This invention relates to a reach adjustable steering column having two telescoping shafts, more particularly to the elimination of the rotational lash between the two telescoping shafts.

5. In such steering columns the two telescoping shafts comprise a first shaft of polygonal shape and a second corresponding polygonal bore for receiving the first shaft.

BACKGROUND OF THE INVENTION

It is known to provide a lash free axailly collapsible steering column ιo. by providing a plurality of spring loaded members located in one of the shafts which abut polygonal surfaces of the other shaft to eliminate torsional lash therebetween. This spring loading can be by spring loaded bal ls, or by utilizing a coi l spring, a rubber block or other resilient member in a blind bore behind a ball or cylindrical roller.

15. in Patent No. 429, 180 the lash is eliminated by balls press-fitted into corresponding bores in one of the shafts, there being provided a rotational ly flexible section between these balls and a fail-safe portion, which fail-safe portion becomes operative at torque levels above a predetermined value.

The embodiments also show examples where either the inner hex shaft 20. is twisted or the outer tube is twisted to provide a pre-load, there still being provided a torsional fail-safe portion in the inner hex shaft.

However, with the invention to Patent No. 429.180 it is apparent that due to the hex shaft, and the outer tube of corresponding shape that the load applied is virtually a point loading at the apices of the hex shaft.

25. in order to eliminate indentation of the tube and/or rounding or other deforming of the apices of the hex shaft the torsional fail shaft portion is required which then transfers the torque to the other end of the hex shaft where the excess torque is transmitted.

It is an object of this invention to provide a lash axially adjustable steering column in which the column is simple and economic to produce and which does not require a fail-safe portion.

BRIEF STATEMENT OF THE INVENTION

5. Thus, there is provided according to the invention, an axially movable column comprising torque transmitting inner and outer relatively axially movable telescopic shafts, said inner shaft having a polygonal shape with at least one large flat surface and said outer shaft having a corresponding polygonal bore therein for receiving said inner shaft characterized by anti- ιo. lash means comprising a tube welded or otherwise attached to said outer shaft and having a corresponding polygonal bore for engaging said inner shaft, said tube being welded in a manner that it applies a pre-load in a torsional sense between the inner and outer shafts on the large flat surfaces thereof.

15. in a further form of the invention the anti-lash means can comprise that the outer shaft at its end or an extension thereof is torsional ly displaced to provide a pre-load to the inner shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

in order to more fully describe the invention reference will now be 20. made to the accompanying drawings in which:

FIG. 1 is a longitudinal cross-sectional view of one form of the invention,

FIG- l a is a view along the lines A-A of FIG. l , and FIG. 2 is an alternative form of the invention.

25. DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 1 and l a of the drawings, the tube shaft 1 is shown, this tube extending downwardly to the steering box or mechanism, and

slidable within this tube shaft is a solid shaft 2 which extends upwardly to which is affixed the steering wheel.

Preferably the shaft 2 is of the shape as shown in FIG. l a having a pair of opposite flats 3 and arcuate joining portions 4.

₅ _ The shaft tube 1 is cylindrical, but at its upper end is formed to have a complimentary shape to the shaft 2 as shown in FIG. 1 a.

According to this form of the invention, there is provided a continuation of the tube 1 as a separate portion 5, this abutting the end of the shaft tube I and is expanded at its upper end to a circular portion 6.

ιo. The extension portion 5 is formed to have a shape complimentary to the shaft 2, and the shaft tube I and the extension portion 5 are joined by a torque tube 7, the torque tube 7 being attached as by welding 8 to the tube snaft i and the extension portion ^c -.

The torque tube 7 is welded f irst to the extension portion 5 and then 15. torque is appl ied to the torque tube 7 and the weld 8 applied between the torque tube 7 and the tube shaft 1 while being restrained to thus very slightly offset the extension portion 5 m a rotational sense from the torque tube 1

The shaft 2 is subject to this pre-load applied between the extension 20. portion 5 and to the torque tube I .

The pre-load chosen is such that the shaft 2 can still slide within the tube shaft 1 and the extension 5 but the pre-load by being applied to the flats of the shaft 2 effectively eliminates any back lash.

Due to the fact that the pre-load is applied to the large area of flats on 25. the shaft 2 torque in the steering motion can be applied without any risk of any indentation or deformation occurring on either component.

Referring now to FIG. 2 the tube shaft I is again at its upper end formed to be complimentary to the shape of the shaft 2, and in this embodiment the torque tube 9 is again welded to the tube shaft I . but this torque tube 9 is deformed at its upper end to have an internal shape

5. complimentary to the shaft 2. In this instance pre-load is again applied by applying torque to the torque tube 9 and restraining it in its pre-stressed condition before the torque tube 9 is welded to the shaft 1. The mechanism generally indicated at 1 1 is the locking mechanism for locking the shaft 2 in its position when the desired extension has been achieved by the driver of

10. the vehicle.

Thus, it will be seen according to the invention, that while the preferred shape of the shaft 2 is shown, other shapes can be provided as long as there are large bearing surfaces for the pre-load to be applied and without causing indentation or deformation of either of the complimentary 15. parts. As the co-operating parts have co-operating large bearing surfaces, the pre-load is distributed across these surfaces, there being no concentrated or point bearing areas which could result in indentation of one or both of the co-operating surfaces

By the invention it will be seen that the complimentary components 20. are able to withstand all torque which is applied to the steering column without there being any need for a flexible portion and a fail-safe portion.

While the invention has been particularly described in relation to the steering columns of a motor vehicle, it is to be realised that the invention is not to be limited thereto, but is applicable to any situation requiring a 25. air of telescopic shafts adapted to transmit torque.

Although various embodiments have been described in some detail it is to be realised that the invention is not to be limited thereto but may include various modifications falling within the spirit and scope of the invention.