A coupling, also commonly referred to as a shaft coupling or joint, is a crucial mechanical component engineered to connect two rotating shafts (typically a drive shaft and a driven shaft) in various mechanical systems. Its primary mission is to transmit torque and rotational motion between the shafts. Unlike clutches that enable temporary disconnection during operation, most couplings form a permanent connection and do not allow shaft separation under normal working conditions. However, specialized torque-limiting couplings are designed to slip or disconnect automatically once the transmitted torque exceeds a preset limit, thus providing overload protection for the connected equipment.
Core Functions
Power Transmission: This is the fundamental function of couplings. They link independently manufactured components like motor shafts and gearbox shafts, facilitating efficient power transfer. Without couplings, manufacturing integrated long shafts for large machinery would be extremely costly and impractical, as it would lead to huge difficulties in transportation, installation, and maintenance. If a part of an integrated shaft malfunctions, the entire shaft has to be replaced, which increases downtime and repair costs.
Accommodating Shaft Misalignment: Perfect alignment of two connected shafts is nearly impossible during manufacturing, installation, or equipment operation (due to thermal expansion or component deformation). Couplings can compensate for three main types of misalignment: parallel misalignment (eccentricity between shafts), angular misalignment (tilted axes), and axial misalignment (end - to - end movement of shafts). This flexibility prevents issues such as excessive vibration, uneven bearing wear, and noise.
Vibration and Shock Absorption: Flexible couplings, especially those equipped with elastic elements, can effectively absorb operational shocks and vibrations. For instance, jaw couplings use elastomeric intermediates to buffer impact forces, reducing the transmission of vibration from the drive shaft to the driven shaft and extending the service life of precision components.
Additional Protective Roles: Some couplings can block heat transfer between the drive side and the driven side, protecting heat - sensitive components. Moreover, the overload protection function of torque - limiting couplings prevents damage to motors, pumps, and other key equipment caused by sudden load surges.
Main Types
Couplings are mainly categorized into two broad types, each with distinct characteristics and application scenarios:
Rigid Couplings: These couplings have no flexibility and require strict alignment of the connected shafts. They feature a simple structure, low production cost, and strong torque - transmission capacity. Common examples include flange couplings, which consist of two flanges attached to the shaft ends and fastened by bolts, and sleeve couplings that connect shafts via a cylindrical sleeve fixed by keys or set screws. They are widely used in scenarios where shaft alignment is easy to maintain, such as in small - sized pumps and gearboxes.
Flexible Couplings: These are further divided into two sub - types. The first type is flexible couplings without elastic elements, such as universal couplings and chain couplings. They can compensate for shaft misalignment but lack buffering capabilities. Universal couplings, like the Hooke's joint, are ideal for connecting shafts with intersecting or tilted axes, which are commonly seen in automotive drive systems. The second type is flexible couplings with elastic elements, including beam couplings and jaw couplings. They combine misalignment compensation with vibration damping. Beam couplings, also known as helical couplings, are made from a single piece of material with spiral - cut slots, offering zero backlash and high precision, making them suitable for robotics and encoder applications.
