US 2104306 A
Description (OCR text may contain errors)
Jan.'4, 1938. G. H. McLEoD' 2,104,306
` l SCREW PROPELLER FiledJune 20, 1936 l Patented Jan. 4, 1938 f Y UNITED STATES PATENT OFFICE f Application'. June zo', 1936, serial No. 86,40() In Newprzealana July 1.o, 1935 Y 6 Claims. (Cl. 170-170) -The invention relates to screwpropellers used more or less usual form, andextending radially on power driven boats of all descriptions, aerofrom the boss 2, rotating through an inner zone, planes and like machines, and also to power while outer blades or extensions 3from the exdriven fans and the like. Y tremitiesof the main blades I, rotate through an 5 The object of the invention `is to provide` an outer zone, whereby a plurality of working sur- 5 improved form of screw propeller or fan,vdesigned faces is provided beyond the radii of the main' to attain a greater degreeof emciency in operablades and resulting in the propeller being formed tion, than known forms of propellers. with duplex blade units. y
A propeller made according to the invention, The extension from the extremity of a main is formed with a plurality of working surfaces, blade I to form an outer blade 3, is in a direction 10 provided by main blades extending radially from outwards from the main blade along said extremthe propeller boss, and by outer blades extending ity,at the required angle and pitch, so that the from the main blades, to ,provide duplex blade line of junction 4 between the outer or tip blade units. 3 thus formed, and the main blade I, is in true The outer blades are in the form of extensions Y relationship t0 the bore 0f the Propeller, 01 in 15 from the extremities of the -main blades, said other Words, the lines 4 formed by the intersecextensions being directed outwardly from, and tions of the outer blades 3 and the main blades forming angles with the main blades, so as to l, are al1 OlSPOSed truly upon the periphery 0f provide working surfaces beyond the radii of the en imaginary Cylinder having its aXiS COhCldent ggvlatter. with the axis of the propeller and its shaft 5. V
The extensions thus formed, provide inclined The angle 0r Set 0f the Outer blades 3 in relasmaller or tip blades at the radial extremities tion to the blades l, varies in accordance with of the main blades of the propeller, the extension the power used for propulsion. or width of said tip blades from the main blades, The degree 0f extension 0f each outer 0r tip g5 commencing at, and increasing from the outer blade 3, from a main blade l, 1S from nothing, 25 extremities of the leading edges of the main starting at the outer extremity of the leading blades according to the usual direction of rotaedge 6 of the latter, to a dimension at the outer tion of the propeller, and increasing towards the extremity of the following edge 'I of the main following edges of the main blades, so that the blade l, approximating from one quarter to one greatest extension or width of the tip blades, third of the width of said main blade I, the 30 is at the following edges of the main blades, outer edge or extremity 8 of said outer or tip blade while the line of junction between each extension 3, being in the form of a shallow convex curve I2. or tip blade and the main blade which carries it, 'Ihe surface area of each outer or tip blade 3, is disposed on the periphery of an imaginary cylcan be equal to from one sixth to one eighth of inder having its axis coincident with the axis of the surface area of the main blade I from which 35 the propeller and its shaft. the tip blade 3 extends, said proportions being Other features are also comprised in the inhowever, merely approximate.
vention which will however, be more particularly 'I'he actual Width or degree of extension of the described with the aid of the accompanying outeror tip blades 3, the area of the latter, and
.40 drawing whereinz the angle at which said outer or tip blades 3 are 40 Figure 1 is a rear elevation, set in relation to the main blades I, are each and Figure 2 a plan view, and all determined by the power used, the revolutions Figure 3 a side elevation of a propeller formed required, the work required to be done, and other according to the invention, while conditions encountered in actual practice.
Figure 4 illustrates by means of a, diagram in- The surface 9 of each outer or tip blade 3 45 corporating a series of sections, the formation 'of `presented to the axis about which the propeller the outer blades, and rotates, is made hollow or concave through its Figures 5 and 6 are a part side elevation, and width or extension from the main blade I, the part sectional view respectively, illustrating a degree of hollowness or concavity increasing in a modification, and also the formation of the outer direction, from the least width or extension of 50 blades, both views being exaggerated to show the the blade 3 from the blade I, so that the greatest Y hollowing of said blades. o degree of hollowness or concavity of the blade 3 In carrying out the invention, the improved is at or close to the greatest Width or extension propeller or fan is formed to rotate through twoy of the latter from the blade I, (Figures 4, 5, 6), distinct and separate zones, main blades I of the effect of which is to allow Water to clear 65 itself without undue turbulence, and at the same time increase the thrust of the propeller.
In addition, for vessels used principally for towing and like purposes, each main blade l may be provided with two outer or tipi blades 3, (Figures 5 and. 6) each as before described, but set to opposite hands, so that increased efficiency of the propeller will alsoy be obtained when same is reversed, as when a vessel is reducing way, or going astern.
A second or additional outer or tip blade 3 may, or may not, have the same set or angle in relation to the inner or main blade l, as the first outer or tip blade.
Where two outer blades 3 are provided on main blade I, the space between said outer blades 3,
can be left open, or be partly or completely filledV in, also the main blades l will be adequately strengthened at the boss 2.
What I do claim and desire to obtain by Letters Patent of the United States of America iszl. A screw propeller comprising main blades extending radially from the propeller boss, andY outer blades extending from the main blades to provide duplex blade units, the main and outer blades forming a plurality of working surfaces, the outer blades being in the form of extensions from the extremities of the main blades, said extensions being directed outwardly from and forming angles with the main blades so as toprovide working surfaces from the radii of the latter, the extension commencing at the outer extremity of the leading edge of the main blade to the axis about which the propeller rotates, said faces being made hollow through their width or lextensionfrom the main blades the degree of concavity of the outer blades, increasing in a direction from Athe least width or extension of the outer blades, so that the greatest degree of concavity, is at or close to the greatest width of the outer blades.
4. A screw propeller, as in claim 1, wherein two outer blades are provided on each main blade, said outer blades being set to opposite hands.
5. A screw propeller as in claim l, wherein the line of junction between each outer blade, and the main blade on which it is formed, is disposed upon the periphery of an imaginary cylinder having its axis coincident with the axis of the propeller and its shaft.
6. A screw propeller as in claim l wherein the outer edges of the outer blades are in the form of shallow convex curves.
GEORGE HARNETT lVICLEOD.