US2839130A

US2839130A - Photoelectric control unit for oil burners and the like

Info

Publication number: US2839130A
Application number: US591176A
Authority: US
Inventors: Clair Donald St
Original assignee: CLAIRDON Inc
Current assignee: CLAIRDON Inc
Priority date: 1956-06-13
Filing date: 1956-06-13
Publication date: 1958-06-17
Anticipated expiration: 1975-06-17

Description

PHOTOELECT-RIC CONTROL mum FOR OIL BURNERS AND THE LIKE Filed June 13. 1956 June 17, 1958 D L I 2,839,130

DONALD ST. CLAIR INVENTOR BY M AGENT United States ast-m i1 5- a g detail free We a. on.

PHQTOELECTREC CQNTRQL UNiT Fill DEL BURNERS AND THE LHQE Donald St. Clair, St. Albaus, N. Y., assignor to Clair don, Ina, Paterson, N. 3., a corporation of New sersey Application June 13, 1956, Serial No. 591,176

8 Claims. oi. res-2s My present invention relates to a safety control unit for heating systems, such as oil burners, utilizing a photoelectric scanner as an indicator of proper or improper operation of the system. A unit of this description has been disclosed in my co-pending application Ser. No. 577,727, filed April 12, 1956.

it is convenient to use a single photoelectric device to check upon the performance of both the pilot light and the main burner of a heating system. A difficulty resides, however, in the need for critically adjusting and positioning the scanner so that it will respond to the relatively weak pilot light but will not give a false indication in response to the infrared afterglow of the heating chamber once the main burner has been extinguished.

The object of my present invention is to provide means for avoiding the above difiiculty and enabling the use of a single photoelectric scanner even in such systems where its positioning close to the pilot flame and shielded from the afterglow is not feasible.

Safety control units of the character referred to gener ally comprise some switching means, such as a relay, arranged to operate near the beginning of a work cycle of the unit to activate the pilot-light assembly, under the control of a timer, for a period of sumcient duration to allow the main burner or burners to be ignited. In accordance with the present invention 1 provide a sensitivity-control circuit for the photoelectric scanner which is adjusted by the timer to a state of increased scanner sensitivity during the period preceding the lighting of the main burner and is restored to a state of normal ensitivity at about the time of deactivation of the pilotlight assembly. According to a more particular feature of my invention, the change in scanner sensitivity is brought about by contacts of the relay through which the pilot-light assembly is activated.

The invention will be described in greater detail with reference to the accompanying drawing whose sole figure is a circuit diagram showing the principal elements of a heating system in combination with a safety control unit embodying my present improvement. This figure is similar to Fig. 1 of my above'identified copending application and illustrates so much of my previously disclosed system as is necessary for an understanding of the instant invention, the same reference characters having been used to designate similar parts. All transformers, auriliary switches and other circuit elements not essential for the. present disclosure have been omitted, along with the air-circulating system usual in such installations and shown in myv earlier application.

The boiler Iltl is provided with one or more burners ll supplied with fuel, e. g. i1 by a pump 12 which in turn is driven by a motor M2; also included in the main fuel line leading to burner 11 is a solenoid-controlled valve S2 and a throttle 17 controlled by a modulator 18. A

pilot nozzle 14 is connected by way of a solenoid-controlled valve S1 to a source of fuel (e. g. gas), not shown, and adapted to be lit by an igniter 15. A photoelectric scanner, comprising a tubular shield 16 in front of a photocell PH, is trained upon the burner 11 and the pilot nozzle 14 so as to receive light from any flame appearing thereon.

A source AC of alternating current, which may be the usual utility mains, is connected across a pair of bus bars and 292, the latter bus bar being grounded. For the sake of simplicity all the circuit elements have been shown to be energizable directly from bus bar 201, although in practice the voltage to some of these elements may be reduced by means of step-down transformers as illustrated in my co-pending application above referred to.

The safety control unit associated with the boiler 10 includes a principal relay RYl, an auxiliary relay RY2, an igniter control relay RYS, a burner-control relay RY6, a flame-failure relay RY7 and an alarm relay RY8; a double triode V1 and a thyratron tube V2; a network of resistors Rib-416 and R8R10, condensers C1-C4 and rectifiers REE, RE2 associated with these tubes; a potentiometer P2 to whose slider the cathode of tube V2 is connected; an alarm device schematically indicated as a lamp AL; and a timer circuit comprising several thermal delay relays Dill, DRZ, DIM and DRS.

The winding of relay RYIl is connected between bus bars 291 and 262 by way of a conductor 204 and a limit switch LS which is closed by the boiler, in a manner well known per se (e. g. in response to falling steam pressure), to send in effect a start signal to the control unit whenever the system calls for heat. The heating coils of delay relays DR} and DR4 are normally energized over the armature and back contact of relay RYl and over the left-hand armature and back contact of relay RY7, respectively. Relay RYfi, whose winding is bridged by condenser C2, is also energizable in the closed condition of limit switch LS in a circuit extending from conductor 204 through the normally closed contacts of delay relay DRE, right-hand back contact and armature of relay RY7, a lead 217, rectifier REl through its winding to ground on bus bar 2&2. Relay RY7 has its winding connected between live bus bar 201 and the plate of thyratron V2 whose cathode is adjustably biased by a voltage divider composed of potentiometer P2 (bridged by condenser Cd) and resistor R10 in series; this voltage divider is connected between ground on bus bar 202 and a positive direct-current lead 229 which is connected to conductor 204 via rectifier R52. Lead 220 also extends to the plates to the double triode V1 which are grounded for alternating current by condenser C1.

