Corrosion Resistant Manhole Shaft And Method Of Making Same

Abstract

This invention is for a corrosion resistant manhole shaft for sewer drains, storm drains and underground vaults and a method of making same which is comprised of tubular elements either cylindrical or noncylindrical of reinforced plastic impervious to moisture and hydrogen sulfide, said tubular members being vertically positioned in a hole in the ground intercepting the path of a sewer line or an underground chamber and extending upward to the level of the ground surface. A removable liner is positioned about the vertically aligned tubular members and radially spaced therefrom. Concrete is poured into the cavity between the exterior of the tubular members and the liner. Thereafter, the liner is removed and sand or other similar fill is poured into the ground hole between the ground hole wall and the hardened concrete. This invention is also for a method of making corrosion resistant manhole shafts by spraying or blowing to a desired thickness a glass reinforced polyester or other plastic which is impervious to moisture and hydrogen sulfide upon the inner surface of existing conventional manhole shafts, so as to form a plastic liner.

Description

In manhole shafts interconnecting with sewer lines and the like, an extremely corrosive agent, hydrogen sulfide gas (H.sub.2 S), tends to be produced from the waste material conducted therethrough, particularly in sewer lines having shallow grades. Because of the highly corrosive nature of this hydrogen sulfide gas, metal tends to so rapidly corrode in its presence that metallic parts in manholes quickly deteriorated and were eventually prohibited from use therein, particularly for internal ladders or steps. This has caused an increasing reliance on the use of concrete for constructing manhole shafts. Unfortunately, after limited use concrete also disintegrated due to the corrosive nature of the hydrogen sulfide gas eventually causing chunks of concrete to spall off the manhole shaft walls.

Although hydrogen sulfide gas is not as great a problem in underground vaults for housing interconnecting underground electrical wire and cable and the like, these vaults, being of concrete composition, tend to seep moisture so that the vault eventually contains sufficient water to cause not only an electrical shorting of the underground wire and cable, but also creates an extreme and dangerous environment when working in said vaults due to possible electrocution of the worker.

The instant invention eliminates these problems by providing an integral tubular section or telescoping tubular sections composed of reinforced plastic which are impervious to moisture and hydrogen sulfide and may be vertically positioned or stacked to anh desired height in a ground hole. A second outer liner is placed about the vertically aligned sections and radially spaced therefrom. The resulting space therebetween is thereafter filled with concrete. After the concrete is sufficiently hardened, the outer liner is removed and the ground hole is filled with impacted sand or the like. It can thus be seen that what results is a manhole housing having a reinforced plastic liner impervious to moisture and hydrogen sulfide.

Where conventional manhole shafts having concrete or other similar linings are already in existence, glass reinforced polyester plastic or other similar plastics which are impervious to moisture and hydrogen sulfide may be sprayed or blown upon the internal surface area thereof until a sufficient thickness is obtained. Upon the hardening thereof, a moisture and hydrogen sulfide resistant manhole shaft is obtained.

Accordingly, it is a primary object of this invention to provide a manhole shaft impervious to moisture and resistant to hydrogen sulfide corrosion.

Another object is to provide a manhole shaft impervious to moisture and resistant to hydrogen sulfide corrosion which is simple to assemble.

Yet another object is to provide a manhole shaft having a liner impervious to moisture and resistant to hydrogen sulfide corrosion.

Another object is to provide an egress and ingress means to said manhole shaft which is resistant to hydrogen sulfide corrosion.

Still another object is to provide a method for fabricating a manhole shaft which is impervious to moisture and resistant to hydrogen sulfide corrosion and is simple to construct.

Yet another object is to provide a method for fabricating a manhole shaft having a liner impervious to moisture and resistant to hydrogen sulfide corrosion.

