Patent Application
20120288329
The present invention relates generally to delivery of hot mix asphalt (HMA) for roadbed construction and, more particularly, to an apparatus for desegregating streams of HMA.
When a roadbed is to be constructed using hot mix asphalt (HMA), the HMA typically is prepared off-site and transferred to the construction site by a transport machine such as, for example, a dump truck. The HMA, which typically is maintained at a temperature between 300 and 400 degrees Fahrenheit, often is loaded onto the dump truck using an elevator, which conveys the HMA to a spout from which it falls into the truck bed. At the construction site, the HMA can be transferred to a paving machine, which deposits the HMA on the roadbed.
If the HMA is to be temporarily stored at the construction site, the HMA can be transferred from the dump truck to a material transport vehicle (MTV). As the term is used herein, a material transfer vehicle (MTV) refers to any type of machine that can be used to transfer HMA to a paving machine. Exemplary MTVs include remixing transfer vehicles (e.g., “self-propelled” transfer machines that include their own drive system), windrow pickup machines (e.g., “towed” transfer machines that do not include their own drive system), components of paving machines that transfer HMA into the paving machine, and the like.
During such a transfer, the HMA exits a chute at the back of the truck and, in some cases, is transferred into a hopper on the MTV. A windrow elevator conveys the HMA from the hopper either directly into the paving machine or into another hopper, where it is temporarily stored until the paving machine is ready to use it. Alternatively, the dump truck may dump the HMA onto the roadbed, while it moves along the roadbed, thereby creating a windrow. In this case, the windrow is picked up from the roadbed (e.g., by a windrow pickup machine) and transferred to the paving machine.
When the HMA is loaded into truck beds, hoppers, and other containers, the HMA segregates. Additionally, segregation occurs when HMA is unloaded onto a roadbed to create a windrow. Larger, heavier pieces of HMA tend to roll to the outside (e.g., away from the peak) of the resulting piles or windrow (the process known as “segregation”). Moreover, during transportation and temporary storage, the load of HMA often develops temperature variations because the material toward the outside of the container tends to cool faster than the material toward the middle of the container. The amount of segregation and temperature variation in HMA has a negative impact on the roadbed's durability. Thus, HMA typically is desegregated (i.e., re-mixed) prior to its roadbed application. A number of devices such as the examples listed below have been developed to perform the desegregation.
U.S. Pat. No. 5,035,534, to Brock and Smith, for an Apparatus for Transferring an Asphalt-Aggregate Mixture, includes transversely disposed variable pitch screw augers on a single shaft mounted in the bottom of storage hopper. The first screw auger is located on one side of a mid portion of the shaft and the second is located on the other side of a mid portion of the shaft. Each of the screw augers has flights of a first pitch at the outer end of the shaft and flights of a second pitch set inwardly. This arrangement is described as allowing the HMA at the center portion of stream to combine with material transported inwardly to center. The description states that the variable pitches allow different sizes of HMA pieces to be mixed and explains that the mixing occurs due to and in the flights of the pitched augers. The material is mixed in the flights and moved toward the center where it falls through the material outlet underneath a cover.
U.S. Pat. No. 5,405,214, to Campbell, for a Paving Machine Incorporating Automatic Feeder Control Gates, uses a first gate mechanism and a second gate mechanism. Raising one and lowering the other shifts discharged materials to one side; raising and lowering the opposite shifts the material to the other allowing management of the flow along both a vertical and horizontal plane. Some mixing also occurs as a result.
U.S. Pat. No. 5,553,968, to Campbell, for a Method and Apparatus for Conveying and Desegregating Aggregate, uses a different approach. Rather than using adjustable gates to move outer materials to the center for remixing, this one uses a notch in the floor of a first drag slat conveyor. The notch is in the center of the first conveyor floor and positioned near the end of the first conveyance path. The small pieces fall through the notch on to a second conveyor, the large pieces fall later thereby re-orienting the small and large pieces along the direction of the conveyor, rather than outside to inside.
