Pipe joints or couplings – With fluid pressure seal – With separate – encased pipe-gripping means
Patent
1993-01-26
1994-10-04
Arola, Dave W.
Pipe joints or couplings
With fluid pressure seal
With separate, encased pipe-gripping means
285373, F16L 1700
Patent
active
053519973
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to pipe couplings for connecting together two plain-ended pipes in a fluid-tight manner, of the type consisting of a tubular casing formed with a longitudinal gap, a sealing sleeve of resilient flexible material arranged within the casing, and tensioning means for reducing the width of the longitudinal gap. In use, the sealing sleeve is placed around the adjacent pipe ends and the tensioning means are tightened to clamp the sleeve against the outer surfaces of the pipe ends to form a fluid tight seal.
BACKGROUND OF THE INVENTION
One known pipe coupling of this type is described in Uk-A-1,582,858. The sealing sleeve is of C-shaped longitudinal cross-section having two lips extending axially inwardly towards one another so as to form a groove between the extension and the web portion. When the casing is tightened around the pipe ends the lips of the sealing sleeve are pressed into sealing engagement with the outer surfaces of the pipe ends to form a seal. In use fluid carried by the pipes passes through the gap between the pipe ends into the space between the outside of the pipe end and the inside of the web portion of the sleeve. The fluid enters the grooves between the extensions of the lips causing the sealing pressure of the extensions against the pipes to increase as the pressure of the fluid increases. A disadvantage of such an arrangement is that substantially the whole of the inner surface of the web portion is exposed to the pressure of the fluid from the pipe. Where the fluid pressure is high, this can cause the casing to bulge out at its axial middle portion.
According to the present invention in a first aspect there is provided a pipe coupling for joining together two pipes in a fluid-tight manner, comprising a tubular sealing sleeve and tensioning means for tightening the casing around the sleeve, the sleeve including two sets of annular inwardly projecting sealing ribs on the inner surface of the sleeve which engage the respective pipe ends in a fluid tight manner.
With this arrangement only the portion of the sleeve between the axially innermost pair of ribs is exposed to the hydrostatic pressure of the fluid in the pipe. The casing is therefore less prone to bulging at high hydrostatic pressures and, in consequence, the casing can be made of lighter construction than a conventional coupling with the equivalent performance specification. This means that the coupling is less expensive and easier to handle during manufacture.
Joining together pipes with plain ends with couplings without the need for pipe preparation is quicker and more economical than other methods such as welding, screw threading, flanging, grooving or shouldering. However because of the enormous axial forces that may be involved in pipelines operating at pressures of say 16 bars, it is difficult to construct a coupling that can reliably withstand such forces.
In the coupling of GB-A-1582858, axial restraint is provided by two frustoconical rings with gripping teeth on their inner edges. The gripping rings are located at the sides of the sealing sleeve and held in position within the casing by means of snap rings. When the casing is tightened the gripping teeth bite into the pipe ends to provide axial restraint for the pipes.
There are a number of disadvantages with this arrangement. The gripping teeth are sharp and are exposed. This presents a hazard to the pipe fitters who might cut themselves when handling the couplings prior to fitting.
The teeth are exposed and may come into contact with water and other corrosive liquids depending on the enviroment in which they are employed. The teeth are usually made of a hard steel that is prone to crevice corrosion.
The geometry of the toothed gripping device is upset on clamping on to the pipe. The specially shaped snap rings that are required to support the gripping rings add to the complexity of the coupling and they only provide partial support for the gripping ring. The snap rings may act as fulcrums over which the teeth are
REFERENCES:
patent: 2201372 (1940-05-01), Miller
patent: 3565468 (1971-02-01), Garrett
patent: 3801141 (1974-04-01), Hollingsworth
patent: 3877733 (1975-04-01), Straub
patent: 4119333 (1978-10-01), Straub
patent: 4518177 (1985-05-01), Deakins
patent: 4627645 (1986-12-01), Sauer
Taylor Neil J. T.
Taylor William
Webb Ian R.
Arola Dave W.
Taylor Kerr (Couplings) Ltd.
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