Patent Document

FIELD OF THE INVENTION 
     The present invention relates generally to sport bars used in vehicles. More particularly, the present invention relates to an adjustable three-piece hydroformed sport bar and a method for forming the same. 
     BACKGROUND INFORMATION 
     Sport bars are a structural body component typically used in convertible vehicles, but also in certain non-convertible vehicles as well. The sport bar spans the width of the vehicle in a convex arc toward the rear of the top roof portion. The sport bar acts as an anchor point for seat belts as well as other features including e.g., lighting fixtures, trim cladding etc. 
     Because of its important safety function in supporting the seat belts, legal automotive standards in certain jurisdictions may require that the sport bar be able to support a threshold level of force load so that it does not fail if the seat belt is subject to large tension during, for example, an abrupt movement or an accident. This consideration favors a robust structure for the sport bar. Automotive head impact safety criteria in certain jurisdictions mandate that the sport bar be soft enough to avoid serious injury if a passenger were to strike his or her head directly against the sport bar at a high velocity during such an accident. This consideration weighs in the opposite direction, favoring a less robust construction. 
     Conventional single piece sport bars generally favor one design criteria over the other, in that they are either too robust for the head impact criteria, or not robust enough for the seat belt load requirements. 
     It is therefore an object of the present invention to provide a sport bar that provides both adequate seat belt load support and flexibility during possible head impact. It is another object of the present invention to provide a sport bar having an adjustable width. 
     SUMMARY 
     The above and other beneficial objects of the present invention are most effectively attained by providing an adjustable sport bar and a method for forming an adjustable sport bar as described and claimed herein. In one example embodiment, the adjustable sport bar is formed from three pieces including left and right outer bar elements and an inner bar element. The inner bar element may have a smaller diameter than the outer tubular bar element or vice versa. The inner tubular bar element is able to slide inside the outer tubular bar elements where it is adjustably fastened to each of the outer tubular bar elements with a bottom gap between the bottom of the inner tubular bar element and the bottom of the outer tubular bar elements. The outer bar elements can be adjusted laterally with respect to the inner bar element. The left and right outer tubular bar elements may include expanded anchor sections to provide for greater yield strength at these sections for seat belt support. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a horizontal view of a three-piece sport bar according to an example embodiment of the present invention; 
         FIG. 2  is an expanded view of area B illustrated in  FIG. 1 ; 
         FIG. 3  is a cross-sectional side view taken along line  3 — 3  in  FIG. 1 ; 
         FIG. 4  is a perspective view of the right end of an outer bar element and the left end of an inner bar element according to an example embodiment of the present invention; and 
         FIGS. 5A to 5D  illustrate a production sequence for forming the three-piece sport bar illustrated in  FIGS. 1 to 4 . 
     
    
    
