Patent Publication Number: US-2007119844-A1

Title: Ceramic hair care heating element

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      The present application is claiming priority of Chinese Patent Application No. 200520133523.X, filed on Nov. 25, 2005, the content of which is herein incorporated by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to home appliances involving electric heating, and more particularly, to hair care appliances having heating elements.  
      2. Description of the Related Art  
      Commonly used hair curlers or hair setters generally employ cylindrical heating elements that contact hair by wrapping hair around the heating element to achieve a desired curling effect. Typical hair curling systems may include a hand-held curling iron featuring a handle, a cylindrical heating element, and an attachment to clamp the hair in place about the heating element. Other systems include a plurality of individual heat rollers that are docked in a power-supply unit and heated prior to application to hair.  
       FIGS. 1A and 1B  illustrate prior art hair curlers typically used in systems described above. In a first example,  FIG. 1A  shows a rope heater  100  for a curling iron. Rope heater  100  includes a glass rope  105  and a resistive wire heater  110 , which is electrically and removably connected to a power source via connectors  115 . In the complete curling iron, rope heater is fit into a conductive sleeve, such as an aluminum sleeve, for use. In a second example,  FIG. 1B  shows a curling iron  120  that includes a positive temperature coefficient (PTC) heating element  125  surrounded by a thermally conductive outer layer  130 . A die-cast piece  135  is provided between heating element  125  and outer layer  130  to facilitate heat transmission to outer layer  130 .  
      The above-mentioned technological approaches utilize a conductive wire or plate that contacts or is proximate to an outer barrel to heat the outer barrel. These configurations, in which there is little or no direct contact between the conductive element and the outer barrel, possess numerous disadvantages, such as extended heating time and uneven heating.  
     SUMMARY OF THE INVENTION  
      It is an object of the present invention to provide hair setting and curling devices and systems that feature a quicker heating time than prior art systems.  
      It is another object of the present invention to provide hair setting and curling devices that provide even heating of exterior surfaces of the devices.  
      These and other objects of the present invention are achieved by a heating element for a hair styling device, including an electrically insulating inner ceramic layer, an electrically conductive resistive heating layer disposed on and in contact with the inner layer, and an electrically insulating outer ceramic layer disposed on and in contact with the resistive heating layer. There is also provided a method for manufacturing the heating element. There is further provided a hair setting device for curling hair including the heating element and a cylindrical barrel surrounding the heating element. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1A  is a side cross-sectional view of a prior art hair setting device, particularly a rope heater.  FIG. 1B  is a front cross-sectional view of a prior art positive temperature coefficient (PTC) hair setting element.  
       FIG. 2  is a side cross-sectional view of a heating unit for use in a hair setting device or system according to the present invention.  
       FIG. 3  is a front cross sectional view of the heating unit of  FIG. 2 .  
       FIG. 4  is a side cross-sectional view of a curling iron incorporating the heating unit of  FIG. 2 .  
       FIG. 5  is a side cross-sectional view of another embodiment of a curling iron incorporating the heating unit of  FIG. 2 .  
       FIG. 6  is a front cross sectional view of the curling iron of  FIG. 5 .  
       FIGS. 7A through 7E  are front cross sectional views of a barrel of the curling iron of  FIG. 5 .  
       FIG. 8  is a circuit diagram of an exemplary electrical setup of the curling iron of  FIG. 3 .  
       FIG. 9  is a circuit diagram of an exemplary control device.  
       FIG. 10  is a top and side view of a hair roller and hair setting assembly utilizing the heating unit of  FIG. 2 . 
    
    
     DESCRIPTION OF THE INVENTION  
      Referring to the drawings and, in particular, to  FIG. 2 , there is provided an embodiment of an electric heating unit for use as a hair curler/setter or for use in a hair styling device. Heating unit  200  includes a resistive heating conductive layer  205  sandwiched between an outer ceramic layer  210  and an inner ceramic layer  215 , end gaps  220  and electrical leads  225 . Electrical leads or wires  225  are electrically connected to conductive layer  205 .  
      End gaps  220  are located at the ends of heating unit  200  due to an extension of outer ceramic layer  210  relative to conductive layer  205  and inner ceramic layer  215 . In the embodiment shown in  FIG. 2 , outer ceramic layer  210  has a length along an axis  230  that is longer than a length along axis  230  of conductive layer  205  and inner ceramic layer  215 .  
