GB1474926A - Hydraulic device for turning an invertible plough - Google Patents

Abstract

1474926 Reversible ploughs E HENGSTLER [trading as ERWIN HENGSTLER FABRIK HYDRAULISCHER HEBEZEUGE] 4 Nov 1974 [21 Dec 1973] 47551/74 Heading A1B An invertible plough is reversed by the piston rod 6 of a double-acting ram 1 supplied from the tractor hydraulic system (not shown) through a pressure-dependent control unit 2 fitted to the ram head. Oil at a pressure of 40 to 90 bars, supplied through conduits 17, 16, depresses a slide valve 10, which opens a valve 13 and connects conduit 16 to an external conduit 36. Piston 43 is forced upwards and a valve 35 opens so that excess oil flows into chamber 32, and displaced oil flows back to the hydraulic oil supply (not shown) through valve 13 and conduits 30, 31. Near to the upper dead centre point, the bolt 24 closes conduit 34. This causes the pressure in conduit 16 to rise to a value of 150 to 180 bars, determined by a pressure limiting valve (not shown) in the tractor hydraulic system (not shown), which is sufficient to depress a changeover piston 11 slightly and to open a valve 12 which permits the full depression of piston 11. This connects conduit 29 to conduit 18 and to conduits 16, 17, and raises the slide valve 10, which in turn closes conduit 36 and valve 13 whilst opening conduit 48. Oil then flows through conduit 18 to open valve 19 and depress piston 43. At the same time valve 35 is closed, and chamber 33 is connected to the return conduit 31 via conduits 36 and 48, so that piston 43 moves down without counterpressure. Protection against premature opening of valve 12 by a high starting surge is provided by a spring-loaded damper piston 46. The rate of depression of piston 43 is controllable by adjustment of a constriction element 15 which partially blocks conduit 29.