Abstract:
An accessory for a vehicle cab or trailer for directing air flow relative to a downstream or towed trailer has apertures configured to direct some air to the space between the vehicle cab or trailer and the downstream trailer.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/794,041, filed Apr. 20, 2006. 
     
     TECHNICAL FIELD 
       [0002]    The disclosure relates to an accessory for a cab or trailer of a semi-trailer truck used to direct air flow around a following or downstream trailer. 
       BACKGROUND 
       [0003]    The gap between the tractor and trailer or between succeeding trailers of a semi-trailer truck causes aerodynamic drag and air turbulence which decreases the fuel efficiency and handling of the truck, especially at highway speeds. To enhance the aerodynamics of the truck, various accessories have been developed to direct air flow smoothly around downstream or following trailers. Such accessories include air fairings and various types of cab extenders to direct air flow over the roof and sides of the trailer. 
         [0004]    Cab extenders along the side of a cab must be able to effectively direct airflow while accommodating the relative movement of the tractor and adjacent trailer or between two adjacent trailers during a turn. To allow this relative motion, some cab extenders include mechanical assemblies which enable wind deflectors to pivot about a mechanical joint during a turn. 
         [0005]    Cab extenders incorporating a flexible plastic flap bolted or otherwise fastened by a multiplicity of fasteners to a metal extender element are known. With this construction, the plastic flap simply flexes in the event it impacts a trailer during a turn. 
         [0006]    Although cab extenders assist in enhancing the aerodynamics of a truck by deflecting air away from the gap between a truck cab and trailer or between successive trailers, further reductions in drag are desirable. 
         [0007]    Therefore, a need exists for an improved cab extender. 
       SUMMARY 
       [0008]    It has been discovered that the provision of a plurality of openings spaced along the length of a rear edge portion of an extender or flap provides further reductions in drag. The shape of these openings can be varied as well as the number of such openings while still providing improved aerodynamic effects. For example, the provision of a single row of spaced apart triangular shaped openings that occupied no more than fifty percent of the area of an aluminum extension flap was tested in a wind tunnel. These tests were accomplished by directing an approximately 60 mile per hour wind in a wind tunnel against the front of a truck [at 0° yaw (parallel to the longitudinal axis of the vehicle) and at 6° yaw (offset by 6° from the longitudinal axis of the vehicle)]. The wind extended rearwardly across the cab extender and flap with a small portion of the wind entering the openings leading to the rear of the flap. The vast majority of the air followed the surface of the extender and flap and was diverted outside of the following trailer. The drag induced by such a head wind for extenders with and without opening containing extender flaps was compared. The embodiment with a triangular shaped opening as described below exhibited approximately a one percent reduction in drag. Other shaped openings were also tested and proved to reduce drag. A wind tunnel of the type disclosed in U.S. Pat. No. 6,820,477, was used for this testing. 
         [0009]    It is believed that the reduction in drag occurs because the openings assist in relieving a vacuum that otherwise forms rearwardly of the cab between the cab and a following trailer (or between successive trailers). Although the space occupied by the openings can be increased beyond fifty percent, it is desirable to maintain a majority of the surface of the flap intact so as to divert a substantial portion of the air along the surface of the flap rather than through drag reducing openings. 
         [0010]    The drag reducing openings in one desirable embodiment are in effect a plurality of air scoops as they are closed in this exemplary embodiment except along a rearwardly extending slit. 
         [0011]    Although these drag reducing openings can be molded or otherwise formed in a flap or extender, in one desirable approach, edges bounding an opening are severed while leaving a retention hinge portion at the forward or leading edge of the opening. Consequently, the severed flap can be bent or pushed rearwardly away from the outer exterior surface of the flap with the hinge portion retaining the connection between the cutout portion of the flap and the remaining portions of the flap. For example, the flap may be displaced to provide a gap between the trailing edge of the flap and adjoining portions of the extender to between 0.05 and 0.3 inch with 0.1 to 0.2 inch being particularly desirable. Top and bottom boundaries above and below the displaced flap can be closed so that the only exit from the scoop is a rearwardly directed slit. 
