US 2280374 A
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Description (OCR text may contain errors)
' April 2.1 1942- cHxL'roNl I 2,280,374
CGNTROLLABLE PI TCH PROPELLER l Filed Feb. 10, 1938 5 Sheets-Sheet 1 lil ---l/II Apri; 21, 1942.1 1R, www,` 2,280,314
-CONTROLLABLE FITCH PRPELLER N Apr 421, j 1
R. H|LTN j 2,280,374
i coNTnoLLABLE `FITCH'PRoPELLI-:R
. Filed Feb. 10. 1938- 5 Sheets-Sheet 5 lNveN-roR Patented Apr. 2l,
UNITED coN'rnoLLABLE'rlrcn raorELLEa Roland Chilton, Ridgewood, N. J., assignor to Wright Aeronautical Corporation, a corporation of New York y Application-February 10, 1938, Serlal-No. 189,775 8 Claims. (Cl. 1711-163) This invention f relates to `variable pitch propellers and particularly topropellers for aeronautical engines. A principal object of the invention `is. to provide improved and simplified blade mounting means wherein the main hub structure is lighter land more compact than in current practice and wherein the production costs are reduced by a simplied geometry of the parts. This is achieved in part by a. novel blade mounting comprising an angular contact ball bearing for each blade which, in the preferred embodiment, may be disassembled for detachment of blades, without disturbing the bearingrace connections which may be permanent, or even integral with the associated member. The invention also includes a novel operating mechanism for the pitch changing function, having `advantages in simplicity, strength and compactness and also affording improved and simpliiied automatic control means.
A further object is. to provide auxiliary means which may be incorporated in case the ability to feather the propeller is desired.
It is well known that one of the prime difculties encountered 4in the development of metal blade propellershas been the destructive effects of resonant vibrations, so that in current practice the sections of the blades end their attachments are far beyond any proportions that can `be justified by calculationv ofthe centrifugal and `3\ bending forces involved in the transmission of CII the power to be handled, in the absence of the vibration effects. For example, the development of any specific size of blade to-satisfactory resistance to vibratory fatigue failure has been t'.
accompanied by a relatively rapid increase in thev diameter of the-blade at the butt. This has involved a corresponding increase in the diameter of the anti-friction bearings which are normally disposed around the butt or shank of the blade. This great lincrease vin 'blade' weights `has cor'- respondingly increased the centrifugal force on the blade bearings with respect to -the forces from bending moments due to torque and thrust. With the current proportions of blade weights and blade bearings the base afforded by the bearing diameter is so' bigand the centrifugal force thereon so high, that the blade is stable in operation against the bending moments to which it is subject. That is tol say, if a single ball or roller bearing of current diameter be used to resist the centrifugal pull of the blade the bending moments from torque and thrust on the blade will never be sufficient to completely unload one side of the bearing races, the effects of the bending' moments being merely to modify the load distribution on the balls.
When the engine is idling and subject to irregular running or backfires, the centrifugal force may be insufficient to produce' stabilization on a single ring of balls, and, accordingly, in current practice, bearing means spaced axially of the blade are used, the loads on such bearings `due to bending moments being regarded as inversely proportional tov their effective spacings. It should be noted that, at any given pitch setting, the bending forces due to torque and thrust,
and the centrifugal force all increase as the square of the rotational speed, wherefore a blade attachment which is stabilized by centrifugal force at any one speed of rotation, is stable at all other speeds (except Afor irregular engine running at very low speeds).
One current construction employs a stack` blade which is made hollow to engage the journals which take no part in resisting centrifugal force. The blade is provided with a heavy flange against which is tted a thrust bearing of necessarily large diameter engaging a heavy ange on a relatively rigid outside hub member. Under operating conditions with the high centrifugal Vforce normally present, this structure is indeterminate as to the distribution of the effects of bending'moments between the stubs which ap- 1 parently are designed to receive them, and the thrust bearing which, when loaded by centrifugal force may resist lbending action on the blade more directly than the spaced journals of the stubs. The distribution of load between the stub bearings and the single thrust bearingswilldepend upon the relative rigidity of these` parts,
and in practice, the proportions are such that the stub has by far the greater exibility under these conditions, the stubs in normal operation actually perform little, if any, duty., In the case where the thrust bearing is of roller type, having a flat face, the stubs may take the shearing action due to the tangential effort from the torque. The present invention teaches that if 4single 'row angular contact type of bearings simplled. f onnfof blade mounting is provided.:
incorporated, wherein provision is made for feathering the blades, and wherein provisionis made for improved lubrication of 'the propeller mechanism. I'he invention also provides ar novel form of blade constructionand mounting for the .the main thrust bearing 22 and the auxiliary or counter-thrust Washer 52 to zero back lash when the shoulder 44 of the nut 40 is screwed tight. It will be seen that the ball bearing 22 is of the angular contact type capable of sustaining radial and axial loads.
