Abstract:
A method for connecting pipe elements together end to end. The method includes providing a coupling having a plurality of segments with at least one camming surface, the segments being joined end to end by a plurality of adjustably tightenable fasteners, positioning a first and a second of the pipe elements in end to end relation, positioning the segments surrounding the ends of the pipe elements, engaging the camming surfaces on the segments with grooves on the pipe elements and tightening the fasteners so as to draw the segments toward one another. The camming surfaces slide into the grooves and move the first and second pipe elements away from one another.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 11/091,216 filed Mar. 28, 2005, which claims priority to U.S. Provisional Application No. 60/556,962, filed Mar. 26, 2004. 
    
    
     FIELD OF THE INVENTION 
     The 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 
     Couplings 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. 
     The 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. 
     It 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. 
     Many 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. 
     It 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 
     The 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:
         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;   positioning a first and a second of the pipe elements in end-to-end relation;   positioning the plurality of segments surrounding ends of the first and second pipe elements;   engaging the first camming surface with the groove in one of the first and second pipe elements;   applying the fasteners to the segments; and   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.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a coupling for connecting two pipes end to end, the pipes being shown in phantom line; 
         FIG. 1A  is a perspective view showing a detail of the coupling depicted in  FIG. 1 ; 
         FIG. 2  is an exploded perspective view of the pipe coupling shown in  FIG. 1 ; 
         FIG. 2A  is an exploded perspective view of an alternate embodiment of a pipe coupling according to the invention; 
         FIG. 2B  is a perspective view of a portion of  FIG. 2  shown on an enlarged scale; 
         FIG. 3  is a side view of a segment comprising the coupling shown in  FIG. 1 ; 
         FIG. 4  is a bottom view of the segment shown in  FIG. 3 ; 
         FIG. 4A  is a side view of an alternate embodiment of a segment having one key and a flange for mating with flanged pipes or fittings; 
         FIG. 5  is a cross-sectional view taken at line  5 - 5  of  FIG. 1 ; 
         FIGS. 5A and 5B  are cross sectional views taken at line  5 - 5  of  FIG. 1  showing alternate embodiments of the coupling according to the invention; 
         FIGS. 6 and 7  are side views of a roller tool forming a groove in a pipe; 
         FIGS. 7A-7G  show side views of various embodiments of roller tools for forming a groove in a pipe; 
         FIG. 8  is a cross-sectional view of an alternate embodiment of the coupling; 
         FIG. 9  is a partial perspective view of an alternate embodiment of a coupling according to the invention; 
         FIGS. 10-15  are longitudinal sectional views of embodiments of pipes having circumferential grooves according to the invention; and 
         FIGS. 16-21  illustrate various fittings and components having circumferential grooves according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       FIG. 1  shows a pipe coupling  10  for connecting two pipes  12  and  14  co-axially end to end. As shown in  FIG. 2 , coupling  10  is comprised of at least two segments  16  and  18 . Each segment  16  and  18  has lugs  20  and  22  respectively, the lugs being positioned at or proximate to each end of the segments. The lugs  20  at each end of segment  16  align with the lugs  22  at each end of segment  18 . Lugs  20  and  22  are adapted to receive fasteners, preferably in the form of bolts  24  and nuts  26  for joining the segments to one another end to end surrounding the pipes  12  and  14 . In one embodiment, shown in  FIG. 1 , the lugs  20  engage the lugs  22  in what is known as “pad-to-pad engagement” with the lugs contacting one another when the segments  16  and  18  are properly engaged with the pipes  12  and  14  as explained below. The lugs may also be attached to each other in spaced apart relation when the segments  16  and  18  are properly engaged with the pipes  12  and  14 , as illustrated in  FIG. 1A . 
     Although 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. 
     For large diameter pipes, it is sometimes advantageous to form the coupling  10  from more than two segments. As shown in  FIG. 2A , pipe coupling  10  comprises segments  16   a  and  16   b  joined to each other and to segments  18   a  and  18   b , also joined to one another. Each segment again preferably has lugs  20  and  22  at each end thereof, the segments being joined to one another end to end by fasteners such as bolts  24  and nuts  26 . The following description of the coupling  10  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. 
