Patent Publication Number: US-10316476-B2

Title: Screed assembly for a paving machine

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to a paving machine, and more particularly to a screed assembly of the paving machine having a temperature sensor to monitor temperature of paving material. 
     BACKGROUND 
     When building roadways, parking lots and the like, paving machines are used to deposit paving material, such as asphalt, on a paving surface to create a flat, consistent surface over which vehicles may travel. The paving machine typically works with a compactor to create a finished mat surface. The paving machine is generally a self-propelled machine designed to receive, convey, distribute, and partly compact the paving material. Typically, the paving machine receives heated paving material in a hopper positioned at a front of the paving machine, conveys the paving material from the hopper to a rear of the paving machine with conveyors, distributes the paving material along a desired width with an auger, and forms the paving material into a mat with a screed assembly. The mat is further compacted by one or more compactors. 
     One or more compactors generally follow behind a paver and compact the mat to a desired degree or extent. The compactor may include a drum assembly having a vibratory mechanism. Both amplitude and frequency of vibration may be controlled to establish degree of compaction. 
     The extent of compaction effort mainly depends on the temperature of the paving material. For example, if sections of the mat are at a lower than preferred temperature, the one or more compactors may have to make additional passes across these sections to ensure sufficient compaction. On the other hand, if sections of the formed mat are at a higher than preferred temperature, compactor operators will have to take caution to avoid over compacting these sections. Therefore, for laying a good finished mat, temperature of the paving material is significant for proper compaction by the screed assembly and thereafter by one or more compactors that follow the paving machine. 
     Current systems include temperature scanning devices and infrared cameras mounted to the screed assembly to scan and determine the surface temperature of the mat surface formed by the screed assembly. These systems measure the surface temperature of the mat surface laid down by the screed assembly. The surface temperature of the mat surface may be different from the core temperature of the paving material. Further, these systems may be expensive. 
     US Patent Application Publication No. 20150003914 discloses a temperature sensor configured to determine the temperature of the screed plate. The screed plate has a top surface, a thickness, and an opening in the top surface. The opening extends into the thickness of the screed plate and receives at least a portion of the temperature sensor. The temperature sensor monitors the temperature of the screed plate and based on the temperature of the screed plate a controller adjusts the heating of the screed plate. 
     However, measuring the temperature of a screed plate may not provide an accurate measurement of the temperature of the paving material that is needed to control the compaction process. 
     SUMMARY OF THE INVENTION 
     In an aspect of the present disclosure, a screed assembly for a paving machine is disclosed. The screed assembly includes a screed plate having a front edge, a first plate having a first thickness. The first plate is positioned in front of the front edge of the screed plate. At least one temperature sensor is coupled to the first plate. The temperature sensor is configured to determine a temperature of a paving material, whereby the temperature of the paving material is measured before the paving material comes into contact with the screed plate. 
     In another aspect of the present disclosure, a paving system is disclosed. The paving system includes a paving machine, a compactor and a controller. The compactor is configured to apply a variable compaction effort to a paving material. The paving machine includes a screed plate having a front edge, a first plate is positioned in front of the front edge of the screed plate. The first plate has a first thickness and a temperature sensor is coupled to the first plate and positioned at least partly within the first thickness and configured to determine a temperature of the paving material, whereby the temperature of the paving material is measured before the paving material comes into contact with the screed plate. The controller is configured receive a temperature data from the temperature sensor and control the variable compaction effort of the compactor based on the temperature data. 
     In yet another aspect of present disclosure, a method for paving a ground surface is disclosed. The method includes providing a paving machine having a first plate in front of a front edge of a screed plate. The first plate has a temperature sensor configured to provide temperature of a paving material, whereby the temperature of the paving material is measured before the paving material comes into contact with the screed plate, providing a compactor applying a variable compaction effort to the paving material, providing the temperature of the paving material to the compactor and adjusting the variable compaction effort of the compactor based on the temperature of the paving material. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a paving system including a paving machine and a compactor; 
         FIG. 2  illustrates a perspective view of the paving machine depicting a screed assembly; 
         FIG. 3  illustrates a perspective view of the screed assembly having a first plate; 
         FIG. 4  illustrates a sectional view of the first plate including a temperature sensor; 
         FIG. 5  illustrates an enlarged cut away view of a screed assembly having a second plate; and 
         FIG. 6  illustrates an enlarged cut away view of the screed assembly having a third plate. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference number will be used throughout the drawings to refer to the same or like parts. 
