Steering wheel with switch assembly

A steering mechanism for a steerable vehicle such as an automotive vehicle, wherein a switch support structure positioned internally of the rim portion of a steering wheel and having incorporated therein a switch assembly including various electric switch units to be manually actuated is retained in position independently of the steering wheel and held against rotation with respect to a steering column tube fixed with respect to the body structure of the vehicle and wherein an optical display unit associated with the switch units or some of the switch units is securely supported in position in front of the steering wheel. The switch units are connected to electrically operated vehicular instruments through wire harnesses including those which are passed through the switch support structure and those which are passed through a member secured to the steering column tube.

FIELD OF THE INVENTION 
The present invention relates to a steering mechanism for a steerable 
vehicle such as a wheeled land vehicle and, more particularly, to a 
vehicle steering mechanism arranged with an accessory switch assembly 
positioned inside the rim portion of the steering wheel of the mechanism. 
BACKGROUND OF THE INVENTION 
One of the recent trends in designing automotive vehicles is to equip an 
automotive vehicle with various extra instruments and accessories. Typical 
examples of these instruments and accessories are audio players and drive 
computers (which are the instruments to display the fuel consumption rates 
and the scheduled times of arrival at the destinations of travel). 
Provision of the additional instruments and accessories has enhanced the 
centralization of the switches and the related wiring arrangements on the 
instrument panel and has made the setups of the instrument panel extremely 
intricate. 
To avoid such problem, it has been proposed to have the switches arranged 
in a steering wheel pad assembly provided in conjunction with the steering 
wheel on which only a warning horn switch has conventionally been mounted. 
The installation of the steering wheel pad assembly in conjunction with 
the steering wheel however lays down a restriction on the placement of a 
display unit associated with the switches. If, for example, the display 
unit is incorporated into the instrument panel as has been customary, the 
switches associated with the display unit are located remote from the 
display unit and will bother a vehicle driver in manipulating the switches 
while viewing the display unit. If, on the other hand, the display unit is 
mounted on a column-tube covering shell enclosing the steering column 
tube, the display unit is located closer to the switches associated 
therewith but may be temporarily concealed behind the steering wheel pad 
assembly when the steering wheel is turned to steer the vehicle. 
The present invention contemplates overcoming these problems by having the 
steering wheel pad assembly supported independently of the steering wheel 
and held against rotation with respect to the steering column tube fixed 
to the body structure of a vehicle. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, there is provided a steering 
mechanism for a steerable vehicle including a body structure having a 
fore-and-aft direction, comprising a hollow steering column tube held 
stationary with respect to the vehicle body structure, a steering shaft 
axially extending in and through the steering column tube, the steering 
shaft having a center axis therethrough and being rotatable about the 
center axis of the steering shaft with respect to the column tube, a 
steering wheel rotatable with the steering shaft about the center axis of 
the steering shaft and having a circular rim portion having a center axis 
substantially aligned with the center axis of the steering shaft, a switch 
support structure positioned internally of the rim portion of the steering 
wheel, a switch assembly mounted within the switch support structure and 
including electric switch units to be manually actuated, a column-tube 
covering member held stationary with respect to the vehicle body structure 
and having at least a rear end portion of the steering column tube 
enclosed therein, retaining means retaining the switch support structure 
in position independently of the steering wheel and holding the switch 
support structure against rotation with respect to the steering column 
tube and the column-tube covering member, and an optical display unit 
securely supported by the column-tube covering member and positioned in 
front of the steering wheel. 
The steering shaft of the steering mechanism thus constructed and arranged 
generally may have a rear end portion axially projecting rearwardly from 
the steering column tube while the steering wheel may form part of a 
steering wheel structure which further comprises a hub member secured to 
the rear end portion of the steering shaft, the switch support structure 
being rotatable about an extension of the center axis of the steering 
shaft with respect to the hub member. 
In this instance, the above mentioned retaining means may comprise a first 
spool member fixed with respect to the steering column tube and formed 
with at least one circumferential groove about the center axis of the 
steering shaft, a second spool member having the switch support structure 
secured thereto and formed with at least one circumferential groove about 
the center axis of the steering shaft, the second spool member being 
rotatable on the hub member about the center axis of the steering shaft, 
and at least one flexible line which is wound partially in the 
circumferential groove in the first spool member and partially in the 
circumferential groove in the second spool member for providing retaining 
engagement between the first and second spool members through the line. 
