Garter Springs are helical extension or compression springs whose ends are connected so that each spring becomes a circle and exerts radial forces. Their primary application is in oil seals. Other uses include small motor belts, electrical connectors and piston-ring expanders.
Design methods for garter springs are continuations of methods developed for helical compression and extension springs. Generally, garter springs are designed with as low a rate as possible to provide a nearly constant force on a seal as it wears.
The garter is essentially a helical extension spring formed into a circular ring with the ends connected on the inside diameter. Thus a garter spring is an endless spring, ignoring that its ends are joined which does not affect the results. A garter spring is easily identified in that it looks like a circle made up of a spring.