Method of joining pipes in end to end relation

CROSS REFERENCE TO RELATED APPLICATIONS

0001This application is a continuation of U.S. application Ser. No. 11/091,216 filed Mar. 28, 2005 now abandoned, which claims priority to U.S. Provisional Application No. 60/556,962, filed Mar. 26, 2004.

FIELD OF THE INVENTION

0002The invention concerns a method of using couplings for joining pipes in end to end relation and effecting a substantially rigid or a flexible fluid tight joint therebetween.

BACKGROUND OF THE INVENTION

0003Couplings for joining pipes together end to end comprise arcuate segments that circumferentially surround co-axially aligned pipes and engage circumferential grooves positioned proximate to the ends of each pipe. The couplings are also used to connect pipes to fluid control components such as valves, reducers, strainers, restrictors, pressure regulators, as well as components to components. Although in the description which follows pipes are described, they are used by way of example only, the invention herein not being limited for use only with pipes per se. It should also be noted that the term “pipe” as used herein refers to straight pipes as well as elbows, tees and other types of fittings.

0004The segments comprising the couplings have circumferential keys that extend radially inwardly toward the pipes and fit within the grooves around the pipes. The keys are typically somewhat narrower than the grooves to permit them to fit within the grooves and bear against the shoulders formed by the grooves to hold the pipes together against internal pressure and external forces that may be applied to the pipes. External forces may arise due to thermal expansion or contraction of the pipes due to changes in temperature as well as the weight of the pipes or components such as valves attached to the pipes, which can be significant for large diameter pipes and valves. Wind loads and seismic loads may also be a factor.

0005It is advantageous that pipe couplings be substantially rigid, i.e., resist rotation of the pipes relative to one another about their longitudinal axes, resist axial motion of the pipes relatively to one another due to internal pressure, and resist angular deflection of pipes relative to one another. A rigid coupling will be less likely to leak, requiring less maintenance, and will simplify the design of piping networks by eliminating or at least reducing the need for engineers to account for axial motion of pipes in the network when subjected to significant internal pressure. Pipes joined by rigid couplings require fewer supports to limit unwanted deflection. Furthermore, valves and other components which may tend to rotate out of position because their center of gravity is eccentric to the pipe axis will tend to remain in position and not rotate about the longitudinal axis under the pull of gravity when the pipe couplings are substantially rigid.

0006Many couplings according to the prior art do not reliably provide the desired degree of rigidity mainly because they use keys having rectangular cross-sections that are narrower than the width of the grooves that they engage. This condition may result in inconsistent contact between the coupling and the pipes which allows too much free play and relative movement, for example, axially, rotationally or angularly, between the pipes. It is also difficult to ensure that such keys properly engage the grooves. Couplings which provide a more rigid connection may be ineffective to force the pipe ends apart at a desired distance from one another so that the keys and grooves are in proper alignment and the pipes are properly spaced. When properly spaced apart, the pipe ends and the coupling cooperate with a sealing member positioned between the coupling and the pipe ends to ensure a fluid tight seal. The movement of the pipes, although small, is effected as the couplings are engaged with each other and the pipe and may require that significant torque be exerted upon the fasteners used to clamp the coupling to the pipes. This is especially acute when pipes to be joined are stacked vertically one above another, and the action of engaging the coupling with the pipes must lift one of the pipes upwardly relatively to the other in order to effect the proper spacing between the pipe ends. For such couplings, it is also difficult to reliably visibly ensure that the couplings have been properly installed so that the keys engage the grooves and the pipes are spaced apart as required to ensure a fluid tight seal.

0007It would be advantageous to provide a coupling that provides increased rigidity while also reducing the force necessary to engage the coupling with the pipe ends to effect their proper spacing, and also provides a reliable visual indication that the couplings are properly installed on the pipes.

SUMMARY OF THE INVENTION

0008The invention concerns a method for connecting pipe elements together end-to-end. The pipe elements have circumferential grooves proximate to each end. The method comprises: <ul id="ul0001" list-style="none"><li id="ul0001-0001" num="0000"><ul id="ul0002" list-style="none"><li id="ul0002-0001" num="0009">providing a coupling comprising a plurality of segments joined end-to-end by a plurality of adjustably tightenable fasteners, each of the segments having a pair of keys projecting radially inwardly, the keys being positioned in spaced apart relation from one another and defining a space therebetween, at least one of the keys on one of the segments having a first camming surface positioned adjacent to one end of the segment, the first camming surface facing away from the space between the keys and being angularly oriented relatively thereto;</li><li id="ul0002-0002" num="0010">positioning a first and a second of the pipe elements in end-to-end relation;</li><li id="ul0002-0003" num="0011">positioning the plurality of segments surrounding ends of the first and second pipe elements;</li><li id="ul0002-0004" num="0012">engaging the first camming surface with the groove in one of the first and second pipe elements;</li><li id="ul0002-0005" num="0013">applying the fasteners to the segments; and</li><li id="ul0002-0006" num="0014">tightening the fasteners so as to draw the segments toward one another, the first camming surface sliding into the groove and thereby moving the first and second pipe elements away from one another.</li></ul></li></ul>

