U.S. patent application number 09/738955 was filed with the patent office on 2001-08-09 for coaxial valve with electric actuating drive.
Invention is credited to Bethe, Gerd, Roth, Martin, Voit, Arno.
Application Number | 20010011715 09/738955 |
Document ID | / |
Family ID | 7932654 |
Filed Date | 2001-08-09 |
United States Patent
Application |
20010011715 |
Kind Code |
A1 |
Roth, Martin ; et
al. |
August 9, 2001 |
Coaxial valve with electric actuating drive
Abstract
A coaxial valve includes an actuating drive, a valve housing
(11), a valve sleeve (12) that is longitudinally slidable in the
valve housing (11) between open and closed positions, and a closing
body (13) arranged coaxially at one end of the valve sleeve (12).
In the closed position, the valve sleeve seals against the closing
body. In the open position, the valve sleeve is spaced from the
closing body, to open a valve opening cross-section (V). The
actuating drive includes an electric servomotor (21) with a linear
actuator (22), and a transmission mechanism (30) for transmitting
the linear movement of the actuator to the valve sleeve. The
transmission mechanism includes a rocker lever with a first end
articulately connected to the linear actuator, a second end
articulately connected to the valve housing, and a middle section
articulately connected to the valve sleeve.
Inventors: |
Roth, Martin; (Taufkirchen,
DE) ; Voit, Arno; (Haushaum, DE) ; Bethe,
Gerd; (Ottobrunn, DE) |
Correspondence
Address: |
FASSE PATENT ATTORNEYS, P.A.
P.O. BOX 726
HAMPDEN
ME
04444-0726
US
|
Family ID: |
7932654 |
Appl. No.: |
09/738955 |
Filed: |
December 15, 2000 |
Current U.S.
Class: |
251/129.2 |
Current CPC
Class: |
F16K 1/123 20130101;
F16K 31/10 20130101 |
Class at
Publication: |
251/129.2 |
International
Class: |
F16K 031/02 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 15, 1999 |
DE |
199 60 330.8 |
Claims
What is claimed is:
1. A coaxial valve for controlling a flow of a liquid or gaseous
flow medium therethrough, comprising: a valve housing with an
inlet, an outlet and a flow passage passing in a longitudinal
direction therethrough from said inlet to said outlet; a closing
body arranged in said flow passage in said housing; a valve sleeve
slidably arranged in said flow passage so as to be slidable in said
longitudinal direction between a closed position in which said
valve sleeve contacts and seals against said closing body to close
said flow passage and an open position in which said valve sleeve
is spaced a distance apart from said closing body to open a valve
flow opening between said valve sleeve and said closing body and
allow the flow medium to flow from said inlet, through said valve
sleeve in said longitudinal direction, through said valve flow
opening and out of said outlet; an actuating drive including an
electric servomotor and a linear actuator coupled to said
servomotor and adapted to output a linear actuating motion; and a
transmission mechanism connected between said linear actuator and
said valve sleeve and adapted to transmit the linear actuating
motion from said linear actuator to said valve sleeve; wherein said
transmission mechanism comprises a rocker lever that extends
transversely relative to said longitudinal direction and that
includes a first end, a second end opposite said first end, and a
middle section between said first and second ends; and wherein said
transmission mechanism further comprises a drive bearing that
articulately couples said first end of said rocker lever with said
linear actuator, a locating bearing that articulately couples said
second end of said rocker lever with said valve housing, and an
actuator bearing that articulately couples said middle section of
said rocker lever with said valve sleeve.
2. The coaxial valve according to claim 1, wherein said linear
actuator is arranged and oriented so that said linear actuating
motion is parallel to said longitudinal direction in which said
valve sleeve is slidable.
3. The coaxial valve according to claim 1, wherein said actuator
bearing comprises a bearing bore provided in said middle section of
said rocker lever, and an actuator journal pin that protrudes
outwardly from said valve sleeve and is received in said bearing
bore.
4. The coaxial valve according to claim 1, wherein said actuator
bearing comprises a socket surface provided at said middle section
of said rocker lever, and a ball surface that is provided on an
exterior of said valve sleeve and is received in said socket
surface.
