US2055928A

US2055928A - Rotating blade means for aircraft

Info

Publication number: US2055928A
Application number: US747341A
Authority: US
Inventors: Russell R Hays
Original assignee: Individual
Current assignee: Individual
Priority date: 1934-10-08
Filing date: 1934-10-08
Publication date: 1936-09-29
Anticipated expiration: 1953-09-29

Description

Sept. 29, 1936. HAYS 2,055,928

ROTATING BLADE MEANS FOR AIRCRAFT Filed Oct. 8, 1954 INVENTOR.

Passe R Hays BY mm A TTORNEY Patented Sept. 29, 1936 UNITED STATES PATENT OFFICE 2,055,928 r ROTATING BLADE MEANS I08 AIRCRAFT Russell 3. Rays, Enoinitu, Calif. Application October 8, 1834, Serial-No. "7,841 8 Claim. (CI. Ml-l) My invention relates to rotating blade means for aircraft, more particularly to means for varying the angles of attack of a rotating blade at different moments of rotation. Variable or dissymmetry of airflow in connection with a direct lift propeller with rotating blade means makes it desirable that the angle of attack of the blade advancing in the direction of motion be reduced and at the same time the retreating blade be increased in order to decrease pitching or rolling moments which would otherwise result from the directional and velocity variations in the airflow encountered by the blades. Various methods and structures have been proposed and attempted to utilize air pressure variations on the blades to effect the deired variation in the blades angle of attack at different moments of rotation which have not been wholly successful because the lag has not been taken into consideration and the angle of attack variation heretofore has given rise to either oscillation or extreme angle of attack or both. Since both oscillation and extreme angle of attack are the source of inefliciency and in many instances of instability, it is desirable that they be reduced or eliminated. Inasmuch as lag is the underlying source of the inefliciency of such angles of attack variating means, it is obvious that the reduction of lag will raise the efllciency of the structure. Lag is the product of weight or inertia of the blade and its rotational velocity.

It is assumed that the weight and velocity of the blade are already the minimum permitted by design and structural relations. Therefore, the principal and first object of my invention is broadly the provision of means for reducing the lag of the aircraft rotating blade means by mak ing a lighter portion of it directly responsive to airflow variations;

Second, to provide a means of this class which is responsive to airflow variations by which the pitch variation is achieved in a rotating blade means through movement of a portion only of the blade rather than the blade as a whole;

Third, to provide a pitch variation means for rotating blades in which a trailing portion of the blade is normally urged to a positive angle of attack to the airflow by reason of resilient or tension members connecting the trailing portion with another portion of the blade:

Fourth, to provide a variable camber blade for a rotating blade which is directly responsive to airflow variations;

Fifth, to provide a pitch variating means for an aircraft rotating blade in which the lift and centrifugal forces operating on the bladesare out of alinement in vertical planes and in which the torque resultant to this disalignment is counterbalanced by a yieldable force such as spring tension in such a manner that the airflow variations effect a predetermined variation in the blades angle of attack;

Sixth, to provide a blade for an aircraft rotating blade means in which movable sections along the blade span effect pitch variations independently of each other and in direct response to air- 10 flow variations; and

Seventh, to provide a means of this class which is very simple and economical of construction, easy of installation, efllcient in its action and wliiich will not readily deteriorate or get out of 16 or er.

With these and other objects in view as will appear hereinafter, my invention consists of certain novel features of construction, combination and arrangement of parts and portions as will be 20 hereinafter described in detail and particularly set forth in the appended claims, reference being bad to the accompanying drawing and to the characters of reference thereon which form a part of this application, in which: v

Figure 1 is a top or plan view of a blade'such as is embodied in my invention showing some of the parts and portions broken away to facilitate the illustration; Fig. 2 is an enlarged sectional view taken through 2-2 of Fig. 1 showing some of the parts in elevation to facilitate the illustration; Fig. 3 is an enlarged sectional view taken through 3--3 of Fig. 1, and Fig. 41s a dia grammatical view of a blade section on a larger scale than that of Fig. 1 and smaller than that of Figs. 2 and 3 and showing by dash lines a varying position of the trailing portion of the blade and showing the forces effective upon the blade with varying airflow, and the operation of the means to be hereinafter described.

Similiar characters ofreference refer to similar parts and portions throughout the several views of the drawing.

