GB1300695A - Automatically reset timer switch - Google Patents

Abstract

1300695 Time switches MALLORY TIMERS Ltd 19 April 1971 [24 Feb 1970] 22442/71 Heading H1N A timer comprises a drive motor, at least one rotatable programme cam, switching means responsive to said cam, timer reset means to automatically reset said cam to a starting point after a programme sequence, and electromagnetic means energized by axial movement of a shaft carrying said cam and de-energized on completion of said sequence, said electromagnetic means when energized maintaining rotation of said cam by said motor. As shown, a synchronous motor 28 drives a gear 34 via reduction gearing 27, and a programming cam assembly 44 on shaft 18 is coaxial with gear 34 such that ratchet teeth 40 on a clutch plate 38 engage with teeth 36 on gear 34 when shaft 18 is moved axially against the action of spring 43. Cam assembly 44 comprises a cam 54 which has a track 54<SP>1</SP> and is fixed to shaft 18 by a pin 46. A cam 52 is frictionally urged against cam 54 by spring washer 53 and has tracks 52<SP>1</SP> and 52<SP>11</SP>, which, with track 54<SP>1</SP>, can selectively actuate switch units 48 while shaft 18 is axially displaced. Switches 48 are plug-in mounted on insulating side plates 15 of the timer housing. Cam 52 may be adjusted relative to cam 54 by depression of a button (58, Fig. 4, not shown) on either side of the housing, the button engaging peripheral teeth on cam 52 to hold it stationary while cam 54 is turned by knob 70. A coil spring 65 surrounding part of cam 52, and with one end secured to the housing base 12, urges shaft 18 to a start position defined by abutment of a tab (90, Fig. 3, not shown) with another tab (92) carried on an adjustable annulus 72. After having pulled annulus 72 forwardly (against a coil spring 74) and rotated it to set a desired start position on a scale on front plate 86, the knob 70 is depressed. At least one switch unit 48 is closed by the axial movement of cams 52, 54, and the motor 28 and a solenoid 98 are energized thereby. By means of lever 96 the solenoid 98 maintains the clutch 32 engaged until shaft 18 has completed a time delay and/or a programme sequence, whereupon the one switch unit 48 is opened and shaft 18 is released to be reset to its start position by spring 65. In a modification (Fig. 6, not shown) the solenoid (98<SP>1</SP>) surrounds the shaft 18 and its plunger armature (100<SP>1</SP>) is carried directly on shaft 18.