US2578087A

US2578087A - Safety pilot foe gas burners

Info

Publication number: US2578087A
Authority: US
Publication date: 1951-12-11
Anticipated expiration: 1968-12-11

Description

Dec. 11, 1951 e. A. PETERSON SAFETY PILOT FOR GAS BURNERS Filed Oct. 12, 1946 IN V EN TOR. GEORGE A. PETERSON BY I 5 A TTORNE Y5 Patented Dec. 11 1951 SAFETY PILOT FOR GAS BURNERS George A. Peterson, Sydney, New South Wales, Australia Application October 12, 1946, Serial No. 702,957

10 Claims.

. l This invention relates to a safety pilot for gas burners, and is directed to an improved solution of the problems of maintaining an adequate pilot '1 flame without waste of fuel and of preventing supply of fuel to the main burner unless the pilot 4 is in proper operation.

While arrangements to shutoff the supply of gas to a, burner when its pilot flame is extinguished have been known, the principles of this invention make possible a device for this purpose.

. control valve 22 and a line 23.

which is simpler and more positive in action than those previously employed. In addition, the invention makes it possible to counteract influences,

such as fluctuations in gas main pressure and drafts of air striking the flame, which may cause extinction of the pilot.

The objects of the invention include the following! To increase the safety and reliability of gasburning appartus;

To minimize the possibility of failure of a pilot (flame, while at the same time economizing on fuel; I

To provide a shut-off control of gas supplied'to the main burner responsive to the condition of the pilot flame which is sensitive and quick in operation;

To maintain a constant pilot flame, notwithstanding extraneous disturbances; and

To accomplish the above-named objectives by means which are simple, rugged, accurate and ,positive in action, and economical to manufacture.

Other objects and advantages of the invention,

more or less ancillary to those stated above, will be apparent to those skilled in the art from the description herein of the preferred embodiment of the invention. H Referring to the drawings:

Fig. 1 is a plan view of a gas burner, pilot, and a Y control devices in accordance with the invention;

Fig. 2 is a partial vertical section, taken onthe plane indicated by the line2'-2 inFig. 1; and

Fig. 3 is an end elevation of the temperatureresponsive device and pilot burner. I

The invention is employed in connection with a main gas burner I I, which may be of any form and be applied to any heating function. The burner H is supnlied through a line 12, a safety Y The pilot burner l1 consists of a sectlonof tubing having a reduced end l8 from which the main pilot flame I 9 is projected to the burner i l. The pilot is supplied from a line 2| through a The valve 22 is operated to throttle the supply of gas to the flame and automatically maintain the desired strength of flame. The valve is by-passed by a connection 24-betWeen the lines 2| and 23, the by-pass incorporating a reduced section of tubing or other restriction graduated to pass the minimum I amount of gas sufiicient to maintain the pilot flame.

-The temperature-responsive portion of the device comprises asleeve 26 threaded into a fixed frame member 21, and having a crosspiece 28 fixed on its free end. Rods 29 fixed in the ends of the crosspiece 28 and a yoke 3| constitute, with the crosspiece and yoke, a rectangular frame. An

expansion rod 32 fixed centrally in the yoke 3| extends between the rods 29 and through the sleeve 26, being free to move longitudinally in the sleeve. The

rods

29 and 32 may be hollow if desired.

The control is exerted through the differential thermal expansion of the rod 32 with respect to the rods 29. To this end, the pilot burner is disposed parallel to and underneath the exposed portion of the rod 32, and is provided with a plurality of small orifices 33 along its length. The flames from the orifices 33 heat the rod 32, but do not heatthe rods 29 to any considerable extent because of their lateral displacement. Heat supplied from other sources, as the furnace walls or the main burner, will affect all the rods substantially equally, and cause no differential expansion, The

rods

29 and 32 and the sleeve 26 are formed of the same material, heat-resisting steel, such as 18-8 stainless steel, being found satisfactory. Any convenient method of fixing these parts in the cross member 21 and 3| may be employed,

Operation of the valves l3 and 22 is accomijplished through a cross bar 34 fixed on the outer end of the rod 32 and thus moved toward'or ;away from the frame member 21 by the differential expansion of the rods. The pilot control valve 22 is normally open, but as the rod 32 expands, its poppet 36, which is control ed by the bar 34, moves toward the seat 31, throttling the pilotflame and maintaining it at the desired intensity. A compression spring 38, tendingto the seat 31.

Thesafety v'a1ve"| 3 is held closed whenthe apparatus is cold by a tension spring 39, attached in any convenient manner to the poppet 4| of the valve and the fixed member 21. The stem 42 of the valve slides in a. bore 43 in the bar 34, and is fitted with a nut 44 adjustable on the stem. The nut is set for a lost motion connection such that the spring 39 holds the valve I3 closed until the rod 32. has expanded approximately sixty per cent of the amount which corresponds to normal operation of the pilot.

