CA1274862A - Method and apparatus for seating a gasket in a large diameter bell - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A hard ring is provided herein for seating a resilient gasket in the bell of a length of plastic pipe having an inner periphery of predetermined interior diameter, a belled end and central axis. The hard ring includes a hard plastic, shaped, non-resilient annulus, the shaped annulus having a particularly-recited structure of seat and seating surface. The shaped annulus further includes a pair of inclined ramps of a par-ticularly-recited structure. The shaped annulus defines a radially-inwardly-opening-junction. One inclined ramp defines a path to the radially-inwardly-open junction. By these structural elements, the resilient gasket may be readily applied to the hard ring by positioning a portion of the gasket in peripheral contact with the radially-inwardly-open junction.

Description

The present invention relates generally to the field of mechanical equipment suitable for forming bells or sockets in one end of length of plastic pipe ~o permit ~oining ad~acent len~ths of plastic pipe in end-to-end Juxtaposition by inserting the unbelled or spigot end of one length of pipe into the bell or socket which is formed in the proximate end of the next ad~acent len~eh of pipe. In particular, the present invention rela~es to a hard ring for seating a resilient gasket in the bell of a length of plastic pipe having a belled end and central axis.
This application is a division of application Serial No.
489,382 filed August 26, 1985.
In prior art types of pipe belling equipment, it has been known to position a shaped mandrel of predetermined configuration and size within a belling machine and serially to advance discrete lengths of plastic pipe, each having one end preheated, into axial alignment with the belling mandrel. Suitable operating mechanisms have been developed and have been utilized either axially to move the pipe onto and over the mandrel, or alternately, axially to move the mandrel into the preheated end 2l) of the pipe for pipe end shaping into the desired bell or hub-shaped configuration. In certain desi~ns, the prior pipe belling operations have been conducted within a suitable environmental chamber where suction forces or pressure forces could be introduced into the chamber to surround the pipe and thereby pull or press the preheated, softened pipe walls u1liformly against the outer periphery of the mandrel.

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In accordance with more recent popular prac~ice, it has become increasingly importan~ ~o provide an internal groove in the bell configuration when the bell or hub shape was formed to provide a convenient annular groove for seating therein a resilient gasket in a manner to facilitate the making up of a leak proof junction between adJacent lengths of pipe in a piping system. Mandrel constructions have been developed by prior workers in the art which are capable of forming a circular, internal groove in the hub configuration for receipt of a gasket l(~ therein when the bell or hub of the plastic pipe was being formed~
llowever, so far as is known to the present applicants, despite all of the efforts of the many prior workers in the field to improve the ~oining procedures and constructions when utilizing plastic pipes, the proper and permanent seating of a sealing gasket in the junction between the spigot end of one length of pipe and the hub end of the next adjacent length of pipe, either with or without a peripheral internal groove formed in the hub, usually present field problems, and this is especially true in large diameter work. Particularly, in many desi~ns the ~askets have been subject to displacement or "fishmouthing" when the joint was being formed. In other instances, when the system was operated under pressure, gasket blow-out could frequently occur in the event of pressure surges in the line.

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In the plastic pipe industry, it i8 the common practice to provide a rubber-or other elastomeric-material gasket to form the seal between ad~acent pipe sections or at the ~unction he~ween a pipe and a fitting. Such gaskets have been configured and designed to facilitate the making-up of the pipe joint in the shortest possible period of tirne in a manner to prevent leakage at the joint upon completion of the system. As the design operating pressures in a piping system increase, the difficulties encountered in providing an efficient and reliable seal have also 1~ increased.
In efforts to solve the sealing problems at pipe ~oints which are inherent in pressure or vacuum piping systems, prior workers in the art have developed gaskets of the type including one or more radially-inwardly-extending lips to press against the spigot end of the connected section of pipe. Additionally, other workers have provided gaskets having an internal peripheral groove within which is seated a locking ring of relatively-hard plastic material to prevent movement of the seal a8 the joint is made up and to discourage gasket blow-out when surges in system _(~ pressure occurred. In other efforts to prevent unseating of the gasket when the pipe ~oint was made up or to aid in preventing gasket blow-out under severe pressure conditions of use, prior workers have also attempted to develop means to lock the gasket within an annular groove which could be formed in the plastic material of the bell during the bell-formin~ operation.

