US2036727A - High speed marine propeller - Google Patents

Description

W'. F STOW Y Q03@ HIGH SPEED MARINE PROPELLER Filed July l2, 1954 2 Sheets-Sheet l 213 w. F. sToW v HIGH SPEED MARINE PROPELLER Filed July l2, 1934 2l Sheets-Sheet 2 Patented Apr. 7, 1936 UNITED STATES PATENT OFFICE 1 Claim.

This invention relates to high speed propellers for motor bo-ats. It belongs to the class of paddle wheel rather than screws, but the paddle wheel as ordinarily constructed is a slow speed device moving against a large area of water, whereas the present invention being designed for speeds of from 2000 to 4000 or more R. P. M. has required such re-organization, re-designing, and re-shaping of parts as to bear but little semblance to its prototype.

The principal object of the present invention is to provide a propeller particularly adapted to speed craft and comparable in its efficiency to the performance of the outboard motor.

Another object of the invention is to provide a propeller especially suited to weedy and shallow waterways.

Still another object of the invention is to construct a propeller that shall more efficiently cooperate with the hulls of small craft and propellers of the screw type with the result for example, that squatting of the stern is prevented and the boat permitted to ride the surface of the water, augmenting the speed possibilities.

Still another object of the invention is to provide a propeller adjustable for obtaining the optimum pitch relief to the type of hull with which it is employed.

Other objects of the invention wil appear as the following description of a preferred and practical embodiment thereof proceeds.

In the drawings which accompany and form a part of the following specification, and throughout the several figures of which the same characters of reference have been employed to designate identical parts:

Figure 1 is a side elevation of the stern portion of a boat illustrating the position of the propeller of the present invention;

Figure 2 is a side elevation of the propeller on an enlarged scale Figure 3 is a stern View of the same boat shown in Figure l;

Figure 4 is a section taken along the line ll--4 of Figure 6;

Figure 5 is a diametrical. cross section, a portion being broken away;

Figure 6 is a plan view partly in section;

Figure 7 is a fragmentary view partly in elevation and partly in section showing the adjusting means; and

Figure 8 is a perspective view of one of the blades or paddles.

In the development of high speed small power craft within the last few years attention has been devoted to improvements in hull design and in the construction of high speed internal combustion motors particularly of the outboard type. Very little attention has been given to the improvement of the propeller, and the conventional screw propeller is in almost universal use, being of relatively small diameter for high speed work and depending upon its velocity of rotation for minimizing slip and delivering the requisite speed to the boat.

The screw propeller has notable deciencies as a propelling instrumentality, the greatest of which of course is slippage, other drawbacks being its tendency to produce cavitation, that is, a vacuum in the back of the hull producing an aerated mass of water in which the propeller must operate, greatly decreasing the propulsive force of the propeller and which causes the stern of the boat to squat inclining the keel downwardly and increasing the resistance of the water to the forward motion of the hull.

As between the ordinary propeller and the conventional paddle wheel, there has been however no choice in high speed work, since the paddle wheel is essentially a slow speed apparatus operating against the resistance of a large mass of water. The paddles of an ordinary paddle wheel also lift water after they have passed rearwardly through a vertical plane embracing the axis of rotation and pull the stern of the boat downward, this tendency being much more marked in the case of the paddle wheel than in the screw propeller.

The screw propeller however has the disadvantage that in weedy waters, its twisting motion causes it soon to become fouled with grass or weed and to become inoperative, while in shallow places it is apt to strike a rock or sand and to shear olf the propeller pin rendering it altogether inoperative.

The present invention relates to a paddle wheel type propeller which has the advantages of a screw and none of the disadvantages thereof and which also lacks those drawbacks inherent in the paddle wheel as ordinarily constructed.

Since the present invention has some of the circumferential aspects of the ordinary paddle wheel, it maybe helpful in order to off-set any pre-conceived conception that it is like other paddle wheels, to call attention to the fact that Figure 2 of the accompanying drawings, original size, is one-fourth of the size of an actual propeller.

Now, referring in detail to the several figures, the numeral I represents the stern portion of a speed boat, 2 being the rear end of the keel. On each side of the boat near the stern is a Well 3 for receiving the upper part of the paddle wheels 4. The lo-wer part of the paddle wheels extend below the bottom of the boat for a distance preferably much less than the diameter of the paddle wheels and preferably extend to a depth below the level of the bottom of the keel so that when riding in shallow waters or in beaching the boat, it can roll on the land on the rims of its paddle wheels.

