GB2589840A

GB2589840A - Extruded roof tile and method of manufacturing an extruded roof tile

Info

Publication number: GB2589840A
Application number: GB1916526.5A
Authority: GB
Inventors: Mcknight Andrew
Original assignee: Marley Ltd
Current assignee: Marley Ltd
Priority date: 2019-11-13
Filing date: 2019-11-13
Publication date: 2021-06-16
Anticipated expiration: 2039-11-13
Also published as: GB2589840B; GB201916526D0

Abstract

A roof tile 1, having a pan 2/5 and a roll 3/6 each extending along the length of the tile, the roll extending from a side of the pan, at least one channel 11-14 in the top surface of the tile, extending laterally across the tile in the width direction of the tile through the pan and terminating at a side of the roll before reaching the top of the roll. The lower in use edge of the channel may have a chamfered curved leading into the channel and the upper side may have a raided step. Also claimed is a method of manufacturer by continuous extrusion using a machine (30) with simultaneously moving cutting and channel forming blades (37/38 Figs. 6-7) which may be timed to form the chamfer and raised portion when cutting channels. The lower side may have anti-capillary grooves (28, 29 Fig. 5). The channels are only located in the pans, and do not extend onto rolls/side overlapping interlocks to prevent capillary action laterally. The tiles may be cementitious e.g. concrete.

Description

EXTRUDED ROOF TILE AND METHOD OF MANUFACTURING AN EXTRUDED

ROOF TILE

The present invention relates to an extruded roof tile, a roof structure and a method of manufacturing an extruded roof tile.

One of the principal causes of water ingress through roof tiles in storm weather conditions is rainwater travelling over the upper end ('head') of the tiles. This occurs from a combination of positive ram pressure of the wind driven rain and negative suction pressure on the tile undersides created by pressure differentials across the roof surface.

There is much prior art on roof tile design to minimise this leakage mechanism and improve resistance to wind-driven and deluge rain conditions. For single lap clay tiles (tile that fit together as a predominantly single layer across the roof surface apart from the sides and top/bottom where they overlap) complex shaped headlocks and weatherchecks are used to provide barriers and direct water back down the file from this vulnerable area. These are very successful in reducing the minimum roof pitch that tiles can be laid from 35 degrees (for traditional tiling designs) to 12.5 degrees and below. Clay files are typically formed by pressing, allowing the complex shaped headlocks to be readily formed as part of the forming process.

For concrete tiles, resistance to headlap leakage is more commonly achieved by close dimensional tolerances giving a fight fit with minimal gaps in the critical sections of the tiles (most notably the low points or pans'), together with barriers on the underside of each file which are positioned a short distance behind the bottom edge of the file, referred to as weather checks. These often incorporate lateral anticapillary channels to prevent water tracking over the surfaces that are in contact through capillarity, a pitch-limiting feature with traditional slating and plain filing where the files are laid two courses thick or double lapped.

Unlike pressed interlocking clay tiles, the forming process for concrete files is most commonly extrusion on shaped pallet moulds. This production process generally operates at speeds exceeding two tiles per second, greatly limiting opportunity to add raised features on the upper surface, or to form them with the precision required to form a headlock such as those described above. Although such features are used on smaller, lower volume products and pressed concrete -2 -files, made at slower speeds, they are rarely found on large format extruded concrete files There have been previous attempts in the art to address headlap leakage vulnerability by forming depressions across substantially the entire tile surface width.

The principle of such depressions is that they disrupt capillary water tracking and direct water to move sideways rather than directly up the file. However, these features are not commonly employed as there is little evidence that they improve wind driven rain resistance or enable tiles to be used at lower pitches.

Studies on the influence of these features undertaken by the inventor showed they tended to direct water laterally to the sides of tiles and into the sidelock channels (located at the sides of tiles for interlocking with adjacent tiles), where it then overflowed or flowed up the sidelock channels and over the headlock (at the top edge of the file), resulting in leakage.

According to a first aspect, the present invention provides an extruded roof file, the file comprising: a pan extending along the length of the tile; a roll extending along the length of the tile, the roll extending from a side of the pan; and at least one channel in the top surface of the file, wherein the channel extends in the width direction of the tile through the pan and terminates at a side of the roll before it reaches the top of the roll.

