US2641237A

US2641237A - Engine fuel control

Info

Publication number: US2641237A
Application number: US675981A
Authority: US
Inventors: Desire J Deschamps
Original assignee: Bendix Aviation Corp
Current assignee: Bendix Aviation Corp
Priority date: 1946-06-11
Filing date: 1946-06-11
Publication date: 1953-06-09
Anticipated expiration: 1970-06-09

Description

June 9, 1953 D. J. DESCHAMPS 2,641,237

ENGINE FUEL CONTROL Original Filed July 51, 1940 CCELERATI NG PUMP CAPACITY TO ENGINE -l NVE NTOR- DEE/HE J. DEEL'HHNPS ATTORNEY Patented June 9, 1953 UNITED? OFFIQE.

EN GIN'E" FUEL CONTRUU Desire Desehalnpsyliutherfordg N; J .-,'-,assign0r; to =Bendix- Aviation:-Corporation; Soutlr Bend, I Ind, a-corpcration of Delaware Continuation? (ifapplication Serial" N02 3481925;

J i117- 31; 194 3 This application "June 1946 ingfiivisional application Serial did-2226;96 ,cfiledi: 10 I May 18, 1951 .byi'DesireJ: Desch'amps as-=- signed to Bendix Aviation Corporation.

While th'eiinvention is: disclosed 1 herein in 1 an emb'odiinenti-which. invclt'es an .engine' ofithe :iuel': injection typ'eyit' wilt:beaapiparentiito those-Who 5 examine :the disclosure, that-the nventir'e con cept, at least inicertainiphasesi-thereof as: "Will appear)? is; applicable to engines: l'i'avingn other means of deliveryxofl fuel in: the combustion chambers 2 An object of the intention is th e c ontrcl 0f the ratiofib'etween thewairrand fuel q-ua'ntities; .bthe? use @oi novel'Lmeans op'eratingi te ni aintai l ratioconstant: (during periods when constancy-" is desirabl'et by ca usinggon the one liaridg the maintenance of fu'el-flew' at *a constant rat atgiven air fiowwand, oi'i th other causing the rate" of 'fuel delivery to v 1 y V matically in responseto every variatio ra te ofiaii delivery; tire'- air cz iiteiry beterms -of mass ai rounds, the

us' to respond te every variaticn in: an supp-1y; whether sue-h variation is duete amanuaily"eff cte'rl-"ciia iii-throttle setting or" to an air"density variati or to a combination of 5 both such causes; The

systenrdisclosed also operates to vary'tlrefuel/air ratio 'in" resp o'nre to" variations in power" output;

engine speed "a niifialtitude' inacc'o-rd ance with the engine requirements. set" forth" byj the engine" manufacturers; wherefore the fuel'jaif'ratioWill' foliowfa giv'en curve;

As already indicated; one object is to ip'iovide." theLrati'G'main'ta1 ing. ap aratus witntheca'pacity' tc" resp one" not only, to air supply. variations butalsbto ever'y' Variation maneuvers rate, as"

resuitingidropoin fuel delivery rate to lie-reflected.

in they: ratio? maintaining apparatus: in such inannerzasi to :eausetsaid ratie maintaining apparatusci to move" automatically to produce an offsettin'gincreaseiinthefuel delivery rate; thereby; restoring: the-predetermined.- constant fuel-air ratios, Conversely, thefinvention further inciudes the conceptrcfiproducingian-oiiesetting deerease oil derived under. pressure from the -:engine oil supply-lines In this connectionaieaturerobthe' invention is-tire: provision oi meanszfor maintaining th'e apparatus suppiied with :oil underl e l1ore-v determined pressure even" during these periods when-the: engine oil pressure 1 is iessz'flthan 'SllfH ficient for such:purposesfi Thus there; is; assultedw. an automatieinaintenancerof :the properfuel' ai ratio notwithstanding occasional deenergization:

of the'eirgi riecilsupplyi Another: feature pf sthe ratioamaintainingrappa;

ra'tusis the 'embo diment ther-em of-I-the concept Y; i of overbalanci gthe apparatus during idlingianda rest -'periods--in the engiriesoperation; wherefore there is assured a relatively-richmixture dininge.

idling 'perieds; -ahd a mixture of -maximum .I'iGh-Je.