      In a preferred embodiment, end gaps  220  are filled with a thermally insulating adhesive material, such as an epoxy or a glue. The adhesive material contacts and bonds outer ceramic layer  210  with inner ceramic layer  215 , and is both electrically and thermally insulating to act as a safety feature to prevent the ends of heating unit  200  from heating up.  
      Preferably, conductive layer  205  is in the form of a conductive film that is deposited on an exterior surface of inner ceramic layer  215 , and may be adhered to inner ceramic base. The film is an electrically conductive film having a resistance sufficient to produce a desired amount of heat upon application of a selected current. Heating unit  200 , due to the ceramic material, emits far infrared radiation upon heating. In an alternative embodiment, electrodes may be adhered to or formed in conductive layer  205  to facilitate connection with leads  225 .  
      In a preferred embodiment, the film forming conductive layer  205  is applied as an even layer to all or substantially all of the exterior surface of inner ceramic layer  215 . Outer ceramic layer  210  is then applied to conductive layer  205  so that at least a substantial portion of an interior surface of outer ceramic layer  210  is in contact with conductive layer  205 . In the embodiment shown in  FIG. 2 , all of the interior surface of outer ceramic layer  210  is in contact with conductive layer  205  except for those portions of the interior surface of outer ceramic layer  210  that are exposed to end gap  220 .  
      When power is switched on, conductive layer  205  will be heated first, and then ceramic layers  210  and  215  are heated directly and evenly due to their direct contact with conductive layer  205 , and will emit far infrared radiation at high temperature.  
      A thickness of the combination of outer ceramic layer  210 , conductive layer  205 , and inner ceramic layer  215  is between about 1.0 mm and about 8.0 mm. In a preferred embodiment, conductive layer  205  has a thickness between about 0.1 mm and about 0.5 mm.  
      In another embodiment, the ceramic material contains aluminum oxide (Al 2 O 3 ) ceramic material. Conductive layer  205  may contain any of a number of compositions such as germanium, borosilicate, ytterbium oxide, a semiconductor ceramic far-infrared material, and bismuth oxide. Preferably, conductive layer  205  does not contain any potentially harmful substances such as lead, mercury, hexavalent chromium, polyether, benzene, and benzoic acid.  
      In another preferred embodiment, the resistive heating film is made from a slurry that is adhered to either inner ceramic layer  215  or outer ceramic layer  210  by sintering. The expansion coefficient of the slurry is preferably substantially the same as that of the material of inner ceramic layer  215  and outer ceramic layer  210 .  
      In a corresponding preferred method for manufacturing heating element  200 , the slurry is first applied to the selected surfaces of inner ceramic layer  215  or outer ceramic layer  210 , preferably by spraying.  
      After applied onto the selected surfaces, the slurry is sintered on the surfaces at a temperature of, e.g., about 1300° C., to form a uniform resistive heating film. In an alternative embodiment, electrodes may be applied to conductive layer  205  by applying additional slurry on the surface of the resistive heating film together with welding leads for electric connections. The additional slurry is then sintered at a high temperature, such as 1300° C., to firmly fix the electrodes to the resistive heating film.  
      Referring to  FIG. 4 , a preferred embodiment of a hair curling iron  400  includes heating unit  200 , a thermally conducting cylindrical barrel  405 , a handle  410 , and a clamp  415 . Curling iron  400  incorporates heating unit  200 , which is inside thermally conducting barrel  405 . Heating unit  200  is inserted into barrel  405  to produce a tight fit, so that barrel  405  surrounds heating unit  200 , and so that all of the exterior surface of outer ceramic layer  210  is in contact with a portion of an interior surface of barrel  405 . In one embodiment, barrel  405  is press fit onto heating unit  200 . Barrel  405  is preferably made from a metal such as aluminum, or a high temperature plastic.  
      Handle  410  is attached to barrel  405 , and leads  225  extend through barrel  405  and are connected to a power supply cord  420 . Clamp  415  includes a thumb press  425 , and a cylindrical portion, or “spoon”,  430 .  
