1. Field of the Invention
The present invention relates to heating units, and more particularly to free standing heating units adapted to efficiently heat by radiation as well as convecting the area surrounding the heating unit.
2. Description of the Prior Art
Freestanding heating units are well known and are generally classified in Class 126, subclass 120 under fireplaces and in subclass 121 under hot air fireplaces. The prior art freestanding heating units include space heaters and Franklin type stoves of the type adapted to burn efficiently several types of organic fuels.
Most iron and steel stoves have an inner firebox chamber separated from an outer shell by an air space. The major portion of the heating effect is accomplished by convection when the air rising between the firebox chamber and the outer shell is heated. The exhaust pipe or connection to the chimney is usually very short and sometimes heavily insulated thus assuring that most of the available radiant energy is lost.
Gas radiant heaters of the prior art types are similar in mode of operation to open fireplaces in that one side of the heater or fireplace is open to freely radiate heat of combustion. Open gas radiant heaters are usually not vented and have been known to consume the oxygen in a room in a short period of time and/or to fill the room with carbon monoxide which causes permanent brain injury or death. If such open gas radiant heaters are not supplied with adequate vents and adequate protective coverage of the open flame they present serious hazards.
Open fireplaces are assumed to have vents which connect to the outside of the building in which they are installed. Open fireplaces have been provided with mesh cover screens and even fireproof glass to protect against discharge of embers from the fuel being burned. Open fireplaces are not provided with efficient burner controls and are known to be generally inefficient unless provided with expensive auxilliary convection heating means.
Completely free standing heating units such as those described in U.S. Pat. No. 3,499,432 are known. The firebox chamber of such units are provided with panes of glass which substantially comprise the side walls of the firebox chamber. When fuels other than natural gas or synethetic gas are burned in the firebox chamber, the unburned carbon in the combustion gasses is known to deposit rapidly on the panes of glass. Smoked glass causes loss of radiant heat, excessive heating of the glass, seriously detracting from the artistic beauty of unit and the ability to observe the fire.
To overcome the problem of producing smoked glass, the heating unit described in U.S. Pat. No. 3,499,432 is provided with a plurality of vertically hinged windows or doors which, when opened, permit a circumferential flow of air across the inside face of the glass panels. A circumferential flow of combustion gasses is induced by a fire ring which introduces a circumferential ring of air adjacent the base or floor of the fire box.
Such prior art heating units, to burn effectively present an excessive amount of air surrounding the fuel and an insufficient amount of air in the center of the fuel being burned. Further, the open doors or windows permit sparks and flaming embers to pop or discharge out of the firebox chamber onto the floor. Heating units having framed glass doors and windows are expensive to manufacture and require factory made parts for service. Fixed solid bottom fireboxes and/or open sided air intakes in fireboxes are known to be difficult to clean as well as to service.
There is an unfulfilled need in art of heating units for a highly efficient combustion unit capable of burning wood, coal, rolled paper, gas and other forms of fuel interchangably.