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Chains and sprockets: How they work together
Chains and sprockets are important elements in the design and mechanisms of machines and equipment. They are indispensable when it comes to the mechanical transfer of motion and force. But what types of chains and sprockets are there and what are their specific characteristics? In this blog article, we’ll dive deep into this topic and take a detailed look at the specifics of the different types of chains and sprockets.
Chains & Sprockets
Chains and sprockets are a fundamental element of mechanics and have evolved over the years to become an essential component in design. Chain drives offer the possibility to transmit drive forces and torques with low slip, interlocking, and without preload.
The combination of chains and sprockets is mainly used in two applications:
- Transferring drive power from a connected motor to another system.
- Transporting workpieces by direct or indirect loading.
Components of an industrial chain
An industrial chain, such as a roller chain, is a mechanical component with movably supported links for transmitting a force. By the engagement of the chain rollers in the gaps of a pinion (sprocket), the force is transferred from the drive wheel to the chain by positive engagement. Since chains consist of individually movable links, they can only transmit tensile forces.
When combining the chain and sprocket, make sure that they have identical specifications and type.
Sprockets and chain idlers
Sprockets, also known as “pinions”, are mechanical components used in combination with chains to enable the transmission of the forces of a drive in the form of a chain drive. A sprocket is usually fixed to a shaft. The teeth of the sprocket interlock into the chain links and thus transfer the torque applied to the shaft to the chain, or vice versa.
Unlike the sprocket, a chain idlers are mounted on a fixed shaft/axis where it can rotate freely with the chain. Chain idlers allow for deflection, changes of direction, and maintain chain tension.
Use of idlers and track rollers
Tension rollers, track rollers or chain guides serve as guides or support or as running surfaces. Depending on the type, they are suited for different loads and operating speeds.
Track rollers should not be mounted on the tensioned side of the chain, but on the loose side of the chain, except for applications requiring reversible operation. Installing the track roller on the tensioned side of the chain unnecessarily increases the tension and thus reduces the service life of the chain.
Make sure that the number of teeth is selected so that the sprocket does not exceed the max. permissible speed.
Note:
- If the number of teeth is less than that of the drive sprocket, the speed of the track roller/chain tensioning sprocket will increase.
- At least 3 teeth of the track roller/chain tensioning sprocket should contact the chain.
Track rollers and chain tensioners can be adjusted in several ways. An eccentric shaft system, clamping arm system or plain bearing system is common here. Automatic tensioning systems reduce maintenance time and effort, and also compensate for chain elongation. However, they are usually only suited for low-speed chains.
Various assembly and disassembly tools, such as chain pin ejectors or roller chain pullers, simplify maintenance and replacement of defective roller chain links.
What are the types of chains and how can they be used efficiently?
Chains are mechanical parts designed to transfer the driving force as a tensile force. In this case, individual links are connected to one another and thus join together into a continuous sequence, the length of which is determined by the number of individual links. Chains are available in a wide range of styles, depending on the application, and are used there to take advantage of their benefits. Chains in different versions can be used:
Roller Chain
The links of roller chains consist of an outer member (also outer tabs) and an inner member (also inner tabs) which are connected to one another by a bolt. A sleeve surrounds the bolt and the sleeve is in turn surrounded by a roller. This design makes it possible to minimize the friction between the chain and sprocket and facilitates smooth movement. You can shop roller chains here.
Block chain
Block chains consist of one-piece chain links that are connected together using a bolt. Compared to other types of chains, they are characterized by high torsional rigidity but also a high weight. Mechanical engineers therefore frequently select block chains made of plastics to reduce weight.
Conveyor chain
The chain links of conveyor chains, also called plate chains, have a flat plate on the outside, which ensures positive engagement of the chain surface. Conveyor chains are often used as a means of transporting small or loose materials and workpieces.
Chain with attachments
Attachments can be mounted on roller chains for conveying smaller workpieces, to which tabs are attached.
The movement of the chain is thereby transmitted directly to the workpieces, thus transporting them along the direction of travel.
