Abstract:
An electric space heater uses the heat generated by quartz-halogen lamps to heat air which may be supplied to heat a local space. The heater conducts air through a heater enclosure in which the lamps are installed. The air path is parallel to the longitudinal axis of the lamps. The air is warmed by conduction from the surface of the lamps and from heated walls surrounding the lamps and which form the air flow path. The walls are heated by radiation from the lamps. The flow path for the heated air and the placement of the heated walls substantially isolate the outer portion of the heater enclosure from the heat generated by the lamps to maintain the temperature of the outer surface of the space heater at or near ambient temperature. The walls also confine the light generated by the lamps to the interior of the space heater. The air flow through the space heater is assisted by an electric fan.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of heaters that are used to heat generally small local spaces. In particular, this invention relates to such heaters that use electrical power as the heat source and especially this invention relates to such heaters that use light producing lamps as the heat generating elements. 
     2. Brief Description of the Prior Art 
     It is known to use small heat generating units to provide auxiliary heating for local spaces that do not receive sufficient heat from central heating units. These heating units are also used to provide heat when other heat sources are not available or to heat small spaces when it would not be justified to use a large central unit that would consume more power and heat more than the necessary space. 
     Space heaters have been constructed that generate heat by burning fuel or which generate heat from electrical power. Among those heaters using electrical power are those which use the heat from incandescent lamps as the heat source. The use of infra red lamps as a radiant heat source in bathrooms is common. It is also known in the art to use incandescent lamps, including infra red lamps, as the heat source in an enclosure through which air is passed and warmed. The warmed air is conducted to the space outside the enclosure to provide heat to that space. 
     The following U.S. Patents are known in the art and are incorporated by reference herein: 
     U.S. Pat. No. 3,575,582 
     U.S. Pat. No. 3,777,728 
     U.S. Pat. No. 4,052,593 
     U.S. Pat. No. 4,164,642 
     U.S. Pat. No. 4,197,447 
     U.S. Pat. No. 4,307,284 
     U.S. Pat. No. 4,309,594 
     U.S. Pat. No. 4,680,448 
     U.S. Pat. No. 4,835,367 
     U.S. Pat. No. 5,013,893 
     U.S. Pat. No. 5,157,239 
     U.S. Pat. No. 5,568,586 
     U.S. Pat. No. 5,954,980 
     U.S. Pat. No. 5,990,460 
     U.S. Pat. No. 6,041,994 
     BRIEF SUMMARY OF THE INVENTION 
     In view of the above, it is an object of the present invention to provide a space heater which uses an incandescent lamp to generate heat. It is another object to provide a space heater to heat air which is conducted through the space heater and which does not substantially heat the exterior of the space heater. It is also an object to provide a space heater which has an increased efficiency over space heaters using conventional incandescent lamps. 
     It is an object of the present invention to provide a space heater which uses quartz-halogen lamps to generate heat in the space heater. It is another object to provide a space heater which uses light generating lamps as a heat source and which confines the generated light to the interior of the space heater. 
     It is an object of the present invention to provide a space heater to heat air supplied to a local space. The space heater being in the form of an enclosure in which a quartz-halogen lamp heat source is mounted and having a path for air to be conducted through the enclosure with a part of the air path passing over the quartz-halogen lamp heat source parallel to the longitudinal axis of the quartz-halogen lamp heat source. Other objects and features of the invention will be in part apparent and in part pointed out hereinafter. 
     In accordance with the invention, a new space heater has improved efficiency in that it produces more usable heat in proportion to the amount of electricity consumed. The heater is an electrical heater which is enclosed and which heats air as the air is drawn through the enclosure. Heat is generated by one or more incandescent lamps which are preferably of the quartz-halogen type. The air path is designed to provide maximum heat transfer to the air, but to minimize the heat transferred to the enclosure to maintain the outer surface of the enclosure at ambient temperature or nearly so. 
     More preferably, the incandescent lamps are of the quartz-halogen type which use an iodine-inert gas fill surrounding a linear tungsten element. The element and fill are confined in a linear quartz tube which is spaced adjacent to the tungsten element. A suitable lamp is commercially available as a 500 watt, 120 volt lamp from Sylvania Corporation, as model 500 T3Q/CL-120V. It will be appreciated that equivalent lamps may be obtained from other suppliers and in other power and voltage specifications. The linear form of the lamps has been found to be especially preferred in this invention, as these lamps give very even heat transfer to the air which is conducted through the enclosure and which flows around the lamp parallel to the longitudinal axis of the lamp. 
     It another significant feature of the invention that, even though a substantial amount of light is generated by the lamp or lamps, no substantial amount of light escapes the enclosure of the space heater. This increases the value of the space heater, since it may be used in places where light is undesirable. For example, the space heater may be used in a bedroom, where light would disturb sleep, or in a photographic dark room, where light would interfere with photo development. 
