GB1254498A - Printing hammers - Google Patents

Abstract

1,254,498. Selective printing. D. V. G. BERRY. 3 Sept., 1970 [9 Aug., 1969], No. 39953/69. Heading B6F. Hammer impression.-A travelling print hammer 1 is mounted on a carriage 2 by one or more leaf springs 3. An electromagnet 5, 6 extends the full line length and rocks the hammer against the force of a cantilever spring 4 fixed to the carriage 2. Upon de-energization of the electromagnet, the hammer is initially impelled by the spring 4 and then moves under its own momentum to cause impact. An adjustable stop (not illustrated) mounted on the carriage 2 limits the hammer travel on its cocking stroke and is set to maintain a small clearance between the end of the hammer and the base of the yoke 6 of the electromagnet. This adjusts the impact force and prevents friction between the hammer and the electromagnet as the carriage moves line-wise. The carriage is guided on one or more rails 7 and is moved by such means as a belt drive from a stepping motor or a pair of electromagnetic clamps acting on a continuously rotating belt. An additional electromagnetic clamp may act on a belt connected to the hammer carriage, the same belt also containing information indicating the position of the carriage. In an alternative embodiment (Figs. 2 and 3), the electromagnet has an E-shaped yoke and the plastics carriage 2 is grooved to ride along the end of the E. The hammer (1) carries a magnetic plate (8) mounted in an aperture in the carriage which supports pillars (10) and (11), the pillar (10) carrying the two leaf-springs (3). The pillars also carry respective impeller springs (4), the free ends of which abut projections (12) of the hammer in its cocked position. The springs 4 come out of contact with the projections during travel of the hammer to its printing position.