GB688202A - Means for measuring the frequency of electric or mechanical impulses - Google Patents

Abstract

688,202. Speedometers. CHAMBERLAIN & HOOKHAM, Ltd., and DEACON, L. O. Feb. 16, 1950 [Feb. 21, 1949], No. 4642/49. Class 106 (iii). [Also in Group XXXVI] Apparatus for measuring the frequency of electrical or mechanical impulses comprises an indicating pointer carried by a spindle intermittently rotated against a return spring by two alternately operative deflecting pawl-andratchet mechanisms responsive to a train of incoming impulses and having a third retaining pawl-and-ratchet mechanism operative to hold the spindle against rotation in the opposite direction; together with a cyclic time control mechanism which renders the deflection ratchet mechanism operative and inoperative over successive alternate time intervals, and renders the retaining ratchet mechanism inoperative at predetermined time intervals, allowing the pointer to reset. An instrument for measuring the frequency of electric or other impulses comprises spindle a, loaded by return spring m, carrying pointer b and ratchet disc c<SP>2</SP> retained by detent pawl j disengagable by electromagnet k. Other ratchet discs c, c<SP>1</SP> freely mounted on the spindle and loaded by return springs i are rotatable by pawls f operated by electromagnets g and disengagable by electromagnets h. Each disc c, c<SP>1</SP> carries a projection d which may engage a corresponding radial arm e on the spindle, which is thereby rotatable against its return spring m. The various electromagnets are sequentially operated and released by switching cams 2, 3, 4 carried by spindle y rotated by ratchet disc 5 electromagnetically stepped by clock x. The instrument is initially in the position shown, and a train of impulses across the terminals n energizes electromagnet g through switch contacts o, p to step disc c<SP>1</SP> and rotate spindle y and pointer b in proportion to the number of incoming pulses while the pawl of disc c is held inoperative by electromagnet h energized through contacts s, t. After a predetermined time, cam 3 opens contacts s, t to release the pawl of disc c, and cam 4 closes contacts v, w to energize electromagnet k and release pawl from disc c<SP>2</SP>, but the spindle is prevented from returning until cam 3 closes contacts s, u to release the pawl of disc c<SP>1</SP>, when the return movement is limited by engagement of arm e with projection d on ratchet disc c. Immediately before, or simultaneously with, the closure of contacts s, u, cam 2 opens contacts o, p and closes contacts o, q, so that the impulses now step disc c during the return movement of the spindle and pointer, and while disc C<SP>1</SP> is inoperative. Thus the pointer is continually and cyclically deflected and reset to indicate the incoming pulse frequency, and the ratchet discs c, c<SP>1</SP> are alternately operative and inoperative so that during pointer resetting, one or other disc is actuated by the incoming impulses, none of which is lost.