Patent Publication Number: US-2006002762-A1

Title: Method and apparatus for spreading aggregate and road building materials related to vehicle speed

Description:
BACKGROUND  
      The present invention relates to methods and apparatuses for delivery of materials such as but not limited to aggregates and more particularly relates to an improved method for delivery of such aggregates from a spreader assembly and a system for controlling that delivery. The invention further relates to an attachable assembly for fixing to a vehicle having a source of granular material and the like and a control system for controlling the delivery of the material from the assembly.  
     PRIOR ART  
      Aggregates are widely used globally in pavement and road construction either for providing a road or pavement base or a durable wear surface which stands up to heavy traffic wear. One method of road construction involves preparing a sub grade surface, coating that sub grade with a layer of bitumen or the like and spreading gravel, metal aggregate road base or the like over the surface of the bitumen. This process is carried out partly by machine and partly by human labour in conjunction with the machine and has been used globally in road pavement constructions for many years. In large scale surfacing operations, machines are used which include a rear hopper from which is discharged the aggregate for the purpose of the surfacing. Due to the high cost of materials it is important to minimise wastage of pavement materials and particularly aggregates to maintain economies. This has proven to be difficult according to the prior art methods, as the use of manual labour in part of the process leads to inaccuracies in the distribution of the materials. Not only is there a high labour cost component when manual input is employed but also a high wastage component due to human error in material spreading.  
      In road construction and resurfacing it is highly desirable that the correct design volume of resurfacing aggregate is applied for economic and safety reasons. If too much aggregate is deposited on a surface, apart from the economic waste, there is a safety hazard from gravel mounds which often result from manual spreading. The prior art apparatuses have not, provided an aggregate discharge assembly which can be accurately controlled to deliver an accurate design quantity of material from a hopper and which may be calibrated and adjusted to compensate for assembly and operation parameters which influence discharge rate and quantity.  
     INVENTION  
      The present invention provides an improved apparatus and method for the spreading of construction materials such as aggregates in such applications as, but not limited to road pavement construction. More particularly, the invention provides an apparatus and method for the automated and controlled delivery of construction materials particularly in road pavement surfacing. The invention operates to accurately spread granular material such as but not limited to aggregate, according to a predetermined rate on to a surface such as a road pavement or the like. The invention further provides an apparatus which is capable of computer control of both small and large material delivery jobs and which removes the inaccuracies of operation of the known equipment and provides economies by reduction of human labour and elimination of materials losses caused by oversupply per unit area.  
      In one broad form the present invention comprises: 
      An apparatus for the controlled delivery of granular materials such as aggregates from a space for receiving and holding said materials to a surface exterior of said apparatus; wherein the apparatus comprises;     control means for adjusting the rate and or quantity of said materials delivered from said apparatus; wherein said control means includes means to receive at least one input parameter and means to convert said at least one input parameter into a mechanical activity performed by said apparatus; wherein said rate or quantity at which said material is delivered is dependent upon said at least one input parameter.    

      Preferably the control means is a computer.  
      In another broad form the present invention comprises: 
      an apparatus for the controlled delivery of granular materials such as aggregates from a space for receiving and holding said materials to a surface exterior of said apparatus; wherein the apparatus comprises;     a programmable logic computer for adjusting the rate and or quantity of said materials delivered from said apparatus; wherein said control means includes a computer input having means to receive at least one input parameter and means to convert said at least one input parameter into a mechanical activity performed by said apparatus; wherein said rate or quantity at which said material is delivered is influenced by said at least one input parameter.    

      In another broad form the present invention comprises: 
      an apparatus for the controlled delivery of granular materials such as aggregates from a hopper for receiving and holding said materials to a surface exterior of said apparatus; wherein the apparatus comprises;     control assembly for adjusting the rate and or quantity of said materials delivered from said apparatus; wherein said control assembly includes mechanical rams operably connected to said hopper, control means to receive at least one input parameter and means to convert said at least one input parameter into a mechanical activity performed by said apparatus; wherein said hopper is adjusted by said assembly to control the rate or quantity at which said material is delivered responsive to said at least one input to said control means. Preferably the control means is a computer.    

