GB1297029A - - Google Patents

Abstract

1297029 Time switehes; retractive snapaction switches MALLORY TIMERS Ltd 6 April 1970 [4 April 1969 (2)] 16233/70 Heading H1N A programme timer, for a domestic clothes drying machine, for example, comprising at least one rotary cam-operated electrical switch is arranged such that axial movement of the cam-shaft, or a portion thereof, actuates a snap switch, said snap switch comprising a contact blade fixed at one end and divided by two longitudinal slots into a central portion and two side portions, each side portion being formed with a depression to render the blade snap-acting, and actuating means coupling the cam-shaft to the central portion of the blade so that axial movement of the cam-shaft causes engagement or disengagement of a contact on the free end of the blade and a second contact. In a first embodiment, as shown, a synchronous motor 46 drives, through gearing 48, a gear 40 meshing with gear 36 integral with a control cam disc 34 loosely journalled on a shaft 20. Cam 34 and programme cams 1 to 7, the latter being keyed to shaft 20, actuate switch blades (such as 118, 118<SP>1</SP>, Fig. 1, not shown). The continuously driven cam 34 controls intermittent drive to the cams 1 to 7 by selectively energizing a solenoid 80 whose plunger 102 rocks lever 86 to lift gear 88 (Fig. 3) thereby coupling motor-driven gear 100 to gears 78, and thus driving pinion 105 which is in mesh with gear 106 (Fig. 1) connected to spring-washer clutch 108 which frictionally drives shaft 20 and hence cams 1 to 7. The switch blades (118, 118<SP>1</SP>) are provided with back-stops (126) such that they do not ride on the falls of the cams thereby reducing wear. Axial movement of shaft 20 rocks a lever 58 whose forked ends form jaws 62, gripping a washer 54 on shaft 20, and 62<SP>1</SP> gripping the centre of a trifurcated blade spring 60 to open and close contacts (72, 74, Fig. 4, not shown) in the supply circuit of motor 46. In a second embodiment (Fig. 5, not shown) an additional motor (84) is energized to drive the programme cams instead of using a solenoid clutch mechanism. Another embodiment (Figs. 6 to 9, not shown) has a shaft divided into two portions (234, 236) and a pull moves one portion only to actuate the snap switch; while in a modification (Fig. 10, not shown) a push on the shaft causes relative axial movement to actuate the snap switch. The modification of Fig. 10 also has the rocker arm (288) extended outside the timer casing for alternative actuation by external means such as a solenoid (not shown).