IMPROVEMENTS RELATING TO THE ELIMINATION OF TORSIONAL LASH IN AN AXIALLY MOVABLE STEERING COLUMN

摘要

In an axially-adjustable collapsible steering column comprising two telescoping shafts 12, 16 having respectively a hexagonal cross-section and a corresponding hexagonal bore, a coupling device 18 tending to cause rotation of the shafts 12, 16 relative to one another to eliminate torsional lash therebetween, comprises wedge blocks 22 which are disposed in radial slots 20 in the shaft 16 and each have a first surface 42 adjustably urged against the opposing surface 24, 26 of the shaft 12 at an off-centre location by co-operation of an inclined second surface 40 with an axially-extending ramp 30 on a collar 28 adjustable axially of the shaft 16 by a nut 34. The ramps 30 are angled transversely of the shaft axis so that the load exerted by each wedge block 22 on the shaft 12 is concentrated at that edge 44 of the block surface 42 most distant from the centre of the surface 24, 26 on the shaft 12. The other edge 46 of each surface 42 is skewed with respect to the shaft axis to ensure proper orientation of the block. Ledges 48, 50 on each wedge block 22 increase the area of the inclined surface 40 and limit the load exerted against the shaft 12. The surface 42 of each wedge block 22 may be coated with a friction reducing plastics material. In another embodiment, Fig. 5 (not shown), there is only a single wedge block which is axially loaded by a spring and an adjusting screw provides for variably pre-loading the spring. In a further embodiment, Fig. 7 (not shown), the spring acts on the wedge block through a secondary wedge.