Patent Publication Number: US-11644130-B2

Title: Pipe couplings

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a division of U.S. patent application Ser. No. 15/378,125, filed Dec. 14, 2016, the disclosure of which is hereby incorporated by reference herein in its entirety. 
    
    
     FIELD OF USE 
     This disclosure relates to piping. More specifically, this disclosure relates to pipe couplings. 
     RELATED ART 
     Pipe elements such as pipes, valves, and meters typically are not made of one piece. Rather, such pipe elements are formed in finite lengths and must be joined. One way of joining such pipe elements is with a pipe coupling. The pipe coupling typically includes a sealing member such as a gasket. Pipe couplings can be difficult to install, typically requiring the installation to both effectively seal a joint between the pipe elements and to prevent separation of the pipe elements against various internal or external forces. 
     SUMMARY 
     It is to be understood that this summary is not an extensive overview of the disclosure. This summary is exemplary and not restrictive, and it is intended to neither identify key or critical elements of the disclosure nor delineate the scope thereof. The sole purpose of this summary is to explain and exemplify certain concepts of the disclosure as an introduction to the following complete and extensive detailed description. 
     In one aspect, disclosed is a pipe coupling comprising a first coupling segment defining opposed ends, one end of the first coupling segment defining a first pivotal mount, and another end of the first coupling segment defining a second pivotal mount; a second coupling segment defining opposed ends, a proximal end of the second coupling segment configured to pivotally connect to the first pivotal mount, and a distal end of the second coupling segment configured to receive a fastener; and a third coupling segment defining opposed ends, a proximal end of the third coupling segment configured to pivotally connect to the second pivotal mount, and a distal end of the third coupling segment configured to receive the fastener. 
     In another aspect, disclosed is a method of installing a pipe coupling to connect a first pipe element to a second pipe element, comprising the steps of bringing a 3-piece pipe coupling into engagement with a first connection groove located proximate a first pipe element end of the first pipe element and with a second connection groove located proximate a second pipe element end of the second pipe element; and tightening the 3-piece pipe coupling about the pipe element ends with a fastener extending through a first fastener pad and through a second fastener pad formed at respective distal ends of two of the three pieces comprising the pipe coupling. 
     Various implementations described in the present disclosure may include additional systems, methods, features, and advantages, which may not necessarily be expressly disclosed herein but will be apparent to one of ordinary skill in the art upon examination of the following detailed description and accompanying drawings. It is intended that all such systems, methods, features, and advantages be included within the present disclosure and protected by the accompanying claims. The features and advantages of such implementations may be realized and obtained by means of the systems, methods, features particularly pointed out in the appended claims. These and other features will become more fully apparent from the following description and appended claims, or may be learned by the practice of such exemplary implementations as set forth hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several aspects of the invention and together with the description, serve to explain various principles of the invention. The drawings are not necessarily drawn to scale. Corresponding features and components throughout the figures may be designated by matching reference characters for the sake of consistency and clarity. 
         FIG.  1    is a perspective view of a pipe coupling in accordance with one aspect of the current disclosure. 
         FIG.  2    is a front view of the pipe coupling of  FIG.  1    in an assembled and untightened position. 
         FIG.  3 A  is a side view of the pipe coupling of  FIG.  1    in an assembled and untightened position with a fastener of the pipe coupling removed. 
         FIG.  3 B  is a sectional view of the pipe coupling of  FIG.  1    taken along line  3 B- 3 B of  FIG.  2   . 
         FIG.  4    is a perspective view of a coupling segment of the pipe coupling of  FIG.  1    in accordance with another aspect of the current disclosure. 
         FIG.  5    is a front view of the coupling segment of  FIG.  4   . 
         FIG.  6    is a top view of the coupling segment of  FIG.  4   . 
         FIG.  7    is a bottom view of the coupling segment of  FIG.  4   . 
         FIG.  8    is a sectional view of the coupling segment of  FIG.  4    taken along line  8 - 8  of  FIG.  6   . 
         FIG.  9    is a sectional view of the coupling segment of  FIG.  4    taken along line  9 - 9  of  FIG.  5   . 
         FIG.  10    is a front view of a pipe connection ring in the form of a split ring with square ends, constructed in accordance with another aspect of the current disclosure. 
         FIG.  11 A  is a front view of a pipe connection ring in the form of a split ring with tapered ends, constructed in accordance with another aspect of the current disclosure. 
         FIG.  11 B  is a detail view of the pipe connection ring of  FIG.  11 A  taken from detail  11 B of  FIG.  11 A . 
         FIG.  12    is a perspective view of a pipe connection ring in the form of a split ring with angled ends, constructed in accordance with another aspect of the current disclosure. 
         FIG.  13    is a front view of the pipe connection ring of  FIG.  12   . 
         FIG.  14 A  is a top view of the pipe connection ring of  FIG.  12   . 
         FIG.  14 B  is a top view of the angled ends of the pipe connection ring of  FIG.  12   , the ends shown contacting one another upon radial compression of the pipe connection ring. 
         FIG.  14 C  is a top view of the angled ends of the pipe connection ring of  FIG.  12   , the ends shown sliding against one another upon greater radial compression of the pipe connection ring than that depicted in  FIG.  14 B . 
         FIG.  14 D  is a top view of the angled ends of the pipe connection ring of  FIG.  12   , the ends shown having slid past one another upon application of still greater radial compression of the pipe connection ring than that depicted in  FIG.  14 C . 
         FIG.  15    is a perspective view of a pipe connection ring constructed in accordance with another aspect of the current disclosure. 
         FIG.  16    is a front view of the pipe connection ring of  FIG.  15   . 
         FIG.  17    is a top view of the pipe connection ring of  FIG.  15   . 
         FIG.  18    is a perspective view of a pipe system using a pipe coupling with the pipe connection ring of  FIG.  10    in accordance with one aspect of the current disclosure. 
         FIG.  19    is a perspective view of a pipe system using a pipe coupling with the pipe connection ring of  FIG.  11 A  in accordance with one aspect of the current disclosure. 
         FIG.  20 A  is a sectional view of the pipe system of  FIG.  18    taken along line  20 - 20  of  FIG.  18    with the pipe coupling is shown aligned with a first pipe element in accordance with another aspect of the current disclosure. 
         FIG.  20 B  is a sectional view of the pipe system of  FIG.  20 A  with the pipe coupling slid over an end of the first pipe element. 
         FIG.  20 C  is a sectional view of the pipe system of  FIG.  20 A  with a second pipe element aligned with the first pipe element. 
         FIG.  20 D  is a sectional view of the pipe system of  FIG.  20 A  with the pipe coupling slid over and aligned with both of the first pipe element and the second pipe element. 
         FIG.  20 E  is a sectional view of the pipe system of  FIG.  20 A  with the pipe coupling tightened around and connecting the first pipe element and the second pipe element. 
         FIG.  21    is a sectional view of a pipe system with the pipe coupling tightened around and connecting the first pipe element and the second pipe element in accordance with another aspect of the current disclosure. 
         FIG.  22 A  is a sectional view of an untightened pipe coupling of the pipe system of  FIG.  18    taken along line  22 - 22  of  FIG.  18   , in accordance with another aspect of the current disclosure in which the pipe coupling is of a flexible type. 
         FIG.  22 B  is a sectional view of the pipe coupling of  FIG.  22 A  in a tightened configuration. 
         FIG.  23    is a sectional perspective view of the pipe coupling of  FIG.  22    taken along line  23 - 23  of  FIG.  22   , in accordance with another aspect of the current disclosure in which the pipe coupling is of a rigid type. 
         FIG.  24    is a perspective view of a pipe system constructed according to another aspect of the current disclosure, the view showing a pipe coupling in a closed position with a fastener, a nut, and a hinge pin shown in exploded relation to a pair of coupling segments of the pipe coupling. 
         FIG.  25    is a sectional view of the pipe system of  FIG.  24    taken along line  25 - 25  of  FIG.  24   . 
         FIG.  26    is a perspective view of a pipe system constructed according to another aspect of the present disclosure, with a pipe coupling of the pipe system in an opened position. 
         FIG.  27    is a front view of the pipe system of  FIG.  26   , with the pipe coupling fastened in a closed position. 
         FIG.  28    is a front view of the pipe system of  FIG.  26   , with the pipe coupling in an opened position. 
         FIG.  29    is a sectional view of the pipe system of  FIG.  26    taken along line  29 - 29  of  FIG.  27   , the view showing the pipe coupling in a tightened position. 
         FIG.  30    is a perspective view of a pipe coupling constructed according to another aspect of the present disclosure, the pipe coupling shown in a closed position with a fastener and a nut shown in exploded relation to a pair of coupling segments of the pipe coupling. 
         FIG.  31    is a front view of the pipe coupling of  FIG.  30    shown in an open position. 
         FIG.  32    is a perspective view of a pipe system including the pipe coupling of  FIG.  30   . 
         FIG.  33    is a sectional view of a rail member used in the pipe coupling of  FIG.  30    together with a gasket engaged by the rail member. 
         FIG.  34    is a perspective view of a pipe system constructed in accordance with another aspect of the current disclosure. 
         FIG.  35    is a top view of the pipe system of  FIG.  34   , with a pipe coupling of the pipe system installed on a pair of pipe elements of the pipe system. 
         FIG.  36    is a perspective view of the pipe system of  FIG.  34   , with the pipe coupling installed on the pipe elements. 
         FIG.  37    is a detail view of the pipe system of  FIG.  34    taken from detail  37  of  FIG.  36   . 
         FIG.  38    is a perspective view of a pipe coupling constructed according to another aspect of the current disclosure, showing a pipe coupling in an untightened position. 
         FIG.  39    is a perspective view of a pipe system constructed according to another aspect of the current disclosure, the view showing a pipe coupling of the pipe system in an untightened position. 
         FIG.  40    is a perspective view of the pipe system of  FIG.  39    showing the pipe coupling in a tightened position. 
         FIG.  41    is a front perspective view of a pipe coupling constructed according to another aspect of the current disclosure. 
         FIG.  42    is a rear perspective view of the pipe coupling of  FIG.  41   . 
         FIG.  43    is a front perspective view of a pipe system with the pipe coupling of  FIG.  41    in a tightened position. 
         FIG.  44    is a sectional view of the pipe system of  FIG.  43    taken along line  44 - 44  of  FIG.  43    showing the pipe coupling in a tightened position. 
         FIG.  45    is a sectional view of a portion of a pipe system with the pipe coupling of  FIG.  41    in an untightened position. 
         FIG.  46    is a perspective view of a pipe system constructed according to another aspect of the current disclosure. 
         FIG.  47    is a perspective view of a pipe coupling constructed according to another aspect of the current disclosure. 
         FIG.  48    is a sectional view of the pipe coupling of  FIG.  47    taken along line  48 - 48  in  FIG.  47   . 
         FIG.  49    is a perspective view of a pipe system constructed according to another aspect of the current disclosure. 
         FIG.  50    is a sectional view of the pipe system of  FIG.  49    taken along line  50 - 50  of  FIG.  49   . 
         FIG.  51    is a perspective view of a semicircular portion of a gasket constructed according to another aspect of the current disclosure. 
         FIG.  52    is a sectional view of the gasket of  FIG.  51   . 
         FIG.  53    is a perspective view of a semicircular portion of a gasket constructed according to another aspect of the current disclosure. 
         FIG.  54    is a sectional view of the gasket of  FIG.  53   . 
         FIG.  55    is a sectional view of a gasket constructed according to another aspect of the current disclosure. 
         FIG.  56    is a perspective view of a gasket for use in a pipe coupling such as the pipe coupling of  FIG.  1    in accordance with another aspect of the current disclosure. 
         FIG.  57    is a sectional view of the gasket of  FIG.  56    taken along line  57 - 57  in  FIG.  56   . 
         FIG.  58    is a sectional view of the gasket of  FIG.  56    taken along line  58 - 58  in  FIG.  56   . 
         FIG.  59    is a perspective view of a gasket for use in a pipe coupling such as the pipe coupling of  FIG.  1    in accordance with another aspect of the current disclosure. 
         FIG.  60    is a sectional view of the gasket of  FIG.  59    taken along line  60 - 60  in  FIG.  59   . 
         FIG.  61    is a sectional view of the gasket of  FIG.  59    taken along line  61 - 61  in  FIG.  59   . 
