Design method of inversion

In assemblies it is occasionally preferable to invert the functions of parts, e.g., to turn a driving element into a driven one, to turn a leader into a follower, to make a female component out of a male one , to convert a fixed part into a movable one, etc.
Sometimes it becomes advisable to invert shapes of parts, e.g., to change a female taper to a male one, a convex spherical surface to a concave one. In other cases it may be more suitable to shift some elements from one part to another, for instance, to move a key from a shaft to a boss, or invert a lever from a puller to a pusher.
Each time the design will acquire new qualities. The designer must carefully evaluate all the advantages and disadvantages of the original and inverted alternatives, taking into account durability, size, design for assembly (DFA), design for manufacturing (DFM) and convenience of operation, and then choose the most suitable version.
The method of inversion is a basic tool of creation for every experienced designer. It significantly lightens the search for solutions as a result of which a rational construction is found. In the above figure a typical example of inversion in mechanical engineering is shown. In design 1 the clevis pin is secured to the lever arm and rotates in the pivot base’s bushings. In the inverted design 2 the clevis pin is fixed to the pivot base and the bushing is in the lever arm. You can see how dimensions of lever and pivot base change from design 1 to 2.