192 clutches and power-stop control – Transmission and brake – Velocipede
Reexamination Certificate
1999-12-30
2001-06-12
Lorence, Richard M. (Department: 3681)
192 clutches and power-stop control
Transmission and brake
Velocipede
C074S473140, C474S070000
Reexamination Certificate
active
06244415
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is directed to control devices for bicycles and, more particularly, to an automatic shifting device for shifting a bicycle transmission.
There are two major types of bicycle transmissions currently marketed. One type of bicycle transmission uses a derailleur to shift a chain from one sprocket to another to change the drive ratio, and the other type uses a planetary gear mechanism disposed inside a rotating hub such as a wheel hub to change the drive ratio. In either case, an operating member such as a lever, push rod or rotatable ring is moved to operate the transmission, and the operating member is connected to a transmission actuating member such as a control wire or link that is pulled or released by the rider to cause the desired movement of the operating member. To facilitate the operation of the transmission in a pull and release manner, a return spring commonly is used to bias the operating member to an initial state. The transmission then is operated by moving the operating member against the progressively increasing force of the return spring and the natural resistance by the transmission to changing gears.
When the transmission actuating member is a control wire, the control wire ordinarily is connected to a shift control device mounted to the bicycle handlebar. The shift control device usually includes a takeup member that winds and unwinds the control wire to perform the pulling and releasing function, and a rotating ring or lever to rotate the takeup member. After a winding operation has been performed to select a desired transmission gear, the takeup member must be maintained in the position corresponding to that gear. Known structures for positioning the takeup member include those merely involving the use of frictional resistance; those in which indentations are formed in the speed-step positions on the side of the fixed elements for engaging protrusions formed on the side of the control members (as described in Japanese Laid-Open Patent Application 3-176290); and those involving the provision of one-way ratchet mechanisms (as described in PCT/JP92/00138).
In shift control devices where positioning is accomplished using frictional resistance or engagement between indentations and protrusions, considerable engagement force is needed to securely maintain the takeup member in the desired position. When the resistance of the return spring is added to the resistance created by such position maintaining structures, the force that must be applied to operate the shift control device can become quite large.
Motor driven bicycle transmissions are becoming more common. Such motor driven bicycle transmissions relieve the rider of the task of manually pulling and releasing the transmission actuating member. Of course, the motor used to cause the pulling and releasing of the transmission actuating member must be designed to withstand the forces noted above. This sometimes makes it necessary to use a relatively large motor which increases the cost, size and weight of the transmission operating mechanism. The larger motor also creates significantly more current drain on the battery used to operate the motor, thus resulting in short battery life. Consequently, motor driven transmissions usually are not used when the size, cost or weight of the bicycle is an important factor, such as in racing environments.
SUMMARY OF THE INVENTION
The present invention is directed to a motor controlled shift control device that is economical to manufacture and which avoids the large forces required to operate prior art shift control devices. In one embodiment of the present invention, a bicycle transmission shifting device includes a motor, a takeup member for pulling and releasing a transmission control element, and a one-way clutch shift control device disposed between the motor and the takeup member for maintaining the takeup member in a plurality of positions.
In a more specific embodiment, the one-way clutch shift control device includes a first member; a second member rotatably mounted relative to the first member for controlling the pulling and releasing of a transmission control element; and a third member coupled between the first member and the second member. If desired, the first member may be structured to immovably fix the shift control device relative to the bicycle, and the second member may be coupled to the takeup member for pulling and releasing a control cable.
In any event, the third member rotates around the first axis in response to rotation of the second member. The third member also moves in the direction of the first axis between an engaged position in which the third member engages the first member, and a disengaged position in which the third member is disengaged from the first member. The second member includes a drive surface for driving the third member in a third direction (which may be the same as the first direction) when the second member rotates in the first direction. The third member includes first and second cam surfaces, wherein the first cam surface causes the third member to move in the direction of the first axis toward the disengaged position during rotation of the third member in the third direction, and wherein the second cam surface causes the third member to move in the direction of the first axis toward the disengaged position during rotation of the second member in the second direction. The third member also includes a positioning surface for preventing the third member from rotating around the first axis when the third member is in the engaged position.
In an even more specific embodiment, the drive surface contacts the third member when the second member rotates in the first direction, the first cam surface contacts the first member when the third member rotates in the third direction, the second cam surface contacts the second member when the second member rotates in the second direction, and the positioning surface contacts the first member when the third member is in the engaged position. The height of the drive surface in the direction of the first axis is greater than the corresponding height of the positioning surface, so the third member remains engaged with the second member when the third member disengages from the first member, thus allowing the third member to rotate in discrete steps. The resulting structure is constructed with few components, is very compact, and does not require large forces to operate the device and maintain the position of the device in a selected gear. Thus, a small motor may be used to operate the shift control device.
REFERENCES:
patent: 4490127 (1984-12-01), Matsumoto et al.
patent: 5254044 (1993-10-01), Anderson
patent: 5799542 (1998-09-01), Yamane
patent: 6146297 (2000-11-01), Kimura
patent: 6162140 (2000-12-01), Fukada
patent: 893336 A2 (1999-01-01), None
patent: 3-176290 (1991-07-01), None
Deland James A.
Lorence Richard M.
Shimano Inc.
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