Dialysis machine with valve clamp arrangement

A dialysis machine 30 comprises a cartridge 40 having a body 42 covered by a less rigid membrane 46 which is deformable under fluid pressure, the cartridge defining at least one valve 70, 72. The cartridge is received between a first platen (31, Fig 2) and a second platen (38, Fig 2) of the machine body. A valve clamp arrangement 80, 82 is provided in the machine body, normally spaced from the cartridge, and comprises a pneumatic actuator 84 which applies a fluid pressure differential directly to the deformable membrane to open and close the at least one valve and a mechanical actuator 86 (e.g. a piston 88 and retraction mechanism 92, see Fig 7 and 8) which is arranged to close the at least one valve by mechanical actuation, physically contacting the cartridge. The mechanical actuator may be biased to a retracted position by the pneumatic actuator and into an extended position by a biasing element (e.g. a coil spring 90 in Fig 7 and 8).