BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view of one embodiment of the system of the present invention.
FIG. 2 is a side view of one embodiment of the mixer of the system of the present invention.
FIG. 3 is a front view of the embodiment of the mixer of FIG. 2 with springs omitted.
FIG. 4 is a top view of one embodiment of the system with infrared chambers omitted to show the relation between the tines of the preferred mixers.
FIG. 5 is a top view of one embodiment of the system with the infrared chambers cut away to show the preferred igniter and an alternative embodiment of the mixer.
FIG. 6A is a side view of the preferred embodiment of the system of the present invention.
FIG. 6B is a bottom view of system of FIG. 6A with the conveyor belt omitted to show the relationship between the tines of the preferred mixer and: the infrared converters of the preferred infrared chamber.
FIG. 7 is a side view of a preferred embodiment of the system of the present invention for use with recycled asphalt that utilizes multiple conveyor belts to tumble the aggregate and tines to mix the tumbled aggregate.
FIG. 8 is a side view of an alternative embodiment of the system for use with recycled asphalt that utilizes ramps to tumble the aggregate.
DETAILED DESCRIPTION OF THE INVENTION
Referring first to FIG. 1, side view of one embodiment of the system 10 of the present invention is shown. The system 10 includes a conveyor belt 12 in communication with a source (not shown) of the aggregate material 22. The conveyer belt 12 preferably takes the form of conveyor belts currently used to transport aggregate material in conventional HMA and WMA manufacturing processes. The belt may be manufactured of a non-combustible material, such as steel, but is preferably a composition belt manufactured of a rubberized material. Such a material is preferred due its gripping properties and price. The conveyor belt 12 is adapted to convey the aggregate material 22 at a predetermined rate from the source to another location, such as a rotating drying drum (not shown). As shown in FIG. 1, the conveyor belt 12 is in a substantially horizontal position. However, the conveyor belt 12 may be inclined at up to a four to one incline and still effectively convey the aggregate material 22. As discussed below, the conveyor belt 12 may include controls to allow the rate of the conveyor belt 12 to be varied based upon the moisture content or temperature of the aggregate material 22.
The system 10 also includes at least one infrared chamber 14. In the embodiment of FIG. 1, the system 10 includes three infrared chambers 14 that are disposed adjacent to one another along the conveyor belt. However, in other embodiments of the system 10, more or fewer infrared chambers 14 may be utilized. As shown in FIGS. 6A and 6B, each infrared chamber 14 preferably contains eight infrared energy converters 90. These infrared energy converters 90 are preferably of the type manufactured by Ray-Tech Infrared Corporation of Charlestown, N.H., and described in connection with the inventor's U.S. Pat. No. 6,227,762. The infrared chambers 14 are mounted in substantially parallel relation to the conveyor belt 22 and are disposed a distance, preferably, four inches, sufficient to allow infrared radiation to penetrate into the aggregate material 22. The infrared chambers 14 are dimensioned to extend over the entire width of the conveyor belt 12 and are manufactured in different sizes to accommodate different widths of conveyor belts 12; typically thirty, thirty-six, sixty and seventy-two inches. As shown in FIG. 5, in instances where sixty or seventy-two inch wide conveyor belts 12 are utilized, two infrared chambers 14 may be mounted in side by side relation to one another to cover the width of the conveyor belt 12.
The infrared chambers 14 are in communication with a source of fuel 16, preferably propane or natural gas. In the embodiment of FIG. 1, fuel 16 is forced in the infrared chambers 14 by a blower motor 25. The blower motor 25 mixes propane fuel with air and delivers the mixture, under pressure, through the manifold 27 to the infrared converters in the chambers 14 to provide uniform heating. The preferred blower motor 25 also includes a shut off valve (not shown) to shut off the flow of fuel 16 to the infrared chambers 14. A control box 18, which is in electrical communication with the blower motor 24 and a source of power 50, preferably controls the operation of the blower motor 25. As described with reference to other embodiments, the control box 18 may also include other controls, such as ignition controls, and speed controls for the conveyor belt. The use of a blower motor 25 and control box 18 is preferred as it allows the infrared chamber 14 to consistently produce a greater amount of heat than may be produced by relying upon the pressure from the source of fuel 16. However, in other embodiments, both the blower motor 24 and control box 18 are eliminated and the flow of fuel 16 to the infrared chambers 14 is controlled via a manually operated valve (not shown), which opens to allow fuel 16 to flow solely via pressurization from the fuel source and is closed to shut off flow completely.
