U.S. patent application number 11/127600 was filed with the patent office on 2006-12-07 for automatic rear airfoil for vehicle.
Invention is credited to Paul Guy Andrus, Gayle Campbell-Andrus.
Application Number | 20060273625 11/127600 |
Document ID | / |
Family ID | 37493443 |
Filed Date | 2006-12-07 |
United States Patent
Application |
20060273625 |
Kind Code |
A1 |
Andrus; Paul Guy ; et
al. |
December 7, 2006 |
AUTOMATIC REAR AIRFOIL FOR VEHICLE
Abstract
A twin bag inflatable rear airfoil for truck or transport
trailer with attached shelves that bridge the surface gap between
the trailer side and top surfaces, and the corresponding side and
top surfaces of the inflatable bags. Shelves also bridge the upper
surface gap between the two bags and provide a platform to deploy a
collapsible yaw control fin. Another set of panels provide airfoil
surfaces in the ground domain and are integral to the organised
automatic folding and stowage of the apparatus. Interrupted ribs
stiffen the inflatable surfaces while allowing them to fold in an
orderly manner.
Inventors: |
Andrus; Paul Guy; (Ancaster,
CA) ; Campbell-Andrus; Gayle; (Ancaster, CA) |
Correspondence
Address: |
Paul G. Andrus
46 Wiltshire Place
Ancaster
ON
L9K 1M5
CA
|
Family ID: |
37493443 |
Appl. No.: |
11/127600 |
Filed: |
May 13, 2005 |
Current U.S.
Class: |
296/180.1 |
Current CPC
Class: |
B62D 35/004
20130101 |
Class at
Publication: |
296/180.1 |
International
Class: |
B62D 35/00 20060101
B62D035/00 |
Claims
1. An inflatable airfoil adapted to be mounted on the rear surface
of a transport vehicle, said vehicle having side and top surfaces,
said airfoil comprising a pair of flexible enclosed bags, said bags
having lateral and lower surfaces wherein said lateral surfaces
have attached rigid shelves oriented parallel to said lateral
surfaces, said shelves extending forwardly to meet said side
vehicle surfaces.
2. An inflatable airfoil adapted to be mounted on the rear surface
of a transport vehicle, said vehicle having side and top surfaces,
said airfoil comprising a pair of flexible enclosed bags, said bags
having lateral and lower surfaces wherein a rigid panel extends
from the lower part of said lateral bag surface downwardly towards
the ground and forwardly to meet said side vehicle surface, said
rigid panel having a rigid support member extending from said rigid
panel to the lower portion of said rear vehicle surface, said rigid
support member having a hinged interruption along the length of
said rigid support member, said rigid support member having one or
more cords attached along the length of said rigid support member,
said cords attaching to the lower surface of said bag such that
upon inflation of said bag, said rigid support member is lifted and
unfolded while said rigid panel is positioned parallel to said
lateral surface.
3. An inflatable airfoil as recited in claim 1 wherein a series of
inelastic cords extent from said lateral surface to attach at
substantially equally spaced points along the length of an elastic
cord such that upon inflation of said airfoil, said elastic cord is
stretched into an arced or semicircular orientation, and such that
upon deflation of said airfoil said elastic cord relaxes and
shortens into a more linear orientation while said inelastic cords
pull said lateral surface into a folded collapsed state.
4. An inflatable airfoil adapted to be mounted on the rear surface
of a transport vehicle, said vehicle having side and top surfaces,
said airfoil comprising a pair of flexible enclosed bags, said bags
having upper surfaces wherein said upper surfaces each have a rigid
shelf oriented parallel to said upper surfaces, said rigid shelves
extending forwardly to meet said top vehicle surface and medially
to approach the rigid shelf that extends medially from the other of
the two bags, one of said rigid shelves having a rigid fin attached
along the medial edge of said rigid shelf, said rigid fin oriented
substantially perpendicular to said rigid shelves when said bags
are inflated, said rigid fin extending upwards above the level of
the rigid shelves when said bags are inflated such that air flowing
over the upper surface of said bags is directed to flow parallel to
said fin.
