Note: Descriptions are shown in the official language in which they were submitted.
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LIGHTWEIGHT CONCRETE MIXER
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention is directed to an apparatus for manufacturing
lightweight concrete during the installation of roof decks of a building
structure.
Discussion of the Related Art
Lightweight concrete is used extensively in the construction of buildings,
and particularly in the installation of roof decks and related roof systems.
When installing a roof deck on a building structure, lightweight concrete is
disbursed, in a slurry coat, to form a topping layer of insulation over
underlying roofing materials. Lightweight concrete typically consists of a
combination of Portland cement, one or more foaming agents, water and
possibly other chemical agents. To insure proper distribution of the
lightweight
concrete, prior to curing, it is important to discharge the lightweight
concrete
mixture on the roof deck shortly after the mixing process. Presently, the
process for manufacturing lightweight concrete for on-site installation
involves
the use of one or more compressors, a pressurized tank for holding chemicals,
a separate cement mixer, a concrete pump and an elaborate series of hoses for
directing water, chemicals, cement, foaming agents and other chemicals to be
mixed and discharged in rapid action. Using this method, the lightweight
concrete is manufactured in batches and then discharged in a slurry coat on
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the roof deck. After each batch is exhausted, subsequent batches are
manufactured and discharged until the installation of the lightweight concrete
roof insulation is complete. The presently used method of on-site manufactur-
ing of lightweight concrete presents several problems and concerns.
Specifically, pressurized hoses have been known to burst, subjecting workers
to potential serious injury. Additionally, the numerous equipment and hoses
needed to mix the components of the lightweight concrete mixture often
become tangled, which results in possible equipment malfunctions and
operational delays. A further problem with the presently used mixing process
is the inability to produce uniform and consistent mixtures of lightweight
concrete which meet code requirements, such as consistency in pull strengths
throughout the roof deck. Because the mixing process, and particularly the
rate and amount of flow of each component in the mixture relies on human
judgment, it is difficult, if not impossible, to produce uniform and
consistent
mixtures throughout multiple batches.
Accordingly, there is an urgent need in the construction industry for a
contained and portable apparatus which is specifically structured for on-site
manufacturing of lightweight concrete in a safe, controlled and highly
predictable process to produce a continuous on demand supply of lightweight
concrete in a consistent, uniform mixture.
Summary of the Invention
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The present invention is directed to an apparatus for on-site
manufacturing of lightweight concrete used for insulation in roof decks and
roof systems of building structures. The apparatus is supported on a
transportable trailer frame and includes a mixer, a concrete pump, and one or
more tanks for holding a mixture of water and chemical products, such as
foaming agents. The chemical agents/water solution is mixed with pressurized
air according to a desired foam density and volume and is pumped through a
foam cylinder ejector. The air/solution mixture exiting the ejector is
directed
into a carburetor which generates a foam product by mechanical impact of the
air/ solution mixture with beads contained in the carburetor. Concrete and the
foam product are combined in the mixer, in accordance with a predetermined
mixture ratio, and released into the concrete pump for forced discharge from
the apparatus and application to a roof structure. A programmable logic
controller controls the discharge rate and the amount of cement and foam
product needed per batch according to the desired mixture ratio.
Brief Description of the Drawings
For a fuller understanding of the nature of the present invention,
reference should be made to the following detailed description taken in
conjunction with the accompanying drawings in which:
Figure 1 is a front, top perspective view of the lightweight concrete
manufacturing apparatus of the present invention, shown partially open to
reveal the major components thereof;
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Figure 2 is a schematic diagram illustrating the components and the
operational flow of materials through a foam generating system of the
apparatus of the present invention;
Figure 3 is a side elevational view of a foam cylinder ejector of the
apparatus; and
Figure 4 is an isolated elevational view of a foam carburetor, shown in
partial cross-section, used for generating the foam product in the apparatus
of
the present invention.
Like reference numerals refer to like parts throughout the several views
of the drawings.
Detailed Description of the Preferred Embodiment
Referring to the several views of the drawings, the lightweight concrete
manufacturing apparatus of the present invention is shown and is generally
indicated as 10. As seen, the apparatus 10 is preferably supported on a
trailer
or chassis frame structure 15 with multiple axles (e.g., triple axle
suspension)
and wheels 18 to support the weight of the apparatus 10. In this preferred
embodiment, the apparatus 10 is intended to be towed by a vehicle, such as a
truck.
The apparatus 10 includes a dual drum mixer 20 which is open on the
top for receiving a loose flowing supply of concrete from a hopper 14 and up
through a hydraulic auger that is operated by a hydraulic auger motor 94. The
cement (concrete) in the hopper 14 is measured in a hydraulic cylinder
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connected to a pressure sensor that measures the PSI. The PSI is converted to
pounds of weight by a PLC (programmable logic controller) 35. One or more
tanks 30 are provided for containing chemical agents and water. In a preferred
embodiment, two 200 gallon individually operated solution tanks hold one or
more foaming agents (in liquid form) mixed with water to provide a solution
that is used to make a foam product. The foam product is then used in the
manufacture of lightweight concrete. In a preferred embodiment, the foaming
agent is a concentrate known commercially as CONCRECELTM. Portland
cement and the foam product are combined in mixer 20 in accordance with a
predetermined mixture ratio.
