Abstract:
A method and apparatus for heating hot mix asphalt (HMA), via collecting fumes from HMA while the HMA is on-board a vehicle and in motion within the vehicle, and igniting the HMA with engine exhaust and using the heat of combustion of the HMA to heat HMA, such as via the floor of a re-mix machine or paver which is capable of churning and mixing the HMA which increases emission of HMA fumes.

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to road building and paving equipment, and more particularly relates to methods and apparatuses for heating surfaces of road building and paving equipment. 
     BACKGROUND OF THE INVENTION 
     In the past, road building and paving equipment designers have endeavored to improve the functionality of such equipment. U.S. Pat. No. 5,851,085 to Campbell shows a gravity-fed paver. This patent teaches the use of engine exhaust to the side of the hopper to facilitate flow of material through the gravity-fed hopper to the screed. Equipment has been made where the flow of material has been facilitated by conveyors or augers, etc., such as U.S. Pat. No. 6,007,272 to Macku. In Macku, the apparatus enjoys a lower center of gravity. 
     While these approaches of using heated wall gravity-fed hopper pavers and low profile slat and remix machines have been used extensively in the past, they do have some drawbacks. First of all, the gravity-fed hopper often requires extra height to the hopper so as to allow the application of a significant amount of heat to the side of the hopper and to facilitate delivery of the hot mix asphalt (HMA) backwards to the screed. These heated wall gravity-fed hoppers could have significant disadvantages in stability, as well as often lower capacity and inconvenient HMA loading methods. Secondly, the low profile slat and remix machines require the use of some type of a conveyor because there is either no or insufficient slope in the hopper to cause the HMA to flow backwards. These low profile slat or remix machines require considerable cleanup owing to the propensity for HMA to stick to and remain on surfaces, especially the lower wall or floor of the HMA storage bin or hopper. 
     Consequently, there exists a need for improved methods and systems for deploying a low profile HMA machine with reduced labor associated with cleanup, especially cleanup of the floor of the hopper or bin. Also, some of the solvents typically used to clean up or to prevent sticking are environmentally unfriendly, such as the use of fuel oil or diesel fuel as a solvent. Often these solvents get into the ground and damage vegetation and can get into creeks and streams, and in extreme cases, into water tables. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a system and method for providing low profile HMA paving equipment tools with increased efficiency in cleanup. 
     It is a feature of the present invention to utilize a heated hopper floor in an HMA paving, remix or slat conveyor material transfer machine. 
     It is an advantage of the present invention to reduce the cost, effort and environmental impact associated with use, cleaning and maintaining low profile or flat bottom HMA hopper machines. 
     It is another advantage of the present invention to reduce the horsepower required to move materials in a remix or slat-equipped paver tractor. 
     It is another advantage of the present invention to reduce the wear on remix or slat-equipped paver tractor material conveying parts. 
     It is another feature of the present invention to mix engine exhaust with fumes recovered from HMA to produce useful heat. 
     It is yet another advantage of the present invention to generate, capture and utilize heat from burning the vapor emissions of HMA material in road building equipment. 
     The present invention is an apparatus and method for heating a floor of a hopper of an HMA road building machine, designed to satisfy the aforementioned needs, provide the previously stated objects, include the above-listed features, and achieve the already articulated advantages. The present invention is carried out in a “wasted heat producing fume-less” manner in a sense that waste of heat content or combustible material in HMA vapors from road building machines, has been reduced. 
     Accordingly, the present invention is a system and method including a road building machine which combines engine exhaust (the ignition source) and HMA vapors (the fuel) to burn to and thereby heat floors, halls or surfaces of road building equipment so as to reduce the amount of HMA which sticks to surfaces of the road building machines, together with the aforementioned advantages. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention may be more fully understood by reading the following description of the preferred embodiments of the invention, in conjunction with the appended drawings wherein: 
         FIG. 1  is a perspective partially dismantled view of the heated floor hopper machine of the present invention, with partial cut-away portions or with items removed to expose underlying structure; the double arrows indicate direction of fume flow, and the dashed lines indicate the general area of the engine which has been removed to reveal underlying portion of the invention.  FIG. 6  is identical to  FIG. 1  except that the augers  109  are replaced with a slat conveyor  609 . 
         FIG. 2  is a view of a rear fume collection system of the present invention. 
         FIG. 3  is a perspective view of the heated floor portion of the present invention. 
         FIG. 4  is an exploded perspective view of the heated floor/auger combination of the front hopper portion of  FIG. 1 . 
