Patent GB-589422-A (GB)
Title: Improvements in or relating to gear-change mechanisms
IPC: G07F15/08
Filed: 1945-03-22
Abstract: 589,422. Prepayment mechanism for meters. SANGAMO WESTON, Ltd., and WESTON, G. E. March 22, 1945, No. 7299. [Class 27] [Also in Group XXIV] Change-speed gearing, for light duty, such as driving price-changing mechanism of prepayment electricity meters, comprises a toothed pinion, e.g., 14, Fig. 9, which slides in the axial direction only, to mesh selectively with any one of the series of concentric rings 12a, of equal-pitched teeth on the face of a disc 11, or cone, and change of mesh is facilitated by applying to the pinion and/or disc a turning movement derived from the selector control during a shift, the pinion being shifted through resilient means which permits delay until the meshing teeth align. The concentric rings of teeth may be in the form of a one-piece disc, e.g., 11, Fig. 9, die-cast or of a moulded plastic. In the price-changing drive of a prepayment electricity meter shown in Figs. 2-4, a driving shaft 40, Fig. 3, carries a disc 41 with facial rings of teeth selectively meshed by a pinion 42 carried in an axially slidable frame 65 and driving through a constant-mesh long-pinion 43 and wheel 45, a second pinion 46, all being mounted for bodily axial movement with the frame 65, the second pinion 46 meshing selectively with rings of teeth on the lower face of a second disc 47, the upper face of which has additional rings engaged selectively by a third pinion 48, independently slidable axially on a final driven shaft 50. An additional range of ratios is provided by a third facially-toothed disc 49, oppositely driven by the second disc 47 through constant-mesh wheels 52, 54, 55, 57 connecting peripheral teeth on the discs, the disc 49 having the rings of teeth on its lower face staggered in relation to those on the adjacent face of the underlying disc 47, so that the sliding pinion 48 engages the rings of the discs 47, 49 alternatively. A still further range of ratios is provided by an alternative drive direct to the third disc 49 from the driving shaft 40 through an idler 59 and a countershaft-pair 60, 62, carried by a pivoted U-shaped frame 95, which holds the countershaft-pair out of mesh until an overtravel of the frame .65 of the first and second selector pinions 42, 46, beyond the limit of the rings on their discs, causes the frame 65 to press on a projection 97, Fig. 2, and pivot the frame 95 downwards to mesh the countershaftpair 60, 62, with their respective wheels. Separate and independent selector controls are provided for shifting the third pinion 48 and the common frame 65 of the first and second pinions 42, 46. The frame 65 is traversed along a fixed guide rod 68, Fig. 4, in the gear-casing 63 by turning a thumb-wheel 72 which projects through a slot in the gear casing (see Fig. 3) and meshes with a wheel 71 secured to a threaded shaft 70 which screws through one side 69 of the frame 65. A similar independent thumbwheel 107, meshing a wheel 106, turns a screwed shaft 103, Fig. 2, which traverses a carriage 100 yoked to the third pinion 48. To facilitate change of mesh the sliding pinions are turned by their respective selector controls during a shift and axial movement is applied to them through resilient means, e.g., bladesprings 67, Fig. 4, for the pinions 42, 46 and a spring-yoke 104, Fig. 2, for the pinion 48 to permit the pinions to lag behind until a suitable meshing point is reached. In both cases a shift occupies one complete revolution of the thumb-wheel 72, or 107. In the case of the thumb-wheel 72, the pinions 42 and 46 are continuously turned during the shift-interval by a toothed wheel 73, Fig. 4, meshing permanently with the thumbwheel 72, and secured to the guide-shaft 68 which loosely carries a wheel 80 constantly meshing the long pinion 43 which connects the selector-pinions 42, 46. The initial turning movement of the shaft 68 dog-clutches the wheel 80 to it, by lifting a pivoted arm 90 out of a notch 92 in a fast clutch-member 77, which arm acts on a spring-returned bellcrank 83 connected to the loose clutch-member 81. The thumb-wheel 72 then turns both pinions 42, 46, in addition to axially traversing them, until its one revolution and with it that of the shaft 68, is complete, whereupon the arm 90, drops back into the notch 92 allowing the dog-clutch member 81 to disengage under the spring-force, thus freeing the pinions 42, 46 from the selector-control for their normal driving function. The action in the case of the third selector-pinion 48 is similar but is carried out by means of a second toothed wheel 108, Fig. 3, permanently secured to the thumb wheel 107 and meshing a pinion 110 secured to the squared final driven shaft 50, so as to turn the latter, and with it the pinion 48 during a shift. The wheel 108 has a gap at one point in its periphery which, at the completion of the one revolution shift, registers with the pinion 110 thereby disconnecting it from the selector-control. Spring-loaded balls 75, 112, Fig. 3, retain the thumb-wheels 72, 107 in their adjusted gear positions and the axial position of the selector-pinions 42, 46 and 48 is indicated externally by pointers 94, 114 (Figs. 3 and 2) secured to the frame 65 and carriage 100 respectively, and moving over fixed linear scales (not shown). In the multiple arrangement shown in Fig. 9, a driving disc 11, driven through peripheral teeth 13, has facial rings of teeth 12a for selective engagement of one side of an axially sliding pinion 14, the other side of which simultaneously engages selectively with similar rings 18a on a second disc 16 which has staggered rings of teeth on each side for selective engagement alternately with one or other of a pair of wheels 19, 26, which slide axially together and are both connected to the final driven shaft 24 through an idler 22. A further range of ratios is provided by arranging for the slidable pinion 14, when it leaves the last rings of teeth on the discs 16, to mesh a wheel 29 with an idler 30 and introduce an alternative geared drive between the discs. Although only one face of the disc 11 is used, both discs are identical for interchangeability.