Steering column clamping mechanism

A rake and reach adjustable steering column is secured in its desired location by means of a clamping mechanism. The clamping mechanism includes a cam on camming surfaces on which rollers held in a body freely run. A bolt extends from the cam and roller arrangement through a mounting bracket for the steering column and through a member fixed to the steering column. The body is rotatable by a handle which, through the cam and roller arrangement, causes thrust washers and other parts to release and clamp the steering column in position.

BACKGROUND OF THE INVENTION 
This invention relates to a steering column clamping mechanism for an 
adjustable steering column and more particularly to steering column 
clamping mechanisms for reach and rake adjustable steering columns. 
A steering column clamping mechanism is known from U.S. Pat. No. 4,788,880 
which clamps a housing of an adjustable steering column perpendicularly to 
the longitudinal direction of the steering column. That mechanism 
comprises a clamping bolt and a lever by which the bolt can be tensioned 
and the column housing fixed, there being a spring-loaded element between 
the housing and bolt with the lever and bolt being coupled by pins whose 
center lines cross that of the bolt when it is in a released condition. 
The pins are provided between a cup fixed to the bolt and the lever, the 
pins being longer than the distance, measured in the longitudinal 
direction, between the cup and lever in the released condition of the 
bolt, a limited degree of tilting of the pins on their supporting points 
being possible. 
A disadvantage of known clamping mechanisms is that when the steering 
column in fixed, there is little feel of the degree of clamping. It is 
desirable that there is a point whereby the lever, when being moved toward 
its clamped or unclamped position, is just a little more difficult to 
move, thus indicating that the desired position has been reached. A second 
disadvantage of known clamping mechanisms is that there is no positive 
indication as the clamping mechanism moves from the clamped position to 
the unclamped position, that is, the point it changes from one position to 
the other position. 
The foregoing illustrates limitations known to exist in present steering 
column clamping 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 
steering column clamping mechanism for use with an adjustable steering 
column, the mechanism having an unclamped condition allowing at least one 
of axial movement of the steering column or tilting movement of the 
steering column and having a clamped condition preventing movement of the 
steering column, the mechanism comprising: an actuating member having at 
least two roller members thereon; and a cam member in rolling engagement 
with the roller members, the cam member having at least two cam tracks 
with at least three zones, a first zone, a second zone anti a third zone, 
the third zone being between the first zone and the second zone, the first 
zone being lower than the second zone and the third zone being higher than 
second zone, the roller members being in engagement with the cam tracks, 
the first zone corresponding to the unclamped condition and the second 
zone corresponding to the clamped condition. 
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.

