Controller for a servo driven document feeder

In a document feeder, a system providing improved control over the spacing between successive documents carried by a track in the feeder, comprising:

• first and second pluralities of rollers associated with the track;
• servo means driving said rollers through coupling means arranged to drive said second plurality of rollers at a higher speed than that of the first plurality of rollers and to maintain a constant speed ratio between the speed of the first and second plurality of rollers;
• a third plurality of rollers positioned after the second plurality of rollers in the track and driven at a constant speed independently by motor means to impart a constant transport speed to documents in the track;
• first sensing means associated with the second plurality of rollers for detecting passage of the trailing edge of a first document and providing a first signal indicating that passage;
• said first sensing means providing a second signal indicating when the leading edge of a second document passes;
• processor means coupled to be responsive to said signals to determine the length of the gap between the respective trailing and leading edges of the first and second documents;
• and
• second sensing means associated with the second plurality of rollers for providing a third signal indicating the passage of the trailing edge of the first document as it leaves the control of the second plurality of rollers;
• said processor means responding to said third signal to provide a servo motor control signal altering the speed of the servo means and thereby altering the length of the gap until a gap of required size is obtained;
• said processor means, after the required gap is obtained, changing the speed of said servo means to a speed imparting the transport speed to the document for entry into contact with the constant speed third plurality of rollers.

In a document feeder including a track along which documents move, a system providing improved control over the spacing between successive documents carried by a track in the feeder, comprising:

• a first plurality of rollers associated with the track;
• first servo means coupled to drive said first plurality of rollers at a variable speed;
• a second plurality of rollers associated with the track;
• said first servo means including coupling means to drive said second plurality of rollers at a speed set higher than that of the first rollers and to maintain a constant speed ratio between the speed of the first and second plurality of rollers;
• a third plurality of rollers following the second plurality of rollers in the track and driven at a constant speed independently by a second servo means to impart a constant transport speed to documents in the track;
• first sensing means associated with the second plurality of rollers for detecting passage of the trailing edge of a first document and providing a first signal indicating that passage;
• said first sensing means providing a second signal indicating the passage of the leading edge of a second document;
• processor means responsive to said signals to determine the distance between the respective trailing and leading edges of the first and second documents;
• second sensing means associated with the second plurality of rollers for providing a third signal indicating the passage of the trailing edge of the first document as it leaves the control of the second plurality of rollers;
• said processor means responding to said third signal to provide a signal altering the speed of the first servo means and thereby altering the length of the gap until a gap of required size is obtained;
• and
• said processor means changing the speed of said first servo means to a speed imparting the transport speed to the document for entry into the constant speed third plurality of rollers.

In a document feeder for accepting documents of varied lengths which are arranged end-to-end and advancing them along a track while imparting the same speed to each document and establishing gaps of equal length between the documents, control means comprising:

• means providing track clock pulses and servo clock pulses;
• an initial gap counter, coupled responsive to first signals indicating the passage of the trailing edge of a first document, to start counting track clock pulses;
• said initial gap counter responding to second signals indicating the arrival of the leading edge of a second document to stop counting track clock pulses and provide a readout indicating the magnitude of the initial gap count between the first and second documents;
• microprocessor means responsive to said readout and to inputs designating a desired gap between documents to provide a control signal to track speed control means to start the correction of said gap and provide a word designating the number of clock pulses to be subtracted to correct the length of the gap;
• said microprocessor means providing subtracter control signals designating whether track clock pulses or servo clock pulses should be subtracted from the other;
• a subtractor and up/down counter coupled to receive said word and said subtractor control signals and perform the designated subtraction between the track clock pulses and the servo clock pulses until equality is established;
• said subtractor and up/down counter providing a subtraction complete signal to said microprocessor means to enable the microprocessor to restore the track speed control means to its original speed.