Note: Descriptions are shown in the official language in which they were submitted.
CA 02243940 2001-04-11
J_
TITLE OF THE INVENTION:
Method of Repairing Cylindrical Workpieces and
Latin Therefor
FIELD OF THE INVENTION
This invention relates to a method of repairing
dril7_ p ipes, and to a new lathe, particularly for use in
repairing drill pise~s.
BACKGROUND OF THE INVENTION
Dri7_7. pipes are thrf=_aded together in use in drill
strings during d~:~il7_ing, for example of oil or gas wells.
One end of a drill pipe has an internally threaded box or
female connection, while the other end has an externally
threaded pin or ma7_e connection so that the drill pipes may
2 o be threaded togeth.e:r . The drill pipe adj acent the box or
pin is enlar:-ged t:~o form an upset and provide strength for
the -oint, but to reduce the cost of making the drill pipe,
the upset typs_ca7.lyy does not extend very far down the pipe
length, typi.cal7_;,~ not much more than about twice the pipe
diameter. The internal bores and threads of the box and pin
are machinec:l prewi;~ely to allow the box and pin to seal
together on sealin~~ surfaces at either end of the threads,
and also perhaps ar_ intermediate points between threaded
port lon;~ .
During drilling, stresses on the drill pipe and
especially on the boxes and pins cause the interior surface
of t_~e :box and the exterior surface of the pin to become
worn, such that the~~ do not seal together, and fluid within
the drill pipe c:an leak. Since drill pipe is expensive,
rather than throw out the drill pipe when it is worn,
~?r;lnng contractors will repair or have the drill pipe
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repaired by refinishing the boxes and pins. The refinishing
is carried out by machining a new set of threads and
sealing surfaces deeper into the box and pin respectively.
This eliminates a part of the enlarged portion of the box
and pin. After several repairs, the enlarged portion of the
box or pin is gradually eliminated until no further repairs
can be carried out and the drill pipe is discarded.
The machining of the drill pipe is typically
carried out using a lathe having a chuck with jaws mounted
in a plane at one end of the lathe . The chucks hold and
rotate one end of a drill pipe against a working tool. The
other end of the drill pipe is held in a steady rest.
Often, the drill pipe will be bent at the end, with the
consequence that when cradled in the lathe, the portion of
the end being worked on does not rotate precisely in a
circle. In this instance, a large amount of metal on the
end of the drill pipe may need to be taken off in order to
obtain a precisely configured box or pin. This limits the
number of times the drill pipe can be repaired, and
consequently increases the operating costs of the drilling
contractor.
SUMMARY OF THE INVENTION
According to one aspect of the present invention,
there is provided a method of allowing multiple repairs of
bent drill pipes without losing too much of the box or pin
material. According to a further aspect of the invention,
a novel chuck and lathe is provided for carrying out the
method of the invention.
There is thus provided in accordance with one
aspect of the invention, a method of repairing a drill pipe
having first and second connector ends, each of the first
and second connectors ends including a threaded portion and
sealing portions, with a lathe having a chuck with
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longitudinally spaced first and second sets of jaws, the
method comprising the steps of mounting the drill pipe in
a lathe, gripping the first connector end of the drill pipe
with each of the first and second sets of jaws, orienting
the first connector end by manipulation of the first and
second sets of jaws into a working position; and rotating
the drilling pipe against a working tool to machine the
threaded portion and sealing portion of the first connector
end and produce a new threaded portion and sealing portion
of the first connector end.
There is also provided in accordance with a
further aspect of the invention, a lathe for machining a
drill pipe, the lathe comprising a chuck, first and second
sets of j aws adj ustably mounted on the chuck, the f first set
of jaws being mounted radially in the chuck at a first
longitudinal position and the second set of jaws being
mounted radially in the chuck in a second longitudinal
position spaced from the first first longitudinal position,
each of the first and second sets of jaws including x and
y positioning jaws, a motor for rotating the chuck; and
means to machine a drill pipe gripped by the jaws.
In a further aspect of the invention, each set
of jaws includes first and second pairs of jaws mounted
orthogonally to each other.
In a further aspect of the invention, the first
set of j aws is mounted further away from the lathe than the
second set of jaws, and the jaws of the first set of jaws
are longer in a direction perpendicular to the orientation
of the first set of jaws than the jaws of the second set of
jaws.
