Horn activation and steering wheel assembly

An automotive vehicle horn activation and steering wheel assembly is providing including a column for transmitting a driving torque input into a steering system; a horn contact plate mounted on the steering column electrically isolated therefrom; a wheel fixably mounted on the column, the wheel having a rim connected by a spoke to a hub; a steering wheel mounting plate fixably connected with respect to the column and electrically connected therewith; a module mounted to the steering wheel mounting plate biased to a first position being electrically isolated from the steering wheel mounting plate, the module having a second position electrically contacting the steering wheel mounting plate; and an electrical lead captured between the horn contact plate and the module with a first end contacting the first contact plate and a second end contacting the module, the first end being biased away from the second end by a current conducting spring captured between the first and second ends, the spring being surrounded by a tubular member.

FIELD OF THE INVENTION 
The field of the present invention is that of automotive steering wheels 
and horn activation assemblies. More particularly, the field of the 
present invention is that of steering wheel and horn activation assemblies 
which also mount a supplemental inflation restraint (SIR), commonly 
referred to as an airbag. 
BACKGROUND OF THE INVENTION 
Steering wheel and horn actuation assemblies have become increasingly 
complex due to the installation of SIR systems. An example of such an 
assembly is found in Fosnaugh et al, U.S. Pat. No. 4,785,144, commonly 
assigned. 
SUMMARY OF THE INVENTION 
The present invention provides the horn activation and steering wheel 
assembly which is an alternative to that described above which eliminates 
a previously required relatively long contact wire that was hard to 
connect and package within the horn activation and steering wheel assembly 
.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIGS. 1, 2 and 3, the horn activation and steering wheel 
assembly 7 of the present invention has a steel shaft column 10. The 
column 10 transmits a torsional input from the driver of the vehicle to a 
steering system (not shown). The column 10 is also electrically connected 
to the ground of the electrical system of the vehicle. Mounted on the 
column 10 is a horn contact plate 12. The horn contact plate has an 
electrically conducting portion 14 typically fabricated from brass or 
other highly conductive material. The conducting portion 14 is generally 
shaped as a flat annular ring and is electrically isolated from the column 
10 by an inner mounting polymeric piece 16. Removed from the drawing for 
clarity of illustration, a coil spring captured between a shoulder (not 
shown) on the column 10 and an internal flange portion (not shown) in a 
bore 18 of the inner mounting member urges the horn contact plate 14 
toward a threaded end 20 of the column 10. 
Fitted over a splined portion 22 of the column is a hub 24 of a steering 
wheel 26. The hub 24 has weldably connected thereto four spokes 28 which 
connect with an outer rim 30 of the steering wheel. A nut 32 is threadably 
engaged onto the column 10 to retain the hub 24 axially upon the column 
10. 
Also fixably connected to the column 10 by the nut 32 is a steering wheel 
mounting plate 34. The steering wheel mounting plate 34 has two holes 36 
allowing it to be fixably connected to the hub 24 by virtue of cap screws 
(not shown). Additionally, the steering wheel mounting plate 34 has a 
larger hole 38 for purposes to be described later and four outer mounting 
holes 40 along its outer perimeter. Lastly, the steering wheel mounting 
plate 34 has a central hole 42 allowing for penetration of the threaded 
end 20 of the column. 
The steering wheel mounting plate 34 is electrically connected with the 
column 10. 
Mounted to the steering wheel mounting plate is a module 42. The module 42 
includes a module pad retainer 44 which is connected by rivets 46 with a 
module base plate 48. Fixably connected to the module base plate 48 are 
four projecting pins 50 having surrounding annular bells 52. Each pin 50 
has a ball lock 54. The module base plate 48 also mounts an SIR inflater 
54, a fabric air bag 56 and a cover 58. 
