US2362914A

US2362914A - Adjustable pitch propeller mechanism for airplanes

Info

Publication number: US2362914A
Application number: US286940A
Authority: US
Inventors: Mcleod Albert Kenneth
Original assignee: AVIAT PATENTS Inc
Current assignee: AVIAT PATENTS Inc; AVIATION PATENTS Inc
Priority date: 1939-07-27
Filing date: 1939-07-27
Publication date: 1944-11-14
Anticipated expiration: 1961-11-14

Description

RPLANES 6 Sheets-Sheet 1 INVENTOR. M677 /'7Ze0 BY I 5 ATTORNEYfi Nov. 14, 1944. A. K. MCLEOD ADJUSTABLE PITCH PROPELLER MECHANISM FOR AI Original Filed Jan. 6, 1956 ,Nov. 14, 1944. A. K. MCLEOD 2,362,914

ADJUSTABLE PITCH PROPELLER MECHANISM FOR AIRPLANES Original Filed Jan. 6, 1936 6 Sheets-Sheet 2 55 so Z4 55 52 lZ/bm rr. 176M BYWM ATTORNEYS Nov. 14, 1944. A, McLEOD 2,362,914

ADJUSTABLE PITCH PROPELLER mmcmuxsm FOR AIRPLANES Original Filed Jan. 6, 1936 6 Sheeqs-Sheet 3 INVENTOR. N w/0d ATTORNEYS Nov. 14, 1944. A. K. M0 500 2,362,914

ADJUSTABLE PITCH PROPELLER MECHANISM FOR AIRPLANES 6 SheetsSheet 4 Original Filed Jan. 6, 1936 INVENTFOR.

Y ATTORNEYS Nov. 14, 1944. A. K. M LEOD ADJUSTABLE PIFTCH PROPELLER MECHANISM FOR AIRPLANES Original Filed Jan. 6, 1936 6 Sheets-Sheet 5 V Wf/l/ ATTORNEYS Nov. 14, 1944. A. K. McLEoD 2,362,914

ADJUSTABLE PITCH PROPKLLER IEGHANISH. FOR AIRPLANES 6 Sheets-Sheet 6 Original Filed Jan. 6. 193a INV ENT OR.

fi/el-f mum BY ,j

ATTORNEYQ details will appear from low. -I describe a preferred embodiment of my lemma-Pa Albert Kenneth McLeod,

Aviation' Pate signor to 2,362,914 H I g V rltornrmn. MECHA: gmsrrron v; .s

Lcs Angcies, Cali1.,as'- I nts, Inc., :Los :Angeles, x

. 1 calif acorporation of California. 1

.Cn'tiridatibhibt; January 6,

application' seriai No. 57,739;

936'.' This application July 27,

' v 193 9 Serial No.-286.940-

This inventionrelates to improvements in an" adjustable pitch propeller m echanism for airplanes.

The objects of this invention are: First, to provide an improved adjusting means i for the propeller blades.

Second, toprovide'improved control ror'su'ch propeller blades when in action.

Third, to providej'e'ffective automatic constant speed electric controls.

Fourth, to provide in improved counterbalance means able blades of thepropeller.

Fifth, to provide an improved tachometer such a combination air for the adjustmeans for-such a combination and control.

Sixth, to provide an improved means for 'manualcontrol of the whole'oiy any of the parts,

including the manual adjustment of the propeller blades. 1 t

Further objects pertaining to economies and the description to folinvention in the followingspecificationand the attached drawings; in which:

Fig. 1 is a fragmentary front elevation'of the hub. of a broken oihpartially section line l of Figs. 2 and 7..

2 is a reduced sectional side elevation view three-blade propeller; with the blades of the same parts partly in'section through the propeller blade'shank on line 2-2 of Fig. 1.'

Fig. 3 is an enlarged view on the planes of lines 3- -3 of Figs. 1, 4.5, and 9, a part of the view showing the worm gear and the hub parts being on line 3-3 of Figs. 1, 4, and 9, while the magnet and the manual driving pinion are onthe plane of line 3-3 of Fig. 5. a a 1 Fig. 4 is a detail sectional view somewhat reduced insize on line 4-4 of Fig. 3, showing the details of the adjusting ring gear means- Fig. 5 is a somewhat tion on lines5-5 of Fig. 3 through the electromagnets, their coils and the electromagnet casing.

Fig. 6 is an enlarged detail of one of the yieldin section on theirr'egular detail composite sectional means on line [1- reduced sectional elevaing support pin means for the braking armature assumes in operation and other the depressible switch member which or for reversing the propelleras emergency rev quires." p

Fig. 9 is a. reduced front elevation view of the three-blade propeller, part of two of the blades being broken away...- v

Fig. 101s an enlarged detail sectional view on] line 10 o of Fig. 9 through one of the propeller blades, there'being added in dotted lines and diagram-the difierent' positions which theblade t details.

]Fig. 11is an enlarged detail sectional view on line H -H of Fig. 9 showing details of the propeller counterweight and its divided attaching ring, the relation and angle of the propeller blade being shown by dotte'dlines;

Fig. 12 is a detail front elevation view of the tachometer with my attachments.

Fig. 13 is an enlarged detail elevation of the rear face of the tachometer with my attachments} 'Fig. 14 is an elevation view from the left hand of Fig. 13 showing the tachometer With'my ad justingstops omitted and the cutaway wall'and I an end view of the'flexible brush member.

Fig. 15 is an enlarged detail elevation view of permits the flexible indicating switch member to automatically' move to position.

Fig. 16 isan enlarged elevation view of my adjusting means for adjusting the rangeof' the tachometer control taken from the right hand of Fig. 12 and the left hand of Fig. 13.

Fig. 17 is an enlarged detail sectional elevation view taken centrally through the adjusting I! of Figs.- 12, 13, and 16.

Fig. 18 is adetail wiring diagram of the entire electric system showing conventional and simple relays and "circuits therefor. The relays are available in many forms, I show two batteries as the simplest.

