The present invention relates to asphalt pavement constructing machines provided with at least one compacting surface vibrated at one or more frequencies selected to prevent asphalt adhering to the compacting surface.

The formation of asphalt pavement topically involves a number of asphalt pavement constructing machines. An asphalt paver typically receives, deposits, and performs at least a partial compaction of the asphalt mix to form a freshly laid asphalt pavement, After initial compaction by the asphalt paver, a compactor, such as, a roller or drum compactor, is topically used for final compaction and finishing of the freshly laid asphalt pavement. During both laying and compaction, adherence of asphalt to the compacting surfaces of the paver and/or compactor may damage the asphalt pavement and generate surface impressions in the top surface of the pavement as the asphalt is compacted, thus, leading to costly repair and delays for the paving contractor. Accordingly, systems have been devised to prevent this occurrence.

With respect to pavers, the current practice for preventing adherence of asphalt involves heating the compacting surface(s), which is typically located on the underside of a screed (or screed plate), to several hundred degrees Fahrenheit. Since it is difficult to heat the screed uniformly, often times the uneven heating will cause the compacting surface to deform, which, in turn, results in an uneven contour of the asphalt pavement and a top surface that has slight depressions. Additionally, large amounts of energy are required for the screed to be preheated, which can take as long as 20 minutes before work can be performed. Furthermore, since the top of the screed typically functions as a working platform for workers, the thermal radiation generated during this process produces an uncomfortably hot working environment.

With respect to compactors, the current practice for preventing adherence of asphalt involves water spray systems. Scrapers are also used, but only to remove asphalt after it adheres to the compacting surfaces of the roller and, accordingly, after impressions have already been left in the top surface of the pavement. In addition to generating undesirable cooling of the asphalt pavement, water spray systems are large and bully. In order to be effective, the water must coat the entire compacting surface of the roller, which may be difficult for a number of reasons, including wind and clogged nozzles. This system also requires numerous components, including large thanks of water that must constantly be refilled, filters that must be checked, and pumps that must operate correctly at all times. In order to ensure complete water coverage frequent inspection and repair is common.

According to its abstract, US 2003/0223816 A1 discloses a controller for use in a vibratory mechanism includes an amplitude control circuit that generates an amplitude control signal that varies from a minimum value to a maximum value. The vibratory mechanism is adapted to vibrate at an amplitude based on an amplitude control signal characteristic. Additionally, the controller includes a frequency control circuit that is operatively coupled to the amplitude control-circuit to produce a frequency control signal that varies based on the amplitude control signal characteristic.

The present invention relates to asphalt pavement constructing machines provided with a compacting surface vibrated at one or more frequencies selected to prevent asphalt mix adhering to the compacting surface.

According to one aspect of the present invention, an asphalt pavement constructing machine comprises an asphalt compacting surface and at least one exciter that vibrates the compacting surface at one or more frequencies equal to or greater than about 100 Hz to prevent asphalt adhering to the compacting surface.

According to another aspect of the present invention, a method for operating an asphalt pavement constructing machine provided with a compacting surface comprises the steps of using the compacting surface to compact asphalt mix on a paving surface during an asphalt pavement formation operation and using at least one exciter to vibrate the compacting surface at one or more frequencies equal to or greater than about 100 Hz to prevent the asphalt mix from adhering to the compacting surface.

• FIG. 1 illustrates a side view of an asphalt pavement constructing machine according to one embodiment.
• FIG. 2 illustrates a compacting surface according to one embodiment.
• FIG. 3 illustrates a side view of an asphalt pavement constructing machine according to another embodiment.
• FIG. 4 illustrates compacting surfaces according to one embodiment.

Turning now to FIG. 1, an asphalt pavement constructing machine according to one embodiment is depicted, As shown, the asphalt pavement constructing machine is a paver 15 configured to receive, deposit, and partially compact asphalt mix 5 and form an asphalt pavement 7 on top of a paving surface 6. As shown therein the paver 15 may be provided with an asphalt hopper 20, an asphalt conveyor 25, an asphalt spreader 30, a screed 40 supported by tow arms, as at 43, and an asphalt compacting surface 45.

