US2007417A - Air propeller with variable pitch - Google Patents

Description

'July 9, 1935. J. AlVAZ 1 AIR PROPELLER WITH VARIABLE PITCH Filed Jan. 2 1935 4 Sheets-Sheet 2 0 Q E W Z a J l iulll July 9, 1935.

J. AIVAZ AIR PROPELLER WITH VARIABLE PITCH 4 Sheets-Sheet 5 Filed Jan 27, 1933 )NueNToR' .IMIL. A

July 9, 1935.

J. AlVAZ AIR PROPELLER WITH VARIABLE PITCH Filed Jan. 2'7, 1933 4 Sheets-Sheet 4 Patented July 9, 1935 UNITED STAT AIR PROPELLER WITH VARIABLE PITCH Jacques A'ivaz, Paris, France Application January 2'1, 1933, Serial No. 653,887

In France February 17, 1932 18 Claims.

My invention relates to propellers or to windwheels adapted for braking purposes, whose pitch can be varied while in operation and in which the variation of the pitch is efiected by a mechanism 6 driven from the propeller driving shaft itself.

' the like.

Other objects of the invention are to devise means whereby the actual pitch of the propeller will be indicated to the pilot, and also means whereby the pitch varying device will be dependent upon the altitude or the engine speed.

With these and other objects in view as will appear from the following description, my invention resides in the combination of parts and provision of means as will be set forth in said description and more fully pointed out in the claims.

Broadly considered the speed-reducing gear between the propeller driving shaft and the blades, includes in accordance with my invention, for each blade, two epicyclic gear wheel trains of contrary and equal or'unequal speed ratios, and so arranged that an operative connection between the propeller driving shaft and the blades can be obtained by the medium of either train, each of which comprises at least one loose wheel which may be braked or held in position by a friction device whereby the corresponding train will be made operative, said loose wheels being preferably common to the various gear wheel trains associated respectively with the various blades.

Various embodiments of such gear and of devices designed to attain the other objects above set forth are illustrated by way of example in the annexed drawings in which:

Fig. l is a lengthwise section of a mechanism in conformity with the invention;

Fig. 2 is a section of a modification;

Fig. 3 is a lengthwise section of a pitch-indicating mechanism;

Fig. 4 is a section on the line 4-4 of Fig. 3;

Fig.5 is a section of a mechanism for actuating the brakes of the loose wheels;

Fig. 6 is a vertical section, on the line 8-6 of Fig. '7, of a mechanism by which the brake mechanism for the loose wheels is made dependent upon the engine speed;

Fig. 7 is a section on the line 1-1 of Fig. 6;

FlFigl. 8 is a partal section entire line 8-8 of 8- F-uFig. 9 is a partial section on the line 9-8 of Fig. 10 is a view of the corresponding pitch-indicating mechanism;

Fig. 11 is a view of a mechanism peculiar to each blade for rotating the latter.

In the form of construction shown in Fig. 1, the driving gearing which connects the propeller 10 shaftl to-each blade carrier 2, chiefly comprises, in peripheral disposition, a plurality (two, three or more) of sets of three epicyclic gear wheel trains. In each set, the planetary pinions 3, 3a, 3b, of the different trains are connected with 15 one another in such manner as to be subjected to a common planet movement, and for this purpose they are'mounted for instance upon a common stud 4 secured to two plates 5. The planetary pinions 3 engage on the one hand a 20 common gear wheel 6 which is concentric with the shaft I and rotates with this latter, and on the other hand a toothed ring I which is secured to the casing. In these conditions, the

aggregate consisting of the plates 5, the studs 25 4 and the different planetary pinions 3, Math, will be rotatedabout the axis of the shaft in the same direction as the latter but at less speed.

