Abstract:
A motor grader can be adapted for laying down a layer of granular material such as base rock or cold mix asphalt by mounting a dispensing hopper attachment onto the front of the motor grader and a spreading and leveling screed onto the moldboard. As the motor grader advances, it pushes a dump truck that continuously loads materials into the hopper. Those materials are in turn continuously discharged at a metered rate of flow through the bottom of the hopper and onto the roadbed. The resulting swath of materials passes between the front wheels of the grader as the grader continues to advance, whereupon the screed engages the swath and spreads the materials in opposite lateral directions while leveling them to the desired depth. The screed has swept-back wings that may be extended as necessary to adjust the overall width of the screed, and outboard shields on the outermost ends of the wings confine the spread materials to the roadbed and prevent their accidental discharge into ditches and the like alongside the roadbed. The crown of the deposited layer can be varied by tipping the nose of the screed upwardly or downwardly to the extent necessary or desired.

Description:
TECHNICAL FIELD 
     This invention relates to the field of motor graders and, more particularly, to an attachment that adapts such machines for laying down, in one pass, a finished layer of aggregate material such as base rock or cold mix asphalt onto roads, streets, parking lots or driveways. 
     BACKGROUND 
     The known method of laying down base rock or cold mix asphalt involves a two-step operation in which the material is first dumped from a truck onto the ground or roadbed. A motor grader then comes along and spreads the material back and forth using its moldboard until the material is at the desired depth, width and slope. Typically, excess material slips into ditches on either side of the roadbed and is wasted. Significant, time-consuming working and reworking of the material may be necessary in order to achieve the desired depth, width and crown of the roadbed, which not only slows the overall process but also increases the likelihood of wasting significant amounts of material. Moreover, excessive handling and manipulation of base rock material can result in the limestone fines becoming separated from the aggregate and settling to the bottom of the layer, detracting from their ability to solidify when wet and hold the aggregate in a solid matrix that provides a better roadbed. Generally speaking, the less handling the better when laying down gravel material. 
     SUMMARY OF THE INVENTION 
     The present invention converts a motor grader into a machine that is capable of laying down in one pass a finished layer of aggregate material such as base rock or asphalt that has the desired thickness, width and profile of the finished product. By laying down the finished product on-the-go in a one-pass operation, significant time and labor savings can be achieved, as well as better control. Furthermore, less handling means a better quality roadbed where base rock is the material being deposited. 
     The present invention contemplates attaching a special distribution hopper to the front end of the motor grader ahead of the front wheels and a special screed to the moldboard behind the front wheels. As the motor grader advances, the hopper continuously receives material from a dump truck being pushed along the roadbed ahead of the grader by the hopper, and such material is continuously metered out onto the roadbed or other surface to form a swath located between the front wheels. The discharged swath of materials is then acted upon by the trailing screed, which skims off excess material from the top of the swath and spreads it laterally outwardly in opposite directions to produce a layer that is wider than the front wheels. Outermost shields at opposite left and right ends of the screed limit the width of the outwardly spreading materials to prevent spillage into ditches alongside the roadbed. The screed is mounted on the front side of the moldboard so as to be in a position to engage and work the materials instead of the moldboard. However, since the moldboard is adjustable in a variety of directions through various hydraulic actuators on the grader, manipulation and adjustment of the moldboard by the actuators can be used to correspondingly adjust the screed. Because the screed is pointed with a pair of diverging wings, adjustment of the nose of the screed upwardly or downwardly relative to the rear ends of the wings results in changes in the shape of the crown that is on the layer of materials being deposited and spread. In one preferred embodiment of the invention, such crown can range from a six inch negative crown to a flat or level crown and to a six inch positive crown at the other extreme. 
