A coupling is a device that connects two shafts for the transmission of power. According to the alignment accuracy and torque required, couplings are rigid or flexible. The shaft coupling is a mechanical component that transmits power by connecting two spinning shafts, such as the driving shaft and the driven shaft. It’s found in motors, pumps, generators, and compressors, among other things.
For shaft misalignment, couplings are used to link shafts of devices that are constructed separately, such as a motor and generator. In terms of mechanical adaptability, Shock loads are absorbed as they are transferred from one shaft to another. Overload protection is also provided.
In this article, you’ll learn the common types of couplings and their functions.
Read more: Understanding the term coupling
Types of Couplings
The followings are the common types of couplings:
- Rigid Coupling
- Sleeve or muff coupling.
- Clamp or split-muff or compression coupling, and
- Flange coupling.
- Flexible coupling
- Bushed pin-type coupling,
- Universal coupling, and
- Oldham coupling.
- Gear coupling
- Bellow coupling
- Jaw couplings
- Diaphragm couplings
- Fluid Coupling
- Constant speed coupling
- Variable speed coupling
When two shafts are exactly aligned, a stiff coupling is utilized. These types of couplings are only intended for use in close proximity. Sleeve or muff coupling, Split-muff coupling, and Flange coupling are just a few examples.
Sleeve or muff coupling
The simplest sort of rigid coupling is the muff or sleeve coupling, which is composed of cast iron. A muff coupling is made up of a shaft, a key, a sleeve or muff, and a hollow cylinder with the same inner diameter as the shaft. A gib head key is used to secure it over the ends of the two shafts.
With the use of a key and a sleeve, power is transferred from one shaft to the other. To transmit the torque, all of the elements must be sufficiently strong.
Clamp or split-muff or compression coupling
Split muff coupling is another name for this type of coupling. The muff or sleeve is divided into two sections and welded together with this sort of linkage. Cast iron makes up the halves. Studs or bolts are used to secure them together.
Both shafts’ ends are joined, and a key is inserted into the shafts’ keyways. The muff has one end that is attached from below and the other end that is attached from above. Bolts and nuts connect the two pieces. This connection is commonly utilized at high speeds. To assemble or disassemble the connection, the shaft position does not need to be changed.
Read more: Understanding the various types of fasteners
Flange types of couplings are made up of two cast iron flanges that are attached to each shaft’s end. The drive is completed by bolting the two flanges together. The purpose of a flange coupling is to join two tubes in a sealed way.
One of the flanges has a projecting portion, while the other has a recess comparable to it. Each flange’s ends are soldered together to ensure that they are properly aligned without causing resistance to the substance passing through them.
It aids in aligning the shaft and bringing it into the same line. Nuts and bolts are used to join the two flanges together. Typically, these couplings are employed in pressured pipe systems. It’s also used for big loads. As a result, it is quite useful for massive shafting.
The three different types of flange coupling include; Unprotected type flange coupling, protected type flange coupling, and marine type flange coupling.
These types of couplings connect two shafts that are misaligned both laterally and angularly. A few examples are Bushed pin-type couplings, Universal couplings, Oldham couplings, Gear couplings, Bellow couplings, Jaw couplings, and Diaphragm couplings
Bushed pin-type coupling
These are particular types of couplings that are utilized when the two shafts are slightly misaligned in terms of parallelism, angular misalignment, or axial misalignment. The rigid flange coupling has been modified. It is made up of two sections that are constructed differently, as well as pins and rubber bushes that cover the pins.
Between the faces of the two sections of the connection, there is a 5 mm clearance. There is no solid link between them and the drive, which is accomplished by compressed rubber or leather bushes.
Hooke’s coupling is another name for universal coupling. Universal coupling is utilized when the axes of two shafts cross at a modest angle. The inclination of two shafts can remain constant, but when motion is transferred from one shaft to another, the inclination changes.
In the illustration above, a universal joint is depicted. These couplings are commonly employed in power transmission. The universal coupling is found in the automobile’s transmission from the gearbox to the differential. Two universal joints are used on each end in these circumstances. One connects the propeller shaft to the gearbox, while the other connects the differential to the opposite end. Universal coupling is also used to transmit electricity to various spindles of a machine.
When there is a lateral misalignment between two shafts, an Oldham coupling is used. The schematic representation of an Oldham coupling is shown below. It is made up of two flanges A and B with slots and a center floating section E with two tongues T1 and T2 as depicted in the diagram.
Pins are used to secure the center section, which is attached to flanges and floating sections. The T1 tongue goes into flange A and allows for back-and-forth motion, while the T2 tongue fits into flange B and allows for vertical movement. As they rotate, these two components of speed will cause the shaft’s lateral misalignment to be corrected.
A modified variant of the flange coupling is the gear coupling. Because of the massive size of the teeth, gear couplings can transmit a lot of torque. Instead of being a single element like a flange coupling, the flange and hub are assembled separately in this form of shaft coupling.
Each joint has an internal and external gear pair with a 1:1 gear ratio. And gear coupling is limited to angular misalignments of 0.01-0.02 inches in parallel and 2 degrees in angular misalignment. For similar uses, gear couplings and universal joints are employed. These are typically employed in heavy-duty situations where a lot of torque has to be transmitted.
Bellow types of couplings have twin coupling ends called hubs and are flexible couplings. The torsional rigidity of these couplings is outstanding, allowing them to reliably transfer velocity, angular position, and torque. Stainless steel is the most common material used. When high precision positioning is necessary, these couplings are used.
Bellows couplings have thin walls and are only slightly flexible when misaligned angularly, axially, or parallelly. The coupling below is welded to the hubs. The torsional stiffness of these couplings is the highest of any servo motor coupling.
This type of coupling is employed in motion control applications as well as general-purpose power transmission. The jaw coupling is designed to transfer torque while decreasing system vibrations and correcting misalignment, protecting other components from damage.
Jaw couplings are made comprised of two metal hubs and an Elastoplast element, sometimes known as a “spider.” Jaw couplings have several advantages, including the ability to manage angular misalignment and reactive loads as a result of misalignment, as well as strong torque to outer diameter capability, chemical resistance, and decent damping capabilities.
Diaphragm couplings are a type of nonlubricated coupling that transmits torque and compensates for misalignment between equipment shafts in high-performance turbomachinery.
Torque is transmitted from the outside to the inside diameter, and then from the inside diameter to the outside diameter, in this sort of coupling. The flexible components in diaphragm couplings are made up of a single or a series of plates. Misalignment can be angular, axial, or parallel with diaphragm coupling. When high torque and fast speed are necessary, this connection is used.
Read more: Understanding gears
Hydraulic coupling is another name for fluid coupling. It’s a hydrodynamic device that uses hydraulic fluid acceleration and deceleration to deliver the rotating mechanical power. It consists of a runner on the driven shaft (input) and an impeller on the driving shaft (output) (output). The impeller functions as a pump, while the runner functions as a turbine.
The tangential component of absolute velocity is low in impellers near their axis. Because the tangential component of absolute velocity is high near the impeller’s periphery, the fluid velocity increases as the impeller accelerate. The kinetic energy of an object increases as its velocity increases. The fluid exits the impeller at a high velocity, impacts the runner blades, exchanges energy, and exits the runner at a low velocity.
That is all for this article, where the common types of coupling are being discussed I hope you learn a lot from the reading, if so, kindly share with other students. Thanks for reading, see you around!