Drilling string shock-absorbing tool

Claim 1

A tool for use in a drill string utilizing drilling fluid to drill a well bore and having utility for absorbing shock loading arising from axial displacement of an attached drilling bit, said tool comprising: telescopically arranged tubular parts comprising an outer barrel and an inner mandrel received in the barrel in spaced relationship therewith so that a space is formed therebetween, said barrel and mandrel being movable longitudinally relative to each other; means at the outer ends of the parts for threadably connecting them into the drill string; means carried by said parts for limiting their relative longitudinal movement; said tubular parts comprising means connecting them for rotation together while permitting telescopic movement; discrete, resilient, solid, temporarily deformable means disposed in the space, said means having a spring rate of less than 100,000 pounds per inch and being substantially out of contact at all times with the barrel and mandrel side walls; a pair of opposed compression means, one such means being carried by the mandrel and extending into the space adjacent one end thereof, the other such means being carried by the barrel and extending into the space adjacent the other end thereof, said compression means being adapted to act against the ends of the deformable means; a body of operating liquid disposed in the space with the deformable means; substantially liquid tight means, at each end of the space, between the mandrel and barrel, for preventing well bore drilling fluid from mixing with the operating liquid; and means for pressurizing the operating liquid to substantially equalize it with the hydrostatic bottom hole pressure.