(WO2005041332-A2)   NOVELTY - Polymer membrane fuel cell stack consists of a filter-press modular arrangement comprising single proton exchange membrane fuel cells and of cooling devices. Each fuel cell comprises ion-exchange membranes and perimetrical sealing gaskets shaped as frames suitable for housing current collectors within their hollow central part. The bipolar plates and the gaskets are provided with passage openings comprising holes.    USE - As electrochemical generator of electrical energy.    ADVANTAGE - The design is directed to prevent the build up of metal ions in the membranes and the consequent voltage decay. The lateral migration inside the ionomer membranes of the metal ions contained in the cooling fluid is prevented.    DETAILED DESCRIPTION - Polymer membrane fuel cell stack consists of a filter-press modular arrangement comprising single proton exchange membrane fuel cells and of cooling devices. Each cell is delimited by a pair of metal bipolar plates (6). It comprises ion-exchange membranes (2) and perimetrical sealing gaskets (8, 10, 14) shaped as frames suitable for housing current collectors within their hollow central part. The bipolar plates and the gaskets are provided with passage openings comprising holes for feeding the reactant gases, for extracting the residual gases with the reaction products, for injecting and discharging a thermostatting fluid. The lateral migration of ions proceeding from the thermostatting fluid inside the ion-exchange membranes is prevented.    DESCRIPTION OF DRAWING(S) - The figure shows the stray current distribution in the stack.    Ion-exchange membranes (2)    Bipolar plates (6)    Gaskets (8,10,14)    Sheets of electrically conductive material for connection of stack to external electrical circuit (12)    Stack plate (15)    Sheet of non-conductive material for electrical insulation of stack plates (17)    Stray currents emitted by annular surface (27)    Annular surfaces (28)    Resulting equipotential surfaces (29)