IL125500A - Manhole for a gravitational sewage system - Google Patents

Abstract

A liner for a manhole (10) in a gravitational sewage system comprising: a thin walled, plastic element (20) having at least two integrally formed pipe sections (26, 27, 28) extending outward from its wall to enable passage for sewage into and out of the liner, said pipe sections being coupled by a trough (29) inside the liner; and a substantially cylindrical upstanding wall (13); wherein the liner is comprised of a material that can be fused directly to a plastic sewer pipe to form a tight seal. 427 כ" ו באדר התשס" ב - March 10, 2002

Description

MANHOLE FOR A GRAVITATIONAL SEWAGE SYSTEM MANHOLE LINER AND SYSTEM FIELD OF THE INVENTION The present invention relates to manholes for gravitational sewer lines, particularly to manholes used in inf astructures such as in streets, roads, industrial and residential areas. Specifically, the present invention relates to liners for sewer manholes and to a completely leak-proof gravitational sewer system.

BACKGROUND OF THE INVENTION Manholes for sewer systems for infrastructures, such as streets, highways, public outdoor areas, etc., are generally much larger than the manholes used in residential dwellings. These larger sewer manholes are often positioned near other infrastructure utilities, such as telephone lines, gas pipes or water lines. Therefore it is of great importance that the sewer pipes leading into these manholes be sealed completely so that no leakage occurs into the surrounding ground, which may penetrate adjacent pipes, such as water pipes, and pollute the drinking water.

At present, such sewer manholes are made primarily of pre-cast concrete. These manholes generally comprise a manhole base member upon which are stacked cylindrically shaped risers with a top section containing a sewer cover capping the manhole. At least two holes are provided in the wall of the manhole, usually at opposite ends of the base member, for receiving inflowing and outflowing sewer pipes. The pipe ends are sealed to the base member at the interfaces with gaskets, caulking or other sealer. Sewage thus flows from residential, commercial or industrial sources through the pipes into the manhole and from there to the main sewer line. These sewer pipes are usually six inches or larger in diameter and are made of rigid material such as steel, asbestos-cement or rigid PVC.

Sewer systems such as described above often have a problem with leakage. This is due to two major factors. Firstly, the sewer pipes used are rigid, and therefore come in sections which limit their seize to a maximum length so that they have to be connected mechanically to one another to cover a longer distance. Such mechanical connections can be a source for leakage. Secondly, the pipes must also be connected to the manhole, where forming a completely leak proof seal is very problematic, particularly where the pipes and the manhole are made of such very different materials as PVC, steel, or asbestos-cement, and concrete respectively.

To overcome this problem there has been introduced piping for sewers made from cross-linked polyethylene which complies with the standards required for sewer lines, such as the ability to withstand elevated temperature a pressure. Cross-linked polyethylene also has the advantage that it is i rible enough to be wound around a drum, forming a pipe of infinite length, « iiinating the need to couple and seal pipe sections. The only coupling required is that of the pipe end to the manhole. Using cross-linked polyethylene pipe for sewer lines satisfactorily solves the first problem mentioned above, i.e. leakage in the pipeline. The second problem, however, relating to leakage at the interface between the pipe and manhole still remains.

Manhole systems using plastic liners are known and were disclosed in . Patents 4,751,799; 5,081,802; 5,386,669 and 5,584,317 among others. None of these patents provides a solution to providing a totally leak-proof sewer system.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a liner for a sewer manhole to permit leak-proof connection of the manhole to sewer pipes.

A further object of the invention to provide a lined manhole for coupling sewer pipes thereto in a leak-proof manner.

Another object of the invention is to provide a gravitational sewer system that is leak-proof, comprising a lined manhole coupled to sewer pipes without the use of gaskets.

Still a further object of the invention is to provide a method of connecting a lined manhole in a leak-proof manner to sewer pipes without gaskets.

In accordance with the present invention there is thus provided a liner for a manhole comprising a thin walled plastic element including a cylindrical wall of a height of about 50 cm, said plastic element having at least two integrally formed pipe sections extending outward from its wall to enable passage for sewage into and out of the liner, said pipe sections fitting through holes in a manhole cast around the liner. The liner with the extending pipe sections is preferably molded as a single unit and is preferably made of an ethylene polymer such as polyethylene or cross-linked polyethylene which can be fused to sewer pipes of the same material to form a leak-proof seal.

