Note: Descriptions are shown in the official language in which they were submitted.
X039
~I 145-212
Roof Tiles
This invention relates to roof tiles, and
relates in particular to a process for manufacturing
a novel type of tile.
Roof tiles are generally made of concrete
and, in recent years, considerable efforts have
been made to manufacture tiles having distinctive
profiles and colours such that an improved appearance
on a roof may be obtained.
In UK Patent 1577321 there is disclosed a process
for manufacturing concrete roof tiles in which
a coloured pigment is added to a quantity of main
tile body forming mortar and mixed therewith, the
quantity of mortar is introduced into a hopper,
a secondary material is added to said quantity
of mortar in the hopper, said secondary material
comprising a second coloured pigment whose colour
is different to that of the first coloured pigment,
the quantity of mortar and the secondary material
are partially mixed in the hopper so as to provide
a mass of mortar with a variegated colour including
substantial areas whose colour is determined predominantly
by the first pigment and areas whose colour is
determined predominantly by the second pigment,
and the mass of mortar is extruded onto a succession
of moving pallets to form a base ribbon which is
compressed and cut into individual tiles, the tiles
having a variegated colour.
In this process disclosed in UK Patent ]577321,
the secondary material is a small quantity of pigmented
slurry which is introduced in such a way as to
produce distinct streaks only in an upper region
of the tile. The body colour of the tile remains
constant.
The present invention is characterised in
that said secondary material is a second auantity
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of main, body-forming mortar, said second coloured
pigment being added to said second quantity of
mortar and at least partially mixed therew;th ~rior
to introduction into the hopper, and the arrangement
being such that throughout the mass of mortar which
is extruded to form the tiles there are, in addition
to the substantial areas whose colour is determined
predominant]v by the first pigment, substantial
areas whose colour is determined predominantly
by the second pigment and substantial areas whose
colour is determined bv a mixture of the first
and second piqments, so that the tiles have a corres-
ponding variegated body colour.
Thus, as opposed to producing distinct surface
streaks, these steps in accordance with the invention
produce a varying body colour. The colours of
the pigments added to the material may vary such
that a wide range of differently coloured tiles
may be formed. For example, red and yellow body
colouring pigments may be added alternately to
the material before it is introduced into the hopper
such that in any batch of tiles the body colour
of successive finished tiles varies from red to
yellow through shades of orange depending on the
mixing in the process. Alternatively, three or
more different pigments may be added.
The manner in which the body colouring pigment~
are added to the material prior to its introduction
to the hopper may vary. The process should be
such that only limited mixing of the body pigments
occurs such that the hody colour of any particular
tile varies and is not sim~ly a uniform combination
of the colours of the pigments.
The manner in which the pigments are mixed
with the tile forming material affects the body
colour variations in the finished tiles. A single
pigment added to the material prior to the introduction
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thereof to the hopper and only partially mixed
therewith will result in colour variations of the
finished tiles between the colour of that pigment
and the natural colour of the tile forming material.
In a process in accordance with the invention,
two pigments similarly only partially mixed with
the material outside the hopper will result in
colour variations of each tile between the colours
of the pigments. It is not however essential for
the pigments to be only partially mixed with the~
tile forming material. For example, batches of
material substantially uniformly coloured with
different pigments may be introduced into the hopper,
and the normal self-mixing of the material occuring
in the hopper leads to uneven mixing of the body
colours. In this way the predominent base colour
of the tiles may vary between two or more colours
over a production run. A combination of the above
instances i.e. incomplete mixing of each pigment
with the material, and se]f mixing of batches of
differently coloured material in the hopper, will
result in random colour variations in each tile
in addition to gradual variations in the preaomiment
base colours during a production run.
The tile forming material may be supplied to
the hopper by means of an elongate rotatinq screw
conveyer which is effective both to mix the tile-
forming material and to pass it to the hopPer. With
such an arrangement, the coloured pigments for the
body may be a2ded to the material within the conveyor
at an appropriate point along its length such that
the required degree of mixing of each pigment occurs.
The further along the conveyor the pigment is added,
the less mixing there will be with the body material.
Different pigments may be added to the material at
approprlately spaced intervals in time such that
desired colour variations of the finished tiles are
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achieved. The time intervals may be regularly or
randomly spaced. The degree of mixing of each p;qment
with the material in the conveyor will affect the
colour variations in each tile, while the time intervals
for which the pigments are added to the material
and the degree of self mixing in the hopper may change
the predominent base colour throughout a production
run.
