Note: Descriptions are shown in the official language in which they were submitted.
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PUSH TOGETHER TUBULAR CONNECTION SYSTEM
Description
Technical Field
This invention relates in general to methods and apparatus for joining pipe
ends and in
particular to methods and apparatus for joining pipe ends without the
necessity of rotating
the pipe.
Background Art
There are a number of applications for joining pipe ends in which it would be
desirable
to join the ends without the necessity of rotating the respective pipes
themselves. One
example would be in the oil industry, and particularly in the area of offshore
production.
On a drilling rig, rotation of one pipe end relative to the other is typically
accomplished
either by use of a hydraulic power tong which requires a specialized crew to
operate, or
a more basic "rope technique" consisting of pulling on a soft rope from the
drilling rig
main winch capstan. Final make-up torque is achieved by using a mechanical
tong. The
maximum amount of rotation achieved in one stroke of such a mechanical
tong/cathead
chain assembly is approximately one-quarter to one-third of a turn without the
necessity
of having to reset the assembly by manual reverse rotation. Production
pipelines, on the
other hand, have.often been welded together in the past.
A suitable push-together connection would have advantages in off shore
applications,
for example, by providing the ability of being able to make-up and disconnect
underwater
connections remotely. Also, a push-together connection would be simple to
implement
and would eliminate costly welding operations which have become almost
prohibitive in
some situations due to the high hourly cost of offshore operations.
One way that the oil industry has attempted to address the problem of creating
a secure
pipe connection, particularly in joining offshore casing and tubing, was by
introducing a
specialized generation of thread connectors using modified A.P.I. threads.
These
threaded connectors are still widely used today, for example, for dimensions
below
twenty-four inches, despite the general requirement of a minimum of two and
one-half
turns of rotation for make-up.
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A threadless connector for large diameter casings has also been used in the
past which
was based upon a snap-ring linkage type mechanism. These "snap-ring" type
connectors offer fast make-up but offer neither the low weight-to-capacity
ratio, nor the
integrity or price competitiveness of the threaded connector for a given
capacity.
Another type connector featuring radial dogs was introduced to replace flange
connections, in a mechanical configuration for drilling riser connections, and
in a
hydraulic configuration for wellhead connections. Recently, the use of dog
type
connectors has been extended to offshore platform anchoring pile connections,
but its
success has been limited by its high cost, due to the large number of parts
and the
relatively heavy section required in the design and manufacture of such a
connector.
In addition to the oil industry, numerous other applications exist for joining
tubular pipe
ends. For example, tubular pipe connections are used in a variety of civil
engineering
applications, including their utilization in providing structural support in
the construction
field. One such use of tubular pipes can be found in the building of
underground tunnels.
More specifically, tubular pipes provide support to large underground tunnels
that are
typically used as roadways or other transportation means. The large scale
construction
of underground tunnels for transportation applications is presently underway
in Europe,
Japan and elsewhere.
In a typical procedure to construct an underground tunnel, a large pipe, or
possibly
several large pipes, is laid by a boring machine and forms the main tunnel.
Next, a
boring machine proceeds to lay relatively smaller curved pipes surrounding the
main
tunnel to provide additional structural support These small curved pipes are
commonly
constructed as 10 foot sections having, for example, a 32 inch outer diameter.
It is then=
necessary to connect these individual sections to provide a single, lengthier
curved pipe
adjacent to the underground structure. The process is repeated, placing these
connected pipe sections parallel to one another for the duration of the
desired length
along the main tunnel, creating in effect a "whalebone" configuration
surrounding the
main tunnel. The voids in and around the pipes will be subsequently filled
with concrete.
In an application such as an underground roadway that reaches upwards to 12
miles,
somewhere on the order of 80,000 connections would be needed to couple the
individual
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pipe sections together to Provide enough support to adequately enlarge the
surrounding
area of the main pipe.
