US1639785A - Propeller - Google Patents

Description

1927 B. u. SEPljLVEDA PROPELLER Filed Jan. 16, 1923 2 Sheets-Sheet 1 avwemtg'cl I da 1927' B. u. SEPULVEDA PROPELLER Filed Jan. 16, 1923 2 Sheets-Sheet 2 Patented Aug. 23, 1927.

UNITED STATES PATENT OFFICE.

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Application filed January 16, 1923. Serial No. 612,909.

This invention refers to a new form of helical propeller blade, based upon a theory which when practically applied gives hydraulic and aerial propellers of greater efficiency than all others heretofore known, as has been practically demonstrated.

The basis of this propeller, like that of almost all propellers in use, is the helix. The difference between the present propeller and the common propellers consists in the distribution of the surface of the blade; the distribution in this propeller being, it might be said, an inversion of that generally used.

It is known that in the common propellersi'nany different forms of blades are found, the object in each case being to increase its efficiency, usually by diminishing the prejudicial resistances by means of the form and disposition of the borders; or seeking a better effect by the transverse adjustment of the propellers surface, it being more or orejudicial resistances,

less curved;"without getting, however, very appreciable differences in the final result byany of these methods.

When conceiving my propeller, I have not regarded as necessary the diminishing of the a point of really small importance (although I have paid attention to this factor) but I have proposed to increase the power by more radical media, and in particular I have tried to facilitate the rotation of the blade by distributing its surface in a novel way.

In one of its various mechanical aspects, the blade, as it is known, may be regarded as'the arm ofa lever, whose power is furnished at its centre of motion, which coincides with the center of rotation of the propeller. The resistance is generated by the fluid in which the blade moves; resistance which is in relation to the surface offered the blade, multiplied by the correspondarm of the lever; or in other words, by the distance from the centre of rotation. If we consider a blade wide at itsextreme end and narrow at its base, in order to move it with a determined speed, we should need a power much greater than we should need to effect. the same speed of rotation if we inverted it, or placed its wide end near the centre of rotation.

These considerations include the fundamental idea, the application of which constitutes my invention.

The principal factors which determine ing power consumption of a propeller are its diameter and speed of rotation. The propeller of my invention turns with much greater speed than do common propellers of equal diameter, weight, and total blade surface, supplied with the same motor power, because it presents less resistance to the turning movement. Consequently, in order to control the speed of rotation of my propeller so that the number of revolutions will not exceed those of a known propeller under the same motive power, my propeller must be of greater diameter than the known propeller, which greater diameter, of course imparts a correspondingly greater weight. These are conditions which are responsible for the advantages in efliciency mentioned above.

The blades form of my propeller, within the fundamental idea previously expressed, and other complementary details contained in the following explanation, is illustrated in the accompanying drawings. These drawings represent:

Fig. 1 shows diagrammatically the outline of a blade in front view;

Fig. 2 shows diagrammatically the outline of a blade in side view;

Fig. 3 shows diagrammatically in heavy lines the developed surface of a blade in accordance with the invention, and in light lines the developed surface of an ordinary blade; 1

Fig. A: is a view of the active face of a propeller embodying the invention;

Fig. 5 is a side view;

Fig. 6 is a view of the passive face;

Fig. 7 is a view of the active face of a. blade;

Fig. 8 is a section taken approximately along the curved line 12-13 of Fig. 7

Fig. 9 is a section taken approximately along the, curved line 1415 of Fig. 7;

Fig. 10 is a, section taken approximately along the curved 'line 17-18 of Fig. 7 f

In all these figures similar reference characters designate corresponding parts in all views.

As may be noted, the hub 3 is, in proportion, more elongated than in common proas it is the length of the hub Which re ulatesalmost exclusively the extension 0 the surface.

The border of entrance 6 of the blade is a straight line (1-1, Figs. 1 and 2) lying in the plane including the axis of rotation,

and inclined backward at an angle to intersect the circumference 8 of the blade at a point opposite, or to the rear of the middle of the hub, at which point it meets the curve '7, which constitutes the border of exit. This curve 7 approaches from the periphery 8 to the axis of rotation 11, and all points of the curve lie preferably in a conic surface produced by the rotation of the line 2-2- about the axis (Fig. 2); or they may lie in the plane represented by the mentioned line ,(Fig. 2).

The blade sections (Figs. 8,9 and '10) are drawn according to the development which corresponds to the concentric circles which determine them for the purpose of indicating clearly the variations of the concavity and convexity of both faces of the blade.

The active surface of the blade is preferably, generally concave. If sections are taken on concentric circles, traced from'the axis of rotation, the line of intersection with the active surface will be more or less curved, according to its position towards the end of the blade, except the one that coincides with the surface of the hub, which will be the only mathematically straight one. This may be observed. in the sections of the blade of Figs. 8, 9, and 10. The greater departure 20 (Fig. 9) from the straight line corresponds to the section taken at the Widest art of the blade, decreasing in the remain mg sections both toward the periphery and toward the hub to zero at these points.