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In United States Patent No. 4,343,480 entitled "Pipe Bell and &asket", which patent is owned by the assignee of the present application, a bell and spigot connection for plastic pipes is disclosed, The paten~ed design employs a gasket groove in the hub and a gasket seated within groove and having a p,air o~
longitudinally-spaced, radially-inwardly-extending lips. The &asket may be utilized either with or without a hard plastic retaining ring intermediate the lips. In the pa~ented configuration, the ex~erior or entrance end of the hub was radially-inwardly-bent after the gasket was seated in the peripheral, inwardly-open groove which was formed in the hub, thereby to retain the gasket within the groove in a manner to prevent gasket blow-out upon surges in system pressure, It has been found that ~he prior art hub and gasket constructions were particularly difficult to form to precise tolerances and this was especially true in large diameter work ~herein the very thickness of the large diameter pipe sidewall constructions resisted efforts satisfactorily to develop the machinery and techniques necessary to form the configurations of bells and gasket grooves within the tolerances required to assure proper gasket performance both when the ~oint was made up and after the piping system was pressurized, The need remains to provide a functional, reliable gasket seating arrangement for the end bells of plastic pipes.

~ s used herein, the term "large diame-ter" is defined to mean plastic pipes having an inside diameter of ten inches and larger.
It is therefore an object of a broad aspect of the present invention to provide a novel hard ring for seating a gasket in a plastic pipe bell of the type set forth above.
It is another object of the present invention to provide a novel hard ring for seating a gasket in a plastic pipe bell that i.s rugged in construction, automatic in operation and reliable when in use.
By one broad aspec-t of this invention, a hàrd ring is provided for seating a re~ilient gasket in the bell of a length of plastic pipe having an inner periphery of predetermined interior diameter, a belled end and central axi~, the hard ring comprising: a hard plastic, shaped, non-resilient annulus, the shaped annular comprising a radially~inwardly-facing annular seat, the seat having a leading edge, a trailing edge and a non-resilient seating surface defined between the leading edge and the trailing edge, the seating surface having a diameter substantially equal to the interior diameter of the pipe, the shaped annulus further comprising a rearward, radially-outwardly-inclined ramp extending forwardly from the trailing edge of the seat and a joined forward, partial, radially inwardly inclined ramp, the junction between the rearward and forward ramps defin-ing the outer periphery of the hard ring, the shaped annulus being configured to define a radially inwardly opening junction, `~

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the junction being defined by walls of hard, pla~tic material, the forward, partial, radially-inwardly-inclined ramp terminating radially outwardly of the inner periphery of the pipe to define a forwardly open annular path to the radially-inwardly-open junction of si~e to receive portions of the resilient gasket therein, the diameter of the annular path being larger than the diameter of the inner periphery of the pipe; whereby the resili-ent gasket may be readily applied to the hard ring at the for-Wr rdly open path by positioning a portion of the gasket in peri-pheral contact with the radially inwardly open junction.
The radially-inwardly-open junction preferably comprises a substantially-radially-extending wall, and an axially-extending wall, the walls intersecting to form an angular junction of sub-stantially ninety degrees. The shaped annulus preferably com-prises a bearing section positioned forwardly of the annular seat, the bearing section defining a cylindrical bearing surface.
The present invention also provides, in another aspect, the combination of the hard ring as defined above, and a resilient gasket in contact both with the radially-extending wall and the axially-extending wall of the radially-inwardly-open junction.
The resilient gasket is preferably U-shaped in cross-sectional configuration, the resilient gasket preferably comprising a rela-tively thin, forward, wiping flange, a relatively thick, rearward sealing flange and a relatively thick base interconnecting the forward wiping flange and the rearward sealing flange. The - 6a -gasket base preferably is rearwardly defined by a thick, sturdy, sharp, angular junction, and the gasket base preferably is for-wardly defined by a sealing corner comprising a sealing face that is angularly inclined relative to the central axis of the length of the plastic pipe. The forward wiping flange and the rearward sealing flange preferably define an annular space therebetween.
The present invention still further provides, in another aspect, the combination of the hard and resilient gasket as above defined, and a hard plastic retaining ring positioned within the annular space. The retaining ring preferably contacts interior portions o the base, the forward wiping flange and the rearward sealing 1ange of the resilient gasket.

