ROOF TILES

Abstract: An interlocking roof tile (1) of which the leading end portion (12) at least as far as the leading end of, and including the underlock (6) is tapered in the direction of the leading edge (5) of the tile (1).

Description: 8QQE__ * _ . ILES The present invention relates to roof tiles and more particularly but not exclusively to roof tiles made of a cementitious mixture such as concrete or other material such as clay which are laid in broken bond, e.g. so called slate and plain tiles. Roof tiles can be made from a cementitious mixture including sand and/or other aggregate, cement, colouring pigment and water plus optionally one or more other additives to facilitate " extrusion, prevent growth of fungus etc. Such tiles have been produced by extrusion for over forty years with apparatus including a hopper-like box which is disposed above a conveyor path and which is charged with the cementitious mixture. The flow of the cementitious mixture is assisted in the box by means of a rotating paddle disposed therewithin. A succession of pallets for moulding the undersurface of the tiles is driven along the conveyor path and beneath the box so that the cementitious mixture forms on the pallets and is compressed therein by means of a rotating roller disposed within the box downstream of the paddle and having a contour which corresponds to the upper surface of the tiles to be formed. The cementitious mixture is further compressed on the pallets as they pass out of the box by means of a slipper which is disposed downstream of the roller and also has a contour which corresponds to that of the upper surface of the tile to form a continuous extruded ribbon of cementitioue mixture on the pallets. The ribbon is subsequently cut into tile forming lengths downstream of the box by means of a — i. suitable cutting knife and the pallets with the formed tiles thereon are conveyed to a curing location. At the curing location, the tiles are conveyed through a curing chamber which is maintained at a high relative humidity and temperature. The curing time is usually in excess of 6 hours. The tiles undergo only a partial curing in the curing chamber from whence they are conveyed to, and stacked, out-of-doors, to complete the curing process. Natural slate and concrete plain tiles are as, is known, laid on the roof in broken bond and double lapped, i.e. so that there there is always a tile underneath the abutting side edges of adjacent tiles to guard against rain and wind driven water entering into the roof space between the abutting side edges. Traditionally, natural slates have a generally flat geometry with a substantially constant thickness of approximately 10mm and have a laid weight of 2 approximately 20-40 Kg/m . On the other hand conventional concrete plain tiles have a cambered geometry, a substantially constant thickness of 2 approximately 12 mm and a laid weight of 75 kg/m . With both natural slate and concrete plain tiles the leading edge (i.e. the lower edge) thickness when the tiles are laid provides an aesthetically pleasing appearance. However, it has long been an object to avoid the necessity to double lap the tiles to reduce the number of laid tiles per roof and therefore the cost but still retain the aesthetic appearance produced by broken bond laying, and a visible leading edge similar to existing clay and concrete plain tiles and natural slates, in particular in the case of retiling old roofs. Applicants have manufactured interlocking extruded concrete slate tiles which avoid the necessity for double lapping and which have the generally flat geometry of a natural slate and a substantially constant edge thickness. However, the leading edge thickness is 25mm and is necessary in order to provide sufficient strength to avoid breaking off, and to accommodate, the interlocks, i.e. the over and underlocks extending along opposite side edges respectively of each tile. Whilst such concrete slate tiles are designed to be laid in broken bond they are not specified in preference to natural slate and conventional plain tiles because the aesthetic appearance is wrong, i.e. the leading edge thickness is twice that of the optimum required thickness. Furthermore, although the undersurfaces of the tiles have been hollowed out to reduce the weight, the laid weight of these known concrete/interlocking slates is 2 still 52 kg/m which is considerably more than that of natural slates so that the replacement of natural slates by concrete slates in retiling would require the additional expense of strengthening or replacing the roof timbers. Even if these known concrete slates were made of material which reduced the weight of tiles, such a step would decrease the leading edge thickness only down to 18mm which is still too thick to compete against natural slates and conventional plain tiles. Accordingly the main object of the present invention is to provide an interlocking roof tile which can be laid in broken bond and in which the aforesaid disadvantages are minimized or avoided. To this end, the present invention consists in an interlocking roof tile, of which the leading end portion including the underlock , at least as far as the leading end of the underlock is tapered in the direction of the leading edge of the tile. By means of the invention the leading edge thickness may be substantially reduced i.e. to as little as approximately 10mm, which is less than that of conventional plain tiles and compares favourably with the body thickness of natural slates. Without changing either the geometry of the pallets or the tile extrusion head, in the case of extruded tiles, a concrete slate tile can be transformed into a plain tile or rather a double-plain tile by a simple operation