Abstract: A propeller drive for watercraft, preferably for ferry boats and car ferries, which has two propellers located one behind the other in the center-line plane. The forward propeller is preferably located on a marine shaft which exits the hull, and can be driven by means of a drive system. The aft propeller is preferably driven by means of a separate drive system, and the aft propeller is realized so that it can pivot by at least about 90 degrees around an axis, the axis being preferably vertical.

Abstract: A system to adjust to the changing draft of ocean-going ships on the aft seal system equipped with several outwardly-directed gaskets and one inwardly-directed gasket, in which, between each two outwardly-directed gaskets a ring-shaped chamber is reserved, to which a feed line for compressed air is connected. Integrated into the feed line is a pressure control mechanism and a discharge channel which can periodically empty into the interior of the ship (bilge), whereby the pressure in the ring-shaped chamber is always maintained slightly below the outside water pressure. The system is characterized by the fact that an electronic draft measurement system is located on the ship's hull to supply electric signals which correspond to the current draft, which signals actuate the pressure control mechanism.

Abstract: A safety device on an aft seal system equipped with at least two gaskets for a ship's propeller shaft, which propeller shaft is sealed with respect to the outside water and with respect to a lubricant chamber, and on which a ring-shaped chamber is reserved between each two gaskets, to which chamber are connected a feed line for compressed air and a discharge channel which can be emptied by means of a solenoid valve which opens and closes periodically. The pressure in the ring-shaped chamber is kept always slightly lower than the respective outside water pressure and the lubricant pressure by means of a pressure regulation mechanism.

Abstract: A seal arrangement for controlling any large bearing clearance in the vicinity of a propeller shaft, such as for a propeller drive system for ships with two concentric propeller shafts rotating in opposite directions, has a housing ring for supporting the sealing lips and a supporting ring for supporting the housing ring and defining a clearance therebetween. This clearance can be sealed, and maintained by means of elastic ring walls disposed between and interconnecting the housing to the supporting ring, so that compensation can be achieved for changes in the clearance during rotation of the propeller shaft.