Patent Description:
This invention concerns improved groove shapes for pipe elements joined by mechanical couplings, and coupling key shapes compatible with improved groove shapes.

As shown in <FIG>, one type of prior art mechanical coupling <NUM> for joining pipe elements <NUM> and <NUM> end to end relies on arcuate projections, known as keys <NUM> that mechanically engage circumferential grooves <NUM> in the pipe elements. While these couplings have proved to be very effective and efficient, the prior art configuration is subject to certain limitations. For example, when such a joint is subjected to loads, especially loads arising from internal pressure induced end loads, axial tensile forces and bending, the joint may not be able to withstand such loads up to the full tensile strength of certain types of pipe. To realize a greater percentage of the potential strength of the pipe element and thereby increase the pressure capacity of a joint, external rings containing grooves may be welded to pipe elements to provide for mechanical engagement with the coupling's keys in a configuration that does not alter the pipe element's sidewall, either by removing material (machined grooves) or by deforming the sidewall (rolled grooves).

While welded external rings may permit a larger percentage of the full pipe strength to be realized at a joint, the disadvantage of this solution is the need to weld rings onto the pipe elements. This procedure adds cost, time and requires skilled welders, complicating fabrication. There is clearly a need for a pipe design that improves the realization of pipe element strength and thereby increases the internal pressure performance and axial tensile loading limits achievable using mechanical couplings without the need for external welded rings.

Document <CIT> discloses a clamp type connector that has two semi-circular halves clamping the ends of conduits together. The ends of the conduits have dual lobes or load shoulders. These load shoulders are axially spaced apart from each other. The clamp has mating conical load shoulders for engaging the other load shoulders. The load shoulders of the clamp and the conduits are separated by flanks which face in opposite directions. In a second embodiment, the load shoulders spaced closest to the ends of the conduits are formed with multiple angles. Similarly, the mating conduit shoulders are formed with multiple angles. The first portion, which is the entry or lead portion, is at a greater angle relative to a plane perpendicular to the axis than the second portion, which is the load portion.

The invention concerns a pipe element according to claim <NUM>. The pipe element has first and second oppositely disposed ends. The pipe element comprises a sidewall surrounding a longitudinal axis and defining a bore. The sidewall has an outer surface. A first groove is positioned in the outer surface. The first groove extends circumferentially around the bore and is positioned proximate to the first end. The first groove is defined by a first plurality of sub-surfaces of the outer surface including:.

In a specific example embodiment the first sub-surface has an orientation angle from <NUM>° to <NUM>° with respect to the longitudinal axis. Further by way of example, the first sub-surface has an orientation angle of <NUM>° with respect to the longitudinal axis. The third sub-surface has an orientation angle from <NUM>° to <NUM>° with respect to the longitudinal axis. In a further example, the third sub-surface has an orientation angle of <NUM>° with respect to the longitudinal axis.

The second sub-surface has an orientation angle from <NUM>° to <NUM>° with respect to the longitudinal axis. In an example embodiment the second sub-surface has an orientation angle of <NUM>° with respect to the longitudinal axis. In a further example embodiment the fourth sub-surface has an orientation angle from +<NUM>° to -<NUM>° with respect to the longitudinal axis.

In an example embodiment the pipe element further comprises a second groove positioned in the outer surface. The second groove extends circumferentially around the bore and positioned proximate to the second end. The second groove is defined by a second plurality of sub-surfaces of the outer surface including:.

In another example embodiment the first and fifth sub-surfaces have an orientation angle from <NUM>° to <NUM>° with respect to the longitudinal axis. Further by way of example, the first and fifth sub-surfaces have an orientation angle <NUM>° with respect to the longitudinal axis. The third sub-surface has an orientation angle from <NUM>° to <NUM>° with respect to the longitudinal axis. In another example, the seventh sub-surface has an orientation angle from <NUM>° to <NUM>° with respect to the longitudinal axis. By way of further example, the third and seventh sub-surfaces have an orientation angle of <NUM>° with respect to the longitudinal axis.

