Patent ID: 7268660

Claim:
A device for indicating that a battery has low power, the device comprising: (a) an indicator having a body movable between a retracted, unactuated position and an extended, actuated position, the indicator being visible when in said actuated position; (b) means for biasing the indicator towards said actuated position; (c) latch means cooperating with a portion of the body of the indicator, when the latch means is in a stop position, to hold the indicator in its unactuated position, the latch means movable between said stop position and a go position which frees the indicator to move, under urging of said biasing means, to said actuated position; (d) a memory alloy wire mechanically associated with the latch means so as to leave the latch means in said stop position when the memory alloy wire is in a relaxed state and to move the latch means to said go position when the memory alloy wire is in a contracted state caused by heating of the memory alloy wire; (e) electrical sensor circuitry in communication with the memory alloy wire, said electrical sensor circuitry adapted to detect when said battery has low power and then cause current flow through said memory alloy wire to heat said memory alloy wire and cause it to change to said contracted state and thereby move the latch means to said go position; and (f) two wire attachment terminals, said terminals having said memory alloy wire secured and electrically connected to them, and wherein said memory alloy wire extends between said attachment terminals, wherein said memory alloy wire is in contact with said latch means at a point between the two terminals, wherein said latch means comprises a rotatable latch member having a protrusion formed thereon, said memory alloy wire running across said protrusion so that said memory alloy wire, when changing to its contracted state, causes a change in rotational position of the latch means by pulling on said protrusion, causing rotation of said latch member, wherein said latch means further comprises a spring exerting a biasing torque against said latch member to urge it rotationally towards said stop position, and said memory alloy wire in contracted state is constructed so as to exert greater and opposing torque on said latch member in order to cause rotation of said latch member from said stop position to said go position, wherein said body of the indicator is elongated and has at least one notch, the notch being shaped to cooperate in a detent manner with said latch member, and wherein said body of the indicator has two notches, said notches being shaped to cooperate in a detent manner with said latch member, one of said notches being constructed so as to permit latching said indicator in said retracted position, and the other of said notches being constructed so as to permit latching said indicator in said extended position.