     The two wings of the screed can be extended and retracted hydraulically from the seat of the motor grader so as to correspondingly adjust the width of the material being laid down. The discharge outlet at the bottom of the distribution hopper has of a pair of side-by-side metering gates that can be independently adjusted so as to correspondingly vary the rate of discharge from the hopper. An operator&#39;s platform is provided on the backside of the distribution hopper to enable an extra worker to ride the machine at that location and operate controls for the metering gates as he observes loading and discharging of the hopper. A rotary agitator inside the hopper helps assure an orderly and even discharge flow from the hopper. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view of a motor grader provided with material distribution apparatus in accordance with the principles of the present invention, a dump truck being illustrated fragmentarily and in phantom at the front end of the apparatus; 
     FIG. 2 is a top plan view thereof illustrating the manner in which materials are discharged from the metering hopper and are then spread out to the desired width by the trailing screed, the screed being shown with its wing portions fully extended; 
     FIG. 3 is an enlarged, fragmentary rear perspective view of the left wing of the screed in its extended condition, illustrating details of construction and showing the moldboard in broken lines; 
     FIG. 3 a  is a fragmentary, further enlarged view of the structure shown in FIG. 3; 
     FIG. 4 is a fragmentary top plan view of the screed in its extended condition corresponding to the rear perspective view of FIG. 3; 
     FIG. 5 is a fragmentary transverse cross-sectional view through the screed taken substantially along line  5 — 5  of FIG. 4; 
     FIG. 6 is a front elevational view of the distribution hopper taken substantially along line  6 — 6  of FIG. 1 with the front wall broken away to reveal details of construction; 
     FIG. 7 is a vertical cross-sectional view through the distribution hopper taken substantially along line  7 — 7  of FIG. 6; 
     FIG. 8 is a further enlarged fragmentary cross-sectional view through one portion of the distribution hopper taken substantially along line  8 — 8  of FIG.  6  and with a sloping internal sidewall of the hopper removed to reveal details of construction of the drive mechanism for the agitating rotor of the hopper; and 
     FIG. 9 is a schematic front elevational view of the screed in operation illustrating the manner in which a positive crown may be imparted to the material being laid down on the roadbed, such view being taken substantially along line  9 — 9  of FIG.  1 . 
    
    
     DETAILED DESCRIPTION 
     The present invention is susceptible of embodiment in many different forms. While the drawings illustrate and the specification describes certain preferred embodiments of the invention, it is to be understood that such disclosure is by way of example only. There is no intent to limit the principles of the present invention to the particular disclosed embodiments. 
     Referring to the figures, a motor grader is shown generally at  10  and includes a wheeled chassis  12  having a pair of laterally spaced front wheels  14  and two pairs of laterally spaced rear wheels  16  and  18 . An engine  20  drives rear wheels  16 , 18  to propel the motor grader along a roadbed  22  or other ground surface, and an operator cab  24  is supported on chassis  12  just ahead of engine  20 . 
     As well understood by those skilled in the art, a fore-and-aft drawbar  26  is attached to the front of the chassis  12  by a ball joint or the like (not shown). Drawbar  26  extends rearwardly from the front ball joint and underneath the upwardly arched chassis  12  to support a blade or moldboard  28  that can be adjusted in a number of different directions to assume a variety of adjusted positions. In this regard, as is conventional, moldboard  28  can be adjusted upwardly and downwardly by a pair of left and right lift cylinders  30  and  32 , each of which can be independently operated so as to change the left-to-right tilt of moldboard  28 . A side shift cylinder (not shown) enables moldboard  28  to be shifted laterally to the left or right relative to drawbar  26 , and a fore-and-aft tilt cylinder  34  (FIG. 1) is coupled to moldboard  28  in such a manner that moldboard  28  can be tipped forwardly or rearwardly about a lower transverse axis to adjust its angle of attack relative to the ground. Moldboard  28  can also be rotated about a vertical axis by means not shown to place moldboard  28  in an oblique attitude relative to the direction of travel of the motor grader, although in connection with the present invention moldboard  28  will normally be perpendicular to the path of travel as illustrated in the plan view of FIG.  2 . 
