Abstract:
An adjustable manhole cover frame assembly suitable for mounting on a manhole basin upper section has an outer ring, capable of resting on the top surface of the upper section, and an inner ring engaging the outer ring by screw threads and having support for a manhole cover. The lower surface of the frame assembly has a part spherically curved surface resting on a similarly curved surface of the manhole basin upper section and which allows the orientation of the frame assembly to be adjusted. Also, the frame assembly itself may have parts with part spherical mating surfaces allowing an upper part to be adjusted for slope when the remainder of the frame assembly has been fixed.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a manhole cover assembly for mounting a manhole cover above a manhole basin. The invention is applicable to adjustment of the slope of the manhole cover, and usually also its height, as necessitated by resurfacing a road surface and/or by frost heave of the surrounding ground. 
     2. Prior Art 
     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 concrete 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. Adjustment of slope may also be necessary, as when the camber of a road is changed. In addition, adjustment of the lateral position may be necessary, especially with catchment basins where the manhole must be positioned accurately close to a curb. 
     Various constructions of adjustable manhole frames have been proposed to deal with height 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 helical 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. 4,075,796, which issued Feb. 28, 1978 to Cuozzo; 
     U.S. Pat. No. 5,095,667, which issued Mar. 17, 1992 to Ryan et al.; and 
     U.S. Pat. No. 5,344,253, which issued Sept. 6, 1994 to Sacchetti. 
     All the above patents are concerned with height adjustment, and show little or no provision for slope adjustment. Most of the patents show upper and lower parts of the frame assembly to be connected by helical threads surrounding the annular upper portion of the frame so that rotation of this upper portion changes its height without any change to its slope. However, some other patents show jack-type screw adjusters which are spaced around the frame and which can be adjusted individually to alter the slope, as well as the height, of the upper frame portion. Such arrangements are shown in the following patents. 
     U.S. Pat. No. 3,930,739, which issued Jan. 6, 1976 to Larsson et al,; 
     U.S. Pat. No. 4,149,816, which issued Apr. 17, 1979 to Piso; and 
     U.S. Pat. No. 4,925,337, which issued May 15, 1990 to Spiess et al. 
     These prior arrangements would appear to have some drawbacks. In particular, they seem to offer only limited slope adjustment. This is especially true of Piso, where more than slight change of slope would seemingly cause binding in the adjusting screws. In Larsson et al. and Spiess et al., the amount of slope adjustment would be limited by binding between outer edges of the upper frame portion and the fixed surrounding structure. Also, these prior patents do not show any seals which would prevent ingress of soil or other material into the mechanical parts if there were to be significant slope adjustment. Larsson et al, and Piso show small seals which would accommodate only a small amount of slope adjustment, while Spiess et al. show no seal at all. 
     It is an object of this invention to provide an adjustable manhole assembly in which substantial slope adjustment of the manhole cover is possible. 
     A further object of embodiments of the invention is to provide a joint arrangement which can maintain a seal against soil and other material entering the manhole basin even when substantial adjustments are made. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the deficiencies of the prior art in relation to slope adjustment by providing at least one part-spherical mating surface between an upper part of the assembly which is subject to slope adjustment and a lower part which remains stationary. 
     Preferably, the slope adjustment does not separate the mating surfaces. 
     In a preferred embodiment, the invention allows lateral adjustment of the cover position such as will allow the cover to be set a precise distance from the curb. 
     In accordance with one aspect of the invention, an adjustable manhole basin cover assembly including an upper section of an annular manhole basin comprises: 
     an upper annular part having a recess for receiving a manhole cover and adapted to mate with an underlying annular surface which is also part of the assembly, the upper annular part and the underlying annular surface having mating surfaces, 
     wherein at least one of the mating surfaces is part spherical, whereby the upper annular part may be adjusted in slope relative to the upper manhole basin section while maintaining a sealing relationship between the mating surfaces. 
     Preferably, both of the mating surfaces are part spherical. Also, the mating surfaces are preferably surrounded by a sealing collar to minimize entry of soil or other matter between these surfaces. 
     The upper annular part may be an adjustable frame assembly for variably spacing the manhole cover above a conventional concrete manhole upper section, in which case the concrete manhole basin upper section and the bottom of the frame assembly have the part spherical mating surfaces. 
     Alternatively, the upper annular part may be an upper portion of the adjustable frame assembly, and the part spherical mating surfaces are provided between the upper portion and a lower portion of the frame assembly. 
