Patent GB-673873-A (GB)
Title: Improvements in or relating to time-keeping mechanisms
IPC: G04C1/08
Filed: 1949-09-30
Abstract: 673,873. Electric clocks. BROWN. T. A., and PERIVALE CLOCK MANUFACTURING CO., Ltd. Sept. 29, 1950 [Sept. 30, 1949], No. 25094/49. Class 139 A time-keeping mechanism comprises a synchronous electric motor, an escapementcontrolled time train, a time-train differential one element of which is adapted to impart energy to an intermediate energy storing means which energy is used to provide a substantially constant torque to drive the time train, a power differential continuously driven by the electric motor and adapted to drive the time train differential, means for intermittently holding one of the elements of the power differential stationary at short intervals of time, whereupon the time-train differential is driven by the power differential to replenish the store of energy in the intermediate energy storing means. The sun wheel 28, Fig. 3, of the power differential 20 is continuously driven by a synchronous motor 24, Fig. 1, and is free to rotate on a spindle 22. The time-train differential 21 comprises two sun wheels 36, 37, planet pinions 38 and a planet carrier 39. The sun wheel 37 is attached to a gear wheel 41 in the clock going train. The sun wheel 33 of the power differential and the sun wheel 36 of the time-train differential are fixed to a common bush 49 freely rotatable on the spindle 22. The bush 49 also carries a ratchet wheel 50, Fig. 4, which cooperates with a pawl 51 to prevent backward (i.e. clockwise, Fig. 4) rotation of the sun wheels 33, 36. The planet carrier 31 of the power differential carries two radially extending arms 34. The planet carrier 39 carries a driving weight 30 and a radial arm 40, Fig. 6. In operation, when the driving weight 30 is at rest against a stop 85, Fig. 6, the carrier 39 is at rest. The arm 40 abuts an arm 55 on a shaft 53 held stationary by a compensating weight 56, Fig. 1. The sun wheel 33 is prevented from moving clockwise by the pawl 51, Fig. 4, and the drive from the motor 24 causes the carrier 31 to rotate clockwise until arrested by the engagement of one of the arms 34, Fig. 4, with a cam 54 on the shaft 53. The sun wheels 33, 36 and the carrier 39 then move anticlockwise to raise the weight 30. The radial arm 40 of the carrier 39 meets the arm 55 on the spindle 53 which is thereby rocked clockwise so that the compensating weight 56, Fig. 1, is raised and the cam 54, Fig. 4, is moved to free the arm 34 and so allow the carrier 31 to rotate again. The driving weight 30 and the compensating weight 56 now descend and the clock train is driven through planet pinions 38, sun wheel 37 and gear wheel 41. The cam 54 is now rocked anticlockwise into the path of the next radial arm 34 which it abuts when the weights 30 and 56 have reached their lowest positions. In a modification the radially mounted driving weight is replaced by a spring. The planet carrier of the time-train differential comprises a pulley 57, Fig. 9, and the weight 60 is carried by a cord 58 attached to the pulley. The planet pinions 38 are mounted in slots 62 in the pulley 57. A pin 63, not shown, projecting from the pulley cooperates with the arm 55 on the spindle 53 which is loaded by a light spring 64, Fig. 13, not shown. In another example the driving weight is replaced by a spring. In this case the planet carrier 39, Fig. 11, has a gear segment 68 which meshes with a toothed spring drum 69 enclosing a driving spring 71. In the original example the ratchet and pawl 50, 51 may be replaced by a detent mechanism comprising a disc 76, Fig. 7, rotatable in a stationary yoke 77 provided with two wedge shaped recesses 79 each containing a spring pressed steel ball 80. The arrangement is such that only anticlockwise rotation of the disc 76 is permitted. Specification 489,855 is referred to.