GB2186521A - Extruding concrete roof tiles with coloured surface streaks - Google Patents

Abstract

The roofing tiles (15) are extruded as a continuous stream onto pallets (2) from a cementitious mixture (6) which is stirred within the extrusion head (5) by means of a rotating paddle (9), and a streaky appearance is produced on that surface of the tiles (15) which is uppermost in use, by introducing a colourant into the mixture (6) through outlets (24) of radially extending paddle pins (11a), or additional projections, of the stirring paddle (9). The colourant is delivered by compressed air, or a pump, through the hollow stirrer shaft (28), to the outlets (24) which face in the opposite direction to that of rotation of the paddle (9), and may discharge above spreaders (26). The extrusion head (5) is provided with a pressure roller (12), and an outlet slipper (13), which contain the upper surface of the tiles. <IMAGE>

Description

SPECIFICATION Concrete roof tiles The present invention relates to extruded concrete rooftiles and more particularlyto so-called throughcolour concrete roof tiles of which that surface which is uppermost in use is provided with a streaky appearance caused by adding a colorant having a differentcolourtothatofthetile properto the cem- entitious mixture so as to impart a simulated weathered appearance to a roof formed from such tiles.

Apparatus for producing extruded concrete roofing tiles have been known for over 40 years and in dude a hopper-like box which is disposed above a conveyor path and which is charged with a cementitious mixture including sand, cement and colouring pigment e.g. red, the cementitious mixture being continuously stirred by means of a rotating paddle disposed within the box. A succession of pal lets for moulding the undersurface ofthetiles is driven along the conveyor path and beneath the box so that the cementitious mixture forms on the pallets and is compressed therein by means of a rotating roller disposed within the box upstream ofthe paddle and having a contour which corresponds to the upper surface of the tile to be formed.The cementitious mixtureisfurthercompressed on the pal lets as they pass outofthe box by means ofaslipperwhich is disposed downstream of the roller and also has a contourwhich corresponds to that of the upper surface ofthe tile, to form a continuous ribbon of cem- entitious mixture on the pallets. The ribbon is subse quentiy cut into tile forming lengths downstream of the box by means of a suitable cutting knifeandthe palletswith the wetformed tilesthereon are conveyed to a curing location.

For many years it has been known to provide extruded concrete roof tiles with a streaky surface appearance, by introducing a colorant in a continuous or random manner into the cementitious mixture within the box, in that area of the box where the cementitious mixture therein will form the upper surface region ofthetiles. Indeed, one ofthefirst methods employed was for a worker to stand beside the box and sprinkle, e.g. with a shovel, charges of colorant in the form of a powder into the cem- entitious mixture in the box but this method never did provide a consistent streaky appearance and was expensive in colorant, time and operating personnel.

Accordingly, more reliable automated methods were developed.

In a more recent known method, colorant in the form of a water/pig ment mixture is fed into the cem- entitious mixture through aflexible hose which ex tendsthrough a rigid metal pipe and projects only a short distance from the end ofthe pipe so as to touch the periphery of the roller. Because of the surge of cementitious mixture around the periphery ofthe roller due to roller rotation, the projecting portion of the rubber hose is randomly deflected to a sufficient extent to cut-offtheflow of colorant so that the colorant is introduced into the cementitious mixture at randomly timed intervals.

In another known method, which is disclosed in U.K. Patent Specification No. 1577321, colorant in the form of a cement slurry is introduced into the cementitious mixture in the box through one or more pipes of which the or each outlet is disposed either a short distance upstream of the paddle or between the paddle and the roller. By means of valves operated by a random signal generator, the colorant is introduced into the cementitious mixture at randomly timed intervals.

In a further known method colorant in the form of an acrylic paint is fed continuously i nto the cem- entitious mixture through a pipe or pipes terminating at a short distance either above the roller or upstream of the paddle. The colorant is stored in a suitable container which in one case is a pressure vessel to which compressed air is supplied to feed the colorant to the cementitious mixture or the container is connected to a continuously operating pump which is switched on and off with the extrusion apparatus.

