Irrigation pipe system

An irrigation pipe system including a tubular coupler member releasably connectable to fluid transport pipes. The tubular coupler member includes wing-like lateral projections for stabilizing and minimizing impact upon the tubular coupler member as it is drawn along a ground surface. Structure is provided for enabling a sprinkler riser to be connected to and disconnected from the tubular member by rotating the sprinkler riser less than about one rotation. A seal is also provided for preventing fluid leakage between the tubular coupler member and the sprinkler riser.

FIELD OF THE INVENTION
 The present invention relates to devices for coupling piping and, more
 particularly, to apparatus for coupling fluid transport piping for
 irrigation.
 BACKGROUND OF THE INVENTION
 Sprinkler irrigation has over the years replaced many other forms of
 irrigation methods because it minimizes erosion, prevents many drainage
 problems, does not require land leveling, and provides light application
 of moisture for irrigating crops.
 Whenever a sprinkler system is referred to by name, the reference is
 usually made to the manufacturer's brand name. Sprinkler systems are
 typically classified by the degree of their portability. For example,
 there are permanent systems, fully portable systems which can be moved
 from one field to another, and semi-portable systems where the piping is
 movable but the pumping plant is in a fixed location.
 A number of manufacturers currently provide fittings for sprinkler systems.
 These fittings include, for example, couplers, "L" and "T" shaped pipe
 connectors, reducers, T-type valves for maintaining hydrants, and
 valve-opener elbows. Such fittings typically appear every 20 to 40 feet
 along portable sprinkler laterals and, therefore, enable ready
 identification of the system's manufacturer.
 In some respects, the couplers, as well as other fittings of existing
 systems possess similar characteristics. For example, most have either one
 or two replaceable rubber gaskets to prevent the loss of water between the
 pipe and the coupler when pressure is applied. Nearly all of these gaskets
 are made to permit water to drain out whenever the line is shut off and
 the pressure is released.
 There are some differences, however, in the way the couplers of different
 manufactures fasten to a pipe. Some have a latch, others are bolted or
 welded and still others have one end rolled or pressed into the pipe. On
 most systems, the coupler makes a flexible joint which allows the
 sprinkler pipe to bend or form an angle with respect to the coupler. Some
 flexibility is desirable, particularly on rolling land.
 Most couplers also have a guide or guard apron that helps to keep dirt from
 being scooped up when the pipe is inserted, or moved.
 Current use of aluminum pipe couplers for sprinkler lines has evolved into
 several popular styles, including so-called "drop lock" or "no-latch"
 couplers and "tow line" or "drag line" couplers. These couplers are fitted
 with one of two styles of Chevron gaskets: a "drain" gasket which, at a
 predetermined pressure drop, is designed to leak water through the coupler
 and a "non drain" gasket which leaks water at a substantially lower
 pressure. A typical locking mechanism for existing couplers is a latch or
 band bolted or welded to the male end of a piece of aluminum tubing.
 Sprinkler pipe fittings are also normally fabricated from cast aluminum or
 galvanized steel. There are several manufacturers of these fittings, the
 basic styles of which have been in use since at least as early as 1970.
 For instance, a representative coupler may be provided with a 3/4" or 1"
 female iron pipe thread to facilitate the installation of a metal (usually
 galvanized steel) riser of about 6" to 36" in length for supporting and
 delivering fluid to sprinklers of varying sizes.
 This sprinkler-riser-coupler-aluminum tubing combination is light in weight
 and is commonly referred to as "hand movable" pipe. Such a system may be
 manually installed and removed, typically by about three individuals. The
 "drag line" or "tow line" styles can be pulled by tractor or machinery but
 it is necessary to manually install and disassemble the systems by two or
 more individuals.
 In either towable or hand movable irrigation systems, the sprinkler coupler
 member may be provided with laterally projecting wings such as those
 described in U.S. Pat. No. 5,511,826. The purpose of such wings is to
 stabilize the coupler member, and thus protect the riser and sprinkler
 from damage, as the coupler is drawn along the ground. That is, the wings
 prevent "riser flop", i.e., rolling of the coupler member forwardly or
 rearwardly, during transport of the coupler member which might otherwise
 expose the riser and/or sprinkler to damage should the sprinkler impact
 the ground. Existing stabilizing wing designs, however, provide limited
 impact protection to the coupler member itself.