Accumulating conveyor chain
This form of transport chain is designed to quickly transport workpieces or pallets. Its special design gives it the ability to run pallets at twice the chain speed.
The accumulating conveyor chain (in the image - WCHE) is usually positioned in a profile (in the image - WCF) on which the guide rollers of the chain rest. The track rollers mounted between the chain guides act as a support surface for the goods to be transported (pallet) and rotate at the same speed as the guide rollers. When the goods are backed up, the transport chain continues to run almost unhindered thanks to the rollers under the workpiece. A double-speed chain sprocket (WESP in the picture) is designed to drive the chain while also deflecting it. On the loose side, the transport chain is supported by a return designed specifically for this type of transport chain (in the image - RNG) and returned within the aluminum profile for double-speed chains.
How is a chain drive installed?
Chain drives are installed on the driving and driven shafts using the sprockets. Idlers and guide rollers must be used depending on the arrangement and course of the chain to prevent sagging and thus jamming of the chain.
Horizontal arrangement
Even with horizontally arranged shafts, some points regarding the direction of rotation of the shafts must be taken into account. The arrangement (1) in the following image shows a correct application.
As shown in the image under arrangement (2) and (3), if arranged incorrectly, the elongation of the chain may prevent the chain links from easily exiting the sprocket teeth.
In particular for arrangement (3), an tensioning idler or the like must be used, since the load underside and the slack upper side of the chain may otherwise contact each other.
Vertical arrangement
In particular, if the shafts are arranged vertically, sufficient shaft offset should be ensured. An offset angle greater than 60° from horizontal is a common cause of chain drive malfunction.
If arranged vertically, the small sprocket should be installed above the large sprocket to prevent the chain from falling off (see 2). In addition, a suited tensioner idler (see 3) should be used.
Sagging
The chain sagging between the two shafts should be between 2% and 4% depending on the application.
A sagging of 4% is the rule, while a sagging of approx. 2% is typically selected in the following use cases:
- With nearly vertical transmission.
- With a shaft spacing of one meter or more.
- With frequent starting and stopping of the chain under heavy load.
- When using the chain in both directions.
Fluctuating Load
If load fluctuations occur regularly in the application, a preload must be applied to the chain with suitable tensioning mechanisms (chain tensioners), which prevents vibrations and thereby reduces noise and material stress.
How is a chain drive maintained?
When it is correctly selected and designed, regular maintenance of a chain drive is usually limited to maintaining proper lubrication. Different methods are available for lubrication.
In some cases, applying lubricating oils to the chain is not desired or permitted, for example in the food sector. For this purpose, maintenance-free versions of chains (usually made of engineering plastics) are available, which do not need to be lubricated for proper operation.
Before lubrication, the chain should always be cleaned of dirt and used lubricating oil with a suitable chain cleaner. Depending on the application, a suitable lubricant with appropriate viscosity and temperature resistance must be selected.
Manual oil lubrication
Manually apply oil using an oil can or brush. Usually at least once a day.
Apply oil evenly 3-4 times over the entire chain length while slowly continuing to rotate the chain. Make sure that limbs or clothing do not get between the chain and the sprocket. Wipe excess oil from beneath the chain with a cloth to prevent the oil from being flung off into the system.
Drop lubrication
Adjust the drop lubrication so that approximately 5-20 drops of oil per minute are applied to the chain.
Placing a simple container above the chain is recommended for splash protection purposes.
Oil bath lubrication
Submerge the underside of the chain approximately 10 mm in the oil.
Use a sealed oil reservoir. Clean the container carefully before installation to remove dust, dirt and other foreign objects. Always ensure the correct oil level. Check the fill level regularly and do not overfill the oil reservoir.
Rotary plate lubrication (slinger plate)
The chain is lubricated with a slinger plate. Immerse the plate approximately 20 mm in the oil. The rotation speed of the plate should be at least 200 m/min.
Forced lubrication via pump
For overheating protection, it is necessary to adjust the oil quantity accordingly.