U.S. Pat. No. 5,642,961, to Campbell, for a Method for Conveying and Desegregating Aggregate, is similar to the U.S. Pat. No. 5,553,968 in that it reorients laterally segregated aggregate on a conveyor to a longitudinally segregated aggregate. The aggregate is then desegregated as it comes into contact with and travels along a second conveyor. This is achieved by discharging smaller pieces onto the second conveyor before the larger.
In U.S. Pat. No. 6,007,272, to Macku and Trygg, for an Asphalt Paver with Remixing Conveyor System, describes a paver, which includes a hopper conveyor to move HMA from hopper to screed, as having at least one pair of spaced apart axially rotatable augers. These augers are disposed in the direction of travel. Each auger has a “tapered peripheral diameter” defining a space therebetween as a “remixing zone.” U.S. Pat. No. 6,099,205, to Macku and Trygg, for an Asphalt Paver with Remixing Conveyer System, describes a similar apparatus.
U.S. Pat. No. 6,481,922, to Boyd, for an Apparatus and Method for Re-mixing Segregated Material, describes a device wherein the outer portions of a moving HMA stream are moved toward the center via augers. Here, the outer portions of the HMA stream drops through a material outlet with the inner portions of the stream. This patent terms the uncovered center portion of the augers, which is positioned directly over the material outlet, a mixing zone, explaining that this is the area in which mixing of the small and large pieces of HMA occurs.
U.S. Pat. No. 7,160,056, to Hoffman and Swearingen, for a Material Transfer Vehicle for Use in Asphalt Paving, describes a material transfer vehicle having a surge bin for storing HMA prior to paving. The surge bin includes counter-handed remixing augers that tend to move the HMA pieces to the center of the bin for remixing. One outlet is provided for releasing the HMA from the surge bin onto a transfer conveyor.
U.S. Pat. No. 7,785,033, to Boyd, for an Apparatus and Method for Fragmenting and Re-Mixing Agglomerated Pieces of Rubberized Asphalt Material, describes a housing having an auger and tine assembly that rotates within the housing. The assembly includes counter-handed auger sections mounted on a shaft, with a tine section mounted on the shaft between the auger sections. The re-mixed material exits the housing through a single opening disposed below the tine section.
The prior art concepts generally do not adequately accomplish the objectives of remixing the HMA to achieve significantly uniform distribution of large and small particulate HMA. For example, even where the distribution's level of uniformity is improved somewhat, the utility of the achievement is mitigated by the fact that the re-mixed HMA often is distributed in a single stream. As the stream is off-loaded, it forms a pile, and a number of large pieces of HMA will tend to roll to the edges of the pile, thereby re-segregating the HMA to a certain degree, as well as diminishing the uniformity of a roadbed profile of delivered HMA. Further, the level of HMA remixing tends to be inadequate with conventional systems and can often be better characterized as concentrating the stream of HMA pieces of all sizes rather than actually remixing it.
It is a first objective of the invention to improve the level of remixing of HMA prior to its delivery to a roadbed.
It is a second objective of the invention to provide a desegregation apparatus that accomplishes the first objective.
It is a third objective of the invention to provide an output stream of HMA that has a flatter profile.
It is a fourth objective to provide means to better mix both small and large pieces of HMA prior to delivery to the roadbed, thereby remixing the stream of HMA rather than simply concentrating the stream into a more narrow flow pattern.
This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used, in isolation, as an aid in determining the scope of the claimed subject matter. At a high level, embodiments of the invention relate to desegregating hot mix asphalt (HMA) prior to roadbed application. Embodiments of the invention relate to a desegregation apparatus that desegregates a stream of HMA that includes particles of varying size.
It should be understood that, as the phrase and variations thereof are used herein, “desegregating a stream of HMA” refers to the process of re-mixing segregated HMA to achieve an HMA stream (i.e., “desegregated HMA” stream) that is more uniform in terms of the distribution of small and large pieces of HMA and in terms of temperature variations throughout the stream. Various features of the invention described herein generally offer advantages over the known prior art (e.g., providing a desegregated HMA stream that is more uniform, providing a more uniform roadbed-profile, and the like).
