Marine propulsion – Electric drive for propelling means
Reexamination Certificate
2000-03-31
2001-11-27
Swinehart, Ed (Department: 3617)
Marine propulsion
Electric drive for propelling means
C114S14400A
Reexamination Certificate
active
06322406
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to the field of propulsion systems for watercraft, such as fishing boats, ski boats, pontoon boats, and other pleasure and utility craft. More particularly, the invention relates to a propulsion system including a pair of electric motor-driven propulsion units for navigating a watercraft in desired directions.
2. Description of the Related Art
In the field of marine propulsion systems for pleasure craft, such as fishing boats, several approaches have been proposed and are presently in use. In one class of propulsion systems, commonly referred to as outboard motors, an engine is packaged with power transmission components and a prop. The engine, typically an internal combustion engine, drives the prop to propel the boat in a desired direction. Outboard motors of this type are typically fitted to the transom of a boat, and may be used in tandem for additional thrust. Steering of outboard motors is typically accomplished by altering the angular position of the motor with respect to the boat. Similar systems, commonly referred to as inboard motors, provide an internal combustion engine within the confines of the boat hull, with a driven prop extending from the hull. The prop, or a rudder, may be angularly positioned to provide the desired directional thrust.
In addition to, or in place of internal combustion engine-based marine propulsion systems, many boats include electric motor drives. In a common application for fishing boats, a trolling motor is used to navigate the boat at relatively low speeds and quietly, providing some degree of movement and navigation. Trolling motors of this type typically include a directional head which rotates a drive tube to position a lower propulsion unit in a desired directional orientation. The drive unit includes an electric motor and prop assembly. When positioned appropriately, the prop assembly exerts a thrust to displace the boat in the desired direction. Conventional trolling motors of this type are most often mounted on a retractable mounting assembly from a bow area of the boat. Conventional designs permit control either via hand levers, hard-wired foot pedals, or radio frequency control.
While propulsion systems of the types described above provide good means of displacement, both at high and low speeds for various activities, they are not without drawbacks. For example, the noise and power associated with outboard and inboard motors are simply unacceptable for many pleasure craft activities, particularly fishing. Conventional trolling motors, on the other hand, while providing a quiet and reliable low speed propulsion system, do not offer the desired degree of navigational freedom and directional control. Moreover, conventional trolling motors may be relatively easily damaged on submerged objects, may become tangled in weeds and underwater plant growth, and offer considerable problems for deployment and storage. More specifically, because the trolling motor mount is commonly rigidly secured to the boat deck, the motor must be deployed before use and stowed after use. The mount itself, along with the trolling motor, detracts from the aesthetic appeal of the boat, and is an encumbrance to free movement on the boat deck. Also, bow-mounted trolling motors undergo substantial shock, particularly during use in rough waters.
There is a need, therefore, for an improved approach to marine propulsion, particularly for small watercraft and pleasure boats. There is, at present, a particular need for an approach which would alleviate the problems with conventional trolling motors and similar electric motor drives, providing enhanced navigational capabilities and control, reducing the need to manipulate the system before and after use, and improving or reducing the encumbrance presented by the system for the boat operator.
SUMMARY OF THE INVENTION
The present invention provides a marine propulsion technique designed to respond to these needs. The technique is based on the use of a pair of electric motor drive units, each driven by a separate electric motor to produce a desired resultant or net thrust. The thrust is directed to navigate the watercraft in desired directions, with control of the rotational speed of the propulsion unit props being coordinated appropriately. The propulsion units may be conveniently positioned in a stem region of the watercraft, and the props lodged within recesses formed within the watercraft hull. The system thus provides inherent protection for the props, and prevents or substantially reduces the risk of entanglement in underwater plant growth or damage by contact with submerged objects. The technique also alleviates the need to affix a trolling motor or its mount to the boat deck, improving the appearance and performance of the craft.
In a present embodiment, the propulsion units include an electric motor positioned within a cavity of the hull, with a driven prop lodged within a recess in the hull. A power transmission assembly provides torque through the hull from the electric motor for driving the prop. The props may be oriented angularly with respect to the longitudinal centerline of the hull, to provide components of thrust directed at oblique angles with respect to the centerline. The props may be driven in a single direction by the electric motors. In a present embodiment, however, the motors are bi-directional, providing for enhanced control capabilities by driving the props in both directions and at various speeds, to provide components of the desired resultant thrust.
REFERENCES:
patent: 686780 (1901-11-01), Steffens
patent: 2154493 (1939-01-01), Norquist
patent: 4311108 (1982-01-01), Horton
patent: 5401195 (1995-03-01), Yocom
Griffith, Sr. Thomas E.
Hoskins Loy
Saunders Robert F.
Tyler Calvin
Bombardier Motor Corporation of America
Fletcher Yoder & Van Someren
Swinehart Ed
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