Exposure time control for photocopying and enlargement - is fitted with simple mechanism comprising spring and bimetal strip

摘要

Exposure time control apparatus for photocopying or enlarging machine comprises a photoresistor and a bimetal strip (1) consisting of a metal strip (11) and a strip (10) of piezoceramic material coated with two metal layers (100, 101) which are connected to a voltage source. One end of the bimetal strip is fixed, while the other end is freely movable and is coupled to a spring (7) so that a lower and an upper position of the strip are its only stable positions. One terminal of the photoresistor is connected to one metal layer, and the other terminal is connected to the other metal layer.