Note: Descriptions are shown in the official language in which they were submitted.
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TITLE
System for the controlled production of concrete from mobile concrete mixer
trucks.
s FIELD OF THE INVENTION
The present invention relates to a system for the controlled production of
concrete, particularly in mobile concrete mixer trucks. The system comprises a
computer
coupled to various sensors monitoring the amount and flowrate of each
component
delivered into a concrete mixing auger, as well as a database that stores the
various
1 o parameters required for a given concrete composition.
BACKGROUND OF THE INVENTION
A mobile concrete mixer truck represents an advantageous way to prepare and
produce concrete on the spot, from one construction site to another. The truck
is therefore
1 s a production plant for ready-to-use concrete, and generally comprises
several tanks for
water, cement, sand and aggregates. Because of its limited capacity, mobile
concrete
mixer trucks are typically used for small quantities or special concrete
compositions, such
as latex-containing concrete. It is also useful for dry concrete used in
shotcret
applications.
Although calibration of mobile concrete mixer trucks is governed by ASTM
C685-95A, it is well known that such manufacturing process lacks precision.
Accordingly, their use is sometimes prohibited even if it would be
economically sound.
However, for latex-containing concrete, their use is tolerated, but if nothing
is attempted
2 5 to improve the technology, it will still represent a marginal technique.
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As stated above, a conventional mobile concrete mixer truck comprises tanks
containing separately the typical constituents of concrete, i.e., aggregates,
sand, water and
cement. The concrete composition may also comprise conventional additives such
as an
s air-entraining agent, a superplasticizer, a latex and the like, that are
also contained in
separate tanks. The aggregates and the sand are generally forwarded to the
rear of the
truck on a conveyor belt in a concrete mixing auger to produce the desired
composition.
The concrete production may be in a continuous manner, but is generally
batchwise.
i o Conventional mobile concrete mixer trucks are generally calibrated only
for a
specific concrete composition. The method of calibration typically comprises
calibrating
the cement first. A revolution counter coupled to a cement wheel adapted to
deliver
cement into the concrete mixing auger indicates the amount of cement
delivered. Then,
by knowing the flowrate of cement per minute, the flowrate of the sand and the
i5 aggregates are adjusted through trial and error, and the size of the
opening of the hatches
corresponding to these flowrates are subsequently determined. Most of the
time, the
concrete workability is adjusted with the water flowrate. The water content in
the various
components of the concrete composition is never taken into consideration, and
the
amount of water added to the composition is not known. Such procedure
therefore allows
a o poor control, and is not practical when several deliveries have to be made
on a given day
whether at the same of various locations, because calibration must be repeated
every time
the concrete composition changes.
It should also be noted that conventional mobile concrete mixer trucks do not
2 s contain a water flowmeter. Rather they generally comprise an incrementing
device that is
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capable of ensuring that a given volume of water has been introduced in the
concrete
composition. There is however no control or indication of the flowrate, and it
is therefore
impossible to assess whether the latter was constant during the addition
period.
s It is trite to anyone of ordinary skill in the art that appropriate control
of the
manufacturing process leads to excellent quality concrete. However, little
effort has been
done in the field so far for controlling the manufacturing process of
concrete, particularly
in mobile concrete mixer trucks.
to SUMMARY OF THE INVENTION
In accordance with the present invention, there is now provided a system for
controlling the production of concrete from a mobile concrete mixer truck
comprising a
tank for each concrete component, the system comprising:
a) an actuator coupled to a hatch for each tank;
15 b) a sensor for monitoring the position of the actuator;
c) a keyboard;
d) a computer processing unit (CPU) coupled to the actuator, the sensor and
the keyboard,
for receiving data from the keyboard, processing the data and sending a signal
to the
actuator for actuation thereof to a predetermined position, the position of
the actuator
z o being monitored by the sensor, thereby monitoring and controlling the
amount and
flowrate of each component into a concrete mixing auger; and
e) a display coupled to the CPU for displaying unprocessed and processed data
from the
CPU to the operator.
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In a preferred embodiment, the CPU comprises a storing unit for storing
information related to previous concrete composition parameters. Also, the
sensor for
water comprises a flowmeter, and the water source is either from a tank
internal to the
truck, or external.
In a second aspect of the invention, there is provided a method for the
controlled production of concrete from a mobile concrete mixer truck
comprising a tank
for each concrete component, the method comprising the steps of
a) entering a predetermined concrete composition into the CPU through the
keyboard;
i o b) actuating the hatch of each tank to a predetermined position, the
position being
monitored with the sensor; and
c) displaying the data related to the concrete and the components onto the
display for
consultation by the operator.
DETAILED DESCRIPTION OF THE INVENTION
The present invention comprises a system for the control of concrete
composition, and particularly for mobile concrete mixer trucks. The system
main
components are: a computer processing unit (CPU) and a storing means such as a
database, a display, a keyboard and various actuators and sensors, the last 4
elements
a o being coupled to the CPU. The display and the keyboard are used as
interfaces with the
operator, while the sensors are gathering and transmitting various data to the
CPU for
processing thereof, and showing onto the display. The CPU then sends a signal
to each
actuator so that the position of the hatch for each tank is controlled to
produce the
concrete composition in accordance with the information entered by the
operator. At the
z 5 end of the manufacturing process, the operator is able to see on the
display the data
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relating to the amounts of the various components into the concrete, and the
volume of
concrete delivered and its volume weight. The water/binder ratio is
continuously
displayed on the display. The water content previously entered by the operator
and the air
content are therefore taken into consideration by the CPU when calculating and
s determining the volume of water to be delivered to the concrete mixing
auger.