In accordance with embodiments of the invention, a stream of HMA is delivered to a desegregation apparatus. The desegregation apparatus includes a desegregation hopper having at least two sidewalls and a bottom surface. An auger assembly is housed within the desegregation hopper and operates to desegregate the entering stream of HMA. According to embodiments of the invention, the auger assembly includes at least one auger shaft extending generally between the sidewalls and spaced above the bottom surface. Sections of counter-handed auger flights are mounted in a serial relationship along the auger shaft and separated by open sections. The auger sections re-mix the HMA by laterally translating different portions of the HMA stream in opposing directions and toward one of the open sections along the auger shaft.
As the desegregated HMA is moved into the open sections of the auger shaft, it exits the desegregation hopper through a number of configurable openings, which are defined in the bottom surface of the hopper and which can be disposed, for example, below corresponding open sections of the auger shaft. In some embodiments, the locations of the openings are configurable using one or more adjustable lower panels. This arrangement improves mixing as the auger sections move some of the larger pieces of HMA from the outer edges of the stream toward the nearest open sections of the auger shaft and, at the same time, move some of the smaller pieces of the HMA outward from the center of the stream preferably thereby separating and moving various particle sizes from a segregated stream to form mixed, desegregated streams. The pieces of HMA that are deflected by the auger will fall to the hopper below, or may tumble within the hopper until caught by the auger. Those that fall to the hopper bottom will eventually be moved to an opening by virtue of the flow of adjacent pieces. Moreover, the openings on the bottom surface can be spaced apart to deliver a number of desegregated HMA streams that are, in some embodiments, generally parallel, thereby providing a flatter HMA-profile on the roadbed or in the paving machine hopper.
A first illustrative embodiment of the invention relates to an apparatus that desegregates a hot mix asphalt (HMA) stream. According to embodiments of the invention, the apparatus includes a desegregation hopper having a front panel, an opposed rear panel, and two opposed sidewalls. The illustrative embodiment includes mixing means for desegregating the HMA stream to produce a desegregated HMA stream. The mixing means includes an auger assembly that is disposed within the desegregation hopper and that extends generally between an inside surface of the first sidewall and an inside surface of the second sidewall. Other aspects of the first illustrative embodiment include configurable outlet means for releasing the desegregated HMA stream from the desegregation hopper.
A second illustrative embodiment of the invention relates to an apparatus that desegregates a hot mix asphalt (HMA) stream by employing a desegregation hopper. The desegregation hopper includes a front panel, an opposed rear panel, and two opposed sidewalls. An auger assembly is disposed within the desegregation hopper and extends generally between an inside surface of the first sidewall and an inside surface of the second sidewall. According to embodiments of the invention, the auger assembly includes two or more pairs of counter-handed auger flights serially mounted on an outside surface of a rotatable shaft that extends through the desegregation hopper. In embodiments, the illustrative apparatus further includes one or more moveable panels that partially cover the bottom of the desegregation hopper.
A third illustrative embodiment of the invention relates to a desegregation hopper that houses an auger assembly. The auger assembly includes a shaft that is rotatably coupled, at a first end with the inside surface of the first sidewall and that extends through the desegregation hopper. The shaft is rotatably associated, at a second end, with the inside surface of the second sidewall. A first outside auger section, a second outside auger section, and at least one inside auger section are serially mounted on a rotatable shaft that extends through the desegregation hopper. In embodiments, a first open section is disposed between the first outside auger section and the inside auger section and is defined by a first section of the shaft having no auger sections mounted thereon. Similarly, a second open section is disposed between the inside auger section and the second outside auger section and is defined by a first section of the shaft having no auger sections mounted thereon. Various embodiments can also include at least one moveable panel extending between a bottom edge of the front panel and a bottom edge of the rear panel.
These and other aspects of the invention will become apparent to those having skill in the relevant arts upon a reading of the following description, drawings, and claims.
Embodiments of the invention are described in detail below, with reference to the attached drawing figures, wherein:
The subject matter of embodiments of the invention disclosed herein is described with specificity to meet statutory requirements. However, the description itself is not intended to limit the scope of this patent. Rather, the inventors have contemplated that the claimed subject matter might also be embodied in other ways, to include different features or combinations of features similar to the features described in this document, in conjunction with other technologies.
