US2321668A - Airplane propeller - Google Patents

Description

June 15, 1943.

c. J. GENTRY AIRPLANE PROPELLER Filed Feb. 28, 1941 Patented June 15, 1943 AIRPLANE PROPELLER.

Cleo James Gentry, Porterville, cane, assignor of one-half to Frederick E. Stone, Porterville,

Calif.

Application February 28, 1941, Serial No. 381,144

dClairns. (Cl. 170-472) This invention relates generally to the class of aeronautics and pertains particularly to im provements in propeller blades.

The present invention has for its primary object to provide an improved air screw blade or propeller blade which is designed in a novel manner to relieve the pressure of air which develops behind the propeller blade and around the rotary center of the propeller whereby to reduce the drag upon the propeller and increase the pulling efiiciency thereof.

A further object of the invention is to provide an improved propeller blade having an air chamber extending longitudinally of the blade with means for admitting air-to and exhausting it from the chamber radially with respect to the axis of rotation of the blade, said means functioning automatically upon the development of a predetermined pressure against the face of the blade around the rotary axis thereof.

The invention will be best understood from a consideration or" the followingdetailed description taken in connection with the acompanying drawing, it being understood, however, that the invention isnot to be considered as limited by the specific illustration or description butthat such illustration and description constitutes a preferred embodiment of the invention,

In the drawing:

Fig. 1 is a view in side elevation of a propeller constructed in accordance with the present invention and showing parts of the interior construction.

Fig. 2 is a sectional view on the line 22 of Fig. 1.

Fig. 3 Fig. 1.

Referring more particularly to the drawing,

is a sectional View on the line 3--3 of the numeral l generally designates a propeller blade, the root or inner end of which is indicated at 2, the tip at 3, and the leading and trailing edges by the numerals 4 and 5, respectively. The numeral 6 designates the back of the blade while the face is indicated by the numeral 1.

In accordance with the present invention there is formedthrough the major portion of the body of the blade an air chamber 8. At the inner end, this chamber merges into the reduced air inlet passageway 9 which opens through the face of the blade adjacent the root thereof, as indicated at H3. At the outer or tip end, the chamber is in communication with the longitudinally extending outlet passage II, which at its outer end opens through the .back of the blade by way of the port l2, as shown.

At each end of the air chamber 8, the face of the blade is provided with a removable cover plate, the inner plate being indicated by the numeral l4, While the outer plate, that is, the plate near'the outer end of the propeller structure, is indicated by the numeral I5. These plates respectively cover inspection openings 56 and I1.

At the inner end of the air chamber 8, a partition plate 18 covers the passage 9 and is provided with a valve opening it. At the outer side of this partition plate there are maintained in spaced alined relation longitudinally of the chamber, the stem guides 29 through which passes a valve stem 2! which carries upon one end the valve head 22 which is adapted to seat in the valve opening l9. This valve opens toward theouter end of the propeller blade.

The inner end of the stem 2| is threaded to receive an adjustment nut 23 and between this nut and the outer guide is an expansion spring '24 which functions to maintain the valve 22 on its seat. The guides 20 are, of course, maintained in place by suitable spiders or form a part of such spiders so as not to interfere with the passage of air through the chamber.

At the outer end of the chamber 8, a partition wall 25 is secured transversely of the chamber, which wall has a central opening 26 therethrough for the reception of a valve body. Between this partition wall 25 and the outlet port H are the two alined spider supported guides 27 which are spaced apart longitudinally of the chamber, through which s'lidably extends the valve stem 28 which upon its inner end supports the valve 29 which is constantly urged into the valve seat opening 26. This stem is. threaded and carries an adjustment nut 38 between which and the outerguide is an expansion spring 3| which constantly functions to maintain the valve 29 seated in the opening 26.

The tension of the springs 26 and SI which control the movement of the inlet and exhaust valves 22 and 29, respectively, are adjusted so that the inner .valve23 will open under a' pressure slightly less than the pressure required to open the outlet valve 29.