 Existing towable or hand movable irrigation pipe coupler members also have
 an upwardly projecting, internally threaded, riser connection for
 threadably receiving the lower end of an externally threaded, sprinkler
 riser pipe. Among the deficiencies of current internally threaded riser
 connector designs is that the threaded connection can lose its sealing
 effect relatively soon after installation. As such, water may drain from
 the connection after the water supply is shut off, thereby causing water
 to pool in large areas and volumes around the coupler member. Such
 circumstances are disadvantageous in terms of water conservation and crop
 damage.
 An advantage exists, therefore, for an irrigation pipe coupler member
 including means for protecting the coupler member from excessive impact
 damage as the coupler member is moved along the ground surface.
 An further advantage exists for an irrigation pipe coupler member including
 means for enabling quick connection and disconnection of a sprinkler riser
 which minimizes water waste and crop damage.
 SUMMARY OF THE INVENTION
 The present invention provides an irrigation pipe system including a
 tubular coupler member having a pair of open ends wherein each open end is
 adapted to receive an end of a respective one of a first and second fluid
 transport pipe. The ends of the first and second pipes each include an
 annular recess which together comprise a first pair of annular recesses.
 The tubular coupler member includes a second pair of annular recesses
 adapted to align with the first pair of annular recesses to form a pair of
 annular cavities. The system further comprises a pair of flexible splines
 disposable through the tubular member and into the pair of annular
 cavities to releasably secure the first and second pair to the tubular
 coupler. A pair of gaskets is also disposed between the ends of the first
 and second pipes and the tubular coupler to prevent fluid leakage between
 the pipes and the coupler member.
 The outer surface of the tubular coupler member preferably includes at
 least one winglike substantially tangential projection for stabilizing,
 i.e., preventing tipping, of the coupler member as it is drawn across a
 ground surface. A sprinkler riser fitting member is disposed on the outer
 surface of the tubular coupler member generally diametrically opposite the
 lateral projection(s).
 According to a first embodiment of the invention, the sprinkler riser
 fitting member comprises a cylindrical member terminating in an outwardly
 directed, substantially annular flange. The flange defines at least one
 gap for receiving at least one inwardly directed lug of a riser lock
 member which is attached adjacent a lower end of a sprinkler riser. The at
 least one lug and the undersurface of the annular flange define
 cooperating means for enabling the sprinkler riser pipe to be quickly
 connected to or disconnected from the sprinkler riser fitting by rotating
 the sprinkler riser less than about one rotation, and preferably less than
 180.degree..
 According to a further embodiment, the sprinkler riser fitting means
 comprises an externally threaded fitting member and an internally threaded
 riser cap threadably connectable to the fitting member. The riser cap
 includes a cylindrical member terminating in an outwardly directed,
 substantially annular flange. The flange may be constructed substantially
 similar to the aforementioned riser fitting flange and may likewise
 cooperate with a correspondingly configured riser pipe lock member such as
 that briefly described above in connection with the first embodiment of
 the invention. Alternatively, the undersurface of the flange may be
 provided with one or more stop members. The stop members preferably
 protrude from the undersurface of the flange a distance sufficient to
 permit an inwardly directed lug of a riser lock member to overcome the
 stop members when sequential compressive and rotational force is exerted
 on the riser lock member yet also retain the riser lock member on the
 flange upon cessation of the aforesaid forces. So constructed, the
 sprinkler riser pipe may be quickly connected to or disconnected from the
 riser cap by pushing the riser pipe inwardly toward the coupler member a
 distance sufficient for the at least one lug to clear the at least one
 stop member and then rotating the sprinkler riser less than one rotation,
 and preferably less than 180.degree., about its longitudinal axis.
 According to all presently preferred embodiments, the irrigation coupler
 system of the present invention includes seal means for preventing water
 leakage between the riser pipe and the riser fitting to promote water
 conservation and crop protection. In addition, the substantially
 tangential stabilizing projections are preferably configured for optional
 protection of the tubular member as it traverses the ground surface.
 Other details, objects and advantages of the present invention will become
 apparent as the following description of the presently preferred
 embodiments and presently preferred methods of practicing the invention
 proceeds.

