US2371187A - Hydeauijcally operated pitch chang - Google Patents

Description

March 13, 1945. H. H. ROBY' A2,371,187

HYDRAULICALLY OPERATED PITCH CHANGING'MECHANISM March 13, 1945.

Filed May 1, 1942 -5 Shee'ts-Sheet- 2 ./Zcd 30 INVENTOR.

Horace @obj ATTORNEY.

March 13, 1945. v H. H. ROBY 2,371,187

HYDRAULICALLY OPERATED PITCH CHANGING MEHANISM Filed May l, 1942 5 Sheets-.Sheet 5 2M Honda@ '9' V BY gd /g Patented Mar. 13, 1945 HYDRAULICALLY OPERATED PITCH CHAN G- ING MECHANISM Horace H. Roby,'Wicl1ita, Kans., assigner, by mesne assignments, to Robert C. Foulston, W. L. Hartman, and John F. Fitz-Gerald, trustees of Roby, Inc., Wichita, Kans., a oorporation of Kansas Application May l, 1942, Serial No. 441,346 3 claims. (ci. 17o-163i c onditions of air density, plane speed, engine speed and power, etc. These conditions vary depending upon whether the plane is taking oiI or flying level at a substantial altitude. Indeed, these conditions may vary considerably during the course of a long flight depending upon the weather conditions, ,the character of the country over which the plane is dying, etc. Accordingly, fixed pitch propellers are generally unsatisfactory. It is highly desirable that an adjustable pitch propeller be provided having a maximum and aminimum pitch position and capable of being held at any selected adjusted intermediate position.

For example, it is desirable that the propeller blades be adjusted to a low pitch during the takeof! period and adjusted to a high pitch position after the plane has gained altitude and assumed a normal level flight. If the propeller blades are given a low pitch during the take-off, the engine can obtain its most efllcient speed substantially immediately, permitting the plane to rise after a relatively short run and to gain elevation essentially rapidly. When takingofl, the plane speed is low and there is a heavy load on the propeller. Internal combustion engines do not develop maximum power at slow engine speeds. Therefore, if

,y `during the take-oil period the pitch of the blades is too high, the resistance offered by the airto rotation of the propeller will hold the engine to a relatively slow speed so that it will be most inf eiilcient when the greatest power is needed. Also, if the pitch of Ythe propeller blades is too high during thetake-oil period, the plane will remain. on the ground a longer time before attaining iiying speed. v It isespecially desirable in the case of lightI airplanes and observation, in-v terceptor, scoutingand fighterplanes that the take-otr time be reduced to a minimum.

,It the propeller is adjusted and held at a low pitch position, the plane will'rise and attain flyjusted to a high pitch position during normal night. The propeller blades will then offer sum cient resistance to hold the'engine at its normal full power speed. e

Furthermore, present day airplanes fly long distances and frequently at high altitudes. When the plane is operated under these conditions, it is often necessary that the propeller blades be held at intermediate positions between the maximum and minimum pitchl positions ii optimum em ciency is to be realized.

Variable pitch propellers are operated both mechanically and hydraulically. When a mechanical control is used, the propeller blades may be rotated through a predetermined pitch range andheld at a selected adjusted position. However, where a hydraulic control is used, it has not been possible to easily position andhold the propeller blades at any selected adjusted intermediate pitch position.

It is .therefore an object of my invention to provide a hydraulic control for a variable pitch propeller that may be manually operated to hold the propeller in any selected adjusted position between a maximum and minimum pitch position.

Another object of my invention is, to provide a hydraulic control o! the abovementioned character that may be easily operated by the pilot when the plane is in ight.

