US2663373A - Reversible pitch propeller - Google Patents

Description

Dec. 22, 1953 N. R. RICHMOND REVERSIBLE PITCH PROPELLER 3 Sheets-Sheet 1 Filed Sept. 14, 1946 INVENTOR -1I!eZ50%fl.H/a'c%m0md BY 114/1414 4. M ATTORNEY Dec. 22, 1953 N. R. RICHMOND REVERSIBLE PITCH PROPELLER 3 Sheets-Sheet 2 Filed Sept. 14, 1946 8 V9 Mm M W a Q .v mm W m c [z o wk n m u A G v 2 m B mm mm wi m $0 I. NM .9 6% MN Q N m\ Dec. 22, 1953 N. R. RICHMOND REVERSIBLE PITCH PROPELLER 3 SheetsSheet 3 Filed Sept. 14, 1946 J I I I l fill/A ril INVENTOR Nelson ll awowli ATTORNEY BYW Patented Dec. 22, 1953 REVERSIBLE rrron PROPELLER Nelson E. Richmond, Thompsonville, Conn., as-

signor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Application September 14, 1946, Serial No. 697,065

25 Claims. 1

This invention relates to hydro-controllable propellers, and particularly to propellers of this type which may be feathered or reversed, and to improved control mechanism operative during unreversing of the propeller blades.

In propellers having pitch changing means capable of turning the blades beyond the normal operative range, in which their pitch angle is usually automatically controlled by a governor, into extreme or special purpose ranges such as feathered or reverse pitch positions, it is usual to operate the propeller blades in the normal range by a relatively low fluid pressure which is adequate to overcome the aerodynamic and centrifugal twisting moments exerted against the blades in this range, and to operate the blades into and out of the extreme positions thereof by a higher fluid presure to which the propeller pitch changing mechanism is subjected only while the propeller is in or being changed to or from these extreme special purpose ranges.

It is an object of this invention to provide improved means for controlling the admission of the higher pressure fluid (hereinafter referred to as the high pressure fluid) to the propeller.

Another object of the invention is to provide improved means operative during unreversing for interrupting the admission of high pressure fluid to the propeller pitch changing mechanism when the propeller has returned to the governor controlled constant speed range.

A further object of the invention is to provide means in the high presure fluid system which is automatically actuated by return of the low pitch stops to operative position for creating a pressure surge in the system to interrupt the supply of high pressure fluid to the propeller.

A still further object of the invention is generally to improve the construction and operation of governor controlled pitch changing propellers.

These and other objects and advantages of the invention will be apparent from the specification and claims, and from the accompanying draw ings which illustrate what is now considered to be a preferred embodiment of the invention.

1 In, these drawings,

. Fig. l is a diagrammatic View showing the propeller hub, the constant speed control means and associated control apparatus for feathering, unfeathering, reversing and unreversing the propeller with the parts shown in the position assumed during unreversing, the constant speed control means and part of the propeller hub being shownin section;

Fig. 2 is a view partly in section showing the -1602) 2 propeller hub on an enlarged scale with the parts in the reverse pitch position;

Fig. 3 is a sectional view of a portion of the hub structure of Fig. 2 with the parts in the feathered position;

Fig. 4 is a sectional view of the hub structure of Fig. 3 with the parts in the position in which the As herein shown, Fig. 1 illustrates diagrammatically the principal elements of a controllable pitch, reversing and feathering type propeller embodying the invention. Such apropeller, as generally indicated by the numeral an, includes a hub l2 splined to a propeller drive shaft 1 4 provided with a plurality of radially disposed blade receiving sockets l6, one of which is indicated in section in Fig. 2. The propeller also includes a plurality of blades I8 one of which is mounted in each socket in the usual manner including suitable anti-friction bearings 20 interposed between a socket abutment 22 and flange 24 on the inner end of the blade so that the blades are freely rotatable about their longitudinal axes in pitch changing directions. Each blade I8 is provided on its inner end within the hub member 12 with a gear sector 26 all of which gear sectors mesh with a master gear 28 journalled in the hub member l2 and rotatable about the axis of shaft l4. Master gear 23 is integral with a rotatable cam so rotated through a cam and follower mechanism including movable piston carried cam fol lowers, one of which is shown at 32, and cooperating opositely directed stationary and movable cam slots 34 and 36. The cam followers 32 are carried by an annular piston 38, reciprocable in a cylinder 39 having a dome-shaped outboard end, the piston having a tubular hub provided with a sleeve is mounted for reciprocation on a tubular shaft extension formed by the I telescoping threaded tubes 42 and 44 carried by shaft l 4. The piston 38 is shown as sealed at the cylinder 39 and at the tubular extension 44 by the usual O-ring seals. From the above desorption, it will be evident that a preponderance of oil pressure upon either side of piston 38 will cause the piston to move and change the pitch of all of the propeler blades [8 in unison.

Oil is conducted from a control unit, generally indicated at 46 (Fig. 1), and driven by gears 48 and 50 in' timed relation to the propeller, to cylinder 39 through two fluid conduits 52 and 54 and 3 communicating channels 56 and 58 leading into the propeller hub. The unit 45 acts to selectively connect one of the lines 52, 54 to governor pressure and to connect the other line with drain in order to move the piston 38 and change the pitch of the propeller blades the required amount to maintain constant speed of the engine and propeller. Thus when the unit supplies fluid, for example oil, under pressure to conduit 54 the oil flows through channel 56, chamber 60 within tubular extension 42, chamber 62 within tubular extension 44 and holes 64 to the rear of piston 38.

