U.S. patent application number 10/227903 was filed with the patent office on 2004-03-04 for molded manhole unit.
Invention is credited to Airheart, Michael.
Application Number | 20040040221 10/227903 |
Document ID | / |
Family ID | 31975999 |
Filed Date | 2004-03-04 |
United States Patent
Application |
20040040221 |
Kind Code |
A1 |
Airheart, Michael |
March 4, 2004 |
Molded manhole unit
Abstract
A corrosion resistant manhole unit having a rotationally molded
plastic manifold forming a hollow chamber for providing access to
sewer pipes to be connected to the manifold. A manifold inlet
connector molded into the manifold for connecting the manifold to
an upstream conduit and allowing an inflow of fluid to the hollow
chamber. A manifold outlet connector molded into the manifold for
connecting the manifold to a downstream conduit so that fluid flows
out of the hollow chamber. A manifold riser molded atop the
manifold having an open top forming an aperture for accessing the
hollow chamber. The manifold riser extending upward from the
manifold towards ground level for allowing equipment and personnel
to access the hollow chamber through the aperture. A watertight
removable riser cap is included for sealing the top of the riser to
close and prevent fluid and debris from entering or leaving the
manifold.
Inventors: |
Airheart, Michael; (Lyman,
SC) |
Correspondence
Address: |
MCNAIR LAW FIRM
P.O. BOX 10827
GREENVILLE
SC
29603-0827
US
|
Family ID: |
31975999 |
Appl. No.: |
10/227903 |
Filed: |
August 26, 2002 |
Current U.S.
Class: |
52/20 ; 220/220;
404/25 |
Current CPC
Class: |
E02D 29/12 20130101;
E02D 29/124 20130101 |
Class at
Publication: |
052/020 ;
404/025; 220/220 |
International
Class: |
E02D 029/14; B65D
088/40 |
Claims
What is claimed is:
1. A single-piece corrosion resistant manhole unit for placement
underground to connect with a conduit system in a watertight manner
and provide access to the conduits for inspection, maintenance, and
repair, said manhole comprising: a rotationally molded polyethylene
manifold forming a hollow chamber for providing access to conduits
to be connected to said manifold; a plurality of lateral manifold
extensions molded into said manifold for connecting to said
conduits to facilitate the flow of fluids through the hollow
chamber; at least one manifold inlet connector included in said
manifold extensions for connecting the manifold to an upstream
conduit spigot and allowing an inflow of fluid to said hollow
chamber; a manifold outlet connector included in said manifold
extensions for connecting the manifold to a downstream conduit bell
and allowing fluid to flow out of said hollow chamber; and, a
manifold riser molded atop said manifold and extending upward from
said manifold towards ground level for allowing equipment and
personnel to access said hollow chamber; whereby a cost effective,
lightweight, and corrosion resistant manhole is provided that can
be quickly and easily installed with watertight seals to reduce the
problems of overflow and surcharge associated with leaking
conduits.
2. The manhole unit of claim 1 including a plurality of reinforcing
ribs molded into said manifold; said reinforcing ribs protruding
from the manifold to increase the structural integrity of the
manifold to withstand external pressures applied to the manifold
when buried underground.
3. The manhole unit of claim 1 including a fluid channel molded
into said manifold between said manifold inlet and outlet
connectors for channeling fluid through said hollow chamber.
4. The manhole unit of claim 3 wherein said fluid channel is
declined to form a downward gradient through said hollow chamber
from said inlet connector to said outlet connector so that fluid is
caused to flow through the hollow chamber in the fluid channel and
continues through the conduit system.
5. The manhole unit of claim 1 wherein said manifold inlet
connector includes an annular seal for sealing between said
manifold inlet connector and said upstream conduit spigot; said
annular seal conforming to surface variations in the shape of said
conduit spigot to form a watertight connection;
6. The manhole unit of claim 5 wherein said annular seal is carried
on an interior side of said manifold inlet connector so that the
annular seal is protected from exposure to environmental corrosive
agents surrounding the conduits.
