Patent Publication Number: US-7591608-B2

Title: Checking density while compacting

Description:
BACKGROUND OF THE INVENTION 
     Modern road surfaces typically comprise a combination of aggregate materials and binding agents processed and applied to form a smooth paved surface. The type and quality of the pavement components used, and the manner in which the pavement components are implemented or combined, may affect the durability of the paved surface. Even where a paved surface is quite durable, however, temperature fluctuations, weather, and vehicular traffic over a paved surface may result in cracks and other surface or sub-surface irregularities over time. Road salts and other corrosive chemicals applied to the paved surface, as well as accumulation of water in surface cracks, may accelerate pavement deterioration. 
     Road resurfacing equipment may be used to mill, remove, and/or recondition deteriorated pavement. In come cases, heat generating equipment may be used to soften the pavement, followed by equipment to mill the surface, apply pavement materials, and plane the surface. Often, new pavement materials may be combined with materials milled from an existing surface in order to recondition or recycle existing pavement. Once the new materials are added, the materials may be compacted and planed to restore a smooth paved surface. 
     U.S. Pat. No. 5,952,561, which is herein incorporated by reference for all that it contains, discloses a real time differential asphalt pavement quality sensor adapted to measure asphalt density in real time using a differential approach. Two sensors, one in the front of a roller and another behind the roller, measure reflected signals from the asphalt. The difference between the reflected signals provides an indication of the optimal compaction and density of the asphalt pavement. The invention looks at the change in variance over successive passes to determine when the optimal level of compaction has been reached. 
     U.S. Pat. No. 6,287,048 which is herein incorporated by reference for all that it contains, discloses an apparatus having a horizontal compacting roller and a side edge confinement roller or shoe for compacting an asphalt concrete lane. A sensor is on the carrier vehicle for sensing the position of a defined edge of the lane, and a control is provided for steering the carrier vehicle so that the horizontal roller and the edge confinement force roller or shoes follow the defined edge of the lane to provide uniform density. 
     U.S. Pat. No. 6,577,141 which is herein incorporated by reference for all that it contains, discloses a system and method of determining the density of pavement material. The invention includes positioning a capacitive proximity sensor, adjacent to but not in direct contact with a pavement material, projecting an electrostatic capacitive field from the sensor in the direction of the pavement material, measuring the strength of the electrostatic capacitive field as detected by the sensor, and correlating the strength of the electrostatic capacitive field to the density of the pavement material. The invention further discloses determining a location and associating the location with a pavement material density. 
     U.S. Pat. No. 6,122,601 which is herein incorporated by reference for all that it contains, discloses a two component system to obtain uniform density of compacted materials and track the compaction of the materials. The first component provides an automated, real-time compaction density meter and method of use to measure the density of the compacted material. The second component provides a Geographic Information System (GIS) for tracking compaction of a surface at specific locations. The two components of the present invention combined provide a system to measure the density of the compacted material and record the location of each density measurement. The components of the present invention can be utilized for many compaction operations, such as the roller compaction of concrete, pavement, soil, landfills, and asphalt pavements. 
     U.S. Pat. No. 5,952,561 which is herein incorporated by reference for all that is contains, discloses a real time differential asphalt pavement quality sensor adapted to measure asphalt density in real time using a differential approach. Two sensors, one in the front of a roller and another behind the roller, measure reflected signals from the asphalt. The difference between the reflected signals provides an indication of the optimal compaction and density of the asphalt pavement. The invention looks at the change in variance over successive passes to determine when the optimal level of compaction has been reached. 
