Patent Publication Number: US-2012027514-A1

Title: Pavement Degradation System with a Diesel Electric Drum

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to pavement and asphalt maintenance equipment. Such equipment can be large, heavy, and difficult to transport. Additionally, these machines may require large amounts of energy to function and may emit many harmful pollutants into the atmosphere. It is desirable to provide improved pavement milling machines that comprise lighter weight, higher efficiency, and easier transport, while maintaining or increasing productivity. Efforts to improve pavement milling equipment are disclosed in the prior art. 
     U.S. Pat. No. 6,227,620 to Page discloses a compact, easily transportable, surface preparation or road mill apparatus which includes a road mill housing or surface treatment unit having a cutter drum powered by its own power source. The apparatus also includes a mounting device for attachment of a working machine, such as the road mill housing, to a land vehicle having a lifting mechanism, preferably of the type provided on “front-end loaders”. The surface treatment unit or road mill housing preferably has an opening for receiving a cylindrical shaft and the mounting device includes an attachment device for attachment to a land vehicle and an interconnected cylindrical shaft upon which the road mill housing can be secured once the shaft is received within the shaft receiving opening. 
     U.S. Pat. No. 7,144,087 to Haroldson discloses systems and methods for milling paving material. A self-powered milling system includes a cutting head to mill the paving material. The cutting head is powered by a milling system motor that speeds up production and enables the milling of very thick asphalt in a single pass. A milling system carriage follows the contour of the ground, provides stability during the milling process, is selectively adjusted to provide cuts at various angles, and enables precise edge milling. A breaker bar holds the paving material down as it tries to lift up during the milling process, and is employed to assist in the breaking up of the milled aggregate. 
     U.S. Pat. No. 4,704,045 to Taylor discloses an apparatus and method for pulverizing asphalt on roadways and similar applications. The asphalt is pulverized by a rotating drum with removable cutting tips which engage a soften underside of the roadway prior to engaging a harder more compact top surface of the roadway. The apparatus designed for receiving and rotating various widths of drums and adaptable for moving the drum along the width of a mobile piece of equipment supporting the apparatus and adjacent a curb and gutter of a roadway. 
     BRIEF SUMMARY OF THE INVENTION 
     In one aspect of the present invention, a pavement degradation machine comprises a motor vehicle with a combustion engine connected to an electrical generator, a pavement degradation assembly with a plurality of cutting elements, the pavement degradation assembly being in communication with an electric motor. The electrical generator is in communication with the electric motor. The combustion engine may comprise an internal combustion engine with spark ignition, compression ignition, homogeneous charge compression ignition, or may comprise a turbine engine. The pavement degradation assembly may be attached to a frame connected to the motor vehicle by an articulated coupling. The frame may comprise geometric strut frame members. The frame may also comprise traction motors in communication with the electrical generator. The traction motors may power treads or wheels. The pavement degradation assembly may comprise a cylindrical drum. In some embodiments, the cutting elements may comprise polycrystalline diamond. 
     The electric motor may be disposed inside the cylindrical drum. In some embodiments, the electric motor may be connected to a hydraulic pump. The hydraulic pump may be connected to one or more hydraulic motors. In some embodiments, the generator may provide motive power to the motor vehicle. The electrical communication between the motor and the generator may comprise power and data. The pavement degradation assembly may comprise a debris removal conveyor, and the conveyor may be in communication with an asphalt recycling machine. The debris removal conveyor and the asphalt recycling machine may be in communication with the electrical generator. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an orthogonal view of an embodiment of a pavement milling machine. 
         FIG. 2  is an orthogonal view of an embodiment of a motor vehicle. 
         FIG. 3  is an orthogonal view of an embodiment of a pavement milling assembly. 
         FIG. 4  is an orthogonal view of another embodiment of a pavement milling machine. 
         FIG. 5  is a perspective view of an embodiment of a drive tread. 
         FIG. 6   a  is a cross-sectional view of an embodiment of a pavement milling drum. 
         FIG. 6   b  is a cross-sectional view of another embodiment of a pavement milling drum. 
         FIG. 6   c  is a cross-sectional view of another embodiment of a pavement milling drum. 
         FIG. 6   d  is a cross-sectional view of another embodiment of a pavement milling drum. 
         FIG. 7  is an orthogonal view of another embodiment of a pavement milling assembly. 
         FIG. 8  is an orthogonal view of another embodiment of a pavement milling machine. 