The flexible line may form a loop and may be wound partially in a 
predetermined direction about the center axis of the steering shaft in the 
circumferential groove in the first spool member and partially in the 
circumferential groove in the second spool member in a direction identical 
with the above mentioned predetermined direction. 
Alternatively, the retaining means of the steering mechanism according to 
the present invention may comprise a first spool member fixed with respect 
to the steering column tube and formed with at least two circumferential 
grooves about the center axis of the steering shaft, a second spool member 
having the switch support structure secured thereto and formed with at 
least two circumferential grooves about the center axis of the steering 
shaft, the second spool member being rotatable on the hub member about the 
center axis of the steering shaft, and at least two flexible lines each 
anchored at one end thereof to the first spool member and at the other end 
thereof to the second spool member, one of the flexible lines being wound 
in one direction about the center axis of the steering shaft partially in 
one of the two circumferential grooves in the first spool member and 
partially in one of the two circumferential grooves in the second spool 
member, the other of the flexible lines being wound in the other direction 
about the center axis of the steering shaft partially in the other of the 
two circumferential grooves in the first spool member and partially in the 
other of the two circumferential grooves in the second spool member.

DESCRIPTION OF THE EMBODIMENTS 
Referring to the drawings, first particularly to FIGS. 1 and 2 thereof, a 
steering mechanism embodying the present invention is shown as largely 
comprising an elongated, hollow steering column tube 1 which is in part 
housed within a column-tube covering shell 2 constructed of, for example, 
a synthetic resin. The steering mechanism herein shown is assumed, by way 
of example, as forming part of a steering system of an automotive vehicle 
and, thus, the steering column tube 1 and the covering shell 2 are fixedly 
held in position with respect to the body structure (not shown) by 
suitable fastening means. The steering mechanism further comprises a 
steering wheel 3 positioned at the rear of the covering shell 2 and 
comprising a circular rim portion 3a and a pair of spoke portions 3b 
radially extending inwardly from the rim portion 3a. Centrally of the 
steering wheel 3 is positioned a steering pad assembly 4 including a 
number of switching push buttons 5 arranged at the rear end of the pad 
assembly 4 in such a manner as to provide easy access thereto from the 
driver's seat of the vehicle. In FIGS. 1 and 2, the steering mechanism is 
shown further comprising an instrument panel 6 having various instruments 
and indicators mounted thereon and fixed with respect to the vehicle body 
structure as is customary in the art. 
Turning to FIG. 3 of the drawings, the steering mechanism embodying the 
present invention further comprises an elongated steering shaft 7 axially 
extending in the steering column tube 1 and coaxially rotatable about its 
center axis with respect to the steering column tube 1 and accordingly to 
the body structure of the vehicle. As is well known in the art, the 
steering shaft 7 is connected at or adjacent its foremost end to a 
suitable steering gear mechanism which in turn is connected through a 
suitable steering linkage to the front road wheels of the vehicle, though 
not shown in the drawings. 
The steering shaft 7 has a rear axial extension having a rearwardly tapered 
axial portion 8 axially projecting outwardly from the rear end of the 
steering column tube 1, and a serrated axial portion 9 extending 
rearwardly from the tapered axial portion 8. The extension of the steering 
shaft 7 further has a threaded end portion 10 extending rearwardly from 
the serrated axial portion 9. 
The previously mentioned steering wheel 3 forms part of a steering wheel 
structure 11 which further comprises a hollow, generally drum-shaped 
central hub member 12 which is coaxial with the rim portion 3a of the 
steering wheel 3. The central hub member 12 has a cylindrical side wall to 
which the spoke portions 3b of the steering wheel 3 are securely connected 
by bolts one of which is shown at 13. The hub member 12 is formed with a 
rearwardly open concavity and has a front end wall portion having an inner 
or rear face defining the front end of the concavity. 
