During the manufacture of cementitious tiles dust accumulates on the tiles, especially when they have been perforated or indented (that is, have perforations which extend only part way through the tile). A coating may be applied to such tiles after they have been made in order to enhance the appearance and performance of the finished tile.

If accumulated dust is not removed from the tiles before the coating is applied, the quality of the coating may be significantly reduced. Any dust remaining on the tiles may also be released into the surrounding air.

It is known to remove dust from articles by applying a vacuum to them but this has not been found to be an effective way to remove dust from cementitious tiles. It is also known to remove dust from articles by blowing the dust away. However, this method is not an effective way of removing dust from all surfaces of a cementitious tile, especially the surfaces of indentations in the tile.

Further, the force required to remove dust from such surfaces can result in the tile being damaged.

According to the invention there is provided a method for applying fluid to a cementitious tile which comprises: supplying a fluid to a chamber; bringing a cementitious tile into the chamber; and withdrawing gas from the chamber so that gas external to the chamber is drawn into the chamber and the fluid supplied to the chamber rises to impinge on the cementitious tile.

The fluid is preferably a liquid. Examples of a liquid which can be usefully employed in a method according to the invention include water, a paint, a preservative, and a waterproofing agent. When water is used a treated cementitious tile is cleaned of dust. When a paint, a preservative, or a waterproofing agent is used, a treated cementitious tile is both cleaned of dust and coated. Coating of the tile has been found to enhance its strength.

Preferably the cementitious tile is moved through the chamber while the fluid impinges on the cementitious tile.

Preferably the cementitious tile is brought into the chamber through an entry port of the chamber and is removed from the chamber through an exit port of the chamber.

Preferably the external gas is drawn into the chamber through the entry and exit ports.

Preferably the external gas is drawn over the cementitious tile as it is moved through the entry and exit ports.

Preferably the fluid rises to a level above the entry and/or exit port.

A plurality of tiles may be moved successively through the chamber. Successive tiles may be separate from one another but preferably substantially abut one another.

Preferably the fluid is supplied to the chamber by a pump.

Preferably unused fluid supplied to the chamber leaves the chamber and is recycled to the chamber.

Methods of the invention have been found to be very effective at removing dust from cementitious tiles, especially from perforated or indented cementitious tiles, compared to known methods of dust removal.

In another aspect of the invention, a similar method may be used to apply fluid to other objects which have been

perforated or indented (that is, have perforations extending only part way through the object).

Accordingly, a further aspect of the invention provides a method for applying fluid to a perforated or indented object which comprises: supplying a fluid to a chamber; bringing a perforated or indented object into the chamber; and withdrawing gas from the chamber so that gas external to the chamber is drawn into the chamber and the fluid supplied to the chamber rises to impinge on the perforated or indented object.

Where the process of forming the perforations or indentations in the object causes dust to accumulate on the object, methods of this further aspect are particularly effective at removing such dust. Objects to which such methods can be applied include perforated wood and perforated metal objects.

It will be appreciated that the disclosure above relating to methods for applying fluid to a cementitious tile also applies to the perforated object of the further aspect.

There is also provided according to the invention apparatus for applying fluid to an object having opposed surfaces and at least one perforation extending from one opposed surface to the other which comprises: a chamber having an entry port for bringing an object into the chamber and an exit port for removing the object from the chamber, the entry and exit ports being defined by opposed surfaces; a means for supplying a fluid to the chamber; and a means for withdrawing gas from the chamber so that, in use, gas external to the chamber is drawn into the chamber through the entry and exit ports and passes over an object when it is in the entry or exit port and so that fluid supplied to the chamber is caused to rise to a level above the entry and/or

exit port and to impinge on the object when it is in the chamber; wherein the opposed surfaces defining the entry and/or exit port are arranged to, in use, be spaced from and extend substantially parallel to the opposed surfaces of an object passing through the port and to cover the said perforation in the said object when the perforation is in the port.

Objects suitable for having fluid applied to them by apparatus of the invention include perforated cementitious tiles.

It will be appreciated that the entry and exit port may be the same port. Preferably, however, the entry and exit port are separate.

If the entry and exit ports are separate they may be at different levels. If the entry and exit port are at different levels, then in use, the fluid may rise to a level above only the lower of the entry and exit port.

Preferably the entry and exit port are at substantially the same level and, in use, the fluid rises to a level above the entry and exit port.

The opposed surfaces which can cover the said perforation are preferably about 10-20 cm long.

The position of one or both of the opposed surfaces which can cover the said perforation may be adjustable so that the distance between the opposed surfaces can be altered.

Preferably the opposed surfaces which can cover the said perforation extend away from the chamber.

Preferably each opposed surface which can cover the said perforation comprises a skirt which is detachable from the chamber. Preferably the skirts are attached to the exterior of the chamber.

