US2916022A

US2916022A - Air interlock control for gas burning apparatus

Info

Publication number: US2916022A
Authority: US
Inventors: Arant Perry
Original assignee: Clayton Manufacturing Co
Current assignee: Clayton Manufacturing Co
Priority date: 1951-04-17
Filing date: 1951-04-17
Publication date: 1959-12-08
Anticipated expiration: 1976-12-08

Description

Dec. 8, 1959 P. ARANT 2,916,022

AIR INTERLOCK CONTROL FOR GAS BURNING APPARATUS Filed April 17, 1951 2 Sheets-Sheet 1 INVENTOR penyAz mfi.

37 you, J/Kmmm/ ATTORNEYS P. ARANT 2,916,022

AIR INTERLOCK CONTROL FOR GAS BURNING APPARATUS Dec. 8, 1959 Filed April 17. 1951 2 Sheets-Sheet INVENTOR United States Patent AIR INTERLOCK CONTROL FOR GAS BURNING.

APPARATUS Perry Arant, San Gabriel, Calif., assignor to Clayton Manufacturing Company, El Monte, Calif, a corpora -tion of California Application April 17, 1951, Serial No. 221,417

4 Claims. (Cl. 122-504) The present invention relates to automatic burner control apparatus and more particularly to control apparatus for use with forced draft gas-burning equipment, such as gas-burning steam cleaners, steam generators, space heaters, and the like.

More specifically, the invention relates to air interlock means for controlling the operation of the main gas valve, and which means will prevent opening of the main gas valve and the flow of gas to the burner, unless the blower providing the forced draft is in operation.

The control means comprising the present invention is particularly adapted for use as a further safety device in conjunction with known safety controls, such as stack switches, pressure switches, thermostats, thermo couplings, automatic ignition and spark control devices, electronic flame rod rectifiers, etc., .which provide for shut ting down of the apparatus, or ignition proving before restarting, but do not afford pnotection against the possible flow of gas to the burner when the apparatus is standing by or not in operation at all. Experience has shown that a number of combustion chamber explosions have occurred, even with machines equipped with ignition failure checking devices, due to the lack of adequate gas flow control means effective during an off period, thus making it possible for the combustion chamber to become filled with explosive gas before the unit is restarted.

The principal object of the invention is to provide auxiliary safety control means which will positively pre vent the flow of gas to the burner of gas-fired apparatus, unless the blower furnishing air for forced draft is in operation.

Another object of the invention is to provide auxiliary control means for a gas burner which will automatically shut off the flow of gas to the burner whenever the apparatus is shut down, either manually or automatically.

Another object of the invention is to provide a safety control for gas burning equipment employing forced draft, which includes air interlock means associated with the blower and main gas valve for preventing the flow of all gas to the burner in the event that the air pressure developed by the blower is below a given minimum.

Another object of the invention is to provide a main gas supply valve which will automatically close and prevent gas flow to the burner in the event of excessive t ss rs l rr n n th a upp y l Another object of the invention is to provide an airpressure operated (diaphragm) main valve for gas-burning equipment .wherein gas flow to the combustion chamher is shut off in event of diaphragm failure.

Still another object bf the invention is to provide a safety controlfor gas burning equipment which is independent of, although adapted for use in conjunction with, the usual safety {controls including those employed for ignition pr oving. and which latter do not afford protection againstthe flow of gas to the burner during an gas to the pilot tube '18.

shut-off cock 22 is connected in the conduit 20 at a point 2,916,022 fatentecl Dec. 8, 1959 Still another object of the invention is to provide a gas supply control valve which will not open except in response to the operation of means actuated by air pressure created by operation of the blower.

Other objects and advantages of the invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which:

Fig. 1 diagrammatically illustrates a preferred form of burner control system for a gas-fired steam generator embodying the principles of the present invention;

Fig. 2 is a vertical sectional viewtaken through the air-pressure operated main gas control valve shown in Fig. 1; and

Fig. 3 is a vertical sectional view through a normally open, spring-loaded air control valve, adapted to be closed by a thermally expansible element, also shown in Fig. 1.

