Downdraught workbench

Abstract

A downdraught workbench 10 comprises a support 12, and an apertured tabletop 30 secured on a base 12A of the support 12. The base 12A is apertured in a central region 12B such that air can flow throug

Description

Field of the Invention The present invention relates to a downdraught workbench, and more specifically to a manually collapsible and erectable downdraught workbench being of a size and construction such that, in its erected condition, provides a robustly supported, stable and downdraught-aided work surface at and on which an individual can work, and in its collapsed condition, is readily portable, transportable, and otherwise generally manoeuvrable by such an individual without mechanical assistance. Background to the Invention Existing downdraught workbenches provide, in their simplest form, a usually grid-like or substantially perforated table top which is securely mounted atop an often substantial and generally enclosed cabinet or other similar closed supporting structure within which is provided motorised air extraction equipment, such as a vacuum pump. As the name suggests, the fundamental purpose of such downdraught workbenches, when operative, is to generate a continuous and substantial flow of air in a generally vertically downward direction from immediately above the table top and the surrounding regions, through the perforations or other apertures provided in said table top, into the interior of the cabinet such that any and all particulate and other airborne matter such as vapours and gases extant immediately above and around the table top are swiftly and safely removed thus eliminating the possibility of inhalation thereof by any individual working above or around the sides of the workbench. There has been, and continues to be an increase in demand for these types of workbench because over the last decade or so, Governments and other Health Authorities, especially in the more developed nations, have become increasingly aware of the respiratory health issues that can arise as a result of the inhalation of noxious substances, and therefore not only has legislation been widely introduced to the limit individual exposure thereto, but this legislation is becoming increasingly stringent as regards the maximum permissible levels of such substances that can be present in the air within which individuals are working for any length of time. One noxious substance of particular concern is a particulate material known as crystalline silica dust, significant volumes of which can be created when cutting, sanding, shaping and otherwise working with various different types of natural stone, whether in a dedicated workshop or on a temporary building site. The respiratory health issues that can arise from inhalation of this substance are so serious that Governments, particularly those of the more developed nations, have already introduced legislation to limit exposure, and more recently this legislation has become significantly tighter, to the extent that it is now practically mandatory for contractors such as commercial stonemasons and building restoration specialists to provide some form of air extraction facility for their workers when there is any possibility of the creation of crystalline silica dust in their work environment. As the reader will readily understand, the large self-contained downdraught workbenches of the type described above (and widely available from, e.g. AirBench Limited, UK) will, given their size and weight, most commonly exist as static, permanent installations within dedicated processing facilities such as laboratories, workshops, tool rooms and the like. As such, these types of downdraught workbench are entirely unsuitable and wholly impractical for use in a temporary construction facility such as a building site, and there is therefore a pressing requirement for more mobile, manoeuvrable downdraught workbench, which is of much smaller size, but which nevertheless provides the same degree of safety as regards removal of noxious substances from the working area. To this end, a number of solutions have been proposed. A first of these is the XtractaBench™ mobile workbench sold by Armorgard Limited (UK). This product is essentially, and exceedingly simply, a cuboid steel enclosure having a base at each corner of which is provided a castor thus rendering the enclosure mobile and capable of being wheeled into some desired position, after which the castors can be locked in position preventing further movement. The enclosure itself is provided with a pair of openable doors in its front side through which suitable, but relatively small air extraction equipment can pass prior to being seated inside the enclosure and on the base thereof prior to closing the doors, and with perforated side panels which can be selectively closed, depending on whether the extracted air is to be vented immediately therethrough, or through some other extract conduit or hose which may be connected to the enclosure. Atop the workbench is provided a perforated metal table top component which is hingedly connected to the rear panel of the enclosure to the rear so as to be pivotable between a flat, closed condition, and an inclined open position. The underside of the perforated metal table top is directly supported by a platen which is provided with a flat base onto which larger, non-airborne particles and other waste materials falling through the perforations in the metal table top can fall and can be collected. At the rear of the platen there is provided an elongate slot through which air, together with particulate material and other substances entrained and otherwise otherwise borne therein is caused to flow as a result of the action of the extraction apparatus provided within the enclosure beneath the base of the platen, after which the air may be subsequently filtered so as to substantially reduce the quantity of noxious contaminants therein, before being ultimately expelled from the enclosure, either through the perforated side walls or appropriate ducting otherwise connected to the enclosure. Further details of the specifics of the device can be found in GB2570348. Although the above device is mobile, and certainly significantly smaller than the static permanent previously described workbenches manufactured and sold by AirBench Ltd, there are still a number of significant drawbacks. Firstly, although the Armorgard product is certainly mobile, not only does the manner in which such mobility is provided introduce unacceptable further risks to operatives working on the workbench, its structure and design are still both fundamentally inflexible and immutable. In essence, the Armorgard workbench is nothing more than a steel box on wheels, and therefore not only cannot it not be collapsed or dismantled in any way, but it is not a piece of equipment that could ever be regarded as humanly portable or easily transportable, and would in all probability require mechanical lifting and loading equipment before it could be transported. Furthermore, as alluded to above, mounting a downdraught workbench on castors can be problematical, if not downright unsafe. To explain further, downdraught workbenches are often subject to very aggressive treatments, impacts and other forces during use, and when the table top of the work bench supports one or more often heavy workpieces, operatives not only often use hammers and chisels, but also electrically powered, hand-held grinding, cutting, sanding and other types of power tool. Thus, it is essential that the workbench as a whole does not move while an operative is carrying out any task whatsoever on the workpiece, both from the point of view of maximising the accuracy and precision of an operative's work, and also from the point of view of ensuring the operative's safety while working with dangerous power tools. The locakable castors proposed in the Armorgard workbench are fundamentally deficient in this regard, in two important respects: (1) the locking mechanisms are insufficiently secure and can easily be disengaged, thus meaning that one or more the castors can move, both unexpectedly and without further hindrance, and (2) the arcuate nature of the castors and their rubberised exteriors mean that there is a possibility that one or more of said castors can slip and / or slide over the surface which supports them and on and to which they are supposedly to be fixed, again introduce the possibility of unexpected movement of the workbench as a whole. An alternative form of mobile workbench is disclosed in EP3434403 (also to Armorgard Ltd), but again this workbench is little more than an inflexible, immutable steel construction also provided on castors, so suffers from exactly the disadvantages of the device of GB2570348. In terms of further more relevant prior art, perhaps the preexisting product most relevant to the present invention is the downdraught woodworking table sold by Scott And Sargeant Wood Working Machinery Limited (UK) under their "iTECH™" brand (see, for example, https: / / itech.info / products / itech-woodworkinQ-downdraft-table-1440x800). It should be mentioned here that there are a great many types and varieties of custom-built woodworking downdraught tables, often created by hobbyists, but in most cases the configuration, structure and function of these types of downdraught workbench is broadly identical to the workbenches already described above, in that: - they have perforated table tops which provide a work surface and can support workpieces, - they have some means whereby the workbench as a whole is supported by the floor on which it rests; if the workbench is wheeled, castors will be provided, or if it is fixed in placed, then most simply fixed legs are provided at each corner of the (usually) rectangular workbench, - they generally have some cavity defined beneath the perforated work top into which fluid can flow from above the table top, and thus the exterior of the workbench generally, and - there is some predetermined space, enclosure or recess defined within the workbench, usually between the tabletop itself and a base panel of the workbench which is disposed only slightly above the floor on which the workbench as a whole rests, and which can accommodate or house suitably sized motorised air extraction equipment. Where the iTECH™ woodworking downdraught table mentioned above importantly differs is that this device is essentially little more than a traditional table, as it is provided only with four fixed-in-place but partly telescopically extendible legs, and beneath the perforated table top there is provided only an enclosed shallow walled cavity into which air can flow from above the perforated table top and through the perforations therein. In all other respects, the table is essentially open in that there exists nothing between the legs, so it would, in principle, be possible to sit comfortably at such a table on any side thereof with one's legs beneath table top and shallow walled cavity region defined beneath that table top, whereas the same cannot be said of any prior art workbench described above. Returning to the iTECH™ table, and specifically the shallow walled cavity defined beneath the table top, no