     In connection with the present invention, motor grader  10  is provided with a material distribution attachment comprising two primary components, i.e., a distribution hopper  36  at the front of the machine and a screed  38  attached to moldboard  28  in the middle of the machine. Dealing first with hopper  36 , it will be seen that such structure generally comprises an open top receptacle having a set of ground engaging wheels  40 . The upper front edge  42  of hopper  36  is lower than the upper rear edge  44  thereof so as to facilitate loading of hopper  36  with granular materials from a dump truck  46  during operation as illustrated in FIG.  1  and as will subsequently be explained in more detail. The exterior of hopper  36  includes a pair of opposite, left and right sidewalls  48  and  50  respectively, an upright exterior front wall  52 , and an upright rear wall  54  that begins at the upper rear edge  44  and extends part way down the back of hopper  36 . A sloping bottom wall  56  extends downwardly and forwardly from the lower extremity of rear wall  54  generally toward front wall  52  but terminates a short distance rearwardly from front wall  52 . A horizontal, relatively short lowermost wall  58  interconnects the lower extremity of front wall  52  and the forward extremity of bottom wall  56 . 
     Inside hopper  36 , a downwardly and rearwardly sloping interior front wall  60  extends from a point part way up exterior front wall  52  down to the forward extremity of bottom wall  56 . A pair of downwardly and inwardly sloping interior sidewalls  62  and  64  converge toward the center of the hopper and intersect bottom wall  56  and the front interior wall  60 . Front wall  52  carries a pair of horizontal rollers  66  that bear against the rear tires  70  of dump truck  46  during operation as illustrated in FIG.  1 . 
     The discharge outlet of hopper  36  is broadly denoted by the numeral  70  and is located in bottom wall  56  adjacent the intersection with front interior wall  60 . Outlet  70  is controlled by a pair of side-by-side metering gates  72  and  74  that are independently shiftable along inclined paths of travel parallel to bottom wall  56  between positions opening and closing respective left and right halves of outlet  70 . In FIGS.  2 , 6  and  7 , gates  72  and  74  are shown in their open position. A pair of independently operable hydraulic piston and cylinder assemblies  76  (only one being illustrated; see FIG. 7) actuate gates  72 , 74  between their open and closed positions, the rear ends of the cylinders  76  being attached to rearwardly projecting, horizontally disposed mounts  78  and  80  on the rear of hopper  36  (FIGS.  2  and  7 ). 
     A transverse agitating rotor  82  spans outlet  72  a short distance thereabove for the purpose of keeping materials agitated and loose near the bottom of hopper  36  to facilitate their discharge through outlet  70 . Opposite ends of rotor  82  pass through interior sidewalls  62  and  64  for ultimate rotational support by suitable bearings located behind such interior walls. The drive for rotor  82  is located outboard of interior sidewall  62  and inboard of outer sidewall  48  as illustrated in FIGS. 6 and 8. Such drive includes a hydraulic motor  84  (FIG. 8) having an output shaft (not shown) that carries a sprocket  86 . An endless chain  88  is entrained around sprocket  86  and around a second sprocket  90  that is fixed to the outboard end of rotor  82 . An adjustable idler sprocket  92  engages the slack side of chain  88  to maintain tension in the chain. 
     Hopper  36  is attached to the front end of chassis  12  by mounting apparatus broadly denoted by the numeral  94 . Apparatus  94  comprises a centrally disposed, upright tower or mast  96  that is fixedly secured to the chassis  12  by suitable means such as bolts (not shown). An upright hydraulic cylinder  98  (FIG. 7) within mast  96  is operably coupled with the upper backside of hopper  36  via suitable coupling means broadly denoted by the numeral  100  so that extension and retraction of cylinder  98  causes hopper  36  to be raised and lowered relative to mast  96 . It is contemplated that during normal working operations, hopper  36  will be fully lowered so that ground wheels  40  are touching the ground and supporting the load of hopper  36  and its contents. On the other hand, for transport purposes between job sites, hopper  36  may be elevated along mast  96  and supported in a raised, transport position (not shown). 
