This application claims priority to U.S. provisional application Ser. No. 61/250160, filed

October 9, 2009, entitled "Parabolic Ramp .Self-Restraining Bell Joint," and U.S. provisional application Ser. No. 6 /301462, filed February 4, 2010. entitled "Simplified Low Insertion Force Seating Device Capable of Self Restraint and Articulation," both of which are hereby specifically and entirely incorporated by reference.

Background

1. Field of the Invention

The invention is directed to couplings and methods of coupling, particularly to bell and spigot couplings and methods. The couplings can be between pipes, fittings, and/or other piping components. The couplings allow for greater pipe deflection and stronger joint retention, with less force needed on insertion.

2. Background of the Invention

Members of the How control industry, such as producers of pipeline components for the transmission of water, gas, oil. or other fluids have focused substantial attention on the problem of creating and maintaining connections between adjacent lengths of pipe, or pipes and lutings, or pipes and valves. In applications where the fluid, such as water for fire mains or water distribution in municipalities, is under high pressure, various means are used to prevent separation of the joints between piping components. Piping components are joined to prevent separation caused by thrust forces, earth movement, and external mechanical forces exerted on piping components. These components include, for example, pipes, couplings, fittings, valves, and fire hydrants. The majority of the solutions can be categorized into either "push-on joints," "mechanical joints/' or "flanged joints."

Iron pipe has traditionally been used to withstand the large pressures that are necessary for municipal water systems and other systems. Those pressures are needed to carry fluids over long distances, to carry large amounts of fluids, and to prevent contamination of the systems in the eveni of a hole or other breach of the system. There are two related problems in the history of using pipes of any sort, including iron pipes - (1 ) creating a secure seal to join the pipes and to withstand large pressure, and (2) bending or deflecting the joints of the pipes to meet the intended use of the pipes.

The first substantial use of cast iron pipe was in Europe in the 17 ^th century. The piping systems of the 17 ^th and 18 ^th centuries primarily had flanged ends that bolted together with lead or rawhide gaskets for sealing. Flanged joints continue to be used for some applications today, but with rubber gaskets. Flanged joint systems are cosily to install and require considerable maintenance.

The first bell and spigot joint was developed by Thomas Simpson of the Chelsea Water

Company in England in 1785. The joint was caulked with juie rope impregnated with pine resin or tallow and sealed in place with molten lead. The bell and spigot joint remained the predominant pipe joint until the advent of the push-on joint, for example the TYTON® Joint, in 1956.

There are numerous methods of securing piping components in series to make up a pipeline, roughly divisible into three main categories: ( ! ) rigid, s with bolted flange

connections; (2) flexible, as with numerous designs such as TYTON® push-on joints and gaskets, or TYTON® combined with self-restraining gaskets bearing toothed inserts, such as FIELD LO 350® Gaskets providing both sealing and autonomous restraint; and ⁽ 3) others with a limited amount of incidental flexibility, such as PVC Pipe with Rieber Gaskets where minor flexibility is possible due to the plasticity of the gasket and pipe materials and (o joint tolerancing.

Push-on solutions are exemplified by U.S. Patent No. 2,953,398, and account for the majority of straight-run pipe connections. In a typical configuration, a spigot of a pipe slides into a bell of another pipe past a tightly fitted gasket. A variation of the push-on joint is evidenced by U.S. Patent No. 2,201 ,372, which employs a compression snap-ring fitted within a special lip of the bell, in order to exert pressure onto locking segments and thus drive them into the spigot, restraining the joint against thrust forces. U.S. Patent No. 3,445,120, likewise employs a gasket with toothed, locking segments encased therein that are generally disposed such that they and the gasket may roll between a locked and a free position. As the gasket bulb rotates under extraction forces, it is intended to eventually to encounter a position in which the segments must compress the gasket lo allow further rotation of the segment and engagement of the teeth with the mating pipe spigot, thus, terminating the rotation and compression of the gasket bulb and restraining the joint.

Other examples of restrained push-on joints include those disclosed in U.S. Patent Nos. 5,295,697, 5,464,228, and 5,067,751. In those references, the connection is effected by either locking segments or wedges within the gasket that engage the spigot. The locking segments possess a groove (hat mates with an annular rib on the bell, such that the rib acts as a rocker, or cam, or during some movements, as a wedge. During insertion of the. spigot into the bell, the segments rotate on the rib, but are prevented from appreciable axial movement by the mating of the rib and groove. Upon experiencing counter-forces tending to effect removal of the spigot, the rib acts as a cam, both causing the. segments to pivot on the rib as an axis, and exerting a radially inward pressure as the segment attempts to slide past the rib. These types of joints depend on compressive force on the rubber gasket to maintain the connection of the pipes.

