The rolling scotch yoke mechanism applied to a small air compressor for oil-free operations

Abstract

The rolling scotch yoke mechanism (RSYM), a variation of the scotch yoke mechanism, is developed in this work. The RSYM is not a mechanism by rigorous definition because the output position is not uniquely determined by the input position, however has several advantages over other reciprocating mechanisms. Unlike a conventional scotch yoke mechanism whose crank pin slides relative to the yoke, the bearing wrapping crank pin of the RSYM rolls without slipping on the yoke in the most range of operation except two small intervals where it slips. Because the friction force is very small in these brief slip intervals, the mechanism generates a much smaller amount of heat than the conventional scotch yoke mechanism. This enables the RSYM to operate in an oil-free condition while retaining all advantages of the scotch yoke mechanism. A double-cylinder air compressor for an oil-free operation was constructed by adopting the RSYM and tested to demonstrate practicality of the design.