GB2081884A - Coal burning space heating stove - Google Patents

Abstract

A wood burning stove converted for coal burning, comprises a removable assembly including a grate assembly (140), means ensuring passage of primary air upwards through the grate assembly, a slotted baffle (142) forming a barrier between primary and secondary combustion chambers, its slots (188) allowing smoke to pass from the primary to the secondary chamber, and a hopper (172, 174). The grate assembly includes four upstanding sides (160, 162, 164) and elongated elements (152, 154, 156) supported to tilt in unison (for riddling) about separate pivot axes. A gap (252) is left between the grate front (162) and the elements (152, 154, 156) to accept a poker. <IMAGE>

Description

SPECIFICATION Coal burning heating apparatus This invention relates to coal burning heating apparatus and in particular to a coal burning parlor stove of high efficiency.

Coal burning stoves have been available for many years. They have been used for centuries in Europe where coal is relatively plentiful. The commercially available European coal burning stoves are therefore highly developed, sophisticated, and in many instances very efficient.

In the United States, coal, like wood, is relatively plentiful and is a comparatively inexpensive alternative to oil, gas or electricity. For many people, coal offers certain advantages over wood in terms of availability, cost, and storage requirements.

Unfortunately however, coal, unlike wood can vary significantly in those characteristics which make it more or less suitable for burning in a home coal stove. Coal is formed from organic matter under great pressure over the years. The variations among coals are related to the differing climatic conditions, different degrees of bacterial action, and the pressure and temperature while the coal is being formed.

Thus, for example, coal can have high inherent moisture content, up to forty percent in lignite; differing degrees of volatiles, high volatile content producing a very smoky burn in most space heaters; and for example different degrees of ash content and fixed carbon. In addition, coal comes in different particulate sizes.

In the United States particularly, the coal burning problem is very difficult if one is attempting to maximize combustion efficiency. The Europeans have developed efficient stoves and these stoves operate with a minimum of difficult. The secret is that the European stove owners are burning European coal and European coal is evenly sized, has a relatively low ash content, and the ash falls easily away from the burning coal in a light flaky powder.

European coal stoves are therefore specifically designed for that type of coal and that type of ash.

Unfortunately, the differences between American and European coal make European stoves generally unsuitable for effective and efficient operation when American coal is used. Ash shakeout and maintenance of proper fuel bed thickness prove to be extremely difficult. Also, the inconsistently sized and shaped American anthracite for example, with its higher, more solid, lumpy ash content, continually foul the grates of the Europen stoves and impede oxygen flow.

Therefore a principal object of the invention is to provide a coal burning heating apparatus for efficiently burning coal of inconsistently sized and shaped lumps which burns to a solid lumpy ash, such as American coal. A coal burning stove should require minimal maintenance, have long life, offer ease of use, and feature long even burning rates. It would be advantageous if the heating apparatus could be converted for either coal or wood burning operation.

According to one aspect of the invention there is provided a heating appliance suitable for burning coal comprising a heat conducting enclosure containing a primary combustion chamber, a baffling arrangement in gaseous communication with the primary combustion chamber, for providing an elongated internal heat exchange path leading to a combustion products exit port, and a primary air supply path for providing air for promoting combustion in the combustion chamber, the enclosure further containing a grate assembly, means for supporting the grate assembly above the primary air supply, means for preventing the primary air escaping from the said combustion chamber without passing through the grate assembly, means for directing unburned coal from a top portion of the appliance to the grate assembly and said grate assembly comprising at least two grate elements, each rotatable about a respective horizontal axis, upstanding front, rear and side walls, means for supporting the front wall grate above the level of the rotatable grate elements for providing access for a slicer element to be inserted for stoking coals in the grate, and means for effecting oscillating movement of the rotatable grate elements.

According to another aspect of the invention, there is provided a heating appliance suitable for burning wood or coal comprising a heat conducting enclosure containing primary and secondary combustion chambers in gaseous communication with one another and a baffling arrangement in gaseous communication with the secondary combustion chamber which establishes an elongated internal heat exchange path leading to a combustion products exit port, the two chambers being separated by an upstanding baffle element which is spaced from a bottom surface of the enclosure to provide an opening for gaseous communication between the two chambers, the appliance including a primary air supply path for promoting combustion in the primary combustion chamber, and a secondary air supply path extending at least along the upstanding baffle for providing preheated air to the opening to the secondary combustion chamber and the appliance further including removable apparatus to adapt it for coal burning comprising (a) means for preventing preheated air at the opening from entering primary combustion chamber and means for communicating exhaust gases from the primary combustion chamber to a first portion of the opening for flow to the secondary combustion chamber and for passage along the elongated heat exchange path, and (b) means for blocking a remaining portion of the opening for preventing air from passing between the primary and secondary combustion chambers, (c) a grate assembly for holding coal, (d) means for supporting the grate assembly above the primary air supply (e) means for effecting an oscillating movement of the grate assembly, and (f) means for directing unburned coal from a top portion of the appliance toward the grate assembly.

The invention also provides, from another aspect, a coal burning equipment for a heating appliance, comprising a grate assembly for holding coal having at least two grate elements, each rotatable about a respective horizontal axis, wall members forming a front, a rear, and two sides of the grate, means for supporting the front above the rotatable grate elements to provide a horizontally-directed slot through which a poker can be inserted for stoking coals, means for supporting the grate assembly in use above an air supply, means for effecting oscillating movement of the grate elements about their horizontal axes, and means for conducting unburned coal toward the grate assembly.

