GB2207164A

GB2207164A - An extension ring for a manhole frame

Info

Publication number: GB2207164A
Application number: GB08815830A
Authority: GB
Inventors: Michael Donatus Flanagan
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-04-27
Filing date: 1988-07-04
Publication date: 1989-01-25
Also published as: GB8815830D0

Abstract

An extension ring (1) for a manhole frame (2) for raising a manhole cover (3) above the level of the manhole frame (2) comprises a ring member (14) having a manhole engaging portion (15) for location in the cover receiving region of the manhole frame (2) and a cover receiving portion (16) for receiving the cover (3). <IMAGE>

Description

Title: AN EXTENSION FRAME, The present invention relates to an extension frame, and, in particular, to an extension frame for a manhole frame, a handhole frame, a gulley trap frame or the like, such as, for example, the type used to support a cover to close the entrance to a sewer or the like. For convenience such frames, whether they are manhole frames, handhole frames, gulley trap frames or any other such frame will be referred to hereinafter as manhole frames. The invention also relates to a manhole frame.

Manhole frames, in general, are used on roads or footpaths to provide access to underground sewers, service ducts and the like, such as, for example, electrical and telephone cable ducts. Usually, they are supported on a masonry shaft built up from the sewer or duct. In general, the frames may be of circular shapes, square shapes, rectangular shape, hexagonal shape or the like which form an inner region for receiving a cover or lid. A flange inwardly directed into the cover receiving region supports the cover. In general, a flange extending around the frame extends outwardly to be embedded in the road surface for keying purposes. However, the problem with known manhole frames in that in due course the masonry shaft supporting the frame very often subsides, and this therefore causes the frame to subside below the level of the roadway.Needless to say, since the frame supports the cover to close the entrance into the vertical shaft, the cover similarly subsides below the level of the road. This has very dangerous consequences. Should a wheel of a vehicle driving along the road at any reasonable speed encounter such a subsided manhole cover, loss of control of the vehicle invariably occurs. This is a particularly serious problem if one of the front wheels of the vehicle engages the subsided cover which can cause an accident, resulting in loss of life.

Equally serious consequences may arise in the event of a subsidence on a footpath in that a pedestrian may trip on portion of the unsubsided footpath adjacent the manhole frame, thus causing serious injury to the pedestrian.

Unfortunately, the only known way of rectifying a subsided manhole frame is to excavate a considerable area of the road surface around the manhole frame, so that the frame can be lifted off the masonry shaft.

The shaft is then built up by suitable masonry means, and the manhole frame is again reset on the shaft at a higher level. The road surface is then filled in around the manhole frame and allowed to settle for a number of days. Subsequently when the surface has fully settled, a final surface layer is applied around the manhole frame. However, the problem with this is that it tends to be a relatively labour intensive and time consuming task, and furthermore, it leads to considerable excavation works being required around a manliole frame which causes considerable delays to traffic and the like. Indeed, where such excavations are carried out on a footpath or the like, there is always the risk of injury to pedestrians, and in particular blind pedestrians.

There is therefore a need for a device which overcomes these problems. There is also a need for a manhole frame which also overcomes these problems. The present invention is directed towards providing such a device and also a manhole frame for overcoming the problems.

According to the invention there is provided an exlellsiol) frame Lol a mallllole frame tìhe extension frame comprising a manhole engaging portion for engaging portion of the manhole frame, and a cover receiving portion for receiving and supporting the manhole cover.

In one embodiment of the invention, the extension frame has a top face and a bottom face and an opening extending through the extension frame from the top face to the bottom face, portion of the opening adjacent the top face forming the cover receiving portion.

Preferably, the manhole engaging portion is provided by portion of the extension frame adapted, in use, to extend into and engage a cover receiving region of the manhole frame. Advantageously, the outer cross sectional area of the manhole engaging portion is of reduced cross sectional area, and is of an axial length to extend in use to a cover engaging flange in the manhole frame.

In another embodiment of the invention, abutment means are provided in the opening for supporting the cover in the cover receiving portion.

In one embodiment of the invention, the extension frame is provided by a ring member, portion of the outer surface of which defines the cover receiving region of the manhole frame to form the manhole engaging portion.

