Sealed combustion gas-fired infrared heater

Abstract

A gas fired infrared heater is provided that includes a burner, a combustion chamber, a cooling air passage for supplying cooling air to the combustion chamber, a combustion air passage for supplying combustion air to the burner; and an outlet passage allowing combustion product gases to exit the combustion chamber. The cooling air passage is separate from the combustion air passage. The cooling air passage and the combustion air passage both draw from the same pressure zone into which combustion products exit.

Description

FIELD OF THE INVENTION

The present invention relates to a gas-fired infrared heating apparatus; particularly a heating apparatus that completely segregates an incoming combustion air flow from an incoming radiation-transmissive panel cooling air flow, both of which draw from the pressure zone to which combustion products exit, and that segregates both from the combustion chamber itself.

BACKGROUND OF THE INVENTION

A heating device having a fuel-fired radiant burner has long been used for heating various enclosures. The heating device here described includes a thin, radiation-transmissive panel that transmits infrared radiation into the space to be heated (e.g., room, tent) and also seals a combustion chamber which houses a radiant from the space being heated. To maintain the integrity of the heating device, the panel must be cooled.

One way to cool the panel is to have a stream of cooling air flow (e.g., by convection) over the panel. An additional way to cool the panel is to provide a coolant outside the combustion chamber. Another way to cool the panel is to use suction generated when combustion air is entrained by gas jets in infrared-generating burners. However, one problem with this approach is that turbulence in the flame area creates enough admixture of combustion products with incoming combustion air to interfere with clean combustion (e.g., these units produced too much carbon monoxide from recirculation.) Another problem with this approach is that back drafts can cause impaired combustion, carbon monoxide formation, or snuffing of the flame.

Accordingly, there is a need for a heating device that satisfies the following conditions, specifically an apparatus that seals off a combustion chamber from the space to be heated and prevents air in the combustion chamber from being used for combustion.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a heating apparatus that seals off a combustion chamber from a heated space and supplies all combustion air to the burner with no possibility of admixture with combustion chamber gases.

One aspect of the present invention includes a burner, a combustion chamber, a cooling air passage for supplying cooling air to the combustion chamber, a combustion air passage for supplying combustion air to the burner, and an outlet passage allowing combustion product gases to exit the combustion chamber. In this apparatus, the cooling air is separate from the entering combustion air.

Thus, according to the present invention, it is possible for the heating apparatus to draw cooling air in without using gas-jet entrainment of the burner by, in part, entraining considerable air as hot products move upward through the outlet passage.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the present invention will be described with reference to the accompanying drawings, wherein:

FIG. 1 is a cross-sectional view of a heater of the invention;

FIG. 2 is a cross-sectional view of a second embodiment of the invention;

FIG. 3 is a cross-sectional view of a third embodiment of the invention;

FIG. 4 is a cross-sectional view of a forth embodiment of the invention;

FIG. 5 is a cross-sectional view of a fifth embodiment of the invention;

FIG. 6 is a cross-sectional view of a sixth embodiment of the invention;

FIG. 6 b is a planar view of the sixth embodiment of the invention; and

FIG. 7 is a cross-sectional view of a seventh embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be described hereinafter with reference to the accompanying drawings.

Referring to FIG. 1, the heater of the invention is designated by a reference numeral 2, and as shown in an exemplary position as being secured to a ceiling 4 of an enclosure to be heated (e.g., tent, bathroom, ice-fishing shanty, mobile home, etc.) A combustion chamber 6 is provided with generally upright side walls 8, 10, a front and rear wall (not shown) and a bottom wall 12, with a radiation-transmissive port therein. The port may extend between the side walls 8, 10 and the front and rear walls of the combustion chamber 6, although it may be desirable, in some instances, to have a smaller port. A sealing barrier 14 is located to close the port, and may be fastened by clamps, spline in groove, or the like (not shown) to the periphery of the front, rear, and side walls of the combustion chamber 6.