     
    
    
     DETAILED DESCRIPTION 
     The present invention can be understood more readily by reference to the following detailed description, examples, drawing, and claims, and their previous and following description. However, before the present devices, systems, and/or methods are disclosed and described, it is to be understood that this invention is not limited to the specific devices, systems, and/or methods disclosed unless otherwise specified, as such can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting. 
     The following description of the invention is provided as an enabling teaching of the invention in its best, currently known embodiment. To this end, those skilled in the relevant art will recognize and appreciate that many changes can be made to the various aspects of the invention described herein, while still obtaining the beneficial results of the present invention. It will also be apparent that some of the desired benefits of the present invention can be obtained by selecting some of the features of the present invention without utilizing other features. Accordingly, those who work in the art will recognize that many modifications and adaptations to the present invention are possible and can even be desirable in certain circumstances and are a part of the present invention. Thus, the following description is provided as illustrative of the principles of the present invention and not in limitation thereof. 
     As used throughout, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a panel” can include two or more such yarn feed tubes unless the context indicates otherwise. 
     Ranges can be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another aspect comprises from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. 
     For purposes of the current disclosure, a material property or dimension measuring about X on a particular measurement scale measures within a range between X plus and industry-standard upper tolerance for the specified measurement and X minus an industry-standard lower tolerance for the specified measurement. Because tolerances can vary between different materials, processes and between different models, the tolerance for a particular measurement of a particular component can fall within a range of tolerances. 
     As used herein, the terms “optional” or “optionally” mean that the subsequently described event or circumstance may or may not occur, and that the description comprises instances where said event or circumstance occurs and instances where it does not. 
     The word “or” as used herein means any one member of a particular list and also comprises any combination of members of that list. 
     In one aspect, a pipe coupling used to join two pipe elements such as two lengths of pipe employs a housing comprising two approximately semicircular coupling segments joined together with nuts and bolts at each end. In order to prevent leaking between the two pipe elements, a gasket is often secured around a joint created at the junction of the two pipe elements. The two coupling segments of the housing surround the gasket and press the gasket around the joint. It is contemplated that a pipe coupling such as that disclosed herein can have more than two coupling segments—for example and without limitation, three coupling segments, each occupying an arc length of approximately 120°; or four coupling segments, each occupying an arc length of approximately 90°. It is also contemplated that a pipe coupling such as that disclosed herein can have a single coupling segment that is able to slide over an end of a pipe element but which occupies an arc length of as much as 360° when tightened. 
     Pipe couplings—and pipe elements—are often cast. Certain features of cast parts may vary in size from one part to another or have surfaces that are rougher or have material properties that are different than if the parts—or certain features of those parts—were processed using a different method such as forging, machining, or stamping. In one aspect, securing the coupling segments to end-facing pipe elements using specifically one or more separate pipe connection rings that are disclosed herein can yield benefits to those who install, service, and otherwise rely on the convenience and integrity of the pipe connections. 
     With previous pipe coupling designs, workers must sometimes follow a significant number of steps to install a pipe coupling. Workers must typically disassemble the entire apparatus and remove the gasket from the housing. Approximately half of the gasket is then forced over one end of one pipe element. An end of the other pipe element is forced into the remaining portion of the gasket, thereby joining the two pipe elements together. To secure the pipe elements, the two halves of the housing are placed around the gasket and then nuts and bolts or other fastening devices are used to complete the installation. Typically, the inner diameter of the gasket is slightly smaller than the outer diameter of the pipe elements. Therefore, the worker must stretch the gasket around the pipe ends. 
     In one aspect, disclosed are a pipe coupling and associated methods, systems, devices, and various apparatus. The pipe coupling includes a coupling segment having an inner surface defining a gasket channel and a ring groove, the ring groove being proximate to an axial end of the coupling segment and defining a groove bottom surface extending from a first end of the coupling segment to a second end of the coupling segment. A gasket is disposed within the gasket channel, and a pipe connection ring is disposed within the ring groove, the pipe connection ring defining a body with two ring ends, the pipe connection ring contacting the groove bottom surface between the first end of the coupling segment and the second end of the coupling segment. The pipe connection ring may be a split ring defining an opening between the two ring ends, which may be square, tapered, angled, or stepped. 
     One aspect of a pipe coupling  100  is disclosed and described in  FIGS.  1 - 3 B . As shown, the pipe coupling  100  includes two coupling segments  200   a,b . The fastening devices  290   a,b —which can also be described as tightening elements—comprise, for example and without limitation, nut and bolt fasteners (shown in  FIG.  2   ). Two bolts  120   a,b  are disposed to interact with nuts  125   a,b  in threaded engagement; however, other types of tightening elements may be used. Each of the coupling segments  200   a,b  of the pipe coupling  100  comprises a first end  211   a,b , a second end  212   a,b , an outer surface  201   a,b , and an inner surface  202   a,b  (shown in  FIG.  3 B ). As shown in  FIG.  3 B , each of the outer surfaces  201   a,b  is contoured to define a gently arched shape that is higher (or more radially outward) towards an axial midpoint of each coupling segment  200  and lower (or more radially inward) towards each of a pair of axial ends of each coupling segment  200 . A pair of fastener pads  221   a , 222   a  protrude from coupling segment  200   a  proximate to the first end  211   a  and  212   a , respectively. A pair of fastener pads  221   b , 222   b  protrude from coupling segment  200   b  proximate to the first end  211   b  and  212   b , respectively. Fastener holes  224   a,b , 225   a,b  are defined in fastener pads  221   a,b , 222   a,b , respectively. As shown, the fastener holes  224   a,b , 225   a,b  are centered within the fastener pads  221   a,b , 222   a,b , although the fastener holes  224   a,b , 225   a,b  may be offset from the center of the fastener pads  221   a,b , 222   a,b . Although the fastener pads  221   a,b , 222   a,b  and fastener holes  224   a,b , 225   a,b  are described in the current configuration, various locations and configurations of fastener pads  221   a,b , 222   a,b  and fastener holes  224   a,b , 225   a,b  may be used. As shown in  FIGS.  3 A and  3 B , the upper and lower coupling segments  200   a,b  respectively include first axial ends  205   a,b  and second axial ends  206   a,b . The pipe coupling  100  includes a gasket  150 . As shown, the gasket  150  is annular and configured to surround and to seal a joint formed by a pair of pipe elements such as pipe elements  110 , 120  (shown in  FIGS.  20 A- 20 E ) that are joined end-to-end. 
     Referring to  FIGS.  1  and  3 B , the respective inner surfaces  202   a,b  of the upper and lower coupling segments  200   a,b  define a gasket groove  240 . The gasket groove  240  is generally C-shaped and is bounded by first and second ridges defining the transition portions  274  and  276  (shown in  FIG.  3 B ). Although gasket groove  240  is shown in  FIG.  3 B  as generally C-shaped, the particular shape of the gasket groove may differ from that shown as long as it receives the gasket  150 . The inner surfaces  202   a,b  further define a first ring groove  250   a  axially spaced from the gasket groove  240 . Similarly, the inner surfaces  202   a,b  further define a second ring groove  250   b  axially spaced from the gasket groove  240 . A first pipe connection ring  300   a  is received within the first ring groove  250   a , and a second pipe connection ring  300   b  is received within the second ring groove  250   b . As shown in  FIGS.  1  and  2   , the first connection ring  300   a  is shaped as an annular member having a body  310  and two plain-end ring ends  320 , 330 . The second pipe connection ring  300   b  can be shaped identically to the first connection ring  300   a . The pipe connection rings  300   a,b  can also be constructed as split rings with tapered ends, as illustrated in  FIGS.  11 A and  11 B . Pipe connection rings with other configurations may also be used, as will be described herein. 
     As shown in  FIG.  2   , the annular shape of the gasket  150  defines a coupling void  105  within the gasket  150  that is configured to receive a pipe element. In practice, when pipe elements are introduced within the gasket  150 , they are placed inside the coupling void  105 . Also shown in  FIG.  2   , a central axis of each of the bolts  120   a,b  may be angled with respect to a vertical axis  425  of the pipe coupling  100  such that heads  612   a,b  of the bolts  120   a,b  sit flush against the top surfaces  314   a , 315   a . The top surfaces  314   a , 315   a  of the coupling segment  200   a  may likewise be angled at respective angles  415   a , 416   a  and corresponding top surfaces  314   b , 315   b  of the coupling segment  200   b  be angled at respective angles  415   a , 416   a  with respect to a horizontal axis  420  when the pipe coupling  100  is in an assembled and untightened state. By adjusting the geometry of the coupling segments  200   a,b , however, the central axis of each of the bolts  120   a,b  may be made parallel to the vertical axis  425  such that heads  612   a,b  of the bolts  120   a,b  sit at an angle with the top surfaces  314   a , 315   a . The coupling segment  200   a  may include bottom surfaces  312   a , 313   a  proximate to the respective ends  211   a , 212   a , and the coupling segment  200   b  may include bottom surfaces  312   b , 313   b  proximate to respective ends  211   b , 212   b , the bottom surfaces  312   a , 313   a  facing the bottom surfaces  312   b , 313   b  when the pipe coupling  100  is in an assembled state. 
     Tightening of the fastening devices  290   a,b  seats the gasket  150  against pipe elements such as the pipe elements  110 , 120 . When tightened about the pipe elements, the pipe coupling  100  restrains the pipe elements from pullout—in other words, the pipe coupling not only seals the joint but prevents separation of the first pipe element  110  from the second pipe element  120 —because a pipe connection ring  300   a,b  is seated inside at least one connection groove of at least one pipe element. The gasket  150  is compressed in sealed engagement with the pipe elements. In some embodiments, the gasket  150  may comprise a single sealing member that extends between the two pipe elements. Such deformation allows the heads  612   a,b  of the bolts  120   a,b  to seat flush against the top surfaces  314   a , 315   a  of coupling segment  200   a  while nuts  125   a,b  seat flush against the top surfaces  314   b , 315   b  of coupling segment  200   b.    
     In the current embodiment, the pipe coupling  100  is assembled in the untightened position of  FIG.  2    before installation onto the pipe elements. The pipe coupling  100  may be also be assembled only partially before installation onto the pipe elements. 
     In one aspect, as shown in  FIG.  3 B  in an assembled but untightened state, the coupling segment  200   a  and the coupling segment  200   b  of the pipe coupling  100  define a noticeable gap  170  therebetween. The pipe connection rings  300   a,b  are respectively positioned in or disposed within the first ring groove  250   a  and the second ring groove  250   b . The first ring groove  250   a  is proximate to a first axial end  205   a,b  of the coupling segments  200   a,b  and the second ring groove  250   b  is proximate to a second axial end  206   a,b  (shown in  FIG.  2   ) of the coupling segments  200   a,b.    
     The gasket  150  is positioned in or disposed within a gasket groove  240  defined in the inner surfaces  202   a,b  of the coupling segments  200   a,b . Each of the inner surfaces  202   a,b  also defines a transition portion  272 , a transition portion  274 , a transition portion  276 , and a transition portion  278 —each of which can also be described as a ridge. The transition portion  272  provides a transition between the first axial end  205   a,b  and the first ring groove  250   a ; the transition portion  274  provides a transition between the first ring groove  250   a  and the gasket groove  240 ; the transition portion  276  provides a transition between the gasket groove  240  and the second ring groove  250   b ; and the transition portion  278  provides a transition between the second ring groove  250   b  and the second axial end  206   a,b . Various detailed characteristics and functions of the pipe connection rings  300   a,b  will be described in connection with the description of  FIGS.  10  through  17   . 
     As shown in  FIG.  3 B , the gasket  150  comprises, for example and without limitation, a pair of sealing ridges  525   a,b , a central rib  530  defining sealing members  557   a,b , a deformation groove  517 , a pair of gasket channels  540   a,b —alternately described as pockets, the gasket channel  540   a  proximate to the sealing ridge  525   a  and the gasket channel  540   b  proximate to the sealing ridge  525   b . In one aspect, the gasket  150  is received within the gasket groove  240  and each of the pipe connection rings  300   a,b , shown in simplified form for the sake of clarity, is respectively received within the ring grooves  250   a,b . In one aspect, in cross-section, the gasket  150  defines an overall height  570  measured in a radial direction from a radially outer surface  515  to a pair of sealing surfaces  526   a,b  of the sealing ridges  525   a,b.    