Still anotherobject of my invention is to provide a hydraulic control oi' the above mentioned character that involves a minimum of working parts to eliminate mechanical troubles as far as possible. i

Other objects and advantages of my invention4 will be apparentl during the'course of the following description. i

In the accompanying drawings forming a part the same,

ing speed after a relatively short run. However,

after the plane assumes a normal level iiight, the resistance oieredby the air to propeller rotation is decreased, the load on theengine becomes less and the engine will speed up.. `The engine must then be ythrottled down and will produce Vbut a portion of the power of which it is capable. For maximum emciency, the propeller should be ad- Fig. l is a side elevation of a hydraulically operated pitch changing mechanism embodying my invention, parts beingl shown in section for clear,- ness of illustration,

' Fig. 2 is a fragmentaryv vertical sectional view,

taken on the line 2-2 ot Fig. 1,

the line 5 5 of Fig. 3, showing an automatic fluid control valve embodying a part ot my invention.

between.

line 8-6 of Fig. 5. l Fig. 7 is a fragmentary vertical sectional view taken on the line 1-1. of Fig. 6, showing a cam comprising a part of the automatic valve mecha- Y nism in a position to close the valve,

Fig. 8 is a view similar to Fig. 7 but showing the cam rotated to a position to open the valve, and

Fig. 9 is a fragmentary view similar to Fig. 3,v

ends of the shanks 20a,v and bearing surfaces for rotation of the sleeves on the spindles is supplied by removable bearing sleeves. Collars 2| have flanges 2la within the housing Il. Thnist'bearings 22 are positioned between flanges Ila and the enclosing ends ila of housing Il. These thrust bearings carry the centrifugal loadimposed when the propeller is rotated. The thrust showing the hydraulically operated pitch changing mechanism without the automatic fluid control valve. i

In accordance with this invention, I mount-a variable pitch propeller on a conventional crank shaft having a hollow outboard end as shown in Fig. l. Mechanism is provided for rotating the propeller blades about their axes in response .to movement of a piston mounted on the forward end of the crank shaft. A bleedr line from the lubricating system of the plane conducts crank case oil into the hollow crank shaft. The pressure developed by the oil pump on the fluid in the crank shaft is suilicient to force the piston outwardly against the forces -acting on the rotating propeller blades. A valve manually operable from the cockpit of the plane controls the` flow of oil into the crank shaft and also the flowy of oil therefrom. By proper operation of the valve, a. requisite amount of oil may be forced into the hollow portion of the crank shaft to move the piston a selected distance. An automatic valve mounted in the crank shaft is provided to hold the oil in the piston.` The automatic valve is operated by fluid pressure in the crank shaft.l

Each time fluid under pressure is injected into the crankshaft, the valve is automatically operated. One injection lof fluid into the crank shaft moves the automatic valve to a closed position and the next injection of uid into the crank shaft moves the valveto an open position.' Thus,

repeated opening and closing of the manually operated valve will cause consecutive injections of duid into thecrank shaft so that the automatic valve may be either opened or closedtc either hold orreleasc the oil in the piston. When the automatic valve is closed, the oil is trapped in the piston. When thegautomatic valve is open, oil 'trapped in the pistonV is released. The torque on the propeller blades will then retract the pisbearings also permit axial rotation of the propeller blades about spindles l2a when the pitch of the blades is changed.

y Helical springs 23 are confined between the shoulders i2b of spindles I2a and-the shoulder 20h ofthe ,outer bearing sleeves. The resilient action of springs 23 urges the propeller blades outwardly and holds the collar flanges 2 la against the inner races of thrust bearings 22. .'Heretofore, it has been customary to use roller bearings in place of springs 23. However, where roller bearings are used. it is necessary to provide for removing play in the bearings by means of shims. This bearing arrangement has proven to be generally unsatisfactory. When a roller bearing assembly of the type shown at 22 is not furnished with resilient vmeans to hold it compactly together, vibrations' created by lpower impulses of ythe engine cause the balls ofthe race to chatter and wear the surfaces of the inner and outer races. Thus, the balls pound themselves4 into the races and a rough bearing is the result. By using springs 23, it is unn to "shim" the bear-l ings with sumcient force to prevent chatteringv or vibration of the balls. Springs 23 also prevent the nanges 2I'a from dropping a'way from thrust bearings 22 4when the. propeller is at rest.

