US3106963A

US3106963A - Rotor for a helicopter

Info

Publication number: US3106963A
Application number: US73077A
Authority: US
Inventors: Posniak Benjamin; George A Mccoubrey; Babiarz Edward
Original assignee: Kaman Aircraft Corp
Current assignee: Kaman Aircraft Corp
Priority date: 1960-12-01
Filing date: 1960-12-01
Publication date: 1963-10-15
Anticipated expiration: 1980-10-15
Also published as: GB1002560A

Description

Oct. 15, 1963 B. POSNIAK ETAL ROTOR FOR A HELICOPTER 4 Sheets-Sheet l Filed Dec. l, 1960 BENJAMA/V POS/WAK GEORGE AMCCOUBREV EDWARD BAB/Anz By /Mfn il 01a Oct. 15, 1963 B. PosNlAK ETAL RoToR FOR A HELICOPTER 4 Sheets-Sheet 2 Filed Dec. l, 1960 Oct. 15, 1963 B. PosNlAK ETAL RoToR FOR A HELICOPTER 4 Sheets-Sheet 3 Filed Dec. l, 1960 d, H Z M Oct. 15, 1963 B, POSNIAK ETAL 3,106,963

ROTQR FOR A HELICOPTER The invention relates to a rotor Afor a helicopter, and the general object of the invention is to provide improved means which enable the several blades of the rotor to be folded so as to reduce the space required for the storage or transportation of the helicopter.

`In a rotor embodying the invention, the outer lifting structure of each blade is pivotally movable about a hinge axis which is outwardly spaced from the lead-lag axis and which is normally substantially vertical. A releasabie device is provided on each blade :for normally holding the outer lifting structure in its extended position, this device when released permitting the lifting structure of the blade to be swung about the hinge axis to a folded position. Preferably, the releasable device engages an arm which is fixedly connected with the lifting structure of the blade and which extends inwardly beyond the pivotal axis. A rotor as above set forth is not herein broadly claimed, such a rotor being set Iforth and claimed in the copendin-g application of Richard H. Hollrock and Robert B. Bossier, lr., Serial No. 128,711, tiled August 2, 1961, for Rotor lfor a Helicopter.

One of the objects of the present invention is to provide various improved features of structure and arrangement for the devices which releasably hold the blades in extended positions and to provide various improved features of structure and arrangement for the means which operate and hold the last said devices.

It may be desirable to fold the several blades of the rotor at different levels, and in accordance with the invention each hinge axis is adjustable to different angular positions with respect to a radial plane through the rotor axis, and means is provided for retaining the parts with the hinge axis in the adjusted position. With the hinge axis of any one blade at a selected angle, the folding movement of the lifting structure is effected at a corresponding level.

In accordance ywith usual practice each blade comprises an inboard member connected with the rotor hub and the lifting structure of the blade and the supporting elements therefor are movable relatively to the inboard member and about a radial axis, this relative rotative movement being provided primarly -for pitch changing during rotor rotation. This capability of relative rotative movement is utilized when the rotor is stationary for changing the angle of the hinge axis relatively to said radial plane preparatory to folding. The before-mentioned retaining means serves for holding the parte in their adjusted positions after the angle of said hinge axis has been changed.

A rotor embodying the invention has other novel and advantageous features which will be more fully understood from the drawings and the following description and claims.

The drawings show a preferred embodiment of the invention and such embodiment will be described, but it will be understood that various changes may be made from the construction disclosed, and that the drawings and description are not to be construed as defining or limiting the scope of the invention, the claims forming a part of this specication being relied upon for that purpose.

Of the drawings:

FIG. 1 is a schematic plan view of a helicopter having a rotor embodying the invention.

FIG. 2 is a plan view of the inboard portion of one blade of the rotor, together with a fragment of the hub.

FIG. 3 is a side view of the blade and hub parts shown in FIG. 2.

FIG. 4 is an enlarged plan of a portion of FIG. 2, this view showing the parts to which the invention -more particularly relates.

FIG. 5A is a vertical sectional view taken along the line 5A-5A of FIG. 4.

FIG. 5B is an extension of FIG. 5A in the outbomd direction.

FIG. 6 is a vertical section-a1 view taken along the line 6-45 of FIG. 4.

FIG. 7 is a view taken in the direction of the arrows 7, 7 in FIG. 4, but showing only the arms that are engaged by the radially movable retaining member.

FIG. 8 is a combined sectional and elevational view taken lalong the line -S-S of FIG. 4, this view showing the radially movable retaining member but omitting the parts with which the retaining member engages.

FIG. 9 is a plan view of the retaining member and associated parts as shown in FIG. 8.

FIG. 10 is a horizontal sectional view taken along the line liti-1) of FIG. 8.

FIG. Ill is an enlarged fragmentary sectional View taken lalong the line 11-11 of FIG. 6.

FIG. l2 is a view generally similar to FIG. 4, but showing the parts in positions wherein the folding is permitted and showing the blade partly folded.

FIG. 13 is a vertical sectional view taken along the :line 13-13 of FlG. 12.

General Organization Referring to the drawings, and more particularly FIG. 1 thereof, 10 represents the fuselage of a helicopter having a rotor which includes mechanisms embodying the invention. The rotor of the helicopter comprises a plurality of generally

radial blades

14, 14 which are connected with a hub 16 and are uniformly spaced about a central vertical axis. The hub 16 is connected with a vertical main shaft (not shown) extending upwardly from the fuselage 10. As shown, the rotor has four blades, but the invention is not necessarily so limited.

When there are four blades, ias shown, the hub 16 preferably has four radi-al arms, one of the anms being shown at 1S in FIGS. 2 and 3. The inboard member -20 of each blade 14 is connected with the corresponding hub arm 18 -for movement about a horizont-al flapping axis at 22 and for movement about a vertical lead-lag axis at 24. For collective and cyclical changes in pitch, the outboard or lifting structure 26 of each blade is rotatively movable relatively to said inboard Imember 2t) and about a radial axis. Such rotative movements of the

structures

26, 26 of the several blades are effected and controlled by means of aerodynamic servo-flaps 2S, 28 carried by the respective lifting structures 216, Z6 and adjustable relatively thereto about axes parallel with said radial axes. Mechanism controlled or actuated by the pilot is provided for moving and controlling the flaps 2S, 28 so as to change and maintain the blade pitches for all conditions of flight.