         FIG. 9  is an orthogonal view of another embodiment of a pavement milling machine. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION AND THE PREFERRED EMBODIMENT 
     Referring now to the figures,  FIG. 1  discloses an embodiment of a pavement milling machine  100 . Milling machine  100  comprises a motor vehicle  101  connected to a pavement degradation assembly  102 . The milling machine  100  traverses a paved roadway  103 . The milling machine may degrade a portion of a paved formation such as a road, side walk, parking lot, patio, or airport runway. The motor vehicle  101  and the pavement degradation assembly may be connected by an articulated coupling  104  and an electrical connection  105 . 
       FIG. 2  discloses another embodiment of a motor vehicle  200 . In this embodiment, the motor vehicle  200  comprises an industrial-duty truck frame  201  with a passenger compartment  202 . An internal combustion engine  203  may be disposed on a load carrying portion  204  of the truck frame. The internal combustion engine may be connected to an electrical generator  205  through a rotational coupling such as a shaft, sleeve, or clutch. Some embodiments may comprise a centrifugal clutch, a clutch with mechanical actuation, hydraulic actuation, or electrical actuation. A gear set may be disposed intermediate the engine and the generator to increase or decrease the rotational velocity of the generator with respect to the engine. The gear set may comprise straight-cut gears, helical gears, planetary gears, or other gears and may comprise multiple selectable gear ratios. A constantly variable transmission may be disposed intermediate the combustion engine and the electric motor. Varying the speed ratio between the engine and generator with these devices may allow added flexibility in electrical output voltage and power from the generator while maintaining the engine at a rotational speed that provides optimum efficiency. 
     The internal combustion engine  203  may comprise a diesel fueled compression ignition engine. In some embodiments, this engine may be fueled with biodiesel, petroleum diesel, vegetable oil, or combinations thereof. The engine may comprise layouts such as inline cylinders, V arranged cylinders, or opposed cylinders. The engine may comprise any number of cylinders, but in a preferred embodiment, the diesel engine comprises a 6 cylinder inline arrangement. Other embodiments may comprise more cylinders, such as in a V-12 arrangement. A greater number of cylinders may reduce harmonic vibrations in the engine components, reducing wear and increasing machine lifetime, and reducing fatiguing noise and vibration experienced by the operator. 
     In other embodiments, a gasoline fueled engine may be used. Gasoline engines may comprise a higher power-to-weight ratio than a comparable diesel engine. Blends of ethanol, methanol, and other alternative fuels may be used to reduce petroleum consumption and minimize adverse environmental impact. Engine configurations as previously detailed may be used. Some embodiments may comprise spark ignition as in a traditional Otto-cycle gasoline engine, while other embodiments may comprise homogeneous charge compression ignition (HCCI) to improve efficiency and minimize fuel use and emissions. HCCI engines allow lean burning conditions that allow improved thermodynamic efficiency. Such conditions would cause severe damage and excessive oxides of nitrogen emissions in a conventional spark ignition engine. 
     The electrical generator  205  may comprise an AC or DC generator. In a preferred embodiment, a three-phase AC generator is used. Preferably, AC power is supplied to the load. In other embodiments, AC power may be rectified to DC to drive a DC load. Alternatively, a DC generator may be used to power a DC load. A power distribution box  207  may comprise one or more power outputs with connectors that correspond to mating connectors on power cables attached to tools such as the asphalt milling assembly disclosed in relation to  FIG. 1 . The power distribution box may also comprise load sensitive controls in communication with the control systems of engine  203 . Heavy electrical loads on the generator may trigger an increase in engine RPM by signaling the engine controls to inject more fuel into the combustion chambers in a compression-ignition engine, or by opening the throttle of a spark ignition engine. The engine controls may also monitor engine exhaust temperature, coolant temperature, cylinder head temperature, and oil temperature and adjust engine operating conditions accordingly by varying fuel flow rate or throttle position. The power distribution box  207  may also comprise circuit breakers to interrupt electrical current if safe operating limits are exceeded. For example, the breaker may interrupt the circuit if there is an electrical short in a load connected to the generator. 
     In some embodiments, the engine and generator may be fastened to a pallet or skid  208 , allowing easy removal and replacement of the power generation unit. This may ease servicing, and allow the power generation unit to be used on multiple machines. The pallet or skid may comprise lift points for attachment to an overhead crane or hoist, and may comprise recesses for placement and removal by forklift. Bolts, clamps, or other devices may be used to fasten the pallet to the truck frame. 
     In some embodiments, the motor vehicle  200  may comprise a traditional gas or diesel engine drivetrain that provides motive power to the vehicle. In other embodiments, power from the electrical generator may be directed to electric motors driving the wheels of the motor vehicle. 