Surrounding .the bases of spindles' Haare ringshaped control arms 2l. -These arms are journaled for rotative movement`about pivot pins 25 which are partially embedded in the hub I2. The arms loosely surround the spindles andv the ends thereof adjacent pivot pins 2l arebifurcated to receive pins 28 projecting from the flanges 2Ia ofthe propeller collars as shown in'Flg. 2. When the control arms are pivoted about pins. 25, they will move the propellers through an arc having the center of the pivot pins 2l as a radius.' This/ movement will increase or decrease the pitch of ton and-.unless checked blades will eontinuetorctate nntiltheyassmneaminimum pitchposition. Inthepreferred' "tofmyinventlon" shown m the nimm-Is designates' a tubular ycrankshaft whicnprojects-'through Y the front wall ofcrank case lijn-the conventional manner. A propeller hub lspllned to f crankshaft'llasbestshowninlll 'end of hub' I2 seals again-st suffice of'holdingringheldinpoeitionbyspacingrlngi' '|3a. A'sealingring l3bfsinfrontofring- I3. f Aconeorhcidingrlng'llisheldtlshtlylgsinst.

the intermicpnoiaal msoe'lsat the :mma

I3 and lochngring Il Il there- Ahollowcylind'ricalhousin'gl'liscarrledby propellerh'nb. Thelsformedintwo partswhichareheldtog'etherbybolts I3 and nutsll. llaresecuredtothebuttends of the propeller blades (not shown). on the threadedpormsodshanksaofsleevesare screwedcollars. Thelma llhas'integml the blades. Mounted on a forward tubular extension I2c of the hub l2 is apiston 2l. Arms2'la integral with the piston are fitted into channels or grooves |2d in the hub and serve to connect with the mds of control arms 2l remote from pivots 25 through pins 23 fastened to the arms by screw bolts shown dotted in Fig. 2. When the piston moves outwardly due to the introduction of hydraulicliquidfthecuntrolarmswillbeplvoted about pins 2l to increase the pitch of the propeller blades. when the piston. moves inwardly upon dischargeof hydraulic liquid, control armsv 2l will be pivoted in the opposite direction about pivot pins 23 to decrease the pitch of the blades.

Anendmclosurethreadedintothetubular extension 12e carries s -flexiblegrlng 3l which sealstheinnerwalloftheplstontoformafluidv Theipistonlslimitedin-itsmovement b y bolt 3|. end c! boltf3l extends throughtheend'otthelistonnndhasahea'dfor adjustment. 23amthe'endmcloslne 23 around'thepermitthehydraulicfluidto-Av enterthepiston. Hydraulicmewltlnnthe pistonwlllforeeitoutwardlymtlltheheadof boltll Them#- l'ldllljplndl Iwhichmjectintqthehollow '7l tmlbpk'eiln'guhedbyldjmtdboltll.

by lock nut 52.

Thus, the stroke of the piston-.may be easily acuda? The boit is heid' m the selected smashed positions sleeve.

regulated without dismantling any parts of the mechanism. Inward" movement of the piston is limited by abutment of bosses 33 and 34 in which position the hydraulic fluid may freely pass through radial channels 34a thus preventing the formation of a seal between the piston and end enclosure 29.

the action of spring 52. When the uid pres- As a source of hydraulic uid, oil from the lubricating system is supplied under pressure to the piston by pump 35. This oil pump is conventional in airplanes to circulate the fluid lubri-l cant from a reservoir or sump through the lubricating system. A fragmentary part of the oil circulating system is shown at 3B. Oil is bled from the line` through pipe 31. This oil passes through valve 35, pipe 39, passage and into the hollow crank shaft through radial passages loa. The core 35a of valve 55 ismanually rotated by control arm 4|. A link 42 connects the arm 4i with a control on the instrument board (not'shown) within the cockpit of the airplane. The control is preferably locatedin a position 4 where it may-be easily operated by the pilot.

When arm 4I is pushed forwardly, -as shown'in `Fig. l, passage 35h through the valve core will connect pipe 31 -with pipe 39 so that pump 35 forces ol under pressure into the crank shaft. If arm 4I is moved in a reverse direction, the enlarged end of passage 38h will move into reg'- ister with pipe 39 and pipe 43. Pipe '43 connects valve 35 with the oil sump. When the valve core' is in the last mentioned position, pipe 31 is shut cifand fluid trapped in the crankshaft and behind the piston will `flow through passage 45, pipe 39, valve passage 38h, and pipe js to theoil sump or reservoir.

