Multi-groove and spline connection between gear shaft of a rotary piston machine with internal axis and method of making such a multigroove spline connection

A gear and cardan shaft arrangement, comprising, an internally toothed gear element having internal splines extending radially between inner dedendum and outer addendum circles said internal splines extending axially all the way through said gear element, a cardan shaft having a head element with external teeth between corresponding ones of said inner dedendum and outer addendum circles, a reference pitch circle for said gear and shaft head elements between said inner dedendum and outer addendum circles having the same nominal diameter for said gear element and said head element, said gear element having an abutment face between the opposite sides thereof extending circumferentially between at least one adjacent ones of said splines thereof and radially only between said inner dedendum and outer addendum circles such that said abutment face is only contactable by said teeth of said head element.