Note: Descriptions are shown in the official language in which they were submitted.
1~019QS
This invention relates to arrangements for coupling
together pipes. The inven-tion is appiicable to the coupling
of pipes made of plastics, glazed or ungla ed clay, pitch-fibre,
asbestos cement, concrete and the like, such as are used in
sewers, drains, cable conduit and the like.
British Patent Specification ~o. 1,080,305 describes
clay piping of the type push-fitted together comprising plain-
end pipe-lengths of round cross-section with an endless peripheral
strip of resilient ma;:erial secured close to each end of each
pipe length and sleeves of slightly resilient synthetic plastic
material, each sleeve having integral internal peripheral ribs
adapted to make sealing engagement with the peripheral strips of
two adjacent pipe-lengths.
The coupling sleeve in Specification No. 1,080,305 is
generally symmetrical. This is not always convenient, for
example, if pipes of different types and/or materials are to be
coupled, e.g., pipes which are completely plain at one end to
permit cutting and jointing.
According to one aspect of the present invention there
is provided the combination comprising a plain-ended pipe length
having adjacent to one end an external peripheral groove with a
peripheral strip of sealing materlal disposed in the groove, and
a coupling member of slightly resilient plastics material mounted
on said end of said pipe length, which coupling member comprises
a unitary sleeve of injection moulded plastics material having
first and second end regions, the first end region being disposed
about the said end and groove of the pipe length, the second end
region projecting from the said end of the pipe length to form a
; coupling socket for receiving an inserted end of a second pipe
leng~h, .he first end region being provided with a uni,ary ~igid
internal peripheral rib of angular cross-section in permanent
snap-in engagement with the said groove and with the sealing
1~ 9~S
material in tlle groove, tile second
end region bcing provided with an internal peripheral sealing
ring of resiliently deformable material for making sealing
ellgagement with a said insertcd end of a second pipe length.
The sleeve may be provided with a plurality of the said
ihs and/or a plurality of sealing rings.
The rib or ribs are preferably of rectangular cross
section.
The sealing ring or rings can be of any sui-.-able
deformable sealing material. The ring can be an internal
projection integral with the sleeve itself and sufficiently
thin to provide the necessary flexibility. Preferably, however,
it is a ring of different material softer than the sleeve. It
can be plastically deformable, but is preferably resilient so
as to maintain sealing pressure throughout the life of the
joint formed with the aid of the coupling sleeve. Suitable
materials include natural and synthetic ruhber and other elasto-
mers, in particular thermosetting and thermoplastic rubbers, and
xesilient plastics materials.
Suitable materials for the sleeve include polypropylene
and polyethylene.
Preferably, the sealing ring or rings and the plastics
sleeve are formed by a two-step integral injection moulding
process, for example, as described in British Patent 1,477,014
and West German Specifications DOS 2603393 and 2715525.
The pipe coupling sleeve is permanently secured to the
end of the pipe, for example by any suitable adhesive.
A considerable inconvenience of the known coupling
sleeves for clay and similar pipes is that the coupling sleeves
are separate articles which have to be fitted to the two pipes
to be joined.
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19Q5
According to a further aspect of the invention there
is provided a metllod of making a pipe length having a coupling
socket comprising a sleeve of plastlcs materialwhich method comprises
injection moulding a sleeve of plastics material which has at or
adjacent to one end an integral ;nternal peripheral rib of
angular cross section, providing at or adjacent to the other end
of the sleeve an internal peripheral deformable sealing ring,
providing an external peripheral groove in the external surface
of a plain-ended pipe length adjacent to one end, providing
a sealirlg material in the said groove, and fitting the first
end of the sleeve onto the said end of the pipe length, with the
internal rib of the plastics sleeve making snap-in permanent
engagement with the groove and forming a seal with the said
sealing material in the groove, with the other end of the plastics
sleeve projecting from the end of the pipe length for receiving
an inserted second pipe length, the sealing ring being disposed
to make sealing engagement with an inserted pipe length.
