Photochromic time delay unit

Claim 1

A photochromic time delay assembly comprising: an opaque housing including first and second compartments, means for closing said compartments against entry of light from outside said housing, a lamp in one of said compartments, a photochromic lens separating said compartments including a layer of photochromic material thereon opeRative to change from a transparent state to an opaque state when exposed to light rays from said lamp, a light dependent resistor having a low resistance when exposed to a high intensity light source and a high resistance when exposed to a low intensity light source, said light dependent resistor being exposed to light from said energized lamp following passage thereof through said photochromic lens, an energization circuit including a switch, said light dependent resistor and an electrically energizable load, said switch connecting said load and light dependent resistor across a power source, means including said switch for simultaneously energizing said lamp when said load is connected across the power source, said light dependent resistor having a low resistance when the switch is initially closed to produce a high voltage across the load, said lamp and lens responding to energization of the load by said switch to cause said lens to become more opaque to produce a time controlled reduction of light impinging on said light dependent resistor to increase the resistance of said resistor to produce a reduced voltage across the load following a time delay.