All the automated methods described above have the disadvantage that pipes projecting into the box can, over a long period of production, impede or interrupt the flow of cementitious mixture passing underneath the roller. This can result in the formation of incomplete tiles and in sometiles being provided with a surface having too much colorant and not with a streaky surface appearance. Moreover, the outlets of the pipes can easily be blocked by the cem- entitious mixture resulting in some tiles being without a streaky appearance, and others having too much colorantthereon due to sudden surges in supply. Thus, it is necessary to stop the extrusion machine to remove the blockages etc., resulting in the expense of down time.Moreover, as the level of cementitious mixture decreases, the pipes are such ject to vibrations from the machine operation and from the successive new charges of cementitious mixture resulting in unacceptable increases in the amou nt of colorant on the ti le su rfaces.

Accordingly, the main object of the present invention is to provide a concrete roofing tile having a streaky upper surface appearance in which the aforesaid disadvantages are minimized or avoided.

To this end and from one aspect, the present invention consists in a method of producing extruded concrete roofing tiles from a cementitious mixture which is stirred by means of a rotating paddle during extrusion, in which a colorant having a different colourto that of the cementitious mixture is introdu- ced into the cementitious mixture to produce a streaky appearance on that surface of the tiles which is uppermost in use, characterized in that the colorant is introduced into the cementitious mixture through the rotating paddle.

From another aspect, the present invention consists in apparatus for producing concrete roofing tiles from a cementitious mixture which is stirred by means of a rotatable paddle, in which a colorant having a different colou rto that of the cementitious mixture is introduced into the cementitious mixture to provide a streaky appearance on that surface ofthe tiles which is uppermost in use, characterized in that the paddle has a hollowshaftand at least one hollow projection extending from the shaft and com- municating with its hollow interior and means for supplying the colorant to the hollow interior ofthe shaft, whereby the colorant is introduced into the cementitious mixture through said at least one hollow projection.

By introducing the colorant through the paddle, an improved and more consistent streaky surface appearance is obtained, the production of incomplete tiles is minimized, the extrusion apparatus is subjectto less down time and the flow ofcolorant may be infinitely varied by varying the numberof hollow projections to provide variations in the streaky surface appearance.

The colorant may be fed into the cementitious mixture through the paddle continuously, intermittently oratrandomlytimed intervals.

In the continuous mode a pump is connected in the supply line between a containerforthe colorant and thehollowshaftofthe paddle andthe pump is switched on or off when the tile extrusion apparatus is switched on or off. Alternatively, the colorant container may be a pressure vessel to which compressed air is supplied to feed the colorant to the paddle.

In the intermittent or random mode, a suitable pump can be used as the feeding means and a valve which is adapted to be opened and closed at randomlytimed intervals, is disposed in the colorant supply line between the pump and the paddle.

The or each hollow projection may be one ofthe existing paddle pins projecting radially from the paddle shaft or one or more additional hollow pro jectionssuch as pins may be fitted orfixed to the shaft.

In order to ensure thatthe hollow outlet of the or each projection is not blocked bythecementitious mixture, the outlet may face in a direction away from or opposite to the direction of rotation ofthe paddle.

As there may be a tendancyforthe colorantflowing from the outlet of the or each hollow projection to spread along and be entrained with the rotating paddle shaft, which would result in the upper surface ofthe tiles being substantially coated with the colorant, in a preferred embodiment, spreader means are associated with the or each outlet for directing the colorantawayfrom the shaft.

The or each spreader means may be a plate, e.g. in the form of a disc or of arcuate configuration, and having a greater dimension or dimensions than that ofthe projection.

In orderthatthe invention may be readily understood, reference will now be made, byway of example, to the accompanying drawings, in which Figure lisa diagrammatic side elevation of an apparatus for making extruded concrete roofing tiles having a streaky surface appearance, Figure2 is a plan view ofthe apparatus of Figure 1, Figure3 is a perspective view to a large scale of a paddleforming part ofthe apparatus of Figure 1, Figure 4 is a diagrammatic end viewto a reduced scale ofthe paddle of Figure 1, Figures 5and 6 are a side elevation and an underneath plan view of one form of hollow projection,fitted to the paddle, and Figure 7 is a plan view of a concrete roofing tile having a streaky surface appearance and produced by the apparatus of Figure 1.

