US2610682A

US2610682A - Control system for fluid fuel burners

Info

Publication number: US2610682A
Application number: US195765A
Authority: US
Inventors: Weber Victor
Original assignee: Robertshaw Fulton Controls Co
Current assignee: Robertshaw Controls Co
Priority date: 1950-11-15
Filing date: 1950-11-15
Publication date: 1952-09-16
Anticipated expiration: 1969-09-16

Description

Sept. 16, 1952 WEBER CQNTROL SYSTEM FOR FLUID FUEL BURNERS Filed Nov. 15. 1950 INVENTOR. Vwop Meben BY ms m Patented Sept. 16, 1952 TIQNTROL SYSTEM FOR FLUIDFUEL BURNERS tVictor Weber, Greensburg, Pa., assignore to Robertshaw-Fulton Controls Company, Greensbnrg Pa v acotporation. ,of Delaware 1 .Application'November 15, 1950, Serial No.2I-95;765

I'll-Claims.

C1 The invention "relates to control systems for. fluid fuel'burners' and mor rpar-ticularly to electrically operable appa'ratus of; this type.

Infl'u-id fuel'burning'apparatus, itvis often de- .sirable to=fiectautomatic operation of the burners bvmeans of atirriingrmechanism. To this :end; it isanobj ect of this invention to'control the admissionvoFfu'el: to theburners in timed intervent the escape-of unburned-"fuel from-the burnersin therevent-of a power failure. I A='preferred ei'nbo'dir'nent o'f-the present inventien comprises amain burnersupplied with fuel by w conduit, the flbw'ofifuel in whichfis' under thecontrolof a=normally closed valve movable to anopen position by a 'd'e'vice responsive to the presence o'f 'flame:at'the pilot burner. Fuel flow to thenorma'elly closed valv and to the pilot burner is controlle'd bya manually operable'valve, the supply of fuel td which isin turn 'controlledby an.electrica1ly-:.operab1e valve.

:An .energizing:circuit for the actuating: means of theselectricali-ytoperablewalve includes a pair of switches invseries'. 'l'lhefirst of the pair is operativelyiaconnected'itdaaclock mechanism. to be openedsand:closed1therebyxand the second switch of theatpairsis .operatively :associated with the manuallyaoperableuvalveito:be. opened when the valve-tie :.close:d sand :close'd. zwhen the :valve J is opened.

efelectric igniter is provided for the" pilot burners-and has an energizing circuit connected inzparazllelz'with thetactuating means of the electrically operablevvalve. eThe' igniter energizing circuittincludes-sa switch operatively associated withzactuatingrmeansiresponsive to the presence ofza flameiatither pilot burner to be'opened in the presence of.-such:flame.and closed in the absence thereof.

:Further.Lobiectsiandladvantages will be apparent :from the :accompanying specification 1 and claims taken'zwithxthe drawing which is a schematicwview of a control-system for a fuel burner ing shown in section.

"Referring to: the drawing, the control system is shown as associated with a main burner I16 whichireceivesp/fuelfrom a supply conduit l2, flow of fueliromzthe supply:conduit l2 to the main burnerlllubeingunder thecontrol'of thermally responsiveivalve. means M, manually operable valve .means. 1 l6, and electrically .openable valve meansgheretshowmas asolenoidivalve 1:8.

. Anlelectric.igniter12fl'cisnisposed in. ignitingzreiation withia pilotburner' 22. inturn disposed in igniting relation:.with1the main burnerle. 1..Ihe pilot burner; 22. is: supplied with fuelrbyxa. conduit 24hconnected therewith, flow ..of;:fuel inrthe -conduit;24. being controlleduby theimanually operable valvelmeans 1 I6. I

A :casing' 2 6 ."may contain the thermally responsive valvemeans H'WhiCh may comprise valve chamber 28 formed in the casing 26 and provided withan inlet opening 30 andLan outlet openingi32. The:outlet..openingifl communicates with a pipe 34 connected toithemain burner I0. Disposediin the valveichamber 28..isa valve seat 36. cooperable with avalveslelement' 38' to :interruptjflow between the inlet; 3:0 andithesoutlet132. A coil spring 40 acts.betweenrawallifl :of'the-valve chamber 28 and the valvamember 38 to bias the valve member 38 intoengagement*withthe valve-seat 36. Depending from the lower side of the valve m-emberi38:iszva valve stem 44 which' extends through a bore 46" in the casing 26. The diameter ofthe, bore46 iszsufiicient to' permit axial-movementofrthevalve stem44-therein. The'free end 48 ofzthe valvelst'em 44 extends beneath the casing .26- tosabutra lever 50 whichis pivoted at one-end 52in. a'; bracket: 51 securednto the casing 26.

