Control units for vehicle powersteering mechanisms

Claim 1

A control unit for vehicle powersteering mechanism comprising: a housing having an inlet for connection to a source of hydraulic fluid under pressure and an outlet for returning hydraulic fluid to said source; a pair of ports for connection to a double chamber hydraulic servomotor the movement of which controls the steering of dirigible wheels of the vehicle; a hydraulic motor provided with a rotatable element and a follower element; a distributor valve means provided with at least one displaceable body, in the form of a sleeve, angularly displaceable with respect to a neutral position, said distributor valve means being operable on rotation of a control shaft connected thereto to divert hydraulic fluid flowing from said inlet through said housing to said outlet to one of said ports and thus to its associated chamber of said servomotor, via said hydraulic motor, the hydraulic fluid being exhausted from the other chamber of the servomotor to said outlet via said other port; means adapted to form a direct connection of said rotatable element of the motor to said control shaft; means adapted to form a mechanical connection of said follower element of the motor to the sleeve like displaceable body of said rotatable distributor valve means; means adapted to limit the displacement of said sleeve like displaceable body with respect to the stationary part of said distributor valve means, and with respect to said neutral position; a plurality of circumferentially spaced longitudinally extending passages provided in said sleeve like displaceable distributor body to feed hydraulic fluid from said inlet, via said motor, to one or the other of said ports when said sleeve like displaceable distributor body is in its displaced position with respect to the neutral position; first passages in said housing communicating with said inlet and with said longitudinally extending passages; second passages in said housing emanating from each of said ports and communicating with said longitudinally extending passages; and radially extending passages in said sleeve like displaceable distributor body communicating with said first passages in said housing, for feeding hydraulic fluid arriving from said inlet to said distributor valve means.