METHOD FOR MAKING ROOFING PLATES

Abstract: A sloping roof structure comprises a supporting struc­ ture (72) and a plurality of elastically flexible, outwardly convexly curved roofing plates (74) mounted thereon. The roofing plates are mounted in a partly overlapping rela­ tionship so that the lower rim portion of each plate overlaps the upper rim portion of an adjacent lower plate. Each roofing plate is fastened to the supporting structure by means of nails (75), screws or other fastening means at a portion intermediate of the upper and lower rim portions of the plate. The initially curved plate is fixed in an at least partly flattened condition, whereby the upper and lower rim portions are resiliently pressed against the supporting structure (72) and the outer surface of the adjacent lower plate, respectively. The curved roofing plates (74) for such a roof structure may be made from a layer (37) of a plastic, deformable material, such as a cement mixture which may be reinforced by fibers. This layer of material may be placed on a curved supporting surface (70) so that the layer of material attains a shape similar to that of the supporting surface. The layer of material may then be hardened or set while supported by the curved supporting surface.

Description: The present invention relates to a method for making roofing plates, said method comprising the steps of continuously forming a substantially planar deformable web-like layer of a hardenable, fibre-reinforced cement mixture material in a plastic condition and moving said layer in its longitudinal direction, successively cutting separate layer lengths from the free end portion of said layer, each length having dimensions corresponding to the dimensions of the roofing plates to be made, and hardening the layer lengths cut. EP-A-67 456 discloses such a method, in which the fibre-reinforced cement mixture material is formed between a pair of spaced belts, which are passed around and backed up by opposite pairs of moving rollers. Prior to curing treatment the plane sheet thus formed may be rolled and compressed into corrugated roof panels or compression-shaped into any desired shape, for example as a roof tile. US-A-1,627,266 discloses a method of making curved roof tiles, wherein a cement mixture is poured into an upwardly open mould and spread to a height corresponding with the rise of the sides of the mould. After casting of the tile a surface texture and colouring may be secured by applying a surface material directly upon the smoothed upper surface of the cement mixture while it is still wet. Roof structures, wherein the roofing plates are in the form of tiles, corrugated roofing plates and plane roofing plates, are well-known. The tiles or roofing plates are normally fastened to a wooden supporting structure by suitable fastening means. Because the outer surface parts of the supporting structure to which the roofing plates are fastened are normally not totally plane (for example due to climatic influences), a more or less pronounced space or gap may be formed between each roofing plate and an overlapping lower portion of an adjacent upper roofing plate. It may be necessary to seal these gaps or spaces by means of sealing means in order to prevent drift snow, dust and the like from passing through the spaces defined between adjacent roofing plates. Furthermore, the varying spaces or gaps are unsightly. The method according to the invention is characterized in passing the layer through a surface treating station for imparting a desired textured pattern to the upper surface of the layer, transferring each of the non-hardened, substantially plane layer lengths to a respective one of a plurality of upwardly convexly curved supporting surfaces, maintaining the material of the layer lengths in a formable condition on the curved supporting surfaces for a time period sufficiently long to impart to each layer length a shape similar to that of the supporting surface, hardening the layer length material while supported by said supporting surface so as to provide curved roofing plates which are elastically flexible and having their upper surfaces provided with a desired textured pattern. By the method according to the invention a textured pattern may be applied to the continuously formed web-like layer in a rational manner and each of the roofing plates cut therefrom may be given a curved shape without influencing the textured pattern previously applied. As the roofing plates are to some extent elastically flexible in the direction of curvature, they may be mounted on a sloping roof structure so that the lower rim portion of each plate overlaps the upper rim portion of an adjacent lower plate. A portion of each plate intermediate of its upper and lower rim portions being fastened to the supporting structure with the initially curved plate in an at least partly flattened condition, whereby the upper and lower rim portions of the plate are resiliently pressed against said supporting structure and the outer surface of the adjacent lower plate, respectively. In this roof structure irregularities of the abutment surfaces of the supporting structure are compensated for by the initially curved, but more or less flattened roofing plate so that a substantially tight roof structure may be obtained without using special sealing means. The individual roofing plates may be fastened to the supporting structure by means of any type of known fastening means or fastening members which may draw or press the intermediate part of the roofing plate towards the abutment surface of the supporting structure. Thus, the fastening members may engage with formations formed on the inner side of the roofing plates, or the fastening members may