CA1239955A - Multiple key segmented pipe coupling - Google Patents

Abstract

ABSTRACT
A segmented pipe coupling for use in high-pressure pipeline assemblies, the coupling segments incorporting plural or multiple keys which engage complementary retention members on the pipe end.

Description

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MIJL~I,F KEY SE(~IEl~TEI) PIPE CO~PLI1~7G
Fi~id o U~ ~n~enti~n This invention relales to segmented couplings for pipeline assembiies emp3Oyed for conveying fiuid, ~md which have particular utility for use in high-pressure applicatior1s.
Segmented c~ouplings are known in the art, and are described in United States Patent Mo. 3,054,629 to Piatelc, issued September 18, 1962. Such couplings have been widely accepted, but have been limited in their u.se to relatively low to moderate pressure environments.
1() Typically, such segmented couplings- com~rise coupling members of arcuate, segmented, usually semi-circular confiGuration which are employed to bridge the mutually presenl:ed ends of a pair of pipes and prevent separation of the pipe er3d~s relative to each other. The segrnented couplings engage the outer periphery of the pipes and are clamped together using any convenient arrangernent of fastening members such as bolLs and nu1s.
The coupling segments e~tend in a continuous .in~ erlcircling the pipe ends, and thus provide the required positive clamping engagernent between the coupling segments and the pipe ends.
ln order to prevent leakage OL pr~ssuri2ed fluid from between the two pipe ends some form of seal is used, such as a ~asket member of a material suitable for use in it.s intended environment. The gasket member is positioned over the pipe encls and is maintained in position by the coupling segments. In these con~structions, the coupling segrnents are usllally each provided with a recess within which the gf~cl;et member is received, the gasket mernber beirlg he]d in sealing contact against the ol~ter surface of :~3~55i - the -~ipe ends by the rlampjng containment prodllced by the coupling segm ents.
Ba~ c)und of the InYention A significant advanta~e in ernpioying segmented couplings is the ability to quickly assemble pipeline svstems on-site. In numerous industrial applications, such as in the gas and oil ~recovery industries, a particular need arises in the on-site rapid assembly of pipeline systems. It is desirable that such pipeline systems be assembled with maximum economy in labor and rnaterials. Because of the relatively high pressures encountered in such pipeline systems (which for the oil recovery industry commonly are of the order of 4,000 Ibs. per square inch or higher) resort has heretofore been made to relatively expensive high-pressure couplings, such as those which required connecting nipples to be welded to the ends of the respective pipes prior to the assembly of the ~oupling. Such welding operation is undesirable in that the mE~nufaeturing operation is performed at a manufacturing plant prior to delivery of the pipes to the assembly site, Emd represents an increase in cost.
~ maior problem which has heretofore precluded the use of segmented couplings in hig~pressllre environrnents is that of providing adequEIte inter-engagement of the couplings and the respective pipes, while at the same time maintaining the strengh Emd integrity of the pipes sufficiently high for them to withstarld the pressures and forces to which the pipeline sr~tem is to be subjected. Segmented couplings require a posit;ve inter-engagement between the coupling segments and the pipes. One typical way of providing Z 5 this has been by providing a groove adjacent to the pipe end, and, by ~23~

providing a complernentary key on the inner periphery of the ~oupiin~
segments, such that the coupling segments7 when assembled onto the pipe end, are physic~l~y keyed into the body of the pipe.
In some industries, where grooving is not possibie or desirable, the pipe end is provided with a collar with a beaded or raised surface or studs which engage the cornplementary Iceys of the coupling.
Such arrangernents are admirable in their performance in relatively moderate-pressure applications, but are often times found wanting in hig}~
pressure applications in view of consideratiorls which arise in such high-pressure applications.
While it is possible to form the coupling segments of sufficient strength to withstand the forces exerted on the coupling when in use, problems are encountered in elimimating deformation and fatigue fracture of the pipe itself, which may res~t in the ~timate total failure of the joint These problems arise in part from the desire to employ standard piping, which, depending upon the industry and end use, vary from plastic to steel.
Such materials when exposed to high pressure are inherently caF~able of deforrnation when subjected to stresses at or approaching their elastic limits. While this problem could be a]eviated by the sue of piping formed from exotic high strength matelials, this is not generally economically feasible.
The problems are further aggravated by the necessity of providing a groove or bead, or studding adjacent the end of the pipe for the reception of the Icey on the coupling. Where grooves are provided, the suggestion has been made to deepen them to provide a greater engagernent for the ? ~ ~ 5 ~

coupliin~ l;eys, however, this re~s~ s in a consecn~ential reduction of .he available cross-sectional area of the pipe at the location of the groove and the resultant weakening of the pipe at that location. A common point of failure of such joints is between the grooved portion of the pipe and the pipe end, which elastically deforms radially inwards thereby allowing the key to disenga~e the groove. This produces a wedging or camming action between the groove wall or the bead or the studs and the key which further aggravates the problern. A circumferenti~l collar or bead, or single row of studding adjacent eacn pipe end similarly provides an insufficient anchor for the coupling when subjected to high pressures.
Where grooved pipe is emp]oyed, attempts to minimize the depth of the grooYe, with ~ conseguenti~l increase in the cross-sectional area of the pipe at the location of the groove, result in turn in a corresponding decrease in the surace area of the groove side wall which is available for contact by the key of the coupling. The consequential increase in the stresses between the key and the pipe? again increase the tendency of the material of the pipe to ~form at that lo~tion under the stresses encountered.
Sum~nary of the Lnven1ion According to the present invenffon, the problems discussed above a.~e mitigated to an extent permitting segmented couplings to be used in high-pressure applications by providing plurQI keys on the ~oupling segments at positions spaced axially thereof. The respective Qrrangements preferably provides a totQI sllrface areQ for contact by the engagement members on the pipe ~vhich exceeds the surface area heretofore available in single conl:act members. The present invention permits the radial extent of the 23~

