US2556351A - Mass load applying means for airfoils - Google Patents

Description

June 12, 1951 TULLEY 2,556,351

MASS LOAD APPLYING MEANS FOR AIRFOILS Filed July 17, 1947 1 INVENTOR.

W FIG. 3

FREDRICK T. TULLEY 7 BY I Emmi Team ATTORNEY Patented June 12, l95l UNITED STATES PATENT MASS LOAD APPLYING MEANS FOR AIRFOILS Fredrick T. Tulley, Columbus, Ohio, assignor to Curtiss-Wright Corporation, a corporation of Delaware Application July 17, 1947, Serial No. 761,627

Claims. 1

The present invention-relates to mass balancing means and mass biasing means for movable control airfoils, such as ailerons and elevators.

For the purpose of balancing or overbalancing an airfoil whose center of gravity would otherwise be aft of its hinge axis it has been usual to provide a mass of heavy metal either in the leading edge of the airfoil or on an arm extending forwardly from the airfoil. In cases where the hinge axis is very close to the leading edge of the airfoil, a mass supported on an arm may be more advantageous by providing greater leverage for the mass, thereby permitting reduction of its Weight. However there is the disadvantage that the arm and mass, if external, impose additional aerodynamic drag; and if internal, with the arm extending into a fixed airfoil, such as a wing or stabilizer, forward of the airfoil to be balanced, the maximum hinge movement of the airfoil is limited by the thickness of the attenuated trailing edge portion of the fixed airfoil.

The present invention provides a novel lever mounting for such a load applying mass whereby the latter is disposed farther forward, in a thicker portion of the fixed airfoil, permitting a wider range of movement of the balanced airfoil for a fixed airfoil of given section. According to the arrangement the lever which carries the mass may be pivoted to the movable airfoil closely adjacent to or substantially in transverse alignment with the center of gravity of the airfoil, which is advantageous in that it reduces the possibility of flutter developing in the airfoil at high air speeds. The lever is pivoted to the fixed airfoil forwardly of the hinge axis of the movable airfoil. One of the lever pivots includes means to provide for the limited fore and aft movement of the lever and mass incidental to movement of lever about the other pivot during hinge movements of the control airfoil. The last-mentioned means preferably comprises a substantially upright link pivoted at one end to the fixed airfoil and at its opposite end to the lever, the link preferably comprising the fore pivot of the lever in order that it may be disposed in the fixed airfoil whose thickness will ordinarily be greater than that of the control airfoil.

The foregoing and other objects and advantages will become apparent from the following description of the structure shown in the accompanying drawings, wherein:

Figure 1 is a fragmentary perspective view of an aileron provided with a mass balance in accordance with the present invention, the wing to which the aileron and balance is attached being shown in phantom;

Figure 2 is a plan view on a larger scale of the mass balance mechanism and adjacent fragments of the Wing and aileron structure; I

Figure 3 is a vertical sectional View of the struc- 2 ture shown in Figure 2, with the aileron in its neutral position; and

Figure 4 is a view similar to Figure 3, but with the aileron in raised position in the full line illustration, and in lowered position in the broken line showing.

In the drawings a fixed part II of the aircraft structure, in this case the main airfoil or wing, has hinged to its trailing edge a control airfoil l2, in this case an aileron. The aileron may be operated by any suitable means, not shown. The

aileron hinge connection, which may be duplicated at any desired number of stations along the span of the aileron l2, comprises fittings l3 and I4 mounted respectively on the wing and aileron and connected by a hinge pin l5. As shown in Figures 2, 3 and 4 the fitting I3 may comprise a central casting of substantially c-shape with attachment brackets secured thereto by rivets which appear in cross-section in Figures 3 and 4.

Extending through the fitting I3 is a pivot pin it which mounts the upper end of a link ll to whose lower end a lever I8 is pivoted by a pin l9. For the purpose of improving flutter characteristics, the aft portion of the lever is pivotally secured at 21 to aileron l2 along an axis that extends through the aileron in close proximity to its center of gravity, being slightly below the center of gravity in the illustrated embodiment, indicated at C.G. in Figure 3. The forward end of the lever carries a mass 22, sufficiently heavy in this case to substantially balance the aileron about its hinge pivot l5 in the neutral position of the parts shown in Figure 3, although it will be understood that the mass may be designed to either overbalance or underbalance the aileron if desired, and is therefore referred to generically as a load applying mass. By applying the load applying mass at or in proximity to the center of gravity of the control airfoil, the forces that tend to cause flutter, i. e., oscillation tending to center about the center of gravity, are opposed so that the control airfoil is-damped and flutter is minimized.

