Fastener device for arresting a vehicle steering wheel to a steering shaft

A fastener device for arresting a hub of a vehicle steering wheel to one end of a steering shaft includes a non-rotatable shaft/hub connection between the hub and the end of the steering shaft and an annular spring element which forms an interlocking fit between the hub and the steering shaft. The interlocking fit is effective in the direction of the longitudinal axis of the steering shaft. The steering shaft comprises a raised face, the face surface area of which facing away from the steering wheel continues into a smaller shaft diameter. The spring element comprises an inner diameter which is smaller with respect to the outer diameter of the raised face. The spring element is radially pliable over at least a part of its axial length and can be fitted over the steering shaft together with the hub and reaches behind the raised face.

TECHNICAL FIELD 
The invention relates to a fastener device for arresting a hub of a vehicle 
steering wheel to one end of a steering shaft. 
BACKGROUND OF THE INVENTION 
A fastener device known from DE 295 16 626 includes a non-rotatable 
shaft/hub connection between the hub and the end of the steering shaft and 
an annular spring element which forms an interlocking fit between the hub 
and the steering shaft in the direction of the longitudinal axis of the 
steering shaft. The spring element is configured as a union nut which is 
applied to the steering shaft rotatable but axially locked and can be 
screwed onto a male thread on the hub. By means of this fastener device 
accidental release of the connection between steering shaft and hub is 
prevented. 
BRIEF SUMMARY OF THE INVENTION 
The invention provides a fastener device by means of which arresting the 
vehicle steering wheel to a steering shaft can be achieved even quicker 
and simpler than by means known hitherto without the risk of the 
connection releasing. In addition, any axial or circumferential play 
between the steering wheel and the steering shaft is eliminated. As a 
result of the fastener device in accordance with the invention 
particularly vehicle steering wheels can be installed very simply in which 
a gas bag restraint system is already fitted. The fastener device 
according to the invention for arresting a hub of a vehicle steering wheel 
to one end of a steering shaft includes a non-rotatable shaft/hub 
connection between the hub and the end of the steering shaft, and an 
annular spring element which forms an interlocking fit between the hub and 
the steering shaft. The interlocking fit is effective in the direction of 
the longitudinal axis of the steering shaft. The steering shaft comprises 
a raised face, the face surface area of which facing away from the 
steering wheel continues into a smaller shaft diameter. The spring element 
comprises an inner diameter which is smaller with respect to the outer 
diameter of the raised face. Furthermore, the spring element is radially 
pliable over at least a part of its axial length and can be fitted over 
the steering shaft together with the hub and reaches behind the raised 
face. 
The fastener device in accordance with the invention is configured as a 
snap-action connection. The actual procedure in fitting the steering shaft 
thus consists substantially merely in sticking the steering wheel hub onto 
the steering shaft. 
One face surface area of the raised face which faces away from the steering 
wheel is configured preferably as a tapered surface area, stated in the 
following as a rearside tapered surface area. The spring element having a 
corresponding tapered surface area engages on this rearside tapered 
surface area, is radially pretensioned and thereby produces an axial 
force. To prevent any axial play the shaft comprises additionally a 
tapered surface area at the front end facing the steering wheel and the 
hub features a tapered mount against the inner surface area of which the 
front-side tapered surface area is biased. At the rearside tapered surface 
area the spring element produces the axial force which is necessary to 
bias the inner surface area against the front-side tapered surface area 
and to lock the hub to the steering shaft axially, radially and 
circumferentially. 
In accordance with a first embodiment the spring element is configured as a 
slotted ring which is received in a circumferential groove on the inner 
side of the hub as a result of which the axial force produced by the 
spring element is introduced into the hub. 
A second embodiment provides for the spring element not being configured as 
a separate part, it instead being integrally connected to the hub by one 
receiving end of the hub, with which the hub is mounted on the steering 
shaft, being configured as the spring element. The hub comprises at the 
receiving end at least one radial full-length slot for producing the 
radial pliancy. 
