Patent Publication Number: US-8530794-B2

Title: Hair iron

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of prior U.S. patent application Ser. No. 12/546,618, filed on Aug. 24, 2009 now U.S. Pat. No. 8,080,764, which claims the benefit and priority benefit, of U.S. Provisional Patent Application No. 61/091,382 filed on Aug. 23, 2008 and U.S. Provisional Patent Application No. 61/142,565 filed on Jan. 5, 2009, the contents of each prior application is hereby incorporated by reference in full. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to the care and treatment of the hair, and in particular to a digital hair iron for styling, curling, flattening, and/or straightening hair. 
     2. Description of the Related Art 
     There has long been a desire to style, flatten curl, and/or straighten hair. Prior hair irons are generally known. 
     SUMMARY OF THE INVENTION 
     A hair iron apparatus preferably includes an upper housing pivotally associated with a lower housing. A first heat transfer plate may be associated with the upper housing and a second heat transfer plate may be associated with the lower housing. A first heater may be affixed to the first heat transfer plate by a first adhesive, and a second heater may be affixed to the second heat transfer plate by a second adhesive. 
     While the invention will be described in connection with the preferred illustrative embodiments, it will be understood that it is not intended to limit the invention to those embodiments. On the contrary, it is intended to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The present digital hair iron and method of using a digital hair iron may be understood by reference to the following description taken in conjunction with the accompanying drawing, in which: 
         FIG. 1  is an exploded, side view of a hair iron according to an illustrative embodiment of the present digital hair iron. 
         FIG. 2  is a schematic illustrating the circuitry of an illustrative embodiment of a digital hair iron according to an illustrative embodiment of the present digital hair iron. 
         FIG. 3  is a partial cut-away front view of a hair iron, in a closed configuration, accordingly to an illustrative embodiment of the resent digital hair iron. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIG. 1 , an exploded, side view of a hair iron  100  is illustrated. The hair iron  100  includes an upper housing  105  associated with a lower housing  110 , as by being pivotally connectable about a first axis to the lower housing  110 . The upper housing  105  and low housing  110  may each have a general convex outer shape, and a general concave inner shape. The upper housing  105  may include a first top side  176 , a first underside  175 , a first forward (or first front) portion  150 , and a first rearward (or first rear) portion  115 . The lower housing  110  may include a second top side  226 , a second underside  225 , a second forward (or second front) portion  165 , and a second rearward (or second rear) portion  155 . Preferably, when pivotally connected, the upper housing  105  is aligned with, and opposes, the lower housing  110  in an elongated clam configuration. The pivotal engagement between the upper housing  105  and lower housing  110  may include a pivot shaft  107  and may be secured with at least two side caps  112 . 
     A rearward portion  115  of the upper housing  105 , may include any number of apertures through which any number of buttons, dials, switches, liquid crystal displays (“LCD”), and the like may be exposed. The rearward portion  115  of the upper housing  105 , may include at least three, and preferably four button apertures  120 ,  125 ,  130 , and  135 , for buttons and at least one LCD aperture  140  for an LCD  250 . In a further embodiment, the rearward portion  115  of the upper housing  105  blends along a slight upper rise  145  to the forward portion  150  of the upper housing  105 . The end user may utilize the blended upper rise  145  as a thumb rest. Similarly, a rearward portion  155  of the lower housing  110  may blend along a slight lower rise  160  to the forward portion  165  of the lower housing  105 . The end user may utilize the blended lower rise  160  as an index finger rest. The upper housing  105  and lower housing  110  may be made of any suitable material having the requisite strength and heat resistance properties to function in a hair iron, such as any suitable metal, metal alloy, or plastic material. Preferably blended plastic including at least about 30% fiberglass reinforcement may be utilized as the material of construction for the upper housing  105  and lower housing  110 . 
