Title of Invention

STEERING SHAFT VARIABLE IN LENGTH FOR STEERING DEVICES OF MOTOR VEHICLES

Abstract

The present invention relates to a steering shaft variable in length for steering devices of motor vehicles, comprising at least two coaxially arranged profiles deviating from the circular form, at least one of them being formed as a tubular part into which the other profile is inserted by its end piece and is axially slid ably mounted therein, but with interfitting hold for transmission of torque, the outer peripheral contour of the inner profile and the inner peripheral contour of the outer profile at least section-wise and approximately conforming with each other and said peripherally closed contours being at least partly formed by successive curved sections, the radii of curvature of the curved sections thereby being positioned along the respective peripheral contour alternately inside and outside of the respective profile and a circumferential gap of for instance variable width along its circumference being defmed between the two profiles, and the gap accommodating a sliding sleeve made of macro-molecular material, characterised in that the sliding sleeve only section-wise and alternately applies along its peripheral contour against the walls of the profiles defining the gap, the sliding sleeve alternately applying. against the convex sections of the inner profile and the concave sections of the outer profile.

Full Text

The present invention relates to a steering shaft which is variable in length for steering devices of motor vehicles, comprising at least two coaxially arranged profiles deviating from the circular form, at least one of them being formed as a tubular part into which the other profile is inserted by its end piece and is axially slidably mounted therein, but with interfitting hold for transmission of torque, the outer peripheral contour of the inner profile and the inner peripheral contour of the outer profile at least section-wise and approximately conforming with each other and said peripherally closed contours being at least partly formed by successive, curved sections, the radii of curvature of the curved sections thereby being positioned along the respective peripheral contour alternately inside and outside of the respective profile and a circumferential gap of possiblyfor instance variable width along its circumference being defined between the two profiles, and the gap accommodating a sliding sleeve made of macromolecular material. In the prior art, comparable devices are known, for example from the following documents : DE-AS 2925 398; DE-OS 1530 971; GB 1542 127; GB 1328 200; US 2772 104; US 2272 900. Above all, the variable length steering shaft for steering devices of motor vehicles disclosed in DE 3624 473 C2 is to be mentioned in this respect. The sliding sleeve positioned between the two profiles described therein contains fins which ex-tend longitudinally along the sliding sleeve on the side thereof which is, relative to the latter, directly opposite the axially slidable profile. Said fins protrude into a free space defined between the paired parts in axial direction of the shaft. They apply against its wall thereby being subjected to deformation. Between two fins forming a pair, an inset made of a material with permanent elasticity is arranged, normally a rubber cord or resilient strip. Although this anticipated construction successfully compensates the play existing between the two profiles, the static friction between the paired parts is so high that the values defined for axial sliding of the profiles cannot reliably be kept. On the basis of the prior art, the present invention is aimed at designing the assembly in such a way that the necessarily existing play between the profiles is compensated, but the values defined for axial sliding of the profiles can nonetheless be reliably and permanently kept. The present invention solves the problem by providing an assembly in which the sliding sleeve only sectionally and alternately applies along its peripheral contour against the walls defining the gap, whereby the sliding sleeve applies alternately against the convex sections of the inner profile and against the concave section of the outer profile. For reasons of expedience, a steering shaft of this type is designed so that with a torque-free steering shaft the transition zones positioned adjacently in radial direction are angularily offset between the application against the respective profile and the following play and that, when seen in circumferential direction, the section of the sliding sleeve positioned between the two transition zones has a play relative to the adjoining profiles. A preferred embodiment of the present invention will now be described with reference to the accompanying drawings, in which : Fig. 1 is a front view of a steering shaft; Fig. 2 is a sectional view of the steering shaft shown in Fig. 1; Fig. 3 is a transverse sectional view shown in Fig. 1 and 2 taken along the line III - III in Fig. 2, but considerably enlarged as compared to said Figs. The steering shaft according to Figs. 1 - 3 comprises of a first profile 1 having a solid cross section, which carries at one end thereof a formed part 3, on which further components of the steering assembly not essential for the present invention are to be attached. The rod-like profile 1 is rolled, cold-extruded or drawn from solid