US2512103A

US2512103A - Mechanism for driving propellers

Info

Publication number: US2512103A
Application number: US522910A
Authority: US
Inventors: Samuel K Hoffman
Original assignee: Avco Manufacturing Corp
Current assignee: Avco Manufacturing Corp
Priority date: 1944-02-18
Filing date: 1944-02-18
Publication date: 1950-06-20
Anticipated expiration: 1967-06-20

Description

June 20, 1950 s.,K. HOFFMAN l-:TAL 2,512,103

MECHANISM FOR DRIVING PROPELLERS Filed Feb. 18, 1944 10 Sheets-Sheet 1 June 20, 1950 s. K. HOFFMAN ETAL 2,512,103

I MECHANISM FOR DRIVING PROPELLERS v Filed Feb. 18, 1944 l0 Sheets-Sheet 2 @www/23 Des-eased June 20, V1950 s. K. HOFFMAN ET Al. 2,512,103

MECHANISM FOR DRIVING PRoPELLERs Filed Feb. 18, 1944 l0 Sheetsj-Sheet 5 June 20, 1950 s. K. HOFFMAN l-:TAL v 2,512,103 MECHANISM FoR DRIVING PRoPELLERs Filed Feb. 1s, 1944 10 Sheets-Sheet 4 June 20, 1950 s. K. HOFFMAN ET AL l 2,512,103

MECHANISM FOR DRIVING PROPELLERS Filed Feb. 18, 1944 v 1o sheets-sheet 5 June 20, 1950 s. K.,HOFFMAN ET Ar. 2,512,103

MECHANISM FOR DRIVING PROPELLERS Filed Feb. 18, 1944 1d sheets-sneer e June 20, 1950 s. K. HOFFMAN ET AL 2,512,103

MECHANISM FOR DRIVING PRoPELLERs Filed Feb. 18, 194A 10 Sheets-Sheet 7 June 20, 1950 s. K. HOFFMAN ETAL 2,512,103

MECHANISM FOR DRIVING PRoPELLERs Filed Feb. 18, 1944 10 Sheets-Sheet 8 [35 Jaa Filed Feb. 18, 1944 s. K. HOFFMAN ETA. 2,512,103

MECHANISM FOR DRIVING PROPELLERS 10 Sheets-Sheet 9 June 20, 1950 s. K. HOFFMAN ET AL 2,512,103

MECHANISM FOR DRIVING PROPELLERS Patented June 20, 1950 y MECHANISM FR DRIVING PRPELLERS `Samuel K.Hoiman, Williamsport, Pa., and Harf old Carriiinea-v deceased, late of Williamsport, f Pai, by Hazel Caminez, executrix, Williamsport, f."Pa.,-i:a'ssignor's )to Aveo" Manufacturing Corpora- UNITED fsf'rAfTEs Param N..oi=i=i :r.

-:=tion; a'corporation of Delaware Application February 18, 1944, Serial No. 522,916

(Cl. 19E-48) "14 Claims. 1 l The-inventonfrelates to mechanism for driving aircraft propellers.

The objects' -of 1 the invention are to provide:

improved mechanism for 'driving a pair "of 'contrarotating prollers; improved means for drivingy contra-rotating propeilers iat a"plurality ofspeed 'ratios relative tof-the engine* speed; improved means whereby'l the` pilot may selectively control the drivingmecha'nism iorroperation at diierent speed ratios fromthefengine' variable speed driving mechanism-for` thel propellerswhich includes toothed s'lidably engageableclutching elements and means for controlling fthe engagement of such elements tofprevent knocking of the-teeth in eiecting speed changes; a unit vof improved.'

construction for -equalizing the* tooth loads on a plurality foi? gears-on a common shaft used for variable speed-driving; `improved torque con- 4speed changesfilimproved*'hydraulic and torque.v

trolled means-for controlling the clutch device for controlled means selectively' controllable `by j the .f pilot for controlling the speedc'hangesjdriving mechanisrn--forcontra-rotating -propellers with vibration dampers for `eliminating the interference eect 'ofblade-passing and to isolate the'vi-y brations from they remainder-fof' the driving mech- Ir anism and thefengine; improved'meansfor lubricating :Y an outboard* bearing. ybetween the `shafts of contra-rotating propellers a toothed lclutching device forfcontrolling the variable speedgear.

r ing and. associated -means which requires elimif nation of appreciable torque: in order to effect engagement ofsthe lclutch teethgr means for -predriving gearsffor differentspeedsv'wiiile appreci-f:

venting engagementof the clutcnjteeth with tine ablev torque =is1 being l'transmitted Ythrough the r overdrive clutobfusediin one 'ofthe driving gears; andother objectswhich will npp'earfrom the de- 'tailed description.

Tnerinventionconsists inthe several novel fea- J tures whicharehereinafterlset forthA and-more .ltparticularlydiinedby'claims' at the conclusion 1 hereof.

in the drawings: Fig.V lisis a vertical central-'longitudinal section f'of driving lnechan-ismernlbodying the: invention,

,r parts ybeing 'shownairrielevation.

Fig. 2 is a transversei---section";taken on line Fig. 3A is a.:centralulongitudinal' section through'.

the main driving gear,1the torque rneterI and associated parts, a' portion of the balk ring-orthe clutch device being 'shownf in elevation.

Fig. 4 is a sectiontaken on line 4--4foiY Fig. 3,

parts being broken away for illustrative'purposes.

` Fig, 5 is a, section taken on line 5-'5 of Figi'. 5a. Fig. 5a isf a. detail illustrating the torque responsive ring, the"driven element', and: thedriving ballsbetween'them.

Fig. 6 is a section taken on line t-5i yof Fig. 1. 'Fig'. 7 is alongitudinal sectionthrough `one 0I l the lay shaft units and its associated gears.

Fig; 7a is a view of a portion of one ofthe'lay shaft units, theflow l"speed driving gear 'and a porbers for shifting the 'balk ring longitudinally.

tion of the sleeve1member being shown in section.

Fig. 3 is a section taken online 3?-8' of Fig. 1

' illustrating'more particularly the mechanism `for shifting the clutch device for variable speed driv- 20 ing.

Fig. 9 is a section'taken on line @e of Fig. 8, parts being broken away.

' 10 is a section takenon line iii-'ISI of Fig. 11 and illustrating more particularly the spring vpressed balls carried'by one of the clutch mem- Fig. 12.

Fig. 15 is a section taken on line l-'i'of Fig. 10.

Fig. 16 is a section' illustrating the overrunning clutch between the low speed driving gear and the driving sleeve forthe clutch device.

Fig. 17 is a vertical longitudinal sectionillustrating the hydraulic device for shifting the clutch, the torque controlled device for locking 'theclutch shifting mechanism, the manually controlled valve-ier controlling the operation of said hydraulicldevice, the switch mechanism for 'indicatingtne clutch. settings, and the valve for 3 controlling the flow of oil to the pitch governor for the blades.

Fig. 18 is a central longitudinal section illustrating the gearing for driving the blade pitch governor, the gearing for driving the engine distributor and magneto, and the automatic pressure responsive device for timing the gear for driving the distributor.

