WO2022125064A1

WO2022125064A1 - Trailer skirt with variable height upper surface

Info

Publication number: WO2022125064A1
Application number: PCT/US2020/063712
Authority: WO
Inventors: Calvin Rhett Bradley
Original assignee: Compagnie Generale Des Etablissements Michelin
Priority date: 2020-12-08
Filing date: 2020-12-08
Publication date: 2022-06-16

Abstract

An apparatus (10) for a trailer (16) that includes a trailer skirt (14) configured for being attached to a trailer (16) of the tractor trailer (12), that has a leading terminal end (20) and a trailing terminal end (22) and a length therebetween. An outer surface (32) and inner surface (34) are spaced from one another in a lateral direction (28). The trailer skirt has an upper surface (38) and a lower surface (40) that are spaced from one another in a vertical direction (30). The upper surface (38) has a first portion (42) located forward of a second portion (44) in the longitudinal direction (26). The first portion (42) is closer than the second portion (44)to the leading terminal end (20) in the longitudinal direction (26), and the second portion (44) is located higher in the vertical direction (30) than the first portion (42).

Description

TRAILER SKIRT WITH VARIABLE HEIGHT UPPER SURFACE

FIELD OF THE INVENTION

[0001] The subject matter of the present invention relates to a trailer skirt used to increase the aerodynamic performance of the tractor trailer. More particularly, the present application involves a trailer skirt with an upper surface that does not have a consistent height along its entire length but instead has a variable height so that compression at the bottom of the trailer skirt is reduced or eliminated to prevent deformation and fluttering of the trailer skirt.

BACKGROUND OF THE INVENTION

[0002] Trailers towed by trucks and similar apparatuses for transporting cargo can be large, unwieldy, and include geometries which invite inefficiencies during travel. One aspect of these inefficiencies concerns the aerodynamics of the trailer. For maximum capacity, the trailer is box shaped which is not the most aerodynamically available option. In an effort to improve trailer aerodynamics, trailers have been built, supplemented, or retro-fitted with trailer skirts (or side skirts), devices affixed to the underside which limit air circulating in the empty space between the trailer’s axles. By reducing the amount of airflow in this space, drag caused by turbulence is reduced and permits the trailer to be towed more efficiently, increasing the gas mileage and performance of the vehicle and its cargo. Trailer skirts are flat panels that are attached to the bottom of the trailer at its sides under the trailer and extend in the longitudinal direction to deflect airflow in a desired manner.

[0003] The bottoms of trailers do not have a consistent vertical height from the ground upon extension in the longitudinal direction. Instead, the bottoms of trailers present a concave shape to the ground, and the trailer skirts with straight top edges are attached to this concave shaped bottom. Because of this arrangement, the bottom of the trailer skirt is put into compression which causes the lower edge of the trailer skirt to assume a wavy shape which can lead to vibration during operation and could prevent optimal aerodynamic performance. In addition to this deformation issue, the hanging of a trailer skirt off of the bottom of the trailer may result in a trailer skirt that is not preloaded and could vibrate due to unsteady forces from air impacting the trailer skirt, which is known as flutter.

[0004] Two different approaches are known to correct these problems. The first involves positioning the front of the trailer skirt inboard from the main, tailing section of the trailer skirt. This out of plane curvature increases stiffness of the skirt panel to reduce vibration and deformation. However, the inclusion of a curved leading section of the trailer skirt may not be desired for many optimized aerodynamic configurations which reduces the performance of the system. The second correction involves adding additional bracket support by increasing the number of brackets or increasing bracket stiffness to hold the trailer skirt in a straighter position with less flexibility. Unfortunately, the addition of stronger or additional brackets adds cost and weight to the design and is not always successful. Further, since the trailer skirt is not under pretension, it may still flutter when subjected to air forces when moving down the road and vibrate which can result in reduced aerodynamic performance. As such, there remains room for variation and improvement within the art.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:

[0006] Fig. 1 is a side view of a tractor trailer with an unattached trailer skirt of the prior art.

[0007] Fig. 2 is a side view of Fig. 1 with the trailer skirt attached to the trailer.

[0008] Fig. 3 is a side view of a tractor trailer with an unattached trailer skirt in accordance with one exemplary embodiment.

[0009] Fig. 4 is a side view of Fig. 3 with the trailer skirt attached to the trailer.

[0010] Fig. 5 is a back side view of a trailer skirt in accordance with another exemplary embodiment.

[0011] Fig. 6 is a side view of the trailer skirt attached to the trailer in accordance with another exemplary embodiment in which the upper surface does not exactly match the bottom surface of the trailer.