A drive shaft l, shown best in Fig. 1 of the drawing, is provided with a head member 2 in the ends of which are mounted

alined bolts

3 and 3 which form an axis H-H for

hinge hangers

4 and 4 which are secured to the spar 5 preferably integrally, which spar 5 forms the leading edge of the blade; This spar 5 is provided with reduced backwardly extending curved hinge portions in, 5b and 50 to which the trailing edge is pivotally connected by means of pins 5d, thusproviding hinge supports between the leading and trailing edges of the blade forming an axis efeach provided with forwardly extending curved portions la which are adapted to fit into curved recesses in the leading member or spar 5, as shown best in Fig. 2 of the drawing, so that the combination of the members 5, 6, and 1 form a blade turning in the direction R.

The trailing portions 8 and I of the blade are hollow, as shown best in Figs. 2 and 3 of the drawing, and therefore very light in construction as compared with the leading edge 5, which leading edge 5 takes nearly all the structural stresses and a large portion of the aerodynamic stresses on the blade. Thus it will be noted that with the rotation of the blade the airflow will tend to aline the trailing portions 6 and I with the leading edge 5 in such a manner that in combination they comprise a blade section having a neutral or very small positive angle of attack to the air flow encountered. This tendency of alinement of the members 5, 6, and I is resisted by means of tension springs 8 and 9 which are secured in holes Se in the leading member or spar 5 and act with tension T on the blade trailing portions 6 and I and tend to force them out of alinement with the nose or front portion of the spar 5 and the direction of the airflow F, shown in Fig. 4 of the drawing.

The relationship between the tension T and the lift L, Fig. 4, acting on the trailing portions of the blade is such as to provide the blade used as a whole with a highly efficient angle of attack to the airflow encountered at any specific moment of rotation of the blade.

It will be here noted that normally the tension T of the spring 8 will urge the trailing section I, Fig. 2 of the drawing, downwardly through an angle B of about thirty degrees from a position in which the portion 1 is raised above the line of alinement to give a negative angle of attack in a position where the leading edge 5 is in alinement with an airflow parallel to the blade of rotation. It will be noted that the tension to be exerted by the spring or springs 8 and 9 at different values of the angle B is dependent upon several factors, some of which are the relative weights and areas of the hingedly joined portions; the position of the hinge axis A-A; the rotational velocity of the blade; the tip speed ratio; the hinge mounting of the blade; the blade section used, and the rolling or pitching moment desired in said blade as a whole. It will be particularly noted that in case of the tip of the blade a solid blade section changes its pitch by reason of the means described without changing its camber. In this instance the center of pressure travel on the section at different angles of attack may be easily derived from known wind tunnel data. From such wind tunnel data the varying leverage effect of .a constant lift L relative to a rocking axis A.A is easily arrived at and the tension T will then be calculated to balance this leverage effect at all times in such a manner as to cause the lift on the section to remain constant at all moments of rotation. Where the blade section is comprised of two movable sections however, variation with camber coincides with the variation in angle of attack, hence it is necessary to conduct wind tunnel tests to determine the varying leverage effect exerted by the lift L on the trailing portion of the blade before the desired tension T variation can be arrived at.

Since the center of pressure travel on the blades of different camber varies widely at different angles of attack it follows that the counterbalancing tension T exerted by the

springs

8 or 8 or other yieldable means may necessarily increase, remain constant, or decrease with movement of the blade section through angle B. In other words, the tension T will vary in accordance with the leverage effect of the lift on the blade or a portion of the blade about the rocking axis A-A in such a manner that either the resultant force or the lift L operating on the blade as a whole may tend to remain constant or vary at different moments of rotation in accordance with the requirements of any particular design. The tension T of a spring 8, as shown, will increase as the angle B decreases, but combinations of springs or other tension means may be used in many instances.

In operation the functioning of the hinged trailing sections of the blade and the tension springs result from either velocity or directional variation in the airflow encountered. For instance, when the airflow F, Fig. 4, changes its relative direction and velocity to F, the lift L' on the trailing portion of the blade decreases. The tension T of the spring which was in equilibrium with the lift L then becomes greater, with the result that the trailing portion of the blade moves downwardly, hence increasing its angle of attack and consequently its lift until the lift L balances the tension T exerted by the spring in this new position.

With the change of the airflow F back to F the reverse procedure takes place with the result that the lift on the trailing portion of the blade tends to parallel. a predetermined tension exerted by the spring through the distance travelled.

The effectiveness of such a pitch variation means is based upon two basic premises. First, that the necessary weight of the blade can be massed in the spar 5 which takes the drive torque and strongest aerodynamic forces; thus the trailing portion of the blade is many times lighter than the blade as a whole. Second, that although the spring exerts a strong tension giving the blade shape, and transmitting the lift on the trailing portion to the heavier structure of the spar, such yielding means have relatively little weight, thus since weight is the primary source of lag and since the lift of the blade as a whole is directly responsive to the varying camber and angle of attack effect of the hinged lighter portion, it follows that the blade as a whole is much more responsive to variations in the velocity and direction of airflow encountered.