Other objects and advantages will be readily apparent from the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a side elevation view of the manhole shaft of the instant invention;

FIG. 2 is a top plan view of the manhole shaft shown in FIG. 1;

FIG. 3 is a detailed view of the telescoping joint of a typical interconnection between tubular sections;

FIG. 4 is a detailed view of the telescoping joint of a typical interconnection between tubular sections, the throat of and the collar of a manhole shaft;

FIG. 5 is a front elevational view of a section of a ladder which may be utilized in conjunction with the manhole shaft in the instant invention;

FIG. 6 is a top view of the ladder section taken on the line 6--6 of FIG. 5;

FIG. 7 is a side sectional view of the ladder section taken on the line 7--7 of FIG. 6;

FIG. 8 is a side elevational view of another embodiment of the manhole shaft used in conjunction with an underground vault; and

FIG. 9 is a top plan view of the embodiment of the manhole shaft shown in FIG. 8.

Referring more particularly to FIGS. 1 and 2, reference numeral 20 designates generally the impervious liner of the manhole shaft. The impervious liner is preferable composed of 40 to 60 percent glass reinforced polyester plastic, but may be of any similar composition which would be impervious to moisture and hydrogen sulfide. Manhole shaft liner 20 is comprised of tubular sections 21 and eccentric conical tubular section 22. It is understood that although liner 20 is shown with one tubular section only, any number can be vertically stacked to obtain the desired height of the manhole shaft, i.e., to the ground surfact level, or may be of integral construction without seams. It is further understaood that although an eccentric conical section is shown which intersects the ground level, a concentric conical section may be utilized without deviating from the scope of the invention herein.

It should be further understood that in cases of existing conventional manhole shafts, particularly those having concrete surfaces, the abovementioned polyester plastic may be sprayed or blown under pressure by the means of a gun or the like against the inner walls and surfaces of the manhole shaft, which upon hardening forms an inner liner or membrane thereon of the aforesaid plastic impervious to moisture and hydrogen sulfide.

The lower rim of eccentric conical tubular section 21 (and all tubular sections) is provided with an offset annular flange which forms an annular pilot portion 23 and a seating shoulder 24. Thus, as each tubular section fits within the top edge of each previously placed tubular section, and shoulder 24 is seated on the rim of the aforesaid previously placed tubular section, as best seen in FIG. 3. All joints and seams are grouted with a moisture and hydrogen sulfide resistant substance to provide a leak-free assembly.

The wall thickness of the tubular sections may be as little as one-sixteenth inch thick, but the thickness thereof will normally be greater and vary depending on the axial load to which the tubular section will be subjected when in service. Having an increased thickness also simplifies the handling and storage thereof and reduces the possibility of damaging the same. It should be further noted that the amount of glass reinforcement in the plastic composition of the tubular section can be varied without deviating from the scope of the invention herein. The more glass which is utilized as reinforcement, the greater the strength the tubular section wall will have.

Seated upon the rim of throat 25 of conical tubular section 22 is adjustable collar 26 which has a first annular flange 27 longitudinally projecting therefrom and a second annular flange 28 longitudinally projecting from the opposite end thereof. Flanges 27 and 28 are offset from the centerline of collar 26 so as to form an annular internal shoulder 29 and an annular external shoulder 30 respect1vely. (See FIG. 4).

Annular shoulder 29 seats upon the rim of throat 25 of conical tubular section 22, as aforesaid, while annular shoulder 30 receives the annular pilot flange 31 which extends longitudinally from a conventional manhole receptacle 32. The longitudinal length of collar 26 may be varied, and concommitantly the height thereof, to permit manhole receptacle 32 to accommodate and position a manhole cover (not shown) in substantially the same plane as the ground surface level.

The tubular section at the base of the manhole shaft is then either imbedded in or placed on a concrete slab base 33 and is provided with cutout sections 34 and 35 to accommodate a sewer or drain pipe 36 or the like (shown in dashed lines). Although only two cutout sections are shown, it is understood that any number thereof consonant with desired design may be utilized to accommodate lateral pipe lines.

