Abstract: A diaphragm press comprises a cylindrical vessel (7) rotating about its longitudinal axis and divided into two diametrically opposing parts by a flexible diaphragm (8). A series of perforated longitudinal channels (10) is fixed to a part of the inner surface of the vessel and connected at one end to an external manifold (12) for collecting the juice. At their other end, the channels (10) are connected to at least one further manifold (15) which is connected to a pumping unit (99) for feeding water under pressure by way of valves (160). The flexible diaphragm (8) is of such dimensions as to perfectly mate with the wall to which the channels (10) are connected and with the channels themselves so as to perfectly close the holes (100) of these channels (10) when the diaphragm is thrust from its rear by the pressurized fluid.