Fig. 19 is a detail view partly diagrammatic of the manual adjusting means comprising the adjustable flexible shaft and pinion with a crank for the-manual control of the concentric outer rin gear and controlling pinions and adjusting worm gears for the propeller blades. 3

Fig; 20 is a similar diagrammatic view where a simple form of electric starting motor ismade use of 1 in this connection by 'merely pushing thebuttonof the starter." 1

. The parts will be identified by their numerals of reference which are the same in all the views. A three-blade propeller is illustrated. l is the I hub. The hub is counterbored 18 being provided with hub of the propeller of barrel form. I is the engineshaitwhichissplined at! intcthehubl andhasacoliarl. Theshai'tiprojectsfrosn the nose of the engine I. x

the inner end of the shaft enlarged conical inner end 1 which ilts into corresponding centering recession the inner endoi. the at l to. receive the hubnut II which forces conical centering ring ll into a corresponding seat I! in the hub. The nut I, when screwed onto the outer end of the shaft 2, forces the conical members I and ii into the hub and centers the same eii'ectively on theshaft. Aspringlocking ring ll isinthe annular recess M in the projecting end of the hl'ibandlocksthehubnut llinplace. 'I'hlsls good practice in use for attaching the propeller hub. 1

Each propeller blade II is revolubly supported upon ashank l6 (see Fig. 1) which is shouldered and screw threaded at ll into the huh I. The

.splines are machined into the shank II and hub l at the same operation. The propeller blade I! is provided with a journal heating it for the journaled outer end of the shank I, the bearing a bushing ll. The inner end of the shank "is a journal and is provided withajournalbearing II withabushing II inserted into the adjusting thrust collar 22. The adjusting thrust collar 22 is secured to the inner end of the propeller by the buttress type of screw thread at 23. The a justing collar is provided with a shoulder 24 and receives the thrust ball bearings 25 which are within the propeller socket 26 integral with hub I and held by the screw thimble 21 threaded into the outer end of the propeller blade socket I6.

28 is the worm gear adiusting means on the 7 end adjusting collar 22. I! is the worm. which controls gear 28. It is retained by the housing 30 which contains-thrust bearings ll, 32 at each end, which are kept in place by the plugs II, 34, screw threaded into the bearing

housing enlargements

35, 35 at the ends of the housing that embrace the ball bearings. The housing II is retained in place by a series of cap screws 36, see Figs. 1, 2, and 3 for the details.

The worms 29 are provided with bearing shafts 31 to each of which is secured a pinion I! by suitable keys 4|, indicated by dotted lines in Fig. 3. These pinions 39 are disposed between the inner spur gear ring 4| and the outer internal threaded gear ring 42, see Fig. 4. The adjusting ring gears 4| and 42 are supported within the annular housing 43, the inner face 44 of which is located by dowel pins 45 on the end of the huh I and is secured by screws to the screw plugs 34 which retain the thrust bearing of the worm 29 in place. The ball bearing ring 46 is fitted securely within the periphery of the housing 43 and is retained by a screw threaded ring nut 41. An inner ball bearing ring 48 for the ring 4| is carried by the spacing sleeve 8 and is clamped in place by the screw threaded ring 49 which clamps the hearing ring 48 against the inner edge of the housing 43 and assists in clamping and holding the same in place. The outer ring gear 42 is tempered and hardened at its periphery to form the outer member or race or the bail bearing therefor and cooperates with the balls 50 which are retained in a suitable ball ring within the bearing ring 45 and the peripheral bearing surface of the ring bearing so that the outerring gear is freely rotatable and adjustable within the casing for the pur- Aspacimsleeveliscn pme of controlling the pinions above-mentioned. A shield 43! is provided for protecting the parts from the elements.

The inner or spur gear 4| is hardened on its inner bearing surface and cooperates with the balls 8| which run in the race within the bearing "ring 48 whereby this inner spur gear readily rotates and is adjustable and in mesh with the These pinions, ring gears, and parts all revolve with the hub. It is clear that, if the outer ring gear 42 is retarded or stopped in iisrelative movement to the ring 4|, this will cause the pinions 39 to rotate and, by their rotation, they cause the operation of the worms 28 and adjust the pitch of the propellers. On the other hand, if the ring spur gear 4| is retarded. it will also have the effect of rotating the aforesaid pinions but in the opposite direction, causing the corresponding adjustment of the pitch of the propellers. I preferably do the retarding with magnetic brake means, but other means are available. The worms 29 have a low helix angle and are adjusted only by the action shown.

I provide armature rings or steel correspondaforesaid pinions 38.

ing to each of the'ring gears and support them parallel to the axes of said 7 yieldingly held inwardly by coil spring cons on. The internal gear ring 4| is provided with armature ring 52 and the external internally-toothed gear ring 42 is provided an armature ring 53. The armature ring 53 is provided with an internal oblique flange l4 toothed on its edge for the purpose of hand or independent manipulation, hereafter to be described The armature rings are each supported by a set of spring pins which are all the same, one of them being detailed in Fig. 6. The pin 58 is carried in a screw sleeve 56 which is screwed into a socket bore 51, which sleeve is held adjlw eblv in place by the lock nut I. The inner end of the pin is screw-threadon pins which are ring gears and are 4 ed and provided with an adjusting screw nut 59.

K coiled spring 0. is on the axle, the tension of which is varied by the nut 59 which reacts upon the outer end of the spring. The inner end of the Spring is bottomed against the screw-threaded sleeve 5.