Those of ordinary skill in the art will appreciate that during a paving operation, asphalt mix 5 is typically loaded onto the paver 15 and temporarily held in an asphalt hopper, such as asphalt hopper 20. Those of ordinary skilled in the art will also appreciate that during a paving operation, one or more asphalt conveyors, such as asphalt conveyor 25, typically transport the asphalt mix 5 from the asphalt hopper 20 and deposit it on a paving surface, such as paving surface 6, whereat one or more asphalt spreaders, such as asphalt spreader 30, which may be in the form of one or more augers, as shown, spread the asphalt mix 5 on the paving surface 6 in a direction that is lateral with respect to a direction of travel of the paver 15. Those of ordinary skill in the art will appreciate that the asphalt mix 5 is compacted after the asphalt mix 5 is deposited on the paving surface 6 and literally distributed on the paving surface 6 by the asphalt spreader 30.

As shown in FIG. 1, the paver 15 is provided with at least one asphalt compacting surface, such as for example, asphalt compacting surface 45, which compacts the asphalt mix 5 to form an asphalt pavement 7 on the paving surface 6. As shown in the present embodiment, the asphalt compacting surface 45 is a generally flat surface located on the underside 41 of a screed 40, which may be provided with a work platform 42 whereupon workers may stand. Those of ordinary skill in the art will appreciate that as the paver 15 travels along the paving surface 6, for example by a track assembly or wheels, as at 16, the asphalt compacting surface 45 exerts a compressive force on the deposited asphalt mix 5 to smooth and at least partially compact the asphalt mix 5, whereby a freshly laid asphalt pavement 7 is formed on the paving surface 6.

According to the invention, the asphalt compacting surface 45 is vibrated at one or more frequencies equal to or greater than about 100 Hz to prevent asphalt adhering to the asphalt compacting surface 45 as the asphalt mix 5 is compacted by the asphalt compacting surface 45.

Tuniing now to FIGS, 1 and 2, as shown, the paver 15 includes one or more exciters 50, including for example electromagnetic, as at 50a (FIG. 2) piezoelectric, as at 50a' (FIG. 4), or hydraulic exciters, as at 50a" (FIG. 4), that vibrate the asphalt compacting surface 45 at one or more frequencies selected to prevent asphalt adhering to the asphalt compacting surface 45 as the asphalt mix 5 is contacted by the asphalt compacting surface 45. Those of ordinary skill in the art appreciate that it is within the scope of the present invention to utilize any number of exciters 50 and to distribute the exciters with respect to the asphalt compacting surface 45 in any manner that excites the asphalt compacting surface 45 in a manner that prevents asphalt from adhering to the asphalt compacting surface 45. In FIGS. 1 and 2, for example, a plurality of exciters 50 are shown located within the screed 40, whereby the asphalt compacting surface 45 is vibrated indirectly by the exciters 50. As shown in FIG. 2, one or more electronics ! 00 may be used to drive the exciters 50 and control the frequency of vibration(s) generated by the exciters 50.

Turning now to FIG. 3, an asphalt pavement constructing machine according to another embodiment is depicted. As shown therein, the asphalt pavement constructing machine is a rolling compactor 60 that may be used for final compaction of pavement 7. As shown in FIG. 3, the rolling compactor 60 is provided with first and second rollers 61, 62. According to one aspect of the present invention, the rollers 61, 62 propel the rolling compactor 60 along the pavement 7. According to another aspect of the present embodiment, the rollers 61, 62 are configured to perform a final compaction of the pavement 7, According to yet another aspect of the present embodiment, the rollers 61, 62 may be used to provide the pavement 7 with a generally smooth finished top surface 7a.