     In an illustrative embodiment, a heater support  170  is affixed to the underside  175  of the forward portion  150  of the upper housing  105 . A male element or tab  171  of the heater support  170  may slidingly engage a female slot or element (not shown) of the underside  175  of the forward portion  150  of the upper housing  105 . Alternatively, the heater support  170  may be screwed or pinned to the underside  175  of the forward portion  150  of the upper housing  105 . In a still further embodiment, a forward end  180  of the heater support  170  may slidingly engage the underside  175  of the forward portion  150  of the upper housing  105  with male and female tabs elements, and a reward end  185  of the heater support  170  may slidingly engage a forward end  190  of a top cover  195  with male and female elements. The top cover  195  preferably houses many of the hair iron&#39;s electrical components between an interior surface of the top cover  195  and the concave underside  175  of the reward portion  115  of the upper housing  105 , as further detailed below. The heater support  170  may be made of any suitable material having the requisite strength and heat resistance properties to function in a hair iron, such as any suitable metal, metal alloy, or plastic material. Preferably blended plastic including at least about 40% fiberglass reinforcement may be utilized as the material of construction for the heater support  170 . Preferably, the heater support  170  is made from a plastic having a higher fiberglass reinforcement percentage than the upper housing  105  and lower housing  110 . Preferably, the heater support  170  has a higher melting point than the upper housing  105  and lower housing  110 . 
     In an embodiment, an insulator  200  is disposed between the underside  175  of the forward portion  150  of the upper housing  105  and the heater support  170 . Without wishing to be bound by the theory, the insulator  200  may prevent the forward portion  150  of the upper housing  105  from becoming too hot to a human&#39;s touch, and may direct heat toward hair during use. The insulator  200  may be made of any suitable material having the requisite heat resistance properties to function in a hair iron, such as a foam, foam polymer, glass foam, or plastic material. Preferably, the insulator  200  may be a high temperature silicone bonded mica laminate. As non-limiting examples, the insulator  200  may be made from silica aerogel, carbon aerogel, alumina aerogel, or chalcogel. Preferably, the insulator  200  has a thermal conductivity of at most about 0.2 Watts/(meter*Kelvin). 
     In a still further embodiment, at least one, and preferably two rocker balls  205  are disposed between the underside  175  of the forward portion  150  of the upper housing  105 , or if present the insulator  200 , and the heater support  170 . The underside  175  of the forward portion  150  of the upper housing  105 , or if present the insulator  200 , may include apertures, recesses, mounts, and the like  210  to receive the rocker balls  205 . Similarly, the heater support  170  may include apertures, recesses, or mounts  210  to receive the rocker balls  205 . The rocker balls  205  may be of any suitable material having the requisite strength and compressibility characteristics to function in a hair iron, such as a plastic material, a foam, a foam polymer, or soft silicone rubber. Preferably, the compressibility of the rocker balls  205  is between about 30 and about 90 (Durometer) shore A, alternatively between about 40 and about 80 (Durometer) shore A, and alternatively about 55 (Durometer) shore A, as tested according to ASTM D2240-05. Without wishing to be bound by the theory, the rocker balls  205  permit the heater support  170 , and a heat transfer plate  215 , to pivot about a second axis, which may assist styling hair. Preferably, the amount of pivotal movement is less than about 8 degrees, alternatively less than about 5 degrees, alternatively less than about 3 degrees. Additionally, without wishing to be bound by the theory, the rocker balls  205  may permit the heater support  170 , and heat transfer plate  215 , to pivot, or be compressed, about the first axis, which may provide a stronger grip on the hair and assist styling hair. 
     The heat transfer plate  215  is preferably made of a material with high thermal conductivity, such as aluminum, brass, copper, diamond, gold, silver, metal alloys, and the like. The heat transfer plate  215  is preferably affixed to the heater support  170 . In an embodiment, the heat transfer plate  215  may be screwed into the heater support  170 , and alternatively the heat transfer plate  215  is slideably engageable with the heater support  170 . 