BRIEF DESCRIPTION OF THE DRAWINGS

0015<figref idref="DRAWINGS">FIG. 1</figref> is a perspective view of a coupling for connecting two pipes end to end, the pipes being shown in phantom line;

0016<figref idref="DRAWINGS">FIG. 1A</figref> is a perspective view showing a detail of the coupling depicted in <figref idref="DRAWINGS">FIG. 1</figref>;

0017<figref idref="DRAWINGS">FIG. 2</figref> is an exploded perspective view of the pipe coupling shown in <figref idref="DRAWINGS">FIG. 1</figref>;

0018<figref idref="DRAWINGS">FIG. 2A</figref> is an exploded perspective view of an alternate embodiment of a pipe coupling according to the invention;

0019<figref idref="DRAWINGS">FIG. 2B</figref> is a perspective view of a portion of <figref idref="DRAWINGS">FIG. 2</figref> shown on an enlarged scale;

0020<figref idref="DRAWINGS">FIG. 3</figref> is a side view of a segment comprising the coupling shown in <figref idref="DRAWINGS">FIG. 1</figref>;

0021<figref idref="DRAWINGS">FIG. 4</figref> is a bottom view of the segment shown in <figref idref="DRAWINGS">FIG. 3</figref>;

0022<figref idref="DRAWINGS">FIG. 4A</figref> is a side view of an alternate embodiment of a segment having one key and a flange for mating with flanged pipes or fittings;

0023<figref idref="DRAWINGS">FIG. 5</figref> is a cross-sectional view taken at line <b>5</b>-<b>5</b> of <figref idref="DRAWINGS">FIG. 1</figref>;

0024<figref idref="DRAWINGS">FIGS. 5A and 5B</figref> are cross sectional views taken at line <b>5</b>-<b>5</b> of <figref idref="DRAWINGS">FIG. 1</figref> showing alternate embodiments of the coupling according to the invention;

0025<figref idref="DRAWINGS">FIGS. 6 and 7</figref> are side views of a roller tool forming a groove in a pipe;

0026<figref idref="DRAWINGS">FIGS. 7A-7G</figref> show side views of various embodiments of roller tools for forming a groove in a pipe;

0027<figref idref="DRAWINGS">FIG. 8</figref> is a cross-sectional view of an alternate embodiment of the coupling;

0028<figref idref="DRAWINGS">FIG. 9</figref> is a partial perspective view of an alternate embodiment of a coupling according to the invention;

0029<figref idref="DRAWINGS">FIGS. 10-15</figref> are longitudinal sectional views of embodiments of pipes having circumferential grooves according to the invention; and

0030<figref idref="DRAWINGS">FIGS. 16-21</figref> illustrate various fittings and components having circumferential grooves according to the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

0031<figref idref="DRAWINGS">FIG. 1</figref> shows a pipe coupling <b>10</b> for connecting two pipes <b>12</b> and <b>14</b> co-axially end to end. As shown in <figref idref="DRAWINGS">FIG. 2</figref>, coupling <b>10</b> is comprised of at least two segments <b>16</b> and <b>18</b>. Each segment <b>16</b> and <b>18</b> has lugs <b>20</b> and <b>22</b> respectively, the lugs being positioned at or proximate to each end of the segments. The lugs <b>20</b> at each end of segment <b>16</b> align with the lugs <b>22</b> at each end of segment <b>18</b>. Lugs <b>20</b> and <b>22</b> are adapted to receive fasteners, preferably in the form of bolts <b>24</b> and nuts <b>26</b> for joining the segments to one another end to end surrounding the pipes <b>12</b> and <b>14</b>. In one embodiment, shown in <figref idref="DRAWINGS">FIG. 1</figref>, the lugs <b>20</b> engage the lugs <b>22</b> in what is known as “pad-to-pad engagement” with the lugs contacting one another when the segments <b>16</b> and <b>18</b> are properly engaged with the pipes <b>12</b> and <b>14</b> as explained below. The lugs may also be attached to each other in spaced apart relation when the segments <b>16</b> and <b>18</b> are properly engaged with the pipes <b>12</b> and <b>14</b>, as illustrated in <figref idref="DRAWINGS">FIG. 1A</figref>.

0032Although lugs are the preferred means for attaching the segments to one another end to end, it is recognized that there are other attachment means, such as circumferential bands, axial pins, and latching handles. These means are disclosed in U.S. Pat. Nos. 1,541,601, 2,014,313, 2,362,454, 2,673,102, 2,752,174, 3,113,791, and 4,561,678, all of which are hereby incorporated by reference.

