CLAMPING MECHANISM FOR AN ADJUSTABLE STEERING COLUMN FOR A VEHICLE

Abstract: A clamping mechanism for an adjustable steering column incorporates a pre-set but variable preload. An operating handle (4) is fitted on a shaft (5) to rotate between clamped and unclamped conditions. Part of the shaft is provided with opposed flats (6) about which a shaft lock washer (7) is non-rotatably fitted. The lock washer operates with a stop member (11) to prevent rotation of the assembly, and a nut (13) is tightened on one end (8) of the shaft to the required preload.

Description: CLAMPING MECHANISM FOR AN ADJUSTABLE STEERING COLUMN FOR A VEHICLE This invention relates to an adjustable steering column for a vehicle and more particularly to a clamping mechanism for an adjustable steering column. In known clamping mechanisms, any required preload of the clamping system is effected manually upon manufacture. These and other clamping systems can also have somewhat complicated constructions to transmit the preload. According to the present invention, there is provided a steering column clamping mechanism for use with an adjustable steering column, the mechanism having an undamped condition allowing movement of the steering column and having a clamped condition preventing movement of the steering column, the clamping mechanism comprising a support bracket having a thickness and a slot therethrough; a steering column bracket slidable relative to the support bracket; at least one stop member being positioned in the support bracket slot; and an operating mechanism having a shaft extending therefrom, the shaft extending through the support bracket slot, the steering column bracket and said at least one stop member, and the operating mechanism being moveable from an undamped condition to a clamped condition; characterised in that when the operating mechanism is in the undamped condition, said at least one stop member is arranged to slidably engage the support bracket slot, and in that portions of the support bracket are arranged to be clamped between the operating mechanism and the steering column bracket when the operating mechanism is in the undamped condition. The preload can be applied automatically during assembly of the clamping mechanism. Preferably, the shaft is non-rota able, is threaded at one end and is tensioned against the support bracket by means of a threaded member tightened to a pre-set preload on the shaft. The threaded member can be a nut. The shaft can be held in non-rota able fashion by means of a shaft lock member fitted about a non-circular portion of said shaft and locking against another part of the mechanism to prevent rotation of the shaft. The shaft lock member can be in two parts, namely a lock washer having at least one cut-away portion to receive a co-operating protrusion of a separate stop member. The invention also extends to an adjustable steering column incorporating a clamping mechanism essentially as defined above. 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 the accompanying drawings, in which:- Figure 1 is a diagrammatic vertical sectional view showing part of the clamping mechanism for an adjustable steering column of a vehicle, Figure 1A is an enlarged view of a portion of the clamping mechanism shown in Figure 1, Figure 2 is a diagrammatic side view of the clamping mechanism shown in Figure 1, Figure 3 is an exploded view of the clamping mechanism and showing the part of it intended to apply a pre-set preload to it, and Figure 4 is a diagrammatic horizontal sectional view of the clamping mechanism shown in Figure 1. Referring to the drawings, Figures 1, 2 and 4 illustrate part of a steering column clamping mechanism for an adjustable steering column 1 supported within bracketry 2 by a resilient channel-shaped bracket 3. Vertical adjustment of the steering column 1, for example, is provided by slots 2A in the bracketry 2. An operating mechanism includes an operating lock handle 4 fitted on a shaft 5 to rotate the shaft 5 between clamped and undamped conditions of the steering column 1. In order to apply a pre-set but variable preload to the clamping mechanism, part of the shaft 5 is provided with opposed flats 6 to give it a non-circular section, so that it can be fitted within a shaft lock washer 7 having a central hole 7B in the form of a double-dee. The shaft 5 in the region of its flats 6 is threaded at 8 to receive a threaded member in the form of a tightening nut 13. The opposite end of the shaft 