At least one mixer 20 is disposed between the infrared chambers 14 and the conveyor belt 12. The mixer 20 is dimensioned and disposed relative to the conveyor belt 12 so as to mix the aggregate material 22 during pre-drying. In the embodiment of FIGS. 2 and 3, the mixer includes a channel 30 that is secured to the infrared chambers 14 or another fixed location above the conveyor belt 12. A plurality of tines 33 are rotatably attached to the channel 30. In this embodiment, the tines 33 preferably include a substantially round rod 34 that extends downward and attaches to a short length of channel stock 36, which is angled downward therefrom. The channel stock 36 contacts the aggregate material 22 and mixes the hot top layer 40 with the cool lower layer 42 to form a substantially homogenous mixture 44. The tines 33 are in communication with at least one spring 26 and are disposed in sufficiently close proximity to the conveyor belt 12 so as to contact the aggregate material 22 conveyed by said conveyor belt. The spring 26 allows the tines 33 to flex while preventing them from becoming entangled with the conveyor belt. In the embodiment of FIG. 2 the tines are joined together via a cross bar 29 to form a rake 31 and a single spring 26 is used to maintain the tines 33 in position. However, in the embodiment s of FIG. 3, 6A and 6B, each tine 33 is independent form the other tines 33 and does not include any spring. In still other embodiments, the tines 33 are each independent and each is in communication with its own spring (not shown), preferably a coil type spring disposed about its pivot point.
Referring again to FIG. 1, the preferred system 10 includes at least three, and preferably eight infrared chambers 14. These chambers 14 are disposed in a row over the conveyor belt 12 such that each infrared chamber 14 is disposed relative to an adjacent infrared chamber so as to form a gap 39 therebetween. In these embodiments, one mixer 20 is preferably disposed within each gap 39. As shown in FIG. 4, the mixers 20 preferably include a plurality of tines 33 forming a plurality of spaces 35 therebetween, and each is dimensioned and disposed within each gap 39 such that each tine 33 of one mixer 20 is aligned with a space 35 of adjacent mixers. In this manner, the aggregate material 22 is thoroughly mixed rather than just having the areas adjacent to the tines 33 mixed.
Referring now to FIGS. 6A and 6B, the preferred system 10 is shown. The preferred system 10 includes eight infrared energy converters 90 per infrared chamber 14. An angled reflector 92 is mounted about each infrared converter 90 such that the infrared energy generated by each converter is concentrated downward toward the conveyor belt 12. Each infrared energy converter 90 is arranged in a perpendicular orientation from the direction of travel of the conveyor belt 12 and each infrared energy converter 90 is spaced slightly apart from an adjacent infrared energy converter 90 in order to allow a mixer 20 to be disposed therebetween. In the preferred embodiment, the mixers 20 are disposed approximately twelve inches apart from each other to allow for substantially continuous mixing of the aggregate material 22. However, larger or smaller spacing may be utilized to achieve similar results.
The preferred mixer 20 includes a cross member 94 that attaches to the frame 75 of the infrared chamber 14 and a plurality of tines 33 that are fixedly attached thereto and extend downward toward the conveyor belt 12. The preferred cross member 94 is manufactured of steel and the tines 33 are likewise manufactured of steel and are welded to the cross member 94. As shown in FIG. 6B, the tines 33 are preferably arranged in an angled relationship along each cross member 94 such that the tine 33 attached to one cross member 94 are angled in an opposite direction from the tines 33 attached to an adjacent cross member 94. In this manner, the aggregate material (not shown) is continuously mixed on the conveyor belt. In FIG. 6B, the tines 33 are shown as being welded to the cross member 94 at an angle. Although such welding may be used, it is shown this way in FIG. 6B for the sake of clarity, as it is preferred that the tines be welded in a direction parallel to the direction of travel of the conveyor belt 12 and that the bottom half of each tine 33 be bent at an angle such that the bottoms of the tines 33 are arranged as shown in FIG. 6B. This attachment method is preferred as the perpendicular weld is better able to withstand the forces applied to each tine 33 than a weld at an angle.
As shown in FIG. 6A, the infrared chamber 14 includes a top portion 77 that is attachec to the frame 75 and disposed opposite the portion of the chamber 14 that is proximate to the conveyor belt 12. In the preferred embodiment of the system 10, this top portion 77 is designed to allow moisture to escape through the top portion 77 of the chamber 14. In a preferred embodiment the top portion 77 of the infrared chamber 14 is manufactured of a material, preferably expanded metal, which allows for the escape of such moisture. However, in other embodiments, the chamber 14 includes a plurality of holes (not shown) that are formed therethrough to allow such moisture to be vented.
Referring now to FIG. 5, another embodiment of the system 10 is shown. This embodiment shows an arrangement of eight infrared chambers 14 disposed in side by side relation. The mixers 20 in this embodiment are not hanging tines 20, but rather but rather is a roller 60 from which a series of teeth 62 extend. The roller 60 is disposed across the conveyer belt 12 and adapted rotate during operation such that the teeth 62 contact the aggregate material 22 and mix it together.
The embodiment of FIG. 5 also shows the preferred igniter 66. The igniter 66 is adapted to ignite the fuel 16 within each infrared chamber 14 so that it may be burned and turned into infrared radiation. In the system of FIG. 5, a single igniter 66 is used to ignite the fuel within each of the infrared chambers 14. This preferred igniter 66 is an elongate tube that extends through each chamber 14, is itself in communication with the source of fuel 16, and operates in a manner similar to a conventional pilot light. The use of a single igniter 66 is preferred as it reduces the overall cost and complexity of the system. However, other embodiments utilize multiple igniters, similar to those utilized in conventional propane gas grills, which are each in communication with a single infrared chamber and are controlled by the control box 18 of FIG. 1. In still other embodiments, there are no igniters and an operator manually ignites the fuel within each infrared chamber.