0033For large diameter pipes, it is sometimes advantageous to form the coupling <b>10</b> from more than two segments. As shown in <figref idref="DRAWINGS">FIG. 2A</figref>, pipe coupling <b>10</b> comprises segments <b>16</b>a and <b>16</b>b joined to each other and to segments <b>18</b>a and <b>18</b>b, also joined to one another. Each segment again preferably has lugs <b>20</b> and <b>22</b> at each end thereof, the segments being joined to one another end to end by fasteners such as bolts <b>24</b> and nuts <b>26</b>. The following description of the coupling <b>10</b> is provided by way of example, and is based upon a coupling having two segments with lugs at either end. Various aspects of the description are applicable to alternate embodiments regardless of the number of segments comprising the coupling or the manner in which the segments are attached to one another.

0034As shown in <figref idref="DRAWINGS">FIG. 2</figref>, each segment <b>16</b> and <b>18</b> has an arcuate surface <b>28</b> facing inwardly toward pipes <b>12</b> and <b>14</b>. A pair keys <b>30</b> project radially inwardly from the arcuate surface <b>28</b>. Keys <b>30</b> on each segment are in spaced apart relation to one another and define a space <b>32</b> between them. As best shown in <figref idref="DRAWINGS">FIG. 5</figref>, to effect the connection between pipes <b>12</b> and <b>14</b>, keys <b>30</b> engage grooves <b>34</b> and <b>36</b> extending circumferentially around pipes <b>12</b> and <b>14</b> respectively. Engagement of keys <b>30</b> with grooves <b>34</b> and <b>36</b> substantially rigidly connect the pipes <b>12</b> and <b>14</b> coaxially to one another and maintain them at a predetermined separation as indicated by the gap <b>38</b>. A sealing member <b>40</b> is positioned within space <b>32</b> and between the arcuate surfaces <b>28</b> of segments <b>16</b> and <b>18</b> and the pipes <b>12</b> and <b>14</b>. The gap <b>38</b> between the pipes <b>12</b> and <b>14</b> provides tolerance facilitating mounting of the coupling and allows pressurized fluid to apply hydraulic pressure to the sealing member <b>40</b> and ensure a fluid tight seal between the pipes <b>12</b> and <b>14</b>.

0035As best shown in <figref idref="DRAWINGS">FIGS. 2 and 3</figref>, each key <b>30</b> preferably has a pair of camming surfaces <b>42</b> positioned adjacent to lugs <b>20</b> and <b>22</b> or otherwise near the ends of the segments. Camming surfaces <b>42</b> preferably face outwardly away from space <b>32</b> and are angularly oriented, as shown in <figref idref="DRAWINGS">FIG. 2B</figref>, with respect to an axis <b>43</b> oriented substantially tangential to the key <b>30</b>. The camming surfaces have an angular orientation <b>45</b> that forms a wedge <b>46</b> adjacent to each lug, also shown in <figref idref="DRAWINGS">FIG. 4</figref>. As the segments <b>16</b> and <b>18</b> are brought into engagement with grooves <b>34</b> and <b>36</b> to connect pipe <b>12</b> to pipe <b>14</b> as illustrated in <figref idref="DRAWINGS">FIG. 5</figref>, the camming surfaces <b>42</b> (see <figref idref="DRAWINGS">FIG. 2</figref>) are the first surfaces to engage the grooves <b>34</b> and <b>36</b>. The wedge <b>46</b> formed by the camming surfaces <b>42</b> provides a mechanical advantage which forces the pipes <b>12</b> and <b>14</b> apart from one another as the lugs <b>20</b> and <b>22</b> of segments <b>16</b> and <b>18</b> are brought toward one another, preferably into pad-to-pad engagement. This wedging action ensures that a separation gap <b>38</b> between the pipe ends (see <figref idref="DRAWINGS">FIG. 5</figref>) will be achieved when the connection between the pipes <b>12</b> and <b>14</b> is effected while reducing the force required to bring the lugs <b>20</b> and <b>22</b> toward each other. Lugs <b>20</b> and <b>22</b> are normally drawn toward each other by tightening nuts <b>26</b> (see <figref idref="DRAWINGS">FIG. 1</figref>). The mechanical advantage obtained by the use of wedge <b>46</b> significantly reduces the torque applied to nuts <b>26</b> needed to bring the lugs <b>20</b> and <b>22</b> into pad-to-pad engagement to separate the pipes <b>12</b> and <b>14</b> by the gap <b>38</b>, and thereby allows large diameter, heavy pipes to be manually connected, even when stacked vertically above one another. Such configurations are a particular problem as the insertion of the keys <b>30</b> into the grooves <b>34</b> and <b>36</b> must lift the entire weight of the pipe to form the gap <b>38</b>. The wedge <b>46</b> makes this effort significantly easier. Preferably, as shown in <figref idref="DRAWINGS">FIG. 2B</figref>, the angular orientation <b>45</b> of camming surfaces <b>42</b>, as measured with respect to axis <b>43</b>, is preferably about 5°, but may be up to about 10° for practical designs.

