US3194296A

US3194296A - Control apparatus

Info

Publication number: US3194296A
Application number: US297910A
Authority: US
Inventors: Richard W Brown
Original assignee: Honeywell Inc
Current assignee: Honeywell Inc
Priority date: 1963-07-26
Filing date: 1963-07-26
Publication date: 1965-07-13
Anticipated expiration: 1982-07-13

Description

July 13, 1965 R. w. BROWN 3,194,296

CONTROL APPARATUS Filed July 26, 1965 3 Sheets-Sheet 1 J1y13,1'96'5 R11/.BROWN CONTROL APPARATUS 3 Sheets-Sheet 2 Fi1ed July 2e, 1965 IOPDJO mm am July 13, 1965 R. w. BROWN CONTROL APPARATUS 3 Sheets-Sheet 3 Filed July 26, 1963 OPOS.

NN Nm Nb. N.

QNPOJE m NQ N United States Patent O 3,194,296 CNTROL APPARATUS Richard W. Brown, Excelsior, Minn., assigner to Honeywell Ine., a corporation of Delaware Filed July 26, 1963, Ser. No. 297,916 8 Claims. (Cl. 158-122) My invention is concerned with an improved control apparatus and particularly a control apparatus which is adapted for use with-a fuel burner installat-ion to check and supervise a fuel valve of a fuel burner installation and to sound an alarm or the like if a leak should 'occur at this valve.

As is well known, fuel burner installations may utilize various arrangements of ignition means, pilot means, main burners and blower to provide safe lightoff and operation of the main burner, under the control of a controlling device responsive to the need for operation of the fuel burner. This control may be derived either as a result of a predetermined process requirement or as a result of the need for heat in an area to be maintained in a given temperature by operation of the fuel burner installation. Combustion safeguard means are provided to supervise operation of the main burner, under the direct control of a main fuel valve which, when open, allows fuel to flow from a main fuel supply pipe or conduit to the main burner where it is then ignited by ignition means, for example a pilot burner. During the standby period of operation, when heat is not required from the fuel burner installation, the main valve is conditioned to be closed. Various failures may occur at this fuel valve, such as small particles of dirt lodging at the seat of the valve, to result in a fuel leak.

The apparatus of my invention provides improved control apparatus to detect such a fuel leak. I recognize that fuel leak detectors are generally old in the prior art. However, prior art fuel leak detectors do not function to provide the improved supervisory features which my invention incorporates.

Specifically, the structure of my invention provides an .arrangement whereby a fuel valve leak detecting apparatus includes a standing pilot which is associated with a thermocouple, a thermo-couple providing a safety pilot means to maintain flow of fuel to the standing pilot so long as llame is continuously detected at the standing pilot. Operatively associatedwith the standing pilot I provide a leak detecting pilot which is to `be ignited by the standing pilot in the event a leak occurs. The leak detecting pilot is connected at the end of a fuel flow circuit or pipe with a valve conditioned to be opened only when the thermocouple safety pilot detects llame at the standing pilot and only when the main fuel valve of the burner installation is conditioned to be closed. Thus, I allow the leak detecting pilot to be operative only if two conditions exist. The first condition is that the standing pilot must be present to ignite the leak detecting pilot in theevent a leak occurs. The second condition is that the main fuel valve must be conditioned to be closed.

As a further feature of my invention I provide flame detecting means whichis associated with the leak detecting pilot to detect flame only at this leak detecting pilot. Furthermore, I provide an arrangement whereby proper operation of my improved apparatus requires t'nat this llame detecting means detect the presence of residual fuel which is downstream of the main valve immediately subsequent to the closing of this main valve.

In other words, it is recognized that a residual amount of fuel will always remain at a position downstream of the main valve immediately after the valve is conditioned to be closed, and after it in fact does close. This residual fuel is supplied to the leak detecting pilot where a molCe rnentary ame is produced. The structure of my apparatus requires that the llame detecting means associated with the leak detecting pilot must detect this momentary llame to insure that the flame detecting means is in fact operative and is capable of detecting a llame.

Furthermore, I provide a timer which is energized only after the flame detecting means detects this residual amount of fuel downstream of the main valve, the timer being conditioned to provide a timing period for burnoff of this residual fuel. As a result the apparatus of my invention indicates a leaky valve, sounds an alarm, or closes a further safety valve which is upstream of the main valve, only when a sustained llame exists at the leak detecting pilot after this timing period.

With these general observations in mind, my invention will be apparent to those skilled in the art upon reference to the following specification, claims, and drawing, of which:

FIGURE l is a show-ing of a preferred embodiment of my invention shown in the de-energized condition,

FIGURE 2 is the same embodiment shown in the standby condition, and

FIGURE 3 is the same embodiment shown in the run condition.

