GB2431683A

GB2431683A - Fixing mechanism for securing a cover plate relative to a hole

Info

Publication number: GB2431683A
Application number: GB0615420A
Authority: GB
Inventors: Jeffrey Mark Radcliffe
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-08-04
Filing date: 2006-08-03
Publication date: 2007-05-02
Anticipated expiration: 2026-08-03
Also published as: GB2431683B; GB0516042D0; GB0615420D0

Abstract

The fixing mechanism, primarily for use with cover plates to cover trenches, road works etc., comprises a coupling mechanism 32 for securing the mechanism to the underside of the cover plate 18 and at least two legs 22 pivotally connected to the coupling mechanism which are movable between a stowed and a deployed position. A collar 30 is threaded on a screw-threaded shaft 34 that is rotatably connected to the coupling mechanism with a number of struts 28 connecting the collar to respective legs so that rotation of the shaft moves the collar and the struts to extend or retract the legs. The coupling mechanism preferably releasably connects the fixing mechanism to the cover plate and may comprise male and female connectors which, once engaged, are locked in place with a locking pin or spring-biased pins. Alternatively the fixing mechanism may comprise a square or rectangular tube which is received in a channel socket in a friction fit. The shaft is preferably rotatable from above the cover plate and the legs preferably include feet with grip formations. The feet, struts or legs may be resiliently deformable.

Description

Title: Cover plates

Description:

The present invention relates to cover plates for covering holes, (e.g. cover plates for covering road holes) cover plate and in particular to an apparatus and method fir securing cover plates in-situ.

The invention relates equally to footpath boards. References to "cover plates' can be substituted for "road plates" or "footpath boards" 1 0 throughout.

Cover plates are used for temporarily closing holes dug in roads or pavements (sidewalks), (e.g. where work is temporarily stopped overnight) to prevent pedestrians and/or vehicles from falling into the hole. Known cover plates generally comprise a relatively thick, load-bearing steel plate, which can support the weight of vehicles or people when placed over the hole. Footpath boards tend to be of more lightweight construction, e.g. having a plastics or fibreglass board rather than a steel plate, owing to being subjected to lower loads in use.

A problem with known cover plates is that they can move under the influence of heavy road-or foot-traffic and/or with prolonged use.

Additionally, it has been known for vandals or thieves to deliberately move or take co er plates away. If the cover plate is moved or taken away, there is an increased likelihood of accidents, which can endanger lives and be costly to compensate for.

A known solution to the above problem is to temporarily bolt the cover plate to the road or pavement surfiice using bolts inserted through pre-drilled holes in the cover plate and road surface. However, under heavy traffic or certain other conditions, the bolts have been known to dislodge and/or protrude above the cover plate not only creating a further hazard (such as a trip or puncture hazard). hut allowing the cover plate to slip.

A need therefore arises for an improved cover plate and/or a cover 1 0 plate that is tamperproof and/or substantially inhibited or prevented from movi 11g.

The present invention aims to provide a solution to one or more of the above problems.

A first aspect of the invention provides a fixing mechanism for 1 5 securing a cover plate relative to a hole to be covered, the fixing mechanism comprising: coupling means for coupling the fixing mechanism to an intended underside of the cover plate at least two legs pivotally connected to tile coupling member and movable between a stowed position and a deployed position in which at least part of each leg engages a wall of the hole: a screw-threaded shaft rotatably connected to tile coupling: a collar screw-threadedi) mounted on tile screw-threaded shaft: and a plurality of struts, each pivotali\ connected to tile collar and to a respective leg.

The above configuration provides a fixing mechanism whereby rotation of the screw-threaded shaft displaces the collar along the shaft, thereby causing the legs to pivot. Preferably, rotation of the screw-threaded shaft causes the collar to move relative to the coupling and the legs to pivot between the stowed and the deployed position.

The coupling means is preferably adapted to releasably couple the fixing mechanism to the cover plate. The fixing mechanism preferably further comprises means for rotating the screw-threaded shaft.

