US2652109A - Gas burner control system - Google Patents

Description

Seprf. 15, 1953 l W `A RAY 2,652,109

- l I GAS BURNER CONTROL' SYSTEM Filed June 24, 1949 Gttomeg Patented Sept. 15, 1953 GAS BURNER CONTROL SYSTEM William A. Ray, North Hollywood, Calif., assignor to General Controls Co., Glendale, Calif., a

corporation of California Application June 24, 1949, Serial No. 101,019

8 Claims.

My present invention relates to gas-burner control systems, and more particularly to one which includes a main burner, a pilot burner, a main valve, and a safety valve, as Well as means responsive to the flame of the pilot burner for so controlling the operation of the safety valve as to prevent passage of gas to the main burner unless the pilot burner is alight.

A system of this character has particular utility in the control of the burner of a cookstove oven, the main valve then being a hand Valve or one controlled by a timeclock. Upon opening the main valve gas is supplied only to the pilot burner where it is ignited through a flash-back tube by a continuously-burning remote pilot which, in a single-point-ignition system, may serve for all the burners of the stove. If the main valve is manually controlled, the pilot burner may be lit by a match. After an interval suflicient for proper energization of the safety means by the name of the pilot burner, the safety valve opens automatically to permit ilow of gas to the main burner where it is ignited by the pilot burner. When, to discontinue heating of the oven, the main valve is closed, both the main and pilot burners are extinguished so that the foregoing procedure must be repeated to reinitiate the heating.

rlhe safety means usually comprises an electromagnet energized by the current generated by a thermocouple heated by the pilot burner llame, or by current from a conventional source controlled by a thermal Switch (commonly of the bimetallic type) responsive to the pilot burner flame. The thermocouple and thermal switch have thermal inertia such that energization of the electromagnet is delayed for a period after flame is established at the pilot burner, and continued after it is extinguished so that there is a delay period subsequent to the closing of the main valve (and resultant extinguishment of the main and pilot burners) during which period the safety means is still energized and therefore incapable of effecting closing of the safety valve.

lf, during said delay period, the main valve is reopened (as may occur if the operator changes her or his mind and decides to continue the heating) gas then passes to both the main and pilot burners so that it accumulates in the oven in an amount such that an explosion may occur when the pilot burner is relighted through the ilashbacl; tube. Flash-back ignition is relatively slow especially when, as is usual, the continuously burning pilot is quite remote, so that a dangerous amount of unburnt gas may pass from the 1 closed. lor full understanding iurther appreciation of its feat and to the appended claims.

In the drawing: Figure 1 is a s assumed in operation; and

Figure l is a schem atic view of a modi tr O1 System according t0 the invention ed con Referringirst more particularly to Figs. 1-3

valve I4,

manually-operable gastrolled solenoid valve.

The safety valve 1s of the pressureabove diaphragm 23.

which a blade-like closure 3B cooperates. The closure 30 is of magnetic material and is fulcrumed on the end of the lower side-arm of a U-shaped magnet core 3 I, the closure being biased into engagement with jet 29 by a spring 32. Around the upper side-arm of the core is a coil 33, passage of current through which effects attraction of the closure-armature 30 out of engagement with jet 23 and into engagement with jet 28. The jets 28 and 23 lead respectively, by way of pipes 34 and 35, to the inlet i6 of the casing and to the atmosphere.

For igniting the main burner I2 there is a pilot burner 36 which is connected to` the gassupply conduit between the main valve I3 and the safety valve I4, the pilot burner being shown in Fig. 1 connected to the inlet of the safetyv valve which is in effect between these two valves. Arranged for heating by the flame of the pilot burner (the contour of which flame, when burning, is indicated at 31) is a thermoelectric generating device comprising a pair of thermocouple elements 3B joined together at one end to form a hot-junction 39 in the region of the fiame, the other ends of the thermocouple elements being connected by wires 4B to the coil 33 of the electromagnet.

