US2596944A

US2596944A - Furnace lighter with mechanically interlocked controls

Info

Publication number: US2596944A
Application number: US15434A
Authority: US
Inventors: Shellenberger Rolfe; Arthur J Poole
Original assignee: Babcock and Wilcox Co
Current assignee: Babcock and Wilcox Co
Priority date: 1948-03-17
Filing date: 1948-03-17
Publication date: 1952-05-13
Anticipated expiration: 1969-05-13

Description

May 13, 1952 2,596,944

FURNACE LIGHTER WITH MECHANICAIJLY INTERLOCKED CONTROLS Filed March 17; 1948 R. SHELLENBERGER ETAL 4 Sheets-Sheet i Fig 4 wpao/k y 1952 R. SHELLENBERGER ETAL 2,596,944

FuiaNAcE LIGHTER WITH MECHANICALLY .INTERLOCKED CONTROLS Filed March 17, 1948 4 Sheets-Sheet 2 42/ 39 4- 422 /25 fi 4 04'' 38 wax" m v I Y DRfiFI FAN/1070A v 3nventors W Gttomeg FURNACE LIGHTER WITH MECHANICALLY INTERLOCKED CONTROLS Filed March 17, 1948 May 1952 R. SHEL'LEN'BERGER ErAL 4 Sheets-Sheet 3' 7 ZSnventors [Po/fie J/zel/enberger & ArZ/w r'j oo/e May 13, 1952 R sHELLENBERGER EI'AL 2,596,944

' FURNACE LIGHTER WITH MECE IANICALLY JENTERLOCKED CONTROLS Shets-Sheet 4 Filed March 17 1948 E D N m c 6 m N m n. m 90!. H X E T U 0 5 H m XV & m. a m T A m m r m A m L L F- E U U C... F

projected into the furnace. After ignition of the main fuel supply, the lighter unit is withdrawn to prevent damage thereto by the furnace heat.

A remotely located control panel, having mechanically interlocked controls, is provided for inserting and retracting the lighter unit and igniting fuel delivered therefrom. A pair of control wheels, levers or knobs mounted on the panel respectively control first the lighter unit position, and second the lighter fuel supply and purging of the lighter fuel line.

The first or air control is movable between off, insert, on and retract positions. In the off position, the lighter unit is withdrawn or retracted and air control valves for the lighter unit positioning cylinder are closed. When the control is moved to the insert position, air is admitted to the cyiinder to project or insert the lighter unit into the furnace.

In the off and insert positions, mechanical interlocking means associated with the air control prevent any movement of the second, or fuel control. Additionally, a latch obstructs continued movement of the air control beyond the insert position until the lighter unit has reached its fully projected, operative position. When the unit reaches such position, it operates means to effect release of the latch to permit continued movement of the air control to the On position.

In the on position of the "air control, the

air supply to the positioning cylinder is interrupted. At the same time, the interlock ng means releases the fuel control so that the latter may be turned from the off position to the purge position. When the fu l control is in any position but its off position, mechanical interlockmeans associated therewith prevent any movement of the air control until the fuel control is returned to its off position.

In the off position of the fuel control, the lighter fuel line is-connected to an oil drain or return line. In the purge position, an air valve connected to the fuel control admit purging air to the fuelline to blow out any foreign matter. After purging of the lighter fuel line, the fuel control is moved to the on position, connecting the lighter fuel line to the fuel supply and closing the purging valve. During all this time, the air control is locked in position by means of the mechanical interlock means associated with the fuel control.

When the main fuel burner of the furnace has been ignited, the fuel control is returned to its off position, and in its return movement passes through the purge position. The lighter fuel line is thus purged of fuel and foreig particles after the ignition operation. When the fuel control is again in the off position, the air control is unlocked for movement to its retract position. When the air control is moved from its on position to its retract position, the fuel control is' locked against any movement. In this position of the air control, air is admitted, to the positionin cylinder to withdraw the ,lighter unit to prevent damage thereto by the furnace heat. After such withdrawal, the air control is moved to the off position, closing its associated air valves. A feature of the invention is the unidirectional movement of the air control, with a ratchet bein provided to prevent retrogressive movement. This further secures the proper sequence of operation.