7. The manhole unit of claim 6 including a seating groove molded
into said interior side of said manifold inlet connector for
receiving said annular seal; said seating groove restricting the
seal from moving when said downstream conduit spigot is slid into
said manifold inlet connector and contacts the seal to form the
watertight connection.
8. The manhole unit of claim 1 wherein said manifold outlet
connector includes a beveled spigot edge at a distal end of said
outlet connector; said beveled spigot edge reducing the thickness
of the distal end of the outlet connector for engaging a seal
member carried by said downstream conduit bell and allowing the
seal member to easily slide over said beveled spigot edge to move
into position around the outlet connector and form a watertight
connection.
9. The manhole unit of claim 1 including a riser extension for
connecting with said manifold riser; said riser extension receiving
said manifold riser to extending the height of said manifold riser
to ground level when buried underground, so that access to said
hollow chamber can be maintained at ground level when the manifold
riser is of insufficient height to reach ground level.
10. The manhole unit of claim 9 including a sealing ring carried by
said riser extension for sealing between said manifold riser and
said riser extension; said sealing ring conforming to surface
variation in the shape of said riser to provide a watertight
connection between said manifold riser and said riser
extension.
11. The manhole unit of claim 10 wherein said sealing ring is
carried on an interior side of said riser extension so that the
sealing ring is protected from exposure to environmental corrosive
agents surrounding the riser extension.
12. The manhole unit of claim 10 wherein said sealing ring includes
a hollow deformable o-ring for compressing against said manifold
riser and forming to the surface shape of said manifold riser to
provide the watertight connection.
13. The manhole unit of claim 10 wherein said manifold riser
includes a beveled riser edge at a distal end of said manifold
riser; said beveled riser edge reducing the thickness of the distal
end of the riser for engaging said sealing ring and allowing the
sealing ring to easily slide over said beveled riser edge to move
into position around the riser and form a watertight
connection.
14. The manhole unit of claim 1 including a removable riser cap for
sealing the manifold riser closed to prevent fluid and debris from
entering or leaving the manifold.
15. The manhole unit of claim 14 including an adaptive seal carried
by said removable riser cap for sealing between said cap and said
manifold riser; said adaptive seal conforming to surface variation
in the shape of said riser to provide a watertight connection
between said manifold riser and said cap.
16. The manhole unit of claim 15 wherein said adaptive seal
includes a hollow deformable o-ring for compressing against said
manifold riser and conforming to the surface shape of the manifold
riser to provide the watertight connection.
17. The manhole unit of claim 14 including a pressure release valve
disposed within said removable riser cap for venting built-up gases
from said hollow chamber.
18. The manhole unit of claim 14 including a vacuum ventilation
valve disposed within said removable riser cap for allowing excess
gases formed in said hollow chamber to be vacuumed out before
attempting to remove said removable riser cap.
19. A corrosion resistant manhole unit for placement underground to
connect with conduits of a sewage system, and the like, in a
watertight manner and provide access to the conduits for
inspection, maintenance, and repair, said manhole comprising: a
molded plastic manifold having a hollow chamber for providing
access to sewage system conduits to be connected to said manifold;
a bell inlet connector extending laterally from said manifold for
connecting the manifold to an upstream sewage conduit to facilitate
the flow of sewage into said manifold; an annular seal carried by
said bell inlet connector for forming a watertight seal between
said bell and said upstream sewage conduit; a spigot outlet
connector extending laterally from said manifold for connecting the
manifold to a downstream sewage conduit to allow sewage to flow out
of the manifold; and, a fluid channel molded into said manifold
between said bell inlet and spigot outlet connectors for channeling
sewage through said hollow chamber; whereby a cost effective,
lightweight, and corrosion resistant manhole is provided that can
be quickly and easily installed with watertight seals to reduce the
problems of overflow and surcharge associated with leaking
conduits.
