US3072177A - Burner safety control - Google Patents

Description

Jan. 8, 1963 A. A. FENNELL BURNER SAFETY CONTROL INVENT R.

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Jan. 8, 1963 Filed July 19. 1957 A. A. FENNELL BURNER SAFETY. CONTROL 5 Sheets-Sheet 2 7 w www Jan. 8, 1963 A. A. FENNELI.

BURNER SAFETY CONTROL 3 Sheets-Sheen'I 5 Filed July 19. 1957 ZEE IN ENTOR. f7 @d @fz/ze@ number of burners.

United States4 Patent 3,072,177 BURNER SAFETY CNTRUL Anthony A. Fennell, Homewood, lll. (379 E. 147th St., Harvey, Ill.) Filed July 19, 1957, Ser. No. 673,016 3 Claims. (El. 153-423) The present invention relates to a novel control system, and more particularly to a novel system adapted to control burners and the like.

Industrial furnaces are frequently provided with a plurality of burners which utilize gas, oil or other suitable fuels. Some means must be provided for shutting off all burners if any one of them goes out so that unburned fuel is not introduced into the furnace from such extinguished burners and subsequently ignited by one of the other burners. It will be appreciated that fuel ignited in this manner might well cause an eXplosio-n. Various control systems have heretofore been proposed, which systems usually incorporate a separate detector for each burner capable of sensing the presence or absence of a flame, and a separate control circuit for each detector.

`Such heretofore proposed control circuits are costly so that the cost of a furnace installation is high especially when the furnace has a considerable number of burners.

An important object of the present invention is to provide a novel control system for a plurality of burners, which system is materially simplified and eliminates duplication of many parts heretofore believed to be necessary so that the system may be installed and maintained relatively easily and economically.

A more specific object of the present invention is to provide a novel control system of the above described type which utilizes separate detectors or fiame sensing devices for each burner and which is greatly simplified as compared with heretofore proposed systems in that it includes only a single control circuit successively and separately connectable with each of the detectors or sensing devices so as to accomplish periodic inspection of each of the burners.

Still another object of the present invention is to provide a novel control system of the type mentioned in the pre"eding paragraph which is constructed so as to shut off the burners in the event of failure of the system to proceed with successive inspection of the burners.

Other objects and advantages of the present invention will become apparent from the following description and the accompanying drawings wherein- FIG. 1 is a schematic view showing a control system incorporating features of the present invention;

PIG. 2 is a schematic view showing a slightly modified control system;

FIG. 3 is a schematic view showing another slightly modified form of the present invention;

FIG. 4 is a detailed diagrammatic showing of the fuel supply control relay employed in the system of FIG. 1;

FIG. 5 is a detailed diagrammatic showing of the sensing circuit relay incorporated in the modified control system of FIG. 2; and

FIG. 6 is a detailed diagrammatic showing of the pulse *timer employed in the modified form of the invention illustrated in FIG. 3.

In FIG. 1 there is shown a control system 10 for conv'trolling burners 12, 14, 16, 18, 20 and 22 in a furnace or the like. While six burners have been shown for the purpose of illustrating the present invention, it will be appreciated that the advantages of the present invention may be realized when the control system is constructed for use with at least two burners and any desired larger Fuel is supplied to the burners from a common pipe 24, and a valve 26 is connected in icc this pipe. This valve is a spring biased solenoid operated valve of known construction such that when the solenoid 28 thereof is energized the valve is ope-n and when the solenoid is deenergized spring means causes the valve to close.

Adjacent the burners are detectors or sensing devices 30, 32, 34, 36, 38 and 40. These detecting or sensing devices are of known construction and may, for example, be of a type which generates an electric signal in respense to heat or light from the flame when the burner is lit. Alternatively, the sensing or detecting devices may be of the resistance type which changes electricity conducting characteristics in accordance with temperature.

ln accordance with a feature of the present invention the control system is provided with only a single relay 42 for controlling the fuel shut off valve 26. The relay is preferably of a fast acting type and of known construction and has terminals connected with the solenoid 28 by wires 44 vand 46, Power is supplied to the relay through lines 48 and 50. Safety switch means generally designated by the numeral 52 is inserted in the line 50 for shutting olf power to the relay and thereby causing the fuel shut off valve to close in the event of a failure of a portion of the control system as described more fully hereinbelow.