When the unit supplies oil under pressure through conduit 52 oil flows through channel 58, oblique,

passages 66, holes 68 through an axial conduit through a communicating axialconduitincluding conduit 12, through radial passages I4 in the side wall of conduit I2 to cylinder 39 on the front or outboard side of piston 38. It will be understood t at whe n side o he i t n i amet s t pressure fluid through one of theabove fluidlines he flui n the e her de Qfih Pisto s c011- nectediq r m rousb th oth r n the usual manner.

Th #51 9 ,5 when 95 the, 3$??? speed c ntr tfl he un t reeves n at nte i r e q t u l. troke in hiqh; it i P v n rqmi movin in t e q ihear d r s beyond a low pitch position determined by the engageme t tthe rwa d end 510i le e 0. ih abutment shoulders, or low pi h stops, IS on a lur l t 9f; latches 8.9.. Wt. he rir iel n19$9 h 1413 9??? nd, s a t -1 9 .4:. he n oa imp em t the is sm n h co s an speed r i sl bab h shape of he-t qtai ihiq e Mit em 8 mm e! q hes sl s ne a n SQ ah up rfat 'h s and it h cement steed a e th t t? bi 'p v su ess pl r b t r e 17! h rein i rd qr b h is 'ie u ir dent; to. bvercomelthe. iriction, aerodynamic and centr pgell-loading on the blades.

t n he movedbeyond the 0on N H aqneon a, range either discuss whenever the presisurefluidis ad mittedi to. the prepares hubv through conduit 52 area, ""I h" pres ureffluid, whenisu pplied to the outboa d1 sneer .piston- 38 through. conduit 52;"isi'su'fii emits overcomeithe. loading on the blades. atf th mrpaenendo; theconstant speed i to" ir l biieith blades into the. feathered posi r'e'of; ."Ih pistonfis stopped in the edp o's'ition, of. the. blades either by the end walls. oi. the; cam slots ,or by, positive mechanical li'rfnit stopsl providedon. the rotatable member 38 the hub structureffand described in Patent ND} 2 0,113 i When the high pressm'e fiuidis supplied to the rear ofthe piston through conduit '54, this pressure: acting on the piston .82 which-is in communicationwitlicharnber 6.2 cotnpresses the spring 84 which admits high pressure fluid through holes 88 and holesjtg to chambered Th Pressure in chamber 90 acting onpiston 92 moves 'thelatter in an outboard directionand, through the action of a sleeve 9 4 the outboard end of which abuts a wedgering 98., movesithe wedge ring in an outboard direction against the action otspring 987a suffiicient distance; topermit the latches 88 to move inwardly at their outboard ends. along the inclined facesB'I of wedgering 88., This inward rummage: the latches 80 is caused by the axial thruster sleeve of piston 38acting, onthelatch shoulders 18] in an outboard direction eccentrically of the latch pivots. The inward moveend spring 98 engages interrupted flange I04 of a sleeve me. As shown particularly in Figs. 3 and 4, the interruptions in the flange IEM extend into the. adjacent end of sleeve Hi6. Sleeve I06 occupies the same, position in both the constant speed and feathered ranges so that in Fig. 3 the sleeve I86 is shown in the position it occupies in the constant speed range, It will be evident that whengovernor pressure is supplied to either the inboard or the outboard side of piston 38, passages '14. arefreelyopen into the outboard end of cylinder 39, since the, fluid pressure, supplied by. the governor acting on piston 82 is notsufiicient to overcome spring 84 and consequently the sleeve I08 remain wholly on the inboard side of. passages l4 However, when fluid; under high pressure is supplied through tube 52, piston 82 compresses. spring Mtand the piston 92 compresses the spring 88 and; moves the uninterrupted portion of sleeve Illtwholl'y on the outboard side of passages M as, shown. in Fig, 2. Ineither case, the pressure fluid is free to pass from the tube 72 throughpassages it, into the portion of cylinder tfi which is, outboard of piston 38.

The governor is shown diagrammatically in Fig. 1 to whichreference is now made. The governor comprises a rotatable drive shaft I08 carrying, gear 5t which meshes with the gear 48 carried, bythe engine driven shaft, I14; A fiange H8 which is, fixed to theupper ends of shaft I08 pivotally supports a. pair of governor fly weights. H2 The-shaft I08 may be made in a single piece, as shown, or, if desired may come prise several sectionsconnecte'd together, as by splined 7 joints.

Intermediate itsends the shaft I88icarries a gear 4 n eshingwithagear IIBj supported on a hollowv axle journalled in a governor base II8 to form a,booste'r pumpproviding a source of fluid pressure. Hydraulic fluid is supplied-to this pump from any convenient source, the source shown hereinbeingthe engine lubricating pump IZil which ,issupplied through a conduit'I22from the engine oilitank or reservoir, I 24 and discharges through conduit IZB, duct I28 andbranch passagel29 to the intake of the booster pump. A relief valve it; limits the pressure in conduit I26 and in conduit itil leading to the engine lubricating system. Oilfrom the booster pump flows through checl; valve I30 and channel I32, through ports in the hollow shaft I08'into annular pressure chamber I34 between annular lands I35 andjsd on a hollow piston rod of a governor pilot valve I401 which is vertically recipe rocable ihthehollow shaft Its by the governor fly weights H2 and a governor speeder spring I42 vvhichact oppositely ona flange I43 on the piston rod. Whenthe pilot valve I48jis forced upwardlylow pressureoil supplied by the booster pump H4, H6 flows from the chamber I34 throughv ports in shaft I08 to channe1 I44 which communicateswith conduit 52, as shown in Fig. 1. Whenthe low pressure OH is connected to conduit 52 the conduit 54 is connected through channel I46 andsuitable ports in shaft I08'b'eneath the land I38 to the booster pump inlet channel I28,

thus establishing a-vent through relief valve I21 of conduit I3I for oil on theinboard side of the pitch changing piston 38. The result of admitting governor pressure fluid through conduit 52 is, as previously described, to move the piston 38 inboard i. e. to increase the pitch of the blades with a resultant decrease in R. P. M. As the governor fly balls H2 slow down they permit the speeder spring I42 to depress the piston rod of valve I48 so that the land I36 cuts oif the low pressure governor fluid passing from chamber I34 to channel I44 when the predetermined speed hasbeen reached for which the governor is set.

