Abstract:
A two-piece doorbeam including a relatively low-cost, low-strength body and a relatively high-cost, high-strength insert. The insert is hat-shaped and crimped within the body. The insert provides improved impact strength where needed, providing the doorbeam the desired strength at relatively low weight and low cost.

Description:
PRIORITY  
       [0001]    This application claims priority from provisional application No. 60/217,791 filed Jul. 12, 2000, and entitled “Roll-formed/Stamped Doorbeam”. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to vehicle doorbeams, and more particularly to such doorbeams with reinforcing inserts.  
           [0004]    2. Description of the Art  
           [0005]    Vehicle doorbeams are widely used in the automotive industry to enhance the impact strength of vehicle doors and thereby enhance automobile safety. A doorbeam typically is roll-formed from steel and includes a hat-shaped beam portion and a pair of paddles at either end of the beam portion. A doorbeam typically is secured within a vehicle door by welding the paddles to the door frame.  
           [0006]    When considering the design of doorbeams—as well as virtually all automotive components—designers seek an appropriate balance among performance, weight, and cost. As part of that balance, it is known that the weight of a doorbeam can be decreased by manufacturing the doorbeam of a relatively expensive material. However, this undesirably increases the cost of the doorbeam. It also is known that the strength of a doorbeam can be increased by manufacturing the doorbeam from relatively thick stock. However, this undesirably increases the weight of the doorbeam.  
           [0007]    In any effort to reduce overall weight, some designers include a reinforcing component on the hat-shaped beam. Examples of this approach are disclosed in U.S. Pat. No. 5,692,797 issued Dec. 2, 1997 to Dancasiu; U.S. Pat. No. 4,796,946 issued Jan. 10, 1989 to Wilson et al; and U.S. Pat. No. 4,684,166 issued Aug. 4, 1987 to Kanodia. In all of these designs, a relatively flat reinforcement is crimped onto a segment of the hat-shaped doorbeam. However, designers continue to seek additional improvements in the performance/weight/cost balance.  
         SUMMARY OF THE INVENTION  
         [0008]    The aforementioned problems are overcome in the present application wherein a doorbeam includes a relatively high-strength, hat-shaped insert crimped into a relatively low-strength body. The assembly provides desired performance at relatively low weight and relatively low cost. In the preferred embodiment, the insert is fabricated of Martinsite; and the beam is fabricated of mild steel.  
           [0009]    The present invention has a variety of advantages over prior techniques. First, the majority of the doorbeam is formed of a relatively inexpensive material. Second, the reinforcing insert provides the necessary impact strength only where needed, thereby decreasing the overall weight and cost of the doorbeam. Third, the beam is manufactured in a variety of lengths by changing only the length of the base member, and not necessarily the insert.  
           [0010]    These and other objects, advantages and features of the invention will be more understood and appreciated by reference to the detailed description of the preferred embodiments and the drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 is a perspective view of a vehicle door including the doorbeam of the present invention;  
         [0012]    [0012]FIG. 2 is a side elevational view of the doorbeam prior to crimping of the body around the insert;  
         [0013]    [0013]FIG. 3 is a sectional view taken along line  3 - 3  in FIG. 2;  
         [0014]    [0014]FIG. 4 is a side elevational view of the fully manufactured doorbeam showing the body crimped about the insert; and  
         [0015]    [0015]FIG. 5 is a cross section of the doorbeam taken along line  5 - 5  in FIG. 4. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]    By way of disclosure, and not by way of limitation, a doorbeam constructed in accordance with a preferred embodiment of the invention is illustrated in FIGS.  1 - 5  and is generally designated  10 .  
       I. Construction of the Doorbeam  
       [0017]    The doorbeam  10  generally includes a base member or body  20  and a reinforcing member or insert  40 . The base member  20  is connected to the door  100 . The reinforcing member  40 , crimped within the base member  20 , increases the impact strength of the doorbeam  10 . The reinforcing member  40  is fabricated of a material having a higher modulus of elasticity and tensile strength than the base member  20 . The reinforcing member  40  has a cross section shaped to improve impact strength.  
         [0018]    The base member  20  is a one-piece integral member including a central portion  22  and end brackets  24  at the opposite ends thereof The impact beam  10  is oriented generally horizontally within the door  100  (FIG. 1). The end brackets  24  are secured to the frame of the door  100  by any suitable means, preferably by being welded thereto.  
         [0019]    The configuration and shape of the end brackets  24  is well known in the art and will vary from application to application depending on the door  100 . Attachment mechanisms other than, or in addition to, the brackets  24  may be included. In the preferred embodiment, the end brackets  24  are integral with the base member  20 . If desired, the end brackets  24  may be fabricated separately from the central section  22  and attached to the central portion  22  by any suitable means, preferably by welding.  
