US2795637A - Safety pilot - Google Patents

Description

Je il, 95? R.- P. FLAGG ETAI- SAFETY PILOT Filed May 51. 1952 I INVENTORS RAYMQND P. FLAG@V STANLEY w. mcKELLs BY RALPH T. osEN ArroR :Y

SAFETY PILOT Raymond P. Flagg, Moundsview Township, Ramsey County, Stanley W. Nickells, St. Louis Park, and Ralph T. Osen, Minneapolis, Minn., assignors to Minneapolis- Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application May 31, 1952, Serial No. 290,956

11 Claims. (Cl. 136--4) This invention relates to safety pilots generally and, more particularly, to a safety pilot or pilot generator of the type wherein a pilot burner for a main burner heats a thermocouple unit, which, in turn, controls a safety valve or other control valve for supplying gas to the main burner, and also to the pilot burner, if desired.

Safety pilots of the above mentioned type are well known in the heating controls art. Considerable work has been done by various controls manufacturers in their efforts to produce such a device that will give a steady electrical output, to assure proper operation of the safety valve throughout the varying operating conditions of the heating system as well as the variations in the gas supply pressure.

One of the chief sources of trouble in the more common safety pilots, now being used, lies in the linting up of the primary air openings in the Bunsen type of pilot burners, resulting in the softening of the pilot ame which, in turn, causes a reduction in the electrical output of the therrnocouple unit. Sometimes the reduction of the output is sufficient to cause the safety valve to close, even when there is a sutlicient pilot ame for igniting the main burner. Frequently, with Bunsen type of pilot burners, the burner port for igniting the main burner becomes clogged, 'resulting in an unsafe condition wherein the thermocouple unit remains energized, keeping the safety valve open when the main burner cannot be ignited by the pilot burner. The changes in the furnace drafts also affect the prior art safety pilots, so as to cause them to bring about a safety shutdown when such a shutdown is unnecessary.

One of the objects of the invention is to provide a safety pilot that will produce substantially a constant output in burner installations where linting conditions are bad and/or where varying gas pressures and furnace drafts are prevalent.

Anotherrobject of the invention is to provide a device, of the type described above, which is sturdy, compact, reliable and inexpensive.

Still another object of the invention is to provide a pilot burner which is easy to assemble and disassemble for manufacturing and cleaning purposes, respectively.

Still another object of the invention is to produce a safety pilot wherein the burner is small and is of the nonaerated type and has a rotatable connector tube that enables the pilot gas supply line to be brought into the safety pilot from any angular direction and can be mounted in any type of burner.

Another object of the invention is to provide a safety pilot that has burners on opposite sides of a thermocouple unit and has shielded ame retention orifices and a flash tube for conducting gas from a main burner to the pilotl burner for igniting the main burner by said pilot burner.

Still further objects of the invention will become apparent upon reading the following detailed description of the invention in conjunction with the accompanying draw- Iings wherein:

Patented .lune 11, 1957 Figure l is a side elevational View of the safety pilot with portions thereof broken away;

Figure 2 is a plan view of the safety pilot with portions thereof broken away;

Figure 3 is an end View of the safety pilot from the main burner side thereof; and

Figure 4 is a cross-sectional View along line 4--4 of Figure 2, with the thermopile shown in phantom andthe connector tube broken away.

As can be best seen in Figure 1 of the drawing, the safety pilot consists of a thermopile 11, a burner 12 for heating the thermopile at its upper hot-junction end 11n and a flash tube 13 for conducting gas from a main burner 14 to a positionover the burner 12 so as to ignite the main burner by a flame issuing from the burner 12.

The thermopile 11, generally speaking, is of conventional construction in that it consists of a plurality of series connected thermocouples 11C in stacked arrangement and insulated from a steel case by means of glass. The lower end 11b of the thermopile case is thickened around the cold-junction ends of the thermocouple elements and, for heat dissipating purposes, one element of each of the thermocouples projects downwardly toward the lower endof the case a short distance beyond where the elementsv are mechanically and electrically connected to form the cold-junctions. Metal wrapped leads 11d are connected to the er1-d elements of the thermopile and are embedded in cement in the case.

