Gasket for pipe coupling and pipe coupling incorporating same

The present invention relates to leak preventing gaskets contemplated for use with segmented pipe couplings, which include a pair of coupling segments adapted to receive a gasket which surrounds a pair of pipe ends to join pipes together or to join a nipple or fitting. The couplings contemplated for use with the gasket of the invention includes types adapted to attach grooved and flare end pipes, or non-grooved pipes in sealed relation to withstand fluids at temperatures up to 230° F. and higher, and at pressures of up to 1,000 psi. The ring-type gasket of the present invention is made of an elastomeric material such as synthetic or natural rubber or combinations thereof, preferably, ethylene polypropylene diene monomer, commonly referred to as “EPDM”. The gasket provides improved sealing through a pair of sealing flanges having relative planar and expansive inner walls, shorter sealing lips, and particular dimensional relationships with the grooved pipe ends. The invention also relates to a coupling incorporating such gaskets, as well as a method of providing a sealed coupling.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to sealing gaskets for mechanical pipe couplings of the type which generally utilize a pair of coupling segments having mated bolt pads in which the gasket is seated and engages the spaced apart juxtaposed ends of a pair of pipes intended to be joined by the mechanical coupling. Mechanical pipe couplings take numerous forms including either grooved end pipes or smooth end pipes which may or may not be flared. The couplings are exemplary and the present invention is contemplated for use wherever gaskets are useful.

2. Description of the Related Art

Pipe couplings incorporating an elastomeric gasket for use in creating and forming a sealed joint between various types of pipes, whether metal or non-metallic, generally include multi-part coupling segments or pipes and fittings or valves, often a pair of coupling segments including mated bolt pads. The segments are bolted together and in the process of joining the coupling parts, the act of closure assists in seating the gasket firmly against the pipe ends. When the coupling segments are brought into juxtaposition for purposes of securement, often radially inward, peripheral and circumferential compressive forces are applied to the gasket. As a consequence the respective sealing surfaces between the gasket and the coupling segments and between the gasket and the pipe ends are intended to engage in face-to-face relation with the objective of creating a fluid tight seal.

Many of these mechanical joining applications are used in pipe systems carrying liquids at temperatures up to about 230° F. and higher, and pressures up to approximately 1000 psi. As well couplings of this type are used with fluids of all types, including toxic and volatile chemicals.

In the past it generally has been believed that gaskets intended for use with multi-part couplings and grooved pipe ends will perform more efficiently if there is a greater amount of elastomeric material present to fill the space between the coupling segments and the pipe. However, although counterintuitive as taught herein, too great an amount of elastomeric material has been found to reduce the effectiveness of the seal between the surfaces of the gasket and the respective coupling segments and pipe surfaces. For example, in grooved pipe connections the gasket prior to its emplacement, although of one piece, has traditionally included sections of differing shapes including an annular ring shaped base which seats into the coupling segment, a pair of downwardly extending legs which nest along the inner sidewalls of the coupling and a pair of relatively wide inwardly extending lips which extend essentially to the ends of the two pipes being coupled. Generally, the upper surface of each lip was connected to the inner wall of the leg portions to form an arcuate surface with each leg. This thickened portion of the lip was considered to be highly desirable. In these prior art devices, when the coupling segments are brought together the distance between the leg and lip is reduced and the leg and lip joining area is reduced in size.

With such arrangements it has often been found that under extremely high temperatures the elastomeric material tends to swell or bulge along its inner curved surfaces and become fused. Generally elastomeric materials used with gaskets include natural and synthetic rubbers and combinations thereof and expansion of the elastomer generally exceeds expansion of the pipe by a significant factor often up to 15-20 times. In particular, with elastomeric materials such as ethylene polypropylene diene monomer (i.e. “EPDM”) fusion of the various components of the gasket under high temperatures is common, and with the result that certain critical sealing areas are left without an effective amount of sealing material.

Moreover, even in the absence of temperatures and pressures sufficient to fuse the gasket material, the distal portions of the inwardly extending lips have been found to exert relatively low pressure against the pipe surface, and often lift upwardly and become fused to the downwardly bulging leg and inner lip portion. In this condition the sealing pressures also often become significantly reduced.

