Patent GB-490827-A (GB)
Title: Improvements in or relating to prepayment electricity meters
IPC: G07F15/00
Filed: 1937-02-16
Abstract: 490,827. Prepayment mechanisms for meters. BRITISH SANGAMO CO., Ltd., BUTHERUS, F. R., and WESTON, G. E. Feb. 16, 1937, Nos. 21114/38 (divided out of 490,389, [Group IV]); and 21115/38 (divided out of 492,649.) [Class 27] A prepayment electricity meter is provided with switching means which interrupt the supply circuit a plurality of times when credit is nearly exhausted in order to warn the consumer that the supply is about to be cut off. As shown, the supply controlling switch comprises, as described in Specification 415,128, [Group XXXVII], a contact rod 142 adapted to be lowered into a mercury cup 153. Rod 152 is connected by a spring 151 with a plate 146 on an actuating rod 147, and in the opencircuit position is held raised by engagement of a detent plate 154 thereon over a locking lever 155. During prepayment a pair of intermeshing gear wheels on shafts 61, 80, and carrying pins 144, 145, are rotated in opposite directions (see arrows) for one revolution by an electric motor. These pins engage over plate 146 and lower it against the action of a spring 150 into engagement with a pivoted latching lever 157. Meanwhile, a detent disc 161 on an axially movable shaft 162 controlled by the quantity mechanism has been brought into the plane of lever 157 so that, when pins 144, 145 release plate 146, lever 157 is held by disc 161 and locks plate 146 in its lowered position with the spring 151 connecting it to the contact rod 152 stressed. Finally, a pin 156 on the shaft 80 trips lever 155 to release contact rod 152 which is lowered rapidly to complete the supply circuit. When credit is exhausted rod 162 is displaced axially under the control of the quantity mechanism to release latch 157 and allow rod 147 and contact rod 152 to be raised by spring 150 to break the circuit. The means for giving warning when credit is nearly exhausted comprises a solenoid 168 whose armature 170 has a pin-and-slot connection with the contact rod 152. The circuit of solenoid 168 is controlled by contacts 185 operated by a rotary cam 184a driven by a gear 177 loose on the shaft 61. Engaging in a radial slot 178 in gear 177 is a pin 172 on a bar 173 slidably and rotatably mounted on shaft 61 by means of a slot 174. A helical spring 181 connected at either end with bar 173 and a stationary barrel 180 urges bar 173 to rotate anticlockwise when the mechanism is in credit, but this is normally prevented by pin 172 also engaging in a slot 179 in the barrel. When the credit is nearly exhausted, a pivoted arm 182 is rocked under the control of the quantity mechanism and displaces pin 172 and bar 173 against the action of a spring 175. Pin 172 is consequently released from slot 179, and is rotated anticlockwise with bar 173 by spring 181 until arrested by engagement of pin 172 with an arm 171 secured to shaft 61. Gear 177, which is engaged by pin 172, is also rotated and drives cam 184a to make and break the circuit of solenoid 168 which causes continued raising and lowering of contact rod 152 and intermittent interruption of the supply circuit. During prepayment, shaft 61 and arm 171 are rotated clockwise through one revolution. Arm 171 restores bar 173 to its initial position with pin 172 engaging in slot 179 and rewinds spring 181.