Thermal transfer color printer for printing on sheets of paper

Claim 1

A thermal transfer color printer for printing a color image on individual separate sheets of a recording medium comprising: supply means for storing sheets of recording medium and supplying one sheet at a time into said thermal transfer color printer; a reversible platen roller rotatably supported in said thermal transfer color printer to transport a single sheet of said recording medium received from said supply means; first and second pinch rollers, each rotatably supported adjacent said reversible platen roller at opposite sides thereof to press the sheet of recording medium against the surface of said reversible platen roller; first guide means for guiding the sheet of recording medium from said supply means to said reversible platen roller so that it is gripped by said reversible platen roller and said first pinch roller; a multicolored ink ribbon supported to move across said platen roller with one face of said ink ribbon forming a guide for transporting the sheet of recording medium along the surface of said platen roller, said ink ribbon having a plurality of color segments successively arranged along its length; a thermal printhead having thermal elements selectively energized by color component electrical signals representing the color image to be printed on the sheet of recording medium, said printhead supporting said ink ribbon at a position facing the surface of said platen roller; printhead moving means for selectively moving said thermal printhead up and down so that, in the up state, the printhead presses said ink ribbon and the sheet of recording medium onto the surface of said platen roller for thermally transferring colored ink from the ink ribbon onto the sheet of recording medium when said thermal elements are energized and, in the down state, said thermal printhead provides a guide path for the sheet of recording medium between said ink ribbon and the surface of the platen roller; platen roller drive means for driving said reversible platen roller in a first direction to load the sheet of recording medium in said thermal transfer color printer; pinch roller shift means for shifting said first pinch roller toward the surface of said platen roller during a first loading time period to retain the sheet of recording medium on the surface of said platen roller to enable said platen roller to feed the sheet of recording medium to said second pinch roller, said pinch roller shift means shifting said first pinch roller away from the surface of said platen roller during a second loading time period to disengage said first pinch roller; slack removing means positioned along said first guide means for applying a force to the sheet of recording medium during the second loading time period to remove slack from the sheet of recording medium, said pinch roller shifting means shifting said first pinch roller back toward the surface of said platen roller to again retain the sheet of recording medium after slack is removed during the second loading time period; ink ribbon drive means for transporting said multicolored ink ribbon in the first direction, said platen roller drive means further transporting the sheet of recording medium in the first direction at substantially the same rate as said ink ribbon, said platen roller drive means also including reverse drive means for transporting the sheet of recording medium in a reverse direction, said platen roller drive means transporting the sheet of recording medium a limited distance to maintain contact between the sheet of recording medium and at least one of said first and second pinch rollers during movement in the first and reverse directions; and electrical circuit means connected to said thermal printhead for supplying the color component electrical signals to said thermal elements while the sheet of recording medium is transported in the first direction.