The thermoelectric generating device, shown schematically in the drawing, may be of any suitable form capable of withstanding the heat of the flame and having low resistance to the flott1 of generated current. As is well known, thermoelectric generating devices of this character are relatively massive so that they heat and cool slowly and therefore, after the flame is extinguished, generation of current continues for an appreciable length of time (say, -15 seconds even when the thermocouple is of the fast-heating type) in an amount sufficient to cause the electromagnet to retain the armature in attracted position. During this period the thermal safety means, constituted by the thermoelectric generating device, the electromagnet, and the auxiliary valve, is therefore ineffective to controll the operation of the safety valve (in a manner to be described). The lag of a conventional thermal switch is still greater than that of the thermoelectric device described.

To initiate operation of the burner system, the main Valve I3 is opened so that gas passes to thepilot burner 36 where, in the arrangement of Fig. 1, it is ignited through a flash-back tube 4 by the ame of a remote continuously-burning pilot 42 connected to the gas-supply conduit ahead of the main valve. Inasmuch as the jet 28 of the auxiliary valve is open, gas passes therethrough to the chamber 26 so that (jet 29 being closed) the gas pressures above and below the diaphragm 23 are equalzed and the diaphragm therefore remains in its normal position, as shown in Fig. 1, under the gravity bias of member 24.

The main closure 2B is held seated by spring 2| and is not rigidly connected to the diaphragm, so that even if conditions were such that the diaphragm were to rise slightly before the presn sures above and below it became equalized, the closure 2Q would be unaffected. To guard against momentary rise of the diaphragm upon opening of the main valve I3, the flow passage of jet 28 may be made relatively large.

When the thermocouple 38 has become heated` to a degree such that electricity is thereby generated in sufficient amount, the armature-closure 30 is attracted by the 'eleotromagnet out of en- 4 gagement with jet 29 and into engagement with jet 28. The resultant reduction of pressure in chamber 26, due to the venting of gas through jet 29 and pipe 35 (and closing of jet 28), permits the gas pressure below the diaphragm 23 to force the same upwardly, the venting of chamber 26 being relativelyslow due to a restriction 43 provided in pipe 35 sov that the diaphragm rises corresponclinglyA slowly. In initial rise of the diaphragm the main closure 20 remains seated under the force of its bias (and because of the lostmotion' connection between it and the diaphragm) but after the head 44 of the closurestem is engaged by th'e member 24, continued rise of the diaphragm effects unseating of the closure, the parts then being in the positions shown in Fig. 2. The gas flowing through the outlet of the safety valve is ignited at the main burner I2 by the flame 31 of the pilot burner.

When, to discontinue-heating, the main Valve I3r is closed, there occurs substantially instantly a partial fall of the diaphragm due to venting of gas below it to the main burner, so that the closure 20 is seated under the force of its bias spring; the parts then being in the positions shown in Fig, 3. Inasmuch as Vthe electromagnet is still energized the jet 29 isr uncovered, as indicated in Fig. 3, so that the diaphragm continues to fall under its gravity bias, but its fall is slow due to the restriction 43 in vent-pipe 35 which limits to a low rate the entrance of air to chamber 28 necessary for the fall of the diaphragm. During' this slow fall of the diaphragm the gas trapped below it (closure 23 being seated) is expelled to the pilot burner 36 at a rate such as to sustain a small flame thereat. This small flame is in-v sufoient to maintain heating of the thermocouple 38, so that after a delay period (as described above) the armaturesclosure 30 is released, the restriction 43 and the capacity of the gas reservoir below the diaphragm (as well as the gravity bias of the diaphragm) being so arranged that the small flame at the pilot burner can be sustained for a period somewhat longer than the normal delay period of the safety means. Upon release ofthe armature-closure the diaphragm falls quickly to its final position due to the opening of jet 25 reopening of the safety valve then being possible only after the electromagnet is reenergized as previously described.

