US2157448A - Model airplane or glider - Google Patents

Description

W. E. BACK May 9, 1939.

MODEL AIRPLANE OR GLIDER Filed Oct. 15, 1937 2 Sheets-Sheet 1 May 9, 1939. w. E. BACK MODEL AIRPLANE OR GLIDER Fi led Oct. 15, 1957 2 Sheets-Sheet 2 WA-TEA r, 7

Patented May 9, 1939 UNITED STATES PATENT OFFIQE Application October 15, 1937, Serial No. 169,293 In Great Britain October 23, 1936 9 Claims.

This invention relates to model airplanes or gliders (hereinafter referred to as gliders) and means for launching such gliders, and has for its main objects to provide an improved glider 5 which will perform satisfactorily both during launching and during flight, Will not be readily damaged if it strikes obstructions and will generally fulfil the requirements of toys of this kind.

To this end a model glider according to the m present invention comprises a longitudinal spar or framework constituting the body of the glider and adapted to carry main and tail planes, a main plane, and resilient means for connecting the main plane to the spar in such a manner that on the occurrence of a lifting force on the plane, sufficient to cause movement of the plane against the action of the resilient means, the angle of incidence of the plane will be reduced. Thus the resilient means are conveniently such that on the occurrence of a lifting force substantially in excess of that exerted thereon during normal flight, the plane will move against the action of the resilient means in the manner referred to. It will be understood of course that the main plane is arranged so that although it can move in the manner mentioned under the action of a sufficient lifting force it is normally held from other movement relative to the body.

When a model glider is being launched, for

.".'. example by means of a stretched elastic or other catapult device, the speed is generally greatly in excess of the normal flying speed with the result that the glider immediately on release from the catapult tends to perform a loop of limited mean radius which may bring it into violent contact with the ground in spite of the fact that the upward part of such a loop is generally of large mean radius as compared with the downward part. With the present invention, however, when during and immediately after the launching operation the glider has a speed substantially in excess of the normal flying speed, the upward pressure on the main plane causes movement of this plane to reduce the angle of incidence with the result that the glider, on

release from the catapult, tends either to perform a loop of large mean radius carrying it a considerable height above the ground before the descending part of the loop occurs, or to rise 50 into the air Without performing a loop. As the speed of the glider falls following launching, the upward pressure on the main plane also falls so that by the time the speed of the glider has fallen to its normal flying speed, the resilient 55 means will have rettuned the main plane to its normal flying position in which the glider will fly or glide satisfactorily at such normal flying speed. It will further be appreciated that by varying the effective force of the resilient means, the performance of the glider on release from the catapult can be varied.

Preferably the main plane is connected to the spar by resilient means disposed at a point in advance of the centre of pressure of the plane so that not only is the angle of incidence of the plane reduced on the occurrence of a lifting force sufficient to cause movement of the plane against the action of the resilient means but the resilient means also permits other movements of the plane if the plane or the body meets an obstruction during flight. In this way the tendency for the glider to be damaged due to meeting such an obstruction is reduced. Thus, the main plane is conveniently connected to the body at a point in advance of the centre of pressure of the plane by one or more resilient bands passing round a part of the plane and anchored to pins or other securing means within the body below the plane. Such resilient band or bands may pass through two holes or slots in the main plane or around the leading edge of the plane and through a hole or slot in the main plane, the movement of the main plane to reduce the angle of incidence taking place about its leading edge or a point adjacent thereto.

The term band is to be understood as including a length of resilient material not necessarily of an endless character and of any suitable crosssection.

When the main plane is connected to the body at a point in advance of the centre of pressure of the plane, in the manner indicated above, independent auxiliary means may also be provided for resisting upward movement of the trailing edge of the plane relatively to the body beyond a predetermined point, such means preferably being resilient and comprising, for example, a rubber band extending between the trailing edge of the plane and a pin or other anchorage on the body. In such an arrangement this rubber band is preferably slack when the plane is in its normal flying position so that it does not come into effective operation until a predetermined upward movement of the trailing edge of the plane has occurred. In an alternative arrangement, the auxiliary means for resisting upward movement of the trailing edge of the plane may include a lost motion device of the pin and slot type permitting limited upward movement of the trailing edge before the auxiliary resilient means resisting such upward movement come into operation. In any case, not only the main means for resiliently connecting the main plane to the body but also the auxiliary means for resisting upward movement of the trailing edge of the plane may be arranged so that the force exerted thereby on the plane can be varied or the point in the upward movement of the trailing edge of the plane at which the auxiliary means come into operation can be altered.

