Automobile steering column interconnector

An interconnector electrically unites a rotatable air bag with a stationary air bag sensor. The interconnector has a hub rotatably associated with a housing to define a radial space including one or more complementary first and second electrically conductive rings. The rings are united with one or more connectors to complete the electrical pathway from the sensor to the air bag.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates generally to an automobile steering column 
interconnector. More specifically, the present invention relates to an 
automobile steering column interconnector that electrically unites a 
rotatable air bag assembly with a stationary sensor using one or more 
conductors that are simultaneously associated with the interconnector hub 
and housing. The conductors are preferably metallic rings that 
electrically unite a stationary interconnector housing with a rotatable 
interconnector hub. 
An increasing number of automobiles have air bag crash systems. The air bag 
crash system typically includes an air bag located on the steering wheel 
facing the driver. The air bag must be in continuous electrical connection 
with one or more sensors in the car body. The sensors provide an 
electrical signal to the air bag crash assembly which instantly inflates 
the air bag in the event of a crash. 
Accordingly, there is a need for an electrical connection between the 
rotatable portion of the air bag assembly which is mounted in the steering 
wheel and the sensors which are in a stationary position in the car body. 
Electrical connections between rotatable and stationary parts of a 
steering wheel are well known. Typically, a coiled electrical conductor, 
known as a clock spring, is united at one end to a stationary housing and 
at the other end to a rotatable hub. Rotation of the hub causes the coiled 
electrical conductor to tighten and to loosen much like a clock spring 
without jeopardizing the electrical connection. 
There is a risk with the coiled electrical conductor that it will fail due 
to over rotation of the steering wheel or through overuse. As a result, 
elaborate methods are used to ensure that the clock spring interconnectors 
do not over rotate and that the interconnectors are installed in their 
proper initial orientation. These measures are costly and add additional 
parts to the clock spring devices which can fail. 
2. Description of the Art 
Automobile steering column interconnectors referred to as "clock springs" 
are well known in the art. Examples of automobile clock springs are shown 
in U.S. Pat. Nos. 5,061,195 and 4,722,690. Automobile clock spring 
interconnectors electrically unite a stationary sensor in a car body with 
an automobile air bag located in a steering wheel via a spirally wound 
coil of electrically conductive tape. An electrical signal from the sensor 
passes to the clock spring through the electrically conductive tape to 
actuate the air bag in the steering column. 
Air bag interconnectors that do not use coiled conductive tape or wire 
windings to create an electrical pathway are also known in the art. For 
example, U.S. Pat. No. 5,009,604 describes an interconnector assembly that 
uses circular, resilient electrically conductive contact members to 
complete the electrical path between the interconnector housing and hub. 
Finally, U.S. Pat. Nos. 4,650,266 and 4,372,633 disclose an apparatus 
useful in satellites for transferring high electrical currents. The 
apparatus disclosed in each of the patents includes a plurality of 
horizontal rolling rings that act in unison to transfer an electrical 
current from a rotatable element to a stationary element. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide an automobile clock 
spring interconnector that unites a rotatable air bag with a stationary 
sensor without the use of a coiled conductive tape. 
It is another object of the present invention to provide an automobile 
clock spring interconnector that uses multiple contact points to unite a 
rotatable air bag assembly with a stationary sensor. 
It is yet another object of the present invention to provide an automobile 
clock spring interconnector that contains redundant contact points that 
electrically unite a stationary sensor to a rotatable air bag. 
In one embodiment, the present invention provides a steering column 
interconnector. The steering column interconnector comprises a housing and 
a hub rotatably associated with the housing to create an annular enclosure 
having a central aperture. A first connector is associated with the 
housing while a second connector is associated with the hub. The housing 
includes at least one housing annular recess associated with an inner face 
of the housing. The housing annular recess contains an electrically 
conductive ring associated with the first connector. The hub includes at 
least one hub annular recess located on the inner face of the hub. The hub 
annular recess is complementary to a housing annular recess. The hub inner 
recess includes an electrically conductive ring associated with the second 
connector. At least one contact ring electrically unites the first 
electrically conductive ring and the second electrically conductive ring. 