A base shelf 37 composed of the same plastic material as are the tubular sections 20 is secured adjacent to the bottom of the lower tubular section so as to substantially seal off the same. Base shelf 37 is provided with a curved portion 38 which extends laterally to form a radius similar to a longitudinal section of the sewer or drain pipe and also extends diametrically across the base shelf so as to intersect either edge of the circumferential edge of the base shaft at cut out sections 34 and 35, thereby completing a circular opening in the wall of the tubular section at that juncture to accommodate the end of sewer or drain pipe 36.

Thus, the ends of sewer or drain pipe 36 which are accommodated in cutout sections 34 and 35 in lower most tubular section 20 also engage the intersecting ends of curved portion 38, so as to be secured thereto and provide, after caulking, with a hydrogen sulfide resistant compound, a watertight egress and ingress means for conducting fluid and the like through the manhole shaft.

FIG. 5 illustrates a section of a ladder 39 which may be utilized in conjunction with the manhole shaft of the invention. Ladder 39 is comprised of the same material as is the manhole shaft liner and is formed with side legs 40 having toe portions 41 for anchoring the ladder to the impervious liner 20 so that the ladder 39 laterally projects into the tubular sections away from the liner 20. Ladder 39 has a face portion 42 which is provided with a front opening 43 for receiving the toe and forward portion of a foot. The lower edge of opening 43 is rolled inwardly (toward the liner 20) to provide a wider step surface as well as a finger-hole 44 (See FIG. 7).

Ladder 39 is secured by tow portion 41 to the inner wall of liner 20 by any means e.g., nylon drive anchors, provided the means utilized are composed of hydrogen sulfide resistant material. Said toe portions 41 are slightly curved to be better accommodated against the inner wall of liner 20 (See FIG. 6). Furthermore, ladder 39 may be constructed in sections which are pre-positioned in each tubular section, or be continuous and placed as an integral unit inside the stacked sections.

FIGS. 8-9 show another embodiment of the instant invention wherein the tubular section 21 at the base of the vertically aligned sections intersects an underground vault 45 which in turn is seated on a concrete slab base 33a. It should be noted that all other elements are similar to the embodiment of FIGS. 1 - 7 and accordingly corresponding elements in FIGS. 8 - 9 are designated by a common number followed by the letter a.

The manhole shaft is made by first preparing a concrete slab base 33 in a ground hole in a conventional manner. A tubular section 21 of glass reinforced polyester plastic is secured thereto. The tubular section which forms the base of the stack is provided with pipe-receptive cutout portions 34 and 35 prior thereto. Base shelf 37 is then secured to base tubular section 21 so that the ends of curved portion 38 thereof are in cooperative relationship with cutouts 34 and 35 to form a framed opening. Other tubular sections are then stacked end on end vertically so that the flange of the bottom rim engages the upper rim of the previously stacked section, as sown, or a single integral tubular section may be utilized.

When the ground surface is approached an eccentric conical tubular section 22 is placed in position on the upper rim of the vertically positioned tubular sections as hereinbefore described. The appropriate height adjustable collar 26 is then seated upon the rim of throat 25 of conical section 22, the manhole receptical 32 is then placed upon collar 26 so as to be flush with the ground surface. All junctions of course are grouted with a moisture and hydrogen sulfide resistant substance to provide a leak-free assembly.

Thereafter, a hollow cylindrical shell 46 (See FIG. 1) is placed about the vertically aligned sections and laterally spaced therefrom. Thereafter concrete of a desired specification is poured in the resulting cavity between the shell 46 and the outer wall of the tubular sections. After the concrete has sufficiently hardened, the shell 46 is removed and the ground hole about the exterior of the newly formed concrete column is filled with sand or the like.