The main plane which is preferably formed of thin plywood is conveniently provided with a reinforcing lath extending along the whole of the under surface of its leading edge, this lath being suitably shaped and conveniently gumrned or otherwise secured to the plane while its centre part rests on an appropriately shaped seating on the upper surface of the body. In such a construction, when one or more rubber bands constitute the main resilient means for connecting the main plane to the body, these bands conveniently pass round the leading edge of the plane and through a slot in the plane immediately behind the lath.

The under surface of the body is preferably substantially straight while the upper surface is curved so that the forward end of the body is deep compared with the after end and in a convenient arrangement the body comprises two identical side members formed of sheet material and connected together in spaced relationship by distance pieces to which the side members are secured, as by adhesive. In such a construction the rubber bands or like resilient means for securing the plane to the body conveniently extend between the side members.

A vertical fin is preferably provided at the after end of the body, this fin lying above a tail plane which is pivotally secured to the lower surface of the body so that it can move about a vertical axis to allow swivelli-ng of this tail plane if one end thereof hits an obstruction.

The catapult device for launching the glider may be of the kind comprising a mast, say 6 or '7 feet high, provided with stays for supporting it substantially vertically on the ground and adapted to have connected to its upper end one end of a length of elastic the other end of which is adapted to engage a hook at the forward end of the glider. The means for connecting one end of the elastic to the uper end of the mast are, however, preferably such that if, during stretching of the elastic, the mast should be pulled over, the end of the elastic will slip from the securing means at the top of the mast. In this way, risk of the mast being pulled by the stretched elastic at high speed towards a person stretching the elastic preparatory to launching the glider should the mast be pulled over by the force of the elastic, is avoided.

The invention may be carried into practice in various ways but one construction according to the invention is illustrated by way of example in the accompanying drawings, in which- Figure 1 is a perspective view of the complete glider,

Figure 2 is a sectional side elevation on an enlarged scale of the forward part of the glider,

Figure 3 is a section on the line $-3 of Figure 2,

Figure 4 is a plan view of the forward part of the glider with the ends of the main plane omitted for convenience,

Figure 5 is a cross-section of the main plane on the line 55 of Figure 1, and

Figure 6 shows a modification.

In the construction illustrated, the glider comprises a spar or framework constituting the body of the glider and formed from two side members A, A connected together and spaced apart by intermediate distance pieces B, B B B connected, for example by gluing, to the side mem bars which are cut away as shown for lightness. Secured to the after end of the body is a vertical fin C formed, for example, of thin plywood while a tail plane D, which may also be formed of thin plywood and is conveniently reinforced at D is pivotally connected, for example by a screw D to the under surface of the body. Secured, as by gluing, to the two side members, as shown, are two cheeks E the upper surfaces of which are shaped to receive the shaped under surface of a lath F extending along and secured as by gluing throughout its length to the under surface of the leading edge of the main plane F which is conveniently also formed of thin plywood. When the main plane is thus formed of thin plywood, the grain of the two sheets constituting the outer plies preferably runs from the leading to the trailing edge. This tends to give greater strength to the plane, enables the plane to be cambered by pressing and also provides flexibility allowing the trailing edge to move upwards under air pressure thus increasing the stability of the airplane or glider and at the same time assisting one of the purposes of the flexible attachment of the plane to the spar in the manner described.

In some cases additional strength may be given to the part of the main plane immediately behind the lath either by securing to the upper or lower surface of this part of the plane an additional sheet of material, for example thin plywood, or by providing short ribs on the upper or under surface of this part of the plane, the ribs or other reinforcement extending from the lath towards the trailing edge but terminating short of the trailing edge so as to leave a flexible portion of the plane adjacent to the trailing edge. In the case of ribs, these would probably be attached to the lath at suitable intervals along the wing span while, in the case of a reinforcement of sheet material, this would preferably extend forwards to a point beyond the after edge of the lath.

