Patent Grant
8911138
The present invention relates to manufacturing of concrete, and more particularly to a system and method for dispensing liquid chemical admixtures and water 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 the rotatable drum on the 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, 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 an oblong shape with an opening at one end. It is mounted at an angle such that the opening 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, 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, 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 may 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 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. Fluid dispensing systems are disclosed in U.S. Pat. Nos. 4,008,093, 5,713,663, and U.S. patent application Ser. Nos. 10/599,130, 11/764,832, and 11/834,002, as examples.
Concrete trucks are commonly equipped with water tanks connected by a hose line directed into the drum opening. In this manner, water can be dispensed into the drum under air pressure in the tank or by pump. Such tank dispensing devices are disclosed in U.S. Pat. No. 4,544,275, U.S. Pat. No. 7,842,096 and U.S. patent application Ser. No. 11/955,737, for example.
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. This is exemplified in U.S. Pat. No. 7,730,903. The present inventors believe that the use of water dispensing equipment is not ideal for the dispensing of liquid chemical admixtures into the concrete mixer drum.
Hence, it is an objective of the present inventors to provide a novel apparatus and method for dispensing both water and liquid chemical admixtures into concrete mixing drums.
The present invention provides a novel system and method for dispensing liquid chemical admixtures and water into a concrete mixer drum, and is useful for mixers in plant installations and especially useful in concrete ready-mix delivery trucks.
An exemplary apparatus or system of the present invention for injecting liquids into a rotatable concrete mixer drum, comprises: a concrete mixer drum which is rotatably mounted to permit rotation about a rotation axis inclined at an orientation of 5-40 degrees relative to level ground and which has an oblong drum body with a inner circumferential wall connecting opposed first and second ends for defining a cavity within which to contain a fluid concrete; one of the two opposed ends of the oblong drum body having an opening to permit loading and unloading of concrete, and the other end being conformed to contain a nominal maximum concrete capacity such that a fluid concrete contained in the drum in the amount of 10%-30% of the nominal maximum concrete capacity presents an air/concrete interface having a first exposed surface area, designated herein as “ESA1,” and such that a fluid concrete contained in the drum in the amount of 70%-100% of the nominal maximum concrete capacity presents an air/concrete interface having exposed surface area, designated herein as “ESA2,” whereby ESA2 is greater than ESA1; a first conduit connected to a water source for introducing water into the mixer drum through the opening, the first conduit being aimed and mounted with respect to the drum opening, whereby 0%-100% of the water introduced through the first conduit into the drum would hit the air-concrete interface within ESA2; and a nozzle connected to a liquid chemical admixture source for introducing liquid chemical admixture into the drum through the opening, the nozzle being aimed and mounted with respect to the drum opening and having a nozzle aperture which is focused such that 75%-100% of the chemical admixture sprayed through the liquid chemical admixture nozzle into the drum would hit the air-concrete interface within ESA1.
An exemplary method of the present invention comprises providing the above-described apparatus on a concrete mixer drum. In preferred embodiments, the liquid chemical admixture nozzle is connected switchably to said pumped or pressurized water source, so that the liquid chemical admixture nozzle can be purged with water. The purging can be performed, for example, at the same time that water is introduced through the conduit into the mixer drum.
The present invention is believed to provide immense improvements over prior art practice, wherein existing nozzles were originally intended to dispense water, and as such are designed to dispense large volumes of fluid quickly and rather indiscriminately onto the inner sides of the drum.
The present invention allows the liquid chemical admixture to be dispensed most effectively and safely, and employs a separate admixture nozzle, which can be purged of cement dust that builds up over time during initial batching/mixing of the concrete and otherwise tends to clog the nozzle.
The effectiveness of the present invention is particularly appreciated when the apparatus is part of an automated slump monitoring and control system, wherein highly concentrated chemical admixture is not sprayed primarily onto the inner drum walls but rather directly into the concrete, so that the slump changes can be made faster and with greater accuracy.
Further advantages and feature of the invention will be described in further detail hereinafter.
Further advantages and features of the present invention may be more readily comprehended when the following detailed description of preferred embodiments is taken in conjunction with the appended drawings wherein:
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.
As mentioned in the background section, concrete delivery mixing trucks having slump control monitoring and control equipment, such as hydraulic and/or electric sensors for measuring the energy for turning the mixing drum, speed sensors for measuring the speed of rotation, temperature sensors for monitoring the atmospheric temperature as well as the mix temperature, and dispensing equipment, as well as the computer processing units (CPU) for monitoring signals from the sensors and actuating the dispensing equipment are by now relatively well known in the industry.