0036The use of keys having camming surfaces is not confined to couplings for joining grooved pipes to one another, but may be used on practically any coupling arrangement having at least one key. <figref idref="DRAWINGS">FIG. 4A</figref> shows a coupling segment <b>51</b> used in conjunction with a similar coupling segment to attach grooved pipe to flanged pipe. Coupling segment <b>51</b> has an arcuate key <b>30</b> with camming surfaces <b>42</b> at either end. As described above, the camming surfaces may be angularly oriented tangentially with respect to the key <b>30</b> and form a wedge <b>46</b> as shown in <figref idref="DRAWINGS">FIG. 4</figref>. Opposite the key is a flange <b>53</b> adapted to engage a mating flange on a flanged pipe. The flanges are secured via fasteners that pass though bolt holes <b>55</b> as is understood for flanged connections. The coupling segment <b>51</b> is attached end to end to its associated coupling segment by attachment means, preferably lugs <b>20</b> positioned near the ends of the segment that align and are engaged by fasteners as is understood in the art and described above.

0037As best shown in <figref idref="DRAWINGS">FIGS. 5 and 5A</figref>, keys <b>30</b> preferably have a shape that will effect a wedging action when they engage grooves <b>34</b> and <b>36</b>. <figref idref="DRAWINGS">FIG. 5</figref> illustrates one configuration wherein keys <b>30</b> have a wedge-shaped cross section. The keys <b>30</b> are defined by an inner surface <b>50</b> facing space <b>32</b>, an outer surface <b>52</b> facing outwardly away from space <b>32</b>, and a radial surface <b>54</b> positioned between the inner and outer surfaces and facing radially inwardly toward the pipes engaged by the coupling. Preferably, the inner surface <b>50</b> is oriented substantially perpendicularly to the axis <b>48</b> and outer surface <b>52</b> is oriented angularly relative to the axis <b>48</b> so as to form the wedge-shaped cross section of keys <b>30</b>. The relative angle <b>56</b>, measured radially with respect to the key between the outer surface <b>52</b> and an axis <b>48</b> oriented substantially co-axially with the longitudinal axes of pipes <b>12</b> and <b>14</b>, ranges up to about 70°, although 50° is preferred (see also <figref idref="DRAWINGS">FIG. 1</figref>).

0038Although surfaces <b>52</b> and <b>54</b> in <figref idref="DRAWINGS">FIG. 5</figref> are shown in cross-section as having a straight profile, they may be, for example, convex, concave or have some other profile shape and still effect a wedging action when engaged with grooves <b>34</b> and <b>36</b>. An alternate embodiment of keys <b>30</b> is illustrated in <figref idref="DRAWINGS">FIG. 5A</figref> wherein surface <b>50</b> has a curved cross sectional profile in the form of a convex radius that substantially blends into radial surface <b>54</b>.

0039As shown in <figref idref="DRAWINGS">FIG. 4</figref>, it is preferred that the radial angular orientation <b>44</b> of camming surfaces <b>42</b> be substantially equal to the radial angular orientation <b>56</b> of the key outer surface <b>52</b> as measured relatively to the longitudinal axis <b>48</b>. It is advantageous to match the radial orientation angles of the camming surfaces <b>42</b> and the key outer surfaces <b>52</b> with one another to avoid point contact when the surfaces engage facing surfaces of the grooves <b>34</b> and <b>36</b> as the coupling is installed in order to mitigate gouging between the surfaces that results from point to point contact.

0040Preferably, the grooves <b>34</b> and <b>36</b> that keys <b>30</b> engage have a shape that is complementary to the wedge-shape cross section of the keys. In general, it is advantageous that the keys have a cross sectional shape that substantially fills the grooves even when the shapes of the groove and key are not exactly complementary. Groove <b>36</b> is described in detail hereafter, groove <b>34</b> being substantially similar and not requiring a separate description. Groove <b>36</b> is defined by a first side surface <b>58</b> positioned proximate to end <b>14</b>a of pipe <b>14</b>, a second side surface <b>60</b> positioned in spaced apart relation to the first side surface <b>58</b> and distally from the end <b>14</b>a, and a floor surface <b>62</b> that extends between the first and second side surfaces. The complementary shape of the groove <b>36</b> to the keys <b>30</b> is achieved by orienting the floor surface <b>62</b> substantially parallel to the radial surface <b>54</b>, orienting the first side surface <b>58</b> substantially perpendicularly to the floor surface <b>62</b> (and thus substantially parallel to the inner surface <b>50</b>), and orienting the second side surface <b>60</b> substantially parallel to the outer surface <b>52</b> (and thus angularly to the floor surface <b>62</b>).

