WO1993017894A1

WO1993017894A1 - Inflatable airbag on personal aircraft

Info

Publication number: WO1993017894A1
Application number: PCT/US1993/002286
Authority: WO
Inventors: Jeffrey T. Haley
Original assignee: Haley Jeffrey T
Priority date: 1992-03-13
Filing date: 1993-03-12
Publication date: 1993-09-16

Abstract

An airbag crash protection device for paragliders and other personal aircraft. A compressed gas bottle (21) or pyrotechnic gas generator inflates the airbag (11) when the pilot presses a trigger (34) retained in his hand at the end of a cord. The airbag has relief valves (12, 15) which maintains a certain pressure and release air upon impact to dissipate energy. For paragliders, the inflated airbag protrudes downward from the seat. For rigid wing aircraft, the airbag is mounted on a structure protruding in front of the pilot and has two lobes, one extending outwardly and the other extending toward the pilot.

Description

INFLATABLE AIR BAG ON PERSONAL AIRCRAFT

This application is a continuation-in-part of U.S. ^"" Application 07/851,471, filed March 13, 1992, entitled 5 INFLATABLE AIR BAG DEPLOYED PRIOR TO IMPACT. _λ*.

BACKGROUND

A casual survey of literature shows that man has wanted to fly since he developed the mental capacity to envy the birds. For over a century, inventors have been developing

10 better and better single person aircraft to pursue personal aviation as a sport. The available forms of personal aircraft now include parachutes, paragliders, motorized paragliders, hang gliders, motorized hang gliders, and ultra-light airplanes.

15 Paragliders are a specialized form of parachute formed in the shape of a wing to achieve a high ratio of forward glide to descent. The wing shape is maintained by assembling the wing from a series of ram air tubes se.wn together with the open end at the leading edge of the wing. Paragliders are

20 typically launched by running down a steeply sloping hillside until the wing inflates and then gliding away from the hill.

Like paragliders, hang gliders are also launched by running down a slope. However, the wing is rigid, typically made of aluminum and cloth, and is supported by the pilot

25 until it is lifted by forward speed through the air.

A frame with wheels, a seat, an engine, and a propeller have been attached to both the fixed wing of a hang glider and to the ram air tube wing of a paraglider, creating motorized forms of each aircraft. Alternatively, the motor and

30 propeller may be mounted on the back of the pilot for a motorized version of a paraglider or on a portion of the wing structure for a motorized version of a hang glider, both of which are then launched on foot. A single seat, very light version of a traditional motorized aircraft is commonly called

35 an "ultra-light" or, if it is designed to be suitable for gliding with the motor turned off, a "motor glider". All aircraft face inherent problems with precise control of their location and movement through the air. By applying lateral forces against the ground, ground vehicles can turn precisely and stop quickly. Although water born vehicles have much greater difficulty stopping quickly or turning with precision than ground vehicles, they are at least constrained to two dimensions on the surface of the water and can remain at rest. In contrast, aircraft move in three dimensions and, except for balloons, are inherently unstable. They must remain moving to avoid falling to the ground. Consequently, it is very difficult to precisely control the locations and movements of aircraft and impossible to stop them except by contact with the ground.

Generally, three categories of events may cause a personal aircraft to begin falling dangerously fast: failure of the wing or control surfaces, pilot error, and down drafts or turbulence. Because paraglider wings are not rigid, a failure of the wing can be caused by turbulence or pilot error. When such failures occur in paragliders, they can generally be corrected after descending anywhere from an insignificantly short distance to 100 meters or more. When the paraglider wing is in this failed condition, it still produces enough parachute like drag to limit the descent rate to between 6 and 12 meters per second (20-40 ft/sec, 1200-2400 ft/min) . The top speed of 12 meters per second (40 ft/sec) with a collapsed paraglider wing will be reached between 1 and 1.5 seconds after the wing collapses, during which the pilot will have fallen between 6 and 12 meters (20-40 feet).

