Since we’ve outlined the shape, construction, and function of the overhead bridge crane, let’s change tact and place a variety of hoist formats under the microscope. Hoists are a touch more ambiguous to define simply because their outlines are fluid. Some models are portable. Some are fixed and others are attached to horizontal overhead tracks that emulate the overhead cranes we’re already familiar with from previous articles. Staying within the confines of predictable hoist engineering, let’s begin with the popular chain hoist. This version of the format assumes a low profile shape that’s built from a straightforward assembly of parts. A hardened steel chain loops around a pulley several times, and the fulcrum of the operation is set by a loop of steel or a hook that fixes the apparatus overhead. Manually operated, this gear is popular for lifting engines out of vehicle compartment and for use in warehouses. A slaughterhouse warehouse is one common example of this design, with the operator using muscle power to lift slabs of frozen beef.
The chain hoist and the following hoist examples we’re about to cover are all governed by loops of steel rope or chain linkages, the type of pulley in use, and the overhead area where the hoist is attached. Motive power is the other factor, one those sore muscles are always glad to see. Today’s chain hoists use enclosed motors with oil-bath gear assemblies that generate high amounts of torque. Having outlined that single tidbit of data, it’s time to continue. The chain hoist divides into a finite knot of evolving forms, with the chain finding replacement forms, such as wire rope. The electric or manual drive is also substituted in many scenarios, optioned out for pneumatic power or some other motive force. Of course, even when air is the powering medium, some form of electronic control is likely to be in place.
Why electronics should be preferred despite a different source of power is no mystery. Electronic circuitry offers greater control than any alternate crane management system. A modern hoist can adopt such circuitry to aid in linear descent and ascent, and in adding transient movement effects. One example of this movement feature would be a dedicated electronics system for decelerating the load as it reaches the ground. Still, these hoists generally focus on shape and function, on the equipping of hooks and lightweight components that reinforce a portable shape where the hoist can be slid by hand. Finally, a wired remote is commonly hooked into the wiring, thus providing a convenience factor for the operator.