In addition it is, however, of advantage when a locking element is provided 
at an end facing away from the outer shell surface area of the hub in the 
region of the steering wheel, this being configured so that it produces a 
force oriented radially inwards and prevents the steering wheel from being 
pulled from the steering shaft by force. 
The locking element may be configured as a rotary ring having an inner 
surface which is non-circular-cylindrical. The spring element also 
comprises a non-circular-cylindrical outer shell surface area which is 
configured so that by rotating the locking element the force oriented 
radially inwards can be produced. 
Furthermore, the locking element may also be configured as a clamp or as an 
axially shiftable ring.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
In FIG. 1 a first embodiment of a fastener device 10 for arresting a hub 12 
of a vehicle steering wheel (not shown fully) to one end of a steering 
shaft 14 is shown. The steering shaft 14 features in the region of its end 
a raised face defined by a rearside tapered surface area 16 facing away 
from the steering wheel, and a front-side tapered surface area 18 facing 
the steering wheel. The angle of taper of the rearside tapered surface 
area 16 is in this arrangement significantly greater than that of the 
front-side tapered surface area 18. Adjoining the front-side tapered 
surface area 18 directly is a splined shaft profile 20 which engages in a 
corresponding splined hub profile 22 in the hub 12 so that the hub 12 is 
connected to the steering shaft 14 non-rotatably. In the region of the 
front-side tapered surface area 18 the hub 12 features a corresponding 
tapered mount having an inner surface area 24 which engages the tapered 
surface area 18. In the region of the largest diameter of the raised face, 
on the inner side of the hub 12, a circumferential groove 26 is provided 
in which a spring element 28 is received as a slotted ring. The spring 
element 28 has a triangular cross-sectional shape with an inclined tapered 
surface area 29 parallel to the tapered surface area 18. The inner 
diameter of the spring element 28 is smaller than the outer diameter of 
the raised face on the steering shaft 14. A collar 30 of the hub 12 
adjoining the groove 26 features an inner diameter which is slightly 
smaller than the outer diameter of the raised face so that the hub 12 
together with the radially pliant spring element 28 can be sticked onto on 
the end of the steering shaft 14, the spring element 28 forming a 
snap-action connection reaching behind the raised face in the locked 
position as shown in FIG. 1. As is evident from the FIGS. 3a und 3b the 
tapered surface area 29 engages in a pretensioned manner the rearside 
tapered surface area 16 in the fitted condition of the steering wheel. 
Thereby, in the locked position, an axial force is produced due to the 
spring element 28 forcing the hub on to the steering shaft 14 in the 
direction of the arrow as shown in FIG. 3a. The inner surface area 24 
engages the front-side tapered surface area 18 so that the steering shaft 
14 is connected to the hub 12 not only by the splined shaft/splined hub 
connection but also by a taper seat. This taper seat in conjunction with 
the spring element 28, the axial forces of which are introduced into the 
hub 12 via the walls of the groove 26, also generates an axial seating of 
the hub 12 on the steering shaft 14 free from play. 
The force of the spring element 28 oriented radially inwards may be further 
increased by providing a locking screw 36. This locking screw 36 is 
screwed into a female thread in a tubular radial protrusion 38 of the hub 
12 and characterized by a conically hollowed face end. At the 
circumferential ends of the spring element 28 protrusions 40 protruding 
radially outwards are provided which together comprise a conical shape 
matching that of the hollowed face end of the locking screw 36. By 
screwing in the locking screw 36 the protrusions 40 are moved towards each 
other circumferentially as a result of which the inner diameter of the 
spring element 28 is reduced. On the side diametrally opposed to the 
protrusions 40 the spring element 28 is supported by a recess 42 at the 
groove 26. 
To secure the steering wheel to the steering shaft 14 the hub 12 merely 
needs to be sticked onto the end of the steering shaft 14. Then the 
locking screw 36 is screwed into place. 
In FIG. 4 the hub 12 is shown perspectively without the spring element 28. 