respective kevs to be decreased, and in ernboaiments employing ~rooves in the pipe wall, the vva]l-thickness of tne pipe at the location of the grooves can be correspondingly increased. This results in an incTease in the minimum cross-sectional area of the pipe at any point longitudinally thereof, with an incTease in the strength of the grooved pipe and an optimized distribution of the stresses exerted on the pipe arld the coupling.
The present invention providcs segmented couplings usable at pressures well above those ordinarily expected îor segmented couplings. In at least one application a grooved pipe and coupling arrangement, normally usable 1 () with a single key at pressures up to 2,000-lbs. per square inch, successfully withstood testing at pressures of at least 4,000 lbs. per square inch, and has been bench tested at pressures of up to 12,000 lbs. per s~uare inch before failing.
Accordingly, the present invention teaches a coupling segment for use l 5 with at least one additional coupling segment to provide a segmented coupling for a pipeJ each OI the segments comprising a body member adapted to contain a sealing means and having an axially extending surface for positioning around a portion of a pipe, and having means thereon for coaction with securing m eans f or securing said coupling segm ent to at least one other coupling segment in encircling relationship with said pipe, the couE>ling segment further including at lest one key carrying portion having a surîace for positioning around a portion of said pipe, and plural keys extending from said surface Or said key carrying portion towards said pipe at posi-tions spaced axially along said surface, each key extending towards sa;d pipe and ~23~

- having a radiallv extending engagement face adapted for engaSJement with an abutment associated with said pipe.

s - ~ D~sc~ption ~f ~ r)ra~rin~s The invention will now be described with reference to the flccompallying drawings, which illustrale preferred embodiments of the present invention, and in whi ch:
Figure 1 is an exploded perspective view of a segmented coupling of the present invention shown in association with a gasket to be employed therewith and the grooved ends of a pair of pipes to be connected to each other by the coupling Fi~ure 2 is a longitudinal -cross-section taken in a horizontal plane through one of the coupling segments of Figure 1 in assembled relationship with the grooved ends of a pair of pi pes, Figure 3 is a longitudinal cross-section corresponding with Pigure 2, but showing a modification of the coupling segment of Figure 2;
Pigure 1 is a cross-section illustrating a preferred form of the coupling segments in the position they occupy prior to final assembly of the segmented coupling;
Figure 5 is a cross-section c~orr2sponding with Pigure 4 il]ustrating the coupling segments in the position they ~s~ e c~l f~na~ e~n~ly <~f ~he e~i~(plklg~
Figure 6 is a longitudinal cross-section corresponding with Figure 2, but showing a flanged segmented coupling flccording to the present invention;

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Figure 7 is ~ lon~tudin~l cross-section corresponding with Figure 2 of an alternative form of coupling segrnent;
Figure 8 is a fragmentary end elevation oî an 5alternstive form of piE~e end prepared for recepffon of the coupl;ng of Figure 7;
Figure 9 is a fragrnentary end elevation of an alternative form of pipe end prepared for reception of the coupiing of Figure 7;
10Figure 10 is a longitudinal cross-section corresponding with Figure 2 of another alternaffve form of coupling segment;
Figure 11 is a longitudinal cross-section corresponding with Figure 2 of still ~nother alternative 15form of coupling segment;
Fi~re 12 is a longitudinal cross-section correspondin~ with Figure 2 of yet another alternative embodirnent of coupling segment;
Figure 13 is a transverse cross-section gener ally 20corresponding with Fi~lre 4 of another alternative forrn of coupling segrnent; and, Fi~lre 14 is a transvelse cross-section generally corresponding with ~igure ~ of still another form of couplirlg segrnent.

~igures 1 throu~n 6 of the drawings each re]ate to embodiments of the invention to be employed with grooved pipe.
Referring more partic-llarly to Fi~ure 1 of the drawings. a seg~rnented coupling is illustrated in disassembled condition, Lhe respective coupling segrnents being indicated at 10 ar~d 12. The coupling segments are identical with each other, and are substantiallv semi-circular in form, each coupling member half being comprised by an arcuate body portion 14 which terminates at its ends in radially outwardly extend;ng bolting pads 16 formed integrally with the body portion 14.
Each of the radially outwardly extending bolting pads 16 includes apertures 18 for the reception of fastening members, which, in the drawings, are shown as headed bolts 20. When in an assembled condition, the respective coupling segments 10 and 12 are secured to each other in encircling relationship with the pipe ends by the headed bolts 20 and conventional nuts or lock nuts 22 threadedly receiYed on the bolts.
Internally of each couplirlg segrnent half 10 and 12 and intermediate the axial length thereof in the embodiment illustrated, is a recess 26 in which a gasket 28 is accornmodated, ~he gasket 28 being emploved to seal the pipes 24 when the couplirlg is in an assemb~ed cond;tion and prevent 20 2 leakage.
Located immediately adjacent the recess 26 in euch coupling segrnent is an axially inner key 30 forrned integrally with the couplirlg segment ~md, spaced from each of the axially inner keys 30 are axially outer keys 32, which similarly are formed integrally with the respective collp!ing

2 5 segrnents.

