US3720387A

US3720387A - Rotary wing system

Info

Publication number: US3720387A
Application number: US00067701A
Authority: US
Inventors: R Foote
Original assignee: VIKING AIRCRAFT CORP
Priority date: 1968-11-15
Filing date: 1970-08-28
Publication date: 1973-03-13
Anticipated expiration: 1990-03-13

Abstract

A rotary wing system for aircraft which comprises a rotatably mounted hub, and a plurality of blades each connected to the hub for rotation therewith by a respective ball joint to permit movement about three coordinate axes including the longitudinal axis of the blade. Blade pitch control means rotatable with the hub is connected to the blades to hold each blade in predetermined position with respect to its longitudinal axis as the blades are rotated. The blade pitch control means is longitudinally spaced from the hub and mounted for reciprocable movement in a plane parallel to the longitudinal axis of the hub. The blade pitch control means includes a linkage connected to each blade at a point spaced from the blade''s ball joint connection to the hub and spaced from the longitudinal axis of the blade.

Description

Wllitfid States 1 21 10111 1 Foote 1 51March 13, 1973 [54] ROTARY WING SYSTEM 2,830,669 4/1958 Klockner ..416/168 x v [75] Inventor: Robert Fame Lake Dallas Tex. 3,072,197 1 1963 Stahmer ..244 6 x [73] Assignee: Viking Aircraft Corporation, Irving, FOREIGN PATENTS OR APPLICATIONS T 42,792 8/1933 France ..244 17.25

22 Filed: Aug. 28, 1970 Primary ExaminerTrygve M. Bl1x [21] Appl. No.: 67,701 Assistant Examiner-Paul E. Sauberer Related U.S. Application Data Atmmey Ha"y G. shaplro [60] Division Of Ser. N0. 776,111, Nov. 15, 1968,1at. N0. ABSTRACT 3,556,674, which is a continuation-in-part of Ser. No. 578,695, Sept. 12, 1966, abandoned.

[52] U.S. Cl. ..244/17.25, 416/20, 416/168 [51] Int. Cl..; ..B64c 27/52 [58] Field of Search.....244/6, 7, 17.11, 17.19, 17.21,

References Cited UNITED STATES PATENTS A rotary wing system for aircraft which comprises a rotatably mounted hub, and a plurality of blades each connected to the hub for rotation therewith by a respective ball joint to permit movement about three coordinate axes including the longitudinal axis of the blade. Blade pitch control means rotatable with the hub is connected to the blades to hold each blade in predetermined position with respect to its longitudinal axis as the blades are rotated. The blade pitch control means is longitudinally spaced from the hub and mounted for reciprocable movement in a plane parallel to the longitudinal axis of the hub. The blade pitch 4/1933 Evans ..244/6 control means includes a linkage connected to each 2/1935 Rutherford et a1. ..244/l7.25 blade at a point spaced from the blades ball joint conll/1948 Dalton ..416/ nection to the hub and spaced from the longitudinal Alldl'CWS X axis of the blade 7/1951 Brzozowski ..416/20 8/1953 Doman ..416/168 X 13 Claims, 13 Drawing Figures il llii i i ll i 146 5 13a l,

92 I 24 96 97 93 a g fi 154 t D loa- ,14

e2 as 76 7a 72 #665 /3B' """liiii. 63 s5 PATENTEDMARI 31913 7,20 387 SHEET 10F 8 I IVENTOR ATTORNEY ROBERT E. FOOTE BY v PATENTEDHAR 1 31975 SHEET 2 UF 8 INVENTOR ROBERT E. FOOTE FIG. 6

ATTORNEY PATENTEBHAR] 3|973 SHEET 3 0F 8 BNVENTOR RDBERT E. FOOTE W? 4% I 1 TTORNEY FIG. 5

' PATENTEDHARICHBYS 3,720,387,

SHEET u 0F 8 FIG. IO

INVENTOR. ROBERT E. FOOTE RNEY PATENTEUMAR] 3197s SHEET 5 BF 8 SHEET 8 UP 8 PATENTEUHARI 3M5 TOR.

ATTOR NEY PATEHTEDHARI 3197a SHEET 7 0F 8 FIG. H

' INVENTOR.

ROBERT E. FOOTE BY ORNEY PATENTEDHAR 1 3191s SHEET 8 OF 8 max dokom uO4Jm EOPOK or Duxi ..U.. #2.?

awn-a HDLIGQ ma. moron or swim 3. 5.8

hu h 2410 Iutnv Snw dvu INVENTOR. BERT E. FOOTE ATTORNEY ROTARY WING SYSTEM This application is a division of my pending application Ser. No. 776,111 filed Nov. 15, 1968, now U.S. Pat. No. 3,556,674, issued on Jan. 19, 1971, which is a continuation-in-part of my application Ser. No. 578,695 filed Sept. 12, 1966, now abandoned.

