Aeronautics and astronautics – Aircraft – heavier-than-air – Helicopter or auto-rotating wing sustained – i.e. – gyroplanes
Reexamination Certificate
1999-09-01
2001-09-25
Jordan, Charles T. (Department: 3644)
Aeronautics and astronautics
Aircraft, heavier-than-air
Helicopter or auto-rotating wing sustained, i.e., gyroplanes
C244S017230, C244S00400R
Reexamination Certificate
active
06293492
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a coaxial twin-rotor type helicopter in which upper and lower coaxial rotors are rotated in opposite directions. More particularly, this invention relates to a coaxial twin-rotor type helicopter having a compact, simple control mechanism. The invention also relates to a coaxial rotor type helicopter in which the rotors are covered by a protective frame.
2. Prior Art Description
Various helicopter structures are known. To realize a small, one-man helicopter that is easy to use, the present inventors are developing a coaxial twin-rotor type helicopter in which thrust and lift are obtained by counterrotating a lower and an upper rotor provided on the same axis. In a twin-rotor helicopter, torque is counteracted by having upper and lower rotors of the same shape rotate in opposite directions. As such a configuration eliminates the need for a tail rotor, and therefore enables the overall dimensions to be reduced, it is a suitable basic configuration for a small, one-man helicopter. The attitude and the direction of the helicopter are controlled basically by tilting the tips of the rotor blades with respect to the horizontal plane, and by controlling the attack angle of the rotor blades.
However, the control mechanisms of such conventional coaxial twin-rotor type helicopters are complex and require a large installation space, making them unsuitable for the type of small helicopter the present inventors are developing. Moreover, when this type of helicopter is used for tasks such as spraying agricultural chemicals, unlike a large helicopter, it is generally flown at a low altitude, and when operated at low altitude, it is usually used in hovering mode. This means there is a high possibility of people working on the ground being struck by the rotors. There is also a high likelihood of the rotors hitting and breaking electric power lines.
An object of this invention is therefore to provide a coaxial twin-rotor type helicopter having a compact, simple control mechanism.
Another object of the invention is to provide a coaxial twin-rotor type helicopter having a compact, simple yaw control mechanism.
Another object of the invention is to provide a safe coaxial twin-rotor type helicopter having rotors that do not hit people or electric power lines or the like.
SUMMARY OF THE INVENTION
The invention achieves the above and other objects by providing a coaxial twin-rotor type helicopter in which an upper rotor and a lower rotor disposed on the same axis are rotated in opposite directions, said helicopter comprising: an airframe, a vertical shaft that rotatably supports the rotors, and a control mechanism that, with respect to a gravitational force direction, can tilt the vertical shaft backward and forward and to either side to thereby tilt tips of blades of the rotors; said control mechanism comprising a first swing member that depends from a lower end portion of the vertical shaft so as to be freely swingable backward and forward and to either side about a swing center point on a center axis of the vertical shaft, a second swing member that depends from the first swing member so as to be freely swingable about the swing center point in a direction at right-angles to the swinging direction of the first swing member, and a control stick that can swing the vertical shaft backward and forward and to either side.
When the helicopter thus configured is in the air, the airframe depends, via the first and second swing members, from the vertical frame to which the rotors are attached. In this state, the airframe can be tilted forward, backward or to either side, with respect to the direction of gravitational force, about a center point on the vertical shaft by moving the control stick in the forward, backward or sideways direction concerned. This tilts the rotor face, thereby enabling the lift direction to be changed. When the control stick is released, the force of gravity causes the vertical stick to return automatically to the vertical.
The coaxial twin-rotor type helicopter of this invention includes a drive transmission mechanism to rotate the twin rotors. The drive transmission mechanism includes first and second planet gear mechanisms, and a drive pinion that rotates internal gears in the first and second planet gear mechanisms in opposite directions at uniform velocity. The first and second planet gear mechanisms are provided with a common carrier. The sun gear of the first planet gear mechanism is connected to rotate integrally with the rotor shaft of the upper rotor, and the sun gear of the second planet gear mechanism is connected to rotate integrally with the rotor shaft of the lower rotor.
The coaxial twin-rotor type helicopter of the invention includes a yaw control mechanism to control airframe yaw. The yaw control mechanism is provided with a differential rotation generator that rotates the common carrier of the first and second planet gear mechanisms. The differential rotation generator comprises a motor, an outer gear-wheel formed on the outer face of the common carrier, and a reduction gear-train between the motor output shaft and the outer gear-wheel. When the motor is not in operation, the upper and lower rotor shafts are driven at a uniform velocity in opposite directions via the first and second planet gear mechanisms. As a result, no torque is generated about the vertical axis of the airframe, so the airframe continues to point in the same direction.
When the motor is operated, the rotational force of the motor is transmitted via the reduction gear-train to the common carrier of the first and second planet gear mechanisms, thereby rotating the common carrier in one direction. This sets up a differential motion between the sun gears of the planet gear mechanisms, producing a difference between the rotational velocities of the two rotors. This generates a turning moment about the vertical axis of the airframe, changing the direction the airframe faces.
In a preferred embodiment of the invention, the rotors of the coaxial twin-rotor type helicopter have a protective frame disposed concentrically over the outer periphery of the rotors. The protective frame serves to prevent the rotors from coming into direct contact with persons working on the ground, and to prevent electric power lines and the like from being cut by the rotors. To ensure that the rotors are not able to come into contact with people or electric power lines, it is preferable for the rotors to be covered by a cylindrical protective net on the periphery of the protective frame. In the event that the protective frame does hit a person or the like, it is also preferable for the periphery of the protective frame to be covered with an air tube to protect the person from the shock of the impact.
Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and following detailed description of the invention.
REFERENCES:
patent: 2156334 (1939-05-01), De Bothezat
patent: 2456485 (1948-12-01), Bendix
patent: 2461347 (1949-02-01), Pentecost
patent: 2954186 (1960-09-01), Bibrey
patent: 3029047 (1962-04-01), Jacobsen et al.
patent: 3126966 (1964-03-01), Agamian
patent: 3669564 (1972-06-01), Garfinkle
patent: 3814351 (1974-06-01), Bielawa
patent: 3921939 (1975-11-01), Garfinkle
patent: 4071206 (1978-01-01), Magill
patent: 4912999 (1990-04-01), Franks et al.
Burns Doane Swecker & Mathis L.L.P.
Dinh Tren
Engineering System Co., Ltd.
Jordan Charles T.
LandOfFree
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