ness at the moment i of resumption 01 engine: In the em bodiment illustrated, said overloalancing-m'eans depends, forits operativenessi upon the feature operation, following a "shut down.

described in the preceding paragraph (namely; the feat-u'repf "maintaining" a r :predetermined oil pressurein'thesystem, even while-me amine is-- at'r'est) but it "also includes "elements arldi-tional toand"coa'cting"with those which: embody said pressure maintaining feature:

Theinv'eiiti'orffurther provi'des"for adjustment ofth'e system (as; for'exampie, during night of anaircraft) 'bysubstitutioii of'anew ratio (Within predetermined 'li'inits) "for th'e"onepreViousiT maintainedjwhenevera leaner or'ri'cher mixture isd'esir'e'd risu'ch adj ustnienfto' be brought about manually f or by operation of "'altitudcontrol1ed" means."

Anotherfeature' of- 'the inventionis the abi lity of the ratio maintairiing apparatus-W var-y its own action automaticaily-and witheutresortingx i apparatus-m trie mei inteke:me

to the extent of temporarily producing a richer ratio of fuel-to-air for a brief period following any movement of the air induction control valve (throttle) in the engine accelerating direction; such action thus producing the same ultimat result as has been produced in the prior art by the use of separate accelerating pumps which deliver an additional quantity of fuel to the fuel intake line, over and above that which is delivered in the normal manner. In reducing, to a concrete exemplification, this novel concept of equipping the ratio maintaining apparatus with the power to increase the predetermined ratio of fuel-to-air, temporarily, and then reestablish said predetermined ratio, I do so in such a manner as to protect the engine against thedanger of stalling. In the prior art types of accelerating devices there has been this danger of stalling, due to the 4 poration. As indicated at 2|, the novel variable delivery mechanism may include alever extending from the pump and adapted to be turned about its rockshaft by movement of the linkage 22 connecting with said lever as indicated, and having at the opposite end thereof a rod 24 adapted to be reciprocated by the pressure of a fluid acting upon a cup-shaped piston 25 which abuts the enlarged end 26 in which the rod termipossibility that the pilot might throttle down the engine immediately after having opened the throttle wide; in which event the sudden decrease of fuel frequently left the previously delivered abnormal supply of air in a condition to interfere with proper combustion of the suddenly decreased quantity of fuel. Such a danger is avoided by my use of compensating means, inherent in the ratio control apparatus itself, which tend to delay the decrease of fuel supply for a brief period following each throttling down movement of the air control valve.

Another object of the invention is to enable the pilot merely by a sudden opening of the throttle, momentarily to increase the fuel-air ratio to cause the engine to accelerate quickly, the automatic fuel-air ratio control mechanism immediately thereafter assuming control of the mixture.

Other objects and features of the invention will become apparent upon examination of the following specification and the accompanying drawing wherein is shown schematically the .preferred embodiment thereof. It is to be understood, however, that the drawing is merely illustrative of the invention and that it is intended to cover equivalent embodiments falling within the invention scope as defined in the appended claims.

In the drawing there is shown a conduit Ii adapted to supply air flowing in the direction OI the arrows to the combustion spaces of an mternal combustion engine, the amount of air supr plied being controllable by an operator-operative throttle means or by manual operation of the throttle indicated at I2, said throttle being shiftable about its central pivot shaft which extends to the exterior of the conduit and is adapted to be turned through a suitablelinkage, not shown, to which the pilot or other operator of the engine will have access.

Fuel may be injected or otherwise supplied to the combustion spaces of the engine by suitable connections, not shown, leading from the outlet pipe l4 of the fuel injection or fuel delivery pump 15, the latter having a drive shaft rotatable by and in timed relationship with the crankshaft or other rotatable part of the engine, not shown. Fuel may be supplied to the pump l6 by a fuel conduit l8 leading (either directly, or by way of a transfer pump, not shown) from the tank l9 constituting the fuel source. The pump 16 may be of any suitable type but is shown herein as being of a construction embodying a novel type of variable delivery control, as described in greater detail and claimed in U. S. Patent No.

2,243,374 granted May 27, 1941 to Desire J.

Deschamps and assigned to Bendix Aviation Cornates. As shown, the portion 26 of rod 24 has a cylindrical extension 21 that is movable toward a stationary abutment 28, and serves to enclose the coiled compression spring 29. A flange 27a is provided on cylinder 21 as an alternative means of actuation of the variable delivery mechanism.

