Patent Grant
10480135
The present invention relates generally to repair and repaving of roadways with asphalt paving material. More particularly, the invention relates to equipment for use in cold in-place repaving of roadways with recycled asphalt material.
Roadway repair is often accomplished by overlaying the existing pavement (whether of concrete or asphalt paving material) with a new layer (often called a leveling course) of concrete or asphalt paving material. Without prior surface treatment, however, this method of repair generally results in the application of insufficient quantities of paving material in the rutted, potholed or otherwise damaged areas, because the overlay will be applied at the same rate per unit of roadway width in damaged areas (which have a greater depth to be filled across the width) as in the undamaged areas. The resulting reduced thickness in the overlay of the previously damaged areas will lead to renewed rutting or other wear damage in the new pavement in relatively short order. However, by milling the surface of the damaged pavement to a uniform surface elevation below the level of the damage, the addition of new pavement will produce a road surface having a consistent elevation across the entire width of the roadway. This repaving technique can be used to return the elevation of a damaged roadway to its original pre-damaged elevation, whereas the placement of a leveling course atop damaged but un-milled pavement will tend to raise the surface of the roadway or some portion thereof above its original elevation. Roadway repair without milling can require the raising of road shoulders, guardrails and manhole covers and the adjustment of overpass clearances, which tasks are unnecessary if a proper milling technique is employed. A use of milling prior to repaving can also permit ready establishment of the proper road grade and slope, and thereby avoid drainage and safety problems. Furthermore, milling typically provides a rough surface that readily accepts and bonds with the new asphalt or other pavement overlay. Finally, milling can provide raw material that can be reclaimed for use in the production of new paving materials.
A milling machine includes a milling drum with a plurality of cutter teeth mounted thereon which is contained within a milling drum housing. The milling machine is adapted to be advanced across a roadway surface while the milling drum is rotated within the housing to “mill” the surface to remove asphaltic or Portland cement concrete pavement in preparation for recycling the pavement and/or in preparation for applying a pavement overlay. The typical milling machine includes one or more conveyors to take the milled paving material from the vicinity of the milling drum and direct it away from the machine and into an adjacent dump truck. A road stabilizer/reclaimer machine is similar to a milling machine in that it comprises a wheeled or track-driven vehicle that includes a milling drum with a plurality of cutter teeth mounted thereon which is contained within a milling drum housing. However, the milling drum of a road stabilizer/reclaimer machine is generally employed to mill or pulverized an existing road bed or roadway to a greater depth than does a milling machine prior to repaving (usually called reclaiming) or prior to initial paving (usually called stabilizing), and it leaves the pulverized material in place.
Cold in-place recycling (“CIR”) equipment can be used to repair damage to a roadway in a single pass, while reusing essentially all of the existing milled paving material. In the CIR process, a milling machine is employed to remove damaged layers of pavement, and the removed paving material is processed, replaced on the roadway and compacted. If a roadway has good structural strength, CIR can be an effective treatment for all types of cracking, ruts and holes in pavement. CIR can be used to repair roadways damaged by fatigue (alligator) cracking, bleeding (of excess asphalt cement), block cracking, corrugation and shoving, joint reflective cracking, longitudinal cracking, patching, polished aggregate, potholes, raveling, rutting, slippage cracking, stripping and transverse (thermal) cracking. The root cause of the pavement failure should always be investigated to rule out base failure. However, CIR can almost always be used when there is no damage to the base of the roadway. Generally, CIR is only half as expensive as hot mix paving (i.e., paving with new asphalt paving material) while providing approximately 80% of the strength of hot mix paving.
CIR can be carried out with the aid of a milling machine or a road stabilizer/reclaimer machine that has been modified by mounting an additive spray bar in the milling drum housing to inject asphalt cement into the milling drum housing. The asphalt cement is then thoroughly blended with the milled material by the milling drum. This blended mixture may then be deposited on the roadway in the form of a windrow to be picked up by a suitably equipped asphalt paving machine, or it may be fed by the milling machine's discharge conveyor directly into the receiving hopper of an asphalt paving machine. When the CIR process is carried out with only a milling machine or stabilizer/reclaimer and an asphalt paving machine, the asphalt cement component of the mixture must be supplied from a separate asphalt cement supply tank carried by a supply truck, vehicle, wheeled chassis or other mobile support that is typically coupled to the modified milling machine or road stabilizer/reclaimer machine. The asphalt cement component is drawn directly from the tank on the supply truck and metered through an asphalt cement flow circuit to the spray bar in the milling drum housing.
