US2822865A - Burner safety control system - Google Patents

Description

Feb. 11, 1958 F. P. HUDSON l BURNER SAFETY CONTROL SYSTEM Filed Aug. 16'. 1954 1N V EN TOR.

BY FRANK P. HUDSON i Aruofiwsr 'BURNER SAFETY CONTROL SYSTEM 'Frank P. Hudson, Decatur, Ga. Application August 16, 1954, Serial No..449,969

4 Claims. (Cl. 158-128) This invention relates to'burner control systems andjis particularly concerned with an electrical control system for use in connection with blower-burner vcombinations by whicha preliminary purging of .the system may befinsured b eforefuel issuppliedandhe burners ignitedl ,In many installations such asin boilers, furnaces, kilns,

driers and the-like, it hasbeen deemed expedientto pro-v vide apreliminary charge or blast of airunder vpressure to the burners and combustion chamber to purgesuch .chamber of present `fuel and gas and thus preclude, or

materiallyreducein incidence and/ or degree of intensity, hazardous uncontrolled combustion or explosion ofresidual fuelfrom prior operations vor fuel such. as may' have ,been suppliedfby` leakage or faulty fuel Asupply equipment subsequent ,to prioroperations. While fuel systemsjhave heretofore been. proposed by which such purging airmay be lsuppliedpriorto the normal iringor'fflight oioftthe burners, suchsystemshave nQtprQVidedadeQuate inter- .relations and combinations with the fuelsupplyryalves .to positively prevent inadvertent or 'systemby whichthe hazards of premature fueLsupply-are reducedtoa minimum.

More specically it is an object of thezpresent` invention to provide a control system for a burner,eombinatiotllincludinga ,purgingair supplyin whichfull andadequate purging before fuel issuppliedmay .he insured.

i Another object ofthe invention is to .providea system .of `the character set forth which will-:be simple,' eifec tive and veiicient and one having suchiuterrelation, com- .bination and cooperation with the conventional control elementstas to insure ya ,proper predetermined sequence of operation and which .will precludeaccidental or'inadvertent improper operation of ,such instrumentalities.

A further object of the invention is toprovide forithe incorporation insuch asystem of timedelaymeans so that by a single operation of amain Control device 'anadequale Preliminary nurensiis automatically insuredlbefore fuel may be-supplied.

It is alsoamollglhe Objects ofthe invention to'relate and combine the ,usualpilot burneras well as the usu'al mainburnerandlits ,fuel supply to the control system in Vsuchrmanner las .to insure .against 4combustion ,of vresidual orjleaked fuel prior to the norm'alvsupply of'fuel initiated after the purging operation is completed.

'The invention also has as anobject the incorporation of pressure responsive means not only insuring-a delay in fuel supplyto the burner until adequate purginglhas `been accomplished but also insuring an adequatejfuel supply pressure before `purging or'fueling Vtakes place Vandduring normal iring periods therewith insuring` shut-'down of operating Yrequirements.

'fuel supply `should such pressurebediminisheddaelow sajfe 2,822,855 Patented Feb, 1 1, 19158 These and other objects, features and advantages of the invention will be apparent from a consideration of the following specification taken in .conjunction with the drawing in which a diagrammatic disclosure of one preferred embodiment of the basic inventive conceptis presented. In Vthe drawing, the conventional burner arrangement and fuel andpilot systemaredepicted by dot and dash lines while the valves and electrical control system of the present invention are shown in full lines.

