Manhole lid to base connection

A manhole assembly including a base, riser, and cap. The base having an upper surface forming a bench, a bottom surface, and a radially outward surface with penetrations there through; and a radial spigot in the radially outward upper edge of the base. The base having a corrosive-resistant layer covering the channels, bench, and radial spigot. Also disclosed is a riser comprised of a corrosive-resistant polymer pipe having a radially outward surface, an inner surface and a bottom surface in contact with, supported by, and sealed to the radial spigot. The cap having a radial spigot, and access hole; the radial spigot in the radially outward bottom edge of the cap resting upon and sealed to an upper edge of the riser. The radially outward surface of the cap and base are aligned with the radially outward surface of the riser.

BACKGROUND OF THE DISCLOSURE

Field of the Disclosure

This disclosure relates to the field of manholes assemblies for access to an underground sewer system with corrosion resistant components.

BRIEF SUMMARY OF THE DISCLOSURE

Disclosed herein is a manhole assembly. The manhole assembly in one example comprising: a manhole base, riser, manhole cap, and cover assembly. The manhole base in one example comprising an aggregate main body having an upper surface forming a bench, a bottom surface, and a radially outward surface with penetrations there through; channels formed in the upper surface of the manhole base fluidly connecting the penetrations; and a radial spigot in the radially outward upper edge of the manhole base. The manhole base having a continuous corrosive-resistant layer covering the channels, bench, and radial spigot. Also disclosed in one example is a manhole riser comprised of a corrosive-resistant structural pipe having a radially outward surface, an inner surface and a bottom surface in contact with, supported by, and sealed to the radial spigot. The manhole cap in one example comprising an aggregate main body having an upper surface, a bottom surface, and a radially outward surface; a radial spigot in the radially outward bottom edge of the manhole cap; the manhole cap having a continuous corrosive-resistant covering the bottom surface, radial spigot, and access hole; the radial spigot in the radially outward bottom edge of the manhole cap resting upon and sealed to an upper edge of the manhole riser; wherein the radially outward surface of the manhole cap is aligned with the radially outward surface of the manhole riser, and the radially outward surface of the manhole base is aligned with the radially outward surface of the manhole riser.

The manhole assembly may be arranged wherein the manhole riser comprises polyvinyl chloride.

The manhole assembly may be arranged wherein the riser consists of polyvinyl chloride.

The manhole assembly may be arranged wherein the aggregate material is concrete.

The manhole assembly may be arranged wherein the manhole base has an outer diameter equivalent and substantially aligned with the outer diameter of the riser.

The manhole assembly may further comprise a wrap seal sealed to the radially outer surface of the riser and the manhole base.

The manhole assembly may be arranged wherein the manhole cap has an outer diameter equivalent and substantially aligned with the outer diameter of the riser.

The manhole assembly may further comprise a wrap seal sealed to the radially outer surface of the riser and the manhole cap.

The manhole assembly may be arranged wherein the riser is a length of straight pipe.

The manhole assembly may be arranged wherein the pipe is a monolithic structure of corrosion resistant material.

The manhole assembly may be arranged wherein a tensile lifting strut extends from the manhole cap, past the riser, to the manhole base to maintain the riser adjacent the manhole cap and the manhole base adjacent the riser.

The manhole assembly may be arranged with the lifting connector transferring lifting force in tension from the manhole cap to the manhole base to the riser.

DETAILED DESCRIPTION OF THE DISCLOSURE

Manhole casings such as disclosed in U.S. Pat. No. 1,712,510 generally comprise a bottom section (1) with a plurality of risers (7) and (8) attached thereto with a manhole cover (18) or lid attached thereto. These manholes allow for access via removal of the manhole cover (18) to a system of fluid conduits (5, 6) which are connected via the open region of the bottom section (1). The bottom sections of such manholes as shown in this example are flat and allow for undirected, horizontal flow of fluid from an inlet pipe or multiple inlet pipes to an outlet pipe.

In other applications, it may be desired to form fluid channels from the inlet pipes to the outlet pipe. Often, the radial angle, elevation, and elevation of each of the inlet pipes and outlet pipe connections to a base may be aligned prior to installation of the overall fluid system so as to allow utilization of pre-set, precast manhole bases. Many such pre-cast manhole bases can be manufactured in standard configurations such as straight through, T, cross, and other standard configurations. Such standard configurations are especially useful where the elevation angle and elevation of the inlet pipes to the outlet pipes can be preset prior to installation of the inlet pipe(s) and outlet pipe.

