GB2073275A - Roofing panel - Google Patents

Abstract

A roof for a building consists of prefabricated panels (11, 13) joined together at the edges. Each panel comprises a pair of thin metal outer webs (16, 17) joined together by thin metal cylindrical spacers (18) which are welded to the webs and arranged close enough together to provide at least sufficient strength and stiffness of the panel for the panel, or a truss formed of two or more panels, to be self-supporting. Spaces beween the spacers may contain similar but shorter reinforcing cylinders (20). The material used may be tinplate and the cylinders may be generally similar to built-up can bodies. The roof panels may be planar or domed. <IMAGE>

Description

SPECIFICATION Roofs and roof elements for buildings This invention relates to roof elements, by which is meant structural components which, by themselves or when assembled with other, generally-similar components, constitute a space structure or part of a space structure to serve as a roof of a building.

The invention is particularly concerned with prefabricated roof elements. Although a large variety of prefabricated elements for roofs of various kinds are availabe, they can tend to be quite expensive and in some cases they employ materials not readily available. In addition, because, by their prefabricated nature, such elements require to be transported to the site where they are to be erected, sometimes over long distances, light weight is a desirable characteristic for the purpose of reducing transport costs. Light weight is of course also desirable for another good reason, viz. that if prefabricated structures are by way of temporary buildings, components that are too heavy are not acceptable because they are unlikely to be proper foundations.

Light weight must be commensurate with structural strength, and whilst numerous designs of roof structure or structural element combining these two desirable characteristics are known and in use, satisfactory mechanical strength in a lightweight roof structure can often only be achieved by the use of expensive and sophisticated materials, or (as for example in the case of geodetic structures), by adopting a particular overall design for the building or other structure in which flexibility of design is sacrificed to the achievement of high strength with low weight.

The present invention is intended to provide roof elements (as hereinbefore defined) in which not only is a high degree of mechanical strength combined with light weight, but in which also the materials used are such as are commonly available and relatively inexpensive, whilst the element may be made in a variety of different forms.

Other important characteristics desirable in a roof element are resistance to leakage or the ability easily to be made leakproof; good thermal insulation properties; and ease of assembly. This invention aims to provide a roof element, and a roof consisting of such elements, which can if desired be readily sealed against leakage, can be made to effect good thermal insulation, and can be assembled from simple components by known techniques.

According to the invention, a roof element comprises a plurality of thin metal webs each in the form of part of a sphere of infinite radius or less, the webs being laterally spaced apart and joined together by an array of spacers in the form of thin-walled hollow cylinders, each having its axis generally perpendicular to the webs to which the cylinder is joined. It will be understood that a plane surface is a sphere of infinite radius, so that the webs may be of frusto-spherical or plane form.

The cylindrical spacers serve not only to join the webs together, but also to provide a means for achieving high resistance to shear stresses. The form of construction thus envisaged enables the assembled roof, comprising elements according to the invention, to have a substantial unsupported span in both the longitudinal and transverse directions.

Where the shear stresses likely to be imposed on the roof structure are relatively moderate, i.e.

such that it is not necessary to put the spacers particularly close to each other, a substantial area of each web may extend between the attachment of one spacer thereto and the next. This may necessitate some stiffening reinforcement of the web, and for this purpose, at least one of the webs then preferably has reinforcing means in the form of further thin-walled hollow cylinders secured at one end to the web and having their other ends free.

Where the webs are substantially planar, the preferred arrangement of the spacer cylinders is that the latter are arranged in parallel rows, the spacers in each row being in positions offset, in the longitudinal direction of the rows, from those of the spacers in the next adjacent row or rows, to define a lattice whose axes are inclined to the said direction, the axes of the spacers being disposed at nodes of the lattice. Where reinforcing cylinders are provided, there are preferably disposed at further nodes of the said lattice. In a typical arrangement of the preferred kind, for use in a roof element where the shear stresses imposed are relatively moderate, there are two said reinforcing cylinders between each spacer and the next along each axis of the lattice.

The form of construction involving spacer and reinforcing cylinders, all of thin-walled form, together with very thin webs, affords considerable flexibility of design. Thus, for example, in areas of the roof element where more severe shear stresses (or indeed more severe compressive or tensile stresses having a significant component in a direction perpendicular to the plane of the web) are to be provided for, the concentration of spacer cylinders can be locally increased, i.e. if necessary all the nodes of the lattice in that area can be occupied by spacers. If more severe stresses are to be provided for over the whole of the element, the reinforcing cylinders can be replaced by spacer cylinders.