Formed in the centre of the plane F behind the lath F is a slot F through which is adapted to pass a rubber band G passing also round the front of the main plane and engaging at its lower ends pins G G passing through holes in the side members so as to connect the plane resiliently to the body in such a manner that the aggregate elastic pull is at a point in front of the centre of pressure of the plane. It will be seen that the rubber band G passes downwards through a gap between the after end of the distance piece B and the forward end of the distance piece B this gap being sufiicient to permit a degree of forward and backward movement of the plane without the band coming into engagement with these distance pieces and the edges of the distance pieces being rounded off to prevent damaging the rubber. Conveniently a strip of flexible material, for example rubber, extends from the distance piece B to approximately the leading edge of the plane, as shown at B to provide a streamline effect, this strip either being thickened or carrying a member B at its after end the upper surface of which runs more or less smoothly into the upper surface of the plane and band G. Pins G G conveniently extend across the space between the side members at points a short distance in advance of the two downwardly extending parts of the rubber band G so as to engage this rubber band on forward movement of the plane, for example if the body of the glider meets an obstruction and the plane is thus jolted forward. In this way the forward or other movement of the plane is permitted but is resiliently resisted in a manner tending to prevent damage of the plane when landing or if an obstruction is struck during flight. It will be understood that the shaping of the upper surfaces of the two cheeks E in relation to the shape of the lath F is such as to maintain the plane normally at right angles to the body while permitting movement of the plane relatively to the body for the purpose referred to.

Secured, as by adhesive, in a part-cylindrical groove extending along the whole of the forward end of the lath F is a length of rubber H of circular cross-section and either tubular or not, adapted to act as a buffer to prevent damage should the forward edge of the plane hit an obstruction, reinforcing strips H of gummed tape or the like passing round the end portions of this rubber buffer. A strip of gummed tape or the like H also conveniently passes round the centre part of the leading edge of the main plane and extends over the adjacent upper and lower surfaces of the plane adjacent to the rubber band G, as shown.

Secured to the centre of the length of the trailing edge of the plane, for example by adhesive tape J, is a length of wire J the adhesive tape and a section of the trailing edge of the plane being cut away, as shown at J so as to expose the centre part of the wire which thus forms a pin round which passes a rubber band K the lower portion of which passes round a pin K extending between the side plates, as shown. Alternatively the band K may pass wholly through the slot and be anchored by a separate pin. The arrangement is preferably such that when the plane occupies its normal flight position, as shown, this rubber band is only slightly in tension.

Secured to the forward end of the body is a tubular rubber buffer L which may carry the hook L adapted to engage the elastic of the launching catapult and is held in place by a metal plate L forming an upward extension from the forward end of a metal member L of channel section secured to the under surface of the forward end of the body and acting as a weight to counterbalance the after portion of the glider.

Instead of the rubber band K directly engaging a pin secured to the trailing edge of the plane, the upper end of this rubber band may have secured to it a slotted link M, as shown in Figure 5, constituting the slotted part of pin and slot mechanism of which the pin is constituted by the pin J In this construction the rubber band would conveniently be arranged with more tension and the link M would be arranged so that it has a part which normally rests on the upper surface of the body, as shown.

Again, if desired, instead of the rubber band K engaging a pin constituted by a length of wire secured to the trailing edge of the plane F as shown, a slot may be provided in the plane adjacent to its trailing edge with a pin extending across this slot to receive the rubber band, in which case the part of the plane surrounding the slot is preferably reinforced by securing to its two faces, as by glue, sheets of thin plywood or other sheet material.

In any case, it will be seen that the rubber band K not only tends to limit the upwardmovement of the trailing edge of the plane above a predetermined point but resists while permitting swivelling of the plane about a vertical axis, for example if the plane hits an obstruction when in flight, thus tending to prevent either end of the plane hitting the Vertical fin C.

In an alternative arrangement, instead of or in addition to providing the rubber band K, the slot F may be arranged nearer the trailing edge than indicated so as to increase the resistance exerted by the rubber band G to swivelling movement of the main plane about a vertical axis.

In a still further alternative arrangement, a light metal or like fitting may be secured to the upper surface of the main plane above the lath F to carry pins round which rubber bands pass, each rubber band passing from its pin either through a slot in the plane or round the leading edge of the plane and being anchored as by a fin'ther pin within the spar. In such an arrangement the pins in metal fitting may be thus normally removed to release the rubber bands when the plane is to be detached from the spar.

