Marine propulsion – Screw propeller – With means effecting or facilitating movement of propulsion...
Reexamination Certificate
1999-01-27
2001-02-13
Morano, S. Joseph (Department: 3617)
Marine propulsion
Screw propeller
With means effecting or facilitating movement of propulsion...
C440S111000
Reexamination Certificate
active
06186845
ABSTRACT:
FIELD OF THE INVENTION
THIS INVENTION relates to motor mounting structures for boats.
BACKGROUND TO THE INVENTION
Small water craft, meaning inflatable boats and rigid hulled boats of up to about eight meters, are usually powered by one (or more) outboard motors attached to a rear transom. The drive shaft of the motor is substantially vertical. At the lower end of the drive shaft there is a gear box through which drive is transmitted to a substantially horizontal propeller shaft. The main advantage of an outboard motor is that the power losses in the drive train between the crank shaft and the propeller shaft are small. The main disadvantages of an outboard motor are that it occupies space at the stern end of the deck thereby reducing available deck space, it is noisy and is unsightly.
Inboard motors are rarely found on the smallest boats where outboards are used almost exclusively. Larger boats use almost exclusively inboard engines. However, there is a size range (say from four meters to eight meters) where some boats have outboard motors and others have inboard motors. An inboard motor is entirely concealed within the structure of the hull and the boat is thus more aesthetically pleasing. The main disadvantage of the inboard motor is that the crank shaft of the motor rotates about a horizontal axis and the propeller shaft also rotates about a horizontal axis but at a lower level. Hence two sets of gearing, usually bevel gearing, and an intermediate shaft, are required to form a power train from the crank shaft to the propeller shaft. Power losses are hence substantial. For this reason inboard and outboard motors of the same rated power will provide substantially different powers at the propeller. As much as thirty percent more power can be lost in the drive train of an inboard motor than in the drive train of an outboard motor.
An inboard motor is approximately twice the weight of an outboard motor for the same power.
Motor mountings have been proposed in which the motor's block is within the hull of the boat, the drive shaft passing through a transom and there being a gear box and propeller externally of the hull. An example of a motor mounting of this type is found in U.S. Pat. No. 3,382,839.
The main object of the present invention is to provide a motor mounting which provides the boat with advantageous handling characteristics.
BRIEF DESCRIPTION OF THE INVENTION
According to one aspect of the present invention there is provided, in combination, an outboard motor having a block, a housing extending downwardly from the block, a gear box within a lower part of said housing, a drive shaft extending from the block to said gear box, a propeller shaft extending rearwardly from said gear box and rotatable about an axis, and a propeller comprising a hub and blades protruding from the hub, the propeller being astern of said housing, a hull including an inclined transom, and means mounting said housing, drive shaft, gear box and propeller on said transom for oscillatory steering movements about an inclined axis which intersects, at a point of intersection astern of said housing, said axis about which the propeller rotates.
Said point of intersection is preferably between a front end of said hub and a rear end of said hub.
According to a further aspect of the present invention there is provided a boat having a hull including an inclined transom, an outboard motor and a mounting structure mounting said motor on said transom for rotary oscillatory steering movements about an inclined axis, a block of the motor being within the hull, a propeller of the motor being outside the hull and a drive shaft of the motor passing through the mounting from said block to drive said propeller, said propeller being mounted for rotation about a drive axis, said mounting structure including means permitting said motor to rotate about a horizontal axis to displace said propeller between a lowered operative position and a raised inoperative position, said inclined axis and said drive axis intersecting to the rear of a vertical line which intersects both said drive axis and said horizontal axis.
Said propeller preferably includes a hub having a front end and a rear end, said inclined axis intersecting said drive axis between said front and rear ends.
Hydraulic cylinders mounted between said motor and a fixed anchorage can be provided for displacing said motor in propeller lifting and lowering movements about said horizontal axis.
In the preferred form said mounting comprises an outer component mounted on said transom for rotary oscillation about said inclined axis and an inner component mounted on said outer component for rotary oscillation with respect to said outer component about said horizontal axis, said motor being carried by said inner component.
According to another aspect of the present invention there is provided, in combination, an outboard motor having a block, a propeller below and to the rear of the block in relation to the direction in which the motor travels, a drive shaft extending downwardly from the block to drive said propeller, the propeller being rotatable about a drive axis and having a hub with a front end and a rear end and blades protruding therefrom, and a mounting structure which includes means for permitting said motor to perform rotary oscillations about a horizontal axis to displace said propeller between a lowered operative position and a raised inoperative position, and means for permitting said motor to perform rotary steering oscillations about an inclined axis, said inclined axis intersecting said drive axis rearwardly of a vertical line which intersects said drive axis and said horizontal axis.
Said inclined axis preferably intersects said drive axis between said front and rear ends of said hub.
In a preferred form said mounting structure includes an outer component for attachment to an inclined transom of a boat, an intermediate component carried by said outer component and free to perform rotary steering oscillations with respect to said outer component about said inclined axis, and an inner component carried by said intermediate component and free to perform rotary oscillations with respect to said intermediate component about said horizontal axis.
According to yet another aspect of the present invention there is provided a boat having a hull, an outboard motor passing through an inclined rear transom of the hull with a block of the motor inside the hull and a propeller outside the hull and mounted on the transom for a first movement about a horizontal axis to enable the propeller to be lowered to an operative position and raised to an inoperative condition, and a second steering movement about an inclined axis which passes close to, or through, the propeller so that the propeller turns on itself thereby to minimise movement of the propeller off the centre line of the boat during steering.
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Morano S. Joseph
Vorys Sater Seymour and Pease LLP
Wright Andrew D.
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