Inlgeneral the system of the present invention maybe =broadly defined as including atime delay switch energized froma maincontrol switch and preferably having interposed a pressure responsive device associated with `the fuel supply means so as to preclude operation should the fuel supply be inadequate. The time delay` switch is alsopreferably under the influence of another pressure responsive means associated with the operation of the fan or blower or air owof thepurging airpressure supply so.as to,Y preclude completion of its circuit in the event that the purge air flow, should be inadequate. Furthermore the time delayswitch'is controlled-by the burner and pilot valves, the ,arrangement being `such that the controlcircuits may notbe energizedwhile the burner or pilot valves are open, hence there. can be no possibility of fuel `supply yduring the purgingperiod. A further circuit supplied by 'the timedelay switch Grits interlocking relay automatically insuresrrthe opellillgrdfeeries arranged automatic valves in a predetermined sequence prior to the possibilityrof opening manual: valves inthe Ysaine-series.

Fig. l is aschematic diagram of my gas burner system.

Fig. 2 isa schematic view ,of` a detail showing amodi- 'ed formof valves whichY may Vbe substituted vfor thecontrol valves of Fig. l.

Fig. 3 is aside elevation of a detail showing one of the manual reset electrically latched valves.

Referring now to the diagramof the drawings, it will be seen that there is here disclosed, by ,way of example, .atwo burner gas system, the burners ,B1 and B2 beingof conventional design and being providedwith the usual ignitingV pilots P1 and P2. Gas ssupplied from a suit able source indicated at G through conduits C1 and C2 to'theburners B1 and B2, respectively. In ythe conduits Cland C2 the usual manualreset electrically latched valves V1 and V2 are provided forthe controlof fuel to the burners. Similarly, gas is supplied'to the pilots P1 and VP2 through `supplypipes S1 and 82, respectively, andconventional electricallycontrolled valves vE1 and E2 are provided for the pilots.

While valves V1 and VZaredescribedherein as being `of the manualreset electricallyflatched typesuch as shown `in 'Fig 3, any electrically controlledvalve maybeused An v`electrically controlled valve is definedas a valve ,which may not be opened until an electric current is received by the valve. As seen in Fig. 1 the valvelmay be opened by theenergy ofthe electric current on itsrsolenoid .directly, orl as seenin Fig. 2, electric solenoid 101,1nay act. as a ,triggeror pilot to cause the valve to `be-openecl byV the energy of air, gas, or hydraulic fluid under pressure through conduit 102 to diaphragm control mechanism 103,. ofthe electricsolenoid may latchan operating vmechanism permitting the valve to be opened manually. Regardless of thesource of energy used to open the vvalve, the

v'the conventional burners, pilotis, valves, fuel supply'pipes and'wiriug-are-shownin broken'lines'while the elements of the present invention are shown in full lines. In considering the above outlined arrangement it will of course be understood that the showing is diagrammatic and is not intended as a disclosure of any particular burner and pilot combination or the fuel supply and wiring therefor. While the present showing contempl-ates a gas burning arrangement, it will be understood that the invention is in no way limited to such fuel and that powdered or liquid fuel may be supplied and controlled in like manner within the scope of the present inventive concept.

The present presentation of connected parts further includes a current supply C, a fused disconnect switch D, induced draft fan interlock E and forced draft fan y interlock F having blower means S, all of which are conventional and customary in the type of arrangement here shown and form no part of the present invention except as to their combination and interrelation with respect to the control system. In this respect, it is also to be understood that different kinds, numbers and arrangements of blowers or natural draft ports may be incorporated in the system without departure from the arrangement and operation of the present invention.

The conventional circuit here shown includes the series connection of the fused disconnect switch D, the induced draft fan interlock E, the forced draft fan interlock F, or an operating diiferential air ow switch performing the same purpose as E and F with the source of current C. In series there is also provided a low gas pressure switch connected by tubing 32 from the gas header G, and/or any other safety interlock desired in the fuel system. From the series connected low pressure switch 31, a conductor 30 leads to a time delay switch 33 of the present system. For actuating time delay switch 33, I

have provided a slow acting coil 34 which is connected to conductor 30 through the circuit traceable from conductor 40 and 48. The other side of coil 34 leads to ground. The relay thus formed by coil 34 and switch 33 is -of thehold down type and includes a second switch Y,

35 connected through conductor 37 to conductor 30. The other side of switch 35 is connected to coil 34 so that once coil 34 is energized it receives current from conductor 30 and remains energized so long as current is supplied to conductor 30. From the time delay switch 33, a conductor 36 extends to individual switches 12, 13,

22 and 23 connecting respectively through conductors 14, 15, 24 and 25 leading to switch 16, solenoid 19, switch 26, and solenoid 29 of valves 10, E1, 20 and E2, respectively. Switches 12, 13, 22 and 23 may be manually controlled disconnect switches or may be contacts on individual burner llame failure safeguard relays.