purpose of minimizingA weight andidestructive vibration.l
The invention will now be better understood with reference to the drawings in which similar numbers indicate similar parts and in which,
Fig. l is a section through the axes of one propeller blade and of the hub,
Fig. 2 is a section on the line 2--2 of Fig. l, Fig.3 is a detail axial section through a preferred blade construction and an alternative hub construction, i
Figs. 4 to '1 inclusive are blade cross-sections on the line 4-1 inclusive of Fig. 3, f
Fig. 8 is'an elevation of the hub and blade rootsv includingV a fragmentary section,
Fig. 9 is a detail section through part of the hub illustrating wiring connections on the line 8 9 of Fig. 2,
Fig. 10 is a detail view of a ratchet unit,
Fig. l1 is a detail view of a lubricating pump,
Fig. 12 is a, perspective view of the alternative hub unit, and
Figs. 13` and 14 are respectively longitudinal and cross-sections through an alternative hub unit.
Referring rst to Fig. 1, i0 designates a conventional engine crankshaft or propeller shaft provided with the standard propeller hub mounting cone I2 and 4splines I4 with which are engaged companion splines on a main hub member I6. In this instance athree-bladed propeller is shown, the hub being provided with three integral annular lprojections I8 provided with integral ball race or track elements 28 co-operating with balls 22 and a companion track or race 24 formed on a blade sleeve member 28. The races are preferably locally hardened and their formation integrally with the rhub I8 isthe preferred embodiment 'of the invention. The prior art shows ball or rollerf bearing unitsv having individual races which must be securedto the hub as by a connections which are eliminated in this invention. The simplification is made possible by the assembly scheme here employed wherein the balls themselves may be disassembled to permit removalof the blade. It will be seen that the inner diameter Aof the race 24l on the external member 28 is vdesigned to pass the external diameter 32 of the hub race member 20. A suitable hole'34 is provided in the member i8 through 'which the yballs may be withdrawn after the member 28 has been moved inwardly as provided for in the clearance indicated at 36.
In the specific showing of.,Fig. 1 a standard form of blade 31 having an out-turned iiange 38 at the butt struck on a large radius or fillet and this flange is engaged by a split nut 48 screwed into threads 42 in the bearing sleeve member 28.
Considering now a bending force applied to the 'maden as indicated by the arrow F, it win be seen that such force will (in the absence of centrifugal force) unload the balls on the right hand side of Fig. l and'apply a thrust force indicated by the arrow T on the right side of the auxiliary thrust washer 52, while an equal and opposite re- "split construction thereof and/or screw threaded action TI will occur on the balls on the left hand side. It will be seen that these reactions occur at diametrically opposedpoints of the bearings whereby they act at a substantial arm or base comparable to or greater than that afforded by `the, axial separation of the stabilizing bearings in conventionalstructures.
f It should be clearly understood, however, that under the iniiuence of the normally predominating centrifugal forces, there will be no reactions T on the thrust washer 52 because the force T will be -insuilicient to completely unload the balls 22 on that side of the bearing because of the predominance of the centrifugal force outwardly along the blade axis. Thus, the effects of bending moments from thrust and torque under normal operation will be to somewhat increase the load on the balls on one side of the bearing 22 and decrease the load on the diametrically opposite balls. Actually, the eiect of the combined centrifugal and bending forces is that of shifting the effective pull on the blade to be somewhat eccentric to the axis thereof but with the proportions shown, this eccentricityis small comparedto the at the root and is taperingly flatted as shown/in Y the -sections Figs. 4 to 'l incl/usivertofconf approximately to theugen'eal exterior profile of .the blade.
The shank 54 has an enlarged conical butt 51 provided with a. ball race track 58 engagingballs 22-a which, in turn, engage companion raceways 62 formed integral with the hub iii-a. It will be seen that this bearing structure is merely an inverted disposition of the showing of Fig. 1, the difference being that in this case, the outer or in-turned race member is formed integral with the hub and the inner or out-turned race member is formed integral with the blade shank. In this case,l the counter-thrust or stabilizing wash er 52-a isengaged by a gear ring 46-a splined to the butt 51 at,64, as shown, and adjusted into iitted contact with the auxiliary thrust ring 62-'4a by means of anut 66. A groove 84-a (Fig. 13) is formed in a thickened portion of the race elelments 62 for disassembly of the balls 22a corre- The blade openings d, with the ball races 62, are lmachined by boring operations using a formed cutter, while the formation of exterior of the hub comprises a simple spherical turning operation.` The bump e is provided to give a greater section thickness at the front of the propeller shaft opening.