In general, the construction of each spacer or reinforcing cylinder is such that each cylinder has, at that end thereof which is joined to a web (or at both ends if both ends are to be joined to webs) a metal end portion. The latter is preferably formed with a generally radial flange, which is joined to the appropriate web.

Each cylinder may be formed in one piece, and for this purpose it may be made by the same techniques, and from the same materials, as is the body of a three-piece food or beverage can, of the built-up kind formed from sheet metal into a cylinder having a side seam. The side seam may be soldered, or bonded by means of suitable adhesives of kinds well known in the canmaking art for such purposes; but preferably the side seam is welded. Similarly, the cylinders themselves may be secured to the webs by adhesive bonding, or by soldering, or by welding.

In alternative embodiments, the spacer cylinders may be in composite form, consisting of a pair of end portions in the form of separate, metal, thin-walled cylindrical members, similar to the reinforcing cylinders and joined by an intermediate portion made of a suitable nonmetallic, thermal insulating material. Preferably in such a case, each metal end portion of each composite spacer has a helical thread of opposite hand to that of the other end portion, the intermediate portion being secured to the end portions by said threads.

The preferred material for the webs and for the spacers (and reinforcing cylinders where provided) is steel, preferably in the form of commerciallyavailable electrolytic tinplate; typically the nominal thickness of this plate, for all the components, is 0.25 mm. However, other metals or alloys may be used for webs and/or cylinders; for example aluminium.

When aluminium is used, adhesive bonding both of the side seams, if the cylinders are of this form, and also between the various components, may be found preferable to the use of welding, though aluminium may be satisfactorily welded using inert-gas shielding techniques.

For most practical applications, the structural roof element according to the invention is in the form of a panel.

The roof will typically be in the form of one or more self-supporting pitched trusses, each built up from a suitable number of the roof panels. Such a truss may for example comprise a pair of the panels each arranged at a pitch angle to the horizontal and joined at the ridge of the truss, the truss then having the form of an inverted V. To give a wider unsupported span, however, these two pitch panels may be separated by a substantially horizontal spacing panel joining the upper edges of the pitch panels.

In a roof element in the form of a pitch panel having a pair of outer said webs joined by said spacers, in a preferred form of construction, at least one of the outer webs is bent away from the other outer web adjacent to a side of the panel, the outer webs at that side terminating in a common plane inclined to the panel, whereby when a similar panel is arranged with its corresponding side abutting the said side of the panel, the outer webs define a zone of box-like configuration at which the two panels can be joined together. The simple but very strong boxlike joint thus obtained may be employed at the bottom edge or at the upper edge of the panel, or both. Trusses of" inverted-V" shape may be made from a series of identical pitch panels each having this form of construction at both sides.

In another form of roof element according to the invention, again where the element is in the form of a panel having a pair of outer said webs joined by said spacers, the webs are bent so that, in endwise cross-section, the panel comprises a plurality of sections of different orientations.

The resulting shape, in cross-section, is cranked. Preferably in such an arrangement, the panel has at least one stiffening web laterally spaced from, and disposed intermediate between, the outer webs across each bend in the latter, the or each stiffening web being bent similarly to the outer webs so as to extend a relatively short distance, into each of the sections of the panel on either side of the bend, at substantially constant spacing from the outer webs, the said webs being joined together by appropriate ones of the said spacers.

According to a further preferred feature of the invention, a structural element according to the invention is in the form of a panel having, in at least one of its sides, said webs formed with laterally-outwardly directed side flanges for securing the panel to another element of a building. Such a panel is preferably joined to another roof element by means of fastening means securing the side flanges of the panel to the other roof element, at least one of the side flanges being spaced from the other roof element by a spacing member adapted to allow airto enter the interior of the panel past the side flange.

The invention also comprehends within its scope a roof for a building, comprising a structural roof element according to the invention, or a plurality of such elements, joined together along respective sides thereof.

The interior of each roof element, at least outside the hollow spacers, is preferably filled with a suitable thermal insulating material such as fibre or foam of a kind well known in the building industry.

Roof panels according to the invention offer a combination of light weight with high mechanical strength; the ability to be made in sizes which can be transported, stored, handled and erected easily and quickly; and the ability to be assembled quickly, with simple conventional fasteners such as bolts and nuts, to form a self-supporting roof structure having a substantial unsupported span, without the need for any additional framework. In addition, the roof can be readily dismantled or altered as required.