Embodiments of the invention are shown by way of
example only in the accompanying drawings, in which:
Figure 1 is a longitudinal section of a coupling sleeve
embodying the invention, and an end of a first pipe to be coupled;
and
Figure 2 illustrates the manufacture of a coupling
sleeve as shown in Fig. l;
Fig. 1 shows in longitudinal section a coupling
sleeve 1 of stepped profile, made of any suitable slightly
resilient plastics material, e.g., polyethylene or polypropylene,
typically 0.04 to 0.06 inches, (1 to 1.5 mm) thick. AdjacenttO the
narrower end 7 is an integralinternalperipheral rib 2,and adjacent
to the wider end 8isan internalsealing ring 3 of rubber or other
resilient material secured to the plastics sleeve.
The narrower end is designed to receive an end of
3-
11019~5
a pipc 6, for examp]e of clayware, provided with an external
peripheral sealing ri.ng 4 of, for example, synthetic or
natural rubber, rubberised bituminous mastic, or resilient
plastics material, generally as described in British Patent
Specification No. 1,080,305. This ring is received in a pcr-
ipheral groove in the pipe surface~
~ - -4-
111)19~)5
The rib 2 typically is of rectangular cross-section
and has a radial height of about 0.050 to 0.070 inch (1.3 to
1.8 mm). It serves for locating as well as for sealing the
pipe end by engaging the external sealing ring of the latter. It
is to be understood that specific dimensions are given herein
by way of example only and the invention is not limited to
articles of such dimensions.
The other end of the coupling sleeve can receive a
plain-ended pipe end 5 of any material, the sealing ring 3
making sealin~ engagement with the external peripheral surface
of the inserted pipe end. This ring is secured to the plastics
sleeve by a bond and/or mechanical keying, preferably by
injection moulding the ring onto the freshly injection moulded
plastics sleeve, or vice versa, for example, as described in
the above-mentioned patent applications.
Preferably, as in the example illustrated, the cross-
section of the sealing ring is such that the ring has a certain
amount of flexibility as well as being resiliently deformable.
A preferred cross-section is basically an isosceles
triangle, with the radlally innermost apex radiused and the
- adjoining sides slightly concave. Typically the sealing ring
3 has a radial height of 0.1 - 0.15 inch (2.5 - 3.8 mm).
~ 9 ~ 5
The larger diameter portion o~ the sleeve has integrally
moulded internal ribs 9 extending in the longitudinal
direction of the sleeve from the step lO and ending short
o~ the sealing ring 3. These ribs help to centralise the
inserted pipe end 5 in particular limit the extent to which
the ring 3 can be compressed by the inserted pipe end e.g.
i~ one pipe mo~es laterally. The ribs aiso facilit ~t~
moulding as explained below. By way o* example, in a
CC71pli~g with ~ diameter in the region of 4 to ~5 inches
(100 to 114 mm), there may be 48 ribs, o~ rectangular cross-
section with a thickness in the circumferential direction of
0.55 to 0.70 .nch (14 to 18 mm).
It will be seen that with a coupling sleeve o$ the kind
described, it is no longer necessary that both of the pipe ends
to be cou~led should be provided with a sealing ring.
The couplil~g sleeve may be provided with an internal
centring ring cr centring projections (not shown).
I~ is not essential that the plastics sleeve should
have a stepped ~rofile; it can be a simple cylindrical
sleeve, or stepped in either direction to suit the
diameters of the pipe ends to be coupled.
The sealing ring and plastics sleeve can be manufactured
separately and fastened together for example by means of any
suita~le adhesive and/or a retaining ring~ Preferably,
however, the c~upling sleeve is manu~actured by a ~o-stage
injectlon moulding process, in which one of the components
is injection moulded ~irst, and the other is then injec~ion
moulded directly onto the ~irst-moulded component.
--6--
.
9OS
Flgure 2 schematically illustrates means for manufacturing
the coupling sleeve by first moulding the sealing ring 3
and then moulding the plastics sleeve onto the ring.
Figure 2 is in ~xial section, the apparatus being rotationally
symmetrical about the axis 11.
