GB1532639A - Electrohydraulic control means for the height adjustment of a cutting mechanism of an agricultural machine - Google Patents

Abstract

1532639 Height adjustment of cutting mechanisms MASCHINENFABRIK FAHR AG 24 Nov 1975 [25 Nov 1974] 48253/75 Addition to 1455010 Heading A1F A working implement 28 of an agricultural machine is pivotally supported by a hydraulic cylinder 11 fed by a pump P via a multi-way valve 14 which is actuable electrically through a multiple switch 22; an electromagnetically actuable shut-off valve 20 and a pressure limiting or throttling valve 21 are connected in parallel between the multiway valve and the cylinder 11. The switch 22 has four positions corresponding to four pairs of contacts; in the RH and RS positions the switch is self-holding in position and the cylinder is operated to respectively raise and lower the cutting implement 28 until the circuits are interrupted by respective limit switches GO, GU and the valve 14 returns to its neutral O position shown; in the RH and RS positions flow is directed through the valve 20 so that operation takes place at a relatively fast speed. In the TH position the implement is raised at the relatively fast speed for so long as the switch position is maintained by the operator. In the TS position the implement is lowered at the relatively fast speed until the lower limit switch GU is switched and relay E is energised to complete the circuit whereby valve 20 is moved to its no-flow position and the pressure limiting or throttling valve 21 becomes operational. Further lowering at relatively slow speed then takes place as long as the TS switch position is maintained by the operator.