Abstract:
Disclosed are improved lightweight rear fairings that automatically retract when the rear doors of the trailer are opened. The fairings preferably each include rearwardly extending arms that stretch back from the hinged trailer doors to sheet rollers. The sheet rollers apply tension to fairing sheets that are secured to both the rollers and the sides of the trailer. The arms are able to rotate relative to the rear doors of the trailer, however rotation limiters restrict the amount that each of the arms may rotate towards the hinge of their respective door. Rotation of the arms away from the door hinges is not limited such that the arms may be rotated away from the hinges until they are flush with their respective doors. The fairing sheets are secured to the sides of the trailer at positions that are substantially forward of the rear doors such that even when the rear doors have been fully opened the rollers are still located rearward of the forward attachment points of the fairing sheets.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to an aerodynamic fairing for an over-the-road cargo container, and more particularly to a fairing that automatically retracts when the doors of the cargo container are opened. 
     BACKGROUND OF THE INVENTION 
     In 2004, the SmartWay Transport Partnership was created by several companies and the United States Environmental Protection Agency with the goal of advancing environmentally responsible logistics and transportation. In 2010, the California Air Resources Board program implemented rules requiring EPA SmartWay-approved fairings to be attached to trailers to reduce the aerodynamic drag on the trailers. Between 2010 and 2015, a dramatic increase in the number of trailers equipped with fairings has occurred with a corresponding increase in development and improvement of these fairings. 
     Two of the more common fairings that have been attached to over-the-road trailers are skirts secured to the underside of the trailer and rear drag reducers that extend from the back doors of the trailer. Each of these fairings present their own set of challenges. Being low to the road, the skirts are often damaged when the trailers pass over railroad tracks. The rear drag reducers are elevated away from the road and are less likely to be damaged from road debris, but the rear drag reducers increase the overall length of the trailer and must be disassembled, disengaged, or removed when the contents of the trailer are to be unloaded through the rear doors. 
     A Notable attempt that was made to solve some of the problems associated with trailer fairings includes the device disclosed in U.S. Pat. No. 7,431,381 issued to R. Wood that claims to cover “an improved method and device for the reduction of aerodynamic drag and for improved performance of bluff base vehicles by increasing the pressure on the bluff base of the vehicle by controlling the wake flow and the interaction of the wake flow with the vehicle bluff base region.” 
     SUMMARY OF THE INVENTION 
     The present invention provides improved lightweight rear fairings that automatically retract when the rear doors of the trailer are opened. The fairings preferably each include rearwardly extending arms that stretch back from the hinged trailer doors to sheet rollers. The sheet rollers apply tension to fairing sheets that are secured to both the rollers and the sides of the trailer. The arms are able to rotate relative to the rear doors of the trailer, however rotation limiters restrict the amount that each of the arms may rotate towards the hinge of their respective door. Rotation of the arms away from the door hinges is not limited such that the arms may be rotated away from the hinges until they are flush with their respective doors. The fairing sheets are secured to the sides of the trailer at positions that are substantially forward of the rear doors such that even when the rear doors have been fully opened the rollers are still located rearward of the forward attachment points of the fairing sheets. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a rear perspective view of two retractable fairings for reducing the parasitic drag of an over-the-road trailer. 
         FIG. 2  shows an upper rear perspective view of two retractable fairings fully deployed and secured to the rear of an over-the-road travel trailer. 
         FIG. 3  shows an upper rear view of two retractable fairings fully deployed and secured to the rear of an over-the-road travel trailer. 
         FIG. 4  shows a top view of two retractable fairings fully deployed and secured to the rear of an over-the-road travel trailer. 
         FIG. 5  shows a side perspective view of a single retractable fairing fully deployed and secured to the rear of an over-the-road travel trailer. 
         FIG. 6  shows a top perspective view of a single retractable fairing fully deployed and secured to the rear of an over-the-road travel trailer. 
         FIG. 7  shows a top view of a partially retracted fairing secured to the rear door of an over-the-road trailer. 
         FIG. 8  shows a side perspective view of a partially retracted fairing secured to the rear door of an over-the-road trailer. 
         FIG. 9  shows a top view of a retractable fairing secured to a rear trailer door that has been opened 90 degrees. 
         FIG. 10  shows a side perspective view of a retractable fairing secured to a rear trailer door that has been opened 90 degrees. 
         FIG. 11  shows a top view of a retractable fairing system on an opening door wherein the fairing system has a rotor arm beginning to rotate away from the hinge of the opening door. 
