Abstract:
The present invention provides a portable apparatus for heating a surface of an object during powder coating. The object is fixed at a location, and a powder comprising a thermal plastic polymer or a thermoset polymer is applied to the surface of the object prior to heating. The apparatus comprises a portable support member, and a portable first heater for heating the surface of the object, the first heater being mounted to the support member.

Description:
SCOPE OF THE INVENTION 
       [0001]    The present invention relates to a heating apparatus for powder coating, and in particular, to a portable heating apparatus for powder coating bathtubs. 
       BACKGROUND OF THE INVENTION 
       [0002]    Powder coating is a painting process by which a thermoplastic polymer or thermoset polymer in the form of a dry powder is applied to an object. The powder is generally applied by an electrostatic gun and the object to be painted is generally electrically grounded. The electrostatic gun imparts a positive electric charge on the powder. The powder is sprayed towards the grounded object by mechanical or compressed air spraying, and then accelerated toward the object by the powerful electrostatic charge. The object is then transported to and placed into an oven where it is heated to a high temperature of about 160 to 210° C. for at least 10 minutes to cure the applied powder. Specifically, the powder particles melt and coalesce to form a continuous film. In the case of using thermoset polymers as the powder, when heated, a chemical cross-linking reaction is triggered between the polymers, thus increasing the molecular weight of the solid coating and giving a hard abrasion resistant coating. 
         [0003]    Powder coating has several advantages over traditional liquid paints, including the fact that powder coatings emit much less volatile organic compounds. Furthermore, powder coatings can produce much thicker coatings than conventional liquid coatings without running or sagging. 
         [0004]    One disadvantage of known powder coating processes is that the curing step must take place in an oven. As such, the object to be painted must be transported to the site of the curing oven. Many objects which are suitable for powder coating are fixed at one location and are not easily portable. Many objects which are suitable for powder coating can also be very difficult to transport because of their size, shape or weight. For example, bathtubs are generally fixed in a bathroom of a building and are difficult to transport because of their large size and weight and their shape. Obstructions which are common in many homes and businesses, such as narrow doorways, make it costly and inconvenient to transport bathtubs out of the home or business and to the site of the curing oven. It would be advantageous to be able to carry out the entire powder coating process, including the curing step, without having to transport the bathtub away from the home or business. 
       SUMMARY OF THE INVENTION 
       [0005]    To at least partially overcome the problems associated with powder coating, the present invention provides a portable heating apparatus for use in powder coating. 
         [0006]    An object of the present invention is to provide a new portable heating apparatus for use in powder coating. 
         [0007]    Another object of the present invention is to provide a heating apparatus for use in powder coating which is portable from one site to another. 
         [0008]    A further object of the present invention is to provide a portable heating apparatus for powder coating objects without having to transport such objects to a curing oven. 
         [0009]    A further object of the present invention is to provide a portable heating apparatus for use in powder coating which shields areas surrounding the object to be powder coated, thus preventing damage to these surrounding areas by the curing step. 
         [0010]    Yet another object of the present invention is to provide a portable heating apparatus for use in powder coating which can be used with bathtubs of many different sizes and shapes. 
         [0011]    In one aspect, the present invention provides portable apparatus for heating a surface of an object during powder coating, the object being fixed at a location, and wherein a powder comprising a thermal plastic polymer or a thermoset polymer is applied to the surface of the object prior to heating, the apparatus comprising: a portable support member, and a portable first heater for heating the surface of the object, the first heater being mounted to the support member. 
         [0012]    The object being powder coated is preferably fixed in a room of a building. Preferably, the object is a bathtub. The bathtub may be fixed in a bathroom of a residential building or a hotel. 
         [0013]    Preferably, the first heater is an infrared heater or a convection heater. When the first heater is an infrared heater, the infrared heater can have wires or filaments or radiant emmitters which are heated, and the wires or filaments emit heat by infrared radiation to the bathtub. When the first heater is a convection heater, the convection heater can have a heating element, where an air steam passes over the heating element to heat the air stream, and the heated air stream then passes to the bathtub. 
         [0014]    The support member preferably has a first end and a second end. The first heater may be movable from a first position between the first end and the second end of the support member to a second position between the first end and the second end of the support member. Preferably, the first heater is mounted to the support member by one or more fasteners, such as one or more clamps. The one or more fasteners are attachable to the support member at multiple positions between the first end of the support member and the second end of the support member. The first heater is movable by moving the one or more fasteners from the first position on the support member to the second position on the support member. 