For example, such slump control systems, which can be used in association with wireless communication systems, are disclosed in U.S. Pat. No. 5,713,663; U.S. Pat. No. 6,484,079; U.S. Ser. No. 09/845,660 (Publication no. 2002/0015354A1); U.S. Ser. No. 10/599,130 (Publication no. 2007/0185636A1); U.S. Ser. No. 11/764,832 (Publication no. 2008/0316856); U.S. Ser. No. 11/834,002 (Publication no. 2009/0037026); and WO 2009/126138. A further exemplary system for monitoring and control using wireless communications in combination with sensors for monitoring various physical properties of the concrete mix is taught in U.S. Pat. No. 6,611,755 of Coffee. These teachings, as well as the patent references as previously discussed in the background section above, are expressly incorporated herein by reference.
Exemplary concrete mixing drums contemplated for use in the present invention include those which are customarily mounted for rotation on ready-mix delivery trucks or on stationary mixers which 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.
It is believed that a number of exemplary embodiments of the invention may be practiced using commercially available automated concrete mix monitoring equipment with slight modifications as would be apparent in view of the invention disclosed herein. Such mix monitoring equipment is available under the VERIFI® name from VERIFI LLC, West Chester, Ohio.
As illustrated in
For purposes of simplifying the diagram, mixing blades are omitted from the illustrations. In concrete mixing trucks, two or more continuous mixing blades are helically arranged and mounted within the drum, such that when the mixer drum 12 is rotated in one direction, the concrete mix (designated as at 22) will be moved towards the closed end 18, and such that when the mixer drum 12 is rotated in the other direction, the concrete will be moved towards the other drum end 19 having the opening 20.
Concrete mixing drums, particularly those on mixer delivery trucks, usually have a “nominal maximum concrete capacity” whereby some space exists between the opening 20 and air/concrete interface (see 24) of the maximum rated concrete capacity. Consequently, if the mixer delivery truck drives up an incline, or is jostled when travelling over a bump or rough section of pavement, spillage of the concrete through the opening 20 is avoided or minimized.
In exemplary embodiments of the present invention, the first end 18 of the concrete mixer drum 12 is conformed to contain a nominal maximum concrete capacity, which for example could be between 2-18 cubic yards, and more preferably between 4-14 cubic yards, such that a fluid concrete (22) contained in the drum 12 in the amount of 10%-30% of said nominal maximum concrete capacity presents an air/concrete interface having a first exposed surface area, designated herein as “ESA1” (and designated in
A first conduit 28 is shown in
A nozzle 34 is shown in
In a preferred embodiment of the invention, an air supply 40 which could be a pressured air tank or other source of air pressure is connected using an air conduit 42 (e.g., hose or pipe) to a liquid admixture tank 38 or tanks as well as to a water tank 36, for providing pressure to drive the liquids 36/38 into the mixer drum 12 through chemical admixture nozzle 34 and/or the optional water nozzle 30 or nozzles. Alternatively, mechanical pumps (not shown) can be used to pump water from the water tank 36 into the mixer drum 12 and to pump liquid chemical admixture from the admixture tank 38 into the mixer drum 12. If the mixer apparatus 10 is located at a mixing plant, of course, the on-site water supply could be substituted for the water tank 36 and any air supply 40.
In other embodiments of the invention, the water nozzle 30 or two or more water nozzles can be connected to the water conduit 28 and water source 36, and can be aimed and mounted so that its spray dispersion 46 can hit any portion of the inner drum wall. For example, the aperture of the nozzle 30 or nozzles can be focused or the nozzle(s) can be aimed so that water can hit the back (closed) end 18 of the drum.
In
Thus, in preferred systems and methods of the invention, water is sent simultaneously through the admixtures nozzle 34 as well as through the water nozzle 30 or nozzles, using the check valve assembly 50/51/52 described above. Hence, the liquid chemical admixture nozzle 34 is connected by a back check valve assembly 50/51/52 to said water conduit 28 to permit the liquid chemical admixture nozzle 34 to be purged with water, the back check valve assembly comprising: a connecting line 50 for connecting the water conduit 28 to the admixture nozzle 34; a first back check valve 51 within the connecting line 50 for permitting water to flow from the water conduit 28 to the admixture nozzle 34 and to prevent liquid chemical admixture 38 from flowing into the water conduit 28; and a second back check valve 52 to prevent water 28 from flowing towards the liquid chemical admixtures source 38.
Accordingly, the present invention provides methods for dispensing liquids into concrete mixer drums, comprising introducing chemical admixture and water into concrete within the mixer drum through separate nozzles, and, where water is introduced into the concrete, the water is introduced through both the chemical admixture nozzle and at least one separate water nozzle, whereby the nozzles are connected conduits connected by the back check valve assembly 50/51/52 and described hereinabove.
