a chain of the type that is used in a reciprocating chain drive . the majority of the chain is constructed of conventional links that mesh with and are driven by rotating sprockets . a specially constructed link is included in the chain to disengage from the sprockets if the reversal controls of the chain drive mechanism malfunction . the special disengaging link is provided with an inclined plate which cams against the sprocket teeth to divert the chain off to the side of the sprocket if the disengaging link reaches the sprocket due to a control malfunction .