If the governor speed falls below the predetermined value, pressure fluid in chamber I 34 will be admitted past the land I38 to channel I46 and conduit 54 to move piston 38 towards low pitch-position, while the fluid on the outboard side of piston 38 will be vented through conduit constantspeed range above described into the special purpose ranges in which the blades are feathered in one extreme position and reversed in pitch at the other extreme position thereof. To this end a high pressure pump I58 providing a separate source of fluid pressure is suppliedfrom reservoir I24 through conduit I52 and discharges through conduit I54 into the governor base H8.

4 The admission of high pressure fluid from pump I58 to opposite sides of piston 38 is controlled in part by the valve mechanism, already described, in the propeller hub and by the governor pilot valve. A solenoid valve I56 controls the fluid pressure on the upper side of land 2I6 on the piston rod of valve I48 to position the governor pilot valve I48 to selectively admit high pressure fluid to either conduit 52 or 54 leading to the pitch control mechanism in the hub. A pressure cut-out switch I58 is also provided for interrupting the operation of the high pressure pump I58 as will later appear. High pressure pump I58 is driven by an electric motor I68 energized by a battery or other suitable source of power I62 through conductor I64, switch I66 and conductor I68. The electric control apparatus controlling the operation of switch I 66, solenoid valve I56includes cut-out switch I58 and also includes push-pull switch I18, push-pull switch I12, solenoid switch I14 and solenoid switch I16. The switches I18 and I12 are normally biased by compression springs I11 and I 18 into an intermediate, switch-open position in which their movable bridging contacts I88 and I 82 are held between and out of contact with two sets of stationary contacts, one of which sets is engaged by the bridging member when the switch is pulled and the other of which is engaged when the switch is pushed. The movable contact member of solenoid switch I66 is constantly biased into open position by a spring I86, while the movable contact member of cut-out switch I58 is constantly biased into closed position by compression spring I88. Solenoid valve I56 is constantly biased to the right as viewed in Fig. 1 by compression spring l88, while themovable switch members of solenoid switches. I14.- and I16 are biased upwardly as viewed in Fig. 1 by tension springs I82 and I94. 'To operate the propeller blades into feathered position the movable switch member of switch I12 is pushed to compress spring I11 and bridge one set of stationary contacts comprising contacts I86, I98 and 288. This completes a circuit from the positive side of battery I62 through conductors I64 and 282 to contact 288, through movable contact I82 to contact I98, through conductor 284 and solenoid 286 of switch I66 closing the circuit of motor I68 to start the high pressure pump I58. The above operation of switch I12 also establishes a circuit from battery I62 through conductors I64 and 282 contact 288, movable contact E82, contact I96, holding coil 288, conductor 2 I8, and contacts of cut-out switch I58. High pressure fiuidwill flow from conduit I54 through channel 2I2 and ports in hollow shaft I88 into chamber 2I4 between larger diameter land 2I6 and smaller diameter land 2 I8 on piston rod of valve I48, thus moving the governor pilot valve upward (Fig. -1) so that high pressure fluid from conduit I54 can pass through holes 228 and channel I32 into chamber I34 within shaft I88 and thence to channel I44 and conduit 52. As previously explained, this fluid will act on the outboard side of piston 38 with sufiicient force to move follower members 32 into the steepersloped, special-purpose range of the cam slots to feather blades I8. As piston 38 reaches the position shown in Fig, 3 in which the blades are feathered, it reaches the limit of travel in this direction either by the engagement of followers 32 with the ends of, cam slots 34, 36 or by engagement of special stops which may be provided for this purpose. High pressure builds up on the discharge side of pump I58 and on the outboard side ofpiston 38 when the piston travel is stopped. This pressure acting through passage 248, which communicates with conduit 52, and chamber 242 of pressure cut-out switch I58 causes movable contact 2II of this switchwhich is carried by piston 243'to open the circuit for holding coil 288, allowing spring I11 to return switch I12 to its intermediate open switch position. This also interrupts the circuit through solenoid 286, resulting in stopping high pressure pump I58 with the propeller blades in feathered position. The engine cannot rotate the propeller in the feathered position of the blades and consequently the propeller and the governor will stop rotating and the blades will remain in feathered position until unfeathered.

In order to unfeather the blades switch I12 is pulled to compress spring I18 and move bridging member I82 into engagement with stationary contacts 222, 224' and 228, thus establishing a circuit from battery I62 through conductors I64 and 282, contacts 226, I82 and 224, conductors 228 and 284 and solenoid 286 to close switch I88 and start the operation of high pressure pump I58. A circuit is also completed from battery I82 through conductors I64, 282, contacts 226, I82 and 222, conductor 238 and solenoid 232 of valve I 56. High pressure flu d now flows from conduit I54 through holes 228 and channel 234 through valve I56, this valve now being moved to the left as viewed inFig. 1 to permit the fluid to pass from channel 234 through channel 236 to act on the upper surface of large diameter land 2I6.' The high pressure'fluid also flowsas before. through channel 2| 2 into chamber 2| 4 where it acts on the bottom surface of land 2l6 and also on the top surface of land 2I8.1,, Since the fluid pressures sate-sea on laud mare sauteed; theipressure on the top surface ofland 218 causes pilot valve'l ifl to be depressed into a position such that the high pressure fluid which passes through holes 228 and channel I32 into chamber I34 isnow permitted to enter the annular passage 238 which com municates with channel I46 and conduit, leading to the inboard side of piston-38, to unfeather the blades.

