Patent GB-874319-A (GB)
Title: Improvements in or relating to selector mechanism for telegraphic printers
IPC: H04L17/26
Filed: 1958-04-09
Abstract: 874,319. Printing telegraph receivers. TELEPRINTER CORPORATION. April 9, 1958 [April 10, 1957], No. 11318/58. Class 40(3) In a telegraph printer in which a type-carrier is moved to select the character to be printed by the selective operation of members actuated in accordance with elements of a signal code combination by cams rotated from a main shaft through half a revolution by clutches and comprising first and second pivoted stop levers disposed on opposite sides of the clutch device to arrest movement of the cam at half revolution intervals, the stop levers are urged towards their release position by resilient means connected to portions of the levers extending beyond their pivots and a latch member disposed in a plane generally transverse to the extensions, pivoted to tilt about an axis extending collaterally with the cam shaft and operated by magnets disposed on opposite sides of the axis of the latch, is moved to a first position in which it blocks one stop lever against movement whilst releasing the other, and to a second position in it blocks the second stop lever against movement whilst releasing the first. The arrangement is applied to a printing telegraph receiver as shown in Specification 799,956 in which the axial and rotational positioning of a type-carrier is effected by pulleys carried on arms which are moved to alternate positions by cams selectively rotated through half a revolution, in response to the elements or impulses of a received code combination, by the clutches in combination with the stop levers and an associated cam controlling the sequential operation of the respective clutch devices. In the diagrammatic arrangement, Fig. 19, the pair of stop levers 450, 458 have extensions 452, 462 co-operating with the associated sequence cam 468 and extension 454, 464 connected by a spring 466 and provided with screws 488 engaging rectangular plates 478, 480 pivoted at 482, 484 and connected by a spring 486. The lower edges of the plates 478, 480 are associated with the ends of the pivoted armature 470 operated by two magnets 474, 476. With the magnet 474 operated, the plate 478 is blocked against movement so that stop lever 450 cannot move when the engagement of its extension 452 with the drop in sequence cam 468 would permit movement. With magnet 476 simultaneously de-energized the stop arm 458 can rock about its axis 460 when its extension 462 engages the drop in the sequence cam 468, and if its upper end is engaged with a tooth on the clutch control member, the main shaft is released for half a revolution so that the associated cam can operate the co-operating arm carrying its pulley. In a modified arrangement, some of the stop levers are controlled by latch plates associated with one latch, whilst the remainder are under the control of separate latch plates and a second latch. In the arrangement shown in Fig. 2 the stop levers 424, 426 and other stop levers (not shown) are controlled by an outer latch 490, as described for the diagrammatic arrangement of Fig. 19, with latch plates 494, 496 pivoted at 498, 500 and engaged by set screws 524 in the extensions 430, 436 of the stop levers 424, 426. The remaining stop levers, exemplified by levers 424<SP>1</SP>, 426<SP>1</SP> of Fig. 17, are controlled by latch plates 510, 512 pivoted at 514, 516 and associated with a latch 506 and operated by magnets 518, 520. All the stop levers are formed of two interconnected parts as indicated in Fig. 2. The portion 424 which is in engagement with the tooth 422 of the clutch disc 420 is formed with an ear 530 connected by a spring 538 to an ear 534 formed on a second portion having the arm 430 integral with the extension 532 which engages the drop on the sequence cam 442. The arm 430 carries a projection 540 engaging the portion 424 which is positively moved when the arm 532 engages the drop in the cam 442, but, should the circumstances arise, the arm 424 can be rocked counterclockwise relative to the composite arm 430, 532 with the extension of the spring 538. In similar manner, the upper arm 426 is positively rocked by the interconnected portion 436 and the arm engaging the sequence cam 442, but can yield, when forced, by the extension of the interconnecting spring similar to spring 538. The latches 490, 506 have rectangular central portions disposed opposite the pole faces of two associated pairs 502, 504 and 518, 520, of U-shaped magnets and have reduced end portions carrying pieces of hardened tool steel co-operating with the ends of the latch members 494, 496, Fig. 2 and 510, 512, Fig. 17. The outer and inner latch plate assemblies 494, 512 which are mounted on the shafts 498 and 516 are shown in Fig. 18, the former comprising narrow portions 622, 624 engaged by stop lever extensions 630, 632 and a wide portion 620 engaged by stop lever extension 628 and carrying an extension associated with the latch 490, whilst the assembly 512 carries two narrow portions 608, 610 and a wide portion 606 haveing an extension coacting with the latch 506. The latch plates carry extensions 612, 626 for attachment of the springs 526, 528. Specifications 813,081, 833,941 and 833,942 also are referred to.