Note: Descriptions are shown in the official language in which they were submitted.
~2~i663
This invention re]ates to thrust restrainers for couplings
in pipelines carrying fluids under-pressure, such as water
mains.
Such pipelines are commonly formed from lengths of pipe,
with or without integral bells and spigots for coupling
purposes, and together with fittings such as couplings,
tees, elbows, wyes, valves and hydrant runouts. A typical
pipeline thus includes a large number of joints between
pipe lengths and fittings, and between adjacent pipe
lengths where the latter have integral bells. Not only
must such joints be fluid tight, but they must also with-
~ stand mechanical forces tending to cause joint separation,
such as static pressure within the pipeline, surge pheno-
mena within the pipe, thermal expansion and contraction,
- 15 and mechanical stresses due to various causes. Where
plain pipe ends are involved in a joint, it is frequently
necessary to provide some means to prevent unwanted with-
-: drawal of the pipe end or movement of it in the joint,
: which is likely to destroy the fluid tight seal.
For the above reason, various restraining devices have
been developed for retaining plain pipe ends within such
joints. These fall into two main classes. Where fittings
are provided with flanges for bolted connection, a com-
bined jointing and restraining device can be used, compris-
~ 25 ing an adapter flange to be bolted to the fitting flange
such as to compress a sealing element, and auxiliary means
to lock the adapter flange to the pipe. An alternative
approach has been to apply a separate clamping ring to the
pipe end, and to secure this by bolts extending longitudin-
ally of the pipe to a flange either integral with the joint
or applied to the joint during installation.
In recent years, the use of pipe moulded from synthetic
plastics such as PVC has become widespread in place of
~276663
-- 2 --
iron and steel pipes. The different properties of these
materials has rendered necessary modifications o the res-
training devices so as LO enable sufficient grip to be
obtained on the pipe. Typically, the flanges or clamping
rings have been split diametrically into two sections,
formed with internal serrations which bite into the pipe
~ surface, the sections being bolted together around the
s` ~5 pipe. Typical arrangements of this type are described in
a booklet "Products for PVC Pipe" (Form No. 124-0481) pub-
lished by Uni-Flange Corporation of Northboro, Mass., and
in United States Patent No. 4,336,959 assigned to the same
corporation.
Such devices are essentially adaptations of conventional
technology for use with plastic pipe, and whilst effective,
they involve a number of manufactured metal parts and a
substantial amount of measurement and assembly, and selec-
tive tightening of nuts and bolts, which although fairly
straightforward, can be awkward and lead to errors under
on-site conditions. Where unflanged connections are in-
volved, it is necessary to use special bell rings as areplacement ~f the flange,as shown on page 7 of the booklet
referred to above, and the installation of such rings en-
tails their being installed from the opposite end of a
length of pipe.
The present invention seeks to provide a restrainer device
for use with plain ended plastic pipe which is effective,
cheap to manufacture, and easy to install with little
opportunity for error.
According to the invention a thrust restrainer for ensuring
the integrity of a joint between a plain ended synthetic
plastic pipe and a fitting receiving the end of the pipe
in sealing relationship, comprises two half sleeve compo-
nents moulded from synthetic plastic mat~rial, said half
sleeves being mateable at mating surfaces to form a full
~766~3
-- 3 --
sleeve, said half sleeves each having a first end portion
having an internal configuration such as to snugly embrace
a bell or flange of the fitting through 180~ of its peri-
phery, and a second end portion having semi-cylindrical
internal configuration having a plurality of parallel
peripheral sawtooth serrations, the minimum radius of the
semi-cylindrical configuration at the peaks of the serra-
tions being slightly less than the outside diameter of the
pipe to be restrained, the half sleeves having internal
longitudinal projecting flanges adjacent their mating sur-
faces, and bolts for securing said flanges ~ogether adja-
cent both said first and said second end portions.
Preferably the maximum radius of the semi-cylindrical con-
figuratio~ at the serrations is slightly greater than the
external diameter of the pipe to be restrained whereby the
material of the pipe may be displaced by the peaks of the
serrations into the spaces between the serrations to form a
rigid connection between the sleeve and the pipe. Prefer-
ably also the semi-circular internal configuration includes
a semi-cylindrical land axially adjacent the serrations on
at least one side and having a radius such as to embrace
the pipe tightly, whereby to control the engagement of the
serrations with the pipe.
