US2641229A - Fluid-powered engine - Google Patents

Description

June 9,. 1953 F. R, BELLOWS FLUID-POWERED ENGINE Filed July 23, 1949 3 Sheet s -Sheet 1 INVENTOR. LEW/5 F. RBELLOWS A 7' TORNEYS June 9, 1953 F. R. BELLOWS 2,641,229

FLUID-POWERED ENGINE Sh 1', 2 .Filed July 23, 1949 I I 3 Sneets ee Fly. 3

INVEN TOR. LEW/5 F. RBELLOWS A T TORNEYS June 9, 1953 F. R. BELLOWS 2,641,229

FLUID-POWERED ENGINE Filed July 23. 1949 3 Sheets-Sheet 5 519.8 BY -W Patented June 9 1953 UNITED 2,641,229 FLUID -POWERED ENGINE Lewis F. R. Bellows, Detroit, Mich., assignor to The Bellows Company, Akron, Ohio, a corporation of Ohio Application July 23, 1949, Serial No. 106,457

14 Claims.

The present invention relates generally to the valve art and is more particularly concerned with a novel and useful, fast-acting, fluid-powered engine for operating fluid valves or other devices by means of a reciprocating floating piston acted on by pressure fluctuation controlled by hand, mechanical, or electrical means, or any suitable combination thereof.

Although such fluid-powered engines have long been known in the art, those conceived prior to the present invention have not been satisfactory for fast, continuous, shock-free action, especially when liquid may be introduced for lubricating purposes or may be formed inside the system of a gas-operated engine.

Engines of this type depend for their operation on reducing the imposed fluid pressure alternativly on opposite ends of a movable piston, and re-equalizing these pressures between piston movements. sure requires channels either through or around the piston, which are of small total area in relation to the vents required to unbalance the travel piston, Obviously, the presence in this system of liquids of high viscosity compared to the operating fluid, which is normally a gas, delays the rebalancing of fluid pressure in the system and precludes rapid action of the piston. Furthermore,

the expansion chamber behind the piston is Rebalancing of the imposed presquired for evacuation of the said fluid when piston movement is to be reversed.

The present invention assures rapid operation in these engines, regardless of the presence of high viscosity liquids in the passageways or vents.

Also, according to this invention, shocks due to stopping rapidly moving pistons can be virtually eliminated and faster piston action can, at the same time, be obtained through the automatic equalization of the operating fluid pressures in these engines during the last 5% of the pistons travel in either direction.

Those skilled in the art will gain a better understanding of the present invention upon referring to the drawings accompanying and forming part of this specification, in which:

Fig. l is a fragmentary, cross-sectional view of a solenoid-controlled engine embodying this invention;

Fig. 2 is a view similar to Fig. 1 with the parts disposed in an intermediate position to indicate the operation of the mechanism;

Fig. 3 is a view similar to Figs. 1 and 2 showing the parts of a similar engine in an extreme position opposite to that of Fig. 1;

Fig. l is an enlarged, sectional view of a head of the piston of Fig. 3, equipped with a springmounted ball check valve member;

Fig. 5 is a fragmentary, cross-sectional view of a solenoid-controlled engine embodying still another form of the present invention, the parts thereof being disposed in neutral or intermediate position;

Fig. 6 is a fragmentary, cross-sectional View of another solenoid-controlled engine embodying this invention;

Fig. 7 is a partially diagrammatic view of an electrical system including a solenoid engine generally resembling that of Fig. 6, said engine being shown in partial section;

Fig. 8 is a partial sectional view of another engine of this invention generally resembling the engine of Fig. 6 and equipped with manual and remote mechanical means for operating said engine; and,

Fig. 9 is an enlarged, sectional view of a head of a piston generally resembling that of Fig. 4, but having a relatively smaller ball check valve member.

The same parts in these several views bear the same reference characters.

Generally speaking, an engine of this invention comprises a housing having an inlet opening in a side wall and exhaust vents in opposing end walls, means for controlling the flow of gas in the housing through said exhaust vents, and a piston in the housing for reciprocating movement between the said opposed ends in response to fluid pressures obtaining in the two portions of the housing separated by the piston head, said piston having a head and skirts projecting in opposite directions from the head and a passage open to said inlet opening and having outlet openings communicating with the exhaust vents. Further, this engine has valve means for controlling flow of fluid into these portions from the housing inlet opening and through the piston head,

this valve means being movable with and relative to the head and disposed within said passage for closing said outlet openings. In the usual form this piston will be secured to a sliding valve mechanism which will move with the piston and with respect to the housing and the member defining the valve openings.