5 is also threaded at 9 to receive the handle 4 and another lock washer 10 is provided to fit about the threaded end 9 of the shaft 5 inside the handle 4. In the form illustrated in Figure 3, both the shaft lock washer 7 and the other washer 10 are provided with cut-away portions 7A, 10A, respectively, in which locate respective protrusions 11A, 12A of co-operating stop members 11, 12. The stop members 11, 12 themselves locate in respective slots in the bracketry 2. The protrusions 11A, 12A prevent the washers 7, 10 from rotating and, in the case of the washer 7 with its double-dee hole fitted on the flats of the shaft 5, means that the shaft 5 is itself prevented from rotation. As a means of reducing noise and improving user feel at the extremes of adjustment, the stop members 11, 12 are of plastics material, so that the aforementioned vertical adjustment is provided with a plastics interface between the other components which are of metal, e.g. steel. Further, the stop member 11 has a light interference fit on the shaft 5 to aid assembly by retaining the parts whilst the nut 13 is tightened. The assembly sequence is to screw the handle 4 to the desired position on the screw threaded end 9 of the shaft 5. The washer 10 and stop-member 12 are fitted in the brackets 2 and 3. The sub-assembly of the lock shaft lock washer 7 and stop member 11 is fitted on the flats 6 and the nut 13 is tightened. A plastics roller 15 is fitted to the shaft 5 in such a manner that the roller 5 is free to rotate. The roller 15 runs in slots in the bracket 3 accommodating the shaft 5 to provide another plastics/metal interface, again to reduce noise. A hardened steel washer 14 is fitted between the handle 4 and handle lock washer 10 to reduce wear between these components. It will be appreciated that the variable adjustment that can be given to the nut 13 provides the required preload of the clamping mechanism. As previously intimated, this means that the assembly can be carried out automatically. The stop members 11 and 12 have a flat rectangular shape with three protruding areas: protrusions 11A, 12A which locate in the cut-away portions 7A, 10A, respectively, of the shaft lock washer 7 and washer 10; and bushings 11B and 12B, respectively, which locate in the central opening of the shaft lock washer 7 and washer 10. As shown in Figure 1A for the stop member 12, the thickness of the flat rectangular portion of the stop members 11 and 12 (shown at "b") is less than the thickness of the adjacent portions of bracketry 2 (shown at "a") . When the handle 4 and shaft 5 are rotated to the clamped position, the portions of the shaft lock washer 7 and washer 10 which extend laterally beyond the edges of the stop members 11 and 12 engage the metal bracketry 2, providing a metal-to-metal clamping, as shown in Figure 4. When the handle 4 and shaft 5 are in the undamped position, the sides of the plastics stop members 11 and 12 engage the sides of the slots 2A, providing a plastics to metal interface when the steering column is being adjusted. As shown in Figure 3, the handle 4 contains a flanged steel threaded insert that the shaft 5 screws into. The steel threaded insert bears upon the steel thrust washer 14 which in turn bears upon the lever lock washer 10. Referring to Figure 1, the lever lock washer 10 bears upon the stop member 12. Between the stop members 11 and 12 is the saddle bracket 3 which carries the adjustable steering column 1. Referring back to Figure 3, the shaft lock washer 7 bears upon the stop member 11 with the clamping force achieved by adjusting the nut 13, which bears upon the shaft lock washer 7. Both stop members 11 and 12 are moulded in plastics. The lever lock stop member 12 locates in the lever lock washer 10 and the shaft lock stop member 11 locates in the shaft lock washer 7. These stop members 11, 12 prevent their respective mating parts 7, 10 from rotating by virtue of the fact that both stop members 11, 12 locate in the side bracket slots identified as 2A in Figure 1. The stop members 11, 12 are free to slide vertically in the slots 2A. Since both stop members 11, 12 are of plastics material, they provide a non-metallic interface between the shaft 5 and the inside edges of the bracket slots 2A, to reduce adjustment noise, but since the stop members 11, 12 are thinner than the bracketry 2, the stop members 11, 12 do not prevent metal- o-metal contact between the bracketry 2 and shaft lock washer 7 and lever lock washer 10.