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The hard plastic ring will hereinafter be referred to as the "EPSMI" ring, an acronym for an extruded pipe socket molded insert. The EPSMI ring of broad aspects of ~he present invention may be molded or otherwise formed of a suitable hard plastic, e.g. polypropylene plastic or perhaps polyethylene plastic and can be formed by molding or otherwise to the exact configuration and dimensions as necessary to properly seat and retain a gasket, a heretofore almost impossible achieYement when mandrel forming the sockets of large diameter plastic pipes.
I(~ The EPSMI ring of broad aspects of the present invention is particularly interiorly formed to seat a resilient gasket of generally-U-shaped or other cross-sectional configuration. In the preferred embodiment, the gasket will be of the type wherein an annular, radiallr-inwardly-open groove is defined to receive therein a retaining ring of relatirely-hard plastic material, for example, a ring of molded polypropylene plastic. The preferred gasket construction comprises a circular arched base, a front, radially-inwardly-projecting leg or flange and a rearward, radially-inwardly-pro~ecting leg or flange of thicker material.
The front leg terminates radially-inwardly to define a leading lip of suitable inner diameter to be conventionally employed to center and initially to wipe the outer periphery of the spigot end of the adjacent pipe section as the bell and spigot ~oint is being formed in the field. The thicker rear leg of the gasket terminates radially-inwardly to define a sealing lip of inner diameter that is designed to press against~ and to seal against, the outer periphery of the spigot end of the adjacent pipe section to provide a leak-tight, easily-made-up ~uncti~n.
The hard plastic retaining ring o an aspect of this invention and the thicker rear leg of the gaske~ are especially designed and u~ilized to prevent unseating of the gasket when the parts are joined together and to discourage gasket blow out after the system is pressurized and in use. In a preferred embodiment, the gasket utilized in conjunction with the EPSMI ring can be 1() similar to the gasket disclosed in our U.S. Patent No. 4,579,354, dated ~pril 1, 1986, entitled "Gasket". As hereinafter set forth, gaskets of other configurations can also be utilized in accordance with the teachings of aspects of the present invention, The resilient gaskets employed in combinations of aspects of this invention are particularly adaptable to be secured in the EPSMI ring following the belling operations and are frictionally-retained bet~een portions of the inner periphèry of the EPSMI ring and the expanded groove or circular pocket which is formed in the socket by the ring during the belling operation.
The body of the mandrel utilized in the invention disclosed and claimed in the above-identified parent application is hollow in order to provide for the introduction of a vacuum therewithin.
The hollow mandrel interior or vacuum chamber is provided with vacuum introduction means and a plurality of vacuum openings which can be positioned to apply suction forces interiorly of the ~L~7~
g heated end of the plastic pipe. These vacuum openings serve to pull the plastic pipe into intimate overall contact with the outer periphery of the mandrel and the EPSMI ring while the bell-shaped configuration is being formed in the pipe end and simultaneously to encapsulate or entrap the hard plastic ring ~ithin the bell-shaped end. Preferably, the vacuum openings are circumferentially-spaced forwardly and rearwardly of the ring-retaining groove equally to apply the suction forces about the hard plastic ring. The vacuum forces acting through the 1~ plurality of vacuum openings pull the softened pipe end into overall, intimate contact with the outer peripheries of the hard plastic ring and the mandrel by applying uniform suction forces interiorly of the pipe to impress the desired bell-shaped configuration in the plastic pipe with the plastic ring secured therein. It is noteworthy that the hard EPSMI ring provides an additional pipe-end-shaping function in conjunction with ~he shaping function of the mandrel whereby the heated end of the pipe will assume the shape of the mandrel with the outer peripheral shape of the hard plastic ring superimposed therein.
~0 The sharply-defined interior configuration of peripheral surfaces of the EPSMI ring can then provide the required cooperating surface conEigurations within the required tolerances to receive and retain a resilient gasket therein.

