192 clutches and power-stop control – Clutches – Velocipede free wheel
Reexamination Certificate
1997-01-27
2001-03-20
Lorence, Richard M. (Department: 3622)
192 clutches and power-stop control
Clutches
Velocipede free wheel
C192S046000, C074S576000
Reexamination Certificate
active
06202813
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is directed to bicycle freewheels and, more particularly, to a pawl noise dampening mechanism for a bicycle freewheel.
The hub of the drive-side wheel (usually the rear wheel) of a bicycle is sometimes provided with an integrated or separate freewheel. The freewheel is usually equipped with a one-way clutch mechanism so that only unidirectional rotational force is transmitted to the bicycle wheel. One-way clutch mechanisms having various structures are known. One known example is a ratchet mechanism in which engagement between pawls and ratchet teeth is employed. When the chain is driven by the pedals and a cog is rotatably driven, the ratchet mechanism transmits the torque from the ratchet teeth to the pawls and rotatably drives an inner component. The pawls are actuated by pawl springs in such a way as to ensure constant engagement with the ratchet teeth. The ratchet mechanism must possess extremely high strength and shock resistance because considerable torque and impact forces are transmitted from the ratchet teeth to the pawls.
When the pedals are stopped or rotated backward, the inner component of the freewheel rotates together with the wheel, creating a rotational movement in relation to the ratchet teeth. Because the inner component has pawls, the pawls and the ratchet teeth move relative to each other. Since the pawls are constantly actuated and pressed against the tooth surfaces of the ratchet teeth by pawl springs, the pawls chatter against the teeth surfaces of the ratchet teeth when performing a rocking movement in conformity with the peaks and valleys of the ratchet teeth. The noise generated by such a ratchet mechanism is unpleasant for the cyclist, and the friction between the pawls and the tooth surfaces of the ratchet teeth wastes energy. The result is that this type of friction wears out the pawls and the tooth surfaces of the ratchet teeth, thus shortening freewheel life.
SUMMARY OF THE INVENTION
The present invention is directed to a bicycle freewheel wherein the engagement between the pawls and ratchet teeth is silent when the bicycle pedals are stopped or rotated backward, and wherein the wear of the pawls and ratchet teeth is reduced. In one embodiment of the present invention, a ratchet mechanism for a bicycle hub includes a first hub member and a second hub member, wherein the first hub member and the second hub member are rotatable relative to each other. A pawl is supported by the first hub member, a ratchet tooth is supported by the second hub member, and a biasing mechanism is provided for biasing the pawl toward the ratchet tooth. A pawl control mechanism is responsive to relative rotation of the first hub member and the second hub member for allowing the pawl to contact the ratchet tooth when the first hub member and the second hub member rotate relative to each other in one direction and for preventing the pawl from contacting the ratchet tooth when the first hub member and the second hub member rotate relative to each other in an opposite direction.
The ratchet mechanism may be incorporated in a hub wherein both the first hub member and the second hub member are coaxially and rotatably supported on a hub axle. A plurality of pawls and ratchet teeth may be provided wherein the pawl control mechanism allows at least one of the pawls to contact a corresponding ratchet tooth when the first hub member and the second hub member rotate in the one direction. On the other hand, the pawl control mechanism prevents the pawls from contacting the ratchet teeth when the first hub member and the second hub member rotate relative to each other in the opposite direction. In a more specific embodiment, the first hub member may be formed as an inner cylindrical member and the second hub member may be formed as an outer cylindrical member coaxially supported radially outwardly of the inner cylindrical member. Alternatively, a hub shell may be coaxially and rotatably supported on the hub axle, wherein the hub shell includes an annular component which forms the second hub member. In this case the second hub member is coaxially supported radially outwardly of the first hub member.
In any event, the plurality of pawls may be supported to an outer surface of the first hub member, and the plurality of ratchet teeth may be supported to an inner surface of the second hub member. The pawl control mechanism may include an annular cage and a clutch. The annular cage may include a plurality of pawl pressure components, wherein each pawl pressure component is adapted to contact a corresponding pawl. The clutch may coupled to the cage and to one of the first hub member and second hub member so that the pawl pressure components do not interfere with the normal operation of the pawls when the first hub member and the second hub member relatively rotate in the one direction. However, the plurality of pawl pressure components retract their corresponding pawls when the first hub member and the second hub member relatively rotate in the opposite direction.
In a more specific embodiment, the clutch may be formed as a circular slide spring having an end coupled to the cage and an outer peripheral surface in contact with the inner surface of the second hub member. When the first and second hub members relatively rotate in the one direction, the slide spring engages the second hub member for moving the pawl pressure components away from engagement with the pawls, thus allowing the pawls to contact the ratchet teeth. On the other hand, when the first and second hub members relatively rotate in the opposite direction, the slide spring engages the second hub member for moving the pawl pressure components to retract the pawls, thus preventing the pawls from contacting the ratchet teeth. This results in silent operation and decreased wear of the ratchet mechanism.
REFERENCES:
patent: 1883966 (1932-10-01), Krause
patent: 2844050 (1958-07-01), Brendel
patent: 2988186 (1961-06-01), Dotter
patent: 4548304 (1985-10-01), Nagata
patent: 4674617 (1987-06-01), Nagano
patent: 4711331 (1987-12-01), Hoffman
patent: 5460254 (1995-10-01), Huang
patent: 2152157 (1985-07-01), None
patent: 56-90127 (1981-07-01), None
patent: 56-164232 (1981-12-01), None
Tabe Koshi
Yahata Yasuhiro
Deland James A.
Lorence Richard M.
Shimano Inc.
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