| 摘要 |
<p>During the cleaning operation, the distance between the point of contact of the scraper with the surface and a preferably fixed reference point is continuously measured and a signal S representing this distance is produced (curve a). At preferably uniform predetermined time intervals, the mean value of the signal S during the duration of the said interval is determined and the difference DELTA S between the instantaneous value of the signal S during an interval and the mean value of this same signal S corresponding to the preceding interval is detected (curve b). When the said difference reaches a predetermined value, for example +/- 1mm (at T2, T3, curve b), the scraper is withdrawn backwards and then, following a predetermined period of time, which may be equal to the duration of at least one of the said intervals, the scraper is brought back into contact with the said surface (curve c). <IMAGE></p> |