"Referring now to Fig. 1 of the drawings, the reference numeral 1 generally identifies a steam generating apparatus including a housing 2 containing a heating coil 3 having an inlet end 3 and a discharge end 3'. The discharge end 3 of the heating coil 3 is connected to a stationary housing 4 by a pipe 4*. A tube 4 has one end thereof secured to the housing 4 and constitutes a continuation of the pipe 4*. A thermally responsive element 4 surrounds the tube 4' and has one end thereof communicating with a chamber 4 in the housing 4 and its other end 4 is closed but free to move for a purpose explained later. Adischarge pipe 4 communicates at one end with the chamber 4 and its other end is connected to a conventional steam separator 5. A conduit -5 conducts the steam from the separator 5 to the point of use. The thermally responsive element 4 extends across a combustion chamber 6 having a gas burner 7 projecting upwardly into the lower end thereof. The burner 7 includes a tubular portion 8 which is connected by an elbow 9 to one end of a 'gas supply pipe 10, the opposite end of said pipe being connected with a main gas supply control valve l'lfwhich will be described in detail later. A manually operable main gas cook 12 is connected in the gas pipe 10 ahead of the valve 11. The valve 11 is designed to control the flow of gas at a feed pressure equal to :a 3" 'to 10 water column. An air supply chamber 13 surrounds the tube '8 of the burner 7 and is disposed below the combustion chamber '6. Forced draft or air under pressure is supplied to the chamber 13 through a duct 14 by a conventional volute blower 15. Air fromthe chamber 13 passes through an opening 16 in the housing 2 andthrough a sleeve 17 disposed above the opening 16 into the combustion chamber 6 for admixture with the gas supplied to the burner 7 for effecting complete combustion of the gas'and'heating of the water in the coil 3.

The burner 7 includes a pilot tube 18, arranged concentrically in the tube portion 8, and having its upper end extending into the combustion chamber 6 and having its lower end connected with one side of a 3-way boss 19 formed integral with the elbow 9. The opposite side 'of the boss 19 is connected to one end of a conduit '20, the other end of which is connected with the inlet side of the main gas cock 12. A conventional solenoid valve 21 is connected in the conduit 20 for controlling the flow of A manually operable pilot that air is mixed with the pilot gas supplied to they pilot tube 18 before it reaches the combustionchamber 6.

The main gas supply control valve 11 is illustrated in detail in Fig. 2 to which'reference will now be made. ,1

This valve comprises a body portion 24 having an inlet chamber 25 and an outlet chamber 26 separated by a partition 27. A portion of the gas pipe is received in a threaded opening 28 on. the inlet side of the valve 11, and another portion of; said pipe is received in a threaded opening'29 on the outlet side of said valve. Thepartition 27fhas a threaded opening 30 in which a threaded annulaf member 31 is mounted. The upper surface of the member 31 is beveled to provide a seat 32 engaged by a rubber sealing member 33 carried by a valve disc 34. The sealing member 33 is centrally apertured to receive a cylindrical sleeve 35 engaged at its opposite ends by Washers 36 and 37. A valve stem 38 is engaged at its upper end with the washer 37, and a valve stemextension 39 has ahexagonal portion 40 intermediate its ends 'engaged 'with the washer 36 and a part that extends through the washer 36, sleeve 35 and washer 37 into a threaded opening 41 formed in the upperendof the valve stern 38, and thus serves to fixedly secure the valve ,;disc 34 to the valve stem 38.;- f z The valve body 24 has an opening 42 formed therein A above the valve disc 34, thisopening'is closed by a cover plate 43 secured to said body portion by a plurality of cap-screws 44. 'A"centrally located hollow projection 45 is formed on the cover 43 and is adapted to receive the upper end of the valve stem extension 39. Ailug' .46 extends downwardly from the inner face of the cover 43 and serves as a support for one forked end' of ailever 47, said lever 'being pivotally connected to the lug 46 by a pin 48.' The opposite or free end of the lever 47 is also forked and portions thereof extend'around the valve stem extension 39 and engage with a convex surface 49 formed above the hexagonal portion 40 of said valve stem extension. A roller 50 is mounted upon the lever 47 adjacentthe lug 46 by a pin 51. The free end of. the lever 47 rests upon the convex surface 49 and normally tends to urge the sealing member 33 intoengagement with the seat 32 by gravity to prevent the flow of gas through the valve. .1