With rigid sections such as are at the tip of the blade the rocking action about a radially extending axis is much more responsive to a tension means opposing airflow variations than to airflow variations opposed to weight distribution of the blade about a fixed axis augmented by the use of pilot planes which must necessarily be out of phase and also limit the responsive action of the blade to such airflow variations.

Furthermore, since the airflow and velocity variations do not occur uniformly along the span of the blade, it follows that the movable trailing portions 6 and 1 will react differently and independently in avoiding extreme angles of attack, thus raising the efliciency of the blade as a whole and it is readily seen that any number of such sections may be used.

In the present instance, the blade described is used in combination with a hinge mounting,

the axis of the hinge making an acute angle C, as shown best in Fig. 1, with the leading edge of the blade. However, it will be seen from the foregoing that such a means of providing a variable camber and pitch is subject to wide variation in application and may be advantageously used upon all types of rotating blade structures.

Though I have shown and described a particular construction, combination and arrangement of parts and portions, I do not wish to be limited to this particular construction, combination and arangement but desire to include in the scope of my invention the construction, combination and arrangement substantially as set forth in the appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In a sustaining rotor for aircraft, a blade consisting of a leading edge portion, a plurality of trailing edge portions in independent pivotal relation therewith, and yieldable means connecting said leading edge portion with said trailing edge portions whereby separate sections may adjust themselves in relationship with the air velocity at their respective locations with a minimum of lag.

2. In a sustaining rotor for aircraft, a blade consisting of a leading edge portion, a plurality of trailing edge portions in independent pivotal relation therewith, and yieldable means connecting said leading edge portion with said trailing edge portions tending to hold said trailing edge portions in certain relative pivotal relation with said leading edge portion, said trailing edge portions being not more than one half as heavy as the leading edge portion, whereby separate sections may adjust themselves in relationship with the air velocity at their respective locations with a minimum of lag.

3. In a sustaining rotor for aircraft, a blade consisting of a leading edge portion, a plurality of trailing edge portions in independent pivotal relation therewith, and yieldable means connecting said leading edge portionwith said trailing edge portions tending to hold said trailing edge portions in certain relative pivotal relation with said leading edge portion, said trailing edge portions being not more than two times as wide as the leading edge portion, whereby separate sections may adjust themselves in relationship with the air velocity at their respective locations with a minimum of lag.

4. In a sustaining rotor for aircraft, a blade consisting of a leading edge portion, a plurality of trailing edge portions in independent pivotal relation therewith, and yieldable means connecting said leading edge portion with said trailing edge portions with varying spring tensions at diflerent sectons whereby separate sections may adjust themselves in relationship with the air velocity at their respective locations with a minimum of lag 5. In a sustaining rotor for aircraft, a blade consisting of a leading edge portion, a plurality of trailing edge portions in independent pivotal relation therewith, and yieldable means connecting said leading edge portion with said trailing edge portions with varying spring tensions at different sections, said spring tensions increasing as the individual trailing sections approach the blade tip whereby separate sections may adjust themselves in relationship with the air velocity at their respective locations with a minimum of lag.

6. In a sustaining rotor for aircraft, a blade consisting of a leading edge portion, a plurality of trailing edge portions in independent pivotal relation therewith, and yieldable means connecting said leading edge portion with said trailing edge portions with varying spring tensions at diil'erent sections, said spring tensions increasing as the individual trailing sections approach the blade tip, said trailing edge portions being not more than one half as heavy as the leading edge portion and not more than twice as wide, whereby separate sections may adjust themselves in relationship with the air velocity at their respective locations with a minimum of lag.

7. In a means of the class described, a blade comprising an elongated leading edge portion rev- Oluble about an axis at right angles to its direction'of elongation, a trailing edge portion in pivotal relation with the rear side thereof, said trailing edge portion being not more than one half the weight of the leading edge portion, and tension means tending to support said leading edge portion and said trailing edge portion in angular relation to each other and variable with the variable pressure exerted thereon.

8. In a means of the class described. a blade comprising an elongated leading edge portion revoluble about an axis at right angles to its direction of elongation, a trailing edge portion in pivotal relation with the rear side thereof,

said trailing edge portion being not more than twice the width of the leading edge portion and tension means tending to support said leading edge portion and said trailing edge portion in angular relation to each other and variable with the variable pressure exerted thereon.

RUSSELL R. HAYS.