GB2426750A

GB2426750A - Mixing tiles on a production line

Info

Publication number: GB2426750A
Application number: GB0610798A
Authority: GB
Inventors: John Lambert; John Fifield
Original assignee: Forticrete Ltd
Current assignee: Forticrete Ltd
Priority date: 2005-05-31
Filing date: 2006-05-31
Publication date: 2006-12-06
Also published as: GB0610798D0; GB0511084D0

Abstract

The invention contemplates a method of manufacturing tiles in a production line having at least two stations, the method including forming the tiles in a series along a conveyor path, and re-arranging the order of the tiles in the series at the stations. It also includes a method which includes loading in a first direction a plurality of tiles to form an array of columns of tiles, and unloading the tiles from the array in a second direction perpendicular to the first direction. Also included is a method of manufacturing tiles including successively feeding a first batch of a plurality of tiles in a series of tiles to form a column of tiles, and interleafing a second batch of a plurality of tiles in the same series of tiles inbetween the tiles of the first batch in the column. It also includes a method of manufacturing tiles in a production line including controllably colouring a cementitious tile during manufacture by adding pigment to a cementitious mix in a screw mixer at a plurality of points along the length of the screw mixer, and mixing the cementitious mix in the screw mixer.

Description

1 2426750 A method and an apparatus for manutacturin2 tiles The present

invention relates to an improved method of manufacturing tiles, and more particularly but not exclusively to a method of manufacturing roof tiles made of a cementitious mixture such as concrete and formed by extrusion. In this specification the term roof tiles also includes "cladding tiles" and "fittings".

Roof tiles of generally rectangular shape with upper and under (in use) surfaces, opposite side edges, upper edges and lower (leading) edges, may be made from a variety of materials such as clay, polymer bound aggregates and cementitious materials such as concrete. Typically, cementitious mixtures include sand andlor other aggregates, cement, colouring pigment and water plus optionally one or more other additives or additions to facilitate extrusion, prevent growth of fungus etc. In general, moulded or pressed tiles provide a larger range of shape and dimension options than extruded tiles. However, as the tile production rate by moulding is low and therefore more costly, extrusion is preferred as a manufacturing method. Tiles of cementitious materials have been produced in an extrusion process for over fifty years.

The extrusion process includes apparatus including an extrusion head comprising 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. A succession of pallets for moulding the under surface of the tiles is driven along the conveyor path and past the box so that the cementitious mixture from the box forms on the pallets and is compressed thereon by means of a rotating roller mounted 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 cementitious mixture on the pallets. The ribbon is subsequently cut into tile forming lengths downstream of the box by means of a suitable cutting knife, optionally with nail holes being formed in the tile forming lengths at the same time.

The pallets with the formed tiles thereon are then conveyed to a curing location.

At the curing location, the tiles are conveyed through a curing chamber which is typically maintained at an elevated relative humidity and temperature. After curing, the tiles are depalleted, for example by means of rotating depalleting wheels disposed on opposite sides of the conveyor path. In operation, the wheels successively enter in between the pallets and tiles, with the tiles continuing along the original conveyor path, and the pallets being carried downwards along a different conveyor path, thereby separating the tiles from the pallets. The depalleted tiles are then conveyed to, and stacked, out-of-doors.

Basic through-colour tiles in a single batch i.e. produced from the same batch of cementitious mix, should preferably be homogeneous in colour and shade. However, variations in the manufacturing process can result in tiles of a batch having different surface finishes. Additionally, if the process involves the injection of colour into tiles being formed to give a more random colouration, for example during extrusion, this can result in an undesirable sequence of tiles having very similar surface patterns, for example stripes. Furthermore, the colour and shade of tiles from different cementitious mix batches can vary significantly. This problem also applies to tiles made from non-cementitious materials such as clay which has an additional process- induced variation when the clay tiles are fired, which is that tiles in different positions in the firing kiln are exposed to different temperatures and atmospheric conditions resulting in tiles of different colours andlor shades.

Therefore, to avoid a laid roof appearing patchy', and to break up repeating patterns within a batch, the roofer is required to hand-sort tiles from different packs to obtain a more even colour and/or surface pattern distribution across the roof as he lays the roof. As the success of this hand-sorting depends to a large extent on the roofer's experience, skill and judgment, this can still result in patchy looking roofs and slow down the roof laying process. Alternatively, the roof tiles can be hand-sorted at the packing stage in the manufacturing process. This addition of labour at the packing stage can slow down the production line and therefore limit output.

Against this background, the present invention seeks to provide an improved method of manufacturing roof tiles in which the aforesaid disadvantages are overcome or at least substantially reduced.

The invention resides in many aspects. The first aspect is in the rearranging, mixing- up or shuffling of the order of the tiles, produced as a series, during production.

Therefore, in broad terms, the invention resides in a method of manufacturing tiles comprising at least two stations in a production line, at which two stations the order of the tiles in a series is re-arranged.

Expressed another way, the invention resides in a method of manufacturing tiles in a production line having at least two stations, said method including forming the tiles in a series along a conveyor path, and rearranging the order of the tiles in the series at said stations.

Preferably, the order of the tiles in a series is re-arranged at a curing station and at a packing station. Even more preferably, the order of the tiles is re-arranged at a loading station for forming an array of tiles and an unloading station. Optionally, the order of the tiles in a series is re-arranged at a third station which is a drying station.

From another aspect, the invention also resides in a method of manufacturing tiles comprising successively presenting a plurality of tiles to one station in a production line in one order and the tiles leaving that station in another order which is different than the first order.

Expressed in another way, the invention also resides in a method of manufacturing tiles comprising successively feeding in a first direction a plurality of tiles to form an array of columns of tiles, and unloading the tiles in a second direction perpendicular to the first direction.

In other words, the invention resides in a method of manufacturing tiles including loading in a first direction a plurality of tiles to form an array of columns of tiles, and unloading the tiles from the array in a second direction perpendicular to the first direction.