A normally open switch is provided in the 4 lighter ignition circuit, and is closed only when the lighter unit is in the projected or inserted position. Should two or more lighter units be used in the same furnace, the normally open switches for all the lighter unit ar connected in series circuit relation so that no lighter circuit can be ignited until al the lighter unit, are in operative position. Additionally,' another normally open switch prevents energization of the ignition circuit until the furnace has predetermined draft conditions, and this switch effects opening of a normally closed valve in the fuel line. 7

The lighter unit Referring more particularly to Figs. 1 through 4 of the drawings, a lighter assembly generally indicated at 20 is shown in operative relation to a main fuel burner 14 mounted in an aperture H in awall of a furnace l5. Lighter assembly 20 includes a mechanical fuel atomizer unit 2|, of a well known construction, having a fuel barrel 22 extending forwardly, and a pair of

ignition electrodes

23, 24 at the fuel atomization tip. Barrel 22 is retracted and projeted within an inwardly extending housing 26 secured to front wall It of the burner housing, and a double acting air cylinder 25 is provided for effect.ng such.

movement.

Main burner I4 is illustrated as a well-known pulverized coal burning type'including a primary air and coal nozzle I1, an impeller l2 and an impeller support member l3, which may also be an oil tube having an atomizer therein, whereby burner I4 is adapted to burn oil, if desired. Secondary air for burner I4 is supplied through secondary air chamber [8 having an outer wall Housing 26 is mounted, intermediate its ends,

in a bracket 21 welded or otherwise secured to primary air and. coal nozzle 11. At its outer end,

housing 26 is supported in a casing 28 secured to the front wall It of secondary air chamber IS. A tubular sleeve 31 slidable in housing 26 and having a transverse end wall 32 supports the fuel barrel 22 and electrode 23. The forward end of the barrel 22 has a plate 29 welded thereto and slidable in housing 26. An arm 33 welded or otherwise secured to barrel 22 is detachably connected to the piston 34 of cylinder 25 by means of a nut 36. Casing 28 has a portion 31 extending from wall It to support a normally open switch 30 having a plunger 38 engageable by an arm 39 on barrel 22, when the lighter 20 is in its fully inserted or operative position, to close switch 36. Suitable sealing means 4| on casing 26 engage sleeve 3| to provide a tight joint sistant metal such as Nichrome, for example. I

Electrode 23 is grounded by direct securement to barrel 22. Electrod 24 is mounted through an insulating bushing 42 on plate 29, and has a radial pin 43 welded thereto and lying in a radial recess in the forward face of bushing 42. Pin 43 maintain the radial end of electrode 24 properly aligned with the radial end of electrode 23, as may be seen in Fig. 4. The rear end of electrode 24 is electrically connected, by a connector 44, to a steel electrode 46 which extends outwardly through an insulating bushing 41 mounted on plate 32. At its outer end, electrode 46 is connected to the terminal 48 of a wire conductor 49, the terminal being mounted on an insulator shield 51 secured to casing l6. Conductor 49 is &9359455;

matically shown in Figs; 8 through 213 and elec.-.

bracket IiI secured', to-its rear-face Bracket-GI may-1 besan integral I structure or may-comprise;

weld uni'tedseotions and: is-formed with fourrearwardly; extending rectangular enclosures- 02 63;;.;6lt,and -,65,:;each. supporting a two-port threeper-t orifour portvalve.

Thefiair" control, for positioning reciprocableg barreLZZ is-awheel I 0 securedto abushing; fI=I on: thespindleof; a-three port valve=fnal Bushing. TI has a radialrflange 'lia tor theiorward face .of. whichlis secured; a ,chain sprocket 14-.. Secured-L tor the rean- .face of: flangefIB is a -latch--p1ate-- 'I=5 haringfouryequally spaced rearwardly projecting pins- 16 and-a radial vfinger; ;I'I.- Pins- I6. 00-,- operate with a spring biased detent arm I8, and serveto-releasably latch wheel- 10 inany of its four operative-positions; A spring biasedlatch. 8.-I- ispositioned. in the path; of. finger-TIT and is se- 40 cured-to the armature Bil-of-v asolenoid 80 on. bracket 6L; When'solenoidi 80 is. energizedrlatchl, 8I ,is drawn-out t the-path of finger -'I'I..=

