Abstract:
A pavement recycling assembly includes a frame defining a grinding chamber and a mixing chamber. The grinding chamber carries a rotatable laterally-extending toothed grinding drum and the mixing chamber houses at least one toothed rotatable mixing wheel. A screed assembly is disposed behind the mixing chamber for extruding said mixture at a desired height so as to form a pavement. Pavement is recycled in-situ using the recycling assembly by grinding existing pavement, adding fluid asphalt to the pavement, optionally adding supplemental pavement, and mixing the fluid asphalt with the existing and/or supplemental pavement. The mixture is then extruded at the proper height by an adjustable screed. The recycling assembly may be suspended under a self-propelled chassis so that it can be shifted laterally to engage a pavement surface selected for repair without moving the entire chassis.

Description:
This application claims the benefit of U.S. Provisional Application No. 60/452,408, filed Mar. 6, 2003. 

   BACKGROUND OF THE INVENTION 
   This invention relates generally to patching and recycling asphalt pavement and more particularly to an apparatus and method for recycling and patching asphalt pavement in-situ. 
   Asphalt pavement often requires replacement or repair, for example by patching. Pavement can be repaired with new material or recycled material, although it is considered desirable to use recycled material for cost and environmental reasons. Recycling typically involves breaking up and removing the old pavement and hauling it to a recycling plant. Then new or recycled material is hauled from a plant to the work site. Other pavement recycling approaches include portable or mobile recycling plants or various types of in-situ recycling equipment. These prior art approaches generally require large or complex equipment, and are not particularly suited for patching operations. Accordingly, there is a need for a compact and simple in-situ pavement recycling machine. 
   BRIEF SUMMARY OF THE INVENTION 
   Therefore, it is an object of the invention to provide a self-contained asphalt recycling assembly. 
   It is another object of the invention to provide a pavement recycling machine which is particularly suitable for patching portions of an asphalt pavement roadway. 
   It is another object of the invention to provide a pavement recycling machine having a recycling assembly which can be laterally shifted to engage a portion of a roadway without moving the entire machine. 
   These and other objects of the present invention are achieved in the preferred embodiments disclosed below by providing a pavement recycling assembly, including a frame having left and right side plates, a top plate, and an open bottom for contacting a pavement surface, the frame defining a mixing chamber and an opening in the top plate in communication with the mixing chamber, A flat anvil is disposed at a forward end of the frame for engaging the pavement surface. A laterally-extending toothed grinding drum is rotatably mounted in a grinding chamber in the frame behind the anvil and ahead of the mixing chamber for breaking up and grinding the pavement. Means are provided for rotating the grinding cylinder and for introducing fluid asphalt into the frame At least one laterally-extending toothed rotatable mixing wheel is disposed in the mixing chamber for forming a mixture of the fluid asphalt and the ground pavement, along with means for rotating the mixing wheel. A screed assembly is disposed behind the mixing chamber for extruding the mixture at a desired height so as to form a pavement. 
   According to another embodiment of the invention the means for introducing fluid asphalt comprises at least one row of spray nozzles. 
   According to another embodiment of the invention the row of spray nozzles is disposed above the opening. 
   According to another embodiment of the invention first and second laterally-extending toothed rotatable mixing wheels are disposed in the mixing chamber. 
   According to another embodiment of the invention the vertical position of the grinding drum is adjustable relative to the frame to change the depth of cut of the grinding drum. 
   According to another embodiment of the invention the anvil is movable longitudinally relative to the frame. 
   According to another embodiment of the invention the anvil is coupled to the grinding cylinder such that the anvil moves rearward as the grinding drum is moved upward and the anvil moves downward as the grinding drum is moved downward. 
   According to another embodiment of the invention a heater is disposed in the frame behind the grinding drum from heating the ground pavement. 
   According to another embodiment of the invention a vertically adjustable material control gate is disposed in the frame behind the mixing chamber for controlling the amount of material flowing into the screed assembly. 