The lack of precise control and rapid descent if the wing fails makes it dangerous to fly personal aircraft close to the ground or other solid objects. The safe distance that must be maintained varies with different aircraft from about 50 meters (165 feet) to 100 meters (330 feet). Of course, this is not always possible because the aircraft must take off and land. In addition, in sport aviation, it is often very interesting to fly close to the ground, especially with gliders. Consequently, sport aviation pilots spend much of their time flying dangerously close to the ground and accidents with serious injuries are not uncommon.

A traditional safety device for sport aircraft is the reserve parachute. Reserve parachutes which can be quickly deployed provide an adequate measure of safety if they are deployed high enough above the ground, typically between 50 meters (165 feet) and 100 meters (330 feet). This is an effective safety device when a problem arises high above the ground which allows the pilot to predict that he may not regain control before hitting the ground. Unfortunately, even with reserve parachutes, serious injuries are quite common because reserve parachutes will not work, or pilots are too busy trying to regain control to deploy them, when close to the ground. In addition to reserve parachutes, for paragliders and parachutists, seat harnesses are available which reduce injuries from impacts by providing cushioning and spreading the impact force on the body. However, the available cushions are not thick enough to absorb the impact force over a long enough distance to reduce the acceleration on the body to safe levels for a pilot with a collapsed paraglider wing falling at speeds between 6 and 12 meters per second (20-40 ft/sec). Even with hard seats which spread the force over a large area and the available cushions, descent with a collapsed paraglider wing will cause compression of vertebrae, may cause internal injuries, and has caused death.

Other human activities present a similar risk of falling to the ground from heights that are too low to allow the use of reserve parachutes, such as construction work, window washing, and rock climbing.

SUMMARY OF THE INVENTION The central concept of the present invention is to place a deceleration cushion between the human and the ground which is thick enough to reduce the impact deceleration, at likely impact speeds, to within safe limits. According to published engineering data, with adequate support and spreading of the forces over the surface of the human body, the human body can withstand approximately 30 to 40 times the acceleration of gravity without injury. Using the figure of 9.8 m/sec ² (32 ft/sec ²) for the acceleration of gravity, and assuming that the human falls onto a surface with is completely unyielding such as rock, concrete, or firmly packed soil, for a human traveling toward the ground at 15 m/sec (55 km/hr, 50 ft/sec, 34 mph) which is the speed that a body achieves in free fall from a height of 26 meters (86 feet), a cushion which applies a constant deceleration to the body and is 45 centimeters (1% feet) thick, the acceleration experienced by the human body will not exceed 30 times that of gravity. Cushions made according to this invention, which do not achieve constant deceleration, are about one meter (3 feet) thick. For paragliders with a collapsed wing, which descend at a maximum speed of 12 m/sec (40 ft/sec), and various other situations where humans should be protected against impact, this thickness is quite sufficient. For other situations, the thickness of the cushion can be increased to accommodate the likely speed of impact.

To avoid problems with the bulk of the cushion when it is not needed, the cushion comprises an air bag with vent holes which is inflated prior to impact. The air bag is specially designed to achieve a high deceleration rate in a short distance and yet not exceed maximum deceleration forces. To achieve inflation prior to impact, the inflation can be triggered by the pilot or by a device such as radar which senses the distance to the ground, calculates the speed at which the ground is approaching, and triggers the inflation if the speed at any particular distance exceeds a safe limit. For pilots that fly in a sitting position with no structure beneath them, such as paragliders and parachutists, the air bag is attached to a seat which is connected by a harness or straps to the pilot. In addition to a very thick cushion under the seat, a portion of the air bag can extend upwardly to protect the back and neck. The inflator can also be located under the seat, or, as most pilots would find more convenient, attached to a backpack like harness.

For pilots who fly with a structure surrounding them, in either a prone or sitting position, the air bag is mounted on a structural support which holds it at a point of likely first impact with the ground directly in front of the pilot. In an ultra-light aircraft, this is usually just in front of the pilot's feet. In a hang glider, two support bars extend from the control bar below the pilot and one extends from the center of the leading edge of the wing above the pilot to a point suspended out in front of the pilot.