      According to a preferred embodiment, the material delivered by said apparatus is road pavement aggregate which is delivered under gravity from said hopper via adjustable gates: which may be adjusted to accommodate a design width for a job and weight per unit area. Preferably, said adjustable gate/s controls the size of an opening from which said aggregate is discharged wherein the size of the opening is adjusted in response to predetermined parameters such as apparatus speed over the ground and quantity of aggregate to be delivered in order to maintain a predetermined volume of aggregate per unit area.  
      In one broad form of the method aspect, the present invention comprises: 
      a method for controlled delivery of a granular material from a hopper to a surface using an apparatus for the controlled delivery of granular materials such as aggregates from a space for receiving and holding said materials to a surface exterior of said apparatus; wherein the method comprises the steps of;     a) inputting at least one operating parameter into a computer in communication with an aggregate hopper attached to said apparatus;     b) activating control by said computer of said hopper in accordance with at least one said operating parameter;     c) allowing a predetermined amount of material to be discharged from said hopper responsive to said at least one input parameter;    

      According to a preferred embodiment, the method comprises the further step of converting said input to a mechanical action thereby allowing at least one gate on said hopper to adjust responsive to said at least one input parameter so that said predetermined amount of material is discharged from said apparatus.  
      According to a preferred embodiment said at east one parameters may include, discharge rate of said material from said hoper in m 3 /unit area, speed of said apparatus, dimensions of said hopper opening, spread rate in kg/m 2 .  
      According to one embodiment the spread rate may be adjusted 0.5 kg per m 2  at any time from minimum to maximum settings. Preferably, the apparatus is adapted as an attachment for mounting to the rear of a tipper truck  
      In another broad form the present invention comprises: 
      an attachment apparatus for the controlled delivery of granular materials such     as aggregates from a space for receiving and holding said materials to a surface exterior of said apparatus; wherein the apparatus comprises;     control means for adjusting the rate and or quantity of said materials delivered from said apparatus; wherein said control means includes a computer having means to receive at least one input parameter and means to convert said at least one input parameter into a mechanical activity performed by said apparatus;     wherein said rate or quantity at which said material is delivered is dependent upon said at least one input parameter and said mechanical activity.    

      According to a preferred embodiment, said mechanical activity is the adjustment of one or more gates to adjust an opening in a hopper. Preferably the attachment is adapted to attachment to a vehicle such as a truck  
      In its broadest from the present invention comprises: 
      a spreader assembly for the controlled delivery to a surface of granular materials such as aggregates from a hopper in communication with a source of said materials external to said assembly; wherein the assembly comprises;     an opening to said hopper which receives said materials from said materials source,     a discharge opening from said hopper,     a gate adjacent said discharge opening;     control means for adjusting the rate and or quantity (weight or volume) of said materials delivered from said hopper; wherein said control means includes a computer having means to receive at least one input parameter and means to convert said at least one input parameter into an output parameter for performing at least one mechanical activity in the assembly; wherein the rate or quantity at which said material is delivered is dependent upon said at least one input parameter and said mechanical activity.    

      In another broad form the present invention comprises: 
      a vehicle including a spreader assembly for the controlled delivery of granular materials such as aggregates from the vehicle to a hopper in said assembly;     wherein the assembly comprises;     an opening to said hopper which receives said materials from said vehicle;     a discharge opening from said hopper,     a gate adjacent said discharge opening capable of regulating the discharge of the granular material;     control means for adjusting the rate and/or quantity (weight or volume) of said materials delivered from said hopper; wherein said control means includes means to receive at least one input parameter and means to convert said at least one input parameter into an output parameter for performing at least one mechanical activity in the assembly which controls the delivery rate and/or quantity of said granular material; wherein the rate or quantity at which said material is delivered is dependent upon said at least one input parameter.    

      Preferably the input parameter or parameters are received and processed by a computer.  
      In another broad form the present invention comprises; 
      a control system for use in the controlled delivery of granular materials such as aggregates from a vehicle mounted spreader assembly including a hopper for holding and discharging said materials from said hopper, wherein the control system comprises;     a programmable logic computer (PLC) for adjusting the delivery rate and/or quantity of said materials delivered from said hopper;     a sensor for detecting the speed of a vehicle to which the assembly is attached, said control system further comprising a computer input having means to receive at least one input parameter and means to convert said at least one input parameter into at least one mechanical activity performed by said apparatus and which regulates the discharge of said materials delivered from the vehicle responsive to said input; wherein said rate or quantity at which said material is delivered is dependent upon said at least one input parameter.    

