Note: Descriptions are shown in the official language in which they were submitted.
CA 02877914 2015-01-13
CIRCUMFERENTIAL DISPLACEMENT SUCKER ROD TONG
FIELD OF THE INVENTION
The invention refers to a tool commonly known as a sucker rod tong used for
assembling and
disassembling threaded sucker rods of oil wells, and more specifically
pertains to a linear drive mechanism
for the second stage tightening to a circumferential displacement of the
sucker rods to a rod coupling.
BACKGROUND OF THE INVENTION
Oilfield wells include the use of sucker rods consisting of 25 to 30 foot
lengths of solid rods with
male threads at each end, threaded together into a rod string that connect the
downhole oilwell pump to the
surface reciprocating drive that in its entirety brings liquid hydrocarbons
from deep within the ground to the
surface.
Each sucker rod threaded male end is screwed into a rod coupling or collar or
box so that the
shoulder of each rod end is tightened against the shoulder of the rod
coupling. The connected and tightened
assembly of sucker rod connected to a rod coupling which is connected to the
next sucker rod forms the rod
string.
The tightening of each sucker rod threaded connection to a specific
circumferential displacement
.. from a hand tight shouldered circumferential position is the method
determined by the sucker rod
manufacturers to achieve the correct tightness between the sucker rod and the
sucker rod collar. Inaccurate
tightness of a connection can cause failure of the sucker rod string within
the well bore.
Hundreds of sucker rod connections typically comprise a rod string in
oilwells. Sucker rod
connections are critical to the operational life of a sucker rod string.
Currently hydraulically powered sucker rod tongs are commonly used to assemble
and disassemble a
string of sucker rods. Current practices involve screwing the sucker rod
connections together manually or
with hydraulic powered sucker rod tongs to the shoulder of the connection and
then without stopping the
sucker rod tongs, they apply rotational torque between the upper and lower
sucker rod connections using the
hydraulically powered sucker rod tong and engage the upper and lower sucker
rod segments on their
respective mating rod flats to the rod coupling. The rod coupling provides the
connection between sucker
rods. Activating the hydraulically powered sucker rod tongs rotates one sucker
rod thread relative to the other
sucker rod thread to achieve a tight connection. As the connection tightens,
the tong ultimately stalls at the
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CA 02877914 2015-01-13
hydraulic pressure preset by the operator assuming the achievement of a
corresponding torque and
circumferential displacement movement of the sucker rod connections relative
to each other. When the tong
rotationally stalls, the operator assumes that the connection has achieved the
predetermined circumferential
displacement position and is properly torqued.
The position at which the rod connections displace from the hand tightened
shouldered
circumferential position is not predictable. Frequently, the operator tests
the position at which the force of the
hydraulically powered sucker rod tongs tightens the connection to and the
operator measures that distance in
comparison to a known circumferential displacement scale or CD Card. The
hydraulic pressure setting of the
hydraulic circuit is adjusted to approach the displacement result desired.
This is an inaccurate, unreliable and
unpredictable method of achieving a circumferential displacement from a known
position. Repeatability of
hydraulic relief valves is dependent on oil flow, viscosity and fluid pressure
drops. Variations within the
relief valves ability to repeat this setting can exceed 10%. The hydraulic
motor that delivers the torque to the
hydraulically powered tong assembly within its design can vary its output
torque given the same input
hydraulic pressure throughout 1 revolution of the motor. The motor can have as
few as 5 power strokes per
revolution and output torque can exceed 20% specifically due to the
rotational position that the motor is in
as torque is being applied to the sucker rod connections. The force which is
required to rotate different sucker
rods and couplings can vary significantly resulting in significant differences
in final circumferential
displacement. The result of the current sucker rod hydraulic powered tongs
design is that circumferential
displacement of the sucker rod connection from a hand tightened shoulder
circumferential position is not
predictable or reliable.
SUMMARY OF THE INVENTION
Despite the known sucker rod tong assemblies, there still exists the problem
of tightening sucker rod
connections to an accurate, repeatable and reliable circumferential
displacement from a shoulder position.
Accordingly, it is an object of a preferred embodiment of the present
invention to consistently
achieve a shoulder point of a sucker rod connection by the mechanical and
hydraulic force limitations of the
first stage of the CD tong drive and to provide a sucker rod tong with the
ability to circumferentially displace
the sucker rod connection to a position that is a physical, mechanical and
adjustable stop achieved by a linear
actuator in one continuous movement.
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CA 02877914 2015-01-13
A hydraulically powered sucker rod tong hereinafter referred to as the CD tong
that, in its first stage
of movement, limits the tightening of the sucker rod connection positively in
its achievement to a hand-tight,
shouldered circumferential position.