In another embodiment, the present invention provides a steering column 
interconnector comprising a housing and a hub rotatably associated with 
the housing to create a radial space. The interconnector includes an 
aperture passing through the hub and the housing, a first connector 
associated with the hub and a second connector associated with the 
housing. A plurality of hub annular recesses are associated with an inner 
face of the hub. Each hub annular recess includes a first electrically 
conductive ring. A plurality of housing annular recesses are associated 
with an inner face of the housing, and each housing annular recess 
includes a second electrically conductive metal ring. One or more circular 
spring contacts electrically unite complementary first electrically 
conductive rings with second electrically conductive rings. 
In yet another embodiment, the present invention provides an automobile air 
bag assembly comprising a motion sensor, an air bag assembly associated 
with a steering wheel, and an interconnector of the present invention for 
providing an electrical path between the sensor and the air bag assembly.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS 
The present invention relates to a steering column interconnector that 
unites a sensor located in an automobile with a steering column located in 
a steering wheel of the automobile. The interconnector of the present 
invention is capable of having a plurality of circuits, and, therefore, 
the interconnector can also unite one or more stationary electrical 
apparatuses with an electrical switch, lamp, indicator, or like element 
located on the steering wheel. 
A preferred embodiment of a steering column interconnector of this 
invention is shown in FIGS. 1-4. Referring to those figures, the steering 
column interconnector shown includes a hub 5 associated with a housing 10 
to create a radial space 11 surrounding an aperture 12. The aperture 12 
passes through the hub 5 and the housing 10. As in conventional clock 
spring interconnectors, the housing 10 is intended to remain stationary 
while the hub 5 is associated with the housing 10 so that it rotates in 
relation to the stationary housing 10. 
The hub 5 and the housing 10 are made from an electrically insulating 
material, such as a plastic. All other nonelectrically conductive elements 
of the interconnector of the present invention are also made of an 
electrically insulating material. A preferred electrically insulating 
material is bakelite, a hard thermoset type plastic. 
The hub 5 includes a first connector 14. The first connector 14 may include 
one or more terminals 15 for uniting the interconnector with electrical or 
electrically actuated devices located in the steering wheel. 
The automobile steering column interconnector of the present invention is 
capable of providing a plurality of electrical connections between 
stationary sites in the automobile and the rotating steering wheel. 
Therefore, the first connector 14 may include the plurality of terminals 
15 associated with, for example, a horn, cruise control, illumination 
devices on the steering wheel, radio controls, windshield wiper controls 
and/or lights. The number of terminals 15 associated with the first 
connector 14 will be limited only by the number of circuits that can be 
associated with the automobile steering column interconnector of the 
present invention. 
The automobile steering column interconnector of the present invention 
includes a second connector 16 associated with the housing 10. The second 
connector 16 includes one or more terminals 17 for uniting various 
electrical devices, ground circuits, and sources of electrical power 
located in the automobile steering wheel interconnector. As with the first 
connector 14, the second connector 16 may include the plurality of 
terminals 17 for uniting apparatuses, such as windshield wipers, cruise 
control, automobile horn and the like, with corresponding electrical and 
mechanical elements located in the automobile body. 
As shown in FIG. 2, the hub 5 includes an outer face 22 and an inner face 
24. The inner face 24 of the hub 5 includes one or more hub annular 
recesses 20. The housing 10 also includes an outer face 21 and an inner 
face 23. The inner face 22 of the housing 10 includes one or more housing 
annular recesses 18. Each useful housing annular recess 18 has a 
complementary hub annular recess 20. That is, a useful hub annular recess 
20 has a housing annular recess 18 located at the same distance from the 
axis of the interconnect and is perpendicularly connectable with a contact 
30. 
One or more of the hub annular recesses 20 must include a first 
electrically conductive ring 26. Likewise, one or more of the housing 
annular recesses 18 must include a second electrically conductive ring 28. 
