US2343416A - Variable-pitch propeller - Google Patents

Description

March 7, 1944. c. KELLER VARIABLE-PITCH PROPELLER 5 Sheets-Sheet 1 Filed May 10, 1940 Fig.1.

a an .I H m m Mimi: :1 a n 2 2 E 7 .r 1. 1 2 5 727 1 M 66m $4 a 2. o M Mam WW 2 o 9 oo 00 w. my n March 7, 1944. c. KELLER VARIABLE-PITCH PROPELLER Filed May 10, 1940 3 Sheets-Sheet 3 III/III Patented Mar. 7, 1944 VARIABLE-PITCH PROPELLER burt Keller, Zurich, Switzerland, assignor to Es cher Wyss Maschinenfabriken Aktiengesellschaft, Zurich, Switzerland, a corporation oi Switzerland Application May 10, 1940, Serial No. 334,443 In Switzerland June 22, 1939 Claims. (Cl. 170-,-163) This invention relates to means for controlling hydraulically-actuated variable-pitch propellers, especially propellers for aircraft, the pitch-adjustment of which is not confined to a normal predetermined range but extends also beyond the limits of such range.

In order to keep the driving engine of propellers working at a constant speed, governing devices, which permit the pitch of the propeller blades to be adjusted within a normal predetermined and comparatively small range of about to 30 are provided. In the case of propellers for aircraft, however, it is also necessary under certain conditions of flight to adjust the blades into more extreme positions, beyond this normal range of pitch-adjustment. Such positions are the feathered position (in which the blades are turned into the direction of flight) and the brak.

ing position. Adjustment of the propeller blades into the feathered position becomes necessary in the case of multi-engined aircraft when one of the engines cuts out. By bringing the blades of the propeller allotted to the inactive engine into the feathered position this propeller can be prevented from responding to the wind, due to the motion of the plane, and so driving the defective engine, to the possible detriment of the latter. The blades are brought into the braking position when it is required to obtain a negative propeller thrust, so as to reduce speed when diving or to reduce the length of the landing run.

The two extreme blade positions just discussed always involve a certain amount of risk when flying, if they cannot be attained with suflicient rapidity or without a deliberate action on the part of the pilot. In order to satisfy these requirements, devices have already been proposed to cause the propeller blades, from a particular position onwards, to offer a greater resistance to adjustment, so that a greater force has to be overcome, than is the case of the normal range of pitch-adjustment. In known constructions of this kind it has been necessary to provide additional means, which have to be operated separately by the pilot in order to adjust the blades beyond the normal predetermined range into more extreme positions. This requires a further manipulation on the part of the pilot and also involves an increase in weight, as well as a more complicated adjusting device which takes up a comparatively large amount of space.

The object of this invention is to provide a controlling device of the kind first referred to which will permit the propeller to be adjusted beyond the predetermined pitch-range into the braking position, on the one hand, and into the feathered position, on the other hand, each by the use only of the same means as are employed for varying the pitch within the limits of the normal predetermined range. By the means of the invention a pitch adjustment over a range of about can be obtained with a minimum number of components, so that weight is reduced to a while the mechanism is very reliable in operation, of compact and simple construction and is easy to manipulate and to service. At the same time, the construction is such as to ensure with certainty that no adjustment of the blades beyond the predetermined normal pitchrange can take place inadvertently or through incorrect functioning of the system or in any way except by intentional manual operation. Thus, movement of the propeller blades into the braking position or into the feathered position is impossible without deliberate action on the part of the pilot.

The present invention meets the above requirements by providing at least one control member adapted to interrupt the supply of pressure medium to the pitch adjusting mechanism proper, when a limit of the predetermined range of pitchadjustment is reached, further actuation of the said blade adjusting devices for the purpose of moving the blades beyond the said predetermined range into more extreme positions being then possible only after a. higher hydraulic adjusting pressure is developed to open an auxiliary valve member for the hydraulic pressure medium.

The controlling device according to this invention also includes a governing member operated by the action of centrifugal force and a changeover member which controls the movements of the blades into their feathered and braking positions, these members being connected to each other in such a way that they can be adjusted by a deliberate operation on the part of the pilot to provide an augmented supply of pressure fluid at a higher pressure. In a controlling device of this kind, therefore, a single external and deliberate action enables a-change-over to be made from the normal working range into either one of the extreme terminal positions of the blades.

The accompanying drawings show, partly in a simplified mode of representation, and by way of example, constructional embodiments of the subject matter of the invention. In these drawmgs,

Fig. 1 is a partial axial longitudinal sectionthrough a variable-pitch propeller for aircraft, to which the present invention is applied, the

2 parisoithsdevicecontrollingthepitchottbe beingillustratedinthepositionwhichthey assumewhenthepropell rrunsatapredeterminednormalspeed.

Hgaflandtshowthepositionsotsomeotthe partsotthepitcheontrollinsdevicewhmthe propellerisrotatingataspeedaboveandbelow, respectivelmtbenmmalnumberoirevoiutions.