The cover member 43 is provided with an opening 52 disposed directly above the roller 50 forthe reception of the lower end of a rod 53., The rod 53 is grooved and carries a sealing O-ring 54 for preventing the escape ofi'g'as from the inlet chamber 2 5 to the atmosphere. The stem 53 forms a part of a conventional steam pressure responsive actuator'55, which includes a housing 5 6- having its base secured to the cover member 43 by cap screws 57. a A piston 58 is mounted upon the upper end of the rod 53 and its top surface is engaged by a flexible diaphragm 59.1 A cover 60 is disposed above the diaphragm 59 and is secured to the housing 56 by a plurality of screws 61. The cover 60 is hollowed out to provide a pressure chamber 62 vabove the diaphragm 59.

A threaded opening .63 is disposed below the diaphragm I i 59, and an externally threaded cylindrical sleeve' 64 is adjustably mounted in said opening. A compression sprlng 65 is arranged in surrounding relation with the rod 53 between the piston 58 and the lower end of the sleeve 64, so that the pressure required in the chamber 62 to effect downward movement of the rod 53 can be varied asdesired. i I i One end of a conduit 66 is connected to the cover 60 1 in the air'tube 89'at apoint between the main gas 'valve in communicating relation with the chamber 62, and'its other end is connected to the steam separator 5 (Fig. 1)

. so that the pressure in said steam separatoris communicated to said chamber and acts downwardly upon the diaphragm 59 tending tcT'efiect downward movement of the-rod;53 against the resistance offered by spring 65. Thusgshould the steam press'urein the separator 5 exceedthe pressure forwhich the spring has been set, the ro d;53 will be, moved downwardly into engagement wth 'theiroller 50 carried by" the lever 47 to force the valve stem ,38 dow'nwardly and thereby cause the sealing member-33nd engagewith the.seat'32 to positively close .7 the :valve 11" and cut 011. all-"communication between the inlet chamber .25 and theioutlet chamber 26. This action,

'11 against the gas line pressure of 6" to 8" water column. J

of course, will cut ofi? the supply of fuel to the burner 7 and provides a safety means to prevent the building up of excess steam pressure in the steam separator 5.

The valve body 24 has a bottom wall provided with 'an opening 67 vertically aligned with the threaded opening 30. A flexible gas seal diaphragm 68 extends acrosstlie opening 67 and is secured at its outer margin to said bot tom wall by a ring 69 and a plurality of screws 70. Washers 71 and 72 are disposed upon opposite sides of the diaphragm 68 with the washer 71 engaging the lower endof the valve .stem 38, which has an aperture provided with threads '73. A spacer member 74 has a shoulder adapted to engage with the washer 72 and a threaded extension 75, which extends through the washer 72, diaphragm 68 and washer71 into engagement with the threads 73. Thus, the diaphragm 68 is firmly secured to the lower end of the valve sten138. i

'A dished member or pan 76 has an outwardly extending flange 77 disposed below' a cooperating flange 78 depending from the valve body 24 in surrounding relation to the diaphragm 68. A flexible air and gas impervious diaphragm 79, of a diameter substantially larger than the diaphragm 68, is disposed between the

flanges

77 and 78, and cap screws 80 secure said diaphragm .and the. dished member 76 to the valve body 24. Thus, an inter-. mediate chamber 77 is formed bythe valve body 24, the flange 78, and the diaphragms 68 and 79. The flange 78 has a vent opening 78 extending ther'ethrough for venting the chamber 77% to the atmosphere to provide for free relative movement of the diaphragms 68 and 79. A diaphragm supporting plate 81 is disposed. in the inter mediate chamber 77 and is engaged with the upper side, of the air diaphragm 79 and provides a support for substantially the entire area of said diaphragm. The plate 81 is secured to the head of the spacer 74-by a screw 82 extending centrally through said plate and into a threaded opening in said spacer. The pen 76 hasan outwardly and upwardly inclined side wall 83 which merges into the flange 77. vThe sidewall 83 is provided with a threaded opening 84 in which a plug 85 is mounted; The plug 85 has a vent orifice o1 bleed opening 86 formed therein which serves as a bleeder for continuously estate lishing communication between a pressure chamber87, jointly defined by the dished member 76 and the diaphragm 79, and the atmosphere. A boss 88 projects outwardly from the sidewall 83 and has one end of a section 89 of an air tube 89 connected thereto, the" 1 Valve 91, l, which will be described in detail later.-

