Apparatus and method for improved ignition of a gaseous fuel burner in an appliance   

Abstract: A method and apparatus for improved ignition of a gaseous fuel in an appliance is provided. More particularly, the shielding of an igniter and the use of thermal convection to direct a flow of gaseous fuel and air across a hot surface of the igniter in order to create proper conditions for the ignition of the gaseous fuel is described.

FIELD OF THE INVENTION

The present invention relates to a method and apparatus for improved ignition of a gaseous fuel in an appliance. More particularly, the present invention provides for a method and apparatus for shielding an igniter so as to create improved conditions for the ignition of a gaseous fuel.

BACKGROUND OF THE INVENTION

For purposes of fuel ignition, gas burner control systems in modern appliances such as a gas oven may use what is referred to as glow bar or hot surface igniters (referred to herein as “igniter”). Typically, such igniters include resistive elements that are heated by the application of an electrical current. The hot surface of the igniter is generally positioned adjacent to a flow of a gaseous fuel. The flow of gaseous fuel is controlled by a manual or electrically operated gas control valve. To achieve ignition, current is applied to the igniter until it reaches a temperature high enough to cause ignition of the gaseous fuel. The gas control valve is then opened and if the proper mixture of air and gaseous fuel is present, ignition occurs and heat is created.

Once the flow of gas is initiated, it is desirable that ignition take place relatively quickly so as to avoid a dangerous build-up of gas in the appliance. Standards such as the National Fuel Gas Code generally set forth limits on the amount of time a gaseous fuel can be allowed to flow before ignition occurs. For example, for certain appliances, a maximum interval of four seconds is allowed for gas flow between the opening and shutting of the gaseous fuel control valve if ignition has not occurred.

Accordingly, the igniter is typically placed close to the gas burner to minimize the distance over which the gaseous fuel must diffuse before reaching the igniter. Ignition of the gaseous fuel requires both a surface at a high enough temperature and the presence, at the heated igniter surface, of the proper mixture of both gaseous fuel and air. The resulting flame is then fed by gaseous fuel from the burner.

Simply placing the igniter adjacent to the burner may not ensure a relatively quick ignition of the gaseous fuel and may not be practical. For example, it may be desirable to shield the igniter from damage such that placement directly adjacent the gaseous fuel burner is not practical. In addition, air currents within an appliance, delays in gas flow after opening the valve, and other factors can contribute to unsatisfactory conditions for ignition.

Accordingly, a method and apparatus for improved ignition of gaseous fuel for an appliance burner would be useful. More specifically, a method and apparatus for reducing the time required for ignition while also eliminating the accumulation of gaseous fuel would be particularly beneficial. Such an invention that can also be used with a shield for the igniter would also provide additional utility.

Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.

In an exemplary embodiment of the present invention, a shield for the igniter of a gaseous fuel burner of an appliance is provided. The shield includes a housing positioned around the igniter. The housing defines an entrance opening for the flow of the gaseous fuel into the housing. The entrance opening is positioned lower than the igniter. The housing also defines an exit opening for the flow of air and gaseous fuel across the igniter and out of the housing. The exit opening is positioned higher than the igniter. A gaseous fuel receptacle is configured with the housing at a position lower than the igniter. The gaseous fuel receptacle is positioned for gaseous communication with the entrance opening of the housing so that gaseous fuel drawn into the gaseous fuel receptacle may travel through the entrance opening of the housing.

In another exemplary aspect of the present invention, a method for igniting a gaseous fuel burner of an appliance is provided. The method includes the steps of providing a shield about the gaseous fuel burner; supplying a gaseous fuel to the gaseous fuel burner; raising the temperature of a surface of an igniter to a temperature sufficient to ignite a mixture comprising the gaseous fuel and air; heating with the igniter so as to create a flow by thermal convection of the mixture; using the shield to channel the flow upward and across the surface of the igniter; and igniting the mixture of air and gaseous fuel flowing across the igniter.

These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:

FIG. 1 provides a perspective view of an exemplary embodiment of an igniter shield of the present invention.

FIG. 2 provides a cross-sectional view of the exemplary embodiment of FIG. 1 installed with a gaseous fuel burner of an appliance.

DETAILED DESCRIPTION

The present invention provides a method and apparatus for improved ignition of a gaseous fuel in an appliance. More particularly, the present invention provides for shielding an igniter and using thermal convection to direct a flow of gaseous fuel and air across the hot surface of the igniter to create proper conditions for the ignition of the gaseous fuel. By directing the flow of gaseous fuel, unnecessary accumulation of gaseous fuel within the appliance can be avoided. Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

FIG. 1 provides a perspective view of an exemplary embodiment of a shield 100 of the present invention. For additional clarity, shield 100 is shown in isolation from a gas appliance. FIG. 2 is a cross-sectional view of the shield 100 installed within an appliance such as a gas oven appliance. A broil burner tube 10 along with a mesh screen or burner surface 20 is configured with burner housing 30 and installed in the top of a cooking compartment. It should be understood that the present invention may be used in a variety of appliances that utilize a burner element supplied by a gaseous fuel that must be ignited during use. Such gaseous fuels as may be used with the present invention include, for example, propane and natural gas.

