GB2198523A - Solid-fuel-fired ranges - Google Patents

Abstract

A solid-fuel-fired appliance has a combustion chamber from which products of combustion are withdrawn through ducts which exit from the chamber via separate outlets 9, 10 located adjacent the fuel bed at a level where the bed is incandescent, the products being brought immediately into contact with a water jacket 11 associated with one duct and an oven structure 14 associated with the other. A user operated flap valve 18 controls the flow of combustion products through either one duct or the other. <IMAGE>

Description

Solid-Fuel-Fired Applicences This invention relates to solid-fuel-fired appliances having a dual or multiple function and is especially, but not exclusively applicable to appliances having cooking and water heating facilities.

One of the problems with solid-fuel appliances is the variation in temperature of combustion products which arises when the fuel bed is periodically recharged with fresh unburnt fuel. In cases where products of combustion leave the combustion chamber at or adjacent the upper end thereof, that is to say after having passed through the fuel bed, there is a substantial drop in temperature immediately after the bed is recharged with fresh unburnt fuel because the latter cools combustion products passing through the fuel bed.

A further problem arising in the case of dual or multiple function appliances is drop in temperature of combustion products after leaving the combustion chamber and before transferring heat to sections of the appliance used for the selected function, for example for cooking or water heating. This requires higher heat output from the combustion chamber than would otherwise be necessary in order to make up for heat losses.

It is an object of the present invention to obviate or mitigate these problems.

According to the invention there is provided a dual or multiple function solid-fuel-fired appliance comprises a combustion chamber within which a fuel bed is supported in use, and alternative flow paths exiting from the chamber through separate outlets at the lower region of the chamber such that, in use, combustion products pass directly from an incandescent zone of the fuel bed to said flow paths, each of said flow paths including heat transfer members associated with one of the functions of the appliance.

Preferably means is provided for selectively opening and closing said flow paths whereby to divert the major proportion of the combustion gases to a selected one of said functions.

In the case of appliances having both cooking and water heating functions, the appliance includes a water jacket and an oven structure, a first one of said flow paths directing products of combustion into heat exchanging relationship with said water jacket, and a second one of said flow paths directing products of combustion into heat exchanging relationship with said oven structure.

Said flow paths are preferably connected at a common junction downstream of said water jacket and said oven structure, valve means being located at said junction and being operable to selectively close one of said flow paths and open the other.

Preferably said first flow path passes directly into said water jacket from the associated combustion chamber outlet and is surrounded by the water jacket.

The flow path advantageously traverses a tortuous path through the water jacket to maximise heat transfer thereto.

Preferably also said second flow path is defined by a wall of said combustion chamber and a wall of said oven structure, the latter wall preferably being finned to increase the surface area available for heat transfer to the oven structure.

Said second flow path may communicate with a hot plate structure between said oven structure and said common junction whereby to transfer heat to said hotpl-ate structure.

The invention also provides a method of reducing heat loss in a solid-fuel-fired appliance having a dual or multiple function comprising withdrawing products of combustion from an incandescent zone of the fuel bed of the appliance along separate flow paths each in direct contact with said zone and bringing said combustion products into immediate contact with heat transferring components associated with respective ones of said functions.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawing which is a transverse vertical section through part of a domestic solid-fuelfired heating and cooking appliance incorporating the invention.

Referring to the drawings, the appliance includes a combustion chamber 1 bounded on one side by a water jacket 2 containing water to be heated, and on the other side by an oven structure 3. Solid-fuel to be combusted in chamber 1 is supported on a grate 4 located at the lower end of the combustion chamber 1. The combustion chamber is bounded by side walls 5, 6, a rear wall 7, a top wall 8 and a front wall (not shown) having a fuel door (not shown) through which the grate 4 is charged with fuel for combustion. Ashes from the grate 4 are withdrawn from an ash pit beneath the grate by way of a suitable opening (not shown), air to support combustion of fuel on the grate 4 being supplied through the ash pit.

Products of combustion may flow from the combustion chamber 1 via separate outlets 9 and 10 located towards the lower region of the chamber just above the grate 4 at a level where there is always a zone of incandescent fuel when the appliance is in use. Thus, the combustion products leaving the combustion chamber flow directly to the outlets 9 and 10 from the incandescent fuel zone and are at a substantially constant temperature determined by the degree of incandescence.

Products of combustion leaving the chamber 1 by way of outlet 9 pass immediately into a duct 11 defining a flow path which passes through the water jacket 2.

Duct 11 communicates at its upper end with an outlet flue 12 leading to an outlet terminal or a chimney (not shown). The duct 11 follows a tortuous path through the water jacket 2 and portions of the water jacket are disposed on both sides of the duct 11, both of which features increase heat transfer to the water jacket.

Products of combustion leaving the combustion chamber by way of outlet 10 enter a duct 13 constituting a second flow path defined between wall 6 of the combustion chamber and a wall 14 of the oven structure 3.

The wall 14 carries a series of spaced parallel heat transferring fins 15 which lie parallel with the direction of flow of combustion products through the duct 13 and maximise heat transfer to the oven structure. At its upper end the duct 13 joins a passageway 16 extending horizontally beneath the upper surface of the appliance. Part of the upper surface is constituted by a hotplate 17 which is heated by the flow of combustion products along the pasageway 16. The lower surface of the hotplate and/or the upper surface of the top wall 8 of the combustion chamber may be finned to increase heat transfer. At its outlet end passageway 16 communicates with the outlet flue 12.

