U.S. patent application number 09/228845 was filed with the patent office on 2001-11-15 for coupling assembly having enhanced axial tension strength.
Invention is credited to HOMBERG, CRAIG A., LOCKARD, WALTER G., METCALFE, PAUL.
Application Number | 20010040376 09/228845 |
Document ID | / |
Family ID | 29581886 |
Filed Date | 2001-11-15 |
United States Patent
Application |
20010040376 |
Kind Code |
A1 |
METCALFE, PAUL ; et
al. |
November 15, 2001 |
COUPLING ASSEMBLY HAVING ENHANCED AXIAL TENSION STRENGTH
Abstract
A coupling assembly for conduit or pipe comprising a first
coupling member, a second coupling member and a locking member. The
first coupling member is optionally a tubular component and the
second coupling member or coupler is optionally a belled component.
The present invention is also optionally provided with an annular
sealing member.
Inventors: |
METCALFE, PAUL; (SOLON,
OH) ; HOMBERG, CRAIG A.; (CUYAHOGA FALLS, OH)
; LOCKARD, WALTER G.; (HUDSON, OH) |
Correspondence
Address: |
F DREXEL FEELING
JONES DAY REAVIS AND POGUE
NORTH POINT
901 LAKESIDE AVENUE
CLEVELAND
OH
44114
|
Family ID: |
29581886 |
Appl. No.: |
09/228845 |
Filed: |
January 12, 1999 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60071159 |
Jan 12, 1998 |
|
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Current U.S.
Class: |
285/305 |
Current CPC
Class: |
F16L 37/148 20130101;
E21B 17/046 20130101 |
Class at
Publication: |
285/305 |
International
Class: |
F16L 037/00 |
Claims
What is claimed:
1. A coupling assembly for connecting sections of conduit together
in a borehole comprising: a first coupling member attached to an
end of a first conduit, said first coupling member having an outer
surface and a circumferential recess in said outer surface; a
second coupling member attached to an end of a second conduit and
adapted for connection with said first coupling member, said second
coupling member having an inner surface and an outer surface, said
second coupling member having a circumferential groove in said
inner surface and a slot in said outer surface, said slot
positioned to provide access to said groove, whereby when said
first coupling member and said second coupling member are in a
connected state said groove aligns opposite said recess to form a
passageway; and a locking member adapted for insertion into said
slot and into said passageway, said locking member providing
resistence against forces tending to separate said first coupling
member from said second coupling member when inserted in said
passageway.
2. The coupling assembly according to claim 1 wherein said locking
member includes a first reduced thickness area near a first end and
a second reduced thickness area adjacent a second end so that said
first end and said second end overlap when said locking member is
fully inserted in said passageway.
3. The coupling assembly according to claim 2 wherein said locking
member includes a handle adjacent said first end.
4. The coupling assembly according to claim 1 further comprising a
second circumferential groove in said inner surface of said second
coupling member and a sealing member adapted for positioning within
said second groove when said first coupling member and said second
coupling member are in a connected state.
5. The coupling assembly according to claim 4 wherein said sealing
member includes a plurality of lobes on both an upper surface and a
lower surface of said sealing member.
6. The coupling assembly according to claim 1 wherein said second
coupling member has a belled region.
7. The coupling assembly according to claim 1 wherein said first
coupling member has a tubular shape.
8. The coupling assembly according to claim 1 wherein said
circumferential recess is wider than said circumferential
groove.
9. A conduit for installation in a borehole comprising: a first
coupling member attached to a first end of said conduit, said first
coupling member having an outer surface and a circumferential
recess in said outer surface; a second coupling member attached to
a second end of said conduit and adapted for connection with a
second conduit having a first coupling member with a recess in an
outer surface, said second coupling member having an inner surface
and an outer surface, said second coupling member having a
circumferential groove in said inner surface and a slot in said
outer surface, said slot positioned to provide access to said
groove, whereby when said second coupling member is in a connected
state with said first coupling member of said second conduit said
groove aligns opposite said recess in said second conduit to form a
first passageway and a locking member adapted for insertion into
said slot and into said first passageway, said locking member
providing resistence against forces tending to separate said
conduit section from said second conduit when inserted in said
first passageway.
