US2438650A - Construction of retractable landing gear - Google Patents

Description

March so, 1948. SAULMER 2,438,650

CONSTRUCTION OF RETRACTABLE LANDING GEARS Filed Feb. 15, 1942 h 2 Sheets-Sheet l In uezzt v j? S a, u lzzaez' March 30, 1948. R. SAULNIER CONSTRUCTION OF RETRACTABLE LANDING ,,GEARS 2 Sheets-Sheet 2 Filed Feb.. 13, 1942 Inventor Sana/Z12,

ie! 1W Patented Mar. 30, 1948 CONSTRUCTION OF RETRACTABLE LANDING GEAR Raymond :Saulnier, Parla -France Application February 13, 1942, ."Serial Il\lo..430,621

,InFranee .May 15,1940

- SectionL-Public Law 690, Aug1i's't-8, 1946 Patent expires May-15,1960

15 Claims. ,1

The present invention relates to retractable landing gear .ofthe type includingza .shockabsorber which carries the .wheel,:pivoted to:.a' fixed point of the airplane structure)andimaintained in the landing or extended: position-by a 4 breakable. strut pivotedron the :onehand to. a fixed point .of the airplane :and, :on :the other hand; 'to a point of theshock absorber.

The invention relates .-.more aparti'cularly 1 to landing gear of this type, in which the" point at which .the strut is pivoted Ito theusho-ok absorber is located closeito the lower endof the-cylinder of the shock absorber, which-ensuresaa verygood resistance during landing.

More specifically, itheginvention relates to retractable landing gearjn whichsthestrut is 'made of two portions :pivotedto .eachother substantially. at the middl'epoint ofxthestrut in such a manner that, when the :gear is in; the landing position-the p'ointof. articulationof the-two portions of the 'strutis beyond thedead,center.:position, so as. .to improve .safety. when landingyindependently of the locking of. the .strut.

According .to;.thev invention, the. folding pr .re-.

tractingv of the .landinggearnis. effected in two steps, the first .of which consists, after. the. strut has been .re1eased,:in breakingdt. soasto cause, in the particularcasejust.abovementioned, the point of articulation'to passptoathe othergsideiof the dead center line, thesecond step-gbeinggperformed by the actionofa .jackjpivoted' on the one hand .to a' fixed :point; off i the airplane and, on the other :hand. .to the end of, a. lever rigid with the. sho,ck'-,absorber, so :as to cause :the :latterv to pivot: about the point at which it is mounted; on the. airplane.

One of :themostserious idifliculties which have to be .dealtwith in retractable landing gear, is to ensure a retraction of a gear with the minimum .of force, xwhich implies an efficientutilization. of .the-poweryof the retracting means.

An obj ect: ofzthe, present invention is vto .provide a retractingsdevice.suohthat the first step, which: starts the .breaking of :thestrut, and the second step which causes the shock absorber to pivot about its-point of articulation onthe airplane, are :zproduce'dby a thrust'directedealong a line making ;an..-angle as small as possible with the optimum direction, accountabeing taken of the power to be exerted.

For this: purpose, according. to. afeature .of my invention; the strut. includes a system, of levers intended .to break thiss'strutand in particular, to movetheu point; of articulation 'thereof :from one side toathe, other of the; deadcenter line.

, According-Qtoranother feature-of; the inven tion, the lifting {device properi is arranged in such inannerthat the lever arm on whichthejack .is to act lengthens, during the lifting movement,

as ;;t he rresistance itself increases, whereby .the power requiredto Joe-exerted by the jack never reachesyeryhigh values, since the ,force requiredtobie exerted at the end of the movement is rel atively.- small.

0ther -features of my inventionwill appear from the following detailed description .of some specific embodiments thereof.

Preferred embodiments of my invention .are

hereinafter, described, with reference to the .ac-

. shockabsorber which carries a wheel .W and-is pivoted ,at-H to a fixed part M of the airplane. The shock absorber. :may be. maintained .or .not in ;its plane, .parallel .to the fore-and-aft ;plane ofv symmetry .of-v :the. airplane, *by a thrustbar,

. the latter ,being :pivoted .llOifl'lfiXGd part of the airplaneat a.pointlocatedbehind point. H,..so thatathemhole can pivot about-a longitudinal axistpassingthrough these-two points. The landing geargfurther includes a strutconstitutedby two portions A and A pivoted toeach. other near the middle point of .the strut: at B. These two portions: are, locked .in :the landing position .by a.loc king.member-.C. whichis shown in a more detailedmanner byFig.i2. This'locking member isipreferably controlled pneumatically by a valve D. Y E and F. are thepoints where. thestrutis pivotedto:'the.-.airp1ane and to the shock absorber, respectively.