Sometimes the CIR process is carried out with a milling machine or stabilizer/reclaimer in train with a cold recycler machine such as the RT-500 that is made and sold by Roadtec, Inc. of Chattanooga, Tenn. The cold recycler machine may include a vibratory screen, a crusher, an onboard source of asphalt cement and a pugmill mixer. When the CIR process is carried out using a cold recycler machine, the recycled paving material that is milled by the milling machine is transferred to the vibratory screen. Oversized material on the screen is conveyed into a crusher on the cold recycler machine, and material passing through the crusher is carried back to the screen by means of a return circuit. Properly sized material is then mixed with asphalt cement from an onboard storage tank in the pugmill mixer. Because the onboard asphalt cement storage tank in a cold recycler machine is limited in size, it may be desirable to convey additional asphalt cement from a separate supply truck to the asphalt cement storage tank on the cold recycler machine, in order to insure that the CIR process can proceed without frequent stops to refill the asphalt cement storage tank on the cold recycler machine. In either configuration of the CIR equipment, the primary component of the new pavement is paving material that is removed from the roadway. The only other component of the new pavement is the asphalt cement carried by the cold recycler machine and/or by a mobile supply vehicle. Since the rate of advance of the equipment engaged in the CIR process is determined primarily by the rate of advance of the milling machine, it is common for all of the components of the CIR process except for the asphalt paving machine to be coupled together so as to move at the same rate during all phases of the CIR process. Such components employed in carrying out a CIR process are frequently referred to as a CIR train.
Asphalt cement performs best in the CIR process when it is applied at a temperature within the range of about 300° to about 350° F. Although the asphalt cement supply truck is typically thermally insulated, it does not include any heating mechanism for maintaining the temperature of the asphalt cement as the CIR process is carried out. Consequently, the asphalt cement in the supply truck will begin to lose heat as soon as the truck leaves the asphalt cement supply terminal. If the CIR process is being carried out at a great distance from the asphalt cement supply terminal, the asphalt cement in the supply truck will have lost a significant part of its heat even before the CIR process is begun. Furthermore, the CIR process may begin at a time of day such that it cannot be completed during a single operating shift. When the temperature of the asphalt cement in the supply truck falls below about 300° F., for whatever reason, its continued use will likely result in a repaired roadway of substandard quality.
Co-pending U.S. patent application Ser. No. 15/855,403 describes a method and apparatus for heating asphalt cement that is carried in an asphalt cement supply tank prior to the use of such asphalt cement in a CIR process. The apparatus described in this application comprises a heater for asphalt cement that is a part of a CIR train. More particularly, the heater is interposed between the asphalt cement supply tank and the component of the CIR train that is dispensing asphalt cement to be mixed with recycled paving material in the CIR process. Preferably, a heater with an infinitely variable heating output between about 300,000 BTUs per hour and about 500,000-750,000 BTUs per hour is employed in the method of this co-pending patent application; however, infinitely variable heaters with heating outputs in this range are difficult to find. Consequently, it would be desirable if an apparatus could be provided that would allow for heating asphalt cement by the required amount using a much simpler heating apparatus.
Among the advantages of a preferred embodiment of the invention is that it provides a method and apparatus that allows the CIR process to continue without concern for the loss of heat in the asphalt cement carried by the supply truck. Yet another advantage of a preferred embodiment of the invention is that it provides an apparatus that employs a simpler heating apparatus than one providing an infinitely variable heating output between its maximum and minimum rated Btu values.
Other advantages and features of this invention will become apparent from an examination of the drawings and the ensuing description.
The use of the terms “a”, “an”, “the” and similar terms in the context of describing the invention are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising”, “having”, “including” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. The terms “substantially”, “generally” and other words of degree are relative modifiers intended to indicate permissible variation from the characteristic so modified. The use of such terms in describing a physical or functional characteristic of the invention is not intended to limit such characteristic to the absolute value which the term modifies, but rather to provide an approximation of the value of such physical or functional characteristic.
Terms concerning attachments, coupling and the like, such as “attached”, “coupled”, “connected” and “interconnected”, refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both moveable and rigid attachments or relationships, unless otherwise specified herein or clearly indicated as having a different relationship by context. The terms “operatively connected” and “operatively attached” describe such an attachment, coupling or connection that allows the pertinent structures to operate as intended by virtue of that relationship. The term “fluid communication” refers to such an attachment, coupling or connection that allows for flow of fluid from one such structure or component to or by means of the other.