"The planetary pinions 3a and 3b respectively gear, on the one hand, with the loose toothed rings 8a: and 8b, and on the other hand, with teeth 9a and 9b formed on a sleeve l0 mounted loose on the propeller hub I l. The rings Ba. and

-8b are loosely rotatable, but may be held in place at will, and with all the desired gradual move- 35 ment, by a suitable braking device, of which only the facings in and H17 are represented. Various embodiments of actuating means for the braking device will be described hereinafter. Furthermore, the diameter of the planetary pin- 40 ion 3 lies between the diameters of the planetary pinions 3a and 317. Hence the ratios of the epicyclic trainsB, 3, I, 80., 3a, 911, I3, l4, and 6,3, 1, 8b, 3b, 917, I3, it are in the contrary sense.

The aforesaid speed-reduction gearing serves 45 to drive the turning mechanism affording the angular displacement of the propeller blades. In the construction herein represented, each propellerblade is provided with its own direct turning mechanism and these latter, the same in 50 number as the blades, are geared to the sleeve Hi.

It will be observed that therein the device comprises only two loose wheels 8a and 8b, which are common to .all the blades. Obviously, the connection between the blades and the sleeve I0 blades turning mechanisms.

.ll mounted on the sleeve II and engaging a pinion is, for each blade, which is keyed to a shaft l5 which imparts the motion to the corresponding turning mechanism, and which rotates in bearings II secured on the shaft I.

An embodiment of a turning mechanism peculiar to each blade will be hereinafter described.

The device adapted to prevent all improper operation of the pitch-varying mechanism, herein consists of a friction device adapted to brake each shaft l5 and comprising the parts l8 to 22.

The operation of the said driving gear is as follows;

The mechanisms for turning the propeller blades, as well as the pinions II, are carried by bearings mouniid on the rotary casing of the propeller, and hence they participate in the rotation of the propeller. On the other hand, the resistance of each propeller blade to angular displacements about its axis is such that the pinions [6 can only be rotated on their axes by a great tangential stress. In these conditions, when therings or sun wheels 80. and 8b are loose, thus preventing any driving stress from being imparted to the pinions I l, there will be no relative displacement of said pinions nor of the wheel i3, and hence this wheel will be rotated about its axis at the same speed as the propeller. This rotation, combined with the rotation of the discs 5 carrying the planetary pinions, will impart to the rings or sun wheels 8a and 8b different resulting speeds, depending upon the driving ratios employed.

When the pilot desires to vary the pitch of the propeller, he throws on one of the brake facings He or l2?) in order to brake or stop the corresponding ring 8a or 8b. If he should thus hold the ring 80. corresponding to the planetary pinion 3a having the maximum diameter, this pinion will rotate the sleeve ID in the same direction as the shaft 8, but at a greater speed. This will produce a relative motion of the wheel 13 with reference to the propeller, and hence with reference to the pinions l4 secured to the propeller casing, so that said pinions I4 will be rotated on their own axes. This will cause the shafts ii to rotate and will actuate the By stopping or braking the other ring 8b corresponding to the planetary pinion 322 having the minimum diameter, this will cause in like manner the rotation of the pinions M on their axes, but in a direction contrary to the preceding.

Indicating device of the actual pitch (Fig. 1)

The pitch varying gear is preferably completed by a mechanism by which the pilot may know the actual value of the pitch. For this purpose, a member whose position is variable according to the pitch of the propeller is connected by a suitable driving gearing with an indicating device which is visible to the pilot. In the embodiment shown in Fig. 1, the said member having a position which depends upon the pitch consists of a ring-shaped nut 21 provided with an annular groove 28in which is slidably engaged the head of a pivoted lever 29 connected on the other hand to an indicating device not shown, for instance by a rod 30. The nut- 21 is mounted on a threaded appendage of the wheel l3 or upon a like part adapted to rotate together with the sleeve III, in such manner that it may be screwed either way in the case of a relative displacement between the wheel I! and the shaft I, and according to the direction of this displacement. For this purpose, the nut 21 is connected with a member 3| having the some movement of rotation as the propeller, and in such manner that it will positively participate in the rotation of said member 2|, but may move lengthwise with reference to this latter. Thus the said member Il may be directly secured to the rotatable propeller casing, or it may be mounted loose on the sleeve III, as shown, and be rotated by sets of epicycloidal gears 32, l3, l4 analogous to the trains], I, 6, the planetary pinions 32 being carried by the studs 4.