Referring to FIGURE l, reference numeral 1t) designates a fuel supply conduit which is connected to a source of fuel which is to be supplied to a fuel burner installation, the components of which are not shown.

The flow of fuel to the fuel burner installation is under the control of a main supply valve 11, having a winding 12 which, when energized, is effective to open the valve and to allow fuel to flow to a conduit 13 which is connected to the burners of the fuel burner installation. Energization of winding 12 of valve 11 is under the control of a controller 14, shown as an open switch.

I have chosen not to show the components of the fuel burner installation, and the manner in which controller 14 energizes these components since the exact manner and structure to accomplish this may take many forms. Controller 14 may in fact be pressure responsive or temperature responsive, and may be an automatic actuator to cycle the fuel burner installation automatically, to satisfy a condition to which the controller is responsive. It suffices to say that there are many ways in which controller 14 may operate a fuel burner installation to establish flame at the burner installation. Furthermore, combustion safeguard apparatus may be provided, and is usually provided, to supervise theproper maintenance of flame at the fuel burner installation.

My invention is concerned with detecting a fuel leak at valve 11 and it is intended that my invention be in addition to the normal combustion safeguard devices provided at a fuel burner installation.

Reference numeral 15 designates a safety valve having a winding 16. Safety valve 15 is connected in fuel-flow series with valve 11 and, as will be apparent, safety valve 15 is normally open and 1s closed only upon the detecting of a fuel leak, or upon a failure of a component of the fuel leak detecting system.

Reference numeral 1'7 designates a manual reset safety pilot Valve having a winding 18 which is connected to be energized from a thermo-couple 19 associated with a standing pilot burner 20. As will be apparent, not only is valve 15 normally open, but valve 17 is also normally open to establish a standing pilot flame at pilot burner 20 to th-us maintain thermo-couple 19 heated to hold valve 17 open and to maintain a switch 21 in a closed condition. Valve 17 is of the general type in which means are provided to manually open the valve. However, switch 21 is closed, and valve 17 is maintained open only if thermocouple 19 is heated.

I have chosen first my apparatus in a de-energized conlWill be, energized Iat the appropriate time.

Referring-to electronic flame detect-ory 24, this amede tectorisof conventional design and includes a pair of elec- Y' Ydition, t-o facilitate the explanationofthe initial sequence` Normally,Y however the of operation ofmy invention. apparatus is continuously energized vduring both the standby (FIGURE 2) and the running (FIGURES) period of operation of an associated fuel burner installation.

" is transferred to a capacitor detector 24, is associated with leak detecting pilot 22 and,

is responsive only tto. dame at leakdetecting pilot 22.:

Means may be provided to shield fiame'rod 23 from flame at standing pilot to insure that the ame rod does not detect a flame at the standing pilot. Y Y

Leak detecting pilot 22 is connected at the .end of ,a fuel conduit 124, having va blower 25 which, When'enerygized, is effective to cause the medium withinV conduit 124" Ito move in the 'direction of the'arrow, towardleak detecting pilotV 22. Also connected-in conduit 124 is a valveV i 26 having a winding V27 which is connected to be energized when winding 12 tof main fuelvalve 11 is de-energized. As will'be app-arent, blower25 andwinding V27 of valve 26 are energizedwhe'n the main fuel valve 11 is .condi tioned to be closed and thus leak detecting pilot 22sarnples themedium downstreanrof mainfuel valve 11 only during periods in which valve11 is conditioned to be closed. Also, as is apparent, immediately after de-energization ofwinding 12 of valve 11, to condition thisvalve to close,

a residual .amount of fuel remains in fuel conduit 13 downstream of valve Y11. This residual .fuel causes a momentary flame to be established at leak detecting pilot 22. This ame is detected bythe ame detecting means including flamerod 23 and electron-ic ame detector 24.

The' detection of residual fuel is necessary to establishv thev energization of a timer 2S having a

timer motor

29,21 clutch 30, Vand switches A,YB, and C. The function of timer 28fis'v to timeV a given time period lduring which burnof of resid-ual fuel takes place, and to render the fuel leak detecting apparatus elfective at the end of this time period.

In the eventA of a fuelk leak, I provide safety cut-oft" means 31, in the form of a bime-tal operated safety switch, Y having a bimetal actuator 32', a heater 33 therefor, a nor-- f mallyrclo-sed kswitch '34, Va normally -open switch '35, and

a manual reset button .':6. V Closed switch V34 of's'afety cutoff means 31 isconnected in' series with Winding 16 of t-o be non-conductive. The nonconduction -`ofi discharge device 57 lallows conductionofhdisch'arg,'device SaitoV i energize a ameV relay 60, having a winding61=gl`afnormally Y closed switch 62,.- and `a1norrnailyoperi vswitchf, Such energiz-ation taking'place vupon the presence of iarrie;V

isnormally closed andclosing of thisswitchconnets the :primary windings of transformers v67=and v68 to power line conductors. 64 uand 165,2it being-i assumed atthistime that there is no callV for operation of anassociated fueliburner installationQand that controller, 14 is open. g;

