135. Modification of the triangular eccentric 91, used on the steam engine in the Paris Mint. The circular disk behind carries the triangular tappet, which communicates an alternate rectilinear motion to the valve-rod. The valve is at rest at the completion of each stroke for an instant, and is pushed quickly across the steam-ports to the end of the next.
This type of cam is also known as a “positive return” cam. This particular example is in the form of a true “Reuleaux Triangle,” whereas 91 is a slight modification.