Abstract:
An aerodynamic device is disclosed for limiting aerodynamic drag on the rear surface of various types of trucks with trailers. The aerodynamic device includes a plurality of rigid members and a flexible sheet designed to create a pyramid-shaped projection pointing away from the rear surface of the trailer. The device members can be quickly disassembled and the flexible sheet collapses so that the aerodynamic device lies flat against the rear surface of the trailer. The aerodynamic device can be attached directly to doors on the rear surface of a trailer or to a mounting frame that may rotate around to the side of the trailer where a roll-up style door is present.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to an aerodynamic device for use on vehicles such as trucks with trailers, and more specifically to a deployable structure that is easily assembled to improve the fuel efficiency of a vehicle and easily disassembled and stored unobtrusively on the vehicle when the device is not in use. 
       BACKGROUND 
       [0002]    The design of a vehicle has typically been governed, at least in part, by both cosmetic and utilitarian considerations. Cosmetic-based design features are intended to enhance the visual appeal of a vehicle to the consuming public. Utilitarian-based features, on the other hand, are designed to achieve the intended purpose of the vehicle. For example, the engine and vehicle size are determined, in part, by how many passengers the vehicle will carry, or what size load will be transported. In recent years, cosmetic and utilitarian concerns have merged to increase focus on preserving cosmetic appeal, while also making the vehicles more efficient so as to reduce fuel costs. 
         [0003]    The amount of power needed to move a vehicle increases as a function of the vehicle speed because of aerodynamic drag. The amount of power necessary to overcome that increased drag directly translates to increased fuel consumption, and thus increased cost of operation. In the United States trucking industry, an estimated 1.7 million trucks use 23 billion gallons of diesel fuel every year, and 65-70% of the energy expended in fuel is to overcome aerodynamic drag on the truck and trailer. Many aerodynamic improvements have been made to the front sides of trucks and trailers to minimize costly aerodynamic drag. These improvements have helped the average fuel economy in the trucking industry rise from 4.5 miles per gallon in the 1980&#39;s to approximately 6 miles per gallon today. 
         [0004]    While those aerodynamic design improvements at the front of a truck and trailer have resulted in some improvement to fuel economy, aerodynamic drag remains a costly problem. This problem is exacerbated by the typical design of the back end of most trailers, which is vertically squared-off. This squared-off rear end creates significant drag on the vehicle, which consumes large amounts of fuel. As with any vehicle, when the trailer body moves through the air, a mass of air is displaced and must flow around the trailer. As the air flows toward the squared-off back end of a trailer, an area of low pressure is created. This area causes a sudden, high-energy, chaotic inrush of turbulent air which creates drag on the rear of the trailer. 
         [0005]    Aerodynamic drag reduction systems in the prior art have not been widely accepted or commercially successful in the trucking industry. The most significant drawbacks in almost all known systems are the following: (1) the complicated processes for installing the systems on a vehicle, (2) the need to permanently modify the vehicle to install the system, (3) the functional difficulties added by the installation and operation of the device such as unloading and loading for trucks with trailers, and (4) the time-consuming nature of deploying and stowing the systems at each loading or unloading station. 
         [0006]    While many solutions to improve the aerodynamic drag at the rear of the truck and trailer have been suggested, none have been widely adopted in the United States by trailer manufacturers or trucking companies. Various reasons have caused this dilemma. First, trailer manufacturers generally design a trailer to maximize its interior cargo space given fixed external dimensions mandated by federal highway regulations. Consequently, aerodynamic design is not the manufacturer&#39;s primary design concern. Second, trailers are often loaded and unloaded at loading docks which require the driver to back the trailer up flush against the loading dock. Any aerodynamic device, therefore, must be easily removable or repositionable to ensure flush loading with the dock. 
         [0007]    There is clearly room for improvement in aerodynamic devices for trailers to overcome the above-mentioned issues. For instance, it would be desirable to create an aerodynamic device that significantly reduces the aerodynamic drag on a trailer caused by the squared-off back end of the trailer. Such a device should also be quick and easy to collapse or deploy during load transfers. It would also be desirable to create such a device inexpensively in order to entice the trucking industry to adopt widespread use of this device. 