Corresponding to the armature rings are annular elets ii for the inner ring 4| and 81 for the outer ring 42. The housing of each of these magnets is a U-shaped annular ring havin grooves, 64, made of pure iron or high grade cast iron or whatever is found to be most eirective as magnets. These magnets are carried by supports Gill secured to the motor housing by cap screws 6| The same are provided with annular coils of wire, the inner and outer 66, constituting the coils of each of said magnets. .The cores of the magnet are external to the coils. These

coils

65 and 66 are, according to the oilicial aircraft requirements. closed coils extending from one side to the other of the battery or source of electric current used. Supported opposite the core of each magnet and within the magnet casing are brake rings 61 of non-magnetic material for the inside and brake rings 68 for the outer magnet. These are rigidly secured to the shells of the magnets by suitable screws 69 (see Fig. 6 and are very accurately spaced from the armature, whereby a very slight excitation of the coils causes,the armatures to contact with the brake with a slight pressure, causing retardation in proportion to the current and to the coeilicient of friction. This structure illustrated is engineered; for direct electrici are,

renti 'Thesa a r I 'altemating current but" would be engineered and designed accordingly] On th outer armature ringSS, I form me tension oblique flange 54 and provide flne gear teeth on the inner edge thereof. I This is for the purpose "of hand or supplemental manipulation of'the exte'rnal ring gear.

JAsmall shaft :18 (see Figs. 7 disposed-in a suitable bearing carryinga'pinion' 12'adapted tome sh withythege'a'r teeth on e invention can" be utilized with loss of'ithefs lal advantag'esf Iri'securing this result,'it' is preferredfto make a master blade 7 by 'makin parts readilyadjustable' and then making the'integral completed master blade from the adjusted structure as .a pattern. Tothis the screw-threaded weight is added. The slight adjust ment 'p'o ible by the\s crew-threaded weight "'l9'mak'esitpossible to adjust and accurately theflange'fl. The shaft Ill is drivenby a'crank 18' connected by a flexible shaft I3 :(Fig; 19), the crank projecting ataconvenient place on the instrument board or within reach of the pilot in the cockpit. If the engine has gone dead and the propellers are notrotating, this enables the'pilotyby pushing the pinion- 12 into engage-- ment, tocrank the same and turn the outer gear ring sufliciently to adjust the propeller'blades .toytheedge or feathering position so-that the .propeller will not offer resistance and will not counterbalance each individual propeller blade by the means here illustrated. The blade is madesubstantially correctbya master blade and this slight variation by the screw adjustment takes care of the complete adjustment'of ,the same.

Very slight adjustment of the pitch of ,the blade makes a great difference in its action. In Fig.- 10, I have indicated this range by showing the-blade in cross section, the full lines showing windmill, thus enabling,in the event of a single propellerumachine, the gliding to groundin a much. larger radius, ;and,-in the event: the 'engine-is one in a multiple-engine planeg thesame out of operation so that can be put, effectively 'flying'may' be continued efficiently with-1a part This means is entirely of the propellers in use. independent of the magnetic electric. apparatus.

InF'ig. 20, I have shown,

the shaft 10 and the pinion 12, a small electric starter motor "I! controllediby the usual starter. button. This is largely indicated diagrammat-- ically and is not detailed becausethe details for such starting motor'are well known and well un-.

derstood. 1 By proper energization, this motor can be made to move the outer ring gear relative to the housing and thus vary thepitch of the blades; Y

In an adjustable pitch propeller, the pitch of installed for driving may openfsealed switches toone-orthe other of the circuits toone or anotherof the magnets, as

' required, and close the proper opposite circuit.

the propeller is varied by. theadjustmentand this induces a difierentaction upon the propeller, particularly in view of the fact thatit israpidly rotating. as well as advancing in' the air. It isa requirement that the propeller be very nicely regulated and balanced by counterweight .in orderto, avoid undue strains. Clearly, to-calculate this definitely would call for carefulconsideration of the material of the propeller and its and I, therefore, work out this balancing by rule of thumb. I illustrate and desoribethe preferred procedure under such circumstances.

In Fig. 11, I show the counterbalance weight 15 secured on a shank 16 by a divided collar 11 to the round part of the propeller blade, the same being suitably clamped thereto, one part carrying the counterweight 15. This is here shown conventionally as a ball but, as a matter of fact, it is of irregular shape to avoid accumulation of ice. The shank radial bore 18. From the center out is a suitably screw-threaded shaft-18l cooperating with the screw-threaded weight 19.1 A gear- I82 is fixed to the end of the shaft 'l8l and meshes with a driving screw 183.. This weight'is adjustable only by special tool or screwdriver operating the screw I83. This internal support and adjustment is provided to prevent dislocation of theparts. which are supported on the propeller arm and subjected to rapid motion and severe strains. A slight adjustment of. the. weight has a very marked effect on the propeller blade. The weight 19 might be form,

16 is provided with a otherwise adjusted with the 76 lwider radius and area of operation i an'd thereby cause the propeller to 'be adjusted against the stop,v which throws the propeller to the'reverse position, gency where the pilotjis required to make a forced landing; By'r'eversing the pitch of the propeliers,"the pilot can'check the speed of the plane and landin a muchsmaller area or field. Also, the circuit may be thus closed to feather the propellers." In the event the engine the control circuits'jare thrown outcompletely andit is possible for the pilot, by the, adjusting crank 10', to edge or feather the blades of the propeller, thereby overcoming their resistance to theiadvance, of the airplane and permitting much ground. If the plane is amu l one, this adjustment can bepmjade so'far as required when any engine unit fails.

I will'now which the automatic control or tachometer control is accomplished. The usual construction of tachometer is made use of along with attachmerits added thereto. The circuit is closed by a circuit breaker used in connection with the throttle of the engine. In Fig. 18 (see lower left of Fig. 18), I show the throttle lever 83 operating the throttle control rod 85. I provide a fixed contact 86' and a sliding contact 81 insulated from the throttle control rod 85. A coil spring 88 on the rod causes the same to be held yieldingly in place. These contacts close the circuit when the throttle lever is moved half or twothirds over and, consequently, the circuit is closed for regulation only when the throttle is half jay open or open to the extent determined upen nc forali the lower speeds represented by movement of the throttle before this contact is made,

the tachometer control is cut out.

I make additions to the usual construction of tachometer on an airplane so that the same can beadjusted for thecontrol of the electric current to the-magnets through the speed ranges which are appropriate to the particular service required. I

I provide such adjustment that may be set to control the propellerblades at the most efilcient angle for operation at 1400 R. P. M. I can also set the same for the most emcient angle of the This is done in an emer goes dead,

discussthe circuits and means by V 'sition which it takes being regularly brought into use at or above the range of the rate indicated up to the high speed limit of the engine. Incidentally, the device should never be set beyond the limit of the high speed of the engine.

