Note: Descriptions are shown in the official language in which they were submitted.
Title: HOVERCRAFT CONTROL SYSTEM
Field of the Invention
This invention relates to a hovercraft air-cushion
system, and control system wherein directed thrust is used to
provide both propulsion and steering. Most particularly, this
invention relates to a hovercraft vehicle that has an improved
air-cushion effect. Further, using the novel control features,
the vehicle may be remotely controlled using a two channel
radio-control, or two function, steering and control arrangement.
Background to the Invention
A variety of designs for hovercraft air-cushion
vehicles have been proposed which rely on paired horizontal
thrusters for propulsion. In one example, U.S. patent
3,265,142 to Winter, separate propeller means are provided
within each thrust tube.
In the prior art, U.S. patent No. 3,605,937 to Kirwan
discloses a hovercraft which is propelled in forward or reverse
directions by a doubly-directed ducted flow of air. Air to
propel an air-cushion supported vehicle is directed in either
the forward or reverse directions by a pair of complementary
front and rear flaps or panels, arranged to rotate within such
opposite ends in an out-of-phase relationship.
The phase relationship of these flaps is such that all
of the available air in the duct may be directed alternately
in the forward or in the reverse directions, or may be pro-
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portioned between such directions. This is accomplished by a
series of linkages that cause these flaps to rotate, in butterfly
valve fashion, in unison at their respective locations. As one
flap opens, the other flap closes. This allows air flow to be
allocated to exit fxom the duct at either end in desired
proportions.
A single fan is proposed in Kirwan to provide both
lift for the vehicle and forward or reverse thrust. This fan
pressurizes the air-cushion cavity or region between 'the
10, vehicle and the grounds and pressurized air for the directed
ducts is drawn directly from this region.
Kirwan relies on the opposed ends of the ducts to provide
forward and reverse propulsion. To effect changes in direction,
steering vanes, in the form of rudders, are placed in the path of
the air exiting the propulsion ducts. These vanes are separately
controlled through rotation of a steering wheel arrangement.
Kirwan mentions the possibility of providing two or
more for ducts to provide a resultant horizontal thrust component.
But he stipulates that such ducts must be arranged so that the
resultant horizontal component of thrust cancels out in a
steady state. He also states that this resultant thrust is
preferably arranged so that the air directed from the ducts
passes in a direction, along a line which passes through the
vertical central axis of the vehicle.
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The consequence of this last stipulation is that
multiple ducts, as proposed by Kirwan, function only to
provide linear propulsion. Steering in such an arrangement
is effected through only the steering vanes.
Kirwan suffers from a deficiency that arises from the
use of a single air-compression fan or propeller. This fan
imparts a rotational momentum to the compressed air, and the
reaction on the fan is transferred to the vehicle as an
inclination or bias to counter-rotate in the opposite
direction to the rotation of the fan blades. While this
tendency may be overcome by vectored thrusts of corrective air
jets emitted horizontally in the appropriate direction, the
accurate balancing of this effect is difficult to control
precisely.
An earlier invention by one of the co-inventors
herein, U.S. 3,746,116 to John Schwingshandl, proposes to
overcome this pivotal effect by dividing the main air cavity
inside the air-cushion vehicle skirts into at least four
separate compartments. Air to each compartment is then
provided through butterfly valves from an intermediate chamber
(described in Schwingshandl as "unseen") located between the
air-cushion cavity and the fan. Through use of the butterfly
valves, the flow of air into each compartment is controlled.
As such, this air_ flow is variable and not pre-fixed, or
determined by fixed vehicular arrangements.
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Schwingshandl relies on the use of rudder blades
placed in the wash from horizontal ducts for directional
controls as well.
These prior art arrangements lack the convenience of
the features of the invention, which will now be described.
Summary of the Invention
In accordance with the invention an air-cushion
vehicle comprises:
(1) a body defining an air-cushion cavity through
which compressed air provides vehicular support;
(2) air pressurization means mounted on said body
providing entry of pressurized air into said
vehicle through an inlet opening of specific
diameter;
(3) an intermediate plenum communicating with
said air pressurization means and communicating
with said air-cushion cavity through plurality
of immediate openings of fixed dimensions
by which pressurized air may flow from said
plenum to said cavity,
wherein said intermediate openings have a total area which is
less than the area of said inlet opening.
By a further feature of the invention, the ratio of
the area of the fan inlet opening to the total area of the
openings communicating the intermediate plenum with the air
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cushion cavity is in the range of from 4 to 1 to 1.25 to l,
and move preferably, about 2:1.