The burner 12 for heating the thermopile 11, consists of two hollow burners 15 and 16 made of sheet metal and arranged in parallel relationship to each other, on opposite sides of the thermopile 11 and in spaced relationship thereto. The burners are formed by stamping and folding a blank of sheet material upon itself in a manner to provide upwardly and outwardly inclined upper surfaces 17 and 18 on the burners 15 and 16, respectively, and upwardly and inwardly inclined at surfaces 19 an'd 20 along the lower edge of the burners 15 and 16,. respectively. The abutting end edges and the abutting bottom edges of the sheet material are then seam welded to provide gas-tight gas chambers or burners. Then the ends of the burners 15 and 16 are bent transversely, as shown at 15a 'and b and 16a and b, respectively, and are spot welded to brackets 21 and 22.

The bracket 21 has a transversely extending bifurcated arm 21a that straddles the upper portion 11a of the thermopile casing 11` and rests on the shoulder provided by the thickened portion-11b of the thermopile casing. The bracket member 21 also has fo-rmed thereon spaced abutment shoulders 2lb that also strad'dle the thermopile case portion 11a at a spaced point from the arm 21a. A screw threaded hole 21C is provided in the bracket 21 for the reception of a set screw 40 to lock the thermopile 'in its assembled relationship with respect to the burner. Additional screw threaded openings 21d are provide-d in the bracket 21 for the reception of mounting screws, in the event that the burner may advantageously be supported with respect to the, main burner by said bracket.

The bracket 22, also, has a transversely extending bifurcated arm 22a at the lower end thereof which straddles the portion 11a of the thermopile case. The bracket 22 extends beyond the upper end of the bracket 21 and has a pair of parallel arms 22b extending over the adjacent end of the burners 1S and 16 and terminates substantially in alignment with the adjacent end of the thermopile, to form a draft protected space therebetween. The two parallel arms 221; and the upper end of the bracket 22 have threaded openings 22C therein for selectively mounting the flash tube 13 in any one of the three positions by means of a screw 2.3 extending through a selected one of the holes 22e and a bracket 13a for the flash tube. Screw threaded holes 22d are also provided inthe bracket yand 25 are closer together.

v 3 22 substantially in alignment with the holes 21d in bracket 21, which holes serve the same purpose as the holes 21d, should it be more desirable to mount the burner 12 with respect to the main burner by the bracket 22.`

It will be noted that relatively large burner orifices or ports 24 and 25 are provided in the surfaces 17 and 18 at irregularly spaced distances and that similar orifices 26 and 27 in surfaces 17 and 18 respectively, are offset inwardly and downwardly outv of alignment with orifices 24 and 25, respectively, and that additional orifices 28 and 29 are still further Vinwardly and downwardly offset with respect to orifices 26 and 27, respectively. The orifices 24 and 25 are irregularly spaced apart so as to provide a more even spreading of llames issuing therefrom `against the thermopile as well as to provide flames of substantially the same height. By placing the orifices closer together, Yeach will tend to aspirate gas for the other. Therefore,

at the lower pressure ends of the burners, the orifices 24 The orifices 26 and 27 are positioned downwardly and inwardly from the orifices 24 andr25 to better carry a flame to and from the orifices 24 and 28 and between the orifices 25 and 29, respectively. The orifices 28 and 29, which are well shielded from drafts, are actually in alignment with each other so as to cause flames issuing therefrom to converge and pass upwardly between the arms 22b, the adjacent end of the thermopile, and the upper end of the bracket 22.

Gas is supplied to the burners 15 and 16 by means ofV the arm 22a and engaging the thermopile along a cir- Ycumferential portion thereof. The tube 30 extends upwardly between the legs of the bifurcated arm 22a and is held in substantially parallel relationship with the edge of the thermopile by the tube 30 engaging the inner end of the bifurcation in said leg 22a.

The header 33 has two annular ribs Vor lianges 35 thereon that straddle the adjacent end of the thermopile case portion 11a, with the portion of the header betweenV said ribs engaging the edge of the thermopile case. The

lends 36 of the header 33, extending beyond the ribs 35,

extend through openings 37 and 38 in the burners 15 and 16, respectively. The surfaces 39 of the ribs 35 are beveled or frusto-conical in shape so as to dimple the `surfaces of the burners 15 and 16 around the openings r37 and 38 during the assembly of the elements of the burner. This provides a rotatable and a substantially gas tight seal between the header and the burners v1S and 16.

