GB2488786A

GB2488786A - Collapsible manhole shield

Info

Publication number: GB2488786A
Application number: GB1103848.6A
Authority: GB
Inventors: Robert James Farrell; Derek May; Richard Jeffery Fryer
Original assignee: RRD INNOVATIONS Ltd
Current assignee: RRD INNOVATIONS Ltd
Priority date: 2011-03-08
Filing date: 2011-03-08
Publication date: 2012-09-12
Also published as: GB201103848D0

Abstract

A manhole shield 1 can be disposed over a manhole or man access opening. The shield has a hollow body with a plurality of planar face or sides A-H, and a top open end 2 and a bottom open end 3. The faces are adapted to be located side by side to allow the shield to be collapsible. The shield may be made from an environmentally friendly lightweight material and the bottom end may be truncated to define an opening or aperture. The body may be pyramidal and define an octagonal frustum. A joint or interface between two faces or sides may be disengeable or separable along the length of an interface.

Description

Manhole safety shield The present invention relates to manhole safety devices. More particularly, but not exclusively, it relates to a manhole safety shield that is erected to prevent injury by falling from height through the aperture of a man access opening or manhole, once the permanent cover has been removed during routine maintenance of underground transformers, utility cables, sewers and the like.

It is known to provide temporary manhole barriers and other safety equipment for use by workmen while attending to a manhole. These devices vary in shape and sizes and may comprise scaffolding type barriers, tent-like structures, hazard cones, safety tape, planks, wooden or metallic sheets and suchlike.

Usually, a manhole will have a resilient and bulky stone, metallic or other permanent lid that is placed over it to cover the manhole at all times and prevents anything passing by or over it from inadvertently falling into the manhole. However, when the need arises for workmen, operatives or engineers to attend to the manhole, they can then undo the lid, which may be provided with a locking mechanism, enabling the workmen to gain access into the manhole for routine maintenance and the like. "Works" is one industry terminology used to collectively define a number of these maintenance or routine checks.

Generally, prior to any works being started in or around an open manhole or man access openings, temporary measures such as barriers, cones, safety tape and the like may be placed around the surrounding, to cordon-off the area and serve as a visual indicator to inform pedestrians, cyclists and other passers-by, that there is a fall hazard, and works are being undertaken nearby, or undemeath, within the manhole, and that they ought to proceed with caution and / or take a prescribed pedestrian diversion route. However, these measures are not always effective in warning pedestrians and cyclist of the hazard, and thereby preventing injury such that there continues to be injuries and some fatalities associated with "manhole falls". Furthermore, within the cordoned off area, the hazard will remain to workmen, operatives or engineers working around the manhole.

Once these temporary measures are installed correctly, the permanent lid is removed and an assessment is usually carried out to determine if the atmosphere below the opcning is suitable for human cntry This assessment can be visual, or monitoring equipment can be passed into the manhole, to study the atmosphere from a safe distance. This is because due to the nature of many manholes, the atmosphere below could could lack oxygen and / or contain flammable or poisonous liquids, gases, fumes, vapour or other hazardous substances. Further, there may be precarious conditions below such that liquids and solids could suddenly fill the manhole, causing flooding, injury or even death. In some situations, the manhole could feature dusty, freezing or volatile temperature conditions, including hot temperatures.

Once this preliminary assessment has been completed successfully, the manhole can be attended to.

FR 2735507 discloses a safety barrier that has four, hinged panels. The front panel forms a gate, and the rear panel is fixed to a temporary cover for the hole which can be moved from an open to a closed position. A small rod is hinged on a foot and is attached to the cover. The rod has a ring which fits over a curved rod which is attached to the upper surface of the cover.

Ti is known from US20092361 80 to provide a manhole construction safety and work platform device having a scaffold catwalk for working on a manhole, providing the safety and work platform with adjustable braces engaging the side of a conical manhole casing. The inner perimeter of the device circumferentially defines a central access opening in order to slidably accept, receive, and fit around the conical section of the manhole casing, as typically used in the utility construction industry The scaffold catwalk has a safety barrier means on the working surface to provide a safe working environment along the outer perimeter.