DETAILED DESCRIPTION OF THE INVETION
 U.S. patent application Ser. No. 09/158,373, filed Sep. 22, 1998 is
 expressly incorporated by reference herein in its entirety.
 Referring to FIGS. 1 and 2, there is illustrated a first embodiment of an
 irrigation pipe system, generally identified by reference numeral 10,
 constructed according to the present invention. System 10 comprises a
 tubular coupler member 12 having first and second open ends 14 and 16
 adapted for connection to ends of first and second fluid transport pipes
 18 and 20, respectively. Pipes 18 and 20 may be dimensioned to receive the
 ends 14, 16 of coupler member 12. More preferably, as illustrated, pipes
 18, 20 are received in the ends of 14, 16 of the coupler member 12.
 Coupler member 12 and pipes 18, 20 may be fabricated from any suitable
 substantially rigid material such as metal or plastic. According to a
 presently preferred embodiment, these components are formed from polyvinyl
 chloride (PVC) or fiber reinforced resin. Pipes 18, 20 may be connected to
 coupler member 12 by any suitable releasable connection means such as
 cooperating threading or the like. However, it is more preferable that the
 coupler member 12 and pipes 18, 20 be joined by flexible spline
 connections of the type described, for example, in U.S. Pat. No.
 5,511,826, the disclosure of which is incorporated herein by reference.
 In a flexible spline connection, annular grooves are provided in the
 coupler member and the pipes that are to be connected to the coupler
 member. When the pipes are mated with the coupler member, the annular
 grooves align to form annular cavities. Thereafter, a flexible spline is
 inserted into and snugly received in the annular cavities to thereby
 prevent separation of the pipes from the coupler member.
 As shown in FIG. 2, coupler member 12 is provided with a pair of annular
 grooves 22, 24 which cooperate with annular grooves 26, 28 respectively
 provided in pipes 18, 20. Pipes 18, 20 are inserted into the open ends 14,
 16 of coupler member 12 until the cooperating groove pairs 22, 26 and 24,
 28 establish annular channels. Thereafter, flexible splines 30 are
 inserted through apertures 32 provided in the sidewall of the tubular
 member 12 which are in communication with annular grooves 22, 24 so as to
 essentially fill the annular channels to prevent separation of the pipes
 18, 20 from the tubular coupler member 12. FIG. 1 shows one such spline 30
 about to be inserted into one of the sidewall apertures 32 and the other
 spline nearly entirely inserted into the other sidewall aperture 32. The
 flexible spline 30 is preferably made of a synthetic resinous material,
 such as polyethylene, polypropylene, polystyrene, PVC, nylon, polyamide,
 and the like. Although these materials are flexible, they are designed to
 resist compression under the typical working pressures of most fluid
 piping systems. Additionally, since the flexible spline 30 is preferably
 not elastomeric, the resulting mechanical lock will not become unjoined
 unless and until the spline is removed back through the aperture 32 in the
 side wall. To facilitate removal, a small length of the spline 30 can be
 left outside of the coupler member 12 (as shown in FIG. 1) so that it can
 be grasped and removed.
 Optionally, a molten or flowable polymer can be injected into the annular
 cavity through aperture 32 and then solidified to form a permanent
 mechanical lock.
 A central region 34 of coupler member 12 is preferably provided with an
 inner annular surface 36 of somewhat reduced diameter the opposite edges
 of which define shoulders 38, 40 (FIG. 2) against which the ends of pipes
 18, 20 come to rest when inserted in coupler member 12. Shoulders 38, 40
 assure precise alignment of groove pairs 22, 26 and 24, 28 and provide
 firm seating of the pipes 18, 20 within the coupler member 12.
 Additionally, either the pipes 18, 20 or, as illustrated, the tubular
 coupler member 12 are provided with additional annular grooves 42 for
 receiving elastomeric O-rings or similar sealing or packing means 44 to
 prevent fluid leakage between the pipes 18, 20 and the coupler member 12.
 A cylindrical fitting member 46 projects from the sidewall of the coupler
 member in the central region thereof. Fitting member 46 is provided with a
 central passageway 48 to establish fluid communication between the fitting
 member 46 and the interior of the coupler member 12. The fitting member 46
 terminates in an outwardly directed, substantially annular flange 50.