In a further aspect of the invention, a workpiece
positioning device is provided so that repeated cuts of
pipes may be made without re-positioning the pipes. In this
aspect of the invention, there may only be one set of jaws.
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These and further aspects of the invention will
now be described.
BRIEF DESCRIPTION OF THE DRAWINGS
There will now be described preferred embodiments
of the invention, with reference to the drawings, by way of
illustration, in which like numerals denote like elements
and in which:
Fig. 1 is a schematic showing a drill pipe in
position on a lathe for machining the box or pin at one end
of the drill pipe;
Fig. 2 is a side view, partly in section, of a
typical drill pipe showing where the chuck of the invention
grips the drill pipe;
Fig. 3 is a top view, partly in section, showing
a chuck for a lather according to the invention;
Fiq. 4 is an end view of a chuck for a lathe
according to the invention;
Fig. 5 is a side view of a chuck and jaws
according to the invention showing a workpiece positioning
device in working position on the chuck;
Fig. 5A is a blow up of a portion of Fig. 5;
Fig. 6 is an end view of the chuck, jaws and
workpiece positioning device;
Fig. 7 is a section, partially exploded, through
the device shown in Figs. 5 and 6 along the line A-A shown
in Fig. 6;
Fig. 7A is a blow up of a portion of Fig. 7;
Fig. 8 is a perspective view of a chuck, jaws and
workpiece positioning device according to the invention;
and
Fig. 9 shows an alignment system for initial
alignment of a workpiece before cutting.
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DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Referring to Fig. 1, there is shown a lathe 10
with a chuck 12 mounted on one side of a lathe motor 14.
The chuck 12 is driven rotationally under power by the
5 lathe motor 14 in conventional fashion. A drill pipe 16
being worked has one connector end 18 resting in a steady
rest or cradle 20, and the other connector end 22 is held
by the chuck 12 in working position against a tool 24. As
the drill pipe 16 rotates, the tool 24 may be moved by
machine assembly 26 in accordance with a desired pattern
that is input by an operator. The tool 24 and machine
assembly 26 form a means to machine work pieces mounted on
the lathe. Any of various conventional tools and associated
machine assemblies may be used, such as boring, facing,
turning, threading and bevelling tools made by such well
known manufacturers as Kennametal Limited, Raleigh, S.C.,
U.S.A., Sandvik Coromant Co., Fairlawn, N.J., U.S.A., and
Valenite Inc. of Madison Hts., MI, U.S.A.
Referring to Fig. 2, a joint between two drill
pipes 16a and 16b is shown. The joint is formed between the
box connection 28 of drill pipe 16a and pin connection 30
of drill pipe 16b. In this patent document, the box and pin
connection both may be referred to as connector ends, which
are enlarged in relation to the rest of the drill pipe.
Each connector end includes mating threaded portions 32 and
sealing portions 34 and 36.
Referring to Figs. 3 and 4, there is shown a
chuck 12 with longitudinally spaced radially oriented first
and second sets of jaws 40, 42 mounted on the chuck 12. The
first set of jaws 40 is mounted in a first longitudinal
position A and the second set of jaws 42 is mounted in a
second longitudinal position B spaced from the first
longitudinal position. Each position A and B is shown
roughly bisecting the jaws. Each of the first and second
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sets of jaws 40, 42 include jaws mounted on x and y axes
for positioning the j aws along the respective axes . In Fig .
4, both x and y axes are in the plane of the figure, while
in Fig. 3, one of the axes is perpendicular to the plane of
the figure. Each jaw 40, 42 has slots 44 formed in the side
of the jaw 40, 42, and the jaws 40, 42 are mounted in the
chuck 12 with ridges 46 received by the slots 44. The slots
44 and ridges 46 form tracks for the jaws to slide on and
retain the jaws 44 within the chuck 12. The jaws 40, 42 may
be adjusted in the chuck 12 by screws 48. The screws 48 are
received by threaded semi-cylindrical slots 50 in the chuck
12. Corresponding threaded semi-cylindrical slots 52 in the
jaws 42 complete threaded holes for receiving the screws
48. The tops of the screws 48 have hexagonal slots 54 for
receiving hex wrenches . Rotation of the screws 48 causes
the jaws 40, 42 to move radially in the chuck 12. The
screws 48, together with the slots 44, 50 and 52 and ridges
46, form means to adjust the position of each of the jaws
in the chuck. Each jaw of each set of jaws is independently
adjustable.
