Road structure – process – or apparatus – Pavement – Vault cover-closure
Reexamination Certificate
1999-02-11
2001-01-30
Pezzuto, Robert E. (Department: 3671)
Road structure, process, or apparatus
Pavement
Vault cover-closure
Reexamination Certificate
active
06179518
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention relates to a manhole cover frame for mounting a manhole cover above a manhole basin. The frame allows adjustment of the height of the manhole cover as necessitated by resurfacing a road surface and/or by frost heave of the surrounding ground.
Manhole basins, which may be a sewer basin having an inlet and an outlet, or may be a catchment basin having only an inlet, are normally cast of concrete. A frame of metal is fixed to the top of the basin and holds the manhole cover. In order to keep the cover level with a road or ground surface it is frequently necessary to alter the height between the manhole cover and the top of the basin, particularly in regions where there is much frost heave; adjustment to the height is usually done when a road is resurfaced.
Various constructions of adjustable manhole frames have been proposed to deal with the adjustment and to avoid replacing concrete parts. In some cases, screw jacks have been used between the annular frame which holds the cover and the top of the concrete manhole basin. In others, an outer ring, supported by the basin, has internal screw threads of large diameter within which is an inner ring having mating screw threads, and which is rotatable to adjust its height. Examples of patents showing such systems are:
U.S. Pat. No. 3,533,199, which issued Oct. 13, 1970 to Pickett;
U.S. Pat. No. 3,629,981, which issued Dec. 28, 1971 to McCaffrey;
U.S. Pat. No. 3,930,739, which issued Jan. 6, 1976 to Larsson et al.;
U.S. Pat. No. 4,075,796, which issued Feb. 28, 1978 to Cuozzo;
U.S. Pat. No. 4,149,816, which issued Apr. 17, 1979 to Piso;
U.S. Pat. No. 4,925,237, which issued May 15, 1990 to Spiess et al., and
U.S. Pat. No. 5,095,667, which issued Mar. 17, 1992 to Ryan et al.
These prior arrangements have some drawbacks. Where, as in the Pickett, McCaffrey, Cuozzo and Ryan et al. patents, reliance is placed on large diameter screw threads between outer and inner rings, these threads become worn and the manhole cover then starts to wobble as vehicles pass over, leading to more wear and possible breakage. The prior art systems using screw jacks have limited range of adjustability since screw jacks are likely to become unstable if extended too far.
SUMMARY OF THE INVENTION
The present invention seeks to overcome these deficiencies, and, to this end, provides a manhole cover frame in which the screw jacks are used to stabilize an inner ring which is connected to an outer ring by large diameter screw threads. This addresses the problem with wobble caused by wear of the large diameter screw threads. The outer ring can retain some contact with the top of the basin by means of a depending skirt and help to stabilize the frame, even when the jacks are considerably extended.
In accordance with the invention, an adjustable manhole cover frame suitable for mounting on an annular top surface of a manhole basin comprises:
an outer ring having a base capable of resting on the top surface and having internal screw threads;
an inner ring having external screw threads engaging the internal screw threads, and having support means for a manhole cover;
the inner ring carrying screw jacks having lower ends suitable for contacting the top surface and capable of being rotated to lift the inner ring;
whereby the inner ring may be rotated within the outer ring to adjust the height of the manhole cover support means;
and whereby the screw jacks may be used to stabilize the inner ring while the outer ring base remains in contact with the annular top surface, and may also be used to lift both rings out of contact with the annular top surface when additional raising of the inner ring is required.
In accordance with another feature of the invention, the outer ring has a depending skirt which overlaps with a generally cylindrical surface surrounding the annular top surface, which skirt limits intrusion of material between the outer ring and the annular top surface when the outer ring base is raised above the top surface. This means that the outer ring is itself telescopingly movable relative to the top of the basin. In this way the frame is provided, in effect, with two stages of telescoping movement, one between the annular top surface of the basin and the outer ring, and one between the outer and the inner rings. This large range of movement is effected by relative rotation of the outer and inner rings and by extension of the screw jacks; even when these jacks are fully extended the telescoping relationship of the parts allows the frame to be reasonably stable.
For good stability, the frame may have three screw jacks disposed substantially equidistantly, specifically at about 120°, around the interior of the inner ring, providing it with three point contact with the annular top surface.
Preferably, the outer ring has a series of recesses which allow the outer ring to be engaged by the surrounding soil and lifted with movement of that soil.
Protrusions, such as vertical ribs, may protrude from the exterior of the outer ring to engage the surrounding soil and prevent rotation of the outer ring with the inner ring when the latter is being rotated.
REFERENCES:
patent: 3392640 (1968-07-01), Zeile, Jr.
patent: 3533199 (1970-10-01), Pickett
patent: 3629981 (1971-12-01), McCaffrey
patent: 3858998 (1975-01-01), Larsson et al.
patent: 3930739 (1976-01-01), Larsson et al.
patent: 4075796 (1978-02-01), Cuozzo
patent: 4145151 (1979-03-01), Helms
patent: 4149816 (1979-04-01), Piso
patent: 4255909 (1981-03-01), Soderstrom
patent: 4614065 (1986-09-01), Papp
patent: 4906128 (1990-03-01), Trudel
patent: 4925337 (1990-05-01), Spiess et al.
patent: 5095667 (1992-03-01), Ryan et al.
patent: 5344253 (1994-09-01), Sacchetti
patent: 5797221 (1998-08-01), Young et al.
patent: 5974741 (1999-11-01), Fukuhara
patent: 6007270 (1999-12-01), Bowman
patent: 2208416 (1997-06-01), None
Adams Thomas
Markovich Kristine M.
Pezzuto Robert E.
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