20. The manhole unit of claim 19 wherein said fluid channel is
declined to form a downward gradient through said hollow chamber
from said bell inlet connector to said spigot outlet connector so
that fluid is caused to flow through the hollow chamber in the
fluid channel and continues through the sewage system.
21. The manhole unit of claim 19 wherein said annular seal is
carried on an interior side of said bell so that the annular seal
is protected from exposure to environmental corrosive agents
surrounding the sewage system conduits.
22. The manhole unit of claim 21 including a seating groove molded
into said interior side of said bell inlet connector for receiving
said annular seal; said seating groove restricting the seal from
moving when said upstream sewage conduit is slid into said bell and
contacts the seal to for a watertight connection.
23. The manhole unit of claim 19 wherein said spigot outlet
connector includes a beveled spigot edge at a distal end of said
spigot; said beveled spigot edge reducing the thickness of the
distal end of the outlet connector for engaging a seal member
carried by said downstream conduit and allowing the seal member to
easily slide over said beveled spigot edge to move into position
around the spigot and form a watertight connection.
24. A corrosion resistant manhole unit for placement underground to
connect with a conduit system in a watertight manner and provide
access to the conduits for inspection, maintenance, and repair,
said manhole comprising: a molded plastic manifold forming a hollow
chamber for providing access to conduits to be connected to said
manifold; a manifold inlet connector molded into said manifold for
connecting the manifold to an upstream conduit and allowing an
inflow of fluid to said hollow chamber; a manifold outlet connector
molded into said manifold for connecting the manifold to a
downstream conduit so that fluid flows out of said hollow chamber;
a manifold riser carried atop said manifold having an open top
forming an aperture for accessing said hollow chamber, said
manifold riser extending upward from said manifold towards ground
level for allowing equipment and personnel to access said hollow
chamber through said aperture; and, a removable riser cap for
sealing the top of said riser to close and prevent fluid and debris
from entering or leaving the manifold; whereby a cost effective,
lightweight, and corrosion resistant manhole is provided that can
be quickly and easily installed with watertight seals to reduce the
problems of overflow and surcharge associated with leaking
conduits.
25. The manhole unit of claim 24 including a riser extension for
connecting with said manifold riser; said riser extension receiving
said manifold riser to extending the height of said manifold riser
to ground level when buried underground, so that access to said
hollow chamber can be maintained at ground level when the manifold
riser is of insufficient height to reach ground level.
26. The manhole unit of claim 25 including a sealing ring carried
by said riser extension for sealing between said manifold riser and
said riser extension; said sealing ring conforming to surface
variation in the shape of said riser to provide a watertight
connection between said manifold riser and said riser
extension.
27. The manhole unit of claim 26 wherein said sealing ring is
carried on an interior side of said riser extension so that the
sealing ring is protected from exposure to environmental corrosive
agents surrounding the riser extension.
28. The manhole unit of claim 26 wherein said sealing ring includes
a hollow deformable o-ring for compressing against said manifold
riser and forming to the surface shape of said manifold riser to
provide the watertight connection.
29. The manhole unit of claim 26 wherein said manifold riser
includes a beveled riser edge at a distal end of said manifold
riser; said beveled riser edge reducing the thickness of the distal
end of the riser for engaging said sealing ring and allowing the
sealing ring to easily slide over said beveled riser edge to move
into position around the riser and form a watertight
connection.
30. The manhole unit of claim 24 wherein said manifold riser is
molded with said manifold as a single unit.
31. The manhole unit of claim 24 including an adaptive seal carried
by said removable riser cap for sealing between said cap and said
manifold riser; said adaptive seal conforming to surface variation
in the shape of said riser to provide a watertight connection
between said manifold riser and said cap.
