Combustible fuel igniting apparatus

Abstract

Fuel ignitor apparatus especially adapted for use in a commercial baking oven having a plurality of fuel burner tubes susceptible of movement in response to changes in ambient temperature. The ignitor apparatus associated with each burner tube is coupled to the latter for movements therewith. Each ignitor is mounted on a wall of the oven in such manner as to enable bodily movement of such ignitor relative to the oven so as to avoid imposing bending stresses on the ignitor or the oven.

Description

This invention relates to apparatus especially adapted for use in an oven of a commercial bakery for igniting a combustible fuel issuing from a burner and maintaining the ignitor in a predetermined position relative to the burner.

BACKGROUND OF THE INVENTION

In a conventional commercial bakery a gas fired oven defines an enclosure or combustion chamber through which goods to be baked are conveyed longitudinally of the oven by chain or other conveyors. Extending transversely of the path traversed by the conveyors is a plurality of burner tubes which are spaced apart from one another so as to enable the interior of the oven to be heated to desired temperature levels.

Each burner is coupled to a source of combustible fuel, such as natural or propane gas, and each burner is provided with ribbon or other fuel outlets through which the gas may pass for combustion. At a selected point along the length of each burner is positioned a fuel ignitor by means of which fuel flowing through the burner outlet may be ignited.

The temperature in the oven normally is controlled by varying the number of burners which are lighted at any given time. For higher temperatures, as may be required by the proper baking of some goods, all or most of the burners are ignited. In other instances, in which the goods being baked do not require higher temperatures, some of the burners may be idle or turned off.

It is conventional to provide as part of the fuel igniting apparatus a spark generator and a flame sensor which is operable to sense the presence or absence of flame issuing from a burner. When fuel initially is discharged from a burner tube it is conventional to ignite such fuel by means of the generation of sparks and form a flame. If the presence of the flame is sensed, the ignitor is disabled. If no flame is sensed after a predetermined time, the ignitor and the flow of fuel through the affected burner are terminated.

The temperature within the oven affects the materials, usually metals, from which the burner tube and the ignitor apparatus are made. In general, the burner and ignitor apparatus materials expand when heated, and contract when cooled. However, due to the differences in materials and differences in lengths of such apparatus, the expansion and contraction rates are not the same, thereby resulting in distortion and movements of the burner and ignitor. Accordingly, it is preferred to attach the ignitor apparatus to the burner tube so that the ignitor apparatus will move in accordance with the movements of the burner tube which, in some instances, may be as much as several inches or centimeters.

Both the burner tubes and the ignitor apparatus associated with each tube extend into the oven from the exterior thereof. Both the burner tubes and the associated ignitor apparatus conventionally are supported on a wall of the oven. In those instances in which a burner tube moves a significant distance due to thermal changes, the associated ignitor apparatus may have to move a significant distance also since it is connected to its associated burner tube. Repeated movements of the ignitor apparatus in response to movements of its associated burner tube imposes significant stress on the component parts of the ignitor apparatus which, in time, can result in structural failure of such apparatus.

Fuel ignitor apparatus that has functioned very well following its introduction to the industry is disclosed in Glidden U.S. Pat. No. 6,808,389. Ignitor apparatus constructed in accordance with the present invention incorporates many of the advantageous characteristics of the patented apparatus, but includes improvements which enhance its operation and minimize its expense.

SUMMARY OF THE INVENTION

Ignitor apparatus constructed in accordance with a preferred embodiment of the invention comprises an electrically conductive outer support sleeve through which extends an electrically conductive ignitor electrode, the electrode being electrically insulated from the outer sleeve by insulators. An electrically conductive, flag-like fuel concentrator is fixed at one end of the outer sleeve and is so positioned adjacent the ignitor electrode as to establish a gap of predetermined width therebetween which may be traversed by sparks for the purpose of igniting fuel issuing from the burner tube. That end of the ignitor sleeve adjacent the fuel concentrator is fastened to the adjacent burner tube so as to move with the latter as it flexes in response to temperature variations. The opposite end of the ignitor sleeve extends through an opening in the oven wall and is accommodated in a bushing in such manner as to be rockable about a vertical axis. The arrangement is such that, when the burner tube deflects, the ignitor will move accordingly, but instead of bending, the sleeve will rock about the vertical axis, thereby avoiding the imposition of bending stresses on the ignitor apparatus.

