GB635572A - Improvement in secondary time-keeping apparatus - Google Patents

Abstract

635,572. Electric clocks. INTERNATIONAL BUSINESS MACHINES CORPORATION. March 24, 1947, No. 7970.. Convention date, April 10, 1946. [Class 139] A secondary clock comprises an annular magnet coil surrounding a plurality of pole elements, an oscillating armature supported for rotary movement about the axis of the magnet coil and having a corresponding number of pole elements, arranged so that upon energization of said magnet coil the armature is rotated by the interaction of the pole elements, and biassing means constantly urging said armature against rotation which means return the armature to its initial position upon de-energization of the magnet coil, the oscillating movement of the armature being transmitted to a time indicating member. The magnet coil 27 is wound round a ring 28 in a U-shaped housing 26 the links of which are held together by bolts 14 passing through the front and back of the casing 10 of moulded insulating material. The confronting ends of the limbs of the housing 26 form opposed pairs of poles 38a, 38b, Figs. 1 and 2. The oscillating armature 40 is journalled on a sleeve 23 surrounding the shaft 24 carrying the minute hand 25 and has a central hub 41 and a circular rim 43 having flange elements 44 forming pole elements corresponding in number to the pairs of poles 38a, 38b. Upon energization of the coil 27 the poles 38a, 38b attract the adjacent poles 44 of the armature 40 which is thereby rotated. During this movement of the armature 40 a pawl 58 fixed thereto rides over the adjacent tooth of a four-toothed ratchet 55 which is prevented from movement by a detent member 62 pivoted on the armature 40. When the coil 27 is de-energized a weight 46 carried by a spring 47 fixed to the armature hub 41 returns the armature to its initial position where the weight 46 is stopped by a leaf spring 50. During the return movement of the armature 40 the pawl 58 steps the ratchet wheel 55 forward one tooth. The movement of the ratchet wheel 55 is transmitted through the gearing 55, 65, 66, 68, Fig. 5, to a gear wheel 69 on the minutes shaft 24. A spring detent 71 engages crown teeth 70 on the gear 66 to prevent backlash. The hours hand 75 is fixed to a sleeve 76 on a hub 77 having an arm 85 carrying a planet wheel 83 meshing with a fixed ring gear 81 'and pinion gear 80 fixed to the minutes the shaft 24. In order that the secondary clock may operate in a system such as is described in Specification 236,199, [Class 139], the gear wheel 69 has upon its rear face a cam surface 87 having two drops 98, 99 and co-operating with two contacts 93, 94 in such a manner as to control the reception of impulses from the master clock as disclosed in the above Specification.