When water is driven up the top surface of a tile it typically collects in, and travels up, the low point in the pan. By providing a channel extending in the width direction through the pan, the flow of any water driven up the top surface of the pan of the file is interrupted (e.g. wind driven rain). The channel therefore collects water that is driven up the top surface of the pan of the tile and forces it to spread laterally, along the length of the channel. The water tends to be contained in the channel and the flow of the water laterally in the channel is further hindered by the increased height as the channel extends through the pan toward and partly up the side of the roll (the side of the roll being higher than the pan). This slows the flow of water because of the potential energy required for the water to flow up the increased height of the roll.

Furthermore, by arranging the channel so that it terminates at a side of the roll before it reaches the top of the roll, water is not channelled over the roll (e.g. into side lock channels for receiving an adjacent tile). The roll preferably has no -3 -channel at the top of the roll. A channel at the top of the roll would allow water to be channelled over the roll, which is undesirable.

Rolls and pans are terms commonly used in the art of roof tile design; a roll refers to a convex curvature in the tile top surface and a pan refers to a concave curvature of the tile top surface. High points on the top surface are typically located on a roll and low points are typically located in a pan. Considering a tile in cross section, there is usually a point of inflection between the pan and the roll, where the curvature switches from concave to convex.

The channel may be arranged to collect water that is driven up the top surface of the tile.

The channel may interrupt a wind driven flow of water up the top surface of the tile, forcing it to spread laterally within the channel.

The extruded tile may comprise on its top surface one or more side underlock channels at the edge of the file for mating with like tiles when fitted to a roof and the channel that extends in the width direction through the pan may terminate before it reaches such a side underlock channel. This prevents water from being channelled into the side underlock channel The file may comprise on its lower surface one or more side overlock channels for mating with one or more side underlock channels of a like tile.

The at least one channel may be located in the headlap portion of the tile.

By providing the channel in the headlap portion of the tile, the channel is more effective at interrupting a flow of any water that is driven up the top surface of the tile, as rain water cannot land directly on the part of the headlap portion above the channel) when the headlap portion is overlapped by a like file. As such, rain cannot circumvent the passage of the channels. Having the channel in the headlap portion also meets aesthetic requirements as the channels cannot be seen when the tile is overlapped by a like tile 0.e. when fitted to a roof).

The roll preferably has no channel at the top of the roll in the headlap portion of the file.

The channel may be tapered at one or both of its ends.

The channel may have a depth (measured from the top surface of the tile adjacent to the bottom edge of the channel, i.e. the edge towards the bottom of the file) of between 1 mm and 10 mm, preferably between 3 mm and 6 mm, and more preferably 5 mm. -4 -

The channel may have a width (measured at the lowest depth of the channel, from the bottom edge of the channel, i.e. the edge nearest the bottom of the tile, to the top edge of the channel, i.e. the edge nearest the top of the tile) of between 1 mm and 10 mm, preferably between 2 mm and 6 mm, and more preferably 3 mm.

The extruded roof tile may comprise a plurality of channels. The plurality of channels may be spaced apart in the direction of the length of the tile. There may be a plurality of channels located in the pan. Any one or a combination of the channels may have any of the features described herein in relation to a channel.

With more channels in the tile, the interruption of the flow of water driven up the surface is enhanced.

The extruded roof tile may comprise a raised portion extending in the width direction of the tile. The raised portion may be adjacent to the channel. The raised portion may be located at an upper edge of the channel. A raised portion such as this provides an additional barrier for water driven up the top surface of the tile.

The raised portion may be arranged to block a flow of water that is driven up the top surface of the tile.

The raised portion may have a height, measured relative to the normal height of the top surface of the tile (i.e. relative to the top surface of the tile adjacent to the channel towards the bottom of the tile) of between 0.5 mm and 5 mm, preferably between 1 mm and 3 mm, and more preferably 2 mm.

The extruded roof tile may comprise a chamfer leading into the channel and extending in the width direction. The chamfer may be adjacent to the channel. The chamfer may be located at a lower edge of the channel and lead into the channel.

The chamfer may guide water driven up the top surface of the tile into the channel.

The chamfer may comprise a curved portion extending on the top surface of the tile with a radius of curvature. The curved portion may extend to a straight portion or sidewall of the channel that meets, and is perpendicular to, the bottom of the channel.

In an embodiment, the channel has a bottom at a lower level than the level of the top surface of the tile adjacent to and behind and in front of the channel in the lengthwise direction of the tile.

The extruded roof tile may comprise at least one anticapillary groove on the underside surface of the tile. The anticapillary groove may be arranged so that, when the tile overlaps the head portion of a like overlapped tile having at least one -5 -like channel in its top surface, the anticapillary groove is offset in the tile length direction from the like channel so as not to overlap with it. Anticapillary grooves interrupt contact portions between tiles in order to disrupt and hinder capillary flow along the contact portions; which is another source of leaking in roof tiles.

