A valve is reciprocable between opened and closed positions along a longitudinal axis and is rotatable about the axis by a rotator mechanism. The rotator mechanism includes first and second parts movable axially and rotatably relative to one another along and about the longitudinal axis. A plurality of shiftable ball elements are located between the first and second parts and are movable along predetermined paths for imparting relative rotation between the parts during relative axial movement therebetween. Each ball is constrained for movement along its predetermined path by surfaces which define a pocket in one member and in which the ball is located. Each of the pockets have a ramp along which the ball moves upon relative axial movement of the parts. A spring biases the ball to one end of the ramp and the ball moves toward the other end of the ramp when the first and second parts move axially towards each other. The ramp is defined by a plurality of surface portions which extend at different angles to a plane extending perpendicular to the longitudinal axis. The surface portion adjacent the one end of the ramp to which the ball is biased extends at the greatest angle to the plane and the angle at which the other surface portions extend to the plane are progressively less as the ramp progresses toward the other end of the pocket.