GB1373442A - Push-to-start timer - Google Patents

Abstract

1373442 Time switches MALLORY TIMERS Ltd 20 Oct 1972 [20 Oct 1971] 48318/72 Heading H1N A timer of the kind wherein a rotatable camcarrying shaft is moved axially to start a timing operation comprises at least one rotatable cam, driving means, switching means responsive to said cam, a clutch for coupling said driving means to said cam means upon axial movement of the said shaft, and a stop member which retains the clutch in engagement upon said axial movement. As shown, a synchronous motor 16 drives an output pinion (20, Figs. 2 and 3, not shown) via reduction gearing 18, said pinion (20) meshing with a gear 54 with serrations 58<SP>1</SP> forming a clutch plate 58 carried on a hub 64 freely rotatable on a shaft 50. A co-operating clutch plate 60, urged away from plate 58 by spring 62, is fixed on the shaft 50 by splines 52, and has a hub 48 with flats to key with a cam 22 and a collar 72. The cam 22 has a recess 22<SP>1</SP> for co-operation with a nose 23<SP>11</SP> carried by a movable contact blade 23, while collar 72 has a projection 78 which can lift a stop member 70. Screws 32 hold cover 30 and hence cylindrical housing 27 in assembly with cup-shaped housing 25. Mating projections and recesses 46, 44 and 38, 36 respectively locate the spring blade 76 of stop member 70 and contact blades 21, 23. Cam 22 is normally axially clear of nose 23<SP>11</SP> and rotation of shaft 50 can set recess 22<SP>1</SP> to a starting position, corresponding to a desired time interval, without any action on the contact blades. Subsequent axial depression of shaft 50 moves cam 22 under nose 23<SP>11</SP> to lift the latter and close contacts 23<SP>1</SP>, 21<SP>1</SP>, and moves clutch plate 60 into engagement with plate 58, the collar 72 also moving to allow blade 76 to drop its end tab 74 on to an annular step 78<SP>1</SP> thereby retaining the shaft assembly in the depressed condition against the retractive force of spring 62. The motor 16 then rotates the shaft 50 and cam 22 until, after the preset time interval, the recess 22<SP>1</SP> allows contacts 211, 23<SP>1</SP> to open, the projection 78 simultaneously lifting stop member 70 to allow spring 62 to restore the shaft, thereby uncoupling the clutch and disconnecting the drive. Slight lost motion between aperture 65 and hub 48 allows the contacts to open with a snap action.