       FIG. 3  discloses an embodiment of a pavement milling assembly  300 . In this embodiment, the pavement milling assembly  300  may be connected to a motor vehicle such as that described in relation to  FIG. 2  by an articulated coupling  301  and an electrical connection  302 . The pavement milling assembly  300  may comprise a milling drum  303  comprising a plurality of cutting elements  304 . In some embodiments, the cutting elements may comprise polycrystalline diamond material to inhibit wear and improve the service life of the cutting elements. In other embodiments, the cutting elements may comprise cubic boron nitride, tungsten carbide, other hard materials, or combinations thereof. Materials resistant to abrasion and heat are preferable to reduce the maintenance requirements by extending the life of the cutters between necessary replacements. The pavement milling machine also comprises drive treads  306  in contact with the road surface. 
     In this embodiment, the milling drum may be driven by an electric motor connected to a generator like that described in relation to  FIG. 2 . The electric motor may drive the drum through a chain drive, a driveshaft, or belt, or the motor shaft may be directly coupled to the drum. In some embodiments, a single speed gear reduction or a multiple speed transmission may be disposed intermediate the motor and drum. The gear reduction or transmission may comprise straight cut gears, helical gears, planetary gears, or other gearing configurations. A constantly variable transmission comprising variable diameter pulleys may be used in some embodiments. Electric motors may be connected to the drive treads  306  and connected to the electrical generator through electrical connection  302  to provide motive power to the pavement milling machine. 
     In other embodiments, the pavement milling assembly may comprise a single electric motor that drives a hydraulic pump. The hydraulic pump may be connected through a hydraulic control system to one or more hydraulic motors attached to the drum. Hydraulic motors may also be disposed on the drive treads  306  to provide motive power to the pavement milling machine. 
     The motor may be connected to the generator by the electrical connection  302 , which may carry electrical power from the generator to the motor, and it may also carry electrical data, such as drum rotational speed, vehicle road speed, and drum torque. Additional information may be communicated between the motor and generator, and displayed on instruments near an operator in the motor vehicle or the pavement milling assembly. 
     In this embodiment, the pavement milling assembly  300  may comprise geometric strut frame members  305 . These frame members may comprise carbon fibers, glass fibers, aramid fibers, or other fibers, and polymer resin to maintain the fibers in a structural form. Composite geometric struts may provide a higher strength to weight ratio than other frame rail geometries. In some embodiments, the frame members may comprise a closed section member, a boxed section, or C, U or I beam geometry. In these embodiments, the frame members may comprise steel alloys, aluminum alloys, composite materials, or other materials. 
       FIG. 4  discloses another embodiment of a pavement milling machine  400 . In this embodiment, the pavement milling machine  400  is connected to an pavement recycling machine  401  and a road roller  402 . As the pavement milling machine traverses a road surface, the milling machine degrades the paved surface creating loose debris that may include cement, asphalt, and aggregate. The debris may be collected and removed from the road surface by a conveyor  403 . The conveyor may comprise a metal or rubber belt, and be powered by a hydraulic or electric motor. In some embodiments, the debris may be delivered to a dump truck or semi truck for removal from worksite. In this embodiment, the debris is poured into the asphalt recycling machine  401 . The asphalt recycling machine may reconstitute the debris by adding additional aggregate and bituminous asphalt or other petroleum or synthetic tar. The recycling machine  401  may then expel the mixture of aggregate and asphalt back onto the road bed. A road roller  402  may then compress the mixture to create a substantially uniform road surface. In this embodiment, the recycling machine  401  and the road roller  402  may be connected to the pavement milling machine  400  by articulated couplings  406  and  407 . Electrical connections and may also be disposed intermediate the pavement milling assembly and the recycling machine and road roller. The electrical connections may be integrated with the articulated couplings, or may comprise cables. The recycling machine and road roller may be powered solely by electrical power from the engine and generator  410  associated with the pavement milling machine  400 . The electrical connectors and may transfer data as well as power. The data may comprise information such as road speed, tool speed, tool power requirements, and operating conditions that may be displayed on instruments visible to an operator. 
     Road speed information from each machine may be input to an electronic control system, and the control system may substantially match road speed among the machines to minimize stress on the articulated couplings and to prevent shocks and traction losses. 
     Arranging the tools in this manner may allow greater efficiency, as each pavement tool draws power from a single generator. The engine driving this generator can be tuned for maximum efficiency at a single operating RPM by adjusting intake and exhaust tract length and flow area, valve size, lift, and duration, and other mechanical parameters. Additionally, the separate tools may provide lighter weight, less maintenance cost, and easier transport by negating the need for individual engines on each tool. In some embodiments, some of the equipment may draw power from the electric generator(s) run by the diesel engine, while the remaining equipment draws its power from other sources. 