The paddle wheels are duplicated on each side of the boat, being driven by an axle 5 connected by the bevel gear set 6 and 'I and drive shaft 8 to a suitable source of power such as an internal combustion engine. The axle and drive shaft are preferably housed within housings 9 and I0 respectively. The ends of the axle pass through suitable apertures in the sides of the wells and since the apertures are designed to be above the water level, it is not necessary to pack them although the shaft may extend through stuffing glands in the sides of the wells 3, if desired. Each propeller comprises a twopart casing il, the parts of which are preferably, although not necessarily divided in a verticalplane symmetrical with the sides of said casing as indicated at I2 in Figures 5 and 6. The peripheral portion I3 of the casing extends below the paddles and engages the ground when the craft touches bo-ttom or goes ashore, the paddles being thus kept out of contact with the ground and the boat being automatically converted into a land vehicle.

The parts of the casing are rmly secured t0- gether in any suitable manner as by the bolts I4. The outer side I5 of the casing has fixed thereto in a substantial manner the internal hub I6, said hub having a tapered bore axially thereof, receiving the tapered end I'I of the axle 5. The end of the axle is threaded and has a nut I8 screwing up against the side I5 of the casing for holding the casing against endwse movement relative to the axle. A key I9 compels the casing to rotate with the shaft. Around the periphery of the casing are mounted a series of stub shafts 20 extending through both sides of the casing and to which are axed the paddles 2l and 22 on opposite sides of the casing. A hub 23 is normally fixed relative to the housing 9, but it can be angularly displaced through a limited arc by adjusting means presently to be described. Within the casing a sun gear 24 is xedly mounted on the hub 23 and has a central aperture which affords a bearing for the hub I6 of the casing. Each of the paddle carrying stub shafts 20 has afxed thereto and in the plane of the sun wheel a planet gear 25. Said gears 25 mesh with idlers 26, which in turn mesh with the sun wheel.

This form of force transmission is ancient, but is here employed for the accomplishment of certain novel ends without any particular claim being made to its specific structure.

It will be understood that the sun Wheel 24 is stationary while the casing II rotates. Rotation of the casing causes the stub shafts 2i) to move circumferentially about the sun wheel, and since they are connected to the sun wheel by the idlers 26, the shafts 20 will be rotated by the gears 25 in mesh with said idlers. Thus, although through rotation of the stub shafts 20 the paddles ro-tate relative to the casing, yet inasmuch as the casing itself rotates, the paddles, maintain a xed .orientation with relation to objects extraneous to the paddle Wheel, for instance, the water. The gears are so set that the working faces of the paddles are maintained in substantially vertical planes and their relation to the Vertical can be varied slightly by adjustment.

It will be understood therefore, that as the paddle wheels rotate in the direction of the arrow in Figure 2, the paddles dip into the water in a vertical direction and that after submergence they travel substantially horizontally rearwardly and that they emerge from the water in a substantially vertical direction. Thus there is practically no lifting of water as in the case of the ordinary paddle and since there is no lifting, there is substantially no reaction to the resistance of the water causing the stern of the boat to squat.

In weedy water, it is obvious that since the blades do go down into the water vertically, they will not twist the weeds, but will descend between them, pushing them apart, that the weeds will be pushed to the rear and since the paddles emerge vertically they will leave the Weeds in the same way as they entered them. The Weeds in fact afford a tractive surface better than the water itself since they are not so mobile as water, and afford more resistance to the rearward thrust of the paddles.

It will be observed particularly from Figures 2 and 8 that the paddles are streamlined so that they enter the Water with the minimum of turbulence, entraining little or no air and consequently practically eliminating cavitation. The streamlining of the upper ends of the paddles also permits them to cleave the water in the direction of emergence with minimum resistance still further reducing the force which would cause the stern to squat.

For the purpose of preventing backlash of the gears, the paddles are preferably mounted upon the stub shafts 20 slightly off center with the dominant area of the blade above the axis of rotation. This produces an unbalanced thrust of the water against the working face of the propeller and keeps it biased in one direction maintaining the teeth of the enmeshed gears always in close contact.