When the air bag is mounted on a structure in front of the pilot instead of under the pilot's seat, it is comprised of two lobes, one which inflates in front of the structure to decelerate the structure before it hits the ground and a second which inflates from the structure toward the pilot to cushion the pilot before he hits the structure and the ground. With this design, the deceleration force can be absorbed over a long distance in a combination of the first air bag, the structural support, and the second air bag. If the impact is light, the first air bag will absorb all of the force, protecting the structure from damage as well as protecting the pilot.

Generally, the air bag must be inflated about one to two seconds before impact. However, it may be inflated much longer before impact, either because the pilot is cautious or nervous or because, after inflating the air bag, the pilot regains control and successfully flies away from the hazard. The pilot may then fly for additional minutes or hours before again needing the safety provided by the air bag. Consequently, rather than open vent holes as used in automobile air bags, the air bags must have relief valves which will keep the air retained in the bag until the pressure on the bag exceeds the force of the spring in the relief valve. The deceleration force achieved by the bag is proportional to the pressure achieved in the bag. Therefore, when the bag is inflated, the release valves retain significant pressure above ambient pressure so that less compression of the bag is required to achieve adequate deceleration forces.

As the bag collapses, an increase in pressure is caused by movement of the air displaced where the bag is collapsing into the remaining volume of the bag. Consequently, pressures will increase the fastest if_. the volume of air displaced per unit distance of collapse is as large as possible compared to the remaining volume in the bag. For this reason, a cylindrical bag will achieve the greatest rise in pressure for each unit distance of collapse. In contrast, a bag with smaller diameter portions and larger diameter portions, such as a conical or tapered bag, will achieve lower increases in pressure per unit distance of collapse because the smaller diameter portions will collapse first, displacing a relatively small volume of air compared with the volume of the remainder of the bag.

The deceleration force achieved is equal to the pressure in the bag multiplied by the surface area on which the pressure is acting. If the diameter of the cylindrical bag, and therefore the surface area on which the force is acting, is relatively large, the pressure required will be relatively small. A smaller required pressure is advantageous because the pressure can be more quickly achieved as the bag collapses and lighter cloth may be used to construct the bag. However, if the diameter of the bag is much larger than the diameter of the seat to which it is attached, rather than the full cross- section of the bag collapsing, the seat will sink into the bag. To prevent such sinking, hinged levers can be attached to the circumference of the seat which fold out and are retained in a horizontal position when the bag is inflated causing the effective diameter of the seat to equal the diameter of the bag. Alternatively, a torus of cloth, with a median diameter equal to the diameter of the bag, may be attached at the top of the bag. Half of the cross-section of the torus will then protrude beyond the diameter of the bag. The seat is affixed at the center of the torus. Air pressure inside the torus will be transmitted through the cloth to the seat, adding sufficient upward forces on the seat to prevent the seat from sinking into the bag. The cylinder will collapse before the seat sinks into the torus.

To achieve a maximum total deceleration with the smallest possible air bag and without exceeding 30g of deceleration force on the pilot, the deceleration force applied by the air bag should be maintained near 30g for as long as possible. If the deceleration is lower than 30g for a significant amount of time, the air bag will have to be thicker to achieve the total deceleration required without exceeding 30g. However, the resistance of air passing through open vent holes does not produce a constant deceleration. When the force on the bag is great, the velocity of the air passing through the vent holes is high and the resistance of the bag to the force is very high. Once the speed of the pilot decreases, the forces are lower and the resistance of the air moving through the vent is lower, decreasing the rate of deceleration. The use of relief valves with substantial spring forces rather than open vent holes presents the added advantage of tending to equalize the rate of deceleration over time. When the force of the air exiting the bag decreases, the spring of the relief valve tends to block the flow of air, retaining a higher pressure in the bag so that it can exert a greater force against the pilot.

In various situations, such as a down wind landing against a hill, the paraglider pilot may foresee an impending crash with substantial forward velocity. In this situation, it is important that the pilot be capable of changing the angle of protrusion of the air bag so that it is facing the direction of travel. In the present invention, the air bag is mounted to a rigid seat which is connected to a harness on the pilot's back and strapped to the thighs of the pilot. By tilting the pelvis and raising or lowering the knees, the pilot can aim the air bag to any likely direction of impact.

