Rotary servo valve

A method of controlling fluid flow using a rotary servo valve, the servo valve comprising:

• a housing defining a cavity and a first layer of ports, the first layer of ports having only three pairs of ports, wherein the three pairs of ports are a first pair of service ports, a pair of pressure ports, and a pair of return ports, the ports of each pair being arranged so as to be diametrically opposed about the cavity the three pairs of ports of the first layer being located at substantially the same axial position along the length of the cavity;
• and
• a spool portion comprising two opposing indented sides and two opposing sides having an increased radius relative to the indented sides, each side of increased radius extending between the two indented sides, and
• wherein the method comprises rotating the spool portion from a neutral position in which each side of increased radius blocks at least one port so as to prevent fluid flow through the valve, to an open position in which fluid flows between each of the service ports of the first pair and a corresponding port of one of the remaining pairs of ports, the fluid passing over an indented side as it flow between said ports.

A rotary servo valve for controlling fluid flow, the servo valve comprising:

• a housing portion defining a cylindrical cavity and a first layer of ports, the first layer of ports having three pairs of ports, including a first pair of service ports, the ports of each pair being arranged so as to be diametrically opposed about the cylindrical cavity, the three pairs of ports of the first layer being located at substantially the same axial position along the length of the cavity;
• and
• a spool portion comprising two opposing indented sides and two opposing sides having an increased radius relative to the indented sides, each side of increased radius extending between the two indented sides, and wherein
• the spool portion is mounted for rotation relative to the cylindrical cavity, from a neutral position in which each side of increased radius blocks at least one port so as to prevent fluid flow through the valve, to an open position in which a fluid flow path is provided between each service port of the first pair and a corresponding one of the remaining ports, each fluid flow path being defined at least in part by one of the indented sides;
• a second housing portion defining a cylindrical cavity and a second layer of ports, the second layer having three pairs of ports including a first pair of service ports, the ports of each pair arranged so as to be diametrically opposed about the cylindrical cavity, the three pairs of ports of the second layer being located at substantially the same axial position along the length of the cavity;
• and a second spool portion comprising two opposing indented sides and two opposing sides having an increased radius relative to the indented sides, each side of increased radius extending between the two indented sides, and wherein
• the second spool portion is mounted for rotation relative to the cylindrical cavity, from a neutral position in which each side of increased radius of the second spool portion blocks at least one port of the second layer so as to prevent fluid flow through the valve, to an open position in which a fluid flow path is provided between each service port of the second pair of the second layer and a corresponding one of the remaining ports, each fluid flow path being defined at least in part by one of the indented sides of the second portion.