The hub member 12 has a cylindrical boss portion 14 axially projecting 
rearwardly from the above mentioned front wall of the hub member 12 into 
the concavity in the hub member 12. The boss portion 14 is coaxailly 
surrounded by the inner peripheral wall of the hub member 12 and is formed 
with an axial bore which is open at both ends thereof. The axial bore in 
the boss portion 14 is formed conformingly to the tapered and serrated 
axial portions 8 and 9. The steering wheel structure 11 as a whole is 
fitted to the steering shaft 7 with the tapered and serrated axial 
portions 8 and 9 of the shaft 7 passed through the axial bore in the boss 
portion 14 and with the threaded rear end portion 10 of the shaft 7 
projecting rearwardly from the boss portion 14 as shown. The steering 
wheel structure 11 is secured to the steering shaft 7 by means of a 
clamping nut 15 which is screwed on the threaded rear end portion 10 of 
the steering shaft 7 to the rear end face of the boss portion 14 through a 
washer 16. The axial bore in the boss portion 14 is aligned with the 
center axis of the steering shaft 7 so that the steering wheel structure 
11 as a whole is held in coaxial relationship to the steering shaft 7 and 
accordingly to the steering column tube 1. 
The central hub member 12 of the steering wheel structure 11 thus 
constructed and arranged has formed in its front end wall portion a first 
pair of axial holes 16a and 16b and a second pair of axial holes 17a and 
17b. Each of the holes axially extends substantially in parallel with the 
center axis of the hub member 12 and is open forwardly at the front end of 
the hub member 12 and rearwardly into the concavity in the hub member 12. 
The axial holes 16a and 16b of the first pair are disposed substantially 
in a diametrically opposite relationship to each other across the center 
axis of the hub member 12. The axial holes 17a and 17b of the second pair 
are also located substantially in a diametrically opposite relationship to 
each other across the center axis of the hub member 12 and further 
radially inwardly of the axial holes 16a and 16b of the first pair. 
The embodiment of the steering mechanism according to the present invention 
further comprises a hollow, generally cylindrical front spool member 18 
which is coaxially secured to the outer peripheral surface of a rear end 
portion of the steering column tube 1 by suitable fastening means (not 
shown). The front spool member 18 is formed with three annular projections 
or flange portion which consist of a rearmost or first flange portion 19a, 
an intermediate or second flange portion 19b and a foremost or third 
flange portion 19c. As will also be seen from FIG. 3, the first, second 
and third flange portions 19a, 19b and 19c are axially spaced apart from 
each other so that the spool member 18 has a rear or first circumferential 
groove 20a between the first and second annular flange portions 19a and 
19b and a front or second circumferential groove 20b between the second 
and third flange portions 19b and 19c. The front spool member 18 
configured as described above is constructed of a suitable electrically 
non-conductive material. 
The front spool member 18 has radially inner and outer or first and second 
annular contact elements 21a and 21b securely attached to the rear end 
face of the spool member 18. The first and second annular contact elements 
21a and 21b are radially spaced apart from each other and are 
substantially coaxial with respect to the spool member 18 as will be seen 
from FIG. 3. The annular contact elements 21a and 21b are located adjacent 
to and slightly spaced apart forwardly from the outer face of the front 
end wall portion of the central hub member 12 as will be seen from FIG. 3. 
The steering mechanism shown in FIG. 3 further comprises a cylindrical 
sleeve bearing 22 which is secured to the outer peripheral surface of the 
cylindrical boss portion 14 of the central hub member 12. The sleeve 
bearing 22 axially projects rearwardly from the rear end of the boss 
portion 14 and coaxially surrounds the nut 15 engaging the threaded rear 
end portion 10 of the steering column shaft 7. Furthermore, the sleeve 
bearing 22 has an annular projection or flange portion 23 located adjacent 
to the front axial end of the sleeve bearing 22, viz., to the inner face 
of the front end wall portion of the hub member 12. The flange portion 23 
is located a predetermined axial distance from the rear end of the sleeve 
bearing 22 for the reason which will be clarified later. The sleeve 
bearing 22 has a smooth outer peripheral surface axially extending between 
the flange portion 23 and the rear axial end of the bearing 22 and serving 
as a bearing surface. 
A hollow, generally cylindrical rear spool member 24 is coaxially received 
on this bearing surface of the sleeve bearing 22 and is axially and 
circumferentially slidable thereon. The rear spool member 24 is formed 
with three annular projections or flange portions which consist of a 
rearmost or first flange portion 25a, an intermediate or second flange 
portion 25b and a foremost or third flange portion 25c. The first, second 
and third flange portions 25a, 25b and 25c are axially spaced apart from 
each other so that the spool member 24 has a rear or first circumferential 
groove 26a between the first and second flange portions 25a and 25b and a 
front or second circumferential groove 26b between the second and third 
flange portions 25b and 25c. 