This invention relates generally to rotary wing aircraft, and more particularly, but not by way of limitation, relates to an improved autogyro having an im proved rotor system.

Even though rotary wing aircraft offer many performance advantages over fixed wing aircraft, particularly in the lower speed ranges, they have not achieved wide spread use. This is at least partially due to limitations in speed, but is due primarily to the relatively high initial cost and relatively high expense of operating and maintaining the aircraft. Both the high initial cost and the high operating expense are to a large extent due to the complexity of the rotor system necessitated by the high loads placed on the rotor blades during operation.

In both powered and autorotating systems, the rotors are hinged about a horizontal axis so as to pivot through a vertical arc. The combination of centrifugal force and'vertical load on the rotating blades causes the bladesto assume an angle with the plane of the hub when the aircraft has no translational velocity. This angle is known as the coning angle. As the aircraft assumes a translational velocity, the air speed over the progressing blade increases, and thus the lift increases, while the air speed over the retreating blade decreases with a consequent decrease in lift. As a result, the angle of the progressing blade to the plane of the hub increase and the angle of the retreating blade decreases until the lift contributed by each of the blades is equal. This angle is known as the flap angle. As the flap angle increases, the length of the path the blade follows increases. Therefore, the blade must first accelerate and then decelerate in order to traverse the longer path. In order to reduce the bending moments on the blades resulting from the flap angle, the blade is also pivotally connected to the hub by a vertical axle which permits the blade to pivot through generally horizontal arc. Pitch control is usually maintained through a suitable means for applying torque through the two pivot axles. As the translational speed of the aircraft increases, the flap angle also increases, thus increasing acceleration and deceleration of the blade.'As a result of the forces on the rotor system and the multitude of bearings required to reduce the loads on the blades, the rotor systems presently in use are relatively complex and require a great deal of expensive maintenance, yet still have a relatively short useful life.

An object of this invention is to provide an improved autogyro.

Another object of this invention is to provide a simplified rotary wing system having a long and troublefree life. I

Another important object of the invention is to provide a rotor system wherein the loads on the blades, other than axial loads due to centrifugal force and vertical loads due to lift, are essentially eliminated. This permits the use of a simpler blade and results in longer blade life.

Another important object of the invention is to provide such a rotor system having means for automatically changing the pitch of the progressing blade so as to keep the flap angle at a minimum, thus reducing the complexity of the hinge structure supporting the blade and materially increasing the life span of the supporting hinge structure.

Another important object of the invention is to provide such a system having a minimum number of pitch control linkages.

Still another object of the invention is to provide such a rotor system for an autogyro.

Another object of the invention is to provide a rotor system having increased efficiency at higher translational velocities.

Still another object is to provide such a system wherein the flap angle does not materially increase with an increase in translational velocity.

These, and other objects are accomplished in accordance with the present invention by mounting a plurality of blades in a rotating hub for rotation therewith, with each blade connected to the hub by means of a respective ball joint hinge permitting movement about three coordinate axis including the longitudinal axis of each blade. The pitch of the blades is controlled by linkage means which rotates with the blades and hub. The linkage means is connected to each of the blades at retention points spaced from the axis about which the blade pivots through the vertical arc and spaced from the longitudinal axis of rotation of the blade so that as the flap angle of each blade increases, the pitch angle of the blade decreases. The linkage means is movable I axially of the axis of rotation of the hub in order to provide collective pitch control. For autorotating applications, no cyclic pitch control is required. For autorotation applications, the axis of rotation of the hub and pitch control linkage means may be changed simultaneously relative to the thrust axis of the aircraft for lateral control and pitch trim control. Cyclic pitch control can be provided for powered rotation applications by changing the angle between the plane of rotation of the linkage means and the plane of rotation of the hub.

In accordance with another aspect of the invention, the rotor system is mounted on an aircraft having conventional lifting wings, pitch and yaw control surfaces, and thrust producing means by a universal joint, preferably a ball joint, disposed between the hub and the center of gravity of the aircraft. Control means is then provided for changing the position of the center of gravity of the aircraft with respect to the plane of rotation of the hub for lateral and pitch trim control of the aircraft. The rotor system also provides a means for prerotating the rotor system to provide jump takeoffs.

