Pipe joints or couplings – With assembly means or feature – Molded joint facilitator
Reexamination Certificate
1999-08-23
2002-04-23
Nicholson, Eric K. (Department: 3627)
Pipe joints or couplings
With assembly means or feature
Molded joint facilitator
C285S055000, C285S222100
Reexamination Certificate
active
06375226
ABSTRACT:
This invention relates to a pipe joint for a multi-layer composite pipe, and method of forming same.
Plastic pipes are used increasingly in the transportation of gases and liquids, including oils and chemicals, which are under a high pressure within the pipe. Whilst techniques, such as orientation and cross-linking exist to improve the pressure resistance of a exist to improve the pressure resistance of a normal thermoplastic pipe wall, it technically and economically difficult to raise the pressure resistance of the pipe higher than around 15 to 20 bars.
Accordingly, multi-layer composite pipes comprising, for example, a thermoplastic inner layer and, outside it, a reinforcing layer, or a high axial strength inner layer and an outer protective layer, have been proposed for use as high pressure pipes.
Normally the reinforcing layer consists of fibres wound helically around the thermoplastic inner layer. The fibres may be bundled in tape form and the tape matrix fused to the thermoplastic inner layer by the use of heat, for example, as described in EP 0 593 449. The reinforcing layer can also be a conductive layer, for example a metal layer, which is spirally wound or seam welded on top of the thermoplastic layer in order to form a reinforcing metal layer of about 0.2 mm to 5 mm thickness over the thermoplastic layer. The reinforcing layer is preferably covered with another protective thermoplastic layer, which may contain, for example, pigments, antioxidants, fillers, and other modifying components.
Such reinforced multi-layer composite pipes are described, for example, in International Patent Application No PCT/FI96/00359, the entire disclosure of which is incorporated herein by reference for all purposes.
In order to form a firm bond between the reinforcing layer and the inner and outer thermoplastic layers, it is components, which can lose the adhesion-promoting ability if they are in contact with certain liquids, including water. Where the reinforcing layer is a metal layer, this must also be protected from any gases or liquids in the pipe, and from the environment, in order to avoid corrosion problems.
The gas or liquid flowing inside the pipe, and environmental moisture from outside the pipe, cannot normally come into contact with the reinforcing layer or the adhesive components due to the presence of the inner thermoplastic layer and the outer protective thermoplastic layer which together cover the reinforcing layer. However, at the ends of the pipe the continuity of the inner layer and the outer protective layer is disrupted, and therefore pipe connections need to be made in such a way that the reinforcing layer does not come into contact with either the gases or liquids within the pipe, or the outer environmental conditions.
Many solutions to the above problem have been proposed, but all have their drawbacks.
WO92/21908 discloses a pipe connection in which the reinforcing layer becomes thinner over a long surface towards the end of the pipe, and ends a distance from the end of the thermoplastic layer, where an extension is formed. An adaptor is fitted inside the extension, and outside the end of the thermoplastic layer the adaptor is attached, by means of threads, to a steel pipe surrounding the end of the pipe. The adaptor has a conical surface which presses the thermoplastic layer against the inner surface of the outside steel pipe.
The disadvantage of this known pipe connection is that liquid, especially from the outside, but also from the inside of the pipe, can relatively easily enter the end of the reinforcing layer, which, due to a small conical angle, is very large and which thus comprises a great amount of adhesive on the surface of the pipe. A high-pressure liquid flowing inside the pipe can get to the end of the reinforcing layer by going around the end of the thermoplastic layer which is fixed between the adaptor and the steel pipe with compressive forces provided by threads.
In this known solution, the extension at the end of the pipe is formed in a usual manner, ie the extension has a conical surface to which a cylindrical part restricted to the end of the pipe is connected. Such an extension cannot be formed to the part of the pipe which has the reinforcing layer, since due to its characteristics the reinforcing layer does not allow the diameter to increase. Therefore it has been necessary to make the reinforcing layer thinner and to end it before the extension, which thus consists of only the thermoplastic layer. The pipe connection becomes then rather long, and the fitting conical surfaces of the extension and that adaptor, which are the best sealing surfaces of the connection, have a relatively small surface area.
Another solution is provided in European Patent Application No 95 10 4955 in which the ends of composite plastic pipes to be connected are each provided with an extension, and a ring-shaped connecting piece is situated inside the pipes at the extended ends thereof, the connecting piece and the extensions of the pipes to be connected having fitting substantially conical surfaces which extend substantially to the ends of the pipes and from which the connecting piece and the extension are welded together. This system works well with glass fibre reinforced pipes, but is difficult to apply when the reinforcing layer is a metal layer, since it is difficult to form the conical extension without splitting the metal reinforcing layer.
A still further pipe connector is disclosed in DE 44 44 097 which shows an electrofusion coupler which is provided with an annular sealing means to seal the cut ends of the composite pipes. However, in this case, the connection is made only between the thin outer protective thermoplastic layers of the pipes to be connected, and there is no connection between the reinforcing layers. The pipe connection therefore represents a weak point in the pipeline, and is vulnerable to internal pressure and axially, applied forces.
EP-A-0253966 discloses a coupler for a pipe comprising an electrofusion coil and mechanical gripping means, the gripping means being arranged to grip the pipe prior to and during fusion, the fusion joint thereafter providing the effective joint for the pipe.
The entire disclosures of all the abovementioned patents are incorporated herein by reference for all purposes.
In one aspect the present invention provides a joint between a pipe connector and a multi-layer composite pipe, wherein a direct mechanical connection is made to the reinforcing layer, or to the layer of high axial strength, thereby giving a pipe connection of enhanced mechanical strength.
In another aspect, the invention further provides, at least in certain preferred embodiments described herein, a joint between a pipe connector and a multi-layer composite pipe which can:
(i) provide a seal against internal fluids flowing in the pipe;
(ii) provide axial strength, preferably to the level of the pipe itself; and
(iii) provide an environmental seal to prevent contaminants such as dirt from entering the sealing region.
In a further aspect, at least in certain preferred embodiments described herein, the joint of the invention provides a connection to both the inner thermoplastic layer and the reinforcing layer of a multi-layer composite pipe, further improving the quality of the connection.
In a first aspect, the invention provides a joint between an end of a pipe and a connector, wherein the pipe comprises a multi-layer composite pipe having at least one reinforcing layer, or layer of high axial strength, at least one inner thermoplastic layer, and at least one outer protective layer, and wherein the connector comprises:
(i) a hollow, tubular enclosure adapted to receive the pipe;
(ii) fusion means adapted to make a fusion connection with the inner thermoplastic layer of the pipe; and
(iii) mechanical gripping means adapted to grip the reinforcing layer or hugh axial strength layer of the pipe;
the fusion means and mechanical gripping means being disposed within the enclosure and the enclosure being adapted, in use, to apply a constraining fo
Dickinson Alan John
Jarvenkyla Jyri Jaakko
Nicholson Eric K.
Uponor Innovation AB
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