The blade viewed from the side (Figs. 2 and 5) presents the form of an almost perfeet triangle.

The blades extremity, or the union point 8 of the borders of entrance and exit, must be at a point varying between the middle 9 of the hub and the posterior extreme 10 of same; but the latter disposition is admissible only in propellersof great diameter, or with relatively narrow blades.

The propeller of my invention may .be constructed, as usual, with two, three, or more blades, provided that their width and number will allow a comparatively large space for the fluid to enter.

The width of the blades, as will be understood from the foregoing explanation,

may be that which is most suitable in each case, taking into consideration, as is usual, the numberof revolutions, the diameter, the fluid in which it is designed to work, etc.

As may be observed in Fig. 3 showing a comparison of the developed surfaces of my propeller blade and one of common type, the concentric circle 5 represents the path of the centre of gravity of the surface of the common blade, or the point of application of the pressures to which'this blade is subjected; and the circle 4, the path of the centre of gravity of; and point of applicaweaves tion of pressure on the blade of my invention. As may be seen, this approaches considerably nearer to the centre of rotation,

.the point at which the resistance is presumed to be applied, reducing theradial distance, or arm of the lever, which allows agreater speed of rotation, thus generating a eater impulsion or traction.

rom the foregoing, it will be seen that 4 part to avoid as far as possible useless resistances. As a result of numerous experiments with bodies moving in different kinds of fluid, ll have observed that it is the' extreme of the border of exit of these bodies which requires to be more sharpened or to have a greater obliquity of the, surface in order to provide the least resistance in proportion to their displacement.

- Reduced to general geometrical terms, the blade form which I have adopted in this propeller is determined by two planes which cut a helical surface, namely, a plane 11 (Figs. 1 and 2) which is a radial plane including the axis of rotation, determines the edge of entrance 6; and .another plane, 2-2 (Figs. 1 and 2) perpendicular to the foregoing and which intersects the axis toward the rear of the hub, and intersects the edge of entrance 6 at the point 8 which is the tip of the blade determining the edge of exit 7 which may be the curved line which approaches towards the centre and which we be situated in a plane parallel to that described as determining the border of entrance, and somewhat advanced in the'di rection of rotation. of the pro ellers as shown in Figs. 11 and 13. Th1s sposition, which does not alter the fundamental prin-, ciples applied by me, will be specially adapted to meet construction needs of propellers for use in the air.

In order to have the terminal point 8 of i the blade at the desired radius in relation. to the hub the helical surface should be generated by a generating line inclined a siliiitable) angle to the axis, as the line, 1-1

The greatest thickness of the blade is not midway between both borders, but is closer. to the border of entrance,as may be observed at 21, 22 and 23' (Figs. 10, 9 and 8). This is very advantageous, especially if it is necessary for the propeller at times to function 1n the reverse d'lrectlon, because the fact of the greater thickness being near to the border of entrance, tends to diminish in great part the convexity of the passive.

surface, and render it more efiicientwhen performing active functions.

As regards the further details of the practical construction, the usual practice should be followed, of constructing these mechanisms so as to soften and to round the edges or entering orsalient angles, especially the keen edged extremeend of the blade. Which results'from its theoretical trace. The borders should generally be relatively thin, but

there is no necessity that they end really in an edge.- Especially the border of exit need only be rounded, approximately to the middle of its length from the periphery, and may increase in thickness and have a bevel cut in the direction of the plane of iotation from there to the hub as indicated by the numerals 12, 161& and 1917 (Figs. 7 8,

end of the hub and intersecting the leading edge at a point approximately in a line passing) through .the longitudinal center of the 2'. A helical propeller as set forth in claim Lsaid blade having a transverse concavity of unequal depth at different points along its active surface.

3. A helical propeller blade as set forth in claim 1, said blade having its greatest thickness near the leading edge.

AVA helical propeller blade as set forth in claim 1, said blade .having its greatest thickness near its leading edge and having a transverse concavity of unequal depth at difi'erent points along its active surface.

5. A propelling screw, comprisin blades, the propulsive surface or" each of W ich decreases in a general Way from the hub to- Ward the periphery, the entrance edge of said surface being disposed in a plane passing through the axis of rotation, said edge being in a straight line from said axis and the exit edge of said surface commencing at a point in the periphery onthe hub and lying in a plane at right angles to-said first plane, said exit edge being curved and contracted in a predetermined mathematical progression toward the centre, said edges intersecting each other at a point in a line passing through the longitudinal center of the hub.

In testimony whereof I have signed my name to this specification.

BENJAMIN URZE JA Sl.'lllll.VEIIM..

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