Fig. 19 is a detail illustrating the spline connections through which the gear for driving the timer is driven.

Fig. `20 is a side elevation of the gear which drives the sleeve on which one of the propellers is mounted and the vibration dampers thereon.

Fig. 2l is an elevation of a portion of the opposite side of the gear illustrated in Fig. 20.

Fig. 22 is a section taken on line 22-22 of Fig. 20.

Fig. 23 is a section taken on line 23-23 of Fig. 21.

Fig. 24 is an elevation of the gear which is nxed to drive the shaft for one of the propellers, parts being broken away.

Fig. 25 is a section taken on line 25-25 of Fig. 24.

Fig. 26 is a perspective illustrating one of the vibration dampers shown in Figs. 24 and 25.

Fig. 27 is a longitudinal section through the propeller shafts and the bearings therefor, and parts thereon.

The invention is exemplified in a two-speed driving mechanism for a shaft 30, the front end of which is provided with splines 3l (Fig. 27) for driving the hub of an outboard propeller and a sleeve 32 around shaft 30 which is provided with splines 33 and functions as a shaft for driving the inboard propeller of a contra-rotation propeller unit. The propellers may be of any suitable construction and are usually provided with variable pitch blades which are adapted to be hydraulically controlled in any manner well understood in the art. The shaft 30 and sleeve 32 are mounted in and project forwardly from a gear-case which is formed of sections and supported from the engine which drives the propellers through the variable speed gearing enclosed in the casing.

This gear-casing comprises a section 34 (Fig. 1) which is secured to and forms a part of the casing of the engine for driving the propellers; a section 35 secured to the front of section 34; a section 36 secured to the front of section 35; a front section 31 secured to the front of section 36; and a wall 36 secured between

Sections

36 and 31.

The variable speed gearing for driving the

shafts

30 and 32 is driven from a gear 38 which is provided with a hollow hub 39 which is journaled in roller bearings 40 in the front wall of casing section 35 and a wall 4i secured by screws` 42 to the rear face of said casing section. The gear 38 is driven by gears 43 and 44 (Fig. 2) each of which is rotated with and driven by one of the crankshafts of a two crankshaft engine (not shown).

Propeller shaft 30 is driven through an externally toothed gear 45 which is Splined as at 46 to the shaft 30. Propeller shaft 32 is driven through an internally toothed ring gear 41 which is splined at 48 to a wheel body 43, the hub of which is splined at 50 to shaft 32. Hollow shaft 32 is journaled in a ball bearing l which is mounted in the casing-section 31 and on a ball bearing 52 around the shaft 30. The inner end of propeller shaft 30 is journaled in a bushing 53 which 4 l is held in the hub 39 of the main drive gear 38. Forwardly of the gear-case, shaft 36 is journaled in a plain bearing 511 which is carried in the front end of the hollow propeller shaft 32. Gear 45, which drives the propeller shaft 35, and gear 41 which drives the hollow propeller sha-ft 32, are adapted to be driven by an annular series of longitudinally extending lay shaft units generally designated 55, which are adapted to be driven at two different speeds relatively to engine-speed.

Each of the lay shaft units 55 (Figs. l and 7) is journaled in a bearing 56 in a wall 35a which is integral with the casing-section 36 and a bearing 51 in the plate 36 which is secured between the contiguous faces of the casing-

sections

36 and 31. Each lay shaft unit 55 (Fig. 7) comprises a low speed driving gear 55, a high speed driving gear 60, a pinion 6l which meshes with and drives the gear 45 which drives the propeller shaft 3u, and a gear 62 which meshes with and drives the ring gear 41 and Wheel body 49 for driving the hollow propeller shaft 32. The pitch diameters of pinions 6| and gears 62 on the lay shafts and gears 45 and 41 are proportioned to drive gears 45 and 41 at the same speed in opposite directions for the contra-rotation of the

propeller shafts

30 and 32. Each lay-shaft unirl 55 is composed of sections which are adapted to be conveniently secured together for equal toothloading of all of the gears on each shaft. The gears 59 on circumferentially alternating layshaft units 55 are staggered and all mesh with a gear 15 through which the lay-shaft units are driven for low speed driving. Except for this staggered relation of the gears 59, the lay-shaft units are alike in construction. Each unit 55 comprises a hollow inner shaft-section 63, and a surrounding sleeve-section 64. A pinion 6I is integral with each shaft-section 63. A gear 59 is integral with each sleeve-section 64. Each shaftsection 63 is provided with a conical portion 65 which ts in a mating conical socket 66 in the sleeve-section 64. The front end of each shaftsection 63 is provided with a conical portion 61 which ts in a mating conical socket in the gear 62. The rear end of each shaft-section 64 is provided with a conical portion 68 which lits into a mating conical socket in gear 66. A bolt 63 extends completely through the hollow shaft-section 63 and is provided with a head 10 which abuts against the front face of the gear 62. A

, nut 1I is screw-threaded to the rear end of bolt 63 and abuts against the rear end of the sleevesection 64 and is adapted t0 force together longitudinally the gear 62 into jammed relation with conical portion 61 on shaft-section 63, and the sleeve-section 64 into jammed relation with the conical portion 65 on shaft-section 63. A second nut 13 is screw-threaded to the nut 1I and is adapted to abut against the rear face of gear 6U, and to force the gear 6l) in jammed relation with conical portion 68 on shaft 64. A lock pin 14 extends through the nut 13 and nut 1| and a slot in the inner end of bolt 69 for preventing relative rotation of nuts 1| and 13 and bolt 59.

In assembling the gearing, the lay shafts are all assembled in their

respective bearings

56 and 51 and the nuts 1l are turned sufficiently to move the conical engaging portions of each shaft 63 into loose relation with the conical sockets in the gears 62 and the sleeve sections 64. Gear 45 is prevented from rotating by locking its associated propeller against rotation.

Gear 15, which meshes with gears 59 on the sleeve sections 64 of all the lay shaft units, is then of Voil from orifice |02.

. said cylinder. piston 99 function asa by-pass valve for conf pressure in the cylinder.

f' the piston 99, and ring 85 forwardly. This movement of piston 99 increases the exposed area of orifice |02 and allows a higher rate of discharge This high rate of discharge correspondingly reduces the pressure in The port |02 in cylinder 93 and trolling the discharge of oil from the engine pressure oil system back to the gear casing to vary Athe pressure in said cylinder. permitted by the orice |02 may be such that when the maximum thrust is transmitted through ring 85, the pressure drop in the cylinder will not exceed 20 lbs. p. s. i. and as said orice is uncovered by the forward movement of piston 93a, there will be an increase in the outflow of oil which results in a greater pressure drop with a resulting decrease of pressure in the cylinder. Decrease in the outflow of oil through orifice |02 causes the oil pressure in cylinder 98 to increase until the thrust of ring 85 is balanced by the As the torque transmitted through ring 85 is decreased, said ring is shifted forwardly by the pressure of oil in the Vcylinder 98 to increase the exposed area of orifice |02, which increases the outiiow of oil from cylinder 98 and reduces the pressure therein. It will thus be seen that the pressure of oil in the cylinder 98 is proportionate to the torque transmitted to the driven member 88. The variation of pressure in cylinder S8 is utilized in controlling the shift of the clutch device 80 to selectively complete said device to drive the lowspeed gear 15 and the high-speed gear 15, as hereinafter described.