The balance of the mechanism now to be de- Y scribed may be used with either of the alternate blade and blade bearing-structures already de# scribed. Referring iirst to Fig. 1, a bevel gear tooth quadrant 68 is formed integral with the sleeves 28 (inthe case of the embodiment of Fig. 3 the corresponding gear quadrant 68-a is formed integral with the ring 46a previously def scribed). Meshed with the gear quadrants 66, is a central control gear 'l0 having an integral sleeve 12 and wormwheel 14 rotatable on a suitable bushing 16 which is in turn supported on a cylindrical extension 'I8 of a hub nut 80 which engages `the standard threads 82 of the engine shaft I as shown. The nut 80 'engages the hub I8 through an external ilange or shoulder 84 while a split ring'86 engaging grooves in the hub |6 and in the nut 80 serves as a puller for removal of the hub.
Surrounding the -hub preferably of duraluminum forgings, comprising the forward portion 88 and the rear portion 60v secured together by bolts 62 and to the hub |8 by bolts 84. A lock nut 86 threaded on an extension 81 of the hub nut 60 further clamps this part, the bushing 16 and front housing 88'. The split housing 88- 80 clamps around oil sealing sleeves 68 (which are not split) and which extend radially inwards around the propeller blade` sleeves 28 t define an annular lubricant reservoir within the housing 88-00 in which lubricant is retained by centrifugal force during operation. Engaged with the wormwheel 14 is a 'worm |00 integral with a shaft having splines |02 and journals |04 engaged in bushings |06 fitted to bosses |08 formed in the housing 88 (as seen in section Fig. 2). The bushings |06 are screw-threaded at |I0 for axial disassembly and the bosses |08 have slots ||2 wide enough to permit the worm shaft |02|04 to be withdrawn laterally and inwardly upon removal of the bushings |06.
Mounted for free axial sliding on the splines |02 are fine tooth ratchet members ||4 of opposite hand, spaced and controlled by a semicircular control sleeve ||6 having in-turned end collars ||8 of horse-shoe" formation engaging grooves in the ratchets' ||4. ratchets ||4 `are -engageable with companion ratchets formed on hubs |22 of levers |24 extending rearwardly within the housing`88-60' and provided at their right hand ends with a ball The controllable y mally held stationary by, a pinion |40 later to be further described. The sleeve |86 of the eccentric is mounted on a xedsleeve |42 integral with a flange |44 rigidly bolted to the standard facing |46 provided onthe engine for the purpose.
The extreme right hand ends of the levers |24 are provided with flats |48 guided for radial means later to be described. This solenoid en gages a ratchet operating lever comprlsingthe arm depending from a hub |62, pivotally embracing the sleeve 12 of themain bevel gear 10, provided at its upper end with a ball connection |64 which operates the ratchet control sleeve I6. 'The lever |60 and the ratchet control sleeve ||6 are normally retained in the central or neutral lposition shown (with both ratchets disengaged) by means of a centralizing spring |68.
The rear face of the housing` 90 is equipped with an insulating disc |10 secured to the housing by screws |12 and carrying concentric slip rings |14 and |16 connected to respective solefor the'latter ring beingseen in section at|16.
|6 is a split housing.
member|26 (Figs. 1 and 8) which is in turn-engaged in an eye |60 of an eccentric strap |62 ros tatable (with the levers |24) upon a stationary eccentric |34 formed integral with a sleeve |36 carrying a bevel gear |38 meshed with and nory These brushes are connected to a suitable battery and electrical switching mechanism (not shown) as by leads |86. The external electric control means to be connected to the wires 4may be identical with that used in other forms of electrically controlled propellers, usually comprising switch gear worked by a speed responsive governor to effect constant speed .propeller operation.
Such extraneousfmechanism', however, forms no part of the present invention and need not be further described. The operation of the propeller pitch control mechanism will now be clear as follows Themechanism so far described may be used with or without the mechanism associated with the normally stationary pinion |40 which mechanism comprises manually controllable propeller feathering means later to be described. -In any event. during normal operation, the eccentric |34 is held stationary and will, in fact, be secured directly to the housing |44 in the case of a nonfeathering propeller.
