FIELD OF THE INVENTION

The present invention relates to adjustable steering columns for vehicles and, more particularly to releasable clamping mechanisms for steering columns operable by a user of the vehicle.

BACKGROUND

The importance of being able to adjust the position of a steering wheel in a vehicle, to enable a user to obtain a comfortable and safe driving position, has long been known. The adjustment may be longitudinal, moving the steering wheel forwards or backwards in the axial direction of the steering column on which the steering wheel is mounted. Alternately, or additionally, the adjustment may be angular, with the angle between the steering column and the horizontal plane (which may be represented by the chassis of the vehicle) being adjustable. In this latter case, the steering column includes one or more universal joints in its connection to the further components of the steering mechanism to permit the tilting of the rotating steering column.

A releasable clamping mechanism typically comprises a manually operated lever that, in a first position, permits movement of the steering column within a limited movement range (dictated by mounting components of the steering column) and, in a second position, engages a mechanical clamping arrangement preventing movement (other than rotation) of the steering column.

European patent application EP 0 408 847 A1 discloses a device for adjusting the reach and height of a steering column of a vehicle. The device comprises a pair of plates, referred to as bearing walls, extending from the vehicle body. Two retaining parts are responsible to hold the steering column with help of a clamping element, which presses the bearing walls against the retaining parts. The clamping element of this device comprises two screws, one extending through the bearing wall and the other abutting the bearing wall. One screw comprises a right-hand-thread and the other a left-hand-thread. A hand-activated-lever is connected with a threaded bush to the threads of both screws and is used to release the steering column by loosening the retaining parts and bearing walls.

United Kingdom patent GB 1 365 965 discloses a longitudinally-adjustable steering apparatus for a vehicle with a clamping device for the adjustment and a deformable element to absorb and dissipate impact energy. The clamping device and the deformable element are connected to each other. As with EP 0 408 847 A1 above, the clamping device comprises a hand-activated lever with a screw-threaded sleeve with two bolts, with a left-hand thread on one bolt and a right-hand-thread on the other bolt. Both bolts extend through the clamping device: one bolt is screwed into the clamping device while the second bolt extends freely through the bore and only abuts against the clamping piece by way of the end face of its head.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present invention there is provided a vehicle having a steering column and a positional adjustment mechanism for the same, the mechanism comprising: a pair of plates attached to the vehicle and extending outwardly on either side of the steering column, with each plate having an inner surface proximate the steering column and an opposed outer surface, with the two plates having aligned openings therethrough; a locking collar disposed between the plate inner surfaces, the collar having a curved portion extending around a portion of the steering column and a respective connection piece at each end of the curved portion, which connection pieces each have an opening therethrough; an elongate locking body extending through the openings in the pair of plates and the respective openings in the locking collar connection pieces; two retaining bodies in threaded engagement with the elongate locking body at respective outer surfaces of the pair of plates, wherein the engagement of one of the retaining bodies is by a right-hand thread and the engagement of the other of the retaining bodies is by a left hand thread; and a lever arm coupled with one of the retaining bodies and operable to rotate the same on its respective threaded engagement with the elongate locking body to pull the pair of plates and connection pieces closer together to produce locking engagement of the plates via the collar with the steering column.

With neither of the retaining bodies in fixed engagement with the plates, assembly of the mechanism is simplified. Preferably, the retaining body without the lever arm has a friction-creating surface in contact with the outer surface of the adjacent one of the pair of plates to resist rotation of that retaining body in the event of rotation of the elongate locking body. By “friction-creating” is meant that the material and/or surface contouring of the retaining body provides a relatively high coefficient of friction when placed against the material and/or surface contouring of the outer surface of the adjacent one of the pair of plates. One the other side of the mechanism, a friction washer may be disposed about the elongate locking body between the retaining body having the lever arm and the outer surface of the adjacent one of the pair of plates. To further secure the components of the positional adjustment mechanism, respective locking nuts are suitably provided in threaded engagement (one with a left-hand thread and the other with a right-hand thread as appropriate) with the distal ends of the elongate locking body adjacent the retaining bodies.

In order to provide tilting adjustment, the aligned openings in the pair of plates preferably comprise arcuate slots in respective planes parallel to the major axis of the steering column, allowing tilting movement of the steering column as the outer portions of the elongate locking body move along the slots when the steering column is not in locking engagement with the pair of plates via the locking mechanism.

Preferably, a respective guide plate is attached to the inner surface of each of the pair of plates, with each guide plate having an opening therethrough aligned with the respective opening in the respective one of the pair of plates. Typically, the guide plate openings will be smaller than the respective openings in the pair of plates, but different designs of guide plates may be used with a common arrangement of pairs of plates in different models in a common vehicle range to reduce differential component cost issues.

Where one or more guide plates as mentioned in the preceding paragraph are used, friction washers disposed about the elongate locking body may be provided between each guide plate and the inner surface of the adjacent one of the pair of plates and/or between each guide plate and the adjacent locking collar connection piece.