From yet another aspect, the invention resides in a method of manufacturing tiles comprising successively feeding a first batch of a plurality of tiles in a series of tiles to form a colunm of tiles, and interleafing a second batch of a plurality of tiles in the same series of tiles inbetween the tiles of the first batch in the column.

Advantageously, the order of the tiles during their production is controllably mixed up or shuffled to remove the need for manually handsorting the tiles either at the packing stage or at the roof laying stage.

Preferably, at least one of the batches of tiles are rotated before forming the column so that the tiles of each batch face a different direction. Advantageously, this assists with the packing of the tiles, for example, if the tiles are orientated in a top-to-tail orientation within a column.

From a further aspect, the invention resides in a method of controllably colouring the colour of a tile during its production. Preferably, this is achieved by adding pigment to the cementitious mix at a mixing step in the production of the tile before the tile is formed, such as a primary step andlor a secondary mixing step. Preferably, the secondary mixing step comprises mixing the cementitious mix in a screw mixer into which pigment is added. Advantageously, different pigments can be controllably added into the screw mixer at multiple points along its length to achieve a multi- coloured product range.

In other words, the invention also resides in a method of manufacturing tiles in a production line including controllably colouring a cementitious tile during manufacture by adding pigment to a cementitious mix in a screw mixer at a plurality of points along the length of the screw mixer, and mixing the cementitious mix in the screw mixer.

From a yet further aspect, the invention resides in the method of pigmentation of a tile during its manufacture. Preferably, pigments can be added to the cementitious mixture at a number of steps throughout the tile manufacture: at a primary mixing step, a secondary mixing step and during tile extrusion. Advantageously, at the secondary mixing step, which comprises mixing the cementitious mix with pigments and water in a screw mixer, the pigments can be controllably added at different points along the length of the screw mixer to achieve different colour effects. For example, short runs of tiles of a particular colour can be achieved by adding different colour pigments at different points along the length of the screw mixer. Also, multicoloured tiles can be produced in this maimer. Preferably, the surface of the tiles can also be additionally and controllably coloured by paint at a paint application station.

Therefore, the ability to controllably produce tiles of different colours or multicoloured tiles combined with the randomisation effect of the present invention can result in packs of tiles of varying colours and colour effects, ready for laying on a roof, without the need for handsorting by the roofer or at the packing stage.

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 schematic diagram of the method embodying the present invention; Figure 2 is a flow diagram showing the steps involved in implementing a method embodying the present invention of a method of manufacturing roof tiles; Figure 3 is a flow diagram showing the steps involved in a primary and secondary mixing steps of the present invention; Figure 4 is a schematic diagram of a tile extrusion step of the present invention; Figure 5 is a flow diagram of a curing step of the present invention; Figure 6 is a schematic diagram of the curing step of Figure 5; Figure 7 is a diagrammatic perspective view of a curing rack used in the curing step of Figures 5 and 6, the curing rack comprising 5 vertical slices' and 32 horizontal slices'; Figure 8 is a diagrammatic perspective view of (a) one of the vertical slices of the curing rack of Figure 7, and (b) one of the horizontal slices of the curing rack of Figure 7; Figures 9 (a) to (e) are schematic diagrams of the 5 vertical slices of the rack of Figure 7, respectively, showing the order in which the slices are filled with roof tiles; Figure 10 is a diagrammatic perspective view of a tile unloading device for unloading the roof tiles from the rack of Figure 7; Figure 11 is a detail diagrammatic end view of the tile unloading device of Figure 10; Figures 12 (a) and (b) are tables showing the order in which the tiles are unloaded from the rack of Figure 7; Figure 13 is a flow diagram of paint production for use in the method of the present invention; Figure 14 is a flow diagram of glaze production for use in the method of the present invention; Figure 15 is a schematic diagram of a drying step of the present invention; Figure 16 is a diagrammatic end view of a tile unloading device at the drying step of Figure 15; and Figures 17 (a) to (d) are tables showing the order in which the tiles are unloaded from columns in the unloading device of Figure 16 into packs; The method of manufacture of the present invention is suitable for the production of roof tiles and associated fittings and accessories, and any other product where product texture, colour or surface variability within and between batches may be problematic.

The present invention is also suitable for the manufacture of products from cementitious materials, clays and any other materials whose processing can result in product texture, colour or surface variability within and between batches. The method is particularly suitable for the manufacture of roof tiles, and because of the adaptability of the method, it is well suited to a factory having a number of production lines, for example, a flat interlocking roof tile production line, a contoured interlocking roof tile production line, and a fittings line. For ease of understanding, however, a single production line is illustrated in Figure 1 and described below, which is a multi-product line of flat interlocking tiles made of cementitious material.

A flat interlocking roof tile (not shown) is of generally rectangular shape, having a substantially flat upper surface formed by extrusion and a shaped under surface moulded by a pallet on which the tile is fonned during manufacture. The tile has an upper edge and a lower (leading) edge, and interlocks extending along its opposite side edges in the form of an underlock and an overlock respectively. The underlock extends along a major portion of the side edge and terminates short of the leading edge of the tile.

The method of manufacture of the present invention is outlined in Figures 1 and 2, and commences at Step 10 (Figure 2) with the receiving and handling of raw materials: aggregate(s) (e.g. sand, limestone), cement, additives (e.g. plasticizers, super-plasticizers, pulverised fly ash, GGBS, powdered limestone, silica fume, colouring agents) and other additions (e.g. particles, fibres). At Step 12, these raw materials undergo a primaiy mixing stage in a primary mixer 28 to form a cementitious mixture 30. At a secondary mixing stage, Step 14, a colouring agent (e.g. liquid pigment) and water are added to the cementitious mixture 30 and mixed in a secondary mixer 32. At Step 16, the pigmented cementitious mixture 34 is conveyed to a tile extrusion station 36 which extrudes the mixture 34 onto tile pallets 38 (Figure 4) or moulds to form uncured (green) tiles. These palleted tiles 40 are carried by a conveyor belt 42 to a curing station 44 where, at Step 18, they are loaded into a rack 46 (Figures 6 and 7) and cured. Following curing, the tiles from the curing station are moved onto a conveyor belt 48 and depalleted at a depalleting station 49 at Step 20.