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In the accompanying drawings, Fig. 1 is a partial, exploded, perspective schematic representation of the belling equipment of the invention disclosed and claimed in the above-identified parent application;
Fig. 2 is an enlarged, partial, side elevational view of the belling mandrel with an EPSMI ring of an aspect of the yresent invention seated thereon in a position just after entering the heated end of a length of plastic pipe, and partially broken away to expose interior construction details;
I~ Fig. 3 is a side elevational view similar to Fig. 2 showing the belling mandrel urged further into the preheated end of the pipe;
Fig. 4 is a side elevational view similar to Fig. 3 illustrating the complete insertion of the belling mandrel in the preheated end of the pipe;
Fig. 5 is a side elevational view similar to Fig. 4 showing the pipe being cooled after the bell-shaped configuration has been completely formed;
Fig. 6 is a side elevational view similar to Fig. 5 showing

2~ the clamps in closed position to hold the pipe while the mandrel is withdrawn;
Fig. 7 is an enlarged, partial, cross-sectional v-iew showing the EPSMI ring of an aspect of the present invention encapsulated in the circular pocket;

~ -- 1 1 Fig. 8 is an enlarged, partial, sectional view sirnila~ to Fig. 7 illus~rating a resilient gasket secured between the ring of an aspect of the present invention and a forward wall of the pocket;
Fig. 9 is a side elevational view of pipe ~unction on reduced scale illustrating a spigot end inserted into the formed bell and partly in section to show interior construction details;
Fig. 10 is an enlarged, partial sectional view similar to Fig. 8 showing a modified hard plastic ring of another aspect of the present invention and a modified gasket constrùction;
Fig. 11 is a sec~ional view similar to Fig. 1~ showing the spigot end of an adjacent pipe length in sealing engagement with the enlarged socket; and Fig. 12 is an enlarged, partial, sectional view similar to Fig. 8 showing a modified gasket construction.
Although specific terms are used in the following description for the sake of clarity, these terms are intended to refer only to the particular structure of the invention selected for illustration in the drawings.
7 Referring now to the drawings, there is illustrated, in Figs. 1 and 2, a mandrel 10 of the type utilized to form a bell-shaped confi~uration in one prehea~ed end 14 of a length of plastic pipe 16. In accordance with the most common practice, the pipe 16 is preferably extruded in known manner from polyvinylchloride pellets and is cu~ into discrete len~ths, e.g.

ten, thirteen or twenty feet prior to introduction to a pipe-belling machine comprising a belling rnandrel. The mandrel 10 comprises generally a hollow cylindrical body portion 18 of diameter greater than ~he outer diameter of the pipe 16 and a shaped, hollow profile or nose portion 20. As illustrated, a hydraulic cylinder 22 is provided in longitudinal axial alignment with the mandrel 10 and has a reciprocating arm 24 secured to the mandrel rear wall 26 to reciprocate the mandrel 10 in known manner in response to activation of the hydraulic cylinder 22. A
1~) vacuum hose 28 communicates with the hollow interior 30 of the mandrel 10 through a conventional air fitting 32 to introduce vacuum forces within the interior cavity 30 of the mandrel from a suitable known vacuum source (not illustrated) to aid in shaping the bell as hereinafter more fully described.
A~ bes-t seen in Figs. 1 and 2, the mandrel body portion 18 is equipped with a plurality of similar, circularly-spaced, vacuum openings 34, 36 to facilitate the application of vacuum forces peripherally exteriorly of the mandrel 10 for EPSMI ring encapsulating purposes in the manner hereinafter more fully set ~ forth. A peripheral groove 38 is formed in the exterior periphery of the mandrel body 18 intermediate its ends and the groove comprises a circular seating face 40 which inclines radially-inwardly from the mandrel front or profile portion 20 toward the mandrel rear and a locking face 42 which extends radially-outwardly from the rearward extent of the seating face 40 to the peripheral surface 44 of the mandrel body portion 18.