As shown in FlG. 3 each hub arm 18 is preferably bifurcated and a pivot block 29 is located between the bifurcations. The block `Z9 has a vertical bearing opening therein for a lead-lag pivot pin which provides for pivotal movement about said axis 24. The inboard blade member 2t) has an outer tubular portion 30 and said member is bifurcated at its inner end as shown in FIG. 2 to provide

bifurcations

32 and 34. The bifurcations embrace said pivot block 29 to which they are pivotally connected for `flapping movements about the axis 22.

The lifting structure 26 of each blade is carried by an inner supporting element 36 and the inner portion 37 of said inner supporting element is tubular and surrounds the tubular portion Si? of the inboard member 2i).

Bearings

38 and 46 are interposed between the

tubular portions

30 and 37, these bearings permitting the outboard portion of the blade to turn relatively to the inboard member for elfecting changes in pitch. Tension-torsion members 4?., 42 are provided for preventing outward movement of the outboard blade portion and for resisting relative rotative movement thereof. The

members

42, 42 have their inboard ends suitably connected with the inboard member 20 and they have their outboard ends connected with the inner supporting member 36 by means of

bolts

44, 44 in

flanges

45, 45.

As shown, the main outboard or lifting structure 26 of each blade 14 comprises a radial spar in which is connected with an outer supporting element 48. The outer supporting element 4S is normally iixedly connected with the inner supporting element 36 by means to be fully described. The spar 46 provides the required airfoil shape for the leading edge of the lifting structure 26 and said spar carries a plurality of panels 50 which serve to provide the required airfoil shape for the trailing portion of the structure. The details of the outboard or lifting structure 26 of the blade may be as set forth in the Lubben, Schauble and McCoubrey application Serial No. 850,953 led November 4, 1959 and entitled Helicopter Rotor and Method of Making a Blade Member Thereof.

An azimuth mechanism, not shown, is provided at the lower end of the main shaft which is hollow. Vertical rods, not shown, extend upwardly from the azimuth mechanism and through the shaft, these rods corresponding in number to the number of blades. The rods are connected respectively with levers one of which is shown at 52 in FIGS. 3 and 4, the levers being pivoted to the hub i6. The outboard end of each lever 52 is connected with the upper end of a vertical link 54. The lower end of the link 54 is connected with one arm of a bell crank 56 which is pivoted at 58 to the inboard member 20. The other arm of the bell crank is connected by a link 6i) with the leading end of a lever 62 which is pivoted to the member 2i). Said lever 62 is pivoted between its ends at 64 and the trailing end of said lever is connected with radial links 66 and 63. The outboard end of the link 68 is connected with a lever 70 pivoted to a bracket 72 on the spar 46. A radial link 74 is connected at its inboard end to the lever itl and said link '74 extends outwardly within the panels Sil. At its outboard end the link 7d is connected to the flap 28 by suitable means, not shown, this means including a bell crank and a transverse link.

When any rod within the shaft is moved upwardly by the azimuth mechanism, the corresponding link 52 is moved downwardly, the link 66 is moved inwardly, and the

links

66, 63 and 74 are moved outwardly. The connection from the link 74 to the iiap 28 is such that outward movement of the link causes the tlap to move in the negative direction, that is, in the direction for downward movement of its leading edge. The increased negative pitch of the iiap tends to move the trailing edge oi the lifting structure 26 downwardly with resultant increased positive blade pitch. The described motions are reversed when the azimuth mechanism causes downward movement of the rod in the shaft.

The azimuth mechanism is pilot operable and by means of said mechanism and the last above described linkage the pilot can control the angles of the aps 28, 2S and can thus control the pitches of the blades collectively or cyclically or both. While differing in some respects, the

, various parts for controlling the pitches of the blades may be constructed as more fully disclosed in the Hartswick application Serial No. 43,830 tiled July 19, 1960 and entitled Rotor Control System for a Helicopter.

Pitch Lock Mechanism A centrifugally controlled means is preferably provided i on each blade for locking the outboard portion of the blade to prevent rotative pitch changing movement relatively to the inboard member 2t? when the rotor is stationary or is rotating below a predetermined speed. The locked position is sometimes referred to as a predetermined initial position.

Referring more particularly to FIGS. 3, 4, 5A and 6, a ring 76 is connected to the inboard end of the tubular portion 37 of the inner supporting element 36, this ring being provided with a notch 7S. The manner of connection of the ring to the tubular portion 37 is hereinafter more fully described, but it is here pointed out that the connection is such that relative rotation is prevented. The inboard member 20 is provided with outwardly extending flanges Si?, 8@ between which there is secured a block 82. The block S2 is bifurcated at its outboard end and a locking member 84 is located between the bifurcations of the block, being movable about a pivot pin S5. At the outboard end of the member 84 is a tooth S8 which is adapted to enter the notch 78 in the ring 76. A compression spring biases the member S41 for entry of the tooth in the notch. The radially inward portion of the member 84 at 92 constitutes a weight which during rotor rotation acts centriiugally to move the tooth 88 out of the notch 78. A pin 94 limits outward movement of the weight portion 92. Preferably, the connection for the ring 76 includes

resilient cushion elements

96, 96 as shown in FIG. 5A. The

cushion members

96, 96 are formed of rubber or equivalent material.

When the rotor is stationary or rotating at less than said predetermined speed, the spring 9@ holds the member 84 with the tooth titi in the notch 78, thus holding the outboard or lifting portion of the blade in its said predetermined initial position. When the rotor is rotated at a speed above said predetermined speed, the weight 92 acts centrifugally in opposition to said spring 90 to move the tooth SS out of the notch 73 so that the outer lifting portion 26 of the blade is free to turn under the control of the ap 28.

