The offset cylinder of a printing machine is brought into pressure engagement at predetermined time intervals first with the form cylinder and subsequently with the pressure cylinder by means of a lever system actuated by a cam disc freely rotatably mounted on the hub of a toothed driven wheel, with pawl means caring for temporary connection of the cam disc with the toothed wheel, with a two-arm lever controlling the position of said pawl means, the position of said two-arm lever controlled by a control lever.