Apparatus for folding blades without changing pitch due to folding
United States Patent Ferris 1 1 Apr. 1, 1975 [54] APPARATUS FOR FOLDING BLADES 2,653,576 11/1953 Mosinskis 416/143 WITHOUT CHANGING PITCH DUE TO 3,428,132 2/1969 Vacca 416/143 3,484,175 12/1969 Vacca 416/143 FOLDING [75] Inventor: Donald L. Ferris, Newton, Conn.  
 [73] Assignee: United Aircraft Corporation, East Hartford. Conn.  
 [22] Filed: Nov. 1, 1973 [2]] App]. No.1 411,863  
 152] US. Cl. 416/143 [51] Int. CL... 1164c 11/06, B64c 11/28, B64c 27/50 [58] Field of Search 416/142, 143; 244/6, 7 A  
 156] References Cited UNITED STATES PATENTS 2.430.767 11/1947 Hirsch 416/147 Primary E.\&#39;amtnerEverette A. Powell, Jr. Assistant Examiner-Louis J. Casaregola Attorney, Agent, or Firm-Maurice B. Tasker [57] ABSTRACT A helicopter rotor has a blade mounted for folding movement. The blade is also mounted for feathering movement about its longitudinal axis and has a blade horn connected to a swashplate by linkage mechanism which provides a zero alpha pitch coupling during blade folding.  
 8 Claims, 8 Drawing Figures PATENTED 3.874. 817  
 SHCEI10F3 TJATENIEBAPR 1191a SHEET 3 OF 3 FIG-5 FIG-3 FIC3-8 APPARATUS FOR FOLDING BLADES WITHOUT CHANGING PITCH DUE TO FOLDING BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to helicopter rotors and particularly to rotors which are used in connection with convertiplanes in which the helicopter rotor blades are folded in flight. More particularly the present invention relates to a novel linkage mechanism between the suashplate and the horns of the rotor blades which permits folding of the blades without disconnection of the linkage or other operating mechanism. Further the present invention permits blade folding without change of blade pitch. i.e. zero alpha pitch coupling or. if pitch coupling is desired. without change of the predetermined pitch coupling.  
 2. Description of the Prior Art US. Pat. No. 3.484.l75. issued Dec. I6, I96) to L.  
 Vacca et al. shows blade folding about a vertical hinge in in a rigid motor. By putting the mechanism of this invention in place of rod I80 ofthis patent. blade fold ing in a rigid rotor could be provided with zero pitch coupling.  
 US. Pat. No. 3.515.500 issued June 2. I970 to J. H.  
 Nachod. shows a blade folding rotor in which the blades are foldable about the blade flapping axis after the pitch changing servos have been disconnected to make the normal pitch changing mechanism ineffective. By substituting the mechanism of the present invention in rod I40 of each blade the disconnection of the servos could be avoided.  
  US. Pat. No. 3.42%.l32. issued to Luigi Vacca et al on Feb. l8. I969. shows a typical example ofa helicopter having an articulated rotor including a lag-lead hinge inherently providing a degree of alpha coupling during flight operations. Applicant&#39;s novel mechanism can be inserted in link 80 of Vacca between the swashplate and the blade horn and the blade can then lead or lag in normal flight with zero alpha coupling. In modified form. adjustable alpha coupling can be provided.  
  The patent to H. Hirsch U.S. Pat. No. 2.430.767. issued Nov. ll. I947. shows a fully articulated blade structure in which the motion transmitting linkage for changing blade pitch includes a universal joint located at the lag-lead hinge about which blade fold can presumably occur. Also the patent to Mosinskis. U.S. Pat. No. 2.658.576. issued Nov. 10, I953. shows another helicopter pitch control system wherein links 36 and 48 in the pitch control linkage are aligned generally along the blade fold axis and by means of bearing assembly 46 permit blade folding without change of blade pitch. The present invention provides a new and improved structure for permitting blade folding without change of blade pitch which is particularly advantageous in convertiplanes wherein blade folding takes place in flight.  
 SUMMARY OF THE INVENTION The present invention is directed to a helicopter rotor having an improved. extremely simple and reliable mechanism in the linkage connecting the rotatable swashplate member and each blade horn by which the blades can be folded either manually or automatically without the need for disconnecting anything connected with the blades or their operating mechanism and wherein the blades are folded without change of pitch. i.e. zero alpha pitch coupling BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of the helicopter rotor embodying the improved linkage mechanism ofthc present invention&#39;.  