Embodiments of the invention will now be described, by way of example only, with reference to the drawings hereof, in which: Figure 1 is a diagrammatic drawing illustrating the principle of a structural element comprising a pair of thin webs, each of frusto-spherical form, spaced apart and joined together by radiallyextending, hollow cylindrical spacers, the element being seen in diametral section; Figure 2 is a partly-cut away view showing part of one end of a building having a roof formed of roof elements in a first embodiment of the invention; Figure 3 is an enlarged end section of the roof at a hip joint of one roof truss; Figure 4 is a similar view illustrating the joint between a pair of trusses of the same roof; Figure 5 is a partly broken-away side elevation of a reinforcing cylinder forming part of the structure shown in Figures 2 to 4;; Figure 6 is a side elevation showing a built up spacer cylinder of the same structure; Figure 7 is a sectional elevation showing a composite spacer cylinder which can be used as an alternative to one-piece spacer cylinders shown in Figures 3 and 4; Figure 8 is a simplified cross-sectional elevation, taken on the line VIlI-VIlI in Figure 9, along part of a prefabricated roof structure formed of roof elements in a second embodiment of the invention; Figure 9 is a simplified cross-section on the line IX-IX in Figure 8; Figure 10 is an enlarged sectional elevation, taken on the line X-X in Figure 1 of part of one of the roof elements shown in Figure 8; and Figure 11 is a diagrammatic sectional elevation taken on the line XI-Xl in Figure 10.

Referring to the Figure 1, the structural element shown somewhat diagrammatically therein comprises a pair of thin metal webs laterally spaced apart. The webs are of spherical form and are concentric with each other, and comprise an outer web 1 and an inner web 2. The webs 1 and 2 are joined together by an array of spacers 3 arranged on a symmetrical lattice defined by great circles of the spheres. Each spacer consists of a thin-walled hollow cylinder, each having its axis generally perpendicular to the webs 1 and 2, i.e.

on a common radius of the spheres.

In the examples to be described with reference to the remaining figures of the drawings, the webs are generally planar in form, i.e. they each define part of a sphere of infinite radius. It will be appreciated that, whether or not the radius of the sphere is of infinite length, the use of thin-walled, hollow cylindrical spacers enables the end of each spacer to engage against, and be joined to, the adjacent web around the entire circumference of the cylinder.

Referring now to Figure 2, a rectangular building such as a warehouse or large shed has four walls of which one end wall 5 is shown. The side walls are each, in this example, built up above the level of the top of the end walls to form a parapet. The roof consists of a number of identical roof trusses 10, joined together to form a continuous span extending from one side wall to the other. Each truss comprises three structural roof elements in the form of panels, viz. a pair of panels 11, 12 which, because they are inclined to the horizontal, will be called pitch panels, and a spacing panel 1 3. The spacing panel 13 is arranged between the two pitch panels 11, 1 2 and, at any given cross-section along its length, is substantially horizontal.

Each roof truss 10 may be so mounted as to slope downwardly from one end to the other, so as to enable rainwater to run off the spacing panel 13. Such a slope is not indicated in Figure 2, however.

The roof panels, which are joined together along respective side edges as indicated by the joints 14, 15 in Figure 2, are of the general kind already described with reference to Figure 1, but in the present example they comprise outer webs which are generally planar. The construction of the spacing panel 1 3 is indicated in Figure 3.The thin upper web 1 6 is joined to the thin lower web 17 by one-piece, thin-walled, hollow cylindrical spacers 18, each joined to the webs by its respective end portions 1 9, each of which has a generally radial flange which is welded to the adjacent web 1 6 or 1 7. Except where it differs at the lower end, each of the two pitch panels 11 and 12 is of generally the same construction as the spacing panel 13, having outer webs 23, 24 joined by cylindrical spacers 1 8 with reinforcing spacers 20 between them.

The cylindrical spacers 1 8 are arranged, in a manner not illustrated for this embodiment but which will be described more fully with respect to the second embodiment and with reference to Figure 1 in parallel rows. The spacers in each row are in positions offset, in the longitudinal direction oF the rows (i.e. parallel to the side walls of the building) from the positions of the spacers in the next adjacent row or rows, to define a diagonal lattice with spacers 1 8 at some, but not all, of the nodes of the lattice. At the remaining nodes of the lattice, there are provided reinforcing means in the form of further thin-walled hollow cylinders 20.Each reinforcing cylinder is of the same diameter as the spacing cylinders 18, but its length is substantially smaller than its diameter, and its single flanged end portion 1 9 is welded to the adjacent web 1 6 or 1 7 to lend stiffness to the latter. The other end of each cylinder 20 is of course free.

The webs 16 and 17, and the spacing cylinders 1 8 and reinforcing cylinders 20, are all made of thin metal, viz. steel, and are constructed in the manner which will be described more fully with respect to the second embodiment. The steel surfaces are coated with metallic tin to resist atmospheric oxidation.