      In a further broad form of a method aspect the present invention comprises: 
      a method for controlled delivery of a granular material from a vehicle mounted spreader assembly to a pavement surface, wherein the assembly comprises     a hopper which receives said materials from said materials source,     a discharge opening from said hopper;     a gate adjacent said discharge opening;     control means for adjusting the rate and or quantity (weight or volume) of said materials delivered from said hopper; wherein said control means includes a computer having means to receive at least one input parameter and means to convert said at least one input parameter into an output parameter for performing at least one mechanical activity in the assembly; wherein the method comprises the steps of;     rate or quantity at which said material is delivered is dependent upon said at least one input parameter and said mechanical activity; wherein the method comprises the steps of,     a) inputting vehicle parameters into said computer;     b) calibrating operation of said spreader assembly;     c) selecting an aggregate size for delivery by said hopper;     d) selecting spread rate weight and allowing conversion to a raw proportional gate position;     e) adjusting values by compensating for tilt and/or road speed;     f) obtaining a repeatable set value for spread rate of aggregate.    

    
    
     DETAILED DESCRIPTION  
      The present invention will now be described in more detail according to a preferred but non limiting embodiment and with reference to the accompanying illustrations; wherein,  
       FIG. 1 : shows a perspective view of a spreader assembly and control console according to one embodiment of the invention;  
       FIG. 2  shows a side elevation of the spreader assembly and control console of  FIG. 1 .  
       FIG. 3  shows a side elevation of the spreader with control console removed and with aggregate delivery gate closed  
       FIG. 4  shows the spreader of  FIG. 3  with aggregate delivery gate partially open.  
       FIG. 5  shows the spreader of  FIG. 4  with aggregate delivery gate fully open.  
       FIG. 6  shows the spreader of  FIG. 1  with hopper detached from a vehicle.  
       FIG. 7  shows a schematic layout of control system elements according to a preferred embodiment  
       FIG. 8  shows a flow diagram of a typical operation of the control system of a computerised spreader box 
    
