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If you landed most of the places and didn’t find a satisfactory answer to your query. Then, This will be the final stop for your query- Clutch.
We will know the definitions and various types of clutches along with their advantages and disadvantages, function and working, and much more down the road.
So, Come with me and get relaxed while I start the journey of Engineers Rail with you.
Let’s dive into the mainstream now…
What is a Clutch?
A clutch is a machine element or device which joins the driver shaft and driven shaft in such a way that the motion of the driven shaft can be stopped from time to time and re-started as and when desired.
During the operation of machine tools and running of automobiles their motion is required to be stopped or re-started from time to time.
As such the anime mover such as the engine or electric motor need not be stopped or re-started due to the inconvenience caused by doing so again and again, So a clutch is used.
The Clutch joins the drive shaft with the driven shaft in such a way that they can be separated as and when required without stopping the prime mover.
The clutch is used in automobiles such as car, trucks, scooters, motorcycles, and various industrial machines.
Parts of Clutch-
Here are some parts of the Mechanical Clutch–
- Clutch Disc
- Pressure Plate
- Diaphragm spring-
- clutch Housing
The flywheel is an input device which connected to the engine’s crankshaft and further it functions as a drive plate.
It is an output disc that is connected to the output shaft which receives the engine’s power and transfers it to the transmission.
This plate is used to engage and disengage the clutch disc from the flywheel.
It is a circular disc with a diaphragmic spring when the center of the spring is pressed. the outer side of this spring moves outside.
As the name indicates, It is used to connect or install a pressure plate and diaphragmic spring.
It is tightened with the help of a bolt to the flywheel.
Types of Clutches-
There are mainly two types of clutches and further, they are divided into sub-types, They two are-
- Jaw Clutch
- Friction Clutch
Here, the Classification of clutches with sub-types is given in the form of a chart shown below:
1. Jaw Clutch-
It is also known as Dog Clutch or Claw Clutch or positive clutch. These clutches are used at places where a positive drive is required.
It means, that the driver and driven shafts have no relative motion or slip between them to join the two shafts in straight contact by interlocking jaws.
These clutches are simple in construction but join the shafts with a shock.
Types of Jaw Clutches-
There are two types of jaw clutches:
- Square jaw clutch
- Spiral jaw clutch
I. Square Jaw Clutch-
It consists of two parts, one part is connected to the driver shaft by a sunk key, and the other part is connected to the driven shaft on which it can rotate as well as slide on it.
Its rotary motion with respect to the driven shaft is prevented by a feather key. The driver and driven studs are joined by slots made on a square jaw.
The driven shaft having slots made in the square jaw can move axially with the help of a lever.
When moved towards the left by the lever, the two jaws engage with each other and the two shafts join together. When moved axially towards the right by the lever, both shafts disengage with each other.
Square jaw clutches are used at places where the two shafts have to be disengaged quickly. They need not be engaged or disengaged in loaded and moving conditions.
Such clutches can transmit power clockwise and anticlockwise or in both directions.
This clutch can join the two shafts within the speed range of 2 to 10 r.p.m. For engaging and disengaging the shafts in the loaded condition the jaws of the clutch should be highly finished and lubricated.
They can transmit power up to 200 KW.
- Related Article: Mechanical Keys: Definitions, Types, Applications and More
II. Spiral jaw Clutch-
This clutch can be operated only in one direction, it can be clockwise or anticlockwise. It can be used in running conditions of shafts.
A special feature of this clutch is that, if it is operated in the wrong direction of power transmission, its jaws being spiral, will not engage the shafts.
This type of clutch is required in automobile engines to connect it with the starter motor and disconnect it from the motor.
The speed of engaging this clutch can be 2 to 150 r.p.m. They can transmit power up to 180 kW.
These are normally used with gears, pulleys, sprocket wheels, etc.
2. Friction Clutch-
It is a mechanical device that transmits torque through surface friction between the faces of clutch lined with cork, asbestos, or other fibrous materials, attached to the driving and driven shafts.
This type of clutch is used with such shafts which transmit power and they have to be stopped and started frequently.
They are also used for machines that have to run on full or partial loads.
To run the driven shaft from the state of rest frictional force is used on the clutch, which attains full speed without slipping between the plates.
In automobiles, a friction clutch is used to connect the engine to the drive shaft. These clutches need precautions to connect the friction surfaces join with ease and driven shat attains full speed slowly.
For this bearing surfaces should be in complete alignment. The friction surfaces should be as close to each other as possible.
Types of Friction Clutches-
There are four types of friction clutches:
- Plate or Disc clutch
- Cone clutch.
- Block and band clutch
- Centrifugal clutch
They are described in detail below:
I. Plate or Disc Clutch-
These are also known as axial friction clutches.
