both preferably slip cast stoneware fired ceramic pieces which are coated with a kiln-fired decorative glaze to enhance their appearance and facilitate cleaning. The wax vessel is preferably a separate unit which can be removed from the base section shown in  FIGS. 2 and 3  for ease of cleaning; however, the base section and wax vessel may be a single structure if desired. Both the base section and the wax vessel may take a variety of decorative shapes and, as will be understood from the following description, may be substantially smaller than conventional tart warmers.  
         [0019]     In accordance with the invention, a temperature regulated heating element seen at  201  in  FIG. 2  is attached to the underside of a contact pad  203  and both are housed within a cylindrical base section  301  seen in  FIG. 3 .  
         [0020]     As shown in cross-section in  FIG. 4 , the contact pad  203  is placed in direct contact with the floor  403  of the wax vessel to provide a large surface area for better heat transfer between the heating element seen generally at  201  and the wax vessel. The heating element consists of a thermistor material  405  sandwiched between two conductive metal contact plates  410  and  411 . A source of an electrical potential, preferably standard household 120 volt A.C., is connected across the contact plates  410  and  411  to supply a heating current to the resistive heating material  405 .  
         [0021]     The resistive heating material  405  preferably comprises a positive temperature coefficient (PTC) thermistor. PTC thermistors have the ability to function as self-regulating heating elements. They can operate at a nearly constant temperature over a broad range of voltage and heat dissipation conditions and can be manufactured in many different configurations including discs and rectangles. Multiple PTCs can be used in parallel to provide constant heating over a larger area. Switching PTC thermistors have a resistance-temperature characteristic that exhibits a very small negative temperature coefficient until the device reaches a critical temperature that is referred to as its “Curie”, switch or transition temperature. As this critical temperature is approached, the devices begin to exhibit a rising, positive temperature coefficient of resistance as well as a large increase in resistance. The resistance change can be as much as several orders of magnitude within a temperature span of a few degrees. Most PTC thermistors are designed to operate with a transition temperature somewhere between 60° C. and 120° C., however, devices can be manufactured that can switch as low as 0° C. or as high as 200° C.  
         [0022]     These desirable heating characteristics are provided at low cost without the need for a separate thermostat. The PTC elements have virtually unlimited live, cause no electrical noise, have no moving parts to wear out, and are very efficient. PTC heating characteristics have been used to advantage in curling irons, hot melt glue guns, diesel fuel heaters, plug-in “night-light” liquid aroma heaters, and other self-regulating heating applications. PTC heating elements are available from Advanced Thermal Products, Inc., St. Marys, Pa. 15857.  
         [0023]     PTC thermistors are particularly advantageous for use as scented wax heaters because they are able to rapidly melt and thereafter maintain the liquefied wax at a predetermined constant temperature above the melting point of the wax to most effectively release the fragrance from the wax. When used in a ceramic heater of the type described in  FIGS. 1-5 , the PTC thermistor should have a transition temperature within the range from 230 to 250 degrees Fahrenheit to maintain the melted wax at a temperature of approximately 180 degrees Fahrenheit.  
         [0024]     The components used to fabricate heating element for a scented wax heater are shown in the exploded perspective view of  FIG. 5 .  
         [0025]     The contact pad  203  is formed from a 0.3 mm aluminum punched plate. Four tabs are punched through the pad  203 , two of which seen at  501  and  502  fold against and retain the mounting tabs  503  and  504  respectively. The tabs  503  and  504  are formed on the 0.3 mm punched steel clamps  505  and  507  respectively. In this way, the clamps  505  and  507  secure the ceramic housing  560  and the other heating element components to the contact pad  203 .  
         [0026]     The PTC thermistor element  405  is clamped between two punched 0.2 beryllium copper contacts  410  and  411  which transfer electrical current to the element using connections (not shown) to the conductors of an electrical power cord  512  which includes a conventional cord switch  514  used to turn the heater ON and OFF. A 0.1 mm insulator pad seen at  510  made from either laminated mica paper or Apical Polyamide film provides an electrical insulating barrier between the contact pad  203  and the upper electrical contact  410  but provides thermal transmission from the PTC element  405  to the contact pad  203 .  
         [0027]     The lower dielectric Insulator pad  521  is constructed of 0.1 mm laminated mica paper or apical polyamide film providing an electrical insulation barrier between the lower contact and the mounting screw  530 . The PTC heating element  405  and the contacts  410  and  411  nest within a molded ceramic housing  560  that provides a structure for holding the PTC element and contact assembly to the decorative ceramic base  301 . The assembly clamps  505  and  507  secure the ceramic heater element housing  560  and PTC assembly to the contact pad  203 .  
         [0028]     The head of the mounting screw  530  nests within a hexagonal recess in the top of the ceramic housing  560  and the threaded end of the screw  530  extends downwardly through the central bore  310  in the ceramic base  301  seen in  FIG. 3 . A threaded nut  535  and a lock washer (not shown) secure the screw  530  and the heating element assembly to the ceramic base  310 .  
         [0029]     The slip cast stoneware fired ceramic base element  301  provides an electrically insulated barrier between the element electrical connections and the user, aligns the upper aroma vessel  101  in thermal contact with the contact pad  203  of the heating element, and provides a support for the power cord  512 .  