         FIG. 12  shows a side perspective view of a retractable fairing system on an opening door wherein the fairing system has a rotor arm beginning to rotate away from the hinge of the opening door. 
         FIG. 13  shows a top view of a retractable fairing system on an opening door wherein the fairing system has a rotor arm that has rotated away from the hinge of the door, but is not yet adjacent to the side wall of the trailer. 
         FIG. 14  shows a perspective view of a retractable fairing system on an opening door wherein the fairing system has a rotor arm that has rotated away from the hinge of the door, but is not yet adjacent to the side wall of the trailer. 
         FIG. 15  is a top view of a retractable fairing system secured to a trailer door that has been fully opened. 
         FIG. 16  is a rear perspective view of a retractable fairing system secured to a trailer door that has been fully opened. 
         FIG. 17  is a front perspective view of a retractable fairing system secured to a trailer door that has been fully opened. 
         FIG. 18  is a close-up perspective view of a rotation arm secured to a trailer door with a rotation mechanism wherein a rotation limiter restricts how far the rotation arm may rotate towards the hinge of the trailer door. 
         FIG. 19  is a close-up top view of a rotation arm secured to a trailer door with a rotation mechanism wherein a rotation limiter restricts how far the rotation arm may rotate towards the hinge of the trailer door. 
         FIG. 20  is a side view of a roller secured to a trailer door via a rotation arm and rotation mechanism. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention may be used with any type of cargo container that experiences drag and is particularly suited for containers that travel at high speeds and are frequently loaded and unloaded. However, for descriptive purposes the present invention will be described in use with over-the-road trailers. 
       FIGS. 1 through 4  show an over the road trailer  5  with a left door  10  and a right door  15  above a wheel assembly  20 . The left door  10  is secured to the left side  25  of the trailer  10  via a left hinge  30  that rotates about a left vertical axis of rotation  35 . The right door  15  is secured to the right side  40  of the trailer  5  by a right hinge  45  that rotates about a right vertical axis of rotation  50 . A left fairing system  55  is secured to both the left side  25  of the trailer  5  and the left door  10  while a right fairing system  60  is secured to the right door  15  and the right side  40  of the trailer  5 . In an exemplary embodiment, the left and right fairing systems ( 55  and  60 ) are symmetrical about a centerline  65  that bisects the trailer  5  and generally passes through the intersection of the left door  10  and the right door  15 . 
     In the illustrated examples, each of the fairing systems ( 55  and  60 ) includes a C-shaped bar  70  with an upper bar  75  secured to the roller top on the fairing system, a lower bar  80  secured to roller tops on the fairing systems, and a vertical bar  85  that extends between the upper and lower bars ( 75  and  80 ). Horizontally extending from the vertical bars is a horizontal bar  90  that connects to the horizontal bar  90  of the other fairing system. The C-shaped bars help to stabilize the fairing system by reducing the amount of rotational torque that is exerted upon the doors of the trailer. In an exemplary embodiment, a locking system is used to secure the horizontal bars together when the fairings are in use such that the fairing system adds an additional layer of security for the contents of the over-the-road trailer. 
       FIGS. 5 and 6  illustrate the left fairing system  55  in detail. While not shown, it should be appreciated that the right fairing system  60  has similar features that mirror those of the left fairing system. Securing the left fairing system  55  to the left door  10  is a rotation mechanism  95  that includes an upper rotor and a lower rotor that are shown in more detail in  FIGS. 18 through 20 . The rotation mechanism  95  is spaced a first distance  100  from the left vertical axis of rotation  35  that is surrounded by the left hinge  30 . Extending away from the rotation mechanism  95  on the left door  10  is a rotation arm  105 . At the distal end of the rotation arm  105  is a sheet tensioner  110  or roller that acts to pull on a first end of a fairing sheet  115 . The rotation arm  105  and sheet tensioner  110  extend back from the left door  10  a second distance  120 . In the illustrated example, the rotation arm  105  and the portion of the left door  10  between the rotation mechanism  95  and the left hinge  30  forms an angle,  122  that is a right angle. As explained in more detail in other portions of the specification, a rotation limiter blocks the rotation of the arm such that the angle  122  may be a right angle or an obtuse angle, but not an acute angle. 
       120  that is a right angle. As explained in more detail in other portions of the specification, a rotation limiter blocks the rotation of the arm such that the angle  120  may be a right angle or an obtuse angle, but not an acute angle. 
