| 摘要 |
A centre pivot irrigator comprises a boom (14) which is pivotally displaceable about a centre pivot (12) and has a series of sections (18) connected end-to-end. Each section is supported by a self-propelled tower (16) having a motor (20) for driving the tower, adjacent sections being able to flex with respect to one another. The various sections are kept in line as the boom rotates about the centre pivot by intermittently switching the various motors (other than that of the last tower) on and off. Switching of each motor is in response to a switching arrangement (24) which detects flexing of adjacent sections with respect to one another beyond a predetermined extent. To prevent damage to the irrigator in the event of malfunction of any of the switching arrangements, means including a programmed logic controller (42) is provided. This is programmed to sense if the motor of a selected tower is on or off for longer than a predetermined length of time and, in response thereto, to shut down the irrigator.
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