Flexible pumping chamber

Pumping unit for an inhalation device for medically active liquids for generation of an aerosol, wherein the pumping unit comprises a tubular member, a check valve, and a counter piece, said counter piece being configured to receive at least a downstream segment of said tubular member and having an interior volume, wherein upstream of said tubular member, a reservoir is directly or indirectly fluidically connected with said tubular member, and downstream of said counter piece, a nozzle unit is directly or indirectly fluidically connected with said counter piece, and wherein the tubular member comprises an upstream section, a downstream section, and the check valve which is positioned between the upstream section and the downstream section, such that a pumping chamber with a pumping chamber volume is defined which comprises the volume of the downstream section of the tubular member and optionally said interior volume of the counter piece, and wherein tubular member and the counter piece move relatively to one another, such that the pumping chamber volume is variable, characterized in that the tubular member comprises at least two mechanically distinct parts, wherein a first part provides said upstream section, and a second part provides said downstream section, and wherein the first part and the second part are connected to each other such as to form an interface section serving as a valve chamber for the valve, wherein the counter piece comprises a riser pipe which extends towards the second part of the tubular member and which is at least partially insertable into the second part of the tubular member;

• and wherein the riser pipe extends through a furthest downstream end of the second part of the tubular member.