Patent Publication Number: US-4320741-A

Title: Fireplace heater stove

Description:
TECHNOLOGICAL CONTEXT OF THE INVENTION 
     In response to the desires and needs of an energy-consuming public, various wood-burning heating systems--some of which fit into fireplaces--have been and are being developed. 
     One such apparatus, disclosed by Loy et al in U.S. Pat. No. 543,702, discloses a cylindrical fire-chamber contained within a cylindrical casing to provide convection heating. The airflow in Loy et al, however, is through &#34;inlet and outlet perforations&#34; which restrict not only the amount of air entering the heating apparatus but also the area of the inner fire-chamber over which the air flows and convection produced. Fitting the Loy et al apparatus into a fireplace is not contemplated. 
     Also showing two concentric cylindrical elements in a wood-burning convection heater, Lewis in U.S. Pat. No. 4,128,094  teaches air flow about the circumference of the inner portion of the structure (shown by arrows 8). Lewis does not readily adapt to being fit into a fireplace. 
     A patent (U.S. Pat. No. 1,255,493) by Williams shows a heater fit into a fireplace wherein cold air is drawn in at a bottom grating and air, heating by convection, is forced out through a top grating. The heater of Williams is rectangular and provides flues which directs, but nonetheless restricts, air flow. 
     Moncrieff-Yates (U.S. Pat. No. 4,096,849), like Williams, shows another fireplace unit which is not cylindrical and sends heat convected air through a duct. Moncrieff-Yates channels air over a bed plate, the angle of which is of great significance. 
     Techniques currently used fail to provide unobstructed, even heating to a flow of air passing through an air gap between two concentric cylinders, the inner cylinder being a firebox enclosed on all sides except for a flue which enters a fireplace chimney. Further, none of the techniques employ the gap between two cylinders--rather than ducts, pipes, or gratings--to provide a path for air to be heated. 
     No suggested apparatuses provide for retrofitting a wood-burning stove into fireplaces of a variety of sizes. Nor do these apparatuses teach the large surface area of heating, the smooth airflow resulting air passing rounded surfaces, and the safety of recessing the hot inner cylinder and permitting only the warmer outer cylinder to jut out. 
     SUMMARY OF THE INVENTION 
     To improve and enhance heaters proposed by others, the present invention provides an inner cylinderical wood-burning firebox sealable except for an exit flue going into a fireplace chimney and surrounded by an outer cylindrical shell both open at the front and separated from the walls and back of the firebox by an air gap. The firebox and outer shell fit into a fireplace, a large plate being attached to the exterior of the outer shell and set to one of various axial positions along the outer shell and being affixed to the fireplace. 
     The firebox is provided with a through-draft and a Venturi down-draft air inlet to enhance the heating therein. A baffle is also included to direct gas flow for secondary burn. 
     Finally, the provision of a coil, through which heatable fluid flows, wound about the firebox to yield a total, combination heating unit is specifically discussed. 
     The present invention, due to its curvature and the direction of airflow (parallel to the axis of the firebox and outer shell), provides even and continuous heating. 
     The outer shell protrudes relative to the firebox. The possibility of an object or person touching the hot, recessed firebox is greatly diminished. The outer shell does not get hot enough to scar if touched or set an object afire. Enhanced safe operation is thus an object of the invention. 
     Being cylindrical, wood as it burns moves to the center of the cylindrical &#34;floor&#34; of the firebox, leading to more thorough burning. 
     Finally, the present invention is aesthetically pleasing and can be readily used in many houses as a fireplace insert or free-standing stove without requiring modifications to the house. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective drawing showing the fireplace stove of the invention fit into a fireplace. 
     FIG. 2 is a front view of the present invention. 
     FIG. 3 is a cutaway front view of the present invention. 
     FIG. 4 is a cutaway side-view of the invention showing an inner cylindrical firebox contained within an outer cylindrical enclosure. 
     FIG. 5 is a cutaway side-view of an embodiment of the invention which includes a wraparound coil element. 
     FIG. 6 is a top-view enlargement of a down draft valve shown in FIG. 5. 
     FIG. 7 is a front-view enlargement of a down draft valve shown in FIG. 5. 
    