Switches 16 and 26 are coupled with valves 10 and 20 in such manner as to be closed when the valves are closed. From these switches the circuits extend to solenoid coils 17 and 27 which operate to disengage a latch such as latch 50 on valves V1 and V2 to permit manual opening of these valves when their coils are energized. A shunting or holding circuit is also provided for the valves V1 and V2 including switches 18 and 28 which are closed when the valves V1 and V2 are manually opened after engagement of the latch, thus shunting out the switches 16 and 26 once the valves V1 and V2 are opened. The conductors 15 and 25 lead to the conventional electrical actuators 19 and 29 of the conventional pilot valves E1 and E2, and thus when these circuits are energized such pilot valves will be opened.

From the foregoing, it will be seen that, without regard for the master time delay switch circuit hereinafter discussed, the foregoing circuit, upon energization, provides for opening of pilot valves E1 and E2 and the unlatching of burner valves V1 and V2, permitting the latter Vto he opened manually, and further provides for the retention of valves V1 and V2 in open position. Such of such switches provides individual overriding manual control or unmonitored control by flame failure safeguard relays of either pilot or main burner. It will also be understood that the opening of valves E1, E2, V1 or V2 will not result in the supply of fuel to the pilots or burners because of the provision of the valves of 10, 20, 11 and 21 of the present system. These latter valves being manually controlled.

In conjunction with the valves 10, 11, 20 and 21 there is provided a master or control circuit for the time delay switch which precludes actuation of the time delay switch to energize the circuits of conductor 36 should one of such valves 10, 11, 20 or 21 be left open. This master circuit includes a conductor 40 extending from one connector of the time delay switch 33 to a switch 41 which is closed when and if the manually operable burner valve 20 of the burner B2 is closed and is opened when the valve 20 is opened. Switch 41 is a companion switch to switch 26 and is operable therewith. From the switch 41, conductor 42 leads to a second series connected switch 43 operable by the valve 21 and closed and opened with the closing and opening of the valve 21. From the switch 43, a conductor 44 leads to a third series connected switch 45 associated with valve 10 as in the manner of switch 41 associated with valve 20. From switch 45, conductor 46 leads to a fourth switch 47 connected with valve 11 in the manner of the connection of switch 43 to valve 21; and froml switch 47, a conductor 48 returnsto the time delay switch 33 completing the circuit therefor.

Since -all of the series connected switches 41, 43, 45 and 47 are associated with these valves in such manner as to be closed to complete the circuit only when the valves are closed, it will be seen that the open position of any of the valves will preclude completion of the circuit. The internal circuit arrangement of the time delay switch is such that power may not pass to coil 34 from the elements, D, E, F, and 31 when the master control circuit is open, nor can current pass therethrough for the conductor 36 and its dependent circuits.

Incorporated with the foregoing circuit in series with switches 41, 43, 45 and 47 may be a dilferential air tlow responsive switch 49 which may be a manometer or diaphragm type switch connected to the boiler to determine whether a draft is flowing through the boiler. r[his -air tlow switch of course is optional; when located in the circuit, it remains open until a draft through the boiler causes it to close.

