Abstract:
A device is shown for transporting asphalt repair materials for use in repairing potholes in asphalt pavements. The device has a body with a hopper compartment for transporting and dispensing asphalt mix materials. A dry, radiant heat source is located in a heating chamber below the hopper compartment and heats the asphalt mix. Exhaust stacks in communication with the dry heat means have a damper system for retaining heat within the heating chamber, the damper system being electronically controlled in response to the temperature within the body of the device.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to truck and/or trailer mounted portable devices for dispensing pavement repair materials and, specifically, to such a portable device for dispensing repair materials for asphalt pavements. 
     2. Description of the Prior Art 
     In the past, as many as three vehicles were sometimes needed to repair openings and potholes in asphalt, concrete and other roadway surfaces. One vehicle provided an air compressor for use with various pneumatic repair tools which were used to dress the hole, crack or cavity to be filled. Another vehicle contained liquid asphalt tack material which would be sprayed into the dressed cavity, and a third vehicle would deliver asphalt mix material to the cavity. The asphalt would then be packed, compacted and leveled by hand to complete the repair. 
     U.S. Pat. No. 4,196,827, issued Apr. 8, 1980, entitled “Portable Machine For Transporting Heated Asphalt Products For Use In Repair Asphalt Pavement” shows a portable machine which was designed to incorporate all phases of the pavement repair into one mobile unit. The machine has a hopper for transporting asphalt mix, and a reservoir below the hopper having a heat source. The reservoir contained liquid asphalt tack material. The heat source is used to heat the liquid tack material, and the tack material is used to heat the asphalt mix in the hopper by heat transfer. Asphalt tack material is also dispensed from the tack material tank by means of spray equipment connected to a discharge valve on the rear of the truck. 
     In spite of being less expensive to operate in terms of material and labor, the previously described device possessed several different disadvantages. For example, the liquid asphalt tank carried on the unit was suitable for road oils and cutbacks but was not well suited for use with asphaltic cements. Also, in the case of the device described in the &#39;827 patent, the liquid asphalt tank was not suited for use with asphalt emulsions, because the volatile contents of the emulsions would be driven off and dry out the materials. 
     U.S. Pat. No. 4,944,632, issued Jul. 31, 1990, and assigned to the assignee of the present invention showed a portable unit with a separate tack oil tank which was provided with its own heat source and which was designed to prevent phase separation of the tack oil materials to overcome some of the deficiencies of the prior art devices. This tank could be used successfully with both emulsions and asphalt cutback oils. 
     Both of the prior art devices utilized a liquid heat transfer medium to heat the asphalt hopper of the device and maintain the asphalt mix materials therein in a workable state. While a liquid heat transfer medium has been used successfully for many years to heat the asphalt hopper, there are disadvantages associated with the use of a liquid medium. Many of these disadvantages relate to the release of volatile components of the medium as it is repeatedly heated during use. The liquid medium must also be maintained and/or replaced at regular maintenance intervals. 
     Accordingly, it is an object of the present invention to replace the liquid heat transfer medium used in the prior art to heat the hopper compartment of an asphalt repair apparatus with a dry, radiant heat source which does not require refill and which does not emit volatile organic emissions to the atmosphere. 
     Another object of the invention is to provide such a dry, radiant heat source for an asphalt repair apparatus which heat source safely and effectively heats the asphalt repair materials without hardening, burning or charring such materials. 
     Another object of the invention is to provide a means for retaining heat from the dry, radiant heat source within the device of the invention, limiting heat loss when the heat source is not operating. 
     Another object of the invention is to provide such an apparatus which is simple in design and economical to manufacture. 
     SUMMARY OF THE INVENTION 
     The portable apparatus of the invention is used to transport heated pavement repair materials for use in repairing roadways and other traffic bearing surfaces. The device includes a body adapted to be mounted on a portable base for transporting the body to a repair site. The body has a hopper compartment with a V-shaped bottom wall for transporting asphalt mix material and a generally V-shaped heating chamber located below the hopper compartment. The V-shaped bottom wall of the hopper compartment defines an upper extent of the heating chamber. A screw conveyor is mounted in the bottom of the hopper compartment for dispensing asphalt mix materials therefrom. An agitator, such as a paddle shaft, is located above the screw conveyor in the hopper compartment for agitating the hopper materials. A dry heat means is associated with the heating chamber for heating the chamber and for transferring heat to the hopper compartment through the hopper bottom wall to maintain the asphalt mix materials in a workable state. 