Preferably, the screw-threaded shaft is rotatably connected at or 1 0 towards its upper end to the coupling. The screw-threaded shaft cai rotate relative to the coupling, but is preferably connected so as to be substantially axially fixed with respect thereto. Preferably. the screw-threaded shaft comprises a screw portion (e.g. a worm screw) that passes through a compiementarily-threaded aperture in the collar. The coupling (i.e. the leg 1 5 boss or spreader bar) is preferably fixed relative to the screw.

Preferably, when in the stowed position, the legs disengage the surface of the road hole.

The collar is preferably axially movable relative to the coupling.

Preferably. rotating the screw-threaded shaft causes the collar to advance along the screw-threaded shaft due to it screw-threaded connection therewith. Thus, rotation of the screw-threaded shaft can cause the collar to move axially relative to the coupling.

The coupling preferably comprises a leg boss or a spreader bar.

Where provided, the spreader bar preferably comprises an elongate member having spaced apart pivot points thereon to which the legs pivotally connect.

Preferably, the pivot points comprise through holes in the spreader bar for receiving a bolt arranged to pass through the spreader bar and appropriately positioned holes in the legs.

Rotation of the screw can he achieved using any suitable means, e.g. manually or automatically. It is envisaged that the screw will be rotatable using a knob, handle or key (hereinafter referred to as a handle). The handle may comprise a crank to facilitate rotation of the screw. One end of the screw may have a formation therein e.g. a bayonet formation, which can be engaged using a complementary end of the handle such that rotation of the handle or key causes the screw to rotate and the struts to actuate. The end of the handle may have T-bar formation for engaging a slot or bayonet-type foriimtion in the end of the screw.

Preferably, the end of the screw to which the handle connects has a formation that is unique such that only one handle will fit into that formation, thereby preventing unauthorised tampering.

The fixing mechanism is preferably detachable from the cover plate.

In order to make the fixing mechanism detachable from the cover plate. a plug and socket arrangement may be provided. A flanged socket may he provided that can be bolted or welded io the intended underside of the cover plate and the leg boss may have a plug that complements the socket such that the two can be coupled together. Preferably, the plug and socket arrangement can he fixed in place. A screw-threaded connection, a clip connection or a bayonet connection may be used for this purpose.

The coupling preferably comprises a male connector adapted to engage a female socket affixable to the cover plate, and a locking means for locking the connector to the socket when the connector is engaged with the socket. Alternatively, the coupling may comprise a female socket adapted to engage a male connector affixable to the cover plate, and a locking means for locking the connector to the socket when the socket is engaged with the connector.

The locking means can take various forms. In a preferred embodiment of the invention, the locking means comprises a first hole in the male connector and a second hole in the female socket, the first and second holes being arranged to align when the connector engages the socket, and a locking pin insertable through the aligned first and second holes. A plurality of first and second holes may be provided and the locking pin may comprise a rod bent into a generally U-shaped configuration having a pair of tines insertable through pairs of aligned first and second holes.

Alternatively. the locking means may be a friction fit between two or more components of the coupling. For example, the coupling may comprise a tubular connector adapted to slidably locate within a channel socket having substantially the same external cross-section as the internal cross-section of the channel member, the channel member further comprising one or more inwardly directed lips overhanging the channel, the lips being arranged to frictionally engage the tube when slidably located in the channel. The tube may have a square or rectangular cross-section.

l'he locking means may comprise a bayonet-type connector, i.e. it may comprise a plurality pins extending radially outwardly from the connector, the pins being arranged to engage generally L-shaped channels or grooves of the socket. A bayonet-type locking means may further comprise a biasing means, such as a helical spring, for biasing the pins into locking engagement with the channels.

Alternatively. the connector may comprise a connector that is screw-threadedly receivable in the socket and the locking means may comprise an axially fixed flange on the connector that can be screw-threadedly tightened 1 5 against the socket or vice-versa.

The ends of the legs are intended to engage with the walls of the road hole to substantially inhibit lateral and/or vertical movement of the cover plate relative to the road hole. In order to facilitate this, pivotally mounted feet may be provided at extreme ends of the legs. the ièet having.

preferably. grip formations thereon to facilitate engagement of the feet with the walls of the road hole.