These clutches are mostly used in automobile engines, machine tools, and agriculture implements. They are made automatic by hydraulic or pneumatic systems.
Types of Plate Clutch-
Depending upon the number of plates. there are two types of plate clutches as described below:
- Single plate clutch
- Multi- Plate Clutch
A. Single Plate Clutch-
Single plate clutch consists of a plate installed between the driver and driven flanges. Both faces of this plate are lined, with friction lining.
In this way, there are two sets of friction surfaces.
It is used in light automobile engines to transmit low torque values.
B. Multip-Plate Clutch-
Multi-plate clutches are used to transmit high-twisting moments. These clutches contain more than one plate which forms two or more pairs of friction surfaces and transmits high twisting moment.
In this clutch, up to twenty plates can be used.
It is used in motor cars, machine tools, earth-moving machines, etc. Its working principle is the same as that of a plate clutch.
Working of Plate Clutch-
Its working principle is described below:
This clutch consists of two flanges A and B. Flange A is fixed rigidly on the driver shaft by a sunk key. Flange-B is fixed on the driven shaft by a feather key or spline key.
It can be slid axially on the shaft Flange-A has a friction lining on its surface made of cork, leather, asbestos, felt, or terrodo.
Flange-B is always in contact with Flange-A due to the axial pressure of the spring installed on the driven shaft.
When the driver shaft moves with the turning moment, there is relative motion between the driver and driven shafts, and the axial pressure of the spring produces frictional force in the direction of the circumference of friction surfaces.
When the frictional force is more than the twisting moment or torque to be transmitted, the frictional surfaces do not slip and power transmission takes place from the driving shaft to the driven shaft.
To stop the power transmission the flange-B is pulled back against the spring with the help of a lever fixed with the sleeve towards the right, thereby separating the two flanges apart.
Thus the power transmission is stopped. For the ease of shifting the flange B against spring pressure, the leverage of the lever is kept at 10 to 12.
The torque transmitted by the clutch depends upon axial pressure, the average radius of frictional surfaces, and the friction factor.
To reduce the rubbing wear of frictional surfaces of clutch plates, the clutches are generally dipped in oil, with the result that rubbing temperature is reduced and clutch operation becomes smooth.
II. Cone Clutch-
It is based on the principle of friction. It contains only one pair of friction surfaces. The driven part is normally lined with cork, leather, wood, or asbestos lining, etc.
But sometimes metal-to-metal contact can also be made. The selection of friction material depends upon pressure and friction-factor.
In the cone clutch, the driver’s conical surface ‘A’ is fixed on the drive shaft with a key.
The internal conical surface of the driver cone should perfectly match the external conical surface of the driven shaft. The driven cone-B is fixed on the driven shaft by a feather key and can be pulled back axially by a fork.
This fork is fixed with driven cone ‘B’ at the back with a sleeve. The cone of the driven shaft has a coiled pressure spring which keeps the driven cone always in contact with the driver cone.
Due to this contact, power is transmitted from the driver shaft to the driven shaft. Therefore, the fork is used to shift the clutch towards the right to bring it to the neutral position.
In this clutch, less axial pressure is required to make contact between friction surfaces. This clutch is suitable for frequent starting and sloping power transmission.
III. Block and band clutch-
Block clutch and band clutch both works on the principle of friction. In a block clutch, friction is produced by a block and in a band clutch, friction is produced by a flexible strip called the band.
Both these clutches are described below:
This type of clutch consists of a revolving drum whose cylindrical surface has one or more blocks fitted with the inside or outside surface.
The driver plate A has two levers fitted on pivots. The levers have a block fitted on the inner surface. These blocks come in contact with the cylindrical surface of the revolving drum.
The power transmission takes place through a friction surface fitted below the block. A drum fitted on a driven shaft by a sunk key receives a turning moment and moves the driven shaft.
The blocks are moved radially to make contact between the driver and driven parts.
The function of this clutch is similar to a block clutch, but in place of a block, a flexible strip or band is fitted. This flexible strip made of steel is connected to the driver shaft at one end and to the driven shaft at the other end.
A drum is provided on the driven shaft on which the steel strip is wound around it. Power transmission takes place due to frictional force between the drum and the steel strip.
The steel strip is lined with suitable frictional material.
It is mainly used in mine equipment to lift the load and road construction equipment in general where heavy loads have to be lifted with jerks and shocks.
IV. Centrifugal clutch-
Centrifugal clutches are generally used along with motor pulleys. They are operated with centrifugal force. It consists of three or more shoes that are fitted inside the rim.
On the outer surface of the shoe, a friction lining is applied.
The shoes are fitted in the boss or spider by springs which apply radially inward force of constant value. During the operation of the clutch, the shoe exerts radial force by its own weight, It is known as centrifugal force.
