Bi-directional motion sensor for mobile storage systems

Abstract

A directional detector for use with a mobile storage system including at least a first movable storage unit with a prime mover adapted to move the shelving unit along a path of movement, and at least one blocking object, such as a second movable storage unit, a stationary storage unit or a wall, positioned on the path, there being an aisle formed therebetween. The directional detector detects the entry of an obstacle into the aisle and prevents movement of the first unit until the obstacle is detected to have left the aisle. The detector includes two light source-detector pairs, the source and detector of each pair mounted to each of the first unit and the blocking object on opposite sides of the aisle, and facing each other. A control unit is connected to the light detectors of the pairs and receives signals therefrom, indicating whether or not the detectors are receiving light from the sources. The control unit uses this information to determine the direction the obstacle moved, either into or out of the aisle. The prime mover is disabled from moving the first storage unit along the path until the obstacle is detected to have left the aisle. In-aisle light sources and detectors may also be provided, for the instances when several obstacles enter the aisle at the same time and leave individually.