Note: Descriptions are shown in the official language in which they were submitted.
1080i~5
BACKGROUND OF THE INVENTION
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l. Field of the Invention
This invention relates to pipe couplings, and more
particularly, to a restraining sleeve-type coupling.
2. Description of the Prior Art
Conventional plain ended pipe, whether made from
metallic or non-metallic materials are usually joined by
mechanical or sleeve-type couplings, or by welding.
Mechanical couplings are normally of the restrain-
ing type which means that they seal the joint against leakage
and have restraining means as well to hold the pipe together
preventing the pipe from separating under the force of inter-
nal pressure. This restraining means generally require the
pipe to be threaded or grooved at the ends, or to have shoulders
fitted to the ends of the pipe to which the couplings are
applied. One disadvantage of such mechanical pipe couplings
is the extensive end preparation required on the pipe to allow
for the use of these couplings on pipe.
Sleeve-type couplings on the other hand usually do
not require any end preparation of the pipe to be functional,
but they have the disadvantage of not providing any joint
restraint for the pipe. External restraint with the sleeve-
type coupling must be provided for the pipe, if required.
Sleeve-type couplings may or may not have an integral center-
ing ring located midway within the pipe coupling for centering
the coupling sleeve correctly over the pipe joint.
Welded joints are common and extensively used for
many pipeline applications, but welding has the disadvantage
of joint rigidity and of permanence. Removal of an individual
pipe from a welded pipeline requires the pipe to be severed
physically from the pipeline.
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10~1)2'~5
For pipelines conveying solids in a liquid or gaseous
medium, there is a problem of providing a coupling between pipe
ends which is restraining and, at the same time, prevents
turbulence and excessive wear. One attempt to overcome this
problem is by use of gasketed flanged joints on the pipe.
Flanged joints are very rigid, however, and this is a disad-
vantage for pipelines that require some joint flexibility to
relieve stresses in the pipe due to slight movement of the
pipeline during its lifetime. Mechanical and sleeve-type
couplings, and bell and spigot-type joints, used on pipe for
conveying solids, are normally also at a disadvantage because
the gap at the joints in the pipeline, which is common for
these types of joints, may cause turbulence in the pipeline
with the result of obtaining possible excessive wear of the
pipe at these joints.
SUMMARY OF THE INVENTION
An aim of the present invention is to overcome the
disadvantages discussed and to provide positive advantages in
a pipe coupling.
The invention contemplates an overall cylindrical
metal sleeve provided inside with a central seating groove for
a removable centering ring and at each side a groove for a
pressure sealing gasket. The sleeve is provided near its ends
with a plurality of spaced-apart tapped holes for set screws.
A preferred centering ring has a solid body of symmetrical
cross-section and includes a peripheral seating face, an
inside face, and extending between the peripheral face and the
inside face a pair of side seating faces extending perpendi-
cularly from the peripheral face to a pair of sealing faces
continuing inwardly in a bevel angled from the side seating
faces toward the inner face. This bevel is effective in caus-
1080275
ing the abutting pipe end to exert an outward radial force on
the centering ring so as to urge the ring more firmly into the
internal groove of the pipe coupling. The ring may either be
a split ring of metal or a continuous ring made from a plastic
or an elastomer preferably have a Shore A Durometer hardness
within the range from about 70 to about 80. Preferably the
inward angle of the side seating faces to the peripheral face
is within the range from about 10 to about 15.
Preferably the set screws are of the type having a
cup end which bites into the metal surface of the pipe end.
They are desirably of a non-corrosive alloy, electrochemically
compatible with the coupling, so as to avoid setting up a
- corrosion circuit.
BRIEF DESCRIPTION OF THE DRAWI~GS
Having thus generally described the invention, it
will be referred to in more detail by reference to the accom-
panying drawings illustrating a preferred embodiment, and,
in which:-
Figure 1 is a vertical cross-section, partly in
elevation, through a preferred coupling,
according to the invention;
Figure 2 is an end elevation of the coupling shown
in Figure 1 with the pipe end in cross-
section;
Figure 3 is a perspective view of a preferred
centering ring forming a part of the
; coupling shown in the previous figures:
Figure 4 is an enlarged fragmentary cross-section,
partly in elevation, of the ring shown in
Figure 3.
.
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108l)~S
DESCRIPTION OF T~E PREFERRED EMBODIMENTS
Referring more particularly to the drawings, the
preferred pipe coupling sleeve is generally indicated by A,
connecting two plain pipe ends s and C.