Referring to both FIGS. 1 and 2, shield 100 includes a housing 110 that is positioned around positioned around an igniter 105. Leads 115 attached to connector 120 and igniter 105 provide electrical power to igniter 105. Upon activation, fingers 125 of igniter 105 become heated and will eventually reach a temperature sufficient to ignite a combustible mixture of air and a gaseous fuel. Igniter 105 is of the hot surface or glow type. Other shapes and configurations other than fingers 125 may be used.

Housing 110 defines an entrance opening 130 for the flow gaseous fuel into housing 110 as illustrated by arrows A in FIG. 1. Entrance opening 130 is positioned lower than the igniter to facilitate the flow of gaseous fuel and air (including a mixture thereof) into housing 110 by thermal convection as more fully described below. Although shown as rectangular in shape, it should be understood that other shapes for entrance opening 130 may be used provided the opening is positioned to allow gaseous fuel and air to be drawn into housing 110.

Housing 110 also defines an exit opening 135 for the flow of gaseous fuel and air across igniter 105 and out of housing 110 as illustrated by arrows B in FIG. 1. Exiting opening 135 is positioned higher than igniter 105 so that gaseous fuel and air rising from igniter 105 may exit housing 110 (higher being defined relative to the flow of gas once heated by igniter 105). Again, although shown with a rectangular shape, exit opening 135 may be constructed with other shapes provided an opening is allowed for the flow of gas from and across igniter 105. Housing 110 also includes a protective grill 140 with apertures 145. Grill 140 serves to protect igniter 105 from contact damage while apertures 145 allow for the flow of gas and conduction of heat.

A gaseous fuel receptacle 150 is positioned adjacent to housing 110. As shown in FIGS. 1 and 2, gaseous fuel receptacle 150 is constructed as a tray having walls 155 and bottom 160. As illustrated by arrows A and their movement into entrance opening 130 of housing 110, gaseous fuel receptacle 150 is positioned for gaseous communication with the entrance opening 130 of housing 110. More specifically, gaseous fuel from burner tube 10 and air can be drawn into the gaseous fuel receptacle 150 and pass into housing 110 for passage across igniter 105. Other shapes and configurations for gaseous fuel receptacle 150 may used provided such allow for the receipt and flow of fuel from burner tube 10 and air as described. In addition, FIG. 2 depicts gaseous fuel receptacle 150 at a position directly below the surface of burner 20. However, other positions may used as well provided receptacle 150 is positioned for the receipt of gaseous fuel and air as stated.

For the exemplary embodiment of FIGS. 1 and 2, shield 100 is shown as an integral or unitary construction of housing 110 and gaseous fuel receptacle 150. For example, sheet metal may be punched or stamped into the desired shaped for both housing 110 and gaseous fuel receptacle 150. However, other constructions may be used including the connection of separate components by fasteners, tabs, or the like. Materials used must be compatible with the temperatures created by burner tube 10 and igniter 105.

Accordingly, in operation, igniter 105 is activated so that the temperature of the surface (such as fingers 125) of igniter 105 is raised to a temperature sufficient to ignite a combustible mixture of gaseous fuel and air. A gaseous fuel such as propane or natural gas is supplied to burner tube 10. For example, a control valve (not shown) may be positioned upstream of burner tube 10 for determining the flow to burner tube 10. Gaseous fuel exits tube 10 and diffuses through burner 20 while mixing with air in the appliance.

As the temperature of igniter 105 increases, air and/or gaseous fuel proximate to igniter 105 will be heated and thermal convection will occur. More specifically, due to density differences from heating the gas surrounding igniter 105, such gas will begin to rise (as shown by arrows B) to create a flow across the surface of igniter 105 and out of housing 110 through exit opening 135. As a result, gaseous fuel and air will be drawn down into gaseous fuel receptacle 150 to enter into housing 110 through entrance opening 130. More specifically, due to the configuration of housing 110 and receptacle 150, shield 100 will channel a flow of gaseous fuel, air, or a mixture of both upward and across the surface of the igniter. Once a combustible mixture of air and gaseous fuel pass over igniter 105 when it is at a sufficiently raised temperature, the mixture will be ignited. Flame will then spread rapidly along burner 20 to ignite gaseous fuel and heat the appliance.

By using gaseous fuel receptacle 150 to capture fuel as it leaves burner 20 and channel the same across a properly heated igniter 105, the unnecessary accumulation of un-ignited fuel within the appliance can be avoided. Ignition of the gaseous fuel in a relatively short period of time after supplying such fuel to burner tube 10 can be accomplished. More specifically, and by way of example, a four second interval or less between the beginning of a flow of gaseous fuel to burner tube 10 and the ignition of such fuel can be achieved.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.