1) Double leg gantry
An overhead traveling crane designed so that the bridge carrying the trolley or trolleys is rigidly supported on two or more legs moving on fixed rails embedded in the floor (via end trucks attached to the bottom of each leg) or on wheels.
A configuration of small trolleys, support track, and electirical cable utilized to provide power to material handling devices while keeping the power cable out of harm's way. The cable is looped or "festooned" by attaching to trolleys supported on a track. Thsi arrangment allows this cable to be "bunched" in an accordian-like fashion so as to keep the cable from becoming entangled in the movement pattern of the device it serves.
Often utilized to "stretch" cable across the bridge of an overhead traveling crane.
3) Double girder crane
An overhead traveling bridge crane that utilizes two bridge beams set atop the runway (end) trucks. Generally this type of crane utilizes a top running trolley hoist which moves along the top of the two bridge beams on its own set of trucks/trolley wheels. The hook from the hoist "falls" between the two bridge beams. Headroom under the crane is increased by utilizing this hoist/crane configuration.