       SUMMARY OF THE INVENTION 
       [0008]    The invention relates to an aerodynamic device for mounting on the rear surface of vehicles such as trucks with trailers. The aerodynamic device comprises two device halves that create a pyramidal shape when the apparatus is deployed. This pyramidal shape lowers aerodynamic drag because it eliminates the sharp change in direction the air experiences as it passes beyond the end of the trailer&#39;s sides and roof. This reduces an area of low pressure at the rear of those vehicles which would otherwise cause turbulent air disturbances and aerodynamic drag. 
         [0009]    One embodiment of this invention includes device halves which each comprise an upper support member and a lower support member that are rigid bars with first and second ends, an angled connection element to couple the second ends of each support member, upper and lower anchor elements attached to the rear surface of the vehicle for coupling the first ends of the support members to the perimeter of the rear surface, and a flexible sheet connected to the perimeter of the rear surface and the support members to create a half-pyramid. The upper anchor element is a hinge-style joint allowing the upper support member to pivot only in a vertical plane transverse to the rear surface of the vehicle. The angled connection element and the lower anchor element both have pin slots for quick insertion and locking of the lower support member which has pins on both ends. 
         [0010]    A method for installing a device half of this embodiment is also disclosed. First the flexible sheet is affixed to a portion of the upper support member, and the first end of the upper support member is connected to the upper perimeter of the rear surface of the vehicle. Similarly, the flexible sheet is next affixed to a portion of the lower support member, and the first end of the lower support member is connected to the lower perimeter of the rear surface. Then the second ends of the upper and lower support members are connected to each other. Finally, the flexible sheet is connected to the upper and lower perimeter of the rear surface to create a half-pyramid shape. 
         [0011]    Another embodiment is adapted to work with vehicles such as trucks and trailers with roll-up style doors instead of two vertically-hinged doors. With this door style, the anchor elements cannot be attached directly to the door. Instead, two mounting frames are installed around the perimeter of the rear surface and all the elements of one device half of the above-described embodiment are attached to the mounting frames. These mounting frames are U-shaped frames that hinge around the side edge of the rear surface of the trailer. The mounting frames also have brackets installed on the rear and side surfaces of the trailer to hold a vertical bar portion of the frame in place against the rear surface or side surface of the trailer. All the remaining structural elements are generally the same as the above-described embodiment, but the anchor elements and the flexible sheet connection points are all on the mounting frame instead of the doors. When the aerodynamic device is retracted or stowed away flat against the rear surface of the vehicle, the mounting frame can then be rotated 270 degrees around the rear surface&#39;s side edge and coupled to the brackets on the side surface. The truck can then back up flush against a loading ramp and the roll-up door is completely unimpeded. 
         [0012]    Still another embodiment is designed for use on roll-up style doors. This embodiment is comprised of a single unit instead of the two device halves of the other embodiments. In this embodiment, the mounting frame is a U-shaped frame which hinges around a side edge of the rear surface. Unlike the earlier-described U-shaped frame, the frame extends to cover the entire rear surface instead of just half. The remaining structural elements of this embodiment are generally the same as those in one device half of the other embodiments, with the exception that the flexible sheet is bigger to create a full pyramid when the apparatus is deployed instead of just half a pyramid. Just as in the embodiment with mounting frames described above, the anchor elements and flexible sheet are all coupled to the mounting frame instead of the rear surface of the vehicle. A set of brackets located on the rear surface and side surface of the vehicle are used to hold the mounting frame in different positions depending on whether the device is deployed or retracted. This embodiment deploys and retracts substantially like the above-described embodiments, but with fewer structural elements. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and, together with a general description of the invention given above, and the detailed description given below, serve to explain the principles of the invention. 
           [0014]      FIG. 1  is a perspective view of an aerodynamic device according to one embodiment of the invention attached to the rear surface of a trailer. 
