Abstract:
The invention provides a locking pin for a steering column lock assembly. The locking pin includes a dual taper defined by the first and second truncated cone portions. The first truncated cone portion narrows at a first angle and the second truncated cone portion narrows at a second angle, wherein the first and second angles are different from one another. The second angle can be less than the first angle. The dual taper of the locking pin reduces the likelihood that extreme tortion will not induce camming forces urging the locking pin out of engagement with a locking plate connected to the steering shaft.

Description:
TECHNICAL FIELD  
       [0001]     The invention relates to a lock for a steering column of a vehicle to prevent the steering wheel from being turned.  
       BACKGROUND OF THE INVENTION  
       [0002]     Steering columns in vehicles normally include a locking mechanism to prevent turning of the steering wheel when the ignition is off and the key is removed. As shown in U.S. Pat. No. 4,258,560, a steering column lock can include a locking plate connected to an upper end of a steering shaft. The steering shaft connects the steering wheel with the steerable tires of the vehicle. The locking plate extends radially from the steering shaft and defines one or more apertures for receiving a locking pin. When the locking pin is inserted in the aperture, the steering shaft is locked.  
         [0003]     The locking pin can define a tapered surface that engages the aperture of the locking plate. The tapered surface can enhance removal of the pin with respect to the locking plate, to enhance and facilitate unlocking of the steering column. For example, the edge of the aperture can slide along the tapered surface of the pin during insertion and removal of the pin, preventing binding between the two parts. However, during unauthorized starting of the vehicle, the steering shaft can be subjected to extreme tortional loading. During the severe torsion that can be generated during an attempted theft of the vehicle, the tapered surface of the locking pin can act as a cam follower surface and the surface of the aperture of the locking plate can act as a cam. In other words, the locking plate can drive the locking pin out of engagement with the aperture when a theft of the vehicle is attempted, making the theft easier.  
       SUMMARY OF THE INVENTION  
       [0004]     The present invention provides a steering column lock assembly including a steering shaft defining an aperture and a locking pin insertable in the aperture and having first and second tapered portions for limiting cam-cam follower cooperation between the locking pin and the aperture. The tapered surfaces define first and second truncated cone portions having different angles. The locking pin can include a first truncated cone portion narrowing from a first end at a first angle to a second end. A second truncated cone portion can extend from the second end and narrow at a second angle to a third end. The first and second angles are different with respect to one another. The second angle is less than the first angle. The first angle can define a tapered surface to enhance unlocking of the steering column. For example, the first truncated cone portion can make it easier to unlock the steering column by sliding against a locking plate in the steering column. The second angle can define a tapered surface that reduces the likelihood that extreme tortional loading will drive the locking pin out of engagement with a locking aperture defined by the steering shaft. For example, the sliding movement described above is reduced by the second truncated cone portion to deter vehicle theft. The two cone portions cooperate to facilitate enhanced removal of the locking pin during authorized vehicle start-up, while simultaneously restricting movement of the pin during unauthorized vehicle start-up.  
         [0005]     Other applications of the present invention will become apparent to those skilled in the art when the following description of the best mode contemplated for practicing the invention is read in conjunction with the accompanying drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]     The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein:  
         [0007]      FIG. 1  is a side view of a steering column assembly according to an embodiment of the invention disposed in a vehicle;  
         [0008]      FIG. 2  is a partial cross-sectional view of the steering column assembly shown in  FIG. 1  wherein the locking pin is engaged with respect to a locking plate member; and  
         [0009]      FIG. 3  is a partial cross-sectional view of the steering column assembly shown in  FIGS. 1 and 2  wherein the locking pin is disengaged with respect to the locking plate member. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0010]     Referring to  FIG. 1 , a vehicle  10  is shown including a steering column assembly  12  mounted in the forward passenger compartment. The steering column assembly  12  extends through the firewall of the vehicle engine compartment and includes a cylindrical upper jacket  14  secured by a bracket assembly  16  to support structure of the vehicle  10 . A shift bowl  18  is supported for limited rotational movement on the upper end of the jacket  14  and may be turned by the vehicle operator through a selector lever  20 . A generally cylindrical housing  22  is secured to the upper jacket  14  and located between the shift bowl  18  and steering wheel  26 . The housing  22  can also support a lever  27  for operating turn signals or headlamps of the vehicle  10 . A steering wheel  26  is drivingly connected to a rotatable steering shaft  28  (best shown in  FIGS. 2 and 3 ). The steering wheel  26  engages the shaft  28  at a hub  29 . The shaft  28  extends axially within the steering column assembly  12  to operably connect the steering wheel  26  with respect to the wheels of the vehicle through a conventional steering gear and linkage.  
