Patent GB-1419265-A (GB)
Title: High speed printer
IPC: B41J2/245
Filed: 1972-11-23
Abstract: 1419265 Printers CENTRONICS DATA COMPUTER CORP 23 Nov 1972 [2 Dec 1971] 54163/72 Heading G4H [Also in Division B6] A character selection and decoding control system is provided for a dot matrix printer using a plurality of print wires spaced along the print line so that each deals with a respective fraction of it. In a printer, a carriage movable transversely to the direction of document movement, and thus along the print line, holds P print wires spaced along the print line, together with their drive coils, the wires being spaced apart so that each prints 1/Pth of the line and the carriage reciprocates through only this fraction of the line length. Each character is built up as a matrix of dots. Thus a given wire prints the top row of its first character, dot by dot, then the top row of its second character, &c. When the top row of each character has been printed, the document advances and the carriage returns so that the second row of each character can be printed, and so on. The paper can alternatively advance continuously, in which case the carriage moves at an angle to compensate. In one embodiment of this, rollers on the carriage move up inclined surfaces, and in another the carriage rides between two inclined parallel rails, cylindrical bearings being provided between grooves in the rails and in the sides of the carriage. In the latter case, the carriage is reciprocated by a motor-driven cam. In one embodiment, the characters to be printed are passed in turn, parallel-by-bit (optionally after conversion from serial-by-bit) into a recirculating shift register which holds the entire line. Successive groups of P characters are supplied in turn to a set of P character generators, one character of the current group to each generator. The generators are conditioned by a row counter to provide (parallel by bit) the appropriate row of the matrix representations of the P characters of the group, each such row being serialized under control of a column counter to feed the respective wire drive coil. Timing is provided by sensing a scale to produce pulses as the carriage moves, and by limit switches for the carriage. Circuits to detect control codes (sound bell, delete data, line feed, carriage return) in the incoming data stream are provided fed in parallel with the shift register. In another embodiment, the recirculating shift register feeds one character at a time in the appropriate order (see below) to a single character generator conditioned according to the column required of the character matrix to provide this one column, one bit of which is then selected according to the row required and entered into a P-bit buffer register at an appropriate position. The buffer register is filled in this way with a corresponding bit of the matrix representations of the P characters currently being printed, the register contents being read out together to control the P wire drive coils when a pulse arrives from sensing the carriage-position scale (indicating registration). Characters can be printed with double height, by printing each row of the matrix twice. The apparatus may be used to plot curves, the shift register being loaded from a core matrix store.