Low inertia servo valve

In a low inertia servo valve including a valve body having an internal cylindrical bore, said bore including a plurality of annular chambers therearound, said annular chambers being distributed axially at selected locations along said bore, said annular chambers comprising means for fluid communication with, respectively, a pressurized fluid source, a fluid return and the fluid input and fluid output ports of a fluid-driven actuator device, the improvement comprising:

• a sleeve mounted within said bore, said sleeve including at least two groups of at least three sets of ports per group, said sets of ports being distributed axially along said sleeve, the ports that comprise each said set having preselected areal dimensions, are radially distributed around the perimeter of said sleeve, opening into corresponding annular chambers, the angular orientation of those ports that comprise a first set of ports within each group being rotated by a preselected angular displacement with respect to the angular orientation of a second set of ports within each group;
• a fluid-flow control member rotatably mounted within said sleeve, said control member including at least a first and a second internal elongated chamber each for containing respectively first and second groups of at least three sets of apertures, the axial distribution of the respective groups of sets of apertures along said control member corresponding to the axial distribution of the groups of sets of ports along said sleeve, the apertures of each said set, having preselected areal dimensions, are radially disposed around the perimeter of said control member, the angular orientations of a first and a second set of apertures in each group being in angular alignment;
• a control member drive means for rotatably reciprocating said control member between a first and a second angular position relative to a null position;
• and
• in each group in said sleeve, a third set of ports that are dimensioned radially such that the angular opening of each port of said third set of ports of each group subtends an arc having a width sufficient to ensure unrestricted fluid flow through a third set of control-member apertures as the control member rotates between the first and second angular positions.