Patent ID: 8678939

Claim:
A coupling device comprising: an inner shaft and an outer shaft sliding along a common axis and each having a concave portion; balls arranged within said concave portion of said inner and outer shafts; each of said balls having a center, a common median plane passing through the common axis and through the center of each of said balls; one said concave portion of one said shafts having a bottom and two flanks located on either side of the common median plane, each of the two flanks having a circular cross-section, a center of said circular cross-section being located at a distance from the center of each of the balls between said common axis and the center of each of the balls and closer to the bottom than the center of each of the balls; and two rails located on either side of the common median plane, wherein each of the two rails has a first bearing face in mating contact with the balls and a second bearing face in mating contact with a respective one of the flanks.