The closing of switch66 completes an energizingfcirf..

cuit for valve 15 whichican ine-traced from power 'linefl conductor 65.throughconductorsf90'and 105,;'v'alve windp-` Y ing 16,

conductors

163, 97 and 98,'switch '34, and conduc-y tors 99 and` 169 to power lineconductor64.".5Fuel now `Y Y ows to 'the-upstream side of valvesrall' and ;17.

valve 15 and closes :this valve upon actuation of the safety cutofrlmeans. -The open switch of safety cutoffmeans 31 is connected in series with an a1armf37 which, when;

open switches

42 and 43. A relay 44,having a winding 45 yand

open switches

46, 47, 48 and 49, is provided to be maintained energized only during the standby condition of an associated fuel burner installation, and to be rstenerf f -giyzed during the detection of the burnotf of residual fuelimmediately alt the eind of a period ofV operation of the main fuel burner installation a-s a check for the operablityVV of ame detecting means'23-24. Relay 50, having a` winding 51,"normally closed switches 52 and 53, and normallyopen V,switches 54 and`55`, is provided to sense a momentary power failure and nt-o also checkV electrical continuity of heater 33 to insure Lthat safety cutotl vmeans 31 is infact operative. i Furthermore, vdeeenergization Vof winding 5i? is effective, by means of switch 53,'toprovide a second.

energizingcircuit for alarm 37 to insure that this alarm

tron discharge devices

56 and 57 operating as a rectication type flame detector, The output ofame rod'22z, when a ame is present at leak detecting pilot l22, is effective to charge a capacitor 58 to the polarity shown. 4This ,charge Valve 17 yis then @opened manually; (Without closing `swit-ch 21) andfstanding pilot'ZQ is ignited, to heat therrno f couple i19.v When :thermo-couple, 19 isheated suihciently, manual opening of; valver17 can Vthen '-bereleased and the Y.. valve remains open, ,withV switch` vZ1" closed so 'long/.ass thermo-coupleV 19 continues to detect dame atstanding pilot Zilli n v f The energizat-ion oftransformer 67 renders -ame d etec.- tor y 24 voperativthe cath-ode heaters of thedi'scharge der. i vices56 and 57'notbeingshown. j p f Energizaticn fof transformer 6S .;..completesan initialY j energizing circuit fonwinding 45V of relaygld'by vai/erfV t a circuit whichcan be traced from the. bottoml terminal" of the vsecondary winding Iof transforme-r v-tlilolgh con# iductior 69, sWitclrSZ V,of relay56,"conductors 70,1'71andV 72, winding 45 o frelay -44jiconductor'73, switch41 of relay 38,'and

conductors

74 and 4,75 tothe upper terminal of this secondary'winding'. v,Er'1e1f,gizf,atio'n 4of thewinding 45 of relay44' is effect-iveto actuateitheswitches Vof thisy relay. The closing ofswitch-.tdcompletesfaholdingc-ir- Y cuit to energize the. winding of'rela'y 44, this'fcircuit being: traced .from the llowerterrninal ofthefsecondary Ywinding i oftr-ansformer; through conductors-69, l'l6`and :77, switch a' 46, conductor 72, winding45, conductor[73 switch 41;, and conductors 74Y and .75, Vto. theV upper Vterminal tof Vthis secondarywinding; 5.

ing.. Y

Theclosin'g obswitch 48;.completesa circuit-which l shunts heaterfv?,` jduring the i standby condition ,off the g Y `fuel burner installation-,hut fonlyso longas ame de- Vtector 24 does not detect the presence .of flame'at leak detecting pilot `2.2i` VThis shuntV circuit canfbe traced from the upper terminal vof heater 'throughconductors y 80,75 gandVSl, switchf48conductors 82 and 83swith v 62-,and conductors 84,5185 and 79'to Vthelowerv terminal -o'fheater33;;V Y

Energization vof "blowerY 25.; is rj'achieve'd" by g means of a l circuit whichcan -be` vtraced from-power,lineconductor 'Y 65' throughconductors l90 and; 91;;s'W/itch4t), fconductors Y conductors 96,197 ,and 98;switchv4',Sandconductors 99 i Y and 100 to power line,co'nductorr64..YV Y

An energizing circuitV fonwinding 27` 'of valve Y26 :can be traced from the above'mentionedtonductor 94 through Stobias discharge device57 Y TheA closing `of switch f 47v completes an"ene`rgizing VcirY cuit for winding 51 .of reim/...570, whichjcanbe traced fromthe lower ,terminalfof fthe, second-ary winding of-.`V transformer 68 through

conductors

69 and 76, switch `47,'

conductor 78, winding 51?,.conductorj79,fheater 33, fand a i conductor tol theupper terminal fthissecondary wind- 99 and 100 to power line conductor 64. Thus, valve 26 is conditioned to open and blower 25 is energized.

