GB2184213A - Telescopic tube assembly - Google Patents

Abstract

A telescopic tube assembly suitable for use as a motorvehicle steering column which is resistant to buckling and adjustable for height, includes an innertube (1) of triangular cross-section and an outertube (2). The tubes (1, 2) are made non-rotatable and play-free relative to each other in the overlap regions by two sliding bushes (5) cast or injection formed on to the inner tube (1), and are mounted to slide relative to each other on the longitudinal axis of the assembly. One side of the inner tube (1) has a recess (4) between the sliding bushes (5) and the overlap region in the region of one sliding bush (5) is of a twisted configuration as viewed in cross-section with respect to the overlap region in the region of the other sliding bush (5). <IMAGE>

Description

SPECIFICATION Telescopic tube assembly This invention relates to a telescopictube assembly suitableforuse as a motorvehiclesteering column which is resistant to buckling and adjustable for height, including an innertube oftriangular cross-section and an outer tube, which tubes are made non-rotatable and play-free relative to each other in the overlap regions by two sliding bushes cast or injection formed on to the innertube, but which areslidable relative to each other on the longitudinal axis ofthe telescopictube assembly.

Motor vehicle steering columns ofthis kind have long been known and have long been used in the automobile industry. In particular private cars of modern types nowadays reach speeds of over 200 kph. In this situation, known telescopictubes give rise to problems which are found at leastto be extremely disturbing. Thus for example at speeds of that kind, vibrations are generated which are in a range of 20to 30 Hz and which cause the inner or outertubeofthetelescopictubeassemblytogointo a condition of natural oscillation such that even the slightest clearance between the inner and outer tubes is sufficient to cause rattling noises.That clearance can occurfor example just because the sliding bushes, which are made of plastics material, contractundertheinfluenceoftemperature,for example at a temperature which is below 20"C.

These is thus a need for a generally improved telescopic tu be assembly having improved precise and play-free guidance ofthe inner tube in the outer tube under all conditions, using means which are verysimplefrom a structural pointofview.

According to the present invention there is provided atelescopictube assembly, suitable for use as a motorvehicle steering column which is resistant to buckling and adjustable for height, including an innertube oftriangularcross-section and an outer tube, which tubes are made non-rotatable and play-free relative to each other in the overlap regions by two sliding bushes cast or injection formed on to the innertube, but which are slidable relative to each other on the longitudinal axis ofthetelescopictube assembly,wherein onesideoftheinnertube hasa recess located between the sliding bushes and the overlap region in the region of one sliding bush is of a twisted configuration as viewed in cross-section with respect to the overlap region in the region ofthe other sliding bush.

The above-indicated arrangementofthe cross-sectional planes relative to each other means that, when the innertube is pushed into the outer tube, a rotarytorque has to be applied, which results in deformation ofthe innertube.

Preferably the above-mentioned deformation is in the range of elasticity ofthe innertube, that isto say, a given angle of rotation about which one cross-sectional plane of one overlap region is twisted relative to a cross-sectional plane of the other overlap region and which is dependent on the dimensions and the material ofthe innertube, may not be exceeded.

The fact that the innertube is twisted in the elastic range means that a stress is produced, which atthe same time represents a return force and presses the corresponding side surfaces ofthe innertube againstthe side surfaces ofthe outertube. This arrangement ensures absolute freedom from clearance between the inner tu be and the outertube, which isthe case even when thesliding bushes shrinkfor example due to a drop in outside temperature, by a certain amount.Also, friction is produced, by the return force, between the sliding bushes ofthe inner and outertubes, and such friction can be so controlled by establishing the above-indicated angle of rotation that it represents the optimum resistance for a motorvehiclesteering column which isadjustableforheight,forthe purposes of height adjustment.

Afurther advantage of the configuration of the telescopictube ofthe invention is that tolerances due to the production processes involved between the inner and outertubes are positively compensated for.

For a better understanding ofthe present invention, andto show an embodimentofthe innovation is described hereinafter with howthe same may be carried into effect, reference will now be made, by way of example to the accompanying drawings in which: Figure lisa view in longitudinal section through a telescopictube assembly according to one embodiment of the invention, Figure2 is a view in cross-section through the telescopic tu be assembly ta ken on line ll-ll in Figure 1,and Figure 3 is a further cross-sectional viewthrough the telescopic tube assembly taken on line Ill-Ill in Figure 1.

The telescopic tube assembly of the invention shown in Figure 1 includes an outertube 2, and an innertube 1 which is of triangular cross-section. Two sliding bushes 5 which are cast or injection formed onto the innertube 1 and which are made from plastics material in known mannerare located in the overlap regions between the innertube 1 and the outer tube 2. The sliding bushes 5form sliding bearings which permit satisfactory sliding movementofthe innertube 1 with respecttothe outertube 2.

According to the invention, between the sliding bushes 5 the inner tube has a recess 4 which in the present embodiment is formed by the wall of one limb ofthetriangular innertube 1 being removed in the appropriate area. This can be seen particularly clearlyfrom Figure 3.

As Figure 2 clearly shows, the outertube 2 is also of a partiallytriangularconfiguration in the overlap regions. Figure 2 also showstheway in which the cross-sectional planes 3 and 6 are twisted relative to each other in accordance with the invention. In this connection,thecross-sectional plane6is shown in dash-dotted lines in Figure 2,forthe sake ofclarityof the drawing.

The innertube 1 which is twisted within its elastic range accordingly acts virtually as a torsion spring.

It will be appreciated that, besides the illustrated configuration ofthe recess 4, other forms of construction are also possible. The important consideration is the reduction in the moment of resistance in the corresponding region of the inner tubel.

Claims (4)

1. Atelescopictube assembly, suitable for use as a motor vehicle steering column which is resistant to buckling and adjustable for height, including an inner tu be oftriangular cross-section and an outer tube, which tubes are made non-rotatable and play-free relative to each other in the overlap regions by two sliding bushes cast or injection formed on to the innertu be, but wh ich areslidablerelativetoeach other on the longitudinal axis of the telescopic tube assembly, wherein one side of the innertube has a recess located between the sliding bushes and the overlap region in the region of one sliding bush is of a twisted configuration as viewed in cross-section with respecttothe overlap region in the region ofthe other sliding bush.

2. Atelescopictube assembly according to claim 1, wherein the inserted inner tube is twisted within its elastic range.

3. Atelescopictube assembly according to claim 1,wherein the recess is formed byan interruption in thewall of a limboftheinnertube.

4. Atelescopictube assembly, substantially as hereinbefore described with reference to Figures 1 to 3 ofthe accompanying drawings.