This configuration, as opposed to the prior art,
provides unrestricted openings between the intermediate plenum
5 and the air-cushion cavity. Such openings are, however, of a
specific limited size. Superior performance has been found
with this arrangement. It is believed that such performance
may be partially due to the dynamic reaction of the flow of
air through these apenings, as well as the customary static
effect of the compressed air on which air-cushion vehicles
rely. This is, however, only a theory.
By a further feature the invention an air cushion
vehicle is provided with a pair of substantially parallel
double-ended ducts, each duct being symmetrically located on
opposed sides of the central axis of the vehicle. Each duct
is connected to a source of compressed air and is provided at
its respective exit ends with respective closure means. These
closure means operate in a complementary fashion from a single .
control, so as to allow compressed air entering said duct to
be proportioned between the respective exit ends of such duct.
The flow from the ends of each respective duct may be
separately controlled.
This arrangement allows the vehicle to be both
propelled and steered by varying the proportions of air
escaping from the ends of the ducts. Through use of two
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ducts, both the linear propulsion and steering functions can
be controlled using only two control inputs, in the same
fashion as in a tracked vehicle.
By a further feature of the invention, control over
the proportions of air exiting the ends of each duct is
effected by closure positioning means that responds to a
radio-controlled signal means which utilizes a single
transmission channel for each duct.
The use of a dual channel radio control system
minimizes cost. Two channel signaling is possible because the
vehicle of the invention can be fully controlled using only
two independent signals: one for the position of the closure
means in each duct.
By a further feature of the invention, air for said
ducts is sourced from an intermediate plenum which plenum is
pressurized by a fan mounted in a fan intake passage. This
intermediate plenum may also supply air to the air-cushion
cavity that provides vehicular support, through openings of a
predetermined fixed size communicating between said plenum and
said cavity. Alternately, the intermediate plenum may supply
air only to the ducts.
These and further features of the invention will be
better understood from the description of the preferred
embodiments which now follow.
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Summary of the Fi ores
Figure 1 is a plan view of a hovercraft with two fan
and two thrust ducts.
Figure 2 is a perspective view of the vehicle of
Figure 1.
Figure 3 is a perspective cut-away of Figure 2 snowing
the linkages within the thrust ducts.
Figure 4 is a plan view cut-away showing the linkages
within the thrust ducts.
Figure 5 is a plan view of an alternate air-cushion
vehicle with one fan and two thrust ducts.
Figure 6 is a cut-away perspective view of the vehicle
of Figure 5.
Description of the Preferred Embodiments
In Figure 1 fan 1 mounted in duct 2 forces air into
thrust plenum 3, as shown in Figure 2. The air from fan 1 is
forced under pressure through openings 4 and 5 into the
thrust tubes 6 and 7. These tubes 6, 7 each have open ends 8,
9, 10 11.
To propel the vehicle forward levers 12 and 13 must be
activated. As shown in Figure 3, rearward movement of lever 12
pushes rod 14 activating crank 15 mounted on the outside of tube
7. Crank l5 rotates on axle 16, which is mounted through tube 7,
to turn crank 17 which is affixed to axle 16 inside tube 7. In
doing so cranks 17 and l5 move parallel to each other. Crank
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17 pulls rod 18 connected to valve 21, pivoting on axle 23 in
opening 11 of tube 7. This closes the opening 8. The same
motion of crank 17 pushes rod 19 connected to valve 20,
pivoting on axle 22 in opening or outlet 8 on the aft end of
tube 7. With valve 20 fully open, valve 21 becomes fully
closed causing the air to exit from tube 7 via outlet 8.
Similarly placing the right hand lever 13 in the same
rearward position, rod 24 activates a linkage contained in tube
6 identical to that contained in tube 7. With both levers pulled
to the rear, the valves 21 and 30 positioned in the front
openings 11 and 10 respectively of tubes 7 and 6 respectively
are fully closed forcing all the air from thrust plenum 3
through openings 4 and 5 and further past valves 20 and 32
in openings 8 and g of tubes 7 and 6 thus propelling the unit
forward.
Reverse is performed by moving levers 13 and 12 fully
forward to the position shown in Figure 3. This activates the
linkages contained in the tubes 7 and 6 in exactly the
opposite manner described above, leaving the valve 20 in
opening 8 of tube 7 fully closed and valve 32 in opening 9 of
tube 6 fully closed. This results in valve 21 in opening 11
of tube 7 being open, and valve 30 of opening 10 of tube 6
being opened. The result is that the air from thrust plenum 3
is forced through openings 4 and 5 into tubes 7 and 6 and past
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valves 21 and 30, and out through openings 23 and 31 of tubes
7 and 6.