     U.S. patent application Ser. No. 11/421,105; which is herein incorporated by reference for all that it contains; discloses a method for recycling a paved surface including the steps of providing a motorized vehicle adapted to traverse a paved surface; providing the motorized vehicle with a plurality of degradation elements, a plurality of foaming elements and a plurality of compacting elements; each plurality being attached to a carriage slidably supported by a bearing surface of an underside of the motorized vehicle; degrading the paved surface with the plurality of degradation elements as the vehicle traverses the paved surface; foaming rejuvenation material by the plurality of foaming elements into the degraded surface as the surface is being degraded; and compacting the degraded surface and the rejuvenation material into a new surface with the plurality of compaction elements as the foaming elements continue to foam rejuvenation material into the degraded surface. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides a compaction system with a first and second array of compaction elements supported by an underside of a motorized vehicle adapted to traverse a degraded surface. A sensor assembly is supported by the motorized vehicle, disposed intermediate the first and second array of compaction elements, and in electrical communication with a controller. The sensor assembly also being adapted to sense a characteristic of an at least partially compacted surface formed after the first array of compacting elements applies a first compaction pressure to the degraded surface. The controller may be in electrical communication with the second array of compaction elements and have an input field for a second compaction pressure. The sensor assembly is also adapted to input the second compaction pressure into the field and the controller adjusts the second array of compaction elements to apply the second compaction pressure to the at least partially compacted surface. 
     In one embodiment the compacting elements may be tampers, rollers, vibrators, and/or plates. The first and second row of compactors as well as the sensor assembly may be in communication with a controller. The sensor assembly may be part of a closed loop system. In one embodiment the controller may have a PC, a microprocessor, a microcontroller, analog circuitry, programmable logic, and/or combinations thereof. The controller may also have electronic components selected from the group consisting of analog filters, digital filters, modems, data input ports, data output ports, power supply, battery&#39;s, memory, wireless transceivers, digital/optical converters, optical/digital converters, analog to digital converters (ADC), digital to analog converters (DAC), modulators, demodulators, clocks, amplifiers, and combinations thereof. 
     The sensor assembly may have density sensors with which the density of the at least partially compacted surface may be measured. The sensor assembly may further include a pressure sensors, position sensors, compressive strength sensor, porosity sensor, pH sensor, electric resistively sensor, inclination sensor, nuclear sensor, acoustic sensor, velocity sensor, moisture sensor, capacitance sensor, and combinations thereof. The sensor assembly may be flexibly coupled to the motorized vehicle and be adapted for stationary placement while the motorized vehicle traverses the roadway. 
     The sensor assembly may also have an actuating element selected from the group consisting of hydraulic actuators, a rack and pinion gear, a smart material actuator, an electric actuator or combinations thereof. One use for the actuator may include making the sensor assembly movable with respect to the rest of the vehicle longitudinally along the axis of the vehicle or transversely normal to the axis, or combinations thereof. Actuators may also be used for pivotable movement of the sensor assembly. 
     The sensor assembly may also have electronic components selected from the group consisting of analog filters, digital filters, modems, data input ports, data output ports, power supply, battery&#39;s, memory, wireless transceivers, digital/optical converters, optical/digital converters, analog to digital converters (ADC), digital to analog converters (DAC), modulators, demodulators, clocks, amplifiers, processors, and combinations thereof. 
     A method of compacting a rejuvenated mix, including the steps of providing a motorized vehicle adapted to traverse a paved surface; providing a sensor assembly intermediate a first and second row of compaction elements; compacting the rejuvenated mix with the first row of compaction elements with a first compressive force; acquiring a characteristic of the compacted rejuvenated mix; determining from the characteristic an adjusted compressive force for the second row of compaction elements; compacting the rejuvenated mix with the second row of compaction elements using the adjusted compressing force. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective diagram of an embodiment of a motorized vehicle for on site recycling of asphalt. 
         FIG. 2  is a perspective diagram of an embodiment of a slidable carriage. 
         FIG. 3  is a perspective diagram of a section of an embodiment of a motorized pavement resurfacing vehicle. 
         FIG. 4  is a perspective diagram of a section of an embodiment of a motorized pavement resurfacing vehicle. 
         FIG. 5  is a perspective diagram of an embodiment of a slidable carriage. 
         FIG. 6  is a perspective diagram of an embodiment of a sensor assembly. 