The clutching device 80 (Figs. 1l and l2) is adapted to alternately and positively drive the low-speed driving gear 15 and the high-speed driving gear 16 and comprises a pair of members |I and II4 which are connected together for conjoint longitudinal movement by a ring |I4a. Member I I3 is provided with a hub which is slidably splined at |II to the sleeve 8| so that it will be driven from sleeve 8| and the driven member 88. Clutch member IIO is provided with a series of external clutch teeth I I2 which are longitudinally slidable into engagement with internal clutch-teeth II3 on the high-speed driving gear 1S. Clutch member ||4 is provided with external clutch teeth H6 which are slidable into engagement with internal clutch teeth |I in the low-speed driving gear 15. The clutching device in its neutral position, as illustrated in Fig. 11, is uncoupled from both of the gears and 16. Clutch members H3 and |I4 (Figs. 13 and 14) are connected for limited relative rotative movement by external teeth on clutch member l I0 and internal teeth |26 on clutch member I4. Opposed springs |21 (Figs. 13 and 14) engage abutments |28 and |29 on rings iixedly secured to members |I9 and H4, respectively, to yieldingly permit this limited relative rotative movement of said clutch members.

The clutch member |I0 is provided with arms |22 which extend radially into an annular space in a shifter ring |35 by which the clutching-device is shiftable longitudinally between neutral and low speed and high speed driving positions. The non-rotatable clutch-shifter ring |36, formed f of sections, is held against rotation and is proteeth |,I2 and |,I6of theclutch members I|0 and The ow of oil 48 I I4, and is provided at its rear end with a conical face |I8 for frctionally .engaging the face of a conical socket I I9 in the gear 16 and at its front end with a conical socket |20 for frictionally engaging a conical face |2| on gear 15. The arms |22 on the clutch member IIB extend through slots |23 in the balk ring (Fig. 3). A series of spring pressed balls (Figs. l0 and 15) are individually confined in tubular guides I3I which are fixedly mounted in the rim of clutch member |I0 and pressed against the inner periphery of the balk ring by springs |32. Balls |30 are adapted to successively seat in curved recesses |33 in the inner periphery of the balk ring when the clutch device is in its neutral position, in similar recesses |34 when the clutch device is in its low speed driving position, and in similar recesses |35 when the :clutch device is in high speed driving position. When the clutch device 80 is in its neutral position, as illustrated in Fig. 11, and the f shifter ring |33 and the clutch member are shifted forwardly, the spring pressed balls |30 will shift the balk ring II1 forwardly and initially cause the conical face |20 on thebalk ring to frictionally engage the conical surface |2| on the gear 15 in advance of the engagement of clutch teeth |I on clutch member II4 with the clutch teeth I I5 in the gear 15. The continued forward movement of the clutch device will cause the balls |30 to move forwardly into the recesses |34 so that the balls will, during the rearward movement of the clutch device, retract the balk ring. The recesses |33, |34, and |35 are elongated circumferentially sufficiently to maintain engagement with the balls |30 when slight relative rotative movement occurs between clutch member IIB and the balk ring. When the clutch device 80 is engaged with the gear 15 and the clutch members ||9 and |I4 are shifted rearwardly away from low-speed gear 15 and to engage the high-speed gear 16, the balls |30 seated in recesses |34, will yieldingly shift the balk ring I |1 rearwardly and cause the conical face I |8 on the balk ring to frictionally engage the conical surface H9 on the high-speed driving gear 16 before the clutch teeth II2 on clutch member II() engage the clutch teeth ||3 on the gear 16. The slots |23 in the balk ring through which the arms |22 on clutch member II() extend are of suiiicient width to permit independent longitudinal shift of the clutch members after the balk ring has engaged gears 15 and 16, respectively. The balk ring |I1 is formed of sections joined at the front side of slots |23 for assembly around the clutch-members with the arms |22 extending through slots |23.

When the ring |35 is shifted forwardly to effect low speed driving, the balk ring will be shifted by spring-pressed balls |30 to cause its friction face |20 to engage the friction face |2| on low-speed gear 15 before the clutch-teeth I6 on clutch member I I4 meet the clutch-teeth I I5 on gear 15. When the ring |36 is shifted rearwardly to effect high-speed driving, the friction face |8 on the balk ring will engage the friction face IIS on the high-speed gear 16 before the clutch-teeth I I2 on clutch-member ||0 meet the clutch teeth I |3 on gear 16.

Shoulder |23BJ (Fig. 3) are provided in the balk ring at one end of the slots |23, which are engaged by arms |22, to prevent the shift of coupling member 4 to bring its clutch teeth into mesh with the mating clutch teeth II5 in the gear 15 until relative rotation occurs between the arms |22 and the balk ring to release said shoulders; Shoulders |23b are provided'nthe'balk' ring in' the opposite end of'slotsl'l2`3, whichare engaged by the arms' |22," to prevent theiclutch'l member I'Ill from'being shifted tov slide clutch teeth H2 into engagement wit'h the' mating clutch teeth I I3 in high-'speed gear'IB until relative rotation occurs between'the balkv ring 'and said coupling member to release said shoulders. This relative rotation is produced by throttle cone trol of' the engine, as 'hereinafter more'fully 'de'- scribed, 'to'permit shift of'the'arms' |22"or' del-1' layed'engagement of the 'clutch'.teeth on'm'em'- bers H4 and Ill) and the gears 15" and'16, re-` spectively.' After the clutch teeth II6 and |I5 are engaged, the 'gear '15 will be positively driven from the clutch device, and after clutchte'eth I I2 and `i I3 are engaged'gear .'16 vwill'be"posii'.ively driven -from the clutch device.'

The lay-'shaft units 55 are driven 'at high and low speeds in relation' to' engine speed fordriving the gears '55 and '47' which "drive the' propeller" shafts "in opposite directions, `and gears" 59 of'the lay-shaft unitsare kept in constant mesh'with the gear 'I5 for low speed driving,'and gears. are kept in constant 'mesh with'the gear 'I6 'for' high-speed driving,"and-as' a result' both" of .the gears I5 and l'are'rotated during low and high speed driving.`

An overrunning clutch "'(Fig'. .16) is provdedbetween the sleeve 8| 'and the 'gear' '.15 'and 'coin-Y prises peripheral c-am surfaces |67 on the sleeve; i and rollers |68' held in rings IML-'and .this makes it possible' for-'the gear 15' to rotate at ahigher speed than the sleeve 8 I when the lay-"shaft 'units are being driven at high speed fromthegear 'i6 and' also makes it'impossible to drive'the sleeve"` 8| at a higher speed than'that at which thegea'r i5 is driven.

