Bicycle chain wheel structure
A bicycle chain wheel structure is configured with a right crank arm portion and an axle portion that are integrally formed together as a one-piece, unitary member. The right crank arm portion has an inner end integrally formed with the axle portion. The right crank arm portion has an outer end with a pedal mounting arrangement. The axle portion has a first end that is integrally formed with the right crank arm portion and a second end with a crank arm mounting arrangement. The axle portion has external threads disposed between the first and second ends of the axle portion. Thus, a portion of a bottom bracket is partially integrated into the bicycle chain wheel structure. Preferably, the chain guard is integrated into the right crank arm as a one-piece, unitary member. This arrangement reduces parts and manufacturing costs of the bicycle chain wheel structure.
1. A bicycle chain wheel structure comprising:
a right crank arm portion having a pedal mounting arrangement;
an axle portion having a first end integrally formed with the right crank arm portion as a one-piece, unitary member and a second end with a crank arm mounting arrangement, the axle portion having external threads disposed between the first and second ends of the axle portion and an internal bore extending between the first and second ends; and
a left crank arm detachably, non-rotatably mounted on the second end of the axle portion,
the crank arm mounting arrangement of the second end of the axle portion including internal threads with a mounting bolt threadedly coupled thereto to axially retain the left crank arm on the second end of the axle portion, and a locking member threadedly coupled to the left crank arm,
the locking member including a first surface facing radially inwardly which is opposed to a first surface facing radially outwardly of the mounting bolt, and
the locking member further including a second surface facing radially outwardly which is opposed to a second surface facing radially inwardly of the mounting bolt such that the locking member covers an axially outwardly facing end surface of the mounting bolt.
2. The bicycle chain wheel structure according to claim 1 , further comprising
a chain guard portion and a plurality of discrete circumferentially spaced chain wheel attachment structures integrally formed with the right crank arm portion as a one-piece, unitary member, the chain guard portion having a continuous annular ring section extending around a central axis of the axle portion, the continuous annular ring section being disposed radially outwardly of the discrete circumferentially spaced chain wheel attachment structures.
3. The bicycle chain wheel structure according to claim 2 , wherein
the internal threads of the crank arm mounting arrangement of the second end of the axle portion are disposed adjacent a free edge of the second end of the axle portion.
4. The bicycle chain wheel structure according to claim 3 , wherein
the crank arm mounting arrangement of the second end of the axle portion includes a plurality of serrations that non-rotatably mate with a plurality of serrations of the left crank arm.
5. The bicycle chain wheel structure according to claim 4 , wherein
the serrations of the crank arm mounting arrangement of the second end of the axle portion are disposed on an external surface of the second end of the axle portion.
6. The bicycle chain wheel structure according to claim 5 , wherein
the external threads of the axle portion includes a first external threads disposed adjacent the first end of the axle portion and a second external threads disposed adjacent the second end of the axle portion, the second external threads having a smaller outer diameter than the first external threads.
7. The bicycle chain wheel structure according to claim 1 , wherein
the crank arm mounting arrangement of the second end of the axle portion includes a plurality of serrations that non-rotatably mate with a plurality of serrations of the left crank arm.
8. The bicycle chain wheel structure according to claim 7 , wherein
the serrations of the crank arm mounting arrangement of the second end of the axle portion are disposed on an external surface of the second end of the axle portion.
9. The bicycle chain wheel structure according to claim 1 , wherein
the internal threads of the crank arm mounting arrangement of the second end of the axle portion are disposed adjacent a free edge of the second end of the axle portion.
10. The bicycle chain wheel structure according to claim 9 , wherein
the crank arm mounting arrangement of the second end of the axle portion includes a plurality of serrations that non-rotatably mate with a plurality of serrations of the left crank arm.
11. The bicycle chain wheel structure according to claim 10 , wherein
the serrations of the crank arm mounting arrangement of the second end of the axle portion are disposed on an external surface of the second end of the axle portion.
12. The bicycle chain wheel structure according to claim 1 , further comprising
a left cone of a left bearing set threadedly mounted to the second end of the axle portion.
13. The bicycle chain wheel structure according to claim 12 , further comprising
a right cone of a right bearing set threadedly mounted to the axle portion adjacent the first end of the axle portion.
14. The bicycle chain wheel structure according to claim 13 , wherein
the crank arm mounting arrangement of the second end of the axle portion includes a plurality of external serrations that non-rotatably mate with a plurality of internal serrations of the left crank arm.
15. The bicycle chain wheel structure according to claim 1 , wherein
the internal bore of the axle portion having a first section arranged at the first end having a maximum internal diameter of the internal bore, a second section arranged at the second end having a minimum internal diameter of the internal bore and at least one intermediate section arranged between the first and second sections having an intermediate internal diameter of the internal bore, each of the sections of the internal bore being arranged to form a non-conical internal surface along an entire axial length of the internal bore with each of the internal sections decreasing in transverse width as the internal surface approaches the second section from the first section.
16. The bicycle chain wheel structure according to claim 1 , wherein
the locking member is a ring shaped member with external threads that threadedly engage the left crank arm.
17. The bicycle chain wheel structure according to claim 16 , wherein
the mounting bolt includes a bore having a torque transmitting surface that is sized to be engageable through a central opening of the ring-shaped locking member after the locking member is threadedly coupled to the left crank arm, the torque transmitting surface being disposed at an inner end of the bore that is spaced axially inwardly from the locking member.
18. The bicycle chain wheel structure according to claim 17 , wherein
the locking member includes a plurality of blind bores that are circumferentially spaced apart that are configured and arranged to non-rotatably engage an installation tool.
19. The bicycle chain wheel structure according to claim 1 , wherein
the mounting bolt includes a torque transmitting surface, the torque transmitting surface and the locking member being arranged and configured such that the torque transmitting surface is engageable after the locking member is threadedly coupled to the left crank arm, the torque transmitting surface being disposed at an inner end of the bore that is spaced axially inwardly from the locking member.