GB483378A - Improvements in or relating to time alarm mechanisms - Google Patents

Abstract

483,378. Alarm mechanism. MAW, T. F., and AGAR, M. F. Sept. 29, 1936, No. 26457. [Class 139] A silent alarm mechanism intended to be worn on the person comprises an indicator element which, when released, presses upon the wearer. In the application shown, the alarm mechanism is embodied in a wrist watch, the indicator being a metal loop 12 pivoted on pins 13, 14 and pressed, when released, against the wrist of the wearer by a coil spring 15. The alarm mechanism is situated between the dial 18 and the front movement plate 19. The alarm setting dial 20 is substantially coplanar with the dial 18, is rigid with a ratchet wheel 21, and is frictionally mounted on the hour hand arbor so as to be driven thereby but adjustable relatively to the hour hand for alarm setting. This setting is achieved by repeatedly depressing a plunger 32 which causes a pawl 30 to rotate the ratchet tooth by tooth anticlockwise until the time mark at which the alarm is desired, is beneath the hour hand. The dial 20 and hour hand then rotate together until the hour marks on dial 20 register with the hour marks on the dial 18, and at the moment of registration the alarm is released by the following means. A cam 34 associated with the dial 20 has a point 35 for actuating a member 49, 48 which is controlled by a spring 50 and lugs 51, 52 coacting with lug 53 and shoulder 54 on a bridge 151 fixed to the front plate 19. A notch 47 in member 48, 49 actuates an arm 37 rigid with an arbor 38 which also carries an arm 36 normally latching a lug 41 on the alarm indicator 12. As the dials 20 and 18 become registered with one another at the alarm time, point 35 rocks member 48, 49 counterclockwise, stretching spring 50. Lug 51 comes behind shoulder 54 and lug 52 is raised free of lug 53. At the exact moment of registration, point 35 wipes past point 49 and spring 50 causes lug 51 to move free of shoulder 54, after which the spring moves part 48 slidably upwards along bridge 151 so that notch 47 rocks parts 37, 38, 36 whereby the latter releases lug 41 on indicator 12 and the latter is pressed by its spring 15 against the wearer's wrist. To reset the mechanism, indicator 12 is raised against spring 15 so that a piece 46 on it restores arm 36 and therefore parts 37, 47, 48, to latched position. The lug 41<1> and piece 46 are on a plate 42. which is slidably mounted on indicator 12 by pin and slot 44, 45 so that by sliding this plate 42 downwards, the lug 41 is locked in a recess 43 and the indicator can not be released. In a modification, Figs. 8 and 9 (not shown), the ratchet wheel 21 is subtantially larger than the alarm setting dial 20 and the indicator 12 is of horse-shoe shape across which is fixed a plate for contact with the wrist. The indicator may be formed as a false back for the watch movement. Reference has been directed by the Comptroller to British Specifications 16418 /92, and 218,200, [both in Class 139], and U.S.A. Specification 1,927,765.