Patent Application
20200101477
Embodiments disclosed herein relate generally to manufacturing of concrete, and more particularly to a nozzle and method for dispensing one or more components such as water and/or liquid chemical admixtures, for example, into a concrete mixer drum.
Concrete is made from cement, water, and aggregates, and optionally one or more chemical admixtures. Such chemical admixtures are added to improve various properties of the concrete, such as its rheology (e.g., slump, fluidity), initiation of setting, rate of hardening, strength, resistance to freezing and thawing, shrinkage, and other properties.
In most cases, chemical admixtures are added at the concrete plant at the time of batching. In a “dry batch” plant, the cement, water, aggregates, and chemical admixtures are added from separate compartments (e.g. bins or silos) into the rotatable drum of the ready mix truck, and the ingredients are mixed together. In a “wet batch” or “central mix” plant, all ingredients are combined and fully mixed in a fixed-location mixer, then dumped into a rotatable drum on a truck. A “shrink mix” plant is similar to a “wet batch” or “central mix” plant, with the exception that the ingredients are only partially mixed in the fixed-location mixer, and then mixing is completed within the truck mixer.
In a typical dry batch process, the “head water” is first added, followed by the aggregate and cement, and then followed by the “tail water.” The chemical admixture is usually added with the head or tail water. In this way, it is diluted and enough water is present to rinse all chemical admixtures into the mixing drum. In addition, chemical admixture may be added directly on the aggregate as the aggregate is being conveyed to the drum, thus ensuring that all chemical admixtures enter into the drum of the ready mix truck.
The drum of a ready mix truck is typically an oblong shape with an inner wall connecting opposed first and second ends for defining a cavity within which fluid concrete can be contained. One of the two opposed ends is an open end to permit loading and unloading of concrete or components necessary to form concrete. It is mounted at an angle, e.g., an orientation of 5-40 degrees relative to level or horizontal ground, such that the open end is at the top.
Mixing blades or fins are mounted in a helical pattern inside the drum. When the drum is rotated in one direction relative to the blades or fins, the mixing blades push the concrete to the lower end of the drum and cause mixing. When the drum is rotated in the other direction relative to the blades or fins, the mixing blades push the concrete up to and out of the opening. The drum can only be filled partially full with fluid, plastic concrete, because otherwise the concrete will tend to splash out from the truck beyond a certain point.
After batching, the truck moves away from the loading area of the plant and, in the case of dry-batch or shrink mix concrete, completes the initial mixing of concrete, before departing for the jobsite. Frequently, it is desirable to add additional fluid (water or chemical admixture) after the concrete is batched and initially mixed, including up to the time of final discharge at the jobsite. This is be done because some chemical admixtures perform better when added after batching. It is sometimes necessary to add additional fluids to compensate for variations in batching of all ingredients (e.g. too little water added at batching) or changes in concrete properties over time (e.g. loss of flowability and other rheological properties).
It is also known to control the “slump” of concrete in ready-mix delivery trucks by using sensors to monitor the energy required for rotating the mixing drum, such as by monitoring the torque applied to the drum by measuring hydraulic pressure and to adjust fluidity by adding fluid into the mixing drum.
Concrete trucks are commonly equipped with water tanks connected by a hose line or the like directed into the drum opening. In this manner, water can be dispensed into the drum under air pressure in the tank or by pump.
It is less common for chemical admixture tanks to be mounted on trucks. When such admixture tanks are present, however, the tank is typically connected to the same hose line used to discharge water into the drum. The chemical admixture may be dispensed into the water line under air pressure or by tank to the pump.
Thus, both water and admixture can be added to the concrete mixing drum from onboard tanks. The water is usually added by pressurizing the water tank, such as with pressure up to about 60 psi, and opening a valve to commence the water addition. However, as concrete or concrete constituents are added to the concrete truck, the concrete materials tend to stick to the water nozzle, resulting in the unwanted addition of small amounts of cement, sand, rocks, etc. to the nozzle. This is illustrated schematically in
Concrete is both loaded and discharged through the same opening past the nozzle, and in typical applications, this can cause the water spout to fill with concrete and become unusable. To counteract this, the nozzle should be cleaned each time the truck is loaded, which is time consuming and is rarely done by the field operators.
Concrete can also “stack up” or become very high when the material is stiff. This means that when the concrete is discharged it fills the entire “throat”, or opening of the drum. The water and admixture nozzle or nozzles are typically in the way of this discharging concrete and can become completely covered. The inside of the nozzle(s) also can become filled with concrete. These issues cause the water nozzle to lose is effectiveness in adding water and can eventually restrict the water discharge from the nozzle completely.
To remedy these issues, the field operators may resort to the use of hammers or other tools to mechanically remove the concrete from the nozzle, or may drill out the nozzle in an effort to rid them of concrete. The admixture nozzles (when separate from the water nozzle) may have the same issues even though they are considerably narrower; cement paste may still end up restricting the nozzle from the inside and/or the outside.
Accordingly, it is an object of embodiments disclosed herein to provide a nozzle that does not suffer from the foregoing drawbacks.
