Note: Descriptions are shown in the official language in which they were submitted.
The present invention relates to power tongs of the
type commonly used in oil fields for making up and breaking
apart threaded connections between drill pipes, casing, tubing,
and the like. More particularly, the present invention relates
to an improved drive mechanism for a power tong assembly such as
described in Canadian patent application No. 256,117, filed
June 30, 1976.
It is frequently necessary in oil field operations
to connect or disconnect joints of pipe which are threadedly
connected together. Strings of drill pipes, for example, comprise
a series of pipe sections joined together at their ends. Power
tongs are employed for making up and breaking apart these
connections and are used to rotate the pipes relative to each
other. A typical power tong includes a mechanism for gripping
the external surface of a pipe section and then rotating the
pipe section while the pipe section to which it is connected
is held stationary or rotated in the opposite direction.
A variety of power tong constructions have been
developed for accomplishing this result. U.S. Patent No.
2,879,680 to Beeman et al, which is commonly assigned with the
present application, is illustrative of one type of tong
construction. Although devices of this type have proved
satisfactory for most oil field operations, extensive use and
experimentation has shown that improvements are needed, particu-
larly with respect to the pipe-gripping mechanism and the means
for urging the mechanism into contact with the pipe.
An improved pipe-gripping mechanism and means for
urging the mechanism into contact with the pipe is described
in the above-identified patent application. In that application,
the power unit for transmitting power to the pipe-gripping
mechanism comprises a single speed motor having a gear train
-2-
:~ i . .. . .
~Qf~ lB
which transforms the single rotational speed of the motor
sha~t into two speed movement of the partial ring. The gear
train includes a motor drive gear meshing with a clutch assembly
including a low-speed clutch gear and a high speed clutch gear
which is selectively actuated by moving a shifting collar which
surrounds the clutch shaft by a conventional shifting assembly.
The low and high speed clutch gears mesh with low and high
speed pinnon gears which are carried by a sleeve. The sleeve
includes gear teeth which mesh pinion idler gears, which in turn
drive rotary idler gears which mesh with gear teeth on the partial
ring. Such a power unit has a number of undesirable features.
It is required that the gears be-manually shifted in order to
provide the desired speed and torque requirements to rotate
the partial ring. Since such clutch assel~lies required for
shifting do not include a synchromesh arrangement, which would
be too costly, problems in aligning the gears to mesh perfectly
without damage to the gears frequently occurs. Further, the
increased cost associated with multiple gears and clutch
assemblies has proved undesirable and less efficient than the
present invention.
Accordingly, an object of the present invention is
to provide a power tong for making up and taking apart joints
of drill pipe, casing, tubing, and the like having an improved
drive assembly.
Another object of the invention is to provide a power
tong having an improved drive assembly comprising a multiple
speed motor, preferably a two speed motor and a drive train
that eliminates shifting and reduces the number of moving parts.
It is still further an object of this invention to
provide a multiple speed hydraulic or pneumatic motor having
two speed ranges and two torque ranges that is coupled directly
~O~B918
through a single series of gears to rotate the partial ring,
thus urging the pipe-gripping mechanism into contact with the
pipe to be rotated.
Accordi~g to the invention, an improved power tong
for rotating a pipe comprises a frame having a throat for re-
ceiving a pipe, a partial ring rotatably mounted on said frame
and having an opening therein which is adapted to be aligned
with said throat so that a pipe may be positioned within said
partial ring, said partial ring defining cam surfaces having
a cam angle of about 1/2 to 5-1/2 degrees positioned on opposite
sides of the center line of said opening, means for rotating
said partial ring about its central axis, die means operatively
associated with said partial ring, said die means including
dies positioned on opposite sides of said center line of said
opening, rotation of said partial ring causing said cam surfaces
to move said die means inwardly so that said dies grip the pipe
on opposite sides thereof for turning movement of said pipe,
and said means for rotating said partial ring comprising a vari-
able speed motor mounted on said frame, and a drive train compri-
sing a plurality of gears coupling said motor to said partial ring.
In the preferred embodiment, the partial ring may be
rotated in either the clockwise or counterclockwise direction
by the power unit and drive train which cooperates with gear
teeth rigidly fixed to the ring.
The power unit and drive train preferably comprises
a multiple speed hydraulic or pneumatic motor, preferably a
two-speed motor, that has two speed ranges and two torque ranges.
