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(11) | EP 0 134 744 A3 |
(12) | EUROPEAN PATENT APPLICATION |
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(54) | Proportional follower spool valve system |
(57) @ A proportional follower spool valve system having a main spool (12) slidable between
end chambers (55, 56) maintained at substantially return pressure. First fluid connections
(40) are controlled by the main spool (12) and they are effective to control output
fluid flow in accordance with the position of the main spool (12). A pilot spool (11)
is slidable within an inner passage (12a) of the main spool. A first (20) and second
(21) driving chamber is formed by the main spool (12) each having a driving area substantially
less than the largest cross-sectional solid area of the main spool (12). Second fluid
connections (11a, 11b) are controlled by the pilot spool (11) for admitting fluid
under pressure 1/ to the first chamber (20) when the pilot spool moves in a first
direction away from the first chamber and 2/ to the second chamber (21) when the pilot
spool (11) moves in a second direction away from the second chamber (21). Each of
the first and second driving chambers are disposed between a respective end chamber
and a passage for return pressure. |