air extraction equipment is or can be provided within this cavity, or indeed the table as a whole. Instead, said shallow walled cavity is provided, in one end wall thereof at one lateral side of the table, with a single circular exit port or air outlet towards and through which air will flow from within the cavity when a suitable negative pressure differential is created at that outlet. Thus it is the clear intention of the iTECH™ table that it is to be connected, for example by means of a length of standard diameter flexible ducting attached to the physical outlet provided in the table, to remotely located air extraction apparatus, and thus whereby air contaminated with sawdust particles can also be effectively routed to some remote location, for example to some area external to the workshop in which such a table might be located. The iTECH™ downdraught table also suffers from a number of disadvantages, mostly due to its intended purpose as a relatively lightweight woodworking table. Firstly, the perforated table top is a single slab of laminated plywood, which is wholly unsuited to supporting heavier stone materials, nor to the working of such stone materials thereon using conventional stone working tools as plywoods in general would very quickly become damaged, and furthermore could become bowed and otherwise deformed after only a relatively short period of use. Furthermore, the table top of the iTECH™ table is securely fixed to the underlying table structure, and cannot therefore be easily replaced, if indeed it can be replaced at all. A yet further disadvantage arises as a result of the nature of the legs of the table which, although securely bolted to the corners of the shallow walled cavity structure which underlies the table top, are formed of a relatively lightweight right angle steel which lies, for each of the four legs, in an exactly perpendicular direction to the horizontal table top. Thus, not only are such legs not intended to be collapsible or even removable without significant effort, their construction and orientation is such that they have an inherent potential for catastrophic buckling if any significant load or impact is applied therethrough, either to one leg in particular, or more generally throughout all four legs. Finally, the iTECH™ table is further disadvantaged in that only a single circular exit port or air outlet is provided in one of the lateral side walls of the shallow walled cavity. Thus when extraction ducting is connected to this outlet and a suitable negative pressure differential applied, for example by a remotely located suction pump, the suction power (usually measured as a pressure in Pascals or N / m2) diminishes linearly along the length (or width) of the table. This means that although the suction strength may be sufficient, and indeed possibly excessive, through those perforations or apertures in the table top disposed most proximate the air outlet, the suction strength applied through those perforations or apertures in the table top more remotely disposed from said air outlet, for example at the opposite side of the table top, is very much reduced, often to the point of being non-existent. It is thus an object of the present to provide a downdraught workbench which is sufficiently robust to withstand the rigours of site usage, particularly stone masonry and the working of stone more generally, and which is yet nevertheless easily, quickly and simply both collapsible and erectable so that the table as a whole can be transported and manoeuvred by only a single operative as required. It is a further object of the present invention to provide a mobile collapsible downdraught workbench whose configuration is such that its mobility is dependent, at least in part, on both its orientation as a whole and on whether the table is in an erected or collapsed condition. It is a further object of the invention to provide a mobile collapsible downdraught workbench which, in erected condition, is or becomes effectively completely immobile. It is a yet further object of the present invention to provide a mobile downdraught workbench having an underlying supporting structure which is not only at least partially collapsible, but very robust and which, cannot fail unexpectedly or catastrophically, for example by buckling. It is a yet further object of the present invention to provide a mobile downdraught workbench which is, at least to some extent, modular in terms of the configuration, arrangement, and ease with which certain essential components thereof can be inserted and removed. Finally, it is a yet further object of the invention to provide a downdraught workbench having a perforated or apertured table top providing a worksurface therefor over the entire surface of which an applied negative pressure differential is relatively evenly distributed, such that the suction strength through any one perforation or aperture is substantially the same as that through any other, at least over a significant majority of the entire table top or working surface area thereof. Summary of the Invention According to a first aspect of the present invention there is provided a downdraught workbench comprising a table top support portion having at least a base on one side of which is secured a planar table top provided with a plurality of apertures therethrough over a significant proportion of the total area of said table top, being that bounded by its periphery, said workbench further comprising at least one pair of leg mountings rigidly secured to, or forming an integral part of the table top support portion and being disposed at a respective one of two opposite sides of said table top support portion and on an opposite side of the base thereof to that on which the table top is secured, each of said leg mountings further having pivotally connected thereto at least one leg assembly capable of pivoting between a first collapsed condition in which said leg assembly is folded underneath the table top support portion and so as to be generally parallel therewith, and a second, erected condition in which said leg assembly is rotated into an upright position in which it subtends an angle of at least 90° with the base of the table top support portion, Characterised in that the base of said table top support portion is provided with one or more apertures in a geometrically central region being at least half the total area of said base, said one or more apertures in said base having a total open area which is at least half of the total area of said central region, said downdraught workbench further being provided with - at least two substantially parallel elongate support brackets disposed in spaced apart relationship between the leg mountings, each support bracket being disposed adjacent a respective one of a two opposing sides of the apertured central region and each having an elongate support lip which extends substantially parallel to the other and underneath the base of the table top support portion thus defining a pair of spaced apart open channels therewith capable of receiving, in sliding fashion, portions of the rim of a removable funnel having a first larger and second smaller openings into, out of and between which fluid may be constrained to flow, said rim being provided substantially around and said first larger opening and having a maximum lateral or transverse dimension greater than distance between the edges of the support lips of the support brackets but less than the total distance between support brackets such that at least some portions of the rim can be received above and supported from underneath by said elongate lips in close proximity to the underside of the base of the table top support portion, the size of the removable funnel and of the larger opening therein being in general correspondence with the size of the table top support portion and the apertured central region thereof respectively such that when the leg assemblies of the workbench are in their erected condition and the removable funnel is slid fully into position beneath the base of the table top support portion, substantially the entirety of said removable funnel is disposed underneath the base of the table top support portion, and the larger opening of said removable funnel is in close proximity with the base of said table top support portion, and is substantially aligned with the apertured central region thereof. According to a second aspect of the present invention there is provided a downdraught workbench as set out immediately above, further comprising the removable funnel, in its fully inserted condition immediately beneath the underside of the table top support portion, and with its larger opening in substantial or complete registration with the apertured central region of the base of said table top support portion. In a yet further aspect of the present invention, there is provided a downdraught workbench as set out above, in standalone condition, that is without an apertured table top or removable funnel, but configured to receive and accept such components in the manner described. In a yet further aspect of the invention, there is provided a downdraught workbench as set out above, wherein one or more of the leg assemblies is removable in that it / they can be disconnected from the leg mountings, instead of being permanently and pivotally connected thereto. Preferably, the apertured table top is releasably secured to one side of the table top support portion and as such is easily removable and manually removable from its conventional operative position. In one preferred configuration, said table top support portion is provided of around a substantial portion of its periphery with one or more upstanding wall portions which together with the base define a shallow cavity within which said table top, being of a cross-sectional shape, size and depth corresponding to such characteristics of the cavity, can be snugly received therewithin such that lateral and transverse movements of the table top within the cavity are resisted on all side of the table top by said upstanding wall portions of said table top support portion. In this preferred arrangement, the cavity is thus essentially open-topped such that the suitably sized and shaped table top can simply be dropped into the cavity from above. Of course, in this particular embodiment, it is an equally simply procedure to remove the table top when the workbench is no longer needed and / or it is desired to collapse the workbench prior to transportation, as the table top can simply be manually lifted upwardly from the cavity. In a more preferred alternative configuration, one or more of the upstanding wall portions provided around all or portions of the periphery of the table top support portion are provided with terminal flanges disposed substantially over and above the cavity defined by the said wall portions and so as to reduce the overall open area thereof and thus prevent a table top corresponding in shape and size to the cavity and disposed therewithin from either being inserted thereinto from above, or being lifted therefrom or otherwise escaping. Thus in this particular configuration, when a table top is fully disposed within the cavity, not only are