Still referring to Figs. 1 and 2, an EPSMI ring 46 is illustrated which is molded or otherwise formed of a hard, essentially non-shrinkable plas-tic, e.g. polypropylenè plastic.
The ring 46 is particularly configured ~o be either manually or automatically applied to the mandrel 10 prior to the pipe belling operation and has its interior peripheral surfaces particularly configured and designed to secure a gasket 48 (Fig. 8) or 50 (Fig. 10) within the pipe bell 52 (Fig. 9) formed in one end of the length of pipe 16 as hereinafter more fully set for~h.
1~ As best seen in Figs. 2 and 7, the EPSMI ring is configured as a shaped annulus and comprises a radially-inr7ardly-facing annular seat 54. The seat 54 inclines inwardly from the trailing edge 56 to a locking shoulder 58 and conforms in diameter, length and inclination to the configuration of the peripheral mandrel ~roove 38. By applying the ring 46 over the mandrel body 18 and ur~ing it forwardly with sufficient force, the ring will be temporarily stre~ched sufficiently to allow the annular seat 54 to slide over the mandrel body and snap into and lock within the mandrel groove 38. A bearing section 60 extends forwardly from ~t~ the seat 54 and is formed of suitable diameter to rest and bear directly upon the outer periphery of the mandrel body portion 18.
A rearward, radially-outwardly-inclined ramp 62 and a forward, partial, radially-inwardly-inclined ramp 64 define the outer periphery of the ring 46. The ramps 62, 64 define a circular outer ring periphery that is greater in diameter than the " ~ "

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diameter of the outer periphery o~ the gasket 48 or 50 and are utilized to extend the bell diameter sufficiently to facilitate placement of the gasket after the bell configuration has been formed and the mandrel removed.
Wi~h EPSMI ring 46 seated and locked wi~hin ~he mandrel groove 38, the mandrel 10 can then be reciprocated upon activation of the cylinder 22 to enter the pipe and to urge the hated end 14 of the pipe 12 over the shaped profile portion 20 of the mandrel and over the outer periphery of the mandrel body 1(~ portion 18. See Figs. 2 and 3. As illustrated in Fig. 4, the forward end of the preheated pipe end portion 14 will expand over the rearward ramp or slope 62 and over and down the forward ramp or slope 64 to form a radially-outwardly~expanded groove 66 in the pipe socket or bel] shaped configuration 52. The pipe end 16 will thus be expanded over the EPSMI ring 64 to form a seating space for a ~asket 48,50, which gasket can then be applied to the bell ~2 once the mandrel has been reciprocated to its initial position. As illustrated in Fi~. 4, the outer configuration of the pipe end about the ring 46 will not be well defined a~ this ~) stage in view of the thickness of the pipe sidewall construction.
A plurality of func~ioning vacuum openings 34, 36 extend radially-outwardly through the mandrel body portion 18 on each side of the peripheral ring retaining groove 38 to communicate the interior of the operating cavity 30 with the atmosphere immediately surrounding the mandrel 10. By applying suction z~

forces within the operating cavity 30, for example by utilizing a vacuum hose 28 and air fitting 32 in a manner well known to those skilled in the art, the suction forces can be imposed interiorly of the heated pipe end 14 to draw the interior periphery of the pipe tightly against the outer periphery of the mandrel 10 and about the outer rearwardly and forwardly ramped periphery 62,64 of the EPSMI ring 46. See E'igs. 5 and 6. Optionally, in lieu of employing suction within the operating cavity 64 to apply vacuum forces through the suction openings 34, 46, the mandrel could possibly be positioned within a pressure chamber, thereby to press the preheated end 14 of the pipe 16 against the mandrel 10 and over and about the EPSMI ring 46. In either event, forces other than atmospheric cause the heated pipe end 14 into in~imate contact with the mandrel 10 and the ring 46, thereby providing a very well-defined shape in the socket or pipe bell 52.
In order to use ~he reciprocating mandrel in the method of the invention disclosed and claimed in the above-identified parent application to impress a bell shape 52 in one end 14 of a length of pipe 16, the pipe end 14 is first rotated within a ~ suitable heater 108 in a manner well-known to those skilled in the art for a sufficient period of time to become pliable enough to permit the bell-forming operations to take place. While the pipe end 14 is being heated, an EPSMI ring 46 can be manually applied over the mandrel profile and body portions 20, 18 and can be secured in the proper position by forcing the ring annular l~) ,.