In these conditions, any movement of the wheel I! with reference to the shaft I, which corresponds to a variation of the propeller pitch, will cause a lengthwise movement of the nut 21 to a corresponding degree.

Modified construction of the pitch varying gear (Fig. 2)

In the modified embodiment of the pitch varying gear shown in Fig. 2, the wheels 8a and 82), cooperating with braking means by which they can be stopped, are as before, common to the different blades, but they gear with common planetary pinions 40, the wheel 8a by means. of internal teeth, and the wheel 8b, by external teeth, so that the speed ratios of the two resulting wheel trains have still contrary algebraic signs. To the planetary pinions is imparted a planet movement about the axis of the propeller, and for this purpose, each pinion is for instance carried by a shaft journaled in the blade carrier 38. Herein, the number of planetary pinions is the same as that of blades, and each pinion is mounted on an extended part of the shafts IS. The movement of the planetary pinions on their own axes is imparted to the shafts l5 by any suitable mechanism, and for instance, as herein represented, the movement of each planetary pinion 40 can be imparted to the corresponding shaft l5 by means of epicycloidal reduction gearing. For this purpose, to each shaft I5 is secured a member 35 carrying planetary pinions 38 which herein consist of spur gear wheels, but bevel gear wheels might also be employed. The said pinions 36 gear on the one hand with an external toothed ring 31 secured to the casing 38 which rotates with the shaft I, and on the other hand, with an internal toothed ring 39 which is loose upon the end of the propeller shaft l5 and participates in the rotation of the corresponding pinions 40. The device for preventing an undesired operation of the pitch varying mechanism, herein consists of a friction device connecting the two rings 8a and 8b together and comprising the elements 43 to 48.

' The operation is as follows. When the rings 8a and 8b are not braked, the aforesaid gear has no internal motion, due to the resistance offered by each shaft l5 to all rotation on its own axis, and thus the wheels 8a and 8b will rotate loosely. The ring 31, driven by the casing 38, rotates about the axis of the shaft l together with this latter and with the blades 2. The shafts l5 of the several blades are stationary as regards motion about their own axes. when one of the rings 8a or 8b is braked, the respective pinions 40 of the blades 2 will rotate on their axes, thus drivingby the medium of the pinion 39-the planetary pinions 36. These latter will thus roll upon the ring 21, hence rotating the shaft IS in a direction depending upon the braking of the ring 8a or of the ring as. Thering which is not braked will rotate loosely, it being driven by the pinion 40. It will I blades is the greatest.

This last-mentioned feature may obviously be employed with equal facility by the use of the device shown in Fig. l. Modification of the pitch-indicating device This modified form, which can be employed with any pitch varying gear, is characterized by the fact that the indicator provided with a pointer, which is visible to the pilot and enables him to know at all times the position of the propeller blades, is controlled by the medium of two different gears one of which is driven from one of the rotating parts of the engine, such as the coupling for the usual speed counter and the other from one of the parts of the pitch varying gear whose motion is in relation on the one hand to the rotation of the motor and on the other hand to the positive motion given to the blades, and for instance, with one of the rings in or 8b.

The pitch-indicating device, which is shown by way of example, in Figs. '3 and 4, essentially comprises a differential device. The toothed ring 54 of thedifferential device is driven from one of may be separate from the case'containing the pitch indicator, and may be incorporated in the pitch-varying gear ,or;in the automatic control mechanism, as will befurther set forth. Herein,

the coupling II is connected with the pitchvarying mechanism, for

instance by a flexible shaft or the like.

control'devtce for the braking of the rings In:

and at (Fi 5) The-facings 12c and lib (Figs. 1 and 2) form part of any known braking device, which may comprise brake-shoes, brake-bands or the like, and the facing carriers can be actuated by any suitable means but it is convenient to connect them togeth'er so that they can be actuated by .one and the same control device. A preferred embodiment of such a device is illustrated in Fig. 5 in which the facing carriers are pivoted at one end and actuated from a common shaft 10 by the medium of inversely disposed crank like members 1|, 1 la, in such a manner that one facing only can be applied at a time on the corresponding wheel. Any desired means may be used to simultaneously rotate the crank like members 1|, lia but particularly suitable means consists, as shown, in a toothed sector 12 pivotally mounted about the same axis as the cranks, rotatable therewith and in engagement with a reciprocable the parts of the motor by means of a coupling connection 55; the toothed ring 58 is actuated by the ring 8a or 8b by means of a coupling connection 51, either directly or by means of- intermediate gearing 58, 59, 60, iii, 62 in gear with the rings 54 and 56. The planetary pinions 53,

