Abstract:
A steering column for a motor vehicle comprises a main body having upper and lower attachment points. The lower attachment point includes at least one closed-end slot having a ramped surface. A washer having a ramped surface is engaged with the ramped surface of the slot, and a fastener extends through the slot and through the washer.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates generally to steering columns for motor vehicles, and relates more particularly to a collapsible steering column.  
         BACKGROUND OF THE INVENTION  
         [0002]    Steering columns for motor vehicles need to be relatively stable in order to support the load of an attached steering wheel during regular driving conditions. Steering columns thus may be attached to an instrument panel support structure by means of an upper and a lower support. Steering columns may also be required under certain circumstances to collapse quickly. In these circumstances, it may be desirable for fasteners connecting the steering column to the upper and lower supports to allow such collapse without impediment.  
         SUMMARY OF THE INVENTION  
         [0003]    The present invention is a steering column for a motor vehicle. The steering column comprises a main body having an upper attachment and a lower bracket. The lower bracket includes at least one slot having at least one ramped surface. A washer having a ramped surface is engaged with the surface of the slot, and at least one fastener extends through the slot and through the washer.  
           [0004]    Accordingly, it is an object of the present invention to provide a steering column of the type described above that is collapsible.  
           [0005]    Another object of the present invention is to provide a steering column of the type described above that is collapsible in a relatively controlled manner.  
           [0006]    Still another object of the present invention is to provide a steering column of the type described above having a lower bracket with at least one ramped surface.  
           [0007]    These and other features and advantages of the invention will become further apparent from the following detailed description of the presently preferred embodiments when read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the invention rather than limiting, the scope of the invention being defined by the appended claims and equivalents thereof. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a side view of a steering column assembly according to the present invention for a motor vehicle.  
         [0009]    [0009]FIG. 2 is a perspective view of a main body of the steering column assembly.  
         [0010]    [0010]FIG. 3 is a perspective view of a portion of the underside of the main body.  
         [0011]    [0011]FIG. 4 is a cross-sectional view taken along line  4 - 4  in FIG. 2 and showing the main body mounted on the steering column assembly. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0012]    [0012]FIGS. 1 and 2 show one embodiment  10  of a steering column assembly according to the present invention for a motor vehicle. The steering column assembly  10  includes a main body  12  that is preferably a casting attached by a mounting bracket  13  to a stationary wall  14 , which may be part of an instrument panel mounting structure. The main body  12  includes a steering column shaft  16 , a yoke  18  and an intermediate shaft attachment  20 . The steering column shaft  16  is adapted to accept a steering wheel (not shown) on its distal end in conventional fashion, and may be tiltable as is well known. The yoke  18  connects the steering column shaft  16  to the intermediate shaft attachment  20 , which in turn is connected to a steering gear (not shown).  
         [0013]    The main body  12  also includes a pair of forwardly disposed, longitudinally extending attachment walls  22  on either side of the steering column shaft  16 . Each of the attachment walls  22  has a forward surface  24  that slopes upwardly. Together, the attachment walls  22  and the angled upper surfaces  24  form ramped slots with opposing upper wedged surfaces. As shown in FIG. 3, opposing surfaces  26  with wedged portions  28  are similarly formed on the lower side of the main body  12 . A pair of generally semi-circular upper attachments  30  are also formed in the main body  12 .  
         [0014]    [0014]FIG. 4 shows one of a pair of lower capsule brackets  32  that connect the main body  12  to the mounting bracket  13 . Each lower capsule bracket  32  includes a fastener such as a stud  34  and a nut  36  that are tightened to hold a washer  38  at a certain preload against the wedged surface  28  of the lower attachment wall  26  of the main body  12 . The washer  38  is acutely angled so as to match the angle of the wedged surface  28  of the main body  12 . The angle of the wedged surface  28 , as well as the angle of the washer  38 , affect the release load needed for the steering column  12  to overcome the preload of the studs  34 . An optional upper angled washer  40  similar to the angled washer  38  may be retained by the stud  34  against the upper wedged surface  24 .  
         [0015]    The attachment walls  22  and  26 , and more particularly the wedged surfaces  24  and  28 , extend into the space circumscribed by the lower capsule brackets  32  such that the lower capsule brackets transmit a major portion of the weight of the steering column onto the mounting bracket  13  and the stationary wall  14 . Similarly, a rearward portion of the steering column assembly  10  is attached to the mounting bracket  13  by an upper capsule bracket  42 . Each upper capsule bracket  42  preferably includes two separate components  44  and  46  that are preferably formed of the same material as the washers  38  and  40 . By way of example, components  44 ,  46  and washers  38 ,  40  can be formed of a plastic material having fiberglass reinforcement fibers incorporated therein and coated with nylon. The components  44  and  46  respectively include acutely angled support walls  48  and  50  engaging opposite surfaces of the main body  12 . Further details of a preferred embodiment of the upper capsule bracket  42  are disclosed in U.S. Pat. No. 5,390,955 and U.S. Pat. No. 5,979,860, the disclosures of which are hereby incorporated by reference. It should be appreciated, however, that any acceptable upper bracket arrangement may be used in the present invention.  
         [0016]    Upon an impact force in the direction of the arrow  60 , the upper capsule brackets  42  release as described in the &#39;955 and &#39;860 patents. The preload on the studs  34  of the lower capsule brackets  32  is preferably quickly overcome such that the angled surfaces  24  and  28  of the main body  12  separate from the washers  38  and  40 . The load at which the main body  12  releases can be altered by changing the angle of the mating surfaces, and also by changing the cross-sectional area of the studs, washers, and nuts of the respective brackets. Regardless of the preload, further resistance is negligible as the main body  12  translates to the left as shown in the drawings. Some or all of the energy of this translation is absorbed by bend straps  62  (only one of which is shown in the drawings) disposed around each of the lower capsule brackets  32 . In a preferred embodiment, each bend strap  62  is a curved piece of metal having a varying thickness, with one end secured by the stud and slidably disposed around the steering column body. A plastic guide  64  may also be provided to hold each bend strap  62  against the steering column body.  
         [0017]    While the embodiments of the invention disclosed herein are presently considered to be preferred, various changes and modifications can be made without departing from the spirit and scope of the invention. The scope of the invention is indicated in the appended claims, and all changes that come within the meaning and range of equivalents are intended to be embraced therein.