In a further embodiment of the invention, adjustment means are provided on the extension frame for adjusting the height of the top face of the extension frame relative to the manhole frame.

In a still further embodiment of the invention, fastening means are provided for securing the extension frame to the manhole frame.

In another embodiment of the invention, eying means extends outwardly of the extension frame to engage the material of the road for keying the extension frame in position.

Additionally, the invention provides a manhole frame for a manhole opening comprising a frame having an opening extending therethrough from a top face to a bottom face and a cover receiving portion for receiving a manhole cover, engagement means for engaging masonry defining the manhole opening, and adjustment means for adjusting the position of the extension frame relative to the engagement means.

Further, the invention provides a method for rising a manhole cover above a manhole frame, the method comprising the steps of removing the-manhole cover from the manhole frame, inserting an extension frame according to the invention into the manhole frame and placing a manhole cover in the extension frame.

The invention will be more clearly understood from the following description of some preferred embodiments thereof, given by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a perspective view of an extension frame according to the invention, Fig. 2 is a partly cut-away perspective view of the frame of Fig. 1, Fig. 3 is a cross-sectional view of a manhole, Fig. 4 is another cross-sectional view of the manhole of Fig. 3 with the extension frame of Fig.

1 in use, Fig. 5 is a perspective view of an extension frame according to another embodiment of the invention, Fig. 6 is a sectional view similar to Fig. 4 with the extension frame of Fig. 5 in use, Fig. 7 is a perspective view similar to Fig. 5 of an extension frame according to another embodiment of the invention, Fig. 8 is a sectional view similar to Fig. 6 of the extension frame of Fig. 7, Fig. 9 is a perspective view of an extension frame according to a further embodiment of the invention, Fig. 10 is a partly cut-away perspective view of an extension frame according to a still further embodiment of the invention, Fig. 11 is a cut-away perspective view of an extension frame according to another embodiment of the invention, Fig. 12 is a sectional elevational view of the extension frame of Fig. 11 in use, Fig. 13 is a cut-away perspective of an extension frame according to a further embodiment of the invention, Fig. 14 is a partly cut-away perspective view of an extension frame according to another embodiment of the invention, Fig. 15 is an exploded perspective view of the extension frame of Fig. 14, Fig. 16 is a sectional elevational view of an extension frame according to a further embodiment of the invention in use, Fig. 17 is a sectional elevational view of a manhole and cover, Fig. 18 is a sectional elevational view of the manhole and cover of Fig. 16 illustrated incorporating an extension frame according to another embodiment of the invention, Fig. 19 is a perspective view of an extension frame according to a still further embodiment of the invention, Fig. 20 is a cut-away perspective view of the extension frame of Fig. 19 in use, Fig. 21 is a perspective view of a manhole frame according to the invention, and Fig. 22 is a ctlt-alay perspec: t i ve view of tl1c manhole frame of Fig. 21.

Referring to the drawings, and initially to Figs. 1 to 4 there is provided an extension frame according to the invention, indicated generally by the reference numeral 1 for a manhole frame 2 to raise a cover 3 of the manhole frame 2 above the level of the manhole frame 2. Before describing the extension frame 1 the manhole frame 2 and cover 3 will first be described with reference to Figs. 3 and 4. The manhole frame 2 is a conventional frame having a central circular portion 4 of cast iron with a top face 5 and a flange 6 extending outwardly of the circular portion 4 also of cast iron cast integrally with the circular portion 4. The manhole frame 2, in use, is supported by the flange 6 resting on a vertical shaft 7 usually of masonry extending into a sewer (not shown), as can be seen in Figs. 3 and 4. A bore 8 extending through the circular portion 4 provides access to the shaft 7.

The bore 8 is stepped at 9 to form a cover receiving region 10 which receives the cover 3. The step 9 supports the cover 3. The cover 3 may be of cast iron or of any other suitable construction or material.

The extension frame 1 comprises a ring member 14 of circular shape and of cast iron, having a manhole engaging portion 15 and a cover receiving portion 16.