In some applications, such standard configuration pre-cast manhole bases are not financially viable due to the constraints placed by non-standard radial angle(s), elevation angle(s), and elevation(s) of the inlet pipes and outlet pipes. One unknown solution is to form a manhole casing with a (cylindrical) manhole having a flat (planar) floor. A volume of grout, concrete, or other aggregate material is then disposed into the manhole base and manually formed into fluid channels. The term “concrete” is used herein to define a heavy, rough building material made from a mixture of broken stone or gravel, sand, cement, and water, that can be spread or poured into molds and that forms a stone-like mass on hardening. Holes are then drilled through the cylindrical manhole base radially inward upon which couplers may be grouted or otherwise attached to the holes drilled through the manhole base at multiple angles to conform to the requirements of the installation.

A sanitary sewer is a system of underground pipes that carries sewage from bathrooms, sinks, kitchens, and other plumbing components to a wastewater treatment plant where it is filtered, treated and discharged. A storm sewer is a system designed to carry rainfall runoff and other drainage to a location where it may be treated, such as by allowing sediments to settle out before the water is discharged.

One additional detriment of sanitary sewers over storm sewers is that sanitary sewer systems are prone to corrosion chemicals which may corrode the linings and structures of many materials commonly found in the construction of manholes, such as concrete, etc.

Manhole assemblies have been found to typically experience significant interior corrosion and deterioration. Nevertheless, hydrogen sulfide, which is common in sewage, is developed due to the presence of sulfur compounds, such as sulfate, sulfite, or other inorganic or organic sulfur. These compounds are reduced to sulfide by sulfate-reducing bacteria normally found in the effluent. The generation of hydrogen sulfide is accelerated in the presence of high temperature and low flow rates.

Coatings have been applied to the inner surfaces of manhole assemblies, but have not been reliable, and are time consuming and expensive.

Linings of plastic material, such as polyvinyl chloride (PVC), applied to the inner surface of a concrete structure are known to provide corrosion resistance for interior corrosion protection against hydrogen sulfide. Such plastic linings are further compatible with plastic pipe now being used extensively in sanitary systems. To date, however, it is extremely difficult to fabricate interior linings and integrate such interior linings into vertical structures and particularly manhole assemblies. Flexible type linings are presently used in pipes covering the upper 270° of the pipe interior. This portion is attacked by the H2S generated from sewage. This flexible material is not easily used on manholes which require 360° protection for the manhole interior.

U.S. Pat. No. 4,751,799, issued Jun. 21, 1988, and U.S. Pat. No. 5,081,802, issued Jan. 21, 1992, disclose liners formed of a rigid or semi-rigid material. These liners are fabricated in sections and applied post production as a corrosive seal to the structural component which is most commonly an aggregate (concrete). The aggregate/concrete portions of this disclosed apparatus in one example conforming to ASTM C478. Generally, each liner section comprises a curved molded member which may, for example, be thermo-formed. Each molded member is provided with a means for securing the liner into the aggregate (concrete) structure. The liner sections are joined together via a bell at the upper end, and a spigot at the bottom end, these connections are generally caulked or otherwise sealed along their engaging edges. The projections of ducktail cross-section extend outwardly from the convex surfaces of the mold members which are arranged with an interior mold assembly and are either joined against the surface of an interior mold member by standard plastic banding or are alternatively joined together end-to-end by individual holding members. These assemblies have been found to lack suitable structural strength and present additional problems in their handling and assembly. In addition, the caulking material has been found to provide unsatisfactory waterproof seams within the manhole assembly structure.

One detriment of pre-cast/grouted/drilled construction methods is that due to the nature of construction, fluid may enter between the pre-cast concrete sections, causing an unsanitary situation when infiltration is not treated and potentially causing damage should the fluid expand in this gap such as by freezing thus cracking the casing, cap, and/or the cylindrical base. Disclosed herein, beginning withFIG. 1, is shown a manhole assembly20including manhole base22, cap risers, and manhole cap particularly formed using a method which allows for one-off or individual casting of the manhole base22and other components with improvements over prior construction methods. One such method is disclosed in U.S. patent application Ser. No. 15/367,121 (The '121 Application) filed on Dec. 1, 2016 incorporated herein by reference.