5. An inflatable airfoil as recited in claim 4 wherein said rigid
fin is hingedly attached along the medial edge of said rigid shelf
such that said fin collapses to be oriented substantially parallel
to said rigid shelves when said bags are deflated.
6. An inflatable airfoil adapted to be mounted on the rear surface
of a transport vehicle, said vehicle having side and top surfaces,
said airfoil comprising a pair of flexible enclosed bags, said bags
having upper and lateral surfaces wherein a series of rigid members
are attached along the length of said upper and lateral surfaces
such that said lateral surfaces are stiffened horizontally and said
upper surfaces are stiffened medially when said bags are
inflated.
7. An inflatable airfoil as recited in claim 6 wherein one or more
of said rigid members along said lateral surfaces has an
interruption along the length of said rigid member such that said
lateral surface folds at said interruption when said bag is
deflated.
Description
BACKGROUND OF THE INVENTION
[0001] The reduction in aerodynamic drag resulting from the
addition of a boattail shaped appendage to a boxed shaped vehicle
has been well examined. Drag reductions of 30% are realistically
possible (NASA/TP-1999-206574, "A Reassessment of Heavy-Duty Truck
Aerodynamic Design Features and Priorities"), and would correspond
to fuel savings of 15% for a transport truck. There are however
several practical requirements that pose difficulties to
implementing such a device on a working transport trailer. The
device must not impede the operation of the trailer doors,
typically swinging double doors on trailers used for long-distance
haulage. The device must present a smooth, gently tapering set of
boattail (side) and backlight (top) surfaces that connect tightly
to the trailer sides and top respectively for optimum aerodynamic
performance. Given practical difficulties in tightly fitting an
inflatable to the hardware laden trailer door perimeter, the
present invention uses rigid shelves to bridge the gap that exists
between the trailer's trailing edge and the inflated bags when the
bags are mounted onto the doors away from the edges and door
hinges. This arrangement is also advantageous in eliminating
undesirable surface contours due to the inflatable bag's surface
bulge that occurs in the transition zone where the airfoil meets
the trailer. Not only must the device not impede door operation,
but it must get out of the way of the doors without any significant
dismantling effort on the part of the operator. Given that the
device operates in a physically hostile environment, it must not
vibrate to a degree that causes premature wear of its structural
components. It should automatically collapse when the trailer stops
so that it is not battered by high winds which could attack it
directly from the side while stopped, unlike its' relatively wind
sheltered position while travelling at highway speed. The present
design comprises dual ram-air inflated bags as a framing structure
for the overlying airfoil surfaces. The force of the inflated bag
internal pressure against the trailer doors is counterbalanced by
the hingedly attached hardware that attaches the airfoil to the
trailer, thereby drawing the hardware tight and minimizing its'
vibration during airfoil operation. The inflation/deflation cycle
occurs slowly and calmly over several minutes. Both of these
aspects relating to the inflated bags minimize wear on the
attachment hardware which is necessary for such a device to last
several years without need for major structural maintenance. An
inflatable however, requires surface shape control and stiffening
in order to remain stable during operation, and avoid surface
vibration and wear. To this end, the present disclosure describes a
series of staggered interrupted ribs attached along the inflated
bags surfaces that provides surface stability during inflation,
while accommodating complex folding for stowage.
[0002] Transport trailers operate in conditions of cross wind
creating an angle of yaw at which the air attacks the trailer,
typically in the 5-10 degree range. Boattail surfaces tend to
perform aerodynamically better in cross-wind (higher yaw)
conditions, however the backlight loses its' drag reducing function
as the angle of yaw rises. In order to preserve backlight
performance in yaw, the present device provides for a vertical fin
to redirect trailer roof air flow directly behind the trailer where
it can contribute to pressure recovery as it would in the zero yaw
condition. The present device overcomes practical operating
difficulties of a fin such as structural integrity(flexibility)
during high cross-wind conditions while still allowing for
automatic deployment and stowage.