From the above description ofthe rotatable connection between the header 33 and the burners 15 and 1,6 and th-e rotatable connection between the connector tube 30 and the header 33, it may be readily understood that with the thermopile removed from the assembly, the lower end of the tube 30 may be swung clockwise, with the header acting las a pivot, to position the collar 34 to one side of the arm 22a. The tube extension 30a may then be withdrawn from the bore 32 in the header, for cleaning purposes. Then, to assemble the burner Vand tube, the tapered end or extension is inserted. in the bore 32 and the tube rotated counterclockwise to reposition the collar 34 above the arm 22a. Insertion of the thermopile 11, with the right-hand end of the thermopile caseibearing vagainst the middle portion of the header 33 and against ,the circumference of the collar 34, andthe other end of the thermopile positioned betweenv the, legsof the Abifurcated arm21a and the members 2lb on the bracket .21, .theset sci-ew 40 may be tightened to frmlyhold the thermopile and the connector tube 30 firmly in assembled relationship with the burners 15 and 16.

Operation With the safety pilot mounted with respect to a main burner, as shown in Figures l and 2 of the drawing, with the lead wires 11d of the thermopile connected to an electrically controlled valve (not shown), for controlling the gas fiow to the main burner in a conventional arrangement, and the gas being admitted to the safety pilot burner through tube connector 30, gas issuing from the pilot burner orifices 24 through 29 may be manually ignited or ignited by some conventional remote ignition means. The flames at the burner orificesY will impinge on opposite sides of the upper or hot junction end of the thermopile case to generate electrical current to energizeY the electromagnet of the safety valve.

The safety valve will remain energized so long as there is a sufficient gas ow to the pilot burner to maintain the hot junction of the thermopile at a predetermined minimum temperature. This gas flow will be such that gas issuing from the main burner can become ignited by part of it passing through the flash tube 13 to the area above the pilot burner. Obviously, if the pilot flame goesV out or becomes suliicientlysmall as to be unable to ignite the gas from the main burner, the safetyvalve will become deenergized and cause safety'shutdown of the gas supply.

Y During normal and unusual draft conditions within the furnace, secondary air will flow upwardly over the outer surfaces ofthe burners 15 and 16 as well as through the flue or chimney-like passage between the burners 15 and 16 and the thermopile case. As long as there are normal draft conditions prevailing n the furnace andthe gas pressure is steady, the liames from the burner will impinge on the thermopile along one line.

Should the drafts fall below normal, the flame will impinge on the thermopile along a line at a lower level than the first mentioned line and thus maintain the heating of the hot junction end, even though a lesser Vamount of secondary air is reaching the burner. The

`reason that the llame lowers on the thermopile is due `to the fact that there is a reduced ow ofl air up betweenthe burner surfaces and the pile to tend to blow the llames away from the thermopile andy to coolV the case and, also, due to the fact that there is less aspirating effect due to the upward flow of air along the outer sur- Afaces of the burners to draw the flame away from the thermopile.

' In the event that theidraft becomes stronger than nor- .mal in the furnace, the ow of air up between the burner and the thermopile will tend to blow the flame away from .the thermopile and thus raise the line of contact of the vflame on the thermopile. This is a desirable result inasmuch as the flame will be harder with additional air ow to the burner orifices and thus will impart suf- -ficient heat to maintain the hot junction at substantially uniform temperature even though the ame is licking a smaller area of the thermopile hot junction .end. In extreme cases, the ame may actually be blown .clear of the thermopile and yet keep it uniformly heated.

Another result produced by the upwardly and inwardly inclined burner surfaces 19 and 20 is the draft limiting action provided by said surfaces due to the fact that, Aalthough the inclined surfaces aid in the inducing of a good draft between the burners and the thermopile, .when normal and low velocity drafts are present in the furnace, the same surfaces tend to limit theamount of fair owby creating air'turbulence between the burner and the thermopile in the Varea of said surfaces, which restricts the rate of airow between the burners and the thermopile. VThis will prevent the flame from being blown Afar enough away-from the thermopile'as to cause no v heating thereof by the flame.` 'Y