The novel features believed characteristic of this invention are set forth in the appended claims. The invention itself, however, as well as other objects and advantages thereof, may best be understood by reference to the following detail description of several illustrative embodiments, when read in conjunction with the accompanying drawings, wherein:

FIG. 1 is a side view of an aircraft constructed in accordance with the present invention;

FIG. 2 is a front view of the aircraft illustrated in FIG. 1;

FIG. 3 is a plan view of the aircraft illustrated in FIG. 1;

FIG. 4 is a plan view of a rotor assembly constructed in accordance with the present invention;

FIG. 5 is a sectional view taken substantially on lines 5-5 of of 4;

FIG. 6 is a view partly in cross-section taken approximately in the plane f line 6-6 of FIG. 4;

FIGS. 7 through 12 illustrate another form of the invention, FIG. 7 being a top plane view thereof;

FIG. 8 is a vertical cross-section taken approximately in the plane of line 88 of FIG. 7;

FIG. 9 is a vertical cross-section taken approximately in the plane of line 99 of FIG. 7;

FIG. 10 is a view partly in cross-section taken approximately in the plane of line l010 of FIG. 7;

FIG. 1 1 is a bottom plan view of the apparatus;

FIG. 12 is a view partly in cross-section taken approximately in the plane of line 1212 of FIG. 9; and

FIG. 13 is a schematic view illustrating the geometric relationship of the rotor hub, the blades and the pitch control means.

Referring now to the drawings, an autogyro constructed in accordance with one form of the present invention is indicated generally by the reference numeral 10 in FIGS. 1-3. The autogyro 10 has a fuselage 12 on which is mounted an engine 13 for driving a pusher propeller 14. A pair of

stub wings

16 and 18 extend from the fuselage 12. A pair of

tail booms

20 and 22 are connected to the ends of the

stub wings

16 and 18, respectively. A pair of

vertical fins

28 and 30 are mounted on the

booms

20 and 22 and support a pair of articulated

control surfaces

32 and 33, respectively, which provide yaw control. A horizontal stabilizer 24 extends between the

vertical fins

28 and 30, and includes an articulated control surface 26 for pitch control. A tubular mast 34 extends upwardly from the center of gravity of the plane and supports a rotor system indicated generally by the reference numeral 36 which is shown in detail in FIGS. 4 and 5. It will be noted that no ailerons are provided on the

stub wings

16 and 18. The control surfaces 26, 32 and 33 are activated by conventional means (not illustrated).

Referring now to FIGS. 4 and 5, a shaft, indicated generally by the reference numeral 38, is connected to the mast 34 by a universal joint, preferably a ball joint as illustrated and indicated generally by the reference numeral 60. The ball joint comprises a tubular member 40 which is received within a sleeve-type spherical bearing member 42. The bearing member 42 is secured on the tubular member 40 by

sleeves

44 and 46. The sleeve 44 is secured to the tubular member 40 by a plurality of set screws, one of which is illustrated at 48. The spherical bearing member 42 is received in a mating bearing ring 50 which is secured within the top of the tubular mast 34 by retaining

rings

52 and 54 and set

screws

56 and 58, respectively. Thus, within the limits permitted by the ball joint 60 comprised essentially of the spherical member 42 and ring member 50, the shaft 38 is freely movable with respect to the mast 34 and therefore with respect to the fuselage 12. The position of the shaft 38 is controlled by four arms 62-65, which are connected to the sleeve 46 at the four quadrants as best illustrated in FIG. 4. Control cables 66-69 are connected to the ends of the arms 62-65, respectively. As can best be seen in FIG. 5, it will be noted that the ends of the arms 62-65 are located in a common plane passing through the center of the ball joint 60.

Cables

66 and 68 are operated in push-pull arrangement to provide lateral control of the aircraft as will presently be described, and

cables

67 and 69 are similarly operated in push-pull manner to provide pitch trim as will presently be described.

A hub assembly, indicated generally by the reference numeral 70, is rotatably mounted on the upper end of the shaft 38. The hub assembly is comprised generally of a tubular body 72 and a pair of tapered

roller bearing assemblies

74 and 76. The inner race 78 of the lower bearing 76 is disposed around the tubular member 40 and between the upper end of sleeve 46 and the lower end of a sleeve 80 which is secured in place on shaft 40 by peripherally spaced screws 81. The outer race 82 of the lower bearing 76 is received within the body 72 and abuts against an annular shoulder 84 formed in the body. The lower bearing 76 transmits an upward thrust from the body 72 to the shaft 38 and thus must support the entire eight of the aircraft, less the weight of the rotor system, at speeds below the stalling speed of the

stub wings

16 and 18. The upper bearing 74 supports the weight of the rotor system when the rotor system is producing no lift. The outer race 86 of the upper bearing 74 is retained within the upper end of the hub body 72 by a keeper ring 88 which is secured to the hub body by bolts 90. The inner race 92 of the upper bearing 74 transmits a downwardly directed load on shaft 40 by a lead path extending through sealing washer 93, abuts against a sleeve 94 which is disposed around the sleeve 80, sealing washer 95, the inner race 78, sleeve 46, bearing member 42, and finally sleeve 44.