     An exemplary embodiment of a paving system  100  is shown in  FIG. 1 . The paving system  100  includes a paving machine  102 , a compactor  104  and a controller  154 . Although the paving machine  102  is depicted in the figures as an asphalt paver, the paving machine  102  may be any kind of paving machine configured to form a layer of paving material on a ground surface. The paving machine  102  includes a tractor  106  having a power source  108 , such as an internal combustion engine, one or more traction devices  110  and a hopper  118 . The traction devices  110  may be operatively coupled to the power source  108  by a transmission mechanism (not shown) to drive the traction devices  110  and propel the paving machine  102 . Although, the traction devices  110  are shown in the figures as wheels, the traction devices  110  could alternatively be tracks or any other type of traction devices. The traction devices  110  could also be combinations of different types of traction devices. For example, the paving machine  102  could include both tracks and wheels. The paving machine  102  also includes an operator station  112  for one or more operators. The operator station  112  includes one or more operator seat  114  and an operation console  116  that may be mounted on a pedestal. 
     The hopper  118  is positioned at the front of the paving machine  102  and contains the paving material that is to be formed into a mat on the ground. The paving material may be dumped into the hopper  118  from trucks that deliver the paving material to a work site. The paving machine  102  may also include one or more conveyors (not shown) at the bottom of the hopper  118 . The conveyors transport the paving material from the hopper  118  to the rear of the tractor  106 . The paving machine  102  may further include one or more augers or other material feed components instead of or in addition to the conveyors. The augers distribute the paving material in front of a screed assembly  120 . As the paving machine  102  travels forward, the paving material is evenly spread and compacted by the screed assembly  120 . 
     The screed assembly  120  is positioned at the rear end of the tractor  106 . The screed assembly  120  is attached to the tractor  106  by tow arms  178  and towed behind the tractor  106  to spread and compact the paving material into the mat on the ground surface. Referring to  FIG. 2  and  FIG. 3 , the screed assembly  120  includes a frame  122 , a screed plate  124 , a first plate  126 , one or more temperature sensors  128 , and one or more extender plates  130 . The screed plate  124  is supported by the frame  122 . The screed plate  124  has a front edge  132 . The first plate  126  is positioned in front of the front edge  132  of the screed plate  124 . The first plate  126  may be attached with the screed plate  124  by welding, press fitting or any other method known in art. In an alternate embodiment, the first plate  126  may be coupled with the frame  122 , such that the first plate  126  is positioned in front of the screed plate  124 . In the embodiment illustrated, the first plate  126  is a nose bar. The nose bar may be coupled adjacent to the front edge  132  of the screed plate  124 . The nose bar is configured to guide the paving material under the screed plate  124 . The nose bar may also pre-compact the paving material prior to the screed plate  124 . 
     Referring to  FIG. 3 , the first plate  126  may define a surface profile  134 , configured to pre-compact the paving material and guide the paving material to the screed plate  124  for further compaction. The first plate  126  further defines an opening  136  extending from the surface profile  134  into a first thickness ‘d’ of the first plate  126 . In the embodiment illustrated, plurality of openings  136  may extend from the surface profile  134  into the first thickness ‘d’ of the first plate  126 . The openings  136  may be bores that extend completely through the first plate  126 . In an embodiment, the openings  136  are blind bores extending partially into the first thickness ‘d’ from the surface profile  134  of the first plate  126 . The openings  136  are configured to receive the temperature sensor  128  within the first thickness ‘d’. 
     In the embodiment illustrated, the temperature sensor  128  is positioned at least partly into the first thickness ‘d’ of the first plate  126 . In an alternate embodiment, the temperature sensor  128  may be positioned completely into the first thickness ‘d’ of the first plate  126 . The temperature sensor  128  is configured to measure the temperature of the paving material before the paving material comes into contact with the screed plate  124 . Referring to  FIG. 4 , the temperature sensor  128  defines a main body portion  128   a  and a cap portion  128   b . The main body portion  128   a  defines a surface having an outer surface profile  138 . The outer surface profile  138  is configured to contact the paving material to determine the temperature of the paving material. 
