Device for balancing forces, in particular weight, acting on a robot arm or the like

A device for balancing forces, in particular weight, acting on a robot arm or the like which is hinged to rotate about an axis, in particular a horizontal axis, said device comprising a rigid auxiliary part hinged about an axis parallel to the axis of the robot arm, said part including two transverse arms extending on either side of its axis and having ends which are symmetrical about said axis, said ends being suitable for bearing against a rectilinear portion of a moving member which is moveable in translation and which is subjected to a return force towards an initial position, said return force being proportional to the distance between said initial position and the position occupied by the moving member, and rotary drive means for rotating the auxiliary part about its own axis at an angular speed which is equal in absolute value to one half of the angular speed of the robot arm, wherein the device comprises:

• at least one other rigid auxiliary part so as to form an even number of auxiliary parts hinged about respective parallel and coplanar axes, with each auxiliary part supporting two transverse arms;
• synchronizing means suitable for rotating said auxiliary parts at angular speeds which are equal in absolute value but which are in opposite directions in pairs;
• at least one of the auxiliary parts being coupled to said rotary drive means;
• and the assembly being set up in such a manner that when the robot arm is in a position in which the resultant couple applied about the hinge axis of the arm by said forces to be balanced is zero, the ends of the transverse arms of all of the auxiliary parts bear simultaneously against the rectilinear portion which is in its initial position.