Revolving plate clamping device

Clamping device consisting of two substantially parallel plates of which one at least may be driven in rotational movement about an axis perpendicular to a surface of the one plate, a plurality of guide cavities hollowed out in said one plate at a distance from the axis and a plurality of corresponding balls inserted into the cavities and gripped between the two plates, each guide cavity forming a cam and providing a bearing surface rising monotonically, covering a non-nil angle of the rotational movement, from a portion of maximum depth to the surface of the plate, characterized in that the portion of maximum depth of the cavity forms a housing for the corresponding ball, which holds the ball in a single determined position, and in that the cavity consists in a portion of lesser depth of a ramp which intercepts the housing in a plurality of points of intersection in the direct vicinity of which the ball forms a first slope tangent with the housing and in the vicinity of which points the ramp has a second slope which is substantially shallower than the first slope, said points of intersection thus being situated on a slope discontinuity comprising an edge.