     When engaged with the first plate  126 , the outer surface profile  138  of the temperature sensor  128  may be substantially flush with the surface profile  134  of the first plate  126  and forms a continuous surface profile i.e. the first plate  126  and the temperature sensor  128  are simultaneously in contact with the paving material. In an aspect of the present disclosure, plurality of temperature sensors  128  may be coupled to the first plate  126  and positioned at least partly within the first thickness ‘d’. The plurality of temperature sensors  128  may be positioned at predefined locations on the first plate  126 . The plurality of temperature sensors  128  are positioned to determine the temperature of the paving material along the complete width of the mat. 
     The temperature sensor  128  may be a “contact” type of temperature sensor, such as, for example, a thermocouple with a sensing junction, a thermostat, resistive temperature detectors (RTD) or any other temperature sensing device known in art. In an embodiment, the temperature sensor  128  may be made of a high heat conductive material such as aluminum or any other material with high heat conductivity. The high heat conductive material is configured to contact and determine the temperature of the paving material when it reaches the screed assembly  120 . 
     In an alternate embodiment, as illustrated in  FIG. 5 , a screed assembly  120   a  may include a first plate  126   a  and a second plate  140 . The second plate  140  is disposed between the first plate  126   a  and the front edge  132  of the screed plate  124 . The second plate  140  is arranged such that the paving material comes in contact with the second plate  140  before compaction by the screed plate  124 . The second plate  140  may define a second thickness ‘t’. The second plate  140  may further define a second surface profile  142 . The second plate  140  has a second plate opening  144  extending from the second surface profile  142  into the second thickness ‘t’ of the second plate  140 . The temperature sensor  128  is positioned at least partly within the second thickness ‘t’ of the second plate  140 . The temperature sensor  128  is configured to measure the temperature of the paving material before the paving material comes into contact with the screed plate  124 . The outer surface profile  138  of the temperature sensor  128  may be substantially flush with the second surface profile  142  of the second plate  140  i.e. the second plate  140  and the temperature sensor  128  are simultaneously in contact with the paving material. In an embodiment, both the first plate  126   a  and the second plate  140  may include at least one temperature sensor  128 . 
     In another embodiment, illustrated in  FIG. 6 , the screed assembly  120  may include a third plate  146 . The third plate  146  is disposed in front of an edge  148  of the extender plate  130 . The edge  148  is located in front of the extender plate  130 . In an embodiment, the third plate  146  may be a tamper bar configured to pre-compact the paving material. In an alternate embodiment, the third plate  146  may be a nose bar. The third plate  146  may define a third thickness ‘h’. The third plate  146  may further define a third surface profile  150 . The third plate  146  has a third plate opening  176  extending from the third surface profile  150  into the third thickness ‘h’ of the third plate  146 . At least one temperature sensor  128  may be positioned at least partly within the third thickness ‘h’ of the third plate  146 . The temperature sensor  128  is configured to measure the temperature of the paving material before the paving material comes into contact with the extender plate  130 . The outer surface profile  138  of the temperature sensor  128  may be substantially flush with the third surface profile  150  of the third plate  146  i.e. the third plate  146  and the temperature sensor  128  are simultaneously in contact with the paving material. 
     The temperature sensor  128  may be mounted to the first plate  126 , the second plate  140  or the third plate  146  using methods known in the art including welding, press fitting or by threaded engagement. Referring to the embodiments illustrated in  FIG. 4 ,  FIG. 5  and  FIG. 6 , the openings  136 , the second plate openings  144  and the third plate openings  176  may have threads. The temperature sensor  128  may have complementary threads to secure the temperature sensor  128  within one or more of the opening  136 , the second plate opening  144  and the third plate opening  176  extending into the first thickness ‘d’, the second thickness T and the third thickness ‘h’ respectively. In an illustration of the present embodiment, the temperature sensor  128  may be a threaded insert. The screed assembly  120  may further include a lock nut  174  for securing the temperature sensor  128  to the first plate  126 , the second plate  140  and/or third plate  146 . 
     In an alternate embodiment, a high heat conductive insert may be coupled with the temperature sensor  128  disposed on the first plate  126 , the second plate  140  and/or the third plate  146 . For example, the high heat conductive insert is positioned within the opening  136  extending into the first thickness ‘d’ of the first plate  126 . The temperature sensor  128  is coupled to the high heat conductive insert. The high heat conductive insert prevents the wearing of the temperature sensor  128 . 
     In yet another embodiment, the screed plate  124  may further include multiple screed plate openings towards the front of the screed plate  124 . The temperature sensor  128  with a thermal insulator may be positioned in the screed plate openings. The thermal insulator is configured to limit the heat transfer from the screed plate  124  to the temperature sensor  128 . 