The control system is provided with switch means generally designated by the numeral 54 for .successively and separately connecting each of the sensing devices Sil-4G with the relay 42. It will be appreciated that the switch means 54 may be constructed in various ways, but for the purpose of illustrating the present invention the switch means 54 is provided with a plurality of fixed switch contacts 56, 58, 60, 62, 64 and 66 cooperable with movable contacts 68, 70, 72, 74, 76 and '78. The fixed contacts are respectively connected with the relay by common wires 80 and 82 and branch wires 84, 86, 88, 90, 92 and 94. The movable contacts are respectively mounted on movable fingers 96, 98, 100, 102, 104 and 1616 which are connected with one terminal of the sensing devices 30-40 respectively by wires 108, 110, 112, 114, 116 and 118. Other terminals of the sensing devices are connected to the relay by wire and branch wires 122, 124, 126, 128, and 132.

Considering FIG. 4, the relay 42 will be seen to include a coil 200 which is connected between line 48 and wire 80. Energization of coil 200 causes a magnetic element 202 to operate a movable contact 204, contact 2114 being electrically connected to both line 50 and wire 126. Relay 42 also includes a fixed contact 2h63 and when magnetic element 292 directs contact 204 to make electrical connection with contact 206, a circuit is completed from line Sil, through the contacts 204 and 2l6-to wire 46, through solenoid 28 and through-wire 44 to line 48. As will be recognized, coil 201i remains energized to preserve completion of the circuit through contacts 204 and 206 to the operating solenoid 23 of valve 26 only so long as switch means 54 and safety switch means 52 continue the circuit from line Sil to wire 8% in a completed condition.

The switch means 54 is provided with a plurality of rotatable cams 134, 136, 138, 140, 142 .and 144 respectively engageable with cani elements 146?, 148, 150, 152, 154 and 156 on the fingers for positioning the fingers to open or close the switch contact points. The rotatable cams are all fixed on a shaft 158 which is continuously driven by an electric motor 169. The rotatable cam members are constructed and fixed on the shaft 15S so that the pairs of switch contact points are successively opened and closed and so that only one pair of the contact points is closed at one time to accomplish inspection of a given burner. The construction may be such that there will be a slight overlapping of the periods during which successive pairs of points are closed so as to pre` vent the relay from closing the shut off valve as the relay is switched from one sensing device to the next. It will be appreciated that since the motor 161i) is continuously operated the cycle of opening and closing of the switches will be continuously repeated. As a result each of the detector devices4 will be connected periodically with the relay.

It will be appreciated that in the event one of the burners goes out, its associated sensing or detector device will signal the relay 42 upon being periodically connected with the relay so that the relay will function to close the valve 26. In order' to prevent an undue lapse of time between the instant a burner goes out and the moment in which its associated sensing device is subsequently connected with the relay, it is necessary to rotate the cam shaft 158 ata speed which enables the entire cycle to be completed inA a relatively short time. While this time interval may be varied somewhat for different installations, it should beas short asl possible and as a result each burner will be inspected for no more than a few seconds during each scanning cycle. Thus the relay 42 must be a fast operating type which is capable of causing the fuel shut off valve to be closed upon receiving a brief signal from one of the scanning devices and before the next scanning device is connected with the relay.