Each leg, strut or foot can be resiliently deformahie such that if the cover plate is not located centrally with respect to the road hole, or if the road hole is not regularly shaped. then positioning errors and inconsistencies can he accommodated. Additionally, by making the legs, struts or feet resiliently deformable, the maximum force applicable to the hole walls can he restricted.

In a preferred embodiment of the invention, each loot comprises a bar or tube affixed at or near an end of each leg at substantially ninety degrees to the longitudinal axis of the leg.

1 0 A second aspect of the invention provides a cover plate comprising a generally planar load bearing plate having an upper surface and a lower surface and a cover plate coupling affixable to the lower surface for releasably coupling a fixing mechanism according to the first aspect of the invention to the underside of the cover plate.

A third aspect of the invention provides a cover plate comprising a generally planar load bearing plate having an upper surface and lower surface. a cover plate coupling affixed to the lower surface and a fixing mechanism according to the first aspect of the invention.

The cover plate is preferably provided with an aperture through which the screw-threaded shaft can be accessed from the opposite side of 1.he cover plate. Thus, a user can stand on top of the cover plate when the cover plate is in-situ, insert the key or handle through the aperture and actuate the struts from the opposite side of the plate.

The aperture, where provided, and the cover plate coupling are preferably located substantially at the centre of the plate. Such a S configuration preferably enables an end of the screw-threaded shaft to be accessible through the aperture.

A further possible advantage stemming from this configuration is that since the upper end of the screw-threaded shaft is preferably axially fixed with respect to the coupling, it is possible to pivot the legs to the deployed position without any part of the fixing mechanism protruding above the upper surface of the cover plate.

A fourth aspect of the invention provides a method of closing a road hole comprising the steps of placing a cover plate over the hole, the cover plate having a fixing mechanism as previously described affixed to its 1 5 intended underside; and moving the legs to the deployed position so that they engage the walls of the road hole.

Preferably, the method further comprises the steps of; applying a force to the legs so that they impart a force to the walls of the road hole SO that lateral movement of the cover plate is substantially inhibited. and/or applying a force to the legs so that they impart a force to the walls of the road hole so that vertical movement of the cover plate is substantiall' nh i hited.

The cover plate can be of any suitable type. Preferably, the cover plate comprises a load bearing plate of metal, e.g. steel. Alternatively, the cover plate can be manufactured of a tough and/or strong glass fibre reinforced polymer (GRP) or a polymeric material. Where the cover plate is manufactured of a polymeric material, it is preferably injection moulded.

The cover plate preferably has integrally formed reiniorcing ribs on its intended under surface and/or grip formations on its intended upper surface.

The edges of the cover plate may be rounded or chamfered to facilitate driving a vehicle onto and off the cover plate and/or to minimise the 1 0 likelihood of pedestrians tripping.

The fixing mechanism has at least two legs although any number may be provided, e.g. three or four.

Preferably, the legs are diametrically opposite one another or spaced at equal intervals around a central point such that opposite forces balance when the legs are moved to the deployed position. The legs arc pivotally mounted, preferably by means of a pintle connection between one end of the leg and a central leg boss.

Alternatively, the legs are pivotally connected, preferably by means of a pintle connection, to opposite ends of a spreader bar. Advantageously, a spreader bar shortens the required leg length for a given spread (i.e. the distance between the feet, when the legs are in the deployed position). By using a spreader bar. the length of each leg can be reduced. which means that the maximum depth into the hole that the fixing mechanism protrudes, is reduced for a given, required spread.

In many jurisdictions, different utilities are, by law, located at different depths below the road or pavement (sidewalk) surface. For example, in the United Kingdom, electricity cables should be buried a minimum of 450mm below the surface, gas pipes should be buried a minimum of 600mm below the surface and water pipes should be buried a minimum of 700 to 800mm below the surface. By utilising a spreader bar, the maximum penetration depth of the fixing mechanism can be reduced to, say 375mm, which means it cannot interfere with essential utilities.

A fourth aspect of the invention provides a method of closing a road hole comprising the steps of placing a cover plate over the hole, the cover plate having a fixing mechanism on its intended underside; 1 5 the fixing mechanism comprising at least two legs movable from a stowed position to a deployed position; and moving the legs such that at least one end of each leg engages a wall of the road hole.