GB 2440535 discloses a barrier apparatus, for use with manholes and the like, to contain sewage surges, storm water and the like. It comprises a collapsible tube having a first end coupled to the bore of the manhole and a second closed end, the tube being movable between a first collapsed position and a second extended position in which the second end is at an elevated height from the first end. The tube is preferably formed from a flexible polymer which is folded in a number of locations when in the collapsed position.

US6607053 discloses a retractable safety cage designed to occupy a minimum amount of vertical space within a manhole and which provides, in an extended position, a safety barrier surrounding the entrance to the manhole or ladder. A fixed upper periphery rail provides a substantially horizontal perimeter around the opening of the ladder. One or more floating periphery rails are suspended therefrom to provide additional perimeter blocking as well as additional support for the ladder user. The safety cage comprises two vertical members that are slideably received in a bracket that can be attached to either a ladder or a support wall. A counterbalance assists movement in the extending direction and slightly impedes movement in the retracting direction.

However, it appears that most of the devices described in these prior art have not achieved widespread use in the industry. Firstly most of the above prior art are are not ideally suited for use in shielding manholes because they are bulky, and may represent an undesirable cost in transportation, in addition to all the equipment that may be necessary for a particular job.

Further, these types of devices do not appear to be cost effective to manufacture and may require undesirable intermediate steps such as the assembly of different parts, all of which may consume time and drive up costs of manufacturing. Finally, most are not environmentally friendly and cannot be seamlessly recycled.

Accordingly, there remains a need for an efficient, cost effective, environmentally friendly manhole shield that is light, relatively easy to set up and does not occupy too much space during storage.

According to a first aspect of the present invention, there is provided a manhole shield, comprising a hollow pyramidal shaped body, having a top open end and a bottom open end, wherein the ends are of unequal size.

Preferably, the device is collapsible.

Advantageously, the device is foldable for ease of transportation and space efficiency during storage.

Preferably the bottom open end is truncated.

Advantageously, the hollow pyramidal shape defines a frusto-conical shape.

Preferably, the device is frustum shaped.

Advantageously the device is conical shaped.

Preferably, the bottom open end is adapted to fit through a manhole.

S

Advantageously, top open end is generally broader or of greater circumference than the bottom open end.

In use, the top open end is adapted to be above a manhole so as to serve as a visual indicator for a hazard warning of the "uncovered" manhole.

in use the top open end is adapted to sit at an elevated height than the bottom open end.

Preferably, the device is adapted to engage itself centrally over a corresponding man access opening or manhole.

Advantageously, the device is adapted to support itself by the contact of its sides with the edges of the man access opening onto which it is installed. This eliminates the need for further mechanical clamping or locking periphery to retain the device within the manhole.

Preferably, the device is adapted to engage the manhole using the force of its own weight against the sides of the manhole, once placed over an open manhole.

Advantageously, the device is adapted to position itself or "self lock" under the force of its own shape and weight against the sides or contact points of a manhole, once disposed thereupon.

Preferably, the device is adapted to engage a circular manhole using the force of its own weight against contacts points of the circumference of the circular man access opening or manhole.

Advantageously, the device is adapted to engage manholes of various shapes and sizes by the contact of its sides with the edges of the manhole so as to fit cooperatively over varying shapes of manholes Preferably, the device comprise 8 sides or faces to define an octagonal frustum.

Advantageously, the device is adapted to correspondingly fit within manholes of certain size ranges.

Preferably, the device is formed of a recyclable material.

Advantageously, the device is formed of a plastics material or other environmentally friendly material. The shield may be made from antistatic, non-static, non-corrosive material or any suitable material that does not emit a spark so as to reduce the risk of explosions by contact with any flammable substances.

Alternatively, the device may be formed of a metallic material having an anti-static coating.

Embodiments of the present invention will now be more particularly described by way of example, and with reference to the figures of the accompanying drawings, in which: Figure 1 is a perspective view of the present invention.

Figure 2 is a cross section of the present invention, installed on a man access opening, along the p1aneXYXXYY of figure 1.

Figure 3 is a top elevation of one embodiment of the present invention showing each of the sides.

Figure 4 is a perspective view of the present invention showing the side by side arrangement of the sides in a collapsed configuration.

Figure 5 is a perspective view of an embodiment of the present invention showing the arrangement of the sides in a triangular configuration.