5. The coaxial valve according to claim 1, wherein said middle
section of said rocker lever comprises two lever portions that
respectively extend around opposite sides of said valve sleeve, so
that said valve sleeve passes through said middle section of said
rocker lever, and said rocker lever surrounds said valve
sleeve.
6. The coaxial valve according to claim 5, wherein said actuator
bearing comprises two bearing bores respectively provided in said
two lever portions respectively at said opposite sides of said
valve sleeve, and two actuator journal pins that respectively
protrude outwardly from said two opposite sides of said valve
sleeve and are respectively received in said bearing bores.
7. The coaxial valve according to claim 5, wherein said actuator
bearing comprises a socket formed of inner surfaces of said two
lever portions facing inwardly toward and surrounding said valve
sleeve, and a ball surface that is provided on an exterior of said
valve sleeve and is received in said socket.
8. The coaxial valve according to claim 1, wherein said drive
bearing comprises a bearing socket provided on said linear
actuator, and a bearing ball that is provided on said first end of
said rocker lever and is received in said bearing socket.
9. The coaxial valve according to claim 1, wherein said locating
bearing comprises a bearing socket provided in said valve housing,
and a bearing ball that is provided on said second end of said
rocker lever and is received in said bearing socket.
10. The coaxial valve according to claim 1, wherein said locating
bearing comprises at least one spring element interposed between
said second end of said rocker lever and said valve housing.
11. The coaxial valve according to claim 1, wherein said valve
sleeve is arranged and retained in said valve housing in a
pressure-equalized manner so that the flow medium does not exert
any influence on said slidability of said valve sleeve in said
longitudinal direction in said valve housing.
12. The coaxial valve according to claim 1, wherein said housing
provides a complete encapsulation, and said valve further comprises
slide seals between said valve sleeve and said housing to seal the
flow medium in said valve sleeve and said flow passage of said
housing.
13. The coaxial valve according to claim 1, being able to withstand
temperatures of the flow medium from 3K to 350K.
14. The coaxial valve according to claim 1, being able to withstand
pressures of the flow medium up to 290 bar.
15. A combination of the coaxial valve according to claim 1 and a
flying craft.
16. A combination of the coaxial valve according to claim 1 and the
flow medium, wherein said flow medium is at a temperature in a
range from 3K to 350K.
17. A combination of the coaxial valve according to claim 1 and the
flow medium, wherein said flow medium is at a pressure of 290 bar.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a coaxial valve for regulating and
shutting off the flow of a fluid or gaseous flow medium.
BACKGROUND INFORMATION
[0002] There are particularly stringent requirements for valves
which are used for regulating and shutting off liquid or gaseous
flow media under extreme conditions such as chemical
aggressiveness, very high or very low temperatures or very high
pressures. Propulsion in aircraft and spacecraft is one field of
application of valves used for shutting off a liquid or gaseous
medium under extreme conditions. In such applications, the valves
are subjected not only to extreme high and low temperatures but
also to extreme temperature changes. In the case of valves for
liquid and gaseous rocket fuels, there are further parameters such
as high mass flow rates, high pressures and short switching times
(opening, closing, positioning).
[0003] For use in particular in aerospace applications, a coaxial
valve is used for shutting off a liquid or gaseous flow medium,
comprising a valve housing, a valve sleeve, and a closing body. The
valve housing has an inlet and an outlet for the medium to be shut
off. The valve sleeve is arranged in the valve housing in an axial
direction between an open position and a closed position, whereby
the valve sleeve is slidable in a longitudinal direction of the
valve housing between the open and closed positions for the purpose
of opening or shutting off the flow of the medium. The medium to be
shut off flows in the longitudinal direction through the valve
sleeve when the valve is open. The closing body is arranged at one
end of the valve sleeve coaxially thereto. The valve sleeve rests
against the closing body in the closed position so as to provide a
seal, and on the other hand, with the valve sleeve in the open
position, the valve sleeve is spaced at a distance from the closing
body for freeing a valve opening cross section therebetween. Such a
coaxial valve further comprises an actuating drive for opening and
closing the valve.