    
      The invention will now be described in detail according to one embodiment, in its application to controlled spreading of road and pavement surfacing. It will however, be appreciated by persons skilled in the art that the spreader apparatus, control system and method of operation may be adapted to applications other than road and pavement surfacing.  
      In a typical road surfacing operation, a spreader, which will normally include a hopper for receiving and holding a road or pavement construction material such as an aggregate, will be preferably detachably attached to the rear of a tuck or other source of material supply by means of pin connections, bolts or nuts or alternative form of connection. The truck will be pre loaded with a supply of a flowable material such as but not limited to road base, aggregate (such as used in road surfacing operations) or other paving material. The material will be required to flow upon elevation of a tipper so granular materials are preferred such as aggregates, road bases sands and the like. The material to be spread as road base or on a pavement surface will be typically funnelled from a tipper into the hopper. The hopper receives and retains material delivered from the tipper for discharge via the spreader box.  
      Referring to  FIG. 1  there is shown a perspective view of a spreader assembly  1  attached to a tip truck  2 . Assembly  1  includes a control console  3  and an operator platform  4 . Control console  3  comprises a programmable logic computer  5  which is responsive to predetermined operating parameters inserted by the operator to control delivery of aggregate  6  from vehicle  2 . Referring to  FIG. 2  there is shown a side elevation of the spreader assembly  1  of  FIG. 1 . Once programmed, assembly  1  operates automatically in response to selected operating parameters which influence the required rate of discharge of aggregate  6  for a predetermined thickness of aggregate layer  7 . Assembly  1  is detachably fitted to vehicle  2  by means of bolts or alternative means. Due to the weight of assembly  1  a fork lift may be required to lift the assembly into position.  
      An operator will stand on platform  4  (as shown in  FIG. 1 ) and operate the spreader assembly  1  by inputting operating parameters into a programmable logic computer (PLC)  5  which is located in frame  8 . PLC  5  may alternatively be located in and operated from the cabin of vehicle  2  or remote from the spreader assembly thereby allowing remote control of spreading operations.  
      Assembly  1  further comprises a gate assembly  9  which is preferably air actuated but could be hydraulically operated. Gate assembly  9  may comprises a single gate or an array of separate gates individually operable. As shown in  FIG. 1 , assembly  1  may comprise individual gates which are individually and selectively operable by means of pneumatic cylinders  11 - 19 . The number of gates can be adjusted according to design requirements. Thus the assembly can comprise a single gate disposed the full width of the assembly or individual gates which allow an operator to make adjustments according to the width of the required aggregate layer  6 . Assembly  1  is attached to tipper  10  via bolts  20  and includes side baffles  21  and  22  to retain aggregate  6  within the assembly envelope. Aggregate  6  gravitates into hopper  23  and is released by gate assembly  24 . Assembly  1  further comprises ground engaging telescopic members  25  and  26  which engage a ground surface when the assembly is released from vehicle  2 . Screeding assembly  27  is adjustable by operation of cylinder  28  (see  FIG. 2 ) and allows variation of the thickness of aggregate  6 . Cylinder  28  is preferably an air operated actuator or electric actuator. Alternatively the cylinder may be hydraulically operated.  
       FIG. 2  shows a side elevation of the spreader assembly and control console of  FIG. 1  with corresponding numbering.  
      Referring to  FIG. 3  there is shown an enlarged cross sectional elevation of a spreader assembly  30  according to a preferred embodiment Spreader  30  comprises a hopper  31  (abbreviated) which receives aggregate  32  from an aggregate supply vehicle (not shown). Hopper  31  communicates with spreader box  33  which temporarily receives and retains until discharge aggregate  32 . The volume capacity of hopper  31  can be manufactured to suit job requirements. Spreader box  33  includes a connection assembly  34  which includes bolts  35  and  36  capable of attachment to a tipper  10  of a vehicle (see  FIG. 1 ). Spreader assembly  30  may be adapted for attachment to a vehicle other than a truck although a tipping truck is a preferred feed source of aggregate/road base or pavement surfacing material for spreader assembly  30 . Assembly  30  further comprises a gate  37  which may either span the width of an aggregate discharge chute opening  38  in spreader box  33  or comprise one of a plurality of similar gates which are independently operable responsive to at least one input.  
      Gate  37  which is pivotally attached at hinge  39 . Gate  37  is operably connected to adjustable air actuated cylinder  40  to enable alteration of the size of a discharge opening  38  through which a material such as aggregate  32  fed into hopper  31  thence spreader box  33  will be discharged from assembly  30 . Cylinder  28  is preferably an air operated actuator or electric actuator. Alternatively, the cylinder may be hydraulically operated. Gate  37  is actuated by means of pneumatic rams  41  which is responsive to an output from PLC which in turn responds to an input parameter as will be described in more detail below. Ram  41  is either directly or indirectly linked to gate  37 . As shown in  FIG. 3 , ram  41  is pivotally connected to arm  42  via pin connection  43 . Arm  42  is in turn pivotally connected to hinge  39  by pin  44 . Arm  42  is therefore capable of movement relative to pin connections  43  and  44 . Ram  41  in operation selectively moves in the direction of arrows  45  and  46 . Movement in the direction of arrow  46  will effect closure of gate  37  whereas movement of ram  41  in the direction of arrow  45  will open gate  37 . Gate  37  may be segmented and therefore adjusted according to the width of spread required or the discharge rate.  
