Endless belt power transmission systems or components – Control for variable input to output speed-ratio – Including belt shiftable axially from one to another surface...
Reexamination Certificate
1998-09-10
2001-11-13
Bucci, David A. (Department: 3682)
Endless belt power transmission systems or components
Control for variable input to output speed-ratio
Including belt shiftable axially from one to another surface...
C474S080000
Reexamination Certificate
active
06315688
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates in general to bicycle derailleurs, and more particularly to a bicycle derailleur including a parallelogram linkage having a link member exhibiting increased flexibility under shear and torsional loading.
BACKGROUND OF THE INVENTION
Bicycle derailleurs are used to effect gear shifts by changing the position of a drive chain between the variable diameter sprockets of a multi-sprocket freewheel or crankset. The position of a chain on a sprocket of a freewheel and on a chainring of a crankset determines the gear ratio of the bicycle at which the rider must pedal. Typically, as shown in
FIG. 1
, a rear derailleur
10
includes a parallelogram linkage
20
that is attached to a bicycle frame element
30
at one end, and to an idler cage
32
at another end, the idler cage laterally urging the chain between the multiple sprockets or chainrings (not shown). A control cable
34
is tied at one end to a shifter mounted proximate the rider's hand on the handlebar or on the downtube of a bicycle frame (not shown), and at the second end to the parallelogram. The parallelogram is typically spring biased in a given direction, requiring the rider to actuate the shifter and tension the control cable in order to deflect the parallelogram and in turn urge the chain in a direction opposite to the spring- biased direction.
A parallelogram linkage
20
typically includes inner and outer links or side plates
40
,
42
, respectively, pivotally connected at axes D and C, respectively, to a b-knuckle
44
(which in turn is attached to the bicycle frame
30
) and pivotally connected at axes B and A, respectively, to a p-knuckle
46
(to which the idler cage
32
is attached), the parallelogram displaceable to precisely position the idler cage
32
and in turn the drive chain onto the desired sprocket. A return spring
48
biasing the parallelogram is typically a helical or coil spring urging together diagonally opposed pivot points of the parallelogram.
As shown in
FIG. 2
, links are typically formed into longitudinal channel members from a flat plate with pivot holes 50-53 located at both ends of resulting flange elements
54
for pivotal attachment to b-knuckles
44
and p-knuckle
46
with a pair of pins (not shown). In such link designs, it is difficult to control the angle of bend of the flange elements
54
with respect to a base element
55
and in turn the overall width W of the link member
40
(
FIG. 2
a
). Accordingly, this may result in binding between the link
40
and knuckle elements
44
,
46
, inhibiting the smooth operation of the parallelogram and potentially even jamming the derailleur. Additionally, as shown in
FIGS. 2
b
(top view) and
2
c
(end view), the four pivot holes
50
-
53
punched into the flanges
54
must be precisely located to ensure proper alignment of the holes both along the length and height of the flanges to ensure “parallelism” of the pivot holes. Again, failure to hold close tolerances in locating the holes will make assembly of links
40
,
42
onto the knuckles
44
,
46
difficult and inhibit the smooth displacement of the parallelogram
20
.
A further consideration in link designs is described in this assignee's pending application Ser. No. 09/005,214, entitled “Hybrid Spring For Bicycle Derailleurs.” In one embodiment of the invention of said application, a hybrid derailleur return spring force is achieved by urging an abutment member attached to one of the links forming the parallelogram against the coil spring during actuation of the parallelogram thereby imparting a transverse force to the coil spring and laterally deflecting the coil spring to produce the desired spring force. In such designs, the extent of lateral displacement of the spring is restricted by contact with the base element
55
of conventional link configurations thereby limiting the spring forces that can be achieved.
A need therefore exists for a derailleur parallelogram link that is sufficiently rigid axially to maintain the distance between the pivot axes during derailleur actuation but is also sufficiently flexible in torsion and shear to permit simple alignment of the pivot holes and easy control of the link width. A need also exists for parallelogram links that permit extended lateral displacement of coil return springs for parallelograms configured with abutment members that laterally deflect the return spring.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a bicycle derailleur having a parallelogram link that is simple to form and assemble, eliminating the need to precisely control link width and pivot hole location during formation of the link. It is another object of this invention to provide a parallelogram link that is substantially rigid axially to maintain the distance between the pivot axes during derailleur actuation and substantially flexible in torsion and shear to permit simple alignment of the pivot holes and easy control of the link width.
It is a further object of the preset invention to provide a parallelogram link that permits extended lateral displacement of the coil return spring in parallelograms configured with abutment members that laterally deflect the return spring.
It is a yet another object of the invention to provide a parallelogram link that is lighter than conventional link configurations.
The bicycle derailleur of the present invention includes an elongated parallelogram link rotatable at first and second ends about substantially parallel first and second pivot axes, respectively, the link being substantially rigid axially along a third axis substantially perpendicular to the first and second axes but also substantially flexible torsionally about the third axis as well as substantially flexible in shear in a plane defined by the first and second pivot axes.
REFERENCES:
patent: 4027542 (1977-06-01), Nagano
patent: 4269601 (1981-05-01), Nagano
patent: 5302155 (1994-04-01), Ishibashi
patent: 5533937 (1996-07-01), Patterson et al.
patent: 5620383 (1997-04-01), Patterson et al.
patent: 5624335 (1997-04-01), Ando
patent: 5860880 (1999-01-01), Oka
Benz Andreas A.
Boehm Robert K.
Duston Tyler D.
Greetis Jacques P.
McLaughlin Scott A.
Bucci David A.
Charles Marcus
Milosevic Milan
Perkins Jefferson
Piper Marbury Rudnick & Wolfe
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