We propose an interferometric device which generates spin-polarized electric currents based on an Aharonov-Bohm ring geometry. The device is driven by a temperature gradient and a magnetic flux without any voltage bias. Remarkably, no ferromagnetic contact is neccessary once the two-path interference effects are present combined with an spin-orbit interaction. A large amplitude of spin current signal occurs where the charge current is small or even vanishing thus easily creating pure spin currents by applying a magnetic field. Our proposal provides an ingredient of information processing devices in a generic caloritronic setup.