Abstract:
A radiant heater includes a radiant heat source and a reflector to direct the bulk of the heat generated by the radiant source in one direction. The shape of the reflector determines the radiant pattern of the heater, and generally defocuses the output to provide a diffuse heat pattern that is substantially free of hot spots.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to electric space heaters. More particularly, the present invention relates to controlling and defining the extent of focusing of infrared radiation from a space heater product.  
       BACKGROUND OF THE INVENTION  
       [0002]     For a variety of reasons, a relatively small space such as a room may require heat. This heat may be in addition to that furnished from existing air treatment systems. One way to provide additional heat is with an electric portable heater. One type of such space heaters is a relatively small, sometimes floor-standing, heater that is configured to run on premises distribution circuits, that is, normal household and business wiring.  
         [0003]     Heaters of various types may emit heat by radiation, convection, or conduction. A non-radiative electric heater may, for example, have one or more heating elements that release heat at comparatively low energy to raise the temperature of a quantity of air. Such heaters may then blow that heated air into a space using one or more fans or other circulation-promoting apparatus, so that a significant proportion of the heating performed by such heaters involves mixing heated air into ambient air, while direct radiation of heat may represent a secondary characteristic of such heaters.  
         [0004]     Typical radiative electric heaters, by contrast, may release the majority of their heat in the form of infrared radiation emitted by one or more heating elements operated at comparatively high energy levels. Such heating elements typically combine infrared radiative heating of objects in the path of the radiation with a small amount of direct heating of the intervening air. Other heater types may combine these modes.  
         [0005]     While some styles of heaters emit their heat from a front side only, the radiative heating elements within such front-radiating heaters typically radiate uniformly in all directions. As a consequence, it may be desirable to use an infrared reflector to redirect heating element radiation that would otherwise radiate upward, downward, or toward the rear of the heater so that as much of the heat as is practical may be directed out the front.  
         [0006]     Radiative heaters may also have fans or other air circulation devices, which circulation devices may promote uniform heating of spaces in which the heaters are installed, may minimize temperature rise in the heater, and may improve the effectiveness of thermostat devices used as part of the heaters to maintain equilibrium temperature in a heated space.  
         [0007]     In some instances, it may be desirable for a radiative heater to provide infrared heating that is focused in a general direction, such as generally in front of the heater, but diffused over a range in that direction to provide heat over a large area.  
         [0008]     Accordingly, it is desirable to provide a radiative heater that can promote diffusion of heat through a broad region generally centered on the front of the heater.  
       SUMMARY OF THE INVENTION  
       [0009]     The foregoing needs are met, to a great extent, by the present invention, wherein in one aspect an apparatus is provided that in some embodiments provides a radiative heater that can promote diffusion of heat through a broad region, which region may in some embodiments be substantially centered on the front of the heater.  
         [0010]     In accordance with one embodiment of the present invention, a radiant heater is provided. The heater comprises a heating element configured to radiate heat, and a reflector located proximate to the heating element. The reflector has a generally parabolic shape with the exception of having a generally middle portion of the reflector displaced, while a first edge and a second edge of the reflector remain approximately in positions associated with the generally parabolic shape.  
         [0011]     In accordance with another embodiment of the present invention, a radiant heater is provided. The heater comprises means for radiating heat, and means for reflecting heat in a direction. The reflecting means has a generally parabolic shape, with the exception of having a middle portion of the reflecting means displaced, while a first and a second edge of the reflecting means remain approximately in positions associated with the generally parabolic shape.  
         [0012]     In accordance with yet another embodiment of the present invention, a method for applying radiant heat is provided. The method comprises the steps of configuring a radiant heat generating device for connection to an electrical power source, displacing a middle portion of a radiant heat reflector configuration from a substantially parabolic shape while leaving a first extent and a second extent of the radiant heat reflector configuration substantially undisplaced, enclosing an electrical power circuit, guarding the radiant heat generating device from physical intrusion, and providing electrical connectivity from the radiant heat generating device to an electrical terminal apparatus configured as a component of the radiant heat applying method.  
         [0013]     There have thus been outlined, rather broadly, certain embodiments of the invention, in order that the detailed description thereof herein may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional embodiments of the invention that will be described below and which will form the subject matter of the claims appended hereto.  
         [0014]     In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in addition to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting.  
         [0015]     As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]      FIG. 1  is a first perspective view illustrating a heater according to an embodiment of the invention.  
         [0017]      FIG. 2  is a section view comparing the reflector shape profiles for a generally parabolic reflector and the reflector according to an embodiment of the invention.  