         [0020]    The central portion  22  includes opposing ends  50  and lateral edges  26  that are crimped about the insert  40  in the manufactured beam. The central portion  22  further defines a longitudinal indented portion  30  to enhance its structural integrity and strength and to provide a locating function as the insert  40  is placed on the body  20  during manufacture. When crimped (see FIGS.  4 - 5 ), the lateral edges  26  are folded upon themselves to define a channel  28 . The indented portion  30  is spaced from the lateral edges  26  and extends along the length of the beam  10 . The indented portion  30  is shown in FIG. 5 as having a hat-shaped configuration. Alternative sections will be apparent to those skilled in the art. The indented portion  30  defines a recess  34 .  
         [0021]    The base member  20  is fabricated of a relatively low cost material having sufficient strength to remain attached to the door and support the reinforcing member during impact. In the preferred embodiment, the base member  20  is fabricated of a low cost, mild steel. The base member  20  may be fabricated of other materials.  
         [0022]    As shown in FIGS. 1, 3, and  5 , the reinforcing member has a hat-shaped section throughout its length and includes feet  42 , a bridge portion  44 , and interconnecting side walls  46 . The side walls  46  extend away from each side from the bridge portion  44 . The feet  42  extend outwardly from the side walls  46  and are generally coplanar with one another. “Hat-shaped” refers to any cross section wherein a substantial strengthening body portion extends away from a pair of opposite feet. The distance between the side walls  46  is generally the same as the width of the indented portion  30  to assist in locating the insert  40  with respect to the body  20 . The shape and configuration of the insert  40  will vary from application to application.  
         [0023]    The feet  42  are secured within the channels  28  by the crimped lateral edges  26 . The channels  28  allow the feet  42  of the reinforcing member  40  to slide relative to and along the length of the base member  20  during impact. The relative movement caused by this sliding helps to prevent the compressive force of an impact from bending the reinforcing member  40  and the base member  20 . Therefore, the sliding of the reinforcing member  40  along the base member  20  during impact improves the impact strength of the doorbeam  10 .  
         [0024]    In the preferred embodiment, the reinforcing member  40  is positioned equidistantly from the opposite ends  50  of the base portion  20 , because the maximum strength is required at the center of the beam. The length of the insert  40  and its location along the body  20  will vary from application to application.  
         [0025]    The reinforcing member  40  is fabricated of a material having a relatively high modulus of elasticity and/or a higher tensile strength than the base member  20 . In the preferred embodiment, the reinforcing member  40  is made out of a Martinsite steel. An example of an appropriate Martinsite steel is Inland M 220  ultra high-strength, low-alloy steel. The Martinsite steel reinforcing member  40  has a higher modulus of elasticity than the mild steel base member  20 . Because the base member  20  is fabricated of a low cost mild steel, the overall cost of the doorbeam  10  is relatively low. The reinforcing member  40  improves the impact strength of the doorbeam  10 , while still enabling a relatively low overall cost.  
       II. Method of Manufacture  
       [0026]    As currently contemplated, the base member  20  is stamped; and the reinforcing member  40  is roll-formed according to processes well know to those skilled in the relevant arts. The inserts  40  are roll-formed at a speed that delivers one insert to each body  20  prior to the final stamping operation in which the lateral edges  26  of the body  20  are crimped about the feet  42  of the insert  40 . Just prior to the crimping operation, the reinforcing member  40  is placed on the base member  20 . The mating or nesting profiles of the insert and the body facilitate the proper positioning of the insert on the body. After the insert  40  is properly positioned, the lateral edges  26  of the base member  20  are folded or crimped around the feet  42 .  
         [0027]    Welding, stamping, or lancing may be used to further secure the reinforcing member  40  to the base member  20 . When used, these methods may prevent the reinforcing member  40  from sliding across the base member  20  during impact.  
         [0028]    The end brackets  24  can be configured and shaped (to include for example angles, holes, ridges and other features) during prior, concurrent, or subsequent stamping steps.  
         [0029]    In an alternative method of manufacture, both the base member  20  and the reinforcing member  40  are roll-formed. The roll-formed reinforcing member  40  is placed onto the roll-formed base member  20  (before the edges  26  are crimped), and the lateral edges are crimped around the feet  42  by a subsequent roll-forming operation. The end brackets  24  can be created by previous stamping operations, roll-forming operations, and/or subsequent stamping operations. The continuous beam web is then cut into individual beams  
         [0030]    The above descriptions are those of preferred embodiments of the invention. Various alterations and changes can be made without departing from the spirit and broader aspects of the invention as defined in the appended claims, which are to be interpreted in accordance with principles of patent law including the doctrine of equivalents.