The motions resulting from each inversion can be quite different, but some inversions
of a linkage may yield motions similar to other inversions of the same linkage. In
these cases only some of the inversions may have distinctly different motions. We will
denote the inversions which have distinctly different motions as distinct inversions.
Figure 2-13 (previous page) shows the four inversions of the fourbar slider-crank
linkage, all of which have distinct motions. Inversion #1, with link 1 as ground and its
slider block in pure translation, is the most commonly seen and is used for piston engines
and piston pumps. Inversion #2 is obtained by grounding link 2 and gives the
Whitworth or crank-shaper quick-return mechanism, in which the slider block has
complex motion. (Quick-return mechanisms will be investigated further in the next
chapter.) Inversion #3 is obtained by grounding link 3 and gives the slider block pure
rotation. Inversion #4 is obtained by grounding the slider link 4 and is used in hand operated,
well pump mechanisms, in which the handle is link 2 (extended) and link 1 passes
down the well pipe to mount a piston on its bottom. (It is upside down in the figure.)