The sealing barrier 14 is desirably of a thin, flexible plastic material which ordinarily softens or melts below 1000° F. Preferred materials for the panel include such thermoplastics as polytetrafluoroethylene (Teflon “TFE”, a trademarked product of E. I. DuPont DeNemours and Company, Inc.) which has an infrared transmissivity of approximately 0.88, poly (tetrafluoroethylene-hexafluoropropylene) (Teflon “FEP”, manufactured by the DuPont Company) which has an infrared transmissivity of 0.97, and polyester materials such as poly (ethyleneterephthalate) a product sold under the name Mylar by the DuPont Company and which has an infrared transmissivity of approximately 0.77. Teflon FEP film having a thickness of approximately 0.002 inches is preferred, since this material is flexible, is highly transmissive of infrared radiation, and is more resistant to high temperatures than many other polymeric materials.

Combustion product gases from a burner 16 which are propelled downwardly toward the sealing barrier 14 are typically hotter than the continuously replenished pool of cooling air (described below), and mix with the upper portion of the latter and rise toward the outlet port 26 before impinging on and damaging the sealing barrier 14.

The sealing barrier 14 is protected from such high temperatures that result from hot gases produced by combustion by cooling air 48 drawn into the chamber 6 in such a way that it pools (in this configuration) or sweeps adjacent to the sealing barrier 14. Teflon, sealing barrier 14, tends to elongate slightly when heated. Cooling air 48 (described below) keeps it below the melting point, but the sealing barrier 14 may absorb enough infrared to warm up and elongate. The reduced pressure in the combustion chamber 6 (created by the stack action, described below, which pulls cooling air through the cooling chamber) could draw the elongated portion toward a combustion-heated area, nearer to a burner 16, such as an ainfrared producing ceramic-faced gas burner. Therefore, to prevent the sealing barrier 14 from melting, one or more fine infrared-reflective wire(s) 42 are provided along an inner surface of the sealing barrier 14.

Located within the combustion chamber 6 is the burner 16. The rearward end of the burner 16 includes a combustion air inlet 18 connected to a control valve 20 that is located outside the combustion chamber 6 and connected to a downstream gas supply 22. While it can be seen from FIGS. 1-7 that a preferable width and length of the burner 16 are at least half of the width and length of the interior of the upper portion of combustion chamber 6, other dimensions are also acceptable.

The combustion air inlet 18, such as a venturi inlet, of burner 16 supplies virtually all of the combustion air used in generating infrared radiation. In the air inlet 18, air is entrained in the jet stream of gas emerging through a small orifice. The gas-air mixture flows through several holes, not shown, in the ceramic front of the burner. It burns close to the burner surface and heats the surface to a high temperature, up to 1700° F. This then loses heat by radiation, creating the infrared ambient.

In FIG. 1, the burner 16 is angled at approximately 8° upward to aid flow of combustion gases away from the burner surface. Radiation exits a radiating surface 3 of the burner 16 in a broad distributed beam through 180°.

A metal screen 24 is provided at a distance from the radiating surface 22 side of the burner 16 in the combustion chamber 6, and heats up and radiates in all directions, some contributing to heat output, and some adding heat to the burner's radiating surface 3 and thus heating it further and intensifying its radiation. In FIG. 1, the metal screen 24 is attached to the side wall 8.

The combustion chamber is provided with an outlet passage 26 that allows combustion product gases to exit the combustion chamber. The outlet passage also draws and pulls air in to cool the sealing barrier 14. The outlet passage includes an air-entrainment by turbulence chamber 30, and a vent 32. The outlet passage 26 is preferably positioned in the top wall (not shown) of the combustion chamber 6 and may extend through the ceiling 4 to the space provided below a vent cap 34. The turbulence chamber 30 is preferably rectangular, although other shapes may be used, and preferably extends approximately the width of the heater 2. The vent, for example, a round pipe 4″ in diameter, extends from the top side of the turbulence chamber 30 to the space provided below the vent cap 34. The vent cap 34 prevents rain and dirt from entering the heater and keeps the pressure in the two pipes substantially the same in all conditions of wind and weather.