[0012] Fig. 7 is a side view of a trailer skirt that has an upper surface that is convex along its entire length.

[0013] Fig. 8 is a top view of the trailer skirt of Fig. 7.

[0014] Fig. 9 is a side view of a trailer skirt that has an upper surface with a convex segments, inclined segment, and flat segments in accordance with another embodiment.

[0015] Fig. 10 is a side view of the trailer skirt of Fig. 9 attached to the trailer.

[0016] Fig. 11 front view of the trailer skirt of Fig. 10.

[0017] Fig. 12 is a front view of the trailer skirt of Fig. 11 with bending members and skirt attachments added to the apparatus to straighten the trailer skirt. [0018] Fig. 13 is a side view of the trailer skirt in accordance with another embodiment in which the bottom of the trailer is composed of a series of I-beams.

[0019] The use of identical or similar reference numerals in different figures denotes identical or similar features.

DETAILED DESCRIPTION OF THE INVENTION

[0020] Reference will now be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, and not meant as a limitation of the invention. For example, features illustrated or described as part of one embodiment can be used with another embodiment to yield still a third embodiment. It is intended that the present invention include these and other modifications and variations.

[0021] The present invention provides for an apparatus 10 that has a trailer skirt 14 attached to the trailer 16 of a tractor trailer 12 to improve its aerodynamic performance. The trailer skirt 14 has an upper surface 38 that has first and second portions 42, 44 that are at different locations from one another in the vertical direction 30. When attached to the bottom surface 50 of the trailer 12, the shape of the upper surface 38 better conforms to this bottom surface 50 so that the amount of compression at a lower surface 40 of the trailer skirt 14 is reduced or eliminated. In some instances, the entire upper surface 38 can be convex in shape, while in other embodiments the upper surface 38 has a convex shaped segment 48 but is not entirely convex in shape, and in yet further arrangements the upper surface 38 is variously shaped.

[0022] Fig. 1 shows a tractor trailer 12 that has a tractor 18 and attached trailer 16. In normal use, the tractor trailer 12 is driven forward in the longitudinal direction 26 and cargo for transport is held in the trailer 16. The trailer 16 is elongated in the longitudinal direction 26 and has a bottom surface 50 that is convex such that the bottom surface 50 is not the same distance in the vertical direction 30 from the ground along the entire length of the bottom surface 50 in the longitudinal direction 26. The trailer skirt 14 has an upper surface 38 that is flat in that the height of the upper surface 38 in the vertical direction 30 does not change along the entire longitudinal length of the upper surface 38 in the longitudinal direction 26. The trailer skirt 14 is an aerodynamic feature placed onto the tractor trailer 12 to improve aerodynamic performance of the tractor trailer 12 during forward movement. In this regard, the trailer skirt 14 deflects air in a desired manner to reduce drag, such as for instance deflecting air away from the trailer tires and suspension so that this air does not engage and slow the tractor trailer 12 down during forward movement.

[0023] The trailer skirt 14 is installed on the trailer 16 and is usually placed in the longitudinal direction 26 between the tractor 18 tires and the trailer 16 tires. One trailer skirt 14 is attached to the left hand side of the tractor 18, and another trailer skirt 14 is attached to the right hand side of the tractor 16. Fig. 2 shows the attachment of the trailer skirt 14 to the trailer 16 so that the upper surface 38 engages the bottom surface 50. Due to the fact that the bottom surface 50 is concave in shape while the upper surface 38 is flat, these two components do not fit nicely onto one another. Instead, their mismatched shapes cause the trailer skirt 14 to be forced against bottom surface 50 so that the center in the longitudinal direction 26 of the trailer skirt 14 is placed into compression. This compression will be most felt at the lower surface 40 of the trailer skirt 14 to result in a series of wrinkles to be formed in the trailer skirt 14 to results in a wavy trailer skirt 14 along its lower surface 40. This deformation will change or reduce the effectiveness of the aerodynamic design of the trailer skirt 14 and will allow the trailer skirt 14 to flutter during forward movement of the tractor trailer 12.