The embodiment of the invention wherein an underground vault is desired is made in the same manner as the previously described embodiment except that after the base slab 33a is formed, an enclosed vault of glass reinforced polyester plastic having a top opening is placed on said base and the base tubular section seats about and interconnects the opening in the top of the enclosed vault. It is understood that the vault may be pre-fabricated before placing on the base, or constructed in place with sheets of said plastic. Also since the vault is totally enclosed except for the top opening, the base shelf 37 is unnecessary and the cut out portions 34a and 35a are located higher in the vault walls. In all other respects this embodiment which includes the underground vault is made similarly to the first embodiment as aforesaid.

Again, where a conventional manhole vault or shaft which is lined with concrete or the like exists, by spraying or blowing under pressure by use of a spray gun or the like, a glass reinforced polyester or other plastic which is impervious to moisture and hydrogen sulfide on the inner walls of the vault or manhole shaft become coated therewith so as to form a shaft or shaft liner of any desired thickness which is non-corrosive.

While several embodiments of the invention have been described, it is understood that the particular embodiments of the invention herein disclosed are for illustrative purposes only and that various changes may be made therein without department from the principles of the invention.

Claims

I claim:

1. The method of making a corrosion resistant manhole shaft for use in ground cavities for underground conduit systems, comprising:

providing an enclosed hollow chamber comprised of reinforced plastic of predetermined thickness impervious to liquids and hydrogen sulfide and having ingress and egress secured to a base situated in a cavity in the ground;

providing a vertically extending tubular section of reinforced plastic of predetermined thickness impervious to liquids and hydrogen sulfide to said hollow chamber so as to permit uninterrupted passage between said tubular section and enclosed hollow chamber;

vertically positioning an annular collar means of predetermined height on the upper edge of said tubular section so as to be in a preselected relationship with the ground surface;

vertically seating a manhole cover receptacle on said collar so as to intersect the ground surface therewith;

placing a hollow shell about said hollow chamber and tubular section so as to be laterally spaced therefrom;

filling the space between said hollow shell and said hollow chamber and tubular section with a fluid substance so as to leave only the manhole cover receptacle exposed; and

removing said hollow shell when said hardening fluid substance is partially hardened.

2. The method of making a corrosion resistant manhole shaft for use in ground cavities for underground conduit systems as described in claim 1 wherein the enclosed hollow chamber is provided by spraying glass reinforced polyester plastic onto the internal surfaces of an existing concrete enclosed chamber.

3. The method of making a corrosion resistant manhole shaft for use in ground cavities for underground conduit systems as described in claim 1 wherein the vertically extending tubular section is provided by spraying glass reinforced polyester plastic onto the internal surfaces of an existing concrete manhole shaft.

4. The method of making a corrosion resistant manhole shaft for use in ground cavities for underground conduit systems as described in claim 1 wherein said tubular section is pre-formed and comprised of glass reinforced plastic.

5. The method of making a corrosion resistant manhole shaft for use in ground cavities for underground conduit systems as described in claim 4 wherein said enclosed hollow chamber is pre-formed and is tubular.

6. The method of making a corrosion resistant manhole shaft for use in ground cavities for underground conduit systems as described in claim 4 wherein said enclosed hollow chamber is pre-formed and is rectangular.

7. The method of making a corrosion resistant manhole shaft for use in ground cavities for underground conduit systems as described in claim 4 wherein said tubular section is comprised of plurality of pre-formed separate tubular elements and said elements are vertically aligned on said hollow chamber.

8. The method of making a corrosion resistant manhole shaft for use in ground cavities for underground conduit systems as described in claim 1 wherein a corrosion resistant means for vertical egress and ingress is positioned so as to radially protrude inwardly from the inner wall of said tubular section.

9. The method of making a corrosion resistant manhole shaft for use in ground cavities for underground conduit systems as described in claim 8 wherein said vertical egress and ingress means is comprised of vertically stacked elements formed so as to provide a face and toes interconnected with a pair of legs, said face having a foot supporting opening formed therein and the toes of said element are secured to the inner wall of said tubular section, said elements comprised of reinforced plastic.