Definition of Coupling and Its Types: A Concise Guide

Introduction

Couplings play an extremely important role in mechanical systems. Are you sure you really know them well enough? You who are reading this article may be an experienced engineer or a user with temporary needs. In any case, JLCMC hopes that this article can help you well and deepen your impression of couplings.

1. Coupling definition

What is coupling? A coupling is a device that connects two shafts or a shaft and a rotating part, rotates together during the transmission of motion and power, and keeps the machine from disengaging under normal operation. Of course, there is more than one type. There are also some couplings with other characteristics (such as elastic couplings). They absorb the vibration and impact transmitted from the mechanical parts to a certain extent under the above conditions to buffer the load on the shaft, to improve the stability and life of the entire mechanical system.

Fig. 1 Coupling diagram

2. Coupling types

I. Rigid Coupling

We can even see the basic characteristics of rigid couplings from the name. When precise docking is required in the transmission to firmly connect the two shafts together, we usually choose rigid couplings. Because of its high precision, ultra-low inertia and high sensitivity, it is widely used in machine tool industry and packaging and printing machinery.

Fig. 2 Rigid Coupling

II. Bellows Coupling

Unlike rigid couplings, the working principle of bellows couplings is to use the bending deformation of bellows to transmit torque. Because its elastic element is composed of metal or non-metal bellows, it allows a certain degree of axial, angular and radial misalignment. This design is to compensate for the misalignment of the shaft, thereby reducing the vibration and noise in the transmission system. In harsh environments, the corrosion resistance and sealing of bellows couplings have become the first choice for engineers.

Fig. 3 Bellows Coupling

III. Universal Coupling

Universal couplings come with cross shafts and bearing assemblies. They are very special couplings. Common ones include single universal joints, double universal joints and cross universal couplings. They can transmit multiple angles and even large angle deviations between shafts. They are usually used in transportation vehicles, such as automobile drive systems, ship propulsion devices and heavy machinery, and have very good transmission performance.

Fig. 4 Universal Coupling

IV. Diaphragm Coupling

Diaphragm coupling is widely used in automobile, aviation, shipbuilding, metallurgy, chemical industry and other fields. Because it is a high-performance metal flexible coupling, when the driving shaft rotates, it can use the elastic deformation of the diaphragm to balance the relative displacement (axial, radial and angular) between the main and moving shafts. This can not only play a role in buffering and shock absorption, but also provide protection when the system is overloaded to avoid damage to mechanical equipment.

Fig. 5 Diaphragm Coupling

V. Quincunx Coupling

Quincunx coupling can also be called claw coupling, named because of its design. It mainly consists of two metal claw discs and an elastomer (usually polyurethane plastic or other elastic materials). When the main shaft rotates, the elastomer and metal claw disc of the Quincunx coupling interact with each other, thereby transmitting rotation and torque to the moving shaft. While transmitting, the elastomer continuously absorbs vibration and compensates for radial and angular deviations, thereby ensuring the smoothness and reliability of transmission. It is particularly suitable for working environments with frequent starting, forward and reverse rotation, medium and high speed, medium torque and high-reliability requirements.

Fig. 6 Quincunx Coupling

VI. Elastic Coupling

Speaking of elastic coupling, we will definitely think of rigid coupling, as if they are born to be opposite to it. Elastic coupling is a connection between shafts by springs, rubber and other elastic elements. These materials themselves have good plasticity and vibration and noise reduction characteristics, so their application scenario is almost completely opposite to that of rigid coupling, and it is often used in fan, pump and compressor drive systems.

Fig. 7 Elastic Coupling

VII. Hydraulic Coupling

Hydraulic coupling, a very unique coupling, uses liquid medium (usually oil) to transmit torque through kinetic energy. It must be said that this power transmission processing method is very effective. The hydraulic coupling has outstanding starting ability under soft start, overload protection and no-load conditions.

Fig. 8 Hydraulic Coupling

VIII. Electromagnetic Coupling

Electromagnetic coupling is a non-contact power transmission device based on the principle of electromagnetic induction. The premise of its creation is to eliminate the need for mechanical connection, to perfectly solve the traditional transmission method of complex daily cleaning and device wear in mechanical systems, which is an innovation of traditional transmission methods. Currently, they are commonly used in high-precision and dust-free environments, and can be seen in vacuum systems, semiconductor manufacturing equipment, and other precision industrial fields.

Fig. 9 Electromagnetic Coupling