Pivot mechanism incorporating means to take up wear between two parts thereof
BACKGROUND OF THE INVENTION 
     This invention relates to a pivot mechanism incorporating means to take up wear between two parts thereof. 
     The invention has particular relevance to car steering columns where historically there has been a problem of how to allow systems such as oar steering columns to pivot, giving positional adjustment, without introducing noticeable backlash or free play into that system, whether that be wear or tolerance induced. FIG. 1 illustrates a simplified arrangement of a car steering column 10 with a steering wheel 1, with the steering wheel movement being illustrated by the arrows A. Reference numeral 2 illustrates a pivot mechanism. 
     Common systems in use today tend to accept looseness and ignore the results, which leads to a poor user response, or alternatively introduce a multitude of plastics and rubber parts to absorb clearances and damp out movement. These can be difficult to assemble and are prone to mishandling. 
     As a result of the former problems, FIG. 2 illustrates a housing 3 or the like, with a bolt 4 or the like intended to secure a mounting bracket 5. Such a construction leads to an inherent clearance illustrated by way of example at 6. 
     FIG. 3 illustrates the tendency to introduce a multitude of plastics and rubber parts and here it will be seen that the mounting bracket 5 is secured between the housing 3 and bolt 4 with the addition of a plastic washer 16 on one side of it and an O-ring 7 and a &#34;top hat&#34; washer 8 on the other side of it. 
     The foregoing illustrates limitations known to exist in present steering column pivot mechanisms. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter. 
     SUMMARY OF THE INVENTION 
     In one aspect of the present invention, this is accomplished by providing a pivot mechanism having means to take up wear between two parts of the mechanism. The means has a male tapered part which nests in a corresponding female part. One of the two parts is resiliently biased towards the other. 
     The foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing figures. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
     FIG. 1 is a simplified view illustrating a car steering column with pivot mechanism; 
     FIG. 2 is a cross-section view of a prior art pivot mechanism; 
     FIG. 3 is a cross-section view of a second prior art pivot mechanism; and 
     FIG. 4 is a cross-section view illustrating an embodiment of a pivot mechanism incorporating means to take up wear between two parts thereof. 
    
    
     DETAILED DESCRIPTION 
     According to the present invention, there is provided a pivot mechanism incorporating means to take up wear between two parts of the mechanism which move relatively to one another, said means including a male tapered part nesting in a corresponding female part, one of the two parts being resiliently loaded towards the other. 
     Referring to FIG. 4 of the drawing, a substantially cylindrical housing 9 surrounds and locates a shaft 10 such as a steering column shaft or a bearing or the like for such a shaft. 
     The housing 9 forms part of a pivot mechanism incorporating means to take up wear between two parts of the mechanism which move relatively to one another and, in the example illustrated, this means is duplicated. 
     The housing 9 is provided with two symmetrically-opposed frusto conical male parts in the form of tapered trunnions 9A which are located in corresponding female tapered parts 11A of respective housing support brackets 11. 
     The external tapered surfaces of the trunnions 9A and the internal tapered surfaces 11 of the housing support brackets 11 are arranged to be mutually non-locking and they function by providing relatively rotatable surfaces which, by urging the tapers together, have no radial or axial free play. 
     The tapered parts are urged together by providing two sprag washers 12, respectively, which are designed to act as springs. Each sprag washer 12 is a simple press fit over parallel trunnion extensions of its respective trunnion 9A adjacent its outer end, where it protrudes through an aperture in the female part 11A. Each washer 12 is pressed on to its trunnion 9A with a preset load. Thus, the male and female parts are resiliently pushed towards one another by the washers 12 and the spring action of the washers 12 takes up any wear at the tapered surfaces so that the clearance is eliminated by the spring action, while allowing relative rotation. 
     It will be appreciated that the present pivot mechanism is easy to assemble, since the housing support bracket 11 is simply located on their trunnions and then the washers 12 are located with a preset load. Only a small number of components are required and the result achieves good wear tolerance and no noticeable looseness or free play.