[0024] Fig. 3 shows the apparatus 10 in accordance with one exemplary embodiment. The apparatus 10 includes a trailer skirt 14 that can be a single panel or can be made of multiple panels. The panels of the trailer skirt 14 may be made out of fiberglass and extend a longer length in the longitudinal direction 26 than in the vertical direction 30 or lateral direction 28. The placement of the trailer skirt 14 is again between the tires of the tractor 18 and trailer 16 in the longitudinal direction 26, but in other embodiments the trailer skirt 14 could extend to the tires of the trailer 16 and may extend rearward of the tires of the trailer 16 in the longitudinal direction 26. Still further, the trailer skirt 14 could extend forward in the longitudinal direction 26 so as to be at or forward of the drive tires of the tractor 18. A length 24 in the longitudinal direction 26 extends from the leading terminal end 20 to the trailing terminal end 22 of the trailer skirt 14. Due to the geometries of the leading and trailing terminal ends 20, 22, the length 24 can be varied based upon the height in the vertical direction 30 the length 24 is measured. As such, the length 24 can be the maximum measured length of the trailer skirt 14 in the longitudinal direction 26.

[0025] The trailer skirt 14 has an upper surface 38 and an oppositely disposed lower surface 40 that are spaced from one another a distance in the vertical direction 30. The upper surface 38 has a first portion 42 and a second portion 44, and the first portion 42 is located forward of the second portion 44 in the longitudinal direction 26 so as to be located closer to the leading terminal end 20 in the longitudinal direction 26. The second portion 44 is located closer to the trailing terminal end 22 in the longitudinal direction 26 than the first portion 42. The first and second portions 42, 44 can extend any length in the longitudinal direction 26 and need not be a point or line but could be a surface with the same or different lengths as one another. The second portion 44 is higher in the vertical direction 30 than the first portion 42. As can be appreciated, if the bottom surface 50 of the trailer 16 is concave in shape, the higher second portion 44 and lower first portion 42 will better fit with this concave shape bottom surface 50. The upper surface 38 in this embodiment is complimentary in shape with the bottom surface 50 so that their convex and concave shapes match and fit with one another.

[0026] Fig. 4 shows the trailer skirt 14 attached to the trailer 16 so that the upper surface 38 engages the bottom surface 50. As these two surfaces 38, 50 are shaped to fit one another, portions of the trailer skirt 14 are not pulled out of position and forced against the trailer 16 upon attaching the trailer skirt 14. Compression or other forces will not be imparted onto the lower surface 40 or other section of the trailer skirt 14 so that wrinkles or waves will not be formed on the trailer skirt 14. The outer surface 32 of the trailer skirt 14 is not deformed in the attachment process and will function to deflect air as intended upon design of the trailer skirt 14 in the apparatus 10 for aerodynamic gains of the tractor trailer 12. During attachment of the trailer skirt 14, the second portion 44 is located higher in the vertical direction 30 than the first portion 42. The bottom surface 50 of the trailer 16 onto which the trailer skirt 14 is affixed can be a single continuous surface that extends along the bottom of the trailer 16, or may be a series of I-beams that are spaced from one another in the longitudinal direction 26 along the bottom of the trailer 16, or may be a combination of these features at the bottom of the trailer 16. As such, it is to be understood that the bottom surface 50 can be a continuous surface or a discontinuous surface onto which the trailer skirt 14 is attached. The bottom surface 50 can extend any distance inboard from the side edge of the trailer 16 in the lateral direction 28. Various mechanisms of attaching the trailer skirt 14 to the trailer 16 are possible, and the upper surface 38 may or may not come into contact with the bottom surface 50 in accordance with various exemplary embodiments. The vertical and longitudinal placements of the first and second portions 42, 44 of the upper surface 38 will prevent interference that leads to compression and subsequent deformation of the trailer skirt 14.

[0027] The upper surface 38 can be variously shaped and need not be convex in shape along its entire length from the leading terminal end 20 to the trailing terminal end 22. Fig. 5 is a back view of the trailer skirt 14 of the apparatus 10 in which upper surface 38 does not have any convex shape but instead only includes flat sections that are parallel to the longitudinal direction 26 and inclined sections that are angled to the longitudinal direction 26 so as to have components of extension in both the longitudinal direction 26 and the vertical direction 30. The first portion 42 of the upper surface 38 is closer to the leading terminal end 20 in the longitudinal direction 26, and the second portion 44 is again farther from the leading terminal end 20 and is higher in the vertical direction 30 than the first portion 42. A third portion 46 is also present and is part of the upper surface 38 and is located closer to the trailing terminal end 22 in the longitudinal direction than is the second portion 44 to the trailing terminal end 22. The third portion 46 is lower in the vertical direction 30 than the second portion 44. In the disclosed embodiment, the first and second portions 42 and 46 are located at the same height as one another in the vertical direction 30. The three portions 42, 44 and 46 are part of the upper surface 38 so that they are integrally formed with the upper surface 38 and are not distinct therefrom so that they are indistinguishable from the rest of the upper surface 38. However, in other embodiments one or all of the portions 42, 44, 46 could be distinguished from the rest of the upper surface 38 such as by being different colors, denoted with lines or other markings, different segments that are adjacent contiguous segments of the upper surface 38 or via any other mechanism. As such, it is to be understood that the upper surface 38 could be a continuous surface and the portions 42, 44, 46 are simply locations along this continuous surface and are otherwise indistinguishable therefrom.

