1. ME6401 – Kinematics of Machinery
Unit 1 – Basics of mechanism
Inversion of mechanisms
Presented by,
R.SUBHAA,
AP/Mech
2. Content
• Inversion of mechanism
• Inversion of four bar chain
• Inversion of single slider crank chain
• Inversion of double slider crank chain
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. • The number of inversion is equal to the
number of link in the kinematic chain.
• The inversion of mechanism may be classified
as;
1) Inversion of four bar chain
2) Inversion of single slider crank chain
3) Inversion of double slider 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. • Link 1 & 2 forms first turning pair, link 2 & 3
forms second turning pair, link 3 & 4 forms third
turning pair, link 4 & 1 forms fourth turning pair.
• 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.
Animations
7. 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.
8. [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.
9. [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.
10. [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.
12. [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.
13. • The line of stroke is
perpendicular to BC
produced.
• This mechanism is
mostly used in
shaping machine
and slotting
machine.
15. 3) Inversion of Double
slider crank chain
• There are four type of inversion of double
slider crank chain mechanism as:
[a] Elliptical trammel
[b] Scotch yoke mechanism
[c] Oldham’s coupling
[d] Donkey Pump
16. [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.
18. [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.
20. [c] Oldham’s Coupling:
• When the distance between two shaft axes is
small, motion is transmitted by oldham’s
coupling.
• At the end of both the shafts there is flanges.
• This flange forms links 2 and 4.
• Both this links forms a turning pair with link 3.
• There is a diametrical slot on both the flange.
• An intermediate piece have a diametrical outside
tongues at right angle on both sides.
21. • When the driving shaft is rotates, the
intermediate piece rotates as well as sides in
groove.
• This intermediate piece also rotates the driven
shaft by sliding as well as rotating motion.
