| 摘要 |
<p>A steel frame (1) attached to the front of a tractor comprises, at its lower part, two supports for hydraulic jacks and at its upper end a frame (3). Two movable arms pivot at (5), to the left and to the right, and are extended at right angles to the tractor by means of the jacks. Each arm has an extension (8) attached to it by a hinge (9). The extensions are operated by a cable (11) attached at one end to guide (12) integral with the extension and bearing on a pulley (13) fixed to the end of the arm. The other end of the cable is connected to the tractor. When the arm is lowered, discs (10) mark a furrow in the soil as a guide in which the other disc must follow on the subsequent pass.</p> |
