US2597521A - Toy glider - Google Patents

Description

May 20, 1952 J. C. PEMBERTON ETAL TOY GLIDER Filed May 25, 1946 2 SHEETS-SHEET 1 L2! I I 22 t FIG 3 LT" JG PEy B RTQN DORRIS RONALD BALDRIDGF.

ATTORNEY May 20, 1952 J. c. PEMBERTON ETAL 2,597,521

TOY GLIDER Filed May 25, 1946 2 SHEETS--SHEET 2 2O C ce FIG 7 FIG 6 JC PEMBERTON AND DORRIS RONALD BALDRIDGE ATTORNEY Patented May 20, 1952 TOY GLIDER J. C. Pemberton, Pasadena,v and Dorris Ronald- Baldridge, Glendale, Calif.

Application May 25, 194.6,.Serial him-672,198

9 Claims. 1.

Our invention relates to aircraft and more particularly to: improved means for controlling the flight of toy gliders.

Arr objectof our invention. is to provide an aircraftwith an airfoil which is: responsive to air:

speed for. stabilizing the. flight of the aircraft under: difierent conditions.

Another object of our invention is to provide an aircraft with a movable airfoil the position of; which is. controlled by the aerodynamic re--' action of." the air thereon during, flight for stabilizing: the; flight of the aircraft under different conditions.

Another object of our invention is to provide a glider with a movable'stabilizer element which.

is" normally held in a position corresponding to stable gliding, but which is movable. in. response to catapulting to a second position which permits catapulting upward to a great height.

Another object of our invention is to. provide a toy aircraft employing a movableairfoil with means for setting the airfoil at oneatta-ck angle during catapulting' and at another attack angle during gliding.

Fig. v iis an enlarged fragmentary sectional view" of thetoy glider;

Fig. 5. is a. fragmentary bottom view of the stabilizer showing the hinge.

Fig. 6 is a free body diagram of forces acting on the. glider during catapulting; and

Fig. 7 is a free body diagram of forces acting on the glider during gliding flight.

Referring to the drawings, there is illustrated av toy glider incorporating the features of our invention. This glider comprises an elongatedbody Ill provided With'a blunt head. ll within which a suitable weight I2 is rigidly secured. The body l tapers rearwardly from the blunt head II to a tail IS; A- launching hook in the form of a rearwardly extending notch I6 is incorporated .on the body beneath the head I I. The glider is provided with a plurality of airfoilswhich enable it to glide stably in the air. These airfoils: include adihedral wing 20 extending transversely of the body forward of the center thereof. a hall-- low fin 21. which: is mounted vertically on. the tail, and a: stabilizer 22 arranged transversely on the tail.

The wingv is mounted rigidly on a block 24 which fits snugly within a slot 25 in the top edge of the body In and. is held therein by means of rubber. bands 26-26.

The stabilizer 22 of thepresentinventionis of variable camber and comprises astationary airfoil: 28 rigidly secured to the body- H1 andmounted transversely thereof betweenthe body In and the front portion of thefin 2i, and also-comprises a movable. airfoil, or elevator, 29; which is supported by hinges 31, 3I- on the trailing edge of the stationary airfoil 28 and extends rearwardly therefrom. The movable airfoil29'extendstransversely of the body I0 through'a triangular. slot 30. between the body l0. and. the rear portion of the fin 24. The airfoil 29 is pivotally movable within the triangular slot 30 between a first, or upper, position against an upper'stop 34 and a secondor'lower, position. against a. lower stop 35. The first position is indicated by solidlinesx and thesecond position by dotted lines in Fig. 4'. In the first or upper position the stabilizer has. a high negative camber andin the second or lower position a low negative camber.

The body and the wing and the fin and the stabilizer elements may be made'of some low density material such as. balsa wood. Or they may be made" of.1ight metal. such as; aluminum. In thelatter case, the; thicker members especially the body and-therfin and: possiblyalso thewing and. the stationary stabilizer airfoil. arepreferably hollowandmade of thin sheet metal.

In the'event that the glider is made of balsa wood, each of the hinges 3|, 3| supporting the elevator 29 is made of a flat hook 32 and a flat loop 33 respectively cemented to the-lower surfaces of thestationary and movable stabilizer elements 28- and: 29;.as illustrated in detail in Figs. 4 and 5. More-particularly, the hook 32 and the loopv33- are preferably composed of a light weight metal, such as aluminum, and are cemented to i the balsa wood'by means of a cellulose and acetone cement.-

In either event; the fin 2i is preferably hollow and thecavitySt therein terminates in an opening 31 at the lower rear side thereof above the elevator '2 9.