Although in the construction illustrated the plane comprises a sheet of thin material to the under surface of the leading edge of which is secured a reinforcing lath, other constructions may, of course, be employed. For example, the plane may be made from one piece of wood suitably hollowed out and shaped by appropriate machinery and tapering from a relatively thick portion adjacent the leading edge to the trailing edge which may be as thin as is practicable. Where the plane comprises thin sheet material such as thin plywood and a reinforcing lath, as shown in the drawings, however, it is possible to camber the plane by a suitable pressing operation and this method is generally preferred.

The drawings illustrate the glider in skeleton form. In practice, however, the side members and upper and under surfaces of the body may be covered with suitable fabric or other sheet material so as to reduce wind resistance due to air eddies. In this case suitable slots, which could be provided with removable cover plates, would be provided to enable the rubber bands to be threaded and, where necessary, stretched into position and the necessary pin or pins inserted to secure them in place.

It will be understood that the main plane can readily be removed from the body by removing one of the pins G G2 and the pin K In order to facilitate the threading and positioning of the rubber band G when the plane is to be replaced, one end of this rubber band is conveniently attached to a short length of tape or the like, as shown at G by which the rubber band can be held in its stretched position while the appropriate pin G is inserted through its looped end.

In a modification two or more rubber bands may be employed, each band being anchored to the spar for example in the same way as the band G, the bands being either superimposed or arranged side by side. Again, two or more alternative holes may be provided to receive the pin G or the pin K or both to permit adjustment of one or both rubber bands.

It will be seen that the mode of attachment of the main plane not only enables the trailing edge to move upwards so as to reduce the angle of incidence when the lifting force exerted on the plane is raised above the normal during the launching operation but also permits the main plane to move against the action of the rubber bands if the body or the plane hits an obstruction thus reducing risk of damage to the plane. Moreover, the formation of the body with a deep forward end tends to protect the vertical pin C from striking an obstruction when the glider is in flight while the pivotal connection for the tail plane D enables this to swivel should one end of it hit an obstruction.

It will also be seen that by disconnecting the rubber bands G and K the main plane can readily be detached from the spar to facilitate packing and transport.

It is to be understood that the constructions more particularly described above are given by way of example only and that these constructions may be modified within wide limits without departing from this invention.

What I claim as my invention and desire to secure by Letters Patent is:

l. A toy glider including in combination a longitudinal framework, a longitudinal seating formed on the framework and having a substantial area, a main lifting plane part of which adjacent its leading edge rests on said seating which is formed to maintain the plane .at the correct angle of incidence for normal flight, at least rubber band acting on the main plane in advance of the center of pressure of the plane to hold the plane normally on the seating but to permit the plane to move about a vertical axis should one end strike an obstruction and to move about a part adjacent its leading edge to reduce the ngle of incidence of the plane on the occurrence of a lifting force thereon substantially in excess of that exerted during normal flight, and means for anchoring each rubber band to the framework.

2. A toy glider including in combination a longitudinal framework, a longitudinal seating formed on the framework and having a substantial area, a main lifting plane part of which adjacent its leading edge rests on said seating which is formed to maintain the plane at the correct angle of incidence for normal flight, at least one slot formed in the main plane adjacent the center of its length and in advance of the center of pressure of the plane, at least one rubber band passing round the leading edge of the plane and through the slot therein, and means for anchoring the rubber band to the framework so as to maintain the plane normally on its seating but to permit it to move about a vertical axis should one end strike an obstruction and to move about a part adjacent its leading edge to reduce the angle of incidence of the plane on the occurrence of a lifting force thereon substantially in excess of that exerted during normal flight.

3. A toy glider including in combination a longitudinal framework, a longitudinal seating formed on the framework and having a substantial area, a main lifting plane part of which adjacent its leading edge rests on said seating which is formed to maintain the plane at the correct angle of incidence for normal flight, at least one rubber band acting on the'main plane in advance of the center of pressure of the plane to hold the plane normally on the seating but to permit the plane to move about a vertical axis should one end strike an obstruction and to move about a part adjacent its leading edge, and resilient means acting on the trailing edge of the plane for limiting upward movement thereof and rotational movement of the plane about a vertical axis.