The two hip joints 14 are shown in end elevation, more clearly in Figure 3, and are formed from laterally-outwardly directed side flanges 21 of the outer webs of the respective panels 11, 1 3 or 12, 1 3, the flanges being bolted together with a stiffening plate 22 which extends over the whole length of the roof. Each pitch panel 11, 1 2 has, at its lower end as seen in Figure 4, the upper web 23 bent away from the lower web 24 adjacent to the lower side edge, as indicated at 25. Lateral edge flanges 26, which are co-planar, are formed on the lower web 24 and on the bent-up portion 25 of the upper web, and the flanges 26 are bolted to similar flanges of the next pitch panel 11, which is abutted to the panel 1 2 as shown, with a stiffening plate 27 between the flanges. As can be seen from Figure 4, the resulting junction between a pair of roof trusses is formed in a zone of box-like configuration which is extremely strong, and which may be reinforced by the provision of reinforcing cylinders 20, as shown, on the non-parallel edge portions of the outer webs 23 and 24.

The lower end flanges 26 of the panels at the extreme side edges of the roof are bolted to the parapet 6 in this example, though they may be secured in any other convenient manner to the walls of the building, for example through an angle-iron or beam secured along the top of the side wall. Elsewhere, the roof is secured to the end walls of the building by beams, blocks or brackets of suitable form (shown diagrammatically at 28 in Figure 2) to which the pitch panels 11, 12 may be bolted as indicated at 29. The elements 28 may consist of beams extending the length of the roof and supported on the end walls of the building; but where the anticipated loading on the roof is sufficiently light to warrant it, they may consist of simple brackets or blocks at the end walls only.

A walkway 30 of suitable material may be provided in the angle between each roof truss 10 and the next. Such a walkway can be arranged as completely to cover the bottom joint 1 5 and so protect the latter from the weather, and more particularly from rainwater collecting over the bottom joint.

The end of each truss 10 can be closed by any convenient means, for example a sheet of light aluminium such as is indicated at 31 in Figure 2, which can be formed with flanges at its upper edges and bolted through these flanges to the roof panels.

The exposed ends of the roof panels can similarly be closed off by plates 32 which are preferably of the same material as the outer webs 16, 17 or 23, 24 of the roof panels, the end closure plates 32 being welded to the webs to ensure watertightness. Alternatively, or in addition, the upper web of each roof panel may be made longer than the lower web so as to provide an end portion of the former extending beyond the end of the panel itself. This end portion can be bent down so as to obturate the open end of the panel, and may be welded or otherwise secured to the end edge of the lower web, or spaced laterally from it so as to provide a means for air to enter from below.The latter arrangement ensures circulation of air through the panel if required for purposes of preventing or reducing condensation within the panel or to reduce differences of air pressure and/or temperature across the outer webs of the roof panels.

It will be seen that each roof truss 10 is selfsupporting, i.e. it provides a clear span without the need for internal or external bracing. This is due to the inherent rigidity imparted to each roof panel by the form of construction described. This rigidity is obtained despite the thin gauge of the metal used.

In a modified form (not shown) of the roof truss shown in Figure 2, both ends of the lower web 17 of the spacing panel 13 are formed with bent-up portions like the portion 25 of the web 23 (Figure 4), and the web 23 of each pitch panel is similarly bent-up at its upper end, so that in place of the simple hip joints 14 shown in Figure 3, there is provided a box joint similar to the lower joint 1 5. In a further modification, using pitch panels having bent-up portions at both ends, the spacing panel 1 3 may be omitted so that each truss is of a simple inverted-V shape.At the expense of a larger number of bottom joints 1 5 for a roof of a given overall span made up of panels of a given width, this arrangement gives a stronger roof than that shown in Figure 2, and also permits the roof to be constructed from panels of a single standard design.

Referring now to Figures 8 and 9, in this second embodiment each roof truss, 40, consists of a pair of roof panels 41, 42 which are identical in construction. In endwise cross-section, each of these panels comprises three sections of different orientations, viz. a horizontal lower side section 43, a pitched section 44 inclined at 45 degrees to the horizontal, and an upper side section 45. The panels 41 and 42 are joined together in an upper joint 46 extending the full length of the roof, and each panel 42 is joined to the next panel 41 in a lower joint 47, also extending the full length of the roof.Since the upper joint 46 is half-way along the topmost portion of the truss, the upper sections 45 may advantageously but optionally, be slightly pitched, as shown in Figures 8 and 9, so as to allow for easy drainage of rainwater The angle of this pitch is preferably about 3 degrees to the horizontal.

