Abstract:
A debris shield is disclosed for preventing debris from being sucked into the recirculate inlet of certain trucks used in the rental truck industry and thereby clogging the air conditioning evaporator coils and other components of the air conditioning system. The shield includes a segmented frame configured to fit over an opening of the system in such a way that any debris sucked into the recirculate inlet within the cab encounters and is arrested by the shield before reaching sensitive components. A method of shielding an automotive air conditioning system from entrained debris also is disclosed.

Description:
REFERENCE TO RELATED APPLICATION 
       [0001]    Priority is hereby claimed to the filing date of U.S. provisional patent application 62/040,267 filed on Aug. 21, 2014, the entire content of which is hereby incorporated by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    This disclosure relates generally to automotive air conditioning and air handling systems and more particularly to air conditioning and air handling systems of medium and heavy duty work trucks such as those used in the truck rental industry. 
       BACKGROUND 
       [0003]    Thousands of medium and heavy duty work trucks are rented to individuals each year by companies such as U-Haul® and others. These trucks are used by renters for short and long haul moving, local hauling, and other purposes. One common truck model used by these companies is the Ford® E Series® truck, platform, to which various trailer configurations may be mounted. 
         [0004]    Truck rental companies have for some time endured a problem with the air conditioning and air handling systems (hereinafter referred to simply as the air conditioning system or AC system) of their truck cabs. More specifically, the interior it air inlets of these systems, which draw in air in the recirculate mode of the system, are located near the floorboard of the cab. When individuals use trucks they have rented for moving, they tend to drop a significant amount of debris into the floorboard. This debris can include, for example, food. paper, hair from pets carried in the cab, dust, and other items. Such debris tends to be drawn into the recirculate inlet near the floorboard of the cab and become stuck on the AC evaporator coil and other components within the system As a result, the evaporator coil and other components relatively quickly begin to clog with debris.  FIG. 1  illustrates the appearance of an actual evaporator coil from a Ford® E Series® rental truck cab after having become clogged with debris. This clogging, in turn, significantly shortens the life cycle of air conditioning coils and components, which must be replaced a more frequent basis. Replacement of evaporator coils in its rental trucks is an expensive and unwanted repair for truck rental companies, 
         [0005]    A need therefore exists for an apparatus and method for preventing debris from entering the air conditioning systems of rental trucks and other medium and heavy duty trucks. It is to the provision of such a method and apparatus that the present invention is primarily directed. 
       SUMMARY 
       [0006]    Briefly described, the invention disclosed in exemplary embodiments herein is a retro-fit debris shield for air conditioning systems of certain truck cabs. The debris shield, when installed, prevents debris from entering the air conditioning systems from the interior of the cab, particularly when the air conditioning systems are operating, in recirculate mode. The debris shield comprises a frame that is segmented and configured to fit over an air inlet opening of the air conditioning system upstream of the evaporator coil and other sensitive components. In one embodiment, an air permeable mesh material spans and is supported by the frame and has a mesh size sufficiently small to prevent airborne debris such as pet hair and dust from passing through the mesh. A truck rental company, as part of routine maintenance, need only remove a plastic kick plate within the cab, insert the debris shield into its designated location, and reinstall the kick plate. Thereafter, debris is arrested by the debris shield and does not pass downstream to the evaporator coil and other components of the system, which consequently do not become prematurely clogged. Replacing the debris shield on a regular maintenance schedule is easy inexpensive, and significantly increases the life cycles of downstream components of the air conditioning system. 
         [0007]    These and other features, aspects, and advantages of the debris shield and method will become more apparent upon review of the detailed description set forth below taken in conjunction with the accompanying drawing figures which are briefly described as follows. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a photograph of an evaporator coil from a Ford® E Series® truck cab after having been in service in a rental truck. 
           [0009]      FIG. 2  is a perspective view of a debris shield according to one embodiment of the present invention. 
           [0010]      FIG. 3  shows a lower portion of the debris shield of the present invention installed over the inlet of the air conditioning system of a rental truck. 
