GB499422A - Sidereal chronometer - Google Patents

Abstract

499,422. Sidereal chronometer. BROWN, G.H. Oct. 21, 1937, No. 28755. Convention date, Oct. 24, 1936. [Class 139] A sidereal chronometer gives in minutes of arc, indications up to 360 minutes, which are directly readable, preferably through windows. It comprises 3 discs: c showing units (0-9), f hundreds (0-3), d tens (0-6), and having associated with it a coaxial sector c with tail e<1> for the numerals 7, 8, 9. The units disc c is driven by jumper mechanism, Figs. 7, 8 (not shown), from the chronometer and each revolution, a tooth g engages a projection i and advances the disc d one division. When the figure 0 is thus presented, it is covered by the sector e showing number 7, the sector having been advanced with the disc by j, one of two projecting pins. The contour of disc d at 0 is concave so that the tooth g rotates only the sector e. This continues until 0 is uncovered when g engages the tail e<1> and rotates sector e and through the other pin j<1> the disc d. Meanwhile, a projection m on a disc d<1>, Fig. 6, fixed to disc d drives the hundreds disc f. This process continues till a reading of about 325 is indicated, when mechanism shown in Fig. 5 causes the withdrawal of the pins j, j<1> and the simultaneous appearance of a temporary tooth l opposite 0. Thus, the device indicates 359, 360 and then by the operation of a lower tooth h opposite the unit numeral 1 which engages the tooth l and rotates the disc d and consequently disc f, it indicates 001. The mechanism for withdrawing the pins j, j<1> consists of a Maltese cross q with 8 slots, rotatably secured at q<1> to the underside of the disc d, a fixed crown r mounted on a bridge and having associated therewith, two pins s, s<1>, a lever n pivoted at n<1> and a ramp (not shown). The cross carries a peg t which between the readings of 325 and 015 forces the tooth l forming part of the lever n, outwards and forcing the other end of the lever up a ramp against the action of a spring n<2> and consequently withdrawing the pins j, j<1>. When the peg t rotates further, the spring n<2> returns the lever to its former position.