  FIG. 2 is a sectional elevation on an enlarged scale of part of the rotor of FIG. 1;  
  FIG. 3 is a simplified. somewhat diagrammatic plan view of the linkage mechanism in the flight position of the blade. the blade horn being omitted in this view;  
 FIG. 4 is an elevation of FIG. 3;  
  FIG. 5 is a plan view similar to FIG. 3 showing the linkage mechanism in blade folded position;  
  FIG. 6 is an elevation similar to FIG. 4 showing the parts in blade folded position;  
  FIG. 7 is a section on line 77 of FIG. 3 showing the scissors carried by the blade spindle for rotating the blade connected part of the linkage; and  
  FIG. 8 is a view taken on line 8-8 of FIG. 7 showing a modified construction for changing blade pitch coupling characteristics.  
 DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIGS. I and 2. I0 indicates a hellcopter lift rotor supported from the helicoptor fuselage (not shown) by a hollow drive shaft I2 which is rotatable about axis 14 and has at its upper end the hub assembly I6 from which four blades 18. 20. 22. and 24 project for rotation therewith. Two of the blades I8 and 22 are mounted on the hub assembly on generally vertical fixed hinge pins 26 in bearings 28 so as to be folded thru an angle of 90 in flight with respect to hub assembly [6 between an extended or operable position and a folded or inoperative position in which they are stopped and stowed within or alongside the fuselage. Prior to folding of blades 18 and 22. the other blades 20 and 24 will be indexed to a fore and aft position. In an alternative rotor system all four blades may be folded. In such case the blades would each be folded thru an angle of 45.  
  Hinge pins 26 are fixed in the hub by locking members 27 best shown in FIGS. 1 and 4. The blades may be folded manually on the ground or they may be folded in flight. Mechanism for such in-flight folding of all four blades of the helicoptor is fully illustrated and described in U.S. Pat. No. 3.484.175. heretofore referred to. and reference is made to this patent for a disclosure of this folding mechanism.  
  Each blade consists of a spindle 30. on which the blade cuff32 is mounted on stack bearings 34 for feathering movement of the blade about the longitudinal axis 36 of the blade. In order to allow blades 18 and 22 to fold relative to the hub assembly 16. the blade spindles 30 for these blades are pivoted about fold pin 26. It will be noted that in this rotor there is a slight amount of built-in coning of the blades shown as the slight upward inclination ofthe axis 36. Other than the feathering movement of the blade about spindle 32. the mounting of the blades on the hub is rigid. The cuff of each blade is provided with the usual born 38 (FIG. I outstanding from the blade cuff 32 which is connected by linkage to the rotating part of the swashplatc assembly. The linkage of blade I8 and 22 is novel and will be fully described hereinafter.  
  The swashplate assembly is mounted on the rotor drive shaft 12 for sliding movement axially of the shaft to change the pitch of all of the blades collectively and also for tilting movement for changing the pitch of the blades cyclically. To this end a collar is slidably mounted on a sleeve 42 fixed on shaft 12. Collar 40 has a convex outer surface 44 on which a bearing 46 having a similarly concave inner surface can rock. The hub 48 of the swashplatc has inner flanges 50, 52 which form a recess to receive bearing 46. The upper flange 50 on hub 48 consists of an annular washer-like plate which is detachably secured to hub 48 by cap screws (not shown) to permit assembly.  
  Outboard of its hub 48 the swashplate is provided with a boss 52a which houses a spherical bearing 54 through which the vertical stem 56 ofa rotating scissors 58 extends. The upper end of stem 56 has an eye 57 through which extends a pivot pin 60 mounted in the bifurcated end of a bracket 62 secured to the rotary hub assembly by cap screws 64. Thus hub 48 and the swashplate structure thus far described comprises the rotatable portion of the swashplate. Farther outboard of hub 48 the rotatable portion of the swashplate has four peripherally spaced lugs 66 to which upwardly ex tending rods are pivoted on pins 69, one for each blade. The upwardly extended rods to non-foldahle blades 20 and 24 are connected directly to the horn 38, while the rods 68 which extend to the foldablc blades 18 and 22 are connected to their horns 38 by means of my novel linkage. Further discussion of control linkage will be limited to that leading to the foldablc blades [8 and 22.  
  The non-rotating portion 70 of the swashplate is mounted on the periphery of the rotatable portion on bearings 72 and carries three lugs 74, 75, and 76, peripherally spaced 90 degrees apart from each other. to which the three servomotors (not shown) are attached for tilting the swashplate in a usual manner. A lug 78 (FIGS. l and 2) is provided on the periphery of the non-rotatable portion 70 of the swashplate to which one end of a scissors 80 is attached by means of a spherical bearing. the other end of the scissors (not shown) being pivotally attached to a fixed part of the airframe of the helicopter.  