Rotor blades indicated generally by the

reference numerals

96, 97 and 98 are mounted on the hub 70 by ball joints indicated generally by the

reference numerals

99, 100 and 101, respectively. Each of the blades 96-98 is of the same construction and has a tubular spar 102 which extends the length of an airfoil 104 formed by fiber glass or other suitable material. Each of the ball joints 99, 100, 101 is comprised of a spherical member 106 which is positioned around the tubular spar 102 and retained in position by a nut 108 threaded onto the end of the spar. The spherical sleeve 106 is positioned within a bearing ring 110 which is retained within the body 72 against centrifugal force by an annular shoulder 112 formed around the opening 114 through which the spar 102 extends.

A suitable valving arrangement (not illustrated) is provided to selectively divert all or a substantial portion of the exhaust gases from the engine 13 through the tubular mast 34. The exhaust gas is passed through the mast 34, through tubular shaft 40, through passageways 122 which are formed by aligned apertures in the tubular member 40 and the sleeves 80 and 94, though the interior of the tubular spars 102, and finally is jetted out through jet nozzles at the tips of the blades to prerotate the rotor for takeoff as will hereafter be described in greater detail. The sealing

washers

93 and 95 slide on

shoulders

124 and 126, respectively, within the hub body 72 to seal the chamber between the interior of the shaft 38 and the tubular spars 102. The sealing

washers

93 and 95 also form grease seals for the

bearings

74 and 76. Bearing 74 is also sealed by a sealing washer 127, and the lower bearing 76 is sealed at the lower end by a sealing means 128. If desired, compressed air from a suitable source may be used in lieu of exhaust gases.

A pitch control means, indicated generally by the reference numeral 130, is comprised of a rod 132 which is reciprocally mounted within a bearing sleeve 134. The sleeve 134 abuts the upper end of the tubular member 40 and is secured within the top of the sleeve 80 by bolts 135. A pitch control member is rotatably journaled on the upper end of rod 132 and is comprised of a hub 144 to which the pitch control member is connected. The member extends radially of the longitudinal axis of the hub assembly. Preferably, the pitch control member comprises three

arms

146, 147 and 148 to provide a spider assembly. Each pitch control arm is formed by a pair of parallel plates shaped substantially as illustrated in FIG. 5. Means is provided for driving or rotating the pitch control member. For this purpose, a bolt 90 fixed to the rotatable hub 70 may be provided with an extension 145. The extension is passed between the parallel plates constituting a pitch control arm, such as the plates of the arm 147, as shown in FIGS. 4 and 5. The hub 144 is rotatably mounted on the rod 132 by upper and lower tapered bearing assemblies 150' and 152 which are retained between nuts.140 and 153 threaded onto rod 132. A coil spring 136 is disposed around rod 132 between a washer 138 and the upper end of the bearing sleeve 134 and normally biases rod 132 upwardly until a nut 142 on the lower end of the rod 132 abuts the lower end of the bearing sleeve 134.

Arms

154, 155 and 156 constituting the pitch horns extend forwardly from the leading edge of each of the

blades

96, 97 and 98, respectively, and are formed by a pair of plates substantially as illustrated in FIGS. 4, 5 and 6. The plates may extend rearwardly around the tubular spar 102 of each of the blades and be embedded in the plastic material 104 used to form the airfoil of the blade. Adjustable means or pitch

links

158, 159 and 160 are each connected at their upper endsto the

pitch control arms

146, 147 and 148 by a universal joint 151, and at their respective lower ends to the

pitch horn arms

154, 155 and 156 by a universal joint 151'. Preferably, and as shown in FIG. 6, ball joints are used.

As shown in FIG. 5, an eyelet 164 is formed at the lower end of rod 132 and a pitch control cable 166 connected tothe eyelet. The pitch control cable 166 extends downwardly through the tubular shaft 40 to a suitable manual control which may be maniuplated to pull the rod 132 downwardly against the force of the biasing spring 136 to selectively decrease the pitch of the blades 96 -98. The pitch control assembly is adjusted such that the blades 96-98 will be at maximum pitch when the rod 132 is biased to the full up position, i.e., when the nut 142 abuts the bottom of the bearing sleeve 134. When the pitch control cable 166 is pulled downwardly to its maximum extent, the blades 96-98 are placedat zero pitch.

ltis very important to note that the pitch horn arms 154156 are located on the blades 96-98 at a point spaced outwardly from the ball joints 99-101, respectively, and further that the ends of the pitch horn arms are connected to their respective pitch links 158-160 in advance of the longitudinal axis of each tubular spar 102, which is the axis of rotation of each blade within the respective ball joints 99-101. Thus, as the flap angle ofeach blade increases, i.e., as the blade pivots upwardly, the pitch links 158-160 hold the ends of the respective pitch horn arms 154-156 at the same position with respect to the hub 70, thus decreasing the pitch of the respective blade. Also, as each blade tends to lead or lag from a given radial position, the pitch links 158-160 are constrained by their described connection to the pitch control arms 146-148 which causes the lower ends of the pitch links to pivot about their upper ends. As a result, the pitch of the blades is changed automatically.

