Ink fountain key control system

Claim 1

In combination with an inker for a printing unit having a fountain roll and a fountain blade extending inward toward the fountain roll along the latter''s length to control the thickness of an ink film withdrawn by the fountain roll past the fountain blade, and a plurality of fountain keys spaced apart in succession along the fountain blade and engaging the outside of the latter to control its spacing from the fountain roll, a control for said fountain keys comprising: electrically operable drive means for adjusting the fountain keys toward or away from the fountain roll; a plurality of switches individual to the respective fountain keys; a plurality of key position sensors individual to the respective fountain keys and arranged to produce signals corresponding to the positions of the respective keys; signal comparing means operable to produce an output signal proportional to the difference between two input signals; means responsive to the operation of a selected switch for connecting the position sensor for the key selected for adjustment and the position sensor for a neighboring key to the input of said signal comparing means to enable the latter to produce an output signal proportional to the difference between the respective positions of said last-mentioned keys; a comparator for comparing the output of said signal comparing means against a reference signal corresponding to the maximum permissible displacement of said selected key with respect to said neighboring key; and means operable by said comparator means for stopping the adjustment of said selected key when its displacement with respect to said neighboring key reaches said maximum permissible value, whereby to limit the flexing of said fountain blade thereat.