The inlet of the air valve '91 has one'end of another air tube section v89 connected'thereto and its opposite end is connected with the air duct 14 'at a point indicated the numeral '92. Thus, the solenoid'valve' 90 is connected 11 and the air valve 91. In the case of a 100 hp. steam generating unit, the main gas valve 11 maybe a 3" valve, in which event the bleeder hole 86 would be 0,177 in diameter to maintain a static air pressure equal'toabo'ut a 3" water column on' the diaphragm 79 when the blower 15 is in operation; such pressure acting on the large area of the diaphragm 79 being adequate 'to open the valve The air valve 91 is shown cross-sectional detail in Fig. 3 and comprises a generallycup-shaped body 94 and a'cover 95-forming a "closure for the open end of said bodyfsaid cover beingisecuredto" said body by a plurality of cap screws96g A boss'97 projects inwardly from the bo'ttomwall of the body94 and forms a guide "for a valve stem'98. The valve stem 98 is conventionally grooved to receive split'contractile' snap rings'99 and 100; 7 5

A disc; 191 is disposed adjacent to snap ring 100 and a compression spring 102 is disposed between the disc 101 and the snap ring 99, whereby the disc 101 is mounted for axial movement on the stem 98 to permit over-travel of the stem 98 toward the right. A compression spring 103 is disposed in the cover 95 on the opposite side of the ring 100 and tends to maintain the disc 101 spaced away from a seat 104 formed on the cover 95. In other words, the spring 103 tends to maintain the air valve 91 open at all times. The stem 98 projects to a point exteriorly of the valve body 94 and is adapted to be engaged by the end '4 of the thermally responsive tube element 4, which is subject to the heat of the gases in the combustion chamber as well as the heat of the liquid being heated in the coil 3, inasmuch as liquid discharged from the tube 4 must reverse its direction of flow infthe tube 4 before it can flow into the discharge pipe 4 The arrangement is such that, should there be a failure of the water supply, the thermally responsive element 4 will expand or elongate and urge the stem 98 toward the right, as viewed in Fig. 3, to effect engagement of the disc 101 with its seat 104 to prevent the flow of air under pressure through the valve 91. Of course, as the air valve 91 closes, the pressure communicated to the chamber 87 of the gas valve 11 will drop, thereby permitting the main gas valve to close automatically and cut off the supply of gas to the burner and prevent buming out of the heating coil. The same result can be effected by the closing of the solenoid valve 90, which will likewise function to shut off the flow of air to the pressure chamber 87, as explained hereinafter.

A conventional electronic flame scanner control device 105 may be combined with the present air operated main gas valve 11 to control the main solenoid valve 90 through conductors 106 and 107, but this is not essential for the reason that the solenoid valve 90 could be controlled by any other conventional means. Likewise, the pilot solenoid valve 21 may be connected through conductors 108 and 109 with the electronic control device 105. shich electronic control devices utilize the principle of flame rectification or flame conduction, and are well known to those familiar with the art. Hence, there is no need for illustrating or describing such devices in detail herein. However either type of conventional control includes an electrode 110 placed adjacent the burner 7 and adapted to ignite the gas pilot 18. The electrode 110 is connected with the electronic control device 105 by a conductor 110', which supplies current of high potential thereto, and arcs to ground on the pilot housing. Another electrode 111, more commonly called a flame scanner rod, is connected to the electronic control device 105 by a conductor 111'.

When the unit is started by manual operation of a push button on the control device 105, or by automatic pressure switch control (not shown), current to the electrode 110 and pilot solenoid valve 21 are simultaneously supplied, so that gas is supplied to and the pilot 18 is ignited. The flame scanner electrode 111 is positioned for contact by the pilot flame and heating thereof causes electric current rectification or conduction and actuates, through the electronic control device 105 and conductors 106 and 107, the solenoid valve 90 in the air line 89 to effect opening of the main gas valve 11. In the event that the pilot 18 is unstable or flame rectification or conduction with the scanner rod 111 is not consistent, the electronic control device 105 will revert back to starting condition, closing the valve 90 and reestablishing ignition through the electrode 110 at the gas pilot 18. If the unit is running at any time without proper flame rectification or conduction (depending upon which type of automatic electronic control device 105 is employed), the power source (electric current), which normally flows through a warp switch (not shown), is interrupted by opening of said switch and the unit is stopped after a period of about one minute.