Shifter-ring |36 is slidably supported byza pair." of diametrically opposite studs |38 (Figs. 8, 9 and' 17) which lare slidably 'guided in brackets' |39` which/'are hired to the vcross-wall 36a'of"'casing section 56. A'rock=sha'ft |40 is pivotally'supe ported in a bracketI'M which is'secured' by bolts" |52 to a cross-wall of the" casingsection 36. Arms' |133 are 'xedlysecured to shaft |46 andl are piv' otally connected at IM'to the' studs I38',"`respec.' tively. An;arm"'|45 is xedly secured'to the cene' tra'l portion of rock shaft |40" and is adapted to rock shaft' Idil and arms |43 to'slidably shift studs |38 and the ring |36 for'shifting the' clutching de'- vice between neutral'and high-speed'and low speed 'driving positions.' The-'ring' |36 is shift'- able rearwardly by arms |43'and '|45 'and'uid underpressure in a hydraulic motor` which comprises a 'cylinder'il'l (Fi'g..1'7)' anda piston |48" in said cylinder 'which'has'secured'thereto a stern |139 to which' is pivoted 'atv |46 the lower 'end of armJ |55.' A spring '|50 betweenpiston |48 and the frontend of cylinder WP urges the piston' rearwardly 'to shiftarm |45in'counterclockwise direction 'for 'shifting the vclutch"devi'ce"for" v wardly. Fluid under pressure in 'cylinderv I4'I'is adapted to shift'arm' |45 in'clockwise directiontto shift shifter ring |36 rearwardly.v Fluid "to` the' cylinderY |41 for 'shifting' the' piston "I ll'iorwardlyV for shifting vthe vshifter ring |36'l`and the clutch device is controlled by a rotatable'valvev |58 (Figs. 8 and 17') which 'is provided' with' an arm |58@ which isfoperable by the pilot through'a suitable connection. A cross-port"I58b'fin'valve" I53,'when"it is in one position, 'is adapted to supply oil'from a ductvr I 59 in th'e'casin'g'irom the oil pressure system'of the engine-to a conduit |59am iff-the gear-casing,V which is #communieatively' connected 'to the" cylinder" I 4-1.)

drain'from 'cylinder 14T' through'conduit I 53a and a 'channel I55`(Figi";17')"int-valve' I58'back into the gear case for drainage'backfto' the' oil reservoir; This exemplie'sfmanually .controlled combined' hydraulic1 and spring means'for'shifting the' clutch device'SUl' Torque-controlled'mechanism forming a control'device' is'provided' for "locking the shifter-'ring device '86 in'neutral; highe'speed'and low-'speed positions." This" mechanism" comprises' 'a 'locking device or: latch'lever""| 52. which 'is' u'lcrume'd' 'on the rear'wall of 'cylinder' I 41;a fingeror'tooth'l 5 I on 'the'lower'end of 'arm' |45 which is adapted 'to be locked' inr'three 'positions'zbyfnotches in' the latchleverl52ia piston |54 slidable in a cylinder Y- |55; Va stem `|53 on the pistonfthe' outer" end .of

which 'is'pivotallynonnected tothe lower'end of the latch lever I'.i 2f,"`ancl` a, spring. v I 5'6ifor shifting piston `I 54'in one^directioni .Tooth I 5 I',when held in the central notch in latch-leven |52, 'willlock the arm' 'I 45 and the. shifterering `I 36in position to'hold the clutchdevice. 80in itsneutral position. Tooth. I5I, when" held 'inthe"'rear notch, 'will lock .arm |45, yring`I36'iand clutchdevic'e' iin low speed position fand' when held 'in'the forward lnotch 'will' hold arm" I 4'5`",'ring I36and clutch device' 86 in 'high 'speeddriving'position. .A/duct" |55.EL in the gearecasingpis 'communicatively `connected with'l'cylin'der'l'55' and byja duct extending through anysuitable.portion'ofthe' casing' to "the cylinder'g' iniwhichH the .pressure of' oil is proportionate' to 1' the'. torque' .being ,transmitted throughi"ringj' 85"1toith'e 'driven member' 83"'and sleeve 8|'. Then'pressure'ofv oil in' the" cylinder |55 'forcesthe'piston llrearwardlyto hold latchlever 'I5'2'in'locking relation' with arm I45'when appreciabletorqueis" being transmitted by the ring tothe" driven member' 88;"at which time the orice |02 restricts" the discharge of oil from cylinder 98'and maintains sufcient 'pressure therein 'to' force piston |54 'rearwardlyand the lever I52'in'its locking position.' When no appreciable torque isbeing transmitted through ring 85, the pressure 'drop which'. results *fromthe increased 'outflow Vof.oil from 'cylinder 98 through -ori'ce'l il2,"'reducesA the pressure' in cylinders Q3 and' 'I'5.5`and"permits spring |56 to shift the piston I5W'orwa'rdly and',disengage lever 'I 52" from A.the

mechanism` for' 'clutch device. 86" wil'lb-e, locked. .by the' latch-'lever .'|52;"'when substantial' torque is'being-tran'smitted'through'the'ring iand said mechanism 'will tbe' automatically released when" no' substantial torquev is being transmitted'I throughfthe' ring' 85: 'I his'ma'kes'it possible 'for 1th'e operator; byslowin'g down the engine through control' of "the'throttl'efto release the lever |52"L to unlock the"shifting'mechanismor shifting'the clutchdevice `8|lffor drivingthe'propeller shafts 3`,"f"'32""at"high' or""lo`w"speeds:" This exemplifies `fmechanism for locking the-"clutchr'device 85 against axial" shift: 'between neutralr Hand" high speed 'and 'low' 'speed `positions'whi'ch is reason'- ablyr'underwcontrol'-ofthe pilot 'by' closingithe throttleior theengine 'so-thatshiting -canbe y:accomplished-fonly whenV substantially no'- torque isibeingy'delivered' from the 'engine tof-the gear'V ing- 'for Ldrivingthe"propelleisr` A pressure' gauge' (not shown), usually located in a convenient pla'ce',--such las inthe-'cockpit of 75 Vtheai-rplane; is-communicatively connected to' the-r Whenthe valve |58 is rotated `toan. alternativerposi'tion, 'oil will l1 cylinder 98 and may be calibrated to indicate the torque being transmittedthrough the ring 85 as reilected'b'y the pressure of the oil in cylinder 96 which pressure is proportionate to the torque.

