Volumetric pump

An apparatus for conveying a fluid from a fluid inlet to a fluid outlet, the apparatus comprising:

• a spool axially movable within a cavity, wherein a first chamber is located at a first axial end of the cavity and a second chamber is located at a second axial end of the cavity, wherein the volume of the first chamber and the second chamber varies depending upon the axial position of the spool within the cavity;
• a valve movable between a first position and a second position, wherein in the first position the valve is configured to convey fluid from the fluid inlet to the first chamber and from the second chamber to the fluid outlet, and in the second position the valve is configured to convey fluid from the fluid inlet to the second chamber and from the first chamber to the fluid outlet;
• and
• a control system configured to control the movement of the spool and the valve;
• wherein:
• the spool and the cavity are a first spool and a first cavity respectively, and the apparatus further comprises a first valve comprising the first spool, the first cavity, the first chamber and the second chamber;
• and
• the valve is a second valve and comprises a second spool axially movable within a second cavity, wherein a first chamber of the second valve is located at a first axial end of the second cavity and a second chamber of the second valve is located at a second axial end of the second cavity, wherein the volume of the first chamber and the second chamber varies depending upon the axial position of the second spool within the cavity.