Digressive valve for a damper
Generally described, dampers having shimmed pistons are configured for use with vehicle suspensions. The dampers generally include a shaft having a piston with compression and rebound valves extending therethrough. The piston interfaces a shim assembly at the valve outlets such that damping fluid flow is controlled through a set of valves in one direction, and the damping fluid flow is limited through the same set of valves in the opposite direction. In this regard, the shim assembly is configured to provide bleed relief of the hydraulic damping fluid at lower shaft speeds and deflect away from the piston higher shaft speeds. The shim assembly generally includes a ring shim that interfaces a shim stack to provide a configurable preload for the deflectable shims and a flow path for the hydraulic damping fluid during bleed relief.
1. A damper having a shimmed piston, comprising:
an elongate shaft having a first end and a fastener configured to retain the piston on the first end, the piston having a proximal end, a distal end, and a first valve extending therethrough; and
a first shim assembly disposed around the elongate shaft at the first end and adjacent to the distal end of the piston, the first shim assembly comprising:
a first shim having a first bleed port in fluid communication with the first valve and a central aperture configured to receive the elongate shaft, the first shim configured to overlap the first valve at the distal end of the piston;
a first ring shim assembled to the first end of the elongate shaft and configured to abut the first shim;
a second shim installed at the first end of the elongate shaft, the second shim interfacing a radially inward projection of the first ring shim and having a first bleed relief such that when the second shim abuts the radially inward projection of the first ring shim, the first bleed relief provides a fluid path across the second shim along a surface of the first ring shim; and
a third shim positioned at a distance from the second shim, wherein the third shim is configured to deflect away from the piston as a result of a contact force by the second shim during deflection of the second shim as a result of damping fluid flow through the first valve.
2. The damper of claim 1 , wherein the first shim further comprises a clocking protrusion positioned relative to the first bleed port, the clocking protrusion configured to position the first bleed port relative to the first valve.
3. The damper of claim 1 , wherein the second shim is deflectable to provide a preload to the first shim assembly in reaction to clamping the piston with the fastener.
4. The damper of claim 3 , wherein a perimeter of the central aperture of the first shim is fixed in a direction along the elongate shaft by the clamping of the piston with the fastener.
5. The damper of claim 1 , wherein the third shim is positioned at a distance from the second shim by a washer positioned therebetween, and wherein the diameter of the washer is smaller than the diameter of the third shim.
6. The damper of claim 1 , wherein the piston further comprises a second valve, and wherein the first shim is configured to deflect away from the first ring shim at portions of the first shim adjacent to the second valve.
7. The damper of claim 1 , wherein the first shim is configured to deflect away from the piston as a result of damping fluid flow through the first valve.
8. The damper of claim 1 , wherein the first ring shim has a wall projecting axially from a surface of the radially inward projection configured to stiffen the first ring shim upon installation.
9. The damper of claim 1 , further comprising:
a second valve extending through the piston; and
a second shim assembly disposed around the elongate shaft at the first end and adjacent to the proximal end of the piston, the second shim assembly comprising:
a fourth shim having a second bleed port in fluid communication with the second valve and a central aperture configured to receive the elongate shaft, the fourth shim configured to overlap the second valve at the proximal end of the piston; and
a second ring shim assembled to the first end of the elongate shaft such that the fourth shim is positioned between the piston and the second ring shim,
wherein the second bleed port provides a fluid path across the fourth shim along a surface of the piston.
10. A shimmed piston for a damper, comprising:
a first valve extending through the shimmed piston; and
a first shim assembly disposed adjacent to a distal end of the shimmed piston, the first shim assembly comprising:
a first shim comprising a first bleed port in fluid communication with the first valve and a central aperture configured to receive an elongate shaft, the first shim configured to overlap the first valve at the distal end of the shimmed piston, wherein the first shim further comprises a clocking protrusion positioned relative to the first bleed port, the clocking protrusion configured to position the first bleed port relative to the first valve;
a first ring shim configured to abut the first shim; and
a second shim interfacing a radially inward projection of the first ring shim and having a first bleed relief such that when the second shim abuts the radially inward projection of the first ring shim, the first bleed relief provides a fluid path across the second shim along a surface of the first ring shim.
11. The shimmed piston of claim 10 , wherein the second shim is deflectable to provide a preload to the first shim assembly in reaction to clamping the shimmed piston with a fastener.
12. The shimmed piston of claim 11 , wherein a perimeter of the central aperture of the first shim is configured to be fixed in a direction along the elongate shaft by the clamping of the shimmed piston with the fastener.
13. The shimmed piston of claim 10 , wherein the first shim assembly further comprises a third shim positioned at a distance from the second shim, wherein the third shim is configured to deflect away from the shimmed piston as a result of a contact force by the second shim during deflection of the second shim as a result of damping fluid flow through the first valve.
14. The shimmed piston of claim 13 , wherein the third shim is positioned at a distance from the second shim by a washer positioned therebetween, and wherein the diameter of the washer is smaller than the diameter of the third shim.
15. The shimmed piston of claim 10 , further comprising a second valve, wherein the first shim is configured to deflect away from the first ring shim at portions of the first shim adjacent to the second valve.
16. The shimmed piston of claim 10 , wherein the first shim is configured to deflect away from the shimmed piston as a result of damping fluid flow through the first valve.
17. The shimmed piston of claim 10 , wherein the first ring shim has a wall projecting axially from a surface of the radially inward projection configured to stiffen the first ring shim upon installation.
18. The shimmed piston of claim 10 , further comprising:
a second valve extending through the shimmed piston; and
a second shim assembly disposed adjacent to a proximal end of the shimmed piston, the second shim assembly comprising:
a fourth shim having a second bleed port in fluid communication with the second valve and a central aperture configured to receive the elongate shaft, the fourth shim configured to overlap the second valve at the proximal end of the shimmed piston; and
a second ring shim positioned such that the fourth shim is positioned between the piston and the second ring shim,
wherein the second bleed port provides a fluid path across the fourth shim along a surface of the shimmed piston.