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1() - ~he respective kevs 30 and 32 are dimensioned, as later disc~ssed, for them to be received within corresponding axially spaced annular grooves 34 formed in the respective pipes adiacent the ends thereof, the respective annular grooves 34 being forrned in a manner laier discussed~
ln use of the segmented coup]ing9 the ends of the pipes 24 are brought into proximity with each other with the gasket 28 in sealing relationship with the pipe ends, the respecti ve coupling segm ents are positioned over the gasket 28 with the gasket contained within the recess 26, and the keys 30 and 32 are inserted into the annu~ar ~rooves 34 in the respective pipe l ends. The bolts 20 are then inserted through the aligned apertures 18 of the coupling segments, and the co~lpling segments are drawn towards each other by tightesling the nuts 22 down on the bolts 20. This draws the respective couplin~ segments towards the pipes, and compresses the gasket 28 into intimate sealing contact with the respective pipe ends.
While the respective coupling segments may be formed by asly known techniques, such as by pressing or drop-forging steel or any other suitable high-strength metal, the respective coupling segments conveniently are formed by close tolerance casting techniques from ductile iron or a similar high-strength metal, and, for the reasons ]ater disc~ssed, may be 2() intentionally left unmac}lined or surface finished, except for the removalof any flashings, riser cores or the like superfluous portions resulting from the casting operation.
It will be appreciated that while the segmented coupling of the present invention is being d~cribed with reference to its application in highpressure applications, the terrn '~high-pressure" is relative to the materials comprising the pipes, and, to the materials comprising the coupling segments. ~or e~iample, in pipeline assemMies wnich are employed for transportingabrasive or corrosive materials under pressure, either in the form of slurries or airborne suspensions of particulate matelial, the coupling segments similariy may be formed from n~on or ~ny other suitable plastics material, such materials having a strength which is substantially lower than steel or ductile iron. In this context, the terrn "high-pressure" is ILsed in relation to the strength of the materials employed in the fabrication of the pipeline system and the coupling segments, the term "high" being used relatively to lhe specific materials employed. When formed of relatively low-strength materials, the segmented couplings of the present invention are inherently capable of withstanding pressures considerably higher than those at which known segrnented couplings formed from the same materials would fail.
In those instances where the coupling segments are formed from nylon or other plastics material which is inherently capable of being injection molded, that techni que would be em ployed.
While the segmented coupling illustrated in the drawings is cvomprised of only two coupling segments, it will be appreciated that the invention is equaUy applicable to segmented couplings cornprising three or more coupling segments for use in conjunction with lal ge diameter pipes. The use of mu]tiple coupling segments facilitates the manual handling of the segments and the assembly of the coupling into the pipes. Additionally, the formation of such large size segmented couplings from m~dtiple coupling segments facilitates the forrning of the respective couplirlg se~ments to closer ~2~3~

tolerances than w~uld t~e possible in the c~se of a ~arge segmented coup~in~
comprised of only two coupling segments.
Having generallv discu~ssed the basic construction of one form of the sevmented coupling according to the present invention, r eference is made to Figure 2 of the drawings, which illllstrates such segmented coupling of Figure I in hori~ontal, longitudina] cross-section, the same reference numerals being errlployed in E7igure 2 as those errlE)loyed in Figure 1.
In Figure 2, it will be noted that the gasket 28, which, by way of illustration, is of a generally U-shaped comiguration, is held compressed 1() within the recess 26 of the respeetive couplinv segments 10 and lZ with axiaUy-extending lips 28a, 28a of the gasket in face contact with the cylindrical lands at the ends of the pipes 24.
Preferably, and having regard to the temperature limitation imposed on gaskets formed from plastics mate~ials, the gasket is formed from a high-strength elastomeric material, and may further be reir~orced and armored to aid in eliminating extrusion of the gasket material into the spaces between the pipe and the coupling under the influence of extremely high pressure imposed thereon.
In order to further reduce the possibility of such extrusion of the 2(J gasket occurring7 rather than to be off-set axially relatively to the recess 26, the axially inner keys 30 constitute a continuation of the radially-extending walls o~ the recess 2fi. In th;s way, the possibility of extrllsiorl of the gasket material between the axial interfaces of the coupling segments nnd juxtapo~sed surfaces of the respective pipes is eliminated.

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- As will be apparent frorn consideration of Figure 2, the forces acting on the respective pipes will act axially of the pipes in a direction to force the pipe ends nway from each other. The required restraint against such movement is provided by the segmented coupling, particularly by the engflgement of the keys 30 and 32 within the grooves 34.
In known se~mented couplings, the axial loading imposed on the respective pipes must be absorbed by a single key associated with each pipe end, and which is received within a single groove formed in the associated pipe end. These extremely high stresses in the keys and in the pipe ends have prec] uded the use of such segm ented couplings in high-pressure applic~tions. ~ither the keys will shear or fracture under the stresses imposed thereon, or, the pipe end with deform elastically or plQsticaUy and pull out of the coupling, or, the pipe will fail in the region of the groove under the influence of the stresses imposed thereon, or com bi nati ons ther eof .
To inCreQse the pressure handling capability of such a seg~lented coupling by increasing the area of SurIace contact between the respective keys and the Qssociated radial walls of the pipe groove, requires an incTease in the depth of the pipe groove which is self-defeating. Any increase in the depth of the grooves results in a decTease in the thickness of the pipe wall in the region of the grooves. The result is a decrease in the axial loading at which the pipe itself will fail.
In the embodiment shown in Figure 2, each of the keys 30 and 32 is formed with that s~rrface oî the key which races inwardly of the coupling and which is presented towards the recess 26, within tolerances, radial and :~2~

