Abstract:
Thermal cleaning of an electrically heated smoking device, and in particular the removal of condensates formed within the smoking device as a result of extended periods of use, is achieved with a cleaning system that utilizes inductive heating that provides efficient and intense localized heating in the cleaning process. The thermal power of the inductive heating process is increased or the power necessary to activate the inductive heating process is decreased by the addition of a magnetic shell by itself or in combination with a magnetic pin.

Description:
TECHNICAL FIELD OF THE INVENTION 
   The present invention relates to methods and apparatuses for using, cleaning and maintaining heat sources used in electrical smoking systems. 
   BACKGROUND OF THE INVENTION 
   Commonly assigned U.S. Pat. Nos. 5,388,594; 5,505,214; 5,530,225; and 5,591,368 disclose various electrically powered smoking systems comprising cigarettes and electric lighters and are hereby expressly incorporated by reference. 
   The smoking systems referred to above are designed with the intention of providing the user with all the pleasures of smoking while significantly reducing the side stream smoke produced during smoking. The smoking system also allows users the added benefit of reinitiating smoking of a cigarette that has been partially smoked, thereby providing the smoker with the ability to suspend and reinitiate smoking as desired. 
   In the operation of the smoking system a non-traditional cigarette is inserted in a heating fixture and heating elements are activated to smoke the cigarette. As a result, condensates may form and collect on the heating fixture. The build up of condensates can affect the functionality of the smoking device and may detract from the flavor and overall pleasure experienced by a user of the device. Therefore, it is desirable to periodically clean the heating fixture of the smoking device in order to rid itself of the condensates that may have collected therein. 
   U.S. Pat. No. 5,878,752, issued Mar. 9, 1999, hereby incorporated by reference, discloses an electrical lighter that has a sleeve, which concentrically surrounds the cigarette heating fixture. The cigarette heater elements transfer heat primarily via conduction to the inner surface of the sleeve and indirectly from this heated inner surface primarily via convection and radiation to other component surfaces to thermally liberate condensates which are deposited thereon during smoking. However, activation of the heating elements may not fully clean the condensates located on other components within the device. A ceramic layer is deposited on the outer surface of the sleeve to electrically insulate a subsequently applied sleeve heating element from the metal sleeve except for an exposed negative contact. In an alternative embodiment, an induction coil for heating the sleeve is shown. 
   As part of the cleaning process, a cleaning unit, in which the smoking device is placed, may be used to aid in the removal of the condensates that have been liberated by the thermal cleaning. The cleaning unit acts in a manner that draws the volatilized condensates from the smoking device. In this process of removing the condensates from the smoking device a catalyst may be used. The volatilized condensates from the smoking device are drawn through the catalyst which breaks down the condensates into primarily water vapor and carbon dioxide. As the catalyst is heated the catalyst becomes more efficient. Thus, the use of inductive heating techniques to heat the catalyst during a cleaning cycle of the smoking device may enhance the performance of the catalyst. However, conventional systems for cleaning the smoking device with the aid of a catalyst have required separate heaters and circuitry for heating the catalyst, which can increase costs and the size of the cleaning system while reducing efficiency. 
   SUMMARY OF THE INVENTION 
   The present invention provides methods and apparatus that enhance inductive heating techniques for the purpose of removing condensates formed within an electrically heated cigarette smoking device. Embodiments of the present invention include a magnetic shell that surrounds inductive heating elements such as radio-frequency excitation coils, which induce electrical current in metallic components of the smoking device. The metallic components, such as a cylindrical canister positioned around the heater blades for the purpose of directing air flow and capturing condensates that are not inhaled by the user, constitute the heating target. The induced electrical current heats the components and volatilizes any condensates that may be collected on the components. The magnetic shell captures elements of the stray magnetic flux and couples that energy to the heating target. 
   A secondary embodiment of the invention provides a magnetic pin which is placed in the center of the cigarette heater, surrounded by the heating blades. The magnetic pin in combination with the magnetic shell provides an increase in coupled power to the heating target of up to 300% over a similar inductive heating technique performed without the magnetic elements. Thus, an increase in heating power is obtained over the heating power without the magnetic elements using the same amount of energy. Therefore, decreased power may be used to heat the heating target or a greater amount of heating power may be transferred to the heating target. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be understood by reading the following detailed description in conjunction with the drawings in which: 
       FIG. 1  is an exemplary electrically heated cigarette smoking system with which a cleaning system in accordance with the present invention may be utilized. 
       FIG. 2  is an exemplary cross-sectional view of the heating element within an electrically heated cigarette smoking system. 
       FIG. 3   a  is an exemplary inductive heating element with a magnetic shell of a cleaning system in accordance with the invention. 
       FIG. 3   b  is an exemplary cross-sectional view of the magnetic shell shown in  FIG. 3   a.    
       FIG. 4  is an exemplary inductive heating element with a magnetic shell and magnetic pin of a cleaning system in accordance with the invention. 
       FIG. 5   a  is an exemplary inductive heating element with a catalyst of a cleaning system in accordance with the invention. 
       FIG. 5   b  is an exemplary inductive heating element with a magnetic shell and catalyst of a cleaning system in accordance with the invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Inductive heating techniques provide the user of an electrical smoking device the ability to efficiently liberate the smoking device from condensates that may build up in the device during normal use. When used in conjunction with a cleaning module, the smoking device can be sufficiently cleansed of the liberated condensates in a environmentally friendly manner. The cleaning module can include an inductive coil of consistent or varying configuration that can be placed around a target, such as a circular tube or canister, and driving circuitry provided to maintain resonant circuit conditions for maximizing efficiency and power transfer to the excitation coils. The driving circuitry should be able to create enough power to sufficiently heat the target, which can be in the form of a canister positioned around an arrangement of electrical heater blades. When power is delivered to the inductive coils, electromagnetic flux is created that passes through the canister. The flux causes electric currents to be created within the canister, which in turn causes the canister to increase in temperature. 
