Patent ID: 7290604

Claim:
A downhole tool, comprising: a housing: a mandrel telescopically positioned within the housing, a portion of the mandrel having an interior flow passage within, the mandrel being adapted to form a first annulus between the mandrel and the housing, the first annulus extending axially from a first sliding seal between the mandrel and the housing to a second sliding seal between the mandrel and the housing, the first annulus having a first port through the housing and a first port to the interior flow passage and having a cylinder bore within a segment of the annulus, the cylinder bore having a floating piston therein, the floating piston being adapted to move sealingly and axially along the cylinder bore between the first port through the housing and the first port to the interior flow passage; a second annulus between the mandrel and the housing, the second annulus extending axially between the second sliding seal between the mandrel and the housing to a third sliding seal between the mandrel and the housing, the second annulus having a second port through the housing and a second port to the interior flow passage and an intermediate segment on the mandrel therebetween, the intermediate segment being adapted to move sealingly and axially in the housing and having an area; and a third annulus between the mandrel and the housing, the third annulus extending from the third sliding seal to a fluid chamber and having a port from the fluid chamber to the interior flow passage of the mandrel, the third sliding seal having an area, the area of the third sliding seal being equal to the area of the intermediate segment.