BURNER

Abstract

An apparatus and method for relieving an ignition pulse that may be created at burner ignition in a gas-fired appliance. The burner is located in a combustion chamber forming part of the appliance such as a water heater. A port for admitting air into the combustion chamber is provided and sufficiently sized to relieve an ignition pulse if created upon burner ignition. The air opening is overlaid with an element made from a material that contains a plurality of small openings and is formed into a cup-shaped configuration so that the total area of the material, including both open and non-open areas is substantially greater than the air opening. The port defines an opening for admitting secondary air into the combustion chamber for some applications. The element that overlies the opening may be constructed from one or more layers of a wire mesh material.

Description

RELATED APPLICATION

This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/125,444, filed Apr. 25, 2008.

TECHNICAL FIELD

The present invention relates generally to gas burners and, in particular, to an apparatus for reducing noise that occurs in some appliances when a burner is ignited.

BACKGROUND ART

It has been found that some burners, such as premixed burners, i.e., burners in which the air needed for combustion is pre-mixed with the fuel prior to reaching the burner ports, will produce a “ignition pulse” when the burner is lit. The ignition pulse can produce a low frequency rumbling noise especially in appliances with combustion chambers that are sealed or combustion chambers in which ports or openings for admitting secondary air are made relatively small. Many appliances today such as gas fired water heaters are required to be flammable vapor ignition resistant (FVIR) systems. To meet a FVIR requirement for the appliance, individual air openings must be very small in order to prevent flame from passing through them. In order to relieve the ignition pulse, a large number of these openings must be used.

DISCLOSURE OF INVENTION

The present invention provides a new and improved apparatus and method for relieving an ignition pulse created at burner ignition while providing a flammable vapor ignition resistant (FVIR) appliance such as a gas fired water heater, room heater, etc.

In accordance with a preferred and illustrated embodiment, a gas-fired appliance is disclosed that includes a burner located in a combustion chamber. A port for allowing the passage of air into and out of, the combustion chamber is provided that is sufficiently sized to relieve an ignition pulse that may be created when the burner is ignited. In accordance with this embodiment, the air opening is overlaid with an element made from a material that contains a plurality of small openings. The material is formed into a cup-shaped configuration so that the total area of the material, including both open and non-open areas of the material, is substantially greater than the area of the air opening.

In a more preferred embodiment, the burner is a pre-mix type burner and the port defines an opening admitting secondary air.

According to a feature of the invention, the material is a wire mesh material and, in a more preferred embodiment, the overlying element is made from two layers of wire mesh material.

In a more preferred embodiment, the element is formed into a tapered cup-shaped element.

The invention contemplates not only an overlying element made from a wire mesh material, but also contemplates the use of a perforated sheet material and/or a perforated ceramic material.

Additional features and a further understanding of the invention will be obtained by reading the following detailed description made in connection with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a gas water heater, which includes a combustion relief apparatus constructed in accordance with a preferred embodiment of the invention;

FIG. 2 is a front elevational view of a combustion relief apparatus constructed in accordance with a preferred embodiment of the invention; and

FIG. 3 is a rear view of the apparatus shown in FIG. 2.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 illustrates a gas fired water heater that includes a combustion relief apparatus constructed in accordance with a preferred embodiment of the invention. For purposes of explanation, a pre-mixed burner 12 is shown installed in a combustion chamber 14 forming part of the water heater 10. The illustrated pre-mixed burner 10 is the subject of U.S. patent application Ser. No. 10/540,695, filed Feb. 4, 2005, entitled Burner and is hereby incorporated by reference.

The illustrated burner is a pre-mixed type burner in which primary combustion air and gas, i.e., natural gas or propane, are pre-mixed prior to entering the main burner housing 12a. In particular, the fuel and primary air enter the burner assembly through a venturi tube opening indicated generally by the reference character 16. For proper operation of the illustrated burner, the combustion chamber 114 in which it is located must have an opening for admitting secondary air.

In general, the burner requires an ignition device to light the burner when heating is desired. This ignition device may be a pilot light or an electronically controlled igniter.

