Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02267860 1999-03-31
CONCRETE BLENDER AND MOLD
FIELD OF THE INVENTION
This invention relates to the field of
manufacture of molded cement articles and in particular
to an efficient portable cement blender which can be
used in territorial regions which have a lack of power
supply, as well as a mold which can utilize reclaimed
sulfur.
BArKGROL1ND TO THE INVENTION
In many regions of the world, the main building
construction material is sand and stone, which dictates
manufacture of buildings and houses from concrete. A
versatile form of the concrete is a cement block, from
which many different forms of building structures can be
made.
However in some of such regions, there is a lack
of power to blend the required sand, cement and stone to
make cement blocks, which results in humans being
required to perform the blending. This is difficult
work, and often results in manufacture of a minimal
number of blocks, many of which are non-uniform or
inferior. In addition, the molds that are used are
often formed of wood, resulting in poor finish to the
blocks and a high wear rate on the molds.
Rapid manufacture of a large number of blocks is
important in regions which have been devastated by
natural disaster, such as hurricanes or earthquakes.
Even if electrical power had previously been available I
such regions, the natural disaster would often destroy
its generation and/or distribution. Thus even electric
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motor-driven cement mixers which are on-site would not
be able to be used. Yet in these regions, rapid
manufacture of new housing units is very important, in
order to avoid disease or death.
HUI~lARY OF THE INVENTION
The present invention :is an apparatus and a
method for manufacture of cement blocks which use a
minimum of power which is so low that the apparatus can
be driven by a portable gasoline generator or by
photoelectric converted power. Thus there is no need
for mains power. The apparatus is portable and can be
transported by trailer to the site where the blocks need
to be manufactured. Thus cement blocks can be easily
and quickly made at the places most needed.
Instead of blending the cement block ingredients
in a rotary mixer, which requires all of the heavy
ingredients for a batch of cement to be mixed at the
same time, and thus requires a. large horsepower motor to
drive the mixing chamber, in a.n embodiment of the
present invention each of the ingredients is fed
progressively at the required rate into the opening of
transporting auger by vibratory feeders. The vibratory
feeders utilize very little power.
The process of transporting the ingredients by
the auger performs the blending process. The
ingredients in the process of blending by means of the
transporting auger are passed from the output of the
auger into the hopper of a molding machine, which
contains a mold having the shaped of a cement block.
The mold with its blended ingredients are
vibrated for about 6 - 12 seconds to release entrapped
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air. The blended ingredients are compressed in the
mold, and after less than a minute the block is forced
out from the mold in a plastic; but self-supporting state
for curing.
In accordance with an embodiment of the
invention, a concrete mixer comprises:
(a) plural horizontal trays for carrying respective
mixture materials to an inlet of a blender,
(b) vibrators fixed to the trays for causing the
trays to transport the materials along the trays to the
inlet of the blender,
(c) the blender having an inlet for receiving the
materials from the trays and an auger for blending the
materials while at the same time transporting the
blending and blended material; to a concrete receptacle,
and
(d) apparatus for controlling the volume of each of
the materials transported to t:he inlet of the blender.
In accordance with another embodiment, a mold
for molding concrete articles is formed of hard
urethane. This provides advantages which allows
otherwise discarded filler material (e. g. sulfur
reclaimed from smokestack cleaners) to be used in the
concrete block, speeding set-up of the concrete and
reducing the cost of the blocka.
Preferably the hard urethane is D-75 urethane.
In accordance with another embodiment, a method
of making molded concrete articles comprises:
(a) transporting each of t:he materials required to
form the concrete article by vibration of respective
materials transporting trays t:o an inlet of an auger,
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(b) blending the materials while at the same time
transporting the blending and blended materials by means
of the auger to a concrete rec:eptacle, and
(c) molding a concrete article using blended
materials contained in the cement receptacle.
BRIEF INTRODUCTION TO THE DRAHfINGS
A better understanding of the invention may be
obtained by reading the detailed description of the
invention below, in conjunction with the following
l0 drawings, in which:
Figure 1 is an isometric view of a blender in
accordance with an embodiment of the invention, and
Figure 2 is a schemati~~ diagram of a system for
producing concrete blocks,
IS Figure 3A is an isometric view of a mold in
accordance with another embodiment of the invention, and
Figure 3B is a block made in accordance with an
embodiment of the invention.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
20 Preferably the blender is mounted on the bed of
a trailer 1, for easy transport to a block manufacturing
site. Bins 3 and 5 are mountE:d on the trailer. The
bins have sloped sides for gravity feeding their
contents (respectively sand and gravel), have open slots
25 or ports 7 and 9 at their bottom sides to allow their
contents to drop below them at: controllable rates.
These rates can be controlled by means of shutters 11
and 13, which can be manually moved between and along
opposing channels disposed along opposite edges of the
30 respective ports 7 and 9 (not shown) to open or close
the ports 7 and 9.