Examples of these and like prior art include commonly assigned U.S. Pat. No. 1,704,003 to Johnson which relates to a pipe joint which incorporates a gasket in the form of a unitary flexible sealing ring spanning the gap between pipes intended for connection. As well, commonly assigned U.S. Pat. No. 1,808,262 to Hele-Shaw discloses a pipe joint comprising a ring of flexible material having inturned flanges adapted to embrace the pipe ends.

U.S. Pat. No. 1,867,891 to Reynolds discloses a pipe joint utilizing elastic material to contain fluid under pressure and the type of prior art sealing gaskets suggested as being appropriate to systems of this type.

Although numerous prior patents have suggested modifications to the shape of the gasket including those used for high pressure services, all have generally included a leg and lip connection area intended for close juxtaposition upon loading of the gasket and/or relatively long inwardly extending lips.

Commonly assigned U.S. Pat. No. 1,899,695 to Johnson discloses a pipe joint sealing ring of flexible material having an opening which when in position in the joint is open to fluid pressure from the pipes so as to be sealed thereby; U.S. Pat. No. 1,931,922 to Damsel, et al. discloses a laminated article in the form of a packing ring which is formed of resilient material and which is coated with a non-corrosive and non-porous plastic material; U.S. Pat. No. 1,967,466 to Damsel discloses a ring for a pipe coupling having an annular cavity in its body;

U.S. Pat. No. 2,013,267 to Damsel discloses a pipe joint in which a channel-shaped packing gasket includes a split, imperforate reinforcing and protecting ring arranged in the gasket at the bottom of a channel and has sufficient rigidity to prevent the gasket from collapsing inwardly.

Commonly assigned U.S. Pat. No. 2,766,518 to Costanzo discloses a method for joining together sections of plastic pipe which includes a gasket of the internal pressure responsive type.

Commonly assigned U.S. Pat. No. 3,080,894 to Young discloses joints between pipes of different diameter and couplings and gaskets for same.

Commonly assigned U.S. Pat. No. 4,561,678 to Kunsman discloses a pipe coupling having a gasket receiving channel for reception of a double-lipped sealing gasket. The lips of the sealing gasket extend almost to the respective ends of a pair of grooved pipes intended for joinder by the coupling.

Commonly assigned U.S. Pat. No. 4,893,843 to DeRaymond discloses a lubricant-free elastomeric gasket which is structured so as to be positioned over an intended pipe without frictional engagement with the pipe.

Other art relating to pipe couplings of various types includes commonly assigned U.S. Pat. No. 4,702,499 to DeRaymond, et al. which relates to hingeable segmented pipe couplings.

Commonly assigned U.S. Pat. No. 5,758,907 to Dole, et al. relates to a pipe coupling having mis-adjustment limiting segments with stop members at their respective ends which prevent misalignment of the coupling segments during their assembly onto the adjacent ends of pipes for fittings. This coupling includes a sealing gasket which is placed in sealing engagement with adjacent ends of the pipes to be joined.

The present invention is directed to gaskets which provide substantially improved seals between the respective sealing surfaces and the coupling components and pipes while avoiding the use of excessive elastomeric material which interferes with the desirable operation of other portions of the gasket when under the influence of compressive forces. By providing supportive gasket sealing lips which resist upward curvature, and flanges which substantially retain their basic configuration under load, and by configuring the gasket to more closely seat between the pipe ends and the assembled coupling, improved sealing can be accomplished, and fusing or other undesirable interaction will be reduced or eliminated.

Although the gaskets disclosed are illustrated as being used with pipe couplings which are adapted to join grooved pipes, the gaskets are also applicable for use in mechanical pipe couplings generally, including non-grooved pipe ends.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings and in particular toFIGS. 1,1C,1D and3, there is shown a gasket10for couplings in accordance with the present invention. While various types of elastomeric materials are contemplated for the gasket, one particular material which has been found desirable is ethylene polypropylene diene monomer, commonly referred to as “EPDM”. As noted however, the present invention contemplates use of other synthetic material or natural rubber materials and combinations thereof.

In the past improved sealing was considered to be best accomplished by providing for increased use of elastomeric material. However, the present invention is directed to gaskets which reduce the amount of elastomeric material in certain areas in a manner which permits a more effective distribution of mechanical compressive sealing forces and enhances the stability of the gasket when subjected to increased heat and pressure, thereby promoting better and more uniform contact with the appropriate surfaces. Further, the gasket avoids excessive expansion and “bunching” of the elastomeric material within the coupling under substantial pressures and temperatures, and promotes more uniformity in the numerous gaskets that generally are found in piping systems.

