Abstract:
An ignitor for use with an industrial oxy-fuel burner, the ignitor being able to ensure ignition of a pilot flame in order to enable automatic ignition of an oxy-fuel burner. The ignitor is characterized by two tubes, one inside the other, concentrically arranged with respect to an electric ignitor rod at the center, the tubes and the ignitor rod forming two annuli for the delivery of oxygen and fuel gas from their respective manifolds to an open end of the tubes for ignition by the ignitor rod. The manifolds are each formed from a single piece of material. The ignitor rod is removable from the rest of the ignitor assembly by means of a pipe-threaded adapter at the rear of the assembly.

Description:
This application claims benefit of Provisional Application 60/109,930 filed Nov. 25, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention generally relates to pilot burners and, more specifically, to pilot burners for automatic ignition of oxy-fuel burners. 
     For automatic ignition of an oxy-fuel burner it is necessary to have a pilot burner and control equipment which ensures that the pilot burner is operating before the main burner begins to operate. The pilot burner typically operates on a gaseous fuel such as propane and oxygen as oxidant rather than air. The use of oxygen offers the advantages of safe operation, high capacity, and small dimensions. 
     While prior art pilot burners have generally performed their function, they are relatively complicated and are relatively expensive to produce. Accordingly, there is a need in the art for an improved pilot burner which is relatively simple in construction, is relatively inexpensive to produce, and has improved reliability and ease of service. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention provides a pilot burner assembly including an ignitor having an electrically conducting rod extending axially from an ignitor head. An axially extending first tube is disposed around the ignitor rod to form a first fluid passageway and has a first tube opening. A first manifold has an eccentric first axial bore therein, a first manifold opening for attachment to a first fluid supply fitting, and a first lateral passageway communicating the first manifold opening with the first axial bore. The first tube is disposed at the first axial bore and the first tube opening cooperates with the first lateral passageway to communicate the first manifold opening with the first fluid passageway. A coupling is provided having an axial coupling bore. The coupling is attached to the first manifold such that the axial coupling bore is aligned with the first axial bore and the ignitor head is received in the coupling such that the ignitor projects through the coupling. An axially extending second tube is disposed around the first tube to form a second fluid passageway and has a second tube opening. A second manifold has an eccentric second axial bore therein, a second manifold opening for attachment to a second fluid supply fitting, and a second lateral passageway communicating the second manifold opening with the second axial bore. The second tube is disposed at the second axial bore, the second tube opening cooperates with the second lateral passageway to communicate the second manifold opening with the second fluid passageway, and the second manifold is attached to the first manifold such that the second axial bore is aligned with the first axial bore and the second manifold opening extends laterally in substantially the same direction as the first manifold opening. 
     The ignitor rod is fitted with an electrically insulating sleeve. The ignitor head is externally threaded and the coupling is internally threaded. The pilot burner also includes an internally and externally threaded adaptor. The adaptor receives the ignitor head therein and the adaptor is received in the coupling such that the ignitor projects through the adaptor and the coupling. 