In the form shown in Figures 8 and 9 the roof is secured to the side walls, 48, of the building by vertical bolts 49 through the lower section 43 of the extreme sidemost roof panels, and to the end walls 5 by further bolts 50. The bolts 49 and 50 restrain the roof from aerodynamic lift during severe gales. Figures 8 and 9 show the roof sloping downwardly towards one of its ends, and a drainage gutter 61 is indicated diagrammatically adjacent the lower end of the roof.

A walkway 62 is laid over each of the horizontal lower runs of roof, to provide access for maintenance purposes. These walkways may be of concrete tiles 63 (Figure 10) with an infill of bitumen 64 at the sides of the walkway. As will be described shortly, each joint 47 is optionally made so as to allow ingress of air to the interior of the roof panels, but where this provision is not made, the joint may be covered, for example with a further infill of bitumen, so as to seal it from rainwater. The walkways also serve to strengthen the upper webs of the roof panels against elastic buckling.

The actual construction of the roof panel 42 is shown in more detail in Figures 10 and 11. The upper web, 51, is again parallel to the lower web, 52, and is spaced from it by an array of thinwalled cylindrical spacers, the majority of which are the simple flanged cylinders 1 8 already described with reference to Figures 3 and 4. It should be noted that in Figure 10, some of the internal cylinders are, for clarity, omitted from the pitch section 44. The webs 51 and 52 are bent through the appropriate angles at the junctions between the three sections 43,44,45 of the roof panel, and in addition there are provided pairs of planar, internal stiffening webs 53 parallel to the planar outer webs 51 and 52 and extending across the bends in the latter.Each stiffening web 53 is bent similarly to the outer webs and extends a short distance to either side of the bend into the corresponding panel section 43, 44 or 45 at a spacing from the outer webs which is substantially constant, i.e. all the webs are parallel to each other.

The side edges of the upper and lower webs 51, 52 are formed with side flanges 66. Along opposite side edges of the roof, Figure 8, these flanges are secured to plate members 67 for closing off the side edges of the roof panels. The open ends of the roof panels may be closed or covered in a manner as already described with respect to the first embodiment. Figure 9 shows a portion 68 of the top web 51 bent over to cover the open end.

Referring to Figures 10 and 11, the joints 46 and 47 are identical and only the joint 47 need be described. The end flanges 66 of two abutting roof panels 41, 42 are secured together by bolts 69, but are spaced apart by a pair of perforated spacing or stiffening plates 70 with a spacing member 71 between the plates 70. The member 71 consists of an injection-moulded web of plastics material extending along the joint, i.e.

along the side of each of the roof panels. This web has vertical grooves 72 on both its sides, the grooves 72 extending past the upper side flanges 66, to permit ingress of air from above the roof to the interior of the panels 41, 42 via the perforations in the stiffening plates 70. The purpose of this air is to reduce condensation within the roof panels. An integral cover portion 73, from which the web of the member 71 depends, prevents entry of water into the grooves 72. A joint such as this may of course be employed between the roof panels in any embodiment of the invention, for example in the joints 14 and 1 5 in Figure 2.However, sufficient protection against condensation may be provided on the internal surfaces of the roof panels; or alternative provision can be made by ventilating these surfaces (for example by allowing for ventilation at the ends of the panels as described earlier herein in connection with the first embodiment, Figure 2); or the fibre or other infilling of the roof panels (mentioned hereinafter) may be such as effectively to prevent significant condensation occurring at all. In any of these three circumstances, ventilation along the side joints of the roof panels is unlikely to be necessary, and the spacing member 71 and perforated plates 70 can be replaced by a single plain stiffening plate like the plate 22, Figure 3, or 27, Figure 4.

As shown in Figure 6, the cylindrical spacers joining the stiffening webs 53 and the outer webs 51 and 52 all together comprise a pair of short double-ended cylinders 54, each securing the stiffening web to the adjacent outer web, and a similar, but longer, cylinder 55 aligned with the cylinders 54 and joining the two stiffening webs together, the various webs being welded to the end flanges of the spacers 54 and 55. At the upper bend the upper web 51, and at the lower bend the lower web 52, is joined to the adjacent stiffening web 53 by special cylinders 56 formed by welding together two mitred halves of a cylinder of the same length as the spacers 54.

