AU2001281580C1 - A seal and a pipe system allowing for misalignment - Google Patents

Description

-1- TITLE: A SEAL AND A PIPE SYSTEM ALLOWING FOR MISALIGNMENT Field of the Invention The present invention relates to seals of the type used to seal adjacent or adjoining components in an assembly.

The invention has been developed primarily for use as a pipe seal and will be described predominantly with reference to this application. It will be appreciated by those skilled in the art, however, that the invention is not limited to this particular field of use.

Background of the Invention Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field.

It is known to use seals to facilitate the connection of adjoining components in situations where pressure differentials would otherwise produce leakage. They are also used in applications where it is important to avoid intermixing of different fluids across an interface between adjoining components in a system. A particularly important application is in pipelines and piping systems, where known seals are prone to a number of inherent disadvantages.

Pipelines and pipe networks are usually formed by interconnecting a multitude of discrete pipe sections. The pipe sections must be securely joined to prevent failure. The joins must also be effectively sealed to avoid leakage and excessive loss of fluid pressure along the pipe. To this end, the sections to be connected are usually configured so that the outer diameter of each male end is marginally smaller than the inner diameter of the corresponding female end of the adjoining section. Such configurations may be achieved by using pipe sections of different size, by forming a circumferential rebate around the outer wall of one pipe section to form a male end, by flaring or WO 02/14719 PCT/AU01/01014 -2the wall of one pipe section to form a female end, by fitting an external collar around the abutting pipe ends so as to overlap the join, or by some combination of these techniques.

This provides the basic mechanical connection, which must then be secured and sealed.

One common form of pipe seal is the O-ring. This type of seal comprises an annular ring, normally of circular cross-sectional profile, formed from an elastomneric material such as rubber. It is typically retained within a circumferential groove formed around one end of a pipe section, normally the male end. The O-ring is sized to protrude Iradially beyond the upper marginal edges of the retaining groove, above the surrounding surface of the pipe end, so that upon insertion into a corresponding female end of an i0 adjoining pipe section, the O-ring is resiliently compressed. In some instances, a circumferential groove is also formed around the inner periphery of the female pipe end to facilitate captive retention of the O-ring and to resist withdrawal of the adjoining pipe sections, following installation.

O-rings of this type have been found to function satisfactorily in relatively small scale and low pressure applications. However, they are problematic in the context of larger scale pipelines such as water and sewage mains, because of the relatively high levels of axial force required in order to. compress the seal during engagement of the adjoining pipe ends. It has also proven to be difficult in practice to locate O-ring seals securely during installation, because of the tendency for these seals to roll along the surrounding surfaces in response to relative axial displacement of the pipe ends during the installation procedure. A further deficiency is that conventional O-ring seals have been found to provide inadequate sealing performance in high pressure applications.

In an attempt to address some of these inherent limitations in conventional O-ring seals, V-shaped pressure seals, or V-seals, have been developed. These seals are also generally annular or ring shaped. However, the cross-sectional profile is typically V or WO 02/14719 PCT/AU01/01014 -3- U-shaped, being defined in profile by a pair of diverging "arms". In use, the seal is positioned such that one arm of the V diverges radially inwardly for sealing engagement with the outer circumference of the male pipe end, while the other arm diverges radially outwardly for sealing engagement with the inner circumference of the adjoining female pipe end. In this configuration, radial compression of the seal involves movement of the arms toward one another and advantageously, this requires considerably less axial installation force than a comparable 0-ring seal. V-seals also have the advantage that, with the valley of the V oriented toward the high pressure side of the junction, the pressure differential across the seal tends to expand the arms of the V outwardly so as to enhance the effectiveness of the seal. In this way, the greater the pressure differential between the interior and the exterior of the pipe under normal operating conditions, the more effective the seal becomes. This feature of pressure responsiveness provides a further improvement over O-ring seals.

One of the difficulties with seals of this type, however, is that in order to ensure optimum performance, the preferred shape of the seal is different depending upon whether the pressure within the pipe is higher than the surrounding pressure or vice versa. The seals are also shaped differently according to whether they are to be used in conjunction with rebated, flared, or collared pipe ends. The proliferation in seals due to these variations spread across a large array of pipe thicknesses and diameters creates production inefficiencies, complicates inventory control, and ultimately leads to increased costs. It also gives rise to a significant potential for operator error during installation because of the possibility of the wrong type of seal being specified or used, or the correct seal being installed in an incorrect orientation.

Furthermore, V-seals are not ideally suited to applications where the relative pressure between the interior and the exterior of the pipe fluctuates between positive and negative values. This is because the seals, being pressure responsive, are directionally biased and if optimised for one situation, they will be compromised in the other.

Accordingly, if pressure across the interface is likely to be intermittently reversed, multiple seals in opposing orientations are required which further adds to the cost and complexity of the installation procedure. In practice, V-seals are also prone to fouling and moving out of position during the installation process.

It is an object of the present invention to overcome or substantially ameliorate one or more of the disadvantages of the prior art, or at least to provide a useful alternative.

DISCLOSURE OF THE INVENTION Accordingly, in a first aspect, the invention provides an annular pipe seal for sealing a connection between a male end of a first pipe section and a complementary female end of a second pipe section adjacent the first, said seal including: a base adapted for sealing engagement with a mating surface of one of said pipe section ends, said base including a plurality of closely spaced radially depending circumferentially extending sealing ribs to enhance said sealing engagement by providing a localised concentration of sealing pressure between the base and the corresponding mating surface; a first sealing portion and a second sealing portion extending from the base, the first sealing portion protruding beyond the second sealing portion, the sealing portions being interconnected such that engagement of the other of said pipe section ends with the seal compresses the first portion to form a first seal and said compression urges the second portion into sealing engagement with said other of said pipe section ends to form a second seal between said one and said other of said pipe section ends.

