Locking device for adjustable steering column assembly

Abstract: A locking device for an adjustable steering column assembly for a vehicle has first and second interengageable disc members (10, 11) each being provided with toothed areas (17, 18) which pass through respective windows (19, 20) of the other disc member to engage in corresponding portions of the steering column. A spring (12) is interposed between the two members to urge them apart which has the effect of withdrawing the toothed profiles out of engagement with the steering column assembly so that they are retracted in the windows. The invention has for its effect to facilitate free movement of a steering column in a fore and aft direction and/or up and down direction, whilst being able to reliably lock the column in position when desired.

Description: This invention relates to a locking device for an adjustable steering column assembly for a vehicle. A problem with known adjustable steering columns is how to prevent them from moving when they are not supposed to and giving them free movement when they are supposed to, particularly in the case of steering columns that adjust up and down and fore and aft. Common systems in use rely either on simple friction clamping systems or on serrated or toothed locking mechanisms. Figure 1 schematically shows a steering column 1 with mounting points 2. The double arrows 3 show the direction of fore and aft adjustment and the double arrows 4 show the direction of up and down adjustment. A locking handle 5 is provided for the friction clamping system. Figure 2 diagrammatically illustrates a typical steering column adjusting device whereby the moving part of the steering column 1 is clamped inside a bracket 6 by a mechanism similar to a vice. Slots 7 are provided for vertical adjustment, whilst a slot is provided in the region of 8 for fore/aft adjustment. The arrangement has a problem of giving sufficient friction to clamp, whilst still being able to move freely in the unlocked condition. Moreover, simple metal-to-metal systems tend to be poor in user feel and the addition of plastics such as plastics spacers 9 tend to introduce creep and wear. Other known arrangements work on a serrated or toothed lock mechanism construction which are quite common on tilting steering columns. Such devices rely on the fixed and moving steering column parts having expensive splined teeth engaging with each other. There is a drawback that these are limited in adjustment position and are expensive. For further information, EP-A-0 440 403 discloses a locking device for an adjustable steering column assembly for a vehicle according to the pre-characterising part of claim 1. According to the present invention, there is provided a locking device for an adjustable steering column assembly for a vehicle, the device including first and second interengageable parts, at least one of the parts having means to lock it against a portion of the steering column assembly and resilient means to urge said parts apart to bring said at least one part out of locking engagement with said portion, wherein said means to lock at least one of said parts comprises an area of serrated or toothed profiles arranged to engage, when the two parts are urged together with a corresponding area of serrated or toothed profiles provided on said portion of the steering column assembly, characterised in that said profiles of said one part engage the profiles of said corresponding area by protruding through a corresponding window in the other of said parts, and in that when the two parts are urged apart, a smooth face is presented to facilitate sliding during adjustment of the steering column assembly. Preferably, both of said parts have means to lock each of them against separate portions of the steering column assembly, so that the resilient means urges both of the parts out of locking engagement. For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to Figures 3 to 8 of the accompanying drawings, in which:- Figure 3 is an exploded view of the two interengageable parts and the resilient means, Figure 4 is a plan view and side view of the resilient means, Figure 5 is a plan view and front view of one of the parts; Figure 6 is a plan view and front view of the other of the parts, Figure 7 is a side view of the two parts in locking condition, Figure 8 is a view similar to Figure 7 showing the two parts out of locking condition by virtue of the resilient means, and Figure 9 is a schematic view showing a portion of the steering column assembly against which one of the parts is intended to lock. Referring to Figure 3, the first and second interengaging parts comprise an outer lock disc member 10 which interengages with an inner lock disc member 11. The resilient means in the form illustrated is a separate, cross-shaped leaf spring 12 interposed between the two disc members 10, 11 and located in respective spring seats 10A, 11A in the disc members. The disc members 10, 11 and the spring 12 can be made of plastics material or metal as preferred. The disc member 10 is provided with a nose 13 which locates the spring 12 and snaps through a central aperture 14 in the disc member 11 to hold the assembly together. This may be further extended to guide the device in its mating part. Means in the form of protrusions 15 on the face of the disc member 11 which faces away from the disc member 10 are provided to act as a guide to locate the disc member 11 in a slot such as the slot 7 or 8 of the steering column mounting bracket 6 or in the mating steering column inner part 16 shown in Figure 9. In the form illustrated, each disc member 10, 11 is provided with two areas of serrated or toothed profiles 17, 18, respectively. Each disc member 10, 11 is also provided with a pair of corresponding windows 19, 20, respectively, through which the toothed profiles of the other disc member can protrude when the two disc members are urged towards one another, the two disc members having perpendicularly opposed toothed areas. Figure 7 shows the disc members in a condition where the resilient bias of the spring 12 has been overcome, whilst Figure 8 shows the condition where the spring 12 has been allowed to push the disc members 10 and 11 apart, thereby retracting the toothed areas 17, 18 into the windows 19, 20 respectively. The locking device is fitted between part of the steering column assembly such as the bracket 6, which is provided with a toothed area corresponding to the toothed areas 18, for example, whilst the steering column inner part 16 is provided with a toothed form such as that shown at 21 with which the toothed areas 17 can engage. In use, with the clamping handle 5 in an unlocked condition, it will be seen that the locking device offers a smooth face to slide against and, in the locked condition of the clamping handle 5, offers a toothed profile on both sides which engages into the bracket and the moving part to prevent further movement, the clamping force exerted across the steering column compressing the spring 12 so that the toothed profiles protrude through the windows beyond both outer sides of the disc members to engage in the similar teeth pressed into the bracket sides (in the case where there is a slot provided for vertical adjustment) and into teeth, which may have been cast, into the side of a slot on the moving member for fore and aft adjustment. The teeth need only protrude through the windows by 0.5-1.0 mm, which then requires a minimum free play when unlocked of 1 mm. Angular mismatch of the two slots for the two types of adjustment can be absorbed by permissible rotational movement between the two disc members. The width of the locking device need only be about 5.5 mm, whilst the disc members can have a diameter of 30 mm but it will be appreciated that they can be of any thickness or shape to suit the particular application. Instead of the leaf spring 12, the resilient means could be integral with one or other of the first and second interengageable parts. A groove (not shown) could also be incorporated in the outside diameter of the device to locate a column support spring which prevents the column from dropping when unlocked. A device of this type needs a guide (13) to locate it correctly with respect to its slot. This is also used as a snap fit to retain the three components, namely the parts 10, 11 and 12, together. The two further supports 15 can be used to stop relative rotation between the device and mating slots to ensure correct angular orientation of the toothed profiles 17, 18 with their respective mating toothed profiles.