An opening 18 extends through the ring member 14 from a top face 17 to a bottom face 19 to provide access into the bore 8 of the manhole frame 2 and in turn into the vertical shaft 7. As can be seen, the outer diameter of the ring member 14 is stepped at 20 to form an abutment face for engaging the top face 5 of the manhole frame 2. The internal diameter of the ring member 14 is stepped at 21 to form an abutment means for supporting the cover 3. The upper portion of the bore 18 above the step 21 is of diameter substantially similar to that of the cover 3 and accordingly forms the cover receiving portion 16. A rim 22 extends around the step 21 for stabilising the cover 3 in the cover receiving portion 16.The manhole frame engaging portion 15 is formed by the portion of the ring member 14 of reduced diameter, and as can be seen, the outer diameter of this portion is substantially similar to the diameter of the cover receiving portion 10 of the manhole frame 2. The length of the portion 15 between the step 20 and bottom face 19 is such as to allow the bottom face 19 to sit on the step 9 in the bore 8 of the manhole frame 2, and the step 20 to sit on the top face 5 of the manhole frame 2.

In use, to raise the manhole cover 3 above the level of the manhole frame 2, the cover 3 is removed from the frame 2. The extension frame 1 is placed in the cover receiving portion 70 of the frame 2 as illustrated in Fig. 4 and the cover 3 is replaced in the cover receiving portion 16 of the extension frame 1.

In the normal course of events, it is envisaged that the extension frame 1 will be used to build up a cover 3 to the surface of a road or footpath to compensate for subsidence of the shaft 7, which in turn would cause the manhole frame 2 to subside below the level of the road. In Fig. 3 a typically subsided manhole frame 2 is illustrated. Fig. 4 illustrates how the extension frame 1 is inserted and on insertion the level of the road is made up at 28 around the extension frame 1, so that when the cover 3 is engaged in the extension frame 1, it will be at substantially the same level as the road surface 29.

Referring now to Figs. 5 and 6 there is illustrated an extension frame 30 according to another embodiment of the invention. This frame 30 is substantially similar to the frame 1 and similar components are identified by the same reference numerals. In this case, a keying means provided by an outwardly extending flange 31 extends outwardly of the ring member 14 above the step 20. Spikes 32 extend downwardly of the flange 31 to engage the existing road surface. The combination of the flange 31 and tlie spikes 32 effectively form a keying means for keying the extension frame 30 in the road surface to avoid any danger of the extension frame 1 being detached from the manhole frame 2.

In this particular embodiment of the invention, it is envisaged that a small portion of the surface of the road adjacent the manhole frame 2 would be removed prior to installing the extension frame 30 in the manhole frame 2, and after that the road surface would be made up to the top face 17 of the extension frame 1, as illustrated in Fig. 6.

Referring now to Figs. 7 and 8 there is illustrated an extension frame 35 according to another embodiment of the invention. This extension frame 35 is substantially similar to the extension frame 30 and similar components are identified by the same reference numeral. The main difference between this frame 35 and the frame 30 is that a flange 36 extending from the ring member 14 is slightly arcuate in cross-section and the spikes 32 have been omitted.

The slightly arcuate flange 36 further facilitates keying of the extension frame to the roadway.

Referring now to Fig. 9, there is illustrated an extension frame according to another embodiment of the invention, indicated generally by the reference nunlelal 40. This frame is substantially similar to that of Figs. 1 to 4 and similar components are identified by the same reference numeral. The main difference between this frame 40 and the extension frame of Figs. 1 to 4 is that adjustment means are provided on the extension frame 40 to permit the relative height of the extension frame 40 to the manhole frame 2 to be adjusted to accommodate cases where the manhole frame 2 has unevenly subsided or where it is desired to provide a single size of extension frame which may be used with manhole frames which have subsided different amounts.In this particular embodiment of the invention, the adjustment means are provided by three screws 41 which engage correspondingly threaded holes 42 in the manhole engaging portion 15. Lock nuts 43 are provided on the screws 41 to secure the screws 41 at a desired height.

As can be seen, the adjusted means in this case provides three point adjustment means at 120 intervals, and accordingly, the height of the extension frame can be adjusted to accommodate a manhole which has unevenly subsided.

In use, the extension frame is placed in the manhole frame 2 as already described with reference to Fig. 4.

The screws 41 are then adjusted until the top face 17 of the cover receiving portion 16 is level with the surface of the road. The lock nuts 43 are then thightened against the bottom face 19 to retain the screws 41 at the desired adjustment. The manhole cover is placed in the cover receiving portion 16 of the extension frame 40.