The invention further provides coal burning equipment including a grate assembly for holding coal, which assembly is constructed to allow air to pass from underneath to the coal bed, the said grate assembly comprising (i) a plurality of grate elements each rotatable about a horizontal axis and having first and second elongated supporting members at its opposite ends, the supporting members defining an axis about which the grate supporting portion with a keyed cross section, (ii) grate element supporting means supporting the grate elements for rotary movement about their respective axes; and (iii) grate element oscillating means comprising a plurality of rocker arms, each connected to one of the grate elements at the keyed cross section thereof by way of a corresponding keyed accommodating aperture in the rocker arm, a connection element interlocking the rocker arms for synchronous pivoting movement about their respective rotation axes, and an arm for moving the connection element back and forth in a substantially linear direction whereby said grate elements are oscillated about their rotation axes by rocking movement of the rocker arms.

The invention is now described by way of nonlimiting example. In the preferred embodiment, the appliance features a heat conducting frame member enclosing a primary combustion chamber, a baffle arrangement in gaseous communication with the primary combustion chamber for providing a long internal heat exchange path, and a primary air supply path for providing air, containing oxygen, for promoting combustion in the primary combustion chamber. A combustion products exit aperture is provided at a top portion of the frame in gaseous communication with the baffle arrangement, and serves as an exit port for combustion products.

The heating appliance has a grate assembly for holding coal wherein the grate assembly has at least two grate elements, each rotatable about a respective rotation axis (preferably horizontal) a front vertical grate, a rear vertical grate, first and second side vertical grates, and support elements for supporting the front vertical grate above the level of the rotatable grate elements for providing a horizontally directed slot through which a slicer (i.e. a flat-bladed poker) can be inserted for stoking the coals in the primary combustion chamber.

The grate assembly is supported above the primary air supply for the primary combustion chamber and is equipped with means for preventing the primary air from exiting the primary combustion chamber without first passing through the grate assembly. The coal supply is obtained by directing coal from atop portion of the heating appliance toward the grate assembly. Preferably, this is a gravity feed system.

The grate elements each have an elongated tooth member portion and a central supporting spine, the spine having, at a central portion thereof and in a supporting dimension normal to the plane of the tooth member, a dimensional extent which is greater than the extent of the spine in the normal direction at the end of the toothed member.

Conveniently, the elongated portion of the tooth member has, at its ends, an annular collar or flange for cooperating with a grate side for capturing the latter along its horizontal rotation axis. The grate element is thereby unable to move longitudinally in the horizontal direction.

The coal supply in the preferred embodiment of the invention has a fixed hopper element cooperatively engaged with an upper frame member for directing coal from an aperture in the upper frame and a movable hopper element adjustably secured to the fixed hopper element at a bottom portion thereof for guiding coal from the fixed hopper element toward the grate elements. The fixed hopper element features a construction whereby first and second component members are adapted to meet cooperatively along a substantially vertical plane whereby the components secure the adjustable hopper in a fixed vertical position during operation of the heating member.

A shaker system is provided for oscillating the grate elements and has a plurality of rocker arms, each arm being connected to a great element at a keyed cross section of the grate at its end, the end passing through a corresponding keyed aperture in a rocker arm connection element. The rocker arms are connected and interlocked to the rocker arm connection element for synchronous pivotal moyement about their rotation axes and a connection arm shifting element is provided for moving the connection element back and forth along a substantially linear path whereby the grate elements are oscillated in a rotary motion about their rotation axes by the rocker arms.

Preferably, the connection element has a body portion having integral therewith L-shaped lugs, one lug for each rocker arm. Each lug has a first cross-sectional area near the body member to which the lug is connected and a second keyed crosssectional area spaced apart from the body member.

Each rocker arm has an aperture having a crosssectional area corresponding to the second keyed cross-sectional area and a thickness at the rocker arm aperture no greater than the minimum distance between the keyed cross-sectional area lug portion and the body member. Thereby a rocker arm can lock onto the L-shaped lug and stably and securely rotate around the first cross-sectional portion thereof.

In another aspect of the invention, a conversion kit is provided for converting a wood burning stove to a coal burning stove. The wood burning stove, for example the Vermont Castings Vigilant TM parlor stove, is initially set up in the field for providing efficient wood burning operation. The Vigilant wood stove has a heat conducting frame enclosing a primary combustion chamber, a secondary combustion chamber in gaseous communication with the primary combustion chamber, and a baffle arrangement in gaseous communication with the secondary combustion chamber for providing a long internal heat exchange path.The Vigilant further has a vertically oriented, downwardly directed baffle for separating the primary and secondary combustion chambers wherein a portion of the baffle is spaced from a bottom surface of the frame for providing an opening intercommunicating the primary and secondary combustion chambers and for providing for gaseous flow therebetween. A primary air supply path provides air for promoting combustion in the primary combustion chamber and a secondary air supply path extends along the downwardly directed baffle for providing preheated air to the secondary combuston chamber at the opening. A combustion products exit aperture at the top portion of the frame is in gaseous communication with the baffle arrangement for providing an exit port for combustion products.