DETAILED DESCRIPTION 
According to the present invention, there is provided a steering column 
clamping mechanism for an adjustable steering column, the mechanism in use 
in an unclamped condition allowing movement of the column in an axial 
direction and/or tilting movement and in a clamped condition serving to 
prevent said movement, and the mechanism having an actuating member 
including a cam means to create said clamped and unclamped conditions. 
The invention also extends to an adjustable steering column incorporating a 
clamping mechanism essentially as just defined. 
The cam means preferably comprises a cam and roller arrangement. 
The roller arrangement can include a body rotatable about an axis extending 
through a cam surface of the cam. The body of the roller arrangement can 
house at least two rollers which are arranged to run on portions of the 
cam surface. The cam surface is arranged to provide a low spot for the 
rollers, which is the unclamped condition of the mechanism, and a higher 
spot for the rollers, which provides the clamped condition of the 
mechanism. An even higher spot can be provided between the former two 
spots, thereby to provide an over-pressure run-in for the rollers to be 
urged by the cam into the position where the mechanism is in its clamped 
condition. The rollers can run freely on pins mounted in the body. 
The body can be rotated by means of a handle. 
In the preferred embodiment, a bolt is held in the body and extends 
co-axially with the axis of rotation of the body. The bolt passes through 
the cam and through a bracket serving to support the steering column on a 
mounting point and also through a member fixed to the steering column. The 
bolt also passes through parts which cause the member to be clamped 
relatively to the bracket when the clamping mechanism is in its clamped 
condition and to allow movement of the member relatively to the bracket 
when the mechanism is in its unclamped condition. 
Referring to the drawings, FIG. 1 illustrates a rake and reach adjustable 
steering column, i.e. one in which a steering wheel 1 can be tilted in the 
directions of the double arrow A and/or adjusted parallel to the 
longitudinal axis of the steering column in the directions indicated by 
the double arrow B respectively. The steering column is held in its 
desired location by means of a clamping mechanism 2. 
The steering column diagrammatically illustrated in FIG. 1 by reference 
numeral 3 (with other possible rake positions thereof) is mounted by means 
of steering column mounting points 4 and 5 in a vehicle. The steering 
column mounting point 5 includes a mounting bracket 6, which is also 
illustrated in FIGS. 2 and 7. 
FIG. 1 also shows a steering column pivot point 7 about which the steering 
column and steering wheel are rake adjustable, and a steering box 8. A 
rake adjustable steering column is one which pivots about a point 7 which 
is remote from the clamping mechanism 2. A tilt adjustable steering column 
pivots about a point at or near the clamping mechanism. 
As best shown in FIG. 2, the steering column clamping mechanism 2 is formed 
around the mounting bracket 6 and includes a cam means 9 in the form of a 
cam and roller arrangement with a cam 10 and at least two rollers 11 
freely running on axles 12 coaxially mounted in a body 13 which is 
rotatable about an axis at right angles to the axles 12. A handle 14 is 
connected to the body 13 to effect rotation thereof to move the clamping 
mechanism 2 between clamped and unclamped conditions. In FIG. 1, the 
handle 14 depicted in full lines indicates the clamped position, whereas 
the unclamped position is illustrated in dashed lines. A bolt 15 or other 
member is secured in the body 13 and extends co-axially with the axis of 
rotation of the body 13. 
As shown in FIGS. 2 and 6, a saddle-like steering column retainer member 16 
is welded to the underside of the steering column 3 and is provided with 
two longitudinal slots 16A, through which the bolt 15 passes, thereby 
allowing movement of the steering column 3 parallel to its axis about the 
bolt 15. 
FIGS. 2 and 7 illustrate that the mounting bracket 6 is provided with two 
slots 6A, which extend at right angles to the slots 16A and through which 
the bolt 15 also passes. The slots 6A allow the tilting movement of the 
steering column 3 relative to the bracket 6 about the double arrow A in 
FIG. 1. 
The bolt 15 or other member extends through the bracket 6 from the body 13 
end of the clamping mechanism and ends in a screw-thread 17 with a nut 18 
which tightens the mechanism to bring the rollers 11 into rolling contact 
with the cam 10. A roller bearing 19 is provided to allow rotation of the 
bolt 15 relative to a part 20. The part 20, which corresponds to the cam 
10 on the opposite side of the bracket 6 (which is likewise constructed on 
the side concerned) has a rectangular protrusion 21 which fits in the slot 
6A of the bracket 6 so that, when the mechanism is in its unclamped 
condition, the part 20 and the cam 10 can slide in their slots 6A for rake 
adjustment of the steering column. 
A pair of thrust washers 22 are provided with a clearance fit about the 
bolt 15 adjacent respective internal faces of the mounting bracket 6 and 
each thrust washer 22 is provided with a rectangular protrusion 23 which 
is slidably mounted in the respective slots 16A of the saddle-like 
steering column retainer member 16. This latter construction allows for 
the movement of the steering column 3 in the direction of its axis when 
the clamping mechanism is in its unclamped condition for reach adjustment 
of the steering column. 
FIGS. 3 to 5 show the cam and roller arrangement of the clamping mechanism 
and it will be seen that the cam 10 has cam surfaces 10A on one face of 
the cam, each providing for a respective roller 11 a low spot 10B for the 
clamping mechanism unclamped condition, a higher spot 10C for the clamping 
mechanism clamped condition and an even higher spot 10D over which each 
roller 11 has to run to reach the clamped condition, this higher spot 10D 
thereby providing means urging and serving to retain by force the rollers 
11 seated in the spots 10C, 10B. Thus, a certain amount of resistance has 
to be overcome, using the handle 14, to rotate the body 13 and therefore 
the rollers 11 to bring the clamping mechanism into and out of the clamped 
condition. The sides of the bracket 6 and the member 16 have sufficient 
resilience to allow the rollers 11 to run over their high spots 10D. 
It will be appreciated that the cam 10 and its cam surfaces 10A can be 
given any desired profile. Furthermore, any desired number of rollers 11 
can be provided. 
The rollers 11 themselves can be mounted as illustrated on individual axles 
12 slotted in the body 13 or, for example, a single axle 12 can be 
inserted through the side of the body 13 through an aperture 13A (FIG. 5) 
in the side of the body 13, thereby mounting both rollers on a single 
axle. 
When the clamping mechanism is in its clamped condition, the parts 10, 20 
and 22 are pressed against the sides of the parts 6 and 16 as described 
hereinabove in order to prevent reach and rake adjustment of the steering 
column 3 and its steering wheel 1.