     As shown in  FIG. 2 , each segment  16  and  18  has an arcuate surface  28  facing inwardly toward pipes  12  and  14 . A pair keys  30  project radially inwardly from the arcuate surface  28 . Keys  30  on each segment are in spaced apart relation to one another and define a space  32  between them. As best shown in  FIG. 5 , to effect the connection between pipes  12  and  14 , keys  30  engage grooves  34  and  36  extending circumferentially around pipes  12  and  14  respectively. Engagement of keys  30  with grooves  34  and  36  substantially rigidly connect the pipes  12  and  14  coaxially to one another and maintain them at a predetermined separation as indicated by the gap  38 . A sealing member  40  is positioned within space  32  and between the arcuate surfaces  28  of segments  16  and  18  and the pipes  12  and  14 . The gap  38  between the pipes  12  and  14  provides tolerance facilitating mounting of the coupling and allows pressurized fluid to apply hydraulic pressure to the sealing member  40  and ensure a fluid tight seal between the pipes  12  and  14 . 
     As best shown in  FIGS. 2 and 3 , each key  30  preferably has a pair of camming surfaces  42  positioned adjacent to lugs  20  and  22  or otherwise near the ends of the segments. Camming surfaces  42  preferably face outwardly away from space  32  and are angularly oriented, as shown in  FIG. 2B , with respect to an axis  43  oriented substantially tangential to the key  30 . The camming surfaces have an angular orientation  45  that forms a wedge  46  adjacent to each lug, also shown in  FIG. 4 . As the segments  16  and  18  are brought into engagement with grooves  34  and  36  to connect pipe  12  to pipe  14  as illustrated in  FIG. 5 , the camming surfaces  42  (see  FIG. 2 ) are the first surfaces to engage the grooves  34  and  36 . The wedge  46  formed by the camming surfaces  42  provides a mechanical advantage which forces the pipes  12  and  14  apart from one another as the lugs  20  and  22  of segments  16  and  18  are brought toward one another, preferably into pad-to-pad engagement. This wedging action ensures that a separation gap  38  between the pipe ends (see  FIG. 5 ) will be achieved when the connection between the pipes  12  and  14  is effected while reducing the force required to bring the lugs  20  and  22  toward each other. Lugs  20  and  22  are normally drawn toward each other by tightening nuts  26  (see  FIG. 1 ). The mechanical advantage obtained by the use of wedge  46  significantly reduces the torque applied to nuts  26  needed to bring the lugs  20  and  22  into pad-to-pad engagement to separate the pipes  12  and  14  by the gap  38 , 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  30  into the grooves  34  and  36  must lift the entire weight of the pipe to form the gap  38 . The wedge  46  makes this effort significantly easier. Preferably, as shown in  FIG. 2B , the angular orientation  45  of camming surfaces  42 , as measured with respect to axis  43 , is preferably about 5°, but may be up to about 10° for practical designs. 
     The 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.  FIG. 4A  shows a coupling segment  51  used in conjunction with a similar coupling segment to attach grooved pipe to flanged pipe. Coupling segment  51  has an arcuate key  30  with camming surfaces  42  at either end. As described above, the camming surfaces may be angularly oriented tangentially with respect to the key  30  and form a wedge  46  as shown in  FIG. 4 . Opposite the key is a flange  53  adapted to engage a mating flange on a flanged pipe. The flanges are secured via fasteners that pass though bolt holes  55  as is understood for flanged connections. The coupling segment  51  is attached end to end to its associated coupling segment by attachment means, preferably lugs  20  positioned near the ends of the segment that align and are engaged by fasteners as is understood in the art and described above. 
     As best shown in  FIGS. 5 and 5A , keys  30  preferably have a shape that will effect a wedging action when they engage grooves  34  and  36 .  FIG. 5  illustrates one configuration wherein keys  30  have a wedge-shaped cross section. The keys  30  are defined by an inner surface  50  facing space  32 , an outer surface  52  facing outwardly away from space  32 , and a radial surface  54  positioned between the inner and outer surfaces and facing radially inwardly toward the pipes engaged by the coupling. Preferably, the inner surface  50  is oriented substantially perpendicularly to the axis  48  and outer surface  52  is oriented angularly relative to the axis  48  so as to form the wedge-shaped cross section of keys  30 . The relative angle  56 , measured radially with respect to the key between the outer surface  52  and an axis  48  oriented substantially co-axially with the longitudinal axes of pipes  12  and  14 , ranges up to about 70°, although 50° is preferred (see also  FIG. 1 ). 
