Overview of Electric Hoists
Electric hoists are material handling equipment used for lifting, lowering, and transporting materials and products. They are powered by an electric motor and have a controller to adjust the lifting parameters. They are efficient in carrying heavy loads and can perform lifting tasks in which the use of conveyors and cranes is impractical and not feasible. The other types of hoists based on the driving mechanism are the pneumatic hoists (or air hoists), hydraulic hoists, and manual hoists.
Electric hoists are positioned overhead above the object to be lifted. They require access to electrical power sources, hence, they are typically found indoors. They are commonly found in warehouses, automotive servicing and machine shops, and manufacturing facilities. Most electric hoists are designed to withstand hazardous and high-temperature environments. There are also electric hoists designed for cleanroom environments that are suitable for handling food and pharmaceutical products. Safety protocols in operating electric hoists must be practiced in all environments.
The use of electric hoists increases operational efficiency by eliminating manual lifting and positioning tasks that require intense effort. They uphold physical ergonomics in the workplace. Electric hoists have faster operation than other types of hoists. They are cost-efficient and consume less space than conveying systems.
Operating Principle of Hoists
Electric chain hoists use a load chain as the lifting medium. The load chain is pulled by a motor that converts electrical energy to mechanical energy used to lift the load. The electric hoist motor is housed inside a heat-dissipating shell, which is typically made from aluminum. The hoist motor is equipped with a cooling fan to dissipate heat quickly during its continuous service and to enable its operation in hot environments.
An electric chain hoist is suspended above the object to be lifted by hooking or mounting it on a rigid structural frame. A hook is attached to the end of the load chain that grabs the object. To commence the lifting operation, the worker switches on the hoist motor. The motor is incorporated with a brake; the brake is responsible for stopping the motor or holding its driven load by applying the necessary torque. The power supply is continuously released by the break during the vertical displacement of the load.
The motor generates torque and transmits it to a series of gears inside the gearbox. The force is concentrated as it passes through the series of gears that rotate the chain wheel to pull the load. As the object increases its distance above the ground, the length of the load chain is collected inside a chain bag, which is typically made from a high wear-resistant textile (e.g., nylon, ABS) or a plastic bucket. The chain bag must ensure the chains are not entangled and are free to slide. The load chain requires lubrication to run smoothly and safely.
Electric chain hoists are equipped with a limit switch that signals the motor to stop automatically in cases where the load exceeds the load rating. They can move the load from one position to another when it is attached to a trolley. The load positioning, as well as the emergency stop, can be manipulated by the worker through the controller.
Electric chain hoists are low maintenance and have easier installation than electric wire rope hoists. They can be used in a variety of environments. The use of electric chain hoists is a cost-effective option.