         FIG. 7  is a perspective diagram of an embodiment of an underside of a motorized pavement resurfacing vehicle. 
         FIG. 8  is a perspective diagram of a section of an embodiment of a motorized pavement resurfacing vehicle. 
         FIG. 9  is a block diagram of electronic components that may be used within the sensor assembly, controller or actuating elements. 
         FIG. 10  is a perspective diagram of a section of an embodiment of a motorized pavement resurfacing vehicle. 
         FIG. 11  is a block diagram of an embodiment of a method for recycling a paved surface. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION AND THE PREFERRED EMBODIMENT 
     In this application, “pavement” or “paved surface” refers to any artificial, wear-resistant surface that facilitates vehicular, pedestrian, or other form of traffic. Pavement may include composites containing oil, tar, tarmac, macadam, tarmacadam, asphalt, asphaltum, pitch, bitumen, minerals, rocks, pebbles, gravel, polymeric materials, sand, polyester fibers, Portland cement, petrochemical binders, or combinations thereof. Likewise, rejuvenation materials refer to any of various binders, oils, and resins, including bitumen, surfactant, polymeric materials, emulsions, asphalt, tar, cement, oil, pitch, or combinations thereof. Reference to aggregates refers to rock, crushed rock, gravel, sand, slag, soil, cinders, minerals, or other course materials, and may include both new aggregates and aggregates reclaimed from an existing roadway. Likewise, the term “degrade” or “degradation” is used in this application to mean milling, grinding, cutting, ripping apart, tearing apart, or otherwise taking or pulling apart a pavement material into smaller constituent pieces. 
     Referring to  FIG. 1 , in selected embodiments, a motorized vehicle  100  may be adapted to degrade and recycle a section of pavement substantially wider than the vehicles width  102 . The motorized vehicle  100  may include a shroud  104 , covering various internal components of the motorized vehicle  100 , a frame  105 , and a translational element  106  such as tracks, wheels, or the like, to translate or move the vehicle  100 , such translational elements being well known to those skilled in the art. The motorized vehicle  100  may also include means  107  for adjusting the elevation and slope of the frame  105  relative to the translational element  106  to adjust for varying elevations, slopes, and contours of the underlying road surface. 
     In selected embodiments, to facilitate degradation of a swath of pavement wider than the motorized vehicle  100 , the vehicle  100  may include one or more slidable carriages  108  supported by a bearing surface  120  of an underside of the motorized vehicle  100  capable of extending beyond the outer edge of the vehicle  100 . In some embodiments, the carriages  108  may be as wide as the vehicle  100  itself, the carriages  108  may sweep over a width approximately twice the vehicle width  102  or more. These carriages  108  may include banks  109  of pavement degradation elements  110  that rotate about an axis substantially normal to a plane defined by a paved surface. Each of these pavement degradation elements  110  may be used to degrade a paved surface in a direction substantially normal to their axes of rotation. The slidable carriages  108  may further comprise a first array  111  of compacting elements  112  followed by a sensor assembly  113  and then a second array  114  of compaction elements  112 . 
     Under the shroud  104 , the motorized vehicle  100  may include an engine and hydraulic pumps for powering the translational elements  106 , the carriages  108 , the pavement degradation elements  110 , or other components. Likewise, the vehicle  100  may include a tank  124  for storing hydraulic fluid, a fuel tank  126 , a tank  128  for storing rejuvenation materials such as asphalt, bitumen, oil, tar, or the like, a water tank  130 , and a hopper  132  for storing aggregate such as gravel, rock, sand, pebbles, macadam, concrete, or the like. 
