A filter plate assembly for a filter press, comprising: a filter frame defining a closed perimeter delimiting an open space , a filter plate supported on the filter frame such that the filter plate extends over the open space, a retainer groove provided on a side of the filter frame facing the filter plate (3, and a diaphragm extending over the open space , and attached to the filter plate assembly, between the filter frame and the filter plate , the diaphragm further comprising: - on a side facing the filter frame, a seal bead for sealing the diaphragm against the filter plate , and - on a side facing the filter plate, a retainer bead received within the retainer groove , such that the diaphragm is retained in position between the filter frame and the filter plate , wherein the filter frame forms a lateral wall of a filter chamber , when in use, characterized in that the seal bead comprises a first seal lip and a second seal lip , wherein the first seal lip is vertically elevated from the second seal lip , wherein the filter plate is arranged on the filter frame so as to allow a limited vertical travel of the filter frame with respect to the filter plate , such that the filter frame has: - a lowermost position, in which only the first seal lip is in contact with the filter plate , and - an uppermost position, in which both the first seal lip and the second seal lip are in contact with the filter plate . a filter frame defining a closed perimeter delimiting an open space , a filter plate supported on the filter frame such that the filter plate extends over the open space, a retainer groove provided on a side of the filter frame facing the filter plate (3, and a diaphragm extending over the open space , and attached to the filter plate assembly, between the filter frame and the filter plate , the diaphragm further comprising: - on a side facing the filter frame, a seal bead for sealing the diaphragm against the filter plate , and - on a side facing the filter plate, a retainer bead received within the retainer groove , such that the diaphragm is retained in position between the filter frame and the filter plate , - on a side facing the filter frame, a seal bead for sealing the diaphragm against the filter plate , and - on a side facing the filter plate, a retainer bead received within the retainer groove , such that the diaphragm is retained in position between the filter frame and the filter plate , wherein the filter frame forms a lateral wall of a filter chamber , when in use, characterized in that the seal bead comprises a first seal lip and a second seal lip , wherein the first seal lip is vertically elevated from the second seal lip , wherein the filter plate is arranged on the filter frame so as to allow a limited vertical travel of the filter frame with respect to the filter plate , such that the filter frame has: - a lowermost position, in which only the first seal lip is in contact with the filter plate , and - an uppermost position, in which both the first seal lip and the second seal lip are in contact with the filter plate . - a lowermost position, in which only the first seal lip is in contact with the filter plate , and - an uppermost position, in which both the first seal lip and the second seal lip are in contact with the filter plate . <EOS>