Preferred embodiments of the invention shall now be described, by way of example oniy. with reference to the accompanying drawings in which: Figure 1 is a schematic side view of a fixing mechanism and cover plate in accordance with the invention; Figure 2 is a schematic diagram showing the various parts of the invention; Figures 3, 4 5 and 6 a sequence for deploying a cover plate in accordance with the invention; Figure 7 is a schematic cross-section through the cover plate, socket, and leg boss of the fixing mechanism shown in Figures 1 to 5: Figure 8 shows, schematically, various ways of imparting resilient 1 0 deformability to the legs, struts or feet; Figure 9 is a schematic side view of an alternative leg arrangement to that shown in Figures 1 to 8: Figure 10 is a perspective view of a variant of the fixing mechanism of Figures 1 to 9; 1 5 Figure 11 is a perspective view of a first variant of the mounting plate of Figure 10; Figures 12 and 13 are perspective views of the fixing mechanism being affixed to a cover plate in different orientations: Figure 14 is a perspective view of a second variant of the mounting plate of Figure 10; Figures 15 and 16 are perspective views showing how tile fixing mechanism can be secured to a cover plate using the mounting plate of Figure 14; and Figures 1 7 and 1 8 arc perspective views showing a third variant of S tile mounting plate of Figure 10.

Figure 1 is a schematic oi one possible embodiment of tile invention.

As can be seen, a cover plate 10 is being used to cover a hole 14 in a road.

The cover plate is held in-situ using a fixing mechanism generally referred to as 12. The fixing mechanism 12 comprises a central leg boss 26 to which legs 22 are pivotally connected. Depending from the leg boss 26 is a screw 34 that engages a collar 30. A strut 28 is pivotally connected to collar and the midpoint of each leg 22.

In use, the cover plate 10 is placed over the road hole 14 and the legs 22 pivoted into engagement with the sidewalls 1 6 of the hole by turning the screw 34.

Also shown in Figure 1 is a chamfer 20 n the edges of tile cover plate 10 to reduce the likelihood of objects catching on the edge thereof A pivotally mounted foot 24 is also provided at the end of each leg 22 to facilitate engagement of the leg with the side wall 16 of the hole 14.

it is anticipated that the various components of tile invention may be sold as a kit of parts. as shown in Figure 2. in any event, it is highly convenient, for handling, maintenance and storage purposes for the fixing mechanism 12 to detach from the plate 32 and/or the cover plate 10. A key 34 is also provided for actuating the screw, details of which will become apparent later.

Figures 3, 4 and 5 show how the invention can be used. In Figure 3, the fixing mechanism 12 is attached to the plate 32, which is bolted to the cover plate 10. l'he leg boss 26 acts as a plug having a screw-threaded outer surface that engages with a complimentarily screw-threaded inner surface of a socket 40 integrated into the plate 32. Thus, the fixing mechanism 12 can be pushed home and screwed tight as indicated by arrows A and B, respectively. The arrangement could, of course, be reversed, i.e. the leg boss 26 could have a screw-threaded inner surface that engages with a complimentarily screw-threaded outer surface of a protrusion affixed to the cover plate.

The next step, as shown in Figure 4, involves positioning C the cover plate 10 over the road hole with the fixing mechanism 12 roughly centrally aligned with the hole 14. Finally, as shown in Figure 5. the key 34 is used to rotate the screw 38 to pivot the legs 22 from a stowed to a deployed position. As can be seen in Figure 5, rotation D of the screw 34 causes the collar to rise E with respect to the leg boss 26. This causes the struts 28 to act outwardly in the legs 22 causing them to pivot to the deployed position whereby they engage F the side walls l 6 of the road hole 14.

As can be seen, the legs engage F the side walls 16 at a slight upward angle, which gives rise to resolved forces in the outward and upward directions. The outward forces inhibit lateral movement of the cover plate 10, whereas the upward forces help to hold the cover plate 1 0 down. Once the cover plate 10 has been installed, the key 38 can be removed.

