Bicycle driving unit with sprocket and cranks - is assembled by friction welding centered components with conical seats

摘要

The bicycle driving unit consists of cranks, sprocket and crank driven shaft. This unit is made without metal machining at the connecting areas, instead being joined by an automatic process on assembling by friction welding. As a result the main sprocket wheel in particular has no undesirable deviations on rotating. The crank (1) has a hollow conical seat (3). The sprocket wheel (5) has a central conically pressed out hub (6) and the shaft (9) has a conical end (11). The sprocket hub is sandwiched between the hollow conical seat and the shaft conical end. The hollow conical seat in the crank is continued as a cylindrical relieving bore (4). The conical components are automatically centred on pressing together and form a well aligned assembly on friction welding.