By having the anticapillary grooves offset, this prevents the channels from interfering with the anticapillary action of the anticapillary grooves.

The extruded roof file may comprise a plurality of anticapillary grooves on the lower surface of the tile.

The channel may be located in the headlap portion of the tile and at least part of the channel may be arranged so that, when the file head portion is overlapped by a like overlapping tile, said at least part of the channel is located at a contact portion between the tile and the overlapping tile. It will be appreciated that in this way, the channels in the top surface of the channel can provide additional anticapillary action by interrupting the contact area with a like overlapping file.

The extruded roof tile may comprise two pans extending along the length of the tile, wherein each pan extends from a respective side of the roll and a respective channel may extend through each pan. There may be at least two channels extending through each pan.

The extruded roof file may comprise two rolls.

According to a second aspect, the present invention provides a roof structure, the roof structure comprising a plurality of any of the extruded roof tiles described above in relation to the first aspect, wherein the roof files are laid in a side-by-side interlocking and a headlap overlapping relationship to form a roof.

The roof may be a low pitch roof. The roof may have a pitch of less than 15 degrees, may have a pitch of approximately 12.5 degrees or may have a pitch less than 12.5 degrees.

The extruded roof tile may be formed of a cementitious material The material may be concrete.

According to a third aspect, the present invention provides a method of manufacturing an extruded roof tile, the tile comprising a pan extending along the length of the tile and a roll extending along the length of the tile, the roll extending from a side of the pan, the method comprising: forming at least one channel by depressing a forming tool into the surface of extruded file material and subsequently removing the forming tool from the tile, wherein the channel extends -6 -in the width direction of the tile through the pan and terminates at a side of the roll before it reaches the top of the roll.

The extruded tile material and the forming tool may move linearly during the depressing of the forming tool.

The file material may move with a linear speed. The linear direction of the movement may be in the same direction as the length of the tile. The tile material may move with a linear speed during the depressing and subsequent removing of the forming tool. The forming tool may move with a linear speed.

The method may comprise forming, adjacent the channel, a raised portion which is formed due to a linear speed differential between the forming tool and the extruded tile material. The linear speed, and linear speed differential, may be in the same direction as the length of the tile. By utilising a speed differential between the forming tool and the extruded tile material to form the raised portion, the raised portion can be formed in the same step of the manufacturing process, and with the same tool, as the forming of the channels. This avoids the need to add additional material to the tile and/or form the raised portion in a separate step, thus increasing the efficiency of the process.

The forming tool may be depressed into the surface of the extruded tile material on a downward stroke and during this, the forming tool may be synchronised with a linear speed the same as that of the extruded tile material.

When the forming tool is removed from the extruded tile material, it may have a linear speed faster than the extruded file material. This may push tile material back to form the raised portion described above. The linear speed of the forming tool may be accelerated when the forming tool is removed from the extruded file material.

The chamfer described above in relation to the first aspect may be formed using a forming tool which is curved. The curved part of the forming tool may be on the side of the forming tool which forms the bottom edge of the channel such that the chamfer is adjacent to the bottom edge of the channel (i.e. towards the bottom of the file as it is intended to be used on a roof) The forming tool may be asymmetrical. For example, the forming tool may have a larger radius of curvature on its front face in order to form the chamfer.

Alternatively, or in addition, the chamfer may be formed due to a linear speed differential between the forming tool and the extruded tile material.

The forming tool may be symmetrical. -7 -

The forming tool may be depressed into the surface of the extruded file material on a downward stroke and during this, the forming tool may have a slower linear speed than the extruded tile material. This may hold back some of the tile material as the forming tool is depressed; such a process may form the chamfer described above. The linear speed of the forming tool may be decelerated when the forming tool is depressed into the surface of the extruded tile material on a downward stroke.

Should the directions of the linear speeds be reversed, as practiced on some production systems, these linear speed settings can also be switched to match.

The linear speeds and changes in the linear speeds may be achieved through mechanical gearing or digital control. The linear speed differences may form a ridge and furrow profile in the tile, further impeding travel of water up the tile surface.

The method may comprise extruding the tile material into a continuous ribbon of extruded tile material. The method may comprise extruding the file material onto a plurality of successive pallets. The method may comprise compressing the extruded file material onto the pallets.