         [0015]    The support member is preferably a vertical support member, with the first end of the support member being a top end, and the second end of the support member being a bottom end. The first heater is movable in the vertical direction between the top end and the bottom end. 
         [0016]    In a preferred embodiment, the apparatus further comprises a portable horizontal support member. The horizontal support member has a third end and a fourth end, and is mounted at the third end to the vertical support member. The apparatus also preferably comprises a portable second heater for heating the surface of the object. The second heater is mounted to the horizontal support member. 
         [0017]    The second heater is preferably an infrared heater or a convection heater. 
         [0018]    The first heater mounted to the vertical support member preferably emits heat to an outside wall of the bathtub, while the second heater mounted to the horizontal support member preferably emits heat to an inside wall of the bathtub. 
         [0019]    In a preferred embodiment, the apparatus further comprises a portable third heater for heating the surface of the object. The third heater is pivotally connected to the second heater by a connecting hinge. The connecting hinge is positioned above the inside wall of the bathtub. The second heater and the third heater can be pivoted towards or away from each other about the connecting hinge, thus allowing a user to direct both the second heater and the third heater in multiple directions. Preferably, the second heater and the third heater are directed towards two different areas of the inside wall of the bathtub. More preferably, the connecting hinge can be positioned inside the bathtub to facilitate directing the second heater and the third heater towards substantially opposed surfaces of the inside wall of the bathtub. 
         [0020]    The third heater is preferably an infrared heater or a convection heater. Like the second heater, the third heater also emits heat to the inside wall of the bathtub. 
         [0021]    Preferably, the apparatus further comprises a portable support arm extending from the third heater and contacting a vertical surface proximal to the bathtub. For example, the arm may contact a corner between the outer edge of the bathtub and an adjacent wall to act as a support for the apparatus. 
         [0022]    The apparatus preferably comprises a portable shielding member for shielding an area surrounding the bathtub from the heat emitted by the first heater, the second heater and the third heater. For example, the shielding member may protect the bathroom walls and floors from heat damage. 
         [0023]    The first heater is preferably movable up and down in the vertical direction. In other words, the vertical height of the first heater is adjustable so that it can heat bathtubs of different heights. 
         [0024]    Preferably, the first heater is mounted to the vertical support member by one or more fasteners, such as a clamp. The fasteners can be attached to multiple vertical positions on the vertical support member. Therefore, for example, when the fastener is moved from a first lower vertical position on the vertical support member to a second higher vertical position on the vertical support member, the first heater, which is mounted by the fastener, is also moved upwards in the vertical direction. 
         [0025]    The second heater and the third heater are preferably movable in the horizontal direction. Therefore, the position of the second heater and the third heater can be adjusted along the width of the bathtub. 
         [0026]    The apparatus preferably comprises a portable inner bar section having a first end extending in the horizontal direction and a second end extending downwardly in the vertical direction. The inner bar section is mounted at the second end to the vertical support member. The horizontal support member preferably has a first outer bar section which extends in the horizontal direction and which is telescopically and slidably connected over the first end of the inner bar section. The first outer bar section has a larger diameter than the inner bar section. By sliding of the first outer bar section relative to the inner bar section, the second heater and the third heater, which are mounted to the horizontal support member, are movable in the horizontal direction. 
         [0027]    The second heater and the third heater are preferably movable in the vertical direction. As such, the vertical height of the second heater and the third heater can be adjusted to accommodate bathtubs of different heights. 
         [0028]    Preferably, the vertical support member has a second outer bar section which extends upwardly in the vertical direction and which is telescopically and slidably connected over the second end of the inner bar section. The second outer bar section has a larger diameter than the inner bar section. By sliding of the inner bar section relative to the second outer bar section, the second heater and the third heater, which are mounted to the horizontal support member, are movable in the vertical direction. 
         [0029]    In another aspect, the present invention provides a method of powder coating a bathtub comprising the steps of: applying a powder comprising a thermal plastic polymer or a thermoset polymer to a surface of the bathtub, heating the surface of the bathtub with a portable heating apparatus, and allowing the thermoplastic polymer or thermoset polymer powder to cure. 
         [0030]    Preferably, the portable heating apparatus used in this method of powder coating is the apparatus as defined above. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]    Further aspects and advantages will become apparent from the following description taken together with the accompanying drawings in which: 
           [0032]      FIG. 1  is a perspective view of an apparatus in accordance with a preferred embodiment of the present invention. 