           [0015]      FIG. 2  is a perspective view of the aerodynamic device of  FIG. 1  showing the interior components of each device half. 
           [0016]      FIG. 3  is a side view of one half of the aerodynamic device of  FIG. 1  without the flexible sheet. 
           [0017]      FIG. 4  is an exploded view showing the structural elements of a device half. 
           [0018]      FIG. 5  is a perspective view of a lower anchor element. 
           [0019]      FIG. 6  is a perspective view of an upper anchor element. 
           [0020]      FIG. 7  is a perspective view of another embodiment of the invention adapted to work with roll-up style doors. 
           [0021]      FIG. 8  is a perspective view of another embodiment of the invention adapted to work with roll-up style doors. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    One embodiment of the invention is shown in  FIGS. 1-6  with an aerodynamic device  10  attached to a rear surface  12  of a vehicle  14 . As illustrated, the vehicle  14  is a trailer with two doors  13  hingedly attached to the rear surface  12  so that they can open outward from the center of the rear surface  12  and swing back along the sides of the trailer. It will be appreciated that this embodiment could be used for other cargo transport vehicles.  FIG. 1  shows how the aerodynamic device  10  appears when it is being used. The device  10  has two device halves  16   a ,  16   b  that are each covered by a flexible sheet  18 . Collectively, the two device halves  16   a ,  16   b  form a generally pyramidal shape. Although it is not shown in this embodiment, a connector or coupling device could be used near the outward point of the pyramid to hold the two device halves  16   a ,  16   b  together. 
         [0023]      FIG. 2  shows the interior structural elements of the aerodynamic device  10  without the flexible sheet  18 . Each device half  16   a ,  16   b  comprises an upper anchor element  20  attached to a door  13  on the rear surface  12 , an upper rigid member  22  coupled to the upper anchor element  20 , an angled connection element  24  coupled to the upper rigid member  22 , a lower rigid member  26  coupled to the angled connection element  24 , and a lower anchor element  28  which couples the lower rigid member  26  to the rear surface  12 . A partial outline of the flexible sheet  18  is shown by dashed lines  30  in  FIG. 2 . 
         [0024]    A side view of the aerodynamic device  10  is shown in  FIG. 3  as it would look deployed without the flexible sheet  18 . As can be seen in the one visible device half  16   a  of  FIG. 3 , the upper rigid member  22  and the lower rigid member  26  are approximately as long as the distance between the upper anchor element  20  and the lower anchor element  28 . This configuration creates an approximate equilateral triangle with sides being the upper rigid member  22 , the lower rigid member  26 , and the rear surface  12  of the vehicle  14 . 
         [0025]    As shown in  FIGS. 1-2 , the flexible sheet  18  for one device half  16   b  is attached around the perimeter of the door or rear surface  12  at certain points  32 ,  34 ,  36 ,  38 . The flexible sheet  18  can be made of any suitable material such as weatherproof durable fabric. The flexible sheet  18  is generally fixedly attached to the rear surface  12  at the points  32 ,  34 ,  36  so as not readily removed. In contrast, the flexible sheet  18  is easily detachable from the rear surface  12  at point  38  near the door handles  15  to allow ready access to the door handles  15 . This removable connection point  38  also allows for access to the interior structural elements when needed to deploy or retract the aerodynamic device  10 . More connection points around the perimeter of the rear surface  12  can also be added to further secure the flexible sheet  18  to the vehicle  14 . It will be appreciated that the flexible sheet  18  may also be easily detachable from the rear surface  12  at points  32 ,  34 ,  36  to permit access to other areas of the rear surface  12 . In this embodiment, the flexible sheet  18  further comprises two interior sleeves  17 ,  19  that fit respectively around the upper rigid member  22  and the lower rigid member  26 . These interior sleeves  17 ,  19  hold the flexible sheet  18  in a proper orientation. 
