Capacitive transducer drive mechanism for the recording pen of a graphical recorder

Claim 1

Apparatus for driving the recording pen of a graphical recorder, comprising: a. a fixedly mounted first conductive element; b. a fixedly mounted second conductive element mounted parallel to said first conductive element and coextensive lengthwise therewith; c. a pair of rollers, one of which is electrically grounded, mounted beyond the ends of said conductive elements having their upper surfaces in a plane located between and generally parallel to said conductive elements; d. servo means responsive to command signals including drive means connected to at least one of said rollers for rotation thereof; e. a non-conductive belt looped about said rollers for rotation therewith; f. recording pen retaining means fastened to said non-conductive belt for movement therewith between the ends of said conductive elements; g. a conductive film on said non-conductive belt of sufficient length so that said conductive film contacts said grounded roller regardless of the position of said recording pen; h. a source of periodic signals connected to one of said conductive elements; and i. first circuit means connected to the other of said conductive elements and said servo means for developing output electrical signals having an amplitude determined by the position of said recording pen, including means for maintaining said conductive element connected to said first circuit means at a substantially zero signal level with respect to the conductive film on said belt.