A suitable resilient member, such as a weak spring M3; is provided forv urging the elevator 29 upward into the first position where it' is held. againsti'the upper stop 34 during gliding flight: The: spring: is preferably mounted within the fin 2| and is in the from of two elongated legs 4! and 42 interconnected by a coil 43 having a few turns. One leg 4| of the spring is hooked at its end onto a pin 44 which extends through the walls of the fin 2| adjacent the lower front end thereof. The other leg 42 of the spring is hooked at its end over the trailing edge of the elevator 29. Preferably the points of attachment of the spring 48 are on a line passing slightly above the hinge axis when the elevator 29 is in the second position against the lower stop 35 as indicated by the dotted line 45 in Fig. 4 for reasons which are explained hereinbelow.

According to our invention, the airfoils of the glider are so designed and arranged on the body of the glider that the glider is capable of stable flight vertically or nearly vertically during launching at relatively high speeds and is furthermore capable of stable gliding at relatively low speeds. In order to achieve stability under both types of conditions, the spring is made sufliciently weak to permit the air pressure to hold the elevator in its lower position at such high speeds but is still sufliciently strong to hold it in its upper position at such low speeds. More particularly the wing 20 is set on the body with its chord about parallel to the longitudinal axis of the body and its center of lift is located behind the center of gravity CG. The attack angle of the wing 28 is positive and about 3 to 5 in glidng flight and is slightly negative in catapulting. Also, the stationary airfoil 28 is set on the body at a positive attack angle of about 1 to 3 greater than the attack angle of wing. The upper stop 34 is so positioned that when the elevator is in its first, or upper, position it forms a negative attack angle of about to with respect to the attack angle of the wing. Also the lower stop 35 is so positioned that when the elevator is in its second, or lower, position it forms a low negative attack angle of about 2 to 4 relative to the attack angle of the wing.

With this arrangement, the forces which act on the glider during vertical launching and during stable horizontal gliding flight and which are of interest here, are those illustrated in Figs. 6 and '7 as more fully explained hereinbelow in connection with the operation of the glider. In

these figures, vector forces to the right and upward are positive and vector forces to the left and downward are negative. Also in these figures, an attack angle of an airfoil is positive if the air reaction on the airfoil during flight produces a positive force; and an attack angle is negative if air reaction on it produces a negative force.

In order to launch the glider, it is attached to a rubber band or other elastic element of a sling by means of the launching hook l6 and is then catapulted upward, nearly vertically. The catapulting action moves the elevator from its first position to its second position almost im mediately because of two factors. In the first place, the high initial acceleration of the glider permits the inertia of the spring 40 to cause it to stretch, thus temporarily relieving the force tending to hold the elevator 29 against the upper stop 34. Secondly when the glider is catapulted, the air speed of the glider is very high and results in the exertion of a relatively strong aerodynamic force on the elevator 29 against the spring tension.

By suitably selecting the constants of the spring, the spring is made weak enough to permit the aerodynamic forces acting on the elevator 28 to hold the elevator against the lower stop 35 only as long as the glider is traveling at a speed higher than some predetermined speed. Preferably this predetermined speed is higher than any speed to be encountered during gliding. Thus during flight at such high speeds, the elevator 29 is held in its second or lower position against the lower stop 35 almost in alignment with the stationary stabilizer element. More particularly, during high speed flight the stabilizer 22 has a relatively low negative camber and the angle between the two stabilizer elements is about 3 to 8.

When the glider is travelling upward vertically, the forces acting on the glider, and of interest here, are those illustrated in Fig. 6. In this figure, four forces are represented: namely, the weight W of the glider, the lift L1 on the wing 20, the lift L2 on the stationary stabilizer element 28, and the lift L3 on the movable stabilizer element 29. The weight W of the glider acts along the longitudinal axis of the glider and vertically downward through the center of gravity CG. The lift L1 on the wing 20 is very small and negative. The lift L2 acting on the stationary member 28 of the stabilizer is positive. Inasmuch as the attack angle of the elevator 29 is negative and relatively small during high speed vertical flight, the aerodynamic force acting thereon is also negative and relatively small, as indicated by the length of the vector L3. The forces L1, L2, and L3 exerted on the respective airfoils 20, 28, and 29 act through the corresponding centers of lift.

