GB2210450A

GB2210450A - Stoking solid fuel

Info

Publication number: GB2210450A
Application number: GB8822292A
Authority: GB
Inventors: Paul Wells
Original assignee: A J Wells & Sons
Current assignee: A J Wells & Sons
Priority date: 1987-09-30
Filing date: 1988-09-22
Publication date: 1989-06-07
Also published as: GB8822292D0; GB8722988D0

Abstract

A solid fuel stove or fireplace has a fire plate 1 with transverse slots 2. Fuel is mechanically fed to the fire plate by a screw feed mechanism 13, 26. Air is supplied through the slots 2 from an air feed 17. The fire on the fire plate 1 burns in a dispersed manner with a conventional solid fuel glow. An ash removal mechanism may be provided (Figs. 5, 6). <IMAGE>

Description

A SOLID FUEL BURNER Field of the Invention The present invention relates to a solid fuel burner, primarily but not exclusively, for domestic use and having a mechanical fuel supply.

Background of the Invention Domestic boilers employing a gravity feed for solid fuel are well known. It is also known to provide a mechanical supply of solid fuel to a fire in a domestic boiler. A retort in the shape of a funnel or invert cone is provided with fuel supplied at its lower apex. Air is introduced peripherally of the retort and combustion occurs within the retort. As combustion continues and as fuel is supplied to the retort ash spreads radially from the upper, open mouth of the retort. The fire is very hot and indeed appears white hot as opposed to a conventional orange colour of a coal fire.

Such a retort has been tested in an open fire and has been found to be unattractive, the reason being that a very hot, small central fire surrounded by ash is visually unattractive.

The Invention The present invention has as an object to provide a solid fuel burner which is visually acceptable in an open fire and/or in a stove.

A solid fuel burner in accordance with the invention comprises: an apertured fire plate; means for mechanically supplying solid fuel to a top side of the fire plate at one edge thereof, and means for supplying air for combustion to an underside of the fire plate, combustion occurring in use on the fire plate with burnt fuel being replaced by further fuel from the supply means.

Preferably the fire plate is arranged to be substantially horizontal in use.

Such a solid fuel burner can be regulated for its fuel to burn in a dispersed manner, that is with the fire not being concentrated centrally, and as such is visually attractive.

Normally the solid fuel will burn with an ash residue.

Conveniently an ash receptacle is provided oppositely of the burner plate from the edge at which the fuel is supplied. It should be noted that some ash may pass through the apertured fire plate but that this will normally be a small proportion only and that the apertured fire plate is in this respect dissimilar from a conventional grate through which the majority if not all of the ash is intended to pass. Means may be provided for mechanically removing the ash from its receptacle.

Preferably the apertures in the fire plate are arranged generally transverse to fuel movement over the plate from the supply means. They may be slots. Ribs may be provided on the fuel supply side of the slots to protect the slots from filling with fuel and/or passing ash. These ribs conveniently are inclined to partially over-lie the slots. The ribs - and associated slots - may be disposed and oriented to encourage spreading of the fuel over the plate. In the preferred embodiment the slots and ribs are arranged in chevron formation.

Whilst it is envisaged that the air supply means may be convective, especially where the burner is incorporated in a stove; the air supply means preferably incorporates an air blower for forced supply of air to the underside of the fire plate. Preferably the burner is controlled by control means adapted to cause the fuel supply means to supply fuel and the air supply means to supply air at variable but complementary rates. In the preferred embodiment, the air supply means has a blower operated by a variable speed motor whilst the rate of supply of the fuel supply means is varied by varying its ON-OFF period ratio.

The fuel supply means and the ash removal means conveniently each comprise a screw feed, although other mechanisms can be envisaged such as a chain conveyor or a vibrator feed or a ram feed. Spirally coiled solid steel screw members have been found to be particularly suitable. Solid fuel can include debris liable to jam the fuel supply means.

