Abstract:
A method and apparatus is disclosed for controlling material feed for asphalt pavers. The material feed system includes a screed, feeder conveyor and a spreader auger. A sensor measures a material volume and transmits this information to an electronic control module (ECM). This information may be used as the target material volume, which the ECM may use to calculate a corresponding conveyor speed and auger speed. The sensor monitors the material volume as paving commences, and the ECM maintains the initial calibrated target size by adjusting the auger and conveyor rotational speeds.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure provides examples in the field of semi-automation and/or automation of machines, in particular, asphalt pavers. 
       BACKGROUND 
       [0002]    Asphalt road paving machines (or asphalt pavers) include a tractor with a hopper for receiving asphalt paving material located at the front of the paver, and a feeder conveyor for delivering the asphalt paving material to the rear of the paver to a spreader auger. The auger distributes the asphalt laterally behind the tractor to the road surface in front of the screed. 
         [0003]    Asphalt pavers include a screed, a heavy assembly drawn behind the paving machine by a pair of pivotally mounted tow arms for smoothing out and compressing the asphalt material. Pavers may include a screed extender frame for adjusting screed width, which may be hydraulically adjustable. 
         [0004]    Road mat thickness is determined in part by asphalt material composition, machine specifics, as well as by the volume of the asphalt material pile placed in front of the screed. Asphalt material composition and screed specifics are typically constants with a specific machine and mix; however, the height of the material pile must be continuously provided by the conveyor and auger as the paver moves forward. Material pile height should remain constant to pave an even surface. Variables affecting a current material pile size include the conveyor speed, and the auger speed. 
         [0005]    Sensors mounted on the end of the screed or screed extender help determine the amount of material in front of the screed. The machine operator may manually set estimated material height, or provide an estimated control gain by using a marked dial or digital input on the control panel, to direct the machine to regulate the material pile to a target size using the auger and conveyor systems. 
         [0006]    Too much material placed in front of the screed results in a ridge once the machine is adjusted to the proper material pile height. Too little material placed in front of the screed results in a dip once the machine is adjusted to the proper material pile height. Some paving machines utilize manual knobs that an operator turns to adjust the gain for a paver to set the target material pile height. This gain signals to an electronic control module (ECM) as to the material height setting, and thus, the conveyor and auger speed. 
         [0007]    U.S. Pat. No. 5,575,583 to Grembowicz et al. describes an apparatus for controlling a material feed system. The apparatus includes a sensor that monitors the amount of material at the edge of the screed and responsively produces a target material height signal, which the operator matches using a rotary switch. It is desirable to provide a system that can provide the proper settings from initial paving. It may also be desirable to automate the process to reduce variability due to operator subjectivity. 
       SUMMARY 
       [0008]    The present disclosure generally relates to automating material feed for a paver to maintain a material pile size. 
         [0009]    In a first embodiment, the paver includes a system for regulating material feed including a screed, a conveyor and an auger. One sensor, or a pair of sensors on the screed measures the amount of material placed in front of the asphalt screed. These sensors may be contact based, sonic based, or may employ another technology. The sensors measure the size of the material pile in front of the screed, and for example, slightly beyond the auger width. 
         [0010]    A sensor measures the initial distance from its position to the feed material adjacent the screed, and transmit this information to an ECM. The ECM uses this initial distance information to calibrate the paver by setting a target pile size to determine a conveyor and auger speed. As the paver and material feed system operates, the sensor continues to monitor the pile, and the ECM continues to determine, set, and adjust a rotational conveyor speed and a rotational auger speed to maintain the target pile size. 
         [0011]    Upon paver initialization, the ECM transmits this auger speed, and conveyor speed, which may be determined by a ratio of the auger speed, to the auger control and the conveyor control. An algorithm within the ECM calculates information such as gains necessary to maintain the pile size, using feedback information provided by the sensor. The calibration and paving process may be initiated with a signal, which may be produced from a button, switch, or upon machine initialization, which signals the ECM to receive the target pile size input from the sensor. The step of guessing a material height or gain with a variable dial may be eliminated. Upon the start of paving, the ECM will compare the current pile size to the target pile size to control the rotational conveyor speed and the rotational auger speed ratio to maintain the target pile size. This auto-calibration option may replace, or be present in addition to manual dials. 
