Abstract: A hydraulic diaphragm-actuated valve has an elastic diaphragm for operation of the pressure-controlled valve, and the diaphragm includes an outer rim configured for being clamped between opposed rigid surfaces, an intermediate flexible portion connected to the outer rim, and a rigid central portion having an outside diameter extending between 0.6 to 0.8 of the radial extent of the intermediate flexible portion from the center of the diaphragm. An inner portion is integrally connected to the intermediate flexible portion, and envelopes at least a part of the rigid central portion, and serves for attachment thereto.