I-t'fiwill be noted that-air control wheelq'lfi has fourpositions each alignedwith a pin I0. These positions aretheiofi*-,.- insert; on and- :re tract? andare alignable with an-indicatorBB on; the-:faceof, pane1.,60, wheel {I0 beingrreIeaSabIy latchable in each position by. engagement of a. pln- 'l6rwithsdetent18. Furthermore, solenoid 80 mustbegenergized to withdraw :latch. 8I. from the path of :finger ,TI before rotation; of wheel [0 counterclockwise. beyond. the -inse1 tposition can be continued.- The; im ortance oi this .vvill; be, apparent as the description proceedst I Control; wheel-.10- also icontrols a; second: air va1ve 8.3' mounted incnclosure 63v Valve--83.isg-a.A fourport; valve.-having',-abushing 84: secured. to; its spindle Bushing B l-has. a radial flangeJBBihavingnaninterlocking cam 85 secured toitsrear. face and-- a.-chain sprocket iifi securedto its front. face? Sprocket 1 86 is"; twicew-the diameter of. sprocket-J4 of valve 12 andis connected there-r zwb esa ol e hain 8 so: that va ve-:83 is rotatedonlvone-halfas fastasvalve 12. Rear-i 5 wardly projecting. pins; 89' arranged circum-r ferentially around cam 85; cooperate, withapivoted bar ilIlon. bracket. 6| to form a ratchetv to, prevent-clockwise movement of valve-B3 and; interconneeted a-lve 'I'2'.- Anidlerpullep 91 keeps chain-1 8f! taut.

Theiffuel; control comprises ahand wh'eel .I 00-- I fixed-ona bushing: I=0I1- securedto' the spindlei-of a four-portruel valve I 02: mounted in enclosure 6-5:;

and:ffuelf :controlsisizprovidecl ib r thezcams- 8 in" this: instance,.:.,comprisesran arcuateicrecesslor .cess: I251, will locki-ic'am SExand-l i'nteroonneeted:

chaimSiQlockefl-d 04.; Wheel I .00"':ismm/ab1e be= s twe t reezpos t onsszffotfiif" puma-mod 1. 3? as indicated by a pointer I06.

Wheel I00 also controls a four-port purge valve; I05: mounted;:in:;enc1osure 0A, .andzhavin a bushing I01 secured ;,.to1 ;its:: spind-len; Bushing-1:: I01. :hasa. radialliange: I08. carrying-non. itsxfor wardziaceta:zsprocket I09.;equal..i s: 7 sprockets! and::interconnect ed.;;therewithrb rollerrrchain; I 1. .Ansmterlookingrcams-I securedvto'rthe rear.afacezoffiangevlxflwand-,carrie&:. a -pin;; I1-I2i.c00perab1e :7.Wi1ih;St0pS"-; I13 'jom'bracketz.., 6 I3: tos'limitangnlanmovement;of vinterconnecteid x, fuelcontroliwheel .-.I00:;to.i-180f.

Th'emmechanicak interlock? between; the efairfii.

and I102, InFigSL-iE) and: 6;;the-;contro1sa-are be in the offf'?positiomxandc'it will; be inotedzthatzy. fueli controlrl Micannot-be opera'tedzr; Theilock,

notch: I15. the periphery ofizcamazl'l'og'havin radius substantially :equahto; that ofrcam; an whemdiametricalzof cam:.8'5, concentric'withzth latter; As :1ong :as:cam:..IIO::jis'. in ther ositie shown; control. .Iflzcanpabez operatedaatrwillal Means: are; provided; however; forzqlocking con-a;- trol. 'Illawhen: control I00 is; in anysbutthecfofi; position; .Thisimeansvcomprisesra pair .of arena-lie notches'a-or. recessesmIZ 02in the peripheryaofleamt 8 5}; which are substantially equal; in radius; with n cam: I I 0'. When: recesses; I 20; are rotated. to; positionidiametrical. of; cam 11 20,-; they:;e'ach cone.- f ormi substantially tostheouter. diameter: and oil cumference of cam-:I I:0;-1.Itwilllbe apparenlrthahip when cam 135511311111. a position from: that; shown, :cam; I Ill-and connected control: I; may-.5:- bexfreely turned: at will; hikewismyirranwbutzth offi positionz of; control; I00; therunbrokenrpor tionxoi the periphery. of cam. I I0, :riding'intzaz control-z 'Iil' against: movement;

The. elect'ricall interlock 601 beclo'secfbeforethe primary windings I31 I 31 ofignition"; transformers- I 30" are connected? across-'theiline andsolenoidlatch-801s energized to izrithdr'aw men-e1 from ;;the path offin'ger 1F 7 on latch" plate "I5? j Switches '30,: 9 0 are-closed whentheir respective lighter unit's are r 11y, -in-- serted'so', vthat. ;arms" 393139" on theiuehbarrelsit strike, the. operating;, buttons: 38;" 38"; to jclosethe switches.