Referring now to Fig. 10, there is illustrated an extension frame according to a still further embodiment of the invention, indicated generally by the reference numeral 45. This extension frame is substantially similar to the extension frame 40, and similar components are identified by the same reference numerals. In this case, the holes 42 are reinforced by providing bosses 46 on the manhole engaging portion 15 which extend into the opening 18.

The bosses 46 provide strengthening for the holes 42 and are cast integrally with the extension frame 45.

In use, the operation of this extension frame 45 is similar to the extension frame 40.

Referring now to Figs. 11 and 12, there is illustrated an extension frame according to another embodiment of the invention, indicated generally by the reference numeral 50. This extension frame 50 is substantially similar to the extension frame 1 and similar components are identified by the same reference numeral. Fastening means, in this case provided by three brackets 51 are provided for securing the extension frame 50 to a manhole frame 2, see Fig. 12.

Each bracket 51 is secured to the manhole engaging portion 15 of the extension frame 50 by screws 53 engaging corresponding threaded holes 54 in the manhole engaging portion 15. Slots (not shown) are provided in the brackets 51 to accommodate the screws 53 and provide for adjustment of the brackets relative to the extension frame 50. Alternatively, a plurality of holes may be provided. Lugs 55 extending from the brackets 51 engage the bottom face 56 of the manhole frame 2, as is illustrated in Fig. 12.

In use, on inserting the extension frame 50 into the manhole frame 2 the brackets 51 are secured so that their lugs 55 engage the lower edge 56 of the frame 2.

Otherwise, operation and use of this extension frame 50 is similar to that of Fig. 1.

Referring now to Fig. 13, there is illustrated an extension frame 60 according to a still further embodiment of the invention. This frame 60 is similar to the extension frame 1 and similar components are identified by the same reference numeral. Fastening means for securing the extension frame 60 to the manhole frame 2 are provided in this case by brackets 61 with lugs 62 which engage the bottom face 56 of the manhole frame 2. Ends 63 of the brackets 61 are threaded and engage clearance holes 64 in bosses 65 integraly moulded on the manhole engaging potion of the extension frame 60. Nuts 66 secure the brackets 61 in the bosses 65.

When the extension frame 60 is mounted in the manhole frame 2, the brackets 61 are engaged in the holes 64 and secured by the nuts 66 so that the lugs 62 engage the lower face 56 of the manhole frame 2. Otherwise, operation and use of this extension frame is similar to that of the frame of Fig. 1.

Referring now to Figs. 14 and 15, there is illustrated an extension frame 70 according to a still further embodiment of the invention. This frame 70 is somewhat similar to the extension frame 1 and similar components are identified by the same reference numeral. The extension frame 70 comprises adjusting means to enable the height from the end face 72 to the top face 17 to be adjusted. The extension frame 70 is provided in three parts, namely a top part 73 identical to the extension frame 1, an intermediate ring 74 and a bottom ring 75. The ring 74 supports the part 73 by engaging the step 20 of the top part 73. The lower ring 75 engages the seat of the manhole frame 2.Threads 76 and 77 on the rings 74 and 75 engage each other, and by screwing the parts 74 and 75 relative to each other, the height from the top face 17 to the bottom edge 72 of the frame 70 is adjusted.

Securing means provided by a grub screw 78 is provided in the ring 75 to engage tulle ring 74 when the two parts leave been screwed to their desired relative position.

Use of this extension frame 70 is similar to the extension frame 1, with the exception that the extension frame 70 permits height adjustment to accommodate manhole frames which have sunk to different levels below the road.

Referring now to Fig. 16, there is illustrated an extension frame 80 according to a still further embodiment of the invention, in use. This frame 80 is substantially similar to the extension frame 70 and similar components are identified by the same reference numeral. In this case, the height of the extension frame 80 is adjustable in similar fashion to the extension frame 70 of Figs. 14 and 15. In this case, the frame is formed in two parts, namely, an upper part 81 and a lower part 82. The upper part 81 is similar to the parts 73 and 74 combined of the frame 70, while the part 82 is similar to the part 75.