     DETAILED DESCRIPTION 
     Those skilled in the art will gain an appreciation of the present invention from a reading of the following description when viewed in conjunction with the accompanying drawings of  FIGS. 1 to 5D , inclusive. The individual reference characters designate the same or similar elements throughout the several views. 
     Referring now to  FIG. 1 , there is shown a horizontal view of an example embodiment of a three-piece sport bar  10  according to the present invention (hereafter referred to as “sport bar”). Sport bar  10  includes left and right outer bar elements  12 , 14  which may be tubular, and which may be composed of metallic material and formed into appropriate shape and size according to hydroforming techniques whereby sections may be formed into shape from a single tubular member. Each outer bar element  12 ,  14  includes an expanded anchor section  22 ,  24  towards the bottom having, e.g., an approximately 20 percent larger tubular width (and 44% larger cross-sectional area) than upper respective left and right non-expanded sections  26 ,  28 . The expanded cross-area gives the anchor sections  22 ,  24  greater structural tensile strength in comparison to the upper sections  26 ,  28 . 
     Seat belt anchors  25 ,  27  attached to the left and right anchor sections  22 ,  24  include threaded sleeves for receiving a seat belt bolt. Thus, when a high degree of tension is applied to a seat belt, the load is transferred to the seat belt anchors  25 ,  27  and borne at the expanded anchor sections  22 ,  24 , which have been expanded to improve their respective load-bearing capacities. 
     Each upper section  26 ,  28  curves inwardly until their respective upper ends face in a horizontal direction toward each other.  FIG. 2  illustrates an expanded view of area B in  FIG. 1  where the left outer bar element  12  is coupled to the inner bar tubular element  16 . It is to be understood that the illustrations of  FIG. 2  apply equally to the coupling between the inner bar element  16  and the right outer bar element  14 . 
     As shown in  FIG. 2 , the inner bar element  16  has a smaller cross-sectional area than the upper section  26  of the outer bar element  12 , and therefore the inner bar element may slide into the end of the outer bar element.  FIG. 4  shows a perspective view of the right end of outer bar element  12  and the left end of inner bar element  16 . As shown, the top of the inner bar element  16  is provided with a hole  38 . In addition, the top of the outer bar element  12  includes a narrow lateral adjustment slot  42 . As the end of the inner bar element  16  penetrates into the ends of the outer bar element  12 , the hole  38  at the top of the inner bar element aligns with the lateral adjustment slot  42  at the top of the outer bar element  12 . A bolt  35  may be received through both the hole  38  and the slot  42  and then fastened with a stationary nut  37 , such as a rivet nut, to affix the top of the inner bar element to the tops of the outer bar elements  12  (the same features are included on the right outer bar element  14  and the right side of the inner bar element  16 ). The location of the fastening may be adjusted longitudinally along the slot  42  to account for different body build variations. Since vehicle body dimensions will vary to some extent due to variability in the installation and assembly process, it is important to be able to adjust the width of the sport bar to accurately fit into a particular vehicle body. Thus, according to the present invention, the outer bar elements  12 ,  14  may be moved rightward and leftward with respect to the inner element  16  to expand or contract the entire width of the sport bar to fit precisely into a particular vehicle. After an appropriate adjustment has been made, and the outer bar  12  element has been fastened to the inner bar  12  element with the bolt  35  and nut  37  coupling, a weld  39 , e.g., a structural MIG weld may be applied at the interface between the outer bar element  12  and the inner bar element  16  to permanently adjoin the elements in an integrated structure. 
     Since the inner  16  and outer bar elements  12 ,  14  are coupled at their respective top portions, there is a bottom gap  30  between the bottom of the outer bar elements  12 ,  14  and the inner bar element  16  in coupling region C where the inner bar element  16  penetrates the outer bar element  12 . The bottom gap  30  is also illustrated in  FIG. 3  which shows a cross-section taken along line A—A of  FIG. 1  that illustrates the inner bar element  16  within the left outer bar element  14  with the bottom clearance gap  30 . 
     The length of the inner bar element  16  is designed so that the region of coupling C (of  FIG. 2 ) is situated in the vehicle directly over where a passengers head would normally be positioned in a driving situation. Region C is therefore the most likely area a head impact is likely to occur. The upper sections of the outer bar elements in this area  26 ,  28 , having relatively smaller cross-section relative to more robust bottom sections  22 ,  24 , have correspondingly reduced structural compressive strengths and thus absorb impact energy and deflect to some extent under compressive forces, softening any head impacts that might occur in this area. The gap  30  between the outer  12 ,  14  and inner  16  bar elements provides space to allow the outer bar elements to deflect inwardly against the inner bar element during impact to reduce the intensity of head impacts, without having the resulting deformation to the outer bar elements affect their attachment to the inner bar element. The structural integrity of the sport bar may thus be safeguarded despite any damage to the outer bar elements that might occur during impacts. 
       FIGS. 5A to 5D  illustrate a production sequence for producing the three bar elements  12 ,  14 ,  16  from a single starter tube.  FIG. 5A  illustrates the starter tube having a uniform diameter and cross-section.  FIG. 5B  illustrates the shape of the tube after it has been bent into an arcuate shape using a tube bender. The bent tube is then placed into a hydroform die in which water is introduced into the interior of the tube at high pressure, expanding portions of the tube according to the shape of the die. As shown in  FIG. 5C , during the hydroforming, the diameters of the outer bottom sections of the tube are expanded, and the diameter of the middle section is unchanged, with transitional sections S 1  and S 2  showing a gradual expansion between the middle and outer sections. The transitional sections are then cut out and removed from the tube, dividing the tube into the three bar elements  12 ,  14 ,  16 . 
     While the inner bar element  16  has been described above as having a smaller outer diameter than the inner diameter of the outer bar elements  12 ,  14  is should be appreciated that the outer diameter of the outer bar elements  12 ,  14  may be smaller than the inner diameter of the inner bar element  16  so that the ends of the outer bar elements  12 ,  14  are insertable into the ends of the inner bar element. Alternatively, the outer diameter of one of the outer bar elements  12 ,  14  may be smaller than the inner diameter of the inner bar element  16  and the inner diameter of the other one of the outer bar elements  12 ,  14  may be greater than the outer diameter of the inner bar element  16 , so that one end of the inner bar element  16  is inserted into one of the outer bar elements  12 ,  14  and the other end of the inner bar element  16  receives the other one of the outer bar elements  12 ,  14 . 
     Thus, the several aforementioned objects and advantages of the present invention are most effectively attained. Those skilled in the art will appreciated that many modifications of the preferred embodiments described hereinabove may be made without departing from the spirit and scope of the invention. Although several preferred embodiments of the invention have been described and disclosed in detail herein, it should be understood that this invention is in no sense limited thereby and that its scope is to be determined by that of the appended claims.

Technology Category: 7