When all the, switches 30;.301 are closed} solenoid 0. :is:energizedto,withdrawalatch .81.;

and I pilot light- I'35 on 1 panel 60 having: a'. resistance I316 in; se1-'ies:-therewith-, is slits.

Ignitiontransformerst I3

0,11 3 0%. are energized: set, that 525w Bushing IOI has a radial flangelll liflmarrying-a .15 h gh;se.condamvoltagei iappliedvtrom secondary:

windings I32, I32 to

conductors

49, 49 to pro- The operational sequence will be best understood by reference to Figs. 5 through 14, with more particular attention to Figs. 8 through 14. In Figs. 8 through 14, a source of air under pressure is indicated .schematically as applied through a conduit I40. and a branch I4I to valves 12 and I05. Valve 83 has connected thereto conduits '52 and 53 for air cylinder 25 and an air exhaust conduit I43. Fuel under pressure is supplied to valve I02 through a conduit I44,.and conduit 56 conducts the fuel to atomizer barrel 22. A branch I46 is connected between two adjacent ports of valve I02 and the fourth port is connected to a fuel drain conduit I41.

In starting up the furnace, the draft devices are first activated. These may comprise an induced draft fan which is turned on first and a forced draft fan which is turned on second. The motor starter of the induced draft fanhas an interlock with switch I25, so that this normally open switch is closed when the draft fan is energized. As explained, this energizes solenoid I26 to open the valve I21 in the main fuel line I44.

In-Fig. 8, the valves operated by controls 10 and I are shown in off position. It will be noted that fuel line 56 is connected to the fuel drain line I41, and

valves

12, 83 and I are closed. The operator first turns air control wheel counterclockwise to the insert position which moves

valves

12 and 83 to the positions shown in Fig. 9. Air is now supplied through conduits I40 and I4I, valve 12 and conduit I48 to valve 83. Valve 83 is now turned so that air under pressure passes through the valve and conduit 52 to operate the piston of cylinder to advance the lighter atomizer barrel 22 into operative relation with the main fuel burner I4 of the furnace. Conduit 53, connected to the opposite end of cylinder 25, is in communication through valve 83 with exhaust conduit I43.

Valves I02 and I05 are still in the off position.

When all ,of the lighter units have reached their fully inserted position, arms 39 and 33' on

fuel barrels

22 and 22 strike buttons 38 and 38' of switches and 30' to close these switches. This closure connects solenoid 80 across conductors I23 and I24 so that the solenoid is energized to withdraw latch 8I from the path of finger 11. Control wheel 10 may now be turned to the on position in which the formerly uppermost recess I20 of cam 85 is moved to a positiondiametrically adjacent cam IIO.

Valves

12 and 83 now occupy the closed position shown in Fig. 10. Control wheel I00 may now be turned 90 to the intermediate purge position, which moves valves I02 and I05 to the position shown in Fig. 10.; In this position, fuel inlet line I44 is still blocked from communication with lighter unit fuel line 53. However, air line I is now connected to fuel line 56 through open valve I05 so that a blast of air is blown through the lighter unit 20fto purge the same. It should be noted that in the position of Fig. 10, control wheel 10 is locked against movement through the interaction of cams 85 and I I0.

The fuel control I00 is now moved to the on position, with the valves I02, I05 occupying the position shown in Fig. 11 and valves 12 and 83remaining in the same position as in Fig. 10. This connects fuel inlet line I44 to lighter unit fuel line 56 through valve I02, with the air sup- 8 ply to the lighter unit being interrupted through closing valve I05. The fuel mixture discharged from atomizer fuel barrel 22 is ignited by the spark produced between

electrodes

23 and 24. Ii will be noted that the electrode 24 through the conductor 49, was previously energized from the secondary winding I22 of transformer I30 due to the energization of primary winding I3I by closure of switches I30 and I30. The lighter unit, being lit, ignites the fuel emitted from burner I4.