The conversion kit, which is suitable for converting stoves like the Vigilant to a coal burning heating appliance, is equipment which features an assembly for preventing preheated air at the opening from entering the primary combustion chamber and includes a first member for directing exhaust gases from the primary combustion chamber through a first portion of the opening to the secondary combustion chamber for passing through the long heat exchange path and a second member for blocking the remaining portion of the opening for preventing secondary air (or combustion products) from passing into the primary combustion chamber from the secondary combustion chamber. A grate assembly for holding coal is provided, a support assembly for maintaining the grate assembly above the primary air supply and an assembly for effecting oscillating movement of the grate assembly are also provided.

Finally, a hopper is provided for directing coal from a top portion of the heating member to the grate assembly under gravity feed conditions. The hopper is adjustable vertically to suit different coal sizes. In further details, the conversion of the Vigilant stove to a coal burning stove can follow the general outline noted above.

In particular, however, according to the preferred embodiment of the invention, the stove is provided with a removable door-type element allowing access to the secondary combustion chamber for removing ash built up therein. Furthermore, a slotted structure is provided for combustion gases escaping from the primary combustion chamber for directing those volatiles toward the secondary combustion chamber.

The invention will now be described in more detail by way of example only with reference to the accompanying drawings, in which: Figure 1 is a front perspective view of the outside of a preferred heating apparatus according to the invention Figure 2 is a rear perspective view of the outside of the preferred heating apparatus according to the invention; Figure 3 is a perspective cutaway front view of the inside of the heating apparatus of Figures 1 and 2 with an internal coal operating assembly removed; Figure 4 is a cross-sectional view along lines 4-4 of Figures 3; Figure 5 is a cross-sectional view along lines 5-5 of Figure 4; Figure 6 is a cross-sectional view along lines 6-6 of Figure 4; Figure 7 is a cutaway perspective front view of the heating apparatus of Figures 1 and 2 showing the preferred coal operating assembly;; Figure 8 is a cross-sectional view along lines 8-8 of Figure 7; Figure 9 is a cross-sectional view along lines 9-9 of Figure 8; Figure 10 is a cross-sectional view along lines 10-10 of Figure 9; Figure ii is a plan view of a typical horizontal grate element; and Figure 12 is a cross-sectional view along lines 12-12 of Figure 7.

The preferred embodiment of the invention, the heating apparatus shown in Figures 1-12 is constructed for burning coal efficiently and can also be converted to a wood burning heating apparatus as described hereinbelow. Conversely, the heating apparatus can be originally purchased as a wood burning device and can be converted to a coal burning stove by application of the principles and the structure of the preferred embodiment. Thus for the purposes of the following description, it should be understood that while the coal burning configuration of the apparatus is the primary configuration being described, the illustrated heating apparatus can be converted from a wood burning configuration to a coal burning configuration and vice versa.

Referring to Figure 1, heating apparatus 8, according to the invention, has an exterior frame or enclosure member 10 preferably made of a heavyduty cast iron. The sides 1 2a, 1 2b, front 1 2c with doors 1 2e, 1 2f, back 129, top 1 2h, at door 14 and bottom 1 2i of the frame member are joined to form an integral airtight unit. The front pivoting doors 12e, 12f, allow the heating apparatus to be opened from the front for both loading if desired and for viewing the combustion when the heating apparatus is used as a fireplace. A top cover 14 of the apparatus, has hinges 1 spa, 1 sub which allow it to pivot to a raised position, whereby coal can be loaded into a primary combustion chamber 16 (Figure 3) through a smokeless loading double door arrangement 17.Top cover 14 is interconnected to a smaller door 1 7a and the combination is designed to maintain the opening substantially clear of combustion gases when the top cover or door 14 is pivoted to an open condition. Thus, even when the stove is in operation, coal can be loaded merely by dropping it into the primary combustion chamber gravity feed hopper 17b (Figure 7). A fireproof seal around the top frame opening provides an air tight fit between cover 14 and the frame member.

Referring to Figures 2 and 3, air is fed to the primary combustion chamber 16 through a primary inlet port 18 and a primary air supply flow path 20 (Figure 3). Inlet port 18 is thermostatically controlled by a thermostat 21 which operates a damper 22 covering an aperture 23 (Figure 6) in the back frame member 129. Thermostat 21 is for example a 5" coil of bimetallic material connected to damper 22 by a flexible chain 24. Heating apparatus 8 is also provided with a damper control lever 25, a rotatable flue member 26, and a manually controlled night air inlet port 27 in side member 12a. (Night air inlet port 27 is of use when the apparatus operates as a wood burning apparatus.) See copending parent application Serial No. 046,326, filed June 7,1979 (a continuation of U.S.Serial No. 837,608, filed September 28, 1977), both of which are incorporated herein by reference. The latter U.S. application has a U.K. equivalent, patent application No.4831178.

Reference may also be made to our copending U.K.

application No. 8021357 dated 30th June, entitled "Improved fuel burning apparatus" which claims a U.S. priority date of 18th June, 1980.

Referring to Figure 3, in which elements essential for efficient coal burning operation have been removed, and wherein efficient wood burning operation can be effected, primary air entering through aperture 23 (Figure 6) travels through primary air supply path 20 to the primary combustion chamber 16. The primary combustion chamber is generally defined by the substantially vertically oriented downwardly extending fireback baffle 28, the side walls 12a and 12b of the frame member, the front doors 12e, l2fandfrontwall 1112c of the fra m e member and the top 12h and bottom 12i frame member panels.

