Brief Description of the Drawing
FIG. 1 is a side view of an aerodynamic toy embodying the invention.
FIG. 2 is a view taken along the plane designated by line 2--2 of FIG. 1.
FIG. 3 is a cross sectional view taken on a plane designated by line 3--3 of FIG. 2.
FIG. 4 is a cross sectional view taken on a plane designated by line 4--4 of FIG. 2.
FIG. 5 is a cross sectional view at enlarged scale taken along a plane designated by line 5--5 of FIG. 3.
Description of the Preferred Embodiment
Referring more particularly to the drawing, reference numeral 12 indicates an aerodynamic toy embodying the present invention. The toy includes an air foil 14 at opposite ends of which are identical composite end plates 16 and 18 which stabilize the air foil during flight and which reinforce the parts of the air foil.
As seen most clearly in FIGS. 3 and 4 air foil 14 is composed of two substantially identical aerodynamic surfaces that are symmetrical with respect to the longitudinal axis of the air foil. The upper surface, as viewed in FIG. 3, includes a convex portion 20a and a concave portion 22a which extends from the convex portion in a smooth discontinuity free configuration. The lower aerodynamic surface as viewed in FIG. 3 includes a convex portion 20b and a concave portion 22b which are substantially identically configured to the configuration of portions 20a and 22a of the upper surface. Portions 20a and 22b are joined at their extremities to form a joint 24, and portions 22a and 20b are joined at their extremities to form a joint 26 that is oppositely and symmetrically disposed with respect to joint 24. The straight line distance between edges 24 and 26 is characterized as the chord of the air foil.
Centrally of air foil 14 is a reinforcing rib 28 with respect to which respective lateral portions of the air foil are symmetrical. As can be seen most clearly in FIG. 2 the lateral portions of the air foil taper inward or converge toward rib 28 so as to form between the respective lateral portions of the air foil a positive dihedral angle, i.e., an angle less than 180.degree.. As seen most clearly in FIG. 4, the surfaces of air foil 14 diverge smoothly from rib 28 at the mid point of the air foil to the respective lateral extremities thereof.
Cooperating with rib 28 to maintain the air foil in the shape described hereinabove and shown in the drawing are end plates 16 and 18. The end plates are of composite construction and include a solid central disc 30 and an annular portion 32 which is secured to the peripheral margin of disc 30 and concentric therewith. In one structure designed according to the present invention, disc 30 is constructed of heavy paper whereas annular portion 32 is constructed of relatively more dense synthetic resinous material, commonly referred to as plastic. The thicknesses of disc 30 and annular portion 32 are exaggerated in FIG. 5 for clarity of disclosure. In fact, the outer surface of each end plate (the lower surface as viewed in FIG. 5) is substantially smooth in view of the fact that the annular portion 32 has a thickness no greater than about 0.010 inches and is adhesively joined to the disc at an overlapping marginal region of the central disc and the annular portion. Accordingly, the respective end plates 16 and 18 afford substantial vertical stability to the toy without creating any significant degree of turbulence. The junction between the air foil and the respective discs 30 is formed by any suitable adhesive, glue or cement whereby a rugged, light weight structure is formed.
Because of the symmetry of the toy with respect to central rib 28, one side of the air foil, the right hand side as viewed in the drawings, is provided with a visual indicium 34 which, as will appear, assists the user in launching the toy. Indicium 34 has no structural or aerodynamic properties, and the same function can be achieved by any suitable visual indicium on the air foil or on one of the end plates 16, 18.