[0004] Up to now, valves of the above described type comprised a
pneumatically operated actuating drive. A pneumatic system such as
the actuating drive of a valve has the disadvantage in that it is
very complex, is associated with the danger of leakage, and in
particular in aerospace applications is problematic in view of the
high reliability which is required. Possible leakage is conducted
away separately in a connecting line.
[0005] Helium is used as a pressure means (control fluid) which is
used primarily as a seal gas between the hot and the cold flow
(turbine propellant gas/fuel) in the turbopumps and during such use
is consumed due to leakage losses. It can thus happen that toward
the end of a mission there is no longer any helium left for
operating the valves. A further disadvantage is the expenditure in
design, weight and cost, required for the helium pipe system and
regulating system to which each fuel valve has to be connected.
Such systems also pose problems concerning their reliability. Since
a compressible gas is used as a pressure medium, the actuation
movement of a valve can only be very coarsely influenced from a
time-related and kinematic point of view. Only an open position and
a closed position are possible, both against an end stop. Defined
intermediate positions and precise control movements are
practically impossible.
[0006] German Utility Model DE 297 06 688 U1 discloses a coaxial
valve as mentioned above, further including a transmission part in
the form of a lever or an articulated lever which is used as a
connection between an actuator and a valve sleeve and which causes
displacement of the valve sleeve in the coaxial valve. In this
arrangement, the transmission part interacts on one side with the
valve sleeve. With such an arrangement there is an inherent danger
that due to the one-sided application of force, the valve sleeve
may jam in the coaxial valve. This is particularly fatal for
applications where maintenance of the coaxial valve is not possible
or possible only at considerable expense, such as for example
during the extreme conditions mentioned in the introduction.
[0007] European Patent Application Publication EP-OS 0 257 906
discloses various embodiments of seat valves in which the
axially-movable seat body is driven by an electric motor via a
spindle/nut arrangement. The emphasis has been placed on achieving
as compact a design of the valve housing as possible. This has been
achieved in that the rotor of the electric motor largely makes use
of the cross section of the flow channel, with the rotor itself
being located in the flow stream of the conveying medium. In this
way, the external diameter of the valve housing corresponds
approximately to the external diameter of the adjoining pipelines.
Such an arrangement is however associated with considerable
disadvantages. The units (bearing, rotor, gearing) which are
incorporated directly in the flow channel, considerably impair the
flow, so that considerable losses in pressure have to be
anticipated. Depending on the physical characteristics of the
flowing medium, large friction moments act on the rotating rotor,
so that an unnecessarily increased amount of power is required to
drive it. Aggressive flow media can chemically/physically attack
bearings, rotor and gearing, and thus considerably shorten their
useful life. Consequently, such a valve design is only suitable for
non-aggressive media of low viscosity, where the throughput is
relatively small.
SUMMARY OF THE INVENTION
[0008] It is an object of the present invention to provide a
control valve, in particular for cryogenic and aggressive rocket
fuels, which is particularly flow-enhancing, relatively simple and
compact in design, and which has a drive that is not located in the
conveyed flow medium. Furthermore, the drive should be arranged so
as to be largely thermally decoupled, and it should consume as
little power as possible. In addition, operation of the control
valve is to be as troublefree as possible. The invention further
aims to avoid the disadvantages of the prior art, and to achieve
additional advantages, as apparent from the present
specification.
[0009] The above objects have been achieved according to the
invention in a coaxial valve for regulating and shutting-off the
flow of a liquid or gaseous flow medium. The valve comprises a
valve housing with an inlet and an outlet connected by a flow
passage for the liquid or gaseous medium, and a valve sleeve that
is arranged in the housing (in the flow passage) axially between an
open position and a closed position, so as to be slidable in a
longitudinal direction between the open position for allowing the
medium to flow in the longitudinal direction through the valve
sleeve, and the closed position for shutting off the flow of the
medium. The valve further comprises a closing body that cooperates
with the valve sleeve to selectively achieve the closure seal or
the open flow passage through the valve. Particularly, on the one
hand the valve sleeve rests against the closing body in the closed
position to provide a seal, and on the other hand, when the valve
sleeve is in the open position, the sleeve is spaced at a distance
away from the closing body so as to free a valve opening
cross-section. The present valve further comprises an actuating
drive for opening and closing the valve by sliding the valve sleeve
selectively in the longitudinal direction between the open position
and the closed position and/or to any desired intermediate
partial-open position therebetween.
