Patent ID: 8813981

Claim:
A crane assembly, comprising: a boom, a cable, and a hook coupled to an end of the boom by the cable on a sheave, wherein the crane assembly is configured for lifting items via the hook; an anti-two block system, comprising: (A) a body that is rigid, comprising: (i) a base having a surface for receiving the hook; (ii) two extensions projecting upward from the base, perpendicular thereto, wherein the extensions extend outside the sheave on opposite sides thereof; and (iii) a fitting on upper ends of the extensions, wherein the fitting couples to a pin of the sheave such that the body is configured to rotate about the pin that the sheave rotates about; (B) a sensor configured to detect upward loading of the body of the anti-two block system relative to a portion of the end of the boom; and (C) a spring biasing the body of the anti-two block system to the pin; wherein the weight of the body of the anti-two block system rotates the body such that the extensions are substantially aligned with the cable between the end of the boom and hook as the boom rotates; and a controller comprising logic configured to prevent movement of the hook in response to a signal from the sensor of the anti-two block system.