Claims: CLAIMS : 1. A steering column clamping mechanism for use with an adjustable steering column (1) , the mechanism having an undamped condition allowing movement of the steering column (1) and having a clamped condition preventing movement of the steering column, the clamping mechanism comprising a support bracket (2) having a thickness and a slot (2A) therethrough; a steering column bracket (3) slidable relative to the support bracket (2) ; at least one stop member (11, 12) being positioned in the support bracket slot (2A) ; and an operating mechanism having a shaft (5) extending therefrom, the shaft (5) extending through the support bracket slot (2A) , the steering column bracket (3) and said at least one stop member (11, 12) , and the operating mechanism being moveable from an undamped condition to a clamped condition; characterised in that when the operating mechanism is in the undamped condition, said at least one stop member (11, 12) is arranged to slidably engage the support bracket slot (2A) , and in that portions of the support bracket (2) are arranged to be clamped between the operating mechanism and the steering column bracket (3) when the operating mechanism is in the undamped condition. 2. A mechanism according to claim 1, wherein the steering column bracket (3) is metal, at least the portion of the operating mechanism which clamps the steering column bracket (3) is metal and said at least one stop member (11, 12) is of plastics material. 3. A mechanism according to claim 1 or 2, wherein said at least one stop member (11, 12) has a thickness (a) less than the support bracket thickness (b) . 4. A mechanism according to claim 1, 2 or 3, wherein the operating machanism shaft (5) is non-rotatable, the shaft being threaded at both ends (8, 9) and the operating mechanism being rotatable relative to the shaft (5) . 5. A mechanism according to claim 4, wherein one end (9) of said operating mechanism shaft (5) is threaded into the operating mechanism, the other end (8) of the shaft (5) being tensioned against the support bracket (2) by a threaded member (13) and the threaded member (13) being tightened to provide a predetermined preload to the steering column clamping mechanism. 6. A mechanism according to claim 5, wherein the threaded member (13) is a nut. 7. A mechanism according to any one of the preceding claims, wherein a portion (6) of the operating mechanism shaft (5) has a non-circular cross-section and wherein the operating mechanism has a shaft lock member (7, 11A) engaging the shaft non-circular cross-section portion (6) , the shaft lock member (7, 11A) engaging the support bracket (2) to prevent rotation of the operating mechanism shaft (5) . 8. A mechanism according to claim 7, wherein the shaft lock member comprises two parts, a first part being a lock washer (7) having at least one cut-away portion (7A) and a second part comprising at least one protrusion (11A) on the stop member (11) , which engages said at least one cut-away portion (7A) on the lock washer (7) . 9. A mechanism according to claim 7 or 8, wherein said portions of the support bracket (2) are clamped between shaft lock member (7) and the steering column bracket (3) . 10. A mechanism according to any one of the preceding claims, wherein the or each stop member (11, 12) has a generally rectangular shape, the longer sides of the or each stop member (11, 12) slidably engaging the support bracket slot (2A) . 11. A mechanism according to claim 10, wherein the portions of the or each stop member (11, 12) adjacent the shorter sides of the or each stop member have protrusions (11A, 11B) extending parallel to the operating mechanism shaft (5) . 12. A mechanism according to any one of the preceding claims, wherein the operating mechanism includes a lock handle (4) . 13. A mechanism according to any one of the preceding claims and further comprising a plastics roller sleeve (15) about the operating mechanism shaft (5) . 14. An adjustable steering column for a vehicle incorporating a clamping mechanism according to any one of the preceding claims.

Inventors: MITCHELL COLIN ANDREW, SPEICH GERALD ANTHONY, MITCHELL, COLIN, ANDREW, SPEICH, GERALD, ANTHONY
Applicants: TORRINGTON CO, THE TORRINGTON COMPANY LIMITED
Application year: 1995
Main classification: B62D1
IPC codes: B62D1