With both

relays

44 and 50 energized,l an energizing circuit is completed for timer 28. This energizing circuit can be traced from power line conductor 65 through

conductors

90 and 91, switch 40,

conductors

92, 93 and 104, clutch 30 and motor 29, conductor 105, switch 49, con'- ductor 106, switch 55,

conductors

107, 97 and 98, switch 34, and

conductors

99 and 100 to power line conductor 64.

The energization of motor 29 and clutch 30 is effective to cause rotation of the motor, and as indicated, switch B closes at seconds after energization of motor 29 and clutch 30. Switches B and C, in series, form a circuit which shunts the closed switch 62 of flame relay 60 to allow frame relay 60 to respond to the residual fuel downstream of valve 11 immediately after the closing of this valve without causing the energization of heater 33.

At the one minute interval, switches A and C open. The opening of switch C again places flame relay 60 in a condition to supervise energization of heater 33 of cutoff device 31 suchthat this heater is energized as flame is detected asa result of an actual fuel leak. The opening of switch A de-energizes motor 29. The switches A, B and C are maintained in their actuated positions by virtue of continued energization of clutch 30. Timer 28 is a spring return timer and subsequent de-energization of clutch 30 causes switches A, B and C to return to the position shown in FIGURE 1,

The apparatus is now in a standby condition as shown in FIGURE 2 wherein

valves

15 and 17 are open, valve 11 is closed, valve 26 is open, blower 25 is energized, timer 28 is in its actuated position with switch A open, switch B closed and switch C open, relay r30 is de-ener gized, and relays 44 and 50 are energized.

The medium downstream of main valve 11 is drawn through open valve 26, by means of blower 25 and is presented to leak detecting pilot 22. If this medium, or atmosphere, contains fuel, this fuel is ignited by standing pilot and is detected as a fuel leak by flame detecting means which includes flame rod 23 and electronic fiame detector 24.

I will now describe the sequence of operation which takes place upon a need for operation of the associated fuel burner unit, as is evidenced by the closing of controller 14. The closing of this controller effects energization of winding`39 of relay 38, to actuate its associated switches. The opening of switch 40 is effective to` de-energize the primary winding of transformer 67 associated with flame detector 24, this primary winding being connected to power line conductor 65 through switch 40. The opening of switch 40 is also effective to de-energize winding 27 of valve 26, blower 25, and timer clutch 30. Switch 42 shorts heater 33 of safety cutoff `device 31 dur ing the run cycle of the associated'fuel burner installation. The opening of switch 41 is effective to de-energize winding 45 of relay 44. Y The closing -of switch 43 is effective to complete a energizing circuit for winding 12 of Valve 11. This ener gizing circuit can be traced froml power line conductor 65 through

conductors

90, 105 and 106 to winding 12, conductor 207, switch 43, and

conductors

108 and 209 to power line conductor 64. Thus, valve 11 is conditioned to open and fuel flows to the associated fuel burner unit. The de-energization lof relay 44, as a result of the opening of switch 41, is effective to cause its switches 46 and 47 to open. The opening of switch 46 opens the above traced holding circuit for winding 45 of relay 44. The openingy of switch 47 opens the circuit which previously shunted the closed switch 54 -of relay 50 and thus relay 50 is maintained energized by way of a circuit which includes only its closed switch 54.

. In the event of apower failure at this time, it is necessary that the starting cycle be repeated to energize relay 50.

The apparatus is now in the run condition as shown in FIGURE 3 where

valves

15 and 18 are open, valve 11 is open to allow fuel to fow to the fuel burner installation, valve 26 is closed, blower 25 is deenergized, flame detector 24 is inoperative, timer 2S has reset so that switches A .and C are closed and switch B is open, relays 38 and 50 are energized, and relay 44 is de-energized. This condition remains until the end of the period of need for operation of the associated fuel burner unit.

At the end of a call for operation of the associated fuel burner unit, as evidenced by the opening yof controller 14, relay 38 is again de-energized. The de-energization of this relay connects the primary winding of transformer 67 to power line conductors 64 and 65 to render the electronic flame detector 24 operative. Furthermore, main valve 11 is closed and the fuel leak detecting apparatus, including valve 26 and blower 25, is actuated. At this time there is residual fuel in fuel conduit 13 downstream of main valve 11. This residual fuel produces a flame at leak detecting pilot 22. This flame is detected by means 23-24 and as a result flame relay is energized.

