Title:
Adjustable manhole installation and method of adjustment
Kind Code:
A1


Abstract:
A manhole installation is provided that permits the height of manhole openings to be easily adjusted when road or ground surface levels have changed. The manhole installation comprises concentric manhole tube members that can be raised or lowered relative to each other are provided. The concentric tube members are each furnished with cooperating elements which, when engaged with each other, permit a graduated raising or lowering of one tube member in relation to the other. Existing manhole installations can also be modified so that positioning the opening of such manholes with a repaired road surface is facilitated.



Inventors:
Gamson, Edward P. (Highland Park, IL, US)
Application Number:
10/179075
Publication Date:
12/25/2003
Filing Date:
06/25/2002
Assignee:
GAMSON EDWARD P.
Primary Class:
International Classes:
E02D29/14; (IPC1-7): E02D29/14
View Patent Images:
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Primary Examiner:
MAYO-PINNOCK, TARA LEIGH
Attorney, Agent or Firm:
HUSCH BLACKWELL LLP (CHICAGO, IL, US)
Claims:

What is claimed is:



1. An adjustable manhole installation comprising: a first generally tubular member having an outer surface, and a first plurality of cooperative height-adjusting engagement elements spaced apart on its external circumference and fixed on the outer surface; a second generally tubular member, having an internal diameter greater than the external diameter of the first generally tubular member such that the first member fits concentrically within the second member, the second member further having an interior surface having a second complimentary plurality of cooperative height-adjusting engagement elements spaced apart on its internal circumference and fixed thereon for cooperative engagement with the first plurality of engagement elements; the first generally tubular member being held generally concentrically within the second generally tubular member by the engagement of the first plurality of height-adjusting engagement elements with the second plurality of height-adjusting engagement elements.

2. The adjustable manhole installation of claim 1 wherein the first and second generally tubular members each comprises a top rim, and when the first tubular member is held concentrically within the second tubular member, the top rim of the first tubular member extends higher than the top rim of the second tubular member.

3. The adjustable manhole installation of claim 1 wherein the first tubular member is of a shorter length than the second tubular member.

4. The adjustable manhole installation of claim 1 wherein the tubular members are comprised of cast iron.

5. The adjustable manhole installation of claim 4 wherein each of the plurality of engagement elements of the tubular members is fixed to a tubular member by fasteners.

6. The adjustable manhole installation of claim 4 wherein each engagement element is cast simultaneously with the tubular member in a unitary casting.

7. The adjustable manhole installation of claim 1 wherein the tubular members are comprised of cast concrete.

8. The adjustable manhole installation of claim 7 wherein each of the plurality of engagement elements of the tubular members is fixed to a tubular member by fasteners.

9. The adjustable manhole installation of claim 7 wherein each engagement element is cast simultaneously with the tubular member in a unitary casting.

10. The adjustable manhole installation of claim 1 wherein each engagement element is affixed to a tubular shaped member with an adhesive.

11. The adjustable manhole installation of claim 1 wherein each engagement element comprises a thin flange formed into a series of steps and risers.

12. The adjustable manhole installation of claim 1 wherein each engagement element comprises a block element placed into a stair-shaped formation.

13. The adjustable manhole installation of claim 1 wherein each engagement element comprises a thin generally horizontal flange and each tubular member has a series of thin generally horizontal flanges, each series of flanges being spaced generally in parallel orientation generally vertically on the cooperating walls of the respective tubular members in a manner similar to the rungs of a ladder such that at least one of the flanges of the series of flanges on the first tubular member engages at least one of the flanges of the series of flanges on the second tubular member.

14. The adjustable manhole installation of claim 1 wherein each engagement element comprises gear-teeth-shaped support elements, which engage each other in a manner similar to the meshing of gears in a machine.