Also shown in Figure 5 is a restraining clip 70. The restraining clip is pivotally mounted to the plate 32 lugs 72 such that it can swing down Linder the effects of gravity or be positioned there by hand. As can be seen 1 0 in Figure 6, the restraining clip 70 has a downwardly oriented U-piece formed by a pair of spaced apart tines 74 and a cross piece 76. A tab 78 extends from the cross piece and is pivotally connected, using a pin 80, to the Jugs 72. In use, the leg 22 is positioned between the tines 74, which inhibit rotational movement of the fixing mechanism 12 with respect to the cover plate 10.

Figure 7 is a schematic cross section through the cover plate 10.

plate 32. leg boss 26 and screw 34.

As can be seen, a plug 40 and socket 26 arrangement is generally provided that enables the fixing mechanism 12 to be detached from the cover plate 10 if desired. The socket 40 is integrated into the plate 32. e.g. by welding or mechanical fastenings. which is in turn affixed to the cover plate. e.g. by welding or mechanical fastenings. The interface 42 between the plug 26 and socket 40 can be screw-threaded or any other suitable connection could be provided, such as a clip, bayonet fitting etc. The leg boss 26 has outwardly protruding lugs 44 to which the legs 22 are pivotally connected using a pintle connection 47.

The screw 34 has a flange 48 that is sandwiched between a pair of oppositely oriented thrust hearings 48 to prevent lateral and axial movement of the screw 34, whilst allowing rotational movement thereof. The bearings 48 are trapped between au inwardly projecting fiaige 50 on the lower end of the leg boss 26 and a locking ring 52.

1 0 The screw 34 is tubular and has a cut-out 54 in the upper end thereof for engaging the key 38. The key 38 can have a simple T-har that engages with the cut-out 54 or a more complex arrangement may be provided.

Access to the top of the screw 34 is via an aperture 56 that passes through the cover plate 10 and plate 34.

Figure 8 shows how the legs 22 can be resilient to accommodate irregularities in the road hole geometry or inaccurate positioning of the cover plate 10. in one possible embodiment, each strut 28 can be formed iii two pieces 28a and 28b that are pivotally connected 58 to one another. A spring 60 may be provided that keeps the strut 28 generally stiff but enables some fiexure if needed. On the right hand side of Figure 8. a spring loadedly telescopic leg is provided 62. Additionally or alternatively, the sole of each foot 24 may have a resilient (e.g. elastometric) pad thereon.

The feet 24 can either he pivotally mounted on the end of each leg 22, as shown, or a rigid connection may he provided such that the foot 24 is maintained at a fixed angle with respect to the leg 22.

Figure 9 shows an embodiment of the invention whereby the legs 22 are extendible. Each leg 22 comprises two box-section steel struts 22a and 22h of dimensions such that one 22b strut can slide inside the other 22a.

Each strut 22a and 22b is provided with a series of apertures 68 through which, when aligned, a pin can be inserted to maintain the leg 22 at a desired overall length.

Figure 10 shows a variant of' the cover plate fixing mechanism shoii in Figure 1. in the following descriptions, identical reference numerals correspond to identical components previously described.

in Figure 10 the cover plate fixing mechanism 12 generally comprises a fixing plate 32, which bolts to the underside of the cover plate 1 5 (not shown). A pair of legs 22 is pivotally connected, at their upper ends, to opposite ends of a spreader bar 70, to which a bush 72 is welded at its mid point. The bush 72 rotatably engages a cylindrical portion of' an elongate screw 34 member that extends downwards, in use, from the securing plate 32. A pair of struts 28 is pivotally connected between a collar 30 and the middle of' the legs 22. The collar 32 screw threadedly engages a threaded portion of the elongate screw 34. Thus, in the same way as previously described, rotation of the scre 34 causes the legs 22 to pivot from a stowed position to a deployed position where they can grip the side walls of a road hole. The detailed construction of the fixing mechanism 12 is as follows: The spreader bar 70 comprises a length of U-section galvanised steel oriented to provide, in usc. a downwardly open channel. The legs also comprise lengths of U-section galvanised steel having external dimensions slightly smaller than the internal dimensions of the channel of the spreader bar 70 to allow the upper ends of the legs to be received within the channel of the spreader bar 70. The upper ends of the legs 22 and the outer ends of the spreader bar 70 have through holes 74 for receiving a bolt 47 that passes through and pivotally secures the end of each leg 22 to the spreader bar 70.