Accordingly, to vary the height from the top face 17 to the bottom edge 72, the upper and lower parts 81 and 82 are screwed together. An additional step 84 is provided in the opening 18 to accommodate a corresponding step 85 on the cover 3.

Fastening means provided by brackets 83 for securing the extension frame 80 to the manhole frame 2 are similar to the brackets 51 described with reference to the extension frame 50 of Figs. 11 and 12. For convenience, similar components of these brackets are identified by the same reference numerals as in Figs.

11 and 12.

In use, the height of the frame is adjusted by adjusting the upper and lower members 81 and 82 relative to each other until the top face 17 is at a desired height to co-incide with the level of the road. A grub screw (not shown) is tightened to secure the upper and lower part 81 and 82 together and prevent them unscrewing. The brackets 83 are then secured as illustrated in Fig. 16.

Referring now to Figs. 17 and 18, there is illustrated an extension frame according to a still further embodiment of the invention, indicated generally by the reference numeral 86. In this case, the extension frame 86 is substantially similar to the extension frame 1 of Figs. 1 to 4 and similar components are identified by the same reference numeral. However, in this case, the extension frame 86 sits on a step 87 of the manhole frame 2. A manhole cover 3 is provided with a stepped cross sectional area at 88.

In use, the step 88 rests on the seat 22 of the extension frame 86. An additional ring member 89 is provided to sit on the seat 9 of the manhole frame 2 to support the cover 3. Fig. 17 illustrates the manhole cover 3 and manhole frame 2 prior to the extension frame being fitted, while Fig. 18 illustrates the extension frame 86 and the additional ring 89 in place.

Referring now to Figs. 19 and 20, there is illustrated an extension frame according to a still further embodiment of the invention, indicated generally by the reference numeral 90. The extension frame 90 is for use with a manhole frame 2 substantially similar to the frame 2 of Figs. 3 and 4. However, the manhole frame 2, in this case, is provided with an additional step 102 to engage a corresponding step 103 on the cover 3. The extension frame 90 comprises an upper ring 91 and a lower ring 92 joined by members 93, all integrally cast. The rings 91 and 92 form an opening 94 which extend through the extension frame 90 from a top face 95 to a bottom face 96. The inner and outer diameters of the upper ring 91 are stepped at 105 and 106 respectively. The step 106 engages the top face 5 of the manhole frame 2. The step 105 engages the step 102 of the manhole frame 2.Abutment means are provided by a face 97 of the bottom ring 92 for supporting the cover 3. The abutment face 97 with an inner face 98 of the upper ring 91 define a cover receiving portion 99. A manhole engaging portion 100 is formed by the outer surface 101 of the bottom ring 92 and the vertical members 93. This manhole engaging portion 100 engages the cover engaging region of the manhole frame 2. Grooves 104 are provided in the cover 3 and engage the vertical members 93.

In use, with the cover 3 removed from the manhole frame 2 the extension frame 90 is placed in the cover receiving region of the manhole frame 2, as illustrated in Fig. 20.. The cover 3 is then inserted in the extension frame 90.

The advantage of this extension frame is provided by virtue of its construction which permits the cover to extend into portion of the manhole frame, while the extension frames described with reference to other embodiments of the invention require that the cover should not extend into the cover receiving region of the manhole frame. Thus, this extension frame will be particularly suitable for relatively small subsidences. This is achieved by virtue of the fact that the extension frame is formed by a pair of upper and lower rings which are joined by vertical members which are accommodated in grooves in the manhole cover 3.

In fact, it is envisaged that adjustment means could be incorporated in the extension frame 90. Such adjustment means may be provided by adjusting screws similar to the adjusting screws used in the embodiments of the invention illustrated with reference to Figs. 9 and 10, where such adjusting screws are provided, they would be engaged in the bottom ring. Alternatively, the adjusting means may be incorporated in the vertical members, the length of which may be adjustable, thereby permitting the top ring to be adjusted away from or towards the bottom ring.