One or both of the opposed surfaces defining the exit port may comprise a channel which extends along the length of the opposed surface in a direction substantially parallel to the direction of travel of the said object when the said object is removed from the chamber through the exit port, the width of the channel being slightly less than the width of the object.

Apparatus according to the invention may further comprise a restricting means disposed in the chamber for restricting upwards movement of the said object when the apparatus is in use and the said object is partly in the chamber and partly in the entry or exit port so that rising fluid in the chamber does not cause the said object to contact the uppermost surface defining the entry or exit port as the object is brought into or removed from the chamber.

Preferably the vertical position of the restricting means is adjustable.

The restricting means may be attached to an internal wall of the chamber. The restricting means may be detachable from the internal wall of the chamber.

The invention also provides use of apparatus according to the invention to apply fluid to an object, preferably a perforated cementitious tile.

Embodiments of the invention are now described in detail, by way of example, with reference to the accompanying drawings in which: Figure 1 shows a cross-section of a preferred embodiment of apparatus of the invention for carrying out preferred embodiments of methods of the invention ; and Figure 2 shows a cross-section of part of the apparatus shown in Figure 1.

The apparatus of figures 1 and 2 comprises a coating chamber 10 and a fluid reservoir 12 for a coating fluid 14.

The chamber 10 is a rectangular box having a bottom wall 16, a top wall 18, end walls 20 and 22 and side walls (not shown). One end wall 20 has an entry port 24 in it and the other end wall 22 has an exit port 26 in it. Upper 28 and lower 30 baffles are disposed above and below the entry port 24 and upper 32 and lower 34 baffles are disposed above and below the exit port 26. The baffles 28,30,32,34 are similar to each other. Each baffle comprises an attachment flange 36 for attaching the baffle to the exterior of the coating chamber 10, and a skirt 38 extending from the flange 36 in a direction generally perpendicular to it. It will be appreciated, therefore, that the baffles 28,30,32,34 are L-shaped in cross-section. The attachment member of each baffle is made from aluminium and the skirt from teflon/rubber.

The entry port baffles 28,30 are shown in detail in figure 2 and are mounted on the wall 20 of the coating chamber 10 so that each skirt 38 is adjacent the entry port 24 and extends away from it in a direction generally perpendicular to the wall 20. Similarly, the exit port baffles 32,34 are mounted on the wall 22 of the coating chamber 10 so that each skirt 38 is adjacent the exit port 26 and extends away from it in a direction generally perpendicular to the wall 22. The gap between the skirts of the entry port baffles 28,30 is just large enough for a cementitious tile to pass between them. The side of each skirt 38 of the exit port baffles which faces the exit port comprises a channel (not shown) which extends along the length of the skirt. The width of each channel is slightly less than the width of the exit port 26. The gap between the skirts of the exit port baffles 32,34 at the edges of the skirts is just large enough for a cementitious tile to pass

between them, but is slightly wider between the middle portion of the skirts because of the channels.

The upper portion of the chamber 10 communicates with the upper portion of an air separation means 40 through an upper drainage conduit 42. The lower portion of the air separation means 40 communicates with the upper portion of the fluid reservoir 12. A vacuum pump 44 is connected to the air separation means 40. The lower portion of the chamber 10 communicates with the upper portion of the fluid reservoir 12 through a lower drainage conduit 46. A drainage tap 48 can close or open the lower drainage conduit 46. A fluid supply channel 50 connects the lower portion of the fluid reservoir 12 to the lower portion of the chamber 10.

Restricting means 52 are disposed in the chamber. The restricting means 52 restrict upwards movement of the tile when it is in the chamber so that it does not contact the upper entry port baffle 28 or the upper exit port baffle 32.

Each restricting means 52 comprises a plastic block attached to a bracket (not shown) mounted from a side wall of the chamber 10. The plastic block is positioned so that its lower surface is above the upper surface of the tile when it is in the chamber but below the level of the upper baffles 28,32.

In use, the fluid reservoir 12 is charged with the coating fluid 14 and the drainage tap 48 closes the lower drainage conduit 46. The coating fluid 14 in the fluid reservoir 12 is pumped out of the fluid reservoir 12 along the fluid supply channel 50 by a fluid supply pump 52 (not shown) and enters the lower portion of the chamber 10. A vacuum drawn by the vacuum pump 44 causes external air to enter the coating chamber 10 through the entry port 24 and the exit port 26 (as shown by the arrows in Figure 1). This causes the coating fluid 14 to rise towards the top of the

coating chamber 10 to a level above the entry and exit port 24,26.

A cementitious tile 54 to be treated (typically the cementitious tile is about three times longer than the distance between the end walls 20,22 of the coating chamber 10) is brought into the chamber 10 through the entry port 24.