       FIG. 2  is a diagram of an embodiment of the slidable carriage  108 . To extend the carriages  108  beyond the outer edge of the motorized vehicle  100 , each of the carriages  108  may include actuators (not shown), such as hydraulic cylinders, pneumatic cylinders, or other mechanical devices known to those of skill in the art, to move the carriages  108  to each side of the vehicle  100 . Each carriage  108  may also include a rake  200  to level, smooth, and mix pavement aggregates, including new aggregates and reclaimed aggregates generated by the pavement degradation elements  110 . As illustrated, a rake  200  may include a housing  201  comprising multiple foaming elements  202  extending therefrom. In selected embodiments, each of the foaming elements  202  may be independently extended and retracted relative to the housing  201 . This feature may allow the foaming elements  202  to be retracted to avoid obstacles such as manholes, grates, railroad tracks, or other obstacles in the roadway. In certain embodiments, each of the foaming elements  202  may be hollow to accommodate a flow of pavement rejuvenation materials for deposit on a road surface. 
     Pavement rejuvenation materials may include, for example, asphalt, bitumen, tar, oil, water, combinations thereof, or other suitable materials, resins, and binding agents. These rejuvenation materials may be mixed with various aggregates, including new aggregates and reclaimed aggregates generated by the pavement degradation elements  110 . The resulting mixture may then be smoothed and compacted to form a recycled road surface. In selected embodiments, the rake  200  may move side-to-side, front-to-back, in a circular pattern, vibrate, or the like to aid in mixing the resulting mixture of aggregates and rejuvenation materials. In certain embodiments, each carriage  108  may include a first array  111  of compacting elements  112  to compact the mix following which a sensor assembly  113  may measure the density of the compacted mix. A second array  114  of compaction elements  112  may then adjust there compaction pressure and/or displacement in order to compact the mix to a desired density. In the current embodiment the compacting elements  112  are tampers  203 . Like the foaming elements  202 , the tampers  203  may, in certain embodiments, be independently extendable and retractable relative to the carriage  108 . 
     The sensor assembly  113  may comprise one or more density sensors  204  attached to actuators  205  adapted to place the sensors  204  on the partially compacted mix for a period of time after being compacted by the first array  111  of compaction elements  112 . The actuators  205  may adjust the sensors  204  such that they may move longitudinally along the axis of the vehicle, transversely normal to the axis, or combinations thereof. Actuators  206  may also be placed on the assembly  113  to control the height of the sensors  204  with respect to the partially compacted mix. 
       FIG. 3  diagrams an embodiment of the first  111  and second array  114  of compaction elements  112  and the sensor assembly  113 . In the present embodiment the first array  111  of compaction elements  112  are plate compactors  300 . The plate compactors  300  may vibrate or have applied pressure to compact the mix. A plate compactor  300  may help smooth the mix and provide a fairly level surface. Following the plate compactor  300  a sensor assembly  113  may be attached to the motorized vehicle  100 . In one embodiment the sensor assembly  113  may be flexibly coupled to the motorized vehicle  100 . In the current embodiment, a spring loaded or hydraulic shock  301  flexibly couples an extendable leg  302  to the motorized vehicle  100 . A sensor  204  for measuring density may be attached to a foot  303  of the extendable leg  302 . This type of configuration may allow the density sensor  204  to be less effected by the vibration of the motorized vehicle  100  as well as the vibrations from the degrading elements  110 , foaming elements  202 , and the compacting element  112 . The spring loaded shock  301  may also help prevent damage to the sensors  204  on rougher surfaces. In one embodiment the actuators  206  adapted to extend and retract the leg  302  may be capable of filtering out the vibrations from the motorized vehicle  100 . The second array  114  of compaction elements  112  may comprise tampers  203  that may apply a variable force and a variable displacement dependent upon the density measured by the sensors  204 . 