Various techniques have been provided at the present time for connecting these
individual curved tunnel pipe sections where the pipe sections themselves
cannot be
rotated. As with the offshore oil industry, one technique presently used in
many
situations, is to join two or more of these pipe sections together by welding,
either by
hand welding or semi-automatic welding processes. Welding is a time consuming
activity, at best. Also, there is the possibility of defects in the welds and
poor workability
of the resulting materials due to heating of the metal. In low temperatures,
countermeasures such as the preheating are necessary. In general, a welding
process
can take somewhere from 2 to 5 hours to weld one connection for a tunnel pipe
section,
depending on the size or complexity of the connection. With this in mind, time
constraints virtually eliminate the practicality of welding each coupling in
large projects
consisting of thousands of pipe sections of the type under consideration.
Another technique which has been proposed for joining pipe ends, where the
pipes
themselves cannot be rotated, is the use of the so-called "adhesion joint."
This method
injects, for example, an acrylic adhesive into the clearance of the joint
interval, after
which a post-line tube is inserted. It is possible to carry out the
construction in a shorter
time than the welding method, but the adhesive may not be applied uniformly,
resulting
in compromised connections. The adhesives may be messy to apply and may. not
furnish the required strength for some connection applications.
U. S. Patent No. 4,487,433, issued December 11, 1984, to Miller, shows an anti-
rotation
coupling wherein similarly pitched and profiled, but oppositely threaded ends,
are
provided for two couplings incorporating an anti-rotation member such as a
tongue and
groove or a hole and dowel pin. The patent seems to be primarily concerned
with
keeping the pipes anti-rotational once the connection is assembled, however.
U.S. Patent No. 4,846,508, issued July 11, 1989, to Pallini, Jr. Et al., shows
a tubular
connector system for joining two pipe ends without the necessity of rotating
the pipe
ends. One pipe end is provided with an external thread and a second pipe end
includes
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multiple thread lead entries. A special tubular connector is also provided
which includes
an internal thread at one end and internal multiple thread lead entries at the
other end.
The tubular connector is first threaded onto the first pipe. Next, the second
pipe is
stabbed into the second end of the tubular connector and the tubular connector
is then
rotated less than a single turn with respect to the second pipe to fully mate
the tubular
connector and the second pipe. It appears that the connector is screwed all
the way in
on a first pipe end and is then "backed-off' a slight amount as the second
pipe end is
screwed in (rotated less than a single turn). Even this slight amount of
rotation would not
be acceptable in many of the applications discussed above, however.
A need exists, therefore, for an improved method and apparatus for joining
tubular pipe
ends, which method does not require the rotation of one pipe section relative
to another.
Disclosure of Invention
The present invention effectively provides an apparatus and method to connect
tubular
pipe sections without the necessity of rotating the pipe sections themselves,
which
thereby overcomes various of the problems discussed with respect to the prior
art, as will
become apparent to those skilled in the art from the detailed description
which follows.
=
The connector system of the invention includes a push-together coupling for
joining two
pipe sections without the necessity of rotating the pipe sections. The
coupling includes
a coupling body having a first tapered end and a second tapered end joined
together at
a respective inner extent thereof, each of the tapered ends sloping inwardly
from the
inner extent to an outer extent thereof to thereby form a respective mouth
opening of the
body.
In one version of the connector system of the invention, each of the first and
second
tapered ends of the coupling body has a specially contoured exterior surface,
the exterior
surface being comprised of a plurality of helical spline wedges. Each of the
helical spline
wedges is oppositely tapered in width from an inner extent to an outer extent
thereof,
whereby the helical spline wedges form an alternating series of lands and
grooves on the
exterior surface of the body as viewed from the respective mouth openings. The
first and
second tapered ends of the coupling body are sized to be received on mating
surfaces
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provided on respective ends of the two pipe sections to be joined to engage
the
respective pipe ends by axial movement of one pipe relative to another.
The helical spline wedges are arranged on the exterior surface of the coupling
along a
dominant axis, the dominant axis being longitudinal or axial rather than
helical. An
assembly force is applied to the coupling and respective pipe ends. The
assembly force
causes the coupling to rotate less than 3600 before the pipes are fully
connected. The
pipes which are being joined together may be arranged to form a relatively
straight line
when assembled, as in a typical oil and gas pipeline or offshore pipeline or
riser.
