| 摘要 |
A multiple plate clutch (33, 34) for a tractor PTO shaft (30) is engaged by an annular piston (37) when hydraulic fluid under pressure is supplied through a line (42). A pressure-responsive variable throttle valve (25) is included in the line (42) and is responsive to the downstream pressure applied via passages (51) to a spool (47) to register large and small grooves (50 and 53) respectively with a flow passage (45) when the said pressure is low and high respectively. This allows an initial rapid flow rate for taking up slack in the clutch but, by virtue of the narrow groove (53), limits the rate at which pressure builds up once the plates have started to engage. The clutch is thereby prevented from snatching. Another hydraulic line (43) feeds the annular piston (39) for a brake (38, 40, 41) on the PTO shaft 30. A two-way changeover valve selectively connects either of the hydraulic lines (42) and (43) to the pressure source and vents the other line to a sump. |