I provide controls associated with the moving part of the tachometer. The tachometer is of usuaL-construction with the drive (not illustrated) operating a gear 89 to drive the pinion 90 of the tachometer, thereby operating its centrifugal governor weights and parts that are connected to control the indicator hand on the dial and show the speed. I cut out a segment of the wall of the case and secure the flexible contact arm 9| to the hand-carrying part 92 of the tachometer, allowing the end of the arm II with contact head 9| to project through this opening.

I provide a curved segment slideway 93, suitably insulated by

blocks

94, 95 to carry the adjustable slide block 96 and cooperating contacts I! and 98 (see Fig. 13).

The contact 91 is secured adjustably on the insulated slide block 86 in position to contact with the contact head 9| on the flexible arm 9|. Contact 88 is pivoted to swing up to permit the flexible arm II with head 92 to pass up past it. The arm Si is adapted to swing down and pass the pivoted contact 98 against the insulated block 99 below. The pivoted contact 98 is provided with insulation ill on its face and is pivoted within the circuit and held yieldingly out by spring lOi (see details particularly in Figs. 13 to The contact II is connected by a flexible conducting wire it so that it does not depend upon the pivotal contact for its electric circuit.

it will be seen that the contact head ll will swing.

uppast the yielding contact 08 without closing the circuit, but on its return will'contact by a wiping contact of the head 9| with the pivoted the relay magnet III which closes the same and relays to the main circuit III which is controlled by the throttle lever, as described, and that this will excite the outer coil 00 which will operate the magnetic brake in that behalf and retard the 42, thereby controlling the pitch of the propeller'bladesand increasing the pitch of the propeller by the advancing edge of the same to secure the stronger action thereof. If the tachometer flexible contact arm 9| swings down, the head ll contacts at and excites the relay circuit I 09 going to the corresponding relay magnet III, and relays to the main circuit III which leads to the inner magnet coil 85 which serves to rotate the actuating worms in the opposite direction, resulting in decreasing the pitch of the propeller blades. These circuits are connected and both returned to the negative posts'of the battery.

I also provide a hot wire connection H2 branched at H3 to the outer coil 6' controlled by sealed push button switch Ill and branched at I to the inner magnet coil 8! controlled by sealed push button switch H6. These push butcontact 98 and, on the further bending of the flexible arm 9|, it will pass the pivotedcontact "98 and automatically go-out of commission and come in engagement with the insulated stop SI.

The insulated slilding block 8! can'be set to any position required on the tachometer, the po indicated and calibrated in R. P. M. With the structure illustrated, it can be set from about 1400 R. P. M. to 2500 R. P. M. or more, within the capacity of the highest speed of the engine. The block SI (see Figs. 13 and 14) is adjustable by means of the lever I03 held yieldingly in place by spring Hit. The lever I is provided with a tooth III to engage the notched segment IIII on the outside along the periphery of the dial face of the tachometer casing. By taking hold of the end of the lever I03 which is in the form of a knob, the slide is released, the pointer swung to the position required, and the spring lever carries the tooth "it into engagement with the notched segment Hi6, holding the same securely in place. The binding posts on the insulated slide block 98 are connected by very flexible cables into the circuit so that the slide is adjusted freely back and forth without interfering with the circuit that is connected to the binding post.

By referring to the wiring diagram, particularly Fig. 18, it will be seen that, when the flexible contact arm 0! passes up tothe control position and the upper contact 81, the current will be delivered to the relay through circuit ill to ton switches are sealed switches and are to be used only in-event of emergency. The breaking of the seal requires the pilot to make explanation and report.

The outer ring-gear 42 is capable of being manipulated manually. as I have explained. It is possible thus to completely control the pitch of the blades by such manipulation. The propeller blades may be feathered to prevent windmilling and to reduce the resistance to permit greater ease of cruising with less than all of the engines in a multiple-engine plane or increasing the radius for coasting down in event of an accident and the stopping of the engine.

.As to the tachometer, I have shown a special construction. The flexible arm 8| insures a rubbing action for the contact and, consequently, insures most effective action. Likewise, it vibrates and, when nearing one or the other of the contacts, its circuit-closing engagement therea with is momentary so as to deliver impulses to the corresponding relay and electromagnet. I

have shown one of the stops adjustable and the other stop pivotal, cooperating with the flexible arm, for the special purpose indicated. However, it is clear that the stops being properly placed, the flexible arm would function without the special construction which facilitates the same. The contacts might be made with any moving part of the tachometer which synchronizes with the indicator part.

The use of the flexible switch arm is of importance because the wiping and vibratory action assures an immediate response and eliminates the pombility of welding at the switch due to the passing of current from the flexible arm to the contact. This switch is particularly adapted for use in the relay circuit because it is possible with this switch to handle a very small amount of current and to provide an eflective contact to actuate the magnetic brakes quickly and positively to produce the desired braking effeet. The switch, due to the lack of welding, will release quickly and effectively in response to very slight movement of the tachometer. In combination with the tilting contact 98, this switch is particularly effective because the automatic control is not put into operation until the engine of the airplane is up to nearly the desired speed. 'I'heflexibleswitcharmcaneasilypassoverthe contact without putting the automatic control ing speed. the contacts have provided such accurate bearings the 'pinions themselves.- 1 ring alone might tureis rotating into operation when the throttle is opened and. when the throttle is at the position for operatand switch are positioned for most effective cooperative action. When the throttle is retarded, the spring ar'm'permits' the switch bladeto slide over the contact and the automatic controlsare effectively put-out of operation forslow or idling'speeds.

