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BACKGROUND OF THE INVENTION 
     This invention relates to a road gully or inspection cover assembly, and more particularly to such an assembly that permits ready adjustment of the vertical position of the cover of the assembly. 
     It is a necessary part of the construction of new roads to incorporate water gullies and manholes therein all of which have to be covered, the covers eventually needing to be at the finished level of the road. 
     Common practice is initially to construct a road to a base course level and thereafter to apply a wearing course of substantial thickness to complete the road. 
     The gullies and manholes are incorporated prior to application of the wearing course, and invariably extend above the base course with their covers located at a level anticipating that of the final wearing course. 
     There is often a considerable period of time, particularly in new housing estates, between laying of base courses and wearing courses, and this can create a number of problems. 
     As the covers project above the surface of the base course by the thickness of the wearing course, they constitute serious obstacles to vehicles with low clearance as well as to pedestrians. They can cause damage to, and can themselves be damaged by, vehicles, particularly road cleaning vehicles incorporating mechanical front shovels. In such situations, the assemblies, or at least the covers thereof, often have to be replaced and the associated manhole or gully cleared of rubble to prevent blockage. 
     Additionally, the finished level of the water gullies, being above that of the base course prior to the application of the wearing course, results in the accumulation of large pools of water on the roads during wet weather. 
     It has been proposed, for example in my European patent no. 0715028, to provide a road gully or inspection cover assembly the position of the cover of which can be adjusted to accommodate the difference in levels between the base course and the wearing course of the road. 
     More particularly, the known assembly comprises a fixed outer frame and an adjustable inner frame slidably supported in the outer frame and capable of being located at any position between a lowermost position and an uppermost position, the inner frame supporting the cover of the assembly whereby the cover can initially be located at the base course level of the road, and subsequently raised and located at the wearing course level of the road. 
     Such an assembly is suitable for situations in which the depth of the wearing course is within certain defined limits whereby strict regulations relating to the extent of overlap of the components of the assembly can be satisfied. 
     In particular, it is necessary to provide a minimum 50 mm vertical overlap of the cover with its supporting frame, and a minimum 50 mm overlap between the inner and outer frames. 
     The standard depth of the outer frame is 100 mm, the thickness of the base plate of the outer frame is 6 mm, and the recommended thickness of the wearing course is 40 mm. The overall relationship between the inner and outer frames of this known assembly is such as to provide a maximum adjustability between the lowermost and uppermost positions of the inner frame, and therefore the maximum depth of wearing course that can be accommodated by the assembly, of 44 mm. 
     SUMMARY OF THE INVENTION 
     It would be desirable to be able to provide a road gully or inspection cover assembly capable of accommodating thicker wearing courses than heretofore, whilst still satisfying British Standard regulations. 
     According to the present invention there is provided a road gully or inspection cover assembly comprising an outer frame having an upstanding outer wall and integrally formed support means extending inwardly of the lower regions of the outer wall over part at least of the peripheral extent of said outer wall, a first temporary inner frame for location within the outer frame, the outer frame and the first temporary inner frame co-operating to support a cover for the assembly in a first, lowermost position associated with the base course level of the road, and a second inner frame which, on removal of the first inner frame from within the outer frame, can be located within the outer frame to support the cover at a higher position associated with the wearing course level of the road. 
     There may be a plurality of second inner frames, one associated with each of a number of different higher positions. 
     Alternatively, the position of the second inner frame relative to the outer frame may be vertically adjustable, for example by providing selectively variable support means reacting between the outer frame and the underside of the second inner frame. 
     In a first embodiment of the invention, the outer frame is of upwardly-open channel shape in transverse section over said part at least of the peripheral extent of the outer wall thereof, the inner wall of the section comprising said support means, the lowermost position of the cover being determined by abutment of the cover with the inner wall of the channel section, the first temporary inner frame surrounding the cover in its lowermost position to close the hollow interior of the outer frame, the second inner frame being received within the channel section of the outer frame to determine the higher position of the cover. 
     In a second embodiment of the invention, the outer frame is of substantially L-shape in transverse section over said part at least of the peripheral extent of the outer wall thereof, the inwardly extending lower leg of the section comprising support means having a horizontal upper surface thereto. 
     The lowermost position of the cover may be determined by abutment of the cover with the upper surface of the support means, the first temporary inner frame also seating on the upper surface of the support means to surround the cover in its lowermost position and to close the outer frame, the second inner frame seating on the upper surface of the support means to determine the higher position of the cover. 
     Alternatively, the first temporary frame may seat on the upper surface of the support means and may be configured to receive thereon the cover, typically a gully grate, to determine the lowermost position of the cover, the second inner frame again seating on the upper surface of the support means to determine the higher position of the cover. 
     The invention is particularly suited to assemblies incorporating covers of generally rectangular shape, it being preferred that the inwardly extending support means are provided at the corner regions only of the outer frame. 