Fig.4showsthepositims whichsomcoithe to be varied Fig. 7 is a section on the line Fig. 6.

Fig.8 shows a-detail of Fig. 1 on an enlarged scale.

Fig. 9 shows a second constructional ment of the pitch controlling device.

Fig. 10 shows in a transverse vertical section a modification oi a detail.

Fig. 11 showsinapartialaxiallongitudinal section through a variablmpitch propeller a further modification oi a detail.

Referringtothedrawingaldenotesahuh casing,whichisflxedtoadrivingshaft P. This casinglsupportsthepropellerbladesl (only one ofwhichisahown) and, atthe sametime,it encloses allthemovingpartsoi'thepitchadlusting mechanism proper. 3 denotes a central. hollow guide tube made in two parts (which, in this case, permits 01 flring through the hub), andonthistube3isflxedapiston4,onwhich a double-acting control cylinder is axially movable. Coupling links 6 connect the cylinder 5 with the respective pins I of the several blade holders 3. By means or the parts 6, I, 3, therefore, longitudinal movement of the control cylinder 5 is converted into rotary motion'oi the propeller blades 2 which are supported in the hub. The blade holders I are each supported byathrustbearinglandradialbearings iflin thehubcasingl. Thepistonlwhichisflxed relatively to the guide tube 3 forms, together with the movable control cylinder I, a servomotor.

The supply and exhaust oi the pressure medium (preferably oil under pressure) to and from the cylinder chambers l3, M, on opposite sides or the piston 4. are effected through two independent longitudinal passages ll, 12 formed in the walls of the central guide tube 3. According tothesenseinwhichtheblades aretobeadjusted. the chamber I3 is connected, in a manner hereinafter more fully described, to a source of oil under pressure, while the chamber It is connectedwithanoiloutlet. orviceversa. This produces endwise movement of the cylinder I and, therewith, a change in the angle of incidence of the blades 2. A spline Ii prevents the axially movable control cylinder I from rotating relativelytothehubcasinz I.

For the purp se or hydr ulically limiting the stroke oi the cylinder I and, therewith, the rotarymovementoithescrewblades I,withina predetermined range'oi pitch-adjustment, a controlrod llisprovided. 'Ihisrodisarrangedwith its axis parallel with the axis of the propeller and, over parts of its length, it'has groups or series of grooves il, ll. It passes freely through VII-VII 01 .thepiston landpartakesinthearialmovement oi the cylinder 3. A part II or this control rod ",iyingbetweenthetwoglblltlsdgromes l1," ismadesmooth; thatistosay,ithasnogrooves init. Thelmgitudinalpassage l2 inthe guide tube 3communicateswithaport ilinthepiston l, whichis also provided with other ports II and 22 of which theportil opens into the chamber Motthecontrol cylinder I.

Commimication between the ports 23 and 2| is controlled bythe control rod II, the groovedpart l3 of which enables communication to be established whereas the smooth part l3 interrupts such communication.

23 denotes an overflow valve which is loaded by a spring 34 and, when in the open position, establishes another path of communication between the ports 23 and 2|. A spring-loaded nonreturn valve 25 controls communication between the cylinder chamber H and the port 20. Communication between the ports I! and 22 is eontrolled by a collar-like part 3| 0! a locking deembodivice 21 whichiseonstructedintheiorm ofa double piston. This locking device 21 is loaded by a spring 23, which tends to force it against the inner wall of the control cylinder 5, so as to prevent the latter irom moving longitudinally. The longitudinal passage II in the guide tube 3 communicates with a port 23 in the piston I which also has other ports, designated 30 and ll, of which the port 3| opens into the chamber i3 in the control cylinder 3.

Communication between the passages 20 and 33 is likewise controlled by the control rod it and in a manner similar to that described with reference to the ports 23 and 2|, that is-to say, the grooved part II of this control rod enables communication to be established between the ports as and 33 while the smooth part I! interrupts such communication. 3! denotes an overflow valve, which is loaded by a spring 33 and, when in the open position, establishes another path of communication between the ports 29 and 30. A spring-loaded non-return valve 34 controls commimication between the chamber l3 in the control cylinder 5 and the port 29. Communication between the ports 3| and 3| is controlled by a second collar-like part 26 of the locking device 21. The collar-like part 23 is pierced by a flne bore 3 while the collar-like part 3! is pierced by aflnebore 31. Itisalsotoberemarkedthat the springs 24 and 33, which respectively load the overflow valves 23 and 32, are of such strength,

that they only allow these valves to open when the pressure of the liquid in the ports 23 and ll, respectively, is considerably greater than that required to adjust the propeller blades within the normal predetermined range of pitch adjustment.

The means controlling the admission of a liquid under pressure to the longitudinal passages II and I2 and the outlet of such liquid from these passages, respectively, which means serve also to keep the speed of the engine driving the pro- 4 peller constant under greatly varying outputs, comprise pendulum levers II, which, when rotated, establish a state of equilibrium with a force exerted by a spring 4!. The pendulum levers ll are pivoted at 43 in a cylindrical casing 43 which is rotated by a cable transmission 4! from the shaft l driving the propeller. On the casing 43. are provided two stops l ll for the pendulum levers II. The latter are operatively connected to a governing spindle 49 adapted to be displaced axially by these levers 4|.