     An operator seat  102  is attached to the backside of hopper  36  near the left end thereof and at such a height that an operator stationed at seat  102  can observe both loading of hopper  36  and discharging of material from the hopper. A set of controls  104  (FIG. 2) are easily accessible to the operator positioned on seat  102 , such controls  104  being operably connected to gate cylinders  76  so that the operator may regulate the positions of gates  72  and  74 . The lift cylinder  98  which raises and lowers hopper  36  is controlled by a suitable control (not shown) located in cab  24 . A pair of upwardly and rearwardly projecting indicator rods  106  and  108  are fixed to respective doors  72  and  74  to provide a visual indication for the operator at seat  102  of the position of gates  72 , 74 , which can be important when outlet  70  is covered by material within hopper  36 . It will be noted from FIG. 2 in particular that outlet  70  is slightly narrower than the width of the space between front wheels  14  such that material discharged through outlet  70  forms what may be termed a ribbon or swath of material having a width no greater than the space between the wheels. Because outlet  70  is centered between wheels  14 , the wheels become disposed on opposite sides of the material swath during discharging and spreading operation. 
     A hook  110  at the front end of hopper  36  (FIGS. 1 and 2) may be used to detachably secure the truck  46  to the front end of hopper  36 . Hook  110  is operated manually by a linkage  112  that runs across the hopper  36  and up the left side thereof outboard of left sidewall  48 . Linkage  112  terminates at its upper end in an operating handle  114  positioned for actuation by the operator stationed on seat  102 . 
     The screed  38  is generally V-shaped in overall configuration when viewed in plan, presenting a pointed body having a nose  116  and a pair of oppositely extending, swept-back, left and right wings  118  and  120 . Generally speaking, the wings  118  and  120  present a forwardly pointed lower screeding edge  122  (FIG. 5) that determines the thickness or depth of the layer of materials formed by the screed. Each of the wings  118 , 120  has as its primary component a tubular, square in cross-section beam  124  that is joined at its inner end with the beam  124  of the other wing. An upright panel or wall  126  is secured to and extends along the front of each beam  124  to prevent material from flowing up and over the top edge of the beam during operation. Wall  26  is secured to beam  124  by a fence  128  that includes four uprights  130 ,  132 ,  134  and  136 . Each of the uprights  130 - 136  is securely affixed at its upper end to wall  126  but is spaced slightly rearwardly from such wall below the point of attachment so as to define a transverse slot  138  between fence  128  and the backside of wall  126  for a purpose yet-to-be-explained. A slide strip  140  is fixed to the top surface of beam  124  along the front edge thereof and is generally co-extensive in length with fence  128 . 
     Each wing  118 , 120  is adjustably extendable and retractable to vary its effective length, thus adjusting the overall width of screed  38 . In this regard, each wing  118 , 120  includes an extendable and retractable wing tip  142  that is shifted in or out by a hydraulic cylinder  144  housed within beam  124 . Each wing  142  is formed in part by a second tubular beam  146  that is of rectangular cross-section and has slightly smaller dimensions than main beam  124 . Thus, wing tip beam  146  is telescopically received within main beam  124  and is guided in its telescoping reciprocation by a pair of spacer plates  148  and  150  (FIG. 5) fixed to front and bottom walls of main beam  124  respectively (FIGS. 3,  3   a  and  5 ). 
     Each wing tip beam  146  has its own front wall extension  152  that is received within horizontal slot  138  between fence  128  and front wall  126 . The lower edge of front wall extension  152  rides upon slide strip  140  on main wing beam  124 . Each front wall extension  152  is welded at its outer vertical edge to an upright member  154  that is in turn welded along its bottom edge to the wing tip beam  146 . 