Claims: A locking device for an adjustable steering column assembly for a vehicle, the device including first and second interengageable parts (10, 11), at least one of the parts having means to lock it against a portion (6) of the steering column assembly and resilient means (12) to urge said parts apart to bring said at least one part out of locking engagement with said portion, wherein said means to lock at least one of said parts comprises an area (17, 18) of serrated or toothed profiles arranged to engage, when the two parts are urged together with a corresponding area (21) of serrated or toothed profiles provided on said portion of the steering column assembly, characterised in that said profiles of said one part engage the profiles of said corresponding area by protruding through a corresponding window (19, 20) in the other of said parts, and in that when the two parts are urged apart, a smooth face is presented to facilitate sliding during adjustment of the steering column assembly. A device according to claim 1, wherein both of said parts (10, 11) have said means to lock each of them against separate portions of the steering column assembly, so that the resilient means (12) urges both of the parts out of locking engagement. A device according to claim 1 or 2, wherein said resilient means (12) is interposed between the two parts. A device according to claim 3, wherein said resilient means (12) is a leaf spring. A device according to claim 4, wherein said leaf spring is cross-shaped. A device according to claim 1 or 2, wherein said resilient means is integral with one of said parts. A device according to any one of the preceding claims, wherein at least one of said parts is provided with means (15) to act as a guide to locate that part in another portion of the steering column assembly. A device according to any one of the preceding claims, wherein each said part and/or said resilient means is made of plastics material. A device according to any one of claims 1 to 7, wherein each said part and/or said resilient means is made of metal. A device according to any one of the preceding claims, wherein each said part is in the form of a disc member. A device according to any one of the preceding claims except claim 6, wherein each said part is provided with a seat (10A, 11A) for said resilient means. A steering column assembly incorporating a locking device according to any one of the preceding claims. An assembly according to claim 12, wherein said corresponding area of serrated or toothed profiles provided on said portion of the steering column assembly is located on a bracket (6) supporting the steering column. An assembly according to claim 12 or 13, wherein said corresponding area of serrated or toothed profiles provided on said portion or one of said portions of the steering column assembly is located on a steering column inner part (16).

Inventors: SPEICH GERALD ANTHONY, SPEICH, GERALD ANTHONY
Applicants: TORRINGTON CO, THE TORRINGTON COMPANY LIMITED
Application year: 1992
Main classification: B62D1
IPC codes: B62D1