When the rotor speedA is decreasing and falls below said predetermined speed, each lifting portion 26 tends to turn to its said initial position. When the blade portion reaches said position, the tooth S8 snaps into the notch 7S. The cushion elements 95, 96 permit slight rotative movement of the ring 76 relatively to the member 28 and they thus absorb shock.

Folding and Retaining Mechanism The outer supporting element 4S is connected with the inner supporting element 36 for pivotal movement about a hinge axis perpendicular to the radial axis of ythe blade. For convenience of description this axis will be referred to as vertical, but during flight it is inclined in a radial plane through the rotor axis iu accordance with the coning angle of the blade and it may at other times be inclined with respect to said radial plane for a purpose to be hereinafter explained.

As best shown in FIG. 5B, the inner supporting element 35 has a vertical aperture therein near its outer end and a vertical hinge pin 98 is iitted within the aperture, a bushing preferably being interposed. The outer supporting element 48 preferably has upper and lower bifurcations Mtl and 192 which are apertured to receive the upper and lower portions of the hinge pin 93, suitable bushings being provided. A collar 164 prevents axial movement of the pin. The described hinge joint permits the lifting structure 26 of the blade and the outer supponting element 48 to be pivotally moved for folding purposes relatively to the inner supporting element 36.

In `order/that folding may be elfected without interfering with the connection for controlling the ap 28, the

before-mentioned

links

66 and 68 are pivotally connected with each other at 166 for relative movement about a vertical pivotal axis which is at least approximately in alignment with the hinge axis. As shown, a bracket 13S is secured to the member 48, and a transverse link is pivoted at its leading end to said bracket for movement about a vertical axis. The link 11G at its trailing end is pivotally connected with the

links

66 and 68 at said axis 166. The link 11G serves to support said

links

66 and 68 and to prevent any substantially forward or rearward shifting of the axis 106. The axis 106 may shift inwardly or outwardly as the

links

66 and 68 are moved to transmit motion to the flap 28, but the axis 166 is in any event near the hinge axis and hinging or folding can be effected without disturbing the connection between the links. Referring particularly to FIG. 3, it will be seen that when folding is effected in either direction by moving the `outboard portion of the blade clockwise or counterclockwise the bracket 1&8 and the link 68 move in substantial unison and without any interference with each other.

Means are provided for releasably retaining the lifting structure 26 of the blade and the outer supporting element 48 in their normal positions, and said means preferably includes an arm such as 112 which is ixedly connected with said outer supporting element and extends inwardly `to a substantial extent beyond the hinge axis. The last said means also includes a relatively movable retaining device, sometimes hereinafter referred to as the first retaining device, which is engageable with the inner end portion of said ann 112 and is adapted in one position to prevent pivotal folding movement of the outer supporting element 48 and the lifting structure 26 relatively to the inner supporting element 36 which device is adapted in another position to permit such pivotal folding movement. As shown, said relatively movable first retaining device is carried by the inner supporting element 36 as shown at 128 and said device is movable relatively to the last said supporting element, preferably rectilinearly, into and `out of engagement with said arm 112.

Preferably there are two

similar arms

112 and 114 which are secured respectively to the upper and

lower bifurcations

180 and 102 of the outer supporting element 4S. The arms l112 and `114 are respectively above and below the inner supporting element 36. As shown, the

members

112 and 114 are apertured at their outer portions to receive and t the hinge pin 98 and they are connected with the

bifurcations

160 and 102 by

bolts

116 and 118. Each of the arms l112 and 114 at the inner end thereof has two loppositely disposed

inclined faces

122, 122 which are exposed toward the hub. Preferably as shown in FIGS. 4, 7, and l2 each of said

arms

112 and 114 is forked at its inner end to provide two transversely spaced

prongs

120, 120. When the prongs 120, 121! are provided, said faces 122, 122 are on said prongs and said faces face toward each other and diverge inwardly.

A retaining device 128 is radially movable along a cylindrical portion 130 of the inner supporting element 36 and when there are |two superposed

arms

112 and 114 on the outer supporting element 48 the retaining device has two superposed portions which are engageable respectively with said superposed arms. Referring particularly to FIGS. 4, 5A, 8, 9 :and l0, the retaining device preferably comprises two companion parts 132, 1'34 that are similar except for reversal. These parts slidably engage the portion 130, and they are engageable with the arms 112 and 1114 and more particularly with the

prongs

120, 120 thereof as hereinafter more fully explained.

A manually operable means is provided for moving the retaining device 128 in the manner above stated. This means may be widely varied as to details of construction, but as shown there are two similar partly

cylindrical members

136, 138 which surround and engage a cylindrical part of the tubular portion 37 of the inner supporting element 36. These members are provided at the top with

ilanges

140 and 141 that are at opposite sides of a radially extending operating member 142, said flanges and said operating member being connected with each other by

bolts

144, 144. Similar flanges and a similar operating member are provided at the bottom but are not fully shown.

The two

parts

132, 134 of the retaining device have

flanges

146 and 148 which are respectively connected by rivets 149 or otherwise with outwardly projecting narrow portions of the partly

cylindrical members

136, 138. The two

parts

132, 134 of the retaining device are additionally connected with the

members

136, 138 by means of bolts 150, 159 at the top and bottom, said bolts extending between said

pants

132, 134 and said `operating

members

142 and 145. Spacers `152, `152 are provided at the top and at the bottom between the

parts

132, 134 and the operating members.

As best shown in FIG. 8, the

parts

132 and 134 are provided near the top with notches having faces 154, 154 which diverge inwardly to engage and tit the diverging faces 122 on the prongs of the upper arm 112. Said notches at their outer ends have opposite beveled faces 156 and 158 which diverge outwardly to facilitate entry of the

prongs

112, 112 into the notches. When the retaining device comprising the

parts

132 and 134 is moved outwardly, the prongs of the arms 112 :and 114 are entered in the notches in the retaining member, and the diverging

surfaces

122, 122 and 154, 154 fit each other so .as to prevent any lost motion at the inner ends of the arms and thus prevent any pivotal movement about the hinge axis.