A trigger for the inflator is located in a place which is convenient for actuation by the pilot and is shielded against accidental actuation. For paragliders and parachutists, it is a shielded push button on a long cord suspended in the palm by a string looped around one or more fingers. It is important that the trigger be held in the pilot's hand so that it can be actuated without removing the hands from the control lines for the paraglider, allowing the paraglider pilot to continue to manipulate the lines in an effort to cause the wing to begin flying again. Locating a hand actuated trigger in any other position will require that the pilot abandon efforts to control the wing in order to deploy the air bag. Likewise, it is important that the trigger be located on the end of a long cord so the pilot has the full range of movement with his hands on the control lines.

Alternatively, the trigger may be designed to be held in the teeth and actuated by closing the jaw. The trigger can be placed in the mouth prior to takeoff and when flying close to the ground. When flying well away from the ground, it can be removed from the mouth and left hanging on the chest.

For a rigid wing aircraft, the trigger is a shielded push button mounted on the controls in front of the pilot. The trigger may be mechanical or electrical depending upon the type of inflator employed. The inflator may be pyrotechnic with an electrical or mechanical igniter? it may be a pressurized gas container with an exploding valve, triggered electrically or mechanically; or it may be a pressurized gas container with a fast acting, none destructive mechanical valve. The inflator may be designed to aspirate ambient air so that the volume of gas which the inflator must generate is smaller than the volume which will fill the bag. A further aspect of the invention is a spring loaded safety mechanism which is depressed by the back of the paraglider pilot when he sits in the harness. When the harness is not in use, the pilot sets a catch to prevent the safety from depressing, thereby preventing an accidental inflation of the air bag. In addition to being held out by the catch which the pilot resets before flying, the safety is also held out by the mechanism which senses that the inflator is fully pressurized and ready for use. If the inflator is not fully pressurized, or the pilot has not reset the catch, the pilot cannot comfortably sit in the seat because the safety mechanism protrudes against his back.

The above described application of the invention for a paraglider or parachute functions well, without adaptation, as a safety device for construction workers on tall buildings, window washers, rock climbers, and others who are exposed to a risk of falling from a height of between 6 and 25 meters (20 and 80 feet) .

DESCRIPTION OF THE DRAWINGS

Figure 1 shows the invention as adapted for use with a paraglider or a parachute. The air bag is inflated.

Figure 2 shows a cross-section of a relief valve.

Figure 3 shows an alternative relief valve. Figure 4 shows a cross-section of the alternative relief valve.

Figure 5 shows the mounting hardware on the bottom of the seat to which the air bag for the paraglider or parachute is attached. Figure 6 is a cross-section of the seat and mounting hardware.

Figure 7 shows the pressure vessel for pressurized gas, a gate valve to retain the pressure in the bottle before it is attached to the harness, a ball valve, and the orifice which connects to the air bag.

Figure 8 shows a spring driven actuator for the ball valve.

Figure 9 is a perspective drawing of one component from figure 8. Figure 10 is a perspective drawing of the case for the hand held trigger. Figure 11 is a cross-section of the case shown in figure 10 and the retaining bar shown in figures 14 and 15.

Figure 12 is a perspective drawing of the push button which fits inside the case of figures 10 and 11, showing the springs which support the push button.

Figure 13 is a view of the underside of the push button.

Figure 14 is a side view of the retaining bar which retains the push button.

Figure 15 is a top view of the retaining bar which retains the push button.

Figure 16 shows the air bag system installed in an ultra¬ light aircraft or a motorized hang glider with wheels. Both an outward projecting and an inward projecting air bag are depicted. Figure 17 is a view of the nose of the aircraft of figure 16 from the interior with the interior air bag removed.