According to a preferred embodiment of the present invention, the CD tong
comprises a linear
geared rack and pinion to provide the second stage of movement drive
integrated with the first stage main
drive gear of the CD tong that following achievement of a shouldered
connection sequentially moves the
main gear of the CD tong to a preset distance to a mechanical stop of the
linear geared rack that is the
circumferential displacement from the shouldered position of the sucker rod
connection.
The linear gear drive that circumferentially displaces a sucker rod connection
from a hydraulically
generated hand tightened position to a specific set distance from that hand
tightened position in one
continuous movement. The mechanical set point for each size and grade of
sucker rod connection is
manually adjusted, set and locked for a complete run of one size of sucker
rods.
According to one aspect of the present invention, there is provided a method
to tighten two sucker
rods around a sucker rod connector after reaching the point of hand tightness,
said method comprising the
step of actuating a linear gear drive to move to a predetermined position, the
linear drive gear being in
operational connection with sucker rod tongs, the movement of the linear drive
gear actuating a
circumferential rotational movement of the sucker rod tongs to a pre-
determined position.
According to another aspect of the present invention, there is provided a use
of a linear gear drive in
a sucker rod tong assembly used in oil wells, said linear gear drive is
operatively connected to a sucker rod
tong adapted to tighten two sucker rods around a sucker rod connector from a
hand-tight first position to a
predetermined second position by rotating a first sucker rod. Preferably, the
linear gear drive is a rack and
pinion, however several linear displacement drives could be adapted for use in
the CD tong assembly
according to a preferred embodiment of the present invention.
According to another aspect of the present invention, there is provided a
sucker rod tong assembly
comprising a linear drive mechanism adapted to tighten a sucker rod to a rod
connector from a first hand-
tight position to a second predetermined position, wherein the linear drive
mechanism is operatively
connected to the sucker rod tong such that positive movement of the linear
drive mechanism actuates
rotational movement of the sucker rod tong to tighten a sucker rod around a
sucker rod connector.
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According to yet another aspect of the present invention, there is provided a
device for use in the
tightening of two sucker rods around a rod coupling, said device comprising a
first stage tightening
mechanism and a second stage tightening mechanism, where the second stage
tightening mechanism is a
linear drive mechanism operatively connected to a sucker rod tong and adapted
to move the sucker rod tong
from a first position circumferential position to a second predetermined
circumferential position.
The sucker rod tong assembly according to a preferred embodiment of the
present invention does
not require the use of electrical instrumentation rather it effects a positive
displacement using mechanical
circumferential displacement movement only.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention may be more completely understood in consideration of the
following description of
various embodiments of the invention in connection with the accompanying
drawings, in which:
FIG. I is an exploded side view of two sucker rods and a rod coupling. The rod
coupling is shown
in cross section.
FIG. 2 is a side view of a CD Tong Assembly with the lower back up wrench of
the CD tong
assembly.
FIG. 3 is a front elevation view of the CD tong assembly according to a
preferred embodiment of
the present invention.
FIG. 4 is a top plan transparent view of the CD tong assembly of FIG. 2 with
the hydraulic cylinder
rack gear disengaged from the pinion gear.
FIG. 5 is a bottom plan view of the CD tong assembly of FIG. 2 with the backup
wrench.
FIG. 6 is a top cross sectional view of the CD tong of FIG. 2.
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Date Recue/Date Received 2021-06-04
FIG. 7 is a top cross sectional view of the CD tong according to a preferred
embodiment of the
present invention, the tong is engaged and rotating the upper sucker rod
connection in relation to the lower
sucker rod connection to shoulder without the hydraulic cylinder rack gear
engaged with the CD tong pinion
gear.
FIG. 8 is a top cross sectional view of the CD tong according to a preferred
embodiment, the tong
engaged and in rotational movement driven by the hydraulic cylinder rack gear
as it is engaged with the
pinion gear to a mechanical stop set and locked with a hand wheel or other
mechanical adjustment.
FIG. 9 is a perspective top transparent view of the CD tong assembly showing
the inner workings
of the assembly according to a preferred embodiment of the present invention.
FIG. 10 is a perspective bottom view of the CD tong assembly according to a
preferred embodiment
of the present invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
As seen in FIG. 1, the upper sucker rod (8) and the lower sucker rod (9) each
include a threaded
pin (10) that screws into coupling (11). A shoulder (12) of the upper sucker
rod (8) and lower sucker rod
(9) is machined to bear against the axial face (13) of coupling (11). The
upper sucker rod (8) and lower
sucker rod (9) provide a set of wrench flats (15) suitable to be engaged by a
sucker rod CD Tong Assembly
(14), as shown in FIG. 2, used for screwing together and tightening the sucker
rods.