Referring now to Figs. 21 and 22, there is illustrated a manhole frame also according to the invention, indicated generally by the reference numeral 110 for supporting a manhole cover 111. The manhole frame 110 is of rectangular shape having a pair of side members 112 joined by end members 113. The members 112 and 113 are of angle section steel. An inwardly directed flange 114 extend from each member 112 and 113 and extends the length of the members 112 and 113 to support the cover 111. Adjustment means to enable the height of the frame to be adjusted relative to the masonry on which it is being supported are provided by adjusting screws 115 which engage nuts 116 welded at the corners of the frame 110. The heads 117 of the screws 115 form engagement means for engaging the masonry.

In this case, a second frame 118 formed by side 119 joined by end members 120 both of metal plate material is provided for resting on the masonry shaft 7 of the manhole and for engaging the heads 117 of the screws 115. The cover 111 is of concrete and is reinforced by reinforcing steel 121.

In use, when the masonry shaft of the manhole has been constructed, the second frame 118 is laid on top of the masonry shaft. The manhole frame 110 is then placed on the second frame 118 and the adjusting screws 115 are adjusted until the top face 123 of the manhole frame 110 is level with the surface of the adjacent road or footpath. Any voids between the adjacent road or footpath and the frame 110 are then filled in and the cover 111 is placed in the manhole frame 110 resting on the flanges 114.

During use, should the masonry of the shaft 7 of the manhole subside, the manhole frame 110 can be raised by adjusting the adjusting screws 115 until the top face 123 of the manhole frame 110 is at the desired level.

It is envisaged that where a considerable subsidence has occurred, a number of extension frames may be required to raise the cover to the correct level of the road. In which case, the manhole frame receiving portion of one extension frame will engage the cover receiving portion of its adjacent extension frame.

Any number of extension frames may be used in this way to build up the level of the cover 3 to the level of the road.

It is also envisaged that the extension frame 1, as well as being used to build up in the case of a subsided manhole frame, could also be used to raise the level of the cover 3 where a road or footpath is being resurfaced or the like.

It will be appreciated that while the extension frames 30 and 35 have been described as comprising keying means provided by a flange extending around the frame, any other suitable keying means could be used. For example, it is envisaged that instead of providing a flange around the extension frame, outwardly projecting portions such as spikes or short flanges may be provided. Indeed, such flanges may or may not be provided with spikes. Similarly, in the case of the extension frame 30 the spikes may be dispensed with if desired.

It will also, of course, be appreciated that while the term manhole has been used throughout, this term is used to include handholes or indeed any other openings which provides access to an underground sewage or underground pipe, duct or the like, such as, for example, frames which are used to provide access to water hydrants, stopcocks, gulley traps and the like.

Indeed, in certain cases, it is envisaged that the extension frame may be provided with a cover, and the cover may be connected or not to the extension frame, and where it is connected, it may be hingedly connected or the like.

It will of course be appreciated that while the extension frames have been described as comprising a circular ring member, they could be provided by a ring member of square shape, rectangular shape, hexagonal or indeed any other desired shape. Further, it will of course be appreciated that while the extension frames have been described as being of cast iron material, they could be of any other suitable material and construction, for example, in certain cases, it is envisaged that they may be of forged metal, they could be of fabricated metal, or machined from a solid block of metal. Further, it will of course be appreciated that they could be of any other material besides metals, for example, plastics material, timber or the like.

While the extension frames have been described for use with a cast iron manhole frame and lid, it could be used with a manhole and lid of any other suitable material, for example plastics or the like.

While particular types of adjustment means have been provided for adjusting the height of the extension frame relative to the manhole frame, it will be appreciated that any other suitable adjustment means could be used without departing from the scope of the invention. For example, it is not necessary that three adjusting screws should be provided, four point adjustment could be provided by providing four adjusting screws. Further, it will be appreciated that instead of using adjusting screws, a cam arrangement could be provided whereby one or a number of cams would be used to move two portions of the extension frame towards and away from each other to accommodate the adjustment. Indeed, it is also envisaged that the adjustment means could be provided by an annular ring which would, in use, rest on the cover engaging step of the manhole frame.The ring would be joined to the extension frame by adjustment means, for example, by screws, cams or the like.

Indeed, in certain cases, the cams may engage the manhole frame directly.

Furthermore, it is envisaged, in certain cases, that the extension frame cod terminate in a closed end which would effectively form a cover. This cover would be used in place of the manhole cover. Indeed, it is envisaged in certain cases that such a fixed cover arrangement in an extension frame would be particularly advantageous, there adjustment means were provided.

