Cranes are used to move materials over variable paths within a restricted area. The major types of cranes are: Jib crane Bridge crane Gantry crane Stacker crane General characteristics of cranes: Used to move loads over variable (horizontal and vertical) paths within a restricted area Used when there is insufficient (or intermittent) flow volume such that the use of a conveyor cannot be justified Provide more flexibility in movement than conveyors Provide less flexibility in movement than industrial trucks Loads handled are more varied with respect to their shape and weight than those handled by a conveyor Most cranes utilize hoists for vertical movement, although manipulators can be used if precise positioning of the load is required 1. Jib Crane Operates like an arm in a work area, where it can function as a manipulator for positioning tasks A hoist is attached to the arm for lifting Arm mounted on the wall or attached to a floor mounted support Arm can rotate 360° The hoist can move along the arm 2. Bridge Crane Bridge mounted on tracks that are located on opposite walls of the facility Enables three-dimensional handling Top riding (heavier loads) or underhung (more versatile) versions of the crane Underhung crane can transfer loads and interface with other MHS (e.g., monorail systems) 3. Gantry Crane Single leg, double leg, and mobile types of gantry cranes Similar to a bridge crane except that it is floor supported at one or both ends instead of overhead (wall) supported Used to span a smaller portion of the work area as compared to a bridge crane The supports can be fixed in position or they can travel on runways Can be used outdoors when “floor” supported at both ends 4. Stacker Crane Similar to a bridge crane except that, instead of a hoist, it uses a mast with forks or a platform to handle unit loads Considered “fork trucks on a rail” Used for storing and retrieving unit loads in storage racks, especially in high-rise applications in which the racks are more than 50 feet high Can be controlled remotely or by an operator in a cab on the mast Can be rack supported
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