      Clamp  415  is attached to barrel  405  via a hinge and a spring mount (not shown). The hinge allows clamp  415  to be rotated to an open position, shown in  FIG. 4 , by pressing thumb press  425 . The spring mount causes clamp  415  to rest at a closed position, where spoon  430  is substantially in contact with or partially surrounds barrel  405 , when thumb press  425  is released.  
      Curling irons such as curling iron  400  are not limited to incorporating a single heating unit. Generally, for smaller diameter curling irons, it is preferable to use a single heating unit to maximize heat uniformity and heating time of the surface of the curling irons. For curling irons having a barrel diameter of up to 1.5 inches, a single barrel design such as curling iron  400  is preferred. For larger curling irons, such as curling irons having barrel diameters of greater than 1.5 inches, a curling iron design that utilizes multiple heating units may be preferred. Alternatively, for curling irons whose barrels are larger than the associated heating units, a single heating unit design may be utilized, as exemplified in  FIGS. 7A through 7C  below.  
      Referring to  FIG. 5 , a curling iron  500  is similar in design to curling iron  400 , with the exception that curling iron  500  incorporates two heating units  200 . Curling iron  500  includes a thermally conducting cylindrical barrel  505 , a handle  510 , and a clamp  515 . In this embodiment, barrel  505  is shaped to accommodate both of heating units  200 .  
      Referring to  FIG. 6 , barrel  505  has three sections integrally formed together to form a single piece. Barrel  505  includes a cylindrical outer portion  530 , cylindrical heating unit receptacle portions  535 , and a support rib portion  540 . Outer portion  530  preserves the cylindrical shape of barrel  505  for hair curling. Receptacle portions  535  accommodate heating units  200  in a tight fit, so that at least substantially all of the exterior surface of each heating unit  200  is in contact with one of receptacle portions  535 .  
      Support rib portion  540  acts as a support to prevent barrel  505  from deforming.  
      In another embodiment, curling iron  400  or curling iron  500  includes a thermal sensor  545  in contact with heating unit  200 , for example between barrel  505  and heating unit  200 . Thermal sensor  545  is electrically in contact with controls and/or indicators located, for example, in handle  510 .  
      The thermal sensor may be connected to a control device, preferably in handle  510 . The control device, which preferably includes a processor, receives temperature information, and indicates a temperature of heating unit  200 . The control device may be set to indicate when a selected temperature has been reached, or may be set to discontinue power to heating unit  200  when heating unit  200  has reached a selected temperature.  
      Referring to  FIGS. 7A through 7E , additional configurations of barrel  505  are demonstrated.  FIGS. 7A, 7B  and  7 C show various alternative configurations of barrel  505  housing a single heating unit, in the event that heating unit  200  is smaller than the diameter of barrel  505 .  
       FIG. 7D  is similar to the configuration of barrel  505  shown in  FIG. 6 .  
       FIG. 7E  shows a configuration of barrel  505  that accommodates three heating without the use of support ribs  540 . In all of the above embodiments, heat transfer time is decreased, as at least substantially all of the exterior surfaces of heating units  200  directly contact a portion of barrel  505 .  
      Although the heating unit and hair curling/setting devices described in the above embodiments are cylindrical in shape, the invention is not limited as such. Any suitable shape may be employed, such as a square tube, a triangular tube and a flat sheet. Other shapes are contemplated that would be suitable for providing heated surfaces for hair straightening or crimping.  
       FIGS. 8 and 9  are circuit diagrams showing embodiments of the electrical setup of curling iron  400 , and of an indicator setup that may be incorporated in curling iron  400 . Referring to  FIG. 8 , a circuit  800  shows how electrical power is transmitted to heating unit  200 . Circuit  800  includes resistive element R 1 , which represents conductive heating layer  205 . Capacitor C 1  is provided to reduce noise, and capacitors C 2  and C 3  are provided as filters.  
      Referring to  FIG. 9 , circuit  900  shows an example of a control device used to indicate a temperature of heating unit  200 . The control device is preferably incorporated into handle  410  of curling iron  400 , and provides indications of the temperature of heating unit  200  and/or the barrel of curling iron  400 . Such indicators notify a user when curling iron  400  is ready for use, provide an indication of time remaining until curling iron  400  is ready, and also act as a safety feature so a user will know that curling iron  400  is hot. Circuit  900  includes a processor chip  905  connected to a thermal sensor  910 , multiple light-emitting diodes (LEDs) D 5 -D 10 , and switches  915  for setting temperatures of LEDs D 5 -D 10 . As heating unit  200  heats up, processor  905  directs the activation of one or more LEDs D 5 -D 10 .  
