Abstract:
A resistive foil heater for a portable inhaler. A reservoir of vapor material, usually a fluid, has transport by the foil to directly heat the material to a temperature sufficient to vaporize the material to the gas phase. The foil may have a dimpled plate shape, or box shape, a capillary or parallel plate shape.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority from U.S. provisional application Ser. No. 61/935,644, filed Feb. 4, 2014. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to an electrical vaporizer for an electronic cigarette or medicinal inhaler. 
       BACKGROUND ART 
       [0003]    The wick has been used for thousands of years to provide lighting in darkness and has progressed in the past several centuries in kerosene lamps and candles. The operation of a wick, in its basic form, utilizes capillary action, in which a liquid is transported inside a small diameter passage, by attractive forces between the passage material and the liquid properties. For example, if a small diameter glass tube is inserted into a water container, the water will rise inside the tube, to a height which is proportional to the difference in surface tension, of the glass and water, and inversely proportional to the tube diameter and the liquids&#39; viscosity. Capillary action is one of the fundamental processes in transporting water in trees from the ground to the leaves. 
         [0004]    In a wick, the cohesive forces between the wick fibers and the liquid surface tension, transport the liquid material upwards, thus increasing the liquid materials&#39; surface area and causing it to evaporate by a heat source such as a candle flame or electric powered wire filament. In a wire filament, such as that described in the U.S. Publication No. 2013/0213419A1, entitled “Electronic Smoking Article and Improved Heater Element”, by C. S. Tucker et al., a wire mesh, instead of a wire, is utilized as the heat source, vaporizing the liquid transported by the wick, from the liquid reservoir. The wire mesh, having a greater surface area, is thus more efficient in vaporizing the liquid in contact with the wick material, than a circular wire. 
         [0005]    The concern with such vaporization methods, is that the heat source is in contact with the wick material, and one the liquid is depleted, the heater elements&#39; temperature rises sufficiently to combust the wick material causing potentially toxic vapors to be generated. FDA and WHO regulators are concerned, but may be years away from issuing any regulations regarding e-cigarettes and vaporizers. 
       SUMMARY OF INVENTION 
       [0006]    The present invention utilizes thin resistive foils instead of wires or wire meshes, to vaporize the wax, liquid, or solid materials to be vaporized in an inhaler. Due to the larger surface area of the foils, they can vaporize equal amounts of material, per unit power, with a lower temperature, and thus minimizing the combustion of the wick, when the liquid material is depleted. 
         [0007]    Many devices employed for aromatic therapy or vaporization utilize resistive wire heating elements or massive plates heated by conduction from resistive wire heaters. These heating methods dissipate more energy to reach the desired temperature for vaporization due the requirement of elevating the temperature of the container which contains the material to be vaporized. 
         [0008]    In contrast, if the heating element is also the container or wick of the vaporizable material, and also if the heating element has ultra low mass, the energy required to reach the desired temperature is minimized and thus portable vaporization devices can be made which are powered by batteries. Another advantage of ultra low mass heaters is virtually instant on off heating capability which allows for precise temperature control which is essential to extract only the low temperature vapor, and not burn the material, which causes harmful or carcinogenic gases to be generated. 
         [0009]    In another embodiment of the invention, by spiraling or folding the resistive foil material, capillary passages formed by the thin foil are maintained in communication with a vaporizable liquid. The liquid media is transported to the heating element surface, where it is vaporized, by capillary action without a wick, thus eliminating the combustion of the organic wick material. In this design, however, the surface of the foil material must be oxidized, to form an insulating barrier, to keep the contacting metal layer from shorting out between each other. 
         [0010]    In yet another embodiment of the invention, thin ceramic sheets (10-12 micrometers) are processed for high surface tension for capillary action, the heated with thick films, to achieve vaporization of the liquid material. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0011]      FIG. 1  is a plan view of an e-cigarette or inhaler having a foil heater of the present invention. 
           [0012]      FIG. 2  is an electric plan of the foil heater of  FIG. 1 . 
           [0013]      FIG. 3  is a perspective view of the foil heater of  FIG. 2 . 
           [0014]      FIG. 4  is a perspective view of an alternate foil heater. 