A right-hand portion 29 of baffle 28 further provides a partial separation between the primary combustion chamber 16 and what, if wood were being burned, would be used as a secondary combustion chamber 30. During wood burning operation, the secondary combustion chamber is connected to and is in gaseous communication with the primary combustion chamber through an opening 31 in baffle 28. As described below, when coal is burned, this opening is partially blocked and serves in partto directcombusted gases toward a long heat exchange path.A combined primary/secondary air supply flow path 32 (Figure 4) is provided, for the primary and secondary combustion chambers, from thermostatically controlled inlet port 18, and comprises a first perforate section 36 (Figure 4) which extends from the inlet port 18 to substantially the beginning of the secondary combustion chamber and a second perforate or apertured conduit 38 which extends within the secondary combustion chamber along a bottom section of baffle portion 29 around opening 31.

There is further provided a third air supply path 40 which may be used to provide air from manually controlled inlet 27 (Figure 2) to the secondary combustion chamber for maintaining minimum wood burning activity 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 of the products of wood burning primary combustion.

Behind the fireback baffle 28 are a plurality of connecting smoke passages 104,106,108 (Figure 4).

These passages direct the spent flue gases from the secondary combustion chamber along a long heat exchange path, first to the left end of the apparatus, (looking from the front), then into an upper channel or passage 106 and back toward the right portion of the stove, and then further up into the uppermost passage 108 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 gases 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 primary combustion chamber, which aids in burning the volatile gaseous products from the burning fuel.

The flue collar 26 is preferably rotatable to allow operation of the apparatus with either a horizontal exit or a vertical exit position. The flue collar is attached to an inclined back portion 50 which is securely positioned on the back and top frame portions of the apparatus. The flue collar is secured to the inclined surface of the back portion by two flue collar bolts 56 (only one is shown). The two bolts are secured on opposed sides of the flue collar.

Referring to Figures 4 and 6, the thermostatically controlled inlet port 18 supplies air for both the primary air flow 20 and primary/secondary air flow 32. Ambient air enters through aperture 23 in frame back wall 129 and is almost immediately divided between the flow paths 20,32 by a dividing plate member 70. That portion of the incoming air which passes into the 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 directs the air flow toward opening 31 in baffle 28. Along flow path 32, however, there are apertures 73 in baffle 28 which divert a portion of the flow to the primary combustion chamber.In order to provide a substantially uniform flow of air into opening 31, (during wood burning operation), 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 4. This provides the necessary volume distribution of the flow to promote substantially uniform air flow in the opening. At the opening 31, the enclosing member 72 ends in a substantially spaced apart parallel alignment with the baffle 28, for example at 80 (Figure 3) so thatthe flow of secondary air is substantially unimpended 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 (during wood burning operation) is increased.

That portion of the ambient air passing through aperture 23 which follows primary flow path 20, passes through the baffle 28 nearthe lower base of the baffle (Figure 3) and is supplied to the primary combustion chamber along side wall 12a. A conduit system can be employed during wood burning operation if desired. Primary air is thus provided to promote a continuous flow of combustion supporting oxygen across the entire bottom depth of the combustion chamber.

Referring to Figures 4 and 5, the baffle arrangement for directing the flue gases along the circuitous heat exchange path in the space between baffle 28 and back wall 129 has a lower baffle 90 and an upper baffle 92. Illustrated lower baffle 90 has 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 12a.

Illustrated baffle 92 extends above baffle 90 and has a pair of tabular cast supporting members 98,100 which support a baffle plate 102 extending substantiallyfrom sidewall 12ato a position near side wall 12b. The flue gases thereby are directed from the horizontally directed passage 104 to horizontally directed passage 106 and then to third horizontally directed passage 108 from which they exit through flue collar 26.

The heating apparatus also has a damper which enables the apparatus both to be used as a parlor stove and as a fireplace. In the position shown in Figure 5, 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.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, for wood burning operation, 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 opened position or otherwise smoke will pour out of the aperture in the top panel 12h.) Referring to Figures 2 and 5, back wall member 12g has a series of corrugations 122,124, 126, which protrude outwardly from the plane of back wall member 129. 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.

Referring to Figure 7, wherein the additional components for burning coal have been added, the stove 8, when it is configured for burning coal includes a grate assembly 140, hopper assembly 17b and a plurality of baffles including upstanding baffles 142, 144. An ash pan 146 is also provided.

The addition of these components effectively convert the stove from a wood burning to a coal burning configuration.

The grate assembly 140 has a plurality of rotatable grate elements 152,154, 156, arranged in a horizon tal plane and which are surrounded at their periphery by a vertical grate assembly having a rear vertical grate 160, a front vertical grate 162, and side vertical grates 164 and 166 (see Figures 7 and 8). The elements of the grate assembly define the coal supporting basket wherein coal combustion takes place.

Coal is directed to the grate assembly through the hopper assembly 17b. Illustrated hopper assembly 17b has an upper fixed hopper 172 and a lower adjustable hopper component 174. By adjusting the height of lower hopper component 174 above the upper planar surface of grate elements 152, 154, 156, the height depending primarily upon the coal particulate size to provide a suitable thickness coal burning bed, a properly configured coal burning region can be obtained.