Theulever 50 is adapted to be moved about its pivot bytiathermally-responsive device which may comprisethe usualexpansible element 56, capillary.tube;58, and bulb 60. .The bulb isdisposed adjacent 'thekpilot burneri'lz'to beheatedbya flame emanating therefrom. Theeexpansible element 56 ismounted. ona'cover62 securedinfiuid sealing? relationsto the. lowerlsideofithe casingLZB byiany suitablemeans (notshown). Movement isltransmitted fromthe:expansible -element. 56- to thelever 5flfibyimeans of a thrust button 64lcarried on the vupper surface .of. the expansible element 56. It willbe apparentithat inthe absence ofa flame at thepilotlburnerfi the expansiblevelement" 56 will be inits contracted condition and I the spring 148 will hold the valve member 38 against the valve seat 36. Itiwill also .be'apparent that a flame emanatingfrom the pilotuburner 22-wil1-be efiective'tojheatthe bulb 60 to' cause expansion of the e-xpansible'element 56, counterclockwise rotation of the lever 50 and movement 3 of the valve member 38 against the bias of the spring 40 and away from the valve seat 36.

The manually operable means I 6 may comprise a simple fuel cock (not shown) mounted in a casing 66 for rotation between fuel flow permitting and fuel flow preventing positions. Manual rotation of the cock may be effected by means of a knob 68 connected to the cock through a stem 10.

Fuel may be admitted to the casing 66 of the manually operable valve means I6 through a conduit I2 connected therewith and egress of fuel from the casing 66 may be had through a pair of outlets. One of the pair of outlets communicates with a conduit I4 which communicates with the inlet 30 of the valve chamber 28 of the thermally responsive valve means I4. The other of the pair of outlets communicates with the conduit 24 connected to the pilot burner 22. The manually operable valve means I6 thus controls the flow of fuel to both the thermally responsive valve I4 and pilot burner 22.

Flow of fuel to the thermally responsive valve means I4 may also be under the control of condition responsive valve means which may comprise a thermostatically controlled valve combined with the manually operable valve means in a manner well known in the art. The thermostatic control for the thermostatically controlled valve may include a temperature sensing element here shown as a bulb I6 exposed to the temperature of the space to be heated by the main burner I and connected to a valve actuating mechanism (not shown) by a capillary tube '18. Since combined fuel cocks and thermostatically controlled valves are well known in the art, further description is believed to be unnecessary.

The solenoid valve I6 is normally closed and is adapted to be opened when the solenoid winding thereof is energized. The solenoid valve I8 is connected to a conduit 80 in communication with the supply conduit I2 and also to the conduit I2 which communicates with the casing 66 of the manually operable valve means I6. Thus, the solenoid valve I8 controls the flow of fuel to the manually operable valve means I6.

A stand-by pilot burner 82 is disposed in igniting relation with the main burner I0 and is connected to the supply conduit I2 by conduits 84 and 86. Flow of fuel to the stand-by pilot burner 82 is under the control of valve means 88 which may comprise a valve chamber 90 formed in the casing 26 and provided with an inlet 92 and an outlet 94. The inlet opening 92 communicates with the conduit 86 and the outlet opening 94 communicates with the conduit 84. A valve seat 98 disposed in the valve chamber 90 is cooperable with a valve member 98 to interrupt flow between the inlet opening 92 and the outlet opening 94.

A valve stem I00 is slidably carried in a bore I 02 formed in the casing 26 and extends between the valve member 98 and a lever 50 of the thermally responsive actuating means. It will be apparent that rotation of the lever 50 under the influence of a flame at the pilot burner 22 will cause an upward movement of the valve stem I00 and associated valve member 98 to move the valve member 98 away from the valve seat 96. When the valve member 98 is not so moved it will be held against the valve seat 96 by the pressure of the fuel supply acting thereon.

A standby pilot control of the type herein disclosed is disclosed and claimed in the copend- 4 ing application of Charles K. Strobel, Serial No. 189,584, filed October 11, 1950.

