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CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority of United States Provisional Patent Application filed May 3, 2011 having Ser. No. 61/481,896 and United States Provisional Patent Application filed Aug. 6, 2011 having Ser. No. 61/515,868. 
    
    
     FIELD OF THE INVENTION 
     This invention is related to road maintenance equipment and more particularly to a road maintenance vehicle having hydraulically deployed rollers which may be used in connection with the patching of road surfaces with asphalt materials. 
     BACKGROUND OF THE INVENTION 
     A variety of road maintenance equipment having various roller configurations has been previously disclosed to enable road crews to smooth or tamp down roadway patching materials, such as asphalt. 
     U.S. Pat. No. 2,778,181 issued to Gray and U.S. Pat. No. 5,088,855 issued to Giliberti both describe vehicle mounted rollers which move from a raised non-use position to a rolling position where the roller is engaged with both the ground and the drive wheel of the vehicle. In this manner, the weight of the vehicle provides the compression, while the drive train of the vehicle turns the roller to move the vehicle. 
     U.S. Pat. No. 2,559,417 issued to Hastings discloses a roller for a road work crew that is mounted to the dump body of the truck. To compact a surface, the dump body is raised to lower the roller against the ground. 
     U.S. Pat. No. 3,873,228 issued to Dunham, U.S. Pat. No. 4,193,710 issued to Pietrowski, and U.S. Pat. No. 6,354,761 issued to Clements each show a variation of coupling a roller to a hydraulically actuated snowplow lift mounted to a work truck. In these patents, the snowplow hydraulics mounted to the front of the vehicle lift and pivot the roller to position the roller. 
     While the prior art discussed above provide some solutions to the problem of providing road maintenance workers with a means to compact road patching materials, they do not provide a road-worthy system providing dual rollers to first flatten, then compact the patching material. 
     SUMMARY OF THE INVENTION 
     The broad purpose of the present invention is to provide a road maintenance vehicle, such as a dump truck, with a pair of selectively deployable rollers. The paired rollers cooperate to initially flatten (front roller) and then compact (rear roller) a road patching material, such as asphalt. The two rollers are mounted adjacent to the front and rear wheels and are hydraulically movable from a stowed position which is remote from the ground to a deployed position, where the rollers are lowered toward the ground. Further, an additional press plate is mounted upon the vehicle which can be raised and lowered to further tamp down the road patching material. 
     The present invention further provides a system for both heating at least one of the two deployable rollers and to provide additional cooling for the vehicle&#39;s prime mover by transferring coolant fluid from the vehicle&#39;s engine cooling system (i.e., the radiator) and pumps the engine-heated fluid through the roller or rollers. 
     In the preferred embodiment, each roller is mounted upon a pair of spaced arms, these arms are pivoted by hydraulic cylinders to raise and lower the rollers as desired. 
     It is an advantage of the present disclosure to provide a road maintenance vehicle including a truck having front and rear rubber road tires supported by a chassis with a truck frame and front and rear metal roller assemblies which are pivotally supported by the truck frame, each roller assembly having a rigid cylindrical roller which is movable from a stowed position where the roller is upwardly suspended from the ground to a deployed position where the roller is against the ground. 
     It is another advantage of the present invention to provide a road maintenance vehicle where the rear roller assembly is deployable vertically downward beyond the front roller assembly when both of the roller assemblies are in their deployed position. 
     It is still another advantage of the present invention to provide a road maintenance vehicle wherein the deployed position of the rear roller assembly is such that a portion of the weight of the truck vehicle is borne by the rear roller assembly, whereby a compressive force is applied by the rear roller upon road patching materials. 
     It is yet another advantage of the present invention to provide a road maintenance vehicle further including hydraulic pumps and linear hydraulic actuators mounted upon the truck vehicle. Wherein the hydraulic actuators are coupled to each of the front and rear roller assemblies and selectively move the roller assemblies between the stowed and deployed positions. 
     It is still yet another advantage of the present invention to provide a road maintenance vehicle wherein the front metal roller assembly is mounted adjacent to the front road tires and the rear metal roller assembly is mounted adjacent to the rear road tires. 
     Another advantage of the present invention is to provide a system for drawing heated coolant fluid from the maintenance vehicle&#39;s engine through at least one of the metal roller assemblies. 