One or more reflectors 36 are provided in the combustion chamber. For example, in FIG. 1, a reflector is provided on the inside surface of each of the side walls 8, 10 of the combustion chamber 6. The reflectors 36 direct the lateral infrared output toward the heated area 38.

The heater 2 includes a cooling air passage 44 for supplying cooling air 48 to the combustion chamber 6 and a separate combustion air passage 46 for supplying combustion air 50 to the burner 16. In FIG. 1, the cooling air 48 is separated from the combustion air 50 for sufficient distance to prevent admixture of the two. This allows segregation of incoming combustion air 50 from the combustion chamber 6 so that combustion products are not recirculated.

The cooling air passage 44 is located within the heater 2 and adjacent to the combustion chamber 6 and shares a common wall with the side wall 10 and communicates with the combustion chamber 6 through a slot 52, which is preferably provided adjacent to the inner upper surface of the sealing barrier 14. If the heater 2 is to be operated at an angle instead of flat, the slot 52 should be in the upper side wall 10. Because the cooling air 48 that is provided to the combustion chamber 6 through the slot 52 is cooler than air within the combustion chamber 6, the cooling air 48 flows down along the inner surface of the sealing barrier 14 to keep it below the melting point.

In FIG. 1, for example, the source of the cooling air 48 is outside the space to be heated 38 (e.g., another room, outside environment, etc.) Also, the width of the slot 52 may approach up to the full width of the combustion chamber 6. The purpose of the slot 52, for example, is to direct cooling air from the cooling air passage 44 into the combustion chamber 6 in the vicinity of the inner surface of the sealing barrier 14 to form a constantly replenished pool of cooling air 48 above the sealing barrier 14 to cool the same.

In FIG. 1, a sensor 54 (e.g., temperature sensing device) is provided in the combustion chamber to detect hot combustion products, for example, in the event of disruption of the sealing barrier 14. The sensor 54 may be provided near the bottom of the inside top surface of the combustion chamber 6, for example, in order to sense abnormal circulation. The sensor 54 may comprise a switch with a thermocouple or the like to open a safety circuit before hot products reach the front of the combustion chamber 6. The sensor 54 may also be a nylon line (which has a melting point well below Teflon) that holds closed a switch in the safety circuit. Other types of known sensors may also be used.

In FIG. 1, the combustion air passage 46 is located within the heater 2 and adjacent to the combustion chamber and shares a common wall with side wall 8 and communicates with the burner 16 through the combustion air inlet 18. Here, the combustion air 50 is drawn through the combustion air passage 46 by the gas jet's entrainment effect. The combustion air 50 becomes warm, which improves combustion efficiency. The combustion air also prevents the top of the heater 2 from becoming overheated so that the heater 2 can be hung on or close to a ceiling or wall, for example, without risking damage thereto. In FIG. 1, for example, the source of the combustion air 50 is outside the space to be heated 38.

It is also possible for combustion air 50 and cooling air 48 to flow together through the vent 32. However, before there is a chance of admixture with combustion products, the mixed-function passage divides into two separate passages 44, 46.

In FIG. 1, a deflector screen 56 is provided as a barrier on the outside of the sealing barrier 14 to protect the sealing barrier 14. The deflector screen 56 may comprise reflective material, such as aluminum.

FIG. 2 is an alternative embodiment of the present invention and like reference numerals denote similar elements described above. In the heater embodiment of FIG. 2, the burner 16 (e.g., infrared generator) is mounted vertically in the combustion chamber 6 and side wall 10 of the combustion chamber 6 slants downwardly adjacent a burner base 58 and beneath the burner 16 at an angle of, e.g., 45° to the horizontal, and is provided with an infrared reflective inner surface 36. The sealing barrier 14 extends from side wall 10 to side wall 8, at an angle of, e.g., 45°-75° to the horizontal.