The manhole assembly and several methods of manufacture will be described in much more detail below, with reference to a base manufactured in one example according to the disclosure of the '121 Application.

The manhole assembly20in this disclosure includes the base22, a riser24and a manhole cap54including the cover assembly26. The cover assembly26is normally at ground level28so as to be easily accessed by personnel needing access to the fluid channels therein and fluid conduits extending therefrom. Commonly, the cover assembly26, including the removable cover30, is disposed in a roadway or sidewalk for easy access. Often, the cover assembly26with removable cover30is formed of cast iron. So as to maintain a planar upper surface with the surrounding ground level, the cover30generally fits within a recess32of an upper ring assembly34and has an upper surface coplanar or substantially coplanar with the ground lever adjacent thereto. In one installation, the upper ring assembly34is attached to or formed with one or more risers36so as to correctly position the upper surface of the cover30at ground level.

In use, the manhole assembly20is assembled within an excavation38. Once the manhole base22is installed, inlet pipe(s)40and/or an outlet pipe42may be attached to the manhole base22. The excavation38outside of the manhole assembly20is then back-filled up to the ground level28, substantially burying the manhole assembly20except normally for the cover30. Access to the interior of the manhole assembly20and components thereof may then be achieved by way of the cover30.

Also shown inFIG. 5is a plurality of fluid channels44. These channels44are commonly open-topped fluid conduits which connect inlet pipes40to the outlet pipe42and allow access thereto.

In most examples, each of the fluid channels44connects to either an inlet pipe40or outlet pipe42. Generally, each inlet pipe40and outlet pipe42is aligned with a penetration46through the manhole base22. Lateral connections may also be made through the manhole cap54, or through the riser24. As shown, one or more of the penetrations46may have a coupling such as a bell connector48and/or flexible entry boot or funnel attached thereto allowing for easy installation of an inlet pipe40or outlet pipe42. Generally, the bell connector48or funnel includes a compression seal gasket ensuring a fluid tight seal between the pipe and the channel penetration46.

As can be seen in the examples, a bench50is provided on an upper surface of the manhole base22. The bench50being substantially horizontal, in one example with a slight radial angle downwards toward the center to allow fluids thereon to flow into the fluid channel44. The bench50may be provided to distinguish individual channels, and to provide a surface upon which users can stand so as to be clear of the fluid passing though the fluid channels44. In this example, the bench50is separated into separate regions which may include a non-skid surface thereupon where a person may stand. Commonly, a user entering the manhole assembly20will stand upon the bench50during inspection and/or maintenance or cleaning of the interior surfaces and components of the manhole assembly20. Thus, a nonskid surface may be desired to reduce slippage. This non-skid surface may be formed during production of a liner as disclosed in the '121 application, or may be formed directly on the casting material in examples where no liner is used.

Disclosed in the '121 Application, the example manhole base22, risers36, and cap shown comprises a cast, aggregate wastewater manhole with a material comprising chemically resistant polypropylene (PP), polymerized vinyl chloride (PVC), high density polyethylene (HDDPE), fiberglass reinforced plastics (FRP) thermoplastic, or other corrosive-resistant material. This corrosive-resistant material forming a corrosive protective liner (CPL)52on the base22, or a CPL56on the inner surface of the cap54. In non-corrosive applications, the manhole base22may not utilize a non-corrosive liner, such as for example stormwater application. In one example, the coating thickness is in a range from 0.12″-0.20″ (3-5 mm), mechanically bonded with the concrete base, cap, or cap riser structure during the precast concrete process disclosed in the '121 Application. The term precast indicating that the disclosed manhole base22and/or other separate components are cast (formed, manufactured, produced) prior to installation at an excavation.

By casting the entire interior structure and surface of the manhole base22in one piece with a corrosive-resistant liner52, and separately casting the manhole cap54with a similar liner56, with substantially no post installation grouting of channels and/or couplers in that these components and the sealed liner are produced in the casting process, the disclosed manhole assembly20demonstrates design criteria essential for long term protection and efficient stormwater, wastewater, sewage, and other fluid transmission.

The disclosed apparatus forms a unique solution for corrosion, abrasion, exfiltration, inflow, and/or infiltration.