Referring to Figures 1 and 2 ofthe drawings, the tile extrusion apparatus comprises, as is known, a conveyor path 1 along which pallets 2 for forming the undersurface ofthetiles are moved in end to end abutment by the main machine drive which is generally indicated at 3. The pallets are moved along a stationary track4 of the conveyor path 1 underneath the extrusion head 5 to be described.

A cementitious mixture 6 including sand, cement and a colouring pigment, for providing through colour tiles, is produced in a mixer (not shown) and is fed bya mixconveyor7 into a hopper-like box8 forming part of the extrusion head 5. a stirring paddle 9 is provided in that area of the box 8where the cementitious mixture will form the upper surface region of the tiles in order to keep the mixture mov- ing in that area. The paddle 9 has a driven shaft 10 mounted in suitable bearings, not shown, in oppositelyfacing sidewalls of the box and a plurality of paddle pins 11 fixed to and projecting radially from the shaft 10.Just downstream of the paddle 9 is a compression roller 12 followed by a slipper 13, both ofwhich have a contoured periphery which corresponds to, and forms, the upper surface of the tiles, in this case contoured, double-roll rooftiles.

As each pallet 2 is moved beneath the extrusion head 5, it receives a charge of cementitious mixture from the upstream end ofthe box 8, which charge forms the undersurface and middle regions ofthe tile, and then a charge from that area ofthe box where the paddle 9 is situated to form the upper surface region of the tile. The rotating roller l2com- presses the cementitious mixture on the pallet 2 to form the upper surface contour and is further com- pressed by the slipper 13 as that pallet 2 passes out from underneath the extrusion head 5. Thus, there is formed on the pallets 2 a continuous, extruded contoured ribbon l4ofcementitious mixture which is cut into tile forming lengths 15 by a reciprocating cutting knife 16.The severed tiles 15 on their respective pal lets 2 are moved away from the extrusion head 5 and along the conveyor path 1 by a take-off conveyor 17 (only part shown) whence they are conveyed to a curing location.

In the known tile making apparatus illustrated in Figures 1 and 2, provision is madeforthe concrete roofing tiles to have a streaky surface appearance. To this end, the shaft 10 ofthe paddle 9 is made hollow, and there are two hollow projections constituted by the paddle pins 11 a which are oftubularform to communicate with the hollow interior of the shaft 10.

A delivery pipe 18 is connected via branch pipes 18A, to opposite ends ofthe shaft 10 of the paddle 9 through suitable rotary seals (not shown) and to a mono pump 19. The pump 19 is in turn connected by a pipe 20to a container 21 containing a colorant 22 of a different colour to that of the cementitious mixture.

The hollow paddle pins 11 a each have a threaded shaft 23 by which it is screwed intq a threaded bore in thehollowshaftl0to be in communication with its hollow interior. Each hollow paddle pin 11 a has an outlet 24which faces in the opposite direction tothe direction of rotation, as indicated by the arrow 25, of the shaft 10 and is disposed, in this embodiment, at any angle of 90" with respect to the axis of the paddle pin 1 lea. Each pin 1 1a has a spreader 26 in theform of a disc having a greater diameter than that ofthe pin, fixed thereto and spaced from the external periphery of the shaft 10 by a lock nut 27.

As will be appreciated from Figures3 and 4, col- orantpumped intothe hollowinterior ofthe shaft 10 in the direction of the arrows 28 flows out of the outlets 24 and onto the spreaders 26 by means of which the colorant spreads out axially and transversely of shaft 10 so as to provide a streaky surface appearance on the finished tiles.

The colorant 22 in this instance is a suitable acrylic paint which is compatible with, and of wetter consistencythan that of, the cementitious mixture. By way of example Applicants havefound that a suitable simulated weathered appearance is provided to a tiled roof if the cementitious material is red and the colorant is black. The pump 19 is of the continuously operating kind which is switched on and off with the tile making apparatus so that colorant is con tinuously delivered by the pump 19through pipes 18 and 18a, into the hollow shaft 10 and outthrough at least one of the paddle pins 11 a of the paddle 9 in the manner illustrated diagrammatically in Figures 4. As shown in Figure 3there are two hollow paddle pins and the direction of the colorant flow into and out of the paddle9 is indicated bythe illustrated arrows.

