Rotary leadthrough

A rotary leadthrough for a printing machine for feeding one of suction or pressurizing medium to a rotor of the printing machine, comprising a stator in which the rotor is rotatable, sealing means disposed between the rotor and stator for providing sealing therebetween regardless of the angular position between the rotor and the stator, said stator adapted to form a cylinder having an axis colinear with said rotor, said rotor forming a journal in said stator, a piston slidably supported in said cylinder between a first position proximal to the rotor and a second position away from the rotor, said sealing means including at least one sealing element contacting said journal in the first position of said piston, wherein in its second position said sealing element is spaced away from said journal, in which second position said piston is stationary relative to said rotor, and piston moving means in operative engagement with said piston for moving it between its first and second position;

• wherein said piston has a cylindrical surface, a plurality of axially disposed bores in said piston, an equal plurality of circular peripheral channels formed in said cylindrical surface, each peripheral channel fluidly communicating with a respective bore, said cylinder having an inner cylinder surface, a plurality of access channels equal to said plurality of peripheral channels formed in said inner cylinder surface, wherein said access channels are fluidly communicating with a respective peripheral channel when said piston is in its first position.