Alternatively, the pipe sections may be arranged along a curved axis when
assembled,
as in the case of an underground tunnel support structure. The exterior
surfaces of the
coupling may also be specially treated, as by roughening, so that the
connection
assembles with a required degree of force, but resists disassembly due to the
action of
the specially treated surfaces engaging mating surfaces of the connection.
In another version of the connector system of the invention, the specially
contoured
surfaces on the coupling and on the respective ends of the two pipe sections
to be joined
are essentially reversed. That is, the coupling has the specially contoured
surfaces on
the interior surfaces of the first and second tapered ends. Likewise, the pipe
ends to be
joined are "pin" ends having mating specially contoured exterior surfaces.
The push-together coupling previously described can be used as a part of a
tubular
connector system for joining two pipe ends where a first pipe end is provided
having a
box end or pin end as described and a second pipe end is provided similarly
having a
box end or pin end as described. The first and second tapered ends of the
coupling are
shaped to mate with the specially machined surfaces provided on the opposing
pipe
ends, respectively, to engage the respective pipe ends by axial movement of
one pipe
relative to another.
In the method of assembling a pipe connection of the invention, a first and
second pipe
ends to be joined are provided as previously described. The first end of the
coupling is
threadedly engaged with the first pipe end until the coupling is supported on
the first pipe
end. The pipe end of the second pipe is then engaged with the second end of
the
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coupling and the second pipe is pushed axially with respect to the coupling
and the first
pipe, whereby the coupling rotates relative to the respective pipe ends and
secures the
pipe ends together.
Additional objects, features and advantages will be apparent in the written
description
which follows.
Brief Description of Drawings
Figure 1 is a perspective view of a coupling used in the tubular connector
system of the
invention.
Figure 2 is a 'partly schematic view of the coupling of Figure 1 being used to
join two
opposing box pipe ends, the pipe ends being shown in partly transparent
fashion for ease
of illustration.
Figure 3 is an exploded view of another version of the coupling of the
invention in which
the coupling has the specially contoured surfaces on the interior of the
tapered ends
thereof for mating with specially contoured exterior surfaces on the pin ends
of the two
pipes to be joined.
Figure 4 is a simplified schematic illustration of a thread on a tubular body
illustrating the
definition of a thread versus a spline.
Figure 5 is a simplified view of an underground transportation tunnel using a
whalebone
superstructure for reinforcement, the superstructure being comprised of
tubular pipe
segments joined end to end in an semi-arcuate arrangement.
Best Mode for Carrying Out the Invention
Turning to Figure 1, there is shown a push together coupling of the invention,
designated
generally as 11. The coupling is used to join two sections of pipe such as the
sections
represented by the opposing box pipe ends 13, 15 in Figure 2. As shown in
Figure 1, the
coupling body has a first tapered end 17 and a second tapered end 19 which are
joined
together a respective inner extent 21 thereof. Each of the tapered ends 17, 19
slopes
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inwardly from the inner extent 21 to an outer extent 23, 25 thereof to thereby
form a
respective mouth opening of the body, such as mouth opening 27.
In the version of the invention illustrated in Figures 1 and 2, each of the
first and second
tapered end 17, 19 has a specially contoured exterior surface. The exterior
surface is
made up of a plurality of of "helical spline wedges" such as wedges 29, 31, 33
illustrated
in Figure 1. These specially designed "wedges" are partly in the form of a
thread and
partly in the form of a spline. Each of the wedges is oppositely tapered from
an inner
extent 35 to an outer extent 37 thereof, whereby the helical spline wedges
form an
alternating series of lands 39 and grooves 41 on the exterior surface of the
body as
viewed from the respective mouth openings 27.
The specially contoured exterior surfaces of the coupling 11 resemble a
"spline" in that
they form alternating lands and grooves 39, 41. They also resemble a spline in
that the
respective wedges 29, 31, 33 are arranged on the exterior surface of the
coupling 11
along a dominant axis 43, the dominant axis being longitudinal or axial rather
than
helical, as in the case of a typical thread. Conversely, however, even though
the wedges
are aligned predominately along a longitudinal axis 43, as will be explained
in greater
detail, there is a radial component of movement during makeup of the pipe
connection.
