NZ587749A - An aerodynamic vehicle cross bar having projections with notches - Google Patents

Abstract

A roof rack cross bar is disclosed. The roof rack cross bar has an approximately rectangular cross section where: (a) the leading face of the cross bar, as it is fitted to a vehicle, is shaped to have an upper and lower forward facing projection; (b) the projections have a plurality of notches that direct air flow around the bar thereby reducing audible noise produced by the cross bar; (c) the region intermediate the two projections is slightly recessed so as to form a groove intermediate the two projections; and (d) the transition between the groove and projections is smooth and the groove presents a concave surface to the airflow.

Description

Received at IPONZ on 10 Jan 2010 PATENTS FORM NO. 5 Appln Fee: $250.00 CreatelP ref: HUB127PNZ PATENTS ACT 1953 COMPLETE SPECIFICATION Complete in the First Instance AN AERODYNAMIC VEHICLE CROSS BAR We, Hubco Automotive Limited, a New Zealand company with a registered office at 102-112 Daniell Street, Newtown, Wellington, New Zealand, and Peter Douglas Hubbard, a New Zealand citizen, c/- 46 Parkhouse Road, Sockburn, Christchurch, New Zealand and David Charles Grove, a New Zealand citizen c/o 102-112 Daniell Street, Newtown, Wellington, New Zealand, do hereby declare this invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in the following statement 1 Received at IPONZ on 10 Jan 2010 AN AERODYNAMIC VEHICLE CROSSBAR TECHNICAL FIELD The invention relates to a vehicle cross bar. More specifically, the invention relates to a vehicle cross bar with a more aerodynamic profile that reduces noise generated from the bar when fitted to a moving vehicle.

BACKGROUND ART Vehicle roof racks are well known in the art typically comprising a leg or legs that retain the rack to the vehicle via direct attachment to the roof or to side rails. The leg or legs then attach to a cross bar on which various accessories or items may be mounted. As should be appreciated, since the cross bar faces directly in to the direction of travel of the vehicle, the cross bar has the propensity to produce considerable noise and drag as the vehicle is driven.

Various cross bars exist to attempt to minimise roof rack noise and drag. Some examples include the Thule Aero™ cross bar, the Whispbar™ cross bar and others.

These types of bar are sometimes very effective at reducing wind noise and drag but they tend to be more expensive to produce and due to their greater complexity shape.

Some cross bars make no attempt to address wind noise whatsoever, an example being a very simple extruded rectangular bar. The industry standard is that this bar has a height of 22mm and a width of 32mm. This type of bar is noisy and has considerable drag but one advantage is that it is very simple and inexpensive to manufacture as it is a very simple metal extrusion shape.

It should be appreciated that it would be useful to produce a simple low cost rectangular cross bar that also reduces wind noise and even drag.

One attempt to address this is taught in WO 01/98109. In this specification a metal extruded rectangular bar includes channels recessed into the cross bar leading face with a view to reducing wind noise. While this technique does reduce wind noise, it is more expensive to manufacture as it requires an operator to press or cut the channels into the metal extrusion thereby taking considerable time and labour to manufacture. The design also leaves sharp edges that can be a hazard when fitting items to the cross bar.

It is an object of the present invention to address the foregoing problems or at least to provide the public with a useful choice.

It is acknowledged that the term 'comprise' may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term 'comprise' shall have an inclusive meaning - i.e. that it will be taken to 2 mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements. This rationale will also be used when the term 'comprised' or 'comprising' is used in relation to one or more steps in a method or process.

Further aspects and advantages of the present invention will become apparent from the ensuing 5 description that is given by way of example only.

SUMMARY OF THE INVENTION The invention broadly relates to a vehicle cross bar used as part of a roof rack system for attaching objects to the roof of a vehicle. The cross bar has improved aerodynamic 10 characteristics compared to many existing cross bars on the market and is easy to manufacture and produce.

In a first embodiment there is provided a roof rack cross bar including an approximately rectangular cross section wherein the leading face of the cross bar as it is fitted to a vehicle is shaped to have an upper and lower forward facing projection and wherein the projections have a 15 plurality of notches therein the direct air flow around the bar thereby reducing audible noise produced by the cross bar.

In a second embodiment there is provided a roof rack cross bar including an approximately rectangular cross section cross bar extrusion along with a casing that fits over at least the leading face of the cross bar extrusion, wherein the leading face of the casing when fitted to the 20 cross bar and fitted to a vehicle is shaped to have an upper and lower forward facing projection and wherein the projections have a plurality of notches therein the direct air flow around the bar thereby reducing audible noise produced by the cross bar.

Advantages of the cross bar include reduced wind noise. By reducing the noise, the drag effect may also be reduced resulting in improved vehicle fuel economy as well.

