Patent GB-748337-A (GB)
Title: Improvements in or relating to equipment for recording or reproducing information on an elongated recording medium
Inventor: BREWSTER ARTHUR EDWARD
IPC: G11B15/34
Filed: 1952-03-06
Abstract: 748,337. Telegraph receivers. STANDARD TELEPHONES & CABLES, Ltd. March 6, 1953 [March 6, 1952], No. 5875/52. Class 40 (3). [Also in Group XX] Telegraph apparatus comprising an elongated recording medium advanced by a driving sprocket engaging evenly spaced perforations includes an arrangement for detecting a defect in the driving arrangements or a breakage of the tape, which comprises a second sprocket rotated by the medium and includes means for detecting a difference between the peripheral speeds of the sprockets. In the diagrammatic arrangement, Fig. 3, the driving sprocket 2 operates an eccentric 26 and a ratchet-and-pawl mechanism 25 to rotate a gear wheel 22, and the second sprocket 5 driven by the tape 1 similarly actuates a second idler gear wheel 23, the wheels 22, 23 meshing with gear wheels 20, 21 and being supported by a yoke member 29. If the sprockets 2, 5 rotate at substantially equal speeds, the yoke member remains stationary, but a defect in the driving arrangement or a breakage of the tape results in unequal speeds of the idlers 22, 23 and movement of the yoke member to the right to close contacts 24 of an alarm circuit. The shaft carrying the sprocket 5 is coupled by discs 15, 14, 13, 12, Fig. 2, to a coiled spring 11 connected to a pin on a hub 7 rotatable on the shaft, and carrying one end of a coiled spring 6 attached to a fixed pin 8. At the commencement of recording, the pin 16 on the disc 15 engages the member 17 to hold contacts 18 of the start circuit closed. Soon after the tape has engaged the sprocket 5, the contacts 18 open to interrupt the initial driving circuit, and for the recording operation a circuit is completed independently of the contacts 18. The employment of the discs 12 ... 15 with the oppositely-directed projections allows the tape to be back-spaced without driving the sprocket 5. Each backspacing operation energizes a magnet 30 the movement of the armature initially rocking a pawl link 31, mounted on a slidable rod 36 associated with a dash-pot 37, into engagement with a notch in a feed wheel 32. The initial movement of link 31 opens contacts 33 so that a retaining pawl 34 is released and the further movement of the armature moves the engaged link 31 and rod 36 to the left. When magnet 30 is de-energized the armature moves to the right disengaging the pawl 31 and closing contacts 33 which effect the re-engagement of the retaining pawl 34. In a modified arrangement, Fig. 1 (Comp.), a motor 42 drives through a worm 43 and worm wheel 44 and clutch 45 a shaft 48 carrying the driving sprocket 2 and a gear 47 meshing the gear 20. The driven sprocket 5 is coupled by a spring 6 to a sleeve 50 carrying a gear 51 meshing with a rotationreversing gear 53 driving the gear 21. The gears 20, 21 drive respective intermeshed pinions 22, 23 mounted in a yoke 40 which moves to the left to close contacts 24 when the speed of the sprocket 5 is different from or less than that of the sprocket 2. A braking lever 55 normally held in a raised position moves into engagement with the sleeve 50 when a lever 57 is actuated against the action of spring 58 by the cover or lid of the apparatus at the beginning of the recording operation.