| 摘要 |
1,187,092. Feeding webs. LUMMUS CO. 8 June, 1967 [27 June, 1966], No. 26541/67. Heading B8R. [Also in Division H4] In a system for determining the amount and direction of sideways displacement of a continuous web, moving in a lengthwise direction, from a reference position, the web intercepts part of a sound wave beam and the attenuation of the beam is measured. In the Fig. 1 embodiment, the web edges move in gaps between transmitting transducers 11, 12 and receiving transducers 13, 14 defining two sound wave beams. Fixed-frequency (e.g. 30 kc./s. or higher) pulsed or continuous wave sound is used. The receiving transducer outputs are A.C. amplified at 22, 32, rectified at 23, 33, D.C. amplified at 24, 34 and compared in voltage comparator 26 whose output feeds meter 36. The relative attenuation of the two beams is dependent on the sideways displacement of the web, and the amplification is adjusted to give a " centre-zero " reading on meter 36 when the web edges are in a desired reference position. The comparator output may also be recorded or control a servosystem for maintaining the web in the desired reference position.
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