While extension frames have been described in which the height of the extension frame is adjusted, this, while in certain cases is preferable, it is not essential. Needless to say, it will be appreciated that other suitable adjustment means for adjusting the height of the extension frame may be provided without departing from the scope of the invention.

Furthermore, it will be appreciated that while particular types of fastening means have been provided for fastening the extension frame to the manhole frame, other suitable fastening means could be used without departing from the scope of the invention.

Indeed, in many cases, the fastening means may be dispensed with altogether without departing from the scope of the invention.

Furthermore, it will be appreciated that where adjustment means are not provided for adjusting the height of the extension frame relative to the manhole frame, extension frames of different heights between the top face and bottom face could be provided to accommodate manhole frames which subsided different amounts. In which case, the distance between the step 20 and 21 would vary for frames of differing height.

It will also, of course, be appreciated that while the extension frame has been described for use with a manhole frame, it could be used in combination with a handhold frame, a gulley frame or the like.

While the extension frames have been described as being of particular construction, other suitable construction or shape of frames could be used without departing from the scope of the invention. Indeed, in certain cases, it is envisaged that the frames need not be closed frames.

Further, while a particular shape and construction of manhole frame has been described with reference to Figs. 21 and 22 any other suitable shape and construction of manhole frame could be provided without departing from the scope of the invention.

Indeed, while the manhole frame of the invention has been described as comprising a particular type of adjusting means, any other suitable type of adjusting means could be used without departing from the scope of the invention. For example, a camming adjustment arrangement or any other suitable adjustment means could be used without departing from the scope of the invention. Needless to say, while the manhole frame has been described as being of rectangular shape, it could be of any other shape or construction, for example. circular shape, hexagonal shape, triangular shape, square shape or the like. Further, it will be appreciated that in certain cases a hinged cover may be mounted on the manhole frame.

It will be appreciated that while only some of the extension frames have been illustrated and described as comprising fastening means for fastening the extension frame to the manhole frame, if desired, all could be provided with fastening means or alternatively fastening means may be dispensed with altogether.

Claims

1. An extension frame for a manhole frame, the extension frame comprising a manhole engaging portion for engaging portion of the manhole frame, and a cover receiving portion for receiving and supporting the manhole cover.

2. An extension frame as claimed in Claim 1 in which the extension frame has a top face and a bottom face and an opening extending through the extension frame from the top face to the bottom face, portion of the opening adjacent the top face forming the cover receiving portion.

3. An extension frame as claimed in Claim 1 or 2 in which the manhole engaging portion is provided by portion of the extension frame adapted, in use, to extend into and engage a cover receiving region of the manhole frame.

4. An extension frame as claimed in Claim 2 or 3 in which the outer cross sectional area of the manhole engaging portion is of reduced cross sectional area, and is of an axial length to extend in use to a cover engaging flange in the manhole frame.

5. An extension frame as claimed in any of Claims 2 to 4 in which the internal cross sectional area of the portion of the opening forming the cover receiving portion defines the outer cross sectional area of the cover.

6. An extension frame as claimed in Claims 2 to 5 in which abutment means are provided in the opening for supporting the cover in the cover receiving portion.

7. An extension frame as claimed in Claim 5 in which the abutment means is provided by a flange extending from the cover receiving portion into the opening.

8. An extension frame as claimed in Claim 7 or 8 in which the extension frame is provided by a ring member, portion of the outer surface of which defines the cover receiving region of the manhole frame to form tlle manhole etigag i ng pot' t i on

9. An extension frame as claimed in Claim 8 in which the outer cross section of the ring member is stepped to form an abutment surface to abut the top edge of the manhole frame in use.

10. An extension frame as claimed in Claim 8 or 9 in which the inner cross sectional area of the ring member is stepped to form the abutment means for supporting the cover.

11. An extension frame as claimed in Claim 10 in which the cover receiving portion extends from the top face to the abutment means.

12. An extension frame as claimed in any of Claims 2 to 11 in which adjustment means are provided on the extension frame for adjusting the height of the top face of the extension frame relative to the manhole frame.

13. An extension frame as claimed in Claim 12 in which the adjustment means is provided by a screw engaging the extension frame and adjustable inwardly and outwardly relative thereto.