   The inductive heating techniques of embodiments of the present invention may be used within an electrical smoking system. An exemplary smoking system  21  is illustrated in  FIG. 1 . The smoking system  21  includes a cylindrical cigarette  23  and a reusable, hand-held lighter  25 . The cigarette  23  is adapted to be inserted in and removed from an opening  27  at the front end  29  of the lighter  25 . The smoking system  21  is used in much the same way as a conventional cigarette. The user puffs on the cigarette end  41  that protrudes out from the opening  27 , thereby obtaining the aroma and flavor associated with the smoke from the combustion of the cigarette  23 . When the use of the cigarette  23  has been exhausted, the cigarette  23  is discarded. 
   The lighter  25  comprises a heating fixture  39 , a power source  37 , electrical control circuitry  33 , a puff sensor  35  and a display indicator  31 . The heating fixture  39  contains the heating elements that pyrolyze portions of the cigarette  23  when a puff is taken by the user. The control circuitry  33  controls the amount of power that is delivered to the heating elements of heating fixture  39  from power source  37 . 
   The puff sensor  35  is sensitive to flow or pressure changes and senses when a user draws on cigarette  23 . The puff sensor  35  provides a signal to the control circuitry  33 , which then activates the appropriate heater blade located within the heating fixture  39 . Each heater blade pyrolyzes an adjacent portion or “heater footprint” on the cigarette  23 . The display indicator  31  may display various information, such as, the number of puffs that remain, the power level, etc. 
   A cross-sectional view of the heating fixture  39  is illustrated in  FIG. 2 . The heating fixture  39  includes at least an outer housing  70 , heating blades  80 , a secondary can  60  and an opening  27 . Other features of the heating fixture  39  are discussed in commonly assigned U.S. Pat. Nos. 5,591,368 and 5,878,752. The heating blades  80  surround the cigarette when it is placed within the heating fixture  39 . In one embodiment the heating fixture  39  comprises eight heating blades  80 . However, the heating fixture  39  may have less than or more than eight heating blades  80 . The heating blades  80  are activated by the control circuitry  33  which controls which blades are heated, how hot and how long they are heated. The heating blades  80  pyrolyze cigarette  23 , which produces the smoke or aerosolized byproducts and condensates. 
   The secondary can  60  surrounds the heating blades  80 . The secondary can  60  acts to direct air flow, keep the outer housing from getting too hot and it collects the condensates in preference to other areas of the heating fixture  39  and smoking device  25 . The secondary can  60  can be used to accumulate a large portion of condensates released during the use of the smoking device  25 . 
   As previously discussed, inductive heating techniques may be utilized to thermally liberate the condensates that are built up on various portions of the heating fixture. Illustrated in  FIG. 3   a  is an embodiment of the present invention in which an increase in inductive heating power is accomplished by placing a magnetic shell  110  so that it surrounds the heating coils  105  and heating target, preferably in the form of an electrically conductive portion of the heating fixture of an electrically heated cigarette smoking system, which in  FIG. 3  is the secondary can  60 . The magnetic shell  110  captures stray magnetic flux generated by the inductive heating process. This stray magnetic flux is then coupled into the heating target. With the use of a magnetic shell  110 , an increase in the inductive power delivered to the heating element can be increased as much as 30%.  FIG. 3   b  illustrates the magnetic shell  110  as seen from the front or rear of the heating elements that the magnetic shell  110  surrounds. 
     FIG. 4  illustrates another embodiment of the present invention in which a magnetic pin  115  is placed between the secondary can  60  and the heating blades, which are enclosed by the secondary can  60 . The magnetic pin  115  captures a large amount of stray magnetic flux and couples this energy into the secondary can  60 . The combination of both the magnetic shell  110  and the magnetic pin  115  captures almost all the stray magnetic flux and couples this energy to the heated element, i.e. secondary can  60 . Thus, magnetic flux is primarily directed to the heating element rather than other metallic elements in the smoking system. The magnetic material used in the magnetic shell  110  and magnetic pin  115  may be any permeable magnetic material such as a ferrite or ferro-dielectric material. 
   The combination of the magnetic shell  110  and pin  115  provides an increase in the thermal energy supplied to the heated element of upwards to 300% compared to inductive heating without the use of a magnetic shell  110  and pin  115 . Therefore, if desired, the amount of thermal power delivered to the heated element can be reduced to one-third the power that would used by inductive heating coils without a magnetic shell and pin. Further, EMI emissions would be expected to be reduced significantly, i.e., by at least one-third. Thus, the cleaning system, which can be powered by direct current or alternating current, is provided with a longer battery life or lower power consumption, and having reduced EMI emissions. 
     FIGS. 5   a  and  5   b,  illustrate an alternative embodiment of the present invention in which a catalyst  120  is used as the heated element.  FIG. 5   a  illustrates the arrangement of the catalyst  120  relative to inductive coils  105 . The catalyst may be used to capture any particles that may be in the air withdrawn from the smoking device undergoing cleaning, or to chemically treat the gases produced during the cleaning process. The heating of the catalyst  120  increases the effectiveness of the catalyst  120  as air is drawn through it. 
     FIG. 5   b  is the heating arrangement of  FIG. 5   a  with the addition of the magnetic shell  110  that surrounds the inductive heating coils  105 . The addition of the magnetic shell  110  increases the thermal energy applied to the catalyst  120  in the same manner as discussed above. 
   While this invention has been described in conjunction with the exemplary embodiments outlined above, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the exemplary embodiments of the invention may be made without departing from the spirit and scope of the invention.