Also disposed within the casing 26 is a thermally responsive switching device I04. Secured to the bottom of a recess I06 formed in the casing 26 is an apertured element I08 formed of suitable insulating material and carrying thereon a pair of contacts III). The contacts IIO are arranged in spaced relation and are engageable by a movable plate II2 to complete a circuit therebetween. A coil spring II4 acts between the movable plate H2 and a closure member I I6 to bias the plate II 2 into engagement with the contacts IIO.

An operative connection is established between the movable plate II2 of the switching device I04 and the lever 50 of the thermally responsive actuating device by a push rod II 8 slidably carried in a bore I20 formed in the casing 26. The push rod II8 extends through the apertured element I08 to engage the movable plate I I0 and also extends beneath the casing 26 to abut the lever 50. It will be apparent that when the expansible element 56 is in its nonexpanded condition, the coil spring H4 of the switching device I 04 will maintain the plate I I2 in engagement with the contacts H0 and that counterclockwise rotation of the lever 50 about its pivot 52, upon expansion of the expansible element 56, will cause upward movement of the push rod H8 and the plate II2 associated therewith to disengage the plate H2 and the contacts IIO.

Movement of the solenoid valve between fuel flow permitting and fuel flow preventing positions is under the control of a timing mechanisms indicated generally by the reference numeral I22. This mechanism includes switch means having a switch blade I24 pivoted at I26 to be movable into and out of engagement with a fixed contact I28. The switch blade I24 is connected to a reciprocal plunger I30 of a timer I32. The clock timer I32 may be of any suitable form and may be manually adjusted to cause axial movement of the plunger I30 at preselected times. It is understood that the timer I32 may also be manually adjusted to set and retain the plunger I38 in its retracted or extended position. As timing devices of this type are well known in the art, further description of the timer I32 is deemed unnecessary.

The switch I24--I28 of the clock actuated mechanism I22 forms a part of an energizing circuit for the solenoid of the solenoid valve I8 and serves to connect the solenoid winding of the solenoid valve I8 to a source of commercial current here shown as line wires LI and L2 as will more fully appear. Thus, movement of the solenoid valve between fuel flow permitting and fuel flow preventing positions is under the control of the timing mechanism I 22.

Movement of the solenoid valve I8 is also under the control of a switch I32 operatively associated with the manually operable valve means I6. The switch I32 also forms a part of the energizing circuit of the solenoid valve I8 and is here shown as including an actuating lever I34 engageable by a cam element I36 carried by the stem 10 of the manually operable valve means I6 to be rotatable therewith. The switch I32 is so designed that rotation of the knob 68 to close the fuel cock of the manually operable valve means I6 will open the switch I32 and rotation of the knob 68 to open the cock of the manually operable valve means I6 will close the switch I32.

The-clockiactuated switch- .1 26'-'-I-28 and-. thea manually operable switch l32-jareconnected in... series in the energizing circuit-of: the: solenoid; winding ofi-theisolenoidivalve I81 This energizin'g. circuit; is completed when both: switches are: closed and may be: traced as follows line. wire L I, wire I '38l wirez I 40; solenoidwinding of'. sole- L noi'd valve- I 8 ,i'wire-: I342, wire I44; switch I32,';wire I4.6,'- cont'act 12K of thexclockactuated. mech'az- I nism: I22; switch: bl'ade I 24,and wire: al.48l-tottline WireaLL.

Ana: energizing circuit f-cr the igniter' 2c is cone necte'd in parallel :with the: solenoid winding of the; solenoid 'valve -I 8 and may 'be traced; as= fol:- lows: wire |3"8 l16 Oft. thei contactseIHlt f cthe switching. device: IIM, movable plate I I2. ofthe: switching-device I063 the othersof thev pair loficonetacts Ill); zofsthe switching device 104-; wire I 59', lower-iterminali of theprimtry windingof a stepdown: transformer I52, upper. terminal of: the,

primary winding of the transformer I52, and. wire. I44: Thus, when the solenoid. winding of the solenoid valve I8 is: energized-and. the switching devi'cea I64 is:closed,.1currentswill flow through. the primarywindin'g ofzthe transformer I521 Energization. of. the primary. windingof' the. transformer. I52 willtcausea current to= be induced in the secondaryswinding. thereof and such.current will fiow through a circuit which may be tracedi as. follows: lower terminal of. the secondary winding of thetransformer I52,.wire I54; ballast resistor. I56,.wire I58, igniter 20, wire I60, ballastiresistor I56 and wire I62 to the upper terminalof. the secondary-winding of. the: transformer I 52.1