     Preferably, spherical mating surfaces are used both between the manhole basin upper section and the frame assembly, and between upper and lower portions of the frame assembly. The lower mating surfaces between the manhole basin upper section and the frame assembly provide a coarse adjustment, while the upper mating surfaces between the upper and lower portions of the frame assembly provide a fine adjustment. The provision of two slope adjustments, by the upper and lower pairs of mating surfaces, also has the advantage that the adjustments can be combined to give some lateral adjustment of the upper portion of the frame assembly. 
     A greater degree of lateral adjustment may be provided by a modified construction in which the precast manhole basin upper section, which has one of the part spherical mating surfaces, is in the form of a precast adapter ring resting on a manhole basin upper section with an annular upper surface, which may be the conventional flat top of a manhole upper section. In this case the manhole cover assembly of this invention can be considered as including this adapter ring as well as the frame assembly resting on it. For the lateral adjustment, the precast adapter ring has its annular top surface formed eccentrically to its lower surface so that the lateral position of the frame assembly relative to the manhole basin can be changed by rotating the precast adapter ring on the manhole basin. 
     According to a second aspect of the invention, an adjustable manhole cover assembly comprises: 
     a precast manhole basin upper section having an annular top surface, the upper section being in the form of a precast adapter ring having an annular top surface and annular lower surface, the annular lower surface being suitable for resting on a manhole basin with an annular upper surface; and 
     a frame assembly having a recess for receiving a manhole cover, the frame assembly having an annular lower surface capable of resting on the annular top surface of the adapter ring so that the last-mentioned annular surfaces form mating surfaces, at least one of said mating surfaces being part-spherical so as to allow slope adjustment of the frame assembly relative to the adapter ring; 
     the precast adapter ring having annular top surface formed eccentrically to its lower surface so that the lateral position of the frame assembly relative to the manhole basin can be changed by rotating the precast adapter ring on the manhole basin. 
     Where the manhole cover assembly has an adjustable frame assembly with a recess for receiving a manhole cover, and has an annular lower surface capable of resting on an annular top surface of a precast manhole basin upper section, the adjustable frame assembly may have an inner frame movable within an outer frame for adjusting the height of the inner frame, and part spherical mating surfaces may be provided on upper and lower portions of the inner frame. As in prior art constructions, the inner frame may have external helical threads engaging internal screw threads of the outer frame, whereby these threads may be used to adjust the height of the inner frame relative to the outer frame for raising the height of the manhole cover support. 
     The invention may also provide a special locking arrangement for locking the manhole cover in place on the frame assembly. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which; 
     FIG. 1 is a sectional elevation of the upper part of a first embodiment of manhole basin having an adjustable manhole cover frame assembly in accordance with the invention; FIG. 1 also indicates a jack used to adjust the slope of the frame assembly; 
     FIGS. 2 a  and  2   b  are enlarged sectional views of mating parts of upper and lower portions of the frame assembly shown in FIG. 1, in different positions of adjustment; 
     FIG. 3 is a view on lines  3 — 3  of FIG. 2 b  showing the underside of a locking nut and adjacent parts; 
     FIG. 4 is a view on lines  4 — 4  of FIG. 2 a , showing a locking washer; 
     FIGS. 5 a  and  5   b  are, respectively, longitudinal and cross-sectional views of the locking washer of FIG. 4; 
     FIG. 6 is a top view of a modified form of the frame assembly with the cover removed; 
     FIG. 7 is a sectional elevation on the frame assembly of FIG. 6, the lower part being taken on lines  7 — 7  of FIG. 6, and the upper part being taken on lines  7 ′— 7 ′ of FIG. 6, and 
     FIG. 7 a  is an enlarged fragmentary view of parts of the assembly shown in FIG.  7 . 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows a manhole cover  10  supported on the top section  12  of a manhole basin by a manhole cover frame assembly  14  which is adjustable in accordance with this invention. The manhole basin of which the top precast section  12  is shown in FIG. 1 is cast of concrete, and has a cylindrical middle section  16  the top portion of which is shown, and which rests on a lower section which is not shown. The top section  12  rests telescopingly on the middle section  16 . The invention allows adjustment of the height and slope of the cover  10  relative to the ground level G. 
