GB1298993A - Timing device - Google Patents

Abstract

1298993 Dashpot-type delay timers AMERACE ESNA CORP 18 Feb 1970 [26 Feb 1969] 7833/70 Heading F2S [Also in Division H1] In a delay timer of the kind in which air flows at a controlled rate through a restricted orifice, the orifice is defined by a porous plug 112 and its flow cross-section is made adjustable by fitting an apertured shutter 122 over the plug's surface The shutter is rotatable about the axis of a screw 120 and the shape of the aperture 124 in it is as shown in Fig. 6, so that the unobstructed area of the plug 112 diminishes progressively as the shutter 122 is rotated. In use, as shown in Fig. 2, to control a switch 54, a solenoid 18 is energized to pull up an armature 20 and thereby raise, through a spring 70 and bush 32, a rod 30 which in turn raises a diaphragm 38 in the timer. This movement causes flow of air from the upper chamber 46 of the timer, through the porous plug 112 and by way of channels 126 and 128 to the lower chamber 48. The latter is closed, i.e. there is no connection to the ambient atmosphere. The switch 54, controlled by a snap-action spring 60-64, is operated by means of a bifurcated switch arm 52 engaged with the rod 30, the delay between solenoid energization and switch operation being determined by (a) the setting of the shutter 122 and (b) the initial position of the solenoid. The latter is adjustable in a vertical direction, its holding screws 162 being mounted in slots 164 for this purpose. On de-energization of the solenoid, the spring 70 assists the armature 20 to descend, carrying the rod 30 downwardly and compressing springs 92 and 102 in the timer. A valve element in the form of an elastomeric ring 86 has hitherto been sealed at its lowermost edge 88 to a ledge 96 on the rod 30. Compression of the springs 92 and 102 breaks this seal to open a flow path through the diaphragm and thereby allow rapid return of air from the lower to the upper chamber, thereby (a) releasing the switch and (b) recharging the upper chamber for the next cycle.