Motion and Power Transmission Devices PDF

Elements of Mechanical Engineering  CHAPTER-7 Motion and Power Transmission Devices  Introduction to motion and power transmission The power is required in various workshop processes specifically in cutting and forming process in a machine tool. The electrical energy is converted to...

Elements of Mechanical Engineering  CHAPTER-7 Motion and Power Transmission Devices  Introduction to motion and power transmission The power is required in various workshop processes specifically in cutting and forming process in a machine tool. The electrical energy is converted to rotational energy by means of an Electrical motor. To perform various operations mechanical energy is used by the machine. Drive is an intermediate mechanism which transmits power and motion from the prime mover to the machine. ▪ Shaft ▪ Axle  Different types of mechanical drives Belt drive: The belts are used to transmit power from one shaft to another by means of pulleys which rotate at the same speed or at different speeds. Image source : http://www.gemtranseng.lk  Different types of Belt Drive 1. Open belt drive: This type of belt drive is used to transmit power when two parallel shaft rotating is same direction. Image source : https://www.slideshare.net  Different types of Belt Drive 2. Cross belt drive: This drive transmits power when shafts are parallel but rotate in opposite direction. Image source : https://www.slideshare.net  Different types of Belt Drive 3. Compound belt drive: This drive is used when large speed ratio required and there is large center distance between two shafts. Power is transmitted from pulley 1 to pulley 4 through intermediate pulley. Image source : https://www.slideshare.net  Different types of mechanical drives Chain drive: Chain drives are positive and in it no slip takes place and thus the velocity ratio will remain constant. They are suitable for small centre distance and it can be used up to 3 meters. They are used for power transmission in bicycles, motor cycles, rolling mills, machine tool, conveyer, etc.  Different types of mechanical drives Gear Drive: A gear is a rotating machine part possessing cut teeth, which mesh with another toothed part in order to transmit toque and power. In earlier days, friction discs were used for transmitting the power from one shaft to another shaft. In such a case, the power transmission capacity depends on friction between surfaces of two discs. Therefore, this method is not suitable for transmitting higher power as slip occurs between the discs.  Different types of Gears 1. Spur Gear In spur gears, teeth are parallel to axis of rotation as shown in figure. It transmit power from one shaft to another parallel shaft. Image source : https://www.motioncontroltips.com  Different types of Gears 2. Helical gear The teeth on helical gears are cut at an angle with axis of gear. In helical gears engagement of gear teeth is gradual as shown in figure. This gradual engagement makes helical gears operate much more smoothly and quietly than spur gears. Image source : https://www.indiamart.com  Different types of Gears 3. Rack and Pinion gear For converting rotary motion into linear motion Rack and pinion gears are used. It is a special case of spur gear in which one gear is having infinite diameter called "Rack” as shown in figure 7.7. Image source : https://www.indiamart.com  Different types of Gears 4. Bevel gear When power is required to be transmitted from one shaft to another shaft which are intersecting to each other, bevel gears are used. Generally, the angle between two shafts is 90⁰ as shown in figure. Image source : https://www.indiamart.com  Different types of Gears 4. Worm and Worm wheel It is used to transmit power from one shaft to another shaft which are non-intersecting and their axes are normally at right angles to each other as shown in figure. Image source : https://www.motioncontroltips.com  Introduction to Coupling A device that is used to connect two shafts together for the purpose of power transmission is known as coupling. Rigid type of coupling used to connect two shafts which are perfectly in axial alignment. Flexible type of coupling used to protect the driving and driven machine members against harmful effect produced due to misalignments of shaft, vibration, sudden shock load.  