The shape of the hull has a decided influence in determining the direction of the flow of water immediately to the rear of the midship section of the boat. For instance, a boat with an abrupt rise in the stern portion will cause an upward deflection of the displaced water while a boat with no rise or a gradual rise in the rear portion of the hull will not deflect the water upward to So great an extent. Since, theoretically at least, the working stroke of the paddles should be at right angles to the direction of the moving current, it is desirable to have the paddles adjustable so that as a result of actual trials, the paddles can be set with their working faces at an angle to produce optimum propulsive efficiency. This adjustment is accomplished by having the hub 23 rotatable through a small angle. The hub has, as is indicated in Figure 5, a recess 21 in its rear end into which the housing 9 projects, the hub being a circumferentially sliding fit upon said housing. Since this adjustment is only infrequently made, it is not necessary to have any particular anti-friction bearing between the hub and the housing, The hubs 23 on opposite sides of the paddle wheel assembly are provided with xed arms 28 connected by any suitable means indicated by the broken line 29 in Figure 6 to a control member 30 by which they may be ad- 75 justed in unison and fixed in adjusted position. Rotation of the hub 23 of course rotates the sun gear 24 and in turn oscillates the idler gears 26 imparting the oscillatory movement to the gears 25 on the stub shafts to which the paddles are mounted.

It will be observed that the paddles 2| and 22 are symmetrically arranged on opposite sides of the casing Il being relatively narrow, and tted as close as possible to the Vertical plane intersecting the train of gearing thus producing a balanced structure with Very small lateral leverage. For the purpose of promoting narrowness of construction, the marginal portion of the casing I I, that is to say, the portion which encloses the planet gears 25 is made narrower than the central portion of said casing. The narrow portion of the casing extends beyond the path of revolution of the paddles and is relatively heavy acting not only as a fly wheel, but also as a tread enabling the boat to roll over rocks, sand bars and submerged debris after the manner of a land vehicle without damage to the propelling mechanism.

In order to keep sand out of the casing Il, the elongated bearings 3| are provided receiving the extending portions of the stub shafts 20, and entering deeply into wells or depressions 32 formed axially on the inner sides of the paddles 2l and 22. Washers 33 are preferably arranged at the bottoms of said recesses or wells against which the ends of the bearings 3l abut. The ends of the stub shafts 20 are preferably polygonal as -indicated at 34 in Figure 5, and seat in correspondingly shaped recesses 35 in the paddles,

see Figure 8. Screws 36 or any other suitable means are employed for preventing endwise displacement of the paddles.

The operation of the novel propelling means above described may be well understood from the foregoing description, it being essentially a high speed device designed to move through a current of water moving swiftly to the rear of the boat and produced by the forward motion of the boat. It is therefore essential to the avoidance of an insurmountable Water resistance against the paddles that the paddle wheels be submerged only to the extent of the substantially horizontal rearward traverse of the paddles.

This implies that the paddle wheels be mounted high with respect to the hull of the: boat which is accomplished by the provision of the wells 3 and the mounting of the axle 5 above the normal water line. In order to maintain the correct submergence of the paddle wheels it is essential that squatting shall not tak-e place which would increase the submergence of the paddle wheels and proportionately develop a back resistance due to the impinging of the water current against the vertically moving paddles which would quickly cut down the speed of the vessel. Such squatting, as has been pointed out, would be due to cavitation or lifting of the water by the paddles, both of which exigencies are avoided by the peculiar novel construction and arrangement of the parts in the present invention.

It will be understood that while I have illustrated and described what I believe to be a preferred and practical embodiment of the invention, the details of construction as disclosed are merely by way of example and are not to be construed as limiting the invention excepting as such limitations are expressed in the terms of the appended claim.

What I claim is:

High speed marine propeller adapted for speeds above 2000 R. P. M. comprising a paddle wheel including a casing mounted to rotate on a hori- Zontal axis, paddles, carried laterally outside of IE' said casing on opposite sides thereof and rotatable with respect thereto, said casing extending peripherally beyond said paddles forming a traction rim and being enlarged widthwise between said paddles and the axis of said casing forming a gear housing, means for driving said casing and said paddles including shafts extending through said casing and on the extending parts of which said paddles are mounted, and a gear train between said shaft driving means within said casing, whereby said paddles rotate as they revolve with said casing so as to keep their working faces in parallel substantially vertical planes throughout the cycle of rotation of said paddle wheel and means adjustably and equally varying the angularity of the working faces of said paddle with respect to the vertical.

WESLEY F. STOW.

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