; The. retraction of .the landing gear. is. obtained lay-swinging .the shock absorber .G about :point absorber.

H, this movement being producedib'y the action ofa jack :V, one of whose ends. is pivoted to the airplane .-..-at a point J, while the other end vis pivoted .to a lever arm-I rigid with the shock Reference character: I designates: the operating. member, N. is :the compressed airinlet; K a distributer. for controllingthe. inflow ofoil under pressure and Q :a' vconduit through which oil 4 is fed to the-distributor. fDistributer K isifurther 3 I connected through pipes K1 and K to the opposite ends of jack V. Finally, valve D is connected through a pipe d to a pneumatic piston P housed in strut A, A. V a

This device operates in the following manner: The first movement of the'operating lever T, in the direction of arrow f opens valve D, which causes compressed air to be fed into pipe d. Pneumatic piston P is actuated by this compressed air and pushes lever L, pivoted about an axis 0, so as to move the locking member of the lever L (see Fig. 2), into inoperativeposition.

During the second part of this first movement, a projection R on lever L strikes a corresponding projection R of portion A of the strut, whereby no risk of an accidental folding of the gear during landing; even tions,

Further,

under the most di-fiicult condireliable extension of the landing gear is assured by the gravity effect of the weight of the thrust of piston P breaks the strut just when the'two projections disengage from each other. At this time, the movement of piston P is stopped by a'lug U. During this movement, the point B about which'the'two portions of the strut are pivoted" to each other, passes from a position below line E-'--F (where it was jammed in order to increase safety in case'ofnon-operation of the locking means) to the position B" on the other side of said line *E-F. The operating lever T is now at the end ofits first movement in the direction of arrow 1 a a a The second movement of this operating lever T, in the direction of the arrow f permits oil under-pressure to pass-through distributor K and through conduit K into the near end of the jack V. This pushes lever I and causes the shock absorber to' swing on its pivot H, whereby the landing gear isfullyfolded.

.Inithe embodiment which has just been described, the operating lever T is given two successive movements, one serving to control the pneumatic piston which starts the breaking of the strut, and the other operating the jack, whichfinishes the retroacting operation.

7 lnfthe'embodiment shown in Fig. 3, the pneumatic control valve D is located between jack V and the point J of fixation thereof to the airplane. In this embodiment, the operation of the lifting device isfsimplified because only the flow of oil through the distributor K requires to be controlled by the control element X.

' When the control lever X of Fig. 3 is moved, 1 oil" under pressure is fed through conduit K to the j'ack,.which tends to .push lever I, on the one hand; and'to open'v'alve D on the other hand. ,As'

lover I resists the thrust thus transmitted there- .the landing gear, the counter-pressure in the jack V, and the action of the elastic cable S,

which is stretched between the strut A, A and the frame M, t Another advantage of the landing gear, ac-

V cording to the invention derives'from the fact that the power necessary for retracting the gear is reducedto a minimum, As above explained, the first movement, which starts the breaking of the strut, by unlocking it, necessitates only a very small force in view of the particular ar- 7 rangement of the levers and the projections carried by the parts of the strut. Furthermore, the

efiective leverageof the arm I, on which the lifting jack acts, increases as the force required ii creases, as above explained.

WhileI have, in the above description, dis-- closed what I deemto be practical and eflicient:

embodiments of the present invention, it should? be well understood thatI do notv wish to be lim--.