perpendicular to the ]ongitudinal axis of the coupling segment throug}1ou~
the entire arcuate extent of the key. Whi~e the respective keys mav be planar throughout the entire arcuate extent thereof, in some circumstances it may be preferred that this surface deviate to determined extents to one side or the other of a medial plane perpzndicular to the axis of the coupling segment, the sr~id surface of the key at all positions along the entire arcuate extent thereof Iying parallel to, but possibly spaced from the said rnedial plane. Such deviation may be employed to cornpensate for possible flexing in the body of the coupling segment under high-pressure loading~ and in order to optimi~e the distribution of stresses acting thereon.
The opposite surface of each of the keys may be selected to optimize strength and preferably is of inclined or buttressed form to facilitate entry of the keys into the associated ~rooves in the pipe ends.
lt may further be desirable that each key be forsned for it to be of maximum permissible radial extent, and may, at least under certain conditions, be in close juxtaposition or even in axial face contact with the axial bottom surî ~ce of the associated groove.
The grooves 34 in the pipe~s may be formed in any convenient manner, it being E~lrti cularly desirable that the axial spacing of the groo~/es be complementary to permit simult~meous engagement of the respective keys.
While in theory, such simultmeous engagement should be obtained in order to optimize the distribution of stresses on respective keys, such a condition cannot be assllred in practice, due to manufacturing tolernnces.
One manner of accornmodating any clearance between the respective radial surfaces of the keys and the juxtaposed radial surfaces of the grooves ~2~

is by~ casting the coupling segments and intentionally eliminating forrn finishing or rnachining or~rations on the radial faces of the keys. NoL only does this achieve a cost aàvantage, but additionally, it facilitates the close contact of the keys within the grooves as the pressure within the pipes progressively increases.
As opposed to being a srnooth planar surface, such as would be formed by a Machining operation, the radial faces of the cast and unfinished keys are inversely pebbled, the inverse pebbling representing the grain size of the sand employed in the casting operation. Additionally, by virtue of the casting operation, it is found that a hardéned skin of 0.005 to 0.01 inches in thickness forms on the coupling members during the casting operation, the hardness of the skin exceeding the hardness of the carbon steel compri.sing the pipes.
Where it is desirable to employ this technique, the radial surfaces of the keys are in engagement with the juxtaposed radial surfaces of the pipe grooves only at positions constituting high-points on the radial surfaces of the keys. hs the pressure within the pipes progressively increases, the stresses exerted on the keys are absorbed exclusively by the said high-points, which, as the pr~ure progressively inc^reases, act to cold-work the juxtaposed radial face of the pipe groove and displace the material of the pipe in direcffons laterally of the h;gh-points, into the pockets in the radial face of the keys constituted by the said inverse pebbling. In this way, minor movement of the material of the pipe is intentionally induced, fmd intentionally is employed to optirnize distribution of the stress applied to the respective keys.

~2~ 5 ~I~ is found in practi ce that the respecti ve coupling segm ents can be c~st with sufficient accuracy that~ when the assembled coupling is subjected to high-pressure loading, the cold-working and pT~stic deformation of the radial face of the pipe groove, possibly accornpanied by some crushing-down of the high-points on the radial surfaces of the keys produces ~ substantial distribution and equalization of the stresses imposed on the respectiYe keys.
~sy providing plural keys and corresponding grooves in the pipe with a combined area of surface engagenrlent of the keys with the pipe which is equal to or greater thnn that provided by a single key and groove, the thickness of the pipe wall in the region of the groove~s is materialTy increasedand a significant increase in strength is achieved.
Thus, in order to obtain an equivalent area of surface contact, the reduction of the w~ll thickness of the pipe with the use of dual keys and dual grooves will result in a decrease in thickness of the pipe wall in the regions of the grooves of 19.52%, while a comparable single key and groove arrangement will res~t in a reduction in the thickness of the pipe wall in the vicinity of the groove of 40.70%.
Figure 3 ill~strates an embodiment in which three keys 30, 32, and 32a are provided for engragement in three corresponding grooves 34 in each pipe end. While each of the keys rnay be of the same radial extent as the others of the keys, th~ rninimi~ing the requ;red depth of the respective grooves and maxirrli ~ing the wall thickness of the pipe at all vicinities in the regions of the grooves, the keys may be formed of progressively increasing r~dial extent progressing in this embodiment from the axial ends of the coupling segments towards the centr~l recess 26 in the coup1ing - segments. The grooves 34 in the pipes will then be correspondingly of progressively increasing depth towards the free end of the pipe and are in fir-tree formation. Alternntively, the outermost pair of keys 30 und 32a may be of greater exient than the central key 32, or vice versa.
While tne discussion of the present invention as related to Figures 1 And 2 has dealt mainly with the manner in which forces acting ~xially of the respective pipes are accomrnodated ar-d absorbed, it will be appreciated that in addition to such axially acting forces, radially acting iorces also will be produced under high-pressure loading. U'hile some radial expansion of the respective pipes will occur under high-pressure loading, major considerations arise in the effect of such radial expansion forces in the respective coupling segments. This aspiect of the invention is now discussed with respect to Figures 4 and 5 of the drawings.
As seen in Figure 4, prior to the tightening down of the nuts, each couplingsegmPnt lO, 12 is of a radius slightly greater than the radius of the pipe, i.e., while the pipe 24 is of an external radius R, taken about the point B, the internal radius Rl of the respective coupoing segrnents is slightly in excess of the radius R, and is taken about the point of Bl. The respective coupling segments are applied to the pipe, they do n~t meet each other in face engagement of the rndial bolting p~ds 16, but insl:ead, are slightly spaced from each other. It iurther will be noted that prior to tighterùng of the bolts 20, the radially extendirlg planar faces of the respective bolting ~ads diver ge from each other in the radi~lly outward direction.

