Patent GB-509410-A (GB)
Title: Improvements in and relating to prepayment meters
IPC: G07F15/08
Filed: 1938-01-11
Abstract: 509,410. Prepayment mechanism for meters. BRITISH SANGAMO CO., Ltd., and WICKHAM, A. H. Jan. 11, 1938, No. 956. [Class 27] Price-changing mechanism for prepayment meters, having provision for fine and coarse adjustment, comprises a pawl 22 adapted to drive a ratchet-wheel 26 for an adjustable portion of each revolution, its point of disengagement being determined by. an adjustable stop pin 15 allowing of adjustment in increments of one tooth of the ratchet, whilst its point of disengagement is determined by a slidable bar 40 having two abutment faces 46 and 47 separated by a distance corresponding to one tooth of the ratchet. During the initial portion of an operative period comprising a predetermined number of rotations of the pawl, the lower face 46 is operative to engage the pawl with the ratchet, whilst for the remainder of the operative period the bar is displaced endwise to bring the upper face 47 into action so that the ratchet is then moved an additional tooth at each rotation of the pawl. The point during the operative period at which the bar is displaced, and additional movement imparted to the ratchet, is adjustable so that further adjustment of the average transmission by increments of a fraction of a tooth of the ratchet is possible. The pawl 22 is pivotally carried by an arm 20 and has lugs 23 and 24 for engagement with the bar 40 and stop pin 15 respectively. The arm 20 is secured to a shaft 16 connected through gearing 17, 18 with a sleeve 19 driven, for example, by a constant-speed motor for collecting a fixed charge, whilst the ratchet 26 is connected through gearing 28, 29 with a shaft 30 connected with the quantity mechanism. Pin 15 is carried by a gear-wheel 14 fast with a dial 13 indicating the coarse increments of adjustment, e.g. threepences, adjustment being effected by a tool engaged with the slotted end of a sleeve 57 connected through pinions 56 and 55 'with the gear 14. For effecting displacement of the bar 40, an arm 31 on shaft 16 steps up a toothed wheel 32 through one tooth at each revolution. As the wheel 32 rotates, a bevel-ended pin 35 thereon ultimately engages a similar pin 37 on a disc 38 on an axially movable shaft 33, displacing the disc and with it the bar 40 which has an arm 39 bearing against the disc under the action of a spring 41. The bar is held in its displaced position by a catch 49 which is released to permit return of the bar at the end of the operative period (e.g. twelve revolutions of shaft 16) by a pin 53 on wheel 32. The point in the operative period at which the bar is displaced is determined by the position of pin 37 and this can be adjusted by rotation of shaft 33 by means of a tool engaged with the slotted end of a shaft 64, coaxial with the coarse adjustment sleeve 58 and gearing with the shaft 33. A dial 59 secured to shaft 33 indicates the fine increments of adjustment, e.g. farthings. In the modified construction of Fig. 3, the bar 40 is controlled by a spring- actuated rod 69, moved by a helical cam 74 driven through gearing 76 from shaft 16, and having an arm 73 adapted to engage an adjustable helical cam 71 on the bar. At the commencement of each operative period, the arm 73 on rod 69 lies at the foot of a step in cam 74 and holds the bar 40 in its rearward position against the action of a weak spring 68. During the initial part of the operative period, rod 69 and bar 40 move slowly forward until, at a predetermined point dependent on the adjustment of cam 71, stop bar 40 reaches the position in which additional rotation is imparted to the ratchet 26. The arm 73 then leaves cam 71 until the end of the operative period, when rod 69 drops into the step in cam 74 and returns the bar 40 to its initial position.