While the push-on type joint has obtained wide acceptance for pipe joints, acceptance for fittings, valves, and hydrants is much lower. The contours of bel 1 sockets of the push-on joint require a high degree of precision for a cast surface. In restrained joints, an additional locking joi t is necessary, which also requires a high degree of precision to manufacture. It often takes a high degree of skill and alignment precision, as well as substantial force (i.e. in the range of 600 to 800 pounds of force for an eight inch size pipe), to assemble joints using the above described push-on type joints. The insertion force with present push-on designs increases proport ionally with conduit diameter. Moreover, insertion forces increase substantially in low-temperature conditions.

A current trend in the industry is to manufacture pipe with wails much thinner than the current designs. Whether the pipe end is produced in a manufacturing plant or is the result of field cuts required to adjust the length of the pipe, such pipes cannot realistically be beveled or have rounded ends. Damage to the gaskets or displacement of the gaskets is a likely outcome when inserting a spigot end of a pipe not properly aligned or without a beveled or rounded end into the bell of another pnsh-on joint pipeline component. A further consequence of the high assembly forces required is that installers favor mechanical joint connections for fittings, valves. and hydrant shoes because they require lower assembly forces. Attempts to design low insertion resistance-joints have been made in the past but these designs were not completely satisfactory because normal conical inner surfaces do not allow for sufficient deflection of the bell and socket joint. For example. U.S. Patent No. 3,815.940 and U.S. Patent Application Publication No. 2009/0060635 both show bells with conical inner surfaces. Cast iron pipe is rigid and does not permit deflection. Creating ductile iron pipe permits slightly greater deflection at the joint. Howe ver, that deflection carries an increased risk of loss of pressure. If the joint is a straight connection, no deflection is possible. If the joint is connected into a cone-shaped annulus, deflection of more than a few degrees would degrade the connection opposite the angle of deflection, ultimately leading to a greater potential for a loss of pressure. Small movements in the earth could, over time, cause leaks in underground piping systems.

Thus there is a need for a connection that is less sensitive to misalignment and temperature extremes, has reduced frictional resistance to the insertion of the spigot until the desired connection is achieved and the coupling is maintained, yet maintains a seal under high pressures, even when the joint is deflected.

Summary of the Invention

The present invention overcomes the problems and disadvantages associated with current strategies and designs and provides new devices and methods for connecting bell and spigot pipeline components. Specifically, one embodiment of the invention solves the problem created by cone-shaped joints by using a parabolic-shaped joint. The joint is less likely to lose restraint and pressure as (he joint is deflected, permitting deflections up to 10 degrees, preferably between 9 and 5 degrees of deflection, and more preferably of 7 degrees of deflection or less. A 90- degree turn can thus be made using approximately 1 (20-foot) pipes over a distance of approximately 300 circular feet with deflections of 6 degrees, as opposed to 30 pipes over a distance of 600 circular feet using 3 degree deflection joints. That greater deflection reduces the number of bend fittings and the amount of trench digging required, and conserves land space.

An embodiment of the invention is directed to a conduit that comprises at least one bell with an end face, an internal portion, and a concave inner surface between the end face and the internal portion. The diameter of the inner surface adjacent to the internal portion is greater than the diameter of the inner surface adjacent to the end lace. in preferred embodiments, the inner surface is a truncated elliptic paraboloid. In preferred embodiments, the conduit has a bell at a first end and a spigot at a second end. Preferably, the conduit is cylindrical and is made of at least one of ferrous metals (e.g. steel and cast iron), non- ferrous metals (e.g. copper-based alloys), or plastic (e.g. PVC or HDPE).

Another embodiment of the invention is also directed to a conduit that comprises multiple openings and at least one opening has a bell that couples to another piping component having a spigot. In preferred embodiments, the inner surface of the bell of the invention is concave. The inner surface is preferably a truncated elliptic paraboloid, in preferred embodiments, the conduit has a bell at a first end and a spigot at a second end. Preferably, the conduit is cylindrical and is made of at least one of ferrous metals (e.g. steel and cast iron), non-ferrous metals (e.g. copper- based alloys), or plastic (e.g. PVC or HDPE).

Another embodiment of the invention is directed to a sealing device. The sealing device comprises at least one segment having a convex outer surface, and a K-type gasket coupled to the segment. In the preferred embodiments, the segment is a locking segment. The locking segment functions as a restraining device and an anti-extrusion device to prevent the joint from separating and the. elastomeric seal from being extruded out of the joint when subjected to high internal hydraulic forces, in other embodiments, a guide segment without teeth is substituted for the locking segment and serves as an anti-extrusion device lor the polymeric material of the sealing portion.

In preferred embodiments, the segment is of a first material and the K-type gasket is of a second material. In preferred embodiments the K-type gasket is comprised of a coupling section and a sealing section. The sealing section is preferably comprised of an upper section and a lower section, each extending from the coupling section. The coupling section, in preferred embodiments, has one or more expansion or contraction grooves in the outer or inner periphery. The locking segment, in preferred embodiments, has at least one engagement device. Preferably, the engagement device is annular.