     The heat transfer plate  215  may be coated with a polysiloxane and ceramic composition. In an embodiment, the ceramic composition includes at least 16 metal ions in an organic solvent. In another embodiment, the ceramic composition includes at least 16 metal ions suspended in an organic solvent. The 16 metal ions of the ceramic composition may include aluminum, calcium, titanium, chromium, manganese, iron, copper, strontium, barium, lanthanum, cerium, praseodymium, neodymium, lead, thorium, and silicon. Preferably the ceramic composition includes about 10.5 aluminum normalized weight percent, based on the total weight percent of metal ions in the ceramic composition, and the normalized weight percent of aluminum may range from between about 0.1 to about 40 percent. Preferably the ceramic composition includes about 6.7 calcium normalized weight percent, based on the total weight percent of metal ions in the ceramic composition, and the normalized weight percent of calcium may range from between about 1 to about 35 percent. Preferably the ceramic composition includes about 15.4 titanium normalized weight percent, based on the total weight percent of metal ions in the ceramic composition, and the normalized weight percent of titanium may range from between about 5 to about 55 percent. Preferably the ceramic composition includes about 10 chromium normalized weight percent, based on the total weight percent of metal ions in the ceramic composition, and the normalized weight percent of chromium may range from between about 1 to about 35 percent. Preferably the ceramic composition includes about 1.9 manganese normalized weight percent, based on the total weight percent of metal ions in the ceramic composition, and the normalized weight percent of manganese may range from between about 0.1 to about 45 percent. Preferably the ceramic composition includes about 7.1 iron normalized weight percent, based on the total weight percent of metal ions in the ceramic composition, and the normalized weight percent of iron may range from between about 2 to about 45 percent. Preferably the ceramic composition includes about 4.1 copper normalized weight percent, based on the total weight percent of metal ions in the ceramic composition, and the normalized weight percent of copper may range from between about 2 to about 35 percent. Preferably the ceramic composition includes about 1.1 strontium normalized weight percent, based on the total weight percent of metal ions in the ceramic composition, and the normalized weight percent of strontium may range from between about 0.01 to about 10 percent. Preferably the ceramic composition includes about 22.1 barium normalized weight percent, based on the total weight percent of metal ions in the ceramic composition, and the normalized weight percent of barium may range from between about 3 to about 55 percent. Preferably the ceramic composition includes about 1.9 lanthanum normalized weight percent, based on the total weight percent of metal ions in the ceramic composition, and the normalized weight percent of lanthanum may range from between about 0.1 to about 5 percent. Preferably the ceramic composition includes about 3.6 cerium normalized weight percent, based on the total weight percent of metal ions in the ceramic composition, and the normalized weight percent of cerium may range from between about 0.1 to about 10 percent. Preferably the ceramic composition includes about 0.4 praseodymium normalized weight percent, based on the total weight percent of metal ions in the ceramic composition, and the normalized weight percent of praseodymium may range from between about 0.01 to about 5 percent. Preferably the ceramic composition includes about 1.3 neodymium normalized weight percent, based on the total weight percent of metal ions in the ceramic composition, and the normalized weight percent of neodymium may range from between about 0.2 to about 10 percent. Preferably the ceramic composition includes about 0.1 lead normalized weight percent, based on the total weight percent of metal ions in the ceramic composition, and the normalized weight percent of lead may range from between about 0.01 to about 3 percent. Preferably the ceramic composition includes about 1 thorium normalized weight percent, based on the total weight percent of metal ions in the ceramic composition, and the normalized weight percent of thorium may range from between about 0.01 to about 3 percent. Preferably the ceramic composition includes about 23.3 silicon normalized weight percent, based on the total weight percent of metal ions in the ceramic composition, and the normalized weight percent of silicon may range from between about 5 to about 45 percent. 
     In an embodiment, the heat transfer plate  215  may be coated with the polysiloxane and ceramic composition in accordance with one or more of the following steps: cleaning; surface etching; priming; application of ceramic composition; and coating of polysiloxane. The heat transfer plate  215  may be cleaned by fine surface abrasion; application of alcohol, acetone, organic solvent, or cleaning solution; or a combination thereof. In an embodiment, the heat transfer plate  215  need not be cleaned prior to application of surface etching. In another embodiment, the heat transfer plate  215  may be cleaned after surface etching. 
     The surface of the heat transfer plate  215  may be etched using a dilute phosphoric acid solution, or other suitable acidic or basic solutions. Without wishing to be bound by the theory, it is believed that surface etching creates minor cuts or pocks into the surface of the heat transfer plate  215 , which improves the bond between the ceramic composition and the heat transfer plate  215  by increasing the surface area of the heat transfer plate  215  and/or increasing a friction fit between the heat transfer plate  215  and the ceramic composition. 
     An aqueous composition including potassium, sodium, aluminum, and ammonium silicate, or combinations thereof may be prepared and used as a primer. Without wishing to be bound by the theory, it is believed that application of the primer as a coating to the heat transfer plate  215  renders the metal surface of the heat transfer plate  215  hydrophilic. The heat transfer plate  215  coated with the primer may be heated to about 350° C. for about 15 to about 20 minutes. Alternatively, the heat transfer plate  215  coated with the primer is placed into an over which is heated to about 350° C. for about 15 to about 20 minutes. 
