System for printing both sides of envelopes

A printing system for printing indicia on opposite sides of relatively thin paper board article receiving envelopes, of the type having a frame along which envelopes are intermittently advanced to be momentarily positioned at plural generally aligned printing stations, the system comprising;

• a supply magazine for said envelopes;
• a plurality of spaced and generally aligned printing stations, each station including an anvil and a printing plate;
• conveying means for feeding the envelopes one at a time from said supply magazine to and through said printers between said printing plate and said anvil in an intermittent fashion, said conveying means including elongated, laterally spaced endless belts substantially spanning the distance from the supply magazine through the exit end of the most remote printer, said printing plates and said anvils being positioned for movement between the laterally spaced belts;
• means located at each printing station to sense an incoming envelope to momentarily interrupt the movement of the envelope and actuate said printer to print said envelope;
• and means locating at least one of said printers on one side of the path of movement of said envelope and another of said printers on the opposite side thereof to thereby print indicia on opposite sides of said envelope.