The energization of ame relay 60 causes switch 63 t-o close. The closing of this switch is effective to complete an energizing circuit for relay 44. This energizing circuit can be traced from the lower terminal of the secondary winding of transformer 68 through

conductors

69, 109 and 110, switch 63,

conductors

111, 71 and 72, winding 45, conductor 73, switch 41, and

conductors

74 and 75 to the upper terminal of this secondary winding. Thus, energization of relay 44 is evidence of the operability of means 23-24 to detect the presence of flame.

As .soon as relay 44 is energized, the above t-raced energizing circuit for motor -29 and clutch 30 -of timer 2S is completed to institute a fuel burnoff period, but to institute this period only if fiame detecting mean-s 23-24 has proven to be operative.

After a `short interval of l5 seconds, yswitch B of the timer closes to shunt heater 33 of safety cutoff means 31. In the event that flame detector 24 had failed and did not detect the presence of flame which is known to exist las a result of the residual fuel downstream of main valve 11, heater 33 of safety cutoff means 31 would have remained energized and, after a time period of energization, safety cutoff mean-s 31 is actuated to open switch 34 and to close switch 35. As has been mentioned, the opening of switch 34 is effective to close valve y15 as an additional safety feature and to energize alarm 37.

Normally however flame detector 24 is operative Iand as a result timer 23 lis energized. However my apparatus first checks the opera'bility of the flame detector and institutes the residual fuel burnoff timing only after the fiame detector operability has been proven.

rifimer 28 allows a one minute period for burnotf of the residual fuel which is known to exist downstream of valve 11. After this one minute interval, switch C is opened and heater 33 of safety cutoff means 31 is again placed under the supervision of flame relay 60. In the event that Valve 11 has failed to close, and that a leak thus exists -at the valves leak detecting pilot 22 continues to .sustain a flame and flame relay 60 remains energized# So long as this relay remains energized, heater 33 of safety cutoff means 31 is also energized and after an additional time period (the timing period of means 31) valve 15 is closed and alarm 37 is energized.

Furthermore, if at any time during the standby period of the associated fuel burner installation (the period of which controller 14 is open) a fuel leak develops at valve 11, flame relay 60 is energized and heater -33 is then energized. After the timing period of safety cutoff means 31, valve 15 will close and alarm 37 will be energized.

From the above description it can be seen that I have provided an improved control apparatus of a type to detect a leak vat a fuel valve, and that my apparatus is constructed and arranged to utilize a standing pilot such that residual'fuel which islknown to exist,gis Ainstituted only afterrthe residual fuel has been detected by Van associated iiame detector. Thus, I provide aniarrangernent Wherebythe various components'arey checked, one Vagainst the lother, to insure that various possible Vcomponent'failures do not result in unsafe operation and reliancejon the operabilityY of'the 4control apparatus, when such operability 10 burnensysterncomprising:V V

Other modifications of my invention will be apparent to those skilled in the art as it is thus intended that;l the? scope of my invention be limited only` by thescope of does not in fact exist. .Y

the appended claims.

claim as my invention: 1. Fuel leak detecting apparatus comprising: a fuel burner unit,

a fuel conduit connected between the fuelburner Vunit` Vand asource of fuel, t Y

` a main vfuel valve connected in the fuel conduit and adapted to admit fuelto the 4fuel burner unit onlyvv during periods of aneed for operation of the ,fuel

burner unit, Y Y a controller operable to determine the periods of a need Y foroperation of Vthe' fuel Vburner unit, V

Va iirst pilot burner having-firstV flame sensing meansy cooperating therewith to sense Vthe presence or absence of flame, Y Y Ya safety pilot valve connected between the fuel conduit and said fir-st pilot burner, controlled 'by said first;

cooperating therewith to sense the presence Vor ab" sence of llame, said second pilot burner being'adapted tovbe mounted in cooperating relation to said iirst second amefsensing meansfrespofn'sive,toflameatsaid, Y i

pilot burner so that fuel Vat said second pilot burner is ignited by ii-ame at said first pilot burner,

Vmeans including a further valve'a-dapted to be connected" Yto the fuellconduit at favposition downstream from the mainpvalve and to 'be connected to said'se-cond pilot burnerV to admit'fuel at said position downstream i to said second pilot burner, K meansV adapted to be controlled 'by the controller and by said first flame sensing means to cause said further valve to open only when flame is sensed at said iirst pilot burner duringl a period when there is no need for operation ofthe fuel burner unit,

and means controlled by'j said second flame sensingV means to prevent'fuel iiow tothe fuel burner unit in 'the event of a fuel leak at the main valve as evidenced o Va fuel valve connected in ysaid fuel supply conduittoi*A control'the flow of fuel therethrough, v