     The frame assembly  14 , in common with some prior art designs, has two parts formed of cast metal, firstly an inner, upper ring part  20  having an internal flange  22  providing a recess for the edge of the manhole cover  10  and having a surrounding helical thread  23 , and secondly an outer, lower ring part  24  having an internal helical thread  24   a  which receives the thread  23 . The inner ring thread  23  subtends just one complete 360° circle; rotation of the inner ring part relative to the normally stationary outer part adjusts its height in accordance with prior art procedures. The rotation can be done by conventional methods, for example by use of a special tool having depending spigots which fit into bores in the top of the ring part  20 ; these bores are described below with reference to FIG.  6 . While some prior art frame assemblies have only the metal parts of the ring as described, here it is preferred that the outer ring part  24  be surrounded by a concrete collar  26  cast around the outer ring part  24 , which reinforces this ring part and provides a larger mating area at the bottom of the frame assembly where it rests on the manhole top section  12 . 
     Typically, in prior art designs, the top precast section  12  has a flat top and the frame assembly  14  would have a flat underside portion resting on this flat top and with a skirt overlapping the top section to provide a seal. However in this invention the upper end of the top section  12  and the lower surface of the frame assembly  14  have mating surfaces,  12 ′ and  14 ′ respectively, which are part spherical. As shown, the part spherical mating surfaces have a center of curvature C 1  below the spatial center of the top manhole section  12 . The mating surfaces are surrounded by a sealing collar  28  having a cylindrical part in contact with the outside of concrete collar  26  and a flared skirt in contact with the part spherical upper surface  12 ′. This sealing collar may be made of glass fiber reinforced polyester or stainless steel. This collar is intended to largely prevent soil or other dirt from entering between the mating surfaces, especially when frost lifts the outer concrete collar  26  and the ring part  24 , and for this purpose, after the collar has been adjusted on the section  12 , it may be secured to this section by nails indicated at  29  which will prevent the collar lifting off the surface  12 ′. The collar can be fixed in this way because the adjustment of slope at this joint is a coarse adjustment, and fine slope adjustment needed subsequently can be effected by the upper pair of mating surfaces to be described below. Nailing this collar in place also helps to prevent unwanted angular movement of the frame assembly during backfilling around this assembly. 
     As shown in FIG. 1, the top precast section  12  has its central aperture  12   a  provided with an annular notch or recess  13  with a generally horizontal lower surface. This notch can receive the lower end of a screw jack  15  shown in broken lines in FIG. 1, this jack having its upper end pushing against the upper portion of the opposite side of the inner ring  20  and serving to adjust the slope of the inner ring. 
     The inner ring  20  itself is formed of upper and lower portions  20   a  and  20   b,  which are also joined by part spherical mating surfaces, having a center of curvature indicated at C 2  above the center of the manhole cover  10 . Details of the joint are shown in FIGS. 2 a  and  2   b , which show enlarged views of the mating parts. As shown, the upper inner ring flange  22  is effectively split to provide the part spherical mating surfaces  20   a ′ and  20   b ′, and the upper part  22   a  of the flange which is integral with the upper ring portion has a series of countersunk bores  30  for receiving the heads of screws  32 . These screws pass through enlarged apertures  34  in the lower part  22   b  of the flange which is integral with the lower ring portion  20   b,  and also pass through elongated lock washers  35  retained by elongated nuts  36  As will be seen in FIGS. 3 and 4, the elongated washers  35  and nuts  36  are long enough to overlap the sides of the apertures  34  and long enough that the ends of the nuts and washers interfere with the inner sides of the part  20   b  to prevent them from rotating. The large apertures  34  allow radial movement of the screws when they have been loosened to allow adjustment of the upper ring portion  20   a  on the lower ring portion between the co-axial position shown in FIG. 2 a  and an eccentric position, such as shown in FIG. 2 b . The outer sides of the nuts and washers are curved so that the screws  32  can come close to the adjacent surfaces of the lower ring part  20   b,  and to allow sufficient movement the outer sides of apertures  34  are sloped, as shown in FIG. 2 a , and recesses  37  are provided to accommodate the nuts and washers in the manner shown in FIG. 2 b.    
     As shown in FIGS. 5 a  and  5   b,  the upper surfaces of the lock washers  35  are roughened and cooperate with rough under surfaces of the areas surrounding the apertures  34 . In addition to inhibiting rotation of the washers, these roughened surfaces help to prevent unwanted movement between the mating surfaces when the screws  32  have been tightened, which otherwise may occur due to traffic passing over the manhole cover which subjects the parts to considerable stress and might tend to move the parts while tension in the screw  32  is reduced. 
