| 摘要 |
1455010 Automatic height control MASCHINENFABRIK FAHR AG 17 Dec 1973 [15 Dec 1972] 58388/73 Heading A1F An implement mounted on an agricultural machine 1 may be raised, lowered, or maintained at a fixed height relative to the machine or to the ground by means comprising a hydraulic ram 5 connected via a hydraulic line 10, one way valve 17 and spool valve 9 to a pump 7, spool valve 9 being operated by a solenoid 13 in circuit with a multi-position switch 14. When the switch is placed in position H (i.e. with the terminals designated H connected) the spool valve causes the ram to raise support 3, whilst placing the switch in position S causes the spool valve to release fluid from the ram thereby lowering support 3, the excess fluid draining into a reservoir 8. The switch in position L brings into operation a mechanism 21 which maintains the position of the support 3 relative to the machine frame, thereby enabling the support to be placed at a distance from the ground, pre-set by a lever 26. This mechanism, which is connected to the support 3 via a rod 24 comprises a semi-circular member 22 pivotally mounted on the machine frame, and switches 29, 30. With the support 3 above (below) the pre-set position, switch 30 (29) is engaged, this causes the spool valve to operate the ram 5 and thereby lower (raise) the member 3 to the preset position after which the switch is disengaged. A probe 35, brought into operation by switching to position T, engages the ground, as the machine advances, undulations in the ground cause the probe to operate one of two switches 36, 37 which in turn operates spool valve 9 thereby causing the ram to raise or lower the support 3 to follow the contour of the ground. In an alternative embodiment, the probe 35 is replaced by a pressure sensitive switch in circuit with the spool valve 9 and hydraulically connected to the ram 5 which is adjusted to partially support the weight of the agricultural implement, the latter therefore glides over the surface of the ground. Variations in surface contour resulting in a pressure change within the ram are detected by the pressure sensitive switch which in turn causes the spool valve to operate the ram thereby raising or lowering the support 3 and enabling the implement to follow the surface contour with no variation in surface pressure. The multi-position switch 14 is spring biased to a central position where all circuits are inoperative; in addition the biasing springs provide a toggle device whereby the switch is self holding in the T or L positions. |