extend through the plate and each have an abutment at its outer end for engagement with the outer surface of the roofing plate. As an example, the fastening means or fastening members may comprise nails, screws, and the like. When the fastening members extend through an opening formed in the roofing plates, such opening and the fastening member mounted therein are preferably covered by the lower overlapping rim portion of the adjacent upper plate in order to prevent rain and other liquid from flowing through such opening. The invention will now be further described with reference to the drawings, wherein Fig. 1 is a perspective and partially sectional view of an extruder for use in making a fiber-reinforced layer of material, Fig. 2 is a perspective view of a rolling, surface treating, cutting and drying station for treating the layer of material formed by the extruder shown in Fig. 1, and Fig. 3 illustrates how curved roofing plates formed in an apparatus or plant as that illustrated in Figs. 1 and 2 may be mounted so as to form a roof structure according to the invention. Fig. 1 illustrates an extruder generally designated by 10 comprising a substantially cylindrical housing 11 with an upwardly extending material inlet 12 at one end and an axially extending extruder nozzle 13 at the other end. A conveyor screw 14 extends axially within the housing 11 and may be rotated by means of an electric motor 15 through a belt drive 16. The extruder nozzle 13 is mounted in an end wall 17, which is fastened to a radially extending flange 18 on the housing 11 by means of bolts 19, and the extruder nozzle comprises inner and outer nozzle tubes 20 and 21, respectively, which define an annular nozzle passage 22 therebetween. The outer nozzle tube 21 is mounted on the end wall 17 by means of a mounting collar 23, and the inner end of the inner nozzle tube 20 is supported on a rotatable central shaft 24 by means of a ball bearing 25. An extrusion member 26 fastened to the inner end of the central shaft 24 is rotatably mounted in a bearing 27 and has a peripheral part extending radially into and obstructing the inlet end of the annular nozzle passage 22. A helically extending extrusion channel 28 is formed in the peripheral part of the extrusion member 26 and interconnects the inner space of the housing 11 and the annular nozzle passage 22. The shaft 24 and the extrusion member 26 mounted thereon may be rotated by means of an electric motor 29 through a suitable drive 30, such as a belt or chain drive. A circular cutting knife 31 is rotatably mounted between a pair of longitudinally extending structural members 32 which form part of an extruder frame 33. The cutting knife 31, which is driven by an electric motor 34, is in contact with a backing pad 35 of a suitable non-metallic material. In operation the electric motors 15 and 29 rotate the conveyor screw 14 and the extrusion member 26 in opposite directions as indicated by arrows in Fig. 1, and the electric motor 34 rotates the cutting knife 31. A formable plastic material or mass, such as a cement mixture, containing reinforcing fibres may now be fed into the material inlet 12. The rotating conveyor screw 14 then forces the material towards the inner surface of the end wall 17, which defines a funnel-shaped inlet to the annular passage 22. The formable mass which is continuously forced into contact with the rotating extrusion member 26 is forced to flow through the helically extending extrusion channel 28 as an extruded flow or stream which is continuously forced into the annular passage 22 in a helical arrangement. While the material is forced or extruded through the channel 28, the orientation of the fibres contained in the material tends to become more or less directed into the direction of movement through the channel 28. This means that the reinforcing fibres contained in the material being forced through the annular passage 22 downstream of the extrusion member 26 have a predominantly peripheral orientation. This predominantly peripheral orientation may to some extent be neutralized during the further extrusion of the material through the annular passage 22. When the extruded cylindrical body formed by the formable material meets the cutting knife 31, the extruded body is continuously cut or slit along a generatrix, and the slit, extruded body may be flattened out by means of suitable guide members 36 extending outwards from the outer surface of the inner nozzle tube 20. Thus, the slit, flattened tubular body is formed into a flat layer 37 of material which may be passed onto a conveyor belt 38 or a similar conveyor device. In Fig. 1 transversely extending, spaced dotted lines indicate the border lines between the now united turns of the helical stream or flow of material extruded into the annular passage 22. As indicated in Fig. 1, the reinforcing fibres in the layer 37 may be orientated more in the transverse direction than in the longitudinal direction of the layer. The orientation of the fibres may, however, to a high extent be varied by varying factors, such as the cross-sectional area and length of the channel 28, the rotational speed of the extrusion member 26, the cross-sectional area and the axial length of the annular nozzle passage 22 downstream of the extrusion member 26, and the extrusion pressure generated within the extruder housing 11. As shown in Fig. 2, the conveyor belt 38 may move the flattened layer of material 37 to a roller station, which is generally designated by 40 and which may, for example, be of the type disclosed in EP-A-82 105303.0. However, in the embodiment shown in Fig. 2, the roller station 40 comprises a pair of oppositely arranged rollers 41 which are rotatably mounted in bearings 