For present purposes, it will be assumed that the gas 6 pilot 18 is lit, and that the conventional electronic control 105 has energized the air control solenoid valve to maintain the same in open position. Air under pressure is then diverted from the casing 14 through the air tube section 89 to the inlet of the air valve 91, which valve is normally maintained open by the spring 103, as above pointed out, so that the air under pressure is further conducted through the tube section 89 and the open solenoid valve 90 and thence through the tube section 89 to the pressure chamber 87 in the main gas valve 11. The air under pressure will act upon the diaphragm 79 and flex it upwardly, thereby raising the valve stem 38 and lifting the sealing member 33 out of engagement with the seat 32 to permit gas to flow through the pipe 10 to the burner 7. The air bleed opening 86 will, of course, permit air under pressure to continuously escape from the chamber 87 to the atmosphere at a restricted rate. Normally, a pressure equivalent to only 3" of water is required to effect opening of the gas valve 11, and the blower 15 is adequate to supply such low pressure at all times. The valve 11 will normally remain open so long as fuel is required to heat the liquid passing through the coil 3. Should the steam demand on the steam generating unit 1 drop to the point where an excess of steam pressure develops in the steam separator 5, such steam pressure will be effective through the conduit 66 to act upon diaphragm 59 causing the rod 53 to move downwardly into engagement with the roller 50 and actuate the lever 47 to move the valve stem 38 downwardlyand thus positively shut off the flow of gas through the valve 11. On the other hand, an independent control of the supply of gas to the burner is possible through the closing of the air valve 91 by the thermal expansion of the element 4, the latter acting on the stem 98 to engage the disc 101 with its seat 104. Any excess expansion of the element 4 cannot damage the valve 91 because of the loose mounting of thedisc 101 on the stem 98 compensating for any valve stem over-travel. When the valve 91 is closed, the supply of air under pressure to the chamber 87 is cut off and pressure in said chamber is immediately reduced by the bleeding of the air from the chamber through the bleeder hole 86 until the pressure in the chamber 87 is reduced to atmos pheric, thus permitting the valve 11 to close automatically.

A further and independent control of the gas valve 11 is provided through the solenoid valve 90 controlled by the conventional electronic flame scanning apparatus 105 which would de-energize the solenoid valve 90 and permit it to close in the event of flame failure. Hence, if the burner flame should go out for any reason, the solenoid valve 90 would be automatically closed, cutting off the supplyof air under pressure to the chamber 87! even though the blower 15 continues to operate, whereby closing of the valve 11 will be quickly effected through the bleeding of air under pressure to the atmosphere through the orifice 86, as previously explained. Moreover, in the event of failure of the blower 15, or manual hut ti w sf the a a at there w uld be o a n e pressure delivered to the chamber 87 and the valve 11 would automatically close to shut off the supply of gas to the burner 7.

It will be clear from the foregoing that the present apparatus provides an air interlock control for the main gas valve 11, which is independent of the usual and conventional controls, and which will prevent all gas from flowing to the combustion chamber 6 unless an adequate supply of air is being furnished to the combustion chamber.

It will be understood that, in the event that the pressure in the gas line connected to the inlet of the valve 11 should rise to about 12" water column pressure, such pressure would overcome the 3" water column pressure of the air in the chamber 87 acting on the diaphragm 79 tending to maintain the valve 11 open, with the result that the valve 11 will be closed, thereby automatically preventing the delivery of'gas at excessive pressure to the burner 7. This feature also constitutes a valuable safety control for the apparatus. T; i

It will also be understood that in the event of any diaphragm failure, the valve 11 will close similar to a check valve due to the intermediate atmospheric chamber 77 and the direction of normal gas flow through the valve, allowing a safe failure. 1 t

It will be understood that various changes may be made in the details of construction and in the arrangement of the parts of the burner control system disclosed herein without departing from the principles of the invention and the scope of the annexed claims.

