Multi-stage diaphragm suction pump

A multi-stage diaphragm suction pump (10), comprising at least two pump chambers (1, 2, 3, 4), each having a fluid inlet (6) having at least one inlet valve, and a fluid outlet (7) having at least one outlet valve, and comprising a suction line, which connects the fluid inlets (6) of the pump chambers (1, 2, 3, 4), wherein successive ones of the pump chambers (1, 2, 3, 4) are each connected to one another by at least one connection line (8, 9, 11) in such a way that, when a differential pressure in the suction line is reached/exceeded, the diaphragm pump (10) changes from parallel operation of the pump chambers (1, 2, 3, 4) thereof to an operating mode of said pump chambers that is at least also serial, and at least one check valve, which opens to a downstream pump stage, is interposed in each of inflow and outflow regions of the at least one connection line (8, 9, 11), and in order to improve an intake pressure, a suction-side opening (12) of the at least one connection line (8, 9, 11) or, in order to improve a suction capacity, a pressure-side opening (13) of the at least one connection line (8, 9, 11) at least in one of the pump chambers (1, 2, 3, 4) is arranged in a region (B, C) of the pump chamber (1, 2, 3, 4) on which a diaphragm associated with said pump chamber rolls first during a pump cycle and wherein a connecting rod that can be pivoted in a connecting rod oscillation plane is assigned to each of the pump chambers (1, 2, 3, 4) of the diaphragm pump (10), and at least in one of the pump chambers (1, 2, 3, 4), the suction-side or the pressure-side opening (12, 13) of the at least one connection line (8, 9, 11) is provided in the connecting rod oscillation plane and wherein at least in one of the pump chambers (1, 2, 3, 4), the suction-side or the pressure-side opening (12, 13) of the at least one connection line (8, 9, 11) and the suction valve are arranged approximately on a line extending transversely to the connecting rod oscillation plane.