42 in a frame, not shown, and the rollers 41 are rotated at the same rotational speed by means of synchronous motors 43. In order to ensure that the material 37 which is fed through the nip defined between the rollers will pass through the nip without sticking to the rollers, the material 37 is passed through a space defined between adjacent runs of a pair of gas-permeable endless belts 44. Each belt 44 is passed around an associated one of the rollers 41, a guide roll 45 and a cylindrical bar or roller 46, which has a small diameter and is stationary or rotatably mounted on a rib of an angle bar 47 extending transversely to the direction of movement of the belts 44. The belts 44 may be retained in the correct position on the rollers 41 by means of photocells, mounted in fork shape members 48, controlling pneumatic or hydraulic cylinders 49 by means of a suitable device (not shown). When passing through the nip between the rollers 41 and the space defined between the adjacent runs of the belts 44, the layer of material 37 is rolled and compressed so that it obtains an increased width and a uniform, reduced thickness. The rolled layer of material 50 leaving the roller station 40 is passed onto a conveyor belt 51 and moved through a surface treating station 52. This station comprises a whipping device formed by a shaft 53, which is rotatably mounted in bearings 54 and extends above and adjacent to the upper surface of the layer of material 50 and transversely to the movement of this layer. A plurality of string or wire lengths have one end fastened to the peripheral surface of the shaft 53 which is rotated by an electric motor 56 through a belt or chain drive 57. When the shaft 53 is rotated by the motor 56, the uncured or unhardened upper surface of the rolled layer of material is whipped by the free ends of the string or wire lengths 55, whereby a desired textured pattern is imparted to the upper surface of the layer 50. It should be noted that a whipping device as that shown in Fig. 2 may be used for treating a layer of material which has been made in any manner. Thus, for example, the layer of material may be extruded in its flat condition. From the surface treating station 52 the rolled layer of material 50 is moved to a cutting station 58, which comprises a pair of motor-driven rim cutters 59 for cutting the rolled layer of material 50 to a desired width, and a rotating cutter 60 for cutting the rolled layer of material 50 transversely into desired lengths or plates 61. The cutter 60 is driven by an electric motor 62 and moved reciprocatingly along transversely extending guide bars 63. Because the layer 50 should be cut transversely while the layer is moving in a longitudinal direction, the guide rods 63 on which the cutter 60 and the motor 62 are mounted are parts of a carriage 64 which may be moved along fixed guide rods 65 arranged on either side of the conveyor belt 51 and extending in the direction of movement of the belt 51 and the layer 50 supported thereby. In order to obtain a clean cut extending at right angles to the direction of movement of the layer 50, the carriage 64 must be moved in a forward direction along the guide rods 65 at a velocity identical to that of the upper run of the conveyor belt 51. The carriage 64 is connected to a chain drive 66 by means of a carrier member 67, which entends into a vertical slot or channel formed in the adjacent end of the carriage. The chain drive 66 is driven by the same motor as the conveyor 51 through a shaft 68 and second chain drive 69. As explained above, the chain of the chain drive 66 moves at the same speed as the conveyor 51. When the carrier 67 reaches the upper run of the chain and starts moving in the same direction and at the same speed as the rolled layer 50, the cutter 60 starts moving transversely along the guide rods 63, and the transverse cutting is terminated before the carrier 67 reaches the end of the upper run of the associated chain. When the carrier 67 moves along the lower run of the chain 66, the carriage 64 is returned to its starting position, and the cutter 60 may now be moved along the guide rods 63 in the opposite direction. It is understood that the length of each plate 61 will correspond substantially to the total length of the endless chain of the chain drive 66. Each of the plates 61 cut from the layer 50 may be arranged on an upwardly convexly curved support plate 70, whereby the still formable plate 61 will obtain substantially the same curved shape. The plates 61 cut from the layer 50 and supported by curved plates 70 may now be passed into a hardening or curing station 71 where the plates are hardened or cured. It should be understood that the plates 61, each of which is arranged on an upwardly convexly curved support plate 70, could be made in any other manner than that described above. The advantages described below in relation to Fig. 3 may be obtained whether the plates are made by the extrusion method described above or by any other method. Fig. 3 illustrates part of a roof structure 72 with a number of horizontally extending, parallel, mutually spaced laths 73 to which a plurality of curved roofing plates 74 of the type produced in the apparatus or plant shown in Figs. 1 and 2, are fastened in an overlapping relationship. The central part as well as the upper and lower edges of each plate 74 overlie a lath 73, and the central part of each plate may be fastened to the underlaying lath by means of one or two nails 75. The curved shape of the plate 74 then ensures that the upper edge thereof is resiliently pressed into engagement with the underlaying lath 73 and that the lower edge of the plate is pressed into engagement with the central part of an underlaying