In addition, in general, the valve means referred to above comprises a body which is movable with and relative to the head of the piston and is disposed within said head to seat sealingly against valve seats on either side of the head around the outlet ports. This body, in accordance with the preferred embodiment of this invention, is resiliently supported so that normally it will stand in such a position that both ports are open; and at the same time, it should be of such size that it may bev acted upon bymeans externalto the piston to unseat itfrom either valve seat. Alternatively, the said body may be so dimensioned r shaped that it will not project through the outlet ports, in which case the. external means for unseating should be designed'to extend into the piston head to effeciitheopening of one or the other outlet port' (Fig. 9)i Further, this body will function together as a double-acting, check-valve mechanism, seating? at onetime against one of the seats and at another time against the other seat to effect reciprocating mo tion of the piston, as will be: described below in details More specifi'cally and with: reference: to Figs;

1, 2 and 8, the present engines?each' oomprise' a housing H having an inlet opening I inthe mid-section: of its: side i all lt an'd a cylindrical space ii communicating with the atmosphere outside the housing through. axially alignedi vents H in opposing end Walls. 5 3.- of the housin'g. Re-- ciprocating piston l1IOVS'll'I the cylinder along the common axis of. vents thunder the influence of differential fluid pressures acting on the'pi'stonand regulated in a manner hereinafter: to be described; This piston comprises a pair of hollow,- cylindrical guides 16 projecting oppositely from a head H having;two outlet ports: I8'com'munieating with vents l-2 and-avalvechamber l9' in" the head. An inlet passage: 253* is: provided: in

head 5 to connect chamber Island inlet Ii A- valve member: comprising a ball 21" is disposed in chamber. I kwherein: it" may move. to limited extent under the influence-of fluid' pressure in the cylinder and under pressure-directly 'applied".

by contact with stationary elements. toibe 'de scribed; to open or close. port'- I8. Ba ll 2 b is spring-mounted, as is clearly: shown in: Fig; 4b opposed, balanced, taperedg'.coil springs 22 being.

provided to assure that both ports [8 will be open and that. the" ball will oc'cnpfg a: static: position in repose. diameter: inarela-tion t'o' chamber |-9= and p'oz tsl 8 that. it will. project. througmeither: port in clcsi'ngl it, but when: engaged. by externalunseating: means the ball. will. nct be: displaced to such an" extent that the oppositeipnrt will be sealed: in: the absence of. a fluid pressure 'difierential across the head. The outer. cylindrical surfaces of guides id bean againstcyl'indric'a-l surfaces 23 defined within housing. H the:portion.of th'e out-- side area of the guides thus engagedcbeingtmore' than half the total of said 'area-,.-whereby-'the. load is at all times distributed wellthroughout the piston and housing, assuring longer-lifevand bet ter performance over protracted periodsa-n'd f-ur thermore assuring propelz'alignment of the piston in the housing. These: engaging; element'si are:

premachined for close fitsto prevent leakagetherebetween during operation;

In thelower centralportion of; the 'pistozn a's:

28 and a. compression spring. 28: which bears:- against the inner end wall of; said recess and In this instance theiball; is ofisuch thereby maintains member 25 in good sealing contact at all times with opposing portions 30. A slot 32 is provided in the lower side of housing H to receive dowel 28, etc., so that the piston and slide member may move reciprocably in engagement with each other and relative to the housing.

Solenoid uni-ts 35 are"- disposed within the housing H Y and are enclosed therein in cylindrical casings 36 secured in position relative to the housing and provided with openings in their side wallsthrough which fluid may flow in its travel from closure openings 8 to exhaust vents I 2. These solenoids are suitably of conventional form within the coils under magnetic force applied whenthecoils are energized and under force of springs 39 when the coils are deenergized. These cores are provided at their outer ends with rubber sealing discs 4:; for engagement with opposing'surface-portions'of the housing wallstos'eal vents I2 when the solenoid circuits are openand the cores are extended to the maximum under the action of springs 39. Connection of thesolenoid coils in each case with a source of electric power (not shown) outside the housing is'efiectedby-means-of a wire clip-4| connected tothe coil and to a cylindrical plug 62 ofthe usual adjustable type extending through an opening provided inside wall-l8 for the purpose andis insulated: from housing H by meansofgaskets 43 of suitable: electrical insulating material-.- Conventional-tin'iing means and relays, neither ofwhich is i1lustrated,-may be providedinthe 3 solenoid control circuits, as those skilled in the artwill understand,. for automatic high speed operation of said solenoids in timed relation to' piston IS.