10. The conduit according to claim 9 wherein said locking member
includes a first reduced thickness area near a first end and a
second reduced thickness area at a second end so that said first
end and said second end overlap when said locking member is fully
inserted in said passageway.
11. The conduit according to claim 10 wherein said locking member
includes a handle at said first end.
12. The conduit according to claim 9 further comprising a second
circumferential groove in said inner surface of said second
coupling member and a sealing member adapted for positioning within
said second groove when said conduit and said second conduit are in
a connected state.
13. The conduit according to claim 12 wherein said sealing member
includes a plurality of lobes on both an upper surface and a lower
surface of said sealing member.
14. A method of assembling conduits in a borehole comprising the
steps of: providing to said borehole a first conduit having a first
coupling member, a second conduit having a second coupling member,
a sealing member, and a locking member, said first coupling member
having an outer surface and a circumferential recess in said outer
surface, said second coupling member adapted for connection with
said first coupling member and having an inner surface and an outer
surface, said second coupling member having a first circumferential
groove in said inner surface, a second circumferential groove in
said inner surface, and a slot in said outer surface, said slot
positioned to provide access to said first groove, whereby when
said first coupling member and said second coupling member are in a
connected state said first groove aligns opposite said recess to
form a passageway, said locking member adapted for insertion into
said slot and into said passageway, said sealing member adapted for
positioning within said second groove when said first coupling
member and said second coupling member are in a connected state;
connecting said first coupling member to said second coupling
member; and installing said locking strap into said passageway.
15. The method according to claim 14 wherein said sealing member
includes a plurality of lobes on both an upper surface and a lower
surface of said sealing member.
Description
[0001] This application claims the benefit under 35 U.S.C. 119(e)
of U.S. Provisional Application Ser. No. 60/071,159 filed Jan. 12,
1998.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention provides a coupling assembly for
plastic pipe, and more particularly a coupling assembly in which
the coupled pipe has enhanced axial tension strength resulting in a
pipe and coupling connection that can withstand high axial loads in
tension, and that require no additional means for maintaining the
coupling assembly in a coupled state. This coupling assembly is
particularly useful in applications that require that multiple
coupled lengths of pipe be pulled long distances through
underground boreholes while maintaining a seal between the coupled
lengths of pipe without disconnecting. The present invention
provides an inexpensive plastic coupling assembly for conduit or
pipe comprising a tubular component, a coupler, an annular locking
strap, and an annular sealing member, the combination being easy to
assemble and disassemble and allowing at least one thousand feet of
such pipe to be pulled through an underground borehole without the
use of additional fasteners to maintain the coupled state.
[0004] 2. Description of Related Art
[0005] Fiber optic transmission lines and other cables have
increasingly replaced metallic electricity-conducting wires. For
various reasons, it has been desirable to bury fiber optic cables,
utility cables and utility pipes underground. To protect the cables
and pipes while underground, the cables or pipes may be placed in a
conduit or duct. See, e.g., U.S. Pat. No. 5,027,864 to Conti, et
al. The cables may be placed in an inner duct, that, in turn, is
pulled through a larger outer duct. See also U.S. Pat. No.
5,087,153, to Washburn.
[0006] One preferred material for underground duct applications is
PVC pipe or tubing, which is normally supplied in lengths of 4, 10
or 20 feet, but may be supplied in other lengths. Each such length
of pipe must be coupled to adjacent lengths by means of a coupling
assembly. A single 20 foot length of 4-inch PVC pipe weighs
approximately 45 pounds. Thus, a tunnel one thousand feet long will
require that some of the coupling assemblies bear an axial tensile
force of at least several thousand pounds due to the combined
effects of pipe weight, frictional drag resulting from the pipe
walls contacting the walls of the borehole while the conduit is
pulled, or contact with other obstructions. When this several
thousand pounds is applied over the surface area contacted by a
locking mechanism in a coupling assembly, the pressure borne by the
locking portion of the coupling assembly may be close to the
tensile strength of PVC. Previously known PVC coupling assemblies
could not bear such loads, or required additional fasteners. Prior
art augmentation of such coupling assemblies greatly increased the
difficulty, expense and even danger of using coupled lengths of
plastic pipe for such applications. Coupling assemblies made from
other materials such as metal were unsatisfactory for reasons such
as weight; limitations of the materials, such as the proneness to
corrosion of some metals (e.g., aluminum or steel); or expense
(e.g., stainless steel).