The piston is subject to the control not only of the spring 29, above referred to, but also of the fluid pressure supplying and control means of which the essential parts include a metering unit 33 corresponding in general to the metering unit similarly designated in the copending application Serial No. 314,587 by Frank C. Mock and filed January 19, 1940, and now U. S. Patent No. 2,447,267, granted August 17, 1948, and assigned to Bendix Aviation Corporation. Also as in the said Mock application, the control means includes valve means 34 controlling the supplying of oil under pressure to act upon the piston 25, but the effect and mode of operation of the valve 34 differs from that disclosed in the said Mock application in various respects, as will be pointed out hereinafter.

The air conduit is shown as including a Venturi section 35 at a point anterior to the throttle, and at a point slightly in advance of the Venturi section 35 there is provided a tube 31 adapted to open into the air stream passing through the conduit, said tube extending into and opening at its other end into a chamber of the metering unit 33 as will be further explained. Due to the location of the entering end of this tube 31 it will be apparent that the tube is subjected to the pressure of the air entering the Venturi section of the conduit. A smaller Venturi tube is positioned in the conduit between the tube 31 and the throat of the main Venturi section, and a tube 4| leads from the throat section of the smaller Venturi 40 to another chamber of the metering unit 33 to be further described.

As in the aforesaid Mock application, the metering unit 33 is divided into four

pressure chambers

43, 44, and 45, the separation of the chambers from each other and from the external atmosphere being assured by the, provision of the

sealing diaphragms

41, 48, 49 and 50. In addition to these small diaphragms there are two large actuating diaphragms 53, 54, each of said diaphragms being fastened at its outer periphery to the housing of the unit, and at its central portion having security upon the rod 55. The diaphragms are shown as formed with an annular groove or depression to permit relatively free axial movement of the rod in response to pressure differences on opposite sides of the diaphragm. The chamber 43 receives one end of the conduit 4| heretofore described, and the chamber 44 receives one end of the conduit 31; consequently the pressure difference between the chambers 43 and 44 will coincide with the pressure difference prevailing between the two points of entrance of air to the respective tubes, and said difference in pressure will vary with every change in mass air flow through the con-'- duit The fuel conduit I8 is also provided with a 23641 ,zsw

51-? Venturi' section: i from the throat of which 1 leads: a-rtube: '61 eterminating as shown: in :the chamber; 4 6 r of the :metering: unit 233 awhile'lsa second: tube 62 leads from a point slightly? iniiadvancefof the" Venturi section of the fuel. conduit 1 to terminate within: the?chamberc45 fof theimetering 4unit 33;

From this :1 it 1 follows that I the. pressure differ? govern ss communication betweenn the": pressure;- fluidisuppiying ipassage 212 oz'rcthe oneahande antl thertwo: associated ipa'ssagessa 13' and il'4 9oni=the other zthe: assage -73 Z-heing a1 discnarg :p'asw side by "the housing member 16:0f the-ivalveyandb atl the other?siderebyl-the i workingface-i: of then piston 325i:-

Theu specific structural: details of lithe: servo motor including r the cup; shaped piston t 2 and 1 the? arrangement ofi the valvemeans 34 v the structural: details: of the meteringaunit in eluding-1 the.=structural: arrangement ofthe cli aphragms ily-48*, lfi an'd t'mfa' th'e'i specific structural: details? of 'th'e flu-i sure responsive I regulator :per: s operator-operative J 1? presof theflpiston zfi 'lfave men al-aimed in thed r sional application Serial No. 226,960 filed Ma y *18 ;k 1951 byf- Desire J; n'eschamps and 1 assigned. ti) Bendix a leviation": Corporation;

Sidrtz'rlgmfftfiek engine I As heretofore noted; ai novel arfeatureo ofi: that: x invention; tendihg 'tol produceeasyvstarting; is: v

thef controt ioi: the piston'ii 52in: suchhm'annerr as to cause itxto move: automatically."to :fnll arichi positionxwhenethe': pilot stopsetheeenginea.. This featurea'risrt-embodied: operating check'slvalve ,1

return flow=-='of2operatingSoil to the iengine tin :casei theiengines-oil pressure sshouldrafall; say;- belowr zones:

engine? stops, alluairr andii fuel L flows 51301335 and:

thesforce-liactings anobcth:diaphragms fl and 54" ialls'itoizerog wheretoforeuthe :valve f 34 moves Eto l the -left 1 uncler ithei action" ofspring r6 5; opening and? allowing oii from oy1inder;-' 51 r to "be right; totheamt capahity*-settirig', thereby male-' ing th e settingof the pnmp correctfor 'the inext be L: available to: assert": such a t iorce upon the pistorrzz 5 notwithstanding; the 'fallingpofi in en gine =oi pressurewthat accompanies the "stopping; of the :ienginez Cylinder: 5i tin'icooperation with i check: :valve: 653v; provides'wsuch a r pressure reservoir.