At Step 22, dry side paint or glaze is applied to the depalleted tiles at a dryside paint/glaze application station 50. At Step 24, the tiles are conveyed to a drying ring 52 to allow the paint or glaze to dry. Finally, the dried tiles are stacked at Step 26 and packed onto wooden pallets (not shown) at a packing station 54.

Referring firstly to Step 10, in this embodiment sand 56 is delivered to a sand receiving hopper 58. The sand 56 is then conveyed via an aggregate conveyor belt to one of four aggregate (sand) storage hoppers 62, 64, 66, 68. Each storage hopper 62, 64, 66, 68 communicates with the first primary mixer 28 via a first intermediate hopper 70 above the primary mixer 28. An aggregate weigh belt (belt weigher) 72 (see Figure 3) connects the aggregate storage hoppers 62, 64, 66, 68 with the first intermediate hopper 70 and provides measured or metered quantities of aggregate to the first intermediate hopper 70. The primary mixer 28 may draw sand 56 from any one or any combination of the four aggregate storage hoppers 62, 64, 66, 68 via the weigh belt 72. One advantage of this is that different grades of sand can be stored in each aggregate storage hopper 62, 64, 66, 68 so that the quality of the cementitious mixture 30 can be controllably varied by drawing sand from different combinations of the aggregate storage hoppers 62, 64, 66, 68.

Figure 3 shows the primary and secondary mixing steps (Steps 12 and 14) in further detail. Metered amounts of the raw materials are supplied to the primary mixer 28 which mixes them to form an unpigmented cementitious mix 30. The timing and metering of the raw materials to the primary mixer 28 are defined by a pre-set cycle in a first control device (not shown) which is programmed to suit the production line.

In operation, the primary mixer 28 calls for sand 56 and the required quantity is measured out by the aggregate weigh belt 72 and supplied to the first intermediate hopper 70. Cement 74 is supplied from a cement silo 76 to a cement screw conveyor (not shown) and then to a cement weigh hopper (not shown) above the primary mixer, which meters the required quantity of cement to the primary mixer. A metered quantity of additives andlor additions is supplied via a pump, or any other suitable means, to the primary mixer 28 from storage containers (not shown). A metered quantity of water 79 is also supplied to the primary mixer 28. A second control device (not shown) measures and monitors the moisture content of the cementitious mix 30 in the primary mixer 28 and controls the water supply in order to maintain or achieve a pre-set moisture content of cementitious mix 30. The unpigmented cementitious mix is prepared to a low defined moisture content.

At the appropriate part of the pre-set cycle, the unpigmented cementitious mix 30 is discharged into a second intermediate hopper 78, and then to the secondary mixer 32 which is a continuous screw mixer. The second intermediate hopper 78 has electronic probes (not shown) which indicate the level of material contained therein which means that if the level of material falls below a pre-defined threshold level, raw materials are automatically metered into the primary mixer 28, i.e. the mixing cycle is re-started.

Measured amounts of various liquid pigments 80 (e.g. colours A, B and C, see Figure 3) are also fed into the secondary mixer 32. The liquid pigments 80 are stored in storage tanks (not shown) and may be fed into the secondary mixer 32 individually or in combination. For the production of multicoloured tiles, the metering of the liquid pigments 80 is controlled to produce a randomly variable coloured concrete mix 34 according to the requirements of the production line. In this embodiment, randomised timers control the metering of the liquid pigment 80. The liquid pigment 80 is supplied according to a pre-set dosage and rate. The liquid pigments can be fed into the continuous screw mixer (the secondary mixer 32) at any point or points along its length. If, for example, red pigment is fed into one end of the screw mixer, grey pigment is fed into the other end and brown pigment fed in half way along the screw mixer, it is possible to provide short runs of tiles having the different base colours (e.g. 10 brown tiles, 10 grey tiles and 10 red tiles) and also multi- coloured products formed in between these short runs.

A measured quantity of water 81 is also added to the secondary mixer 32 to obtain the required workability of mix 34 which is then conveyed to the tile extrusion station 36 at Step 16.

The tile extrusion stage (Step 16) is in conventional manner according to the extrusion of flat interlocking tiles and is illustrated in Figure 4. The extrusion process comprises coating a plurality of pallets 38 with the pigmented cementitious mix 34 from the secondary mixer 32. This is achieved by the conveyor belt 42 driving pallets 38, pre- coated with mould release oil, beneath a hopper-like box 82 which is fed by the pigmented cementitious mix 34 from the secondary mixer 32.

As the pallets 38 pass successively beneath the box 82, the cementitious mixture forms on the pallets 38 and is compressed thereon by a rotating paddle 84, a shaping roller 86 and a slipper 88 to form a continuous ribbon 90 of extruded cementitious mixture on the pallets 38. The ribbon 90 is cut into tile forming lengths or tiles 40 at a cutting station 92 by means of a cutting knife. The pallets 38 with the formed tiles 40 are conveyed on the pallets 38 to a curing station 44 or location for partial curing (Step 18).

In this embodiment, metered injections of pigment for example, red and/or black pigment (not shown) is also added to the cementitious mixture 34 at the extrusion step 16 to give a multicoloured effect. The pigment is injected in such a way that the top few millimetres of the tile are coloured only. Although in this embodiment the pigment is injected into the cementitious mix 34, it can also be applied by any other suitable means. Furthermore, the pigment can also be applied to the ribbon 90 of extruded cementitious mixture on the pallets or the tiles 40 on their respective pallets 38.

Optionally, at this stage, the tiles 40 on pallets 38 may be "glazed" or "lacquered" at a wetside glaze application station 94 before curing. The glaze is prepared on site, which will be described later with reference to Figure 14, and applied to the tiles 40 on their respective pallets 38 in a paint applicator unit (not shown).

The tiles on their respective pallets are then conveyed along the conveyor path to the curing station 44. Referring to Figures 5 and 6, the curing step (Step 18) comprises the steps of loading the tiles 40 on their pallets 38 into a rack 46 at a loading station 98 via two tile loading devices 100, 102 (Step 96), followed by Step 97 of moving the loaded rack 46 into a designated curing chamber 104. Each production line has a number of separate curing chambers, rather than one individual curing chamber, to ensure efficient production by not having to wait for the individual curing chamber to be filled before starting curing. A pre- set curing cycle is then activated (Step 106).