     Each main beam  124  has three generally L-shaped brackets  156 , 158  and  160  welded to the top surface thereof and projecting rearwardly therefrom at spaced locations therealong. The downturned outer legs of brackets  156 ,  158  and  160  support a guide strap  162  that extends parallel to main beam  124  in rearwardly spaced relation thereto. Guide strap  162  bears against and reciprocably guides a trailing tubular, rectangular in cross-section wing tip beam  164  that is spaced slightly behind and extends parallel to the first wing tip beam  146 . As illustrated in FIG. 5, trailing wing tip beam  164  projects downwardly below the level of wing tip beam  146  to the same extent as the main beam  124 . Thus, even though the lower extremity of the front wing tip beam  146  is not quite as low to the ground as main beam  124 , this difference is made up for by the trailing wing tip beam  164  such that, in effect, the lower front edge  122  of screed  38  is at the same level along the full length of the wing from the inner end to the outer end thereof, even when the wing tip  142  is fully extended. 
     The trailing wing tip beam  164  is fixed at its outer end to the front wing tip beam  146  via a fore-and-aft extending plate  166  (FIGS. 3,  3   a  and  4 ) that spans the outer ends of beams  146  and  164  and is welded thereto and to the upright member  154 . At its inner end the trailing wing tip beam  164  has a rectangular lug  167  welded thereto that projects forwardly into overlying relationship with the top surface of main beam  124 , for the purpose of helping to support and guide trailing wing tip beam  164  during its extension and retraction. A long guide strip  168  is welded to the rear face of main beam  124  and bears against the front face of trailing wing tip beam  164  during adjusting reciprocation of the latter. Thus, during such adjusting movement of trailing wing tip beam  164 , the beam is trapped between rearwardly disposed guide strap  162  on the one hand and forwardly disposed guide strip  168  on the other. 
     Trailing wing tip beam  164  is also supported by a relatively short rectangular plate  170  that is housed within trailing wing tip beam  164  and bears against the upper inside surface of the top wall of such beam. At its inboard end, plate  170  is supported by an upright bolt  172  that passes through a slot  174  in the top wall of trailing wing tip beam  164 . Bolt  172  is suspended from the rear end of a support plate  176  that is fixed at its front end to the upper surface of main wing beam  124 . At its outboard end the plate  170  is supported by an upright bolt  178  that hangs from the rearwardly extending, horizontal leg  180  of a generally L-shaped mounting bracket  182  having an upright leg  184  that is attached to the lower rear extremity of moldboard  28  via attaching bolts  186  and  188 . Mounting bracket  182  is not fixed to but instead merely overlies main beam  124 . Support plate  178  has an upstanding handle  190  of generally T-shaped configuration that projects upwardly through slot  174  in trailing wing beam  164 . The head of handle  190  is wider than slot  174  such that when bolts  172  and  178  are removed, support plate  170  cannot fall to the inside bottom surface of trailing wing tip beam  164  and become inaccessible. In addition to this keeping or retaining function, the head of handle  190  is also adapted to be grasped manually during assembly and disassembly operations. 
     The outermost ends of wings  118  and  120  are provided with upright shields  192  and  194  respectively that confine the material as it is being leveled and spread laterally by screed  38 . Each of the shields  192 , 194  is bolted to the fore-and-aft plate  166  of wing tip  142  and projects forwardly a substantial distance therefrom. Each shield  192 , 194  can be height adjusted by virtue of a slotted relationship with the bolts that secure the shield to plate  166 . 
     The two mounting brackets  182  at opposite ends of moldboard  28  serve as components of mounting structure that secure the screed  38  to moldboard  28 . In addition to brackets  182 , such mounting structure also includes an upstanding lug  196  on screed  38  at nose  116 , a corresponding lug  198  fixed to the backside of moldboard  28  at the lateral center thereof near its top edge, and a rigid link  200  pivotally connected at its opposite ends to lugs  196  and  198 . Screed  38  is thus securely attached to moldboard  28  and is held against significant movement relative thereto. However, by virtue of the various hydraulic cylinders that adjust moldboard  28 , screed  38  can likewise be adjusted. 
     Operation 
     Operation and use of the distribution attachment in accordance with the present invention should be apparent from the foregoing description. With particular reference to FIGS. 1 and 2, however, a brief further description of the operation is in order. 
