Boat drive with variable-pitch propeller

Details Boat drive with variable-pitch propeller Boat drive with variable-pitch propeller

2000-08-04

2001-06-26

Avila, Stephen (Department: 3617)

Marine propulsion

Screw propeller

Variable pitch

C416S147000

Reexamination Certificate

active

06250979

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a boat drive. More particularly this invention concerns such a boat drive with a variable-pitch propeller.
BACKGROUND OF THE INVENTION
As described in U.S. Pat. No. 5,073,134 a standard boat drive has a housing, a tube shaft rotatable in the housing about a shaft axis and having axially opposite front and rear ends, a hub carried on the shaft rear end, and a plurality of radially projecting vanes pivotal on the hub. An axially shiftable core shaft extending coaxially in the tube shaft has a rear end rearward of the tube-shaft rear end and a front end forward of the tube-shaft front end. Mechanism connecting the core-shaft rear end with the vanes pivots the vanes on the hub on axial displacement of the core shaft. An axial-thrust bearing on the core-shaft front end is connected via another coaxial shaft to a piston having front and rear faces exposed in respective front and rear compartments formed by a cylinder fixed in the housing and surrounding the piston. Thus pressurization of the front compartment shifts the core shaft rearward and pressurization of the rear compartment shifts the core shaft forward.
The problem with this construction is that it is axially quite long. This makes it impossible to incorporate in an outboard drive, and even fairly complex in inboard or other drive types.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to provide an improved boat drive.
Another object is the provision of such an improved boat drive which overcomes the above-given disadvantage, that is which is relatively short.
SUMMARY OF THE INVENTION
A boat drive has according to the invention a housing, a tube shaft rotatable in the housing about a shaft axis and having axially opposite front and rear ends, a hub carried on the shaft rear end, and a plurality of radially projecting vanes pivotal on the hub. An axially shiftable core shaft extending coaxially in the tube shaft has a rear end rearward of the tube-shaft rear end and a front end forward of the tube-shaft front end. Mechanism connecting the core-shaft rear end with the vanes pivots the vanes on the hub on axial displacement of the core shaft. A pair of oppositely directed axial-thrust bearings on the core-shaft front end are contained in and surrounded by a hollow piston having front and rear faces axially flanking the thrust bearings. A cylinder fixed in the housing and surrounding the piston forms with the respective faces thereof front and rear compartments so that pressurization of the front compartment shifts the core shaft rearward and pressurization of the rear compartment shifts the core shaft forward.
Since the bearings are inside the piston, the entire assembly can be greatly reduced in length. In addition the provision of extra structure between the axial-thrust bearings and the piston is eliminated, further simplifying the structure.
The core-shaft front end according to the invention has a radially projecting flange braced against and lying between the bearings. The piston has an axially extending sleeve coaxially extending through one of the compartments and surrounding the core shaft. Formations on the sleeve and housing inhibit rotation of the sleeve and piston relative to the housing. These formations are splines.
The cylinder according to the invention has a removable front end cap forming a front wall of the front compartment. Similarly the piston includes a forwardly open cup containing the bearings and a removable front plate closing the cup and forming the front face. A passage through the tube shaft for lubricating a space between the core shaft and tube shaft.


REFERENCES:
patent: 4744727 (1988-05-01), Muller
patent: 4897056 (1990-01-01), Muller
patent: 5073134 (1991-12-01), Müller
patent: 5967753 (1999-10-01), Muller

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