'5 position which corresponds on the dial 68 to the value of the propeller pitch.- When the pitch of the propeller is being changed, the ring 8a or 8b which remains stationary or whose motion is increased in speed with reference to the speed of its motion when the pitch remains constant, im-

parts this variation of motion to the correspondthe rings 54 and will rotate at different rates, thus effecting an angular displacement of the shaft 54 in the same direction as the ring which has the greater speed. The pointer 61 is thus displaced until the pitch again becomes constant, that is, when the operation of varyingthe pitch has terminated. In this manner, the pointer shows the actual value of the, pitch.

In particular, this device may consist of a cam 59 (Fig. 3) which is'mounted on the shaft of the pointer 61 and controls the delivery power fluid to the engine, in such manner as to throttle this delivery, when. the propeller pitch value comes rack 13. In the embodiment illustrated the crank like members consist of appendages of the sector 12 to which is pivoted one end of each facing carrier, the pivot connections being so located that by turning the sector 12 in either direction out of the middle position here shown, one facing will be applied against the cooperating wheel while the other facing is moved away from the other wheel.

. vThe rack 13 may be actuated by any convenient means and the hydraulic device illustrated in Fig. 5 is given solely as an example. In this device, the rack 13' is secured to a piston 14 movable in a cylinder. 15 provided at each end with condults 18 and 19 leading to a four-way cock situated within reach-of the pilot or controlled at a distance, and connected on the other hand with a source of fluid under pressure, such as the lubricating oil of the motor, and with a suitable discharge chamber or receptacle.

Thus the fluid under pressure can be caused to act on either side of the piston 14, thereby moving the latter and the rack 13 in one direction or in the other, from the middle position illustrated.

Governing-device for making the pitch-varying year dependent upon the speed of the motor An improvementin the pitch varying gear above described'consists in providing it further with a regulating device or governor by which the brakes will be operated, with or without the interposition of a servo-motor, such governor being optionally under the control of the pilot. In this way, the pitch of the propeller will be Varied automatically according to the altitude, or in short, according to the speed of the motor.

Such governing device will essentially comprise a centrifugal governor of any known type driven by the engine by means of suitable gear, and it operates the brake actuating means either directly or by the medium of power means of any known type, whether mechanical, hydraulic or electric. I

An embodiment of such a governing device is illustrated by way of example in Figs. 6 to 10.

In this embodiment a centrifugal governor including the weights 8! acting. through a plate 88 on -a two arm lever pivoted on a stud 88 is driven from! the engine by means of the shaft 85 the bevel gear wheels 88 and 85, the friction coupling 83 and the spur wheel 88, loosely mounted on a shaft ll carried by a casing 82. The brake operating means includes for instance, a movable member responsive to a fluid under pressure and a control valve, as above described in connection with Fig. 5, such control valve is actuated by the centrifugal governor by means of the lever 88. Fig. 9 distinctly shows a combination of means for this purpose. n the stud 88 is keyed a lever 9| the other end of which is pivoted at 82 on the valve-piston slidable in a valve-cylinder provided with ports 84 and 85 respectively connected to the conducts l8 and 18 leading into the cylinder 15 and within an inlet port 95 connected to the source of fluid under pressure and with discharge ports 81 connected to the discharge receptacle. The piston 88 is peripherally provided with recesses and the whole acts as a four-way cock, simultaneously connecting the inlet, 88 with any one of the ports 88, 85 and the second with one of the discharge ports 81, or pre-' venting all communication between any two of the aforesaid ports.