32. The manhole unit of claim 31 wherein said adaptive seal
includes a hollow deformable o-ring for compressing against said
manifold riser and conforming to the surface shape of the manifold
riser to provide the watertight connection.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to manhole structures, and the
like, for gaining access to underground facilities such as sewers,
pipelines, valves, etc, in order to inspection, repair, and
maintenance the facilities. More particularly, the present
invention relates to a single-piece, rotationally molded
polyethylene manhole unit that incorporates a bell inlet connector
and spigot outlet connector for quick and reliable watertight seals
without external rubber sleeve seals.
BACKGROUND OF THE INVENTION
[0002] In the construction of underground water and sewer
facilities, it is a standard practice to place a series of manholes
at regular intervals to provide access to the pipelines for
inspection, repair, and maintenance. Most often, these manholes are
constructed of concrete shaped into a cone or similar configuration
of sufficient size to allow cleaning equipment, or even an entire
person, to enter the manhole.
[0003] Typically, the concrete manholes are made from prefabricated
sections, which are assembled at the plant or on site. However, the
assembly of these manholes requires a substantial mount of time,
labor and equipment due to the substantial weight of the preformed
concrete sections. Additionally, because the concrete is not easily
machines or prefabricated with precision, it is difficult to fit
the concrete manholes to existing pipelines without leaks.
Unfortunately, leakage represents a significant problem to closed
water and sewer systems because silt and other contaminates find
their way into the manholes and pipes, eventually building-up and
interfere in the operation of the sewer and water systems by
causing the systems to overflow or produce a surcharge of
wastewater at the treatment facilities. In order to prevent leaks,
it is common to use flexible rubber boots or sleeves attached
around the outside of the pipe connections. Over time, however,
because these rubber boot seals are disposed around the outside of
the pipes, they are overly exposed to the elements and are easily
corroded, which ultimately causes the seals to fail and cause
leaks. Additionally, the concrete manholes themselves crack and
split due to environmental conditions and corrosive agents in the
system that disintegrate the concrete, allowing additional
contaminants into the system.
[0004] In order to combat the corrosive agents affecting manholes,
U.S. Pat. No. 3,745,738 discloses a corrosion resistant manhole
formed from concrete and lined with glass-reinforced polyester. The
manhole is formed through a labor intensive, time consuming and
expensive process of pouring concrete around the glass-reinforced
polyester lining and allowing the concrete to harden. Given today's
extremely strong and durable advanced composite materials, it is
unnecessary to perform such a complicated operation to provide a
strong and corrosion resistant manhole. Additionally, there is no
disclosure for improving the method of sealing the sewer pipes to
the manhole to prevent corrosion of the seals. Accordingly, a more
cost effective manhole with a simplified installation process that
provides a durable watertight seal is needed.
[0005] U.S. Pat. No. 5,361,799 sought to improve on the manhole by
providing a watertight wastewater access fitting formed from
preformed plastic, which is inexpensive and essentially impervious
to corrosive chemical agents found in sewer systems. However, this
manhole still uses the external rubber sleeve seals around the
exterior of the sewer pipes and fails to address the problem of
preventing leaks caused by corrosion of the seals. Additionally,
the manhole fails to include any reinforcing structures to
strengthen the structural integrity of the manhole sufficient to
expose the manhole to the pressures applied deep underground and
therefore is of limited use and unsafe for persons to enter.
Accordingly, there is a need for a watertight reinforced corrosion
resistant manhole that does not require an external rubber seal to
connect pipes and can maintain its structural integrity when buried
deep underground.
[0006] Therefore, it is an object of the present invention to
provide a molded plastic manhole unit having reinforcing structural
members for strengthening the manhole to withstand external
pressures applied against the manhole when buried underground.
[0007] It is an object of the present invention to provide a molded
plastic manhole unit having watertight seals protected from
overexposure to corrosive agents surrounding the pipes so that the
integrity of the seals is maintained to prevent overflow and
surcharge caused by leaks.