The primary air enters the primary combustion chamber at a level below the grate assembly. it will be recalled that primary air enters through one of two paths. The first path 20 provides the primary air to the left side portion of the apparatus while the second path 32 provides primary air through apertures 73 in baffle 28. It is important that this air not bypass the grate assembly and the bed of burning coal supported therein; and therefore, a baffle structure is employed to prevent the primary air from bypassing the coal bed. At the left side of the grate assembly, baffle member 144 here, in combination with side grate 164, prevent the primary air from bypassing the grate assembly on the left hand portion of the apparatus, the front of baffle 144 mating with the front panel 1 2c of the heating apparatus.A similar structure having baffle 142 and vertical grate 166 prevent primary air from bypassing the coal bed on the right side of the primary combustion chamber. At the front of the grate assembly, vertical baffle 162 has a gasket material 180 secured thereto which provides sealing engagement with the front doors 1 2e and 1 2f when they are closed. This construction prevents primary air from bypassing the grate assembly at the front of the stove.

At the rear of the primary combustion chamber the rear vertical baffle blocks the path of primary air attempting to bypass the coal bed there. Further, at this rear section, a left hand portion of the opening 31, up to at least vertical baffle 142, is blocked by a plate-like element 182 to prevent primary air andlor combustion products from escaping therethrough, to prevent secondary air from being provided thereat, and for cooperating with the baffle 28, vertical rear grate 160, and side grate 142 to prevent primary air from bypassing the grate assembly. In addition, the blockage element 182 is preferably a removable door element which can be removed as desired to permit removal of the ash material accumulating behind it. An ash pan 146 is provided beneath the grate assembly. The products of combustion exit the primary combustion chamber through slots 188.

Referring to Figures 7 and 8, the grate assembly is assembled into the stove in the stove as follows.

Starting from the "empty primary combustion chamber" of Figure 3, the right side baffle member 142 is first placed in position. Next, the rear vertical grate 160 is inserted into its operative position adjacent side baffle member 142 and is in part supported thereby. Baffle 142 thus prevents longitudinal movement of rear grate 160 and helps prevent forward transverse movement of grate 160 by a mating protruding rib member 189. The rib member 189 engages the rear grate in a substantially sealing relationship for preventing either combustion gases from exiting other than through slots 189a or primary air from bypassing the primary combustion chamber.

Next, the left baffle 144 is inserted into the primary combustion chamber and is supported by the rear vertical grate on one side and by a protruding tab member extending from the front frame 12c. Next, a shaker mechanism 192 is assembled outside the stove and is placed into the stove near to its operative position. The shaker assembly, as described in more detail below, has a plurality of rocker arms 194 connecting a connection element 196 to the horizontal grate elements 152, 154, 156. The connection element 196 is moved in a substantially linear direction by a rod member 198 which in turn connects to a shaker handle 200 at the front of the stove.

Next, the horizontal grate elements 152,154,156 are inserted, first into the grate supporting apertures provided in the right baffle 142 and thereafter into the grate supporting apertures provided in the left baffle 144. Before being inserted into the left baffle apertures, however, ends 210 of the horizontal grate elements are inserted through supporting apertures 203 of the rocker arms 194, and then through the apertures in the baffle 144. The grate elements are moved to the left to their extreme stop position (corresponding to the termination of the keyed structure on ends 210); and thereafter the right vertical grate 166 and the left vertical grate 164 are placed in position. Grate 166 is positioned to the right of a flange or collar 206, and resting, in the illustrated embodiment, on the right end 208 of the horizontal grate elements.Each grate element has the flange 206 positioned to the left of right vertical grate 166 to prevent lateral right hand movement of the horizontal grate elements. Thus, the horizontal grate elements are "captured" and are thereby longitudinally fixed in an operative position.

The final element of the grate assembly, the front vertical grate 162 is inserted into capturing channels on the right and left vertical grates respectively.

Thereby the front vertical grate is captured and held against horizontal movement; that is, the interlocking configuration of the side vertical grates and the front vertical grate prevents the side grates from moving in a lateral horizontal direction. There is thus formed a grate assembly defining a coal supporting "basket". The bottoms 207 of the vertical grate elements are preferably "toothed" to further direct primary air into the coal bed.

Each of the illustrated horizontal grate elements 152, 154, 156 has an identical structural configuration (see Figure 11). Each horizontal grate element has at one end, for example an end 208, the flange or collar 206, and at its other end 210, a keyed cross-sectional area which mates with a corresponding keyed area in the rocker arms 194 of the shaker assembly. The keyed cross-sectional portion 210 has a limited longitudinal extent.

The central portion of the horizontal grate elements are "toothed". That is, a series of protruding tooth-like members 212 extend outward on both sides of a central perforated spine 214 (Figures 8 and 11). These grate elements, when in their operative positions, form a substantially planar surface for supporting the coal particulate and yet a substantially open surface for allowing ash to settle therethrough.

The supporting spine 214 is particularly advantageously structured to reduce warpage of the grate element. Therefore, the spine has a greater vertical extent at its center than it does at either end. This greater vertical extent provides greater support and effectively reduces warpage of the horizontal grate elements under the high temperatures to which they can be exposed during the coal burning process.