[0003] Given that the transport trailer is a road vehicle, drag
relating to underbody airflow as well as flow around the rear
wheels near the ground figures significantly in overall drag. The
present device overcomes difficulties in practically cleaning up
the airflow in this domain in order to approach theoretical minimum
drag. To this end the present disclosure further describes a set of
panels that provide for ground domain streamlining of airflow. A
major difficulty in the deployment of rigid or semi-rigid panels as
airfoil surfaces behind a trailer is the weight and complexity of
adequate structural reinforcement, particularly if the panels are
large enough to perform well aerodynamically and are not collapsed
automatically when the trailer stops, thereby exposing them to
severe ambient wind gusts. The present device overcomes these
problems by anchoring the panels to the inflated bags, and by using
bag surface tension to lift and lock panel support members into
position and dampen their vibration. Graham (U.S. Pat. No.
6,854,788 B1) has used radially oriented collapsible tension
bearing struts to stabilize the boattail surfaces. These struts are
disposed and function in a manner similar to the radially oriented
cords inside the inflatable bags of Andrus (U.S. Pat. No. 6,409,252
B1), the difference being that Graham creates boattail surface
tension (that offsets strut tension) by bending semi-rigid flexible
sheets for boattail surfaces, whereas Andrus uses air pressure
within the inflatable bags. The panel support members of the
present disclosure differ from the tension bearing radially
oriented cords/struts of Andrus (U.S. Pat. No. 6,409,252 B1) and
Graham (U.S. Pat. No. 6,854,788 B1) in that they are rigid folding
struts that lock into position when the boattail panels are
deployed thus fixing the panels against movement both laterally and
medially, and therefore do not depend upon boattail surface tension
to be stiffened. The main advantage of this approach over that of
Graham (U.S. Pat. No. 6,854,788) is that the panels can be easily
collapsed automatically when the airfoil is not in use without
having to open the trailer doors. The panels as disclosed herein
therefore do not depend on trailer door closure in order for them
to assume an aerodynamically effective angle relative to the side
of the trailer. Examples of scenarios in which automatic collapse
of the panels would be preferable include stopping or city driving
when severe ambient winds prevail in order to avoid wind damage,
parking in a trailer yard in order to avoid parking damage and
space usage, and having a damaged airfoil during long distance
delivery such that it is not safe to deploy yet not near repair
shop.
SUMMARY OF THE INVENTION
[0004] The invention relates to rigid panels, ribs and fins for an
inflatable trailer airfoil. While the inflatable approach provides
size and vibration tolerance with minimum weight and easy
collapsibility, there are airflow surface domains that are better
treated with a relatively rigid sheet. The panels are deployed in
three domains. The first are shelves that bridge the airfoil
surface gap that occurs between the trailing edges of the trailer
and the inflated bags because of door hinging and other hardware
mounting restrictions for the bags, as well as practical
considerations relating to inflatable shape control in the
transition zone where the trailer meets the airfoil. Another set of
shelf panels bridge the gap between the two bags' top surfaces, and
support a fin that corrects for the undesirable effects of
crosswind (yaw) on drag reduction by the backlight (top) surface of
the airfoil. The last set of panels extends the airfoil surface
below the lowest level to which the bags can extend due to trailer
door handle access requirements and practical limitations in the
extent to which the bags hang when deflated. This last set of
panels also plays a role in the orderly method of deflation and
stowage such that the airfoil is resistant to severe wind and
weather while stowed. In order to stiffen the majority of the
airfoil surface with a minimum of weight and materials, a series of
interrupted ribs are attached along the inflatable surfaces. The
rib interruptions allow the bags to fold for stowage. A flexible
surface skin is then added to cover the ribs and provide a smooth
airflow surface. With respect to aerodynamic or fuel saving
function, the components may be grouped into those working in the
boattail (side surface) domain and those working in the backlight
(top surface) domain, as each of these could work independently of
the other. A cheaper and lesser performing version of the present
invention could be constructed using only the boattail aspects, or
alternatively only the backlight aspects.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 is a perspective view of the airfoil fully
deployed.