~8 As shown in Figure 5, upon tightening of the boltst the respective coupling segments ~ex about the center thereoi, which at that time is in line or face engagement with the pipe, this resulting initially in the radially innermost portions of the radia] bolting faces beina brollght into engagement with each other, thus trapping the gasket 28 within the coupling segments and inhibiting any possibility of extrusion of the gasket member in a radially outward direction t~tween the juxtaposed faces of the bolting of the pads.
Continued tightening of the bolts 20 results in the juxtaposed faces of the bolting pads being drawn towards and rotated slightly into face contact with each other, thus pr~stressing the body of the ~espective ~oupling segments. This pr~stressing of the respective coupling segments acts in opposition to the forces acting to expand the coupling segments in a radial direction, and also, acts in opposition to the forces acting to expand the coupling segments in a radial direction, and also, acts in opposition to the forces exerted on the respective pipes and which act to expand the pipes in a raàial direction.
While a segrnented coupling has been oescribed for coupling the adjacent ends of a p~;r of pipes to each other, it will be appreciated that the segmented coupling of the present invention also firlds applic~tion in a flanged coupling for connecting a single pipe to sorne other member, such as the flanged outlet coupling of a high-pressllre pump.
Figure 6 of the drawings il]ustrates such a flanged segmented coupling incorporating dual keys as described above with reference to Figure 2, the same reference numerals being used in Figure 6 to iden~ify thc~se integers which are in common with Figure 2.

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In Figure 6, the respeetive coupiing segments extend to onlv one side of the g~3sket containing recess 26, and, each of the coupling segments includes a radi~11y extending flange 36 provided with appropriate bolt holes 37. The gasket 38, represents one half of the gasket 28 previously described, and inc]udes an axially extending lip 38a for engagement with the land at the end of the pipe 24, the gasket includingt a continuous circumferential lip 40 for eng~gement with a planar surface of the member to which the segmented coupling is to be attached.
Whiie the invention has been des~ibed ~ith reference to segrnented coup]ingrs for use with standard grooved pipe, the invention has equal utility in se,c~mented couplings for t~se in other applications, as will be evident from the following description with reference to Pigrures 7 througth I1, in which the salT)e referenc~ numerals are used to identify those inte~ers which are in common with the previously descri~ed embodiments.
In Pigure 7 there i3 shown a transverse cross-section through a coupling segment for use with plain-ended pipe, which, by virtue of the elimination of the grooving thereof, may either be st~ndard pipe, or, may be steel or stainless steel thin wall pipe. For the ptlrpose of convenience, in Pigure 7 the pipe has been shown as stand rd pipe, it being understood that thin wall pipe could be subst;tuted therefor.
In Figure 7 the required at>utment rnemt>ers 40 for engagement by the keys 30 and 32 of the coupling segment 10 are comprised by continuous rings which have been welded or otheruise secured to the outer periphery of the pipe in any known manner. In the case, more partict~ar1y, of thin wall pipe, the abutrrlent rnerrl~ers 40 may be provided by bead rolling the .

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pipe Irom the interior thereof Lsing adaptations of the machines disclosed in United States Patents 3,903,722, Thau, ~r. e$ al, issued Septernber ~, 1975; or, in 3,995,466, KImsman, iss-led December 7. 1976. Alternatively, instead of providing continous rolling beads on the exterior of the E?ipe, a plura]itv of arcuate radially-extending abutrnent rnembers may be formed thereon ernploying the apparatus disclosed and claimed in United States Patent , Gibb et al, issued . Alternatively, and as is illustrated in Pigure 8, the abutment mernbers rnay be cornporised by studs 40~ welded or otherwise secured to the outer periphery of the pipe, the studs of the abutment members for engagernent by the respective keys either being arranged axially in line with each other, or, in staggered or overlapping relationship in an axial direction as indicated in chain-dotted lines in Figure 8.
Alternatively; and as is illustrated in Figure 9, the respective abutment members may be formed of arcuate segments welded or otherwise attached to the pipe periphery as shown at 40b, and, the arcuate abutmerlt members of the respective abutments may be arranged in circumferentially spaced relationship and st~ggered relatively to the abutment members 40c of the next adj~3cent abutment. and, if required, the respectiYe arcuate segments 40b und 40c may be of different radial extent to each other, as illustrated in Figure 9, in the manner disc~Lssed previously with respect to Figure 3.
In Figure 10 there is shown a coupling segment p~rticularly adapted for use with either thin wall rnetal pipe or, plastic pipe. While in Figure 10 the respective mernbers have been indicated as being formed of rnetal, 2l it will be understood that the respective members equallv well could be formed from pla~tics mate~ial such as iUustrated in Figure l1.
In Figure lOr the respective pipes 24 each are provided with ~ grooved collar 42 which is welded or brazed to the pipe in known manner, or, which in the case of a plastic pipe is. cernemted or heat fused to the pipe end in known manner. By forming the respective grooves ior reception of the keys 30 and 32 within the collar 42, the integrity of the pipes 24 is maintained and the necessity of grooving or beading the pipes is elirninated.
ln Figure 20, there is illustrated a modified form of gasket 44 of generally T-shaped cross-section which is held compressed against the ends of the collars 42 by the respective coupling segments.
As an alternative to the provision of a centrally located gasketr such as the gaskets 28 or 44, the respective coupling segments can be internally grooved as illustrated at 46 in Fi,~,ure l1, and contain O-rings to be positioned over the respective lands of the collar 42 on each side of the grooves receiving the keys 30 and 32. In Figure 11 the respective integers have been illustrated as formed of plasti~s rnaterial. The respective integers, with the exception of the O-rings 48, equally well co~d be f ormed from rnetal. Where O-rrings are emp3Oyed, it rnay be desirable to provide additional 2() sealing means between rnated fac~s of the se~nents.