The device of the invention does not require any access
from a free end of a pipe or fitting during assembly, is
simple to apply, and requires no measurements or adjust-
ments,;thus substantially reducing the risk of assembly
errors.
Further features of the invention will be apparent from
the following description of a preferred embodiment there-
of with reference to the accompanying drawings.
In the drawings:
~X7~ 3
~ 4 --
Figure 1 is a perspective view showing a restrainer in
accordance with the invention applied to a coupling between
two lengths of plain ended synthetic plastic pipe;
Figure 2 shows one half sleeve used in the restrainer, the
upper half of the figure showing one quadrant of the half
sleeve in plan, and the lower half showing the half sleeve
in section;
Eigure 3 is an end elevation of the half sleeve; and
Figure 4 is a sectional detail of a portion of the sleeve
showing the internal serrations on a larger scale.
Referring to Figure 1, two lengths 2 of synthetic plastic
pipe, for example, polyvinyl chloride pipe used for water
mains, are seen entering a sleeve coupling 6, which may
also be moulded from polyvinyl chloride, and has at each
each end a bell 8 which receives the end of a pipe to be
coupled, the bell also housing a sealing element (not
shown~, which renders the joint watertight. In order to
prevent the pipe from pulling out of the joint or moving
excessively relative to the seal, it will be necessary in
at least some locations to provide restrainers 10 to lock
the pipe into the coupling. Only one restrainer 10 is
shown in position in the drawing, in order that one of the
bells 8 can be seen. Each restrainer 10 consists of two
half sleeves 12, secured together at flanges 14 by bolts 16.
One half sleeve 12 is shown in more detail in Figures 2 and
3. It is moulded in one piece rom polyvinyl chloride and
one end portion has an internal profile 18 such as snugly
to engage the external profile of a bell 10 around 180 of
its periphery, whilst the other end has a semi-cylindrical
internal profile 20 to engage a pipe 2 or 4. It has mating
surfaces 22 designed to mate with corresponding surfaces on
a second, usually identical, half sleeve 12, and ad~acent
~276663
-- 5 --
outwardly extending flanges 24 having reinforced bolt holes
26 so that the flanges of mating half sleeves may be bolted
together by the bolts 16 adjacent both end portions. In
order to maintain a reasonably even wall thickness and save
material, the surfaces 22 are formed with recesses 26, and
the outer surfaces of the half sleeve with ribs 28, which
stiffen it and help transfer forces to and from the flanges
24.
As best seen in Figure 4, the internal profile 20 is formed
with a plurality of parallel peripheral sawtooth serrations
30. These serrations have peaks 32 at which the internal
radius of the profile is slightly less than that of the
pipe 2 or 4, separated by valleys 34 of which the internal
radius of the profile is slightly greater than that of the
pipe 2 or 4. The serrations are axially flanked by lands
36, 38 at which the internal radius is intermediate between
that of the peaks and valleys of the serrations and such as
tightly to embrace the external diameter of a pipe 2 or 4.
During installation of a pipeline, the pipes 2 and 4 are
pushed into the ends of the coupling 6, in which the seals
have previously been installed, two half sleeves 12 are
assembled around each bell of the coupling and the adjacent
portions of pipes 2 and 4, and the bolts 16 are tightened,
engagement of the serrations 30 of the half sleeves with
the pipe being controlled by engagement of the surfaces 22
with each other and the lands 36, 38 with the pipe. The
peaks 32 penetrate the pipe material and displace it into
the valleys 34 thus locking the sleeves to the pipes and
the pipes to the bells.
It will be understood that, with suitable adjustment of the
profiles 18, similar restrainers may be used to hold a
plain pipe end within a belled pipe end, or within a
flanged joint to a valve or similar device.
~27G663
It should be noted that the device does not require access
to a free end of a pipe or fitting for the installation of
any parts, and no adjustments or measurements are required
during installation since correct fitting is ensured mere-
ly by tightening the bolts 16. The absence of longitudinal
- strainer bolts eliminates a source of unbalanced forces or
excessive stresses due to misadjustment.
The half sleeves 12 may be injection moulded from material
which is preferably harder than the polyvinyl choride used
for the pipe, in order to promote the penetration of the
pipe surface by the serrations 30. A suitable material is
a thermoplastic polyethylene terephthalate (PET) moulding
compound, such as the glass fibre reinforced compounds sold
by Du Pont under the trade mark RYNITE.