Referring to Figures 8, 9 and 10, the shaker assembly 192, as noted above, has a connection element 196 which connects the plurality of rocker arms 194 so that, when the connection element is moved along a substantially lineariy directed path by rod member 198, the rocker arms all move simultaneously therewith and pivot about respective horizontal axes 220 of the respective horizontal grate assemblies. Each rocker arm has two apertures, the first upper aperture 203 through which the keyed end 210 of the horizontal grate element extends, and the second aperture, a keyed slot aperture 224 designed to swing around and beneath a key portion of an L-shaped lug 226 which is integral with the connection element 194.Each rocker arm is secured for rotating movement around the L-shaped lugs 226 by passing the rocker arm at the keyed aperture 224, set at a substantial angle preferably greater than 45 to the vertical (Figure 9), over the lug 226, and then rotating the rocker arm to its vertical position.

Thereby, each rocker arm can rotate about the lug 226 for a limited angular extent while remaining stably and securely fastened thereto. The shaker arm rod 198, which had been previously positioned at its free end in an aperture at the end of the connection element 196, extends, at its other end, through the front of the heating apparatus and connects to the shaker handle 200, for movement thereby.

As noted above, the hopper assembly comprises the upper fixed hopper element 172 and a lower moveable hopper element 174. The upper hopper member has integral therewith lugs 201 which rest on the upper frame member 12h at the loading aperture therein. Thus the entire hopper assembly can be easily removed, for example, if it is desired to burn wood.

Hopper element 172 is composed of two components which mate along substantially vertical seams 240 and are connected at the seams, for example, by a screw connection. The upper hopper 172 has door 17a at the top thereof which is interlinked to the upper aperture door 14 so that when the upper door is opened the lower door will thereafter open automatically with it. In this way, condensation at the top of the hopper is reduced and the quantity of gases passing into the area being heated is reduced.

In a preferred embodiment of the invention, the hopper elements are interconnected so that upper hopper member 172 holds lower hopper number 174 in a press fit. The press fit is aided by ribs 242 on the upper hopper components and lip 244 on the lower hopper respectively. The ribs and lip structure provides an increased degree of stability to the hopper system.

The blockage member 182 closes the portion of opening 31 which extends into what will become a slightly reduced size primary combustion chamber.

This blockage member is preferably, for example, screw mounted so that it can be removed periodically to remove ash from behind baffle 28. The ash accumulates there during normal operation of the stove.

In operation, the damper is moved to the open position to obtain higher stack temperatures, for example when the apparatus is operating in the spring orfall, or when the coal is first being lit. Thus the damper advantageously enables the stove to adapt to different coal operating modes of the apparatus.

There is thus achieved a coal burning heating apparatus which provides a large quantity of primary air beneath a grate assembly, which provides baffles to direct the primary air through the grate assembly and hence through the burning coal bed, the air being heated as it passes therethrough to help improve the combustion efficiency in the primary combustion chamber. When the damper is closed, smoke leaving the primary combustion chamber is forced and is directed by baffle 142 (which has the only exhaust opening for combustion products) to exit through a right hand portion 250 of the opening 31. The combustion products thereby pass through the elongated heat exchange path described above and thereby, a higher efficiency coal burning apparatus is achieved.

The illustrated ash removal apparatus is especially effective for American coal. The ash removal system uses a dual operation whereby movement of shaker handle 200 causes axial rotation of the horizontal grate elements 152, 154, 156, and simultaneosuly, the front vertical baffle 162 is supported by the side vertical grates above the plane of the horizontal grate elements so that a slicer member or flat-bladed poker can be inserted into a slot 252 between the bottom of the front vertical grate and the top plane of the horizontal grate elements for further advantageously assisting in ash removal.

Claims (32)

1. A heating appliance suitable for burning wood or coal, comprising a heat conducting enclosure containing primary and secondary combustion chambers in gaseous communication with one another and a baffling arrangement in gaseous communication with the secondary combustion chamber which establishes an elongated internal heat exchange path leading to a combustion products exit port, the two chambers being separated by an upstanding baffle element which is spaced from a bottom surface of the enclosure to provide an opening for gaseous communication between the two chambers, the appliance including a primary air supply path for promoting combustion in the primary combustion chamber, and a secondary air supply path extending at least along the upstanding baffle for providing preheated air to the openings to the secondary combustion chamber and the appliance further including removable apparatus to adapt it for coal burning comprising (a) means for preventing preheated air at the opening from entering primary combustion chamber and means for communicating exhaust gases from the primary combustion chamber to a first portion of the opening for flow to the secondary combustion chamber and for passage along the elongated heat exchange path, and (b) means for blocking a remaining portion of the opening for preventing air from passing between the primary and secondary combustion chambers, (c) a grate assembly for holding coal, (d) means for supporting the grate assembly above the primary air supply (e) means for effecting an oscillating movement of the grate assembly, and (f) means for directing unburned coal from a top portion of the appliance toward the grate assembly.

2. An appliance according to claim 1, wherein the grate assembly comprises at least two grate elements, each rotatably oscillatable about a respective horizontal axis, upstanding grate walls forming a front, a rear and two sides of the grate, and means for supporting the grate front above the level of the rotatable grate elements, thereby providing a horizontally directed slot for a poker for stoking coals in the primary combustion chamber.

3. An appliance according to claim 2, wherein each rotatable grate element is an elongated member having a toothed portion and a central supporting spine, a middle portion of the spine being of greater thickness than towards the ends of the elongated member to guard against warping.

4. An appliance according to any of claims 1 to 3, wherein the apparatus further comprises side baffles, means for supporting the side baffles in spaced apart relationship from the bottom of the enclosure to accommodate a portion of the primary air supply leading to the space beneath the grate assembly, there being supporting apertures in the side baffles and the exhaust directing means allowing for oscillatory movement of portions of the grate assembly.