Coupling members of the type illustrated in Figures 10 and l1 find particlllar applicat;on in either thin-wall rnetal pipe systems or plastic pipe systems employed for conveying s1urries or airborne p~rticulate materials.
In systems, owing to deviations produced in the flu;d flow, and possibly 252 eddy currents which occur at the adjacent ends of the pipes, there is a - tendency îor the pipes to abrade more rapidly in the vicinity of the coupling, with a progressive decrease in the thickn~s of îhe pipe v,1all. In such applications, the provision of the grooved sleeve 42 reinforces the pipes in these positior~; of accelerated wear, thus extendirlg the useful life of the piping svstem.
In some npplications, it is desired that a minimum of discontinuity be incurred at the juncture between the pipe ends, and, that the pipe ends be brought into intirnate abutting relationship with each other. An adaptation of the segrnented coupling of the present invention to such reqlJirementS
is illustrated in Figure 12 of the drawings, in which the resplective keys 30 and 32 are provided with inclined radial faces, and, the pip~e is grooved to provide corresponding inclined abutment surfaces. In this embodiment, upon tightening of the segmented coupling about the pipe ends, the respective keys 30 and 32 force the respective pipes 24 axially towards each other l 5 to bring the radial end faces of the pipes into the required abutting engagem ent.
~hj1e the ~ouplingsegments so far described have each been of generally arcuate confi~G,uration, it will be appreciated that the external configuration of the respective coupling segments is of no particular consequence provided that they provide, in combination, the required encircling relationship with the pipe and maintain the resp2ctive keys in proper orientation within the grooves associ ated with the keys.
Additionally, while in each of the ernbodirnents so far de~;cribed, the respective keys have been iormed integrally with the respective coupling segments, it will b~ understood that the respective keys could be forrned - se2aratelv and positioned in appropriate recesses in the coupling segrnents subsequent to the manufactl~re ihereof, or, be incorporated into the coliplirlg segments by virtue of the segments being cast or otherwise formed around the keys, with the key in situ. Two such examples are shown in ~igures 13 and 14 of the drawings.
In Figure 13 the body lOa of the couplirlg segrnent is cast or otherwise formed with recesses lOb for the reception of keys 30a, or alterrlatively, the keys 30a are positioned within the rnols~, and the body of the coupling segment lOa is cast around the keys with the keys in situ. In the case oî
1() Figure 14, which illustrates a n~olded coupling segment lOc formed from a pla~stics material, the body of the coupiing segment is formed ei-ther with ~rooves for the reception of metal keys 30b and 32b, which, for convenience, are shown of difierent internal radius, or, the keys 30b and 32b are positioned in the mold prior to the injection moldlng of the body of the coupling segment, and sre thus molded in situ. In such an application, clearly it is undesirable fcr the segmented coupling to be capable of rotating relatively to the keys. Such rotation radily can be prevented by forming the outer peripnery of the keys for them to bn other than arcuate, for exarnple, they can be forrned with their outer periphely of polygonal or other forrn.
Various additional modifications of the preferred embodirnents of the segmented coupling described above can be made without departing from the scope of the appended clairns, and, various materials rnay be subscituted for tho.se disclosed, depending on the specific application and intended use of the segrnented coupling, again without departing frorn the scope of the - 25 appended claims, the description above with r~spect to the several ernbo~iiments of the ins~ention being by ~ay of example onlv as to preferre~
embodiment:.s of the inYention.

Claims (24)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A coupling segment specifically for use in a piping system of high-pressure relative to the pipe strength in conjunction with at least one additional coupling segment comprising:
a substantially unfinished high-strength metal casting of iron having substantial ductility and providing an arcuate member having an internal recess for the reception of a gasket;
a pad at each circumferential end of said arcuate member and cast integrally with said arcuate member, each said pad being adapted to receive securing means for securing said pad to the pad of an adjacent arcuate member with said arcuate members encircling a pipe;
at least one portion of said arcuate member extending axially to one side of said internal recess; and, plural axially spaced continuous arcuate keys integral with and extending inwardly of the inner periphery of said axially extending portion, said keys respectively being for engagement within correspondingly axially spaced grooves in the periphery of said pipe for resisting relative axial movement between said coupling segment and said pipe under axial loading, each said key having an unfinished engage-ment face having an inversely pebbled surface produced in the casting thereof and which faces towards said internal recess, said engagement faces at all positions along the circumferential extent of said keys being substantially radial and perpendicular to the axis of generation of said arcuate member, said inversely pebbled surface of each said key being capable of crushing down and cold working the material of said pipe to provide equalization of the stresses imposed on said keys when under axial loading.

2. The coupling segment of claim 1, including portions of said arcuate member extending oppositely from each side of said internal recess, and plural axially spaced continuous arcuate keys integral with and extending inwardly of the inner periphery of each said axially extending portion, said keys being for engagement within correspondingly axially spaced grooves in the peripheries of adjacent axially aligned pipes for resisting relative axial movement between said pipes and said coupling segment under axial loading, each said key having an unfinished engagement face having an inversely pebbled surface produced in the casting thereof and presented towards said internal recess, said engagement face of each said key at all positions along the circumferential extent thereof lying substantially radial and perpendicular to the axis of generation of said arcuate member, said inversely pebbled surface of each said key being capable of crushing down and cold working the material of said pipes to provide equalization of the stresses imposed on said keys when under axial loading.

3. The coupling segment of claim 1, in which each said pad has a clamping face which converges from its radially outermost portion towards a plane which includes the longitudinal axis of generation of said arcuate member.