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The contents of the bins drop onto elongated
trays 15 and 17 respectively, which trays are disposed
each with one end region under a respective port 7 and
9. The other end region of each tray 15 and 17 is
disposed above the open end 21 of an auger 19. The auger
19 contained in a tube has one end 21 open and flared,
into which the material transported on the trays drops.
The trays 15 and 17 have upwardly extending sides around
three sides, and are open at their ends 23 and 25.
l0 Controllable vibrators 27 and 29 are fixed in
contact with the underside of the respective trays 15
and 17, preferably under the locations where the sand
and gravel drop from bins 3 anal 5 to the trays. The
vibrators can be controlled by respective rheostats 31
or the equivalent mounted in a. control box 33 The
vibrators can be type Eriez 4'~A pan feeders which are
sold by Eriez of Canada Limited, Mississauga, Ontario,
Canada. The vibrator variable control can be type
FT115, sold by the same company. In a successful
embodiment, the trays were made of mild steel, 36" long
by 8" wide.
It has been found that each of the above tray
and vibrator structures can feed, by means of vibration,
between 12 oz. and 12 tons per hour of sand and stone
along the tray 15 or 17, all controllable by control 31
(which is clearly a very broad range).
It is preferred that cement should be added to
the mixture for blending by means of a round cross
section 8" diameter pipe 35, which has its outlet above
the inlet 21 to the auger 19. An inlet 37 to the pipe
is flared upwardly, and is disposed under a bin 39
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which contains the cement. A shutter 40 is disposed
across the outlet to the bin 39, similar to shutters 11
and 13. A vibrator 41 is fixed preferably to the bottom
of the pipe 35 under the inlet. The vibration amplitude
(i.e. the feed rate) of vibrator 41 is also controlled
by means of a control rheostat 31.
A water tank 43 is also mounted on the trailer
1, at a height which is above the opening 21 to the
auger 19. A hose 45 from the tank 43 feeds water into
l0 the opening 21 at a rate that is controlled by a valve
47. The valve 47 can alternatively be located adjacent
the tank 43 as shown or adjacent the opening 21 to the
auger 19; the latter location may be more convenient
when the operation is set up, since it is closer to the
controls 31 where an operator may be located.
In operation, the shutters 11, 13 and 40 and
valve 47 are closed. Cement is loaded into bin 39, sand
is loaded into one of bins 3 or 5 (say bin 3), and stone
(e.g. gravel) is loaded into the other bin. Water is
loaded into tank 43.
The shutters 11, 13 and 41 and valve 47 are
opened partway, and auger 19, driven by an electric
motor (not shown) is started. The vibrators 27 and 29
are turned on by means of a power switch (not shown) and
the feed rates of the trays are adjusted by means of
controls 31.
At this time it is preferred that the exit of the auger
19 should cause its effluent t:o pass into a sampling
bin. Blending of the mixture occurs in the auger
3o itself .
The quantity of each of the sand, stone and
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cement is controlled by controlling the corresponding
vibrator feed rate using rheostats 31 and by the amount
which the shutters 11, 13 and 40 are opened, and the
amount of water in the mixture is controlled by the
degree to which the valve 47 is open.
By sampling the effluent of auger 19 and
adjusting the feed rates of th.e three dry ingredients
using controls 31, and by adjusting the water valve 47,
the correct proportions of ingredients are blended by
the auger. Once the correct proportions have been
noted, the location of the di~~charge end of auger 19 is
moved to the opening of a hopper for a cement block
molding machine. Water is used with manufacture of
blocks using ordinary cement, but is not used when
blocks containing sulfur instead of cement are
manufactured.
By the use of vibratory feeders, the amount of
electric power required to operate the blender is
minimized, thus increasing its; efficiency. Indeed, a
three vibrator system as described above has been found
to require only 2 HP to continuously turn out about 18
to 20 cubic yards per hour of concrete, blended with
cement, sand, stone and water as described above. It is
believed that this could not ~>reviously be done with
such little power.
The amount of power is so low, that it can be
provided by means of one or more banks of solar cells
49. The solar cells can be mounted on a base which is
hinged at one side to a support 51, and manually or by
motor rotated about the hinge and fixed to a rod 52 to
obtain an optimum angle to the sun as the day
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progresses. The output power of the solar cells 49 can
be converted to the voltage anal a.c. frequency required
by the vibrators in a well known manner, e.g. by an
inverter. This allows the blender to be totally self-
contained in the field.
Alternatively, a fossil fueled electric
generator can be used to provide the requisite power,
and can be mounted on the trailer 1. It should be noted
that due to the low horsepower required to operate this
1o blender, inexpensive and readily available generator can
be used.
It is preferred that the auger 19 should be
hinged or rotatably pinned under its open end 21, to a
support 51, so that during transport the discharge end
of the auger can be swung upwardly to be fastened
approximately vertically, swur.~g to the side or swung
inwardly of the trailer, for easy transport.
Alternatively, the open end 21 of the auger can be
unfastened and the auger removed for transport in a
cradle or other fixing apparatus on the trailer 1.