I ited thereto, as changes maybe made in the arrangement, disposition and form of the parts,

without departing from the principle otthe pres-- ent invention, as comprehended within the scope.-

of the appended claims. V

What I claim is:

r 1. A retractable landing gear including a shock absorber pivoted to the airplane proper, a member adapted to run on the ground carried by said. shock absorber, a jointed strut pivoted at one end. to the airplane proper and at the other endto the shock absorber, said strut'being broken in,

the folded position of the landing gear and; straightened in the extended .position of said. landing gear, means for locking said strut in the: landing. position, means carried by the strut forbringing said locking means out of action and to, because stnitA-A is locked and therefore cannot break, jack V compresses spring Y (see Fig. 4') and permits valve D to be opened by the compressed air from the pipe N, so that compressed air is passedto operate the piston P, so as to move locking member 0 into inoperative position 'and'start the breaking of the strut in the manner explained above. The jack then bears against the piece Z, provided in the Valve D for limiting its movement, and pushes on the lever I so as to retract the shock absorber.

i The landing gear according to the invention has many advantages, among which the following may be cited: 1

, First, the safety obtained when landing is very high, since'the shock absorber is well adapted to r resist transverse stresses, because it is braced at a very low point by the strut. The strut cannot break accidentally since, even when it is not positively locked, said strut is biased in the extended substantially simultaneously starting the breakf ing of said strut, and a jack interposed between the airplane proper and said shock absorber for finishing'the folding movement started by the above mentioned means.

. 2. A retractable landing gear including a shock absorber pivoted to the airplane proper, a member adapted to much ,the ground carried by said shock absorben a jointed'strut'pivoted at one end to' the airplane proper and at the other end to the shock absorber, said strut being madeof two parts pivoted to each otherat the middle point of the strut'and being broken in the folded position of the landinggear and straightened in the extended positionof said landing gear so that said middle point passes slightly beyond the dead center line of the strut, means for locking said strut in the landing position, means carried by the.

strut for bringing said'locking me'ans out ofaction and substantially simultaneously bringing above mentioned means T back said middle point on 'the'other side of said dead center line, and a jack interposed between the airplane properiand said'shock absorber for finishing the folding movement started by the 3. A'retractable landing gear ber' adapted'to run on the ground carried by said to the shock absorber, saidstrut being broken in the folded 'position, of the landing "gear an}?! including a shock 1 absorber pivoted to the airplane proper, a'memstraightened in "the ''i'ztzified position 'of said landing gear, sfir'ii i'g 'ii'iIn loklfig 'ali'd Strut in the mnmngposnmmpne ti 'eariscarried by the strut for brii'i'g ifl g 'safd iockmgmeans out of actionandsubstantiallly si-friiiltafri'ollsly starting the hi 'akingof sai'd fii'ii'tfa jack interposed between the airplane f'pro'pfand said shock absorbr "fon'filiis'hihg 'the folding'l'ri'otem'ent started by 'the abov mentioned means, and "means for feeding 'li'quid tinder 7 pressure to Said jack.

4. A retractable l'l lfdifig'gafrih'ollidihgashock absorber "pivoted to the""ei.irp1an'e :pr'eper, a membrada'ptedto when the ground-carried by 'said shook "absorber, a jointed strut IliVOt'eH at one the folded position of the landing gear and straightened in the "iitlidd position of said landing ge'arjspring ineansTorlo'ckingsaid strut in the landing position, 'pneuinatic means carried by the strutforbrin'ging said lookingmeans' out of action and substantially"simultaneously starting the breaking "of said strut, a j efk interposed between'th e airplane propfr and said shockacsorber for finishing the folding movement started 'by the above i'ri'enti'on d 'in'e'ans, hydraulic means 'for feeding liquid under pressure to said jack, sndacommtn operating m'emb'erfor successively operating said pneuin'atic 'means and said hydraulic mean I 5. A'retractab'le Ianuinggearinducin ashock absorber pivotedto' the"airplane"proper, 'a member "adapted to :run "on thegroundcarried by said shock absorber, "a 'joint'd "strut pivoted at one end to' theai'rpla'ne 1 proper "and *at' the other end to the shook "ibsblb'r, 'saidjstrut being broken in the folded position "of the landing "gear and straightened in the extended position of said landing gear, spring means "forlocking said strut in the landing position, pneumatic means carried by'thestrut'for bringing-said locking means out of action "and substantially simultaneously starting thebreaking of said st'rut; a jack interposed betweenith'e airplane proper ena said shock absorber for finishing the folding movement started by the above m'enti'dnedmeans; hydraulic means for feedin liquidunder pressure tosaid jack, "a 'lever' -a'dapted to be' given two different movements, means operated by said lever for one of said movements foroperatingsaid pneumatic means and means "operated-by the loth'er movement of said lever 'for operating "said hydraulic means. i g I v 6. 'A retractable landing gear" including a shock absorber pivoted to the *aii plane proper, a member adapted to run on thegrofind oarridbysaid shock absorber, a "jointed strut pivoted at one end to the airplane propenand-at the other end to the shock "absorber,"said'strutbeing broken in thefolded positionbfthe landing gear and straightened in the extended p'o'sition of said landing gear, spring means for locking said strut in the landing position, pneumatic means carried by the strut for bringing-{said locking irieans out of action and substari ally simultaneously starting the breaking of s'aid strut, a jack" inter- 1 posed between the airplaneproper and said shock absorber for finishing, When eXpandedQthe folding movementstarted bythe-above mentioned means, said jack having lost motion to give it a slight play at the beginning of its operation to complete t-he folding 'in'oin'errient, hydraulic means for-feeding-lidu r'pressure to'said jack, an a'ir valve for-conti'o Imgsaid 'pn'eumatic *nieans adapted to be opend by the "expanding movement of said jack corresponding to the takplane o'f the t'y'pe involviiig ariorinaily vertical 6 ing up of "said play, and valve means for "open atin'gsaid hydraulic'nieans.

