Abstract:
A telescopically adjustable steering column includes a locking wedge positioned by a collar which applies locking force to a steering shaft having an externally splined lower portion mated with an internally splined tube connected to a steering pump.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to adjustable steering mechanisms and more specifically to axially extensible steering column assemblies having a locking mechanism for fixing the axial position of the steering wheel. 
     2. Description of the Prior Art 
     Telescoping steering column assemblies are known and have become common accessories in several types of vehicles as they provide some desirable advantages. Extensibly adjustable steering columns are most frequently seen in automobiles, however, an increasing number of industrial or farm vehicles such as trucks, tractors, and fork trucks are being offered with adjustable columns. Among the advantages inherent in an adjustable column is the convenience of having the steering wheel located in position to satisfy the personal preferences of various operators. The usual and well known telescopic steering wheel is composed of a tube slidably carried inside a second tube. The first tube is connected to the steering wheel and the second tube is connected to a steering gear apparatus that translates the rotary motion of the first tube into motion to steer a vehicle. Both tubes are incorporated together by any of a multitude of complicated devices which usually use levers, wedges, pins, or expandable legs to act as a locking means. Even steering wheel adjustment apparatus that only telescope extensibly are usually complex and consequently expensive to manufacture. 
     Tiltable steering wheels often include a telescopic adjustment, however, these combinations are even more complicated and expensive to manufacture than the telescopically adjustable devices. 
     SUMMARY OF THE INVENTION 
     According to the present invention an improved axially extensible steering column is provided. More specifically, a steering column of the present invention has an improved system of holding the steering wheel in a desired position through the use of a simple locking collar and a circular split wedge. 
     Another feature of the invention resides in the use of an externally splined steering shaft and an internally splined steering shaft housing tube to minimize the occurrence of any inaccuracy in the steering mechanism. These splines of the steering shaft engage the splines of the tube in close fitting relationship thereby eliminating unwanted lash between the steering wheel and the steering box. 
     Another advantage of the proposed invention is that adjustment is easy, safe, and smooth with either hand even when the vehicle is moving, as the locking collar, which has externally cast protrusions for affording a good gripping surface, need only be rotated a portion of a turn to lock or unlock the mechanism. 
     Still another feature of the invention is that there is little possibility of the steering wheel being lifted out of the steering column housing. 
     Further features of the invention are that the assembly has few operating parts, is rust proof has no external linkages to get out of adjustment, and is easy to assemble and service. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The preceding and other features and advantages of the invention will be apparent from the following specification and from the appended drawings wherein: 
     FIG. 1 is a cross sectional view of a portion of an adjustable steering column assembly; 
     FIG. 2 is a partially fragmented and sectioned portion of the upper part of the adjustable steering shaft assembly; 
     FIG. 3 is a sectional view of the adjustable steering column assembly taken along line 3--3 of FIG. 2 after the broken out sections have been reconstructed into place; 
     FIG. 4 is a sectional view taken generally along the plane designated as 4--4 of FIG. 2; 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The cooperative arrangement of the adjustable steering column means can be seen in FIG. 1 wherein the adjustable steering column assembly is generally indicated by 10 and more specifically is composed of a steering shaft 12, having an externally splined lower portion 14, a smooth surfaced upper portion 16, slidably and telescopically carried in a tube 18 which is internally splined as shown by 20. These splines are dimensionally compatible with the splines at the lower portion of the steering shaft. A steering wheel means (not shown) would generally be affixed to the upper termination point (also not shown) of the steering shaft 12. The smooth surfaced upper portion 16 is of a smaller circumference than the splined lower portion 14 of the steering shaft 12 as shown by margin 22. 
     The tube 18 has an aperture 24 at its lowest portion 26 for receiving a coupling pin 28 which fixes a steering box means shaft 30 having an apertured upper end 32 for receiving the coupling pin 28. The steering box means 34 is not limited to any specific type or apparatus and could be hydraulic, hydrostatic, pneumatic, or mechanical such as a recirculating ball or a rack and pinion, or any other type of transfer mechanism that would convert steering shaft rotational input into vehicle steering motion. 
     Thus, it is apparent that rotational movement of the steering shaft 12 will be transferred to a tube 18 by the means provided by the externally splined lower portion 14 of the steering shaft 12 and its cooperative interaction with the internally splined tube 18. Furthermore, axial rotation of the steering shaft 12 and the tube 18 will communicate axial rotation to the steering box means 34 as the steering box means shaft 30 is coupled to the lower portion 26 of the tube 18 with the coupling pin 28 passing through the tube aperture 24 and the apertured upper end 32 of the steering box means shaft 30. 
     It is also apparent from FIG. 1 that the steering shaft 12 can be telescopically adjusted through tube 18 without severing engagement or loosing rotational transferability between the steering shaft 12, the tube 18, and the steering box means shaft 30. 
     FIG. 4 clearly shows the splined configuration and the relationship of the steering shaft 12 and the tube 18. 
     Returning to FIG. 1 the method of locking or clamping the steering shaft 12 in a desired telescoped position will be apparent when the components of the locking assembly, generally indicated by 40, are cooperatively associated with the steering shaft 12 and the tube 18. The view of FIG. 2 will also be helpful in representing the locking assembly. 
