Industrial robots may consist of an articulated structure comparable to that of the human arm, mounted on a base in a horizontal or vertical position, and having at its extremity a mobile holder for the toolholder (so-called vertical robots). They may also consist of a rectilinear structure often moving on a vertical axis of which the holder forms the terminal part of the operating mechanism often moving on a horizontal axis (horizontal robots). These robots could equally be placed on a beam (beam robots).