Electrically operated valve for controlling flow of hydraulic fluid

An electrically operated valve for controlling flow of hydraulic fluid to or from apparatus which uses the hydraulic fluid flow controlled by the valve, the valve comprising:

• a valve housing;
• a spool slidable in a spool chamber in the valve housing;
• a first fluid conduit extending through the valve housing for connecting the spool chamber with a source of pressurized fluid;
• a second fluid conduit extending through the valve housing for connecting the spool chamber with a reservoir of fluid;
• and
• a third fluid conduit in communication with the spool chamber which delivers fluid to or receives fluid from the apparatus which uses the hydraulic fluid flow controlled by the valve;
• wherein:
• the spool is biased to a rest position by a pair of opposed springs;
• the spool in the rest position thereof closes off the first and second fluid conduits from the spool chamber and thereby prevents flow of fluid to and from the third fluid conduit;
• the valve has a first electric coil associated with a first end of the spool and which can be activated to displace the spool from the rest position thereof to open the first fluid conduit to the spool chamber, whilst keeping closed the second fluid conduit, and thereby to allow pressurized fluid to flow from the first fluid conduit to the third fluid conduit;
• and
• the valve has a second electric coil associated with a second end of the spool and which can be activated to displace the spool from the rest position thereof to open the second fluid conduit to the spool chamber, whilst keeping closed the first fluid conduit, and thereby to allow fluid to flow from the third fluid conduit to the second fluid conduit;
• wherein a sleeve surrounds the spool and defines the spool chamber in which the spool is slidable, the sleeve having a first port through which the first fluid conduit communicates with the spool chamber, a second port through which the second fluid conduit communicates with the spool chamber and a third port through which the third fluid conduit communicates with the spool chamber, and wherein the valve has an adjustment mechanism for sliding the sleeve relative to the valve housing.