Abstract:
A hot wire igniter for igniting a gaseous or atomized fuel is disclosed. The coil of the hot wire igniter is formed from a thin high temperature, iron, chromium, aluminum alloy having a center section that is tightly wound. The coil turns initially do not touch one another and each end of the coil is attached to a rod that is received within an insulator member. The rods are connected to a power source. The coil portion of the hot wire igniter is received within a gas collector box which is attached to the burner to be ignited. Application of the power source to the lead-in rods causes the coil of wire to reach a temperature in excess of the ignition temperature of the fuel mixture which surrounds same causing the ignition of the mixture.

Description:
This application is a continuation-in-part of application Ser. No. 10/655,399 filed on Sep. 5, 2003 now abandoned. 
    
    
     TECHNICAL FIELD 
     The present invention relates, in general, to an igniter and, more particularly, to a hot wire igniter that can be used for the ignition of a gaseous or atomized fuel in various types of appliances. 
     BACKGROUND ART 
     Gas grills typically utilize propane gas, natural gas or some type of manufactured gas as their fuel source and a spark ignition system to ignite same. Such a spark ignition system when used in gas grills or other gas appliances, such as pool water heaters, can be affected by environmental factors. For example, such a spark ignition system may operate erratically in a very damp and/or windy environment. Also, the operation of such a spark ignition system in a gas grill can be adversely affected by organic contamination from the foods being grilled. In addition, such a spark ignition system is noisy when actuated since it typically utilizes a piezoelectric impact-type igniter that is mounted on a sheet metal panel which effectively transmits the igniter actuation noise into the surrounding atmosphere. An electronic spark ignition device may be used which emits a series of spark pulses that produces a potentially annoying “ticking” sound. Furthermore, the routing and/or positioning of the electrical wiring within an appliance using a spark ignition system is critical since the heat generated within the appliance might adversely affect the wiring. Also, due to the high frequency nature of the spark produced by such ignition systems, the routing and/or positioning of the wiring within the appliance can affect the efficiency of the resulting spark. In addition, because such spark ignition systems produce high voltages, any defects in the wiring or any deterioration thereof can adversely affect the resulting spark. 
     In view of these disadvantages associated with presently available spark ignition devices, it has become desirable to develop another type of ignition device, such as a hot wire igniter, for igniting the fuel utilized within the appliance. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the problems associated with utilizing a spark ignition device for igniting a gaseous or atomized fuel by providing a hot wire igniter that operates at a significantly lower voltage and higher current than presently available spark ignition devices. In addition, the lower voltage does not include a high frequency component. The coil of the hot wire igniter of the present invention is formed from a thin high temperature, iron, chromium, aluminum alloy having a center section that is tightly wound. The coil has a unique geometry and each end of the coil is welded to a rod that is enclosed within an insulator member. The rods are typically connected to a DC power source. Alternatively, an AC power source or a chopped DC or chopped AC power source can be utilized as the power source. Application of the power source to the rods causes the coil of wire to reach a temperature in excess of the ignition temperature of the fuel mixture that surrounds and may penetrate same causing the ignition of the mixture. The use of a hot wire igniter, rather than a spark ignition device, permits the igniter to be used in very damp or windy environments. Thus, the hot wire igniter of the present invention can be readily used within a gas grill that is stored outdoors or a pool water heater that is used outdoors. In addition, the operation of the hot wire igniter of the present invention is not adversely affected by organic contamination from foods that are grilled in a gas grill or the sauces that may be used thereon since the surface of the hot wire igniter reaches a temperature that causes such contamination to be readily burned off and any leakage current resulting from organic contamination which would normally absorb or ground a high voltage spark and render it ineffective is insignificant. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a typical embodiment of a hot wire igniter of the present invention. 
         FIG. 2  is a front elevational view of the typical embodiment of the hot wire igniter shown in  FIG. 1 . 
         FIG. 3  is a right side elevational view of the typical embodiment of the hot wire igniter shown in  FIG. 1 ; the left side elevational view being a mirror image of this Figure. 