 As illustrated most clearly in FIGS. 1, 4 and 7, flange 50 is provided with
 at least one or more, preferably two or more, gaps 52. The gaps 52 are of
 suitable size and disposition to receive a corresponding number of
 inwardly directed fingers or lugs 54 of a riser lock member 56 (FIGS. 1
 and 2). The riser lock member 56 is preferably fixedly attached adjacent a
 lower end of a sprinkler riser 58, the upper end of which riser is
 typically threadably connectable to a sprinkler (not illustrated). Both
 the sprinkler riser 58 and the riser lock member 56 are desirably formed
 from compatible rigid materials, either metallic or plastic. For example,
 the riser lock member and sprinkler riser may both be manufactured from
 aluminum, zinc, PVC or fiber reinforced resinous plastic. If made of
 metal, the riser lock member 56 may be screwed, riveted or welded to the
 sprinkler riser 58. If formed from plastic these parts may joined adhesive
 bonding, solvent bonding or, alternatively, they may be molded as a single
 unit.
 The lugs 54 engage the undersurface of flange 50 in the manner shown in
 FIG. 2. That is, once the lugs have passed through corresponding gaps 52
 in flange 50, the riser lock member 56 and sprinkler riser 58 are rotated
 about the longitudinal axis of the sprinkler riser whereby the lugs come
 into sliding contact with undersurface of the flange.
 A cylindrical elastomeric shaft seal 60 (FIGS. 1, 2 and 6) is desirably
 provided between the riser lock member 56 and fitting member 46 to prevent
 leakage between the sprinkler riser 58 and the riser lock member. Shaft
 seal 60 may be made of any suitable natural or artificial rubber or
 rubber-like compound having a durometer of about 70. As seen in FIG. 6 the
 upper and lower edges 62, 64 of the shaft seal are preferably beveled, as
 are the seating surfaces 66, 68 provided therefor in the riser lock member
 56 and cylindrical fitting member 46 (FIG. 1).
 To promote axial compression of shaft seal 60, which compression is
 converted to radial expansion of the seal for enhancing the sealing effect
 thereof, the undersurface of the flange is desirably provided, for each
 lug 54 that engages therewith, a camming surface 70 (FIGS. 3, 4 and 5)
 defming an angle of between about 5.degree. to about 10.degree. with
 respect to horizontal. Hence, as the lugs 54 slidingly and rotatingly pass
 along the camming surfaces 70 the riser lock member 56 axially squeezes
 the shaft seal 60 which causes the seal to fill any gaps between the seal
 and the riser lock member 56, the cylindrical fitting member 46 and the
 sprinkler riser 58. To reduce wear of both the lugs 54 and camming
 surfaces 70, at least a portion of the upper surfaces of the lugs 54 is
 provided with a slope which substantially corresponds to the slope of the
 camming surfaces 70.
 Contiguous with each camming surface 70 the undersurface of flange 50 is
 preferably provided with a substantially horizontal landing surface 72
 which seats the sprinkler riser with respect to the coupler member. The
 landing surface preferably terminates in a stop member 74 to prevent
 over-rotation and undesirable slippage of the lugs 54 into gaps 52. When
 in engagement with the landing surfaces 72, the lugs 54, under the
 compression spring type force exerted by seal 60 and through their
 integral connection with the riser lock member 56 and sprinkler riser 58,
 securely and sealingly connect the sprinkler riser 58 to the coupler
 member 12.
 As most clearly shown in FIG. 5, the lowermost ends of the camming surfaces
 70 are preferably slightly downwardly displaced with respect to the
 landing surfaces 72 to establish stop shoulders 76 for the lugs 54 to
 ensure that the sprinkler riser 58 does not become disconnected from the
 coupler member 12 through inadvertent reverse rotations of the sprinkler
 riser 58 and/or the riser lock member 56. Thus, when one wishes to remove
 the sprinkler riser 58 from the coupler member 12, the sprinkler riser or,
 more preferably, the sprinkler riser lock member 56 is grasped and rotated
 in a direction opposite the direction of installation until the lugs come
 into contact with stop shoulders 76. At this point the sprinkler riser 58
 and/or riser lock member 56 is pressed inwardly toward the coupler member
 12 a distance sufficient to permit passage of the lugs 54 beneath the stop
 shoulders 76 whereby reverse rotation of the sprinkler riser may continue.
