Abstract:
A cam locking assembly for an adjustable steering column. The assembly includes a tie bolt that is secured relative to the steering column. A lever member is positioned for rotation about the tie bolt. A caming unit is positioned about the tie bolt adjacent the lever member. The caming unit has a roller assembly positioned between a pair of opposed cam plates. One of the cam plates is associated with the lever member and rotates therewith and the other plate is fixed relative to such rotation. Each cam plate has a plurality of ramped recesses on its internal surface such that rotation of the one plate causes the rollers to ride up the ramps such that the plates are pushed apart. The pushed apart ramps cause clamping upon the steering column to lock its position.

Description:
This application claims the benefit of U.S. provisional application No. 60/362,811 filed Mar. 8, 2002. 

   BACKGROUND 
   The present invention relates to adjustable steering columns. More particularly, the present invention relates to a cam locking assembly for use in conjunction with an adjustable steering column. 
   For user convenience, many vehicles provide a steering column that permits tilting or tilting and telescoping thereof to meet the users preferences. Upon proper adjustment, the steering column must be fixed to prevent movement of the steering column during vehicle operation. It is desired to provide a locking mechanism that allows relatively easy release to allow adjustment, but also provides adequate fixing of the steering column. 
   SUMMARY 
   The present invention provides a cam locking assembly for an adjustable steering column. The cam locking assembly includes a tie bolt that is secured relative to and extends from the steering column. A lever member is positioned for rotation about the tie bolt. A caming unit is positioned about the tie bolt adjacent the lever member. The preferred caming unit has a roller assembly positioned between a pair of opposed cam plates. One of the cam plates is associated with the lever member such that the plate rotates with the lever and the other plate is fixed relative to such rotation. Each cam plate has a plurality of ramped recesses on its internal surface such that rotation of the one plate causes the rollers to ride up the ramps such that the plates are pushed apart. The pushed apart ramps cause clamping upon the steering column in a locked position. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an exploded isometric view of a cam locking assembly in accordance with a first embodiment of the present invention. 
       FIG. 2  is an isometric view of an assembled cam locking assembly of  FIG. 1 . 
       FIG. 3  is an isometric view of a cam plate in accordance with a first embodiment of the present invention. 
       FIG. 4  is a side elevational view along the line  4 — 4  in  FIG. 3 . 
       FIG. 5  is an isometric view of the caming unit of the cam locking assembly of  FIG. 1  with a cut away portion removed for clarity. 
       FIG. 6  is a cross-sectional elevational view of a cam locking assembly in accordance with  FIG. 1  associated with a steering column assembly. 
       FIG. 7  is a cross-sectional elevational view of a cam locking assembly in accordance with a second embodiment associated with a steering column assembly. 
       FIG. 8  is an isometric view of an exemplary spline plate used in conjunction with the cam locking assembly of  FIG. 7 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The present invention will be described with reference to the accompanying drawing figures wherein like numbers represent like elements throughout. Certain terminology, for example, “top”, “bottom”, “right”, “left”, “front”, “frontward”, “forward”, “back”, “rear” and “rearward”, is used in the following description for relative descriptive clarity only and is not intended to be limiting. 
   Referring to  FIGS. 1–5 , a first embodiment of a cam locking assembly  10  in accordance with a first embodiment of the present invention is shown. The cam locking assembly  10  generally includes a tie bolt  12 , a thrust bearing assembly  18 , a lever member  20  and a caming unit  30 . 
   The tie bolt  12  terminates in a retaining plate  14  at one end and an is generally free at the opposite end  15 . The retaining plate  14  may be an integrally formed flange, as illustrated, or the retaining plate  14  may be formed as a separate washer or the like secured along the tie bolt  12 . The free end  15  is configured for securement relative to a steering column (See  FIGS. 6 and 8 ). For example, the free end  15  is preferably threaded to receive a nut  17  or the like. 
   The lever unit  20  preferably includes an extending handle  22  connected to a plate  24 . The plate  24  has an aperture  26  therethrough configured to receive the tie bolt  12  such that the plate  24  may be rotated thereabout. A sleeve member  16  may be provided about the tie bolt  12  to help facilitate rotation of the lever unit  20 . If a sleeve member  16  is provided, the aperture  26  is configured to fit about the sleeve member  16 . In the illustrated embodiment, the thrust bearing assembly  18  is positioned between the retaining plate  14  and the lever plate  24  to further facilitate rotation of the lever unit  20 . The thrust bearing  18  may otherwise be positioned. For example, if the tie bolt  12  rotates with the lever unit  20 , the thrust bearing  18  may be positioned between the steering wheel bracket  102  and the nut  17 . Furthermore, more than one thrust bearing may be utilized. The thrust bearing assembly  18  can have various configurations, but generally comprises a plurality of roller elements retained in a cage or the like. The opposite side of the lever plate  24  is configured to engage the caming unit  30 , as will be described in greater detail hereinafter. 