     Preferably, the V-shaped bottom wall of the hopper compartment forms an upper, uninsulated common wall with the heating chamber. The heating chamber also has oppositely extending, insulated bottom wall portions. In a preferred embodiment of the invention, the dry heat means comprises a pair of oppositely arranged retort tubes located within the heating chamber on either side of the V-shaped bottom wall of the hopper. The retort tubes are heated by a thermostatically controlled gas burner for supplying dry, radiant heat to the bottom wall of the hopper. Each retort tube forms a single pass loop which has a burner installed at one extent thereof and which communicates with an exhaust stack at the opposite extent thereof. In a preferred arrangement, each retort tube is provided in the shape of an inclined U arranged in a plane which is generally parallel to a selected one of the oppositely extending, insulated bottom wall portions of the heating chamber. Each retort tube has a pair of outlets to the exterior of the tank, one of the outlets having the burner mounted therein and the other of the outlets being connected to the exhaust stack. 
     A damper system is installed in the exhaust stacks for limiting heat loss from the heating chamber. A damper in each exhaust stack remains in the open position while the burners are operating to provide adequate air flow for the burners. A control system monitors an output signal from a thermostat mounted in the heating chamber, and, when the heating chamber has reached a desired temperature, the control system turns off the burners and actuates a solenoid that moves the dampers to a closed position. This prevents heated air from flowing out of the exhaust stacks, retaining heat within the heating chamber. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features believed to be characteristic of the invention are set forth in the appended claims. The invention itself however, as well as a preferred mode of use, further objects and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is a perspective view, partly broken away, of the body of the present invention showing the radiant heat source and exhaust stacks thereof and prior to installation of the damper system; 
     FIG. 2 is a front view, partly broken away, of the exhaust stacks of FIG. 1 with the damper system installed; 
     FIG. 3 is a side view of the exhaust stacks of FIG. 2; 
     FIG. 4 is a side view of the lever arm of FIG. 2; 
     FIG. 5 is a end view of the body of FIG. 1 showing the damper system and exhaust stacks installed; and 
     FIG. 6 is a schematic view of the electronic control system of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows a portable device  11  used for heating asphalt prior to application of the asphalt to a surface. Device  11  is available commercially under the trademark Pro-Patch from H.D. Industries of Jacksonville, Tex. 
     Device has a body  12  containing a hopper compartment  13  having a V-shaped bottom wall  15 . A paddle shaft  17  is located near a lower portion of bottom wall  15 , paddle shaft  17  being rotated to agitate asphalt in hopper  13 . Asphalt flows downward in hopper  13  and is dispensed by a screw conveyor  19 , which rotates to move portions of asphalt longitudinally and out of hopper  13 . 
     Asphalt in hopper  13  is heated using retort tubes  21 ,  23  located in a heating chamber  24  under bottom wall  15 . Each tube  21 ,  23  is U-shaped, tubes  21 ,  23  connecting to an outer wall  25  of device  11  and being in communication with the exterior of device  11 . Tube  21  begins at inlet  27  and ends at outlet  29 , and tube  23  begins at inlet  31  and ends at outlet  33 . Burners  35 ,  37 , preferably for use with propane, are located in inlets  27 ,  31 , respectively, for producing heat within tubes  21 ,  23 , which radiantly heat bottom wall  15 . When burners  35 ,  37  are not operating, an electric heater  39  located in heating chamber  24  may be used to heat bottom wall  15 . 
     Outlets  29 ,  33  are connected to an inner surface  45  of each exhaust stack  41 ,  43  at an opening  47  located near the lower end of each stack  41 ,  43 . In this embodiment, exhaust stacks  41 ,  43  are formed of rectangular metal tubing and are oriented vertically near outer wall  25 . Exhaust stacks  41 ,  43  provide for adequate air flow while burners  35 ,  37  are operating and provide a path for heat to move from within tubes  21 ,  23  to the exterior of device  11 . 
     To improve retention of heat within device  11  when burners  35 ,  37  are not operating, an electronically-controlled damper system is installed in exhaust stacks  41 ,  43 . The damper system is shown partially installed in FIGS. 2 and 3 and fully installed and attached to device  11  in FIG.  5 . 
     Referring to FIGS. 2 and 3, stacks  41 ,  43  are shown detached from device  11  (FIG.  1 ). To provide space between inner surface  45  and outer wall  25 , an extension  49  is attached to each opening  47  and standoffs  51  are mounted to inner surface  45 . Extensions  49  are cylindrical and have a radius approximately equal to that of openings  47  and slightly less than the radius of outlets  29 ,  33 , allowing the ends of extensions  49  to fit within outlets  29 ,  33 . A stop  53  is located on the upper portion of each extension  49  for limiting the amount of extension  49  that can be inserted into outlets  29 ,  33 . In this embodiment, standoffs  51  are formed as rectangular boxes and serve as the upper point for attaching inner surface  45  of exhaust stacks  41 ,  43  to outer wall  25  (FIG.  1 ). 