On completion of the curing cycle, at Step 108, the rack 46 is moved to an unloading station 110 where the cured tiles 40 on their respective pallets 38 are unloaded from the rack 46 via a tile unloading device 112 and fed onto the conveyor belt 48 for depalleting (Step 114). Due to the slow curing nature of cementitious materials, the tiles achieve only a portion of their fully cured strength at this curing Step 18 and continue to gain in strength over time until they are fully cured.

The rack 46 is shown in Figure 6 and comprises a three dimensional framework or frame for supporting and housing tiles on their respective pallets 40 as an array in the frame. In this embodiment, the rack consists of 30 vertical columns, each column 116 having a capacity to house 32 horizontally orientated tiles 40 on their pallets 38. The rack 46 has a front face 118, a back face 120 and two side faces 122, 124 and is arranged so that it is 5 columns wide along its front and back faces 118, 120, and 6 columns deep along the side faces 122, 124. Alternatively, the rack 46 can be described as comprising 5 vertical slices' 126 (twodimensional array) through the depth of the rack 46, each vertical slice 126 (shown in Figure 8(a)) comprising 6 columns. The rack 46 can also be described as comprising 32 rows of horizontal slices 128, each horizontal slice 128 being 5 column widths wide and 6 column depths deep (shown in Figure 8(b)). The rack 46 has a total capacity of 960 tiles on pallets 40.

The tiles 40 on pallets 38 are loaded horizontally and upper edge (where the hanging nibs are located) first into the rack 46. When fully loaded, the rack 46 has a layered stack-like configuration although the tiles 40 are supported from the sides of the rack 46 and not actually stacked in the sense of resting upon one another. This means that tiles 40 on their respective pallets 38 can be removed and replaced without disturbing the adjacent tile above and below. The rack 46 is open on all its sides and within the array of loaded tiles 40 such that gases and water vapour can freely circulate among the tiles 40 during the curing process.

The method of loading and unloading the curing rack is designed to mix around, shuffle or re-arrange the order of the tiles 40 leaving the conveyor belt (as a series) so as to create a more random distribution of tiles in a resultant tile pack to avoid colour patching' on a laid roof. This is partly achieved by loading the tiles 40 on their pallets 38 from the conveyor belt 42 into the rack 46 slice-by-slice, column-by- column but unloading them from the rack 46 row-by-row. The tile bearing pallets 38 are loaded into the rack tile-by-tile. The order of the tiles are further randomised at the drying, and packing steps (Steps 24 and 26) which will be described later.

The rack 46 is loaded by the two tile loading devices, a front-loading device 100 and a back-loading device 102. In this example, each device 100, 102 consists of at least thirty two shelves, defining a column, arranged in a carousel-like construction, hereinafter referred to as a carousel. The front-loading device 100 is arranged at the front face 118 of the rack 46 above the conveyor belt 42, and the back-loading device 102 at the back face 120 of the rack 46 above the conveyor belt 42, which also runs underneath the rack 46. The shelf at the lowest position of each carousel is co- operable with the conveyor belt 42 to receive a tile bearing pallet 38 travelling on the conveyor belt 42. The rotation of each carousel is timed such that once the lowest shelf is occupied by a tile bearing pallet 38 from the conveyor belt 42, the shelf rises away from the conveyor belt 42 and an adjacent shelf is brought into co-operation with the conveyor belt 42 to receive the next tile bearing pallet 38 in the row of tile bearing pallets on the conveyor belt 42. Once a column of thirty two shelves is filled, a pushing device (not shown) pushes the thirty two tiles 40 carried by their respective pallets 38 into a colunm 116 of the rack 46. The pushing device can push the tile bearing pallets 38 different distances depending on the destination column in the rack 46. To ensure that production does not stop, the back-loading device 102 is loaded with tiles 40 on pallets 38 while the tiles 40 on pallets 38 in the front-loading device are being loaded into the rack 46. In other words, the front-loading and back- loading devices form a supported array of tiles (in the rack) from two directions, the devices alternating between one another.

In this embodiment, the columns of each rack slice 126 are filled with tiles 40 on their respective pallets 38 from the conveyor belt 42 in the order shown in Figure 8(a). That is, the third column from the front face 118 is filled first by the front-loading device 100, followed by the column from the front face 118 which is loaded by the back- loading device 102. Next, the front-loading device 100 loads the 2' column from the front face 118, followed by the 5th column from the front face 118 being loaded by the back-loading device 102. Finally, the column at the front face 118 is loaded by the front-loading device 100 and the column at the back face (6th column from the front face) is loaded with tiles by the back-loading device 102. This sequence of tile loading into the columns of a slice 126 is repeated for the remaining four slices of the rack (slices 2 to 5 shown in Figure 7), the slices being filled up from left to right of the rack. The mixing up of the tiles 40 from the order in which they are made can be more readily appreciated by reference to Figures 9(a) to (e) which shows the filling order of each of the vertical slices 126 in the rack 46. Each column in each table of Figure 9 represents a column 116 in a rack slice 126.

For ease of understanding, the position of a tile 40 within the rack 46 can be referred to with respect to its three-dimensional Cartesian coordinates within the rack 46 such that the x axis co-ordinate denotes the rack slice position across the width of the rack (1 to 5), the y axis co-ordinate denotes the colunm position from the front face 118 through the depth of the rack 46 to the back face 120 (ito 6) and the z axis coordinate denotes the row number (1 to 32) up the height of the rack. The position of the first tile to be loaded into the rack is shown in Figure 7 as #1 and is at rack slice 1, depth 3, row 32 (1,3,32). The last tile tobe loaded is shown as #960 in Figure 7 and its co-ordinates are (5, 6, 1).