     The invention summarized above comprises the constructions hereinafter described, the scope of the invention being indicated by the subjoined claims. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     In the accompanying drawings, in which one of various possible embodiments of the invention is illustrated, corresponding reference characters refer to corresponding parts throughout the several views of the drawings in which: 
     FIG. 1 is a perspective view of a space heater in accordance with the present invention; 
     FIG. 2 is an exploded view of the space heater shown in FIG. 1; 
     FIG. 3 is a broken view of the space heater shown in FIG. 1; 
     FIG. 4 is a right side view of the space heater shown in FIG. 1, in cross-section, taken along the plane  4 — 4  in FIG. 5; 
     FIG. 5 is a top cross-sectional view of the space heater shown in FIG. 1, taken along the plane  5 — 5  in FIG. 4, and 
     FIG. 6 is a schematic diagram showing a simplified electrical circuit for the lamps and controls of the space heater. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the drawings more particularly by reference character, reference numeral  10  refers to a space heater according to the invention shown in FIG.  1 . The space heater  10  is generally in the shape of a rectangular prism  12 , as shown. The space heater  10  forms prism  12  with a series of external walls  14 ,  16 ,  18 , and  20 . The prism  12  is truncated by a top  22  and a bottom  24 , to form the enclosure of the space heater  10 . It will be appreciated that the walls, top and bottom of the space heater  10  will be formed of a durable material, for example aluminum or stainless steel sheet, or other equivalent material. The joinery may be by any conventional method, including welding, brazing and the use of fasteners, or combinations of methods as is known in the art. 
     Wall  16  of the space heater  10  forms the back of the space heater. A conventional on-off electrical switch  26  is placed on wall  16 , as shown. Switch  26  communicates with the interior of space heater  10  through opening  28 , shown in FIG. 2. A variable thermostatic control  30  is mounted on wall  16 , also as shown. Control  30  is mounted to plenum  32  and communicates with the interior of space heater  10  through opening  34 , as shown in FIG.  2  and FIG.  4 . If desired, space heater  10  may have a power cord strain relief  36  installed in a hole  38  in wall  16  for a power cord. Switch  26  and control  30  are electrically connected through their associated openings to cooperate with the heat generating lamps  40 ,  42 , as known in the art, as described further herein and as shown in FIG.  6 . 
     Turning to FIG. 1, walls  14  and  18  have forwardly extending projections  44  and  46 , respectively. Wall  16  may also have a forwardly extending projection  48 . Projections  44 ,  46  and  48  form a clip which may retain an air filter  50 , shown partially broken in FIG.  1 . Air filter  50  may be of conventional construction, for example fiberglass or equivalent material as is commonly used in furnace filters. It is preferred however that air filter  50  be a POLYTRON filter or equivalent. Wall  16  has a foraminous grill  52 , shown in the lower portion of wall  16 . Air filter  50  is held snugly over grill  52  by projections  44 ,  46  and  48 , as shown. If desired, air filter  50  may be held to wall  16  by a conventional fastener, such as a VELCRO (TM) fastener strip  53 , shown in FIG. 3, to provide a secure and snug fit of air filter  50  to wall  16 . Grill  52  is the opening through which air enters the interior of the space heater  10 . Air filter  50  is used, if desired, to remove debris and dust from the air to be heated. Air filter  50  thus keeps the interior of space heater  10  clean and prevents odors caused by heated dust. 
     The interior of space heater  10  has a circuitous air path defined by a series of partitions, tubes and ducts which guide the flow of air, as described herein. Vertical partition  54  is spaced behind wall  16  and is generally parallel to wall  16 , as shown. Partition  54  has an opening  56  therein and a fan housing  58  is mounted over opening  56 , as shown, using conventional fasteners. Fan and motor unit  60  is contained in housing  58  and is connected to a source of electrical power, as described herein. 
     Horizontal partition  62  joins the upper edge of vertical partition  54  and extends to front wall  20  and to side walls  14  and  18 . Partition  62  is spaced downwardly from top  22  and forms an insulating dead air space  64  with top  22 , as shown. A generally horizontal baffle  66  extends across the interior of space heater  10  at an intermediate location, as shown. Baffle  66  extends from vertical partition  54  to front wall  20  and to side walls  14  and  18 . Baffle  66  is spaced from bottom  24 , as shown, and forms a plenum  68  which guides the flow of air through space heater  10 . 
     Baffle  66  has two openings  70  and  72  therein, as shown. Openings  70  and  72  communicate with plenum  68 . Vertical tubes  74  and  76  are placed concentrically around openings  70  and  72  and are joined to baffle  66  at the edges of openings  70  and  72 . Vertical tubes  74  and  76  extend upwardly from baffle  66  and terminate at a location spaced from horizontal partition  62 , as shown. Ducts  78  and  80  extend downwardly from horizontal partition  62  and surround vertical tubes  70  and  72 , and are spaced therefrom, as shown. Ducts  78  and  80  share a common side  81  and terminate at a location spaced above baffle  66 . 
     The front wall  20  of the space heater  10  has a foraminous grill  82  in the upper portion of wall  20 , as shown in FIG.  2 . The openings in grill  82  provide an exit for air moving through the space heater  10  and complete the air path through the space heater  10 . Baffle  66  may have a thermal overload thermostat  84  mounted thereon in the air path, as shown. Thermostat  84  may be set to disconnect the electrical components of the space heater  10  when the air in the interior of space heater  10  reaches a predetermined high value, such as 200 degrees F. The thermostat  84  may reset at a predetermined low value, such as 160 degrees F. 