In the form of the invention as hereinbefore described, the pitch horn arms 154-156 are positioned outward and in advance of the ball joint connections 99-101 of the blades to the hub. It is within the scope of the invention to position the pitch horn arms inward and to the rear of the ball joint connections.

FIGS. 7 through 12 illustrate the invention with reference to cyclic pitch control in lieu of the previously described lateral and pitch trim controls. Also, the form of the invention shown in FIGS. 7 through 12 includes another means for imparting starting rotation to the blades; and further, another form of hub structure is shown. The elements which are common to the form of the invention shown in FIGS. 4, 5 and 6 have the same reference characters applied thereto.

Regarding the hub assembly, and as shown in FIG. 8, a hollow shaft 168 is bolted to the tubular mast 34. The universal joint connecting the shaft 168 to the mast 34 is positioned within the rotor hub 170 and secured in position on the shaft 168 as by a nut 172 threaded onto a mating threaded portion 174 on the shaft. The upper end of the shaft 168 is provided with means for retaining the joint between the shaft and the hub assembly. For this purpose, a flange 176 may be provided to engage the opposite end of the joint 60 which preferably is of the ball type.

The hub 170 pivotally connected to the shaft 168 by the ball joint 60 preferably is in four parts to facilitate assembly of the parts. As shown in FIGS. 8 and 9, a joint retainer member 178 is surrounded by a bearing sleeve 180. The sleeve has an internal shoulder 182 to retain the hub to the mating bearing member or ring 50 of the ball joint. The sleeve also has two longitudinally spaced

external shoulders

184 and 186 for retaining the

inner races

78 and 92 of the

respective bearings

76 and 74. The hub assembly is completed by a pair of hub halves or

members

188 and 190 secured to one another by a plurality of bolts 192 (FIGS. 7 and 8). The

hub members

188 and 190 surround and maintain the joint retainer member and bearing sleeve in position, and thereby the universal or ball joint connection of the hub assembly to the shaft is maintained in desired position. Also, the hub members are formed to provide seats for the

outer races

86 and 82, respectively, of the

bearings

74 and 76.

Also, and as shown in FIG. 8, the

hub members

188, 190 are formed to provide, when assembled, a plurality of radial openings 194 each adapted to receive and for seating of the ball joints 99, 100 and 101 for the

respective blades

96, 97 and 98. As shown, the hub members are formed internally to retain the outer race 110 of each ball joint. Externally, the hub members are formed in the areas surrounding each opening 194 with retaining means 196 cooperable with mating retaining means 198 formed in

clamp members

200 and 202. As shown in FIG. 7, the clamps are secured to one another and in place by a series of bolts 204.

As shown in FIGS. 8 and 9, sealing

rings

206 and 208 are positioned in recesses to provide a seal between the

hub members

188, 190 and the bearing sleeve 180. To facilitate suitable positioning of each blade with respect to the hub, a sleeve 210 of elastomeric material is provided about each blades tubular spar, FIG. 8 showing the sleeve surrounding a portion of the spar 102. The

clamps

200 and 202 are formed to furnish a seat for the outer periphery of the sleeve.

As shown in FIG. 7, the plurality of blades 96-98 are each mounted on their respective spars 102 as previously described. Also, the pitch horns 154-156 are connected to their respective blades and, as shown in FIGS. 7 and 10 with reference to pitch link 159, the pitch links 158-160 are respectively connected to the pitch horns at their upper ends by universal joints 151, preferably of the ball type. The lower ends of the pitch links are respectively connected to a rotatable pitch control member 212 of a swash plate assembly generally designated 214. The connections of the pitch links to the rotatable member 212 are by universal joints 151 preferably of the ball type.

As shown in FIGS. 8, 9 and 11, the swash plate assembly 214 includes a rotatable pitch control member 212 and a member 216 which is stationary in the sense that it is non-rotatable. The swash plate assembly is movable as a unit along the shaft 168 and may be angularly related with respect to the shaft about a ball joint. Preferably, the pitch control member 212 is formed to provide a number of

pitch control arms

213, 215 and 217 equal to the number of blades (FIG. 11). The pitch control member or the arms thereof extend radially of the hub assembly's longitudinal axis, or the axis provided by the shaft 168.

As shown in FIGS. 8 and 9, the pitch control member 212 is rotatably related to the stationary member 216 by a bearing 218 intermediate an extension 220 of the member 216 and the internal bore 222 of the pitch control member. The extension 220 is provided with an annular opening 221. A universal joint 224, preferably of the ball type, surrounds the shaft 168 and is confined for movement along the shaft by an outer spherical surface 226 provided at the inner diameter of the extensions opening 221.

