摘要:
An elapsed time indicator or delay switch including a cylindrical housing of non-magnetic material closed at one end by a base of magnetic material. A pair of spaced apart electrically conducting terminals insulated from and extending into and through the base. A permanent magnetic piston slidably positioned within the housing, spaced from said base and having a viscous fluid therebetween. A pressure releasable piston retainer disposed above the piston for limiting the movement thereof and a flexible deformable diaphragm, proximate the retainer, closing the opposite end of the housing. The device is initiated upon pressure being applied to the diaphragm which thereupon deflects the retainer and releases the piston that in turn is attracted toward the base and moves theretoward at a rate dependent, among other factors, on the fluid viscosity, the magnetic force, initial spacing and the clearances between the housing and the piston. Piston travel terminates upon contact with the inner terminals and electrical shorting thereof which may be used to indicate the end of the elapsed period.