If, before termination of the delay period dui'- ing which the auxiliary valve is still in energized condition, the main valve I3 is reopened, the small flame sustained at the pilot burner instantly expands to full size and ignites the gas which then passes to the main burner due to the opening of closure 20 with rise of the diaphragm under the gas pressure below it and the low pressure above it in the vented chamber 25. The possibility of explosion due to passage of unburnt gas from the main burner is thus avoided. As was mentioned in the statement of invention, even if a flash-back igniter for the pilot burner 36 is provided, there would still be the possibility of explosion in a small space such as that of a coolzstove oven (unless the main-burner-ignitihg flame were actually sustained) because of the inherent delay of the flash-back arrangement.

In the modified form of the invention shown in Fig. 4, the parts corresponding to those of Fig. 1 have been assigned the same numerals; a prime mark having been added to slightly modified parts. The arrangement of Fig. 4 differs materially from. thatwofr Fig. 1 only in that instead 'of employing the space below the diaphragm of the safety valve as a reservoir from which, upon closing of the main valve, gas is supplied to the pilot burner at low rate, there is provided a separate reservoir, generally indicated at l, and means for expelling the gas therefrom. This reservoir is connected to the conduit il between the main valve I3 and the safety valve E4 and comprises a pair of dished members 52 which are clamped together with the margin of a flexible diaphragm 53 therebetween. When the main valve I3 is opened the diaphragm 53 rises to the position shown in broken lines under the pressure of the gas below it. When the main valve is closed the diaphragm falls under the gravity bias afforded by a disk 54 attached to the central part of the diaphragm, the rate of fall of the diaphragm being limited by the flow capacity of a small vent pipe 55 in the top of the reservoir.

In the safety valve I4 of Fig. 4 the diaphragm 23 carries a simple disk-like closure 56, the only other difference in this safety valve from that of Fig. l being that the vent-pipe 35' of the auxiliary valve has no restriction. In Fig. 4 the pilot burner 35 is shown connected to the conduit immediately ahead of the safety valve, instead of to the inlet thereof, but the effect is obviously identical.

The operation of the system of Fig. 4 is substantially the same as that Yof Fig. 1: Upon opening of the main valve i3 the diaphragm 53 of reservoir 5i rises to its broken-line position to which position it is conditioned (in the same manner as is the safety-valve diaphragm 23) by the pressure of the gas supplied to the reservoir. When, to discontinue heating, the main valve is closed, the safety-valve closure 56 falls quickly to seated position due to the fact that the vent pipe 35 is unrestricted and fluid can pass freely through the jet 29 which is uncovered during the ensuing delay-period of the thermoelectric device. The gas expelled from reservoir 5| therefore passes to the pilot burner 36. To limit flow from the reservoir to the desire low rate a restriction 5l may be inserted in the connection between the gas-supply conduit and the reservoir in place of, or in addition to, the restricted vent 55. It will be observed that both of the safety valves is and I4 are of the type which open under the pressure of the gas unless the thermal safety means, constituted by the thermoelectric device and the electromagnetic auxiliary valve, is in condition to prevent such opening.

The term energized as used in the description and claims in connection with the thermal safety means, is intended to mean that the safety means performs its function, or is set into operation, in response to the heat produced by the pilot-burner flame, the thermal energy of the iiame effecting electrical operation of the safety means if such as the thermocouple shown or a bimetallic switch is employed, or mechanical operation if a system such as includes an expansion-rod device or a thermal bulb is employed.

The specific embodiments of my invention herein shown and described are obviously susceptible of modification Without departing from the spirit of the invention, and I intend therefore to be limited only by the scope of the appended claims.