         [0012]    A sensor produces a first target material height signal indicative of an initial material height at the edge of the screed, and transmit this signal to an ECM. The ECM calculates or sets a gain corresponding to the target material height. As the paver moves and material is delivered by the conveyor and auger, the sensors continue to detect an actual material height at the edge of the screed. This signal is transmitted to the ECM, which compares the actual and target material height signals, and determines a target rotational speed of the auger and conveyor to maintain the target material height. 
         [0013]    The paver continuously senses and transmits the material pile height information to the ECM, which adjusts the auger and conveyor speeds accordingly. A machine which has been auto-calibrated may begin paving with the proper speeds and speed ratio. 
         [0014]    The feed conveyors and spreader augers may be mechanically or electronically coupled together, and accordingly, the rotational speed may be expressed by a ratio between the conveyor rotations per minute (RPM) and the auger RPM. In an alternate embodiment, a second pair of sensors measures the amount of material deposited by the conveyor to the auger. When sensors are employed to detect the amount of material delivered by the conveyor to the auger, the conveyor speed is be independent of the auger speed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The foregoing and other features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only several embodiments in accordance with the disclosure and are, therefore, not to be considered limiting of its scope, the disclosure will be described with additional specificity and detail through use of the accompanying drawings. 
           [0016]    In the drawings: 
           [0017]      FIG. 1  is a side view, showing the general construction of an asphalt paving machine including an example apparatus of the present disclosure; 
           [0018]      FIG. 2  is a schematic representation of an example system; 
           [0019]      FIG. 3  shows an example operator control panel; 
           [0020]      FIG. 4  shows an example screed station control panel, all arranged in accordance with at least some embodiments of the present disclosure; and 
           [0021]      FIG. 5  is a flow chart, illustrating an example method of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the Figures, may be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and make part of this disclosure. 
         [0023]    The present disclosure relates to apparatus and methods of calibrating an initial or target pile size, and maintaining that pile size. The present disclosure contemplates using sensors, e.g. paddle, acoustic, ultrasonic sensors or other types of sensors, to measure the material pile size during calibration and throughout the paving process. Example systems may eliminate the manual adjustment of knobs for gains, and instead, auto-calibrate the pile size. 
         [0024]    Prior designs required manual estimations and settings, i.e. a gain to be manually set for each job to create the target material pile size. Because the setting of these manual settings by the rotary switch requires some training and experience for consistency, there is a high probability that it will be incorrectly set at the beginning of paving job, resulting in inconsistent material height regulation when the gain is adjusted to the proper setting. Traditional pavers require close monitoring by the screed operator when paving commences until it is adjusted to the proper setting. Example systems of the present disclosure allow a paver to initialize with the proper gain and settings. 
         [0025]      FIG. 1  shows an example paver  010 . Tow arms  130 , one located on each side of paver  010 , pull the screed  100  and screed extender  110 . An auger  300  is located in front of the screed  100 . 
         [0026]      FIG. 2  depicts a schematic representation of an example system that includes an asphalt paving machine  010  of the type with which an example method may be implemented. It will be appreciated that the present disclosure may be useful for automatic calibration with other types of earth moving machines, and with similar machines that operate with a sensor as part of the machine control system. 
         [0027]    Asphalt paver  010  includes rotatable conveyor  200 , which feeds material 040 to rotatable auger  300 . Auger  300  is adapted to receive asphalt 040 discharged from the conveyor  200  and spread asphalt 040 in front of screed  100  to form material volume 050, which the screed  100  compresses into laid asphalt road mat 025. 