-liame sensing means responsive to a tiame atvsa-id` pilot5 burner, Y

controllable fuel flow means adapted to be connected to g the fuel supply conduit at -a position downstreamof 'I thefuel valveto selectively sample for fuelwithin the "fuel supply conduitrat vsaid position downstream,

i a second pilot burner operatively associated with saidcontrollable fuel flow means and with said continu.-

i ously burner pilot burner so that fuel supplied to said second pilot burner by said fuel .flow means is ignited by said continuously burning pilot burner,

means includingsaidflame sensing means adapted tol control -saidrfuel flow means to connect said second pilot burner jin fuel flow relationy toisaid position downstream of the fuel valve only whenthe fuel'.

fuelvalve; the apparatus comprising:`

valve isic ortd-itionedLtoibo closed fat a time V:when a` Y fiar/nev is sensed Y at said continuously burning pilot: burner,

and means including second flamesensing meansjr'espony sive only to a Vflame Iat said 'secondf pilot burner for preventing fuel flow through said fuel-sut'ply'conduit,Vv

' in the event ofarne being presentatY saidsecond pilot 3.;Fue lY 'lealcdetecting apparatus ffor'usejywith Ya fueljf a fuel supply conduit connected between said fuelV burn-f p erand arsoureof fuel 'y f' t a main valve in saidi fuel supply conduit to control-the', l fuel'tosaidfuelburner; N i

a continuously-,burning:pilot: Vburner. andrst flame sensingI` means responsive; to :the presence Y of name -thereat,

a second pilot burner associated` with` said continuously.

burning pilot burnelrso, that saidpontinilously burni ing* pilotburner constitutesfigniting means. 'fonsaid f secondpilotburner, L p, Y i g sampling; means inclt1ding-a -normally closedrvalve and` a fuel conduit"adapted:tobejconnected tosaid sec-f ond .pilot burner and to thefuelsupply conduit atl a Aposition intermediate the Vfueljlburner and ;the;A mainfuelvalve,V means including: said first liame sensing means to ene t giletsaidnormallyclosed, valvelonlyfwhen' the. main i fuel yalve-is conditioned tobe closed atiaftirnewhenf` l Y va ame is sensed at-'saidvcontinuously tburningipilot; `burner,y l

secondpilotburner, Y v checking vmeans 'controlled by Vsaidsecond flame sensing means and operative upon 'themornentary'estab-f 1ishmentof-ame at said second gpilot` burner due-"to lresidual fuel; at the Vposition"intermediate theV fuelv burner and theffmain yfuel lvalve@as-ffuelan-orrnally existsy immediately;` after closing =of the zmain' fuel f valve,VV Y and safety means Ycontrolled by'saidsecond Yflame sens- VVing means andoperative upon :the presence of; apro-tY Y longed liameatsaid second Vpilot afterthenclosingfoftf V1 Y the :main valve to` prevent fuel owf1hr91igh5ai@ i 4x Fuel leakdetecting :apparatus Vfor a ifuely burner. system, operativeto detect ajfu'elgleak latr a main d 1 afuel burner system, Y 'Y e s Y a fuel supply conduitjccmn'ectedbetweensaid:fuellburnnY er system anda source'of fuel,L i

a main fuel valve having anoperator, saidrmain fuelz valveconnected in said fuel supply conduitto conl trol the fueliiow therethrough l v y r Y Aa continuously ',burning 'pilot burner fanddirst llameV sensing means. responsive to the; presence of llameV Vthereat Vto' ,maintainL-fueliiiow..tosaid continuously burning pilotburner,v l i a second pilot uburnerl associated with said continuouslyVV buring pilot burner, said v continuouslyA buring pilot :1

burner constituting -ignition meansjgfor E said second zg t Vpilotburn'er, 1

sampling means Vincluding aV normallyfclosedY valve and" Y Y' a samplingconduitiadapted V"to be connected to saidsecond pilot burner and to the fu'elj'supply` conduit ataposition Whichisintermediate'fthe fuel-.burner system andthe mainfu'elyalvef* 'v p ,Y l means including said ,rfstV Harrie sensing f 'rneansLV Var -fV ranged to open said normally closed ,valyeonlywhen the main fuellvalve operatorjis conditioned to' Vclos'e} V the main fuel valve at a time when a me'is sensed at said continuously burning pilot burner, i

vsecond flame sensing means responsive to flame at said second pilot burner, timing means,

checking means controlled bysaid second flame sensing means and operative upon the establishment of ame `at said second pilot burner due to the presence of residual fuel which exists at the position intermediate the fuel burner system `and the main fuel valve immediately after the closing of the main fuel valve,

means including said checking means to energize said timing means to begin a timing interval for burning off of the residual fuel upon operation of said checking means,

and safety means controlled by said second flame sensing means and by said timing means and operative upon the presence of liame at said second pilot burn er after'the expiration of said timing interval to prevent fuel flow to said fuel burner system.