Figure 18 shows the air bag system mounted in a hang glider.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS For aircraft without wheels flown in a sitting position, such as paragliders and parachutes, the preferred embodiment stores the folded air bag under a seat 14. The inflator is most conveniently located on a harness 25 which straps to the back of the pilot. This back pack like harness contains a rigid surface to increase the comfort and protection for the pilot.

The inflator can be a pyrotechnic gas generator, as is used in automobiles, or a pressure vessel containing pressurized gas. The pressure vessel is the preferred embodiment for most applications. It is less expensive than the gas generator. It can be inexpensively refilled by any scuba diving shop. Once filled, it remains stable over time. Pyrotechnic gas generators are of questionable stability over many years, especially when subjected to the elements of outdoor use. Once discharged, the pyrotechnic generator must be entirely replaced at a cost equal to the original. However, its igniter is much smaller and lighter than the spring actuated valve required for the pressure vessel, the generator itself is much smaller and lighter than the pressure vessel, and it can inflate an air bag more quickly than the pressure vessel with a spring actuated ball valve. This may give it the deciding advantage for applications where speed of inflation is critical. The speed of inflation with the compressed gas vessel can be increased by replacing the ball valve with an exploding valve which must be replaced after each use. Such exploding valves are well described in the prior art for automobile air bag systems.

The inflator can be smaller and lighter if it is designed to aspirate ambient air with a venturi when it fills the bag. However, with such a design, one must be sure that no objects block the aspiration intake holes. This problem presents a sufficient risk that the preferred embodiment is a nonaspirating type inflater.

Figure 1 shows the pressure vessel 21 mounted to the harness 25 with mounting blocks 23 and mounting straps 22. The spring actuator for the ball valve is located inside the actuator case 31. A manual actuator knob 32, which serves as a manual backup for the spring actuator, protrudes through the actuator case 31. An actuator signal transmission cord 33 emerges from the actuator case 31 and connects to a hand held trigger 34. The transmission cord is long enough that the trigger on the end can be retained in the pilot's mouth or the pilot's hand without restricting the freedom of movement of the hand. Consequently, it is as long as the highest reach of a long armed pilot. To prevent the center of the transmission cord from hanging down when the pilot's hand is low, the center of the cord is affixed to the harness at the pilot's shoulder. The trigger includes a loop of string 35 for retaining the trigger in the hand while the fingers are used for other purposes. The base of the trigger case 342 is covered with velcro loops 343 so that it can be temporarily affixed to any location on the harness where the pilot chooses to glue velcro hooks. See Figure 11. A panel of cloth 26 connects the backpack like harness 25 to the seat 14, allowing considerable flexible movement between the harness and the seat. It is important that the panel of cloth be wide enough so that the backpack like harness does not place any restrictions on movement of the seat by the pilot. When flying, movement of the seat can be used to control the wing and, more importantly, in a crash situation, it is important that the seat be movable to aim the air bag to a position directly in front of the pilot if the pilot has a horizontal velocity, such as a downwind landing into a hillside.

A flexible filler tube 13 connects from the orifice of the ball valve to the air bag 11. Mounted in the side of the air bag are one or more relief valves 12 and 15. The relief valves retain the inflating air inside the air bag until a force is placed on the air bag by the impact.

The air bag has a cylindrical shape which, in the paraglider application, is 66 centimeters (26 inches) in diameter and about 90 centimeters (36 inches) high. To prevent the seat from sinking into the air bag upon impact and displacing less air with each centimeter of movement then would be displaced by a collapse of the cross-section of the cylinder, a torus 16 is mounted at the top of the air bag. Pressure inside the torus is transferred by the cloth of the torus to the seat, causing no collapse above the connection to the torus until the cylinder below is fully collapsed.

Inside the air bag, retaining straps 17 maintain the torus in its proper shape and allow a strong connection from the seat to the air bag so that the air bag may be positively aimed by a movement of the seat to aim the air bag to the direction of impact. Figure 2 shows a cross-section of a bursting style relief valve. An inner circular ring 151, with a rounded inside corner, and an outer circular ring 152 are clamped onto the cloth of the air bag 11 by clamping screws 153. The cloth of the air bag 11 is then cut away and a burst plug assembly 150 is mounted in its place. The burst plug assembly consists of an interior rubber seal 155, and exterior rubber retainer 154, a central spacer 157, a steel washer on each side 156, and a screw 158 and nut 159 which hold the assembly together. One end of a retaining strap 149 is bolted under the nut 159 and sewed to the surface cloth of the air bag 11.