-""a balanced piston valve.

According to the position of spindle 49 fluid under pressure for eifecting adjustment of the blades 2 is allowed to flow into either one and simultaneously to be discharged from the other of the above mentioned longitudinal es II and I2. The axial displacements of the governing spindle 49 are transmitted to a cup 48 (shown on an enlarged scale in Fig. 8) povided at its upper end with an extension 48 which is adapted to cooperate with two stops 41 and 48. The stop 48 is designed as a threaded piston engaging into a corresponding thread 99 of a surrounding hood 9|. The latter is fixed relatively to the piston 48. The stops 41 and 48 prevent the governing spindle 49 from being moved, within the normal working range of the governing mechanism,.by the action of centrifugal force or by the spring 42, to a greater extent than corresponds to the stroke prescribed for this spindle.

To a shaft 82 formed integral with the piston 48 is fixed a cable pulley 58 worked by a cable 94 which passes also over a pulley 88. The latter can be rotated by means of a hand lever 58 by a deliberate operation on the part of the pilot By rotating the piston 48 by means of the hand lever 58 and the cable transmission 55, 84, 58, the force exerted by the spring 42 can be varied. This enables the centrifugal force exerted by the levers 4| to be brought into equilibrium with the force of the spring 42 in the mid-position of the governing spindle 49 for different numbers of revolutions of the casing 48. Thus the normal speed of the propeller can be adjusted to any desired value. The extension 48 of the cup 48 is so constructed, that within the normal working range of the control device, within which range the device acts as a centrifugal governor, the stop 4'! and the piston 48 permit unhindered working of the governing spindle 49 under the influence of the pendulum levers 4|.

The lower part of the governing spindle 49, as depicted in the drawings, is furnished with annular grooves 62, 89, 84, 85 and 88 and packing surfaces 61 81, 88, 69, I and 'Il forming in effect, With the help of these parts an increased fluid supply at an increased pressure is afforded by two pumps 12 and 18 when required (and in a manner to be more fully described hereinafter). This augmented supply is delivered to the longitudinal passages H or I! of the tube 8. The pumps I2 and 18 are housed in the same casing as the governing spindle 49 and take oil from a common suction branch 14, which may be connected either to the lubricating system of the engine or to a separatereservoir (neither of such sources being shown in the drawings). The pump 12 delivers into a pressure duct having two branches 1! and 18, while the pump 18 delivers into another pressure duct with two branches l1 and 18. An overflow or loaded relief valve 19, controlled by a spring 19 enables the pressure in the branches i and 18 to be kept constant; when the pressure rises above a prescribed value this valve permits parts of the fluid under pressure to flow of! directly into the suction branch 14.

The same relief valve 19 can also be lifted by a deliberate action on the part of the pilot through a system of transmission rods and levers 80, in which case the whole of the liquid delivered by the pumps 12 and 18 can then flow directly into the suction branch 14, so that the hydraulicallyactuated mechanism for varying the pitch is set out of action.

The relief valve I9 is rigidly connected to a piston 8|, having two faces 82 and 88, which are of equal area and which do not communicate with each other spatially. Into the space bounded by the face 82 opens a channel 84, while a channel 88 opens into the space bounded by the piston face 88. A spring-loaded non-return valve 8'! permits of an overflow of liquid from the branch 11 into the branch 18, while preventing reverse flow, from 18 into II. The references 85 and 85 denote two conduits effecting a connection between the bore in which the governing spindle 49 is lodged and the longitudinal passages II and I2 of the tube 8, respectively.

The hand lever 58 for actuating the cable transmission 82, 94, has three ranges of movement 88, 89 and 98 indicated on a plate 92, as shown in Fig. 6. Two springs 93 and 94 tend to hold the lever 58 in its mid-position. The range of movement 88 corresponds to the normal working range of the controlling device; within this range of control the propeller blades can only be adjusted within a predetermined normal range of pitch-adjustment. Within this range the lever 58 can be moved by hand into any desired intermediate position, in which it is self-locking. The range of movement 89 corresponds tothat extreme position of the governing spindle 49, in which it initiates shifting of the propeller blades into the feathered position, while the range 99 corresponds to that position of the said governing spindle in which it initiates shifting of the propeller blades into the braking position. In order to shift into the ranges of movement 89 and 99, it is necessary to actuate a press button 95. This retracts a spring-controlled pawl 96 in a radial direction,

through a distance equal to the radial length of a shoulder 91 or 98 of the plate 92. In the ranges of movement 89 and 99 the lever 56 is not self locking. If it be released, the springs 93 and 94 tend to bring it back into its mid-position.