In the illustrated embodiment, the tank construction includes a mounting plate 20 (sometimes referred to as a door) which serves as a means for at least partially mounting the burner 12 within the combustion chamber 14. The plate 20 also serves as a cover for closing off an opening in the tank wall which provides access to the combustion chamber 14 and through which the burner is inserted into the combustion chamber.

In accordance with the illustrated embodiment, the mounting plate 20 also defines a secondary air opening 24 through which secondary air is admitted into the combustion chamber 14. The opening 24 also serves as a combustion relief port for relieving the ignition pulse that is generated when the burner is ignited.

As seen in FIGS. 1 and 2, the secondary air opening 24 is sufficiently sized to relieve the ignition pulse. The opening 24 is preferably overlaid with a material containing small ports. This results in a burner apparatus that is FVIR. Wire mesh or other FVIR material of sufficient durability is at most, 40% open space. If the secondary air opening 24 is overlaid with a flat piece of material, the 60% blockage may not provide adequate open area to relieve the ignition pulse. In many cases, there is insufficient space available to increase the size of the opening enough to offset the blockage.

In accordance with the invention, the element 30 has a total surface area (including both the non-open and open areas of the material) that is greater than the area of the opening 24. The effective “opening” of the element 30 is determined by the number of openings per unit area multiplied by the size or area of each opening multiplied by the total surface area of the element. It should be noted here, that the total effective open area provided by the element 30 does not have to be equal to or greater than the area of the secondary opening. The total effective opening provided by the element 30 must be sufficient to relieve the ignition pulse generated when the burner is lit.

In accordance with the invention, and as seen best in FIGS. 2 and 3, a wire mesh material that is drawn or formed into a tapered cup shaped element 30 overlies the opening 24. By forming the wire mesh material into a cup shape, the total area of the holes in the wire mesh material can be increased up to a point where it is substantially equivalent to the area of the secondary air opening 24. As a consequence, the cup-shaped wire mesh material 30 does not reduce the open area, but does inhibit a flame from passing through the secondary air or combustion relief port 24.

Two layers of cup-shaped wire mesh material can be nested together to enhance flammable vapor ignition resistance for the appliance.

Wire mesh materials including, but not limited to, temperature and corrosion resistant metals are contemplated by the present invention. Perforated material such as cast/formed ceramic or formed/drawn perforated sheet metal is also contemplated.

It should be noted here, that the present invention should not be limited to a gas-fired water heater or the construction shown in FIG. 1. The invention contemplates the use of the invention in other appliances and with other types of burners. In addition, the wire mesh element can be formed into shapes other than that shown in the figures. For example, the wire mesh material can be formed in a semi-spherical or cylindrical shape. The element 30 should be shaped so that the total area of the openings defined by the wire mesh or perforated material is sufficient to allow the free passage of the ignition pulse.

It should be noted, that the present invention has been disclosed in connection with a pre-mixed burner and a secondary air opening. Principles of this invention, however, are applicable to other types of burners including non pre-mixed burners. For some appliances, using non pre-mixed burners, an “air opening” is required in order to admit combustion air which may be primary combustion air rather than secondary combustion air.

Although the invention has been described with a certain degree of particularity, it should be understood that those skilled in the art can make various changes to it without departing from the spirit and scope of the invention as hereinafter claimed.

Claims

1. A gas-fired appliance comprising:

a) a burner located in a combustion chamber of said appliance;

b) an air port for admitting air into said combustion chamber, said air port being sufficiently sized to relieve an ignition pulse that is generated when said burner is ignited;

c) said opening being overlaid with a material that contains a plurality of small openings, said material being formed into a cup-shaped configuration such that the area of said material is substantially greater than the area of said air opening.

2. The apparatus of claim 1 wherein said material is a wire mesh material.

3. The apparatus of claim 2 wherein said material includes two layers of wire mesh material.

4. The apparatus of claim 1 wherein said material is formed into a tapered cup-shaped element.

5. The apparatus of claim 1 wherein said cup-shaped element is formed from a perforated sheet metal.

6. The apparatus of claim 1 wherein said element is formed from a perforated ceramic material.

7. The apparatus of claim 1 wherein said material is formed into a semi-spherical cup-shaped element.