Once filled, the rack 46 is transferred to the designated curing chamber (Step 97) where the tiles 40 on their respective pallets 38 undergo the curing cycle. The tiles 40 on their respective pallets 38 must be loaded onto the tile conveyor belt 48 in such a way as to allow continuation of the process after curing. In this embodiment, the tile bearing pallets 38 are presented upper edge first (i.e. hanging nibs first) to the conveyor belt 48 to ensure correct orientation during depalleting. Therefore, the rack 46 is rotated (turned) after it leaves the curing chamber 104 and before unloading the tiles 40 on their respective pallets 38 onto the conveyor belt 48.

A further re-arrangement of the order of the tiles 40 on their respective pallets 38 from the order in which they were formed is introduced during the unloading of the tile bearing pallets 38 from the rack 46 (Step 114). At the unloading station 110, the back face 120 of the rack 46 faces the tile unloading device 112, shown in Figure 10. The tile unloading device 112 has substantially the same dimensions as a vertical rack slice 126 (i. e. thirty two tiles high and 6 tiles deep, as shown in Figure 8(a)) to enable it to receive the cured tiles 40 on their respective pallets 38 housed in one slice of the rack 126. A pusher (not shown) pushes the tile bearing pallets 38 in one rack vertical slice 126 into the tile unloading device 112. The lowest row 130 of tile bearing pallets 38 in the unloading device 112 (i.e. one horizontal row of a vertical slice of the rack) is then lowered onto the conveyor belt 48 for transportation to the depalleting station 49. Then, the next row 132 of tile bearing pallets 38 in that vertical slice is lowered to the conveyor belt 48 and fed onto the conveyor belt 48. This unloading process is repeated until the remaining tile bearing pallets 38 in the rack 46 have been unloaded onto the conveyor belt 48. Figure 11 shows an end view of the unloading device 112 and the mechanism by which the shelves are able to move vertically.

Referring back to Figure 7, it will be clear that the first tile 40 on its respective pallet 38 to be unloaded from the rack is the last one loaded i.e. tile #960. The order of unloading of the remaining tile bearing pallets 38 in the rack 46 is shown in Figure 12.

Once unloaded from the rack 46, the tiles 40 on their respective pallets 38 are conveyed from the curing station 44 to the depalleting station 49. By way of example, the depalleting station 49 comprises a corridor of rotating depalleting wheels (a depalleter) which are positioned in two substantially parallel lines, one line on each side of the path of the moving tile bearing pallets 38. As a tile bearing pallet 38 carrying a tile 40 approaches the peripheral regions of the depalleter, the depalleting wheels successively enter in between the tile 40 and the pallet 38 to separate one from the other.

As the depalleted tiles 40 continue to travel on the conveyor belt 48 towards the dryside paint/glaze application station 50, they are visually inspected for cracks, flaws and other damage. If damaged, they are manually removed from the conveyor belt 48 and discarded. Once at the dryside paint/glaze application station 50, paint or glaze is applied to the tiles 40 in a paint applicator unit (not shown). In this embodiment, the paint and the glaze are produced at a paint production station 136, which production process is shown in Figures 13 and 14 respectively.

Referring firstly to the production of paint and Figure 13, the required quantity of resin, such as an acrylic emulsion resin, is added to a mixer having collapsible blades and the mixer is started, at Step 138. The mixer functions as a mixing vessel and as a storage container for the paint. Simultaneously, at Step 140, water and mill base (slurry of pigments, fillers and other additives) are fed to the mixer and all these ingredients are mixed together. Thirdly, at an optional step, Step 142, a film former is added and the mixer mixes further to complete the mixing cycle. The mixing cycle is a pre-programmed or pre- set cycle specifying the amounts of materials to be mixed, the sequence that they are added to the mixer and the mixing time. Once the mixing cycle is complete, the resultant paint in the mixer is sampled and tested to assess whether it meets the requirements of the production line (Step 144). If so, it is moved to the dryside paint/glaze application station on the production line (Step 146). If not, the paint is quarantined for disposal (Step 146).

Referring now to Figure 14, clear glaze for use in the production line is also produced at the paint production station. The ingredients of water, resin (such as a styrene- acrylic emulsion), a film former, an antifoam agent and a wetting agent (optional) are all measured or metered into a mixer at Step 148. The mixer is the storage container for the glaze, into which collapsible blades are fitted. At Step 150, the mixer is started and the ingredients are mixed according to a pre-set mixing cycle. Once the mixing cycle is completed, the glaze is sampled for testing (Step 152). As for the paint, if the glaze satisfies the requirements of the production line, it is moved to the dryside paint/glaze application station (Step 154), and optionally moved to the wetside glaze application station. If it does not, the glaze is quarantined for disposal (Step 156).

The wetside glaze and/or the dryside paint/glaze application stations 94, 50 are rinsed with water in between production runs. The waste water from the rinsing of the two stations is collected and fed into a primary holding vessel (not shown) where solid waste (e.g. particulates) and floating waste (e.g. surface films such as oil) are removed. The cleaned-up water is then stored in a secondary holding vessel for reintroduction to the production line, for example, at the primary mixer 28. The recycling of water in the method of manufacture of tiles reduces water usage, waste disposal costs and the environmental impact of the production process After the dryside paint/glaze application station 50, the tiles 40 are conveyed to the drying ring 52 to allow the tile paint or glaze to dry. In this embodiment, the drying ring 52 is open to the atmosphere and allows a period of time for the paint or glaze to dry, or at least film form, before packing. In the case of flat interlocking tiles, as in the present example, the tiles 40 are loaded into the drying ring 52 with half the tiles facing one way and the other half facing the other way to accommodate the tile nibs when stacking. The drying ring 52 introduces an additional element of randomising the order of the tiles 40.

In this embodiment, the drying ring 52 comprises forty-eight columns 158 arranged in a ring formation, wherein each column 158 can accommodate forty-two horizontally oriented tiles 40. The drying ring 52 has an outside face 160 and an inside face 162 and can rotate about its central vertical axis 164. As can be seen from Figure 15, a loading station 165 and an unloading station 167 are provided at the drying ring 52.