It is a further object to provide a method of shedding concrete from one or more surfaces of a nozzle.
Embodiments disclosed herein provide a system and apparatus for introducing one or more liquids into a cavity, such as a concrete mixer drum. In certain embodiments, the apparatus includes a nozzle suitable for dispensing one or more liquids, such as water and/or liquid chemical admixtures, into a cavity such as a concrete mixer drum, and is useful for mixers in plant installations and especially useful in concrete ready-mix delivery trucks. Also disclosed is a method of introducing one or more liquids into a cavity such as a concrete mixer drum.
More specifically, in certain embodiments a nozzle boot is provided, the nozzle boot surrounding a portion of a nozzle shaft or other support member, the boot being expandable and collapsible and having a boot outlet. In some embodiments, the boot is expandable and collapsible in multiple directions, including axially and radially (e.g., relative to the support member). In certain embodiments, the boot surrounds a portion of a nozzle shaft or support member, and is suitable for introducing via the boot outlet, such as by injection, one or more liquids into a cavity, such as a rotatable concrete mixer drum.
In some embodiments, a nozzle assembly can introduce more than one component into the mixer drum independently. In some embodiments, such a nozzle assembly has a nozzle boot, a nozzle shaft, a nozzle shaft inlet, a nozzle boot inlet, a nozzle shaft outlet, and a nozzle boot outlet, wherein the nozzle boot surrounds a portion of the nozzle shaft. In certain embodiments the nozzle shaft functions to both support the nozzle boot, and to introduce a component into a concrete truck mixer drum. Thus, the nozzle shaft inlet is configured to fluidly communicate with a source of a first component to be introduced to the mixer drum, such as a source of admixture, and is in fluid communication with the nozzle shaft outlet. In certain embodiments, the nozzle boot inlet is configured to communicate with a second component to be introduced into a mixer drum, such as a source of water, and is in fluid communication with the nozzle boot outlet. When the second component is allowed to flow into the nozzle boot via the nozzle boot inlet, it causes expansion of the nozzle boot. As a result of that expansion, concrete that has previously adhered to the surface of the nozzle boot (e.g., the outer surface and/or the inner surface) is subjected to tension as the boot expands. Due to the limited tensile strength of concrete, the concrete cracks and breaks away from the nozzle boot, shedding the nozzle of unwanted concrete.
Thus, embodiments disclosed herein removes concerns due to concrete build-up on the nozzle. When the operator adds fluid, the nozzle expands laterally and circumferentially to break concrete off. The force of the fluid flowing through the nozzle creates the expansion needed to break apart the concrete.
In certain embodiments, a system for injecting fluids such as chemical admixture and/or water, into a rotatable mixer drum, such as a rotatable concrete mixer drum, is provided. The system can include a mixer drum that is rotatably mounted to permit rotation about a rotation axis inclined at an orientation of, for example, 5 to 40 degrees relative to level ground and which may have an oblong drum body with an inner circumferential wall connecting opposed first and second ends for defining a cavity within which to contain a fluid, such as fluid concrete. One of the two opposed ends may have an opening to permit loading and unloading of the fluid concrete from the cavity. The system may include a source of a first component such as chemical admixture, and/or a source of a second component such as water. The system may include a nozzle, the nozzle including a support member and a nozzle boot surrounding at least a portion of the support member, the nozzle boot having a nozzle boot inlet and a nozzle boot outlet spaced from the nozzle boot inlet and a volume between the nozzle boot inlet and the nozzle boot outlet, the nozzle boot inlet being in fluid communication with the source of the first component and/or with the source of the second component, and being expandable upon the introduction of the first component into the volume, and collapsible upon the withdrawal of the first component from the volume. The support member may also function to introduce a component into the mixer drum.
A more complete understanding of the components, processes and apparatuses disclosed herein can be obtained by reference to the accompanying drawings. The figures are merely schematic representations based on convenience and the ease of demonstrating the present disclosure, and is, therefore, not intended to indicate relative size and dimensions of the devices or components thereof and/or to define or limit the scope of the exemplary embodiments.
Although specific terms are used in the following description for the sake of clarity, these terms are intended to refer only to the particular structure of the embodiments selected for illustration in the drawing, and are not intended to define or limit the scope of the disclosure. In the drawing and the following description below, it is to be understood that like numeric designations refer to components of like function.
The singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.
As used in the specification, various devices and parts may be described as “comprising” other components. The terms “comprise(s),” “include(s),” “having,” “has,” “can,” “contain(s),” and variants thereof, as used herein, are intended to be open-ended transitional phrases, terms, or words that do not preclude the possibility of additional components.
It should be noted that many of the terms used herein are relative terms. For example, the terms “upper” and “lower” are relative to each other in location, i.e. an upper component is located at a higher elevation than a lower component, and should not be construed as requiring a particular orientation or location of the structure.
The terms “top” and “bottom” are relative to an absolute reference, i.e. the surface of the earth. Put another way, a top location is always located at a higher elevation than a bottom location, toward the surface of the earth.