It will be: apparent that the parallel circuit which includesth'e energizing circuit for the sole-: noid winding of the solenoid valve I8 and the energizing circuit for the igniter will be inter.- ruptedby the openin of either the clock actuated switch I26UI28orthe manual switch I32. It will also. be apparent that the energizing circuit of the. igniter 2i]. will lee-interrupted by the opening of the thermally responsive switching device I04.

Operation Assuming that the apparatus is in the condition shown in the d'r'awinggwith no flame existing at any of the burners and it is desired to adlust'the apparatus for automatic operation, the timer I32 is set to move theplunger I to close the switch ZS-I28 at a selected time and the knob 68 is rotated to move the fuel cock of the manually 0perable valve means I6 to an open position; Such rotation of the-knob 68 will cause-the cam element I to engage theactuating lever I34 of the switch I32 to close the switch I32 so that when the timer I32'moves the switch blade I24 into engagement with the contact I28, the previously traced energizing circuit for the solenoid winding or" the solenoid valve I8 is completed and the solenoid valve I8 will assume itsfuel now permitting" position. Fuel will then flow from the supply conduit: I2 through the conduit BILsolenoid valve I8; conduittIZ, manually operablenvalve means I6, and conduit 24 tothei pilot burner 22. I

Since the, bulb of the thermally-responsive actuating. meansis in its unheated condition, the mechanismiinlthe casing, 26 will be in the position shownimthe drawingwith the thermally responsive valve means .I4 preventing flow of fuel to the main..burner II], the standby pilot valve-88 preventingiflow of fuel'to. the standby pilot burner 65f Current;.fiowingathmuglrltheigniten 202 .wilrlai'se itstemperatureszrflicientlytczcanseignition.of the;- fuel flowing:fromrthel pilotz bumeri22ttu:producea flanrezdiizectediagainst thesbulb. fill".

Asatheatempetature citzthebuib Iifliaincreases, the

expansihle element: 56.:will" expand, causing an up-; ward movement raoiithe thrust :button; 64. and. counterclockwise rotation of the 1ever.'5Il about;its pivot 52. .Asv hereinbefore. described,l.such rotation of .the lever 50 will cause opening of thenor mally: closed. valve; means-IA; and. standby: .pilot switchingrdevicel. 1011:. outzofziengagement: with the contacts-1L0; J. I

TfilISfi1B1lWi1LfiQW frcmxhcimanually. operable. valvesmeans I E throughtheconduit 1:4, in-18110138111. ing;.30i= otwallve: means M -valve. chamber.28',. past. valve; seat; 3 5-,. thtonghithe. outlet: opening 32, of; thewalrze means I.4.-, and through conduit; to: the: mai'n:burner -10 where:-itt..will heignitedbv the;

flame at the pilot burner 22. Fuel will also. flow from; that supplyf. conduit. I2, through the conduit 8 6:. toxthea valve: chamber: BIL of: the: standbyrpilot i valve; 8.&' past-'ethei'valvexseat 36, through 111185.011trr'.

letxopeningflfl .oitthe.:standbypilotvalve 8.8; and...

through the:- conduit. 8b. mthezstandby pilotburnermainibummxtulrlln...

When the plate; I 22: ofi-theswitching: device- .tflfi 'isrmovedcutof. engagement. with; thecontact. I1 (I,

the; energizing: circuitioiutheienitenlfl'. iszintere I rupted: :and: theiigniten-i II; will; be: deenergized.

control, Tot thethermostatically actuated {valve associatedi withmanually-operable valve means:

IS in accordance with the: temperaturesensed by;

the; temperature sensing element 76;".

Whenthe timer;3.2' of the clock actuated meche; anism I22 acts to move the switch blade I24-out;

. of engagementwiththe contact. I28,j the energizingcircuitof. theqsolencid Winding of the solenoid.

valved-8' iszinternupted a-nd the solenoid winding is .deenergized-.x The solenoid valve I8: will then act: to shutiofli alltheflow of. fuel from, the sup.-

. ply conduit Ii2v through the conduit 80;. Thus, the

fuelsupply to themainbumer I0 andto the pilot burner 22v will be 'cut oil and. the flames at said burnersrw-illlie-extinguished.