In another example, the sixth sub-surface has an orientation angle from <NUM>° to <NUM>° with respect to the longitudinal axis. Further by way of example, the second and sixth sub-surfaces have an orientation angle of <NUM>° with respect to the longitudinal axis. In another example, the fourth and eighth sub-surfaces have an orientation angle from +<NUM>° to -<NUM>° with respect to the longitudinal axis.

The invention further encompasses, in combination, a pipe element as described above and a coupling. In one example embodiment the coupling comprises a plurality of segments attached to one another end to end surrounding the first end of the pipe element. Adjustable attachment members are positioned at each end of the segments for attaching the segments to one another. At least one arcuate projection is positioned on one side of each of the segments and engages with the first groove. The at least one arcuate projection comprises a plurality of mating surfaces including:.

In an example embodiment a gap is positioned between the fourth mating surface and the fourth sub-surface. In a further example, the at least one arcuate projection comprises a recess therein forming the gap between fourth mating surface and the fourth sub-surface.

A further example embodiment comprises, in combination, a pipe element as described above and a coupling. By way of example the coupling comprises a plurality of segments attached to one another end to end surrounding the first end of the pipe element. Adjustable attachment members are positioned at each end of the segments for attaching the segments to one another. At least one arcuate projection is positioned on one side of each of the segments and engages with the first groove. The at least one arcuate projection comprises a plurality of mating surfaces including:.

By way of example, a gap is positioned between the fourth mating surface and the fourth sub-surface. In a further example the at least one arcuate projection comprises a recess therein forming the gap between the fourth mating surface and the fourth sub-surface. In an example embodiment the coupling comprises no more than two segments.

<FIG> shows an example mechanical pipe coupling <NUM> joining example pipe elements <NUM> and <NUM> according to the invention. Coupling <NUM> comprises segments <NUM> and <NUM> attached end to end to surround a central space <NUM> which receives the pipe elements <NUM> and <NUM>. Attachment of the segments to one another is effected by adjustable attachment members <NUM> and <NUM> which, in this example, comprise lugs <NUM> and <NUM> that respectively project from opposite ends of each segment <NUM> and <NUM>. Lugs <NUM> and <NUM> in this example have reinforcing gussets <NUM> and openings <NUM> that receive fasteners <NUM>, in this example studs <NUM> and nuts <NUM>.

As shown in the sectional view of <FIG>, each segment (<NUM> being shown in section) has two arcuate projections, also known as keys <NUM> and <NUM> positioned on opposite sides of each segment. Keys <NUM> and <NUM> project toward the central space <NUM> and mechanically engage respective circumferential grooves <NUM> and <NUM> in each pipe element. A fluid tight joint is ensured by a ring seal <NUM> captured and compressed between the segments <NUM> and <NUM> and the pipe elements <NUM> and <NUM> when fasteners <NUM> (see <FIG>) are adjustably tightened to draw the segments <NUM> and <NUM> toward one another and into engagement with the pipe elements to form the joint.

<FIG> shows pipe element <NUM> and its groove <NUM> in detail. In this example pipe element <NUM> comprises a sidewall <NUM> surrounding a longitudinal axis <NUM> and defining a bore <NUM>. Groove <NUM> is positioned in an outer surface <NUM> of the sidewall <NUM>. Groove <NUM> extends circumferentially about the bore <NUM> and is positioned proximate to an end <NUM> of the pipe element <NUM>. As shown in <FIG>, the position of the groove <NUM> with respect to the pipe end <NUM> is coordinated with the coupling <NUM> so as to provide lands <NUM> for sealing engagement with the glands <NUM> of the ring seal <NUM>.

