US Patent 8215401 Expandable ball seat

Apparatus for a drop ball activated device, where a ball seat is concentrically and axially slidably disposed within an outer sleeve having a first internal cylindrical surface, wherein the ball seat comprises at least one radially extending lug, which in a first position extends radially inwards from the internal cylindrical surface, thereby defining a first ball seat diameter less than the diameter of the drop ball. The sleeve comprises at least one groove in its internal surface, and the lug may be received in the groove, thereby defining a second ball seat diameter at least as large as the diameter of the drop ball.