Roller profile for hourglass roller bearings in aircraft
View Patent ↗An edge flap arrangement for an aircraft wing includes a main flap element and an actuator for moving the main flap element relative to the aircraft wing. A linkage arrangement supports the main flap element and includes a drop hinge link arrangement having a fixed strut secured to the aircraft wing and a drop link secured to the main flap element. The fixed strut and the drop link are connected by a hinge point having an hourglass bearing assembly having hourglass shaped rollers with a circular cross section symmetrical about a longitudinal axis, first and second axial ends, and an exterior surface. The exterior surface defines a concave engagement surface having a first radius of curvature R 1 and a second radius of curvature which is greater than the first radius of curvature R 1 . The first radius of curvature is between 50 and 95 percent of the second radius of curvature.
1. An hourglass bearing assembly installed in an edge flap arrangement of an aircraft, the hourglass bearing assembly comprising:
an inner raceway defining a radially outwardly facing convex surface having an inner raceway radius of curvature Ri;
an outer raceway defining a radially inward facing convex inner surface having an outer raceway radius of curvature Ro, the outer raceway being positioned around the inner raceway;
a plurality of rollers disposed between the inner raceway and the outer raceway, each of the plurality of rollers having an hourglass shape and being in rolling engagement with the inner raceway and the outer raceway;
each of the plurality of rollers having:
a circular cross section symmetrical about a longitudinal axis;
a first axial end and a second axial end;
an exterior surface extending between the first axial end and the second axial end;
the exterior surface defining a concave engagement surface extending outwardly from a central portion of the roller,
the concave engagement surface having a first radius of curvature R 1 extending from the central portion to each of two first transition zones Z 1 positioned on opposing sides of the central portion and
the concave engagement surface having a second radius of curvature R 2 extending outwardly from each of the two first transition zones Z 1 to each of two second transition zones Z 2 ; and
the second radius of curvature R 2 is greater than the first radius of curvature R 1 ; and
the first radius of curvature R 1 is between 50 percent and 95 percent of the second radius of curvature R 2 .
2. The hourglass bearing assembly of claim 1 wherein the aircraft is a commercial aircraft having a wingspan of about 60 meters or more.
3. The hourglass bearing assembly of claim 1 , wherein the first radius of curvature R 1 is between 70 percent and 92 percent of the second radius of curvature R 2 .
4. The hourglass bearing assembly of claim 1 , wherein the exterior surface defines an extended area for engagement positioned between each of the second transition zones Z 2 and each of two third transition zones Z 3 , the third transition zones Z 3 being positioned outwardly from a respective one of the second transition zones Z 2 .
5. The hourglass bearing assembly of claim 4 , wherein:
a first distance L 1 is defined between the two first transition zones Z 1 ;
a second distance L 2 is defined between the two second transition zones Z 2 ;
a third distance L 3 is defined between the two third transition zones Z 3 ; and
the first distance L 1 having a magnitude between 40 percent and 60 percent of the third distance L 3 .
6. The hourglass bearing assembly of claim 4 , wherein:
a first distance L 1 is defined between the two first transition zones Z 1 ;
a second distance L 2 is defined between the two second transition zones Z 2 ;
a third distance L 3 is defined between the two third transition zones Z 3 ; and
the first distance L 1 having a magnitude between 48 percent and 51 percent of the third distance L 3 .
7. The hourglass bearing assembly of claim 4 , wherein the extended area defines an area of engagement with a rolling surface of a bearing race, the area of engagement engages the rolling surface when the roller and bearing race are in a loaded condition.
8. The hourglass bearing assembly of claim 7 , wherein a peak stress of the roller occurs inwardly from the two third transition zones.