US2873736A - Hot air furnace - Google Patents

Description

Feb. 17, 1959 R. w. R055 2,873,736

HOT AIR FURNACE Filed July 9, 1956 3 Sheets-Sheet 1 l/VVEA/TOR RIQHARD W. ROSS R. W. ROSS HOT AIR FURNACE Feb. 17, 1 959 3 SheetS Sheet 2 Filed July 9, 1956 uvvs/vwk RICHARD W. ROSS HTTDIIVDS Feb. 17, 1959 R. w. R055 2,873,736

HOT AIR FURNACE Filed July 9, 1956 5 Sheets-Sheet 3 /M/EA/r0/? RICHARD W. ROSS United States Patent nor AIR FURNACE Richard W. Ross, Winfield, British Columbia, Canada 7 Y Application July 9, 1956, Serial No. 596,719

8 Claims. 01. 126-116) This invention relates to improvements in hot air furnaces.

An object of the present invention is the provision of a furnace having a main heating chamber mounted on a fire box in order that a wall of the former comes into direct contact with the fire in the box.

Another object is the provision of a hot air furnace in which air is circulated in a tortuous passage several times along the walls of a fire box in order to absorb a maximum amount of heat before being directed out of the furnace.

A further object is the provision of a furnace in which air is kept in contact with a fire box for a comparatively long time without the necessity of increasing the size of the furnace beyond that of the known furnaces of a similar capacity.

This furnace includes a fire box spaced from the bottom, side walls, and an end wall of a casing, and a main heating chamber on top of said box. This heating chamber extends the full width of the device and forms the top of the fire box. In fact, the chamber may be made so that part of it extends downwardly into this box. Air entering the furnace to be heated, moves along the bottom thereof beneath the fire box, up and back along the sides of said box, whence it is directed into the main heating chamber at one end thereof. The opposite end of the main chamber is connected to a plenum chamber mounted thereabove within the casing. Hot air ducts extend from the plenum chamber to the areas to be heated. The gases from the fire in thefire box pass outwardly through the rear end thereof and upwardly .to a secondary combustion chamber which is bounded above and below by the plenum and main heating chambers,

respectively. Means is provided for directing these gases from said secondary combustion chamber to a flue. If desired, a passage may be provided from this secondary chamber upwardly therefrom and back across the top of the plenum chamber. Any fuel may be burned in the fire box, such as coal, sawdust, oil or gas.

Examples of this invention are illustrated in the accompanying drawings, in which,

Figure l is a perspective view of the furnace looking at the back thereof,

Figure 2 is a vertical section taken substantially on the line 22 of Figure 3,

Figure 3 is a vertical section-taken substantially on the line 33 of Figure 2,

Figure 4 is a front elevation of the furnace,

Furnace 5 is a horizontal section taken on the line 55 of Figure 2,

Figure 6 is a horizontal section taken on the line 6-6 of Figure 2,

Figure 7 is a horizontal section taken on the line 77 of Figure 2,

Figure 8 is a fragmentary vertical section taken on the line 8-8 of Figure 3, and

Referring to the drawings, 10 is a hollow base having a flat top 11. The base may be formed with two iongitudinal passages 12 and 13, separated by a central vertical partition 14. Air to be heated is supplied to the passages 12 and 13 in any suitable manner. In this example, a recirculating duct 18 is connected to the passage 12 at the back of the furnace, and another duct 19 extends from a suitable source of fresh air, such as outside the building being heated, and is connected to passage 13. If desired, a suitable air flow control, not shown,

may be provided in duct 19. Relatively large openings 22 and 23 are formed in the top of the base at opposite sides thereof adjacent the front end of the furnace; see Figure 7.

A casing 26 extends upwardly from the base 10. 'This casing is formed with front and rear walls 27 and 28,

side walls 30 and 31, and a top 32. 7

An open-topped fire box 36 is mounted on top of the base 10 and is spaced from the sides and back end of the casing to form side air passages 37 and 38 and end air passages 39 and 40. By referring to Figure 7, it will be seen that the fire box is located between the base openings 22 and 23 and extends to the front end of the base. If coal or wood is to be burned in the furnace, the firebox will be provided with the necessary grates. How: ever, in the illustrated form of the invention, an opening 44 is formed in the front wall of the box and has a collar 45 projecting outwardly therefrom through the casing for receiving an oil or gas burner unit, not shown. A relatively large opening 47 is formed in the back wall of the box extending from the top to bottom thereof substantially midway between its opposite sides; see Figures 6 and 8.

A casing forming a main heating chamber 50 is mounted on top of the fire box. This chamber casing extends laterally and longitudinally to the walls of the casing, and it forms the top or most of the top of the fire box. If desired, a portion 51 of the bottom of the heating chamber may project downwardly into the fire box, as shown in Figures 3 and 8. The heating chamber is sealed on the fire box and to the casing walls by means ofany suitable type of furnace cement.