As shown in <FIG>, groove <NUM> comprises a first sub-surface <NUM> shown oriented perpendicular (<NUM>°) relative to the longitudinal axis <NUM>. The orientation angle <NUM> of first sub-surface <NUM> may range from <NUM>° to <NUM>° with respect to the longitudinal axis <NUM>, with an orientation angle of about <NUM>° being advantageous. First sub-surface <NUM> faces away from the end <NUM> of the pipe element <NUM>. A second sub-surface <NUM> is oriented at an angle with respect to the longitudinal axis <NUM>. Second sub-surface <NUM> is positioned in spaced relation away from the first sub-surface <NUM> and faces the end <NUM> of the pipe element <NUM>. A third sub-surface <NUM> is contiguous with the first sub-surface <NUM>, is oriented at an angle with respect to the longitudinal axis <NUM> and slopes toward the second sub-surface <NUM>. A fourth sub-surface <NUM> is contiguous with both the second and third sub-surfaces. The fourth sub-surface <NUM> is shown oriented parallel (<NUM>° angle) to the longitudinal axis <NUM>, but its orientation angle <NUM> may range from +<NUM>° to -<NUM>° for a practical design. The terms "perpendicular", "parallel" and "oriented at an angle" mean perpendicular or parallel or oriented at an angle with respect to a reference axis within normal manufacturing tolerances for the pipe element in question.

In a practical design, second sub-surface <NUM> may have an orientation angle <NUM> from about <NUM>° to about <NUM>° relative to the longitudinal axis <NUM>; an orientation angle <NUM> of about <NUM>° is considered advantageous for certain applications. Similarly, the third sub-surface <NUM> may have an orientation angle <NUM> from about <NUM>° to about <NUM>° relative to the longitudinal axis <NUM>, and an orientation angle <NUM> of about <NUM>° is considered advantageous for certain applications.

As further shown in <FIG>, pipe element <NUM> may have a second end <NUM> oppositely disposed from the end <NUM> (which may thus be considered the "first" end), the second end <NUM> having a second groove <NUM> with a groove configuration similar to the first groove <NUM>. In this example embodiment second groove <NUM> comprises a fifth sub-surface <NUM> shown oriented perpendicular (<NUM>°) to the longitudinal axis <NUM>. The orientation angle <NUM> of fifth sub-surface <NUM> may range from <NUM>° to <NUM>° with respect to the longitudinal axis <NUM>, with an orientation angle of about <NUM>° being advantageous. Fifth sub-surface <NUM> faces away from the second end <NUM> of the pipe element <NUM>. A sixth sub-surface <NUM> is oriented at an angle with respect to the longitudinal axis <NUM>. Sixth sub-surface <NUM> is positioned in spaced relation away from the fifth sub-surface <NUM> and faces the second end <NUM> of the pipe element <NUM>. A seventh sub-surface <NUM> is contiguous with the fifth sub-surface <NUM>, is oriented at an angle with respect to the longitudinal axis <NUM> and slopes toward the sixth sub-surface <NUM>. An eighth sub-surface <NUM> is contiguous with both the sixth and seventh sub-surfaces. The eighth sub-surface <NUM> is shown oriented parallel (<NUM>° angle) to the longitudinal axis <NUM>, but its orientation angle <NUM> may range from about +<NUM>° to about -<NUM>° for a practical design.

In a practical design, sixth sub-surface <NUM> may have an orientation angle <NUM> from about <NUM>° to about <NUM>° relative to the longitudinal axis <NUM>; an orientation angle <NUM> of about <NUM>° is considered advantageous for certain applications. Similarly, the seventh sub-surface <NUM> may have an orientation angle <NUM> from about <NUM>° to about <NUM>° relative to the longitudinal axis <NUM>, and an orientation angle <NUM> of about <NUM>° is considered advantageous for certain applications.

Grooves <NUM>, <NUM> may be formed in pipe elements <NUM> and <NUM> by roll grooving, as shown in <FIG>. As shown by way of example for groove <NUM> in pipe element <NUM>, the pipe element is cold worked while being rotated between an inner roller <NUM> that contacts the inside surface <NUM> of the pipe element, and an outer roller <NUM> that contacts the pipe element outer surface <NUM>. Typically, the inner roller <NUM> is driven (rotated about an axis <NUM> parallel to the longitudinal axis <NUM> of the pipe element <NUM>). The driven inner roller <NUM> rotates the pipe element, which, in turn rotates the outer roller <NUM> about an axis <NUM> as a result of contact friction between the rollers and the pipe element. The outer roller <NUM>, being an idler, is usually forced toward the inner roller <NUM> with a hydraulic ram <NUM>, deforming the pipe element and forming the groove <NUM> having a shape dictated by the shapes of the inner and outer rollers <NUM> and <NUM>. Grooves <NUM> and <NUM> may also be formed by machining operations.