Another embodiment of the invention is directed to a conduit coupling system. The system comprises at least two piping components and a sealing device. A fust component has a bell and a second component has a spigot, the spigot is adapted to mate with the bell. The bell includes a first end and a second end, wherein the first end coupled to the first component. The bell socket has a concave annular inner surface and a diameter of the annular inner surface adjacent to the first end of the bell socket is greater than a diameter of the annular inner surface adjacent to the .second end of the bell socket. The sealing device with a segment comprising a convex outer surface and a K-type gasket coupled to the segment. The sealing device is adapted to fit between the bell socket and the spigot end.

In preferred embodiments, the segment is a locking segment. Each locking segment is adapted to engage an outer surface of the spigot. The inner surface of the bell socket is preferably a truncated elliptic paraboloid. Each component preferably comprises a bell at a first end and a spigot or bell at a second end and each component is cylindrical. Each component can be made of ferrous metals (e.g. steel and cast iron), non-ferrous metals (e.g. copper-based alloys), or plastic (e.g. PVC or HDPE).

Tn preferred embodiments, the locking segment is of a first material and the K-type gasket is of a second material. Preferably, the first material is harder than the material of the spigot. In preferred embodiments, the K-type gasket has a coupling section and a sealing section. The sealing section is preferably comprised of an upper section and a lower section, each extending from the coupling section. Preferably the locking segment has at least one engagement device. In preferred embodiments, the sealing device is annular.

Another embodiment of the invention is a method of coupling at least two conduits of the invention. The method includes the steps of positioning a sealing device inside a bell coupled to one end of a first conduit, inserting a spigot of a second conduit through the sealing device inside the bell, and partially removing the spigot from the bell. A locking segment of the sealing device engages the outer surface of the spigot as the spigot is partially removed from the bell. The sealing device is adapted to move axially within the bell in the direction of the insertion of the spigot and the movement is assisted by the presence of expansion and contraction grooves in the coupling section of the gasket. This movement allows the locking segment to be displaced from the path of the incoming spigot with little increase in insertion force. The axial movement may be confined to one segment of the. sealing device to accommodate angular and radial misalignment of the incoming spigot. The sealing device is adapted to move in the direction of the partially removed spigot from the bell in response to internal hydraulic pressure to effect a seal to the spigot that rests in an angular and radial misaligned position.

In preferred embodiments, the bell has a first end and a second end, the first end is coupled to the first conduit. The bell has a concave annular inner surface, and diameter of the annular inner surface adjacent to the first end of the bell socket is greater than a diameter of the annular inner surface adjacent to the second end of the bell socket.

In certain embodiments, radial loading of the locking segment increases as the spigot is removed from the belt. The radial loading of the locking segment can increase exponentially as the segment moves toward the front of the bell following the parabolic curve toward the vertex. Preferably, the sealing device includes at least one locking segment comprising a convex outer surface, and a -iype gasket coupled to the locking segment. Preferably the K-type gasket is compressed upon insertion of the spigot. The withdrawal of the spigot end can be due to external forces or internal hydraulic forces.

Other embodiments and advantages of the invention are set forth in part in the description, which follows, and in part, may be obvious from this description, or may be learned from the practice of the invention.

Description of the Drawings

The invention is described in greater detail by way of example only and with reference to the attached drawings, in which:

Figure I is a partial cross-sectional view of an embodiment of the system of the invention.

Figure 2 is a partial cross-sectional view of an embodiment of the bell of the invention.

Figure 3 is a partial cross-sectional view of an embodiment of the gasket of the invention.

Figure 4a is a partial cross-sectional view of an embodiment of the locking segment of the invention.

Figure 4b is a partial cross- ectional view of an embodiment of the locking segment of the invention as it interacts with the inner surface of the bell socket.

Figure 5 is a partial cross-sectional view of an embodiment of the anti-extrwsion segment of the invention.

Figure 6 is a partial cross-sectional view of an embodiment of the system with the spigot prior to insertion into the bell.

Figure 7 is a partial cross-sectional view of an embodiment of the system with the spigot inserted into the bell.

Figure 8 is a partial cross-sectional view of an embodiment of the system with the gasket compressed more on the upper side due to deflection of the spigot. Figure 9 is a partial cross -sectional view of an embodiment of the system with the locking segment engaged.

Figure 10 is a cross-sectional view of an embodiment of the system with the spigot deflected within the bell.

Figures 1 1 -13 are pictures of experimental engagement patterns.

Description of the Invention

As embodied and broadly described herein, the disclosures herein provide detailed embodiments of the invention. However, the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. Therefore, there is no intent that specific structural and functional details should be limiting, but rather the intention is that they provide a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention.