Further exemplary systems and methods of the invention further comprise a water meter 29 and water valve 27 for controlling and monitoring the amount of water introduced into the concrete mixer drum 12; and further comprising a liquid chemical admixture meter 31 and admixture valve 33 for controlling and monitoring the amount of liquid chemical admixture into the concrete mixer drum 12. This is particularly effective when used in combination with the aforementioned back check valve assembly 50/51/52 illustrated in
In a further exemplary embodiment of the invention, an additional air line (designated as at 42a) may be used to connect the admixture tank exhaust valve 39 to the admixture conduit 32 so that pressurized air can be used to purge the admixture conduit 32 and admixture nozzle 34. A one-way check valve 39B is used in the line 42a to prevent admixture from entering line 42a. Thus, in further exemplary systems and methods of the invention, the admixture valve 34 and admixture conduit 32 can be purged with air as explained above.
In further exemplary embodiments of the invention, both an admixture nozzle 34 and at least one water nozzle 30 are employed, each having a spray aperture (diameter) which is smaller than the inner diameter of the respective conduit (32/28) which feeds liquid to the respective nozzles 34/30. In other words, the admixture nozzle 34 aperture will have a smaller diameter than the admixture conduit 32, while the water nozzle 30 or nozzles will have a smaller diameter than the water conduit 28. In still further exemplary embodiments, the admixture nozzle 34 aperture or apertures will have combined cross-sectional area that is smaller than the combined cross sectional area of the water nozzle 30 aperture or apertures.
Exemplary admixture nozzles 34 as well as water nozzles 30 can be made of plastic (e.g., nylon, PVC, etc.) or metal (e.g., brass) and can be aimed and mounted with respect to the drum opening using any known means. The nozzles may have coatings of silicone or other low-friction material to enhance ease of cleaning. With respect to aiming and mounting with respect to the drum opening, metal nozzles can be welded into position onto brackets or hopper located outside of the concrete mixing drum, although this is not preferred, because nozzles are often bent out of position by the force of aggregates loaded into the drum, and hence would be difficult to adjust. More preferably, the admixture nozzle 34 and water nozzle(s) 30 are aimed and mounted in place using adjustable brackets and clamps which permit the nozzles to be adjusted along x, y, and z planes, so that the nozzles can be installed and adjusted without substantial inconvenience.
As summarized previously, an exemplary method of the invention involves providing the above-mentioned apparatus 10 on a concrete mixer drum, and particularly on a concrete mix truck. In preferred embodiments, the liquid chemical admixture nozzle 34 is connected to the check valve assembly 50/51/52 (illustrated in
Thus, for example, the nozzle assembly 60 shown in
The principles, preferred embodiments, and modes of operation of the present invention have been described in the foregoing specification. The invention which is intended to be protected herein, however, is not to be construed as limited to the particular forms disclosed, since these are to be regarded as illustrative rather than restrictive. Skilled artisans can make variations and changes without departing from the spirit of the invention.
| Number | Name | Date | Kind |
|---|---|---|---|
| 4008093 | Kitsuda et al. | Feb 1977 | A |
| 4356723 | Fay | Nov 1982 | A |
| 4478514 | Hudelmaier | Oct 1984 | A |
| 4544275 | Hudelmaier | Oct 1985 | A |
| 4786179 | Kaminski | Nov 1988 | A |
| 4789244 | Dunton et al. | Dec 1988 | A |
| 4792234 | Doherty | Dec 1988 | A |
| 5653533 | Green | Aug 1997 | A |
| 5713663 | Zandberg et al. | Feb 1998 | A |
| 5895116 | Kreinheder et al. | Apr 1999 | A |
| 6042258 | Hines et al. | Mar 2000 | A |
| 6042259 | Hines et al. | Mar 2000 | A |
| 6224250 | Kreinheder et al. | May 2001 | B1 |
| 6484079 | Buckelew et al. | Nov 2002 | B2 |
| 6611755 | Coffee et al. | Aug 2003 | B1 |
| 7246009 | Hamblen et al. | Jul 2007 | B2 |
| 7386368 | Andersen et al. | Jun 2008 | B2 |
| 8118473 | Compton et al. | Feb 2012 | B2 |
| 8727604 | Compton et al. | May 2014 | B2 |
| 8746954 | Cooley et al. | Jun 2014 | B2 |
| 8764272 | Hazrati et al. | Jul 2014 | B2 |
| 20050141338 | Jarvinen et al. | Jun 2005 | A1 |
| 20050159843 | Oberg et al. | Jul 2005 | A1 |
| 20070185636 | Cooley et al. | Aug 2007 | A1 |
| 20080316856 | Cooley et al. | Dec 2008 | A1 |
| 20090037026 | Sostaric et al. | Feb 2009 | A1 |
| 20100188925 | Huber et al. | Jul 2010 | A1 |
| 20110029134 | Hazrati et al. | Feb 2011 | A1 |
| 20120250446 | Cook et al. | Oct 2012 | A1 |
| Number | Date | Country |
|---|---|---|
| 879199 | Oct 1961 | GB |
| 2010111204 | Sep 2010 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20120250446 A1 | Oct 2012 | US |
