EP3359761A1

EP3359761A1 - Temporary access platform

Info

Publication number: EP3359761A1
Application number: EP16790677.5A
Authority: EP
Inventors: Philip Waters
Original assignee: Individual
Current assignee: Individual
Priority date: 2015-10-06
Filing date: 2016-10-06
Publication date: 2018-08-15
Also published as: GB201517628D0; WO2017060708A1; GB2543059A

Abstract

A temporary access platform for deployment within a structure having vertical or steeply inclined internal walls is provided. The platform enables work to be carried out with such structures wherein otherwise the worker would not have an adequate footing. The temporary access platform comprises a retention assembly having abutment means mounted on an actuator, whereby the actuator is operable to urge the abutment means into contact with the internal walls of the structure so as to retain the platform in position within the structure. The retention assembly supports one or more platform plates which combine to form a load supporting floor from which a worker can operate.

Description

TEMPORARY ACCESS PLATFORM

Filed of the Invention

The present invention relates to temporary access platforms and in particular temporary access platforms for deployment within structures that have vertical or steeply inclined internal walls.

Background of the Invention

The interiors of tall steep pipe and ductwork structures, such as lift shafts, oil refinery cracking towers, chemical plants, bridges and dams, etc., present serious and dangerous access and work positioning problems because of the absence of floor space afforded by their vertical or steeply inclined internal walls.

When repair or maintenance work needs to be carried out in such structures access to the internal walls of these structures can be achieved using ropes, hoists, ladders and scaffolding depending on requirements. However, these existing access approaches have various drawbacks, such as long set-up times or interference with the work procedures.

For instance, whilst roped access is fast and flexible and rarely interferes or obscures the work process, it does not provide a solid platform with even low stretch ropes absorbing much of the energy directed into the job, even in confined pipes.

Scaffolding, on the other hand, can take weeks to set up and its very structure can obscure the work surface with tubes and struts, which in turn necessitates repeated time consuming re-adjustment.

Scaffolding is commonly deployed around the internal walls of the structure to provide solid footing, with the structure's core left open for its entire height, often many tens of metres, to enable roped access technicians to move swiftly from worksite to work-site throughout the entire structure's height. However, in structures with narrowly spaced internal walls (e.g. spaced less than a metre apart), scaffolding becomes an impediment and as a result solid scaffolding platforms are simply unavailable.

In these circumstances operators sometimes resort to the use of slightly over-size boards cut On the fly' and jammed widthways between the internal walls of a structure to form a platform. As will be appreciated from Figure 1 , these 'platforms' use a pull-rope and foot power to wedge them in place, as a kind of width-ways cam or pit-prop.

However these 'platforms' can be very difficult to secure in structures where the spacing of the structure's internal walls prevents the operator from bending over at the hips or reaching their feet.

Further, these 'platforms' are highly unstable, even more so when the inter-wall space is greater that a metre, and can only be used in limited directions and tentatively at best. They are prone to failing without warning, and are a serious danger when using power chisels, drills and such.

In addition, the time saved by using these 'platforms', is often lost due to the need to repeated wedge the 'platform' in position every time it becomes dislodged.

Other solutions for providing temporary access platforms within structures with vertical or steeply inclined internal walls include wire suspended platforms and bracket supported platforms.

Both of these options have their own disadvantages. In the case of wire suspended platforms it is that they generally require abundant space top-side to accommodate suspension jibs, counter-weight baskets and such, and the lifting gears and motors take up too much room on small platforms themselves. Also, on longer drops, the cables yield to elastic deformation.

Whereas in the case of bracket supported platforms the operator needs to physically attach the brackets to the internal walls of a structure (either mechanically or with adhesive), which can damage the structure's walls. Also, in some situations, the option of physically attaching brackets to the internal walls is not available due to the material that the walls are made from. Summary of the Invention

In view of the state of the art it is suggested that if a replacement could be found for scaffolding and other heavy access systems, and a more reliable, easily utilised lightweight platform could be employed, much time could be saved and the work in structures with vertical or steeply inclined walls (e.g. pipes, tubes, and ductwork) could be made safer, more efficient, more effective, and produce longer lasting results, thus reducing future downtimes.

To this end the present invention provides a temporary access platform for deployment within a structure having vertical or steeply inclined internal walls, wherein said platform comprises: a retention assembly having abutment means mounted on an actuator, whereby the actuator is operable to urge the abutment means into contact with the internal walls of the structure so as to retain the platform in position within the structure; and a load supporting floor formed from at least one platform plate supported by the retention assembly. Essentially the retention assembly exerts perpendicular, or near perpendicular, forces to the vertical or steeply inclined internal walls of a structure at a sufficient force to lock the platform firmly in place within the structure.

The skilled person will appreciate that the access platform of the present invention, once retained within the structure, provides an operator with a solid platform to work from and in so doing enables the operator to apply more force into the job than would otherwise be possible if the operator was solely hanging from an access rope.

In the absence of the access platform of the present invention an operator trying to work in a structure with vertical or steeply inclined internal walls would not be able to achieve as much purchase when working on the structure. Preferably the retention assembly may be provided with a plurality of abutment means and the actuator is operable to urge the abutment means away from one another and into contact with the internal walls of the structure.

In this way the platform can form a plurality of connections with the surrounding internal walls of the structure rather than a single continuous connection. In this way the platform may also be provided with passages therethrough around the perimeter of the platform. It will be appreciated that forming a plurality of connections with the surrounding internal walls of the structure enables the platform of the present invention to be deployed in a wide range of different shaped structures; ranging from circular and partially circular wall arrangements through to polygonal shaped (such as square) wall arrangements.

However although the provision of a plurality of abutment means is preferable it is envisaged that as an alternative a single continuous abutment means may be provided around the wall facing surface of the retention assembly without departing from the general inventive concept. In this way, the radial expansion of the assembly can force the abutment means into contact with the surrounding wall surfaces of the structure.

Preferably the platform may also comprise at least one passage that provides a way through the platform when such is retained within a structure. There are a variety of benefits to providing a platform which does not completely block the structure. The passages may be provided through the middle of the platform and/or around the perimeter of the platform (see above).

One benefit provided by passages is that the platform can accommodate existing fixtures within the structure, such as access ladders, pipes and access gangways.

Another benefit is that said passage(s) allow for objects to be passed through the platform. Examples of objects that might pass through the platform include abseil ropes, air ducts and power lines.