The method may comprise cutting a continuous ribbon of extruded file material mixture into a plurality of tiles. The forming of the at least one channel and the cutting of the extruded tile material mixture into a plurality of tiles may be performed in the same operation by the forming tool. This avoids the need to carry out the cutting using a separate tool and/or step, again increasing the efficiency of the process.

Alternatively, the forming tool may operate independently to a cutting tool which cuts the extruded tile material mixture into a plurality of tiles. Whilst this is more complex in terms of the overall control of the manufacturing, it avoids a potential conflict between the optimum movement sequences for the forming tool and cutting tool respectively (e.g. respective optimum linear speeds and directions).

The channel may be formed in a headlap portion of the file.

The method may comprise forming a plurality of channels. The plurality of channels may be spaced apart in the direction of the length of the tile.

The method may comprise forming at least one anticapillary groove on the underside surface of the tile. The anticapillary groove may be arranged so that, when the tile overlaps the head portion of a like overlapped tile having at least one -8 -like channel in its top surface, the anticapillary groove is offset in the tile length direction from the like channel so as not to overlap with it.

The at least one anticapillary groove may be formed by extruding and compressing of the tile material mixture onto one of a plurality of successive pallets.

In this way, the pallets can be used as molds for the underside of the files.

The method may comprise conveying the extruded tile material to a cutting and forming tool. The conveying may be carried out using a plurality of successive pallets and a conveyor belt.

The channel may be formed in the headlap portion of the tile and at least part of the channel may be arranged so that, when the file head portion is overlapped by a like overlapping tile, at least part of the channel is located at a contact portion between the tile and the overlapping tile.

The tile may comprise two pans extending along the length of the tile, wherein each pan extends from a respective side of the roll and wherein the method comprises forming a respective said channel extending through each pan.

Any of the rolls and pans may be formed by compression of the file material onto a pallet.

The method may produce at least one file per second, preferably at least two files per second.

The method may be used to manufacture any of the extruded roof tiles according to the first aspect.

It will be appreciated that aspects of the present invention may be suitable for use with low pitch roofs. They may be particularly useful with, but not limited to, use with roofs with a pitch around 12.5°..

According to a fourth aspect, the present invention provides an extruded roof tile, the tile comprising: at least one channel in the top surface of the tile, wherein the channel extends in the width direction of the tile; and a raised portion extending in the width direction of the tile, adjacent to the channel.

It will be appreciated that some features of the present invention are useful for a range of tiles, and so they are not necessarily limited to files that comprise a pan and a roll (although they may be particularly advantageous in that regard). Features of the present invention may be suitable for flat tiles. The combination of both a raised portion and a channel may be very effective at preventing leakage due to wind driven rain on flat tiles. By utilising both a channel and a raised portion, -9 -the flow of any water driven up the top surface of the pan of the tile is interrupted by both of these features.

The channel may terminate before it reaches the side edges of the tile.

The tile may comprise any of the features described above in relation to the first aspect.

According to a fifth aspect, the present invention provides a method of manufacturing an extruded roof tile, the method comprising: forming at least one channel by depressing a forming tool into the surface of extruded tile material and subsequently removing the forming tool from the tile, wherein the channel extends in the width direction of the tile, and the extruded tile material and the forming tool more linearly during the depressing of the forming tool; and forming at least one raised portion, wherein the raised portion extends in the width direction of the tile, adjacent to the channel, and the raised portion is formed due to a linear speed differential between the forming tool and the extruded tile material.

As discussed, it will be appreciated that aspects and features of the present invention are useful for a range of tiles, including flat tiles and pan/roll tiles. Furthermore, by utilising a speed differential between the forming tool and the extruded file material to form the raised portion, the raised portion can be formed in the same step of the manufacturing process, and with the same tool, as the forming of the channels. This avoids the need to add additional material to the tile and/or form the raised portion in a separate step, thus increasing the efficiency of the process.

The method may be used to manufacture any of the extruded roof tiles according to the first or fourth aspect.

The method may comprise any of the features described above in relation to the third aspect.

