Floating seal

Abstract

A seal 41 for enclosing the sides of a volume 21 has a flexible membrane 43 forming a sidewall extending around the perimeter of the volume 2, with a height extending from an upper edge 47a to a lower

Description

The present disclosure relates to seals used to help generate downforce to hold an apparatus on a non-horizontal surface, against the force of gravity, whilst the apparatus travels across the surface. The present disclosure also relates to an apparatus including the seal. There are many situations where it can be necessary to access high up or inaccessible places. This may include, for example, the inspection, repair, maintenance, coating, painting, treatment and cleaning of surfaces such as walls, roofs and ceilings. Typically, this is labour intensive and costly, and also comes with risks to the workers involved and infrastructure. To address this, climbing robots and automated systems have been considered. In general, wall-climbing robots that use suction employ a curtain to enclose a volume between a chassis of the robot and the wall. Air is then pumped from within this volume, forming a vacuum so that the device achieves adherence to the wall. These devices are however very small and lightweight, and do not create sufficient adherence to the wall to support the weight of a payload such as a spray head and similar components. Furthermore, they require clean smooth surfaces to maintain adherence. Simply scaling up existing wall-climbing robots results in a device that is too heavy and unable to support its own weight let alone the combined effects of its own weight and that of the payload. Robots that adhere to the surface they are climbing using down force (or the ground effect) have also been considered, such as WO 2022 / 129886. Whilst these provide greater adherence and load carrying, these require a large area to generate sufficient downforce. This makes the robots hard to manoeuvre, and unable to operate on uneven or dirty surface, or clear obstacles on surfaces. According to a first aspect of the invention, there is provided a seal arranged to enclose the sides of a volume, the seal having: a flexible membrane forming a sidewall extending around the perimeter of the volume, the wall having a height extending from an upper edge to a lower edge, defining a first direction; and a base portion provided on the lower edge of the sidewall, the base portion arranged to engage and move over a surface, wherein the base portion has a sealing surface extending outward from the wall, wherein the sidewall and base portion are flexible in the first direction, and rigid in a second and third direction, perpendicular to each other and the first direction. The flexing of the seal in the first direction (towards or away from the surface the unit is travelling over), allows the seal to maintain good contact with uneven or dirty surfaces, maintaining adherence, even as the seal is moved over dirty or uneven surfaces or obstacles. However, by being more rigid in the other directions, the seal does not collapse in one itself under reduced pressure in the volume. The floating seal may include two or more reinforcement rings incorporated into the membrane. The reinforcement rings may extend around at least part of the perimeter of the chassis and spaced from each other along the first direction. The base portion may extend around the perimeter of the sidewall. The base portion may have a sealing surface perpendicular to the sidewall The base portion may be formed of a multi-layer structure having at least: a first layer and a second layer. The first layer may comprise a plurality of fingers. Each finger may extending around a portion of the perimeter of the base portion. Each finger may interlock with adjacent fingers around the perimeter of the base. The second layer may support the first layer. The material of the fingers may be more rigid than the material of the second layer. The floating seal may comprise a microfibre cover on an edge arranged to engage the surface over which the chassis travels, the microfibre cover comprises a plurality of multidirectional fibres. The use of a microfibre cover improves the quality of the seal, reduces friction and prevents damage of the other components of the seal. The plurality of fibres may comprise a plurality of fibres of a first material and a plurality of fibres of a second material, the first material being harder than the second material. The fibres may be “V” shaped. Using multi-directional fibres prevents snagging or catching. The mixture of hard and soft materials further improves the quality of the seal, without causing too high friction that prevents the chassis from moving. The microfibre cover may be arranged at a lower edge of the floating seal, facing downwards and into and out of the volume formed under the lower face of the chassis. A ratio of the height of the floating seal in the first direction to the height of the formations in the first direction may be 9:1. According to a second aspect of the invention, there is provided an apparatus arranged to generate downforce acting in a first direction, the apparatus having: a chassis having a lower face arranged to face in the first direction, the lower face extending over a first planar area; means to draw air from a volume formed under the lower face of the chassis, to generate a low pressure region between the chassis and a surface over which the chassis travels, to generate downforce to hold the chassis on the surface; and a plurality of formations