GB1590771A

GB1590771A - Heating apparatus

Info

Publication number: GB1590771A
Application number: GB4831/78A
Authority: GB
Original assignee: Vermont Castings Inc
Current assignee: Vermont Castings Inc
Priority date: 1977-09-28
Filing date: 1978-02-07
Publication date: 1981-06-10
Also published as: DE7808996U1; IE780260L; NL7806627A; NO145737B; CH621618A5; NO781278L; DK174778A; SE429261B; ATA222778A; SE7802505L; DE2812962A1; FR2404806A1; AT373373B; BE865139A; DE2812962C2; IE46204B1; NO145737C; FR2404806B1; CA1088831A

Abstract

A heat-conducting cabinet (10) contains a primary combustion chamber (16) and a secondary combustion chamber (30) communicating with said primary chamber (16). A vertical baffle (28) oriented from top to bottom separates said combustion chambers. Part of this baffle (28) stops short of a lower surface of the cabinet to create an opening (31) which connects said primary and secondary chambers and allows the gases to circulate between them. A primary feed pipe (20) introduces air into said primary chamber (16). A secondary feed pipe (32) positioned at least along the baffle (28) oriented from the top introduces preheated air into the secondary combustion chamber (30) through the opening (31). An opening (26) through which the combustion products leave is located at the top of the cabinet (10) and is in communication with the secondary combustion chamber (30). The primary feed pipe (20) introduces the air into the primary combustion chamber (16) through virtually the whole of its width. <IMAGE>

Description

(54) IMPROVEMENTS IN HEATING APPARATUS (71) We, VERMONT CASTINGS, INC., a corporation organised and existing under the laws of the State of Vermont, United States of America of Randolph, Vermont, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed.

to be particularly described in and by the following statement: This invention relates to heating apparatus and concerns heating apparatus which may be used as a stove suitable for burning wood.

Wood-burning stoves have been available for centuries. One well-known wood-burning stove is the Franklin stove which, while being practical for its time, burned wood inefficiently. That stove, like most cast iron stoves available today, provides for updraft combustion, such as is found in a fireplace and in which the volatile gases (volatiles) which are driven off as the wood hllrns are generally left unburned. The ur- burned volatiles remain for two reasons, first because the gases, by the time they have left the wood, are generally too cool for secondary combustion and second, because oxygen that is admitted to the stove coals at the base of the fire mass, causing the gases to rise through an oxygen-deficient atmosphere.The loss of the volatile gases is a serious problem, because they represent approximately half of the total heat value of the wood. It is as though one were to run an open line of natural gas up a chimney without bothering to ignite it first.

In addition, the volatile gases given off from the wood without being ignited may also condense on the cool sides of long metal flue pipes and drip out as creosote which may sometimes be inadvertently and dangerously burned, in their solid creosote form, as a chimney fire.

This invention provides heating apparatus comprising an enclosure of heat conducting material enclosing a primary combustion chamber, a secondary combustion chamber in gaseous communication with said primary combustion chamber, and an arrangement of baffles providing an internal flame path in gaseous communication with said secondary combustion chamber, said flame path having a plurality of horizontally directed passages, a vertically orientated, downwardly directed baffle separating said primary and secondary combustion chambers, a portion of which is spaced from a bottom surface of said enclosure to define an opening connecting said primary and secondary combustion chambers for providing said gaseous communication therebetween, a primary air supply path for providing air from a first controlled inlet port in said enclosure for promoting combustion in said primary combustion chamber, a secondary air supply path for providing air for promoting combustion in said secondary combustion chamber, and a combustion products exit aperture at a top portion of said enclosure and in gaseous communication with said internal flame path.

Preferably, the secondary air supply path extends at least along said downwardly directed baffle for providing preheated air to said secondary combustion chamber at said opening.

Preferably also, a thermostatically controlled air inlet port is provided for supplying air to said primary and secondary supply paths.

Said enclosure may have a pivoting top cover for providing a smokeless loading aperture in said frametop when said top cover is pivoted to an open condition.