         FIG. 5  is an exhaust/HMA fume fluid schematic of a circuit of the present invention. 
         FIG. 6  is an alternate embodiment of the present invention shown in  FIG. 1  where the augers  109  are replaced with a slat conveyor  609 . 
         FIG. 7  is a perspective view of a rear end of a paver of the present invention which includes a screed. 
     
    
    
     DETAILED DESCRIPTION 
     Now referring to the drawings wherein like numerals refer to like matter throughout, and more specifically referring to  FIG. 1 , there is shown a central section of an HMA fume/exhaust mix heated floor hopper machine of the present invention, generally designated  100 , which includes a hopper and mixing apparatus  101 , a conveying tunnel  102  (note that portions of the device have been removed to reveal underlying components), auger  109 , driver station  120 , driver seat  122 , engine  126 , shown as a dotted line because it has been removed from the figure to reveal underlining components. and chassis  127 . Items  101 ,  102 ,  109 ,  122 ,  126  and  127  are preferably similar or identical to components of prior art remixing road pavers such as described in the above-referenced Macku U.S. patent and the prior art road paver manufactured by Cedarapids, Inc. of Cedar Rapids, Iowa. Engine  126  is drawn as a simple block, but it may include numerous related systems and/or components not limited to components of a hydraulic pump and system, an electrical system and other systems. The means for moving hot mix asphalt (HMA) from said hopper toward said rear end can be any type of arrangement, such as the conveying tunnel  102  (which extends beneath the engine  126 ) in combination with a plurality of re-mix augers  109 , or it can be a slat conveyor (shown in  FIG. 6 ) which also is disposed in the conveying tunnel  102  or still other ways. Throughout this discussion, reference may be made to an HMA hopper machine, remix machine or slat conveyor transfer machine or the like. It should be understood that the present invention is intended to apply to any HMA device which has an internal combustion engine and which has a surface which is desirable to heat so as to improve performance of the HMA and/or improve the interaction of the HMA with the surface. 
     Now referring to  FIG. 2 , there is shown a rear portion of an HMA hopper machine of the present invention, together with an HMA fume collection system adapted for a rear-mounted HMA elevating conveyor  202 . Rear-mounted HMA elevating conveyor  202  is shown with an elevating conveyor cover  204  and a vacuum fume collection hose  206  which extends from the enclosed areas about the rear-mounted HMA elevating conveyor  202  toward the HMA hopper machine. Also shown is a fume capturing shroud  208  and a vacuum fume collection hose  210 , which are disposed at the rear of the HMA hopper machine. These HMA fume collection systems are believed to be representative of the numerous ways of capturing HMA fumes. Similar to  FIG. 2  in its function of HMA fume collection is a screed version  700  as shown in  FIG. 7 .  FIG. 7  shows a rear portion of a paver tractor  701  having a rear auger  702  which is disposed transversely so as to move material from the center out to the edges of the screed  708 . Above the rear auger  702  is a fume collection hood  704  which is coupled to fume collection hose  706 , which is similar to hose  206  of  FIG. 2 . 
       FIG. 3  is a perspective view of the heated floor of the present invention. The heated floor assembly  300  is intended to convey the details which could be used to implement a heated floor in an HMA hopper re-mix machine. It should be understood that slat conveyor-type HMA transfer machines, as well as any other type of HMA system, could be used, the re-mix type being selected here as being representative. 
     The heated floor assembly  300  has a heated floor bottom  302  which has a heated gas inlet end  304  at one end and a heated gas outlet end  306  disposed in the center. The gases, which are heated from engine exhaust and from the combustion of the HMA fumes, enter through heated gas inlet end  304  and proceed through either duct work  330  ( FIG. 1 ) or other air passages to heated gas inlet ports  312  where the heat gas will flow into a cavity or chamber toward heated gas outlet ports  314  and then out heated gas outlet end  306 . It should be understood that an infinite number of ways could be used to direct the airflow under, around and through any heated floor assembly. The one example shown here is intended to be representative of the many other arrangements which could be employed. In this exemplary embodiment, the heated gas inlet ports  312  are fed from beneath by ducts  330  ( FIG. 1 ) extending outwardly from heated gas inlet end  304 . The heated gas outlet ports  314  are ducted below to the heated gas outlet end  306 , where the heat gases are allowed to escape. In both cases, the ducts  330  are disposed below the heated floor bottom  302  and are best shown in  FIG. 1 . 