Figure 11 shows the pattern in which the various cylinders are arranged. In this figure, the full-length spacer cylinders 18 are indicated diagrammatically by a circle enclosing an "X", the intermediate spacer cylinders 55 similarly by a circle enclosing an erect cross, and the reinforcing cylinders 20 by a plain circle. From Figure 11 it will be seen that the spacers 1 8 and the spacers 54, 55 are arranged in rows parallel to the ends of the roof panel. These rows are indicated by phantom iines 57 in Figure 11. The spacers 18 in each row are in positions offset, in the longitudinal direction, from the positions of the spacers 1 8 in each next row, so that these spacers define a square lattice 58 whose axes are at 45 degrees to the rows 57. The spacers 1 8 lie with their axes intersecting every third node of this lattice.At the remaining nodes are reinforcing cylinders 20 (Figure 5).

Figure 11 also shows holes 60 formed through the lower web 52 (which are aligned with further holes, not shown, through the upper web 51) to accommodate the bolts 50, Figures 8 and 9.

In this example the spacers 54, 55 or the spacers 56 as appropriate, are placed at every node of the lattice intersecting the stiffening webs 53, but it desired they may be provided only in the rows 57. In the latter case the remaining nodes may for example be occupied by spacers 54 without the intermediate spacers 55; or by spacers 54 with cylinders 20 in place of the spacers 55; or may be left empty. Any of these expedients will save weight as compared with the arrangement shown in Figure 11: this arrangement with full spacers at every node along the stiffening webs is only required where mechanical strength considerations call for it.

In the same way, it will be appreciated that where greater shear strength of the whole panel is required, this can be achieved, at the expense of greater weight, by providing spacer cylinders 1 8 at every node of the lattice 58 (other than where intersected by stiffening webs 53), or at every other node instead of at every third one as shown.

Similarly where lighter weight is required, and where strength considerations permit, there may be a reduced number of the full-length cylinders 18, e.g. one cylinder 1 8 for every three reinforcing cylinders 20 in the direction parallel to the sides of the panel. Again, the stiffening webs 53 are optional, but where they are provided they may extend over the whole panel or a larger part of it than shown in the drawings; and there may be any required number of such webs. Stiffening webs may be provided in the roof panels 10, 11, 12 of Figures 2 to 4 in any suitable manner as in the panels 41 or 42, though they would not need to be bent since the panels 10 to 12 are themselves planar.

In any embodiment of the roof structures exemplified in this description, the various spacing and reinforcing cylinders 1 8, 20, 56 may conveniently be of the construction, shown variously in Figure 5, 6 and 10, consisting of a thin sheet of tinplate whose opposed edges are joined in a welded longitudinal side seam 59. Such cylinders may be made on conventional machines of the kind used for making can bodies of the same construction; and indeed can bodies of standard sizes may actually be employed. A typical roof panel 41 or 42 (Figure 10) has its outer webs 51,52 and stiffening webs 53 made from 0.25 mm tinplate, the spacing cylinders 18 being 200 mm high. The pitch of the square lattice 58 in this example is 0.1 metre, the reinforcing cylinders 20 being 10 mm high.All of the cylinders 18,20, 54-56 are of 0.27 mm wall thickness and 75 mm diameter, and are welded to the various webs by spot welding. Each of the outer webs 51,52 measures 1 metre x 9 metres and has an electroferritic coating to provide corrosion resistance. This coating may be replaced, if desired, by a zinc coating on at least the upper surface of the roof panel. The various internal surfaces of the panel may also be given a corrosion-resistant coating, e.g. an electroferritic layer with an additional layer of wax. As has been suggested already above, the interior of the panel may have a loose infill of a suitable fibre or foam material to reduce heat loss by convection through free circulation of air within the panel. In addition, the underside of the lower web of each roof panel may be white, to offer good light reflection.

A panel 41 or 42 as described above has an approximate weight of 10 kg/m2 without coatings, infill and joints. The complete roof may weigh about 13 kg/m2. Such panels have adequate strength, over a 9 metre length of roof span, to sustain a uniformly distributed load of at least 720 N/m2.

The panel size may be up to 3 metres in width without introducing problems of transport. A truss comprising panels of this size can still sustain the abovementioned uniformly distributed load.

It will be appreciated that additional loads such as lighting, maintenance scaffolding, and other services can be suspended from discrete points on the roof panels, provided the panels are designed to allow for such loads.

A number of possible variations in the design and construction of the roof panels, and of roofs consisting of such panels, have already been mentioned above. Many others will suggest themselves, within the scope of this invention, to the person knowledgeable in the arts represented here. For example, the axes of the lattice 58 in Figure 11 may be parallel with the sides and end of the panel instead of at 450 thereto. The upper surface of the roof may be covered with any suitable covering, particularly if the roof is intended to be permanent, or if it is subject to particularly severe weather conditions. An example of such a covering consists in nonoverlapping tiles, hexagonal or rectangular, bonded to the roof with a conventional bitumen adhesive compound.The suspension load capacity of the roof panels must of course be suitably increased (e.g. by providing a greater density of the spacer cylinders 1 8 as already discussed) to match the increased weight of the panels due to the addition of tiles.

