Bicycle crank assembly
A bicycle sprocket crank assembly is comprised of first and second crank arms joined to a spindle. One of the crank arms and the spindle may be fabricated as a unitary structure, or both cranks arms may be formed as separate structures and joined together. In either case the spindle has at least a first coupling end with an internally tapped axial bore defined therein and the second crank arm forms at least a first socket at its axle end. At least a first wedging sleeve is provided and is disposed about the first coupling end of the spindle. The first wedging sleeve conforms to the shapes of both the first coupling end of the spindle and the hollow cavity in the first socket. Either the coupling end of the spindle or the hollow cavity is axially tapered, and the wedging sleeve is tapered to match. The wedging sleeve is split in an axial direction, so that as the first socket is drawn onto the first coupling end of the spindle, the wedging sleeve is increasingly forced in between the inner radial surface of the hollow cavity of the socket and the outer radial surface of the coupling end of the spindle.
1. A bicycle sprocket crank assembly, comprising:
a. a spindle comprising a first coupling end and a second coupling end opposite said first coupling end, wherein said first and second coupling ends each comprise an internally tapped axial bore defined therein and said first and second coupling ends are each tapered such that an annular cross-sectional area of said first and second coupling ends narrows in an axial direction with increasing distance from each other;
b. a first crank arm comprising an axially oriented first socket for engagement with said first coupling end;
c. a second crank arm with an axially oriented second socket for engagement with said second coupling end,
d. wherein said first and second sockets each have a hollow cavity defined therein, and said first coupling end of said spindle fits into said hollow cavity of said first socket, and said first coupling end and said hollow cavity of said first socket are mating elements, and said second coupling end of said spindle fits into said hollow cavity of said second socket, and said second coupling end and said hollow cavity of said second socket are mating elements;
e. a first wedging sleeve disposed about said first coupling end of said spindle;
f. a second wedging sleeve disposed about said second coupling end,
g. wherein said first and second wedging sleeves each comprise an inner surface and an outer surface and said first and second wedging sleeves conform to the shapes of said first and second coupling ends, respectively, and said hollow cavity of said first and second crank arms, respectively, and said inner surfaces of said first and second wedging sleeves are axially tapered to match the taper of said first and second coupling ends, respectively, and wherein said outer surfaces of said first and second wedging sleeves have a cylindrical shape such that said hollow cavities of said first and second sockets completely, radially surround said first and second coupling ends and said first and second wedging sleeves, and said first and second wedging sleeves are each split longitudinally in an axial direction along the entire length of said first and second wedging sleeves and thereby radially expands as said first and second coupling ends of said spindle are advanced into said hollow cavity of said first socket and second socket, respectively;
h. a first threaded fastener; and a second threaded fastener, said first and second threaded fasteners each having a shank and a head, wherein said shank of said first and second threaded fastener is engageable in said internally tapped axial bore of said first and second coupling end, respectively, and wherein said head of said first and second threaded fastener immobilizes said spindle and said first and second crank arm relative to each other to create a torsional connection between the first and second crank arms and the spindle and simultaneously eliminate axial movement in the first and second wedging sleeves.
2. A bicycle sprocket crank assembly according to claim 1 , wherein said first and second wedging sleeves are internally tapered split bushing.
3. A bicycle sprocket crank assembly according to claim 2 , wherein said head of first threaded fastener bears against said first wedging sleeve and said head of said second threaded fastener bears against said second wedging sleeve.
4. A bicycle sprocket crank assembly according to claim 1 further comprising
a. a first annular stop spacer disposed about said first coupling end and abutting said first wedging sleeve; and
a second annular stop spacer disposed about said second coupling end and abutting said second wedging sleeve.