         [0028]    A sensor  400  is mounted on the screed extender  110 , and while  FIG. 2  only shows one sensor  400  at the end of screed extender  110 , a second sensor may be mounted on the other end of screed extender  110 . Sensor  400  should be adjusted to be pointed to a spot on pile 050 which should be maintained at a relatively constant height to create an even road mat 025. For example, a good spot to point sensor  400  would be just beyond the auger  300  edge. Operator station  700  and screed station  750  provide control over the paving process. 
         [0029]    A second sensor  475  may be associated with paver  010 . The second sensor  475  senses the amount of asphalt material 050 placed by conveyor  200  to the auger  300  and transmits corresponding signals in response to respective sensed excesses and deficiencies of asphalt material 040. Sensor  475  measures the material 050 in front of the auger  300  to vary the speed of the conveyor  200  to increase or decrease the material 040 delivered to auger  300 . By using a second set of sensors  475  to detect the amount of material 040 delivered to the auger  300  by conveyor  200 , the speeds of the auger  300  and the conveyor  200  can be independently adjusted. Without this sensor  475 , it would be difficult to determine the independent conveyor  200  and auger  300  speed, and thus they could be tied together by an adjustable ratio. Thus, sensor  475  may replace a conveyor speed and auger speed ratio knob. Regardless, knobs on tractor control station  700  and screed control station  750  may still be retained for a manual setting or override of the target pile size calibration and application. 
         [0030]    As paver  010  moves and pulls screed  100 , sensor  400  transmits the material size information to ECM  450 , which adjusts conveyor  200  and/or auger  300  speeds accordingly to ensure target pile size is maintained. 
         [0031]    Referring to  FIG. 3 , an example tractor operator station  700  is shown. Operator station  700  is generally located on the tractor at the rear of the machine  010 , and has independent controls for the conveyor  200  and the auger control  300 . The left and right sides of station  700  perform the same functions for each respective side of the conveyor  200  and auger  300 . For example, conveyor panel  709  controls the right side of conveyor  200  with reverse button  708 , auto button  707 , and manual override button  706 . These buttons  706 - 708  operate in the same manner for left conveyor panel  702 . Furthermore, buttons  706 - 708  operate in a similar manner for auger panel  703 , including reverse, auto, and manual settings as indicated by the respective symbols. In one embodiment, the dials  701  on panel  704  are to adjust the target amount of material 040 the conveyor  200  delivers to the auger  300  when sensor  475  is employed. Panel  704  is used when button  707  on panel  709  or its corresponding button in panel  702  is activated to the “Automatic” or “Auto” mode. The left and right dials on panel  704  control the amount of material 040 delivered by the conveyor  200  to the auger  300 . The manual buttons are “Manual Overrides” which momentarily activate the conveyors or augers at a fixed high speed. 
         [0032]    In an alternate embodiment, the magnitude of the conveyor ratio signal may be adjusted by the relative position of the conveyor ratio dials  701  in panel  704 . For example, “slow” or “−” represents a minimum speed ratio of the conveyor speed to the auger speed, while “fast” or “+” represents a maximum speed ratio of the conveyor speed to the auger speed. Thus, the conveyor speed may be calculated as a ratio of the auger speed. Left and right side of auger  300  may be controlled by left and right sides of panel  703 . 
         [0033]    Referring to  FIG. 4 , screed station  750  is located on the screed  100  of  FIG. 2 . A signal producing switch or button  715  initiates the program of calibrating the target material height at the edge of the screed  110 . A material height dial  710  is turned to adjust the target height of material 050, at the edge of the screed  100 . The material height dial  710  adjusts a signal indicative of a target amount of asphalt material 050 at the edge of the screed. The magnitude of the material height signal is adjusted by the relative direction and increments of the dial  710 . For example, “low” or “−” represents a lesser amount of material, while “high” or “+” represents a greater amount of material 040 at the end of the screed. 
         [0034]    In an alternate embodiment, a separate auto-calibrate button  715  may not be present. Upon starting the paver  010 , the ECM&#39;s auto-calibrate function immediately senses the pile size 050, and sets the target height of material to be controlled by auger  300  and conveyor  200 . 
