Patent ID: 7128170

Claim:
A down-hole tool comprising: a body having a through-bore; a mandrel having a through-bore and being axially slidable in the body bore to actuate and de-actuate the tool, the mandrel being slidable by hydraulic forces of drilling mud pumped under pressure along said body through-bore: and a valve to control access of said drilling mud to the mandrel, and thereby to control hydraulically the movement of the mandrel, wherein the valve has an actuate and a deactuate position, in the actuate position of which valve said drilling mud actuates the tool and in the deactuate position of which valve said drilling mud does not actuate the tool, and wherein the valve comprises a control piston slidable in the mandrel bore, against the force of a return spring by drilling mud pressure, from a low-pressure position to a high-pressure position.