     Still another advantage of the present invention to provide a road maintenance vehicle further including a rigid substantially flat plate that is pressed downward from the vehicle toward the ground. 
     Still further objects and advantages of the invention will become readily apparent to those skilled in the art to which the invention pertains upon reference to the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The description refers to the accompanying drawings in which like reference characters refer to like parts throughout the several views and in which: 
         FIG. 1  is a side plan view illustrating a road maintenance vehicle embodying the invention with a compression plate mounted upon the front of the vehicle and with the roller assemblies deployed; 
         FIG. 2  is a side plan view illustrating the road maintenance vehicle embodying the invention with the roller assemblies stowed; 
         FIG. 3  is a partial side view of one roller assembly in a stowed position; 
         FIG. 4  is a partial side view of the roller assembly of  FIG. 3  in a deployed position; and 
         FIG. 5  is a partial side view of one roller assembly with engine coolant lines; 
         FIG. 6  is a diagram showing the engine coolant routed through the roller assembly; 
         FIG. 7  is a perspective view of a roller having heating tubes passing through an internal cavity; 
         FIG. 8  is a top plan view of a containment wall which distributes the heated coolant fluid through lines running through roller; 
         FIG. 9  is a top plan view of a support web mounted within the roller; 
         FIG. 10  is a schematic view of a pneumatic embodiment incorporated into a vehicle air braking system; and 
         FIG. 11  is an alternate embodiment of the heating system  70 ′. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the FIGS., an improved road maintenance vehicle  10  is illustrated. Vehicle  10  is preferably a conventional truck  12  having a dump bed  14  for transporting various roadway surface patching materials  15 , such as asphalt. Vehicle  10  includes a pair of steerable front rubber tires  16  along with at least one pair of rear rubber road tires  18 , which are typically the drive wheels of a road maintenance vehicle. In other embodiments, the front wheels can either be the lone motive wheels (i.e., a front wheel drive) or work in combination with the rear wheels (i.e., in an all-wheel drive configuration). Under normal road operation, the front and rear tires  16 ,  18  bear the weight of the vehicle as it travels down the roadway. 
     In addition to the typical components found upon a conventional truck, vehicle  10  includes a pair of surface patching roller assemblies  20 ,  22  mounted to the frame  24  of the truck. A compression plate  25  is also mounted to the frame  24 , in the embodiment illustrated, the compression plate  25  is mounted to the front end of the truck. 
     Referring now to  FIGS. 1 and 2 , there is shown side view of the vehicle  10 . In this exemplary view, a hydraulic actuator (cylinder), motor, or pneumatic cylinder  27  is mounted to the front of vehicle  10 . Hydraulic actuator (cylinder)  27  having a movable piston  29  that translates linearly when activated in the directions of arrow  31 . In one non-limiting example, piston  29  is a threaded shaft cooperating with a rotating motor  27  to translate linearly in and out of the motor. The end of piston  29  is coupled to an enlarged, substantially flat and rigid compression plate  25 , such that when the hydraulic actuator  27  moves, the compression plate  25  is raised and lowered with the piston  29 . Actuator  27  is movable from: 1) a deployed position where the compression plate  25  abuts the ground  44 ; to 2) a stowed position, shown in  FIG. 2 , where the plate  25  is upwardly suspended relative to the ground  44 . 
     As shown in  FIG. 10 , when using air to operate cylinder  27  (pneumatic), the cylinder  27  can be tied into the vehicle&#39;s air brake system  105  if present with an air line  106  running through the vehicle&#39;s wheel brakes  107 . In the embodiment illustrated, there are two pressure regulators  110 ,  112 . The first regulator  110  regulates the whole pneumatic system, which is set at a higher rate than the braking system  105 . This is because higher pressure is needed to rapidly move the cylinder  27  to tamp with plate  25 . 
     The second regulator  112 , regulates pressure at a lower rate or same as the braking system  105 . If air or pressure is needed, the air cylinder tank  114  will then back up the brake system, the brake system is always active, the compressor  116  will then stay on until pressure has been stabilizes. To ensure continuous operation, the compressor  116  may have a fly wheel (not shown) on it, which is turned by the engine. A second air tank  118  ensures that the cylinder  27  has a ready source of pressurized air available. 
     The hydraulic actuator  27  are coupled to and powered by at least one conventional hydraulic pump  46 , which is preferably powered by the vehicle&#39;s prime mover (not shown). 