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seat 54 into the mandrel peripheral groove 38~ A hydraulic cylinder 22 or other type of exterior operator which is employed to ~eciprocate the operating arm 24 is then functioned to push the operating arm 24 rearwardly, thereby to move the mandrel 10 rearwardly to its rearward, belling position 68. See Fig, 4 and Fig. 5. In this position, the previously softened pipe end 14 will be urged over the mandrel profile portion 20 and will be radially outwardly expanded over the mandrel body portion 18 and outwardly and about the EPSMI ring ramp surfaces 62, 64 until ~he l~) outer periphery of the pipe end 14 approximat~s the combined outer peripheries of the mandrel profile portion 20, the mandrel body por~ion 18 and the seated EPSMI ring 46.
While it is contemplated at the present time that the hard plastic EPSMI ring 46 will be positioned upon the mandrel 10 by employing manual operations, it is expected that this operation can be and may be automated, whereby the ring 46 can be automatically applied over the mandrel profile and seated within the groove 38 prior to the initiation of the belling cycle.
Once the mandrel 10 is urged to its rearward, belling position 68, forces other than atmospheric are then employed to pull or press the heated end 14 of the pipe 16 into intimate, overall contact with the outer periphery of the mandrel and the outer periphery of the ring 46. In the illustrated embodiment, it is contemplated that suction forces will be introduced through the vacuum hose 28, within the hollow interior mandrel cavity 30 ~27~

and these suction forces, opera~ing through the plurality of vacuum or suction openings 34, 36 will cause the pipe e~ld 14 to be pulled into intimate overall contact with the mandrel profile 18,m 20 and the associated EPSMI ring 46. The shape of the pipe end will be varied by -the suction forces from the rather slack exterior periphery without well-defined angles, as illus~rated in Fig. 4, to the well-defined peripheral shape as best seen in Figs. 6 and 7.
With the parts in position illustrated in Fig. 5, the end 14 of the pipe 16 can then be cooled rapidly in know~ manner, for example by applying cooling liquid through a plurality of nozzles 70 to set the plastic in the desired bell-shaped configuration and to encapsulate the hard plastic ring 46 within a radially expanded annular pocket 72 which has thus been formed in the pipe end. Once the pipe end has cooled and with ~he EPSMI ring encapsulated within the expanded ring shape 72, the mandrel 20 can then be removed axially from the pipe bell shaped configuration 12 in known manner by activation of the cylinder 22. A pair of opposed clamps 110, 112 of half-circle ~n configuration are then moved from their open position as illustrated in Fig. 1 to their closed position as shown in Fig. 6 to hold the pipe end in the fixed position while the mandrel 10 is hydraulically pulled out. The belling operation can be repeated with the next serially-advancing length of plastic pipe.
(Not shown). It is noteworthy that the groove-locking face 42 ~27~

interacts with the ring-locking shnulder 58 to prevent unseating of the EPSMI rin~ during the belling operation when the mandrel 10 is urged within the preheated end 14 of the pipe length 16 and the inclined seating face 40 functions to permit the inclined annular seat 54 of the ring to slip off of ~he mandrel when the clamps 110, 112 are closed and the mandrel is withdrawn from the forward pipe bell.
As illustrated in Fig. 9, the operation of the reciprocating mandrel 10 of the invention disclosed in the above-identified 1~) parent application with the ring 46 seated thereon produces a finished, bell shaped configuration 52 in one end 14 of a length of plastic pipe 16 with an ePSMI ring 46 permanently secured therein to facilitate receiving a resilient gasket 48~ 50 suitable for making up the junction between adjacent lengths of pipe when a piping system (not illustrated) i6 to be fabricated.
It ~ill be appreciated that the operation of the hydraulic cylinder 22, the suction forces through the vacuum hose 28 and vacuum openings 34, 36, the movement of the mandrel 10 axially into and out of the pipe end 14, the opening and closing oE the claims 110, 112 and the function of the spray nozzles 70 can be automated in well-known manner to provide a completely automatic, cyclical operation that is capable of successively belling a plurality of plastic pipes as they are serially advanced to the belling mandrel. Additionally, as abo~e set forth, if desired, it would also be possible to automate the placing of the EPSMI
ring upon the mandrel at the start of each belling cycle.