At least one first electrically conductive ring 26 must be complementary 
to a second electrically conductive ring 28. Each first electrically 
conductive ring 26 is electrically united with the first connector 14 
while each second electrically conductive ring 28 is electrically united 
with the second connector 16. 
The first electrically conductive ring 26 and the second electrically 
conductive ring 28 are made of electrically conductive material. It is 
preferred that the electrically conductive rings 26, 28 are manufactured 
out of copper or a copper alloy. It is also preferred that the first 
electrically conductive ring 26 and the second electrically conductive 
ring 28 are flat. However, it is not necessary that the electrically 
conductive rings 26, 28 are flat, and they may be U-shaped, they may 
contain a plurality of bumps, or they may take on any texture or shape 
that is useful for maintaining a constant and reliable electrical path 
between the first electrically conductive ring 26 and a corresponding 
second electrically conductive ring 28. The electrically conductive rings 
26 and 28 may also be constructed to relieve the stresses placed upon the 
contact 30 when it is located between the first and the second 
electrically conductive rings 26 and 28. 
The first electrically conductive rings 26 and the second electrically 
rings 28 may generally be circular in shape and are sized to fit into the 
housing annular recess 18 and the hub annular recess 20, respectively. 
Alternatively, the housing annular recess 18 or the hub annular recess 20 
may be associated with the hub 5 and the housing 10 after the first 
electrically conductive rings 26 and the second electrically conductive 
rings 28 have been associated with the inner faces 23 and 24, 
respectively. 
One or more first electrically conductive rings and/or one or more second 
electrically conductive rings may not be totally electrically conductive. 
This can be accomplished by manufacturing a portion of the electrically 
conductive ring out of a non-electrically conductive material or, 
alternatively, coating a portion of the electrically conductive ring with 
a non-electrically conductive material. Such semi-electrically conductive 
rings are useful in situations which it is desired to have the rotation of 
the steering wheel intermittently activate or deactivate an electrical 
connection. 
When the interconnector includes a plurality of the first electrically 
conductive rings 26 and the second electrically conductive rings 28, then 
they are located in a radial pattern beginning at about the aperture 12 
radiating away from the aperture 12 towards an outer wall 25 of the 
steering column interconnector. In some instances, it will be desirable to 
electrically unite adjacent or nonadjacent first electrically conductive 
rings 26 or second electrically conductive rings 28. This can be 
accomplished by including an electrically conductive bridge 27 between two 
adjacent or non-adjacent electrically conductive rings 26 and 28. 
The electrical paths through the interconnector is completed in the present 
invention with one or more of the contacts 30. The contacts 30 may be any 
element or combinations of elements that are able to simultaneously rotate 
and conduct an electrical current or signal. A preferred contact circular 
spring 31 is shown in FIGS. 2, 5A and 5B. The preferred contact 30 is a 
single piece of electrically conductive material formed into a circular 
spring having a first end 32 and a second end 33 that overlap but that are 
not connected. The circular spring contact 31 shown in FIGS. 5A and 5B is 
slightly compressible allowing it to be located and slightly compressed 
between the first electrically conductive ring 26 and the hub annular 
recess 20 and the second electrically conductive ring 28 located in the 
housing annular recess 18. The compressibility of the circular spring 
contact 31 acts to relieve compression strain on the contact ring. 
The contact 30 may taken on other shapes and forms. For example, the 
contact 30 may be a continuous metallic ring. A continuous metallic ring 
has been successfully used in the interconnector of the present invention. 
However, some continuous metallic rings are prone to stress failure due to 
material composition of the ring and stress factors, such as dimensions of 
the ring and/or loads thereon or the like. A continuous metallic ring 
contact made out of a resilient, electrically conductive material is, 
therefore, preferred. However, the cost of the material used to construct 
the continuous metallic contact ring might make the use of such a 
continuous metallic contact ring prohibitive. 