In carrying out the unfeathering operation during flight the switch H2 is heldout manually while the piston 38 moves the blades from the feathered position, shown in Fig. 3, until the propeller starts to windmill. This can be determined by watching either the propeller or the engine speed indicator. Theswitch I12 is then released, the high press'uresource I50 will be immecliately shut oil and the governor will take over.

To reverse the pitch of propeller blades IS the pilot; pushes switch" I"!!! to bridge the stationary contacts 24%, 2 .6, 24 8 and 259. As a result four circuits will be established: (1) a circuit from battery I 52 through conductors I64, 252 and 254, contacts 256, i 88 and 248, conductor solenoid 206 of switch I66 and pump motor 569 of high pressure pump I; (2) a circuit from battery I62 through conductors I 64,252 and 254, contacts 253, I85 and 2M holding coil258, conductors 26$ and 2H] and contacts of the pressure cut-out switch I58; (3) a circuit from the battery It? through conductors I64, 252 and 25s, contacts 250, I80 and 246, conductor 262' and solenoid coil 232 of valve I56; and" (4) a circuit from-battery I62 through conductors I 64, 252 and 254', contacts 250, I86 and 246, conductorsifl and 26L normally closed switch 245' of solenoid switch W6, conductor 25I and coil 253 of solenoid switch Fi l. High pressure-fluid is now supplied from conduit l54 through holes 220, valve i56 and conduit'236 to the upper side oflland 2 I 6. Highpressure fiuid also passes through channel 212 to chamber 2 I 4 where it acts on the upper surface of land are and on the lower surface of land 2I=6. Pilotvalve I45 consequently moves downward to admit high pressure fluid from chamber I34 past the upper surface of land I38 into annular chamber 238 and communicating channel I46 and conduit 5t.

The high pressure fluid flows as previously described through passage 56, chamber and holes 64 to the inboard side of piston 38 to move the latter in an outboard direction, this pres sure acting on piston 38 being sufiicient to force the piston 32 to the right (Fig. 2), allowing access of the high pressure fluid to'piston fl" which moves wedge ring'96 against the action of spring 98' and permits the sleeve 40 to override latches 80 as shown in Fig. 2. During this movement of piston 38 the fluid on the outboard side of the piston has been vented through ports M,

tubes I 2 and T0, oblique passages 66, passage 58" and conduit 52 which is in communication through channel I and the hollow interior of the valve stem of governor pilot valve M0 with the'l'ow pressurefluid duct I28. position. of the parts in which propeller blades I8 are in reverse is shown in me. 2.

It will be noted that the sleeve IOGmoves across the holes, or ports, 14 as the spring 98 is compressed during the reversing operation. A ball check valve 268 is provided in the outboard end of the passage in tube 12 which seats against the end or a tubular member 29Ilstalced in position in tube 12. A compression spring 292' constantly urgesthe. halt valve against its seat to maintain this end' of tube '12 normally closed; However, during the movement of sleeve i06-from the left-hand side of ports I4 to the right-hand side thereof in the operation of movingthe propeller blades to reverse pitch, ports H! are blocked by sleeve I 06. Check valve 288, however, then opens to permit fluid on the outboard side of piston 38 to flow from cylinder 39 into tube I2 so that the outboard end of cylinde-r 39 is connected throughout this operation to vent either through ports 14 or check valve 288.

When the cam followers 32 have reached the outboard ends of the cam slots, or when the reverse pitch stops have engaged, if such stops are employed, the pressure on the inboard side of the piston 38 and in the conduits leadin theretohuil'ds up to the full pressure developed by the high pressure pump I50. This pressure in conduit 54 is transmitted through the fluid in a channel 264 to act on the right-hand end of the valve 266 and move the latter to the left admitting fluid to the chamber 242 of pressure cut-out switch I 58 and causing the switch to open its contacts and interrupt the holding coil circuit for switch IHl. Switch I16 will therefore move to its normal intermediate position shown in Fig. 1 when the blades have reached reverse pitch position and as a result all four circuits which were completed by pushing in switch He will be opened.

Means is provided, however, for maintaining the'coil 2.32 of solenoid valve I55 energized following the above described automatic return of switch Hi] to its open position. It will he re called that circuit (40 above described energized solenoid 253 of switch I'M. The closing of switch I'M establishes a circuit from battery I62, through conductors I 54 252, 255 and 25?, movable switch member 259, conductors 2t"? and 262 and solenoid 232 of valve I56. A hol ing coil circuit is also established for solenoid switch I'l from battery I62, through conductors I 64, 252-and 25?, contact 255, conductor 26f, normally closed switch 249 of solenoid switch H6, conductor 25I and solenoid 253;

It will thus be evident that when switch [it opens following a reversing operation, the valve 56 remains energized. As a result the low pressure fluid from the governor booster pump flows throughcheck: valve 530, channel 234, valve [55, channel 236 to the upper side of land 215 which will keep the governor pilot valve his in the down position and maintain the propeller in reverse pitch;