As shown in the drawings, a small clearance is provided between the two

parts

132 and 134 of the retaining device. These parts are held by the outwardly projecting narrow portions of

members

136, 138 and they are also held by the bolts 150, 'y and the spacers 152, 1-52. These several holding means for the parts I132 and 134 are flexible within narrow limits, and said parts are forced toward each other and into iirm engagement with the portion -130 of the supporting element 36 when the inwardly diverging faces 154, 2154 on said members are engaged with the inwardly diverging faces '122, 122 on the

prongs

120, 120. The extent of actual movement of said parts toward each other may be very small, but the movement avoids any possible lost motion between said

parts

132, 134 and said portion 138.

The means for radially moving the retaining device 128 also includes a manually operable lever which is connected with the inner supporting element 36 for moving about an axis perpendicular to said radial axes, together with a generally radial link which is pivotally connected at its respective ends with said lever and with said retaining device 128 so that the lever upon pivotal movement serves to move lthe retaining device either into or out of engagement with the arm 112, or the

arms

112 and 114. Th pivotal axis of the lever and the axes of pivotal connection of the link are so related that an overcenter toggle action is provided when the lever moves the retaining device into engagement with the arm.

The before-mentioned lever is preferably a bail 166 which is pivoted to the tubular portion -37 at 162, a similar pivot l163 being provided at the opposite end. The bail is connected with the operating member 142 by a link 164, the link being pivoted to the bail at 166 and being pivoted 'to the operating member 142 at 168. A similar link l169 is provided at the opposite side. With the parts in the positions shown in IFIGS. 2, 3, 4 and 5A, the retaining device -128 is firmly engaged with the arms L12 and :114 to prevent any movement about the hinge or folding axis. The parts are so proportioned that there is a toggle action when the bail is moved to the position shown, the pivotal axis 166 being overcenter with respect to the

axes

162 and 168. The

links

164 and 169 iare adjustable in length to ensure proper toggle action. During operation, the parts are held in the positions shown partly by the toggle action and partly by the centrifugal force acting on the bail during rotor rotation.

Means for Holding Hinge Axis at Selected Angle ln accordance with the invention, the hinge axis for range.

folding is angularly adjustable with respect to a radial plane through the rotor axis and an optionally usable means is provided for retaining said hinge axis at any one of a plurality of angles with respect to said radial plane so that folding of the outboard lifting structure may be effected yat a selected one of a plurality of levels.

The inner supporting member 36 and the parts carried thereby are rotatively movable relatively to the inboard member 2t) and about a radial axis in the conventional manner for pitch changing purposes. The last said rotative movement serves to change the angle of the hinge axis with respect to a radial plane through the rotor axis, but such angular change is merely incidental and has no significance during normal operation. However, this capability of angular adjustment of the hinge axis is preferably utilized obtaining the before-mentioned hinge axis angle that is desirable for folding. When folding is to Vbe effected, the inner supporting member is manually moved to locate the hinge axis at a selected angle. The flap 2S constitutes the effective portion of the pitch changing means `and this flap has no pitch changing effect when the rotor is idle and when folding is to be effective. The pitch changing means therefore leaves the inner supporting element 36 and the hinge means free to be rotatively `adjusted relatively to the inboard member. A manually operable retaining device, sometimes hereinafter referred to as the second retaining device, is provided for retaining said inner suporting member and the hinge device in any one of a plurality of positions to which they may have moved with the result that folding of the outboard lifting structures may be effected as above described. The tooth I38 of the pitch lock mechansm ordinarily holds the hinge axis at a predetermined position `when the rotor is idle, and if this is not the desired position for folding said tooth is manually disengaged.`

The details of the means or device for retaining the inner supporting member in a selected position may be widely varied, but the presently preferred means is shown in the drawings and will be described. The before-described ring 76 is not mounted directly on the portion 37 but it is so mounted by means of an interposedring 170. The ring 7 6 is so connected =with the ring l174? that relative rotation is prevented. The two rings are hereinafter sometimes referred to as a ring structure. The portion 37 of the inner supporting member 36 and the ring 171i are provided with an annular series of inteimeshing splines or teeth 172 which prevent any relative rotation but which permit the ring 17% to be moved radially inwardly or outwardly. The inboard member Ztl is provided with an annular series of teeth 174 and the ring 17@ is provided with an `annular series of teeth 176. The teeth 176 are adapted to intermesh with the teeth 1174 when the ring 17@ is moved radially inwardly to an operative position. Suitable means, such as a stop i177, is provided for preventing the ring 17u from moving inwardly beyond the operative position wherein there is full interengagement of the

teeth

176 and 174.

When the ring 17d is in the inoperative position shown in FIG. 4, the inner supporting element 36 and the parts carried thereby can be turned to adjust the hinge axis to any one of a plurality of angles within a reasonable The pitch lock tooth 88 must have been irst disengaged from the ring '76. inasmuch as the element 36 and the parts thereon are normally moved rotatively only by the ap 2.8, it is obvious that, with the rotor idle, neither the flap 2S nor its control linkage offers any substantial resistance. However, some resistance is offered by the tension-

torsion members

42, 42.

-After the turning to locate the hinge axis yat the required angle, the ring 17d is moved to its operative position as shown in FIG. 13, and in said position the ring serves yas a retaining device to prevent any relative rotative movement of the inner supporting element 36, and the hinge axis is held at a selected angle. Said ring 170,

when -in its inoperative position, leaves said inner supporting member 36 and the parts carried thereby free for conventional rotative movements under the control of the flap 2S.

A manually operable means is provided for moving the retaining device 17@ into and out of its operative position and preferably the handle orY bail i169 is used for this purpose.

The ring 170 is provided with upper and lower bosses 17S and 18d to which are secured upper and

lower tubes

182 and 184 as best shown in FIG. 1l. the upper and lower operating members `142, 145 are

rods

156, 188 which extend radially inwardly and into the respective tubes 132., 184. Each

tube

182, 184 has an inturned ange 190 at its outer end and each rod 185, 18S has an outwardly projecting annular llange thereon which engages the flange 19t) on the tube. These interengaged flanges prevent any inward movement of fthe tubes and of the ring 17d relatively to the rods beyond the positions that are shown. Springs '194, 196 respectively surround the rods 1556, 188, the outer ends of the springs abutting against collars on the rods and the inner ends of the springs `abutting against the ends of the

tubes

182, 184. Preferably, but not necessarily, the ring 171i is provided with a third boss 198 and a third tube `2021. Connected between the member 136 and the last said boss and tube is a third rod 264 provided with a third `spring 206.