In order to permit longitudinal positional adjustment of a steering wheel attached to the steering column, the mechanism preferably comprises a telescoping arrangement of the steering column permitting longitudinal movement of the steering wheel (in a direction parallel to the major axis of the steering column), which telescoping arrangement is locked against longitudinal movement when the steering column is in locking engagement with the plates via the locking collar. It is a benefit of the present arrangement that a single locking mechanism may be used with both tilt and longitudinal adjustment.

Whilst, the locking mechanism may be operated by a manual lever mounted adjacent the steering wheel, additionally or alternately a user-operable foot pedal and a linkage arrangement coupling the same to the lever arm may be provided to allow foot-operated release and engagement of locking of the steering column.

Preferably the adjustment mechanism further comprises one or more springs attached between the lever arm and the vehicle and arranged to bias the adjustment mechanism into locking engagement. The or each spring may be directly attached to the lever arm, or may be operatively coupled thereto via one or more linkages.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example only, in which

Figure 1 shows a representation of a tractor having a steering column adjustment mechanism;

Figures 2 and 3 show in perspective view the assembled components of a steering column adjustment mechanism suitable for use in the tractor of Fig. 1 ;

Figure 4 is a front elevational view of a part of the assembly of Fig. 2 looking in the direction of arrow A in Fig. 2;

Figure 5 is equivalent to Fig. 4 but cut-away through the elongate locking body on line B-B in Fig. 2;

Figure 6 is a plan view, looking in the direction of arrow D in Fig. 2 of the elongate locking body with additional components mounted thereon; Figure 7 is equivalent to Fig. 6 but cut-away through the elongate locking body on line C-C in Fig. 2; and

Figure 8 is a plan view of the assembly of Fig. 2 looking in the direction of arrow D.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

The invention will now be described in the following detailed description with reference to the drawings, wherein preferred embodiments are described in detail to enable practice of the invention. Although the invention is described with reference to these specific preferred embodiments, it will be understood that the invention is not limited to these preferred embodiments. But to the contrary, the invention includes numerous alternatives, modifications and equivalents as will become apparent from consideration of the following detailed description.

Referring to Figure 1 , a utility vehicle in the form of a tractor 10 is shown having a cab 12 and an engine compartment 14. A chassis 16 which is partly visible connects front wheel suspension and steering assembly 18 and rear axle assembly 20. Within the cab 12 there is provided a steering wheel 22 mounted on a steering column 24. The steering wheel is provided with an adjustment mechanism (described below) which permits longitudinal movement (indicated by arrow L) and tilt movement (indicated by arrow T) of the steering wheel 22 relative to the cab 12 to enable a user to establish a safe and comfortable driving position.

Figures 2 to 8 show, in perspective and close-up views, the components of a steering column adjustment mechanism embodying aspects of the present invention.

Beginning with Figures 2 and 3, a steering column 24 is supported by a positional adjustment mechanism for the same, indicated generally at 26. The upper end of the steering column has a splined ferrule and bolt arrangement 28 by means of which the steering wheel 22 (Fig. 1) may be attached. The lower end (not shown) of the steering column 24 is attached to the further components of the vehicle steering mechanism, suitably via one or more universal joints to permit tilting of the steering column relative to the vehicle.

The adjustment mechanism 26 includes a pair of plates 30 attached to the vehicle and extending outwardly on either side of the steering column 24. Each plate 30 has an inner surface 30A proximate the steering column 24 and an opposed outer surface 30B, as shown particularly in Fig. 8. The two plates 30 have aligned openings 32 through them. As shown in Fig. 3, the openings 32 suitably comprise arcuate slots in respective planes parallel to the major axis of the steering column, allowing tilting movement of the steering column 24 as described further below.

A locking collar 34 is positioned between the plate inner surfaces 30A. The collar 34 has a generally omega (Q) shaped profile with a curved portion 34A extending around a portion of the steering column 24 and a respective connection piece 34B at each end of the curved portion 34A as shown in Fig. 7. The connection pieces 34B each have an opening 34C extending therethrough.

An elongate locking body 36, in the form of a generally cylindrical bar with threaded ends, extends through the openings 32 in the pair of plates 30 and the respective openings 34C in the locking collar connection pieces 34B.

Two retaining bodies 38, 40 are provided in threaded engagement with the elongate locking body 36, close to the distal ends thereof, at respective outer surfaces 30B of the pair of plates 30. The engagement of a first one of the retaining bodies 38 (to the right in Fig. 7) is by a right-hand thread. The engagement of the other of the retaining bodies 40 (to the left in Fig. 7) is by a left hand thread.

A lever arm 42 coupled with one of the retaining bodies 40 and is operable to rotate the same on its respective threaded engagement with the elongate locking body 36. As the body 40 rotates in a first direction, the threaded engagement moves it along the locking body, towards the centre, to pull the pair of plates 30 and connection pieces 34B closer together. This results in tightening of the curved portion 34A of the locking collar 34 around the steering column 24 to produce locking engagement of the plates 30 via the collar 34 with the steering column 24.