The above described controlling deuice works in the following manner:

In Fig 1 the various parts are shown in the position which they assume whenthe propeller is running at the normal predetermined speed. The governing spindle 49 is in its mid-position, in which the stops 41 and 48 do not affect its movement in any way and in which the annular 5o groove 68 connects the branch 15 and the annular groove 62 connects the branch 18 directly with the suction branch 1.4. The release valve 19 and the non-return valve 81 are closed. The fluid delivering pumps 12 and I3 circulate the pressgre fluid in closed cycles, so that none of it is delivered either into the longitudinal passage II or into the passage l2. The condition just described (and characterised by the short-circuiting of the pressure fluid) are those which, in practice, are likely to be maintained for the longest periods, as, for instance, in the case of commercial aircraft, in steady flight. Such a short-circuited condition with regard to the pressure fluid can be produced at any time by lifting the release valve 19, for which purpose the system of levers and rods must be deliberately manipulated by the pilot.

If the speed of the propeller and of the engine which drives it rise above a predetermined normal value. the centrifugal force acting on the levers 4| overcomes the force exerted by the spring 42 and the parts then assume the position shown in Fig. 2, in which the governing spindle 49 has been shifted, compared with the position shown in Fig. 1, somewhat upward, the stops 4! and 48 still having no restraining influence on its movement. The surface ll of the governing spindle ll now closes the branch I! of the pressure duct or the pump 12, while the pump 13 is short-circulted, as before, through the annular groove-OI of the spindle. The pressure fluid passes from the branch 16, through the annular groove 04 and the conduit 8!, into the longitudi-- nal passage ll. At the same time, the annular groove II allows pressure fluid to escape from the longitudinal passage l2 and through the conduit Il into the suction branch 14. These movements of the pressure fluid cause the propeller blades 2 to be adjusted to a steeper pitch, the result being that the propeller absorbs more power. Consequently, the driving engine is slowed down until it again reaches the normal predetermined speed, thus bringing the governing spindle 49 back again into its mid-position.

The adjustment of the blades 2 to a steeper pitch is effected in the following manner: The oil under pressure admitted to the longitudinal passage II of the tube 3 passes through the port ll and by way of the grooves II in the rod is, into the port 30 and thence through the port 3| into the chamber, l3 in the control cylinder 5. This latter will, therefore,'be moved upward, liquid under pressure passing out of the chamber l4 past the opened non-return valve 25 into the valve 81, so that the volume of liquid delivered by the pump I3 is added to that delivered by the pump I2. The pressure prevailing in the annular groove it reacts through the channel 84 upon the surface 82 of the piston ll. The action of the spring 18 on the release valve II is thereby supplemented. so that a greater pressure is now required to open this valve.

Thus, when the additional source of pressure 13 cuts in, its pressure will be brought to bear on the release valve 19, which determines the magport Ill and thence into the longitudinal passage it. Since the control rod It takes part in the longitudinal movement of the cylinder 5, its smooth part I! will, in the course of the longitudinal movement in question be brought into a position in which it will interrupt communicationbtween the ports 29 and 30. This corresponds to one of the terminal positions of the normal predetermined range of pitch-adjustment. As soon as this interruption has taken place, the spring 28 can force the locking device 21 outwards, as the flne bore 31 in the part 15 of the device 21 allows the enclosed oil to escape. Thus the. control cylinder 5 is now locked. A similar locking action also takes place when the supply of oil under pressure through the longitudinal passage II is interrupted for any reason, at any time. Further displacement of the cylinder I upward, beyond the positioned mentioned, so as to bring the blades into the fully-feathered position for example, is only possible when by a deliberate action on the part of the pilot on the lever 5 the governing spindle 49 has been shifted into the position in which pressure medium at a higher pressure than is needed for the pitchadjustment within the above menloned normal predetermined range is supplied to the longitudi nal passage II.

If the propeller blades 2 are to be adjusted into the feathered position, the governing spindle is must be brought into the position shown in Fig. 4, and if the propeller blades are to be adjusted into the brak ng position said spindle 49 must be moved into the position shown in Fig. 5. On movement of the piston 48 into the position shown in Fig. 4, the stop 41 carries with it the cup 48 and this, in its turn, carries with it the governing spindle 4! until the pendulum levers ll are arrested by the stop ll When the various parts are in the positions shbwn in Fig. 4, the action of the pendulum levers II is eliminated and the spindle 4! works simply as a changeover valve (with no automatic restoring action), its pack ng surface Bl shutting oil the branch II and its packing surface H shutting off the branch II. Closure of the branch ll results in the liquid delivered by the pump 13 opening the non-return nitude of the fluid presure in the qmtrolling device. Consequently the pressure in the branch It will rise to a higher value than it can attain when only the spring 18 acts on the valve I8.

Oil under pressure passes through the groove 64 and the conduit into the longitudinal passage ll, while oil in the longitudinal passage I2 is released through the conduit 85 and the annular groove 65 into the suction branch IA. The oil under pressure, now delivered through the passage II to the mechanism of adjustment for the propeller blades flows under increased pressure and in greater volume, thus eifecting rapid movement of the blades 2 into their feathered position.

