The history of the piston seal may be traced far beyond the Industrial Revolution, for the problems inherent in sealing a moving piston within a cylinder were well known to the early Greek and Roman engineers. Substantial progress in piston sealing technology was not made, however, until the 17th and 18th centuries, and it was the advent of the steam engine that was to spawn the many and elaborate piston packings of the reciprocating engine. The invention of the modern piston ring is generally attributed to John Ramsbottom, who announced his self-tensioning device in the mid-19th Century. In some respects, the piston ring used in current engineering practice is superficially the same as the Ramsbottom ring, but it is important to note that many of the features of piston rings in reciprocating machinery emerged in the steam rather than in the internal combustion engine age. In this paper, we trace the history of the piston ring from the early civilizations to the present day and establish the current state of technology of piston rings in the light of their varied history. It is widely recognized that a substantial proportion of the power loss within a reciprocating engine is attributable to piston-ring-liner interactions, and there is a pressing need for a better understanding of the sealing and lubrication process in order to minimize these losses. Much of the progress in piston ring technology is attributable to materials, but important and recent developments in the field of lubrication analysis have enhanced our understanding of piston ring operation. It is now possible to identify the role of geometrical features of the rings in determining important operating characteristics of a ring pack such as sealing, lubrication and lubricant transport and there are indications that novel design features will further enhance piston ring performance in the future. In addition to providing the historical background to piston ring development, this paper will also serve to introduce some of the basic concepts of piston ring operation developed in recent years which form the basis for the analysis presented in detail in Parts II and III.

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