The assembly and. disassembly' of the engine out, aswill be appreciated when it"isconsidered thatthe end Walls of the housingH" are separate elements'removably, but fluid-tightly secured-to- H the piston.

the -operation of this engine, air or o'ther suitable fluid,. preferab'yy' a gas, is introduced into housing If throughin-let I and flo ws into the spaces'on-opposite sides of piston head IT through passage 24]; chamber l9 and ports I81 in-Fig. 1:, and with head l 'i bearingagainst left coil casing-.36,.ba1l 2!: is engaged with the said" casingandis disposed so that bothrightandleft ports l8 are open. Both right and left vents I2 are closed and-the air pressure on both sidesof the'piston' head therefore, is balanced and 'the' piston is in staticposition. Right coil 35 is'the'n' energized, resulting in the opening of right vent I2 to: the" atmosphere, as illustrated in Fig; I. The ball isr for'ced;. under the resulting airpressure differential across the piston head, int'o se'aL ing. engagement against the'right side of the-said head closing right-port l8: Th'e'flow of live-"air" .through inlet I passage: 20 and into the left of Fig. lis relatively simple and easily carried I With-the p1ston= in-its extreme" left position, as indicated chamber through left port I8 continues, causin the piston to travel to the right with the ball remaining seated as indicated in Fig. 2. When the travel of the piston, to the right is nearly completed, the ball engages right coil casing 36 and is unseated. Piston travel is completed when the piston head engages casing 36, as illustrated in Fig. 3, and the ball at this stage is so positioned as described above that both right and left ports I8 stand open. Right coil 35 thereupon may then be deenergized, resulting in the closing of right vent I2 and balancing of air across the piston head through chamber I9 and ports I8. Thus the piston again is in a neutral condition and motion of the piston is not again begun until the left coil 31 is energized resulting in the opening of left port I2 and unbalancing of the air pressure across the piston head and consequently seating of the ball to the left. The piston, consequently, may be reciprocated intermittently between the two extreme positions indicated in Figs. 1 and 3 and may be operated in this way continuously depending upon the type of control and operation desired.

The engine of Fig. 5 differs from that of Fig. 3 only in the form of valve member for controlling piston ports 18. Instead of the ball of the former, a dumb-bell plug 50 is provided. The enlarged, rounded end portions of this plug are of such size as to be capable of closing the ports and projecting therethrough for engagement with opposing ends of casing 36.

Furthermore, the plug can move lengthwise in chamber I9 and in repose will allow air flow through both ports I8, a pair of opposed balanced coil springs 22 bearing on the ends of plug 50 assuring this condition. The operation of this device, therefore, is essentially the same as that of the device of Fig. 3 inasmuch as the two closure openings may, under certain circumstances, be

open at the same time, as indicated in Fig. 5 or one or the other may be closed and the plug moved from one position to another to accomplish this effect rapidly and under relatively small air pressure differentials. I Furthermore, the outlet ports will both stand open when plug 50 is displaced to a maximum degree by engagement with either coil casing 36, provided there is no substantial air pressure differential across the piston head. I

The engine of Fig. 6 differs from that of Fig. 3 in several important respects, but the two are of the same general design and operation andembody the same basic invention. The ball valve member 2i is disposed in chamber I9 of piston head I! where it is centered in repose between balanced coil springs 22 so that the ports I8 will not be sealed untimely by the ball under external forces such as gravity. As a difference, solenoid casings 65 of this valve are unslotted but have axial recesses 66 facing vents l2 and solenoid cores 61 are axially recessed at 68 to receive and retain compression springs 69. The noses of cores 61 carry rubber pads I0 of square crosssection to seal and project into the vents when the coil is deenergized and compression springs 69 exert their effect without interference by magnetic forces in coils 31. Plugs 42 are disposed in end walls I3 of the valve housing and are electrically insulated therefrom by gaskets 43 and electrically connected to coils 31 by clips 4|.