I claim as my invention:

l. In a gas-burner control system: a main burner; a gas-supply conduit leading to said main burner; a pilot burner connected to said conduit for igniting said main burner; a main valve in the conduit ahead of said pilot burner connection and said main burner; a normally-closed safety valve in the conduit between the pilot burner connection and the main burner; thermal safety means, energized by the heat of the flame of the pilot burner, for so controlling the operation of said safety valve that passage of gas to the main burner is obstructed when said safety means is unenergized, said safety means heating and cooling relatively slowly so that, after heating, there is a delay period subsequent to the closing of the main valve during which period the safety means is ineffective to prevent passage of gas through the safety valve to the main burner in the event of reopening of the main valve; means forming a gas reservoir communicating with the conduit between the main valve and the safety valve; and means, conditioned by the pressure of the gas supplied to said reservoir when the main valve is open, for supplying gas from the reservoir to the pilot burner during said delay period, said supplying means including flow-restricting means such that the gas is supplied from the reservoir at a rate so low that the small flame thereby sustained at the pilot burner is ineffective to maintain energization of said safety means, the pilot burner connection to said conduit being substantially unrestricted whereby the pilot flame can instantly expand to full size in the event that the main valve is reopened during the delay period.

2. In a gas-burner control system: a main burner; a gas-supply conduit leading to said main burner; a pilot burner connected to said conduit for igniting said main burner; a main valve in the conduit ahead of said pilot burner connectionv and said main burner; a normally-closed safety valve in the conduit between the pilot burner connection and the main burner; thermal safety means, energized by the heat of the ame of the pilot burner, for so controlling the operation of said safety valve that passage of gas to the main burner is obstructed when said safety means is unenergized, said safety means heating and cooling relatively slowly so that, after heating, there is a delay period subsequent to the closing of the main valve during which period the safety means is ineffective to prevent passage of gas through the safety valve to the main burner in the event of reopening of the main valve; means forming a reservoir receiving gas from said conduit when the main valve is open; means, conditioned by the pressure of the gas supplied to said reservoir when the main valve is open, for expelling gas from the reservoir to the pilot burner when the main valve is closed; and means for so restricting the passage of gas from the reservoir to the pilot burner that the small flame thereby sustained at the pilot burner is ineffective to maintain energization of said safety means, the pilot burner connection to said conduit being substantially unrestricted whereby the pilot flame can instantly expand to full size in the event that the main valve is reopened during the delay period.

3. In a gas-burner control system: a main burner; a gas-supply conduit leading to said main burner; a pilot burner connected to said conduit for igniting said main burner; the main valve in the conduit ahead of said pilot burner connection and said main burner; a normally-closed safety valve in the conduit between the pilot burner connection and the main burner, said safety valve being of the type adapted to open under the pressure 7 of the 'gas in the conduit; thermal safety means energized by the heat of the flame of the pilot burner, said safety means acting when unenergized to prevent opening of said safety valve and to permit it to open when energized, said safety means heating and cooling relatively slowly so that, after heating, there is a delay period subsequent to the closing of the main valve during which period the safety means is ineffective to prevent opening of the safety valve in the event of reopening of the main valve; means forming a reservoir receiving gas from said conduit when the main valve is open; means, conditioned by the pressure of the gas supplied to said reservoir when the main valve is open, for expelling gas from the reservoir to the pilot burner when the main valve is closed; and means for so restricting the passage of gas from the reservoir to the pilot burner that the small flame thereby sustained at the pilot burner is ineffective to maintain energization of said safety means, the pilot burner connection to said conduit being substantially unrestricted whereby the pilot flame can instantly expand to full size in the event that the main valve is reopened during the delay period.

4. In a gas-burner control system: a main burner; a gas-supply conduit leadingr to said main burner; a pilot burner connected to said conduit for igniting saidk main burner; a main valve in the conduit aheadof said pilot burner connection and said main burner; a normally-closed safety valve in the conduit between the pilot burner connection and the main burner, said safety valve being of the type adapted to open under the pressure of the gas in the conduit and to close quickly when that pressure is reduced due to the closof the main valve; thermal safety means energized by the heat of the flame of the pilot burner, said safety means acting when unenergized to prevent opening of said safety valve under said gas pressure and to permit it to open when energized, said safety means heating and cooling relatively slowly so that, after heating, there is a delay period subsequent to the closing of the main valve during which period the safety means is still energized and therefore ineffective to prevent opening of the safety valve in the event of reopening of the main valve; means forming a reservoir communicating with the conduit between the main valve and the safety valve so that it is supplied with gas when the main valve is open; and means, conditioned by the pressure of the gas supplied to said reservoir when the main valve is open, for expelling the gas from the reservoir to the conduit when the main valve and the safety valve are closed, said expelling means including flow-restricting means such that the gas is supplied to the conduit at a rate so low that the small name thereby sustained at the pilot burner is ineffective to' maintain energization of said safety means, the pilot burner connection to said conduit being substantially unrestricted whereby the pilot fiar .e can instantly expand to full size in the event that the main valve is reopened during the delay period.