To unreverse the ropeller blades the switch Iwis. pulled out to cause the bridging member [89. to connect contacts 268'and 2'I0.- This establishes a circuit from the battery I62 through I conductors rec, 2'52 ancllzm, contacts 216, list and 268,- conductor 212,- solenoid 214 of solenoid switch i i-'6, conductors 216, 218/, 2H1 and contacts of pressure cut-out switch I58 thus actuating' solenoid switch We to open switch 249 and close switches 264 and 232 Opening: of switch 249- breaks the ci'rcuitfor" holding coil 253 of solenoid switch in causing 259 to open and interrupt the circuit including solenoidv 232 of valve 255, thus returning valve I56 to the position shown in Fig. .1. As solenoid switch I16 closes, a holding coil" circuit is established for the coi=1 '2-'l'4- from" battery I62 through conductors #64, 25-2 and 255, movable contact 282, coil 2T4, conductors 216-, 218, m and cut out switch tit. closings? solenoid switch l'lt'also' cstablishes a circuit to "energize the solenoid 206: controlling energization of motor I60 of high pressure p-ump' I50. This circuit includes the battery I62, conductors I 64, 252 and 255, movable contact 284, conductors 286, 250 and solenoid 206.

The control apparatus is shown in Fig. 1 in the position which it occupies after switch I has established the above described circuits to unreverse the blades and has been released and spring I18 has returned it to its intermediate position. Since a holding coil circuit is immediately established for coil 214 of switch I16, it is not necessary to hold the switch I10 out manually. Accordingly, this switch is shown in its intermediate position which it would occupy following an initiation of the unreversing operation in which the pilot has pulled out on switch I10 and has then released it.

High pressure fluid from the pump I50 discharged through conduit IE S acts on the lower face of land 2:8 to raise the pilot valve I40 in the governor shaft as previously described in connection with the feathering operation, it being noted that the solenoid 232 of valve IE5, a in the feathering operation, is not energized to admit high pressure fluid to the top of land 2I6. Consequently the high pressurefluid flows through holes 220, passage I32, chamber 534 in governor drive shaft I08, past the lower edgeof land I30, into conduit M4 and conduit 52 leading to chamber 53 in the propeller hub. The high pressure fluid passes through oblique passages 65 (Fig. 2), hole 68, tube 10 and tube 12, holes 14 and slots I04 in sleeve use to the right-hand, or outboard,

'side of piston 33 thus moving this piston inboard from the reverse pitchrange into the normal, governor controlled range.

It will be noted that as the piston 38 moves inboard the latches 8% are prevented from moving outward by their engagement with sleeve 40 until the sleeve has reached the position shown in Fig. 4 in which it has moved inwardly'beyond the latch faces 18. At this moment the latches, under the action of centrifugal force and also under the action of spring'BB acting on wedge ring 96, move outwardly about'their pivots into the position shown in Fig. 4 in which their latch'faces 18 again constitute low pitch limit stops to prevent outboard movement of sleeve 40 under governor oil pressure. At the same time that the latches 88 move outwardly sleeve S08 has moved inboard with wedge ring 9% and occupies the position shown in Fig. 4 in which it closes the holes 14 in tube 12 through which the high pressure fluid is being supplied to piston 38. As a result, a high pressure surge occurs in the high pressure fluid line including conduit '52and channel I 45 which is communicated through channel 240 to chamber 242 of the pressure cut-out switch, causing this switch to openits contacts and de-energize the holding coil 214 of switch I16. The deenergization of relay I16 immediately opens switch 284 and shuts down the high pressure pump I50. The piston is now inboard of latch faces 18, comprising the low pitch-stops and the governor willtake over and control the pitch of the blades to maintain the predetermined speed for which the governor is set.

When the high pressure pump I50 is cut off at the end of the reversing operation, the inboard side of piston 38 is connected to the outlet for the low pressure acting on piston 82 to maintain spring 85 compressed. -Piston 82 consequently moves to the left (Fig. 2) and closes ports 85 10 leading to chamber 90. Piston 92, however, re mains in the position shown in Fig. 2 because latches 80, being held in Fig. 2 position by sleeve 40, hold wedge ring 96 in the extreme outboard position thereof against the action of spring 98.

During the unreversing operation, movement of wedge ring 96 to the left in Fig. 2 moves piston 92 with it causing the fluid trapped in chamber by the closing of ports 86 to be compressed. A ball check valve 29I is provided for permitting this trapped fluid to escape into chamber =62.

It will be evident that as a result of this invention a particularly simple and reliable means has been provided which is entirely automatic for returning the propeller to governor operation following initiation of the unreversing operation by the pilot. It will further be evident that the improved means above described insures that the propeller will be subjected to the high pressure fluid only during the short time that it is actually required for moving the blades in the special purpose ranges beyond the normal governor controlled range. It will further be noted that the improved means of this invention for returning the control to the governor does not require the attention of the pilot during unreversing, the only action of the pilot which is required being the pulling out of the switch I10 to initiate the unreversing operation.

While one embodiment of the invention has been shown and has been described and illustrated in the accompanying drawings it will be understood that this particular embodiment of the invention is shown for purposes of illustration only and that various changes in the construction and operation of the mechanism may be made without departing from the spirit and the scope of the invention as defined in the appended claims.

What it is desired to secure by Letters Patent 1. In combination, a propeller having variable pitch blades, a hydraulic pitch changing motor therefor, a governor controlling the admission of fluid to said motor in a normal operating'range of pitch variation, a source of fluid pressure for operating said motor to move said blades beyond the governor controlled range, a fluid passage for connecting said source with said motor, pressure responsive means connected with said fluid passage for controlling said fluid pressure source, and means for creating a pressure surge in said fluid from said source to actuate said pressure responsive means when said propeller blades have been moved to feathered position or reverse position and also when in unreversing movement they have reached the normal governor controlled range, said surge creating means including a valve for temporarily altering the flow of fluid from said source to said motor incident to movement of said blades in unreversing movement past a predetermined position into said normal range.