           [0011]      FIG. 4  shows an upper portion of the debris shield of the present invention installed over the inlet of the air conditioning system of a rental truck, 
           [0012]      FIGS. 5   a  through  5   f  show in sequence a preferred method of installing a debris shield of the present invention onto the air conditioning system of a rental truck, 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    As mentioned above, passenger cabins of trucks after used in the rental truck industry, such as the Ford® E Series® truck, exhibit a problem in that the air intake of the air conditioning system often ingests debris such as dust, hair, leaves, food, and other items during use of the truck by renters. This causes the evaporator coils of the air conditioning systems of such trucks to become clogged prematurely with debris, requiring costly repairs.  FIG. 1  illustrates an evaporator coil removed from a Ford® E Series® rental truck cab after a nominal period of use. The evaporator coil  1  has cooling vanes  2  through which metal tubing extends. Evaporating refrigerant flows through the tubing, which chills the vanes of the coil. Air is circulated by a fan (not shown) through the evaporator coil and into the passenger cabin and thus cools the passenger cabin. In the recirculate or “max cool” mode of such an air conditioning system, cabin air is drawn into a recirculate intake behind the dash of the passenger cabin, passes though the evaporator coil, into the cabin, and is drawn again back into the recirculate intake. The air is thereby “recirculated” through the passenger cabin to effect quick or maximum cooling in hot environments. It is in this recirculate mode that debris from the cabin floorboard and floating debris from the cabin environment is drawn into the recirculate inlet and clogs the evaporator coil and other components. 
         [0014]      FIG. 2  shows a debris shield according to one embodiment of the invention for blocking debris that otherwise might be drawn into the air conditioning system as described above. The debris shield  5  preferably is made of molded plastic and includes a mid-portion  6 , an upper portion  7 , a lower portion  8 , and a bottom cage  10 . The upper portion and the mid-portion are attached to one another by means of a living hinge  11  so that the upper portion  7  can articulate with respect to the mid-portion in the direction indicated by arrows  12 . Similarly, the bottom cage  10  is attached to the bottom portion  8  by means of a living hinge  13  so that the bottom cage can articulate along the hinge  13  with respect to the lower portion  8 . 
         [0015]    The upper, mid, and lower portions each comprise a peripheral frame  9  that is spanned by numerous intersecting ribs  14  that together define a mesh. The mesh formed in the lower portion  8  and the cage  10  has significantly smaller opening sizes than the mesh in the mid and upper portions for reasons discussed in more detail below. Various slots  16 , fastener holes  17  and offsets  18  are a part of the debris shield. These features help to conform the debris shield  5  to structures of the air conditioning ductwork and allow for its attachment to the ductwork with fasteners such as screws. 
         [0016]      FIG. 3  shows a portion of a debris shield according to this invention installed in the cab of a Fore E Series truck to prevent debris from being drawn into the recirculate inlet of the air conditioning system. In this image, a kick-plate covering has been removed and the debris shield has been installed covering an air inlet opening. Air for the recirculate inlet normally is drawn in through an air inlet opening  26  in the air conditioning ductwork. The air is drawn through air inlet opening  26  of the air conditioning system, which is located near the firewall  27  of the cab. At least part of the air inlet opening  26  normally is just above the floorboard and/or transmission cowl  23  of the passenger cabin, and therein lies the problem. Debris from the floorboard is rather easily drawn into the air inlet opening resulting in a clogged evaporator coil as discussed above. In  FIG. 3 , the lower portion of the debris shield covers the lower portion of the opening  26  and the arcuate bottom cage  18  extends downwardly therefrom substantially to the floorboard. The cage  18  curves back upwardly so that it can rest against and/or be attached to the floorboard and/or ductwork at the bottom of the air inlet opening  26 . The living hinge  13  allows the cage  18  to articulate with respect to the lower portion  8  of the debris shield to, among other things, facilitate installation and attachment to the ductwork. 
         [0017]    It can be seen in  FIG. 3  that the slots  16  formed in the frame of the debris shield align with and receive various features such as reinforcement ribs  27  that may be a part of the air conditioning system ductwork. Once in place, the debris shield can be attached to the ductwork by means of screws  24  or other appropriate fasteners. The offsets  18  formed in the frame of the debris shield allow the shield to conform to the shapes of structures such as the edge of a firewall cover as illustrated in  FIG. 3 . While not shown in  FIG. 3 , the frame and openings of the debris shield  5  also may support a finer mesh material such as a non-woven fabric mat for arresting airborne debris or pieces of floorboard debris that are smaller than the mesh openings formed by the ribs  14  of the debris shield. While it is not necessarily intended that such a finer mesh material function as a traditional cabin air filter, some filtering of airborne dust and other material may nevertheless occur when the AC system is in the recirculate mode. 