lateral and transverse movements of the table top substantially if not completely prevented by the surrounding upstanding wall portions around the periphery of the table top support portion, but also, the typically short (e.g. 5-60mm) terminal flanges provided on the upstanding wall portions effectively cover a corresponding portion of the edges of the table top and thus preclude any vertical motion thereof when fully disposed within the cavity. Of course, in this configuration, it is necessary to provide the workbench with some means whereby the table top can be inserted into the cavity, and in this regard, it is also further preferred that either: - at least one slot is provided in at least one of the said upstanding wall portions provided around the periphery of the table top support portion, or - at least one opening is provided by the absence of at least one ofthe said upstanding wall portions provided around the periphery of the table top support portion, said slot or opening preferably being provided in one, shorter side ofthe table top support portion when said portion, and thus the workbench as a whole is rectangular, said slot or opening being of a width and depth sufficient to accommodate the corresponding largest dimensions of the table top and whereby the latter may be slid into and through the slot or opening and thus ultimately completely into the cavity defined by the other remaining upstanding wall portions provided around the periphery ofthe table top support portion. In the embodiment wherein a slot is provided in one of the upstanding wall portions provided around the periphery of the table top support portion, for example by means of a cut-out, it is most preferred that the lowermost edge of the slot is spaced apart from, and thus (when the workbench is stood upright on its legs) disposed above the base ofthe table top support portion by some small amount, such that the slot is disposed more towards, and provides access to the upper reaches ofthe cavity. In this particular configuration, firstly, when the table top is being slid through the slot, it adopts a slightly inclined condition with one point of contact being at its remote end which lies on the base ofthe cavity and a second point of contact being that where the underside ofthe table top contacts the lower edge of the slot which is raised above the base by some small amount. This slight inclination can thus render it somewhat easier to slide the table top, because the slight inclination of the table during sliding is then slightly gravity assisted. There is a further advantage to this particular configuration, because when the table top has been fully slid through the slot and its remote end has reached the remote end ofthe cavity and the proximal end has passed completely through the slot, the table top drops into its desired flat, horizontal condition within the cavity, again under gravity, with a positive sound as the table top drops fully onto the base ofthe table top support portion, thus providing a clear indication to an operative that the table top has been fully inserted. Furthermore, in this condition, the table top is retained within the cavity by the lip. In the alternative preferred configuration, wherein at least one opening, most usually at an end of the cavity when the table top support portion, table and indeed workbench as a whole is rectangular, is provided by the absence of at least one ofthe said upstanding wall portions provided around the periphery of the table top support portion, then of course a lower edge of said opening would be provided by the edge of the base of the table top support portion, and thus the opening as whole would automatically be disposed immediately above said base. In this configuration, the table top would against be capable of being slid into and through the opening, but its motion and orientation during such sliding would of course be horizontal, and the table would be fully inserted when its remote end came into abutting relationship with the remote upstanding wall portion disposed directly opposite the opening. Again, in this configuration, the positive sound of impact between the remote end of the table top and said remote upstanding wall portion would provide a useful ready indication to an operative that the insertion of the table top into the cavity was complete. As suggested above, the invention preferably provides means whereby the downdraught workbench is mobile, and in this regard, a handle may be bolted or otherwise secured to a first leg mounting such that said handle projects outwardly from one side of the workbench as a whole, and a pair of castors may be bolted or otherwise secured to a second leg mounting, being most preferably oppositely disposed relative to the first leg mounting, said castors also thus projecting outwardly from an opposite side of the workbench, whereby, when the leg assemblies connected to each respective leg mounting are folded in their collapsed condition, the workbench as a whole can be up-ended or lifted at one end into an inclined position approaching the vertical wherein the castors are in direct contact with the floor and the workbench as a whole can be simply wheeled away using the handle, easily and manually by a single person, to wherever it is next desired to erect it, or to and into, for example, a van for transportation. Most preferably, in the preferred embodiments mentioned above, wherein an opening or slot is provided through which a table top of suitable size and shape can be slid, said opening or slot is provided in one and the same side of the workbench as that at which the handle is provided, thus always ensuring that when the workbench is being wheeled around in the manner described but without the table top having first being removed from, and thus being present within the cavity, the table top is retained in the cavity under the action of gravity. In the preferred configuration wherein at least one opening is provided by the absence of at least one of the said upstanding wall portions provided around the periphery of the table top support portion, there is nevertheless provided a raised edge portion or lip, much smaller in height relative to the remaining upstanding wall portions provided around the periphery of the base of the table top support portion, such that the opening is effectively raised slightly above the base of the table top support portion. The provision of this raised edge portion or lip thus provides some limited containment of the table top within the cavity, and this arrangement as a whole has similar advantages and benefits to those described above in relation to the cutting out of a suitably sized and shaped slot in one of the upstanding wall portions in that some portion ofthe end face of the table top most adjacent the raised edge or lip lies beneath it when the table top is completely inserted into the cavity and thus rests completely on the base ofthe cavity. Furthermore, in this condition, in order to remove the table top, it is necessary to firstly lift the relevant end of the table top over and above the raised edge or lip before it can be slid from the cavity. Preferably, each leg assembly consists of a framework, most preferably of square tubular metal sections welded, bolted or otherwise firmly secured together, said framework comprising at least a pair of parallel leg members joined together with at least one, and preferably two cross-members which are, most preferably, perpendicularly disposed relative to the leg members. Each said leg assembly is preferably pivotally connected to a respective leg mounting be means of a pair of bolts, each of which passes through both one end of the leg mounting, one end of one leg member, and is received and secured in a suitably positioned bolt retaining member, whereby not only is each end of each leg member robustly and securely attached to and within the leg mounting and at either end thereof, but the leg assembly as a whole can rotate relative to the leg mounting. Most preferably, respective adjacent outer (and thus easily accessible) surfaces of each leg member and leg mounting are provided with respective portions of a releasable clasp, such as a lever clasp or toggle tensioner clasp or similar, such that when a leg assembly is in its fully erected condition, the respective clasp portions can be manually releasably engaged, tensioned, and (ideally) snapped into their locked or closed condition whereby each leg member ofthe leg assembly is effectively firmly, but releasably locked in position relative to the leg mounting. Each leg mounting preferably consists of at least two elongate planar plate sections, a first of which is, in use is secured to an underside ofthe table top support portion at one or other side thereof, for example using bolts or by welding, and a second section which subtends an obtuse angle with the first section such that it is outwardly splayed relative thereto, the interior surface of which thus provides a contact surface against which upper ends of the leg members abut when the leg assembly is mounted inside the leg mounting and the legs are rotated into their fully erected condition. The second section ofthe leg mounting thus provides the means whereby not only is the fully erected orientation of the leg members outwardly inclined relative to the table top support portion of the workbench (in which position they provide a more structurally robust support therefor, as opposed to a purely vertical orientation), but also portions of the outer surfaces of the second section of the leg mountings and respective leg members are immediately adjacent, allowing for easy positioning and fixing of, and thus easy access to respective parts ofthe releasable clasps which are most preferably secured to both leg members and to said immediately adjacent surfaces of the second section of said leg mountings. Further preferably, the leg mountings further comprise a pair of end plate sections joined to both the first and second plate sections and through which the bolts which secure the upper ends of the leg members to the leg mountings pass. As the skilled reader will understand, said end sections provide additional structural strength for the leg mountings, and at both ends thereof, as the end sections effectively resist and prevent any tendency there might otherwise be for the first and second sections of the leg mountings to become increasingly splayed outwardly under significant loadings. In one embodiment, the elongate support brackets which, in use, support the removable funnel of the downdraught workbench, are separate discrete components secured either directly to the underside of the table top support portion, or to the leg mountings, in suitable positions proximate opposite sides of the table top support portion and preferably at least partially within or adjacent said leg mountings, and substantially between them. In another preferred embodiment, the elongate support brackets are integrally formed with and thus form part of the leg mountings, in particular the first planar plate section thereof. Thus, in this particularly preferred embodiment, the support brackets, and in particular the elongate lips thereof, are essentially