in this manner the power input of the motor substantially remains constant and to a large extent independent of the respective load condition of the consumer fig3 shows a schematic representation of a multiple piston pump 60 arranged in the space 27 and comprising a plurality of individual pumps 61 disposed in a star shaped array each individual pump 61 is a piston pump whose piston rod 62 is pressed against the circumference of the eccentric ring 29 by a spring not shown the piston rods 62 are cyclically actuated by the eccentric ring 29 each individual pump 61 comprises an inlet and an outlet not shown the outlets are connected with each other and extend to the pressure connector 41 the inlets are openings through which oil from the reservoir 28 is taken in and fed to the individual pump the oil which is supplied to the consumer connected with the hydraulic unit is withdrawn from the reservoir 28 since the housing 10 has a round shape withdrawal of oil results in a rapid level drop consequently the inlets of the upper individual pumps 61 are possibly no longer submerged this condition is prevented by the auxiliary reservoir 47 as shown.