provided on the lower face, the formations on the lower face arranged to form an effective surface area on the lower face, the effective surface area being larger than the first area. The provision of formations or projections on the lower surface of the chassis increases the effective surface area that can be achieved in a given footprint of a unit. This means a vehicle or robot including the chassis with formations can have a smaller footprint, but still provide high adherence and load carrying. Since the device has a smaller footprint, is it more manoeuvrable, can access more difficult locations, and can even operate over curved surfaces. The formations may comprise a plurality of projections arranged over at least part of the lower face of the chassis. The projections may be conical or truncated conical in shape, having a base at the lower face, and a height extending in the first direction. Cones have been found to be particularly effective at increasing the surface area, but it will be appreciated other shape formations may also be used. The projections may be arranged in a regularly repeating array over at least part the lower face of the chassis. The projections may be hollow. The projections may have an open base. The apparatus may further include a floating seal extending in the first direction from the chassis. The floating seal may be arranged to enclose the sides of the volume formed under the lower face of the chassis, and move over the surface over which the chassis travels. The floating seal can flex in the first direction (towards or away from the surface the unit is travelling over), allowing the seal to maintain good contact with uneven or dirty surfaces, maintaining adherence. However, by being more rigid in the other directions, the seal does not collapse in one itself under the reduced pressure in the volume. The flexibility of the seal also guides the chassis over obstacles. The floating seal may comprise a membrane forming a sidewall extending from the chassis in the first direction, around the volume formed under the lower face of the chassis. The membrane may be arranged to compress and extend in the first direction. The floating seal may include two or more reinforcement rings incorporated into the membrane. The reinforcement rings may extend around at least part of the perimeter of the chassis and spaced from each other along the first direction. The floating seal may comprise a base portion arranged to engage the surface over which the chassis travels. The base portion may extend around the perimeter of the chassis. The base portion may have a sealing surface parallel to the lower face of the chassis. The base portion may be flexible in the first direction, and rigid in a second and third direction, perpendicular to each other and the first direction. The base portion may be formed of a multi-layer structure having at least: a first layer and a second layer. The first layer may comprise a plurality of fingers. Each finger may extending around a portion of the perimeter of the base portion. Each finger may interlock with adjacent fingers around the perimeter of the base. The second layer may support the first layer. The material of the fingers may be more rigid than the material of the second layer. The floating seal may comprise a microfibre cover on an edge arranged to engage the surface over which the chassis travels, the microfibre cover comprises a plurality of multidirectional fibres. The use of a microfibre cover improves the quality of the seal, reduces friction and prevents damage of the other components of the seal. The plurality of fibres may comprise a plurality of fibres of a first material and a plurality of fibres of a second material, the first material being harder than the second material. The fibres may be “V” shaped. Using multi-directional fibres prevents snagging or catching. The mixture of hard and soft materials further improves the quality of the seal, without causing too high friction that prevents the chassis from moving. The microfibre cover may be arranged at a lower edge of the floating seal, facing downwards and into and out of the volume formed under the lower face of the chassis. A ratio of the height of the floating seal in the first direction to the height of the formations in the first direction may be 9:1. The lower face of the chassis may comprise one or more opening extending therethrough. The means to draw air from a volume formed under the lower face of the chassis may be arranged to draw air through the at least one opening. The apparatus may comprise a grille arranged to cover at least the one or more opening. The grille may be arranged over the first planar area of the lower surface. The grille may be arranged below the formations on the lower chassis, such that the grille is between the formations and the surface over which the chassis travels. The use of the grille prevents the passage through which air is drawn (and the impellers etc... responsible for drawing air) becoming clogged with dirt and debris. Where the grille is provided over the formations on the lower surface of the chassis, it enables the entire area of the chassis to operate as a filter. With a larger area, it is longer before the grille becomes clogged by debris and needs clearing. The formations may be formed on a plate attachable to the chassis. The plate may be locatable relative to the seal. The grille may be locatable relative to the plate and / or seal. According to a third aspect of the invention, there is provided an apparatus