In the event of a failure of the motor 161B or some other mechanical breakdown which would cause the cam shaft 158 to stop it would be possible for a single sensing or detector device to remain connected with the relay 42. Under such condition` it might be possible for a burner associated with another sensing device to go` out without being detected. However, in accordance with a feature of the present invention this possibility is eliminated by the provision ofthe above mentioned switch means 52. In this embodiment, the switch means S2 has a fixed contact 162 and a cooperable contact 16a which is axially movable on a rotatably supported shaft 166. A y weight governor type device 168 is driven by the shaft 166 for raising the contact 164 into engagement with the contact 162. The shaft 166 is in turn driven from the cam shaft 158 through bevel gears 178 and 172. Thus, in the event the cam shaft 158 is stopped for any reason, the shaft 166v will also be stopped and the fly weight device will cause thecontact 164` to be disengaged from the contact 162. When thisoccurs power to the relay 42 is shut off and the fuel valve 26 is closed.

FIG. 2-shows a slightly modified form of the present invention which is similar to the above described control system as indicatedI by the application of identical reference numerals with the suffix a added to corresponding elements. Th's embodiment differs primarily in the construction of the safety switch means. More specifically, the safety switch means 52a` comprises a relay 174 for connecting portions of the wire 50a only when electricity is supplied for energizing the relay through the wires 176 and 178. These wires are connected with terminals of a small generator 180 which is driven from the cam shaft 158a through gears 170:1 and 172a. Thus, whenever the cam shaft 158a is stopped, the generator 180 is stopped so that the relay 174 is deenergized and the relay 42a is disconnected from the main power source.

With specific reference to FIG. 5, the relay 174V will bey seen to include a coil 288 which is-connected in electrical series circuit with generator 180 by the wires 176 and 178. The relay 174 also includes a magnetic element 210 which is controlled by the coil 208 to actuate a movable contact 212. The movable contact 212 is arranged to coact with a fixed contact 214 in completing a circuit from linel 50a, through the contacts 212 and 214 and through a wirer216- to the movable contact of relay 42a., As will be recognized, cessation of the operation of generator 180 serves to deenergize coil 208 whereby tov open the circuit through contacts 212 and 214. 'Ihis in turn opens the circuit from line 58a through the contacts of relay 42a to the line 48a.

FIG. 3 shows another slightly modified form of the present invention which is similar to the above described structures as indicated by the application of identical reference numerals with the sufiix b added to corresponding elements. This embodiment also differs primarily in the construction of the safety switch means 52b. In this embodiment the switch means 52b comprises a pulse type or periodically energized timer 182. Such timers are of known construction and usually include a holding circuit which must be periodically energized in order to prevent opening of the main power line contacts. In the present installation the timer holding circuit has terminals connected. by wires 184 and 186 to a fixed contact 188 and a contact 190 on a movable finger 192. A cam 194 fixed on the cam shaft 158b is constructed so as to operate the movable finger 192 to close the contacts 188 and 19t) periodically during each-revolution of the cam shaft. Thus, if for any reason the cam shaft is stopped the timer will not be periodically energized and it will functionto disconnect the relay 42h from the main power source.

Turning to FIG. 6 for a more detailed consideration of the pulse timer 182, line 48b will be seen connected to wire 184Y through a coil 218 and to relay 42b through a fixed contact 228 and a movable contact 222. Coil 21S operates amagnetic element 224 toactuatethe movable contact 222, magnetic element 224 being mechanically connected to an air dashpot 226. Movable contact 222 is biased normally to open the circuit through the contacts22t1 and 222 by means of a tension spring 228. Thus, spring 228 biasesV the contacts 222 and 220 into open configuration whereas air dashpot 226 opposesthis action in order to delay opening of the contacts for a short time interval after a deenergization of coil 218. As will be recognized, a failure in theV periodic closing, of contacts 188 and 190 opens theV circuit from line 50h, through wire 186, wire 184 and coil 218 to the line 48b. Upon deenergization of coil 218 in this manner, spring 228 eventually overcomesthe mechanical resistance of dashpot 226 to open the contacts 220 and 222., This opening of the circuit through contacts 220 and 222V in effect opens the circuit to the coil of relay 42b to which contact 222V is connected by aV wire23fi.V A wirev 232 connects the movable contact of relay 42b. to; the, line Sib.

