Rotation prevention device for an orbiting member of a fluid

Abstract

A rotation preventing/thrust bearing device for an orbiting member of a fluid displacement apparatus is disclosed. The rotation preventing/thrust bearing device includes a discrete fixed portion, a discrete orbital portion and bearing elements. The fixed and orbital portions each include an annular race and a ring which covers the end surface of the race. Both rings have a plurality of holes or pockets in an axial direction. The radius of the fixed pockets is greater than the radius of the orbital pockets. The bearing elements, one of which is placed between each opposing pair of pockets, roll at radius R1 with regard to the fixed race and roll at radius R2 with regard to the orbital race. The sum of rolling radii R1 and R2 is substantially equal to the radius of the orbiting member. Rotation of the orbiting member is thereby prevented by the bearing elements which interact with the edges of the opposing pairs of pockets and the bearing elements carry axial thrust load from the orbiting member to the fixed race. By setting radius R2 smaller than radius R1, while maintaining the sum of these radii substantially equal to the orbit radius, the size and weight of the orbital race and the orbital ring can be reduced, which in turn reduces the overall weight of the orbital member of the fluid displacement apparatus. A reduction in the weight of the orbital member simplifies the construction of the apparatus by reducing the size of balance weights.