S. In combination: t

a fuel burner unit having a main valve to control the flow of fuel to a main burner,

a controller operative to selectively control said main valve to be open or to be closed,

a continuously burning first pilot burner having first flame detecting means associated therewith to maintain fuel flow to said first pilot burner so long as flame is detected thereat,

a second pilot burner, arranged to be ignited by said first pilot` burner, having second flame detecting means associated therewith to be responsive only`to a llame at said second pilot burner,

a fuel flow conduit connecting said second pilot burner to the downstream side of said main valve, said fuel ow conduit including means controlled by said controller and by said first flame detecting means to allow said second pilot burner -to sample for fuel at the downstream side of said main valve only when said main valve is controlled to be closed at a time when flame is detected at said rst pilot burner,

time delayed safety cutout means having an actuator and switch means to be actuated after a time period of energization of said actuator,

means to render said safety cutout kmeans actuator inoperative when said main valve is controlled to be open,

a relay having a winding and switch means controlled thereby, checking means to check the operating of said second llame detecting means and including said relay winding to initially energize said relay winding when said main valve is initially controlled to be closed and a flame detected at second pilot burner, means including said relay switch means to subsequently maintain said relay Winding energized so long as said main Valve is controlled to be closed,

a timer, including switch means, to time for a given interval the burnoif of residual fuel at the downstream side of said main valve subsequent to said main valve being controlled to be closed, means including said relay switch means to energize said timer upon energization of said relay winding,

means including said timer switch means and said relay switch means to render said safety cutout means actuator inoperative during said given interval,

and means including said second flame detecting means to render said safety cutout means actuator operative if llame is detected at said second pilot burner subsequent to said given time interval.

6. Control apparatus for use with a fuel burner unit comprising:

a main burner,

a main valve adapted to control the How of fuel to said main burner,

a controller operative to selectively control said main valve to be open or closed,

a continuously burnin-g first .pilot burner having first Itia-me detecting means .associated therewith to maintain fuel flow to said iirst pilot burner so llong as flame is detected thereat,

-a second pilot burner, arranged to be ignited by said iirst pilot burner, and having second flame detecting means associated therewith to be responsive only to a flame at said second pilot burner,

a fuel liow conduit adapted to connect said second pilot burner to the downstream side of the main valve, said fuel flow conduit including means adapted to be contnolfled bythe controller and by said first flame detecting means lto sample for fuel at the downstream side of the main valve only when the main valve is controlled tobe closed at a time :when ame is detected at said iirst pilot burner,

Y a relay having a wind-ing and switch means controlled thereby, checking means to check the operation of said second llame detecting means and including said relay winding to initially energize sa-id relay winding when the main valve is initially controlled to be closed and t-he residual fuel downstream of the main valve causes a liame to be detected at said second pilot burnerrmeans including said relay switch means to subsequently maintain said relay wind-ing energized, v

a timer, including switch means adapted to time for a given time interval Ithe burnolf of the residualr fuel at the downstream side of the main valve subsequent to the main valve being controlled to be closed, means includ-ing said relay switch means to energize said timer upon energization of said relay Winding,

means including said timer switch means and said relay switch means to render said safety cutout means actuator inoperative during said ,given time interval,

and mea-ns including said second flame detecting means to render said safety cutout means actuator operative if flame is detected at said second pilot burner subsequent .to said given time interval.

fl. Control apparatus for use with a fuel burner unit comprising:

a main burner,

sa main valve adapted to control the flow of fuel to 'said m-ain burner,

, ya continuously burning tirs-t pilot burner having rst iame detecting means associated therewith,

a second pilot burner, arranged to be ignited by said iirst pilot burner, having second flame detecting means associated therewith and adapted to be responsive only t-o a ame at said second pilot burner,

a fuel flow conduit adapted to connect said second pilot burner Vto the ldown-stream side of the main valve, said vfuel ow conduit including means adapted to be controlled by said controller and by said tirst flame detecting means to facilitate sampling for fuel at the downstream side of the main valve only when the main valve is controlled to be closed at a time when ame is detected at said first pilot burner,

means to render said safety cutout means actuator inoperative when said main valve is controlled to be open,

a first relay having a winding and switch means controlled thereby, checking means to check the operation of said second flame detecting means and including said first relay winding to initially energize said first relay Winding when the main valve "is inirtially controlled to be closed and a ame is *detectedA at lsaidsecond pilotburner as Va result of residual Y fuel, means including said rst relay'switch Ameans to maintain said rst relaywindin-g energized when'a diamo .is thus detected,

a second relay having :a winding and switchrtmeans controlled thereby, meansV including said second re- .lay winding andlcontnolled by said rst relayzswitch"A means to initially energize said 'secondrelaywindf ingiupon energization o'f said firstv relaywinding,

.means including said second relay switch means to maintain said vsecond relay wind-ing energized,V

mea-ns including said first relay-winding and controlled by said second relay switch l*means* to energize said iirs't Vrelay Winding Vwhen the -m'ain yvalvev iscontrolled tobe closed andfsaid second relay Winding is deencrgizedL a timersv including'switch means, adapted'to time for` a -given time interval theburnoliof residual fuel at the downstream side o'f-` the main kvalve subsequent to the main` valve being controlled toI be closed, means Y including said irsftgandjsecond* relay switch means to energize said timer lupon energizjation ;of said r'st and-second rel-aywindings; .i

means including said timer'switch means and said-first relay switchvmeans toirender said safety cutout means `actuator inoperative vduring said given time- Y interval, Y t ,Y g

and means includinggsaid second flame detecting means Ato render said safety cutout means vactuatorv operative when llame is detected Vat saidzsecond pilotVV burner g subsequent to said given time interval.