When the parts are in the position shown in Fig. 5, which position they assume when intiating adjustment of the propeller blades to the braking position, the extension 48 on the cup 46 bears against the stop piston 48, while the pendulum levers 4| are arrested by the stop The packing surface 61 now shuts oil the branch I8 and the packing surface Ill shuts oi! the branch 15, so that the volumes delivered by the pumps 12 and 13 are added together in the branch 16. The pressure prevailing in the annular space 64 reacts through the channel 88 upon the face 83 of the piston 8|, The pressure of the additional pump 13, therefore, again takes effect on the release valve 19, which determines the magnitude of the fluid pressure in the controlling device. Thus theclosing force acting on this valve is increased, so that a higher pressure is now required to open it. The branch 16 is connected, through the annular grooves 54 and the conduit 85 with the passage i2 and the passage H is connected through the conduit 85 and the annular groove 63 with the suction branch ll. Under the influence of the increased liquid pressure and with the increased volume delivered the propeller blades 2 are rapidly adjusted into the braking position, in which they remain as long as the hand lever 56 is held in the range of movement ll.

When the higher pressure of the liquid supplied, in a manner above described, to the passage is capable of opening the overflow valve 32, the liquid can flow through this valve out of the port 29 and, by-passing the control rod It, can enter the port II, with the result that the locking device 21 is moved inward far enough to permit the pressure medium to flow from the port 30 into the port 3| and so into the cylinder chamber ii. The resulting further movement of the control cylinder 5 upward, is, owing to the higher pressure of the actuating liquid, more rapid than in the case of the normal predetermined range of pitch-adjustment. The longitudinal movement of the cylinder 5 to the left can be finally arrested by a stop 5 and if, when this extreme position is reached, the pressure in the passage ll be also reduced, the device 21 will lock the cylinder 5 in that position also.

If, on the other hand, the speed of the propeller and its driving engine drop below a predetermined figure, the force exerted by the spring 42 overcomes the centrifugal force acting on the pendulum lever i and the parts then assume the position shown In Fig. 3-. The surface I0 of the spindle 40 then shuts oi! the pressure branch from the suction branch 14. The pump 13 is still short-circuited through the annular groove 02. Pressure oil can now pass through the annular groove 04 and the conduit 30*, from the branch I0 into the passage I2 while, through the conduit 00 and annular groove 03 pressure oil is released from the passage II to pass into the suction branch 10. The result of these movements of the pressure fluid is to bring about a reduction in the pitch or angle of incidence of the propeller blades, so that the power absorbed by the propeller decreases and the engine driving same therefore speeds up again to the predetermined number of revolutions causing the pendulum levers I to return the governing spindle. 40 to its mid-position.

The pressure 011 supplied to the longitudinal passage I2 passes from this into the port 20 and thence, past the grooves I3, into the port 2 I and, after the locking device 21 has moved inward, through the port 22 into the cylinder chamber II. The cylinder 0 is thus moved downward until the smooth part I0 of the rod I0 masks the ports 20 and 2|. In order to permit further downward movement of the cylinder 0, from the position just described, an increase in the oil pressure must be brought about by a deliberate shifting of the hand lever 50 into the range 00 or so, the increased oil pressure opening the overflow valve 23, whereupon the oil under this higher pressure, passes from the port 20, through the opening uncovered by the said valve 23, into the port 2I and thence through the port 22 into the chamber Il. The other reactions which take place should be clear from what has been stated, at greater length, above, so that any more detailed description of them at this stage would be superfluous.

The controlling device described has the advantage that it does not permit motion of the propeller blades 2 beyond a predetermined normal range of pitch-adjustment without deliberate manipulation of the hand lever 50. On the other hand the propeller blades 2 return automatically and positively from the more extreme positions to the normal range of pitchadjustment when the lever 50 is released. All the operations are controlled by the governing spindle 49, which acts sometimes as a speed governing device and sometimes only as a changeover member which can be actuated manually pressure source or pump III which supplies the fluid pressure required for adjustment of the propeller blades within the normal range of pitchchange-over piston "I being held in such a case in the mid-position shown in Fig. 9. On the rod 10 of the change-over piston III are mounted two plates 0 and IIIwhich serve to compress the spring I01. When the spring I01 is compressed by the plate H0, or III, the change-over piston IOI cuts off the direct passage of the fluid de livered by the pump I00 to the suction branch II! and, consequently, the delivery of the pump I06 is added to that of the pump I 00. .The fluid under pressure can now get past the non-return valve H3 into the pressure duct Ill. An over-' fiow or release valve 0 determines the magnitude of the system. I