     Accordingly the first and second inner frames will include downwardly extending leg portions at the corner regions thereof adapted to seat on, and co-operate with, the support means on the outer frame, the extents of the first and second inner frames between the corner regions being of lesser depth than the corner regions. 
     Conveniently the outer frame and the second inner frame include adjustable attachment means operable to effect a connection between the sidewalls thereof once the inner frame is located at a desired level relative to the outer frame, for example one or more vertical slots in one of the frames and a locking bolt on the other frame. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a vertical section through a first assembly according to the invention at a corner thereof, the left hand side of which shows the cover in its lowermost position, and the right hand side of which shows the cover in a higher position; 
     FIGS. 2,  3  and  4  are vertical sections through part of a second assembly according to the invention at a corner thereof in different stages of assembly; 
     FIG. 5 is a plan view from above of the corner of the outer frame of the assembly of FIGS. 2 to  4 ; 
     FIG. 6 is a section on the line VI—VI in FIG. 5; 
     FIG. 7 is a view of one side of the second inner frame of the assembly of FIGS. 2 to  4 ; 
     FIGS. 8 and 9 are vertical sections through part of a third assembly according to the invention at a corner thereof with the cover in its lowermost and higher positions respectively. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1, the illustrated assembly includes a generally rectangular outer frame indicated generally at  2  for location in the foundations of a road under construction to surround a gully pot therein. 
     The outer frame includes an outwardly projecting peripheral flange  4  upstanding from which is a sidewall  6  defining the frame, and typically 100 mm high. Diagonally across each corner of the frame  2 , and integrally formed with the sidewall  6 , is an inwardly projecting support portion  8  having a horizontal upper surface or ledge  10  thereon located typically 50 mm above the base of the frame  2 , and whereby the sidewall  6  projects 50 mm above the ledge  10 . 
     The assembly includes a temporary inner frame indicated generally at  12  having a depth of 50 mm and adapted to seat on the ledges  10  at the corners of the outer frame  2 . 
     The inner frame  12  comprises an upstanding peripheral wall  14  and, across the corners thereof, an inwardly projecting support portion  16  having a horizontal upper surface or ledge  18  thereon. 
     The inner frame  12  and the ledges  18  are configured to receive thereon and support a gully grate  20  for the assembly whereby the upper surface of the grate  20  is level with the upper ends of the aligned sidewalls  6 , 14  of the outer and inner frames  2 , 12  respectively, this being the anticipated level of the base course of the road. 
     Thus it will be appreciated that, after construction of the base course and with the grate  20  in position, the top surface of the grate is level with, to form a continuation of, the surface of the base course. 
     Before laying the wearing course, it is necessary to raise the grate  20  to the anticipated level of said wearing course, and this is achieved as follows. 
     The grate  20  is removed from the inner frame  12 , and the inner frame  12  is removed from the outer frame  2 . A second, permanent inner frame indicated generally at  22  is positioned within the outer frame  2 . The inner frame  22  comprises an upstanding peripheral wall  24  and, across the corners thereof, an inwardly projecting support portion  26  having an upper surface or ledge  28  thereon. 
     The inner frame  22  is typically 90 mm deep whereby, with the frame  22  supported on the ledge  10  of the outer frame  2 , the upper end of the inner frame  22  is located at the anticipated surface level of a 40 mm thick wearing course, 140 mm above the base of the outer frame  2 . 
     The ledges  28  on the inner frame  22  are so positioned as to support the grate  20  thereon whereby the upper surface of the grate  20  is also level with the anticipated surface level of the wearing course. 
     Clearly the height of the inner frame  22  can be chosen dependent upon the depth of wearing course to be used, or packing could be provided between the ledges  10  on the outer frame  2  and the lower ends of the support portions  26  of the inner frame  22 . 
     Referring to FIGS. 2 to  7  there is shown an assembly including a rectangular outer frame indicated generally at  30  for location in the foundations of the road under construction to surround a manhole therein. 
     The general configuration of the frame  30  is similar to that of FIG. 1 except that the solid support portions  8  of FIG. 1 are replaced by hollow U-section profiles defined by upstanding walls  32  inwardly of the sidewall  6  and terminating midway up the sidewall  6 , typically 50 mm above the base of the outer frame  30 . 
     A manhole cover is indicated generally at  34  and includes a rectangular top plate  36  and an integral depending peripheral flange  38 . Closure of the assembly is effected by locating the cover  34  in the outer frame  30  to seat on and to be supported by the upper ends of the walls  32  as shown in FIG.  2 . In this position of the cover  34  there is an annular space between the cover and the upstanding wall  6  of the outer frame  30 , and this space is filled by a temporary inner frame  40  supported on the base of the outer frame  30  which serves to locate the cover in position and to prevent the ingress of undesirable material into the assembly. 
