Patent GB-545910-A (GB)
Title: Improvements in and relating to clock mechanisms
IPC: G04C13/02
Filed: 1940-11-13
Abstract: 545,910. Electric clocks. TELEPHONE MANUFACTURING CO., Ltd., SMITH,' S. J., and TERRY, R. S. G. Nov. 13, 1940, No. 16422. [Class 139] In pendulum-operated clock mechanisms, a free pendulum receives energizing impulses from a falling gravity arm at equal periods of time, the gravity arm being released electrically at the predetermined periods of time governed by the action of an attendant pendulum which is in itself maintained in synchronism with said free pendulum by electrical impulses transmitted at each fall of said gravity arm, the attendant pendulum being synchronised against error either of losing or gaining rate accumulated during a synchronising period by a mechanism adapted to impart a corrective impulse to said attendant pendulum either retarding or accelerating it. The main pendulum 1 swings freely and preferably has a period of one second. The attendant pendulum 8, having period of preferably half a second, swings in relative or closely approximate synchronism with the main pendulum, and at the end of a fixed period, say half a minute, and at the end of a swing, closes contact 10 (Fig. 1, not shown) in the manner described in Specifications 470,562 and 470,586. Magnet 7 is thus energised and withdraws latch 6 to release gravity arm 4, the roller 3 of which gives an impulse through the pallet 2 to the pendulum 1. As the gravity arm 4 descends further it closes contacts 4a to operate restoring magnet 14 and magnet 15 which operates lever armature 16 bearing serrated pallets 17a, 17b yieldingly pivoted on the armature. If pendulum 8 is not in perfect synchronism with the. free pendulum, its flexible spring 8a engages one or other of the pallets 17a, 17b and receives a correcting impulse; otherwise the spring enters the neutral space between the pallets and receives no impulse. In an alternative arrangement, (Fig. 3, not shown), the contacts 4a energise magnet 15 only, armature 16 closing certain contacts to energise restoring magnet 14. To prevent shock or damage 'resulting through a weakening of the current causing the roller 3 to remain in the path of the pallet 2 when the main pendulum is swinging back, the pallet 2 may be mounted on an arm 19 pivoted in a yielding manner on the pendulum as shown in Fig. 4. The pallet is retained in operative position by abutment 21 which still allows the pallet to be drawn over the roller if the latter is not withdrawn. In an alternative arrangement (Fig. 5, not shown) a contact spring on the pendulum makes contact near the limit of its swing with a contact spring on the gravity arm if the latter is still in a fallen position to provide a direct circuit through the restoring magnet and through a warning lamp. In yet another arrangement (Fig. 6, not shown) a catch hook on the pendulum engages a spring toggle on the gravity arm and raises it to such a height that the electromagnet can complete the elevation of the arm into the latched position. The attendant pendulum may be connected to clock mechanism or impulse transmitting mechanism for operating slave clocks. Alternatively the operating magnet windings on slave clocks may be included in the circuit of the latch release magnet 7.