Although the examples described above all employ planar outer webs in the roof panels, it is important to understand that the invention is equally applicable to the construction of a domed roof, in which the dome is formed generally as described with reference to Figure 1. For example, a roof panel may consist of a planar portion of any desired plan shape, with an integral dome rising from it. To achieve this, it is simply necessary to form the outer webs to define the dome as part of a sphere, with flat portions extending from the base of the dome, these webs being joined together, and reinforced as necessary, using cylindrical members, with or without stiffening webs, in the manner already described. A roof for a rectangular building may then consist of one or more of such panels, joined together at straight edges of their planar portions.Such a roof having a number of domes will offer considerable mechanical strength and load-bearing capacity.

One possible drawback of an all-metal roof is the ease with which heat from inside the building may be lost (or the building overheated by the sun) through conduction of heat by the spacing cylinders 18, 54, 55. Figure 7 shows one possible form of cylindrical spacer which reduces this conduction.

In Figure 7, there is shown a composite spacer comprising a pair of thin-walled, hollow cylindrical metal end portions 75, each of which is generally similar to one of the reinforcing cylinders 20 (Figure 5) but which is provided with a helical thread. The cylindrical end portions 75 are welded to the outer webs (which for the purposes of Figure 7 are taken arbitrarily to be the webs 1 6 and 17 of Figure 3). The threads of the two end portions 75 may optionally be of opposite hands.

A load-bearing, hollow sleeve 76 of a suitable non-metallic thermal insulating material is secured to the threaded end portions 75 to complete the spacer. The sleeve 76 may be of a suitable grade of fibre chipboard.

Claims (42)

1. A roof element comprising a plurality of thin metal webs each in the form of part of a sphere of infinite radius or less, the webs being laterally spaced apart and joined together by an array of spacers in the form of thin-walled hollow cylinders, each having its axis generally perpendicular to the webs to which the cylinder is joined.

2. A roof element according to Claim 1, wherein at least one of the webs has reinforcing means in the form of further thin-walled hollow cylinders secured at one end to the web and having their other ends free.

3. A roof element according to Claim 1 or Claim 2, in which the webs are substantially planar and wherein the spacers are arranged in parallel rows, the spacers in each row being in positions offset, in the longitudinal direction of the rows, from those of the spacers in the next adjacent row or rows, to define a lattice whose axes are inclined to the said direction, the axes of the spacers being disposed at nodes of the lattice.

4. A roof element according to Claim 3 when dependent on Claim 2, wherein the reinforcing cylinders are disposed at further nodes of the said lattice.

5. A roof element according to Claim 4, wherein at least one web has two said reinforcing cylinders between each spacer and the next along each axis of the lattice.

6. A roof element according to any one of the preceding claims, wherein each cylinder is joined to a said web by a thin-walled, hollow cylindrical metal end portion of the cylinder.

7. A roof element according to Claim 6, wherein each said end portion is joined to the appropriate web by welding.

8. A roof element according to Claim 6 or Claim 7, wherein each said end portion has a generally radial flange, the flange being joined to the appropriate web.

9. A roof element according to any one of Claims 6 to 8, wherein the whole of each cylinder is of thin-walled generally-cylindrical construction.

10. A roof element according to Claim 9, wherein each cylinder is in one piece.

11. A roof element according to any one of Claims 6 to 8, wherein each of at least some of the said spacers is in composite form comprising a pair of said thin-walled, hollow cylindrical metal end portions axially spaced apart and joined together by a generally-cylindrical intermediate portion of non-metallic, thermally insulating material.

12. A roof element according to Claim 11, wherein said non-metallic thermally-insulating material is fibre chipboard.

13. A roof element according to Claim 11 or Claim 12, wherein said intermediate portion is hollow.

14. A roof element according to any one of Claims 11 to 13, wherein each metal end portion of each composite spacer has a helical thread of opposite hand to that of the other end portion, the intermediate portion being secured to the end portions by said threads.

1 5. A roof element according to any one of the preceding claims, wherein each cylindrical metal component joined to a web is formed from thin metal sheet whose opposed edges are joined in a longitudinal side seam.

16. A roof element according to Claim 1 5, wherein said side seams are welded.

17. A roof element according to any one of the preceding claims, wherein each thin-walled hollow cylindrical component joined to a web is of steel.

1 8. A roof element according to any one of the preceding claims, wherein the thin metal webs are of steel.