[0007] Continuous lengths of plastic tubing have been used for
underground duct applications. The method for installing this type
of conduit into a horizontal borehole is by pulling long lengths of
the tubing from a spool through the borehole. The most often used
plastic tubing is polyethylene ("PE"), supplied on large, heavy
spools, each containing some 600 feet of tubing. Such tubing
generally has a wall thickness of 0.320 inch in a four-inch
diameter. While inexpensive and widely available, PE tubing suffers
from several drawbacks. Adjacent lengths must be butt sealed
together by appropriate welding with a specialized apparatus. Both
the tensile strength and crush resistance of PE tubing are less
than that of a material such as PVC pipe. Such tubing frequently
suffers from increased ovality due to the flattening effect of
being coiled on the spool. A contractor installing the tubing must
feed each spool from a specially designed apparatus, upon which
each spool must be mounted in turn. When the end of the spooled
tubing is released, it can dangerously whip around, potentially
causing serious injury to workers and others. In a related effect,
PE has a considerable "memory" of the curvature it has been forced
to adopt while on the spool, as a result of which the PE tubing
retains a strong tendency to curl after it is removed from the
spool. Finally, tubing is often wasted if the length of the
borehole does not equal the length of a multiple number of spools
of tubing.
[0008] PVC pipe lengths have several advantages over continuous
lengths of coiled tubing. With PVC pipe, the exact number of
lengths needed for a job can be stacked together and delivered in
an ordinary flatbed truck minimizing time, manpower, equipment and
wasted material. PVC pipe has greater tensile strength and crush
resistance than polyethylene tubing, and has better resistance to
developing ovality. Because the lengths have not been forced to
bend prior to use, they do not suffer from "memory" problems found
with PE tubing.
[0009] Use of PVC pipe has not been without disadvantages.
Previously known PVC pipe couplings typically required
augmentation. Thus, numerous steps were performed in prior art
methods to assemble the coupled lengths of PVC pipe. One method
requires cementing the joint together after it is assembled. The
typical coupling for such PVC pipe is a bell and spigot type
coupling, in which each length of pipe has one end slightly belled
outward (the coupler) and the other end not belled (the tubular
component). The belled end is enlarged to a degree sufficient to
allow a non-belled end of an adjacent length to enter, forming a
sealed coupling when properly cemented together.
[0010] The cementing process includes all the known difficulties
associated with PVC cement, including the use of noxious, hazardous
solvents and the time required for the PVC cement to cure. The most
serious drawback of this type of glued-together coupling for use in
applications requiring installation by pulling through a
substantially horizontal borehole is the lack of resistance to
axially applied tension when in the coupled state. This drawback
has only previously been overcome by augmenting the PVC cement with
other fastening means, typically radially inserted screws. In order
to securely attach the lengths together, screws such as
self-tapping metal screws are inserted radially into the coupling
assembly adding an additional step, equipment, and personnel. But,
even with this improvement, additional time for the glue to cure is
needed in advance of the time when the pipe is to be pulled through
the tunnel. As a result, it is normally necessary to pre-assemble
several hundred feet or the entire string of glued- and
screwed-together PVC pipe, before the pulling process can be
started.
[0011] An additional drawback of using bell and spigot coupling
assemblies results from the diameter of the bell end, which is
larger than the remainder of the pipe. This increased diameter
makes the installation of the pipe through the underground borehole
more difficult due to increase drag especially when rocks, roots,
or other obstructions are encountered. The screw heads also
increase the installation difficulties because they extend radially
outwardly from the bell further increasing the outside diameter of
this portion of the pipe and provide a location for encountering
snags with obstructions.