Figure 2 illustrates a schematic side view of
certain elements of the structure, feeding a molding
machine. The concrete mixture blended in the auger 19
is lifted up and discharges ir.~to a hopper 53. A
concrete block mold 55 is disposed with its upper
opening below and if necessary to one side of the hopper
53. A side of the hopper above the opening to the mold
55 has a door or port 57 which can be opened manually or
more preferably pneumatically. The bottom of the mold
is fixed to a vibrator 59.
When the blended effluent (concrete mix) of the
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auger 19 drops into the hopper 53, it gradually fills
it. Once enough concrete mix is contained in the
hopper, an operator opens port 57, allowing the concrete
mix to drop into the mold 55. Once the mold has been
filled, or slightly overfilled, the operator closes port
57. The operator then causes vibrator 59 to begin
operation, e.g. for about 6 to 12 seconds, which causes
the concrete mix to release any entrapped air or other
gases. The operator then causes the top of the mold to
close (not shown), and the molding machine to compress
the concrete mix in the mold t:o preferably about 2200
pounds per square inch (which is more than twice the
ASTM standard of 1000 pounds per square inch).
After a predetermined ~~ompression time (e. g.
about 10 seconds), the cement mix has been rendered into
a plastic state, and the top c>f the mold is removed.
The bottom of the mold is pushed upwardly, pushing the
set-up block upwardly. Once i.t clears the upper sides
of the mold, a pusher plate can push the plastic
concrete block to one side, tc> a curing table.
While manual operation or control of the block
making apparatus has been described, operation is
preferably pneumatically controlled, and control of the
pneumatic sequence can be automated by a mechanical or
electro-mechanical or other controller.
Another embodiment of this invention relates to
the structure of the mold itself. Previous molds were
typically made of steel. Such molds have been found to
wear very quickly when used repetitively to form
concrete blocks, thus increasing the cost of a
production line.
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A block which utilizes waste and poor quality
sulfur had previously been invented, e.g. sulfur
recovered from smokestack cleaners. Blocks can be made
using, by volume, about 51~ sa.nd, about 29$ stone and
12~ cement or 8~ - 9~ sulfur, the sulfur being heated to
230° F.
Materials for sulfur-based concrete blocks is
described, for example, in Canadian patent 1,279,661
issued January 29, 1991, invented by Garry L. Tucker.
While that sulfur can be used in the manufacture
of concrete blocks, it has not. been able to be used in a
practical manner for the reason that the heated sulfur
was found to freeze immediately on contact with the
steel of the molds, thus precipitating out of the
mixture and ruining at least the surface of the blocks.
I have discovered that I can make concrete
blocks using the mixture that includes sulfur by forming
the mold out of dense, very hard D-75 urethane. I have
discovered that the sulfur does not freeze on contact
with the urethane. Therefore the poor quality sulfur
reclaimed from smokestack cleaners can be recycled into
useful concrete blocks which c:an be used as construction
materials.
In addition, I have discovered that the mold
made of hard urethane does not: wear as quickly as steel,
and experiments have shown that it outlasts a steel mold
for the described application 5:1. A mold 61, formed of
such urethane, which can be u~;ed as mold 55 in Figure 2,
is shown in Figure 3A to make a cement block such as
that shown in Figure 3B. Indeed, with the system
described above, and with the ingredients described
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above including the reclaimed sulfur, allows manufacture
of the blocks at low cost.
In order to add the su:Lfur, the sand can be
heated to 230° F. or above to (to allow for cooling
during processing) and the powdered sulfur added to the
sand. When the sulfur touches the sand it is heated up
to substantially the same temperature. Heating the sand
also drives off the moisture from the sand. All of the
surfaces which touch the sand (and therefore the sulfur,
to such as the hopper surface, the transporting tray, the
auger and the inside of the pipe in which the auger is
housed) are coated, e.g. by spraying, with hard
urethane, so that the sulfur will be protected from
freezing. The mixture should be kept flowing through
the auger so that it will not solidify prior to entering
the mold.
While a block made of ordinary cement typically
has a strength of about 1,000 - 1,200 psi, a block made
of sulfur in place of cement as described above have
been tested to have strength of about 12,000 psi. While
a block made of ordinary cement is eaten away within a
few months when exposed to suJ.furic acid (as may be
contained in acid rain) a block made of sulfur in place
of cement as described above has been shown to be
virtually unaffected by the sulfuric acid over several
years. It has also been shown not to disintegrate when
immersed in salt water or when covered in pig urine.
Clearly, with low cost per block, the low levels
of power required to operate t:he apparatus, the ability
to supply the low power levels from a portable generator
or by power conversion from the sunlight, and the
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portability of the entire apparatus, it is ideally
suited to produce concrete blocks for housing units and
buildings in disaster areas and in underdeveloped
regions. Since the apparatus is so simple to use,
relatively uneducated workers can be readily trained to
manufacture the blocks.
A person understanding the above-described
invention may now conceive of alternative designs, using
the principles described herein. All such designs which
fall within the scope of the claims appended hereto are
considered to be part of the present invention.
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