     Although surfaces  52  and  54  in  FIG. 5  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  34  and  36 . An alternate embodiment of keys  30  is illustrated in  FIG. 5A  wherein surface  50  has a curved cross sectional profile in the form of a convex radius that substantially blends into radial surface  54 . 
     As shown in  FIG. 4 , it is preferred that the radial angular orientation  44  of camming surfaces  42  be substantially equal to the radial angular orientation  56  of the key outer surface  52  as measured relatively to the longitudinal axis  48 . It is advantageous to match the radial orientation angles of the camming surfaces  42  and the key outer surfaces  52  with one another to avoid point contact when the surfaces engage facing surfaces of the grooves  34  and  36  as the coupling is installed in order to mitigate gouging between the surfaces that results from point to point contact. 
     Preferably, the grooves  34  and  36  that keys  30  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  36  is described in detail hereafter, groove  34  being substantially similar and not requiring a separate description. Groove  36  is defined by a first side surface  58  positioned proximate to end  14   a  of pipe  14 , a second side surface  60  positioned in spaced apart relation to the first side surface  58  and distally from the end  14   a , and a floor surface  62  that extends between the first and second side surfaces. The complementary shape of the groove  36  to the keys  30  is achieved by orienting the floor surface  62  substantially parallel to the radial surface  54 , orienting the first side surface  58  substantially perpendicularly to the floor surface  62  (and thus substantially parallel to the inner surface  50 ), and orienting the second side surface  60  substantially parallel to the outer surface  52  (and thus angularly to the floor surface  62 ). 
     Preferably, the keys  30  and the lugs  20  and  22  are sized and toleranced so that when the lugs  20  are in pad-to-pad engagement with the lugs  22 , i.e., in contact with each other as shown in  FIG. 1 , the keys  30  engage the grooves  34  such that the keys&#39; outer surface  52  is either just contacting the second side surface  60  in what is called “line-on-line clearance” (see the left halt of  FIG. 5 ), or is in spaced relation to the second side surface  60  of the groove, as defined by a gap  64  no greater than 0.035 inches (shown on the right half of  FIG. 5 . Furthermore, the radial surface  54  is also in either line on line clearance with the floor surface  62  (left half,  FIG. 5 ), or in spaced relation to floor surface  62 , as defined by a gap  66  no greater than 0.030 inches (right half,  FIG. 5 ). The inner surface  50  is nominally in contact with the first side surface  58  as shown in  FIG. 5 , 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  30  and grooves  34  and  36  circumferentially around any pipe joint, creating an effectively rigid joint. Joint rigidity may be further augmented by the use of teeth  31  that project outwardly from the various surfaces of keys  30  as best shown in  FIG. 2 . Teeth  31  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  FIG. 1A . 
     Analogous 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  FIG. 5A . Couplings having such keys, for example, the convex shaped key  30 , may have surfaces  52  that just contact the second side surface  60  in line on line clearance (left side,  FIG. 5A ), or be in spaced relation to surface  60  (right side,  FIG. 5A ), having a gap  64  between the surfaces  52  and  60  of about 0.035 inches. Again, surfaces  54  and  66  may also be in line on line clearance or may be separated by a gap  62 , preferably no greater than 0.030 inches. 
     Alternately, as shown in  FIG. 5B , wedging action of keys  30  may also be ensured when inner surface  50  and outer surface  52  contact groove surfaces  58  and  60 , respectively, but radial surface  54  is in spaced relation to the groove&#39;s floor surface  62  with a gap  66 . The right side of  FIG. 5B  shows various straight sided key surfaces  50 ,  52  and  54  and counterpart straight sided groove surfaces  58 ,  60  and  62  giving the groove and the key substantially complementary shapes. The left side of  FIG. 5B  shows a convexly curved outer surface  52  engaging a straight surface  60 , as an example wherein the shape of the key and the groove are not substantially complementary. Note that groove floor surface  62  is shown on the left side to be angularly oriented with respect to the surface of pipe  12 . 