  The present invention is principally concerned with the linkage mechanism between the rotatable portion ofthe swashplatc and the blade horns 38 ofthe foldablc blades.  
  Herein. as shown most clearly in FIG. 2. the fold pin 26 for each blade I8 and 22 has a depending. axial extension 82 which has an integral flange 84 that is secured to the lower end of the pin by cap screws 86. A first pivot arm 88 is pivoted on extension 82 on a horizontal pin 90 in such manner as to permit arm 88 to move freely about its pivot. To this end arm 88 is formed with a chamber 92 to receive extension 82 and the walls of the chamber are cut away at 93 to permit a wide angular movement of arm 88. At its free end arm 88 is pivotally connected by a pin 89 to the end of rod 68. the lower end of which is pivotally connected to lug 66 of the swashplate by pin 69. Herein pivot 90 for arm 88 lies on the axis of fold pin 26.  
  The hub of first pivot arm 88 has an integral depending axial extension 96 which carries a bearing sleeve 98 and forms the journal for the hub of a second pivot arm 100. An annular plate I02 secured to the end ofcxtension 96 by cap screws I04 holds pivot arm [00 in posi tion to swing about the axis of the hub of first pivot arm 88. Pivot arm 100 has an offset end 106 (FIG. 6) to which a rod [08 is connected by pivot pin 110. The other end of rod I08 is connected to blade born 38 by a pivot pin 112. A scissors 116 is pivotally connected at 118 to the blade spindle 30 and has a depending stem [19 which passes through a spherical bearing 120 in second pivot arm 10f causing the latter to pivot about extension 96 as the blade pivots about fold pin 26 dur&#39; ing blade folding.  
  From FIGS. 3 to 6 it will be noted that second pivot arm 100 lies below first pivot arm 88 and in the ex tended position of the blade shown in FlG. 3 is angularly related to it. By reason of its offset. upturned end 106. the free end of second pivot arm 100 lies alongside that of first pivot arm 88. Thus in the extended position of the blade, pivot pins 89 and H0 of the first and second pivot arms are aligned. Any vertical movement of rod 68 by the swashplate results in a like vertical movement of rod 108, since arms 88 and 100 move together without relative movement one to the other. Folding of the blade. however. results in swinging the second pivot arm [00 about its bearing 98 on first pivot arm 88. The latter does not move about its pivot 90 and consequently there is no change in blade pitch as a result of folding.  
 OPERATION ln diagrammatic views 3-6 the operation of the improved linkage mechanism this far described has been shown fora single blade. In the extended position of the blade (FlGS. 3 and 4) tilting of the swashplatc results in cyclic change in blade pitch during which rod 68 is raised and lowered to swing first pivot arm 88 about its horizontal pivot 90. Since second pivot arm 100 is carried by the hub of pivot arm 88 for movement relative to the latter only about a generally vertical axis. pivot arm 100 will move with arm 88 as a unit to raise and lower rod 108 connected to the blade horn. This joint movement of arms 88 and 100 will result in increasing and decreasing the pitch of the blade.  
  Preliminary to folding the blades 18 and 22, the rotor is stopped and the blades are indexed to bring blade 20 or 24 over the tail cone of the fuselage. All blades are then placed in neutral pitch. which is the position ofthe parts shown in FIG. 4. With the above steps accomplished, folding of the blades 18 and 22 to the HO. 5 position will result in swinging arm 100, by scissors I [6, without change in blade pitch since arm 100 moves about bearing 96 which is on the axis of fold pin 26.  
  In FIG. 8 a modified form of the invention is shown which provides normal helicopter operation. without folding, with capability to vary the blade pitch to lead/- lag coupling by adjustment made on the ground. To accomplish this it is necessary only to provide a pin 122 in the hub of second pivot arm 100 which. upon angular adjustment of arm [00 on its bearing 98 can be projected into one of several registering holes 124 in axial extension 96 and bearing 98 of pivot arm 88 to lock pivot arm [00 in its new position of angular adjustment relative to arm 88. Preferably. as shown in FIG. 8, the pin should be extended through the entire hub of arm 100. It will be understood that the FIG. 8 modification is the same as that shown in FIG. 2 with the addition of the selectively positioned locking pin. With the HO. 8 modification the scissors [[6 can be omitted ifdcsired.  
 and additional clearance may be required between the ends of arms 88 and 100.  
  It will be evident that by this invention it has been made possible by a very simple and reliable mechanism to select any desired blade coupling by on-the-ground adjustment from zero alpha up in a pitch increasing or decreasing direction. or. if blade folding is desired. to fold blades without interfering with blade pitch control. all without any disconnection of linkage or other control mechanism.  
