| 摘要 |
2102614 9220992 PCTABS00017 An instrument for detecting the presence of a body, comprising a detector (2) and a housing (1) in which the detector (2) is accommodated. The housing (1) is provided with at least one guide passage (6) for transmission to the detector (2) of one or more signals originating from the body. The housing (1) is also provided with means for supplying a gas flow (8), for example, compressed air, and a means for discharging at least a part of said flow through the guide passage (6) in such a way that, during operation, at least a part of the cleaning gas leaves the housing (1) via the transmission passage (6). At the same time the invention relates to a rolling mill provided with means for determining velocities of the products to be rolled. The means for determining recording velocity comprises at least two of the instruments above and a processing unit which is linked to receive the signals from those instruments for ascertaining the velocity of a product detected by the instruments.
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