Uponvextinguishment; of the flame; at the pilot.

burner 22;.the; bulb '60 Will 0001' causing contrac tionaofzthe expansible element 56. and. clockwise.- rotationxof: the. levenil). about, its pivot 52' under theibiaa ofi the-springsy luand 4.: As hereinbefore: set; .fortlr,=,:. such.: clocl wise:. rotation of; the levenifl: wilhpermit thezvalvei member: 33. of the valve-means- I4: tozengage its;:seat..'3 63' and the valve member: 98. oft-he standby pilot. valve 88 will en gage: itszseatsfie Thus,.zthe-fuel Supply to the standby pilotzburner. I12 will 'be cut off and the flame. thereatewillzbeextinguished. .l The apparatus isnowinthe condition shown'in the drawing withrtuel: :sunnln toall burners prevented.

It. willab'ezapparent; fromlthev foregoing that the. ihereinrdisclosedrapparatus provides a. control system ronfluid fuel 'burners wherein a single clock actuated swi'tch is effe'ctive to control ad-' missionyignitionandcut-ofi of fuel thereby pro vi'dlh'g for a simple economical clock control and that it accordingly. accomplishes' the objects of the invention.

as aflameexlstsat thepi-lotzburnerx.

Although a specific embodiment of the invention has been shown and described, it will be apparent that many modifications may be made by those skilled in the art. Such modifications may be made in the details of construction and arrangement of parts without departing from the scope of the invention as set forth in the appended claims.

It is claimed and desired to secure by Letters Patent:

1. In a fluid fuel burner control system having main and pilot burners, ignition means for igniting fuel flowing from the pilot burner, valve means responsive to the presence of flame at the pilot burner for controlling the supply of fuel to the main burner, manually operable valve means for controlling the supply of fuel to said last named means and to the pilot burner, and timing means for controlling the supply of fuel to said manually operable valve means at preselected intervals.

2. In a fluid fuel burner control system having main and pilot burners, means for igniting fuel flowing from the pilot burner, valve means responsive to the presence of flame at the pilot burner for controlling the supply of fuel to the main burner, manually operable valve means for controlling the supply of fuel to said last named means and to the pilot burner, main valve means for controlling the supply of fuel to said manually operable valve means, electrically operable actuating means for said main valve means, an energizing circuit for said electrically operable actuating means, a switch in said energizing circuit, and timing means for moving said switch between open and closed positions at preselected intervals.

3. A control system as claimed in claim 2 wherein said energizing circuit includes a switch operatively associated with said manually operable valve means to be closed when said manually operable valve means is in fuel flow permitting position and open when said manually operable valve means is in fuel flow preventing position.

4. In a fluid fuel burner control system having main and pilot burners, means for igniting fuel flowing from the pilot burner, means responsive to the presence of flame at the pilot burner for controlling the supply of fuel to said main burner,

condition responsive means for controlling the flow of fuel to said last named means, manually operable valve means for controlling the flow of fuel to said condition responsive means and to the pilot burner, main valve means for controlling the supply of fuel to said manually operable valve means, electrically operable actuating means for said main valve means, an energizing circuit for said electrically operable actuating means, a switch in said energizing circuit, and timing means for moving said switch between open and closed positions at preselected intervals. 5. In a fluid fuel burner control system having main and pilot burners, means responsive to the presence of flame at the pilot burner for controlling the supply of fuel to the main burner, manually operable valve means for controlling the supply of fuel to said last named means and the pilot burner, an electric igniter for the pilot burner, main valve means for controlling the supply of fuel to said manually operable valve means, electrically operable actuating means for said main valve means, and timing means for simultaneously energizing said electric igniter and said electrically operable actuating means.

6. A control system as claimed in claim 5 8 wherein thermally responsive means ar provided for deenergizing said electric igniter when a flame is established at the pilot burner.