     In one aspect, the gasket  150  is ring-shaped (as shown in  FIG.  18   ) with various axially outer drafted edges and axially inward drafted edges defined on the sealing ridges  525   a,b . The pair of sealing surfaces  526   a,b  of the sealing ridges  525   a,b , respectively, are intended to contact pipe elements placed inside of the gasket  150  to provide a fluid seal for the pipe elements. The sealing surfaces  526   a,b  face radially inwardly and extend substantially axially at rest, thereby being coannular with each other. Accordingly, in one aspect, the shape of each of the sealing surfaces  526   a,b  approximates a cylinder that is about coaxial with the pipe elements intended to be used with the pipe coupling  100 . Thus, the sealing surfaces  526   a,b  appear as lines that are parallel with an axial direction of the gasket  150  and an axial direction of the pipe elements  110 , 120  in cross-sectional view, as shown in  FIGS.  20 A- 20 E . Any angle with respect to the pipe elements  110 , 120  is minimal. The axial ends of each sealing surface  526   a,b  may be rounded or chamfered or otherwise shaped to ease the insertion of pipe elements  110 , 120 . 
     The gasket  150  may be made of rubber, plastic, cork, wood, metal, ceramic, polymer, elastomer, rosin, foam, any combination of the foregoing materials, or any material suitable for sealing two pipe elements joined in end-to-end relationship. A “pipe element” can include, for example and without limitation, pipes, valves, meters, fittings, or any other piping structure suitable to be sealed. 
     The gasket  150  defines the gasket channels  540   a,b . The gasket channels  540   a,b  are pockets into which fluid media may flow when the gasket  150  is in use. The gasket channels  540   a,b  are tubular channels in the current embodiment but may be various shapes in various embodiments. When placed in sealing contact with an exterior surface of a pipe element, the gasket channels  540   a,b  allow some fluid pressure to aid in sealing the sealing ridges  525   a,b  against the pipe elements  110 , 120  by exerting pressure against an axially outer surface of the sealing ridges  525   a,b , although such use is not necessary for successful sealing of the gasket  150 . The central rib  530  decreases in thickness from a radially outermost portion to its termination radially inward. 
     In addition, when the gasket  150  is in use, the sealing members  557   a,b  act to prevent substantial fluid media flow into the gasket channels  540   a,b . When placed in sealing contact with exterior surfaces of pipe elements, a pair of sealing surfaces  532   a,b  of the sealing members  557   a,b  prevent substantial fluid media flow into gasket channels  540   a,b , retaining fluid media flow in a groove between the sealing members  557   a,b . The gasket may comprise a plurality of central ribs, each with at least one sealing member and at least one sealing surface, which perform the same function as described above to prevent substantial media flow into the gasket channels. One problem that the central rib  530  can alleviate is the buildup of fluids in the gasket channels  540   a,b . For example, in applications where fluid media is water in cold temperature environments, preventing water buildup in the gasket channels  540   a,b  can lead to damage to the gasket  150  if the water freezes and, thereby, expands. 
     As shown in  FIGS.  4 - 9   , the coupling segments  200  respectively define the outer surface  201  and the inner surfaces  202  as differing in various aspects to the outer surfaces  201   a,b  and inner surfaces  202   a,b  of the coupling segments  200   a,b  of  FIGS.  1 - 3 B . In particular, the gently arched shape of the outer surfaces  201   a,b  is broken towards each of the axial ends  205 , 206  of each coupling segment  200  by a plurality of edge treatments  260  corresponding to a plurality of groove bottom segments  270  shown in  FIGS.  7 - 8   . In one aspect, the edge treatments  260  are planar surfaces that help maintain a more constant thickness of the coupling segment in portions of the coupling segment defining the ring grooves  250   a,b . In one aspect, this ensures that the pipe coupling  100  does not become too thin in any one area. In another aspect, this reduces the amount of material used to form the coupling segment  200  to only the amount required the minimum thickness. In another aspect, a more constant thickness improves the manufacturability of the coupling segments  200  by facilitating more even cooling of a coupling segment after it has been cast or molded. 
     In various aspects and as shown in  FIGS.  4 - 9   , the coupling segment  200  respectively defines the fastener openings  224 , 225  in fastener pads  221 , 222  proximate to the first end  211  and the second end  212 . In one aspect, the fastener openings  224 , 225  may be capsule-shaped and extend in an axial direction defined by the pipe coupling  100 , though the fastener openings may have various other shapes in other aspects, including a circular or rectangular shape, and can extend in a direction orthogonal to the axial direction or in other directions as desired for particular installations. In one aspect, to facilitate the manufacture of the coupling segment  200 , an inner surface of the fastener openings  224 , 225  are drafted as shown in  FIG.  5    and other surfaces shown in  FIGS.  4 - 9    of the coupling segment  200  are drafted as shown. In one aspect, each of the fastener pads  221 , 222  tapers toward the first end  211  and the second end  212  as shown in  FIGS.  6  and  7   . In one aspect, the gasket groove  240  is centered axially in the coupling segment  200 . In one aspect, each of the ring grooves  250   a,b  is positioned axially outward from the gasket groove  240  as shown in  FIGS.  7  and  9   . In one aspect, the groove bottom segments  270 —which can also be described as flat portions of a groove bottom surface defined in the inner surface  202  of the coupling segment  200 —of the ring grooves  250   a,b  are each flat in cross-section as shown in  FIG.  8   . In one aspect, the groove bottom segments  270  of the ring grooves  250   a,b  are flat in cross-section and parallel to an axial direction of the coupling segment in cross-section as shown in  FIG.  9   . In one aspect, the groove bottom segments  270  form a substantially half-polygonal shape in a radially oriented plane. In one aspect where a pair of coupling segments  200  is assembled in a pipe coupling  100 , the groove bottom segments  270  of both coupling segments  200  form a ten-sided polygonal profile. In another aspect, the total number of groove bottom segments  270  can be greater than or less than ten. In one aspect, when the coupling segments  200   a,b  are formed with the groove bottom segments  270 , an outer surface  304  (shown in  FIG.  10   ) of the substantially circular pipe connection rings  300   a,b  may contact only a portion of the ring grooves  250   a,b . In one aspect, the groove bottom segments  270  enable portions of an outer surface  304  of the pipe connection ring  300  to slide more easily during tightening of the pipe coupling  100  while the pipe connection ring  300  compresses due to the shape and orientation of the groove bottom segments  270  and the reduced contact surface area between the outer surface  304  of the pipe connection ring  300  and the groove bottom segments  270 . The ring grooves  250   a,b  may also have a radiused profile instead of the polygonal profile shown. 
     As shown in  FIG.  10   , the pipe connection ring  300 —which can be described as a split ring—defines a body  310  with the two ring ends  320 , 330  and the opening  340  between the two ring ends  320 , 330 . The two ring ends  320 , 330  of the pipe connection ring  300  of  FIG.  10    are square and respectively define end surfaces  321 , 331 , though the pipe connection ring  300  can have different end configurations, such as the other end configurations to be described herein. When uncompressed as shown, the opening  340  of the pipe connection ring  300  defines an angular opening A 1 , which can be measured in degrees. The magnitude of the opening  340  determines whether the pipe connection ring  300  is to be used for a flexible-type pipe coupling or a rigid-type pipe coupling. The opening  340  is larger for rigid-type pipe couplings than it is for flexible-type pipe couplings. For a pipe system disclosed in accordance with an aspect of the current disclosure, only the pipe connection ring needs to be changed in order to convert the pipe coupling from a flexible-type to a rigid-type, or vice versa. 
     In addition, the pipe connection ring  300  defines a first axial end surface  301 , a second axial end surface (not shown) distal from the first axial end surface  301 , an inner surface  303 , an outer surface  304 , an overall inner radius  1091 , and an overall outer radius  1092 , the overall inner radius  1091  and the overall outer radius  1092  measured from a central axis  305  of the pipe connection ring  300 . The body  310  of the pipe connection ring  300  defines a radial ring thickness  306  (i.e., a thickness of the pipe connection ring  300  in a radial direction) and an axial ring thickness  308  (i.e., a thickness of the pipe connection ring  300  in an axial direction) shown in  FIG.  14 B  that is constant between the pipe connection ring  300  as shown and the pipe connection ring  300  as compressed in a radial direction (i.e., when the pipe coupling  100  is in an assembled and tightened state). The proportions between the radial ring thickness  306  and the axial ring thickness  308  need not be constant in every embodiment of the pipe connection ring  300  nor between the uncompressed and compressed states of the pipe connection ring  300 . 
     The pipe connection ring  300  shown in  FIG.  10    and other exemplary pipe connection rings  300  such as those shown in  FIGS.  11 A- 17    can be formed from a flat blank of raw material such as, for example and without limitation, carbon steel and stainless steel including spring steel grades of each. The pipe connection ring  300  shown can be formed using one or more material removal processes such as, for example and without limitation, machining, stamping, punching, laser-cutting, abrasive-water-jet-cutting, and chemical milling or etching, optionally in combination with forming processes such as, for example and without limitation, casting, forging, stamping, bending, and three-dimensional printing. 
       FIGS.  11 A and  11 B  depict a pipe connection ring  300  constructed according to another aspect of the current disclosure. In addition to the aforementioned common features of the pipe connection ring  300 , at least one ring end  320 , 330  of the pipe connection ring  300  shown in  FIGS.  11 A and  11 B  is tapered. As shown in  FIG.  11 B , the ring end  330  includes an inside edge  334  and an outside edge  336 . The inside edge  334  is oriented at a first taper angle A 2  with respect to a radial direction of the pipe connection ring  300 , and the outside edge  336  is oriented at a second taper angle A 3  with respect to the same radial direction. In one aspect, the first taper angle A 2  is about 70° and the second taper angle A 3  is about 80°, though the magnitude of either the first taper angle A 2  or the second taper angle A 3  can be any angle less than about 90 degrees. As shown, the first taper angle A 2  and the second taper angle A 3  are sized such that a taper width  1132  defined by the inside edge  334  is equal to a taper width  1133  defined by the outside edge  336 . The taper width  1132  and the taper width  1133  can be adjusted and made to vary to ease insertion or radial compression of the pipe connection ring  300 . Because of the taper, a width in a radial direction of each of the ring ends  320 , 330  and each of the corresponding end surfaces  321 , 331  is less than the radial ring thickness  306  of the untapered portion of the body  310 . 
       FIGS.  12 - 14 D  illustrate the pipe connection ring  300  constructed according to another aspect of the current disclosure. Referring to  FIGS.  12 - 14 A , the pipe connection ring  300  includes a body  310  defining the two ring ends  320 , 330  having respective end surfaces  321 , 331  (end surface  331  shown in  FIG.  14 A ) that are each angled with respect to the central axis  305  (shown in  FIG.  13   ) of the pipe connection ring  300  and separated from one another by the opening  340  and the angular opening A 1  when the pipe connection ring  300  is in an uncompressed state. In one aspect, the angular opening A 1  is, for example and without limitation, about 27°. The end surfaces  321 , 331  extend at a cut angle A 4  to an axial direction of the pipe connection ring  300 . The cut angle A 4  may be of the same magnitude for each end surface  321 , 331  and may measure about 45°. The cut angle A 4  of the end surface  331  may vary from a cut angle of the end surface  321 , however, and either end surface  321 , 331  can vary from about 45°. Also shown in  FIG.  14 A , the pipe connection ring  300  defines the first axial end surface  301 , the second axial end surface  302  distal from the first end surface  301 , the inner surface  303 , and the outer surface  304 . 
