US 2715200 A
Description (OCR text may contain errors)
United This invention relates to ignition devices, and especially to ignition electrode units, for gas burners.
Ignition electrode units to which the present invention pertains are of the type used especially, though by no means exclusively, in bakery ovens and the like. Accordingly, electrode units of this type are relatively long so that they may extend from the outside of the oven through the heavily insulated and accordingly deep front wall thereof to afford an external terminal connection with wiring, yet provide a sparking electrode in igniting proximity with a gas burner in the interior of the oven. Conventional ignition electrode units of this type comprise ceramic insulators or end pieces through which extends a long conductor having a wire terminal at one end and carrying a sparking electrode at the other end, and a long tubular mounting sleeve which is interposed between the end pieces and surrounds the conductor. While previous ignition electrode units of this type are satisfactory insofar as their burner igniting performance is concerned, their rigid construction gives rise to frequent breakdown or malfunction, due especially to ready breakage of the ceramic end pieces by the differential expansion of the conductor and mounting sleeve in the* hot oven, with the result that these previous units frequently require costly repair or replacement with ensuing temporary loss of oven performance.
lt is an object of the present invention to provide an ignition electrode unit of this type which is highly eicient and reliable in performance and, in comparison to prior units, assuredly long-lasting and unaffected by the differential expansion of the conductor and mounting sleeve.
Another object of the present invention is to provide an ignition electrode unit of this type with a resilient member, preferably a spring, which takes up the dif ferential expansion of the conductor and mounting sleeve in such wise that the ceramic end pieces are not in any way subjected to harmful stresses springing from the uneven expansion of these parts.
It is a further object of the present invention to provide an ignition electrode unit of this type in which the ceramic end pieces are in an exceedingly simple structural manner securely locked to the opposite ends, respectively, of the mounting sleeve against rotation thereon without requiring any harmful forced it between these parts.
Another object of the present invention is to provide an ignition electrode unit of this type in which the conductor is in an exceedingly simple structural manner securely locked directly to a ceramic end piece against rotation therein, yet has free axial play therein for the take-up of the differential expansion of the conductor and mounting sleeve by the before-mentioned spring without exerting the least stress on this or the other ceramic end piece.
It is a further object of the present invention to provide an ignition electrode unit of this type in which the ice ceramic end pieces are of identical construction, thereby not only reducing the number of different stock parts for the instant unit, but also greatly facilitating the error-less assembly of the parts of the unit.
It is another object of the present invention to provide an ignition electrode unit of this type of which the conductor is a single Wire of uniform cross-section throughout for its ready assembly with the other parts of the. unit, and carries at one end beyond the adjacent ceramic end piece a collar for lengthwise adjustable safe mounting therein of the sparking electrode by a readily accessible set screw in the collar.
A further object of the present invention is to provide an ignition electrode unit of this type of which the parts .i are few in number and of exceedingly simple construction, and lend themselves to quick assembly by eicient mass production methods at very low cost and without requiring any special skill, and to equally quick disassembly for the repair or replacement of any part thereof if necessary.
Further objects and advantages will appear tok those skilled in the art from the following, considered in conjunction with the accompanying drawings.
In the accompanying drawings, in which certain modes of carrying out the present invention are shown for illustrative purposes:
Fig. l is a perspective view of an installed ignition electrode unit embodying the present invention.
Fig. 2 is an enlarged longitudinal section through the installed ignition electrode unit, taken substantially on the line 2 2 of Fig. l;
Fig. 3 is an enlarged cross-section through the unit as taken on the line 3 3 of Fig. 2;
Fig. 4 is an enlarged fragmentary longitudinal section through an ignition electrode unit embodying a modified form of the present invention; and
Fig. 5 is an enlarged fragmentary longitudinal section through an ignition electrode unit embodying another modified form of the present invention.
Referring to drawings, and more particularly to Fig. l thereof, the reference numeral it! designates an ignition electrode unit which is shown installed, in the present instance, in the front wall of a bakery oven or the like. The front wall of the oven comprises outer and inner walls 12 and 14, respectively, and the space therebetween is usually filled with suitable heat-insulating material (not shown). interposed between the outer and inner oven walls 12 and 14 is a sleeve i6 through which to introduce into the interior of the oven the instant electrode unit 10 as well as a gas supply pipe 18 for a gas burner unit 2t) having the flame side 22. The outer ends of the gas supply pipe 18 and electrode unit l@ are suitably mounted in a cover plate 24 on the outer oven wall 12. rThus,
the outer end of the electrode unit 10 may removably be mounted in the cover plate 24 by means of a set screw 26 (see also Fig. 2). The inner end of the electrode unit 10 may conveniently be secured to the burner unit 2t) by means of a strap 28. The cover plate 24 is preferably also provided with a peephole which is normally closed by a pivoted cover 3%. rhe cover Si) may be turned into open position to observe through the peephole which is normally closed by a pivoted cover 39. The cover 30 may be turned into open position to observe through the peephole the ignition of the burner unit 20 at the flame side 22 thereof, as well as the ames themselves for their possible regulation if necessary. The tip 32 of the sparking electrode 34 of the ignition unit 10 is in this instance shown somewhat bent into proximity to the flame side 22 of the burner unit 2i), and the strap 2S may conveniently be interrupted at 36 so that the sparking action of the electrode tip 32 may be observed through the peephole in the cover plate 24.