A specific embodiment of the present invention will now be described by way of example, with reference to the accompanving drawings in which : Figure 1 is a front perspective view of a heating apparatus according to this invention; Figure 2 is a rear perspective view of the heating apparatus of Figure 1; Figure 3 is a cut-away front perspective view of the heating apparatus shown in Figs. 1 and 2; Figure 4A is a cross-sectional schematic view of the rotatable flue collar in the rear exit position of the apparatus; Figure 4B is a cross-sectional schematic view of the rotatable flue collar in the top exit position; Figure 5 is a cross-sectional view facing the back of the fireback baffle along lines 5-5 of Figure 3; Figure 6 is a cross-sectional view taken along lines 6-6 of Figure 5; Figure 7 is a cross-sectional view taken along lines 7-7 of Figure 3; and Figure 8 is a cross-sectional view taken along lines 8-8 of Figure 5.

Referring to the accompanying drawings and first to Fig. 1, the wood-burning heating apparatus or stove 8 comprises an enclosure 10 preferably of a heavy-duty cast iron. The sides 12a, 12b, front 12c with doors 12e, 12f, back 12g, top 12h, and bottom 12i of the enclosure are joined to form an integral air tight unit. The front pivoting doors 12e, 12f, allow the heating apparatus to be opened from the front for both loading of wood and for viewing the fire when the heating apparatus is used as a fireplace as later described. A ;top cover 14 of the enclosure has hinges 15a, 15b which allow it to pivot to an upward position, whereby wood may be loaded into a primary combustion chamber 16 (Fig. 3) through a smokeless loading aperture 17 when the apparatus is used as a stove as later described.The aperture size is designed to sweep the opening clear of smoke when the top cover is pivoted to an open condition. Preferably the ratio of aperture cross-sectional area to the flue gas output exit cross-sectional area is about three to ne. Thus, even when the stove is in operation, firewood may be reloaded merely by dropping wood into the primary combustion chamber. An asbestos seal around aperture 17 provides an air tight fit between cover 14 and the enclosure.

Referring to Figs. 2 and 3, air is fed to the primary combustion chamber 16 through a primary inlet port 18 and a primary air supply tube 20 (Fig. 3). Inlet port 18 is thermostatically controlled by a thermostat 21 which operates a damper 22 covering an aperture 23 (Fig. 6) in the back 12g of the enclosure. Thermostat 21 is for example an 8" coil of bimetallic material connected to damper 22 by a flexible chain 24. Heating aparatus 8 is also provided with a damper control lever 25, a flue member 26, and a manually controlled night air inlet port 27 in side member 12a.

Referring to Figure 3, primary air entering through aperture 23 travels through primary air supply tube 20 and is heated by the fire which surrounds the tube. Thus, the primary air is preheated and helps to keep a hotter fire going with less air and wood consumed. The primary combustion chamber is bounded by a substantially vertically oriented downwardly extending fireback baffle 28, the side walls 12a and 12b of the enclosure, the front doors 12e, 12f and front wall 12c of the enclosure and the top 12h and bottom 12i enclosure panels.

A right-hand portion 29, of baffle 28 further provides, a partial separation between the primary combustion chamber 16 and a secondary combustion chamber 30. The secondary combustion chamber is connected to and is in gaseous communication with the primary combustion chamber through an opening 31 in baffle 28. A secondary air supply flow path 32 is provided, for the secondary combustion chamber from thermostatically controlled inlet port 18, and comprises an imperforate section 36 (Figure 5) which extends from the inlet port 18 to substantially the downstream end of the secondary combustion chamber and a perforate or apertured conduit 38 which extends within the secondary combustion chamber along a bottom section of baffle 29 around opening 31. The detailed nature of the secondary air supply is described in more detail below.

There is further provided a third air supply path 40 which may be used to provide air from manually controlled inlet 27 to the secondary combustion chamber during night or other selected periods of low heat output operation. Air supply path 40 further provides additional oxygen for secondary combustion in the secondary combustion chamber.

Behind the fireback baffle 28 are a plurality of connecting, horizontally extending smoke passages 104, 106, 108 (Figure 5).