<FIG> and <FIG> show a combination pipe element (<NUM> and/or <NUM>) and coupling <NUM> connecting the pipe elements end to end. <FIG> shows in detail, the cross sectional geometry of the arcuate projections or keys <NUM> and <NUM> effecting mechanical engagement with circumferential grooves <NUM> and <NUM> in each pipe element <NUM> and <NUM> initially upon assembly of the joint, i.e. prior to the application of internal pressure induced end loads, axial tensile forces and bending loads.

In this example embodiment, key <NUM> comprises a plurality of mating surfaces including a first mating surface <NUM> shown oriented perpendicular to the longitudinal axis <NUM> and in facing relation with the first sub-surface <NUM>. Note initially upon assembly there usually will be a gap between first mating surface <NUM> and first sub-surface <NUM> because the angular relationship between sub-surface <NUM> and sub-surface <NUM> tends to bias the location of key <NUM> away from sub-surface <NUM>. A second mating surface <NUM> is oriented at an angle with respect to the longitudinal axis <NUM>, is spaced away from the first mating surface <NUM>, and contacts the second sub-surface <NUM> initially upon assembly. A third mating surface <NUM> is oriented at an angle with respect to the longitudinal axis <NUM> and is contiguous with the first mating surface <NUM>. Third mating surface <NUM> contacts third sub-surface <NUM> initially upon assembly. A fourth mating surface <NUM> is between the second and third mating surfaces <NUM> and <NUM>, is in facing relation with the fourth sub-surface <NUM> and in spaced apart relation therefrom thereby forming a gap <NUM>. The gap <NUM> is ensured by the fourth mating surface <NUM> comprising a recess in the arcuate projection (key) <NUM>. Similarly, key <NUM> also comprises a plurality of mating surfaces including a fifth mating surface <NUM> shown oriented perpendicular to the longitudinal axis <NUM> and in facing relation with the fifth sub-surface <NUM>. A gap is typically present between the fifth mating surface <NUM> and the fifth sub-surface <NUM> initially upon assembly because the angular relationship between sub-surface <NUM> and sub-surface <NUM> tends to bias the location of key <NUM> away from sub-surface <NUM>. A sixth mating surface <NUM> is oriented at an angle with respect to the longitudinal axis <NUM>, is spaced away from the fifth mating surface <NUM>, and contacts the sixth sub-surface <NUM> initially upon assembly. A seventh mating surface <NUM> is oriented at an angle with respect to the longitudinal axis <NUM> and is contiguous with the fifth mating surface <NUM>. Seventh mating surface <NUM> contacts seventh sub-surface <NUM> initially upon assembly. An eighth mating surface <NUM> is between the sixth and seventh mating surfaces <NUM> and <NUM>, is in facing relation with the eighth sub-surface <NUM> and in spaced apart relation therefrom thereby forming a gap <NUM>. The gap <NUM> is ensured by the eighth mating surface <NUM> comprising a recess in the arcuate projection (key) <NUM>.

In a practical design, the mating surfaces will have orientation angles matched to the respective sub-surfaces they contact. Thus the first mating surface <NUM> may have an orientation angle <NUM> from about <NUM>° to about <NUM>° with respect to the longitudinal axis <NUM>, with an orientation angle of about <NUM>° being advantageous. The second mating surface <NUM> may have an orientation angle <NUM> from about <NUM>° to about <NUM>° with respect to the longitudinal axis <NUM>. An orientation angle <NUM> of about <NUM>° is considered advantageous for certain applications. The third mating surface <NUM> may have an orientation angle <NUM> from about <NUM>° to about <NUM>° with respect to the longitudinal axis <NUM>. An orientation angle <NUM> of about <NUM>° is considered advantageous for certain applications. The orientation angle <NUM> of the fourth mating surface <NUM> may range from about +<NUM>° to about -<NUM>° with respect to the longitudinal axis <NUM>.

