US2578806A - Propeller - Google Patents

Description

Dec. 18, 1951 L. JOHNSON PROPELLER Filed June 4, 1949 INVENTOR. L AWRENCE JO HNSON ATTOR/VfX 20f, the same general proportions, and

Patented Dec. 18, 1951 UN IT-ED STATES PATENT OFFICE PROPELLER Lawrence Johnson, 'Freeport, N. Y.

ApplicationgJune l, 1949, SerialNo...9'7,;2.5,-7

8 Claims.

This invention relates to, propellers, more particularly to propellersv for marine purposes.

It is primarily within the contemplation of my invention. to provide a propeller which will enable greater speed to, be obtained than is possible with conventional propellers of the same size and area; and it is my purpose to attain this objective by providing :a propeller blade of such construction that it will both have a greater effective area than conventionalblades will cut down considerably on slip.

Many attempts have been made'to accomplish greater speed and reduce slip, the most common expedient being to put a rak-ein the blade, thereby advancing the pitch towards the leadingedge. While this arrangement has been known to give increased blade area, it has generally been found to be unsatisfactory, particularly because it is inefiicient when operated in reverse. With my invention, I obviate the disadvantages inherent in conventional methods of obtaining greater effective area, andI accomplish this by a construction which does not add to the propeller diameter, but which nevertheless gives improved. results, both in forward and reverse operation. vAnd I have found that where conventional propellers of a given area and diameter willemploy only one-third of the blade as. the effective area, I have succeeded with, my

invention in obtaining for similarlyisized blades more than 50% effective area.

And Ihave accomplished the above objectives of my invention without adding to the complexity or fabricating difliculties of propeller manufacture.

Other objects, features and advantages will appear from the drawings and thedescription hereinafter given.

Referring to. they drawings,

Figure 1 is a front view showing a three-blade propeller according to my invention.

Figure 2 is an enlarged fragmentary front view of the propeller of Figure 1, showing thereon construction lines for laying out the blade.

Figure 3 is a fragmentary side view of Figure 2, and

Figured is an end view of Figure 2.

The drawings illustrate a three-blade propeller, each of the blades being formed and contoured according to my invention, as will more clearly hereinafter appear. It is to be understood, however, that my invention is not limited to the particular construction illustrated, and is adaptable with equal force and effect to propellers of more or fewer blades.

The blade construction shown includes a hub It of conventional construction; and extending outwardly therefrom is a plurality of blades, each being identical in construction. The propeller diameter is indicated by the letter D in Figure 1, the blade tip edges H extending to the circumference t2 of the circle whose diameter is D. The propeller axes l3, known also as the tip radii. of the blades, extend from the center [4- of the boss to points IE on said propeller circumference 12. These propeller axes, frequently referred to as the true layout center lines, are the. reference lines to determine the relativeangll-lardisposition of the blades 1'6 with. respect to eachother. In the present instanceytheangle between: each of the axes I3 is The construction of; each blade l6, according to .my'inyention is, in one aspect thereof, distinguishable from conventional blades in that the tip radiusor axis: k3 is not employed as a reference line for laying out the contour of the .leadingand trailing edges H and 1 land the said tip edge-11L. Instead,:a new layout reference, line .l.9a-.is..employled "for thisypurpose on each of the blades. This layout line 19 is drawnfrom said point 15 on the blade tip inwardly towards the hub, so as to. form an angle with the propeller axis 13.;sufliciently small so that line 'li9 will .intercept and extend: within :the bore 26 of the hub H}. I have found that excellent results areobtainable when said angle identified as A, between lines 13 and 19, is between 1 to 4; and- I have obtainedexceptionally good results when said angle-is- 2".

Having-'obtained'layout center 19, the tip edge H is-then drawn by employing a predetermined tip radius C, the generating center of are l I being point 21 ,ywhich is the intersection of layout center line l9 and ,centerline 22, the latter being normal to axis I3. Thereafter, employing point 2| as the generating point, layout arcs, 23,24 and,,2 5 (and additional arcs. where the 'lengthcf' the, blade warrants it) are drawn, using predetermined, radii therefor. It is preferredjthat the radiifor drawing, arcs, ll, 23, '2'4 and '25 be the same as would normally be employed, under given conditions, in designing a conventional blade where the axis is is employed as the layout reference line.

