United Technologies Corporation

Sikorsky Aircraft Corporation

William L Noehren

Donald L Ferris

Edward S Hibyan

Francis E Byrnes

Peter C Ogle

Jules G Kish

Stephen V Poulin

Leonard J Doolin

Charles J Isabelle

Lee N Hager

Robert J Durwin

Ralph D Costanzo

Hugh L Kearney

Edward A Beno

A coil spring (50) for use in an overrunning spring clutch assembly having a central arbor (16) for centering and supporting the coil spring (50) in an overrunning operating mode. The coil spring (50) includes teaser coils (52) disposed at each end thereof, central coils (54) disposed intermediate the teaser coils (52), and transition coils (56) disposed between and adjoining the teaser coils (52) and the central coils (54). The coil spring (50) is characterized by each of the transition coils (56) having an interface surface (56.sub.IS) being substantially complementary to a corresponding external bearing surface (16.sub.ES) defined by the central arbor (16) of the spring clutch assembly. Such substantially complementary relationship limits the radial deflection of the transition coils (56) in the overrunning operating mode, thereby reducing vibratory bending stresses in the coil spring (50).

Coil spring for overrunning spring clutches

A mid-beam jointed reconfigurable bearingless main rotor (BMR) assembly that includes reconfiguration joints that facilitate BMR assembly reconfiguration by main rotor blade removal or folding to reduce the structural envelope of a helicopter for rapid deployment, routine transport, and/or storage. The BMR assembly comprises a rotor hub structure that includes a plurality of radially extending flexbeams, combinations of torsion flexure members and main rotor blades disposed in combination with corresponding flexbeams, and torque tube subassemblies disposed in combination with corresponding flexbeams and torsion flexure member, main rotor blade combinations. Each reconfiguration joint is formed by a combination of an outboard joint segment of a flexbeam and an inboard joint segment of the corresponding torsion flexure member. The rotor hub structure is fabricated so that the configuration joints are purposefully located at radial stations that are subjected to minimal flapwise loading, which for aerodynamic efficiency and manufacturing considerations should not exceed about fifteen percent of the overall span of the BMR assembly. The torque tube subassemblies are fabricated to provide access to the respective reconfiguration joints. For reconfiguration by the removal technique, each torque tube subassembly includes one or more access panels. For reconfiguration by the folding technique, each torque tube subassembly includes a removable splice tube.

Mid-beam jointed reconfigurable bearingless main rotor assembly

A retractable helicopter rotor in which the rotor and its blades, the swashplate and the pitch change rods are retracted and extended as a unit during the helicopter rotor retraction/extension mode of operation, wherein the connection between the rotor support system and the fuselage constitutes a single interface between overlapping circumferentially extending flanges of each, and with the bolts joining those flanges being loaded in compression.

Retractable helicopter rotor

An articulated helicopter rotor wherein the blade-to-hub connection consists of a spherical elastomeric bearing connected to the hub and a composite yoke connected thereto in series and consisting of a plurality of unidirectional high strength fibers bonded together to form a continuous strap which passes through a central opening in the elastomeric bearing and is pin-wrap connected to the hub at a single station and to the blade at two spaced stations produces a construction which is light in weight, easy to manufacture, ballistrically tolerant, redundant, and readily visually inspectable for structural integrity.

Articulated helicopter rotor within an improved blade-to-hub connection

An external composite wrap (34) of composite fibers (36) is added to the flap flexure portion (14) of a flexbeam (10), which is composed of predominantly unidirectional fibers (32) extending along the length of the flexbeam in (vertically) stacked layers (31). The fibers of the external wrap are disposed at an angle to the unidirectional ply fibers. The external wrap serves to reduce the interlaminar shear stresses in the unidirectional plies and increase the torsional stiffness of the flap flexure portion without significantly increasing the flexural stiffness of the flexbeam. The latter is accomplished by tailoring the thickness of the external wrap relative to flexbeam station (longitudinal position) and optimizing the angle of the external wrap fibers.