0041Preferably, the keys <b>30</b> and the lugs <b>20</b> and <b>22</b> are sized and toleranced so that when the lugs <b>20</b> are in pad-to-pad engagement with the lugs <b>22</b>, i.e., in contact with each other as shown in <figref idref="DRAWINGS">FIG. 1</figref>, the keys <b>30</b> engage the grooves <b>34</b> such that the keys' outer surface <b>52</b> is either just contacting the second side surface <b>60</b> in what is called “line-on-line clearance” (see the left halt of <figref idref="DRAWINGS">FIG. 5</figref>), or is in spaced relation to the second side surface <b>60</b> of the groove, as defined by a gap <b>64</b> no greater than 0.035 inches (shown on the right half of <figref idref="DRAWINGS">FIG. 5</figref>. Furthermore, the radial surface <b>54</b> is also in either line on line clearance with the floor surface <b>62</b> (left half, <figref idref="DRAWINGS">FIG. 5</figref>), or in spaced relation to floor surface <b>62</b>, as defined by a gap <b>66</b> no greater than 0.030 inches (right half, <figref idref="DRAWINGS">FIG. 5</figref>). The inner surface <b>50</b> is nominally in contact with the first side surface <b>58</b> as shown in <figref idref="DRAWINGS">FIG. 5</figref>, but there may be a gap there as well for certain tolerance conditions. As a practical matter, however, it is difficult and costly to make pipes and couplings perfectly round and to the exact dimensions desired, so that there will be intermittent contact between various surfaces of the keys <b>30</b> and grooves <b>34</b> and <b>36</b> circumferentially around any pipe joint, creating an effectively rigid joint. Joint rigidity may be further augmented by the use of teeth <b>31</b> that project outwardly from the various surfaces of keys <b>30</b> as best shown in <figref idref="DRAWINGS">FIG. 2</figref>. Teeth <b>31</b> bite into the groove surfaces of the pipes, augmenting friction to help prevent rotational displacement of the pipes relatively to the couplings. The same relationships between the various surfaces mentioned above may also be achieved when the lugs are attached to one another in spaced apart relation as shown in <figref idref="DRAWINGS">FIG. 1A</figref>.

0042Analogous relationships between the key surfaces and the surfaces comprising the grooves are contemplated even when the keys do not have a shape complementary to that of the groove, as shown in <figref idref="DRAWINGS">FIG. 5A</figref>. Couplings having such keys, for example, the convex shaped key <b>30</b>, may have surfaces <b>52</b> that just contact the second side surface <b>60</b> in line on line clearance (left side, <figref idref="DRAWINGS">FIG. 5A</figref>), or be in spaced relation to surface <b>60</b> (right side, <figref idref="DRAWINGS">FIG. 5A</figref>), having a gap <b>64</b> between the surfaces <b>52</b> and <b>60</b> of about 0.035 inches. Again, surfaces <b>54</b> and <b>66</b> may also be in line on line clearance or may be separated by a gap <b>62</b>, preferably no greater than 0.030 inches.

0043Alternately, as shown in <figref idref="DRAWINGS">FIG. 5B</figref>, wedging action of keys <b>30</b> may also be ensured when inner surface <b>50</b> and outer surface <b>52</b> contact groove surfaces <b>58</b> and <b>60</b>, respectively, but radial surface <b>54</b> is in spaced relation to the groove's floor surface <b>62</b> with a gap <b>66</b>. The right side of <figref idref="DRAWINGS">FIG. 5B</figref> shows various straight sided key surfaces <b>50</b>, <b>52</b> and <b>54</b> and counterpart straight sided groove surfaces <b>58</b>, <b>60</b> and <b>62</b> giving the groove and the key substantially complementary shapes. The left side of <figref idref="DRAWINGS">FIG. 5B</figref> shows a convexly curved outer surface <b>52</b> engaging a straight surface <b>60</b>, as an example wherein the shape of the key and the groove are not substantially complementary. Note that groove floor surface <b>62</b> is shown on the left side to be angularly oriented with respect to the surface of pipe <b>12</b>.