A problem in the art capable of being solved by the embodiments of the present invention is coupling piping components and maintaining the assembly, it has surprisingly been discovered that certain configurations of the interior surface of a bell socket increase ease of assembly and allow for deflection between components. Furthermore, it has surprisingly been discovered that certain configurations of the outer surface of a gasket increas the gasket's ability to maintain assembly during use of the components including tinder high pressure applications.

Figure 1 depicts a cut away view of the components of the upper segment of system 100.

System 100 includes a spigot 105. a bell 1 10, and a sealing device 1 15. Each of spigot 105, bell 1 10, and sealing device 1 15 is shown in partial cross-section. In the preferred embodiment, each of spigot 105. bell 1 10. and sealing device 1 15 is annular in shape having a common axis below Figure L Each of spigot 105, bell 1 10. and sealing device 1 1 can have any diameter that may be commonly found in piping systems. Preferably the diameter of each of spigot 105, bell 1 10, and sealing device 1 15 is between one-half inch and one hundred and twenty inches, more preferably between one-half inch and seventy two inches.

In a preferred embodiment, system 100 is used to join lengths of pipes. The pipes can be of any length. Additionally, one pipe can have one spigot end and one bell end, two spigot ends, two bell ends, or a combination thereof. In other embodiments, there can be at least one spigot and/or bell located along the length of the pipe positioned perpendicularly or at an angle to the axis of the pipe. In iher embodiments, system 100 can be used to join two or more pipes to other components (e.g. fire hydrants, valves, and/or fittings), or can be used to join components together. System 100 can be used for any fluid, for example gas. water, or oil. In the preferred embodiment, sealing device 1 15 has a gasket end 120 and a locking segment i 25. However, in certain embodiments, segment 125 can be an ami-extrusion element (described herein).

In the preferred embodiment, piping components 105 are made of ductile iron, steel, or plastic and segments 125 are made of a substantially rigid material such as ductile iron, steel, or hardened plastic however other material may be used, preferably but not limited to ferrous metals (e.g. steel and cast iron), non-ferrous metals (e.g. copper-based alloys), or plastic (e.g. PVC or HDPE). Pipes can have walls of any thickness, preferably, but not limited to, between 1/8 inch and 1 ¾ inches. Fittings can have walls of any thickness, preferably, but not limited to, between ¼ inch and 2 inches.

In the preferred embodiment, sealing device 1 15 is of a diameter larger than spigot 105 and has an annulus at the back with a diameter slightly smaller than the diameter of spigot 105. The sealing device 1 15 is preferably dimensioned such that spigot 105 can be inserted into sealing device 1 1 without encountering intentional resistance until such lime as it reaches the inner end of bell 1 10. Insertion forces are reduced by several orders of magnitude compared to compression type seals. If resistance is encountered during insertion of the spigot into the locking segment, due to the plasticity of the gasket and assisted by the compression groove 330, the segment is able to reduce the resistance by moving up and away from contact with the spigot.

Figure 2 depicts a cut away view of a section of a bell 1 10. The center line of the bell 1 10 is illustrated by a dashed line 12. The outer shape of bell 1 10 is best described by the relative external diameters of the pipe's different points. Bell 1 10 has an external diameter at the point 205 and a smaller external diameter at point 206 some length along the bell f 10. The transition of the external surface of bell 1 10 from point 205 to point 206 is a gradual curve providing that .section of the bell 1 1 with the appearance of a bell. Preferably a constant external diameter is maintained between point 205 and 207 with a gradual change of external diameter from point 207 to 206. The internal section of the bell 1 10 (from point 205 to point 260) is referred to as the bell socket 220. Bell 1 10 is usually integrally formed but for the purpose of this disclosure can be divided into a number of sections. T he first section extends from point 205 to point 230. The internal radius of bell 1 10 between center line 12 and point 20.5 (Rl ) is greater than the internal radius of bell i 10 between center line 12 and point 234 (R2). The transition of the inner surface from internal radius R1 to R2 is a smooth curve and is referred to as bell throat 225. An example of a .smooth curve is a segment of a circle of predetermined radius. An effective radius 232 for the smooth transition depends on the distance from point 205 to point 230. internal radius R 1 and internal radius R2. Preferably, radius 232 is adapted Co facilitate insertion of spigot 1 5 into bell 1 10.

The second section of bell 1 10 extends from point 230 to point 231. The second section includes a retainer portion 233 extending from point 230 to point 234. The interna) radius at point 230 is R2 and immediately transitions to an internal radius R3 between center line 12 and point 234. R3 is greater than R2. The portion of the second section from reference point 234 to reference point 2 1 is provided with an inner surface 235 that is concave with reference to the center line 12. The concave inner surface 235 may have a variety of shapes, including but not limited to a truncated cone, a truncated elliptic paraboloid, a truncated sphere, or a combination thereof. Preferably, the curve of inner surface 235 has a nose or "vei lex" of a paraboloid aligned in an axial direction opening away from the "directrix." As explained herein, concave inner surface 235 provides a function that enables the ease of assembly and allows for increased angle of deflection by spigot 105 inserted into the bell 1 10.