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Experience has shown that the nozzles 70 will nnly partially cool the shaped bell 52 and when the mandrel 10 has been reciprocated outwardly of the bell shaped configuration 527 the pipe end 14 will continue to be cooled through contact with the cooler ambient air. The natural memory of the plastic material of the pipe will cause the bell-shaped configuration to shrink and tend to attempt to return to the initial unexpanded shape.
This shrinkage further acts to lock the EPS~I ring within the bell shaped configuration. Upon removal of the mandrel, the n added shrinkage of the bell shaped socket 52 will occur both forwardly and rearwardly of the ring 46 (without shrinking the ring 46). thereby to produce a forward inner diameter section 74 and rearward inner diameter section 76 that is less than the inner diameter of the ring annular seat 54. It will be noted that, due to the hardness of the polypropylene plastic material which comprises the ring 46, there will be no tendency of the ring either to expand or to shrink during any of the belling operations. Rather, the dimensions of the ring 46 remain essentially the same throughout the belling cycle, thereby 2~ providing ~he exact shaped profile required for optimum gasket seating.
As illustrated in Figs. 8 and 9, the EPSMI ring 46 is illustrated in use with a resilient gasket 48, which gasket is characterized by a generally-U-shaped configuration comprising a relatively-thin forward or wipin~ flange 78, a relatively-thick - 20 ~
sealing flange 79 and a relatively-thick base or we~ 80 which interconnects the legs or flanges 78, 79. The in~erconnection between the base 80 and the sealing flange 79 is formed to a thick, sturdy, sharp angular ~unction 82 which is especially adapted to a~oid "fishmouth" or gasket dissociation when the pipe ~oint between adjacent lengths of pipe is made up. See Fig. 8.
The gasket 48 may be similar to the gasket construction illustrated in our above-identified U.S. Patent No. 4,579,354 and may be used in conjunction wi~h a polypropylene or other hard 1() plastic retaining ring 84.

Referring to Figs. 7 and 8, the EPSMI ring 46 is configured to provide a forwardly-facing, sharp angular junction 88 which defines an acute angle between the generally-axially-aligned interior wall 90 and the generally-radially-extending interior wall 92. The angular ~unction 88 is especially designed to receive and securely seat therein the thick sea~ing corner 82 of the gasket 48, thereby to discourage unseating of the gasket by the stresses imposed when the pipe junction 96 between adjacent lengths of pipe 16, 98 is made up. As illustrated in Fig. 9, -~) when the pipe junction 96 is formed, the gasket seating corner 82 remains associated within the ring angular junction 88 and the forward and rearward flange lips 100,102 will bend and seal against the outer periphery of the spigot end 104 of the adJacent pipe length 98. Simultaneously, the gasket 48 will have its sealing corner 106 ti~htly pressed into sealing engagement 6~

