What Are Flexible Shaft Couplings?
Flexible Shaft Couplings are a type of shaft couplings.
Couplings (shaft couplings) are mechanical elements that connect a drive shaft and a driven shaft and transmit power, and are available in two types: rigid couplings and Flexible Shaft Couplings. Flexible Shaft Couplings absorb misalignment between the drive and driven shafts to reduce vibration and load on the bearings, as well as wear and trouble due to misalignment.
Rigid couplings are the most efficient for power transmission with zero backlash, although the drive and driven shafts must be coupled without misalignment.
Applications for Flexible Shaft Couplings
Fig. 1: Application examples of Flexible Shaft Couplings
Flexible Shaft Couplings are generally used as shaft couplings for machines that are subject to high vibration and shock. In particular, due to their excellent absorption of vibration and misalignment, they are often used as shaft couplings for servomotors when high-precision positioning is required, and for high-load equipment and machines with inconsistent rotational speeds.
Jaw and Oldham types, with sleeves and spacers, are characterised by their high maintainability. By removing the spacers, the drive and driven shafts can be dismantled and reassembled without having to move them. They are therefore also used as shaft couplings in pumps, compressors and blowers.
Principle of Flexible Shaft Couplings
Fig. 2: Misalignment (Misalignment)
Couplings Play Four Important Roles
Transmission of power from the drive shaft to the driven shaft
Absorption of mounting errors between drive and driven shafts
Absorption of vibrations from the drive shaft so that they do not propagate to surrounding equipment
Not transferring heat from the drive shaft to the driven shaft.
Flexible Shaft Couplings in particular excel in the second and third points above. Flexible couplings are made by inserting discs, sleeves, spacers, high damping rubber or other materials between the two shafts, or by slitting them to add flexibility. This allows a certain degree of misalignment between the drive and driven shafts (eccentricity, misalignment, axial displacement, etc.), and the flexibility absorbs vibrations and impacts to maintain stable rotation.
The ability to tolerate misalignment of the drive and driven shafts makes it possible to reduce the machining accuracy of each component to a certain extent. As a result, production costs are reduced and the assembly and adjustment of the machine is easier. In addition, when Flexible Shaft Couplings are used for coupling motors, the heat generated by the motor during operation is shielded to a certain extent by the coupling.
Types of Flexible Shaft Couplings
Fig. 3 – Types of Flexible Shaft Couplings (1)
Fig. 4: Types of Flexible Shaft Couplings (2)
Other Information on Flexible Shaft Couplings
Selection of Couplings
The following is a flow chart for selecting a coupling depending on the installation and operating conditions.
Checking the required transmission torque
Checking the installation conditions
Consideration of whether angular errors and axial displacements need to be absorbed
Consideration of the type of coupling (selection of sleeve material and flexible construction)
Consideration of ensuring a service factor (safety factor SF) depending on whether forward or reverse rotation is required
Checking the positioning accuracy from the mechanical elements of the power transmission, e.g. catalogue values.