In the neutral position of the aileron I2 shown in Figure 3 the link H is substantially upright; but as shown in Figure 4 it swings rearwardly about pivot 55 as the aileron is raised, and forwardly as the aileron is lowered. In the illustrated embodiment greater up travel than down travel of the aileron was desired, and for this reason the mass 22 is slightly above a mid-position between the upper and lower surfaces of wing II in the neutral position of the aileron shown in Figure 3.

It will now be seen that the arrangement described, by placing the lever pivot means l6, ll, [9 forwardly of aileron hinge axis l5, disposes the mass 22 in a substantially thicker portion of the wing ll than would be the case if the lever arm were rigid with the aileron, for a lever arm of same effective length.

It will be understood that any desired number of mass load applying units of the kind illustrated in Figures 2, 3 and 4 may be applied along the span of the aileron or other control airfoil. Where two or more such units are provided, their corresponding pivot axes should be aligned, and all of the axes should either be parallel or converge to a common point as will be well understood by those skilled in this art. While the axes of aileron hinge and of the several pivots are referred to as being substantially transverse of the aircraft it will be understood that this terminology is intended to include cases where the axes are somewhat angularly related to a true transverse axis by reason if dihedral, or of positive or negative sweepback, of the trailing edge of the aircraft structure with which they are associated.

It will also be understood that the structure specifically shown and described herein represents only one preferred embodiment of the inventive principles that are involved, and that these principles may be otherwise embodied without departing from the spirit of the invention or from the scope of the appended claims.

I claim as my invention:

1. In an aircraft having a fixed airfoil and a control airfoil hinged forward of its center of gravity upon a first substantially transverse axis to the trailing edge of said fixed airfoil, the combination of a plurality of levers each pivoted to the control airfoil upon a second substantially transverse axis that extends through the control airfoil adjacent to said center of gravity, said levers extending forwardly into said fixed airfoil and each having at its forward end a load applying mass housed within said fixed airfoil, a link for each lever disposed within the confines of said fixed airfoil, said links being pivoted to their respective levers intermediate of the load applying mass and said second axis, and said links being pivoted to the fixed airfoil along a third substantially transverse axis disposed forwardly of the first axis, each of said levers applying the load of its load applying mass to the control airfoil principally in a direction that is substantially normal to the plane of the control airfoil.

2-. In an aircraft structure having an airfoil hinged forward of its center of gravity upon a first substantially transverse axis to a trailing edge of said structure, the combination of a plurality of levers each pivoted to the airfoil upon a second substantially transverse axis that extends through the airfoil adjacent to said center of gravity, said levers extending forwardly into said structure and at their forward ends having mass load applying means housed within said structure, a link for each lever disposed within the confines of said structure, said links being pivoted to their respective levers intermediate of the mass load applying means and said second axis and being pivoted to the fixed airfoil along a third substantially transverse axis disposed forwardly of the first axis, each of said levers applying the load of its load applying mass to the airfoil principally in a direction that is substantially normal to the plane of said airfoil.

3. In an aircraft having a fixed substantially horizontal airfoil with spaced upper and lower surfaces at the trailing edge thereof and a control airfoil whose leading edge extends into the space between said surfaces, the control airfoil 4 being hinged forward of its center of gravity upon a first substantially transverse axis to the trailing edge of said fixed airfoil, said axis being substantially closer to the upper surface than to the lower surface, the combination of a plurality of levers each pivoted to the control airfoil upon a second substantially transverse axis that extends through the control airfoil adjacent to said center of gravity, said levers extending beneath said first axis and forwardly into said fixed airfoil, each of said levers having at its forward end a load applying mass housed within said fixed airfoil, a link for each lever disposed within the confines of said fixed airfoil, said links being pivoted at their 1 lower ends to their respective levers intermediate of the load applying mass and said second axis, said links being pivoted at their upper ends to the fixed airfoil along a third substantially transverse axis disposed forwardly of the first axis, and the links being substantially upright when the control airfoil is in its neutral position, each of said levers applying the load of its load applying mass to the control airfoil principally in a direction that is substantially normal to the plane of the control airfoil.

4-. In an aircraft having a fixed airfoil and a control airfoil hinged upon an axis forward of its center of gravity to the trailing edge of said fixed airfoil, the combination of a lever pivoted to the control airfoil at a point therewithin whose longitudinal location is adjacent that of said center of gravity, said lever extending forwardly into said fixed airfoil and carrying at its forward end a load applying mass that is disposed within said fixed airfoil, and a link pivoted to the lever intermediate of said mass and the pivot of the lever to the control airfoil, said link being pivoted to the fixed airfoil forwardly of said axis and being disposed within the confines of the fixed airfoil,

' s the lever being arranged to apply the load of said load applying mass to the control airfoil principally in a direction that is substantially normal to the plane of the control airfoil.