extensions to one or other of the planar plate sections of the leg mountings or they extend between the end sections joined thereto. In a most preferred configuration, the support brackets are constituted essentially of elongate lips which extend from and over a substantial portion of the length of the first planar plate sections of the leg mountings. In any event, howsoever said elongate support brackets and their elongate lips may be provided, and however they may be configured, it is most preferred that they are shorter in overall length relative to the leg mountings or the first and second planar plate sections thereof, so that whereas the first planar plate sections of the leg mountings may generally have the same length as the corresponding dimensions of the table top support portion to which they are secured, the elongate lips which are thus provided underneath said table top support portion will be of reduced length, for example maybe 60%-95% of the corresponding relevant dimension of the table top support portion, which will in most preferred embodiments be its width. In a most preferred arrangement, the elongate lips are lie generally parallel with the first planar plate section of each and both leg mountings but spaced apart therefrom, such that together with the underside planar surface of the table top support portion, said elongate lips define a channel of sufficient depth to receive and accommodate the rim of the removable funnel, and equally the relative separation of the leg mountings provided, which are preferably disposed towards or at either side of the table top support portion are suitably distant from one another such that the lateral or transverse distance between the base sections of the integrally formed elongate support brackets is marginally greater than the largest lateral or transverse dimension (e.g. most preferably the width) of the rim of said removable funnel. In preferred embodiments, the majority of the width of the elongate lips is disposed substantially parallel to the (usually horizontal) underside of the table top support portion of the workbench, one or both of said elongate lips may be provided with inclined (downwardly, away from the underside of the table top support portion) terminal flanges, to further increase the ease with which the removable funnel may be slid into position immediately underneath and adjacent the underside of the table top support portion, and to allow for those parts of the body of the removable funnel immediately adjacent the rim surrounding the larger opening thereof and which depend therefrom, usually at an initially shallow angle but one that increases with axial length in along the direction of the funnel as the body thereof decreases in size from the larger opening to the smaller one. In some preferred embodiments, one or more vertically depending end or stop wall sections is provided, either on one of the longer sides of the table top support portion (when rectangular), or proximate one end of the elongate support brackets, said one or more stop wall sections effectively providing a barrier up to and against which the rim of the removable funnel comes into contact when being slid into the workbench underneath the table top support portion and within the channels defined at each side thereof by the elongate lips of the support brackets and the underside of said table top support portion. In most preferred embodiments, the stop wall section takes the form of a skirt which is secured to and depends from one longer side of the table top support portion. Naturally, the depth of the skirt must at least be sufficient so that some portion of it at least partially closes off one end of the channels defined between the underside of the table top support portion and the elongate lips of the support brackets (whatever form these may take). As the skilled reader will appreciate, such partial or complete closing off of the end of these channels ensures that when the rim of the removable funnel is inserted into the channels and slid therealong, its maximum extent of travel, and thus its final position lateral or transverse position underneath the table top support portion is determined when that rim comes into abutting contact with the skirt or other end or stop wall section which may be provided, either at the ends of the elongate support brackets, or on the table top support portion. While the provision of these particular features does of course render the table "handed" in that the removable funnel can only be properly and fully inserted from one side of the table, it is nevertheless obvious from which side this insertion should occur, and further ensures that when the removable funnel has been completely and fully inserted underneath the table top support portion, it automatically adopts the correct position, being that where its larger upper opening is in substantial or complete registration with the apertured central region of the base of the table top support portion. In most preferred embodiments, the various portions, sections and members of which the structure of the downdraught workbench are constituted are ideally of mild steel, for example being between 2-4mm thick, whereas the table top is constituted most preferably of a mouldable or castable plastics material, which may be reinforced with fibres such as carbon or glass fibres. A most suitable material for the table top is glass fibre reinforced plastics (GFRP), and most preferably the plastics material is a reclaimed or recycled plastics material. Most preferably the table top is of a thickness in the range 10-50mm, and most preferably between 20-35mm thick. In other embodiments, and particularly when a more lightweight workbench is required, it is preferred that the structure of the workbench is constituted predominantly or entirely of Aluminium, or other metal or alloy thereof having a density 50% or less than that of mild steel. Thus the present invention provides a collapsible downdraught workbench which is not only mobile in that it can be very quickly, easily and simply collapsed into a mobile condition and wheeled from one location to another, the present invention also provides a downdraught workbench which is at least somewhat of not substantially modular in that the important components thereof, specifically the table top itself and the removable funnel, can very easily, and above all manually, be inserted and removed from the workbench, either for replacement or prior to transportation. Finally, the configuration of the downdraught workbench is such that the insertion and positioning of these removable, replaceable components is so simple and self-evident that even the most inexperienced operatives can complete the insertion and location process without any significant training, and furthermore, the configuration of the workbench of the present invention is such that it is practically impossible for the removable components to be improperly or incorrectly installed. Yet further, and in certain embodiments, the downdraught workbench of the present invention not only ensures the correct insertion of the modular, removable components, but the configuration is such that the insertion also ensures complete and correct positioning of these components for optimum operation. In particular, as regards the removable funnel, the complete insertion of this component underneath the table top support portion ensures automatic registration between the larger opening of the removable funnel and the apertured central region of the base of the table top support portion, thus maximising the transfer of suction pressure being applied at the smaller opening through and into the upper reaches of the downdraught workbench. This in turn leads to higher efficiency removal of particulate materials being created when operatives are working with power tools on the upper surface of the apertured table top, especially on workpieces of friable materials. Further advantages and benefit of the present invention will become apparent from the following specific embodiment of the invention which is described by way of example and with reference to the accompanying drawings wherein. Brief Description of the Drawings Figures 1 and 2 show perspective views the downdraught workbench according to a first embodiment of the invention from the front and rear of the unit respectively, Figure 3 shows a perspective view of the downdraught workbench shown in Figures 1 and 2 from underneath and from the rear of the unit, Figure 4 shows a plan view of the downdraught workbench shown in Figures 1 and 2 from directly above the unit, Figure 5 shows a perspective view of the downdraught workbench shown in Figures 1 and 2 from underneath and from the front of the unit, Figure 5A shows a schematic perspective view of one leg mounting in isolation, and according to one embodiment of the invention, Figure 6 shows an isometric front elevation view of the downdraught workbench of Figures 1 -5 with a removable funnel inserted into and substantially underneath the unit as would be normal in use, Figure 7 shows a perspective view of the downdraught workbench of Figure 6 with the removable funnel shown in a state of partial insertion / removal, Figure 8 shows a perspective view from the front and above the downdraught workbench of Figures 1-5 prior to insertion of the removable apertured table top and thus showing both the cavity inside the workbench into which said apertured table top is inserted prior to use, as well a large apertured region in the base thereof, Figure 9 shows a partial perspective view from above a downdraught workbench according to a modified aspect of the present invention prior to insertion of an apertured table top, Figure 10 shows a partial perspective view of the downdraught workbench of Figure 9 with an apertured table top having been completely inserted into the workbench as would be the case in use. Detailed Description Referring firstly to Figures 1 and 2, there is shown a perspective view of a downdraught workbench indicated generally at 10 being rectangular in shape and comprising firstly a table top support portion indicated generally at 12 to the underside ofwhich, and on opposite (shorter) sides of which are provided leg mountings indicated generally 14. Leg mountings 14 will typically be either bolted or welded to the underside of table top support portion 12. To and within each leg mounting is pivotally mounted respective identical leg assemblies 16, which in Figures are shown with telescopically extensible portions 16B which extend from within or retract into respective parent leg members 16A to allow the overall height of the table top support portion 12, and in some very specific circumstances, its attitude relative to the most conventional (and illustrated) horizontal condition, to be adjusted as desired. As is common for telescopically extensible leg portions 16B such as shown, these may be secured in place relative to the parent leg members from which they extend by means of simple cotter pins or bolts or the like which can be inserted through apertures 20 provided in both parent leg members 16A and leg portions 16B when such are mutually aligned at some desired extension position, as is