Patent GB-719220-A (GB)
Title: Improvements in and relating to speed or rate indicators
IPC: G01R11/60
Filed: 1951-06-06
Abstract: 719,220. Periodic-counter speedometers. SMITH METERS, Ltd., and MORRIS, F. June 6, 1952 [June 6, 1951], No. 13450/51. Class 106 (3) A speed or rate indicator comprises a pointer driven from a rotary element and periodically returned to zero when the drive is interrupted, a second pointer associated with the first and adapted to retain the position to which it is set, and a power drive independent of the rotary element and periodically effective to interrupt the drive from the rotary element to the first pointer and to return the first pointer to zero. The invention is described as applied to a maximum. demand indicator for use with an electricity meter. A.rotary element of the meter, not shown, drives a pointer 7, Fig. I, carried by a shaft 6, through a. gear train .75, 71, 17, 16, 13 and 12. The pointer 7 co-operates with a maximum demand pointer 9 in the usual way. The gear 17 is carried by a spindle 18 one end of which is supported by a lever 19. Co-axial with the gear 12 is a cam disc 21 which is periodically rotated, as described later, for one revolution so that the end 28 of lever 26 pivoted thereto meets a pin 25 on the gear 12 and so returns it and the pointer 7 to zero. At the start of the revolution of the disc 21 a pin 20 on the lever 19 is raised from the slot 22 in the disc 21 so that gear 17 is disengaged from the gear 16. As the disc 21 teaches its initial position at the end of the revolution a fixed stop 31 causes the lever 26 to rock clockwise against the spring 30 from the position of Fig. 3 to that of Fig. 4, and the end 28 of the lever frees the pin 25 so that the drive to pointer 7 may be immediately resumed In a modification (Fig. 5, not shown) the stop lever is positively constrained in each direction of its movement, The cam disc 21 is periodically driven from a motor 41, Fig. 1, which rotates, through a friction clutch, Fig. 8, not shown, a gear 43 mounted coaxially with the disc 21. The gear 43 carries a pin 46 and a disc 23 connected to the disc 21 carries a freely pivoted lever 45 and a pin 47. The normal relative positions of the parts 45, 46, 47 are shown in Fig. 6. When the gear 43 is rotated counter-clockwise, however, the pin 46 moves the lever 45 from the full line position, Fig. 6, to the dotted line position wherein it abuts the pin 47 so that continued rotation of the gear 43 is transmitted to the disc 21 which as described above returns the pointer 7 to zero. When the disc 23 completes its revolution a projection 48 on the lever 45 meets a nose 49 of a stop lever 50 which is thereupon rocked clockwise until it abuts the stop 43, Fig, 7, and the discs 21, 23 are thereby arrested. When the drive from the motor 41 is next interrupted the spring 51, Figs. 6 and 7, rocks the stop lever 50 counterclockwise to return the lever 45 to its initial position, Fig. 6. Means for manually setting the pointers 7 and 9 to zero may be provided. For this purpose the pointer 9 is connected to a gear 56, Fig, 9, normally braked by a member 57. A pinion 66 connected to the pointer 9 meshes with a large gear 67 having a pin 69 The lever 19 is extended downwardly at 65 to co-operate with an arm 61 of a manually operable lever 59. On movement of the lever 59 against a spring 63 the arm 61 rocks the lever 19 to disengage the gear 17 from the gear 16, Fig. 1, and an arm 70 of the lever 59, Fig. 9, meets the pin 69 to rotate the gear 67 and return the pointers 7, 9 to zero.