Front bicycle suspension assembly with inertia valve
View Patent ↗A front bicycle suspension assembly having an inertia valve is described. The front bicycle suspension assembly may include at least upper and lower telescoping tubes defining an interior volume in which a damping tube containing an inertia valve is positioned. During compression, a piston rod of the bicycle suspension assembly occupies a successively greater portion of the damping tube.
1. A bicycle suspension assembly, comprising:
an upper tube configured for coupling to a bicycle frame;
a lower tube configured for coupling to a bicycle front wheel, the lower tube in telescoping engagement with the upper tube;
a damping assembly including;
a damping tube coupled to the lower tube;
a piston rod coupled to:
a) the upper tube; and
b) a piston in sealed, sliding engagement with the damping tube;
the piston and the damping tube defining a compression fluid chamber and a rebound fluid chamber, wherein a damping fluid moves between the compression chamber and the rebound chamber during compression movement of the suspension assembly and the piston rod occupies a successively greater portion of the damping tube during the compression movement;
an opening communicating with the compression chamber;
an inertia valve comprising an inertia mass, the inertia valve having an open position wherein the inertia mass does not block at least a portion of the opening and a flow of damping fluid is permitted through at least a portion of the opening, the inertia valve normally biased to a closed position wherein the inertia mass is positioned to block more of the opening such that the flow of damping fluid through the opening is reduced relative to the open position of the inertia valve; a spring, the spring configured to apply a force to the suspension assembly tending to extend the piston rod relative to the damping tube;
wherein the spring and the damper cooperate, in the absence of a terrain-induced upward acceleration of the suspension assembly above a predetermined threshold sufficient to move the inertia valve to the open position, to prevent significant compressive movement of the suspension assembly in response to rider-induced pedaling forces on the suspension assembly, and wherein the inertia valve is movable to the open position in response to a terrain-induced upward acceleration of the suspension assembly above the threshold to permit significant compressive movement of the suspension assembly.
2. The bicycle suspension assembly of claim 1 further comprising a pressure-relief valve in fluid communication with the compression chamber and for allowing additional portions of the piston rod to enter the damping tube when the damping fluid pressure inside the compression chamber exceeds a predetermined pressure threshold and regardless of the position of the inertia mass.
3. The bicycle suspension assembly of claim 1 , wherein the threshold upward acceleration that permits significant compressive movement of the suspension assembly is between about 0.1-3 G's.
4. The bicycle suspension assembly of claim 1 , wherein the threshold upward acceleration that permits significant compressive movement of the suspension assembly is less than about 2 G's.
5. The bicycle suspension assembly of claim 1 , wherein the threshold upward acceleration that permits significant compressive movement of the suspension assembly is between about 0.25 and 1.5 G's.
6. The bicycle suspension assembly of claim 5 , wherein the threshold upward acceleration that permits significant compressive movement of the suspension assembly is between about 0.4 and 0.7 G's.
7. The bicycle suspension assembly of claim 1 :
wherein the upper and lower tubes define a first suspension fork leg;
a second upper tube and a second lower tube define a second suspension fork leg;
the first suspension fork leg is connected to the second suspension fork leg by a crown; and
the spring is contained within the second fork leg.
8. The bicycle suspension assembly of claim 1 , wherein the suspension assembly comprises a bicycle suspension fork.
9. An acceleration-sensitive bicycle suspension assembly comprising:
a crown configured to be rotatably coupled to a bicycle frame;
an upper tube joined to the crown;
a lower tube in telescoping engagement with the upper tube, the lower tube configured for coupling to a bicycle front wheel;
a damping system including an acceleration-activated compression damping control mechanism, comprising:
a damper tube coupled to the lower tube and having a bore partially defining a first chamber containing damping fluid;
a second chamber in fluid communication with the first chamber via a compression fluid flow circuit;
a piston rod having an upper portion coupled to the upper tube and a lower portion within the first chamber;
wherein a relative movement of the piston rod in a direction such that an increased volume of the piston rod enters the first chamber expels an amount of damping fluid from the first chamber to the second chamber via the compression fluid flow circuit;
an acceleration-sensitive inertia valve for at least partially controlling the fluid flow resistance of the compression fluid flow circuit, the inertia valve comprising:
a valve shaft, distinct from the piston rod, coupled to the lower tube and having one or more fluid flow ports intersecting the outer surface of the valve shaft intermediate the ends of the valve shaft, the one or more fluid flow ports defining a portion of the compression fluid flow circuit; an inertia mass surrounding the valve shaft and having a first position and a second position, the inertia mass biased towards the first position, wherein:
when an upward acceleration of the bicycle front wheel is less than a predetermined acceleration threshold, the inertia mass remains in the first position at least partially blocking the one or more fluid flow ports, thereby restricting the rate of fluid expulsion through the inertia valve;
when an upward acceleration of the bicycle front wheel is greater than the predetermined acceleration threshold, the inertia mass moves towards the second position providing less blockage of the one or more fluid flow ports, thereby allowing a less restricted rate of fluid expulsion through the inertia valve; and
the suspension assembly thereby providing a first damping response to forces that produce upward acceleration of the bicycle front wheel above the predetermined acceleration threshold, and providing a second damping response, firmer than the first damping response, to forces that produce upward acceleration of the bicycle front wheel below the predetermined acceleration threshold.
10. The suspension assembly of claim 9 further comprising a second valve at least partially controlling the fluid flow resistance of the compression fluid flow circuit.
11. The suspension assembly of claim 10 wherein the second valve comprises a blow-off valve configured to:
a) substantially inhibit compression fluid flow through the blow-off valve in response to a pressure in the first chamber below a predetermined pressure threshold; and
b) to allow compression fluid flow through the blow-off valve in response to a pressure in the first chamber above the predetermined pressure threshold.
12. The suspension assembly of claim 11 wherein the predetermined pressure threshold is above a level induced by rider pedaling forces.
13. The suspension assembly of claim 9 further comprising a piston coupled to the piston rod, the piston in sliding engagement with the bore of the damper tube, the piston having at least one fluid flow passage.
14. The suspension assembly of claim 9 wherein the acceleration-sensitive inertia valve is located within the lower tube.
15. The suspension assembly of claim 9 wherein the predetermined acceleration threshold is:
a) above a level induced by rider pedaling forces;
b) below a level induced by forces from uneven terrain traversed by the front wheel;
whereby the suspension assembly operates:
a) with a first damping response over uneven terrain;
b) with a second damping response, firmer than the first damping response, over smooth terrain, the second damping response more efficiently than the first damping response converting rider pedaling energy into forward motion of the bicycle.
16. The suspension assembly of claim 15 wherein the predetermined acceleration threshold is between 0.2 G's and 2.0 G's.
17. The suspension assembly of claim 15 wherein the predetermined acceleration threshold is between 0.3 G's and 1.6 G's.
18. The suspension assembly of claim 15 wherein the predetermined acceleration threshold is between 0.4 G's and 1.2 G's.
19. The suspension assembly of claim 9 wherein the one or more fluid flow ports comprise two or more fluid flow ports, the two or more fluid flow ports configured to provide fluid forces impinging on the interior portions of the inertia mass that are substantially symmetrically balanced about a centerline of the inertia mass, whereby accuracy of the movement of the inertia mass in response to acceleration forces is improved relative to an inertia mass that moves in the presence of impinging fluid forces that are not symmetrically balanced, the improvement resulting from reduction of contact forces between the inertia mass and the valve shaft.
20. The suspension assembly of claim 9 further comprising an air spring.