against the forward interior wall 114 of the cxpanded groove 66, to function additionally to assure a leak-proo junction between the parts. As illustrated, the bent flange lips serve to assure a concentric annular clearance space 94 between ~he spigot end 104 and the pipe bell 52.
In Figs. 10 and 11 there is illustrated a modified ZPSMI
ring 46' and modified gasket 50, wherein the ring 46' is molded or otherwise formed to provide a reversely-curved securing ~unction 88'. As shown, the modified gasket 50 is molded or 1~ otherwise formed to define a similarly-configured, relatively-thick seating shoulder 82'. The interaction between the securing ~unction 88' and the seating shoulder 82' functions to prevent gasket displacemen~ when the pipe joint is made up. As illustrated, the forward and rearward sealing lips 100', 102' of the flanges 79', 78' bend as necessary tightly to seal against the spigot end of the ad~acent pipe section 98 to provide a leakproof junction when the system is pressurized. As illustrated, the modified EPSMI ring 46' is similarly formed to fit within the mandrel groove 38 and comprises an annular seat ~0 54' defined between the trailing edge 56~ and the locking edge 58'. If desired, a hard plastic annular locking ring 116' can be employed to additionally insure proper gasket seating.
In the embodiment illustrated in Fig. 12, the EPSMI ring 46 is similarly configured to provide a forwardly-facing, sharp, angular ~unction 88 which defines an acute angle for securely z seating the modified gasket 48'. The angular ~unction 88 i5 especially designed to receive and securely seat therein the thick seating corner 82' of the modified gasket 48'~ thereby to discourage unseating of the gasket by the stresses imposed when the pipe junction between ad~acent lengths of pipe 16, 98 is made up. In the manner hereinafter described, when the pipe Junction is formed, the gasket-seating corner 82' will remain associated within the ring angular junction 88 and the forward and rearward flange lips 100', 102' of the forward and rearward flanges 78', 1(~ 79' will bend and seal against the outer periphery of the spigot end 104 of the adjacent pipe len8th 98. Simultaneously, the modified gasket 48' will have its thicker sealing corner 106' tightly pressed into sealing engagement against the forward interior wall 114 of the expanded groove 66 to additional function to assure a leak-proof Junction between the parts. The enlarged sealing corner 106' of this embodiment provides additional strength and additional sealing capability between the gasket 48' and the forward interior wall 114.

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Claims (9)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A hard ring for seating a resilient gasket in the bell of a length of plastic pipe having an inner periphery of pre-determined interior diameter, a belled end and central axis comprising:
a hard plastic, shaped, non-resilient annulus, said shaped annular comprising a radially inwardly facing annular seat, said seat having a leading edge, a trailing edge and a non-resilient seating surface defined between said leading edge and said trail-ing edge, said seating surface having a diameter substantially equal to the interior diameter of said pipe, said shaped annulus further comprising a rearward, radially outwardly-inclined ramp extending forwardly from said trailing edge of said seat, and a joined forward, partial, radially-inwardly-inclined ramp, the junction between said rearward and forward ramps defining the outer periphery of said hard ring, said shaped annulus being configured to define a radially-inwardly-opening junction, said junction being defined by walls of hard, plastic material, said forward, partial, radially-inwardly-inclined ramp terminating radially outwardly of said inner periphery of said pipe to define a forwardly-open annular path to said radially-inwardly-open junction of a size to receive portions of said resilient gasket therein, the diameter of said annular path being larger than the diameter of the inner periphery of said pipe;

whereby said resilient gasket may be readily applied to said hard ring at said forwardly-open path by positioning a portion of said gasket in peripheral contact with said radially-inwardly-open junction.

2. The hard ring of claim 1 wherein said radially-inwardly-open junction comprises a substantially-radially-extending wall, and an axially-extending wall, said walls intersecting to form an angular junction of substantially ninety degrees.

3. The hard ring of claim 2 in combination with a resilient gasket in contact with said radially extending wall and with said axially-extending wall of said radially-inwardly-open junction.

4. The hard ring and resilient gasket combination of claim 3 wherein said resilient gasket is generally U-shaped in cross-sectional configuration, said resilient gasket comprising a rela-tively thin, forward, wiping flange, a relatively thick, rearward sealing flange and a relatively thick base interconnecting said forward wiping flange and said rearward sealing flange.

5. The hard ring and resilient gasket combination of claim 4 wherein said gasket base is rearwardly defined by a thick, sturdy, sharp, angular junction.

6. The hard ring and resilient gasket combination of claim 5 wherein said gasket base is forwardly defined by a sealing corner comprising a sealing face that is angularly inclined relative to the central axis of the length of said plastic pipe.

7. The hard ring and resilient gasket combination of claim 5 wherein said forward wiping flange and said rearward sealing flange define an annular space therebetween.

8. The hard ring and resilient gasket of claim 7 in further combination with a hard plastic retaining ring positioned within said annular space.

9. The hard ring, resilient gasket and retaining ring com-bination of claim 8, wherein said retaining ring contacts inter-ior portions of said base, said forward wiping flange and said rearward sealing flange of said resilient gasket.