| 摘要 |
<p>A hydraulic sectional control valve includes separate pump pressure and function control spools 3,5. The spools may be actuated independently and sequentially to provide raising, holding and power down functions for earthmoving and construction vehicles. Additional function control spools may be added in the valve structure to provide multiple function control. Spool 3 is biassed open, in which condition pressurisation of the inlet chamber 20 of spool 5 is prevented. As shown, the spools are arranged to be actuated by a common pilot control valve, the spool 3 being closed prior to opening of spool 5. In Fig. 4 (not shown) separate pilot control is provided for the two spools. <IMAGE></p> |