Gas enters through the burner base 58 from a controlled source of supply, which is not shown. The gas jets through a small orifice 60 and entrains the primary air required for combustion. The gas-air mixture penetrates numerous openings, not shown, in the front surface of the burner 16 which is usually ceramic or heat-tolerant steel. When the gas-air mixture burns at this surface it heats the surface to very high temperatures and causes it to give off radiant heat. The combustion products that form at the burner surface rise and exit through the vent 32. Combustion products exit through the upper portion of the compound vent cap 34, which keeps the hot products emerging from the vent segregated from the air going into the cooling air passage 44 and combustion air passage 46. This arrangement allows the ambient atmospheric pressure in the vent 32 and in the air intakes 44, 46 to essentially be identical (e.g., improves efficiency of heater and negates wind-generated pressure changes and their effects.)

Combustion air 50 is drawn through a segregated combustion air passage 46 by the gas jet's entrainment effect. As shown in FIG. 2, the combustion air 50 passes along the back of the burner 16, this has at least the following desirable effects: It becomes somewhat warm, which improves combustion efficiency, and it keeps the back of the heater 2 from becoming overheated.

Cooling air 48 is drawn through a segregated cooling air passage 44 by the suction created by ascending combustion products in the vent 32 (e.g., draw created in a well-designed fireplace.) It enters the combustion chamber through a cooling air slot 52 provided, for example, adjacent to the inner upper surface of the sealing barrier 14. Being cooler than air within the combustion chamber, the cooling air flows down along the inner surface of the sealing barrier 14 and keeps it well below its melting point.

FIG. 3 is an alternative embodiment of the present invention and like reference numerals denote similar elements described above. In the heater embodiment of FIG. 3, a partition 62, provided in the heater 2 and extending in a generally vertical direction, segregates the combustion air passage 46 from the cooling air passage 44. As shown in FIG. 3, the bottom wall of the cooling air chamber 48 and the combustion air chamber 50 is the downwardly sloping (e.g., 15°-75° from sealing barrier 14) side wall 8 of the combustion chamber 6. The side wall 8 extends the full width of the heater 2.

A cooling air slot 52 is preferably provided in the side wall 8 to convey cooling air into the combustion chamber 6 adjacent to the sealing barrier 14. If the burner 16 is operated off the horizontal (e.g., 20°), then the slot 52 should be preferably provided at the raised side of side wall 8 in order to better allow cool air to sweep across the sealing barrier 14 by convection.

As shown in FIG. 3, a conduit 64 (e.g., a pipe or duct, etc.) connects the turbulence chamber 30, which communicates with the combustion chamber 6 and is provided above the burner 16, with the vent 32. The conduit 64 penetrates, e.g., the upper portion, the side wall 8 of the combustion chamber 6 in a sealed manner.

Although not shown in the drawings, a bottom wall should be provided on the turbulence chamber 30, if the burner 16 does not seal it off from the combustion chamber 6.

Combustion air 50 is provided into the burner 16 via an inlet 18 (e.g., venturi inlet) that is provided in the combustion air passage 46.

Side wall 10 of the combustion chamber 6 is downwardly sloping (e.g., 15°-75° from sealing barrier 14). A reflector 36 is provided on the inside surface of the side wall 10 and directs infrared generated by the burner 16 downward and out through the sealing barrier 14.

A second window 66 (e.g., preferably made of Teflon) is provided adjacent the sealing barrier 14 and away from the heater 2. Window 66 may be located in the outside wall of a structure to be heated. Heater 2 can be then located entirely outside the structure with the beam of infrared it generates largely penetrating window 66 to provide heat inside the structure. The small amount of infrared absorbed in the thermoplastic film of window 66 heats it only slightly, and that heat is dissipated by convection into the surrounding outdoor air to keep the film well below its melting point. Sufficient space 80 should generally be allowed between heater 6 and window 66 to permit convection-generated cooling to occur.