The use of any and all examples or exemplary language (e.g., “such as” and “preferably”) herein is intended merely to better illuminate the invention and the preferred embodiments thereof, and not to place a limitation on the scope of the invention. Nothing in the specification should be construed as indicating any element as essential to the practice of the invention unless so stated with specificity. Several terms are specifically defined herein. These terms are to be given their broadest reasonable construction consistent with such definitions, as follows:
The term “asphalt cement” includes asphalt cement of various types and formulations in liquid form, as well as foamed asphalt cement and asphalt cement emulsions which are capable of fluid flow.
The term “milling machine” refers to a machine having a milling or working drum that is adapted to be placed into contact with a roadway or road base surface for removing a portion of the surface. The term “milling machine” includes but is not limited to machines that are sometimes referred to as road stabilizers and roadway reclaiming machines. The term “milling machine” also includes a CIR-modified milling machine, as hereinafter defined.
The term “CIR process” refers to a use of cold in-place recycling (“CIR”) equipment to repair damage to a roadway, by removing damaged layers of pavement, processing the paving material so removed, replacing the removed and processed paving material onto the roadway, and compacting it.
The term “CIR-modified milling machine” refers to a milling machine which has been modified by the addition of an asphalt cement flow system including a spray assembly that is mounted in the milling drum housing to dispense asphalt cement into the milling drum housing.
The term “CIR train” refers to a plurality of items of equipment including, but not limited to, a mobile asphalt cement supply tank and a milling machine (which may or may not be a CIR-modified milling machine), which items of equipment are used, or intended to be used, in a CIR process. A CIR train may include a cold recycler machine, and it will also include an asphalt paving machine, although the asphalt paving machine may be employed at a time subsequent to the passage of the other components of the CIR train to pick up a windrow of processed paving material from the roadway.
The term “processing direction” refers to the primary direction of travel of a CIR train as it operates on a roadway.
The term “downstream”, as used herein to describe a relative position on or in connection with an asphalt cement flow circuit that is a part of, or that relates to, the invention, refers to a relative position in the direction of the flow of asphalt cement from the supply tank to the component of a CIR train that is dispensing asphalt cement to be mixed with recycled paving material in a CIR process according to the invention.
The term “upstream”, as used herein to describe a relative position on or in connection with an asphalt cement flow circuit that is a part of, or that relates to, the invention, refers to a relative position in a direction that is opposite to the direction of the flow of asphalt cement from the supply tank to the component of a CIR train that is dispensing asphalt cement to be mixed with recycled paving material in a CIR process according to the invention.
The invention comprises a method and apparatus for heating asphalt cement that is discharged from a mobile asphalt cement supply tank in order to facilitate the use of such asphalt cement in a CIR process. A heating assembly for asphalt cement comprises a heater and a heat modifying component. This heating assembly is interposed in the asphalt cement flow circuit between the asphalt cement supply tank and the component of the CIR train that is dispensing asphalt cement to be mixed with recycled paving material in the CIR process. More particularly, the heating assembly is located downstream of the asphalt cement supply tank and upstream of the component for dispensing asphalt cement to be mixed with recycled paving material. The heater component of the heating assembly comprises a burner and an asphalt cement coil. Asphalt cement to be heated is pumped through the asphalt cement coil, and the burner directs hot gases of combustion across the asphalt cement coil so that heat may be transferred from the hot gases to the asphalt cement flowing through the coil.
In some embodiments of the invention, the heater may include multiple asphalt cement coils across which hot gases of combustion are directed. In some embodiments, the heater may be provided with multiple burner nozzles, each of a different size, so that fuel can be selectively directed through nozzles of different sizes to change the heat output from the burner. In addition, the heater may also be provided with valves or other mechanisms that can change the fuel flow rate to the burner to change the heat output.
The heat modifying component of the heating assembly is adapted to modulate the amount of heat transfer from the hot gases of combustion to the asphalt cement in the asphalt cement coil in order to control the temperature of the asphalt cement in the asphalt cement flow circuit downstream of the heating assembly. This modulation is preferably carried out by modifying the air flow and/or the asphalt cement flow through the heater. In some embodiments of the invention, the heat modifying component comprises a by-pass valve that is arranged to blend unheated asphalt cement with asphalt cement that is heated by the heater in such a manner so as to obtain the desired asphalt cement temperature in the blend. In other embodiments of the invention, the heat modifying component comprises an air flow regulator assembly that controls the flow of the hot gases of combustion generated by the burner across the asphalt cement coil, in order to control the amount of heat transfer from the hot gases to the asphalt cement in the coil. In these embodiments of the invention, multiple exhaust vents are mounted to the heater, each of which is provided with a damper or other control mechanism that selectively allows or blocks the flow of hot gases of combustion across the asphalt cement coil of the heater. The exhaust vents and dampers are so located that operation of the dampers can change the path of hot gases of combustion within the heater, thereby changing the flow pattern of hot gases of combustion across the asphalt cement coil, and thereby changing the amount of heat transferred by the hot gases of combustion to the asphalt cement within the coil.