While the preferred embodiments of theV present invention have beenshown and described herein, it-v is obvious thatmany structural detailsmay be changed without departing from the spirit/and scope of the appended claims.

The invention is claimed as follows:

1. A control system. for a plurality of burners comprising:v valve meansV forv operating. said burners; relay means for` regulating said valve means; circuit means for actuating. said relay means inrresponsev to thecondition of said burners, said circuit meansvincluding a plurality of sensing circuits connected inparallel and.. adapted to be individually associated with said burners externall to the flames thereof, each of said sensingcircuits including a sensor adapted to be disposed adjacent a burner anda switch connected in series with said` sensor; rotatable shaft meansta plurality of cams affixed to said shaft means and arranged to operate said switches in a repetitive sequence; and means responsive to the rotation, of said shaftmeans for de-energizing the circuit means upon cessation of rotation of any part of said shaft means.

2. A control system for a plurality of burners comprising: valve means for operating saidburners; relay means for regulating said valve means; circuit means for actuating said relay means in response to the condition of said burners, said circuit means including a plurality of sensing circuits connected in parallel and adapted to be individually associated with said burners external to the dames thereof, each of said sensing circuits including a sensor adapted to be disposed adjacent a burner and, a

normally open switch electrically connected in series with said sensor; rotatable shaft means; a plurality of cam means afxed to said shaft means and arranged momentarily to close said switches in a repetitive sequence; a power source; and control means connected in circuit between said source and said relay means, including a control switch operated by a cam on said shaft, said control means passing power to said relay means when said control switch is regularly and periodically closed by said cam, said control means blocking power to said relay means upon interruption of the periodic operation of said control switch.

3. A control system according to claim 1 wherein said rotationally responsive means includes periodically energizable control means connected to said circuit means for maintaining said circuit means connected to a power Q5 source upon said control means being periodically energized, said rotationally responsive means further including means periodically operated upon rotation of said shaft means for periodically energizing said control means.

References Cited in the tile of this patent UNITED STATES PATENTS 2,291,385 Gossett July 28, 1942 2,295,045 Mettler Sept. 8, 1942 2,304,200 Plein et al. Dec. 8, 1942 2,327,690 Ackerman Aug. 24, 1943 2,581,942 Collins et al Jan. 8, 1952 2,692,962 Thomson Oct. 26, 1954 2,736,371 Rafenstein Feb. 28. 1956

Claims (1)

1. A CONTROL SYSTEM FOR A PLURALITY OF BURNERS COMPRISING: VALVE MEANS FOR OPERATING SAID BURNERS; RELAY MEANS FOR REGULATING SAID VALVE MEANS; CIRCUIT MEANS FOR ACTUATING SAID RELAY MEANS IN RESPONSE TO THE CONDITION OF SAID BURNERS, SAID CIRCUIT MEANS INCLUDING A PLURALITY OF SENSING CIRCUITS CONNECTED IN PARALLEL AND ADAPTED TO BE INDIVIDUALLY ASSOCIATED WITH SAID BURNERS EXTERNAL TO THE FLAMES THEREOF, EACH OF SAID SENSING CIRCUITS INCLUDING A SENSOR ADAPTED TO BE DISPOSED ADJACENT A BURNER AND A SWITCH CONNECTED IN SERIES WITH SAID SENSOR; ROTATABLE SHAFT MEANS; A PLURALITY OF CAMS AFFIXED TO SAID SHAFT MEANS AND ARRANGED TO OPERATE SAID SWITCHES IN A REPETITIVE SEQUENCE; AND MEANS RESPONSIVE TO THE ROTATION OF SAID SHAFT MEANS FOR DE-ENERGIZING THE CIRCUIT MEANS UPON CESSATION OF ROTATION OF ANY PART OF SAID SHAFT MEANS.

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