     Referring now to  FIGS. 3 and 4 , there is shown an enlarged partial side view of the front roller assembly  20  of vehicle  10 . It should be appreciated that the operation of the front roller assembly  20  and rear roller assembly  22  are substantially the same. Rather than describe identical components and operations in this disclosure, only the front roller assembly  20  will be discussed in detail, with the understanding that one skilled in the relevant art should be able to take the following disclosure related to front roller assembly  20  and apply those teachings to the rear roller assembly  22 . 
     Roller assembly  20  includes an elongated rigid cylindrical roller  26  that is rotatable about a central axle  28 . The roller  26  is rotatably supported by a pair of spaced pivot arms  30 , which are rotatably coupled to axle  28  at each end of the cylindrical roller  26 . In the embodiment illustrated in the FIGS., pivot arm  30  has a general L-shape with an elongated roller leg  32  depending from the end of a mounting leg  34 . Each pivot arm  30  is also rotatably secured to frame  24  at a pin  36 . 
     Roller assembly  20  also includes a hydraulic actuator or motor  40  having a movable piston  41  that translates linearly when activated in the directions of arrow  42 . In one non-limiting example, piston  41  is a threaded shaft cooperating with a rotating motor  40  to translate linearly in and out of the motor. The end of piston  41  is coupled to at least one of the arms  30  by a pinned linkage  43  such that when the hydraulic actuator  40  moves, the arm  30  pivots about pin  36  to raise and lower the roller  26 . As shown in  FIGS. 1 and 4 , actuator  40  is movable from: 1) a deployed position where the roller  26  abuts the ground  44 ; to 2) a stowed position, shown in  FIGS. 2 and 3 , where the roller  26  is upwardly suspended relative to the ground  44 . 
     The hydraulic actuators  40  are coupled to and powered by at least one conventional hydraulic pump  46 , which is preferably powered by the vehicle&#39;s prime mover (not shown). 
     Referring back to  FIGS. 3 and 4 , each roller assembly (i.e., both roller assemblies  20  and  22 ) further preferably includes a bumper or positive stop  50  which is fixed upon the frame  24  to limit the movement of pivot arms  30 . In the preferred embodiment of the invention, the positive stop  50  corresponding to the front roller assembly  20  is located along frame  24  to limit the movement of pivot arm  30  and its roller  26  such that the bottom edge of front roller abuts the ground  44 , but does not lift the vehicle  10 . That is, the front roller assembly  20  bears little to no weight of the vehicle  10 . Instead, the front tires  16  are left upon the ground to allow vehicle  10  to be steered as a conventional motor vehicle. 
     In this preferred embodiment, the positive stop of the rear roller assembly  22  is positioned relative to the pivot arm to allow the roller of rear roller assembly  22  to not only abut the ground  44 , but to bear a portion of the vehicle&#39;s weight when in the deployed position shown in  FIGS. 1 and 4 . Importantly, the rear roller assembly  22  is only permitted to accept some of the weight typically borne by the rear tires  18  to ensure that the drive tires  18  continue to provide motive force for the vehicle. For example and without limitation, the rear roller assembly  22  may be movable approximately one to three inches beyond the vertical limit of front roller assembly  20  to allow some of the vehicle&#39;s weight to be applied by the rear roller to aid in compacting any patching material  15 . 
     It should be appreciated that the above described differences in allowable vertical displacement of the front and rear roller assemblies  20 ,  22  enables the present invention to initially smooth and spread patching material  15  placed upon/within a pothole or crack  62  with the front roller assembly  20 . That now-spread material  15  is then compacted by the weight-bearing rear roller assembly  22  as the vehicle  10  drives over the pothole  62  receiving the patching material. 
     Referring now to  FIGS. 5-9  an alternate embodiment of a road maintenance vehicle  10  is illustrated. In this embodiment, at least one of the two roller assemblies  20 ,  22  include a heating system  70  which transfers coolant heated by the vehicle&#39;s engine  71  from the vehicle&#39;s engine cooling system, e.g., radiator  72 , through the roller or rollers  26  to heat the exterior surface of the roller(s). As has been mentioned prior, the following description will be focused on the front roller assembly  20  with the continued understanding that these teachings can be applied to the rear roller assembly  22  by one skilled in the relevant art. 