Figures 3 and 4 show the detail of an alternative relief valve. A metal retaining strip 125 is riveted or screwed to the base 121 with the cloth of the air bag 11 in between. A hole in the base plate 121 is covered by a cover 122 which is larger than the hole and prevents the air from escaping unless the pressure becomes great enough to overcome the springs 123 and 124. The springs are held to the base plate and the cover by screws and nuts 126. To reduce the pressure which is required to open the valve, a single spring 123 can be used. To increase the pressure, one or more additional springs 124 can be added. The spring force on the relief valve should be set higher for heavier people and lower for lighter people to obtain the optimum deceleration for each. The correct spring force can be determined by strapping the pilot or another object of the same weight to the air bag system, suspending the pilot or weight from a known height which is not high enough to deflate the entire bag, dropping the assemblage onto a firm surface, and measuring the remaining height of the bag after all movement stops. If the remaining height is too great, the spring force can be decreased. If the remaining height is too low, the spring force can be increased.

To reduce the amount of air that will escape from the air bag when pressure is applied, one or more of the air relief valves can be retained in a closed position by putting a longer screw through the cover and through a hole in the center of a strip of metal (not shown) which is inserted through the hole and is long enough to retain the base plate 121 on each side of the hole.

Figure 5 shows two metal rings which clamp the cloth of the air bag 11 at its top to affix it to the seat. Figure 6 shows the two rings in cross-section, along with the adjoining components. The smaller ring 146 is placed inside a slightly smaller hole in the top of the bag 11. The rim of the bag is sewn around a cord 19 to create a bulge which will be retained by the metal rings 144 and 146. Also sewn to the bag at this point and retained by the rings 144 and 146 are the straps 17 which carry tensile forces to the lower portion of the bag. Also clamped between the two rings is a disk of cloth 18 slightly larger than the rings to prevent air leakage. The two rings are clamped together by screws 145. The upper ring 144 is wider than lower ring 146 and, after the bag is clamped between the rings, the upper ring is clamped with screws 143 to a blind nut 141 sunk into the surface of the seat 14. If the seat 14 is contoured rather than flat, varying thickness spacers 142 are placed between the contoured seat 14 and the flat upper ring 144. When the bag is folded, it is protected by a plastic cover (not shown) with four protruding hooks that hook into holes 147 in the upper ring 144. The protruding hooks hook the outer edges of the holes 147. Consequently, the force of the bag inflating easily causes the hooks to release.

Figure 7 shows the details of the components which connect the pressure vessel 21 to the air bag 11. The pressure vessel is made of aluminum. To make it lighter, it can be made of thin walled aluminum wrapped with carbon fibers. The mouth of the vessel is threaded and a threaded casing 284 of a valve is screwed in. The valve is a slow acting gate valve so that, if it is opened when the bottle is filled with pressure but not securely mounted to a retaining device, it will not become propelled like a rocket. The gate 283 is connected by a smooth stem to fine threads which are pulled by many turns of a knob 28. The smooth stem passes through a high pressure seal 282. The knob 28 is retained on the valve casing 284 by a set screw 285. The gate 283 seats against a seal 281 to contain the pressure.