[0028] The portions 42, 44, 46 are located along the flat sections of the upper surface 38 that are parallel to the longitudinal direction 26, and the second portion 44 is located on a section of the upper surface 38 that is elevated from the two sections onto which the first and third portions 42, 46 are located. The second portion 44 in all of the various embodiments may be higher than the first and third portions 42, 46 and the amount higher can be different in accordance with different embodiments. In various embodiments, the distance from the lower surface 40 to the second portion 44 in the vertical direction 30 is 2%, 3%, 4%, 5%, from 5%- 10%, from 10%- 15 %, from 15%-20%, or up to 25% higher/longer than the distance from the lower surface 40 to the first portion 42 in the vertical direction 30 and from the lower surface 40 to the third portion 42 in the vertical direction 30. In the instances where the lower surface 40 is not completely parallel to the longitudinal direction 26, the previously mentioned percentages will apply with the standard being the greatest height of the trailer skirt 14 from the lower surface 40 to the upper surface 38. In this regard, the heights of the portions 42, 44, 46 will be measured relative to the lowest vertical position of the lower surface 40 regardless of its position in the longitudinal direction 26 and once these three heights are measured the above mentioned percentages may be established. However, it is to be understood that regardless of the percentage difference, the second portion 44 need only be higher in the vertical direction 30 than the first and third portions 42, 46 in certain embodiments of the apparatus 10.

[0029] The trailer skirt 14 includes bending members 62 and skirt attachments 64 located at different positions along the length 24. The bending members 62 and skirt attachments 64 can be configured in a variety of manners, for example they may be configured as those disclosed in United States patent publication number 2018/0290695 Al the contents of which are incorporated by reference herein in their entirety for all purposes. The bending members 62 are mounted onto the bottom surface 50 of the trailer 16 or another part of the trailer 16 and include elongated bending beams that are in sliding engagement with skirt attachments 64. The skirt attachments 64 are rigidly mounted to the inner surface 34, and the elongated bending beams of the bending members 62 can slide through the skirt attachments 64. In Fig. 5, bending members 64 and skirt attachments 64 are located in the longitudinal direction 26 at the same positions as the three portions 42, 44, 46. Additional bending members 64 and skirt attachments 64 are located at additional positions along the longitudinal direction 26 as well. Brackets not shown in Fig. 5 can be attached to the trailer skirt 14 to attach the trailer skirt 14 to the bottom surface 50 of the trailer 16.

[0030] The upper surface 38 need not be completely complimentary with the bottom surface 50, and it may be the case that the upper surface 38 shown in Fig. 5 does not exactly match the shape of the bottom surface 50 of the trailer 16. However, if the shape of the upper surface 38 is closer to the shape of the bottom surface 50 than would otherwise be the case of the upper surface 38 is completely flat and parallel in the longitudinal direction 26, then this shape will still function to reduce compression on the trailer skirt 14 even through all of the compression of the trailer skirt 14 is not eliminated. Fig. 6 shows another embodiment of the apparatus 10 in which the trailer skirt 14 is attached to the trailer 16. The trailer 16 has a bottom surface 50 that has a concave shape upon extension in the longitudinal direction 26. The bottom surface 50 has a radius of curvature 58 that establishes the concave shape of the bottom surface 50. The trailer skirt 14 has an upper surface 38 that is convex in shape but is not an exact match with the bottom surface 50 so that the upper surface 38 is not exactly complimentary in shape. The upper surface 38 has a radius of curvature 60 that establishes the convex shape of the upper surface 38 in the longitudinal direction 26. The radius of curvature 60 is not the same as the radius of curvature 58 so that the two surfaces 38, 50 are not complimentary in shape and do not fit exactly when the trailer skirt 14 is attached. The radius of curvature 60 is larger than the radius of curvature 58, but in other embodiments the radius of curvature 58 may be greater than the radius of curvature 60.

