Patent ID: 7690999

Claim:
A shaft coupling comprising: two axially opposed rotary members having rotation axes that can be positioned so as to be parallel to and not aligned with each other, said rotary members having axially opposed surfaces axially facing each other, each of said axially opposed surfaces being formed with a plurality of guide grooves each axially facing and extending perpendicular to one of the guide grooves formed in the other of said axially opposed surfaces; rolling elements each disposed between a pair of axially facing guide grooves at a portion where the pair of axially facing guide grooves cross each other so as to roll while being guided by the pair of axially facing guide grooves; and a retainer for restricting movements of said rolling elements in a radial direction of said rotary members, whereby power is transmitted between said rotary members through said rolling elements; wherein said retainer has elongated holes formed therein, each of said elongated holes extending perpendicular to a diametric direction at a location corresponding to the portion where the respective pair of axially facing guide grooves cross each other; and wherein said rolling elements are respectively rollably disposed in said elongated holes.