BRIEF DESCRIPTION OF THE DRAWINGS Further aspects of the present invention will become apparent from the following description that is given by way of example only and with reference to the accompanying drawings in which: Figure 1 illustrates a perspective view from above of one embodiment of the leading edge of 30 the cross bar; Figure 2 illustrates a detail perspective view of the leading face of the cross bar; Figure 3 illustrates a detail perspective view of one end of the cross bar; Figure 4 illustrates a front elevation view of a section of the cross bar leading face; Figure 5 illustrates a plan view of one side of the cross bar view from above; Figure 6 illustrates a bottom view of one side of the cross bar when viewed form underneath; 3 Figure 7 and illustrates a comparative study of the sound pressure levels emitted by the improved cross bar described compared to other types of cross bar on the market.

DETAILED DESCRIPTION As noted above, the invention broadly relates to a vehicle cross bar used as part of a roof rack system for attaching objects to the roof of a vehicle. The cross bar has improved aerodynamic characteristics compared to many existing cross bars on the market and is easy to manufacture and produce.

In a first embodiment there is provided a roof rack cross bar including an approximately rectangular cross section wherein the leading face of the cross bar as it is fitted to a vehicle is shaped to have an upper and lower forward facing projection and wherein the projections have a plurality of notches therein the direct air flow around the bar thereby reducing audible noise produced by the cross bar.

In one embodiment, the region intermediate the two projections is slightly recessed so as to form a groove intermediate the two projections. Optionally, the transition between the groove and upper and lower projections is smooth and the groove presents a concave surface to the airflow. In one embodiment, the groove runs along the length of the cross bar leading face.

In one embodiment, the distance between the two projections and the region intermediate the 20 two projections ranges from 1 to 20mm, more preferably approximately 3 to 8mm.

In a further embodiment, the notches are transverse grooves located at spaced apart intervals along the length of the cross bar. The notches may be inserted at regular intervals. In one embodiment, the notches are spaced at asymmetric intervals. Further, the notches in the upper projection may be offset from the notches in the lower projection.

In one embodiment, the notch walls may have a rounded profile.

Without being constrained to a set size, the notches in one embodiment may be 0.5 to 30mm deep and may be spaced approximately 5 to 100 mm apart.

Without being bound to any specific theory, the inventors understand that the multiple notches on the leading face of the cross bar reduce the amount of noise by reducing the amount of 30 vortex shedding occurring by air as it moves over the cross bar leading face. The multiple notches appear to introduce various small airstreams that disturb or destroy the vortex effect behind the crossbar.

In a further embodiment, the cross bar may be formed from two parts, the first being an extruded rectangular cross section bar and the second being a casing the fits over the rectangular cross 35 bar and wherein the casing includes features on the forward face of the cross bar.

Optionally, the casing may be an injection moulding. 4 In the above embodiment, the casing extrusion may slide over the cross bar extrusion. In this embodiment, the casing is sized to have a snug fit over the cross bar extrusion. Alternatively, the casing may be fitted in place by use of a mechanical fastener or fasteners such as a bolt or rivet or instead may be held in place via a chemical fastener such as an adhesive. In a further 5 alternative embodiment, the casing may be over-moulded onto the cross bar extrusion.

The use of a casing is useful as the casing may be made from an inexpensive and easily moulded material such as plastic thereby dramatically reducing the manufacturing time and cost compared to for example the bar taught in WO 01/98109.

In a second embodiment there is provided a roof rack cross bar including an approximately 10 rectangular cross section cross bar extrusion along with a casing that fits over at least the leading face of the cross bar extrusion, wherein the leading face of the casing when fitted to the cross bar and fitted to a vehicle is shaped to have an upper and lower forward facing projection and wherein the projections have a plurality of notches therein the direct air flow around the bar thereby reducing audible noise produced by the cross bar.

As noted above, advantages of the cross bar include reduced wind noise. By reducing the noise, the drag effect may also be reduced resulting in improved vehicle fuel economy as well. The leading face design described dramatically reduces the noise produced by a standard inexpensive rectangular cross section bar. Use of a casing over a standard bar also makes the improved design highly cost effective and simple to manufacture and obtain materials for.

WORKING EXAMPLE The invention is now described with reference to a detailed description of an embodiment of the cross bar of the present invention.

Referring to Figures 1 to 6 there is illustrated an example of a roof rack cross bar generally 25 indicated by arrow 1. The cross bar 1 shown is made up of a standard rectangular cross section metal extrusion 2 onto which a casing 3 has been fitted.

In the example shown, the casing 3 fully encloses the metal extrusion 2 although it should be appreciated that partial enclosure by the casing 3 may also be completed.

In a further alternative, the bar extrusion 2 may have no casing 3 and instead be one continuous 30 extrusion and/or injection moulded piece of the exterior shape shown in the Figures.