5. An appliance according to claim 4, wherein the grate assembly includes an elongated toothed member having first and second elongated extensions projecting from respective ends thereof which are received in the supporting apertures to position the toothed member on a horizontally directed rotation axis, one extension having a flange for cooperating with an upstanding grate wall to secure the latter in a given position along the horizontal rotation axis.

6. An appliance according to any of claims 1 to 5, which has a top coal-loading hole and the coal directing means comprises a fixed hopper element open to the hole and a movable hopper element adjustably secured to a bottom portion of the fixed hopper element, for guiding coal from the latter toward the grate assembly, the fixed hopper element having first and second component members adapted to meet along substantially vertical seams and to secure the movable hopper element adjustably therebetween by a press fit.

7. An appliance according to claim 2 or any claim dependent on claim 2, wherein the grate front has a gasket member on a side facing forwardly for providing a seal when a front door assembly of the appliance is closed, whereby primary air from beneath the grate assembly cannot by-pass the coal bed by passing between the front door assembly and the grate front.

8. An appliance according to claim 1, wherein the grate assembly comprises a plurality of grate elements each supported so as to be rotatably oscillatable about a horizontal axis defined by first and second elongated supporting portions at its ends, each grate element having one supporting portion having a non-circular keying portion, and the means for oscillating the grate comprises a plurality of rocker arms, each connected to the keying portion of a respective one of the grate elements, the rocker arms having correspondingly shaped keying apertures therefor, a rocker arm connection element for interlocking with the rocker arms to effect synchronous pivoting movement thereof about their rotation axes, and a connection element shifting arm for moving the connection element back and forth in a substantially linear direction whereby the grate elements are oscillated about their rotation axes by the rocker arms.

9. An appliance according to claim 8 wherein the connection element comprises a member having spaced apart L-shaped lugs integral therewith, one for each rocker arm attached thereto, each lug having a first cross-sectional area nearest the said member to which said lug is connected and a second keyed cross-sectional area spaced apart from said body member, and each said rocker arm has an aperture having a cross-sectional area correspond ing to said keyed second cross-sectional area and a thickness at said rocker arm aperture no greater than the minimum distance between the lug portion having the keyed second cross-sectional area and said body member, whereby a said rocker arm can lock onto the L-shaped lug and stably and securely rotate a limited angular extent around the first cross-sectional portion thereof.

10. An appliance according to any of claims I to 9, further comprising means for removably securing the said blocking means in position whereby the blocking means can be removed for access to the secondary combustion chamber for removing ash accumulating therein.

11. An appliance according to any of claims 1 to 10 wherein the exhaust gas communicating means has slit apertures at an upper portion thereof for gaseous flow from the primary combustion chamber to the secondary combustion chamber.

12. An appliance according to any of claims 1 to 11, further comprising a damper member moveable between a first position wherein combustion products of said apparatus have a high stack temperature and a second position wherein said combustion products have a lower stack temperature.

13. An appliance according to claim 12, wherein the first position of the damper allows combustion products to pass from the primary combustion chamber directly to the exit port, the damper in the second position cutting off direct communication with the port whereby the combustion products are constrained to pass via the secondary combustion chamber and the heat exchange path to the port.

14. Acoal burning equipmentfora heating appliance, comprising a grate assembly for holding coal having at least two grate elements, each rotatable about a respective horizontal axis, wall members forming a front, a rear, and two sides of the grate, means for supporting the front above the rotatable grate elements to provide a horizontallydirected slot through which a poker can be inserted for stoking coals, means for supporting the grate assembly in use above an air supply, means for effecting oscillating movement of the grate elements about their horizontal axes, and means for conducting unburned coal toward the grate assembly.

15. Equipment according to claim 14, wherein the grate elements each comprise an elongated member having a toothed portion and a central supporting spine, the spine having, in a supporting direction normal to the plane of the toothed portion, an extent which is greater at the centre thereof than at the ends of the toothed member

16. Equipment according to claim 14 or claim 15 wherein each of the grate elements comprises an elongated toothed member having first and second elongated supporting extensions projecting from respective ends thereof, the extensions cooperating with apertures in a support to position the grate elements along horizontal rotation axes, one extension of each element having a flange for locating a side wall of the grate along said horizontal rotation axis.

17. Equipment according to claim 14, 15 or 16, wherein the coal conducting means comprises a fixed hopper element for support by a heating appliance and having a coal-receiving aperture, and a movable hopper element, adjustably secured in the fixed hopper element at a bottom portion thereof for guiding coal from said fixed hopper element toward the grate assembly, the fixed hopper element, comprising two component members adapted to meet along substantially vertical seams and to secure the movable hopper adjustably therebetween.

18. Equipment according to any of claims 13 to 17, wherein the grate front has a gasketing member on one side for sealing to the inside of a heating appliance when a front door assembly thereof is closed, to prevent air for combustion from bypas sing the coal bed by passing between the door assembly and the grate front.

19. Equipment according to claim 13, 14, 15,16, 17 or 18, further comprises a damper member moveable between a first position wherein exiting combustion products have a high stack temperature and a second position wherein the combustion products have a lower stack temperature.

