| 摘要 |
<p>A control valve comprises a first spool (22), a second spool (24) encircling at least part of the first spool (22) and angularly moveable relative thereto, and a sleeve (32) encircling at least part of the second spool (24), the second spool (24) being angularly moveable relative to the sleeve (32), the first and second spools (22, 24) having first and second series of ports (28, 30) registrable with one another, depending upon the relative angular positions of the first and second spools (22, 24), to control communication between at least a pressure line (16), a return line (18) and a control line (50) provided in or connected to the sleeve (32), the second spool (24) and the sleeve (32) having third and fourth series of ports (66, 68), axially spaced from the first and second series of ports (28, 30) and registrable with one another, depending upon the relative angular positions of the second spool (24) and the sleeve (32), to control communication between at least the control line (50) and the return line (18), and latch means (56) operable to resist movement of the second spool (24) relative to the sleeve (32).</p> |