well known. Leg portions 16B are provided with feet 16C which may be screwingly secured within the ends of said leg portions 16B to provide a means for finer height adjustment of each individual leg assembly, and also to provide some means of compensating for uneven floor surfaces. Also, as regards the relative cross-sections of the inner (lower) extending leg section and the outer (upper) leg section within which it may slide, in this Figure it can be seen that the cross-sectional shapes are both square, but this need not be the case. In fact, in some particularly preferred embodiments, and in order to cut down possible rattle and other vibration-caused noise, the cross-sectional shape of the inner extending leg section may be U-shaped, whereas of course the outer fixed leg section will, in most embodiments, always be square or rectangular. Both leg assemblies 16 are further provided with a pair cross-or brace members 22 which are welded in place between in perpendicular to the parent leg members 16A, and provide structural support for each leg assembly. As will be described further below, each leg assembly 16 is pivotally mounted to and in this particular embodiment within a respective leg mounting 14 so each leg assembly is capable of being rotated towards one another as shown by arrows 22, 24 from the erected, substantially upright but also slightly outwardly splayed condition shown in the Figures into an effectively collapsed condition (not shown) in which both leg assemblies lie essentially parallel to the base of the table top support portion 12, but spaced apart therefrom. Of course, in the erected, upright condition shown in Figures 1 and 2, it is essential that the leg assemblies be securely fixed in place relative to the leg mountings and in a completely reliable manner such that it is practically impossible for any leg assembly to move when the workbench is in use, i.e. when operatives may be working thereat and thereon. In this regard, in one embodiment, each parent member 16A may be locked to its respective leg mounting by simply releasably bolting one to the other. For instance, suitably positioned and correspondingly sized apertures may be provided in both leg members and the respective leg mountings and a cotter pin or quick-release locking bolt could simply be inserted through both said apertures to lock one or both of the leg members of the leg assembly to the respective leg mounting. However, in a more preferred arrangement, releasable hook and latch type locking means 26 are provided, with a first part of the mechanism being fixed to the exterior surface of each of the leg members 16A in upper regions thereof, and the second parts of each of the two mechanisms being fixed to those surfaces of the leg mountings disposed immediately adjacent the said surfaces of the leg members when the leg assemblies are in their erected condition, as shown. A most preferred type of hook and latch type lock means 26 useful in this regard is a toggle latch or toggle clamp, which the skilled reader will appreciate not only provide secure locking of the leg members 16A to the leg mounting, but include quick-release functionality, so the legs members 16A can quickly be released from their erected, locked-in-place condition and folded away into their collapsed condition underneath the table top support portion of the workbench. In terms of the other major components of the downdraught workbench of the embodiment of the invention in Figures 1 -2, there is provided a substantially apertured table top 30 which is of a size, shape and depth to be received snugly within a correspondingly shaped and sized cavity defined in an uppermost region of the table top support portion such that once the table top 30 is dropped into the cavity, lateral and transverse movement (being motions within the horizontal plane with which the table top lies parallel when the workbench is in its erected condition) are largely if not completely precluded, as will be further described and explained below. In the Figures, the table top 30 is essentially a deep sided grid structure, typically between 15-35mm thick, and constituted of a rigid plastics material which is robust enough to withstand harsh treatments and significant impacts to which it may be subjected in use, and also slightly resilient such that under extreme loads and impacts, its failure mode is plastic deformation as opposed to brittle fracture. In preferred embodiments the table top may be simply cast or moulded. As the skilled reader will immediately understand from the above, the table top 30 can easily be removed and replaced, by simply lifting it upwardly out of the cavity in which it is conventionally seated and away from the workbench. Indeed, it is an advantageous feature of the present invention, in all embodiments, that the table tops are easily removed and replaced, for instance when they become damaged, and as such they are intended to be consumable items. Finally, workbench 10 is further provided, on the outward facing side wall of one leg mounting 14, with a carry or moving handle 32, and on the opposite leg mounting, on outward facing surface of the side wall thereof, with a pair of spaced apart freely rotating castors wheels 34, which as can be seen more clearly in Figure 2, are securely bolted to said leg mounting side wall. These parts can also be seen in Figure 4 which provides a plan view of the workbench, and as the skilled person can readily understand, when table top 30 is removed and the connection between the leg assemblies and their respective leg mountings is released, and said leg assemblies are rotated into their fully collapsed condition, the workbench can then either be relatively easily be lifted as a whole by means of handle 32, or alternatively handle 32 may be used to raise that end of the workbench by an amount sufficient to bring the wheels of the castors into contact with the floor so that the workbench can then be simply wheeled away. Referring now to Figures 3 and 5 (in which previously used reference numerals denote previously described parts), these Figures show different perspective views of the underside of the workbench 10 and in these Figures, it can be immediately seen that table top support portion 12 has a base 12A which is provided, in a central region thereof, with a large elliptically shaped aperture or cutout 12B through which an elliptical region of the apertured table top 30 can naturally be seen. Additionally in these Figures, the nature, configuration and interior surfaces of the leg mountings 14 is visible, and it can also be seen that along one of the longer edges of the table top support portion 12, between the leg mountings provided at opposite sides thereof, there is provided a depending skirt panel 40 which, together with adjacent end panels 14A of the leg mountings, provides a substantially continuous skirt along that particular (longer) side of the workbench, said skirt being disposed adjacent the corresponding side of the table top support portion 30 and substantially flush therewith. The purpose and function of this skirt will become apparent later in this specific description. Within the interior of each of the leg mountings 14 visible in Figures 3 and 5, mounting brackets, two of the four of which can be seen and are referenced 14X, are provided whereby the proximal ends of the each of the leg members 16A may be fixedly and rotatably connected to and within the interior of the leg mountings. The skilled reader will of course understand that other connection means are possible and the invention is in no way limited to the use of any specific type or form of mounting. Indeed, while it is of course preferred that the leg assemblies be pivotally connected to the leg mountings, in certain aspects of the present invention, this may not be an essential requirement. For example, in certain embodiments, the leg assemblies may be simply fixed in place relative to leg mountings, or they be releasably connected thereto so as to be removable. As the leg mountings 14, at least in one specific embodiment of the invention, may serve multiple functions, further explanation thereof is merited, and in this regard, and with specific reference to Figure 5A, it can be seen that a leg mounting 14 may consist essentially of a number of planar panels, some or all of which may be either welded together or bent into shape from a single planar precursor sheet of metal or alloy of appropriate size and shape. Specifically, leg mounting 14 includes a pair of identical shorter end panels 14A between which extends a top panel 14B and a longer end panel 14C. Shorter end panels 14A have the shape of an irregular pentagon, with upper and lower edges 14A-I and 14A-II being generally parallel, a first forward edge 14A-III being generally perpendicular to upper edge 14A-I, second forward edge 14A-IV extending in inclined fashion between edges 14A-111 and 14A-II, and rear edge 14A-V extending between upper and lower edges 14A-I and 14A-II and being also inclined relative thereto. The particular angle of inclination of edge 14A-V relative to upper edge 14A-I is greater than the perpendicular by an amount 6° as shown. This angle is important because end panel 14C is thus also similarly inclined relative to panel 14B, and given that the leg assemblies 16, or more specifically the upper ends of the parent leg members 16A of the leg assemblies, are pivotally mounted to and on the interior surface of said panel 14C, the degree of inclination of that surface also ultimately determines the degree of inclination of said leg assemblies, as can be clearly seen in Figures 1, 2, 3, and 5. Typically the deree of inclination 6° may be in the region of 2-15°, and results in both leg assemblies being somewhat outwardly splayed relative to one another. This configuration can provide a marked increase in overall stability and structural strength of the workbench as a whole, not least because such inclination of the leg assemblies renders it practically impossible for any one leg assembly to become deflected under significant load into some position where the entire leg assembly was disposed underneath the table top support portion of the workbench, for example as could be the case when the leg assemblies perpendicularly mounted directly to the table top support portion. As may further be seen from Figure 5A, the leg mounting structure is essentially a hollow one, as all the various panels define a hollow interior, which can thus be relatively easily accessed, for example for the purpose of drilling holes or mounting, e.g. by bolting or welding, mounting brackets 14X. A yet further important feature of the leg mounting 14 is that along its front facing side, it is firstly provided with a continuous front panel 14D having depth d and extending between portions of respective and opposing end panels 14A, and projecting generally perpendicularly from and in front of a substantial portion of panel 14D are two further panels, one being an elongate lip or ledge 14E, which in turn is provided with a downwardly inclined terminal flange 14F of corresponding length. Thus, although forming an integral part of the leg mounting, when two leg mountings are welded or bolted