Several examples of the disclosed apparatus formed using the disclosed construction method also provide ease of installation. The joints between the manhole base22, riser24, manhole cap54, cap risers36, and cover assembly26may be assembled with a fluid impervious seal using a capped heated extrusion weld, butyl caulking, flexible joint seal, or other methods. Once the manhole assembly20with a manhole base22, riser24, cap54, and cover assembly26is installed it is ready to be put into service, often without any sealant cure time required. The disclosed manhole assembly20provides water-tight connections which resist settling, expansion and contraction stresses after the manhole has been installed.

Adherence to municipal design standards and allowances for inflow and infiltration (I&I) in sanitary and wastewater sewage systems can be accomplished with the disclosed manhole assembly20and production method.

The optional non-skid surfaces on the bench portions50of the disclosed manhole base22may be made of, or coved with, a corrosive-resistant, textured layer; they are safe and secure for maintenance staff in a confined, difficult working environment.

As previously disclosed, a high strength mechanical bond may be achieved by using aggregate and steel lattice or similar anchoring systems. Pipe penetrations46and optional connectors such as, for example, bell connectors48may be molded for specific installation configurations during manufacturing/casting of the manhole base22. This molding of the penetration and/or bell connector often negates the need to field core (drill) and attach ancillary connections after casting. Installation time and costs are substantially reduced by molding the connections into the manhole base22.

In one example production method as disclosed in the '121 application, concrete or other casting material is poured around a pre-formed corrosive-resistant liner and male mold assembly while the liner and male form of the manhole base22is in an inverted position; the cap54and cap risers36may be made by the same process, in an upright orientation when cast. In one example the casting exceeds a minimum 4000 P.S.I. casting. In one example, a high-strength mechanical bond between the corrosive-resistant liner and concrete is achieved by way of a well-proven interface consisting of specifically-sized clean aggregate and steel coil/lattice bonded to the bottom of the liner. With vibrated concrete attaching itself to this continuous multi-faceted bonding medium, intruding forces of groundwater backpressure is not of concern.

The disclosed manhole base22with an optional liner is a component of a manhole base assembly20for new manhole construction or for manhole rehabilitation. Microbial induced corrosion (MIC) has been increasingly evident in concrete manhole casings and related sanitary sewer structures for decades. MIC occurs when sulfuric acid, generated from raw sewage, reacts with the properties of cement to diminish the integrity of concrete manhole bases and related structures.

Hydrogen sulfide (H2S), in anaerobic and aerobic forms, has the capacity to severely damage concrete components. Prior to 1980, heavy metals in wastewater retarded the growth of bacteria in sewer systems, minimizing MIC. Since the US Clean Water Act (1980) mandated the elimination of certain toxic heavy metals—lead, chromium, mercury, arsenic, cadmium—from wastewater, effluent MIC has reached acute levels in sanitary and wastewater sewage systems; these heavy metals are toxic to humans and other life forms, including bacteria. Now, bacterial colonies flourish and assist with the generation of H2S gas and, with oxidation, H2SO4. Acidic deterioration of sanitary sewer pipelines and manholes has increased substantially. Coating systems that once protected concrete structures are known to fail. Splash and turbulent water flow exacerbate the destructive effect on concrete manholes. More aggressive corrosion can be expected when septic conditions exist, which may also result in leaking pipe connections. Other contributing factors, such as drop connections or a large number of entry points introduced into the structure, create more acid corrosion problems.

The disclosed method and manhole assembly20improves resistance to MIC by removing any gaps between the channel body and the outer wall. The optional gapless liner covering the channel body of the base, utilizing a riser24with no concrete or similar composition also improves resistance to MIC.

These new conditions require revised design parameters for many components in the sewage transmission system, including manholes. Liner material, such as fiberglass reinforced plastic (FRP) and polypropylene (PP), can be applied to newly poured concrete to provide a dense, impervious and continuous corrosive-resistant lining for the manhole base22, cap54, and/or cap risers36to protect the concrete substrate from destructive acid attack. This deteriorated concrete condition can be prevented in one example with thermoplastic barriers that isolate the sewage from the concrete components of the manhole assembly20, or using non-concrete materials.