A hydraulically controlled governor |86 (Fig. 18) for varying the pitch of the propeller blades, is mounted on the top of the casing section and may be of a construction well understood in the art. This governor is controlled by a, valve |16 on the stem |49 of piston |43"'which'shifts the arm and the shifter-ring |36 for the clutch device 8D. Valve |10 i's slidable in a cylinder |10@ xed in the casing-section 3G. The front end of the cylinder |165' communicates with a conduit |1| in plate 36 and'is connected to the oil pressure system of the en'gine.A When the shifter-ring |36 and the clutch device 83 'are in low speed driving position, at which time the piston stem |49 is in its rearward'position, the valve |16 will uncover ports |12 in' cylinder |182# and cause oil under pressure to flow through a conduit |13 in the gear casing to the governor |86 for automatically controlling its operation to set the propellerv blades' at the desired pitch for low speed operation, as well understood in the art. When the clutch device S6 is in high speed driving position, piston-stern |49 will be in its forward position and valve |15) will be positioned forwardly of the ports' |12 so that oil from the governor 86 and conduit |13 can drain through ports |12 .and escape from the rear end of cylinder |108' around the steiny of the valve |10 which will eliminate the pressure of the fluid in governor |86. 'rl

A hollow drive shaft |16 (Figs. k3 and 13) is;

well understood in the art. A gear |112- is sehub of gear 2 l0; a gear 2|5 journaled on a bushwhen automatic time regulation is not desired.

nected to the valve 228.

ing on the hub of vgear 2|0.; and opposite helical splines 2|6 on the shaft 2|4 which interflt with corresponding splines in the hub of gear 2li. The distributor and magneto are driven by any suitable gearing from the gear 2 l5. Axial movement of the shaft 2|4 through oppositely inclined helical splines 2|3 and 216 is adapted to rotate gear 2|5 relatively to gear 2|0 for timing the operation of the distributor and magneto. The front end of shaft 2|4 is journaled and slidable in a bearing 2|4 which is held in the wall M in the gear-casing. Shaft 2|4 is also slidably and rotatably mounted in a bearing sleeve 2||EL which is xedly secured in a hub on the cylinder 22| which is fixed to the casing-section 34.

The automatic means for shifting the shaft 2| 4 to vary the timing of the distributor and magneto, comprises 'a piston 2|8 which is slidably mounted in a cylinder 22|. The piston 2|8 has a hub in which is journaled a bushing 2K8' which is longitudinally movable with shaft 2|4. The piston 2|8 is slidably guided axially and held against rotation by the fixed bearing 2MB. This permits the piston 2|8 to slide in, and causes it to longitudinally shift shaft 2|4, while permitting the shaft to rotate. A spring 222 in cylinder 22|, urges the piston 2|8 and the shaft 2|4 rearwardly toward a stop ring 222B in the rear end of the cylinder 22|. A nut 223 on the vrear end of shaft 2|4 holds piston 2|8 on the bushing 2|8' in which the shaft 2| 4 rotates. A chamber 224 for fluid is formed in the casingsection34 and communicates with the rear end of the cylinder 22|. The huid under pressure inchamber 224 is adapted to shift shaft 2|4 forwardly against the force of spring 222 for causing the splines 2|3, 2|6 to rotate shaft 2|4 and gear 2|5 relatively to gear 2|() for varying the timing of gear 2|5, and this pressure is con trolled by the pressure in the intake manifold b of the engine, a Sylphon bellows 226 which is communicatively connected by a tube 225 with the manifold b, and a slide-valve 228 actuated by said bellows. The bellows 226 is mounted in acasing 221 which is iixed on the top of casing-section 34. The bellows 226 is in opposed relation with a bellows 221ia which compensates for altitude. The bellows 226 is operatively con- The valve 228 controls the ilow of oil in the engine pressure system'in a duct 23|) to a duct 23| which communicat'es with the chamber 224. The valve 228,.also controls the W of oil from conduit 23| to a conduit 232 to permit the oil from 'chamber 224 to drain back into the case responsively to the variation in the pressure in the manifold. A manually shiftable rotary valve 229 is includedin the conduit 23) to cut off the oil pressure to the conduit 23| and chamber 224 The construction described exemplifies hydraulic timing control for the gear 2|5 which is controlled by the pressure in the intake manifold of the engine.

`In the operation of.contrarotating propellers, the passing of thefblades results in an aerodynamic interference effect which tends to produce torsional vibration in the propeller shafts.

y The invention provides vfor isolating and damping such eiects on the gear 45 which is xed to the propeller shaft 30, is driven by the body 49 of the internal gear 41 which is fixed to shaft 32 (Figs. 20-26) by series of inertia members for damping torsional vibrations oisaid gears,

respectively., These dampersare' tuned y.to the.. frequencyat -which\the rblades of the contra-- rotation-propellers passy oneanother and havea xed value dependingV upon thenumber -of propeller'bladesused, for example,` with propellersprovided with three blades sixth orderof dampers are used.v These inertia. members rotate with the propellers and act vto isolatev from the engine and thegearing between'the 1 engine andgears 41' and 45 any torsional vibration caused by the passingiblades irrespective of thespeed of rotation of fthe propellers after they are once properly tuned. l

Inertia members (Figs. 24 tof126) yare carried-- bytheebody ofthe gear 45 which is splined to the propeller shaft 3B and `by thebody- 49 `of.Y gear 41 (Figs-20.430 23);

Afseries 4of six segmentallyshaped inertia mem' f bers 235 is conned between the body of gear 45 andV a ring 235y which-is secured by bolts 231 to saidbody. Each -member 235 lis provided `adjacent each end .with-a :cylindrical hole 238 Iwhich extendstherethrough. A roller 239 extends f through each of the holes .2331and is Iprovided withY a head which abuts againstthe :outer face of ring 235,c and a plate `24El-bolted to ring 236 engages the heads of the two rollers in eachy member 23'5tohold the rollersagainstsaxial movement; Each roller 239*also.extends.through longitudinally aligned cylindrical holes 24H in the f body .of wheel 45 `and va cylindrical hole v238, in. the inertia member .235. The ,diameter of the .l holes 238- and 241. is equal andfgreaterthan the l. diameter of rollers :235. The axes ofthe rollers 239, holes 238 and 4i for each *.Ivnember 235 are equidistantly spaced apart. During rotation of .f gear 45the-inertia `members .235.vvill be'subjected to centrifugal force which Vwill cause en n gagernent between rollers 235 andholes '238 in said members at the points nearest the axis of rotation of said gear, ,l and the: engagement .off rollers 23S-with holes 124i at the'points farthest from the axis of rotation of saidgear. The forces required to move said members toward said axis against centrifugal forcefandinertia and the rolling-.action betweenl the opposite portions of rollers 239 and the oppositely curved portions:- of the. holes A238. and24l, damp the torsionalY vibrations in the gear 45. y.

A series of six segmentally shaped inertia hierrrv bers 244 is confined between Athe body 49 of gear... 41 and `a` flange 245 whichis integral with said'v body. Each member .244. is, provided adjacent each end with a cylindrical. hole 241v whichv extends therethrough. A- roller 248 extends through each of holes.241 and is provided with a head .which abuts against the outer face of flange 245,`anda plate 249 bolted to flange 245engages the head of the two rollers in each member 244 to hold therollers against axialr movement. Each roller 243 extends -throughelongitudinally aligned cylindricalholes `25!)v in the Abody ofwheel 49 and flange 245 and throughfa cylindrical hole 241 in the inertia memberv 244. Theidiameter of the holes 241 and 255 is equal and greater than the diameter of roller 248. `Theaxes of the rollers 1 243,:,holes 241 and251for each member 244 are equidistantly spaced'apart. During rotation of the body of gear 41., which-.is secured to the f propeller shaft l32, inertia members 244 will be 2 45 atpoints'. farthestrfrom :the :axisjof rotation of said body. Members -244-'moveragainst cen-V trifugal force andinertia and by the vrolling action betweenthe oppositevportions of rollers 248 Iand-the opposite portions of holes 241 and 25),

damp ythe-torsional.fvibration in the body of gear-41.