Referring now toFIGS. 1,1C,1D and3, the gasket10has been found to provide superior leak resistant sealing surfaces. The gasket10includes a flexible ring, in which a circular ring-like base member12has a pair of inwardly extending flanges14,16formed integrally therewith as shown, with each flange extending inwardly in the radial direction and oriented generally outwardly at an acute angle to the ring-like base member12prior to installation into a mechanical pipe coupling, each flange having a radially innermost sealing surface18,20, each of which includes an axially inwardly facing lip22,24when installed in a coupling, each lip forming an acute angle with the base member12when the gasket is uncompressed. As can be seen in the drawings the flanges14,16are formed integrally with the ring-like base member12.

Referring now toFIG. 2andFIG. 5, a fully assembled coupling26is shown which connects pipe ends28,30having peripheral grooves32,34in a known manner. The coupling segments capture and retain the gasket10inFIG. 1. InFIG. 5, the gasket10is shown when subjected to the compressive forces created when the coupling segments are joined.

As best shown inFIG. 1in its uncompressed state, lips22,24of gasket10have a length “L” shorter than conventional gaskets. It has been found that rather than lessening the effectiveness of the lips, decreasing their length provides increased pressure responsiveness of lips22,24against the pipe surfaces, with a resultant improvement of the seal.

As well, flanges14,16of the gasket10have a configuration which promote and generate sealing pressure against the pipe surface, providing structural rigidity for the gasket between the coupling housing and the pipe surface. In addition to the fluid pressure within the coupling, a flange configuration such as those as shown in the drawings has been found to advantageously transmit forces to the lip to enhance sealing pressure. Whereas as in general prior gaskets were configured to include relatively loosely connected peripheral legs which were virtually hinged to the ring-like base member by an arcuate inner wall of each leg, the present invention provides a thickened wall cross-section on the flange and a zone of open area with arcuate connecting surfaces between the inner surface—or backwall—of the base member of the gasket and the upper inner area of the flange member. It has been found that through this modification in shape and dimension the sealing pressure distribution between the gasket and the pipe surface is enhanced.

For example, in prior art gaskets, on the assumption that the full extent of lips functioned as a sealing surface, the dimension “W” (FIG. 1A) from the tip of the lip to where it joined the leg was such that the ratio of dimension “W” to dimension “A” (FIG. 5) was maintained at about 0.5 or greater. In the present invention, the ratio of the width “S” of the flange inFIG. 1C, and the dimension “A” is preferably maintained between about 0.30 and 0.40 and it is not only as or more effective in sealing, but is significantly less susceptible to upward curling of its distal end portions and failure. Indeed, it has been found that as part of the overall flange configuration the shorter lip increases the lip's functionality in the sealing process, as is evidenced inFIGS. 16 and 17, which show the sealing pressure increasing above zero under portions of the lip. InFIGS. 16-17, “E” denotes the location of the planar annular inner wall of the flange, i.e. wall42inFIG. 1Cand wall94inFIG. 6.

A comparison of the prior art pressure distribution as shown inFIG. 15with the pressure distribution of the present invention inFIGS. 16 and 17illustrates the greater uniformity of the distribution pattern inFIGS. 16 and 17as compared to the sudden rise to a peak inFIG. 15, followed by a sudden drop in pressure. Furthermore, as can be seen inFIGS. 15-17, to the extent that the lips were provided in prior gaskets, maximum sealing pressure was at or near the corner—or heel—of the leg, whereas the gaskets of the present invention place the maximum sealing pressure axially inwardly of the flange, or in the vicinity of the planar inner wall of the flange. This shifting of the location of maximum pressure has been found to enhance the sealing effectiveness of the combined flange and lip, thus preventing lifting of the lip and loss of the seal. Given the propensity of the distal end of the lip of prior gaskets to curl upward under heat and pressure, this repositioning of sealing forces is significant.

