US 3715171 A
A propeller for a powered boat wherein the blades of the propeller are open through centrifugal force to propel the boat and are closed when the boat is not being powered so as to reduce drag on the boat. The blades are maintained in the closed position by operation of ceramic magnets disposed adjacent the tips of the blades.
Claims available in
Description (OCR text may contain errors)
ite States aterit 11 1 Kettner 1 Feb. 6, 1973   References Cited  Inventor: Robert E. Kett rier, East Grand UNITED STATES PATENTS Rap1ds, Mlch.
3,255,826 6/1966 Beck ..4l6/l42 X 3,591,311 7/l971 Butler ..416/l42  Assignee: Michigan Wheel Corporation,
Grand Rapids, Mich Primary Examiner-Everette A. Powell, Jr.
Attorney-Walter E. Pavlick, Harold D. Shall and 22 Filed: May 14,1971 Tegland  Appl. No.: 143,510  ABSTRACT A propeller for a powered boat wherein the blades of 521 u.s.c1 ..416/142 the propeller are p through centrifugal force to  Int. Cl. ..B63h 1/24 P p the boat and are closed when the boat is hot 58 Field of Search ..29/211 N; 416/3, 142, 143, being P d w reduce g boat. The 416/153 blades are mamtamed 1n the closed p0s1t1on by operation of ceramic magnets disposed adjacent the tips of the blades.
10 Claims, 5 Drawing Figures FOLDABLE PROPELLER BACKGROUND OF THE INVENTION I. Field of the Invention The invention relates particularly to yacht propellers and is intended especially for use in connection with that class of yachts which are adapted to be propelled both by sail and any other powering device, such as an internal combustion engine. However, the invention may be employed in the construction of propellers for any style of vessel to which it is applicable.
2. Description of the Prior Art Many sail boats also utilize an auxiliary inboard engine to power the boat when not under sail. However, when not in use the blades of the propeller produce a drag on the boat, particularly when sailing at slow speeds. Consequently, propellers have been provided which will fold through the action of the water moving past them and which will open upon the introduction of a centrifugal force when the boat is under power. With these folding propellers, however, when the sail boat heels to one side or another, the weight of the blade itself causes unfolding thereof producing the undesirable drag. To remedy this, many prior art devices have been provided to retain the propeller blades in their folded positions when not in use. These devices These included means for automatically folding the propellers when not in use, such as that shown in Thompson U.S. Pat. No. 938,290, wherein a spring urges the propeller blades to a folded position. These prior art devices have been very complex in structure, subject to failure and expensive to manufacture.
SUMMARY OF THE-INVENTION Therefore, it is an object of this invention to provide a durable, simple, inexpensive means to automatically hold the propeller blades in the folded position when not in use while permitting said blades to be automatically opened upon the introduction of centrifugal force when the boat is powered.
Another object of this invention is to provide a propeller having blades contoured so as to be in a mating relationship when folded together.
A further object of this invention is to provide ceramic magnets glued in the tips of the propeller blades to hold the blades in their folded position when the boat is not under power to reduce a drag on the boat while permitting the blades to be open upon centrifugal action of the propeller.
These and other objects of this invention will become apparent from the following detailed description when taken in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of the propeller incorporating this invention with the blades thereof extending in radial direction as when the boat is under power;'
FIG. 2 is a plan view of the propeller shown in FIG. 1 with the blades folded to a closed position as when the boat is under sail;
FIG. 3 is a side elevational view of the propeller shown in FIG. 2;
FIG. 4 is a sectional view taken along the lines IV- IV of FIG. 3; and
FIG. 5 is an enlarged cross-sectional view taken along the lines VV of FIG. 1
DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring more particularly to the drawings, a propeller assembly indicated generally at 10 comprises two major parts. The major parts include a mounting means or hub member 12 and a pair of propeller blades 14 and 16 with such propeller assembly 10 being powered by a drive shaft 18.
The hub member 12 is comprised of a generally cylindrical body portion 20 which has the forward portion thereof tapered inwardly to facilitate the flow of water thereby. Internally of the body portion 20, a pair of bores 22 and 24 are provided. The bore 24 is of smaller diameter than bore 22 and is somewhat tapered inwardly. The intersection between the bores 22 and 24 provides a shoulder 26 which is engaged by a nut 28 positioned within the bore 22. The nut 28 has internal threads which are adapted to cooperate with external threads provided on the end of the drive shaft 18. Consequently, the drive shaft 18 is inserted into bore 24 and 22 and the nut 28 is screwed onto the end of the shaft and engages the shoulder 26 to secure the shaft to the hub.
To prevent rotation of the nut and thus prohibit the nut from become unscrewed from the shaft, the nut is provided with a cross-hole and a cotter pin 30 is inserted through openings in the hub, through the holes in the nut and secured in place by bending over the ends of the cotter pin.
The end of the hub 12 opposite the drive shaft 18, is provided with a pair of cars or bifurcations 31 and 34. The bifurcations 32 and 34 are spaced apart a sufficient distance to accommodate the reception of the stems 36 and 38 of the propeller blades 14 and 16, respectively.