These pasages direct the spent flue gases from the secondary combustion chamber, which may be considered to be the volume behind the aperture 31 and immediately downstream thereof, to the left end of the apparatus, (looking from the front), then into an upper channel or passage 41b and back toward the right portion of the stove, and then further up into an uppermost passage 41c and back toward the left portion of the stove, where they finally exit through the flue collar 26. The secondary combustion chamber, taken together with the smoke passages, make up the flame path. Since the heat of the flue gas is considerable, and is transferred to the surfaces of the stove as the flue gases traverse the passages, a significant amount of heat is given off to the room rather than being lost up the chimney. In addition since the passages are adjacent to the primary combustion chamber, higher temperatures are maintained within the fire inass itself, which aids in burning the volatile gaseous products from the burning wood.

Referring to Figures 4A and 4B, flue collar 26 and the enclosure are adapted to allow the collar to be positioned to provide either a horizontal flue pipe exit (Fig. 4A) or a vertical flue pipe exit (Figure 4B) position. The flue collar is attached to an inclined back portion 50 which is securely positioned on the back and top of the enclosure 10. The flue collar is secured to the inclined surface of the back portion by two flue collar bolts 56 (only one of which is shown in the figures). The two bolts are secured on opposed sides of the flue collar.

Referring to Figure 4A, an extended portion 60 of the flue collar contacts vertically orientated section 62 of the back portion 50 for additional orientation and alignment support. By removing the flue collar bolts, (located on opposite sides of the flue), and rotating the flue collar 1800, the orientation shown in Figure 4B may be obtained.

This orientation provides the top exiting stove and is maintained by replacing the bolts 56. The extended portion 60 of the flue collar 26 is now positioned against the horizontally oriented section 64 of portion 50 Referring to Figures 5 and 6, the thermostatically controlled inlet port 18 preferably supplies air for both the primary and secondary air flow paths. Ambient air enters through aperture 23 in frame back wall 12g and is almost immediately divided between the primary and secondary flow paths by a dividing plate member 70. That portion of the incoming air which passes into the secondary flow path 32 is directed along the fireback baffle 28 and is constrained to follow a path adjacent to the fireback baffle by an enclosing member 72.

Enclosing member 72 not only directs the secondary air flow toward opening 31 in baffle 28, but in order to provide a substantially uniform flow of air into opening 31, the cross sectional area of the supply path defined by enclosing member 72 in combination with baffle 28 increases substantially as the path approaches the opening, as shown in Figure 5. This provides the necessary volume distribution of the flow to promote substantially uniform air flow in the opening. Thus, combustion air is provided substantially evenly around the opening 31. At the opening 31, the enclosing member 72 ends in a substantially spaced apart parallel alignment with the baffle 28, for example at 80 (Fig. 3) so that the flow of secondary air is substantially unimpeded into the secondary chamber at opening 31.The secondary air supplied at opening 31 is also preheated due to its proximity with baffle 28 so that the efficiency of the secondary combustion chamber is increased.

That portion of the ambient air passing through aperture 23 which follows primary flow path 20, passes through the baffle 28 near the lower base of the baffle (Figure 3) and is supplied to the primary combustion chamber along an open ended slotted conduit which extends from baffle 28, along side wall 12a, and for approximately onefifth the distance along the bottom of front wall 12c. The slotted conduit has a cross-sectional area which is substantially constant (Figure 7). The conduit comprises a horizontally extending J-shaped element 84 and a vertically upwardly extending cast member 86 which together define the elongated slot 88. Primary air is thus provided to promote a uniform flow of combustion supporting oxygen across the entire depth of the combustion chamber.

Thus the air provided by primary flow path 20 enters the primary combustion chamber along the bottom left-hand surface of the chamber (looking from the front), and traverses the chamber toward the right hand side panel 12b, providing combustion along the entire bottom of the wood supply. Upon reaching the right-hand portion of the apparatus, the air flow is directed toward and through opening 31 and exits through the circuitous flow path provided by the baffle arrangement extending between baffle 28 and rear wall 12g.

Referring to Figures 5 and 8, the baffle arrangement for directing the flue gases along the circuitous path through the space between baffle 28 and back wall 12g comprises a lower baffle 90 and an upper baffle 92. Lower baffle 90 is comprised of two cast plate members 94 and 96 which meet along their length to form baffle 90 when the fireback baffle 28 is put into position. Baffle 90 extends substantially from side wall 12b to a position near side wall 12Q. Baffle 92 extends above baffle 90 and comprises a pair of tabular, cast, supporting members 98, 100 which support a baffle plate 102 extending substantially from side wall 12a to a position near side wall 12b.The flue gases thereby are directed from a first horizontally directed passage 104 to a second horizontally directed passage 106 and then to a third horizontally directed passage 108 from which they exit through flue collar 26.