     The rearward most end of the fairing sheet  115  is secured to the sheet tensioner  110  that acts to pull the rearward most end of the sheet towards the forward most end of the sheet. As the door transitions from a fully closed orientation (shown in  FIG. 6 ) to a fully open orientation (shown in  FIGS. 15 and 16 ) the amount of fairing sheet  115  between the two ends decreases and the sheet tensioner  110  acts to take up the slack sheet such that the fairing sheet  115  remains taught as it is deployed or retracted. 
     At the forward most end of the fairing sheet  115  is a mount  125  that is secured to the left side  25  of the trailer. In the illustrated embodiment, the mount  125  is a vertically oriented track with a C-shape that is configured to secure a bulbous front end of the fairing sheet  115 . In an exemplary embodiment, the vertically oriented track has a selectively openable bottom end that allows a user to feed the bulbous end of the fairing sheet up the track and then close the opening when the bulbous end is fully secured within the track. In the illustrated example, the track of the mount  125  fully extends from the top of the cargo container to the bottom of the cargo container, however it should be appreciated that multiple spaced-apart tracks may be utilized as a single mount and still be within the scope of the invention. 
     The mount  125  is located a third distance  130  from the left hinge  30  that surrounds the left vertical axis of rotation  35 . In the illustrated example, the sum of the first distance  100  plus the second distance  120  is less than the third distance  130 . As the doors of the trailer are opened, the three distances do not change however the spatial relationship between the three distances does change. 
     In the fully deployed configuration that occurs when the doors of the trailer are closed, the fairing sheet  115  includes two primary planar surfaces, the forward primary planar surface  135  and the rearward primary planar surface  140  are joined by an intermediary surface  145  that is adjacent to the left hinge  30 . As can be seen in  FIG. 5 , the intermediary surface  145  of the fairing sheet is adjacent to substantially all of the left hinge  30 . In other words, in the fully deployed configuration, the left hinge  30  is almost fully covered by the fairing sheet  115 . As illustrated in  FIG. 6 , substantially all of the forward primary planar surface is located adjacent to the left side  25  of the container, the intermediary surface  145  of the fairing sheet  115  is located adjacent to the left hinge axis, and a portion of the fairing sheet  115  is wound around the sheet tensioner  110 . 
     The rearward primary planar surface  140  acts to turn the abrupt 90 degree edge of the door into a smoother transition that guides air towards the back of the trailer. As the trailer is moving at high speeds, a low air pressure zone is created behind the rear doors which creates a parasitic drag on the trailer and reduces the overall fuel efficiency of the tractor trailer combination. With the addition of the rearward primary planar surface  140 , the air is directed into the region of low pressure that forms behind the trailer and the parasitic drag experienced by the tractor trailer combination is decreased. While the aerodynamic impact of the forward primary surface  135  is not as significant as the rearward primary planar surface  140 , the forward primary planar surface  135  creates a smooth side surface and a smooth transition to the rearward primary surface  140 , both of which contribute to the overall aerodynamic characteristics of the trailer. 
     As can be seen in  FIG. 6  as well as  FIGS. 12 and 20 , in the illustrated example there are snag reducers  150  that surround the left vertical axis of rotation and slightly offset the fairing sheet  115  from the left hinge  30 . The snag reducers  150  act to provide a slight gap between the fairing sheet  115  and the left hinge  30  such that when the fairing sheet flexes or moves it will not rub against or snag upon the left hinge  30 . In an exemplary embodiment, the snag reducers are constructed of polytetrafluoroethylene such that the surfaces are resistant to being coated by road grime that could act as an abrasive upon the fairing sheet  115 . 
       FIGS. 7 and 8  illustrate an example of a fairing system on a door that has been opened a sufficient amount such that the forward primary planar surface  135  and the rearward primary planar surface  140  have become a single planar surface as the fairing sheet  115  is no longer bent around the snag reducers  150  and/or the left hinge  30 . As the door is opened past the configuration shown in  FIGS. 7 and 8 , the left fairing system  55  begins to exert an opening torque on the left hinge  30  such that the left door  10  will automatically open without further interaction from the operator of the trailer. In  FIGS. 7 and 8  (as well as in  FIGS. 5 and 6 ), the sheet tensioner  110  is pulling the fairing sheet almost directly away  155  from the left hinge  30 /left vertical axis of rotation  35 . As a result of the direction of the exerted force, there is practically no rotational torque exerted by the left fairing system  55  in  FIGS. 5 through 8 . As the door is opened past the configuration shown in  FIGS. 7 and 8 , the rotational torque exerted on the left hinge  30  is increased such that the trailer door may open automatically without further intervention of the operator of the trailer. The exact amount the door must be opened for automatic continued opening to occur will depend on several factors that include the pulling strength of the sheet tensioner  110 , the length of the first distance  100  and the second distance  120 , the internal friction of the left hinge  30 , and the orientation of the trailer. For example, it will be more difficult for the left fairing system to fully open the left rear door of a tractor trailer that is parked facing up a steep hill compared to a the left door of a tractor trailer that is parked on flat ground. 
