Patent GB-1137773-A (GB)
Title: Improvements in calendar clocks for automatically following the gregorian cycle
IPC: G04B19/257
Filed: 1966-03-29
Abstract: 1,137,773. Calendar clocks. R. DESSOMVILLE. March 29, 1966 [April 13, 1965], No. 13794/66. Heading G3T. A calendar clock mechanism comprises a month indicator drum 54 formed with projections (44)-48, a leap year indicator drum 55, formed with a rib 43, a first member 28 and a second member 26, a ratchet wheel 23 having thirty one teeth, a carrier 10 actuated by the clock gearing (not shown) and returned by a spring 18 after each daily cycle, and a pawl 21 fixed to the carrier, the first member co-operating with the rib and the projections to receive four operative positioning and the second member co-operating with the ratchet wheel to receive two operative positioning, the month indicator drum having fingers 49, 50 for rotating the leap year indicator drum 360 degrees each four complete turns of the month indicator drum. A lever 7, co-operating with the profile 6 of a cam 5 driven by the clock gearing, rotates the carrier 10 clockwise and at the end of twenty four hours the return anti-clockwise movement of the carrier causes a pawl 20 to engage one of seven pins 51 attached to a week day indicator drum 52 thereby advancing it one day. An air shock absorber 14 having a piston 16 clamps the return movement of the carrier 10. The ratchet wheel 23, having a projection 25 containing a notch 24 is fixed to a spindle 3 which by gearing (not shown) controls numerical date indicating drums (57, 58), Fig. 6 (not shown), and also rotates the drum 54 by gearing (not shown) one twelfth of a revolution when the ratchet wheel has advanced thirty one teeth. The first member 28, mounted idle on the spindle 3, has a slit 29 which engages a ball 53 and the member 28 is rotated clockwise by a spring 22 engaging a rib 27 of the member. The member 28 is formed with three steps 33, 32, 31 which co-operate with the projections 44-48 and the rib 43 to permit four operative positions of the member 28 causing a displacement of the ratchet wheel by the pawl 21 of one, two, three or four ratchet teeth at the end of a month of 31, 30, 29 or 28 days respectively when the return anti-clockwise movement of the carrier 10 takes place; i. e. the engagement of the steps with the projections and the rib allows the member 28 to rotate different amounts for days corresponding to 31st December, 30th April, 29th February, or 28th February so that the return anti-clockwise movement of the carrier 10 causes the member 28 to cam the pawl 21 over three, two, one or no teeth until a slot 30 allows the pawl to engage the ratchet wheel and rotate it by one, two, three or four teeth respectively. The second member 26, mounted idle on a spindle 2 rests on the ball 53 and has two positions (one position corresponding to end of the month days and one position corresponding to other days) depending whether or not the ball is in the notch 24, the second member being so shaped that in its raised position, the pawl 21 is cammed away from the ratchet wheel for a distance of three ratchet teeth. Thus during the anti-clockwise stroke of the carrier 10, the pawl 21 slides over the first and second members for an amplitude of three ratchet teeth and at the end of the stroke advances the ratchet wheel by one tooth. At the ends of months of 31, 30, 29 or 28 days, the ball 53 enters the notch 24 and the second member 26 occupies its depressed position so that when the return anti-clockwise movement of the carrier 10 takes place, the pawl slides over the member 28 for an amplitude of three, two, one or no teeth respectively, this being determined by the engagement of the member 28 with the projections 44-48 and 43. Configurations of dots on the side faces of the leap year indicator drum 55 give a visual indication in a window of the clock dial of the number of years before a leap year.