(Machinery Part, spare parts)

What is a pulley?
A pulley is also called as a sheave. Chains, ropes and lines can run over a pulley because a pulley is usually designed with a groove along its edge. Different from gears, pulleys don't have teeth or cogs. But both gear and pulley can be used for transmit rotational motion and realize mechanical advantage.
If a pulley is used in sailing, it is usually known as a block.
At DEMY we primarily produce pulleys with plastic covers. These pulleys with plastic covers can be extensively used as casters, rollers or rolling-elements for sliding doors and windows, etc.

Why choose DEMY pulleys?
1. Wide range of plastic cover for your option:
We adopted wide range of engineering plastics for producing the plastic cover our pulleys, including PA, PA 66, PA 66 with 30% GF, POM and PU, etc.
2. Pulley housings made of plastic, aluminium, zinc, pressed steel, etc. are all available here. The materials of pulley housings are customizable.
3. The outer ring of pulleys can be made of both plastic material (POM, PP, PA, nylon) and metal material.
4. The inner rings are made of carbon steel with zinc plated. Feature with good corrosion resistance.
5. Wide range of colors for your option: white, black, yellow, gray, brown, etc.

More information about pulleys (simple machines):

About belt and pulley system:
When two or more pulleys share one belt and those pulleys are in different diameters, we will be able to achieve a mechanical advantage. And the mechanical advantage is determined by pulley's pitch diameter.

About rope and pulley system:
When two or more sheaves are used together and connected to each other by one rope or cable, the sheave compound is usually called as a block and tackle.
A block and tackle is included in list of simple machines because it is regularly applied to change the direction or magnitude of a force and further to achieve a mechanical advantage. The mechanical advantage of a block and tackle is usually determined by the number of supporting ropes or cables.

Other applications of pulleys (to achieve mechanical advantage):
For their good capability of achieving high mechanical advantage, pulleys are extensively used in some heavy duty operations. For example, a large compound pulley system is usually used in cranes to offer an easier cargo lifting. Pulley systems are also regularly used in davits to help lower ships and boats. We can also find pulley systems in hoisters, elevators, winches and so on.