in place in opposed relationship at opposite sides of the underside of the table top support portion, (as shown in previous Figures and previously described), the particular panels 14B, 14D, 14E, and 14F of each leg mounting together form what is in essence a an internal support bracket structure whereby, for example, a removable funnel may be easily inserted underneath the table top support portion, and equally easily withdrawn from that position, in the manner of a simple drawer, as will further be described below in relation to Figure 6 and subsequent Figures. The effective support bracket structure that is created underneath the table top support portion of the workbench when two such leg mountings are bolted or welded to the underside thereof can of course be provided in different fashion. For example, it is possible, in some embodiments, for a pair of oppositely disposed and generally identical discrete and separate support brackets of similar shape, size and configuration to the effective support bracket structures created by the leg mountings of Figure 5A to be similarly secured to the underside of the table top support portion of the workbench, in appropriate positions within and between more simple leg mountings not provided with panels 14E, 14F, and these would of course provide the same functionality in that a removable funnel could be slid into and from a desired position immediately underneath the table top support portion, and most importantly, such that the opening of the funnel was in registration with the apertured region of the base of said table top support portion. In any event, the provision of support brackets, or suitable support bracket structures, regardless of how these may be configured and provided, should be considered as falling within the scope of the present invention. Referring now to Figure 6, there is shown an isometric front elevation view of the workbench 10 of previous Figures, albeit without the apertured table top 30, handle 32 and castors 34, and feet 16C, purely for clarity purposes. In this Figure, the workbench 10 is shown having a removable funnel indicated generally at 50 having been slid into its conventional operative position immediately underneath table top support portion 12. Removable funnel 50 has a hollow interior passageway defined by an essentially frustoconical surrounding body 52 (or more accurately a frustum section of a hyperboloid of revolution) which also defines, and extends axially (in the figure, vertically) between a larger opening which is preferably elliptical, and a smaller opening which is preferably circular (see Figure 7 and description thereof). Of course, these shapes are somewhat determined by the functions they are to perform. On one hand (as regards the larger opening), an elliptical opening is provided because the table top support portion in rectangular, and of course the aperture 12B (Figures 3, 5) provided in the base 12A thereof is, in some embodiments, elliptical. On the other hand (as regards the smaller circular opening), in use, a usually circular, standard diameter (e.g. 100-200mm) circular flexible duct 54 is usually firmly and sealingly connected to, over and completely around the smaller opening, which is thus ideally also circular. Other configurations are of course possible and should be considered as being encompassed by the present invention. As can further be seen in Figure 6, around the uppermost end of the removable funnel, there is provided a thick (e.g. 10-35 mm) rim 56 which is preferably substantially rectangular or provides a substantially rectangular periphery for the larger opening of the removable funnel. Although in Figure 6, only a single longer edge of the rim 56 is visible, it can instantly be seen that the thickness dimension of the rim is an important consideration, as is its overall length, or more specifically the largest distance between the two most remotely disposed opposite sides thereof, because it is by means of this rim that the removable funnel as a whole is supported in position, in particular by the elongate lips 14E provided on each of the leg mountings 14, as particularly described above in reference to Figure 5. Thus, in order that the rim of the removable funnel, and thus the removable funnel itself can be slidingly inserted, in drawer-like fashion above and over the elongate lips 14E of the leg mountings, the maximum thickness of the rim must be less than the vertical (in the Figure) distance between the upper surfaces of said lips and the underside of the table top support portion 12 beneath which said lips are disposed and underneath which they extend, substantially from one (longer) side of said table top support portion to the other. It should be mentioned here that the shape of the rim 56 is perhaps of lesser importance as compared to its maximum lateral dimension (that being the total distance from one side of the rim to the other, clearly seen in this Figure) because in order for a rim of any shape to be slid into and within the channel-like openings defined between the elongate lips and the underside of the table top support portion, the maximum lateral dimension must be both: - greater than the lateral distance between the most proximal edges of said elongate lips (thus ensuring that at least some portion of the rim can be supported thereby) and - less than the lateral distance between respective front panels 14D of the leg mountings (thus ensuring that the rim can actually fit laterally into the space between these panels). For instance, in some embodiments, the rim may be elliptical, and thus be of corresponding shape to the larger opening of the removable funnel which it surrounds and thus partially defines, but as long as the maximum (major axis, for an ellipse) dimension of such a rim meets the requirements above, then it will fit in the drawer-like opening defined underneath the table top support portion, and be supported by said elongate lips. Brief mention is also merited here of the terminal flanges 14F provided along the remote ends of the elongate lips 14E, and which it can be seen in this Figure are inclined downwardly relative thereto. Although these terminal flanges do not, in most cases, support the rim 56 of the removable funnel after complete insertion as they are sufficiently downwardly inclined to be separated by a small distance from those portions of the surface ofthe body 52 which lie most proximate thereto, the free edges of said terminal flanges can nevertheless serve to prevent lateral chatter or other movement ofthe removable funnel when the workbench is in use, and in circumstances where there may be significant amounts of play, i.e. spare space, between the most remotely disposed opposite edges of the rim of the removable funnel, and the front panels 14D most adjacent thereto. In this case, and if the removable funnel moves laterally, it is more likely that a relevant portion of the outer surface of the body 52 comes into contact with the free edge of one or other of the said flanges 14F before the rim contacts a respective panel 14D, and therefore excessive lateral movement ofthe removable funnel while in use can be more quickly arrested. A further optional feature ofthe workbench is shown in dotted line in Figure 6, this being a crossbrace or strut 57 being provided at both ends thereof with suitable formations complementary in shape and size to the cross-sectional shape ofthe respective opposite cross-members 22. In the embodiment shown in this Figure, these cross-members have quadrangular, most commonly square cross-sections, and therefore the formations 57X provided at the end of any notional strut 57 would ideally be U-shaped so as to be capable of slotting over each cross-member 22 and provide the required bracing effect therebetween. In other preferred embodiments, the cross-sectional shape ofthe cross-members 22 ofthe leg assemblies is circular or elliptical, and the strut 57 is provided in the form of a diagonal scaffolding brace suitable for use in quick erection scaffolding towers, such as those sold under the trade name "Youngman Boss", or those commonly referred to as "Boss scaffolding towers", as these braces are preconfigured with suitable end formations which allow them to be quickly, simply and manually snapped into position over circular, standard sized scaffolding poles. The skilled reader will immediately appreciate how such a brace may provide immediate and significantly improved structural rigidity to the workbench as a whole, as when braced in the manner shown, each leg assembly is prevented from splaying relative to the other, and thus only remaining mode of failure is buckling, which any under normal use conditions is extremely unlikely. Referring now to Figure 7, the removable funnel 50 is shown in a state of partial insertion / removal from the position shown in Figure 6. In this Figure, the generally rectangular nature of rim 56 of the removable funnel can be appreciated, as well as the generally elliptical and circular shapes of, respectively, the upper and lower openings defined at different upper and lower ends of the body 52 thereof. In this particular embodiment, although the rim is continuous, within the rim are provided openings 58, which reduce the overall material requirement and thus the overall weight of the removable funnel as a whole, and furthermore help define grab handle portions (one pair of which are referenced at 58X) on (ideally) all corners of the rim 56 and by means of which it is easy for operatives to obtain solid purchase on the removable funnel during insertion and removal. Although the removable funnel 50 is shown in Figure 7 with duct 54 still attached, in the majority of circumstances said duct would only be attached after the removable funnel had been fully inserted underneath the table top support portion, and similarly the ducting would be detached prior to removal of the removable funnel from this condition. Referring now to Figure 8, an alternative perspective view of the workbench 10 is provided, from the rear, in contrast to the views of the front provided by Figures 6 and 7. Specifically, what distinguishes the front (longer) side from the opposite rear side of the workbench is, most simply a skirt panel 12A which as can be seen in this Figure is secured to and depends from the table top support portion 12 by a distance approximately equal to depth of the leg mountings 14, and specifically the end panels 14A thereof. As the skilled reader will immediately appreciate, this skirt panel 12A effectively prevents access to the support bracket structures provided directly underneath the table top support portion 12 because whereas the elongate lips of the support bracket structures are provided at some specific distance between the upper and lower edges of the end panels 14A, the lower edge of said skirt panel, being substantially the same depth as the end panels 14A, automatically descends beneath the level of the elongate lips. Therefore, not only does skirt panel prevent an operative from inserting and removing, or using other terminology, loading and unloading the removable funnel from this particular side of the workbench in the manner described above with reference to