GB2128129A

GB2128129A - Production of roofing tiles

Info

Publication number: GB2128129A
Application number: GB08322401A
Authority: GB
Inventors: John Richard Blake
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-08-20
Filing date: 1983-08-19
Publication date: 1984-04-26
Also published as: GB2128129B; GB8322401D0

Abstract

Roofing tiles are produced from cementitious material filled into a mould cavity 10 at A, and vibrated at B to consolidate it. Then the mould cavity is closed by a head 28 having a perforated, shaped lower surface. Vacuum is applied to the head via a line 38 to suck air and water from the cementitious material, with continued vibration. This leaves a nearly completely set tile as shown at D. <IMAGE>

Description

SPECIFICATION Production of roofing tiles This invention relates to methods and apparatus for producing roofing tiles.

My U.K. Patent Application 8317939 describes slate- or stone-effect roofing tiles which can be produced by moulding techniques. The present application describes a moulding technique by which continuous production of these and other tiles can be effected.

In one aspect the present invention provides a method of producing roofing tiles, comprising: (a) filling a mould cavity with a cementitious composition; (b) applying over the mould cavity a mould closure head, the mould closure head having a liquid permeable wall adjacent the mould cavity; and (c) subsequently applying a vacuum to the side of the permeable wall remote from the mould cavity, to suck water from the cementitious composition through the permeable wall; steps (a) and (b) being taken in either order.

Preferably the mould cavity is vibrated to consolidate the cementitious material, prior to and/or during the steps of applying the mould closure head and the vacuum.

In a second aspect, the present invention provides apparatus for producing roofing tiles, comprising: a mould cavity; a mould closure head for closing the mould cavity, the closure head having a liquid permeable wall adjacent the mould cavity; and means for applying a vacuum to the side of the permeable wall remote from the mould cavity, to suck water from a cementitious composition placed in the mould cavity through the permeable wall.

For continuous production, preferably there are a plurality of mould cavities, and means for conveying the mould cavities through an operational station at which the mould closure head closes the cavity and the vacuum is applied. Preferably there are means for vibrating the cavity to consolidate the cementitious material, and the virbrating means may be at the operation station and/or at a location upstream from the operation station.

Preferably the mould cavity is lined by a mould insert. The mould insert may be flexible or resilient and provide a vacuum seal against the closure head at the edges of the mould cavity. The mould insert may be provided with mould configurations for producing a given surface configuration in the resulting tile, and if so tiles with different surface configurations can be produced can be produced simply by changing the insert.

Examples of the invention will now be described with reference to the accompanying diagrammatic drawings, wherein: Figure 1 is an overall schematic perspective view of an apparatus according to the invention, Figure 2 is a diagrammatic cross-section of a mould cavity, Figures 3A and 3B are cross-sections showing the mould cavity of Figure 1 fitted with two alternative mould inserts, Figure 4 is a diagrammatic cross-section of a holder for the mould cavity, Figures 5to 9 show successive stages of a method according to the invention, the section of Figure 9 being at right-angles to those of Figures 2 to 8, Figure 10 is an exploded perspective view of an alternative mould closure head, Figure 11 is a sectional view of the closure head of Figures 10, over a mould cavity, and Figure 12 is another sectional view of part of the closure head of Figure 10.

Referring to the drawings, a conveyor (not shown) conveys trays or pallets 10 along the path 12 (Figure 1). The tray or pallet 10, shown also in Figure 2, forms a mould cavity, and in particular has a shoulder 14 at one edge which corresponds to a lateral extension of the tile described in Application 8317939 which provides an interlocking formation.

As shown in Figure 3A, the tray 10 is lined by a flexible mould insert 16 which can be made inexpensively from plastics foil. The insert 16 is pre-formed, e.g. by vacuum forming, to a configuration which produces the desired mould shape for the shape and texture of the upper surface of the tiles to be produced. It is simply drop-fitted in the mould cavity.

In the case of particularly large features of shaping the floor of the mould cavity 10 can be shaped to support the insert 16, as in the case of the shoulder 14 discussed above, but normally this is unnecessary, and undesirable because it makes the mould tray more complicated and less applicable to differently shaped tiles.

Alternatively, as shown in Figure 3B, the mould cavity 10 can be lined by a resilient semi-hard or flexible rubber mould insert 18. This too is moulded to a configuration to provide in the upper surface of the resulting tile a desired shape and texture.

The edges 1 6a of the flexible insert 16 of Figure 3A extend over the top edges of the trays 10, and the upper edges 18a of the rubber insert 18 in Figure 3B are slightly proud of the top edges of the tray. This enables the inserts 16, 18 to provide a peripheral seal around the mould cavity when a mould closure head described later is lowered against it.

As shown in Figure 1, the conveyor indexes the trays 10 (with the inserts 16 or 18) along the path 12.

