GB1458558A - Hudidity compensated control device - Google Patents

Abstract

1458558 Automatic control XEROX CORP 6 May 1974 [7 May 1973] 19758/74 Headings G2H and G3N A humidity-sensitive control device, for regulating the dispensing of toner particles to a developer mix in a multi-colour electro-photographic printing machine, includes means 44 detecting the "developability" of the mix, humidity-responsive means 46 which adjusts the output signal of means 44 and feeds the adjusted signal to the energizing means of a particle dispenser. The detecting means 44 comprises a transparent electrode 48 upon which toner particles are deposited and through which light is passed to a photosensor 54. When the output of means 44 indicates that the "developability" is too low it is fed to the inputs of three logic channels (60, 62, 64) Fig. 2 (not shown) which correspond to three colour developer units 28, 30, 32. The logic channels each contain means for distinguishing between two ranges of values of the output of means 44 and actuate a respective particle dispenser accordingly for a whole or half period. The humidity-responsive means 46 comprises a humidity sensor (110), Fig. 3 (not shown) e.g. a lithium chloride cell, whose resistance is inversely proportional to the humidity, connected in a wheatstone bridge. The sensor output is compared with a reference (112), and then used to correct the output of a gating circuit (118) whose inputs are the outputs of the three logic channels of means 44. The corrected output then actuates the energizing means, e.g a motor, which dispenses the particles by oscillating the appropriate container with a humidity-dependent amplitude.