The position of equilibrium, fora given speed of the motor and of the centrifugal governor,

can be modified by the action of an antagonistic spring 88 (Fig. 6) which is so arranged that its action can be modified by the pilot at will, by means of a suitable device, optionally reversible, which acts through the medium of a rod 98.

When the pitch-indicating gear is not contained within the box carrying the dial visible to the pilot, it is preferably mounted in the casing which contains the aforesaid governing device. Herein, the ring l'of the differential mechanism of the type represented in Fig. 3 is actuated from a distance by the pitch-varying mechanism, by means of the connection 55 (Fig. 10). The ring 58 is actuated, through the medium of the gearing 82, SI, 58, 59, by a ring 58, secured to the ring 88, which is driven by the motor.

Blade-turning device (Fig. 11)

This mechanism, which is independent of the manner in which it' is actuated by the engine shaft, is essentially characterized by the fact that it comprises an automatic clutch device, arranged in such manner that the power transmission from the engine shaftwill be automatically cut off at each end position of the blades.

The said mechanism preferably comprises, as herein represented, a device consisting of a stationary screw I8l, and a nonrotatable nut Ils slidable along the said screw, thus making the driving gear quite irreversible and increasing the speed reducing ratio. For this purpose, a differential screw might also be employed. The nut I82 is pref rably connected with the blade by a rack I83 mounted-on the nut I82 and engaging a toothed sector I88 secured to the arm 2 carrying the blade. The screw IN is loose on the shaft I5 which is driven as above set forth, and a coupling device I85, provided with a spring I85, by which the shaft I 5 may be connected with the screw IN, is mounted at each end of the screw. The coupling devices may be of any suitable type, for instance with clutch teeth, and each device comprises a projection I 81 situated on the path of the nut I82 and between this nut and the corresponding spring I88, and hence the spring will be compressed by the nut when this latter reaches the end of its stroke on one side or the other,.thus eflecting the automatic unclutchins.

It will be noted that the device providing for irreversible action is mounted against the blades. and that the wear can be taken up by varying the distance between the axis, for instance by means of an eccentric ring I88 mounted around the ball bearings.

What I claim is:

1. In a variable pitch propeller mechanism comprising a plurality of blades, a driving shaft for rotating said propeller, means for simultaneously varying the pitch of said blades and means for holding the pitch after change, said pitch varying means including two epicyclic toothed wheel trains having speed reducing ratios of opposite algebraical signs, each train comprising planetary means rotated in dependence on the propeller rotation and a sun wheel coaxial with said shaft and rotatable relative thereto, so that said sun wheels normally rotate with the propeller, braking means cooperating with said sun wheels to produce relative rotation between both said sun wheels in either direction, and pitch holding means consisting in friction means normally restraining said epicyclic trains against any differential motion, 1. e. atleast when said braking means are out of application.

2..In a variable pitch propeller mechanism comprising a plurality of blades, a driving shaft for rotating said propeller, means for simultaneously varying the pitch of said blades and means for holding the pitch after change, pitch varying means'including two epicyclic toothed wheel trains having speed reducing ratios of opposite algebraical signs, each train comprising planetary means rotated in dependence on the propeller rotation and a sun wheel coaxial with said shaft and rotatable relative thereto, so that said sun wheels normally rotate with the propeller, braking means cooperating with said sun wheels to produce relative rotation between both said sun wheels in either direction, and pitch holding means consisting in friction means affording a friction coupling directly connecting together both said coaxially disposed sun wheels.

3. In a variable .pitch propeller mechanism comprising a plurality of blades, a driving shaft for rotating said propeller, means for simultaneously varying the pitch of said blades and means for holding the pitch after change, two epicyclic toothed wheel trains having speed reducing ratios of opposite algebraical signs, each train comprising planetary means rotated in dependence on the propeller rotation and a sun wheel coaxial with said shaft and rotatable relative thereto, so that said sun wheels normally rotate with the propeller, friction means normally restraining said epicyclic trains against differential motion, means for momentarily and selectively varying the rotation resisting load on said sun wheels to produce difference between said resisting loads and thereby a differential motion and means responsive to such differential motion for moving the bladesto vary the pitch thereof.

