Drill string shock absorber

Claim 2

A shock absorber apparatus for use in a drill string, comprising: telescopically disposed and slidably splined mandrel and housing members, one of said members being adapted for attachment to a drill string and the other of said members being adapted for attachment to a drill bit; an elongated, helical coil spring reacting between said members to absorb longitudinal vibrations and shock loads; and a hollow flow tube having one end portion sealingly slidable with respect to said housing member and another end portion sealingly slidable with respect to said mandrel member, said flow tube defining wall surfaces of a chamber that encloses said coil spring and contains a lubricating oil, said flow tube being arranged to transmit the pressures of a drilling fluid within said members to said oil.

Claim 3

The apparatus of claim 1 wherein said mandrel member has a transverse cross-sectional area that is subject to the pressure of said lubricating oil.

Claim 4

The apparatus of claim 2 further including spline means for preventing relative rotation of said housing and mandrel members, and fluid passage means extending past said spline means for conveying said oil during telescoping movement thereof in a manner to provide a dashpot effect to damp out peak load changes.

Claim 5

The apparatus of claim 3 further including coengageable seal means on said mandrel and housing means adjacent said spline means for preventing leakage of said oil to the exterior of said members.

Claim 6

The apparatus of claim 1 wherein said coil spring has a rectangular section and provides a relatively low spring rate.

Claim 7

A shock absorber apparatus for use in a drill string, comprising: an elongated tubular housing having its upper end adapted for connection to a drill string; a mandrel extending upwardly into the lower end of said housing and being sealingly slidable relative thereto; spline means for corotatively coupling said mandrel and said housing; an elongated hollow flow tube within said housing, said tube having an outwardly directed shoulder at its upper portion that is sealingly slidable with respect to said housing and an external seal surface on its lower portion that is sealingly slidable with respect to said mandrel, an intermediate portion of said flow tube being spaced inwardly of said housing to provide an annular cavity; and an elongated spring means positioned in said cavity and arranged to react between said housing and said mandrel to provide a yieldable resistance to longitudinal relative movement and thereby to substantially absorb and otherwise attenuate vibration and shock loads, said cavity and the interior spaces adjacent said spline means being filled with a lubricating oil.

Claim 8

A shock absorber apparatus for use in a drill string, comprising: an elongated tubular housing having its upper end adapted for connection to a drill string; a mandrel extending upwardly into the lower end of said housing and being sealingly slidable relative thereto; spline means for corotatively coupling said mandrel and said housing; an elongated hollow flow tube within said housing, said tube having an outwardly directed shoulder at its upper portion that is sealingly slidable with respect to said housing and an external seal surface on its lower portion that is sealingly slidable with respect to said mandrel, an intermediate portion of said flow tube being spaced inwardly of said housing to provide an annular cavity; and an elongated spring means positioned in said cavity and arranged to react between said housing and said mandrel to provide a yieldable resistance to longitudinal relative movement and thereby to substantially absorb and otherwise attenuate vibration and shock loads, said cavity and the interior spaces adjacent said spline means being filled with a lubricating oil.

Claim 9

The apparatus of claim 6 wherein said spring means is a helical coil of rectangular section constructed and arranged to provide a low spring rate.

Claim 10

The apparatus of claim 7 wherein said outwardly directed shoulder functions to transmit the pressure of drilling fluids within said apparatus to said lubricating oil, said mandrel having a transverse cross-section area subject to the pressure of said oil.

Claim 11

The apparatus of claim 8 wherein the clearance between said spline means provide restricted fluid passages for said oil during sliding movement of mandrel relative to said housing, thereby to provide a dashpot effect to substantially damp out peak load changes.