arranged to generate downforce acting in a first direction, the apparatus having: a chassis having a lower face arranged to face in the first direction, the lower face extending over a first area; at least one opening extending through the lower face; means to draw air from a volume formed under the lower face of the chassis, through the at least one opening, to generate a low pressure region between the chassis and a surface over which the chassis travels, to generate downforce holding the chassis on the surface; and a grille arranged to cover the at least one opening. The use of the grille prevents the passage through which air is drawn (and the impellers etc... responsible for drawing air) becoming clogged with dirt and debris. The grille may be arranged over the first planar area of the lower surface. The grille may be arranged below the formations on the lower chassis, such that the grille is between the formations and the surface over which the chassis travels. Where the grille is provided over the formations on the lower surface of the chassis, it enables the entire area of the chassis to operate as a filter. With a larger area, it is longer before the grille becomes clogged by debris and needs clearing. Features discussed in relation to any particular aspect may be applied, mutatis mutandis, to any other aspect unless mutually exclusive. Embodiments of the invention will now be described by way of example only, with reference to the following drawings in which: Figure 1 schematically illustrates a wall climbing unit; Figure 2 illustrates a chassis assembly for use in the unit of Figure 1; Figure 3 illustrates the chassis assembly of Figure 2 in cut-through view; and Figure 4 illustrates the chassis assembly of Figure 2 in exploded view. Figure 1 schematically illustrates a unit 1, such as a wall climbing unit. The wall climbing unit 1 comprises a body or chassis 3, with parallel tracks 5a, 5b mounted on opposing sides 7a, 7b of the chassis 3. The tracks 5a, 5b are driven by a motor (not shown), to rotate around axes extending between the sides 7a, 7b such that the wall climbing unit 1 is propelled along a forward direction generally indicated by the arrow A. Various options for steering and changing the forward direction will be understood by the person skilled in the art. The sides of the chassis 7a, 7b are spaced from and parallel to each other, extending generally along the forward direction A, defining a length of the chassis 3. The spacing of the sides 7a, 7b defines a width of the chassis 3, and the height of the sides 7a, 7b defines a height of the chassis 3. The chassis 3 also includes upper and lower faces 9a, 9b, extending parallel to and spaced from each other. The upper and lower faces 9a, 9b extend between the sides 7a, 7b at the top and bottom of the sides 7a, 7b. The upper and lower faces 9a, 9b extend along the length of the chassis 3 and across the width, and are spaced by the height. The upper and lower faces 9a, 9b define a planar footprint of the chassis 3 (the flat area over which the chassis 3 lies). The chassis 3 further includes front and rear faces 1 la, 1 lb extend parallel to and spaced from each other. The front and rear faces 1 la, 1 lb are arranged at opposite ends of the length of the chassis 3 and extend across the width of the chassis 3 and extend the height of the chassis 3. The sides 7a, 7b, upper and lower faces 9a, 9b and front and rear faces 1 la, 1 lb define an enclosed volume (not shown) of the chassis 3. This may enclose the motor and other components for operation of the unit 1. The chassis 3 is also provided with an air guide assembly 13. This includes an inlet on the lower face 9b of the chassis 3, an outlet 17 on the upper face 9a, and a conduit 19 extending between the inlet and outlet 17. The conduit 19 houses an impeller / fan (not shown) which is configured to draw air from the volume 21 beneath the wall-climbing unit 1, through the inlet, the conduit 19, and the outlet 17. This creates an area of low pressure underneath the wall-climbing unit 1, creating negative lift which helps the wall-climbing unit 1 adhere to the surface it is moving on. In the following description, reference will be made to the up and down directions, above and below, and down-force it will be appreciated down is the direction from the upper face 9a of the chassis 3 to the lower face 9b (or from the chassis 3 to surface it is moving over), up is opposite to down, and above / below are defined with reference to these directions. The surface over which the unit 1 moves may be horizontal (with the unit on the top side or under side), vertical, or at any other angle. It will be appreciated that the inlet, the conduit 19, and the outlet 17 and the impeller may have any suitable shape, size, direction and configuration. Furthermore, in some examples, multiple inlets and / or outlets 17 and / or conduits 19 (each branching from and / or to one or more inlets / outlets) may also be provided. A chassis assembly 23 (not sown in Figure 1) is provided on the underside of the chassis 3. Figures 2 to 4 show the chassis assembly 23 in more detail. Figure 2 shows the chassis assembly 23 in perspective view, Figure 3 shows a cross-sectional view of the chassis assembly 23 and Figure 4 shows an exploded view of the components of the chassis assembly 23. The chassis assembly 23 includes a plate 25 that either forms the lower face 9b of the chassis 3, or is fitted to the lower face 9b of the chassis 3, such that it acts as the lower face 9b. The plate 25 includes