a pneumatic pinch valve assembly having a lever , a piston supporting a pressing piece , and a fluid tube receiving space formed between the lever and the pressing piece for receiving fluid tubes is disclosed . air is introduced into a cavity to actuate the piston in order to pinch a fluid tube between the lever and the pressing piece to intercept a fluid flow through the tube . a pinching action control feature is located between the piston and the pressing piece and is used to protect the fluid tube by limiting one or more amounts of compression of the fluid tube during operation . the amount of compression of the fluid tube is able to be adjusted so that the fluid tube is not easily deteriorated during long - time operation .