| 摘要 |
1533630 Detecting sheets ultrasonically EASTMAN KODAK CO 17 Sept 1976 [22 Sept 1975] 38694/76 Heading G1G In a method of detecting the presence of sheets of material moving along a predetermined path, ultrasonic energy is transmitted through the path and the phase of the energy on each side of the path is compared so that when the phase difference exceeds a predetermined value a signal is generated. The method enables the passage of multiple sheets of paper, plastics or metal to be detected. An ultrasonic signal is transmitted from a transducer 17 and received by a transducer 18 connected via an amplifier 23 and a zero crossing detector 28 to a phase comparator 30. A signal from an oscillator 20 is also supplied to the comparator via a zero crossing detector 22. If only a single sheet passes between the transducers, the phase shift between the transmitted and received ultrasonic signals is not sufficient for a comparator 34 to provide an output signal. However, if multiple sheets are passing between the transducers, the comparator 34 supplies an alarm signal or switches off the sheet feeding machine. |