   According to another embodiment of the invention, a pavement recycling machine includes a wheeled chassis. A pavement recycling assembly is suspended under the chassis, the chassis being selectively movable vertically and laterally relative to the chassis. The recycling assembly includes a frame having left and right side plates, a top plate, and an open bottom for contacting a pavement surface, the frame defining a mixing chamber and an opening in the top plate in communication with the mixing chamber a toothed grinding cylinder rotatably mounted in a grinding chamber in the frame ahead of the mixing chamber for breaking up and grinding the pavement; means for rotating the grinding cylinder; at least one spray nozzle for introducing fluid asphalt binder into the frame; at least one toothed rotatable mixing wheel disposed in the mixing chamber for forming a mixture of the fluid asphalt binder and the ground pavement; means for rotating the mixing wheel; and a screed assembly disposed behind the mixing chamber for extruding the mixture at a desired height. 
   According to another embodiment of the invention, the recycling machine includes a feed hopper for receiving supplemental pavement, and a conveyor from moving the supplemental pavement from the feed hopper to the opening of the mixing chamber. 
   According to another embodiment of the invention, the recycling machine includes a feed hopper for receiving supplemental pavement, and a conveyor from moving the supplemental pavement from the feed hopper to the opening of the mixing chamber. 
   According to another embodiment of the invention, an in-situ method of recycling asphaltic pavement includes providing a pavement recycling assembly which has a frame having left and right side plates, a top plate, and an open bottom for contacting a pavement surface, the frame defining a mixing chamber and an opening in the top plate in communication with the mixing chamber; a toothed grinding cylinder rotatably mounted in a grinding chamber in the frame ahead of the mixing chamber for breaking up and grinding the pavement; means for rotating the grinding cylinder; at least one spray nozzle for introducing fluid asphalt binder into the frame; at least one toothed rotatable mixing wheel disposed in the mixing chamber for forming a mixture of the fluid asphalt binder and the ground pavement; means for rotating the mixing wheel; and a screed assembly disposed behind the mixing chamber for extruding the mixture at a desired height. 
   A selected area of asphaltic pavement is broken up and ground using the grinding drum. Fluid asphalt is introduced to the ground pavement. A mixture is creating of the fluid asphalt and the ground pavement using the mixing wheels. The mixture is extruded through the screed to create a pavement. 
   According to another embodiment of the invention, the method of recycling asphaltic pavement further includes suspending the pavement recycling assembly under a chassis so that it is laterally movable relative to the chassis; and selectively moving the pavement recycling assembly laterally left or right relative to the chassis so that the recycling assembly is aligned with a pavement surface to be recycled 
   According to another embodiment of the invention, the method of recycling asphaltic pavement further includes providing a hopper mounted to the chassis for receiving supplemental asphaltic pavement; and introducing supplemental pavement from the hopper into the mixing chamber along with the ground pavement and the fluid asphalt. 
   According to another embodiment of the invention, the method of recycling asphaltic pavement further includes providing a hopper mounted to the chassis for receiving supplemental asphaltic pavement; and introducing supplemental pavement from the hopper into the grinding chamber. 
   According to another embodiment of the invention, the method of recycling asphaltic pavement further includes selectively limiting the quantity of asphalt which passes from the mixing chamber to the screed assembly. 