`s-shafts, dampen thetorsona'l-vibration which re-` sults from the aerodynamic? interference effect t ofthe oppositely rotating;propeller 'blades Vand i isolates them4 from the engine; and the gearing-.f

between the engine andthe gearing on the r-peller shaftsf- Lubricating oil is :supplied` from the engine pro-1 pressurelsystem through la .ducty :|88 (Fig. 18) and' ports 188e; to annannularv cond-uitli` (Figs.t3 f

and-18) whichiisnformedfbetween a tube |90 and `the-hollow shaft 116.: From annular; conduit 439? l oil flows through radial ports I9!" to anfannular conduit i 92 lwhich f isrformed .between ltheA inner periphery of propeller shaft 353 -and a .tube I93 `2 and the hub of ngear i-rand aport IQ/li'tothe Oil also: flows Some-vof rthisroil ilows' through a port (Fig. 2'7')l forwardlyfto radial- :ducts'it tto the l.bearing- 54 lbetween the `contra-rotating shafts 32 and-39. The bearing 543is securedinthe shaft f 32 -by a pin H51;w Leakage oil canfflow fromthe rear end of bearing ,5 4 throughthe annu-larspace,

between shafts 3e and 32 '.to rthe ball-bearing ,52

...from which-it drains into thegear casing; Leake.

age oil from the front of bearing 54 can allow vrto anannular groove Zfin the periphery'of shaft.'

35 which is connected by :radial ports 24| toan:

annular-groove 242. inra darin or head 203 Which-1; is nxed .in shaft 3l),A into the interior of tube 1I 931 from which it'returns tothe gear-casing through tubesiS and 190.- An oil-seal is provided at,

the front of bearing `54 for preventing'the escape of. oiloutwardly from saidbearing, and comr prises a'sleeve 20.4 Varoundshaft 39 .and-movable f therewith; a carbon sealing ring 29,5 .-slidably k; confined in sleeve 254 and rengaging the front end 'f subjected to centrifugal force which-Will cause rollers '2481with holes 250 inbody .49 and flange ofr bearing 54;- a plurality of elastic gaskets 208 y which are V-shaped in-cross-section and extend x around shaft 3U and in sleeve 264 a follower ring- I2115 engaging. the foremost l gasket 203; and

springs 259 between'the front endiof sleeve 204 f and the follower which press the follower rear- Wardly -to compressthe gaskets against the sealing ring 255+ The vertex-of rings 258 and the contiguous surfaces on sealing ring 235 and follower ring 245 extend forwardly so that the gaskets 205 -are' tightly pressed againstrshaft 3l) to preventthe escape or `loss of oil from groove l$36 1 :.in said shaft.-

The operation will be as follows: assuming the engine is supplying power to the main drive gear 38 through gears 43 .and 44 which are driven by the crank shaft of the engine, and the clutching .,device di) is in-its forward position, the driving 5 drive the torque responsive ring through balls B1 between said ring and said driving member;

.the ring will drive `the driven memberA 4Sy 'through the balls 52;. the driven member 38 will drive sleeve 8| and the clutch members H5 and H4 of the slidable-clutching device Si); clutch teethy l I6 on clutch member H4 will be engaged); qwithclutch teeth II5 to pQsitivelyLdrivethe,low

speed gear 15; the propeller shafts 30 and 32 will be driven through the lay-shaft units 55 and gear 15; gear 2| 5 (Fig. 18) will be driven to drive the distributor and magneto from gears 2 0 and 2||; the gearing for driving the governor |86 will be driven from shaft |16 which is driven by propeller shaft 30; valve |58 will be set in position to drain the oil from cylinder |41 so that spring |50 will hold piston |48 and the clutch shifting device in its low speed driving position; the torque transmitted through ring 85 will control the pressure in cylinders 98 and |55 to hold latch-lever |52 so the arm |45 of the clutch shifting mechanism will be locked in the rear notch in said lever; friction face |20 of ball: ring I1 will be engaged with the friction surface |2| on gear 15; valve |10 will be in its forward position to deliver oil through conduit |13 to the governor |86; and the abutment |60 on piston stem |49 will control the spring pressed movement of arm |6| and rod |62 to cause contacter |66 to close switch |69 for indicating to the pilot that the clutch device is positioned for driving the propeller shafts at the low speed ratio. The gear 15 will be positively driven from sleeve 8| through clutch teeth |I and ||6 to drive the lay-shaft units 55. Propeller shaft 30 will then be driven in one direction through gear 45 and gears 59 of the lay-shaft units 55 and propeller shaft 32 will be driven through gear 41 and the gears 62 on said lay-shaft units. The propellers will then be driven in opposite directions from the engine at the low speed ratio.

When the pilot desires to shift the clutch device 80 for driving the propeller shafts at the high speed ratio, he will first rotate valve |58 to deliver oil under pressure from conduit |59 through valve port |58b and conduit |59a to the rear end of cylinder |41 which will tend to shift the piston |48 forwardly. The arm |45 then remains locked in the rear notch of latch-lever |52 so that the clutch device 80 remains in low speed driving position. Next, the pilot will close the engine throttle until no appreciable torque is transmitted through the ring 85 which will cause the pressure in communicating cylinders 68 and |55 to be reduced so that the spring |56 will shift piston |54 forwardly to swing lever |52 to release arm |45 of the clutch shifting mechanism. The pressure in cylinder |41 will then act to move the piston |46 forwardly and shift arm |45 to urge the shifter-ring |36 rearwardly, and the friction face |8 on the balk ring will engage the friction face IIS on the gear 16. The arms |22 will move rearwardly until they are arrested by shoulders |23b on the balk ring to prevent the clutch teeth ||2 on clutch member ||0 from engaging the clutch teeth ||3 on gear 16. The friction faces I|8 and ||9 will urge gear 16 toward synchronous speed with the clutch members I |0 and I I4. The clutch members will then be held in neutral position while this occurs, and the contactor |66 will close switch |68 (Fig. 17) to indicate the neutral position of the clutch device. The gear 16 and the balk ring ||1 are then usually rotated slower than the clutch members. As the engine slows down the clutch members will slow down until they attain a speed slightly lower than the speed of the gear member 16. When this occurs, the arms I 22 will rotate slightly relatively to the balk ring I|1 in a direction opposite to the rotation of said arms. The shoulders |23b will then be moved out of the path of arms |22 and permit the rearward movement of the clutch member I I0 and its clutch teeth ||2 to slide into engagement with the teeth II3 on gear 16 as the result of the pressure of fluid in cylinder |41 and the forward movement of piston |48, for positively driving the propeller shafts at high speed ratio from the engine through high speed gear 16. The rearward movement of piston |48, on the completion of the shift of the clutch and the abutment |60, will cause contactor |66 to be shifted to close switch |61 for indicating to the operator that the shift to high speed ratio has been completed. The clutch will be held in high speed position while valve |58 remains set to supply fluid under pressure to cylinder |41. Valve |10 will then permit fluid to be drained through conduit |13 from the governor` |86. The throttle for the engine will then be opened to drive the propellers at high speed which will increase the torque transmitted through ring and cause an increase of pressure in cylinders 98 and |55. This increase of pressure will shift piston |54 to rock latch-lever |52 into position to lock arm |45 of the clutch shifting mechanism in high speed driving relation. While the gear 16 is positively driving the Propellers through the lay-shaft units 55, the overrunning clutch will permit the low-speed driving gear 15 to rotate faster than the clutch member and sleeve 8|.