Whenever the propeller rotates, carrying with it the ratchet levers |24, these in turn drive the eccentric strap |32 around the fixed eccentric |34 whereby the ratchet levers |24 are given an oscillating swing .as indicated by the dotted lines |24-a, making two strokes per propeller revolution. The right and left hand driving ratchets l |22, Figs. 2 and l0 partake of this oscillating motionl and the ratchet-teeth are proportioned so that the swine subten'ds considerably more than one but less than two ratchetteeth. With the parts in the neutral position shown i. e.` with the solenoid armature |56. the control lever. |60 and the control sleeve ||6 in the central position v ture |58 willbe moved to the right and the control sleeve IIS will carry the ratchets ||4 to the left of Fig. 2 engaging the left hand ratchet with the driving ratchet hub |22 of the lever |24 and, accordingly, the ratchet` I I4 and with it the worm will be advanced one tooth for each cycle of the lever `|24 i. e., one tooth for each rotation of the hub.
In this specific embodiment the armature |58 has been shown as directly connected to the ratchet control lever |60 whereby the magnetic flux acting on the armature will also act as the ratchet spring, permitting the necessary slight axial movement of the ratchet for engagement of successive teeth. In. the instant case the proportions are appropriate to approximately 100 teeth on the ratchet,.which, accordingly, comprises the rststep of a propeller operating reduction gear trainlgivinga reductioni of 100 to 1 between the rotations of the hub and of the Worm |00. This is multiplied by a second large reduction between the worm |00 andthe wormwheel 14 whereby the bevel gear.10 is slowly rotated whenever one of the solenoids |56--I51 is energized, communicat-` ing-its.:y motion` through the. third reduction comprises by .the propeller blade. quadrant gears 68 wherebyfotheblades arev slowly. moved to simultai'ieously. increaseforl vdecrease their pitch accord-v ing-ltovyvhichbf the isolenoids is energized. The wormi .f|. 00 :will-.have a veryv low helix anglev preferabiyfhavingonly oneylead wherebyfit is irreversible, that is to say',it .cannot be `made to over.- run'by'any .force applied to the worm` gear 14 so that they propellery is lockedin any speciiicjpitch position whereat the solenoids ISS-|51 may be cle-energized. n I n Itis well known that the forces involvedv in operating controllable pitchpropellers are of -large order, the principal resistance to be overcome being the centrifugal ,flattening couple by which the blades are urged towards the zero pitch position in operation, and added to this force is the friction on the blade bearings Whenever the control is moving lthe blade towards increased pitch. One of the features of this invention resides in the relative ruggedness of the eccentric, lever and worm gear mechanism whereby the control forces are transmitted.
An additional feature of the invention resides in a novel lubrication system now to be described.-
Due to the largev centrifugal forces present, trouble has been encountered in controllable prop ellerswith leakage of, the lubricant and with the centrifugal drying out of the parts near the center of rotation. As has already'been said, theV inwardly projectingsleeves 98 define a circumferential reservoir,.within the perimeter of the housing 88-90 which reservoir has no running nts since the sleeves 28.are tightly clamped into vthis housing and, accordingly, afford a completely oil tight structure. ,Y
, Disposed at the perimeter of the housing 90, so as to be subject=tothe centrifugal force of the lubricant retained therein by the sleeves 98, is a small pump comprising a body |90 (Figs. 1 and 11) screwed intogthe housing at |92 and having a bore |94 in which operates the ball piston |96 articulated to the lever |24 at |98. The ball head of the piston over-runs inlet holes 200 on its outstroke which creates a vacuum in the cylinder |94 assisting centrifugal force in filling cylinder with lubricant. A small non-return delivery valve 202 communicates with a passage 204 and, by means of a tube B and a suitable drilling 208 in the hub I6, delivers oil to the bearing of the eccentric strap |32 wherefrom a small duct 2| 0 leads lubri cant to the ball |26 of lever |24. There is thus i set up a circulation of lubricant from reservoir fcomprised within the perimeter of the housing 88-90 to the central part of the mechanism.v
This system is also preferably connected through the large lightening holes 2 2 and a suitable drilli ing 2|4 in the hub nut 80 to lubricate the bearing bushing 16 and therefrom the wormwheel 14 and worm |00. l
When it is desired to additionally incorporate the feathering feature whereby the propeller may be brought to 90 mean pitch for cruising with the engine stopped, the parts now to be described will be incorporated. tioned that the housing |44 is provided with an internalsleeve 2|6 equipped with oil sealing rings 2I8 of the piston ring type, engaging a suitable liner 220 in the, insulating rear cover |10 and within the oil tight enclosure thus formed in common with the interior of the housing 88-90 there is disposed the bevel pinion |40 engaged with the` bevel gear |38 of the eccentric |34 as previously described. The pinion |40 hasa shaft 222 splinedj `at 224 yinto an armature shaft 226 of an electric motor 228 mounted on an extension 230 of the housing |44 by through bolts 232. The armature 234 ofthe motor is disposed below the center line of the fields 236, the armature being given slightv axial float underthe restraint-of a spring 238, which normally forces the armature downwards to engage a cone clutch 240 rigid therewith, withv a ,fixed clutch face 242 formed on the housing extension 230. By means oi` vthis spring 238co.