The third section of bell 1 10 extends from point 2 1 to point 240. The portion of the third section from point 231 to point 239 defines the heel seat for the gasket 120 and the portion of the third section of bell 1 10 from point 239 to point 240 defines the socket shoulder where the gasket 120 is held in place.

The fourth sections of bell 1 10 extends from point 240 to point 260. This section has a sloped portion 250 that is referred to as the clearance slope. The radius from the center line 12 to point 242 (R4) is larger than the external radius of the spigot 105 in Figure 1. The second portion of the fourth section includes a relatively flat surface in the lower portion from point 242 to point 249 that is referred to as the land. The third portion of the fourth section extends from point 249 to point 260. Point 260 is referred to as the land stop and has an internal radius R5 that is substantially equal to the internal radius of spigot 105. Typically, spigot 105 is the end of the pipe opposite to pipe bell 1 10. Illustrated in Figure 3 is a cut away view of the upper segment of a gasket 120 used with the pipe bell I !O illustrated in Figure I . Gasket 120 is preferably made of an elastomer.

However, other materials that are flexible, appropriate for the fluid, and provide a tight seal can be used. For example, gasket 120 can be made of SBR (Styrene butadiene rubber), EPDM (ethylene propylene diene monomer rubber). itirile. NBR (Nitrile butadiene rubber), and/or other synthetic and natural rubbers. In the preferred embodiment, gasket 120 is of a singl durometer rubber. However, in other embodiments, two or more durometer rubbers can be used. Gasket 120 is preferably a K-type. lip, or wiper seal design, conforming to and fitting within the bell 10. Gasket heel 305 and gasket shoulder 310 mate with gasket heel seat 239 of bell 1 10 and socket shoulder 240 (as described with respect to Figure I ). In the preferred embodiment, gasket heel 305 is slightly larger than gasket heel seat 239, thereby compressing gasket heel 305 so that it is firmly anchored in bell socket 220 with gasket shoulder 310 against socket shoulder 240.

Gasket 120 has a front edge portion 31 (also referred to as the front edge slope or segment edge) adapted to be disposed feeing towards the open end of bell 1 10 that is illustrated in Figure 1 , Gasket 1 0 also has a substantially cylindrical portion 320 that, when inserted into bell 1 10. forms a gasket orifice. Gasket 120 includes a primary translation slope 325. The primary translation slope 325 allows for compression and translation of the rest of the gasket 120 whenever forc is exerted on the front edg portion 1 . Gasket 120 has an expansion and contraction groove 330 formed on the upper surface. In the preferred embodiment, expansion and contraction groove 330 is an annular cutout along the outer surface of gasket 120. However, in other embodiments, expansion and contraction groove 330 can be located on the inner surface of gasket 120. In other embodiments, there can be multiple expansion and contraction grooves located at various locations about gasket 120. Furthermore, expansion and contraction groove 330 can have any cross-sectional shape, including but not limited to triangular, rectangular, trapezoidal, and semicircular. The back edg of gasket 120 is formed as a concave pressure annulus pocket 340. Hydraulic pressure against pressure annulus pocket 340 increases the sealing pressure of lip seal 335 against the mating spigot 105. While annulus pocket 340 is shown as a single curved indentation, annulus pocket 340 can have multiple indentations and can have other shapes. Additionally, annulus pocket 340 can be of another material more compressible than the material of gasket 120. Gasket heel seal 239 and socket shoulder 240 mate with and retains sealing device 1 15. In a preferred embodiment, adjacent to socket shoulder 240 is clearance slop 250. Clearance slope 250 permits passage of the water or other fluid into the pressure annulus groove of sealing device 1 15 (described herein). In a preferred embodiment, the inner portion of bell socket 220 is land 249, which extends from clearance slope 250 to land stop 260. Land 249 provides clearance for spigot 105 and limits over-deflection of the joint. Land stop 260 limits the insertion depth of spigot 105, while land radius 265 assists in casting by eliminating a sharp inner corner between land 249 and land stop 260.

Front edge slope 315 is the surface to which the locking segment 125a or anti-extrusion segment 125b is coupled. In the event that the edge of spigot 105 contacts the segment 125, in the preferred embodiment, front edge slope 31 is angled such that segment 125 and gasket 120 will be deflected outward and away from spigot 105. allowing the passage of spigot 105 through gasket orifice 320. Contraction groove 330 facilitates th bending or buckling of the gasket 120 and the gasket orifice 320. In operation, the primary translation slope assists in stabilizing the front portion of gasket 120 and transferring forces to the expansion and contraction groove 330, which will bend and/or buckle to assist in the movement out of the path of an inserted spigot 105 until spigot 105 comes into contact with the front edge of lip seal 335. The effect of moving a portion of the gasket 120 out of the path of an inserted spigot !05 is to substantially reduce the friction thereby reducing the amount of force necessary to insert the spigot 105 into the bell 1 10.