           [0033]      FIG. 2  is a side view of the apparatus shown in  FIG. 1 . 
           [0034]      FIG. 3  is a perspective view of a heater of the apparatus of  FIG. 1  with the cover lifted off. 
           [0035]      FIG. 4  is a perspective view of one side of the heater of the apparatus of  FIG. 1 . 
           [0036]      FIG. 5  is an exploded view of the vertical support member and the horizontal support member of the apparatus of  FIG. 1 . 
       
    
    
       [0037]    Throughout all the drawings and the disclosure, similar parts are indicated by the same reference numerals. 
       DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0038]    Reference is made to  FIGS. 1 to 5  which show a preferred embodiment of the present invention. 
         [0039]      FIGS. 1 and 2  illustrate an apparatus in accordance with a preferred embodiment of the present invention. The apparatus  10  is used for the curing step when powder coating a conventional bathtub  500 . 
         [0040]    The apparatus  10  comprises a pair of vertical support members  12  having a first top end  14  and a second bottom end  16 . The bottom end  16 , as shown in  FIG. 1 , is enlarged and rests on the floor  700  adjacent to the bathtub  500 . 
         [0041]    The apparatus  10  also comprises a pair of horizontal support members  18  having a third end  20  and a fourth end  22 . The horizontal support members  18  are mounted at the third end  20  to the vertical support members  12 . 
         [0042]    In an alternative embodiment, the apparatus  10  comprises a single vertical support member  12  and a single horizontal support member  18 . In yet another alternative embodiment, the apparatus  10  comprises a single support member. 
         [0043]    The vertical support members  12  and the horizontal support members  18  are preferably made of metal, more preferably steel. 
         [0044]    A first heater  24  is mounted to the pair of vertical support members  12 . Preferably, the first heater  24  is mounted to the pair of vertical support members  12  by clamps  60 , as shown in  FIG. 5 . 
         [0045]    A second heater  26  is mounted to the pair of horizontal support members  18 . Preferably, the second heater  26  is mounted to the pair of horizontal support members  18  by clamps  90 . The clamps  90  are pivotally connected to the horizontal support members  18  by hinges  92 . The second heater  26  can be pivoted about hinges  92  so as to allow a user to point the second heater  26  in different directions. 
         [0046]    A third heater  28  is pivotally connected to the second heater  26  by a connecting hinge  30 . 
         [0047]    Preferably, the first heater  24 , second heater  26  and third heater  28  are infrared heaters. In an alternative embodiment, the first heater  24 , second heater  26  and third heater  28  are convection heaters. 
         [0048]    The heating element of the first heater  24  is present on one side of the first heater  24 , and faces an outside wall  502  of the bathtub  500 . As such, the first heater  24  emits heat to the outside wall  502  of the bathtub  500 . 
         [0049]    The heating elements of the second heater  26  and the third heater  28  are present on one side of the second heater  26  and the third heater  28 , respectively. The heating elements of the second heater  26  and the third heater  28  are positioned so as to face downwards at an inside wall  504  of the bathtub  500 . As such, the second heater  26  and the third heater  28  emit heat to the inside wall  504  of the bathtub  500 . 
         [0050]    The second heater  26  and the third heater  28  are pivotally connected to each other by the connecting hinge  30 . The second heater  26  and the third heater  28  can be pivoted towards or away from each other about the connecting hinge  30 . This allows a user to point both the second heater  26  and the third heater  28  in multiple directions. For a bathtub  500  with a larger width, the user can pivot the second heater  26  and the third heater  28  away from each other about the connecting hinge  30  so as to be able to emit heat to a larger surface area of the inside wall  504  of the bathtub  500 . 
         [0051]    A support arm  34  preferably extends from the third heater  28  and contacts a vertical surface proximal to the bathtub  500 . In  FIGS. 1 and 2 , the support arm  34  extends from the third heater  28  and rests in the corner between an outer edge of the bathtub  500  and an adjacent wall  600 . The support arm  34  acts as a support for the apparatus  10 . The support arm  34  is preferably made of metal, more preferably steel. 
         [0052]    A shielding member  36  is used to shield the area surrounding the bathtub  500  from the heat emitted from the first heater  24 , the second heater  26  and the third heater  28 . The shielding member  36  in  FIGS. 1 and 2  rests on the outer edge of the bathtub  500  and protects the wall  600  and the bathroom floors  700  from heat damage. 
