Patent GB-917525-A (GB)
Abstract: 917,525. Counting-apparatus; zeroizing- mechanisms. SMITH & SONS (ENGLAND) Ltd., S. Sept. 4, 1959 [Sept. 9, 1958], No. 28929/58. Class 106 (1). A meter having a member driven in accordance with a quantity to be measured comprises a clutch through which said member is driven, means for engaging and disengaging the clutch with a snap action, a part which is movable to reset the said member and manually operable means for actuating the clutch, the arrangement being such that the clutch is disengaged before the resetting part is moved. As described, for a telephone fee pulse counter, 50 c.p.s. pulses to be counted are amplified and cause the armature of an electromagnet to rock, thereby rocking a lever carrying a pin 28, Fig. 2, which moves a pawl 31 over one tooth of a ratchetwheel 33, the spring-urged return movement of the pawl 31 producing the working stroke. The ratchet 33 is mounted on a hollow shaft which carries a units pointer 11, Fig. 7. A hundreds pointer 12 is driven by reduction gearing 36, 37, 39, 40 from the shaft of the ratchet 33. There is provided also a resettable pointer 10 driven at the same rate as the units pointer 11 but resettable to zero when desired. The pointer 10 is mounted on a spindle 41 extending through the hollow shaft of the ratchet 33 and driven from the ratchet 33 via a clutch comprising a toothed disc 43 meshing with a pinion 55 carrying a zeroizing heart-shaped cam 57. To zeroize the pointer 10, a button 68, Fig. 3, is depressed thereby raising a vertical slide 64. The raising of the slide 64 tensions a spring 62 to which is attached a bar magnet 59, to such an extent that the magnet is snapped from a first limiting position to a second limiting position, these positions being defined by the embracing double-cranked ends 60 of a magneticcircuit forming member. The movement of the magnet 59 causes spring fingers 45a on which the magnet is mounted to disengage the clutch member 43. A projection 64b on the bar 64 causes a lever 71 to pivot, one of a pair of spaced lugs 71a, 71b thereon engaging the heat-cam 57, thereby zeroizing the pointer 10. Means are provided to ensure that the clutch is disengaged before the lugs 71a, 71b engage the cam 57. These means comprise bell-crank levers 73, 79, and in operation, the pin 64b first engages the arm of the bell-crank lever 73 which by a lostmotion connection, is permitted to move without also moving the lever 71, thus removing the holding influence of a spring 76 on the lever 71. The lever 71 is still held, however, by the engagement of a lug 71c in a slot 79b of the bellcrank lever 79. Further movement of the lever 64 causes the pin 64b to rotate the lever 79, thereby releasing the lever 71 which snaps into engagement with the heart cam 57, the clutch 42 being at this stage positively disengaged. When the pressure on the button 68 is released, the lever 71 is returned to its original position by the action of the lost-motion connection with the bell-crank lever 73, which is spring urged downwards. In order to prevent a count being registered if the indicator is shaken, a balanced lever 80 is provided, which is pivoted about its centre and provided with weights 84, a forked end 80a being disposed in the path of movement of the pin 28. When the indicator is shaken, the resultant swinging movement of the forked end brings a broad prong 80b in the path of the pin 28, thereby preventing operation of actuating pawl 31.