         [0018]      FIG. 3  is a graph showing the relative heat profiles of a heater having a generally parabolic reflector and a heater according to an embodiment of the invention.  
         [0019]      FIG. 4  is an isometric cutaway view of a heater reflector and associated elements according to an embodiment of the invention.  
         [0020]      FIG. 5  is a second perspective view illustrating the louvers and feet of an embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0021]     The invention will now be described with reference to the drawing figures, in which like reference numerals refer to like parts throughout. An embodiment in accordance with the present invention provides a radiant heater with infrared reflectors for one or more heating elements generally configured for broad heat diffusion in a generally forward direction.  
         [0022]      FIG. 1  is a perspective view that shows an embodiment in accordance with the present invention. Shown is a heater  10  with a housing  12 , and a grille  14  that generally prevents direct access to a heating element  16 .  FIG. 1  also shows additional features of a heater, such as a base  18 , feet  20 , an electrical cord  22  with a plug  24 , a handle  26 , a power switch  28 , a tip switch (internal), a thermostat  30 , an indicator light  32 , and a thermal overload  34 .  FIG. 1  further shows the fittings  36 ,  38 , and  40  used to attach the defocused reflector  42  to the visible side of the housing  12  and to maintain the broad diffusion capability of the reflector  42 .  
         [0023]     A housing  12  of the type shown is generally suitable for containing and preventing inadvertent contact with electrical components and for providing a rigid mechanical framework in which heating element  16  and the defocused reflector  42  may be mounted and held in comparatively immovable relationship to the other components therein. A housing  12  may be made of metal, suitable nonmetals, or a combination thereof, and may be formed of one or more pieces by a variety of manufacturing methods such as punching and pressing metal parts, molding plastics, and the like. Component parts may be given corrosion-resistant finishes where appropriate. Parts may be joined to form an integral whole using fastenings such as screws, rivets, and clips, integral attachment fittings such as self-hinges, barbs, and receptacles, and assembly materials and processes such as welds, solders, and glues if needed.  
         [0024]     The grille  14  shown is one of a variety of suitable embodiments. Grilles  14  of comparable function may be welded or otherwise bonded from suitable materials, or may be punched and pressed, cast, or formed by other processes suitable to the materials chosen. A typical grille  14  may be mounted substantially permanently to the housing  12 , for example with clips, screws, barb fittings, spring tension, and the like.  
         [0025]      FIG. 1  shows a heating element  16 , one of many common types of heating elements that may be suitable for the instant invention. Suitable types include resistive ribbon, the so-called CALROD® type, a resistance wire wound on an insulating core, and a fused-quartz-jacketed heating element, as well as other types. Any heating element type, when applied to the instant invention, may have a generally linear configuration and generally uniform radial distribution of radiant energy about a longitudinal axis. Typical materials for a resistive heating element include nickel-chromium-iron alloys.  
         [0026]     A base  18  is shown in  FIG. 1 . The base  18  shown separates potentially warm regions of the housing  12  from a surface on which it would otherwise rest, and is one of various embodiments capable of performing this function. While many portable heaters incorporating the inventive apparatus may have bases, heaters intended for mounting to a wall or overhead support, for example, may not include bases on which they can stand. Still other heaters may have separate bases or stands to which they may be permanently, adjustably, or removably attached.  
         [0027]     Feet  20  are shown beneath the base  18 . Where used, feet  20  may be of any suitable shape, and may be variously insulating, skid-resistant, and/or made from thermosetting (non-melting) material as appropriate. The use of feet  20  may in some embodiments enhance airflow beneath the base  18  bottom surface. This is addressed further under  FIG. 5 , below. The number of feet  20  used may be as few as one for some embodiments, while other embodiments may use any number, although it may be anticipated that many embodiments use three or four feet  20 .  
         [0028]     A flexible power cord  22  terminated in a 3-wire plug  24  is shown. A typical cord  22  may also be terminated in a 2-wire plug  24 . A flexible or semirigid cord  22 , substantially permanently attached to the housing  12 , may provide utility to a space heater without imposing a requirement on a user to manage a separate electrical wiring arrangement. Notwithstanding the desirability of a built-in cord  22  for some applications, a cord  22  that can plug into a socket on the heater may also be used. Similarly, for other applications, electrical contacts at fixed locations such as terminals or free-hanging wires within the housing  12  may be provided so that a user can make electrical connections, which connections may use conduit, premises wiring materials, electrical cord, or the like. In such applications, cover plates may allow electrical connections made by the user to be guarded against intrusion or disruption.  