     As shown in  FIG. 6 , the roller heating system  70  includes an electric pump  74  that is fluidly coupled to the vehicle&#39;s engine cooling system, preferably prior to the point where engine-heated coolant enters the radiator  72 . In this manner, the coolant will be at its highest temperature when pump  74  re-routes the fluid through conduit  76  to the roller  26 . 
     Referring now to  FIGS. 7-9 , roller  26  is this embodiment is a cylindrical tube having a rigid outer wall  78 . The two ends of the roller tube are enclosed by end caps  80 . End caps  80  each include a water-tight roller bearing  82  in its center. Axle  28  passes through bearing  82  into the central cavity  83  of the roller tube. In this embodiment, axle  28  is also tubular having a central bore  84  which receives a fitting  86  which couples the conduit  76  to the axle  28 . 
     The axle  28  is further supported by a manifold wall  90  contained within cavity  83  proximate to the end cap  80 . As shown in  FIG. 9 , manifold wall  90  includes a second water-tight bearing  91  that receives and rolls upon the end of the axle  28 . The radially outer edges of wall  90  seal off the inner portion of the cavity to form a small distribution chamber  92 . At least one hole  93  in the axle  28  allows fluid passing through the axle  28  to enter and fill chamber  92 . A plurality of elongated tubes  94  are fluidly mounted through the radially outer portion of the wall  90  allowing coolant that fills chamber  92  to pass through the roller. 
     Each tube  94  is adjacent to, and preferably in direct contact with the inner face of the roller wall  78 . The tubes  94  are also preferably evenly spaced about the roller wherein the heat from the fluid passing through the tube  94  is transferred evenly to the roller&#39;s outer wall  78 . 
     Additional support webs  96  may be placed within cavity  83  to further support the tubular wall  78 . Each web  96  includes a cut-out  98  which allows the elongated tubes  94  to freely pass therethrough. 
     At the opposing end of the roller  26 , another manifold wall  90  cooperates with a second end cap  80  to form a small collection chamber  100  which is fluidly coupled to a second axle  28 . A conduit  102  returns the coolant back to the radiator  72 , preferably just downstream of where the heating system  70  is coupled to the vehicle&#39;s cooling system. 
     It should be appreciated that through this heating system  70 , the present invention takes advantage of the latent heat in the engine cooling system of the vehicle  10  to heat the roller  26  while also reducing the burden on the engine&#39;s cooling system by drawing some of the heat into the rollers. 
     Referring now to  FIG. 11 , an alternate embodiment of the heating system  70 ′ is illustrated. In this embodiment, the heated fluid handling system remains substantially stationary within the rotating roller  26 . As the roller  26  turns because of the water tight bearing  82 . The end of axle shaft  28  has a threaded cross fitting mount  120  at both ends inside the roller. With the cross fittings  120  there are a plurality, e.g., three (3), connections for tubes  94 . Tubes  94  are in close proximity to the roller&#39;s inner wall while remaining separate to allow free rotation of the roller. As the heated fluid flows thru, the heat is released to the roller, then returns to the engine cooling system completing the closed loop system. 
     From the foregoing description, one skilled in the art will readily recognize that the present invention is directed to an improved road maintenance vehicle having a movable compression plate and a pair of selectively deployable rollers. The paired rollers cooperate to initially flatten and then compact a road patching material. The two rollers are mounted adjacent to the front and rear wheels and are hydraulically movable from: 1) a stowed position in which the rollers are remote from the ground; to 2) a deployed position, where the rollers are lowered to the ground. The compression plate providing an additional means for compressing patching material. While the present invention has been described with particular reference to various preferred embodiments, one skilled in the art will recognize from the foregoing discussion and accompanying drawings that changes, modifications, and variations can be made in the present invention without departing from the spirit and scope thereof.

Summary:
An improved road maintenance truck includes a pair of hydraulically powered roller assemblies mounted to the underside of the vehicle frame and a vertically movable compression plate mounted to the vehicle frame. Each roller assembly has a compressive roller which runs the width of the truck. Two hydraulic actuators on each end of the vehicle raise and lower the roller into place. These independent rollers allow a road patching crew to selectively lower the roller for repairing road while initially flattening the patching material with the front roller and compacting the patching material with the rear. The compression plate is mounted to an actuator which selectively raises and lowers the compression plate to compress road patching materials. A roller heating system draws engine coolant through the rollers to heat the rollers and to reduce the heat built-up in the engine.