The motor is mounted on the rearward portion of the tong assembly -
and comprises a drive shaft with a gear mounted thereon. A
~ _4_
... ,~ :
.: ; ,
1~)i5 ~39~8
pinion gear assembly meshes with the drive gear of the motor and
is rotated in either direction at either speed or torque range.
A pair of pinion idler gears mesh with the pinion gear and in
turn drive rotary idler gears which are positioned adjacent a
rotary gear mounted on the parital r:ing. The rotary gear rota-
tion drives the partial ring in a desired direction for moving
the pipe mechanism into
-4a-
~88~L8
engagement with the pipe to be rotated.
A die carrier is mounted on the tong and is rotatable
relative to the ring. The die carr:ier includes link members
which are pivotally mounted on the carrier and have dies
positioned to grip the external surface of the pipe section which
is to be rotated. The link members are arranged to cooperate
with specially designed cam surfaces on the ring so that, when
the ring is rotated relative to the die carrier, the dies are
moved into engagement with the pipe section. After the movable
dies have engaged the pipe section, further relative movement
between the ring and the die carrier is prevented and the pipe
section is therefore rotated to make up or break apart a threaded
joint of pipe.
Figure 1 is a plan view of the front portion of a
power tong according to the invention;
Figure 2 is a plan view of the entire power tong of
Figure 1 with the top plate of the frame, the door and the die
carrier removed;
Figure 3 is a vertical cross section view taken along ~ -
20 the lines 3-3 in Figure 2 to show the rotary gear-rotary idler
arrangement; and
J Figure 4 is a vertical cross section view taken along
the line 4-4 in Figure 2 to show the motor drive, pinion gear,
and pinion idler arrangement.
Referring now in detail to the drawings, the frame 2 of
the power tong includes an upper plate 4 and a lower plate 5
spaced apart and bolted to the sidewalls 7. The frame 2 has
an arcuate front portion defining a throat 10 for receiving
a pipe section such as a section of drill pipe, casing, tubing
30 or the like.
Pivotally mounted to the frame 2 adjacent the throat
--5
:' ' :' ' , ' . ',, . ,
10 by means of a hinge pin 24 is a door 26 which may be
opened by means of handle 28 to allow a section of pipe to
be placed in the throat 10 of the power tong. Pivotally attached
at 30 to the door 26 is one end of a spring-loaded piston
assembly 32. The other end of the piston assembly 32 is
pivotally attached at 34 to the frame in order to retain the
door in the open or closed position. The door and piston assembly
are shown in the closed position in solid lines and ln the open
position in phantom lines. Optionally, the door 26 may include
a latch mechanism (not shown) which cooperates with a correspond-
ing hook (not shown) mounted on the frame 2 so that the door 26
can be securely locked in place after a pipe section has been
placed into the throat 10.
The pipe-gripping mechanism includes a partial ring 40 -
which comprises a rotary gear mounted for rotation within the
frame 2 and has an opening 42 which is adapted to align with
the throat 10 of the frame. The ring 40 includes a projection
44 which extends around the outer circumference of the ring
and defines upper and lower shoulders 46 and 48, respectively,
which can abut against rollers, not shown, for support. Rigidly
secured to the outer periphery of the projection 44 of the
ring 40 are gear teeth 50.
The ring 40 may be rotated relative to the frame 2
by means of drive train 60 shown in Figures 2-4. The drive
train 60 includes a motor 300 with a downwardly extending shaft
302 having a drive gear 304 mounted thereon. The drive gear
304 is mounted between the upper and lower plates 4 and 5
and rotates a pinion 400 having a pinion gear 404 which rotates
with a shaft 402 rotatably mounted along the major axis of
the tong assembly. The pinion 400 meshes with pinion idler
gears 500 which are situated on either side of the pinion gear
--6--
91~
400. The point of contact of the pinion gear 400 with the
pinion idler gears 500 is on a line substantially perpendicular
to the major axis of the tong assembly. Pinion idler gears
500 rotate rotable idler gears 600, which in turn rotate the
rotary gear associated with the partial ring 40.
Referring to Figure 4, the motor 300 is mounted above
the upper plate at the rear end of the tong assembly. The motor
300 is a multiple speed motor, preferably a two speed motor
having two speed ranges and two torque ranges. The motor is
preferably hydraulically or pneumatically powered, and it
has been found that hydraulic motor number C270S manufactured
by the Staffa Company of Massachusetts, can be successfully
used with the apparatus of this invention.