Figure 4a depicts a cut away view of the upper segment of segment 125. where segment

125a is a locking segment. Locking segment 125a is preferably made of AISI type 4140 steel (chromium steel-). However other hard and durable materials can be used, for example AiSf type 431 stainless steel. In preferred embodiments, segment 125 may be coated with an anticorrosion coaling. The outer surface 405 of locking segment 125a is preferably a curved surface that makes contact with the concave inner surface 235 of bell socket 220. The curvature of outer surface 405. as shown in Figure 4a, is merely for illustration purposes. The curvature can be greater or smaller than shown in Figure 4a. In the preferred embodiment outer surface 405 is convex, more preferably a truncated paraboloid. However, in other embodiments, outer surface 405 can be another convex surface, a linear surface, or a concave surface. Preferably outer surface 405 opens away from bell throal 225. When the outer surface 405 of locking segment 125a moves against the inner surface 235 of bell socket 220. the locking element 125 acls as a cam follower and the inner surface 235 of the bell socket 220 acts as a cam. That cam action facilitates locking segment 125a in wedging between bell socket 220 and spigot 105, forcing the teeth 410 of locking segment 125a into the outer surface of spigot 105 and providing restraint against extraction of spigot 105. Due to the elasticity of gasket 1 1 locking segments 125a have freedom to move to maintain contact between outer surface 405 and the inner surface 235 of bell socket 220. Thus, segment 405 can accommodate misalignments between (he two surfaces caused by, for example, casting variability in the bell 1 10. as well as a differential caused by the elliptical path of the locking segments 125a during deflection not matching exactly to inner surface 235.

The interaction between the outer surface 405 of locking element 125 and the inner surface

235 of the bell socket 220 is better illustrated in Figure 4b. As stated previously, inner surface 235 of the bell socket 220 is concave and in a preferred embodiment follows the shape of a truncated paraboloid. Therefore, for every horizontal displacement X of locking element 125 the action of the outer surface 405 of the locking element 125 against the inner surface 235 the bell socket 220 there will be a vertical displacement Y of the locking element 125 commensurate with the function defining the .shape of inner surface 235 of the bell socket 220. While locking segment 125a is shown with two teeth 410, one or more teeth can be used. For thin walled spigots or PVC spigots, there will be more teeth 410 located closer together than in embodiments using thick wall iron spigots.

Another function of locking segments 125a is to assist in moving gasket 120 away from spigot 105 as spigot 105 is inserted into bell 1 10. Segment mounting slope 41 is angled such that the corresponding mating front end slope 315 of gasket 120 will help deflect gasket 120 up and away from the path of spigot 105 so that passage is not impeded. Locking segment 125a is aided by primary translation slope 325 of gasket 120, which supports the portion of gasket 120 forward of expansion and contraction groove 330.

In the preferred embodiment, segments 125 are equally spaced and mounted to front end slope 15 of gasket 120. Segments 1 5 reinforce the elastic gasket material against extrusion between throat 225 and spigot 105. In order for segment teeth 410 to penetrate spigot 105, it is preferable for locking segment 125a to be made of a material harder than spigot 105.

Figure 5 depicts a cut away view of the upper segment of segment 125. where segment

125b is an anti-extrusion segment for non -restraining joint gaskets. In embodiments where restraint between a mating bell 1 10 and spigot 105 is not desired or needed, segment 125b can be made without teeth as shown in Figure 5. The toothless segment 125b functions similarly to the locking segment 125a in helping gasket 120 to facilitate deflection and preventing extrusion of gasket 120 between throat 225 of bell socket 220 and spigot 120, but has no teeth to penetrate spigot 105 and provide restraint. In some embodiments, both locking segments 125a and toothless segments 125b can be used in the same restraining device 1 1 .

Figures 6-9 depict cot away views of the steps of inserting socket 1 5 through sealing device 1 15 and into bell 1 10. In Figure 6, spigot 105 is aligned with bell 1 10. In the preferred embodiment, the centerline of spigot 105 is aligned with the center line of bell 1 10. However, in other embodiments, spigot 1 5 can be inserted into bell 1 10 at an angle. The angle can be less than 15°, preferably, the angle is between 5° and 9°, and more preferably the angle is 7° or less. Upon contact and continued insertion of spigot 105 (as shown in Figure 7). Hp seal 335 will bend and stretch over spigot 105 imparting axial and circumferential tensile forces to gasket 1 0. The tensile forces cause the secondary translation slop 345 to force segments 125 into contact with spigot 105.