[0012] The present invention provides a simpler, stronger, and
easier to assemble coupling assembly than any known heretofore.
SUMMARY OF THE INVENTION
[0013] A major difficulty that must be overcome when pulling any
duct through an underground borehole or other passage is the high
axial tension the duct and its coupling assemblies must withstand.
This is particularly true for lengths of duct held in the coupled
state by known coupling assemblies. The present invention provides
an inexpensive plastic coupling assembly for conduit or pipe,
comprising a first coupling member, a second coupling member and a
locking member. The first coupling member is optionally a tubular
component and the second coupling member or coupler is optionally a
belled component. The present invention is also optionally provided
with an annular sealing member. The combination is easy to assemble
and disassemble and allows at least one thousand feet of such pipe
to be pulled through an underground borehole without the use of
additional fasteners to maintain the coupled state. The coupling
assembly may be assembled without the use of tools by manually
inserting the tubular component into the coupler and then inserting
the locking strap into a slot and into a locking strap passageway.
The coupling assembly may be disassembled without the use of tools
by performing the installation sequence in reversed order. When
assembled, the locking strap is disposed in a locking position
between the coupler and the tubular component and the annular
sealing member is disposed in a sealing position between the
coupler and the tubular component. The coupling assembly remains
locked and sealed when subjected to high axial pulling forces. The
coupling assembly of the present invention requires no augmentation
to its strength for axial tension, the locking strap providing
sufficient strength when in its locking position that no additional
fasteners or glue are needed to maintain the coupling assembly in
the coupled state.
[0014] The coupling assembly of the present invention further
provides a smooth, obstruction-free inner surface and a relatively
smooth outer surface. The outer surface is generally convex,
although it preferably has a central constant-diameter portion. The
outside diameter of the coupler is only slightly greater than the
diameter of the pipe or tubular component, and the outside diameter
of the coupler tapers to a smaller diameter toward the end of the
coupler. The coupling is therefore relatively smooth and avoids the
possibility of snags or excessive frictional interactions with the
walls of or obstructions within the borehole through which the pipe
is installed.
[0015] The preferred coupler has an inner surface that includes a
groove used in locking the coupling assembly together, a stop
surface used to prevent over-insertion of the tubular component,
and a groove for an annular seal.
[0016] The coupling assembly of the present invention further
provides high strength against lateral forces tending to bend the
coupling assembly and result in breakage of either the locking or
sealing function. This strength derives from the depth of insertion
of the tubular component into the coupler and from the strength of
the materials of construction of the coupler, and the relative
positions of the locking ring and sealing member. The method of the
invention is simpler than previously known methods, due to the
advantages of the present invention.
[0017] As will be appreciated, the invention is capable of other
and different embodiments, and its several details are capable of
modifications in various respect, all without departing from the
spirit of the invention. Accordingly, the drawings and description
of the preferred embodiment are to be regarded as illustrative in
nature and not restrictive.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The present invention satisfies the needs noted above as
will become apparent from the following description when read in
conjunction with the accompanying drawings wherein:
[0019] FIG. 1 is a view of a preferred conduit having the coupling
elements that form the coupling assembly of the present
invention.
[0020] FIG. 2 is a view of a preferred coupler component.
[0021] FIG. 3 is a view of a preferred locking key.
[0022] FIG. 4 is a view of a preferred sealing member.
[0023] FIG. 5 is a view of a preferred conduit assembly with an
installed locking key.
[0024] FIG. 6 is a view of a preferred tubular component.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0025] The following description is made with reference to the
drawings. As shown in FIGS. 16, the preferred coupling assembly of
the present invention includes a coupler 12, a tubular component
14, a locking key 16, and an annular sealing member, such as
annular sealing seal 18.