From the foregoing, it will be seen that in the operation of' the present apparatus the coil 34 for the time delay switch V33 may not be energized unless all of the valves 10, 11, 20 and 21 are closed. When such valves are closed, the'switch 33 may be energized through the series connected devices D, E, F and 31. Such energization will not however immediately energize the circuit of conductor 36 since such energization is delayed by the switch 33 until a predetermined lapse of time sufficient to complete the purging of the system. After such purging, the switch 33 will energize the circuits of conductor 36 opening the pilot valves E1 and E2 and unlatching for manual operation the valves V1 and V2. With such valves open, the manual valves 10, 11, 20 and 21 may then be opened to supply the pilots and the burners with fuel for normal operation. It will thus be seen that the present ysystem precludes opening of any of the electrically controlled valves during purging of the system should any of the manual valves be opened.

Y The low pressure switch also precludes operation of any of valve opening. As hereinbefore indicated, the invenoperation, when current is supplied through the time -de- .g

lay switch, assumes the switches 12, 13, 22 and 237to tion is not limited or restricted to any particular structural features of the individual components, and it will be understood that numerous changes, modifications, and the full use of equivalents may be resorted to in the 5 practice of the invention without departure from the spirit or scope thereof as set forth in the following claims.

I claim:

1. A control system for fuel burners having in combination, blower means, a source of current, a first circuit from said source of current, a switch actuatable by air from said blower means and connected to said circuit for supplying current from said source of current through Said circuit Upon actuation of said switch, a

time delay switch connected to said circuit and actuatable upon the flow of current in said circuit, a second circuit connected to said time delay switch to receive current from said source of current upon the lapse of sufficient time after said actuation of said time delay switch, a solenoid connected to said second -circuit and actuatable by current flowing therein, a fuel valve of a fuel burner connected to said solenoid, said solenoid permitting opening of said fuel valve upon actuation of said solenoid, a valve connected in series with said fuel valve, said last mentioned valve being constructed and arranged to prevent fuel from entering said fuel burner when closed, a pair of switches connected to said last mentioned valve and openable thereby, said switches being constructed and arranged to close upon closing of said last mentioned valve and to open upon opening of the same, a third circuit connected between one of said pairs of switches and said time delay switch, said time delay switch being constructed and arranged to remain open as long as said one of said pairs of switches is open, the other of said pairs of switches being interposed in said second circuit between said time delay switch and said solenoid, a normally open switch connected in parallel with said other of said switches, and means operably associated with said solenoid and operable to close said normally open switch upon energization of said solenoid.

2. The control system as set forth in claim 1 including a pilot fuel burner, a pilot valve and a safety valve in series with said pilot valve to prevent fuel from entering said pilot fuel burner when closed, a switch connected to said safety valve, said last mentioned switch being constructed and arranged to -be opened when said safety valve is open and closed when said safety valve is closed, said last mentioned switch being connected in series in said rst circuit.

3. The control system set forth in claim 1 including an air flow switch connected to said fuel burner and in series with said one of said pairs of switches, said air How switch being constructed and arranged to be closed when suicient air is passing through said fuel burner and to be open when insuthcient air is passing through said burner.

4. The control system set forth in claim 1 including a pilot fuel burner, a pilot valve, a safety valve in series with said pilot valve to prevent fuel from entering said pilot fuel burner when closed, a switch -connected to said safety valve, said last mentioned switch being constructed and arranged to be opened when said safety valve is opened and closed when said safety valve is closed, said last mentioned switch being connected in series in said rst circuit and an air ilow switch con nected to said fuel burner in series in said first circuit, said air flow valve being constructed and arranged to be closed when suiicient air is passing through said fuel burner and to be open when insutl'icient air is passing through said burner.

References Cited in the le of this patent UNITED STATES PATENTS 2,020,710 Warner Nov. 12, 1935 2,127,445 Hardgrove Aug. 16, 1938 2,212,352 Plein Aug. 20, 1940 2,297,821 Whempner Oct. 6, 1942 2,385,699 Fox Sept. 25, 1945 2,474,941 Hasselhorn et al. July 5, 1949

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