         [0029]     A handle  26  is an optional feature of a portable heating device  10 . If present, a handle  26  may, for example, be insulating and/or made from thermosetting (non-melting) material. A handle  26  may instead be predominantly metallic, where a metallic handle may in some embodiments be attached to the housing  12  using insulating standoffs or clips. A handle  26  may also be an integral part of the housing  12 , for example.  
         [0030]     A power switch  28  is shown in  FIG. 1 . This may be a basic on-off switch  28  or may additionally function to allow selection between multiple power settings. For example, a three-position switch  28  can have high and low output positions and an off position, while other switch  28  styles may allow one or more intermediate output settings as well. For some embodiments, there may be no power switch  28 , such as for permanently-mounted heaters  10  operated from fixed remote controls.  
         [0031]     The use of multiple output settings may include two or more output levels and multiple output functions. The number of output power levels available may be determined by details of implementation. For example, a heater with a single element  16  and an on-off switch  28  may have a single output level. A heater with two unequal heating elements  16  can power the lower alone, the higher alone, or both in parallel to get three output levels, which requires a four-position switch  28  (off-low-medium-high) and appropriate internal wiring. Alternate embodiments may, for example, omit one of the three “on” positions to provide a two-level heater, may reduce power by configuring elements in series rather than in parallel, or may remove power to elements in series (to increase) or parallel (to reduce) power output.  
         [0032]     The embodiment shown in  FIG. 1  combines forced-air and radiant heating by adding a fan internal to the heater  10 , which fan runs at some switch  28  settings in conjunction with heating element  16  and with a second heating element substantially concealed behind the visible reflector  42 . The second heating element is positioned between a second reflector (not shown) and the visible reflector  42 , which two reflectors create an air slot through which fan-forced air passes at some switch  28  settings. Inlet air in support of this operating mode is admitted in the embodiment of  FIG. 1  through louvers in the base and rear of the enclosure  12 , as discussed below under  FIG. 5 .  
         [0033]      FIG. 1  further shows an optional built-in thermostat  30 . A thermostat  30  allows a self-contained portable heater  10  to be self-regulating, switching itself on when an ambient temperature drops below a minimum and switching itself off when the ambient temperature exceeds a maximum. A thermostat  30  may have hysteresis to permit power cycling to occur at moderate intervals. Since the heater  10  itself may need to cool after cycling off before it can sense the ambient temperature, a thermostat  30  may need greater hysteresis than would be required if, as in an alternate embodiment, the thermostat  30  were installed in the heated space but remote from the heater  10 .  
         [0034]      FIG. 1  further illustrates an optional indicator light  32 . An indicator light  32  can be configured to indicate when power is applied to the heater  10  or when heat is being emitted by the heater  10 . Alternative embodiments could indicate both of those functions, or could have contact closures to permit remote detection of the mode of the heater  10 .  
         [0035]      FIG. 1  further shows a thermal overload circuit interrupter  34 . A thermal overload interrupter  34  may be used to automatically shut down the heater  10  in event of an overtemperature or overcurrent event. The externally visible element of the thermal overload interruptor  34  in  FIG. 1  is a reset button. Thermal overload interrupters  32  may be resettable or nonresettable. Resettable types may be reset using, for example, a push or a pull element, a toggle, or an automatic cycling device with no actuator. Fuses may be used as interrupters.  
         [0036]     A tip switch (entirely enclosed within the housing in the embodiment shown and thus not visible in the figures shown) is a device to immediately remove power from a heater  10  if the heater  10  is tilted outside an allowed range or is knocked over. In some embodiments a tip switch may also detect if a heater is picked up. Fixedly mounted heaters may not use a tip switch. Some styles of tip switch may be integral with the power switch  28 , the thermostat  39 , or the overload circuit interrupter  34 .  
         [0037]      FIG. 2  is a section view that shows both a substantially parabolic reflector configuration  50  that approximates a shape known as a parabolic cylinder, and the generally nonparabolic reflector profile  52  of the inventive apparatus. It may be observed that the bulk of the radiant energy reflected by a generally parabolic shape  50  of the type shown, with a heater element  54  located proximal to its focus, travels along a roughly parallel path. The defocused reflector shape  42  of the inventive apparatus, by contrast, may have its heater element  16  located away from any focal point of the reflector  42 . This may result in increased scattering of the reflected heat, so that there is a less intense, more distributed zone of highest heat proximal to the grille  14  of  FIG. 1 .  