   The present invention and its advantages over the prior art will become apparent upon reading the following detailed description and the appended claims with reference to the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The subject matter that is regarded as the invention is particularly pointed out and distinctly claimed in the concluding part of the specification. The invention, however, may be best understood by reference to the following description taken in conjunction with the accompanying drawing figures in which: 
       FIG. 1  is a perspective view of a pavement recycling machine constructed in accordance with the present invention; 
       FIG. 2  is a side elevational view of the pavement recycling machine of in  FIG. 1 ; 
       FIG. 3  is a partial sectional view of the pavement recycling machine of  FIG. 2  showing the internal components of a recycling assembly; 
       FIG. 4  is a perspective view of a recycling assembly; 
       FIG. 5  is another perspective view of the recycling assembly of  FIG. 4 ; and 
       FIG. 6  is a schematic side view of an alternative recycling assembly. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to the drawings wherein identical reference numerals denote the same elements throughout the various views,  FIGS. 1 and 2  illustrate the general layout of an exemplary asphalt pavement recycling machine  10 . As used herein, the terms “asphalt” or “asphalt binder” refer to an asphaltic binder, while the term “pavement” refers to a mixture of asphaltic binder and an aggregate. It is noted that the term “asphalt” is sometimes used by those skilled in the art interchangeably to refer to either an asphaltic binder alone or to the finished pavement. The recycling machine  10  has a wheeled chassis  12  which carries a power plant  14  of a known type such as a Diesel engine, a hydraulic fluid reservoir  16 , cab  18  with operator controls, a feed hopper  20 , and a conveyor  22 . A pavement recycling assembly  24  is suspended under the chassis  12 . The chassis  12  also carries an asphalt binder tank  26  for carrying fluid asphaltic binder, and heating fuel tanks  28  for carrying propane or a similar fuel. In the particular example illustrated, the chassis  12  is carried on a steerable pair of front wheels  30  and a steerable pair of rear wheels  32 . One or more of the wheels may be driven by any known means. For example, a known type of hydraulic drive may be used in which the power plant  14  drives a pump (not shown) which supplies a flow of pressurized hydraulic fluid through a system of control valves and conduits to one or more hydraulic motors (also not shown), to drive the wheels  30  and  32 . Similar pumps, piping, and valves may be used to drive other hydraulic components described below. Seating and controls for the machine operator of a known type are provided in the cab 18 . The feed hopper  20  receives paving material (i.e. new or recycled asphalt pavement) to be fed to the recycling assembly  24 . The feed hopper  20  is carried at the forward end of the recycling machine  10  so that it may be supplied from a dump truck which proceeds ahead of the recycling machine  10 . The feed hopper  20  includes a screw feeder  34  driven by a hydraulic motor  36  which moves the paving material from the sides of the hopper  20  to a central outlet  38 . The conveyor  22  receives material from the central outlet  38  and carries it to the recycling assembly  24 . The conveyer  22  is mounted under the chassis  12  above the recycling assembly  24  and includes an inclined forward section  40  and a level aft section  42 . In the illustrated example the conveyor is about 30.5 cm (12 in.) wide. 
     FIGS. 4 and 5  illustrate the recycling assembly  24  in detail. The recycling assembly  24  is carried on a frame  44 , which is built up from steel plate or sheet. The frame  44  includes spaced-apart left and right sidewalls  46  and  48  that extend from the forward end  50  to the aft end  52  of the frame  44 . A curved top panel  54  covers the internal components of the recycling assembly  24  and forms part of the flow path therethrough. The frame  44  could optionally be integrated with the chassis  12 . The forward end of the frame  50  includes a forward mounting slot  56 , which is defined by parallel, horizontally-oriented first and second bearing plates  58  and  60 , and a vertically oriented third bearing plate  62  which are arranged to from a square-sided “C” channel. The bearing plates  58 ,  60 , and  62  are constructed of heavy steel plate or an equivalent material, and may optionally include flat wear pads  64 . The wear pads  64  reduce friction and may be made from oil-impregnated plastic of a known type, or a similar material. 
   The aft end of the frame  52  includes an aft mounting slot  66 , which is defined by parallel, horizontally-oriented fourth and fifth bearing plates  68  and  70 , and a vertically oriented sixth bearing plate  72  which are arranged to from a square-sided “C” channel. The bearing plates  68 ,  70 , and  72  are constructed of heavy steel plate or an equivalent material, and may optionally include flat wear pads  74 . The wear pads  74  reduce friction and may be made from oil-impregnated plastic of a known type, or a similar material. 