    
     DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, the heater stove 2 of the present invention is shown in its environment, fit into a fireplace 4. A firebox 6 is shown as a cylinder having a front face 8 in which a door 10 is placed and having its cylindrical wall 12 (see FIGS. 4 and 5) extending into the fireplace 4. Encompassing the firebox 6 is an outer cylindrical shell 14 which has no front face and which is connected to a front plate 16. The front plate 16 is sealedly affixed to the fireplace 4. The firebox 6 and the outer shell 14 are shown connected to each other by brackets 18, 20, 22, and 24. A ring-shaped gap 26, between the firebox 6 and the outer cylindrical shell 14, in FIG. 1 is also shown in the front view of FIG. 2 and the cutaway front view of FIG. 3. Bolts 28 and 32 (also shown in FIG. 2) are provided in FIG. 1 for affixing the front plate 16 to the fireplace 4. Bolts 30, 34, and 36 connect front plate 16 to a flange ring 17 which attaches the front plate 16 to the outer cylindrical shell 14. In both FIG. 1 and FIG. 2 through-draft elements 38 and 40 are shown located in the door 10. In a preferred embodiment, the through-draft elements 39 and 40 can screw and unscrew to cover or uncover an air opening (not shown), thereby allowing less or more air to enter the firebox 6. 
     FIG. 3, which illustrates a front view cut away behind the front plate 16, shows legs 42 on which the outer cylindrical shell 14 rests. A stove-pipe 44 passes through a hole in the top of the outer cylindrical shell 14 and through a hole in top of the firebox 6. A baffle 46 is more clearly seen in the side view of FIG. 4, which also shows the stove-pipe 44 entering the chimney 47 of the fireplace 4. 
     Referring to FIG. 4, it is readily seen how the baffle 46 causes gases in the firebox 6, generated when wood is burned therein, to circulate and promote secondary burning within the firebox 6. The baffle 46, together with the cylindrical shape of the firebox 6, contributes to the complete and efficient burning of the wood fuel. In the view of FIG. 4, additional brackets 48, 50, 52, and 54 are shown on the right side connecting the firebox 6 to the outer cylindrical shell 14. A similar bracket arrangement would also be provided on the left side. 
     It should be noted that the function of these brackets is to provide a support and connection between the firebox 6 and outer cylindrical shell 14 and may, therefore, include any number of arrangement of brackets which do not notably obstruct or direct any flow of air between the front and rear of the ring-shaped gap 26. 
     In operation, wood (not shown) is burned in the firebox 6 (of FIG. 4). Through-draft 38 is opened as desired to feed in air. The air in the firebox 6 circulates due to the baffle 46 heating the cylindrical wall 12 as well as the back face 56 of the firebox 6. Chimney smoke passes to the chimney 47 via stove-pipe 44. As the firebox 6 heats, cool room air enters the bottom of the ring-shaped gap 26 as indicated by the dashed arrow. The cool air travels to the rear of the heater stove 2 and is heated by the firebox 6 as it travels. As the heated air moves toward the rear of the heater stove 2 it rises. The heated air is expelled throughout the top portion of the ring-shaped gap 26 as shown by the dashed arrows. 
     With regard to this air flow it should be understood that the bottom portion of the ring-shaped gap 26 comprises approximately the lower half of the ring-shaped gap 26 while the top portion comprises approximately the upper half. Convection currents, it should also be noted, need not flow straight back and straight out (as illustrated by the dashed arrows) but may also follow curved flow paths, the rising of the air as it passes to the rear depending on the heat in the firebox 6 and the temperature in the room among other factors. 
     Referring now to FIG. 5, another embodiment of the invention is shown in cutaway side view. In addition to through-draft elements 38 and 40, a down-draft element 58 with a Venturi aperature 60 is included to inject a controlled stream of room air into the firebox 6 as desired. The exact structure of the down-draft element 58 is depicted in FIGS. 6 and 7. The top view of FIG. 6 shows a cover 64 which can rotate about a pivot point 66 to expose the Venturi aperture 60 to greater air inflow. FIG. 7 shows the round Venturi aperture 60 surrounded by a pipe housing 67, extending through the outer cylindrical shell 14 and the cylindrical wall 12 into the firebox 6. 
     Referring back to FIG. 5, the heater stove 2 is shown having fluid carrying tubing 68 would about the firebox 6 inside the outer cylindrical shell 14. Cold gas or water pumped through the tubing 68 will be heated. A combination air convection heater and hot water heater, for example, can be provided by the embodiment of FIG. 5. An adjustment screw 62 (or screws), of preferably an Allen head type, passes through the flanged ring 17 to contact outer cylindrical shell 14 and is used to permit motion of the outer cylindrical shell 14 relative to the front plate 16, i.e., into or out from the fireplace 4. To fit into a deeper fireplace, the adjustment screw(s) 62 may be loosened, the firebox 6 and outer cylindrical shell 14 pushed deeper (i.e., to the left in FIGS. 4 and 5) into the fireplace 4, and the adjustment screw(s) 62 retightened. 
     It should be realized that, although the present invention shows a circular cylinder embodiment, other cylindrical embodiments (such as elliptical or squared) are also within the scope of the invention. Similarly, while the door 10 is illustrated as square, it may also be round and, if desired, large enough to comprise the front face 8 of the firebox 6. Other such modifications are also within the scope of the invention.