As evidenced by the anaerobic process, the eventual disintegration of the concrete components of a manhole assembly20is often the result of a hydrogen sulfide attack. More aggressive corrosion can be expected when septic conditions exist, which may also result in leaking pipe connections. Other contributing factors, such as drop connections or a large number of entry points introduced into the structure, create more acid corrosion problems.

The disclosed manhole base20and construction method ensures complete coverage of the channel body, and gapless attachment of the liner to the concrete casting.

Looking toFIGS. 1, 2, and 4are shown cross-sectional views of a manhole assembly20using the disclosed apparatus. In this example, the manhole base22has a radial recess or spigot58in the upper, radially outward edge thereof. This spigot58having a substantially vertical surface60and a horizontal surface62cooperating to form the spigot58for receiving the riser24. In one example, the surface60is tapered inward to allow for easier connection to the riser24. In one example the taper is between 1° and 5°. The riser24resting solely on the bottom surface62of the spigot58and not engaging the upper surface50. In one example an ASTM C443-compliant gasket66is applied between the radially inner surface64of the riser24and the vertical surface60of the spigot58. In one example a Hamilton Kent Tylox™ Type “C” gasket model #5796 is used as the gasket66. In another example, an ASTM C990 “Mastic” joint may be utilized instead of or in combination with a gasket66.

One additional advantage of using a spigot58on the base22, and a spigot80on the cap54is that such large diameter pipes forming the riser24are generally cylindrical and often not perfectly cylindrical. Deformation may occur during manufacture, during cooling, transport, and/or storage. The disclosed apparatus allows for easy attachment of the base22, riser24, and cap54and the riser will be pressed back into a cylinder at the connection ends by the spigots58/80. In examples using an angled spigot, as shown in the example ofFIG. 4B, this is even more easily accomplished. In the example shown, the angle110between the inner surface of the riser and the vertical surface60of the spigot may be between 1° and 10°. In one example and angle of between 2° and 5°. This may also be achieved by chamfering the inner surface or bottom inner edge112of the riser24as also shown inFIG. 4.

In addition, a seal68may be used between the longitudinally bottom edge70of the riser24and the bottom surface62of the spigot58. This seal68may be a fluid component such as grout, fluid silicone, mastic, etc., or a manufacture's seal such as rubber tape, rolling tube seal, etc.

The disclosed connection between the riser24and the manhole base22in one example provides for a smooth outer surface transition between the base22and the riser24which allows for the use of an ASTM C877-compliant external joint wrap72which seals to the outer surface of the base22and the riser24, hindering fluid passage. The joint wrap72extends circumferentially around the base22and the riser24sealing the outer surfaces of the two components. The joint wrap72may be tape, polymer films, silicone, hardening fluids, resin impregnated fabrics, and combinations thereof. Looking toFIG. 2for example, it can be seen that the radially outward surface76of the riser24is aligned with the radially outward surface78of the manhole base24. Prior known installations using a bell on the base required a larger outer diameter on the base than the riser, commonly precluding application of an external joint wrap72.

In one example, the manhole base22is cast of steel reinforced, cast monolithic with an integral corrosion resistant liner. In one example the liner is corrosion resistant, for example resin hardened fiberglass. In one example the manhole base22incorporates compression gasket pipe connections which are ASTM C923-compliant.

In one example, no structure is required outside of the pipe's OD, thus the overall outside diameter of the manhole assembly20relative to known assemblies using a bell on the base and/or cap is reduced from 58″ to 51″ for a common 48″ ID Manhole. This represents a 23% reduction in footprint, translating directly into less concrete required to construct the manhole assembly.

Commonly, PVC manhole riser pipe comes from the manufacturer in 22′ lengths, meaning that up to a 25′ deep MH can be constructed with a Base (˜1.5′), Riser (< or =22′), and cover assembly26with hat96+cover30(˜1.5′). Such PVC pipe can be ordered in lengths greater than 22′ if required for a deeper manhole than 25′ (which is 95% of all manholes).

48″ precast concrete manhole risers weigh ˜800# per vertical foot. Typically they are manufactured in 1′ increments up to 4′ and are stacked one on top of the other in the field to achieve the desired height (depth). Each joint requires extra sealant, labor & materials, and is a potential source of infiltration or exfiltration. Typical precast manholes have 3 or more joints, where the manhole assembly20disclosed herein has only 2.