A further benefit of providing a way through the platform is that, when it is safe to do so, debris generated by the work being carried out of the structure can be removed through the platform rather than being left to accumulate on the platform. Preferably the abutment means may each comprise a surface area capable of forming a frictional relationship with the internal walls of the structure. In this way, when the temporary access platform is no longer required, it can be removed without leaving any structural damage behind. That is to say it does not rely on mechanical fixings that require formation of permanent receiving holes in the structure's internal walls. Depending on the shape of the structure's internal walls the surface area may preferably be either: substantially flat, curved, or orthogonal in shape. It will be appreciated that substantially flat surface areas are most applicable when the internal walls are substantially flat. However when the internal walls are curved, as is the case in tubular structures, a curved surface area is more appropriate. It will be appreciated that the surface area should at least be curved about a vertical axis, which is preferably co-axial to the surrounding tubular structure within which the platform is to be deployed.

It is also envisioned that the abutment means can make contact with corner regions of structures. On these occasions the surface area of the abutment means is preferably orthogonal (i.e. right angled) in shape; although alternative angled shapes may be employed to suit the angle of the corner region of a particular structure.

Further preferably the surface area may be formed from: rubber, high density foam, a plate with an array of projections, tyre like tread patterns, short term adhesives or sticky climbing shoe rubber (e.g. Stealth Rubber TM), hardened steel teeth, or VelcroTM/bolt on foot pad materials pertinent to the substrate to which they are to abut, or combinations thereof.

These options are considered preferable because they facilitate the formation of a frictional relationship with internal walls of different types (e.g. metal, brickwork, etc.). By way of a specific example, one complementary arrangement would be sticky climbing rubber to hardened refractory glass.

Preferably the retention assembly may comprise at least one inflatable body with one or more abutment means provided around the periphery thereof, whereby said abutment means are urged into contact with the internal walls of the structure as the inflatable body is inflated.

In this way the retention assembly might be formed from a single inflatable body or multiple inflation bodies which combine to provide the completed retention assembly. In the case of the combinable inflation bodies it is envisaged that them may take the form of complementary segments of the whole and/or stackable portions of the whole. Alternatively the retention assembly may comprise a mechanically operated drive means that is operable to urge the abutment means into contact with the internal walls of the structure.

Further preferably the mechanically operated drive means may be manually operable. In this way the operator can actuate the retention assembly by hand. Alternatively the mechanically operated drive means may be motor driven, pneumatically or hydraulically operable.

Preferably the platform may further comprise a plurality of platform extension plates that engage with the at least one platform plate of the load supporting floor to increase the size of the floor. In this way the total floor space provided by the platform can be increased once the platform is retained against the internal walls of the structure.

It is envisioned that the platform plates may be incorporated into or pre-attached onto the retention assembly in a partially or fully deployed state by virtue of the expansive action of the assembly. The plates may take the form of interleaving or folding plates or roll out co-inflating drop-thread boards and such.

Further preferably each of the abutment means may comprise a support surface configured to support at least a portion of a platform extension plate. In this way any load placed applied to the platform via the extension plate can be transferred to the region where the abutment means and the structure's internal walls make contact with one another. It is will be appreciated that this helps to prevent the platform from sagging in the middle (i.e. the part of the platform furthest away from the retained parts of the platform).

Preferably the retention assembly may further comprise a central support frame that is at least partially supported by the abutment means. In this way the load can be transferred from the centre of the platform to the edges where the abutment means contact the surrounding walls.

Preferably the retention assembly may be toroid shaped and said at least one passage is provided by the central hole of the toroid. Advantageously the toroid shape is not torus in shape because the pushing force generated in the direction of the walls of the surrounding structure is not sufficiently focused to ensure that the abutment means are adequately urged against the walls.

Further preferably at least a portion of the central support frame is received within the centre of the retention assembly toroid. It is envisioned that adopting a toroid shape allows for a lighter construction for a given platform diameter. The shape also provides a natural passageway through the platform.

In addition, in the case of the inflatable embodiment of the present invention, a torus shape enables the retention assembly to be pushed against a solid surface on both the outside (i.e. surface internal walls) and the inside (i.e. structural core). This enables the amount of inflated body employed to be reduced, which in turn reduces the occurrence of sagging in the middle of the platform.

Preferably the central support frame may be provided with safety rails to guard the passage through the platform. In this way an operator cannot accidentally fall through the passage in the platform.

Preferably the platform may further comprise deployment connection means for securing the platform to a delivery tool while the platform is being deployed within the structure. In this way the platform can be lowered in to the interior of structure and held in position until the retention assembly has been operated to retain the platform in position. The connection means can also be used to retrieve the platform from the structure at the end of the job.

Preferably, for example in the case of larger platform arrangements, the load supporting floor may comprise a plurality of wedge-shaped segmental plates. In this way the plates can be easily delivered into the interior of the structure and then positioned on the retention assembly to form the floor.

In the case of smaller embodiments of the platform, the platform top may be incorporated into or pre-attached onto the expansion body or retention assembly and be partially or fully deployed by virtue of the expansive action of said body. These might be made up of interleaving or folding plates, roll out co-inflating drop-thread sheet boards and such. Further preferably the segmental plates may be hinged together, or otherwise loosely linked together. By connecting the plates together in this way the act of positioning the plates on the retention assembly to form the floor is made easier. This is considered particularly beneficial when the structure is too narrow for an operator to bend down to fit the plates. Also, the hinged relationship means that the plates can be folded together for easy storage and transport within the confines of the structure.

Although the access platform of the present invention is considered suitable for use in a variety of structures having vertical or steeply inclined internal walls, structures having a circular cross-section are considered of particular interest. In view of this the retention assembly may be configured to retain the platform within a tubular structure, and wherein preferably the structure has a circular cross-section.

In addition to the platform described above, the present invention also provides for methods of employing the platform. In this regard the present invention provides a method of deploying a temporary access platform within a structure having vertical or steeply inclined internal walls, said method comprising: delivering an access platform according to the present invention into the interior of the structure using a delivery tool; operating the actuator of the retention assembly so as to urge the abutment means into contact with the internal walls of the structure so as to retain the retention assembly in position within the structure; and locating at least one platform plate on the retention assembly so as to form a load supporting floor.

Preferably operating the actuator may comprise pumping fluid (i.e. a gas or a liquid) into the actuator thereby inflating the actuator and urging the abutment means on the periphery thereof into contact with the internal walls of the structure. Such fluids may be mobilized by compressors, pumps, impellers or compressed gas vessels.

Alternatively operating the actuator may comprise manually operating a mechanical drive means to urge the abutment means into contact with the internal walls of the structure.