       FIGS.  14 B- 14 D  show the behavior of the pipe connection ring  300  of  FIG.  12    as it undergoes progressively increasing radial compression inside the pipe coupling  100  and exerted by continued tightening of the pipe coupling  100 . In  FIG.  14 B , at a given compression magnitude, the end surfaces  321 , 331  move toward one another in the movement directions  1700 , 1702 , respectively, until the end surfaces  321 , 331  are brought into contact with one another. In  FIG.  14 C , when a greater amount of radial compression is applied to the pipe connection ring  300  than that depicted in  FIG.  14 B , the end surfaces  321 , 331  begin to slide past one another in the movement directions  1704 , 1706  along a common slip plane  1710 . As the end surfaces  321 , 331  slide past one another, a ring end axial thickness  309  begins to measure greater than the axial ring thickness  308 . Finally, in  FIG.  14 D , upon application of a particular greater amount of radial compression to the pipe connection ring  300  than that depicted in  FIG.  14 C , the end surfaces  321 , 331  disengage from one another and move circumferentially past one another, as indicated by the movement directions  1700 , 1702 . In one aspect, the radial compression of the pipe connection ring  300  is limited by the geometry of the ring groove  250   a,b . A width of the ring groove  250   a,b  in an axial direction in the pipe coupling  100  that is narrower than necessary to accommodate the ring end axial thickness  309 —particularly the ring end axial thickness  309  that increases as the ring ends  320 , 330  of the pipe connection ring  300  begin to slide past one another—may limit radial compression to the point at which the ring ends  320 , 330  of the pipe connection ring  300  contact the sides of the ring groove  250   a,b.    
       FIG.  15 - 17    illustrate the pipe connection ring  300  constructed according to another aspect of the current disclosure. The body  310  of the pipe connection ring  300  defines the outer surface  304 , the inner surface  303 , the first axial end surface  301  extending from the outer surface  304  to the inner surface  303 , and the second axial end surface  302  opposite the first axial end surface  301  and extending from the outer surface  304  to the inner surface  303 . As shown, a portion of the body  310  proximate to the first ring end  320  of the two ring ends  320 , 330  is positioned axially adjacent to a portion of the body  310  proximate to the second ring end  330 . A portion of the body  310  proximate to the first ring end  320  defines a slip surface  322  and includes the ring end  320  defining the end surface  321 , and a portion of the body  310  proximate to the second ring end  330  defines a slip surface  332  and includes the ring end  330  defining the end surface  331 . Shoulder  325 , 335  respectively defining shoulder surfaces  323 , 333  may be present at the base of the respective stepped portions  328 , 338  and distal to the respective ring ends  320 , 330 , or each of the stepped portions  328 , 338  may transition into a non-stepped portion of the body  310  of the pipe connection ring  300  without a shoulder or shoulder surface being formed. 
     The pipe connection ring  300  shown in  FIGS.  15 - 17   —which, again, can be described as a split ring even though the ring ends  320 , 330  are in contact with one another because the ring ends  320 , 330  are still not connected—defines the opening  340  between the ring end  320  and the shoulder  335  and between the ring end  330  and the shoulders  325 . As shown, the ring ends  320 , 330  face the respective shoulders  325 , 335  and contact the respective shoulders  325 , 335  when the pipe connection ring  300  experiences sufficient radial compression. When uncompressed as shown, the opening  340  of the pipe connection ring  300  defines the angular opening A 1  and an overlapping angle, both of which can be measured in degrees. In one aspect, the stepped portion  328  proximate to the first ring end  320  and the stepped portion  338  proximate to the second ring end  320  can be said to nest inside one another. As shown, the axial ring thickness  308  measured at the overlapping portions  328 , 338  is less than or equal to the axial ring thickness  308  measured at a portion of the body distal the overlapping portions  328 , 338 . 
       FIGS.  18  and  19    depict two variations of the pipe system  90 , illustrating how different types of rings may be used with systems otherwise identically constructed. 
     Referring to  FIG.  18   , the pipe system  90  again includes the first pipe element  110 , the second pipe element  120 , and the pipe coupling  100  connecting an end of the first pipe element  110  to an end of the second pipe element  120 . The pipe coupling  100  includes coupling segments  200   a,b , each coupling segment  200   a,b  having an inner surface defining ring grooves in the manner disclosed hereinabove, and housing the gasket  150 . The pipe system  90  employs square-ended pipe connection rings  300  of the type disclosed with regard to  FIG.  10   . 
     Referring to  FIG.  19   , the pipe system  90  again includes the first pipe element  110 , the second pipe element  120 , and the pipe coupling  100  connecting an end of the second pipe element  120  to an end of the first pipe element  110 . The pipe coupling  100  includes the coupling segments  200   a,b , each coupling segment having an inner surface defining a ring groove in the manner disclosed hereinabove, and housing a gasket  150 . In one aspect, the foregoing components may be constructed identically as the corresponding components in the pipe system  90  shown in  FIG.  18   . The differentiating components of pipe system  90  of FIG.  19  are the tapered-ended pipe connection rings  300  of the type disclosed with regard to  FIGS.  11 A and  11 B . 
     It may be advantageous for the entire pipe coupling  100  to be able to slide past an end  115  of the pipe element  110  during installation of the pipe coupling  100  as shown in  FIGS.  20 A- 20 E . As shown in  FIG.  20 C , for example, being able to slide the entire pipe coupling  100  past the end  115  of the pipe element  110  during installation may facilitate the accurate alignment of the first pipe element  110  with the second pipe element  120  because the pipe coupling  100  need not obscure the joint while still being installed on the first pipe element  110 . Being able to slide the entire pipe coupling  100  past the end  115  of the pipe element  110  during installation also permits one to assemble the pipe coupling  100  before installing it on the pipe elements  110 , 120 . Moreover, the pipe elements  110 , 120  and the pipe coupling  100  can be heavy or difficult to position or align, and it is often easier to assemble the pipe coupling  100  as a separate step before installing the pipe coupling  100  on the pipe elements  110 , 120 . To facilitate sliding of the entire pipe coupling  100  over the end  115  of the pipe element  110 , the pipe connection rings  300   a,b  and the inner surface  202   a,b  of the coupling segments  200   a,b  may have an inner diameter that is greater than an outer diameter of the pipe elements  110 , 120  when the pipe coupling is in an assembled but untightened state (i.e., in an uncompressed condition). The gasket  150  may also have an inner diameter that is greater than an outer diameter of the pipe elements  110 , 120  when the pipe coupling is in an assembled but untightened state, or the gasket  150  may have one or more portions that extend radially inward past an outer surface of the pipe elements  110 , 120 . 
       FIGS.  20 A- 20 E  illustrate the installation of the pipe coupling  100  on the pair of pipe elements  110 , 120 . The pipe coupling  100  is introduced to a pair of pipe elements  110 , 120  in the preassembled but untightened position of  FIGS.  1 - 3 B . Each pipe element  110 , 120  may define a connection groove  112 , 122  proximate to an end of each pipe element  110 , 120  for alignment with pipe connection rings  300   a,b  and to prevent separation of the first pipe element  110  from the second pipe element  120 . In the currently described method, the pipe coupling  100  is axially aligned with the end  115  of the first pipe element  110  as shown in  FIG.  20 A . The pipe coupling  100  is installed by placing the end  115  of the first pipe element  110  in a coupling void  105  defined by the pipe coupling  100  and sliding the pipe coupling  100  over the end  115  of the first pipe element  110  as shown in  FIG.  20 B . As shown in  FIG.  20 B , an inner diameter of the gasket is greater than an outer diameter of the first pipe element  110  and the second pipe element  120 , resulting in the sealing surfaces  526   a,b  and the sealing surfaces  532   a,b  of the gasket  150  being a small distance away from an outer surface  111  of the first pipe element  110 . The sealing surfaces  526   a,b  and  532   a,b  may contact the outer surface  111  in other aspects. In one aspect, the entire pipe coupling  100  is slid beyond the connection groove  112  of the first pipe element  110  so that the pipe connection rings  300   a,b  and each of the axial ends  205   a,b  and  206   a,b  have passed the connection groove  112  or at least the end  115  of the pipe element  110 . In another aspect, it may not be necessary to slide the entire pipe coupling  100  beyond the connection groove  112  or the end  115 . As shown in  FIG.  20 C , the second pipe element  120  having an end  125  is introduced in end-facing relationship to the end  115  of the first pipe element  110 . 
     As shown in  FIG.  20 D , when the second pipe element  120  is aligned with the first pipe element  110 , the pipe coupling  100  is moved such that the gasket  150  is positioned around the ends  115 , 125  of the pipe elements  110 , 120  and the pipe connection rings  300   a,b  are aligned with the connection grooves  112 , 122 . 
     As shown in  FIG.  20 E , when the coupling segments  200   a,b  are clamped down or tightened around the pipe elements  110 , 120  by tightening the nuts on the bolts or by any other tightening method, the gasket  150  deforms into sealing engagement against the outer surfaces  111 , 121  of the pipe elements  110 , 120  and the pipe connection rings  300   a,b  sit respectively within the connection grooves  112 , 122 . A radially innermost portion of the respective inner surface  303   a,b  of each of the pipe connection rings  300   a,b  may contact a radially innermost portion of a connection groove surface  116 , 126  that defines a groove bottom of the connection grooves  112 , 122 . 
     When the pipe coupling  100  is a flexible-type pipe coupling, a space or gap  1200  (shown in  FIG.  22 B ) may remain between the pipe connection ring  300  and the radially innermost portion of the connection groove surface  116 , 126  of the connection groove  112 , 122  of the pipe element  110 , 120 . The gap  1200  may exist only at specific points or around the full circumference of the pipe connection ring  300 . The pipe connection ring  300  can be configured to compress only to a certain point at which an inner diameter of the pipe connection ring  300  is greater than the outer diameter of the radially innermost portion of the connection groove surface  116 , 126 . The gap  1200  allows or the spaces allow a limited amount of freedom for the pipe elements  110 , 120  to move within the pipe coupling  100 , which can be beneficial for some installations including those in earthquake-prone geographic areas. If the pipe connection ring  300  is allowed to compress further, then even complete tightening of the pipe coupling  100  will not cause the pipe connection ring to fully compress. In that event, the coupling segments  200   a,b  will deform uniformly and leave no space between the pipe connection ring and the radially innermost portion of the connection groove surface  116 , 126 . This results in a rigid-type pipe coupling, in which the pipe elements  110 , 120  have no clearance with which to move within the pipe coupling  100 , which may prove advantageous for some installations including those in which the fluid inside the pipe elements  110 , 120  is at high pressure. An example of a rigid-type configuration is illustrated in  FIGS.  20 A- 20 E . 
     An axial end surface such as the first axial end surface  301   a,b  or the second axial end surface  302   a,b  of the pipe connection rings  300   a,b  may contact an axially outermost portion of the connection groove surface  116 , 126  (i.e., axially outermost meaning closest to the ends  115 , 125 ) that defines a sidewall of the connection grooves  112 , 122 . The connection rings  300   a,b  may not contact the sidewalls of the connection grooves  112 , 122  in other aspects until an internal or external force, such as fluid pressure within a pipe system  90 , acts to separate the pipe elements  110 , 120 , and the connection rings  300   a,b  thereby engage the sidewalls and groove bottoms to prevent this separation. In some aspects, a gap can remain between the transition portions  272 , 274 , 276 , 278  of the inner surface  202   a,b  of each coupling segment  200   a,b  and a radially outermost portion of the outer surfaces  111 , 121  of the pipe elements  110 , 120  upon clamping down the coupling segments  200   a,b , or the transition portions  272 , 274 , 276 , 278  of the inner surface  202   a,b  of each coupling segment  200   a,b  can come into partial or complete contact with the outer surfaces  111 , 121  of the pipe elements  110 , 120  in other aspects. 
     When the pipe coupling  100  is aligned on the joint of the pipe elements  110 , 120  as shown in  FIG.  20 E , the fastening devices  290   a,b  are used to draw the coupling segments  200   a,b  together. In one aspect, this takes the form of fastening devices  290   a,b  compressing the fastener pads  221 , 222  toward each other. In one aspect, the pipe coupling  100  is rigid and includes no deflection of the coupling segments  200   a,b . In another aspect, the coupling segment is deformable between a non-assembled state and an assembled and tightened state, each coupling segment  200   a,b  of the pipe coupling  100  deflecting at least slightly when the pipe coupling  100  is tightened. In various aspects, when the coupling segments  200   a,b  travel toward each other and deform under the tightening of the fastening devices  290 , the gasket  150  is deformed in accord therewith. In one aspect, a rigid or semi-rigid gasket  150  may be included. The process for accommodating such a material may be altered from that described herein; for example and without limitation, however, the gasket  150  can comprise the deformation groove  517  to allow a place for material to flow upon deformation of the gasket  150 . 
