Pressure spring for a thermoprinter

Claim 1

A thermoprinter comprising a supporting frame; a printing plate mounted in said supporting frame and including a line of typing means of an electric resistance material for printing line by line on a thermosensitive recording strip and means for selectively supplying heating current to said typing means; pressing means for prEssing said strip into contact with said printing plate during the printing of each line, said pressing means including a holder connected with said supporting frame, a leaf spring supported at its end in said holder in operative relation to the printing plate and extending in the line direction thereof with such a curvature in its unloaded condition that a convex lateral surface of the leaf spring faces the printing plate, and means for locking said holder to said supporting frame in a position in which said leaf spring is pressed against the printing plate with a substantially uniformly distributed pressure in the length direction of the leaf spring; and an advancing mechanism for stepwise advancing said strip across the printing plate, said mechanism including actuator means for applying local bias forces in the direction away from the printing plate in points on said leaf spring situated a short distance from either end thereof supported in said holder, whereby the leaf spring is relieved from pressure contact with the printing plate when said strip is to be advanced.