Valve used in a hydraulic drilling jar

Abstract

An improvement in a valve used in a hydraulic drilling jar. A fluid chamber is divided into a first chamber and a second chamber by a restrictive bore. An annular valve is mounted on the exterior surface of the mandrel between a first shoulder and a second shoulder. The valve has a first end, a second end and an exterior surface. The valve substantially obstructs the flow of fluid within the fluid chamber when the valve is positioned in the restrictive bore. The valve has a first bypass passage whereby fluid passes from the first chamber to the second chamber creating a time delay as the valve slowly moves out of the restrictive bore whereupon the telescopic movement of the mandrel in a first direction is unrestricted. The valve has a second bypass passage whereby fluid passes from the second chamber to the first chamber creating a time delay as the valve slowly moves out of the restrictive bore whereupon the telescopic movement of the mandrel in a second direction is unrestricted. The valve is slidably moveable on the mandrel between the first shoulder and the second shoulder such that the second shoulder obstructs the second bypass passage when the mandrel moves in the first direction and the first shoulder obstructs the first passage when the mandrel moves in the second direction.