15. An adjustable manhole installation comprising: a first generally tubular member having an outer surface, and a first plurality of stair-shaped elements spaced apart on its external circumference and fixed on the outer surface; a second generally tubular member having an internal diameter greater than the external diameter of the first generally tubular member such that the first member fits concentrically within the second member, the second member further having an interior surface having a second complimentary plurality of stair-shaped elements spaced apart on its internal circumference and fixed thereon for cooperative engagement with the first plurality of stair-shaped elements; the first generally tubular member being held generally concentrically within the second generally tubular member by the engagement of the first plurality of stair-shaped elements with the second plurality of stair-shaped elements.

16. The adjustable manhole installation of claim 15 wherein the first and second generally tubular members each comprises a top rim, and when the first tubular member is held concentrically within the second tubular member, the top rim of the first tubular member extends higher than the top rim of the second tubular member.

17. The adjustable manhole installation of claim 15 wherein the first tubular member is of a shorter length than the second tubular member.

18. The adjustable manhole installation of claim 15 wherein the tubular members are comprised of cast iron.

19. The adjustable manhole installation of claim 18 wherein each of the plurality of stair-shaped elements of the tubular members is fixed to a tubular member by fasteners.

20. The adjustable manhole installation of claim 18 wherein the respective stair-shaped elements and generally tubular members are a unitary casting.

21. The adjustable manhole installation of claim 15 wherein each stair-shaped element is affixed to a tubular shaped member with an adhesive.

22. The adjustable manhole installation of claim 15 wherein each stair-shaped element comprises a thin flange formed into a series of steps and risers.

23. An adjustable manhole installation comprising: a first generally tubular member having an outer surface, and a first plurality of block-shaped supports arranged in a stair-shaped formation spaced apart on its external circumference and fixed on the outer surface; a second generally tubular member having an internal diameter greater than the external diameter of the first generally tubular member such that the first member fits concentrically within the second member, the second member further having an interior surface having a second complimentary plurality of block-shaped supports spaced apart on its internal circumference and fixed thereon for cooperative engagement with the first plurality of block-shaped supports; the first generally tubular member being held generally concentrically within the second generally tubular member by the engagement of the first plurality of block-shaped supports with the second plurality of block-shaped supports.

24. The adjustable manhole installation of claim 23 wherein the first and second generally tubular members each comprises a top rim, the second tubular member being adjustable relative to the second tubular member such that the top rim of the second tubular member is moveable relative to the top rim of the first tubular member.

25. An adjustable manhole installation for use at and below the surface of the ground or a road surface, comprising: a first tubular member having a top surface, an outer surface and a first series of stair-shaped elements about its outer surface; a second tubular member having an internal diameter greater than the external diameter of the first tubular member, further having an interior surface and a corresponding second series of stair-shaped elements about the interior surface; the first tubular member fitting generally concentrically within the second tubular member so that the first series of stair-shaped elements engages the second series of stair-shaped elements such that the first tubular member can be set at a desired height relative to the ground or road surface; the first tubular member being adjustable, within the second tubular member such that the second tubular member can be raised or lowered, within the first tubular member, relative to the ground or road surface, in graduated steps.

26. The manhole installation of claim 25 wherein the first and second tubular members are constructed of cast iron and the stair-shaped elements are cast integrally with the tubular members.

27. The manhole installation of claim 25 wherein the first and second tubular members each comprise several series of stair-shaped elements such that the stair-shaped elements are substantially about the entire inner circumference of the first tubular member and the outer circumference of the second tubular member.

28. A method of adjusting a manhole installation to level its opening with a ground or road surface, including the steps of: providing a manhole installation having a first tubular member having an interior surface, and a second tubular member having a smaller diameter than the diameter of the first tubular member and an exterior surface; providing a plurality of stair-shaped support elements, spaced apart, on both the interior surface of the first tubular member and the exterior surface of the second tubular member; placing the second tubular member within the first tubular member at a desired height within the first tubular member; and, rotating the second tubular member, within the first tubular member, to cooperatively engage the stair-shaped elements of the first tubular member with the stair-shaped elements of the second tubular member.