This latter preferably includes weak drive links, conveniently shear pins, arranged to fracture in event of jamming.

Means is preferably provided for detecting a fuel feed jam. This may be in the form of a detector of temperature at the fuel exit from the supply means, which detects the drop in temperature as the fire dies down and causes the air supply blower to be switched off. Alternatively, a temperature detector may be provided at a drive motor for the supply means to detect rise in temperature of the motor on incipient jamming of the fuel and to switch off the air blower.

To help understanding of the invention, three specific embodiments thereof will now be described with reference to the accompanying drawings, in which: Figure 1 is a side view of a burner of the invention installed in an open fireplace; Figure 2 is a lager scale scrap plan view of the burner of Figure 1; Figure 3 is a scrap side view in partial cross-section of the burner of Figure 1; Figure 4 is a side view similar to Figure 1 of a burner of the invention installed in a stove; Figure 5 is a view similar to Figure 1 of a similar burner of the invention equipped with ash removal means; and Figure 6 is a view similar to Figure 3 of the burner of Figure 5.

First Embodiment of the Invention Referring first to Figures 1 to 3, the burner has a fire plate 1 which is of trapezium shape in plan. The plate 1 is of plate steel and has six slots 2 arranged in chevron formation, with their inner ends closer to the shorter parallel edge 3 of the plate 1. Each slot 2 is partially overlain by a respective steel rib 4 welded to the plate 1 at the edge of its slot 2 nearer the edge 3 of the plate and extending at approximately 300 up and over the slot 2. The extent of the ribs 4 is such as to just cover the slots 2 in plan whereby any fuel or ash pushed over the slots - as described below - will not fall directly from the free edges of the ribs into and through the slots. The ribs 4 are of course in the same chevron arrangement as the slots 2.

The fire plate 1 is removably accommodated in a fabricated steel structure 5 which has a base plate 6. The fire plate 1 is removable for cleaning of the base plate 6 in the event of a small quantity of ash and/or fuel dust falling onto the base plate 6. Integrally fabricated with the structure 5 is a fuel reception chamber 7. This has a bottom plate 8 at the same level as the fire plate 1, two side plates 9,10, in alignment with the angled edges 11 of the fire plate, whereby the fuel reception chamber 7 tapers rearwardly, and a top plate 12. A fuel supply duct 13 of circular section steel pipe is welded to a rear wall 14 of the fuel reception chamber 7. Fuel supplied forwards along the duct 13 fills the chamber 7 to the full width of the fire plate edge 3. The chevron formation of the ribs 4 spreads the fuel to cover the fire plate 1 as the fuel is moved forwards - whilst burning - over the fire plate.

The top plate 12 and rear wall 14 extend laterally beyond the side plate 10 to define with a further, outer side 15, the base plate 6, lower extensions of side plate 9 and the rear wall 14 and the framework 5, a plenum chamber 16. This underlies the fuel reception chamber 7 and the fire plate 1.

Combustion air is prided via a duct 17 welded to the rear wall 14 to the plenum chamber 16 and passes up through the slots 2 for burning of the fuel on the fire plate 1.

At the front edge of the fire plate 1 an ashpan 19 is provided for receiving ash which falls forward over the front edge 18. The burner is installed in an otherwise conventional fireplace having a fire back 20 and a decorative front 21.

Behind the burner, outdoors as shown, a fuel hopper 22 is provided. Beneath the fuel hopper 22 within a protective housing 23 is arranged a variable speed air blower 24 at the rear end of the air duct 17. The fuel supply duct 13 is connected to a chute 5 of the hopper 22. A coiled-steel-rod, fuel-feed-screw 26 extends in the duct 13 from a rear end 27 of this forwards under the chute 25 as far as the rear of the fuel reception chamber 7. At the rear end 27 of the duct 13, the feed screw 26 is driven by a shaft 28 journalled at the rear end 22 and in turn driven by a chain and sprocket drive 29 from motor and gear box 30. Its sprockets and the shaft 28 are drivingly connected by a shear pin 31. Control circuitry in a box 32 is housed in the housing 23 and operated by a control 33 at the fireplace.