The rotatable pitch control member 212 of the swash plate assembly is connected to and rotated by the hub assembly 170. As shown in FIG. 9, this function may be accomplished by a link assembly 228. The link assembly comprises a pair of

links

230 and 232 pivotally connected to each other at 234. The link 230 is pivotally connected at 236 to an apertured lug 238 provided by or secured to the lower hub member 190. The link 232 is pivotally connected at 240 to an eyebolt 242 which is secured to the rotatable member 212. The connection comprises a ball joint 244 having a ball 246 through which the eyebolt 242 is extended and secured. The ball is confined by race 248 mounted within an opening provided in the rotatable member 212.

The vertical position and the angular relationship of the swash plate assembly 214 along the length of and with respect to the shaft 168 is controlled by the pilot through the medium of a plurality of control rods 250 connected to a suitable number of arms provided by the non-rotatable member 216 (FIG. 11). As hereinbefore described, the hub assembly 170 is fixed against longitudinal movement with respect to the shaft 168; however, the hub assembly may be angularly related to the shaft by the universal or ball joint connection 60.

For powered rotation or for prerotating the rotor for takeoff, rotation may be imparted to the hub assembly 170 by a gear train drive. As shown in FIGS. 8 and 9, a shaft 252 is journaled in

bearings

254 and 256 supported in retainer 178. The shaft 252 is connected to suitable power driving means (not shown) as well known in the art. The upper end of the drive shaft 252 is fixed to a gear 258 which is part of a gear assembly 260. The assembly includes an idler gear 262 intermediate the gear 258 and gear means 264 or teeth provided on the internal diameter of an opening in the upper hub member 188. The idler gear is mounted in a bearing 266 on a stud 268, the stud being extended into the retainer 178. The gear assembly may be protected by a cover plate 270.

OPERATION In the operation of the aircraft 10 with the form of rotor system illustrated in FIGS. l-6, either a conventional takeoff or a jump takeoff can be employed. In either case, the rotor assembly can be prerotated by actuating the control cable 166 so as to move the pitch control means downwardly against the biasing force of the coil spring 136, thus moving blades 96-98 to zero pitch. Then the exhaust gas from the engine 13 or compressed air is diverted by a valving system through the mast 34, the tubular shaft 38, out through the three passageways 122, and through the tubular spars 102 to the jet nozzles 120 at the tips of the three blades. It will be appreciated that with the rotor blades at zero pitch, a very low thrust is required to accelerate the blades to a speed sufficient for takeoff. For a jump takeoff, the pitch control cable 166 is then suddenly released so that the blades will quickly change to maximum pitch. The inertia of the rotor system will then cause the aircraft to raise a short distance, at which time the propeller 14 will provide sufficient thrust to move the aircraft forward and establish autorotation of the rotor system.

After a translational velocity has been established, the progressing blade, blade 97 in FIG. 3 for example, has a relative wind velocity approximately equal to the rotational velocity of the blade plus the translational velocity of the aircraft. On the other hand, the retreating blade, blade 98 in FIG. 3 for example, has a relative wind velocity approximately equal to the rotational velocity of the blade less the translational velocity of the aircraft. As a result, the lift on the progressing blade 97 will be substantially greater than the lift on the retreating blade 98, if the same pitch angle, i.e., angle of attack, were maintained. Since the centrifugal forces acting on the blades are equal, blade 97 would tend to rise to a higher angle with respect to the plane of the hub, i.e., have a higher flap angle, so as to reduce the effective lift of the progressing blade to equal that of the retreating blade. However, in accordance with an important aspect of this invention, as the progressing blade 97 tends to rise, the pitch link 159 acting on the pitch horn arm decreases the pitch of the blade, thus decreasing the angle of attack so that the lift of the blade is reduced. In this manner, the flap angle is materially reduced, and in fact can be substantially eliminated. Since the flap angle is substantially reduced, the accelerating and decelerating forces on the blade 97, and hence the loads on the ball joint 100 connecting the blade to the hub are substantially reduced, thus reducing the load bearing requirements of the joint and increasing the useful life of the blades.

Lateral control is achieved by changing the angle of the shaft 38 with respect to the mast 34 so as to change the position of the center of gravity of the aircraft with respect to the plane of rotation of the hub. This is achieved by means of the

control cables

66 and 68.

Control cables

67 and 69 are used to change the angle of attack of the coning plane for trim purposes. As the forward speed of the aircraft increases, the stub wings l6 and 18 begin to produce lift in the conventional manner, thus decreasing the load on the rotor system. The blades of the rotor system may then be trimmed to a low pitch angle by operating control cable 166 in a manner to move rod 132 downwardly. This significantly decreases the drag produced by the rotor system, and thereby increases the high speed performance of the aircraft. As a result of the automatic control of the pitch angle of each blade, even high translational velocities do not produce significant flap angles.