     While the left fairing system  55  does not exert a substantial torque on the left hinge  30  in the examples shown in  FIGS. 5 through 8 , the pulling by the sheet tensioner  110  does exert a torque upon the rotation mechanism  95  that is proportional to the second distance  120 . To counteract this torque, in an exemplary embodiment, the sheet tensioners  110  include C-shaped bars  70 , highlighted in  FIGS. 1-3 and 8 , which balance the pulling forces of the sheet tensioners. In  FIGS. 1-3 , the two C-shaped bars  70  are connected to each other through horizontal bars  90 , however in  FIG. 8  the horizontal bar  90  has been rotated downward such that it is fully adjacent to the vertical bar  85 . The C-shaped bars  70  may also be allowed to rotate relative to the sheet tensioners  110  such that they do not limit the amount that the doors may be opened. For example, if an exemplary C-shaped bar was shown in  FIG. 15 , it would have rotated to be located primarily between the mount  125  and the sheet tensioner  110  instead of between the sheet tensioner  110  and the left door  10 . 
       FIGS. 9 and 10  show the left fairing system  55  where the left door  10  has been opened 90 degrees relative to a fully closed position. In the illustrated example, the sheet tensioner  110  is no longer pulling the sheet in a direction  155  directly away from the left hinge  30  so an opening torque is applied to the left hinge  30  that acts to automatically pull the left door  10  into the fully opened position shown in  FIGS. 15 through 18 . While the rotational torque may not be as high as in  FIGS. 11 and 12  where the sheet tensioner is pulling orthogonal to the left vertical axis of rotation, in an exemplary embodiment the rotational torque exerted on the configuration shown in  FIGS. 9 and 10  is sufficient to automatically open the door. 
       FIGS. 11 and 12  illustrate the moment in the rotation of the left door  10  when the rotation arm  105  begins to rotate about the rotation mechanism  95  away from the left hinge  30  or left vertical axis of rotation  35 . In  FIGS. 5 through 10  the sheet tensioner  110  has been at a changing location, but at a constant distance from the left hinge  30 /left vertical axis of rotation  35 . Starting at  FIGS. 11 and 12  in the opening process, the sheet tensioner  110  begins to increase its separation from the left hinge  30 . In the illustrated example, there is a sheet length  160  between the sheet tensioner  110  and the mount  125  when the rotation arm  105  begins to rotate about the rotation mechanism  105 . The relationship between the sheet length  160  and door rotation at the moment the rotation arm  105  begins to rotate away from the left vertical axis can be represented as: 
               S   L     =           D   4   2     -     D   2   2         -     D   1             
wherein S L  is the sheet length  160 , D 4  is the third distance  130 , D 2  is the first distance  100 , and D 1  is the second distance  120 . As highlighted in  FIG. 11 , the sheet tensioner  110  is located a substantial distance  165  from the left side  25  of the trailer  5  when the rotation arm  105  begins to rotate away from the left vertical axis of rotation  35 .  FIG. 12  also highlights the series of snag reducers  150  that are secured about the left hinge  30  to protect the fairing sheet  115  from snags and tears. The slightly larger diameter of the snag reducers  115  relative to the left hinge  30  can be seen in the figure. In an exemplary embodiment, each of the snag reducers  150  circumscribes the left vertical axis of rotatation  35  and are able to freely rotate about the axis such that they act like bearings for the fairing sheet  115 .
 
       FIGS. 13 and 14  illustrate a door that has almost been fully opened. As highlighted in  FIG. 13 , the angle  122  that was a right angle in  FIG. 6  has become an obtuse angle. The sheet tensioner  110  has increased its distance from the left hinge  30 . While the substantial distance  165  shown in  FIG. 11  has been decreased, there is still separation between the left side  25  of the trailer and the sheet tensioner  110 . 