         [0038]     Formation of the nonparabolic, defocused reflector  42  of the inventive apparatus may be realized by bending a self-supporting parabolic reflector  50  into the generally nonparabolic profile shown and stabilizing the defocused reflector  42  so formed using deflection fittings such as screws, rivets, clips, tabs, or brackets. The defocused reflector  42  profile of  FIG. 2  may also be formed by pressing the reflector material directly into the preferred shape using a die, fitting the material into a groove, slot, guide, series of retention fittings, or the like that are integral with or retained by the housing  12 , curving the reflector material around a forming profile, or otherwise shaping the reflector material to achieve the properties herein described.  
         [0039]      FIG. 3  is a graph comparing the heat distribution intensities of a parabolic reflector and the inventive reflector. Curve  60  represents the heat distribution characteristic of a parabolic reflector, while curve  62  represents the heat distribution characteristic of an embodiment of a reflector in accordance with the present invention. Evident in the graph is that the peak energy in the region of highest radiative intensity for the paraboloid reflector may be appreciably greater than the corresponding region for the inventive apparatus.  
         [0040]      FIG. 4  is a view of a defocused reflector  42  with first, second, third, and fourth attachment apparatuses  36 ,  72 ,  40 , and  76 , where each of the mounting apparatuses  36 ,  72 ,  40 , and  76  supports a corner of the defocused reflector  42 . The defocused reflector  42  further employs first and second deflection fittings  38  and  74  that maintain the attached reflector  42  in a defocused orientation. The first and second attachment apparatuses  36  and  72  may in some embodiments take the form of a single rod around which an upper edge  78  of the reflector  42  is formed. In some embodiments, a bottom edge  80  of the reflector  42  may likewise be formed around a rod serving as the third and fourth attachment apparatuses  40  and  76 . Such rods may penetrate the housing  12  and be attached thereto by fastenings  82 , or may be attached by other suitable methods. In other embodiments, the first, second, third, and fourth attachment apparatuses  36 ,  72 ,  40 , and  76  may be realized in the form of tabs or equivalent fittings integral with or attached to the reflector  42 . Such tabs may be inserted into slots, screwed or riveted, or welded to the housing  12 , or may be integral with the housing  12 .  
         [0041]     Deflection fittings  38  and  74  are shown in  FIG. 4 . The fittings assist in establishing the shape of the reflector  42  and in stabilizing the curve thereof. Such fittings may be fastening hardware of various styles, such as screws, as shown in  FIG. 4 , or rivets, or may, for example, be established as tabs attached to or formed out of the housing  12  material. In some embodiments, fastening hardware may be secured to an inner housing wall and thus not visible outside the housing  12 .  
         [0042]      FIG. 4  further shows mounting brackets  84  and  86  that carry a heating element  16 . As shown, the reflector  42  provides support for the brackets  84  and  86 . This arrangement couples the shape of the reflector  42  to the position of the heating element  16 . Other arrangements, such as one in which the heating element brackets are attached to the housing  12 , may permit the reflector  42  shape and heating element  16  position to be varied independently. Electrical wires  90  provide power to the heating element  16 .  
         [0043]     Alternative reflector  16  shapes may also provide effective defocusing, such as a vee shape or a “washboard” shape in place of the approximate paraboloid of a focused reflector. Similarly, placing the heating element  16  away from any functional axis of focus of a reflector of any configuration may further reduce and distribute heat concentration.  
         [0044]      FIG. 5  shows an oblique view from below. Here, the feet  20  may be seen to be able to position the base  18  off a floor. Since air flow into the heater  10  by back louvers  92  and bottom louvers  94  can promote the forced-air modes of operation described above for the embodiment shown, the use of feet  20  as indicated may be desirable. Alternative embodiments can provide for air flow into the heater  10  without bottom louvers  94 , in which embodiments inclusion of feet  20  may nonetheless be desirable.  
         [0045]     Although an example of the defocused radiative heater  10  is shown with insulating feet  20  to rest on a floor, it will be appreciated that the heater  10  can be used attached to a vertical surface such as a wall or hung from a ceiling using a suitable support mount. Also, although the heater  10  is useful for space heating in spaces intended for human occupancy, it can also be used both for warming other habitable spaces, such as barns and kennels, and for performing such functions as maintaining air temperatures above freezing in manufacturing and storage facilities, machinery rooms, and the like.  
         [0046]     The many features and advantages of the invention are apparent from the detailed specification, and, thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirit and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to that fall within the scope of the invention.