Different types of Coupling 1. Muff or Sleeve Coupling Sleeve couplings are nothing but just sort of thick hollow cylinder/pipe called as sleeve or muff. The sleeve is manufactured keeping the diameter of shaft in mind so that the shaft fits perfectly into the sleeve. The driver & driven, both the shafts are then inserted into each side of the sleeve. Image source : https://www.slideshare.net  Different types of Coupling 2. Flange coupling Flange coupling is also an easy to manufacture coupling and is similar to sleeve coupling. Here, there are flanges on either side of the 2 sleeves as shown in figure. Both the flanges consist of equal number of threaded holes for bolting purpose. Flange couplings are used for medium & heavy-duty industrial applications. Image source : https://www.quora.com  Different types of Coupling 2. Muff Coupling In split muff coupling, the sleeve or muff isn’t a single different part instead it is split into two. The muffs are semi-cylindrical in shape which then fits over the shaft as shown in figure. The special feature of this coupling is that it can be assembled and disassembled without changing the position of shaft. Image source : https://www.quora.com  Different types of Coupling 3. Oldham Coupling There are three-piece flexible shaft couplings that are used to connect driving and driven shafts in mechanical power transmission assemblies. The power is transmitted from driving shaft to driven shaft through the intermediate piece which rotates as well as slides in the slots. Image source : https://grabcad.com  Definition of clutch and Single Plate Clutch Clutch: Function of clutch is to control the flow of mechanical power within a machine 1.Single Plate Clutch: It is a type of friction clutch in which power is transmitted by means of friction between the contact surface usually called clutch plates. Single plate clutches are used in trucks, buses, and cars. Image source : https://www.mecholic.com  Different types of Clutches 2.Multi-plate clutch It is a type of clutch in which the multiple clutch plates are used to make frictional contact with the flywheel of the engine in order to transmit power between the engine shaft and the transmission shaft of an automobile vehicle. Image source : https://www.mecholic.com  Different types of Clutches 3. Cone clutch It is used in low peripheral speed applications. Power boats are the example of places where cone clutches are used. one of the major disadvantage is the cone angle operation of the clutch is highly dependent on the cone angle if the cone angle is smaller than 20 degrees it becomes difficult to disengage the clutch frequent maintenance required because the small amount of wear on the cone surface. Image source : https://www.mech4study.com  Different types of Clutches 4. Centrifugal Clutch: To keep the clutches in the engaged position centrifugal clutch uses centrifugal force, instead of spring force. In these types of clutches, the clutch is operated automatically depending upon the engine speed. Image source : https://www.mecholic.com  Definition of Brake and Band Brake Brake : Brakes are mechanical devices which absorb the kinetic energy of the system & convert it into any other form of Heat energy in order to stop a moving system. 1.Band brake: It is contains a lever & a band which gets rubbed against the drum (wheel). One end of the lever is attached to a fix point also called as pivot point & force is applied to the other end. The band consists of a flexible leather belt OR steel lined with friction material as shown in figure Image source : https://pigeonsblue.com  Different types of Brakes 2. Block brake The blocks maybe wooden or any other friction lined material. More the number of blocks, more is the braking force & thus higher the rate of retardation Image source : https://www.slideshare.net  Different types of Brakes 3. Shoe brake S1 and S2 are the two shoes in internal expanding brake. The outer surface of the shoes are lined with some friction material to increase the coefficient of friction and to prevent wearing away of the metal. Each shoe is pivoted at one end about a fixed fulcrum O1 and O2 and made to contact a cam at the other end as shown in figure. Image source : http://sounak4u.weebly.com  References: ▪ Books: Elements of Mechanical Engineering S.B.Mathur, S. Domkundwar; Dhanpat Rai & Sons Publications. Basic Mechanical Engineering T. S. Rajan; Wiley Eastern Ltd. Fundamental of Mechanical Engineering G. S. Sawhney; PHI Publication New Delhi. Elements of Mechanical Engineering Sadhu Singh; S. Chand Publisher. Basic Mechanical Engineering P. K. Nag, Kartikeya Tripathi C. B. Pawar Tata McGraw-Hill Education Basic Mechanical Engineering. Shanmugam_ S. Ravindran - -McGraw-Hill Education Basic Mechanical Engineering-Pearson Education (2018) , Pravin Kumar Elements of Mechanical Engineering- P.S.Desai, S.B. Soni; Atul Prakashan References: ▪ Video Links https://www.youtube.com/watch?v=0mb_XMGja_c (Belt drive) https://www.youtube.com/watch?v=P4rNX0gCm3E&t=3s (Gear drive) https://www.youtube.com/watch?v=Y5lsvb_gq4o (Oldham coupling) https://www.youtube.com/watch?v=9idc0CzMjCo (Flange coupling) https://www.youtube.com/watch?v=fpNQrDKEUKE ( Muff coupling) https://www.youtube.com/watch?v=HY_PjmHRxuE (Single plate clutch) https://www.youtube.com/watch?v=HrmWNBwHBQ0 (Centrifugal Clutch) https://www.youtube.com/watch?v=crLuEnCY3WA (Band brake) https://www.youtube.com/watch?v=Wte8uQ9f9LI (Block brake) www.paruluniversity.ac.in