Similarly, the fifth mating surface <NUM> may have an orientation angle <NUM> from about <NUM>° to about <NUM>° with respect to the longitudinal axis <NUM>, with an orientation angle of about <NUM>° being advantageous. The sixth mating surface <NUM> may have an orientation angle <NUM> from about <NUM>° to about <NUM>° with respect to the longitudinal axis <NUM>. An orientation angle <NUM> of about <NUM>° is considered advantageous for certain applications. The seventh mating surface <NUM> may have an orientation angle <NUM> from about <NUM>° to about <NUM>° with respect to the longitudinal axis <NUM>. An orientation angle <NUM> of about <NUM>° is considered advantageous for certain applications. The orientation angle <NUM> of the eighth mating surface <NUM> may range from about +<NUM>° to about -<NUM>° with respect to the longitudinal axis <NUM>.

<FIG> illustrates another example embodiment wherein coupling 20a joins pipe elements 22a and 24a. In this example embodiment the sub-surface 92a on pipe element 22a and its mating surface 112a on key 50a of coupling 20a are oriented at about <NUM>° to the longitudinal axis <NUM>. Similarly, sub-surface 76a on pipe element 24a and its mating surface 104a on key 52a of coupling 20a are oriented at about <NUM>° to the longitudinal axis <NUM>. As evidenced by the absence of gaps between mating surface <NUM> and sub-surface <NUM> and mating surface <NUM> and sub-surface <NUM>, the joint is shown subjected to internal pressure induced end loads and /or axial tensile forces, as explained in detail below.

Example pipe elements <NUM> and <NUM> (or 22a and 24a), when used in combination with the example coupling <NUM> (or coupling 20a, respectively) provide a marked improvement over prior art direct mechanical roll groove or machined groove coupling systems. The improved performance is due to a better axial load distribution, which, unlike prior art couplings, is not borne entirely at the first and fifth sub-surfaces <NUM> and <NUM>. Rather, a portion of the axial load is borne by the sub-surfaces <NUM> and <NUM> as a result of contact between the third mating surface <NUM> and the third sub-surface <NUM> and the seventh mating surface <NUM> and the seventh sub-surface <NUM>. These mating surfaces on the coupling and sub-surfaces on the pipe elements are oriented at an angle with respect to the longitudinal axis <NUM>. Thus, when, as shown in <FIG>, the pipe joint is subjected to internal pressure induced end loads and /or axial tensile forces, the pipe elements <NUM> and <NUM> (or 22a and 24a) move axially away from one another, the aforementioned mating surfaces <NUM> and <NUM> ride up angled sub-surfaces <NUM> and <NUM> to come into greater wedging, clamping contact with the mating surfaces <NUM> and <NUM> respectively, until mating surfaces <NUM> and <NUM> firmly contact the first and fifth sub-surfaces <NUM> and <NUM> of the pipe element <NUM> and <NUM> (or 24a and 22a). The internal pressure induced end loads and /or axial tensile forces are thus resisted not only by contact between mating surfaces <NUM> and <NUM> of the coupling and sub-surfaces <NUM> and <NUM> of the pipe elements, but also by the wedging, clamping contact of mating surfaces <NUM> and <NUM> with angled sub-surfaces <NUM> and <NUM>. Keys <NUM> and <NUM> (also 50a and 52a) are designed so that they do not completely fill their respective grooves <NUM> and <NUM>. Rather, as the pipe joint is loaded, pipe elements <NUM> and <NUM> push away from one another until sub-surfaces <NUM> and <NUM> come into contact with mating surfaces <NUM> and <NUM> respectively. This will open a gap between sub-surfaces <NUM> and <NUM> and their respective mating surfaces <NUM> and <NUM>. The spaced relation of the fourth mating surface <NUM> from the fourth sub-surface <NUM> and the spaced relation of the eighth mating surface <NUM> from the eighth sub-surface <NUM> provide the needed space to ensure that contact is achieved between sub-surface <NUM> and mating surface <NUM> as well as between sub-surface <NUM> and mating surface <NUM>.