The present invention also permits the use of a lubricant groove without meaningful loss of overall sealing pressure. Although lubricant grooves are considered desirable, an open channel on a sealing surface has tended to reduce sealing efficiency. However with the flanges having a lubricant groove as shown inFIGS. 1 and 1C, the planar inner wall of the flange is located directly above the lubricant groove. For flanges having no lubricant grooves as shown inFIG. 6, the maximum pressure is generated at or near the vicinity of the planar inner wall of the flange as shown at point “E” inFIG. 17. In such instance, the reduction in sealing pressure shown inFIG. 16which is caused by the groove will not exist, and the pressure will be at a maximum between imaginary “groove” points “C” and “D”, shown inFIG. 6for illustrative purposes only, and as shown inFIG. 17.

In addition, by configuring the inner annular peripheral inner surfaces40,42of flanges14,16as shown inFIGS. 1 and 1C, i.e. as planar surfaces at an acute angle to the peripheral ring-like base member12, it will be appreciated that upon mechanical compression of gasket10within a coupling as shown inFIGS. 1D and 5, the inner peripheral surfaces40,42assume an arcuate, or slightly “bulged” generally conical configuration (i.e., convex and inward). As shown inFIG. 1Dthis provides pressure responsiveness and improved supportive sealing forces in a direction toward the surfaces of the pipe ends. Although the annular peripheral surfaces40,42ofFIGS. 1 and 1Care only slightly bulged inwardly, nevertheless it can be seen that they retain their planar or near-planar shape thereby enhancing the sealing pressure responsiveness of the lowermost surfaces of the flanges14,16and lips22,24.

Correspondingly, the radially outward sealing forces against the coupling halves are also improved. By minimizing the lengths of lips22,24, and by maximizing the planar and relatively expansive inner flange walls40,42, the tendency for the flanges to collapse and the lips to become fused under high temperatures to the inner peripheral surfaces13,40and42is eliminated, even when subjected to water pressures in the range of 1000 psi and temperatures in the range of 230° F. and higher, notwithstanding the expansion factor of the elastomer which can be 15-20 times the expansion of the metal coupling components.

The flange configuration has been found to provide particularly advantageous results for high pressure, high temperature applications. For example, in prior art gaskets44such as shown inFIG. 1A, the inner wall surface46is arcuate in shape, and the dimension “W” extends from the heel of the leg47to the tip of the lip48. The ratio of dimension “W” to dimension “A” is about 0.5 to about 0.9, where “A” is the distance from the pipe groove to the end of the pipe as shown inFIG. 5.

In a preferred embodiment of the present invention, as shown inFIGS. 1C and 1D, the ratio of the flange width “S” of the flange16to the dimension “A” shown inFIG. 5is about 0.25 to about 0.45, and preferably from about 0.30 to about 0.40. A broader range of about 0.20 to about 0.50 is also foreseeable. The inner wall42of the flange of the inventive gasket shown inFIG. 1Cis planar and has been increased in size to increase the pressure activated sealing of the connection as shown inFIG. 1D, when the flange is compressed within the coupling and subjected to high temperature fluid.FIG. 1Bshows the prior art gasket ofFIG. 1Awherein relatively long lip48touches backwall50when the gasket is compressed within a coupling, thereby providing the potential for the fusion of the lip to the backwall50under high temperatures. This is believed to be partly due to the lack of structural support provided by arcuate inner wall46which, under compression forces, acts as a hinge between lip48and ring-like base member43, rather than as a support for the gasket components. Although leg47(only one shown) and sealing surface49(only one shown), based upon conventional design as shown inFIG. 1A, are intended to provide sealing against the pipe surfaces, as illustrated inFIG. 15, the sealing pressures are not effective over the entire surfaces, and this is believed to be due substantially to the absence of structural support by arcuate inner leg wall46.

As noted inFIGS. 1 and 1C, the gasket flanges of the present invention in their uncompressed state are preferably at an angle “α” of about 60-85 degrees relative to the upper wall12and thus unlikely to act as a relatively weak hinge as in the prior art.