The construction of the ignitor apparatus disclosed herein enables the advantageous characteristics of the apparatus shown in the aforementioned patent to be obtained, but provides substantial cost reductions.

THE DRAWINGS

FIG. 1 is a fragmentary view, partly in side elevation and partly in section, illustrating ignitor apparatus constructed in accordance with the invention and mounted on a support forming part of an oven wall;

FIG. 2 is an exploded view of apparatus shown in FIG. 1, but omitting the oven wall and the mounting means for the ignitor apparatus;

FIG. 3 is an elevational view of one end of the ignitor apparatus;

FIG. 4 is a greatly enlarged, fragmentary detail of that portion of FIG. 3 within the dotted line circle; and

FIG. 5 is a greatly enlarged view illustrating the details of the ignitor apparatus mounting means and the range of movement of the ignitor apparatus.

DESCRIPTION OF THE DISCLOSED EMBODIMENT

Ignitor apparatus constructed in accordance with the disclosed embodiment of the invention is designated generally by the reference character 1 and is adapted for installation in a commercial baking oven of the kind having a combustion chamber or enclosure formed by walls, one of which is shown at 2 in FIG. 5. Although not shown in the drawings the oven includes within the enclosure one or more conveyors which support and transport products longitudinally of the oven from an oven inlet to an oven outlet. The oven enclosure may include one or more longitudinally spaced sections each of which has apparatus (not shown) for controlling temperature. At longitudinally spaced intervals each of the oven sections has laterally extending combustible fuel burners, one of which is shown at 3 in FIGS. 3-5, and each such burner extends transversely of the path along which the bakery products are moved by the conveyors, as is conventional. Each burner 3 includes a hollow tube 4 which partially occupies an opening 5 in the oven wall 2 and is supported by a support member 6 that is secured to the oven wall 2 by suitable means such as bolts 7. The burner tube 4 has a fitting 8 at one end thereof and external of the oven for connection to a supply of combustible fuel such as natural or propane gas. At one side of the tube 4 is a ribbon fuel outlet 9 (FIGS. 3 and 4) through which the fuel gas may pass into the interior of the oven. Depending on the size of the oven, the burner tube may be eight or more feet in length.

The ignitor apparatus 1 comprises an electrically conductive sleeve 10 having plugs 11 and 12 at opposite ends thereof. Each plug is formed of known electrically insulating material which is capable of withstanding without adverse consequences the heat within the oven. Each plug has an axial bore 13 through which extends an electrically conductive ignitor electrode 14. The electrode 14 is bent at one end as at 15 to form an extension 16 which extends obliquely and terminates in a terminal 17 which parallels the electrode 14.

That portion of the electrode 14 which spans the plugs 11 and 12 is encircled by an electrically non-conductive tube 18 formed of suitable material, such as Teflon.

Pinned or otherwise suitably fixed to the electrode 14 adjacent the plug 12 is a transversely extending, restraining pin 19 that is accommodated in a recess or slot 20 formed in the outer surface of the plug 12. The opposite end of the electrode 14 is threaded as at 21 for the accommodation of a nut 22. The threaded end of the electrode is encircled by a spring 23 which bears against the outer surface of the plug 11 and the confronting surface of the nut 22 so as constantly to exert a yieldable force on the electrode to maintain the restraining pin 19 in the slot 20. At the free end of the threaded end of the electrode is a fitting 24 which electrically connects the electrode to wiring forming part of an ignition circuit and an ignition sensor proving unit (ISPU) of the kind disclosed in the aformentioned U.S. Pat. No. 6,808,389.