The cathode of the right-hand section of tube V1 is connected to ground through an individual voltage divider R2, R5 in series with resistor R6 which is common to both cathodes of this tube; the cathode of the left-hand section is connected to ground through its individual voltage divider R1, R4 in series with resistor R6. The junction between resistor R2, R5 is connected through a large balancing resistor R3 to the common terminal of resistors R1, R4 and is further connected through resistor R9 and a lead 221 to the grid of thyratron V2 and through a resistance-capacitance network RS, C3 of large time constant to conductor 215 leading to the righthand grid of tube Vl; the left-hand grid of this tube is grounded.

The heating coil of delay relay DRZ and the winding of auxiliary relay RYZ are energizable in parallel over a circuit including the front contact and armature of relay RYS, a conductor 223 and the front contact and armature of principal relay RY Relay RYZ has its front contact and armature connected in series with the make contacts of delay relay DRZ between conductor 204 and a lead 219 extending toward the right-hand front contact of relay-RY7. Alarm lamp AL is operable in a circuit including a conductor 215, back contact and armature of relay RY8, a conductor 223, and the front contact and armature of relay RY1. i

Burner-control relay RY6 has its winding connected between ground bus bar 202 and the make contacts of thermal relay DR5 whence extends a conductor 218 to live bus bar 201 via the left-hand front contact and solenoid S1; an outer left-hand armature of relay RY5 is connected to the right-hand front contact of relay RY6. The modulator 18 has a grounded input terminal and two ungrounded input terminals HL and HR marked fast and slow, respectively. Terminal HR is connected via a lead 212 to the back contact associated with the right-hand armature of relay RY6 which, like its lefthand armature, is connected to bus bar 201. Terminal BL is connected via a lead 211 to the back contact associated with the outer left-hand armature of relay HY 5. Modulator 18 is arranged, in a manner known per se and illustrated in greater detail in my copending application, to move throttle 17 to wide-open position in response to energization of its fast terminal HL and to nearly closed position in response to energization of its slow terminal HR. The front contact associated with the left-hand armature of relay RY6 is connected via a lead 209 to the ungrounded input terminals of motor M2 and main valve solenoid S2.

Photocell'PH has its anode connected via a lead 214 to the high-voltage terminal of potentiometer P2 at its junction with resistor R10. In accordance with the present invention, the cathode of this photocell is connected to lead 215 (which extends to the right-hand grid of tube V1) not directly, as in my prior application, but through contacts operated by the ignition-control relay RY5. For this purpose the relay RY5 is provided with an extra (right-hand) armature which is connected to lead 215 and Whose front contact is tied to the photocell cathode via a conductor 115; a potentiometer P is connected between conductor 115 and ground, its slider being tied to the back contact of the right-hand armature of relay RY5. Potentiometer P is so adjusted that the normally balanced amplifier V1 is efiectively unbalanced by the current drawn by photocell PH when the latter sees the flames of burner 11 but not when its cathode is excited by spurious infrared radiation from the surrounding heating chamber; when the potentiometer is bypassed in the actuated condition of relay RY5, the sensitivity of the circuit is increased so that unbalance occurs in response to the relatively weak flame on pilot nozzle 14.

a The operation of the system illustrated in the drawing will now be described.

Closure of limit switch LS energizes the principal rel-ay RY1 and removes heating current from thermal relay DR1 whose delay period, as indicated in the drawing, is assumed to be 30 seconds. Relay RY1, in operating,

also closes a gap in the alarm circuit of device AL but this circuit has meanwhile been broken by the energization of relay RY8 in parallel with relay RYlover the still-closed contacts of delay relay DR1. The operation of relay RY8 actuates relay RY2, whose energization is without immediate effect so far as the present disclosure is concerned, and supplies heating current to the coil of thermal relay DR2 whose delay period has been assumed to be seconds.

Current from auxiliary bus bar 204 also flows through the closed contacts of thermal relay DR4, assumed to have a delay period of 45 seconds, and energizes relay RY5. The latter, at its inner left-hand armature, connects bus bar 201 to conductor 208 and, thereby, to igniter 15 and pilot valve solenoid S1. If. a flame appears on nozzle 14,. as it should under normal operating conditions, photocell PHis excited and, after an interval of about one second determined by the time constant of network R8, C3, drives the right-hand grid 'of amplifier tube V1 sutficiently positive to draw a current capable of ionizing the thyratron V2 by raising the potential of the junction 'betweenresistors R2 and R5 to which the grid of the thyratron isconnected. Relay RY7, which is slow-releasing as indicated, is thus'energized.