The ring gears for'adjusting the propellers I with a special ball bearing with hardened parts which :I" consider desirable in this behalf. It is clear the pinionsto the external and internal gears, the rings wouldnot need tobeprovided' with as they willbecarried-by In this behalf also, one be made use of by, for instance. connecting the starting motor shown in Fig. to return the same to initial position. By taking time for the manipulation of the gear rings, it mightbe accomplished by inFig. 19, when, suflicint as the pilot could turn the crank'in either direction and make complete adjustments for all purposes, control, feathering, or reverssirable to provide the braking surface with the brake lining material interposed to secure this braking action. However, it -might be accomplished with a strong enough current without that, with proper fitting of I As to the electromagnetic brake, I find it de-,

could be effectively the crank illustrated of course, one rlngwould be shaft into a I This application a hub; a blade extending j shaft extending parallel of said hub; means s for the current the result accomplished without' the The advantages ofthe be omitted in such a As to the rela' interpositionof relays". relays would, of course, structure.

I have shown direct current. for alternating current as well, mentioned.

the wiring in each instance for The same could be engineered as previously I desire-to claim the invention specifically as 'wellfasbroadly; v I f I I Y is a continuation of my application Beriai-No. 57,739, 'illed January 6, 1936.

I claim as my invention:

1. In an adjustable, pitch combination of a rotatable'member includin I V outward from said hub, means fonpivotally securing said blade to said hub to turn about an axis of said blade;

toythe rotational axis 7 for journalling said-pinion shaft relative to saidrotatable member; means for dperatively connecting said pinionshaft' and said blade to translate rotation of said pinion turning of said blade to vary the pitch thereof; a pinion on said pinion shaft; an

" outer gear comprising a ring gear providing internal teeth meshing with said gear providing external teeth meshing with said pinion: bearing means the necessity for contact between the parts.

I have shown-a special armature ring The'ring gears themm'agnetic metal and Again, carried by the ringgears. selves might be made 'of pinion; an inner for said outer and irmer "gears; a pair'of brake means for respectively retarding said inner and outer-gears while said dispense with these, intervening parts without, I

however, securing the advantages accomplished thereby. V; I A

\ The invention comprehends employment of means for momentarily retarding the inner and outer gears selectively while the rotatable structo move the, gears relative to the rotatable structure, while avoiding. looking or stopping of that gear which is momentarily retarded, this being accomplished by the two elec- 'hub is rotating and including a pair of ring armatures, means for yieldably attaching same 'respectively'to said gears and a pair of electromagnetic. means disposed respectively adjacent said ring armatures, said electromagnetic means ring of magnetic material of U-shape providing an annular winding spaceand a winding therein, each ring of magnetic material providing a braking surface contactable with the tromagnetic means respectively including a ,pairv of normally-open circuits, and a control means for momentarily closing either of the circuits selectively for a period of time insuflicientito stop either of the p p tarily decelerate the braked gear with respect to the prevailing speed of the rotatable structure. The invention also comprehends an annular elect-romagnetic element, such as the annular electromagnet 62, providing a winding and a braking surface, with a means for energizing the winding at intervals and a means for applying a retarding force to the gear means fora shorter period-of time than the periodlof time during which the electromagnetic element is energized, this last-named means lncludingfan armature operatively'connec'ted to the gear means and spring means resiliently holding the armature away from the electromagnetic element but exerting a resilient force which is overcome by energization of the electromagnetic elementand corresponding attraction of the armature to retard thearmature by light frictional contact with the electromagnetic element. The first portion of the period of energization of the electromagnetic element is used up in an advancing movement of the armature toward the electromagnetic element so that short periods of re tardation can be obtained with longer periods of energization of the electromagnetic element.

gears but suillcient to momen- I corresponding yieldably-secured armature when said winding is energized 'thereby' applying a braking force to the corresponding gear to rotate said pinion; relay means providing sets of contacts; main circuits for respectively connecting said sets of contacts in circuit with said windings to energize same individually; a tachometer providing means movable in response to the rotational speed of said hub and a flexible switch blade driven thereby, said tachometer providing a movable part; a pair of contacts mounted on said movable part to be moved together relative to said flexible switch blade and disposed in the normal path of movement of said blade, said flexible switch blade flexing to pass one of said contacts in moving into and from an intermediate position therebetween in which it can electrically contact each of said contacts individually-in response respectively to an increase and decrease in the rotational speed of said hub; circuits. connectin s id contacts and said flexible blade to said relay means to energize one of said windings when said flexible switch blade electrically engages one of said contacts-and to energize the other of said .windings when said flexible switch blade engages the other one of said contacts; and insulating means on that one of said contacts first reached by said flexible switch blade when the speed of said hub increases for preventing electrical contact therebetween untilsaid switch blade assumes said inter-mediate position.

, propeller adaptedto be coupled with the shaft of an: engine, the

a pinion 2. In combination: a variable-pitch propeller; pitch varying means for varying the pitch of said propeller while rotating and including two electric circuits and means responsive to the energization of one circuit to increase the pitch andmeans responsive to the energization of the other peller speed, and means for automatically preventing energisation of either of said circuits during movement of said circuit-energizing contact from said end position at one side of both the contacts to said intermediate position between the contacts whereby said circuit-energiaing contact is inoperative to control the pitch of said propeller until it assumes said intermediate position.

3. In combination: a variable-pitch propeller; pitch varying mean for varying the pitch of said propeller while rotating and including two electric circuits and means responsive to the energization of one circuit to increase the-pitch and means responsive to the energization of the other. circuit to decrease the pitch; and means for selectively energizing said circuits, said means including av tachometer providing a -movable member which advances as the speed of said propeller increases, a flexible blade operatively connected to said movable member to advance from a low-speed position to a higher-speed position as said movable member advances. flrst and second contacts spaced from and insulated from 40 each other and positioned in the path of travel of said flexible blade, means for electrically connecting said flexible blade and one of said contacts in one of said circuits and for electrically connecting said flexible blade said contacts in the other oi said circuits to energize said circuits selectively in response to electrical contact between said flexible blade and speed of said engine constant at a desired value within a few revolutions per minute irrespective of adjustment of said manually-adjustable means within a normal range oi power outputs. this means including a variable-pitch propeller driven by said engine. pitch-varying n :chanism rotating with said propeller, electric means for operating said pitch-varying mechanismand including a pair of control circuits adapted when selectively energized to increase and decrease re-' spectively the pitch of said propeller, control means independent of adjustment of said manwilly-adjustable 'means within said normal range oi power outputs for selectively energizing said control circuits in response to a deviation of engine speed from a desired value to increase the pitch 01 said propeller when the speed of said engine increases slightly and to decrease the pitch of said propeller when the speed 0! said engine decreases slightly thereby maintaining said speed constant within a few revolutions per minute, and automatic means for rendering said control means inoperative to actuate said electric means until the speed of said engine reaches said desired value.