     It is found that the preferred configuration defined by pad-to-pad engagement of lugs  20  and  22  in conjunction with the tolerance conditions as describe above provides several advantages. The engagement of inner surface  50  with first side surface  58  forces pipes  12  and  14  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  64  and  66  (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  10  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  20  and  22  provides a reliable visual indication that the coupling  10  is properly engaged with the pipes  12  and  14 . 
     If it is desired to have a more flexible coupling  10  to allow greater angular deflection, then the gaps  64  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  64  between surfaces  52  and  60  preferably be ½ of the size of gap  38  between the ends of pipes  12  and  14  as shown in  FIG. 5 . 
     It is also feasible to have keys  30  engage grooves  34  and  36  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  20  and  22  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  FIG. 9 , it is preferred to employ a tongue  110  adjacent to the lug  20  on segment  16  that fits into a recess  112  adjacent to lug  22  on segment  18 . The tongue prevents sealing member  40  from blowing out through a gap between the lugs  20  and  22  when the joint is subjected to high internal pressure. 
     As illustrated in  FIG. 6 , groove  36  is advantageously formed by cold working the material forming pipe  14 . In a preferred embodiment, groove  36  comprises a first side surface  37  positioned proximate to the end of pipe  14 , a second side surface  60  positioned in spaced apart relation to the first side surface and distally to the end of the pipe, and a floor  41  that extends between the first and second side surfaces. Preferably, the second side surface is angularly oriented relatively to the floor at an angle  43  that is than 90 degrees. 
     A roller tool  68  is used having a cross sectional shape at its periphery substantially identical to the desired shape of the groove. The roller tool  68  is forcibly engaged with the outer surface  70  of pipe  14  around its circumference, either by moving the roller tool around the pipe or moving the pipe about its longitudinal axis  48  relatively to a roller tool. Preferably, a back-up roller  72  engages the inner surface  74  of the pipe  14  opposite to the roller tool  68 . The pipe wall  76  is compressed between the roller tool  68  and the back-up roller  72 . Use of the back-up roller  72  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. 
     During cold working to form the groove  36  having the angularly oriented second side surface  60 , it is found that significant friction is developed between the roller tool  68  and the pipe  14 . The friction is caused by the contact between the angled surface  78  on the roller tool  68  that forms the angularly oriented second side surface  60  of groove  36 . Because it is angled, points along angled surface  78  are at different distances from the axis of rotation  80  of roller tool  68 . Due to their different distances from the axis  80 , each of the points on the surface  78  will move relative to one another at a different linear speed for a particular angular velocity of the roller tool  68 . The points farthest from the axis  80  move the fastest and the points closest to the axis move the slowest. Thus, there is a velocity differential along the angled surface  78  which causes the surface to slip relatively to the second side surface  60  of groove  36  as the roller tool  68  rotates relatively to the pipe  14  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. 
     To mitigate the generation of excessive heat, the roller tool  82 , shown in  FIG. 7 , is used to form a groove  84  in pipe  14 . In groove  84 , the second side surface  86  has a first surface portion  88  oriented angularly relative to the floor surface  90 , and a second surface portion  92 , positioned adjacent to the floor surface  90  and oriented substantially perpendicular to it, thereby reducing the size of the angularly oriented second side surface  86 . By reducing the size of the angled surface regions on both the roller tool  82  and the groove  84  the friction caused during cold working to form the groove is reduced. The first surface portion  88 , being angularly oriented, still provides the advantages as described above for the second side surface  60 . An example of a coupling  10  engaging a groove  84  is shown in  FIG. 8 . 
     The roller tool  82  has a circumferential surface  94  with a cross sectional shape complementary to groove  84 , the shape comprising a first perimetral surface  99  oriented substantially perpendicularly to the axis of rotation  80  of roller tool  82 , a second perimetral surface  98  positioned in spaced relation to the first perimetral surface  96  and oriented substantially perpendicular to the axis  80 , a radial surface  100  extending between the first and second perimetral surfaces and oriented substantially parallel to axis  80 , and an angled surface  102  positioned adjacent to perimetral surface  100  and oriented angularly to the axis  80 . The angled surface  102  is preferably oriented up to about 70° relatively to axis  80 , and most preferably at about 50°. Surface  102  slopes away from the second perimetral surface, thereby making contact with the pipe when forming the groove  84 . 
