| 摘要 |
A self-leveling hydraulic system (10) controls at least two functions including a boom (14) and a bucket (16). Double acting cylinders (18, 20) are provided for both the boom and the bucket, the cylinders being controlled by separate boom and bucket directional control valves (26, 28), and source of pressure (22) supplying the control valves. A self-leveling valve (34) is in fluid communication with the rod end of the cylinder, whereby flow from the rod end of the boom cylinder (18) is split into first and second flows. A first passage communicates the first of the flows to the head end of the bucket cylinder (20) to supply a sufficient flow to maintain the bucket at a level position as the boom is raised, and a second passage communicating the second of the flows back through one of the control valves to a tank. The self-leveling valve (34) includes a spool structure (36, 38) for controlling the rate of flow being delivered to and returned from the boom (18) and bucket (20) cylinders, and a pressure-compensated valve structure (40, 42) connected to the spool structure for maintaining the ratio of hydraulic flow between the rate being delivered into the head side of the boom cylinder and the rate being exhausted from a rod side of the boom cylinder (18) during raising and lowering cycles of the boom (14). |