6. A combination as deflned in claim 5 including as an additional means a switch means electrically connected to said control circuits to render same inoperative when said switch means is and the other or a said hub to turn about an said flrst and second contacts, and means for yieldably and movably mounting that one of said contacts which is flrst reached by said flexible blade in moving from said low-speed position to said higher-speed position to permit said flexible blade to displace said one of said contacts from its path of travel in moving into an intermediate position between said contacts, said blade flexing in moving from said intermediate position to permit passage thereof beyond said one of said contacts in returning to its said low-speed position.

4. A combination as defined in claim 3 in which the yieldably-mounted contact includes an insulating member contactable by said flexible blade in moving from said low-speed position toward its position intermediate said contacts whereby said contact is displaced from the path oi travel of said flexible blade by contact between said blade and said insulating member thus preventing electrical contact between the flexible blade and the yieldably-mounted contact until said blade assumes its intermediate position between said contacts.

5. In combination with an engine: manuallyadiustabie means for changing the power output oi said engine;

and means for maintaining the 16 a momentary in inoperative position-and to render same operative when said switch means is in operative posltion, and means operatively connecting said switch means and said manually-adjustable means for maintaining said switch means in said inoperative position when said manually-adjustable means is positioned below said normal range and for moving said switch means to operative position when said manually-adjustable means is moved to a position within said normal range.

7. In an adjustable pitch propeller adapted tobecoupledwiththeshaitoianengine,the combination 0!: a rotatable structure including a hub; a blade extending outward from said hub; means for pivotally securing said blade to axis of said blade; an outer gear comprising an internally-toothed gear ring concentric with the rotational axis of said hub; bearing means for journalling said outer gear for rotation about said rotational axis of said hub; an inner gear externallytoothed and concentric with the axis of rotation oi said hub; bearing means for Journalling said inner gear for rotation about said rotational both said inner and outer gears; a pinion shaft carrying said pinion; means for iournalling said pinion shaft relative to said rotatable structure to rotate about its own axis at a position spaced irom the axis of rotation of said hub; means operatively connecting said pinion shaft to said propeller blade to turn same in proportion to the angular movement of said pinion: and annular armature for each of said gears: means for respectively mounting said armatures relative to said gears and including resilient means for biasing said armatures toward their respective gears; a braking ring disposed adjacent each armature but spaced very slightly therefrom when said resilient means retract said armatures but being ccntactable by said armatures in an annular zone oi contact upon overcoming the biasing force; and means for momentarily slapping either armature against its braking ring and for quickly releasing it thereby imparting retarding force to the gear assoaxis of said hub: a pinion meshing with ciated therewith'without 'means, including an annular electromagnetic for a period of slapping contactbetween tardation being.

including switch means 7 contacts, a third contact adapted. to, be. positational speed of said ,8. In an adjustable pitch propeller adapted to an engine, the com-- stopping thereof. said means associated respectively with each braking ring and means for momentarily and selectively energizing said electromagnetic means time insufllcientto stop the corresponding armature and gear but sufflcient tomomentarily decelerate-this gear iwith respect to the rotatablestructure through a momentary the corresponding armature and braking ring,

sumcient to :slightly change the .said last- -na'med means providing two spaced pitch of .the propeller,

this -momentary retioned between said 1 two spaced contacts, means z for operatively connecting said third contact and gone ofsaidspacedcontactsto oneof said electromagnetic means and foroperatively connecting said third contact and the other of said spaced contacts to the other 'of means, a flexible arm carrying said third contact -at-an* outer end thereof, "means for 'pivotally mountlngthe other endofi said arm whereby said third contact may swing into contact with said electromagnetic either of said spaced contactsank! means for moving said arm which is on said pivotally mounted means in response to deviations of" rohub from a desired value.

be coupled with'the shaft of bination of a rotatable structure including a hub; a blade extending outward from said hub; means for pivotally securing said; bladeto said hub to turn about an axis of said blade; an

to turn same 'inproportion to the angular move-,

outer gear comprising an internally-toothed a ear ring concentric with the rotational axis of said hub; bearing means for joumalling said outer gear 'for rotation about said rotational axis of said hub; an inner gear extemallytoothed andconcentric with the rotational axis of said hub; bearing means for joumalling said inner gear for rotation about said rotational axis of said hub; a pinion meshing withboth said inner and outer gears; a pinion shaft carrying said pinion; means for joumalling said pinion shaft relative to said rotatable structure to rotate about its own axis ata position spaced from the axis of rotation of said connecting said pinion shaft to said propeller blade to turn same in proportion to the angular movement of said pinion; and means for momentarily retarding said inner and outer gears selectively while said rotatable structureis rotating to move said gears relative' to'said' rotatable structure while avoidinglocking or stopping of that gear which is momentarily'retarded,

said means including a pair of electromagnetic associated. with said" inner braking the, motion thereof, each electromagnetic means including an armature connected to one of said innerand outer gears, an electromagnet for attracting said armature, and a resilient means biasing said armature and said electromagnet away from each other, energization of said :electromagnet exert-'- ing suflicient attraction between said armature and said electromagnet 'to overcome the biasing force of said resilient means, said electromagmeans respectively and outer gears for netic means including a pair of circuits nor-a mally open but acting when closed to "brake said inner and outer gears selectively, and a control means for rapidly making and breaking either of said circuits selectively in response to a deviationin propeller speed from a. desired value, the

hub; means operatively' riod of time between including eachmaking and subse-. uent' breaking being insumcient to stop either of said gears but suflicient to momentarily decelerate the braked gear with respect to, the prevailing speed of said rotatable structure thereby. momentarily retarding it tochange the pitch of said propeller. 1

