Patent ID: 7163058

Claim:
A hydraulic jar device, for use in underground wells, where the jar device is installed in a pipe string led down into the well, and designed to provide upward or downward percussions from the jar device, where the jar device comprises: a casing member, a connector sleeve, and a jar, the casing member and connector sleeve each having separate longitudinal through bores, while the jar has a bore and a gateway so that hydraulic liquid may pass in the jar device, and where the jar device is provided with a piston associated with a valve, comprising: a ball, a valve seat having a curved contact surface, and a lower valve body, designed to close and open a bore during the percussion cycle, the piston valve being designed, respectively, to close off the inflowing hydraulic liquid and to open when the spring force of a tension spring exceeds the pressure from the inflowing hydraulic liquid, so that the piston will displace the jar relative to the casing member, whereby the jar exerts a force against the casing member in order to carry out the percussion, characterized in that a guide is positioned in the immediate vicinity of the valve seat and designed to prevent the ball from movement in the lateral direction of the jar device or when the jar device undergoes a strong lateral acceleration, the guide and the valve seat being made up of surface parts of the same piece of material.