In use fuel F, conveniently so-called pearls, in the hopper 22 is fed intermittently forwards through the duct 13, to the chamber 7 and burns on the fire plate 1. Air is continuously blown forwards through the air duct 17 to the plenum chamber and up through the slots 2 to the burning fuel Via the control 33, the volume rate of the air blower 24 is varied. The fuel feed motor 30 is of a fixed type, but the fuel flow rate is controlled in accordance with the air flow rate by varying the length of intermittent, repeated fuel feed periods.

Solid fuel can contain debris. Should this jam the feed screw 26, the shear pin 31 will fracture and fuel supply will cease. The fire will go out without burning into the fuel reception chamber 7 because air is not supplied along the fuel supply duct 13. To switch off the air supply in event of the fire going out, a temperature transducer 34 positioned on the bottom plate 8 is arranged to stop the air blower 24 (and the motor 30) in the event of a drop in temperature of the chamber 7. A further temperature sensor 35 is positioned on the fuel feed motor 30, whose temperature may rise in the case of an incipient fuel jam prior to a complete jamming and shearing of the pin 31 and consequent ceasing of fuel supply. The sensor 35 is arranged to stop the air blower 24 and switch off the fuel feed motor 30 in the event of a rise in temperature of this.Whichever sensor operates, burning down of the fire will alert the householder of the need to clear the fuel jam.

Second Embodiment In an alternative embodiment shown in Figure 4, the fuel burner is incorporated into a stove 40. This has a steel or cast iron body 41 having open-able front doors 42 with translucent panels 42' whereby the glow of the fire can be felt and seen even with the doors 42 closed. A fire plate 101, fuel reception chamber 107, plenum chamber 116, fuel supply duct 113 and air supply duct 117, equivalent to the components 1,7,16,13 and 17 are provided and will not be described in detail. The rear wall 114 of the fuel reception chamber 107 is incorporated as part of the rear wall 43 of the stove. The base plate 106 of the burner structure 105 and plenum chamber 116 is spaced above the bottom wall 44 of the stove, and an ashpan 45 is positioned between the base plate 106 and bottom wall 44.The stove is in other respects conventional having a baffle plate 46 and optional boiler panels 47. The burner within the stove operates in like manner to the burner of Figure 1 in the fireplace.

Third Embodiment Referring now to Figures 5 and 6, the burner there shown is identical to that of Figures 1 to 3 except that ash removal means 250 is additionally provided. A fire plate 201, fuel reception chamber 207, plenum chamber 216, fuel supply duct 213, fuel drive screw 226, chain and sprocket drive 229, fuel hopper 222, fuel chute 225, drive motor (not shown), air supply duct 217, and air blower 224, are all provided and will not be described in detail.

The deep ash pan 19 is replaced by a shallower ash collector 251 positioned to receive ash falling over the front edge 218 of the fire plate 201. The ash removal means has a spiral steel-rod screw 252 which extends in an ash duct 253 and ends at its front end in the ash collector 251. The ash duct is welded to the ash collector. It extends back beneath the plenum chamber 216 and in line beneath the fuel supply duct 213. Beneath the mouth of the fuel chute 225, the ash duct 253 has a depending opening 254. The screw 252 extends back to a drive sprocket 255 which is in mesh with the chain 229. Thus the ash removal screw 251 is driven in synchronism with the fuel supply screw 226 when the drive motor (not shown) activates the latter. Thus the screw 252 draws ash from the ash collector 251 to the opening 254 when it falls into a removable container 256. Since the ash is cold by the time it reaches the opening 254, the container can be provided with a plastics material liner 257 which is conveniently secured around the opening 254.

