| 摘要 |
<p>A forage harvester (11), pulled via its tongue (16) by a tractor, has dividers (19, 21) between which a crop row (18) is received, and each divider has a row sensing unit (41, 43) of a guidance control system bolted to it. The crop row passes between a pair of arms (47, 48) of the units. An arm is deflected, when the machine is misaligned with the row, the arm having an upright pivot shaft (79). Each arm carries an actuator plate (95) which closes a corresponding sensing switch (145, 147) to trigger a guidance control circuit (45) to steer the harvester by way of a piston and cylinder (33) moving the tongue to return the harvester to alignment with the crop row. These first and second switches are connected to an electrically responsive control valve arrangement (185) which controls the cylinder. To avoid the two sensing switches (145, 147) sending contradictory signals simultaneously to the control valve arrangement (185), first and second relays (201, 203) are connected between the respective switches and the control valve arrangement, and the first and second switches are also connected to the relay coils of the second and first relays respectively. This causes the first switch (145), when closed, to open the second relay (203), and the second switch (147), when closed, to open the first relay (201).</p> |