  While only two embodiments of the invention have been shown and described herein. I do not wish to be limited to the particular detailed construction shown. as various modifications will be evident to one skilled in this art which fall within the scope of the following claims.  
 I claim:  
  1. In a helicopter rotor. a drive shaft. a hub on said shaft including a fold pin fixed in said hub having a depending axial extension. a blade mounted on said pin for folding movement. said blade having a horn. a swashplate on said shaft having a portion rotatable with said shaft. a first pivot arm pivotally mounted on the extension of said pin for pivotal movement about a horizontal axis. a first link pivotally connecting said first ivot arm to the rotatable portion of said swashplate. a second pivot arm journalled on said first pivot arm for pivotal movement about an axis coincident with the axis of said pin. and a second link pivotally connecting said second pivot arm to said blade horn.  
  2. In a helicopter rotor. a drive shaft. a huh on said shaft including a fold pin fixed in said hub having a depending axial extension. a blade mounted on said pin for folding movement. said blade having a horn. a swashplate on said shaft having a portion rotatable with said shaft. a lirst pivot arm pivitally mounted on the extension of said pin for pivotal movement about a horizontal axis. said first pivot arm having a depending extension. at first link pivotally connecting said first pivot arm to the rotatable portion of said swashplate. a second pivot arm journalled on said depending extension of said first pivot arm. the axis of said journal normally coinciding with the axis of said pin. and a second link pivotally connecting said second pivot arm to said blade born.  
  3. In a helicopter rotor. a drive shaft. a hub on said shaft including a fold pin fixed in said tub having a depending axial extension. a blade mounted on said pin for folding movement. said blade having a horn. a swashplate on said shaft having a portion rotatable with said shaft. a first pivot arm pivotally mounted on the extension of said pin for pivotal movement about a horizontal axis. a first link pivotally connecting said first pivot arm to the rotatable portion of said swashplate. a second pivot arm journalled on said first pivot arm for pivotal movement about an axis coincident with the axis of said pin. a second link pivotally connecting said second pivot arm to said blade horn, said second pivot arm being journalled below and angularly related to said first pivot arm in the flight position of the blade. and said second pivot arm having its free end offset horizontally and upwardly extended to bring the corresponding pivots for said first and second links into alignment.  
  4. In a helicopter rotor. a drive shaft. a hub on said shaft including a pin fixed in said hub. said pin having an axial depending extension. a blade spindle mounted on said pin for blade folding movement. a blade mounted for pitch changing movements about the longitudinal axis of said spindle. said blade having a horn. a swashplate on said shaft having a portion rotatable with said hub. a first pivot arm pivotally mounted on said fold pin extension for movement about a horizontal axis. a link connected at a point remote from the pivot of said first pivot arm for connecting the latter with the rotatable portion of said svvashplatc. a second pivot arm journalled on said first pivot arm for swinging movement with said blade about the axis of said fold pin extension, and a second link connecting said second pivot arm at a point remote from its journal to said blade horn.  
  5. The combination of claim 4 in which the horizontal pivotal axis of said first pivot arm intersects the axis of said fold pin.  
  6. The combination of claim 5 in which the points on said first and second pivot arms at which said first and second links are connected thereto are equidistant from the axis of said fold pin.  
 7. The combination ofclaim 5 in which a scissors carried at one of its ends by said blade spindle has its other end extended downward and operativcly connected with said second pivot arm for swinging the latter about said fold pin with said blade.  
  8. ln a helicopter. a generally vertical drive shaft. a hub on the upper end of said shaft including a fold pin fixed in said hub and having a depending extension. a blade spindle mounted on said pin for folding movement. a blade on said spindle having a blade horn for effecting feathering movement of said blade about the longitudinal axis of said spindle. a swashplate on said shaft having a fixed portion and a rotatable portion. a first pivot arm mounted on a horizontal pivot which intersects the axis of said fold pin. a link connecting the free end of said first pivot arm with the movable portion of said swashplate. a second pivot arm journalled on a depending extension of said first pivot arm which lies in the axis of said pin. a link pivotally connecting the free end of said second pivot arm with said blade horn. said second pivot arm being normally angularly positioned relative to said first pivot arm and beneath the latter and having its free end horizontally offset and upwardly directed to bring the corresponding pivots for said first and second links into alignment in the normal flight position of the blade. said second pivot arm having a spherical bearing located at a point spaced from the axis of said hinge pin. and means for swinging said second pivot arm in unison with said blade spindle upon folding movement of said blade comprising a scissors pivotally supported at its upper end on said blade spindle and having its other end depending and extended through said spherical bearing on said second pivot arm.