       FIG. 4  diagrams an alternate embodiment of the first  111  and second array  114  of compaction elements  112  and the sensor assembly  113 . The first array  111  of compaction elements  112  comprises tampers  203  and the second array  114  of compaction elements  112  comprises one or more rollers  400 . The tampers  203  may apply a first compaction pressure determined by a controller  401  to the mix  402 . The compaction pressure may be designated such that the mix  402  is evenly distributed and relatively smooth on the surface. The density of the partially compacted mix  402  may then be measured with the sensor assembly  113 . The sensor assembly  113  may then send a data signal to the controller  401  comprising the density measurements. The controller  401  may then send a data signal to an input field of the second assembly  114  of compaction elements  112 . From the input field the compaction pressure of the second array  114  of compaction elements  112  may be set. The compaction pressure of rollers  400  may be adjusted by altering the height of the rollers  400  with respect to the vehicle  100 . A maximum pressure may be applied by the rollers  400  if they are extended to the point where the back translational elements  106  are lifted off of the ground. At this point a large part of the weight of the vehicle may be on the rollers  400 . In the current embodiment the sensor assembly  114  comprises a wheel/track  403  with multiple sensors  204  attached around its circumference. The sensors  204  may be extendable from the wheel/track  403  allowing the sensor  204  to be on the surface of the mix  402  for an extended period of time. With more time to make a measurement the sensors  204  may be more accurate. This configuration may also allow the vehicle to move forward while a sensor  204  remains stationary so that measurements that require an extended period of time may be taken. 
       FIG. 5  is a diagram of an alternate embodiment of the pavement recycling vehicle  100 . The sensor assembly  113  is slidably mounted on a chassis  500  comprising a rack gear  501 . The sensor assembly  113  may comprise a pinion gear and motor (not shown) which when turned may move the sensor assembly  113  along the underside of the vehicle  100 . The sensor assembly  113  may be capable of moving forward towards the front of the vehicle  100  or reverse towards the rear of the vehicle  100  depending on the direction the pinion gear is turned. Sensors  204  may be mounted on actuating elements  206  that extend toward the ground. The actuating elements  206  may be hydraulic actuators, a rack and pinion gear, a smart material actuator that extend or retracts based on an applied electric or magnetic field, an electric actuator or combinations thereof. Sensors  204  that may be used include density sensors, pressure sensors, position sensors, compressive strength sensor, porosity sensor, pH sensor, electric resistively sensor, inclination sensor, nuclear sensor, acoustic sensor, velocity sensor, moisture sensor, capacitance sensor, and combinations thereof. 
       FIG. 6  is a diagram of and embodiment of a sensor assembly  113 . In the current embodiment the sensor  204  is adapted for stationary placement while the motorized vehicle  100  traverses the roadway. The sensor  204  may be positioned inside of a rubber, foam, or other flexible medium  600  in order to reduce the amount of vibrations transferred from the vehicle  100  to the sensor  204 . Other embodiments may include placing a segment of foam, rubber, or other shock absorbing material  601  on the leg  302  of the sensor assembly  113 . The sensor assembly  113  may be slidably mounted to a carriage  108  on the motorized vehicle  100 . In the current embodiment the sensor assembly  113  may extend the leg  302  until the sensor  204  is the desired distance from the ground. In some cases the shock absorbing material  601  and/or sensor  204  may be extended to the point that it is in contact with the ground. The friction created between the sensor  204  and/or shock absorbing material  601  and ground may provide enough force to keep the sensor  204  in place as the vehicle  100  moves forward. Once the sensor assembly  113  reaches the end of the carriage  108 , a hydraulic cylinder  602  may be used to push the assembly  113  back to a starting position. The hydraulic cylinder  602  may then retract and allow friction between the ground and assembly  113  keep the sensor  204  stationary while measurements are taken. Other embodiments (not shown) may include attaching the hydraulic cylinder  602  to the sensor assembly  113  and retracting the cylinder  602  according to the speed that the vehicle  100  is traveling. 
       FIG. 7  diagrams the underside of a motorized vehicle  100  with a sensor assembly  113  as described in  FIG. 6 . In one embodiment the sensor assembly  113  may be attached to the carriage  108  comprising the first row  111  of compaction elements  112 , foaming elements  202 , and degrading elements  110  or be independent. In the present embodiment the back translational element  106  may also be the second row  114  of compaction elements  112 . This may help decrease the overall length of the pavement resurfacing vehicle  100 . 