As shown in Figure 2, the first and second tapered ends 17, 19 of the coupling
11 are
sized or shaped appropriately to be received on mating internal surfaces 45,47
provided
on the respective box ends of the two pipe sections 13, 15 to be joined. As
will be
appreciated with respect to Figure 2, an assembly force must be applied to the
coupling
11 in order to form a connection between the two pipe sections 13, 15. The
assembly
force causes the coupling 11 to rotate less than 360 before the ends 13, 15
are fully
connected. Preferably, the assembly force causes the coupling to rotate less
than 900,
and most preferably less than about 45 before the pipe ends are fully
connected.
Figure 4 is a simplified representation which further illustrates the combined
spline/thread
nature of the helical spline wedges of the invention. As has been discussed,
the wedge
surfaces are acted upon by an assembly force causing the coupling to move
primarily
along a longitudinal or axial path of travel. With a typical thread form of
pipe connection,
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the dominate axis is normally helical. There are also not as many turns per
inch with the
special helical spline wedges of the invention as compared to a normal thread
form.
Figure 4 is intended to be a simplified representation of a thread form of a
tubular
connection. Thus, with respect to Figure 4, the angle a is approximately 45 .
For an
angle generally less than almost 45 , more of a push connection is achieved.
Where the
angle a is greater than about 45 , more of a torque force connection results.
In the case
of a is equal to 00, a pure spline connection results.
In order to makeup the connection, a selected coupling end 19 is first
inserted
approximately halfway into the mating pipe end 15. The coupling is generally
free
stabbing until about the halfway point, at which resistance is encountered
from the wedge
lands and grooves making contact. In the preferred design, the lands and
grooves
contact first before the respective 49, 51 make contact. The second pipe end
13 is then
pushed in the direction of the first pipe end as with a hydraulic tool. For
the ten start
coupling illustrated in Figure 1, the coupling rotates approximately 36
radially during
makeup before the pipe outer extents 53, 55 make contact. Contact between the
pipe
ends 53, 55 and engagement with the coupling Ills achieved without any
rotation or
torque of the respective pipe ends 13, 15.
Figure 3 shows another version of the connection system of the invention in
which the
specially contoured surfaces on the coupling 12 and opposing pipe ends 14, 16
are
essentially reversed. That is, the helical spline wedge surfaces 18, 20 on the
coupling
12 are one the interior of the first and second tapered ends. Similarly, the
respective
opposing pipe ends to be joined 14, 16 are "pin" ends having specially
contoured exterior
helical spline wedge surfaces 22,24. The makeup of the connection is in other
respects
identical to that previously described.
Figure 5 is a simplified illustration of a tunnel system including tunnel
segments 57, 59
of poured concrete. The tunnel segment 59 has a supporting super structure
comprised
of a "whalebone" arrangement of tubular pipe segments 61, 63. In the example
illustrated in Figure 5, each pipe segment 61, 63 is approximately ten feet
long and has
an OD of approximately 32 inches. The pipe segments are joined end to end, as
previously described, in order to make each "whalebone" section. The pipe
interiors and
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surrounding void is then typically filled with concrete. The improved push-
together
coupling of the invention can be used to quickly and efficiently assemble the
tunnel segments described.
An invention has been provided with several advantages. The push-together
connection of the invention allows two pipe sections to be joined without the
necessity of rotating the pipe sections. This can be particularly advantageous
in
applications such as surface line pipe connections, undersea pipe systems and
tunnel super structure supports. The coupling is relatively simple in design
and
economical to manufacture. Previous connections systems requiring welding of
the pipe ends required on the order of five hours per connection whereas the
connection system of the invention can be made up in about five minutes or
less.
The multiple wedge segments forming the specially contoured surfaces of the
coupling assist in holding the opposing pipe ends together to keep them from
inadvertently separating. That is, multiple wedge surfaces are present at the
connection unlike a regular threaded connection in which the thread runs out
at
the outer extent of the pipe ends. The additional contact area provides a more
secure connection overall.
