Patent GB-163773-A (GB)
Title: Improvements in or relating to transmitters for electric recording and signalling systems
IPC: G08B5/22
Filed: 1920-02-20
Abstract: 163,773. Wilson, J. S., (Buckley, A. B.). Feb. 20, 1920. Tell-tale apparatus for signalling liquid levels comprises a rotatable member which, when displaced from its normal position by the movement to be signalled, operates one of two electric impulse transmitters and is thereupon restored step by step by electric impulses which simultaneously affect the receiving apparatus, and which continue to be sent until the rotary member has regained its normal position. If the current fails, the apparatus automatically signals a -correct reading as soon as communication is reestablished. In the liquid-level apparatus shown, a drum 2 is rotated, as the liquid rises or falls, by a metal tape 1 attached to a float, the rim 61 and counter 62 being graduated to indicate the level. The drum 2 is geared to one wheel 6 of a differential gear, so that a rotation of the drum causes a rotation of the disc 14. This disc is then restored to its normal position by electric impulses actuating the other wheel 10 of the differential gear, in the following manner. The clock-work or other motor 45 is connected through a differential gear 48a, 48b and other gear wheels to two flyarms 44, 44a, Fig. 2, which are normally prevented from rotating by the projecting rim 15 of the wheel 14, but can rotate independently of one another when released. The rim 15 is cut away over part of its circumference, so that, when the liquidlevel rises or falls one unit, either the arm 44 or the arm 44a is released by the rotation of the disc 14 and is rotated about the axis 54 or 54<a> by the motor 45. The rotation is retarded by a vane 58 or 58a, and during each revolution a projection 59 or 59<a> makes contact with a spring 60 or 60<a> so as to send an impulse to line and at the same time to energize one or other of two electromagnets such as 24. Each electromagnet actuates its appropriate wheel 17 or 18 through ratchet mechanism shown in Fig. 3. Thus either the wheel 17 or the wheel 18 is actuated according as the water rises or falls. These wheels form part of a differential gear and serve to rotate the sleeve 11 and wheel 10 and so to restore the plate 14 to its normal position, when further rotation of the fly-arm 44 or 44a ceases. Provision is made for the case of a sudden rise or fall of liquid-level great enough to rotate the plate 14 through more than half a revolution. To this end the spindles 54, 54<a> of the fly-arms are mounted on frames 39, 40, which can be rocked about pivots 41, 42, by moving the rod 38, so that one of the fly-arms 44, 44a may be free to rotate and the other be obstructed even when the disc 14 has rotated through more than hall a revolution. The rod 38 is moved to rock the frames 39, 40 by a pin 37 which engages in the steep part 37a of a groove formed on the face of a scroll-plate 36, which is geared down from the plate 14. Impulses are thereupon sent out until the scroll plate 36 and frames 39, 40, regain their normal positions. In a modification, the rotating fly-arms 44, 44a, are replaced by pivoted arms provided with time-lag devices. These arms on being released close the electric circuits described above, and are thereupon retracted by electromagnetic means. The' ratchet-and-pawl mechanism referred to above comprises a lever 22, Fig. 3, which is pivoted at 25 and bears a pawl 21 and the armature 23 of the magnet 24. The pawl 21 under pressure of the spring 43 rotates the wheel 18 one step when the magnet 24 is deenergized, and is then locked against the wheel by the stop 21<a>. So long as the magnet is energized, on the other hand, the wheel 18 is locked by a dog 27 on a lever 26, the stud 28 of which engages in a notch 29 in the lever 22. According to the Provisional Specification, the rotation of the fly-arm spindles 54, 54a may restore the disc 14 mechanically, and the impulses sent to line may be positive for one fly-arm and negative for the other, or may be sent over separate circuits.