     In order to exclude dirt and asphalt from between the mating surfaces of parts  20   a  and  20   b , a sealing collar  38  is provided with a cylindrical portion  38   a  surrounding the outer top of the ring portion  20   a , and a bottom flange  38   b.  This flange lies on top of a washer  39  held in a recess at the top of the outer, lower ring part  24 , and having its inner edge sealing against the outer side of the inner ring part  20   b  by means of O-ring  39   a,  Again, this collar  38  may be of glass fiber reinforced polyester. As seen in FIG. 2 b,  the collar is resilient enough to accommodate the movement of the upper ring portion  20   a  relative to the lower ring part  20   b.  When this movement occurs, bitumen will normally be holding the flange  38   b  of the seal, and the washer  39 , in place so that dirt does not enter below the washer  39 . The movement of the upper ring portion  20   a  will usually be limited to about 3° or 0.5 cm; the greater movement occurs between the mating surfaces  12 ′ and  14 ′. 
     FIGS. 2 a  and  2   b  also show a dirt excluding barrier positioned internally of the screws and mating surfaces, this being provided by a cylindrical plastic skirt  40  which is suspended from its upper edge portion by a fiber ring  42  which fits within a recess  44  in the inner surface of the upper ring portion  20   a . As seen in FIG. 1, this plastic skirt  40 , which may be formed of various polymers, extends down to well below the lower pair of mating surfaces  12 ′ and  14 ′, and thus tends to exclude dirt from both the upper and lower pairs of spherical mating surfaces. Grease may be used around the screw threads  23  and  24 , but not between the mating surfaces  12 ′ and  14 ′ or  20   a  and  20   b . Since the rotation of the inner ring part  20   a  inside part  20   b,  to alter the manhole cover height, may tend to rotate the frame assembly on the concrete section  12 , generally radial cooperating notches may be provided in the mating surfaces  12 ′ and  14 ′ to inhibit such rotation of the frame assembly. 
     In use, the mating surfaces  12 ′ and  14 ′ between the concrete section  12  and the frame assembly  14  may used to allow the frame assembly to be orientated vertically even if the concrete parts, after back filling, are found to be tilted. The mating surfaces between the frame parts  20   a  and  20   b  are usually adjusted at a later stage, after resurfacing of a road has occurred, and it is found that slope adjustment is needed. This involves loosening screws  32 , moving the upper portion  20   a  so that screws  32  slide along the apertures  34 , and then tightening the screws. The upper, inner frame part  20  can also be rotated as needed to bring the manhole cover up to the road level. 
     FIGS. 6,  7  and  7   a  show details of a similar construction, but one in which the manhole basin top section  12   a  has a conventional flat top, and in which the upper mating surface of this top section is provided by a precast concrete adapter ring  50  with a flat undersurface and an outer depending skirt  52  which locates on the outer surface of the manhole top portion  12   a . The adapter ring has a dome shaped top providing the part spherical lower mating surface  50 ′ which receives the frame assembly  14 , which is similar to that of the previous embodiment. 
     The only difference between the frame assembly and that of the previous embodiment is the provision of a locking mechanism for locking the cover  10  to the upper ring portion  20   a;  an enlarged view of the coacting parts is shown in FIG. 7 a.  As shown the upper ring part  20   a  has its flange  22   a  divided into upper and lower portions  60  and  61  joined by an inwards facing cylindrical surface  62 ; the outer edge of the cover  10  has a complementary shape. This surface  62  communicates with two part-circular side recesses  64  having horizontal upper and lower surfaces, these recesses being diametrically opposed on opposite sides of the ring part  20   a  as indicated in FIG.  6 . These side recesses are each arranged to accommodate a D-shaped locking element or pawl  66  which is rotatable on a vertical shaft  68  held in a vertical bore near the outer edge of the cover  10 , and the top of which has a non-circular socket  69  for receiving a key for rotating the shaft and for locking or unlocking the cover. The non-circular socket is preferably an 8 or 10 sided socket so that it can only be rotated by using a special and unusual key, to prevent tampering. 
     It will be clear that the locking parts and side recess could be alternatively arranged differently between the coacting parts,; i.e. the rotatable parts could be provided in the stationary ring part rather than in the cover, 
     FIG. 6 also shows two diametrically opposed vertical bores  70  for receiving spigots of a tool which is used for rotating the upper ring part  20  relative to the lower ring part, for height adjustment, as mentioned above. 
     Although the invention has been described as having two sets of part-spherical mating surfaces, a simple version of the invention may be made with only one pair of mating surfaces, or even with only one part spherical surface which can slide on a complementary mating surface in such a way as to maintain contact between the mating surfaces during slope adjustment. For example, the two parts  20   a  and  20   b  of the upper ring may provide all of the slope adjustment, with the lower surface of the frame assembly being flat and resting on a flat concrete upper section.