The term “concrete” as used herein will be understood to refer to materials including a cement binder (e.g., Portland cement optionally with supplemental cementitious materials such as fly ash, granulated blast furnace slag, limestone, or other pozzolanic materials), water, and aggregates (e.g., sand, crushed gravel or stones, and mixtures thereof), which form a hardened building or civil engineering structure when cured. The concrete may optionally contain one or more chemical admixtures, which can include water-reducing agents, mid-range water reducing agents, high range water-reducing agents (called “superplasticizers”), viscosity modifying agents, corrosion-inhibitors, shrinkage reducing admixtures, set accelerators, set retarders, air entrainers, air detrainers, strength enhancers, pigments, colorants, fibers for plastic shrinkage control or structural reinforcement, and the like. Exemplary concrete mixing drums contemplated for use in the present invention include those that are customarily mounted for rotation on ready-mix delivery trucks or on stationary mixers that may be found in mixing plants. Such mixing drums have an inner circumferential wall surface upon which at least one mixing blade is attached to the inner surface so that it rotates along with the mixing drum and serves to mix the concrete mix, including the aggregates contained within the mix. For example, the rotatable concrete mixer drum may be mounted to permit rotation about a rotation axis inclined at an orientation of 5-40 degrees relative to level ground, and may have an oblong drum body with an inner circumferential wall that connects a first closed end and a second end that has an opening for loading and unloading concrete from the drum.
Turning now to
In certain embodiments, nozzle boot 20 surrounds a portion of the shaft 15, and is coupled to the nozzle body member 11 at or near one end, such as by adhesion, and/or mechanically such as with a clamp or the like (not shown).
The nozzle boot 20 may be permanently fixed to the nozzle body member 11, or removably attached so that it can be easily replaced with a new nozzle boot 20 from time to time. The nozzle boot 20 and nozzle body member 11 can also be constructed as a single integral piece. In certain embodiments, the nozzle boot 20 forms a water nozzle that surrounds and is at least partially coaxial with the shaft 15. This reduces the overall size of the nozzle.
In certain embodiments, the nozzle boot 20 is expandable and collapsible.
When concrete 100 has adhered to the nozzle boot 20, such as the outer surface of the nozzle boot 20 as shown in
Suitable materials of construction for the nozzle boot 20 are materials that provide the necessarily elasticity enabling the nozzle boot 20 to repeatedly expand and contract, such as elastomeric materials, high density polyethylene (HDPE) and non-stick plastic.
In some embodiments, the nozzle boot 20 may be a bellows, such a flexible material whose volume can be changed, e.g., expanded, such as by the introduction of water or gas (e.g., air) under pressure, or compressed, such as by ceasing the introduction of water or gas under pressure. The bellows can have a concertina or accordion shape. For example, as shown in
Suitable pressure that may be applied to the nozzle boot 20 to expand the nozzle boot is preferably about 2 psi, and may be as high as about 60 psi.
As shown in
In certain embodiments, the outlet of the nozzle boot 20 has an inside diameter only slightly larger than the outside diameter of a portion of the shaft outlet 16, so as to create a slight friction fit for the nozzle boot 20 on the shaft 15. For example, as seen in
As shown schematically in
A nozzle was tested in the lab using an AC pump to simulate the water pressure of a concrete mixer truck. The external bellows of the nozzle was constructed out of a Porsche 911 CV joint. The internal shaft was plastic, which is not suitable for commercial applications but is suitable as a mock up for testing purposes. The entire assembly had the correct components of an internal shaft for support which acted as an admix nozzle. The bellows and stops were installed as shown in
The first test system was covered in hydraulic cement (not typical for real production of concrete) and allowed to sit for one day. Hydraulic cement hardens very quickly but does not contain the rest of the ingredients of concrete (e.g., sand, stone). After the cement was allowed to harden, the pump was turned on and the bellows expanded in multiple directions, shattering the hardened cement, which caused it to fall off the bellows.
Further tests were conducted using conventional ˜3500 psi compressive strength concrete using 3 inch aggregate, 517 pounds per yard of cementitious materials. The concrete was produced in the afternoon of day 1 and packed onto the nozzle and allowed to sit for one full day before testing. This is an extreme case in that most use cases the nozzle will be expanded at least once at the end of the day. The pressure was monitored to ensure that it did not exceed the pressures seen during normal concrete operations. The pressure was measured at the nozzle at 8 psi. Upon expansion of the bellows, the concrete shattered and fell off of the bellows.
Even further tests were conducted to simulate the concrete hitting the nozzle when exiting the drum. The nozzle was pushed into a bucket of concrete 5 times and then allowed to sit for 1 day. The water was then shot though the system and the results were the same. The stop on the internal shaft of the nozzle kept the concrete from entering the inside of the bellows and when test was complete the concrete fell of the nozzle completely.
In all cases, the inside shaft and the external bellows were examined for concrete build up. Only minimal remained, mostly just the dust of hardened concrete.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2018/033685 | 5/21/2018 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 62510908 | May 2017 | US |