With the parts in the positions shown in FIGS. 2, 3, 4 and 5A the springs l194, 196 and Zilli are fully expanded. When folding is to be effected, the bail 16d is moved inwardly to withdraw the retaining member 12S so as to release the

arms

112 and 114 thus permitting the outer portion of the blade to swing about the hinge axis in either direction. FIG. l2 shows the arms moved out of their normal positions. When the bail 16d is moved as `above stated, the ring 176 is moved inwardly to engage the teeth 174 with the teeth 176 and to thus retain -the element 36 and its attached parts against any relative rotative movement. The

springs

194, 196 and 211i) are compressed and they hold the ring 17d in its inner position. Preferably, a spring biased latch 268 is provided which is pivoted to the portion 37, this latch having a hook which is engageable in a notch in the bail 169 so as to retain the bail in the position corresponding to the releasing or inoperative position of Vthe retaining device 12S and corresponding to the operative position of the retaining device 170.

It should be particularly observed that the teeth 176 of the second retaining device engage the teeth 174 before the first retaining device 12S is moved suiciently to fully release the

arms

112 and 114. Thus there is no intermediate position wherein the outboard portion of the blade would be free to move about the hinge axis and wherein the inner supporting element 36 would at the same time be free to move about its radial axis. lf there were such an intermediate position, the outboard portion ofthe blade might be so moved out of ycontrol by a gust of wind or otherwise, `and the weight of the angularly positioned outboard portion of 'the blade would then tend to turn the inner supporting element 36 about its said radial `axis. This turning tendency might be such that the operator could not effectively resist it. If the inner supporting element 36 were permitted to so turn, the folding axis would be moved out of its intended angular position and folding at the intended level could not be effected.

When the blades are to be folded, it is necessary for the pilot or operator to decide upon a general plan of folding. In accordance with one plan the blades are turned to approxi-mately diagonal positions. As shown in FlG. 1, the blade in position A is folded countercloclewise to the position shown at A in full lines and the blade art position B is also folded counterclockwise to the position shown at B in full lines. The blade at position C is folded clockwise to the position shown at C in full lines and the blade at position B is folded clockwise to the position shown at E in full lines. As shown in FIG. 1, the blades Connected with A and C are above the blades B and D, but this pattern of folding is not essential.

Referring for example to the blades at the normal positions A and B it will be seen that the axes for these blades must be at different angles for the bla-des to fold into the superposed positions shown by full lines. It is therefore necessary for the operator before folding each 'blade to adjust the angle of the folding to such a position as to bring the blade to the predetermined level w-hen folding has been effected. ln adjusting the angle of the hinge axis the operator proceeds as follows:

(l) He manually disengages the tooth S8 of the pitch lock mechanism so that this tooth will not interfere with fthe adjustments that must be made.

(2) By means of the bail 166 or otherwise he then rotates the inner supporting element 36 and the outer portion of the blade so that the hinge axis Ais at the angle that is necessary for folding the blade at the required level. When the inner supporting element is so rotated the retaining device 128 remains engaged so that there can be no pivotal movement of the lifting portion about the hinge axis. The rotation is effected in opposition to the resistance offered by the tension-torsion members 4Z, 42, but no substantial resistance is offered by the linkage for moving the ap 28.

(3) Having rotated the inner supporting element 36 to place the hinge axis at the required angle, he next moves the bail from the position shown in FlGS. 2, 3 and 4 to the position shown in FIG. 12, the bail being then engaged and held by the latch 258. In moving the bail to the position shown in FIG. 12, the operator has withdrawn the retaining member 128 so that the arms 112 and 13.4 are free to move as required for folding and he has also, by means of the rods 186 and the springs 194, moved the ring 175 to the position shown in IFiG. 13 wherein the teeth 176 on the ring are interengaged with the teeth 4174- on the tubular portion 30. These intermeshing teeth lock the hinge axis at the angle to which it has been manually adjusted. In this position, the springs are compressed and they prevent any movement of the ring 170 in the outward or disengaging direction. As previously explained, there is no intermediate position `wherein the blade is free to move prematurely about its hinge axis.

(4) Having positioned the folding axis at the proper angie and having released the outboard pontion of the blade for hinging or folding movement, he then swings it in the proper direction to the selected folded position. When there are four equally spaced blades as shown, the angles `of the hinge axes are such that the lifting structures of adjacent blades are in superposed relationship. More specifically stated the lifting structures of the blades A and B are in superposed relationship and the lifting structures of the blades C and D are in superposed relationship.

The invention claimed is:

l. A helicopter rotor having a hub and a plurality of generally radial blades, each comprising in combinationz' an inboard member connected with the hub,

an outboard lifting structure,

inner and outer supporting elements for said lifting structure, said inner element being connected with the inboard member for relative rotative movement about a radial axis and said outer element being iixedly connected with the lifting structure and being connected with the inner element for pivotal folding movement about a normally vertical hinge axis,

an arm fixedly connected with the outer supporting element and extending inwardly substantially beyond said pivotal axis which arm at its inner end has two transversely spaced prongs having inwardly diverging faces,

a retaining device comprising two separate parts each guided on said inner supporting element movable relatively thereto into and out of an operative position wherein it is in engagement with saidA arm and means for moving the two said parts of the retaining device in unison along said inner supporting element and into and out of said operative position of said device which means is sutiiciently flexible to permit slight movement of said parts towards and from each other, said two parts of the retaining device having inwardly diverging faces respectively engageable with the inwardly diverging faces of the prongs on said arm when said retaining device is in its said operative position which said diverging faces when engaged with each other serve to move the two parts of the retaining device toward each other and into firm engagement with said inner supporting member and also when so engaged serve to prevent lost motion between the retaining device and the arms.

