Patent GB-450694-A (GB)
Title: Improved method and means for controlling electrical apparatus, particularly electric clocks
IPC: G04C11/00
Filed: 1935-02-05
Abstract: 450,694. Synchronous electric motor clock systems. F.B.M. GEAR SYNDICATE, Ltd., 15, Victoria Street, Westminster, BROWN, W. S. F., Brewerswood House, Cranbrook, Kent, and TENNISON, A. J., Kingswood, Littleheath Road, Selsdon, South Croydon, Surrey. Feb. 5, 1935, No. 3727. [Class 139] The secondary clocks of a system are each driven by a self-starting synchronous motor connected to the hands or their equivalent through either of two gear trains, one of which normally drives, while the other drives at a far greater speed for setting purposes. The master clock comprises a similar motor driving a time shaft through a similar two-speed gear train, an auxiliary timing mechanism which drives the master clock during current stoppages, and means which moves in accordance with the duration of current stoppage, and, on current resumption, allows the time shaft driven by the master synchronous motor to take over the drive only when it has picked up the lost time. The changing of the gear trains in the master and secondary clocks is effected automatically by stopping of the driving motors, so that when the clocks are reset their driving motors have again to be stopped to change the gear drives back to normal. Secondary clock. A self-starting synchronous motor 13, Figs. 1, 2 drives through gearing 14, 15, 12 and shaft 11, a planet member 16 carrying shafts 17, 18 to which are secured planet wheels 19, 20 and 21 22, respectively. The wheels 20 22 mesh with a wheel 23, integral with a ratchet wheel 24, normally locked against rotation by a detent 42, Fig. 2. The shafts 17, 18 are thereby rotated through wheels 20, 22, the wheel 21 on shaft 18 driving the hands 28 through gearing 25, 27 carried on a sleeve 26, and the usual gearing 29, while wheel 19 idly drives a sleeve 30 carrying a ratchet wheel 31. When the current fails, a spring biassed lever 32, Fig. 2, pivoted at 33 and normally attracted at 34 by the motor 13, is released, and a pawl 35 is actuated thereby to advance a ratchet wheel 36, shaft 37, and cam 38. The cam through an arm 39 and shaft 40 rocks a detent 41 into engagement with ratchet wheel 31 and frees the ratchet wheel 24. When the current again becomes available, the hands 29 are driven at a far greater speed through gearing 11, 19 (rolling on fixed wheel 30) 20, 23, 22, 21, 25, 27, 29, until the lost time has been picked up, when the current supply is again momentarily broken, as hereinafter described. This causes the pawl 35 to advance the ratchet wheel 36 and cam 38 another step to reverse the detents 41, 42 so that the drive to the hands reverts to normal, the cam 38 being so shaped that the detents 41, 42 are always reversed at successive stoppages of the motor. In another embodiment, the direction of rotation of the synchronous motor is reversed at each stoppage thereof to effect the gear change for resetting or normal running. In this case both gear trains include ratchet-andpawl mechanism whereby the hands are driven uni-directionally irrespective of the direction of rotation of the motor, and means are provided to ensure the motor starting in the correct direction. A spindle 71, Fig. 5, geared to the motor carries rigid therewith a disc 70, Figs. 5, 6, and a flywheel 74 rotatably mounted on the spindle carries a pin 73 coacting with a notch 72 in the disc 70. Pawls 75, 76, pivoted at 77 to the disc 70 and biassed by a spring 78 carry arms 79, 80, which are rocked by the pin 73 in passing from one to the other end of notch 72, to bring the detents 75, 76 alternately into engagement with a notched projection 81 on the frame plate 50. Thus, when the motor comes to rest, the fly-wheel tends to continue running and comes to rest with the pin 73 at one end of the notch 72. In this position the detent 75, Fig. 6, for example, is operative, and will permit the disc 70 to rotate in clockwise direction only, and when the motor again stops, the pin 73 moves to the other end of the slot 72, the detent 76 becomes operative and the motor therefore can only start in the reverse direction. Master clock. The master clock comprises a synchronous motor driving a wheel 112, Fig. 8, through alternative gear trains controlled automatically by the motor stoppages as described above. The wheel 112 is rigid with the crown wheel 115 of a differential gear, the planet member 117 of which carried by a shaft 114 is normally locked, so that the crown wheel 115 drives through planet wheels 116, crown wheels 118, 119, and gearing 121, 128, the seconds spindle 122 connected to the usual hands 125, 126, through reduction gearing 127. Rigid with shaft 114 is a disc 129 connected to discs 133, 136 through reduction gearing 130. These discs are normally locked by a pin 141, Figs. 9, 10, engaging aligned peripheral notches therein, the pin 141 being carried by an arm 137 normally held by a mains fed magnet 139 against the action of a spring 140. When the supply current fails, the hands 125, 126 are driven by the auxiliary mechanism comprising a pendulum 148, electrically or otherwise maintained, which through a pawl 144 and ratchet wheel 146 advances the shaft 122. The pawl is normally held out of engagement with ratchet wheel 146 by an extension 142 of the arm 137, and is released for operation when the magnet 139 de-energizes. The discs 129, 133, 136 are also released, and the shaft 114 is now driven by shaft 122 through the differential gear 115 ... 119. Hence the discs are rotated in accordance with the time of operation of the auxiliary mechanism. When the supply current again becomes available, the auxiliary mechanism still continues to drive the hands until the synchronous motor driving the wheel 112 at greatly increased speed restores the shaft 114 and discs to normal when the pin 141 drops into the aligned notches in the discs to lock them and the wheel 112 takes over the drive to the hands, and reverts to its normal speed as hereinafter described. Master clock control circuits. Fig. 12 shows secondary clock motors 189 and the master clock motor 188 connected to the mains 185, 187 through a normally closed contact 181. An " alternate break " magnet 160 is also normally energized and its armature 170 is associated with a disc 175 whereby an arm 176 is rocked from either of contacts 178, 179 to the other when the magnet 160 de-energizes. During normal running the contacts are as shown, so that when the supply current fails the arm 176 is rocked to contact 179. The arm 137 is also rocked to release discs 129 ... , as described above, and moves contact 149 over to contact 151. When the current supply is resumed, the master and secondary clock motors drive at the resetting rate as described above until, when the arm 137 is again rocked to lock the discs 129 ... , the magnet 182 is energized over contacts 176, 179, 150, 149 and opens contact 181 to stop the motors and change their gear trains to normal. The Provisional Specification describes a slightly different electric control arrangement in which a two-way switch is controlled by the differential mechanism connecting the master synchronous motor and the auxiliary driving mechanism. The auxiliary mechanism may be arranged to commence working when the current fails, but where it operates continuously it should be corrected occasionally by the synchronous system. It may be dispensed with in the case where the current is interrupted manually to restore the gear trains to normal as soon as the secondary clocks are reset.