       FIG. 8  is a diagram of the sensor assembly  113  and first  111  and second row  114  of compaction elements  112 . In the present embodiment the sensor assembly  113  may be a part of a closed loop system. The first array  111  of compaction elements  112  may receive an input parameter from the controller  401  designating the compaction pressure of the tampers  203 . In the present embodiment the sensor assembly  113  may comprise an optical and/or acoustic transducer  800 . The transducer  800  may emit a signal  801  towards the compacted mix  402 . Once the signal  801  reaches a first boundary  802  between the air and mix  402  a reflection  803  may occur. A second reflection  804  may take place at a second boundary  805  between the newly at least partially compacted mix  402  and the under layer  806  of pavement. The sensor assembly  113  may also be adapted to receive the reflections  803 ,  804  using an acoustic and/or optical sensor  807 . The received reflections  803 ,  804  may be converted to an analog or digital electrical signal or left as an optical or acoustic signal for processing by the controller  401 . The signals may be filtered and amplified before being sent to the controller  401 . The controller  401  may then be able to determine a parameter of the newly compacted mix  402  by comparing the phase, intensity, and delay time between the two received reflections  803 ,  804  and/or comparing the received reflections  803 ,  804  to a known reference. From the comparison the density of the newly compacted mix  402  may be determined. Once the density is known the controller  401  may send a signal specifying the second compaction pressure to the second row  114  of compaction elements  112  to further compact the mix  402  so that it reaches a desired density. The controller  401  may be a PC, a microprocessor, a microcontroller, analog circuitry, programmable logic, and/or combinations thereof. 
       FIG. 9  diagrams further electronic components  900  that may be used within the sensor assembly  113 , controller  401  and actuating elements  206 . The electronic components may include analog filters  900 , digital filters  901 , modems  902 , data input ports  903 , data output ports  904 , power supplies  905 , batteries  906 , memory  907 , digital/optical converters  908 , optical/digital converters  909 , analog to digital converters (ADC)  910 , digital to analog converters (DAC)  911 , processors  912 , clocks  913 , amplifiers  914 , wireless transceivers  915 , modulators  916 , demodulators  917  and combinations thereof. 
       FIG. 10  is a diagram of an embodiment of the sensor assembly  113  and first  111  and second row  114  of compacting elements  112 . The sensor assembly  113  comprises a first  1000  and second set  1001  of legs  302 , the first  1000  comprising an emitter  1002  and the second  1001  comprising a receiver  1003 . The emitter  1002  may be a gamma source, a neutron source, a current source, a voltage source or combinations thereof. The receiver  1003  may acquire the energy emitted from the corresponding source and relay information to the controller  401  regarding the received information. From the information the controller  401  may be able determine a parameter of the mix  402  including; density, receptivity, conductivity, capacitance and combinations thereof. In other embodiments the legs  302  may be used to measure parameters of the mix  402  including but not limited to; pressure, position, compressive strength, porosity, pH, inclination, nuclear properties, acoustical properties, velocity, moisture content or combinations thereof. Combinations of sensors may be used in conjunction with one another to obtain multiple parameters of the compacted mix  402  simultaneously. One such combination may include a density sensor and an inclination sensor. The density sensor may ensure that the mix  402  is compacted to the desired density while the inclination sensor may sense changes in the grade of the pavement and the compaction elements  112  may adjust accordingly. 
       FIG. 11  is a block diagram of a method  1100  for compacting rejuvenated mix comprising the steps of providing  1101  a motorized vehicle adapted to traverse a paved surface; providing  1102  a sensor assembly intermediate a first and second row of compaction elements; compacting  1103  the rejuvenated mix with the first row of compaction elements with a first compressive force; acquiring  1104  a characteristic of the compacted rejuvenated mix; determining  1105  from the characteristic an adjusted compressive force for the second row of compaction elements; compacting  1106  the rejuvenated mix with the second row of compaction elements using the adjusted compressing force. 
     Whereas the present invention has been described in particular relation to the drawings attached hereto, it should be understood that other and further modifications apart from those shown or suggested herein, may be made within the scope and spirit of the present invention.