 Once the lugs 54 come into alignment with gaps 52, the sprinkler riser 58
 and riser lock member 56 may simply be lifted from engagement with the
 coupler member 12. The aforementioned components thus collectively
 function as sprinkler riser connection means for releasably connecting the
 sprinkler riser 58 to the coupler member 12 by rotating the sprinkler
 riser less than about one rotation, and preferably less than about
 180.degree., about its longitudinal axis.
 Referring to FIGS. 1, 3, 7, 8 and 9 there illustrated a further presently
 preferred aspect of the irrigation pipe system according to the present
 invention. The irrigation pipe systems described herein are not fixed with
 respect to the land they irrigate. That is, they may be manually or
 mechanically towed across the land to any desired location. Unless care is
 taken during towing, however, the system may be jostled to an extent where
 the various components may become inadvertently loosened or the coupler
 may rotate about its longitudinal axis to the point where the sprinkler
 riser "flops" to the ground which may result in damage to the sprinkler
 riser or sprinkler.
 Accordingly, the present invention provides means for reducing impact and
 coupler member rolling during towing of the irrigation pipe system.
 Preferably, these means comprise at least one or, more preferably, two
 wing-like lateral projections 78 disposed on an outer surface of the
 coupler member 12 and extending substantially tangentially thereto. As
 used herein, the phrase "substantially tangentially" shall be construed to
 mean that any portion of the proximate edges 80 of the lateral projections
 78 at which the lateral projections are joined to the coupler member 12
 (FIGS. 3 and 9) may be disposed either at a true tangent with respect to
 the outer surface of the tubular member or, as illustrated in FIG. 3, up
 to an arc length corresponding to an angle of no greater than about
 60.degree. with respect to the point of tangency "T".
 Each lateral projection 78 preferably includes first and second end
 portions 82, 84. As most clearly depicted in FIG. 8, each of the first and
 second and portions 82, 84 are respectively disposed toward a central
 longitudinal axis "A" of the coupler member 12 in a plane extending at an
 angle B of about 10.degree. to about 20.degree., and more preferably about
 15.degree., with respect to the central longitudinal axis "A.degree.. Such
 angular disposition of the first and second portions 82, 84 of the lateral
 projections 78 reduces the impact experienced by the coupler member as it
 traverses the ground during towing.
 Additionally, each of the first and second end portions 82, 84 of the
 lateral projections 78 includes a distal edge 86 (FIGS. 7 and 9) extending
 outwardly from a respective one of the first and second open ends 14, 16
 of the coupler member 12 toward said central region 34 thereof at an angle
 .theta. of about 15.degree. to about 35.degree., and more preferably about
 27.degree., with respect to the central longitudinal axis A. This
 substantially linear and comparatively shallow-angled distal edge 86, when
 serving as a leading edge of the lateral projection 78 in the direction of
 towing, reduces the resistance and minimizes the impact experienced by the
 coupler member as it is towed across the ground.
 Preferably, each lateral projection 80 is structurally reinforced by one or
 more gusset plates or similar reinforcement 88 extending between the
 lateral projections and the outer surface of the coupler member 12 (FIGS.
 1 and 7).
 Referring to FIGS. 10 and 11, there is illustrated a further embodiment of
 an irrigation pipe system, generally identified by reference numeral 100,
 constructed according to the present invention. System 100 is in many
 respects constructed substantially similar to system 10 discussed above.
 Accordingly, only those elements of system 100 which materially depart in
 structural configuration and/or function from their counterparts in FIGS.
 1-9, or which are otherwise necessary for a proper understanding of the
 invention, will be described in detail.