     During use, one operator is positioned within cab  24  and a second operator is positioned at seat  102 . The operator in cab  24  controls forward motion of grader  10 , as well as lifting and lowering of hopper  36 , extension and retraction of wings  118 , 120 , up and down adjustment of screed  38 , and fore-and-aft tilting of screed  38  for controlling the crown applied to the material, if any. Depending upon the depth of the layer of material to be placed on roadbed  22 , screed  38  will be adjusted closer to or further above the roadbed. A corresponding adjustment of side shields  192  and  194  may be necessary to assure that the lower edges thereof are engaging and riding along roadbed  22  during forward movement of the grader. 
     A dump truck  46  is backed up to the grader until its tires  70  come into abutting engagement with rollers  66  on the front of hopper  36 , which has previously been lowered sufficiently to place its wheels  40  in contacting engagement with roadbed  22 . As the bed of truck  46  is raised as illustrated in FIG. 1, material is discharged from the bed into and through the open top of hopper  36  where it begins to issue from discharge outlet  70 . As the grader is then advanced, the grader pushes truck  46  along with it so that the contents of the truck are continuously discharged into the awaiting hopper  36  at a rate determined by the tilt angle of the truck bed. 
     The operator situated on seat  102  observes the ongoing process and adjusts gates  72  and  74  as may be necessary or desirable to suitably regulate the flow of material as it emanates out of the bottom of hopper  36 . As illustrated in FIG. 2, such discharged material forms a swath  202  that is disposed between front wheels  14  of the grader, due to the central location of outlet  70  and the fact that it is no wider than the distance between such front wheels. 
     As the screed  38  then engages the discharged swath  202 , the top portion of the swath is skimmed off and deflected laterally outwardly in opposite directions due to the swept back nature of wings  118  and  120  of screed  38 . Swath  202  is thus widened out and leveled down to produce in one pass a final layer  204  behind screed  38  having a width determined by the outboard shields  192  and  194 . 
     This process of unloading materials from truck  46 , metering them out of hopper  36 , and spreading them with screed  38  continues on an ongoing, non-stop basis until the truck is empty. At that time, forward motion of the grader is halted, and the truck pulls away to obtain a new supply of material, during which time the next loaded truck maybe backed into position at the front of hopper  36 . Once the next truck is properly positioned, the grader begins to advance again, continuing the process that was temporarily halted when the previous truck became empty. 
     In many instances there will be no need to engage the retaining hook  110  with the truck. However, where the roadbed or other surface is sloping down hill, it may be advisable to secure the hook  110  onto the truck to assure maintenance of the proper relationship between the truck and hopper  36 . 
     FIG. 9 illustrates one example of a crown that can be imparted to the layer of materials  204  on roadbed  22 . By cocking up screed  38  to a slight extent at its leading extremity, the nose  116  of screed  38  will be slightly higher than the outer ends of its wings  118 , 120 . Consequently, layer  204  will be provided with a positive crown that is somewhat higher in the center than at its outer ends, and there will be a gentle slope in opposite left and right directions from the central crown. In one preferred embodiment, the crown can be varied between a six-inch negative crown and six-inch positive crown. Of course, layer  204  can also be configured to have essentially no crown at all and to instead be essentially perfectly flat from one lateral extremity to the other. It is also contemplated that the wings  118  and  120  maybe extended to such an extent that the overall width of screed  38  can be varied from twelve feet to twenty feet. 
     Although preferred forms of the invention have been described above, it is to be recognized that such disclosure is by way of illustration only, and should not be utilized in a limiting sense in interpreting the scope of the present invention. Obvious modifications to the exemplary embodiments, as hereinabove set forth, could be readily made by those skilled in the art without departing from the spirit of the present invention. 
     The inventor(s) hereby state(s) his/their intent to rely on the Doctrine of Equivalents to determine and assess the reasonably fair scope of his/their invention as pertains to any apparatus not materially departing from but outside the literal scope of the invention as set out in the following claims.