The present invention also provides a method of releasing a temporary access platform according to the present invention that is retained with a structure having vertical or steeply inclined internal walls, said method comprising: removing the at least one platform plate from the retention assembly; operating the actuator of the retention assembly to move the abutment means away from the internal walls of the structure so that there is clearance between the retention assembly and the structure; operating a delivery tool to relocate the platform. Preferably operating the actuator may comprise decompressing the actuator so that the abutment means are no longer urged against the internal walls of the structure. It is appreciated the abutment means may be actively and further withdrawn from the internal walls to significantly reduce the footprint of the platform to aid relocation.

Alternatively operating the actuator may comprise operating a mechanical drive means to retract the abutment means away from the internal wall of the structure.

Further, the present invention provides a method of allowing multiple operators to work within a common structure having vertical or steeply inclined walls at the same time, said method comprising: deploying a plurality of temporary access platforms according to the present invention within said structure so as to provide multiple work regions within the structure.

Brief Description of the Drawings

The present invention will now be described with reference to various preferred embodiments shown in the drawings, wherein: Figure 1 shows an example of an access solution of the prior art;

Figure 2 shows a first embodiment of the access platform of the present invention in use;

Figure 3 shows the first embodiment of Figure 2 in an undeployed state;

Figure 4 shows the first embodiment of Figure 2 in a partially deployed state; Figure 5 shows a second embodiment of the access platform of the present invention in a partially deployed state;

Figure 6 shows a third embodiment of the access platform of the present invention in an uninflated state; Figure 7 shows the third embodiment of Figure 6 in an inflated state;

Figure 8 shows a fourth embodiment of the access platform of the present invention being delivered within a tubular structure;

Figure 9 shows the fourth embodiment shown in Figure 8 being deployed by an operator;

Figure 10 shows the fourth embodiment shown in Figure 8 retained in place within the tubular structure;

Figure 1 1 shows a sectional schematic that represents the central support frame employed in the third and fourth embodiments of the present invention; Figure 12 shows the retention assembly of a fifth embodiment of the access platform of the present invention in an undeployed state;

Figure 13 shows the retention assembly of a sixth embodiment of the access platform of the present invention in an undeployed state;

Figure 14 show the access platform of Figure 13 in a partially deployed state; Figure 15 shows a seventh embodiment of the access platform of the present invention in an undeployed state;

Figure 16 shows a preferred embodiment of a platform plate of the access platform of the present invention; and

Figure 17 shows a preferred arrangement of a load supporting floor formed from a plurality of interconnected platform plates.

Detailed Description of the Preferred Embodiments

The temporary access platform of the present invention will now be described with reference to collections of preferred embodiments. The majority of the embodiments described hereinafter are designed for deployment within generally circular, tubular structures (such as vertical pipes, chimneys, cracking towers, reactor vortex cones, etc.). However it is envisioned that the access platform of the present invention can also be employed in structures with other cross-sectional shapes, e.g. rectangular, square, and other polygonal shapes. In this regard, Figure 15 is particularly relevant.

It is also envisioned that the temporary access platform of the present invention may also be deployed within framed structures, such as a crane tower, space-frame, pylon or flare boom, with the abutment means configured so as to adhere to, and possibly also mechanically lock onto, the structural bracing members.

It would be lighter than existing alternatives. It may be seen that a very lightweight model could be used as a rescue platform or safe way-stage, temporarily deployed in very tall structures currently accessed only by ladder.. V masts and such.

The majority of the embodiments shown employ an inflatable retention assembly to push against the vertical or steeply inclined walls and retain the platform in place within a structure. By way of a guide an angle of about 35 ° from vertical and below would be considered a steep incline, although it is appreciated that the angles will be affected by the frictional grip provided by the walls. That is to say the more slippery the surface the more keenly the incline of a wall is felt.

However it is also envisioned that a mechanically operable retention assembly can be employed without departing from the scope of the present invention. In this regard, and in addition to the described embodiments, it is also envisaged that hydraulically operated pistons may also be employed. It is appreciated that each type of retention assembly provides its own particular advantages over the prior art.

As described above, Figure 1 shows one example of an access solution provided by the state of the art. This type of ad-hoc solution is most commonly used in confined structures to provide the operator with a solid base to press against when working on target work region within the structure.

It will be appreciated that in the absence of a solid base, an operator supported solely by twin access/safety ropes 1 will not be able to apply the same level of force to a target region within a structure (in this case a tube 2) because of the natural 'give' in the ropes. In order to create a solid base an operator wedges a plank 10, which has a length greater than the diameter of the tube 2, against the internal walls of the tube. The operator achieves this by simultaneously stamping down 6 on one end of the plank 10 with a leg 4 and pulling up 5 the opposite end of the plank with an arm 3 using a pull cord 7. Once wedged in position the plank 10 affords the operator a temporary solid base to work off.

In order to remove the plank 10 the operator simply lifts the same leg 4 that stamped down on the plank and, by virtue of a foot retaining strap 8 attached to the plank 10, dislodges the plank from the tube 2. As already detailed above this system, although simple and quick to use, is not as safe as it could be, particularly as the distance between the structure's internal walls increase.

In view of the limitations of the prior art shown in Figure 1 , and described

hereinbefore, the present invention provides a number of advantages, which include: · Very short set up times compared to systems currently available;

• Low mass of kit required and thus highly manoeuvrable;

• Capacity to expand and contract radial dimensions rapidly;

• Ability to micro adjust on the fly;

• Capacity for safe multi stacking within the work tube (isolating drop dangers within operational layers;

• Variety of flooring options;

• Variety of operation and design structures to fit the wide range of pipe

varieties;

• A variety of footpad abutment tools and surfaces to best interact with the

work-tube substrate/surface.

The above advantages, and more, will become apparent upon consideration of the various embodiments of the present invention shown in the Figures and as described hereinafter. Figures 2 to 4 show a first embodiment of access platform of the present invention which takes the form of a mini three-legged inflatable unit that is particularly suitable for use in confined structures where the distance between the internal walls is limited (for example between about 500mm and 1500mm). Figure 2 shows the access platform is use within a tubing structure 2 and an operator 13 at work on a target region within the tubing. The operator 13 is primarily supported by twin access/safety ropes 1 . The access platform is also connected to a support line 12, which is used to deliver the platform into a desired location within the tubing 2.

The access platform is provided with an inflatable retention assembly 16 having a plurality of abutment means in the form of three friction foot pads 17. In the inflated state the retention assembly forces the friction foot pads 17 against the internal walls of the tubing and locks the assembly 16 in place. As the assembly only makes contact with the surrounding tubing 2 at discrete points around the perimeter thereof it is possible to provide through ways or passages that pass through the platform and avoid completely blocking the tubing 2. As will be appreciated from Figure 2, this allows for the operator's twin access/safety ropes to go passed the platform rather than piling up on the platform and causing a tripping and/or entanglement hazard. The passages/through ways also allow dust and debris (created by working on the internal walls) to escape.