At the loading station 165, there are two tile loading devices 166, 168, a front-loading device 166 facing the outside face 160 of the drying ring 52 and above the conveyor belt 48, and a back-loading device 168 facing the inside face 162 of the drying ring 52 and above the conveyor belt 48, which runs underneath the drying ring 52.

The tiles 40 are loaded into each column 158 of the drying ring 52 such that each tile is orientated at 180 relative to the tile above and below it, as shown in Figure 16.

This is because, in this example, the tiles 40 are preferably stacked and packed in a top to tail' formation i.e. lower edge to upper edge, to accommodate the tile hanging nibs on the undersurface of the tile 40 at the upper edge.

The tile loading devices 166, 168 at the drying ring 52 are similar to the two tile loading devices of the curing rack 100, 102, in that they consist of shelves 180, defining a column, arranged in a carousel. However, the tile loading devices at the drying ring 166, 168 comprise at least twenty-one shelves 180 which are double- spaced from each other. The shelf 180 at the lowest position of each tile loading device 166, 168 at the drying ring 52 is co-operable with the conveyor belt 48 to receive a tile 40 traveling on the conveyor belt 48.

The orientation of tiles 40 traveling along the conveyor belt 48 to the drying ring 52 is upper edge (hanging nibs) first and so the frontloading device 166 sequentially picks up the first 21 tiles from the conveyor belt 48 in this orientation, elevating them sequentially by one shelf height, and pushes them into an intermediate set of shelves (not shown) which rotate the tiles horizontally by 180 before pushing them into a column of the drying ring 158 leading edge first. As the shelf 180 of the drying ring front-loading device 166 is double-spaced along the vertical axis, these twenty-one tiles accommodate every other shelf of the drying ring column 158. The next twenty- one tiles continue along the conveyor belt 48 to the back-loading device 168 which picks up these tiles upper edge (hanging nib) first and loads them into the gaps remaining in the same column 158 of the drying ring 52 without rotating them. As the shelf 180 of the drying ring back-loading device 168 is also double-spaced along the vertical axis, these twenty- one tiles accommodate the remaining shelves of the drying ring column 158, between those already housing the tiles unloaded from the front- loading device 166 i.e. the tiles from each of the loading devices 166, 168 are interleafed.

It will be appreciated that the interleafing of the tiles by the double loading device arrangement (i.e. the front- and back-loading devices 166, 168) at the drying ring 52 introduces a yet further stage of mixing up (randomisation) of the order of the tiles 40 from the order in which they were formed.

The drying ring 52 then rotates, anticlockwise in this example, to present an empty column to the front and back tile loading devices 166, 168. The remaining columns of the drying ring 52 are filled in this way. The first tile 40 unloaded from the curing rack, tile #960, will be the first tile loaded into the drying ring, at the top of the first column. The first 42 tiles in the drying ring, from top to bottom, are #960, #797, #896, #861... #922 etc..

The first column of tiles loaded into the drying ring 52 are then unloaded at the unloading station 167 once the drying ring 52 has rotated anticlockwise (by 2700 in this example) and the column has reached the unloading station 167. The unloading of the drying ring 52 starts with the bottom tile (#92 2) of the first column of tiles loaded, and continues up the column to tile #960. Then, the second column is unloaded also starting with the bottom tile. The rotation of the drying ring 52 is dictated by the speed of unloading of the tiles from the drying ring 52. It will be appreciated that the columns which have just been emptied of tiles remain empty until the drying ring 52 rotates (90 in this example) and brings those columns back to the tile loading devices 166, 168.

At the unloading station 167, all forty-two tiles of one column 158 are pushed out into a tile unloading device 182 which is similar in construction to the unloading device 112 at the curing chamber 104. However, in the tile unloading device 182 of the drying ring, the shelves (not shown) are collapsible to enable the tiles 40 to be stacked in groups or packs of seven. Each stack of seven tiles 40 is placed on and travels along a conveyor belt 184 to a banding station (not shown) where the tile stack is banded with a plastic sleeve or strap to form a pack. The packs are then doubled up to form two packs on top of each other, i.e. a double pack, which are then conveyed to the packing station 54 for packing into a larger consignment e.g. a wooden pallet (not shown). A particular production line may necessitate the adjustment of the orientation of the individual packs by rotating every alternate pack to ensure that they all have the same orientation before reaching the packing station. Figure 17 shows the configuration of the tiles within the packs as they are unloaded from the drying ring. It will be appreciated that Figure 17 shows the order of unloading of the 960 tiles originating from the curing rack 46. This assumes that none of the tiles were discarded after curing. It will also be appreciated that whilst the unloading order of 960 tiles is shown in Figure 17, the drying ring 52 has capacity for more than 960 tiles.

At the packing station 54, the conveyor belt 184 splits into two paths, an upper path and a lower path, which each lead to two separate packing points. The two packing points receive alternate double packs which are loaded onto separate wooden pallets.

It will be appreciated that the packing of alternate double packs into two separate pallets introduces a yet further randomisation of the tile order. Optionally, the pallets of loaded tiles are spin-wrapped before being fed out into a stockyard where the tile pack loaded pallets are stacked for subsequent sale.

The present invention may be embodied in other specific forms without departing from its essential attributes as defined in the statements of invention herein rather than the foregoing description as indicating the scope of the invention.

For example, the above description describes a single production line for the production of cementitious interlocking flat roof tiles. It will be appreciated that the single production line is suitable for the production of different types of products e.g. different types of plain roof tiles. Also, the invention is equally applicable to other production lines of other types of tiles or associated products. Furthermore, the method of manufacture described herein is applicable to, and particularly suited to, multiple production lines. For example, if there are two production lines requiring different cementitious mix compositions or colours, four additional aggregate storage hoppers are provided together with a second primary mixer and an associated intermediate hopper. If there are three production lines (e.g. a flat interlocking tile line, a contoured interlocking tile line and a fittings line), the contoured interlocking tile line and the fittings line share the same cementitious mix and so eight sand storage hoppers are provided together with two primary mixers and three secondary mixers, where the first primary mixer feeds the contoured interlocking tile line and the fittings lines, and the second primary mixer feeds the interlocking flat tile line. However, the mixers can be adapted to feed any of the lines, e.g. in the case of breakdown of one of the mixers or lines.