         [0018]      FIG. 4  illustrates the mid-portion  6  and upper portion  7  of an installed debris shield covering duct  26  of the air conditioning system ductwork. Again, the slots accommodate ribs and the frame of the debris shield is attached to the ductwork of the air conditioning system with screws. The living hinge  11  permits the upper portion  7  of the debris shield to articulate inwardly with respect to the mid-portion. In this way, the upper portion can more easily extend along and conform to the top portion of the air inlet opening  26  such that the entire opening between through which air is drawn is covered by the debris shield when installed. The debris shield thus prevents or greatly reduces ingestion of unwanted debris from bottom adjacent the floorboard of the cabin all the way to the top of the opening far above the floorboard. Further, the finer mesh material  14  ( FIG. 2 ) attached to the debris shield provides a barrier for smaller pieces of debris such as food, paper, and the like. These types of debris are more likely to congregate on the floorboard of the vehicle near the lower portion and the cage of the debris shield. 
         [0019]      FIGS. 5   a  through  5   f  show sequentially one preferred method of installing the debris shield of this invention in the cab of a truck, in this case a Ford® E Series® truck. In these figures, a finer mesh material  39  in the form of a non-woven fabric mat is shown spanning and supported by the frame and mesh of the debris shield to provide a barrier for tiny or airborne debris particles as well as larger ones such as food. In  FIG. 5   a,  the debris shield is prepared by pre-bending the upper portion along the living hinge  11 . In the embodiment of the debris shield shown in these figures, the upper portion itself may be divided into two sections by a separate living hinge so that the upper portion can be pre-bent into an L-shape as shown in  FIG. 5   a.    FIG. 5   b  shows the pre-bent debris shield being inserted top first upwardly through the opening between the ductwork and the firewall.  FIG. 5   c  shows the debris shield being moved further upwardly. 
         [0020]    In  FIG. 5   d,  the debris shield has been moved completely upwardly into the opening and the bottom cage of the debris shield is located near the bottom of the opening. In the process of moving the debris shield to this position the upper portion of the debris shield engages the top of the opening. Further upward movement of the debris shield from this point causes the pre-bent upper portion to begin to bunch up and thereby conform to the contours of the upper portion of the opening. This is perhaps best seen in  FIG. 4  where the upper portion  7  is seen to be bent in such a way that it conforms to the contours of the ductwork surround the upper portion of the opening. In  FIG. 5   e,  the arcuate bottom cage of the debris shield is pressed into place engaging at the bottom of the opening. After this step, the debris is in position and can be attached to the ductwork of the air conditioning system with screws as shown in  FIG. 3 . The final result is shown in  FIG. 5   f  where the debris shield is seen to be in tight fitting conformance with the periphery of the opening completely covering the inlet opening through which air is drawn into the air conditioning system. 
         [0021]    With the debris shield installed as described, and debris from the floorboard or elsewhere that might otherwise be drawn into the air conditioning system engages and is stopped by the debris shield, and particularly the arcuate bottom cage portion and the lower portion. Lighter and/or airborne debris is stopped by all portions of the debris shield. Eventually, the debris shield itself may be become somewhat clogged with debris that has been captured. At this point, and more preferably on a predetermined maintenance schedule, the debris shield is simply and easily replaced with an inexpensive new debris shield. As a consequence, the air conditioning evaporator coil and other internal components of the air conditioning system are kept cleaner and more clog-free thus prolonging their life and saving substantial money in repairs for truck rental companies. 
         [0022]    The invention has been described herein in terms of preferred embodiments and methodologies considered by the inventor to represent the best modes of carrying out the invention. It will be understood by the skilled artisan, however, that a wide array of additions, deletions, and modifications, both subtle and gross, may be made to the exemplary embodiments presented herein without departing from the spirit and scope of the invention itself. For example, while the shape of the shield illustrated herein has been designed for use with a particular model of truck, debris shields of other shapes and configurations might well be designed for installation in other truck models. In such cases, the installation methodology also might be a bit different due to different configurations of air conditioning ductwork in such other truck models. These and other modifications are possible all within the spirit and scope of the invention as delineated only by the claims hereof.