48″ PVC MH Risers weigh approximately 110 pounds per vertical foot. Typically manufactured in 22′ lengths and are cut to length in the field to achieve the desired height (depth). Typical PVC manholes only have 2 joints, reducing labor, materials, and infiltration/exfiltration points.

Similarly, an internal seal74may be added, such as grout, silicone, polymers, or other materials added after connection of the riser24to the inner surfaces of the riser24and the inner surface of the manhole base22.

FIGS. 1, 2, and 3show a similar attachment of the manhole cap54to the riser24where the manhole cap54comprises a radially outer and vertically lower edge forming a spigot80having a radially inner surface82facing the inner surface64of the riser24and an upper surface84resting on the longitudinal end86of the riser24. Thus, the entire weight of the cap54rests on the end surface of the riser24and no bell is required.

In one example an ASTM C443-compliant gasket88is applied between the radially inner surface64of the riser24and the vertical surface82of the spigot80. In one example a Hamilton Kent Tylox™ Type “C” gasket model #5796 is used as the gasket88. In another example, an ASTM C990 “Mastic” joint may be utilized instead of or in combination with a gasket88.

Where the fluid level in the fluid channels44is unlikely to rise to the level of the spigot82, the gasket88may be omitted.

As with the connection between the manhole base22and the riser24, the connection between the manhole cap54and the riser24may be sealed with a seal90positioned used between the longitudinally upper edge86of the riser24and the surface84of the spigot80. This seal90may be a fluid component such as grout, fluid silicone, mastic, etc., or a manufacture's seal such as rubber tape, rolling tube seal, etc.

The disclosed connection between the riser24and the manhole cap54in one example provides for a smooth outer surface transition between the manhole cap54and the riser24which allows for the use of an ASTM C877-compliant external joint wrap92sealing to each of the manhole cap54and the riser24, hindering fluid passage. The joint wrap92extends circumferentially around the cap54and the riser24sealing the outer surfaces of the two components. The joint wrap92may be tape, polymer films, silicone, hardening fluids, resin impregnated fabrics, and combinations thereof. Looking toFIG. 2for example, it can be seen that the radially outward surface76of the riser24is aligned with the radially outward surface94of the manhole cap54. Prior known installations using a bell on the manhole cap required a larger outer diameter on the manhole cap than the riser, commonly precluding application of an external joint wrap92.

In one example, the riser24is a length of straight pipe formed of a corrosive-resistant material. Such pipes generally coming in straight lengths using additional connectors, or a bell/spigot pipe having a bell connector on one end and a spigot on the opposing end. By utilizing a straight pipe, with spigots on each of the base and cap, the bell may be omitted from the pipe. The riser24may comprise chemically resistant polypropylene (PP), polymerized vinyl chloride (PVC), high density polyethylene (HDDPE), steel, lined steel, stainless steel, copper. brass, fiberglass reinforced plastics (FRP) thermoplastic, or other corrosive-resistant material with similar load bearing (structural) characteristics. In one example the riser is monolithic, consisting of one unbroken, unsegmented material. By so forming the manhole assembly20with a monolithic riser24, the outer diameter, weight, and other benefits are accomplished.

In addition, root intrusion is reduced in that joints between riser sections are eliminated. In one example, the main joints are first between the manhole cap54and the riser24, and second between the riser24and the manhole base22.

One significant advantage of this over other known installations, such as that utilized by the Ipex™ company, is the use of the spigot58on the base, and a similar spigot80on the manhole cap54whereas the prior art has utilized a bell on the base and a bell on the cap, thus sealing the base and the cap to the outer radial surface of the riser sections. The Ipex™ application thus requiring a larger excavation, larger/heavier/more difficult to install or transport manhole base and cap.

In one example, the gaskets66and82are secured to the manhole base22and manhole cap54prior to connection to the riser24.

Testing has shown that the wraps72/92are sufficient for sealing the components, and the gaskets66,82,68, and90are not required for sealing of the manhole assembly20. In some jurisdictions, such gaskets are legally required. In one example, the gaskets66,82,68, and90extend circumferentially about the components between which they seal.

FIGS. 1, 2, 3, and 6also show additional components of the manhole assembly20. These including a sliding or telescoping access collar or (hat)96. The sliding hat96positionably engaging a surface defining an access hole98of the manhole cap54. The access hole98extending through the manhole cap54, hat96, risers36, and cover assembly26. The cover30closing the access hole98from undesired entry.