According to a preferred embodiment of the invention, the liner includes a trough coupling the pipe sections inside the manhole.

Further according to a preferred embodiment, the liner is constructed from polyethylene, polyethylene copolymers or cross-linked polyethylene. The liner pipe sections are preferably at least 15 cm in length, and their thickness is at least 0.5 cm, depending on the pipe diameter.

There is also provided in accordance with the invention a method of construction of a leak proof manhole for a gravitational sewage system including forming a thin walled plastic liner including a cylindrical wall of a height of about 50 cm, and at least two integrally formed pipe sections extending outward from its wall, joined by a trough inside the liner. A concrete manhole base member is cast about the liner, so that the pipe sections of the liner extend through holes in the wall of the manhole. One or more pre-cast risers may be placed over the base member, and a top section with a manhole cover placed on top.

BRIEF DESCRIPTION OF THE DRAWINGS Figure la is a perspective view of a manhole base member in accordance with the present invention; Figure lb is a partially cut-away view of a manhole base member in accordance with another embodiment of the present invention; Figure 2 is a plan view of a manhole base member in accordance with one embodiment of the invention; Figure 3 is a cross-sectional side view of a manhole in accordance with the present invention; and Figure 4 is a sectional plan view of the manhole in Figure 3, taken at 90 degrees.

DETAILED DESCRIPTION OF THE DRAWINGS Referring now to Figures la, 2,3,4, there is shown a concrete manhole 10 constructed and operative in accordance with one embodiment of the present invention. Manhole 10 includes a base member 12, a cylindrical riser 14 and a top section 16 having an opening 17 with a cover 18 on top. Inside the manhole is a plastic liner 20 covering the floor 22 and interior wall 24 of the base member. Pipe sections 26, 27 and 28 are integral parts of the liner 20 and extend through holes in the concrete wall of the base member 12. These pipe sections 26, 27 and 28 should extend at least 15 cm out from the base member to enable them to be connected to sewer pipes.

The liner 20 with the pipe sections 26, 27 and 28 is preferably made of a polyethylene polymer as a single unit having no seals. Because the pipe sections 26, 27 and 28 extend out of the side wall 13 of the manhole base member 12, they can be fused to the ends of similar sewer pipes by electrofusion, without requiring any mechanical seals at the concrete opening of the manhole.

The liner is preferably constructed from polyethylene, polyethylene copolymers or cross-linked polyethylene. The thickness of the liner can vary depending on the size and requirements of the manhole. The liner pipe sections are preferably at least 15 cm in length, and their thickness is at least 0.5 cm, depending on the pipe diameter. Liner 20 includes a trough 29, or open pipe, coupling the pipe sections inside the liner, as shown in Figure 2. Trough 29 is provided for maintenance purposes. Fig. lb shows a partially cut away view of a manhole according to another embodiment of the invention, with two inlet pipes 26 and 27, and three outlet pipes, 28, 28' and 28", coupled by a trough 29'.

Since cross-linked polyethylene pipe can be of infinite length because it is flexible enough to be wound around a drum and it conforms to the standards required for sewer pipe, it is the preferred plastic polymer for sewer pipes according to the invention. However, other plastic piping may also be used, the principle being that the liner extension pipes be directly fiisable with the sewer pipe forming a perfect seal and avoiding having to make a mechanical seal between the concrete manhole and sewer pipe which is difficult to make absolutely leak-proof.

The construction of such a manhole with the liner in accordance with the invention is as follows. First, a thin walled plastic liner is formed, including a cylindrical wall of a height of about 50 cm, and at least two integrally formed pipe sections extending outward from its wall. The portion of the pipe sections inside the liner are formed as troughs, or open pipes. A concrete manhole base member, usually cylindrical, is cast about the liner. In this way, the pipe sections extend through two holes in the wall of the base section of the manhole.

A cylindrical pre-cast concrete riser is generally placed on top of the base member over and surrounding the liner, and mates with the upper wall edge of the base member. Further concrete cylindrical risers can be added to make the manhole the desired height. The liner extends upwards within the manhole for at least 50 cm, and the base section of the manhole extends upwards at least to cover the liner, and possibly higher. A top section having a hole with a manhole cover then caps the manhole.