In practice, the maximum rate of supply to the pilot flame should be at least twice the operating rate, and the arrangement of the two v'alves should be such that the safety .valve Happens enough to permit ignition of the main burner before the pilot burner valve 22 closes enough to afiect the pilot flame substantially. ""Overrun of the valve is prevented by throttling otthe pilot by the valve 22.

, .By virtue of the lost motion connection between the, rod 32 and the valve lS, if the. pilot should Zbecome extinguished, the 'valve'l3 Will'rapidly close. The rod 32, being substanti'allyhotter Ithanthe rods 29, will cool much more rapidly.

.LIThe heat loss by radiation is approximately proportional to .the fourth power'of the absolute temperature. The temperaturedifference of the rods, and thus their length difference, will thus vary v'viithv time, when. the .pilot is extinguished, according to anexponential' curve which drops very steeply at first. As soon as the differential contraction amounts to about forty per cent, (which will be in.a smallfraction' of'the total cooling time, the valve 13 will close'and 'shut-ofi the main burner. In practice, the apparatus'may ,be designed to operate' with about" 500 degrees Fahrenheit temperature difierence between" the rods32 andi29.

1 Since the operationdepends upon' the'linear ;expansion .of the rods, and the force is applied directly to the valves in a directionparallel to the axis of the rods, the control apparatus will be exceptionally positiveand accurate 'in operation.

It should be noted that the specific-former" the valves, except insofar astinvolves suitability for practical operation in" the combination disclosed L.herein,.is immaterial, and the illustration'of' the valves. herein may be regarded as" schematic. The poppet type of valve-is regarded as most suit- .,.able, however. The dimensions of the'valves will of course vbe readily determinable in terms of "the fuel requirements-of the burners, the length -and thermal expansion coeflicient of the rOds -ZB and the exposed portion ofthe rod 32, and-the preferred operating temperature differential-hm tween the rods'32 and-"29.

Itlwill beobvious to those skilledin the'art that a remote electrically-operated valve may be substituted for the direct-operated valve I3 .1 by installing a switch,of a well-known type opieratedyloy a small movement'of its actuator in f position. to be operated by the-rod 32 or bar 3 l.

"With' this construction, "substantiallyinstaniztaneous opening ,andclosing of the mainburner valve Will result.

The operation of the control-device to regulate thepilot flame through the differential expansionof the rods andthe action of the valve-"22 .will be apparent from the foregoing description. If-la draft should .afl'ect the "pilot flame; f-the .,.effect .oi theflame onthepcentral-rod32 w111 be decreased, causing contraction"otithe'rod and .greater. opening. of the valve 22.

An optional feature of the invention 'is the 4 provision of a shield 41 of sheet metal or the like surrounding the pilot burner I! and the exposed portion of the rod 32 Such a shield, which should be provided with openings at top and bottom for circulation of air, Will tend. to confine the heat from the pilot burner to the rod 32 and shield the rods 29 from the burner.

-The specific.description herein of the preiferred mode of employment of the invention 10 should not be regarded as restrictive, since the .scope of the invention is to be determined from "the appended claims.

iII'..claim:

1.. Ina heatingdevice, a main burner, a pilot 32 iburner therefor, a normally closed valve for supplying the main burner, a normally open valve for supplying theflpilot burner, a thermally responsive. control device exposed to the heat of the pilot burner, a member moved by the control device, lost motion coupling means connecting'gthe main burner valve to the member so "that'fthe valve will be'opened' afteria'predetermined movement of the member; and means connectingthe pilot burner valve to thermemher so" that the valve will be operated toward its closed position by movement of the member,

" the pilot burner'valve being adapted to regulate the: pilot burner to.maintain a normal .pilot flame and'thus hold the main'burner valve open,"the

controlv device being connected to. close the main burner valve upon its initial coolingin the event of extinction of the pilotflame.

In a heating device, amainburner; a'pilot burner therefor; a normally closedvalve' forsupplying the main burner, a normally openvalve for supplying the, pilot burner, a linearly "expansible member exposed to heat from the pilot burner, alinearly expansible member relatively unexposed to heat from the pilot burner; a mem- 40 her moved by the difierential linear thermalex- 'pansionof the "members, lost motion coupling means connecting themain burner valve to the .member so that the valve will be opened'after a predetermined movement of the member; and imeans connecting the pilot burner valve to the member so that the valve will be operated toward its closed position by the said movement of the member.