7. A retractable "landing "gear facc'ordin'g to Claim "6 further including iever adapted to operate said last 'ni'e'n'tione'id valve means "in such manner that a first displacement-or said lever causes the jack totakeu'p its 'p'iayamim'ove mer t in the 'sam'ediretibh tiailse's said 'jackto finish thefoldirig ofthe l'andinggear.

8. In a retractable-landing gearfor "airplanes, the combination of,"an elongated member pivoted at one end" to the-airplane owner and adapted to swing from a downwardiyeiitendin position 'to a substantially fhorizontalflpbs'ition, "an "airplane supporting member carried u on the free'end of said elongated memberga jack pivote'd 'at'one end to the airplane and'atitsotherend to the upper part of s'aid'elongated member for operating said elongated member into inoperative horizontal positiona jointed'sti'utipivoted at one end to the airplane properan"d at the other to the elongated member'jand'bein'gmovablefrom a folded position in which saidelong'atedmember extends substantially horizontally to an extended position in'whioh Saidelongated member extends downwardly, 's aid strut comprising a" pair ofstrut members having a pivotal "connection which moves past the deadcenter"of"the"strut when the strut approaches its'e'xtieiite iitendefd position, Jatchmeans' on thestrutbrid'gi'ng said piv. otal connection "so "as to il iold "sai d strut in its extended position, ,"and fluid operated "rneans on the strut for operating said l'a tch means into inoperativepos'ition and for "mot/inten pivotal connection toward folded pastime-cites the dead center of thestrut, eas tobreak" theistrut.

v '9. In a retractable anuinggear for "an "airplane involving an elon'ga'tedfin'einberfhaving 'a round engaging element "at its lower end and 'Ineans at its upper "endfor' pivotal "connection with the airplane to enable"said elongated membier to be retracted from a s'libs'tantiallyvertical tudinal axes of said sections, said bre'akjoint in. cluding a fixed joint element onfthe-l'owersection projecting alongside or "an"'a'djacent portion of the upper section emanating-a"cam urface, said break joint further comprising-a," latch pivoted onthe upper section'hayihg"a"camf operatively 'engageable with the cam s'u'rface whereby the lower" section is swu'rig away 'from the upper section whenever said latch is in'ovedonitsp'ivot in one direction;said latch furtherhavin'g a detent portion latchable witha portion on the lower section when the sections are intheir extended positions, a hydraulic cylinderand'piston assembly mounted and operating longitudinallybn said upper section with a portion: of itspiston enga'geable with said cam to inove it in'sa'id one'direction-so as to sequentially disengage-said detent portion from latching relation to "thef lower section and swingsai'd lower s'ectionre ativ'e to-said upper section thereby partiallyfolding 'the strut,

and hydraulic means 'for co'rfi-pletifigthe folding of the strut.

Y 10. In a retractable "landing gear rer enairof said elongated member and an .joint swingably connecting. the sections, latch from said other section with elongated member having a ground engaging ele-, ment at its lower end and'means for pivotingit at its upper end to an airplane, andafoldable strut extending between the lower part of said elongatedmember and a part of the airplane, said strut comprising anupp'er section pivoted at its upper end to the airplane and a lower section pivoted at its lower end to the lower part off center break means for locking the sections in extension of each other, said latch means comprising a cam pivoted on one section and a cam surface on the other section, a fluid cylinder and piston'assembly mounted longitudinally on said one section, said ,piston being operatively 'engageable with said'cam so asto move said cam against said cam surface so as to swing the sections relative to each other sufliciently to break the joint and permit the strut to move into folded position when said assembly is operated, and means for completing the folding of the sections.