On top of the assembly 16 is located a load supporting floor formed from a plurality of interrelated platform plates. Further details of a preferred example of the

interrelated platform plates is shown in Figure 17 and will be described in more detail below. The floor serves to provide the operator with a solid footing to work from, thereby giving the operator more purchase when applying force to the target work region (e.g. drilling).

An armoured inflation/deflation control line system 1 1 connects the inflatable retention assembly to a hydraulic/pneumatic pressure source. As the skilled person will be well versed in the operation of these pressure sources to inflate inflatable bodies it is not considered necessary to describe such in too much detail herein. However, where appropriate, further details about the hydraulic/pneumatic systems will be provided.

Turning now to Figure 3, wherein an undeployed, uninflated platform 20 is shown, the access platform will be described in more detail. For the sake of clarity neither the operator 13 nor the support line 12 is shown; although in normal use they would be present.

During the delivery of the access platform into a tubing 2 the platform is typically uninflated. This makes it easier to get the platform into the structure and deliver it to a target location therein because the friction foot pads 17 are held more closely to the body of the retention assembly.

The elasticated collapse assist band 18, which urges the inflatable body to a deflated state, also serves to maintain the reduced footprint of the platform as it is delivered into the tubing 2. The plate segments 15 that form the load supporting floor in the deployed platform are held in folded arrangement during the delivery, once again to reduce the footprint of the platform during its delivery.

The platform of the first embodiment is also shown as having a test rig attachment ring 19, although this is not essential, which is used to test the 'slip load' of the unit by the addition of excessive weights from below. This may be desirable in novel or rescue situations such as where pipe interiors are contaminated with slippery residues or the need to establish a Safe Working Load (e.g. normally between a third and a half of the slip/fail load).

As can be appreciated from Figure 4, once the platform reaches the target region of the structure the retention assembly 13 is inflated via the armoured inflation/deflation control line 1 1 to form the inflated platform 21 .

Once the retention assembly has been inflated and the friction foot pads 17 forced against the internal walls of the tubing 2 to lock it in place, the previously folded platform plate segments can be unfolded and arranged on top of the retention assembly 13 to provide a floor.

As will be described in more detail later, by resting at least a portion of the plates on the top edges of friction foot pads 17 it is possible to transfer the load from the middle of the platform to the internal walls of the structure 2.

Those segments of the platform plates that are not supported by the friction foot pads are instead supported by those platform plates that are supported by the friction foot pads. It is envisaged that that the different segments may be provided with wedge shaped edges to facilitate this interaction.

Although not shown in Figures 2 to 4 it is envisioned that the inflatable body of the retention assembly may be formed from a single chamber due to limited size of the platform. However, it is also appreciated that the inflatable body may be formed from a plurality of inflatable chambers. This arrangement is considered to provide additional structural strength to the platform, although this may be unnecessary in the smaller units and more appropriate as the size of the access platform being used is increased. Figure 5 shows a larger version of the platform shown in Figure 2 to 4 by way of a second embodiment in the form of a three metre pentagonal inflation body with frame supported platform.

As will be appreciated from the scale provided by the operator hanging from the twin access/safety ropes 1 , the platform of the second embodiment is larger than that of the first embodiment. As such it can be deployed within structures 2 that have much larger distances between the internal walls.

As with the retention assembly of first embodiment, the second embodiment is provided with a plurality of friction foot pads 17 around the periphery of the retention assembly's inflatable body. In order to accommodate for the increase in size five friction foot pads (rather than three) are provided. It is appreciated that the number of friction foot pads 17 can be varied as appropriate without departing from the general concept of the present invention.

It will be appreciated that the retention assembly of the second embodiment works in essentially the same way as the first embodiment to retain the platform against the internal walls of the structure 2.

However as the size of the retention assembly is increased and the distance between the centre of the platform, and the secured outskirts thereof gets bigger, it is considered desirable to provide additional support components to help transfer any load applied to the platform towards the walls and away from the middle of the platform to prevent it sagging. To this end the platform is provided with a support frame 1 18, which rests on the top edge of each of the friction foot pads 17. The support frame 1 18 is made up of five support sub-sections 1 16, each of which can be delivered separately to the location of the retention assembly once it has been retained in position. It is envisaged that the platform support frame might be made from such traditional materials as 7075 aluminium alloy, tubing, steel, fibre glass, or more novel composites such as Carbon fibre polymers or fibre polymer pulltrusion girders.

Each of the support sub-sections 1 16 rests on the top edge of a friction foot pad 17. Preferably the friction foot pads 17 are provided with upstanding projections 1 19, against which the ends of each sub-section can push to further assist in retaining the sub-sections 1 16 in position. It is envisaged that the upstanding projections 1 19 may be provided as upward continuations of the friction foot pads 17.

The sub-sections 1 16, of which there are five in the shown embodiment (i.e. one for each frictional foot pad 17), in turn engage with a central compression ring 1 17. In this way each sub-section 1 16 is restricted at both ends thereof, thereby providing structural rigidity and strength to the access platform.

It will be appreciated that the construction of the support frame 1 18 is such that once in position any loads applied to the frame are transferred outwards towards the friction foot pads and the surrounding walls rather than downwards onto the centre of the inflatable body. The platform plates 15 (shown here being delivered) are then located onto the support frame to form the load supporting floor of the platform.

In order to aid in the delivery of the access platform into the structure 2 one of more connection means (shown but not numbered) are provided. Although only one of the connection means shown in Figure 5 is connected to a line, it is appreciated that some or all of the connection means may be connected to a line during the delivery of the access platform in to the structure 2.

However, having said that, it is envisaged that the primary delivery and transient suspension system employed during re-deployment of this unit would be the central armoured control cable 1 1 and its support line 12, shown here connected via the armoured control unit 14. As in the first embodiment, passages/through ways 1 21 are provided around the perimeter of the platform to avoid the structure being completely blocked by the platform. As can be seen from Figure 5, the passages 121 accommodate existing furniture within the structure, such as ladders 120 for example. Figures 6 and 7 show a third embodiment of the present invention in the form of mini inflatable twin toroid design. The third embodiment, as with the first embodiment, is considered suitable for use in confined structures where the internal walls are relatively close together (e.g. between about 500mm and 1500mm).

In this embodiment the friction foot pads 17 are, in use, urged against the internal walls of the surrounding structure by a pair of inflatable toroid-shaped bodies 29, 30. Each toroid shaped body 29, 30 is provided with a plurality of friction foot pads 17 (only three visible on each body).