plate so as to cover the nail head or heads thereon. EXAMPLE Roofing plates having a slate-like surface, may be made from a layer of hardenable or curable cement mixture containing reinforcing polypropylene fibers. This layer of material may be made by means of an extruder as that shown in Fig. 1, but can also be made in any other suitable manner. The layer of material is moved past a whipping device similar to the surface treating station 52 shown in Fig. 2. The string or wire lengths of the whipping device may be made from polyamide of the type used in grass trimmers as those marketed by Black & Decker. The string or wire lengths may, alternatively, be made from synthetic rubber of the type normally used for making O-rings and other sealing members. Any other sufficiently wear-resistant material having a suitable relationship between elasticity and specific weight such as steel wire may be used. The diameter of the string or thread lengths is preferably about 2 mm, and the axial spacing of the wire or string lengths on the rotatable supporting body or shaft 53 may be 5-25 mm, preferably 8 mm. Each string or thread length extends 150-250 mm from the outer peripheral surface of the shaft or body member 52, when the layer of material to be treated is moved past the shaft 52 so that the distance between the surface of the layer material to be treated and the peripheral surface of the shaft or body member 52 is 40-55 mm. The latter distance should be chosen in dependency of the rotational speed of the shaft or body member on which the wire or string lengths are fastened. Thus, for the above distance the rotational speed should be 1500-3000 rpm, preferably 2000-2100 rpm. The speed of movement of the layer of material past the whipping device is less critical. However, this speed of movement may, for example, be about 5m/minute. The shaft or body member 52 may be mounted so that its axis of rotation extends at right angles to the movement of the layer of material to be treated. It has been found, however, that better results are obtained when the rotational axis of the rotating body 52 defines an acute angle with the direction of movement of the layer of material. This angle should normally not exceed 30° and is preferably 10°-15°. The layer of material which may, for example have a thickness of about 4 mm, may be cut into rectangular plates with a plate length of about 600 mm. Each of these plates is arranged on and supported by an upwardly convexly curved support plate where it is hardened or cured. The radius of curvature of the plate may, for example, be about 15 m, providing an arch with a rise of about 3-4 mm. The finished, cured plates are used as roofing plates in roof structures as illustrated in Fig. 3.

Claims: A method for making roofing plates (74), said method comprising the steps of continuously forming a substantially planar, deformable, web-like layer (37) of a hardenable, fibre-reinforced cement mixture material in a plastic condition and moving said layer in its longitudinal direction, successively cutting separate layer lengths (61) from the free end portion of said layer, each length having dimensions corresponding to the dimensions of the roofing plates to be made, and hardening the layer lengths cut, characterized in passing the layer (37) through a surface treating station (52) for imparting a desired textured pattern to the upper surface of the layer, transferring each of the non-hardened, substantially plane layer lengths (61) to a respective one of a plurality of upwardly convexly curved supporting surfaces (70), maintaining the material of the layer lengths (61) in a formable condition on the curved supporting surfaces (70) for a time period sufficiently long to impart to each layer length a shape similar to that of the supporting surface, hardening the layer length material while supported by said supporting surface so as to provide curved roofing plates (74) which are elastically flexible and having their upper surfaces provided with a desired textured pattern. The method according claim 1, characterized in that said web-like layer (37) of material is formed by an extrusion process. The method according to claim 1 or 2, characterized in that said web-like layer (37) of material is formed by a rolling process. The method according to any of the claims 1-3, characterized in that said continuously formed web-like layer (37) is moved along a conveyor (51) and wherein the layer lengths (61) are transferred to the respective supporting surfaces (70) at the end of the conveyor. The method according to any of the claims 1-4, characterized in that the fibre-reinforced cement mixture material contains polypropylene fibers. The method according to any of the claims 1-5, characterized in that the thickness of said layer (37) of material is about 4 mm. The method according to any of the claims 1-6, characterized in that each of said supporting surfaces (70) is convexly curved with a radius of curvature of about 15 m. The method according to any of the claims 1-7, characterized in that the length of each of said layer sections (61) is about 600 mm. The method according to any of the claims 1-8, characterized in that the textured pattern is imparted to the upper surface of the layer (37) by means of a whipping device (53,55). The method according to claim 9, characterized in that the whipping device comprises a rotatable shaft (53) and a plurality of string or wire lengths (55) having their one end fastened to the peripheral surface of the shaft.

Inventors: GREGERSEN, JOHAN CHRISTIAN, NIELSEN, JENS PETER
Applicants: DANSK ETERNIT-FABRIK A/S
Application year: 1985
Main classification: E04D3
IPC codes: B28B11, B44C1, E04D1, E04D3, B29C47, B29C59, B29C53