         [0035]    Conveyors  200  may be controlled by conveyor panel  712  and auger  300  may be controlled by auger panel  713 , or conveyor  200  and auger  300  may be controlled simultaneously with panel  714 , on the screed station  750 . In addition to reverse and manual override buttons, screed station  750  panels  712  and  713  each have a pause button  711 . 
         [0036]    After setting up the prefill to a desired volume 050, as determined by calculation or experimentation, an operator initiates the disclosed method with auto button  707  or its corresponding button on left conveyor panel  702 , on operator station  700 , and then presses the Auto Calibrate button  715  on screed station  750 . Sensor  400  continuously measures a distance x and send the distance information signal to an ECM  450 . ECM  450  uses the distance (material height) information and paver  010  properties, and determines a conveyor  200  speed and an auger  300  speed to maintain that material height. The ECM  450  transmits this to the conveyor control  705  and auger control  350 . When paver  010  is initiated to start paving, paver  010  commences at these determined speeds, or in an alternate embodiment, initializing the machine  010  automatically begins the calibration process, followed by paving. 
         [0037]      FIG. 5  is a flow chart outlining the method  501  of the disclosure. A prefill material volume 050 created in front of the screed  100  is measured with a sensor  400 , as in operation  510 . In operation  520 , this material pile information is sent to the ECM  450 , and set as a target pile size in operation  230 . Before paving commences, in operation  540 , the ECM  450  determines an auger and a conveyer speed, and in operation  550 , transmits this information to the auger and conveyor controller. Upon starting the paver, the auger  300  and conveyor  200  turn at the determined speeds. During paving, as the conveyor and auger deposit material in front of the screed, the pile height varies and shifts. Thus the sensor periodically or continuously (e.g. seconds, or milliseconds, or any time interval) monitors the current pile size (i.e., detected pile size), and sends the information to the ECM, as in operation  560 . In operation  570 , the ECM compares the detected pile size to the target pile size, and transmits the appropriate signals to the conveyor and auger controls to adjust the conveyor and auger speeds, as in operation  580 , to maintain the target pile size. 
         [0038]    In an automatic mode, the ECM  450  increases the auger rotational speed in response to the actual material height being less than the target material height, i.e., the amount of asphalt material near the edge of the screed being below that of the target amount of material. This target material height is automatically determined by the sensor and the calibration program. Alternately, the control  450  reduces the auger rotational speed in response to the actual material height being greater than the target material height, i.e., the amount of asphalt material near the edge of the screed being greater than that of the target amount of material. 
       INDUSTRIAL APPLICABILITY 
       [0039]    This system may be used in asphalt pavers to reduce, minimize, and/or restrict operator variability. Example systems may allow an asphalt paver to accurately distribute material for the screed for the entire project. 
         [0040]    The present system may be used when paving a road, parking lot, or other asphalt or aggregate surfaces. One advantage of the present disclosure lies in the commencing of the initial paving process; the operator does not have to guess an initial gain or auger and/or conveyor speed. The operator is not required to set a dial or guess the prefill material amount that the paver attempts to replicate; the paver measures a prefill material, and adjusts the auger and/or conveyor in response to the detected prefill material. 
         [0041]    A prefill material pile size may be created in front of the screed, as typical in the industry. This prefill material to be created is determined before paver initialization, so the paver has a beginning frame of reference. 
         [0042]    The prefill material pile volume is measured with a sensor and sent to the ECM, as a target pile size. As paving commences, the ECM determines an auger and a conveyer speed, and transmits this information to the auger and conveyor controller. Thus, upon starting the paver, the auger and conveyor turn at the appropriate speeds to deliver an accurate amount of feed material. During paving, the sensor periodically monitors the current pile size, and the ECM transmits the appropriate signals to the conveyor and auger controls to adjust the conveyor and auger speeds to maintain the target pile size. 
         [0043]    The paver may be automated to reduce operator error, but retains manual override features. 
         [0044]    While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.