1. A direct electric current generation system comprising at least one polymer membrane fuel cell stack, means for feeding a fuel, optionally hydrogen, in parallel to the anodic compartments of said cells, means for feeding air in parallel to the cathodic compartments of said cells and means for adjusting the temperature of said cells comprising circulating a coolant inside said cells at constant flow-rate, wherein the water and thermal management of the system is regulated by acting only on the flow-rate of said air feed and on the cell inlet temperature of said coolant.
2. The system of claim 1 wherein the pressure of said air inside the cells is adjusted by acting on its flow-rate across a component imposing a calibrated pressure drop.
3. The system of claim 2 wherein said component imposing a calibrated pressure drop is a reticulated current collector.
4. The system of claim 3 wherein said reticulated current collector comprises at least one member selected from the group consisting of metal foam, metal mesh, expanded or perforated sheet and sintered material.
5. The system of claim 2 wherein said calibrated pressure drop is comprised between 1.2 and 2.5 times the stoichiometric flow-rate.
6. The system of claim 1 wherein said feeding of a fuel in parallel to the anodic compartments of said cells and said coolant circulation inside said cells are oriented in countercurrent.
7. The system of claim 6 wherein said air feed to the cathodic compartments of said cells is oriented in concurrent with respect to said coolant circulation and in countercurrent with respect to said fuel feed to the anodic compartments.
8. The system of claim 1 wherein said means for feeding a fuel in parallel to the anodic compartments of said cells consist of a hydrogen recirculator comprising at least one pump or ejector, a humid hydrogen purge and a pure dry hydrogen replenishment.
9. The system of claim 1 wherein said coolant constant flow-rate is between 10 and 50 lmin per square meter of active area.
10. The system of claim 1 wherein said means for feeding air in parallel to the cathodic compartments of said cells comprise at least one compressor or one fan.
11. The system of claim 1 wherein the water balance is maintained so as to withdraw the sole water produced by the combination of said fuel and said air inside said fuel cell stack through the anodic purge and the cathodic exhaust, without any additional external supply of water.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A tool (2) for the manufacture of a can body carried by a transformation machine (1) comprising:
a lower tool part (3) operably affixed to and supported by the transformation machine (1), an upper tool part (4) operably supported to be linearly movable toward, and away from the lower tool part (3), the upper tool part (4) including a servo drive arrangement (5), the upper tool part (4) comprising a first extrusion punch (7) in operable arrangement with the servo drive arrangement (5), the upper tool part (4) operably arranged concentric to a center axis (6), a first downholder (9) in operable arrangement with the first extrusion punch (7), the upper tool part (4) comprising a second extrusion punch (8) operably arranged in the interior of the first extrusion punch (7) so as to be movable along the center axis (6), the lower tool part (3) having a planar surface (17) for supporting a planar metal sheet (18) to be formed finally into the can body, the lower tool part (3) having a stepped through-passage (19) therein concentric with the center axis (6), the stepped through-passage (19) including an annular step (20), the first extrusion punch (7) for operatively passing within the stepped through-passage (19) above the annular step (20), the second extrusion punch (8) for operatively passing within the stepped through-passage (19) below the annular step (20),
the first downholder (9) in operative arrangement with the first extrusion punch (7) for initially applying a controlled force to the planar sheet (18) for forming a pre-can body cup from the planar metal sheet (18), the servo drive arrangement (5) which is operable selectively electronically switchable between a first operating mode and a second operating mode, the first operating mode of the servo drive arrangement (5) is a position controlled operation for detecting the position of the extrusion punch (7) and moving the extrusion punch (7) based on feedback of the detected position of the extrusion punch (7) in accordance with a predetermined travel distance-time curve for moving the first extrusion punch (7) in a coordinated manner with the second extrusion punch (8) above the annular step (20) until the first extrusion punch (7) reaches the annular step (20) and the second operating mode is a force controlled operation for controlling electronically the force applied by the first extrusion punch (7) to the pre-can body cup between the first extrusion punch (7) and the annular step (20) in a downhold function by detecting the force applied by the first extrusion punch (7) to the pre-can body cup for ensuring correspondence to a predetermined force or a predetermined force graph, the switching of the servo drive arrangement (5) from the first operating mode to the second operating mode is executed when the first extrusion punch (7) changes its function from a draw function to the downhold function at the annular step (20),
the second extrusion punch (8) arranged coaxially with the first extrusion punch (7) for further drawing and stretching the pre-can body cup below the annular step (20) for forming the can body, and,
the first extrusion punch (7) and the second extrusion punch (8) are driven to run in the same direction.