Referring now toFIGS. 1,1C,1D and5, each sealing surface18,20of the gasket of the embodiment shown includes a peripheral groove36,38directly beneath the inner generally conically shaped walls40,42. It has been found that gaskets are more easily seated if their sealing surfaces have a suitable liquid lubricant over the entire gasket. Preferably the lubricant is one having a vegetable base such as the gasket lubricant marketed by Victaulic Company of America under the trademark Victaulic® brand coupling lubricant, commonly referred to as “VIC-LUBE” brand lubricant. By providing peripheral grooves36,38, the lubricant tends to fill the grooves and upon application of compressive forces by the coupling segments upon closure thereof, the grooves36,38tend to trap the lubricant and gradually release it to the surrounding surfaces on both sides of the groove, thereby promoting smooth and uniform seating of the gasket sealing surfaces and avoiding pinching of the gasket surface between the pipe and the coupling housing as the coupling tightening process progresses. This in turn reduces undesirable gasket extrusion.

Upon completion of the coupling segment joining process, the grooves36,38become substantially flattened and virtually eliminated, as shown in the cross-sectional view inFIG. 5. However, as noted, because of the initial presence of the lubricant on the surfaces18,20and in grooves30,38, followed by a gradual release thereof during the tightening procedure, lubrication of the critical sealing areas surrounding the grooves and extending over the entire sealing surface is achieved.

Referring now toFIG. 4, there is shown a portion of an alternative embodiment of the invention. Gasket60is configured similarly to gasket10ofFIGS. 1,1C and3, with the addition of surface treatment in the form of knurling62,64provided on sealing surfaces66,68. Although any type of surface roughening treatment is contemplated, one preferred form is as shown, i.e., in the form of a plurality of almost microscopic grooves oriented and extending in a crisscross or cross-hatched pattern. Although the grooves are less deep than the grooves36,38ofFIGS. 1 and 3, the pattern is capable of trapping lubricating oil and the areas affected by the distribution of lubricant oil during the coupling tightening process is more easily distributed along a wider area. In all other respects, the embodiment ofFIG. 4is the same as the embodiment ofFIGS. 1 and 3in that an elastomeric ring-like base member70is provided with inwardly extending flange members72,74as shown. The knurling62,64on sealing surfaces66,68also assist in compensating for small surface imperfections on the pipes.

Referring toFIG. 6, there is shown a portion of another alternative embodiment80of the gasket of the present invention, wherein an elastomeric ring-like base member82is provided having a radially inwardly extending flange members84(only one is shown). In this embodiment, inwardly extending lips86(only one shown) are configured to have tip ends which are formed by the intersection of an arcuate surface88with flat sealing surface90to promote contact between the sealing surface92and the lip86with the surface of the pipe end.

The lip86will remain in full contact with the pipe surface, assisted by the water pressure acting downwardly on the upper surface88, and will resist contact with inwardly bulging annular inner flange wall94should that occur and inwardly bulging backwall96should that occur, thereby avoiding fusion between the inner surfaces at elevated temperatures of up to about 230° F. and higher. Due to the shorter lips88, and the substantially elongated and planar flange inner wall94, there is less elastomeric material to be contacted as the backwall96bulges inwardly at under compression and at elevated temperatures. Moreover, the planar inner wall surface94and the relatively substantial flange84provides structural support for the gasket and promotes uniform sealing pressures against the pipe surface under pressure, while planar inner annular wall surface retains its generally planar or near planar shape. In some instances, the inner annular wall will bulge slightly inwardly, but will nevertheless retain its generally near planar shape.

Referring now toFIG. 7, a portion of still another alternative embodiment91of the gasket of the present invention is shown, wherein an elastomeric ring-like base member93has radially inwardly extending flange member95formed monolithically therewith as in the previous embodiments. The axially extending lips (only lip98shown) are configured substantially as shown inFIG. 6, but with the additional provision of lubricating oil trapping grooves (only groove97is shown) which traps and gradually releases the lubricant upon compression of the gasket within a coupling assembly as described in connection with the gasket and coupling assembly shown inFIG. 5.

Referring now toFIG. 8, a portion of the gasket90ofFIG. 7is shown in a coupling assembly in the compressed configuration, with portions of the coupling assembly components shown for illustrative purposes. Elastomeric ring-like base member gasket71has generally radially inwardly extending flange members94,102formed monolithically therewith, with axially inwardly extending lips98,106as shown partially inFIG. 7. Lubricating oil trapping grooves97,108are substantially flattened when the gasket is fully compressed as shown, with the support walls of flange members94,102and inner backwall104shown bulging inwardly, yet avoiding fusion and/or contact with relatively shorter lips98,106as shown.