In this way, the seal is preferably adapted to facilitate the assembly of a plurality of discrete pipe sections in series to form a pipeline.

Preferably, the first portion of the seal includes a first sealing rim and the second portion includes a second sealing rim displaced axially and radially from the first. The connection means preferably include a bridge section extending between the first and second sealing rims. The connection means preferably also include a resilient connection accommodating a limited degree of pivotal or rocking movement between the bridge section and the base.

Preferably, the base portion of the seal is adapted to be captively and sealingly retained within a channel or groove extending circumferentially around an outer surface of the male end of the first pipe section. More preferably, the base of the groove is inclined toward the proximal end of the first pipe section, to resist axial displacement or dislocation upon insertion into the female end of the adjoining pipe section.

In the preferred embodiment, the rims are positioned such that with the seal supported on the male end of the first pipe section, and upon axial engagement with the second pipe section, the female pipe end initially passes over the second sealing rim to engage the first rim. Upon engagement of the female pipe end with the first sealing rim, the first portion of the seal including the first rim preferably beings to compress. In response to that compression, and upon further insertion, the bridge section preferably rotates or rocks relative to the base, whereby the second sealing rim is urged radially outwardly into sealing engagement with the interior surface of the female pipe end.

Preferably, the seal includes a first outwardly diverging generally V-shaped notch extending circumferentially between the first sealing portion and the base. Similarly, a second outwardly diverging generally V-shaped notch preferably extends -6circumferentially on the opposite side of the seal between the second sealing portion and the base. The first and second notches preferably converge toward one another, to define a neck region in the seal. The neck region is preferably adapted to facilitate the pivotal or rocking movement between the bridge section and the base, during which the first notch closes while the second notch opens, or vice versa.

In one preferred embodiment, the cross-sectional profile of the seal as defined by the base, the first and second sealing rims and the intermediate V-notches, is generally K-shaped.

Each of the V-notches is advantageously adapted to perform a pressure responsive function, whereby an increase in pressure on either side of the seal urges the respective rim and the associated side of the base apart with respect to one another and into enhanced sealing engagement with the adjacent pipe walls. Advantageously, because the notches are oppositely oriented, the seal is pressure responsive on both sides.

Preferably, the seal is formed as a unitary component, from a suitable elastomeric material such as rubber, polyurethane, polyethylene, nylon, Nitrile, silicone or the like.

It will be appreciated, however, that in alternative embodiments, the seal may be formed in multiple components, from multiple materials, or from similar materials of different stiffness, density, resiliency, flexibility or the like. It may also be internally reinforced or externally braced if required.

The connection means may additionally or alternatively include a fluid or a gel adapted to pass between the first and second portions of the seal or other means to provide the desired interaction.

According to a second aspect, the invention provides a pipe system including a first pipe section having a male end and a second pipe section having a complementary IND -7-

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female end, the male and female ends being adapted for connection in overlapping relationship to join the pipe sections together, the male end or the female end r incorporating a first circumferential recessed channel disposed to permit a limited extent of relative radial displacement of the female end in response to axial misalignment 00 5 between the pipe sections, thereby to accommodate a limited degree of relative 0 rotational displacement about an axis normal to the axes of the adjoining pipe sections, and the male and female ends being integrally formed in corresponding outer and inner Nsurfaces of respective ends of the pipe sections; wherein the male or female pipe end incorporates a second circumferential channel, spaced apart from the first channel and adapted in use to locate and captively retain a pipe seal as defined above in an overlapping region between the male and female pipe ends.

According to a third aspect, the invention provides a pipe system including a first pipe section having a male end and a second pipe section having a complementary female end, the male and female ends being adapted for connection in overlapping relationship to join the pipe sections together, the male end or the female end incorporating a first circumferential recessed channel disposed to permit a limited extent of relative radial displacement of the female end in response to axial misalignment between the pipe sections, thereby to accommodate a limited degree of relative rotational displacement about an axis normal to the axes of the adjoining pipe sections, the male or female pipe end incorporating a second circumferential channel, spaced apart from the first channel and locating and captively retaining a pipe seal as defined above in an overlapping region between the male and female pipe ends.

IND -8- By this means, the channel in the male pipe end or spigot effectively translates the female corner nip point, up to the limit of relative rotational displacement about the normal axis between the adjoining pipe sections.

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Preferably, the first channel is recessed into the male pipe end. Preferably also, the

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00 5 second channel is also recessed into the male pipe end, forwardly of the first channel.

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OO Preferably, the system is adapted for use with a double-rimmed pressure seal, as previously defined. This type of seal is particularly advantageous in the present context,

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N because the neck region, between the base and the bridge section, readily deforms to accommodate the relative rotational displacement between the adjoining pipe sections, without compromising the performance or efficiency of the seal in any way.

Preferably, the male end also incorporates a circumferential land between the first and second channels, defining a zone of minimal radial clearance between the male and female pipe ends. Preferably, the circumferential land thereby tends to define the point or region of relative rotation between the adjoining pipe sections about the normal axis.

Preferably, a nose section of the male pipe end disposed forwardly of the second channel and the seal has a diameter less than that of the circumferential land, so as to permit an additional degree of said relative rotational displacement generally about the land surface before the outer peripheral rim section abuts the adjacent inner peripheral surface of the surrounding female pipe end.

