Patent ID: 7048074
Filing Date: 2006-05-23
Classification: E21B

Abstract:
1. A control system for a percussion drive of an earth drilling unit having a housing, a drilling tool, a pulling or thrusting drive with pulling or thrusting means, a percussion piston, a pressure chamber belonging to the percussion piston and a pressure medium feed, which can be connected and disconnected, for the operation of the percussion piston, comprising: a pressure tube including a wall defining a pressure chamber within said tube, said pressure tube having a valve or a through-hole in the wall of said tube to provide a connection from the pressure medium feed to the pressure chamber belonging to the percussion piston; said pressure tube being mounted such that it can be displaced axially between two positions via the pulling or thrusting means within said housing, whereby said valve or through-hole is open in one position and closed in a second, axially displaced position; wherein said pressure tube is held by a spring element in a basic position with the valve closed or the through-hole closed.