Piston pump

A piston pump comprising a cylinder with an inner cylinder wall and at least one working space, which piston pump further comprises a piston including a piston head which is provided with a lateral surface facing the cylinder wall and a front surface facing the working space, the piston head's lateral surface being provided with a first projection and a second projection extending round the entire circumference of the lateral surface and abutting the cylinder wall, thereby forming an annulus between the piston head and the cylinder wall which is delimited by the projections in the axial direction;

• and that the first projection is designed such that a pressurised fluid in the annulus flows past the first projection and out into the working space while the second projection is designed so that the pressurised fluid is prevented from flowing past the second projection and out of the annulus, wherein the piston head and the projections are provided as a single integrated unit in that the projections are not formed with separate packings mounted on the piston head, and in an elastic material, and that the piston head is provided with at least one piston head channel for delivery of the pressurized fluid to the annulus.