Planetary gear transmission systems or components – With means to vary drive ratio or disconnect drive – Gear shiftable axially to disconnect or vary ratio
Reexamination Certificate
1999-12-29
2001-12-04
Marmor, Charles A (Department: 3681)
Planetary gear transmission systems or components
With means to vary drive ratio or disconnect drive
Gear shiftable axially to disconnect or vary ratio
C475S288000
Reexamination Certificate
active
06325739
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is directed to bicycle transmissions and, more particularly, to internal hub transmissions that use planetary gear mechanisms.
A typical internal hub transmission for a bicycle includes a hub axle for retaining the transmission to a bicycle frame, a driver rotatably supported relative to the hub axle, and an output member rotatably supported relative to the hub axle. The driver usually is mounted with a sprocket for receiving a driving force from a chain connected to the pedal cranks, and the output member usually is a hub shell that is connected to the wheel spokes which, in turn, are connected to the wheel rim. A planet gear mechanism usually is disposed between the driver and the hub shell for communicating the rotational force from the driver to the hub shell through a plurality of transmission paths which change the drive ratio of the transmission. In a three speed hub, for example, the planet gear mechanism may include a first sun gear and a second sun gear rotatably supported relative to the hub axle, an intermediate gear unit rotatably supported relative to the hub axle, wherein the intermediate gear unit meshes with the first and second sun gears, and a ring gear meshing with the intermediate gear unit.
Changing the gear ratio in a planet gear mechanism usually involves selectively stopping the rotation of the first and second sun gears relative to the hub axle. This usually involves coupling the first sun gear to the hub axle using a coupling member interposed between the first sun gear and the hub axle, and then coupling the second sun gear to the hub axle using another coupling member interposed between the second sun gear and the hub axle. Sometimes a single coupling member is used to perform both functions. Such a coupling member usually takes the form of an elongated member that slides along the hub axle, wherein the coupling member initially engages a first stopper on the first sun gear and a first stopper on the hub axle and then slides along the hub axle to that the coupling member engages a second stopper on the second sun gear and a second stopper on the hub axle. If the width of the elongated member is less than the distance between the first stopper on the first sun gear and the second stopper on the second sun gear, there may be a time while the elongated member is being moved from the first sun gear to the second sun gear that the coupling member is disengaged from both the first sun gear and the second sun gear, thus causing a break in the power transmission path between the driver and the hub shell and causing freewheeling of the hub shell.
SUMMARY OF THE INVENTION
The present invention is directed to an internal hub transmission for a bicycle wherein a coupling member which selectively engages a sun gear does so without causing freewheeling of the hub when shifting from one gear to another. In one embodiment of the present invention, an internal hub transmission for a bicycle includes a hub axle for retaining the transmission to a bicycle frame, wherein the hub axle has an axle axis; a driver rotatably supported relative to the hub axle; an output member rotatably supported relative to the hub axle; and a planet gear mechanism. The planet gear mechanism includes a sun gear rotatably supported relative to the hub axle and movable in a direction of the axle axis; a planet gear carrier rotatably supported relative to the hub axle; a planet gear rotatably supported to the planet gear carrier, wherein the planet gear meshes with the sun gear; and a ring gear meshing with the planet gear. The sun gear moves in the direction of the axle axis between a first position, wherein the sun gear is nonrotatably coupled to a coupled member, and a second position, wherein the sun gear is decoupled from the coupled member. The coupled member is one of the hub axle, the driver, the planet gear carrier, and the output member. A stop member is disposed on one of the sun gear and the coupled member, and a complementary stop member disposed on the other one of the sun gear and the coupled member. At least one of the stop member and the complementary stop member includes a surface that pushes the sun gear away from the coupled member toward the second position.
In a more specific embodiment of the present invention, an internal hub transmission for a bicycle includes a hub axle for retaining the transmission to a bicycle frame, wherein the hub axle has an axle axis; a driver rotatably supported relative to the hub axle; an output member rotatably supported relative to the hub axle; and a planet gear mechanism disposed between the driver and the output member. The planet gear mechanism includes a first sun gear rotatably supported relative to the hub axle; a second sun gear rotatably supported relative to the hub axle; an intermediate gear unit rotatably supported relative to the hub axle, wherein the intermediate gear unit meshes with the first sun gear and the second sun gear; and a ring gear meshing with the intermediate gear unit.
In this embodiment, a sun gear stop mechanism is provided for selectively nonrotatably coupling at least one of the first sun gear and the second sun gear relative to the hub axle. The sun gear stop mechanism includes a first stop member spaced apart by a first width from a second stop member, wherein the first stop member and the second stop member are coupled to one of: 1) the first sun gear and the second sun gear; or 2) the hub axle. The sun gear stop mechanism also includes a complementary stop unit, wherein the complementary stop unit is coupled to the other one of: 1) the first sun gear and the second sun gear; or 2) the hub axle. The complementary stop unit moves between the first stop member and the second stop member for selectively engaging at least one of the first stop member and the second stop member, wherein a portion of the complementary stop unit that engages the at least one of the first stop member and the second stop member has a second width greater than the first width.
In an even more specific embodiment, the first stop member and the second stop member are coupled to the hub axle, and the complementary stop unit comprises a first complementary stop member disposed between the first sun gear and the hub axle and a second complementary stop member disposed between the second sun gear and the hub axle, wherein the complementary stop unit moves in the direction of the axle axis. To ensure a reliable switching operation, at least one of the first stop member, the second stop member and the complementary stop unit includes a surface that pushes the complementary stop unit away from the selectively engaged first stop member or second stop member.
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Deland James A.
Marmor Charles A
Pang Roger
Shimano Inc.
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