Patent GB-436787-A (GB)
Title: Improvements in and relating to electric meters
IPC: G01R11/60
Filed: 1935-06-19
Abstract: 436,787. Supply meters. BRITISH THOMSON - HOUSTON CO., Ltd., Crown House, Aldwych, London. June 19, 1935, No. 17625. Convention date, June 20, 1934. [Class 37] A demand meter comprises an intervaldemand member 13 which is advanced over predetermined intervals of time in accordance with the measurements of a meter 10 and periodically reset to a zero position at the end of each interval, a maximum-demand member 53 which is advanced in accordance with the maximum advance of the member 13 over a number of said time intervals, and means for resetting the member 53 to a zero position comprising a motor 19, a normallydisengaged driving connection between the motor and said member, manually-controlled means for establishing a driving connection to initiate a resetting operation, and means for automatically interrupting the driving connection at the completion of the resetting operation. The meter 10 drives the shaft 30 carrying the member 13 through a friction clutch 33 and gearing, as shown, and simultaneously drives a disc 37 carrying a pin 36. A rack 40, oscillated by timing mechanism 21 driven by the motor 19, periodically restores the shaft 30 and member 13 to zero position by the co-operation of an arm 41 with the pin 36. The timing mechanism includes a shaft 43, which is continuously driven by the motor and connected by a spring 44 to a gear wheel 45 secured to a hollow shaft 46, which is loosely mounted on the shaft 43 and carries a disc 48 and an eccentric 47. Rotation of the shaft 46 is prevented by the engagement of a stop lever 49 pivoted on the disc 48 with a fixed stop 50 until the lever is released by a pin 51 carried by a lever mounted between pins 51<1> on the disc 42. On release of the stop lever 49, the sleeve 46 makes one revolution under the tension of the spring 44, whereupon the lever 49 again engages the stop 50 and prevents further rotation until another predetermined interval has elapsed. The rotation of the eccentric 47 oscillates the rack 40 to reset the shaft 30 and member 13. The maximum demand member 53 is carried by a shaft 14 geared by wheels 15, 16 to a pointer 17 moving over a scale 18. In order to reset the pointer 17 and member 53, the meter reader releases a seal or lock passing through a hole 26 or 26<1>, raises an arm 24<1> mounted outside the meter casing, and pushes in a pin 24, which causes axial movement of a shaft 23 carrying a gear wheel 54. The teeth of this wheel are cut away over a small portion 57 of the inner periphery, so that the gear wheel 58, which is continuously driven by the motor 19, does not normally drive the gear wheel 54, the wheels being maintained out of mesh with each other by a spring 59. On pushing in the wheel 54, however, it meshes with, and is driven by the wheel 58, and at the same time the end of the shaft 23 engages the shaft 14 and moves the latter axially against the action of a spring 68 and brings the members 61, 62 of a friction clutch into engagement. As soon as the wheel 54 starts to rotate, a pin 55, which normally engages a slot in a fixed frame member 64, is moved behind the back of the frame member, so that the gears 54, 58 are maintained in mesh until the former has made a complete revolution and the pin 55 again enters the slot, the pin 24 having meanwhile been returned to its inoperative position by the meter reader. A pin 56 on the back of the gear wheel 54 drives the gear wheel 15 through a projection 60 and returns the pointer 17 and maximum demand member 53 to their zero positions, the reading of the pointer 17 being at the same time transferred to a normally idle accumulating register 12 through the friction clutch 61, 62. An overrunning clutch 72 may be provided between the motor 19 and the gear trains to facilitate testing of the apparatus.