The load sharing which provides improved performance is effected by the geometries of the keys <NUM> and <NUM> and the respective grooves <NUM> ad <NUM> which they engage as well as the method of assembling and using the coupling and pipe elements according to the invention. In an example embodiment of one method of assembly, described for pipe element <NUM> and coupling <NUM> with reference to <FIG>, comprises contacting the third sub-surface <NUM> of groove <NUM> with a portion (third mating surface <NUM>) of the arcuate projection (key) <NUM>, and contacting the second sub-surface <NUM> of groove <NUM> with another portion (second mating surface <NUM>) of the arcuate projection (key) <NUM>. When the combination includes the second pipe element <NUM> the assembly proceeds similarly; contacting the seventh sub-surface <NUM> of groove <NUM> with a portion (seventh mating surface <NUM>) of the arcuate projection (key) <NUM>, and contacting the sixth sub-surface <NUM> of groove <NUM> with another portion (sixth mating surface <NUM>) of the arcuate projection (key) <NUM>.

An example method of using the coupling <NUM> having arcuate projections <NUM>, <NUM> engaged with grooves <NUM>, <NUM> of the pipe elements <NUM> and <NUM> is illustrated with reference to <FIG> and <FIG> and comprises assembling coupling segments <NUM> and <NUM> about pipe elements <NUM> and <NUM>, such that keys <NUM> and <NUM> are located within grooves <NUM> and <NUM>, respectively (<FIG>). Fasteners <NUM> are then installed and tightened to connect attachment members <NUM> and <NUM> and ensure that at least mating surfaces <NUM> and <NUM> come into contact with sub-surfaces <NUM> and <NUM> respectively. As shown in <FIG>, forces are applied to the coupling (arising from system pressure, gravitational or other end loads) which create a tensile force between the pipe elements and the coupling, thereby causing respective portions of the arcuate projections (first and fifth mating surfaces <NUM>, <NUM>) to engage respective first and fifth sub-surfaces <NUM> and <NUM> of grooves <NUM> and <NUM>, and other portions (third and seventh mating surfaces <NUM> and <NUM>) of the arcuate projections <NUM> and <NUM> to respectively engage the third and seventh sub-surfaces <NUM> and <NUM>.

Claim 1:
A pipe element (<NUM>, <NUM>, 22a, 24a) having first and second oppositely disposed ends (<NUM>, <NUM>), said pipe element comprising:
a sidewall (<NUM>) surrounding a longitudinal axis (<NUM>) and defining a bore (<NUM>), said sidewall (<NUM>) having an outer surface (<NUM>);
a first groove (<NUM>) positioned in said outer surface (<NUM>), said first groove (<NUM>) extending circumferentially around said bore (<NUM>) and positioned proximate to said first end (<NUM>), said first groove (<NUM>) being defined by a first plurality of sub-surfaces of said (<NUM>, <NUM>, <NUM>, <NUM>) outer surface (<NUM>) including:
a first sub-surface (<NUM>) oriented at a constant angle with respect to said longitudinal axis (<NUM>) and facing away from said first end (<NUM>);
a second sub-surface (<NUM>) oriented at a constant angle (<NUM>) of <NUM>° to <NUM>° with respect to said longitudinal axis (<NUM>), said second sub-surface (<NUM>) being in spaced relation away from and facing toward said first sub-surface (<NUM>);
a third sub-surface (<NUM>) contiguous with said first sub-surface (<NUM>), said third sub-surface (<NUM>) oriented at a constant angle (<NUM>) of <NUM>° to <NUM>° with respect to said longitudinal axis (<NUM>) and sloping toward said second sub-surface (<NUM>); and
a fourth sub-surface (<NUM>) contiguous with said third and second sub surfaces (<NUM>, <NUM>), said fourth sub-surface (<NUM>) being oriented at a constant angle (<NUM>) with respect to said longitudinal axis (<NUM>).