     The tube 18 has a counterbored recess 36 formed in its upper end 38 which provides a positioning means for a steering shaft washer 42 which has an inside circumference nominally the same as the circumference of the smooth surfaced upper portion 16 of the steering shaft 12 which is, as pointed out earlier, smaller than the circumference of the externally splined lower portion 14 of the steering shaft 12. 
     Positioned on the upper surface 44 of the steering shaft washer 42 is a split circular wedge ring 46 having the inside surface 48 parallel to the smooth surfaced upper portion 16 of the steering shaft 12. The outside surface 50 of the wedge ring 46 defines an inclined plane 52 with the base portion 54 thicker than the top portion 56 when measured in relationship to the inner surface 48. A split 58 (FIG. 3) is formed in the wedge ring 56 and generally runs from the base portion 54 through the top portion 56. The split 58 can be readily seen in FIG. 3. Three partial slits, one shown as 84 of FIG. 3, are formed in the top portion of the ring. These slits do not sever the ring as does split 58. 
     In a preferred embodiment the wedge ring 46 would be of a resilient plastic elastically deformable material such as &#34;Delrin&#34; or &#34;Celcon&#34;, however, it could alternatively be made of other material such as a metal. 
     Although the split wedge ring is disclosed in this preferred embodiment, the invention would work functionally as well if a set of wedges were in place of the split wedge ring. The wedges would present slightly more complex production and assembly difficulties, however. These wedges would have the same cross sectional shape at the split wedge ring. 
     A steering shaft collar 60 having an inclined landing surface 62 formed therein is threadably attached to the upper end 38 of the tube 18 by means of external threads 64 on a tube 18 and internal threads 66 of the same size and pitch, on the steering shaft collar. The steering shaft collar may be tightened into position by means of the threads 64 and 66 forcing the split circular wedge ring 46 to be compressed against the smooth surfaced upper portion 14 of the steering shaft 12 by means of the inclined landing surface 62 riding up against the outside surface 50 of the wedge ring 46 and thereby wedging the wedge ring 46 into the cavity provided between the steering shaft 12 and the inclined landing surface 62. The split circular wedge ring 46 will thus tightly grip the steering shaft 12 preventing the steering shaft 12 from being telescopically movable in the tube 18. 
     To release and reposition the steering shaft the steering shaft collar 60 is rotated counterclockwise to release wedging pressure between the inclined landing surface 62 of the steering shaft collar 60, the split circular wedge ring 46, and hence the steering shaft 12. A gentle upward or downward tug on the steering wheel (not shown) will force the wedge ring 46 outward, freeing the steering shaft 12 and permit telescopic movement of the steering shaft 12 in the tube 18. 
     A decalcomania (not shown) may be positioned on the steering shaft collar to indicate direction of rotation to lock or unlock the adjustment apparatus. Alternatively, instructions indicating adjustment procedures could be formed in relief on the surface of the steering shaft collar. 
     There is little possibility of the steering wheel (not shown) which is attached to the steering shaft being pulled all the way out of the steering column housing or the tube. The splines of the steering column will contact the washer 42, which has a smaller internal diameter than the maximum diameter of the splined portion of the steering shaft 12, thereby limiting the travel of the steering shaft. 
     The threads 64 of the steering shaft collar 60 are of sufficient length to inhibit the accidental disengagement of the steering shaft collar from the tube 18. The steering shaft collar can, however, be removed for service, transportation, or other needs. 
     The steering shaft collar 60 is equipped with a groove 68 that provides a retaining device for an O-ring 70 positioned to ride on the smooth surfaced upper portion 14 of the steering shaft 12. In order to provide a steering shaft collar 60 that is easy to grasp the collar 60 has externally cast protrusions 72 to facilitate turning it. 
     The fluted surface of the steering shaft collar does not project all the way to the lower portion thereof. This is to discourage the operator from placing his adjusting hand close to the bottom of the steering shaft collar where it may be exposed to possible pinching between the collar and the housing cover plate 86. 
     The adjustable steering column assembly, referring to FIG. 1, is carried in the housing 74 that has a bushing 76 positioned in its upper portion 78. The bushing 76 is held in place by the housing 74 and the housing cover plate 86. The bushing 76 supports the upper end 38 of the tube 18 in the housing 74. The tube 18 is equipped with the recessed bearing surface 80 around its circumference which is provided to contain the bushing 76. 
     In order to reduce the transmission of direct vibration between the steering box means shaft 30 and the steering shaft 12 when the steering column is in the unextended position, an elastic buffer or resilient cap 82 is positioned on the apertured upper end 32 of the steering box means shaft 30. Several positions on the steering shaft 12 in the tube 18 are shown in the dotted line views A and B of FIG. 1 where position A would show the deepest penetration of the steering shaft 12 and position B would show the steering shaft 12 in its upmost extended position (i.e. the externally splined lower portion 14 of the steering shaft 12 contacts the steering shaft washer 42). 
     Thus, it is apparent that there has been provided in accordance with the invention an adjustable steering column that fully satisfies the objects, aims and advantages set forth above. Although the invention has been described in conjunction with a specific embodiment thereof it is evident that modifications and variations will be apparent to those skilled in the art in light of the foregoing description. For example, the spines on the steering shaft could be replaced with Woodruff keys. Accordingly, it is intended to embrace all such alternatives and modifications as fall within the spirit and broad scope of the appended claims.