0044It is found that the preferred configuration defined by pad-to-pad engagement of lugs <b>20</b> and <b>22</b> in conjunction with the tolerance conditions as describe above provides several advantages. The engagement of inner surface <b>50</b> with first side surface <b>58</b> forces pipes <b>12</b> and <b>14</b> into substantially precise axial position relative to one another. Because these surfaces bear against one another when the coupling is installed on the pipes they will not shift axially when internal fluid pressure is applied. Thus, designers need not take into account lengthening of the piping network due to internal pressure during use, thereby simplifying the design. The relatively small gaps <b>64</b> and <b>66</b> (which could be zero) ensure adequate rigidity and prevent excessive angular displacement between the pipes and the couplings, while the tolerances necessary to limit the gaps within the desired limits allow the coupling <b>10</b> to be manufactured economically. It also allows the grooves in the pipes, valves or other fittings to be manufactured economically. The gaps work advantageously in conjunction with the normally encountered out of roundness of practical pipes to provide a rigid joint. The pad-to-pad engagement of lugs <b>20</b> and <b>22</b> provides a reliable visual indication that the coupling <b>10</b> is properly engaged with the pipes <b>12</b> and <b>14</b>.

0045If it is desired to have a more flexible coupling <b>10</b> to allow greater angular deflection, then the gaps <b>64</b> at one or both ends of the coupling may be made larger than the aforementioned limit of 0.035 inches. For flexible couplings, it is found advantageous to have gap <b>64</b> between surfaces <b>52</b> and <b>60</b> preferably be ½ of the size of gap <b>38</b> between the ends of pipes <b>12</b> and <b>14</b> as shown in <figref idref="DRAWINGS">FIG. 5</figref>.

0046It is also feasible to have keys <b>30</b> engage grooves <b>34</b> and <b>36</b> without a gap under all tolerance conditions. This configuration takes advantage of the wedging action of the keys to provide a rigid joint. It is not practical, however, to have this configuration and also maintain pad to pad engagement of lugs <b>20</b> and <b>22</b> because it is very difficult to economically manufacture couplings and pipes to the necessary tolerances to ensure both pad to pad engagement and full contact circumferential wedging engagement of the keys and grooves. For the configuration wherein pad-to-pad engagement is not nominally held, as shown in <figref idref="DRAWINGS">FIG. 9</figref>, it is preferred to employ a tongue <b>110</b> adjacent to the lug <b>20</b> on segment <b>16</b> that fits into a recess <b>112</b> adjacent to lug <b>22</b> on segment <b>18</b>. The tongue prevents sealing member <b>40</b> from blowing out through a gap between the lugs <b>20</b> and <b>22</b> when the joint is subjected to high internal pressure.

0047As illustrated in <figref idref="DRAWINGS">FIG. 6</figref>, groove <b>36</b> is advantageously formed by cold working the material forming pipe <b>14</b>. In a preferred embodiment, groove <b>36</b> comprises a first side surface <b>37</b> positioned proximate to the end of pipe <b>14</b>, a second side surface <b>60</b> positioned in spaced apart relation to the first side surface and distally to the end of the pipe, and a floor <b>41</b> that extends between the first and second side surfaces. Preferably, the second side surface is angularly oriented relatively to the floor at an angle <b>43</b> that is than 90 degrees.

0048A roller tool <b>68</b> is used having a cross sectional shape at its periphery substantially identical to the desired shape of the groove. The roller tool <b>68</b> is forcibly engaged with the outer surface <b>70</b> of pipe <b>14</b> around its circumference, either by moving the roller tool around the pipe or moving the pipe about its longitudinal axis <b>48</b> relatively to a roller tool. Preferably, a back-up roller <b>72</b> engages the inner surface <b>74</b> of the pipe <b>14</b> opposite to the roller tool <b>68</b>. The pipe wall <b>76</b> is compressed between the roller tool <b>68</b> and the back-up roller <b>72</b>. Use of the back-up roller <b>72</b> provides a reaction surface for the roller tool. The back-up roller also helps ensure that accurate groove shapes are achieved by facilitating material flow during roll grooving.

0049During cold working to form the groove <b>36</b> having the angularly oriented second side surface <b>60</b>, it is found that significant friction is developed between the roller tool <b>68</b> and the pipe <b>14</b>. The friction is caused by the contact between the angled surface <b>78</b> on the roller tool <b>68</b> that forms the angularly oriented second side surface <b>60</b> of groove <b>36</b>. Because it is angled, points along angled surface <b>78</b> are at different distances from the axis of rotation <b>80</b> of roller tool <b>68</b>. Due to their different distances from the axis <b>80</b>, each of the points on the surface <b>78</b> will move relative to one another at a different linear speed for a particular angular velocity of the roller tool <b>68</b>. The points farthest from the axis <b>80</b> move the fastest and the points closest to the axis move the slowest. Thus, there is a velocity differential along the angled surface <b>78</b> which causes the surface to slip relatively to the second side surface <b>60</b> of groove <b>36</b> as the roller tool <b>68</b> rotates relatively to the pipe <b>14</b> to form the groove. The relative slipping between the roller tool and the pipe causes the friction. Excessive heat caused by the friction can result in a break down of the roller tool bearing lubricants and make the roller tool too hot to handle when changing tools for a different size pipe. The roller tool must be allowed to cool before it can be changed, resulting in lost time.