Fi~ure 2 ~hows a generally cylindrical core 12 of an
- injection moulding machine, the latter bein~ provided wlth
means for moving the core in the axial direction. The
.. Cor9 h~ a circl~m~erential g~oo~e 14 with a cr~rs-eeo_ion
corresponding to the seal~ng ring ~. Between this groove
and the end of the core, the external surface o~ the latter
is stepped and provided with longitudinal slots 15
corresponding to the ribs 9 to be moulded on the plastics
slee~e as shown in Figure 1.
Init~ally, the core is in the position shown at the
le~t of Figure 2~ ~n which the groove 14 ~s within a first
split cavity block 16 provided with one or more injection
moulding nozzles 17. The core and the cavity bloc~ 16
have conventional locking meanQ 18 such that when the
cavity block 16 i~ closed about the core, the in~ection
nozzle is or nozzles are aligned with the groove 14.
Rubber or other elastomeric material is then injected into
the groove 14.
The cav1ty block 16 is then opened and the core is
moved axially to the position shown at 12a in Figure 2 in
which its end face abuts the end of a second core 19 and
both cores are within a second split cavity olock 20.
The core 19 has a central axial in3ection nozzle 21 whlch
'
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~l~lg~S
: communicates with a multiplicity of radial passages 22
formed by radial slots in the end face of the core 19
(and/or ~he core 12). These passages communicate with
a generally tubular moulding cavity 2~ which is defined
by the internal surface of the cavity block 20 (which is
- stepped to correspond to the external profile of the
plastics sleeve), the external surface of the core 12
and the exposed external surface of the moulded sealing
! ring 3 which has been carried by the oore into the seconQ
cavity block, and the external surface of the end region
of the second core 19; this last includes peripheral
i - rebates defining the portions of the moulding cavity
¦ corresponding to the rib 2 and the adjoining end part of
¦ the plastics sleeve. A peripheral groove 24 for
i ~ 15 moulding the rib 2 is thereby defined at the interfac~
of the cores9 and the radial passages 22 communicate with
this groove. Alternati~ely, the groove 24 can be
defined partly or wholly ~y a rebated portion of the end
of the core 12.
Plastics material is now injected through the nozzle
21 and radial passages 22 into the cavity 23 where it
contacts the exposed surface of the sealing ring and becomes
bonded to the latter as described in the above mentioned
patent applications. The slots 15 facilitate the flow
of the plastics material to the regions of the moulding
ca~ity remote from the passages 22.
--8--
)19~5
The cavity block 20 is then opened and the core 12
is retracted, after which the moulded plastics sleeve together
with the sealing ring is stripped from the core, for example
by the core passing through a stripping ring mounted between
the block 20 and the block 16. In this connection, the core 12
may have two axially separable parts which meet at the groove 14
and can be separated to facilitate separation of the sealing ring
from the groove, as described in our West German Specification
DOS 2715525. However, the coupling sleeve shown in Figure 1,
is particularly suitable for pipes of relatively small diameter,
for example 4 inches (100 mm) and the plastics sleeve and
sealing ring can, with dimensions such as those given by way
of example above, be sufficiently flexible to be stripped from
the core without widening of the groove 14, that is to say the
core can be constructed more simply than in the above mentioned
earlier patent application, with a groove of invariable dimensions
in a one-piece core. Stripping is also facilitated by the fact
that the rib 2 ismoulded at tke interface of the cores.
The cavity blocks 16 and 20 are shown as separate
components. Alternatively, a single cavity block may contain
two axially spaced regions, the core 12 being disposed in a
first such region for moulding of the sealing ring, and being
thereafter moved, with the sealing ring, into the second region
in which the second moulding cavity 23 is defined.
The particular construction of the cores and cavity
block or blocks will depend on the materials to be moulded. The
plastics sleeve will in general be a thermoplastic material,
in particular polyethylene or polypropylene, but the rubber
sealing ring may be either thermoplastic or thermosetting. To
provide desired temperature in the moulding cavities, the cavity
blocks and/or cores may be provided with thermal insulation and/
or heating means and/or cooling means in the regions of the
moulding cavities.
