Marine propeller

• US 4,370,096 A
• Filed: 08/29/1979
• Issued: 01/25/1983
• Est. Priority Date: 08/30/1978
• Status: Expired due to Term

• Current Assignee: Marine Propulsion Limited
• Original Assignee: Propeller Design Limited
• Inventors: Church, Leslie G.
• Primary Examiner(s): Powell, Jr., Everette A.
• Application Number:
  US06/070,868
• Time in Patent Office: 1,245 Days
• Field of Search: 416/189 R, 416/237, 416/189 RA
• US Class Current: 416/189
• CPC Class Codes: B63H 1/16 having a shrouding ring attached to blades
• CPC Class Codes: B63H 1/26 Blades

Abstract

A marine ring propeller comprising blades, each having parallel edges and a constant cross-section, and a ring in the form of an annular shroud fixed to the outer ends of the blades. The shroud is typically frusto-conical on its inner surface and curved on its outer surface to provide an aerofoil cross-section, apart from the leading edge which is provided with a concave bevel on either or both of the inner and outer surfaces.

Claims

1. A marine ring propeller comprising:

a plurality of elongated propeller blades positioned around a central hub, each blade having leading and trailing edges which are straight and parallel to each other, each blade being smoothly curved concavo-convex in cross-section with the leading edges being beveled to be substantially parallel to the plane of rotation of the propeller;

the cross-section of each blade being constant along the length of the blade;

a shroud shaped as an annular wall fixed to the outer ends of the blades and having an inner surface and outer surface, the inner surface being frusto-conical so as to be converging toward the downstream end of the propeller at an angle between 1° and

15°

to the rotational axis;

said inner surface being substantially flat from the trailing edge of the annular wall forward to a point axially forward of the point of contact with the leading edge of the propeller blade;

said outer surface being essentially of smoothly curved convex shape when viewed in cross-section.

2. The propeller of claim 1 wherein the longitudinal axis of each blade is positioned along a radius of the shroud.

3. The propeller of claim 1 in which the taper of the inner surface of the shroud is substantially 6 degrees from the central axis.

4. The propeller of claim 1 wherein the blades are at an angle of 20 to 80 degrees to the axis of rotation.

5. The propeller of claim 4 wherein the blade angle is between 30 and 68 degrees.

6. The propeller of claim 1 wherein the longitudinal axis of each blade is angled between 10 degrees forward and 20 degrees rearward of the plane perpendicular to the central axis of the propeller.

7. The propeller of claim 6 wherein the longitudinal axis of each blade is angled between 5 degrees forward and 10 degrees rearwardly of the plane perpendicular to the central axis of the propeller.

8. The propeller of claim 7 wherein the longitudinal axis of each blade is angled at approximately 7 degrees rearward of the plane perpendicular to the central axis of the propeller.

9. The propeller of claim 1 wherein the number of blades is between two and twelve.

10. The propeller of claim 1 wherein the number of blades is between three and six.

11. The propeller of claim 1 wherein the trailing edge of each blade has an under surface which meets the plane passing through and leading and trailing edges of the blade at an angle between 0 and 35 degrees.

12. The propeller of claim 1 wherein the leading edge of the inner surface of the shroud is beveled at a point forward of said flat area.

13. The propeller of claim 12 wherein the bevel at the leading edge of the inner surface of the shroud is at an angle of 15°

to 45°

from the central axis of the propeller.

14. The propeller of claim 1 wherein the leading edge of the outer surface of the shroud is beveled.

15. The propeller of claim 14 wherein the bevel at the leading edge of the outer surface of the shroud is at an angle of 5°

to 35°

from the central axis of the propeller.

16. The propeller of claim 12 or 14 wherein at least one of the bevels at the leading edge of the shroud is slightly concave.

17. The propeller of claim 1 wherein the ratio of the shroud length to the blade width, as measured in a direction parallel to the central axis of the propeller, is between 1:

1 and 5;

1.

18. The propeller of claim 17 wherein the said ratio is approximately 2.5:

1.