4. In combination with an air screw propeller with variable pitch, pitch varying means, an engine for rotating said propeller, a governor responsi e to the engine speed and controlling said pitch varying means to automatically cause a pitch variation in response to a variation -in the engine speed and adjusting means actuatable at will during operation of the governor to vary will the end engine speeds-allowed.

5. a variable pitch propeller mechanism com ing a plurality of blades, a driving shaft for rotating said propeller and a pitch varying gear adapted to afford an operative connection between said shaft and the various blades to vary the pitch thereof, a pitch varying gear including. two speed reducing epicyclic' toothed wheel trains, a sun wheel of each train being coaxial with said shaft and rotatable relative thereto and carrying gear teeth provided externally on one wheel and'internally on the other,

a planetary pinion in mesh with both said teeth,

means for rotating said pinion around the driving shaft in dependence on the propeller rotation, means for momentarily producing a difference in the rotation resisting loads on said sun wheels whereby producing a rotation of said pinion about its own axis, and means responsive to this rotation of said pinion for moving the blades where'- by varying the pitch thereof.

6. In a variable pitch propeller mechanism a 'pitch varying gear as in claim 5 wherein further the means responsive to the rotation of the planetary pinion for moving the blades includes a second speed reducing epicyclic train comprising two sun wheels and at least one planetary pinion, one sun wheel being solid with the planetary pinion of the first namedepicyclic train,

.means stationarily securing the other sun wheel to the propeller, a planet carrier rotating with the propeller and means responsive to the rotation of said planet carrier about its own axis for moving the blades whereby varying the pitch thereof.

'7. In a. variable pitch propeller mechanism comprising a plurality of blades, a hub for supporting said blades and a pitch varying gear including a rotatable screw-threaded member stationary carried by the hub and anon rotatable but lengthwise shiftable screw-threaded member in mesh with the preceding one, said members being located close to the blade, and a motion transforming contrivance operatively connecting said endwise movable member to the blade to transform a linear endwise motion of said member into an angular motion of the blade, such contrivance comprising strictly the requisite number of members for performing such transformation without any non motion-transforming gearing member.

8. In a variable pitch propeller mechanism comprising a plurality of blades, a hub for supporting said blades and a pitch varying gear, said pitch varying gear including a plurality of sets of a stationary and rotatable screw carried by said hub and of a non rotatable but lengthwise shiftable nut in mesh with said screw, each set being associated to a corresponding blade and located close to said blade, and a motion transforming contrivance operatively connecting said nut to the blade to transform the linear endwise motion of the nut into an angular motion of the blade, suchcontrivance comprising strictly the requisite number of members for performing such transformation without any non motion transforming gearing member. p

9. In a variable pitch propeller mechanism pitch-varying gear as in claim 8, wherein further said motion transforming contrivance includes a rack solid with the endwise movable member and spur wheel teeth rigidly carried by the blade and comprising a plurality of blades, 9. driving shaft for rotating said propeller and a pitch'varying gear adapted to aiford an operative connection between said shaft and the various blades to vary the pitch thereof, said pitchvarying gear including two epicyclic toothed wheel trains having speed reducing ratios of opposite algebraical signs, each train comprising planetary means rotated in dependence on the propeller rotation and a sun wheel coaxial with said shaft and rotatable relative thereto, so that said sun wheels normally rotate with the propeller, friction means normally restraining said epicyclic trains against diil'erential motion means for momentarilyand selectively varying the rotation resisting load on said sun wheels to produce difference between said resisting loads, and thereby a differential motion, plucomprising a plurality of blades, a hubhaving a. socket for carrying said blades, a driving shaft for rotating said propeller and a pitch varying gear, said pitch varying gear including a screwthreaded shaft rotatably journaled in said socket about an axis parallel to the hub axis and stationary with respect to the hub, a nut longitudinally movable onv said shaft, rack teeth rigidly carried by said nut, spur wheel teeth rigidly provided on the blade and in mesh with said rack and gearing means adapted to rotate said shaft in contrary directions.

