Expanded – threaded – driven – headed – tool-deformed – or locked-thr – Externally threaded fastener element – e.g. – bolt – screw – etc. – Head having counter-sinking means
Reexamination Certificate
1999-10-29
2001-02-20
Wilson, Neill (Department: 3627)
Expanded, threaded, driven, headed, tool-deformed, or locked-thr
Externally threaded fastener element, e.g., bolt, screw, etc.
Head having counter-sinking means
C411S107000, C411S424000, C411S999000, C301S105100
Reexamination Certificate
active
06190102
ABSTRACT:
DESCRIPTION
1. Field of the Invention
The present invention refers to a stud for connecting a wheel and a brake element to the hub unit of a motor vehicle.
2. Background of the Invention
To fix the rim and the brake element (disc or drum) to the hub unit of a wheel, most of the known solutions provide that the rim, a flange of the brake member and a flange of the hub or hub/bearing unit are axially flanked so as to align bores formed in these elements. Studs are then driven in said bores from the axially inner side of the hub flange.
An example of this prior art is illustrated in axial cross section in FIG.
1
. Usually, four or five studs
10
are employed each having a head
11
and a stem
12
with a threaded end portion
13
and a length
14
having an axial knurling
15
of overall cylindrical shaped proximate to the head
11
.
The studs
10
are forcefully driven into circular axial bores
16
formed in the radial flange
17
of the hub
18
with radial interference of the cylindrical knurlings
15
with respect to the bores
16
. After this forced insertion, first the brake member and then the wheel rim (not shown) are inserted from the outside on the end portions of the stud stems. Finally, outer nuts (not shown) are screwed and tightened with a predetermined torque.
The knurlings
15
serve to rotationally lock the studs relative to the hub flange both when the aforesaid tightening torque is applied and when the nut is unscrewed for removing the wheel and/or the brake member.
Such locking effect can nevertheless fail due to the same forced driving step itself. In order that the knurling may engrave the material of the flange, the studs are previously hardened and tempered. However, the crests of a knurling are particularly difficult to harden in that, being sharp parts, they tend to decarburize. Therefore, in being forcefully driven as said, the crests of the knurling are abraded and the anti-rotation coupling loses its efficiency. This problem, besides being uncontrollable, appears when in attempting to tighten the nuts, the studs rotate, rendering this operation difficult.
It is of primary importance that the studs are precisely oriented parallel to the axis of rotation, as they must pass through the series of aligned bores of the brake member and the rim. If this is not the case, a difficulty is encountered in trying to mount the brake and/or the rim, that in some cases cannot be slipped on the studs.
The above cited forced coupling also involves a problem concerning the angular position of the studs. In fact, if the radial interference between the knurling
15
of the stud and the bore
16
of the hub flange is excessive, the position of the projecting part of the stud may vary considerably as the application of an excessively high driving force adversely affects the accuracy with which the stud remains positioned after its insertion. It is known that the driving inevitably involves an angular deviation which is uncontrollable and to some extend proportional to the force being applied.
A further problem concerning the driving lies in that, owing to the considerable radial interference required, lumps of material
20
removed from the bores
16
are inevitably formed on the axially outer face
19
of the hub flange. Formations of this kind are undesired as they constitute protrusions on the outer face
19
. Instead, this face should ideally provide a completely flat surface against which the brake member abuts.
Moreover, the above discussed conventional driving technique causes deformation of the hub flange outer surface in form of local swellings near the bores.
In addition, the high axial driving forces cause further deformation in form of radial undulations on the axially outer face of the hub or beating flange.
Owing to all of these factors, the outer surface
19
does no longer provide a flat resting surface perpendicular to the axis of rotation. As a result, anomalous vibration occurs in operation.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide improved studs capable of being coupled to the hub unit of motor vehicle wheel in such manner as to obviate the above discussed drawbacks.
This object is accomplished, in accordance with an aspect of the invention, by the provision of a stud for connecting a wheel and a brake element to a motor vehicle wheel hub, the stud comprising a head and a stem with a threaded end length and a length having an axial knurling proximate to the head and adapted to be driven with radial interference into an axial bore of a radial flange portion fast for rotation with the hub, wherein the stud comprises at least one knurled surface having an area other than zero in a projection on a plane perpendicular to the longitudinal axis of the stud, said at least one knurled surface being adapted to co-operate with said radial flange portion for preventing rotation of the stud relative to said flange portion.
In accordance with another aspect of the invention, there is provided a hub bearing unit for a motor vehicle wheel, the unit having a radial flange portion with a plurality of axial bores formed therein for accommodating with radial interference a plurality of studs for securing a brake member and a wheel rim to said flange portion, wherein said plurality of studs includes at least one stud as set forth herein above.
REFERENCES:
patent: 2056688 (1936-10-01), Peterka et al.
patent: 4396309 (1983-08-01), McCormick
patent: 5516248 (1996-05-01), DeHaitre
patent: 5802680 (1998-09-01), Postelwait
Maldera Carlo
Vignotto Angelo
Merchant & Gould P.C.
SKF Industrie S.P.A.
Wilson Neill
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