Take-off device for airplanes

1. Technical Field

The present invention generally relates to a take-off device for aircraft and vehicles, and more particularly to a take-off device for airplanes that permits an airplane to accelerate to a lift-off speed.

2. History of Related Art

Take-off devices for aircraft are generally known, be they catapults for military aircraft on aircraft carriers, or be they take-off devices for gliders in the form of motor-driven winch arrangements for a take-off rope or rubber ropes.

All these known devices have in common that they have fixed site installations, which most typically encompass the whole device and also include only an accepting hook for the take-off device on the aircraft side; thus, the device can be applied only to the fixed site. In addition, all these devices are heavy and, in the case of those on aircraft carriers, are not transportable.

A take-off device that can be joined to the aircraft or vehicle and thus has practically no fixed site components would be desirable. The desirable take-off device would also be capable of being applied in light aircraft without any large modifications for fixed sites, such that the device could also be applied outside the aircraft or vehicle.

A take-off and accelerating device includes a telescopic arrangement, at least one pressure accumulator, means for retracting an inner tube and at least one middle tube, and means for blowing off pressurised gas. The telescopic arrangement has an outer tube, the inner tube, and the at least one middle tube. The inner tube, the outer tube, and the at least one middle tube are adapted to slide against each other and are airtight. The at least one pressure accumulator has a valve for release of an outflow of compressed gas out of the at least one pressure accumulator into the telescopic arrangement. The at least one pressure accumulator includes means to open the valve and means to damp the outer tube, the inner tube, and the at least one middle tube against each other at ends of their respective sliding motions. The outermost tube is mounted in a frame. The device is adapted to be installed on-board a vehicle. The means for retracting is adapted to retract the inner tube and the at least one middle tube from a telescopically extended condition into a retracted condition. The means for blowing off pressurised gas is adapted to blow off pressurized gas after extension of the telescopic arrangement.

The disclosed invention will be described with reference to the accompanying drawings, which show important sample embodiments of the invention, wherein:

FIG. 1 is a schematic representation of a basic construction of a take-off device according to principles of the invention;

FIG. 2 is a longitudinal section view of an embodiment of the present invention;

FIG. 3 is a detailed view of the cardan mounting and its interaction with other parts of the device according to principles of the invention;

FIG. 4 is a view of an embodiment of a damping device 21 ( 1 ) according to principles of the present invention; and

FIG. 5 is a view of a modification of the embodiment of the invention shown in FIGS. 2, 3 , and 4 .

FIG. 1 shows in schematic representation a basic construction of a take-off device according to principles of the invention. A wing of an aircraft is referenced 1 , a centre line of lift of the wing 1 being referenced 2 . Essentially in a section from a longitudinal axis of the aircraft and a centre line of lift 2 , a frame 3 of a cardan mounting is arranged such that the frame 3 can pivot about a horizontal axis 8 .

Through and guided by the frame 3 runs an outermost tube 4 of a telescopic arrangement 7 , the telescopic arrangement 7 including the outermost tube 4 , a middle tube 5 , and an inner tube 6 . The frame 3 of the cardan mounting engages with a vertical axle 37 on a sleeve 9 . The sleeve 9 surrounds the outermost tube 4 .

In a retracted condition of the telescopic arrangement 7 , a centre of gravity of the telescopic arrangement 7 is essentially in the centre of the frame 3 , so that no turning moments have to be considered. The take-off device is driven from the retracted condition with compressed gas. A rear end of the inner tube 6 presses against a push-off point present on the ground. The telescopic arrangement 7 expands to about three times a length of the telescopic arrangement 7 when in the retracted condition and provides the aircraft with a necessary take-off speed. When the telescopic arrangement 7 has completely extended, the telescopic arrangement 7 is drawn in by compressed gas in a similar fashion to the manner in which the telescopic arrangement 7 expands. Compressed gas present in the telescopic arrangement 7 that is no longer required after push off is discharged through a main release valve and guided rearward by a funnel 10 . On the outermost tube 4 , there is a pressure chamber 11 which, following expulsion of gas from the middle tube 5 and the inner tube 6 , is filled with compressed gas, which compressed gas is then used to retract the tubes again. After the end of the take-off procedure, the take-off device is fixed in the aircraft in a turning moment-free position.

In the following Figures the construction and method of working of the telescopic arrangement are described in more detail. FIG. 2 shows a longitudinal section of an embodiment of the present invention. The frame 3 with the sleeve 9 and other details yet to be shown are omitted and the telescopic arrangement 7 is shown in the fully-extended position.

