US Patent 7313866 Spring assist knife

A spring assist folding knife and method of biasing a blade in a folding knife. The folding knife includes a blade, liner, and handle. The blade includes a first recess for receiving a pivot pin. The blade includes a second recess offset from the axis of rotation. A latch cam having an offset pin is located relative to the second recess. The liner includes an arcuate slot in which the offset pin of the latch cam is located. The arcuate slot within the liner or handle also includes a convex extension. A spring is configured to provide a force in the direction of blade opening and provides the force throughout the entire range of blade motion. The spring applies its force to the offset pin to bias the blade in the closed position until the blade reaches a predetermined angle. Then the spring biases the blade to the open position.