To thelever I02 is jointed a rod 0, which is articulated in its turn to a lever III having its fulcrum at H6. The lever II'I carries a sleeve H8 adapted to be pressed against a plate I20 which is fixed to a rod I2I arranged immediately below the shaft of the piston I03. The reference I22 denotes a spring hearing at one end against a plate I23 also fixed to the rod I 2| and at the other end against a plate I24 fixed to the shaft of the valve III. When the lever I02 is deliberately operated by the pilot so as to swing downward about its pivot I00, the shaft of the piston I03 is pressed against the rod I2I whichis forced in its turn against the shaft of the valve II5. Again, when the said lever I02 is swung .upward about its pivot I00, the sleeve lI3 is pressed ,againstthe plate I20 of the rod I2l.' In both cases the spring I22 is compressed, whereby the loading on the valve m is increased.- This involves a rise in the liquid pressure within'the controlling device, so that a greater volume .of

J pressure medium and an increased hydraulic of flow and a more symmetrical arrangement,

and which then enables more extremepositions I of the blades to be reached- The const ictional embodiment shown in Fig. 9 differs from the one already described mainly by the fact that a governing member 09, which is moved by the action of pendulum levers I00, and a change-over member IOI, which enables the blades to be adjusted into their feathered and braking positions, are constructed as two separate units, though housed in the same casing I00. The members 90 and MI are coupled by a lever I02 and can be adjusted by a threaded piston I03 which is operatively connected with this lever and has a pulley I00 mounted on it for a cable transmission adapted for manual operation by a hand lever I09. By an intentional manipulation of this lever I09 an additional source of pressure,

in the form of a pump I 00, can be added to the minal position (e.

' only. when the one limit pressure are available for the adjustment of the propeller. blades beyond the normal predetermined range of pitch-adjustment.

In order to secure greater cross sectional areas two or more control rods arranged parallel with the axis of the propeller, moving with the axially displaceable cylinder and passing through the stationary piston maybe provided, as shown in Fig. 10 in a transverse vertical section. In this figure the reference I30 denotes the displaceable cylinder and BI the propeller shaft'made in two Darts whilst the references I32 and I33 denote 7 two control rods and the references I 34 and I3! locking means for the cylinder I30.

Under certain circumstances it sumcesjfor the blades to be adjustable to only one-extreme terg., to the (braking position). In such a case it is necessary, if the control member be constructed, as shown in Fig. 11, in the form ofa rod I36 with two groups of grooves I3! and I "and a smooth portion I30 between them, for this smooth portion I30 to come into action normal range of pitch-adjustment is reached. When the other limit of this range is reached. movement of the axially. displaceable cylinder HI, and thus of the means proper effecting the adjustment of the vented by? a stop The invention blades beyond this limit is pre- I42 on the fixed piston I00. mavalso beapplied to ships" of the predetermined v propellers, to propeller wheels for rotary machines, e. g., blowers and turbines with adjustable rotor blades. and on similar machines.

What is claimed is:

1. In a variable-pitch propeller in combination, a hub, a plurality of blades arranged on said hub for adjustment about their longitudinal axis, means displaceable by the action of a hydraulic pressure medium and comprising a piston arranged coaxially to said hub and a cylinder coaxialiy dispiaceable relative to said piston and operatively connected to the blades for efiecting the adjustment thereof, ports in the piston for the admission and exhaust or hydraulic pressure medium to and from the cylinder chambers on opposite sides of this piston, a rod with two groups of grooves and a smooth part between these latter, said rod being mounted for movement with the cylinder in a directionparallel to the axis of the propeller shaft and passing through said piston, the admission and exhaust of pressure medium through the ports in the piston being permitted by the groups of grooves in the control rod or cut-oi! by the smooth part thereof according to the relative position of the piston and the displaceable cylinder, and auxiliary valve members for the hydraulic pressure medium allowing of by-passing said control rod for the purpose of supplying further pressure medium to the one or the other or the cylinder chambers in order to effect a further adjustment of the blades, any by-passing of said control rod being possible only after increased hydraulic adjusting pressure has been able to open one of said auxiliary valve members.

2. In a variable-pitch propeller in combination, a hub, a plurality of blades arranged on said hub for adjustment about their longitudinal axis, means displaceable by the action of a hydraulic pressure medium and comprising a piston arpressure to said blade-adjusting means, a member determining the magnitude of the hydraulic pressure acting upon the blade adjusting means, a

governing member operated by the action of centrifugal forces and a change-over member, both these members controlling the distribution of the hydraulic pressure medium to said bladeadjusting means, a further member adapted to interrupt the supply of hydraulic pressure medium to said blade-adjusting means when a limit of a normal predetermined pitch range is reached. auxiliary valve means for the hydraulic pressure medium, which permit a further actuation of said blade-adjusting means for the purpose of moving the blades beyond that predetermined pitch range only after increased hydraulic adlusting pressure has been able to open said auxiliary valve means, and means connecting said governing member and said change-over member in such a way that they can be adjusted by a deliberate manual operation for the purpose of connecting said additional source of hydraulic pressure to said other source'of hydraulic pressure, said member determining the magnitude of the hydraulic pressure acting on the bladeadjusting means being thereby acted upon in such a way as to increase the hydraulic pressure, so that a greater quantity of pressure medium and an increased hydraulic pressure are available for ranged coaxially to said hub and a cylinder 00- axially displaceable relative to said piston and operatively connected to the blades for eifecting the. adjustment thereof, ports in the piston for the admission and exhaust of pressure medium to and from the cylinder chambers on opposite sides of this piston, a rod mounted for movement with the cylinder in a direction parallel to the axis of the propeller shaft and passing through said piston, the admission and exhaust of the pressure medium through the ports in the piston being controlled by said rod in dependence on the relative position of the piston and the displaceable cylinder, and spring-loaded overflow valves arranged in said piston and which, when the admission of pressure medium to the cylinder chambers has been shut ofl by the conol rod and after the pressure of the hydraulic medium has been increased, open to allow pressure medium to by-pass the control rod and to flow into a chamber of the displaceable cylinder on the one or the other side of the piston, so as to producea further movement of the cylinder and thus a further adjustment of the propeller blades.