During operation of the apparatus, as the paddle 9 rotates, the black paint 22 is injected continuously into the red cementitious mixture 6 in a controlled variable position. The locus ofthis position generally forms a sinusoidal curve in relation to the uppersurface of extruded ribbon 14 and thus the upper surfaces of the concrete tiles. The pressures obtaining within the box 8 then cause a variable tile surface colourdueto the controlled distribution oftheinjec- ted black paint, as will be seen from the tile 15 in Figure 7 which has a streaky surface appearance.

It should be appreciated that whilst a particular embodiment has been described, various modifications may be made without departing from the scope of the invention. For example, the streaky surface appearance can be provided on, flat, plain and cladding tiles and different colour combinations can be used otherthan that described.

The colorant may be fed to one end only ofthe hollow shaft of the paddle with the other end being blind or blocked-off.

In another embodiment a second paddle, possibly of smaller size, is disposed at any appropriate loca tion within the box, e.g. above the roller, and the speed of the second paddle can be varied so asto run at a greater or lesser speed than the surface speed of the tiles to give variations in the streaky surface appearance should this be desired. The colorant either ofthe same or a different colour is supplied to the second paddle instead of or in addition to the paddle 9.

Claims (15)

1. A method of producing extruded concrete roofing tiles from a cementitious mixture which is stirred by means of a rotating paddle during extrusion, in which a colorant having a different colourto thatofthecementitious mixture is introduced into the cementitious mixture to produce a streaky appearance on that surface of the tiles which is uppermost in use, characterized in that the colorant is introduced into the cementitious mixture through the rotating paddle.

2. A method as claimed in claim 1, characterized in thatthe colorant is fed into the cementitious mixture through the paddle continuously, intermittently or at randomly timed intervals.

3. Apparatus for producing extruded concrete roofing tiles from a cementitious mixture which is stirred by means of a rotatable paddle, in which a colorant having a different colour to that of the cem- entitious mixture is introduced into the cementitious mixture to provide a streaky appearance on that surface ofthetiles which is uppermost in use, characterized in that the paddle has a hollow shaft and at least one hollow projection extending from the shaft and communicating with its hollow interior and meansforcommunicatingwith itshollowinterior and means for supplying the colorant to the hollow interior ofthe shaft, whereby the colorant is introduced into the cementitious mixture through said at least one hollow projection.

4. Apparatus as claimed in claim 3, characterized a pump is connected in a colorant supply line between a containerforthe colorant and the hollow shaft ofthe paddle to continuously introduce the colorant and in that means is provided for switching the pump on oroffwhen thetile producing apparatus is switched on or off.

5. Apparatus as claimed in claim 3, characterized in thatthe colorant is introduced continuously from a container in the form of a pressure vessel to which compressed air is supplied to feed the colorantto the paddle.

6. Apparatus as claimed in claim 3, characterized in that the colorant is introduced intermittently or at randomly-timed intervals and a valve which is adapted to be opened and closed at randomly timed intervals, is disposed in a colorant supply line between a pump and the paddle.

7. Apparatus as claimed in any one of claims 3 to 6, characterized in that one of the existing paddles pins projecting radially from the paddle shaft or one or more additional hollow projections such as pins may befitted orfixedtothepaddleshaft.

8. Apparatus as claimed in any of claims 3to 7, characterized in that the or each hollow projection has an outlet which faces in a direction away from or opposite to the direction of rotation of the paddle.

9. Apparatus as claimed in claim 8, characterized in that spreader means is associated with the or each outletfor directing the colorant away from the shaft.

10. Apparatus as claimed in claim 9, characterized in that the or each spreader means is a plate having a greater dimension or dimensions than that ofthe projection.

11. Apparatus as claimed in claim 10, characterized in thatthe plate is in the form of a disc or of arcuate configuration.

12. A method of producing extruded concrete roofing tiles according to claim 1 and substantially as hereinbefore described.

13. A method of producing concrete roofing tiles substantially as hereinbefore described with reference to Figures 1 to 7 ofthe accompanying drawings.

14. Apparatus for producing concrete roofing tiles, substantially as hereinbefore described with re ferenceto Figures 1 to 7 ofthe accompanying drawings.

15. A concrete roofing tile whenever produced by the method claimed in anyone of claims 1,2,11 and 12 orthe apparatus claimed in anyone of claims 3 to 11 and 14.