  By means of electrical transport measurements we have studied the rectified
motion of vortices in ratchet potentials engineered on over-damped Josephson
junction arrays. The rectified voltage as a function of the vortex density
shows a maximum efficiency close a matching condition to the period of the
ratchet potential indicating a collective vortex motion. Vortex current
reversals where detected varying the driving force and vortex density revealing
the influence of vortex-vortex interaction in the ratchet effect.