2. A tool according to claim 1, wherein the second extrusion punch (8) is arranged longitudinally movably in a passage formed centrally in the first extrusion punch (7).
3. A tool according to claim 1, wherein the first extrusion punch (7) is tubular.
4. A tool according to claim 1, wherein the first downholder (9) and a first downholder counter surface (21) are in operable arrangement with the first extrusion punch (7) during the first operating mode.
5. A tool according to claim 4, wherein a second downholder and a stationary second downholder counter surface are in operable arrangement with the first extrusion punch (7) during the second operating mode.
6. A tool according to claim 5, wherein the second downholder comprises a pressure ring (10) in operable arrangement with the first extrusion punch (7).
7. The tool according to claim 5, wherein the stationary second downholder counter surface is formed by an annular step (20) which is arranged at a fixed distance from the first downholder counter surface (21).
8. The tool according to claim 4, wherein the first downholder counter surface (21) is formed by the planar surface (17).
9. The tool according to claim 1, wherein the servo drive arrangement (5) is also for controlling the second extrusion punch (8) operable selectively electronically in a position or force-controlled manner.
10. A method for the manufacture of a can body with a tool (2) carried by a transformation machine (1), the tool (2) including a lower tool part (3) operably affixed to and supported by the transformation machine (1), an upper tool part (4) operably supported to be linearly movable toward, and away from the lower tool part (3), the upper tool part (4) including a servo drive arrangement (5), the upper tool part (4) comprising a first extrusion punch (7) in operable arrangement with the servo drive arrangement (5) and operably arranged concentric to a center axis (6), a first downholder (9) in operable arrangement with the first extrusion punch (7), the upper tool part (4) comprises a second extrusion punch (8) operably arranged in the interior of the first extrusion punch (7) so as to be movable along the center axis (6), the lower tool part (3) having a planar surface (17) for supporting a planar metal sheet (18) to be finally formed into the can body, the lower tool part (3) having a stepped through-passage (19) therein concentric with the center axis (6), the stepped through-passage (19) including an annular step (20), the first extrusion punch (7) for operatively passing within the stepped through-passage (19) above the annular step (20), the second extrusion punch (8) for operatively passing within the stepped through-passage (19) below the annular step (20), a second extrusion punch (8) arranged coaxially with the first extrusion punch (7), the servo drive arrangement (5) for operable selective electronic switching between a first operating mode which is a position controlled operation and a second operating mode which is a force controlled operation said method comprising the steps of:
forming a pre-can body cup by deep drawing in a predetermined draw direction from a pre-cut planar metal sheet (17) by deep-drawing with the servo drive arrangement (5) by detecting the position of the extrusion punch (7) and moving the extrusion punch (7) based on feedback of the detected position of the extrusion punch (7) in the first operating mode in accordance with a predetermined travel distance-time curve causing the first extrusion punch (7) to move in a coordinated manner with the second extrusion punch (8) until the first extrusion punch (7) reaches the annular step (20) and,
in a second step, deep drawing and stretching the pre-can body cup in the same predetermined draw direction for forming the can body by the servo drive arrangement (5) electronically switching to the second operating mode for causing the first extrusion punch (7) of the first deep-draw step serving as a downholder in operable relationship with the annular step (20) for the second deep-draw step and for controlling electronically the force applied by the first extrusion punch (7) to the pre-can body cup during downholding and for detecting the force applied by the first extrusion punch (7) to the pre-can body cup for ensuring correspondence to a predetermined force or a predetermined force graph to produce the can body.