     The train of road construction equipment may include degradation equipment, transporting equipment, aggregate processing equipment, and paving equipment. The processing equipment may include ovens that heat debris recently removed from the road bed or other aggregate that is supplied and/or mixed with the recently removed debris. The processing equipment may also mix new aggregate with the recently removed aggregate. 
     The degradation equipment may include the milling drums, including drums with high pick density for micro-milling the pavement. Micro-milling may include operating the drum at a faster rate than traditional drums, but milling at a shallower depth or translating the milling machine at a slower pace while the drum rotates at the higher RPM. The micro-milling may produce finer aggregate that may be recyclable in situ. In some embodiments, a drum designed for micro-milling may cut at a depth of ½ inch or less. In other embodiments, the milling drum comprises the traditional pick density and spacing. 
       FIG. 5  discloses an embodiment of a pavement milling machine  500  comprising a traction drive tread  501  with an electric traction motor  502 . The electric traction motor may be attached directly to a drive tread frame  503  and be electrically connected to a power distribution harness  504 . Power for the electric motor may come from an engine and generator unit disposed on the pavement milling machine or a connected motor vehicle. Locating the drive motors in the drive tread frame may minimize the mechanical complexity, weight, and required maintenance, compared to hydraulic or mechanical drives. The pavement milling machine may comprise multiple drive treads. In a preferred embodiment, the pavement milling machine comprises four drive treads positioned substantially at the corners of the milling machine frame. Each drive tread may comprise a traction motor. In some embodiments, only the front or only the rear drive treads may comprise motors. 
       FIG. 6   a  discloses another embodiment of a pavement degradation assembly  600 . In this embodiment, the degradation assembly comprises a plurality of cutting elements  601  disposed on an outer diameter of a hollow drum  602 . An electric motor  603  is disposed within the drum  602 . The electric motor comprises a driveshaft  604  rotationally fixed to the drum  602 . A rigid sleeve  605  fixes the housing of the electric motor  603  to a support  606  of a milling machine. Electrical connections may connect the motor  603  to an electrical power source, such as an electrical generator. 
       FIG. 6   b  discloses the pavement milling drum associated with  FIG. 6   b  in an orthogonal cross-sectional view. Drum  602  comprises bearings  607  and  608 . Bearing  607  connects the drum  602  to frame support  606 . A rigid sleeve  605  is disposed in an inner diameter of bearing  608 . Mounting bolts  609  pass through drive side frame support  610 , through rigid sleeve  605 , and thread into the housing of motor  603 . Bearings  607  and  608  may comprise ball bearings, tapered roller bearings, needle bearings, plain bearings, or other bearing designs. In some embodiments, the bearings may comprise hydrodynamic bearings with a pressurized lubrication system. 
       FIG. 6   c  discloses another embodiment of a pavement milling assembly  600 . In this embodiment, two electric motors  610  and  611  are disposed within a drum  612 . Providing two electric motors may reduce vibrations from torsional loading of the drum or from weight imbalance. 
       FIG. 6   d  shows an isometric cross-sectional view of a pavement degradation assembly comprising two direct-current electric motors  610  and  611  comprising commutators  613  and  614 . In other embodiments, alternating-current motors may be used. 
       FIG. 7  discloses another embodiment of a pavement degradation assembly  700 . In this embodiment, the pavement degradation assembly may be connected to an engine and generator through electrical connection  701 . An electric motor  702  may be attached to a frame  703 , and may drive a hydraulic pump  704 . Hydraulic pump  704  pressurizes a working fluid, and the working fluid may be delivered to hydraulic motors through hydraulic lines  705 . Hydraulic motors may be disposed adjacent to and driving a degradation drum  706  and drive treads  707 . The hydraulic system may comprise a control system that limits the motor speed at the drum and drive track motors. 
       FIG. 8  discloses another embodiment of a pavement milling machine  800 . Milling machine  800  comprises a combustion engine  801  connected to an electrical generator  802 . Electric motors may be mechanically connected to a degradation drum  803  and drive tracks  804 . The combustion engine and electric generator may be attached to a pallet or skid  805  that is easily removable from the milling machine  800  for replacement or repair. 
       FIG. 9  discloses another embodiment of a pavement milling machine  900 . In this embodiment, the milling machine comprises a turbine engine  901  connected to an electrical generator  902 . Milling machine  900  also comprises drive wheels  903 . The drive wheels may be driven by electric motors electronically connected to the electrical generator  902 . Turbine engines may comprise a higher power-to-weight ratio than piston engines, and may reduce the difficulty of transporting the milling machine. Additionally, many turbine engines are able to burn a wide variety of fuels including gasoline, Diesel fuel, kerosene, biological fuels such as biodiesel and ethanol, and other mineral and organic fuels. 
     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.