Acccleratione richer when the pilot opens the 'air throttle brisklyi: l/Vith thewontrol as desoribecli above hownoas icon nectingzithtonghla; swiv emanate-'5 rand: i

at-xcylinder." 5 I and a 'cothe: latter: preventingi;

A springal I in icylin'derit t; allows the piston?" rtoomoveito tlrefiliinit of its 'StI'OkeJWhBnT thevoihpressureBreaches;:say, 35 lbs; When the:

1 space 1 5; moving rpiston'tt 25 1 to. r the justzathe opposite-would happh rdueiiitbfi therxlag -i in the operation 10f the controln Tor ofisetev this;-; I take-advantage 1' of the vvery low pressure which? exists in theintakei' manifold aheacl of thenair 5 throttle valve -:l2 in: providing forl 'operation .off.

the accelerating pump; shown :at 98 Diaphragm; 92i of this pumpjfunction's to producethe desired i. enrichment up'on sudclen "op'eningiofx thefthrottl h It functions? as follows: With 1 the" engine criin ningJatiidlingxspeecl;the-air:ithrottletvalve l 2 nearlyifcompletelyxclosedand.:the pressure ahea of. i this .1 valve-,9 or engi'ne 'r intake manifold press sure; is thell' ol'llys to 17 inches ofmercury :ab:-.-"-

solute; whereas-at full power, this" pressure reaches around528 inches withna (naturally aspirateclsenginevand may be'42 or'-more in 'casez-of': asupercharged:engine: This ,low pressure -un-r der" these circumstances, holds the diaphragm SZ againsttstop 93, and compresses=springsr94:t. If the air throttle is quicklyi'opened, the-pres? sure: immediately;increases; relieving: the "sueti'onrz; in? compartment 9 i, and the' springs '94 push the diaphragm. to the: left; thereby forcing .fuel out of" compartment?96 1until diaphragm 92 abutsstop fll; This fuel leaves through:check ivalvey fit a-nd iente'rs compartment 46,'1 ,by, way. of c con cluit 198; To get'this result;.athe' passage 6I v-con+- nectingcompartment 4 6 with the ven'turi throat-L.

in fue1 conduit '8 8 should I be" relatively: small;

When the: throttle is. again. cl'osed,zthez'redu'cedpressure in: 9'! will 'permitnreturn' of diaphragm? ill a little larger than needed: to balance the-, forcer acting against" fuel diaphragm- :54; it 1 would then belpossible -to 'havea calilorateol passage lil'l put-- tingeoompartments :43 and AAA-in communication with-each other .in: order to reduce-the cliiierential 1 pressure :in: these two compartments-in such-a ways that the'zforce' derived. normally irom thelargeair diaphragm just-balances :the fuel. diaphragm;

As shown, this passage it! has a valve-H12 which normally, allows restricted flow from l 43-" to ii. If, now; we close-this valve we increasei' the-control" valve 34 will immediatelyiincrease the output of the fuel'injection pumpr [6; although; thefair flow entering ith'e' engine has-'not increased. Thus themixture becomes i richer. Conv'erselml openingatheivalve':Il2=beyond its normal setting;v will correspondingly; lean out the mixture;

A 5 similar arrangement on th'e fuel diaphragm" unit couldgive corresponding results; but may not always '1 be advisable because of the oliflic'ulty r of sealing a .valve which would" pass 'fuel instead of. air.

The'valve'l tfoould also be operated'ibya-means of an ireva'cuatedr ibellows "similar: to" the onedisclosed'zin theMockU 81: Patent No. 2,447,267 (aboverefer red to) to :correct for changes in tem perature andibarometric pressure; thus acting as t of the mixture.