In addition to automatically controlling the pitch of each blade so as to minimize the flap angle under high speed operation, the rotor system is also very economical to construct and has a very long service life. It will be noted that except for the ball joint 60, ball joints 99-101 and

bearings

74, 76, 150 and 152, the entire hub and control assembly requires no precision machine parts. The entire control of the rotor system is accomplished by five control cables. The rotor system also permits the use of high pressure gas or air to prerotate the rotor system by piping the gas through the mast 34, shaft 38, hub 70 and the spars 102 of the individual rotors to the jet nozzles. The entire rotor system can be removed from the aircraft for servicing merely by disconnecting the five control cables and removing the bolts 58 so that the shaft 38 can be separated from the mast 34. Assembly and disassembly of the rotor system then requires nothing more than conventional hand tools to loosen the various bolts. Because of the reduced loads placed upon the various bearing structures and the blades as a result of the automatic pitch control, the entire rotor assembly can be expected to have a long and trouble-free service life. Similar economies in construction and servicing, coupled with long and trouble-free service life, are afforded by the form of rotor system illustrated in FIGS. 7-12.

In both forms of the invention the rotary wing system comprises a hub assembly, the assembly 70 and the assembly l70,'mounted for rotation about its longitudinal axis. A, plurality of blades, the

blades

96, 97, 98 are each connected to the hub assembly by respective ball joints 99, 100, 101. To control the pitch of the blades, a

pitch control member or the arms thereof, the

arms

146, 147, 148 of the member 130 and the

arms

213, 215 and 217 of the member 212, extend radially from the aforesaid longitudinal axis. The pitch control member is rotated by the hub assembly through the medium of the connecting means 145 in the showing of FIGS. 4-6 and the linkage 228 in the showing of FIGS.

7-12.

Respective pitch links

158, 159 and 160 are provided for each of the blades. Each pitch link is connected to the pitch control member and each blade by respective universal joints, the

joints

151 and 151. The universal joint connection of each pitch link with its respective blade is at a point spaced from the longitudinal axis of the blade. To facilitate such spacing the blades are provided with the

pitch horns

154, 155 and 156 which extend from the blades in a plane perpendicular to the longitudinal axis of each blade.

In the form of the invention shown in FIGS. 7 through 12, the coaction of the parts of the rotor system and the advantages furnished thereby are essentially the same as hereinbefore described with regard to the form of the rotor system illustrated in FIGS. 4, 5 and 6 with relation to the craft as shown in FIGS. 1, 2 and 3. It will be apparent that the main difference in the two forms of the invention resides primarily in the means for providing pitch control. In the form of the invention shown, more particularly in FIGS. 4, 5 and 6, lateral control and pitch trim control are accomplished by the cable actuated

arms

64, 66 and

arms

63, 65. Also, collective blade pitch is controlled by the cable actuated pitch control means 130. In the system of FIGS. 7 through 12, cyclic and collective pitch control is accomplished by the swash plate assembly 214 actuated by by the rods 250.

It is believed that the interaction of the significant parts of each of the illustrated and described formsof rotor system may be better visualized by reference to FIG. 13 which illustrates the geometry of the relationship of the rotor hub, each of the blades and the pitch control means. To simplify the showingof FIG. 13, and to relate such showing to the forms of the invention as hereinbefore described, point A refers to each of the

balljoints

99, and 101 for each of the

blades

96, 97 and 98, respectively. Point B refers to the universal or ball joints connecting each of the upper ends of the pitch links 158, 159 and 160 to their respective pitch armsl46, 147 and 148 (FIGS. 4, 5 and 6), or to the universal or ball joints connecting the lower ends of

pitch links

158, 159 and 160 to the arms of the pitch control member 212 of the swash plate assembly 214 (FIGS. 7-12). Point C refers to the universal or ball joints connecting each of the pitch links 158, 159 and 160 to the blades pitch

horns

154, and 156, respectively, in both of the illustrated and described forms of the invention. The motion of each blade about point A as controlled by the geometry of its linkage to points B and C afi'ords automatic pitch change, coupled with blade flapping and/or lead and lag with but one ball joint at point A permitting all motions for each blade.

It will be apparent that the hub structure shown in FIGS. 7 through 12 may be used in the form of the invention illustrated in FIGS. 3-6. Also, the gear train drive may be used in lieu of the exhaust or gas or compressed air means as illustrated in FIGS. 1-6.

The pitch links 158-160 are rigid, although of adjustable length. If desired, the pitch links may take the form of dampeners in order to reduce any oscillation tendency of the system, although this will normally not be a problem due to the substantial elimination of the flap angle. The exhaust gases from a conventional reciprocating engine may be used to prerotate the blades for a jump takeoff as described, gases of combustion from a turbine used for forward propulsion may be used; compressed air from a suitable source may be used; or the described gear train drive may be used.

Although the rotary wing system of the invention has been illustrated with reference to three blades, it will be understood that any desired number of blades in excess of two may be used.