5. In a gas-burner control system: a main burner; a gas-supply conduit leading to said main burner; a. pilot burner connected to said conduit for igniting said main burner; a main valve in the conduit ahead of said pilot burner connection and said main burner; a normally-closed safety valve in the conduit between the pilotr burner connection and the main burner, said safety valve being of the pressure-operated -typewhich includes a diaphragm subjected on one side to, and movable in one direction under, the gas pressure at the inlet of the safety valve, said diaphragm carrying a closure -arranged to permit ow through the safety valve when the diaphragm is moved in said one direction, the safety valve also including an auxiliary valve and means controlled by the auxiliary valve for applying pressure to the other side of the diaphragm to effect movement of the same in an opposite direction toward closure-seating position; thermal safety means energized by the heat of the flame of the pilot burner for so operating said auxiliary valve vas, to prevent movement of the diaphragm from closure-seating position when the safety means is deenergized, said safety means heating and cooling relatively slowly so that, after heating, there is a delay period subsequent to the closing of said main valve during which period the safety means is still energized and therefore incapable of preventing movement of the diaphragm toward closure-unseating position in the event of reopening of the main valve; means forming a reservoir communicating with the inlet of the safety valve; and means, conditicned by the pressure of the gas supplied to said reservoir When the main valve is open, for expelling the gas from the reservoir to the pilot burner when the main valve and the safety valve are closed, said expelling means including nowrestricting means such'that the gas is expelled from the reservoir at a rate so low that the small flame thereby sustained at the pilot burner is ineective to maintain energization of the safety means.

d. ln a gas-burner control system: a main burner; a gas-supply conduit leading to said main burner; a pilot burner connected to said conduit for igniting said main burner; a main valve in the conduit ahead of said pilot burner connection and said main burner; a normallyclosed pressure-operated safety valve in the conduit between the pilot burner connection and the main burner and comprising a diaphragm whose inner side is subjected to the pressure of the gas at the inlet-of the safety valve,- a closure carried by said diaphragm and arranged to permit flow through the safety valve when the diaphragm is moved outwardly underthe pressure of the gas in said inlet, an auxiliary valve, and means controlled by said auxiliary valve for applying pressure to the outer side of the disphragm to effect inward movement of the same toward closureseating position; thermal safety means energized by the heat of the fiame of the pilot burner for so operating said auxiliary valve as to prevent outward movement of the diaphragm from closure-seating position when the safety means is deenergized', saidsafety means heating and cooling relatively slowly so that, after heating, there is a delay period subsequent to the closing of said main valve during which the safety means is incapable of preventing said outward movement of the diaphragm in the event of reopening of the main valve; means forming -a lost-motion connection between the closure and the diaphragm whereby the closure is seated before the completion of said inward movement of the diaphragm so that, when said main valve is closed, after the closure is seated the gas in the inlet of the safety valve is expelled therefrom to the pilot burner by the continued inward movement of the diaphragm; and means so retarding said inward' movement of the diaphragm that the small flame thussustained at the pilot burner 'is inefdevice subjected to the ame of said pilot burner for energizing said electromagnet.

WILLIAM A. RAY.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,300,146 Downe Oct. 27, 1942 2,346,704 Ray Apr. 18, 1944 2,444,490 Bellinger July 6, 1948

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