Having the vent 64, the combustion air passage 44 and the cooling air passage adjacent to each other eliminates any effects of wind-generated pressure changes and prevents any conditions of wind or weather from creating back drafts. Locating the heater 6 in outdoor space rather than inside the structure to be heated eliminates hazards related to indoor heating, such as carbon monoxide poisoning and gas leakage.

FIG. 4 is an alternative embodiment showing a second window 66 installed on an upper, center portion of a tent 68. However, the second window 66 may also be installed in work shacks, ice fishing houses, hunting shacks, campers, etc., so that the heater can be used in multiple locations.

The tent 68 includes a tent frame 70 (e.g., four or six legs), straps 81 (e.g., Velcro, snap, etc.) provided at various locations to fasten the tent 68 to the frame 70, a heater 2 (e.g., FIG. 2) having an air-cooled sealing barrier 14, and a second window 66 installed on an upper, center portion of a tent. The circumference of the second window is larger than that of the sealing barrier 14 so that tent material at its edges is not heated by the excessive infrared ambient. The second window 66 is transparent to infrared. The heater 2 is entirely separate from, but is supported by a part of the tent frame 70 above the second window 66 so that it radiates heat into the tent 68.

The heater 2 may be attached to a stand (e.g., 10′ tall) and used, for example, as an overhead patio heater.

FIG. 5 is an alternative embodiment of the present invention and like reference numerals denote similar elements described above. The heater 2 shown in FIG. 5 includes a vent 32, side walls 8, 10 that are provided with multiple cooling air slots 52 to admit drawn-in cooling air 48, a sealing barrier 14, a combustion air passage 46 providing combustion air 50 to a burner 16 that is mounted vertically in the combustion chamber 6.

In outdoor locations, the pressure at cooling air slots 52 and vent 32 is substantially similar and change similarly with the wind. Accordingly, air within the heater 2 moves only in response to heat produced convection.

This allows use of much more efficient infrared-producing burners than the steel-can-heated-from-inside currently used in most outdoor heaters. The more efficient burners have flame which burns in the surface of ceramic or woven-steel. The pressure differential that brings the gas-air mixture through the plurality of holes in the ceramic or steel to its surface is small. For example, it is produced by gas at relatively low pressure (11-12 inches water column for LP, 4 inches for natural gas) flowing through a small orifice. This both entrains air and drives the gas-air mixture to the radiating surface. Thus, the more efficient type of burner requires wind-pressure control like that provided in this heater, because a slight breeze drives the flame back into or away from the ceramic or steel and drops efficiency.

FIG. 6A is an alternative embodiment of the present invention and like reference numerals denote similar elements described above. The body of the heater 2 shown in FIG. 6A is of a cylindrical shape, for example, and includes an outer wall made up of a cylinder 74 (e.g., 6″ pipe), a base 76, and a sealing barrier 14 (preferably, Teflon) provided between the cylinder 74 and the base 76. The sealing barrier is attached to the cylinder 74 and the base 76, for example, by a plurality of fixtures 78 (e.g., hose clamps, etc.) Cooling air and combustion air are drawn together from a compound vent (not shown) into combined passage 82. A passage for combustion air with top and bottom walls shown as 83 and side walls not shown, which define a passage 85 from the common passage 82 without obstructing the vent 84. Teflon cooling air continues past the openings to combustion air passage to cooling air passage 44 and thence to flow cooling air 48 down along the inner side of the radiation transmissive panel. This cool air moves downward rapidly while combustion products move upward rapidly creating a shear plane which prevents combustion product heat form reaching the radiation transmissive panel.

A cooling air chamber 44, provided generally vertical to the base 66 and adjacent to the sealing barrier 14, draws cooling air 48 to the sealing barrier 14 and the base 66. The heater includes a tall cylindrical burner 16 that is located approximately in the center of the heater 2 and extends in a downward, vertical direction towards the base 76.

FIG. 6B is a cross-sectional view taken along lines 6B-6B of FIG. 6A.