   Returning to  FIG. 2 , the chassis  12  includes two spaced-apart downward-extending front posts  76 , and two spaced-apart downward extending rear posts  78 . The front and rear posts  76  and  78  on each side are tied together by a longitudinally-extending side beam  80 . A forward transverse rail  82  and an aft transverse rail  84  are suspended underneath the chassis  12 . The forward transverse rail  82  is visible in  FIG. 1  and both of the transverse rails  82  and  94  are shown in dashed lines in  FIG. 2 . The forward and aft transverse rails  82  and  84  are constructed of square-section steel tubes or a similar material. The forward transverse rail  82  extends between the pair of forward posts  76  and the aft transverse rail  84  extends between the pair of rear posts  78 . 
   The frame  44  of the recycling assembly  24  is mounted to the chassis  12  by way of the forward and aft transverse rails  82  and  84 . The forward transverse rail  82  is received in the forward mounting slot  56  of the frame  44 , and the aft transverse rail  84  is received in the aft mounting slot  66 . A forward traversing unit  86  is mounted on the forward traverse rail  82  (see  FIG. 1 ) and connected to a forward pivot  88  of the frame  44 . An aft traversing unit (not shown) is mounted on the aft traverse rail  84  and connected to an aft pivot  90  of the frame  44 . Both the forward and aft traversing units may be a known type of hydraulic piston-cylinder unit. The forward and aft transverse rails  82  and  84  are mounted so they can move vertically relative to the front and rear posts  76  and  78 . A pair of forward lift units  91  and a pair of rear lift units  93 , which may be known hydraulic piston-cylinder assemblies, are connected to the chassis  12  and the transverse rails  82  and  84 , so as to selectively move the transverse rails up or down. Thus mounted to the chassis  12  as described above, the entire recycling assembly  24  may be selectively raised or lowered and shifted laterally left or right relative to the chassis  12  of the recycling machine  10 . This enables a section of pavement that is away from the center of a road lane to be repaired without having to steer the entire recycling machine  10  into an adjacent lane, which is useful in patching operations. 
   Referring to  FIGS. 3 ,  4 , and  5 , the basic components of the recycling assembly  24  comprise an anvil  92 , a grinder drum  94 , a mixing chamber  96 , one or more arrays of spray nozzles  98 , and a screed assembly  100 . 
   The grinder drum  94  is a cylindrical assembly having a plurality of grinding teeth  102  disposed about its periphery. For a pavement patching application, the width of the grinder drum  94  (and thus the recycling assembly  24 ) would be about 0.9 m (36 in.) to about 1.2 m (48 in.). It is also possible to make the grinder drum  94  and recycling assembly  24  wide enough that an entire road lane may be recycled in one pass. The number and pattern of the teeth  102  is varied depending upon on the desired mesh size of the finished pavement. The grinder drum  94  is received in a grinding chamber  104  which is defined by the top plate  54  of the frame  44 . The grinder drum  94  is rotated about its axis by a hydraulic motor  106  or other suitable means and is mounted to the frame  44  at each end by a flat drum plate  108  which is captured at its edges by vertical rails  110 . The drum plates  108  are movable vertically relative to the frame  44  to adjust the grinding depth. In this example the drum plates  108  are moved by a plurality of hydraulic piston-cylinder assemblies  112 . The grinder drum  94  is capable of removing the entire thickness of a layer of asphalt pavement, and the typical depth of cut may be from about 2.5 cm (1 in.) to about 15.2 cm (6 in.) depending upon the depth of damage present. 
   The anvil  92  is a thick, flat plate disposed at the front end  50  of the recycling assembly  24 . The recycling assembly  24  rides on the anvil  92  thus providing a height reference for the grinding operation. The anvil  92  has an upstanding side plate  114  attached to each end thereof. Each of these side plates  114  is clamped to an L-bracket  116  by a retainer  118 , and has front and rear inclined surfaces  120  and  122 . Each of the L-brackets  116  is in turn attached to one of the drum plates  108  at an angle. When the grinding drum  94  is raised or lowered, the L-bracket  166  moves in the slot created by the retainer  118  and the rear inclined surface  120  of the side plate  114 . This causes the anvil  92  to move forward when the grinding drum  94  is lowered and rearward when the grinding drum  94  is raised. This keeps the longitudinal distance between the grinding drum  94  and the anvil  92  approximately constant as the depth of cut is changed. 
