This invention relates to a rake and/or reach adjustable steering column device.
A rake adjustable vehicle steering column is one that can be adjusted in a vertical direction.
A reach adjustable vehicle steering column is one that can be adjusted towards or away from the front of the car, which although it is not in a strictly horizontal direction will for reference purposes and to distinguish from vertical adjustment be referred to hereafter as "horizontal" adjustment and movement in a "horizontal" direction.
In the event of a crash there is a need for columns to be locked in both the vertical and horizontal direction. Normally the vertical locking is by means of a friction clamp and this moves to its extreme setting in the event of a crash.
Examples of known adjustable vehicle steering column assemblies are shown and described in GB-A-2 281 539 and GB-A-1 546 949.
According to the present invention, there is provided a rake and/or reach adjustment steering column device having first means to clamp a steering column in a desired adjustment position and second means to maintain substantially the adjustment position of the device in the event of a vehicle crash, wherein the second means comprises at least one cam having an engagement surface,
the cam being pivotally mounted at a cam pivot to the first means and there being at least one other engagement surface for engagement with the cam on or fixed to a support member for the steering column, characterisd in that the engagement surface of the or each cam has one extremity at a greater radial distance from its cam pivot then another extremity of that engagement surface near the cam pivot, thereby to result in a greater engaging force as the cam rotates in one direction.
The first means can include a bolt and handle assembly which in a clamped position clamps a steering column at a vertically-adjusted location-adjusted location relative to a support member for the steering column.
The second means is a toothed cam and said at least one other engagment surface can be a rack mechanism associated with the both of the first means, the cam and rack being preferably resiliently urged together. The rack is preferably fixed to a column support bracket whereas the cam is pivotally mounted to the bolt and sprung towards the rack so that the teeth on the cam engage on the rack. Relative vertical movement between the rack and cam causes cam rotation and the teeth on the cam then lock tightly with the teeth on the rack.
A similar cam and rack arrangement can be used for horizontal and reach locking, a rack being fixed to a reach adjust bracket with a toothed cam on the same bolt.
The advantage of both locking arrangements is that the higher the load on the lock the greater the locking force.
For a better understanding of the present invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:-
Figure 1 is a diagrammatic end view, partly in section of a rake and reach adjustable steering column device with cam locks,
Figure 2 is a diagrammatic side view showing the camming action of the device of Figure 1,
Figure 3 is a similar view to Figure 2 showing the disengagement of the camming action of the device of Figure 1, and
Figure 4 is a side view of the device of Figure 1 showing the camming action of a reach cam lock.
Referring to the drawings, a vehicle steering column device generally shown at 25 includes a clamping bolt 26 which passes through slots in respective flanges of the steering column support bracket 23 and is clamped in position by means of a clamping handle 27 which acts on, for example, washers 28 to clamp or unclamp the steering column 21 relative its support bracket 23. Other forms of clamping means can be used instead.
In order to maintain substantially the adjustment position of the device 25 a toothed cam 29 is engageable with a vertical toothed or serrated locking rack 30 fixed by welding or whatever to the bracket 23. This arrangement may be duplicated on the other side of the column with cam 29' and rack 30'.
As seen in Figure 2 the cam 29 (29') is urged towards the rack 30 (30') by a spring 31. The cam 29 has serrations or teeth 29A which are urged by the spring 31 onto the teeth 3 0A of the vertical rack 30.
The teeth 29A, 3 0A are normally engaged but by the action of spring and clearly the "pear" shape of the cam with the engagement surface carrying the teeth 2 9A at an extremity 32 being at a greater radial distance than the teeth on the engaging surface of an extremity 33 near the cam pivot results in a greater engaging force as the cam rotates, thereby producing a jamming effect. The load and locking are thus self-generating.
To disengage the cam the handle 27 rotates the bolt 26 causing a key 34 in a keyway 35 to rotate the cam 29 clockwise out of engagement.
The reach lock is similar with a cam 3 9 engaging with a serrated "horizontal" rack 40 under influence of a spring 41. The rack 40 is fixed to a reach adjustment bracket 44. The cam 3 9 pivots on bolt 21 and cam teeth 3 9A engages with rack teeth 40A in the same way as the rake adjustment. The cam 39 is similar in shape and action to the cam 29.
Instead of teeth or serrations on the cams and/or racks, one or both of the engagement surfaces of the cams and racks can be provided with a substantially smooth surface such as a fine blasted surface.

We Claim:-
1. A rake and/or reach adjustment steering column device having first means to clamp a steering column in a desired adjustment position and second means to maintain substantially the adjustment position of the device in the event of a vehicle crash, wherein the second means comprises at least one cam having an engagement surface, the cam being pivotally mounted at a cam pivot to the first means and there being at least one other engagement surface for engagement with the cam on or fixed to a support member for the steering column, characterisd in that the engagement surface of the or each cam has one extremity at a greater radial distance from its cam pivot then another extremity of that engagement surface near the cam pivot, thereby to result in a greater engaging force as the cam rotates in one direction.
2. A device according to claim 1, wherein the first means includes a bolt and handle assembly which in a clamped position clamps a steering column in the adjustment position at a vertically and/or horizontally adjusted location relative to said support member for the steering column.
3. A device according to claim 2, wherein the or each cam is mounted on the bolt of the bolt and handle assembly.
4. A device according to claim 1, 2 or 3, wherein the or each cam is toothed or serrated.
5. A device according to any one of the preceding claims, wherein said at least one other engagement surface is a toothed rack.
6. A device according to any one of the preceding claims, wherein said at least one cam and said at least one other engagement surface are resiliently urged together.
7. A rake and/or reach adjustment steering column device, substantially as hereinbefore described with reference to the accompanying drawings.
8. A vehicle steering column assembly incorporating a device according to any one of the preceding claims.