In the example shown, the hat96comprises a cylinder100and a radially protruding rim102. The rim102resting on the manhole cap54, or on a riser36when risers are used. The cover assembly26resting above the rim102and in some applications attached thereto.

The cylinder100having a radially inward surface providing part of the access hole98, and a radially outward surface106adjacent to or in contact with a radially inward surface104of the hat96. This arrangement allowing for vertical positioning of the hat96relative to the manhole cap54and allowing for risers36and vertical adjustment thereof such as by application of spacers, grout, etc. to raise the cover assembly26to the ground level28as previously discussed.

In one example, a gasket108is attached to the inner surface98of the manhole cap54and sealed to the outer surface106of the hat96. This providing a sliding seal between the hat96and the, manhole cap54hindering fluid there past.

FIG. 2also shows a plurality of lifting components114cast into the manhole base22and manhole cap54. These lifting components114may be substantially equivalent to those disclosed in U.S. Pat. No. 3,499,676 incorporated herein by reference. These lifting components114allow the manhole base22and manhole cap54to be independently lifted, carried, and stored without impact damage to manhole base22or manhole cap54.

In the example shown inFIG. 2, andFIG. 5, the lifting studs114(114a-114c) protrude outward from the manhole base22and manhole cap54. This is to allow easy attachment of lifting devices such as chains, ropes, straps, cables, connectors etc. Thus, in one example a lifting connector116having a first end118attached to a lifting stud114of the manhole cap54and a second end120attached to a lifting stud114of the manhole base22. As the lifting studs114of the manhole cap54are attached to a lifting device and raised, the lifting connector116is put in tension and transmits the lifting force to the manhole base22. Thus as the manhole cap54is lifted, the riser24and manhole base22are also lifted.

In one example, the lifting connector116is a length of rigid material. In one example the lifting connector116is a length of metal. In one example the lifting connector116is a length of U-channel.

To facilitate attachment of each lifting connector116to the manhole base22and manhole cap54the lifting connector may have surfaces defining holes122there though at the first end118and the second end120. A portion of a bolt, protrusion, or the lifting studs114pass through the surfaces defining holes122and maintain the lifting connector116in position and allow transference of the lifting force.

In one example, the lifting studs114have a male threaded end, threaded into a female threaded insert within the manhole base22and/or manhole cap54. Thus, the lifting studs114pass through the holes122and are threaded into the female receivers. In one example, the female receivers are cast into the manhole base22and/or manhole cap54.

The lifting connectors116also providing structural support to the manhole assembly20by securing the base, riser, and cap in relative position. In several environmental conditions, such a structural connection is particularly useful. First; where there is a condition of high ground water, the components may tend to “float” or reposition and thus become detached. Second; earth movement (e.g. earthquake) may cause the components to become detached without some structural connection. Third; when the surrounding ground freezes, causing “frost heave” may cause the components to become detached.

In addition, the listing connectors116may intermittently or consistently provide compression strength to the manhole assembly20. For example, a heavy vehicle driving over the manhole assembly20in the ground may impart a substantial compression load on the riser24. The lifting connectors116in such a situation will resist compression and provide compression strength to the manhole assembly20.

The following definitions are used in this disclosure:

Bell and Spigot: A connection between two sections of pipe, or between a pipe and a connector, or between two fluid connectors. The straight “spigot” end of one section is inserted in the flared-out “bell” end of the adjoining section; the joint is sealed by a caulking compound or with a compressible ring.

Bell: a pipe connection having an inner radial surface which is larger in diameter than the inner radial surface of the adjacent portion of the connection. The radial outer surface of a pipe or connector has an outer end surface which contacts the inner radial surface of the bell and forms a fluid connection thereto.

Spigot: a pipe connection having an outer radial surface which fits into an inner radial surface “bell” of a connecting fluid conduit and forms a fluid connection thereto.

Tapered: to diminish or reduce in thickness toward one end.

Aggregate: any of various loose, particulate materials, as sand, gravel, or pebbles, added to a cementing agent to make concrete, plaster, etc.

While the present invention is illustrated by description of several embodiments and while the illustrative embodiments are described in detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications within the scope of the appended claims will readily appear to those sufficed in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of applicants' general concept.