         [0011]     Referring now to  FIGS. 2 and 3 , the steering column assembly  12  according to the invention includes a steering shaft  28  defining at least one receiving portion  38  and a locking pin  40 . The receiving portion  38  can be an aperture or can be a notch. The locking pin  40  is selectively insertable in the receiving portion  38 . The locking pin  40  is moveable between at least two positions. In a first position corresponding to a locked position, the locking pin  40  is insertable in the receiving portion to prevent rotation of the steering shaft  28 . In a second position corresponding to an unlocked position, the locking pin  40  is disengaged with respect to the receiving portion  38  and the steering shaft  28  is rotatable.  
         [0012]     The steering shaft  28  is shown mounted for rotation in a first longitudinal recess  32  defined by the steering column housing  22 . The housing  22  also defines a second recess  34  for receiving the locking pin  40 . The locking pin  40  can be slidably mounted within the second recess  34  of the steering column housing  22 . The second recess  34  can extend parallel to the first recess  32  and be offset with respect to the first recess  32 . In an alternative embodiment, the second recess could extend radially from the first recess.  
         [0013]     The housing  22  is also shown supporting a locking cylinder  24 . The locking cylinder  24  can receive a key  25 . The key  25  can be inserted in the locking cylinder  24  and rotated to move a gear train  30  and slide the locking pin  40  relative to the housing  22  within the second recess  34 . For example, when the key  25  is removed from the locking cylinder  24 , the locking pin  40  is inserted in the receiving portion  38 .  
         [0014]     A plate member  36  can be immovably associated with respect to the steering shaft  28 . The receiving portion  38  is shown defined by the plate member  36 , however, the receiving portion could be defined by the steering shaft  28 . The plate member  36  is rotatably locked with respect to the steering shaft such that the plate member rotates in response to rotation of a steering shaft  28  and insertion of the locking pin  40  in the receiving portion  38  defined by the plate member  36  prevents rotation of the steering shaft  28 .  
         [0015]     The plate member  36  rotates the receiving portion  38  in response to rotation of the shaft  28 . During rotation of the plate member  36 , the receiving portion  38  intermittently communicates with the second recess  34 . The locking pin  40  can be inserted with respect to the receiving portion  38  when the receiving portion  38  is in communication with the recess  34 . As shown in  FIGS. 2 and 3 , the receiving portion  38  can extend in parallel relation to the steering shaft  28 .  
         [0016]     The locking pin  40  includes a first truncated cone portion  42  narrowing from a first end  44  at a first angle  46  to a second end  48 . The locking pin  40  also includes a second truncated cone portion  50  extending from the second end  48  and narrowing from the second end  48  at a second angle  52  to a third end  54 . The first and second truncated cone portions  42 ,  50  can extend concentrically with respect to one another. The first and second angles  46 ,  52  are different. The second angle  52  can be less than the first angle  46 . By way of example and not limitation, the second angle  52  can be one-half of the first angle  46 . For example, the second angle  52  can be four degrees and the first angle  46  can be eight degrees.  
         [0017]     The first and second truncated cone portions  42 ,  50  can be inserted in the receiving portion  38 . The receiving portion  38  and locking pin  40  can cooperate in cam-cam follower relationship. For example, the first truncated cone portion  42  can be angled to enhance sliding between the locking pin  40  and the receiving portion  38 . Enhanced sliding engagement between the locking pin  40  and the receiving portion  38  can be desirable during authorized insertion and removal of the locking pin  40  with respect to the receiving portion  38 . For example, the angled surface  56  of the first truncated cone portion  42  can guide insertion of the locking pin  40  with respect to the receiving portion  38  and alleviate slight misalignments between the two parts. Also, the angled surface  56  of the first truncated cone portion  42  can communicate torsion from the receiving portion  38  to axial force urging the locking pin  40  out of engagement with the receiving portion during authorized vehicle start-up.  
         [0018]     The second cone portion  50  can be angled to be less likely to cooperate in cam-cam follower relationship with the receiving portion  38  than the first truncated cone portion  42 . For example, the second truncated cone portion  50  is flatter than the first truncated cone portion  42  to reduce the likelihood that torsion will urge the locking pin  40  out of engagement with the receiving portion  38 . Extreme torsion can occur during an attempted theft of the vehicle. It has been determined that the present invention reduces by one-half the force urging the bolt  40  out of the receiving portion  38  during extreme torsion loading. Specifically, the urging force generated torsion loading.  
         [0019]     While the invention has been described with reference to an exemplary embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.