The nose section preferably incorporates a tapered, frusto-conical outer surface oriented so as to facilitate surface-to-surface contact between the male pipe end and the adjacent inner surface of the female pipe end, thereby avoiding a relatively sharp spigot corner nip point, at the limit of relative rotational displacement.

In a particularly preferred embodiment of the invention, the pipe sections are formed from fibre reinforced cement (FRC), and the male and female end formations, ID -8a-

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O including the various grooves, channels and lands as defined, are moulded or machined into the corresponding outer and inner surfaces on the respective ends of these sections.

Advantageously, a plurality of straight pipe sections manufactured in accordance with this aspect of the invention may be joined end to end in series to form a curved 00 5 pipeline, or a gently radiused corner in an existing pipeline, without the need for o separately manufactured curved pipe sections, elbow junctions, or the like.

Brief Description of the Drawings A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a front elevational view showing a seal according to a first aspect of the present invention; Figure 2 is a side elevation showing the seal of Figure 1; Figure 3 is a cross-sectional view taken along line III-III of Figure 1; Figure 4 is an enlarged cross-sectional view fthe seal taken from Figure 3; Figure 5 is a cross-sectional view showing the seal of Figures 1 to 4 in position on the male end of a first pipe section, ready for engagement with the female end of an adjoining pipe section; WO 02/14719 PCT/AU01/01014 -9- Figure 6 is a cross-sectional view similar to Figure 5, showing the adjoining pipe sections fully engaged with the seal in the operative position; Figures 7 to 19 are a series of cross-sectional views similar to figure 4, showing a variety of alternative embodiments of the invention, designed for different pipe sizes, pressures, materials, situations and applications; Figure 20 is a side elevation showing a pipe section according to a second aspect of the invention; Figure 21 is an enlarged side elevation showing the spigot formed on the male end of the pipe section of figure Figure 22 is a cross-sectional view of the pipe section of figure Figure 23 is an enlarged cross-sectional view of the spigot on the male end of the pipe section; Figure 24 is an enlarged cross-sectional view of the socket on the female end of pipe section; Figure 25 is an enlarged cross-sectional view showing the inter-engagement of the spigot of the first pipe section with the socket on the female end of a second like pipe section at the inner radius of a bend, in response to relative rotation between the two pipe sections; and Figure 26 is an enlarged cross-sectional view similar to figure 25, but showing the interaction between the adjoining pipe sections at the outer radius.

PREFERRED EMBODIMENTS OF THE INVENTION Referring initially to Figures 1 to 4, the invention provides an annular pressure seal 1 for joining and sealing first and second pipe sections in a pipeline. The seal includes a base 2, a first sealing portion 3, and a second sealing portion 4 (as best seen in Figure 4).

WO 02/14719 PCT/AU01/01014 The first portion includes a first sealing rim 5, while the second portion includes a second sealing rim 6 displaced axially and radially from the first with the seal in the relaxed configuration. The first and second sealing portions are interconnected by means of a bridge section The seal further includes a first outwardly diverging V-shaped notch 12 extending circumferentially between the first sealing portion 3 and the base. Similarly, a second outwardly diverging V-shaped notch 13 extends circumferentially on the opposite side of the seal, between the second sealing portion 4 and the base. The first and second notches 12 and 13 converge toward one another, to define an intermediate neck 14 in the seal.

This neck is adapted resiliently to accommodate a limited degree of pivotal or rocking movement in either direction between the bridge section 10 and the base, during which the first notch 12 progressively closes while the second notch opens, or vice versa. The cross-sectional profile of the seal as thus defined by the base, the first and second sealing portions, the intermediate V-notches and the neck is generally K-shaped.

The seal is ideally formed as a single, unitary component from a suitable elastomeric material such as rubber, polyurethane, nylon, silicone or the like. It will be appreciated, however, that in alternative embodiments, the seal may be formed from multiple components, from multiple materials, or from similar materials of different stiffness, density, resiliency, flexibility or other material characteristics. It may also be internally reinforced or externally braced if required.

Figures 5 and 6 show the use of the seal to form a fluid tight connection between a male end 15 of a first pipe section 16 and the complementary female end 17 of a second pipe section 18, as part of a pipeline assembly. The male end 15 of the first pipe section is defined by means of an annular external rebate 19 formed in the outer side wall of one end of that pipe section. Similarly, the female end 17 is defined by means of an annular PCT/AUO 1/01014 Received 01 August 2002 -11internal rebate 20 formed in the inner side wall of the adjoining pipe section 18. In the connection region, the outer diameter of the male pipe end 15 is marginally less than the inner diameter of the corresponding female pipe end 17, to allow for a limited degree of overlapping interengagement. This system is particularly well suited for use with pipes formed from fibre reinforced concrete (FRC), which typically have relatively thick side walls. It should be appreciated, however, that similar interengagement between the pipe sections may be achieved in other ways, depending upon the material from which the pipe is fabricated, for example by using pipe sections of different diameter, by flaring or pre-belling the female pipe end, by an external collar adapted to slide axially over the join, or by a combination of these or other means.

The base portion 2 of the seal is then captively and sealingly retained within a groove 25 extending circumferentially around the outer surface of the male pipe end The groove is advantageously inclined toward the end of the section, so as to resist axial displacement, dislocation or rolling of the seal out of position upon engagement with the female end of.the adjoining pipe section. The asymmetry of both the seal and the groove also helps to prevent inadvertent installation of the seal in the incorrect orientation. The preferred angle of inclination is between 50 and 300, and is ideally around 100 to the horizontal with respect to the axis of the pipe section).