Iclaimr t 1. Gas-fired apparatus, comprising: a burner; a gas supply valve connected with said burner for controlling the supply of gas thereto; a blower for supplying air under pressure to said burner, ,said gas supplyvalve including a' seat, and a valve disc cooperable with said seat to control the flow of gas through said gas supply valve to said burner, a diaphragm in said gas supply valve on the outlet side of said valve disc, a valve stem connecting said diaphragm with said valve disc, and means providing a pressurechamber on the side of said diaphragm remote from said valve disc; a conduit interconnecting said blower-and pressure chamber for conducting air under pressure from said blower to said pressure chamber for effecting opening of said gas supply valve, an air 'shut-oflf valve connected in'said conduit for shutting ofi the supply of air under pressure to said pressurechamber; and bleeder means establishing communication between said pressure chamber 1 and the atmosphere for continuously bleeding a portion of the air under pressure from said pressure chamber to the atmosphere, whereby upon closing of said air shut-01f valve, the pressure in said pressure chamber will be vented to the atmosphere and the gas supply valve will automatically close.

2. Gas-fired apparatus, comprising: a burner; a gas supply valve connected with said burner for supplying gas thereto; a blower for supplying air under pressure to said burner, said gas supply valve having an inlet, an outlet, a seat between said inlet and outlet, and a valve disc cooperable with said seat to control the flow of gas through said gas supply valve to said burner; a diaphragm on the outlet side of said valve disc; means operatively connecting said diaphragm with said valve disc; means providing a pressure chamber on the side of said diaphragm remote from said seat; a normally open air control valve having an inlet and an outlet and a seat between said inlet and'outlet, a valve disc engageable with said last-mentioned seat, a stem connected with said last-mentioned valve disc, and spring means normally maintaining said last-mentioned disc out of engagement with its seat; a conduit connecting the inlet of said air valve with said blower; a conduit connecting the outlet of said air valve with said pressure chamber of said gas supply valve to eifect opening of said gas supply valve when said blower is in operation; and a thermally responsive elementtactive on the stem of said air valve to close the same against'said spring pressure to shut oii the air pressure to said pressure .chamber of said gas supply valve tothereby allow-saidgas supply valve to close. 3. ..Gas-firedf apparatus as defined in claim 2, in which the air control valve includes means compensating for overtravel of the thermally responsive element.

4. Gas-fired apparatus, comprising: a burner; a gas supply ,valve connected with said burner for supplying gas thereto; a blower for supplying air under pressure to said burner, said gas supply valve having an inlet, an out let, a seat between said inlet and outlet, and a valve disc cooperable with said seat to control the flow of gas through said gas supply valve tosaid burner; a diaphragm on the outlet side of said valve disc; means operatively connecting said diaphragm with said valve disc; means providing a pressure chamber on the side of said diaphragm remote from said seat; a normally open air control valve having an inlet and an outlet and a seat between said inlet and outlet, a valve disc engageable with said last-mentioned 'seat, a stem connected with said last-mentioned valve disc, and spring means normally maintaining said last-mentioned disc out of engagement with its seat; a conduit connecting the inlet of said air valve with said blower; a conduit connecting the outlet of said air valve with said pressure chamber of said gas supply valve to effect opening of said gas supply valve when said blower is in operation; a thermally responsive element active on the stem of said air valve to close the same against said spring pressure to' shut 01f the air pressure to said pressure chamber of said gas supply valve to'thereby allow said gas supply valve to close; and an air shut-01f valve connected in, said last-mentioned conduit for shutting 01f the'supply of air to said pressure chamber to eflect closing of said gas supply valve independently of said thermally responsive element. 6 t t References Cited in the file of this patent V UNITED STATES PATENTS 792,087 Thomson June 13, 1905 880,402 Reynolds Feb. 25, 1908 1,384,247 Fox July 12, 1921 1,539,630 Beaird May 26, 1925 1,609,891 Smith Dec. 7, 1926 1,645,506 McKee Oct. 11, 1927 1,721,800 Wunsch July 23, 1929 1,961,933 Irwin June 5, 1934 2,169,683 Dunham Aug. 15, 1939 2,170,342 Bailey Aug. 22, 1939' 2,175,866 Arnold Oct. 10, 1939 2,321,109 Sellers June 8, 1943 2,396,032 Waterman Mar. 5, 1946 2,405,573 Frisch Aug. 13, 1946 2,422,178 Blizard June 17, 1947 Niesmann Jan 22, 1952