     In an embodiment, the surface profile  134  of the first plate  126 , the second surface profile  142  of the second plate  140  and the third surface profile  150  of the third plate  146  may be different. In an alternate embodiment, the surface profile  134  of the first plate  126 , the second surface profile  142  of the second plate  140  and the third surface profile  150  of the third plate  146  may be identical to each other. Further, the first plate  126 , the second plate  140  and the third plate  146  may have same thickness i.e. the thickness ‘d’, thickness ‘t’ and thickness ‘h’ are same. In another embodiment, the first plate  126 , the second plate  140  and the third plate  146  may have different thickness i.e. the thickness ‘d’, thickness T and thickness ‘h’ are different. 
     As shown in  FIG. 3 , the screed assembly  120  may further include plurality of position detectors  152 . The position detector  152  may be configured to provide location of the screed plate  124  or any of its other associated component. The position detector  152  may be any one or a combination of a Global Positioning System (GPS), an Inertial Navigation System or any other known position detection system known in the art. The position detector  152  may also receive or determine the positional information associated with the temperature sensor  128 . The positional information from the position detector  152  and a temperature data from the temperature sensor  128  are transmitted to the controller  154  (shown in  FIG. 1 ) for further processing. 
     Referring to  FIG. 1  and  FIG. 3 , the controller  154  may be communicably coupled with the temperature sensor  128 , the position detector  152 , the paving machine  102  and the compactor  104 . In illustration of present embodiment, the controller  154  is located at a remote location. In alternative embodiments, the controller  154  is disposed on the paving machine  102  or on the compactor  104 . In another embodiment, the controller  154  may be located at a remote location. The controller  154  may be a microprocessor or any other electronic device to control a plurality of devices. In an embodiment, the controller  154  may be an electronic control module (ECM). The controller  154  may be configured to receive signals from various devices, but not limited to, the temperature sensor  128  and the position detector  152 . In an alternate embodiment, the controller  154  may also be configured to transmit signals to various devices, but not limited to, a display unit  156 . The controller  154  further includes a memory unit  158  and a processing unit  160 . 
     The memory unit  158  may include one or more storage devices configured to store information used by the controller  154  to perform certain functions related to the present disclosure. The processing unit  160  may include one or more known processing devices, such as a microprocessor or any other device known in the art. In the embodiment illustrated, the memory unit  158  and processing unit  160  may be included together in a single unit. In an alternate embodiment, the memory unit  158  and the processing unit  160  may be incorporated separately. 
     The controller  154  may store a standard temperature data for the paving material. In the embodiment illustrated, the standard temperature data refers to the temperature of the paving material at which a proper finished mat is created on the ground surface. In an alternate embodiment, the memory unit  158  may also store an algorithm to compare the temperature data received from the temperature sensor  128  with the standard temperature requirement. 
     The controller  154  receives the temperature of the paving material from the temperature sensor  128 . The controller  154  is configured to control temperature of the screed plate  124  according to the temperature data received from the temperature sensor  128 , for example, if the temperature of the paving material is lower than the standard temperature, then the controller  154  may transmit signal to increase the temperature of heating elements present in the screed plate  124 . The controller  154  further receives the positional data of the temperature sensors  128  from the position detectors  152 . The sensed position data output from the position detector  152  and the temperature data from the temperature sensor  128  may be recorded onto high capacity discs or cards (not shown) for maintaining a historical record of the thermal profile of the mat surface as laid. 
     The processing unit  160  utilizes information from the position detector  152  and the temperature sensor  128  to formulate a heat map of the ground surface. The heat map indicates the temperature of the paving material at various locations on the ground surface. Further, the controller  154  may transmit the temperature data, the positional data or the heat map to the compactor  104 . 
     The compactor  104  is configured to compact soil, gravel, concrete, or asphalt in the construction of roads and foundations. As illustrated in  FIG. 1 , the compactor  104  includes a compactor frame  162 , having a front compacting drum  164  and a back compacting drum  168  coupled therewith. In an embodiment, the front compacting drum  164  may include a front vibratory apparatus  166  associated therewith, whereas the back compacting drum  168  may also include a back vibratory apparatus  170  associated therewith. The compactor  104  applies variable compaction efforts to the paving material for further compaction after the ground surface is paved by the paving machine  102 . 