Figure 6 is a perspective view of an embodiment of the present invention showing an alternative the arrangement of the sides in a triangular configuration.

Figure 7 is a top elevation of an embodiment of the present invention showing a triangular configuration.

Figure 8 is a top elevation of an embodiment of the present invention showing a triangular configuration.

Figure 9 is a diagram demonstrating how the present invention achieves stability in the presence of a force from one or more directions.

Figure 10 is a plan view of the side of a manhole, showing the position of a manhole's permanent cover and a manhole frame.

Figure 11 is a top elevation of an open manhole, showing the position of the ledges and edges of the manhole frame.

Referring now to the figures and to figure 1 in particular, a manhole shield 1 comprises a hollow pyramidal shaped frustum, provided with eight planar sides or faces. It has a larger top open end 2 and a smaller bottom open end 3. The sides are denoted A to H. Side B is a reflection of H in size and shape. Similarly, side D and F are equal in size and shape, as are C, E and G. Side A is it's own size and shape, and is not equal to any other side. All sides, apart from those labelled B and H, have a line of symmetry from the top edge to the bottom edge.

Thus, the internal angles (not shown) of each opposite interface of each respective side, apart from those labelled B and H, are the same. The internal angles are not symmetrical on each opposite interface of sides B and H. This is because A is at a smaller angle to the vertical (or to the horizontal), than sides C, E and G. Therefore the internal angles of the sides B and H, at their interfaces with A, are different to the internal angles of their respective interfaces with C and G. As side A is at a smaller angle to the vertical (or to the horizontal) than C,E and G, it is therefore larger in size, which enables the shield to be foldable, generally flatly. (figure 4) The sides are so constructed as to allow the shield 1 to be collapsible. In a preferred embodiment, four of the sides are generally identical in surface area, being so disposable diametrically opposite each other, as seen from figure 1. These sides are made to have a larger surface area than the other four sides of the manhole shield. Each of the "bigger" sides (denoted by B,D,F, & H) are disposable adjacent 2 separate "smaller" sides (in surface area).

For example side B is located between side A and side C). The interface between one side to the next is flexible, to allow the device to be foldable.

The shape of the shield 1 allows it to be correspondingly couplable with the sides of the manhole. The sides labelled B, D, F and H are adapted to be substantially at the same angle to the vertical axis 10 (figure 2) (or to the horizontal), to ensure that the top opening level 11 of the device is substantially horizontal to the ground 12, and to ensure that the weight of the shield is spread evenly so that the downward and sideways forces exerted on each of the respective edges (14, 15) of the manhole in which it is disposed, by the weight of the device, are spread evenly on each side. This also ensures that the invention is self centering within the manhole. In addition, sides A, C, E and G (figure 1) are each adapted to negotiate around a ledge' 20 (Figure 11) that is in each corner of an opening frame of a manhole. This is because while a manhole is covered by its permanent lid, the ledge 20 would normally be the part of the manhole cover's frame 21 that supports the manhole's permanent lid 19, and sides A, C, E and G are each adapted to be in contact with sections of the ledge 20. Sides A, C, E and G are not necessarily designed to support the shield 1 against any part of the edge 22 of the opening, however it would not make a significant difference if these sides engage the edges 22, provided the device is disposed within a man access opening in a manner as prescribed such that at least any two of the sides B, D, F and H engage the ledges 20 of the manhole.

Thus, the sides B, D, F and H (figure 1) are adapted to support the shield 1 within a man access opening, by resting against the edges 22 of the opening, while the sides named A, C, F and G provide resilience to the device by preventing it from folding in on itself when disposed within a man access opening (figure 9). Because the sides B, D, F and H are all in contact with the edge 22 of the manhole, if side B is pushed inwards, in a lateral direction that is perpendicular to the manhole edge upon which it is resting, then sides A and C convert that inwards lateral motion of B into outwards lateral directions that are perpendicular to that exerted on B, therefore frying to push sides H and D outwards in opposite directions. These motions are impeded by the sides of the manhole as D and H are resting against the sides of the manhole and cannot move. This restricts movement of side B as illustrated by the arrows in figure 9.