The heating apparatus is also provided with a damper 110, controlled by the lever 25, which enables the apparatus both to be used as a parlor stove and as a fireplace.

In the position shown in Figure 8, the apparatus can be used as a fireplace with the flue gases exiting from the primary combustion chamber along a path generally indicated by arrow 114. This provides updraft combustion. When the damper is closed, that is, placed in a position indicated by dotted line 116, the heating apparatus operates as a stove and the flue gases exit substantially as shown by the arrow 120 (Figure 3). (When fuel is loaded into the apparatus through top cover member 14, the flue must be in the closed position or otherwise smoke will pour out of the aperture 17 in the top panel 12h.) Referring to Figures 2 and 8, back wall member 12g has a series of corrugations 122, 124, 126, which protrude outwardly from the plane of back wall member 12g.

These corrugations provide additional heat radiation surfaces for the heating apparatus for increasing the heat delivery to the surrounding air. In addition, the corrugations provide convenient means for channeling "night air" from the manually controlled inlet port 27 to the secondary combustion chamber through night air flow path 40. Thus, the lowermost corrugation 126 is blocked off by a plate 130 and is used to channel the night air into or at least towards the secondary combustion chamber.

The opening 31 has a height of from 3 to 414 inches and is preferably 4 inches high.

A height substantially greater than 4 inches increases the heat output of the heat output of the apparatus and also its conversion efficiency.

The described apparatus, while designed primarily for wood-burning applications, can also be adapted for coal burning. A basket-shaped continer of coal can be inserted through top aperture 17. The basket rests on the bottom 12i of the frame and the coal is then burned in substantially the same manner as when the stove is used to burn wood.

There has been described a compact woodburning heating apparatus having an exceedingly high efficiency due both to its secondary combustion chamber and secondary air supply supporting it, as well as, when the damper is closed, to its long flue gas flow path and horizontal combustion pattern.

A larger wood-burning heating apparatus in accordance with this invention may have its secondary combustion chamber positioned alongside of and not behind the primary combustion chamber.

WHAT WE CLAIM IS: 1. Heating apparatus comprising an enclosure of heat conducting material enclosing a primary combustion chamber, a secondary combustion chamber in gaseous communication with said primary combustion chamber, and an arrangement of baffles providing an internal flame path in gaseous communication with said secondary combustion chamber said flame path having a plurality of horizontally directed passages, a vertically orientated, downwardly directed baffle separating said primary and secondary combustion chambers, a portion of which is spaced from a bottom surface of said enclosure to define an opening connecting said primary and secondary combustion chambers for providing said gaseous communication therebetween, a primary air supply path for providing air from a first controlled inlet port in said enclosure for promoting combustion in said primary combustion chamber, a secondary air supply path for providing air for promoting combustion in said secondary combustion chamber, and a combustion products exit aperture at a top portion of said enclosure and in gaseous communication with said internal flame path.

2. Apparatus as claimed in claim 1, in which the secondary air supply path extends at least along said downwardly directed baffle for providing preheated air to said secondary combustion chamber at said opening.

3. Apparatus as claimed in claim 1 or 2 wherein said secondary air supply path comprises a first imperforate conduit section connected to a supply port and a second apertured section positioned substantially around said opening connecting said primary and secondary combustion chambers for supplying air substantially evenly across a substantial portion of said opening.

4. Apparatus as claimed in claim 3 wherein said secondary air supply path has a variable cross-sectional area, said area being a maximum at approximately the intersection of said imperforate and apertured sections.

5. Apparatus as claimed in claim 2, 3 or 4 wherein said enclosure has a thermostatically controlled inlet port for supplying air to said primary and secondary supply paths.

6. Apparatus as claimed in any preceding claim wherein said enclosure has a pivoting top cover for providing a loading aperture in said frame top when said top cover is pivoted to an open condition.

7. Apparatus as claimed in claim 6 wherein the ratio of the area of the loading aperture to the area of the exit aperture is approximately three to one.

