Kinematic Chains: Inversions

Inversions of Kinematic Chains:

In the earlier posts it was stated that a mechanism is a Kinematic Chain  having one link fixed -- and also that a chain with 'N' number of links would result in 'N' number of mechanisms. It was also discussed that 

• a non-Grashof chain would give us 4 Nos. of Double Double-Rocker mechanisms and 
• a Grashof chain would give us two Crank-Rocker mechanisms, a Double Crank mechanism,  and a Double-Rocker mechanism. 

Out of all the above mechanisms it would be useful to consider the inversion of Slider-Crank mechanism only, since it gives you some extremely useful mechanisms for practical applications. 

1. Inversion of First type: 

We will try to understand the first inversion by means of a diagram, posted below;

As you may observe, the Fig. this shows one of the most common applications of the first inversion. Can you identify, from the Fig. which is the application we are talking about?  We are talking about;

1. Steam Engines.
2. Internal Combustion Engines i.e. Car Engines.

In both the cases the Piston '4' is the driver which make the Crank '2' rotate by repeatedly pushing-and-withdrawing-action on the crank.

2. Inversion of Second Type:

In this type of inversion you can see, from the Fig. posted below, the connecting rod '3' is fixed and the Link-'4' oscillates. 

This is a unique arrangement and is used in some of the Steam-Engines  since it permits the use of simple ports, instead of the complicated valves, for steam inlet and outlet. One more very useful applications of second-inversion is  the Quick-Return portion of the Crank-Shaper mechanism, shown below;

In case of this arrangement the rotation of the Crank '2' is translated into a slow Working -Stroke and a Quick-Return of the Ram.

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