that springs for biasing the non return valves 211 are not shown in fig2 fig2 shows the crank mechanism 206 with the sliding block guideway 207 of the piston 205 the crank mechanism 206 has a drive shaft 209 to which a disk 222 is fastened the disk 222 carries the crankpin 220 which is arranged with the eccentricity e 1 the crankpin 220 reaches through the elongated hole 221 of the sliding block guideway 207 and into the sliding block 208 where it is received in a bearing bushing 219 the plunger pump 201 of a second embodiment in fig2 shows the arrangement of the pump outlet 204 behind the pump inlet 203 both ports being radially arranged on the circumference of the plunger pump 201 the ports 203 204 are integrated in a pressure piece 223 which is mounted on the plunger pump 201 the piston 205 has a flattening 224 on its side close to the pump inlet 203 and the pump outlet 204 the flattening 224 guarantees a communication of the pump outlet 204 with the pump chamber 210 which is independent of the position of the piston 205 in this embodiment both non return valves 211 are loaded or biased by a respective spring the piston 205 has three regions with different diameters 225 227 the diameters increasing from the bearing 212 through the region of the seal 215 to the bearing 213 which is no longer shown with these steps 225 227 of piston diameter any wear particles which arise are prevented from being distributed into the regions of.