Importance

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Abstract

For use in a string of drill pipe terminating in drill collars and a drill bit, a shock sub is disclosed which, in the illustrated and preferred embodiment, incorporates telescoping upper and lower mandrels. The upper mandrel incorporates a pin connection and supports concentrically deployed, inner and outer tubular sleeves defining an internal cavity. The lower mandrel incorporates an upstanding sleeve which telescopes into the cavity between the sleeves of the upper mandrel. A two-chamber fluid damping system constrains movement of the lower mandrel sliding in the cavity of the upper mandrel. The two chambers are defined by meshed splines which permit telescoping movement, but which prevent relative rotational movement.

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First Claim