It is to be noted that during launching the net force due to the entire stabilizer is small and positive since the lift L3 acting on the elevator is less than the lift Lz acting on the stationary stabilizer element 28. This small positive force is equalized by the small negative lift on the wing. The fact that the force on the stationary stabilizer element 28 is in front of the force acting on the elevator 29 and is greater than the latter force permits the small negative lift on the wing 20 to counteract the turning moment of the two forces L2 and L3 acting on the stabilizer elements. Thus by virtue of the balance of the forces thus attained, the glider may be shot upward like an arrow and thus catapulted upward to high altitude without looping back to its starting point.

As the altitude of the glider increases, its speed is gradually reduced. As the speed is reduced the air pressure on the elevator decreases. Finally when the force exerted by the air pressure on the elevator becomes less than that exerted by the spring, the elevator is urged upward from the second position to the first position. During the upward movement of the elevator from the second position to the first position the line 45 between the ends of the spring moves away from the hinge axis, thus increasing the mechanical advantage of the spring and thus achieving a toggle action which causes the elevator to snap from the second position into the first position. Preferably the constants of the spring are so selected that the movement of the elevator into the first position occurs at a predetermined air speed slightly greater than any gliding speed that may be encountered. Thus the glider may be catapulted to a maximum altitude before the camber of the stabilizer is changed to the'relatively high value corresponding to gliding flight.

As-soon as-the==e1evator-is moved to -its=first-' position-in the manner hereinabovedescribed, the glider usually executes a tight loop=wliich= ends im a* horizontal stable-- gliding attitude. Sometimes a loop-is not executed, especially 'ifthe direction of catapulting' divergessomewhat from the-vertical Inthe-latter case; the gliderfa'lls directly downward andthe upwardly directed air forces actingon the wing and'the stabilizenduring the fall cause the glider to nose downwardly and thereupon to enter a stable gliding condition;

Whentheglider is inahorizontal gliding attitud'e, the forc'esacti-ng' on it; and ofinterest here, are those illustrated in Fig. '7. Inthis figure fbur forces are again represented, namelyy the WeightW- of the glider; the life" I31 on the wing 21 the lift Lz" on the stationary stabilizer element 24B; and the lift L's" on'- the movable stabilizer element 29'. Asbefore, the weiglit 'Wacts downwardly" througli the center of gravity CG but is now almost perpendicul'ar to the longitud nal axis of the glider; In: this case the lifting force on-the wing 2 0 i's very large and is positive because in gliding flight the wing assumes a positive attack angle. The lift L2 acting on the stationarymember 28 of the stabilzer is'positive and somewhat larger than during-launching because of the increasedpositiveattackangle of the stabilizer element in the gliding attitude. The lift L3" acting on the movable member 29 of the stabilizer is now very much larger because of the relativelylarge negative attack angl assumed bytheelevator during gliding flight. It is to be noted that in glidi'ngfii'g-ht the' net 'n'ega- Q tive, or downwardly acting, force produced by the two stabilizer elements acting together counteracts the force due to the weight W about a transverse axis through the center of lift of the wing. The problem of restoring the glider to stable level flight in case it deviates from such flight depends upon other factors which need not be discussed here since they are well known to those skilled in the art.

From the foregoing explanation of our invention it is clear that we have provided a glider with a stabilizer of variable camber which permits the glider to be catapulted to a relatively high altitude and then to assume a stable gliding condition at that altitude. Our invenion makes stable flight of a glider possible both under vertical launching and gliding conditions by virtue of the fact that the net force produced by the stabilizer is positive and small during the launching and is negative and large during gliding and by virtue of the fact that the lift applied to the wing is negative and small during the launching and is positive and large during gliding flight. The mechanism which we have provided for so controlling the flight of the glider is simple, inexpensive, and positive acting. Clearly many variations in the detailed arrangement and orientation and design of the parts of a glider may be made, without departing from the true spirit and scope of our invention. While we have described our invention with particular reference to its application to a toy glider, it will be clear that it may also be applied to other gliding aircrafts, including rockets, and also to other aircrafts which are launched at higher speed than their normal flight speed.

It is therefore to be understood that although we have described our invention in detail with reference to. a preferred embodiment thereof. the invention is not to be limited thereto but only by the scope of the appended claims.

solely by aerodynamic forces acting. on said movable airfoil during-freeflight for-producing alarge lift onsaidstabilizer at low air-speeds and a small lift on said stabilizer-at'high" air speeds.