As the cementitious tile passes through the entry port 24 air is drawn into the coating chamber over the surface of the cementitious tile 54 in the same direction as the direction of travel of the tile. This air flow removes dust from the surface of the tile. As the cementitious tile 54 enters the coating chamber 10, coating fluid 14 rising towards the top of the coating chamber impinges on the surface of the cementitious tile. Dust present on the surface of the cementitious tile, including dust in any perforations or indentations of the tile, is removed by the passage of coating fluid over the surface of the cementitious tile.

Unused coating fluid which returns to the bottom of the coating chamber 10 under the influence of gravity collects upstream of the drainage tap 48. Remaining unused coating fluid passes into the air separation means through the upper drainage conduit 42. The air separation means 40 acts to prevent coating fluid entering the vacuum pump 44 and allows the coating fluid to return to the fluid reservoir 12.

The coated cementitious tile 54 leaves the coating chamber 10 through the exit port 26. As it leaves the coating chamber, external air is drawn into the exit port 26 over the surface of the cementitious tile 54 in the opposite direction to the direction of travel of the tile and removes surplus coating fluid from it. The channels in the skirts of the exit port baffles ensure that there is sufficient passage of air over the surface of the cementitious tile to remove the surplus coating fluid. Removal of surplus coating fluid allows the

cementitious tile drying time and wastage of coating fluid to be reduced.

The restricting means 52 restrict upwards movement of the cementitious tile 54 in the chamber 10 caused by rising coating fluid 14. This prevents the cementitious tile 54 from contacting the upper baffles 28,32 which would otherwise cause a reduction in the flow of air over the upper surface of the tile as it passes through the entry 24 or exit port 26.

When a cementitious tile 54 having perforations in it is brought into the coating chamber through the entry port 24, air is drawn into the coating chamber between the tile and the skirts 38 of the entry port baffles 28, 30 in the same direction as the direction of travel of the tile. Some air may also pass from one side of the tile to the other through the perforations in it to remove dust that has collected in the perforations. When the perforated tile is removed from the chamber through the exit port 26, air is drawn into the coating chamber between the tile and the skirts 38 of the exit port baffles 32,34 in the opposite direction to the direction of travel of the tile. Air may also pass from one side of the tile to the other through the perforations in it to remove coating fluid from the perforations.

The width of the entry port and the length of the entry port baffles 28,30 should together be long enough to cover any perforation in the tile when that perforation moves into the coating chamber. Similarly, the width of the exit port and the length of the exit port baffles 32,34 should together be long enough to cover any perforation in the tile when that perforation moves out of the coating chamber. In this example, the maximum length of a perforation is about 10-20 cm.

If any perforations in the tile 54 are not covered by the entry or exit port and their respective baffles when the tile moves into or out of the coating chamber 10, it has been found that there can be a drop in the vacuum pressure in the coating chamber as the perforated part of the tile enters or leaves the coating chamber. This drop in vacuum pressure is caused by air passing directly into the coating chamber through the perforation instead of being forced to enter the chamber through the gap between the upper and lower surfaces of the tile and the skirts of the baffles. A drop in vacuum pressure in the coating chamber is undesirable because the level of the coating fluid can drop below the tile being coated. The passage of air over the upper and lower surfaces of the tile is also reduced. Consequently, the amount of dust that is removed from the tile as it enters the coating chamber and the amount of surplus coating fluid that is removed from the tile as it leaves the coating chamber can be reduced.

It is preferred that a tile is moved through the chamber while being coated and that a plurality of tiles are moved successively through the chamber. A gap may be left between successive tiles. However, this causes the vacuum pressure in the coating chamber to drop each time the gap between two tiles passes through the entry or exit port. It is preferred that successive tiles substantially abut one another. If the fluid 14 is a coating fluid such as a paint, a preservative, or a waterproofing agent, the edges of each tile which contact the adjacent tiles when the tiles substantially abut one another may subsequently be coated once they have moved through the coating chamber.

Successive cementitious tiles can be brought to and removed from the coating chamber 10 on a conveyor which supports only the edges of the tiles. A tile leaves the

coating chamber when it is pushed out of the chamber by the next tile to be coated. Once all the tiles to be treated have passed through the coating chamber 10, the drainage tap 52 is opened to allow coating fluid 14 that has collected in the coating chamber 10 to return to the fluid reservoir 12.

It will be appreciated that other embodiments fall within the scope of the invention. For example, instead of using baffles to cover any perforations in a tile as it is moved into or out of the coating chamber, the walls of the coating chamber itself could be sufficiently long to cover the perforations.

It will be seen that methods and apparatus according to the invention are particularly effective at removing dust from, and coating, cementitious tiles, especially tiles which have one or more indentations or perforations.