         [0053]    The shielding member  36  can be made of any heat-resistant material. Examples include, but are not limited to, fire retardant materials such as gypsum, perlite, rock wool, asbestos cement and calcium silicate. 
         [0054]      FIGS. 3 and 4  illustrate the first heater  24  in detail. The first heater  24 , the second heater  26  and the third heater  28  preferably have the same construction. The heating element  50  of the first heater  24  is present on one side of the first heater  24 . On the other side of the first heater  24  is a cover  52 . 
         [0055]    In the case where the first heater  24 , second heater  26  and third heater  28  are infrared heaters, the heating element  50  is preferably a grid of wires or filaments. The wires or filaments can be made of any material that is commonly used for infrared heaters, including tungsten, carbon, and alloys of iron, chromium and aluminum. Optionally, the wires or filaments can be protected by a heat-resistant quartz glass shield. Optionally, a gold coating on the quartz glass shield can be used to reflect the infrared radiation and direct it towards the object to be heated. 
         [0056]    The heating element  50  is present on one side of the first heater  24 , second heater  26  and third heater  28 . The grid of wires or filaments of the heating element  50  is heated, and then emits this heat by infrared radiation to the bathtub  500 . 
         [0057]    In the case where the first heater  24 , second heater  26  and third heater  28  are convection heaters, the heating elements can be any material that is commonly used for convection heaters. For example, Nichrome 80/20 wire, ribbon or strip, composed of 80% nickel and 20% chromium, can be used as the heating element material. Other materials that can be used as the heating element material include Kanthal (FeCrAl) wires and Cupronickel (CuNi) alloys. A fan or air compressor can be used to pass an air stream over the heating element to heat up the air stream. The fan or air compressor then moves the heated air stream to the bathtub  500 . 
         [0058]    In the preferred embodiment, a propane tank  32  provides gas energy to the first heater  24 , second heater  26  and third heater  28  to heat the grid of wires or filaments  50 . 
         [0059]    When the cover  52  is lifted off of the first heater  24 , the combustion chamber  54  of the first heater  24  is exposed, as shown in  FIG. 3 . The combustion chamber  54  of the first heater  24  receives propane gas from the propane tank  32  through a pipe  56 . A spark plug or ignition device or catalytic reaction in the combustion chamber  54  lights the propane gas mixed with air in the combustion chamber  54 . This combustion reaction in the combustion chamber  54  produces heat for heating the heating element  50 . In turn, the heating element  50  emits heat by infrared radiation to the bathtub  500 . 
         [0060]    An alternative embodiment to using gas is to use electricity. The first heater  24 , second heater  26  and third heater  28  convert electricity into heat. Specifically, an electric current is sent to the heating element  50  and encounters resistance, thus resulting in the heating of the heating element  50 . 
         [0061]    Handles  58  are present on the first heater  24  for lifting the first heater  24  and transporting it. 
         [0062]      FIG. 5  illustrates the vertical support member  12  and the horizontal support member  18  in detail. 
         [0063]    The first heater  24  is preferably movable up and down in the vertical direction. Specifically, the vertical height of the first heater  24  is adjustable to accommodate bathtubs  500  of different heights. 
         [0064]    The second heater  26  and the third heater  28  are preferably movable in both the horizontal direction and in the vertical direction. In other words, the position of the second heater  26  and third heater  28  can be adjusted along the width of the bathtub  500 . Furthermore, the vertical height of the second heater  26  and the third heater  28  can be adjusted to accommodate bathtubs  500  of different heights. 
         [0065]    As mentioned above, the vertical support member  12  has a first top end  14  and a second bottom end  16 . The bottom end  16  is enlarged and rests on the floor  700 . 
         [0066]    A clamp  60  has a pair of hook elements  62  which are designed to hold the first heater  24 . The clamp  60  comprises a hollow tube  64  which is telescopically and slideably connected over the vertical support member  12 . Specifically, the hollow tube  64  of the clamp  60  has a larger diameter than the vertical support member  12 , thus allowing the clamp  60  to slide up and down relative to the vertical support member  12 . A threaded screw  66  fits into an opening  68  in the hollow tube  64  of the clamp  60 . 
         [0067]    When the clamp  60  is adjusted to the desired height on the vertical support member  12 , the user inserts the screw  66  into the opening  68  of the clamp  60 . The screw  66  frictionally engages the vertical support member  12 , thus securing the vertical position of the clamp  60  on the vertical support member  12 . 