     The first tube is disposed concentrically around the ignitor rod and the first fluid passageway is annular. Spacers are disposed between the first tube and the ignitor rod to maintain the ignitor rod substantially concentric in the first tube. The first tube opening is lateral and the first manifold comprises a cylindrical wafer. The first manifold opening is internally threaded. The coupling is a cylindrical wafer. The axial coupling bore has a smaller diameter than the first axial bore, the first axial bore extends through the first manifold, and an end of the first tube abuts against the coupling. The axial coupling bore is concentric with the first axial bore. The second tube is disposed concentrically around the first tube and the second passageway is annular. Spacers disposed the between the first tube and the second tube to maintain the first tube substantially concentric in the second tube. The second tube opening is lateral. The second manifold is a cylindrical wafer. The second manifold opening is internally threaded. The second axial bore has a greater diameter than the first axial bore, the second axial bore extends through the second manifold, and an end of the second tube abuts against the first manifold. The second axial bore is concentric with the first axial bore. The manifolds are formed of a single piece of material. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     These and further features of the present invention will be apparent with reference to the following description and drawings, wherein: 
     FIG. 1 is a plan view, partially broken away, of a pilot burner for automatic ignition of oxy-fuel burners according to the present invention; 
     FIG. 2 is a plan view, partially broken away, of the pilot burner of FIG. 1 in a partially assembled condition; 
     FIG. 3 is a plan view, partially broken away, of an ignitor assembly of the pilot burner of FIG. 1; 
     FIG. 4 is a rear elevational view of the pilot burner of FIG. 1; 
     FIG. 5 is an enlarged front elevational view of the pilot burner of FIG. 1; 
     FIG. 6 is a cross-sectional view taken along line  66  of FIG. 1; and 
     FIG. 7 is an elevational view of the pilot burner of FIG. 1 installed in a furnace wall. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIGS. 1-6 illustrate a pilot burner  10  according to the present invention which includes an ignitor assembly  12 , an oxidant manifold assembly  14 , and a fuel or gas manifold assembly  16 . As best shown in FIG. 3, the ignitor assembly  12  includes an ignitor  18 , an insulator sleeve  20 , and a threaded adapter  22 . The ignitor  18  has a rod  24  extending axially from an externally threaded head. The rod  24  is sized to extend the full length of the pilot burner  10  such as, for example, 10 inches. A suitable ignitor  18  is Crown ignitor #21065. The insulator sleeve  20  is sized to extend the full length of the ignitor rod  24  and to closely fit onto the rod  24  and electrically insulate the rod from the oxidant manifold assembly  14 . For a rod  24  having an outer diameter of about ⅛ inch, for example, the insulator sleeve  20  can have an inner diameter of about ⅛ inch and an outer diameter of about {fraction (3/16)} inches. The insulator sleeve  20  can be of any suitable electrically insulating material which can meet required environmental conditions such as, for example alumina. The threaded adapter  22  is a standard pipe adapter for connecting the external thread of the ignitor  18  with the internal thread of the oxidant manifold assembly  14  as described in more detail hereinafter. 
     As best shown in FIGS. 2 and 6, the oxidant manifold assembly  14  includes an oxidant manifold  26 , a coupling  28 , and an oxidant tube  30 . The oxidant manifold  26  has an axially extending opening or bore  32  therethrough which is sized for closely receiving the oxidant tube  30  as described in more detail hereinafter. The oxidant manifold  26  also has a radially extending opening  34 . The opening  34  is sized and adapted for receiving a threaded check valve of an oxidant supply line. Preferably, the opening  34  is partially threaded, such as ½ inch pipe thread, and has an unthreaded frusto-conically shaped bottom surface. A small radially extending passage  36  connects the bottom surface of the opening  34  with the bore  32  to provide gas flow communication between the opening  34  and the bore  32 . The oxidant manifold  26  is preferably a wafer of standard bar stock and more preferably a wafer of a standard round bar stock. The bore  32  is preferably eccentric or offset from the center of the manifold  26  so that a smaller size of common bar stock can be utilized while providing adequate space for the opening  34 . The oxidant manifold  26  can be formed of any suitable material such as, for example, stainless steel. 
     The coupling  28  has an axially extending opening  38  sized and adapted for receiving the ignitor assembly  12  therein. Preferably, the opening  38  has an internal thread, such as a ½ pipe thread, for receiving the external thread of the adapter  22  of the ignitor assembly  12 . The coupling  28  is rigidly secured to the oxidant manifold  26  with the bore  32  and opening  38  generally coaxially aligned such that the ignitor rod  24  and the insulator sleeve  20  extend through the oxidant manifold bore  32 . Preferably, the coupling  26  and the oxidant manifold  26  are welded together by a bead  40  extending around the entire periphery of the coupling  28  as shown to both secure the coupling  28  and the oxidant manifold  26  together and seal the interface therebetween. The coupling  28  can be formed of any suitable material such as, for example, stainless steel. 