2. A helicopter rotor having a hub and a plurality of generally radial blades, each comprising in combination:

an inboard member connected with the hub,

an outboard lifting structure,

inner and outer supporting elements for said lifting structure, said inner element being connected with the inboard member for relative rotative movement about a radial axis and said outer element being tixedly connected with the lifting structure and being connected with the inner element for pivotal folding movement about a normally vertically hinge axis,

an arm fixedly connected with the outer supporting element and extending inwardly substantially beyond said pivotal axis which arm at its inner end has two oppositely disposed inclined faces which are exposed toward the hub,

a retaining device guided on the inner supporting element for rectilinear radial movement into and out of an operative position which retaining device is constructed and arranged to provide two oppositely disposed inclined faces respectively engageable with said inclined faces on the arm to prevent pivotal folding movement when said device is in its operative position and to permit said pivotal folding movement when said device is out of its operative position,

a manually operable lever connected with the inner supporting element for movement about an axis perpendicular to said radial axis, and

a generally radial link which is pivotally connected at its respective ends with said lever and with said retaining device so that the lever upon pivotal movement serves to move the retaining device either into or out of engagement with the arm, the pivotal axis of the lever and the axes of pivotal connection of the link being so related that an overcenter toggle action is provided when the lever moves the retaining device into engagement with the arm.

3. A helicopter rotor as set forth in claim 2,

wherein said arm at its inner end has two transversely spaced prongs,

wherein said inclined faces are on said prongs and face toward each other, and

wherein said inclined faces on the retaining device face away from each other and are adapted to engage said inclined faces on the prongs.

4. A helicopter rotor having a hub and a plurality of generally radial blades, each comprising in combination:

an inboard member connected With the hub,

an outboard lifting structure,

inner and outer supporting elements for said lifting structure, said inner element being connected with the inboard member for relative rotative movement about a radial axis and said outer element being xedly connected with the lifting structure and being connected with the inner element for holding movement about a normally vertical pivotal hinge axis,

two superposed arms iixedly connected with the outer supporting element at the top and bottom thereof and extending inwardly substantially beyond said pivotal axis which superposed arms are respectively l2 relatively to the inner supporting element which device is adapted in another position to permit such pivotal folding movement, and

manually operable means when the rotor is idle for above and below the inner supporting element, and 5 retaining the inner supporting element and the hinge a retaining device carried by said inner supporting eleaxis in any one of a plurality of rotatively different ment and radially movable relatively thereto which positions to which :they may have been moved, said retaining device has two super-posed portions that retaining means serving to hold the hinge axis at a respectively move into or out of engagement with corresponding one of a plurality of angles with resaid superposed arms, said device when in engagespect to the inboard member and with respect to a ment with the arms preventing pivotal folding moveradial plane through the rotor axis with the result ment of the outer supporting element and the lifting that folding of the outboard lifting structure may be structure about said hinge axis and relatively to eected at a selected one of a plurality of levels. said inner supporting element and said device when 8. A helicopter rotor having a hub and a plurality of out of engagement with the arms permitting such generally radial blades, each comprising in combination: pivotal folding movement. an inboard member connected "ith the hub and having f 5. A helicopter rotor as set forth in claim 4, a radial outer tubular portion,

wherein a manually operable bail is connected with an outboard lifting structure, f

the inner supporting element at opposite sides therean inner supporting element having a radial inner tubu- Y of for movement about an axis perpendicular to 2o lell'eltol Wbeb SUYTOUUS he tubular P'OIOU ofthe said radial axis, and mbeefl member, y

wherein two oppositely disposed generally radial links bearings lntepeeed between said tubular portions to are provided each of which is pivotally connectedV at faellltate relative rotative movement ci said inner its respective ends with said bail and with said re- Supporting member and 0f Peris baffled thereby taining device so that the bail upon pivotal moveabout e edleleXlS, ment serves to move the retaining device either into an buffer Sllbpemg elem-eilt XediY C Olleted With the or out of engagement with the arms, the pivotal axis hflllg SfllCUe ebd f'JODEeCed .Wlth 'the inner SUP- of the bail and the axes of pivotal connection of the P01" ting elemell't for 1 51V0l31-f0d1ng IHOVemeDt about link being so related that an overcenter toggle action e nc'meuy Velleal binge 2}X1S, is provided when the bail 'moves the retaining device 30 a felellVeiY HlOVebe Tealbmg de VlCe adapted 1D One into engagement with Said armsposition to prevent pivotal folding movement. of the 6. A helicopter rotor having a hub and four equally hftmg SlU-eure eltlVeiY i0 tbe limer SUPPOfbllg ele' spaced generally radial blades, each comprising in commeltWbleb d eVlee 1S etlepied m another POSIUOH l0 bmation: permit such pivotal folding movement,

an inboard member Connected with the hub, a retaining ring connected with the tubular portion of the inner supporting element at the inner end thereof an outboardilitinff structure 1 a which ring is movable inwardly and outwardly relailnner and outer supporting elements for said lifting structure, said inner element being connected with the inboard member and said outer element being tively to the last said tubular portion but is held against rotation relatively thereto, and

ixedly connected with the lifting structure and being 4G two Selles 0f tee/lb IeSPeClVelY 0D Sald fing and 011 connected with the inner element for pivotal folding Bald lboed member Which teeth are interengageable movement about a normally vertical hinge axis which upon mWeId mbvemelbof Seid fing S0 that tbeX Pfeis angularly adjustable relatively to said inboard mem- Vent 2111.5 Teltlve rotativeL movement of said inner ber and relatively to a radial plane through the rotor sujppofmg element and 0L tbe lafs ea{led 'thereby axis and Which axis is so adjustable independently Wlth me feebllhet S21-1d 'hlnge axis is held at a of the hinge axis for each other blade, 4D selected angle with respect to a radial plane through relatively movable retaining device adapted in one the mier axle position to prevent pivotal folding movement of -the 9' A behcopef feter eS Set .fOrth `111 `Claim 8,

lifting structure relatively to the inner supporting ele- Wherfm there 15 @0l/1de@ e lllg elllelufe that Includes l,

