The General Information on the Industrial Clutches (Coursework Sample)

Industrial Clutches
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Industrial Clutches
Introduction
A clutch is defined as a machine member that is used to disengage or engage the engine from the transmission rod. It is used to connect the driven shaft to the driving shaft so that the driven shaft may be stopped or started at will, without necessarily stopping the driving shaft. Clutches are mainly used in the automotive industry. For example, in vehicles, a clutch plate is placed between the transmission shaft and the engine. The clutch system is one of the most crucial parts in a vehicle. The system enables a rotating drive shaft to be connected to another shaft, either when both of them are at rest or are in relative motion. When the engine is idling, it develops inadequate torque for the power transmission to be completely engaged. To achieve a smooth engagement between the driving shaft and the driven shaft, the clutch must be gradually engaged so as take up the power drive until the transmitted torque from the engine is sufficient enough to propel the vehicle. Where the gears are changed, the clutch disengages the transmission shaft from the engine. Therefore, the clutch disengages the driving shaft from the engine where necessary and takes up the transmitted power smoothly. The clutch system comprise of a pressure plate, clutch disc plate, friction material, flywheel, pressure plate, clutch cover, linkages, and a clutch diaphragm spring.
The clutch progressively engages the transmission shaft by allowing some amount of slippage between the input shaft and the flywheel. However, the clutch slipping mechanism generates a considerable amount of heat energy because of friction between the flywheel and the clutch disc. At high sliding velocities, excessive heat energy is generated. As a result, there is rise in temperature at the disc surface. The rise in temperature leads to thermo-mechanical problem, such as thermo-elastic stability and thermal deformations, which sometimes lead to wear, thermal cracking, and other mechanical failures.
The clutch enables the power from the engine to be transmitted gradually when the driven shaft is started, interrupts power transmission to avoid the cases of gear clashing, and prevents engine stalling when the driven shaft is stopped. When the clutch is engaged, there is power transmission between the driving shaft and the driven shaft. At this point, the clutch pedals are fully raised. When the clutch is disengaged, the power transmission between the driving shaft and the driven shaft is interrupted. At this point, the clutch pedal is fully depressed.
The components of a clutch system perform the following functions: The flywheel is a large, aluminum or steel disc. It is mounted to the crankshaft of the engine. It role is provide balance for the engine, reducing or dampening the frequencies of engine vibrations, and provides a surface where the clutch is mounted. The flywheel has teeth around its circumference where for mounting the starter motor, which is used to crank and crank and engage the engine. The clutch disc is a plate with a hub at its center. The disc is covered with a steel material, sandwiched between the pressure plate and the flywheel. The function of the hub is to fit the spines of the driving shaft. When the clutch is active, the disc squeezes between the pressure plate and the flywheel. At this point, the power is transferred by the hub from the engine to the transmission shaft. Principally, the disc provides quick engagement between the engine crankshaft and the driven shaft. It also allows for firm transmission of torque. The pressure plate, also known as the clutch cover, is a spring-loaded friction surface that is used to lock the clutch firmly. The plate is firmly bolted to the flywheel surface. It has heavy release springs, thrust fingers or ring for the release mechanism, a metal cover, heavy release springs, and a metallic pressure surface. The function of the thrust fingers or rings is to release the spring’s clamping force when the clutch system is disengaged.
The throw-out bearing, also known as the release bearing, supports and centers the power transmission shaft. The clutch cable is a mechanical release mechanism in some vehicles. The master cylinder is a force-amplifying cylinder for the vehicles with the hydraulic brake. It role is to multiply forces. The slave cylinder is used together with the master cylinder in vehicles with hydraulic system.
