Blood treatment cassette with film valve and inelastical spacer as well as blood treatment apparatus

A blood treatment cassette comprising a cassette body having a hard part and a film, wherein the film is connected with the hard part and at least partially covers the hard part,

• wherein the hard part comprises a valve base that cooperates with a section of the film adjacent the valve base to form a valve, wherein the valve is configured to be moved from a first open position in which the valve base and the section of the film adjacent the valve base do not touch each other to a second closed position in which the valve base and the section of the film adjacent the valve base touch each other when a force is applied to the section of the film adjacent the valve base,
• wherein the hard part and the film are connected to each other along surfaces of channel bars of the hard part that extend alongside chambers or channels of the hard part, wherein the surfaces of the channel bars to which the film are attached define a main contact plane,
• wherein the blood treatment cassette comprises, in the area of the valve, at least one hump which is integrally formed with the hard part and which projects through and beyond the main contact plane, and
• wherein the hump locally displaces a portion of the film lying above the hump away from the main contact plane so as to sustain the valve in the first open position:
• (i) while the blood treatment cassette is in a non-use condition and (ii) while the blood treatment cassette is subjected to negative pressures applied within the blood treatment cassette during a sterilization process of the blood treatment cassette.