Bolts 14 are provided to secure end walls 13 to the main body of the valve housing as indicated in Fig. 6.

.The flow of air between ports I8 and vents 6 I2 in this Fig. 6 engine differs from that of the foregoing devices in that it flows around the end of casings 65, passageways I5 being provided between portions of said casings and end walls I3. The engine of Fig. 7 generally resembles that of Fig. 1, but is provided with an end wall I3 as shown in Fig. 6. Thus electrical connections to solenoid coils 31 are made through the ends of the engine housing and solenoid casings 65 are unslotted, and a space is provided between a portion of each of these casings and main body H of the housing and end walls I3 to define-a. passageway 15 for air flow between ports I8 and vents I2. As before, ball 2I is spring-mounted on opposed, balanced, coil springs 22 and piston I6 is operated by means of air delivered through inlet I of body H, solenoid cores 38 regulating air flow through vents I2, as described above. Terminals 42 are connected to a source of electric current (not shown) by means of lines and transformer 8I, line voltage being delivered 1 through wires 83 to the transformer. A pair of switches 85, which may be the conventional limit-, micro-, or foot-types, or may be relays, are pro- Vided in lines 80 to govern the flow of current to the solenoids; and the circuit is grounded as indicated at 81.

The engine of Fig. 8 likewise bears a general resemblance to that of Fig. l, but is not provided with solenoid means and is not, electricallycontrolled in its operation. This engine comprises the usual body portion I0 with its air-inlet I and piston I5 with its spring-mounted ball 2| to regulate the flow of air through the piston head and through ports I8, as described in detail above. Further, piston I5 carries a sliding element 25 of a slide valve assembly. fEnd walls of the engine close the opposite ends of body H and have cylindrical axial projecting portions 9I I telescopically disposed within guides I6. Axial apertures 92 are provided in portions 9I and at their outer ends these apertures are enlarged and provided with screw threads for the receipt of valve members 94 which are screwed thereinto and define vents 95. Flow of air through the engine thus is generally the same as described in the discussion of Fig. 1 device to the point where where air emerges through ports I8, whereupon it flows through apertures 92 and out of the, engine through vents 95. To regulate the flow of air through the engine and through these Vents manual means, such as indicated at the left side of Fig. 8, may be provided. This means includes a valve stem or plunger 96 disposed within the enlarged portion of aperture 92 on the left side of the engine for sealing engagement with member 94. A compression spring 91 bears against the plunger and against the opposing part of member 9I and resiliently urges this sealing engagement of these parts. A hand lever 99 is disposed adjacent to the engine for engagement with the outer end of stem 96, whereby motion of the lever toward the engine will result in compression of spring 91 and opening of vent to the ends and objects described above. Means for remotely and mechanically operating this Fig. 8 engine is indicated on the right side of this drawing and comprises a valve body I00 having an inlet port passageway IOI communicating with right vent 95 of the engine through a conduit I02. This body I00 further is provided with an outlet port passage I03 which is threaded and into which is screwed a valve sealing member I04, defining an outlet port I05.

Valve-Esters lotjtquite iilie stem 96"; is providewtd close and seal portiils-iby fii'm en'ga'gement' with: body l ed-and a' compression-spring. l08isp1o'' vided withiir' passage l -3" toresiliently urge this engagement, after the manner described a above in reference to the" spring 91;