With the seal thus located, the pipe sections are positioned ready for engagement, as shown in Figure 5. As engagement proceeds, the female pipe end initially passes over the second rim 6, to engage the first rim 5. This occurs because in the relaxed condition the first rim 5 protrudes radially outwardly beyond the second rim. Upon further advancement, the first portion 3 of the seal, including the first rim 5, begins to compress radially inwardly. In response to that compression, and upon further engagement, the bridge section 10 rotates about the neck 14 relative to the base. In response to this WO 02/14719 PCT/AU01/01014 -12rotation, and due to the relative rigidity of the bridge section, the second sealing rim 6 is urged radially outwardly into sealing engagement with the interior surface of the female pipe end. During this process, the base of the seal is retained securely in position within the inclined groove 25 in the male pipe end. Finally, the configuration of the seal with the pipe ends fully engaged is shown in Figure 6. In this configuration, the first rim forms a first seal and the second rim forms a second seal with the internal surface of the female pipe end. Ideally, with the seal compressed in position, the first rim, the second rim and the intermediate bridge section lie in substantially the same plane, such that the bridge portion also performs a sealing function. The inner edge of the retaining groove 25 incorporates an inclined shoulder 30, corresponding to an inclined face 31 formed in the first portion of the seal. With the pipe ends fully engaged and the seal compressed in position, this shoulder abuttingly supports the face 31 on the seal, to ensure adequate sealing pressure is maintained at the first rim. At the same time, the base seals against the inner surface of the retaining groove. In this configuration, with the seal in a state of resilient compression, a secure fluid tight connection is formed between the adjoining pipe sections.

In this configuration, the first and. second V-notches 12 and 13 are advantageously adapted to perform a pressure responsive function. Thus, an increase in relative pressure on either side of the seal urges the respective rim and the corresponding side of the base more forcefully into engagement with the surrounding pipe walls, thereby to enhance the effectiveness of the seal. Because the notches are oppositely directed, the seal is pressure responsive in both directions and so its performance is not compromised irrespective of whether the pressure within the pipe is positive or negative relative to the surrounding atmosphere.

WO 02/14719 PCT/AU01/01014 -13- Figures 7 to 19 are a series of cross-sectional views, showing seals in a similar orientation to that shown in figure 4, according to a number of alternative embodiments of the invention. Corresponding features are denoted by equivalent reference numerals, and so these alternative embodiments are not described individually in great detail.

Nevertheless, certain salient features should be noted.

Firstly, with most of these seals, it will be apparent that the inner face of the base 2 incorporates an axial array of circumferentially extending ribs 35, and interstitial grooves 36. These ribs are disposed for engagement with the mating outer surface of the circumferential retaining groove or recess 25, which extends around the outer periphery of the associated male pipe end. By virtue of the reduced total contact area, the localised pressure concentrations in the vicinity of the ribs provide improved sealing performance between the base of the seal and the retaining groove. This feature has been found to be particularly significant in preventing slow leakage under low-pressure conditions, when the pressure-responsive sealing enhancement provided by the V-notches is at a suboptimal level. Similar ribbing formations may additionally or alternatively be provided 9 on one or more of the outer surfaces of the seal if required, to enhance sealing and resist leakage between the sealing rims and the mating inner peripheral surface of the surrounding female pipe end, again particularly under low-pressure conditions.

It will also be noted that in a number of the seals, for example those illustrated in figures 7 to 10, the first sealing portion 3 and/or the associated rim are relatively thicker than in the seal illustrated, for example, in figure 4. This minimises the risk of the lip inadvertently folding back over itself either during the installation procedure, or subsequently under adverse pressure conditions. This feature also provides additional overall "bulk" to the seal. This improves sealing performance as well as enhancing the retention force at the interface between the adjoining pipe sections, which can be WO 02/14719 PCT/AU01/01014 -14particularly important when larger radial clearance spaces between the male pipe spigot and the surrounding socket are involved.

In the case of figures 8 and 10, the stiffness of the seal will further increase nonlinearly when the two halves of the rear portion on either side of the V-notch 12 come into contact with one another, thereby actively resisting further compression.

In the embodiments shown in figures 11 and 12, the arrangement is somewhat similar except that the resistance created upon contact between the rearward legs is I)translated into a pulling motion at the top of the seal, thereby assisting the forward leg to rotate upwardly in the desired manner. It will be appreciated that this configuration provides a supplementary mechanism for enhanced engagement between the seal and the surrounding pipe end.

With the seal shown in figure 13, the upper legs operate by a mechanism similar to that of the other seals. However, it will be seen that the underside of this version incorporates a circular profile and functions in a manner similar to that of a conventional O-ring seal. In this case, the groove in the pipe spigot would be relatively narrow in order to preserve pipe strength, but sufficiently deep to prevent rearward movement of the seal as the adjoining pipe sections engage during assembly.

In the embodiment shown in figure 15, the seal is provided with increased thickness at the base to improve the initial "bulking" of the seal upon installation, and thereby increase the retention force, without compromising the intended sealing mechanism.

In the embodiment shown in figure 18, it will be noted that the thickness of the neck region 14 has been increased, to enhanced the overall stiffness of the seal and to minimise the risk of either or both of the sealing lips or supporting portions inadvertently folding back during installation or under excess pressure conditions. In this and other WO 02/14719 PCT/AU01/01014 embodiments, it will also be observed that there is a reduction in the radius of curvature between the leagues and base of the seal. This stiffens the seal, provides more "feedback" during installation, and potentially also provides a tighter sealing arrangement.