29. The method of adjusting a manhole installation of claim 28, including the step of lifting and rotating the second tubular member, within the first tubular member, engaging the stair shaped support elements of the second tubular member with different stair shaped support elements of the first tubular member such that a new desirable height for the second tubular member is set, when the ground surface level has been changed.

30. The method of adjusting a manhole installation of claim 28, including the step of providing a top rim on the second tubular member such that the top rim is placed at the ground surface level.

Description:

FIELD OF THE INVENTION

[0001] The present invention concerns a novel manhole installation that permits the easy adjustment of the relative height of the entrance to a manhole such that a manhole cover can be easily laid generally flush with the ground or the surface of a roadway. The present invention is generally directed towards new installations of manholes but can be easily adapted to be used with existing manhole installations.

BACKGROUND OF THE INVENTION

[0002] Access to subterranean conduits, such a storm sewers, sanitary sewers and others, is generally accomplished through manhole structures. Manhole structures are often found below roadways, as roadways generally correspond with municipal rights-of-way. The openings of such structures are, therefore, generally located on roadway surfaces.

[0003] Generally, manhole structures include a cast iron tube or a reinforced concrete cylindrical shell connecting a surface opening to a subterranean conduit. Additionally, a structure surrounding and supporting the connecting tube or cylinder is constructed to maintain an opening from the surface to the conduit despite movements and shifts (either due to surface pressures or tectonic forces) in the earth surface.

[0004] These manhole structures, therefore, are typically, imposing elements below the surface of the ground or roadway. The manhole structure is also constructed such that the load of vehicles, generally taken by the roadway, is supported by the manhole structure. As such, when new access to subterranean passageways is required, a new manhole installation is constructed, generally at great cost and effort. Further, because of their access at a road surface, when repairs to roads are required, existing manhole installations are often torn up and reconstructed. Such repairs and reconstructions can be very expensive and time consuming.

[0005] Further still, because of their location on roadway surfaces, the upper portion of the manhole structure must fit flush with the road surface so that vehicles are afforded a smooth ride. Because a manhole structure is not merely an opening in the roadway, but instead is often a complicated structure (as described above), adjusting the manhole entrance to be flush with the roadway surface, especially after road repair or resurfacing, can be difficult.

[0006] A device and method of using the device are discussed hereinafter that permit the surface level position of a manhole to be adjusted in response to surface level changes due to construction or reconstruction of roadways. Further, the device and method are an inexpensive, quick and easy way of repositioning an existing manhole entrance onto the surface of a roadway.

SUMMARY OF THE INVENTION

[0007] In accordance with the present invention, an adjustable manhole installation for use at and below the surface of the ground or a road surface is provided. The adjustable manhole installation comprises an inner generally tubular member having an exterior circumferential surface, and a first plurality of cooperative engagement elements spaced apart on that external circumferential surface and extending from and fixed on that exterior circumferential surface. Further, an outer generally tubular member, having an internal diameter greater than the overall diameter of the inner generally tubular member, such that the inner member fits concentrically within the outer member, is also provided. The outer tubular member defines an interior circumferential surface having a second plurality of complimentary cooperative engagement elements on its internal circumference.

[0008] In a preferred embodiment, the cooperative engagement elements are stair-shaped support members. The first plurality of stair-shaped support members are fixed on the external surface of the inner generally tubular member for cooperative engagement with the second plurality of stair-shaped elements on internal surface of the outer tubular member. The inner generally tubular member is then held concentrically within the outer generally tubular member by the engagement of the stair-shaped elements.

[0009] Further, the inner tubular member is subsequently adjustable, within the outer tubular member such that the inner member can be raised or lowered, within the outer member, relative to the ground or road surface, in graduated steps. By lifting the inner member, to a level equal to the height of a rise from one step to another in the stair-shaped structural element, and rotating the inner tubular member relative to the outer tubular member, the inner tubular member can be raised (by rotating one way) or lowered (by rotating the other way) relative to the ground surface

[0010] In a first embodiment, the height of adjustment is determinable by the height of the step risers in the stairs. Typically, the step height is determined by the thickness of road surfacing repair in a geographic area.

