Press with two drive motors

Method for operating a press (10), the press (10) comprising:

• a plunger (21) which is movable by a press drive (25) in a stroke direction H;
• wherein the press drive (25) includes a first drive motor (26) and a second drive motor (27) which are connected to the plunger (21) via a drive unit (33);
• wherein the drive unit (33) includes a first eccentric (34) connected to the first drive motor (26) and a second eccentric (36) connected to the second drive motor (27);
• wherein the first eccentric (34) is operatively connected to main connecting rod (35) and the second eccentric (36) is operatively connected to a control connecting rod (37);
• wherein drive unit (33) further comprises a multi-arm lever (38) operatively connected via a first pivot bearing (39) to the main connecting rod (35) and via a second pivot bearing (40) to the control connecting rod (37) and via a third pivot bearing (41) to the plunger (21);
• a control arrangement (28) for controlling at least the first drive motor (26) and the second drive motor (27) for moving the plunger (21) and applying a plunger force thereto in accordance with a predetermined characteristic plunger curve (K);
• wherein the two drive motors (26, 27) are controlled in accordance with the characteristic plunger curve (K) in such a way that at least one additional condition (Z) which is independent of a change of plunger position (P) as predetermined by the characteristic plunger curve (K) and/or the plunger force (F) is fulfilled;
• and,
• wherein each of the first pivot bearing (39) and the second pivot bearing (40) and the third pivot bearing (41) include in each case two drive components (G1, G2) supported to be movable relative to each other and wherein a first additional condition of the at least one additional condition (Z) is fulfilled when the two drive components (G1, G2) in each of the first pivot bearing (39) and the second pivot bearing (40) and the third pivot bearing (41) have a predetermined relative movement between the two drive components (G1, G2) for maintaining a predetermined minimum thickness of a lubricant film therebetween independent of whether the plunger (21) changes the plunger position (P) or whether the plunger (21) is moving or is stopped, said method comprising the following steps:
• providing a change in the plunger position (P) and/or the plunger force (F) directive via the characteristic plunger curve (K);
• providing the at least one additional condition (Z) which is independent of the change in the plunger position (P) and/or the plunger force (F) provided by the characteristic plunger curve (K);
• operating the first drive motor (26) and the second drive motor (27) in such a way that the change in the plunger position (P) and/or the plunger force (F) corresponds to the characteristic plunger curve (K) and, additionally the first additional condition of the at least one additional condition (Z) is fulfilled.