US2131217A

US2131217A - Automatic variable pitch propeller

Info

Publication number: US2131217A
Application number: US115620A
Authority: US
Inventors: Brumwell Vincent Boyd
Original assignee: Individual
Current assignee: Individual
Priority date: 1936-12-12
Filing date: 1936-12-12
Publication date: 1938-09-27
Anticipated expiration: 1955-09-27

Description

I P 7, 1938. v. B. BRUM-WELL 2;1 3l, 2l7

AUTOMATIC VARIABLE PITCH PROPELLER Filed Dec. 12,1936

I Inventor A itorneys Patentedsept. 27 1938 UNITED STATES PATENT OFFICE.

s. 2,131,211 AUTOMATIC vaamam rrron rnoPELLEa Vincent Boyd Brnmwell, San Diego, Calif. a Application Decemberlz, 1936, Serial No. 115,620

My invention relates 'generally to propellersan arrangement whichreduces the strain on the' crankshaft and engine, and which permits the engine to turn at the samespeed at any altitude while the throttle is open.

Another important object of my invention is to provide a propeller of the character indicated in which there is practically no" pull when landing.

Other important objects of my invention will be apparent from a reading of the following description taken in connection with the drawing, wherein for purposes of illustration I have shown a preferred embodiment of my invention.

In the drawing:= Figure 1 is a general front elevational view of the embodiment.

Figure 2 is a front elevational view of one of the propeller blades.

Figure 3 is a horizontal sectional view taken through Figure 2 approximately on the line 38 and looking downwardly in the direction of the arrow.

Figure 4 is a front elevational view. of the back section of the hub. Figure 5 is a side elevational view of the assembled hub sections. I

Figure 6 is a horizontal sectional view taken through Figure 4 approximately on the line 66 and looking downwardly in the direction of the arrow.

Figure '7 is a top plan view of Figure 5. Referring in detail to the drawing, the numeral 5 generally designatesthe hub of the propeller which is composed of the front section 6' and the rear section l.- These sections are substantially similar, each being provided with a transverse bore 8 with the requisite keyways! therein to receive the propeller shaft. Each section 8, I is provided in its upper part with a semi-cylindrical chamber 10 and in its lower part below the bore 8 with a similar semi-cylindrical chamber II which isreversed with respect to the chamber Ill, but longitudinally aligned therewith.

Around the outer wall of each of these chamhers is a land l2 which is disposed at an'approximate 45 degree angle and which operatively cooperates with the correspondingly shaped and angulated grooves It in the corresponding annulus It which is fastened to the arm or shaft ii of the corresponding propeller blade It. The 1 upper part of the annulus It has a reduced cylindrical portion I! which is received in andturns in the reduced semi-cylindrical portion ll of the corresponding one of the chambers I0 and II, the shaft or arm l5 working through the receivl0 ing opening I9 in the top or bottom or end of the chamber. I

Each of the sections t and I is provided with a corresponding plurality of registrable' bolt receiving holes 20 in which are disposed the 15 bolts 2| to lock the sections together in registry as indicated in Figure 5 and in Figure 7.

' With the annuli ll of the respective propeller blades l6 mounted in the chambers formed by'the registration of the chambers l0 and II, upon 20 assembly of the sections 6 and I in the manner indicated, the propeller is assembled for use and installation on the propeller shaft (not shown).

, The numeral 22 designates the trailing edge of the propeller blade l6, while the numeral 23 25 designates the leading edge of the propeller blade.

In this connection it is to be noted'that the trailing edge-is oil-center with respect to the leading edge, so that most of the wind pressure will be on the trailing edge. 30

For a successful applicationlof the invention the propeller blade must be constructed so that are again equal. The 'blade also must be constructed so that at every different engine speed the pitch of the propeller must be at the most advantageous pitch. Thus in highaltitude or 45 stratosphere flying where theair is thin, as'the higher altitude is reached the wind pressure decreases gradually on the blades It. The centrif- Y ugal force increases slightly as the engine turns faster. The blades are forced out further. Thus 50 the pitch increases until the wind pressure and centrifugal force are equal. This givesa maximum propeller efliciency for stratosphere flying. As the plane gains altitude the pitch increases on the blades anddecreases when descending. when u landing the engine is idling and the pitch is back to zero or no pitch. Opposed blades are forced in opposite directions of rotation in imparting the pitch.

The grooves I3 and the lands l2 are arranged that when the propeller blades are in the pitch of zero or no pitch, and the hub is turned faster, the centrifugal force will force the blades to rotate outwardly so as to increase the pitch of the blades as far as full speed and until full speed is reached. As the hub is slowed down, the pitch of the blades becomes automatically lessened until the zero pitch position is reached at idling speed of the engine. The greatest angle obtainable is about 45 degrees or slightly more. As a higher altitude is reached in an aeroplane equipped with a propeller in accordance with the present in-- vention, the centrifugal force will exceed the wind pressure on the trailing edge of the blades, so that the blades will be forced to an increased pitch whereat the wind pressure on the trailing edges of the blades will equalize the force of the centrifugal force.

Although I have shown and described herein a preferred embodiment of my invention, it is to be definitely understood that I do not desire to limit the application of the invention thereto, and any change or changes may be made in the materials, and in the structure and arrangement of the parts, within the spirit, of the invention and the scopeof the subjoined claims.

What is claimed is:-

I. An automatic change pitch propeller of the class described comprising a hub adapted for mounting on a propeller shaft, said hub having radially extending portions each formed with a circular chamber and an opening in its outer end communicating with the chamber, propeller blades carried by said radialportions and each having a shaft part passing through the opening and a circular part slidably located in the chamber, each blade having its trailing edge off-center with respect to the leading edge to provide a greater wind pressure on the trailing surface than on the leading surface, means in the chamber and means on the circular portion for partly rotating e the blade when the same moves axially, said circular portion having unimpeded sliding movement in the chamber aside from the frictional engagement of such means on the circular portion with the means in the chamber, the parts being radially extending portions each provided with a chamber and each chamber having a circular outer part and a circular inner part, the inner part being of larger diameter than the outer part, an angularly disposed land on the cylindrical wall of the enlarged inner part of said chamber, propellers extendingjnto the radially extending portions of thehub and each having on its inner end a circular portion of two diameters, the smaller portion having sliding movement in the smaller part of the chamber and the larger part having sliding movement in the larger part of the chamher, said larger part having an inclined groove therein for'slidingly engaging the land, said circular portion having unimpeded sliding movement in the chamber aside from the frictional engage ment of the land with the walls of the groove, each blade and its circular portion moving axially outwardly under the action of centrifugal force of the rotating hub, each blade having its trailing edge oil-center with respect to the leading edge to place the major portion of the blade surface to the rear of the center of the blade, whereby the greater wind pressure will be exerted on the traili'ng surface,.the parts being constructed and arranged to cause increased pitch of the blade when the same is moved outwardly by centrifugal force and the pitch is decreased by axially inward movement of the blade when the wind pressure on the blade exceeds the centrifugal force.