As seen in FIGS. 5, 6, 7 and 8, the CD tong assembly (14) and upper sucker rod
(8) is shown with
the lower back up wrench (17) of the CD tong assembly (14). To tighten the
threaded connection between
the upper sucker rod (8) and the lower sucker rod (9) to the required
circumferential displacement, first the
CD tong assembly (14) is maneuvered to engage with the mating rod flats (15)
of the upper sucker rod (8)
and the lower sucker rod (9) on either side of the rod coupling (11). Then,
the CD tong assembly (14) is
activated to rotate the connecting threads of the upper sucker rod (8) and the
lower sucker rod (9) into the
rod coupling (11) to a hand tight, shoulder circumferential start position.
The CD tong assembly's (14) first
gear hydraulic motor drive stage (25) does not have the mechanical ability to
exceed the rotational forces
required to exceed a hand tight connection between the upper sucker rod (8)
and the lower sucker rod (9)
and the rod coupling. Once the rotational force is achieved to a hand tight
shouldered position of the sucker
rod connection, a hydraulic sequence valve automatically shifts and engages
the second gear hydraulic
cylinder linear drive stage (30) of the CD tong assembly (14) which is the
linear hydraulic cylinder (31)
driven rack (32) and pinion gear assembly (33). The hydraulic cylinder driven
rack (32) then extends,
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Date Recue/Date Received 2021-06-04
rotating the pinion gear assembly (33) until the hydraulic cylinder driven
rack (32) stops against a
mechanical stop (34) that has been adjusted to an exact position that is the
circumferential displacement
from the hand tight shouldered position for the size and grade of sucker rod
of the assembly.
In FIGS. 5, 6, 7, 8, 9 and 10 the CD tong assembly (14) includes a rotational
upper jaw (1) to engage
the upper sucker rod (8) flats (15) and a backup wrench (17) for engaging the
lower sucker rod (9) flats
(15). The upper jaw (1) includes one gripper (19) pivotally attached to a gear
segment (20) and outer geared
ring assembly (22) by way of pins (21). Pins (21) allow gripper (19) to pivot
in and out of engagement with
the upper sucker rod (8) flats (15), while gear segment (22) renders upper jaw
assembly (1) rotationally
relative to the CD tong housing (23).
FIG. 2 shows the backup wrench (17) of the CD tong assembly (14). FIG. 3 shows
the CD tong
assembly (14) disengaged from the sucker rods.
FIG. 4 shows a transparent view of the CD tong assembly (14) and illustrates a
gear drive train (24)
that couples a hydraulic motor (25) to upper jaw (1). The gear drive train
(24) includes two drive gears (26)
so that at least one of them remains in driving contact with gear segment (22)
at all times, as shown in FIG.
6, as gear segment (22) has a discontinuity or opening (27) for receiving and
releasing upper sucker rod (8).
The two drive gears (26) reduce drive speed from the input pinion gear (28) to
input segment gear (22). A
hydraulic motor (25) is coupled to and turns input pinion gear (28) and
rotates drive gear train (24) at a
reduced speed to provide upper jaw (1) with sufficient torque to be able to
screw sucker rods (8) and (9)
into coupling (11) to a hand tighten shoulder torque. To disassemble or
unscrew at least one sucker rod (8)
or (9) from coupling (11), the rotational direction of motor (25) is reversed.
When the hydraulic pressure within the hydraulic system powering the hydraulic
motor (25)
achieves a set fixed hydraulic pressure a hydraulic pressure sequence valve is
activated directing hydraulic
oil to a hydraulic cylinder (31) activating that hydraulic cylinder (31) to
move a geared rack (32) to a
mechanical threaded stop (34) ensuring that the rod connection has achieved
circumferential displacement
from the hand tightened shoulder position of the connection.
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The CD tong assembly (14) geared rack (32) driven hydraulically by hydraulic
cylinder (31) engages
with pinion gear (28) to displace the connection between the upper sucker rod
(8) and the lower sucker rod
(9) from a hand tight shouldered torque to a circumferential displacement from
the shoulder tight position of
the connection. The distance that the geared rack moves corresponds to an
accurate circumferential
displacement of the connection from the hand tight shouldered torque and is
determined by a mechanical
threaded stop (34) that is adjusted manually and set by a hand wheel 05). It
is unique that the circumferential
displacement of the connection is determined by a fixed distance traveled to a
mechanical stop by the
hydraulic cylinder (31) powered geared rack (32).
Once the connection between the upper sucker rod (8) is circumferentially
displaced by a
predetermined distance relative to the lower sucker rod (9), the linear gear
drive will stop moving.
The above-described embodiments of the present invention are intended to be
examples only.
Alterations, modifications and variations may be effected to the particular
embodiments by those of skill in
the art without departing from the scope of the invention, which is defined
solely by the claims appended
hereto.
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