[0031] Even though the radii of curvatures 58, 60 are not identical, the convex shape of the upper surface 38 will still function to reduce some of the compression imparted onto the trailer skirt 14 when attached to the trailer 16. The convex shape of the upper surface 38 establishes a first portion 42 that is located lower in the vertical direction 30 than the subsequent second portion 44, and the second portion 44 is higher in the vertical direction 30 than the subsequent third portion 46. The upper surface 38 has a convex shaped segment 48 and the three portions 42, 44, 46 are all located along this convex shaped segment 48 of the upper surface 38. The convex shaped segment 48 may extend along the entire length of the upper surface 38 or may extend along less than the entire length of the upper surface 38 in the longitudinal direction 26. The convex shaped segment 48 may be 10%, from 10%-25%, from 25%-45%, from 45%-50%, from 20%-50%, from 50%-75%, from 75%-90%, from 20%-90%, from 10% -100%, or from 20%-100% of the length of the upper surface 38 in the longitudinal direction 26. A first mounting bracket 52 is located at the same longitudinal position as the first portion 42, and a second mounting bracket 54 is located at the same longitudinal position as the second portion 44. A third mounting bracket 56 is positioned at the same longitudinal position as the third portion 46. The mounting brackets 52, 54, 56 can be rigidly attached to the trailer skirt 14 and to the bottom surface 50 or other portion of the trailer 16 to function to hold the trailer skirt 14 onto the trailer 16. Additional mounting brackets that are unlabeled in Fig. 6 can be located at different longitudinal positions along the trailer skirt 14 to provide further attachment support to the trailer skirt 14 and the trailer 16.

[0032] The tractor trailer 12 is shown engaging the ground 66 in Fig. 6. The first portion 42 is closer to the ground 66 in the vertical direction 30 than the second portion 44. Additionally, the third portion 46 is closer to the ground 66 in the vertical direction 30 than the second portion 44. The trailer skirt 14 is spaced from the ground 66 in the vertical direction 30 and the outer surface 32 faces outboard in the lateral direction 28 to deflect air in a desired manner upon driving the tractor trailer 12.

[0033] Another arrangement of the trailer skirt 14 of the apparatus 10 is shown in Figs. 7 and 8. The upper surface 38 is convex along its entire length in the longitudinal direction 26, and the lower surface 40 has a concave surface along its entire length in the longitudinal direction 26. As such, the convex shaped segment 48 extends along the entire length of the upper surface 38. The second portion 44 is higher in the vertical direction 30 than the first portion 42 and the third portion 46. This highest point can be measured by measuring from the lowest point of the lower surface 40 vertically upward to the three portions 42, 44, 46. This lowest point may not be under any of the three portions 42, 44, 46 but may be offset from one, two or all of the three portions 42, 44, 46 in the longitudinal direction.

[0034] Mounting members 52, 54, 56 are all located at the three portions 42, 44, 46. In this regard, the trailer skirt 14 has an outer surface 32 and an oppositely disposed inner surface 34 that are separated from one another in the lateral direction 28 and define between them a width 36 of the trailer skirt 14. The width 36 may be variable along the longitudinal direction 26 or can be the same along the entire length 24 of the trailer skirt 14. The mounting brackets 52, 54, 56 are not attached to upper surface 38, but are instead attached to the inner surface 34. The height of the mounting brackets 52, 54, 56 may extend up to the heights of the portions 42, 44, 46, or could be higher depending upon attachment availability of the trailer 16. The trailer skirt 14 extends straight in the longitudinal direction 26 and does not have a curved or inclined front section positioned inboard in the lateral direction 28 as do some trailer skirts 14 when installed on the trailer 16. This extension can be completely in the longitudinal direction 26 or may be inclined relative to the longitudinal direction 26 such that all portions of the trailer skirt 14 are angled the same relative to the longitudinal direction 26. However, the design of the apparatus 10 with the trailer skirt 14 allows for the trailer skirt 14 to have any portion positioned inboard in the lateral direction 28 than other portions of the trailer skirt 14 in accordance with various embodiments.

[0035] Figs. 9 and 10 illustrate another embodiment of the trailer skirt 14 in which the upper surface 38 has a shape that varies at different points in the longitudinal direction 26. In Fig. 9, from the leading terminal end 20 the upper surface 38 is flat and is parallel to the longitudinal direction 26 and extends to a convex shaped segment 48. The first portion 42 is located in this initial section of the upper surface 38. The convex shaped segment 48 of the upper surface 38 extends along approximately 10% of the length of the upper surface 38 to a flat section that extends slightly downward in the vertical direction 30 at an angle to the longitudinal direction 26. The upper surface 38 at this point steps upward to another flat section that is parallel to the longitudinal direction 26 and at which the second portion 44 is located. The upper surface 38 extends downward in the vertical direction 30 with another convex shaped portion that is almost flat all the way to the trailing terminal end 22, and the third portion 46 is located in this section of the upper surface 38. As such, the second portion 44 is higher than the first and third portions 42, 46 in the vertical direction 30, but the upper surface 38 has a very complex shape along its length.