When the pilot desires to shift from high speed ratio to low speed ratio, the valve |58 is rotated into position to drain the oil from cylinder |41 to permit the spring |50 to be released for shifting piston |48 rearwardly, but the arm |45 is then locked in the front notch of latch lever |52 because of the torque being transmitted through the ring 85. The pilot will next, by the throttle control,l slow down the engine so that there will be no appreciable torque transmitted through the ring 85 and oil from the engine pressure system will then flow from the cylinder 98 to reduce the pressure therein and in the cylinder |55, which is communicatvely connected to cylinder 98Su1iciently to permit the spring |56 to shift piston |54 forwardly and disengage latch-lever I 52 from the arm |45 of the shifting mechanism for the clutch device 80. When the arm |45 is released by latch-lever |52, the force of spring |50 in cylinder |41 will be applied to shift arm |45 rearwardly. The balk ring |I`| will then be shifted forwardly by the spring pressed balls |36 which are initially seated in recesses |34 until the conical face |20 on clutch member II4 engages the conical face I2I on the gear 15 which will tend to drive said gear and the balk-ring at synchronous speed. The engagement of friction faces |20 and I2I will cause gear 15 to be rotated faster than the clutch members IIO and ||4 and cause the shoulders |23a to arrest arms |22 and the clutch members in neutral position. The contactor |66 will then `close switch |66 for indicating the shift of the clutch device to its neutral position. If the clutch teeth |I5 and ||6 were permitted to engage at this time, they would tend to wedge together upon decrease of the torque being supplied to the propellers due to the springing effect of the rollers |08 and the cam surfaces |01. The pilot will next momentarily open the engine throttle to increase its speed which will normally tend to drive the propellers through the over- J-running clutch rollers |08, and then rotation of the clutch members necessary to cause the rollers |08 to drive 'gear 15 causes arms |22 to rotate out of the path of shoulders |23a. At this time the clutch members and gear 15 will be rotated at substantially the same speed and the contacter |66 Willcloseswitch |68 toyindicate tothe-pilot that the clutch device is in'its neutral position. To complete the shift for low speed driving, the pilot again closes the throttle so no appreciable torque will be transmitted through the ring 85 and the pressure in cylindersv 9B and |755v willA be reduced to permit spring |56 to shift latch-lever |52 to release arm` |45, whereupon'thespring |50 in cylinder |41'will shift arm `|55I and the clutch members to'slide clutchteethli. and into engagement fori driving the "propellers at low speed ratio. This shift will be made Without substantial torque on the rollers |08 and the gearing will then be operated at the low-speed ratio as before described. The contactor |85 will then close the y'switch |69 for indicating the clutch device has been shifted to low speed driving position. As the/engine throttle is opened to drive the propellers, the torque transmitted through ring 85 will cause an increase of pressure in cylinders 98 and 4|55 to lock the clutch device in its low'fspeed driving position.

After the ylow yspeed shift is completed, the pilot will then open the throttle the desired amount for engine'operation. As torque is again supplied to the propellers, one set of springs |2'l will compress and relative movement will occur between clutchmember I0 and lid until teeth |25 engage againstfteeth |26 to form a positive drive between members l0 and |14. We prefer to have the torque in low-speed vdriving transmitted through the positive engagement of teeth |25 and |26 and 5 and H6 and in such event it is necessary thatv the back lash or play between the teeth|25 and |26 be less (in terms of angular travel) thanv the angular travel necessary to cause the lrollers |08 of the overdrive clutch to lock sleeve member 8| with gear 15'. In some driving instances, however, it maybe desirable to have the torque transmitted through the rollers |08 and to utilize the teeth H5, H6, |25 and l 25 as a safety device in event of failure of the overdrive clutch. In the case` of the latter operation the angular travel to ,engage rollers |08 would be less than that required for engage ment of teethA |25 and |25.

If the propellers should start to speed up so that the shift to low-speed vcould not be completed, the pilot canagain shift the clutch to high-speed position as before described. The friction driving faces ||8 and I I9 have sufficient holding force to drive the engine, from the propeller so that the clutch teeth ||5, I6 will be driven sufiiciently close to synchronous speed to permit said clut'hf, teeth to mate andslide into engagement. .A l

The vfriction surfaces r.between the highjspeed drive gear 'l5 and theffriction surface ||8 on the balk ring are preferably of suiiici'ent capacity to prevent any windmilling of Athe propeller blades during the shifting period from increasing the speed of said gear with'such rapidity, that the clutch teeth'if and ||3 cannotbeengaged for positive drive of the engine by the propellers.

The invention exemplifies two speed transmission gearing for driving contra-rotational propellers through a series of lay-shafts which remain in mesh with high and loW speed gears and a clutch forxselectively controlling the high speed and low speed operation of the propellers relatively to the engine.

The invention also exemplifies a slidable toothed clutch for drivably engaging the high and low speed driving gears and means for C011- scope of the invention.

18 trolling the Aclutch to prevent knocking of the clutch teeth in effecting speed changes; the invention also exemplies a clutch which is torque controlled tol control the engagement of the clutch with the high and low speed gears.

The invention also exemplifies a clutch device with a balk ring which retards the engagement of the clutch with the gears and is controlled by a, relative speed between the clutch and the gear; the invention also exemplifies hydraulic and torque controlled mechanism for controlling the shifting of the clutch.

The invention also exemplifies a lay-shaft unit which can readily be assembled with the high and low speed gears for uniformly loading the teeth on the gears. An application filed by us November 2, 1949, Serial No. 125,058 describes and claims the Lay Shaft Unit as divisional subject matter of this application.

The invention also exemplifies high and low speed gearing which is provided with vibration dampers for isolating the vibrations due to blade passing from the variable speed gearing and the engine.

The invention also exemplifies improved automatic means for controlling the timing of the distributor and generator.

The invention also exemplifies an outboard bearing between the contra-rotating propeller shaft and means for supplying oil through the inner shaft to said bearing.

