Patent GB-367012-A (GB)
Title: Improvements in electric clocks and phonic motors
IPC: G04C3/16
Filed: 1930-11-11
Abstract: 367,012. Electric clocks. GRAHAM, R. P. HOWGRAVE-, 21, Worsley Road, Hampstead, London. Nov. 11, 1930, No. 33969. [Class 139.] In an electric clock, phonic motor or like apparatus a reciprocating member and a continuously rotating member, carry magnetic bodies arranged to move in a common magnetic field, the reluctance of the magnetic circuit being rhythmically varied by the movement of the vibrator and the rotating member to cause them to move synchronously. An invar steel pendulum 2, Fig. 1, suspended by strips 6 carries a bar 3, of soft iron or other magnetic material, adapted to swing between soft iron yokes 4, Figs. 1 and 2, carried on a frame 5, slidable on a guide 7 and suspended by invar steel bars 8 and brass rods 9 to correct for temperature variations. The yokes 4 carry windings 21, and between their lower polepieces 11, Fig. 2, rotates a soft iron bar 12 attached to a shaft 13 having a flywheel 14. Mounted on shaft 13 is a cylindrical surfaced wedge-shaped contact strip 15 which engages a spring contact strip 16 mounted to slide vertically on a post 17 under the adjustment of a screw 18 to vary the time of contact per revolution. To alter the time during a revolution at which this contact takes place the post 17 is mounted on a radial plate 19, Fig. 3, adjustable about the pivot 13 by means of a screw adjustment 20. Operation. To start this master clock, the pendulum is swung and the disc 14 rotated by hand until they move synchronously, when the bar 3 moves into line with the yokes 4 as the bar 12 moves into line with the polepieces 11 of the yokes 4. The windings 21 are fed from a constant voltage supply through the contact device 15, 16 and when this is adjusted so that the coils are energized for the short period when the bars 3 and 12 are passing through their respective optimum positions of magnetic field the pendulum and rotor will continue to move synchronously. In another embodiment, Figs. 6 and 7, a reed a securely clamped at c carries an iron mass b adapted to vibrate between polepieces e of yokes e, f bearing windings j, the rotor carrying salient poles g rotating between the poles f. The contact device for the coils j comprises a commutator i on the rotor shaft h. A similar contact breaking device m on shaft A may energize magnets k synchronously with coils j to supplement the effect of the latter. Alternatively k and j may be energized slightly out of time with each other, in which case the magnets k are preferably situated to the side of the centre of swing of reed a, interaction between the magnets k (symmetrically placed with respect to the plane of oscillation of reed a to prevent torsional stress) and armature u maintaining the vibration amplitude constant. In all forms of the invention the drive may be applied to the vibrator by mechanical, electrical or electromagnetic means, but a mechanical drive is preferably applied to the rotor. Alternatively, the energy of the yoke electromagnets may provide the driving power. When the vibrator or rotor is driven the magnetic circuit elements may comprise permanent magnets. In this case the vibrator may be driven by an amplitude regulating magnet such as k, Figs. 6 and 7, displaced to the side of the centre of swing of the vibrator and energized by a contact on the rotor shaft, the yoke coils being dispensed with. Any suitable vibrating system may be used, and suitable means for maintaining constant the time of oscillation provided. Magnetizing coils may be provided on both vibrator and rotor. Two methods of regulating the voltage supply are described. According to the Provisional Specification the constant voltage may be obtained from a suitable dynamo generator operated by a slave motor, a number of which besides secondary clocks, indicators and other time controlled apparatus may be driven by current impulses derived from contact devices on the rotor shaft of a master clock as described.