an outer rim 27 that extends around the perimeter of the plate 25 (and chassis 3). The outer rim 27 has a thickness extending down away from the chassis 3, defining the height of the plate 25. A panel 29 extends across the area of the plate 25 (and lower face 9b of the chassis 3). The panel 29 extends from the top of the rim 27, such that the rim extends below the panel 29. The panel 29 includes an opening 31 to form the inlet of the air guide assembly 13. Within the area of the panel 29 bounded by the rim 27, an array of projections 33 are formed on the downward facing surface 35 of the panel 29. As best shown in Figure 3, the projections 33 are substantially conical (or truncated conical) in shape. The projections 33 are hollow, with the base of the projections 33 open onto the upward facing surface 37 of the panel 29. Around the edges of the panel 29, the projections 33 may be formed as portions of the cone, cut off in a plane perpendicular to the panel 29. The projections 33 are arranged in a regularly repeating pattern, formed of columns of projections 33 arranged along the length of the panel 29 (corresponding to the length of the chassis 3). Adjacent columns are offset along the length, such that projections 33 in one column are aligned to the gap between projections 33 in the adjacent columns, along the length of the panel 29. Projections 33 in alternate columns are therefore aligned with each other along the length of the panel 29. The projections 33 formed along the centre column across the width of the panel 29 and the centre row along the length of the panel 29 have a central bar 39 splitting the internal space of the projections 33 in two. On the centre column, the bars 39 in the projections 33 line up along the length of the panel 29 and in the centre row, the bars 39 line up across the width of the panel. The central bar 39 is a structural rib to assist in production. This is entirely optional and may be omitted. The projections 33 extend down from the panel 29 to a height aligned with the bottom of the rim 27 of the plate 25, or just above of the bottom of the rim 27. In addition to the plate 25, the chassis assembly 25 also includes a curtain seal 41 that encloses the sides of the volume 21 underneath the chassis 3. The volume 21 under the chassis 3 is thus enclosed between the surface over which the chassis 3 travels, the curtain seal 41 and the downward facing surface 35 of the panel 29. The curtain seal 3 is formed of a flexible membrane 43 forming a sidewall which extends downwards from the chassis 3, and extending around the perimeter of the chassis 3. The sidewall 43 has an inner facing surface 43a facing into the volume 21 under the chassis 3, and an outer facing surface 43b facing outwards. The sidewall 43 is located inside the space bounded by the tracks 5a, 5b, and so the tracks 5a, 5b are outside the enclosed volume 21. A first rigid band 45a is formed at the top edge 47a of the sidewall 43, proximal the chassis 3, and a second rigid band 45b is formed at the bottom edge 47b of the sidewall 43 distal from the chassis 3. The sidewall 43 also includes a number of reinforcing rings 49, extend around the permitter of the volume. The rigid bands 47a,47b and reinforcing rings 49 are formed of material that is more rigid than the membrane forming the sidewall 43, or thicker portions of the membrane forming the sidewall 43. The bands 47a,47b and reinforcing rings 49 extend in loops around the perimeter of the volume 21, and extend only a portion of the height of the membrane 43 (the distance between the top edge 47a and bottom edge 47b). The bands 47a,47b and reinforcing rings 49 are spaced from each other and may be embedded into the sidewall 43, or formed separately. Where the bands 47a,47b and reinforcing rings 49 are formed separately, they may be attached to the sidewall 43, or otherwise located at the correct position of the sidewall, for example by grooves, or other location features. Figures 2 to 4 illustrate a separately formed reinforcing ring 49 midway along the height of the sidewall 43. The bands 47a,47b and reinforcing rings 49 act to ensure the sidewall 43can compress and extend along its height, in a bellows fashion, but does not collapse or expand into or out of the volume 21, in a direction parallel to the plane defined by the surface the unit 1 moves over. The curtain seal 41 also includes a base portion 51 at the lower edge 47b of the sidewall 43. In use, it is the base portion 51 that rests on the surface over which the chassis 3 travels. The base portion 51 is wider than the sidewall 43. and forms a sealing surface 53 which engages the surface over which the chassis 3 travels. The base portion 51 comprises a number of layers 55, 57, 65 as best shown in Figure 4. Each layer is in the form of a ring extending around the perimeter of the sidewall 43, with a width that extends out of both sides of the sidewall 43. Each layer forms a functional structure in the base portion 51. The first layer 55 is an underlying spine layer. The spine layer 55 is formed of a plurality of rigid members 59. Each rigid member 59 extends around a portion of the perimeter of the side wall 41, and has interlocking projections 61 extending in the plane of the layer 55. The interlocking projections 61 on adjacent rigid members 59 engage each other such that a flexible joint 63 is formed between the rigid members 59. The joint 63 can flex up and down, but not in the perpendicular directions. The rigid members 59 of the spine layer 55 may be planar, or may have