operating with the clutch240, the armature 234 and the pinion |40 and eccentric |34 are-held stationary duringl all ,normal operation. However, when'it is desiredto feather the propeller,
the motor armature 234 is energized, and the Amagnetic pull from the field 236 moves the armature upwards against the spring 238 (slight play for this purpose being arranged at the upper bearing 243) and the armature is free to rotate and turn the eccentric |34 through the bevel gear |38 and pinion |40.
It will be understood that this external energization for feathering is necessary because as the feathering operation proceeds, the rotationr of` the propeller will progressively cease so that the lever and ratchet mechanism will cease to operate from the eccentric |34 if this be maintained stationary. Unfeathering is 4obviously only possible by rotation of the eccentric |34 -with respect to the then stationary propeller.
While I have described my invention in detail in its present preferred embodiment, itwill be obvious to those skilled in the art, after understanding my invention, thatA various changes and modifications may be made therein without departing from the spirit or scope thereof. I aim in the appended claims to cover all such modications and changes.
I claim as my invention:
1. A controllable pitch propeller for an engine including in combination a hub, blades mounted thereon for pitch changing rotation, an electric motor secured to said engine, means .to energize and to immobilize said motor at wi11,'a normally' stationary eccentric mounted for rotation with the hub axis and drivably associated with said rmotor and pitch changing gearing operatively eccentric normally fixed to said engine, a crossshaft in said propeller having right and lett hand ratchets, lever means organized for oscillation upon said shaft and having companion ratchets, means to engage and disengage either pair of companion ratchets, means by which said lever is oscillated from said eccentric by rotation relative thereto, gearing operatively connecting said cross-shaft to the propeller blades, and means to rotate said eccentric for the. purpose of completely feathering" said propeller blades.
3. In an engine driven propeller having blades adapted to rotate the same upon energization of said motor for feathering pitch change to stop rotatable in pitch, a normally stationary member 'on the' engine concentric with the propeller, vpitch changing mechanism selectively connectible to the blades, in the `propeller, and driven by said member, by which bladev pitch changes may 'be effected during propeller operation by the relativemovement between the propeller andengine, and independent power means for rotating `said member to provide a source of power for blade pitch changes during propeller inactivity..
upon effecting selectivel connection between the blades and the pitch changing mechanism, said power means comprising an electric motor, the means for effecting selective connection between said blades and said pitch changing mechanism comprising propeller hub carried solenoid operated clutches.
4. In an engine driven propeller having blades changing gearing operatively connecting saidv blades to said reaction member, motor means normally immobilizing said reaction member and said engine, said reaction member comprising a cam ring on the engine and said pitch changing gearing comprising a cam follower movable with and with respect to the propeller, and means to clutch the cam follower to drive the blades for t pitch change.
6. In an engine driven propeller having blades rotatable in pitch; a normally stationary member journalled on the engine and coaxial with the propeller; pitch changing mechanism in the propeller driven by said member upon relative rotation between the propeller and member andy including propeller carried selectively operable clutches, by which, upon clutch engagement,
blade pitch'changes may be eiected during propeller operation with the member stationary; and motor means independent of engine operation but ,secured to the engine, drivably connected to said .normally stationary member, selectively energizable to rotate said. member to effect bladepitch changes, upon clutch engagement, when the propeller is not rotating.
7. A controllable pitch .propeller for an engine including in combination a hum, blades mounted thereon for pitch changing rotation, a motor secured to said engine, means to energize and to immobilize said motor at will, a normally stationary cam member mounted for rotation on the hub axis and drivably associated with said motor, and pitch changingA gearing operatively connecting said cam member with said blades, and including therein a selectively operable clutch.
8. A controllable pitch propeller for an engine including in combination a hub, blades mounted thereon for pitch changing rotation, a motor secured to said engine, means to energize and to immobilize said motor at will, a normally stationary actuating'member mounted for rotation on the hub axis and drivably associated with said motor, and pitch changing gearing operatively connecting sald actuating member with said blades and including therein a selectively operable clutch.