5. In an aircraft having a fixed airfoil and a control air-foil hinged upon an axis forward of its center of gravity 'to the trailing edge of said fixed airfoil, means for minimizing flutter of said control airfoil comprising a lever pivoted to the control airfoil 'at a point therewithin whose fore and aft location is adjacent that of said center of gravity, said lever extending forwardly into said fixed airfoil and having at its forward end a load applying mass within said fixed airfoil, and means pivoting the lever for limited floating movment intermediate of the mass and the aforementioned pivot of the lever to the fixed airfoil, said means providing fore and aft movement of said mass and lever according to movement of the pivot connection between the lever and control airfoil during hinge movements of the latter, the lever being arranged to apply the load of said load applying mass to the control airfoil principally in a direction that is substantially normal to the plane of the control airfoil.

6. In an aircraft structure having an airfoil hinged upon an axis forward of its center of gravity to the trailing edge of said structure, means for minimizing fiutter of said airfoil com prising a lever pivoted to the airfoil at a point therewithin whose fore and aft location is adjacent that of said center of gravity, said lever extending forwardly into saidstructure and having at its forward end a load applying mass within said structure, said lever being pivoted to said structure between the mass and the airfoil pivot of the lever, and one of the pivots of the lever providing for relative fore and aft movement thereof as required by the other pivot during hinge movements of the airfoil, the lever being arranged to apply the load of said load applying mass to the airfoil principally in a direction that is substantially normal to the plane of the airfoil.

7. In an aircraft structure having an airfoil hinged, upon an axis adjacent its leading edge, to a trailing edge of said structure, the combination of a lever pivoted to the airfoil aft of said hinge axis, a link pivoted to said structure and to said levr forward of said hinge axis, and a load applying mass on said lever forward of the latters pivot to the link, the lever being arranged to apply the load of said load applying mass to the airfoil principally in a direction that is substantially normal to the plane of the airfoil.

8. In an aircraft having a main airfoil and a control airfoil hinged along an axis near its leading edge to the trailing edge of said main airfoil, means for loading said control airfoil comprising a lever pivotally connected to the control airfoil at a point therein materially aft of said hinge axis, said lever extending forwardly into said main airfoil and having at its forward end a load applying mass within said main airfoil, means disposed forward of said hinge axis for pivotally mounting said lever on said main airfoil at approximately the mid-section of said lever, and means associated with one of the pivotal connections of said lever for providing relative longitudinal movement between the lever and the respective connection according to hinge movement of said control airfoil, the lever arm acting on said control airfoil extending materially into said control airfoil so as to reduce pivot connection stresses and to restrict the limits of movement of said mass within said main airfoil for predetermined hinge movement of the control airfoil.

9. In an aircraft having a main airfoil and a control airfoil hinged along an axis near its leading edge to the trailing edge of said main airfoil, means for loading said control airfoil so as to minimize flutter comprising lever structure pivotally connected to the control airfoil at a point therein materially aft of said hinge axis, said lever structure extending forwardly into said main airfoil and having at its forward end a load applying mass within said main airfoil, means for pivotally mounting said lever structure on said main airfoil, and means associated with one of the pivotal connections of said lever structure for providing relative longitudinal movement between the lever structure and respective connection according to hinge movement of said control airfoil, the lever arm acting on said control airfoil extending materially into said control airfoil to approximately the location of its center of gravity so that said mass is effective to apply a damping force at said center of gravity for minimizing flutter.

10. In an aircraft having a main airfoil and a control airfoil hinged along an axis near its leading edge to the trailing edge of said main airfoil, means for loading said control airfoil and minimizing flutter thereof comprising a lever pivotally connected to the control airfoil at a point in proximity to its center of gravity, said lever extending forwardly into said main airfoil and having at its forward end a load applying mass within said main airfoil, means for pivotally mounting said lever on said main airfoil, and means associated with one of the pivotal connections of said lever for providing relative movement between the lever and respective connection according to hinge movement of said control airfoil, the lever arm acting on said control airfoil applying the load of the load applying mass to the control airfoil at approximately said center of gravity principally in a direction that is substantially normal to the plane of said airfoil for opposing forces tending to cause flutter of said control airfoil.

FREDRICK T. TULLEY.

REFERENCES CITED The following references are of record in the file of this patent:

FOREIGN PATENTS Number Country Date 423,752 Great Britain Feb. 7, 1935 678,479 Germany July 17, 1939

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