       FIGS. 15 through 17  show doors that are in a fully opened configuration with fully retracted fairing systems. In  FIG. 15 , the sheet tensioner  110  is pressed against the left side  25  of the trailer at a first point of contact  170  that is located a fourth distance  175  from the left vertical axis of rotation  35 . In the illustrated example, the square root of the first distance  100  squared plus the second distance  120  squared is substantially less than the length of the third distance  175 . If the rotor arm  105  had not rotated away from the left vertical axis of rotation  35 , the square root of the first distance  100  squared plus the second distance  120  squared would have been substantially equal to the length of the third distance  175 . It should be appreciated that in some embodiments the left side of the trailer will include thin wear plates configured to contact the sheet tensioner  110 . The applicant herein defines the thin wear plates to be part of the left side  25  with regards to determining the first point of contact for the left side  25 .  FIG. 15  also highlights how the first point of contact  170  is located between, and distant from, both the left hinge  30  and the mount  125  that secures the forward end of the fairing sheet  115 . 
     While the various fairing configurations have been discussed in detail with regards to the process that occurs when the trailer door is opened, the process of deploying the fairing is simply the reverse process of retracting the fairing with the exception of the retractable fairing not automatically closing the trailer door after a certain stage of the process has been reached. Like the door opening process where the fairing automatically retracts when the door was opened, the deployment of the rear fairing occurs automatically when a user closes the trailer doors. 
       FIGS. 18 and 19  show detailed illustrations of the rotation mechanism  95  and the rotation arm  105  near the left door  10 . In the illustrated example, the rotation mechanism includes a vertical cylinder  180  that passes through a tube  185  secured to the left door via a fastener  190 . The tube  185  is constructed to allow the rotation arm  105  to rotate on a horizontal geometric plane while maintaining the same elevation. In the illustrated example, the vertical cylinder  180  is formed as a continuous construction with the rotation arm, however it should be appreciated that in other embodiments the components of the rotation mechanism  95  will be completely distinct from the components of the rotation arm  105 . A rotation mechanism  95  is shown that limits the rotation of the arm  105  towards the left hinge. The rotation limiter includes a protrusion  200  that extends horizontally from the vertical cylinder  180 . A block  205  is positioned such that when the rotation arm  105  rotates to a right angle  122  relative to the left door  10 , the protrusion  200  contacts the block  205  and prevents further rotation of the arm  105 . In the illustrated example, a rotation limiter  195  is shown as a distinct feature from the rest of the rotation mechanism  95 , but the inventor contemplates single piece rotation mechanisms. For example, instead of utilizing a separate block, the protrusion of the vertical cylinder could be configured to travel a specific path in the tube  185  that limits the rotation of the arm.  FIG. 19  illustrates yet another type of a rotation limiter where a length of wire  210  is stretched from a first point  215  on the left door  10  to a second point  220  on the rotation arm  105 . The length of wire is configured such that when the wire  210  is taught, the rotation arm  105  will be at the desired maximum rotation relative to the left door  10 . 
       FIG. 20  shows the structure of the left fairing system when the fairing is fully deployed on a fully closed door. The fairing system includes a large air gap  225  that is substantially bounded by the sheet tensioner  110  or sheet roller, an upper rotation arm  230 , a lower rotation arm  235 , and the left door  10 . Since the vertical tube  180  is directly adjacent to the left door  10 , the large air gap  225  is still substantially bounded by the left door even if the air gap does not fully extend to the left door  10 .  FIG. 20  also shows the sheet tensioner  110  or roller equipped with an auxiliary ratcheting tensioning device  240 . The ratcheting tension device  240  is configured to allow a trailer operator to rotate the sheet tensioner thereby increasing the amount of tension on the fairing sheet  115 . While the fairing sheet is preferably constructed of a resilient material that is resistant to stretching and road grime, it is expected that over time the fairing sheet  115  may stretch a small amount thus decreasing the tension of the fairing sheet  115 . The ratcheting tension device  240  allows a trailer user to take up that additional slack in the fairing sheet  115 . 
     Another feature contemplated by the inventor is the ability to temporarily disengage the rotation limiter  95 . For intermodal trailers that are carried by both over-the-road tractors as well as trains, it is desirable to be able to temporarily and easily disengage the rotation limiters  95  so when carried by a train multiple trailers may be closely packed end-to-end. In one example, the wire  210  that extends between a first point  215  on the left door  10  and the second point  220  on the rotation arm is disconnectable from the door, the rotation arm, or both to allow the rotation arm to fully rotate towards the left hinge  30 . In another example, the protrusion  200  and block  205  of the rotation limiter  95  are removable or moveable to a location where they do not prevent the arm from rotating towards the door hinge of the trailer. 
     The inventor contemplates several alterations and improvements to the disclosed invention. Other alterations, variations, and combinations are possible that fall within the scope of the present invention. Although various embodiments of the present invention have been described, those skilled in the art will recognize more modifications that may be made that would nonetheless fall within the scope of the present invention. Therefore, the present invention should not be limited to the specific examples described.