material, the cross-section thereof being shown in Fig. 3. Said cross-section is formed with rounded corner areas between which pressed-in grooves are defined, the transition between the rounded corners and the pressed-in grooves being continuously and curved. The second profile 2, which also carries a hinge part 6 at its end, is formed as a tube and is shaped with a cross-sectional configuration shown in Fig. 3, which approximately matches the one of profile 1 r insofar as the hollow profile too is provided with rounded corner areas and pressed-in grooves in-between, the rounded corners and the pressed-in grooves continuously merging into each other. The cross-sectional configurations or peripheral contours of the two profiles 1 and 2 are formed by successive, curved sections. The radii of curvature of said curved sections along the respective peripheral contour are alternately positioned inside and outside of the respective profile 1 or 2. Moreover, the individual radii of curvature differ in size. This is particularly clearly shown in Fig. 3. The inside dimensions of the outer profile 2 and the outside dimensions of the inner profile 1 differ to such an extent that between the two parts a considerable play exists. Said play forms or defines a circumferential gap having a variable width along its circumference. In order to partly bridge said play or gap, respectively, and to further sliding of said parts relative to each other, a sliding sleeve 7 made of a suitable plastic material having a low coefficient of friction is attached to the inner profile 1. The peripheral contour of the sliding sleeve substantially matches that of the profile 1 supporting it. When the sliding sleeve 7 is mounted according to its purpose, its peripheral contour slightly differs from the contour it had in its non-mounted condition. Upon mounting, the sliding sleeve 7 is slightly deformed and thus pre-stressed. The wall thickness of the sliding sleeve 7 is substantially the same along its circumference. Several such sliding sleeves 7 can be arranged along the length of the steering shaft, in particular two such sliding sleeves. In this case, the sliding sleeves 7 are distanced from each other. Now, with respect to said sliding sleeve 7, it is essential that it applies along the peripheral contours of the two profiles 1 and 2 alternately against the convex sections 10 of the inner profile 1 and against the concave sections 11 of the outer profile 2 and furthermore that it extends along concave sections 11 of the inner profile 1 with a play and spacing. In this way, transition zones 12 and 13 are formed both at the inner profile 1 and the outer profile 2, representing the tangential area in which the sliding sleeve 7, before being applied against the respective profile 1 or 2, passes into an area subject to play relative to the profile 1 or 2, respectively, said play having the shape of a narrow curved wedge. With a torque-free steering shaft (Fig. 3) the transition zones 12, 13 adjacently positioned in radial direction are angularily offest be- tween application against the respective profile 1, 2 and the successive play and, viewed in peripheral direction, the section of the sliding sleeve 7 positioned between the two transition zones 12, 13 has a play relative to the respective adjoining profiles 1, 2. Angular off-set of the two transition zones 12 and 13, being adjacently positioned in radial direction, is approximately 10°. In the areas where the sliding sleeve 7 applies against the concave sections of the outer profile 2, grooves 8 extending in longitudinal direction are defined in the sliding sleeve. The groove 8 extending in longitudinal direction may have differing dimensions over the length of the sliding sleeve 7, In the longitudinal centre area of the sliding sleeve 7 the dimensions of said groove are enlarged as compared with the sections of the groove extending against the faces of the sliding sleeve 7. Due to the manufacturing process, profiles 1 and 2 or their surfaces, respectively, have dimensional tolerances. Thanks to the aforementioned measures concerning dimensioning of the groove 8, only slight frictional forces become effective during an operational length adjustment of the steering column. By reducing the wall thickness in said area as a result of said groove dimensioning, the sliding sleeve is rendered more resilient in the area where it acts as a compensating spring. Thanks to this suggestion the areas of contact between the inner and the outer profile 1 and 2 and the sliding sleeve 7 are reduced as compared with the prior art so that more favourable conditions exist with respect to axial sliding of the two profiles against each other. In addition, the sliding sleeve 7 with its respective sections positioned between the two transition zones 12 and 13 acts like a leaf spring thanks to which turning of the steering wheel is subjected to a certain steering resistance which is initiated practically without any play. The play necessarily existing for constructional reasons is no longer felt as such by the driver actuating the steering wheel. As compared with the prior art, the substance of the present invention is that the tangential transition zones 12 and 13 which are adjacently positioned in radial direction are, at their respective outside and inside, angularily offset between application and the scope of the sliding sleeve 7 subject to play, so