GB1212011A - Improvements in and relating to telegraphic printing devices employing a type wheel - Google Patents

Abstract

1,212,011. Selective printing. EXCHANGE TELEGRAPH CO. Ltd. 12 Jan., 1968 [9 Jan., 1967], No. 1207/67. Heading B6F. [Also in Divisions G4-G6] A single type wheel 3 in a telegraphic tape printer is rotatable for type character selection by a stepper motor 2 according to a coded electrical input. The motor shaft has six discrete positions and is geared to the type wheel 3 in a 6À1 ratio to define 36 positions of the type wheel. Hammer impression mechanism.-A print hammer 5 is actuated by a solenoid 4 through a rocker lever 6 and reset by a second solenoid 8. Paper feed arrangements.-Tape is fed to a printing position by an escapement mechanism comprising a pallet 14 oscillated by two solenoids 9 acting on a rocker lever 13 and coacting with an escapement wheel 12 coaxially mounted on a shaft A with a friction feed roller 11. The feed roller 11 coacts with a spring-loaded pressure roller 10. Ink-ribbon mechanism.-An ink ribbon 7 is driven by a synchronous motor 16 through a gear mounted on a pivoting lever (not shown), the gear engaging either of two gears, one associated with each ribbon spool 15. If a spool becomes exhausted, tension in the ribbon stalls the motor, which then rotates in the reverse direction, the lever pivoting so that the gear mounted thereon engages the alternative spool gear, as described in Specification 1,088,603. Electrical control.-The electrical input co m prises sinusoidally oscillating current, the motor 2 stepping once for each time the current becomes zero. Pauses in the current oscillation at maximum or minimum current trigger electronic circuitry which actuates the print hammer solenoids in turn after a delay to permit the motor 2 to settle, and after a further delay, actuates the paper feed solenoids. The machine may idle, owing to a continuous train of sinusoidal pulses, for 1-5 seconds, after which the stepper motor is automatically switched off with the type wheel positioned so that a "blank" character is in the printing position. The positioning of the type wheel is achieved by a photo-cell 17 activated by a bulb 19, light being cut off by a lug 18 in the " blank " character position. The photo-cell also acts to inhibit the action of the print hammer when a space is required.