Patent ID: 9347290
Filing Date: 2016-05-24
CPC Classification: E21B

Claim Text:
1. A fluid-saving pump down tool to transport a wireline tool string downward through a well casing, comprising: a main shaft having a concentric seat fixed thereto toward a lower end of said main shaft; a hollow expandable cylinder forming a variable-diameter piston concentrically disposed on said main shaft and seated against said concentric seat; a bow spring assembly surrounding said variable-diameter piston and fixed to said main shaft located at one end of said bow spring assembly; and a sliding thrust bushing configured to slide along said main shaft outside said hollow expandable cylinder spring assembly; said hollow expandable cylinder formed of an elastomeric material and having a reduced wall thickness intermediate a defined length thereof, wherein said reduced wall thickness intermediate said defined length thereof flexes outward under fluid pressure from fluid pumped into a wellbore, and wherein said fluid pressure from said fluid pumped into said wellbore bears against said variable-diameter piston causing said wireline string tool to be conveyed through said well casing.