     Several features of the gasket  150  ease installation as described. Friction can cause installation of rubber gaskets to bind against outer surfaces  111 , 121  of pipe elements  110 , 120 . With reference to the method shown  FIGS.  20 A- 20 E , axially outer drafted edges and axially inner drafted edges of the gasket  150  are both drafted to ease the pipe elements  110 , 120  into the coupling void  105 . Axially outer drafted edges and axially inner drafted edges also help to prevent rollover of the sealing ridges  525   a,b  of the gasket  150  while sliding the pipe coupling  100  on and off, as the drafted profiles are less likely to bind against the outer surfaces  111 , 121  of the pipe elements  110 , 120 . Additionally, sealing surfaces  526   a,b  are substantially parallel to the outer surfaces  111 , 121  of the pipe elements  110 , 120  even when the gasket  150  is not tightened against the pipe elements  110 , 120 . Additionally, the axially outward position of the central rib  530  with respect to the sealing ridges  525   a,b , prevents the central rib  530  from obstructing the installation of the pipe coupling  100  before deformation of the gasket  150 . When the coupling segments  200   a,b  are clamped down, the gasket  150  deforms, and the central rib  530  contacts the outer surfaces  111 , 121  of the pipe elements  110 , 120 . This configuration allows the gasket  150  to slide onto the pipe elements  110 , 120  without biasing the sliding in one direction and prevents binding of the sealing ridges  525   a,b  during installation. These features prevent the gasket  150  from rolling over when the pipe coupling  100  is installed on the pipe elements  110 , 120  and allows the gasket  150  to be properly placed over the joint between the pipe elements  110 , 120  for proper sealing, among other advantages. When the gasket  150  is properly aligned over the joint and engaged against the outer surfaces  111 , 121  of the pipe elements  110 , 120 , each of the sealing members  557   a,b  may contact the outer surfaces  111 , 121 . 
       FIG.  21    shows the pipe coupling  100  assembled and tightened around and connecting the pipe elements  110 , 120 . The pipe elements  110 , 120  respectively comprise shoulders  118 , 128  defining sidewalls  119 , 129  instead of having connection grooves  112 , 122 . One of the axial end surfaces  301   a,b  or the axial end surfaces  302   a,b  of each of the pipe connection rings  300   a,b  may contact one of the sidewalls  119 , 129  of the shoulders  118 , 128  to engage the pipe elements  110 , 120  when an internal or external force, such as fluid pressure with the pipe system  90 , acts to separate the pipe elements  110 , 120 . This contact prevents separation of either pipe element  110 , 120  from the pipe coupling  100  or from each other once the pipe coupling  100  is tightened. The pipe coupling  100  disclosed herein could be used with plain-end pipe elements as well that do not incorporate a connection groove  112 , 122  or a shoulder  118 , 128 . 
     In one aspect, the pipe elements  110 , 120  are approximately the same diameter, although non-uniform diameter pipe elements may be also be joined by adjusting the dimensions of the pipe coupling  100  appropriately. In one aspect, each of the pipe elements  110 , 120  has ends  115 , 125  that define a diameter equal to a diameter of the respective pipe elements  110 , 120 . In another aspect, the ends  115 , 125  can be flared slightly. Grooves  112 , 122  can be formed using one or more of at least two methods: rolling and machining. If the grooves  112 , 122  are machined, the pipe elements  110 , 120  are less likely to have flares on the ends  115 , 125  and are more likely to resemble the geometry shown. If the grooves  112 , 122  are rolled, however, the pipe elements  110 , 120  are more likely to have ends  115 , 125  which are flared, though rolled pipe elements  110 , 120  may not have flares in other aspects. As such, the pipe coupling  100  can be made to accommodate the potential flaring of ends  115 , 125 . When the ends  115 , 125  are flared, the pipe coupling  100  can be sized to fit over the largest possible flare of the ends  115 , 125  based on standard tolerancing for creating the grooves  112 , 122 . 
     Referring to  FIGS.  22 A and  22 B , the pipe coupling  100  is shown as a flexible-type coupling with the fastening devices removed for clarity. As shown, the pipe connection ring  300   b  is a split ring constructed identically as the pipe connection ring  300  shown in  FIG.  10   , with square ring ends  320 , 330  and the angular opening A 1 . In an uncompressed condition as shown in  FIG.  22 A , a gap  2200   a  is defined between an outer surface  304  of the pipe connection ring  300   b  and the groove bottom surface at the first end  211   a  of the coupling segment  200   a , and a gap  2200   b  is defined between an outer surface  304  of the pipe connection ring  300   b  and the groove bottom surface at the second end  212   a  of the coupling segment  200   a . Though the pipe connection ring can be configured to contact the groove bottom surface around the entire circumference of the pipe connection ring  300   b , as shown the pipe connection ring  300   b  contacts the coupling segments  200   a,b  only at respective midpoints  1202 , 1204 . 
     The angular opening A 1  between the ring ends  320 , 330  (shown in  FIG.  10   ) is small enough for the ring ends  320 , 330  of the pipe connection ring  300   b  to contact one another before the inner surface  303  of the pipe connection ring  300   b  contacts the connection groove surface  116  of the pipe element  110 . In other words, radial compression of the pipe connection ring  300   b  is limited to a predetermined magnitude that is less than a magnitude of the radial compression that would bring all of the components of the pipe coupling  100 —including the coupling segments  200   a,b , the pipe connection ring  300   b , and the pipe element  110 —in contact with one another. While the geometry of the coupling segments  200   a,b  and the fastening devices  290   a,b  could be adjusted to produce a similar result yielding a flexible-type pipe coupling, adjusting the angular opening A 1  of the pipe connection ring is a simple and convenient approach. 
     In a compressed condition as shown in  FIG.  22 B , a gap  1200  remains between the pipe connection ring  300   b  and the connection groove surface  116  of the connection groove  112  of the pipe element  110 . Though shown for simplicity as extending around the entire circumference of the pipe connection ring  300   b , the gap  1200  may only exists at specific points. With the ring ends  320 , 330  in contact with one another, the pipe connection ring  300   b  cannot be compressed further, and continued application of compressive force deforms the coupling segments  200   a,b  in the manner described with regard to  FIG.  2   . The gap  1200  allows a limited amount of freedom for the pipe element  110  to move within the pipe coupling  100 , which can be beneficial in earthquake-prone geographic areas as previously noted. If, however, the magnitude of the ring opening is sufficiently large, then even full tightening compression will not cause the ends to meet, and in that event, the coupling segments  200   a,b  will deform uniformly and leave no gap of the type shown by the gap  1200 . This results in a rigid-type coupling, in which the pipe element  110  has no clearance with which to move within the pipe coupling  100 , which can be beneficial for high-pressure environments. In addition to the configuration illustrated in  FIGS.  20 A- 20 E , an example of a rigid-type configuration is illustrated in  FIG.  23   , to be described in detail herein. 
     In one aspect, the pipe coupling  100  includes a tightened position and an untightened position, the pipe connection ring  300   a,b  being in the uncompressed condition when the pipe coupling  100  is in the untightened position and the pipe connection ring  300   a,b  being in a compressed condition when the pipe coupling is in the tightened position. An inner diameter of the pipe connection ring such as that equal to twice the overall inner radius  1091  of the pipe connection ring  300   a,b  may be smaller in the compressed condition than twice the overall inner radius  1091  of the pipe connection ring  300   a,b  in the uncompressed condition. 
       FIG.  23    is a front sectional perspective view of the pipe coupling under full compression, showing no circumferential space between the pipe connection ring  300  and the coupling segments  200   a,b . Also, an opening  345  remains between the two ring ends  320 , 330 . The remaining gap represented by the opening  345  between the ring ends  320 , 330  under full compression is a common characteristic of a rigid-type coupling. 
     A pipe coupling constructed according to another aspect of the current disclosure is depicted in  FIGS.  24 - 25   . In one aspect, a pipe coupling  2700  includes coupling segments  2710 , 2710 ′, each generally arch-shaped in the same manner as the pipe coupling  100  shown in  FIGS.  1 - 3 B . The coupling segment  2710  has two ends, with a fastener pad  2730   a  protruding proximate to one end, and an eyelet member  2770   a  protruding from an opposite end of the coupling segment  2710 . Similarly, the coupling segment  2710 ′ has two ends, with a fastener pad  2730   b  protruding proximate to one end, and an eyelet member  2770   b  protruding from an opposite end of the coupling segment  2710 ′. Fastener holes  2732   a,b  are defined in the fastener pads  2730   a,b , respectively, and eyelet holes  2772   a,b  ( 2772   b  not shown) are defined in the eyelet members  2770   a,b , respectively. A fastener  2720  extends through the fastener holes  2732   a,b  and is secured in place with a nut  2725 . A hinge pin  2780  with a head  2780   a  extends through the eyelet holes  2772   a,b  and can be secured in place with any suitable securement member (not shown), such as by attachment of another head on the hinge pin  2780  after it has been guided through the eyelet holes  2772   a,b.    
     In this arrangement, with the fastener  2720  removed, the coupling segments  2710 , 2710 ′ can be pivoted with respect to the hinge pin  2780  to bring the pipe coupling  2700  to an open position, facilitating the positioning of the pipe coupling  2700  at a desired location between the pipe elements  110 , 120 . Specifically, as shown in  FIG.  25   , a gasket  2750  is contained within the coupling segments  2710 , 2710 ′ and is positioned to bridge a gap  2730  between the respective ends  115 , 120  of the pipe elements  110 , 120 . With the gasket  2750  in position, the coupling segments  2710 , 2710 ′ can be pivoted about hinge pin  2780  to a closed position of the pipe coupling  2700 . The fastener  2720  can then be passed through the fastener holes  2732   a,b  and secured in place by nut  2725 , which is then tightened to put the gasket  2750  under compression. As shown in  FIG.  25   , the coupling segments  2710 , 2710 ′ respectively include rims  2712   a,b  and  2712   a ′,b′. In the tightened position, rims  2712   a,b  and  2712   a ′,b′ contact the respective connection grooves  112 , 112  of the pipe elements  110 , 120  to lock the pipe coupling  2700  in place and to seal the gap  2730  with the gasket  2750 . Although the gasket  2750  is shown in  FIG.  25    as having a circular cross-section, other cross-sectional shapes exhibiting acceptable sealing properties can also be used with the pipe coupling  2700 . 
       FIGS.  26 - 29    depict a pipe coupling constructed in accordance with another aspect of the current disclosure. In one aspect, a pipe coupling  2900  includes arch-shaped coupling segments  2910 , 2912 , 2914 . The coupling segment  2910  has two ends, with a fastener pad  2930  protruding proximate to one end, and a pair of spaced eyelet members  2910   a,b  protruding from an opposite end. Similarly, the coupling segment  2914  has two ends, with a fastener pad  2930 ′ protruding proximate to one end, and a pair of spaced eyelet members  2914   a,b  ( 2914   a  shown in  FIGS.  27  and  2914     b  shown in  FIG.  29   ) protruding from an opposite end. The coupling segment  2912  has two opposed ends, with one eyelet member  2912   a  protruding proximate to one end and positioned between the pair of eyelet members  2910   a,b , and another eyelet member  2912   b  (shown in  FIG.  29   ) protruding proximate to an opposite end and positioned between the pair of eyelet members  2914   a,b . Fastener holes  2932 , 2932 ′ ( 2932 ′ not shown) are defined in the fastener pads  2930 , 2930 ′, respectively, and a fastener  2720  extends through the fastener holes  2732   a,b  and is secured in place with a nut  2725 . The eyelet members  2910   a , 2912   a , 2910   b  define a set of axially-aligned eyelet holes (not shown) that receives a hinge pin  2980 . Similarly, the eyelet members  2914   a , 2912   a , 2914   b  define another set of axially-aligned eyelet holes (not shown) that receives a hinge pin  2980 ′. Hinge pins  2980 , 2980 ′ can be secured in place within their respective eyelet members by connecting mechanisms such as a bolt  2935   a  and a nut  2935   b  (both shown in  FIG.  26   ) and by connecting mechanisms such as a bolt  2936   a  and a nut  2936   b  (shown in  FIG.  29   ). 