The stems 36 and 38 are relatively flat with the stem 36 being positioned on top of stem 38. Openings are provided in the stems and a pin 40 extends through a corresponding opening in bifurcation 32 and is seated in a bore 42 provided in bifurcation 34. The pin 40, therefore, provides a pivot around which the blades 14 and 16 can rotate. To secure the pin 40 within the opening in bifurcation 32 and the bore 42 in bifurcation 34, an aperture is provided in the pin 40 and is adapted to receive a small cotter pin 44 extending through a portion of bifurcation 32 and having the ends thereof bent over to prevent extraction.
When it is desired to remove the propeller blades 14 and 16, it is merely necessary to remove the cotter pin 44, place a tool with a tap-hole 46 in communication with bore 42 and tap the pin 40 from the openings.
The propeller blades 14 and 16 are contoured so that the external surface of the blades when in the folded position do not present an obstruction for the passage of water so as not to present a drag on the boat. Furthermore, the blades are constructed to be in a generally juxtaposed relationship while the stems thereof are positioned within the bifurcations 32 and 34 of the hub one upon another.
The outer extremity of each propeller blade 14 and 16 is provided with a round hold 48 positioned along the centerline thereof. A circular ceramic magnet 50 of a diameter slightly smaller than the holes 48 is posithe ceramic magnet with the epoxy glue is important in that it protects the magnet from being exposed to water and electrolysis that might take place.
OPERATION In the operation, when the boat is not under power, the blades 14 and 16 are arranged to pivot automatically into a trailing position with respect to the hub 12, this action occurring primarily as a result of relative aftward movement of the water past the blades during nonpowered forward movement of the boat. The blades thus pivot from the radial position shown in FIG. 1 to the trailing position in FIGS. 2 and 3. The blades are contoured so that they cooperate in a mating relationship. When the blades are in the cooperating mating relationship, the ceramic magnets 50 disposed in each of the blades with dissimilar magnetic polarity adjacent each other causes the blades to be held together in the folded position regardless of the position of the boat.
Whenever it is desired to apply power through such a folded propeller, rotation of the shaft 18 and the propeller hub 12 will move the blades outwardly to the position shown in FIG. 1 by the action of centrifugal force upon the blades. Whenever rotation of the propeller ceases, the blades will fold under the influence of the relative aftward movement past the blades as the boat glides forwardly.
Accordingly, it is apparent that a simple, inexpensive, trouble free, automatically operated foldable propeller has been provided which reduces to a minimum the drag provided by a propeller when the boat is under sail.
What is claimed is:
l. A foldable propeller adapted to be connected to a drive shaft for rotation thereby comprising (a) mounting means adapted to be secured'to the drive shaft, (b) a first propeller blade pivotally secured to said mounting means, (0) a second propeller blade pivotally secured to said mounting means and rotatable with respect to said first propeller blade so that said propeller blades are movable toward and away from each other, (d) magnet means associated with said first and second propeller blades and holding said blades together when pivoted to positions adjacent each other.
2. The foldable propeller set forth in claim 1 wherein said first and second blades are contoured so that that they will be in mating relationship when pivoted to positions adjacent each other and whereby said blades will pivot outwardly upon the action of centrifugal force.
3. The foldable propeller set forth in claim 1 wherein said magnet means comprises a first magnet device mounted adjacent the tip of said first blade and a second magnet device mounted adjacent the tip of said second blade whereby said magnet devices will be in engagement when said blades are pivoted to a folded position adjacent each other and whereby said blades will move to an unfolded position upon rotation of the drive shaft.
4. The foldable propeller set forth in claim 2 wherein said magnet means comprises a first magnet device secured by glue adjacent the tip of said first blade and a second magnet device secured by glue adjacent the tip of said second blade whereby said magnet devices will be in engagement when said blades are pivoted to positions adjacent each other. i
5. The foldable propeller set forth in claim 1 wherein said magnet means is mounted on the inner surface of said blades by glue and a coating of glue covers said magnet means so as to be protected thereby.
6. The foldable propeller set forth in claim 5 wherein a hole is provided on the inner surface of each blade and said magnet means comprised a pair of magnet devices, each glued in a hole with the surface of the coating of glue substantially flush with the inner surface of said blades.
7. The foldable propeller set forth in claim 5 wherein said first and second blades are pivotally secured to said mounting-meansfor rotation about a common axis. 8. The foldable propeller set forth in claim 1 wherein said first and second blades are pivotally secured to said mounting means for rotation about a common axis.
9. The foldable propeller of claim 7 wherein said mounting means comprises a body portion having bifurcations extending from the rearward end thereof and said first and second blades having stems thereon extending between said bifurcations with pin means mounted in said bifurcations and extending therebetween through openings in said blade stems to pivotally mount said blades for rotation.
10. The foldable propeller of claim 9 wherein said first and second blade stems are mounted within said bifurcations with one on top of the other while said blades are contoured so as to be in a side-by-side relationship.