Oil well bumper sub

Claim 1

A bumper sub of the type including an elongate cylindrical body in which a circular body shoulder forms a part thereof and from which a first bore extends upwardly as well as a longitudinally grooved second bore that extends downwardly; first and second tubular end pieces removably mounted on the upper and lower ends of said body, with said second end piece being connecteD to a tubular drill bit supporting assembly; a driven elongate tubular mandrel which extends downwardly through said first end piece, said first and second bores and said second end piece into said drill bit supporting assembly, which bumper sub is characterized by: a. a cylindrical stop that projects outwardly from said mandrel at an intermediate position thereon and slidably engages said bore; b. a plurality of rolling means arranged in rows and disposed in radially aligned, circumferentially spaced, longitudinally extending sets of grooves formed in said mandrel below said stop as well as in said body below said body shoulder, with said rolling means locking said mandrel and body together against relative rotational movement but permitting longitudinal movement of said mandrel relative to said body, and with downward movement of said mandrel relative to said body being limited by said stop when it contacts said body shoulder and with upward movement of said mandrel relative to said body being limited by said stop when it contacts said first end piece; c. a flowable lubricant within said body in sufficient quantity to substantially fill the same, and in which stop a plurality of circumferentially spaced, longitudinal channels are formed on the exterior surface thereof to permit longitudinal flow of said lubricant in said body as said mandrel moves longitudinally relative thereto, with said channels continuing downwardly on said mandrel to communicate with said grooves; and d. first and second sealing means disposed in first and second cylindrical recesses formed in said first and second end pieces that slidably seal with said mandrel, which sealing means and lubricant cooperatively prevent entry of drilling mud and foreign matter into said bore and first and second bores to impede the free movement of said rolling means.