US 5,330,239 A · Pipe coupling

Abstract

A pipe coupling or connection comprises a female coupling component and a mating male coupling component. Each component is matingly threaded for coupling engagement, and each is provided with an adjacent frusto-conical sealing surface. The sealing surface is provided with a controlled surface roughness, viz. very shallow fine surface variations, preferably formed as microgrooves at a pitch small relative to the pitch of the threads. The slope of the frusto-conical surface of the sealing area of the male component is slightly mismatched with that of the sealing area of the female component to simulate the bearing force vs. axial distance characteristic of shrunk-fit circular cylindrical sealing surfaces. The slight mismatch enables the sealing pressure to be above a design minimum throughout the entire sealing area yet higher at each end of the sealing area. As the coupling is assembled, thread interference in the vicinity of the sealing surface lags the occurrence of interference between the sealing surfaces. Load threads are provided with negatively inclined load flank faces. The slope of the load thread pitch line of the male element is slightly steeper than the slope of the load thread pitch line of the female element.

Claims23

Dependent claims

A pipe connection of the type having a female component and a mating male component, each matingly threaded for connection therebetween, and each provided with a sealing area adjacent the threaded area, the sealing area of the coupling components being formed as mating frusto-conical surfaces, at least one of such surfaces having controlled surface roughness;

the respective sealing areas of the components being in axially aligned sealing engagement when the pipe connection has been assembled;
characterized in that:
(a) the slopes of the frusto-conical sealing surfaces are each relatively shallow;
(b) the slope of the frusto-conical sealing surface of the male component is selected to be slightly less than that of the frusto-conical sealing surface of the female component such that the sealing bearing load relative to axial distance of the contacting sealing surfaces of the components when the components have been assembled qualitatively simulates that of a pair of mating shrunk-fit circular cylindrical sealing surfaces;
and
(c) the slope of the load thread pitch line of the male component relative to the axis thereof is slightly steeper than the load thread pitch line of the female component relative to the axis thereof.

3 more elements

A pipe connection of the type having a female component and a mating male component, each matingly threaded for connection therebetween, and each provide with a sealing area adjacent the threaded area, the sealing area of the coupling components being formed as mating frusto-conical surfaces, at least one of such surfaces having controlled surface roughness;

the respective sealing areas of the components being in axially aligned sealing engagement when the pipe connection has been assembled;
characterized in that:
(a) the slopes of the frusto-conical sealing surfaces are each relatively shallow;
(b) the slope of the frusto-conical sealing surface of the male component is selected to be slightly less than that of the frusto-conical sealing surface of the female component such that the sealing bearing load relative to axial distance of the contacting sealing surfaces of the components when the components have been assembled is characterized by a relatively uniform sealing force at least equal to a design minimum force throughout the axial length of the sealing area between the end regions of the sealing area, a distal sealing force peak at the distal end (relative to the male component) of the sealing area, and a proximal force peak at the proximal end (relative to the male component) of the sealing area, the proximal force peak being substantially higher than the distal force peak but less than the force at which deleterious galling of the sealing area occurs, and the distal force peak being substantially higher than the uniform sealing force between the end regions of the sealing area but less than the force at which deleterious galling of the sealing area occurs;
(c) when the connection is being assembled, interference between the sealing surfaces occurs before any occurrence of any radially-directed interference of the load threads of the male and female components in the vicinity of the sealing surfaces;
(d) upon complete assembly of the connection, any interference between the load threads is insufficient to tend to pry the sealing surfaces apart to an extent that would reduce the sealing bearing load below the minimum design value for the connection;
and
(e) the slope of the load thread pitch line of the male component relative to the axis thereof is slightly steeper than the load thread pitch line of the female component relative to the axis thereof.

5 more elements

the respective sealing areas of the components being in axially aligned sealing engagement when the pipe connection has been assembled;
characterized in that:
(a) the slopes of the frusto-conical sealing surfaces are each relatively shallow;
(b) the slope of the frusto-conical sealing surface of the male component is slightly less than that of the frusto-conical sealing surface of the female component;
(c) when the connection is being assembled, interference between the sealing surfaces occurs before the occurrence of any radially-directed interference of the load threads of the male and female components in the vicinity of the sealing surfaces;
(d) upon complete assembly of the connection, any interference between the load threads is insufficient to tend to pry the sealing surfaces apart to an extent that would reduce the sealing bearing load below the minimum design value for the connection;
(e) the slope of the load thread pitch line of the male component relative to the axis thereof is slightly steeper than the load thread pitch line of the female component relative to the axis thereof;
and
(f) the mismatch in inches per inch between the slopes of the frusto-conical sealing surfaces of the male and female components is less than the nominal interference in inches at the gauge points of the said sealing surfaces.

6 more elements

For use in a pipe connection of the type having a female component and a mating male component, each matingly threaded for connection therebetween, and each provided with a sealing area adjacent the threaded area, the sealing area of the coupling components being formed as mating frusto-conical surfaces, at least one of such surfaces having controlled surface roughness;

the respective sealing areas of the components being in axially aligned sealing engagement when the pipe connection has been assembled;
a female component of the foregoing type characterized in that:
(a) the slopes of the frusto-conical sealing surfaces are each relatively shallow;
(b) the slope of the frusto-conical sealing surface of the female component is selected to be slightly greater than that of the frusto-conical sealing surface of the male component such that the sealing bearing load relative to axial distance of the contacting sealing surfaces of the components when the components have been assembled is characterized by a relatively uniform sealing force at least equal to a design minimum force throughout the axial length of the sealing area between the end regions of the sealing area, a distal sealing force peak at the distal end (relative to the male component) of the sealing area, and proximal force peak at the proximal end (relative to the male component) of the sealing area, the proximal force peak being substantially higher than the distal force peak but less than the force at which deleterious galling of the sealing area occurs, and the distal force peak being substantially higher than the uniform sealing force between the end regions of the sealing area but less than the force at which deleterious galling of the sealing area occurs;
(c) when the connection is being assembled, interference between the sealing surfaces occurs before any occurrence of any radially-directed interference of the load threads of the male and female components in the vicinity of the sealing surfaces;
(d) upon complete assembly of the connection, any interference between the load threads is insufficient to tend to pry the sealing surfaces apart to an extent that would reduce the sealing bearing load below the minimum design value for the connection;
and
(e) the slope of the load thread pitch line of the female component relative to the axis thereof is slightly less steep that the load thread pitch line of the male component relative to the axis thereof.

5 more elements

Dependencies are inferred from the claim text.

Pipe coupling

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Pipe coupling

Life of this patent

Abstract

Claims23