Figure 7, but, most advantageously and slightly less obviously, said skirt panel also provides a useful backstop forthe removable funnel, and particularly the rim thereof when it is being inserted at the opposite side. In this regard, and in certain embodiments, this feature also determines another preferred dimension of the rim 56 of the removable funnel. To explain further, in order that the skirt panel properly serves its purpose in providing a backstop from said rim so as to limit the extent of travel thereof over the elongate lips when the removable funnel is being inserted, and also to ensure that the removable funnel adopts a correct position directly, fully and immediately underneath the base 12A of the table top support portion 12, the transverse dimension of said rim (being that perpendicular to the lateral dimension of the rim visible in Figure 6) must be essentially the same as the width of the table top support portion. Using an elliptical analogy, this minor axis dimension of the rim is equivalent to the table width (the distance between its two longest sides), and yet further preferably the minor axis of the larger elliptical opening ofthe removable funnel must be essentially the same as that of the elliptical aperture 12B previously described. In a most preferred arranged, the thickness ofthe rim is only marginally less (e.g. of the order of only 1 -4mm) less than the distance separating the elongate lips 14E and the underside ofthe table top support portion 12 (or specifically the base 12A thereof) so that opposing sides ofthe rim are a somewhat snug fit the channels defined between said elongate lips and the underside ofthe base ofthe tale top support portion. Not only might this give rise to some mild frictional resistance during sliding, but more importantly this ensures that the uppermost surface ofthe rim is very close, if not actually in contact with the underside of the base of the table top support portion, and thus air loss through any interstice that might exist between the rim and said surface is minimised when air is being sucked at significant velocity through the funnel from above the table top, as will be the case when the workbench is being used. The skilled person should also understand that the correct and complete insertion ofthe removable funnel should, in preferred embodiments, also ensure that the larger opening ofthe removable funnel is substantially and preferably completely and thus optimally aligned with the corresponding elliptical aperture 12B, thus further improving the efficacy of air removal from atop the table top when work is occurring thereon and as a result, dust, fumes and other noxious particulate matter may be being created. It can also be seen from Figure 8 that the workbench 10 is shown without table top 30 in place, and thus a cavity 12C provided in the upper reaches ofthe table top support portion 12 can clearly be seen. More specifically, this table top receiving cavity 12C is defined by virtue of upstanding wall portions 12D which are provided on each of the four sides of the table top support portion 12 and completely around its periphery. As can also be seen, said table top support portion 12 is additionally provided with a base 12A, which may be disposed some short distance (e.g. a few, or a few tens of mm) beneath the cavity. Within a substantially central region of said base 12A, there is provided an elliptical aperture, possibly by means of cutting out a relevant shape from. As no removable funnel is present in the workbench in this Figure, it is of course possible to view the far side leg assembly through said elliptical aperture. Also shown in Figure 8 are bolt holes 12A-1 provided in the base 12A which, when an apertured table top is disposed within the cavity 12C, allow bolts (not shown) to pass from the underside of the base into correspondingly sized and positioned, ideally counter-sunk, apertures provided in the apertured table top, and whereby upon tightening, the bolts rigidly secure the table top to the base 12A. Of course in this embodiment, there is then largely no need for the other retaining features of the workbench, so in certain embodiments these latter retaining features may be regarded as optional. Furthermore, also illustrated in the Figure at dotted line 40X is a possible further optional feature, which is that skirt 40 may be cut back somewhat to this line so that its lower edge is made substantially higher. Not only does this reduce the overall weight of the workbench without compromising the purpose and function of said skirt (to act as a backstop for the removable funnel when this is being inserted underneath the table top support portion), but said cut-away skirt 40 would then not impede the free ends of the legs in the leg assemblies 16 when they are collapsed by rotating towards one another and upwardly through 90 degrees (or slightly more) from the condition shown in the Figure to their fully collapsed condition. This cut-aweay portion of the skirt 40 is especially useful if, as is preferred in some embodiments, the free ends of the legs are provided with heavy duty casters, as is sometimes required and requested to further enhance the mobility of the workbench as a whole. Of course such casters must be extremely heavy duty in order to bear the very significant loads to which they may be subjected, but also their configuration must be such that in use, i.e. when the workbench is static and operatives are working thereat, any all rotation is completely precluded, for obvious reasons. In this regard, it has been proposed to fit each leg free end with a particular type of raising and lowering caster known as the Footmaster™ heavy duty levelling caster, which may be rated up to loading capacities of nearly 300kg each, meaning that a workbench fitted with 4 such casters, all other components permitting, could safely bear loads of nearly 1200kg, which is far in excess of what the workbench of the present invention is designed to be capable of carrying. Referring finally to Figures 9 and 10, there is shown a downdraught workbench 100 according to a modified embodiment of the present invention. This workbench is broadly very similar to that previously described in that it is provided with a table top support portion 112, leg mountings 114 and leg assemblies 116 pivotally secured and mounted therein, table top support portion 112 is slightly reduced in depth because (and referring backto Figure 8) instead of the table top-receiving cavity 12C being provided in an upper region of said table top support portion, somewhat separated from the base 12A, the table top support portion 112 is provided with a base 112A on to which a number of spacer ribs 112E are directly secured, for example by adhesive, and at the remote (in the illustration) end of said table top support portion there is provided a open slot 112F extending over substantially the entire width of the table top support portion, said slot arising as a result of the absence of one of the side wall panels 112D which are provided around the remaining sides of the table top support portion and thus the remainder of its periphery. In addition to side walls panels 112D, the table top support portion 112 of this embodiment is also provided with a single continuous lip panel 112X which projects inwardly of the cavity defined beneath it and perpendicularly away from the remaining side wall panels 112D of which said lip forms part. Of course, along the length of the slot 112F said lip is not supported, except at those ends where it is connected to respective opposite side wall panels 112D. Referring briefly to Figure 10, wherein the end of the table top support portion in which slot 112F is provided is foremost, a table top 130 is shown having already been slid into and through the slot 112F and then completely into the cavity defined within the table top support portion 112. Table top 130 is again apertured as required, and in this regard is provided with a plurality of individual apertures 132 arranged in an elliptical pattern over a substantial centrally disposed, also elliptical region of said table top. Thus, in this embodiment, as opposed to having a simple moulded or cast plastics grid which is simply dropped into a receiving cavity of the table top support portion, as in the previous embodiment, in this embodiment, the table top is not only slid horizontally into position within a suitable shaped and sized cavity through the slot 112F, wherein it is similarly prevented from lateral and transvere movements by virtue of being a snug fit within said cavity, but additionally in this embodiment, the continuous lip 112X effectively also prevents the table top 130 from moving vertically upwards away from the support ribs 112E on which it usually rests. Thus, in this embodiment, the table top is more securely contained within the cavity. In most preferred embodiments, the central elliptical region of the table top 130 and in which the elliptical pattern of apertures 132 is provided, when completely and fully inserted into the table top support portion as shown in Figure 10, substantially coincides with and is preferably the same size as one or both of: -The elliptical aperture 112 B provided in the base 112A of the table top support portion, and - the larger elliptical opening of the removable funnel. Referring briefly back to Figure 9, although in some embodiments, the elliptical aperture 112B completely open, but in some other preferred embodiments, it may be quarterered as indicated schematically by the dotted lines 112B-X and comprised of 4 quarter elliptical aperture segments defined between, on the one hand the peripheral elliptical outline, and internally by a cruciform internal brace section 112B-X, if such is provided. Naturally such a cruciform brace section would provide the base 112Awith slightly improved structural rigidity and robustness. A further feature shown in Figure 10, but equally applicable to all other previously mentioned embodiments of the invention are the releasable locking means 126 used to secure the leg assemblies 116 to leg mountings 114. These releasable locking means can be seen more clearly in Figure 10 than in Figures 1 and 2, and it can be seen in this Figure that these may be hook and latch 5 type releasable locking means, such as toggle clamps or toggle latches. The skilled reader will know exactly how these mechanism function, so further description is not provided here except to mention that these type of locking mechanism are particularly useful for the present invention because not only are they suitable for ensuring respective adjacent generally planar surfaces of adjacent components are securely but releasably locked together, they are also quick to operate, 10 so the workbench as a whole can be reduced to its collapsed condition very quickly when it is no longer required, or when it is desired to move it to a new location. In some particular preferred embodiments, similar types of releasable locking means to those illustrated may be used, except they are more heavy duty in that they include bolts components which, when tightened, ensure that the locking means cannot be accidentally released from its locked condition. 15

