Surface vessel with a waterjet propulsion system

Details Surface vessel with a waterjet propulsion system Surface vessel with a waterjet propulsion system

2000-03-06

2001-05-29

Morano, S. Joseph (Department: 3617)

Marine propulsion

Jet drive

Direction control for fluid jet

C440S038000, C440S111000

Reexamination Certificate

active

06238257

ABSTRACT:

BACKGROUND OF THE INVENTION
In most surface vessels having waterjet propulsion systems, the pump is mounted within the hull adjacent the stern transom with at least a portion of the pump and the pump discharge nozzle above the surface of the water. The water jet is discharged through a discharge conduit leading from the pump that passes through the transom and impinges on a steering nozzle mounted on the outside of the stern transom. The location of the outlet from the pump discharge conduit at the water surface permits the actuators for the steering nozzle and reversing deflector of the propulsion system to be above the water, thus simplifying the installation and maintenance of the actuators and the hydraulic lines leading to the actuators. Also, it is common to provide access ports in the pump above the waterline to permit the pump to be serviced without drydocking the vessel.
Generally, the intake opening to the water supply conduit for the waterjet pump is located on the bottom of the hull a short distance forward of the pump and just far enough below the waterline to ensure that water is taken in under most operating conditions of the vessel. The location of the intake opening at a minimum height below the pump improves efficiency, as compared to a deeper location, by minimizing the vertical distance that the pump has to pump the water from the intake opening to the pump rotor.
A disadvantage of having the waterjet pump relatively close to the water surface is the reduced hydraulic head of water at the pump inlet. The reduced suction head reduces the capability of the pump to absorb high power at slow speeds due to the onset of cavitation.
The pump has to be larger than it would have to be if the suction head were greater in order to provide high power output at slow speeds without cavitation.
Another disadvantage of most previously known waterjet propulsion systems is the relative complexity of the actuators for the steering nozzle and the reversing deflector and the outboard location of the actuators. The actuators are usually hydraulic piston/cylinders and require that several hoses pass through openings in the transom, which complicates the construction of the transom and requires seals in each opening. If there is a failure of an actuator or a hose, hydraulic fluid is lost to the environment. The outboard actuator systems for the steering nozzle and the reversing deflector are also not easily repaired when the vessel is at sea.
One previously known arrangement for actuating the steering nozzle and reversing deflector of a marine waterjet propulsion system, which is described and shown in U.S. Pat. No. 3,807,346, includes concentric shafts that extend vertically downwardly from a portion of the vessel hull that is located above the steering nozzle and reversing deflector, which are pivotally mounted on a bracket for rotation about a common vertical axis that coincides with the axis of the concentric shafts. The lower end of the inner shaft is coupled to the steering nozzle, and the lower end of the outer shaft is coupled to reversing deflector. The inner shaft is driven by a piston/cylinder steering actuator that is located within the vessel hull and is coupled by a steering lever to the upper end of the inner shaft. A piston/cylinder reversing actuator is coupled between the steering lever and the upper end of the outer shaft so as to pivot the reversing deflector relative to the steering nozzle.
The steering/reversing mechanism of U.S. Pat. No. 3,807,346 has the advantages of requiring only a single penetration of the hull of the vessel and of enabling the steering and reversing actuators to be located within the vessel hull, where they are protected from the hostile water environment and can be serviced readily. The rotation of the reversing deflector about a vertical axis is, however, highly disadvantageous, inasmuch as in the retracted position for ahead propulsion, the reversing deflector resides laterally of the steering nozzle where it creates a large drag. In addition, an inactive positioning of the reversing deflector laterally of the steering nozzle requires additional athwart-ship space, which is limited in many waterjet propulsion applications.
When a waterjet propulsion system is installed at the waterline of the vessel, most parts of the installation can be located above the water surface and do not contribute drag. Locating a water jet propulsion system in a fully submerged location to attain the advantages described above presents significant problems from the points of view of minimizing drag, minimizing the number of penetrations of the hull requiring seals, constructing the system so that it can be easily maintained and repaired, and avoiding installing hydraulic or electrical apparatus outside of the hull.
SUMMARY OF THE INVENTION
One object of the present invention is to provide a surface vessel having a waterjet propulsion system that is installed in a position in which it is fully submerged. For any given size of waterjet pump, the pump is capable of absorbing more power at slow speeds without cavitation than previously known vessels propelled by water jets, and the noise and degree of disturbance of the surface of the water generated by the propulsion system are significantly reduced. Another object is to provide a waterjet propulsion system in which the pump is installed in a mechanically and structurally efficient manner on a specially configured hull that enables the pump to be installed and serviced from outside the hull and the actuators for a steering nozzle and a reversing deflector to be located within the hull. It is also an object to provide a waterjet propulsion system that is mechanically and structurally efficient, relatively simple in construction, extremely robust, compact in size, and of low weight.
An additional object is to have the reversing deflector mounted for pivotal movement about a horizontal axis so that when it is positioned for ahead propulsion, it lies above the steering nozzle where it takes up less athwart ship space and produces less drag than it would in a position laterally of the steering nozzle. A further object is to provide actuation of the steering and reversing apparatus by mechanisms that are compact in size, of low weight, and very rugged, that generate rotational and translational motions, respectively, that require only one penetration of the hull, and in which all or nearly all components located outside the hull are mechanical, thus minimizing the possibility of leakage of a hydraulic fluid into the water.
The foregoing and other objects are attained, in accordance with the present invention, by a surface vessel which has a hull having an aft portion that includes a main stern transom, an intermediate transom located below and forwardly of the main transom, and an aft bottom section that extends from the lower edge of the main stern transom forwardly to a location generally above and proximate to the intermediate transom. A water intake conduit has an inlet opening in the hull forward of the intermediate transom and an outlet opening within the hull forward of the intermediate transom. A waterjet propulsion pump is mounted in an opening in the intermediate transom and includes a forward part connected forward of the intermediate transom to the outlet of the intake conduit and an aft part extending aft from the intermediate transom. A pump rotor is received in the forward part and a stator received in the aft part. A steering nozzle is pivotally mounted on the aft part of the pump housing to intercept a water jet discharged from the pump and coupled to the lower end of a steering shaft that is rotatable about a steering axis and extends upwardly from the steering nozzle through an opening in the aft bottom section and has an upper end portion located within the hull. A steering actuator located within the vessel hull is coupled to the steering shaft for rotating the steering shaft about the steering axis. According to one aspect, the present invention is characterized in that at least an aft porti

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