. Flowi of oil to orfrom piston 21'through the. crank shaft is controlled by avalve designated generally by the numeral 44 having a tubular valve body 45. The forward end of a valve body is fixedlyl connected to' a boss on the hub endl enclosure 29. A bearing seal l supports theA inner end of the valve body against the internal wall of the crank shaft. The valve body is formed in two parts 45a and 45b'which are connected by a valve plug 41 shown in Fig. 5, The valve plug has a longiiudinal passage 41a which is normally closed by ball valve 45'. Helical sure inthe crank shaft is cut on by operation of valve ",spring 52. slides the plunger inwardly against locking ring i53. Each reciprocating of plunger 5i rotates camf54 ninety degrees. Ro-

tation of the cam actuates the pin to unseat l and permit seating of the ball valve 48.

Referring now to Figs. 5 through 8 where is best shown the manner in which the cam 54 is operated and the rotative actuation of the ratchets 51 and 55 and-explaining the operation of the valve 44 assuming the cam in the position shown in Figs. 5 and '1, the manual control valve 39 in .the position shown in Fig. 1 and that hydraulic fluid is being injected..by pump 35; the plunger 5i is moved outwardly by introduction of hydraulic fluid. Abutment 5Ic during this movement ofthe plunger 5i. contacts the adjacent tooth of ratchet 5 5 rotating the ratchet and cam forty-ve degrees from that shown in Figs. 5 and 1 to `a position shown in Fig. il.V As suggested,

the teeth of ratchets 51 and 55 are staggered.

l When the uid pressure upon valve 5i is vreleased by'movement of control valve 35 to connect pipes 39 and 43, the hydraulic fluid moves from'the crankshaft toward the sump. Spring 52 urges plunger 5i inwardlyand abutment 5Ib engages the adjacent tooth of ratchet 51 rotating cam 54 ari'additional forty-five degrees orto a hori.

zontal position parallel with pin 55 when ball 'valve 45 is at its maximum open position. t

With every injection of hydraulic fluid, plunger ,El is forced outwardly against the action of spring 52 and with release of pressure on the hydraulic fluid, plunger 5i moves in a reverse direction due to action vof the spring. Both out# ward and -inward movements of plunger 5i cause a forty-five degree rotation of the cam 54, the

combined reciprocation causing a ninety degree rotation of the cam due to positioningof the abutments 5lb and 5Ic and the staggered arrangement of the ratchets 51 and 55. As the 'cam rotates to the forty-:liveA degree position spring 49 conned between plug 55 and ball valve 4s urges the ball valve' to a seated position.

To unseat the ball valve there is located inwardly of plug 41 and within valve body 45 a plunger 5|l connected by a restricted neck to hollow open ended reciprocating sleeve 5in shown rectangularin cross section invFig. 6. A sleeve extension of plug 41 extends into the end of the rectangular sleeve 5ia' and is surrounded by compression' spring 52 which abuts itsouter end on plug 41 andits' inner end on reciprocating sleeve 5Ia. Within the rectangular' reciprocating sleevev 5la is a cam 54 keyed to a pin- 55 between two ratchets 51 and 55. These ratchets have four teeth positioned ninety degrees apart and are shown in Fig. 8, it will slide pin 55 to move ball valve 45 away from its seat. The-fluid then iiows from the hollow. crank shaft chamber around loosely fitting plunger 5l, through slots 45e in the valve body, through ports 41b in plug 41, around the unseated ballvalve 45, through passages 41c and 25a and behind 'piston 21.