With the seal illustrated in figure 19, the rearward leg 3 is significantly thicker and bulkier than the forward leg, so as to provide increased retention force and again to minimise the possibility of the associated lip from folding back onto itself.

It will be appreciated from the various embodiments illustrated that the overall shape, as well as the configurations of the individual constituent elements of the seal, may be adjusted and optimised to suit the particular size of the pipe, the material properties of the seal, the nature of the pipe sections to be joined, the size of the clearance between them, the pressure conditions, and other operating parameters. In particular, it should be appreciated that the bridge section and associated neck region may be substituted by other forms of connection means. The seal may, for example, incorporate a fluid or a gel able to move between the first and second portions of the seal during compression and installation. Other arrangements based on mechanical movement, fluid pressure and the like are also contemplated.

The seal according to this first aspect of the invention provides a number of important advantages. Firstly, it compresses radially far more easily than a conventional O-ring seal and therefore requires significantly less axial force on the adjoining pipe sections in order to install. At the same time, by virtue of the dual sealing rim arrangement and the synergistic interaction between them, sealing performance is substantially improved. Because the seal is pressure responsive, it can be used in relatively high pressure applications and because it is double sided, only one seal is required even in situations where the pressure within the pipe intermittently alternates WO 02/14719 PCT/AU01/01014 -16between positive and negative values. The seal does not readily foul or move out of position during installation and once installed, cannot subsequently move out of position. Because the same seal configuration can be used in virtually any application, it substantially improves production efficiency and streamlines inventory control.

Moreover, because of its asymmetrical shape, the seal cannot easily inadvertently be installed in an incorrect orientation, which substantially eliminates the risk of operator error. The seal enables a smooth, substantially flush pipe connection both internally and externally, without the need for collars, flanges or other external fittings. Not only does this produce a superior aesthetic result, also reduces inventory and manufacturing costs.

Furthermore, it substantially reduces the thickness and depth of trenches required in the case of underground pipes, which in turn substantially reduces excavation and installation costs. In all these respects, this aspect of the invention represents a practical and commercially significant improvement over the prior art.

The second aspect of the invention will now be described with particular reference to figures 20 to 26. In broad terms, this second aspect provides a mechanism to permit a limited degree of rotation between adjoining pipe sections, about an axis that is normal to the longitudinal axes of those sections.

In this context, the term "rotation" is used to describe the situation where one pipe section is coupled to another (either by means of an external collar or by means of a male spigot formed on the end of one pipe section and a complementary female recess formed in the in the corresponding end of the next pipe section), and then moving the free end of the second pipe so that an included angle is formed between the axes of the adjoining pipes. This rotational capacity is of considerable benefit in that it avoids stress concentration and accumulation in the pipe joints in situations when the pipes are not WO 02/14719 PCT/AU01/01014 -17precisely axially parallel. Stress build-up in these circumstances can eventually cause pipes to crack.

For this reason, previous attempts have been made to provide pipe joints with some degree of rotational capacity in the sense described. Typically, known systems of various types have dictated relatively large radial clearances between the male and female pipe ends in order to accommodate the desired rotation. Unfortunately, however, this constraint gives rise to significant difficulties in terms of seal location and retention during installation and assembly. Moreover, in use, it seriously compromises seal performance, reliability and longevity.

In this second aspect, which aims at least to ameliorate some of the deficiencies of the prior art, the invention provides a pipe system including a first pipe section 51 having a male end 52 and a second pipe section 53 having a female end 54 (see figures 19 to 23). The male and female ends are adapted for connection in overlapping relationship to join the pipe sections together. The connection is sealed using an angular pipe seal, which is preferably a double-acting K-seal of the type previously described (not shown for the sake of clarity in figures 20 to 26).

Referring particularly to figures 21 and 23, the male pipe end 52 incorporates a first circumferential recessed channel 60, the function of which will be described more fully below. The male pipe end also incorporates a second circumferential recess, groove or channel 61, spaced forwardly of the first channel 60 toward the proximal end of the associated pipe section 51. The second channel 61 is adapted to locate the pipe seal in an overlapping region 62 between the male and female pipe ends in the assembled configuration. The second channel is therefore essentially analogous in structure and function to the circumferential groove 25 illustrated in figures 4 to 6 in connection with the first aspect of the invention.

WO 02/14719 PCT/AU01/01014 -18- The male pipe end or spigot 52 also incorporates a circumferential parallel land between the first and second channels 60 and 61. This land represents the section of maximum external diameter of the spigot, and thereby defines a zone of minimal radial clearance in the overlapping region 62 between the male and female pipe ends. The land section is therefore the part of the male pipe end upon which the female end will primarily bear, and its diameter is as close to the internal diameter of the surrounding female pipe end as process capabilities and manufacturing tolerances will allow, while still ensuring a clearance fit.

With particular reference to figures 25 and 26, it will be appreciated that the first channel 60 is configured to permit a limited extent of relative radial displacement of the female pipe end in response to axial misalignment between the pipe sections.

Importantly, this allows the joint to accommodate a limited degree of relative rotational displacement about any axis normal to the longitudinal axes of the adjoining pipe sections. Because the parallel land section 65 is relatively short and constitutes the zone of minimal radial clearance in the overlapping region between the pipe ends, it allows this rotation to occur with minimal restriction in the manner of a pseudo "ball joint".