Insertion of spigot 105 through sealing device 1 15 will result in spigot 105 contacting locking segment 125. Ordinarily this would increase the friction exerted in spigot 105.

However, in the preferred embodiment, as spigot 105 contacts locking segment 125, the forces exerted on the gasket 120 cause the gasket 120 to bend at contraction groove 330 and allow for the longitudinal and axial displacement of segment 125 along concave inner surface 235. The displacement of the gasket allow and guide the translation of segment 125 out of the way of incoming spigot 105 with a minimum force.

The displacement of segment 125 is caused by a combination of axial and radial movement in response to the. orientation of the incoming spigot 105 and dimensional variations of the joint components. The displacement of segment 125 can include off-axis rotation of segment 125 in response to spigot 105 being deflected or offset. The energy stored in gasket 120 as a result of the displacement keeps segment 125 in contact with spigot 1 5. insertion of spigot 105 through sealing device 1 15 induces axial tensile forces in sealing device 1 1 . or at least positions segment 125 to better engage spigot 105 when there is a withdrawal of spigot 105 from bell 1 10 (as shown in Figure 8). The circumferential tensile forces exerted on lip seal 335 to form a seal between lip seal 335 and spigot 105. The seal is amplified when the joint is pressurized and the material of gasket 120 causes the seal to be pressed more tightly against spigot 105 and the inner surface of bell 1 10 (as shown in Figure 8). Gasket 120 can move independently of segment 125 once segment 125 is seated. Spigot 105 does not have to be fully inserted into bell 1 10 to seal. In the preferred embodiment, spigot 105 will be sealed once the inserted end of spigot 105 is inserted past lip seal 335, at which point, system 1 0 is water tight.

Once the spigot 105 is in place, the spigot 105 or the bell 1 1 may be subjected to separation forces that tend to separate the spigot 1 5 from the bell 1 10. The separation forces may arise either from external forces or as a result of the internal pressure in the pipe. As shown in Figur 9, separation forces cause the teeth 410 to engage spigot 105. The teeth 410 are engaged due to radial loading caused by the outside surface of the segments 125 bearing against th progressively decreasing curved inner surface 235 of bell 1 10. Since, in the preferred embodiment, bell 1 10 is shaped such that the diameter decreases at an increasing rate from gasket heel seat 239 to bell throat 225. withdrawal of the spigot is met with increasing resistance as the similarly formed outer surface 405 of segments 125 is wedged between (he bell 1 10 and the mating spigot 105. The flexibility that allows segment 125 to translat out of the path of the incoming spigot 105 also allows segment 125 to rotate into an off-axis position to maximize the engagement of teeth 410 with a misaligned or radially offset spigot 1 10 and to reduce the possibility of point-loading conditions.

When the joint is extended (pulled apart), (he outer surface 405 of segment 125 mates with the inner surface 235 of bell socket 220 and forces teeth 10 into the outer surface of spigot 1 5 due to the parabolic wedging action of the outer surface of locking segment 1 5 being drawn in the direction of its vertex. Withdrawal of spigot 105, either due to external forces or the internal hydraulic action caused by pressurizing the joint, causes teeth 410 to engage spigot 105 and the convex outer surface 405 of locking segment 125 to engage the corresponding concave inner surface 235 of bell socket 220. As the withdrawal motion is continued, the engagement between the outer surface 405 of locking segment 125 and inner surface 235 is intensified by the increasingly smaller diameter of bell socket 220. This increases the inward radial loading on teeth 410, forcing them (o further engage spigot 1 5. Extension of the joint is minimized due to the outer surfac of locking segment 125 encountering an exponentially decreasing diameter of the inner surface 235 during pull-back, which exponentially increases the rate of radial loading of teeth 10 engaging spigot 1 5. In embodiments where there are multipl locking segments. (he engagement pressure on Ihe outer surface of locking segments 125 would be relatively equal since bell 1 10 and .spigot 105 are in the form of concentric circles when axially aligned.

Figure 10 depicts a cross-sectional view of a spigot 1005 coupled to a bell 1010 deflected at an angle Θ. The outer surface of segment 1025 facilitates a deflection, or bending, of the joint between spigot 1005 and bell 1010 by moving along inner surface 1020 of bell 1010. If Θ is defined as the angle of deflection as measured from the ccnterline CL of the bell 1010 and spigot 1005 components, then in the direction of deflection, segment 1025 will move along curve 1020 in the direction of the vertex, or smaller end of curve 1020. At the other end of the coupling, in the opposite direction away from deflection, the opposing segment 1035 will move along the curve 1020 away from the vertex. Segments mounted around the gasket. 1015 at intermediate locations between segment 1025 and segment 1030 will follow an elliptical path. The outer surfaces of these intermediate segments will maintain contact with the concave inner surface 1020 of bell 1010 due to the continuously changing shape of inner surface 1020. The major axis of (he elliptical path can be defined by h ~ tangent (Θ) times the effective diameter as measured across the outside surface of opposing segments. In the preferred embodiment. 0 is less than or equal to 1 '\ more preferably Θ is less than or equal to 10°. however, Θ can be another angle.