Referring toFIG. 9, there is shown a portion of still another alternative embodiment of the gasket of the present invention, shown at110, wherein an elastomeric ring-like member112is configured as in the previous embodiments, but includes a pair of flange members (only flange member114is shown) and sealing surfaces (only surface116is shown). A peripheral groove118is in the form of an inverted “V” shaped notch90which traps lubricating fluid and gradually releases it to the surrounding surface areas upon compression within a coupling assembly. The inverted “V” shaped notch90is provided to retain lubricating oil in a manner similar to the inverted “U” shaped grooves in the previous embodiments; however; the “V” shaped notch90assumes a flattened configuration upon compression in a more uniform and gradual manner, and ultimately assumes an almost completely flattened shape when the gasket is subjected to compressive forces within a peripheral coupling. In addition, the gradual flattening procedure and the relatively slow release of lubricant to the surrounding areas helps to distribute the lubricating oil more evenly in those areas adjacent the notch, thus assisting in perfecting the seal between the gasket and the pipe ends.

Referring now toFIG. 10, there is shown still another alternative embodiment of the present invention wherein a gasket120is provided with radially inwardly extended flanges (only flange122is shown) and inwardly extending lips (only lip124is shown) which extend axially inwardly from the flanges and which form a continuation of a sealing surface126which extends along the radially inward end of flange122. The gasket120includes sealing lips (only124shown) which are configured similarly to the sealing lips shown inFIG. 8, with the addition of the provision of an inverted rectangular shaped peripheral groove128located directly beneath inner flange wall130. Inverted rectangular shaped groove128retains lubricating oil in a manner similar to the previous grooved embodiments and gradually releases the lubricating oil to the surrounding areas as the compression process takes place within a coupling assembly similar to the manner previously described in connection with the previous embodiments. By gradually releasing the lubricating oil to the surrounding areas according to the changing configurations of the groove128, the inverted rectangular shaped groove assists in completing the seal between sealing surface126and the pipe end.

Alternatively, other types of systematic surface irregularities, including grooves and notches, may be used to retain lubricating oil and release it on a systematic and gradual basis during tightening of the coupling so as to assist in compensating for the surface imperfections on the pipe ends. For example, the inverted rectangular shaped groove128may alternatively be square in cross-section, or any other shape.

Referring now toFIG. 11there is shown still yet another embodiment in the form of gasket130having peripheral ring-like base member132. In the embodiment ofFIG. 11, radially extending flange members134,136include inner support walls138,140, comprised of an alternating series of generally trapezoidal shaped solid wall members144respectively separated by alternating correspondingly generally trapezoidal shaped spaces142to form an entire circular shaped loop or wall, only part of the loop being shown inFIG. 12. As can be seen in the cross-sectional view ofFIG. 11the inner walls138,140complement the radially inwardly extending lips146,148to enhance the application of sealing pressure against the surfaces of the pipe ends. The surfaces150,152inFIG. 11represent the inner surfaces of the trapezoidal shaped solid wall sections144, whereas the inner surfaces154,156inFIG. 11represent the inner wall surfaces of the flange wall corresponding to spaces142.

Referring again toFIG. 11in conjunction withFIG. 12, the radially innermost sealing surfaces158,160include generally inverted “U” shaped peripheral grooves162,164which function in a manner similar to the peripheral shaped grooves of the previous embodiment. The peripheral shaped grooves retain lubricating oil when applied to the entire surface of the gasket prior to installing the gasket within the pipe coupling. As the pipe coupling segments are drawn together to a closed position, the grooves162,164gradually become flattened against the pipe surfaces as described in connection with the previous embodiments and gradually release lubricating oil to the surrounding areas to perfect the seal between the sealing surfaces158,160and the respective pipe ends. As the process of tightening the coupling segments progresses, the flange members134,136rotate inwardly until the pipe sealing surfaces158,160become substantially horizontal and engage the outer surfaces of the pipe ends and the inner support wall sections144become somewhat compressed and provide radially directed support forces to assist in perfecting the seal between the peripheral outer surface131of peripheral base member132, and the coupling, and between the sealing surfaces158,160of the flange members134,136and the pipe ends. The inner support wall138as shown, which as noted, is constructed of alternating sections of generally trapezoidal shaped sections of solid elastomeric material144, has been found to provide effective structural support forces for the sealing surfaces of the lips146,148with respect to the pipe coupling and the pipe ends. In particular, the alternating sections of the support wall138provide supportive forces on the inwardly extending lips146,148in applying sealing pressure against the pipe surfaces.

