Note: Descriptions are shown in the official language in which they were submitted.
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Jaw Assembly
Field of the Invention
The present invention relates to a jaw assemblies for gripping tubulars.
Background
Hydrocarbon wells are typically drilled to a selected depth in order to
intersect a
hydrocarbon bearing geological formation. While the depth of these formations
is
typically several thousands of feet, the practical manufactured length of pipe
used for
drilling and casing these wells is generally no more than forty feet.
Therefore, it is
necessary to construct the required long strings of pipe using short sections
with
threaded connections at each end.
As the hydrocarbons in deep formations can generate pressures over ten
thousand pounds per square inch and the weights of pipe strings used in
drilling and
casing wells may weigh millions of pounds, it is essential that the threaded
connections
be able to reliably withstand these pressures and tensile loads. The threaded
connections must also be able to be reliably disconnected and reconnected
should
problems occur in the drilling and casing of hydrocarbon wells.
Equipment used in the make up and breakout of drilling and casing tubulars
include casing running tools, tongs and bucking units. Jaw assemblies in these
tools grip
the tubular and some cases, rotate the tubular to make up or break out the
string. As
the jaw assembly grip force is necessarily high, it is important that the
tubular surface
not become damaged by the gripping surfaces, or dies, or the jaw assembly.
Such
damage often occurs when the die surfaces do not properly contact the tubular
surface,
causing points of high force that tend to gouge the tubular surface, and
points of no
contact at all, resulting in incomplete gripping. As well, tubulars and
couplings to be
gripped are not perfectly circular and often have surface imperfections that
can prevent
full, even contact of the die surface with the tubular or coupling surface.
Again poor
contact in turn leads to improper gripping, possible slippage during make up
and
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breakout operations and possible damage to the tubulars and couplings.
It is also desirable to be able to utilize a singular jaw assembly for a range
of
tubular diameters, with only need to change out the dies. This reduces non-
operational
time needed to set up the make up or break out tool and improves the
efficiency at
which a variety of tubulars can be made up or broken out.
Some jaw designs have been created to allow movement of the die-carrying jaw
on a pivot point that in turn pivots on geared sections of the jaw assembly.
In such
designs, a first edge of a die surface contacts the tubular first and then the
jaw assembly
pivots to make further contact between the die and the tubular. Torque and
force from
the gripping and rotation of the tubular is transferred through the singular
fulcrum of
the pivot point to the make up or break out tool. Furthermore, when two of the
jaw
assemblies have pivoted to grip the tubular, further jaws are effectively
prevented from
pivoting, and held into position by virtue of the positioning of the first two
jaw
assemblies.
Therefore, there is a need for improved technology for reliably making and
breaking these tubular connections to the stringent specifications of
manufacturers and
threading operations. Furthermore, there is a need for an apparatus that can
grip
tubulars with greater precision and more flexibility than present tools.
Summary
A jaw assembly is taught, said jaw assembly comprising a lever arm defining a
lever arm pocket on a top surface thereof, said lever arm pocket having sides
and a
bottom face, a cam roller moveable along a cam surface and a die holder
removably and
pivotably received in the lever arm pocket and having a gripping surface for
gripping the
tubular, said die holder having sides and a base. Movement of the cam roller
along the
cam surface serves to pivot the die holder within the lever arm pocket.
Brief Description of the Drawings
The present invention will now be described in greater detail, with reference
to the
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following drawings, in which:
Figure 1 is a perspective view of a detail of one embodiment of the jaw
assembly of the
present invention;
Figure 2 is a side elevation view of one embodiment of the jaw assembly of the
present
invention;
Figure 3 is a bottom perspective view of one embodiment of the jaw assembly of
the
present invention;
Figure 4 is a top perspective view of one embodiment of the jaw assembly of
the
present invention; and;
Figure 5 is a side elevation view of one embodiment of the jaw assembly of the
present
invention, showing the circular path of swivel movement of the die holder
within the
lever arm pocket;
Figure 6 is a sectional elevation view of one embodiment of the jaw assembly
of the
present invention on a cam surface of a gripping tool; and
Figure 7 is a sectional view of one example of a backup assembly, showing the
jaw
assembly of the present invention in a retracted position.
Description of the Invention
The jaw assemblies of the present invention are advantageously designed to
make up or break out tubulars and couplings of a range of outside diameters
(OD).
They can be used in any number of tools including but not limited to casing
running
tools, tongs and bucking units, and collectively referred to as gripping tools
for the
purposes of the present invention.
A self-aligning jaw mechanism is preferably provided on each jaw assembly to
compensate for irregularities in pipe size, shape and surface and also provide
sufficient
clearance when the jaws are retracted to accommodate a variety of tubular and
coupling sizes. The clearance provided by the present jaw assembly makes it
possible to
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load couplings first into the gripping tool while still allowing adequate
clearance for any
misalignment.
With reference to Figures 1-6, the present jaw assembly 2 comprises a jaw
roller
26 rotatably received in a lever arm 80. More preferably the jaw roller 26 is
rotatably
affixed to the lever arm 80 by means of a jaw pin 100 preferably retained by a
retaining
ring 110. An 0-ring 112 is preferably further included to prevent ingress of
debris
between the jaw roller 26 and the lever arm 80. The lever arm 80 further
comprises a
channel 82 that travels over cam surfaces 28 of a gripping tool. A lever arm
pocket 84 is
formed on the lever arm 80 as well.