Other examples of the contacts 30 useful in the present invention are shown 
in FIGS. 6A, 6B, 7 and 8. FIGS. 6A and 6B show a lateral spring contact 
34. The lateral spring contact 34 consists of a metal spring having two or 
more turns located between the housing annular recess 18 and the hub 
annular recess 20 so that its axis of rotation is parallel to the inner 
face 23 and the inner face 24. The lateral spring contact 34 is 
compressible and, therefore, provides the preferred strain relief 
properties of the contact 30. 
FIG. 7 is a ball/spring contact 35. The ball/spring contact 35 differs from 
the other contacts described because it is stationary. A spring 36 of the 
ball spring contact 35 shown contacts the first or the second electrically 
conductive ring 26 or 28. A ball 37 then contacts the opposite 
electrically conductive ring. The ball 37 is preferably located inside the 
spring 36. It is preferred that the spring 36 is tapered inwardly to 
provide a nest for the ball 37. Both the spring 36 and the ball 37 are 
made of an electrically conductive material. The spring 36 urges the ball 
37 towards the electrically conductive ring 26 or 28 and also provides the 
preferred strain relief properties. 
FIG. 8 shows a ball contact 38. The ball contact 38 is an electrically 
conductive ball that simultaneously contacts the first and the second 
electrical conducting rings 26 and 28. In this embodiment, as in other 
contact embodiments, strain relief can be incorporated into the electrical 
conductive rings 26 and 28 by making them V-shaped or spring shaped. 
FIG. 9 illustrates a coil spring ring 39. The coil spring ring 39 acts as 
an electrical conductor between the first and the second electrical 
conducting rings 26 and 28. To this end, a coil spring is formed into a 
circular ring as shown in FIG. 9. The ring 39 is compressed between the 
conductive rings 26 and 28 of the interconnector. 
The contacts described above are by no means the only contacts that are 
useful in the interconnector of the present invention. As described above, 
any contact that can provide a continuous electrical pathway between the 
first electrical conductive ring 26 and the second electrical conductive 
ring 28 can be used. 
One or more of the contacts 30 may be associated with each of the 
electrically conductive rings 26 and 28. The contact 30 is necessary only 
to complete a desired circuit. Therefore, there may be instances where the 
first electrically conductive ring 26 is not united with a complementary 
second electrically conductive ring 28 by the contact 30. This situation 
might occur, for example, where an automobile does not include a feature 
that is intended to be operated by the particular electrically conductive 
path. Therefore, the clock spring interconnector of the present invention 
is inherently versatile in that the ultimate number of circuits comprising 
the steering column interconnector is dictated by the number of 
electrically conductive rings that are united by the contact 30. 
As mentioned above, the contacts 30 are made of at least in part of 
electrically conductive material. It is preferred that the contacts 30 are 
made from copper or a copper alloy. It is also preferred that the contact 
30 have a spring-like nature making the contact 30 slightly compressible. 
This feature of the contact 30 becomes important when the hub 5 is united 
with the housing 10. Slightly compressing the contact 30 between the first 
electrically conductive ring 26 and the second electrically conductive 
ring 28 insures that the contacts 30 are always being urged toward the 
electrically conductive rings 26, 28 thereby facilitating continuous and 
effective electrical connection between the hub 5 and the housing 10. 
Furthermore, compressing the contacts 30 keeps them from slipping out of 
the housing annular recess 18 and the hub annular recess 20. 
One or more contact rings may be associated with each of the usable 
electrically conductive rings 26 and 28. It is preferred that at least two 
of the contacts 30 are associated with each of the electrically conductive 
rings 26 and 28. That way, if one contact 30 becomes oxidized or loses its 
electrical effectiveness, then a second contact 30 will be available to 
maintain the electrical path across the steering column interconnector. 
It should be understood that various changes and modifications to the 
presently preferred embodiments described herein will be apparent to those 
skilled in the art. Such changes and modifications may be made without 
departing from the spirit and scope of the present invention and without 
diminishing its attendant advantages. It is, therefore, intended that such 
changes and modifications be covered by the appended claims.