The invention is not to be understood as restricted to the details set forth since these-may be modified Within the scope of the appended claims without departing from the spirit and Having thus described the invention, what We claim as new and desire to secure by Letters Patent is:

l. Engine driven transmission gearing for driving contra-rotational coaxial propeller shafts comprising coaxial gears, each gear being provided with clutch teeth, an engine driven slidable clutch between and coaxial with said gears and provided with clutch teeth for slidably engaging the clutch teeth on the gears, respectively, a balk-ring axially slidable on the clutch and provided with friction faces at its ends for respectively engaging the coaxial gears, and with slots, the clutch comprising a pair of. members movable together longitudinally, spring and stop means between the members for permitting limited relative rotation of the members, and means for axially shifting the clutch and the balk-ring, an engine-driven overrunning clutch for driving one of said gearsand means controlled by the relative speed of the clutch and the gears for controlling the engagement of the clutch-teeth. I

2. Engine driven transmission gearing for driving contra-rotational coaxial propeller shafts, comprising coaxialgears,I each gear being provided with clutch teeth, an engine driven slida-ble clutch betweemcoaxial with said gears and provided with'clutch teeth `for slidably engaging the clutch teeth on the'gears',lrrespectively, a balk-ring axially slidableonthe clutch and provided with frictionv faces at its ends for respectively engaging the coaxial gears, and with slots, the clutch comprising a pair of members movable togetherlongitudinally, springend stop means between theV members -for lpermitting `limited relative rotation of the members,'and

means for axiallyjshifting the clutch and ythe balk-ring, an engine-driven overrunning clutch for driving oneof said gears; means controlled by the relative speed of the clutch-and the-'gears for controlling the engagement ofl the clutch teeth, and torque controlled means for locking the clutch in 10W-speed, neutral and high-speed driving positions.

3. Engine-driven transmission gearing for driving contra-rotational propeller shafts, coin-Y prisng coaxial gears, each provided with clutch teeth, an engine driven slidable clutch provided with teeth for slidably engaging the clutch teeth on the gears, respectively, combined spring and huid pressure meansf for slidably shifting' the clutch toy alternately engage they clutchteeth on said gears, andy hydraulic means responsive to variations in the torque of theengine for lock-- ing said spring and fluid pressure means to hold the clutchv into' engagement With said gears, rcw spectively, and in neiu'jra-ll position.

4. Engine driven transmission gearing Yfor driving contra-rotational propeller shafts, comprising' coaxial gears, each providedV with clutch teeth, an engine driven slida-ble clutch provided With teeth for slidably engaging the clutchy teeth on the gears, respectively, combined spring and duid pressure means for slidably shifting the clutch to alternately engage the clutch teeth on said gears, torque controlled hydraulic means for locking the spring and iiuid pressure means to hold the clutch in engagement with said gears, respectively, and in a` neutral position, and means controlled by said spring and. fluidpressure means for indicating the positions of the clutch.

5. Engine driven transmission gearing for driving contra-rotational coaxial propeller she-its, comprising coaxial gearsy of dierent pitelr diameters, each provided with clutch teeth, an axially slidable clutch between said gears, co'- axial with said gears and provided with teeth. for slidably engaging. the clutch teeth on the gears, respectively, a balk-ring around and slidable on the clutch and provided with friction faces at its ends for respectively engaging the high and low speedl gears, means for slidably shifting the clutch and for shifting. the` balkring for engaging its friction faces with said gears in advance of the engagement of the clutch teeth, the balli-ring being limitedly rotatable relatively to the clutch, andI means on the balkring for holding the clutch in a neutral position and preventing engagement of the clutch with the gears, an engine-driven overrunning clutch for driving one of said gears, the balkring being releasable by varying its relative rotation to the clutch to permit the clutch teeth to engage the `clutch teeth on the gears, respectively.Y

6- Engine driven transmission gearing for driving contra-rotational propeller shafts, comn prising coaxial gears, each provided with clutch teeth, a driving sleeve, a clutchaxially slidable on' thev Sleeve coaxial with said shafts and including relatively rotatable members provided with teeth for slidably engaging the clutch teethy on the gears, respectively, a balk-ring around and slidable on the clutch and provided with friction faces at its ends for respectively engaging the gears, means for slidably shifting the clutch, means for axially shifting the balk-ring by the clutch-shifting means for engaging its friction faces with said gears in advance of the engage ment of the clutch teeth, the balk-ring being slidable and rotatable relatively to the clutch, stop-means for the clutch on the balk-ring for preventing engagement of the clutch with the gears, an over-running clutch between the sleeve and one of the coaxial gears, the balk-ring being rotatable tov release the clutch and permity its clutch teeth to engage theV clutchk teeth on the gears by relative movement of the clutch and the gears, respectively.

-7. Engine driven transmission gearing for driving contra-rotational coaxial propeller shafts, comprising coaxial` gears, each gear being providedv with clutch teeth, an engine driven slidableclutch between and coaxial with said gears and provided withv clutchy teethv for slidably engaging theclutch teeth,y on thefgears, respectively, a balk-ring around andv axially slidable on the clutch and provided with friction'r faces at its ends for respectively' engaging the coaxial gears, and with, slots, means on the clutch extending through and movablerelatively to the ringaxiallyand rotatively inthe slots, means in the slots for arresting the axial movement of the clutch after the balk-ring is fixedly engaged with the gears and. before the teeth on the clutch engage the gears, means for axially shifting theA means extending through thering to shift the clutch, theA balk ring being `controlled by the relative speed of the clutch and the gears when the ring is frictionally engaged with the gears for disengaging the arresting meansto permit the teeth onthe clutch to engage the clutch teeth on the gears', and torque controlled means for locking the clutch engagedv Withthe coaxial gears respectivel-y.

8. Engine driven transmission gearing for driving contra-rotational coaxial propeller shafts, comprising coaxial gears,` each gear being provided with clutch teeth, an engine driven slidable clutch between and coaxial with said gears and provided with clutchl teeth for slidably engaging the clutch teeth on the gears, respectively, a balk-ring around. and` axially sldable on the clutch and provided with friction faces at its ends for respectively engaging the coaxial gears and movable into a neutral position, and with` slots, means on the clutch extending through and movable relatively to the ring axially and rotatively in the slots, means inl the slots for arrestingv the axial movement of the clutch after the balk-ring is frictionally engaged with the gears and before the teeth on the clutch engage the gears, means for axially shifting the means extending through the ring to shift the clutch, the balk-ring being controlled by the relative speed of ythe clutch and the gears when the ring is frictionally engaged with the gears for disengaging the arresting -means to permit the teeth on the yclutch to engage the clutch teeth on the gears, and torque controlled means for lockingr the clutch engaged with the coaxial gears respectively and in an intermediate neutral position.

9. Transmission gearing comprising coaxial driving and driven members, a ring longitudinally movable relatively to and surrounding said members, driving means between the ring and one of said members which permits longitudinal sliding movement of the ring, the inner periphery of the ring and the outer periphery of the other member being provided with mating longitudinally extending helica-lly inclined recesses, balls in said mating recesses connecting said other mem ber and the ring for longitudinal movement of the ring produced by torque, hydraulic means for shifting the ring longitudinally, and valve-means for the hydraulic means, responsive to the longitudinal movement of the ring.