[0008] It is an object of the present invention to provide a molded
plastic manhole unit resistant to the corrosive effects of acids
and other corrosive chemical agents present in sewage system
pipelines.
[0009] It is an object of the present invention to provide a molded
plastic manhole unit incorporating a riser extending to ground
level to provide access to the manhole interior for the inspection,
maintenance and repair of the sewer pipes.
SUMMARY OF THE INVENTION
[0010] The above objectives are accomplished according to the
present invention by providing a single-piece corrosion resistant
manhole unit for placement underground to connect with a conduit
system in a watertight manner and provide access to the conduits
for inspection, maintenance, and repair.
[0011] The manhole comprises a rotationally molded polyethylene
manifold forming a hollow chamber for providing access to conduits
to be connected to the manifold. In the preferred embodiment, the
manifold includes a plurality of lateral manifold extensions molded
into the manifold for connecting to the conduits to facilitate the
flow of fluids through the hollow chamber. A manifold inlet
connector is included in the manifold extensions for connecting the
manifold to an upstream conduit spigot for allowing an inflow of
fluid to the hollow chamber. A manifold outlet connector is
included in the manifold extensions for connecting the manifold to
a downstream conduit bell for allowing fluid to flow out of the
hollow chamber. Additionally, a manifold riser is molded atop the
manifold and extends upward from the manifold towards ground level
for allowing equipment and personnel to access the hollow chamber.
A removable riser cap is included for sealing the top of the riser
to close and prevent fluid and debris from entering or leaving the
manifold. As a results, a cost effective, lightweight, and
corrosion resistant manhole is provided that can be quickly and
easily installed with watertight seals to reduce the problems of
overflow and surcharge associated with leaking conduits.
[0012] In a further advantageous embodiment, the manhole unit
includes manifold reinforcing elements formed into the manifold
during the rotational molding process for increasing the structural
integrity of the manifold. Preferably, the manifold supports are a
plurality of reinforcing ribs protruding from the sides and bottom
of the manifold. The ribs reinforce the hollow chamber to withstand
external pressures applied to the manifold when buried
underground.
[0013] In the preferred embodiment, the manhole unit includes a
fluid channel molded into the manifold between the manifold inlet
connector and manifold outlet connector for channeling fluid
through the hollow chamber. The fluid channel is declined to form a
downward gradient through the hollow chamber from the manifold
inlet connector to the manifold outlet connector so that fluid is
caused to flow through the hollow chamber in the fluid channel and
continue through the conduit system.
[0014] Preferably, the manifold inlet connector includes an annular
seal for sealing between the manifold inlet connector and upstream
conduit spigot. The annular seal conforms to surface variations in
the shape of the conduit spigot to form a watertight connection.
Advantageously, the annular seal is carried on an interior side of
the manifold inlet connector so that the annular seal is protected
from exposure to environmental corrosive agents surrounding the
conduits.
[0015] In the preferred embodiment, the manhole unit includes a
riser extension for connecting with the manifold riser. The riser
extension receives the manifold riser to extending the height of
the manifold riser to ground level when buried underground so that
access to the hollow chamber can be maintained at ground level when
the manifold riser is of insufficient height. A sealing ring is
carried by the riser extension for forming a watertight connection
between the manifold riser and the riser extension. The sealing
ring is carried on an interior side of the riser extension so that
it is not exposed to environmental corrosive agents surrounding the
outside of the conduits.
[0016] Preferably, an adaptive seal is also carried by the
removable riser cap for conforming to surface variations in the
shape of the manifold riser to provide a watertight connection
between the riser and the removable riser cap.
