Patent GB-677040-A (GB)
Title: Facsimile transmitters
IPC: H04N1/06
Filed: 1950-08-18
Abstract: 677,040. Copying-telegraphy. STANDARD TELEPHONES & CABLES, Ltd. Aug. 18, 1950 [Oct. 19, 1949], No. 20502/50. Class 40 (iii). In a facsimile transmitter having supporting means and driving means for a rotary scanning drum terminating at each end in a flat disc, each disc has a central recess in its flat face for receiving the supporting means in a readily separable engagement and means is provided on one of the discs within the boundary of its flat face for connecting the disc to the driving means, the driving connection being automatically separated on removal of the drum. Drum construction and driving arrangement. The drum 12 comprises a tubular member of aluminium closed by circular flat discs 13, 14, the upper disc having a bush with a conical recess engaged by the end of a spring-biased positioning member 92 and the lower disc has a recess 18 for the conical end of a driving-shaft 35. An annular channel 19 in the base 14 carries a fixed block 20 engaged in the driving condition by a pin 47 resiliently mounted in an arm 41 located between a collar 37 and a disc 39 secured to the shaft 35. The arm 41 is resiliently connected by a spring 44 to the disc 39 and has a pin 43 engaging a gap 40-40<SP>1</SP> of the disc. The matter to be transmitted is wrapped round the drum with one edge aligned with a reference line 26 and is held in position by garters 25 in the form of coil-springs. A sleeve 52 rotatably mounted on the shaft 35 carries a worm-wheel 53 driven by an electric motor 58 and a ratchet-wheel 54 associated with a trigger 67 controlled by the armature 78 of a phasing magnet. The trigger is carried by an extension of a semi-circular yoke connected by springs to a semi-circular friction washer embracing the sleeve 52. When the phasing magnet is energized the trigger is freed to engage the ratchetwheel 54 and to rotate therewith, the drive of the shaft 35 being effected by the engagement of the trigger with a dog 89 on a collar 90 keyed to the shaft. The magnet is energized by an impulse applied to the transmitter and to the distant receiver by the operator when the drum has been inserted and positioned. Additionally the insertion and positioning of the drum causes contacts 107, 13, to be closed by a member 110 on a collar 94 attached to the member 92. The drum is guided into the scanning position by a dished member 96 pinned to the positioning member 92 and by bent rods 100 converging towards the extremities of the member 96. Optical scanning apparatus and traversing mechanism. The light-source 136, projecting tube 128, pick-up tube 138, photo-electric cell 143 and a small motor driving a light-chopper disc are mounted on a carriage SK carrying a half-nut 165 normally used in engagement with a screw-threaded shaft 162 driven from the motor 58. During the downward movement of the carriage a spring drum 154 is wound up and at the end of the downward travel a projection on the carriage closes contacts 185 so that a solenoid 176 is energized to allow the carriage to be retracted by the spring drum 154. If a short message is to be transmitted, a hole 187 punched in the paper a little below the end of the message allows a feeler 195, mounted on the carriage, to complete a circuit for the solenoid 176 to withdraw the half-nut 165 from the shaft 162. Projections 196 also mounted on a rotatable shaft on the carriage SK move the spring garters 25 during the scanning process, and a rod rotated when the half-nut is moved by the solenoid 176 rotates the feeler 195 and projections 196 clear of the garters 25 during the return movement of the carriage. The phasing magnet is de-energized when the magnet 176 is energized so that the drive of the shaft 35 is disconnected.