20. Coal burning equipment including a grate assembly for holding coal, which assembly is constructed to allow air to pass from underneath to the coal bed, the said grate assembly comprising (i) a plurality of grate elements each rotatable about a horizontal axis and having first and second elongated supporting members at its opposite ends, the supporting members defining an axis about which the grate element rotates, and each grate element having a first supporting portion with a keyed cross section; (ii) grate element supporting means supporting the grate elements for rotary movement about their respective axes; and (iii) grate element oscillating means comprising a plurality of rocker arms, each connected to one of the grate elements at the keyed cross section thereof by way of a corresponding keyed accommodating aperture in the rocker arm, a connection element interlocking the rocker arms for synchronous pivoting movement about their respective rotation axes, and an arm for moving the connection element back and forther in a substantially linear direction whereby said grate elements are oscillated about their rotation axes by rocking movement of the rocker arms.

21. Equipment according to claim 20, wherein the connection element comprises an L-shaped lug for each rocker arm, the lugs each having a first cross-sectional area through which the lug is connected to the connection element and a second, keyed cross-sectional area spaced apart from the connection element and each rocker arm has an aperture having a cross-sectional area corresponding to said keyed second cross-sectional area and a thickness at said rocker arm aperture no greater than the minimum distance between the lug portion having the keyed second cross-sectional area and the connection element, whereby each rocker arm can lock onto its L-shaped lug and securely and stably rotate through a limited angular extent around the first cross-sectional portion thereof.

22. A heating appliance suitable for burning coal comprising a heat conduction enclosure containing a primary combustion chamber, a baffling arrangement in gaseous communication with the primary combustion chamber for providing an elongated internal heat exchange path leading to a combustion products exit port, and a primary air supply path for providing air for promoting combustion in the combustion chamber, the enclosure further containing a grate assembly means for supporting the grate assembly above the primary air supply, means for preventing the primary air escaping from the said combustion chamber without passing through the grate assembly, means for directing unburned coal from a top portion of the appliance to the grate assembly and said grate assembly comprising at least two grate elements, each rotatable above a respective horizontal axis, upstanding front, rear and side walls means for supporting the front wall grate above the level of the rotatable grate elements for providing access for a slicer element to be inserted for stoking coals in the grate, and means for effecting oscillating movement of the rotatable grate elements.

23. The appliance according to claim 22, wherein the supporting means includes apertures, for supporting the rotatable grate elements for rotary movement, the apertures being provided in the air escape preventing means.

24. The appliance according to claim 23 wherein each grate element comprises an elongated toothed member having two elongated supporting portions extending from its respective ends and received in the said supporting apertures to position the grate element along a horizontally directed rotation axis, one elongated supporting portion having an annular collar for locating a grate side along the horizontal rotation axis.

25. The appliance according to claim 22, 23 or 24, further wherein the grate elements each comprise an elongated member having a toothed portion and a central supporting spine having at a central portion thereof, in a supporting dimension normal to the plane of the toothed portion, a depth which is greater than the depth at the ends of the toothed member.

26. The appliance according to any of claims 22 to 25, wherein the coal directing means comprises a fixed hopper element for receiving coal from an aperture in the enclosure, and a movable hopper element, adjustably secured to a bottom portion of the fixed hopper element for guiding coal from the fixed hopper element toward the grate elements, the fixed hopper element having first and second component members which meet along substantially vertical seams and have means for securing the movable hooper in a fixed position.

27. The appliance according to any of claims 22 to 26, wherein the grate front has a gasketing member on a side thereof facing the front of the heating appliance member for providing a seal when a front door assembly is closed, so that air from beneath the grate assembly cannot by-pass the combustion region by passing betwenn the front door assembly and the grate front.

28. The appliance according to any of claims 22 to 27, wherein the grate assembly comprises a plurality of grate elements each rotatable about a horizontal axis and having two elongated supporting portions, at its opposite ends, which define a rotation axis for the grate element, and each grate element having a first end with a keyed cross section; the said supporting means supports the grate elements for rotary movement about their respective axes, and the grate oscillating means comprise a plurality of rocker arms, each connected to a keyed cross section of a respective grate element by way of a corresponding keyed aperture in the rocker arm, a rocker arm connection element interlocking with the rocker arms for effecting synchronous pivoting movement of the grate elements about said rotation axes, and an arm for moving the connection element back and forth in a substantially linear direction to oscillate the grate elements in a rotary motion.

29. The appliance according to claim 28, wherein the connection element comprises a body member having integral therewith an L-shaped lug for each rocker arm, each lug having a first cross-sectional area adjacent the body member to which the lug is connected and a second keyed cross-sectional area spaced apart from the body member, and each rocker arm has an aperture having a cross-sectional area corresponding to said keyed second crosssectional areas, and a thickness at said rocker arm aperture no greater than the minimum distance between the keyed second cross-sectional area lug portion and the body member, the arrangement being such that each rocker arm can lock onto its L-shaped lug and stably and securely rotate around the first cross-sectional portion thereof.

30. The appliance according to any of claims 22 to 29, further including a damper member moveable between a first position wherein exiting combustion products have a high stack temperature and a second position wherein the combustion products exiting the appliance have a lower stack temperature.

31. A heating appliance able to burn wood or coal, substantially as herein described with reference to and as shown in the accompanying drawings.

32. Coal burning equipmentfora heating ap pliance, substantially as herein described with refer ence to and as shown in Figures 7 to 12 of the accompanying drawings.