US3053325A

US3053325A - Aeronautical propeller

Info

Publication number: US3053325A
Application number: US147529A
Authority: US
Inventors: Paul F Ferreira
Original assignee: Individual
Current assignee: Individual
Priority date: 1961-10-25
Filing date: 1961-10-25
Publication date: 1962-09-11
Anticipated expiration: 1979-09-11

Description

Sept. 11, 1962 P. F. FERREIRA 3,053,325

AERONAUTICAL PROPELLER Filed Oct. 25, 1961 2 Sheets-Sheet 1 Paul F F erreira l N VEN TOR.

Wynn; H

Attorney:

Sept. 11, 1962 P. F. FERREIRA 3,053,325

AERONAUTICAL .PROPELLER Filed Oct. 25, 1961 2 Sheets-Sheet 2 Paul F Ferreira INVENTOR.

BY 2mm 3,053,325 Patented Sept. 11, 1962 3,653,325 AERONAUTICAL PROPELLER Paul F. Ferreira, Box 111, Honolulu, Hawaii Filed Oct. 25, 1961, Ser. No. 147,529 6 Claims. (Cl. 170159) This invention relates to propellers and particularly to propellers for aircraft.

Briefly, the invention comprises a propeller having an enlarged arro whead shaped tip portion which has a concave forward face that substantially improves the efficiency of the propeller.

Accordingly, it is a primary object of the invention to provide a propeller having extremely high efiiciency for its diameter and pitch.

It is still another object o fthe invention to provide a propeller which is so designed that it will efficiently absorb a large amount of power particularly since its tip speed is reduced.

It is still another object of the invention to provide a propeller which will operate more efficiently at extremely high tip speeds.

It is still another object of the invention to provide an improved propeller which is suitable for use on aircraft, helicopters, and marine craft.

It is still another object of the invention to incorporate the advantages and efficiencies of the principles of a delta wing for use in propellers for improving the efiiciency thereof, particularly at the tip portions which are normally operated in the vicinity of sonic speeds.

These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout, and in which:

FIGURE 1 is a front elevational view of a preferred form of my invention;

FIGURE 2 is an enlarged end or plan view of the propeller shown in FIGURE 1;

FIGURES 3, 4, 5, 6, 7, 8, 9 and 10 are enlarged crosssectional views taken on lines 33, 44, 5-5, 6*6, 77, 8-8, 9-9 and 1010, respectively on FIG- URE 1.

FIGURE 11 is a front elevational view of a modified form of my invention;

FIGURE 12 is a horizontal cross-sectional view taken substantially on the plane of line 12-12 of FIGURE 11;

FIGURE 13 is a vertical cross-sectional view taken substantially on the plane of line 1313 in FIGURE ll;

FIGURE 14 is a cross-sectional view taken substantially on the plane of line 1414 in FIGURE 11;

FIGURE 15 is an elevational View of a portion of a third form of my invention;

FIGURE 16 is a cross-sectional view taken substantially on the plane of line 16-16 of FIGURE 15; and

FIGURE 17 is a rear elevational View of a fourth form of my invention.

Referring to the drawings, and particularly FIGURES 1 through 10, it can be seen that my propeller it includes a flat circular central hub 12 and

conventional propeller blades

14 and 16 projecting radially from opposite sides of the hub 12 and formed integrally therewith. The

blades

14 and 16 are of conventional air-foil crosssectional shape and the trailing edge and leading edge of each blade diverge from one another in a radially outward direction. As can be seen in FIGURES 8, 9 and 10, the blades are twisted so that the radially inner portions of the blades have a greater angle of attack or pitch than the radially inner portion thereof because of the greater linear velocity of the radial outer portions. It is also to be noted that the back sides of the blades are flat as shown at 18 and the forward surface of the blades are convex as shown at 29.

The ends of the blades 14 and '16 are secured to delta or arrowhead-

shaped tiups

22 and 24, respectively. Since the

tips

22 and 24 are identical to one another, only the tip 22 will be described in detail.

The delta-shaped tip 22 is defined by a slightly convex outer leading edge 26, a slightly convex inner leading edge 28 and a substantially radially extending trailing edge 36 The back side of the tip 22 is substantially flat as shown at 3-2 and is coplanar with the back surface of the outer end portion of blade 14 as shown in FIGURE 7. Two

convex ridges

34 and 36 are formed on each side of the forward face of the tip 22, and these ridges extend in slightly curved paths which are parallel to the leading

edges

26 and 28. The forward face of the tip 22 is hollowed out between the

ridges

34 and 36 so as to form a concave portion 38. As shown more clearly in FIGURES 3, 4 and 5 the concave portion 38 and the

ridges

34 and 36 gradually decrease in thickness as they approach the trailing edge 30 so as to provide a relatively sharp trailing edge. It is also to be noted that any cross-section such as 3-3, 44 and 5-5 taken through the tip 22 by a plane perpendicular to the longitudinal axis of the propeller is of streamlined airfoil shape similar to the cross-sectional shape of the