     Then, the heat transfer plate  215  may be cooled to about 90° C. to about 125° C. The cooled and primed heat transfer plate  215  may be sprayed or painted with a thin coat of ceramic composition. The ceramic composition may a mixture of at least the above-identified 16 metal ions in powered form (mesh #320-150) suspended in an organic solvent of alcohol or aliphatic solvents such as C 2  (ethanol or ethane) up to C 10  (dodecanol), including 2,3 dimethyl butane. A coating of polysiloxane, such as for example triethoxysilane ((C 2 H S O) 3 SiH), may then be applied to the heat transfer plate  215 . The coating of polysiloxane may be cured by heating the heat transfer plate  215  to about 200° C. to about 220° C. for between about 15 and about 20 minutes. Alternatively, the coating of polysiloxane may be cured by placing the heat transfer plate  215  into an oven which is heated to about 200° C. to about 220° C. for between about 15 and about 20 minutes 
     Without wishing to be bound by the theory, it is believed that the heat transfer plate  215 , coated as described above, may be used within a digital or analogue hair iron to create anions, or positive ions, when the coated heat transfer plate  215  is heated above 60° C. In an embodiment, the heater  220  is heated by high current and the heat is transferred through the thermal epoxy to the heat transfer plate  215 . It is further believed that far infrared (thermal waves) are caused to be transferred through the ceramic composition and the anions, or positive ions, are transmitted to the hair having advantageous effects on the hair shaft, which make it more manageable. 
     A heater  220  (shown in  FIGS. 2 and 3 ) may be disposed between the heater support  170  and the heat transfer plate  215 . An adhesive  217  may affix the heater  220  to the heat transfer plate  215 . Preferably, the adhesive  217  is a thermally conductive epoxies. In an embodiment, with respect to  FIG. 3 , the insulator  200  may be associated with the first forward portion  150 ; the heater support  170  may be associated with the first insulator  200 ; the heater support  170  may be associated with the heat transfer plate  215 ; the heater  220  may be associated with the adhesive  217 ; and the heat transfer plate  215  may be associated with the heater  220 . Without wishing to be bound by the theory, it is believed that the epoxy, adhesive  217  aids in the heat transfer between the heater  220  and the heat transfer plate  215 , and beneficially eliminates the need for spring clamps and other mechanical elements, which may cause electrical disturbances. Further, without wishing to be bound by the theory, it is believed that the epoxy, adhesive  217  aids in promoting even heat transfer from the heater  220  to the heat transfer plate  215  and minimizes “cold spots.” Preferably, the epoxy, adhesive  217  is applied as a uniform thin coating or film having a thickness ranging from between about 0.002 millimeters to about 0.5 millimeters, alternatively from about 0.002 millimeters to about 0.4 millimeters, and alternative from about 0.02 millimeters to about 0.3 millimeters. In an embodiment, a suitable epoxy, adhesive  217  includes Dow Corning 3-6752 silicone epoxy, which may have a thermal conductivity at 25° C. of about 1.8 watts per meter Kelvin, and a hardness (shore scale) of about 87A. The heater  220  may be made of any material having the requisite heat resistance and electrical properties to function in a hair iron, such as a metal, metal alloy, carbon, plastic, or ceramic. 
     In an embodiment, a second heater support  170 ′ is affixed to the underside  225  of the forward portion  165  of the lower housing  110 . A second male element or tab (not shown) of the second heater support  170 ′ may slidingly engage second a female slot or element  172 ′ the underside  225  of the forward portion  165  of the lower housing  110 . Alternatively, the second heater support  170 ′ may be screwed or pinned to the underside  225  of the forward portion  165  of the lower housing  110 . In a still further embodiment, a lower forward end  180 ′ of the second heater support  170 ′ may slidingly engage the underside  225  of the forward portion  165  of the lower housing  110  with male and female elements, and a reward end  185 ′ of the second heater support  170 ′ may slidingly engage a forward end  300  of a lower cover  305  with male and female elements. The lower cover  305  preferably houses some of the hair iron&#39;s electrical components between itself  305  and the underside  225  of the reward portion  155  of the lower housing  110 , as further detailed below. The second heater support  170 ′ may be made of any suitable material having the requisite strength and heat resistance properties to function in a hair iron, such as any suitable metal, metal alloy, or plastic material. Preferably a blended plastic including at least about 40% fiberglass reinforcement may be utilized as the material of construction for the second heater support  170 ′. Preferably, the second heater support  170 ′ is made from a plastic having a higher fiberglass reinforcement percentage than the upper housing  105  and lower housing  110 . Preferably, the second heater support  170 ′ has a higher melting point than the upper housing  105  and lower housing  110 . 