Referring to the drawings, and particularly to
With reference to
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With continued reference to
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The desegregation hopper 32 includes a front panel 40, an opposed rear panel 42, a first sidewall 44, and a second sidewall 46. According to embodiments, the front panel 40, the rear panel 42, and the sidewalls 44 and 46 define an enclosure, with openings at the top and bottom. In the illustrated embodiments, the top of the desegregation hopper 32 can be open; however, alternative implementations of the invention can include partially covering the top of the desegregation hopper 32 such as, for example, by including a cover having one or more inlets defined therein.
In some embodiments, the front panel 40 and rear panel 42 can be substantially parallel and, in other embodiments (such as in the embodiment illustrated in
Additionally, as is further illustrated in
As individuals having skill in the relevant arts will appreciate, when HMA (not illustrated herein for the purposes of clarity and brevity) is introduced to the desegregation hopper 32 from above, the HMA encounters the mixing means 34. In accordance with various embodiments of the invention, the mixing means 34 is operable to desegregate (e.g., re-mix) the HMA before it exits the desegregation hopper 32 from openings in the bottom surface 43. To accomplish desegregation of the HMA, the mixing means 34 generally employs an auger assembly 35 that moves larger, heavier pieces of HMA that have shifted to an outside edge of the HMA stream toward one of at least two openings, which are referenced by numerals 43c and 43d in
With particular reference to
In the embodiments depicted in
As is illustrated in
The auger blades 60b and 61b are fixed to the outside of the mounting plate 60a and 61a, respectively. In accordance with various embodiments of the invention, auger blades 60b and 61b can be constructed according to any number of various configurations. That is, for example, in some embodiments, auger blades 60b and 61b can have varying depths (e.g., radial distances from the auger shaft 50 to the outside edge of the auger blades 60b and 61b), various frequencies (e.g., the number of turns about the axis defined by the auger shaft 50), various pitches, and the like.
In embodiments of the invention, the auger shaft 50 is provided with open sections 68 and 70, which are sections of the auger shaft 50 that do not have auger sections mounted thereon. For example, in the embodiment depicted in
As is illustrated in
In some embodiments, as depicted in
As depicted in the drawings, the outlet means 36 includes at least one and preferably a plurality of panels 76, 78, and 80. In embodiments of the invention, the panels 76, 78, and 80 can be removably and/or slidably coupled, at a first respective end 82, 86, and 90, to the bottom edge of the front panel 40. The panels can be coupled to the front panel 40 using any number of removable and/or adjustable coupling means 94. Coupling means 94 can, as depicted in
Additionally, as is further illustrated in
In operation, the mixing means 34 is powered by an auger-drive motor 52 and, in operation, the auger-drive motor 52 rotates the auger shaft 50 about its axis. This rotation, in turn, causes the auger sections 54, 58, and 62 to rotate and mix the segregated HMA, producing a desegregated HMA stream. The outlet means 36 are operable to further control the roadbed-profile of the HMA stream. In this manner, the desegregation apparatus 10 of the invention allows for some degree of control over the roadbed-profile of the HMA as it exits the desegregation hopper 32 and is distributed by a paving machine. The desegregated HMA stream exits the desegregation hopper 32 via the outlet means 36. The configurable openings of the outlet means 36 allow the hopper to deliver the desegregated HMA streams either closer together or further apart, depending, for example, on a project's parameters, while retaining the advantage of a thoroughly re-mixed HMA stream, as well as obtaining a more uniform roadbed profile of the delivered HMA streams.
The present invention has been described in relation to particular embodiments, which are intended in all respects to be illustrative rather than restrictive. Alternative embodiments will become apparent to those having skill in the art to which the invention pertains, without departing from its scope.
From the foregoing, it will be seen that this invention is one well-adapted to attain all the ends and objects set forth above, together with other advantages which are obvious and inherent to the system. It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by, and is within the scope of, the claims.