The manner of launching the toy of this invention can be appreciated by reference to FIG. 1. The user orients the toy so that visual indicium is to the right hand side of rib 28. The four fingers of the right hand are engaged on edge 24 symmetrically of rib 28, i.e., two fingers are disposed on either side of the rib. The thumb is engaged with edge 26 on or adjacent rib 28. The user, in an overhand motion, then throws the device in a generally horizontal direction, simultaneously imparting a spinning or rotative motion to the air foil in the direction indicated by the arrow 36 in FIG. 3. Stated otherwise, such direction of rotation is such that, as viewed in FIG. 1, edge 24 moves toward the viewer and edge 26 moves away from the viewer. The toy is thus launched with combined translational movement and rotative movement through the air. As a result of such translational and rotative movement through the air, there is relative movement between the air and the surfaces of air foil 14 which imparts lift to the toy so that the toy will glide for a long distance, and if thrown with sufficient vigor, can be made to climb and even loop.
The foregoing maneuvers are made possible in part by the composite construction of the end plates which, because of the relatively larger weight of peripheral portion 32, has rotative inertia which assists in maintaining the rotational movement imparted by the user of the device. Moreover, the positive dihedral angle of the two laterally spaced air foil portions stabilizes the traveling air foil with respect to the roll axis. That is to say, if the longitudinal axis of the toy assumes a non horizontal position, there is an increase in the relative angle of attack between the lower end of the air foil and the relatively moving air. This restores the longitudinal axis of the toy to a horizontal position. Moreover, because of the dihedral angle, the mass of the outer ends of the air foil is greater than the center which, in conjunction with the composite construction of end plates 16 and 18 affords substantial stabilizing forces on the toy during flight. The composite construction of the end plates, in that they enhance continuation of rotation of the end plates, also improve stability by exploiting the gyroscopic effect which arises as the discs rotate.
The toy of the invention can also be launched in an underhanded manner so long as the direction of rotation referred to above is achieved. The hand grip on the toy is the same as is described above; however, the launching of the device is achieved by an underhanded swinging motion so that when the toy is launched along a translational path the direction of rotation will be as indicated by arrow 36, i.e. on convex surface portion 20a leads the concave portion 22b on the side of joint 24 opposite from convex portion 20a. When launched in an underhanded manner, the toy will perform a downward loop and return to the launcher.
Contributing to the excellent aerodynamic properties and stability of the present invention is the substantial thickness of the air foil, that is, the camber or overall dimension of the air foil in a direction perpendicular to the chord, the chord being the straight line distance between edges 24 and 26. As shown in FIG. 3, the maximum camber is at least about three-eighths the length of the chord and this dimension occurs approximately one-fourth of the chordal length rearward (rightward as viewed in FIG. 3) of edge 24. The consequence of this substantial camber, in a ratio of at least about 3 to 8 to the chord length, is that smooth air flow over the upper surface, i.e. over surface 20a is sustained for higher angles of the attack with respect to the direction of translation. Although as the air foil rotates, each surface eventually stalls, i.e. the air flowing thereover eventually goes from laminar flow to turbulent flow, the stall appears at a substantially high angle so that the loss of lift is minimized. It will be noted in FIG. 4 that the camber of the air foil decreases toward the longitudinal mid point of the air foil whereas the chord length remains approximately the same.
One toy designed according to the present invention is formed of relatively stiff paper, the exterior of which is coated with plastic paint so as to make it smooth, strong and totally air impervious. The air foil has a length of approximately 8 inches. The chord length of such exemplary device is approximately 2 inches and the diameter of end plates 16 and 18 is about 3 inches. Such exemplary toy has a weight of approximately 9 grams. Accordingly, there is substantial active surface of the end plates which affords stability, reduces if not eliminates side slip, and, because of the presence of relatively dense annular portion 32, provides substantial rotational inertia which facilitates smooth and continued rotation of the device.
Thus it will be seen that the present invention provides an aerodynamic toy of simple construction, low cost, and substantial stability both in smooth air and in mildly turbulent air. Because of the carefully balanced aerodynamic properties present in the toy, it can be flown either straight by beginners or can be made to perform numerous more complicated maneuvers by those having more experience in its use. Although one embodiment of the invention has been shown and described, it will be obvious that other adaptations and modifications can be made without departing from the true spirit and scope of the invention.