     This dual hinge pin arrangement allows the coupling segment  2910  to pivotally move with respect to the coupling segment  2912  about the hinge pin  2980 , and it allows the coupling segment  2912  to pivotally move with respect to the coupling segment  2914  about the hinge pin  2980 ′. In this manner, the pipe coupling  2900  can be moved between a closed position shown in  FIG.  27    to an open position shown in  FIG.  28   . In the open position, the pipe coupling  2900  can be positioned to surround a gasket  2950  that covers a gap  2990  between the ends  115 , 125  of the pipe elements  110 , 120  (shown in  FIG.  29   ). Once at that position, the pipe coupling  2900  is moved to a closed position, then the fastener  2920  is inserted through the fastener holes  2932 , 2932 ′ in the fastener pads  2930 , 2930 ′, respectively. The nut  2925  is then tightened about the fastener  2920  to put the pipe coupling  2900  under compression to reach the tightened position shown in  FIG.  29   . 
     As shown in  FIG.  29   , the coupling segment  2910  defines a gasket cavity  2910   c  and includes rims  2915   a,b , and the coupling segment  2914  defines a gasket cavity  2914   c  and includes rims  2915   a ′,b′. In the tightened position shown, the rims  2915   a,a ′ contact the connection groove  122  in the pipe element  120 , and the rims  2915   b,b ′ contact the connection groove  112  in the pipe element  110 . Additionally, the gasket cavities  2910   c , 2914   c  compress the gasket  2950  to hold it against the pipe elements  110 , 120  over the gap  2990 . Gasket  2950  is shown having a cross-sectional shape that includes a mushroom-shaped portion  2950   a  from which an annular tongue  2950   b  extends radially inwardly. However, other cross-sectional shapes exhibiting acceptable sealing properties can also be used with the pipe coupling  2900 . 
       FIGS.  30 - 33    depict a pipe coupling constructed in accordance with another aspect of the current disclosure. In one aspect, a pipe coupling  3300  includes arch-shaped coupling segments  3310 , 3315 . The coupling segment  3310  has an exterior surface  3312  and two ends, with a fastener pad  3330  protruding proximate to one end, and a pair of bearing blocks  3310   a,b  protruding from the exterior surface  3312  proximate to an opposite end. Similarly, the coupling segment  3315  has an exterior surface  3312 ′ and two ends, with a fastener pad  3330 ′ protruding proximate to one end, and a pair of bearing blocks  3315   a,b  (bearing block  3315   b  shown in  FIG.  33   ) protruding from the exterior surface  3312 ′ proximate to an opposite end. Fastener holes  3332 , 3332 ′ (both shown in  FIG.  32   ) are defined in fastener pads  3330 , 3330 ′, respectively, and pin apertures (not shown) are defined in the bearing blocks  3310   a,b  and  3315   a,b . A fastener  3320  extends through the fastener holes  3332 , 3332 ′ and is secured in place with a nut  3325 . 
     The pipe coupling  3300  also includes an arcuate rail member  3340  having a support block  3344  extending radially outward from the exterior surface of rail member  3340 , the support block  3344  supporting a pair of upper rails  3341 , 3342  and a pair of lower rails  3343 , 3345  (the lower rail  3343  shown in  FIG.  31    and the lower rail  3345  shown in  FIG.  33   ). The pair of upper rails  3341 , 3343  respectively defines arcuate slots  3341   a , 3342   a , and the pair of lower rails  3343 , 3345  respectively defines arcuate slots  3343   a , 3345   a  (slot  3345   a  not shown). A guide pin  3380  extends through the arcuate slots  3341   a , 3342   a  and is supported at its ends by the bearing blocks  3310   a,b . The ends of the guide pin  3380  are provided with heads  3380   a,b  (shown in  FIG.  33   ) to retain the guide pin  3380  within the bearing blocks  3310   a,b . Similarly, a guide pin  3382  (also shown in  FIG.  33   ) extends through the arcuate slots  3343   a , 3345   a  and is supported at its ends by the bearing blocks  3315   a,b . The ends of the guide pin  3382  are provided with heads  3382   a,b  to retain the guide pin  3382  within the bearing blocks  3315   a,b .  FIG.  30    shows the pipe coupling  3300  in a shipping configuration, with the coupling segments  3310 , 3315  and the arcuate rail member encircling an annular gasket  3350 , secured together by the fastener  3320  and the nut  3325 . 
     As shown in  FIG.  32   , the arcuate rail member  3340  has a general H-shaped cross-section, with lower legs  3340   a,a ′ terminating in ends  3340   b,b ′, respectively. When the fastener  3320  and the nut  3325  are removed, the pipe coupling  3300  can be moved to open positions such as those shown in  FIGS.  31  and  32   . The pipe coupling  3300  is opened by sliding the coupling segment  3310  circumferentially along the upper rails  3341 , 3342  toward the support block  3344 , and by sliding the coupling segment  3315  circumferentially along the lower rails  3343 , 3345  toward the support block  3344 . In other words, the fastener pads  3330 , 3330 ′ are moved away from one another.  FIG.  32    shows the annular gasket  3350  as positioned between the respective ends  115 , 125  of the pipe elements  110 , 120 . Then, the lower legs  3340   a,a ′ of the rail member  3340  are positioned to straddle the gasket  3350 , such that ends  3340   b,b ′ contact the connection grooves  112 , 122 , respectively, of the pipe elements  110 , 120 . To secure the pipe coupling  3300  to the pipe elements  110 , 120 , the coupling segments  3310 , 3315  are both slid circumferentially along their respective rails away from the support block  3344 , such that the fastener pads  3330 , 3330 ′ are moved toward one another. The fastener  3320  is inserted through the fastener holes  3332 , 3332 ′, and the nut  3325  is tightened to lock the pipe coupling  3300  in place about the ends  115 , 125  of the pipe elements  110 , 120 . 
       FIG.  33    provides a cross-sectional view of the annular gasket  3350  and the rail member  3340 , which defines an inner surface  3610 . The gasket  3350  is ring-shaped and includes an annular body  3352  having a radially outer surface  3354  that interacts with the inner surface  3610  of the rail member  3340 . The annular body  3352  includes an arcuate section  3355  having opposed ends that terminate in circular ribs  3356 , 3356 ′. 
       FIGS.  34 - 37    depict a pipe coupling constructed in accordance with another aspect of the current disclosure. In one aspect, a pipe coupling  3700  includes arch-shaped coupling segments  3710 , 3710 ′, each generally arch-shaped in the same manner as the pipe coupling shown in  FIGS.  1 - 3 B . The coupling segment  3710  has two ends, with a fastener pad  3730  protruding proximate to one end, and a leg  3712  extending downwardly from an opposite end. The leg  3712  is bent horizontally proximate to its end to form a bearing member  3740  having a bearing surface  3740   a . The coupling segment  3710 ′ has two ends, with a fastener pad  3730 ′ protruding proximate to one end, and a leg  3714  extending upwardly from an opposite end. The leg  3714  is bent horizontally proximate its end to form a bearing member  3742  having a bearing surface (not shown). Fastener holes  3732 , 3732 ′ are defined in the fastener pads  3730 , 3730 ′, respectively. A fastener  3720 , having a head  3720   a , extends through the fastener holes  3732 , 3732 ′ and is secured in place with a nut  3725 . A washer  3727  may also be placed on the fastener  3720  between the fastener pad  3730 ′ and the nut  3725 . The coupling segments  3710 , 3710 ′ have interior surfaces defining a gasket channel  3716  in which is seated an annular gasket  3750 . The annular gasket  3750  seals the joint between the ends of the pipe elements  110 , 120  when the elements are aligned end-to-end within the pipe coupling  3700  (as shown in  FIGS.  35  and  36   ). When the pipe coupling  3700  is fully tightened, as shown in  FIGS.  35 - 37   , the bearing members  3740 , 3742  interlock as a result of spring tension, countering the force of the tightened fastener  3720 , exerted through the legs  3712 , 3714 . The bearing surface of the bearing member  3742  presses against the bearing surface  3740   a  of the bearing member  3740  to provide securement of the pipe coupling  3700  at the end opposite the fastener pads  3730 , 3730 ′, a resulting frictional force between the bearing surface of the bearing member  3742  and the bearing surface  3740   a  of the bearing member  3740  helping to secure the pipe coupling  3700  in the tightened position shown. 
       FIG.  38    depicts a pipe coupling constructed in accordance with another aspect of the current disclosure. In one aspect, an adjustable pipe coupling  4100  includes three arcuate coupling segments  4110 , 4120 , 4130 , circumferentially spaced from one another as indicated by gaps  4190 , 4190 ′, 4190 ″ defined by the coupling segments  4110 , 4120 , 4130 . The coupling segment  4120  may include a plurality of recessed portions  4121 , and the coupling segments  4110 , 4130  may include a plurality of similar recessed portions. The coupling segments  4110 , 4120 , 4130  each has an interior surface that defines a gasket groove receiving an annular gasket  4150 . The pipe coupling  4100  also includes a belt  4140  constructed of a strip of rigid material such as metal, though the choice of material of the belt  4140  can also be non-metallic. The belt  4140  defines apertures  4132 , 4132 ′ proximate to ends  4142   a,b , respectively, of the belt  4140 , respectively, and is wrapped around the outer periphery of the coupling segments  4110 , 4120 , 4130 . Bends  4102 , 4102 ′ orient the ends  4142   a,b  in an outwardly flaring position, defining fastener pads  4145 , 4145 ′. Apertures  4132 , 4132 ′ are axially aligned to admit a threaded fastener  4122 . Washers  4127 , 4127 ′ are placed about the upper and lower ends, respectively, of the fastener  4122 . A nut  4125  is threaded onto the upper end of the fastener  4122  and when tightened, exerts downward pressure, through the washer  4127 , on the fastener pad  4130 . Similarly, a head  4125 ′ of the fastener  4122 , when the fastener  4122  is tightened, exerts upward pressure, through the washer  4127 ′, on the fastener pad  4130 ′. In this manner, the belt  4140  exerts circumferential compression upon the coupling segments  4110 , 4120 , 4130 , which in turn, exert such compression upon the annular gasket  4150  to effect sealing of a joint of pipe elements  110 , 120  (pipe element  110  shown in  FIG.  39   , pipe element  120  not shown) oriented end-to-end within the pipe coupling  4100 . 
       FIGS.  39 - 40    depict a pipe coupling constructed in accordance with another aspect of the current disclosure. In one aspect, an adjustable pipe coupling  4200  is constructed similarly to the pipe coupling  4100  in that the pipe coupling  4200  also employs use of a belt and multiple movable coupling segments, but uses a different number of coupling segments and a different securement mechanism. The pipe coupling  4200  includes four arcuate coupling segments  4210 , 4212 , 4214 , 4216 , circumferentially spaced from one another as indicated by gaps  4290 , 4291 , 4292 , 4293  defined by the coupling segments  4210 , 4212 , 4214 , 4216 . The coupling segments  4210 , 4212 , 4214 , 4216  have interior surfaces that define a gasket groove (not shown) receiving an annular gasket  4250 . The pipe coupling  4200  also includes a belt  4240  constructed of a strip of rigid material such as metal, though the material of the belt  4240  can also be non-metallic. The belt  4240  includes an outer surface  4240   a  and opposed ends  4244 , 4244 ′. Bends  4242 , 4242 ′ are formed into the belt  4240  proximate to the ends  4244 , 4244 ′, respectively, such that the end portions of the belt  4240  contact and are permanently joined to, the outer surface  4240   a  using any sufficient method such as, for example and without limitation, welding, adhesives, or mechanical fastening. The belt  4240  is wrapped around the outer periphery of the coupling segments  4210 , 4212 , 4214 , 4216 . Blocks  4230 , 4230 ′, each having ends with internally-threaded bores (not shown), are passed through the loops in the belt  4240  formed at bends  4242 , 4242 ′, respectively. Externally-threaded fasteners  4220   a,b  mesh with the internal threads of the bores in the blocks  4230 , 4230 ′ to result in the assembled but untightened configuration shown in  FIG.  39   . The fasteners  4220   a,b  can include heads  4225   a,b , which are configured with a hex or other recess to facilitate tightening of the fasteners  4220   a,b . When the fasteners  4220   a,b  are tightened, the bends  4242 , 4242 ′ are drawn toward one another and result in the tightened configuration shown in  FIG.  40   . In this manner, the belt  4240  exerts circumferential compression upon the coupling segments  4210 , 4212 , 4214 , 4216 , which in turn, exert such compression upon the annular gasket  4250  to effect sealing of a joint of the pipe elements  110 , 120  (pipe element  120  not shown) that are oriented end-to-end within the pipe coupling  4200 . In a tightened configuration, the coupling segments  4210 , 4212  may contact each other at a joint  4294 , the coupling segments  4212 , 4214  may contact each other at a joint  4295 , the coupling segments  4214 , 4216  may contact one another at a joint  4296 , and the coupling segments  4216 , 4210  may contact one another at a joint  4297 . 