0050To mitigate the generation of excessive heat, the roller tool <b>82</b>, shown in <figref idref="DRAWINGS">FIG. 7</figref>, is used to form a groove <b>84</b> in pipe <b>14</b>. In groove <b>84</b>, the second side surface <b>86</b> has a first surface portion <b>88</b> oriented angularly relative to the floor surface <b>90</b>, and a second surface portion <b>92</b>, positioned adjacent to the floor surface <b>90</b> and oriented substantially perpendicular to it, thereby reducing the size of the angularly oriented second side surface <b>86</b>. By reducing the size of the angled surface regions on both the roller tool <b>82</b> and the groove <b>84</b> the friction caused during cold working to form the groove is reduced. The first surface portion <b>88</b>, being angularly oriented, still provides the advantages as described above for the second side surface <b>60</b>. An example of a coupling <b>10</b> engaging a groove <b>84</b> is shown in <figref idref="DRAWINGS">FIG. 8</figref>.

0051The roller tool <b>82</b> has a circumferential surface <b>94</b> with a cross sectional shape complementary to groove <b>84</b>, the shape comprising a first perimetral surface <b>99</b> oriented substantially perpendicularly to the axis of rotation <b>80</b> of roller tool <b>82</b>, a second perimetral surface <b>98</b> positioned in spaced relation to the first perimetral surface <b>96</b> and oriented substantially perpendicular to the axis <b>80</b>, a radial surface <b>100</b> extending between the first and second perimetral surfaces and oriented substantially parallel to axis <b>80</b>, and an angled surface <b>102</b> positioned adjacent to perimetral surface <b>100</b> and oriented angularly to the axis <b>80</b>. The angled surface <b>102</b> is preferably oriented up to about 70° relatively to axis <b>80</b>, and most preferably at about 50°. Surface <b>102</b> slopes away from the second perimetral surface, thereby making contact with the pipe when forming the groove <b>84</b>.

0052Wedging action between the keys <b>30</b> and grooves in the pipes can be achieved for groove cross sectional shapes other than those described above. The main criterion for wedging action is that the width of the groove at the surface of the pipe be greater than the width of the groove at the floor of the groove. <figref idref="DRAWINGS">FIGS. 10-15</figref> show various groove configurations meeting this criteria. <figref idref="DRAWINGS">FIG. 10</figref> shows a groove <b>114</b> partially defined by a side portion <b>116</b> having a concave cross sectional shape. <figref idref="DRAWINGS">FIG. 11</figref> shows a groove <b>118</b> partially defined by a side portion <b>120</b> having a convex cross-sectional shape. In <figref idref="DRAWINGS">FIG. 12</figref>, the groove <b>122</b> is partially defined by a side portion <b>124</b> having first and second angled portions <b>124</b>a and <b>124</b>b, the first angled portion <b>124</b>a having a greater slope than the second angled portion <b>124</b>b. <figref idref="DRAWINGS">FIG. 13</figref> shows a groove <b>126</b> partially defined by a side portion <b>128</b> having a first angled portion <b>128</b>a with a slope less than the second angled portion <b>128</b>b. Combinations of radius and angled portions are also feasible, as shown in <figref idref="DRAWINGS">FIG. 14</figref>, wherein groove <b>130</b> has a radius portion <b>132</b> and an angled portion <b>134</b>. <figref idref="DRAWINGS">FIG. 15</figref> illustrates an example of a groove <b>136</b> having a wedge-shaped cross sectional profile, there being no floor portion of any significance as compared with the other example grooves. The groove <b>136</b> is defined by side portions <b>136</b>a and <b>136</b>b oriented angularly with respect to one another. Common to all of the designs is the characteristic that the width <b>138</b> of the groove at the surface of the pipe is greater than the width <b>140</b> of the groove at the floor of the groove. Note that, although it is preferred that the floor be substantially parallel to the pipe surface, it may also be curved, as shown in <figref idref="DRAWINGS">FIG. 10</figref>, or non-existent, as shown in <figref idref="DRAWINGS">FIG. 15</figref>, which has no floor, the floor width being essentially zero. The floor may also be angularly oriented as shown in <figref idref="DRAWINGS">FIG. 5B</figref>.

0053Roller tools for creating grooves as described above are shown in <figref idref="DRAWINGS">FIGS. 7A-7G</figref>. In <figref idref="DRAWINGS">FIG. 7A</figref>, roller tool <b>101</b> is rotatable about axis <b>80</b> and has a radially facing surface portion <b>103</b> flanked by a first surface portion <b>105</b> and a second surface portion <b>107</b>. Roller surface portion <b>105</b> is preferably oriented perpendicularly to axis <b>80</b> and results in the formation of a substantially vertical groove side surface. Roller surface portion is concave and results in the convex groove side surface <b>120</b> as shown in <figref idref="DRAWINGS">FIG. 11</figref>.

