PUSHER SEAL P054
A design that has a spring loaded dynamic plastic, elastomer or rubber like part. Sometimes the term is used to describe any mechanical seal design other than a bellows type.
The Crane #9 (#109 International) is a typical pusher seal
In this design you can see that the springs are pushing a Teflon® wedge (plastic) to the shaft and the remaining spring force is used to keep the lapped seal faces in contact.
These designs are notorious for fretting the expensive shaft or sleeve.