FIG. 7 is an alternative embodiment of the present invention and like reference numerals denote similar elements described above. In heater 2 shown in FIG. 7, for example, cooling air 48 sweeps along the inner surface of the sealing barrier 14 by convection. This enables considerable turbulence in the combustion chamber 6, so that all the air in the combustion chamber 6 contains some carbon dioxide. Therefore, to prevent combustion chamber 6 air from being used as combustion air 50, combustion air 50 is provided from a completely separate source, e.g., combustion air passage 46.

Vertical rise of combustion products (e.g., through a vent 32) is necessary to draw cooling air 48 in the cooling air passage 44 to cool the sealing barrier 14. In FIG. 7, for example, the vent 32 is provided outside the room to be heated 38. For example, an 8″ length of 3″ pipe may be used. The design structure shown in FIG. 7 allows the heater 2 to be more compact.

In this detailed description of the preferred embodiments, reference is made to the accompanying drawings, which form a part hereof, and within which are shown by way of illustration specific embodiments by which the invention is practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the invention.

Claims

1. A gas fired, infrared heating apparatus, comprising: a burner; a combustion chamber; a cooling air passage for supplying cooling air to the combustion chamber; a combustion air passage for supplying combustion air to the burner; and an outlet passage allowing combustion product gases to exit the combustion chamber, wherein the cooling air passage is separate from the combustion air passage.

2. A heating apparatus of claim 1, wherein said cooling air passage and said combustion air passage derive from the same pressure zone into which the outlet passage empties.

3. The heating apparatus of claim 1, wherein the combustion chamber further comprises a lower wall providing a generally downwardly open port closed by a sealing barrier that is over 80% transmissive of infrared radiation and prevents gaseous interchange between the combustion chamber and a heated space.

4. The heating apparatus of claim 3, wherein said sealing barrier is made of a material which melts below 1000° F.

5. The heating apparatus of claim 3, wherein said sealing barrier is made of Teflon.

6. The heating apparatus of claim 3, wherein the cooling air enters the combustion chamber through an opening in the cooling air passage adjacent to an inner upper surface of the sealing barrier.

7. The heating apparatus of claim 1, further comprising a compound vent cap provided above an upper side of the outlet port, wherein said compound vent cap draws outside air for the cooling air passage and the combustion air passage without allowing any admixture of outgoing combustion products with incoming air.

8. The heating apparatus of claim 1, wherein the outlet passage extends in a vertical direction from the burner.

9. The heating apparatus of claim 1, wherein the combustion air enters into a burner venturi.

10. The heating apparatus of claim 1, wherein the combustion air passage is located along the back of the burner.

11. The heating apparatus of claim 3, wherein an infrared-reflective wire adjacent to an inner surface of the sealing barrier prevents the sealing barrier from displacing inward.

12. The heating apparatus of claim 3, further comprising a heat sensor device positioned within the combustion chamber and positioned above the sealing barrier, wherein the heat sensor device is capable of cutting off a gas supply to the burner.

13. The heating apparatus, according to claim 1, wherein said heating apparatus is provided outside of a structure to be heated, whereby said heating apparatus projects an infrared ambient through an infrared transmissive window into said structure.

14. A gas-fired heating apparatus, comprising: a burner; a combustion chamber; an outlet passage allowing combustion gases to exit the combustion chamber; means for supplying combustion air from the same pressure zone to which combustion products exit from the burner; means for preventing said entering combustion air from mixing with gases in the combustion chamber; and means for segregating combustion air from cooling air prior to entry into the combustion chamber.

15. A heating apparatus, according to claim 14, wherein said supplying means is a combustion air passage.

16. A heating apparatus, according to claim 14, wherein said cooling air is supplied to the combustion chamber in a cooling air passage, from the same pressure zone to which combustion products exit from the burner.

17. A heating apparatus, according to claim 14, wherein said outlet passage is provided outside a room to be heated so that said heating apparatus is more compact.

18. The heating apparatus, according to claim 14, wherein said heating apparatus is provided outside of a structure to be heated, whereby said heating apparatus projects an infrared ambient through an infrared transmissive window into said structure.