The inner tube 6 has a base 12 at a rear end of the inner tube 6 . The base 12 contains a filling valve 13 and a lead-through 14 for a control gas pipe 15 . The control gas pipe 15 passes through the inner tube 6 along a length of the inner tube 6 and opens into a valve 16 at a front end of the inner tube 6 . The inner tube 6 is designed as a pressure accumulator for the working compressed gas. With the valve 16 closed, the inner tube 6 is filled to a required working pressure from an external high-pressure source, such as a pressure bottle or a compressor, via the filling valve 13 .

At a forward end of the inner tube 6 , the inner tube 6 is surrounded by an inner guide ring 18 . The inner tube 6 is provided with a seal 17 ( 1 ). The seal 17 ( 1 ) is fastened to the inner tube 6 via a screw thread. At a rear end of the middle tube 5 is an outer guide ring 19 ( 2 ). The outer guide ring 19 ( 2 ) similarly has a seal 17 ( 2 ). The seal 17 ( 2 ) of the outer guide ring 19 ( 2 ) is fastened in a similar manner to the seal 17 ( 1 ) of the inner guide ring 18 . Between the middle tube 5 and the inner tube 6 is a cylindrical clearance 20 ( 1 ). The cylindrical clearance 20 ( 1 ) is sealed by the guide rings 18 and 19 ( 2 ) with the seals 17 ( 1 ) and 17 ( 2 ). In a rear part of the cylindrical clearance 20 ( 1 ) there is a damping device 21 ( 1 ), shown here in summary as a spring and considered further in FIG. 4 .

Between the outermost tube 4 and the middle tube 5 , the mutual seal is approached in the same way as between the inner tube 6 and the middle tube 5 , so that an inner guide ring 18 and an outer guide ring 19 ( 3 ) with seals 17 ( 3 ) are present, whereby a cylindrical clearance 25 arises, in which, similarly, a damping device 21 ( 3 ) is arranged. At the forward end of the outermost tube 4 sits the funnel 10 . The funnel 10 can be slid lengthwise and seals, with a ring 22 , radially opening holes 23 of a main release valve 24 . The funnel 10 is worked into the head piece 26 of the outermost tube 4 . Two relief valves 27 are shown.

Towards a forward end of the middle tube 5 , for instance about ⅕ of the length of the middle tube 5 , which is controlled by the length of the damping device 21 ( 3 ), the middle tube 5 has a row of holes 28 . The holes 28 , when the telescopic arrangement 7 is in the extended position, come to lie in the region of the damping device 21 ( 3 ) and serve to ventilate the cylindrical clearance 20 ( 1 ) during extension and—as described in more detail later—to retract the telescopic arrangement 7 back again.

The outermost tube 4 carries, at a similar position to the middle tube 5 , a double row of holes 29 and, at some distance from the holes 29 (e.g., at about {fraction (1/20)} of the tube length) a further row of holes 30 . The holes 30 are configured as non-return valves and are, for instance, covered by an elastomer band 31 . The holes 29 and 30 open into the pressure chamber 11 . The pressure chamber 11 is equipped with a bleed valve 32 .

FIG. 3 shows in detail the cardan mounting and interaction of the cardan mounting with other parts of the device according to principles of the invention. While the left hand side of FIG. 3 shows part of what is shown in FIG. 2, the right hand side of FIG. 3 is a plan view of central-to-forward part of the outermost tube 4 . The frame 3 of the cardan mounting of the telescopic arrangement 7 can pivot about the horizontal axle 8 . The horizontal axle 8 is mounted on the aircraft side.

An axle 37 perpendicular to the horizontal axle 8 and standing perpendicular to the plane of FIG. 3, has mountings. The mountings can each be slid in a groove 36 . A first groove 36 is visible, while a second groove 36 (not shown) is below the outermost tube 4 on an under side of the sleeve 9 . The telescopic arrangement 7 can rotate to a limited extent around the horizontal axle 37 and is limited by two hard shock absorbers 38 . The shock absorbers 38 are provided with spring elements that engage on one end with the horizontal axle 8 and on the other end with the sleeve 9 . The sleeve 9 is clamped firmly to the outermost tube 4 with screws 39 , the screws 39 being indicated by their axes.

Two shock absorbers 40 engage on the vertical axle 37 . One of the shock absorbers 40 is invisible below the outermost tube 4 . The shock absorbers 40 have other positive engagement on suitable positions on the funnel 10 . The shock absorbers 40 are hard in relation to shortening and very yielding in relation to extension, exhibiting a pronounced hysteresis characteristic.