Welded to the outer surface of the sleeve 10 as at 25 is an electrically conductive ground rod 26 to the free end of which is fixed an electrically conductive, flag-like fuel gas concentrator 27. The concentrator 27 includes an electrically conductive, flag-like plate 28 having a free end 29 which is bent so as to occupy a position spaced from the free end 17 of the electrode 14 by a gap 30 of predetermined width. The width of the gap is such as to enable sparks to jump from the electrode free end 17 to the free end 29 of the plate 28. To enhance the ability of sparks to traverse the gap 30 the free end 17 of the electrode is knurled as shown at 31 and the free end of the accumulator plate 28 is provided with a sharp edge 32. See FIG. 4.

As is best shown in FIG. 5, the ignitor apparatus 1 is mounted on the oven wall 2 adjacent a burner tube 4 so that when installed the sleeve 10 extends through an oversized opening 33 in the mounting plate 6 which is adjacent the opening through which the burner tube 4 extends. Secured to the mounting plate 6 and externally of the oven is a mounting ring 34. A bushing 35 has an annular body 36 having an annular projection 37 which extends through the mounting ring 34 and is secured thereto by a set screw 38. The bushing 35 has an axial bore which extends in opposite directions from a central point 39 and forms two annular passages 40 and 41, both of which taper inwardly from opposite ends toward the central point 39.

The bushing body 36 has a pair of opposed pivot and securing screws 46, each of which has a head at one end and a pointed free or opposite end which bears upon the sleeve 10. The head of each screw is accommodated in a counterbore 44. The head of each screw seats on the base of its respective counterbore which is so located as to preclude movement of the screws inwardly a distance sufficient to pierce the wall of the sleeve 10. However, the pointed ends of the screws do slightly indent the wall of the sleeve 10, thereby preventing movement of the sleeve transversely of the bushing and establishing a pivot axis about which the tube may rock from side to side as is indicated in dash lines in FIG. 5.

Following installation of the ignitor apparatus 1 on the oven wall the sleeve 10 is secured to the burner tube 4 by a bracket 46 (FIG. 3) having an arm 47 terminating at one end in a foot 48 which is fixed to the adjacent burner tube 4. The opposite end of the arm 47 forms a partial loop 49 which partially encircles the ignitor sleeve 10. The ignitor apparatus 1, therefore, is secured at all times to the adjacent burner tube 4 so as to enable the ignitor apparatus to move with the burner tube in those instances in which it moves in response to variations in ambient temperature within the oven.

It has been found that, in virtually all instances, the movement of a burner tube due to temperature variations is in a substantially horizontal plane. Since the ignitor assembly sleeve 10 extends beyond the opposite ends of the bushing 35, the tapers of the passages 40 and 41 should be sufficient to enable the sleeve to partake of adequate movement to avoid the imposition of bending stress on the sleeve 10 or on the support 6 when the sleeve moves. In the event the movement of the burner tube is not purely horizontal, the annular configuration of the passages 40 and 41 through the bushing will enable the ignitor sleeve 10 to move with the burner tube regardless of its direction of movement.

The heat of the oven may generate steam as a result of the baking of products or from the heating of air within the sleeve 10. Accordingly, vent openings 50 are formed in that portion of the sleeve 10 which is external of the oven to enable air and/or steam to pass therethrough. Also external of the oven the ignitor sleeve 10 supports a terminal for electrical circuitry 51 which completes the ignition and ground circuit to the ISPU apparatus (not shown) in the manner referred to in U.S. Pat. No. 6,808,389.

The disclosed ignitor apparatus is representative of a presently preferred embodiment of the invention, but is intended to be illustrative rather than definitive thereof. The invention is defined in the claims.

