Abstract: A pump has an axial drive shaft with a cam fence that extends radially outwardly from an axis of the drive shaft. The cam fence axially displaces, in respective cylinders, each of a plurality of elongate pistons arranged in parallel to and around the axis and angularly spaced apart from each other. The axial position of an outer margin of the cam fence varies as a function of its radial angle with the axis. In one part of the operation of the pump, a piston is withdrawn to uncover a radial inlet port to draw fluid into the cylinder from an internal reservoir volume formed in the drive shaft. In a second part of the operation, the drive shaft is further rotated to open a cylinder end port by means of a rotary valve and closing the side port of the cylinder with a portion of the drive shaft body. In a third part of the operation, the piston is advanced to push fluid out of the cylinder end port into an output chamber.

Abstract: A pump has an axial drive shaft with a cam fence that extends radially outwardly from an axis of the drive shaft. The cam fence axially displaces, in respective cylinders, each of a plurality of elongate pistons arranged in parallel to and around the axis and angularly spaced apart from each other. The axial position of an outer margin of the cam fence varies as a function of its radial angle with the axis. In one part of the operation of the pump, a piston is withdrawn to uncover a radial inlet port to draw fluid into the cylinder from an internal reservoir volume formed in the drive shaft. In a second part of the operation, the drive shaft is further rotated to open a cylinder end port by means of a rotary valve and closing the side port of the cylinder with a portion of the drive shaft body. In a third part of the operation, the piston is advanced to push fluid out of the cylinder end port into an output chamber.