3. In a variable-pitch propeller in combination, a hub, a plurality of blades arranged on said hub for adjustment about their longitudinal axis,

adjusting the blades beyond the said normal predetermined pitch range.

4. In a variable-pitch propeller in combination, a hub, a plurality of blades arranged on said hub for adjustment about their longitudinal axis, means displaceable by the action of a hydraulic pressure medium and operatively connected to said blades, an operation of said means eflecting ,an adjustment of the blades and thus a variation of the propeller pitch, a source of hydraulic pressure supplying liquid under pressure to said blade-adjusting means, an additional source of hydraulic pressure also adapted to supply liquid under pressure to said blade-adjusting means, a member determining the magnitude of the hydraulic pressure acting upon the blade-adjusting means, a governing member operated by the action of centrifugal forces and a change-over member, both these members controlling the ther actuation of said blade-adjusting means for means displaceable by the action of a hydraulic the purpose of moving the blades beyond that predetermined pitch range only after increased hydraulic adjusting pressure has been able to open said auxiliary valve means, means connecting said governing member and said changeover member in such a way that they can be adjusted by a deliberate manual operation for the purpose of connecting said additional source of hydraulic pressure to said other source of hydraulic pressure, and means allowing the pressure of the cut-in additional source of acting on the member determining the magnitude of the hydraulic pressure medium, to increase the hydraulic pressure, so that a greater quantity of pressure medium and an increased hydraulic pressure are available for adjusting the blades beyond the said normal predetermined pitch 5. In a variable-pitch propeller in combination, a hub, a plurality of blades arranged on said hub for adjustment about their longitudinal axis, means displaceable by the action of a hydraulic pressure medium and operatively connected to said blades, an operation of said means effecting an adjustment of the blades and thus a variation of the propeller pitch, a source of hydraulic pressure supplying liquid under pressure to said blade-adjusting means, an additional source of hydraulic pressure also adapted to supply liquid under pressure to said blade-adjusting means, a member determining the magnitude of the hydraulic pressure acting upon the blade-adjusting means, a governing member operated by the action of centrifugal forces and a change-over member, both these members controlling the distribution of the hydraulic pressure medium to said blade-adjusting v means, a common casing housing the governing member and the change-over member, a further member interrupting the supply of hydraulic pressure medium to said blade adjusting means when a limit of a normal predetermined pitch range is reached, auxiliary valve means for the hydraulic pressure medium, which permit a further actuation of said blade-adjusting means for the purpose of moving the blades beyond that predetermined pitch range only after increased hydraulic adjusting pressure has been able to open said auxiliary valve means, and means connecting said governing member and said change-over member in such a way that they can be adjusted by a deliberate manual operation for the purpose of connecting said additional source of hydraulic pressure to said second source of hydraulic pressure, said member determining the magnitude of the hydraulic pressure acting on the blade-adjusting means being thereby acted upon in such a way as to increase the hydraulic pressure, so that a greater quantity of pressure medium and an increased hydraulic pressure are available for adjusting the blades beyond the said normal predetermined pitch range.

6. In a variable-pitch propeller in combination, a hub, a plurality of blades arranged on said hub for adjustment about their longitudinal axis, means displaceable by the action of a hydraulic pressure medium and operatively connected to said blades, an operation of said means etlecting an adjustment of the blades and thus a variation of the propeller pitch, a pump supplying liquid under pressure to said blade-adjusting means, an additional pump also adapted to supply liquid under pressure to said bladeadjusting means, a member determining the magnitude of the hydraulic pressure acting upon the blade-adjusting means, a governing member operated by the action of centrifugal forces and a change-over member, both these members controlling the distribution of the hydraulic pressure medium to said blade-adjusting means, a common casing housing said two pumps and the governing and change-over members, a further member interrupting the supply of the liquid under pressure to said blade-adjusting means when a limit of a normal predetermined pitch range is reached, auxiliary valve means for the liquid under pressure, which permit a further actuation oi said blade-adjusting means for the purpose of moving the blades beyond that predetermined pitch range only after increased hydraulic adjusting pressure has been able to open said auxiliary valve means, and means connecting said governing member and said change-over member in such a way that they can be adjusted by a deliberate manual operation for the purpose of connecting the additional pump to said second pump, said member determining the magnitude of the hydraulic pressure acting on the bladeadjusting means being thereby acted upon in such a way as to increase the hydraulic pressure. 50 that a greater quantity of liquid and an increased hydraulic pressure are available for adjusting the blades beyond the said normal predetermined pitch range.

