Pipes and tubular conduits – Combined – With end structure
Reexamination Certificate
2000-04-13
2001-08-14
Brinson, Patrick (Department: 3752)
Pipes and tubular conduits
Combined
With end structure
C138S155000, C285S222100
Reexamination Certificate
active
06273142
ABSTRACT:
BACKGROUND ART
The invention concerns a flexible pressure pipe with an associated end-fitting having an axially extending through opening, where the pipe is of a non-bonded structure comprising a number of layers including an extruded polymer inner lining extending into the through opening.
Flexible pressure pipes are used for a variety of applications, including water supply lines, sewage lines and lines for transporting chemicals such as liquid ammonia and phosphoric acid and also high pressure offshore flexible pipes for the oil and gas industry.
The joint between the inner lining and the end-fitting must be able to resist the axial tensile load acting on the inner lining, when the flexible pipe is descending over a great length, and also such stresses which arise as a consequence of temperature fluctuations.
Conventionally, said joint is provided by squeezing the inner lining between an outer conical ring and an inner conical ring which is pressed in between the inner lining and the carcass of the pipe. The effect of this squeezing will, however, diminish gradually as the plasticizer disappears from the plastic material of the lining.
Another drawback is that temperature stresses can arise in the joint because the plastic material has a high coefficient of expansion.
In the document GB 891 611 A is described a tamber-proof fitting for attachment to the end of a hose having a liner of substantially plastic material with a braided covering thereon. By assembling, an end of the liner is squeezed between an inner nipple and an outer body member having, on the innerside, sharp ribs which by the squeezing is forced into the material of the liner forming complementary share grooves in the liner. This known technique cannot be used for pipes having an inner carcass which not allows the liner to be squeezed and the nipple to be screwed in. Furthermore, the share grooves in the liner functions with a dangerous notch effect which is not acceptable for high-quality flexible pressure pipes exposed to high loads.
SUMMARY OF THE INVENTION
The object of the invention is to provide a flexible pressure pipe with an associated end-fitting of the type mentioned in the opening paragraph in which the joint between the inner lining of the pipe and the end-fitting is a simple and cheap structure and provides a greater resistance to axial tensile loads acting on the inner lining than has been known before.
This is achieved in that on the outer surface of the end part of the inner lining at least one annular groove is formed, a lock ring is attached to the inner lining by means engaging said annular groove, and the lock ring is attached to the end-fitting, whereby the inner lining can be firmly connected to the end-fitting in a simple and time efficient manner.
The lock ring can be attached to the annular groove in the inner lining by a substantially corresponding annular rib on the inner surface of the lock ring. This embodiment is very simple.
To compensate for inevitable tolerances of the inner lining and in the preparation of the joint between the lining and the lock ring, in another expedient embodiment the lock ring can be attached to the annular groove in the inner lining by a circlip which is fitted into both said annular groove in the inner lining and an opposing groove in the inner surface of the lock ring.
A particularly strong connection between the inner lining and the lock ring is obtained when the annular groove in the outer surface of the inner lining is formed by rolling, such that the material of the lining will be strengthened and imparted with a better structure by cold hardening.
For improving the strength of the joint between the lock ring and the inner lining, the annular groove in the outer surface thereof can be formed as a segment of circle and the depth of the groove can be between 0.2-0.5 times the thickness of the lining.
The lock ring can easily be mounted on the inner lining when it has a transverse slit or consists of two or more sectors of a circle.
In a particularly advantageous and strong embodiment, the lock ring can be fitted into a holding groove formed in the wall of the through opening of the end-fitting, and for securing this connection between the lock ring and the holding groove there may be a gap filled with a casting material, e.g. a polymer such as epoxy.
The invention also concerns a method for assembling a flexible pressure pipe with an associated end-fitting having an axially extending through opening, where the pipe is of a non-bonded structure comprising of a number of layers including an extruded polymer inner lining extending into the through opening. Said method comprises: removing the layers surrounding the lining at the end of the pipe, rolling at least one annular groove in the outer surface of the end part of the inner lining, placing a lock ring consisting of two or more sectors of a circle around the end part of the lining such that a rib on the lock ring, or a circlip which engages a groove in the lock ring, engages the groove rolled in the outer surface of the end part of the lining, securing the lock ring sectors, and attaching the lock ring to the end-fitting. The method can advantageously be performed in situ.
REFERENCES:
patent: 959187 (1910-05-01), Witzenmann
patent: 4275769 (1981-06-01), Cooke
patent: 4813715 (1989-03-01), Policelli
patent: 4875717 (1989-10-01), Policelli
patent: 4895185 (1990-01-01), Champleboux et al.
patent: 225 220 (1910-09-01), None
patent: 810 452 (1951-08-01), None
patent: 891 611 (1962-03-01), None
Brinson Patrick
McCormick Paulding & Huber LLP
NKT Flexibles I/S
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