What is claimedis:

1; ln a system for controlling the *mixture -of air and fuel for delivery tolanl enginehaving an 92' to theright allowing: fueltoi enter 96 :at.

' cluringlthe period of deceleration; thus preve'ntthe pressure difference between it and 44= and v 'altitiicl'e correcting device to vary'the richn'ess' F airisupply conduit; a throttle therein"adapted to"- Q be adjustably positioned, and fuel supply means having an output proportional to the engine speed and whose output at any given speed is variable, 7

a member movable to control the output of said fuel supply means, an automatic fuel-air flow responsive ratio control mechanism to actuate said member to regulate automatically the fuel-air ratio at all operating positions of said throttle and at different engine speeds, said control mechanism including means responsive to the fuel input to said supply means, and accelerating pump means operated by the throttle to affect said fuel input responsive means so as to increase the fuel output from the supply means to said engine.

2. In a'system for controlling the mixture of air and fuel for delivery to an engine having an air supply conduit, a throttle therein and fuel supply means having an output proportional to the engine speed and whose output at any given speed is variable, automatic fuel-air ratio control mechanism including means responsive to air flow in the air supply conduit and other means responsive to fuel flow to said supply means to act on the fuel supply means to control automatically the fuel-air ratio at all operating positions of said throttle, a member movable to control the output of said fuel supply means, and mechanism interconnecting said output control member, said automatic control mechanism and said throttle including means to actuate said con- 3. In a system for controlling the mixture of air and fuel for delivery to an engine having an air supply conduit, a throttle therein and fuel supply means having an output proportional to the engine speed and whose output at any given speed is variable, automatic fuel-air ratio control mechanism including means responsive to air flow in the air supply conduit and other means responsive to fuel flow to said supply means to act on the fuel supply means to control automatically the fuel-air ratio at all operating positions of said throttle, a member movable to control the output of said fuel supply means, and mechanism interconnecting said output control member, said automatic control mechanism and said throttle including means to cause said automatic mechanism to actuate said output control member to control the fuel-air ratio, and said last mentioned means includin air supply conduit pressure responsive means affected by any sudden opening movement of the throttle to act upon said fuel flow responsive means to actuate said output control member to increase the fuel until said automatic mechanism responds to the more open position of the throttle.

4. In a system for controlling the mixture of air and fuel for delivery to an engine of the type including an air supply conduit, a throttle therein and fuel supply pump means driven by said engine and whose fuel output at any given engine speed is variable, a first fluid pressure operated mechanism responsive to air flow through said supply conduit, a second fluid pressure operated mechanism responsive to flow of fuel to the intake of said fuel supply pump means, said first and second mechanisms coacting on the fuel supply pump means to control the output thereof and thereby control automatically the fuel-air ratio; the improvement comprising a third fluid pressure operated mechanism responsive to the pressure in said conduit between the throttle and the engine and associated with said first and second fluid pressure operated mechanisms and said fuel supply pump means for changing the action of said first and second mechanisms on said pump means to momentarily increase the fuel delivery to the engine upon a sudden opening of said throttle so as to obtain a fuel-air ratio favorable to fast acceleration.

5. In a fuel system for an internal combustion engine, an air conduit, a fuel conduit, operatoroperative throttle means for controlling the flow through said air conduit, regulating means including a servo-piston for controlling the flow through said fuel conduit, said regulating means including means responsive to fluid flow through said air and fuel conduits so as to regulate said servo piston in such manner as to maintain said flow in accordance with a predetermined formula establishing a ratio between air and fuel flow, at all times, including the starting period of the engine, and means including an accelerating fuel pump having a diaphragm responsive to change in the fluid pressure in said air conduit and thereby to a quick movement of said operatoroperative throttle means toward the full-open position to provide a fuel output, and conduit means operatively connecting the fuel output of said fuel pump directly to said fluid flow responsive means to cause said fuel output to act upon said fluid flow responsive means so as to effect movement of said servo-piston, in the direction corresponding to an increased fuel delivery to the engine.