4. The coupling segment of claim 1, in which the radius of the inner periphery of said arcuate member is slightly greater than the outer radius of the pipe to be associated therewith.

5. The coupling segment of claim 1, in which the radially extending face of each key is of a radial extent equal to the radial extent of each other said key.

6. The coupling segment of claim 1, in which the radially extending face of one said key is of different radial extent to the radial extent of the next adjacent key.

7. A segmented coupling for use in a piping system of high-pressure relative to the pipe strength, said segmented coupling comprising:
plural arcuate members each comprised of a substantially unfinished high-strength metal casting of iron having substantial ductility and providing an internal recess;
an elastomeric gasket positioned within said recess;
a pad at each circumferential end of each said arcuate member and cast integrally therewith, each said pad being secured by securing means to the pad of the next adjacent arcuate member for said arcuate members to be brought into encircling engagement with at least one pipe with said gasket in sealing engagement therewith;

at least one portion of each said arcuate member extending axially to one side of said internal recess; and, plural axially spaced continuous arcuate keys integral with and extending inwardly of the inner periphery of said axially extending portion of each said arcuate member, said keys respectively being for engagement within correspond-ingly axially spaced grooves in the periphery of said pipe for resisting relative axial movement between said arcuate members and said pipe under axial loading, each said key having an unfinished engagement face having an inversely pebbled surface produced in the casting thereof and presented towards said internal recess, said engagement faces at all positions along the circumferential extent of said keys lying substantially radial and perpendicular to the axis of generation of the associated arcuate member, said inversely pebbled surface of each said key being capable of crushing down and cold working the material of said pipe to provide equalization of the stresses imposed on said keys when under axial loading.

8. The segmented coupling of claim 7, including portions of each said arcuate member extending oppositely from each side of said internal recess, and plural axially spaced continuous arcuate keys integral with and extending inwardly of the inner periphery of each said axially extending portion, said keys being for engagement within correspondingly axially spaced grooves in the peripheries of adjacent axially aligned pipes for resisting relative axial movement between said pipes and said arcuate members under axial loading, each key being unfinished and having an inversely pebbled surface produced in the casting thereof presented towards said internal recess, said engagement face of each said key at all positions along the circumferential extent thereof lying substantially radial and perpendicular to the axis of generation of the associ-ated arcuate member, said inversely pebbled surface of each said key being capable of crushing down and cold working the material of said pipe to provide equalization of the stresses imposed on said keys when under axial loading.

9. The segmented coupling of claim 7, in which each said pad has a clamping face which converges from its radially outermost portion to its radially innermost portion towards a plane which includes the longitudinal axis of generation of said arcuate member.

10. The segmented coupling of claim 7, in which the radius of the inner periphery of each said arcuate member is slightly greater than the outer radius of the pipe to be associated therewith.

11. The segmented coupling of claim 7, in which the radially extending face of each said key is of a radial extent equal to the radial extent of each other said key.

12. The segmented coupling of claim 7, in which the radially extending face of one said key is of different radial extent to the radial extent of the next adjacent said key.

13. A coupling segment specifically for use in a piping system of high-pressure relative to the pipe strength in conjunction with at least one additional coupling segment to provide a segmented coupling for grooved pipe, each said coupling segment comprising:
a substantially unfinished high-strength casting of material having substantial ductility and providing an arcuate member having an internal recess for the reception of a gasket;
securing means associated with each said arcuate member for securing said arcuate member to another said arcuate member with a series of said arcuate members encircling a pipe;
at least one portion of said arcuate member extending axially to one side of said internal recess; and plural axially spaced continuous arcuate keys integral with and extending inwardly of the inner periphery of said axially extending portion, said keys respectively being for engagement within correspondingly axially spaced grooves in the periphery of said pipe for resisting relative axial movement between said coupling segment and said pipe under axial loading, each said key having an unfinished engagement face having a pebbled surface which faces towards said internal recess, said engagement faces at all positions along the circumferential extent of said axially extending portion, said keys respectively being for engagement within correspondingly axially spaced grooves in the periphery of said pipe for resisting relative axial movement between said coupling segment and said pipe under axial loading, each said key having an unfinished engagement face having a pebbled surface which faces towards said internal recess, said engagement faces at all positions along the circumferential extent of said keys being substantially radial and perpendicular to the axis of generation of said arcuate member, said inversely pebbled surface of each said key being capable of crushing down and cold working the material of said pipe to provide equalization of the stresses imposed on said keys when under axial loading.

14. A segmented coupling specifically used in a piping system of high-pressure relative to the pipe strength, said coupling comprising:
plural arcuate members each comprised of a substant-ially unfinished high-strength casting of a material having substantial ductility and providing an internal recess;
an elastomeric gasket positioned within said recess;
securing means for securing said arcuate members in encircling engagement with at least one pipe with said gasket in sealing engagement therewith;

at least one portion of each said arcuate member extending axially to one side of internal recess; and, plural axially spaced continuous arcuate keys integral with and extending inwardly of the inner periphery of said extending portion of each said arcuate member, said keys respectively being for engagement within correspondingly axially spaced grooves in the periphery of said pipe for resisting relative axial movement between said arcuate members and said pipe under axial loading, each said key having an unfinished engagement face having an inversely pebbled surface which faces towards said internal recess, said engagement faces at all positions along the circum-ferential extent of said keys lying substantially radial and perpendicular to the axis of generation of the associated arcuate member, said inversely pebbled surface of each said key being capable of crushing down and cold working the material of said pipe to provide equalization of the stresses imposed on said keys when under axial loading.