The operation of relay RY7 transfers the energizing circuit of relay RY8 from the contacts of thermal relay DR1 to those of thermal relay DR2 and auxiliary relay RY2 so that thecircuit of alarm device AL'will remain open after relay DR1 opens its contacts. Relay RY7 also connects heating current to thermal relay DR5 whose delay period has been assumed to be- 15 seconds. Afterthis period has elapsed, relay DR5 closes its con tacts and operates burner-control relay RY6.

The operation of the last-mentioned relay actuates fuel pump 12 and opens the main valve controlled by solenoid S2. Modulator 18, which previously had operated throttle 17 to nearly closed position by virtue of the potential applied to its slow input HR over the back contact of relay RY6, remains in its position since the connection to its fast input HLis open at the outer left-hand armature of relay RY5. Enough fuel reaches the burner 11, however, to allow the same to be lighted by the flameon pilot nozzle 14.

Relay RY7, in operating, also removed heating current from delay relay DR4 so that after 45' seconds the circuit of relay RY5 is broken and the latter relay releases. de-energized and potentiometer P is again connectedin the circuit.

If the burner 11 has been properly lit, photocell PH continues to unbalance the amplifier V1 so that thyratron V2 remains ionized and relay RY7 holds up; Modulator 18 is now operated to move throttle 17 to its wide-open position and burner 11 obtains fuel at maximum rate. L

When the needs of boiler 10 have been satisfied, limit switch LS opens and removes the potential from auxil iary bus bar 204, thereby breaking the operating circuit of alarm relay RY8, principal relay RY1 and the other fast-acting relays shown. The system then returns to normal.

If at any time in the above-described cycle the photocell PH should have been insufliciently energized withv limit switch LS closed and the contacts of delay relay DR1 opened, the non-operation or release of flametailure relay RY7 would have de-activated alarm relay RY8 and operated the device AL over the front contact of relay RY1. Such insufficient energization would occur it, with potentiometer P in, circuit (relay RY5 unoperated), the flames on burner 11 should go out while the boiler still calls for heat, the remaining background radiation being ineifective to excite the scanner PH, V1 in its normal condition of reduced sensitivity.

It will be appreciated that the specific circuit connec tions shown and described illustrate but one possible mode of realization and that the invention may be embodied in a variety of modifications, which will be readily apparent to persons skilled in the art, without departing from the spirit and scope of the appended claims. e

I claim:

1. In a heating system, in combination, a burner, fuelsupply means for feeding fuel to a burner, a pilot nozzle adjacent said burner, igniter means for lighting said pilot nozzle, switching means operable'in response to the need Igniter 15 and pilot valve solenoid S1 arenow for operation of the said burner, first relay means operable under the control of said switching means for establishing a first operating circuit for the actuation of said igniter means, photoelectric scanner means positioned to be excited in the lighted condition of said pilot nozzle and of said burner, adjuster means including contacts of said first relay means for adjusting said scanner means to a condition of relatively high sensitivity in the operated condition of said first relay means and to a condition of relatively low sensitivity in the unoperated condition of said first relay means, timer means responsive to operation of said switching means for measuring a time interval sufiicient for the lighting of said pilot nozzle, second relay means controlled by said scanner means for inactivating said first relay means following the lighting of said pilot nozzle, third relay means controlled by said second relay means for establishing a second operating circuit for the actuation of said fuel-supply means, and circuit-breaker means jointly controlled by said timer means and by said second relay means for inactivating both said first and third relay means in the unexcited condition of said scanner means at the end of said time interval.

2. The combination according to claim 1, further comprising an alarm circuit and fourth relay means jointly controlled by said second relay means and by said timer means for closing said alarm circuit substantially concurrently with the operation of said circuit-breaker means.

3. The combination according to claim 1, wherein said timer means comprises a principal relay responsive to said signaling means and thermal relay means controlled by said principal relay.

4. The combination according to claim 3, wherein said thermal relay means has a delay time of the order of a major fraction of a minute.

5. In a heating system comprising a main burner and a pilot nozzle, in combination, first electrically operable means for lighting said pilot nozzle, second electrically operable means for feeding fuel to said burner, circuit means for sequentially actuating said first and said second electrically operable means, photoelectric scanner means trained upon said pilot nozzle and upon said burner, control means responsive to said circuit means for maintaining said scanner means at a relatively high level of sensitivity before actuation of said second electrically operable means and at a relatively low level of sensitivity thereafter, and delayed-action alarm means controlled by said scanner means and by said circuit means for indicating flame failure a predetermined period after operation of said first electrically operable means.

6. The combination according to claim 5, wherein said scanner means comprises a photocell and an amplifier having an input circuit connected to be energized from said photocell, said control means including resistance means in said input circuit and contacts for selectively by-passing said resistance means.

7. The combination according to claim 6, wherein said first electrically operable means comprises a relay, said contacts being controlled by said relay.

8. The combination according to claim 5, wherein said delayed-action alarm means includes a thermal relay.

References Cited in the file of this patent UNITED STATES PATENTS 2,170,497 Gille Aug. 22, 1939 2,388,124 Crews Oct. 30, 1945 2,440,700 Rosche May 4, 1948 2,662,591 Hanson Dec. 15, 1953