7. In a fluid fuel burner control system having main and pilot burners, an electric igniter for the pilot burner, means responsive to the presence of flame at the pilot burner for controlling the supply of fuel to the main burner, condition responsive valve means for controlling the flow of fuel to said last named means, manually operable valve means for controlling the flow of fuel to said condition responsive valve means and to the pilot burner, main valve means for controlling the supply of fuel to said manually operable valve means, electrically operable actuating means for said main valve means, an energizing circuit for said electric igniter and said electrically operable actuating means, a switch in said energizing circuit, and timing means for moving said switch between open and closed positions.

8. A control system as claimed in claim '7 wherein said energizing circuit includes a second switch operatively associated with said manually operable valve means to be moved between open and closed positions thereby when said manually operable valve means is moved between fuel flow permitting position and fuel flow preventing positions.

9. In a fluid fuel burner control system having main and pilot burners and a source of electric power, a normally closed valve for controlling the supply of fuel to the main burner, an electric igniter for the pilot burner, means responsive to the presence of flame at the pilot burner for opening said normally closed valve, manually operable valve means for controlling the supply of fuel to said normally closed valve and to the pilot burner, valve means for controlling the supply of fuel to said manually operable valve means, electrically operable actuating means for said main valve means, connecting means between said electrically operable actuating means and said source, said connecting means includin a clock actuated switch, an energizing circuit for said igniter, said igniter energizing circuit being connected in parallel with said electrically operable actuating means, a switch in said igniter energizing circuit, and means for operating said last named switch.

10. A control system as claimed in claim 9 wherein said last named means is responsive to the presence of flame at the pilot burner.

ll. In a fluid fuel burner control system having main and pilot burners and a source of electric power, a normally closed valve controlling the supply of fuel to the main burner, an electric igniter for the pilot burner, manually operable valve means for controlling the supply of fuel to said normally closed valve and the pilot burner, main valve means for controlling the supply of fuel to said manually operable valve means, electrically operable actuating means for said main valve means, connecting mean betw en said electrically operable actuating means and said source, said connecting means includin a clock actuated switch and a second switch operatively associated with said manually operable valve means, an energizing circuit for said igniter, said igniter energizing circuit being connected in parallel with said electrically operable actuating means, a switch in said igniter energizing circuit, and means responsive to the presence of flame at the pilot burner for opening said normally closed valve and said last named switch.

12. In a fluid fuel burner control system having 9 main and a plurality of pilot burners, means for igniting fuel flowing from one ofthe pilot burners, means responsive to the presence of flame at said one pilot burner for controllingflthe supply of fuel to the main burner, manually operable valve means for controlling the supply of fuel to said last named means and said one pilot burner, means responsive to the presence of flame at said one pilot burner for controlling-the supply of fuel to another of the pilot burners,]main valve means for controlling the supply of fuel to said manually operable valve means, electrically operable actuating means for said main valve means, an energizing circuit for said electrically operable actuating means, a switch in said energizing circuit, and timing means for moving said" switch between open and closed positions at preselected intervals;

13. In a fluid fuel burner control system having main and a plurality of pilot burners, means responsive to the presence of flame at one of the pilot burners for controlling the supply of fuel to the main burner, means responsive to the presence of flame at said one pilot burner for controlling the supply of fuel to another of the pilot burners, manually operable valve means for con- 25 ;fuel to another of the pilot trolling the supply of fuel tosaid first named means and said one pilot burner, an electric igniter for said one pilot burner, main valve means for controlling the supply of fuel to said manually operable valve means, electrically operable actuating means for said main valve means, and timing means for simultaneously energizing said electric igniter and said electrically operable actuating means.

, 14. In a fluid fuel burner control system having main anda plurality of pilot burners and a source I of electric power, a normally closed valve conally operable valve means for controlling the sup- .-pl y of fuel to said normally closed valve and said fone pilot burner, main valve means for controlling the supply of fuel to said manually operable valve means, electrically operable actuating means for "said main valve means, connecting means between said electrically operableactuating means and said source, said connecting means includa clock actuated switch and a second switch .o peratively associated with said manually operable valve means, an energizing circuit for said igniter, said igniter energizing" circuit being connected in parallel with said electrically operable actuating means, a switch insaid igniter energiz- Qing circuit, means responsive to the presence of flame at said one pilot burnerfor opening said normally closed valve and said last named switch, and means responsive to the presence of flame at said one pilot burner for controlling the flow of burners. VICTOR WEBER.

REFERENCES CITED UNITED STATES PATENTS Name Date Meacham Sept. 22, 1936 Number