Bicycle dropper seat post assembly with a narrow gas spring cartridge
A dropper post assembly for supporting a bicycle seat may have an outer tube and an inner tube having a clearance portion and an upper end that includes an inward facing axial stop surface that defines a laterally extending abutment plane. A spring cartridge assembly has a cartridge cross-sectional that is less than 90% of the interior cross-sectional area of the clearance portion. A lower engagement member is disposed toward a lower end of the inner tube and substantially fills a lateral between lower end of the cartridge tube and the inner tube. A post head member has a front fastening aperture, a lowermost part of which lies in a laterally extending post head plane that is disposed axially inboard from the abutment plane.
1. A dropper post assembly for supporting a bicycle seat, the dropper post assembly comprising:
an outer tube extending axially along a post axis between a lower end and an upper end;
an inner tube that is axially translatable relative to the outer tube between an extended position and a retracted position, the inner tube having an interior bounded by a sidewall having a clearance portion disposed axially between an upper end and a lower end that is disposed within the outer tube, the clearance portion having an interior cross-sectional area taken in a lateral direction that is perpendicular to the post axis;
a spring cartridge assembly configurable using an actuator assembly in an unlocked configuration in which the spring cartridge assembly biases the inner tube toward its extended position and a locked configuration, and comprising:
a) a cartridge tube removably disposed within and axially translatable with the inner tube relative to the outer tube and providing an interior cylinder volume bounded by a cartridge sidewall, the cartridge tube having an upper end secured to the upper end of the inner tube such that relative lateral movement between the upper end of the cartridge tube and the upper end of the inner tube is inhibited, a lower end that is disposed at the lower end of the inner tube, the cartridge tube having a cartridge cross-sectional area taken in the lateral direction that is less than 90% of the interior cross-sectional area whereby a lateral gap is provided between at least some of the cartridge sidewall and the clearance portion;
b) a piston movably received within the cylinder to provide a first chamber a lower side of the piston, and a second chamber disposed on an opposing, upper side of the piston, whereby moving the inner tube toward the retracted position expands the first chamber, the piston including a valve that is configurable in an open position in which fluid communication is established between the first chamber and second chamber and the spring cartridge assembly is in the unlocked configuration, and a closed position in which the first chamber is fluidly isolated from the second chamber and the spring cartridge assembly is in the locked configuration;
c) a lower seal assembly disposed at a lower end of the cartridge tube and sealing a lower end of the cylinder and a cartridge rod extending axially through the lower seal assembly between an inner end engaging the piston and an outer lower end at the lower end the outer tube; and
a bumper positioned laterally between the clearance portion and the cartridge sidewall within the lateral gap thereby inhibiting lateral movement of the cartridge tube relative to the inner tube.
2. The dropper post assembly of claim 1 , wherein the cartridge tube has a length in the axial direction and the bumper has a length in the axial direction that is less than 50% of the length of the cartridge tube.
3. The dropper post assembly of claim 2 , wherein the bumper has a length in the axial direction that is less than 20% of the length of the cartridge tube.
4. The dropper post assembly of claim 1 , wherein the bumper is formed from different material than the cartridge tube.
5. The dropper post assembly of claim 1 , wherein the bumper is removable from the lateral gap.
6. The dropper post assembly of claim 1 , wherein the bumper comprises at least one of plastic, rubber and foam.
7. The dropper post assembly of claim 1 , further comprising a lower engagement member disposed toward the lower end of the inner tube and substantially filling the lateral gap thereby inhibiting relative lateral movement between lower end of the cartridge tube and the inner tube, wherein the lower engagement member is axially insertable into the lower end of the inner tube or is integrally formed with the inner tube.
8. The dropper post assembly of claim 7 , wherein the lower engagement member is disposed entirely within the interior of the inner tube.
9. The dropper post assembly of claim 7 , wherein the cartridge tube is axially translatable relative to the lower engagement member and is axially insertable into and removable from the inner tube while the lower engagement member is installed.
10. The dropper post assembly of claim 7 , wherein the lower engagement member comprises a clip that is partially received within a complimentary groove formed in the inner tube sidewall.
11. The dropper post assembly of claim 7 , wherein the lower end of the inner tube comprises a lower tube engagement member and wherein the lower engagement member comprises a second engagement member configured to releasably engage the lower tube engagement member and an axially extending captive sidewall whereby when the lower engagement member is inserted the captive sidewall is disposed laterally between the lower end of the cartridge tube and the inner tube sidewall.
12. The dropper post assembly of claim 11 , wherein the lower engagement member further comprises a lower abutment surface, and wherein when the lower engagement member is inserted with the second engagement member engaging the lower tube engagement member the cartridge tube is retained axially between the lower abutment surface and the axial stop surface, whereby relative axial movement between the cartridge tube and the inner tube is inhibited.
13. The dropper post assembly of claim 12 , wherein the captive sidewall extends axially from the abutment surface and cooperates with the abutment surface to at least partially define a tube recess sized to accommodate the lower end of the cartridge tube, wherein when the lower engagement member is inserted the captive sidewall lower end of the cartridge tube is nested within the tube recess.
14. The dropper post assembly of claim 12 , wherein the upper end of the cartridge tube does not include a fastening mechanism for restricting the axial movement of the cartridge tube relative to the inner tube.
15. The dropper post assembly of claim 11 , wherein the lower tube engagement member and the second engagement member comprise complimentary threads.
16. The dropper post assembly of claim 1 , wherein the upper end of the inner tube includes an inward facing axial stop surface and a lowermost portion of the axial stop surface lies in a laterally extending abutment plane, and wherein the post head member comprises a front mounting portion projecting forwardly beyond a perimeter of the inner tube sidewall and comprising a front fastener aperture wherein a lowermost part of the front fastener aperture lies in a laterally extending post head plane that is disposed axially inboard from the abutment plane.
17. The dropper post assembly of claim 1 , wherein the cartridge cross-sectional area is less than 85% of the interior cross-sectional area.
18. The dropper post assembly of claim 17 , wherein the cartridge cross-sectional area is less than 80% of the interior cross-sectional area.
19. The dropper post assembly of claim 1 , wherein the bumper laterally encircles the cartridge tube.
20. The dropper post assembly of claim 1 , wherein the bumper substantially fills the lateral gap.