Certain example embodiments will now be described by way of example only and with reference to the accompanying drawings, in which: Figure 1 shows a plan view of an extruded roof file; Figure 2 shows an isometric view of an extruded roof tile; Figure 3 shows an isometric view of two extruded roof tiles when fitted to a roof, one overlapping the head portion of another; Figure 4 shows a partial transverse cross section of the tile of Figure 1 along line A-A shown in Figure 3; -10 -Figure 5 shows a longitudinal cross-section of two like extruded roof files, one overlapping the head portion of another as they would be when fitted to a roof; Figure 6 shows a schematic diagram of a machine used in the manufacturing of extruded roof tiles; Figure 7 shows an isometric view of a cutting and forming tool used in the manufacturing of extruded roof tiles; and Figure 8 shows a graph comparing the wind driven rain performance of the tiles shown in Figures 1 to 3 compared to unmodified tiles (without any channels). Figure 1 shows a plan view of an extruded roof tile 1. The extruded roof tile 1 has a first pan 2 extending along the length L of the tile 1 and a first roll 3 also extending along the length L of the tile 1. The first roll extends from a first side 4 of the first pan 2 in the width direction W of the tile. The extruded roof tile 1 also has a second pan 5 extending along the length L of the tile 1 and a second roll 6 extending along the length L of the tile. The second pan 5 extends from a second side of the first roll 3 in the width direction W to the side of the second roll 6.

A headlap portion 7 of the file is located towards the top edge 8 of the tile 1 and extends a distance D from the top edge. The headlap portion 7 is the area of the top surface of the file 1 that is covered, or overlapped, by a like tile from above when a plurality of tiles are fitted to a roof structure (this overlapping arrangement can be seen more clearly in Figure 3).

Figure 1 also shows side underlock channels 9 in the top surface of the tile 1 located at the left hand edge of the tile. The side underlock channels extend along the length L of the edge of the tile 1. The side underlock channels 9 interlock and mate with corresponding side overlock channels 10 located at the right hand side on the lower surface of a like tile (the side overlock channels of the file 1 are visible in Figure 3) when adjacent tiles are fitted to a roof structure.

Figure 1 also shows four channels 11, 12, 13, 14 in the top surface of the file. The four channels are located in the headlap portion 7 and extend in the width direction W of the tile 1, with two channels (first channel 11 and second channel 12) extending through the first pan 2 and two channels (third channel 13 and fourth channel 14) extending through the second pan 5.

The first channel 11 and second channel 12 extend through the first pan 2 and terminate at a side 4 of the first roll 3 before they reach the top of the roll 24. The top of the roll 24 is located along the length L of the tile at the highest point in the curvature of the roll, seen more clearly in Figure 2.

The first and second channels 11, 12 also terminate before they reach the side underlock channels 9 on the left hand edge.

The third channel and fourth channel 13, 14 extend through the second pan 5 and terminate at the second side of the first roll on the left and a side 25 of the second roll 6 on the right before they reach the top of the respective rolls.

The first and second channels 11, 12 are spaced apart from one another in the direction of the length L of the tile, as are the third and fourth channels 13, 14.

Figure 2 shows an isometric view of the tile 1, where the top edge 8, and the curvature of the first roll 3, second roll 6, first pan 2 and second pan 5 can be seen more clearly. From this figure it can be seen that the curves and rolls form a continuous curvature of the tile, with local maxima respectively at the top of the rolls and bottom of the pans. There are inflection points in the curvature between each pan and an adjacent roll.

Figure 3 shows an isometric view of a first file la and a second, overlapping, like tile lb. The second tile lb overlaps the headlap portion 7 of the first tile la in the manner it would when the tiles are fitted to a roof structure. The lower surface of the second tile lb is in contact with the top surface of the first tile 1a at contact points 15. Contact points 15 extend along the length of the pans in the headlap portion 7.

Figure 4 shows a partial cross-section of the tile 1 shown in Figure 1 along line A-A in Figure 3 through the first 11 and second channel 12. It will be appreciated that the third channel 13 and fourth channel 14 have a similar cross-section. It will also be appreciated that the structure of each of the four channels is similar.

Each channel has a depth X from a top surface of the file 16 to the bottom of the channel 17. A first side wall 26 of the channel (towards the bottom edge of the tile) comprises a chamfer 18 extending from the top surface of the tile 16 towards the bottom of the channel 17. The chamfer 18 has a radius of curvature R and extends into a straight portion 27 of the first side wall 26 that meets, and is perpendicular to, the bottom of the channel 17. A second side wall 20 of the channel (nearer to the top edge 8 of the tile than the first side wall 26) comprises a straight portion 21 that extends perpendicular to the bottom of the channel 17. The straight portion 21 extends above the level of the portion of the top surface 16 of the tile nearer to the bottom edge of the tile than the channel to form a step 22 at the upper edge of the channel. The step extends a distance Y above that portion of the -12 -top surface 16 of the file at the top edge of the channel. The height of the step 22 then decreases in a direction towards the top edge of the file 8.