Associated with the motor is a drive shaEt 302 which is
mounted on a shaft 306 and rotates therewith. The drive shaft
302 is journalled into a bearing 308 mounted in lower plate
5. Fixedly secured around drive shaft 302 is a drive gear
304 which rotates at two different speed and torque ranges and in
either direction depending upon the desired operation to be
performed. Drive gear 304 meshes with pinion gear 404 oE pinnon
400. Pinion 400 includes a vertical shaft 402 rotatably
mounted and extending between upper and lower plates 4 and
5. The shaft 402 has bearings 406 mounted in surrounding
engagement therewith for connecting the pinion gear 404 for
rotation with the shaft 402. Spacers 408 are provided associated
with snap rings 410 to vertically center the gear 404 between
the upper and lower plates 4 and 5.
Pinion gear 404 meshes with pinion idler gear 504
which is part of the pinion idler assembly 500. The pinion
idler assembly include a vertical shaft 502 rotatably mounted
and extending between the upper and lower plates 4 and 5 and
--7--
.
,., . . , .. ; : , . :
Q~
the pinion idler gear 504 is fixedly mounted to the rotatable
shaft 502 in a manner similar to the pinion assembly 400.
Pinion idler gear ~04 meshes in turn with the rotary idler
gear 604.
Referring to Figure 3, the rotary idler assembly
600 is shown to include a vertical shaft 602 rotatably mounted
and extending between the upper and lower plates 4 and 5 for
rotation therein. Similarly mounted to the shaft 602 is a
rotary idler gear 604 which is rotated by the pinion idler
gear, not shown in Figure 3, which in turn rotates the partial
ring 40 by meshing with gear teeth 50 mounted on the outer
periphery of the partial ring 40. It is thus seen that the
partial ring can be rotated in either direction at two speeds
and at two different torques without interposition of complicated
clutch mechanisms, thus avoiding damage to the gears during
shifting.
The pipe-gripping mechanism further includes a die
carrier 100 which is mounted for rotation on the tong and has an
opening 101 which is adapted to align with the throat 10 of the
frame and the opening 42 of the partial ring. The die carrier
100 includes upper and lower arcuate plates 102 and 104,
respectively, spaced apart by spacer sleeves 106. The plates
102 and lOd~ are held in position by bolts 108 which have a
lower threaded end portion 110 which is threaded into a threaded
opening 112 in lower arcuate plate 104. The upper and lower
arcuate plates 102 and 104 of the die carrier 100 have a
plurality of guide wheels 114 rotatably mounted thereon. The
guide wheels 114 are rotatably mounted on shafts by means of
suitable bearings. The shafts extend through openings in the
upper and lower arcuate plates 102 and 104 and are retained
by nuts 120 housed in grooves 122 in the arcuate plates. These
--8--
~8~
guide wheels 114 ride in grooves 124 and 126 defined in the
lower and upper surfaces, respectively, of the partial ring 40.
This construction permits the partial ring 40 and the die
carrier 100 to rotate relative to one another. As will be
appreciated, the grooves 124 and 126 may be defined in the upper
and lower plates 102 and 104 of the dis carrier 100 and the guide
wheels 114 rotatably mounted on the upper and lower plates 4
and 6 so that the die carrier is rotatably mounted on the
frame rather than the partial ring, as described in the above-
identified patent application.
Pivotally mounted to the die carrier 100 by hinge
pins 130 and 132 are a pair of link members 134 and 136,
respectively. The link members each include similarly shaped
upper and lower arcuate wall portions. Only the upper wall
portions 138 and 140 of the link members 134 and 136, respectively,
are shown in the drawings. The link members also each include
a cylindrically shaped side wall portion 142 and 143, respectively.
Each of the link members 134 and 136 normally carries a front
die 144 and 146, respectively, and a rear die 148 and 150,
respectively. The dies are mounted on the side wall portions
142 and 143. Each of the link members 134 and 136 also includes
head rollers 152 and 154, respectively, which are rotatably
mounted by head roller pins 156 and 158, respectively, between
the arcuate upper and lower wall portions and act as cam
followers. The front and rear dies are typically provided
with serrated faces which grip the pipe section. Although
front and read dies have been illustrated, it will be appreciated
that each of the link members 134 and 136 may only carry one
die with the dies mounted in opposed relationship.
