A simple lifting mechanism that vertically lifts heavy objects through a sprocket or drum. It is lightweight, compact in structure, and easy to use, suitable for simple lifting work in construction. Lifting blocks can be divided into single-sheave blocks, double-sheave blocks, and multi-sheave blocks according to the number of sheaves. According to the connection method between the block and the lifted object, they can be divided into four types: hook-type blocks, chain-ring-type blocks, ring-type blocks, and spreader-beam-type blocks.
A lifting block is an important lifting tool. It has a simple structure, is easy to use, and can repeatedly change the direction of the traction steel rope of the block or block system, as well as lift or move rotating objects. Especially when blocks are combined into a block system, used in conjunction with a winch, mast, or other lifting machinery, lifting blocks are widely applied in construction and installation operations. Product specifications range from 0.03 to 320 tons, with wheel systems from single sheave to ten sheaves. Lifting attachments include hooks, chain rings, rings, and spreader beams for users to choose from. They are convenient to use, versatile, and can be operated manually or mechanically. They are mainly used in factories, mines, agriculture, electric power, construction, and other production and construction sites, as well as for machine installation and cargo lifting in docks, shipyards, and warehouses.
A single lifting block can only change the direction of force and cannot save effort; however, a block system composed of two blocks can achieve the purpose of saving effort while also changing the direction of force. During lifting and transport operations, a single-sheave block can be used as a guide block; a block system can be used with a winch for lifting purposes.
The ball and roller bearing wheel cores used in lifting blocks are national standard bearings, with two per sheave. Different specifications can be adopted according to the lifting tonnage. Standard bearings are suitable for high-speed operation and are maintenance-free.
Lifting blocks are also called iron blocks or pulleys. They are used in lifting operations in conjunction with rigging, lifting attachments, winches, etc., to transport and hoist various structural equipment and components. They are indispensable lifting tools.
Pulleys are classified by usage into fixed pulleys, movable pulleys, guide pulleys, and pulley systems, etc.
(1) Fixed pulley. A fixed pulley is used to support the movement of flexible parts. When the rope is under force, the rotor rotates, but the position of the shaft remains unchanged. In use, it can only change the direction of the steel wire rope and does not save effort.
(2) Movable pulley. A movable pulley is installed on a moving shaft and rises or falls together with the object being towed. Using a movable pulley saves effort, but it cannot change the direction of the applied force.
(3) Guide pulley. A guide pulley, also known as an open-side pulley, is similar to a fixed pulley and can only change the direction of the rope without saving effort.
(4) Pulley system. A pulley system is a lifting tool composed of a certain number of fixed pulleys, movable pulleys, and rigging. It can both reduce traction force and change the direction of the pulling force. In hoisting projects, pulley systems are often used to lift heavy mechanical equipment with less traction force. For example, when using a 0.5 to 20 ton (5 to 200 kN) winch to pull the outgoing end of the pulley system (commonly called the running line), it can complete the hoisting task of equipment or components weighing from several tons to hundreds of tons.
