Bicycle frame rear suspension with flexing frame segment
View Patent ↗A bicycle frame includes a substantially rigid front frame portion and a substantially rigid rear frame portion. A link is connected to the rear frame portion by a first pivot and to the front frame portion by a second pivot. A rear frame segment is rigidly connected at a first end to the rear frame portion and pivotably connected at a second end to the front frame portion by a third pivot. The rear frame segment is flexible parallel to an axis of the third pivot.
1. A bicycle frame comprising:
a substantially rigid front frame portion;
a substantially rigid rear frame portion;
a link connected to the rear frame portion by a first pivot and connected to the front frame portion by a second pivot;
a rear frame segment rigidly connected at a first end to the rear frame portion and pivotably connected at a second end to the front frame portion by a third pivot, the rear frame segment being flexible parallel to an axis of the third pivot;
wherein the first pivot floats in an arc about the second pivot which is fixed relative to front frame portion as the rear frame portion pivots relative to the front frame portion about the third pivot, and wherein the rear frame segment flexes to enable the first pivot to move in the arc about the second pivot as the rear frame segment pivots about the third pivot between a rest position and a fully pivoted position; and
wherein the rear frame segment behaves as a leaf spring as it flexes, the rear frame segment and the pivots being configured so that the rear frame segment provides a spring force that varies between opposing and promoting pivoting of the rear frame portion about the third pivot as the rear frame portion is pivoted about the third pivot between a rest position and a fully pivoted position.
2. The bicycle frame of claim 1 wherein the rear frame segment comprises a leaf spring.
3. The bicycle frame of claim 1 wherein the substantially rigid rear frame portion comprises a seat stay, a chain stay and a bridge stay, the seat stay and the chain stay being substantially rigidly connected together at their proximal ends and each being substantially rigidly connected to the bridge stay, and the flexible rear frame segment being substantially parallel and aligned with an imaginary line between the junction between the seat stay and the chain stay and the third pivot.
4. The bicycle frame of claim 1 wherein the seat stay and the chain stay comprise forked stay pairs configured to receive a bicycle wheel therebetween.
5. The bicycle frame of claim 1 further comprising a shock absorber pivotably connected between the link and the front frame portion to oppose pivoting of the rear frame portion relative to the front frame portion in a clockwise direction about the third pivot.
6. The bicycle frame of claim 1 wherein the rear frame segment and the pivots are configured to provide a spring force opposing rotation of the rear frame portion about the third pivot from a rest position to a point along the travel of the arc of the first pivot about the second pivot and to thereafter provide a spring force promoting rotation of the rear frame portion about the third pivot to a fully pivoted position.
7. The bicycle frame of claim 1 wherein the rear frame segment is integrally formed with the rear frame portion.
8. The bicycle frame of claim 1 wherein the rear frame segment comprises a leaf spring configured to be substantially laterally rigid.
9. The bicycle frame of claim 8 wherein the leaf spring is made of a metal.
10. The bicycle frame of claim 8 wherein the leaf spring is made of composite material.