Aeronautics and astronautics – Aircraft – heavier-than-air – Fluid sustained
Reexamination Certificate
1999-07-13
2001-01-30
Swiatek, Robert P. (Department: 3643)
Aeronautics and astronautics
Aircraft, heavier-than-air
Fluid sustained
C244S02300R, C060S716000
Reexamination Certificate
active
06179247
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a personal air transport or “PAT” which is capable of taking off and landing vertically as well as hovering, if desired. The PAT can maneuver, forward and back as well as side to side, and is capable of traveling forward at a reasonable speed.
Small vertical take-off and landing (VTOL) aircraft have been constructed in various configurations. The most well known is the helicopter which operates with powered rotor blades arranged above the craft body that rotate about a substantially vertical axis, and a powered tail rotor that rotates about a substantially horizontal axis. The pitch of the tail rotor blades is controlled in the cockpit by two pedals—one for the right foot and one for the left—which permit the operator to rotate the craft about the vertical axis or to hold it in a fixed, stable orientation by pressing on the right or left pedal, as desired. The pitch of the upper rotor blades is controlled by two levers: an up-down lever which changes the pitch if all blades at once and a directional “joystick” that selectively changes the pitch of the blades as they rotate through a 360° arc. The joystick is used to tilt the craft and thus impart lateral motion.
Another craft which is capable of VTOL utilizes shrouded rotor blades for extra lift. Instead of arranging the lifting blades in open air, as in the case of a helicopter, they are placed in a vertical “wind tunnel”. As air is drawn in, it passes over a smooth upper rim of the tunnel, reducing the air pressure on this rim in accordance with Bernoulli's Principal. Such a shroud thus not only prevents the air from exiting outward, horizontally from the rotor blades, it also adds lift by this application of Bernoulli's Principal, thereby adding a multiple of about 1.5 to the static thrust as compared to an unshrouded set of rotor blades.
VTOL craft which utilize shrouded rotor blades are therefore considerably more efficient and require less energy to remain airborne. Aircraft of this type are known from the U.S. Pat. Nos. 3,614,030; DES 292,194; 5,213,284 and 5,881,970.
For one reason or another, none of these aircraft designs has risen to the level of commercial practicality.
SUMMARY OF THE INVENTION
It is a principal object of the present invention to provide a personal air transport (“PAT”) which is capable of vertical take-off and landing (VTOL) and which is exceedingly safe to fly, notwithstanding engine failure.
It is a further object of the present invention to provide a PAT, capable of VTOL, which is exceedingly simple and easy to control and easy to operate.
It is a further object of the present invention to provide a PAT, capable of VTOL, which requires a minimum of energy to remain airborne.
These objects, as well as other object which will become apparent from the discussion that follows, are achieved, in accordance with the present invention, by providing a stable, shrouded platform with a plurality N of engines distributed around a circle substantially equidistant from each other, with each engine arranged to provide upward thrust along a substantially vertical axis. If the number N of engines is made greater than or equal to five, the PAT can retain its stable orientation in space and continue to fly even in the event of an engine failure.
Preferably, the number N is made equal to at least 10. In the preferred embodiment of the present invention, disclosed herein, where the craft is about 10 feet wide, N=13.
The present invention takes advantage of the fact that small yet powerful internal combustion (IC) engines, as well as jet engines, are available commercially. The power-to-weight ratio of such engines is comparable to that of larger air-cooled IC engines used for full sized aircraft.
Because of its reduced noise and reduced exhaust pollutants as compared to a two-cycle engine, it is advantageous to select a four-cycle IC engine. The somewhat lower power to weight ratio of this engine is offset by the greater torque that is available at lower RPM.
Also, for reasons of balance and reduced vibration, it is advantageous to select a twin cylinder reciprocating engine with opposed pistons or possibly even a Wankel engine. The two cylinder IC engine has the additional advantage, over a single cylinder engine, that it will continue to operate, even though one of the two cylinders may temporarily cease producing power.
Finally, it is advantageous to select a glow plug engine over a spark plug ignited engine because a spark plug ignition system is considerably more complex and prone to failure as compared to a glow plug.
In a preferred embodiment of the present invention the engine drives a propeller having a diameter in the range of 12-20 inches. This dictates that the engine should have a cubic inch displacement in the range of 1.0 to 3.0.
Preferably a muffler system is provided to substantially muffle the noise of the various engines. Such a system may include a single large muffling “ring” which surrounds the PAT and receives the exhaust from all engines.
As a particular example, the PAT may be powered by thirteen one or two-cylinder, four cycle engines available commercially from Echo Inc., 400 Oakwood Road, Lake Zurich, Ill. 60047. Such an engine may deliver over 50 pounds of static thrust when outfitted with a multiple blade, 20 inch propeller with a 6 inch pitch.
At full power, ten of these engines can lift over 500 pounds without a shroud. In a shrouded configuration ten such engines can lift about 1.5 times this weight or 750 pounds.
Assuming a craft weight of 225 pounds and a full tank (20 gallons) of fuel weighing 125 pounds, the craft will be able to lift a payload of about 400 pounds.
Add three more engines and thirty percent more power, and the craft becomes a nimble flyer which can rapidly rise off the ground and fly horizontally in any desired direction.
Control of the PAT is effected in two ways:
(1) Small moveable paddles which enable the craft to rotate about its central vertical axis under control of the operator, and
(2) Individual throttle control of each engine, thus controlling the engine speeds.
All of the engine speeds are controlled as a single group to cause the craft to rise, fall or hover. The speed of each engine is also controlled separately in a manner to be described hereinbelow to cause the craft to tilt in any desired direction and thus to move horizontally.
Preferably, the engine throttles are controlled by servo-motors which, in turn, are controlled electronically. A first throttle lever is used by the operator to increase or decrease the speeds of all engines at once. A joystick is used to control the relative speeds of the engines and thus the tilt of the craft.
As in the case of a conventional helicopter, pedals are provided to enable the operator to rotate the craft. These pedals mechanically actuate two “paddles” or flaps arranged beneath the engines on opposite sides of the craft, in the downwash of the driven air, to rotate the craft about its vertical axis.
The PAT according to the invention is preferably configured as follows:
A substantially horizontal circular inner platform is arranged at the center of the craft to carry the craft passengers. The inner platform carries a seat for at least one person and has a preferably transparent, hemispherical enclosure arranged as a “bubble” over the passenger seat for protecting the passengers of the craft and providing a smooth surface for the flow of air. The enclosure extends downward to the circular outer extremity of the inner platform which has a diameter D
1
.
A substantially horizontal annular outer platform is arranged coaxially and surrounds the inner platform. The outer platform has a central opening with a second diameter D
2
, this second diameter being greater than the first diameter. The annular outer platform has a shroud forming a substantially smooth upper surface extending inward and downward into the space between the inner platform and outer platform.
At least one thruster is arranged in the space between the inner and outer
Milde Hoffberg & Macklin, LLP
Swiatek Robert P.
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