Short Answer:

Torque transmission in couplings refers to the process of transferring rotational power or twisting force from one shaft to another through a mechanical connection known as a coupling. The main purpose of torque transmission is to ensure smooth power transfer between connected shafts without slippage or misalignment.

In simple terms, when one shaft rotates, the coupling helps transmit the torque generated by the driving shaft to the driven shaft efficiently. It allows power transfer even when there are slight misalignments, vibrations, or movement between the connected parts in a mechanical system.

Detailed Explanation :

Torque Transmission in Couplings

Torque transmission in couplings is one of the most important functions in mechanical power transmission systems. Couplings are mechanical devices used to connect two shafts together to transmit torque and rotational motion. They ensure that the power produced by the prime mover (such as a motor or engine) is delivered effectively to the driven machine (such as a pump, gearbox, or conveyor).

The main objective of torque transmission is to provide a reliable and efficient transfer of rotational energy while maintaining alignment and reducing stress on connected components. The design of the coupling, its material, and its flexibility all affect how effectively torque is transmitted.

1. Concept of Torque Transmission

Torque is a rotational force that tends to produce rotation around an axis. In a mechanical system, torque transmission means passing this force from one rotating shaft to another without loss of energy or slippage.

A coupling acts as a mechanical link between two shafts. When the driving shaft rotates, it produces torque. The coupling then transmits this torque to the driven shaft, ensuring both rotate together at the desired speed and direction.

Torque transmission in couplings is governed by several important factors such as:

• The strength and stiffness of the coupling material.
• The type of coupling used (rigid or flexible).
• The amount of misalignment allowed between shafts.
• The operating conditions such as load, speed, and temperature.

Efficient torque transmission requires the coupling to maintain firm contact and alignment between the shafts, ensuring minimal power loss.

2. Types of Couplings Based on Torque Transmission

The way torque is transmitted depends on the design of the coupling. Generally, couplings are classified as rigid or flexible based on their function.

1. a) Rigid Couplings:
   Rigid couplings provide a solid mechanical connection between two shafts. They are used where precise alignment is possible, and no flexibility is required. The torque transmission here is purely mechanical — through friction, keys, or bolts.
   Examples include:

• Sleeve coupling
• Flange coupling
• Muff coupling

Rigid couplings transmit torque efficiently but cannot absorb vibrations or misalignments.

1. b) Flexible Couplings:
   Flexible couplings allow some degree of misalignment and absorb shocks and vibrations while still transmitting torque effectively. They use elastic or flexible materials such as rubber, springs, or flexible discs.
   Examples include:

• Oldham coupling
• Jaw coupling
• Gear coupling
• Universal joint

In flexible couplings, torque transmission occurs partly through mechanical contact and partly through elastic deformation of the flexible material.

3. Mechanism of Torque Transmission

Torque transmission in couplings can occur through various mechanisms depending on the coupling type:

1. a) Direct mechanical contact:
   In rigid couplings, torque is transmitted through direct contact between the coupling parts and the shaft surfaces. The connection is often made using keys, splines, or bolts.
2. b) Frictional force:
   In friction-type couplings, torque is transmitted through the friction generated between mating surfaces. Examples include friction disc couplings and clutches.
3. c) Elastic deformation:
   In flexible couplings, torque is transmitted by elastic deformation of the flexible element, which absorbs misalignment and vibration while still transferring power.
4. d) Magnetic or fluid transmission:
   In special types of couplings like magnetic or fluid couplings, torque is transmitted without direct physical contact — using magnetic fields or fluid motion.
5. Importance of Torque Transmission in Couplings

Torque transmission plays a vital role in ensuring the proper functioning and longevity of machinery. Its importance can be understood through the following points:

• Efficient Power Transfer: Ensures that mechanical energy from the driver reaches the driven machine with minimal losses.
• Protection from Overload: Some couplings are designed to slip or disconnect when excessive torque occurs, protecting equipment from damage.
• Reduction of Vibration: Flexible couplings help absorb vibrations and shocks, ensuring smoother operation.
• Compensation for Misalignment: Torque can still be transmitted even if shafts are slightly misaligned.
• Improved Machine Life: Reduces stress on bearings and shafts, thus increasing the lifespan of mechanical components.

5. Factors Affecting Torque Transmission

The efficiency of torque transmission depends on several parameters:

• Type of coupling and its material strength.
• Accuracy of shaft alignment.
• Operating torque and speed.
• Type of load — steady or fluctuating.
• Lubrication and maintenance condition.

Proper design and maintenance of couplings ensure that torque is transmitted efficiently and safely.

Conclusion:

Torque transmission in couplings is the process of transferring rotational force from one shaft to another. It is essential for the smooth and efficient operation of machines. Depending on the type of coupling, torque can be transmitted by mechanical contact, friction, or elastic deformation. Proper torque transmission reduces wear, absorbs vibration, and ensures power is delivered without loss or damage. Therefore, couplings are an essential part of every mechanical system where power or motion must be transmitted between rotating parts.