         [0012]    The opening defining components and the defined openings can otherwise be formed, such as by molding. 
         [0013]    Various shaped openings can be used. In addition, there is no requirement that the openings be the same shape along the length of a given flap, although the utilization of symmetric openings is expected to provide more uniform aerodynamic characteristics and can be viewed as aesthetically pleasing. 
         [0014]    The present invention is directed toward all new and non-obvious features and method as disclosed herein both individually and in various combinations and sub-combinations with one another. There is no requirement that an embodiment achieve any specific one or more, or all of the advantages set forth herein. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a side view of a semi-trailer truck having cab extenders according to a first embodiment. 
           [0016]      FIG. 2  is a top plan view of a semi-trailer truck having cab extenders according to the first embodiment positioned along the sides of a cab and along the sides of a trailer. 
           [0017]      FIG. 3  is a top plan view of a cab extender with air flow openings through the extender not visible in this figure. 
           [0018]      FIG. 4  is a side elevational view of the cab extender of  FIG. 3 . 
           [0019]      FIG. 5  is an exploded partially broken away isometric view of a cab extender according to the first embodiment. 
           [0020]      FIG. 6  is a top plan view of the cab extender of  FIG. 5 . 
           [0021]      FIG. 7  is a cross-sectional view of a portion of the cab extender of  FIG. 6 . 
           [0022]      FIG. 8  is a top plan view of a cab extender according to a second embodiment. 
           [0023]      FIG. 9  is a top plan view of a cab extender according to a third embodiment. 
           [0024]      FIG. 10  is an enlarged view of a cab extender and attached flap having a plurality of lengthwise spaced apart drag reducing openings positioned along the length of the flap. 
           [0025]      FIG. 11  is an enlarged side elevation view of a portion of the flap and extender of  FIG. 10 . 
           [0026]      FIG. 12  is a transverse sectional view of a portion of the flap and extender of  FIG. 11 , taken along lines  12 - 12  of  FIG. 11 . 
           [0027]      FIG. 13  is a vertical sectional view, taken along lines  13 - 13  of  FIG. 11 , illustrating an end view of a drag reducing opening. 
           [0028]      FIG. 14  is a side elevation view of a portion of an alternative embodiment of an extender and flap. 
           [0029]      FIG. 15  is a vertical sectional view, taken along lines  15 - 15  of  FIG. 14 . 
           [0030]      FIG. 16  is a vertical end view, taken along lines  16 - 16  of  FIG. 14 . 
           [0031]      FIG. 17  is a side elevational view of a portion of another example of an extender and flap, showing yet another drag reducing opening shape. 
           [0032]      FIG. 18  is a transverse sectional view, taken along lines  18 - 18  of  FIG. 17 . 
           [0033]      FIG. 19  is a side elevational view of yet another form of a flap showing non-symmetrical drag reducing openings. 
       
    
    
     DETAILED DESCRIPTION 
       [0034]      FIGS. 1 and 2  illustrate a semi-trailer truck  20  including cab extenders  22  according to one embodiment. While the cab extender  22  is primarily designed to close the gap  30   a  between the cab  24  of the tractor  26  and the trailer  28 , the extender can be applied to the gap  30   b  between trailers as well. In addition, the cab extender can close the gap along the top of a tractor or trailer as well as along the sides thereof. As shown in greater detail in  FIGS. 5 to 7 , the illustrated cab extender  22  has two primary components or portions to fill these gaps: 1) an extender  32  typically mounted to the cab  24  and closing a portion of the gap  30   a  and/or  30   b ; and 2) a flap  34  mounted to the extender  32  or coupled to the extender by a support and filling in a second portion of the gap  30   a  and/or  30   b . The flap  34  can be flexible or rigid. The flap  34  has a plurality of lengthwise spaced apart drag reducing openings  35  along its length as explained below. 
         [0035]      FIGS. 3 and 4  depict a cab extender having a flap  36  that is comprised of metal, plastic or other suitable material and in the form shown is connected to the rear edge portion of a metal cab extender  38 . The flap  36  is connected to the rear edge portion of the extender  38  by a multiplicity of metal capscrews  40 , washers  42 , and nuts  44 . When mounted in place, the flap can be sandwiched between the metal extender and a metal reinforcing bracket  46 . A metal bracket  47  holds the extender  38  at a desired angle relative to the cab  24 . 