It is appreciated that by providing two (or more) smaller inflatable bodies rather than a single larger inflatable body a more rigid, less spongey structure can be achieved. Furthermore it is envisioned that providing a plurality of independently inflated retention bodies reduces the risk of complete unit failure in the event of a puncture or material failure of one of the bodies.

In addition, and as detailed above, each inflatable body may also be comprised of multiple internal chambers to further enhance the structural rigidity of the bodies (see Figure 1 1 ).

As with the second embodiment the retention assembly of the third embodiment is provided with a central support frame 25. In contrast, however, to the second embodiment, the central support frame is located within the central space of the inflatable bodies rather than on top of or above the inflatable body. As a result the inflatable body/bodies can push against both the surrounding structure's internal walls and the central support frame. As detailed above, this arrangement increases the structural rigidity of the platform.

The central support frame 25 is provided with a plurality of vanes 28 which are arranged around a central hub 27 to define a passage or through way through the platform. Thus, in contrast to the first and second embodiments of the present invention the passageway of the third embodiment is provided through the middle region of the platform rather than at the periphery of the platform. However, having said that, it will be appreciated that the spaced arrangement of the friction foot pads 17 around the perimeter of the toroids 29, 30 means that gaps are also provided around the periphery of the platform; albeit to a lesser extent that is the case in the first and second embodiments.

The access platform is also provided with a toroid core cover 23 which aligns with the passageway and preferably rests on the vanes 28 to cover at least a portion thereof and provide at least part of a load supporting floor. However, in order to maintain at least some access through the platform the cover 23 is preferably provided with a cut out 24.

The central support frame 25 is further provided with a plurality of extender plate locator pits 26. As will be appreciated upon consideration of Figure 7, which shows the twin mini toroid shaped inflatable bodies in an inflated state 31 , the pits 26 cooperate with the top edges 32 of the friction foot pads 17 to locate and support a plurality of interlocking extension platform plates 32. Arranging the extension plates around the periphery of the platform serves to increase the floor space available to the operator.

The fourth embodiment of the present invention, which is shown in Figures 8 to 1 1 , relates to a larger scale variant of the toroidal design shown in Figures 6 and 7. However, in contrast to the third embodiment, the fourth embodiment employs a single (rather than a twin) toroid shaped inflatable body 56. It is envisaged that a multi-body system could be employed without departing from the scope of the present invention.

Figure 8 shows the fourth embodiment of the access platform of the present invention being delivered within a structure 2.

In a similar way to the third embodiment described above the retention assembly is comprised of a toroid shaped inflatable body with a plurality of friction foot pads 17 provided on the outer surface, such that when the body is inflated the pads 17 are urged into frictional contact with the internal walls of the structure 2 and thereby lock the platform in position. Once again it will be appreciated that the spaced arrangement of the friction foot pads 17, with spacing regions 57, facilitates the creation of gaps between the temporary platform and the walls of the surrounding structure when the body is fully inflated. Also, as with the third embodiment, the retention assembly is also provided with a central support frame/core 59, which in the shown embodiment is formed from two complementary component parts 50 and 53 for easier delivery in to the structure. However, it is appreciated that the core 59 could be delivered as a single unit without departing from the present invention. The component parts 50 and 53 connect together at connection points 54 to form the central support frame/core which is then received within the central space of the toroid shaped inflatable body 56.

As described above in relation to the third embodiment, the central support frame/core 59 serves to restrict the inflation of the inflatable body 56 into the central space of the toroid and thereby increases the rigidity of the platform structure when it is retained within a structure.

The component parts 50, 53 of the central support frame 59 are provided with cut outs to accommodate, amongst other things, the inflation manifold 22 of the inflatable body 56 and a dump valve opener 60 (see Figure 9). The delivery and construction of the access platform is facilitated by a suspension and emplacement cage 49, which is in turn connected to a delivery line (shown but not numbered). Both the central support frame/core 59 and the inflatable body 56, which is connected via connection means 55, are attached to the cage 49 via lines.

It will be appreciated that by adjusting the lengths of the lines the inflatable body 56 and the central core 59 can first be aligned and then brought into connection with one another to form the completed retention assembly 61 of the platform which is shown in Figure 9.

It will be appreciated that in the embodiment shown in Figures 8 to 10 the platform plates that help form the load supporting flooring of the platform are integrally formed with the central support frame/core 59. As in the other embodiments of the present invention, the area of the floor space available to the operator can be further increased by positioning interconnectable extension plates 65 over the inflated region 67 on the top of the retention assembly (see Figure 10).

In order to guard against the operator accidently falling through the central passageway through the platform it is envisaged that a guard rail 62 can be provided on the platform. In the shown example the guard rail 62 is provided with a plurality of alignment pins 63 that are inserted into complementary holes 64 in the retention assembly. However alternative methods of attachment can also be employed without departing from the scope of the present invention. The manifold 22 is provided with a non-return control line valve/socket 66 which prevents the inflatable body from unintentionally deflating during use. As will be appreciated from Figure 10, the armoured inflation/deflation control line 1 1 is detachable from the platform when it is not required so as to avoid it becoming an obstruction to the operator when they are working on the internal walls of the structure 2. The cage 49 can also be disengaged and removed for the same reason.

Once again, although not visible from the outside, it is appreciated that the inflatable body may be provided with one or more baffles to define a plurality of internal chambers within the inflatable body and thus increase the rigidity of the structure.

Turning now to Figure 1 1 , which shows a schematic cross-sectional view of a twin toroidal design in accordance with the present invention, the interior of the inflatable bodies 29, 30 shown in Figures 6 and 7 can be better appreciated. In addition it will be appreciated by person skilled in the art that the following description also applies, to a certain extent, to the central support frame/core employed in the embodiment shown in Figures 8, 9 and 10. As described above in relation to Figures 6 and 7 the retention body is comprised of a central support frame 25 located within the central space of toroid shaped inflatable bodies 29, 30. Multiple friction foot pads 17 are located around the periphery of the inflatable bodies. Also, multiple platform plates 32 are locatable on the retention body to help form a load supporting floor 73. It will be appreciated from Figure 1 1 that the toroidal designs of the third and fourth embodiments employ an arrangement wherein the weight of the platform plates 32 and the supporting floor 73 is supported by the friction foot pads at one end thereof and the central support frame at the other end thereof.