A bush 72 is received and welded into the channel of the spreader bar 70 at its midpoint. A through hole (not shown), aligned with the centreline of the hush 72, is provided in the spreader bar 70 and the plate 32 to enable the upper end of the elongate screw 34 to be accessed, as previously described in relation to Figures 5 and 7.

The collar 30 comprises a pair of plates 78 and a pair of spacer blocks 80. The plates 78 and spacer blocks 80 are arranged to contact the elongate screw 34. The inner surfaces of the plates 78 and spacer blocks 80 are provided with grooves or projections that engage the screw thread of the screw 34. Thus, by rotating the screw 34 (depending on the direction of rotation) the collar 30 can he made to move axially in either direction along the screw 34.

The struts 28 each comprise a pair of flat plate members 82 that are pivotally connected, at their lower ends. by bolts, to opposite sides of the collar 30. and at their upper ends. by bolts. to approximately the midpoint of each leg 22.

A galvanised steel tube 76 is welded perpendicularly, at its midpoint, to the outside of the end of each leg 22 to form a foot 24.

The fixing mechanism 12 is secured to the cover plate (not shown) using any one of a variety of connectors, which are explained in detail below: In Figure 10, a generally square galvanised steel mounting plate 32 is provided with a through hole 84 close to each corner. The mounting plate 32 is secured to the underside of the cover plate using; bolts that pass through each hole 84 and correspondingly positioned holes in the cover plate (not shown); threaded studs welded to the underside of the cover plate 1 5 that are aligned with and pass through each hole 84 in the plate 32 so that the plate 32 can be secured using nuts: or rivets.

The plate 32 has a pair of spaced apart, steel tabs 86 welded perpendicularly thereto. The tabs 86 have aligned through holes therein for receiving a generally U-shaped retainer 88 formed from a piece of bent metal tubing. In use, the spreader bar 70 locates between the tabs 86 and the retainer 88 passes through the holes in the labs 86 and correspondingh positioned holes in the spreader bar 70. The fixing mechanism 12 can he detached from mounting plate 32 (and hence, the cover plate) by removing the retainer 88.

Figure 11 shows a variant of the mounting plate 32 shown in Figure 1 0. A generally flat, square mounting plate 32 has a through hole 90 at each corner for receiving a bolt or stud as previously described so it can be secured to the underside of the cover plate (not shown). The plate 32 has a large central aperture 92 so that the top of the elongate screw 34 can be accessed, in use, from above the cover plate. Four L-section steel stubs 94 are welded to the underside of the plate 32 to generally define two 1 0 perpendicular channels 96 for receiving the spreader bar 70 of the fixing mechanism 12 in one of two perpendicular orientations. Each stub 94 has two holes 98 for receiving a retainer pin 88 as described with reference to Figure 10. Using this arrangement, the fixing mechanism 12 can be affixed to the cover plate in one of two perpendicular orientations as required by the circumstances.

Figures 12 and 1 3 show how, using the mounting plate described with reference to Figure 11, the fixing mechanism can be connected to the cover plate 10 lengthwise or width wise, respectively. In Figures 12 and 13, the cover plate 10 is manufactured of injection moulded plastics having a 2() generally flat upper surface 1 8, chamfered edges 20 and a plurality of longitudinal and transverse reinforcing ribs 100 integrally moulded into its underside.

Figure 14 shows a variant of the mounting plate 32 of Figure 11. A generally flat, square mounting plate 32 has a through hole 90 at each corner for receiving a bolt or stud as previously described so it can be secured to the underside of the cover plate (not shown). The plate 32 has a large central aperture 92 so that the top of the elongate screw 34 can be accessed, in use, from above the cover plate. Eight flat steel stub plates 102 are welded in pairs at right angles to one another on the underside of the plate 32 to generally define two perpendicular channels 96 for receiving the spreader bar 70 of the fixing mechanism 12 in one of two perpendicular orientations. A generally L-section lip piece 104 is welded to each stub plate 102 to create a lip 106 that overhangs each ofthe channels 96.