           [0015]      FIG. 5  is an electrical plan and heater side plan view of a capillary foil heater for a vaporizer. 
           [0016]      FIG. 5A  is a top view of the apparatus of  FIG. 5 . 
           [0017]      FIG. 6  is an electrical plan and heater perspective plan view of an alternate capillary foil heater for a vaporizer. 
           [0018]      FIG. 7  is an electrical plan of another capillary heater for a vaporizer. 
           [0019]      FIG. 8  is a perspective view of an alternate embodiment with gravity fed inhalation material fluid storage. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    With reference to  FIG. 1 , a vaporizer  11  is shown having a housing  13  that has a common cigarette form factor, and would be useful as a medicinal inhaler or an electronic cigarette. The housing  13  is cylindrical with a central axis of symmetry. The housing may be plastic or glass. Within the housing, a coaxial inhalation tube  15  extends proximately 60 percent of the length of the housing. The inhalation tube has an end  16  in common with the end  18  of housing  13  intended to be near the lips of the user. 
         [0021]    Within the housing  13 , but spaced from housing end  18  is a fluid reservoir  17  which is coaxial with housing  13 . Reservoir  17  may be semi-rigid sponge material that holds a supply of inhalation material, usually a fluid, such as propylene glycol, that can flow within the reservoir material in response to pressure drops. A pressure drop is established by a capillary tube  19  that extends into the reservoir material near housing end  18  and extends from the reservoir along the access of the housing to a heater foil panel  21  which is a thin film of conductive material, such as aluminum. The diameter of capillary tube is several microns in a hollow glass fiber. The distant end of the fiber is adhered to the foil  21 . 
         [0022]    Foil  21  is thin film panel that is less than 50 microns thick. The panel can be planar, but preferably has a dimple or well for holding a supply of inhalation material fluid received from the capillary tube  19 . The panel is approximately two square millimeters in area and is supported on opposite sides by wires  23  and  25 , with the dimple or well being centrally located between the wires. The conductive wires  23  and  25  extend rearwardly from opposites sides of the conductive panel towards battery  33 . Conductive wire  23  terminates at a pressure switch  27  having a first switch member  29  which is a hinged leaf spring that is spaced a small distance from the second switch member  31  which is an arm connected to the conductive wire  23 . When a user inhales through the inhalation tube  15 , the pressure switch closes because the hinged leaf spring member  29  contacts the second switch member  31  thereby closing the switch. This causes wire  23  to be an electrical communication with the positive terminal of battery  33 . The negative side of battery  33  is connected through a resistor  35  to wire  25  on the opposite side of foil panel  21  from the wire  23 . Closing of the switch  27  causes current to flow through resistor  35  and across the foil  21 , causing resistive heating of the foil while the switch is closed. Because the foil is very thin, its resistance is relatively high causing the heater to sufficiently hot to vaporize the inhalation material fluid that is supported on the foil, particularly in a foil well if provided. Resistance of the foil is between 0.2 and 0.5 ums. Temperature of the foil can reach 1,200 degrees F. if no liquid is on the foil. With liquid on the foil, the temperature of the foil ranges between 400 and 600 degrees F. which is sufficiently for vaporization of the liquid. The higher temperatures that arise without liquid are adequate for cleaning the foil in instances where there could be a momentary gap in delivery of fluid from the capillary tube  19 . Since the reservoir is removed from the foil, there is no combustion and no inhalation of foreign materials. The inhaler of the invention operates until the reservoir is depleted. 
         [0023]    In  FIG. 2 , an alternate embodiment is shown. As before the foil panel  21  is mounted near an end of the glass inhalation tube  15 . The fluid reservoir, capillary end housing are not shown. The foil is supported within the inhalation tube by an insulative ring  24  mounted to the end of the inhalation tube  15 . Wires  23  and  25  provide power to opposites sides of the thin film foil panel  21 . Power is supplied to the foil by an adjustable, constant voltage power supply  14  that has a manual on-off switch  28 , operated by a push button that extends through the housing. When the housing is gripped by the fingers, a finger can push down on the switch creating momentary heating of the foil and vaporizing fluid which has been delivered to the foil panel  21 . An external power supply is used to supply input DC voltage, typically 3 to 12 volts DC to connector  34 . The connector has positive and negative terminals that supply the voltage to wires  23  and  25  responsive to actuation of switch  28 . 