The rear spool member 24 thus configured is axially and circumferentially 
slidable on the previously mentioned bearing surface of the sleeve bearing 
22 and axially projects rearwardly beyond the rear end of the sleeve 
bearing 22. The axial movement of the spool member 24 toward the front end 
wall portion of the hub member 12 is limited by the flange portion 23 of 
the sleeve bearing 22. The spool member 24 is, furthermore, constructed of 
a suitable electrically non-conductive material. 
The rear spool member 24 has radially outer and inner or first and second 
annular contact elements 27a and 27b securely attached to the front end 
face of the spool member 24. The first and second contact elements 27a and 
27b are radially spaced apart from each other and are substantially 
coaxial with respect to the spool member 24. The annular contact elements 
27a and 27b are located adjacent to and slightly spaced apart rearwardly 
from the inner face of the front end wall portion of the central hub 
member 12 as will be seen from FIG. 3. 
The rear spool member 24 on the sleeve bearing 22 constitutes the first 
spool means in the steering mechanism according to the present invention. 
Likewise, the previously described front spool member 18 constitutes the 
second spool means in the steering mechanism according to the present 
invention. 
The first and second contact elements 21a and 21b on the front spool member 
18 are electrically connected to the first and second contact elements 27a 
and 27b, respectively, on the rear spool member 24 by slidable connector 
means. In FIG. 3, such connector means is shown comprising first and 
second conductive strip members 28a and 28b each constructed of an 
elastic, electrically conductive material. The first and second conductive 
strip members 28a and 28b are securely fitted to the front end wall 
portion of the central hub member 12 through the axial holes 17a and 17b, 
respectively, in the wall portion. The first and second conductive strip 
members 28a and 28b are elastically pressed each at one end against the 
first and second contact elements 21a and 21b, respectively, on the rear 
end face of the front spool member 18 and at the other ends thereof 
against the first and second contact elements 27a and 27b, respectively, 
on the front end face of the rear spool member 24. Thus, the first 
conductive strip member 28a provides sustained electrical connection 
between the first contact element 21a on the front spool member 18 and the 
first contact element 27a on the rear spool member 24. Likewise, the 
second conductive strip member 28 b provides sustained electrical 
connection between the second contact element 21b on the front spool 
member 18 and the second contact element 27b on the rear spool member 24. 
In the embodiment of the steering mechanism as shown in FIG. 3, the 
previously mentioned steering pad assembly 4 is shown comprising an 
accessory switch support structure 29 which is largely composed of an 
annular bracket member 30 and a generally drum-shaped finisher or casing 
member 31. The casing member 31 has a side wall portion secured along its 
front end to an outer end portion of the bracket member 30. The casing 
member 31 further has a rear end wall portion formed with a plurality of 
openings 32 and rearwardly spaced apart from the bracket member 30 so as 
to form an internal space therebetween. The bracket member 30 is securely 
attached along its inner circumferential end portion to the rear end face 
of the rear spool member 24 by suitable fastening means such as screws 33 
as shown. 
Within the open internal space thus formed in the accessory switch support 
structure 29 is positioned an electric switch assembly 34. The switch 
assembly 34 is supported by the annular bracket member 30 through a 
bracket member 35 secured to the bracket member 30 by screws 36 as shown. 
The previously mentioned switching push buttons 5 form part of the 
accessory switch assembly 34 and rearwardly project through the openings 
32 formed in the rear end wall portion of the casing member 31. 
The steering mechanism illustrated in FIG. 3 further comprises wire harness 
arrangements. Such arrangements comprise a first pair of electric wire 
harnesses 37a and 37b which extend, though not shown, from the electric 
circuits of suitable electrically operated vehicular instruments such as, 
for example, an electric warning horn, a motor-driven wind-shield wiper 
and a drive computer (not shown). The wire harnesses 37a and 37b are 
anchored and electrically connected at their leading ends to the first and 
second contact elements 21a and 21b, respectively, on the rear end face of 
the spool member 18. 