 A significant distinction between system 10 and system 100 lies in the
 construction of its sprinkler riser connection means. More particularly,
 system 100 includes a cylindrical riser adapter 102 having a central
 passageway 104 in fluid communication with the interior of tubular coupler
 member 112. Riser adapter 102 is preferably provided with external
 threading 106 (FIGS. 10, 11 and 16) which matingly engages with internal
 threading 108 of a riser cap 109 (FIGS. 11 and 14). The use of external
 threading 106 improves the strength of the riser adapter 102 by providing
 a thicker and stronger adapter wall reinforced by external threads which
 function as support bands to minimize cracking of the riser adapter 102
 due to bending forces created by physical manipulation and incidental
 impact of the sprinkler riser 158. Moreover, each of systems 10 and 100
 overcome the problems of currently existing internally threaded riser
 connector designs which readily lose fluid seal and allow water waste and
 promote water pooling and crop damage in the vicinity of the sprinkler.
 Riser cap 109 may be fabricated from metal or, more preferably, PVC or
 fiber reinforced resinous plastic material. In addition, the exterior
 surface of the riser cap is preferably provided with one or more
 protrusions 111 to facilitate its manual installation and removal from the
 riser adapter 102.
 FIGS. 10 through 14 reveal that the riser cap 109 includes a cylindrical
 fitting member 146 having a central passageway 148 to accommodate
 sprinkler riser 158. The fitting member 146 terminates in an outwardly
 directed, substantially annular flange 150. Flange 150 is provided with at
 least one gap 152 (FIG. 13) of suitable size to receive at least one
 inwardly directed finger or lug 154 of a riser lock member 156 (FIGS. 10
 and 11). The riser lock member 156 and sprinkler riser 158 are preferably
 formed of compatible rigid materials and may be attached to one another in
 the manner of riser lock member 56 and sprinkler riser 58 described
 hereinabove in connection with FIGS. 1 through 9.
 Lug 154 engages the undersurface of flange 150 in the manner shown in FIG.
 11. That is, the lug 154 is passed through gap 152 and pressed downwardly
 until it clears a stop member 174 protruding from the undersurface of the
 flange 150. Thereafter, the sprinkler riser 158 is rotated and released
 such that the lug 154 comes into contact with the undersurface of the
 flange 150. Preferably, flange is provided with at least two such stop
 members 174 whereby the user may selectively rotate the sprinkler riser in
 either direction to connect or disconnect the sprinkler riser to and from
 the coupler member 112. As seen in FIGS. 13 and 14, an additional and
 optional stop member 174a may be provided to limit the range of rotation
 of the lug 154 to about 90.degree. when engaged with the undersurface of
 flange 150.
 As the lug is pressed downwardly over stop member 174 and comes to rest
 against the flange 150, it axially compresses a sprinkler riser shaft seal
 160 thereby causing the seal to radially expand and prevent fluid leakage
 between the seal, the riser adapter 102, and the riser cap 109. The
 preferred construction of seal 160 is shown in 15. Conversely, seal 160
 functions in the manner of a compression spring to releasably yet firmly
 maintain contact of lug 154 with flange 150.
 Seal 160 may be made from any natural or artificial rubber or rubber-like
 material having a durometer of about 70. It preferably has a bifurcated
 construction such that the lower portion thereof is separated into spaced
 apart annular ridges 160a, 160b which define an annular gap 160c
 therebetween. The gap 160c may be filled with fluid during operation of
 system 100, thereby spreading the ridges 160a, 160b and enhancing the
 sealing effect of the seal.
 Like those described above in connection with system 10, the sprinkler
 riser connection means of system 100 enable the sprinkler riser 158 to be
 connected to and disconnected from the coupler member 112 by rotating the
 sprinkler riser less than one rotation, and preferably less than about
 180.degree., about its longitudinal axis. As such, each design offers
 substantial time savings in respect to installation, removal and
 maintenance versus other irrigation sprinkler systems, especially other
 large-scale systems, presently known in the art.
 Referring again to FIGS. 10 and 11, another aspect of the invention is an
 irrigation pipe coupler 100 comprising a tubular member 112 having a
 central longitudinal axis, a central region and first and second open
 ends. The first and second open ends are adapted for respective connection
 to first and second pipes. A fitting 102 includes a cylindrical member in
 fluid communication with the tubular member. The fitting 102 is capable of
 receiving a sprinkler riser in a locking relationship with the fitting.
 The fitting 102 includes an externally threaded fitting member 106 and an
 internally threaded fitting member 109 threadably connectable to the
 externally threaded fitting member. A seal 160 is compressible between the
 externally threaded fitting member 106 and the internally threaded fitting
 member 109, for forming a seal between the cylindrical member and the
 sprinkler riser 158.