' 9. In an adjustable pitch propeller adaptedto be coupled with the shaft of an engine, the coin-:-

bination of; a rotatable structure including a hub; a blade extendingoutward from saidhub; means; for pivot-ally securing said blade to said hub to turn about an axis of said blade; an outer-gear comprising aninternally-toothed gear ring concentric with the. rotational axis of said hub; bearing means for "joumalling said outer gear for rotation about said rotational axis of saidhub; an inner gearexternally-toothed and concentricwith the axis of rotation of said hub;

bearing means for 'journalling-said inner gear for-rot'ation about said rotational'axis of said hub; a pinion meshing with both said inner and outer gears; a pinion shaft carrying said pinion; means for joumalling said pinion shaft relative to said rotatable structure to rotate about its own axis at a position spaced from the axis of rotation of said-hub;v means operatively c'onlne ctin'g' said pinion shaft to said propeller bl'ade each of said gears; means for respectively mounting said armatures relative to said gears and including resilient means for biasing said armatures toward their respective gears; a' braking ring disposed adjacent each armature but spaced very slightly'therefrom when said resilient means retract said armatures but being contactable by said 'armatures in an annular zone ot contact upon overcoming of the biasing force: and means for momentarily v slapping either armature against its braking ring and for quickly releasing itthereby imparting a momentary retarding force to the gear associated therewith withoutstopping thereof, said means I an annular electromagnetic means as* sociated respectively with each braking ring and means responsive. to changes in speed of said propeller for momentarily and selectively energizing said electromagnetic means for a period of which said last-named means includes a switch means adapted when in one position'to send current toone ofsaid electromagnetic means and when in another position to'send current .to the other of said electromagnetic -means, and impulse-creating means responsive to change in rotational speed of said hub for adjusting said switch means to send a momentary current to that one of said electromagnetic means effective in changing the pitch 'of said propeller in a direction to counteract said slight change in engine speed.

v 11. In an adjustable pitch propeller adapted to be closely coupled with the shaft of an engine, the combinationof: a rotatable structure including a hub and an annular housing, said housing "providing. an outward-extending wall a slight and a peripheral wall extendingfrom said outward-extending wall in a direction away from said hub; a stationary plate extending outward from the axis of rotation oi said hub to a position near said peripheral wall of said housing to cooperate therewith and with said outwardextending wall in defining a substantially closed annular chamber around the axis of rotation of said hub, saidv chamber being much larger in a plane normal to said axis of rotation than in a direction parallel to said axis of rotation; an inner externally-toothed gear in said annular chamber, said inner gear lying in a plane perpendicular to said axis of rotation and normally rotating with said rotatable structure; bearing means for freely journalling said inner gear about said rotational axis of said hub; an outer internally-toothed gear comprising a gear ring with an outer periphery somewhat smaller than said peripheral wall of said housing, said outer gear normally rotating with said rotatable structure and lying in said plane perpendicular to said axis of rotation, said inner gear lying within said outer gear; a bearing means disposed between said periphery of said ring gear I and said peripheral wall of said housing to freely journal said gear coaxially with respect to said rotational axis of said hub; an externallytoothed pinion positioned" in said annular chamber in said plane perpendicular to said axis and meshing with both said inner and outer gears, said inner and outer gears -being disposed radially with respect to said pinion; a rotatable pinion shaft towhich said pinion is secured and extending parallel to but spaced from said rotational axis of said hub; means for journalling said pinion shaft with respect to said rotatable structure; a propeller blade extending outward from said hub; means for pivotally securing said propeller blade to said hub to turn about the axis of said blade; means for operatively connecting said blade and said pinion shaft to turn said pinion and said blade simultaneously through proportional angles; an electromagnetic means including inner and outer windings, inner and outer electromagnetic cores respectively partially encompassing said inner and outer windings and disposed in a plane parallel to but spaced a short distance from said first-named plane perpendicular to said axis. two spaced electrical contacts electrically connected respectively to said windings, and a third electrical contact movable in response to changes in propeller speed from a desired value to electrically contact said two spaced contacts selectively to energize said windings selectively; and

means for respectively retarding the normal rotation of said inner and outer gears with respect to said rotatable structure upon energization of said inner and outer windings.

12. In an adjustable pitch propeller including pivoted blade means, an armature normally rotating with said propeller and gear means for turning said blade means in proportion to a relative motion between said armature and said pro eller, the combination oi: an electromagnetic element adjacent said armtaure and cooperating therewith in defining a flux gap; means for resiliently mounting said armature for movement toward said electromagnetic element by electromagnetic attraction to decrease the size of said flux gap to such extent that said armature comes into contact with said electromagnetic element when said electromagnetic element is energized to create a retarding force 011 said armature to slow this armature with respect to said propeller; circuit means for energizing said electromagnetic element; and means for rapidly making and breaking said circuit means in response to avchange in the speed of said propeller from a desired value for retuming the propeller speed to such desired value, said last-named means including means for making and breaking said circuit means at such rate as to create a plurality of rapidly recurring electric impulses, each of such short duration that application thereof to said electromagnetic element will momentarily retard but not stop the rotation of said armature.

13. In an adjustable pitch propeller including pivoted blade means, an armature normally rotating with said propeller and gear means for turning said bladein proportion toa relative rotation between said armature and said propeller, the combination of: an electromagnetic means adjacent said armature; for resiliently mounting said armature to permit resilient movement thereof toward and into braking contact with said electromagnetic means when said electromagnetic means is energized, thus-creating a retarding force on said armature to slow this armature with respect to said propeller; and means for energizing said electromagnetic means to move said armature against the actionof said yielding means and into brief slapping relationship with said electromagnetic means to change the pitch of said blade means,

said means deenergizing said electromagnetic I means before stopping of said armature can take place, said yielding means being biased to urge said armature away from said electromagnetic means to delay contact of the armature with the electromagnetic means when the electromagnetic means is energized and thereby cause the periods ture by of contact to be substantially shorter than the periods of electromagnetic energization, said means for energizing said electromagnetic means including a circuit providing two spaced contacts and a third contact for selectively engaging said spaced contacts in response to a deviation in propeller speed from a desired value.