ment which device is adapted in another position to 0 Sad fetal-1mg fmg Whleh H113 Structure has an eX- permit such pivotal folding movement, and a Posd notch@ ih@ ?eflpbe'y 'fbefebfV 'find F manually operable means for retaining said hinge axis wherein there 1S Pfeilded a lOeklng device on the in- *i at any one `of a plurality of angles to which it may board member hel/111g e eOh Winch 1S adapted t0 t have been adjusted relatively to said inboard menienfer SEK? mmm and. 1S mellelly' movable Out 0f ber and relatively to said radial plane, said retaining said noten Said loekllg deVlCe belng automatically means being operable independently of that or" ana0 @rable lo mol/e Sad teeth Into Said notch when other blade so that folding of the Outboard lifting the rotor is stationary or rotating at aspeed below structure may be eected at a selected one of a plua Prfdetermmed Speed S0 as the leek Seid lllel' Sb?- rality of levels and in parallel superposcd relatioupgftmgelement agamt elaflve 'aiming mevemelt ship with the lifting structure of another blade. and ,Sad locking device bemg COIlSl'uCed t0 Het centiiifugally to move said tooth out of said notch 7. A helicopter rotor having a hub and a plurality of generally radial blades, each comprising in combination:

an Iiriboard member connected with the hub,

an outboard lifting structure,

inner and outer supporting elements for said lifting structure, said inner element being connected with the inboard member for rotative movement relatively thereto about a radial axis and said outer element being fixedly connected with the lifting structure and being connected with the inner element for pivotal folding movement about a normally vertical hinge axis,

a relatively movable retaining device adapted in one position lto prevent pivotal foldirny movement of the outer supporting element and the lifting structure when the rotor is rotating at or above said prede-termined speed and to thereby release said inner supporting element to permit relative turning movenient thereof. 65 l0. A helicopter rotor having a hub and a plurality of generally radial blades, each comprising in combination:

an inboard member connected with the hub, an youtboard lifting structure, inner and outer supporting elements for said liftingV structure, said inner element being connected with the inboard member for rotative movement relatively thereto about a radial axis and said outer element being iixedly connected with the lifting structure and being connected with the inner element for folding movement about a normally vertical pivotal axis,

a first retaining device movable into and out of an operative position at which it prevents pivotal folding movement of the 'outer supporting element and the lifting structure relatively to the inner supporting element,

a second retaining device movable inwardly and outwardly into and out of an operative position for retaining the inner supporting element in any one of a plurality lof rotatively different positions to which it may have been moved, said retaining means serving to hold the hinge axis at a corresponding one of a plurality of angles with respect to the inboard member and with respect to a radial plane through the rotor axis with the result that folding of the outboard lifting structure may be effected at a selected one of a plurality of levels,

a manually operable lever pivotally connected with the inner supporting element,

a link connecting the lever with the last said retaining device for enabling the lever to move the last said device into and out of its said operative position, and a latch on the inner supporting member .for holding the lever in a position corresponding to said operative position of the last said retaining device.

ll. A helicopter rotorY as set forth in claim 10,

wherein a compressible spring is interposed between said link and said second retaining device which spring is compressed to hold the device in its said operative position when the lever is held by the latch.

l2. A helicopter rotor as set forth in claim 1G,

wherein said manually operable lever is connected with the inner supporting element for movement about an axis perpendicular to said radial axis, and

wherein a generally radial link is provided which is pivotally connected at its respective ends with said lever and with said second retaining device so that the lever upon pivotal movement thereof serves to move the last said retaining device either into or out of its said operative position, the pivotal axis of the lever and the axes of pivotal connection of the link are so related that an overcenter toggle action is provided when the lever moves said second retaining device out of its said operative position.

13. A helicopter rotor having a hub and a plurality of generally radial blades, each comprising in combination:

an inboard member connected with the hub,

an outboard lifting structure,

inner and outer supporting elements for said liilting structure, said inner element being connected with the inboard member and said outer element being fixedly connected with the lifting structure,

mechanism operable during rotor rotation for changing the pitch of said lifting structure,

hinge means connecting said outer supporting element and the lifting structure with said inner supporting element for pivotal folding movement about a normally vertical hinge axis,

means connecting said inner supporting element with said inboard member for rotative movement of said inner supporting element and of said hinge means relatively to the inboard member independently of the action of said pitch changing mechanism,

a first retaining device movable into and out of an operative position at which it prevents pivotal folding movement of the outer supporting element and the lifting structure relatively to the inner supporting element,

a second retaining device movable into and out of an operative position at which it retains said inner supporting element with the axis of the hinge means at any one of a plurality of angles with respect to the inboard member and with respect to a radial plane through the rotor axis with the result that folding of the outboard lifting struc-ture may be effected at a selected one of a plurality of levels, and

id a single means movable in one direction [for simultaneously moving said rst and second retaining devices out of and into their respective operative positions and serving upon lever movement in the reverse direc-tion to move said first and second retaining devices simultaneously into or out of their respective operative positions.

14. A helicopter rotor as set forth in claim 13,

wherein the last said means is constructed and arranged to move said second retaining device sufficiently -to `be effective before said first retaining device has been moved sufficiently to be ineffective.

15. A helicopter rotor as set forth in claim 14,

wherein rst retaining device is movable radially outwardly to its operative position, and

wherein said second retaining device is movable radially inwardly to its operative position.

16. A helicopter rotor as set forth in claim 13,

wherein the last said means includes a manually operable lever movable in opposite directions with respect to the inner supporting element and also includes elements connected with said lever and serving upon lever movement in one direction to simultaneously move said first and second retaining devices out of and into their respective operative positions and serving upon lever movement in the reverse direction to move said first and second retaining devices simultaneously into or out of their respective operative positions.

17. A helicopter rotor as set forth in claim 16,

wherein said first and second retaining devices are connected with each other for radial movement in unison,

wherein said lever is connected with the inner supporting element for movement about an axis perpendicular to said radial axis, and

wherein a generally radial link is provided which is pivotally connected at its respective ends with said lever and with said retaining devices so that the lever upon pivotal movement serves to move the retaining devices radially inwardly or radially outwardly, the pivotal axis of the lever and the axes of pivotal connection of the link being so related that an overcenter toggle action is provided when the lever moves the retaining devices radially outwardly to move the first retaining device into its operative position and to move the second retaining device out of its operative position.