a depth with an upper facing surface 59a, a lower facing surface 59b, and sides 59c,d. The lower surface 59b may be narrower than the upper surface 59a, such that the sides 59c,d taper inwards. The second layer 57 is a support layer. The support layer 57 is in the form of a flexible membrane extending around the perimeter of the sidewall 43. The support layer 57 acts to hold the rigid members 59 in the spine layer 55 together whilst still allowing flexibility. The support layer 57 may be planar or any suitable shape. The support layer 57 may be formed of the same material as the side wall 43 or a different material. The support layer 57 may be wider than the spine layer 55, narrower or the same width. A microfibre cover 65 is provided on the lower side of the base portion 51. The microfibre layer 65 has a lower surface 67a and sides 67b, 67c extending upwards and outwards. The microfibre layer 65 is fixed on the underside of the spine layer 55, and extends up the sides 59c, 59d of the spine layer 55 and support layer 57, and optionally extends part way of the inner surface 43a and / or outer surface 43b of the sidewall 43. The microfibre cover 65 contains a plurality of “V” shaped fibres supported on a base sheet. The fibres are secured at the apex of the “V” such that the two sides extend away from the base. The fibres are arranged multi directionally (i.e. the fibres do not all point in the same direction) to prevent the cover 65 snagging as the chassis 3 is moved over objects. To achieve the correct balance of forming a seal but having sufficiently low friction that the chassis 3 can still move, a mix of materials is used for forming the fibres. Therefore, at least some of the fibres are made from a first, relatively soft material such as PVC. whilst other fibres are made of a relatively hard material, such as Teflon. The fibres of different materials are intermixed across the whole cover. In one example, the ratio of the first type of fibres to the second type may be 50:50, but any ratio may be used. The layers 55, 57, 65 of the base portion may be secured together by any suitable means, such as adhesive, screws, rivets, interengaging projections, Velcro®, or moulding / over-moulding. The lower edge 47b of the sidewall 43 includes a ledge portion 69 extending inwards from the inner surface 43a, perpendicular to the main sidewall 43. This ledge is formed at the second rigid band 45b, and may form the second rigid band 45b. The base portion 51 of the seal 41 is secured to the ledge portion 69, underneath the sidewall 43. The base portion 51 may be secured to the sidewall 43 by over-moulding using the support layer 65. Alternatively, adhesive, and / or mechanical fixing means such as screws, interengaging projections, Velcro® or the like (not shown) may be used. As best shown in Figure 3 or 4, a pair of ledges 75a, 75b are formed at the top of the sidewall 43 of the curtain seal 41. The ledges 75a, 75b are formed on the inner surface 43a of the sidewall 43. The ledges 75a, 75b may contribute to the stiffness at the first rigid band 45a. A first of the ledges 75a is at the top of the sidewall 43. Therefore, upper ledge 75a forms the upper face of both the sidewall 43 and the chassis assembly 23. The second ledge 75b is spaced below the first ledge 75a, thus defining a channel 79 between the ledges 75a, 75b. The channel 79 faces the interior of the seal 41, and extends around the perimeter of the seal 41. The rim 27 of the plate 25 on which the projections 33 are formed is received within the channel 79 to locate the plate 25 relative to the channel 79. For example, the material of the sidewall 43, rim 27 and ledges 75a, 75b may allow a push fit to be formed. The chassis assembly 23 further includes a grille 81 comprising an array of holes 83 formed in a planar plate 85. The grille 81 extends over the entire cross-sectional area inside the curtain seal 41 and thus extends over the same area as the plate 25. The grille 81 is located in the channel 79, between the rim 27 of the plate 25 and the lower ledge 75b. Therefore the grille 81 is below the plate 25. The height of the channel 79 is such that the grille 81 and plate 25 are a tight fit, and vertical movement is restricted. The height of the projections 33 on the plate are such that the projections 33 either touch the grille 81 or are just above it. The completed chassis assembly 23, with the plate 25 and grille 81 is fixed on the underside of the chassis 3. This may be by any suitable means. In one example, adhesive or other permanent means may be used. In other examples, temporary fixings may be used. The use of temporary fixings allows the chassis assembly 23 to be removed and replaced / repaired if it becomes damaged and / or worn. One example of temporary fixing is screws 71. The screws 71 may pass up through the grille 81 and plate 25 into the chassis 3, or may pass from the chassis 3 down into the plate 25. Alternatively, projections on the upper surface 77 of the seal 41 and / or the upper surface 37 of the panel 29 forming the plate 25 may couple to corresponding formations on the chassis 3. Velcro® may also be used. It will be appreciated that any combination of fixing means may also be used. The screws or other fixing means may cause compression of the rim 27 and sidewall 43 to ensure the chassis assembly 23 seals to the underside of the chassis 3. In use, the chassis 3 is provided onto a surface, with the tracks 5a, 5b and the microfibre cover 65 engaging the surface. The surface may be vertical, upside down or at