Marine propeller attachment and assembly

BACKGROUND OF THE INVENTION

This invention relates to flow-through propeller apparatus and more particularly to an anticavitation attachment for a flow-through propeller, and the combination thereof.

The substantial power output of marine, pleasure craft engines in recent times has accentuated the age-old problem of cavitation-ventilation around the propeller blades. This includes flow-through propellers. Several different and specialized propeller constructions have been devised by a few of the manufacturers in efforts to lessen cavitation. Some of these seem to be somewhat effective. However, purchasers frequently do not purchase these specialized units, probably because of unawareness of the problem, or because of high cost, or because of conflicting claims made for the specialized units, or other reasons. Further, once a conventional propeller is purchased, the cost of another specialized one is quite prohibitive.

SUMMARY OF THE INVENTION

It is an object of this invention to provide a unique anticavitation attachment to a flow-through propeller, whereby a ring extending around the periphery of the propeller hub governs waterflow characteristics for anticavitation purposes. The novel ring attachment has a special relationship between the outer ring and axially and radially extending spokes, to fit onto the rear end portion of the flow-through hub.

The novel attachment unit is relatively inexpensive in comparison to a special propeller. It can be attached in a minute or two, simply by removing the nut that retains the propeller in place, positioning the attachment, and replacing the nut. It operates in combination with the hub, forming a part of the assembly. It can be purchased as part of a new propeller assembly, or can be purchased for combination with a used propeller. The unit has proven in tests to have desirable anticavitation action.

These and other objects, features, and advantages will be apparent upon studying the following specification in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the combination flowthrough propeller and anticavitation attachment;

FIG. 2 is an enlarged side elevational view of the anticavitation attachment;

FIG. 3 is a rear end elevational view of the combination in FIG. 1, with the securement nut removed;

FIG. 4 is a sectional, fragmentary, side elevational view of the rear end portion of the flow-through propeller and attachment combination;

FIG. 5 is a perspective view showing a modified form of the attachment in combination with a flow-through propeller; and

FIG. 6 is a side elevational enlarged view of the modified attachment in FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now specifically to the drawings, the combination 10 there illustrated includes the subcombination flow-through propeller 12 and the subcombination anticavitation attachment 14.

Flow-through propeller subassembly 12, in operation, is attached to the conventional depending underwater power assembly (not shown) of a conventional marine engine apparatus (not shown). The flow-through propeller subassembly is normally attached to a splined drive shaft (not shown) which extends through the center of the hollow hub. One typical attachment of the propeller assembly to the drive shaft employs the illustrated resilient, cooperably configurated bushing 16, as of rubber, which is housed by and secured to a surrounding collar 18. The rearward end of collar 18 projects radially inwardly behind bushing 16 to form a rear mounting surface 18' and to retain bushing 16. Shaft-receiving openings 16α and 18α in the bushing and collar are aligned when assembled. Collar 18 is in turn secured to an outer sleeve 20 by a plurality, here three, of struts 22, defining arcuate exhaust flow-through passages 24 therebetween (FIG. 3). Outer sleeve 20 extends rearwardly considerably further than the mounting means formed by elements 16 and 18 to define a cylindrical passage communicating with the arcuate passages 22 for flow of the exhaust gases therethrough and out the open rear end of the sleeve into the water.

A plurality of propeller blades 26 project radially from the outer periphery of sleeve 20.

The rear cylindrical end of outer sleeve 20 of the hub assembly preferably has a taper on its inner surface, such taper being rearwardly-outwardly at an angle of about 15°—20° to the axis.

Anticavitation subassemably 14 cooperates with the rear of the flow-through propeller. Specifically, subassembly 14 includes an outer ring 30, an inner ring 32, and a plurality of spokes 34 therebetween. Inner ring 32 is considerably forwardly offset, axially, with respect to outer ring 30, is smaller, and is concentric therewith. The forward face of inner ring 32 is an abutment surface to engage the rear surface 18' of the mounting means for the hub subassembly. It includes a cylindrical passage 32α that aligns with passages 16α and 18α for extension of the drive shaft therethrough, so that the threaded securement nut 36 can mount subassembly 14 as well as subassembly 12 on the drive shaft. Spokes 34 extend from inner mounting ring 32 radially outwardly and rearwardly back to outer ring 30. These spokes join with outer ring 30 rearwardly of the forward portion of ring 30, for example at the rear end portion of ring 30, defining a plurality of generally V-shaped recesses or pockets 40 between the spokes and the outer ring. These pockets are radially positioned and oriented to receive the rear terminal edge portion of sleeve 20 of the hub subassembly as shown in FIG. 4. Outer ring 30 extends forwardly of the rear edge of sleeve 20, over a portion of the outer periphery of the hub subassembly, fitting tightly against surface portions, e.g. 20α, of this hub to prevent waterflow between the hub and the attachment.

The forward portion of outer ring 30 is a radially extending face 30α around the periphery of the hub and projecting radially outwardly therefrom, and terminating at the outer peripheral edge in a water-shearing edge 30ά. Surface 30α is preferably substantially normal to the hub axis, or forwardly at a small acute angle of about 10°—20° to the normal. Preferably, the peripheral surface of outer ring 30 slopes radially inwardly-rearwardly away from this shearing edge 30ά. In other words, this edge 32b should be at an acute angle.

It is intended that a stagnant water zone be created immediately forwardly of face 30α, with the water flowing over the stagnant zone causing a shearing action over the edge 30ά at the juncture of front face 30α with the peripheral surface of ring 30, altering the velocity gradients and therefore the pressure gradient. The exhaust gases that flow out the rear end of the hub tend to curl around the hub edge and follow forwardly along the low-pressure zone that occurs along the hub periphery. The attachment ring shears off the gases as they reach the shearing edge 30b and hence before they reach the vicinity of the propeller blades.

A less preferred form of the device is illustrated in FIGS. 5 and 6 to include the same subassembly 12 and a slightly modified attachment subassembly 140. In this modified device, the forward inner smaller mounting ring 132 is thinner, the rearwardly radially outwardly extending spokes 134 are straight rather than curvilinear, and the rearward outward ring 130 is basically cylindrical in configuration, rather than frustoconical as in the preferred previously described form.

It is conceivable that certain minor deviations in construction may be made in the apparatus illustrated without departing from the concept presented.

3,589,833