The inner surfaces of the side portion of the partial
ring 40 facing the throat 10 are provided with three arcuate
_g_ .. :
lQ~ 8
depressions on both sides of the pipe section. These depressions
are positioned adjacent the link members 134 and 136. Depressions
160 and 161 serve as a neutral cam surface for receiving the
head rollers 152 and 154, respectively, when the pipe-gripping
mechanism is in its initial rest position. The depressions 162
and 163 serve as cam surfaces for urging the front dies 144
and 146 into gripping engagement with the pipe section when
the ring 40 is rotated in the clockwise direction. The
depressions 164 and 165, in like manner, urge the front dies
into gripping engagement with the pipe section when the ring 40
is rotated in the counterclockwise direction.
The cam surfaces 162, 163, 164, and 165 have a specially
designed and critical "cam angle" which must be employed in
order to properly engage the front and rear dies with the pipe -
section. More particularly, the "cam angle" must be about
1/2 to 5-1/2 degrees, and preferably 2 to 3 degrees, with 2-1/2
degrees being most preferred to obtain the necessary enyagement
for proper pipe handling.
The "cam angle" is defined as the angle formed ~y
lines originating at the center of rotation of the partial ring
40 and a point on a line perpendicular to the center line of
the throat 10 and passing through the center of rotation and
terminating at the point on the cam surface at which the cam
follower is positioned when the dies are in contact with the
pipe section. The "cam angle" is illustrated as "A" in Figure
2. The angle "A" is constructed as follows using the cam surface
163 as illustrative. A point "B" on the cam surface 163 is
found at which the dies 144, 146, 148, and 150 engage the
pipe. This point "B" is independent of the pipe diameter since
different si~e link members 134 and 136 are used depending
upon the pipe diameter. A line "C" is drawn between the center
-10-
10~91~
of rotation oE the partial ring 40 and the point "B". A
line "D" is then drawn between point "B" at the angle "A" from
line "C" so that the line "D" intersects a line "E" which is
perpendicular to the center line "E"' of the throat at a point
"G" which is between the center of rotation of the partial
ring 40 and the neutral cam surface 162 which is adjacent point
"B". The cam surface 163 and also the cam surface 165 form
a portion of a circle having a center at point "G". The cam
surfaces 162 and 164 are constructed in similar manner.
Referring now in more detail to the arrangement of
the front and rear dies relative to the axis of rotation of
the ring 40. It will be seen in Figure 2 that a circle drawn
about this axis may be divided into four quadrants by the center
line "F" of the throat 10 and the line "E" passing through the axis
of rotation perpendicular to the center line. The rear dies
148 and 150 are located in adjacent rear quadrants and the
front dies 144 and 146 are located in adjacent front quadrants
of the circle. The link members 134 and 136 are so mounted
that the cam surfaces ~rge the front dies 144 and 146 toward
the pipe in an approximately radial direction. Accordingly,
the front dies serve a dual purpose, namely, they not only
grip the pipe section themselves but also urge the pipe section
into engagement with the rear dies 148 and 150.
Mounted to the upper plate 4 of the frame 2 is an
arcuate brake band 170 having flange portions 172. Bolts 174
extend through openings (not shown) in the flanges 172 and
serve to attach the brake band 170 to brackets 176. The brackets
176 are welded to the upper plate 4 and the bolts 174 are
retained by nuts 178. The brake bank 170 partially surrounds
and frictionally engages the outer periphery of the upper plate
102 of the die carrier 100. The brake band 170 is restrained
.
against vertical movement by retainers 180 which are bolted
at 1~2 to the upper plate 4. Spring 184 is attached to brake
bank 170 at the rear end to slightly tension the brake band
away from the die carrier 100.
The bolt head of the rear bolt 108 is elongated to
form a spacer 201. The top of the elongated bolt head has a
threaded opening which receives the threaded end of bolt 190.
Pivotally mounted on bolt 190 is a retainer plate 192 which
has an opening which receives backing pin 194. Backing pin
194 has a shoulder which retains the backing pin in retainer
plate 192. Backing pin 194 can be inserted into one of openings
196 and 198 in the upper plate 102 of die carrier 100. Openings
196 and 198 are positioned one on either side of backing lug
200 when the opening 101 in the die carrier 100 is aligned with
the opening 42 in the partial ring 40. The backing lug 200
is mounted in a recess in the upper surface of the partial ring
40. The backing lug 200 is retained in place by bolt 204 which
is threaded into a threaded opening in the partial ring 40.