Inasmuch as the space between the header -3-3- and the bracket 22 is fairly small, and in view of the fact that the space above the orices 23 and 29 is very well shielded from drafts by the flash tube 13 and the mounting arms 22b on the bracket 22, the flames issuing from the orifices 28 and 29 and, to .a lesser extent, the orices 26 and 27 will be much lmore stable or less likely to be blown out than the orifices 24 and 25, Also, due to their position between the orifices 24 and 25, each row of burners may be readily reignited by the flames existing over the header, should either one or both of said rows become extinguished. Furthermore, the iiames provided over the header by the orices-26 through 29 will assure that any gas from the main burner passing along the flash tube 13 will become ignited and thus assure igniting of the gas at the main burner, when said burner is turned on.

While there is no danger of this pilot burner becoming linted up, as in conventional burners, due to the fact that it has no primary air openings, there is a chance that the connector tube might get clogged up with gum deposits in areas kwhere the gasses used contain a lot of foreign particles. From the above description of the safety pilot structure and how it is assembled, it is readily apparent that the pilot may be quickly disassembled and the connector tube removed for cleaning purposes and then be quickly assembled. There is no chance of it being reassembled improperly as no adjustments are necessary, due-to the structural details of the safety pilot. From the above description of the structure and operation of the safety pilotit is apparent that due to the good mixing of the gas and secondary air provided by the arrangement of the burner orices and the burner shape and spacing with respect to the thermopile, blue and non-blowout ames are obtained. The arrangement enables relative large diameter orices to be used in the burners that reduce clogging and give low gas velocity and high flame velocity characterisics for the flames.

While the preferred modification of the invention has been described in detail above, it is deemed to be obvious that various changes may be made in the preferred modification without departing from the spirit of the invention. Therefore, the scope of the claims should be determined solely from the appended claims.

What we claim as our invention is:

l. In a combined pilot burner and thermoelectric generator, the combination comprising a thermopile, a burner having spaced parallel portions extending along opposite sides of said thermopile near the Shot junction end thereof and spaced a short distance therefrom, said burner portions having a common header and having spaced orifices directed upwardly and laterally toward the hot junction end of said thermopile, and bracket means for supporting said thermopile and said burners, said burner portions having flat side wall portions extending parallel to said thermopile and inwardly and upwardly inclined flat bottom wall portions for directing and limiting air flow to and between said burners and thermopile.

2. A combined pilot burner and thermoelectric generator comprising a laterally elongated thermopile, a pair of burners extending transversely along opposite sides of said thermopile near the hot junction end thereof and spaced a short distance therefrom, said burners being connected at one of their ends to a common header and having spaced orifices directed longitudinally and laterally toward the hot junction end of said thermopile, said burners also having i wardly and longitudinally extending at bottom surfaces, and bracket means for supporting said thermopile in assembled relationship with said burners.

3. In combination, temperature responsive means having a horizontally and vertically extending at surface portion at one end thereof to be heated and a thickened portion at the other end thereof providing agenerally horizontal extending fiat shoulder, a non-aerated burner extending along said surface portion in spaced relationship thereto and having a plurality of spaced orifices directed at an acute angle to said surface portion to providegenerally uniform flames impinging at an acute angle on said one end thereof, said burner having a flat surface portion inclined laterally toward said temperature responsive means and longitudinally and upwardly toward said horizontally and vertically extending hat surface portion ,and being spaced from and in opposed relation to said shoulder, said fiat surface and at shoulder coacting to produce a turbulent air condition between said `surface and said generator when an excessive amount of air tendsto flow therebetween.

4. In a thermoelectric generator, the combination comprising a supporting bracket :having-Aa pair of spaced parallel members with laterally extending bifurcated arms substantially in opposed relationship, a pair of elongated and parallel sheet metalburners extending between said members and secured thereto, aligned inlet openings in the opposed sides of said burners, a tubular header having spaced ribs thereon near each end of said header, said ribs having frusto-conical surfaces that engage and depress the surface of said burner sides with the ends of said header positioned-in said openings, a radial bore in said header between said ribs, a connector tube having a reduced diameter ,and bevelled surface swivelly positioned in said bore and having an intermediate portion extending through one of said bifurcated arms, a collar-iixedon said tube and bearingV against the header side of said one arm, and thermofcoufple means positioned between said bracket members, burners, header and collars.