         [0036]    The embodiment shown in  FIG. 5  includes an extender  32 , which is preferably made of a rigid material such as sheet metal, with aluminum (0.06 inch thick) being a specific example. As shown in  FIGS. 1 and 2 , the extender  32  is typically fastened to a cab  24  or trailer  28  and extends rearwardly across a portion of the gaps  30   a  and/or  30   b . To close a second portion of these gaps  30   a ,  30   b , the embodiment further includes a flap or extension edge portion  34 . The flap  34  can be made of the same material as extender  32  or of one or more other materials, such as plastic, rubber or other flexible material. If a flap is made of a flexible material, it will flex and bend without damaging a downstream trailer in the event the trailer is engaged by the flap during a turn. To increase the rigidity and durability of the flap  34 , the distal end of the flap  48  can optionally have an enlarged free edge, such as the rounded bead  49  extending the full length of the flap edge opposite to the flap edge which is coupled to the extender. In addition, the flap can be enlarged at the proximate or extender engaging edge to strengthen the flap where it is coupled to the extender. Although not required, the flap can be enlarged along the entire proximate edge. 
         [0037]    Using plastic for the flap  34  simplifies its manufacture because the flap  34  can be molded with the drag reducing opening defining components and simply trimmed to length. Alternatively, the openings can be punched or otherwise formed. If punched, a hinge portion can be left in place to hinge an opening bounding back element to the flap. Specific exemplary materials for the flap include aluminum or other metal materials, composite materials, EPDM rubber, and high density polyethylene (HDPE) plastic. The thickness of the flap may vary, with one exemplary thickness being about 0.086 inch for HDPE, about 0.157 inch for EPDM rubber and about 0.06 inch for aluminum. The length of the flap is variable and typically corresponds to the top to bottom length of the gap. The width of the flap is also variable and is typically sized such that the flap and extender extend across about 50 to about 80 percent of the gap. Again, this is variable as the flap need only be wide enough to direct a significant portion of the air past the front of the downstream trailer. A typical flap is from about six to about twelve inches wide and in a desirable form is about six inches wide. 
         [0038]    As shown in  FIGS. 5 and 6 , the illustrated extender  32  and flap  34  slidably engage each other along adjacent side edges. The illustrated extender  32  has a flange edge  50  defining a channel  52  for receiving the flap  34 . The channel  50  in this case can assume any convenient cross-sectional shape, and can be generally circular as shown. To simplify its manufacture, this flange end  50  can be constructed from sheet metal with a side edge rolled into the partial circle  50 . The flap has a channel receiving proximate or side edge  54  for insertion into the channel  52  of the extender  32 . The channel receiving edge  54  in this embodiment is shaped to fit into and mate with the channel defining wall of the flange edge  50 . In this embodiment, the flap side edge  54  includes a portion  55  of generally circular cross-section which is inserted into the interior of the channel  52 . The flap side edge  54  defines a slot  59  shaped to receive the correspondingly shaped flange edge  50 . The portion  55  is typically sized slightly larger in cross-sectional dimension than the extender channel  52  so that, when inserted, portion  55  is deformed slightly and increases the frictional engagement of the flap to the extender. The channel receiving edge  54 ′ may also include additional structure, such as the projecting lip edge  56  and extender engaging shoulder  58  which interlock the extender  32  and the flap. By interlock, it is meant that the structure, which may take other forms, prevents the flap  34  from pivoting or rotating relative to the extender  32 . Because the extender  32  and flap  34  slidably engage each other, each portion may expand and contract relative to one another along the channel  52 . As a result, the metal extender may expand and contract, for example, more rapidly than the flap  34  in response to temperature change, without wrinkling or thermally stressing the flap  34 . However, if both the extender and the flap are of the same material, such as aluminum, they will expand and contract together even if the flap overlays the extender and is simply screwed, bolted or otherwise secured to the extender with plural fasteners. 