2: A'- glider having a body-member; a'wingextending transversely across saidbody member and having its chord disposed substantially parallel=to the longitudinalaxis of saidbody member, a stabilizer including a fixed airfoil an-d a -movable airfoil, said fixed airfoil being" disposed on said body member behind-said wing and oriented at a positive attack angle-relative to-the chord of said Wing, said movable" airfoil being disposed behind said fixed airfoil and being" pivotally' movable about an axis transverse to" said bodymember, and means located entlrel'y on said aircraft and controlled solely by aerodynamic forces acting on said movableairfoil during free flight for producing anegative lift on said stabilizer at low air-speedsand a positivelifton said-stabilizer at'highair speeds.

3. In apparatus for controlling; thefli'ghtof an aircraft having abody member, a stabilizer of I variable camber and means controlled solely by aerodynamic" forces acting on a portion of said stabilizer for varying the camber" thereof whereby a large lift is applied to said stablizer at low speeds and a small lift is applied thereto at high air speeds.

- 4. An aircraft comprising a longitudinal body member, a wing on said body member, a stabilizing air foil positioned behind said wing and pivotally movable between a first position of high negative attack angle and a second position of low negative attack angle, and resilient means interconnecting said body member and said airfoil operative to urge said airfoil against air pressure acting thereon into said first position only at relatively low air speeds.

5. An aircraft comprising a longitudinal body member, a wing on said body member, a stabilizer positioned behind said wing and set at a positive attack angle, an elevator hinged on the trailing edge of said stabilizer and movable be-- tween a first position of high negative attack angle and a second position of low negative attack angle, and resilient means operative to urge said elevator against air pressure acting thereon into said first position only at relatively low air speeds.

6. An aircraft comprising a longitudinal body member, a wing on said body member, a stabilizer positioned behind said wing and set at a positive attack angle, an airfoil hinged on the trailing edge of said stabilizer and movable between a first position of high negative attack angle and a second position of low negative attack angle, a hollow fin mounted on said body member, and a spring arranged within said fin attached at one end to said body and at the other end to said air foil, the two points of attachment lying on a line slightly above the hinge axis when said airfoil is in its first position, said spring being adapted to urge said airfoil from said first position to said second position.

7. A glider comprising a longitudinal body member, a wing extending laterally across said body member, means including a movable airfoil for controlling the aerodynamic turning moment about the axis of said wing during flight, said airfoil being movable from a first position in which said glider possesses inherent gliding stability at relatively low speeds and another position in which there is substantially no aerodynamic turning moment about said axis at high speeds, the aerodynamic forces acting on said air foil during flight tending to urge said airfoil in a direction extending from said first position toward said second position and resilient means located entirely on said glider acting to urge said airfoil in a direction extending from said second position toward said first position in opposition to such aerodynamic forces, said resilient means having a strength sufiicient to maintain said airfoil in said first position at such low speeds but not at such high speeds.

8. In an aircraft, a longitudinal body member, an airfoil hinged about an axis transverse to said body member and located behind the center of gravity of said aircraft, said airfoil being movable about said axis between a first angular position and a second angular position, the attack angle in said first position being negative and relatively high and the attack angle in said second position being relatively low, and a spring mounted to urge said airfoil from said second position to said first position, the constants of said spring being such that said spring urges said airfoil into its first position against aerodynamic pressure acting thereon when the airspeed is less than a predetermined amount but permits said airfoil to be urged into its second position against aerodynamic pressure acting thereon at higher airspeeds.

9. In a glider adapted to be catapulted into the air at a speed greater than a gliding speed, a longitudinal body member, a wing extending laterally across said body member, an airfoil structure of variable camber mounted on said body member, and means located entirely on said glider and comprising a spring operative below a predetermined airspeed for setting the camber of said airfoil structure at such a value as to maintain the aerodynamic moment about the axis of said wing at a relatively high value at such gliding speed, said means being operativeat such greater speed for setting the camber of said airfoil structure at such a value at which the aerodynamic moment about the axis of said wing is maintained at a relatively low value at such greater speeds whereby the glider may be launched substantially vertically upwardly at such greater speeds.

J. C. PEMBERTON. DORRIS RONALD BALDRIDGE.

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

UNITED STATES PATENTS Number Name Date 1,947,982 Gerhardt et al. Feb. 20, 1934 2,061,953 Sampson Nov. 24, 1936 2,292,416 Walker Aug. 11, 1942 2,438,309 Zimmerman Mar. 23, 1948

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