     In a preferred embodiment of the present invention the ports  310 ,  312 , and  314  are shown as rectangular holes with a transverse line in a mid section. This line is an end of a slider fume flow control gate which can be adjusted by the user to change the amount of flow through the port. In a preferred embodiment, the slider fume control gates are configured to cause the fumes to flow in a direction which is counter to the flow of the HMA by the augers  109  ( FIGS. 1 and 4 ). This counterflow fume direction is preferred because it applies the hottest fumes to the coolest HMA being carried by the augers  109 . However, in some situations, it may be desirable to use a parallel flow fume direction which can be accomplished by manipulation of the slider fume control gates. It should be understood that other forms of control of fumes through the port other than a slider gate could be utilized as well, such as valves, doors, etc. 
     The present invention may be more fully understood by now referring to  FIG. 4 , which shows a partially and differentially exploded view of the heated floor remix auger combination assembly  400  of the present invention. 
     There are shown four remix augers  109 . The two augers labeled  404  are shown exploded from the curved auger elevated floor segments  402 , while the two augers labeled  406  are shown exploded with the curved auger elevated floor segments  408  away from the heated floor bottom  302 . End caps  310  are shown and serve to enclose the area above the heated floor bottom  302  and below the curved auger elevated floor segments  402  and  408 . This is the cavity in which the heated air circulates and thereby heats the curved auger elevated floor segments  402  and  408  and thereby heats the HMA disposed in the hopper and mixing apparatus  101 . 
     Now referring to  FIG. 5 , there is shown a simplified diagram of the circuit of fluids used in the HMA heating process of the present invention. 
     There is shown a fume fan  502  which creates a vacuum and thereby pulls in fumes from the HMA via vacuum fume collection hose  206  or other hoses, etc. The HMA fumes are blown into an exhaust and HMA fume combination/combustion area  504  where engine exhaust from the engine ignites the HMA fumes and cause combustion and release of energy as heat. The now hotter mixture of exhaust and HMA fumes (post combustion) is blown into surface to be heated  506 . This can be a heated floor cavity as described herein, or it can be any type of apparatus or assembly which can transfer heat from the burnt or possibly still burning HMA fumes into a surface which contacts HMA. The heating of the surface which contacts the HMA surface tends to heat the HMA itself and tends to reduce sticking of the HMA to the surface. Numerous reasons and approaches to heating the HMA or HMA contacting surfaces may be employed. Once the combusted or re-heated mixture of HMA fumes and exhaust transfers heat to the desired surface, it then can be exhausted to the exhaust pipe  508  to atmosphere. 
     In operation, the apparatus and method of the present invention as described in  FIGS. 1-5  could function as follows: 
     Firstly, a hopper machine  100  is provided which accepts HMA in a hopper and mixing apparatus  101  and transports it rearward via conveying tunnel  102 . 
     Fumes are collected off the HMA at the rear of the hopper machine or in any implement which is deployed behind the hopper machine and directed back toward the hopper. Exhaust from the engine  126  is collected and directed toward the hopper. The fumes from the HMA and the engine exhaust are mixed. Due to the high temperature of the engine exhaust, the fumes from the HMA burn, giving off heat. 
     This combustion of HMA fumes results in generation of more heat which is used to heat the floor of the hopper machine  100 . 
     After the combustion occurs, the product heat and the engine exhaust vapors are circulated under the heated floor of the paver  100  where heat is transferred to the heated floor and the re-heat/combusted HMA and exhaust vapors exit the paver through exhaust pipe  508 . 
     Throughout the above description, HMA is described as the material to be used. It should be understood that the present invention is directed to any type of road surface. It is believed that recycled asphalt products could be used, cold mix asphalt, and even in certain applications with any appropriate modifications, concrete could be the paving material. In some of these alternate or non-HMA materials, it should be noted that they may not produce or emit any combustible fumes. Hopper and mixing apparatus  101  may comprise a rectangular box or an angled rectangular or circular bin or any shaped container and material mixing and transfer apparatus which is suitable for the paving material being used. It is also contemplated that the floor of the hopper bin could be heated with a source other than engine exhaust and other than combustion of HMA fumes. An independent fuel or means for heating of air to be blown beneath the floor of the hopper bin is also contemplated. 
     It is thought that the method and apparatus of the present invention will be understood from the foregoing description and that it will be apparent that various changes may be made in the form, construct steps, and arrangement of the parts and steps thereof, without departing from the spirit and scope of the invention or sacrificing all of their material advantages. The form herein described is merely a preferred exemplary embodiment thereof.