AU673594B2 - Gas burner - Google Patents

Description

1-

AUSTRALIA

PATENTS ACT 1990 COMP L E T E SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

so e o e 4 e e *f k Name of Applicant: JETMASTER FIREPLACES PTY LTD A.C.N. 003 900 203 Actual Inventor: Address for Service: Invention Title: DAVID FORRESTER SHELSTON WATERS Margaret Street SYDNEY NSW 2000 "GAS BURNER" Details of Associated Provisional Application No: PL9524 dated 22nd June, 1993 The following statement is a full description of this invention, including the best method of performing it known to us:- 2 The present invention relates to gas burners and in particular gas burners for use in gas fired imitation coal or log fires or the like.

In the past, decorative gas fires of the kind described above have generally utilised a gas burner comprising a pipe having a plurality of openings or holes extending longitudinally along the pipe. Gas is passed through the pipe and ignited adjacent the holes where the gas would mix with secondary air for combustion. The flames thus formed are then directed over strategically placed ceramic fibre imitation logs or coals to produce a burning fire effect.

A major problem with these types of fires has been trying to meet with the constantly tightening .ooa restrictions set on permissible emission levels of pollutants such as carbon monoxide, carbon dioxide and oxides of nitrogen otherwise known as NOx Not only has it proved almost impossible to meet these stringent emission standards with a pin hole burner of the kind described above, the construction of the fire and placement of the ceramic logs or coals becomes extremely important. In this regard it has been found that the placement of the coals and resulting flame impingement has a noticeable effect on the total emission levels and in particular the CO/CO ratio.

2 For example, it has been found that the CO-CO 2 ratio increases undesirably when the concentrated burning gas flame is allowed to impinge directly on the logs or -3coal ceramic radiants. Accordingly, the ceramics generally have to be placed strategically to specifically reduce the flame impingement. However, this is not desirable as the ceramic radiants are not then adequately heated and therefore do not provide a good heating or decorative glowing effect.

This sensitivity to construction is also undesirable as fires of this nature are often transported in kit form and assembled on site where emission monitoring equipment is not usually available.

It is an object of the present invention to overcome or at least ameliorate one or o more of the above discussed disadvantages of the prior art.

10 According to the invention there is provided a gas fired burner comprising: an open topped receptacle having a base and side walls; a deflector plate disposed in said receptacle and spaced apart from said base to define one or more gas outlets extending substantially around and being adjacent the side walls, said deflector plate being disposed to support an overlying layer of porous noncombustible material; a gaseous fuel supply; and an air/fuel mixing device adapted to deliver an air/fuel mixture to between said base and deflector plate to disperse the mixture substantially evenly through the or each gas outlet and into the layer of porous 4 non-combustible material.

Desirably, the porous non-combustible material comprises vermiculite or other similar substance, preferably in a granular or particulate form and desirably having an average diameter of In a preferred embodiment, the receptacle is substantially rectangular and the deflector plate is sized to provide a peripheral gap between the plate and receptacle side walls of approximately 10-20mm.

In a preferred form the air/fuel mixing device is a venturi which preferably has two injectors: one in the i venturi inlet and one at or adjacent the throat of the .venturi.

In a preferred embodiment the venturi is disposed underneath the receptacle and includes an elbow portion extending from the throat of the venturi to connect with a substantially centrally located inlet in the base of the receptacle. In this embodiment the second injector is preferably disposed at or adjacent the elbow of the venturi. The first injector is preferably the main full power output injector and the second injector is a smaller injector which is utilised when the burner is turned down t, a low setting.

It is also preferred that the venturi includes an adjustable air control baffle. Desirably, the burner also includes a conventional gas pilot assembly.