The wire harness arrangements further comprise a second pair of wire 
harnesses 38a and 38b anchored and electrically connected each at one end 
thereof to the first and second contact elements 27a and 27b, 
respectively, on the front end face of the rear spool member 24. The wire 
harness 38a is anchored at the other end thereof to conductive fittings 
39a securely attached to the rear end face of the rear spool member 24 by 
one of the previously mentioned screws 33, while the wire harness 38b is 
anchored at the other end thereof to conductive fittings 39b which are 
securely attached to the rear end face of the spool member 24 by another 
one of the screws 33, as shown. 
The wire harness arrangements of the steering mechanism illustrated in FIG. 
3 are complete with a third pair of wire harnesses 40a and 40b which are 
anchored each at one end thereof to the above mentioned fittings 39a and 
39b, respectively, by the screws 33. The third pair of wire harnesses 40a 
and 40b are thus electrically connected to the second pair of wire 
harnesses 38a and 38b, respectively, and extend into the previously 
described switch assembly 34. The wire harnesses 40a and 40b are 
electrically connected to the various switch units (not shown) forming 
part of the switch assembly 34 and associated with the push buttons 5. 
The steering mechanism shown in FIG. 3 further comprises a cord arrangement 
providing mechanical coupling between the front and rear spool members 18 
and 24 therethrough. Such cord arrangement comprises a pair of lengthy, 
flexible cords consisting of first and second cords 41a and 41b of, for 
example, a resilient synthetic resin such as Nylon. 
The cord arrangement further comprises elastic first and second guide tubes 
42a and 42b which are closely passed through the previously mentioned 
axial holes 16a and 16b, respectively, in the front end wall portion of 
the hub member 12. Each of the guide tubes 42a and 42b has a front end 
portion axially projecting forwardly from the hub member 12 and a rear end 
portion axially projecting rearwardly from the hub member 12. The front 
end portions of the first and second guide tubes 42a and 42b terminate in 
the neighborhood of the first and second circumferential grooves 20a and 
20b, respectively, of the front spool member 14. On the other hand, the 
rear end portions of the first and second guide tubes 42a and 42b 
terminate in the neighborhood of the first and second circumferential 
grooves 26a and 26b, respectively, of the rear spool member 24. The guide 
tubes 42a and 42b have flanges 43a and 43b, respectively, which are 
securely mounted or integrally formed thereon. The flanges 43a and 43b are 
retained to the inner or rear end face of the front end wall portion of 
the central hub member 12 by suitable retaining means (not shown). The 
guide tubes 42a and 42b are thus secured to the end wall portion of the 
hub member 12. 
The first and second cords 41a and 41b are slidably passed, each partially, 
through these first and second guide tubes 42a and 42b, respectively. The 
first cord 41a passed through the first guide tube 42a extends forwardly 
and rearwardly from the opposite ends of the tube 42a and has opposite end 
portions wound in the first circumferential grooves 20a and 26a, 
respectively, in the front and rear spool members 18 and 24. Likewise, the 
second cord 41b passed through the second guide tube 42b extends forwardly 
and rearwardly from the opposite ends of the tube 42b and has opposite end 
portions wound in the second circumferential grooves 20b and 26b, 
respectively, in the front and rear spool members 18 and 24. The 
directions in which the first cord 41a is wound in the circumferential 
grooves 20a and 26a in the front and rear spool members 18 and 24 about 
the respective center axes of the spool members are identical with each 
other. Similarly, the directions in which the second cord 41b is wound in 
the circumferential grooves 20b and 26b in the front and rear spool 
members 18 and 24 about the respective center axes of the spool members 
are identical with each other but opposite to the winding directions of 
the first cord 41a. In the arrangement shown in FIG. 3, it is assumed, by 
way of example, that the first cord 41a is wound in a counter-clockwise 
direction in the first circumferential groove 20a in the front spool 
member 18 and in a counter-clockwise direction in the first 
circumferential groove 26a in the rear spool member 24 when viewed from 
the rear sides of the spool member 18 and 24. On the other hand, the 
second cord 41b is assumed to be wound in a clockwise direction in the 
second circumferential groove 20b in the front spool member 18 and in a 
clockwise direction in the second circumferential groove 26b in the rear 
spool member 24 when viewed from the rear sides of the spool members 18 
and 24. 
The first cord 41a has one of its opposite extreme and portions retained to 
the front spool member 18 and the other of the extreme end portions 
retained to the rear spool member 24 by suitable retaining means (not 
shown). Likewise, the second cord 41b has one of its opposite extreme end 
portions retained to the front spool member 18 and the other of the 
extreme end portions retained to the rear spool member 24 by suitable 
retaining means (not shown). 
