Flat Jack

The Freyssinet flat jack is a thin, hydraulic device, capable of developing considerable forces in a simple and economic manner.

Initally designed by Eugene Freyssinet as part of a concrete prestressing mean, to be used under specific circumstances, flat jacks were subsequently implemented in numerous ways, in particular to exert or transmit forces while counterbalancing the relevant strains.

The Freyssinet flat jack is a malleable steel capsule made up of two steel welded together, the connection being in the shape of a cylindral or toric rim. Tow adjutages, one of which serves as a vent, allow fluid to be injected under pressure; this push aside the two faces of the jack whilst the strain incurred modifies the shape of the rim, whose radius increases slightly.