Belt and chain tensioners reduce belt or chain slack and transmit drive torque uniformly. They also reduce noise and vibration; decrease sprocket, pulley, belt, and chain wear; and increase the life of drive components. In drives, belts and chains are installed with enough tension to create a level of friction that causes the belts or chains to grip the pulleys and the pulleys to turn. Most belt drives consist of flat leather, rubber, or fabric belts running on cylindrical pulleys, or belts with a V-shaped cross section running on grooved pulleys. V-belts require less tension than flat belts because their greater surface area creates more friction. Chain drives that use sprockets are reliable systems for long-running, continuous drive applications with limited shock and torque loads.

Some belt and chain tensioners are fixed in place after installation, while others provide various means of adjustment.

• Manual belt and chain tensioners require operators to adjust screws or unbolt and reposition parts to obtain the proper tension.
• Spring-loaded tensioners automatically maintain tension as belts or chains wear and stretch.
• Floating tensioners are mounted on chains and belts, typically with two opposing pulleys or sprockets.
• Tension rings spin with the drive and mount either inside the belt or chain, or between the drive and the driven pulley or sockets.

Belt and chain tensioners sometimes specify the maximum tension rated to maintain in the drive; however, not all tensioners carry this rating. End-of-travel limit switches for floating or spring-loaded tensioners indicate when a tensioner has run out of adjustment and may require repositioning.

Belt and chain tensioners are available in a variety of sizes, styles, and materials. They can handle different minimum and maximum loads as well as temperatures. With chain drives, maximum chain pitch is an additional consideration. Belt and chain tensioners are used in machinery and equipment, automobiles, bicycles, conveyor belts, and numerous other applications.

The following video shows the operation of an automatic chain and belt tensioner.

Video credit: ROSTA AG

Applications

Perhaps the chain tensioner application that is most recognized is found in the chain drive of single speed bicycles.  The tensioner is typically located near the sprocket on the rear wheel. Other applications include automotive belt tensioners as well as industrial belt and chain tensioners for power transmission applications.

Image credit:

Hangzhou Chinabase Machinery Co., Ltd.