At a filling station A, they are filled with a pre-gauged quantity of mortar, filled with fine aggregate, or other desired cementitious composition. At a station B, they are previbrated to settle the mortar to a pre-determined level in relation to the displacement caused by the mould closure head described below.

The conveyor then takes the trays 10 into an operational station C, where they are clamped in a holder (Figure 4). This is supported on car-engine type vibration mountings 22, and is vibrated by a vibrator 24. The vibrator can be a high frequency mechanical, pneumatic or hydraulic vibration unit at a preset frequency and amplitude. The vibration consolidates the mortar, as shown in Figure 5, so that its upper surface is flattened, the water which it contains tends to come to the surface, and any trapped air also escapes (which is important to the strength of the resulting tile). The present levels of vibration are adjusted to ensure this action. The pre-vibration at station B can be effected by similar means.

Next, as shown in Figure 6, a sheet of filter tissue 26 is placed over the top of the mould cavity, and a mould closure head 28 is lowered and clamped over the mould, pivoting on hinges 30 (Figure 1). The closure head 28 has an internal chamber 32, and its bottom surface is a finely perforated metal sheet 34, with male projections 36 to produce any desired recesses in the undersurface of the tile. If required any slight projections on the undersurface of the tile can be produced by cutting away portions of the metal sheet to give slight female depressions.

Ideally, the pre-gauged quantity of mortar will have been consolidated by the preceding steps to a level such that the dowward pressing of the male impression tool formed by the closure head will cause the mould to be filled entirely, without seepage of excess and without the formation of voids within the mould, but the following steps will prevent problems if the filling is not quite ideal. The purpose of the filter sheet 26 is to prevent undue seepage of neat cement and fine aggregate into the fine holes drilled in the metal sheet 34.

The closure head is lowered, and clamped in a closely timed sequence while vibration is applied.

Vacuum is then applied to the internal chamber 32, via a pipeline 38 and a storage tank 40 from a vacuum pump 42. This stage is shown in Figure 7.

The vibrations consolidate the mortar, bringing the water and any air bubbles to the surface, from where they are sucked into the chamber 32 through the filter sheet 26 and the perforations in the metal sheet 34. The suction also causes the closure head to press down firmly on the mortar in the mould, assisting consolidation and firmly shaping the mortar, and also ensuring that the edges 16a or 18a of the mould insert seal between the closure head and the tray 10.

This positive removal of the water (which was required to enable the mortar to flow) greatly strengthens the resulting tile.

When the water is in the chamber 32, it flows by gravity and by the action of the vacuum towards the hinges 30, from which end of the chamber there are drain pipes 44 leading to the vacuum storage tank 40.

It is assisted in this path at a late stage of the timed cycle of operations by the ingress of air to be chamber 32 through an air inlet 46 which is opened at this stage (Figure 8). This also assists in releasing the closure head from its sealing arrangement around the mould cavity, so that it can be lifted away from the mould and the set cement, hinged about the hinges 30 (Figure 9). Any remaining water in the chamber 32 now drains away through the pipes 44.

The filter tissue sheet 26 further aids the parting effect. In practice, the tissue always remains with the set cement and the closure head comes up clean, ready for the next operational cycle.

With the constant reduction in the volume of the mortar as water is removed, the pressure within the mould reduces and pulls down on the closure head to give what amounts to a kind of vacuum moulding effect. The result is a tile which is very well formed, and nearly completely set, as shown at D in Figure 1, where the mould cavity 10 is removed from the holder 20. Thus the tile can be removed from the mould cavity quite quickly, and the mould cavity can be used again.

As an alternative to the prforated metal sheet 34 described above, the closure head could have its lower surface made from a cast or tooled porous materiai such as pumice stone orsintered metal.

This may be used to produce quite cheaply a multi-head unit, increasing the production rate still further. With a suitable scavenging and cleaning-off operation, such a head may even eliminate the use of the filter tissue 26 and the time involved in positioning it and subsequently stripping it off.

For the use in developing new forms of tile, the closure head 28 may have a mortar inlet 48, leading from a suitable funnel or hopper. This permits pumping of mortar directly into the mould cavity while the closure head is in position, using a vibratory feed tube aided by a screw feed along its length. The amount of mortar required can thus be gauged accurately.

Figures 10 to 12 illustrate an alternative form of the mould closure head. This is built around a wooden frame 50 having hinges 52 corresponding to the hinges 30 of Figures 1 to 9. The frame 50 has a cover plate 54 over iongitudinal Z-section stiffening members 56. Atthe bottom of this frame is a composite cavity closure member 58 comprising an upper plate 60, a perforated lower plate 62, and an intermediate mesh 64 (e.g. a sheet of expanded metal) which is loosely positioned on the lower plate 62 and spaces the plates 60, 62 apart. The lower plate 62 is hinged to the frame 50 by hinges 66, and Figures 10 and 11 show the lower plate in two alternative positions, though in normal use it is screwed against the upper plate 60. A closed cell rubber seal 68 around the periphery of the lower plate 62 seals the two plates together.The lower plate 62 has a water extraction and vacuum pipe 70 communicating with the narrow space between the plates 60,62 defined by the mesh 64.