A pipe 38, without upset, is shown gripped by the
chuck 12 in Fig. 3, with its pin connection 39 extending
forward from the chuck 12 in working position. In this
instance, the chuck 12 may be located as close as is
feasible to the pin connection 39. In the case of machining
connector ends of drill pipe 16a or 16b, the front set of
jaws 40 may be centered at the position marked A in Fig. 2,
and the rear set of j aws 42 may be centered at the position
marked B in Fig. 2. The exact location of the jaws will
depend to some extent on the length of upset as indicated
by the notation C in Fig. 2. If the upset is large enough,
as with box connection 28, both sets of jaws 40, 42 may fit
on the upset as shown in Fig. 2. With a short upset it may
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be possible only to fit one of the sets of jaws on the
upset.
As shown in Figs. 3 and 4, it is preferable that
there be two mutually orthogonal pairs of jaws in each set
of jaws, for a total of eight jaws. It is possible to use
only six jaws, with three jaws mounted at 120° to each
other in each set, but this makes it difficult for the
operator to adjust the drill pipe. While such a design does
allow manipulation of the connector end of the drill pipe
in both the x and y directions, it is hard to adjust
because rotation of any two jaws necessarily changes the
position of the drill pipe in both x and y directions. With
the design shown in Figs. 3 and 4, two jaws can be operated
independently for each of the x and y directions.
The jaws 40 of the front set of jaws are
elongated by addition of jaw pieces 56 screwed by screws 58
onto the sides of the jaws. The jaw pieces 56 make the
total jaw length, in a direction along the chuck
(perpendicular to the plane defined of the first set of
jaws) , greater than the length of the jaws 42 of the second
set of j aws . Both sets of j aws may be elongated in this
manner if possible, but there is not enough room for the
second set of jaws 42 to be extended in the chuck shown. In
the case of jaws 42, the body of the chuck gets in the way
on one side of the j aws and on the other side the lathe
motor itself must be connected by a drive (conventional and
not shown) to the chuck and this leaves no room for
additional jaw length. The additional length of jaws
permits the jaws to grip the pipe firmly.
In the method of operating the lathe with the
chuck of Figs. 3 and 4, the first step is to mount the
drill pipe in a lathe with one end of the drill pipe 16
resting in steady rest 20. Next, one connector end 22
(either end 16a or 16b) of the drill pipe is gripped with
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each of the first and second sets of jaws 40, 42, by
insertion of the drill pipe into the chuck and tightening
the jaws 40, 42 onto the drill pipe. The operator may then
rotate the drill pipe to determine if the connector end 22
is rotating in a circle. Conventional means may be used to
determine the deviation of the rotation from a circle. If
the connector end 22 is not rotating in a circle, within
measurable tolerances, then the connector end may be
oriented by manipulation of the first and second sets of
jaws into a working position. The connector end may be
moved in either or both of the x and y directions by
screwing of the x and y jaws respectively. Once orientation
of the jaws is complete, the drilling pipe may be rotated
against the working tool. Both the threaded portion and
sealing portions of the connector end may be machined to
produce a new threaded portion and sealing portion of the
connector end. The method of the invention is believed
applicable to any cylindrical work piece with an end
requiring work, but has particular utility for machining a
box or pin connection of a drill pipe. While the connector
end is being worked, the other end of the relatively
flexible drill pipe rests on the steady rest 20. The drill
pipe, once repaired, may be returned to the drilling
contractor and used again for drilling. As the drill pipe
is used and the connector ends become worn again, the drill
pipe can continue to be repaired by repetition of the
method of the invention until insufficient upset remains to
permit further machining of the connector ends.