When the operator observes that fuel from main burner I4 has been ignited, he turns fuel control I00 backward to the purge position which closes valve I02 and opens I05 to apply a blast of air through the lighter unit to purge the same of residual fuel. This is shown schematically in Fig. 12. The fuel control I00 is then turned further to the ofi" position, closing valve I05 and connecting fuel line 56 to drain line I41 through conduit I45 and valve I02.. Likewise, the interlocking cam is now again in the position of Fig. 7 so that air control I00 may again be moved. The. operator moves control I00 in the counterclockwise direction to the retract position, schematically shown in Fig. 13. Valve 12 is now opened so that air is supplied through valve 83 and conduit 53 to the forward end of cylinder 25 to move the piston of the latter to withdraw or retract atomizer barrel 22 rearward from the furnace opening. The other end of cylinder 25 is connected through conduit 52 and valve 83 to'exhaust conduit I43. When the lighter units have been fully retracted, control 10 is again returned to the oif position schematically shown in Fig.7.

The described arrangement thus provides a novel mechanically controlled furnace burner lighter in which the controls are mechanically interlocked so that a predetermined sequence of operation must take place. For example, the air control cannot be moved to the on position until all lighter units are fully inserted, energizing solenoid 60 to withdraw latch 8I. Thi latch, in the extended position, prevents movement of control 10 beyond the insert position. Also, the ignition current cannot be turned on until such time as all the lighter units are all fully inserted. The "fuel control I00 cannot be operated until air. control 10 is in the on position, after which the fuel controls lock the air control in the on position until such time as the fuel control has been returned to the off position.

In passing in either direction between the off and on positions, the control I00 operates its connected valve I05 to apply a purging air blast to the lighter unit 20. The pin II2 oncam III), cooperating with stops I I 3, permits movement of control IIO.only through and return. The detent T8,co0perating with pins 16 on latch plate 15, releasably holdscontrol 10 in anyone of its four positions and assures proper positioning of cam 85 to release cam IIO when control 10 is in the on position. Due to the direct interengagement of the interlocking cams 85,

and H0 there is no possibility of failure of the interlocking, as may occur when solenoid controls are used, for example. The interlocking control action is by direct mechanical engagement of cooperating elements. For example, switch 30 is open until arm 39 depresses its operating button 38 when lighter unit 20 is in the fully inserted position.

While ianspecificwembodiment of the invention fihasbeen shown-and described indetail to illus- ."i.trate;1the application of the principles thereof, it :should be understood that the invention may be embodied otherwisewithoutdepartingfrom such -r.-p'rinciples.

Welclaim: -.1.:In a furnace "lighter unit-including 'a fuel rzatomizerghaving a fuel supply conduit-connected "thereto, and a pair *ofignition-electrodes;mecha-- inism' operable to insert-said unit into operative :.-relation with a main fuel burner in the furnace "and" to retract the same therefrom; means-for ilapplying an electric potential to saidelectrodes to produce "an ignition spark; first manually: oparable control means-.selectivelv operable to con- :zdition;isaidmechanism'to insert said unit :and to retract said unit; second-manually operable con- -trolmeans controlling the supply of fuel to-said :supply :conduit; mechanical interlockingmeans operable by saidfirst and second control means,

"said: interlocking means including latch means locking-saidsecon'd control means against-opieration; *and release means operable, responsive to full insertion of said unit into operativerela- :tion with the furnace main fuel burner'by said *mechanism under control of said first control -:means, to release said latchmeans.

:2. In a furnace lighter unit includinga fuel tatomizenhaving-a fuel supply conduit connected "thereto, and'a pair of ignition electrodes, mechani=moperable to insert said unit into operative *rrelation withthe main'fuel burner of thefurnace "'anditoretract thesame' therefrom; means for rapplying'an electric potential to said electrodes "to producean ignition spark; first control means operable to condition said mechanism to insert iisaidunit and to retract said unit, and movable between :oif, insert,"on and retract positions; latchmeans normallyeifective to-prevent 1-continued movement of said first controlmeans beyond the insert'position when moving to- "ward the-on-position; second control means controlling the supply of'fuel-to said supply conduit and movable between a fuel off and a *fuel on[ position; mechanical interlocking -:mea-ns operativelyassociated' with said first and second :control means; said interlocking means locking said second controlmeans against movement -except-when said first control means is in the' onposition and locking said first control mmeansragainst movement in any but. the off -positionof said second control means; and means operable, responsiveto full insertion of the unit vinto such operative relation,-to release said latch .meansto unlocksaid first control means for continued movement to the on position.