   The caming unit  30  generally comprises a pair of opposed cam plates  32  and  34  with a roller assembly  40  positioned therebetween. The preferred roller assembly  40  includes a plurality of rollers  44  maintained in a retainer plate  42 . Referring to  FIGS. 3 and 4 , the preferred cam plates  32  and  34  will be described. Each cam plate  32 ,  34  is a generally planar disk with a central bore  35  configured to receive the tie bolt  12 . One or more alignment notches  33  may be provided along the disk. For example, the notches  33  may align with a tab on the retainer clip  50  to ensure that the cams are in an initial locked position. 
   One surface of the disk has a plurality of ramp recesses  36 . In the preferred embodiment, three evenly spaced recesses  36  are provided. Fewer or more recesses  36  also may be provided. The recesses  36  include a deep trough portion  37  and a shallow trough portion  39 , each configured to receive at least a portion of one of the rollers  44 . A ramp  38  extends between the trough portions  37 ,  39 . As shown in  FIG. 5 , the ramp recesses  36  on opposite plates  32 ,  34  are preferably reversed from one another, i.e., the ramps  38  of one of the plates  32  extend clockwise while the ramps  38  of the other plate  34  extend counter-clockwise. As such, in the unlocked position each roller  44  is positioned in a pair of opposed deep troughs  37 . As the plates  32 ,  34  are rotated relative to one another, as will be explained hereinafter, the rollers  44  ride up the opposed ramps  38  until the rollers  44  are received in the respective shallow troughs  39 . The positioning of the rollers  44  within the diminished depths of the shallow troughs  39  causes the plates  32  and  34  to push apart and thereby lock the steering column. The troughs  39  preferably have a semi-circular configuration such that the rollers  44  are retained therein. 
   The opposite side of each plate  32 ,  34  has a locking protrusion  41  extending therefrom. The preferred protrusion  41  is positioned about the central bore  35  and has an elongated configuration with opposed flat sides  43 . The protrusion  41  may have various configurations. Furthermore, more than one protrusion may be provided. The protrusion  41  of plate  32  is configured to be received in the bore  26  of the lever plate  24  such that cam plate  32  rotates in conjunction with the rotation of the lever plate  24 . Other means of securing the cam plate  32  to the lever plate  24  may also be used. The protrusion  41  of plate  34  is received in a bore  104  of the column mounting arm (see  FIG. 6 ) to prevent rotation of the plate  34 . With respect to engagement, each plate  32 ,  34  may alternatively be provided with a receiving bore and the respective engagement surfaces, the lever plate  25  and mounting arm, be provided with protrusions. In the preferred embodiment, the protrusions  41  extending from the plates  32  and  34  are identical such that a single plate may be manufactured and utilized for both plates  32  and  34 . 
   Referring to  FIGS. 1 ,  2  and  6 , a retainer clip  50  is preferably provided to unitize the cam locking assembly  10 . The retainer clip  50  preferably has a first lip  54  configured to engage the retaining plate  14 . The opposite end of the clip  50  has a second lip  56  configured to engage the fixed cam plate  34 , thereby unitizing the cam locking assembly  10 . In the preferred embodiment, the second lip  56  is configured such that upon securing of the cam locking assembly  10  onto a steering assembly, see  FIG. 6 , the moves out of the way to prevent trapping of the lip  56  between the cam plate  34  and the bracket  102 . The retainer clip  50  includes a lever passage  52  configured to fit about the lever unit handle  22 . The retainer clip  50  rotates with the lever unit  20  and therefore, the lever passage  52  can provide a close fit about the handle  22 . The retainer clip  50  can be manufactured in various manners and is preferably molded from polypropylene or the like. 
   Referring to  FIG. 6 , the cam locking assembly  10  is assembled and the tie bolt  12  is passed through a steering column  100 , positioned between a pair of opposed brackets  102 . As the cam locking assembly  10  is positioned, the protrusion  41  of cam plate  34  is received in the bore  104  of bracket  102 . The tie bolt  12  is then secured via the nut  17  or the like and the cam plate  34  is thereby fixed relative to the bracket  102 . Rotation of the handle  22  causes rotation of cam plate  32  between a lock position wherein the rollers  44  are positioned in the shallow troughs  39 , thereby applying pressure to the opposed brackets  102 , and an open position wherein the rollers  44  align with the deep troughs  37  such that the pressure is relieved. The steering column  100  can then be adjusted. A wave spring (not shown) or the like may be provided to preload the assembly  10 . 
   Referring to  FIGS. 7 and 8 , an alternate embodiment of the present invention is shown. The cam locking assembly  10  is substantially the same as in the previous embodiment. However, cam plate  34  of the present invention is connected to a spline plate  60 , instead of directly to the mounting bracket  102  or column  100 . The spline plate  60  in turn has splines  62  which are configured to mate with splines (not shown) on the column  100  and an alignment protrusion  64  received in the column  100  to prevent rotation of the spline plate  60  or cam plate  34 . The spline plate  60  may also include a sleeve  66  positioned about the shaft. The cam locking assembly  10  is positioned within the brackets  102 . A spring  68  or the like is positioned about the tie bolt  12  and biases the spline plate  60  away from the column  100 , such that upon release of the cam locking assembly  10 , the spline plate  60  releases the column  100  such that it can be tilted or extended. As will be understood, the cam plate  34  may directly engage the steering column  100  or bracket  102  or other engagement means, including the above described spline plate  60 .