Figure 11 shows male projections 36 on the underside of the perforated sheet 62, similar to those of Figures 1 to 9, and also a female depression 72 for producing a projecting nib in the resulting tile which can be used to hang the tile on a roof batten. The depression 72 is provided with the air inlet 46, corresponding to that of Figures 1 to 9.

The mould closure head of Figures 10 and 11 can be used with the rest of the apparatus depicted in Figure 1, and in exactly the same manner, e.g. with a filter tissue as previously. The use of a narrow space defined by the mesh 64, in place of a chamber 32, speeds up the flow of air and water in this space, so that water is removed more quickly once it has passed through the perforated plate 62, and the process as a whole is thus speeded.

However, Figure 12 shows an advantageous modification which is fitted to the closure head of figures 10 and 11. One of the male projections 36 is replaced by a rubber diaphragm 74, located in cut-out in the composite closure member 58, with a vertically movable shaping member 76 above it. An air bellows 78 acts on the shaping member 76, fed from air line 80. The mould closure head is placed over the mould (and the edges sealed) with the diaphragm 74 in a relatively retracted position shown at 74a, e.g.

with a negative pressure applied to the bellows 78.

Thus, initially, there is a bigger void in the mould cavity than there is mortar filling it. This ensures that pressure is not needed on the closure head to close the mould, and prevents mortar being forced out of the edges of the mould and forming flash lines. Next, pressure is increased on the bellows, to force the diaphragm 74 down and ensure that the mortar is forced into all the cavities of the mould. At the same time or slightly after, the vacuum is turned on through the pipe 70, to extract water. An advantage of this is that the amount of mortar loaded into the mould and its precise composition become less critical, because any variations are taken up by the diaphragm 74 sinking to a greater or lesser extent.

If desired the shaping member 76 and bellows 78 could be replaced by a simple shaped soiid block 82, acted on directly by air pressure within a cup-shaped cover 84 over the diaphragm 74. It will also be appreciated that the variable projection thus provided could be mechanically operated, instead of pneumatically operated.

Claims

1. A method of producing roofing tiles, comprising: (a) filling a mould cavity with a cementitious composition; (b) applying over the mould cavity a mould closure head, the mould closure head having a liquid permeable wall adjacent the mould cavity; and (c) subsequently applying a vacuum to the side of the permeable wall remote from the mould cavity, to suck water from the cementitious composition through the permeable wall; steps (a) and (b) being taken in either order.

2. A method according to claim 1 where in the mould cavity is vibrated to consolidate the cementitious material, prior to and/or during the steps of applying the mould closure head and the vacuum.

3. A method according to claim 1 or claim 2 wherein the mould closure head has a variable projection which can project into the mould cavity, and wherein the projection is in a relatively retracted condition when the head is applied over the mould cavity, and is subsequently pushed into the cementitious composition.

4. A method of producing roofing tiles, substantially as any described herein with reference to the accompanying drawings.

5. Apparatus for producing roofing tiles, comprising: a mould cavity; a mould closure head for closing the mould cavity, the closure head having a liquid permeable wall adjacent the mould cavity; and means for applying a vacuum to the side of the permeable wall remote from the mould cavity, to suck water from the cementitious composition placed in the mould cavity through the permeable wall.

6. Apparatus according to claim 5 wherein there are a plurality of mould cavities, and means for conveying the mould cavities through an operational station at which the mould closure head closes the cavity and the vacuum is applied.

7. Apparatus according to claim 5 or claim 6 wherein there are means for vibrating the cavity to consolidate the cementitious composition.

8. Apparatus according to claim 6 having vibrating means for vibrating the cavity to consolidate the cementitious composition, located at the operational station and/or at a location upstream from the operational station.

9. Apparatus according to any one of claims 5 to 8, wherein the mould cavity is lined by a mould insert.

10. Apparatus according to claim 9 wherein the mould insert is flexible or resilient and provides a seal against the closure head at the edges of the mould cavity.

11. Apparatus according to claim 9 or claim 10 wherein the mould insert is provided with mould configurations for producing a desired surface configuration in the resulting tile.

12. Apparatus according to any one of claims 5 to 11, where in the mould closure head has a variable projection which can project into the mould cavity in use.

13. Apparatus according to claim 12 including means for applying pressure to the variable projection to force it into the mould cavity.

14. Apparatus according to claim 13 wherein said means for applying pressure is pneumatically operated.

15. Apparatus for producing roofing tiles, substantially as any described herein with reference to the accompanying drawings.