3. Ina furnace lighter unit including a-fuel .atomizerhavinga nozzle, and having a fuel-supply conduit connected to said no zle and a pair of ignition electrodes adjacentsaid nozzle, mech-' ani m operable to insert said unit .into operative l relation with the main fuel burner of the furnace ,sitions; latch means normally effective to pre-' vent continued movement of said first control means beyond the insert position when movin toward the on? position; a first valveconltrolling the ,supply of ,fuel .to said nozzle through 'rsaid supply conduit; second control means \movable 'hetween off* and "on positions toropen -and shut said firstvalve; a 'second'valve interposed between saidsource and said-supply conduitiand mechanically connectedto said second control means-said second control means, inop- -erating said first valve between its open and :closed positions, first opening and then closing said-.second valve to purge said supply conduit and nozzle with the nch-combustible pressure fluid both before and after fuel is suppliedthere- .to, with-:saiol first and secondcontrol means land locking said second-control :means against move- .mentexcept when said firstcontrol means is in interlocking means operatively associated the on positioniand,lockingsaid firstlcontrol lmeans against movement in any :but the" off position ofsaid second control means.

a. In-a furnace lighter unit includinga fuel atomizer, having .a nozzle, .andwhavingna .fuel supply conduit connected totsaid nozzle; and a a pair of rignition; electrodes adjacent-said lnozzle, mechanism operable to insert said=unit into opera'tive relation -with-thegmain fuel-burner of the furnacelandto retract=the same therefrom; a source of non-combustible fluid under pressure; means for applying an electric potential tosaid electrodes to produce an ignition-spark; first control means operable to -condition-=said mechanism to insert -said unit and to retract said unit and movable between 'off, insert, on and retract positions; latch- -means 91101- mally effective toprevent continued :movement of said first control means beyondthe finsert" position when moving toward the on position;

a first valve controlling the -supply of fueltoasaid nozzle through saidsupply circuit; second control -means movable between off and' fon positions .toopen and shut said "first valve ;1 a second-valve interposed between said source and said: supply conduit andmechanically'connected .to; said sec- .ondcontrol means; :said second controleme'ans, in :operating' said first-valvebetween its open and closed positions; first opening and :then closing said second valve to -purge-said supplyi conduit and nozzle with the-non-combustibleepressure fluid both before andaftertfuelis supplied thereto; -mechanical interlocking means operativelyassociated withwsaid first and second-control means; 'said l interlockingrmeans locking said --second control means iagains't'rmovementiexcept --when;zsaid first'control :means::is- Einxthe on:'po- :sitionand lo'cking'saidfirst control meansiagainst movement xin-"anwbutthe off:position of :"said second control: means; 'an'dvmeans i'opera'b'le, :re-

sponsive to" full-insertion eo'f the unit into such operative relation, to release said latch means to unlock said first control means for continued movement tof the"on position.

5. In a furnace lighter unit including a fuel atomizen'having a: fuel supply conduit connected thereto, and a'pa ir of ignition electrodes mech- .anism'-operable to insert said unit-intooperative relation with the main fuel burner or the furnace .:and 'to. 'retract'ithe same therefrom; means for applying 'an' electric: potential to said: 'electrodes to produce an 'ignitionxspark; firstzc'ontrol means operable to condition 'said'mechanism to insert 'said unit and to retract; saidzuni't and movable between off, insert, ion and 'frer tract, positions; latch meansnormally effective -to.-prevent continued movement of said' firstcontrol means *beyond'the insertaposition' when moving toward the on position; second control means controlling the supply ofrfuel totsaidsupply conduit and movable between a fuel off and a fuel on position; mechanical interlocking means operatively associated with said first and second control means; said interlockin means locking said second control means against movement except when said first control means is in the on position and locking said first control means against movement in any but the off position of said second control means; a solenoid operable to withdraw said latch means; normally open switch means controlling the energization of said solenoid; and means on said unit operable, when the unit is fully inserted into such operative relation, to close said switch means to unlock said first control means for continued movement to the on position.