     The heat in the space heater  10  is generated by a quartz-halogen lamp or lamps, in this embodiment shown as a pair of lamps  40  and  42 . It will be understood that a single lamp may be used or that other multiples of lamps may be used depending on the power output of the lamp or lamps and the desired capacity of the space heater  10 . As shown in FIG. 2, lamps  40  and  42  are positioned coaxially in tubes  74  and  76  and are also coaxially positioned with ducts  78  and  80 . Lamps  40  and  42  are linear bulbs and when placed in tubes  74  and  76  have substantially the entire surface of lamps  40  and  42  exposed for heat transfer to the surrounding air and surrounding structure of the space heater  10 . Lamps  40  and  42  are placed in suitable electrical fixtures  86  and  88 , as shown, and are connected into the electrical circuitry of the space heater  10  by suitable wiring, as known in the art. 
     A schematic diagram for an electrical circuit for the space heater  10 , using conventional 110 volt alternating line current, is shown in FIG.  6 . In this circuit, heat generating lamps  40  and  42  are in parallel with each other and with the motor of fan and motor unit  60 . The on/off switch  26  and the variable thermostat  30  are each in series with the array of lamps  40  and  42  and with the motor of fan and motor unit  60 . The high temperature thermostat  84  is also in series with the array of lamps and fan motor. It will be appreciated that there are a variety of equivalent wiring configurations that would be suitable for the space heater of the invention, as is known in the art. 
     OPERATION OF THE DEVICE 
     In use, the space heater  10  of the invention is turned on by closing switch  26 . Thermostat  30  samples the temperature of the ambient air surrounding the space heater  10  and if that temperature is below the setting of the thermostat  30 , the circuit to lamps  40  and  42 , and to the motor of fan and motor unit  60 , is closed. The outer surfaces of quartz-halogen lamps  40  and  42  rapidly become hot due to the close proximity of the quartz tube to the internal tungsten filament of the lamps  40  and  42 . The fan of fan and motor unit  60  draws the ambient air through filter  50  and grill  52  into the interior of space heater  10 . 
     The air entering space heater  10  passes through fan and motor unit  60  into plenum  68 , as shown by the arrows in FIG.  4 . From plenum  68  the air passes through openings  70  and  72  into the interior of tubes  74  and  76 , passing upwardly through tubes  74  and  76  and out of the tubes  74  and  76  into ducts  78  and  80 , as shown. In ducts  78  and  80  the direction of the air is reversed to flow downwardly over tubes  74  and  76  and over the interior surfaces of ducts  78  and  80 . When the air reaches baffle  66  its direction is again reversed to flow upwardly around the outer surfaces of ducts  78  and  80  and up through the interior of space heater  10 , as shown. The temperature of the air exiting ducts  78  and  80  is sampled by high value thermostat  84 . When the air flow reaches top partition  62  its direction is again changed to flow through exit grill  82  into the ambient surroundings. 
     The interior structure of the space heater  10  is preferably constructed of metals which are good heat conductors, such as copper or aluminum. In particular, tubes  74  and  76  and ducts  78  and  80  may use these materials. The surfaces of these structures are also preferably coated with a black body coating, such as a carbon black paint  90 , to efficiently absorb radiant energy from lamps  40  and  42 . As the air passes over lamps  40  and  42  it contacts substantially the entire surface of each of the lamps, longitudinally and about the 360 degree circumference of the lamps. The air is warmed by conduction from the intimate contact with lamps  40  and  42  and absorbs some heat radiated from the lamps. In addition, a portion of the radiated heat is absorbed by the material of tubes  74  and  76 . This absorbed heat is in turn conducted to the air passing over both the interior and exterior surfaces of tubes  74  and  76 . However, some of the heat absorbed by tubes  74  and  76  is radiated to the material of ducts  78  and  80  where it in turn is passed by conduction to the air passing through and around ducts  78  and  80 . It will be appreciated that while the space heater  10  is shown with the lamps, tubes and ducts oriented primarily vertically, the operation of the device would remain substantially the same in many orientations which were not vertical. 
     With a fan which moves about thirty to thirty-five cubic feet per minute for each 500 watt lamp, or about sixty cubic feet per minute for the two lamp configuration shown in the drawings, the temperature of the air is raised about 105 degrees F. That is, with ambient air at seventy degrees F., the air exiting the space heater  10  is about 175 degrees F. This is an increase of about fifteen degrees F. over conventional heater designs using incandescent lamps and operating with the same power consumption. Moreover, the temperature of the external surfaces of the space heater  10  is not substantially changed from the temperature of the ambient air. In particular, back wall  16  and top  22  do not experience a substantial change in temperature. This feature could permit the space heater  10  to be incorporated into other structures, such as an end table or other furniture, for example. Further, the circuitous path of the air and the enclosing structure act as a black body, effectively confining the bright light produced by the lamps  40  and  42 , so that no light escapes from the enclosure of the space heater  10 . 
     In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained. As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.