[0036] Mounting brackets 52, 54, 56 are attached to the trailer 16 and are positioned in the longitudinal direction 26 so that each one of them is at the same longitudinal position as each one of the first, second, and third portions 42, 44, 46. The trailer skirt 14 is lifted into position and attached to the mounting brackets 52, 54, 56 as shown with reference to Fig. 10. Here, the mounting brackets 52, 54, 56 are attached to the inner surface 34 of the trailer skirt 14 and the second mounting bracket 54 can be attached first. The first and third mounting brackets due to the lower positioning of the first and third portions 42 and 46 are farther from their necessary attachments to the first and third mounting brackets 52 and 56. The first and third portions 42, 46 will be pulled upwards in the vertical direction 30 so that the inner surface 34 proximate to the first and third portions 42, 46 can be attached to the first and third mounting brackets 52 and 56 to achieve attachment as shown in Fig. 10. As shown, a gap from the upper surface 38 to the bottom surface 50 is present along some of the first section of the upper surface and some of the convex shaped segment 48. The first portion 42 does not engage the bottom surface 50, but the second and third portions 44 and 46 do in fact engage bottom surface 50. The shape of the upper surface 38 does not exactly match the bottom surface 50 that it engages so some compression is still present in the trailer skirt 14. However, the pulling of the first and third portions 42, 46 a distance upwards in the vertical direction 30 will eliminate this compression and in fact cause tension to be put onto the lower surface 40 and the bottom section of the trailer skirt 14 as indicated by the arrows in Fig. 10.

[0037] Fig. 11 is a front view of the apparatus 10 of Fig. 10 in which the trailer skirt 14 is put into tension. When tension is applied to the trailer skirt 14 it will have to adjust for this by bending outward or inboard in the lateral direction 28, and the bottom section of the trailer skirt 14 is the part of the trailer skirt 14 that will become bent. In Fig. 11, the bottom of the trailer skirt 14 is bent outboard in the lateral direction 28 upon the application of tension onto the trailer skirt 14. The bottom surface 50 is shown as extending along the entire lateral width of the bottom of the trailer 16 in the lateral direction 28. The first mounting bracket 52 engages the bottom surface 50 and the inner surface 34 and holds the trailer skirt 14 onto the trailer 16, and the width 36 of the trailer skirt 14 can be seen as being constant along the entire height of the trailer skirt 14.

[0038] To correct the outboard bending of the trailer skirt 14 due to the application of tension, one or more bending member 62 and skirt attachment 64 assemblies can be incorporated into the apparatus 10. Fig. 12 shows the addition of one or more of these bending member/skirt attachment 62, 64 combinations to straighten out the trailer skirt 14. The bending member 62 is attached to the bottom surface 50 and has an elongated beam that slides through the skirt attachment 64 which is rigidly attached to the inner surface 34. The elongated beam of the bending member 62 functions to pull the trailer skirt 14 either inboard or outboard in the lateral direction 28 when the trailer skirt 14 is deflected upon hitting an obstacle when driving. Additionally, the bending member 62 functions to pull the deflected trailer skirt 14 back into a vertical orientation upon being deflected by the application of tension brought about by connection to the trailer bottom 50 as discussed. The bending member 62 thus acts to reshape the trailer skirt 14 in the lateral direction 28 so that it assumes a vertically oriented position as shown in Fig. 12. The trailer skirt 14 may still be in tension via the attachment, but the bending members 62 act to pull the trailer skirt 14 into a desired orientation via the application of their own force thereon. Any bending deformation is removed by the bending members 62, and the trailer skirt outer and inner surfaces 32, 34 assume their designed for shapes and positions so that the desired, designed for aerodynamic performance of the trailer skirt 14 is achieved. Although the bending member 62 and skirt attachment 64 function to pull the trailer skirt 14 back into its desired position, these components are not always required in various embodiments because it could be the case that tension is not imparted onto the trailer skirt 14 upon attachment, or because deformation does not occur or is not excessive enough to require correction via the bending member 62 and skirt attachment 64.

[0039] When the trailer skirt 14 is in tension via the arrangement of the first and second portions 42, 44 and/or the attachment method as previously discussed, the tension in the trailer skirt 14 functions to pre-load the trailer skirt 14 and provide stiffness to the trailer skirt 14. If the trailer skirt 14 is pre-tensioned it will not flutter or will not flutter as much upon the tractor trailer 12 driving down the road. This will cause the trailer skirt 14 to vibrate less and less deformation of the trailer skirt 14 will result so that better aerodynamic gains will be realized. Application of tension to the trailer skirt 14 preloads the panels of the trailer skirt 14 which increases the initial stiffness of the trailer skirt 14 and prevents it from being deformed or from fluttering during normal driving operations.

