Fluid reaction surfaces (i.e. – impellers) – Having positive means for impeller adjustment – Motor bodily rotatable with impeller hub or shaft
Reexamination Certificate
2000-02-15
2001-09-11
Look, Edward K. (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
Having positive means for impeller adjustment
Motor bodily rotatable with impeller hub or shaft
C416S158000, C416S159000
Reexamination Certificate
active
06287077
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a boat drive. More particularly this invention concerns an adjustable-pitch propeller for a boat.
BACKGROUND OF THE INVENTION
A boat drive with a standard variable- or adjustable-pitch propeller is described in U.S. Pat. No. 5,073,134. It has a drive housing projecting from a hull of a boat, a tube shaft journaled in the housing and centered on a main axis, and a drive for rotating the tube shaft. A propeller hub mounted on the propeller shaft is provided with a plurality of adjustable-pitch propeller blades rotatable about respective axes generally radial of the main axis. Respective blade-adjustment rods extending parallel to the propeller shaft are shiftable axially to adjust a pitch of the blades and the hub has an end turned toward the housing and a free end turned away from the housing. A pitch-adjustment push rod passing through the propeller shaft and projecting out of the hub with one extremity of the push rod at the free end of the hub is axially shiftable in the propeller shaft by a double-acting piston-and-cylinder unit in the housing connected to the opposite extremity of the push rod. Another such system is described in German 3,118,230.
In German patent 878,906 of Wels the core shaft is axially fixed in the tube shaft and pivotal to change the setting of the propeller vanes. A worm gear meshing with a gear wheel on the core shaft is used to effect the desired rotation.
German patent 1,065,339 of Fischer has an axially displaceable core shaft whose front end is threaded in an axially fixed nut that can be coupled to the tube shaft for joint rotation therewith or coupled to the housing so that, when the tube shaft rotates relative to the housing, the screw moves axially in the nut and changes the vane setting.
These systems are all quite complex. Those with a core shaft normally rotating relative to the tube shaft are subject to considerable wear. The hydraulic arrangements often must be pressurized at high pressure to maintain a vane setting, and the all systems are quite complex.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to provide an improved adjustable-pitch propeller for a boat drive.
Another object is the provision of such an improved adjustable-pitch propeller for a boat drive which overcomes the above-given disadvantages, that is which is of simple construction and long service life.
SUMMARY OF THE INVENTION
A boat propeller has according to the invention a housing adapted to be fixed to a boat, a hub rotatable about a main axis on the housing, a plurality of generally radially projecting vanes pivotable on the hub, and an operating core shaft coaxially received in the hub, rotatable about the main axis but axially nondisplaceable relative thereto, and having a rear end projecting axially from the hub and a front end. A yoke is fixed to the rear core-shaft end and respective rods fixed to the yoke are connected to the vanes for pivoting the vanes on angular movement of the core shaft about the main axis. A cylinder axially fixed in the housing at the front core-shaft end holds an axially displaceable piston. A nut element having a nonbinding internal screwthread is threaded on a screw element. One of the elements is axially coupled to the piston and the other of the elements is axially coupled to the core-shaft front end. The cylinder can be pressurized to axially displace the piston and, by axial-to-rotary conversion via the elements, rotate the core shaft.
Thus with this system the axial stroke of the piston is converted by the nut/screw transmission into rotation of the core shaft, with the appropriate mechanical advantage. A modest pressure in the cylinder can effect the desired adjustment of the vanes about their radial axes and similarly very little pressure need be maintained to hold a vane setting. Using a very steep screwthread between the nut and screw allows a relatively long displacement of the piston to effect a relatively small rotation of the core shaft for extremely fine adjustment of the vane setting with a relatively simple low-pressure hydraulic system.
The yoke and core-shaft rear end are formed with complementary binding screwthreads. More particularly the core-shaft rear end is formed with an external binding screwthread and the yoke is formed with an internal binding screwthread. As is standard the term “binding” means that virtually the only way to relatively rotate two parts joined together by a binding screwthread is to apply angularly opposite forces or torques to them as no normally encountered amount of purely axial pressure will cause relative rotation. With a nonbinding screwthread, which typically is fairly steep, axial force applied to the one of the parts will readily cause the other to rotate.
The screw element according to the invention is fixed to the core shaft and the nut element is fixed to the piston. In addition the drive has a tube shaft rotatable in the housing about the main axis, coaxially surrounding the core shaft, and having a rear end carrying the hub. The core shaft is axially fixed shaft in the tube shaft while permitted to rotate about the main axis relative to the tube shaft. This fixing means is at the front end of the core shaft.
REFERENCES:
patent: 2501617 (1950-03-01), Roesch
patent: 2747676 (1956-05-01), Berninger et al.
patent: 2792064 (1957-05-01), Smith
patent: 2958382 (1960-11-01), Covert et al.
patent: 3092186 (1963-06-01), MacLean
patent: 5073134 (1991-12-01), Muller
patent: 878 906 (1953-06-01), None
patent: 1 065 339 (1960-02-01), None
patent: 31 18 230 (1983-01-01), None
Dubno Herbert
Look Edward K.
Nasyc Holding S. A.
Nguyen Ninh
Wilford Andrew
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