Control valve for switching a hydraulic piston-cylinder unit for the purposes of driving an oscillatory machine part

摘要

A self-propelled combine harvester having a mechanically actuated directional control valve for a hydraulic piston-cylinder unit used for driving the cutter bar in an oscillatory manner. A switching bracket is used to axially move the mechanically actuated directional control valve from a first end position to a second end position and from the second end position to the first end position. A latch is used to periodically latch a piston valve stationary. A first plunger and second plunger are alternatively and axially moved by a first spring and second spring. The first plunger and the second plunger alternatively move the valve piston from the first end position and the second position and from the second position to the first position. The valve piston will be released from the first end position or the second end position one end position from which it was arrested or latched. The switching between the first end position and the second end position and from the second end position is thereby alternatively accomplished. This process of switching-over the valve piston will not be interrupted if there is a sudden decrease in pressure because the process is effected by means of the biased springs.