Operation of this first previously represented modification of the first embodiment proceeds as follows. In a rest, or starting, position of the telescopic arrangement 7 , the middle tube 5 and the inner tube 6 are retracted completely into the outermost tube 4 . The control pressure gas pipe 15 , which goes outside the take-off device forward of the pilot (not shown) of the aircraft, is at first without pressure. As soon as the valve 16 is impacted with the control pressure, the valve 16 in the head piece (referenced 33 ) of the inner tube 6 opens and allows the gas stored inside the inner tube 6 to flow out. The rising pressure in the middle tube 5 exerts a force on the cross sectional area of the inner tube 6 , which forces the inner tube 6 to the rear relative to the middle tube 5 . Simultaneously, the pressurised gas flows through the still-open throttle valve 41 in the head piece (reference 34 ) of the middle tube 5 into the inside of the outermost tube 4 . Thereby, a force arises on the cross sections of the middle tube 5 and the inner tube 6 , which force moves the middle tube 5 rearward relative to the outermost tube 4 surrounding the middle tube 5 . Since the inner tube 6 , however, is pressing on an anchor point in the surroundings, the outermost tube 4 and the middle tube 5 move forwards, and the aircraft, onto which the force so operating via the horizontal axle 8 of the frame 3 is transmitted, is accelerated. By adjusting the cross section of the throttle valve 41 , the middle tube 5 and the inner tube 6 can be fully extended almost simultaneously. Towards the end of the sliding path of the middle tube 5 and the inner tube 6 , the guide rings 18 meet the damping devices, further details of which are shown in FIG. 4 .

During the whole of the extension process, the cylindrical clearance 20 ( 1 ) ventilates directly to the outside and the cylindrical clearance 25 ventilates into the pressure chamber 11 via the holes 28 and 29 . Shortly before reaching the final position of the middle tube 5 , the row of holes 30 is opened by the seal 17 ( 3 ) of the guide ring 18 ; shortly before the main release valve 24 comes into action, a portion of the pressurised gas present in the outermost tube 4 is blown off at full pressure into the pressure chamber 11 via the holes 30 .

On reaching full extension, the movement impulse of the middle tube 5 and the inner tube 6 is transmitted to the outermost tube 4 via the damping devices 21 ( 1 ) and 21 ( 3 ), which performs a movement to the rear relative to the aircraft that is facilitated by the grooves 36 and limited and damped by the shock absorbers 38 . This relative movement of the outermost tube 4 to the rear causes the ring 22 carrying the funnel 10 to slide forward and thereby release the openings 23 of the main release valve 24 and, due to the hysteresis characteristic of the shock absorber 40 , also keeps the shock absorbers 40 open. The tubes 4 , 5 , and 6 are now without pressure. The blown off pressurised gas guided to the rear by the funnel 10 generates an additional thrust, which additional thrust supports the take-off process.

The air present in the pressure chamber 11 can now only flow back through the holes 29 , since the holes 30 are closed by the elastomer band 31 . The air present in the pressure chamber 11 flows into the cylindrical clearance 25 and exerts a force on the cross section thereof, which force pushes the middle tube 5 into the inside of the outermost tube 4 . As soon as the row of holes 28 in the middle tube 5 come to lie within the seal 17 on the outer guide ring 19 of outermost tube 4 , the air streams out of the pressure chamber 11 into the cylindrical clearance 20 between the middle tube 5 and the inner tube 6 , whereby the inner tube 6 is fully retracted. Thereupon, the blow-off valve 32 on the pressure chamber 11 can be, for instance, electrically activated and the whole system made pressureless.

An embodiment of a damping device 21 ( 1 ) is presented in FIG. 4 . The aim which is addressed in particular here lies primarily in the time extension of the power thrust, thus in the reduction of the momentum change per time unit, since

F=dp/dt

where

F=Force

dp/dt=time dependent change of momentum

Secondarily, the aim of removing from the system a part of the kinetic energy due to frictional work in the telescopic arrangement can be addressed. The embodiment according to FIG. 4 has, to this end, the following construction. On the inner tube 6 , following the inner guide ring 18 , sit several, for instance, 40 pieces, of plastics material rings 45 and O-rings 46 , arranged alternately, as shown to the left of the break line in FIG. 4 . This arrangement is closed, for instance, in each case by a plastics material ring 45 , so as to produce the same conditions for all the O-rings 46 . Between the plastics material rings 45 and the O-rings 46 and an inner wall of the middle tube 5 there is a separation to facilitate access to the holes 28 for the air in the cylindrical clearance 20 ( 1 ).