Preferably, the heating assembly is adapted to heat asphalt cement continuously as it is withdrawn from the asphalt cement supply tank, so as to continuously increase the temperature of the asphalt cement at a rate of about 1.0° F. per gallon at a flow rate of about 30 gallons/minute, or at a greater rate of temperature increase at a lower flow rate, or at a lesser rate of temperature increase at a higher flow rate, in order to insure that the asphalt cement that is discharged from the heating assembly is within a predetermined acceptable range of temperatures for use in the CIR process.
In order to facilitate an understanding of the invention, the preferred embodiments of the invention, as well as the best mode known by the inventors for carrying out the invention, are illustrated in the drawings, and a detailed description thereof follows. It is not intended, however, that the invention be limited to the particular embodiments described or to use in connection with the apparatus illustrated herein. Therefore, the scope of the invention contemplated by the inventors includes all equivalents of the subject matter described herein, as well as various modifications and alternative embodiments such as would ordinarily occur to one skilled in the art to which the invention relates. The inventors expect skilled artisans to employ such variations as seem to them appropriate, including the practice of the invention otherwise than as specifically described herein. In addition, any combination of the elements and components of the invention described herein in any possible variation is encompassed by the invention, unless otherwise indicated herein or clearly excluded by context.
The presently preferred embodiments of the invention are illustrated in the accompanying drawings, in which like reference numerals represent like parts throughout, in which arrows marked with “AC” indicate the direction of flow of asphalt cement and arrows marked “AF” indicate the direction of flow of heated air and gases of combustion, and wherein:
This description of preferred embodiments of the invention is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description of this invention. The drawing figures are not necessarily to scale, and certain features of the invention may be shown exaggerated in scale or in somewhat schematic form in the interest of clarity and conciseness.
Power from the engine is also transmitted, by means known to those having ordinary skill in the art to which the invention relates, to rear track drive assembly 26 and front track drive assembly 28. A CIR-modified milling machine may include one or two rear drive track assemblies (such as rear track drive assembly 26), and two front drive track assemblies (such as front track drive assembly 28). Some or all of these track drive assemblies can be turned to the left and to the right for steering purposes. Other embodiments of CIR-modified milling machines (not shown in the drawings) may include wheel drive assemblies instead of track drive assemblies. The drive assemblies are attached to lifting columns that include internal linear actuators (not shown) which can be activated to raise and lower the frame of the machine with respect to the roadway surface to change the depth of milling being carried out. Since milling drum 22 is mounted for rotation in milling drum housing 24 on the frame of the machine, raising the frame on the lifting columns can raise the milling drum out of contact with the roadway surface, and lowering the frame on the lifting columns can lower the milling drum into contact with the road surface so as to make a cut of the desired depth. Operator's station 18 includes all of the controls necessary for driving and steering the CIR-modified milling machine, rotating milling drum 22, and controlling all other operations of milling machine 12.
CIR-modified milling machine 12 includes asphalt cement spray assembly 30 that is mounted within the milling drum housing and adapted to dispense asphalt cement obtained from input supply line 32 which is in fluid communication with supply tank 34 on asphalt cement supply truck 16. Asphalt cement metering flow mechanism 36 is mounted on the front end of milling machine 12 and is in fluid communication with output supply line 38, heating assembly 14 and input supply line 32 from supply truck 16. Flow mechanism 36 comprises a pump that operates to draw asphalt cement from supply tank 34 of supply truck 16, through input supply line 32 into heater 14, and out of heater 14 through output supply line 38 to spray assembly 30, which dispenses asphalt cement into milling drum housing 24, where it mixes with paving material milled from the roadway. An alternative asphalt cement flow circuit from asphalt cement supply tank truck 16 to milling drum housing 24 of the CIR-modified milling machine is illustrated in
Paving machine 10 includes a conventional conveyor system comprising longitudinally disposed conveyors (not shown) and a transversely disposed screw auger (also not shown) for delivering the mixture of asphalt cement and recycled paving material from hopper 42 to a position just in advance of floating screed 44 where it is discharged onto the surface to be paved. The screed compacts and levels the asphalt mat on the repaired roadway.
