Pedal-operated crank drive assembly for a bicycle

Abstract

A pedal-operated crank drive assembly for a bicycle includes a crank axle, a crankset rotatably disposed on the crank axle and including a tubular mount portion which surrounds the crank axle, a crankarm having a drive delivering head which is coupled to the crank axle to be rotated therewith and which has a plurality of angularly displaced recesses, a plurality of pawls disposed respectively in the recesses to be movable between driving and idle positions, and an annular toothed member disposed on the tubular mount portion to couple with the pawls to form a uni-directional mechanism. A plurality of biasing members are disposed to bias a respective one of the pawls to the driving position. A flexible annular shield member is disposed to prevent entry of extraneous dirt into the drive delivering head.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiment of the invention, with reference to the accompanying drawings, in which:

FIG. 1 is a partly sectional view of a conventional crank drive assembly for a bicycle;

FIG. 2 is a cross-sectional view of the conventional crank drive assembly shown in FIG. 1, taken along lines II-II thereof;

FIG. 3 is a sectional view of the preferred embodiment of a pedal-operated crank drive assembly for a bicycle according to this invention;

FIG. 4 is a fragmentary enlarged sectional view of a portion of the preferred embodiment;

FIG. 5 is a schematic side view of the preferred embodiment; and

FIG. 6 is a cross-sectional view of the preferred embodiment shown in FIG. 3, taken along lines VI-VI thereof.

Claims

1. A pedal-operated crank drive assembly for a bicycle including a bottom bracket shell which has a tubular wall that confines an accommodation chamber extending along a rotating axis, and that extends along the rotating axis to terminate at left and right peripheral walls, said pedal-operated crank drive assembly comprising: a crank axle which is adapted to be mounted to be rotatable relative to the tubular wall about the rotating axis, which includes an intermediate segment that is adapted to be received in the accommodation chamber of the tubular wall, left and right mounting segments that extend from said intermediate segment and beyond the left and right peripheral walls, respectively, and a right coupling segment that extends from said right mounting segment to terminate at a coupling end;a crankset disposed on and rotatable relative to said right mounting segment about the rotating axis, and including a chainring carrier which has a proximate major wall surface that is adapted to confront the right peripheral wall, and a distal major wall surface that is opposite to said proximate major wall surface along the rotating axis, anda tubular mount portion which is opposite to said chainring carrier along the rotating axis, and which is disposed to surround said right mounting segment;a right crankarm including a drive applying end for receiving a pedaling drive, anda drive delivering head which is opposite to said drive applying end to deliver the pedaling drive, and which is coupled to said right coupling segment so as to be rotated with said crank axle about the rotating axis, said drive delivering head having a forward major wall surface which confronts said distal major wall surface, and which has an accommodating opening extending away from said distal major wall surface and along the rotating axis to form an inner surrounding wall surface that is spaced apart from said tubular mount portion to define an annular accommodation space, and that has a plurality of recesses which are angularly displaced from one another about the rotating axis;a plurality of pawls disposed respectively in said recesses, and movable between a driving position, where said pawls extend radially into said annular accommodation space, and an idle position, where said pawls are retracted radially and respectively into said recesses;an annular toothed member which is disposed on said tubular mount portion, and which extends into said annular accommodation space to engage said pawls so as to form a uni-directional mechanism that enables transmission of the pedaling drive when said annular toothed member engages said pawls in the driving position to thereby drive said chainring carrier to rotate in a clockwise direction, and that disenables the transmission of the pedaling drive when said annular toothed member passes over said pawls and forces said pawls to the idle position to thereby permit said chainring carrier to remain unmoved in a counterclockwise direction;a plurality of biasing members which are respectively received in said recesses, and each of which is disposed to bias a respective one of said pawls to the driving position; anda flexible annular shield member which is fitted in said accommodating opening.

2. The pedal-operated crank drive assembly of claim 1, wherein said drive delivering head is integrally formed with said drive applying end.

3. The pedal-operated crank drive assembly of claim 1, further comprising two annular anti-friction bearings which are interposed between said chainring carrier and said right mounting segment, and between said tubular mount portion and said right mounting segment, respectively, so as to permit rotation of said crankset relative to said right mounting segment.

4. The pedal-operated crank drive assembly of claim 1, wherein said flexible annular shield member has an outer peripheral edge portion that is disposed to be engaged with said inner surrounding wall surface, and an inner peripheral edge portion that is opposite to said outer peripheral edge portion in radial directions, and that is kept dragging on said tubular mount portion when said drive delivering head is rotated about the rotating axis so as to prevent entry of extraneous dirt into said annular accommodation space.

5. The pedal-operated crank drive assembly of claim 4, wherein said inner surrounding wall surface includes smaller-diameter and larger-diameter inner surface segments which are disposed proximate to and distal from said forward major wall surface, respectively, and which define said accommodating opening and said annular accommodation space, respectively, and an annular shoulder surface segment which is formed between said smaller-diameter and larger-diameter inner surface segments, said outer peripheral edge portion of said flexible annular shield member being configured to abut against said larger-diameter inner surface segment and said annular shoulder surface segment.

6. The pedal-operated crank drive assembly of claim 1, wherein said right coupling segment has an external toothed portion which extends parallel to the rotating axis, said drive delivering head having an internal toothed portion which threadedly engages said external toothed portion so as to couple said drive delivering head to said crank axle.