Abstract: A collapsible pump chamber is provided which includes several functional elements of a pump device. For example, the collapsible pump chamber may be a bellows which includes a functional element of an outlet vane, a functional element of a biasing feature, and a functional element of a spin chamber. Consequently, a functional element of all of the downstream functions are incorporated into the bellows. This can significantly reduce costs; due to reduced tooling, and assembly, for example. Dunnage means is provided for occupying volume within the collapsible pump chamber to improve pump priming. The dunnage means may be free floating or associated with the inlet valve. A process for severing the functional element of the outlet valve, the functional element of the biasing feature, and the functional element of a spin chamber from the collapsible pump chamber during assembly.