       FIGS.  41 - 45    depict a pipe coupling constructed in accordance with another aspect of the current disclosure. In one aspect, a twist-on adjustable pipe coupling  4400  includes three arcuate coupling segments  4410 , 4420 , 4430  having respective first axial ends  4411 , 4421 , 4431  and respective second axial ends  4412 , 4422 , 4432  (second axial ends  4422 , 4432  shown in  FIG.  42   , second axial end  4412  shown in  FIG.  44   ). The coupling segments  4410 , 4420 , 4430  are circumferentially spaced from one another as indicated by gaps  4490 , 4491 , 4492  defined by the coupling segments  4410 , 4420 , 4430 . The coupling segments  4410 , 4420 , 4430  each has an interior surface that defines a gasket groove receiving an annular gasket  150  (such as the gasket  150  shown in  FIG.  3 B ) and have threads  4480  on their exterior surfaces. The pipe coupling  4400  also includes an annular collar  4440  having a circular body  4441  from which gripping lugs  4442 , 4444 , 4446  extend radially outwardly, the gripping lugs  4442 , 4444 , 4446  circumferentially spaced from one another by a predetermined angle  4495  (shown in  FIG.  43   ). The annular collar  4440  is provided with internal threads  4485  (shown in  FIG.  42   ), which mate with the external threads  4480  of the coupling segments  4410 , 4420 , 4430 . Thus, when the pipe coupling  4400  is shipped, the annular collar  4440  can be screwed onto the coupling segments  4410 , 4420 , 4430  to hold them in place about the annular gasket  150 , resulting in the configuration shown in  FIGS.  41  and  42   . 
       FIGS.  44  and  45    illustrate the installation of the pipe coupling  4400  onto pipe elements  110 , 120  that have connection grooves  112 , 122  proximate their respective ends  115 , 125 . The coupling segments  4410 , 4430  are shown housing the gasket  150 , which straddles a gap  4490  remaining between the ends  115 , 125  of the pipe elements  110 , 120 . Additionally, the axial ends  4410   a,b  of the coupling segment  4410  extend radially inward to terminate in respective edges  4413 , 4414  that align with connection grooves  122 , 112 , respectively, similar to that shown with respect to the coupling segment  4430  in an untightened configuration of  FIG.  45   . Similarly, the axial ends  4431 , 4432  of the coupling segment  4430  extend radially inwardly to terminate in respective edges  4433 , 4434  that align with connection grooves  122 , 112 , respectively, as shown in  FIG.  45   . Rotation of the annular collar  4440  about the coupling segments  4410 , 4430  results in a tightened configuration shown in  FIG.  44   , where the edges  4413 , 4414  and  4433 , 4434  now contact the connection grooves  122 , 112 , thereby locking the pipe coupling  4400  onto the respective pipe elements  120 , 110 . 
       FIG.  46    depicts a twist-on pipe coupling  4900  constructed similarly to the pipe coupling  100  shown in  FIGS.  41 - 45   , except that the pipe coupling  4900  uses different threading configurations. In one aspect, the twist-on pipe coupling  4900  includes three arcuate coupling segments  4910 , 4920 , 4930  circumferentially spaced from one another as indicated by gaps  4990 , 4991 , 4492  (gap  4991  not shown) defined by the coupling segments  4910 , 4920 , 4930 . The coupling segments  4910 , 4920 , 4930  each has an interior surface that defines a gasket groove receiving an annular gasket  4950 , and have threading  4912 , 4914 , 4916  on their exterior surfaces (threading  4916  not shown). The width of the region of threading  4912  tapers from a first end  4911   a  to a second end  4911   b  of the coupling segment  4910 , and the width of the region of threading  4914  tapers from a first end  4921   a  to a second end  4921   b  of the coupling segment  4920 . Though not shown, coupling segment  4930  exhibits the same tapering of the region of the threading  4916  on its exterior surface from a first end  4931   a  (not shown) to a second end  4931   b . The pipe coupling  4900  also includes an annular collar  4940  having a circular body  4941  from which gripping lugs  4970 , 4972  extend radially outward, the gripping lugs circumferentially spaced from one another by a predetermined angle (similarly to the angle  4495  in  FIG.  43   )—the angle measuring approximately 180 degrees in  FIG.  46   . The annular collar  4940  includes an inner surface  4980  that carries a plurality of threading ribs  4942 , 4942 ′, 4942 ″, which mate with the external threading  4912 , 4914 , 4916  of the coupling segments  4910 , 4920 , 4930 . Rotation of the annular collar  4940  onto the coupling segments  4910 , 4920 , 4930  compresses those segments upon the annular gasket  4950 , which effects a seal at the joint between the ends of the pipes contacted by the annular gasket  4950 . Prior to that tightening, the pipe coupling  4900  can be slid along a pipe such as the pipe element  110  and positioned at the joint to be sealed. 
       FIGS.  47  and  48    depict a pipe coupling constructed in accordance with another aspect of the current disclosure. In one aspect, a coupling  5000  includes coupling segments  5010 , 5010 ′, each generally arch-shaped in the same manner as the pipe coupling shown in  FIGS.  1 - 3 B . Referring to  FIG.  47   , the coupling segment  5010  has two ends, with a fastener pad  5030   a  protruding proximate to one end, and another fastener pad  5030   b  protruding from an opposite end. Similarly, the coupling segment  5010 ′ has two ends, with a fastener pad  5030   a ′ protruding proximate to one end, and another fastener pad  5030   b ′ protruding from an opposite end. Fastener holes  5032   a,b  are defined in the fastener pads  5030   a,b , respectively, and fastener holes  5032   a ′,b′ (fastener hole  5032   b ′ not shown) are defined in the fastener pads  5030   a ′,b′, respectively. A fastener  5020  extends through the fastener holes  5032   a,a ′ and is secured in place with a nut  5025 ; though not shown, a fastener identical to fastener  5020  extends through the fastener holes  5032   b,b ′ and is likewise secured by a nut. The coupling segments have inner surfaces defining a gasket groove in which are seated a pair of annular gaskets  5050 , 5052 . 
       FIG.  48    shows the shape of annular gaskets  5050 , 5052 , along with the associated inner surfaces of coupling segment  5010  (which mirror those of the coupling segment  5010 ′). Coupling segment  5010  includes an arcuate body  5012  and a central annular rib  5014  extending radially inwardly from the body  5012  at a center of a width  5018  of the coupling segment  5010 , the central annular rib  5014  having an end  5014   a . The coupling segment  5010  includes an inner surface  5016  defining a first pipe seat  5060  and a second pipe seat  5062 . Gaskets  5050 , 5052  are seated within the coupling segment  5010 , the gasket  5050  disposed between the central annular rib  5014  and the pipe seat  5060 , and the gasket  5052  disposed between the central annular rib  5014  and the pipe seat  5062 . Gasket  5050  is ring-shaped and includes an annular body  5064   a  having a radially outer surface  5066   a . The radially outer surface  5066   a  interacts with the inner surface  5016  of the coupling segment  5010 . The annular body  5064   a  includes a side portion  5068   a  extending radially inwardly from the radially outer surface  5066   a , the side portion  5068   a  contacting a surface of the central annular rib  5014  and terminating at an end  5070   a . The annular body  5064   a  also includes an axially outer surface  5072   a  extending from the radially outer surface  5066   a , opposite the side portion  5068   a , at an angle with respect to the radially outer surface  5066   a . Extending radially inwardly from the axially outer surface  5072   a  is a sealing rib  5074   a , terminating in a tip  5076   a . The body  5064   a  further defines a gasket channel  5078   a  axially between the end  5070   a  and the tip  5076   a . The gasket channel  5078   a  is a pocket into which fluid media may flow when the gasket  5050  is in use. The gasket channel  5078   a  is shown as a tubular channel but can have other shapes. When placed in sealing contact with an exterior surface of a pipe element, the gasket channel  5078   a  allows some fluid pressure to aid in sealing the sealing rib  5074   a  against a pipe element, although such use is not necessary for successful sealing of the gasket  5050 . 
     Gasket  5052  in  FIG.  48    has a shape in cross-section that is a mirror reflection of the shape in cross-section of the gasket  5050 . Thus, the corresponding elements of gasket  5052  have been numbered identically to those of gasket  5050  except with a “b” suffix. 
       FIGS.  49  and  50    depict a pipe coupling constructed in accordance with another aspect of the current disclosure. In one aspect, a gasketless pipe coupling  5200  includes coupling segments  5210 , 5210 ′, each generally arch-shaped in the same manner as the pipe coupling  100  shown in  FIGS.  1 - 3 B . Referring to  FIG.  49   , the coupling segment  5010  has two ends, with a fastener pad  5230   a  protruding proximate to one end, and another fastener pad  5230   b  protruding from an opposite end. Similarly, the coupling segment  5210 ′ has two ends, with a fastener pad  5230   a ′ protruding proximate to one end, and another fastener pad  5230   b ′ (not shown) protruding from an opposite end. Fastener holes  5232   a,b  are defined in fastener pads  5230   a,b , respectively, and fastener holes  5232   a ′,b′ (hole  5232   b ′ not shown) are defined in fastener pads  5230   a ′,b′, respectively. A fastener  5220  extends through the fastener holes  5232   a,a ′ and is secured in place with a nut  5225 ; though not shown, a fastener identical to fastener  5220  extends through the fastener holes  5032   b,b ′ and is likewise secured by a nut. 
     Referring to the sectional view of  FIG.  50   , the coupling segment  5210  includes an inner surface  5212  on which a coating  5250  adheres. The coating  5250  is molded to conform to the geometry of the inner surface  5212  and may be constructed of rubber. The coating  5250  may include a central section  5270  extending over a gap  5290  between ends  115 , 125  of pipe elements  110 , 120 , respectively. The coating  5250  may further include first angled sections  5272   a,b  extending radially inwardly at an angle from respective ends of the central section  5270  and first straight sections  5274   a,b  extending axially outwardly from the angled sections  5272   a,b . Shoulder sections  5276   a,b  extend radially inwardly from respective straight sections  5274   a,b . Second straight sections  5278   a,b  extend axially outwardly from respective shoulder sections  5276   a,b , and second angled sections  5280   a,b  extend radially outwardly at an angle from respective ends of the second straight sections  5278   a,b . Finally, end sections  5282   a,b  extend radially outwardly from respective ends of the second angled sections  5280   a,b . Thus, sections  5276   a,b ,  5278   a,b , and  5280   a,b , together with the portions of inner surface  5212  contacting those sections, form key sections that extend into connection grooves  122 , 112  of pipe elements  120 , 120 . Upon full tightening, at least the axially inner surfaces  5284   a,b  and the radially inner surfaces  5286   a,b  respectively contact the connection grooves  122 , 112 , thereby effecting a seal of the gap  5290  without a gasket. The gap  5290  may be effectively zero in some installations. 
       FIGS.  51 - 55    disclose various gasket configurations that may be used with one or more of the pipe coupling configurations exemplified herein. 
       FIGS.  51  and  52    depict sections of an annular gasket  5400  constructed similarly to the gasket  2950  disclosed in  FIG.  29   . Gasket  5400  is shown having an annular body  5402  with a cross-sectional shape that includes a mushroom-shaped portion  5404  from which an annular tongue  5406  extends radially inwardly, the annular tongue  5406  configured to extend within a gap between pipe ends when assembled into a coupling. 
