The present invention refers to a process for obtaining a plant extract containing condensed tannins, with astringent characteristics, modified by copolymerization, to be used for tanning and retanning of skins; it also refers to the plant extract thus obtained; and it also refers to the use thereof for treating hides. A substrate transfer apparatus according to the present invention includes a multijoint arm whose one end is arranged on a base and the other end is connected to a hand for supporting a substrate, a linear guide for guiding a rectilinear movement of the hand, and a belt driving mechanism for moving the hand along a guide rail of the linear guide. A sensor is utilized for sensing the position of the disc relative to the guide and to provide a signal to an actuator that operates to cause the finger to move to its outwardly extended position. A power supply circuit is housed by the housing and is adapted to input a line voltage from the elongated line conductor and output direct current voltages. Of course, many other embodiments in accordance with the invention are included within the scope of the present invention.