[0040] Fig. 13 shows another embodiment of the trailer skirt 12 in which the lower surface 40 and most of the upper surface 38 are both flat and parallel to the longitudinal direction 26. The upper surface 38 includes three tabs that extend from portions of the upper surface 38 and the three portions 42, 44, 46 are located at these three tabs, in addition to three mounting brackets 52, 54, 56. The second portion 44 and second mounting bracket 54 are again located higher in the vertical direction 30 than are the first and third attachment locations 42, 46 and the first and third mounting brackets 52, 56. The upper surface 38 includes only straight, flat horizontal and vertical surfaces and does not include any convex or inclined surfaces. The bottom surface 50 in this case is made up of the bottom surfaces of a plurality of I-beams of the trailer 16. The I-beams are spaced from one another in the longitudinal direction 26 and as a result the bottom surface 50 is not a continuous bottom surface but is discontinuous at different locations in the longitudinal direction 26. The I-beams for a bottom surface 50 that is not concave but instead is arranged in a parallel orientation to the longitudinal direction 26. The mounting brackets 52, 54, 56 can be attached to the I-beams and the arrangement presented will cause the lower surface 40 and the bottom section of the trailer skirt 14 to be placed into tension. In the various embodiments discussed, since the trailer skirt 14 is attached to the bottom of the trailer 16 the top of the trailer skirt 14 is not a free edge, and the tension in the bottom of the trailer skirt 14 will not cause compression in the top of the trailer skirt 14 because this attachment will instead transfer the compression to the trailer 16 and due to its size and strength it will not cause the trailer 16 to deform.

[0041] It is to be understood that the apparatus 10 can be arranged to work with bottom surfaces 50 that are concave in shape, straight in shape, or irregular in shape. Further, the trailer skirt 14 could have a convex upper surface 38 or mounting brackets 52, 54, 56 that attach to the trailer 16 so that no compression or tension is imparted onto the trailer skirt 14. In other embodiments, the match may not be exact so that compression is still present, but the magnitude of compression is reduced or not as much compression is imparted. In other embodiments, the match may be great enough and combined with the attachment method so that tension is imparted onto the trailer skirt 14. The bottom surface 50 may be bottoms of I- beams of the trailer 16 or can be bottoms of side walls of the trailer 16 or can be combinations of these surfaces, and or may be other portions of the trailer 16. The mounting brackets 52, 54, 56 and bending members 62 can be attached to the same or different ones of these surfaces of the trailer 16.

[0042] The trailer skirt 14 features an upper surface 38 that is shaped differently than the counterpart bottom surface 50 to which it is attached. This difference in shape is selected so that tension is applied to the trailer skirt 14 by having the ends of the trailer skirt 14 pulled farther in the vertical direction 30 than the middle of the trailer skirt 14. The other embodiments include an upper surface 38 that is shaped the same as the bottom surface 50, and this embodiment will still remove compression that would otherwise be imparted onto the trailer skirt 14 to improve its aerodynamic performance. As described herein, the attachment mounting brackets 52, 54, 56 could be, but do not necessarily have to be, positioned so that they are not all at the same position in the vertical direction 30.

[0043] The upper surface 38 can be shaped so that it changes height in the vertical direction 30 upon extension in the longitudinal direction 26 along at least 50% of the length 24 of the trailer skirt 14. In this regard, along at least 50% of the length 24 the upper surface 38 is either increasing or decreasing in height in the vertical direction 30 and is not maintaining the same position in the vertical direction 30 upon extension in the longitudinal direction 26. If the upper surface 38 were convex along its entire length in the longitudinal direction 26, then it would be shaped so that it changes height in the vertical direction 30 upon extension in the longitudinal direction 26 along 100% of the length 24. As such, embodiments exist in which some of the length of the upper surface 38 does maintain the same height in the vertical direction 30 along some of its length 24 in the longitudinal direction 26. However, the upper surface 38 should vary along some of the length 24 in the vertical direction 30 so that first and second portions 42, 44 can likewise vary in vertical position. In other embodiments, the upper surface 38 changes height in the vertical direction 30 upon extension in the longitudinal direction 26 along at least 80% of the length 24.

