Note: Descriptions are shown in the official language in which they were submitted.
This invention relates to a transition means which makes it possible for
pipes of polyethylene, for example, dimensioned for one standard to be joined
to fittings which are dimensioned for pipes of a different standard, which may
be of similar but not identical inner diameters or outer diameters.
There are several standards which are not compatible with one another
with respect to pipes. The nominal metric outside diameter series standard is
the most commonly used standard in the world, but some other pipes
themselves fall into several different categories, some being dimensioned over
the exterior of the pipes, some in the interior of the pipes, and some using
the
imperial system. Furthermore, the wall thickness may vary. As a result, an
inventory problem is encountered which finally adds cost to the end user, and
it
is an object of this invention to provide a transition means which will
greatly
reduce inventory costs.
Specifically, in metric dimensioned pipes, there are four classes namely
6, 9, 12 and 15 which are required for pressures of 600 kPa, 900 kPa, 1200
kPa and 1500 kPa, respectively. The wall thickness for each pipe nominal
diameter but of different class will obviously vary, but the diameters are
identified as the outer diameters, not the inner diameters of the pipes.
In imperial measurements, there are different standards for the United
Kingdom, Australia, the United States of America and Ireland. In the United
Kingdom, for example, high density pipes and low density pipes for classes C
and D have the same outside diameters for the same nominal sizes. Australian
rural pipe is specified on the inside diameter (for example 2 inch bore).
However, most Australian pipes are according to metric standards.
In the United States of America there are three series, namely 160, 75
and 100, and the nominal sizes vary from inside diameter to outside diameter.
A further class SDR9 has a nominal size which is not close to either inside
nor
outside diameter. Furthermore, the Irish standards have both heavy and normal
1
CA 02153634 2001-O1-10
gauge but the nominal sizes are not readily identifiable with the outside pipe
diameter in all instances.
PRIOR ART
The closest prior art which is known to the applicant is the applicant's
own Patent Application PCT/AU94/00406 (Australian Application 72236/94),
which disclosed a fitting substantially identical to a fitting illustrated
herein.
The closest prior art referred to in that specification was US Patent No.
4043576 in the name of RIECH and LEHMANN of Switzerland and assigned
to George Fischer Aktiengesellschaft. No prior art at all is known to the
applicant wherein a spigot is used as a transition means to accommodate
pipes which might vary slightly in diameter, but be required for a relatively
small inventory of fittings. Spigots can be produced inexpensively, but
fittings
require the use of expensive plastics materials and a number of components.
BRIEF SUMMARY OF THE INVENTION
Accordingly, the present invention provides a fitting and transition
means for connection of a polymeric pipe to said fitting, wherein the diameter
of said pipe may vary slightly, said transition means comprising a double-
ended hollow spigot having a first end of outer diameter to be retained in
said
fitting, a second end with a plurality of annular barbs which extend radially
outwardly and are of diameter to engage an inner surface of said pipe with an
interference fit, and a radially projecting annular flange between said spigot
ends, said fitting comprising a hollow body having an external thread
extending
at least part way along it from one end, an axially outer internal cylindrical
surface extending inwardly from said fitting one end and defining a mouth of
diameter to accommodate said spigot annular flange, the inner end of said
axially outer internal cylindrical surface terminating in an annular shoulder,
a
further internal cylindrical surface
extending inwardly from said shoulder and being of diameter to accommodate
said spigot first end, a resilient gasket surrounding said spigot first end, a
nut
threadably engaging said fitting external thread, said nut having at one end
an
internal thread co-operable with said body external thread, and an inner
2
CA 02153634 2001-O1-10
surface which converges outwardly towards its other end from an abutment
surface, said nut including an internal annular should between its said ends,
and
a deformable gripping member having an outer surface which also
converges outwardly and an inner surface which comprises radially inward
barbs, and including a radially outstanding abutment surface which is abutted
by said annular shoulder of said nut upon said tightening of the nut,
the dimensions of said spigot nut, gripping member, gasket and body
being such that, said second spigot end is adapted to enter an end of a
polymeric pipe, said first end is adapted to enter said hollow body and extend
through said resilient gasket, wherein tightening of the nut causes relative
co-
operative movement of said converging surfaces to reduce diameter of said
gripping member and enable its said barbs to grip an outer surface of said
pipe and also compress said pipe over said spigot second end, while urging
said spigot axially into said hollow body in turn deforming said gasket to
effect
said sealable engagement thereof, with said shoulder of said body and an
outer surface of said spigot first end.