     The locations of the upper ends of the walls  32  ensures that the upper surface of the cover  34  is level with the upper end of the wall  6  and with the anticipated level of the base course of the road, as is the upper end of the temporary frame  40 . 
     Thus it will be appreciated that, after construction of the base course and with the cover  34  in position, the top surface of the plate  36  is level with, to form a continuation of, the surface of the base course. 
     Before laying the wearing course, it is necessary to raise the cover  34  to the anticipated level of said wearing course, and this is achieved as follows. 
     The cover  34  is removed from within the outer frame  30 , as is the temporary inner frame  40 . A second permanent inner frame indicated generally at  42  is positioned within the outer frame  30  as shown in FIG.  3 . The inner frame  42  comprises an upstanding peripheral wall  44  and, across each corner thereof, an increased thickness support portion  46  having an upper surface or ledge  48  thereon and adapted to be received within an associated one of the U-section profiles at the corners of the outer frame  30 . 
     The inner frame  42  is typically 140 mm high with the ledge  48  located 50 mm from the top thereof, the depth of the cover  34 . 
     Thus, with the inner frame  42  seating in the outer frame  30 , and with the cover  34  supported on the ledges  48  of the inner frame  42 , the upper end of the wall  44  and the upper surface of the top plate  36  of the cover  34  are positioned at the anticipated level of a wearing course 40 mm thick. 
     If a thicker wearing course is to be provided, it will be appreciated that a taller inner frame  42  may be provided, or the illustrated frame  42  may be raised as shown in FIG. 4 by inserting support means, for example a settable filler material or support blocks, in the U-sections of the outer frame  30 , to achieve the desired level for the cover  34 . 
     FIG. 5 shows the U-section profile of the outer frame  30  defined between the sidewall  6  of the frame  30  and the upstanding wall  32  at the corners of the frame  30 , the line of the temporary inner frame  40  being shown in dotted lines. 
     FIGS. 5 to  7  show one of a number of connection means provided on the outer frame  30 , in the form of a nut and bolt combination  50  extending through a hole in the side extent of the wall  6 , for securing the inner frame  42  to the outer frame  30  once the final position of the inner frame  42  is determined. The connection means further include, for each nut and bolt combination  50 , a vertical slot  52  in a side extent of the wall  44  of the inner frame  42  which permits vertical adjustment of the frame  42  relative to the outer frame  30 , the combination  50  being tightened once the final position of the frame is achieved, thereby supplementing the positioning of the frame  42  provided by the portions  46  thereof. 
     The combination  50 /slot  52  may typically provide for up to 40 mm vertical adjustment. 
     Referring to FIGS. 8 and 9, there is shown an assembly similar to that of FIGS. 2 to  7  but in which the outer frame, referenced  54 , includes, at the corners thereof, a solid support portion  56  similar to that of the outer frame  2  of FIG.  1 . As in the embodiment of FIGS. 2 to  7 , the cover  34  of FIGS. 8 and 9 is supported in its lowermost position by abutment with the outer frame  54 , more particularly with the support portion  56 , with the temporary inner frame, referenced  58 , also seating on the support portion  56  to fill the space between the cover  34  and the outer frame  54 . 
     The higher position of the cover  34  is determined by a permanent inner frame referenced  60  similar to the inner frame  42  having increased thickness support portions  62  at the corners thereof which seat on the support portions  56  of the outer frame  54 . The function and operation of this embodiment conforms with that of the embodiment of FIGS. 2 to  7 . 
     In all embodiments, the provision of separate temporary and permanent inner frames associated with the base course level and the wearing course level of the road respectively ensures that all British Standard regulations relating to the extent of vertical overlaps of components can be readily met, whilst at the same time enabling accommodation of a variety of thicknesses of wearing courses in excess of the conventional thickness of 40 mm. 
     Clearly the precise construction and configuration of the various frames can be altered from that described and illustrated without departing from the scope of the basic invention, while the material of the temporary frame can be chosen to suit particular requirements. Where this temporary frame supports, as in FIG. 1, the material may be steel. In non-supporting situations as shown in FIGS. 2 to  9 , the temporary frames may be of relatively cheap, lightweight material such as plastic. 
     It will be appreciated that the temporary frames are simple to remove prior to raising the cover to the wearing course level, and can be stored for subsequent usage, the overall invention providing a high degree of flexibility and adjustment for the final wearing course level such as may be required for example when block paving is superimposed on the wearing course.

Summary:
A road gully or inspection cover assembly comprises an outer frame having an upstanding outer wall and integrally formed support structure extending inwardly of the lower regions of the outer wall over part at least of the peripheral extent of the outer wall, a first temporary inner frame for location within the outer frame, the outer frame and the first temporary inner frame co-operating to support a cover for the assembly in a first, lowermost position associated with the base course level of the road, and a second inner frame which, on removal of the first inner frame from within the outer frame, can be located within the outer frame to support the cover at a higher position associated with the wearing course level of the road.