However it is also envisaged that the toroidal designs of the third and fourth embodiments might also be adapted to employ a similar floor supporting

arrangement to that shown in Figure 5, wherein the weight of the platform plates 32 and the supporting floor 73 is supported by the friction foot pads at one end thereof and a compression ring at the other end thereof. In this alternative arrangement, as with Figure 5, any weight placed on the centre of the retention assembly is

transferred outwards toward the friction foot pads and the surrounding walls rather than being placed on the central support frame/core.

Therefore it will be appreciated by the person skilled in the art that the central support frame core shown in the third and fourth embodiments does not necessarily need to bear the weight of the load supporting floor in those embodiments of the present invention that employ a toroidal shaped inflatable body with a central support frame core. Even when the central support frame core does not support the weight of the load supporting floor it still provides its other functions (e.g. access to interior of inflatable body of retention assembly and passageway therethrough, etc.).

Returning now to the central support frame 25, as already described above such comprises a central hub 27 around which a plurality of vanes 28 are connected so as to define a passageway 69 through the central support frame 25.

The inflatable bodies 29, 30 are provided with a plurality of internal wall retention baffles 72 which define a number of chambers within the inflatable bodies. Each inflatable body is provided with an inflation/deflation valve 75, which is in turn connected to a compressed air in/out manifold 76. The manifold 76 is provided with compressed air line couplings 77, which are attachable to inflation and the deflation air lines 70 that run through the armoured inflation/deflation control line 1 1 . The armoured inflation/deflation control line 1 1 is connected to the central support frame 25 by way of a conduit attachment nozzle 71 .

Also provided within the armoured inflation/deflation control line 1 1 is the sender cable which communicates with a pressure sensor 74 on the manifold 76 to enable the internal pressure of the inflatable bodies to be monitored at all times. As a further safety measure the inflatable bodies 29, 30 are provided with overfill anti-burst pressure release valves 78.

It is envisioned that in all of the inflatable variants of the access platform of the present invention similar materials can be used to construct the inflatable bodies employed by the retention assembly.

It will be appreciated that a range of suitable material for the inflatable bodies employed in the present invention are known in the inflatables industry. With that said it is considered important that the inflatable bodies are made from suitable low or non-stretch elastomeric fabrics. One example of which is Spectra™ 1000 cloth incorporated with elastomeric laminations. Other suitable alternatives include chlorosulfonated polyethylene (CSPE) synthetic rubbers (CSM), such as

HyperlonTM, or PVC, Urethane and other rubber based fabrics.

In addition, it is envisaged that heat and sonic welding techniques can be employed to achieve the desired shapes of the inflatable bodies described hereinbefore in a reliable and affordable way.

A more simple arrangement that enables the provision of passageways through the platform might be achieved by employing stiff 'IT shaped half pipes to 'Hold-Off sections of the inflated body or bodies' outer abutment surface(s) in order to prevent them directly abutting the inner walls along the full height of the platform. It is appreciated that with the concave surface of the half pipe facing outward to the surrounding walls, this would facilitate the creation of a through void or passageway when the half pipe is pushed up against the inner walls of the structure by the more central inflation body. The passageway would then permit ropes, lines and such to pass the inflated body of the platform in a manner similar to other embodiments of the present invention.

As described above the present invention may employ single or multiple inflatable bodies to retain the platform in position. In view of this the ability to individually control the inflation of separate pneumatically independent compartments within each inflatable body is significant. It is envisioned that the use of compartments and also built in structures, which can act both as baffles (to control attached surfaces from 'ballooning'), and as internally over pressured reinforcing struts to further rigidify the inflatable bodies.

As in the case of the struts within the steel framework of a pylon or bridge, for example, it is envisioned that these internal struts can give increased structural integrity to inflatable body and enable it to resist deformation when loaded, by transferring load to the abutment means/friction foot pads.

In order to enable an operator to control the inflation and deflation of the inflatable bodies of the access platforms control means 14 are provided (see Figures 2, 5 and 9).

As will be appreciated from the Figures, the operator 13 will have a shielded button control unit 14 situated on the armoured high strength umbilical 1 1 for ease of use. This will control the inflation and deflation of the inflatable components of the retention assembly and can be fitted with mini displays to provide feedback information from embedded pressure sensors, where desired.

For additional safety the inflatable bodies will also have a safety pressure release burst prevention valves set appropriately below the rupture point of the pneumatic system. Auto non-return valves can stop the system failing if a supply line (e.g. air line) is cut. In addition, system overrides can be incorporated topside (i.e. outside the structure) where the compressor or tank is located, and emergency purge valves built into the inflatable body of the retention assembly so that it may be deflated rapidly in case of emergency, or from below without resorting to cutting open the inflatable body with a safety knife. The operator thus has greater ease of operation. This is a major consideration for the smaller access platforms used in pipes less than a metre in diameter, where it will be difficult for the operator to reach down to the feet and manipulate the controls.

In a separate family of embodiments of the access platform of the present invention the retention assembly employs mechanical means rather than the expansion of one or more inflatable bodies to urge the abutment means of the friction foot pads against the internal walls of the structure within which the access platform is to be retained.

Figure 12 shows a fifth embodiment of the access platform of the present invention, which takes the form of a manually operable three legged scissor jack style platform. For the sake of clarity the load supporting top floor has been omitted and only three of a total of the six legs of the retention assembly unit of the access platform are shown. It is appreciated that the number of legs may be varied without departing from the general concept of present invention.

The retention assembly comprises a central low angle thread screw rod 92, upon which is rotatable mounted a travelling node 91 . At the top end of the screw rod is provided a fixed node 86 that is fixed so that it cannot rotate relative to the screw rod. It is envisioned that the positions of the fixed node and the travelling node could be interchanged without departing from the general concept of the present invention.

The assembly is provided with three scissor jack type arms, each having a pair of connection points at each of their ends.

The fixed node 86 is provided with a plurality (in this case three) of connection means each of which is pivotally engaged with a connection point of three respective scissor jack style arms 90. Similarly the travelling node 91 is also provided with a plurality (i.e. 3) of connection means, which also each pivotally engage with an adjacent connection point of said scissor jack style arms 90.

The connection means of the fixed 86 and travelling node 91 are aligned so that the ends of each respective scissor jack style arm 90 are held in alignment.

The pair of connection points provided at the opposite ends of each arm is attached to a friction foot pad 93 by way of a foot plate 84. Each foot plate 84 is slidably mounted to at least one connection point 89 of each respective arm via a shaft 88 so that the connection points 87, 89 associated with the foot plate 84 can move closer together when the scissor arms 90 are operated.

As will be appreciated upon consideration of Figure 12, because of the linkage between the fixed and travelling nodes, rotating the screw rod 92 will cause the travelling node to move relative to the fixed node in a straight line. Depending on the direction of rotation of the screw rod 92 the nodes 86, 91 will either move closer together or further apart.