2. In combination, a propeller having variable pitch blades, a-hydraulic pitch changing motor therefor, a source of fluid pressure, a governor controlling the admission of fluid to said motor from said source in a normal operating range of pitch variation, means including a second source of fluid pressure for operating said motor to move said blades beyond said governor controlled range into feathered and reverse pitch ranges, hydraulically actuated means for disabling said second fluid pressure source, and means for automatically actuating said disabling means when said blades have been moved by said motor to feathered position or reverse pitch position, a valve, a hydraulic connection. between said valve, said source and said disabling means, and means for automatically actuating said valve to actuate said disabling means, when in the unreversing movement said blades have reached the normal governor controlled pitch range.

3. In a propeller having mechanism actuated by a pressure surge, a fluid line leading to propeller, means for creating a pressure surge influid flowing in said line comprising a normally open valve in said line, mechanical stop means for limiting pitch changing movement of said propeller and means controlled by stop means for closing said valve while fluid is flowing in said line to thereby create a pressure surge.

4. In a propeller, a plurality of variable pitch blades, a blade pitch changing motor, means for supplying operating fluid to said motor including a pump and a fluid line leading from said pump to said motor, means actuated by a pressure surge in said line to disable said pump. means for creating a pressure surge comprising a normally open valve in said fluid'line, mechanical stop means for limiting the blade pitch changing movement of said propeller and means controlled by said stop means for closing said valve while fluid is flowing in said line to thereby create a pressure surge.

5. In combination, a propeller having variable pitch blades, a fluid operated pitch changing motor therefor, a source of fluid pressure, a

governor controlling the admission of fluid from said source to said motor to vary the pitch or said blades in a normal operating range of pitch variation, means including a source of fluid at a pressure higher than the governor controlled fluid for operating said motor and moving said blades into and out of a special purpose range beyond said governor controlled range, pressure responsive means for interrupting said higher pressure source, and means governed by said fluid motor for actuating said pressure responsive means in special purpose position thereof and also when moving out of special purpose range said motor reaches said normal governor controlled range, said means for actuating said pressure responsive means including means for temporarily altering the pressure of said higher pressure fluid incident to movement of said blades out of said special purpose range past a predetermined position into said normal range.

6. In combination, a propeller having variable pitch blades, a fluid operated pitch changing motor therefor, a source of pressure fluid, a governor controlling the admission of fluid to said motor to vary the pitch of said blades in a normal operating range of pitch variation, means including a source of fluid at a pressure higher than the governor controlled fluid for operating said motor and moving said blades into and out of a reverse pitch range beyond said governor controlled range, pressure responsive means for interrupting said higher pressure source, means connecting said pressure responsive means with said higher pressure source and means automatically operative during unreversing movement of said blades for creating a pressure surge in said connecting means for operating said pressure responsive means to cut on: said higher pressure source and return said motor to governor operation.

'7.- -In combination, a propeller having variable pitch blades movable in extreme feathered and reverse pitch ranges and in an intermediate governor controlled range, a fluid operated pitch changing motor, a source of pressure fluid con.- trolled by said governor for supplying fluid to said motor for moving said blades in said intermediate range, high pitch and low pitch stops defining the limits of said intermediate range, means including fluid at a pressure higher than the governor controlled fluid for supplying fluid to said motor to override said limit stops and move said blades into said feathered and reverse pitch ranges, means for supplying said higher fluid to said motor to move said blades from the feathered and reverse pitch positions into said intermediate range, means for controlling admission of said higher pressure fluid to said motor including pressure responsive means acted on by said higher pressure fluid, and means for automatically operating said pressure responsive means in the feathered and reverse pitch positions of said blades and also when in unreversing movement said motor has moved past said low pitch limit stop into said intermediate governor controlled range.

8. In combination, a propeller having reversible pitch blades, a fluid operated pitch changing motor therefor, a governor controlling the admission of low pressure fluid to said motor to vary the pitch of said blades in a, governor controlled range, low pitch stop means limiting the movement of said blades by said governor controlled fluid, means including a fluid at a pressure higher than the governor controlled fluid for moving said blades past said stop means into reverse pitch position, and back into said governor controlled range, means for controlling the ad'- mission of said higher pressure fluid to said motor including a pressure responsive device subjected to said higher pressure fluid, and means governed by said motor during the unreversing movement thereof for creating a pressure surge in said higher pressure fluid after said blades have passed said low pitch stop means into said governor controlled range for actuating said pressure responsive device to interrupt the supply of said higher pressure fluid.

9. In combination, a propeller having variable pitch blades, a fluid operated pitch changing motor therefor, a governor controlling the admission of relativelylow pressure fluid to said motor to vary the pitch of said blades in an intermediate governor controlled range, stop means limiting the movement of said blades by said governor controlled fluid beyond said range in either direction, means including a fluid at a pressure higher than the governor controlled fluid for moving said blades past said stop means into and from feathered and reverse pitch positions, means for cutting off the supply of said higher pressure fluid as said blades are moved into feathered position and as said blades'are moved from reverse pitch position into said governor controlled range.

10. The combination claimed in claim 6 including a fluid line connecting said source and said motor and in which the means for creating the pressure'surge comprises a valve in said fluid line.

11. The combination claimed in claim i in which the means for creating the pressure surge comprises a valve in the pressure line leading to said motor and said stop means defines the low pitch position of said blades and comprises an element moved by said higher pressure fluid out of its blade pitch limiting position, and in which said valve is controlled in its movement into surge creating position by the return of said low pitch limit stop means to said limiting position.

