Method and apparatus for controlling hydraulic drifters

Claim 2

In an improved hydraulic circuit for controlling the feed force and impact force exerted by a hydraulic drifter that includes an impact mechanism including a hydraulically-actuated, reciprocating piston for causing the impact force and a feed mechanism powered by a hydraulic motor for moving the impact mechanism toward and away from the formation being drilled, the improvement comprising: first means for supplying pressure fluid to the impact mechanism; second means for supplying pressure fluid to the feed mechanism; and, third means interconnecting said first and second means for fluid communication, said third means including normally-closed valve means, presettable to open in response to a predetermined pressure in said second means permitting fluid flow from said second means to said first means when the pressure in said second means exceeds the predetermined pressure, whereby the impact mechanism receives fluid under pressure from the feed mechanism.

Claim 3

The hydraulic circuit of claim 1 wherein said second means includes pressure reducing means for limiting the maximum fluid pressure applied to the hydraulic motor.

Claim 4

The hydraulic circuit of claim 2 wherein said valve means is preset to open at a pressure above maximum prEssure in said second means.

Claim 5

The hydraulic circuit of claim 2 wherein said second means also includes bypass means providing a fluid flow path around said pressure reducing means, said bypass means having a one-way valve disposed therein permitting flow around said pressure reducing means in one direction and preventing flow around said pressure reducing means in the opposite direction.

Claim 6

The hydraulic circuit of claim 4 wherein said one-way valve is oriented to prevent flow through said bypass means when said second means is supplying pressure to the feed mechanism in a direction to cause the feed mechanism to move the impact mechanism toward the formation to be drilled.

Claim 7

In an improved hydraulic circuit for controlling the feed force and impact force exerted by a hydraulic drifter that includes an impact mechanism including a hydraulically-actuated, reciprocating piston for causing the impact force and a feed mechanism powered by a hydraulic motor for moving the impact mechanism toward and away from the formation being drilled, the improvement comprising: an impact pump connected in fluid communication with the impact mechanism; impact valve means arranged to interrupt the fluid communication between said impact pump and impact mechanism; feed valve means; a feed pump connected in fluid communication with said feed valve means; first and second conduits providing fluid communication between said feed valve means and the hydraulic motor; pressure-reducing valve means located in said second conduit for limiting the fluid pressure in the hydraulic motor to a predetermined value; a third conduit connecting said second conduit in fluid communication with the impact mechanism; and, pressure-responsive valve means in said third conduit for providing fluid flow through said third conduit to the impact mechanism from said feed pump when the pressure in said second conduit and pressure-reducing valve means exceeds said predetermined value to provide additional fluid power from the feed pump for operation of the impact mechanism when the hydraulic motor of the feed mechanism is at or near stall condition.

Claim 8

In an improved hydraulic circuit for controlling the feed force and impact force exerted by a hydraulic drifter that includes an impact mechanism including a hydraulically-actuated, reciprocating piston for causing the impact force and a feed mechanism powered by a hydraulic motor for moving the impact mechanism toward and away from the formation being drilled, the improvement comprising: an impact pump connected in fluid communication with the impact mechanism; impact valve means arranged to interrupt the fluid communication between said impact pump and impact mechanism; feed valve means; a feed pump connected in fluid communication with said feed valve means; first and second conduits providing fluid communication between said feed valve means and the hydraulic motor; pressure-reducing valve means located in said second conduit for limiting the fluid pressure in the hydraulic motor to a predetermined value; a third conduit connecting said second conduit in fluid communication with the impact mechanism; and, pressure-responsive valve means in said third conduit for providing fluid flow through said third conduit to the impact mechanism from said feed pump when the pressure in said second conduit and pressure-reducing valve means exceeds said predetermined value to provide additional fluid power from the feed pump for operation of the impact mechanism when the hydraulic motor of the feed mechanism is at or near stall condition.

Claim 11

The method of claim 7 wherein the step of diverting a portion of the pressure fluid includes presetting the valve means to open when the hydraulic motor is at or near stall.

Claim 12

The method of claim 7 including the step of closing the valve means to prevent the diversion of the pressure fluid when the pressure in the feed mechanism is below the predetermined value.