      For example, LEDs D 5 -D 10  may each represent a different temperature gradation. When heating unit  200  initially begins heating, processor  905  may direct D 5  to flash until a first temperature is reached. After the first temperature is reached, D 5  remains steadily on, and D 6  begins flashing until a second temperature is reached. This process is continued until all of LEDs D 5 -D 10  are steadily on, indicating that curling iron  400  is ready for use. This description is purely exemplary, as any number of LEDs may be utilized and configured to alert a user to various temperatures or operating conditions.  
      In an alternative embodiment, heating unit  200  is incorporated as one of a plurality of heating units as a part of a hair curling system. Each heating unit is fitted with a thermally conductive sleeve. Each of the plurality of heating units may be removably connected to a power source connected to a hair curling device, and separately applied to a user&#39;s hair. The device may serve as both a port to store the heating units, and also as an electrical plug-type port to heat the units.  
      Referring to  FIG. 10 , a hair roller  1000  includes a heating unit  200  attached to a plastic insulator  1010 . Heating unit  200  includes a resistive heating conductive layer  205  sandwiched between an outer ceramic layer  210  and an inner ceramic layer  215 , an end gaps  220  and electrical contact wires  225 .  
      A hair setter assembly  1020  incorporates multiple hair rollers  1000 , and includes a setter cover  1030 , a setter base  1040 , and a power grid  1050  connected to a power cord  1060 . Setter base  1040  is constructed to provide a base to removably accommodate each roller  1000  for both heating and storage. Contact wires  225  are constructed to specifically connect with power grid  1050 , so the user may selectively plug in individual hair rollers  1000  for heating and remove for use. Cover  1030  is typically in a clear plastic. Plastic insulator  1010  allows the user to easily remove each hair roller  1000 .  
      The use of heating units  200  in a hair setter assembly provides numerous advantages over the prior art, including quick heating, far infrared emission, and an inherent thermal mass. Prior are setter assemblies required that each roller have a bulky mass to retain heat for curling. Setter assemblies described above have an inherent thermal mass to retain heat due to the ceramic layers, eliminating the need for large masses of material required in prior art assemblies. Furthermore, the improved heating time allows a user to re-use individual curlers during hair setting. Therefore, for example, a 7-roller setter can be used to curl hair like a prior art 12-roller setter.  
      In an alternative embodiment, the heating unit is provided as a flat sheet, having a conductor sandwiched between two ceramic layers, that is flexible to be able to wrap around hair or wrap hair in a spiral configuration. In this alternative embodiment, so-called “flexible ceramics” or flexible ceramic hybrid materials may be utilized. The heating unit may also be utilized as a flat plate, e.g., to serve a hair straightening function.  
      The heating element of the present invention has numerous advantages, including the physical properties of uniform heat generation and far infrared emission after heated. The heated ceramic base can directly emit strong far infrared that has a potential therapeutic function.  
      The heating element of the present invention also provides superior watt density without sacrificing structural integrity or requiring additional conductive components. In prior art curling irons that utilize resistance wire coils, wires must be decreased in thickness, i.e., gauge, to increase watt density. Such curling irons having very thin wires present an increased risk that the wires would fail, and are also complex to manufacture. Curling irons utilizing PTC pellets require additional die cast components to conduct heat. The heating units of the present invention provide thin conductive films having high film density without the risk of failure, the increased number of components, or the complexity of prior art devices.  
      Because the conductive surface heating film is preferably sintered onto the ceramic base after the resistance slurry material is sprayed on surface of the ceramic base, the film is uniform, thus resulting in even temperature distribution and long service life. Also, the conductive film heats uniformly, resulting in a uniform heating of the ceramic layers and the outer barrel of the hair curler or curling iron. Furthermore, because the conductive material contacts at least a substantial portion of the surfaces of the ceramic layers, the time required to heat the ceramic layers, and thus the hair curler or curling iron, is reduced.  
      It should be understood that various alternatives, combinations and modifications of the teachings described herein could be devised by those skilled in the art. The present invention is intended to embrace all such alternatives, modifications and variances that fall within the scope of the appended claims.