Rotary type hydraulic servo-mechanism

In a rotary type hydraulic servo-mechanism of the type including a hollow cylindrical casing closed at both ends thereof and having at least one partition wall radially and inwardly projecting from the inner surface of said casing and extending toward the center axis thereof;

• a cylindrical input shaft passing axially and concentrically through said casing;
• a driven output member rotatably mounted on said input shaft within said casing and having one end thereof extending out of the casing as an output portion, and having at least one partition wall radially and outwardly projecting from the outer periphery thereof and extending toward the inner surface of said casing;
• said partition walls of said casing and said output member defining therebetween at least one pair of hydraulic drive chambers;
• a servo-valve mechanism provided between opposed cylindrical sliding surfaces of said input shaft and said output member and comprising mutually opposed axial grooves formed in the cylindrical outer surface of said input shaft and in the cylindrical inner surface of said output member;
• first hydraulic fluid supplying and discharging passage means formed in said input shaft and connecting said grooves in said input shaft to a hydraulic fluid source and a fluid reservoir;
• second hydraulic fluid supplying and discharging passage means formed in said output member and connecting said grooves in said output member to said hydraulic drive chambers;
• and means for generating a counter-torque against a rotational force applied to said input shaft;
• the improvement wherein said means for generating a counter-torque comprises:
• means positioned around said input shaft and comprising at least one pair of isolated hydraulic fluid reaction chambers which are hydraulically isolated from one another;
• said reaction chambers being formed at a side of said input shaft diametrically opposite to said servo-valve mechanism and communicating with said second hydraulic fluid supplying and discharging passage means through passage means formed in said output member;
• each of said reaction chambers being defined by a first radial face on a first radial wall formed on said input shaft and a second radial face on a second radial wall circumferentially opposing the first radial face and formed on said output member;
• said first and second walls having their radially outer and inner ends in sliding sealed engagement with the inner surface of said output member and with an outer surface of said input shaft, respectively;
• said first and second radial faces having the same area;
• and
• said pair of reaction chambers comprising a first reaction chamber for imposing to said input shaft a torque counteracting the rotation of said input shaft in a first circumferential direction, and a second reaction chamber for imposing to said input shaft a torque counteracting the rotation of said input shaft in a second opposite circumferential direction, whereby upon introduction of hydraulic fluid into one of said reaction chambers a reaction force is exerted on said input shaft against and relative to said output member for causing relative rotation between said input shaft and said output member.