Land vehicles: wheels and axles – Wheel – Tension wheel; e.g. – spoke
Reexamination Certificate
2002-12-23
2004-04-06
Stormer, Russell D. (Department: 3617)
Land vehicles: wheels and axles
Wheel
Tension wheel; e.g., spoke
C301S095107
Reexamination Certificate
active
06715844
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to bicycle type wheels and especially to such wheels including tensioned spokes connecting a rim to a hub. More specifically, the invention relates to front and rear, radially and tangentially laced, tensioned spoke wheels comprising a hub, a rim and a plurality of spokes connecting the rim to the hub, and a mechanism for attaching the spokes at the rim to reduce spoke stresses and breakage and/or rim stresses.
2. Description of the Prior Art
Spoked wheels, especially for bicycles, are laced generally in one of two spoking patterns. Radially spoked wheels, with spokes extending generally radially outwardly from hub flanges, are used as front wheels for bicycles. Tangentially spoked wheels, with spokes extending tangentially or nearly so, relative to the hub flanges, are used as rear bicycle wheels. In both cases, the longitudinal axis of a spoke deviates from a radial orientation relative to the intersection of the center plane of the wheel and the rotational axis of the wheel. This is illustrated in
FIGS. 5 and 6
, which are based upon
FIGS. 2 and 1
, respectively, of U.S. Pat. No. 4,583,787 (“Michelotti”), the disclosure of which is incorporated herein by reference.
FIG. 5
illustrates what we will call the centering angle of a spoke, in the context of a rim
10
which has a radius R. In the drawing, the radius R coincides with the center plane of a wheel including the rim
10
, the center plane being perpendicular to the axis of rotation of the wheel and intersecting the center line of the rim. The longitudinal axis, designated SA, of a spoke (not shown) attached to a left hub flange (not shown) deviates from the rim radius R by an angle designated CA for centering angle. In the drawing, the spoke axis SA intersects the rim radius R outside of the rim
10
. Because of this deviation, a spoke connected to the rim
10
and a left hub flange (not shown) exerts a lateral force which is balanced, more or less, depending on the spoking pattern, by an opposite lateral force exerted by a spoke (not shown) connected to the rim
10
and a right hub flange (not shown). These lateral forces keep the rim centered in the wheel center plane and provide essential lateral stability to radially spoked wheels and to tangentially spoked wheels. Thus, the name centering angle.
FIG. 6
illustrates what we will call the torsional angle of a spoke, in the context of a rim
12
which has a radius R. In the drawing, the radius R coincides with the center plane of a wheel including the rim
12
, the center plane being perpendicular to the axis of rotation of the wheel and intersecting the center line of the rim
12
. The longitudinal axis, designated SA, of a spoke
14
attached to a right or left hub flange (not shown) deviates from the rim radius R by an angle designated TA for torsional angle. Because of this deviation, which is found in tangentially spoked wheels, primarily used as rear driving wheels, the spoke is operable to transmit a pulling or torsional force from a rotating hub to the rim
12
, tending to cause the rim to rotate. Thus, the name torsional angle. Generally speaking, there is no torsional angle in wheels which are radially spoked.
If it were not for the torsional and centering angles of spokes, securing them to a rim would be a fairly simple matter. It is, however, a complicated matter to secure spokes to a rim. This is further complicated because the centering angle and the torsional angle are not constant in bicycle wheels on a moving bicycle. The weight of a rider, forces associated with turning, forces associated with braking and forces associated with acceleration, among other things, can and do cause small but not insignificant changes in these angles and these changes occur very rapidly during cycling. These angle changes cause stresses in spokes, particularly where they are fastened to the rim, typically by internally threaded nipples. Various attempts to deal with these stresses are discussed below.
The Michelotti patent discloses a bush which is received in a spoke bore in a rim. The bush is configured with two cylindrical co-axial bodies for receiving the conical head and the cylindrical section of an internally threaded nipple which receives the threaded end of a spoke. The bush is further configured to minimize deviation between the common axes of the cylindrical bodies and the longitudinal axis of the spoke. Apart from difficulties associated with properly orienting the bushes to achieve the desired result, this approach does not begin to account for dynamic changes in the centering angle and the torsional angle.
Another prior art method is illustrated in
FIG. 2
which shows a rim
20
, in cross-section and a spoke
22
connected to the rim
20
. The rim
20
has a rounded spoke bed indicated at
24
which is raised, as indicated at
26
, adjacent to sidewalls
28
of the rim
20
, and lower in the middle, as indicated at
30
. A spoke bore, indicated at
32
, has an axis which is oriented, so far as possible, to coincide with the longitudinal axis of the spoke
22
, taking into account the centering angle as well as the torsional angle, if any, of the spoke
22
. A nipple
34
is internally threaded and is attached to a threaded end
36
of the spoke
22
. Portions of the bottom end
38
of the nipple
34
engage the rounded rim floor
24
while other portions of the bottom
38
of the nipple
34
do not engage the rim floor
24
. This condition is exacerbated under dynamic conditions when the centering angle and the torsional angle are changing. The resulting stresses tend to concentrate in the unthreaded portion of the spoke
22
, immediately adjacent to the threaded portion
36
.
Referring now to
FIGS. 3 and 4
, an extended nipple
40
, similar to the nipple shown in the Michelotti patent with a head
6
, has a head
42
which is seated on a substantially flat rim floor
44
of a rim
45
. As can be seen in
FIG. 4
, however, only a small portion of the underside
46
of the head
42
of the nipple
40
seats against the rim floor when it engages a spoke
47
extending through the rim
45
. In this arrangement, the spoke hole, indicated at
48
, is inclined so that its axis coincides generally with the longitudinal axis of the spoke, taking into account the centering angle and, if necessary, the torsional angle. The nipple
40
has a slot, indicated at
49
in
FIG. 4
, which is engageable by a screwdriver or the like to properly tension the spoke
47
.
Bicycle wheel rims encounter large stresses at spoke locations. Typically, a spoke extends through a spoke hole in the rim and is connected inside of the rim to an internally threaded nipple. Low spoke count wheels, i.e., in the range of 14 or 16 spokes up to 20 or 24 spoke wheels have higher spoke tensions than conventional wheels with 28 or more spokes. Consequently, low spoke wheels have a higher stress concentration where the spokes are connected to the rim than conventional wheels because each spoke must carry a higher load when there are fewer spokes so that the total tension in the spokes which centers the rim and the hub within the rim is about the same as in a higher spoke wheel. Some have undertaken to reinforce and/or reduce rim weight while providing adequate strength at spoke connection points, in rather remarkable ways. EP 0 715 001 A1 discloses the idea of extruding a rim section having a spoke bed of a given thickness, masking spoke connection points and chemically removing material from the rim except under the masks, resulting in a rim with thickened portions coinciding with spoke connection points and reduced thicknesses elsewhere on the rim. U.S. Pat. No. 6,402,256 B1 discloses a rim that is made from a rim section having a spoke bed with a given thickness and the mechanical removal of spoke bed material in between the spoke connection points. This produces a rim that is reinforced at spoke connection points.
SUMMARY OF THE INVENTION
The present invention is based upon the discovery of an impr
Purdue David C.
Purdue John C.
Stormer Russell D.
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