INVERSION OF MECHANISM

MECHANISM, Inversion of Mechanism
CLASSIFICATION OF INVERSION,

1. SUBMITTED TO:- SUBMITTED BY:- MR. PANKAJ SIR CH MURLIDHAR CH MURLIDHAR TRUBA INSTITUTE OF ENGINEERING AND INFORMATION TECHNOLOGY SESSION:-2015-19 ME-A TOPIC:- INVERSION OF MECHANISM

2. MECHANISM

3. Inversion of Mechanism

4. CLASSIFICATION OF INVERSION

5. 1) Inversion of four bar chain This is simplest types of kinematic chain in which four rigid links are connected by four pin joints. The four bar chain has four turning pairs.

6. A link which can make complete revolution is known as crank. The fixed link is known as frame. The opposite link of frame is known as connecting rod. The oscillating fourth link is known as lever or rocker.

7. According to grashaf’s law for four bar mechanism the sum of the shortest and longest link length should be smaller than the sum of the remaining length, if there is to be continuous relative motion between the link. GRASHAF’S LAW :- S+l < p+q

8. APPLICATION OF 4 BAR MECHANISM

9. Coupled wheel of locomotive(Double Crank) If the links 2 and 4 are made of equal length in four bar chain, we get double crank quadric chain which is used to transmit the motion from one wheel to another of a locomotive. Link 1 is fixed to maintain fixed centre distance between the wheels and link 3 represents coupling rod which connects two rods and is parallel to fixed link. The mechanism is used to transmit the rotary motion of a wheel which acts as driver to another wheel mounted.

10. Beam engine(Crank and lever mechanism) The function of this mechanism is to convert rotary motion of crank into oscillatory motion of lever and finally into reciprocating motion of piston. Here, crank AB rotates about fixed centre A, lever CDE rotates about centre D and at end of lever E, additional linkages i.e. piston rod and piston is connected, which reciprocates the cylinder.

11. Watt's engine indicator(Double lever mechanism) Link 1 is fixed, link 2 is ABC and link 3 is CDP, both act as levers. Link BE and link ED form link 4 since no relative motion between them. The point E is connected to piston of indicator cylinder i.e. displacement is proportional to pressure of the gas.

12. WATTS MECHANISM This mechanism is used to trace a straight line roughly. It has four links of which one of the link is fixed. The rest two can oscillate about the centres . The point p1 is such that p1B/p1C = DC/AB. Then for small oscillation of DC and AB the point P1 will trace a straight line roughly.

13. 2) Inversion of single slider crank chain In mechanism when there is one sliding member, the four bar chain is known as single slider crank chain. The inversion of slider crank chain are pendulum pump, oscillating cylinder engine, rotary internal combustion engine, crank and slotted lever quick-return motion mechanism and whitworth quick-return motion mechanism.

14. In a single slider crank chain, the links 1 and 2, links 2 and 3, and links 3 and 4 form three turning pairs while the links 4 and 1 form a sliding pair. The link 1 corresponds to the frame of the engine, which is fixed. The link 2 corresponds to the crank ; link 3 correspondsto the connecting rod and link 4 corresponds to cross-head. As the crank rotates, the cross-head reciprocates in the guides and thus the piston reciprocates in the cylinder.

15. [a] Pendulum pump: When the sliding pair is fixed, the mechanism is known as pendulum pump. As the figure, link 2 (crank) rotates, link 3 (connecting rod) oscillates about a pin C and the piston attached to piston rod (link 1) reciprocates in the cylinder.

16. [b] Oscillating cylinder engine: In this mechanism link 3 is fixed. The link 2 rotates, the link 1 (piston rod) reciprocate and the link 4 (cylinder) oscillate about a pin A.

17. [c] Rotary internal combustion engine: This mechanism is used in multi cylinder engine. It consists of several cylinders in one plane and all revolve about fixed center O, as shown figure. The crank (link 2) is fixed. When the connecting rod (link 4) rotates, the piston (link 3) reciprocates inside the cylinder forming link 1.

18. Rotary internal combustion engine diagram

19. [d] Crank and slotted lever quick-return motion mechanism: In this mechanism, link 1 is slider which slide in slotted lever. The slotted lever is link 4. link 3 is fixed where the center of crank attached. Link 2 is crank which rotates in clockwise direction. Link 4 is the arm which oscillates about point C. A short link DE transmits the motion with reciprocates with the tool along line of stroke.

20. The line of stroke is perpendicular to BC produced. This mechanism is mostly used in shaping machine and slotting machine.

21. Whitworth quick-return motion diagram

22. 3) Inversion of Double slider crank chain There are two type of inversion of double slider crank chain mechanism as: [a] Elliptical trammel [b] Scotch yoke mechanism

23. [a] Elliptical Coupling: In this mechanism two slots are cut at right angles in a plane which is fixed. Two blocks slide in these two slots. Two sliding blocks form two links, which are of sliding type. Two sliding blocks are connected by one link. Point on this link at anywhere generate ellipse, when any ne blocks slides in its slot.

24. Elliptical coupling diagram

25. [b] Scotch yoke mechanism: This mechanism converts rotary motion to reciprocating motion (simple harmonic motion). It is used in vibration exciter to produce vibration of desired frequency. This Chain has two revolute pairs and two prismatic pairs. The first inversion is with a link with revolute pair and prismatic pair is fixed.

26. Scotch yoke mechanism diagram

27. Any Question