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BACKGROUND OF THE INVENTION This invention relates generally to couplings for 5 steering shafts and more particularly to couplings used in steering shafts with larger degrees of angular misalignment.

Steering shafts are frequently made using two shaft members connected by a rubber coupling. The rubber coupling 10 provides axial and torsional dampening.

As the angular misalignment between the two shaft members increases, the bending stress on the rubber coupling increases. This increases the fatigue on the rubber 15 coupling and reduces its effective lifetime.

The foregoing illustrates limitations known to exist in present steering shaft couplings. Thus it is apparent that it would be advantageous to provide an alternative directed 20 to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.

SUMMARY OF THE INVENTION 25 In one aspect of the present invention, this is accomplished by providing a steering lower shaft assembly coupling comprising a lower shaft member, an upper shaft member, an elastomeric member and a pair of connecting means for pivotally connecting the upper shaft member and the 30 lower shaft member to the elastomeric member.

The foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing 35 figures.

BRIEF DESCRIPTION OF THE DRAWING FIGURES FIG. 1 is a simplified view of a steering shaft assembly incorporating the present invention;

FIG. 2 is a plan view illustrating the steering lower shaft assembly coupling shown in FIG. 1;

FIG. 3 is a side view of the steering lower shaft assembly coupling shown in FIG. 2;

FIG. 4 is a plan view illustrating a second embodiment of a steering shaft lower assembly coupling of the present invention; and

FIG. 5 is a side view of the steering lower shaft assembly coupling shown in FIG. 4.

DETAILED DESCRIPTION FIG. 1 shows a steering column comprising an upper shaft 31 and a lower shaft 30. The lower shaft 30 is connected to a steering box 1. A steering wheel 9 is connected to the upper shaft 31. The upper shaft 31 is supported by one or more bearings 5. The upper shaft 31 of the steering column is connected to the lower shaft 30 of the steering column by a steering lower shaft assembly coupling 10. FIG. 1 shows a first embodiment of the steering lower shaft assembly coupling 10 of the present invention.

FIGS. 2 and 3 show the details of the first embodiment of the steering lower shaft assembly coupling 10. The steering lower shaft assembly coupling consists of a lower and upper shaft members 30 and 31 pivotally connected to an elastomeric member 20. The upper shaft member 31 is the driving member and the lower shaft member 30 is the driven member. The

steering lower shaft assembly coupling 10 rotates about an axis of rotation 40.

The elastomeric member 20 provides axial and torsional dampening between the shaft members 30 and 31. The elastomeric member 20 also accommodates some angular misalignment between the shaft members 30 and 31.

A pair of supports 32 connect each shaft member 30, 31 to the elastomeric member 20. Each support 32 is attached to the elastomeric member 20 using screws 54. The screws 54 pass through a dog-bone shaped backing plate 50. Two backing plates 50 are used, one for each member 30, 31. The backing plates 50 prevent the screws 54 from wearing through the elastomeric member 20. The elastomeric member 20 has raised bosses 52 under each backing plate 50 where the screws 54 attach the backing plate 50 to the elastomeric member 20. This raises the backing plates 50 away from the elastomeric member 20 and allows some flexing to occur.

Each shaft member 30, 31 terminates in a yoke 22. The ends of each yoke 22 are pivotally connected to the elastomeric member 20 by supports 32. As shown in FIG. 3, a bearing 26 is interposed between the yoke end and the support 32. Not all applications of the steering lower shaft assembly coupling 10 require a bearing 26 in the pivotal connection.

Each yoke 22 rotates about an axis of pivot 42. Each axis of pivot 42 is at a 90 degree angle to the axis of rotation 40. Each axis of pivot 42 lies in a plane. The two planes for the axes of pivots 42 shown in FIGS. 2 and 3 are parallel to each other.

The steering lower shaft assembly coupling 10 is a mechanism for the transfer of steering shaft torsional

movement through an angle with vibrational damping in the axial and torsional directions of the connecting shaft members. The steering lower shaft assembly coupling 10 is different than a classical universal joint mainly because of the torsional stiffness of the elastomeric member 20 which replaces the rigid cross component. Without the pivotal connections, the elastomeric member 20 would undergo large deformations when under torque, thereby changing the 90 degree relative angle between the two yokes and therefor changing the distribution of the load components.

For applications with smaller allowed angular mismatches and with longer connecting shafts, the steering lower shaft assembly coupling 10 described above is suitable. For applications where the misalignment angle is higher and the shaft members are short, the rotational center of the steering lower shaft assembly coupling 10 can shift causing an unacceptable increase in run-out. For these applications, the preferred embodiment, described below, is used.

A preferred embodiment of the steering lower shaft assembly coupling 10 is shown is FIGS. 4 and 5. In the preferred embodiment, two pair of pins 28 are connected to outer edge of the elastomeric member 20. Each pin 28 extends outward from the elastomeric member 20 at a 90 degree angle to the adjacent pins 28. Each pin is also at a 90 degree angle to the axis of rotation 40. Each shaft 30, 31 terminates in a yoke 22'. The ends of each yoke 22' are pivotally connected to pins 28. As shown in FIG. 4, a bearing 26 is interposed between the yoke end and the pin 28. Not all applications of the steering lower shaft assembly coupling 10 require a bearing 26 in the pivotal connection.

Each yoke 22' rotates about an axis of pivot 42'. Each axis of pivot 42' is at a 90 degree angle to the axis of rotation 40. The two axes of pivots 42' lie in the same plane.

When the two yokes 22' are pivotally connected to the elastomeric member 20 in the same plane, the center of rotation of the steering lower shaft assembly coupling 10 remains in the same point as the angular offset between the shaft members 30, 31 increases. This reduces run-out of the steering shaft.