In an alternative embodiment to the one described above, a colouring agent may also be controllably added at the primary mixing step 12 to the primary mixer 28.

Therefore, it will be appreciated that various colour effects can be achieved by adding various pigments at one of, or a combination of, three steps: the primary mixing step 12, the secondary mixing step 14 and the extrusion step 16. Additionally, as has been described above, pigments can be controllably added at different points along the screw mixer at the secondary mixing step to thereby achieve yet further colour effects.

In yet another further embodiment, paint andlor glaze applied at the wetside and dryside stations is not produced at the paint production station on site but is brought ready prepared as required. Indeed, in an alternative embodiment, there are no wetside glaze application andlor dryside paintlglaze application stations. Also, the paint and glaze mixing cycles described above are examples only and may vary depending on the production line.

In instances where there has been no dryside paint or glaze application, there is no need for the tile to go through a drying ring. Therefore, in a further embodiment, where there is no drying ring in the production line, the tiles are conveyed from the curing chamber to the packing station.

Furthermore, it will be appreciated that the configurations of the rack, curing chamber and drying ring, together with their associated tile loading and unloading devices, may vary. For example, the rack may comprise more than or less than five vertical slices consisting of columns having a capacity of more than or less than thirty-two tiles.

Also, although the method of manufacture has been described in relation to 960 tiles (i.e. one full curing rack), it will be appreciated that factory production in real life is actually continuous. Furthermore, the curing chamber may be rotary or the curing rack may be round. Similarly, the tiles may be stacked in any number other than 7.

Accordingly, the tile ordering in Figures 9, 12 and 17 are to be taken as a non-limiting examples based on the rack and pack dimensions described.

Although the tiles have been described as being loaded into the curing rack and drying rings horizontally orientated, they can equally be loaded and subsequently packed in any other orientation. Also, whilst the loading of the tiles into the curing rack and drying ring columns has been described as top to bottom, the columns can also be filled bottom to top. Instead of the curing rack slices being filled up from left to right of the rack, they can be filled in any order.

Similarly, it is possible to load the rack or drying ring row-by-row and unload them column-by-column. What is necessary to shuffle or re-arrange the order of the tiles is to load the tiles, one-by-one, into an array in one direction, and then unload them in another direction from the array, which is preferably perpendicular to the first direction.

In another embodiment in which there is a drying ring, the drying ring is provided with a single loading device which loads the tiles into the drying ring in a single orientation. It will be appreciated that there is less randomisation of the order of the tiles in this embodiment, than in the embodiment described above. The drying ring may have different formats than the format described herein, for example the drying ring may be enclosed.