     In an embodiment, a second insulator  200 ′ is disposed between the underside  225  of the forward portion  165  of the lower housing  110  and the second heater support  170 ′. Without wishing to be bound by the theory, the second insulator  200 ′ may prevent the forward portion  165  of the lower housing  110  from becoming too hot to a human&#39;s touch, and may direct heat toward hair during use. The second insulator  200 ′ may be made of any suitable material having the requisite heat resistance properties to function in a hair iron, such as a foam, foam polymer, glass foam, or plastic material. Preferably, the second insulator  200 ′ may be a high temperature silicone bonded mica laminate. As non-limiting examples, the second insulator  200 ′ may be made from silica aerogel, carbon aerogel, alumina aerogel, or chalcogel. Preferably, the insulator  200 ′ has a thermal conductivity of at most about 0.2 Watts/(meter*Kelvin). 
     In a still further embodiment, at least one, and preferably two lower rocker balls  205 ′ are disposed between the underside  225  of the forward portion  165  of the lower housing  110 , or if present the second insulator  200 ′, and the second heater support  170 ′. The underside  175  of the forward portion  225  of the lower housing  110 , or if present the second insulator  200 ′, may include apertures, recesses, mounts, and the like  210 ′ to receive the lower rocker balls  205 ′. Similarly, the second heater support  170 ′ may include apertures, recesses, or mounts  210 ′ to receive the lower rocker balls  205 ′. The lower rocker balls  205 ′ may be made from a soft silicone rubber. Preferably, the compressibility of the lower rocker balls  205 ′ is between about 30 and about 90 (Durometer) shore A, alternatively between about 40 and about 80 (Durometer) shore A, and alternatively about 55 (Durometer) shore A, as tested according to ASTM D2240-05. Without wishing to be bound by the theory, the lower rocker balls  205 ′ permit the second heater support  170 ′, and second heat transfer plate  215 ′, to pivot about a second axis, which may assist styling hair. Preferably, the amount of pivotal movement is less than about 8 degrees, alternatively less than about 5 degrees, alternatively less than about 3 degrees. Additionally, without wishing to be bound by the theory, the lower rocker balls  205 ′ may permit the second heater support  170 ′, and second heat transfer plate  215 ′, to pivot, or be compressed, about the first axis, which may provide a stronger grip on the hair and assist styling hair. 
     The second heat transfer plate  215 ′ is preferably made of a material with high thermal conductivity, such as aluminum, brass, copper, diamond, gold, silver, metal alloys, and the like. The second heat transfer plate  215 ′ is preferably coated with a polysiloxane and ceramic composition containing at least 16 metal ions and other organic composites. In an embodiment, the ceramic and at least 16 metal ions and other organic composites are suspended in the polysiloxane. The second heat transfer plate  215 ′ is preferably affixed to the second heater support  170 ′. In an embodiment, the second heat transfer plate  215 ′ may be screwed into the second heater support  170 ′, and alternatively the second heat transfer plate  215 ′ is slideably engageable with the second heater support  170 ′. 
     A second heater  220 ′ ( FIG. 3 ) may be disposed between the second heater support  170 ′ and the second heat transfer plate  215 ′. A second adhesive  217 ′ may affix the second heater  220 ′ to the second heat transfer plate  215 ′. In an embodiment, with respect to  FIG. 3 , the second insulator  200 ′ may be associated with the second forward portion  165 ; the second heater support  170 ′ may be associated with the second insulator  200 ′; the second heater support  170 ′ may be associated with the second heat transfer plate  215 ′; the second heater  220 ′ may be associated with the second adhesive  217 ′; and the second heat transfer plate  215 ′ may be associated with the second heater  220 ′. Without wishing to be bound by the theory, it is believed that the epoxy aids in the heat transfer between the second heater  220 ′ and the second heat transfer plate  215 ′, and beneficially eliminates the need for spring claims and other mechanical elements, which may cause electrical disturbances. Further, without wishing to be bound by the theory, it is believed that the epoxy aids in promoting even heat transfer from the second heater  220 ′ to the heat transfer plate  215 ′ and minimizes “cold spots.” Preferably, the epoxy, or second adhesive  217 ′, is applied as a uniform thin coating or film having a thickness ranging from between about 0.002 millimeters to about 0.5 millimeters, alternatively from about 0.002 millimeters to about 0.4 millimeters, and alternative from about 0.02 millimeters to about 0.3 millimeters. In an embodiment, a suitable epoxy includes Dow Corning 3-6752 silicone epoxy, which may have a thermal conductivity at 25° C. of about 1.8 watts per meter Kelvin, and a hardness (shore scale) of about 87A. The second heater  220 ′ may be made of any material having the requisite heat resistance and electrical properties to function in a hair iron, such as a metal, metal alloy, carbon, plastic, or ceramic. 
