US Patent 7478484 Chalk line apparatus with a spool configured to avoid cavitation

A chalk line apparatus having a housing defining a chamber within which a supply of chalk can be stored and a reel within the chamber and mounted for rotation relative to the housing around a first axis. The housing has an opening through which a flexible line emanating from the reel can extend to outwardly of the housing for use. The reel has a spool defining a support against and around which a flexible line can be wrapped. The spool is rotatable around the first axis and has an axial extent. The spool is configured so that line wrapped around the support does not have a substantially cylindrical shape centered on the first axis over any substantial portion of the axial extent of the spool.