14. An extension frame as claimed in Claim 13 in which three adjusting screws are provided, each extending axially into the extension frame through the bottom face, each adjusting screw being located at 180 relative to its two adjacent screws.

15. An extension frame as claimed in Claim 13 or 14 in which a locking nut is provided on each screw to lock the screw in position relative to the extension frame.

16. An extension frame as claimed in any of Claims 12 to 15 in which an annular plate is provided for, in use, sitting on a cover engaging flange in the manhole frame, the annular plate being mounted to the extension frame by the adjustment means.

17. An extension frame as claimed in Claim 12 in which the extension frame is provided by two portions, the two portions being joined together by the adjustment means.

18. An extension frame as claimed in Claim 17 in which the two parts are threaded and engage each other with screwing action.

19. An extension frame as claimed in Claim 18 in which securing means are provided to secure the two parts together in a desired relative position.

20. An extension frame as claimed in any preceding claim in which fastening means are provided for securing the extension frame to the manhole frame.

21. An extension frame as claimed in Claim 20 in which the fastening means is provided by a bracket extending from the extension frame for engaging portion of the manhole frame.

22. An extension frame as claimed in Claim 21 in which the fastening bracket extends from the opening adjacent the bottom face to engage the manhole frame.

23. An extension frame as claimed in any preceding claim in which the extension frame is circular of shape.

24. An extension frame as claimed in any of Claims 1 to 22 in which the extension frame is of square shape.

25. An extension frame as claimed in any of Claims 1 to 22 in which the extension frame is of rectangular shape.

26. An extension frame as claimed in any of Claims 1 to 22 in which the extension frame is of hexagonal shape.

27. An extension frame as claimed in any preceding claim in which keying means extends outwardly of the extension frame to engage the material of the road for keying the extension frame in position.

28. An extension frame as claimed in Claim 27 in which the keying means is provided by a flange extending radially outwardly of the extension frame.

29. Extension frames substantially as described herein with reference to and as illustrated in the accompanying drawings.

30. A manhole frame for a manhole opening comprising a frame having an opening extending therethrough from a top face to a bottom face and a cover receiving portion for receiving a manhole cover, engagement means for engaging masonry defining the manhole opening, and adjustment means for adjusting the position of the extension frame relative to the engagement means.

31. A manhole frame as claimed in Claim 30 in which the adjustment means is provided by a plurality of adjusting screws extending into the bottom face of the extension frame at spaced apart locations, the engagement means being provided by the heads of the screws.

32. A manhole frame as claimed in Claim 30 in which locking nuts are provided to lock the adjusting screws in a desired position.

33. A manhole frame as claimed in any of Claims 30 to 32 in which an abutment means for supporting the cover extends from the extension frame into the opening spaced apart from the top face thereof.

34. A manhole frame as claimed in Claim 33 in which the abutment means is provided by a flange.

35. A manhole frame as claimed in any of Claims 30 to 34 in which the frame is of circular shape.

36. A manhole frame as claimed in any of Claims 30 to 34 in which the frame is of square shape.

37. A manhole frame as claimed in any of Claims 30 to 34 in which the frame is of rectangular shape.

38. A manhole frame as claimed in any of Claims 30 to 34 in which the frame is of hexagonal shape.

39. A manhole frame substantially as described herein with reference to and as illustrated in the accompanying drawings.

40. A method for rising a manhole cover above a manhole frame, the method comprising the steps of removing the manhole cover from the manhole frame, inserting an extension frame according to any of Claims 1 to 29 into the manhole frame and placing a manhole cover in the extension frame.

41. A method as claimed in Claim 40 in which the method includes the step of replacing the manhole cover in the extension frame.

42. A method as claimed in Claim 40 or 41 in which the method includes the step of fitting the manhole cover into the cover receiving portion of the extension frame.

43. A method as claimed in any of Claims 40 to 42 in which the method includes the step of filling in portion of a road or footpath adjacent the extension frame.

44. A method as claimed in any of Claims 40 to 43 in which the method also includes the step of adjusting the adjusting means so that the top face of the extension frame is substantially level with the road or footpath surface.

45. A method substantially as described herein with reference to and as illustrated in the accompanying drawings.