         FIG. 4  is a top plan view of the typical embodiment of the hot wire igniter shown in  FIG. 1 . 
         FIG. 5  is a bottom plan view of the typical embodiment of the hot wire igniter shown in  FIG. 1 . 
         FIG. 6  is a front elevational view of the heating coil utilized in a typical embodiment of the hot wire igniter of the present invention. 
         FIG. 7  is an end elevational view of the heating coil shown in  FIG. 6 . 
         FIG. 8  is a perspective view of a typical gas collector box containing the typical embodiment of the hot wire igniter of the present invention and showing the attachment of the gas collector box to a typical burner within a gas grill. 
         FIG. 9  is a perspective view of a typical gas collector box and showing the attachment of the typical embodiment of the hot wire igniter shown in  FIG. 1 . 
         FIG. 10  is an enlarged top plan view of a typical burner and a typical gas collector box having the coil portion of the typical embodiment of the hot wire igniter shown in  FIG. 1  therein and showing the attachment of the gas collector box to the top surface of the burner. 
         FIG. 11  is an enlarged front elevational view of a typical burner and a typical gas collector box containing the coil portion of the typical embodiment of the hot wire igniter shown in  FIG. 1 . 
         FIG. 12  is a cross-sectional view of the burner and the gas collector box taken across section-indicating lines  12 - 12  in  FIG. 11 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the Figures where the illustrations are for the purpose of describing the preferred embodiment of the present invention and are not intended to limit the invention described herein,  FIG. 1  is a perspective view of a typical embodiment of the hot wire igniter  10  of the present invention. The hot wire igniter  10  is comprised of two (2) lead-in rods  12 , a coil  14  of wire whose opposite ends are each attached to one of the ends of the rods  12 , an insulator member  16  and a mounting bracket  18 . 
     The rods  12  are solid in construction, circular in cross-section and have an outer diameter of about 0.045 inches to 0.125 inches. The rods  12  are typically formed from nickel chrome (NiCr) material, an iron, chromium, aluminum alloy, stainless steel, or the like, and are received within substantially parallel longitudinally extending bores (not shown) provided within insulator member  16 . The portions  20  of the rods  12  emanating from the end  22  of the insulator member  16  are usually swaged providing flat surfaces for the attachment of electrical terminals (not shown). In addition, the swaged portions  20  of rods  12  are usually bent outwardly with respect to one another permitting the easy attachment of the aforementioned electrical terminals. (Alternatively, the swaged portions  20  of the rods  12  can be eliminated and the electrical attachment thereto can be internal within the insulator member  16 ). The electrical terminals are connected to a power supply (not shown), such as a DC voltage source. Alternatively, the power supply can be an AC voltage source (not shown) or a chopped DC or AC voltage source (both not shown). The portions  24  of rods  12  emanating from the opposite end  26  of insulator member  16  are usually bent outwardly with respect to one another in order to provide a gap between the ends  28  thereof, as shown in  FIG. 4 . Each end  30  of coil  14  is welded to a rod  12  adjacent its end  28  and the coil  14  is positioned so as to be recessed within the gap provided between the ends  28  of the rods  12 . As shown in  FIGS. 2 and 3 , the mounting bracket  18  includes a sleeve portion  32  which may have a compression member therein (not shown) to grippingly engage the outer surface of the insulator member  16 . In addition, the mounting bracket  18  has an aperture  34  therein, as shown in  FIGS. 1 ,  4  and  5 , permitting the mounting of the igniter  10  within a collector box which is typically used in a gas grill that utilizes traditional spark ignition devices. Alternatively, the igniter  10  can be mounted directly to the burner within the grill or can be attached to the grill through a mounting or attachment arrangement. 