Linear position sensors are installed on the hatches controlling the flow of
sand
and aggregates into the mixing auger. The sensors provide the operator with
the size of
the opening of the hatches of the sand and aggregates tanks. After proper
calibration and
i o conversion through the CPU, the operator views on the display the actual
flowrate of sand
and aggregates into the mixing auger.
Flowmeters are installed to measure the flow of any additive and water into
the
concrete. These flowmeters are selected and calibrated to be accurate for the
various
i s flowrates to be measured. For example, the water flowmeter is preferably
adapted for
flowrates higher than that for the additives, which is adapted to measure
smaller
flowrates. These flowmeters can inform the operator on the fluid flow in the
pipe and
advise on the total volume of air and water added to the concrete mixture.
z o The following is an example of the method for the production of a given
concrete composition. To produce such a composition, the operator selects a
predetermined concrete composition based on a pre-programmed database into the
computer. The operator then obtains on the display the recommended flowrates
for such
compositions and the corresponding size of opening for the hatches of the
tanks
2 s containing the concrete components, to produce the desired concrete
composition. The
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display also indicates the water flowrate that the operator should target to
obtain the exact
water/binder ratio. The computer then sends a signal to the actuators to open
each hatch
to an opening corresponding to the desired flowrate. An important aspect is
that the
values displayed to the operator on the display take into consideration the
water content
s of the sand and aggregates, so that the water/binder ratio is optimal and
precise. The
water content of the sand and aggegates is entered into the CPU through the
keyboard at
the beginning of the production operations, so that the CPU takes these values
into
consideration before determining the appropriate flowrate of water into the
auger. The
subsidence is adjusted with a super-plasticizer so that the amount of water
added to the
1 o composition is not modified. For concrete compositions with a small
water/binder ratio, a
water reducer can be directly added to the water tank to modify the concrete
workability.
Such water reducer are common and well known in the field to anyone of
ordinary skill in
the art.
1 s Following the completion of the delivery of the concrete composition, the
air
content of the concrete composition is entered through the keyboard, and the
CPU
calculates and displays on the display the exact volume of concrete produced.
The system
can also be connected to a printer that will print the various quantities of
each component
of the concrete composition on a sheet, as well as the volume weight and total
volume of
a o concrete delivered.
With the present system, calibration of the various delivering elements
forming
the truck is much simpler and accurate. Further, such calibration does not
need to be
repeated every time a composition is prepared. Also, importantly, the water
content of
2 5 the various components of the concrete composition is taken into
consideration during
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data processing to determine the amount of water to be added, and the
corresponding
preferred flowrate. As a result, the operator can precisely control not only
the amount of
each component into the concrete composition, but also their flowrates. All
this data is
shown on the display, and the operator is free to change any parameter through
the
keyboard during concrete manufacturing.
The calibration should preferably be performed whenever the nature of either
of the components of the concrete composition is changed. In operation, the
production
of a concrete composition from a mobile concrete mixer truck comprising the
system of
i o the present invention follows the following simple procedures.
The operator initially selects a concrete composition from the concrete
composition database. If no such composition exists, the system should be
calibrated, and
the database updated to include the new parameters. Subsequently, the computer
suggests
i5 a size of opening for the hatch of each component of the concrete to be
prepared, as well
as an appropriate water flowrate. The water flowrate takes into consideration
the water
content of the various components of the concrete to obtain an optimal
water/binder ratio.
If a new concrete composition is produced, the composition is entered into the
2 o database, and the appropriate amounts and flowrates of the various
components are
calculated to produce the desired concrete composition. A significant
advantage of the
system is that the operator does not need to recalibrate the parameters that
have already
been calibrated and entered into the database. Further, since the system
comprises a water
flowmeter, it is possible to permanently control the flowrate of water.
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According to ASTM-C685 standard, there is a requirement that the controls
and methods of control be accessible and easy to read to any person, and that
for all the
components in the concrete composition. This includes a flowmeter for water
and liquid
additives, linear position sensors for both hatches for the sand and the
aggregates
s respectively, and a pulse counter for the cement wheel.
Still according to C-685 standard, the total concentration of water must be
included in the calculation of the water/binder ratio, including also free
water around the
particles. The present system has been designed to ensure appropriate flow of
fine and
i o coarse particles whatever their water content and the state of
compactness. Further, since
the water concentration in the fine and coarse particles can be entered in the
CPU for the
determination of the water amount and flowrate, the calculation of the
water/binder ratio
is precise and optimal for the concrete composition desired. Such controls
ensure a
precise concrete composition because the addition of each component into the
concrete-
i s mixing auger is carefully monitored and controlled throughout the
operation.
The present system is therefore useful not only for exactly knowing the
concrete composition and amount thereof delivered, but also because the
database
contains all the necessary parameters required to be able to produce such
composition.
The present system should preferably contain a vibrator coupled to the cement
wheel. This vibrator is activated automatically at even intervals, for example
every 60
seconds, to remove cement stuck to the surface of the cement wheel.
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The display provides all the necessary information to the operator and the
concrete buyer. According to the C-685 standard, the production process of
concrete
requires that the amounts of concrete exiting the truck be visible at any
time. The display
also shows the composition of the concrete and the real value of the
water/binder ratio.
s The operator is therefore capable of immediately correcting any amount or
flowrate of a
component that is defective.
While the invention has been described in connection with specific
embodiments thereof, it will be understood that it is capable of further
modifications, and
1 o this application is intended to cover any variations, uses or adaptations
of the invention
following, in general, the principles of the invention, and including such
departures from
the present description as come within known or customary practice within the
art to
which the invention pertains, and as may be applied to the essential features
hereinbefore
set forth, and as follows in the scope of the appended claims.