The relative movement of the nodes 86, 91 will in turn act upon the scissor arms 90 to cause them to extend or contract which serves to urge the foot plate 94 (and the associated friction foot pad 93) towards or away from the internal walls of a surrounding structure (not shown).

The rotation of the screw rod 92 can be manually carried out by using an appropriate tool on the rotation nut 82 provided at the end of the screw rod 82. Also provided at the top end of the screw rod is a rotator eye hole 83. Alternatively the operator may employ a hand held power tool (e.g. electric, or air driven).

In addition to providing a connection means for attachment of delivery line, it is envisioned that the hole could be used to in combination with hand cranked brace hook to rotate the screw rod.

A stop cap 95 is provided at the opposite end of the screw rod 92 to the rotation nut 82 to prevent the travelling node falling off the end of the screw rod as the result of over rotation in a particular direction.

In order to prevent the unwanted rotation of the screw rod 92 and any associated relative movement of the nodes 86, 91 the retention assembly is also provided with a locking block 85 and a locking plate 85a, both of which have apertures shaped to receive an anti-rotation safety pin 81 . In order to prevent unwanted rotation of the system the pin 81 is inserted through the apertures in both the locking plate 85a and the locking block 85 thereby preventing the screw rod 92 being rotated relative to the locking block 85.

In order to support the floor (not shown) of the access platform the foot plates 84 are provided with support surfaces 94 at their top edges. It use the platform plates will be supported by the support surfaces 94 on the foot plates 84 and the locking block 85 in the centre of the retention assembly.

An alternative form of mechanical actuator is shown in a sixth embodiment of the present invention. The sixth embodiment, which takes the form of a manually operated four legged cam-lock access platform, will now be described with reference to Figures 13 and 14.

As can be seen from the underside view of Figure 13 the retention assembly is provided with four friction foot pads 17. Each of the of the foot pads 17 is slidably mounted to the main body of the retention assembly by virtue of the relationship formed between a pair of arms 104 and a pair of sleeves 99 provided on the main body. Each arm 104 is received within a sleeve 99 that is slidably mounted to associated slider guide rails 100 provided on the main body of the retention assembly. Each sleeve 99 is provided with a hole through which a locking pin 103 can be passed. Each arm 104 is provided with a plurality of holes which can be aligned with the hole in the sleeve 99 before the locking pin 103 is passed through both holes to lock the arm 104 and the sleeve 99 together.

By providing a plurality of holes along the length of the arm 104 it is possible to allow for friction foot pads 17 to be extended further away from the main body of the retention assembly as is required to suit greater inter-wall distances.

Each sleeve 99 is connected to a central rotatable activation cam 101 by way of a drive rod 102 so that rotation of the cam can be transferred into linear movement of the sleeve 99 and its associated friction foot pad arm 104. Although only the bottom cam arrangement can be seen in Figure 13 it will be appreciated that a second identical arrangement is provided for driving the upper arms 104 of the foot pads 17.

The main body of the retention assembly is formed from two sections, each with a cam arrangement, that are secured together with four brackets 107 positioned evenly around the perimeter of the retention assembly. Both activation cams 101 are fixed to a central operation drive shaft 97, which is in turn provided with a manual operation wheel 96 and a rotator eye hole 83 similar to that shown in Figure 12.

In order to secure the access platform in position the operator rotates the operation wheel 96 to work the cams 101 . It will be appreciated that by employing a simple mix of leverage and primitive lightweight gearing to convert rotational torque into expansive pressure, cam-locks can generate accurately targeted localised forces that urge the friction foot pads outwards and in this way the retention assembly can be retained against the internal walls of a surrounding structure.

Once again the friction foot pads are provided with support means 106 upon which the support sub-sections 1 16 and the platform plates 1 13 that form the load supporting floor of the platform can rest (see Figure 14).

The friction foot pads shown in the embodiments so far have all had a relatively flat surface area, although it will be appreciated that a curved surface area would be advantageous when pressing against internal walls that are curved (such as in a tubular structure). However it is envisioned that alternative shapes of foot pad could be employed without departing from the general concept of the present invention.

In view of this Figure 15 show a seventh embodiment of the present invention, which takes the form of a manually operated four legged cam-lock access platform with corner shaped friction foot pads. The majority of the components shown in Figure 15 are the same as those described with relation to Figures 13 and 14. However it will be appreciated that the

substantially flat foot pads 105 employed in Figures 13 and 14 have been replaced with corner shaped foot pads 1 12 mounted on a corner engaging foot plate 1 10.

Preferably each of the corner engaging foot plate 1 10 is mounted to the arms 104 by way of self-centring attachment joints 1 1 1 .

Also visible in Figure 15 (but hidden from view in Figure 13) is the drive shaft universal joint 109, which allows the operator greater flexibility when operating the drive wheel 96 from a hanging position.

Turning now to the load supporting floor which is placed upon the retention assembly of the platform to complete its construction, Figures 16 and 17 provide examples of suitable designs of the platform plates that help form the floor.

Figure 16 shows a 'C'-shaped plate 34 with a slot 35 that provides access to a central hole 37. The slot 35 allows the plate to be located on the retention assembly even when the control lines 1 1 are still attached. In view of this, the plate shown in Figure 16 is considered particularly suitable for use with the inflatable family of embodiments of the present invention. Once the plate 34 is in position a cover 36 can be inserted into the slot to form a complete plate with a hole in the middle through which the control lines 1 1 pass.

Preferably the plate is provided with an additional hole 38 which is covered by a lid 39 with a finger hole 40 to aid its removal. It will be appreciated that by removing the lid 39 access can be provided through the plate. In use the hole would be aligned with a passage through the retention assembly below so as to provide a passage through the entire access platform.

Figure 17 shows another example of a flooring arrangement suitable for use with the retention assemblies described above; and in particular the embodiment shown in Figures 2 to 4. The flooring 41 is essentially formed from two main types of segment plates that interlock with one another to form the complete floor.

Primary plates 42, which, in use, partly rest on the top edge of the friction foot pad (see Figure 2 to 4 for example) and are located in place by side arms 43, are neighboured on either side by secondary plates 44, which in use do not rest on the foot pad.

The interface 46 formed between each primary and secondary plate comprises an outwardly sloping face on the primary plate 42 and an inwardly sloping face on the secondary plate 44. In this way the primary plate 42 actually extends below a portion of the secondary plate 44 and supports it so that edge of the secondary plate is effectively held up by abutting edge of the primary plate.

It will therefore be appreciated that whilst it is foot pads than held support the primary plates it is the primary plates that support the secondary plates.