[0044] While the present subject matter has been described in detail with respect to specific embodiments and methods thereof, it will be appreciated that those skilled in the art, upon attaining an understanding of the foregoing may readily produce alterations to, variations of, and equivalents to such embodiments. Accordingly, the scope of the present disclosure is by way of example rather than by way of limitation, and the subject disclosure does not preclude inclusion of such modifications, variations and/or additions to the present subject matter as would be apparent.

Claims

CLAIMS What is claimed is:

1. An apparatus for a tractor trailer, comprising: a trailer skirt configured for being attached to a trailer of the tractor trailer that has a leading terminal end and a trailing terminal end and a length that extends in a longitudinal direction from the leading terminal end to the trailing terminal end, wherein the trailer skirt has an outer surface and an inner surface that are spaced from one another in a lateral direction and that define between them a width of the trailer skirt, wherein the trailer skirt has an upper surface and a lower surface that are spaced from one another in a vertical direction; wherein the upper surface has a first portion and a second portion, wherein the first portion is located forward of the second portion in the longitudinal direction, and wherein the first portion is closer than the second portion to the leading terminal end in the longitudinal direction, wherein the second portion is located higher in the vertical direction than the first portion.

2. The apparatus as set forth in claim 1 , wherein the upper surface has a third portion that is located rearward of both the first and second portions in the longitudinal direction, and wherein the third portion is closer than the first and second portions to the trailing terminal end in the longitudinal direction, wherein the second portion is located higher in the vertical direction than the third portion.

3. The apparatus as set forth in claims 1 or 2, wherein the upper surface has a convex shaped segment that extends from the first portion to the second portion, and wherein the first portion and the second portion are located on the convex shaped segment.

4. The apparatus as set forth in claim 3, wherein the upper surface extends from the leading terminal end to the trailing terminal end in the longitudinal direction, and wherein the entire upper surface from the trailing terminal end to the leading terminal end is convex in shape. The apparatus as set forth in any one of claims 1-4, further comprising a first mounting bracket that is located in the longitudinal direction at the same position as the first portion, wherein the first mounting bracket is attached to the trailer skirt and is configured for being attached to a bottom surface of the trailer; and a second mounting bracket that is located in the longitudinal direction at the same position as the second portion, wherein the second mounting bracket is attached to the trailer skirt and is configured for being attached to the bottom surface of the trailer; wherein the second mounting bracket is located higher than the first mounting bracket in the vertical direction. The apparatus as set forth in claim 5, wherein the bottom surface of the trailer is flat in shape upon extension in the longitudinal direction. The apparatus as set forth in claim 5 , wherein the bottom surface of the trailer is concave in shape upon extension in the longitudinal direction. The apparatus as set forth in any one of claims 3 or 4, wherein a bottom surface of the trailer is concave in shape and has a radius of curvature that is different than a radius of curvature of the convex shaped upper surface. The apparatus as set forth in any one of claims 1-8, wherein the lower surface of the trailer skirt extends from the leading terminal end to the trailing terminal end in the longitudinal direction, and wherein the entire lower surface from the leading terminal end to the trailing terminal end is concave in shape. The apparatus as set forth in any one of claims 1-9, wherein the height of the upper surface changes in the vertical direction upon extension of the upper surface in the longitudinal direction along at least 50% of the length of the trailer skirt. The apparatus as set forth in claim 10, wherein the height of the upper surface changes in the vertical direction upon extension of the upper surface in the longitudinal direction along at least 80% of the length of the trailer skirt. The apparatus as set forth in claims 2 and 5, further comprising a third mounting bracket that is located in the longitudinal direction at the same position as the third portion, wherein the third mounting bracket is attached to the trailer skirt and is configured for being attached to the bottom surface of the trailer, wherein the second mounting bracket is located higher than the third mounting bracket in the vertical direction, wherein attachment of the first, second, and third mounting brackets to the bottom surface of the trailer causes the first and third portions to be displaced more in the vertical direction than the second portion towards the bottom surface of the trailer to result in the lower surface of the trailer skirt being put into tension. The apparatus as set forth in any one of claims 1-13, further comprising: a bending member configured for being attached to the bottom surface of the trailer; a skirt attachment attached to the trailer skirt, wherein the bending member is in sliding engagement with the skirt attachment, and wherein deflection of the trailer skirt in the lateral direction by a deflection force is resisted by the bending member such that the bending member urges the trailer skirt in the lateral direction opposite to the deflection force. The apparatus as set forth in any one of the preceding claims, wherein the bottom surface of the trailer comprising I-beams that are spaced from one another in the longitudinal direction. The apparatus as set forth in claim 1, wherein the trailer skirt is configured for being put into tension when the trailer skirt is attached to the trailer.

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