Alternatively, the tile forming material may
be mixed by means of one or more batch mixers, i.e.
a large cylindrical pan or suitable container having
a mixing element therein, from which it is transmitted
either directly or via a suitable conveyor to the
hopper. With such an arrangement, one pi~ment may
be added to one batch mixer and a further pigment
added to a second batch mixer such that the material
in each mixer has a substantially uniform colour,
different to that in the other mixer. Material from
the two mixers is then introduced into the hopper
such that partial mixing occurs either within the
hopper itslef or during the conveying of the material
to the hopper. Material from each mixer may be passed
to the hopper at appropriately spaced time intervals
such that desired colour variations of the finished
tiles throughout a production run are obtained.
Alternatively, the material may be mixed in
a single batch mixer in which case a first pigment
is added to one batch, a second pigment to the next
and so forth, differently coloured material from
subse~uent batches being partially mixed in either
the hopper or on a conveyer.
In addition to providing the variegated body
colour, it may be desired to provide surface streaks,
by adding a surface colouring Pigment or pigments
to the materjal within the hopper. A black secondary
pigment may be added to the material within the hopper
such that black streaks are provided on the tile
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surface. Alternatively, a number of differently
coloured secondary pigments may be introduced into
the hopper such that multiple coloured streaks are
provided. The addition may be via supply means which
are laterally movable back and forth relative to
the hopper such that the position of the streaks
on the tiles changes. In a conventional hopper,
the means for compressing the tile forming material
against the pallets includes a roller rotatable about
a lateral axis, and it has been found that by adding
the secondary pigment or pigments to the surface
of the material at a position above the roller, streaks
are formed on the top surface of the tile. Lateral
movement of the secondary pigment supply means above
the roller causes variations in the position of the
streaks on the upper surface of the tile. Longitudinal
displacement of the supply means away from the roller
is undesirable since this alters the depth of the
streaks and may result in the streaks being formed
unnecessarily below the surface of the tile.
Two embodiments of the invention will now be
described, by way of example only, with reference
to the accompanying drawings, wherein:
Fig. 1 is a diagrammatic view of apparatus
taken in accordance with the invention;
Fig. 2 is a view of part of the apparatus in
the direction of arrow II in Figure 1;
and Fig 3 is a diagammatic view of alternative
apparatus.
Reerring to Figure 1, tile forming apparatus
includes a hopper 1 adapted to receive tile forming
material, e.g. concrete mortar, supplied from a
feed conveyor 2 via a chute 3. The conveyor 2 includes
inlets 4 for dry sand/cement mix and water, and a
rotating screw 5 adapted to mix the mortar and urge
it towards an outlet 6, disposed above the chute
3. A rotating paddle 7 within the hopper urges the
mortar down towards a roller 9 which compresses the
material onto a succession of pallets 8. The pallets
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8 are linked together and driven rightwardly as shown
in Figure 1. The mortar then passes under a slipper
]0 which finally compresses the mortar and shapes
its upper surface. The mortar emerges as a continuous
ribbon 11 which is cut into individual tiles 12 by
the blade 13 of the guillotine 14. Thereafter, further
handling of the tiles is conventional.
The feed conveyor includes further inlets 15
located towards its outlet end for the supply of
a pigment dispersion or slurry to the mortar within
the conveyor. Two or more differently coloured pigments
may be introduced to the mortar at regular or random
intervals, and the arrangement is such that partial
mixing occurs in the downstream end of the conveyor
and in the hopper whereby the finished tiles 12 are
provided with a variable base colour. For example,
red and yellow pigment dispersions may be introduced
to the mortar at respective five and ten second time
intervals such that the mortar entering the hopper
changes in colour from red through various shades
of orange to yellow, and then back through orange
to red. The extruded tiles in any batch thus contain
a mixture of these colours in varying degrees.
Colouring material is also added to the tile
forming material within the hopper via tubes 16,
and in this way coloured streaks are provided on
the upper surface of the ribbon 11. As shown in
Fig 2, six supply tubes 16 are mounted, in groups
of 3, to rail members 17 extending laterally across
the hopper, the tubes being coupled to the rotating
arms 27 of a motor 18 whereby the tubes are moved
back and forth above the roller and the material
within the hopper. In this way, the position of the
streaks provided on the upper surface of the ribbon
changes. The illustrated arrangement has a capacity
for up to six different streaking colours, and the
colourinq pigments mav be pumped to the tubes 16
at regular or random intervals.
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An alternative arrangement is illustrated in
Figure 3, where secondary hoppers 20 are located
above the main hopper ~. As shown, the secondarv
hoppers are adapted to receive three differently
coloured batches of material, which may be prepared
one by one in a sin~le batch mixer, or in three separate
batch mixers. Material from the secondary hoppers
is released into the main hopper at appropriate time
intervals, and self-mixing in the main hopper is
such that the body colour of the tiles varies between
the colours of the three batches.
The combination of a variable body colour and
streaks on the upper surface provides the tile of
the preferred embodiment with a distinct and attractive
appearance.