It is also contemplated that the valves may be set to be actuated under the effects of centrifugal force whenth'e propeller speed attains a certain degree or a certain number ofrevolutions per minute.

Th entrance to the air admission passageway 9 from the port H1 is preferably covered by a screenguardior wall '9'.

Due to the'provision .o'f'the air transmitting or carrying passage or chamber which extends longitudinally through the propeller blade opening through the face of the blade at its inner end and through the back of the blade at its outer end or tip, the operating efiiciency of the blade is greatly increased. As a result, it is possible to construct the blade with a ridge or flange 32 along the trailing edge of the face so that the blade may take a greater bite in the air and thus increase its pulling action.

In the use of solid propeller blades on air craft, there is built up between the propeller blade and the body of the airplane, an air pressure which tends to retard the forward motion of the plane. In other words, the propeller drives a mass of air rearwardly so rapidly that it in effect works against itself and after a predetermined speed has been reached by the propeller, this massed air begins to move with the propeller or is churned by the propeller and forms what might be termed an air lock. When this point is reached, the operating efiiciency or .value of the propeller is also reached and an increased speeding would have no advantage since the propeller would merely churn the mass of air interposed between itself and the body of the plane.

In the operation of the present invention, when the propeller has reached a certain speed where this back pressure begins to build up around the rotary axis of the propeller, such pressure will enter the port I adjacent the inner or root end of the propeller and will open the valve 22. The massed air which has begun to accumulate behind the rapidly turning propeller will then be diverted through the propeller blade by way of the chamber 8. This air passing longitudinally through the propeller blade acts upon the outer valve 29 and causes it to open and is then discharged or shot out through the tip of the blade through the port l2 which opens through the back of the blade. As a result of this diversion of the air which accumulates between the propeller and the body of the airplane, the built-up pressure between the propeller and airplane body is relieved and the speed of the propeller may be greatly increased before the condition of air lock would be reached. As a result of the action of the air pressure relieving means for the propeller, the face of the propeller blade may be formed with the flange 32 to give to the propeller a greater bite and, therefore, a greater pulling power.

It will, of course, be understood that the opening of the valves 22 and 29 does not take place until a certain pressure is developed and it is contemplated as being within the scope of the invention to adjust the valves so that they will respond to centrifugal action rather than .to air pressure and thus open at a predetermined propeller speed rather than at a predetermined air pressure.

By means of the present invention it is believed that at least a third of the air which is normallly blown back against the airplane fuselage or other part of the plane by the propeller will be diverted through the air chamber and the exhaust valve at the outer end of the propeller. By this means there is avoided the action of the propeller working against itself in blowing air back against the fuselage and thus retarding the forward motion of the plane on which it is mounted.

The preferred construction ofthe present invention includes the use of valves, as illustrated and described, for withholding the passage of air through the chamber of the propeller blade until a predetermined pressure is reached, but it is contemplated as being within the scope of the present invention to use a blade constructed as illustrated but without the control valves, Of course, it will be apparent that movement of air longitudinally through the blade will commence immediately but such movement will be restricted somewhat by reason of the smallness of the inlet and outlet ports, the volume of air moving through the blade increasing as the speed of the propeller increases and, consequently, as the pressure of air between the propeller and fuselage of the plane increases. Such a construction would, of course, result in the diversion of a portion of the air and the prevention of the building up of a high pressure between the propeller blade and the body of the plane.

What is claimed is:

1. The improved propeller blade as herein described, comprising a blade body having a longitudinally extending chamber therein and having an air inlet port leading to the chamber through the face of the blade adjacent the root end thereof and an air outlet port leading from the chamber through the back of the blade and adjacent the tip thereof, the front and back faces of the body being imperforate between said ports and valve means adjacent the inner and outer ends of said chamber for controlling movement of air longitudinally therethrough and opening toward the outer end of the blade and functioning to control the admission of air to the chamber through the inlet port and the exhaustion of air from the chamber through the outlet port.