[0017] In a further advantageous embodiment, a pressure release
valve is disposed within the removable riser cap for venting
built-up gases from the hollow chamber. Additionally, a vacuum
ventilation valve may also be disposed within the removable riser
cap for vacuuming out any excess gases formed in the hollow chamber
before attempting to remove the removable riser cap.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The construction designed to carry out the invention will
hereinafter be described, together with other features thereof. The
invention will be more readily understood from a reading of the
following specification and by reference to the accompanying
drawings forming a part thereof, wherein an example of the
invention is shown and wherein:
[0019] FIG. 1 is a perspective view of the manhole unit according
to the invention;
[0020] FIG. 2 is a bottom view of the manhole unit according to the
invention;
[0021] FIG. 3 is a top view of the manhole unit according to the
invention;
[0022] FIG. 4 is an exploded view of the manifold inlet connector
according to the invention;
[0023] FIG. 5 is a top view of the removable riser cap according to
the invention;
[0024] FIG. 6 is a side view of the removable riser cap according
to the invention;
[0025] FIG. 7 is a cross-section view of the removable riser cap
according to the invention;
[0026] FIG. 8 is a top view of a manhole unit having a plurality of
manifold inlets according to the invention; and
[0027] FIG. 9 is a perspective view of the manhole unit connected
to a riser extension for raising the manifold riser to ground level
according to the invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0028] Referring now to the drawings, the invention will be
described in more detail. Referring to FIG. 1, a single-piece
corrosion resistant manhole unit, designated generally as A, is
shown for placement underground to connect with a conduit system in
a watertight manner and provide access to the conduits for
inspection, maintenance, and repair. For purposes of describing the
preferred embodiment, the conduit system is a series of sewer pipes
transferring waste fluid to a treatment facility. The invention is
not limited to sewage systems and may be used in to gain access to
pipe interiors for a variety of closed fluid transfer systems.
[0029] The manhole is formed as a single piece unit, preferably
through a rotational molding process. In the preferred embodiment,
the material used to construct the manhole unit is a polyolefin
plastic resin, most preferably polyethylene. Polyethylene is
preferred because of its extremely strong and durable nature, and
its ability to resist corrosive agents such as acids and corrosive
gases such as methane and hydrogen sulfate.
[0030] As shown best in FIG. 1, the rotationally molded
polyethylene manhole unit includes a dome shaped manifold,
designated generally as 10, which forms a hollow chamber with
various apertures for connecting to the sewer pipelines. The hollow
chamber provides quick and convenient access to the pipe interiors
for inspection, maintenance and repair. While the preferred
embodiment of the manifold is of a domed shape as shown in FIG. 1,
the manifold may be formed to any desired size and shape, depending
on the amount of access required by people and equipment.
[0031] Manifold 10 includes a plurality of lateral manifold
extensions molded into the manifold for connecting to the sewer
pipes. The manifold extensions include at least one manifold inlet
connector for connecting to an upstream pipe, and a manifold outlet
connector for connecting to a downstream pipe. In the preferred
embodiment, the manifold inlet connector is a bell inlet connector
12 for connecting the manifold to an upstream conduit spigot 13
(FIG. 2) for allowing an inflow of fluid to the hollow chamber. The
manifold outlet connector is a spigot outlet connector 14,
typically disposed on an opposite side of manifold 10 from bell
inlet connector 12. Spigot outlet connector 14 allows the manifold
to connect to a downstream conduit bell 15 (FIG. 2) for allowing
fluid to flow out of the hollow chamber. It is commonly used and
known in the art that each section of conduit or pipe be formed
with a bell connector end and a spigot connector end. Each conduit
bell connecting end receiving the spigot end from the preceding
section of pipe. Each conduit bell 15 incorporates a seal member
for forming a watertight seal between the conduit bell and
preceding conduit spigot end. As best shown in FIG. 2, by
incorporating the same type of bell connector with a watertight
seal member into the manifold and the standard spigot outlet
connector, the manhole unit can be easily and quickly installed
without the need for adaptor pipe sections and external sleeve
seals that wrap around the outside of the pipes, preventing
unnecessary exposure of the seal to corrosive agents surrounding
the pipes.