6. For use in a fuel system for an internal combustion engine having an air conduit, a fuel conduit, and operator-operative throttle means for controlling the flow through said air conduit; regulating means including a servo-piston for controlling the flow through said fuel conduit, means responsive to fluid flow through said air and fuel conduits so as to regulate said servopiston in such manner as to maintain said flow in accordance with a predetermined formula establishing a ratio between air and fuel flow, at all times, including the starting period of the engine, and means including an accelerating pump having a diaphragm responsive to the fluid pressure in said air conduit and thereby to a quick movement of said operator-operative throttle means toward the full-open position to act upon said fuel flow responsive means so as to effect movement of said servo-piston, in the direction corresponding to an increased fuel delivery to the engine, said accelerating pump further having a fuel chamber and pair of passages directly connecting the chamber to said fuel flow responsive means and thereby to said fuel conduit, one of the passages permitting rapid flow of fuel in one direction only and out of said fuel chamber to affect said fuel flow control means, in response to throttle opening, and the other of the passages permitting the return of fuel to said chamber from said fuel flow responsive means at a relatively low rate to prevent stalling of the engine in response to the subsequent throttle closing.

7. For use in controlling the mixture of air and fuel for delivery to an engine having an air supply conduit, a throttle therein adapted to be adiustably positioned, and a pump havingfuel inlet and outlet conduits, the inlet conduit connected to a source of fuel and the outlet conduit connected to said engine; the combination comprising an air pressure operated diaphragm, an air chamber and a fuel chamber separated by said diaphragm, spring means to bias said diaphragm in a first direction, a pair of conduits for connecting the fuel chamber to a source of fuel, one of the conduits permitting rapid flow of fuel in one direction only and out of said fuel chamber upon movement of said diaphragm in said first direction, and the other of the conduits for the return of fuel to said chamber at a relatively slow rate upon movement of said diaphragm in a second direction, a third conduit for connecting the air chamber to the throttle controlled air supply conduit so that upon a rapid opening of said throttle the movement of said diaphragm in said first direction may be efiected for discharging fuel from said fuel chamber, means to vary the fuel output from said pump to said engine, a fourth conduit directly connecting said pair of conduits to said last mentioned means, and said last mentioned means being directly affected by the fuel discharged from the aforesaid fuel chamber to momentarily increase the fuel output to said engine by said pump.

8. The combination defined by claim 7 in which said other conduit is so restricted and arranged as to retard the return flow of fuel to the fuel chamber and thereby momentarily retard said output varying means from decreasing he fuel output from said pump to said engine upon a rapid closing of said throttle.

9. In a system for controlling the mixture of air and fuel, for delivery to an internal combustion engine, an air conduit, a fuel conduit, manually actuated means for controlling the flow through said air conduit, means including a servo-piston for controlling the flow through said fuel conduit, means for delivering the contents of said fuel conduit to the combustion chambers of the engine concurrently with the delivery of the contents of said air conduit to said combustion chambers, whereby the contents of said two conduits become commingled in said combustion chambers, to produce a mixture in which the air and fuel bear a predetermined ratio, one to the other, in accordance with the concurrently prevailing settings of said above-recited air flow controlling means and fuel flow controlling means, and means for subjecting said piston to fluid under pressure, said last named means comprising a cylindrical reservoir, a fluid conduit leading thereto from a pressure source, a nonreturn valve in said conduit, and a second conduit leading from said first conduit to said servopiston, and a spring-pressed piston in said cylindrical reservoir, to control the pressure maintained therein.

10. In a system for controlling the mixture of air and fuel for delivery to an engine having an air supply conduit and a throttle therein adapted to be adjustably positionel; the combination comprising fuel supply pump means having an output proportional to the engine speed and driven by said engine at a variable speed and whose output at any given speed is variable, a member movable to control the output of said fuel supply pump means, an automatic fuel-air ratio responsive control mechanism including means responsive to fuel input to said pump means, said control mechanism to actuate said member to regulate automatically the fuel-air ratio at all operating positions of the throttle, and fluid pressure responsive means effective upon rapid opening of the throttle to directly and momentarily act upon the fuel input responsive means to cause said output control member to increase the fuel supplied from said fuel pump.

DESIRE J. DESCI-IAMPS.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,996,590 Rockwell Apr. 2, 1935 2,103,126 Sugihara Dec. 21, 1937 2,240,515 Partington May 6, 1941 2,273,670 Udale Feb. 17, 1942 2,293,043 Coffman Aug. 18, 1942 2,402,332 Lee, 2nd June 18, 1946 2,447,265 Beardsley, Jr. Aug. 17, 1948 FOREIGN PATENTS Number Country Date 113,026 Australia May 2, 1941