A turbo diesel engine 50 drives operation of hydraulic motors which, in
turn, drive several of the components of the apparatus. A fuel tank 90 holds a
supply of fuel for operating the diesel engine 50. A control panel 70 is
provided
with controls and gauges for operating, regulating and monitoring operation of
the several components throughout the mixture and discharge process,
including a hydraulic system and the diesel engine 50. The hydraulic system
used for controlling the operation of most of the components includes a
hydraulic oil tank 80 for containing the hydraulic fluid of the system and a
transmission for delivering hydraulic fluid to the motors which drive the
mixer
20, concrete pump, air compressor and other components. In particular, the
mixer has dual hydraulic reversible mixer motors 95 that turn mixing paddles
in the mixer 20. The mixer motors have a self packing bearing system 96. The
hydraulic oil in the hydraulic system is cooled by cooling fans 32 as the
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hydraulic oil travels through the cooling radiator 38. The hydraulic air
compressor 60 has a filter 42 with a separate cooling system.
Referring now to Figure 2, the foam generating system of the apparatus
is described in more detail. Initially, the foam generating solution is made
by mixing the liquid foam concentrate with water according to a controlled
mixture ratio. The foam concentrate is pumped from a container 1, such as a
55 gallon drum, to the two 200 gallon tanks 30 with use of a diaphragm pump
2. The pumped foam liquid concentrate is directed through a flow meter 3 that
measures the rate of flow in order to obtain the proper solution mixture ratio
of
foam liquid concentrate and water that is filled into the 200 gallon tanks 30.
A
supply of water 98 is delivered from a water supply source and is directed
through a water meter 97. More specifically, the amount of water is measured
by an electronic magnetic drive water meter 97. The PLC (programmable logic
controller) 35 communicates with the flow meter 3 and the water meter 97 to
determine and control the amount of foam liquid concentrate and water being
filled into each of the two 200 gallon tanks 30. Accordingly, the solution of
foam liquid concentrate and water in each of the tanks 30 is accurately
measured and controlled to maintain the desired ratio of foam liquid
concentrate to water in the solution. The foam solution is mixed in the non-
pressurized 200 gallon tanks 30 to provide a uniform solution mixture
throughout the entire filled volume of the tanks.
From the tanks 30, the solution is pumped and pressurized by at least
one of two diaphragm pumps 24 for pressurized delivery of the solution
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through a foam cylinder ejector 25. The volume of the solution is adjusted by
air pressure that is delivered from the air compressor holding tank 40 using
controls on a foam control panel 22. The air compressor 60 replenishes a
supply of pressurized air that is contained in the holding tank 40. The foam
volume and density is adjusted by regulating the air injection and solution
flow
rate as the air and solution enter the foam cylinder ejector 25. In the
ejector
25, the desired amount of air and solution are combined under pressure. The
pressurized flow of air/solution mixture exiting the foam cylinder ejector 25
enters a foam carburetor 65 for generating a foam product. Specifically, the
pressurized flow of air/ solution mixture is mechanically impacted with beads
65D (see Figure 4) within the foam carburetor 65 which creates the foam
product. The PLC 35 regulates the amount of foam product per batch via a
pneumatic ball valve 12.
Referring to Figure 3, the foam cylinder ejector 25 includes a one inch
solution inlet hose 25A and a one half inch air inlet hose 25B. The air inlet
hose 25B is fitted with a high pressure hydraulic check valve 25C to prevent
back flow through the inlet hose 25B. Accordingly, using the foam control
panel 22, as shown in Figure 2, the pressurized flow of air from the holding
tank 40 is delivered into the foam cylinder ejector, through the inlet hose
25B,
at an adjusted pressure and flow rate according to the desired volume and
density of the foam product to be subsequently generated in the carburetor.
Further, the flow rate of the solution is controlled at the foam control panel
22
for delivery through the inlet hose 25A and into the foam cylinder ejector 25
at
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the controlled rate to achieve the desired volume and foam density. The foam
cylinder ejector 25 further includes a pressurized solution outlet hose 25D
for
directing the pressurized air/ solution mixture to the foam generator 65. The
pneumatic ball valve 12 is operated in order to control the rate of flow of
the
pressurized air/ solution mixture into the foam carburetor 65.
Referring to Figure 4, the foam carburetor 65 is shown. The foam
carburetor is open at both ends to permit flow of foam materials therethrough.
A first end of the foam carburetor is fitted with a PVC reduction coupling 65A
that communicates with the main body 65C of the foam carburetor. In a
preferred embodiment, the main body 65C is formed of schedule 40, four inch
PVC pipe. The reduction coupling 65A is approximately one inch in diameter.
Accordingly, as the pressurized flow of air/foam solution mixture is directed
into the carburetor, through the reduction coupling, the mixture expands at a
1:4 ratio as it is impacted against polyethylene beads 65B packed within the
interior of the carburetor body 65C. Mesh screens are fitted within the
carburetor body, near the opposite ends, to contain the beads 65B therein.
The mechanical impact of the air/ solution mixture with the beads 65B
transforms the mixture into the foam product which exits at the larger (4
inch)
end of the carburetor body 65C.
As noted above, the foam product is mixed with cement in the dual drum
mixer 20 to create the desired lightweight concrete product. For each batch,
the PLC 35 controls the predetermined amount of foam product and cement
released into the dual drum mixer 20. Specifically, the pneumatic ball valve
12
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is operated by the PLC 35 to control the amount and the rate of release of
foam
product from the foam carburetor 65 into the dual drum mixer 20. Similarly,
the PLC 35 controls the amount of cement delivered from the hopper 14 into
the dual drum mixer 20 for the controlled ratio of foam product to cement for
each batch of lightweight concrete produced by the apparatus 10. The cement
in the hopper 14 is measured by a hydraulic cylinder connected to a pressure
sensor. The PLC 35 communicates with the pressure sensor and converts the
PSI to pounds of weight. The PLC 35 then controls the discharge of cement
from the hydraulic auger 11 into the dual drum mixer 20 according to the
predetermined ratio of cement to foam product per batch.
While the instant invention has been generally shown and described in
accordance with a preferred and practical embodiment thereof, it is recognized
that departures from the instant disclosure are contemplated within the spirit
and scope of the present invention.
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