1. A diaphragm valve comprising a retainer having a plate portion, a diaphragm having a sealing section, a valve seat and a spring for pressing the sealing section of the diaphragm against the valve seat through the retainer, and characterized in that a predetermined number of apertures are respectively provided at positions along the plate portion of the retainer behind the sealing section of the diaphragm.WATER POWER CONTROL VALVE
2. A diaphragm valve according to claim 1, wherein a predetermined number of concave portions are formed in place of said predetermined number of apertures.
3. A diaphragm valve according to claim 1, wherein the shape of each of said apertures is substantially rectangular.
4. A diaphragm valve according to claim 2, wherein the shape of each of said concave portions is substantially rectangular.
5. A diaphragm valve comprising a retainer having a plate portion, a diaphragm having a sealing section, a valve seat and pressure means for pressing the sealing section of the diaphragm against the valve seat through the retainer, Filterand characterized in that a predetermined number of apertures are respectively provided at positions along the plate portion of the retainer behind the sealing section of the diaphragm. Instrumentation Ball Valves
6. A diaphragm valve according to claim 5, wherein a predetermined number of concave portions are formed in place of said predetermined number of apertures.
7. A diaphragm valve according to claim 5, wherein the shape of each of said apertures is substantially rectangular.
8. A diaphragm valve according to claim 6, wherein the shape of each of said concave portions is substantially rectangular.

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