As shown in Fig. 2, the ignition electrode unit 10, hereinafter sometimes referred to as unit, comprises two preferably cylindrical end pieces 38 and 4t) of heatresistant and electrically non-conductive ceramic material, an electrical conductor 42 in the form of a single wire of uniform cross-section throughout, and an outer tubular spacer sleeve 44 of steel or any other suitable heatresistant material between the ceramic end pieces 38 and 49. The end pieces 38 and 40 have diametrically reduced portions 46 and 48, respectively, which are received with a sliding fit in the mounting sleeve 44, and the opposite ends of the latter bear against annular shoulders d and 52 on the end pieces 38 and 40, respectively. Extending with a sliding fit through round holes 54 and S6 in the end pieces 38 and 40, respectively, is the conductor 42. In order to lock the conductor 42 against rotation in the unit 10, the former is provided with one, and preferably two diametrically opposite keys 58 and 60 which, as shown in Figs. 2 and 3, are received in key ways 62 and 64, respectively, in the ceramic end piece 46, thus providing a splined connection between the conductor 42 and end piece 40. Conveniently, the keys S8 and 60 are simply swaged from the solid wire stock of the conductor 42 in the manner best indicated in Fig. 3.
The opposite end piece 38, though not used in the present instance for locking the conductor 42 against rotation in the unit 10, is nevertheless provided with the same key ways 62 and 64', and is in all other respects identical with the end piece 46 so that these end pieces may be used interchangeably.
The conductor 42 may in its inner end press-fittedly or otherwise securely receive the sparking electrode 34 which may be an electrical conductor of any suitable, especially heat-resistant metal, such as commercially known Nichrome, for instance. The conductor 42 is near its inner end preferably provided with further lateral projections 70 and 72 (Fig. 2) which, like the keys 58 and 6i), are conveniently swaged from the solid wire stock of the conductor 42, and serve as shoulders to bear against a washer 74 on the adjacent end of the ceramic end piece 40.
Surrounding the outer end of the conductor 42 is a preloaded compression spring 76 which is interposed between a spring-retainer 78 and a washer 8f) on the adjacent end of the ceramic end piece 38 (Fig. 2). Received on the threaded outer end of the conductor 42 is a suitable terminal 82 for wiring w (Fig. l). The terminal 82 serves also to hold the spring-retainer 7 8 in place.
In use, the greater length of the unit is subjected to i construction of the unit lt), the differential expansion of the conductor 42 and mounting sleeve 44 fail to set up any stresses whatsoever in the unit lt) and especially in the readily breakable ceramic end pieces 38 and 4t), the spring 76 acting to take up the differential expansion of the conductor 42 and mounting sleeve 44 without harm to any of the parts of the unit.
ln order to hold the tip 32 of the sparking electrode 34 in igniting relation with the flame side 22 of the burner unit 20, it is also necessary to lock the ceramic end pieces 38 and 40 against rotation in the mounting sleeve 44. To this end, the diametrically reduced portions 46 and 48 of the end pieces 38 and 40, respectively, are provided with ats 86 and 88, respectively, against which the adjacent ends of the mounting sleeve 44 are conveniently deformed, preferably in the manner indicated in Fig. 3. Thus, Lperipherally spaced portions 90 and 92 of the originally cylindrical inner end of the mounting sleeve 44 may conveniently be depressed inwardly to form spaced flat shoulders in engagement or near engagement with spaced portions of the flat 88 on the end piece 40. The outer end of the mounting sleeve 44 may similarly be deformed to provide flat shoulders in engagement or near engagement with spaced portions of the flat 86 on the end piece 38. Of course, the flat shoulders in the opposite ends of the mounting sleeve 44 are formed therein prior to the assembly of the latter with the end pieces 38 and 40, and care is taken in the assembly of these parts that the ceramic end pieces 38 and 4t) slide freely into locked interengagement with the opposite ends of the mounting sleeve 44 without sustaining any damage.
