Abstract: An expansion mechanism of the type that may be used with a seal for sealing a connection about the upper end of a concrete structure, such as providing as seal across a manhole frame, optionally one or more spacer rings, and the upper end of a manhole chimney or riser, or which may be used with a seal for internally sealing a connection between a pair of pipes. The expansion mechanism includes a pair of ring portions and a pair of expansion mechanisms that include pivotal connections to the ring portions such that the assembly may be moved or folded between a folded configuration, in which the assembly has a reduced profile to allow the assembly to be moved into place at the sealing site, and a deployed configuration, in which the assembly has a cylindrical shape and is expandable to compress the seal against a cylindrical surface.