Suspension damper having inertia valve and user adjustable pressure-relief

1. A suspension damper operable between a compressed position and an extended position, comprising:

a compression chamber having a volume reducing in response to operation of the suspension unit from the extended position to the compressed position;

a reservoir chamber;

damping fluid for flowing between the chambers;

an inertia valve at least substantially closing a first fluid path between the compression and reservoir chambers when in a closed position and movable to an open position in response to an acceleration of at least a portion of the damper, such acceleration equaling or exceeding a first threshold;

a pressure relief valve at least substantially closing a second fluid path between the compression and reservoir chambers when in a closed position and movable to an open position in response to pressure in the compression chamber equaling or exceeding an externally adjustable second threshold,

wherein at least one setting of the second threshold is operable so the pressure relief valve opens in response to a severe shock and remains closed in response to a mild shock;

a rebound chamber having a volume reducing in response to operation of the suspension unit from the compressed position to the extended position;

gas disposed in the reservoir chamber;

an upper tube;

a damper shaft fixed to the upper tube;

a lower tube receiving at least a portion of the upper tube;

a cartridge tube fixed to the lower tube;

a piston supported by the damper shaft and disposed in the cartridge tube; and

a compression valve operable to dampen flow of the damping fluid through the first path from the compression chamber to the reservoir chamber,

wherein the piston divides a chamber of the cartridge tube into the compression and rebound chambers.

2. The suspension damper of claim 1 , wherein the reservoir chamber is defined between the upper and lower tubes and the cartridge tube.

3. The suspension damper of claim 1 , wherein the cartridge tube houses the inertia valve, the compression valve, and the pressure relief valve.

4. The suspension damper of claim 3 , wherein the cartridge tube houses the reservoir chamber.

5. The suspension damper of claim 1 , further comprising a bladder made from a flexible material, disposed in the reservoir chamber, and housing the gas.

6. The suspension damper of claim 1 , wherein the acceleration is from the extended position to the compressed position.

7. The suspension damper of claim 6 , wherein the inertia valve comprises:

an outer flow tube having first and second flow ports formed through a wall thereof;

an inner flow tube disposed within the outer flow tube so that an annulus is formed therebetween and having a head isolating the first flow port from the annulus;

an inertia mass made from a high density material, having a recess formed therein, and movable between the open and closed positions, wherein the recess provides fluid communication between the first and second flow ports in the open position;

a spring biasing the inertia mass toward the closed position;

a pocket receiving the inertia mass in the open position; and

a check valve allowing flow from the pocket and obstructing flow into the pocket.

8. The suspension damper of claim 1 , wherein the pressure relief valve has a bleed providing limited fluid communication between the compression and reservoir chambers in the closed position.

9. The suspension damper of claim 8 , wherein the bleed is externally adjustable.

10. The suspension damper of claim 9 , further comprising an externally located and hand operable controller operably coupled to the pressure relief valve, wherein operation of the controller adjusts the second threshold and the bleed.

11. The suspension damper of claim 1 , further comprising an externally located and hand operable controller operably coupled to the pressure relief valve, wherein operation of the controller adjusts the second threshold.

12. The suspension damper of claim 1 , wherein:

the first threshold is operable so that the inertia valve opens in response to a medium shock and remains closed in response to the mild shock, and

the setting of the second threshold is further operable so that the pressure relief valve remains closed in response to the medium shock.

13. A suspension damper operable between a compressed position and an extended position, comprising:

a compression chamber having a volume reducing in response to operation of the suspension unit from the extended position to the compressed position;

a second chamber

damping fluid for flowing between the chambers;

an inertia valve at least substantially closing a first fluid path between the compression and second chambers when in a closed position and movable to an open position in response to an acceleration of at least a portion of the damper, such acceleration equaling or exceeding a first threshold,

a first pressure relief valve at least substantially closing a second fluid path between the compression and second chambers when in a closed position and movable to an open position in response to pressure in the compression chamber equaling or exceeding an externally adjustable second threshold; and

a second pressure relief valve at least substantially closing a third fluid path between the compression and second chambers when in a closed position and movable to an open position in response to pressure in the compression chamber equaling or exceeding a third threshold.

14. The suspension damper of claim 13 , further comprising:

a rebound chamber having a volume reducing in response to operation of the suspension unit from the compressed position to the extended position; and

gas disposed in the second chamber,

wherein the second chamber is a reservoir chamber.

15. The suspension damper of claim 14 , further comprising:

a shock absorber housing the compression and rebound chambers; and

a reservoir tube housing the reservoir chamber, the pressure relief valves, and the inertia valve.

16. The suspension damper of claim 14 , further comprising a floating piston disposed in the reservoir chamber and isolating the gas from the damping fluid.

17. The suspension damper of claim 16 , wherein the inertia valve comprises:

a reservoir shaft connected to the reservoir tube and having a flow port formed through a wall thereof.

an inertia mass made from a high density material and movable between the open and closed positions, wherein the inertia mass covers the flow port in the closed position and exposes the flow port in the open position;

a spring biasing the inertia mass toward the closed position;

a pocket receiving the inertia mass in the open position; and

a check valve allowing flow from the pocket and obstructing flow into the pocket.

18. The suspension damper of claim 17 , wherein:

the second pressure relief valve comprises a base connected to the reservoir shaft and a cap connected to the base,

the first pressure relief valve comprises:

a control shaft connected to the reservoir tube and extending through the floating piston,

a seat fastened to the cap;

a valve element at least partially received by the control shaft and having a head; and

a spring biasing the head toward the seat.

19. A suspension damper operable between a compressed position and an extended position, comprising:

a compression chamber having a volume reducing in response to operation of the suspension unit from the extended position to the compressed position;

a second chamber;

damping fluid for flowing between the chambers;

an inertia valve at least substantially closing a first fluid path between the compression and second chambers when in a closed position and movable to an open position in response to an acceleration of at least a portion of the damper, such acceleration equaling or exceeding a first threshold, and

a pressure relief valve at least substantially closing a second fluid path between the compression and second chambers when in a closed position and movable to an open position in response to pressure in the compression chamber equaling or exceeding an externally adjustable second threshold,

wherein:

at least one setting of the second threshold is operable so the pressure relief valve opens in response to a severe shock and remains closed in response to a mild shock,

the acceleration is from the extended position to the compressed position, and

the inertia valve comprises:

an outer flow tube having first and second flow ports formed through a wall thereof;

an inner flow tube disposed within the outer flow tube so that an annulus is formed therebetween and having a head isolating the first flow port from the annulus;

an inertia mass made from a high density material, having a recess formed therein, and movable between the open and closed positions, wherein the recess provides fluid communication between the first and second flow ports in the open position;

a spring biasing the inertia mass toward the closed position;

a pocket receiving the inertia mass in the open position; and

a check valve allowing flow from the pocket and obstructing flow into the pocket.