[0032] In the preferred embodiment shown in FIG. 1, the manifold
also includes a manifold riser 16, preferably molded into the top
of manifold 10. The riser extends in an upward direction from the
manifold towards ground level for allowing equipment and personnel
to access the hollow chamber when buried several feet underground.
Because the manhole unit is molded, the riser can be formed to any
height and is not limited to a specific height range. Once the
manhole unit is installed and connected to conduits through the
bell inlet connector and the spigot outlet connector, it is
necessary to provide a removable riser cap 18 to cover and seal the
riser providing access to the hollow chamber. This provides a
completely enclosed manhole unit that prevents debris and fluids
from entering or leaving the manhole, thereby reducing the
possibility of overflow and surcharge of the sewage system.
[0033] Because the manifold is intended to be buried underground,
often times deep underground, the manifold is designed with a
plurality of manifold reinforcing elements that increase the
structural integrity of the manifold. In the preferred embodiment,
the reinforcing elements are a plurality of reinforcing ribs
protruding from the domed sides 22 and base 26 of the manifold.
Reinforcing ribs 20 are equally spaced around the domes sides 22 of
the manifold. As shown best in FIG. 2, additional reinforcing ribs
24 are shown protruding from base 26 of manifold 10. Together,
reinforcing ribs 20 and 24 substantially increase the structural
rigidity of the manifold, allowing it to be buried deep
underground. Reinforcing ribs 20 and 24 are formed into the sides
and base of the manifold during the rotational molding process. As
such, the reinforcing ribs are fully integrated into the manifold
retaining its single piece construction.
[0034] In the preferred embodiment, a fluid channel 28 is disposed
in the hollow chamber of manifold 10 for channeling fluid through
the hollow chamber from bell inlet connector 12 to spigot outlet
connector 14, as best shown in FIG. 3. Fluid channel 28 is formed
as a recess on the interior side 30 of manifold base 26 for
channeling water through the hollow chamber, designated generally
as 32, from bell inlet connector 12 to spigot outlet connector 14.
Preferably fluid channel 28 is declined to form a downward gradient
through the hollow chamber from the bell inlet connector to the
spigot outlet connector so that fluid is caused to flow through the
hollow chamber along the fluid channel and into the downstream
conduit. In the preferred embodiment, the fluid channel has a total
downward fall of approximately one inch. As shown in FIG. 2,
because fluid channel 28 is recessed into base 26 of manifold 10,
it protrudes from the base along with reinforcing ribs 24. The
reinforcing ribs extend from the side of the protruding fluid
channel to approximately bottom edge 34 of manifold 10.
[0035] As shown in FIG. 8, the manhole unit can be rotationally
molded so that the manifold includes a plurality of bell inlet
connectors 12a, 12b, and 12c for connecting the manifold to a
plurality of upstream conduit spigots and allowing an inflow of
fluid into the hollow chamber. Accordingly, fluid channels 28a,
28b, and 28c extend between the plurality of bell inlet connectors
and spigot outlet connector 14 to channel the fluid through the
hollow chamber of the manifold.
[0036] Referring now to FIG. 4, in the preferred embodiment, bell
inlet connector 12 includes an annular seal 36 for conforming to
exterior surface variations in the conduit spigot to be inserted
into the bell inlet connector. Annular seal 36 forms a watertight
connection between interior side 38 of bell inlet connector 12 and
the exterior side of the conduit spigot, as shown in FIG. 2.
Annular seal 36 is carried on interior side 38 so that the annular
seal is not exposed to environmental corrosive agents disposed
around the outside of the conduits. As such, the seal is less
likely to fail than traditional rubber sleeves and will maintain
the integrity of the conduit system for extended periods of time.
Preferably, the annular seal is an o-ring type seal of the type
commonly used in the bell connecting ends of the conduits.