         [0026]      FIGS. 4-6  show the interior structural elements of one device half  16   a  in more detail. In this embodiment the upper anchor element  20  is a hinge-style anchor that allows the upper rigid member  22  to only pivot in one plane away from the rear surface  12 . The upper anchor element  20  also has a storage element  60  such as a sleeve adapted to hold the lower rigid member  26  when the aerodynamic device  10  is retracted. For example, the upper anchor element  20  in the embodiment shown in  FIG. 6  comprises a base plate  58 , the storage element  60 , and a generally flat projection  62  extending perpendicular to the base plate  58  and having a pin hole  64  cut there through. The upper rigid member  22  has a first end  42  adapted to couple the upper rigid member  22  to the upper anchor element  20 . In the embodiment of  FIG. 4 , the first end  42  of the upper rigid member  22  comprises at least two generally flat legs  63  with at least one pin hole  65  cut through each leg  63 . The flat legs  63  then fit over the flat projection  62  so that a pin can be inserted through pin holes  64  and  65  to pivotally couple the upper rigid member  22  to the upper anchor element  20 . The upper rigid member  22  has a second end  44  that is rotatably attached to the angled connection element  24  such that it is free to rotate around the long axis of the upper rigid member  22 . 
         [0027]    The angled connection element  24  has a pin slot  46  on the opposite end from the connection to the upper rigid member  22 . As shown in  FIG. 4 , the angled connection element  24  is a hinge joint comprising two element halves  23 ,  25 , each including at least one leg  27 ,  29 , respectively, and a hinge pin  31  coupling the legs  27 ,  29  of the respective element halves  23 ,  25 . The element halves  23 ,  25  can then rotate in one plane about the hinge pin  31 . One skilled in the art will appreciate that the angled connection element  24  could also be a solid angled joint without this hinging capability. The lower anchor element  28  is attached to the lower perimeter of the door  13  or rear surface  12  and comprises an operational sleeve  48  and a storage element  50  such as a sleeve, each designed to accept the lower rigid member  26 . The operational sleeve  48  and the storage element  50  each have a pin slot  47  as shown in  FIG. 5 . The lower rigid member  26  has a pin  52  near each end designed to fit into the pin slots  46 ,  47  on the angled connection element  24  and the lower anchor element  28 . It will be appreciated by one skilled in the art that alternate locking pin mechanisms can be used in this arrangement, including a pin slot being cut into the lower rigid member  26  and an internal pin on the interior surface of the lower anchor element  28  adapted to engage that pin slot. It will further be appreciated by one skilled in the art that the storage element  60  of the upper anchor element  20  and the operational sleeve  48  and storage element  50  of the lower anchor element  28  may include flanges adapted to allow the lower rigid member  26  to enter the sleeve or element(s) even if not exactly angled correctly. 
         [0028]    The invention also contemplates a method for constructing or deploying the aerodynamic device  10 . First the flexible sheet  18  is connected to connection points  32 ,  34 ,  36 ,  38  around the perimeter of the rear surface  12 . Next the upper rigid member  22  is slid into the sleeve  17  of the flexible sheet  18 , and the lower rigid member  26  is similarly slid into the sleeve  19  of the flexible sheet  18 . Then the first end  42  of the upper rigid member  22  is coupled to the upper anchor element  20  as described previously. The lower rigid member  26  is then inserted as shown by arrow  72  into the operational sleeve  48  of the lower anchor element  28  with the pin  52  on the lower rigid member  26  entering the pin slot  47  on the lower anchor element  28 . The upper rigid member  22  is pivoted away from the rear surface  12  of the vehicle  14  and the angled connection element  24  is rotated around the other end of the upper rigid member  22  to line up the pin slot  46  on the angled connection element  24  with the pin  52  on the other end of the lower rigid member  26 . Once the lower rigid member  26  is fully inserted as shown by arrows  72 ,  74  into both the angled connection element  24  and the lower anchor element  28 , the lower rigid member  26  is rotated so that the pins  52  lock into the ends of the pin slots  46 ,  47 . After these steps have been completed for both device halves  16   a ,  16   b , the aerodynamic device  10  has been deployed. 