The asphalt cement flow circuit illustrated in
Heater 114 of heating assembly 146 is illustrated in some detail in
Both linear actuator 168 and linear position sensor 169 are operatively attached to controller 174, shown schematically in
Controller 174 may embody a single microprocessor or multiple microprocessors that include components for controlling the temperature of the asphalt cement used in the CIR process, as well as components for controlling the operations of modified milling machine 12 or cold recycler machine 46, based on input from a machine operator and on sensed or other known operational parameters. Controller 174 may include a memory, a secondary storage device, a processor and other components for running an application. Various other circuits may be associated with controller 174 such as power supply circuitry, signal conditioning circuitry, solenoid driver circuitry and other types of circuitry. Numerous commercially available microprocessors can be configured to perform the functions of controller 174. It should be appreciated that controller 174 could readily be embodied in a general purpose computer or machine microprocessor capable of controlling numerous machine functions for a modified milling machine such as modified milling machine 12 or a cold recycler machine such as cold recycler machine 46.
Heating assembly 246 includes a heat modifying component comprising an air flow regulator assembly that is operatively attached to heater 214. More specifically, the air flow regulator assembly comprises upper exhaust vent 190 with upper damper 192 mounted therein, and lower exhaust vent 194 with a lower damper (not shown, but substantially identical to upper damper 192) mounted therein. Both upper exhaust vent 190 and lower exhaust vent 194 are mounted so as to be in fluid communication with coil chamber 180. In addition, both upper damper 192 and the lower damper are controlled by linear actuator 196 that is operatively attached to controller 174, so that either upper damper 192 is open and the lower damper is closed (as shown in
Burners 159, 121, 124 and 177 are preferably multi-stage burners that may be configured in any of various ways. The SDC Series oil burner sold by the Beckett Corporation of North Ridgeville, Ohio has a single fuel nozzle that operates according to two different pressure ranges to produce two different heat outputs. The RG5D light oil burner sold by Riello S.p.A. of Legnago, Italy has two fuel nozzles that operate according to different flow rates to produce two different heat outputs. The WL20 oil burner sold by Weishaupt Corporation of Mississauga, Ontario has two solenoids that operate to supply two different flow rates to a single nozzle to produce two different heat outputs. Other burner assemblies may be employed that are adapted to produce one or more than one heat output. Preferably, a burner is employed that is adapted to produce a maximum of at least about 400,000 BTUs per hour.
During the operation of a modified milling machine or a cold recycler machine according to the embodiment of the invention illustrated in
Preferably, heating assembly 246 is adapted to heat asphalt cement continuously as it is withdrawn from the asphalt cement supply tank, so as to continuously increase the temperature of the asphalt cement at a rate of about 1.0° F. per gallon at a flow rate of about 30 gallons/minute, or at a greater rate of temperature increase at a lower flow rate, or at a lesser rate of temperature increase at a higher flow rate, in order to insure that the asphalt cement that is discharged from the heater is within a predetermined acceptable range of temperatures for use in the CIR process.
Heating assembly 246 is located downstream of supply tank 134 in an asphalt cement flow circuit that is in fluid communication with a mechanism for dispensing asphalt cement on recycled paving material removed from a roadway by a milling machine in a CIR process. The heating assembly is adapted to heat the asphalt cement coming from the supply tank prior to its being dispensed on the recycled paving material that has been removed from the roadway. Heating assembly 246 may be a stand-alone unit located behind the asphalt cement supply truck, or it may be mounted to the asphalt cement supply truck, to a CIR-modified milling machine or to a cold recycler machine.
Although this description contains many specifics, these should not be construed as limiting the scope of the invention but as merely providing illustrations of the presently preferred embodiments thereof, as well as the best modes contemplated by the inventors for carrying out the invention. The invention, as described and claimed herein, is susceptible to various modifications and adaptations, as would be understood by those having ordinary skill in the art to which the invention relates.
This application is a continuation-in-part of U.S. patent application Ser. No. 15/855,403 which was filed on Dec. 27, 2017 and claims the benefit of U.S. Provisional Patent Application No. 62/441,631 that was filed on Jan. 3, 2017. This application also claims the benefit of U.S. Provisional Patent Application No. 62/629,296 which was filed on Feb. 12, 2018.
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| Number | Date | Country |
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| WO 2018128888 | Jul 2018 | WO |
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| 20190153681 A1 | May 2019 | US |
| Number | Date | Country | |
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| 62441631 | Jan 2017 | US | |
| 62629296 | Feb 2018 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15855403 | Dec 2017 | US |
| Child | 16259599 | US |