Although plate segments can be deployed separately, it is considered particularly advantageous if they are at least loosely connected together, and preferably hinged, in the shape of the floor by elasticated cord 48, for example. As described above this arrangement is particularly helpful when the operator does not have adequate space to bend over and position each of the plates individually.

Preferably the flooring may also be provided with extension plates 45, which are mountable relative to the primary/secondary plates to extension the floor area. As with the example of Figure 16, at least one of the plates may be provided with a hole and a removeable cover 47 so as to provide access to a passageway through the platform.

By way of a general comment in relation to the floor component of the access platform of the present invention load supporting floor can be formed from a single appropriately pre-cut sheet, slab, or grill, or a sectional unit or series of sections set in place on top of the locking unit. It may take the form of radial sections, floorboards, concentric sections or plates of various shapes that overlay and or interlock to form a usable platform over the locking unit. In is envisioned that the friction surface of the friction foot pads may be varied for differing tube wall surfaces. It is appreciated that the surfaces of internal walls vary from the polished glass of high temp catalytic cracking towers to the degrading brickwork of Victorian era underground railway vents. Surfaces can be adapted easily with stick on rubber, high density foams or simply Dacron reinforcing tape, to Velcro on sheets of sticky rock climbing rubber, to bolt on plates of mini needles to mechanically bite into a consistently friable, but competent surface, such as old brickwork, or the flaking paint within the rusty riveted steel tubes.

It is envisioned that the friction foot pads employed in the present invention will generally have to be stiffer in the vertical plane, and semi flexible in the horizontal plane, in order to conform to variable tube radii within their given range of operation (e.g. smaller radii for narrower pipes, larger radii for wider pipes, and flat feet for box shaped pipes); thus achieving maximum surface contact and adhesion.

The vertical stiffness will be such as to ensure that loads applied to the foot tops by the stiff platform above will not overly deform and peel the pad away from the wall leading to local bond failure.

It is appreciated that there is a need for the weight of the access platform to be kept to a minimum and in view of this the materials used in the construction should be strong yet lightweight. Some examples of suitable materials include Hypalon™, titanium, aluminium, fibre composites, tubular steel, and high density foams such as neoprene or PVC closed cell FT-280/300 foam.

Claims

1 . A temporary access platform for deployment within a structure having vertical or steeply inclined internal walls, wherein said platform comprises: a retention assembly having abutment means mounted on an actuator, whereby the actuator is operable to urge the abutment means into contact with the internal walls of the structure so as to retain the platform in position within the structure; and a load supporting floor formed from at least one platform plate supported by the retention assembly.

2. The platform of claim 1 , wherein the retention assembly comprises a plurality of abutment means and the actuator is operable to urge the abutment means away from one another and into contact with the internal walls of the structure.

3. The platform of claim 1 or 2, further comprising at least one passage that provides a way through the platform when such is retained within a structure.

4. The platform of claim 1 , 2 or 3, wherein each of said abutment means comprises a surface area capable of forming a frictional relationship with the internal walls of the structure.

5. The platform of claim 4, wherein the surface area is either: substantially flat, curved, or orthogonal in shape.

6. The platform of claim 4 or 5, wherein the surface area is formed from: rubber, high density foam, a plate with an array of projections, or combinations thereof.

7. The platform of any of claims 1 to 6, wherein the retention assembly comprises at least one inflatable body with one or more abutment means provided around the periphery thereof, whereby each of said abutment means is urged into contact with the internal walls of the structure as the inflatable body is inflated.

8. The platform of any of claims 1 to 6, wherein the retention assembly comprises a mechanically operated drive means that is operable to urge the abutment means into contact with the internal walls of the structure.

9. The platform of claim 8, wherein the mechanically operated drive means are manually operable.

10. The platform of claim 8, wherein the mechanically operated drive means are motor driven, pneumatically operable or hydraulically operable.

1 1 . The platform of any of the preceding claims, further comprising a plurality of platform extension plates that engage with the at least one platform plate of the load supporting floor to increase the size of the floor.

12. The platform of claim 1 1 , wherein each of said abutment means comprises a support surface configured to support at least a portion of a platform extension plate.

13. The platform of any of the preceding claims, further comprising a central support frame, at least a portion of which makes contact with the abutment means.

14. The platform of any of the preceding claims, wherein the retention assembly is toroid shaped and said at least one passage is provided by the central hole of the toroid.

15. The platform of claim 14, wherein the central support frame is received within the centre of the retention assembly toroid.

16. The platform of claim 15, wherein the central support frame is provided with safety rails to guard the passage through the platform.

17. The platform of any of the preceding claims, further comprising deployment connection means for securing the platform to a delivery tool while the platform is being deployed within the structure.

18. The platform of any of the preceding claims, wherein the load supporting floor comprises a plurality of wedge-shaped segmental plates.

19. The platform of claim 17, wherein the segmental plates are hinged together.

20. The platform of any of the preceding claims, wherein the retention assembly is configured to retain the platform within a tubular structure, and wherein preferably the structure has a circular cross-section.

21 . A method of deploying a temporary access platform within a structure having vertical or steeply inclined internal walls, said method comprising: delivering an access platform according to any of the previous claims into the interior of the structure using a delivery tool; operating the actuator of the retention assembly so as to urge the abutment means into contact with the internal walls of the structure so as to retain the retention assembly in position within the structure; locating at least one platform plate on the retention assembly so as to form a load supporting floor.

22. The method of claim 21 , wherein operating the actuator comprises pumping fluid into the actuator thereby inflating the actuator and urging the abutment means on the periphery thereof into contact with the internal walls of the structure.

23. The method of claim 21 , wherein operating the actuator comprises manually operating a mechanical drive means to urge the abutment means into contact with the internal walls of the structure.

24. A method of releasing a temporary access platform according to any of claims 1 to 20 that is retained with a structure having vertical or steeply inclined internal walls, said method comprising: removing the at least one platform plate from the retention assembly; operating the actuator of the retention assembly to move the abutment means away from the internal walls of the structure so that there is clearance between the retention assembly and the structure; operating a delivery tool to relocate the platform.

25. The method of claim 24, wherein operating the actuator comprises decompressing the actuator so that the abutment means are no longer urged against the internal walls of the structure.

26. The method of claim 24, wherein operating the actuator comprises operating a mechanical drive means to retract the abutment means away from the internal wall of the structure.

27. A method of allowing multiple operators to work within a common structure having vertical or steeply inclined walls at the same time, said method comprising: deploying a plurality of temporary access platforms according to any of claims 1 to 20 within said structure so as to provide multiple work regions within the structure.