Claims

1. A downdraught workbench comprising a table top support portion having at least a base on one side of which is secured a planar table top provided with a plurality of apertures therethrough over a significant proportion of the total area of said table top, said workbench further comprising at least one pair of leg mountings rigidly secured to, or forming an integral part of the table top support portion and being disposed at a respective one of two opposite sides of said table top support portion and on an opposite side of the base thereof to that on which the table top is secured, each of said leg mountings further having pivotally connected thereto at least one leg assembly capable of pivoting between a first collapsed condition in which said leg assembly is folded underneath the table top support portion and so as to be generally parallel therewith, and a second, erected condition in which said leg assembly is rotated into an upright position in which it subtends an angle of at least 90° with the base of the table top support portion, Characterised in thatthe base of said table top support portion is provided with one or more apertures in a geometrically central region being at least half the total area of said base, said one or more apertures in said base having a total open area which is at least half of the total area of said central region, said downdraught workbench further being provided with- at least two substantially parallel elongate support brackets disposed in spaced apart relationship between the leg mountings, each support bracket being disposed adjacent a respective one of a two opposing sides of the apertured central region of said base and each having an elongate support lip which extends substantially parallel to and underneath the base of the table top support portion thus defining a pair of spaced apart open channels therewith capable of receiving, in sliding fashion, portions of the rim of a removable funnel having a first larger and second smaller openings into, out of and between which fluid is constrained to flow within said funnel, said rim being provided substantially around and said first larger opening and having a maximum lateral or transverse dimension greater than distance between the edges of the support lips of the support brackets but less than the total distance between support brackets such that at least some portions of the rim can be received above and supported from underneath by said elongate lips in close proximity to the underside of the base of the table top support portion,the size of the larger of said removable funnel being in general correspondence with the size of the apertured central region of said base such that when the leg assemblies of the workbench are in their erected condition and the removable funnel is slid fully into position beneath the base of the table top support portion, substantially the entirety of said removable funnel is disposed underneath the base of the table top support portion, and the larger opening of said removablefunnel is in close proximity with the base of said table top support portion, and is substantially aligned with the apertured central region thereof.

2. A downdraught workbench according to claim 1 wherein said table top support portion is provided of around a substantial portion of its periphery with one or more upstanding wall portions which together with the base define a shallow cavity within which the apertured table top, being of a cross-sectional shape, size and depth corresponding to the dimensions of the cavity, is snugly received therewithin such that lateral and transverse movements of the table top within the cavity are resisted on all side of the table top by said upstanding wall portions of said table top support portion.

3. A downdraught workbench according to claim 2 wherein one or more of the upstanding wall portions provided around all or portions of the periphery of the table top support portion are provided with terminal flanges disposed substantially over and above the cavity defined by the said wall portions and so as to reduce the overall open area thereof and thus prevent a table top corresponding in shape and size to the cavity and disposed therewithin from either being inserted thereinto from above, or being lifted therefrom or otherwise escaping.

4. A downdraught workbench according to claim 3 wherein either- at least one slot is provided in at least one of the said upstanding wall portions provided around the periphery of the table top support portion, or- at least one opening is provided by the absence of at least one ofthe said upstanding wall portions provided around the periphery of the table top support portion,said slot or opening being of a width and depth corresponding to the relevant dimensions of the table top and whereby the latter may be slid into and through said slot or opening and thus ultimately completely into the cavity defined by the other remaining upstanding wall portions provided around the periphery of the table top support portion.

5. A downdraught workbench according to claim 4, wherein a slot is provided, and wherein the lowermost edge ofthe slot stands proud of the base of the table top support portion such that the slot is disposed more towards, and provides access to the upper reaches ofthe cavity.

6. A downdraught workbench according to claim 4 wherein an opening is provided, said opening being formed by the absence of at least one ofthe said upstanding wall portions provided around the periphery of the table top support portion, and wherein there is further provided araised edge lip, much smaller in height relative to the remaining upstanding wall portions provided around the periphery of the base of the table top support portion, such that the opening is disposed slightly above the base of the table top support portion by an amount corresponding to the height of said lip.

7. A downdraught workbench according to any preceding claim wherein the apertured tabletop is releasably secured to and on the base of the table top support portion by means of bolts.

8. A downdraught workbench according to any preceding claim and further provided with - at least one handle secured to a first leg mounting such that said handle projects outwardly away from the table top support portion and from one side of the workbench as a whole, and- a pair of castors secured to a second leg mounting disposed on the opposite side of the workbench relative to the first leg mounting such that said castors project outwardly from that side of the workbench,whereby, when the leg assemblies connected to each respective leg mounting are folded in their collapsed condition, the workbench as a whole can be up-ended or lifted at one end into an inclined position approaching the vertical by means of the handle and in doing so, the castors come into direct contact with the floor and the workbench as a whole can be wheeled away.

9. A downdraught workbench according to claim 8 when dependent on any of claims 4-6 wherein the handle is provided at the same side of the workbench to that at which the opening or slot is provided.

10. A downdraught workbench according to any preceding claim wherein each leg assembly consists of a framework of metal sections secured together, said framework comprising at least a pair of parallel leg members joined together with at least one cross-member which is perpendicularly disposed relative to the leg members.

11. A downdraught workbench according to claim 10 wherein each leg assembly is pivotally connected to a respective leg mounting by means of a pair of bolts, each of which passes through both one end of the leg mounting, one end of one leg member, and is received and secured in a suitably positioned bolt retaining member whereby not only is each end of each leg member secured to and within the leg mounting and at either end thereof, but the leg assembly as a whole can rotate relative to the leg mounting.

12. A downdraught workbench according to either claim 10 or 11 wherein respective adjacent outer surfaces of each leg member and leg mounting are provided with respective portions of a releasable clasp such that when a leg assembly is in its fully erected condition, the respective clasp portions can be manually connected together so as to be locked and whereby each leg member of the leg assembly is effectively firmly but releasably locked in position relative to the leg mounting.

13. A downdraught workbench according to any of claims 10-12 wherein each leg mounting consists of at least two elongate planar plate sections, a first of which is, in use is secured to an underside of the table top support portion, and a second section which subtends an obtuse angle with the first section such that it is outwardly splayed relative thereto, the interior surface of which thus provides a contact surface against which upper ends of the leg members abut when the leg assembly is mounted inside the leg mounting and the legs are rotated into their fully erected condition.

14. A downdraught workbench according to claim 13 wherein the leg mountings further comprise a pair of end plate sections joined to both the first and second plate sections and through which the bolts which secure the upper ends of the leg members to the leg mountings pass.

15. A downdraught workbench according to any preceding claim wherein the elongate support brackets are one of:- separate discrete components secured to one of: the underside of the table top support portion, and the leg mountings, so as to be disposed at least partially within or immediately adjacent said leg mountings and between them, and- integrally formed with the leg mountings so as to form part thereof.

16. A downdraught workbench according to claim 15 wherein the and each support bracket is constituted essentially of an elongate lip which extends from and over a substantial portion of the length of the first planar plate sections of the leg mountings.

17. A downdraught workbench according to claim 16 wherein the and each elongate lip of the support bracket is shorter in overall length relative to the leg mountings, so that whereas the first planar plate sections of the leg mountings have the same length as the corresponding dimensions of the table top support portion to which they are secured, the elongate lips are of a reduced length of between 60%-95% of the corresponding relevant dimension of the table top support portion.

18. A downdraught workbench according to claim 16 or 17 wherein the and each elongate lip lies parallel with the first planar plate section of the and each leg mounting but spaced apart therefrom, such that together with the underside planar surface of the table top support portion, the and each elongate lip defines a channel of sufficient depth to receive and accommodate the rim of a removable funnel, and the leg mountings are spaced apart from one another by an amount greater than the largest lateral or transverse dimension of the rim of said removable funnel so as to be capable of accommodating said removable funnel therebetween.

19. A downdraught workbench according to any of claims 16 to 19 wherein the majority of the width of the elongate lips is disposed substantially parallel to the underside of the base of the table top support portion, and at least one of said elongate lip is provided with downwardly inclined terminal flanges.20 A downdraught workbench according to any preceding claim wherein the table top support portion is further provided with at least one skirt section which vertically depends from at least one of the longer sides of said table top support portion, said at least one skirt section providing an abutment surface up to and against which a rim of a removable funnel comes into contact when being slid into the workbench underneath the table top support portion and within the channels defined at each side thereof by the elongate lips of the support brackets and the underside of said table top support portion.

21. A downdraught workbench according to any preceding claim further comprising a removable funnel, said removable funnel having a larger opening and a smaller opening, said larger opening corresponding in size to the apertured central region of the base of said table top support portion, such that when said removable funnel adopts is fully inserted condition such that it is disposed immediately beneath the base of the table top support portion of the workbench, the larger opening of said removable funnel is in complete registration with the apertured central region of said base of said table top support portion.

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