The chamfer 18 guides wind driven rain that flows up the top surface 16 of the tile into the channel 11 so that the channel tends to collect the rainwater and interrupts its flow up the file. The increased height of the step 22 provides an additional barrier to the flow of wind driven rain and enhances the ability of the channel 11 to impede the flow of water up the top surface 16 of the file. The formation of the channels in the manufacturing of the tiles will be described in more detail with reference to Figures 6 and 7.

Figure 5 shows a cross-section of two like extruded roof tiles la, lb. The headlap portion 7 of the first tile la is overlapped by the second tile lb as they would be when fitted to a roof structure. Features on the underside 23 of the tiles la, lb can be seen more clearly in this figure.

The files comprise two anticapillary grooves 28, 29 on the underside surface 23. The anticapillary grooves 28, 29 extend in the width direction W at a portion of the tile lb where it would otherwise contact the headlap portion 7 of the overlapped tile la. The anticapillary grooves disrupt capillary flow of water along contact areas by interrupting said contact area.

The anticapillary grooves 28, 29 are arranged so that, when the tile overlaps the headlap portion 7 of a like overlapped tile having channels 11, 12 in its top surface 16, the anticapillary grooves 28, 28 are offset in the tile length direction L from the channels 11, 12 so as not to overlap with them. This prevents the channels 11, 12 from interfering with the anticapillary action of the anticapillary grooves 28, 29.

It will be noted that because the anticapillary grooves 28, 29 do not overlap with the channels 11, 12 when two like tiles are overlapped, the channels 11, 12 can be located at a part of the headlap portion 7 of the file where it would otherwise contact the underside 23 of an overlapping tile. In this way the channels can provide additional anticapillary action by interrupting the contact area.

The manufacturing of the extruded roof tile will now be described with reference to Figures 6 and 7.

Figure 6 shows a schematic diagram of a machine 30 used in the manufacturing of extruded roof tiles. Cementitious tile material 31 is fed into an extruding mechanism 32. The extruding mechanism comprises an extruding portion 32 that extrudes the tile material 31 into a continuous ribbon of extruded tile -13 -material 33 and compresses the ribbon of extruded tile material 33 onto a plurality of successive pallets 34 using a compressing portion 40 that applies a downwards force.

The top side of the pallets 34 act as a mold for the extruded tile material 33 and when the extruded tile material 33 is compressed onto the pallets 34, features on the top surface of the pallets indent the extruded tile material to form tile features on the underside of the files such as the anticapillary grooves and side overlock channels.

The successive pallets 34 are conveyed along a conveyor belt 35 in a leftward direction as seen in the figure.

After the compression, the pallets 34 (and compressed and extruded tile material 33) are conveyed to a cutting and forming tool 36. The cutting and forming tool 36 comprises two forming portions 37 and a cutting blade 38. In operation, the forming portions 37 are depressed into the top surface of the extruded file material 33 and subsequently removed in order to form the channels 11, 12, 13, 14 in the top surface of the tiles described above. This depression occurs as the extruded file material 33 and pallets are simultaneously linearly conveyed. The cutting and forming tool 36 also moves linearly during this process, in the same direction as the pallets 34 and extruded file material 33. When the forming portions 37 are depressed into the top surface of the extruded tile material 33, the cutting blade 38 is also depressed into the material, cutting the continuous ribbon of extruded material 33 at a cutting point 39 when the cutting and forming tool 36 reaches its lowest point in order to separate the individual tiles 1. The cutting and forming tool 36 then returns back to its original position and therefore follows a cyclic path of movement, each cycle producing one file 1. The path of movement is indicated by the arrows in Figure 6.

This process can produce approximately 2 tiles per second. The individual files 1 are then conveyed for further processing.

The chamfer 18 and step 22 described above in relation to the cross-section of the channels can also be formed using the cutting and forming device in the process described above by careful timing and selection of the linear speed of the cutting and forming device 36 relative to the extruded tile material 33. For example, on the downward stroke as the cutting 38 and forming portions 37 travel into the surface of the tile material 33, the cutting and forming tool 36 is synchronised with the linear speed of the extruded material 33 and pallets 34, or runs at a linear -14 -speed which is slightly slower, thus holding back some of the file material as it passes down (i.e. towards the base of the file, to the right in the figure). This forms the chamfer. On return after the cutting and forming tool has reached its lowest position, thus cutting the tile, the linear speed can be accelerated (e.g. faster than the linear speed of the tile) which pushes file material back towards the head of the tile (i.e. to the left in the figure), thus forming the step 22 adjacent to the top edge of the channels. The step is therefore formed due to a linear speed differential between the forming tool and the extruded tile material.

