Concrete Manhole

Manhole barrels and other more or less massive concrete structural elements, are joined together to form larger structures intended to contain and/or conduct fluent material, such as sewage.

According to the prior art, such structural elements are manufactured not far from the sites at which they are going to be used. After having been transported to a site, they are assembled into larger structures, such as manholes. The assembly process is generally seen to by the contractor or subcontractor responsible for installing the larger structures.

The assembly procedure is simple and straightforward, unless it is also necessary to seal the joints between the elements, as by inserting gaskets, mastics, or the like, therebetween. More particularly, the contractor or subcontractor is not well-prepared to carry out sealing procedures. Frequently, the sealing procedure is badly done by unskilled hands or a worker whose usual function is to manhandle the elements being assembled. On the other hand, the contractor or subcontractor may call in a skilled craftsman, which means added costs.

Finally, if the joint is to be sealed by a gasket, this can be dislodged or malpositioned by the very act of assembling the structural elements.

According to my invention, a structural element such as a concrete manhole barrel has a generally conical annular gasket embedded in the end thereof, so as to provide in effect an integral, unremovable, but flexible part of the barrel. Also according to my invention, such gasket was in place in the form in which concrete was poured in order to create the barrel. For example, a frusto-conical pallet closes the lower end of a cylindrical barrel form, as usual, except that the pallet has a groove therearound. Before filling the form with concrete (and usually steel reinforcement), the gasket is placed in the groove, so that when the concrete is poured, the gasket becomes embedded in the concrete. Preferably, the interior of the gasket is provided with anchors projecting from the surface thereof, in order to assure a tight bond between the concrete and the gasket.

The barrel is otherwise created following the usual procedures and hauled to the site where it will be used, as by seating it on a base, with its gasket end up, and inserting the concrete header end of a second barrel, so that the resilient material of the gasket is compressed between the two barrels such as to provide a substantially water-tight seal between the two barrels. Being effectively integral with the lower barrel, there is no danger that the gasket will be dislodged or malpositioned during assembling the upper barrel to the lower barrel. In effect, the site contractor or subcontractor procedes with assembling the barrels without having to complicate his task by having to see to sealing the joint or to taking extra precautions to see that the assembly procedure does not adversely affect whatever prior art sealing expedient he might otherwise have seen fit to provide.

While the foregoing description and that which follows is mostly in terms of specific structure, namely, manholes, it is to be understood that such particularity while convenient, is not meant as limitation.

FIG. 1 is a fragmentary, partly-sectional view of a concrete manhole barrel end according to my invention;

FIG. 2 is a sectional view illustrating the preliminary phase of a procedure according to the invention, for creating a concrete manhole barrel having an integral sealing gasket,

FIG. 3 being an enlargement of the encircled portion of FIG. 2;

FIG. 4 is a top plan view of a gasket for use as shown in FIGS. 1 and 2, (N.B., certain detail has been omitted from this view for clarity);

FIG. 5 is an elevation partly in section of a pair of barrels joined together,

FIG. 6 being an enlargement of the encircled portion of FIG. 5.

It is to be noted that the Figures are neither drawn to actual scale nor/to scales consistent with one another. Dimensions, materials, and procedures are well-known and, on the whole, are prescribed by specifications issued by various governmental or other authorities, and, for the most part, would not contribute here anything to understanding the nature or practice of my invention. However, of background interest here are pages 69-78 of CONCRETE PIPE DESIGN MANUAL, First Edition 1970, prepared by the American Concrete Pipe Association, 1501 Wilson Boulevard, Arlington, Va. 22209.

In FIG. 1, the upper or pallet end of a concrete manhole barrel 1 has a gasket 2 embedded in said end. Gasket 2 has a frustoconical portion 3, an annular seat flange portion 4, which portions, save for anchors 5, sealing flanges 6, and sealing ridges 7, consist of uniform thickness resilient sealing material, such as rubber. As will be seen from FIG. 4, the gasket 2 is on the whole a sort of ring, from the interior of which project the spaced sealing flanges 6. Flanges 6 extend continuously around the ring, as do the sealing ridges 7 projecting from the upper surface of the seat flange portion 4.

The anchors 5, shown as continuous annular flanges, which have a cross-section substantially in the form of frusta of cones are joined to the exterior of the gasket, oriented as shown in FIG. 1.

The lower surface 8 of seat flange portion 4 is everywhere flat, except for continuous annular anchors 5 projecting downwardly therefrom, and is everywhere in contact with the concrete of the end of the barrel 1. The external surface 9 of portion 3 is everywhere frustoconical, except for anchors 5, and also is everywhere in contact with the concrete of the end of the barrel 1.

In addition, frusto-conical portion 3 is itself embedded in the concrete of the end of the barrel 1, and its exposed internal surface 10 is everywhere frustoconical, and, in effect a continuation of the frustoconical surface 11 extending continuously around the inner extremity of the barrel 1.

When the barrel is finished, the internal surface 10 of the gasket is substantially continuous (except for flanges 6) with surface of the interior of the barrel. In FIG. 5 is shown a manhole-like structure comprising barrel 1, having a barrel 21 on top, wherein the barrel 21 is closed by a cover 22 and the whole structure is supported by a concrete base 23, at the bottom of an excavation 24.

As will be seen from FIG. 5, the lower end of the barrel 21 has a male frusto-conical header end complementing the female frusto-conical pallet end of the barrel 1. The sealing flanges 6 of the frusto-conical portion 3 of gasket 2 are compressed against the frusto-conical surface 25 of the male header end of barrel 21, and an annular flat seat 26, extending radially inwardly at the larger extremities of the frustoconical male header end of barrel 21, has sealing ridges 7 compressed against it. The compressive force is of course due to the weight of barrel 21 and cover 22.

The number of sealing flanges 6 is in itself not critical. However, the space between header end and pallett end and between sealing flanges should be such that when the sealing flanges are compressed they will seal, but will not be deflected all the way to surface 10, or into contact with their nearest neighbor. It is also important that gasket portion 3 not bear the weight of the barrel or barrels above it, i.e., the weight of barrel 21 is to bear directly on barrel 1, not through the gasket. Preferably, the concrete ends of barrels 1 and 21 are in direct contact with each other. Thus, the upper surface 10a at the end of barrel 1 provides a seat which contacts or seats on a corresponding seat provided by the corresponding lower surface 25a of barrel 21, or at least the weight of the upper barrel is borne by flange portion 4 of gasket 2 in the event that 10a does not reach the corresponding lower surfaces 25a of barrel 21. (N.B., the surface 10a and 25a are shown as slightly separated in the enlarged view of FIG. 6 for clarity.) The uppermost sealing flange 6a serves a dual function in that when the barrel is poured it keeps the concrete out of the spaces between the sealing flanges. The flange 6a actually contacts the pallet 20 in order to bar ingress of concrete to groove 20a.

As will be seen from FIG. 2, groove 20a is not deep enough to fully accept gasket. This is necessary because when the concrete is poured, the weight thereof will force the gasket more deeply in the groove by collapsing flanges 6 and ridges 7 to a certain extent, preferably just enough to position surfaces 10 and 11 as shown in FIG. 1, when the gasket becomes loaded by the fresh concrete poured into the form.