| 摘要 |
<p>The device, for an agricultural tractor pulling a plough etc., uses a sensor wheel (26) which contacts the ground when the plough is in the working position. The 3-point lifting device (3) for raising and, lowering the plough has a hydraulic working cylinder (7) controlled by the vertical force acting on the sensor wheel (26). Pref. the sensor wheel (26) is supported by a square support arm which can slide within a square sleeve in response to the vertical force acting on the wheel (26), with an associated pair of switch contacts operated when the vertical force is above a given value. This switch is coupled in the electrical circuit of the magnetic valve controlling the working cylinder (7).</p> |