Referring now to figure 2, the shield 1 is adapted such that the distance from an edge of the manhole (or interface 15), on a proximal end to an edge of the manhole shield at a distal end, denoted by X, is greater than the distance between interface 15 and the edge 14 of the opening in which it is disposed. This reduces the risk of the device become unstable within the opening, and thereby rotating out of the opening around interface 15, as a result of a downwards force (generally on the side that is in contact with interface 15), or pull force, or if an upwards force is applied on an opposite side (generally on a side that is opposite or adjacent to that side with a contact with interface 15).

Figure 3 shows a top elevation of the shield 1. The top of sides B and its opposite side F at the top open end 2 are adapted to be substantially parallel or diametrically disposed to be opposite facing. Similar characteristics are observed for sides D and its opposite side H. In the same manner, the device is such that the bottom of the sides B and its opposite side F at the bottom open end 3 are parallel, and the bottom sides D and its opposite side H at the bottom open end 3 are parallel.

In order for the device to fold, its eight sides are of paramount significance in achieving this operation such that when side F (the opposite side to A) is motioned towards side A, sides B and H fold around or engulf sides D and F. The top of the sides B and H run parallel to each other and the bottom of side B and H run parallel when folded flat. Therefore the top sides A and its opposite side E are parallel, and the bottom of sides A and its opposite side E are parallel when folded flat. This is illustrated in figure 4.

The distance between the two adjacent interfaces on the foot of side A, has to be designed to be more than half the thickness of a side B, half the thickness of side H, and the thickness of both sides D and F, providing all sides labelled B, D, F and H are made of a uniform thickness, to enable the invention to fold flat and into a collapsible configuration, as outlined above. This can be seen in figure 4, as the shield 1 will assume the same shape at the bottom of the sides as is assumed at the top.

In addition, the shape of the device prevents it from falling through, into the opening of a manhole for which it is designed, when unfolded or folded.

In an alternative embodiment or additionally, the shield 1 may be adapted to have connection mechanism allowing it to be adjustable so as to be used on triangular, square or circular manholes, such that one or more of its sides could be made to split open or "unfurl" along the length of the side in a position that is considered a interface, for example on one of either "corners" or "joints" of side E (the side opposite side A), such as between side E and F. This serves the purpose that the shield 1 is then transformed by folding into a triangle for use within triangular manholes, and could be later unfolded and reconnected for use with non-triangular manholes. In use, the folding to achieve this function would be done by placing side D inside side F (figure 6), whereby the external face of side F would be in contact with or facing the internal face of side G. Alternatively, the external face of side C could be facing the internal face of side E, depending what side of side E the split is created to be.

Alternatively, side F could be placed to face the inside of side D(figure 5), and therefore the external face of side E would be facing the internal face of side C(not shown), or the external of side G would be facing the internal of side E as in figure 5, depending what side of side E the split is created. However whether disposed within a three sided manhole or four sided manhole, the shield 1 will retain all its intrinsic properties, except the end of the smaller opening will be much smaller when the it is adapted for use with triangular manholes than if it was deployed, unadjusted, in a square shaped manhole. This split can also help in the application of the shield 1 where space is limited above the manhole for example, when a person is working below the manhole tethered to a winch on an A-Frame. Unlike a Davit arm set up, where the shield could be lifted up along the cable and then passed along the davit arm out the way, the A-frame would restrict the upwards movement of the invention, and there would be insufficient space created above the manhole for the person to escape from below.

Therefore the shield 1 could be split and unwrapped from the cable and removed in a lateral direction across the cable by the person working above the opening.

To install the shield 1, a workman, engineer or other user must place the smaller open end through an opened man access opening / manhole, engaging the sides of a manhole. Please note that the circumferential / perimeter of the manhole opening must be smaller than the perimeter of the larger open end of the shield, otherwise the shield will go through the opening, which is undesirable.

Generally, the shield's centre of gravity is below the man access opening in which it is placed, and it will engage the sides 22 once placed within the opening. It has at least two of sides labelled B, D, F and H in contact with the edge 22 of the man access opening. And the distance x is greater than the distance between interface 15 and the opposite edge to 14, denoted y, as illustrated in figure 2.