The speed changes may also form a ridge and furrow profile in the tile, further impeding travel of water across the file surface. For example, the forming tool may be decelerated momentarily relative to the linear speed of the tile material as it is withdrawn from the surface and the resulting localised retardation of tile material behind the tool (described above) may cause the material to be pushed against the face of the forming tool so that it is also forced upwards, thus producing a ridge and furrow effect.

Should the extrusion direction be reversed, as practiced on some production systems, these speed settings can also be switched to match.

These speed changes can be achieved through mechanical gearing or digital control.

Figure 7 shows an isometric view of a cutting and forming tool 36 used in the manufacturing of extruded roof tiles. This particular cutting and forming tool has the forming portions 37 located in front of the cutting portion 38.

The effect of the above described channels in the top surface of the tile was tested in a wind tunnel to simulate wind driven rain and the channels were found to achieve a significant benefit. The results of this testing are shown in Figure 8.

The method of test adopted by the industry, upon which the test method was based, is CEN/TR 15601: 2012 Hygrothermal performance of buildings, "Resistance to wind-driven rain of roof coverings with discontinuously laid small elements".

Two different roof structures were tested: one formed from (unmodified) tiles with no channels and one formed from like tiles but modified to have two channels in the headlap portion of each tile, similar to the tiles shown in Figures 1 to 3. Both roof structures were formed with a 6m rafter length and a 100mm headlap between tiles.

-15 -The roof structures were tested at wind speeds of 13m/s (Wind Driven Rain) using a wind tunnel and a system to simulate rain conditions. The roof structures were tested at a range of pressures, as detailed below.

In accordance with CEN/TR 15601: 2012, the wind driven rain tests were run through 5 minute pressure steps underneath the tile installation of the roof structure, beginning at a pressure of 20Pa and decreasing down to -70Pa. Each test was run for 50 minutes and the leakage was monitored throughout this period. Three repeats of each test were taken and an average was calculated from the results. The rate of leakage was then calculated from the average of each test set, by dividing the average by time duration, and a 10 point graph was formulated (one data point for each pressure step) as shown in Figure 8.

A roof structure that has not displayed signs of leakage before negative pressure is applied across the chambered roof space during wind driven rain testing is declared as a "pass".

As shown in Figure 8, the modified tiles when tested for wind driven rain achieved a pass, as initial leakage was not recorded until a negative pressure of -50Pa (i.e. after negative pressure was applied under the tiles). The total amount of leakage was 0.07L.

Also shown in Figure 8 are the comparative results for the unmodified tiles at 12.5° pitch. The unmodified tiles failed wind driven rain testing at 12.5°, leaking at OPa, before negative pressure was applied, producing very high rates of leakage, and a total average of 9.5L.

The above described test was also carried out for the unmodified tiles at a roof pitch of 15°, the results of which are also shown Figure 8. At a 15° pitch the unmodified tiles pass wind driven rain testing, with initial leakage starting at -40Pa, but this is still earlier than the modified tiles, with channels, at 12.5° pitch. The unmodified tiles at 15° pitch resulted in a total amount of leakage of 0.7L.

The modified files were also tested in a wind speed of Om/s (Deluge) condition at 100mm headlap, 12.5° pitch and 6m rafter length. No leakage was detected during the deluge testing, which confirms a pass under a deluge test.

Based on the above described results it can be concluded that compared with unmodified tiles, the additional features of the channels increased negative differential suction pressure required to initiate leakage by -60 Pa and reduced the minimum roof pitch before leakage occurred by at least 2.5 degrees.

-16 -It will be appreciated that files of the modified design are therefore particularly useful for use on low pitch roofs, for example, for use in roofs with a pitch of around 12.5°.

