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[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.
[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.
[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.
[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]
[0020]
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[0022]
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[0025]
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[0027]
[0028] Referring now to the drawings, the invention will be described in more detail. Referring to
[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
[0031] Manifold
[0032] In the preferred embodiment shown in
[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
[0034] In the preferred embodiment, a fluid channel
[0035] As shown in
[0036] Referring now to
[0037] A seating groove
[0038] In the preferred embodiment shown in
[0039] Referring to
[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
[0041] Referring to
[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.