18. A helicopter rotor as set forth in claim 17,

wherein a latch is provided which is adapted 'to hold said lever in the position corresponding to the inopertive position of the first retaining device and the operative position of the second retaining device.

19. A helicopter rotor as set .fforth in claim 16,

wherein said lever is connected with the inner supporting element for movement about an axis perpendicular to said radial axis,

wherein a generally radial link is provided which is pivotally connected a-t its respective ends with said lever and with said retaining devices so that the lever upon pivotal movement serves to move the retaining devices radially inwardly or radially outwardly,

wherein compressible springs are superposed between said retaining devices,

wherein means is provided for limiting inward movement of said second retaining device beyond its operative position with the result that said springs are compressed when the first retaining device is Inoved toits inoperative position, and

wherein a latch is provided which is adapted lto hold said lever in the position corresponding to the inoperative position of the first retaining device and the operative position of the second retaining device.

20. A helicopter rotor having a hub and a plurality of 15 generally radial blades, each comprising in combination:

an inboard member connected with the hub,

an outboard lifting structure,

inner and outer supporting elements for said lifting structure, said inner element being connected with the inboard member and said outer element being fixedly connected With the lifting structure and being connected With the inner element for pivotal folding movement about a normally vertical hinge axis,

a relatively movable retaining device adapted in one position to prevent pivotal folding movement of the outer supporting element and the lifting structure relatively to Ithe inner supporting element which device is adapted in another position to permit such pivotal folding movement,

mechanism operable durinfy rotor rotation for changing the pitch of said lifting structure,

means connecting said inner supporting element With said inboard member for rotative movement of said inner supporting element and `of sm'd hinge means relatively to the inboard member independently of the action of said pitch changing mechanism, and

manually operable means when the rotor is idle for retaining the inner supporting element and the hinge axis in any one of a plurality of rotatively dierent positions to Which they may have been moved, said retaining means serving to hold the hinge axis at a corresponding one of a plurality of angles With respect to the inboard member and with respect to a radial plane through the rotor axis with the result that folding of the outboard lifting structure may be effected at a selected one of a plurality of levels.

21. A helicopter rotor as set forth in claim 20,

wherein the mechanism for changing the fpitch of said lifting structure includes an aerodynamic servo-flap carried by said lifting structure together with ap controlling means extending along the blade from the hub to the flap which flap has no pitch changing eifeot when the rotor is idle and therefore leaves the inner supporting member and the hinge means free to be rotatively adjusted relatively to the inboard member.

22. A helicopter rotor as set forth in claim 20,

wherein said rotor has four equally spaced blades, and

wherein the inner supporting member and the hinge device of each blade are rotatively movable independently of those of each other blade so that folding lof the lifting structure of each blade may be effected at a selected level and in parallel superposed relationship with the lifting structure of another blade.

References Cited in the file of this patent UNITED STATES PATENTS 1,144,471 Gustafson et al June 29, 1915 1,291,237 Sturrock Jan. 14, 1919 1,989,544 Campbell Jan. 20, 1935 2,029,484 Howard et al. Feb. 4, 1936 2,467,579 Boudreau Apr. 19, 1949 2,497,040 Williams Feb. 7, 1950 2,658,576 Mosinskis Nov. l0 1953 2,812,961 Brown et al Nov. 12, 1957 2,815,820 Papadakos Dec. 10, 1957 2,966,947 Batesole Jan. 3, 1961 FOREIGN PATENTS 668,895 Germany Dec. 12, 1938

Claims

6. A HELICOPTER ROTOR HAVING A HUB AND FOUR EQUALLY SPACED GENERALLY RADIAL BLADES, EACH COMPRISING IN COMBINATION: AN INBOARD MEMBER CONNECTED WITH THE HUB, AN OUTBOARD LIFTING STRUCTURE, INNER AND OUTER SUPPORTING ELEMENTS FOR SAID LIFTING STRUCTURE, SAID INNER ELEMENT BEING CONNECTED WITH THE INBOARD MEMBER AND SAID OUTER ELEMENT BEING FIXEDLY CONNECTED WITH THE LIFTING STRUCTURE AND BEING CONNECTED WITH THE INNER ELEMENT FOR PIVOTAL FOLDING MOVEMENT ABOUT A NORMALLY VERTICAL HINGE AXIS WHICH IS ANGULARLY ADJUSTABLE RELATIVELY TO SAID INBOARD MEMBER AND RELATIVELY TO A RADIAL PLANE THROUGH THE ROTOR AXIS AND WHICH AXIS IS SO ADJUSTABLE INDEPENDENTLY OF THE HINGE AXIS FOR EACH OTHER BLADE, A RELATIVELY MOVABLE RETAINING DEVICE ADAPTED IN ONE POSITION TO PREVENT PIVOTAL FOLDING MOVEMENT OF THE LIFTING STRUCTURE RELATIVELY TO THE INNER SUPPORTING ELEMENT WHICH DEVICE IS ADAPTED IN ANOTHER POSITION TO PERMIT SUCH PIVOTAL FOLDING MOVEMENT, AND MANUALLY OPERABLE MEANS FOR RETAINING SAID HINGE AXIS AT ANY ONE OF A PLURALITY OF ANGLES TO WHICH IT MAY HAVE BEEN ADJUSTED RELATIVELY TO SAID INBOARD MEMBER AND RELATIVELY TO SAID RADIAL PLANE, SAID RETAINING MEANS BEING OPERABLE INDEPENDENTLY OF THAT OF ANOTHER BLADE SO THAT FOLDING OF THE OUTBOARD LIFTING STRUCTURE MAY BE EFFECTED AT A SELECTED ONE OF A PLURALITY OF LEVELS AND IN PARALLEL SUPERPOSED RELATIONSHIP WITH THE LIFTING STRUCTURE OF ANOTHER BLADE.