that the section of the sliding sleeve 7 positioned between the two adjoining transition zones 12, 13 freely extends in the gap 4, allowing it to act there like a spring when a torque is applied onto the steering column. Legend as to reference numbers 1 first profile 2 second profile 3 formed part 4 gap 5 grooves 6 hinge part 7 sliding sleeve 8 groove 9 10 convex section 11 concave section 12 transition zone 13 transition zone Claims 1. Steering shaft variable in length for steering devices of motor vehicles, comprising at least two coaxially arranged profiles (1, 2) deviating from the circular form, at least one of them being formed as a tubular part into which the other profile (1) is inserted by its end piece and is axially slidably mounted therein, but with interfitting hold for transmission of torque, the outer peripheral contour of the inner profile (1) and the inner peripheral contour of the outer profile (2) at least section-wise and approximately conforming with each other and said peripherally closed contours being at least partly formed by successive curved sections, the radii of curvature of the curved sections thereby being positioned along the respective peripheral contour alternately inside and outside of the respective profile(1, 2) and a circumferential gap (4) of for instance variable width along its circumference being defined between the two profiles (1, 2), and the gap (4) accommodating a sliding sleeve (7) made of macro-molecular material, characterised in that the sliding sleeve (7) only section-wise and alternately applies along its peripheral contour against the walls of the profiles (1, 2) defining the gap (4), the sliding sleeve (7) alternately applying against the convex sections of the inner profile (1) and the concave sections of the outer profile (2). 2. Steering shaft variable in length according to claim 1, characterised in that with a torque-free steering shaft the transition zones (12, 13) adjacently positioned in radial direction are angularily offset between application against the respective profile (1( 2) and the successive play and, viewed in peripheral direction, the section of the sliding sleeve (7) positioned between the two transition zones (12, 13) has a play relative to the respective adjoining profiles (1, 2). 3. Steering shaft variable in length according to claim 1 or 2, characterised in that the wall thickness of the sleeve (7) along its perimeter is substantially the same. 4. Steering shaft variable in length according to claim 2, characterised in that the angular off-set of the transition zones (12, 13) is approximately 10°. 5. Steering shaft variable in length according to claim 1, characterised in that several sliding sleeves (7) are arranged along the length of the steering shaft. 6. Steering shaft variable in length according to claim 5, characterised in that the sliding sleeves (7) arranged along the steering shaft are distanced from each other. 7. Steering shaft variable in length according to claim 1, characterised in that the areas where the sliding sleeve (7) applies against the concave sections of the outer profile (2) grooves (8) extending in longitudinal direction are defined in the slid ing sleeve (7). 8. Steering shaft variable in length according to claim 7, characterised in that the grooves (8) have differing dimensions along their longitudinal extension. Summary: Steering shaft variable in length for steering devices of motor vehicles comprising two coaxially arranged profiles (1, 2) deviating from the circular form, one of them being formed as a tubular part into which the other profile (1) is inserted by its end piece and is axially slidably mounted therein but with interfiling hold for transmission of torque. The outer peripheral contour of the inner profile (1) and the inner peripheral contour of the outer profile (2) approximately conform with each other. The peripherally closed contours are formed by successive, curved sections, the radii of curvature of said curved sections thereby being positioned along the respective peripheral contour alternately inside and outside of the respective profile (1, 2). Between the two profiles (1, 2) a circumferential gap (4) is defined. Said gap (4) accommodates a sliding sleeve (7) made of macromolecular material. The sliding sleeve (7) only section-wise and alternately applies along its peripheral contour against the walls of the profiles (1, 2) defining the gap (4), whereby the sliding sleeve (7) alternately applies against the convex sections of the inner profile (1) and against the concave sections of the outer profile (2). With a torque-free steering shaft the transition zones (12, 13) adjacently positioned in radial direction are angularily offset between application against the respective profile (1,2) and the successive play. Viewed in peripheral direction, the section of the sliding sleeve (7) positioned between the two transition zones (12, 13) has a play relative to the adjoining profiles (1, 2). (Fig. 3).

Documents:

679-mas-1998- abstract.pdf

679-mas-1998- claims duplicate.pdf

679-mas-1998- claims original.pdf

679-mas-1998- correspondence others.pdf

679-mas-1998- correspondence po.pdf

679-mas-1998- description complete duplicate.pdf

679-mas-1998- description complete original.pdf

679-mas-1998- drawings.pdf

679-mas-1998- form 1.pdf

679-mas-1998- form 26.pdf

679-mas-1998- form 3.pdf

679-mas-1998- form 4.pdf