any other angle at which gravity would act against the chassis 3 staying in a desired position. As air is drawn from the volume 21 under the chassis 3, the chassis assembly 23 forms a seal, and so an area of low pressure is formed. The chassis 3 defines an effective surface area of the internal volume, to cause downforce holding the chassis on the surface it is mounted on. The projections 33 on the plate 25 increase the effective surface area without increasing the footprint of the chassis 3. As the tracks 5a, 5b are driven, the chassis 3 then moves over the surface. The seal 41 is flexible in the up / down direction, meaning the seal 41 moves over obstacles and debris. However, the seal is rigid in the directions parallel to the plane, so the surface the chassis 3 is moving over, meaning the volume 21 is maintained in size, and remains closed. In this way, the seal can be considered a floating seal as it moves over the uneven / dirty surface, maintaining the enclosure of the volume 21, and the down force. The microfibre cover 65 assists in maintaining the seal enclosing the volume 21, whilst also protecting the curtain seal 41 and interior of the volume 21. The cover 65 moves debris away from the chassis 3 as it travels. The grille 81 prevents any debris that does become loose in the volume 21 from being drawn into the air guide assembly 31. Furthermore, but the grille 81 extending over the entire footprint of the volume, the effective size is increased, meaning it needs to be cleared less frequently. The arrangement discussed above is given by way of example only. In the above examples, the seal 41 (formed by the sidewall 43 and base portion 51), projections 33 on the underside of the chassis 3 and grille 81 are provided as an assembled unit 23 that is fixed to the chassis 3. This is by way of example only. The seal 41, projections 33 and grille 81 may be provided as two or more separate elements separately secured to the chassis 3 in any suitable way. In some wall climbing units 1, the seal 41 may be used without one or both of the projections 33 and grille 81. In other wall climbing devices 1, the projections 33 and / or grille 81 may be used on their or together. Alternative means may be provided to enclose the volume 21. The arrangement of the plate 25 with the projections 33 is given by way of example only. The projections 33 may be formed directly onto the chassis 3, or may be provided in any other way. Furthermore, the pattern of projections 33 is given by way of example only. Any suitable pattern of the projections 33 may be provided. The projections 33 need not be regularly arranged over the chassis 3 footprint. In some examples, there may be variation in density / positioning of projections 33 over the chassis 3. In some examples, as discussed above, the projections 3 may be provided over the entire footprint of the chassis 3. However, in other examples, projections 33 may be provided in defined areas only. The shape of the projections 33 discussed above is also given by way of example only. The projections 33 may have any three dimensional shape that increases the effective surface area of the underside of the chassis 3 (i.e. the total surface area compared to the footprint bounded by the curtain seal 41). In some examples, instead of separate projections 33, other formations may be used. For example, the underside of the chassis 3 may be provided with ridges, undulations or other types of three-dimensional shapes that increase the surface area compare to a flat face. The formations may be mirrored in the upper face 37 of the plate 25, or the upper face 37 may be flat. The projections (or other formations) 33 may be solid, hollow or partially hollow. Where the projections (or other formations) 33 are hollow, they may be open or closed on the upper face 37 of the plate 25. The projections (or other formations) 33 may cover between 20 and 60% of the downward facing surface 35 of the panel 29, with the remainder of the surface area being formed by downward facing surface itself. However, it will be appreciated that this is by way of example only and more or less of the surface may be covered by projections or formations 33. Typically, the projections (or other formations) 33 may project by 10mm or more below the panel 29. However, it will be appreciated that this is by way of example only, and the projection may extend by more or less. The ration of the height of the gap between the chassis 3 and the surface over which the unit 1 moves and the height of the projections (or other formations) 33 below the plate may be 9:1 in one example, In other examples, this may vary. The height of the gap between the chassis 3 and the surface over which the unit 1 moves may also be considered as the height from the bottom of the tracks 5a, 5b or floating seal 41. Where the projections (or formations) 33 have inclined sides (such as cones), the sides may have an angle of between 25 and 45 degrees to the panel 29. Again, it will be appreciated that this is by way of example only, and the angle may be different. Where a separate plate 25 is used to support the formations on the underside of the chassis 3, it may have a rim 27 around the outer edge of the perimeter. As discussed above, the rim 27 may extend around the full perimeter. In other examples, the rim 27 may only extent round part of the perimeter in one or more separate sections. The rim 27 may also be omitted altogether. The plate 25 may be the same material as the chassis 3, or a different material. In one example the