Finally, the embodiment of FIG. 5 include one hygrometer 70 for determining the moisture content of the aggregate at the at least the start of the preheating process and another hygromgeter 70 at the end of the preheating process. In such embodiments, the hygrometers are in communication with a conveyor control (not shown), which slows the conveyor belt 12 or speeds up the conveyor belt 12 based upon the amount of moisture within the aggregate material 22. Thus use of such a control is preferred in when the system is used in connection with warm melt asphalt manufacturing as it allows for careful control of the amount of moisture while maximizing the speed of the process in instances where there are minimal amounts of moisture within the aggregate. In other embodiments, the hygrometer is replaced by a thermometer, which measures the temperature of the aggregate material 22 and controls the speed of the conveyer belt 12 accordingly.
In operation, the conveyor belt 12 conveys the aggregate material 22 from its source and under the infrared chambers 14 at a predetermined rate. The fuel 16 flows to the infrared chambers 14, which burn the fuel 16 causing the infrared chambers 14 to emit infrared radiation therefrom. The infrared radiation contacts the top surface of the aggregate 22 that is conveyed on the conveyor belt and acts to heat the top portion 40 of the aggregate material 22 proximate to said infrared chambers 14. The mixer 20 then mixes the aggregate material 20 such that heated layer 40 and unheated layer 42 of aggregate material 20 are mixed together, allowing the unheated aggregate material proximate to the conveyor belt to rise to the top surface proximate to the infrared chamber. The infrared radiation from the infrared chamber 14 then heats the mixed aggregate material 44 to effectively pre-heat and pre-dry the aggregate material 44.
Experimentation with the system 10 of the present invention has shown that, although the mixers 20 of FIGS. 1-5 work well with non-recycled asphalt aggregate, they are not always effective when used in connection with recycled asphalt aggregate. Accordingly, the inventor developed the alternative systems 10 shown in FIGS. 7 and 8. The system 10 of FIG. 7 utilizes multiple conveyor belts 12 that are spaced apart to allow the aggregate 22 to tumble from one conveyor belt 12 to the adjacent conveyor belt 12. Once tumbled, the aggregate is mixed preferably by moving through the tines 33 of a mixer 20, which is shown as the mixer described in connection with FIGS. 1-4 but may take the form of any of the mixers 20 described herein. This method is preferred in connection with the use of recycled asphalt aggregate material 22 as the tumbling of the aggregate material 20 facilitates the release of moisture therefrom and allows the aggregate to be heated to lower temperatures than would otherwise be necessary to effect drying. This lower temperature heating prevents the asphalt material within the aggregate from changing to a liquid state, which reduces the risk both clumping of the material and of the asphalt igniting during the drying process.
FIG. 8 shows an alternative embodiment of the system of FIG. 7 in which the tumbling action caused by multiple belts 12 is achieved through the use a series of ramps 75 that are disposed proximate to the conveyor belt 12. The ramps 75 each include a ramp surface 76 that is disposed at an angle from a plane formed by the conveyor belt 12 and is dimensioned to allow the recycled asphalt aggregate 22 to pushed up the ramp by aggregate 22 that is in contact with the conveyor belt 12 and to tumble back onto the belt 12, effectively mixing the heated portion 40 of the aggregate 12 and the unheated portion 42 of the aggregate material 22 together. As shown in FIG. 7, once tumbled the aggregate material 22 passes through a mixer 20, which further mixes the aggregate material 22. The embodiment of FIG. 6 shows four ramps 75 that are equally spaced. However, any number of ramps 75 maybe utilized and these ramps may be spaced at any distance apart.
The system 10 of the present invention may be sold in a kit form for inclusion in existing manufacturing processes. Such kits include the infrared chamber(s) 14 and the mixer(s) 20 and are adapted to be installed in asphalt manufacturing plants with existing conveyor belts. Other embodiments of the preheating kit may include any of the options discussed above in connection with the system, and may also include a source of fuel 16.
The invention also includes a method for pre-drying an aggregate material for use in an asphalt manufacturing process. In its most basic form, the method includes the steps of conveying an aggregate material under a source of infrared radiation, first heating a portion of said aggregate material using infrared radiation, mixing said heated portion of said aggregate material with an unheated portion of said aggregate material, and second heating said mixed aggregate material.
The preferred method includes eight heating steps and six mixing steps. Some embodiments of the method also include the steps of measuring the moisture content and/or temperature of the aggregate and controlling the speed of the conveyor belt based upon a result of the measuring step.
Although the present invention has been described in considerable detail with reference to certain preferred versions thereof, other versions would be readily apparent to those of ordinary skill in the art. Further, although the invention was developed for use in connection with aggregates used as paving materials, it is readily adapted for use with aggregates used for other purposes, such as livestock feed, or the like. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained herein.
Patent Application
20070268778
