Patent GB-173807-A (GB)
Title: Improvements in and relating to printing telegraph receivers
IPC: H04L19/00
Filed: 1920-08-09
Abstract: 173,807. Alexander, A. E., (Newsprinter Corporation). Aug. 9, 1920. Electric driving- mechanism; keyboard operators.-In a typeprinting telegraph a standard typewriter mechanism forms part of the receiver, and power is supplied through a constantly rotating shaft, the line currents merely releasing, stopping, or generally controlling the action of the motive power. A number of plungers is helically disposed about an axis, and can be rotated to bring a selected plunger under a bar which, when depressed, moves the selected plunger to operate a corresponding type-bar to print a selected character, perforate paper, &c., the type-bar mechanism being of standard type. A paper carriage 4 slides on ball-bearings and carries a platen 6 and paper supply roll 7. Type-bars 9 are operated through links &c. from levers 10. A rotatable drum 11 carries helically-disposed plungers 13 corresponding with the various characters to be printed. The plungers are normally held by springs with both ends of each plunger projecting from the cylinder, one end being wider and the other narrower than slots formed in a bar 34. The drum is rotated to bring the selected plunger with its wide end immediately under the bar 34. Depression of the bar then operates the selected plunger, causing the other end of the plunger to engage a lever operating the corresponding lever 10. A constantly driven shaft 62, Fig. 14, drives a differential gear 18. One side of this gear tends to drive, through friction-member 19, the spindle of drum 11. A transmitter of known type has a drum 32<a> with pins corresponding in number and arrangement with the plungers 13. Drum 32<a> is driven through friction-gear 35, and may be arrested in selected position by means of a selected stop projected into the path of the corresponding pin. As the drum rotates, alternating current impulses are sent to line through a commutator 36. These impulses cause the polarized armature of a magnet 38 to effect a corresponding number of half-oscillations. The armature is formed with a forked member 23 engaging a starwheel 22 controlling rotation of the drum 11, which is thus rotated a corresponding number of steps. When drum 32<a> is arrested, the last impulse continues as a direct current and holds the armature, so that rotation of drum 11 is arrested with the selected plunger under bar 34. Differential gear 18 tends to drive a shaft 38 through friction-member 50, but rotation of shaft 38 is prevented by a detent device 37, 40, 42. When the direct current above-mentioned comes over the line, a magnet 45 which does not respond to alternating current (owing to high impedance) attracts its armature 46 secured to a shaft 44, and so releases the detent mechanism, allowing shaft 38 to rotate and depress the bar 34 through eccentrics 51. The selected plunger is thus depressed and operates a corresponding lever 55 which in turn operates the corresponding type, letter shift, spacing, or other lever 10 of the typewriter. Carriage-returning mechanism.-The carriage is returned by power derived from the shaft 62. A clutch member 68 riding loosely on the shaft is integral with or connected to a pulley on which is wound a cord 70 secured to the carriage. A differential gear housed in a drum 77 is driven from shaft 62. One member of this gear is secured to a fly-wheel 86. The other member is secured to a sleeve on which is mounted a second clutch member 73 slidable upon but rotating with the sleeve. Member 73 has a peripheral groove engaged by a fork-lever 133. Members 68, 73 have pins 74 which can be brought into or out of engagement by movement of member 73. When these pins engage, the resistance to rotation of member 73 due to the carriage feed spring causes fly-wheel 86 to accelrate, so that the carriage is returned under the inertia action of the fly-wheel, without undue shock. The return mechanism is brought into operation by allowing the drum 11 to move more than one complete revolution without operation of the printing shaft 38. A disc 120 on the spindle of drum 11 has a spiral groove in its face. A lever 123 pivoted at 124 has an extension 125 capable of slight movement towards and away from the disc 120, so that a pin 129 on this extension can be engaged with, or removed from, the spiral groove. The pin is disengaged each time the shaft 38 is operated, by means of a cam disc 137 on the shaft engaging the upper end of the extension 125. When the drum 11 is rotated without operation of shaft 38 the pin rides in the spiral groove and rocks lever 123, which in turn operates the clutch member 73 through a rod 130 and the lever 133. A lug 121 on disc 120 also engages a projection on extension 125 and arrests rotation of the drum 11 at a predetermined position. This mechanism allows a number of receivers to be brought into unison when desired, by operation of the transmitter. Line-spacing mechanism.-An electromagnet 87, when energized, attracts its armature 90 and raises an extension 92. This occurs when the carriage has been returned, in which position the extension 92 is under an arm pivoted on the platen spindle and carrying a pawl which engages a ratchet-wheel secured to the spindle. The circuit of the magnet is closed by a contact carried by the carriage and engaging a fixed contact. An additional contact is also provided in circuit with the magnet and operated by one of the plungers 13 and a corresponding bar 10 under control of the transmitter, so that when the carriage is in the returned position any desired number of additional line-space movements can beeffected.