Multi-stage sprocket assembly for bicycle

A multi-stage sprocket assembly for a bicycle comprising:

• a small sprocket;
• a large sprocket disposed coaxially with the small sprocket;
• a shift assist projection provided to the large sprocket for assisting a shifting movement of a chain from the small sprocket to the large sprocket;
• a guide face for guiding an outer side face of a link plate of the chain,
• said guide face being formed in a side face of a second tooth of the large sprocket facing the small sprocket, said second tooth being forwardly adjacent, relative to a moving direction of the chain, a first tooth of the large sprocket which comes into engagement with a leading portion of the shifting chain;
• said shift assist projection being so displaced toward the small sprocket that said projection comes into engagement with the shifting chain portion at a position forwardly distant from a position of said engagement between the leading end of the shifting chain portion and said first tooth by a distance which is substantially an integer multiple of a disposing pitch of the large sprocket teeth;
• said shift assist projection having such a radial height as to prevent said projection from extending into a rotary drive-moving path of the chain as fully engaging the large sprocket for propelling the bicycle.

A multi-stage sprocket assembly for a bicycle comprising:

• a small sprocket;
• a large sprocket disposed coaxially with the small sprocket;
• a shift assist projection provided to the large sprocket for assisting a shifting movement of a chain from the small sprocket to the large sprocket;
• a guide face for guiding an outer side face of a link plate of the chain,
• said guide face being formed in a side face of a second tooth of the large sprocket facing the small sprocket, said second tooth being forwardly adjacent, relative to a moving direction of the chain, a first tooth of the large sprocket which comes into engagement with a leading portion of the shifting chain;
• said shift assist projection being so displaced toward the small sprocket that said projection comes into engagement with the shifting chain portion at a position forwardly distant from a position of said engagement between the leading end of the shifting chain portion and said first tooth by a distance which is substantially an integer multiple of a disposing pitch of the large sprocket teeth;
• said shift assist projection having such a radial height as to prevent said projection from extending into a rotary drive-moving path of the chain as fully engaging the large sprocket for propelling the bicycle;
• and
• chain-hook preventing means provided at a side face of said shift assist projection facing the small sprocket;
• when said shift assist projection comes aside an inner link plate of the shifting chain portion, said chain-hook proventing means allowing an outer link plate of the chain portion forwardly adjacent said inner link plate to radially move closer to the small sprocket while preventing said outer link plate from being hooked at said shift assist projection.

A multi-stage sprocket assembly for a bicycle comprising:

• a small sprocket;
• a large sprocket disposed coaxially with the small sprocket;
• a shift assist projection provided to the large sprocket for assisting a shifting movement of a chain from the small sprocket to the large sprocket;
• a guide face for guiding an outer side face of a link plate of the chain,
• said guide face being formed in a side face of a second tooth of the large sprocket facing the small sprocket, said second tooth being forwardly adjacent, relative to a moving direction of the chain, a first tooth of the large sprocket which comes into engagement with a leading portion of the shifting chain;
• said shift assist projection being so displaced toward the small sprocket that said projection comes into engagement with the shifting chain portion at a position forwardly distant from a position of said engagement between the leading end of the shifting chain portion and said first tooth by a distance which is substantially an integer multiple of a disposing pitch of the large sprocket teeth;
• said shift assist projection having such a radial height as to prevent said projection from extending into a rotary drive-moving path of the chain as fully engaging the large sprocket for propelling the bicycle;
• and
• an auxiliary shift assist projection disposed with substantially one pitch distance rearwardly in said drive direction from said shift assist projection.