7. In a variable-pitch propeller in combination, a hub, a plurality of blades arranged on said hub for adjustment about their longitudinal axis, means displaceable by the action of a hydraulic pressure medium and operatively connected to said blades, an operation of said means eifecting an adjustment of the blades and thus a variation of the propeller pitch, a source of hydraulic pressure supplying liquid under pressure to said blade-adjusting means, an additional source of hydraulic pressure also adapted to supply liquid under pressure to said bladeadjusting means, a member determining the magnitude of the hydraulic pressure acting upon the blade-adjusting means, a governing member and a change-over member combined in a single spindle controlling the distribution of the hydraulic pressure medium to said blade-adjusting means, a further member adapted to interrupt the supply of the hydraulic pressure medium to said blade-adjusting means when a limit of a normal predetermined pitch range is reached, auxiliary valve means for the liquid pressure medium, which permit a further actuation of said blade-adjusting means for the purpose of moving the blades beyond that predetermined pitch range only after increased hydraulic adjusting pressure has been able to open said auxiliary valve means, means allowing of shifting said spindle by a deliberate manual action for the purpose of connecting said additional source of hydraulic pressure to said second 'source of hydraulic pressure, and means allowing the pres-;

sure of the cut-in additional source to act on said member, which determines the magnitude of the hydraulic pressure that operates the bladeadjusting means, to increase the hydraulic pressure, so that a, greater quantity of pressure medium and an increased hydraulic pressure are available for adjusting the blades beyond the said normal predetermined pitch range.

8. The combination of a propeller having adjustable blades; a hydraulic cylinder and piston motor connected to adjust said blades through th normal range of pitch adjustment and also through an excess range beyond said normal range, the working space or said motor which tends to move the blades into said excess range having three communicating ports connected in parallel, namely, a normal supply port, a by-pass supply port, and an exhaust flow port; means rendered active by the functional motion of the motor to close the normal supp y port at a p in in the working stroke of the motor corresponding to the normal range of pitch adjustment; a loaded valve in said by-pass port, said valve opening in the direction or supply flow to said working space; a check valve in th exhaust port arranged to open in the direction of exhaust flow; primary regulating means controlling the supply and release of hydraulic fluid to said ports at pressures insuflicient to open said loaded valve; secondary regulating means controlling the sup- .ply of hydraulic fluid to said ports at a pressure sumcient to open said loaded valve; means re- 9. The combination of a propeller having adjustable blades; a hydraulic cylinder and piston motor connected to adjust said blades through the normal range of pitch adjustment and also through an excess range beyond said normal range, the working space of said motor which tends to move the blades into said excess range having three communicating ports connected in parallel, namely, a normal supply port, a by-pass supply port, and an exhaust flow port; means rendered active by the functional motion or the motor to close the normal supply port at a point in the working stroke of the motor corresponding to the normal range of pitch adjustment; a loaded valve in said by-pass port, said valve opening in the direction of'supply flow to said working space; a check valve in the exhaust port arranged to open in the direction of exhaust flow; primary regulating means controlling the supply and release of hydraulic fluid to said ports at pressures insufllcient to open said loaded valve; secondary regulating means controlling the supply or hydraulic fluid to said ports at a pressure sufilcient to open said loaded valve; means responsive to the speed of rotation of the propeller connected to operate said primary regulating means; and manually operabl means having two ranges of action in one of which it adjusts said speed responsive means to modify its controlling action,

and in another of which it suspends the action of said speed responsive means and actuates said secondary regulating means.

10. The combination of a propeller having adjustable blades; a cylinder and piston motor connected to adjust said blades through a normal pitch-varying range and through an additional range in at least one direction, said motor being characterized by dual supply ports leading in parallel to at least one working space, one or said dual supply ports being so arranged that motion of the piston to the end of the normal pitch adjusting range entails closure 01' such supply port, whereby the range in motion oi! the piston may be limited to such normal adjusting range; a loaded valve arranged to control flow through the second 01' said supply ports and adapted to open in the direction of supply flow; a first pump for delivering hydraulic fluid under pressure; a second pump for delivering hydraulic fluid under pressure; pressure limiting means adjustable selectively to limit the pressure of fluid delivery to two intensities, one insuflicient and the other siltflcient to open said loaded valve; and a controller having at least two characteristically diflferent ranges of motion, in one of which ranges it disconnects one pump, adjusts the pressure limiting means to establish the lower intensity and connects the other pump to deliver to said dual ports under control of said pressure limiting means and 01 said controller, and in the other of which ranges it sets the pressure limiting means to establish the higher intensity and connects both pumps to deliver under control of the pressure limiting means to said dual ports,

CURT KEILER.

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