A preferred embodiment of the invention will ttow be described, by way of example only, with reference to the 5 accompanying drawings in which: Figure 1 is a schematic front elevation of a gas fire incorporating a gas burner according to a first embodiment of the invention; Figure 2 is a side elevation of the gas fire shown in Figure 1; Figure 3 is a schematic inverted plan view of the gas fire shown in Figure 1; Figure 4 is a schematic front view of a fully assembled decorative coal fire of the kind shown in Figure 1; and Figure 5 is a schematic plan view of the fully S•assembled fire shown in Figure 4.

e Referring to the drawings, there is shown a gas fire 1 incorporating a gas burner assembly shown generally at 2. The gas burner includes an open topped receptacle 3 having a base 4 and side walls A deflector plate 7 is disposed within the receptacle 3 and spaced apart from the base 4 by means of spacer nuts and post assemblies 8. The deflector plate 7 is positioned to define a single continuous peripherally S"extending gas outlet gap 9. In other embodiments, the gap 9 may comprise a plurality of openings formed, by example, as perforations in the periphery of the plate 7.

An air/fuel mixing device in the form of a venturi assembly 11 is disposed adjacent the underside of the base 4 of receptacle 3. The venturi 11 is preferably made of cast iron and includes a tapered inlet 12 and a 6 throat portion 13 which extends into an elbow portion 14. The elbow 14 terminates at an outlet 15 which is connected, preferably by welding, to a substantially centrally located inlet aperture 16 provided in the base 4 of receptacle 3.

A first main injector 18 is disposed within the tapered inlet portion 12 of the venturi and is connected to a main fuel supply manifold 19 via a first connecting fuel pipe A second low setting injector is connected with the elbow 14 of the 7enturi to inject fuel substantially .along the axis of the venturi at the outlet 15. This S"second injector 21 is also connected to the fuel supply manifold 19 via a second connecting pipe 22.

The venturi 11 also includes an air regulating baffle 23 that is movable axially into and out of the o: inlet 12 to vary the air supply.

In use, the fire is assembled substantially as shown in Figure 4 and 5. This entails filling the tray or receptacle 3 with vermiculite granules 25 which are preferably of between 3mm and 5mm average diameter. The receptacle is filled to just below an upper edge 26 and a layer of ceramic fibre imitation coals 28 are positioned on top substantially as shown in Figure 6. In the preferred form a gap of 12-15mm is left in between each coal brick. A second staggered layer of bricks is then arranged as shown followed by a third layer so as form an elongate pyramid structure of the desired size.

-7- During operation, gas is injected via the main injector 18 into the venturi 11. A component of primary air is thus entrained and mixed with the gas in the venturi prior to passage through the inlet 16 in the receptacle 3.

The air-gas mixture is then directed upwardly against the deflector plate 7 which causes it to disperse substantially evenly between the base 4 and underside of the deflector plate 7 and out toward the peripherally extending gas outlet gap 9. From here the air-gas mixture permeates through the vermiculite from around the peripheral edges of the plate 7 for even combustion with readily available additional adequate secondary air adjacent the surface of the vermiculite, the natural draw from the fire 'sucking' the S: o flames toward the centre of the fire. The flames thus formed are able to 'lick' through and around the coal bricks to effectively heat the radiant material and provide a pleasing natural fire effect.

The air fuel mixture can be adjusted via the axially moveable venturi baffle 23 S* until the desired flame effect is achieved. If the fire is to operate on a very low setting, the secondary injector 21 is operated alone. This has been found to provide more even combustion and reduce the likelihood of blow back or irregular burning.

It has been found that the gas burner assembly according to the invention is able to operate with 8 surprisingly low emission levels that readily meet the requirements of relevant pollution control standards and regulations such as AG 108 1975 type 1.

In the preferred embodiment described, the coals are made from ceramic fibre coated with a black glaze and colloidal silicate. A decorative grate 30 is also provided which is cast or fabricated in the known manner.

In an alternative embodiment, the ceramic fibre coal bricks are replaced with decorative fibre logs.

Sample specifications of two models of gas fires according to the invention operable with natural gas or LPG are listed below.