     As stated above, the top cover  195  preferably houses many of the hair iron&#39;s electrical components between itself  195  and the underside  175  of the reward portion  115  of the upper housing  105 . The top cover  195  may be screwed to the underside  175  of the rearward portion  115  of the upper housing  105 . Alternatively, a reward portion  230  of the top cover  195  may slideably engage the underside  175  of the reward portion  115  of the upper housing with male and female tabs. In this embodiment, preferably an area of the top cover  195  near its forward end  190  is adapted to be screwed into the underside  175  of the rearward portion  115  of the upper housing  105 . Accordingly, in this embodiment, the top cover  195  is affixed to the underside  175  of the rearward portion  115  of the upper housing  105  using only one screw. 
     The lower cover  305  may be screwed to the underside  225  of the rearward portion  155  of the lower housing  110 . Alternatively, a reward portion  230 ′ of the lower cover  305  may slideably engage the underside  225  of the reward portion  155  of the lower housing  110  with male and female tabs. In this embodiment, preferably an area of the lower cover  305  near its forward end  300  is adapted to be screwed into the underside  225  of the rearward portion  155  of the lower housing  110 . Accordingly, in this embodiment, the lower cover  305  is affixed to the underside  225  of the rearward portion  155  of the lower housing  110  using only one screw. 
     The top cover  195  and lower cover  305  may each include a top spring housing  285  and a lower spring housing  310 , respectively. The top and lower spring housings  285  and  310  may oppose each other in vertical alignment. When the hair iron  100  is assembled a spring, or biasing spring,  197 , may be disposed within the top and lower spring housings  285  and  310 . The spring  197  provides resistance and separates the upper housing  105  and lower housing  110 , or biases the upper housing  105  and lower housing  110  apart from each other, until a user acts against the spring  197  force exerted by the spring. The top and lower spring housings  285  and  310  may be located at any point along the top cover  195  and lower cover  305 ; however, without wishing to be bound by the theory, they are preferably located toward the rear of the top cover  195  and lower cover  305  to provide leverage to the user. 
     Between the top cover  195  and upper housing  105  may be housed the following components: at least one circuit board  235 , at least one microprocessor  240 , at least one voltage regulator  245 , at least one LCD  250 , at least one audio buzzer  251 , at least one current controller  253 , at least three and preferably four buttons,  255 ,  260 ,  265 , and  270 , and all of which are in electrical communication with each other. Also in electrical communication with the aforementioned electrical components are the heater  220 , the second heater  220 ′, optionally at least one thermal fuse  275 , optionally at least one lower thermal fuse  275 ′, optionally at least one thermister  280 , and optionally at least one lower thermister  280 ′. In an embodiment either or both of the thermal fuse  275  and the lower thermal fuse  275 ′ are present. In an embodiment either or both of the thermister  280  and the lower thermister  280 ′ are present. In an embodiment, the thermal fuse  275  is affixed to the heater  220  or heat transfer plate  215  by a suitable adhesive including a commercially available thermal conductive epoxy. In an embodiment, a suitable epoxy includes Dow Corning 441 silicone D4 epoxy, which may have a heat transit ratio of 1 watt per meter Kelvin and a hardness of about 40. In an embodiment, the lower thermal fuse  275 ′ is affixed to the second heater  220 ′ or second heat transfer plate  215 ′ by a suitable adhesive including a commercially available thermal conductive epoxy. In an embodiment, a suitable epoxy includes Dow Corning 441 silicone D4 epoxy, which may have a heat transit ratio of 1 watt per meter Kelvin and a hardness of about 40. Preferably, the epoxy is applied as a uniform thin coating or film having a thickness ranging from between about 0.002 millimeters to about 0.5 millimeters, alternatively from about 0.002 millimeters to about 0.4 millimeters, and alternative from about 0.02 millimeters to about 0.3 millimeters. 