A workpiece positioning device will now be
described in relation to Figs. 5-8. A chuck 12 with jaws 40
and 42 are used as described in relation to Fig. 3. The
workpiece positioning device uses a frame or spider
assembly 71 for repeated exact positioning of a tool joint
pipe 38 within chuck 12. The pipe 38 has a shoulder 89. The
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spider assembly 71 has four arms 80 extending from a hub
82, which when the spider assembly 71 is fixed to the chuck
is aligned with the opening in the chuck which receives the
pipe to be worked on. Each arm 80 terminates outwardly at
a pedestal 84 from which a cam pin 70 extends parallel to
the axis of the hub 82. A spider mounting frame 65 formed
of four arms disposed between the jaws 40 is secured to the
chuck 12 using T-slot blocks 62 and capscrews 64. Each arm
of the spider mounting frame 65 has a cam pin receiving
hole 86 and cam 63 for receiving and securing the cam pins
70 of the spider assembly 71. At the hub 82 is a tool joint
jig 69 with a shoulder 88, the bore 90 of the tool joint
jig 69 being sized to snugly receive a connector end of a
pipe 38. The spider assembly 71 is supplied with a locking
nut 72 threaded onto a ring 85 screwed onto the hub 82 over
a collet 73, a bushing 74 within hub 82 and a jam wing nut
75 that threads onto exterior threads 83 of the tool joint
jig 69. See Fig. 7A in particular for these features. The
tool joint jig 69, hub 82, locking nut 72, collet 73,
bushing 74 and wing nut 75 permit a tool joint pipe to be
secured within the spider assembly 71 in a fixable, and
repeatable position. Bushing 74 inside diameter is about
the same size as the central portion of the tool joint jig
69 for it fits snugly within the tool joint jig 69. A
keyway 99 on the tool joint jig receives a key 97 in the
bushing 74 (See Fig. 5A).
Operation of the spider assembly for cutting
workpieces is according to the following face and chase
procedure.
1 Install spider mounting frame 65 into machine chuck 12
with t-slot blocks 62 and capscrews 64.
2 Install top jaws 40 with top jaws capscrews 76.
3 Install tool joint pipe 38 into chuck 12 a
predetermined distance conventionally determined
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according to the work order, secure with top jaws 40
by turning operating screw 48A and align pipe I.D.
with alignment jaws 42, by turning operating screws
48B.
5 4 Cut tool joint as per work order.
5 Move tool post 92 with alignment dials 94, 96 and 98
until they engage shoulders of the pipe 38 as
illustrated in Fig. 9, and set dials to "0" reading.
6 Back off tool post 92 and remove alignment dials 94,
10 96 and 98.
7 Install tool joint jig 69 onto tool joint pipe 38
until shoulder 88 makes-up tight to shoulder 89.
8 Install spider assembly 71 into spider mounting frame
65 and lock in cam pins 70 in position with cams 63.
with the tool joint jig 69 in the hub 82.
9 Install jam wing nut 75 onto tool joint jig 69 to
align bushing 74 such that shoulders 87 and 91 abut
and tighten up.
10 Tighten up locking nut 72 to lock in position collet
73.
11 Unlock and remove jam wing nut 75.
12 Unlock cams 63 and remove spider assembly 71.
13 Unscrew and remove tool joint jig 69.
14 Loosen-up operating screws 48B to back-up alignment
jaws 42 to clear tool joint o.d.
15 Loosen-up operating screws 48A to back-up top jaws
40
and remove tool joint pipe 38.
16 Install damaged tool joint pipe through chuck 12 to
predetermined distance (do not tighten jaws 40).
17 Install tool joint jig 69 onto damaged tool joint pipe
until shoulder 88 makes-up tight to shoulder of
damaged tool joint pipe.
18 Install spider assembly 71 onto tool joint jig 69.
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19 Install jam wing nut 75 and tighten-up to spider
assembly 71.
20 Line-up one cam pin 70, which may be marked for this
purpose, in relation to a correspondingly marked
socket 86 on spider mounting frame 65 and install
spider assembly 71 with tool joint pipe 38 as one unit
and lock-in cams 63.
21 Tighten-up top jaws 40 by turning operating screws 48A
onto tool joint pipe 38 and align tool joint pipe 38
with alignment jaws 42 by turning operating screws
48B.
22 Unlock and remove jam wing nut 75.
23 Unlock cams 63 and remove spider assembly 71.
24 Unscrew and remove tool joint jig 69.
25 Check alignment of pin seal faces by seal alignment
jig 92 with alignment dials 94, 96 and 98. Move tool
post 92 until dials read "0" (do not re-adjust dials).
26 Recut tool joint 38 (face & chase operation or as step
4) .
27 Repeat steps 14 to 26 for another damaged tool joint
pipe.
A person skilled in the art could make immaterial
modifications to the invention described in this patent
document without departing from the essence of the
invention that is intended to be covered by the scope of
the claims that follow.