In the embodiment of the steering mechanism according to the present 
invention, the column-tube covering shell 2 is integral with a display 
support structure 44 which is positioned above the hub member 12 and which 
is formed with a horizontally elongated slot 45 at the rear end of the 
support structure 44. The display support structure 44 has an optical 
display unit 46 securely mounted therein by suitable fastening means such 
as screws 47 as shown and facing rearwardly through the slot 45 in the 
support structure 44. The optical display unit 46 may be constituted by, 
for example, a light-emissive-diode display device or a liquid-crystal 
display device and is electrically connected through wire harnesses 48 and 
48' to a suitable control circuit (not shown) which is arranged on the 
body structure of the vehicle. 
When, now, a driver's turning effort is applied to the steering wheel 3, 
the turning motion of the wheel 3 is transmitted from the central hub 
member 12 to the steering shaft 7. The steering wheel structure 11 and the 
steering shaft 7 are therefore rotated as a single unit about the center 
axis of the shaft 7 with respect to the steering column tube 1 which is 
held stationary with respect to the vehicle body structure. The turning 
motion of the steering shaft 7 is transmitted to the steering gear 
mechanism (not shown) and thereby operates the steering linkage to steer 
the front road wheels of the vehicle. 
If, in this instance, the steering wheel 3 is caused to turn clockwise as 
viewed from the rear side of the wheel 3, the first cord 41a leading from 
the guide tube 42a on the turning hub member 12 is partially unwound from 
the first circumtial groove 20a in the front spool member 18 and 
additionally wound in the first circumferential groove 26a in the rear 
spool member 24. At the same time, the second cord 41b leading from the 
guide tube 42b on the clockwise turning hub member 12 is partially unwound 
from the second circumferential groove 26b in the rear spool member 24 and 
additionally wound in the second circumferential groove 20b in the front 
spool member 18. As a consequence, the first cord 41a is partially 
transferred from the front spool member 18 to the rear spool member 24 
through the first guide tube 42a, while the second cord 41b is partially 
transferred from the rear spool member 24 to the front spool member 18 
through the second guide tube 42b. It therefore follows that the rear 
spool member 24 is urged to turn clockwise by the tension in the first 
cord 41a being additionally wound on the spool member 24 and 
counter-clockwise by the tension in the second cord 41b being partially 
unwound from the spool member 24. The first and second cords 41a and 41b 
being arranged to be taut with substantially equal tensions, the forces 
thus urging the rear spool member 24 to turn in the clockwise and 
counter-clockwise directions are cancelled by each other. The rear spool 
member 24 carrying the switch support structure 29 is for this reason 
caused to circumferentially slide on the previously mentioned bearing 
surface of the sleeve bearing 22 turning with the steering wheel structure 
11 and the steering shaft 7. The rear spool member 24, switch support 
structure 29 and switch assembly 34 are, as a consequence, maintained in 
their initial angular positions with respect to the steering column tube 1 
irrespective of the turning motions of the steering wheel structure 11 and 
the steering shaft 7. In a like manner, the rear spool member 24, switch 
support structure 29 and switch assembly 34 are held in situ when the 
steering wheel structure 11 is caused to turn counter-clockwise when 
viewed from the rear side of the steering wheel 3. 
When the first and second cords 41a and 41b are being transferred between 
the front and rear spool members 18 and 24 through the first and second 
guide tubes 42a and 42b, respectively, by the rotation of the steering 
wheel structure 11 with respect to the steering column tube 1, each of the 
guide tubes 42a and 42b is caused to elastically deflect toward the center 
axis of the steering shaft 7 by the tension in each of the cords 41a and 
41b. Such deflection of the guide tubes 42a and 42b produces axial 
components in the tensions of the cords 41a and 41b being wound on and 
unwound from the rear spool member 24 which is axially slidable on the 
bearing surface of the sleeve bearing 22. The axial components of the 
tensions in the cords 41a and 41b urge the rear spool member 24 toward the 
front end wall portion of the hub member 12. The rear spool member 24 can 
therefore be moved with certainty into the axial position closely engaging 
the flange portion 23 of the sleeve bearing 22 by such axial components if 
the spool member 24 might have been rearwardly displaced a certain 
distance from such an axial position before the wheel structure 11 is 
turned. The rear spool member 24 is in this manner elastically held in the 
axial position engaging the flange portion 23 of the sleeve bearing 22. 