0* Capacity GAS TYPE Gas Cons Gas Cons Injector Boost Gas Min. Max. Min. Injector Press (MJ/H) (MJ/H) (mm) (mm) (kPa) NATURAL 30 39 2.50 1.35 1.00 30 39 2.50 1.35 1.00 e e 2 0 LPG 36 39 1.60 .45 2.75 39 39 1.65 2.75 0 Although the invention has been described with reference to a specific example, it will be appreciated by those skilled in the art, that the invention may be embodied in many other forms.

Claims (13)

1. A gas fired burner comprising: an open topped receptacle having a base and side walls; a deflector plate disposed in said receptacle and spaced apart from said base to define one or more gas outlets extending substantially around and being adjacent the side walls, said deflector plate being disposed to support an overlying layer of porous non- combustible material; a gaseous fuel supply; and an air/fuel mixing device adapted to deliver an air/fuel mixture to between said 10 base and deflector plate to disperse the mixture substantially evenly through the or each S" gas outlet and into the layer ofpo:rous non-combustible material.

2. A gas fired burner according to claim 1 wherein the porous non-combustible material is in a granular form having an average diameter of between 3mm and

3. A gas fired burner according to claim 1 or claim 2 wherein the deflector plate is *1 15 sized to provide a peripheral gap between the plate and receptacle side walls of approximately 10mm to

4. A gas fired burner according to any one of the preceding claims wherein the porous non-combustible material comprises vermiculite or other similar substance.

A gas fired burner according to any one of the preceding claims wherein the air/fuel mixing device is a venturi having two injectors, one in the venturi inlet and one at or adjacent the throat of the venturi.

6. A gas fired burner according to claim 5 wherein the venturi is disposed underneath the receptacle and includes an elbow portion extending from the throat of the venturi to connect with a substantially centrally located inlet in the base of the receptacle.

7. A gas fired burner according to claim 6 wherein the second injector is disposed at or adjacent the elbow of the venturi.

8. A gas fired burner according to any one of claims 5 to 7 wherein the first injector is the main full power output injector and the second injector is a smaller injector for use when the burner is turned down to a low setting.

9. A gas fired burner according to any one of claims 5 to 8 wherein the venturi includes an adjustable air control baffle. S*

10. A gas fired burner according to any one of the preceding claims further comprising one or more layers of ceramic fibre imitation coal bricks or logs disposed on or over the underlying layer of porous non-combustible material.

11. A gas fired burner according to claim 10 wherein the ceramic fibre imitation coal bricks or logs are disposed to provide intermediate gaps therebetween of approximately S 15 12mm to

12. A gas fired burner according to claim 11 wherein the ceramic fibre imitation coal bricks or logs are arranged in a staggered multiple layer pyramid-type construction having its highest point located in line with or adjacent the centre of the deflector plate.

13. A gas fired burner substantially as hereindescribed with reference to the accompanying drawings. Dated this 4th Day of September, 1996 JETMASTER FIREPLACES PTY LTD Attorney: CAROLINE M. BOMMER Fellow Institute of Patent Attorneys of Australia RA$i 25 of SHELSTON WATERS ABSTRACT A gas fired imitation coal brick or log fire (1) comprising an open topped receptacle having a base and side walls The fire includes a deflector plate disposed in the receptacle and spaced apart from the base to define one or more gas outlets extending substantially around the side walls The deflector plate is disposed to support an overlying layer of porous non-combustible material The gas burner also includes a conventional fuel supply (19) and an air/fuel mixing device (11) adapted to deliver an air/fuel mixture to between the base (4) *and deflector plate The deflector plate disburses 15 the mixture substantially evenly through the gas outlets and into the layer of porous non-combustible material In a preferred form, the mixing device or venturi (11) has a first main injector (18) disposed within the 20 inlet portion of the venturi and a second low setting injector disposed at or adjacent the throat (14) to inject fuel substantially along the axis of the outlet .:e