     Wedging action between the keys  30  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.  FIGS. 10-15  show various groove configurations meeting this criteria.  FIG. 10  shows a groove  114  partially defined by a side portion  116  having a concave cross sectional shape.  FIG. 11  shows a groove  118  partially defined by a side portion  120  having a convex cross-sectional shape. In  FIG. 12 , the groove  122  is partially defined by a side portion  124  having first and second angled portions  124   a  and  124   b , the first angled portion  124   a  having a greater slope than the second angled portion  124   b .  FIG. 13  shows a groove  126  partially defined by a side portion  128  having a first angled portion  128   a  with a slope less than the second angled portion  128   b . Combinations of radius and angled portions are also feasible, as shown in  FIG. 14 , wherein groove  130  has a radius portion  132  and an angled portion  134 .  FIG. 15  illustrates an example of a groove  136  having a wedge-shaped cross sectional profile, there being no floor portion of any significance as compared with the other example grooves. The groove  136  is defined by side portions  136   a  and  136   b  oriented angularly with respect to one another. Common to all of the designs is the characteristic that the width  138  of the groove at the surface of the pipe is greater than the width  140  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  FIG. 10 , or non-existent, as shown in  FIG. 15 , which has no floor, the floor width being essentially zero. The floor may also be angularly oriented as shown in  FIG. 5B . 
     Roller tools for creating grooves as described above are shown in  FIGS. 7A-7G . In  FIG. 7A , roller tool  101  is rotatable about axis  80  and has a radially facing surface portion  103  flanked by a first surface portion  105  and a second surface portion  107 . Roller surface portion  105  is preferably oriented perpendicularly to axis  80  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  120  as shown in  FIG. 11 . 
     Similarly, roller tool  109 , shown in  FIG. 7B , has a radially facing surface portion  111  extending between a perpendicular surface portion  113  and a convex surface portion  115 . Such a roller produces a groove with a concave side surface  116  as shown in  FIG. 10 . 
     Additional roller embodiments  117  and  119 , shown in  FIGS. 7C and 7D , each have a surface portion  121  with a first face  123  angularly oriented with respect to axis  80 , and a second face  125 , also angularly oriented with respect to axis  80 , but at a different angle. In roller tool  117 , the slope of the first surface portion is greater than the slope of the second surface portion, and this roller produces a groove  122  as shown in  FIG. 12 . In roller tool  119 , the slope of the first surface portion is less than the slope of the second surface portion, and this roller produces a groove  126 , having an angularly oriented side surface  124  as shown in  FIG. 13 . 
     Roller tool  127 , shown in  FIG. 7E , has no radially facing surface, an angled surface  129  intersects with a surface portion  131  that is substantially perpendicular to the axis of rotation  80 . Roller tool  127  is useful for creating the groove shown in  FIG. 15 . 
     Roller tool  133 , shown in  FIG. 7F , has a curved radially facing surface  135  and an angularly oriented surface  135  as well as a perpendicular surface  137 . The curved surface may be convex, concave, sinusoidal, hyperbolic, or irregularly curved. 
     As shown in  FIG. 7G , the roller  139  may have a radially facing surface  141  that is angularly oriented with respect to the axis of rotation  80 . A groove as shown in  FIG. 5B  is produced by such a tool. 
     While 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,  FIG. 16  shows an elbow fitting  140  having circumferential grooves  142  at either end. Grooves  142  may have any of the cross sectional profiles illustrated in FIGS.  5  and  10 - 15  or their variations as described above. Similarly, the Tee fitting  144  shown in  FIG. 17  has grooves  146 , 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.  FIG. 18  shows a fitting  148  having a wedging groove  150  adjacent to one end and a flange  152  at the opposite end. Fitting  148  allows a piping network using mechanical couplings to be joined to another network coupled using flanges. Furthermore, as illustrated in  FIGS. 19 and 20 , other types of fittings such as a reducer  154  ( FIG. 19 ) used to join pipes having different diameters, or a nipple  156  ( FIG. 20 ) may also benefit from having respective grooves  158  and  160  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. 
     As further shown in  FIG. 21 , components related to control of fluid flow, such as a valve  162  may also have grooves  164  that are like those described above to couple the valve to pipes, fittings or other components using mechanical couplings as described herein. 
     Pipe 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.