12. In a variable pitch propeller mechanism, comprising a plurality of blades, a hub for carrying. said blades and a pitch varying gear, said pitch varying gear including a plurality of nut and screw contrivances associated respectively with the various blades, one element of each contrivance is stationary and rotatable and the other non rotatable but endwise shiftable, a plurality of motion transforming contrivances each of which operatively connects one of said endwise movable members to the associated blade to trans-. form a, linear motion of said member into an angular motion of the blade and meansadapted to simultaneously rotate the rotatable members of the various nut and screw contrivances, such means including two epicyclic toothed wheel trains normally frictionably restrained against differential motion and means for momentarily and-selectively producing a differential motion of one train in a direction and of the other in the opposite one.

13. In a variable pitch propeller mechanism comprising a plurality of blades, a hub for carrying said blades and a pitch varying gear adapted to move said blades to vary the pitch thereof, said pitch varying gear including two toothed wheel trains having speed reducing ratios of opposite algebraical signs and including an epicyclic gear, each of said trains having planetary means rotatable about an axis fixed with respect to the hub and a sun wheel of each train being coaxial with said hub and rotatable relative thereto, friction means normally restraining said epicyclic trains against differential motion, means for momentarily producing a differential motion of either train and means responsive to such differential motion for angularly moving the blade.

14. In a variable pitch propeller mechanism comprising a plurality of blades, a hub for carrying said blades and a pitch varying gear adapted to move said blades to vary the pitch thereof, said pitch varying gear including two toothed wheel trains having speed reducing ratios of opposite algebmical signs and normally frictionally restrained against diiferential motion, each train including an epicyclic gear having planetary means rotatable about an axis ilxed with respect to the hub and asun wheel coaxial'with said hub and rotatable relative thereto, means for momentarily and selectively ying the rotationresisting loads on said sunwheels to produce difference between said resisting loads, and means responsive to a diflerential motion of either train for angularly moving the blade.

15. In a variable pitch propeller a pitch varying gear as in claim 7 and wherein said motion transforming contrivance includes a rack solid with the endwise movable member and spur wheel teeth rigidly carried by the blade and in mesh with, said rack, and means for bodily moving said endwise movable member transversely of the blade axis for adjustment of the rack and spur wheel engagement.

16. In a variable pitch propeller mechanism comprisng at least one blade, a hub for carrying said blade and a pitch varying gear adapted to move said blade 'to vary the pitch thereof, said pitch varying gear including a screw-threaded shaft parallel to the hub axis, a nut longitudinally movable on said shaft, rack teeth rigidly carried by said nut, spur wheel teeth rigidly provided on the blade and in mesh with said rack, bearing means stationary carried by the hub and supporting one end of said shaft both for rotation of said shaft about its own axis and for pivoting motion at least in a plane perpendicular to blade axis, other bearing means stationary carried by the hub and supporting the opposite end of said shaft for rotation of said shaft about its own axis and including an excentric ring surrounding said shaft and angularly adjustable about its own axis.

17. In a variable pitch propeller mechanism comprising at least one blade, a hub carrying said blade and a pitch varying gear adapted to move said blade to vary the pitch thereof, .said pitch varying gear including a rotatable screwthreaded member stationary carried by the hub and a nonrotatable but lengthwise shiftable screw-threaded member in mesh with the preceding one, a motion transforming contrivance operatively connecting said endwise movable member to the blade to transform a linear endwise motion of said member into an angular motion of the blade, means adapted to transmit rotation to said rotatable member, such means includng one-way clutches disposed respectively and inversely at each end of the rotatable member to drive the latter in contrary directions, and means responsive to the blade angular adjustment for'automatically unclutching the actual driving clutch for each end position of the blade.

18. In combination with an air screw-propeller with variable pitch, pitch varying means, an engine for rotating said propeller, a governor responsive to the engine speed and controlling said pitch varying means, to automatically cause a pitch variation in response to a variation in the engine speed, such governor consisting in a centrifugal regulator including rotatable flying weighted parts driven in dependence on the engine speed, resilient means urging said flying parts in counteraction to the flying force on said parts and means for more or less energizing at will said resilient means while said weighted parts are rotating.

JACQUES AIvAz.

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