Hydraulic rotary distributor, particularly for power steering mechanisms

A hydraulic rotary distributor for power-assisted steering gear comprising a first rotary member solid in rotation with an input shaft, and a second rotary member solid in rotation with an output shaft, the said first and second rotary members forming between them fluid passages intended to control the fluid flow between a pressure source and at least one compartment of a power-assistance motor as a function of the relative angular position of said first and second rotary members, said distributor further comprising locking means responsive to a control pressure so as to prevent the relative rotation between said first and second rotary members from a non-operating position in response to the application of a torque to the input shaft, until said torque applied to the input shaft is greater than a predetermined value, one of the rotary members comprising an external cylindrical surface sealingly cooperating with an internal cylindrical surface on the other rotary member, said locking means comprising at least one ball or roller member radially urged towards the bottom of a notch defined in the said external cylindrical surface under the influence of the control pressure acting on a pressure-responsive member movably carried by the other of said rotary members, said pressure-responsive member defining a notch confronting the notch on said one rotary member and said notches receiving said ball or roller member.