blades

14 and 16. Therefore, it is apparent that when the propeller rotates in a counterclockwise direction as viewed in FIG- URE 1 and indicated by the arrows R that the direction of airflow over the tip 22 is substantially parallel to the section lines 33, 44 and 5-5, and also the direction of flow of this air is also generally perpendicular to the longitudinal axis 40 of the propeller. Therefore, since the air flowing over the tip portion 22 is in effect flowing over a streamlined airfoil of the shape shown in FIGURES 3, 4 and 5 the relative movement between the air flowing over the tip 22 and the surfaces of the tip 22 create a great amount of thrust in the direction of the arrows T shown in FIGURES 2. A port-ion of this thrust is created by the positive angle of attack of the fiat surfaces 32 of the tip. However, most of the thrust is created by the air flowing over the

convex ridges

34 and 36 into the concave portion 28. The is because in flowing over the ridges the velocity of the air is increased thereby creating a reduced pressure on the back sides of the ridges and in the depression or convex portion 36.

Due to the relatively large area of the

tip portions

22 and 24, they obviously absorb a great deal of power in relation to the

blades

14 and 16 "because they are rotating or traveling at a greater linear speed.

The

tips

22 and 24 are in effect miniature delta wings. Therefore, they have all the advantages and characteristics of delta wings which are known to have improved aerodynamic characteristics at extremely high speeds, particularly speeds in the vicinity of sound and above.

It is to be noted that the forward surface of the outer end of each

blade

14 and 16 merges smoothly into the ridges 36 as shown at 42.

FIGURES 11 through 14 illustrate a modified form 44 of my propeller. The propeller 44 comprises a circular hub 46 integrally formed with S-

shaped blades

14 and 16 of circular cross-section. These blades terminate in and merge with delta-shaped tips 22 and 24' of identical configuration and size. The

tips

22 and 24 except their leading

edges

26 and 28 are straight. Also, it is to be noted that the blades 14' and 16' are connected with the trailing edges 30 of the tips and merge and blend into the rear end of the edges 36'.

While the blades 14' and 16' are shown as being circular in cross-section it is apparent that they could be of streamline or teardrop cross-sectional shape.

In the third form of my invention illustrated in FIG- URES and 16, the tips are substantially of the same design and configuration as shown in FIGURES 1 and 11. One of the tips is shown at 22 and differs from the other forms primarily in that a reinforcing rib 48 extends longitudinally down the center of the tip and projects from the forward face thereof. The rib 48 is substantially triangular in cross-section and has a pointed leading edge a shown at 50. The primary purpose of the rib 48 is to reinforce and strengthen the relatively thin central portion of the tip, particularly where it is recessed as shown at 38". The tips are mounted on the ends of blades 14" which are as illustrated in FIGURE 15 circular in cross-section. The blades on which the tips are mounted are substantially the same shape and design as illustrated at 14 and 16' in FIGURE 11.

FIGURE 11 illustrates a fourth form of my invention which differs primarily over the previous forms in that the blades 14" and 16" are substantially straight in a radial direction rather than being F-shaped as illustrated in FIGURES 11 and 15. However, these blades are either circular or teardrop-shaped in cross-section. While the blades are shown supporting

tips

22 and 24" of the same design illustrated in FIGURE 15, these tips may be of the designs illustrated in FIGURES 1 and 11 if desired.

The hubs of all the propellers illustrated are preferably provided with a central bore 13 for receiving a conventional drive shaft. The hubs may also be provided with conventional bores 15 (see FIGURE 1) arranged in a circular pattern around the central bore 13 for receiving bolts which extend through a radial flange on a drive shaft.

If desired, the blades such as 14 and 15 in FIGURE 1 of the propellers may be provided with dihedral, particularly if they are to be used in helicopters. By dihedral, it is meant that the outer ends of the propeller blades are tilted forwardly or backwardly in relation to the hub 12.

By providing the propeller blades with the

tips

22 and 24, it is possible to make a propeller of much smaller overall diameter which will absorb as much power as a conventional propeller of considerably larger diameter. The advantages of this are readily apparent. For example, it permits the landing gear of the aircraft on which the propellers are used to be made much shorter thereby saving weight and materials, and it reduces the tip speed of the propellers thereby permitting them to operate more efficiently.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention as claimed.

What is claimed as new is as follows:

1. A propeller comprising a blade, means for securing one end of the blade to a power source, the other end of said blade secured to an enlarged tip of deltoid shape, said tip having leading edges projecting forwardly of the leading edge of said blade and converging to a point, convex ridges formed on the forward surface of the tip parallel to and adjacent to said leading edges of said tip.

2. A propeller as defined in claim 1 wherein said tip is provided with a concave area between said ridges.

3. A device as defined in claim 1 wherein said ridges and the thickness of said tip at said concave area gradually decrease in thickness in a direction toward the trailing edge of the tip.

4. A device as defined in claim 3 wherein said blade is circular in cross-section.

5. A device as defined in claim 4 wherein said blade extends in an arcuate path between said securing means and tip.

6. A device as defined in claim 3 wherein a reinforcing rib is formed on the forward surface of said tip and extends along the median line thereof.

References Cited in the file of this patent UNITED STATES PATENTS 1,427,307 MaKenney Aug. 29, 1922 2,422,388 Billings June 17, 1947 2,511,502 Gluhareff June 13, 1950