performed either on the upper surface of the extruded cementitious material ribbon or tile forming lengths, severed from the ribbon. Thus, the invention provides interlocking roof tiles which have the appearance and perceived thickness of plain tiles or similar thickness to natural slate and which are capable of being laid either in straight or broken bond and of being made to a laid weight of say 2 approximately 20 to 28 kg/m , whereby to form a completely satisfactory replacement for natural slate roofing. Tiles made in accordance with the invention may be of flat or of cambered geometry, whichever is preferred or desirable. For example to produce a look-alike concrete slate a tile of fiat geometry is acceptable and may be even be preferred. In some instances it may be aesthetically desirable for the underlock not to be visible when laid, to which end the underlock may end short of the leading edge of the tile. With such a construction it is possible to have the undersurface of the leading edge portion of the tile beyond the leading end of the underlock disposed generally parallel to the opposed upper surface of the tile, which reduces the amount of material required to make the tile and therefore its weight. Conveniently, therefore, there is a step between the leading end of the underlock and the undersurface of the adjacent leading edge portion of the tile beyond the underlock. Applicant has made such tiles with a reduction in the thickness of the leading edge of approximately 6mm. Preferably the underloσks for such tiles will be typically approx. 8mm thick at the thickest point reducing to approx 4mm thick at the overlapping portion. Furthermore, by means of the tapered leading end portion of the tile, the tile undersurface in the leading edge region can abut closely against the upper surface of the next adjacent lower line of the tiles . The scale of the thining to produce the tapered leading end portion of the tile advantageously enables there to be an overlap with each next adjacent lowest line of tiles cf typically 75mm approx. and the tile to have, conveniently, with tiles of cambered geometry to have a camber of approx .1600-1800mm . radius cf curvature. Advantageously, the tile is made of any of the cementitous mixtures or materials described in the specification of our PCT/GB88/00591 application, the subject matter of which is incorporated into the specification of this application by reference. In order to provide a plain tile instead of a concrete slate, the upper surface of the extruded ribbon or tile forming lengths are provided with a continuous or non-continuous groove, e.g. by means of a knife or wheel, which extends from the upper edge or end to the leading end or edge of the tile. Thus, there is, in effect, produced a one piece tile which has the appearance of two plain tiles. It should be understood that, in this specification reference to a plain tile includes such a tile having the appearance of two or more plain tiles. In order that the invention may be more readily understood, some embodiments thereof will now be described, by way of example, with reference to the accompanying drawings, in which:- Figure 1 is a top plan view of one embodiment of concrete roof tile made in accordance with the invention and in the form of an interlockinα concrete slate. Fiσures 2 and 3 are UDDΘΓ an 1 pad.r.σ pnri or edσe views resnprtivplw nf t * hp slshps nf Riπnrp 1. Fiπnrp & i * . -, t * nn nlan VIPV. nf another embodiment in t * hρ form nf •* . rπncrete _ nt r1 ockinσ double nlain H 1 P. FI ΠDΓPS 5 and 6 are unnpr 1 ps inr. pnri nr PIΪΠP VI P P resDectivelv of the tile of Fiαυre 4. Fiσure 7 is an underneath plan view of the concrete slate of Figure 1 and the plain tile of Figure 4, Figures 8 and 9 are opposite side views respectively of the concrete slate of Figure 1 and plain tile of Figure 4, Figures 10 and 11 are cross-sections taken along the lines A-A and B-B respectively of Figure 7, Figure 12 is a diagrammatic cross-section through a roof structure tiled with the concrete slates of Figure 1 or plain tiles of Figure 4, Figure 13 is diagrammatic perspective view of a tiled roof tiled with the slates of Figure 1, Figure 14 is a diagrammatic perspective view of a tiled roof tiled with the plain tiles of Figure 4, Figures 15 and 16 are opposite side views similar to those of Figures 8 and 9 of another embodiment , and Figures 17 and 18 are cross-sections similar to those of Figures 10 and 11 of the embodiment of Figures 15 and 16. The concrete slate 1 shown in Figures 1,2 3,7,8,9,10 and 11 is of generally rectangular configuration when considered in plan, and has upper and undersurfaces 2 and 3 respectively, an upper edge 4, a lower (leading) edge 5 and interlocks extending along its opposite side edges i the form of an underlock 6 and an overlock 7, which respectively engage with the over and underlocks of adjacent tiles of the same row. In the leading edge region cf the tile the underlock 6 ends short of the leading edge to provide a cut-out 8, which enables the aesthetic appearance of a natural slate and normal plain tile to be maintained because the underlocks do not extend to the leading edge of the tile and are therefore not visible when the tiles are laid on a roof. As is shown in Figure 7 the undersurface 3 of the tile is provided with two or more hanging nibs such 9 and wind barriers 10. The tile may be provided with nail holes (not shown) adjacent the nibs 9. or, alternatively, as is preferred, securing clips (not shown) may be used instead of nails. Also, the undersurface 3 has hollowed out portions 11, as is known, to reduce weight . The tile 1 is of cambered geometry with the camber extending from the upper edge 4 to leading