       FIGS.  53  and  54    depict sections of an annular gasket  5600 , having an overall cross-sectional shape resembling a stylized letter “C.” The gasket  5600  includes an annular body  5610  having an arcuate radially outer surface  5620 . Side sections  5622   a,b  extend radially inwardly from ends of the arcuate radially outer surface  5620 , and side sections  5622   a,b  terminate in respective ridges  5630   a,b . Sealing ribs  5640   a,b  extend radially inwardly at an angle from the ridges  5630   a,b , and terminate at respective ends  5650   a,b . The body  5610  further defines a gasket channel  5670  extending radially outwardly from ends  5650   a,b . A gasket channel  5670  is a pocket into which fluid media may flow when the gasket  5600  is in use. The gasket channel  5670  is shown as a tubular channel but can have other shapes. When placed in sealing contact with an exterior surface of a pipe element, the gasket channel  5070  allows some fluid pressure to aid in sealing the sealing ribs  5640   a,b  against a pipe element, although such use is not necessary for successful sealing of the gasket  5600 . 
       FIG.  55    depicts a cross-section of a portion of another annular gasket  5800 . The gasket  5800  is ring-shaped and includes an annular body  5802  having a substantially straight radially outer surface  5804  having opposed ends from which side sections  5806   a,b  extend radially inwardly and axially outwardly. Sealing ribs  5808   a,b  extend radially inwardly from the side sections  5806   a,b  and are defined by first angled sections  5810   a,b  respectively extending radially inwardly and axially inwardly at an angle from the side sections  5806   a,b  and further defined by second angled sections  5812   a,b  respectively extending axially inwardly and radially outwardly at an angle from the first angled sections  5810   a,b . The second angled sections  5812   a,b  terminate in respective tips  5814   a,b . The body  5802  further defines a gasket channel  5816  extending radially outwardly from the tips  5814   a,b . The gasket channel  5816  is a pocket into which fluid media may flow when the gasket  5800  is in use. The gasket channel  5816  is shown as a tubular channel but can have other shapes. When placed in sealing contact with an exterior surface of a pipe element, the gasket channel  5816  allows some fluid pressure to aid in sealing the sealing ribs  5808   a,b  against a pipe element, although such use is not necessary for successful sealing of the gasket  5800 . 
     In one aspect, the gasket  150  comprises the geometry shown in  FIGS.  56  through  58    including a pair of sealing ribs  520   a,b  and a plurality of tabs  550  distributed circumferentially about and protruding from the central rib  530 . In cross-section, the gasket  150  defines the overall height  570  measured from the radially outer surface  515  to the sealing surfaces  526   a,b  of the sealing ridges  525   a,b . The overall height  570  can be reduced as shown—in comparison to the overall height  570  of the gasket  150  shown in  FIG.  3 B . In one aspect, reducing the overall height  570  causes the gasket  150  to protrude radially outward less with respect to a given inner diameter of the gasket  150 , giving the gasket  150  a lower profile to allow the coupling segments  200   a,b  and the pipe connection rings  300  to have smaller diameters to closer match the diameter of the pipes and thereby lower the amount of tightening necessary to engage the pipe elements  110 , 120 . 
     In another aspect, reducing the overall height  570  causes the gasket  150  to protrude radially inward less than the distance shown in  FIG.  3 B  relative to the respective inner surface  202   a,b  of the coupling segments  200   a,b  or the respective inner surfaces of the pipe connection rings  300   a,b . By reducing the overall height  570  of the gasket  150  as shown, with or without the inclusion of the tabs  550 , the pipe connection rings  300   a,b  of the pipe coupling  100  can be made to align with the connection grooves  112 , 122  or on the outside of the shoulders  118 , 128 , at a point in the installation process before the gasket  150  contacts the pipe elements  110 , 120  or before the gasket  150  compresses significantly. In one aspect, a user may choose to rely on tactile sensation (i.e., may rely on “feel”) in addition to or instead of visual clues to confirm proper alignment of the pipe coupling  100  with the pipe elements  110 , 120 . In one aspect, tactile confirmation that both of the pipe connection rings  300   a,b  are simultaneously engaged in the connection grooves  112 , 122  or on the outside of the shoulders  118 , 128  can be more difficult as the gasket  150  compresses. Delaying compression of the gasket  150  can be achieved, for example and without limitation, by reducing the overall height  570  of the gasket  150 . 
     In one aspect, as shown, each of the tabs  550  when bent individually and the plurality of tabs  550  when bent simultaneously are easily bendable in an axial direction so as not to interfere with installation of the gasket completely over the ends  115 , 125  of either of the pipe elements  110 , 120 . In one aspect, an innermost diameter of the gasket  150 , as measured to a radially inward facing portion of a tab surface  551 , is less than the outer diameter of the pipe elements  110 , 120 . When sliding a gasket such as the gasket  150  shown in  FIG.  58    completely over the end  115 , 125  of either of the pipe elements  110 , 120 , one of the respective ends  115 , 125  of the pipe elements  110 , 120  contacts an axially outward facing portion of the tab surface  551  of each of the tabs  550 , causing each of the tabs  550  to bend. When the gasket  150  is slid back in the other direction, including when the pipe elements  110 , 120  are positioned end-to-end but with a slight gap, the tabs  550  can unbend and extend into the gap between the pipe elements  110 , 120 . In such aspect, axially outward facing portions of the tabs  550  face axially outward facing portions of the respective ends  115 , 125  of the pipe elements  110 , 120 . The tabs  550  can thus engage the ends  115 , 125  to separate the end  115  from the end  125  and to provide proper spacing for the pipe connection rings  300   a,b  to align with the connection grooves  112 , 122 . The gap created between the end  115  and the end  125  by the tabs  550  can be at least equal to an axial thickness of the tab  550  as viewed in cross-section such as in  FIG.  58   . The geometry of the pipe elements  110 , 120  and or features of the pipe coupling  100  can be adjusted as necessary to accommodate the axial thickness of the tab  550  including additional space for any manufacturing tolerances. 
     In one aspect, each of the tabs  550  bends easily when the gasket  150  is slid completely over the end  115 , 125  of one of the pipe elements  110 , 120  because each of the tabs  550  is rounded on each axially outward edge. In another aspect, each of the tabs  550  bends easily in the described condition because each tab  550  is separate and distinct from every other tab  550  and therefore bending of each of the tabs  550  in an axial direction does not require the simultaneously stretching or deformation of any material adjacent to the tab  550 —such as would be the case were the geometry of the tab  550  such as that shown in  FIG.  58    to continue circumferentially around the gasket  150 . In one aspect, when the gasket  150  is viewed along its axis, each of the tabs  550  also tapers from the central rib  530 , defining taper tangent lines  555   a,b  extending toward a radially inward facing portion of the tab surface  551  and angled with respect to a line  557  extending through a center of the gasket. With this taper, the cross-sectional area of the tab  550  effectively decreases towards the radially inward facing portion of the tab surface  551  and therefore increasing less force is required to cause the tab  550  to bend at the radially inward facing portion of the tab surface than is required to cause the tab  550  to bend proximate to its connection to the central rib  530 . In addition, because the taper on each tab  550  causes less surface area of each of the tabs  550  to contact the pipe elements  110 , 120 , the frictional forces created when sliding the gasket  150  completely over either of the respective ends  115 , 125  of the pipe elements  110 , 120  are reduced. In one aspect, for example and without limitation, the circumferential length of the gasket including tabs  550  can be less than the circumferential length of the gasket not including tabs. In one aspect, a total of six tabs  550  are evenly spaced circumferentially around the gasket  150 , where each tab  550  is spaced apart from each adjacent tab by an angle of 60°. In another aspect, a smaller quantity or a greater quantity of tabs  550  are spaced circumferentially around the gasket  150 , and the tabs  550  need not be spaced evenly. In one aspect, an intersection between the tab surface  551  and a radially inward facing surface of the gasket  150  includes a radius or other fillet, reducing or eliminating any stress concentration at the intersection. 
     In one aspect, each of the sealing ribs  520   a,b  extends substantially radially inwardly and increases in thickness from a radially outside position to a radially inside position. In one aspect, each of the sealing ribs  520   a,b  defines an axially outer surface  521   a,b  extending from the radially outer surface  515  to an end of an axially outer drafted surface  522   a,b , respectively. Each of the axially outer surfaces  521   a,b  is angled or slanted with respect to a radial direction of the gasket  150 . The angle of each of the axially outer surfaces  521   a,b  is consistent around the circumference of the gasket  150 , so that each of the axially outer surfaces  521   a,b  is shaped as a truncated cone. In one aspect as shown, each of the axially outer surfaces  521 ,a,b is angled, for example and without limitation, between about 19° and about 22° degrees with respect to a radial direction. 
     Each of the axially outer drafted surfaces  522   a,b  extends from an axially outermost edge of the gasket  150  to the corresponding sealing surface  526   a,b . In one aspect, each of the axially outer drafted surfaces  522   a,b  may be rounded, slanted, or have any one of various other shapes in cross-section. In one aspect, such cross-sectional shapes translate to the three-dimensional shape of a cone or a paraboloid. Such shapes are truncated, as a full cone or paraboloid would not typically allow insertion of pipe elements in the gasket  150 . In one aspect as shown, each of the axially outer drafted surfaces  522   a,b  is angled, for example and without limitation, between about 27° and about 28° with respect to a radial direction. Extending from each of the sealing surfaces  526   a,b  is an axially inner drafted surface  527   a,b . In one aspect, each of the axially inner drafted surfaces  527   a,b  may be rounded, slanted, or have any one of various other shapes in cross-section. In one aspect, such cross-sectional shapes translate to the three-dimensional shape of a cone or a paraboloid. Such shapes are truncated, as a full cone or paraboloid would not typically allow insertion of pipe elements in the gasket  150 . Each of the axially inner drafted surfaces  527   a,b  defines the termination of the sealing ridge  525   a,b  along an axially inward direction. 
     In another aspect, the gasket  150  comprises the geometry shown in  FIGS.  59  through  61    including the pair of sealing ribs  520   a,b  and the plurality of tabs  550  distributed circumferentially about and protruding from the central rib  530 . In one aspect, each of the tabs  550  is positioned axially between the sealing member  557   a  and the sealing member  557   b . In one aspect, the overall height  570  can be further reduced as shown—in comparison to the overall height  570  of the gasket  150  shown in  FIG.  3 B  and in comparison to the overall height  570  of the gasket  150  shown in  FIG.  58   . In one aspect, reducing the overall height  570  causes the gasket  150  to protrude radially outward less with respect to a given inner diameter of the gasket  150 , giving the gasket  150  a lower profile to allow the coupling segments  200   a,b  and the pipe connection rings  300  to have smaller diameters to closer match the diameter of the pipes and thereby lower the amount of tightening necessary to engage the pipe elements  110 , 120 . 
     In another aspect, reducing the overall height  570  causes the gasket  150  to protrude radially inward by less than the distances shown in  FIGS.  3 B and  58    relative to the respective inner surface  202   a,b  of the coupling segments  200   a,b  or the respective inner surfaces of the pipe connection rings  300   a,b.    
     Although several embodiments of the invention have been disclosed in the foregoing specification, it is understood by those skilled in the art that many modifications and other embodiments of the invention will come to mind to which the invention pertains, having the benefit of the teaching presented in the foregoing description and associated drawings. It is thus understood that the invention is not limited to the specific embodiments disclosed hereinabove, and that many modifications and other embodiments are intended to be included within the scope of the appended claims. Moreover, although specific terms are employed herein, as well as in the claims which follow, they are used only in a generic and descriptive sense, and not for the purposes of limiting the described invention, nor the claims which follow. 
     One should note that conditional language, such as, among others, “can,” “could,” “might,” or “may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or steps. Thus, such conditional language is not generally intended to imply that features, elements and/or steps are in any way required for one or more particular embodiments or that one or more particular embodiments necessarily include logic for deciding, with or without user input or prompting, whether these features, elements and/or steps are included or are to be performed in any particular embodiment. 
     It should be emphasized that the above-described embodiments are merely possible examples of implementations, merely set forth for a clear understanding of the principles of the present disclosure. Any process descriptions or blocks in flow diagrams should be understood as representing modules, segments, or portions of code which include one or more executable instructions for implementing specific logical functions or steps in the process, and alternate implementations are included in which functions may not be included or executed at all, may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those reasonably skilled in the art of the present disclosure. Many variations and modifications may be made to the above-described embodiment(s) without departing substantially from the spirit and principles of the present disclosure. Further, the scope of the present disclosure is intended to cover any and all combinations and sub-combinations of all elements, features, and aspects discussed above. All such modifications and variations are intended to be included herein within the scope of the present disclosure, and all possible claims to individual aspects or combinations of elements or steps are intended to be supported by the present disclosure.