As shown in FIG. 3, the rolling compactor is provided with asphalt compacting surfaces 63, 64 that are cylindrical in shape and located on the outer circumferential surface of the rollers 61, 62 that propel the rolling compactor 60 along the pavement 7. Those of ordinary skill in the art will appreciate that as the rollers 61, 62 propel the rolling compactor 60 along the pavement 7 that the asphalt compacting surfaces 63, 64 exert a heavy compacting force on the pavement 7. Those of ordinary skill in the art will appreciate that the heavy compacting force exerted by the asphalt compacting surfaces 63, 64 compacts the pavement 7. Those of ordinary skill in the art will appreciate that the heavy compacting force exerted by the asphalt compacting surfaces 63, 64 preferably provide the pavement 7 with a generally smooth finished top surface 7a.

According to one aspect of the present embodiment, the asphalt compacting surfaces 63, 64 are vibrated at one or more frequencies. According to another aspect of the present embodiment, the asphalt compacting surfaces 63, 64 are vibrated at one or more frequencies to prevent asphalt adhering to the asphalt compacting surfaces 63, 64 as the pavement 7 is compacted by the asphalt compacting surfaces 63, 64.

Turning now back to FIG. 3, as shown the rolling compactor 60 includes a plurality of exciters 50', including, for example electromagnetic, as at 50a fig, 2) piezoelectric, as at 50a' (FIG. 4), or hydraulic exciters, as at 50a" (FIG. 4), that vibrate the asphalt compacting surfaces 63, 64 at one or more frequencies selected to prevent asphalt adhering to the asphalt compacting surfaces 63, 64 as the freshly laid pavement 7' is compacted by the asphalt compacting surfaces 63, 64. Those of ordinary skill in the art will appreciate that it is within the scope of the present invention to utilize any number of exciters 50' and to distribute the exciters with respect to the asphalt compacting surfaces 63, 64 in any manner that excites the asphalt compacting surfaces 63, 64. In FIGS. 3 and 4, for example, a plurality of exciters 50' are shown located within the rollers 61, 62, whereby the asphalt compacting surfaces 63, 64 are vibrated indirectly by the exciters 50, such as, for example, by placing the exciters 50 in direct contact with an inner cylindrical surface 61a, 62a of the rollers 61, 62. As shown in FIG. 2, one or more electronics 100' may be used to drive the exciters 50' and control the frequency of vibration(s) generated by the exciters 50' .

Advantageously, by employing vibrations at frequencies in excess of the frequencies used for compacting efficiency, i.e. frequencies in excess of about 70 Hz, compaction efficiency will not be degraded. While those of ordinary skill in the art will appreciate that an optimal frequency may be deduced from empirical observation, according to the invention the frequency vibration is substantially equal to or greater than about 100 Hz. According to yet another aspect of the present embodiments, the frequency vibration may be substantially equal to or greater than about 1 kHz. According to another aspect of the present embodiments the frequency of vibration may be in the ultrasonic range and substantially equal to or greater than about 20 kHz.

Advantageously, the principals of the aforementioned embodiments may be utilized in conjunction with currently known systems, i.e. heating, scrapers, as at 80, 81 (FIG. 3), or water systems, for preventing asphalt adherence or may obviate the use of one or more currently known systems. Advantageously, by controlling the frequency of vibration, the adherence of asphalt to the asphalt compacting surfaces on asphalt pavement constructing machines, including, for example, the asphalt compacting surface 45 on paver 15 or asphalt compacting surfaces 63, 64 on the rolling compactor 60, may be prevented

The detailed descriptions of the above embodiments are not exhaustive descriptions of all embodiments contemplated by the inventors to be within the scope of the invention. The present description depicts specific examples to teach those skilled in the art how to make and use the best mode of the invention. Those skilled in the art will appreciate variations from these examples that tall within the scope of the invention. Those of ordinary skill it the art will also appreciate that some conventional aspects have been simplified or omitted.