Figures 15 and 16 show how the spreader bar 70 is adapted, by having a first, chamfered edged plate 108, and a pair of L-section pieces 110 welded thereto. In use, the spreader bar 70 can be slid into either channel 96 of' the mounting plate 32 so that the chamfered edges 112 engage the lip 106 of the lip pieces 1 04. The L-sectioned pieces 110 engage the flat reverse faces 114 of the lip pieces 104. Thus, the spreader bar 70 can be retained securely to the plate 32.

The fixing mechanism 12 comprises a central leg boss 26 to which legs 22 are pivotally connected. Depending from the leg boss 26 is a screw 34 that engages a collar 30. A strut 28 is pivotally connected to collar 30 and the midpoint of each leg 22.

Figures 17 and 18 are detailed views of a bayonet-type connector 116 for connecting the fixing mechanism of Figure 10 to a mounting plate 32. A stub tube 11 8. which receives the hush 72 (that rotatably retains a cylindrical portion of the elongate screw member 34), extends upwards beyond the top of the spreader bar 70. Four short, radially extending locking pins 120 are provided at 90 degree instances around the middle of the stub tube 118. The mounting plate 32 has a tubular stub tube 122 having internal diameter slightly larger than the external diameter of the stub tube 118 of the fixing mechanism 12, for receiving the latter 118. The mounting 1 0 plate stub tube 122 has four L-shaped cut-outs 124 having a first longitudinal section 124a aligned with and arranged to receive the locking pins 120 of the fixing mechanism stub tube 118, a second transverse part I 24b, and a third locking part I 24c.

A helical compression spring 126 locates around the mounting plate stub tube 122 and biases a ring 128 towards the *free end of the stub tube 1 22. The ring 1 28 is prevented from coming loose by an outwardly projecting flange 130 at the free end of the stub tube 122.

Thus, the fixing mechanism 12 can be connected to the mounting plate 32 by aligning the locking pins 120 with the first part 124a of the L-shaped cut-outs, pushing the whole fixing mechanism 12 towards the mounting plate 32 (against the action of the spring 126). rotating the fixing mechanism clockwise so that the locking pins 120 move along the transverse part 124b of the L-shaped cut outs 124 and into the locking part 124c thereof, and allowing the spring 126 to push the locking pins 120 into the locking part I 24c of the L-shaped cut outs. The locking mechanism 12 can be disconnected using the reverse method.

l'he invention is not limited to the details of the above embodiments, for example. any mechanism may be used for pivoting the legs from a stowed to a deployed position, such as a ratchet, chain or belt.

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Claims

Claims: 1. A fixing mechanism for securing a cover plate relative to a

hole to be covered, the fixing mechanism comprising: a. coupling means for coupling the fixing mechanism to an intended underside of the cover plate; b. at least two legs pivotally connected to the coupling member and movable between a stowed position and a deployed position in which at least part of each leg engages a wall of the hole; c. a screw-threaded shaft rotatably connected to the coupling; d. a collar screw-threadedly mounted on the screw-threaded shaft: and e. a plurality of struts, each pivotally connected to the collar and to a respective leg.

1 5
2. A fixing mechanism as claimed in claim 1, wherein the coupling means is adapted to releasably couple the fixing mechanism to the cover plate.

3. A fixing mechanism as claimed in claim 1 or claim 2. further comprising means for rotating the screw-threaded shaft.

4. A fixing mechanism as claimed in any of claims 1. 2 or
3. herein the legs disengage the wall when pivoted to the stowed position.

5. A fixing mechanism as claimed in any preceding claim, wherein the collar is axially movable relative to the coupling means.

6. A fixing mechanism as claimed in any preceding claim, wherein the coupling means comprises a leg boss or a spreader bar.

7. A fixing mechanism as claimed in any of claims 2 to 6, wherein the means for rotating the screw-threaded shall comprises a key. knob or 1 0 handle.