As described in connection with the previous embodiments, the sealing surfaces158,160can alternatively include other surface irregularities to assist in perfecting the seal such as knurled surfaces, inverted “V” shaped notches, inverted square shaped and rectangular shaped notches, or the like, in order to either retain lubricating oil therein for the assembly process for the coupling and/or to compensate for general imperfections on the pipe surfaces.

Referring now toFIG. 13there is shown still another alternative embodiment of the gasket for couplings as shown inFIGS. 11 and 12in which gasket180includes inner support wall179in which the trapezoidal shaped solid elastomeric sections of the inner support wall138ofFIG. 11have been replaced by wider generally trapezoidal shaped sections184of solid elastomeric material. In this embodiment, the spaces182between the generally square shaped solid elastomeric sections184are configured as trapezoidal shaped spaces are also wider than spaces142inFIGS. 11 and 12and are arranged in a circular array as shown.

Referring now toFIG. 14there is shown a cross-sectional view taken along lines14-14ofFIG. 13, in which the alternating sections of generally trapezoidal shaped sections184of solid elastomeric wall material are shown separated by generally trapezoidal shaped spaces or indentations182. In all other respects the gasket ofFIGS. 13 and 14is identical to the gasket ofFIGS. 11 and 12, including the lips186.

As can be seen from both the gaskets ofFIGS. 11-14, the inner wall which is formed of sections of variously shaped sections of solid material separated by spaces of various alternative configurations, the solid material portions become compressed upon assembly of the coupling segments with the gasket seated within the segments of a completed coupling and to provide the requisite forces against the inner surface of the coupling and the outer surface of the pipes, respectively, to effect the seal against leakage of liquid under pressure. By configuring the annular inner wall of the gasket with sections of solid material separated by spaces of various configurations, the solid material sections are permitted to provide the necessary forces for the sealing surfaces of the gasket against the respective coupling and pipe components, while the spaces provide space to permit the solid sections of material to expand without dangerous contact with surfaces which might otherwise cause fusion of components of the gasket when subjected to substantial pressures and temperatures generally encountered in certain applications. Various types of wall configurations may be used, including triangular, circular, oval, and other solid sections separated by correspondingly shaped spaces.

Referring toFIG. 15, there is shown a computer generated graph of the sealing pressure distribution of the sealing surface49(shown inFIGS. 1A and 1B) and the pipe surface with prior art gaskets of the type discussed. The pressure is measured from the tip of the lip48to the end of the leg. As can be seen, the “sealing” pressure is non-existent over the length of the lip48; then it ramps up toward the heel (or end) of the leg, and then returns to zero at the end of the leg.

In contrast,FIG. 16shows a computer generated graph of the sealing pressure for the gaskets of the present invention as shown inFIGS. 1 and 1C, wherein a solid flange is provided with an inner flange wall which is planar and relatively elongated, the lip length “L” is shorter, with the ratio S/A being about 0.30 to about 0.40, and the flange sealing surface includes a lubricant retaining groove21located at point “E” inFIG. 16. Although the sealing pressure on the pipe surface drops between points “C” and “D” (which represent the lubricant retaining groove), it has been found that the benefits of the lubricant dispersing effect provided by the groove far outweigh the drop in sealing pressure at the groove, and therefore the optimal presence of a groove does not adversely affect the overall sealing performance of the gasket.

Referring toFIG. 17, there is shown a graph of sealing pressure distribution over the sealing surface of a gasket as shown inFIG. 6, wherein the sealing surface does not include a lubricant retaining groove. In this embodiment the pressure is distributed in a relatively uniform fashion. In this embodiment, a part of the lip provides sealing against the pipe surface due to what is believed to be the transmittal of forces of the flange member84and the planar inner flange wall94inFIG. 6.

While the invention has been shown and described with respect to preferred embodiments, it will be understood by those skilled in the art that various modifications and changes may be made therein without departing from the spirit and scope of the invention.