The casing of the gate valve 284 is connected to the casing of a ball valve 294 with a union 27 retained by a flange 293 with a seal 271 to contain the pressure. The union allows the pressure vessel and its gate valve to be removed and replaced without turning the gate valve relative to the ball valve. The ball valve includes a casing 294, a ball 291, high pressure seals 299, and a stem 292. As a check to be sure that the system is pressurized and ready to go, a pressure indicator 296 is mounted just upstream from the ball valve. It consists of a small hole which acts as a cylinder and a piston mounted on the tip of a rod with a shoulder 296 which pushes against a spring 297, both of which are retained by a cover 295. The amount of pressure is indicated by the amount of the rod 296 which protrudes when the ball valve is closed and the gate valve is opened. The casing of the gate valve opens into the bag with a seat 290 against which the bag 11 is retained by a clamp 298. Along the stem of the ball valve 292 the ball valve casing 294 protrudes to a flange which supports the actuator case 31 to which it is attached by screws 301. As depicted in figure 8, the end of the ball valve stem 292 is square to engage the actuator crank 302. The actuator crank 302 and the manual actuator knob 32 are retained by a nut 321. The other end of the actuator crank has a slot to create a fork and, at right angles, a hole to receive a round connector 303. The round connector 303 has a square hole in its center to receive the guide shaft 306 which is square as shown by the hole depicted in the spring retainer 304 in figure 9. A spring 305 surrounds the guide shaft 306. One end of the spring presses against the spring retainer 304 and the other end presses against the guide shaft base 308. The guide shaft is retained by a set screw 307 mounted in the guide shaft base 308. The guide shaft base 308 pivots on a shaft 309 of which one end is affixed to the actuator case 31 with a nut (not shown) .

When the spring 305 is cocked, the spring catch 311 holds the spring retainer 304. Figure 8 shows the spring catch 311 in the cocked or retained position while it shows the actuator crank 302 and the spring 305 in the uncocked position. When the catch 311 is uncocked and the actuator crank 302 is depressed to cock the mechanism, the arms which protrude on each side of the spring retainer 304 press against the interlock arms 312 to press the catch 311 into a cocked position. The catch 311 and the interlock arms 312 are two different protruding portions of a single metal part which is attached with a pivot 310 to the guide shaft base 308. Two identical parts comprise the catch 311 and interlock arm 312, one on each side of the spring.

The catch 311 is held in place against the force of the spring 305 by a collapsing arm made of two sections 314 and 317. The collapsing arm is connecting to the catch at one end with pivot 313 and connected to the guide shaft base with another pivot 318. At the location of pivot 318, the guide shaft base 308 is milled on each side to be only slightly thicker than the actuation cable 331. Two identical parts 317 are attached on each side of the milled portion of guide shaft base 308 with the pivot 318. At the center of the collapsing arm there is a short fat hinge pin 315 with a set screw 316 which clamps the actuator cable 331. Mounted on the hinge pin 315 on the outside of the arms 317 are two identical arms 314. The two pieces of catch 311 are then mounted on the outside of the two arms 314 with pivot 313. The pivots 310, 313, and 318 and the hinge pin 315 are each held in place by snap rings fitted in grooves on each end (not shown) .

A spring 319 presses on the hinge pin 315 to push the collapsing arm away from the guide shaft base 308 and retain the catch 311 in an open position, ready to be cocked whenever the ball valve is open. The sheath of the transmission cord 33 passes through a hole in the edge of the actuator case 31 and is retained in the guide shaft base by a set screw 300. Because the hinge pin 315 is located to one side of a straight line between pivot 313 and pivot 318, the force of spring 305 acting against the catch 311 tends to cause the collapsing arm to collapse. Likewise, the spring 319 tends to cause such collapse. These collapsing forces are opposed by the actuation cable 331.

The actuation cable 331 passes through the actuation transmission sheath 33 to the actuation switch or trigger 341. See figures 10 and 11. The actuation cable 331 continues through a small hole in the case of the trigger 341 and terminates in a round metal swage 347. The trigger actuation surface (push button) 344 is pushed away from the base of the trigger case 341 by four springs 346. The springs push it against the retainer bar 345 which retains the push button 344 within the case 341. Adjacent ledges on the retainer bar 345 and the push button 344 retain the swage 347 until the push button 344 is depressed. The releasing of the swage allows the actuation cable 331 to slide in the transmission sheath 33 which allows the collapsing arm 314 and 317 to collapse, releasing the catch 311.