Fig. 4 shows a modified interlock between a mounting sleeve 44 and a ceramic end piece 40. In this case, there is inwardly deformed in the mounting sleeve 44' a transverse bead 94 which, in the assembled relation of the parts 40 and 44', is in engagement or near engagement with the at 88 on the end piece 40.
Fig. 5 shows another modified form of the invention. In this case, the swaged lateral stop shoulders 70 and 72 near the inner end of the conductor 42 in Fig. 2 are replaced by a suitably secured collar 98 which acts as a stop for the conductor and receives a readily accessible set screw 100 for the lengthwise adjustable mounting of the sparking electrode 34' in a bore 102 in the conductor.
The instant ignition electrode unit in its various forms secures several important advantages. Thus, the instant unit has, in comparison to previous units of this type, an exceptionally long useful life during which it will efficiently and reliably perform its designated function of igniting a gas burner unit. This is due primarily to the take-up of the differential expansion of the conductor and mounting sleeve by the described spring without setting up any stresses whatsoever in the readily breakable ceramic end pieces. The differential expansion take-up spring further permits the entirely satisfactory, though non-binding interlock between the ceramic end pieces and the mounting sleeve on the one hand, and between the ceramic end pieces and the conductor on the other hand, against rotation of these parts relative to each other, without imposing on the ceramic end pieces any strain whatsoever which might conceivably lead to breakage of the same. The identical construction of the ceramic end pieces not only reduces the number of different stock parts for the instant electrode unit, but also greatly facilitates the error-less assembly of the parts of the unit to the extent where even unskilled labor will satisfactorily perform the task of assembling these parts, Thus, regardless of any scheduled mode of assembling the parts of the instant electrode unit, the assembler need, by virtue of the identical construction of the ceramic end pieces at both ends of the unit, pay no attention whatsoever to the assembly of these end pieces with the mounting sleeve for no possible error can arise from the assembly of these identical end pieces with the mounting sleeve. The preferred and modified forms of the interlock between the ceramic end pieces and the mounting sleeve are structurally exceedingly simple, and so is the specific interlock between the conductor and either one of the ceramic end pieces. Thus, it is an exceedingly simple operation to deform the opposite ends of the mounting sleeve in the manner shown in Fig. 3 or in the manner shown in Fig. 4, and the formation of the keys on the conductor by the simple expediency of swaging them from the solid wire stock of the conductor is especially ingenious. Equally ingenious is the molding of the ceramic end pieces with the key ways, for this involves no greater cost than if they were molded without key ways. The provision of a collar in one of the modified forms of the electrode unit affords a convenience stop shoulder for the conductor and a secure mount for a readily accessible set screw with which to hold the sparking electrode in lengthwise adjusted position and also against rotation on the unit. The number of parts of which the electrode unit is composed is exceedingly low, and all the parts are simple in construction and readily lend themselves to quick assembly by efficient mass production methods at very low cost and without requiring any special skill. The instant electrode unit lends itself equally Well to quick disassembly of its parts for the repair or replacement of any part or parts thereof.
The invention may be carried out in other specific ways than those herein set forth Without departing from the spirit and essential characteristics of the invention, and the present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.
1. A long ignition electrode unit for gas burners in bakery ovens and the like, comprising two apertured ceramic end pieces of which the aperture of at least one end piece has a longitudinal key way; a mounting sleeve interposed between and abutting said end pieces and interlocked with at least said one end piece against rotation relative thereto; an electrical conductor extending through said sleeve with clearance therefrom and being axially slidably received intermediate its ends in the apertures in said end pieces, said conductor having a key received in the key way of said one end piece, and opposite shoulders of which one shoulder engages the outer end of a certain t3 end piece and the other shoulder is outwardly spaced from the other end piece; and a spring interposed between said other shoulder and other end piece and adapted resliently to hold said end pieces and sleeve in said abutting relation and take up all differential expansion of said conductor and sleeve on subjection of the unit to heat.
2. A long ignition electrode unit as set forth in claim 1, in which said conductor is of solid wire stock, and said key is a swaged projection of said wire stock.
3. A long ignition electrode unit as set forth in claim 1, in which said conductor is of solid wire stock, and said one shoulder and key are swaged projections, respectively, of said wire stock.
4. A long ignition electrode unit as set forth in claim 1, in which both of said end pieces are identical and, hence, interchangeable.
References Cited in the le of this patent UNITED STATES PATENTS 1,288,898 Hunter Dec. 24, 1918 1,361,688 Courson Dec. 7, 1920 1,647,099 MacDonald Oct. 25, 1927 2,545,945 Ensign et al Mar. 20, 1951