     A damper  55  is rotatably mounted within each exhaust stack  41 ,  43  just below standoff  51 . Dampers  55  are formed from flat plates and are sized to block the interior of stacks  41 ,  43  when rotated from a vertical orientation towards a horizontal orientation. Dampers  55  rotate on an axis that is parallel to inner surface  45 . A small shaft  57  extends inward from each damper  55 , shafts  57  being fixedly attached to dampers  55  and coaxial with the axis of rotation of dampers  55 . A central rod  59  is connected at its outer ends to the inner ends of shafts  57  by couplers  61 , rotation of rod  59  causing rotation of dampers  55 . A lever arm  63  is mounted to a central portion of rod  59 . As shown in the profile view of FIG. 4, lever arm  63  has a hole  65  for receiving rod  59  and an elongated hole  67  for connecting lever arm  63  to an actuator. 
     FIG. 5 shows exhaust stacks  41 ,  43  and damper system installed on device  11 . Rod  59  is connected to shafts  57  with couplers  61 , and lever arm  63  is attached to rod  59 . A solenoid  69  has a connector  71  and is mounted to body  12 . Elongated hole  67  (FIG. 4) of lever arm  63  is rotatably attached to connector  71 , allowing solenoid  69  to rotate rod  59  and dampers  55  when solenoid  69  is actuated to move connector  71  vertically. 
     In addition to the mechanical components, the damper system comprises electrical sensors and control components. A thermostat  73  is mounted within body  12  and near heating chamber  24 , thermostat  73  producing an output signal relative to the temperature within heating chamber  24  that is monitored by a control module  75 . Control module  75  is also mounted within body  12  and controls the operation of burners  35 ,  37  and controls solenoid  69  to open and close dampers  55  in response to the output signal from thermostat  73 . 
     FIG. 6 is a schematic drawing of the electronic controls for the damper system of the preferred embodiment. Thermostat  73  is connected to control module  75  through leads  77 ,  79 , and  81  and through contact block and terminal block  85 . To provide power for the electrical components, a battery  87  is connected to control module  75  through leads  89  and  91 , with circuit breaker  93  connecting leads  89 ,  91 . Leads  95  and  97  provide for grounding of control module  75  and battery  87 , respectively. Wiring harness  99  provides a three-wire connection between solenoid  69  and control module  75 . 
     Referring to the figures, in operation, a volume of asphalt mix materials is placed in hopper compartment  13  to be heated and dispensed for use in repairing an asphalt pavement. When thermostat  73  produces an output signal that indicates a low temperature in heating chamber  24 , control module  75  sends electrical signals through wiring harness  99  that cause solenoid  69  to move or remain in an extended position, opening dampers  55  in exhaust stacks  41 ,  43 . Control module  75  also commands burners  35 ,  37  to begin operation, a flammable gas being injected into burners  35 ,  37  and ignited. The heat from burners  35 ,  37  heats retort tubes  21 ,  23 , which begin to radiate heat to the lower surface of bottom wall  15 , heating hopper  13  and the asphalt within hopper  13 . Since dampers  55  are open, heated air flows out of outlets  29 ,  33  of retort tubes  21 ,  23  and through exhaust stacks  41 ,  43 , ensuring adequate air flow for proper functioning of burners  35 ,  37 . When asphalt is heated to a workable state, screw conveyor  19  is rotated to dispense asphalt while paddle shaft  17  rotates to reduce bridging of the asphalt within hopper  13  and ensure a steady supply of asphalt to screw conveyor  19 . 
     When the output signal from thermostat  73  indicates the temperature of heating chamber  24  has reached a desired temperature, control module  75  commands burners  35 ,  37  to cease operation and commands solenoid  69  to move to a retracted position, closing dampers  55 . With dampers  55  closed, heated air is prevented from flowing out of retort tubes  21 ,  23 , limiting heat loss from heating chamber  24 . As the temperature in heating chamber  24  decreases to below the desired temperature, control module  75  commands solenoid  69  to reopen the dampers  55  and commands burners  35 ,  37  to reignite. Dampers  55  also remain closed when electric heater  39  is used to heat heating chamber  24 . 
     While the invention has been shown in only one of its forms, it is not thus limited but is susceptible to various changes and modifications without departing from the spirit thereof.