This chamber is not very deep and is formed at the back end of the bottom thereof with openings 54 and 55, the opening 54 communicating with the air passages 37 and 39 therebelo-W, and the opening 55 with the air passages 38 and 40; see Figures 2, 6 and 8. By referring to Figures 5 and 9, it will be seen that the back end of the heating chamber is indented to form a smoke channel her with part thereof broken away.

57 extending from the bottom to the top thereof, the end wall 28 of the furnace casing forming the outer wall of said channel. This channel is directly above the opening 47 in the back of the fire box, and partitions 59 and 60 extend downwardly from the chamber on opposite sides of the box opening to the top of the base 10. These partitions are sealed to the base and to casing wall 28 by a suitable furnace cement. Thus, the channel 57 extends from the fire box opening upwardly to an area above the main heating chamber which forms a secondary combustion chamber 62, the top of which is formed by a wall 63 extending from side to side of the casing, and forwardly from the back wall thereof to a point 64, see Figure 3, spaced from the front wall thereof. The heating chamber is provided at its forward end with an upwardly extending projection 66 which forms a large hot air outlet 67 communicating with a plenum chamber 68 positioned between the wall 63 and the top 32 of the furnace casing. The projection 66 opens into the plenum chamber at the forward end of the wall 63. Any desired number of hot air ducts 70 may extend outwardly from the plenum chamber through the side and back walls of the casing. If it is desired to draw air from the plenum chamber at one or more points considerably above the Patented Feb. 17,1959

furnace, the casing 26 may be extended upwardly to increase theheight of said chamber.

The products of combustion may be removed from the secondary chamber 62 in any desired manner. It is, however, preferred to provide a pipe 76 extending through the heating chamber projection 66 from said secondary chamber. The forward end of this pipe communicates with'a corresponding opening in the front wall 27 of the casing,'and a pipe 78 may extend upwardly therefrom along said 'front wall to a-horizontal pipe 79 which extends back across the top 32 of the casing to a smoke pipe 80 which extends to a flue, not shown.

When this furnace is in use, the fuel is burned in the fire box 36. The products of combustion move out through the opening 47 at the back of this box up through the channel 57, into the secondary combustion chamber 62, andthrough pipes 76, 78, 79 and 80 to the line. Atthe same time, air from the areas being heated is directed into the base passage 12 by pipe 13. If it is desired to add fresh air to the system, said air is directed into the base passage 13 by duct 19.- Thus, air entering the furnace moves along the passages 12 and 13 beneath the base top-11', up through the base openings 22 and 23, along the'sides of the box through passages 37 and 38, up through the latter and passages 39 and 40 into the openings 54 and 55 of the main heating chamber 59. This air is preheated as it moves through the space beneath the fire box, and along the sides and back thereof into the heating chamber. This chamber is relatively large, but not very deep. As the bottom 51 of the heating chamber forms the top or the main portion of the top of the fire box, the flame in the latter heats the air in said chamber. At the same time, the products of combustion in the secondary chamber 62 heats the main heating chamber from above and as they pass through the pipe 76. In addition to this, the products of combustion in chamber 62 also heat the bottom of the plenum chamber 68. Furthermore, as these products of combustion move along pipes 78 and 79, they transfer additional heat to the air in the plenum chamber. Actually, the air entering the back of the furnace at the bottom thereof fol lows a tortuous passage along the bottom of the fire box, back along the sides thereof, up at its back end, forwardly between the top of the fire box and the bottom of th secondary combustion chamber, up into the plenum chamher and back therethrough. The gases from the fire also follow a tortuous passage back through the fire box, up past the back end of the main heating chamber, across the top of the latter, up through pipe 78, and back through pipe 79. All the walls of the fire box, excepting the front wall thereof form heat exchange surfaces, while the top and bottom of the main heating chamber and the bottom of the plenum chamber also form heat exchange surfaces. In this way, the air passing through the furnace is directly exposed to heat exchange surfaces during practically its entire journey through the furnace, and it is kept therein for a comparatively long time. This ensures a maximum transfer of heat within a limited space.