In the preferred embodiment, when the joint is deflected, the outer surface of locking segment 125 follows a curve described by an ellipse in a plane inclined to the axis of the spigot. Each half of the ellipse on either side of the minor axis is a curve close enough in shape to a parabola so that the ellipse conforms closely to the paraboloid of bell 1 10 as the joint is deflected.

In the preferred embodiment, the inner surface 235 of bell 1 10 and the outer surface 405 of segment 125 follow the shape of truncated paraboloids, one positioned inside the other. The two paraboloids are axially aligned when the joint is in the undetected position. Paraboloids are surfaces generated by rotating a parabola about its central axis.

In the preferred embodiment, no lubrication between spigot 105 and sealing device 1 15 is required. However, in other embodiments, lubricants can be used, for example dry film lubricants. The lubricant can ease in assembly and provide corrosion protection to sealing device 1 15. In 8 inch pipe, for example, the force used to insert the spigot 105 into the bell 1 10, is between 25 to 100 pounds. With that level of force the insertion can be completed manually, without the use of mechanical devices other than to lift the piping component.

The following examples illustrate embodiments of the invention, but should not be viewed as limiting the scope of the invention.

EXAMPLE

An experiment using two lengths of 8 inch pipe was conducted. One pipe had a bell as described herein while the other had a spigot as described herein. The two lengths were joined using a sealing device as described herein. The pipes were sealed at their respective open ends and the internal cavity was pressurized. The experiment was conducted first with the pipes having no deflection and then with the pipes having 5.7° and 7.0° of deflection. The results are compiled in Table I ,

If ^* t ^* is defined as the angle of deflection between the axis of the bell socket and the spigot, through moderate angles of deflection, the locking segments following the major axis of an ellipse projected onto a plane inclined at Θ" perpendicular to the axis will, on the side of the complementary angle { 180 ° - 9) be positioned nearer the vertex of the paraboloid of the bell socket, and those on the corresponding angle of deflection, Θ, corresponding to the longer side of the major axis of the ellipse will follow the curve of the paraboloid and be positioned further out on the major axis, bui still in close proximity to the bell socket. Thus the elliptical path of the deflected segments rotating within the paraboloid helps maintain proximity between the paraboloid outside surfaces of the locking segments and the paraboloid sur ace of the bell socket through moderate angles of deflection within the limits of the joint. At the center of rotation (during deflection), the segments are not displaced much beyond that of their original position on the circle perpendicular to the axis of the spigot. The displacement or translation of the segments includes the ability to rotate into an off-axis position to improve the engagement with a misaligned spigot and to provide equalization of pressure between the bell curve and the spigo end through the segments. Thus, the engagement pattern of the segments is approximatel balanced around the spigot whether deflected or not through moderate angles of deflection of the joint. The advantage of this embodiment is that the joint less likely to lose engagement or restraint as the joint is deflected, permitting deflection angles up to 10 degrees, preferably between 5 and 9 degrees, and more preferably 7 degrees or less. A 90-degree turn can thus be made using approximately 15 (20-foot) pipes over a distance of approximately 300 circular feet with deflections of 6 degrees, as opposed to 30 pipes over a distance of 600 circular feet using 3 degree deflection joints. That greater deflection reduces the number of bend fittings and the amount of trench digging required, and conserves land space.

The validity of this assertion can be seen by the engagement pattern of segment teeth of a gasket on a pipe spigot as shown in Figures 1 1 - ! 3 for a joint that was deflected 5.7". and pressurized to <S2S.2-psi before the gasket body ruptured. It can be seen that the engagement pattern follows an elliptical path about the pipe spigot, and the depth of penetration of the teeth are approximately equal, indicating relatively equal pressures between the bell socket, segments and spigot, even though the joint is deflected. The joint in the photographs withstood a pressure of 828.2-psi before failure of the prototype gasket made of a catalyst-activated po!yurethane. Even thought the gasket rubber failed, the joint maintained engagement and did not separate. The joints did not separate in any of the tests; ail failures were due to leaks caused by tearing of the rubber when the tensile strength was exceeded due to internal pressure.

Other embodiments and uses of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. All references cited herein, including all publications, U.S. and foreign patents and patent applications, are specifically and entirely incorporated by reference. It is intended that the specification and examples be considered exemplary only with the true scope and spirit of the invention indicated by the following claims. Furthermore, the term "comprising" includes the terms "consisting of and "consisting essentially of," and the terms comprising, including, and containing are not intended to be limiting.