Switch actuator means of the time delay type

Claim 1

Time delay means for operating an electrical switch mounted in a switch box, said switch having an operating lever projecting from the face of said switch box and being pivotable between ON and OFF positions, comprising: (a) a switch plate (2) adapted for mounting on the face of the switch box, said switch plate containing an aperture (10) for receiving the switch lever; (b) a hollow cylinder (14) secured to said switch plate, one end of said cylinder being closed and the other end being open to atmosphere; (c) a piston (16) arranged for sliding movement in said cylinder; (d) one-way seal means (18) connected with said piston for defining a substantially fluid-tight chamber adjacent the closed end of said cylinder, said seal means comprising a flexible annular seal secured to the end of said piston remote from said closed cylinder end, said seal having a generally cup-shaped configuration with an annular circumferential lip portion in sliding engagement with the inner circumferential wall surface of said cylinder, said lip portion extending toward the open cylinder end; (e) spring means (22) biasing said piston toward the said cylinder open end; (f) activating means (30) for displacing said piston against the biasing force of said spring means toward a first position adjacent the closed end of the cylinder, thereby to force fluid out of said chamber via said seal means, said seal means being operable, when said piston is in the first position, to gradually leak fluid back into said chamber at a predetermined rate, whereby said piston is displaced by said spring means toward a second position adjacent the open end of said cylinder; (g) vent means for venting said chamber when said piston is in an intermediate position between said first and second positions, said vent means comprising a slot (14b) contained in and extending axially from the open end of said cylinder; and (h) a switch lever operating member (26) pivotally connected intermediate its ends with said switch plate for movement about a pivot axis normal to said switch plate, said operating member being adapted for engagement at one end with said lever, the other end (26c) of said operating member extending through said slot for engagement by said piston when said piston is adjacent said intermediate position, said operating member being pivoted by said piston from a switch-on position to a switch-off position when said piston is displaced from its intermediate position to its second position, respectively, whereby said piston travels at a given velocity from said first position to said intermediate position, and at a higher velocity from said intermediate position to said second position, thereby to quickly pivot said operating member from the switch-on position to the switch-off position.