The value of this centrifugal force depends upon the speed of the moving shoe.
When the value of centrifugal force is less than the force of the spring, the position of the shoe is maintained, but when the value of centrifugal force increases the shoes move outwards and apply pressure on the inside surface of the driven drum.
This pressure or force is equal to the difference between centrifugal force and spring force. When the speed of the driver shaft increases, the shoe exerts more pressure on the drum and more power is transmitted.
These clutches are used under such conditions when the driver has a minimum fixed speed and the clutch is to be operated.
It is specially used when I.C. engines have to be started in loaded conditions. These are normally used in belt conveyors and working machine drums. Rotor drives of helicopters also use these clutches.
Advantages and Disadvantages of Friction Clutches-
Here are some benefits and Limitations of friction clutches-
Advantages of Friction Clutches-
Friction clutch has the following advantages:
- Driver and driven shafts join without shock.
- Power transmission is possible on both sides, forward and backward.
- If the power transmission exceeds its limit both sides of the clutch started slipping, So this clutch acts as a safety device also.
- Friction plates can be changed easily when their surfaces wear out.
Disadvantages of Friction Clutches-
Friction clutch has the following disadvantages:
- The limitation of this type of clutch is the shaft speed which is never constant. This is due to the wear of friction surfaces which takes place during the running of the engine.
Desired Properties of Friction Clutches-
Some important points regarding friction clutch are:
- The contact surfaces should produce friction force which may transmit load with a minimum of pressure between the plates.
- The heat produced between the friction surfaces should be dissipated quickly and there should be a minimum absorption of heat.
- The material of friction surfaces should be hard and tough so that equal pressure may act on the friction surfaces.
Other types of clutches-
Apart from the clutches we have discussed above, there are some other types of clutches mentioned below:
- Magnetic clutch
- Eddy-current clutch
- Trip clutch
1. Magnetic Clutch-
These clutches work on the principle of the effect of magnetic region on ferromagnetic particles. The value of the turning moment of these clutches depends upon the ferromagnetic particle’s resistance to shear stress.
2. Eddy Current Clutch-
These clutches function on the principle of magnetic reaction of included eddy-currents between driver and driven parts.
When two rotors move with respect to each other in a magnetic area, then eddy currents are induced, and a turning moment reaction takes place between the driver and driven parts.
3. Trip Clutch-
During the transmission of turning moment when some undesirable circumstance arises, such as over speed of the elevator, etc. the trip clutch breaks the contact between driver-driven parts or braking action takes place.
In this way, no turning moment is transmitted.
Working of Clutch-
- When the clutch pedal is pressed, the release bearing is pushed by a clutch lever.
- Which further compresses the diaphragmic spring, As you know, When force is applied to the center of the spring, The corner of the spring comes out with a pressure plate.
- The pressure plate is attached to the clutch plate which also further disengages from the flywheel.
And from there the power transmission from the input shaft does not travel to the output shaft.
- Further, When the clutch peddle is released, the spring again gains its original shape and further engages the pressure plate with the clutch plate.
- This further starts the power transmission from the input to the output shaft.
This is how the clutch plate works.
Functions and Uses of a Clutch-
- The driver and driven shafts can be connected and separated as and when desired with the help of a clutch.
- Transmission of power can be made from driver to driven shaft with the help of clutch, intermittently.
- When a machine is fully or partially loaded, then the clutch is used to transmit power.
Difference between Clutch and Brake-
- During the operation of the clutch, the driver part is in motion at the beginning and the driven part is in a stationary condition. Later, when the clutch is connected, both driver and driven parts join to move together.
- Whereas during the action of the brake it remains stationary at the beginning and the machine part is in motion. After applying the brake the machine part also comes in a stationary position.
- In this way, the clutch and brake have a similarity in that both of them have no relative motion between them at the end of the operation.
Likewise, there is a dissimilarity between clutch and break actions and they are-
- In the operation of the clutch, both parts are in motion at the last stage, and in the operation of a break, both parts remain stationary at the end of operations.
Difference between Clutch and Coupling-
- The function of the clutch is to connect the drive shaft with the driven shaft and to disconnect them as and when required.
- Whereas the function of a coupling is to join two shafts to increase their lengths. Likewise, the common function of clutch and coupling is to join two shafts,
- But the main difference is that clutch connects and disconnects shafts in their running position, whereas coupling connects and disconnects shafts in their stationary position.
This is now the end of the Clutch Journey at Engineers Rail. I hope you gained all the information you need regarding the clutch.
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Abhishek Tiwary is a blogger by passion and a Quality Engineer by profession. He completed his B.Tech degree in the year 2017. Now working in a reputed firm. He loves to share his knowledge with others.