During turning of the steering wheel structure 11 with respect to the 
steering column tube 1, the first and second conductive strip members 28a 
and 28b retained by the central hub member 12 of the steering wheel 
structure 11 are caused to turn together with the wheel structure 11 about 
the center axis of the steering shaft 7. Both of the front and rear spool 
members 18 and 24 being held at rest with respect to the steering column 
tube 1, the first conductive strip member 28a is caused to slide at the 
opposite ends thereof on the annular first contact elements 21a and 27a on 
the front and rear spool members 18 and 24, respectively. Likewise, the 
second conductive strip member 28b is caused to slide at the opposite ends 
thereof on the annular second contact elements 21b and 27b on the front 
and rear spool members 18 and 24, respectively. The electrical connection 
between the wire harnesses 37a and 40a and the electrical connection 
between the wire harnesses 37b and 40b are thus maintained through the 
first and second conductive strip members 28a and 28b, respectively, 
independently of the turning motion of the steering wheel structure 27. 
While two cords 41a and 41b are used in the embodiment shown in FIG. 3, 
only a single cord may be utilized in lieu of the two cords. FIG. 4 of the 
drawings shows part of an embodiment using such a single cord. 
In the arrangement shown in FIG. 4, there are provided front and rear spool 
members 18' and 24' as counterparts of the front and rear spool members 18 
and 24, respectively, of the embodiment illustrated in FIG. 3. The front 
spool member 18' is formed with two annular projections or flange portions 
which consist of a rear or first flange portion 19a and a front or second 
flange portion 19b axially spaced apart from the first flange portion 19a 
so as to form a circumferential groove 20 therebetween. Similarly, the 
rear spool member 24' is formed with two annular projections or flange 
portions which consist of rear and front or first and second flange 
portions 25a and 25b so as to form a circumferential groove 26 
therebetween. The front and rear spool members 18' and 24' thus configured 
are arranged similarly to their respective counterparts in the embodiment 
of FIG. 3 but in combination with a loop of a single flexible cord 41 of, 
for example, a resilient synthetic resin such as Nylon. The cord 41 is 
passed through elastic first and second guide tubes 42a and 42b 
respectively passed through the axial holes 16a and 16b in the central hub 
member 12 (FIG. 3) and having flanges 43a and 43b, respectively, securely 
mounted or integrally formed thereon similarly to their respective 
counterparts in the embodiment of FIG. 3. 
The single cord 41 is wound approximately a half turn in the 
circumferential groove 20 in the front spool member 18' in a certain 
direction about the center axis of the spool member 18' and further wound 
approximately a half turn in the circumferential groove 26 in the rear 
spool member 24' in a direction identical with the direction in which the 
cord 41 is wound on the front spool member 18'. Each of the elastic guide 
tubes 42a and 42b is thus caused to elastically deflect toward the center 
axis of the steering shaft 7 (FIG. 3) by the tension in the cord 41. The 
cord 41 is in this fashion held taut on each of the front and rear spool 
members 18' and 24' with the result that the rear spool member 24' 
slidably received on the outer peripheral surface of the sleeve bearing 22 
(FIG. 3) is urged to maintain a certain angular position with respect to 
the front spool member 18' about the center axis of the steering shaft 7. 
FIG. 5 shows still another embodiment of the steering mechanism according 
to the present invention. In the embodiment herein shown, the casing 
member 31 forming part of the switch support structure 29 has an upper 
frame portion 49 formed with a horizontally elongated window 50 which is 
substantially coextensive with and rearwardly spaced apart from the rear 
end face of the optical display unit 46, as will be better seen from FIG. 
6 of the drawings. The frame portion 49 thus provided at the rear end face 
of the display unit 46 is adapted to reduce the external light allowed to 
reach the rear end face of the display unit 46 so that a vehicle driver is 
permitted to clearly view the figures on the rear end face of the display 
unit 46 without being bothered by the light reflected from the rear end 
face of the display unit 46. The frame portion 49 being spaced apart from 
the rear end face of the display unit 46, furthermore, the spoke portions 
3b of the steering wheel 3 are freely movable therebetween and accordingly 
the steering wheel 3 is permitted to turn without being interfered by the 
frame portion 49.