The module 42 is biased to a first position from the steering wheel 
mounting plate 34 by springs 60 which push up against the top portion of 
the bells 52. The springs 60 bottom end (as shown in FIG. 2) presses 
against the steering wheel mounting plate 34. A top portion 62 of the pin 
50 is surrounded by an elastomeric or polymeric grommet 64. Thus, pin 50 
and steering wheel mounting plate 34 are electrically isolated from the 
module base plate 34. The module pad retainer 44 has a central opening 66 
which allows for penetration of the threaded end 20 of the column. 
To electrically connect the module pad retainer 44 with the conducting 
portion 14 of the horn contact plate, there is provided a wireless 
electric lead 68. The wireless electric lead has a first contact 70 which 
electrically connects with the conducting portion 14 of the horn contact 
plate and a second lead 72 which makes continual contact with the module 
pad retainer 44. The ends 72 and 70 are spring biased away from one 
another by a conducting coil spring 74 fabricated from a tin-coated 
musical spring steel. The coil spring will typically have a spring rate of 
approximately two pounds per inch, having 14 coils per inch with a 
diameter of 0.5 min. Each lead has a spring mounting stud 76 and stud 
members 78 which are captured in longitudinal slots 80 provided in a 
polymeric tubular insulator 82 which surrounds the spring 74. The 
insulator 82 at its opposing end has a slot 84 provided for installing the 
ends 70 and 72. 
Electrical lead 68 is positioned through a slot provided in the hub 24 and 
penetrates through the inner hole of an SIR exciter coil 86. To align the 
lead 68, there is provided a tower member 87. As shown, tower member 87 is 
one piece. However, it may be desired to comprise several different 
pieces. If desired, the tower 87 may be made to be integral with the 
insulating portion 16 of the horn contact plate 12. Not shown for clarity 
of illustration is a steering lock and an associated insulator which 
typically will abut an end of the horn contact plate toward the column end 
20 (with the exception of that portion of the horn contact plate which is 
contacted by the lead 68). 
Referring to FIG. 1, a void 88 is provided to allow a wire (not shown) from 
the coil 86 to be connected to the inflater 54. 
To actuate the horn, the module 42 will be pushed downward against the 
biasing of spring 60 to cause the bell housing 52 to contact the steering 
wheel module plate at least at one of its four locations. The above action 
causes the module 42 to come into its second position wherein it is 
electrically connected to the steering wheel mounting plate 34. 
Current then flows from a source of electric energy 96 to a horn 98 located 
remotely through a lead wire 99 shown schematically to the conducting 
portion 14 of the horn contact plate to the first lead 70. Current then 
flows through the conducting wire 74 to the second lead 72 to the module 
pad retainer 4, through rivet 46 to module base plate 48 to bell housing 
52 to steering wheel mounting plate 34, to the nut 32, column 10 and then 
to ground, completing the current and thereby activating the horn. 
The electric lead 68 eliminates a previous lead wire which connected the 
horn contact plate conducting portion 14 to the module pad retainer 66. 
This wire had to be sufficiently long enough to allow it to be attached to 
the module pad retainer 44 before assembly of the module 42 to the 
steering wheel mounting plate 34. The length of the wire had to be 
sufficiently long to be easy to assemble. However, a sufficient length was 
found to be inconvenient due to the proper placement of the lead wire 
after the module 42 was assembled to the steering wheel mounting plate 34. 
If not done correctly, such a wire could cause rattling vibrational noise 
which could be an irritant to an occupant of the vehicle. Also, the prior 
wire could short or get cut on a sharp edge of the steering wheel 
assembly. 
To assemble module 42 to the steering wheel mounting plate, the pins 50 are 
aligned with the holes 40 in the mounting plate and simply pushed 
inwardly, allowing the ball locks 52 to then pop back out, retaining the 
module plate to the steering wheel mounting plate 34. 
While this invention has been described in terms of a preferred embodiment 
thereof, it will be appreciated that other forms could readily be adapted 
by one skilled in the art. Accordingly, the scope of this invention is to 
be considered limited only by the following claims.