[0026] The coupling assembly is designed to assemble easily and by
hand, but to strongly resist both high axial tension and high
lateral stress. The coupler 12 is formed at one end of a section of
the tubing and has an inner surface 20, an outer surface 22, and a
pipe wall 72. The coupler 12 has a curved region 24 at which both
the inner diameter ("ID") and the outer diameter ("OD") of the
curved region 24 gradually increase until the inner diameter of
curved region 24 exceeds the outer diameter of the tubular portion
of the coupler 12. Resistance to snags on roots and rocks is
greater on the pipe coupling according to this invention due to the
gradual transition of the coupler OD. The prior art coupling design
offers no transition, but has a 90 degree edge that is from 0.5 to
0.75 inches high per side. The coupling of this invention makes a
minor 0.25 inch transition over approximately 1.5 inches. The inner
surface 20 of the curved region 24 also provides a stop surface 70
to prevent over insertion of the tubular component 14.
[0027] The curved region 24 terminates into a slightly tapered
region 26. The slighty tapered region 26 is provided with a seal
groove 28 and a locking strap groove 30 on inner surface 20. Seal
groove 28 is shallow, approximately 0.07 to 0.08 inches, allowing
for a thicker pipe wall 72 and the resultant increase in tensile
strength of the pipe joint. This is critical because the seal
groove 28 is one of the weakest areas of the pipe joint in pure
tensile strength loading. Even with the thicker pipe wall, the OD
of the coupler 12 can be made smaller, nominally 5.0 inches,
compared to the competing coupled pipe design that are 5.5 or 6.0
inches in diameter. The reduced OD allows for the drilling of a
smaller hole for installation of the pipe thus reducing
installation cost based on reduced drilling time and labor.
[0028] The slightly tapered region 26 of the most preferred
embodiment is at least approximately 6 inches in length that
enables greater engagement and depth of overlap of the coupling 12
compared to the prior art devices. Engagement and depth of overlap
of the pipe joints has direct impact on the strength of the joint
while being bent. Analysis indicates that lower overlap results in
a significant decrease in the ability of the joint to withstand
bending. The competing design has only 4 inches of engagement of
the pipe.
[0029] Coupler 12 is also provided with a slot 54 in region 26 that
extend from outer surface 22 to locking strap groove 30 on inner
surface 20. Slot 54 is formed tangent to the centerline of locking
strap groove 30.
[0030] The tubular component 14 is formed at the other end of the
tubing. The tubular component 14 has an inner surface 32 and an
outer surface 34. Outer surface 34 is provided with a locking strap
recess 36. Locking strap recess 36 is provided with a wider width
than locking strap groove 30 to provide an adjustability feature
enabling the insertion of locking strap 16 without further
positioning of tubular component 14 and coupler 12. When the
tubular component 14 is installed in coupler 12, the locking strap
recess 36 is opposite locking strap groove 30 to form locking strap
passageway. The tubular component 14 is also provided with a
beveled or chamfered end surface 38 adjacent the tube end 74. The
preferred tubular component 14 is constructed from a thermoplastic
material.
[0031] The locking strap 16 is made of any plastic material
possessing sufficient tensile strength to withstand the pressure
exerted on the pipe such as nylon and includes a handle portion 40
and a body portion 42. Handle portion 40 is permanently attached to
one end of body portion 42 and is provided with a grip portion 44
that is attached approximately perpendicular to body portion 42 to
aid in inserting and de-installing the locking strap 16. Body
portion 42 has a first reduced thickness area 46 at a handle end 48
and a second reduced thickness area 50 at forward insertion end 52.
Reduced thickness areas 46, 50 have half the cross section width of
the full section of the remainder of the locking strap 16. This
reduction of the cross section enables the overlapping of the ends
48, 52 of the locking strap 16 to bear the load of the entire
circumference of the engagement between the locking strap 16 and
the mating locking strap groove 30 and locking strap recess 36.
This is necessary because when the locking strap 16 passes through
the slot 54 of the coupler 12 and into the locking strap
passageway, there would be a loss of engagement with a portion of
the passageway. To eliminate this loss of engagement and to
construct a stronger joint, the reduced spline cross section
enables the overlap of the ends of the spline. The performance of
ultimate tensile pull increases by as a result.
