  In this talk we review some recent results on the infrared properties of the
gluon and ghost propagators in pure Yang-Mills theories. These results are
obtained from the corresponding Schwinger-Dyson equation formulated in a
special truncation scheme, which preserves gauge invariance. The presence of
massless poles in the three gluon vertex triggers the generation of a dynamical
gluon mass (Schwinger mechanism in d=4), which gives rise to an infrared finite
gluon propagator and ghost dressing function. As a byproduct of this analysis
we calculate the Kugo-Ojima function, required for the definition of the
non-perturbative QCD effective charge within the pinch technique framework. We
show that the numerical solutions of these non-perturbative equations are in
very good agreement with the results of SU(3) lattice simulations.
