In an industrial facility, motors and turbines use energy to produce rotational mechanical motion. In order to harness this motion to perform useful work, there must be a way to transmit it to other components and machines. One method of power transmission is through the use of chain drives and sprockets.
Chain drives consist of an endless series of chain links, which mesh with toothed sprockets. Chain drives are used to perform three basic functions: transmitting power, conveying materials, and for timing purposes.
Transmitting Power
Chain drives are used to transmit power from one component to another. Specifically, they transfer speed and torque through the use of a linked chain and sprockets. Chain drives are well suited for this task because the sprocket teeth and chain setup results in a positive speed ratio and the ability to transfer a large amount of torque within a compact space. Chain drives are used in many types of industrial applications, such as:
- Rigging and moving heavy materials
- Hydraulic lift truck fork operation
- Increasing or decreasing a driver’s output speed by altering gear ratios between the driver and the sprocket being driven
- Overhead hoists
- Operating conveyer belts
Conveying Materials
Chain drives are used in many types of industries to move, slide, carry, push and pull a variety of materials. These drives can be used to move objects directly by attaching pockets, buckets, frames, or meshes to the chains. They can also be used indirectly, such as turning rollers, which, in turn, move a conveyor belt.
Timing Purposes
Chain drives can also be used to synchronize or time movements. For example, industrial combustion engines use chain drives to control valve timing.
Advantages and Disadvantages
There are several advantages and disadvantages of using chain drives over other types of mechanical transmission systems available.
Advantages
- Do not slip or creep, and so are more efficient than belt drives
- Are more compact than belt drives
- Operate effectively at high temperatures
- Are often easier to install than belt drives
- Do not deteriorate due to oil, grease, sunlight, or age
- Can withstand abrasive conditions
- Can operate in wet conditions
- Can be used on reversing drives
Disadvantages
- Cannot be used in applications where the drive must slip
- Require more precise alignment than belt drives
- Typically require frequent lubrication
- Are noisy and can cause vibrations
- Do not have the load capacity or service life of gear drives
Dimensional Variables
Chain drives are used in many different applications, covering a large range of speeds and loads. With the exception of a few specialized cases, the dimensions of roller chains remain in proportion to each other as the overall size changes. The four dimensional variables that describe a roller chain are pitch, width, pin diameter, and the thickness of the link plates. Understanding these common dimensions will allow personnel to more efficiently communicate issues with regards to the chain drive during maintenance, replacement, or any other process involving chain drives.
Pitch – As described earlier, pitch is the measured length between the centers of the holes in the link plates. The pitch of the chain links must reflect the size of the sprocket teeth. The other three measurements are directly proportional to the chain’s pitch.
Width – The width is defined as the distance between the inner link plates. The width is approximately 5/8th of the link pitch.
Pin Diameter – The pin diameter is the diameter of the pin connecting the inside and outside link plates together. The pin diameter is approximately 5/16th of the link pitch, and about half the size of the roller diameter.
Link Plate Thickness – The inner and outer link plates are the same thickness, which is approximately 1/8th of the link pitch. The thickness of link plates for the heavy series of any pitch chain is approximately the same as the thickness of the plates on the next larger pitch standard series chain.