12. In a propeller pitch control mechanism, a fluid operated pitch changing motor, a pump for supplying fluid under relatively low pressure, a speed governor for controlling the supply of low pressure fluid to said motor, retractible stop means for limiting the movement of the motor by said fluid beyond a predetermined position corresponding to a predetermined low pitch, means for constantly biasing said stop means into position to limit the movement of said motor, a pump for supplying fluid under a relatively high pressure, pressure responsive means acted on by said high pressure fluid for overcoming the bias of said stop means to permit the motor to retract said stop means and move into a position corresponding to reverse pitch, and means controlled by the unreversing movement of said motor for interrupting said high pressure pump when said motor has reached said predetermined low pitch position and returning said motor to governor control.

13. In a propeller, propeller blades, blade pitch control mechanism, a fluid operated blade pitch changing motor having a reciprocable member, a pump for supplying fluid under relatively low pressure to act on said member, a speed governor controlling the supply of fluid to said motor, a retractible low pitch limit stop, means for constantly urging said stop into position to limit the movement of said member under the action of said low pressure fluid, a second pump for supplying fluid under relatively high pressure to said motor for retracting said stop and moving said member beyond said stop means into a position operative during unreversing movement of said motor when said member has moved past said" stop means into the governor controlled range for creating a pressure surge in sai high pressure fluid to actuate said pressure responsive means and stop said second pump.

14. In a propeller, propeller blades, blade pitch I control mechanism, a hydraulic double acting propeller blade pitch changing motor, a pump for supplying fluid under relatively low pressure,

fluid lines, one leading to one side of said motor and the other leading to the other side of said 5 pitch variation, means including a fluid pump motor, a speed governor controlling the selective admission of fluid to said motor through said fluid lines, means for preventing the movement of said motor beyond a low pitch position of said blades while under control of said governor comprising a retractible low pitch limit stop, means for retracting said stop to permit said motor to move to reverse pitch position including a second pump for supplying fluid to said motor under pressure, pressure responsive means for control ling the operation of said pressure pump, means connecting said pressure responsive means with the line which is supplying high pressure fluid to said motor in the unreversing movement of said ,"14 said valve momentarilyas said motor moves into the governor controlled range.

15. In a propeller pitch control mechanism, a

double acting fluid operated'pitch changing motor, a pump for supplying fluid under relatively low pressure, fluid pipe lines, one leading to one side of said motor and theother leading to the other side of said motor, a speed governor controlling admission of fluid to said motor, having a pilot valve for selectively admitting fluid to said lines, means for operating said pilot valve, a ,re-

. tractible stop fOr preventing movement of said motor by said low pressure fluid beyond a predetermined low pitch position, a high pressure fluid source for retracting said stop to enable said motor to move into reverse pitch position, a pressure responsive means connected into the high pressure fluid line into which fluid is admitted for unreversing said motor, said pressure responsive means controlling said high pressure source, means operative to create a pressure surge in said unreversing high pressure, line, said last mentioned means being controlled by the return of said stop means to its normal operative position and such return of said stop means being controlled by the movement of said motor into its normal governor controlled operating range 16. In a propeller pitch control mechanism, a

double acting fluid operated propeller pitch .for controlling the'admission of low pressure fluid to operate said motor over a normal pitch changing range, a retractible stop for limiting the movement of said motor in a predetermined low pitch position, fluid lines leading to opposite sides of said actuating member,said governor having a pilot valve selectively controlling the admission of fluid to said lines, means for controlling said source of high pressure including a pressure responsive device communicating with the unreversing fluid line, said pressure responsive means being responsive only to substantially the full line pressure of said high pressure source, and

mean in said unreversing line controlled by the movement of said stop means into operative position behind said fluid actuated member for obstructing the flow of fluid in said unreversing line to create a full line pressure surge therein.

17. In combination, a propeller having reversible pitch blades, a fluid operated pitch changing motor therefor, a source of low pressure fluid,

a governor controlling the admission of said low pressure fluid to said motor to vary the pitch of said blades in a normal intermediate range of supplying fluid under a higher pressure than said governor controlled fluid for moving said blades beyond said normal range into reverse pitch position and from said reverse pitch position back into said normal range, and control mechanism for controlling said pump including an electric motor for driving said pump, manually operative mean for energizing said-electric motor for reversing and unreversing, means for maintaining the circuit for said electric motor energized fo1- lowing initiation of blade changing movement in either direction by said manual means, a cut-out switch in said electric motor circuit and means responsive to movement ofsaid fluid motor into reverse pitch position and also, during unreversing movement of said fluid motor, into the governor controlled range for operating said cut-out switch to interrupt said electric motor circuit.

.. 1.8., In a propeller. pitch control mechanism,. a

double acting fluid'. operated propeller pitch changing motor. including a reciprocable actuating member, means for supplying low pressure fluid to opposite sides of saidactuating member including a pump and fluid lines connectingthe discharge of said pump to opposite sides of said member, a speed governor selectively controlling the admission of fluid to said lines to control the pitch of the propeller in anormal range of pitch variation, a retractible low pitch limit stop for limiting the movement of said actuating member in a pitch decreasing direction, means for moving said actuating member beyond said low pitch limit stop including a high pressure fluid "pump for supplying highpressure fluid to said motor, means associated with said governor for selectively admitting said high pressure fluid to said fluid lines, manually operable means for starting said high pressure pump and maintaining the latter inoperation, pressure responsive means communicating with said lines for controlling the operation of said pump, and means for creating a pressure surge in said unreversing line to operate said pressure responsive means and stop said pump, said last mentioned means including a valve in said unreversing line for creating a pressure surge at a predetermined position of said actuating member for stopping said high pressure pump and returning said motor to governor control.