14. In an adjustable pitch propeller including the combination of: gear means normally rotating with said propeller; means for operatively connecting said gear means to said blade means in such manner that retardation of said gear means with respect to said propeller will change the pitch of said blade means; an annular electromagnetic element including a winding; connected to said winding; means responsive to a change in propeller speed from a desired value for energizing said winding at intervals; and means for applying a retarding force to said gear means for a shorter period of time than the period of time during which said electromagnetic element is energized, said means including an armature operatively connected to said gear means, and spring means resiliently holding said armature away from said annular electromagnetic element but exerting a resilient force which is overcome by energization of said electromagnetic element and corresponding attraction of said armature to retard said armalight frictional contact with said electromagnetic element, the first portion of the period of energization of the electromagnetic element being used up in an advancing movement armature toward said electromagnetic element in opposition to said spring means so yielding means circuit means electrically blade means, the combination of:

that short periods of retardation can be obtained with longer periods of energization of said electromagnetic element.

15. In an adjustable pitch propeller adapted to be driven by an engine and including pivoted blade means, the combination of: a magnet housing adapted to be secured to said engine at a position between the engine and said propeller, said magnet housing including inner and outer electromagnetic elements; gear means rotatable with said propeller and operatively connected to said blade means to change the pitch thereof; inner and outer ring gears operatively connected to said gear means and normally rotating with said propeller; inner and outer armatures respectively adjacent said inner and outer electromagnetic elements; means for securing said armatures respectively to said inner and outer ring gears, said means including spring means normally retracting said armatures from contact with said electromagnetic elements whereby during normal rotation of said propeller said armatures are spaced from said electromagnetic elements; and means for selectively energizing said electromagnetic elements to draw said armatures into frictional engagement therewith to retard selectively the rotation of said armatures with respect to said propeller without immobilization of same, said means for selectively energizing said electromagnetic elements comprising two spaced electrical contacts respectively connected to said electromagnetic elements, a third contact movable to selectively engage said spaced contacts to selectively energize said electromagnetic elements, and means for moving said third contact into its selective engagement with said spaced contacts in response to a deviation in propeller speed from a desired value.

16. In an adjustable pitch propeller adapted to be driven by an engine and including pivoted blade means, the combination of: a magnet housing adapted to be secured to said engine at a position between the said magnet housingincluding inner and outer electromagnetic elements; gear means rotatable with said propeller and operatively connected to said blade means to change the pitch thereof inner and outer ring gears operatively connected to said gear means and normally rotating with said propeller; inner and outer armatures respectively adjacent said inner and outer electromagnetic elements; means for securing said armatures respectively to said inner and outer ring gears, said means includin spring means normally retracting said armatures from contact with said electromagnetic elements whereby during normal rotation of said propeller said armatures are spaced from said electromagnetic elements; and means for selectively energizing said electromagnetic elements to draw said armatures into frictional engagement therewith to retard selectively the rotation 01' said armatures with respect to said propeller without immobilization of same, said last-named means including circuit means respectively connected to said electromagnetic means, relays providing electrical contacts respectively in said circuit means, and means for selectively controlling the operation of said relays in response to a deviation oi engine speed from a desired value. 17. In an adjustable pitch propeller ada ted to be driven by an engine and including pivoted a magnet housing adapted to be secured to said engine at a pysition between the engine and said pro-v engine and said propeller,.

peller, said magnet housing including inner and outer electromagnetic elements; gear means rotatable with said propeller and operatively connected to said blade means to change the pitch thereof; inner and outer ring gears operatively connected to'said gear means and normally rotating with said propeller; inner and outer armatures respectively adjacent said inner and outer electromagnetic elements; means for securing said armatures respectively to saidinner and outer ring gears, said means including spring means normally retracting said armatures from contact with said electromagnetic elements whereby during normal rotation of said propeller said armatures are spaced from said electromagnetic elements; and means for selectively energizing said electromagnetic elements to draw said armatures into frictional engagement therewith to retard selectively the rotation of said armatures with respect to said propeller without immobilization of same, said last-named means including circuit means respectively connected to said electromagnetic means, relays providing electrical contacts respectively in said circuit means, and manually operable switch means respectively in said circuit means for selectively controlling the energization of said electromagnetic means.

18. In an adjustable pitch propeller including blade means pivoted in a housing, the combination of: gear means normally rotating with said housing; an annular armature associated with said gear means to rotate therewith, said armature providing a braking surface; means for operatively connecting said gear means to said blade means in such manner that retardation of said armature and gear means with respect to said housing will change the pitch of said blademeans; an annular electromagnetic element including a winding and a braking surface; mounting means for mounting said electromagnetic element and said armature for relative movement therebetween from a normal spaced position in which said braking surfaces are spaced from each other to a braking position in which said braking surfaces are in contact with each other, said mounting means including resilient means exerting a biasingi'orce tending to separate said braking surfaces, energization of said electromagnetic element exerting an attractive force between said electromagnetic element and said armature sufllcient to overcome said biasing force to bring said braking surfacesinto braking engagement with each other to retard the rotation of said armature and said gear means with respect to said housing; circuit means for energizing said winding of said electromagnetic element; and means for rapidly making and breaking said circuit means in response to a change in the speed of said propeller from a desired value for returnin the propeller speed to such desired value, said last-named means including meansfor making and breaking said circuit means at such rate as to create a plurality of rapidly recurring electric impulses, each of such short duration that application thereof to said electromagnetic element will momentarily retard but not s p the rotation of said armature whereby said armature is moved relative to said housing by repeated application of such momentary retardations to change the pitch of said blade means to the degree necessary to return the propeller speed to the desired value.

, ALBERT KENNETH McLEOD.