15. In combination:
a conduit member of a conduit system;
said conduit member having plural axially spaced key receiving engagement members adjacent at least one end thereof, each said engagement member being formed of ductile material;

a segmented coupling embracing and secured to said end of said conduit member, said coupling including:
plural acuate members each providing an internal recess, each said member being comprised of a substantially unfinished high-strength casting of a material having substantial ductility, at least one portion of each said arcuate member extending axially to one side of said internal recess;
a gasket positioned within said recess;
securing means securing said arcuate members in encircling engagement with said conduit member, with said gasket in continuous sealing engagement with said one end of said conduit member; and, plural axially spaced continuous arcuate keys integral with and extending inwardly of the inner periphery of said axially extending portion of each said arcuate member;
said keys respectively being spaced axially correspond-ingly with said engagement members of said conduit member and each being engaged with the engagement face of a said engagement member, said keys resisting relative axial movement between said coupling and said conduit member when under axial loading;
each said key having a substantially unfinished engage-ment face having an inversely pebbled surface produced in the casting of the associated segment and which faces towards said internal recess, and, which is engaged with a radially extending engagement face of an associated engagement member, said engagement faces of said keys and said engagement members lying substantially radial and perpendicular to the axis of generation of the associated arcuate member, said inversely pebbled surface of said engagement face of each said key being capable of crushing down and cold working the associated engagement member of said conduit member, to provide substantially uniform distribution of the stresses imposed upon said keys when said keys are subjected to axial loading.

16. The combination of claim 15, in which said engagement members are defined by grooves formed in the outer periphery of said conduit member.

17. The combination of claim 15, in which said engagement members are provided by attachments secured to the outer periphery of said conduit member.

18. A piping system, comprising in combination:
plural lengths of pipe arranged in axially aligned relationship, each said pipe having axially spaced key engagement members adjacent the ends thereof;
at least one conduit member providing transitions between respective said pipes, each said conduit member having axially spaced key engagement members adjacent the ends thereof;
said key engagement members each being comprised of a ductile material; and plural segmented couplings embracing and secured to adjacent ends of said pipes and conduit members, each said coupling including:
plural arcuate members each having an internal recess and each comprised of a substantially unfinished high-strength casting of a material having substantial ductility;
a gasket positioned within said recess;
securing means securing said arcuate members in encircling engagement with said pipes and conduit members, with said gasket in continuous sealing engagement with the ends of said pipes and said conduit members; and, plural axially spaced continuous arcuate keys integral with and extending inwardly of the inner periphery of each said arcuate member;
said keys respectively being spaced axially correspond-ingly with said axially spaced engagement members of said pipes and said conduit members, and each being engaged with an engagement face of a said engagement members of said pipes and coupling members, said keys resisting relative axial movement between said pipes and said coupling members when said piping system is subjected to pressure loading;
each said key having an unfinished engagement face produced in the casting thereof having an inversely pebbled surface which is engaged with a said engagement member;

said engagement faces of said keys and said engagement members lying substantially radial and perpendicular to the axis of generation of the associated arcuate member;
said inversely pebbled surface of each said key being capable of crushing down and cold working the juxtaposed radial face of the associated engagement member, to provide substantially uniform distribution of the stresses imposed upon said keys when said keys are subjected to axial loading.

19. The system of claim 18, in which said engagement members are defined by grooves formed in the outer periphery of said pipes and conduit members.

20. The system of claim 18, in which said engagement members are attachments secured to the outer periphery of said pipes and said conduit members.

21. A method of providing stress equilization in inter-connectons between conduit members of a conduit system when subjected to internal pressure loading, comprising the steps of:
providing said conduit members with plural axially spaced engagement members adjacent to the ends thereof, and which each provide radially extending engagement faces, each said engagement member being comprised of a material of substantial ductility that is plastically deformable;

arranging said conduit members with ends thereof in axial alignment with ends of adjacent conduit members;
providing segmented couplings clamping adjacent ends of adjacent coupling members to each other;
providing each said coupling with plural keys each having a radially extending engagement face for engagement with a said radially extending engagement face of said engagement members, and positioning said keys with said respective engagement faces of said keys and said engagement members in juxtaposition with each other;
forming the segments of each said segmented coupling and the keys thereof as unitary substantially unfinished high-strength castings of a material having substantial ductility, and in which the radial faces of said keys, at least, have an inversely pebbled surface produced in the casting of said segments; and subjecting said conduit members and said couplings to oppositely acting axial loading forces to cause the inversely pebbled surface of the radial engagement faces of said keys to crush down and to cold work the juxtaposed radially extending engagement face of the juxtaposed engagement member, and to progressively produce substantially uniform distribution of the stresses imposed on the respective keys by progressive crushing down of said pebbled surfaces of said keys and cold working of the material comprising said engagement members.

22. The method of claim 21, including the steps of providing said engagement members by forming plural grooves adjacent the ends of said conduit members, each providing a radially extending engagement face.

23. The method of claim 21, including the steps of attaching engagement members to the outer circumference of said conduit members, each said engagement member providing a radially extending engagement face.

24. A method of assembling a conduit system including the steps of:
securing adjacent ends of conduit members to each other, each said conduit member having axially spaced radially extending plastically deformable engagement faces adjacent the ends of said conduit members, by applying a segmented coupling to the adjacent ends of said conduit members, each said coupling including plural radially extending keys of high strength material of substantial ductility and with a substantially unfinished inversely pebbled surface thereon produced in the casting of respective segments of said coupling; and pressurizing said conduit system to produce axial stressing of said key engagement faces of said conduit members and crushing down said pebbled surfaces of said keys to cold work the material of said engagement faces, to equalize the compressive loads exerted on the respective keys and engagement faces, and, thus accommodate dimensional variations in the axial positioning of the respective said keys and engagement faces.