The leading face 4 of the cross bar 1 includes special features designed to reduce wind noise. Note that the term leading face refers to the side of the cross bar facing into the airstream as the cross bar moves forward when attached to a vehicle. The direction of movement forwards is indicated by arrow A. The term leading face is used in a similar manner to the term leading 35 edge used in aeronautical of sailing terminology being the side of the bar 1 that the airstream first hits and tries to move around.

A traditional flat faced rectangular cross section bar presents a sudden flat face to the air and as the air passes over the bar 1, vortex shedding occurs resulting in considerable noise in the audible spectrum. The faster the vehicle is travelling, the louder the noise.

The front face 4 of the bar 1 includes an upper and lower projection 5,6 that have a series of 5 notches 7 therein. The notches 7 in the top projection 5 are offset from the notches 7 in the lower projection 6. In the example shown, the notches 7 are cut into the projections on an angle and the sides of each notch 7 rounded.

Between the two projections 5,6 the intermediate region 8 presents a smooth concave surface to the airstream 4. Whilst not wanting to be bound to a specific theory, the intermediate region 8 10 is understood to disperse air through the notches 7.

The notches 7 are understood to reduce or remove the vortex shedding effect thereby eliminating or at least reducing wind noise from the cross bar 1.

To confirm the reduction in wind noise a trial was completed using an independent authority with a test wind tunnel. The cross bar described above was provided to the authority along with a 15 traditional rectangular extrusion cross bar and a cross bar as described in WO 01/98109 with channels cut out of the metal extrusion itself. Three other commercially available cross bars were also tested in comparison including the Whispbar™ manufactured by the applicant and three other key competitor cross bars sold as being aerodynamic.

The trial involved testing each cross bar in a wind tunnel replicating the wind generated by a car 20 moving at 100 km/h. The sound pressure level was measured for a range of frequencies including the range of 100-400 Hz that is normally heard the loudest by the human ear.

The results of the trial are shown in Figure 7.

As shown, the worst or noisiest cross bar was the standard rectangular bar as expected. The invention bar performed at a similar level to the bar taught in WO 01/98109 although it should 25 be noted that manufacture of the invention cross bar is considerably quicker and less expensive than the channel design of WO 01/98109.

Interestingly a competitor bar sold as being aerodynamic almost performed as badly as the rectangular bar in the 100-400Hz region whilst two other bars also sold as being aerodynamic designs were worse than the invention bar but at least better than a rectangular bar.

The Whispbar™ that is sold as having a quiet design was indeed the least noisy bar by a considerable margin.

The above results confirmed that the invention design is at least as quiet as existing designs if not quieter than designs currently sold as being aerodynamic.

Aspects of the present invention have been described by way of example only and it should be 35 appreciated that modifications and additions may be made thereto without departing from the scope of the claims herein. 6 Received at IPONZ on 8 August 2011

Claims (14)

WHAT IS CLAIMED IS:

1. A roof rack cross bar with an approximately rectangular cross section wherein: a. the leading face of the cross bar as it is fitted to a vehicle is shaped to have an upper and lower forward facing projection; b. the projections have a plurality of notches that direct air flow around the bar thereby reducing audible noise produced by the cross bar; c. the region intermediate the two projections is slightly recessed so as to form a groove intermediate the two projections; and d. the transition between the groove and projections is smooth and the groove presents a concave surface to the airflow.

2. The cross bar as claimed in claim 1 wherein the groove runs along the length of the cross bar leading face.

3. The cross bar as claimed in any one of the above claims wherein the distance between the two projections and the region intermediate the two projections ranges from 1 to 20mm.

4. The cross bar as claimed in any one of the above claims wherein the notches are grooves orientated in a transverse direction relative to the cross bar and located at spaced apart intervals along the length of the cross bar.

5. The cross bar as claimed in claim 4 wherein the notches are at regular intervals.

6. The cross bar as claimed in any one of the above claims wherein the notches in the upper projection are offset from the notches in the lower projection.

7. The cross bar as claimed in any one of the above claims wherein the notch walls have a rounded profile.

8. The cross bar as claimed in any one of the above claims wherein the notches are 0.5 to 30mm deep.

9. The cross bar as claimed in any one of the above claims wherein the notches are 5 to 100 mm apart.

10. The cross bar as claimed in any one of the above claims wherein the cross bar is formed from two parts, the first being an extruded rectangular cross section bar and the second being a casing fitted to the leading face of the cross bar and wherein the casing is shaped to have an upper and lower forward facing projection and wherein the projections have a plurality of notches therein.

11. The cross bar as claimed in claim 12 wherein the casing is an injection moulding.

12. The cross bar as claimed in claim 10 wherein the casing in an extrusion that slides over the cross bar extrusion.

13. The cross bar as claimed in claim 12 wherein the casing is sized to have a snug fit over the cross bar extrusion. 7 Received at IPONZ on 8 August 2011

14. A cross bar substantially as hereinbefore described and with reference to the Example and Figures 1 to 7. Hubco Automotive Limited By their attorneys CreatelP Per: 8