     The coil  14  is formed from an iron, chromium, aluminum alloy wire which can be subjected to temperatures from 1000° F. to about 2,500° F. The wire is typically 0.004 to 0.030 inches in diameter and the center section of the coil is tightly wound, as shown in  FIG. 6 . Typically, the coil  14  includes about six full coil turns, however, a lesser number of turns can be utilized. A minimum of two full coil turns is typically required to obtain the heat concentration that is provided by the adjacent coil turns. The coil turns typically have an outer diameter of about 0.030 to 0.250 inches and the overall length of the coil  14  is about 0.050 to 0.500 inches resulting in the ratio of the coil length to the coil outer diameter to be in the range of about 1.5:1 to 3:1. When formed, the coil turns typically do not touch one another and the ratio of the gap between adjacent coil turns to the thickness of the wire forming the coil  14  is about 0.50:1 to 2.5:1. The oppositely disposed ends  30  of the coil  14  are substantially straight and concentric with the longitudinal axis of the coil turns but offset therefrom so as to be positioned adjacent the outer radius of the coil turns. During the welding process, the coil  14  is oriented such that the coil turns are positioned substantially above the oppositely disposed ends  30  of the coil  14  in order to provide support and protection for the coil turns after the coil  14  has been welded adjacent to the ends  28  of the rods  12 . It should be noted that the ratio of the outer diameter of the coil turns to the diameter of the rods  12  is about 0.5:1 to 6:1. During the conditioning and prove-in phase of the igniter  10 , the coil  14  is heated by the application of a current source thereto for a pre-determined period of time annealing the coil  14  and causing a protective aluminum oxide coating to form on the surface of the coil  14 . Through usage, the coil turns may contact one another. It should be noted that the protective oxide coating that forms on the outer surface of the iron, chromium, aluminum alloy wire utilized for coil  14  prevents electrical shorts if, because of coil sag and/or deformation due to usage and/or handling, adjacent coil turns touch one another during operation. 
     Suspending the coil  14  of wire between the rods  12  adjacent their ends  28  may cause the coil  14  to sag and/or deform through usage. The aforementioned geometry utilized for the coil  14  overcomes the problem of sag and/or deformation. In the present invention, the outer turns of the coil  14  heat the inner turns of same. The innermost coil turns typically experience the hottest temperatures and are the ones most likely to sag and/or deform when heated. Through usage, the innermost turns of the coil  14  may sag and/or deform but since these turns are of a relatively small radius, few in number, and are supported by the outer coil turns, the amount of sag and/or deformation is insignificant and, therefore, does not significantly affect the operation of the igniter  10 . Any deformation of the coil turns that may occur allows the gas-air mixture to enter the gaps between adjacent turns to assist in the ignition of the gas-air mixture and compensates for any decrease in the operating performance of the coil  14  due to any increase in the electrical resistance of same through usage. It should be noted that the oppositely disposed ends  30  of the coil  14  radiate and/or conduct a substantial portion of the heat contained therein to the surrounding air and to the ends  28  of the rods  12  to which they are attached. By radiating and/or conducting such heat, the oppositely disposed ends  30  of the coil  14  are at a lower operating temperature than the coil turns, and thus, typically do not sag and/or deform. Because the heat is concentrated in the innermost coil turns, any coil sag and/or deformation is minimized and does not adversely affect igniter performance. It should be further noted that the coil  14  of wire can be immersed in the resulting flame without any adverse effects and readily operates within same. 
     Referring now to  FIG. 9 , a perspective view of a typical gas collector box  40  showing the attachment of the hot wire igniter  10  of the present invention thereto is illustrated. The gas collector box  40  is comprised of a housing  42  and a mounting bracket  44  attached thereto. An aperture  46  is provided in the mounting bracket  44 . Gas collector box  40  has an opening, shown generally by the numeral  48 , thereto. The bottom surface  50  of gas collector box  40  has an aperture (not shown) therein. The hot wire igniter  10  of the present invention is attached to the gas collector box  40  such that the portion of the insulator member  16  adjacent the end  26  thereof is received within the aperture (not shown) in the bottom surface  50  of gas collector box  40  and a fastener  52  is received through aperture  34  in mounting bracket  18  to firmly attach mounting bracket  18  to bottom surface  50  of gas collector box  40 . In this manner, the portions  24  of the rods  12  emanating from the end  26  of insulator member  16  and the coil  14  attached thereto are within the gas collector box  40  and adjacent the opening  48  thereto. 
