GB1315742A - Intermittent drive mechanism - Google Patents

Abstract

1315742 Escapements MALLORY TIMERS Ltd 28 May 1971 [29 June 1970] 18058/71 Heading F2X [Also in Division H1] An intermittent drive mechanism comprises a constant-speed drive 22, a first cam 38 rotatably driven thereby, a second cam 43 coaxial with cam 38 and relatively rotatable, energy storage means 46 coupling the cams together and storing energy on advance of the first cam relative to the second cam; stop means 48, 50, normally preventing rotation of the second cam and intermittently in response to rotation of the first cam permitting limited rotation of the second cam whereby energy stored in means 46 advances the second cam with a snap action; and mechanical damping means 28 to retard the snap-action advance of an output member driven by the second cam. As shown, a drive for a programmer, for example, comprises a synchronous motor 20 driving a constant speed member 22 via reduction gearing 20<SP>1</SP>, 20<SP>11</SP>, 36. Member 22 comprises a gear 34 integral with a gear 32 and snail cam 38 and is coupled to a gear 43 by pre-stressed torsion coil spring 46. Gear 32 may be used for subinterval-switching, for example. Gear 43 has an integral cam-like projection 40 which normally prevents rotation of gear 43 by abutting one of two spring urged stop pawls 48 or 40. Motor 20 thus stresses spring 46 until the cam 38 lifts the pawl restraining projection 40, whereupon gear 43 is rapidly driven until, after 180 degrees rotation, projection 40 abuts the other stop pawl. Gear 43 meshes with a gear 52 coupled to an output pinion 54 via a unidirectional clutch (84, 86, Fig. 3, not shown) such that output pinion 54 performs intermittent 180 degree steps. To avoid excessive wear due to too vicious stepping a damping escapement 28 retards the motion of gear 52. This comprises a ratchet wheel 59 staked to gear 52 and cooperating with teeth 70, 72 on a slidable member 58 such that wheel 59 can only rotate by reciprocating the slider 58. A second motor 18 provides rapid advance of the output pinion 54, when desired, by means of gears 18<SP>1</SP>, 17 and 76, overrunning the unidirectional clutch to gear 52. Output pinion 54 may also be driven at a slower rate than the normal programme cycle (for a long soak in a washing machine, for example) by providing a greater gear reduction from motor 18, and de-energizing motor 20.