Aeronautics and astronautics – Aircraft – heavier-than-air – Helicopter or auto-rotating wing sustained – i.e. – gyroplanes
Patent
1998-02-06
2000-10-31
Eldred, J. Woodrow
Aeronautics and astronautics
Aircraft, heavier-than-air
Helicopter or auto-rotating wing sustained, i.e., gyroplanes
384507, 384508, 384511, 384 49, 384226, B64C 2700, F16C 4306
Patent
active
06138948&
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a bearing, and to a method of disassembling such a bearing. The bearing is suitable for use with a variable pitch propeller blade.
It is known to preload bearings in a propeller blade root assembly so as to allow bearing assemblies to remain loaded under all aerodynamic conditions. The blade bearings allow the pitch of the blade to be changed in flight. However, they also serve to lock the blade within the propeller hub. The root assembly may have an enlarged end such that the root cannot be extracted from the propeller hub whilst the bearings are in position, necessitating the hub to split.
According to a first aspect of the present invention, there is provided a bearing arrangement comprising: a first member having a first bearing surface movable with respect to a second member having a second bearing surface such that a load on bearings positioned between the first and second surfaces can be substantially removed; and a third member having engaging means for engaging at least one of the bearings such that movement of the third member urges the bearings towards an access port where they can be removed.
It is thus possible to remove the bearings from between the bearing surfaces.
Advantageously, the third member has a plurality of projections for engaging the bearings. The projections may define recesses therebetween for accepting individual bearings. The third member may be a ball rake for engaging ball bearings.
Preferably, the third member may be moveable in a first direction in order to bring the engaging means into engagement with one or more of the bearings, and moveable in a second direction to sweep the bearings towards the access port.
Preferably, the first member is a rotatable shaft supported, in use, at a first end thereof within a recess in the second member. The first member may be moveable axially with respect to the second member such that the distance between the bearing surfaces of the first and second members can be altered. Thus a clearance can be produced such that the bearings can be inserted into or extracted from the gap between the bearing surfaces.
Preferably, the third member, or a support thereof, extends along the first member to a position where it is accessible for manipulation. The third member may be rotated around the axis of the first member to move the bearings towards the access port.
Advantageously, a catching tool may be provided at the access port so as to receive the bearings. The catching tool may comprise a guide tube having a tang extending therefrom.
The bearing may be used at the root of a propeller blade. In such an embodiment, the first member is the propeller blade root and the second member is the propeller hub. The third member may be a ball rake supported on a sleeve encircling the blade root and slidable parallel to the longitudinal axis of the blade. The blade root has a first bearing surface formed at an enlarged foot thereof. The first bearing surface faces radially outward and towards the tip of the propeller blade. A complimentary surface opposing the first bearing surface is provided within the hub. The insertion of ball bearings between the bearing surfaces allows the blade to be rotatably mounted within the hub and also prevents the blade from being extracted from the hub. Once the bearings are in place, the blade is moved outwardly from the hub so as to preload the bearings. The preloading may be performed by tightening a locking/preload nut on the sleeve. The nut bears against a surface at the propeller hub. The sleeve is profiled such that the motion of the sleeve preloads the bearings.
In order to extract the bearings, the preload is released by releasing the locking/preload nut on the sleeve. The blade is moved inwardly into the hub in order to create a gap between the bearing surfaces sufficiently large to allow the ball bearings to move away from the second bearing surface and to align with the access port. The ball rake may be moved radially inwardly of the propeller hub (i.e towards the foot of the blade
REFERENCES:
patent: 1982283 (1934-11-01), Briner
patent: 2315574 (1943-04-01), Anderson
patent: 3148922 (1964-09-01), Roessler, Jr.
patent: 4913564 (1990-04-01), Stephan et al.
patent: 5195396 (1993-03-01), Kamiya et al.
patent: 5507094 (1996-04-01), Lederman
patent: 6019518 (2000-02-01), Yoon
Dowty Aerospace
Eldred J. Woodrow
LandOfFree
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