Claims

1. In an oven assembly wherein combustible fuel is emitted from a burner tube within a combustion chamber, said burner tube being susceptible to distortion and movements in response to changes in ambient temperature, said fuel being ignitable by sparks generated by an ignition circuit having ignitor and ground electrodes spaced from one another by a spark gap and carried by a support member in such position as to locate said gap in the path of fuel emitted from said burner tube, said support member being coupled to said burner tube for movements therewith, the improvement comprising means mounting said support member in said chamber for bodily rocking movements of said support member relative to said chamber in response to and in the directions of said movements of said burner tube.

2. The assembly according to claim 1 wherein said mounting means comprises a bushing having a passage in which said support member is accommodated, means for securing said bushing to said chamber, and adjustable coupling means operable to maintain said support member in said bushing and enable pivotal movements of said support member relative to said bushing about an axis.

3. The assembly according to claim 2 wherein said coupling means comprises at least one pin in engagement with said support member and preventing movement of said support member transversely of said axis.

4. The assembly according to claim 3 wherein said pin defines said axis about which said support member is rockable.

5. The assembly according to claim 2 wherein the passage in said bushing is tapered inwardly from opposite ends of said passage.

6. The assembly according to claim 2 wherein said axis is substantially vertical.

7. The assembly according to claim 1 including at least one opening in said support member externally of said chamber and through which gas may pass into said support member.

8. The assembly according to claim 1 wherein at least one of said electrodes is knurled adjacent said gap.

9. The assembly according to claim 1 wherein said ground electrode comprises a flag having a sharp edge confronting said gap.

10. An ignitor construction for use in igniting a combustible fuel, said construction comprising an elongate, tubular support member having opposite ends and being formed of electrically conductive material; electrically conductive ignitor and ground electrodes electrically insulated from one another and carried by said support member in such positions relative to one another as to establish a gap across which an electrically generated spark may jump; and swivel means mounting said support member between the ends thereof for bodily rocking movements of said support member about an axis.

11. The construction according to claim 10 wherein said swivel means comprises a bushing through which said support member extends, and including pivot means reacting between said bushing and said support member for enabling said rocking movement of the latter about said axis relative to said bushing.

12. The construction according to claim 11 wherein said bushing includes a passage therethrough, said passage flaring in opposite directions from a point between opposite ends of said passage.

13. The construction according to claim 11 wherein said pivot means comprises a pair of opposed pins carried by said bushing and extending toward one another for engagement with said support member on opposite sides of the latter, and limit means for limiting movement of said pins in a direction toward said support member following engagement of said pins with said support member.

14. The construction according to claim 10 wherein at least one of said electrodes has a knurled surface adjacent said gap.

15. The construction according to claim 10 wherein one of said electrodes comprises a flag one end of which confronts the other of said electrodes and forms with the other of said electrodes the boundary of said gap.

16. The construction according to claim 15 wherein said edge of said one of said electrodes has a sharp surface confronting the other of said electrodes.

17. The combination of an elongate burner tube susceptible of distortion and movements in response to changes in ambient temperature, said burner tube having an opening therein through which combustible fuel may flow along a path, and an ignitor for igniting fuel flowing through said opening, said ignitor comprising an elongate support member supporting a spark electrode and a ground electrode spaced from one another a distance to establish therebetween a spark gap; means independent of said burner tube mounting said support member in a position alongside but spaced a selected distance from said burner tube; and means coupling said support member to said burner tube for maintaining said support member in such position that said spark gap lies in the path of fuel flowing through said opening, said mounting means enabling said support member and the electrodes carried thereby to swivel in response to said movements of said burner tube and maintain said support member at said selected distance from said burner tube.

18. The combination according to claim 17 wherein said mounting means comprises a bushing having a passage in which said support member is accommodated, and adjustable coupling means operable to maintain said support member in said bushing and enable rockable movements of said support member about an axis relative to said bushing.

19. The combination according to claim 18 wherein said coupling means comprises at least a pair of pins in engagement with said support member, said pins defining said axis and preventing movement of said support member transversely of said axis relative to said bushing.

20. The combination according to claim 18 wherein the opening in said bushing is tapered inwardly from opposite ends of said opening.