     The oxidant tube  30  is sized to closely fit within the bore  32  of the oxidant manifold  26  and to extend the full length of the ignitor rod  24  and the insulator sleeve  20 . The oxidant tube  30  fully extends into the bore  32  and abuts the forward end of the coupling  28  with the ignitor rod  24  and the insulator sleeve  20  axially extending through the oxidant tube  30 . The inner diameter of the oxidant tube  30  is sized to form a first or oxidant annular passageway  42  for the oxidant between the inner surface of the oxidant tube  30  and the outer surface of the insulator sleeve  20 . For an insulator sleeve  20  having an outer diameter of about {fraction (3/16)} inches, for example, the oxidant tube  30  can have an outer diameter of about ⅜ inches and a wall thickness of about 0.035 inches. 
     At least one opening  44  is preferably provided in the oxidant tube  30  to cooperate with the oxidant manifold passageway  36  to communicate the oxidant manifold passageway  36  with the first annular passageway  42 . The oxidant tube  30  is rigidly secured to the oxidant manifold  26  with the passageway  36  and the opening  44  aligned. Preferably, the oxidant tube  30  and the oxidant manifold  26  are welded together by a bead  46  extending around the entire periphery of the oxidant tube  30  as shown to both secure the oxidant tube  30  and the oxidant manifold  26  together and seal the interface therebetween. The oxidant tube  30  can be formed of any suitable material such as, for example, stainless steel. 
     As shown in FIG. 5, suitable spacers  48  are provided for maintaining the oxidant tube  30  and the ignitor rod  24  generally coaxial to maintain the shape of the first annular passageway  42 . The spacers  48  can advantageously be spot welds between the tube  30  and the sleeve  20 . 
     As best shown in FIG. 1, the gas manifold assembly  16  includes a gas manifold  50  and a gas tube  52 . The gas manifold  50  has an axially extending opening or bore  54  therethrough which is sized for closely receiving the gas tube  52  as described in more detail hereinafter. The gas manifold  50  also has a radially extending opening  56 . The radial opening  56  is sized and adapted for receiving a threaded check valve of a gas supply line. Preferably, the opening  56  is partially threaded and has an unthreaded frusto-conically shaped bottom surface. A small radially extending passage  58  connects the bottom surface of the opening  56  with the bore  54  to provide gas flow communication between the opening  56  and the bore  54 . The gas manifold  50  is preferably a wafer of standard bar stock and more preferably a wafer of a standard round bar stock. The gas manifold  50  can be formed of any suitable material such as, for example, stainless steel. Preferably, the gas manifold  50  and the oxidant manifold  26  are substantially identical except for the diameters of the respective bores  54 ,  32  therethrough. 
     The gas manifold  50  is rigidly secured to the oxidant manifold  26  with the bores  54 ,  32  generally coaxial and the oxidant tube  30 , the ignitor rod  24 , and the insulator sleeve  20  extending through the gas manifold bore  54 . Preferably, the gas manifold  50  and the oxidant manifold  26  are welded together by a bead  60  extending around the entire periphery of the manifolds  26 ,  50  as shown to both secure the gas manifold  50  and the oxidant manifold  26  together and seal the interface therebetween. 
     The gas tube  52  is sized to closely fit within the bore  54  of the gas manifold  50  and to extend the full length of the ignitor rod  24 , the insulator sleeve  20 , and the oxidant tube  30 . The gas tube  52  fully extends into the bore  54  and abuts the forward end of the oxidant manifold  26  with the oxidant tube  30 , the ignitor rod  24 , and the insulator sleeve  20  axially extending through the gas tube  52 . The inner diameter of the gas tube  52  is sized to form a second or gas annular passageway  62  for the gas between the inner surface of the gas tube  52  and the outer surface of the oxidant tube  30 . For an oxidant tube  30  having an outer diameter of about ⅜ inches, for example, the gas tube  52  can have an outer diameter of about ½ inch and a wall thickness of about 0.049 inches. 
