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-link-type blocks, ring-type blocks, and spreader-beam-type blocks.
Lifting blocks are an important lifting tool. They have a simple structure, are easy to use, and can repeatedly change the direction of the traction steel rope of the block or block assembly, as well as lift or move operating objects. Especially when blocks are combined into a block assembly, used in conjunction with winches, masts, 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 links, rings, and spreader beams for user selection. They are convenient to use, have a wide range of applications, and can be operated manually or mechanically. They are mainly used in production and construction in factories, mines, agriculture, electric power, construction, 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 assembly composed of two blocks can achieve the purpose of saving effort while changing the direction of force. During lifting and transport operations, a single-sheave block can be used as a guide block; a block assembly 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, also known as iron blocks or pulleys, 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 assemblies, etc.
(1) Fixed pulley. A fixed pulley supports 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 force application.
(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 assembly. A pulley assembly 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 pull. In hoisting engineering, pulley assemblies 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 assembly (commonly referred to as the running line), it can complete the hoisting task of equipment or components weighing from several tons to hundreds of tons.