 The sprinkler riser 158 has a lock member 156 having a lug 154 connected
 thereto, and the fitting 106 has an undersurface of the fitting, for
 receiving the lug, to lock the sprinkler riser 158 to the externally
 threaded fitting member 106 or the internally threaded fitting member 109.
 In the example, the undersurface is on the bottom of a flange portion 150.
 In other variations (not shown) of the exemplary embodiments, the mating
 undersurface may alternatively be an undersurface of the externally
 threaded fitting member or an undersurface of the internally threaded
 riser cap.
 In the exemplary embodiment, the cylindrical member (which is connected to
 the tubular member 112) is a part of the externally threaded fitting
 member 106, and the internally threaded fitting member is the riser cap
 109. In an alternative embodiment (not shown), the cylindrical member
 connected to the tubular member may have an internal thread, and the riser
 cap may be in the form of an externally threaded plug having a central
 bore for receiving the sprinkler riser 158. The plug would be configured
 to engage and compress the seal 160 in the same way as riser cap 109.
 FIGS. 17 and 18 show a variation of the exemplary embodiment, in which the
 seal 160' has a bifurcated construction, such that a portion thereof is
 separated into inner and outer spaced apart annular ridges 160a' and
 160b', respectively. Seal 160" differs from the seal 160 shown in FIG. 15
 in the following significant respects: Either the internally threaded
 fitting member 109 or the externally threaded fitting member 106 has a
 bore 103' for receiving the seal 160'. In the example, the externally
 threaded fitting member 106 has the bore 103'. The outer annular ridge
 160b' of the seal 106' has a height that is greater than a height of the
 bore 103'. The inner annular ridge 160a' is shorter than the outer annular
 ridge 160b'. The height of the inner annular ridge 160a' is smaller than
 the height of the bore 103'. Additionally, as shown in FIG. 18, the seal
 160' seats on a seating surface 161' of the externally threaded fitting
 member 106'. The seating surface 161' has an angle .alpha., so that the
 seating surface is deeper at an outer circumference 162' than at an inner
 circumference thereof 162'. The angle .alpha. is about 5 degrees. In
 addition, a bevel angle .beta. of about 25 degrees is provided at the
 inner circumference of the seating surface 161'.
 The variations shown in FIGS. 17 and 18 improve the sealing of the coupling
 100, seal 160' and threaded cap joint by providing a positive mechanical
 seal between these components. The mechanical sealing is achieved when the
 threaded cap 109 is tightened onto the seal 160'. The taller seal of FIGS.
 17 and 18 is compressed into the coupling bore 103' by the cap 109. The
 angle .alpha. causes the outer lip of the seal 160' to expand against the
 wall 165' of the cap 106', thus providing a pre-loaded mechanical seal
 between the sprinkler riser 158 and the threaded cap 106'. This sealing
 effect is independent of fluid pressure.
 The radius R at the outside diameter of the seal 160' prevents the pinching
 of the seal 160' as it is compressed by the threaded cap. The radius R may
 be, for example, about 0.06 inches (1.5 millimeters).
 The shorter inner lip 160a' prevents pinching of the seal 160' between the
 bore 165' and the riser 158 during riser pipe installation.
 Although the embodiments of the sprinkler riser fitting means disclosed
 herein are preferred because of their comparative ease of manufacture, it
 is contemplated that other designs of such means will become apparent to
 the reader which are consistent with the scope and sprit of the present
 invention. For instance, the one-piece sprinkler riser fitting member 46
 of system 10 may be constructed as a two-part assembly similar to the
 threaded fitting 102 and riser cap 109 arrangement of system 100, and vice
 versa. Similarly, the fitting members 46, 146 may terminate in gapped,
 inwardly directed flanges rather than gapped outwardly directed flanges.
 Thus, the lugs 54, 154 may be outwardly rather than inwardly directed in
 order to engage with such flanges.
 Although the invention has been described in terms of exemplary
 embodiments, it is not limited thereto. Rather, the appended claim should
 be construed broadly, to include other variants and embodiments of the
 invention which may be made by those skilled in the art without departing
 from the scope and range of equivalents of the invention.