plate 25 and / or chassis 3 may be carbon fibre, however, it will be appreciated that other materials may be used. Any suitable wall or membrane may be used to form the sidewall 43 of the floating seal 41. In one example, the sidewall 43 may be rubber, but this is by way of example only. Similarly, any suitable material or mixture of materials may be used in the base portion 51. In one example, the fingers 59 in the spine layer 55 may be made of acrylonitrile butadiene styrene (ABS), whilst the support layer is polypropylene. However, it will be appreciated that other materials may be used. The side wall 43 and base portion 51 of the floating seal 41 are flexible in the up / down direction, and rigid in the perpendicular directions. In the example discussed above, this is achieved by reinforcing rings 49 that help hold the shape of the sidewall 43, and the structure of interlocking fingers 59 in the base portion 51. It will be appreciated that this is by way of example only. The directionality of the parts of the seal can be achieved in any suitable way. For example, bracing or support members, or reinforcing members may be provided, living hinges or other pivots may be provided, or material with directional flexibility may be used. Where bands 47a,47b and reinforcing rings 49 are used, any number of bands 47a,47b and reinforcing rings 49, with any suitable spacing may be used. The bands 47a,47b and reinforcing rings 49 may be integral with or separate from the sidewall 43. Where separate, the bands 47a,47b and reinforcing rings 49 may be attached to otherwise located relative to the sidewall 43. The base portion 51 may incorporate any suitable number and arrangement of layers 55, 57, 65. In one example, all they layers may be functional. However, non-functional layers may also be provided. The layers may be provided in any suitable order. In some examples, the sidewall 43 may also be made of a layered structure, with the layers oriented parallel to or perpendicular to the layers in the base portion. In the example discussed above, the sidewall 43 and base portion 51 extend all the way round the perimeter of the chassis 3. This is by way of example only. The sidewall 43 and / or chassis may be formed in one or more portions spaced around the perimeter. The arrangement of the micro fibre cover 65 is also given by way of example. The microfibre cover 65 may have any suitable arrangement of fibres and different materials. In some examples, a different type of cover such as a brush type cover or other sealing strip with reduced friction may be used. In one example, the fibres are evenly distributed over the cover 65, and the different materials are evenly mixed over the cover 65. In other examples, the overall density of fibres and / or the proportion of the fibres made by different materials may vary. The grille 81 discussed above is given by way of example only. Any suitable mesh, net or filter may be used that allows passage of air but which captures larger debris and prevents it being drawn into the air guide assembly 13. In the example discussed above, the grille 81 is provided over the entire footprint of the chassis 3, and below the projections 33 on the underside of the chassis 3. However, this is by way of example only. The grille 81 may be above or below the projections 33 and / or may enclose a smaller area (for example only the area of the inlet through which air is drawn. In the example discussed above, the grille 81 has a regular arrangement of holes 83 of the same size. It will be appreciated that the size and / or spacing of holes in the grille 81 may be varied over the area of the grille 81. Typically, the sidewall 43 in the seal 41 may have sides extending perpendicular to the base of the chassis 3. Therefore, the bottom of the seal 41 / chassis assembly 23 is the same as the footprint of the chassis 3. However, this is by way of example only. In some examples, the sidewall 43 may be perpendicular, but the sidewall may be offset inside or outside the edges of the chassis 3, so the footprint of the seal (and hence the enclosed volume) is smaller or larger than the footprint of the chassis. Alternatively, or in addition, the sidewall 43 may be tapered inwards or outwards. In one example, the chassis 3 may have a footprint of approximately 300mm by 420 mm, but this is by way of example only, and the chassis 3 could have any size. The cubic chassis 3 shown in Figure 1 and discussed above is given by way of example only. The chassis 3 may have any shape or structure, and may include a top cover or similar to provide the appearance of the unit. As a result of the high downforce generated, the wall climbing unit can carry heavy loads. It may carry equipment and materials required for various purposes such as inspection, measurement and characterisation of surface, cleaning, painting, applying of other media or coatings such as protective coatings, repair, maintenance and other treatment. The unit may include the components and reservoirs / stores necessary for these purposes as a standalone wall climbing unit 1, or may include a connection to base unit provided at ground level. The wall climbing unit 1 may be used on walls, roofs and ceilings and other surfaces. It may be used in the interior or exterior of buildings, storage units, silos, tanks, bridges, walls and other structures. These applications are given by way of example only. It will be appreciated that the wall climbing unit can be used in any situation where remote access and adherence to a surface is needed.

