US 1300552 A
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-APPL'ICAT|0N FILED MAXI8.'I9I8.
Patentmi Apr. 15, 1919.-
' snares AIRPLANE-PROPELLER.
Specification of Letters Patent.
Patented Apr. 15, 1919.
Application filed May 18, 1918. Serial No. 235,287.
To all whom it may concern:
Be it known that I, LESTER S. BARR, a citizen of the United States, and residing at Washington, District of Columbia, have in vented certain new and useful Improvements in Airplane-Propellers, of which the following is a, specification.
1 The present invention relates to propellers and more particularly to the type adapted for use in tractor airplanes, that is the type of propeller which is located at the front of the airplane. It is well lmown that the hub and the portion of the blades joining the hub afi'ord surfaces which resist the movement of the airplane. In some constructions, in order to reduce this resistance, a conical or convexedly curved cap has been mounted in front of the central part of the propeller, the surface of the cap forming a stream line with the fuselage. In none of the present machines, as far as I am aware,'has any provision been made to put the head resistance mentioned above, to any useful purpose.
' It is the principal object of this invention to provide a propeller which will utilize the head pressure at the hub and adjacent thereto to aid in turning the propeller; will auto-' matically conduct away the air striking the central part of the propeller so that it does not impinge on-the fuselage and retard the plane, and furthermore will produce a reduced pressure at the center of the propeller thereby augmenting the force turning the same. Other objects and features of novelty will be apparent from the description taken in connection with the drawings in which:
Figure 1 isa front elevation-of a propeller constructed in accordancewith the present invention; and
Fig. 2 is a section taken substantially on the line 22 of Fig. 1.
Airplane propellers in general use at present are made of wood and have relatively large hubs, first because of the type of fastening employed to secure the propeller to the propeller shaft and second because the stresses are greatest at the hub, these stresses including that due to the centrifugal pull of the blades and the cantaliver action of each blade. According to my invention, however, the diameter of the hub for securing the propeller to its shaft is relatively small, and a construction is provided just outside the hub which utilizes the impact or deflection of the air due to the velocity of the airplane to aid in turning the propeller.
Referring to the drawings the reference numeral 10 indicates the hub of the propeller which may be formed with the tapered bore 11 and the key-ways 12 for the purpose of mounting the propeller on its shaft. It is to be observed that the hub is relatively small compared to the usual airplane propeller construction. Preferably the propeller is made from metal and is one integral piece, although the invention is not limited to this material nor to the integral structure. Spaced from he hub 10 and concentric therewith is a ring 13. The rear edges of the ring and hub are connected by a walll l thereby forming an annular chamber 15 between said parts. At the front ends of the hub and ring are the blades 16 which are interposed and secured to said parts and constructed and arranged to utilize the impact and deflection of the air to aid in turning the propeller. Furthermore these blades act as reinforcing members between the ring and hub. They also give the air 'a circular motion within the chamber for a purpose presently to be mentioned. The parts thus far described in effect constitute a spider which corresponds to the hub in the usual propeller construction.
Secured to the outside of the ring 13 are the main blades 17 which are of the usual form. Each of these blades is formed with a radial air passage 18 which extends from the annular chamber 15 to adjacent the tip of the blade the passage opening at the trailing edge 19 thereof. As shown in Fig. 2 the inner ends 20 of these passages are flared out or funnel shaped so as to provide a better entrance for the air.
In the operation of the propeller the main blades 17 of course drive the plane in the usual way. The air striking the central portion of the propeller however impinges on i the blades 16 and thereby aids, due to the impact and deflection of the air, in turning the propeller. Because of the inclination of the blades 16. the air after it leaves the same is given a circular motion in the chamber 15 thereby conducting it to the passages 19. Thus. the passages 19 relieve the chamber 15 from any accumulation of air. Furthermore although these passages are relatively small compared to the chamber locity imparted to the air in the said pas- I sages is considerable, due to the centrifugal force generated in the air by the rotation of A the propeller blades. Thus the main blades with the passages therein act as an exhauster to reduce the pressure of air in chamber 15, thereby adding to the pulling power of the propeller. It will be observed further that the discharge of air at the edge 19 of the blades tends to offset the reduction of pressure at the trailing edges thereof and consequently tends to reduce the retarding efiect of this reduction of pressure. The spider construction which is used for connecting the main blades to the tively light, is sufliciently strong to withstand the forces to which it is subjected and yet permit embodying in its construction the features mentioned above. I
Although a specific embodiment of the inventionhas been described it is to be understood that it is not limited to the exact form shaft, although relaing a central hub, a concentric ring spaced from the hub, a-wall joining the rear ends of the hub and ring thereby forming an annular chamber open at the front of the propeller, blades secured to said ring each blade having an air passage formed therein ex tending from said chamber to the'end of the blade and having i tsouter opening at the trailing edge of! the blade, and blades connecting the front ends of the hub and ring constructed and arranged to effect a circular motion of the air entering the chamber to direct the same to the -inner ends of-said passages, said blades members. v
' In testimony whereof I afiix my signature.
LESTER S. BARR.
alsoa'cting as reinforcing