Raiser for manhole cover

Abstract: A concrete well having an upper axial portion (10) decreasing in width axially from a larger bottom cross section to a smaller cross section at an upper opening of the well. The well includes an annular raiser (12) which is injection-molded of a plastic material and is located on the upper end surface (11) of the well surrounding said opening to extend the well axially upwards. The raiser has depressions (19) which extend in the peripheral direction of the raiser alternatingly on one side and the other of the raiser. The depressions are arranged in groups regularly spaced from each other by transverse solid portions (21) of the raiser. A well covering (13, 14) is supported on the raiser.

Description: This invention relates to a concrete well having an upper axial portion decreasing in width axially from a larger bottom cross section to a smaller cross section at an upper opening of the well, said well comprising an annular raiser injection-molded of a plastic material, which is supported by the upper end surface of the well, surrounding said opening, to extend the well upwards, and a well covering supported by said raiser, depressions extending in the peripheral direction of the raiser alternatingly on one side and the other of the raiser, said depressions being arranged in groups regularly spaced from each other by radial solid portions of the raiser. It is common practice and has been so for several years to make also the raiser of concrete as a concrete ring although obvious drawbacks are inherently connected with such a concrete ring. Since the molded concrete ring always has very rough surfaces including the annular end surfaces thereof, it is difficult to obtain a tight connection between the ring and the well so that fine grain material from the surrounding ground will leak into the well between the upper end surface thereof and the abutting lower end surface of the concrete ring if there is not provided some kind of tight joint therebetween. Moreover, the concrete ring does not provide a planar and even supporting surface for the well covering when it is located directly on the upper annular surface of the concrete ring as it usually is. As a consequence thereof the well covering will rock on the concrete ring when vehicles are passing over the covering, which means that the concrete ring eventually will crack. Finally, the concrete ring is heavy and the mounting thereof is cumbersome. US-A-3 926 533 discloses a system for adjusting the level of the upper edge of a manhole installed in a roadbed, comprising a spacer which forms depressions between lateral and middle walls alternatingly on one side and the other of the spacer, transverse braces being provided in the depressions between said walls. The transverse braces have their transverse edges below the upper end plane of the spacer and above the lower end plane of the spacer, respectively. The spacer engages a ring at the lower and upper ends thereof. Said rings are profiled to engage not only said lateral and middle walls of the spacer but also the transverse braces thereof. The object of the invention is to provide a raiser which eliminates the drawbacks of the concrete ring raiser accounted for above, and also eliminates the use of profile rings as in US-A-3 926 533. In order to achieve this object the raiser has obtained the characterizing features of claim 1. In the preferred embodiment of the invention the raiser is made of PELD and preferably of fiber reinforced PELD to increase the strength of the raiser. It is also preferred that the depressions of the raiser contain a filler which may comprise sand, mortar or plaster and is filled into the depressions at the site where the raiser is to be mounted. However, the preferred filler comprises a rigid or substantially rigid plastic foam such as polyurethane foam, such filler stiffening up the raiser so that it can stand a higher load from vehicles passing over the well cover. The polyurethane foam adheres to the walls of the depressions and can be applied to the raiser at the site of manufacture so that the raiser can be delivered with filler in the depressions ready for use. In order to explain the invention in more detail an embodiment thereof will be described below, reference being made to the accompanying drawings in which FIG 1 is a fragmentary vertical cross sectional view of the upper portion of a well provided with the raiser according to the invention, FIG 2 is an enlarged cross sectional view taken along line II-II in FIG 3, and FIG 3 is a plan view of the raiser. The well, which may be a surface water well or an access well or any other type of well made of concrete has a wider lower portion (not shown in the drawings) and an upper portion 10, FIG 1, which decreases in width over the axial length thereof to form at the top of the well an annular circular planar end surface 11. On top of the well portion 10 a raiser 12 forming a circular ring is supported on the annular surface 11 to extend the well axially upwards. The raiser supports a circular covering ring 13 with a cover 14, the covering ring and the cover conventionally being made of cast iron. The raiser 12, disclosed in more detail in FIGS 2 and 3, forms upper and lower circular end surfaces 15 and 16 and inner and outer cylindrical surfaces 17 and 18. It is injection-molded of PELD (polyethylene of low density ranging from 0.949 to 0.965) and preferably is coloured by means of a black pigment in order to have improved ability of withstanding the influence of ultraviolet radiation when stored outdoors. The raiser has a number of circularly extending depressions 19 in the top thereof, which are provided alternatingly with corresponding depressions 20 in the bottom, as seen in the direction from the center of the raiser towards the periphery thereof. The depressions are arranged in groups by being separated regularly by radial solid portions 21 extending over the entire thickness of the raiser and forming spokes therein. Moreover, the depressions are defined by side and bottom wall portions of unitary thickness which are shaped with relief by the side wall surfaces including an angle of about 5 degrees with the perpendicular of the bottom surface. The raiser being injection-molded combines a low consumption of material with improved ability of standing pressure imparted to it by vehicles passing over the well covering, but this ability can be further improved by filling the depressions 19 on one side of the raiser with sand or by filling these depressions as well as the depressions 20 on the lower side with mortar or plaster. This can be done at the site where the raiser is to be mounted. However, in the preferred embodiment the depressions 19 and 20 are filled with rigid or substantially rigid plastic foam 22 as has been indicated to the left in FIG 2, and it has been found advantageous to use for this purpose polyurethane foam that adheres to the walls of the depressions. In this latter case the raiser can be delivered from the site of manufacture with the filler in the depressions, ready for use. The raiser described is circular but other configurations are possible, for instance rectangular or square. Moreover, the end surfaces of the raiser need not be parallel; they may include a small angle.

Claims: Concrete well having an upper axial portion (10) decreasing in width axially from a larger bottom cross section to a smaller cross section at an upper opening of the well, said well comprising an annular raiser (12) injection-molded of a plastic material, which is supported by the upper end surface (11) of the well, surrounding said opening, to extend the well upwards, and a well covering (13, 14) supported by said raiser, depressions (19, 20) extending in the peripheral direction of the raiser alternatingly on one side and the other of the raiser, said depressions being arranged in groups regularly spaced from each other by radial solid portions (21) of the raiser, characterized in that said radial solid portions (21) of the raiser (12) have their upper and lower radial edges in the respective upper and lower end planes of the raiser and that the raiser engages directly at said end planes said upper end surface of the well (10) and a frame (13) forming part of said well covering (13, 14). Concrete well as in claim 1 wherein the raiser (12) is made of PELD. Concrete well as in claim 1 or 2 wherein the plastic material is fiber reinforced. Concrete well as in any of claims 1 to 3 wherein the depressions (19, 20) at least at one side of the raiser (12) contain a filler (22). Concrete well as in claim 4 wherein the filler is sand, mortar or plaster. Concrete well as in claim 4 wherein the filler (22) is rigid or substantially rigid plastic foam. Concrete well as in claim 4 wherein the filler (22) is polyurethane.

Inventors: SKOENVALL TAGE, SKOENVALL, TAGE, Skönvall, Tage 
Applicants: SKOENVALL TAGE, SKOENVALL, TAGE
Application year: 1991
Main classification: E02D29
IPC codes: E02D29