         [0024]    In  FIG. 3 , the foil panel is seen to be having a central dimple  22  that serves as a well for inhalation material, usually a fluid. A capillary delivers the fluid directly to the well. Opposite sides of the foil panel  21  are spot welded to the conductive wires  23  and  25 . 
         [0025]    In  FIG. 4 , the wires  23  and  25  are seen to be connected to a box shaped foil panel  21  where the box serves as an inhalation material container. The box has four lateral sides and a bottom, but an open top. The open top receives inhalation material fluid from the capillary. Heating of the foil box panel to a temperature above 400 degrees F. causes vaporization of the fluid, thereby generating smoke. A preferred material for the foil is a nickel chromium alloy having temperature characteristics similar to Nichrome wire used in toasters. 
         [0026]    With reference to  FIG. 5  a thin resistive foil  31  of the kind previously described has been wound in a spiral manner to form a capillary having a diameter appropriate for wicking liquid  35  from the liquid container  33 . The foil has been oxidized so that conductive wires  41  and  43  will not short. Rather, the wires  41  and  43  make contact with the foil at reagents where the oxide has been removed in order to apply power from a battery  45  that actuated by a switch  47 . As the spiral foil  31  wicks material upwardly, the foil is heated to 400 degrees C. or more and material within the capillary is vaporized by the heat and exits through the top of the capillary. In the top view of  FIG. 5A  the turns of the spiral foil are seen to be non-contacting due to oxide treatment of the foil that prevents shorting. 
         [0027]    In  FIG. 6 , resistive foil  51  is seen to be accordion pleated and has oxide coatings on opposite sides of the foil. The pleats  52  are sufficiently closely spaced so that the wick liquid  55  from the liquid container  53 . Wires  61  and  63  are connected to opposite ends of the pleats  52  at regions where oxide coatings are removed for good electrical contact with the resistive foil  51 . The wires draw power from a battery  69  which can be momentarily actuated by a switch  67 . Liquid  55  is drawn into the interstices between the pleats  52  where it is heated and vaporized, moving upwardly where it is drawn into an inhalation tube. 
         [0028]    In  FIG. 7 , thin parallel ceramic plates  71  are spaced apart by a slight distance that allows capillary action with regard to liquid  75  that is in the liquid container  73 . The thin ceramic plates have opposite sides to which thick film conductive members  74  and  76  are applied. For example, an aluminum film may be sputtered onto the ceramic plates for making electrical contact to wires  81  and  83  that are connected to opposite terminals of battery  89  that is actuated by switch  87 . When the switch is actuated, current flows from the battery to the metal contacts  74  and  76 , thereby heating the outward ceramic plates causing fluid between the plates that has been wicked upwardly to become vaporized. Vapor moves upwardly, causing further wicking of the liquid material so long as power is supplied by the battery. The ceramic plates are approximately the same size as the metal foil described with reference to  FIG. 1 , with a sufficient thickness to be self supporting. 
         [0029]    In the embodiment of  FIG. 8 , all elements are the same as in  FIG. 2  except that a gravity fed inhalation fluid material storage tube  60  extends perpendicularly above inhalation tube  15 . The fluid material flows by gravity onto a dimple  62  of the heated thin film foil panel  21 . The storage tube  60  has a diameter of one to three millimeters and holds a few ml. of inhalation fluid material. The tube  60  is pushed in place into the circumferential periphery of inhalation tube  15  and may be removed when empty or no longer desired and replaced by a fresh inhalation fluid material storage tube of similar dimensions. The storage tube  60  is pushed down into inhalation tube  15  until the tip of the storage tube is a short distance from foil panel  21 . As fluid material is vaporized from the heated foil panel, a drop of fluid material near the heated foil panel drops onto the panel for vaporization. Care must be taken so that vaporization does not occur in storage tube  60  and so the storage tube  60  must be a short distance from the heated foil panel. A tube indexing locator, not shown, may be placed above the heated foil panel to stop the downward motion of the storage tube  60  upon insertion into the inhalation tube  15  to prevent vaporization of inhalation fluid material in the storage tube.