     In an illustration of the present embodiment, the compactor  104  may include a receiver  172 . The receiver  172  is configured to receive compactor control commands from the controller  154  based on the temperature data. In an embodiment, the controller  154  may control the variable compaction efforts of the compactor  104  based on the positional data associated with the temperature data. Therefore, the compaction effort of the compactor  104  may be varied based on the different temperatures of the paving material associated with different locations. This helps in ensuring proper compaction of the paving material along the entire mat. The receiver  172  further generates control commands for the front vibratory apparatus  166  and the back vibratory apparatus  170  to vary the compaction efforts i.e. changing energy transfer between compactor  104  and the mat. The front vibratory apparatus  166  and the back vibratory apparatus  170  may have an adjustable vibration amplitude, adjustable vibration frequency and/or adjustable vibration direction. Varying energy transfer could also include turning one or both of front vibratory apparatus  166  and back vibratory apparatus  170  on or off. In an embodiment, the heat map is transmitted to the display unit  156  disposed in the compactor  104 . 
     The controller  154  may be communicably coupled to the display unit  156 . In an embodiment, the display unit  156  may be remotely connected with the controller  154 . In an alternate embodiment, the display unit  156  may be in communication with the controller  154  using a wire. In another embodiment, the display unit  156  may be any portable device which may be operated by a personnel present outside the paving system  100 . The display unit  156  may be configured to display the temperature data from the controller  154 . The display unit  156  may also be configured to display the heat map generated by the controller  154 . The display unit  156  may be included in the paving machine  102 . In an alternate embodiment, the display unit  156  may be positioned in the central station for remotely controlled machines. In an embodiment, the operator may also manually adjust the compaction efforts of the compactor  104  according to the heat map. 
     INDUSTRIAL APPLICABILITY 
     In operation, the paving machine  102  receives the paving material in the hopper  118 , positioned in front of the paving machine  102 . The augers conveys the paving material from the hopper  118  to the rear of the machine with conveyors and distributes the paving material along a desired width. The screed assembly  120  includes the temperature sensor  128 , positioned partly within the thickness of the first plate  126  to measure the temperature of the paving material before it comes in contact with the screed plate  124 . The first plate  126  pre-compacts the paving material and guides the paving material to the screed plate  124 . During paving operations, it is important to receive accurate readings of the temperature of the paving material when it first comes in contact with the screed plate  124 . Further, it is also useful to determine the temperature of the paving material prior to the compaction process by the compactor  104 . The compactor  104  applies variable compaction effort on the mat of paving material formed by the screed plate  124  based on the temperature of the paving material. The determined temperature of the paving material is transmitted to the controller  154 . The controller  154  may control the temperature of the heating elements present in the screed plate  124  according to the temperature of the paving material. The heating of the screed plate  124  helps in better shaping and spreading of the paving material during paving process by the paving machine  102 , when the temperature of the paving material is less than a desired temperature. The controller  154  further generates the heat map of the mat and transmit the heat map to the compactor  104 . The controller  154  controls the variable compaction effort of the compactor  104  according to the heat map and the temperature data. The compaction effort may be varied by varying amplitude and frequency of the vibration of the front vibratory apparatus  166  and/or the back vibratory apparatus  170 . Additionally, the controller  154  may also give instructions to one or more compactors  104  to make additional passes to for desirable compaction of the paving material. 
     Compaction effort necessary to obtain desired degree of compaction depends on the temperature of the paving material. As the temperature sensor  128  provides correct temperature of the paving material, the variable compaction effort of the compactor  104  is controlled. This helps in preventing over compaction or less than optimal compaction of the paving material and thereby ensuring good quality of mat surface. Thus, determination of accurate temperature value of the paving material improves the compaction process and results in the proper finished mat surface. 
     Further, as the plurality of temperature sensors  128  are provided, the controller  154  continue to receive the temperature data of the paving material when one or more of the plurality of temperature sensors  128  fail. Thereby, ensuring smooth functioning of the paving system  100  and proper compaction of the mat surface. 
     While aspects of the present disclosure have seen particularly shown and described with reference to the embodiments above, it will be understood by those skilled in the art that various additional embodiments may be contemplated by the modification of the disclosed machines, systems and methods without departing from the spirit and scope of what is disclosed. Such embodiments should be understood to fall within the scope of the present disclosure as determined based upon the claims and any equivalents thereof.