External wrap of composite flexbeam

The lag-torsion flexure portion (16) of a flexbeam (10) having segregated lag-torsion flexure portions (16) and flap flexure portions has multiple longitudinal lobes (98A-98G, 100A-100G) formed by multiple grooves (90A-90F, 92A-92F) extending from the upper (94) and lower (96) surfaces of the lag-torsion flexure portion to a central planar portion (102) thereof. The bases of the grooves are radiused (r) for favorable stress distribution while allowing for torsional and lead/lag softness in the lag-torsion flexure portion. The preferred number of grooves is an even number, such as six, resulting in an odd number of lobes. The lobes may decrease in height from the central lobe to the edgemost lobes (FIG. 12A). The lobes may be radiused at the upper and lower surfaces of the lag-torsion flexure portions (FIG. 12B). The lobes may be formed of alternate layers of unidirectional longitudinal fiber (32) extending the length of the flexbeam and elastomeric material (112) (FIG. 12D). Furthermore, the central planar portion (102) of the lag-torsion flexure portion may include layers (110) of fibers laid up at an angle to the unidirectional longitudinal fibers (FIG. 12C).

Lobed composite flexbeam

A nearly spherical laminated elastomeric bearing has a non-circular latitudinal cross-section to accommodate high torque loads in elastomer bending rather than in shear. The nearly spherical profile of the bearing accommodates tilt primarily in shear. Both inwardly and outwardly extending lobes, or splines, are disclosed. The nearly spherical, lobed bearing is useful for a constant velocity joint.

Elastomeric high torque, constant velocity joint

A cross-beam helicopter rotor in which the torque tube enveloping the flexible spar is supported in relation thereto by an elastomeric primary snubber which is readily replaceable in the field and which utilizes a snubber retainer plate bonded to the spar with an elastomer layer of selected shape factor so that the retainer plate remains adhered to the spar while accommodating all blade and spar pitch and flapping motions and so that the retainer plate elastomer layer is substantially more durable than the elastomer layers of the primary snubber. This primary snubber may be used in combination with an auxiliary snubber.

Cross-beam helicopter rotor with readily replaceable snubber

A helicopter rotor having at least one blade projecting from the central hub and mounted for pitch change, flapping and lead-lag motion and including a lead-lag damper mounted to be pivotally movable in a selected plane and connected to the blade through a pivotal link connection to avoid the adverse effects of pitch and flap coupling.

Helicopter rotor having lead-lag damper operable with pitch and flap

A helicopter cross beam rotor is shown including upper and low coaxial composite blade spars at right angles secured by tension bolts which pass through the composite spars and are held by threaded nuts to a rotor hub at the upper end of a rotor drive shaft. A metal cap plate above the upper spar and a spar-to-spar filler piece are also provided. Torque between the spars and the rotor hub is reacted by intermeshing ribs and grooves on the confronting faces of the hub, the filler piece and the cap plate. The bolt holes in the composite spars are oversize so that the bolts do not react torque between the rotor hub and the composite spars.

Torque reacting means for the hubs of cross beam rotors

A cross-beam helicopter rotor wherein the pitch actuator shaft passes through an elliptically shaped hole in the unidirectional, composite helicopter spar, each of selected dimension so that the stress concentration factor across the spar at the hole is minimized when the spar is carrying balanced centrifugal blade loads. The shaft also passes through a centering pin which is supported in the spar hole by an elliptically shaped plug of selected dimension so that when supported from the spar hole by elastomer of selected shape factor, durometer and dimension, the plug and pin are load isolated from the spar and the stress concentration factor across the spar at the hole is substantially unchanged from that of the unplugged hole both during balanced and unbalanced centrifugal blade load operation of the spar, and so that the elastomer transmits unbalanced centrifugal blade loads therethrough from the spar to the plug and pin for centering the rotor.

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Trumbull, CT, United States of America

William L Noehren