Located at the junction of the duct 11 and passageway 16 with the outlet flue 12 is a flow control valve shown as a flap valve 18 pivotally mounted on a horizontal spindle 19 so as to be movable between a first position 20 in which it is clear of the upper end of duct 11 and closes the end of passageway 16, and a second position 21 in which it is clear of passageway 16 and closes the upper end of duct 11. The flap valve 18 is operable by a user by means of a control handle located externally of the appliance and not shown in the drawing.

When a user wishes to use either the oven or the hotplate or both, that is the cooking facility of the appliance, the flap valve 18 is operated to bring it into position 21 in which the upper end of duct 11 is closed. This prevents the flow of combustion products along duct 11 and greatly reduces heat input into the water jacket 2. Combustion products can leave the chamber 1 only via duct 13 and passageway 16 so heating the oven structure 3 and hotplate 17.

When the oven and/or hotplate is no longer required, the user moves the flap valve 18 to position 20. Flow of combustion products along duct 13 and hence heating of the oven structure 3 and hotplate 17 ceases.

The opening of duct 11 permits the flow of combustion products from outlet 9 through the water jacket to the outlet flue 12, thereby heating the water jacket 2 and bringing the water heating facility of the appliance into operation.

It will be understood that during use of the cooking facility, heating of the water jacket 2 does not cease completely, as a certain amount of heat from the combustion chamber wil be transferred by conduction through the structure of the appliance. However, the major part of the heat output from the combustion chamber passes to the oven structure and the hotplate.

By virtue of the arrangement described both water heating and cooking facilities can be provided in a single appliance combined with efficient operation and controllability. By withdrawing combustion products at the lower region of the combustion chamber where the fuel bed is incandescent, the temperature of the combustion products is essentially stable and largely unaffected by re-fuelling. By the provision of separate outlets each leading directly to the water heating and cooking functions, heat loss before transfer to these functions is minimised. In addition the provision of a multiple pass flow path passing through and hence surrounded by the water jacket provides efficient transfer of heat to the water.

Various modifications may be made without departing from the invention. For example the appliance may be a solid-fuel-fired space heating and cooking appliance which may or may not include water heating facilities. The hotplate described in the embodiment may be omitted and the flow path through the water jacket could be a single pass path. Where a multiple pass flow path is provided flow control means may be incorporated to select the passes utilized dependent on heat output required.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims (16)

1. A dual or multiple function solid-fuel-fired appliance comprises a combustion chamber within which a fuel bed is supported in use, and alternative flow paths exiting from the chamber through separate outlets at the lower region of the chamber such that, in use, combustion products pass directly from an incandescent zone of the fuel bed to said flow paths, each of said flow paths including heat transfer members associated with one of the functions of the appliance.

2. An appliance according to claim 1 wherein means is provided for selectively opening and closing said flow paths whereby to divert the major proportion of the combustion gases to a selected one of said functions.

3. An appliance according to claim 1 or 2 having both cooking and water heating functions, the appliance including a water jacket and an oven structure a first one of said flow paths directing products of combustion into heat exchanging relationship with said water jacket, and a second one of said flow paths directing products of combustion into heat exchanging relationship with said oven structure.

4. An appliance according to claim 3, in which the flow paths are connected at a common junction downstream of said water jacket and said oven structure, valve means being located at said junction and being operable to selectively clo.se one of said flow paths and open the other.

5. An appliance according to claim 3 or 4 wherein said first flow path passes directly into said water jacket from the associated combustion chamber outlet.

6. An appliance according to any of claims 3 to 5 wherein said first flow path is surrounded by said water jacket.

7. An appliance according to any of claims 3 to 6 wherein said first flow path transverses a tortuous path through said water jacket.

8. An appliance according to any of claims 3 to 7 wherein said second flow path is defined by a wall of said combustion chamber and a wall of said oven structure.

9. An appliance according to claim 8 wherein said wall of said oven structure is finned to increase the surface area available for heat transfer to the oven structure.

10. An appliance according to any of claims 3 to 9 wherein said second flow path communicates with a hotplate structure between said oven structure and said junction.

11. A solid-fuel-fired appliance substantially as hereinbefore described with reference to the accompany drawing.

12. A method of reducing heat loss in a solid-fuelfired appliance having a dual or multiple function comprising withdrawing products of combustion from an incandescent zone of the fuel bed of the appliance along separate flow paths each in direct contact with said zone and bringing said combustion products into immediate contact with heat transferring components associated with respective ones of said functions.

13. A method according to claim 12 wherein flow of combustion products is restricted to one of said flow paths at any one time.

14. A method according to claim 12 or 13 wherein said functions comprise a water heating function and a cooking function.

15. A method of reducing heat loss in a solid-fuelfired appliance having a dual or multiple function substantially as hereinbefore described.

16. Any novel subject matter or combination including novel subject matter disclosed in the foregoing specification or claims and/or shown in the drawings, whether or not within the scope of or relating to the same invention as any of the preceding claims.