[0006] FIG. 2 is a perspective view with the airfoil's outer skin
removed from the left bag to expose the underlying framing
structures.
[0007] FIG. 3 is a rear view of the airfoil fully deployed with the
internal elastic and inelastic cord arrangements schematically
depicted within the left bag.
[0008] FIG. 4 is a rear view of the airfoil when collapsed with the
outer skin removed from the right bag and the internal cord
arrangements shown within the left bag.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0009] The device is comprised of a pair of inflatable bags 10 that
are inflated upon forward motion of the trailer 11 by ram air
intake scoops 12 that extend above the trailer roof line 13 from
each bag 10. The bags 10 are pressed together along a central cleft
14 when inflated, and this union has a stabilising effect on the
apparatus. The boattail 15 and backlight 16 surfaces are reinforced
by a series of staggered interrupted ribs 17 to create rigidity
during inflation, while enabling complex folding during deflation.
A boattail shelf 18 is fixed to the boattail surface 15 and extends
forwardly to meet the trailer side 19. The boattail surface 15 is
anchored to the medial edge 20 of the base of each bag via a series
of cords 21 that extend radially from the medial edge 20 to the
boattail surface 15. A backlight shelf 22 is fixed to the backlight
surface 16 and extends forwardly to meet the trailer roof line 13,
and medially to meet the opposite shelf. A yaw control fin 23 is
hingedly attached to one of the backlight shelves 22, and to the
medial surface 24 of one bag within the central cleft 14. The fin
23 is thereby firmly yet flexibly held in a vertical orientation
during inflation, but collapses during deflation. Air approaching
the trailer at an angle of yaw shown as .psi. is redirected by the
fin 23 to flow parallel to the fin (and the trailer 11). Rigid
boattail panels 25 are attached to and extend downward from the
lower boattail surface 15 of each bag to the bottom of the trailer
11, and if desired down further down towards the road. The panels
are held stiffly in their deployed position by hinged rods 26 that
extend from the lower trailer door 27 to the panels 25. The rods 26
are lifted and held firmly in their deployed positions by cords 28
that insert into the lower surface 29 of each bag 10. Vertically
oriented cords 30 within each bag extend from the lower 29 to the
backlight 16 surfaces. The backlight surface 16 is thereby anchored
to the hinged rods 26 (via the vertical cords 30) so that the
backlight surface 16 is not variably lifted by the backlight
airflow. While the hinged rods 26 bear the lift load, the more
dominant internal pressure load upon the underside of the backlight
surface 16 is evenly offset by the internal pressure on the lower
surface 29 via the vertical cords 30. The arrangement of the
combined vertical 30 and radial 21 cord arrays ensures a
symmetrical static force balance which prevents shape distortions
in the bag such as sagging during inflation. This system is
disclosed in Andrus (U.S. Pat. No. 6,409,252 B1). The combined
vertical 30 and radial 21 cord arrays in conjunction with the
staggered interrupted ribs 17 allow for substantially planar
(gently curved) boattail 15 and backlight 16 surfaces while
avoiding deep surface dimpling which would weaken surface stability
when inflated. Elastic cords 31 are attached to the radial cords 21
(and by extension to the boattail surfaces 15) in a semicircular
orientation during inflation, so that when internal bag pressure
drops, the elastic cords 31 contract and draw the boattail surfaces
15 into a flatly folded condition. This system is a refined version
of that disclosed in Andrus (U.S. Pat. No. 5,236,347). A covering
skin. 32 extends from the boattail 18 and backlight 22 shelves to
be fixed under tension along its' trailing edge 33 at the rearward
end of each row of interrupted ribs 17. The air drag can by further
reduced by treating the underbody airflow by either adding side
trailer skirts, or by adding a shroud 34 around the rear wheel
apparatus. In either case the boattail panels 25 may then be
extended below the lower edge 35 of the trailer 11 towards road
level so that this domain is optimally treated as well with respect
to its' aerodynamic drag. A recirculating zone 36 of airflow is
created behind the panels 25 and over the lower surface 29 of the
bag 10.
* * * * *