In use, the shield 1 has many uses and can be applied to man access openings in any industry that have potential fall hazards in their work environments, including utilities, shipbuilding, food manufacturing, petroleum industries, wind turbines, construction of new properties and the like. When in use over a manhole or other man access opening, the shield 1 is deployed over a square shaped manhole such that part of its structure "sticks-out" above the ground, as shown in figure 2. However, it may also be disposable over other non-square shaped manholes, for example, triangular or circular manholes.

The hollow frustum shape with a narrow bottom open end, is an ideal hazard prevention tool, in as far as preventing industrial fall from height hazard/risk. This risk is covered under the HSE Guidance safe work in confined spaces 1ND258. Such risks occur where there arc uncovered manhole openings above storage tanks, silos, sewers, chambers, shipbuilding (on each deck), openings at the top of a wind turbine tower, loft access openings during construction of properties, and any other fall from height risk that occurs when a permanent cover is removed from a man access opening.

Generally, prior to an approach to open man access openings, an assessment is usually carried out to determine the atmosphere below the opening, including leaving the opening bare and uncovered (essentially in a state in which it is a fall hazard) to vent and enable monitoring, to determine if the atmosphere beneath is conducive and safe for a workman to undertake work.

In such an instance, the use of the shield 1 would be advantageous, in that the shield would be installed within the man access opening so as to be visible to all passers by, and would prevent the fall hazard whilst the manhole is being assessed. In such circumstances, the hollow nature of the shield is a particularly useful aspect, as it would allow for venting, or for an engineer to slide in thcrcthrough, monitoring equipment operated from above ground, for example an optical instrument, fume sensor, or dust removal equipment, along with its associated cables and suchlike. In addition, since the shield is hollow then conversation between a workman inside the manhole or below the surface with those above is still possible.

Preferably, the shield 1 is made from "antistatic" material or any suitable material that does not emit a spark so as to reduce the risk of explosions by contact with any flammable substances. In addition, it is important that the materials be corrosion resistant, or do not deteriorate upon contact with waste, chemicals, petroleum products and toxic substances.

Further it is desirable that the material is resistant to ultra violet light (IJV) as UV can deteriorate the condition of some materials, and thus would jeopardise the integrity of this device, causing it to fail to bear the weight of a person falling onto it.

There are many methods by which the manhole shield could be made. In a preferred process, the shield would be made using a plastics extrusion process and welding. This would entail the steps of taking an extruded recycled thermoplastic sheet material, for example extruded polypropylene, which could include additives to the raw plastic, such as colourants, UV inhibitors and internal antistatic agents. Typical thickness may be between 10mm to 15mm, although it will be apparent to the man skilled in the art to alter accordingly the thickness depending on the method of manufacture employed, the type of material used and the person threshold weight, for which, in an incident or misadventure, the shield must be able to support. Thus thickness may be altered to greater than 15mm, or less than 15mm according to such factors.

Additives may be added to the raw plastic to achieve the desirable product specification as described above. An extruded continuous hinge, preferably of recycled plastic, for example extruded polypropylene, which also contains similar additives within the plastic material, of substantially similar specification as the sheet material would also be required.

The desirable shapes of each side would be cut out, by method of band saw, router or other suitable method, from the said extruded recycled plastic sheet. A chamfer is then cut at the full length of every interface of every side (not shown), on both faces of each side at the same angle, therefore tapering each interface of each side to a point that is considered the centreline of the thickness of each side. This would allow for all the sides to rotate freely around the pivot/folding points of the product without interference or conflict between any two adjoining sides. The effect would be a folding article that uses a hinge. The hinge is also cut to length to be fitted at each interface, at a length that is substantially the full length of the interface, although this is not mandatory. One wing (male) of the continuous hinge which is cut to length is a right cuboid in shape (not shown). A recess (female) has to be made within the side, along the length of the interface, and perpendicularly to the thickness of the side, to the same size and shape of the said wing. Typical size for the wing is 3mm thick. The position of this recess through the thickness of the side is determined by the shape of the wing in relation to the interface of the hinge, and the interface should be aligned with the centreline of the thickness of the side. The idea is that the female recess accepts the opposed male wing, and the two components may be bonded using a technique such as a heat fusion, or more specifically socket fusion. This recess could be "routered" out of the interface of the side, by use of a router tool.