         [0039]    The extender and flap in this  FIG. 5  form are desirably sized to tightly mate together in frictional engagement. As a result, fasteners are not required. However, a fastener which allows relative expansion of the components can be employed. For example, a single screw or bolt type fastener may join the flap and extender. Consequently, the components are free to expand and contract relative to one another (those portions above the fastener are unrestricted from relative sliding and those portions below the fastener are similarly unrestricted) so that the flap does not wrinkle or buckle as a result of thermal stresses. In contrast, if plural spaced-apart fasteners are used, which can be used, the portion of the flap between two fasteners could buckle unless relative motion is otherwise accommodated or the materials have the same thermal expansion properties. 
         [0040]    More specifically,  FIGS. 6 and 7  illustrate a single self-tapping screw  60  that penetrates the extender and flap and firmly holds an inserted flap  34  in the channel  52  of the extender  32 . The screw  60  is thus an additional optional means to ensure that the flap  34  does not loosen in the channel  52 . Thus, while  FIGS. 6 and 7  show a self-tapping screw, and such a fastener is typically employed, such a fastening device is neither needed nor required. As other examples, the flap  34  can be designed to snap into the flange  50  of the extender  32 , or the flange  50  can simply be shaped to hold the channel receiving end  54  of the flap  34  in place. Alternatively, the flap  34  can be widened at the top such that this widened portion would engage the top of the channel  52  and comprise a stop to prevent the flap from sliding downward beyond the stop. Other stops can also be used. 
         [0041]    The manner in which the flap  34  slidably engages the extender  32  facilitates the replacement or exchange of the flap  32 . A cab can be provided with a standard extender, and the flap can changed as necessary to best close the gap depending upon factors such as the width of the cab relative to the trailer and the distance between the cab and trailer. While a standard width trailer is typically 96 or 102 inches wide, the cab width may vary substantially. The distance or width of the gap between cab and trailer may vary as well. As such, by providing flaps of different widths, a flap can be selected to more properly close the gap between the cab and trailer. Again, plural fasteners  40  can be used in the alternative. 
         [0042]      FIGS. 8 and 9  illustrate alternative embodiments of a cab extender which accommodates cabs of varying widths relative to a downstream trailer. In  FIG. 8 , the main body  33  of extender  32   a  (excluding an inwardly projecting top flange  37 ) is co-planar with the side of the cab  24 , and the flap  34   a  is curved to direct airflow  62  around the trailer  28 . In  FIG. 9 , the main body  33   b  of extender  32   b  is angled outwardly relative to the longitudinal axis and the side of the cab at an angle α. Although variable, α. is typically between about zero and about thirty degrees. The flap  34   b , coupled to the angled extender, in this example, is a substantially planar member which, together with the extender  32   b , directs air flow  62  around the trailer  28 . From  FIGS. 8 and 9 , it can be seen that the extender  32   b  can be standardized at a fixed angle α, relative to the longitudinal axis of the cab. In addition, the flaps may be manufactured of various curved or otherwise shaped configurations and then selected to divert air past a downstream trailer for a given cab width and gap. 
         [0043]    Other approaches for mounting cab extender flaps to a cap extender can also be used, such as disclosed in U.S. Pat. No. 5,658,038. As an alternative, the openings  35  can be formed in the extender  32 , rather than in an attached flap or extension such as  34 . However, the use of a flap  34  facilitates its separate replacement without requiring the replacement of the extender  32 . 
         [0044]    With reference to  FIGS. 10-13 , the cab extender  32  is shown with a flap  34  secured thereto, such as by cap screws  40 . A plurality of spaced apart generally triangular shaped drag reduction openings  35  are provided in flap  34 . These openings desirably are sized so that the bulk of the air (see arrows  100  in  FIG. 12 ) passes along the exterior surface  102  of flap  34  and is diverted past a downstream trailer. Although variable, desirably less than fifty percent of the surface area of flap  34  is occupied by openings  35 . 
