Fluid pump with flexible pump chamber

A fluid pump, particularly for connection to the blood circulatory system of a living being, comprising a pump chamber (1) having an inlet opening (2) at one end thereof and an outlet opening (3) at the opposite end thereof, a first non-return valve (4) connected to the inlet opening and permitting a fluid flow only in the direction into the pump chamber (1) through the inlet opening, and a second non-return valve (5) connected to the outlet opening and permitting a fluid flow only in the direction out from the pump chamber (1) through the outlet opening, the inlet and the outlet (2,3) being movable in relation to each other in the direction of the extension of the pump chamber (1) between the inlet and the outlet (2, 3) and being connected to controllable drive means (6;

• 12, 13, 14, 15) for periodic movement thereof alternatively towards and away from each other in said direction of extension, the interior volume existing in the pump chamber (1) between the inlet (2) and outlet (3) being variable in correspondence with the relative distance between them in said direction of extension, characterized in that the pump chamber (1) on the outside thereof is acted upon by the surrounding pressure, that it has a wall at least partially of a flexible material, and that it under the influence of a pressure difference, which is caused by the surrounding pressure exceeding the interior pressure of the pump chamber (1) and which is greater than the required opening pressure difference for the first non-return valve (4) connected to the inlet (2), is collapsible by a volume at least corresponding to the maximum increase of said interior volume of the pump chamber when the inlet (2) and the outlet (3) are moved away from each other, said collapsibility being provided by one nor more defined wall portions (11) having a reduced wall thickness.