Claims

Claims 1. A method of manufacturing tiles in a production line having at

least two stations, said method including forming the tiles in a series along a conveyor path, and re- arranging the order of the tiles in the series at said stations.
2. A method according to Claim 1, wherein the first station is a loading station for forming a supported array of tiles, the order of the tiles in the series being re-arranged by forming columns or rows of the tiles of the supported array from two directions, and alternating the forming of the columns or rows between the two directions.
3. A method according to Claim 2, including forming the supported array column-by- column.
4. A method according to Claim 3, wherein the supported array is formed by conveying the tiles in a series to the loading station, successively loading the tiles into the loading station to form a supported column of tiles, pushing the column of tiles from the loading station in the first direction to form a column of the supported array.
5. A method according to Claim 4, including forming the columns of tiles in the supported array from two directions at two loading stations, by pushing the column of tiles at one loading station to form the column of tiles in the supported array, and at the same time loading the other loading station with tiles to form the supported column of tiles.
6. A method according to any of the preceding claims, wherein the second station is an unloading station for unloading the tiles from the supported array, the order of the tiles in the series being re-arranged by unloading the tiles in a direction perpendicular to the direction in which the tiles were loaded to form the supported array.
7. A method according to Claim 6 when dependent on Claim 3, including forming the supported array by loading the tiles column-by-column, and unloading the tiles from the supported array by removing them row-by-row.
8. A method according to Claim 7, including unloading the supported array by pushing the tiles in a line of adjacent columns of the supported array to the unloading station, and lowering the lowest row of tiles of the columns to the conveyor path.
9. A method according to any of the preceding claims, including curing the tiles at a curing location which is between the first and second stations.
10. A method according to any of claims 2 to 5, including forming the columns of the tiles of the supported array from two directions by successively feeding a first batch of the tiles in the series to form a column of tiles, and interleafing a second batch of tiles in the same series inbetween the tiles of the first batch in the column.
11. A method according to Claim 10, wherein at least one of the batches of tiles are turned before forming the column so that the tiles of each batch face a different direction.
12. A method according to claim 10 or claim 11, including re-arranging the order of the tiles in the series at the second station by unloading the columns of tiles from the supported array, creating a plurality of stacked tiles from one colunm of the tiles, and re-ordering the order of the stacks within one column.
13. A method according to any of claims 10 to 12, including drying the tiles at a drying location which is between the first and second stations.
14. A method according to claims 1 to 9 and claims 10 to 13, wherein the tiles are conveyed first to the curing location and then to the drying location.
15. A method according to any of the preceding claims including controll ably colouring a cementitious tile during manufacture by adding pigment to a cementitious mix in a screw mixer at a plurality of points along the length of the screw mixer, and mixing the cementitious mix in the screw mixer.
16. A method according to any of the preceding claims, including extruding the cementitious mix to form a continuous ribbon, cutting the ribbon into tile forming lengths to form the tiles, and adding pigment to the cementitious mix before the tile is extruded.
17. A method according to any of the preceding claims, including controllably colouring the surface of the tiles after the tile is formed.
18. A method of manufacturing tiles including loading in a first direction a plurality of tiles to form an array of columns of tiles, and unloading the tiles from the array in a second direction perpendicular to the first direction.
19. A method according to Claim 18, further including forming a array of tiles column-by-column, and unloading the tiles from the array by removing them row-by- row.
20. A method according to Claim 19, wherein the array is formed by conveying the tiles in a series to a loading station, successively loading the tiles into the loading station to form a supported column of tiles, pushing the column of tiles from the loading station in the first direction to form a column of the array.
21. A method according to Claim 19 or Claim 20, including unloading the array by pushing the tiles in a line of adjacent columns of the array to an unloading station, and lowering the lowest row of tiles of the columns to a conveyor path.
22. A method according to any of claims 19 to 21, including forming the columns of the array from two directions, and alternating the forming of the columns between the two directions.
23. A method according to Claim 22, including forming the columns of tiles in the array from two directions at two loading stations by pushing the column of tiles at one loading station to form the column of tiles in the array, whilst loading the other loading station to form the supported column of tiles.
24. A method according to any of claims 18 to 23, including controllably colouring a cementitious tile during manufacture by adding pigment to a cementitious mix in a screw mixer at a plurality of points along the length of the screw mixer, and mixing the cementitious mix in the screw mixer.
25. A method according to any of claims 18 to 24, including extruding the cementitious mix to form a continuous ribbon, cutting the ribbon into tile forming lengths to form the tiles, and adding pigment to the cementitious mix before the tile is extruded.
26. A method according to any of claims 18 to 25, further including controllably colouring the surface of the tiles after the tile is formed.
27. A method of manufacturing tiles including successively feeding a first batch of a plurality of tiles in a series of tiles to form a column of tiles, and interleafing a second batch of a plurality of tiles in the same series of tiles inbetween the tiles of the first batch in the column.
28. A method according to Claim 27, wherein at least one of the batches of tiles are turned before forming the column so that the tiles of each batch face a different direction.
29. A method according to Claim 27 or Claim 28, including controllably colouring a cementitious tile during manufacture by adding pigment to a cementitious mix in a screw mixer at a plurality of points along the length of the screw mixer, and mixing the cementitious mix in the screw mixer.
30. A method according to any of claims 27 to 29, including extruding the cementitious mix to form a continuous ribbon, cutting the ribbon into tile forming lengths to form the tiles, and adding pigment to the cementitious mix before the tile is extruded.
31. A method according to any of claims 27 to 30, further including controllably colouring the surface of the tiles after the tile is formed.
32. A method of manufacturing tiles in a production line including controllably colouring a cementitious tile during manufacture by adding pigment to a cementitious mix in a screw mixer at a plurality of points along the length of the screw mixer, and mixing the cementitious mix in the screw mixer.
33. A method according to Claim 32, including extruding the cementitious mix to form a continuous ribbon, cutting the ribbon into tile forming lengths to form the tiles, and adding pigment to the cementitious mix before the tile is extruded.
34. A method according to Claim 32 or 33, further including controllably colouring the surface of the tiles after the tile is formed.
35. Apparatus for manufacturing tiles including: a first conveyor for conveying tiles in a series in a production line, a frame for receiving and supporting tiles in spaced apart relationship in columns and rows, and a first loading device for receiving and loading the tiles into the frame, the first loading device including a column of shelves for receiving and supporting the tiles, the shelves being arranged such that they are moveable to co-operate with the first conveyor and to receive a tile travelling on the first conveyor to move the tiles from the first conveyor to the frame.
36. Apparatus according to Claim 35, further including a second loading device including a column of shelves for receiving and supporting the tiles, the shelves being arranged such that they are moveable to cooperate with the first conveyor and to receive a tile travelling on the first conveyor to move the tiles from the first conveyor to the frame.
37. Apparatus according to Claim 36, wherein the first and second loading devices are located at different sides of the frame and are arranged to alternately load columns of tiles into the frame from two directions.
38. Apparatus according to Claim 37, wherein the first and second loading devices are located at oppositely facing faces of the frame.
39. Apparatus according to Claim 37 or Claim 38, wherein the first and second loading devices are arranged so that while one column of tiles is being loaded from one of the loading devices into the frame, the other loading device is receiving tiles to form a column of tiles supported by the loading device.
40. Apparatus according to any of claims 35 to 39, further including a first pushing device to push the tiles from the first loading device to the frame.
41. Apparatus according to claim 36 or any claims dependent thereon, further including a second pushing device for pushing the tiles from the second loading device to the frame.
42. Apparatus according to any of claims 35 to 41, further including an unloading device for receiving and supporting the tiles from the frame, said unloading device including a line of adjacent columns of shelves, each row of shelves being moveable to co-operate with a second conveyor to feed the tiles onto the second conveyor.
43. Apparatus according to Claim 42, further including a third pushing device for pushing the tiles from the frame to the unloading device.
44. Apparatus according to any preceding claim, wherein the frame includes thirty vertical columns, each column being arranged to support thirty-two tiles, the columns of the frame being arranged in a rectangular configuration so that the frame is five columns wide and six columns deep.
45. Apparatus according to any preceding claim, wherein the loading device includes thirty-two shelves defining a column.
46. Apparatus according to any preceding claim, wherein the unloading device includes six adjacent columns, each column being arranged to support thirty-two tiles.
47. Apparatus according to any preceding claim, further comprising a further frame for receiving and supporting the tiles at a drying station, said further frame including forty-eight columns arranged in a ring formation, each colunm being arranged to support forty-two tiles.
48. Apparatus for manufacturing tiles including a mixer for mixing cementitious mix for forming the tiles, said mixer being arranged so that pigment can be fed into the mixer along its length.
49. Apparatus according to Claim 48, wherein the mixer is a screw mixer.
50. Apparatus according to Claim 48 or 49, further including control means for metering the feeding of the pigment into the mixer.
51. A method of manufacturing tiles according to Claim 1 and substantially as hereinbefore described.
52. A method of manufacturing tiles according to Claim 18 and substantially as hereinbefore described.
53. A method of manufacturing tiles according to Claim 27 and substantially as hereinbefore described.
54. A method of manufacturing tiles according to Claim 32 and substantially as hereinbefore described.
55. Apparatus for manufacturing tiles, substantially as hereinbefore described with reference to Figures 1 to 17 of the accompanying drawings.