Patent EA-004284-B1 (EA)
Title: Hydraulic drill string accumulator
Inventor: KRIESELS PETRUS CORNELIS
IPC: E21B21/10
Filed: 2001-11-27
Abstract: 1. A hydraulic accumulator for use in a drill string having a fluid passage for supply of fluid to a hydraulic drill string tool, the accumulator comprising a body provided with connecting means for connecting the accumulator to the drill string and an expansion chamber in fluid communication with the fluid passage when the accumulator is connected to the drill string by the connecting means, the expansion chamber being expandable between a first volume and a second volume which is larger than the first volume, and wherein the expansion chamber is provided with means for moving the expansion chamber from the first to the second volume upon a fluid pressure increase in the fluid passage and for moving the expansion chamber from the second to the first volume upon a pressure decrease in the fluid passage, wherein the expansion chamber has a first outlet opening in fluid communication with an inlet opening of the hydraulic drill string tool when the accumulator is connected to the drill string by the connecting means wherein said means for moving the expansion chamber from the first to the second volume and from the second to the first volume enables fluid flow from the fluid passage through the expansion/chamber to the first outlet opening when the expansion chamber is moved in the second volume and said means disables fluid flow from the fluid passage through the expansion chamber to the first outlet opening when the expansion chamber is moved in the first volume, and wherein the expansion chamber has a second outlet opening in fluid communication with a part of the fluid passage down stream the accumulator when the accumulator is connected to the drill string by the connecting means. 2. The accumulator of claim 1, wherein the expansion chamber is movable between first and second volumes by virtue of a cylinder/piston arrangement wherein the piston is movable in the cylinder between a first position in which the chamber has the first volume and a second position in which the chamber has the second volume. 3. The accumulator of claim 2, wherein the piston in the first position blocks fluid flow from the fluid passage through the expansion chamber to the first outlet opening thereby disabling said fluid flow. 4. The accumulator of claim 2 or 3, wherein the cylinder/piston arrangement is provided with a spring biasing the piston from the second to the first position. 5. The accumulator of claim 2, 3 or 4, wherein the hydraulic area of the piston is smaller when the piston is in the first position than in the second position. 6. The accumulator of claim 5, wherein the expansion chamber is provided with an inlet in fluid communication with the fluid passage, the inlet having an annular end against which the piston in the first position thereof is biased, the annular end being of a smaller diameter than the piston diameter. 7. The accumulator of any one of claims 2-6, wherein the cylinder is arranged substantially concentrically in the drill string with an annular space between the cylinder and the drill string when the accumulator is connected to the drill string by the connecting means, and wherein the first outlet opening is in fluid communication with said annular space. 8. The accumulator of any one of claims 1-7, wherein fluid communication is enabled via the second outlet opening when the expansion chamber is moved in the first volume. 9. The accumulator of claim 8 or 9 when dependent on any one of claims 2-7, wherein the second outlet opening is provided in the piston. 10. The accumulator of any one of claims 1-9, wherein the accumulator is connected to the drill string by the connecting means, and wherein said hydraulic drill string tool is a percussion hammer arranged to drive percussion drill bit of the drill string. 11. The accumulator of claim 20, wherein the percussion hammer is arranged to receive a first stream of fluid from the expansion chamber, and wherein the drill bit is arranged to receive a second stream of fluid from the fluid passage, the first stream being separate from the second stream. 12. The accumulator of claim 11, wherein the percussion hammer is arranged to receive the first stream of fluid via the first outlet and the drill bit is arranged to receive the second stream of fluid via the second outlet.