Claims

1. A solid fuel burner comprising: an apertured fire plate arranged to be substantially horizontal in use, means for mechanically supplying solid fuel to a top side of the fire plate at one edge thereof, and means for supplying air for combustion to an underside of the fire plate, combustion occurring in use on the fire plate with burnt fuel being replaced by further fuel from the supply means.

2. A solid fuel burner as claimed in claim 1, wherein the fire plate is arranged to be substantially horizontal in use.

3. A solid fuel burner as claimed in claim 1 or claim 2, including ash reception means at another edge of the fire plate, mechanical supply of fuel displacing ash over the other edge into the reception means.

4. A solid fuel burner as claimed in claim 3, including means for mechanically removing ash from the ash reception means.

5. A solid fuel burner as claimed in any preceding claim, wherein the fuel supply means and the ash removal means where provided is/are screw feed(s).

6. A solid fuel burner as claimed in claim 5, wherein the screw feed(s) incorporate(s) spirally coiled solid steel screw member(s).

7. A solid fuel burner as claimed in claim 4 or either of claims 5 and 6 as appendant to claim 4, wherein the ash removal means extends beneath the fire plate with the fuel being supplied to the one edge towards the back of the burner and the ash being removed from its reception means at the front of the burner.

8. A solid fuel burner as claimed in claim 7, wherein the fuel supply means and the ash removal means extend substantially horizontally with the fuel supply means being arranged over the ash removal means.

9. A solid fuel burner as claimed in claim 8, wherein the fuel supply means includes a connection for a fuel hopper above the supply means and the ash removal means includes a connection for an ash disposal container beneath the removal means.

10. A solid fuel burner as claimed in any preceding claim, wherein the apertured fire plate includes elongate apertures for air supply, the apertures extending generally transverse to fuel movement over the plate from the fuel supply means.

11. A solid fuel burner as claimed in claim 10, wherein the elongate apertures are arranged in chevron formation, with the apertures converging towards the fuel supply-means.

12. A solid fuel burner as claimed in claim 10 or claim 11, wherein the elongate apertures are provided with ribs on the fuel supply side thereof.

13. A solid fuel burner as claimed in claim 12, wherein the ribs are inclined to at least partially over-lie the apertures.

14. A solid fuel burner as claimed in any preceding claim, including a structure incorporating a fuel reception chamber arranged to receive fuel from the fuel supply means and an air plenum chamber arranged to receive air from the air supply means, the fire plate being accommodated on the structure with its one edge at a fuel outlet of the fuel reception chamber and the fire plate at least partially over-lying the plenum chamber.

15. A solid fuel burner as claimed in claim 14, wherein the fuel reception chamber opens progressively from an output end of the fuel supply means to its outlet and is arranged above and behind the fire plate.

16. A solid fuel burner as claimed in claim 15, wherein the plenum chamber extends at once beside and below the fuel reception chamber (as well as below the fire plate) whereby the air supply means has an output to the plenum chamber adjacent the output to the fuel reception chamber from the fuel supply means and the air supply means extends parallel to the fuel supply means.

17. A solid fuel burner as claimed in claim 16, including a temperature detector on the fuel reception chamber for switching off the fuel supply means in the event of a blockage thereof.

18. A solid fuel burner as claimed in any preceding claim, wherein the air supply means is convective.

19. A solid fuel burner as claimed in any one of claims 1 to 17, wherein the air supply means includes an air blower.

20. A solid fuel burner as claimed in claim 19, wherein including a controller for varying together the speed of the air blower and the on/off period ratio of the fuel supply means and the ash removal where provided to match air supply to fuel feed.

21. A solid fuel burner as claimed in any preceding claim, wherein the burner is adapted for use as an open fire.

22. A solid fuel burner as claimed in any one of claims 1 to 21, wherein the burner is adapted for use in a stove.

23. A solid fuel burner substantially as hereinbefore described with reference to Figures 1 to 3 or Figure 4 or Figures 5 and 6 of th? accompanying drawings.