a device for lifting loads and people in a vertical or nearly vertical direction (freight and passenger elevators; mine, skip, and construction hoists). The term “load-lifting machine” includes machines of various types of construction and kinematic schemes. Such simple devices as jacks, block and tackle, winches, and compound pulleys, as well as complex devices such as self-propelled, fully rotatable loading boom cranes, or automatic loaders, are part of this category.
Load-lifting machines may be stationary, self-propelled, or movable, depending on their application. They may have continuous or intermittent action and may be driven electrically, by an internal-combustion engine, or by some other power source. Their load capacity ranges from a few kilograms to several tons. Many load-lifting machines provide horizontal motion (such as many types of cranes) in addition to the lifting, lowering, and holding of loads at a predetermined elevation. Upon simultaneous operation of the lifting and horizontal-motion mechanisms the load may be moved along any desired path.
The principal parts of load-lifting machines are the frame, the lifting mechanism, and the carrying (grasping) system. Self-propelled machines are equipped with a mechanism for movement; rotating types are equipped with a rotation mechanism. The load-grasping mechanism, like the design of the machine itself, depends on the size, weight, and nature of the load to be moved, as well as on the technical aspects of manufacturing process involved. For lifting and lowering people the machine is equipped with cabins and cages; for moving piece goods it has hooks and various special grips; and for bulk materials, it has buckets, dippers, or graders.
E. I. RIDEL’