Optical displacement transducer scale - of alternate transparent and opaque strips, esp. for controlling tool traverse motions on injection moulding machines

摘要

Linear movement of one piece of machinery relative to another is determined by reference to a scale of alternate transparent and opaque strips of identical width. The moving part carries a pair of photocells, having their axes normal to that of the scale and separated by a distance which is not a direct multiple of the width of the strips. The photocell response to passing the optical contrasts of transparent and opaque strips, in either direction, are automatically counted and incremented by a suitable computing device to monitor and control the position of the moving part and the limits of its travel. Used esp. for monitoring the opening or closing of a plastics injection moulding tool, with a precision based on strips about 1 mm. wide. The non-contact, optical measurement is not susceptible to wear and does not depend upon clean electrical contact between moving or impinging surfaces.