   One or more arrays of spray nozzles  98  may be mounted at several locations in the recycling assembly  24 . The number, spacing and positioning of the spray nozzles  98  may be varied to suit a particular application. In one arrangement, the spray nozzles  98  are disposed in transverse rows  124  and  126  each having four nozzles equally spaced across the width of the recycling assembly  24 . The spray nozzles  98  are connected to the fluid asphalt binder tank  26  through appropriate pipes, pumps, and valves of fluid a known type (not shown), in order to allow selective discharge of the fluid asphalt binder through the spray nozzles  98 . 
   The mixing chamber  96  is disposed behind the grinding drum  94 . The mixing chamber  96  is defined by the side walls  46  and  48  of the frame  44 , a baffle  128  disposed behind the grinding drum  94 , and partially by the top plate  54 . The bottom of the mixing chamber  38  is defined by the roadbed “R” below the recycling machine  10 . The mixing chamber  96  receives laterally-extending toothed first and second mixing wheels  130  and  132 , which are mounted for rotation in the frame  44  and driven by hydraulic motors  134  and  136 . An opening  138  is formed through the top plate  54  over the mixing wheels  130  and  132  and serves to admit material from the conveyor  22  to the mixing chamber  96 . The opening  138  is wide enough so that material from the centrally-positioned conveyor  22  will fall into the mixing chamber  96  no matter how far left or right the recycling assembly  24  is shifted. 
   The screed assembly  100  is disposed behind the mixing chamber  96 . The screed assembly  100  includes a heated screed  140  of a known type having a rounded or angled nose  142  and a flat bottom  144 . The height of the screed  140  (and thus the thickness of the pavement exiting the recycling machine  10 ) is controlled by a screed actuator  146  such as the illustrated hydraulic piston-cylinder assembly. 
   The operation of the recycling machine  10  will now be described with respect to  FIG. 3 . The recycling machine  10  is driven forward over an area of pavement to be patched. The recycling assembly  24  is shifted laterally to align with a specific pavement area as required. If necessary depending upon ambient conditions, the existing pavement is heated with a pre-heater (not shown) such as a steam box or a propane burner suspended ahead of the recycling assembly  24 . The front end of the recycling assembly  24  rides on the anvil  92  thus providing a height reference. The grinder drum  94  is lowered to the appropriate depth and rotated, causing the teeth  102  to break up and grind the old pavement into small pieces. For purposes of illustrative clarity, the flow of old pavement, asphalt binder, and new asphalt is not shown in  FIG. 3 . Fluid asphalt may be added by the first row  124  of spray nozzles  98  positioned in the grinding chamber  104 . The introduction of fluid asphalt cools and lubricates the grinding teeth  102  and also provides a portion of the asphalt binder needed to bring the mixture of old, ground pavement and new pavement to the required properties for re-application as finished pavement. 
   The mixture then enters the mixing chamber  96  where it is mixed by the mixing wheels  130  and  132 . If needed, additional fluid asphalt may be added to the mixture from the second row  126  of spray nozzles  98 . In a typical application, it is estimated that a quantity of asphalt binder equal to about 1.5% to about 2.0% by volume of the total mixture of new asphalt and recycled asphalt will result in a satisfactory finished pavement. By introducing the asphalt binder at several locations, lubrication is provided to the operating parts of the recycling assembly  24 . Furthermore, a more consistent final pavement product is obtained if a portion of the total required amount of asphalt binder is added to the mixture in stages rather than at a single point in the recycling process. In many cases the recycling machine  10  will be used to repair potholes, drive wheel ruts, or other areas where portions of the original pavement are missing. Accordingly, supplemental pavement (typically new, but recycled material may be used) in the required amount is transported to the mixing chamber  96  from the feed hopper  20  by the conveyor  22 , and enters the mixing chamber  96  through the opening  138 . 
