Aeronautics and astronautics – Aircraft – heavier-than-air – Helicopter or auto-rotating wing sustained – i.e. – gyroplanes
Reexamination Certificate
1999-06-16
2001-09-25
Barefoot, Galen L. (Department: 3644)
Aeronautics and astronautics
Aircraft, heavier-than-air
Helicopter or auto-rotating wing sustained, i.e., gyroplanes
C244S060000
Reexamination Certificate
active
06293491
ABSTRACT:
The invention concerns a vertical take-off and landing aircraft having a plurality of rotors for producing downthrust and drive thrust.
A vertical take-off and landing aircraft of that kind is distinguished in that for example like a helicopter it can take off and land vertically and fly like an airplane in horizontal flight, being then supported not by a lift rotor but by rigid airfoils.
Besides vertical take-off and landing jet-propelled aircraft with pivotable thrust and lift jets or an additional lift jet engine or both, aircraft are also known, which are referred to as tilt rotor aircraft which are equipped at the end of each of the airfoils with a respective rotor which can be pivoted together with the associated drive engine. In one pivotal position the rotors generate a downwardly directed lift thrust which permits the aircraft to take off and land vertically. In another pivotal position the rotors generate exclusively a thrust jet for producing forward propulsion while at the same time the lift required for the aircraft to fly is generated by the airfoils. A great disadvantage of an aircraft of that kind is that the demands which are made on the rotor when taking off and landing vertically are quite different from when the rotor is generating thrust for horizontal flight. For that reason the rotors of a tilt rotor aircraft are always the result of a compromise and do not provide for optimum fulfilment either of the task of generating forward propulsion for horizontal flight nor the task of generating lift in the vertical take-off and landing situation. Added to that is the difficult interplay of the power characteristics of the drive assemblies which often necessitate rotor blade adjustment and which also cannot be optimised without compromises being made, both in terms of horizontal flight and also for vertical take-off and landing.
The object of the present invention is thus to provide an alternative to the state of the art, which at least in part obviates the disadvantages thereof.
The object of the present invention is attained by a vertical take-off and landing aircraft comprising a plurality of lift and thrust rotors, wherein all rotors have their own electric motor as a drive.
An essential advantage of such an aircraft is that the individual electric motors can be operated and controlled in a simple fashion and over a wide power range quickly. reliably and with a high level of efficiency. That makes it possible to resolve the problem of power distribution to the individual lift and thrust rotors in a simple elegant fashion by suitable control of the electric motors. During vertical take-off and landing the lift rotors practically exclusively take shaft power, in the transition from vertical to horizontal flight both the lift rotors and the thrust rotors are then driven while in purely horizontal flight it is only the thrust rotors that are to be driven. It is therefore necessary for the available power to be suitably rapidly and flexibly distributed. That aspect also applies in regard to power distribution as among the individual lift and thrust rotors respectively. With the electric motors provided in accordance with the invention that power distribution effect is implemented by electrical power control substantially more easily than for example in the case of mechanical drives or by suitable control of individual internal combustion engines.
In comparison with internal combustion engines, electric motors not only enjoy the advantage that they are easier and faster to control but in addition in a practical situation they can also be designed for virtually any power range with a high level of efficiency and a good power-to-weight ratio. That permits particularly efficient implementation of the principle of a large number of rotors each having its own respective drive, wherein the drives are to be designed in accordance with the number of rotors only for affording a fraction of the total power to be produced. In addition a large number of small motors afford the advantage of enhanced overall fail-safety as the failure of only one cut of many rotors is less serious in terms of consequences than the failure of a single rotor or one out of two rotors. As moreover each electric motor in itself is substantially more reliable and substantially less susceptible to wear than an internal combustion engine, because of the small number of moving components, the aircraft enjoys substantially enhance overall reliability.
The use of many lift rotors which can be individually controlled by way of their respective drive motors finally affords very much more extensive options for flight control than hitherto.
In order to make full use of the great advantages which the invention offers in particular in terms of control of the individual drives a preferred aircraft provides that each electric motor has its own frequency converter connected upstream thereof. The frequency converters permit simple rapid control of the respective electric motors, with a high level of efficiency.
A preferred aircraft is one in which the frequency converters are connected to a dc power supply system or network. That dc power supply system is preferably fed by at least one internal combustion engine with a directly coupled generator. The advantage of such a concept is that the electrical energy required to power the electric drives does not have to be stored in batteries or accumulators, with a disadvantageous power-to-weight ratio, but can be carried on board in the form of internal combustion engine fuel which enjoys a particularly high level of energy density in relation to weight, and can be easily converted into electrical energy by means of one or more internal combustion engines and corresponding generators. In such an arrangement the internal combustion engines can be operated at a constant speed and in a relatively narrow power range as they do not serve for directly driving rotors but for generating power. In that way the internal combustion engines can be specifically designed for that operational situation and can be especially efficient.
In order further to enhance the fail-safe aspect of the overall system, a preferred aircraft provides for two dc power systems or networks for supplying power to the frequency converters, each being supplied by a respective internal combustion engine with generator and being connectable together.
Preferably the generators are polyphase current generators, with a rectifier connected at the output side of each thereof. Polyphase current generators have the advantage of affording a high level of efficiency and great reliability. The rectifiers connected on the output sides of the polyphase current generators feed the dc power supply or network with which the frequency converters are supplied. The frequency converters convert the direct current into a polyphase current again, but with a controllable frequency, in order in that way to control the speed or input power of the electric motors. Overall that arrangement affords a highly reliable and also very simple system, which affords rapid response, for power supply and power control for the individual drive motors.
Preferably the aircraft has sixteen lift rotors. On the one hand, that makes it possible to achieve a particularly large overall rotor area without for that purpose having to provide a single giant rotor with all the problems that this entails. The advantage of a large rotor area is that the power required to produce the necessary lift decreases with increasing rotor area. If the area covered by the rotors overall (referred to as the rotor area) is doubled, then the power required to generate a given lift is reduced for example by about 30%.
In addition, a large number of rotors which are each individually driven by a respective electric motor in conjunction with the above-described operating system for control of the electric motors affords the advantage that by individual control of the individual rotors, it is possible to achieve many different modes of lift distribution, for example to compensate
Barefoot Galen L.
Christie Parker & Hale LLP
LandOfFree
Vertical take-off and landing aircraft does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Vertical take-off and landing aircraft, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Vertical take-off and landing aircraft will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2540889