Claims

1. A seal arranged to enclose the sides of a volume, the seal having:a flexible membrane forming a sidewall extending around the perimeter of the volume, the wall having a height extending from an upper edge to a lower edge, defining a first direction; anda base portion provided on the lower edge of the sidewall, the base portion arranged to engage and move over a surface, wherein the base portion has a sealing surface extending outward from the wall, wherein the sidewall and base portion are flexible in the first direction, and rigid in a second and third direction, perpendicular to each other and the first direction.

2. The seal of claim 1, including two or more reinforcement rings incorporated into the membrane.

3. The seal of claim 2, wherein the reinforcement rings extend around at least part of the perimeter of the sidewall and are spaced from each other along the first direction.

4. The seal of any preceding claim, wherein the base portion extends around the perimeter of the sidewall.

5. The seal of claim 4, wherein the base portion has a sealing surface perpendicular to the sidewall.

6. The seal of any preceding claim, wherein the base portion is formed of a multilayer structure having at least:a first layer comprising a plurality of fingers extending around a portion of the perimeter of the base portion; and and a second layer supporting the first layer.

7. The seal of claim 6, wherein each finger interlocks with adjacent fingers around the perimeter of the base portion.

8. The seal of claim 6 or claim 7, wherein the material of the fingers is more rigid than the material of the second layer.

9. The seal of any preceding claim, further comprising a micro fibre cover the lower edge of the sidewall, the microfibre cover comprising a plurality of multidirectional fibres.

10. The seal of claim 9, wherein the plurality of fibres comprises a plurality of fibres of a first material and a plurality of fibres of a second material, the first material being harder than the second material.

11. The seal of claim 9 or claim 10, wherein the fibres are “V” shaped.

12. The seal of any of claim 9 to 11, wherein the microfibre cover extends part way up both faces of the sidewall.

13. The seal of any preceding claim, comprising connecting means to connect the seal to a chassis of an apparatus moving over the surface, such that the seal encloses a volume on an underside of the apparatus.

14. The seal of claim 13, wherein the connecting means is arranged at the upper edge of the sidewall.

15. The seal of claim 13 or claim 14, wherein the connecting means is arranged to locate a plate forming a lower part of the chassis.

16. The seal of any of claims 13 to 15, wherein the connecting means is arranged to locate a grille extending across the volume enclosed by the sidewall.

17. An apparatus arranged to travel over a surface and to generate downforce acting in a direction towards the surface, the apparatus having:a chassis having a lower face arranged to face in the direction towards the surface;a seal as claimed in any preceding claim, extending in the direction towards the surface, the seal arranged to enclose the sides of a volumeformed under the lower face of the chassis, and move across the surface over which the apparatus travels, the direction towards the surface being parallel to the first direction; andmeans to draw air from the volume formed under the lower face of the5 chassis, to generate a low pressure region between the chassis and thesurface over which the apparatus travels, to generate downforce to hold the apparatus on the surface.

18. The apparatus of claim 17, wherein the lower face extends over a first planar 10 area, the apparatus comprising a plurality of formations provided on the lowerface, the formations on the lower face arranged to form an effective surface area on the lower face, the effective surface area being larger than the first area.

19. The apparatus of claim 18, wherein a ratio of the height of the seal in the first 15 direction to the height of the formations in the first direction is 9:1.

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