Iclaim:

1. In an aircraft, the combination of a fuselage, lifting wings, yaw control means, pitch control means, and forward propulsion means, a mast extending substantially from the center of gravity of the craft, a rotatable hub assembly, means including a shaft and a universal joint permitting tilting of the rotational axis of the hub assembly, the shaft being connected to the mast and the hub assembly being mounted for rotation about the shaft, a plurality of blades rotatable with the hub assembly, each blade being structurally connected to the hub assembly solely by means of a rigid spar extending between the blade and a ball joint connecting the spar to the hub assembly for movement relative thereto independent of the other spars, and collective blade pitch control means rotatable with the hub assembly, the blade pitch control means comprising a pitch control member spaced from the hub assembly and mounted for reciprocable movement towards and away from the hub assembly along the axis of said shaft, an arm extending from each blade, and a respective pitch link spaced from each blade and from the hub assembly, said pitch links each being connected to the pitch control member and to their respective arms by universal joints.

2. In an aircraft as set forth in claim 1, wherein the shaft is connected to the mast by a universal joint.

3. In an aircraft as set forth in claim 1, wherein the pitch control member is longitudinally spaced from the hub assembly and mounted for reciprocable movement along the axis of the hub assembly, and manually operable means for changing the position of the pitch control member along said axis.

4. In an aircraft as set forth in claim 3, wherein the pitch control member is rotatably mounted on a second shaft reciprocably related to the first-named shaft.

5. In an aircraft as set forth in claim 1, wherein at least one blade has a fluid jet nozzle directed rearwardly at a point outboard of a ball joint, a first fluid passageway extended from the jet nozzle through the ball joint into the interior of the hub assembly, and the hub assembly has a second fluid passageway extending therethrough in communication with the first fluid passageway, whereby upon the introduction of fluid under pressure in the second fluid passageway the fluid will emanate from the jet nozzle and rotate the hub assembly and blades.

6. In an aircraft as set forth in claim 1, wherein the hub assembly is connected to the shaft by a universal joint; wherein the pitch control member is connected to the shaft by a universal joint; and wherein a manually operable non-rotatable member is associated with the pitch control member for changing the position of the pitch control member along the length of and angularly with respect to the shaft.

7. In an aircraft as set forth in claim 1, wherein the shaft is a tubular member, a drive shaft positioned to extend within the shaft, and gear means intermediate the drive shaft and the hub assembly for rotating the hub assembly and blades.

8. In an aircraft as set forth in claim 1, wherein the hub assembly comprises a tubular body, the tubular body being mounted on the shaft, the shaft having a sleeve extending therefrom and fixed thereto, a pair of longitudinally spaced bearing assemblies positioned in said tubular body, the inner race of one bearing assembly being disposed around the shaft and the inner race of the outer bearing assembly being disposed around the sleeve, means for retaining said inner races against longitudinal movement, and means for retaining the outer races in the tubular body.

9. In an aircraft as set forth in claim 1, wherein the hub assembly is connected to the shaft by a ball joint, a joint retainer member in engagement with the mating bearing member for said ball joint, a bearing sleeve surrounds said mating bearing member and the joint retainer member, a pair of hub members are connected to each other and surround and maintain the joint retainer member and the bearing sleeve in position, a pair of spaced bearing assemblies are positioned between the bearing sleeve and the hub members, and the hub members are formed to provide a plurality of radial openings for seating the ball joints connecting the blades to the hub assembly.

10. In an aircraft as set forth in claim 9, wherein the pitch control member is positioned on the shaft below the hub assembly and mounted for reciprocable movement on the shaft, and manually operable means for changing the position of the pitch control member on the shaft.

11. In an aircraft as set forth in claim 2, including cable means connected to the shaft for moving the shaft relative to the mast for providing lateral control or the aircraft.

12. In an aircraft as set forth in claim 4, including spring means for biasing the second shaft to the high pitch position.

13. In an aircraft, the combination ofa fuselage, lifting wings, yaw control means, pitch control means, and forward propulsion means, a mast extending substantially from the center of gravity of the craft, a shaft connected to the mast, a hub assembly including a tubular body rotatably mounted on the shaft rotation about an axis, the shaft having a sleeve extending therefrom and fixed thereto, a pair of longitudinally spaced bearing assemblies positioned in said tubular body, the inner race of one bearing assembly being disposed around the shaft and the inner race of the other bearing assembly being disposed around the sleeve, means for retaining said inner races against longitudinal movement, means for retaining the outer races in the tubular body, a plurality of blades each connected to the hub assembly for rotation therewith by a respective ball joint, and blade pitch control means rotatable with the hub assembly, the blade pitch control means comprising a pitch control member extending radially from said axis and a pitch link connected to the pitch control member and to each blade by respective universal joints, the connection of each blade by respective universal joints, the connection of each pitch link to each blade being at a point spaced from the longitudinal axis of the blade.