Filter plate assembly for a filter press, and such a filter press

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, 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, wherein 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.