Dot matrix line printer

Abstract

A dot matrix line printer comprised of a main frame assembly and a shuttle frame assembly hinged thereto for limited pivotal movement around a horizontal hinge axis. The main frame assembly carries a paper drive subassembly and an adjustable platen subassembly. The shuttle frame assembly carries one or more hammer banks and a shuttle drive motor for shuttling each bank to move the hammers thereof along a print row extending across the width of the paper parallel to the front face of the platen. By pivoting the shuttle frame assembly up and away from the main assembly, ready access is afforded to the paper path for loading and to the hammer banks for servicing. Each hammer includes a hammer element mounted on the free ends of first and second spaced parallel leaf springs for linear movement toward and away from a paper to be printed upon. The parallel leaf springs are anchored at one end and biased to impact the hammer element against the paper. A magnet is provided for producing a magnetic force, via a path including a block of magnetic material sandwiched between the springs, to normally hold the hammer element in a retracted position against a pole pin. A coil wound on the pole pin is energized to null the magnetic field to permit the springs to propel the hammer element against the paper to print a dot thereon. The leaf springs are not relied on to define the magnetic field path through the hammer element, thus allowing springs of nonmagnetic material to be used thereby permitting optimization of their spring properties. A platen is mounted on leaf springs to enable the spacing between the platen and hammers to be varied while maintaining the essential perpendicularity between the platen front face and direction of hammer element movement.