         [0068]    By sliding the hollow tube  64  of the clamp  60  up and down on the vertical support member  12 , the first heater  24 , which is held by the clamp  60 , is also moved upwards and downwards in the vertical direction. 
         [0069]    The apparatus  10  preferably comprises an inner bar section  70 . The inner bar section  70  is preferably made of metal, more preferably steel. The inner bar section  70  has a first end  72  which extends in the horizontal direction and a second end  74  which extends downwards in the vertical direction. The inner bar section  70  is mounted at the second end  74  to the vertical support member  12 . 
         [0070]    The horizontal support member  18  has a first outer bar section  76  which extends in the horizontal direction. The first outer bar section  76  of the horizontal support member  18  is telescopically and slideably connected over the first end  72  of the inner bar section  70 . The first outer bar section  76  has a larger diameter than the inner bar section  70 . By sliding the first outer bar section  76  of the horizontal support member  18  relative to the inner bar section  70 , the second heater  26  and the third heater  28 , which are both mounted to the horizontal support member  18 , are movable in the horizontal direction. 
         [0071]    In use, the user slides the first outer bar section  76  of the horizontal support member  18  relative to the inner bar section  70  until the second heater  26  and the third heater  28  have reached a desired horizontal position. A threaded screw  78  is inserted into an opening  80  in the first outer bar section  76  and frictionally engages the first end  72  of the inner bar section  70  so as to secure this horizontal position. 
         [0072]    The vertical support member  12  has a second outer bar section  82  which extends upwardly in the vertical direction. The second outer bar section  82  is telescopically and slideably connected over the second end  74  of the inner bar section  70 . The second outer bar section  82  has a larger diameter than the inner bar section  70 . By sliding of the inner bar section  70  relative to the second outer bar section  82 , the second heater  26  and the third heater  28 , which are mounted to the horizontal support member  18 , are movable in the vertical direction. 
         [0073]    In use, the user slides the second end  74  of the inner bar section  70  relative to the second outer bar section  82  of the vertical support member  12  until a desired height for the second heater  26  and the third heater  18  are reached. A threaded screw  84  is inserted through an opening  86  in the second outer bar section  82 . The threaded screw  84  frictionally engages the second end  74  of the inner bar section  70 , thus securing this vertical position. 
         [0074]    To powder coat the bathtub  500 , a powder comprising a thermal plastic polymer or a thermal set polymer is applied to the walls  502 ,  504  of the bathtub  500 . Preferably, the powder is applied to the surface of the bathtub  500  by an electrostatic gun. The electrostatic gun imparts a positive electric charge on the powder, and the powder is sprayed towards the surface of the bathtub  500  by mechanical or compressed air spraying and then accelerated toward the bathtub by the powerful electric charge. The powder can be applied to both the outside wall  502  and the inside wall  504  of the bathtub  500 . The apparatus  10  of the present invention is used to heat the outside wall  502  and the inside wall  504  of the bathtub  500  to cure the applied powder. 
         [0075]    The apparatus  10  of the present invention is portable. As such, for powder coating objects such as a bathtub  500 , there is no need to remove the bathtub  500  from the home or business, and transport the bathtub  500  to a curing oven. Instead, the portable apparatus  10  of the present invention is brought directly to the site of the bathtub  500  to be powder coated. 
         [0076]    The apparatus  10  of the present invention is portable from one site to another and therefore, can be transported between homes and businesses to powder coat many different objects at many different locations. 
         [0077]    The apparatus  10  of the present invention can be used with bathtubs  500  of many different sizes and shapes. Specifically, the vertical height of the first heater  24  can be adjusted to accommodate bathtubs  500  of many different heights. Both the vertical height and horizontal position of the second heater  26  and the third heater  28  can be adjusted. Further, the second heater  26  and the third heater  28  can be pivoted towards or away from each other so as to accommodate bathtubs  500  of many different widths. 
         [0078]    The shielding member  36  protects the areas surrounding the bathtub  500 , such as the wall  600  and the bathroom floors  700 , from heat damage. This allows the apparatus  10  of the present invention to be used in homes and businesses without causing damage to areas surrounding the object to be powder coated. 
         [0079]    Although this disclosure has described and illustrated preferred embodiments of the invention, it is to be understood that the invention is not restricted to these particular embodiments. Rather, the invention includes all embodiments that are functional or mechanical equivalents of the specific embodiments and features that have been described and illustrated herein. Many modifications will now occur to those skilled in the art. For a definition of the invention, reference is made to the following claims.