8. A fixing mechanism as claimed in any preceding claim, wherein the coupling means comprises a male connector adapted to engage a female socket affixable to the cover plate, and a locking means for locking the 1 5 connector to the socket when the connector is engaged with the socket.

9. A fixing mechanism as claimed in any of claims 1 to 7, wherein the coupling comprises a female socket adapted to engage a male connector affixable to the cover plate. and a locking means for locking the connector to the socket when the socket is engaged with the connector.

10. A fixing mechanism as claimed in claim 8 or claim 9, wherein the locking means comprises a first hole in the male connector and a second hole in the female socket, the first and second holes being arranged to align when the connector engages the socket, and a locking pin insertable through the aligned first and second holes.

11. A fixing mechanism as claimed in claim 10, wherein the connector and socket eacl1 comprise a plurality of first and second holes.

12. A fixing mechanism as claimed in claim 11, wherein the locking pin comprises a rod having a generally U-shaped configuration and a pair of tines insertable through pairs of aligned first and second holes.

13. A fixing mechanism as claimed in any of claims 8 to 12, wherein the 1 5 coupling means comprises a tubular connector adapted to slidably locate within a channel socket having substantially the same external cross-section as the internal cross-section of the channel member, the channel member further comprising one or more inwardly directed lips overhanging the channel, the lips being arranged to frictionally engage the tube when slidably located in the channel.

14. A fixing mechanism as claimed in claim 13, wherein the tube has a square or rectangular cross-section.

15. A fixing mechanism as claimed in claim 8 or claim 9. wherein the S locking means comprises a plurality of pins extending radially outwardly from the connector, the pins being arranged to engage generally L-shaped channels or grooves ol the socket.

16. A fixing mechanism as claimed in claim 15, wherein the locking means 1 0 further comprises a biasing means for biasing the pins into locking engagement with the chaimels.

17. A fixing mechanism as claimed in claim 16, wherein the biasing means comprises a spring.

1 8. A fixing mechanism or cover plate as claimed in claim 8 or claim 9.

wherein the connector is screw-threadedly receivable in the socket.

1 9. A fixing mechanism as claimed in any preceding claim, further comprising a foot mounted at an end of each leg.

20. A fixing mechanism as claimed in claim 19, wherein each foot comprises a bar or tube affixed at or near an end of each leg at substantially ninety degrees to the longitudinal axis of the leg.

21 -A fixing mechanism as claimed in claim 1 9, wherein each loot is pivotally mounted on the leg.

22. A fixing mechanism as claimed in any of claims 19, 20 or 21, wherein each foot has grip formations thereon. 1 0

23. A fixing mechanism as claimed in any preceding claim, wherein each leg, strut or foot is resiliently deformable.

24. A fixing mechanism substantially as hereinbefore described with 1 5 reference to and as illustrated in the accompanying drawings.

25. A cover plate comprising a generally planar load bearing plate having an upper surface and a lower surface and a cover plate coupling affixable to the lower surface for coupling a fixing mechanism according to any of claims I to 23 to the underside of the cover plate.

26. A cover plate as claimed in claim 25, wherein the cover plate coupling is adapted to releasably couple the fixing mechanism to the underside of the cover plate.

27. A cover plate comprising a generally planar load bearing plate having an upper surface and lower surfttce, a cover plate coupling affixed to the lower surface and a fixing mechanism according to any of claims I to 23.

28. A cover plate as claimed in claim 26 or claim 27, further comprising an 1 0 aperture, the aperture and the cover plate coupling being located substantially at the centre of the plate.

29. A cover plate as claimed in any of claims 26, 27 or 28, wherein an end of the screw-threaded shaft is accessible through the aperture.

30. A cover plate as claimed in claim 29 when dependent on claim 7, wherein the end of the screw-threaded shaft accessible through the aperture comprises a formation for engaging the key, knob or handle.

31. A method of covering a hole comprising the steps of: placing a cover plate over the hole. the cover plate having a fixing mechanism as claimed in any one of claims I to 23 affixed to its intended underside; and moving the legs to the deployed position so that they engage the walls of the road hole.

32. A cover plate substantially as hereinbefhre described with reference to and as illustrated in the accompanying drawings.

33. A method of covering a hole substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

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