In a further aspect, the present invention provides a fitting and a
transition means for connection of a polymeric pipe to said fitting which
transition means is adapted to accommodate pipes of different diameters,
said transition means being adapted to fit into the fitting as a single
piece construction to join pipes of differing standards to said fitting,
wherein
said transition means includes a double ended hollow spigot having a first end
of outer diameter to be retained in said fitting, a second end with a
plurality of
annular barbs which extend radially outwardly and are of diameter to engage
an inner surface of said pipe with an interference fit, and a radially
projecting
annular flange between said spigot ends,
said fitting adapted to receive the transition means, including a hollow
body having an external thread extending at least part way along it from one
end, an axially outer internal cylindrical surface extending inwardly from
said
fitting one end and defining a mouth of diameter to accommodate said spigot
annular flange, the inner end of said axially outer internal cylindrical
surface
2a
CA 02153634 2001-O1-10
terminating in an annular shoulder, a further internal cylindrical surface
extending inwardly from said shoulder and being of diameter to accommodate
said spigot first end, a resilient gasket surrounding said spigot first end,
and
a nut threadably engaging said fitting external thread, said nut having at one
end an internal thread co-operable with said body external thread, and an
inner surface which converges outwardly towards its other end from an
abutment surface, said nut including an internal annular shoulder between its
said ends, and
a deformable gripping member having an outer surface which also
converges outwardly an inner surface which comprises radially inward barbs,
and including a radially outstanding abutment surface which is abutted by said
annular shoulder of said nut upon said tightening of the nut,
the dimensions of said spigot, nut, gripping member, gasket and body
being such that, said second spigot end is adapted to enter an end of a
polymeric pipe, said first end is adapted to enter said hollow body and extend
through said resilient gasket, wherein tightening of the nut causes relative
co-
operative movement of said converging surfaces to reduce diameter of said
gripping member and enable its said barbs to grip an outer surface of said
pipe and also compress said pipe over said spigot second end, while urging
said spigot axially into said hollow body in turn deforming said gasket to
effect
said sealable engagement thereof, with said shoulder of said body an outer
surface of said spigot first end.
Even with the transition means referred to in the specification, at the
time of writing this specification, there is a need for a total of 250
transition
2b
spigots and 50 tapered gripping members to meet the requirements for seven
pipe sizes, but the lower cost of the transition spigots renders the inventory
requirements viable. Otherwise, if independent fittings for respective pipe
dimensions were required, there would of course be a requirement for 250
fitting sizes instead of 7. These figures are expected to vary with the
passage
of time, and in particular with the rationalisation of standards.
BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiments of the invention are described hereunder in detail with
reference to and are illustrated in the accompanying drawings in which:
Fig 1 is a partly sectioned side elevation showing a fitting and spigot
assembly associated with a pipe, before its assembly to the fitting;
Fig 2 shows the manner in which the assembly is achieved; and
Fig 3 shows an alternative arrangement wherein the fitting used differs
from the fitting illustrated in our aforesaid Patent Application.
Referring first to Figs 1 and 2, a polyethylene pipe 10 has an inner
diameter 11 which is somewhat similar to an inner diameter 12 within a hollow
body 13, and there is provided a gripping member 14 made from a deformable
material (in this embodiment being acetal which is a material of greater
hardness than polyethylene used in a pipe), the gripping member having an
outer surface 15 which converges outwardly towards a mouth 16 of nut 23, the
gripping member 14 having radially inwardly extending barbs 17, and the inner
diameter of gripping member 14 being as close dimensionally as is reasonably
feasible to the outer diameter of pipe 10.
The fitting comprises a hollow body 13 having an external thread 21
which is threadibly engaged by an internal thread 22 of a nut 23. The thread
of
the body extends approximately half way along the body from the mouth end.
There is an axially outer internal cylindrical surface 24 of the body 13 which
is
of relatively large diameter and which extends into the body 13 from its mouth
3
end and terminates in an annular shoulder 25, and the inner diameter 12 is of
the axially inner internal cylindrical surface 26 which, as shown in Fig 2 is
subsequently engaged by a first end 27 of a hollow spigot 28.
