kinematic inversions

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Inversions of 3R 1P Kinematic Chain or Inversions ofInversions of 3R-1P Kinematic Chain or Inversions of

Slider Crank Chain

In this four bar kinematic chain four links shown by blocksIn this four bar kinematic chain, four links shown by blocks

are connected through three revolute pairs T1, T2 and T3

and one prismatic pair.

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Second InversionSecond Inversion

In this case link 2 is fixed and link

3 works as crank. Link 1 is a

slotted link which facilitates

movement of link 4 which is a

slider. This arrangement gives

quick return motion mechanism.

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Third Inversion

fThis inversion is obtained by fixing link

3. Some applications of this inversion

are oscillating cylinder engine and

crank and slotted lever quick return

motion mechanism of a shaper

machine. Link 1 works as a slider

which slides in slotted or cylindrical

link 4. Link 2 works as a crank.

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Fourth Inversion – Pendulum Pump

It i bt i d b fi i li k 4 hi h i lidIt is obtained by fixing link 4 which is slider.

Application of this inversion is limited. The

pendulum pump and hand pump arependulum pump and hand pump are

examples of this inversion. In pendulum

pump link 3 oscillates like a pendulum andpump, link 3 oscillates like a pendulum and

link 1 has translatory motion which can be

used for a pumpused for a pump.

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Inversions of 2R-2P Kinematic Chain or Double Slider CrankInversions of 2R 2P Kinematic Chain or Double Slider Crank

Chain

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Third Inversion

This inversion is obtained by fixing link 4. The mechanism so obtained is called

elliptical trammel which is shown in Figure 1.32. This mechanism is used to

draw ellipse. The link 1, which is slider, moves in a horizontal slot of fixed link 4.

The link 3 is also a slider moves in vertical slot. The point D on the extended

portion of link 2 traces ellipse with the system of axes shown in the figure, the

position coordinates of point D.

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Crank: A side link which revolves relative to the frame is called a crankCrank: A side link which revolves relative to the frame is called a crank.

Rocker: Any link which does not revolve is called a rocker.

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Grashof Type 1: s + l < p + q Linkages have at least one fully

rotatable link Three

Th (1) Sh t t b i th fThree cases:(1) Shortest bar is the frame

• Double crank

(2) Short bar is the side link(2) Short bar is the side link

• Crank rocker

(3) Shortest bar is the coupler

Crank-rocker mechanism: In a four bar linkage, if the shorter side link revolves

(3) Shortest bar is the coupler

• Double rockerg

and the other one rocks (i.e.,oscillates), it is called a crank-rocker mechanism.

Double-crank mechanism: In a four bar linkage, if both of the side links revolve,

it is called a double-crank mechanism.

Double-rocker mechanism: In a four bar linkage, if both of the side links rock, it

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is called a double-rocker mechanism.

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