T he valvestemis' carried in suitable supporting structure through which itextends for engage m'ent with a cam H0 carried on a reciprocating element l I I. Cam I l G is mounted in such" a way that on passing the stem I01 in'travel tothe left, i. or towardthe engine, the stem will be driven into body" HG, opening port I05; Ohthe other hand-,nwhen cam l'lfl'is' move'cl in the opposite direction it does riot" depress the' stem, but is turned on apivotby'the stem and port H r-e maiiissealed under the action of spring will Referring to Fi'g. 9",. a piston *head" I'I 'I, .quite like I head'l 1, described above,. is illustrated in engagement-on its left-side with a coil casing H Shaving an axially disposed lug I projecting through left outlet port I22 of the" head. As in said head:- f'l, a chamber I24 is provided in head Hi and a passageway I25 connects this chamber with: a sourceof air under pressure, as for instance; inlet I of an engineihousing; Right and left ports I22 are sealed by means of-a ball l2? disposed in chamber" I24, this ball di fiering, however irom ball z'l inlthatlit-is so dimensioned with" respect to the said ports I22 that it can-- not project to any appreciable extent therethrough forengagement' with a" coil: casing such as casing 36 of the Fig, 1 device. However, ball I21- is similai other respectsto ball '2 I", being, for"example, displaceable to a-maximum extent due to the: action of lug- I 20', so that inthe position illustrated in'Fig; 9 the ba'llseals neither of the outlet ports and the" piston is ina neutral position with air pressure balanced across the head." Also, asbefor'e, a pair of'opposed balanced springs- I29 areprovided in'ch'amber [24* to bear against" opposite sidesofthe ball and'r'esiliently oppose movement of the ball toward either of the outlet'ports'. These springs-,like those described in detail-abovashould not function under any ordinary operating circumstancesto stop the now of airthrough' either of the outletp'o'rt's in the head} Closure of the outlet ports in this manner independentlyof the ballii; e when the ball is not positioned to sealingly close oneo'r the othefo'f the ports, may result in the piston being moved at times when such movement isnotdesired} Having thusdescribed the resent invention so th'atthose skilled-111 13116 art'ma'y beable to" understand" and practice the s'am'e, I statethat what- I desire-to secure by'Let ters Patent is de fine'd in what is claimed:

I claim it An engine comprising a housing' havi-ng an inlet opening and exhaust vents, -means' for open-' ing and closing said verit's;a piston in said housing havinga head and-skirts projecting in o'pposite directionsfrom the head, said piston hav ing la; passage opento said inlet'opening and" having outlet openings from thep'ass'age com municating with sa'i'd' vents, and means movable With' and' relative t'o' the head anddisposed within'sai'clpassage and supported by the piston: for" closing one of said outlet openings under predetermined fluid pressure circumstances and closing the other said opening under other fluid pressure circumstances;

2. An engine comprising ahousin'g having: an inlet openin'gi exhaustvents; mean's 'for open ing! and closing said vents, a piston in: said housing having a head and skirts projecting in opposite directions'from the: head; said piston havinga passage opento said inlet opening and having outlet openings from the passage communicating with said vents', means/movable with and relative to the head and disposed within said passage for closing one of said outlet opening's under predetermined fluid pressure circii-mstances and closingtheother said opening under other" fluid pressure circumstances,- and resilient n'ieansin said head and movable therewith andengaging the closure means for resiliently opposing movement of said closure means-toclose eitherof saidoutlet openings.

3. Anengine comprising ahousing having an inlet opening and exhaust vents, means for opening and-closing's'aid vents, a'piston' in said hous ing having ahead and skirts projecting in op: posite directions from the head, said pistonhaving a" passage open to said inlet opening and having outlet openings from the passage communicating with said vents, means including a ball movable with and relative to the head" and disposed within said paessage for closing one' of said outlet openings under predetermined fluid pressure-circumstances andclosing the other said opening under other fluid pressure circumstances, amrmeans'including a pair ofopposed balanced springs in the head and engaging the ball to resiliently oppose movement of'the ball to close either of said outlet openings.

4. An engine comprising a-housing having an inlet opening and-"exhaustvents, means for opening' and closing said" vents, a piston in said housing having a head and skirts projecting in opposite directions fromthe'h'ead, said piston hav-' ing a passage open to said inlet opening and having outlet openings from the passage communicating with said vents, and means movable" with and relative to the headand disposed Within said passage for closing said outlet openings,

sai d mean's' being responsive to' fluid pressure dif-- ing'a passage open-to said inlet opening and hav ing outlet openings from the passage communi catin'g Withsaid-vents, and means including a ball movable 'wi'th and relative to the head and disposedwithin said passage for closing said outlet-openings, said means being responsive to fluid pressure differentials-- across thehead to close the outlet opening on'the low pressure side or the piston andto occupy aneutral positionwith the said outlet openings communicating witheach other when there is ndsubstantial pressure v dif ferentials across: the head to" close the cadet op'eningon the low pressure: side 01? the piston and to occupy" a neutral' position: with the said outlet openings communicating with each-other when there is no substantial pr'essu'r'e differential across said 'he'a'dl- 6. An electrically controlled'; air p'owered engin'e comprising 'ahousing having an inlet open-- ing and exhaust vents, electrical meansfor'openi ins and closing said vents in timed: relationi-a reciprocating piston in said housing, said piston havng a head and hollow cylindrical guides extending from the head and having remote open ends and inlet openings at adjacent ends, and a valve member in said head having an inlet opening and a valve chamber communicating with said guide inlet openings, and a ball movable with and relative to the head and disposed in the valve chamber for closing said guide inlet openlngs.