[0011] In another embodiment, the height-adjusting elements comprise rows of upwardly angled teeth-elements that interlock in the manner of gear teeth. Rotation of the inner tube member and engagement of teeth causes the inner member to be raised, or lowered, with respect to the outer tube member, and to the road surface.

[0012] In another embodiment, the height-adjusting elements comprise a series of block-shaped support elements, affixed to each tubular member, each block-shaped support element being set in a step pattern such that it resembles a stair. In this embodiment, the block height and placement is determined by the road surfacing repair practices in a geographic area. Such practices vary from one geographic area to another such that, for example, in colder climates thicker road surfaces may be used so as to prevent the formation of cold weather damage (such as those caused by freeze and thaw cycles) and in temperate climates, free of freeze and thaw cycles, thinner road surfaces may be used. In colder climate areas, therefore, the block heights can often be greater and in warmer climates, block heights can often be smaller.

[0013] The use of such blocks permits greater surface area for securing the support elements (such as by welding, adhesives or fasteners) to the tubular members. In this manner the support elements are strengthened, providing a stronger combination when the tubular elements are joined.

[0014] In another embodiment, the stair or block or tooth height-adjusting elements are cast into the tube members at the time of the casting of the tube members. In this embodiment, the thickness of the tube wall can be varied so as to form the stair elements. The height-adjusting elements being sculpted out of the thickness of the tubular member, thus provide a thickened and structurally stronger tube element with stronger height-adjusting members, that can be better capable of surviving sheering forces as a result of being formed integrally with the tube member.

[0015] In another embodiment, a series of concentric support ring segments, having spaced apart gaps, are provided on the interior surface of the inner tubular member and on the exterior surface of outer tubular member. The spaced apart gaps are of a length greater than or equal to the length of the ring segments, such that the ring segments of the inner tubular member can be raised or lowered through the ring gaps of the outer tubular member, the inner tubular member can then be rotated, such that its ring segments engage and bear on the ring segments of the outer tubular member thereby providing support for the inner tubular member.

[0016] In another embodiment, an existing manhole installation can be modified, to include some height-adjusting elements by, for example, welding such elements to the interior wall of an existing manhole installation, and inserting, into the existing manhole, a new tubular member element having cooperating height-adjusting elements. The combination can then be adjusted in the manner described above.

[0017] In all of the above examples, the support elements can define, on any one or more of the support element segments, an opening through which a bolt, cotter pin, key or other elongated element, can be inserted to lock one set of support elements of an inner tubular member to a support element of the outer tubular member.

[0018] A more detailed explanation of the invention is provided in the following description and claims and is illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1 is a cut-away view of a typical manhole installation of the prior art.

[0020] FIG. 2 is an exploded cut-away view of a manhole installation of the present invention.

[0021] FIG. 3 is an exploded cut-away view of another embodiment of a manhole installation of the present invention.

[0022] FIG. 4 is an exploded cut-away view of still another embodiment of a manhole installation of the present invention.

[0023] FIG. 5 is an exploded cut-away view of another embodiment of the manhole invention of the present invention.

[0024] FIG. 6 is a perspective view of an embodiment of the manhole installation of FIG. 2, partially cut away to show a feature of the invention.

[0025] FIG. 7 is a perspective view of an embodiment of the manhole installation of FIG. 4, partially cut away to show a feature of the invention.

