GB1337175A - Intermittent motion mechanism - Google Patents

Abstract

1337175 Escapements MALLORY TIMERS Ltd 26 May 1971 [17 June 1970] 17143/71 Heading F2X An intermittent drive mechanism includes a slider 44 arranged to be reciprocated by the action of a rotary input cam 30, and a rotary output member 34 subject to a spring bias tending to rotate it, the rotation of the output member 34 being alternately permitted and prevented by the reciprocation of the slider 44. A motor drives a reduction gear train, a gear 38 of which carries the cam 30. Slide 44 has a centrally disposed aperture 48, a pair of elongate apertures 50, 50<SP>1</SP> intended to receive guide posts (not shown), and a pair of oppositelylocated steps 53, 53<SP>1</SP> projecting inwardly of the aperture 48. The output member 34 includes a step 56 adapted to engage the steps 53, 53<SP>1</SP> of slider 44. When the mechanism is assembled, the cam 30 and output member 34 mate within aperture 48. The member 34 is urged to rotate by a coil spring 64 sandwiched between the cam 30 and the member 34, being attached at one end to a post 66 on gear 38 and at the other end to a post 68 on member 34. The member 34 is preferably formed as an integral piece comprising the step 56, a pinion 60, a ratchet wheel 70, and a bearing 72. When the mechanism is first assembled, coil spring 64 is twisted so that the two ends of the coil are adjacent each other. In operation, the gear 38 is driven clockwise and the cam 30 presses against the slopes 55 of the steps 53, 53<SP>1</SP> to cause slider 44 to move back and forth on surfaces 58, 58<SP>1</SP> within the mechanism housing. Assuming step 56 is in engagement with step 53, as slider 44 moves to the left, step 56 becomes disengaged from step 53 thus allowing the energy in coil spring 64 to be released to rotate the output member 34 clockwise through 180 degrees until step 56 engages step 53<SP>1</SP>. Then as slider 44 moves to the right, the process is repeated with step 56 leaving step 53<SP>1</SP> and member 34 rotating a further 180 degrees until it becomes engaged again with step 53. An intermittent rotary motion is thus imparted to the output member 34, the pinion 60 of which is coupled to the cams of a timing mechanism, and the ratchet wheel 70 of which co-operates with a pivotally mounted double pawl (not shown) to form a damping means.