Strip measuring and centering system

A system for locating at least one edge of a moving strip of material having a reflective surface, comprising:

• an ultrasonic transducer positioned adjacent the path of said moving strip, and oriented at an acute angle toward said at least one edge so that an acoustic pressure wave is transmitted on top of the surface of said strip through air,
• circuit means for causing said transducer to emit ultrasonic pulse in air at a time T on top of said surface of said strip and in the direction of said at least one edge, and
• detector means connected to said ultrasonic transducer for detecting acoustic diffractions caused by said at least one edge, and
• means for determining the location of said at least one edge from the time T of emission of said ultrasonic pulse and time of detection of said acoustic diffractions.

A system for locating edges of a moving linear strip of material having a thickness and pair of edges, comprising:

• an ultrasonic transducer having anultrasonic beam with a width wider than the thickness of said strip and positioned and oriented at an angle of 0 or at an acute angle toward at least one edge of said strip so that at a time T an acoustic pressure wave is transmitted on top of at least one surface of said strip through the air,
• circuit means for causing said transducer to emit an ultrasonic pressure wave through the air and on top of said at least one surface of said strip and in the direction of said at least one edge, and
• detector means connected to said ultrasonic transducer for detecting acoustic diffractions caused by said pressure wave passing said at least one edge, and
• means for determining the location of said at least one edge from the time T of emission of said ultrasonic pulse and time of detection of said diffractions.