At the same time, the first circumferential channel or recess 60, between the land and the transitional shoulder between the spigot and the normal outer diameter of the pipe, allows the female pipe to rotate about the parallel land section, without coming into contact with the section of the spigot behind the seal (see figure 25). Without this recess, in order to accommodate the same degree of rotation, the radial clearance between the male and female pipe ends would need to be so great as to seriously compromise the performance of the seal. Thus, in contrast to previously known systems, with the channel 60 incorporated as described, the radial clearance between the male and female WO 02/14719 PCT/AU01/01014 -19pipe ends in the region of the land can be minimised or substantially eliminated, thereby contributing greatly to seal location, retention and performance.

At the same time, in order to maximise the extent of the desired rotation, a leading nose section 66 of the spigot, disposed forwardly of the second channel adjacent the outer rim, has a diameter less than that of the land, and is formed to define a tapered, frusto-conical surface 68. This surface 68 is inclined at a specified angle, predetermined so as to provide or at least approximate surface-to-surface contact between the nose section 66 of the male pipe end and the surrounding inner surface of the female pipe end.

In this way, the nose section reduces the effective length of the spigot in a rotational context, but without reducing the actual extent of overlapping engagement between the spigot and the surrounding female pipe end. Advantageously, the outer rim of the nose section is this chamfered so as to minimise contact pressure and avoid a relatively sharp spigot nip point at the limit of rotational displacement.

In essentially the same way, a chamfer 69 on the inner peripheral edge of the female pipe end minimises stress concentrations in the first channel 60 and effectively avoids a relatively sharp socket nip point at the limit of rotational displacement. -I Advantageously, the chamfer 69 also provides a tapered lead into the female recess, and interacts with the tapered and chamfered end of the male spigot, to assist in positioning of the seal, and to accommodate a greater degree of rotation and axial misalignment, during installation. This feature is particularly advantageous because in practice, contractors often attempt to insert the male pipe into the female at an angle.

The pipe is then typically rotated into an approximately parallel position, with the insertion and assembly being accomplished in effect, simultaneously. Without the tapered lead provided by a combination of the frusto-conical nose on the male spigot and the chamfer on the rim of the female socket, pipe assembly in this way is significantly PCT/AUO 1/01014 Received 01 August 2002 restricted. Consequently, the contractor must place the pipe in a position where the axes of the adjoining sections are close to parallel, and then slide the new section axially along the ground until assembly is accomplished. In most practical situations this is time-consuming, awkward, and runs the risk of introducing foreign material into the joint as the bottom edge scrapes along the ground. Although not illustrated, it will be appreciated that much of the functionality described could alternatively be achieved by forming corresponding grooves, recesses, chamfers and lands on the inner surface of the female pipe end. A complementary combination of the two approaches could also be used, to maximise the extentof relative rotation between the pipe sections.

The use of a pressure seal of the type previously described in connection with the first aspect of the invention is particularly advantageous in conjunction with the pipe connection system according to this second aspect, because the neck region of the seal, between the base and the bridge section, readily deforms resiliently to accommodate the relative rotational displacement without compromising the performance or efficiency of the seal in any way. Moreover, this seal is stably located and captively retained in its seat within the second circumferential groove, so as to minimise the likelihood of inadvertent dislocation during rotational movement between the adjoining pipe sections about a normal axis in the manner described. Nevertheless, it will be appreciated that other seal arrangements, such as O-ring and V-seals may alternatively be used.

The pipe sections may be formed from any suitable material including most plastics, metals, concretes, terracottas, FRPs and the like. In a particularly preferred embodiment of the invention, however, the pipe sections are formed from fibre reinforced concrete (FRC), and the male and female end formations, including the various grooves, channels, chamfers and lands, are moulded or machined into the corresponding WO 02/14719 PCT/AU01/01014 -21outer and inner surfaces of the respective ends of these sections. This material has been found to provide significant advantages in terms of strength, durability, versatility, impact resistance and resistance to corrosion and environmental degradation, as well as production cost.

The preferred method of fabrication whereby the spigots and sockets are integrally formed with the pipe ends is particularly well adapted for use with relatively thickwalled FRC pipes. Advantageously, this method also obviates the need for separate collars and the like around the joints, which greatly reduces assembly time, facilitates the installation procedure, and further reduces inventory and production costs. It should be appreciated, however, that the various features of the system as described could also be integrally formed by other fabrication methods suitable to the materials used for the pipes, or alternatively incorporated into collars or other supplementary fittings if required. In that sense, the first and second pipe sections incorporating the fittings and features permitting rotational engagement as defined may not necessarily be in the form of substantially identical pipe sections joined in end to end relationship, but may alternatively, for example, be in the form of a pipe section and a collar, junction or other complementary component.

In terms of application, the capacity to "rotate" one pipe relative to another is particularly useful in situations where a pipeline needs to be laid in bad soils, which include highly expansive soils such as black soil and marine silts, or in mine subsidence areas, for example. The capacity for a limited degree of pipe rotation in this sense is also of value where line deflection is needed in order to bring a pipeline around a relatively large radius comer. In such situations, pipe rotational capacity can eliminate the need for additional fittings such as bends and junctions the resultant system is therefore WO 02/14719 PCT/AUO1/01014 -22cheaper, requires fewer components, and makes use of fewerjoints, which ultimately leads to increase strength, capacity and reliability.

Rotational capacity is also of benefit where a degree of flexibility in the pipeline adjacent rigid structures is required. For example, where a pipe is joined to a rigid structure such as a revetment wall, a manhole, a pit or the like, it is of benefit if the system can rotate as the soil outside the rigid structure subsides over time, and the pipeline drops. In such circumstances, non-rotating joints are prone to failure at the Sjuncture between the pipe and the adjoining structure.

