Bottom bracket bearing assembly for a bicycle

A bottom bracket bearing for a bicycle is provided which includes an axle, a pair of ball bearings, a flanged cup, and an adjusting cup disposed within a five-way tube. The axle has a reducing quadrangle extending from both ends thereof, and a continuation area between the quadrangle portion an a cylindrical portion of the axle, and has a flat circular flange formed adjacent the cylindrical portion. A joint-packing is positioned against the flat circular flange, the thickness of the joint-packing extending at least 1 mm beyond the flat end of the flanged cup, thereby substantially preventing the crank with the chain wheels from contacting the flanged cup.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a bottom bracket bearing assembly for a 
bicycle, and more particularly to a frame for easily mounting the chain 
wheel with a crank on it. 
2. Prior Art 
A conventional bottom bracket assembly as shown in FIG. 4A, includes an 
axle sleeve A, an axle A1, balls A2, ball seat A3 and nuts A4. All of 
those parts are mounted in a five-way tube A5, as shown in FIG. 4B. In 
practice, it has been found that the conventional assembly has some 
shortcomings. That assembly is difficult to mount, the parts easily loosen 
and fall out, due to the combination not sealing fully. Because of high 
accuracy required for the parts, the production and the assembly is 
difficult and unsuited for normal production. 
Subsequently, a new axle frame with two flanges was developed to improve on 
the above-mentioned shortcomings. As shown in FIG. 5A, this second prior 
art assembly comprises an axle B, an axle sleeve B1, ball bearings B2, B3, 
flanged cup B4, adjusting cup B5, five-way tube B6 and ring B7. The 
assembly of those parts is shown in FIG. 5B. The axle B has two flanges 
B01 and B02 formed thereon, one of a bigger diameter and the other of a 
smaller diameter. In assembly, the larger diameter flange B01 is set in a 
caulking groove B11 of the axle sleeve B1, and the smaller flange B02 is 
set in a shaft bore B12 of the axle sleeve B1. Along with the other parts, 
the axle sleeve B1 is retained within five-way tube B6 for securing the 
axle B tightly in the combination and further for improving the mounting 
accuracy and reducing the production-cost of the assembly. 
Therefore, the problems of the conventional bottom bracket bearing seem to 
be solved, but in practice, a new problem is found. One head of the axle B 
joins with an assembly of a crank and a chain wheel. Referring to FIGS. 5A 
and 5B, the two heads of the axle B are shown to be a reducing quadrangle, 
the continuation area between the reducing quadrangle and the cylindrical 
portion of the axle is formed by four tapers. The function of the 
quadrangle is to secure the assembly of the crank and the chain wheels, as 
shown in FIG. 6A. There are, however, some big problems associated 
therewith. 
The chain wheels C are fastened on the crank D, and a through-hole D1 is 
formed in one end of the crank D for securement to the quadrangular head 
of the axle B. The assembly of the chain wheels C and the crank D is 
fastened on the axle B at the end of the quadrangular head, and the crank 
D is made of an alloy that is softer than the axle B. The through-hole D1 
of the crank D is formed smaller than the axle B, and it is secured on the 
tapers of the axle B by a nut E from the end of said quadrangular head. 
But, corresponding to the different magnitude of force applied when 
tightening the nut E, the crank D is secured on the axle in different 
positions, to cause the base line of the chain wheels C to be out of 
alignment. That alignment error allows the chain to jump off the chain 
wheels C during running or when changing speed, which is one of the 
problems with that assembly. 
A second problem results form the fact that the material of the crank D is 
softer than the axle's material. After pressing against the tapers for 
some time, the through-hole D1 of the crank D becomes enlarged to form a 
tapered hole from the side corresponding to the tapers of the axle, 
causing the chain wheels C to shake on the head of the axle B, as shown in 
FIG. 6A. Further, that condition may cause the chain wheels C to touch 
against the flanged cup B4 and cause damage. 
