Abstract: A daisy wheel printer having a platen, a translatable carriage, a pair of parallel support rods for the carriage, a pressure roller control mechanism, and electrochemical dirve mechanisms for the carriage and the platen has a unitary cast base member incorporating all of the support members required for these elements. The unitary base member also integrally incorporates a support platform for the electrical power components, a separate integral chamber for the electronic control components, and a thermally conductive heat sink for conducting away heat generated by the electrical components.The unitary base member also provides electromagnetic radiation shielding and static discharge protection without the need for additional shielding or ground components.The carriage assembly for the printing element includes a one piece die cast lower support brace, and an upper carriage assembly incorporating the detachable ribbon cartridge drive mechanism and a simple one piece ribbon latching device.

Abstract: In a rotary printer control system, a dual mode servo for controlling the velocity and position of a rotary print wheel and a print wheel carriage is normally operated at a relatively high gain value. When the servo is switched from the velocity mode to the position mode, the length of time the servo remains in the position mode is monitored and, if this exceeds a predetermined maximum time period, the gain of the servo loop is switched to a relatively low value in order to reduce oscillations of the print wheel or carriage about the HOME position. The gain reduction is accomplished by inserting a supplemental R-C network in parallel with the high gain R-C network, and the range or ratios of the relatively high gain to the relatively low gain values is from about 10 to about 30.

Abstract: In a dual mode servo for a rotary printer control system for controlling the velocity and position of a rotary print wheel and a print wheel carriage, the analog counterpart of a digital desired velocity multibit character is generated by a bidirectional digital to analog converter so that the analog desired velocity signal has a maximum value range lying both above and below a zero reference level, thereby eliminating the need for additional analog level converting circuitry.

Abstract: A speed normalization circuit for eliminating the need to fine tune a servomechanism, such as a daisy wheel printer, after manufacture, for example, in order to compensate for speed variations caused by tolerance variations throughout the manufacturing process and evidenced by variations in the actual print wheel speed and the actual carriage speed, is disclosed. In operation, when a restore sequence is called for (power up, remote restore, cover open/resume, check/resume), the carriage is restored to the leftmost home position and is then stepped three times by an identical amount (twelve increments, 1/120 of an inch per increment). The average value of the actual carriage speed for these three movements is determined and a compensation value is selected. If the carriage speed is too slow, the nominal speed value stored in a read only memory look-up table is incremented by a fixed value (i.e.