GB424577A - Improvements in or connected with revolution counting apparatus - Google Patents

Abstract

424,577. Revolution-counters. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London, and GRIFFITHS, L., 78, Biggin Hall Crescent, Stoke, Coventry. Aug. 23, 1933, No. 23479. [Class 106 (iii)] [See also Group XXXVII] In revolution-counting apparatus wherein a tachometer generator such as that described in Specification 395,404, [Group XXXV], drives a contact make-and-break device for intermittently feeding an electromagnetic counter of known construction, the contact-making device comprises a base for substitution for or addition to the end-plate at the non-driven end of the generator, and means are provided to ensure that the time of closed contact and the rate of contact opening are substantially constant irrespective of the speed of the driving spindle. The make-and-break device, which is driven through reduction gear by a worm 2 on the tachometer generator spindle, comprises a cam spindle 11 carrying a tripping pin 13 which is connected by a spiral spring 16 to a cam 15, the rotation of which is arrested by the upturned end of a leaf spring 14 until after rotation through about 270 degrees the pin 13 depresses the spring 14 and releases the cam, which thereupon is rotated rapidly by the spiral spring 16 until it is arrested by the pin 13. To prevent a too rapid rotation of the released cam, there may be provided a centrifugal brake comprising two bob-weights 35 mounted on the free ends of springs 36 and adapted to engage frictionally a fixed ring 37, the springs being secured to a spindle 33 carrying a steeply pitched worm driven by a toothed wheel 31 on the cam shank. Fig. 6 shows a uni-directional drive 39 for the cam spindle 11. The cam 15 may be made of an insulating material ; the material known under the Registered Trade Mark " Textolite " may be used. The plate 1 takes the place of the usual generator end-plate and supports a moulding 10.