   As the recycling machine  10  continues to advance, the mixed pavement passes from the mixing chamber  96  to the screed assembly  100 . The screed assembly  100  extrudes the material out at the desired height to form a finished pavement. The finished pavement may then be consolidated by a roller (not shown) in a known fashion. 
     FIG. 6  illustrates schematically an alternative recycling assembly  200 . The basic components and operation of the recycling assembly  200  are similar to that of the recycling assembly  24  described above. The recycling assembly includes a grinding chamber  202  containing a rotatable toothed grinding drum  204 , a heater  206 , a mixing chamber  208  housing a pair of toothed grinding wheels  210 , a material control gate  212 , an adjustable screed  214 , and one or more rows of spray nozzles  216 . In this embodiment, a conveyor  218  is arranged to deliver the additional pavement directly to the grinding chamber  202 . 
   The recycling assembly  200  is carried forward over an area of pavement to be patched. If necessary depending upon ambient conditions, the existing pavement is heated with a pre-heater such as a steam box or a propane burner  220  suspended ahead of the recycling assembly  200 . The front end of the recycling assembly  200  rides on an anvil  222  thus providing a height reference. The grinder drum  204  is lowered to the appropriate depth and rotated, causing its teeth  224  to break up and grind the old pavement into small pieces. For purposes of illustrative clarity, the flow of old pavement, asphalt binder, and new asphalt from the grinding chamber  202  to the mixing chamber  208  is not shown in  FIG. 6 . Fluid asphalt may be added by a first row  226  of spray nozzles  216  positioned in the grinding chamber  202 . The introduction of fluid asphalt cools and lubricates the grinding teeth  224  and also provides a portion of the asphalt binder needed to bring the mixture of old, ground pavement and new pavement to the required properties for re-application as finished pavement. 
   The mixture then enters the mixing chamber  208  where it is mixed by the mixing wheels  210 . If needed, additional fluid asphalt may be added to the mixture from additional rows  228  and  230  of spray nozzles  216 . If required, supplemental pavement (typically new, but recycled material may be used) in the required amount is transported directly to the grinding chamber  202  from a feed hopper (not shown) by the conveyor  218 . 
   The heater  206  is mounted behind the grinder drum  204 . The heater  206  may comprise a row of burner nozzles fed by propane or other suitable fuel, provided from heating fuel tanks  28  (see  FIG. 1 ). The number and size of the burner nozzles is selected to provide adequate heat to the material passing through the heater  206  to heat the pavement to the proper working temperature for the mixing and patching operation. As the recycling machine  10  moves forward, the mixture of ground pavement, new pavement, and asphalt binder passes under the heater  206  where it is exposed to the flame from one or more burners. 
   The material control gate  212  is disposed behind the mixing chamber  208 . The material control gate  212  is a generally rectangular barrier. Known means are provided for raising and lowering the material control gate  212  to a desired height. The material control gate  212  controls the volume of material which passes to the downstream screed assembly  214 . 
   As the recycling machine  10  continues to advance, the mixed pavement passes from the material control gate  212  to the screed assembly  214 . The screed assembly  214  extrudes the material out at the desired height to form a finished pavement. The finished pavement “F” may then be consolidated by a roller (not shown) in a known fashion. 
   The foregoing has described a pavement recycling and patching apparatus and a method for recycling pavement. While specific embodiments of the present invention have been described, it will be apparent to those skilled in the art that various modifications thereto can be made without departing from the spirit and scope of the invention. Accordingly, the above description of the preferred embodiment of the invention and the best mode for practicing the invention are provided for the purpose of illustration only and not for the purpose of limitation, the invention being defined by the claims