Machine Design

Controller handles heavy-duty hydraulics

In conventional off-road equipment such as bulldozers and loaders, the hydraulics use a load-sensing control system. It usually gives priority to only one actuator, sometimes completely denying power to the rest.

M6 control blocks from Bosch Rexroth, Hoffman Estates, Ill., avoid this problem by using load-independent flow distribution. Whenever the hydraulic pump can't deliver enough flow to satisfy all the actuators' demands, the system reduces flow for all actuators, rendering them slower but still functioning. The blocks are also designed to handle the heavy-duty wear and tear of tough terrain, and be quick and accurate as well.

The M6-15 and M6-22 blocks, for example, supply operating pressures up to 420 bar with flows of 200 and 350 liters/min, respectively. Both are monoblocks, but can be extended to a seven or eightfold block by adding directional valve elements. The M6-15 works with variable-displacement pumps and has an optional priority valve for supplying hydraulics to power-steering systems and special two-pilot operated check valves that prevent loader buckets from lowering during long drives. It also has a float position function in port A3 that switches electrically or hydraulically to prevent cavitation on spool axes two and three

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