[0037] A seating groove 40 is molded into interior side 38 of the
bell inlet connector for receiving annular seal 36. The seating
groove holds the seal in position and restricts the seal from
moving when the upstream conduit spigot 13 is slid into the bell
inlet connector and contacts the seal to form the watertight
connection. The conduit spigot will push the annular seal into
seating groove 40 and form the watertight connection between the
exterior side of the upstream conduit and the interior side of the
bell inlet connector.
[0038] In the preferred embodiment shown in FIG. 1, spigot outlet
connector 14 includes a beveled spigot edge 42 at distal end 44 of
the spigot outlet connector. The beveled spigot edge reduces the
thickness of the distal end of the spigot outlet connector for
first engaging the seal member carried by the downstream conduit
bell. This allows for the distal end of the spigot connector to
easily be inserted through the seal member so that the seal member
slides up and over the beveled spigot edge and moves into position
around the spigot outlet connector to form a watertight connection.
As discussed above, because the seal member is disposed on the
interior side of the conduit bell, it is not exposed to the
environmental corrosive agents that effect traditional seals
wrapping around the outside of the connection point.
[0039] Referring to FIG. 9, a riser extension 46 is shown connected
with manifold riser 16 to extend the height of the riser to ground
level when buried deep under ground so that the hollow chamber can
still be easily accessed from ground level when the manifold riser
is of insufficient height. Riser extension 46 also includes a
sealing ring 48 for forming a watertight connection between
manifold riser 16 and the riser extension. The sealing ring is
carried on interior side 50 of the riser extension and is held in
place by a riser seating groove 52. As with the annular seal
carried by the bell inlet connector, the sealing ring of the riser
extension is disposed between the interior side of the riser
extension and the exterior side of manifold riser 16 so that the
sealing ring is not exposed to environmental corrosive agents
surrounding the conduits. Preferably, the sealing ring used by the
riser extension is a hollow deformable o-ring that compresses
against the outside surface of the riser and conforms to the
surface shape of the manifold riser to provide a watertight
connection.
[0040] As it can be difficult to insert the manifold riser into the
riser extension because of the protrusion of the sealing ring, the
riser includes a beveled riser edge 54. The beveled riser edge
reduces the thickness of distal end 56 of the riser which engages
the sealing ring. This allows the distal end of the riser to easily
be inserted between the sealing ring, and-as the riser extension is
slid over the riser, the sealing ring slides over the beveled riser
edge and moves into position around the sides of the manifold riser
to form a watertight connection.
[0041] Referring to FIGS. 5, 6, and 7, the removable riser cap will
now be described in more detail. As shown in FIG. 5, the riser cap
includes a plurality of recessed handles 54 for removing the riser
cap from the riser. In order to prevent unauthorized tampering with
the manhole unit, handles 54 are removable, and once removed, the
riser cap is extremely difficult to take off. As best shown in FIG.
6, removable riser cap 18 includes a pressure release valve 56 for
venting any built-up gases within the hollow chamber of the
manifold. Pressure release valve 56 may be combined with or
replaced by a vacuum ventilation valve capable of allowing a vacuum
mechanism to vacuum out an gases formed in the hollow chamber
before attempting to remove the riser cap. As shown in FIGS. 6 and
7, removable riser cap 18 also includes an adaptive seal 58 for
adjusting to surface variations in the shape of the interior
surface of the manifold riser to provide a watertight connection
between the riser and the removable riser cap. As with the sealing
ring for riser extension 46, the adaptive seal for the removable
riser cap is preferably a hollow deformable o-ring capable of
compressing against the interior side of the riser into which the
cap is inserted so that the o-ring conforms to the interior surface
shape of the manifold riser and provides a watertight
connection.
[0042] While a preferred embodiment of the invention has been
described using specific terms, such description is for
illustrative purposes only, and it is to be understood that changes
and variations may be made without departing from the spirit or
scope of the following claims.
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