Socket welding is a process usually associated with pipes and fittings, however, the process is the same for the method of welding the shield, as in it has male and female components. The welding plates are designed and made to accept the geometry of the welding areas of this product. In socket welding, preferably, the plates should be heated to a temperature between about 130°C and 17 1°C, but this can vary depending on a number of factors such as the grade of the material used and the melting parameters of the material.

Once the required temperature is reached, the wing is inserted within the female welding plates to heat all surfaces of the wing, and the male welding plates are inserted into the recess to heat all surfaces of the recess until they are soft. Once this state of softness is adequately reached, the wing is removed from within the hot plates, and the other hot plates are removed from within the said recess, after which the wing is pushed into the recess, to assume the correct position, and both parts are pushed together until all the plastic has cooled and solidified into a permanent bond. At this point, any excess material that interferes with the full rotation movement of the hinge can be removed. The process can be repeated until all interfaces are joined.

A core drill or router tool could also be used to create a hole in the top proportion of each of the four large sides, generally anywhere on the portion of the planar faces that in use, sit above the manhole. This is to help with handling the product, therefore making installation and removal of the product easier.

In an altemative method, holes may be drilled through the side and wing so as to join the two components by way of rivets.

However, when using a method such as rotational moulding, then there would be no need for any welding, and the sides could then be anywhere between 3mm to 6mm thick.

If there is to be a split on either interface of side E, then a simple tongue and groove configuration could be routered into the opposite adjoining faces of each interface, establishing a connection that will remain intact under compression when the shield is installed in a manhole.

It is not considered necessary to chamfer the interface at the position of the split.

While the method above largely describes small scale production, it will be apparent to the man skilled in the art how the method can be modified to increase efficiency for large scale manufacturing such that other principles in injection moulding or rotational moulding may be employed, for example, the product can be made as a single unit, eliminating the need for any welding or riveting.

In addition, the shield may be used during inspection of a manhole, once the permanent cover has been removed, a workman will usually stand on the edge of the fall hazard! access opening, peering in and leaning over the opening as part of a visual check. During such inspection, a sheet of wood, plastic or metal may be placed over the opening, and over the surrounding manhole frame, to prevent people falling through. However, this is then subsequently removed to allow light to enter the opening for inspection. The hollow nature of the shield would obviate the need for this as it would not only allow for the passage of light through it, illuminating the inside, and enabling the workman to carry out visual inspections, but it would also provide safely protected from falling through the opening and causing injury or a fatality However should a workman! pedestrian inadvertently trip and fall over the opening of a manhole having the shield, they would slide down the intemal faces until they become contained and supported by more than one side. They cannot fall through because the shield is adapted to bear a weight, for example that of an average man. While this may be a design consideration, it will be appreciated by the skilled addressee that modifications such the material used, inclusion of re-inforcements, for example steel wires running within the insides of the faces and! or connectors on the joints! hinges may be used to ensure that the construction is robust and unyielding.

Further, since inspections can be carried out which include the necessary use of mobile camera equipment, such equipment being controlled from above ground, and would produce a visual report of apparatus that is not directly visible from the opening, another application of the present invention is that it allows for the passage of equipment and necessary cables to enable such works, whilst allowing for the works to be carried out safely as the fall hazard is prevented.

When maintenance works are to be carried out using apparatus from above the opening, they can be achieved by people working from above the opening, or people working below the opening. A further advantage of the shield in addition to being able to prevent a pedestrian / cyclist and the like falling through the opening of the manhole and causing injury to themselves, it would also prevent such a fall from causing injury to a workman working beneath the shield, inside the man access opening, or injuring themselves by impact against any mechanical equipment that may be beneath.

When maintenance work is being undertaken using apparatus, from above the opening, it sometimes involves the passage of hoses for the purpose of extracting or "vacuuming" excess waste/material. Preferably, the opening of the smaller open end is adapted to be of corresponding or larger size than the circumference of a larger hose, typically 25 0mm.

Further, in addition to allowing a hose through, it is adapted to have sufficient space in the sides to allow for visibility, so that the workman may be able to see past the smaller open ending, even after a hose has been inserted.

In addition, there sometimes arises a need for pipes or other cleaning equipment to be fed below the opening to spray and clean the apparatus below. These would usually be done by a workman or two, coordinating in holding the equipment and directing it, whilst looking through the opening and standing on the edge of the fall hazard. Since their attention is usually focused on the hoses/pipes, they are not always aware of the position of the edge upon which they stand, and if they are operating in wet conditions, this may present a slip hazard.