      Assembly  30  further comprises a screeding assembly  47  comprising a downwardly depending strut  48  connected at one end to pivoting hinge  49  via pin  50 . Arm  51  is also pivotally attached at one end to hinge  49  and at the other end to electrically actuated cylinder  53  via pin connection  52 . Electrically actuated cylinder  53  is also linked to the PLC. Cylinder  53  includes ram  55  capable of movement in the direction of arrows  56  and  57 . When ram  55  moves in the direction of arrow  56  strut  48  moves about pin  50  causing screeding assembly  47  to move in the general direction of arrow  58 . Screeding assembly  47  can therefore move forwards or backwards. This enables the depth of the layer of discharged material to be adjusted.  
       FIG. 4  shows the spreader of  FIG. 3  with aggregate delivery gate  37  partially open. Aggregate  32  is shown discharging from spreader box  33  to pavement surface  59  as the assembly advances in the direction of arrow  60 .  
      In the case where bitumen is laid and is covered with gravel/aggregate/road base, to ensure that the vehicle does not travel over the freshly laid bitumen the vehicle may discharge the surfacing gravel/aggregate/road base, as it reverses in the direction of arrow  60   a  This ensures that the vehicle travels only on the discharged gravel/aggregate/road base, and not on the bitumen.  
      Screeding assembly  47  trails discharge chute opening  38  and maintains aggregate  32  at a predetermined thickness. The clearance distance d between screeding assembly  47  and ground surface  58  will dictate the thickness of the material  32 .  
       FIG. 5  shows the spreader of  FIG. 3  with aggregate delivery gate  37  fully open and screeding assembly  47  disposed at an angle allowing a greater aggregate thickness. Screeding assembly  47  may be rotated in the opposite direction by retraction of ram  55  in the direction of arrow  56 . By adjusting air operated gate  37  and screeding assembly  47  the discharge rate and thickness can be adjusted during delivery and responsive to one ore more predetermined input parameters, such as vehicle speed or motion.  
       FIG. 6  shows a perspective view of the spreader assembly of  FIG. 1  with corresponding numbering detached from a vehicle.  
       FIG. 7  shows a schematic layout of control system elements according to a preferred embodiment  FIG. 7  is best read in conjunction with  FIG. 8  which shows a schematic flow diagram of the steps of operation of the spreader assembly.  FIG. 7  shows the preferred locations of speed sensor, electronic transmitters and switches. Vehicle speed sensor  70  is located on or near chassis  71 . Tilt position transmitter  72  is preferably located at the rear of the vehicle. Likewise the electronics for operation of the gate positions are located near the gates. Each gate includes a proportional gate position transmitter  73  with proportional gate open limit switch  74  and proportional gate closed limit  75 .  
       FIG. 8  shows a flow diagram of the operation of the spreader assembly according to a preferred embodiment. An important objective of the computer controlled spreader assembly is to ensure that the required amount of material is discharged to eliminate wastage by oversupply of material and to ensure consistency of delivery to meet design requirements. Accurate delivery of granular material from a moving hopper charged by a material supply is difficult to achieve as it is dependent upon a number of fixed and variable parameters whose relationship is constantly changing during delivery as some external and unpredictable influences may change delivery rate and conditions for a linear distance. The vehicle which discharges the aggregate material may influence discharge rates due to tyre circumference, differential ratio, road speed translating into pulses/revolution. The truck includes a pick up sensor which senses road speed. it also includes a tilt sensor which detects body tilt angle. The pick up sensor detects road speed pulses per revolution A signal proportional to body tilt angle is emitted preferably between 4-20 mA. A proportional signal relative to stroke position if proportional gate is emitted between 0-10 vDC. Proportional gate position limit switches set open and closed position limits. The PLC contains four main programs. The first of these is a vehicle safety check program which allows an operator to check to determine if operation is available. Operator console switches and selections are checked to ensure operation is available. If all safeties are clear an indication lamp is set to ON. Alternatively, an error message is displayed and the proportional gate is disabled from operating. The operator may then rectify any problems and re establish available operation  