The sleeve A is a one-piece cylindrical metal body
having an inside surface 15, an outside surface 17 and respec-
tive end surfaces 19 and 21.
Midway of its length, the body of the sleeve A is
provided with an annular rectangular groove having a base
surface 18 and respective side surfaces 20 meeting the base
surface in slightly rounded corners. A preferred radius for
the corners is about 1/32". To each side of the groove D the
body is provided with annular grooves 25 and 27 of the cross-
section shown, accommodating elastomeric gaskets 29 and 31
respectively of the shape shown, which bear against the groove
surfaces and the outside surfaces of the pipe ends B and C and
provide a seal between them.
The groove D receives a centering ring E of special
construction and shape, against which the pipe ends B and C
bear.
Towards each respective end, the body of the sleeve
A is provided with a plurality of equally spaced-apart tapped
openings 43 respectively to accommodate set screws F engaging
the respective pipe ends B and C.
The ring ~ may be a split ring having a solid body
of metal, preferably ductile iron or steel. Or, it may be a
continuous non-metallic ring having a solid body of a plastic
material as shown, for example, polyurethane, or an elastomer,
; for example, natural or synthetic rubber. The ring E is
symmetrical and has a substantially flat peripheral bearing
face 50 joined by side bearing faces 52 and 54 perpendicular
"
lOl~V;~7~
to the face 50 with rounded corners therebetween. The ring E
has a substantially flat inner face 56 and bevelled side faces
58 and 60 extending between the faces 52, 54 and the face 56
for contact with the pipe ends. Desirably, the bevel of the
faces 58 and 60 will be at an angle within the range from about
10 to about 15 from the faces 52 and 54.
Where the ring is of metal it will be of steel or
ductile iron and slightly undersize in respect of the groove
and split in the radial direction or otherwise to facilitate
the distortion needed to get it into the groove. In the event
of the ring being of synthetic rubber or plastic material it
is continuous. The non-metallic material is selected to be
soft enough to allow distortion of the ring for insertion but
hard enough to resist its coming out of the groove and to
resist undue deformation by the pipe ends. A preferred
material would have a Durometer hardness within the range
from about 70 to about 80. Examples of suitable materials
are polyurethane, styrene butadiene rubber and nitrile rubber,
with polyurethane preferred.
In typical ring sizes for 4 to 12 inch diameter
couplings, the width from face 52 to face 54 will run to
15/32nds of an inch and faces 52 and 54 will be 3/8th of an
inch wide and the total thickness of the ring from the peri-
pheral face 50 to the inside face 56 will be from about 3/4
of an inch. For 14 to 2A inch diameter couplings, typical
dimensions will be from face 52 to face 54, 23/32nds of an
inch, faces 52 and 54 will have a width of 19/32nds, and the
thickness from face 50 to face 56 will be about 1 inch.
Preferably special set screws F having a cup point
are used for securing the sleeve A to the pipe ends B and C.
The size of the screws may range from about 5/8th of an inch
1080Z75
to about 3/4 of an inch. Such a screw has an included angle
in the cup point of about 118 + 5, as for example, shown in
ANSI Standard B18.6.2 - 1972, published by the American
Soceity of Mechanical Engineers, New York, the disclosure of
which is hereby incorporated by reference. The set screws are
desirably of a non-corrosive alloy, desirably electrochemi-
cally compatible to the coupling material so as to avoid
setting up a corrosion circuit. Thus, the material of the
set screws is heat treated alloy steel, or a hardened carbon
steel with the alloy steel preferred for corrosion protection.
Desirably, the alloy steel should meet the AISI (American Iron
& Steel Institute) composition requirements for AISI 4137 or
AISI 8740 low alloy steel. In completing the joint, the set
screws are preferably tightened to a torque within the range
from about 60 to about 80 ft/lbs., uniformly applied about
the joint.
Generally speaking, couplings of the invention are
applicable to pipes having nominal diameters from about 4
inches to about 24 inches. The applicant's coupling is uni-
versal in nature, that is to say, it has the capacity to hold
pressure and provide strength and restraint, and adequately
fill the gap between pipe ends. It has the added advantage
that by removing the center ring, the sleeve may be used as
an ordinary pipe sleeve. It can also be used as an ordinary
coupling (non-restraining) where the pipes are to be re-
strained by other means. The coupling also provides the
joint flexibility needed for assembling pipe in a pipeline
with a long radius curve.
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