         [0030]     When the switch  514  is turned ON, the PTC heating element provides rapid warm-up of the scented wax to a precisely controlled temperature which is above the melting point of the scent block but below fire hazard temperature. The resulting wax melting and warming unit accordingly provides safe, healthy, low-cost, energy efficient and reliable operation.  
         [0031]     An electrical switch may be added to automatically turn off the heating element when the scent holder is removed from the heating unit. The heating assembly, including the contact plate, may be supported for vertical movement against pressure supplied by a resilient element, such as a Belleville washer, and a contact switch positioned to turn on when the assembly is pressed downward by the weight of the scent holder, and to turn off, removing power from the heating element, when the scent holder is lifted off the heating unit. The pilot light (not shown in  FIG. 5 ) may be integrated into the housing of the switch  514  or may be positioned on the outside of, or be visible through an opening through, the housing  301  of the base unit to indicate when the unit is being powered, thereby reminding the user to turn to unit off when it is not in use.  
         [0032]     A further embodiment of the invention shown in  FIG. 6  comprises a regulated electric heater  601 , a scent holder  603  which is supported by the heater  601 , a tea-light candleholder  604  which nests in and is supported by the scent holder  603 , a tea-light candle  605  which is supported by the candle holder  604 , and a translucent dome  606  which is also supported by the wax holder  603 . The heater  601  is preferably constructed as shown in  FIG. 5 . The scent holder  601  is supported by the heater  601  and forms a bowl of adequate size to accept and hold one or more blocks of unmelted scented wax in the location illustrated at  103  in  FIG. 1 . Aromatic oils may also be placed in the bowl. The upper rim of the scent holder  603  defines two annular interior rims  611  and  612  which engage with and support the candle holder  603  and the dome cover  606  respectively. The dome cover is translucent and is illuminated by the candle  605 , and defines a circular opening at the top through which the heat from the candle and the aroma liberated by the heated scent in the scent holder  603  is expelled and which further permits fresh air to enter and to circulate as the candle burns, enhancing the amount of aroma liberated by the heated scent. The dome, candle, and candle holder may be easily removed for cleaning. Moreover, as in the case of the arrangement shown in embodiment of  FIGS. 1-4 , the scent holder may be separated from the heating element  601  for cleaning, which is often most easily accomplished by placing the scent holder in the freezer compartment of a refrigerator to solidify any remaining in the holder, which may then be easily separated from the holder. In addition, multiple pie-shaped reservoirs may be formed in the interior bottom surface of the scent holder to receive and keep separate several different scents, permitting the user to combine aromas as desired.  
         [0033]     The candle shown in  FIG. 6  may be replaced with an electric lamp, such as a candle simulating flickering lamp bulb which mates with and receives power from a socket in a lamp holder positioned and supported in the same way as the candle holder  604 . Electrical conductors embedded in the scent holder  603  and passing from the lamp holder to a mating female connector in the heater can be used to provide power to the electric lamp using the same power cord that supplies household voltage to the heating element.  
         [0034]     Still another embodiment is shown in  FIG. 7 . The regulated electric heater  711  is mounted in a ceramic base unit  714 . The receptacle  720  sits on top of the base unit  714  and holds a scented wax or other aromatic material that liberates a scent when heated. A dome cover  730  sits on top of and is supported by the receptacle  720  and includes numerous vent openings as seen at  735  which allow the scent to escape. The base unit  714 , the receptacle  720  and the dome cover  730  may all be formed as slip cast stoneware fired ceramic pieces. The dome cover  730  and the receptacle  720  may be decorated with glaze patterns. The dome cover  730  and the scent receptacle  720  may be removed for cleaning.  
         [0035]     As seen in  FIG. 7 , the regulated electric heater, which preferably takes the form of a PTC thermistor, is attached to the underside of a metal support plate  740 . The base unit  714  is similar in construction to the base unit shown in detail in  FIG. 5  with the following differences:  
         [0036]     First, the support plate  740  may be rigidly affixed to the ceramic base housing  714  and includes an opening through which a flexible switch leaf-spring blade of the switch  760  projects. The switch  760  is held in a closed position when the scent receptacle  720  is placed on the base unit, but the flexible blade of switch  760  deflects upwardly to an open position when the receptacle  720  is removed from the base. In this way, whenever the base unit is removed when power is applied through the cord switch (not shown in  FIG. 7  but seen at  514  in  FIG. 5 ), the heating element is automatically de-energized.  
         [0037]     Second, a pilot  770  is interconnected with the heating element  711 , the switch  760 , and the conductors of the power cord  750  and is illuminated whenever the heating element is energized. The sidewalls of the scent receptacle  720  extend downwardly forming a skirt around the periphery of the base unit  714 . Upwardly extending U-shaped notches are formed on opposing sides of this skirt. The first of these notches provides a passageway through which the electrical power cord  750  passes, and the other notch provides a window through which the user can view the pilot light  770 . The configuration shown in  FIG. 7  accordingly permits the base heating element to be used with receptacles and/or receptacle covers on any desired color or decorative style since the receptacle effectively surrounds the entire base unit with the exception of the passageways through which the power cord passes and through which the pilot light is viewed.  
         [0038]     Conclusion  
         [0039]     It is to be understood that the embodiments of the invention which has been described is merely an illustrative application of the invention, and numerous modifications may be made to the structures shown without departing from the true spirit and scope of the invention.