3. In aheating device, a main burner, a pilot burner therefor, anormally closed valve for supplying themain burner,-a normally open valve "forsupplying the pilot burner, a linearly expansible member exposed to heat from the pilot '..burner," a. linearly expansible-member relatively unexposed to heat from the pilot burner, a mem- 'ber' moved by the differential linear thermal-expansion of the members, lost motion coupling means connecting the main burner valve to" the member so that the'valve Will be opened'after a so'predetermined movement of the member, and .lmeansconnecting the pilot burner valve to" the S IIIGmbBIlSO thatthe valve will be 'operated to- "ward its" closed position bythe-saidmovement ofthe'member, the pilot burner valve thus regllsulating .the pilot burner to maintainthe-main burner valve open'as long'as 'thepilot' burner "is "lit.

4; In a heating device, a main burner; ap'ilot burner therefor, a normally closed valve for supplying the main burnena normally' open valve for supplying 'the'pilot burner, a. linearly -e'xpansible member-exposed to heat'fromitthe pilot burner, a linearly expansib'lemembenrela- "v .tively unexposed to heat from the pilot-burner, a member moved '-'-by the "diflerer'itial ilthermal expansion of the members from a cold position to a hot position, lost motion coupling means connecting the main burner valve to the member so that the valve will be opened after a movement of the part at least half way from its cold to its hot position, and will be fully opened when the member is substantially in its hot position, and means connecting the pilot burner to the member so that the valve will be operated toward its closed position by the said movement of the member, the pilot burner valve being adapted to regulate the burner to maintain the member in its hot position.

5. In a heating device, a main burner, a pilot burner therefor, a normally closed valve for supplying the main burner, a normally open valve for supplying the pilot burner, a lost motion coupling control device exposed to the heat of the pilot burner, a member moved by the control device from a cold position to a hot position, means connecting the main burner valve to the member so that the valve will be opened after a movement of the member at least half way from its cold to its hot position, and will be fully opened when the member is substantially in its hot position, and means connecting the pilot burner valve to the member so that the valve will be operated toward its closed position by the said movement of the member, the pilot burner valve being adapted to regulate the burner to maintain the member in its hot position.

6. In combination, a heat responsive device comprising a sleeve fixed at one end, a cross bar fixed on the free end of the sleeve, a rod slidably mounted in the sleeve and extending from the free end thereof, a yoke fixed on the extended end of the rod transversely thereof, and bars disposed parallel to the rod and fixed in the cross bar and yoke, the sleeve, rod, and bars all having substantially equal coefiicients of thermal expansion, whereby exposure of the device to a heat source more intimately coupled with the exposed portion of the rod than with the bars will cause differential expansion thereof and. attendant reciprocation of the rod within the sleeve, and whereby uniform exposure of the device to heat will be ineffective to reciprocate the rod; a pilot burner comprising a section for igniting a main burner and a section adapted to heat the exposed portion of the rod; a control valve for the pilot burner, and means connecting said bars and the valve for closing the valve in response to said differential expansion of the bars.

7. A pilot burner and control device comprising a pilot burner, a throttling valve therefor, a first thermally expansible bar exposed to heat from the pilot burner, a second thermally expansible bar parallel to the first and less exposed to heat from the pilot burner than the first bar, the bars having equal coeflicients of expansion, and means connecting said bars and the valve for closing the valve in response to differential expansion of the bars produced by heat from said pilot burner.

8. A pilot burner and control device comprising a pilot burner, a throttling valve therefor, a first substantially horizontal thermally expansible bar exposed to heat from the pilot burner, a second thermally expansible bar parallel to and laterally displaced from the first and less exposed to heat from the pilot burner than the first bar, the bars having equal coefiicients of expansion, and means connecting said bars and the valve for closing the valve in response to difierential expansion of the bars produced by heat from said pilot burner.

9. A pilot burner and control device comprising a pilot burner, a throttling valve therefor, a first thermally expansible bar, a second thermally expansible bar parallel to the first, the bars having equal coeflicients of expansion, the pilot burner including a burner underlying the first bar and adapted to heat the first bar more effectively than the second bar, and means connecting said bars and the valve for closing the valve in response to differential expansion of the bars produced by heat from said pilot burner.

10. A pilot burner and control device comprising a pilot burner, a throttling valve therefor, a first thermally expansible bar exposed to heat from the pilot burner, second and third thermally expansible bars parallel to the first bar and symmetrically disposed on opposite sides of the first bar, the second and third bars being less exposed to heat from the pilot burner than the first bar, and the bars having equal coefficients of expansion, and means connecting said bars and the valve for closing the valve in response to difierential expansion of the bars produced by heat from said pilot burner.

GEORGE A. PETERSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,448,530 Gentzel Mar. 13, 1923 1,842,126 Snow Jan. 19, 1932 1,842,334 Te Pas Jan. 19, 1932 1,856,502 Morley et a1 May 3, 1932 1,943,045 Te Pas Jan. 9, 1934 1,963,043 Dougherty June 12, 1934 1,974,319 Toelle Sept. 18, 1934 2,032,045 Branche et al Feb. 25, 1936 2,196,316 Long Apr. 9, 1940