The backing pin 194 abuts against the backing lug 200 and causes
the partial ring 40 and die carrier 100 to move in unison with
their openings 42 and 101, respectively, aligned while the
opening 42 in the partial ring 40 is being aligned with the
throat 10 in the frame.
In operation, the opening 42 in the partial ring 40
is aligned with the throat 10 in the frame 2 so that the pipe
section may be inserted into the interior of the partial
ring. In inserting the pipe, the door 26 is pivoted open to
allow the pipe to be placed in the throat 10 and then closed.
When inserted the exterior surface of the pipe section comes
into contact with the rear dies 148 and 150 of link members
134 and 136, respectively, and the longitudinal axis of the pipe
-12-
~~
section is approximately coincident with the axis of rotation
of the partial ring 40. After the p;pe section is in position,
power is applied by the motor to rotate the partial ring 40
either clockwise or counterclockwiseO For the purpose of
illustration, it will be assumed that the partial ring 40 is -
rotated in a clockwise direction.
As the ring 40 begins to rotate in a clockwise direction
from the posotion shown in Figure 1, the die carrier 100 will
remain stationa~y because of the frictional engagement of
the die carrier 100 with the brake band 170. Therefore, the cam
surfaces 162 and 163 on the partial ring 40 will move relative
to the cam followers 152 and 154 on the link members 134 and
136, respectively. Upon continued rotation of the ring 40,
the cam surface 162 will cause the link member 134 to pivot
in a counterclockwise direction about the hinge pin 130 upon
which it is mounted and, in like manner, the cam surface 163
will cause the link member 136 to pivot in a clockwise direction
about its hinge pin 132. These movements of the link member
134 and 136 will bring the front dies 144 and 146 into gripping
engagement with the surface of the pipe section. Because of
the specially designed cam surfaces and the carefully selected
"cam angle", the force exerted by the dies on the pipe is
concentrated at or near the center of rotation of the pipe
section. Moreover, the force is evenly distributed and controlled
so that the pipe is gripped tightly enough to allow proper
torque to be applied without crushing or damaging the pipe.
After the front dies 144 and 146 are brought into
contact with the pipe section, further relative movement between
the cam followers 152 and 154 and the cam surfaces 162 and
163 is not possible. Accordingly, the die carrier 100 will
begin to rotate in unison with the ring 40. The pipe section,
.
.. . . . . .
~Q~9~3
being tightly gripped by the front and rear dies against
relative movement with respect to the die carrier, also will
begin to rotate in a clockwise direction. This rotation may
be continued for as many revolutions as may be required in order
to make up or break apart a threadecl connection between one
end of the pipe section and another pipe section positioned
in alignment therewith~
After the pipe section has been rotated sufficiently
to make up or brake apart the joint, the tong may be freed from the
pipe section by rotating the ring 40 in the opposite direction,
namely, in the counterclockwise direction in terms of this
illustration, to position the cam followers 152 and 154 in the
neutral cam surfaces 160 and 161, respectively. With the
parts in this position, the front dies 144 and 146 may be
disengaged from the pipe section and the tong may be moved
rearwardly to free the rear dies 148 and 150 from contact with the
surface of the pipe section. Thereafter, the ring 40 may be
further rotated in the counterclockwise direction, if necessary,
to position its opening 42 in alignment with the throat 10.
The rotation~of ring 40 will also cause die carrier 100 to
be rotated back into its initial rest position by reason of
the cooperation between backing pin 194 and backing lug 200
so that the pipe section may pass out of the tong.
As will be appreciated, the tong is also capable of
rotating the pipe section in a counterclockwise direction. In
order to accomplish this, the tong is operated in a manner
substantially as described above, the only difference being that
the partial ring 40 is rotated in the opposite direction and
the cam surfaces 164 and 165 on the partial ring 40 cooperate
with the cam followers 152 and 154.
It is to be understood that while one form of the
invention has been illustrated, there are other forms which
-14-
fall within the scope of the invention. For example, the linkmembers which carry the dies can be mounted on the die carrier
so that the link members are moved perpendicular to the center
line of the throat of the partial ring at all times rather
than pivotally. Further, the drive mechanism utilizing a two-
speed motor with a single gear train can be utilized in spinner
mechanisms for spinning sections of a pipe after the joints
are broken by a power tong assembly. Accordingly, the invention
is not to be limited to such specific form except as provided
by the appended claims.
-15-
- , . .
:. ~ . :. , ' '
, , . , : : : ' . . .