[0032] The coupling assembly is also provided with an annular
sealing member, such as annular sealing seal 18. Seal 18 is has an
upper surface 56 and a lower surface 58 and is generally
rectangular in cross-section. Both the upper surface 56 and lower
surface 58 are provided each with three sealing lobes 60. Each
sealing lobe 60 forms a separate sealing surface when seal 18 is
installed in the coupling assembly as compared to only one sealing
surface if a seal with another cross-section, such as circular or
rectangular, was used. The cross-sectional dimensions of seal 18
are small, approximately 0.200 inches by 0.122 inches in the most
preferred embodiment but other dimensions could be used, enabling
the load bearing pipe wall thickness to be maximized due to the
multiple sealing lobes, without compromising sealing functionality.
The minimized cross-sectional dimensions of seal 18 also allow seal
groove 28 to be shallow, allowing for a thicker pipe wall 72 and
the resultant increase in tensile strength of the pipe joint. This
is critical because the seal groove 28 is one of the weakest areas
of the pipe joint in pure tensile strength loading.
[0033] If a circular cross-sectional seal was used, as in similar
competing products, and the wall thickness of the coupling remained
the same, the diameter of the pipe would have to increase. This
would require that a larger hole be drilled in the earth resulting
in increased installation costs due to increased incremental
drilling time and labor. The OD of the pipe coupling in the most
preferred embodiment is nominally 5.0 inches and could be less
compared to 5.5 to 6.0 inches of prior art coupled pipe
designs.
[0034] Moreover, if the circular cross sectional seal was used, the
insertion force would increase, requiring the use of tools to
assemble the pipe joint. Insertion forces for the coupling of this
invention are about a fourth of what it would be if a circular
cross sectional seal were used thus enabling the joint to be
assembled without tools. In the event disassembly of the joint is
required, the low compression and drag of the seal 18 on the pipe
allow disassembly of the joint without tools.
[0035] To assemble the pipe coupling, seal 18 is placed into seal
groove 28 of coupler 12 of a first tube. Tubular component 14 of a
second tube is then inserted into coupler 12 of the first tube.
Tubular component 14 is inserted until chamfered surface 38 rests
against the inner surface of curved transition region 24. Seal 18
does not provide too much resistance during the insertion of
tubular component 14 because of its reduced cross-sectional
dimensions but forms an effective seal due to its multiple lobes 60
pressing against the outer surface 34 of tubular component 14. When
fully inserted, chamfered surface 38 rests against the inner
surface of curved transition region 24. Locking strap recess 36 of
tubular component 14 aligns with locking strap groove 30 of coupler
12 to form a locking strap passageway. Locking strap recess 36 may
be provided wider than groove 30 to allow some degree of
adjustability. The two pipes are now in position for locking. The
forward end 52 of locking strap 16 is inserted through slot 54 on
coupler 12. Locking strap 16 passes through the slot 54 and is
received into locking strap passageway. Locking strap 16 is
completely inserted causing forward end 52 to overlap with handle
end 48 and the handle 40 to abut against the outer surface 22 of
coupler 12 creating a strengthened coupling.
[0036] If disassembly of the pipe coupling is needed, this can be
accomplished without resort to tools. Handle 40 can be grasped to
pull locking strap 16 out of locking strap passageway. Because of
the slight adjustability of the pipe coupling due to the recess 36
being slightly wider than groove 30, tubes on either side of the
coupling can be moved away from the coupling and also due to the
decreased cross-section of the seal, the pipe coupling can be
separated.
[0037] The coupling assembly of this invention may be favorably
used with pipes made from a variety of materials, including a metal
or a thermoplastic or a thermoset plastic. For practical reasons
this invention is particularly useful in pipes made from thermoset
plastic materials, such as ethylene, ethylene-propylene copolymers
and others, but especially PVC. In principal, however, the coupling
assembly may be conveniently used with thermoset plastic pipes.
[0038] Having described in detail the preferred embodiment of the
present invention, it is to be understood that this invention could
be carried out with different elements and steps. This preferred
embodiment is presented only by way of example and is not meant to
limit the scope of the present invention which is defined by the
following claims.
* * * * *