MECHANISM, Inversion of Mechanism CLASSIFICATION OF INVERSION,

1. SUBMITTED TO:- SUBMITTED BY:-
MR. PANKAJ SIR CH MURLIDHAR
CHMURLIDHAR

2. MECHANISM
When a kinematic chain with one of its link is fixed, is
called a mechanism.
A mechanism is a skeleton diagram of a machine to
transmit the definite motions between various links.
Example: type writer, clock work, etc.

3. Inversion of Mechanism
When the number of links in kinematics
chain is more than three, the chain is
known as mechanism.
When one link of the kinematic chain at
the time is fixed, give the different
mechanism of the kinematic chain.
The method of generating different
mechanism by fixing a link is called the
“inversion of mechanism”.

4. CLASSIFICATION OF INVERSION
FOUR BAR CHAIN OR QUADRIC CYCLE CHAIN
SINGLE SLIDER CRANK CHAIN
DOUBLE SLIDER CRANK CHAIN

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.

10. Coupled wheel of locomotive(Double crank)
Beam engine(Crank and lever mechanism)
Watt’s engine indicator(Double lever mechanism)
Watts mechanism

11. 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.

14. 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.

16. 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.

18. 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.

20. 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.

21. 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.

23. [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.

25. [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.

27. [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.

28. Rotary internal
combustion engine
diagram

29. [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.

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

32. Whitworth quick-
return motion diagram

33. 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

34. [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.

35. Elliptical coupling
diagram

37. [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.

38. Scotch yoke
mechanism diagram