Abstract: A ribbon supply apparatus including a support in which a ribbon supply spool and a take-up spool are rotatably mounted. The supply and take-up spools and the support are designed so that these spools can be mounted in the support in only one way, the correct way. The ribbon is supplied on a tubular core member which is mounted on a cylindrical member which is part of the supply spool. The ribbon supply spool has a large gear thereon which is used in a braking and feeding mechanism which is used to incrementally feed the ribbon to a print station associated with the apparatus. The ribbon take-up spool is identical to the ribbon supply spool, but the ribbon take-up spool is mounted in a reversed manner when compared to the ribbon supply spool. A driving gear, coupled to the large gear on the take-up spool is part of the braking and feeding mechanism which also includes a "dancer arm". The dancer arm controls a loop of ribbon which is fed to the print station.

Abstract: A method and apparatus for controlling the adjustment of printer hammers which impact against an associated moveable member on which characters are present. Each hammer includes a coil which is energized at the appropriate time, taking into consideration the "flight time" of the associated hammer. These flight times are determined by detecting a change in the back EMF in the energizing current to the coil. These flight times are averaged to obtain a running average of the last several successive flight times (for each hammer in the printer), and successive timing pulses from a timing disc are used to obtain an almost instantaneous velocity of the moveable member (like a printer drum) just prior to a character to be printed. The last several successive flight times are stored in a non-volatile RAM of a controller to enable the printer to be ready at a next start up.

Abstract: A stepping motor has an attached encoder which provides automatic commutation point alignment for maximum efficiency and torque during closed-loop operation. Novel use of a fine line encoder along with a phase mapping circuit permit shaft/rotor alignment of the stepping motor with minimum commutation errors, and without the need for manual adjustments.

Abstract: An apparatus and method are disclosed for determining the position and angular velocity of a print drum. The apparatus includes a detector that is positioned proximate to the drum, and a processor coupled to the detector. The drum has a cylindrical body with a plurality of alphanumeric characters and a sequence of marks, including an index mark and a plurality of timing marks uniformly disposed about the circumference of the body, the timing marks being in relative alignment with the characters such that each character is associated with a pair of timing marks. The index mark is used to designate a start or reference location on the body.