A coupling is a device used to connect two rotating shafts to transmit torque from a driving shaft to a driven shaft. Beyond this primary function, couplings compensate for shaft misalignment, cushion shock loads and vibrations, and serve a protective role during overloads. In mechanical engineering, they are an indispensable component of drive systems.
Main Types and Classification
Based on their operating principle and design features, couplings are divided into several main groups:
Rigid Couplings: Used for rigidly connecting shafts that are precisely aligned. They do not compensate for misalignment and require accurate installation.
Flanged Couplings: Consist of two hubs connected by bolts. Simple and reliable.
Sleeve (Muff) Couplings: A simple sleeve connecting the shaft ends. Used in light-duty machinery.
Flexible/Elastic Couplings: Feature a flexible element that absorbs vibrations and allows for small shaft displacements.
Jaw (Spider) Couplings: The most common type. Contain an elastomeric spider insert between two metal hubs. Cost-effective and serviceable.
Tyre/Flexible Rib Couplings: Use a toroidal (doughnut-shaped) rubber or polyurethane element. Good for compensating misalignment.
Grid (Snake Spring) Couplings: Use a steel grid spring in a sealed housing. Applied for high-torque applications.
Compensating (Misalignment) Couplings: Allow shafts to operate under significant misalignment.
Gear Couplings: Transmit high torque through geared hubs. Require lubrication.
Universal Joints (Cardan Joints): Allow transmission of rotation at an angle.
Special and Control Couplings:
Friction Clutches: Allow smooth engagement/disengagement of torque transmission.
Safety (Overload) Couplings: Automatically disengage or slip when the load exceeds a set limit.
Design and Operating Principle: Example of a Jaw Coupling
The Jaw Coupling with an Elastomeric Spider is a classic example of a flexible coupling.
Construction: Two metal hubs with interlocking jaws. Between them is a spider-shaped insert made of an elastomer like polyurethane, Hytrel, or NBR rubber.
Operating Principle: Torque is transmitted through the jaws compressing and shearing the elastomeric spider. This deformation absorbs shocks and allows for angular, parallel, and axial shaft misalignment.