2. The improved propeller blade as herein described, comprising a blade body having a longitudinally extending chamber therein and having an air inlet port leading to the chamber through the face of the blade adjacent the root end only thereof and an air outlet port leading from the chamber through the back of the blade and adjacent the tip only thereof, an air pressure actuated valve means adjacent each of the inner and outer ends of said chamber and opening only toward the outer end of the blade and functioning to control the admission of air to the chamber through the inlet port and the exhaustion of air from the chamber through the outlet port, and an adjustable tensioning means for and normally resisting the opening movement of each of said valves.

3. The improved propeller blade as herein described, comprising a blade body having a longitudinally extending chamber therein and having an air inlet port leading to the chamber through the face of the blade adjacent the root end only thereof and an air outlet port leading from the chamber through the back of the blade and adjacent the tip only thereof, an air pressure actuated valve means adjacent each of the inner and outer ends of said chamber and only opening toward the outer end of the blade and functioning to control the admission of air to the chamber through the inlet port and the exhaustion of air from the chamber through the outlet port, and a, flange forming an integral part of the blade body on the face thereof and adjacent the trailing edge.

4. The improved propeller blade of the character described, comprising a blade body, a chamber formed in and longitudinally of the body and having an. air inlet port opening through the face of the blade adjacent the root end and an air outlet port opening through the back of the blade adjacent the tip end, a partition plate extending across the chamber adjacent each end, each of said plates having an opening constituting a valve seat, a pair of spaced alined guides arranged upon the tip side of each partition plate, a, valve stem slidably supported in each pair of guides, a valve head carried by each stem and engaging in the valve opening of the adjacent plate, spring means encircling each valve stem and constantly urging movement of the valve through the stem to seated position, and means for varying the tension of the springs.

5. The improved propeller blade of the character described, comprising a blade body, a chamber formed in and longitudinally of the body and having an air inlet port opening through the face of the blade adjacent the root end and an air outlet port opening through the back of the blade adjacent the tip end, a partition plate extending across the chamber adjacent each end, each of said plates having an opening constituting a valve seat, a pair of spaced alined guides arranged upon the tip side of each partition plate, a valve stem slidably supported in each pair of guides, a valve head carried by each stem and engaging in the valve opening of the adjacent plate, spring means incircling each valve stem and constantly urging movement of the valve through the stem to seated position, means for varying the tension of the springs, and means for forcing air into said inlet opening, comprising a flange formed along the trailing edge of the blade upon the face of the blade.

6. In a propeller blade construction of the character described, a blade body having an air chamber therein and extending longitudinally thereof, said chamber communicating at the root end of the blade with an air admission port open.- ing through the face of the blade and said chamber communicating at the tip end of the blade with an air exhaust port opening through the back of the blade, a shiftable air admission control element in the end of the chamber adjacent to said admission port, a shiftable air exhaust control element in the chamber adjacent the exhaust port, and resilient means regulating movement of said elements and dififerently tensioned whereby that element adjacent the admission port Will open in advance of the element adjacent the air exhaust port under the eifects during the operation of the blade of air pressure and centrifugal force.

7. The improved propeller blade, comprising a blade body having a longitudinally extending chamber therein and having an air inlet port leading to the chamber through the face of the blade adjacent the root end thereof and an air outlet port leading from the chamber through the back of the blade and adjacent the tip thereof, the front and back faces of the blade body being imperforate between said ports, and a valved partitioning means across and closing each end of the chamber, the valves of said partitioning means being arranged to open in the direction of the tip of the blade.

8. A propeller blade of the type set forth in claim '7 in which said valves are designed to open in sequence toward the blade tip in response to centrifugal action and a predetermined air pressure thereon.

CLEO JAMES GENTRY.

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