11. In a retractable landing gear for an airplane, a normally vertical shock-strut pivoted atrits upper end to the airplane,a foldable brace strut extending between the lower part of the shock-strut and a part of the airplane remote from the pivotal point of the shock-strut, said foldable brace strut comprising upper and lower sections pivoted to the airplane and thelower part of the shock strut, respectively, and an, off

center break joint pivoting the ,sections together for folding relative to each other and for substantial longitudinal alignment of the sections in their unfoldedposition, said break joint comprising a movable latch member mounted on one of the sections andlockably engageable with the other section in the aligned relation of the 'sections, said latch member having acam portion engageableafter release of the latch member a portion of said other section so as to move the latter so as to break the joint and impart preliminary movement of the sections relative to each other toward ,folded position, said upper section having a hollow portion, and operating means comprising a fluid piston andicylinder in said hollow portion and assembly mounted withlongitudinally with re- ;spect to the uppersection and operatively en- ;gageable with said movable latch member.

12. In a retractable landing gear for an vairplane, the combination of a longitudinally acting shock absorber pivoted'at one end to the airplane for swinging from a depending vertical operative position to a substantially horizontal inoperative position, a groundrengaging element on thefree end of said shock absorber, meansfor moving said shock absorber into, and out of operative position, a foldable strutpivoted atone end to the airplane and at its other end .to the shock absorber adjacent toits said free end to brace the shock absorber in its'operative position, said foldable strut comprising a pair of sections hinge means arranged ofi center on the sideof the strut remote from the shock absorberland hingedly connecting the sections together and permitting the sections to pivot-out of longitudinal alignment to enable the strut to fold toward the shock absorber as the shock absorber is swung upwardly from its vertical operative position toward its inoperative horizontal position, the oil center location of the pivotalpoint of said-hinge means precluding the pivoting of said sections out-of V longitudinal alignment in the opposite direction, latch means bridging and interconnecting the hinged ends of the strut sections for locking the sections when in longitudinal alignment, and cooperating means carried by'the adjacent ends of said strut sections for'releasing said latch means and formovingth'esections past their oil-center relation toward folded position to permit the sections to pivot in a strut-folding operation.

13. In a retractable airplane landing gear, a longitudinally acting shock absorber pivoted at its upper end to the airplane to extend downwardly in extended position'and havin a ground engaging element at its lower end, a foldable strut pivoted at its lower end to the lower part of said shock absorber and at its upper end to the airplane at a point at one side of the pivotal point of the shock absorber, said strut comprising a pair of sections, means hinging the sections together at their inner ends to fold'toward the shock absorberas the landing gear is retracted to inoperative position and'to reach a position past dead center when restored to aligned position as the landing gear is extended to operative position, locking means for locking the sections together as they move into their aligned position, a lever connected to the upper end of the shock absorber and turning on the pivot of the shock absorber, a jack located at the strut side of the shock absorber and having one end connected to said lever and its opposite end to the airplane, and operating means for working the jack to retract and extend the shock absorber, said operating means including means responsive to the portion on said other of the )strut members to V latch the strut members, whereby the movement of the latch means towards inoperative position causes the cam elementto move the strut members relative to eachother and thereby break the strut. w

15, A retractable landing gear as described in claim 8 wherein said jack comprises afiuid operated cylinder-piston unit and a valve mounted on oneend of the cylinder, said valve being responsive to the fluid pressure in said unit and controlling the supply of fluid to said fluid operated means on the strut.

" I RAYMOND SA ULNIER.

, 1 REFERENCES CITED The following references are oflrecord in the file of this patent:

' 'UNI'VI'ED STATESPATENTS Number Date Name 1,171,075 Taylor Feb, 8, 1916 1,329,533 McCarrol Feb. 3, 1920 2,292,671 7 Sumner Aug. 11,1942

7 r V FOREIGN PATENTS Number Country 1 Date 464,144 Great Britain Apr. 13, 1937 7 518,073 Great Britain Febjl6, 1940 7 518,130 Great Britain Feb, 19,1940

704,202 Germany ;Mar. 26,1941

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