0054Similarly, roller tool <b>109</b>, shown in <figref idref="DRAWINGS">FIG. 7B</figref>, has a radially facing surface portion <b>111</b> extending between a perpendicular surface portion <b>113</b> and a convex surface portion <b>115</b>. Such a roller produces a groove with a concave side surface <b>116</b> as shown in <figref idref="DRAWINGS">FIG. 10</figref>.

0055Additional roller embodiments <b>117</b> and <b>119</b>, shown in <figref idref="DRAWINGS">FIGS. 7C and 7D</figref>, each have a surface portion <b>121</b> with a first face <b>123</b> angularly oriented with respect to axis <b>80</b>, and a second face <b>125</b>, also angularly oriented with respect to axis <b>80</b>, but at a different angle. In roller tool <b>117</b>, the slope of the first surface portion is greater than the slope of the second surface portion, and this roller produces a groove <b>122</b> as shown in <figref idref="DRAWINGS">FIG. 12</figref>. In roller tool <b>119</b>, the slope of the first surface portion is less than the slope of the second surface portion, and this roller produces a groove <b>126</b>, having an angularly oriented side surface <b>124</b> as shown in <figref idref="DRAWINGS">FIG. 13</figref>.

0056Roller tool <b>127</b>, shown in <figref idref="DRAWINGS">FIG. 7E</figref>, has no radially facing surface, an angled surface <b>129</b> intersects with a surface portion <b>131</b> that is substantially perpendicular to the axis of rotation <b>80</b>. Roller tool <b>127</b> is useful for creating the groove shown in <figref idref="DRAWINGS">FIG. 15</figref>.

0057Roller tool <b>133</b>, shown in <figref idref="DRAWINGS">FIG. 7F</figref>, has a curved radially facing surface <b>135</b> and an angularly oriented surface <b>135</b> as well as a perpendicular surface <b>137</b>. The curved surface may be convex, concave, sinusoidal, hyperbolic, or irregularly curved.

0058As shown in <figref idref="DRAWINGS">FIG. 7G</figref>, the roller <b>139</b> may have a radially facing surface <b>141</b> that is angularly oriented with respect to the axis of rotation <b>80</b>. A groove as shown in <figref idref="DRAWINGS">FIG. 5B</figref> is produced by such a tool.

0059While grooves adapted to achieve significant wedging action with the keys of a coupling have been described applied to pipe ends, such grooves may also be used in conjunction with pipe fittings as well. For example, <figref idref="DRAWINGS">FIG. 16</figref> shows an elbow fitting <b>140</b> having circumferential grooves <b>142</b> at either end. Grooves <b>142</b> may have any of the cross sectional profiles illustrated in FIGS. <b>5</b> and <b>10</b>-<b>15</b> or their variations as described above. Similarly, the Tee fitting <b>144</b> shown in <figref idref="DRAWINGS">FIG. 17</figref> has grooves <b>146</b>, preferably adjacent to each of its ends, the grooves being adapted to develop wedging action to couple the fitting to pipes or other fittings as described herein. <figref idref="DRAWINGS">FIG. 18</figref> shows a fitting <b>148</b> having a wedging groove <b>150</b> adjacent to one end and a flange <b>152</b> at the opposite end. Fitting <b>148</b> allows a piping network using mechanical couplings to be joined to another network coupled using flanges. Furthermore, as illustrated in <figref idref="DRAWINGS">FIGS. 19 and 20</figref>, other types of fittings such as a reducer <b>154</b> (<figref idref="DRAWINGS">FIG. 19</figref>) used to join pipes having different diameters, or a nipple <b>156</b> (<figref idref="DRAWINGS">FIG. 20</figref>) may also benefit from having respective grooves <b>158</b> and <b>160</b> that are like those illustrated and described above that increase the wedging action between the coupling and the groove to ensure either a stiffer or more flexible joint, depending upon the tolerances of the coupling as described above.

0060As further shown in <figref idref="DRAWINGS">FIG. 21</figref>, components related to control of fluid flow, such as a valve <b>162</b> may also have grooves <b>164</b> that are like those described above to couple the valve to pipes, fittings or other components using mechanical couplings as described herein.

0061Pipe couplings according to the invention incorporate the advantages of a rigid or flexible connection with a reliable visual indicator for confirming that the coupling properly engages the pipes to effect a fluid tight joint. The couplings provide a mechanical advantage which allows manual assembly of piping networks of substantial diameter despite their weight. The couplings have tolerances allowing them to be economically produced and still yield a substantially rigid joint between pipes.