Boring or penetrating the earth – Wedging slip assembly for supporting a pipe or rod
Reexamination Certificate
2003-02-24
2004-11-23
Bagnell, David (Department: 3672)
Boring or penetrating the earth
Wedging slip assembly for supporting a pipe or rod
C166S075140, C166S077530, C166S085500, C166S382000
Reexamination Certificate
active
06820705
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
N/A
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
N/A
INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISK
N/A
BACKGROUND OF THE INVENTION
Friction support means in the oilfield are typically called “slips” and are a combination of a sharp toothed front profile for engaging a cylindrical pipe and a tapered back for engaging a tapered bowl. The more load the cylindrical pipe pulls down on the slips, the more they slip down the bowl and wedge more tightly against the pipe. It is inherent that in normal slips, the coefficient of friction against the pipe must be greater than the coefficient of friction against the tapered bowl, because the bowl angle provides a vertical component of force on the slip segments. The slip segment has the choice of slipping against the pipe or down the bowl, but the bowl has a tapered face looking up. With a similar coefficient of friction, the friction of the bowl wall plus the upwardly facing bowl exceeds the friction against the pipe.
The conventional means of providing the higher friction between the slip segments and the pipe is to provide sharp teeth which dig into the pipe wall, giving the equivalent of high friction with the wall. In many applications this is acceptable. In the case of laying of subsea pipelines with corrosion resistant coatings, the sharp teeth are not acceptable. The sharp teeth cut into and destroy the coatings.
BRIEF SUMMARY OF THE INVENTION
The object of this invention is to provide slip segments which will support pipe without defacing the exterior surface of the pipe.
A second object of the present invention is to provide slip segments which effectively provide a greater force against the supported pipe member than is provided (reacted) against the supporting bowl.
A third object of the present invention is to provide a mechanical advantage between the rear of a slip segment and the front of the slip to make the slip act as if the force on the front of the slip segments is greater than the force on the rear of the slip segments.
BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS
FIG. 1
is a half section of a slip of this invention taken along lines “
1
—
1
” of FIG.
2
.
FIG. 2
is a section thru the slip assembly taken along lines “
2
—
2
” of FIG.
1
.
FIG. 3
is a simplified 2 dimensional model of a conventional slip assembly.
FIG. 4
is a simplified diagrammatic model of the slip of this invention to show why it works.
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patent: 6471439 (2002-10-01), Allamon et al.
patent: 2002/0061224 (2002-05-01), Allamon et al.
patent: 2003/0173117 (2003-09-01), Mason et al.
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