Abstract: A reciprocating drive mechanism, capable of producing a substantially trapezoidal velocity profile, reciprocates the hammer banks of a dot matrix printer, or printers in general, at a relatively high frequency (40 HZ), and a high constant velocity (34 to 40 in/sec). Utilizing a set of non-linear springs, the hammer banks are reciprocated at one of the many possible resonant frequencies of the non-linear spring mass system, thus minimizing power consumption. Single action solenoids or a voice coil type motor is servo controlled to compensate for the energy loss due to damping. An optical switch establishes the zero position of the hammer banks at midlength of the travel. A velocity transducer measures the velocities at all positions. By integrating the velocities, the positions at any time of travel is known for proper placement of the print dots.

Abstract: Print hammer apparatus comprising a hammer preferably having a non-magnetic flexure provided with a magnetic hammer head and stylus and held in a normally retracted position by a permanent magnet. A pole piece, for concentrating magnetic flux onto the hammer head, is in magnetic contact with the permanent magnet and defines a slot in which the hammer head is received. The hammer head is separated from the pole piece by a minute air gap. An electromagnet is operable, upon activation, to release the hammer from its retracted position for printing. The unique pole piece and hammer head combination and the use of non-magnetic flexures in specialized forms maximize hammer speed for pre-selected forces at pre-selected retracted distances. Positioning the stylus at the center of percussion of the flexure and alignment of longitudinal axes of hammer head, the pole piece ofthe electromagnet, and the stylus also contribute to superior performance.