[0026] FIG. 8 is an exploded cut-away view of another embodiment of the manhole invention of the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS

[0027] Although the present invention is susceptible of embodiment in various forms, there is shown in the drawings a number of presently preferred embodiments that are discussed in greater detail hereafter. It should be understood that the present disclosure is to be considered as an exemplification of the present invention, and is not intended to limit the invention to the specific embodiments illustrated. It should be further understood that the title of this section of this application (“Detailed Description of an Illustrative Embodiment”) relates to a requirement of the United States Patent Office, and should not be found to limit the subject matter disclosed herein.

[0028] Referring to the drawings, it can be seen that the present invention relates to openings permitting access to subterranean systems, such as sewers, drainpipes, deep tunnel systems, electrical installations and others. FIG. 1 shows a typical opening, known as a manhole installation 10, giving access to a subterranean conduit 12. The manhole installation 10 is generally comprised of a tubular member 14, having a top rim 16 and an inner surface 18. It can be seen that the surrounding area is comprised of the ground surface (or roadway) 2, soil or roadway base 4, concrete grouting 6 and a manhole casing 8. It is to be understood that the subsurface installation shown in FIG. 1, and which forms the basis of FIGS. 2, 3, 4, 5 and 8, is shown for illustrative purposes only and is not meant to be a limitation of the invention. The device of the present invention can be adapted and used in a number of different below surface installations without departing from the novel scope of the present invention.

[0029] Referring now to FIGS. 2, 3, 4, 5 and 8 manhole installations 20, 40, 60, 80 and 100 (respectively) of the present invention are shown. FIGS. 2, 3, 4, 5 and 8 further show, in phantom lines, a proposed new road way level 36, which has been included to illustrate one of the reasons or uses for the device of the present invention. It can be seen, and will be understood as the present invention is disclosed, that the manhole installation 10 of the prior art can be interchanged, between the ground or road surface 2 and a subterranean conduit 22, with a manhole installation of the present invention with very little modification.

[0030] Referring to FIG. 2, manhole installation 20 comprises a first tubular member 24, having a top rim 26 and an inner surface 28. Manhole installation 20 further comprises a second tubular member 30, having a smaller diameter than the interior diameter of first tubular member 24, and fitting concentrically within first tubular member 24. Second tubular member 30, further comprises an exterior surface 31 and a top rim 33. A plurality of stair-shaped support elements 32 are provided on the inner surface 28 of first tubular member 24 and a second plurality of stair-shaped support elements 34 is provided on exterior surface 31 of second tubular member 30 for cooperation with the first plurality of stair shaped support member 32.

[0031] FIG. 6 is a cut away view of a first tubular member 24 and a second tubular member 30 in an engaged position. As can be seen, the top rim 33 of second tubular member 30 is at new road surface 36, whereas the top rim 26 of tubular member 24 is at the original road surface level 2. It is to be understood, that although top rim 26 is shown at the original road level 2, top rim 26 of the present invention can be located at any position below road level 36 without departing from the novel scope of the present invention. It is noted, that in the use of the present invention to make a modification of an existing manhole installation (as shown in FIG. 1, and described below), the existing manhole installation top rim can be at or above the original road level 2.

[0032] FIG. 6, further, shows the interlacing of the stair-shaped support elements 32 and 34, and the use of a locking bolt 35, which can be inserted into any one or more openings (not shown) in run elements 32R and 34R. It is to be understood that different types of locking means can be used, including cotter pins, clamps, bolts, adhesives, and the like, that are preferably removable, without departing from the novel scope of the present invention. Further, locking means can also be used on adjacent riser elements of the stair supports of the present invention without departing from the novel scope of the present invention.

[0033] The use of locking nut 35, or other locking means, provides an added means, besides the weight of the tubular members and any friction developed between the support elements, of maintaining the tubular manhole members locked together. The use of such locking means can help keep a second tubular member from sliding off of a first tubular member. Further, the use of such locking means can prove a deterrent to the theft of the second tubular member, particularly in situations, as explained below, where a smaller or lighter second tubular member is utilized.