6. In a furnace lighter unit including a fuel atomizer having a nozzle, and having a fuel supply conduit connected thereto, and a pair of ignition electrodes adjacent said nozzle, mechanism operable to insert said unit into operative relation with the main fuel burner of the furnace and to retract the same therefrom; means for applying an electric potential to said electrodes to produce an ignition spark; a source of noncombustible fiuid under pressure; first control means operable to condition said mechanism to insert said unit and to retract said unit and movable between ofi," insert, on and retract positions; latch means normally effective to prevent continued movement of said first control means beyond the insert position when moving toward the on position; a first valve controlling the supply of fuel to said nozzle through said supply conduit; second control means movable between off and "on positions to open and shut said first valve; a second valve interposed between said source and said supply conduit and mechanically connected to said second control means; said second control means, in operating said first valve between its open and closed positions, first opening and then closing said second valve to purge said supply conduit and nozzle with the non-combustible pressure fluid both before and after fuel is supplied thereto; mechanical interlocking means operatively associated with said first and second control means; said interlocking means locking said second control means against movement except when said first control means is in the on position and locking said first control means against movement in any but the off position of said second control means; a solenoid operable to withdraw said latch means; normally open switch means controlling the energization of said solenoid; and means on said unit operable, when the unit is fully inserted into such operative relation, to close said switch means to unlock said first control means for continued movement to the on position.

7. In a furnace lighter unit including a fuel atomizer, having a fuel supply conduit connected thereto, and a pair of ignition electrodes, mechanism operable to insert said unit into operative relation with the main fuel burner of the furnace and to retract the same therefrom; means for applying an electric potential to said electrodes to produce an ignition spark; first control means operable to condition said mechanism to insert said unit and to retract said unit and movable between off, insert, on and retract positions; latch means normally effective to prevent continued movement of said first control means beyond the insert position when moving toward the on position; second control means controlling the supply of fuel to said supply conduit and movable between a fuel off and a fuel on position; mechanical interlock ing means operatively associated with said first and. second control means; said interlocking means locking said second control means against movement except when said first control means is in the on position and locking said first control means against movement in any but the off position of said second control means; a solenoid operable to withdraw said latch means; normally open switch means controlling the energization of said solenoid; means on said unit operable, when the unit is fully inserted into such operative relation, to close said switch means to unlock said first control means for movement to the "on position; an electric circuit including said ignition means, said switch means and said solenoid; a normally open switch interposed between said circuit and a source ofelectric energy; and means for closing said switch only in response to operation of the energizing control means of the furnace draft creating devices.

8. In a furnace lighter unit including a fuel atomizer having a nozzle, and having a fuel supply conduit connected thereto, and a pair of ignition electrodes adjacent said nozzle, mechanism operable to insert said unit into operative relation with the main fuel burner of the furnace and to retract the same therefrom; means for applyingan electric potential to said electrodes to produce an ignition spark; a source of non-combustible fluid under pressure; first control means operable to condition said mechanism to insert said unit and to retract said unit and movable between off, insert, on and "retract positions; latch means normally efiective to prevent continued movement of said first control means beyond the insert position when moving toward the on position; a first valve controlling the supply of fuel to said nozzle through said supply conduit; second control means movable between off and "on positions to open and shut said first valve; a second valve interposed between said source and said supply conduit and mechanically connected to said second control means; said second control means, in operating said first valve between its open and closed positions, first opening and then closing said second valve to purge said supply conduit and nozzle with the non-combustible pressure fluid both before and after fuel is supplied thereto; mechanical interlocking means operatively associated with said first and second control means; said interlocking means locking said second control means against movement except when said first control means is in the on position and locking said first control means against movement in any but the off position of said second control means; a solenoid operable to withdraw said latch means; normally open switch means controlling the energization of said solenoid; means on said unit operable, when the unit is fully inserted into such operative relation, to close said switch means to unlock said first control means for movement to the on position; an electric circuit including said ignition means, said switch means and said solenoid; a normally open switchv interposed between said circuit and a source of electric energy; and means for closing said switch only in response to operation of the energizing control means of the furnace draft creating devices.

