  All-electric devices for the generation and filtering of spin currents are of
crucial importance for spintronics experiments and applications. Here we
consider a quantum dot between two metallic leads in the presence of spin-orbit
coupling, and we analyze in the frame of a scattering matrix approach the
conditions for generating spin currents in an adiabatically driven two-terminal
device. We then focus on a dot with two resonant orbitals and show by specific
examples that both spin filtering and pure spin current generation can be
achieved. Finally, we discuss the effect of the Coulomb interaction.