After the piston has been moved outwardly a distance sumcient to increase the pitch of the propeller bladesa. desired amount, it will'be necessary to close vthe |ball' valve 45 and hold the hydraulic fluid behind the piston. To effect th's result. manually' operated valve 55 must be actuated one time more to move the cam through vninety-degrees when the cam 54 is again in va vertical position as shown in Fig. 5 and ball valve 45 is closed. f

Should the pilot desire the propeller pitched to its maximum, movement of the control valve 55 to permitadrnlssion ofthe hydraulic. fluid will accomplish this result. If va minimum pitch or feathering'of the blades is desired, this is effected by operating the manual control I5 so the hydraulic fluid will drain'back into the sump or reservoirand this resultis obtained when the cam 54 is in a horizontal position and bail valve wise and for the same reason, increasing the pitch is a relatively slow operation permitting actuation of the control valve 33 at any time to give the propeller blades a selected pitch. To maintain the pitch of the. propeller in any ilxed selected position, the operation is that heretofore described, namely the hydraulic iluid is introduced until piston 21 by means of arms 21a has moved the blades to the desired pitch. Control valve r38 is then actuated to rotate the cam to a position where ball valve 48 is closed and the iluid is trapped behind the piston.

Attention is directed to the fact that the automatic valve M is centered within the crank shaft so that every moving part oi the valve operates along the center of the crank shaft. Thus, none of the parts will be influenced by centrifugal force.

If it is desired to have only two selected pitch positions of the propeller blades, one for taking on and the other for normal cruising, the hydraulically operated valve 44 may be omitted.`

Fluid pressure inthe crank shaft `and behindv piston 21 will then be released. The wind resistance acting on the propeller blades will provide suillcient torque to move piston 21 inwardly and expel the hydraulic fluid therein. After the plane gains sufficient altitude to assume normal level flight, the pitch of the propeller blades may be increased to the maximum pitch position by operating the manually controlled valve 3l to connect pipes 31 and 39. 'Ihe crank case oil, acting as the hydraulic iluid, is injected into the crank shaft by pump 35. This iluid enters the piston and forces the same outwardly until its travel is limited by engagement of bolt 3| with member 29. Valve 38 remains open until it is again desired to reduce the pitch of the propeller blades.

It will be readily appreciated, however, that the automatic valve 4l is a desirable 'feature for the reason that it may be used to hold the piston 21 at a selected adjusted position between the inner and outer limits of its travel. This is a decided advantage. When using valve M, should the propeller bladesY be in the maximum pitch position and the blades have been given too much pitch, piston 21 may be easily retracted a slight distance until the propeller blades have the'proper pitch.

It may thus be'seen that I have achieved the 'o0 objects of my invention. I have provided a hydraulically operated pitch changing mechanism for variable pitch propellers that may be easily operated by the pilot. .By the use of my mechanism the propeller bladesmay be held in any selected adjusted position bestsuited to existing conditions of airdensity, plane speed and engine speed and power.

It is to be understood that the form of my invention'herewith shown and described is to be taken as a preferred example of the same and that various changes in the size, shape and arrangement of parts may be resorted to without departing from the spirit of my invention or the scope of the appended claims.

Having thus described my invention, I claim:

l. In combination with a variable pitch propeller, a hydraulically operated pitch changing mechanism comprising a iluid pressure operated means connected to the propeller blades for adlusting their pitch, a manually operated valve controlling the ilow of duid to and from the iluid pressure operated means, a iluid passage between the manually operated valve and the fluid pres'- sure operated means, and an automatic valve mechanism in said passage, said automatic valve mechanism including a rotatable cam adapted in diilerent adjusted positions to open and close the automatic valve mechanism, and a fluid pressure actuated means operated by successive operations of the manually operated valve cooperative with the cam to move it to said different adjusted positions.

2. In combination with a variable pitch propeller, a hydraulically operated pitch changing mechanism comprising a uid pressure operated means connected to the propeller blades for adjusting their pitch, a manually operated valve controlling the ow of iluid to and from the iluld pressure operated means, a iluid passage between the manually operated valve and the fluid pressure operated means, and an automatic valve ymechanism in said passage, said automatic valve mechanism including a rotatable cam adapted in dierent adjusted positions to open and close the' mechanism in said passage, said automatic valvev mechanism including a rotatable cam adapted to open and close the automatic valve mechanism, ratchet Wheels rotatable with the cam, and a fluid actuated plunger having. pawls engageable with the said ratchet wheels to rotate. the cam.

HORACE H. ROBY.

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