초록 ▼

The edge of a web of material is inserted in a gap in a detector head between an ultrasonic blockage transmitter and an ultrasonic blockage receiver such that the magnitude of the pulse of sound from the transmitter that is received by the receiver is related to the portion of the web that blocks th

The edge of a web of material is inserted in a gap in a detector head between an ultrasonic blockage transmitter and an ultrasonic blockage receiver such that the magnitude of the pulse of sound from the transmitter that is received by the receiver is related to the portion of the web that blocks the beam of sound and thereby the position of the edge of the web. A compensation transmitter and compensation receiver are mounted proximate to the blockage transmitter and blockage receiver and transmit similar sound signals across the gap but are unoccluded by the web. The output of the compensation receiver is detected and used to normalize the values of the signal received from the blockage receiver to compensate for the effect of transient changes in ambient conditions. The apparatus includes a controller with a microprocessor which receives the electrical pulses from the two receivers, determines the peak values of the pulses, averages pulse peak values to provide averaged values which reduce the effect of spurious signal variations, and normalizes the value of the blockage receiver signal with the compensation receiver signal to provide an error correcting output signal which can be used to bring the position of the web back to a desired position. A plurality of detectors can be operated by a single microprocessor using multiplexing techniques.

대표청구항 ▼

Ultrasonic web edge detection apparatus comprising: (a) a plurality of detector heads, each having an ultrasonic blockage transmitter, an ultrasonic blockage receiver, an ultrasonic compensation transmitter and an ultrasonic compensation receiver, the blockage transmitter and blockage receiver arran

Ultrasonic web edge detection apparatus comprising: (a) a plurality of detector heads, each having an ultrasonic blockage transmitter, an ultrasonic blockage receiver, an ultrasonic compensation transmitter and an ultrasonic compensation receiver, the blockage transmitter and blockage receiver arranged in the head with the web edge received in a gap between the blockage transmitter and the blockage receiver, the compensation transmitter and the compensation receiver located in close proximity to the blockage transmitter and receiver so that sound transmitted from the compensation transmitter to the compensation receiver is free from the web edge; (b) transmitter amplifier means for driving the blockage and compensation transmitters to produce ultrasonic sound output; (c) receiver amplifier means for amplifying the electrical output of the blockage and compensation receivers produced in response to sound received; (d) digital processing means for normalizing the signal from the blockage receiver with the signal from the compensation receiver and for determining the position of a web edge received between the blockage transmitter and the blockage receiver by such normalization; and (e) multiplexing means connected for selectively connecting the transmitter amplifier means and the receiver amplifier means to transmitters and receivers respectively in the detector heads so that the digital processing means can normalize the outputs from the plurality of the detector heads.