What I claim as my invention is:

1. In a hot air furnace, an outer casing having front, back and side walls, and a top, an open-topped fire box within the casing extending from the front wall and spaced from the side and back walls thereof, said fire box having a bottom and side and end walls, the end wall of the fire box spaced from the outer casing back wall having anoutlet opening therein; a shallow relatively wide ens ing forming a-main heating chamber resting on the top of the fire box and completely closing said top, said heating chamber casing projecting beyond the side walls and said end wall of the'fire box to the side and back walls of the outer casing, a wall spaced a little above the heating chamher and extending'to the'outer casing walls to form therebelow a shallow secondary combustion chamber above s'aid'heating chamber, and thereabove a plenum chamber within-the outer casing at the top of the latter, passage means extending from the outlet opening of the fire box through but completely-separate from the heating chamber to the secondary combustion chamber, means connected to the secondary chamber to remove combustion gases therefrom, said heating chamber casing having air openings therein on opposite sides of the passage means and near the outer casing back and side walls, passagemeans extending upwardly from the opposite end of the heating chamber casing past the secondary combustion chamber to the plenum chamber, and 'means connected to the outer casing near the top thereof to remove hot air from the plenum chamber.

2. A hot air furnace as claimed in claim 1 including means for directing air to the air openings of the heating chamber casing, comprising a tortuous passage within the outer casing extending along the bottom and the side walls and an end wall of the fire box.

3. A hot air furnace as claimed in claim 1 including means for directing air to the air openings of the heating chamber casing, comprising two separate tortuous passages within the outer casing, each of said passages extending along the bottom of the tire box, back along a side wall thereof, and up along an end wall thereof.

4. A hot air furnace as claimed in claim 3 in which the passage means from the fire box outlet opening runs between the portions of the tortuous passage extending along the end wall of said box.

5. A hot air furnace as claimed in claim 1 in which the means for removing combustion gases from the secondary chamber comprises a pipe extending from said chamber through the passage means between the main heating and plenum chambers and out through the outer casing Wall.

6. A hot air furnace as claimed in claimfi including a pipe running from the pipe extending through the passage means between the heating and plenum chambers up along the adjacent wall of the outer casing and across the top of the latter.

7. In a hot air furnace, a hollow base having a top, an outer casing mounted over the base and having front, back and side walls and a top, an open-topped fire box mounted on the top of the base within the outer casing extending from the front and spaced from the side and back wall thereof, said fire box having a bottom and side and end walls, the end wall of the fire box spaced from the outer casing back wall having an outlet opening therein, the spaces between the side and back walls of the casing and the box forming air passages, opening in the base top near the front wall of the casing between the sides of the box and the casing side Walls, at least one opening in the base remote from the openings in the top thereof, air entering the base through the last-mentioned opening travelling through said base and the top openings thereof into the air passages, a shallow relatively widecasing forming a main heating chamber resting on the top of the fire box and completely closing said top, said heating chamber casing projecting beyond the side walls and said end wall of the fire box to the side and back walls of the outer casing, a wall spaced a little above the heating chamber and extending to the outer casing walls to form therebelow a shallow secondary combustion chamber above said heating chamber, and thereabove a plenum chamber Within the outer casing at the top of the latter, passage means extending from the outlet opening of the fire box through but completely separate from the heating chamber to the secondary combustion chamber, means connected to the secondary chamber to remove combustion gases therefrom, said heating chamber casing having air openings therein near the outer casing back and side 'walls and in communication with said air passages, passage means extending upwardly from the opposite end of the heating chamber casing past the secondary combustion chamber to the plenum chamber, and means connected to the outer casing near the top thereof to remove hot air from the plenum chamber.

8. In a hot air furnace, an outer casing having front, back and side walls, and a top, an open-topped fire box within the casing extending from the front wall and spaced from the side and back walls thereof, said fire box having a bottom and side and end walls, the end wall of the fire box spaced from the outer casing back wall having an outlet opening therein; a shallow relatively wide casing forming a main heating chamber resting on the top of the fire box and completely closing said top, said heating chamber casing projecting beyond the side walls and said end wall of the fire box to the side and back walls of the outer casing, a Wall spaced a little above the heating chamber and extending to the outer casing walls to form therebelow a shallow secondary combustion chamber above said heating chamber, and thereabove a plenum chamber within the outer casing at the top of the latter, passage means extending from the outlet opening of the fire box through but completely separate from the heating chamber to the secondary combustion chamber, said heating chamber casing having air openings therein near the outer casing back and side walls, a hot air duct extending upwardly from the opposite end of the heating chamber casing to the plenum chamber, said duct being the full width of the heating and plenum chambers, a pipe extending from the secondary chamber through said duct and out of the outer casing, and means connected to the outer casing near the top thereof to remove hot air from the plenum chamber.

References Cited in the file of this patent UNITED STATES PATENTS 130,913 Gaston Aug. 27, 1872 400,886 Williams Apr. 2, 1889 661,629 Wattles Nov. 13, 1900 709,107 McDonald Sept. 16, 1902 924,815 Nelson June 15, 1909 1,026,777 Swett May 21, 1912 2,672,858 Iorolemon Mar. 23, 1954

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