Another problem is seen during repair of the assembly, as when the assembly 
of the crank D and the chain wheels C or the axle unit B fail and are 
taken apart from each other. During manufacture, the crank D is pressed on 
the axle B, the tapered hole of the through-hole D1 being pressed on the 
axle's tapers tightly. The through-hole D1 is thereby enlarged and when 
installed again it will axially approach the flanged cup. If the repairman 
uses excessive force during threading of the nut, or disassembly and 
mounting of the crank, many times, the chain wheels C will touch against 
the flanged cup on the axle B, as shown in FIG. 6B. Such contact blocks 
the rotation of crank D, causing damage to the crank D. 
SUMMARY OF THE INVENTION 
The present invention provides a bottom bracket bearing assembly for a 
bicycle, which includes an axle, ball bearings, a flanged cup and an 
adjusting cup. The axle has a pair of axially spaced flanges, each with a 
circular arc formed on both sides thereof. A reducing quadrangle extends 
from each end of the axle, and a continuation area is disposed between the 
quadrangle and the cylindrical portion of the axle and is formed with two 
pairs of tapers. Two ball bearings are respectively mounted on the outer 
side of the two axle flanges. The flanged cup and the adjusting cup are 
mounted on the axle, on opposing ends thereof, with their respective male 
threads retaining the axle in the five-way tube of the bicycle. A circular 
bead is formed at the base portion of the tapers, adjacent the side where 
the assembly of the crank and the chain wheels is mounted. A flat circular 
flange is disposed adjacent the cylindrical portion of the axle and a flat 
segment extends between the tapers. A joint-packing is mounted against the 
flat circular flange, the thickness of the joint-packing being about the 
same as the length of the tapers. The outer side of the joint-packing 
should extend slightly beyond the flat end of the flanged cup, so that the 
crank assembly cannot come into contact with the flanged cup.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1, the present invention is shown to include an axle 1, 
ball bearings 2, a flanged cup 3, an adjusting cup 4 and joint-packing 5. 
All of those parts are assembled within a five-way tube 6 of a bicycle. 
The axle 1 is cylindrical with a pair of separate axially spaced flanges 11 
formed thereon, each flange 11 having a circular arcuate surface formed on 
both sides thereof. A reducing quadrangle 12 extends from each end of axle 
1, with the continuation area between the quadrangle 12 and the 
cylindrical portion of the axle being in the form of a circular bead with 
a flat segment 13 and two pairs of tapers 131 formed thereon, and a flat 
circular flange 14 formed adjacent the cylindrical portion of axle 1. The 
ball bearings 2 include a plurality of balls held in a ball retainer. 
The flanged cup 3 and the adjusting cup 4 each have external surfaces 
formed with male threads 31 and 41, and internal surfaces formed with 
counter bores 32 and 42, respectively. The flanged cup 3 and adjusting cup 
4 each have shaft holes 33 and 43 formed therein, and rubber sealing rings 
331 and 431 are respectively secured thereto. 
The joint-packing 5 has a shaft hole 51 formed centrally therethrough. The 
diameter of shaft hole 51 being about equal to the outside diameter of the 
portion of axle 1 having the flat segment 13 and the tapers 131. The 
thickness of joint-packing 5 being equal to the length of the flat segment 
13 and the tapers 131. 
In the assembly, as shown in FIGS. 2A and 2B, the two ball bearings 2 are 
set on said axle I from the two ends thereof and are disposed against the 
outside circular arcuate surfaces of the flanges 11, respectively. Next, 
the flanged cup 3 and adjusting cup 4 are set on the axle 1 and retain the 
ball bearings 2 in respective counter bores 32 and 42, while holding all 
of the above-mentioned parts in the five-way tube 6 by engagement of their 
male threads therewith. Lastly, the joint-packing 5 is set on the flat 
segment 13 of the axle 1, against the flat circular flange 14. The 
opposing side of the joint-packing 5 extends beyond, by at least 1 mm, the 
flat end portion of the flanged cup 3. When mounting the alloy crank 7 
with the chain wheels 8 on one head of said axle 1, as shown in FIG. 3, 
the outside flat of said joint-packing 5 provides a locating surface for 
the mounting and securement of the crank 7.