The right-hand retaining body 38 (the retaining body without the lever arm) is a friction disc having a friction-creating surface 38A in contact with the outer surface 30B of the adjacent one of the pair of plates 30 to resist rotation of that retaining body 38 in the event of rotation of the elongate locking body 36. A friction washer 44 disposed about the elongate locking body 36 is provided between the retaining body 40 having the lever arm 42 and the outer surface 30B of the adjacent one of the pair of plates 30.

Respective locking nuts 46, 48 are provided in threaded engagement with the distal ends of the elongate locking body 36 adjacent the retaining bodies 38, 40, the locking nuts having respectively right- and left-handed threads as for their adjacent retaining bodies.

The arcuate slots providing the aligned openings 32 in the pair of plates 30 allow tilting movement of the steering column 24 as the outer portions of the elongate locking body 36 move along the slots when the steering column is not in locking engagement with the pair of plates via the locking mechanism, that is to say when the lever arm 42 has not been rotated to a position to cause the locking collar 34 to tighten around the steering column 24.

As can be seen particularly in Fig. 3, a respective guide plate 50 is preferably attached to the inner surface 30A of each of the pair of plates 30 by mounting bolts 52. Each of the guide plates 50 has an opening 54 therethrough, which opening is generally aligned with the respective opening 32 in the one of the pair of plates 30 to which it is attached. The opening 54 in at least one of the guide plates 54 is smaller than the respective opening 32 in the one of the pair of plates 30 and serves to constrain the extent by which the steering column may be tilted. Across a range of models of a particular vehicle such as the tractor 10 of Fig. 1 , different extents of tilt may be accommodated by use of guide plates 50 having different opening 54 dimensions, but with all models in the range being supplied with the same design for the two plates 30 and elongate locking body 36.

Additional friction washers 56, disposed about the elongate locking body 36, are provided between each guide plate 50 and the inner surface 30A of the adjacent one of the pair of plates 30, and also between each guide plate 50 and the adjacent locking collar connection piece 34B.

As shown in Fig. 3 and Fig. 5, the steering column 24 preferably comprises a telescoping arrangement (outer sheath portion 24A movable longitudinally on central core portion 24B) permitting longitudinal movement of a steering wheel 22 attached to the steering column 24 in a direction parallel to the major axis of the steering column. The outer sheath portion 24A is split at 24C in the vicinity of the locking collar 34, such that the telescoping arrangement is locked against longitudinal movement when the steering column is in locking engagement with the plates via the locking collar. Whilst the engagement and disengagement of the steering column positional adjustment mechanism may be controlled by a manually-operated lever adjacent the steering wheel (22; Fig. 1), in a preferred embodiment it is engaged by a foot pedal 58 as shown in Fig. 2. The foot pedal 58 is connected via a first link arm 60 to a crank 62 rotatably mounted on a support shaft 64. An extension to the crank 62, on the opposite side of the support shaft 64 to the connection of the first link arm 60, is connected via a second link arm 66 to a distal end of the lever arm 42 coupled to effect rotation of the left-hand retaining body 40. Depressing the foot pedal 58 rotates the crank 62 which lifts the distal end of the lever arm 42 causing the retaining body 40 to rotate on its threaded engagement with the elongated locking body 36 away from the plate 30, thereby releasing the clamping pressure on the locking collar 34 and freeing the steering column for both tilting and longitudinal adjustment.

To return the mechanism to a locked configuration, the foot pedal 58 may simply be raised but, in a preferred configuration, one or more springs 68 are attached between the lever arm 42 and the vehicle and arranged to bias the adjustment mechanism into locking engagement. Whilst the one or more springs 68 may be attached directly to the lever arm 42, an indirect attachment is preferred with a spring 68 attached between an extension lug 70 of the crank 62 and the vehicle body to bias the foot pedal 58 to the “up” position, and hence bias the adjustment mechanism to the locked position. As will be readily understood, other arrangements such as cables may be used to connect the foot pedal 58 to the lever arm 42, and other spring arrangements may be provided to bias the arrangement to the locked position.

In the foregoing, the applicants have described a positional adjustment mechanism for a vehicle steering column 24 which has a pair of plates 30 on either side of the steering column, with the two plates having aligned openings 32. A locking collar 34 between the plates engages with an elongate locking body 36 extending through the openings in the pair of plates and in the locking collar. Two retaining bodies 38, 40 are provided in threaded engagement with the elongate locking body 36 at respective outer surfaces of the pair of plates 30, wherein the engagement of one of the retaining bodies is by a right-hand thread and the engagement of the other of the retaining bodies is by a left hand thread. A lever arm 42 coupled with one of the retaining bodies 40 rotates the same on its respective threaded engagement with the elongate locking body 36 to pull the pair of plates closer together to produce locking engagement of the plates 30 via the collar 34 with the steering column 24.

From reading the present disclosure, other modifications will be apparent to persons skilled in the art. Such modifications may involve other features which are already known in the field of vehicle steering systems and component parts therefore and which may be used instead of or in addition to features already described herein