Diaphragm valve

A diaphragm valve for controlling a flow of gaseous or liquid fluid and including a valve housing having a substantially circular valve chamber, into which opens a central channel, and on each side thereof a first side channel and a second side channel, respectively, each of said channels having an external connection for fluid, said side channels each being separated from said central channel by a respective one of two substantially parallel valve seat means extending like chords across said valve chamber and each providing a substantially linear valve seat for an elastic diaphragm adapted to be brought into and away from sealing contact with at least one of said valve seat means, and two individually operable control means adapted both to press a respective linear portion of said diaphragm against a respective valve set means, thereby to shut passage of fluid between said central channel and a respective side channel, and to positively raise a respective portion of said diaphragm off a respective one of said valve seat means, thereby to open a flow passage between said central channel and said respective side channel.