         [0045]    With reference to  FIG. 11 , in one specific approach, the flap  34  is made of aluminum or other metal. Upper and lower boundaries  104 , 106  and a rear boundary  108  of the opening are formed by cutting through the metal of the body of the flap  34  at these locations. An unsevered hinge portion  110  is left in place. As a result, a deflectable tab or flap element  112  is provided that can be pushed inwardly and away from the exterior surface  102  of the flap  34  (see  FIG. 12 ). The trailing edge  120  of this deflectable tab  112  is shown in both  FIGS. 11 and 12 . As a result, an air flow gap  114 , in this case a longitudinally or vertically extending slit is provided between the trailing edge  120  of deflection tab  112  and the rear surface  130  of flap  34 . The width of the slit  114  can be varied with 0.05 inch to 0.3 inch being desirable and 0.1 to 0.2 inch being particularly desirable. 
         [0046]    Triangular shaped openings as shown in  FIG. 11 , with an air slit having a width of 0.2 inch, resulted in a one percent reduction in measured drag (compared to the truck with two extenders and flaps without openings  35 ) in a wind tunnel when a truck was impacted with air traveling at 60 miles per hour at 0° and 6° yaw. In this example, there were two extenders and extender flaps, one at each side of the truck. Each flap had twelve such triangular shaped openings  35  having side edges  104  and  106  of a length of one and one-half inches and a rear edge  108  of a two inch length. In addition, the top and bottom edges of the deflection tab  112  were closed by upper and lower closure pieces  140 , 142  (see  FIG. 13 ). In an alternative approach, the top and bottom portions of the opening were closed by tape overlying the rear of the tab  112 . Therefore, in this example, the only exit from the air scoop formed by the deflection tab  112  was through the slit  114 . As indicated by arrow  115  in  FIG. 12 , only a small quantity of air actually passes through the exit slit  114 . This air  115  assists in reducing a vacuum that is believed to otherwise form behind the flap  34  to thereby reduce the drag caused by the extender. 
         [0047]      FIGS. 14-16  illustrate a flap  34 ′ having rectangularly shaped openings  35 ′. The prime designation simply indicates an alternative embodiment. In the embodiment of  FIG. 14 , in one manufacturing approach, lower and upper boundaries  150 , 152  and a rear boundary  154  of a displaceable air deflection tab  156  are formed, leaving a hinge portion  158 . The hinge portion  158  can be bent as shown in  FIG. 15  to provide first and second wall portions  160 , 162  with wall portion  160  extending away from the main body of the flap  34 ′ and the wall portion  162  extending parallel to the main body of the flap. Alternatively, the air deflection tab  156  can be bent in the manner shown in  FIG. 12 . The top and bottom portions of this defined opening can be closed, such as by closure members  170 , 172  shown respectively in  FIGS. 14 and 15 . When closed in this manner, air exits through a rearwardly extending slit  180  in this example. The bulk of the air, indicated by arrows  182  in  FIG. 15 , passes along the exterior surface  184  of flap  34 ′ and is deflected along the outer sides of the following trailer. A small amount of air, indicated by arrow  186 , passes through the opening  180  to again relieve the vacuum behind the flap and reduce the drag. This construction is also illustrated in  FIG. 16 . 
         [0048]      FIGS. 17 and 18  illustrate an embodiment of a flap  34 ″ with semi-circular air deflection tabs  190  closed at their perimeter by closure member  192  and having an air exit slit  194  as can be seen in  FIG. 18 . 
         [0049]      FIG. 19  illustrates an embodiment  34 ′″ with air deflection openings of varying shapes  35 ′″,  35 ″″ to illustrate that, although desirable, the air deflection openings are not required to be symmetrical. 
         [0050]    In a particularly desirable form, the air deflection scoops have a rearwardly extending exit opening, such as in the form of a slit. However, the openings are not be limited to this shape or to this location. Also, although less desirable, the upper and lower boundaries of the air deflection scoops can be left entirely or partially open. 
         [0051]    Having illustrated and described the principles of our developments with respect to several desirable embodiments, it should be apparent to those of ordinary skill in the art that these embodiments can be modified in arrangement and detail without departing from the inventing principles disclosed herein. We claim all such modifications.