Water-jet drive mechanisms of this type are known. They serve to drive or to drive and control ships. In the latter case, it is possible for the above-mentioned elbow to be pivotable about a substantially vertical axis. The pivot axis of the elbow and the axis of rotation of the pump may thereby be located coaxially or eccentrically to one another. The pump axis can also be installed inclined. (U.S. Pat. No. 3,098,464, German OS No. 2 757 454).
In the drive mechanisms of the mentioned and similar type, the water jet applies itself to (in effect sticks to) the bottom surface of the ship behind the elbow or pump and thereby entrains large amounts of water from the surroundings. This results in a loss of the thrust and a lowering of the boat.
The basic purpose of the invention is to avoid this disadvantage, namely to take care that the jet comes free better from the ship and thus carries out no or at least almost no damaging action.
The basic purpose of the invention is attained with a water-jet drive mechanism, wherein a gas is supplied to the water jet at the ejector passage. It is thereby particularly advantageous to develop the invention so as to provide a passageway which connects the ejector passage to the outside air and supplies such gas to the water jet. This construction of the invention has namely the advantage that, in the case of pivotable elbows, the air-supply output pivots with the ejector passage. This avoids having the air sucked in by the water pump or the like.
The invention achieves the following advantages. The ejecting angle of the water jet is maintained which reduces the friction on the hull of the ship; this results in an increase of the thrust. Furthermore it is achieved that water is not entrained from the surroundings. This results in a lesser lowering of the ship and a smaller wave formation.