Claims

-17 -CLAIMS 1 2. 3. 4. 5. 6. 7.An extruded roof tile, the file comprising: a pan extending along the length of the tile; a roll extending along the length of the tile, the roll extending from a side of the pan; and at least one channel in the top surface of the tile, wherein the channel extends in the width direction of the file through the pan and terminates at a side of the roll before it reaches the top of the roll.
An extruded roof file as claimed in claim 1, wherein the channel is located in a headlap portion of the tile.
An extruded roof tile as claimed in claim 1 or 2, comprising a plurality of channels, wherein the plurality of channels are spaced apart in the direction of the length of the tile.
An extruded roof tile as claimed in any preceding claim, comprising a raised portion extending in the width direction, adjacent to the channel.
An extruded roof tile as claimed in claim 4, wherein the raised portion is located at an upper edge of the channel.
An extruded roof tile as claimed in any preceding claim, comprising at least one anticapillary groove on the underside surface of the tile, wherein the anticapillary groove is arranged so that, when the file overlaps the head portion of a like overlapped file having at least one like channel in its top surface, the anticapillary groove is offset in the tile length direction from the like channel so as not to overlap with it.
An extruded roof tile as claimed in any preceding claim, wherein the channel is located in the headlap portion of the file and at least part of the channel is arranged so that, when the tile head portion is overlapped by a like overlapping tile, said at least part of the channel is located at a contact portion between the file and the overlapping tile.
-18 - 8. An extruded roof tile as claimed in any preceding claim, comprising two pans extending along the length of the tile, wherein each pan extends from a respective side of the roll and wherein a respective said channel extends through each pan.
9. A roof structure, comprising a plurality of roof tiles as claimed in any preceding claim, wherein the roof tiles are laid in a side-by-side interlocking and a headlap overlapping relationship to form a roof.
10. A method of manufacturing an extruded roof tile, the tile comprising a pan extending along the length of the tile and a roll extending along the length of the tile, the roll extending from a side of the pan, the method comprising: forming at least one channel by depressing a forming tool into the surface of extruded tile material and subsequently removing the forming tool from the tile, wherein the channel extends in the width direction of the tile through the pan and terminates at a side of the roll before it reaches the top of the roll.
11. A method as claimed in claim 10, wherein the forming tool is curved in order to form a chamfer leading into the channel on the surface of the tile.
12. A method as claimed in claim 10 or 11, wherein the extruded tile material and the forming tool move linearly during the depressing of the forming tool.
13. A method as claimed in claim 12, comprising forming, adjacent the channel, a raised portion which is formed due to a linear speed differential between the forming tool and the extruded tile material.
14. A method as claimed in claim 13, wherein the raised portion is located at an upper edge of the channel. 30
15. A method as claimed in any of claims 10 to 14, comprising cutting a continuous ribbon of extruded tile material mixture into a plurality of tiles, wherein the forming of the at least one channel and the cutting of the extruded tile material mixture into a plurality of tiles is performed in the same operation by the forming tool.-19 -
16. A method as claimed in any of claims 10 to 15, wherein the channel is formed in a headlap portion of the file.
17. A method as claimed in any of claims 10 to 16, comprising forming a plurality of channels, wherein the plurality of channels are spaced apart in the direction of the length of the tile.
18. A method as claimed in any one of claims 10 to 17, comprising forming at least one anticapillary groove on the underside surface of the tile, wherein the anticapillary groove is arranged so that, when the tile overlaps the head portion of a like overlapped tile having at least one like channel in its top surface, the anticapillary groove is offset in the tile length direction from the like channel so as not to overlap with it.
19. A method as clamed in claim 18, wherein the at least one anticapillary groove is formed by extruding and compressing of the tile material mixture onto one of a plurality of successive pallets.
20. A method as claimed in any of claims 10 to 19, wherein the channel is formed in the headlap portion of the tile and at least part of the channel is arranged so that, when the tile head portion is overlapped by a like overlapping file, at least part of the channel is located at a contact portion between the tile and the overlapping tile.
21. A method as claimed in any of claims 10 to 20, wherein the tile comprises two pans extending along the length of the file, wherein each pan extends from a respective side of the roll and wherein the method comprises forming a respective said channel extending through each pan.
22. A method as claimed in any of claims 10 to 21, used to manufacture an extruded roof file as claimed in any of claims 1 to 8.
23. An extruded roof tile, the tile comprising: at least one channel in the top surface of the tile, wherein the channel extends in the width direction of the tile; and -20 -a raised portion extending in the width direction of the file, adjacent to the channel
24. A method of manufacturing an extruded roof tile, the method comprising: forming at least one channel by depressing a forming tool into the surface of extruded tile material and subsequently removing the forming tool from the tile, wherein the channel extends in the width direction of the file, and the extruded tile material and the forming tool move linearly during the depressing of the forming tool; and forming at least one raised portion, wherein the raised portion extends in the width direction of the tile, adjacent to the channel, and the raised portion is formed due to a linear speed differential between the forming tool and the extruded tile material.