Increasing the rotational capacity of a pipe system is also advantageous in that greater rotation will facilitate shorter radius bends, and thereby allow for more versatility in application, which in turn enhances the marketability of the system. The present invention allows these various advantages to be obtained, in a system that is not inherently compromised in terms of the arrangement or performance of the pipe seals.

In all these respects, the second aspect of the invention therefore also provides both practical and commercially significant improvements over the prior art, whether used in _J conjunction with the first aspect, or independently of it.

Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that the invention in its various aspects may be embodied in many other forms.

Claims (46)

1. An annular pipe seal for sealing a connection between a male end of a first pipe section and a complementary female end of a second pipe section adjacent the first, said seal including: a base adapted for sealing engagement with a mating surface of one of said pipe section ends, said base including a plurality of closely spaced radially depending circumferentially extending sealing ribs to enhance said sealing engagement by providing a localised concentration of sealing pressure between the base and the corresponding mating surface; a first sealing portion and a second sealing portion extending from the base, the first sealing portion protruding beyond the second sealing portion, the sealing portions being interconnected such that engagement of the other of said pipe section ends with the seal compresses the first portion to form a first seal and said compression urges the 15 second portion into sealing engagement with said other of said pipe section ends to form a second seal between said one and said other of said pipe section ends.

2. A seal according to claim 1, whereby a plurality of like seals are adapted to facilitate assembly of a series of pipe sections to form an effectively continuous pipeline.

3. A seal according to claim 1 or 2 wherein the first sealing portion defines a first sealing rim and the second sealing portion defines a second sealing rim displaced axially and radially from the first rim.

4. A seal according to claim 3 including a bridge section extending between the first and the second sealing rims.

PCT/AU01/01014 Received 26 September 2002 -24- [AMENDED PAGE] A seal according to claim 4 wherein the bridge section includes a resilient connection element disposed to accommodate a limited degree of pivoted or rocking movement between the bridge section and the base.

6. A seal according to any one of the preceding claims, wherein the base portion is adapted to be captively and sealingly retained within a recessed channel or groove extending circumferentially around an outer surface of the male end of the first pipe section.

7. A seal according to claim 6, wherein a base of the groove is forwardly inclined toward the proximal end of the first pipe section at an angle of between 5 degrees and around 30 degrees with respect to the axis of the pipe, to resist axial displacement of the seal upon insertion into the female end of an adjoining pipe section.

8. A seal according to claim 6 or 7, wherein the sealing ribs are positioned for engagement with the groove or channel recessed into the outer surface of the male pipe end.

9. A seal.according to any one of claims 3 to 8, wherein the first and second sealing rims are positioned in relative axial and radial spatial relationship such that with the seal supported on the male end of the first pipe section, and upon axial engagement with the second pipe section, the female pipe end initially passes over the second sealing rim to engage the first rim at first instance.

10. A seal according to claim 9, wherein upon sliding axial engagement of the female pipe end with the first sealing rim, the first portion of the seal including the first rim begins to be compressed, and wherein in response to that compression and upon further axial insertion, the bridge section rotates or rocks relative to the base, whereby the second sealing rim is progressively urged radially outwardly into simultaneous sealing engagement with the interior surface of the surrounding female pipe end. AMIVCFnFn SHFET PCT/AU01/01014 Received 01 August 2002

11. A seal according to any one of the preceding claims, wherein the seal includes a first outwardly diverging generally V-shaped notch, extending circumferentially between the first sealing portion and the base on a first side of the seal.

12. A seal according to claim 11, wherein the seal further includes a second outwardly diverging generally V-shaped notch, extending circumnferentially between the second sealing portion and the base, on a second side of the seal.

13. A seal according to claim 12, wherein the first and second notches converge .I toward one another, to define a generally centrally disposed neck region in the seal.

14. A seal according to claim 13, wherein the neck region is adapted to facilitate the pivotal or rocking movement between the bridge section and the base, during which the first notch closes while the second notch opens, or vice versa.

A seal according to claim 14, wherein the cross-sectional profile of the seal as defined by the base, the first and second sealing rims, the V-notches and the intermediate neck region, is generally K-shaped.

16. A Seal according to any one of claims 12 to 15, wherein each of the V-notches is adapted to perform a pressure responsive function, whereby an increase in pressure on either side of the seal urges the corresponding rim and the adjacent side of the base apart with respect to one another and into enhanced sealing engagement with the adjacent pipe walls.

17. A seal according to claim 16, wherein the notches are oppositely oriented, such that the seal is pressure responsive on both sides.

18. A seal according to any one of the preceding claims, wherein the seal is formed as a unitary component, from a suitable elastomeric material selected from a group comprising rubber, silicone, polyurethane, polyethylene and nylon. A A C'F' In nr,%~ 26

19. A seal according to any one of the preceding claims, wherein the seal is formed as a composite component from multiple materials, or from similar materials of different stiffness, hardness, density, resiliency, flexibility or other material characteristics.

A seal according to any one of the preceding claims, wherein the seal is internally reinforced or externally braced.

21. A pipe system including a first pipe section having a male end and a second pipe section having a complementary female end, the male and female ends being adapted for connection in overlapping relationship to join the pipe sections together, the male end or the female end incorporating a first circumferential recessed channel disposed to permit a limited extent of relative radial displacement of the female end in response to axial misalignment between the pipe sections, thereby to accommodate a limited degree of relative rotational displacement about an axis normal to the axes of the adjoining pipe sections, and the male and female ends being integrally formed in corresponding outer and inner surfaces of respective ends of the pipe sections; wherein the male or female pipe end incorporates a second circumferential channel, spaced apart from the first channel and adapted in use to locate and captively retain a pipe seal as defined in any one of claims 1 to 20 in an overlapping region between the male and female pipe ends.

