Rotary pilot valve

Claim 1

An improved fluid control valve employable for an electrohydraulic step motor comprising: a. a stationary sleeve composed of an assembly of a plurality of individual sleeve portions; b. a spool having a plurality of land portions and capable of axially sliding in the stationary sleeve; c. a first gear mounted on an end of the spool to be engaged with a second gear mounted on the output shaft of an electric pulse operated motor provided for driving the spool; d. a threaded connection between the other end of the spool and the inner end of the rotary output shaft of a hydraulic motor producing an output torque on the other end of the output shaft thereof; e. the axial length of at least one sleeve portion of said stationary sleeve being equal to the axial length of a land portion of said spool and, with each end face of said one sleeve portion being provided with at least one fluid supply port to control fluid flow and being closed by the land portion of said spool when said spool is positioned at the neutral position; f. each of said fluid supply ports constituting a rectangular area open to said end face in its one end and, a circular area disposed at the other end of the rectangular area spaced from said end face whereby in response to an increase of the axial movement of the spool from the neutral position, one of the rectangular areas is opened and then, the circular area is opened; g. an oil supply line; and h. oil load lines connected between said stationary sleeve and said hydraulic motor in order to supply pressure fluid introduced from the oil supply line to said hydraulic motor through either of said fluid supply ports.