Patent GB-362518-A (GB)
Title: Improvements in or relating to clocks
IPC: G04C3/04
Filed: 1930-09-10
Abstract: 362,518. Electric clocks. SMITH, S. J., Hollingsworth Works, Martell Road, West Dulwich, London. Sept. 10, 1930, No. 37924/29. [Class 139.] Escapements; balances; ratchet gearing.-An electric clock in which the scape wheel rotates half a tooth each time it is acted upon by the pallet (directly or indirectly), has locking means to prevent retrograde movement of the scape wheel which comprise two stop pawls moved alternately to the crests and roots of the teeth on the scape wheel or on a wheel connected thereto, at each successive movement of the wheel. The wheel 15 and a wheel 16 geared thereto are driven half a tooth at a time by a pallet 17 on an armature lever 18 which is oscillated in each direction by magnets 19, 20. With both magnets de-energized a steel spring 21 holds the pallet in a neutral position as shown. The hairspring 5 of balance 4 is anchored to the balance staff and to a block 7 on a lever 8 which is pivoted coaxially with, and swings parallel to, the balance. This lever is held by a thin wire spring 13 in a block 14 and coacts with spring blades 9, 10 anchored at 11, 12. Fixed bracket 14 is adjustable towards the balance for regulation. Pawls 23, 24 of semicircular shape are mounted on arms 25, 26 which are integral with arms 29, 30 pivoted at 27, 28. When one pawl is at the crest of a tooth, the other is at the root, locking the wheel. When the pallet 17 drives, one pawl is forced up out of the teeth and the other descends to lock them, the wheel 15 thereby moving half a tooth. Springs 31, 32 press the pawls down, through pins 33, 34. With the alternation of pawls 23, 24, the arms 29, 30 will rise and fall to rock a lever 35 pivoted at 36 and having pins 40, 140 to actuate the blades 9, 10. A spring 37 snaps this lever 35 each side of its dead central position. As the balance moves anticlockwise, Fig. 1, spring 5 tends to carry lever 8 anticlockwise also. Pawl 23 is now on the crest of a tooth and its arm 29 has risen to throw lever 35 clockwise. This presses up on blade 9 and a little later the lever 8 through its momentum (and wheel 43) presses blade 9 up further, to close contacts 9, 41. When the balance rotates in the opposite direction, lever 35 is rocked anticlockwise and contacts 10, 42 are closed. The parts are wired as shown to a battery 45. With the balance rotating anticlockwise pawl 23 is on the crest of a tooth, contacts 31, 47 are closed and at the end of the balance swing, contacts 9, 41 are closed. This completes a circuit 45, 44, 11, 9, 41, 47, 31, 48, 20, 49, 45 to energize magnet 20. This actuates pallet 17 to drive wheels 15, 16 and reverse the pawls 23, 24. In the opposite direction of balance swing, contacts 32, 50 and 10, 42 are closed to actuate magnet 19. In a modification, the parts 13, 14 are dispensed with and the lever 8 actuates a regulator carrying the usual curb-pins for the hairspring. Otherwise the construction is the same as in Fig. 1. In a further modification, Fig. 4, the wheels 15, 16 are coaxial, and the pawls 170, 171 therefor are integral with a common member 172 pivoted on a rod 181. This member 172 is also pivoted to the armature 180 of a magnet 200, the armature being on a spring blade 210. As the magnet is energized and de-energized, its armature rocks the pawls 170, 171 alternatively into and out of engagement with the wheels 15, 16. Alternately, a second magnet may be used for the armature 180. The balance may be replaced by a pendulum.