If the inner tube 6 is extended so far that the rearmost plastics material ring 45 strikes the outer guide ring 19 ( 2 ) of the middle tube 5 , the O-rings 46 are pressed together, as shown on the right of the break line in FIG. 4 . The whole spring path of all the O-rings 46 results in a braking path for the inner tube 6 . As soon as the O-rings 46 are sufficiently compressed together such that the O-rings 46 touch the inner wall of the middle tube 5 , frictional forces arise; therefore, frictional work between the O-rings 46 and the inner wall results. The elasticity of the O-rings 46 and the pressurised gas flowing in through the holes 28 free the O-rings 46 again from the position shown and thereby permit the retraction of the inner tube 6 .

Although shown on the middle tube 5 and the inner tube 6 , the representation applies in the same way for the damping device 21 ( 3 ) between the outermost tube 4 and the middle tube 5 . The head piece of the inner tube 6 has been omitted, as the head piece does not contribute to the function described.

Obviously, the damping device 21 ( 1 ) can individually be addressed differently, as long as the damping device 21 ( 1 ) distributes the changing of the impulsion to a limited and defined path and reduces at least a part of the kinetic energy via frictional work.

A modification to the embodiment according to FIGS. 2, 3 , 4 is the subject of FIG. 5 . The telescopic arrangement 7 is shown in FIG. 5 in the fully retracted position. Instead of taking the pressurised gas control pipe 15 through the high pressure gas store present in the inner tube 6 , the valve 16 arranged in the head piece 33 of the inner tube 6 is controlled from the head side of the arrangement. To this end, the pressurised gas control pipe(referenced 15 a ) passes through the head piece 26 of the outermost tube 4 and is anchored there. From the head piece 26 , the pressurized control pipe 15 a runs through one of always-open throttle valves 41 and then reaches a boring 47 . The boring 47 is open towards the front in the head piece 33 of inner tube 6 . The head piece of the inner tube 6 leads to the valve 16 . The pressurised gas control pipe 15 a is sealed in the boring 47 with an O-ring 48 .

A schematically shown control valve 49 opens the way for the pressure control gas to the valve 16 , whereby the valve 16 can be opened. Closing of the valve 16 after completion of the take-off process can be effected either pneumatically or mechanically using means not shown.

Further detail applicable to FIGS. 2-4 and to the modification shown in FIG. 5 includes a securing rod 50 , which, for instance, is fastened to the head piece 33 of the inner tube 6 using a tripod 51 . The securing rod 50 passes through, for instance, the centre of the throttle valve 41 in the head piece 34 , is taken with play through a boring 52 in the head piece 26 , and ends in a support 53 fastened airtight thereto. At the forward end, the securing rod 50 has a groove 54 with a somewhat semi-circular cross section in which a securing screw 55 can engage. The securing screw 55 carries a heavily spring loaded ball 56 at a tip thereof, so that the securing rod 50 must be pulled back against the force of the spring loaded ball 56 . The force of the spring loaded ball 56 can be so adjusted such that the telescopic arrangement 7 remains secured in the retracted position against all normal vibration, such that the force of the spring loaded ball 56 is also sufficient to compensate for the forces generated by the control gas pressure on the cross section of the boring 47 , and such that the force of the full working pressure can nevertheless pull the securing rod 50 out of a snap locking position. Obviously, this conditional detent can be otherwise configured as long as the conditional detent fulfils the noted aims.

The arrangement of the pressurised gas control pipe 15 a (or 15 ) shown in FIG. 5 has the advantage over that shown in FIG. 2 of a short path. The control valve 49 must here be configured as a non-return valve against the working pressure.

On the support 53 there is an electro-magnetic sensor 57 , which, by known electronic means, can establish whether the securing rod 50 is retracted and/or moves. In other words, the sensor 57 functions as a position and movement sensor.

Although appearing different from the basic concept underlying the previous description, the device according to principles of the invention also permits site-fixed application. The take-off device, guided in the frame 3 is anchored to the ground, and the middle tube 5 , the inner tube 6 , or possibly further such, are extended by the action of the pressurised gas. Both unmanned aircraft (i.e., drones) and vehicles are objects that can be accelerated using embodiments of the invention. The object to be accelerated has a centre of gravity essentially at the now forward end of the outermost tube 4 . The take-off process thereby operates in a similar fashion to that on an aircraft carrier. A particular advantage is the easy transportability of the device according to principles of the invention, in which all the functions described, apart from the direction of movement, remain essentially unchanged.