      The second program allows setting of truck parameters. Road speed is the critical parameter which is a function of the product of tyre circumference, differential ratio and road speed pulses/pulses per revolution. A third program allows for gate calibration which is required daily to establish if the spread rate delivered is commensurate with the spread rate prescribed. This is carried out by performing spread rate and mat tests prior to commencing a job. A fourth program allows loading of truck operation parameters. An aggregate size parameter is loaded by an operator. This parameter will be the staring point for determination of the remaining operating parameters which must accommodate aggregate size. The operation program is loaded with parameters which correspond to aggregate size. The spread rate weight is selected by the operator and converted to a raw proportional gate position. This result is then compensated for by the tilt feedback value. The proportional gate tilt compensated position is then calculated by a ratio of the raw proportional gate position and the truck tilt angle. The road speed compensated value is then calculated by a ratio of the proportional gate tilt compensated position and the calculated road speed. This result provides the operating set value for the proportional gate position. The set value then provides an accurate repeatable spread rate of aggregate on the ground.  
      The operator console screen displays operating parameters, truck operating status, selected aggregate recipe and weight, recipe details and error or fault messages.  
      The proportional gate position is controlled by the calculated set value compared to the position feedback signal. The comparison result will activate either an open or close command signal for the gates. Gates  11 - 19  are each activated by individual selector open and close switches which actuate solenoids connected to each drive cylinders for each gate. Timed pulse open signal opens solenoid valves for each material gate.  
      In use, the operator stands on the operator platform and selects the required amount of aggregate. Next, gate assemblies are opened in accordance with a corresponding input parameter or parameters. The operator console is preferably push button digital operation. Once the gate assemblies are set with reference to the kglm 2  discharge rate set for a particular job, aggregate is fed into the hopper and eventually onto a road surface. A speed sensor linked to a tail shaft of the vehicle will precipitate a response parameter which may adjust the opening of gate assemblies which in turn adjusts the discharge of aggregate to maintain the design discharge rate for a particular job. The function of sensor is to detect the number of pulses determined by rotation of the tail shaft and relay this information to the PLC for appropriate adjustment of the gate assembly. According to one embodiment the sensor includes a cog on the tail shaft which reads pulses commensurate with the degree of travel of a vehicle wheel. The PLC, knowing the number of pulses can calculate the distance of travel of the wheel or horizontal speed and adjusts the gate assembly to either increase or decrease discharge of the material to be spread according to the design spread rate for a particular job. In an alternative embodiment, the PLC may make the gate assembly adjustments with reference to an alternative parameter such as wheel revolutions. The assembly may further comprise an incline meter to determine the angel of a truck body and an absolute linear displacement sensor which determines the precise position of the spread rate screeding assembly.  
      According to one embodiment there are nine individual gate assemblies, which are opened and closed by separate individual air actuated pneumatic rams. These may alternatively be hydraulically or electrically actuated. This enables an adjustment of the width of aggregate discharge opening. Gate arms may be forced open by pneumatic air and the aggregate in the hopper. The spread rate screeding rack controls the amount of gravel spread onto the road surface via an electric actuator. The range and degree of movement that the actuator controls forward or reverse movement is predetermined by the PLC. The computer receives it operating data from such parameters as road speed, angle of truck body, and an absolute linear displacement which determines the precise position of the spread rate. The PLC program will calculate from the input parameters the job discharge rate requirements and adjust the gate assembly accordingly, to ensure correct kg/m 2  discharge or spread rate.  
      The present invention herein described according to a preferred embodiment has numerous advantages over the prior art Firstly, the computer control eliminates the human error which prevails in the prior art methods and apparatuses by allowing accurate control of the discharges of material by adjusting in the event of vehicle stoppages or slow down. The computer accurately controls the material spread rate in each and al operations and leaves the operator free to assume a monitoring role which includes watching for obstructions such as power lines. It is a mandatory requirement in road surfacing in which aggregate is spread from a hopper to employ an observer with a 5099 ticket whose mandate is to watch for power lines to ensure no snagging. This activity requires at least one individual but where a computer controlled assembly is employed in accordance with the invention, the operator of the assembly can also function safely as an observer due to the automation provided by the logic computer. The invention being adaptable as an attachment to a vehicle frees a tipper when not attached to the box spreader to be employed elsewhere. It also enables adaption to relatively small spreading jobs. For example jobs as small as 300 mm wide to 900 mm wide may be performed. The computer controlled apparatus can be used in spreading up and down hills or around corners and may be transported on public roads day or night. The spreader assembly may be switched from manual to automatic (computer driven) operation or from computer to manual operation.  
      It will be recognised by persons skilled in the art that numerous variations and modifications may be made to the invention as broadly described herein without departing from the overall spirit and scope of the invention. Examples of such variations include use of a single gate or plurality of gates to close the hopper opening, use of a hydraulic cylinder rather than an air actuated ram.