8. Apparatus as claimed in claim 6 or 7 wherein an asbestos sealing member is provided around the top cover for sealing the loading aperture when the top cover is in a closed condition.

9. Apparatus as claimed in any preceding claim further including a flue collar on said enclosure having one position providing a top exiting heating apparatus and in a second position a rear exiting heating apparatus.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. by dotted line 116, the heating apparatus operates as a stove and the flue gases exit substantially as shown by the arrow 120 (Figure 3). (When fuel is loaded into the apparatus through top cover member 14, the flue must be in the closed position or otherwise smoke will pour out of the aperture 17 in the top panel 12h.) Referring to Figures 2 and 8, back wall member 12g has a series of corrugations 122, 124, 126, which protrude outwardly from the plane of back wall member 12g. These corrugations provide additional heat radiation surfaces for the heating apparatus for increasing the heat delivery to the surrounding air. In addition, the corrugations provide convenient means for channeling "night air" from the manually controlled inlet port 27 to the secondary combustion chamber through night air flow path 40. Thus, the lowermost corrugation 126 is blocked off by a plate 130 and is used to channel the night air into or at least towards the secondary combustion chamber. The opening 31 has a height of from 3 to 414 inches and is preferably 4 inches high. A height substantially greater than 4 inches increases the heat output of the heat output of the apparatus and also its conversion efficiency. The described apparatus, while designed primarily for wood-burning applications, can also be adapted for coal burning. A basket-shaped continer of coal can be inserted through top aperture 17. The basket rests on the bottom 12i of the frame and the coal is then burned in substantially the same manner as when the stove is used to burn wood. There has been described a compact woodburning heating apparatus having an exceedingly high efficiency due both to its secondary combustion chamber and secondary air supply supporting it, as well as, when the damper is closed, to its long flue gas flow path and horizontal combustion pattern. A larger wood-burning heating apparatus in accordance with this invention may have its secondary combustion chamber positioned alongside of and not behind the primary combustion chamber. WHAT WE CLAIM IS:

1. Heating apparatus comprising an enclosure of heat conducting material enclosing a primary combustion chamber, a secondary combustion chamber in gaseous communication with said primary combustion chamber, and an arrangement of baffles providing an internal flame path in gaseous communication with said secondary combustion chamber said flame path having a plurality of horizontally directed passages, a vertically orientated, downwardly directed baffle separating said primary and secondary combustion chambers, a portion of which is spaced from a bottom surface of said enclosure to define an opening connecting said primary and secondary combustion chambers for providing said gaseous communication therebetween, a primary air supply path for providing air from a first controlled inlet port in said enclosure for promoting combustion in said primary combustion chamber, a secondary air supply path for providing air for promoting combustion in said secondary combustion chamber, and a combustion products exit aperture at a top portion of said enclosure and in gaseous communication with said internal flame path.

10. Apparatus as claimed in any pre

ceding claim wherein said opening connecting said primary and secondary combustion chambers has a height of from 3 to 441 inches.

11. Apparatus as claimed in claim 10 wherein said opening connecting said primary and secondary combustion chambers has a height of approximately 4 inches.

12. Apparatus as claimed in any preceding claim wherein said enclosure has a corrugated back panel.

13. Apparatus as claimed in any preceding claim wherein said vertically orientated, downwardly directed baffle is parallel to the long dimension of said primary combustion chamber.

14. Apparatus as claimed in claim 13 wherein said primary air path extends and is apertured along a first short side of the primary combustion chamber away from said opening connecting said primary and secondary combustion chambers, said opening being bounded on one side by a short side of the enclosure which also forms the other short side of the primary combustion chamber, whereby the flow of gas across the primary combustion chamber is substantially from said first short side, parallel to said baffle and then through said opening.

15. Apparatus as claimed in any preceding claim wherein said primary air path includes a slotted air tube conduit having a downwardly directed slot and comprising, in cross-section, a J-shaped horizontally directed portion extending from a vertical wall of said enclosure and an upwardly directed vertical portion extending from a horizontal bottom wall of said enclosure.

16. Apparatus as claimed in any preceding claim further comprising a manually controlled air supply path for providing a controlled amount of preheated air from a manually controlled inlet port to said secondary combustion chamber, said air being supplied along a wall spaced away from said baffle.

17. Heating apparatus substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.