A die holder 86 is removably positioned within the lever arm pocket 84, and is
preferably pivotably held in place by a retaining clip 98 or other suitable
means known
in the art. The die holder 86 can be fitted with different sizes of dies 88
for contact with
and gripping of tubulars 12 of different sizes to be made up or broken out. In
an
unengaged and neutral position, the die holder 86 preferably defaults to rest
in a
position in which both first end 90 and second end 92 of the die 88 protrude
equally
from the lever arm 80 into the central bore 14.
Preferably, one or more spring plungers 96, and more preferably four spring
plungers 96, one in each corner of a bottom face 102 of the lever arm pocket
84 serve to
bias the die holder 86 in this neutral position.
When the jaw assembly 2 is retracted by movement of the jaw assembly 2 along
the cam surface 28 for insertion of a tubular 12 or coupling, a biasing means
94 is
provided to urge one of either the first end 90 or the second end 92 of the
die 88
towards the central bore 14, thereby causing a swivel movement of die holder
86 in the
lever arm pocket 84. The orientation of a slope of the cam surface 28 of the
gripping
tool and the protrusion of one end of the die 88 maximizes clearance in the
bore 14 to
accommodate tubulars 12 and couplings into the bore 14. The present
orientation of
the die 88 when the jaw assembly 2 is in the retracted position provides
maximum
clearance between the die 88 and the tubular 12 to be inserted. This clearance
allows
for loading and unloading tubulars 12 in an automated process. For
illustrative
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purposes only, an example of a jaw assembly in a retracted position in the
embodiment
of a backup wrench assembly is depicted in Figure 7.
It would be well understood by a person of skill in the art that while first
and
second ends 90, 92 are assigned as left and right ends respectively in the
Figures, that
the assignment of these ends is completely random and that in a different cam
surface
slope design, the second end 92 can just easily be the end to protrude without
departing from the scope of the present invention.
More preferably the biasing means 94 takes the form of a free moving push rod
that may protrude from the bottom surface 102 of the lever arm pocket 84 and
into
channel 82. As the jaw assembly 2 moves into a retracted position, said push
rod comes
into contact with the cam surface 28 and as a result the push rod is pushed
against a
base 104 of the die holder 86 to actuate the swivel movement. In a most
preferred
embodiment, movement of the push rod serves to provide approximately 2" of
diametric clearance for tubulars and couplings entering the machine.
As the jaw assembly 2 then moves along the cam surface 28 to grip the tubular
12, the biasing means 94 loses contact with the cam surface 28, thereby
removing any
push against the second end 92 of the die 88 and allowing the die holder 86 to
swivel
back to its neutral position, aided by the bias of the spring plungers 96.
As the jaw assembly 2 moves along the cam surfaces 28, to grip the tubular 12,
contact of the tubular 12 with the die holder 86 preferably overcomes the
biasing action
of the one or more spring plungers 96, to swivel and position the die holder
86 as
needed to ensure full contact with and gripping of the tubular 12. The
swiveling
movement of the die holder 86 in the lever arm pocket 84 is advantageous as it
allows
for better contact with the tubular or coupling in the presence of
irregularities on the
surface of the tubular 12 or coupling to be gripped.
In a preferred embodiment, as illustrated in Figure 5, the base 104 of the die
holders 86 that contacts the bottom face 102 of the lever arm pocket 84 are
each
shaped to allow the die holder 86 to swivel within the lever arm pocket 84 to
adjust to
fit around the tubular 12 or coupling to be gripped. More preferably, the
circular arc of
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swivel movement of the base 104 of the die holder 86 in the bottom face 102 of
the
lever arm pocket 84 is concentric to the circular arc of swivel movement of
the sides of
the die holder 86 within the sides of the lever arm pocket 84. The concentric
relationship of these swivel arcs is illustrated in Figure 5.
This concentric relationship of the swivel arcs provides the desired movement
in
a compact jaw assembly 2 size. Furthermore, the present design of die holder
86 and
lever arm pocket 84 provides several load bearing surfaces to accommodate the
high
gripping loads, as well as the torque.
The sides and base 104 of the die holder 86 are always in contact with
corresponding sides and bottom face 102 of the lever arm pocket 84, allowing
for load
from gripping and rotating the tubular 12 to be transmitted directly from the
die face 88
to the lever arm 80 and the jaw assembly 2. More specifically, the sides of
the die
holder 86 transmit torque forces to the jaw assembly 2 while the base 104
transmits
gripping force.
To accommodate tubulars or couplings of different diameters, the jaw
assemblies 2 are rotated along cam surfaces 28 to retract the jaw assemblies 2
out of
central bore 14. At the same time biasing means 94 makes contact with the cam
surfaces 28 and causes end 90 of the dies 88 to protrude into a position where
the
largest clearance is created in bore 14, as described above with reference to
the home
position of the jaw assemblies 2.
In the foregoing specification, the invention has been described with a
specific
embodiment thereof; however, it will be evident that various modifications and
changes
may be made thereto without departing from the broader spirit and scope of the
invention.
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