Thermal printer

Claim 1

In a thermal printer including a thermal head movable in a scanning direction along a platen supporting a recording paper thereon, an ink ribbon having a thermally transferrable ink layer interposed between said thermal head and the recording paper for effecting printing by application of heat from said thermal head to said ink ribbon to transfer ink from the ink layer to the paper, a ribbon guide roller movable toward and away from said platen for guiding said ink ribbon to be pressed toward the paper and separated therefrom on a downstream side of said thermal head with respect to the scanning direction of said thermal head, and operating means for operating said ribbon guide roller for an erasing operation so as to move it in pressure contact for holding said ink ribbon in contact with the paper on the downstream side of said thermal head to allow ink on the paper to bond to the ink layer and, subsequently, to be lifted off from the paper, the improvement wherein said operating means for said ribbon guide roller comprises: a pivotable arm (33) supporting said ribbon guide roller on one end portion and having a second end portion thereof which is movable so as to pivot said first end portion; a pivotable lever (25) having a first portion, and a second portion which is actuatable so as to pivot said first end portion; a solenoid (19) connected to said second portion of said lever which is actuatable ON and OFF for pivoting said first portion of said lever to a pivoted position and for releasing said lever back to a release position, respectively; an arm driving spring (26) connected between said second end portion of said arm and said first portion of said lever for transmitting the force of said first portion of said lever, when pivoted to said pivoted position by actuation of said solenoid ON, through a tensile spring constant of said arm driving spring to said second end portion of said arm, whereby said ribbon guide roller on said first end portion of said arm is pressed against the ink ribbon and the paper on said platen through the tensile force of said arm driving spring, which dampens the transmitted force and ensures that said ribbon guide roller is gradually brought into pressure contact with the paper in order to avoid cutting said ink ribbon and to accomodate different thicknesses of paper.