         [0029]    To retract or stow away the aerodynamic device  10  when a truck arrives at a loading dock, for example, the following steps may be taken. First the removable connection point  38  of the flexible sheet  18  must be detached from the rear surface  12  of the vehicle  14 . Next the lower rigid member  26  is removed from the angled connection element  24  and the lower anchor element  28  by twisting the pins  52  out of the respective pin slots  46 ,  47 . The lower rigid member  26  is then slid out of the sleeve  19  of the flexible sheet  18 . The lower rigid member  26  is then stored in the storage elements  50 ,  60  and locked into the pin slot  47  of storage element  50  to lie flat against the rear surface  12 . Finally, the upper rigid member  22  pivots downward toward the rear surface  12  of the vehicle  14 , and the angled connection element  24  can be rotated to lie flat against the rear surface  12 . Now the entire aerodynamic device  10  is lying flat against the rear surface  12  and access to the door handles  15  is available. This method can be repeated for both device halves  16   a ,  16   b  at a loading dock. 
         [0030]    Another embodiment of the invention shown in  FIG. 7  is adapted to work with vehicles having roll-up style doors  113 . In this embodiment, an aerodynamic device  110  has generally the same elements as the embodiment shown in  FIGS. 1-6 , but additional elements and features are described as follows. Each device half  116   a ,  116   b  now further comprises a mounting frame  182  which includes an upper frame member  184 , a lower frame member  186 , and a vertical frame member  188 . The upper and lower frame members  184 ,  186  are coupled to hinges  190  on a side edge  192  of the rear surface  112 . The vertical frame member  188  holds each device half  116   a ,  116   b  in place by coupling to brackets  194  located on the rear surface  112 . Side brackets  198  on the side surface  196  are used to secure the device half  116   b  to the side surface  196  when the device half  116   b  is swung away from the rear surface  112  (as shown in phantom). 
         [0031]    Instead of attaching to the rear surface  112 , the upper and lower anchor elements  120 ,  128  attach directly to the mounting frame  182 . Similarly, the flexible sheet  118  connects to the mounting frame  182  rather than the rear surface  112 . The flexible sheet  118 , upper rigid member  122 , angled connection element  124 , and lower rigid member  126  assemble and disassemble in generally the same manner as the other embodiment described above. When the elements are stowed flat against the mounting frame  182 , the entire device halves  116   a ,  116   b  can be rotated 270 degrees around the side edge  192  and locked flat against the side surface  196  using brackets  198 . This embodiment maintains the functionality of both the aerodynamic device  110  and the roll-up style door  113 . 
         [0032]    Another embodiment of the invention shown in  FIG. 8  is adapted to work with vehicles having roll-up style doors  213 . In this embodiment, an aerodynamic device  210  has many of the same elements and characteristics of the above-described embodiments, but the two device halves  16   a ,  16   b  are replaced with a single mechanical assembly of elements attached to a single, albeit larger, mounting frame  282 . The larger mounting frame  282  again has an upper frame member  284 , a lower frame member  286 , and a vertical frame member  288 . The upper and lower frame members  284 ,  286  are coupled to hinges  290  on a side edge  292  of the rear surface  212 . The vertical frame member  288  holds the mounting frame  282  in place by coupling to brackets  294  located on the rear surface  212 . Side brackets  298  on the side surface  296  are used to secure the mounting frame  282  to the side surface  296  when the mounting frame  282  is swung away from the rear surface  212  (as shown in phantom). 
         [0033]    Like the other embodiments, this embodiment includes an upper anchor element  220 , an upper rigid member  222 , an angled connection element  224 , a lower rigid member  226 , a lower anchor element  228 , and a flexible sheet  218 . Each of these elements function like those described above, but the anchor elements  220 ,  228  and the flexible sheet  218  now couple to the large mounting frame  282  near the center of the rear surface  212 . The flexible sheet  218  is also larger in this embodiment to create a one-piece pyramid shape. Other than these new features, the device functions substantially the same as the previous embodiment described. One skilled in the art will realize the various elements and frame members of each embodiment can be made out of any suitable material. 
         [0034]    This invention is not to be limited by what has been particularly shown and described, except as indicated by the following claims.