19. The combination as claimed in claim 15 in which the surge creating means comprises a valvein the line leading to one side of said motor which is momentarily closed during the retrac-' tion and the return movement of said stop means and in which a ball check valve is provided in parallel to permit flow of fluid in said line during the closure of said valve during reversing movement.

20. The combination claimed in claim 18 in which the low pitch limit stop includes a movable detent which normally limits the movement of said actuating member in a pitch decreasing direction and in which a spring biased member is provided to hold said stop means in position to prevent release of said stop when said low pressure fluid is acting in said lines, and piston means for moving said spring biased member against the action of its spring to permit said stop to be retracted when 'said high pressure fluid pump is started, a valve controlled by said spring biased member for momentarily closing, during both reversing and unreversing movement of said memher, the line leading to the side of the said actuating member vented during reversing, and valve means parallel with said first mentioned Valve for venting said side of said actuating member during reversing movement.

21. In combination, a propeller having reversible pitch blades, fluid operated pitch changing mechanism therefor including a reciprocable pressure responsive member and fluid lines communicating with opposite sides of said member, a governor controlling the admission of low pressure fluid to said lines to vary the pitch of said blades in a normal range of pitch variation, a pump for supplying fluid to said member at a higher pressure than said governor controlled pressure for moving said blades beyondsaid normal range into reverse pitch, a solenoidvalve controlling the admassion of said higher pressure fluid to said fluid lines, manually ,controlled switch mechanism for energizing said solenoid and starting said pump to supply fluid to said member and reverse the pitch or said blades,

means for stopping said pump when saidv blades reach the limit of their reversing movement, and means which is energized by the closing of said switch to initiate a reversing operation for mainhigher pressure than said governor controlled pressure for moving said blades beyond said normal range into reverse pitch, a solenoid valve controlling the admission of said higher pressure fluid to said fluid lines, manually controlled switch mechanism for energizing said solenoid and starting said pump to supply fluid to said member and reverse the pitch of said blades, means for stopping said pump when said blades reach the limit of their reversing movement, a second switchmeans for unreversing said blades including a manual switch for starting said pump, a relay energized by said second switch means, said relay having contacts for interrupting said solenoid circuit and for completing a holding circuit for said relay, a pressure responsive cutout controlling said holding circuit communicating with the pressure fluid line for unreversing said blades, and means controlled by said member for creating a pressure surge in said unreversing line when said member has returned said blades to said normal range.

23. A propeller having controllable pitch blades and a pitch changing motor, a governor controlling the operation of said motor to control the propeller blade pitch within .a predetermined range, limit stops cooperating with said motor to define said range and prevent movement of said blades under governor control beyond range, manually controlled means having a connection with one of said stops and with said governor for disabling said one of said limit stops and said governor, and forming a connection with said pitch changing motor for manually controlling the pitch changing motor to move the blades outside of said predetermined range, and manually controlled means coacting with said first mentioned manually controlled means for forming a connection with said motor for controlling the pitch changing motor to return said blades to a position within said range from without said range, means connected with said last mentioned manually controlled means for inactivating said last mentioned manually controlled means, mechanism including means actuated by movement of said motor as said blades move to a position within said range from without said range, cooperating with said one stop to automatically restore said one stop and having a connection with said inactivating means to automatically actuate said inactivating means and thereby inactivate said last mentioned manually controlled means when said-propeller blades in returning into said predetermined range pass the position determined by said one stop, and

means responsive to inactivationof said last mentioned manually controlled means automatically 17 pitch blades and having a normal pitch range, a reverse pitch range, a reverse pitch position at the extreme end of the reverse pitch range, a fluid operated pitch changing motor therefor, a source of fluid pressure, a governor controlling admission of fluid from said source to said motor to vary the pitch of the blades in said normal operating range, means connected with said governor for disabling the same, means connecting said source with said motor and said governor disabling means in said reverse pitch position including means directing fluid from said source to said motor to maintain said blades in said reverse pitch position, and directing fluid to said governor disabling means to disable said governor, a separate source of fluid pressure and means, including said disabling means, for directing fluid from said separate source to said motor to move said blades from said reverse pitch position into said normal range, and means actuated by the unreversing movement of said motor at a preselected point in said unreversing movement for automatically interrupting the supply of fluid from said separate source to said motor and automatically restoring control to said governor.

25. In combination, a propeller having variable pitch blades and having a normal pitch range, a reverse pitch range and a reverse pitch position at the extreme end of the reverse pitch range,

a fluid operated pitch changing motor therefor, 30

a source of fluid pressure, a first relief valve connected with said source to limit said pressure, a governor controlling admission of fluid from said source at said limited pressure to said motor to vary the pitch of said blades in said normal operating range, means connecting said source at said limited pressure with said motor in said reverse pitch position including means directing fluid from said source at said limited pressure to said motor to maintain said blades in said reverse pitch position, a second relief valve connected with said source and set to relieve at a pressure higher than said first relief valve, means connected with said first relief valve disabling the same to thereby provide a second fluid pressure, and means, including means actuated by said second fluid pressure disabling said governor, for directing fluid at said second pressure to said motor to move said blades from the reverse pitch position into said normal range, and means actuated by the unreversing movement of said motor at a preselected point in said unreversing movement for automatically interrupting the supply of fluid at said second pressure to said motor and said governor disabling means and automatically restoring control to said governor.

NELSON R. RICHMOND.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,402,065 Martin June 11, 1946 2,406,196 Chilman Aug. 20, 1946 2,423,191 Kopp July 1, 1947

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