The nut 23 has an internal abutment surface 31 which upon tightening of
the nut 23 over the body 13 bears against an annular abutment surface 32 of
the gripping member 14 as seen in Fig 2. The inner surface 33 of nut 23
converges outwardly to be co-operable with the outer surface 15 of gripper
member 14, so that as the nut is tightened the effective diameter of gripper
member 14 is reduced, in the embodiment shown the gripper member 14 being
a split collet.
A spigot 28, besides its first end 27 has a second end 35 which is of a
diameter which will suit a specific production run of pipes, whether they be
metric or imperial, different pipes will require different spigots 28. The
second
end 35 is provided with a plurality of radially outstanding barbs 36, and as
seen
in Fig 2, when the nut 23 is tightened, the barbs 36 engage the inner wall of
pipe 10 while the barbs 17 of gripper member 14 are arranged to lie
intermediate to the barbs 36 and thereby slightly distort the pipe walls and
achieve a good firm grip of pipe 10, both the inner and outer surfaces of the
ends of which being firmly clamped by the respective barbs.
The resilient sealing gasket 38 is in this embodiment an O-ring, and it is
urged inwardly into the body 13 by tightening of nut 23, there being provided
a
stepped sleeve 39 as in our aforesaid Patent Application. The nut pressure
then deforms the O-ring 38 to effect a very positive seal both against the
outer
surface of the first end 27 of spigot 28 and against both the cylindrical
surface
24 and the shoulder 25 of the body. It will be noted from Fig 2 that the first
end
27 of spigot 28 projects into the internal surface 26 which is in the fitting
body
13 and extends inwardly from the mouth end 16 of the nut 23, beyond the
4
~1~~~~~
shoulder 25. Thus the connected end of pipe 10 is restrained against
deflection
of a bending type as well as against withdrawal from the body 13 of the
fitting.
The end 40 of the body 13 will take various shapes, and as illustrated
comprises a hollow projecting nipple 41 which has a thread to mate with a
standard pipe fitting. However, the end 40 can be a duplicate but of different
diameter from the mouth end of the fitting, so as to be able to join with
pipes of
different diameters. A radially outer flange 43 separates a first and second
end
of spigot 28, and also provides an abutment at the first side which bears
against the sleeve 39 and an abutment on the second side which bears against
the end of the pipe 10.
It will be seen that upon assembly, the spigot is driven with its second
end 35, the barbed end, into the end of pipe 10, and the whole assembly can
then be pushed into the body 13, past the sleeve 39 and the resilient gasket
38
to finally engage the inner surface 26 of the body, and at the same time the
gripping member 14 is restrained against inward movement after the resilient
gasket 38 has been deformed, and further tightening in the nut causes radial
closure of the split collet 14 over the outer surface of pipe 10, with the
barbs of
the split collet lying between the barbs 36 of the second end 35 of the spigot
28. Tightening of the nut also performs a secondary function of urging the
spigot axially into the whole embodiment, so that the spigot is firmly clamped
with respect to the body.
The above embodiment has specific reference to a fitting similar to one
described and claimed in our aforesaid Patent Application. However, it is not
necessary that a fitting which is universal in its construction should be
used,
and Fig 3 shows a second embodiment where the sleeve 39 is dispensed with,
and the body 13a can therefore be of shorter length, the O-ring 38a being
compressed by the flange 43a, and the spigot first end 27a being shorter than
in the first embodiment. Other features of construction are substantially
similar
5
21~~6~4
to the first embodiment except that the fitting is somewhat shorter than in
the
first embodiment, and similar elements bear the same designation numbers
with the suffix "a".
In this specification a "nominal" size refers to a pipe dimension (say of 2
inch outside diameter) which is within five percent (5%) of a 2 inch
dimension.
For the purpose of this specification, a pipe is regarded as being within
"nominal" size if its actual outside diameter lies within ten percent (10%) of
the
"nominal" size - for a 2 inch pipe, between 1.080 inches and 2.020 inches.
A pipe of polyethylene of that size can be expanded by twelve percent
(12%) of the nominal 2 inches by the barbs on the second end of the spigot,
but
not less than two percent (2%) to ensure satisfactory pipe retention.
To accommodate up to seven sizes of the aforementioned standards, it
is necessary for an inventory to include 250 hollow spigots, but only 50
gripping
members, which, being split rings, are capable of considerable diametral
compression.
6