[0034] In FIG. 3, manhole installation 40 comprises a first tubular member 44, having a top rim 46 and an inner surface 48. Manhole installation 40 further comprises a second tubular member 50, having a smaller diameter than the interior diameter of first tubular member 44, and fitting concentrically within first tubular member 44. A plurality of stair-shaped (height-adjusting) support elements 52 is provided on the inner surface 48 of first tubular member 44 and a second plurality of stair-shaped (height-adjusting) support elements 54 is provided on the exterior surface 51 of second tubular member 50 for cooperation with the first plurality of stair shaped support member 52. It can be seen, however, that second tubular member 50 of the present embodiment, is of a lesser overall length than second tubular member 30 shown in the previous embodiment.

[0035] As the proposed change in level in most street repairs amounts merely to generally no more than several inches, the device of the present embodiment of the invention is designed to span only slightly more than those several inches in increased relative height. It is to be understood that the size of the second tubular member can vary depending on need without departing from the novel scope of the present invention.

[0036] The stair-shaped support elements 34, 54 and support members 32, 52 can be made from any variety of members formed into stair-shaped elements and members, including thin flanged members formed of steel, plastic, concrete, iron or other resilient and strong materials that may be formed, molded or shaped into stair-shapes. It will be understood by persons having skill in the art that any material having desirable qualities can be used to form the stair-shaped elements and members without departing from the novel scope of the present invention.

[0037] In FIG. 4, manhole installation 60 comprises a first tubular member 64, having a top rim 66 and an inner surface 68. Manhole installation 60 further comprises a second tubular member 70, having a smaller diameter than the interior diameter of first tubular member 64, and fitting concentrically within first tubular member 64. A plurality of height-adjusting block support elements 72, arranged in a manner resembling a stair, are provided on the inner surface 68 of first tubular member 64 and a second plurality of block support elements 74, cooperatively arranged in a stair-like shape, is provided on the exterior surface 71 of second tubular member 70 for interlocking cooperation with the first plurality of block support member 72.

[0038] It can be seen in FIG. 4, that the overall length of second tubular member 70 is generally the same as that of second tubular member 30 of FIG. 2. However, it is to be understood that the overall length of second tubular member can be made to any desired length, as in second tubular member 50 of FIG. 3, without departing from the novel scope of the present invention.

[0039] FIG. 7 shows a cut away view of a first tubular member 64 and a second tubular member 70, of FIG. 4, in an engaged position. As can be seen, the top rim 73 of second tubular member 70 is at new road surface 36, whereas the top rim 66 of tubular member 64 is at the original road surface level 2, in the manner described above, with respect to FIG. 6. FIG. 7, further, shows the interlocking of the block-shaped height-adjusting support elements 72 and 74, and the use of a locking clamp 75, which can be placed onto openings or indentations (not shown) in block elements 72B and 74B, so as to keep second tubular member 70 in place in manhole installation 60.

[0040] In FIG. 5, manhole installation 80 comprises a first tubular member 84, having a top rim 86 and an inner surface 88. Manhole installation 80 further comprises a second tubular member 90, having a smaller diameter than the interior diameter of first tubular member 84, and fitting concentrically within first tubular member 84. A series of platform support elements 92 is provided on both the inner surface of the first tubular member and on the outer surface of the second tubular member. Height-adjusting support elements 92 are comprised of concentric ring segments 94 having gaps 96 therein. The series of platform support elements 92 are cooperatively placed to engage each other, such that the ring segments 94 of one tubular member interlace with the ring segments 94 of the other. Interlacing of ring segments 94 is caused by rotation of second tubular member 90 such that the ring segments 94 of one tubular member are aligned with the gaps 96 of the other.

[0041] The second tubular member 90 can be lowered until a desired number of support elements 92 of both tubular members 84 and 90 are interlaced vertically. The second tubular member 90 can then be rotated to complete the interlacing of support members 92 and the locking of one tubular member with the other, at a desired level. It is preferred that in the present embodiment, supplemental locking means, such as bolt 35 of FIG. 6 or clamp 75 of FIG. 7, be utilized. Such locking means can provide additional restraint against unwanted rotation of the second tubular 90 member in relation to the first tubular member 84.