Thereafter, in order to obtain points that will define the contour of edges l1 and 18 of the blade, arcs 26, 21, 28, 29, 30 and 3! are drawn, employing as generating points the points 32, 33 and 34, these being the intersections of the layout line IS with the said layout arcs 23, 24 and 25. The radii 35, 36, 31, 38, 39 and 40 are of predetermined lengths, these being preferably the same as would be normally employed to produce blade contours by conventional methods where the propeller axis I3 is used as a reference layout line. In this manner, points 4|, 42, 43, 44, 45 and 46 are obtained which, when joined, will produce the desired propeller outline.

From a predetermined point 41 on center line 22, selected in accordance with the requirements of the particular case, section thickness outlines 48, 48 and 50 are drawn, the disposition of said thickness outlines being determined by the direction of lines 5|, 52 and 53, drawn from point 41 through the said contour generating points 32, 33 and 34, respectively. The said layout line It! is employed as a reference line for determining not only the contour of the blade, as aforesaid, but

also the angle of obliquity of the blade.

It is accordingly evident that the whole face of the propeller is ofiset with respect to the propeller axis l3, the angle of offset being the angle A between the layout and axis center lines. This produces a working surface of propeller which will act on a larger body of water than is possible with those conventional blade constructions in which the propeller axis tip radius is employed as a layout center line. I have found, particularly where the layout center 19 intersects axis 22 within bore 20 of the hub, that the propeller will cut into considerably more water and hold it against the face thereof, and will reduce the amount of slip, to a greater extent than is possible with conventional propeller constructions, and will, at the same time, permit efficient operation of the propeller upon a reversal of directions.

In the above description, the invention has been disclosed merely by way of example and in preferred manner, but obviously many variations and. modifications may be made therein which will still be comprised within its spirit. It is to be understood, therefore, that the invention is not limited to any specific form or manner of practicing same, except insofar as such limitations are specified in the appended claims.

I claim:

1. In a propeller, a hub and a blade joined thereto and extending outwardly to the propeller circumference, the hub having a central bore therein, the peripheral contour of the blade comprising tip, leading and trailing edges interconnected to form a continuous contour, the tip edge being intersected by the blades propeller axis extending from the center of the bore to the propeller circumference, the blade having a layout reference line extending inwardly from the outer terminal of the propeller axis to a layout center spaced from the center of the bore and on a center line thereof normal to the said propeller axis, whereby the said layout line is angularly disposed with respect to the said propeller axis, the said leading and trailing edges being defined by points constituting the respective intersections of a plurality of spaced layout arcs generated from said layout center and arcs drawn from the spaced intersections of said layout arcs and said layout line.

2. In a propeller, the combination according to claim 1 the tip edge having a portion thereof in the form of an arc, adjacent the trailing edge of the blade.

3. In a propeller, the combination according to claim 1, the angle between the said layout line and propeller axis being between 1 and 4 degrees.

4. In a propeller, the combination according to claim 1, the angle between the layout line and propeller axis being 2 degrees.

5. In a propeller, the combination according to claim 1, the said layout center being within the said bore of the hub.

6. In a propeller, a hub and a blade joined thereto and extending outwardly to the propeller circumference, the hub having a central bore therein, the peripheral contour of the blade comprising tip, leading and trailing edges interconnected to form a continuous contour, the tip edge being intersected by the blades propeller axis extending from the center of the bore to the propeller circumference, the blade having a layout reference line extending inwardly from the outer terminal of the propeller axis to a layout center spaced from the center of the bore and disposed within the bore, whereby the said layout line is angularly disposed with respect to the said propeller axis, the said leading and trailing edges being defined by points constituting the respective intersections of a plurality of spaced layout arcs generated from said layout center and arcs drawn from the spaced intersections of said layout arcs and said layout line.

'7. In a propeller, the combination according to claim 6, the sectional thicknesses of the blade being measured on lines drawn from a selected point on a center-line normal to said propeller axis to said spaced intersections of the layout arcs and said layout line.

I 8. In a propeller, a hub and a blade joined thereto and extending outwardly to the propeller circumference, the hub having a central bore therein, the peripheral contour of the blade comprising tip, leading and trailing edges interconnected to form a continuous contour, the tip edge being intersected by the blades propeller axis extending from the center of the bore to the propeller circumference, the blade having a layout reference line from which points defining said peripheral contour are measured, said layout line extending inwardly from the outer terminal of the propeller axis and intersecting said bore, whereby the said layout line is angularly disposed with respect to the said propeller axis.

LAWRENCE JOHNSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 683,808 Smith Oct. 1, 1901 FOREIGN PATENTS Number Country Date 400 Great Britain of 1882 423,400 Great Britain Jan. 31, 1935 439,471 Great Britain Dec. 6, 1935

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