Whatever position levers 12 or 13 are initially, the
opposite of that position places an equal and opposite
reaction. Inasmuch as the linkages are independent they may
be placed in opposite positions to accommodate clockwise or
counter clockwise motion. If lever 12 were pulled rearward
and lever 13 pushed forward, then the air in tube 7 would leave
by way of opening 8, but the air in tube 6 would exit by the
front opening 10, directing the front of the vehicle to the
right. Maintained in this position the vehicle would rotate
continuously clockwise. When lever 13 is pulled rearward and
lever 12 forward, the air in tube 7 is forced out through
opening 11 and from tube 6 through opening 10 causing the
front of the vehicle to go left. Maintained in this position
the vehicle will rotate counter clockwise.
Alternately, levers 12 and 13 could be left in an
intermediate or neutral position causing the vehicle 'to remain
at rest. Figure 4 shows the valves 21 and 20 in openings ll
and 8 respectively of tube 7, and 30 and 32 of openings 10 and
9 respectively of tube 6 in this intermediate position. The
force produced at the front of the vehicle is thereby
cancelled out by an equal force produced in the rear of the
vehicle.
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Figure 2 shows a vehicle with two fans, wherein thrust
fan 2 in duct 2 is intended for thrust, as described above, and
lift fan 39 in duct 38 mounted on the front of the vehicle is
intended to provide a source of pressure for lift. The lifting
air is forced into lift plenum 40 filling left plenum 40. Air
then flows into the air-cushion cavity 50 directly through
principal outlets 34, 35, 36, 37 in the common wall 51 between
the lift plenum 40 and the air-cushion cavity 50. This fills
the air-cushion cavity located underneath the common wall 51
and within peripheral curtain 42 with pressurized air. Some
air is also directed outwardly against the curtain 42 by way
of small curtain-supporting tubes 41.
It has been found that a superior lift effect is
obtained if the combined area of the outlets is on the order
of half the area occupied by the fan 39.
The lift plenum 40 is separated in the embodiment of
Figure 2 from the thrust plenum 2 by a dividing wall 43. In
the case of, the thrust plenum 2, it has been found that,
preferably, the effective area of the duct outlets 8, 9, 10,
11, allowing for the effect of the valves 20, 21, 30, 32 may
be on the order of the surface area of fan 2; certainly, no
greater; and more preferably no more than 50 percent of the
area of the fan 2.
Figure 5 and 6 show a small combined plenum 54 serving
for both thrust and lift. The propulsion and directional
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functions within the ducts 6 and 7 in this embodiments are
exactly the same as the aforementioned linkages from Figure 3
and 4. The the total area of the cutlets 34, 35, 36 and 37
that provide lift is again no more than the total area of the
fan la, which provides both lift and th~°ust. Further, the
effective area of the thrust outlets 8a, 9a, 10a, lla on the
combined unit should preferably be not be more than about 50
percent of the total area of the fan 1. It is possible for
the combined unit to have a ratio of 1:1 for total fan to
total outlet areas effective as an upper limit, but a ratio of
between 3:2 and 4:3 is preferred. This is a preferred
embodiment for toy radio-controlled hobby-type vehicles
because of the convenience of having only one fan.
Figure 3 shows manual controls 12, 13 for propulsion
and steering. In Figure 5 electrically controlled actuators
55a, 55b are coupled through shafts 56a, 56b that are
analogous to rods 24, 14 in Figure 2. These actuators 55a, b
receive signals through wires 57 from a radio receiver 58,
equipped with an antenna 59.
By reason of the combined functions of the thrust
ducts 6, 7, it is sufficient for receiver 58 to have twa
channels only: This suits this embodiment particularly to the
toy or hobby market:
On a 14-1/2 inch toy model that has been built thrust
outlets 8a, 9a, 10a, 11a of 1.4 inch diameter were provided
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with an intake fan diameter of 4.2 inches. The lift outlets
34, 35, 36 and 37 on the same unit were 1.25 inches in
diameter.
The motor for the fax (not shown) was a Kyosho AP29
operating at 16000 rpm off 6 re-chargeable nickel cadmium
batteries providing 7.2 volts. This unit weighs 2 lbs. 6 oz.
' and can lift a 3 lb. payload. Tt has a ground clearance of
1-1/4 inches when unloaded.
The foregoing has constituted a description of
preferred embodiments which are intended only to be exemplary
of the invention. The invention in its basic and more
particular aspects is further described and defined in the
claims which now follow.