edge 5 as will be apparent from Figures 8 to 11. In accordance with the invention, and to enable reduction of the leading edge thickness, and as will be readily apparent from Figures 8 to 12, the leading end portion 12 of the tile at least as far as the leading end of the underlock 6 is tapered in the direction of the leading edge 5 i.e. is thinned, by making the pallets on which the tiles are extruded of an appropriate shape, thereby to produce a leading edge which is aesthetically acceptable. It should be appreciated that tapered area extends transversely across the undersurface of the tile except for the hollowed out positions. Furthermore, the undersurface 13 of the leading portion beyond the underlock 6 extends generally parallel to the upper surface 2 of the tile with there being a step 12a between the undersurface 13 and the undersurface of the tapered leading end portion 12. The plain tile la illustrated in Figures 4,5 and 6 differs from the concrete slate illustrated in Figures 1 and 2 only in that it has a longitudinal groove 14 running the full length of the tile la to form a one piece two tile plain tile la, each of which is designated by the reference lb. In Figure 12, the tiles 1 or la are mounted on battens 15 fixed to roof rafters such as 16 with the roof felt being shown at 17. Figures 13 and 14 respectively show how the concrete slates ' 1 and plain tiles la (tiles lb) appear as a tiled roof with their narrow, aesthetically acceptable leading edges 5. The embodiment of Figures 15 to 18 differs from those of Figures 1 to 3 and 7 to 11, and Figures 4 to 11 in that the tapering leading end portion 12 of the tile merges or extends into the undersurface 13 of the leading edge portion of the tile in the direction of the leading edge 5 without a step 12a to form a tapered undersurface 18, which extends transversely across the tile and which is inclined at an angle to the upper surface of the tile. The tapering nature of the surface 18 can be readily appreciated from Figures 17 to 18. The tiles of Figures 15 to 18 lie in a similar manner to those of Figures 1 to 3,7 to 11 and Figures 4 to 11 as shown in Figures 12 to 14. However, an advantage of the embodiment of Figures 1 to 3.7 to 11 and Figures 4 to 11 as compared to that of Figures 15 to 16 is that less material is required for the leading edge portion between the leading end of the underlock 6 and the leading edge 5, thereby further reducing the weig t of the tiie. Whilst particular embodiments have been described, it should be appreciated that the invention is not limited thereto but includes all modifications and variations falling within its scope. For example, in the embodiment of Figure 4 the groove 14 need not extend the whole length of the tile, e.g. it may be eliminated in the region of the overlap. Moreover, whilst the invention is particularly applicable to extruded roof tiles made of cementitious mixtures, such as concrete, the roof tiles could equally be made of clay which could be pressed, moulded or extruded and, the cementitious material or concrete tiles can also be made by a pressing or moulding operation. Furthermore, it should be understood that the expression "roof tiles also includes cladding tiles.

Claims: C AIMS 1. An interlocking roof tile of which the leading end portion including the underlock , at least as far as the leading end of the underlock, is tapered in the direction of the leading edge of the tile. 2. A roof tile as claimed in claim 1, wherein the leading edge has a thickness of approximately 10-12mm. 3. A roof tile as claimed in claim 1 or 2, and capable of being made to a laid weight of 2 approximately 20 to 40 Kg/m. 4. A roof tile as claimed in any one of claims 1 to 3, wherein the underlock has a thickness which reduces from about 8mm at its thickest location to about 4mm at that position of the tile which, in use, overlaps the uppersurface of at least one tile of the next adjacent line of tiles. 5. A roof tile as claimed in any one of claims 1 to 4 and capable of being a slate tile and a plain tile. 6. A roof tile as claimed in claim 5, and having a longitudinal groove in its uppersurface to form a one piece, two tile plain tile. 7. A roof tile as claimed in any one of claims 1 to 6, and being capable of having an overlap, in use, with at least one tile of the next adjacent line of tiles of at least approximately 75mm. 8. A roof tile as claimed in any one of claims 1 to 7, and designed to be laid in straight and broken bond. 9. A roof tile as claimed in any one of claims 1 to 8 wherein the undersurface of the leading edge portion of the tile beyond the leading edge of the underlock is disposed generally parallel to the opposed uppersurface of the tile. 10. A roof tile as claimed in any one of claims 1 to 9, wherein there is a step between the leading end of the underlock and the undersurface of the adjacent leading edge portion of the tile beyond the underlock, 11. A roof tile as claimed in any one of claims 1 to 9, wherein the taper of the leading end portion including the underlock merges into the undersurface of the adjacent leading edge portion of the tile. 12. A roof tile as claimed in any one of claims 1 to 11, and of cambered geometry with the camber being approximately 1600-1800mm radius of curvature. 13. A roof tile as claimed in any one of claims 1 to 11 and of flat gemoetry. 14. A roof tile as claimed in any one of the proceding claims, wherein the underlock ends short of the leading edge of the tile. /

Inventors: FIFIELD JOHN ALFRED, HAMMOND LESLIE GERALD, FIFIELD, JOHN, ALFRED, HAMMOND, LESLIE, GERALD
Applicants: ANCHOR BUILDING PRODUCTS LTD, ANCHOR BUILDING PRODUCTS LIMITED
Application year: 1989
Main classification: E04D1
IPC codes: E04D1