Having the present invention installed stops the risk of such a hazard, but allows for the maintenance works to be carried out in its entirety A proportion of the invention also stands proud of the opening and if an average adult was standing nearby it would extend from the ground to around the knee height, therefore being visible to any passer-by Further, the presence of solid sides, apart from possible locations of apertures for handles means that any splashes of liquids that do occur within the manhole are not dispersed out of the manhole, thus "splash back" cannot occur from within the opening to the outside of the manhole, contaminating or causing injury or slip hazards around the opening.

When works are carried out below the opening, a person would enter the opening when safe to do so. There would also be another person above ground to monitor safety and also to aid in a rapid escape of the opening if required. To enable this rapid escape, the person below the opening would be attached to a winch line, which would be controlled by a winch on davit arm. Thus, the hollow nature of the present invention is useful for such an action as it means a winch line can be passed through in addition to sufficient light so that the person above the opening can lift it out of the opening, passing it over the cable, over the davit arm and winch, therefore removing it as a hazard to the person being winched out of the opening.

Additionally, although it is desirable for the present invention to be made of resilient material, it is also desirable that the invention be made of a lightweight material, so that a workman working below the surface can push the shield out of the opening effortlessly should there be a problem with person working above.

Further, since a proportion of the invention is proud of the opening, and the supporting sides of the invention sit on the edge of the opening, it reduces the risk of tools or equipment being accidentally knocked into the opening from besides the opening.

A further application is within most towers of wind turbines, where there is a ladder that climbs up to the top and into the "nacelle", where all the mechanical apparatus is housed. The opening between the tower and nacelle is a fall hazard to anyone working within the nacelle, and is one application where the present invention could be used to prevent that hazard.

Having described and illustrated the principles of the invention with reference to a preferred embodiments thereof, it will be apparent that the invention can be modified in arrangement and detail without departing from such principles. Accordingly, in view of the many possible embodiments to which the principles may be put, it should be noted that the detailed embodiments are illustrative only and should not be taken as limiting the scope of the invention.

Claims

Claims 1. A manhole shield adapted to be disposable over a manhole or man access opening comprising a hollow body having a plurality of planar faces or sides; the shield has a top open end and a bottom open end, wherein, the faces are adapted to be located side by side, to allow the shield to be collapsible.
2. A manhole shield as claimed in claim 1, wherein the shield is made substantially from an environmentally friendly lightweight material.
3. A manhole shield as claimed in claim I, wherein the bottom end is truncated to define an opening or aperture.
4. A manhole shield as claimed in claim I, wherein the top end is octagonal and defines an opening or aperture.
5. A manhole shield as claimed in claim 1, wherein hollo\v body comprises a hollow pyramidal shape defining an octagonal frustum.
6. A manhole shield as claimed in claim 1, wherein in use, the shield is disposable over an open manhole to locate the top end proud above the horizontal plane of the ground or surface which the manhole penetrates so as to be a visible thereupon.
7. A manhole shield as claimed in claims I and 4, wherein the top open end is greater in circumference than the bottom open end, in use, the top open end being adapted to be at an elevated height than the bottom open end.
8. A manhole shield as claimed in claim I, wherein in use the shield is adapted to engage itself generally centrally over a manhole, once disposed over it, using the force of its own weight and by contact of its sides with the edges of the man access opening onto which it is installed.
9. A manhole shield as claimed in claim 1, wherein in use the shield is adapted to engage itself generally centrally over a manhole using the force of its own weight and by contact of its sides with the ledges of the opening frame of a man access opening onto which it is installed.
10. A manhole shield as claimed in any one of the preceding claims, wherein at least one joint or interface between two faces or sides is disengageable or separable substantially along the length of the interface.
11. A manhole shield as claimed in any one of the preceding claims, wherein in use, the shield is so designed to fit cooperatively over varying shapes of manholes.
12. A manhole shield as claimed in any one of the preceding claims, wherein in use, the shield is so designed to be steady and unyielding so as to support a weight, for example the weight of a person.
13. A shield substantially as described herein, with reference to the figures of the accompanying drawings.