GB594353A - Improvements in or relating to stroboscopic stroke or revolution counters - Google Patents

Abstract

594,353. Speedometers. SELFPRIMING PUMP & ENGINEERING CO., Ltd., and MOUTRAN, F. Dec. 15, 1944, No. 25254. [Class 106 (iii)] [Also in Group XX] The speedometer comprises a stroboscope adapted to produce two series of momentary views of an observed vibrating or rotating object under the control of a rotary lobed cam actuating two pairs of contacts set at an angle to each other, the phase difference between each flash of the two series being an angle of 360 other than - where a is the number of cam a lobes. The views may be produced by providing a flash of light each time a break occurs at either pair of contacts. The flashes occur at unequal time intervals, the relative positions of the object when illuminated thereby indicating whether the speed of the stroboscope is synchronous with that of the object or is an harmonic thereof. As shown, a discharge lamp 1, e.g. a neon lamp, is connected to a transformer 3 also connected to a battery 4 through a make-and-break device 5 of the type described in Specification 557,551, [Group XX], driven through a shaft 16 by an electric motor 7, connected through a variable resistance 10 to mains 9 and provided with a speed indicator 8. The device 5 comprises a cam 11 which co-operates with pairs of contacts 12, 13 set at an angle to each other so that the tuning of contacts 13 is displaced relatively to that of 360 contacts 12 at a phase angle of other than - a degrees defined above. The contacts 12, 13 are so disposed that each makes and breaks contact at the time when a break occurs at the other pair. A condenser 6 bridges the device to prevent arcing and to enhance the electrical impulse at a break, while a switch is included in the connection to contact 13 to allow of speed checks. The Specification describes views presented by a rotating arrow as object when the stroboscope is run at different speeds on each side of and including the speed of the arrow.