In the case of the further embodiments of the fastener device, the latter 
is configured as a snap-action connection for facilitated mounting. In the 
second embodiment of the fastener device depicted in FIG. 5, the steering 
shaft 14 is no different from the steering shaft 14 shown in FIGS. 1 to 3. 
The spring element 28 is not configured as a separate part, the receiving 
end of the hub 12, with which the hub 12 is sticked onto the steering 
shaft 14, being instead configured as the spring element by the inner 
surface area 24 adjoining a collar 48 protruding radially inwards. This 
collar features a tapered surface area 52 sitting close on the tapered 
surface area 16 in the fitted condition of the steering wheel. Several 
radially extending through slots 50 in the hub 12 endow the receiving end 
with a radial pliancy. The inner side of the hub 12 is, the same as in the 
case of of the embodiment depicted in FIGS. 1 to 3, provided with a 
splined hub profile 22 and the inner surface area 24 adjoining the latter. 
The steering wheel is mounted on the end of the steering shaft 14 by its 
hub 12 in the direction of the arrow, the collar 48 thereby sliding along 
the tapered surface area 18 as a result of which the hub 12 is flared 
radially until in conclusion the collar 48 has attained the rearside 
tapered surface area 16 in press-contact therewith. The radial force has, 
due to the tapered surface area 16, an axial force component by means of 
which the hub 12 is retained free from axial or circumferential play on 
the steering shaft. 
The embodiment depicted in FIG. 6 differs from that shown in FIG. 5 in that 
an additional locking element is provided which prevents the hub 12 from 
being pulled off of the shaft 14 by it exerting a force oriented radially 
inwards on the hub 12 in the region of the slotted receiving end. The 
locking element is configured as a rotary ring 53 comprising an inner 
surface area 54 which is not circular-cylindical but oval in 
cross-section. The receiving end of the hub 12 also features an outer 
shell surface area 56 which is likewise not circular-cylindrical but oval 
in cross-section. For fitting, the rotary ring 53 is slipped over the 
shell surface area 56 and the hub 12 sticked onto the steering shaft 14 
together with the rotary ring 53. Subsequently, by rotating the ring 53 on 
the receiving end of the hub 12 a force oriented radially inwards is 
generated so that the tapered surface area 52 in the region of of the 
collar 48 forming the spring element is biased even further against the 
rearside tapered surface area 16. 
Instead of the rotary ring 53 a clamp 62, e.g. in the form of a kind of 
hose clamp, as is shown in FIG. 7, may be made use of, which is slipped 
over on the slotted receiving end of the hub 12 and tightened following 
installation of the hub 12. 
In the fifth embodiment of the fastener device shown in FIG. 8 the locking 
element is configured as a ring 68 axially shiftable on the outer shell 
surface area of the hub 12. Between the ring 68 and a stop (not shown) on 
the rearside of the steering wheel a pretensioning element in the form of 
a spring 70 is mounted on the hub. The spring 70 shifts the ring 68 in the 
direction of the end of the hub 12. Since the outer shell surface area of 
the hub 12 is slightly conically flared towards the receiving end, the 
ring 68 is unable to slip off of the hub 12. For fitting the steering 
wheel the ring 68 is pushed against the force of the spring 70 slightly in 
the direction of the steering wheel, and then the hub 12 is sticked on the 
steering shaft 14, the hub 12 is flared slightly radially. After the hub 
12 has been mounted, the ring 68 can again be released so that it due to 
the spring 70 is shifted axially towards the receiving end until it clamps 
in place on the conical outer shell surface area. In this arrangement a 
force oriented radially inwards is exerted on the hub 12 which allows the 
hub 12 to be even more firmly seated on the steering shaft 14. Without the 
ring 68 being shifted the hub 12 can no longer be removed from the 
steering shaft 14. Due to the axial force exerted by the spring 70 on the 
ring 68 any unintentional release of the ring 68 on the outer shell 
surface area is eliminated.