9. In a furnace lighter unit, including a fuel atomizer having a nozzle, and having a fuel supply conduit connected thereto, and a pair of ignition electrodes adjacent said nozzle, a double acting air cylinder operable to insert and retract said unit relative to the main fuel burner of the furnace; means for applying a relatively high electric potential to said electrodes to produce an ignition spark; a control panel having first, second, third and fourth valves mounted thereon; a source of non-combustible fluid under pressure connected to said first valve; conduit means interconnecting said first and second valves; a positioning control mechanically connected to said first and second valves and movable between oif, insert, on and retract positions; a fuel control mechanically connected to said third and fourth valves and movable between a fuel off and a fuel on position; said first valve being open in the insert and retract" positions of said positioning control and closed in the other two positions thereof; said second valve being operable, in the insert and retract positions of said positioning control, to connect one end of said cylinder to said conduit means and the other end to exhaust, and vice versa, respectively; said third valve connecting said supply conduit to a source of fuel and to a fuel drain in the on and off positions, respectively, of said fuel control, and being closed in intermediate positions thereof; said fourth valve connecting said source to said supply conduit in an intermediate position of said fuel control to purge said supply conduit and nozzle with the non-combustible pressure fluid both before and after fuel is supplied thereto; and being closed in the off and on positions thereof; mechanical interlock means in direct mechanical connection with said controls; said interlocking means locking said fuel control against movement except when said positioning control is in the on position and locking said positioning control against movement in any but the off position of said fuel control; latch means normally effective to prevent continued movement of said positioning control beyond the "insert. position when moving toward the on position; a solenoid operable to withdraw said latch means; normally open switch means controlling the energization of said solenoid; and means on said unit operable, when the unit is fully inserted into such relation with the main burner, to close said switch means to unlock said positioning control means for continued movement to the on position.

10. In a furnace lighter unit including a fuel atomizer having a nozzle, and having a fuel supply conduit connected thereto, and a pair of ignition electrodes adjacent said nozzle, means for applying an electric potential to said electrodes to produce an ignition spark; a source of non-combustible fluid under pressure; a first valve controlling the supply of fuel to said supply conduit; control means operable to open and close said first valve; and a second valve interposed between said source and said supply conduit and mechanically connected to said control means; said control means, in operating said first valve between its open and closed positions, first opening and then closing said second valve to purge said supply conduit and nozzle with the non-combustible pressure fluid both before and after fuel is supplied thereto.

11. In a furnace lighter unit including a fuel atomizer having a nozzle, and having a fuel supply conduit connected thereto, and a pair of ignition electrodes adjacent said nozzle, means for applying an electric potential to said electrodes to produce an ignition spark; a source of non-combustible fluid under pressure; a first valve controlling the supply of fuel to said supply conduit; control means movable between 01f, intermediate and on positions to open and close said first valve; and a second valve interposed between said source and said supply conduit and mechanically connected to said control means; said control means, in the off and on positions, closing said second valve and, in the intermediate position, opening the same to purge said supply conduit and nozzle with the noncombustible pressure fluid both before and after fuel is supplied thereto.

12. In combination with a furnace and its main fuel burner, forced draft means for the furnace, a fluid fuel burning ignition unit for the furnace burner, means for projecting said unit into the furnace and retracting it therefrom, fuel supply means for the unit, means for purging the unit, means for igniting the fuel upon its introduction to the unit, mechanical interlock means preventing the introduction of fuel to said unit before purging, a control for the forced draft means, and additional interlock means associated with said control and the igniting means and acting to prevent operation of igniting means unless the forced draft control has been operated to activate the forced draft means.

13. In combination with a furnace and its fuel burner, a fluid fuel burning ignition unit for the furnace burner, said unit having a nozzle arranged to deliver fuel therefrom; fluid fuel supply means for said unit; a source of non-combustible fluid under pressure; means for directing the non-combustible fluid through said nozzle to purge the latter of residual fuel and foreign matter; means for igniting the fluid fuel upon its delivery from the nozzle; and mechanical interlock means preventing the introduction of fluid fuel to said unit before purging.

ROLFE SHELLE-NBERGER. ARTHUR J. POOLE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 508,739 McNaughton Nov. 14, 1893 1,333,785 Sweeney Mar. 16, 1920 1,941,411 Mulholland Dec. 26, 1933 2,354,999 Ladd Aug. 1, 1944 2,382,483 Holden Aug. 14, 1945