5. In a thermoelectric generator, the combination comprising a supporting bracket having a pair of spaced parallel members with laterally extending bifurcated arms substantially in opposed relationship, a pair of parallel sheet metal burners extending between said members and secured thereto, aligned inlet openings in the opposed sides of said burners, a tubular header having spaced ribs thereon near each end of said header, said ribs having frusto-conical surfaces that engage and dimple the surface of said burner sides around said header, with the ends of said header rotatably positioned in said openings, a radial bore in said header between said ribs, a connector tube having a reduced diameter and bevelled surface swivelly positioned in said bore and having an intermediate portion extending through one of said bifuricated arms, and a collar fixed on said tube and bearing against the header side of said arm, said bracket members, burners, header and collars being so arranged that a thermocouple means may be held therebetween.

6. In a safety pilot, the combination comprising heat responsive means having a pair of side surfaces to be heated, and a pair of non-aerated burners adjacent to but spaced from said surfaces and having a plurality of orices therein for directing a plurality of flames laterally and upwardly against said surfaces, the position and shape of said burners with respect to said heat responsive means being such as to form a flue therebetween to induce a desired flow of combustion supporting air between said burners and said surfaces and to prevent an excessive flow therebetween that would lift the flames out of operative relationship with said heat responsive means.

7. In a 'combined pilot burner and electric generator, the combination comprising a thermocouple unit, a burner having portions thereof extending along opposite sides of and spaced from' said unit, a plurality of spaced orifices in said burner portions for directing flames against said unit near one end thereof, said burner portions having flat air flow controlling surfaces inclined laterally and longitudinally toward said one end, and an orifice at one end of said burner inwardly of said plurality of orifices to provide a draft protected flame for reigniting said plurality of orifices should they accidentally become extinguished. A

' 8. A combined pilot burner and electric generator comprising a vertically extending thermocouple unit, a pair of vertically elongated burners extending along opposite sides of and in spaced parallel relationship with said unit, a plurality of horizontally spaced orifices in said burners for directing flames at an acute angle against said unit near one end thereof, said burners having at their bottom edges thereof fiat air flow controlling surfaces inclined laterally and upwardly toward an intermediate portion'of said unit, a header conduit extending between one end of each of said burners and abutting said unit, and an orifice in said burners generally above said header and lower than said plurality of orifices to provide draft protected ames for reigniting said plurality of orifices should they aceidentally become extinguished.

9. A pilot generator comprising thermoelectric means having a surface to be heated, a non-aerated elongated burner laterally spaced from said means and having a plurality of orifices along a top edge thereof directed upwardly and laterally toward said means, said burner having end members engaging the ends of said thermoelectric means to thus form a passage therebetween for the iow of air to support combustion of fuel at said orifices, said burner also having an outwardly and downwardly inclined surface at the bottom portion thereof to form a chimney-like passage and anair scoop with said thermoelectric means that aids optimum air flow but prevents excessive air ow.

10. In a safety pilot, the combination comprising a flame sensing means having a substantially at and vertically extending surface to be heated and a substantially 'fiat and vertically extending burner adjacent to but spaced from said surface and having orifice means therein for directing a ame horizontally and vertically against said surface, the position and shape of said burner with respect to said ame sensing means being such as to provide a flue extending along a portion of said flame sensing means to induce a proper How of combustion supporting air between said burner and said flame sensing means as to cause said flame at said orifice means to heat said surface substantially uniformly at all times.

ll. A safety pilot comprising heat responsive means yhaving a surface to be heated, a burner adjacent to but spaced from said surface and having a supporting means thereon and an orifice therein for directing a flame against said surface, and an angularly detachable coupling means for connecting said burner to a source of fuel, one portion of said coupling means being positioned in the burner and said means having an abutment surface in one plane which engages a forked opening in said supporting means when angularly revolved, and which is further positioned in another plane by abutment with said heat responsive means.

References Cited in the tile of this patent UNITED STATES PATENTS 1,921,778 Roberts Aug. 8, 1933 2,311,785 Sparrow Feb. 23, 1943 2,374,701 Ray May 1, 1945 2,454,229V Sparrow Nov. 16, 1948 2,665,321 Flagg Jan. 5, 1954 2,670,394 West Feb. 23, 1954

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