4. A toy glider including in combination a longitudinal framework, a longitudinal seating formed on the framework and having a substantial area, a main lifting plane comprising a strip of sheet material to the lower face of the leading edge of which is secured, as by adhesive, a reinforcing lath extending substantially throughout the length of the leading edge of the plane and part of which rests on said seating which is formed to receive the lower face of the lath and thus maintain the plane at the correct angle of incidence for normal flight, at least one slot formed in the main plane adjacent the center of its length and in advance of the center of pressure of the plane, at least one rubber band passing round the leading edge of the plane and through the slot therein, and means for anchoring the rubber band to the framework so as to maintain the lath on the seating, but to permit the plane to move about a vertical axis should one end strike an obstruction and to move to re duce the angle of incidence of the plane on the occurrence of a lifting force thereon substantially in excess of that exerted during normal flight.

5. A toy glider including in combination a longitudinal framework, a longitudinal seating formed on the framework and having a substantial area, a main lifting plane comprising a strip of sheet material along the lower face of the leading edge of which is attached, as by adhesive, a reinforcing lath part of which rests on the seating which is formed to receive the lower face of the lath and thus maintain the plane at the correct angle of incidence for normal flight, a slot formed in the plane adjacent the center 01" its length and immediately behind the reinforcing lath, at least one rubber band passing round the leading edge of the plane and through the slot, and means for anchoring the rubber band to the framework below the plane so as to maintain the lath on the seating but to permit it to move about a vertical axis should one end strike an obstruction and to move to reduce the angle of incidence of the plane on the occurrence of a listing force thereon substantially in excess of that exerted during normal flight.

6. A toy glider including in combination a longitudinal framework adapted to carry a main lifting plane and a tail plane, the framework comprising two identical side members formed of sheet material connected to one another and spaced by distance pieces to which the side mem bers are secured, as by adhesive, with gaps between the distance pieces, a longitudinal seating formed on the framework and having a substantial area, a main plane comprising a strip of sheet material to the lower face of the leading edge of which is secured, as by adhesive, a reinforcing lath extending substantially throughout the length of the leading edge of the plane and part of which rests on said seating which is formed to receive the lower face of the lath and thus maintain the plane at the correct angle of incidence for normal flight, at least one slot formed in the main plane adjacent the center of its length and in advance of the center of pressure of the plane, at least one rubber band passing round the leading edge of the plane and through the slot therein and between two of the distance pieces and means for anchoring the rubber band within the framework so as to maintain the plane on its seating but to permit it to move above a vertical axis should one end strike an obstruction and to move about a part adjacent its leading edge to reduce the angle of incidence of the plane on the occurrence of a lifting force thereon substantially in excess of that exerted during normal flight.

7. A toy glider including in combination a longitudinal framework, a longitudinal seating formed on the framework and having a substantial area, a main lifting plane part of which adjacent its leading edges rests on said seating which is formed to maintain the plane at the correct angle of incidence for normal flight, at least one slot formed in the main plane adjacent the center of its length and spaced from the leading edge, at least one resilient rubber band passing round the leading edge of the plane and through the slot, means for anchoring the rubber band to the framework below the plane, and stops disposed a short distance in front of at least one part of the rubber band which extends from the main plane to the anchoring means to impose an increased resistance to forward movement of the plane beyond a predetermined point.

8. A toy glider including in combination a longitudinal framework adapted to carry a main lifting plane and a tail plane, the framework comprising two identical side members formed of sheet material connected to one another and spaced by distance pieces to which the side members are secured as by adhesive with gaps between the distance pieces one gap constituting a slot in the upper face of the framework, a longitudinal seating formed on the framework and having a substantial area, a main plane comprising a strip of sheet material along the lower face of the leading edge of which is attached, as by adhesive, a reinforcing lath part of which rests on the seating which is formed to receive the lower surface of the lath and thus maintain the plane at the correct angle of incidence for normal flight, a slot formed in the plane adjacent the center of its length and immediately behind the reinforcing lath, at least one rubber band passing round the leading edge of the plane and through the slot therein and through the said slot in the upper face of the framework which is of sufficient dimensions to permit limited fore and aft movement of the main plane, in addition to swinging movement about a vertical axis should one end of the plane meet an obstruction and means for anchoring each rubber band to the framework.

9. A toy glider having a longitudinal frame-

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