     In order to mount the gas collector box  40  with the igniter  10  attached thereto to a typical burner, the mounting bracket  44  is usually placed against the top surface  60  of the burner  62  in a gas grill  64 , as shown in  FIG. 8 . A fastener  66  is then received within aperture  46  in mounting bracket  44  of gas collector box  40  to attach the gas collector box  40  and the igniter  10  to the top surface  60  of the burner  62 , as shown in  FIG. 10 . In this manner, the opening  48  to the gas collector box  40  is adjacent the outlet ports  68  in the bottom portion of the burner  62 , as shown in  FIGS. 11 and 12 . Gas emanating from ports  68  in burner  62  is received through the opening  48  to the gas collector box  40  and mixes with air therein permitting ignition of the gas-air mixture within the gas collector box  40  by the coil  14  of the igniter  10 . The result is that the gas emanating from ports  68  in burner  62  is ignited within several seconds after power is applied to the igniter  10 . It should be noted that the gas collector box  40  with the igniter  10  attached thereto can be mounted to the side surface or to the bottom surface of the burner  62 , rather than to the top surface  60  thereof. Alternatively, the igniter  10  can be utilized without a gas collector box by mounting the igniter  10  directly to the burner  62  or to the body of the gas grill such that the coil portion thereof is adjacent to the outlet ports of the burner. 
     The hot wire igniter  10  of the present invention offers a number of advantages over presently available spark ignition systems for gas appliances. For example, the hot wire igniter  10  exhibits increased resistance to moisture, especially in those situations where the appliance is exposed to rain, and is resistant to carbon build-up on the coil  14 . In addition, any degradation in the operation of the igniter  10  due to organic contamination, such as foods, sauces, etc., in a gas grill is not nearly as great as that which occurs for spark ignition devices since the igniter  10  burns off any such contaminants and any leakage current that results from organic contamination and which would normally absorb or ground the high voltage spark, rendering the igniter ineffective or making it inoperable, is insignificant. The coil  14  within the igniter  10  is also resistant to mechanical shock and vibration since it is formed from a metal alloy, rather than a brittle ceramic-like material, such as silicon carbide or silicon nitride igniters, and is protected because it is recessed between the ends  28  of the rods  12 . Also, the protective oxide coating that forms on the outer surface of the coil  14  prevents electrical shorts if adjacent coil turns touch one another during operation. Furthermore, the routing and/or positioning of the wiring within the appliance when utilizing the igniter  10  is not as critical as the positioning of such wiring when a spark ignition device is utilized since the igniter  10  utilizes a very low voltage, 2 to 5 volts DC, which does not include a high frequency component for operating purposes. Alternatively, an AC power source or a chopped DC or chopped AC power source of any voltage can be utilized. In addition, operation of the igniter  10  is virtually silent when compared with the operation of spark ignition devices that typically utilize noisy piezoelectric impact-type devices to generate the required spark pulses. Such devices are typically mounted on a sheet metal panel which effectively transmits the actuation noise produced by the device into the surrounding atmosphere. If an electronic spark ignition device is used, the resulting series of spark pulses produces a potentially annoying “ticking” sound. Also, the igniter  10  may be less expensive to produce than presently available electronic spark ignition devices and is more reliable than such devices since it requires fewer parts. Lastly, the portion of the igniter  10  that includes the coil  14  is readily receivable within a collector box used for a spark ignition device permitting the easy replacement of such a spark ignition device by the igniter  10 . 
     Certain modifications and improvements will occur to those skilled in the art upon reading the foregoing. It is understood that all such modifications and improvements have been deleted herein for the sake of conciseness and readability, but are properly within the scope of the following claims.