[0042] Referring to FIG. 8, manhole installation 100 comprises a first tubular member 104, having a top rim 106 and an inner surface 108. Manhole installation 100 further comprises a second tubular member 110, having a smaller diameter than the interior diameter of first tubular member 104, and fitting concentrically within first tubular member 104. Second tubular member 110, further comprises an exterior surface 111 and a top rim 113. A plurality of gear-teeth-shaped height-adjusting support elements 120 are provided on the inner surface 108 of first tubular member 104 and a second plurality of gear-teeth-shaped height-adjusting support elements 122 is provided on exterior surface 111 of second tubular member 110 for cooperation with the first plurality of gear-teeth-shaped support members 120. It will be understood, by persons having skill in the art, that although the gear-teeth-shaped members 120, 122, are shown as rows of gear teeth, any variety of tooth-shaped elements and cooperating tooth-shaped elements, having any number and size of “teeth”, can be used without departing from the novel scope of the present invention.

[0043] In the operation of a manhole structure of the present invention, referring to FIG. 2, first tubular member 24 is installed between ground level a subterranean pipe or other laterally situated opening or system 22 in a manner well known in the art. First tubular member 24 includes a first plurality of stair-shaped structural elements 32, giving an appearance of a spiral stairs, on its interior face 28. Second tubular member 30 is placed concentrically within first tubular member 24 and includes a plurality of complimentary second set of stair-shaped structural elements 34 for engagement with the first stair-shaped elements 32.

[0044] Initially, first tubular member 24 and second tubular member 30 are adjusted, in the manner described above, so that top rim 33 of second tubular member 30 is at ground level 2. When a change in ground surface level occurs, as a result of surface construction or repair, the second tubular member can be lifted, rotated and re-seated, such that the complementary stair-shaped structural elements 32 and 34 are re-engaged, and the top rim 33 of second tubular member 30 is set to the new surface level 36.

[0045] In one embodiment of the present invention an existing manhole 10, as shown in FIG. 1, can be modified to work with a device of the present invention. In such a modification, stair-shaped structural elements, such as those shown in FIGS. 2, 3, and 4, are added to an existing manhole installation 10, by bolting, welding or otherwise affixing the structural elements to the inner surface 18 of manhole installation 10. It is to be understood that the device of the present invention can be adopted to existing manhole installations, which can have been constructed in shapes other than tubular. In such situations, provided that a segment near the top rim of the manhole opening has a circular cross-section stair-shaped structural elements, or at least one level of stair-shaped runners (similar to concentric rings 94 of FIG. 5), can be affixed thereto. Upon the attachment of such structural elements, a second tubular member (as shown in FIGS. 2, 3 and 4), having a smaller diameter than the existing manhole installation 10 and comprising cooperative stair-shaped support elements, can then be placed concentrically within the existing tubular member, and adjusted, as described above. In this manner, the existing manhole structure can be brought to a desired roadway or ground level. This embodiment of the present invention is useful in preserving current manhole installations and facilitating their continued use subsequent to surface construction and/or repair.

[0046] Further, modification of existing manhole installations can be accomplished using a second tubular member of smaller overall length, such as tubular member 50 of the embodiment shown in FIG. 3, thus preserving existing installations and saving materials and costs.

[0047] It is to be understood that modifications to existing manhole installations made of all types of materials, including reinforced concrete, cast iron, steel and others, can be made, by attaching stair-shaped support elements, or the like, using fasteners of various types known in the art, including bolts, adhesives and others, without departing from the novel scope of the present invention.

[0048] Although illustrative embodiments of the invention has been shown and described, it is to be understood that various modifications and substitutions can be made by those skilled in the art without departing from the novel spirit and scope of the invention.