     At least one opening  64  is preferably provided in the gas tube  52  to cooperate with the gas manifold passageway  58  to communicate the gas manifold passageway  58  with the second annular passageway  62 . The gas tube  52  is rigidly secured to the gas manifold  50  with the passageway  58  and the opening  64  aligned. Preferably, the gas tube  52  and the gas manifold  50  are welded together by a bead  66  extending around the entire periphery of the gas tube  52  as shown to both secure the gas tube  52  and the gas manifold  50  together and seal the interface therebetween. The gas tube  52  can be formed of any suitable material such as, for example, stainless steel. 
     As shown in FIG. 5, suitable spacers  68  are provided for maintaining the gas tube  52  and the oxidant tube  30  generally coaxial to maintain the shape of the second annular passageway  62 . The spacers  68  can advantageously be spot welds between the tubes  30 ,  52 . 
     With the ignitor assembly  12 , the oxidant manifold assembly  14 , and the gas manifold assembly  16  assembled in this manner, the first and second annular passageways provide adjacent and coaxial paths for the oxidant and the gas respectively (best shown in FIG.  5 ). While the illustrated embodiment has been described with the first or inner passageway  42  being provided for the oxidant and the second or outer passageway  62  being provided for the gas, it should be noted that the use of the passageways  42 ,  62  can be interchanged. The second or outer passageway  62 , however, is preferably used for the gas because it may be maintained at a higher temperature and therefore it is less likely to have condensation formed therein. Note that the flowing oxygen can act as a coolant. When the gas is supplied in an inner passageway which is isolated or insulated from the heat of exterior flames, the temperature of the gas can drop within the passageway until condensate is formed therein. As appreciated by those skilled in the art, this is a situation to be avoided. 
     FIG. 7 illustrates the above-described pilot burner  10  installed in the wall  70  of a furnace. The rod  24 , sleeve  20 , and tubes  30 ,  52  of the pilot burner  10  extend through the wall  70  such that the manifolds  26 ,  50  are on the outside of the furnace wall  70  and the free ends of the rod  24 , sleeve  20 , and tubes  30 ,  52  are on the inside of the furnace wall  70 . The pilot burner  10  is secured to the furnace wall  70  in any suitable manner. A first fitting, such as a check valve  72 , connects an oxidant supply line  74 , preferably oxygen, to the opening  34  of the oxidant manifold  26  and a second fitting, such as a check valve  76 , connects a gaseous fuel supply line  78 , preferably propane, to the opening  56  of the gas manifold  50 . A cable  80  connects a transformer to the ignitor to selectively supply a suitable voltage thereto. 
     To fire the pilot burner  10 , an electric spark is generated by means of the transformer and the ignitor  18 . The first check valve  72  is opened to initiate a flow of oxygen through the first check valve  72 , the oxidant manifold opening  34 , the passageway  36 , the oxidant tube opening  44  and into the first annular passageway  42 . The oxygen flows down the first annular passageway  42  to the forward free end of the oxidant tube  30  where it exits the pilot burner  10 . The second check valve  76  is opened to initiate a flow of gas through the second check valve  76 , the gas manifold opening  56 , the passageway  58 , the gas tube opening  64  and into the second annular passageway  62 . The gas flows down the second annular passageway  62  to the forward free end of the gas tube  52  where it exits the pilot burner  10 . Preferably, each of these operations are performed by an automatic controller. Once the gas and oxygen each arrive at the forward end of the pilot burner  10 , the desired flame  82  is obtained. 
     Typically, a UV sensor monitors the pilot burner  10  to verify that it in fact is successfully burning. Once such verification is made, the sensor signals the controller to activate the main burner of the furnace. 
     It can be appreciated from the above description, that the pilot burner  10  of the present invention is relatively simple and inexpensive to produce. Seals are achieved by welds and pipe threads. The manifolds are machined from common bar stock. The assembly is relatively reliable and easy to service with simple seals and simple removal of the ignitor. It can also be appreciated that the modular nature of the manifold and tube assemblies enables additional manifolds and tubes to be stacked beyond the two of the illustrated pilot burner if additional concentric annular passageways are desired. 
     The present disclosure describes several embodiments of the invention, however, the invention is not limited to these embodiments. Other variations are contemplated to be within the spirit and scope of the invention and appended claims.