GB821047A - Improvements relating to keyboard-operated devices - Google Patents

Abstract

821,047. Typewriters &c. DIRKS, G. April 23, 1957 [Jan. 23, 1956], No. 33508/55. Class 100(4) [Also in Group XL(b)] A record controlled keyboard-operated machine has a photo-electric device which stops the feed of the record tape if a key or type, lever does not return to a predetermined position, so that jamming of the keys cannot occur due to signals being sensed faster than the keys can operate, a clearing bar which pushes back jammed keys and means for moving, the record, tape back one step, so that the section of record not printed due to jamming may be sensed again. The light beam may be interrupted by either the type levers or the key levers. Pulses from the photo-cell are fed to . the control arrangement shown in Fig. 2, which includes a flip-flop 9, an amplifier 10, a gas discharge stage 11 and a mechanical portion 12. A positive pulse is generated when the light beam is interrupted, which causes gas discharge tube 25 to fire and energize relay 28 to close contacts 28<SP>1</SP>. Closing contacts 28<SP>1</SP> energizes relay 31 which moves armature 32 away from arm 33 so that shaft 34 can turn roller 35 to advance the record tape one step. A negative pulse is generated as the light beam is interrupted by the key returning to rest, this resets the circuit ready for the next positive pulse to initiate another step forward of the record tape. Fig. 4 shows an arrangement for continuous movement of the record tape in direction 46a. When the tube 51 fires, under control of photo-cell 45, relay 54 holds contact 54<SP>1</SP> in position a to energize the clutch of 55 and rotate roller 58. If the light beam is interrupted for longer than a pre'-determined time;"relay 54 becomes de-energized and contact 54<SP>1</SP> moves to position b and de-energizes the clutch and operates the brake of 55. Jammed key levers are reset by lever 63, Fig. 5, moved in direction 67 by armature 64 and lever 65 and magnet 66 when the light beam is interrupted for longer than normal. When the latter happens relay 54 is not energized, therefore contact 54<SP>2</SP> is closed and 54<SP>3</SP> is open, allowing capacitor 68 to charge through resistor 69. This voltage on capacitor 68 fires tube 73 and current flows through magnet 66. At the same time pin 77 closes contacts 78 which energizes magnet 80 to move armature 82 away from arm 83 and allow one rotation of shaft 84 in direction 89. During this rotation tape 49 is moved back one step so that the same portion may be sensed by means 60 for a second time. No signals are sensed during reverse movement of tape 46.