     In an embodiment, the voltage regulator  245  provides direct current to the microprocessor  240  and the LCD  250 . The current regulator  253 , as instructed by the microprocessor  240 , regulates current to the heater  200  and/or  200 ′. 
     The LCD  250  is preferably in alignment with the LCD aperture, or window,  140  and the buttons  270 ,  265 ,  260 , and  255  are preferably in alignment with the button apertures, or windows,  135 ,  130 ,  125 , and  120 . The buttons  270 ,  265 ,  260 , and  255  may protrude through the button apertures  135 ,  130 ,  125 , and  120 . Preferably, the buttons  270 ,  265 ,  260 , and  255  are level with or recessed within the button apertures  135 ,  130 ,  125 , and  120 . Without wishing to be bound by the theory, recessed buttons reduce the chance that the user unintentionally depresses a button. Moreover, it is preferred that the force to depress each button be high enough to minimize unintentional depression of the button, yet low enough to allow ease of depression. Accordingly, the force needed to depress each button may range from about 130 grams force to 310 grams force, alternatively from about 150 grams force to about 260 grams force, and alternatively about 260 grams force, plus or minus 50 grams force. 
     In an embodiment each button is assigned one main function: an up button  270 , a down button  265 , a mode button  260 , and a power button  255 ; however, the order of buttons and their respective main functions may vary. As a non-limiting example, the order of buttons may be a mode button (corresponding to  270 ), an up button (corresponding to  265 ), a down button (corresponding to  260 ), and a power button (corresponding to  255 ). In an alternative embodiment, there are three buttons—an up button, a down button, and a power button—wherein depressing at least two of the buttons (preferably the up and down buttons) at the same time triggers the fourth mode function. 
     Depressing the power button  265  turns the hair iron  100  on and off. Depressing the mode button  260  allows the user to control various functions of the hair iron  100 , including setting the hair iron  100  to automatically turn off after a set amount of time, sounding an alarm utilizing the audio buzzer  251  after a set amount of time, and the like. Depressing the mode button  260  also allows the user to observe various information, including the current temperature of the plates in degrees Fahrenheit, Centigrade, Kelvin, or Rankin, the total number of hours and/or minutes that the hair iron has been used, the total number of hours and/or minutes that the hair iron has been used during a session, as well as the serial number of the hair iron. The information is preferably displayed on the LCD  250 . 
     Depending on the mode that the hair iron is in, depressing the up button  270  has different functions. For example, if the hair iron is in “temperature mode” depressing the up button  270  will increase the temperature of the heaters  220  by a set amount, as regulated by the microprocessor  240 , typically one degree, five degrees, or any other desired increment of temperature. In an embodiment, each time the up button  270  is depressed the audio buzzer  251  may sound an “beep” indicating a change in temperature setting to the user. Similarly, if the hair iron is in “temperature mode” depressing the down button  265  will decrease the temperature of the heaters  220  by a set amount, as regulated by the microprocessor  240 , typically one degree, five degrees, or any other desired increment of temperature. In an embodiment, each time the down button  265  is depressed the audio buzzer  251  may sound an “beep” indicating a change in temperature setting to the user. If the temperature sensor, thermister  280 , fails and either heater  220  gets too hot, the respective thermal fuse  275  or  275 ′ will trip causing the hair iron to turn off. 
     In another example, if the hair iron is in “timing mode” depressing the up button  270  will increase the amount of time that the hair iron will stay on before automatically shutting off, and depressing the down button  265  will decrease the amount of time that the hair iron will stay on before automatically shutting off. In an embodiment, each time the up button  270  or down button  265  is depressed the audio buzzer  251  may sound an “beep” indicating a change in timing setting to the user. In alternative embodiments, the buttons may be replaced by rotatable dials, switches, and the like. 
     A power cord (not shown) may be disposed in electrical communication with a power receiving module  117 , which may be affixed to the upper housing  105  and/or lower housing lower housing  110  and provide electrical power via the voltage regulator  245  to the circuit board  235  and the remainder of the electrical components of the hair iron  100 . Preferably, the power cord (not shown) is secured between the upper housing  105  and the lower housing  110  at their rearward ends. A power cap  121  may secure the power receiving module  117  to the lower housing  110 , preferably by screwing the power cap  121  to the lower housing  110 . 
     Specific embodiments of the present analogue and digital hair irons have been described and illustrated. It will be understood to those skilled in the art that changes and modifications may be made without departing from the spirit and scope of the inventions defined by the appended claims.