GB1376743A - Digital clock - Google Patents

Abstract

1376743 Counting apparatus; transfer mechanism UNITED GAS INDUSTRIES Ltd 24 Jan 1972 [25 Jan 1971] 3044/71 Heading G4D [Also in Division G3] In a digital clock having a pair of seconds drums 23, 24 for indicating seconds up to 59, a pair of minutes drums 21, 22 for indicating minutes up to 59 and an hours drum 20 a plurality of transfer gears 30, 33 mounted on a common shaft 26 are provided between successive drums for transfering increments drives from one drum to the next. As shown a syn chronous motor 11 is coupled by reduction gear 12 to a continuously rotating transfer plate 13. Transfer plate 13 carries a ring of pairs of Geneva teeth 14 which mesh with and intermittently rotate a transfer gear 34. Gear 34 is a compound gear which on its left face carries teeth which drivingly engage gear teeth on the right face of seconds drum 24. The drum 24 has some pairs of Geneva teeth on its left face which intermittently drive transfer gear 33. Transfer gear 33 intermittently drives the tens of seconds drum 23. The transfer gear, Geneva type coupling is employed between all the drums. To prevent the additive effect of backlash from one end of the series of gears to the other a backlash adjuster plate 40 is mounted to rotate freely on shaft 25 relative to tens of seconds drum 23 within which it is located. Plate 40 is keyed to rotate intermittently with the seconds drum 24 and has a portion which co-operates with compound transfer gear 32. Gear portion 54 of transfer gear 32 engages the rim 42<SP>1</SP> of adjuster plate 40 which determines a series of fixed angular positions which the gears 32 can take up. The adjuster plate 40 thereby pushes the gear 32 into its appropriate angular position and locks it there if the tens of seconds drum 23 has not done this positively. The rim 42<SP>1</SP> has a rebate which once in every revolution of plate 41 frees gear 32 and allows it to rotate. The clock may be manually adjusted by knob 45 on shaft 25. Minutes drum 22 is formed in two parts the left hand part being pinned to the shaft 25 and the right hand part being rotatable relative to the left hand part. An overridable clutch 48 couples the two parts so that they are normally rotated together by the synchronous motor 11. When it is desired to adjust the time setting, the parts rotate relatively, drive from the minutes drum 22 being transferred to succeeding drums. In an alternative embodiment drums 23, 22, 21 are independently adjustable by thumb wheels co-operating with the respective transfer gears. An overridable clutch is provided between each thumb wheel and its associated transfer gear.