19. A roof element according to Claim 1 7 or Claim 18, wherein the steel is coated with an oxidation-resistant coating.

20. A roof element according to Claim 19, wherein the said coating is metallic tin, the metal being tinplate.

21. A roof element according to any one of the preceding claims in the form of a panel having, in at least one of its sides, said webs formed with laterally-outwardly directed side flanges for securing the panel to another element of a building.

22. A roof element according to any one of the preceding claims in the form of a pitch panel having a pair of outer said webs joined by said spacers, at least one of the outer webs being bent away from the other outer web adjacent to a side of the panel, the outer webs at that side terminating in a common plane inclined to the panel, whereby when a similar panel is arranged with its corresponding side abutting the said side of the panel, the outer webs define a zone of boxlike configuration at which the two panels can be joined together.

23. A roof element according to any one of Claims 1 to 21, in the form of a panel having a pair of outer said webs joined by said spacers, the webs being bent so that in endwise cross-section the panel comprises a plurality of sections of different orientations.

24. A roof element according to Claim 23, wherein the panel comprises at least one first section, at least one second section laterally displaced from the first section or sections, and a further section joining the or each first section to the next adjacent second section or to each next adjacent second section, the or each said further section being inclined to the sections connected thereby.

25. A roof element according to Claim 23 comprising one said first section, one said further section and one said second section, wherein the second section is inclined with respect to the first section by an angle substantially smaller than that between the first section and the same further section.

26. A roof element according to Claim 25, wherein the angle of inclination between the first section and said further section is 30.

27. A roof element according to any one of Claims 24 to 26, wherein the angle of inclination between the or each said first section and the further section or sections connected therewith is 450.

28. A roof element according to any one of Claims 22 to 27, having at least one stiffening web laterally spaced from, and disposed intermediate between, the outer webs across each bend in the latter, the or each stiffening web being bent similarly to the outer webs so as to extend a relatively short distance, into each of the sections of the panel on either side of the bend, at substantially constant spacing from the outer webs, the said webs being joined together by appropriate ones of the said spacers.

29. A roof element in the form of a panel according to Claim 21, or to any one of Claims 22 to 28 when dependent on Claim 21, when joined to another roof element by means of fastening means securing the side flanges of the panel to the other roof element, at least one of the side flanges being spaced from the other roof element by a spacing member adapted to allow air to enter the interior of the panel past the side flange.

30. A roof element according to Claim 29, in combination with a said spacing member and a said other roof member, wherein the spacing member comprises a web extending along the side of the panel, the web having grooves extending past at least one of the side flanges of the latter for ingress of air therethrough to the interior of the panel.

31. A combination according to Claim 30, wherein the other roof element is an element according to any one of Claims 1 to 28, the spacing member having said grooves on both sides of its web.

32. A roof for a building, comprising a roof element according to any one of Claims 1 to 28, or a plurality of such roof elements, joined together along respective side edges thereof.

33. A roof for a building comprising a plurality of panels according to Claim 29, wherein the said other roof elements comprise, along opposite side edges of the roof, plate members for closing off the side edges of the corresponding roof panels.

34. A roof according to Claim 32 or Claim 33 wherein each roof panel forms part of a combination according to Claim 30 or Claim 31.

35. A roof element according to any one of Claims 1 to 28 wherein the interior of the element, at least outside the hollow spacers, is filled with a thermally insulating material.

36. A roof element in the form of a pitch panel, constructed and adapted to be arranged substantially as hereinbefore described with reference to, and as illustrated in, Figures 2 to 6 of the drawings hereof.

37. A roof element in the form of a spacing panel, constructed and adapted to be arranged substantially as hereinbefore described with reference to, and as illustrated in, Figures 2, 3, 5 and 6 of the drawings hereof.

38. A roof element in the form of a panel, constructed and adapted to be arranged substantially as hereinbefore described with reference to, and as illustrated in, Figures 5, 6, and 8 to 11 of the drawings hereof.

39. A roof element according to any one of Claims 36 to 38, but in which the spacers are constructed and arranged substantially as hereinbefore described with reference to, and as illustrated in, Figure 7 of the drawings hereof.

40. A roof for a building comprising at least one pair of pitch panels according to Claim 36, and between the pitch panels of the or each pair a spacing panel according to Claim 36, the roof being constructed and arranged substantially as hereinbefore described with reference to, and as illustrated in, Figures 2 to 4 of the drawings hereof.

41. A roof for a building comprising roof panels according to Claim 38, the roof being constructed and arranged substantially as hereinbefore described with reference to, and as illustrated in, Figures 8 to 11 of the drawings hereof.

42. A building having a roof according to any one of Claims 32 to 34,40 or 41.