Not shown in the drawings is a mechanical safety which is actuated by the body of the pilot pressing against the backpack like harness. The safety is spring loaded so that when no one is in the harness, the safety is on and the trigger cannot actuate the ball valve and inflate the air bag. Consequently, the air bag can be inflated only when a pilot is sitting in the seat. The safety includes a catch which the pilot can set after removing the harness. The catch prevents the safety from being depressed such as by a tight packing of the equipment in a carrying bag. When the catch is on, it will be impossible for the pilot to feel comfortable in the seat because the safety will be pressing against his back. Consequently, it will be difficult for the pilot to launch without releasing the catch, thereby preparing the air bag system for deployment. The safety is also configured to CO

completing its inflation before the pilot strikes it. The inner bag then deflates through its regular relief valves. When the air bags are inflated, they are supported by both the circular support on which they are mounted 61 plus an additional support ring 62 which insures that the air bags keep the correct position prior to and during impact. When the inner air bag is packed, it is retained by a cover 66. All of these components, which are numbered in the 60's, are the same for the hang glider and for the ultra-light. The outer air bag for the hang glider (not shown) is cylindrical with a torus 16. The outer air bag for the ultra¬ light 46 is identical except that the base is in the shape of a horse shoe to leave room for the nose wheel 43. When the air bag inflates, the air pressure causes it to drape 48 closely against the nose wheel 43. On the hang glider, when the outer bag is packed, it is retained by a round pop-off cover 55. The cover for the ultra-light (not shown) is the same except that it has a horse shoe shape.

Claims

I claim:

1. A safety device for pilots of small aircraft flown in a sitting or recumbent position in a seat, comprising: an air bag adapted to be affixed to the underside of the se such that, when inflated, it is the portion of the aircraft closest to the earth, an inflator affixed to an entrance port o the air bag, and an actuator for actuating the inflator.

2. The device of claim 1 wherein the air bag has an outer surface which is cylindrical.

3. The device of claim 2 wherein the outer surface of the air bag has a torus shape, larger in diameter than the cylinder, between the cylinder and the seat.

4. The device of claim 1, further comprising: a relief vent i the air bag.

5. The device of claim 1, further comprising: a burstable relief valve in the air bag.

6. The device of claim 1, further comprising: a spring loaded pressure relief valve in the air bag.

7. The device of claim 1, wherein the inflator comprises: a vessel for pressurized gas and a valve connected to the vessel with an exit orifice connected to the entrance port of t air bag.

8. The device of claim 1, wherein the actuator comprises: a trigger by which the pilot can actuate the inflator at will.

9. The device of claim 1, wherein the actuator comprises: a transmission cord for transmitting the actuation to the inflator, the cord having two ends and being attached to the inflator at a first of the two ends; and ao means attached to the second of the two ends for actuating the inflator by a movement of the pilot.

10. A safety device for pilots of small aircraft with a rigid structure extending beneath the pilot, comprising: an air bag adapted to be affixed to the rigid structure such that, when inflated, it is the portion of the aircraft closest the earth, an inflator affixed to an entrance port of the air bag, and an actuator for actuating the inflator.

11. The device of claim 10 wherein the air bag has an outer surface which is cylindrical.

12. The device of claim 11 wherein the outer surface of the air bag has a torus shape, larger in diameter than the cylinder, between the cylinder and the seat.

13. The device of claim 10, further comprising: a relief vent in the air bag.

14. The device of claim 10, further comprising: a burstabl relief valve in the air bag.

15. The device of claim 10, further comprising: a spring loaded pressure relief valve in the air bag.

16. The device of claim 10, wherein the inflator comprises: a vessel for containing pressurized gas and a valve connecte to the vessel with an exit orifice connected to the entrance po of the air bag.

17. The device of claim 10, wherein the actuator comprises: a trigger by which the pilot can actuate the inflator at will.

18. The device of claim 10, wherein the actuator comprises: a transmission cord for transmitting the actuation to the inflator, having two ends, and attached to the inflator at a first of the two ends; and means attached to the second of the two ends for actuating the inflator by a movement of the pilot.

19. The device of claim 10, wherein the air bag is disposed such that, upon inflation, it protrudes from the structure both away from and toward the pilot.