Normally, the release bearing remains stationary when the cutch is active and the clutch pedal is released. The bearing does not move with the pressure plate. The operation of the clutch is normally accomplished either with a hydraulic mechanism or mechanically. For the system with mechanical linkages, either a cable or a lever-and –shaft arrangements are incorporated. Mechanically operated clutches consist of pivot point, levers, and linkages. They found majorly in old-model vehicles or mechanical systems. These clutches require routine lubrication. They are only designed for small scale operations, such as operating small systems. A cable-operated clutch system is comparatively simpler. The cable is used to connect the clutch pedal to the clutch release fork. The cable-operated clutches are normally simple, flexible, and compact. However, there life span is very short. The cables gradually stretches and breaks eventually. Due to wear and age.
On the hydraulically-operated clutches, a master cylinder is normally operated directly by the clutch pedal assembly. The master cylinder is connected to a slave cylinder through a high pressure tubing. A hydraulic clutch only requires a small pedal force to be engaged. Due to their flexibility, the hydraulic clutches can be adapted in many configuration.
The clutches are integral component of any machine drive mechanism. The application of clutches in industries continue to gain momentum day by day. The purpose of this literature review is to establish the current knowledge on industrial clutches in relation to the types, design, and areas of application in the industries. The literature has been obtained from various engineering journals, articles, and books. Due to space limitation, the paper only gives a summary of the topic.
Types of Clutches and their Applications
Clutches are categorized based on three major criteria. The types of clutches according to these criteria are as discussed below:
Classification Based on theMethod of Torque Transmission
1. Positive clutch (Dog clutch). The positive clutches are applied when positive drive is required. In this type of clutch, grooves are evenly cut either onto the driven member or the driving member. The clutches have extracted parts located in both the driven and driving member. When the driver releases the pedal, the extracted parts insert into the grooves and both the driven and driving shaft rotates together as one unit. When the driver pushes the clutch pedal, the extracted parts leave the grooves. As a result, the engine shaft rotates itself without driving the power transmission shaft. The figure below shows parts of a positive clutch.
Fig 1. Parts of a positive clutch
2. Friction clutch. These type of clutches are used in the applications where the driven shaft is started or stopped regularly. They are used in applications where the machine operated is fully or partially loaded. In these clutches, force of friction is used to disengage or engage the clutch. A friction surface plate is inserted between the driven shaft and the driving shaft. When the clutch pedal is released, the driven shaft and the driving shaft of the clutch come in contact. The force of friction works between the two shafts. So, when the driving shaft rotates, it moves with the driven member, engaging the clutch. There are four sub-categories of friction clutch. They include:
a. Cone clutch. Clone clutch consist of a cone attached onto the driven shaft. The shape of the sides of the flywheel in this type of clutch are also conical. The contact surface are lined with a friction material. The cone can be disengage or engage from the flywheel through clutch pedal.
Fig 2. Cone Clutch
b. Single Disc Clutch.  In this type of clutch, the flywheel is mounted onto the engine shaft and the pressure plate is fixed to the gear-box shaft. The pressure plate mounted in such a way that it is free to move on the shaft spindle. A friction surface plate is located between the pressure plate and flywheel. Some springs are attached into the compressed position between the plates. When the clutch pedal is released, a force is exerted on the friction surface by the pressure plate. The pressure exerts the force due to the spring action. So, the clutch is active position. The clutch is disengaged by pushing the clutch pedal. The parts of a single disc or plate clutch is as shown below.
Fig 3. Single disc clutch
 c. Multi-Disc Clutch. This type of clutch similar to the single disc or plate clutch. However, it has two or more clutch plates fixed between the pressure plate and the flywheel. A multi-disc clutch are normally used in applications that involve transmission of large torques. The clutch consists of the inside and outside discs. The inside discs are made of steel. They are screwed to the driven shaft to allow for rotational motion, except for the last disc. The outside discs are made of bronze. They are held by bolts are fixed onto the driving shaft by the use of screws. The multi-disc clutches are more compact than the single clutches. They are majorly used in machine tools and motor vehicles. The parts of a multi-disc clutch are shown in the figure below.
Fig 4. Multi-disc clutch
d. Diaphragm Clutch. This type of clutch is similar to single disc. However, in diaphragm clutches, the diaphragm springs are used to exert pressure on the...