It is to be understood that the liner pipe sections can extend from the liner wall, and thus from the manhole, at different elevations, depending on the specific design requirement of the manhole. Similarly the liner pipe extensions can be of individual varying diameters.

It is a particular feature of the present invention that the system and method permit the industrial production or prefabrication of manholes, or at least the base sections of manholes, including leak proof couplings. These ready-made manholes can be placed on site and rapidly coupled to sewage piping, without requiring breakage of holes in the walls of pre-cast manhole sections and subsequent repair on site, as required in conventional sewage system laying methods.

It will be appreciated by persons skilled in the art that the scope of the present invention is not limited to what has been shown and described hereinabove, merely by way of example. Rather, the scope of the invention is limited solely by the claims which follow. 10 125500/2

Claims (19)

1. A liner for a manhole in a gravitational sewage system comprising: a thin walled, plastic element having at least two integrally formed pipe sections extending outward from its wall to enable passage for sewage into and out of the liner, said pipe sections being coupled by a trough inside the liner; and a substantially cylindrical upstanding wall; wherein the liner is comprised of a material that can be fused directly to a plastic sewer pipe to form a tight seal.

2. A liner as in claim 1, wherein said upstanding wall extends at least 50 cm in height.

3. A liner as in claims 1-2, wherein the extending pipe sections are of a length to protrude past the wall of the manhole at least about 15 centimeters.

4. A liner as in claims 1-3, wherein the liner including the extension pipe sections is made of an ethylene polymer fusable with a similar sewer pipe.

5. A liner as in claims 1-4, wherein the liner is molded as a single unit.

6. A liner as in any of the previous claims having pipe extensions fusable with cross-linked polyethylene pipe.

7. A liner as in any of the previous claims, wherein said liner is formed of a material selected from the group consisting of polyethylene, polyethylene copolymers or cross-linked polyethylene.

8. A pre-fabricated manhole for a gravitational sewage system comprising: a plastic liner including a thin walled plastic element having at least two integrally formed pipe sections extending outward from its wall to enable passage for sewage into and out of the liner, said pipe sections being coupled by a trough inside the liner, and a substantially cylindrical upstanding wall; a base member cast around said plastic liner so that said pipe sections extend through holes in said base member; wherein the liner is comprised of a material that can be fused directly to a plastic sewer pipe to form a tight seal.

9. The manhole as in claim 8, further comprising one or more pre-cast concrete risers.

10. The manhole as in claim 8 or 9, further comprising a top section with opening and manhole cover over the base member and optionally over the one or more risers.

11. A manhole as in claims 8 to 10, wherein the integrally formed pipe sections of the liner extend at least about 15 cm out from the manhole.

12. A manhole as in claims 8- 11, wherein said upstanding wall is about 50 cm high.

13. A manhole as in claims 8-12, wherein the liner is made of poly ethyl polymer.

14. A leak-proof gravitational sewage system comprising a manhole as in claims 8-13, wherein the liner pipe extensions are fused directly to compatible sewer pipes.

15. A system as in claim 14, wherein the sewer pipes are constructed from cross-linked polyethylene.

16. A method of constructing a pre-fabricated manhole for a gravitational sewage system comprising: forming a thin walled plastic liner including a cylindrical wall of a height of about 50 cm, and at least two integrally formed pipe sections extending outward from its wall and coupled by a trough inside the liner, said liner being comprised of a material that can be fused directly to a plastic sewer pipe to form a tight seal.; casting a concrete manhole base member about the liner, so that said pipe sections of the liner extend through holes in the base member of the manhole and said base member extends at least as high as the liner; and covering said manhole with a top section having a manhole cover.

17. The method as in claim 16, further comprising placing one or more precast risers over said base member, and beneath said top section.

18. The method as claimed in claims 16 and 17, further comprising fusing the liner pipe sections to sewer pipes in a totally sealed manner.

19. The method as in claim 18, wherein the pipes are fused by electrofusion. WORD 6 - WINWORD/ANNE/SPECS/633-98am + D-2