7. A solenoid-controlled engine comprising a housing having an inlet opening and exhaust vents, solenoid units controlling said vents, a piston in said housing having a head and skirts projecting in opposite directions from the head, said piston having a passage open to said inlet opening and having outlet openings from the passage communicating with said vents, and means movable with and relative to the piston and disposed in said passage for closing said outlet openings.

8. A solenoid-controlled engine comprising a housing having an inlet opening and exhaust vents, solenoid units therein controlling said vents, casings for said units, a piston having a head between said casings and skirts telescoping the latter, said piston having a passage open to said inlet opening and having outlet openings from the passage to the spaces between said piston and said casings, and means movable with and relative to the piston and disposed in said passage for closing said outlet openings.

9. A solenoid-controlled engine comprising a housing having an inlet opening and exhaust vents, solenoid units therein controlling said vents, casings for said units, a piston having a head between said casings and skirts telescoping the latter, said piston having a passage open to said inlet opening and having substantially circular outlet openings from the passage to the spaces between said piston and said casings, and a ball carried by said piston in said passage and having a diameter greater than the diameter of said outlet openings, said ball being movable relative to said piston to project through and close either of said outlet openings and contact either of said casings.

10. A solenoid-controlled engine comprising a housing having an inlet opening and exhaust vents, solenoid units therein controlling said vents, casings for said units, a piston having a head between said casings and skirts telescoping the latter, said piston having a passage open to said inlet opening and having substantially circular outlet openings from the passage to the spaces between said piston and said casings, and an elongated plug movable with said piston and disposed in said passage and having enlarged rounded end portions larger than said outlet openings, said plug being movable relative to said piston to project through and close either of said outlet openings and contact either of said casings.

11. An engine comprising a housing having an inlet opening and exhaust vents, manual means for opening and closing said vents, said means comprising spring-mounted plungers movable to close said vents and operating levers associated with said plungers, a piston in said housing having a head and skirts projecting in opposite directions from the head, said piston having a passage open to said inlet opening and having outlet openings from the passage communicating with said vents, and means movable with and relative to the head and disposed within said passage for closing said outlet openings.

12. An engine comprising a housing having an inlet opening and exhaust vents, mechanical means for automatically opening and closing said vents, said means comprising valve bodies having inlet ports and outlet ports communicating with said exhaust vents, spring-mounted plungers movable to close said outlet ports, and cam means to engage said plungers and move them relative to said bodies, a piston in said housing having a head and skirts projecting in opposite directions from the head, said piston having a passage open to said inlet opening and having outlet openings from the passage communicating with said vents, and means movable with and relative to the head and disposed within said passage for closing said outlet openings.

13. An engine comprising a housing having an inlet opening and exhaust vents, manual means for opening and closing said vents, a piston in said housing having a head and skirts projecting in opposite directions from the head, said piston having a passage open to said inlet opening and having outlet openings from the passage communicating with said vents, enlarged opposed abutment members in said piston and secured to the housing and telescoped in said skirts, and means including a spring-mounted ball movable with and relative to the head and disposed within said passage for engaging said abutment members and closing said outlet openings.

14. An engine comprising a housing having an inlet opening and exhaust vents, mechanical means for automatically opening and closing said vents, a piston in said housing having a head and skirts projecting in opposite directions from the head, said piston having a passage open to said inlet opening and having outlet openings from the passage communicating with said vents, enlarged opposed cylindrical abutment members in said piston having axial apertures communieating with said passage and vents and being supported by and secured to the housing and telescopicall related to said skirts, and means movable with and relative to the head and disposed within said passage for closing said outlet openings.

LEWIS F. R. BEILOWS.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 234,649 Boland Nov. 23, 1880 358,520 Westinghouse Mar. 1, 1887 2,369,505 Ward Feb. 13, 1945 2,372,813 Darling Apr. 3, 1945

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