GB586086A - Synchronizing mechanism - Google Patents

Abstract

586,086. Picture transmission systems; synchronous movements. FINCH, W. G. H. Nov. 10, 1944, No. 22220. Convention drate, Jan. 19. [Class 40 (iii)] [Also in Group XXXV] In a picture transmission system, synchronism between the receiver and transmitter drums is maintained by operating the receiver drum at an average speed which is the same as that of a synchronous motor which is driven by signals continuously produced at the transmitter and transmitted to the receiver and acting on the motor. Fig. 1 shows the circuit of a receiver in which a recording drum 21 is brought into operation when incoming signals energize relay 45. This energizes relay 66 and rocks lever 61 to move pinion 75, Fig. 2, into engagement with crown-wheel 81 of the differential combination 75, 81, 72. The circuit of the D.C. driving motor 24 for the drum is also closed. Pinion 75 is keyed on the shaft 74 of motor 24 and pinion 72 is rigid with the shaft 71 of a low power synchronous motor 37 which is driven by synchronizing oscillations derived from the signals. If the speed of pinion 75 and drum 21 departs from synchronous.speed, wheel 81 rotates and moves by its spindle 82 and arm 93, gear-wheel 94 loose on shaft 71. This drives a pinion 96, the spindle 97 of which carries the moving arm of a rheostat in the field winding of motor 24. In the alternative arrangement of Fig. 4, spindle 97 carries a contact arm 111 having a contact piece 113 moving between contacts 114, 115. The field circuit of motor 24 includes a resistor 116 and with this in circuit the motor runs too fast so that contact piece 113 is moved to engage contact 114 as well as 115, whereupon relay 122 is energized to short circuit resistor 116 and close a holding'circuit through 115. Motor 24 then runs slower than synchronous speed and piece 113 moves clockwise till it disengages both contacts 114 and 115, whereupon relay 122 releases and resistance 116 is again put into the motor circuit and the motor runs fast again.