58. Contr-o1 apparatus for use with a fuel vburner unitA toV detect a fuel leak ata given portion ofthe fuel burner unit, Y comprising: t

a fuel burner unit',

l controller means operzaljlyY connectedto -said lfuelf burner unit, I

y a continuously burning" pilot burnerfand a rstarnef Y Ydetector :responsive yto name :thereatt 'Y Y t a second'pilot burnerfarnanged to belignitednby'sai continuously burningqpil'otburner and'h'aving :a cor'v' ytroll-able fuel ow conduitadaptedrto be connected toa -given portion o'f the fuelfbriutnerrunitgf,41 Y i means controlled byfsaid rstfilamead-etector"andgsaid tiona-llybeing admitted thereto; i Y

second flame detectingxmeans.responsive toilamewat Y Ysaid 'secondvpilot'iau'rnerg residual fuelis normally-burned ofi." 4 ',Referensciie'd-byfne Examiner y `UNITED siATEs PArElsIIsY ,z5-32214; `1li/5o FREDERICK 1L.' MATTEsoNJn, VPrimm-y' Examinewf MEYER v PERLIN; f JAMESV WESTHAVER;

controller `means Vtofsazmp-l'eior fuelfat `the given por-f tion of the `fuelbiirnei unit wfhenifuel `is not V-intenv Y

Claims

1. FUEL LEAK DETECTING APPARATUS COMPRISING: A FUEL BURNER UNIT, A FUEL CONDUIT CONNECTED BETWEEN THE FUEL BURNER UNIT AND A SOURCE OF FUEL, A MAIN FUEL VALVE CONNECTE IN THE FUEL CONDUIT AND ADAPTED TO ADMIT FUEL TO THE FUEL BURNER UNIT ONLY DURING PERIODS OF A NEED FOR OPERATION OF THE FUEL BURNER UNIT, A CONTROLLER OPERABLE TO DETERMINE THE PERIODS OF A NEED FOR OPERATION OF THE FUEL BURNER UNIT, A FIRST PILOT BURNER HAVING FIRST FLAM E SENSING MEANS COOPERATING THEREWITH TO SENSE THE PRESENCE OR ABSENCE OF FLAME, A SAFETY PILOT VALVE CONNECTED BETWEEN THE FUEL CONDUIT AND SAID FIRST PILOT BURNER, CONTROLLED BY SAID FIRST FLAME SENSING MEANS TO ALLOW FUEL TO FLOW TO SAID FIRST PILOT BURNER SO LONG AS FLANE IS SENSED THEREAT, A SECOND PILOT BURNER HAVING SECONG SENSING MEANS COOPERATING THEREWITH TO SENSE THE PRESENCE OR ABSENCE OF FLAME, SAID SECOND PILOT BURNER BEING ADAPTED TO BE MOUNTED IN COOPERATION RELATION TO SAID FIRST PILOT BURNER SO THAT FUEL AT SAID SECOND PILOT BURNER IS IGNITED BY FLAME AT SAID FIRST PILOT BURNER, MEANS INCLUDING A FURTHER VALVE ADAPTED TO BE CONNECTED TO THE FUEL CONDUIT AT A POSITION DOWNSTREAM FROM THE MAIN VALVE AND TO BE CONNECTED TO SAID SECOND PILOT BURNER TO ADMIT FUEL AT SAID POSITION DOWNSTREAM TO SAID SECOND PILOT BURNER, MEANS ADAPTED TO BE CONTROLED BY THE CONTROLLER AND BY SAID FIRST FLAME SENSING MEANS TO CAUSE SAID FURTHER VALVE TO OPEN ONLY WHEN FLAME IS SENSED AT SAID FIRST PILOT BURNER DURING A PERIOD WHEN THERE IS NO NEED FOR OPERATION OF THE FUEL BURNER UNIT, AND MEANS CONTROLLED BY SAID SECOND FLAME SENSING MEANS TO PREVENT FUEL FLOW TO THE FUEL BURNER UNIT IN THE EVENT OF A FUEL LEAK AT THE MAIN VALVE AS EVIDENCED BY THE PRESENCE OF FLAME AT SAID SECOND PILOT BURNER.