22. A pipe system according to claim 21, wherein the first channel is recessed into the male pipe end.

23. A pipe system according to claim 21 or claim 22, wherein the second channel is recessed into the male pipe end, forwardly of the first channel. PCT/AUO 1/01014 Received 26 September 2002 -27- [AMENDED PAGE]

24. A pipe section according to claim 23, wherein the male pipe end incorporates a circumferential land intermediate the first and second channels, defining a zone of minimal radial clearance between the male and female pipe ends.

A pipe system according to claim 24, wherein the circumferential land defines a point or region of relative rotation between the adjoining pipe sections about the normal axis.

26. A pipe system according to claim 25, wherein a nose section of the male pipe end disposed forwardly of the second channel has a diameter less than that of the circumferential land so as to facilitate the relative rotational displacement about the land.

27. A pipe system according to claim 26, wherein a nose section incorporates a tapered fi-usto-conical outer surface orientated to facilitate surface-to-surface contact between the male pipe end and an adjacent inner surface of the female pipe end.

28. A pipe system according to claim 27, wherein an outer rim of the nose section is chamfered, so as to minimise contact pressure and avoid a relatively sharp spigot nip point at the liihit of rotation displacement. j

29. A pipe System according to any one of claims 21 to 28, wherein an inner peripheral edge of the female pipe end is chamfered, to minimise stress concentrations in the first channel and avoid a relatively sharp socket nip point at the limit of rotational displacement.

30. A pipe system according to claim 29, wherein the chamfered peripheral edge of the female pipe end provides a tapered lead into the female recess, and thereby provides increased tolerance for rotation and axial misalignment during installing. PCT/AUO 1/01014 Received 26 September 2002 -28- [AMENDED PAGE]

31. A pipe system according to any one of claims 21 to 30, wherein the first and second pipe sections are substantially identical, with the male end in the form of a spigot at one end and the female end in the form of a complementary socket at the other end, thereby enabling a series of like sections to be joined in end to end relationship to form a pipe line..

32. A pipe system including a first pipe section having a male end and a second pipe section having a complementary female end, the male and female ends being adapted for connection in overlapping relationship to join the pipe sections together, the male end or the female end incorporating a first circumferential recessed channel disposed to permit a limited extent of relative radial displacement of the female end in response to axial misalignment between the pipe sections, thereby to accommodate a limited degree of relative rotational displacement about an axis normal to the axes of the adjoining pipe sections, the male or female pipe end incorporating a second circumferential channel, spaced apart from the first channel and locating and captively retaining a pipe seal as defined in any one of claims 1 to 20 in an overlapping region between the male and female pipe ends.

33. A pipe system according to claim 32, wherein the first channel is recessed into the male pipe end.

34. A pipe system according to claim 32 or claim 33, wherein the second channel is recessed into the male pipe end, forwardly of the first channel. A pipe section according to claim 34, wherein the male pipe end incorporates a circumferential land intermediate the first and second channels, defining a zone of minimal radial clearance between the male and female pipe ends.

AMENDED SHEET 31.0ct. 2002 13:39 PCT/AUO1/01014 Received 31 October 2002 -29- [AMENDED PAGE]

36. A pipe system according to claim 35, wherein the circumferential land defines a point or region of relative rotation between the adjoining pipe sections about the normal axis.

37. A pipe system according to claim 36, wherein a nose section of the male pipe end disposed forwardly of the second channel has a diameter less than that of the circumferential land so as to facilitate the relative rotational displacement about the land.

38. A pipe system according to claim 37, wherein a nose section incorporates a tapered J frusto-conical outer surface orientated to facilitate surface-to-surface contact between the male pipe end and an adjacent inner surface of the female pipe end.

39. A pipe system according to claim 38, wherein an outer rim of the nose section is chamfered, so as to minimise contact pressure and avoid a relatively sharp spigot nip point at the limit of rotation displacement.

A pipe system according to any one of claims 32 to 39, wherein an inner peripheral edge of the female pipe end is chamfered, to minimise stress concentrations in the first channel and avoid a relatively sharp socket nip point at the limit of rotational displacement.

41. A pipe system according to claim 40, wherein the chamfered peripheral edge of the female pipe end provides a tapered lead into the female recess, and thereby provides increased tolerance for rotation and axial misalignment during installing.

42. A pipe system according to any one of claims 32 to 41, wherein the first and second pipe sections are formed from fibre reinforced concrete, and the male and female ends are integrally formed in corresponding outer and inner surfaces of respective ends of the pipe sections.

43. A pipe system according to any one of claims 32 to 42, wherein the first and second pipe sections are substantially identical, with the male end in the form of a spigot at one end and the female end in the form of a complementary socket at the other end, thereby enabling a series of like sections to be joined in end to end relationship to form a pipe line.

44. A pipe system according to any one of claims 21 to 43, wherein the first and second pipe sections are formed of fibre reinforced concrete.

An annular pipe seal for sealing a connection between a male end of a first pipe section and a complementary female end of a second pipe section, said seal being substantially as herein described with reference to any one of the embodiments of the invention illustrated in the accompanying drawings and/or examples.

46. A pipe system being substantially as herein described with reference to any one of the embodiments of the invention illustrated in the accompanying drawings and/or examples.