[0010] Particularly according to the invention, the actuating drive
comprises a rotational electric servomotor including a linear
actuator, and a transmission part or mechanism coupled between the
linear actuator and the valve sleeve so as to transmit the linear
movement of the linear actuator to the valve sleeve. The
transmission part or mechanism comprises an adjusting lever
embodied as a rocking lever that extends in a direction generally
transverse relative to the longitudinal direction of motion of the
valve sleeve. A first end of the rocking lever or adjusting lever
is articulately connected by a drive bearing to the linear actuator
of the servomotor, while the second end of the adjusting lever is
articulately coupled by a locating bearing to the valve housing,
and a middle section of the adjusting lever between the first and
second ends is articulately connected by an actuator bearing to the
valve sleeve. With such an arrangement, the adjusting lever
transmits the linear motion of the linear actuator of the
servomotor to a linear motion of the valve sleeve, while accurately
transmitting the driving force along the linear path of the motion
of the valve sleeve and avoiding alignment errors and the like
between the valve axis and the drive axis. The two opposite ends of
the adjusting lever are slidable and articulated respectively in
the drive bearing and the locating bearing, while the middle
section of the adjusting lever is articulated via the actuator
bearing to the valve sleeve.
[0011] One advantage of the coaxial valve according to the
invention is its high reliability even under extreme conditions. A
further advantage consists of one valve sleeve being
pressure-equalised, thus requiring only modest actuating power.
Another advantage consists of its flow shape with the seal seat
being easily adjustable and exchangeable.
[0012] A further advantage of the coaxial valve according to the
invention consists of it being steplessly adjustable with high
precision between the open position and the closed position. Yet
another advantage consists of its actuating time between the open
position and the closed position or from a defined position to
another defined position being freely selectable. A still further
advantage of the coaxial valve according to the invention consists
of it being electrically controllable in a simple way. There is
another advantage in that, in contrast to pneumatically controlled
valves, no leakage problems can occur. Furthermore, it is a
significant advantage of the coaxial valve according to the
invention in that it can easily be electrically implemented in
various environments. No screws can fall into the flow medium
space, and the coaxial valve can easily be flushed out with gas. In
this way, the danger of freezing during operation with cryogenic
media can be avoided.
[0013] The special type of the adjusting lever in the form of a
rocking lever and the way it is held and arranged, in particular
via coupling with the valve sleeve in a middle region, reduces the
danger of the valve sleeve jamming. This is because, in contrast to
the prior art, impingement or coupling of force on the valve sleeve
so as to move the valve sleeve is now not merely on one side, but
instead the coupling of drive forces onto the valve sleeve from
several sides is possible.
[0014] De-coupling of the electric drive from radial pressure and
shrinking forces is ensured. Furthermore, constraining forces as a
result of alignment errors between the valve axis and the drive
axis are avoided.
[0015] A preferred embodiment of the invention provides for the
actuator of the servomotor to be movable co-linear or parallel to
the longitudinal direction of displacement of the valve sleeve.
[0016] Another preferred embodiment of the invention provides for
the actuator bearing to comprise an actuator cog or journal pin
provided on the exterior of the valve sleeve, and a bearing bore
that is provided in or on the adjusting lever and that accommodates
the actuator cog therein. In this arrangement, the force is
introduced over a large area into the thin-walled sliding sleeve.
Also, manufacturing expense is reduced due to a simple shape and a
reduced number of parts.
[0017] An alternative embodiment provides for the actuator bearing
to be formed by a ball surface provided on the exterior of the
valve sleeve, and by a socket surface provided on the adjusting
lever, whereby the socket surface accommodates the ball
surface.
[0018] A preferred improvement of the invention provides for the
adjusting lever in the region of the actuator bearing to be
configured so as to surround the valve sleeve, e.g. with two
portions of the lever extending respectively around opposite sides
of the valve sleeve. On each side of the valve sleeve, a respective
bearing bore accommodating a respective actuator cog, is provided
in the adjusting lever.
[0019] According to one embodiment of the invention, the drive
bearing comprises a bearing ball provided at one end of the
adjusting levers and a bearing socket provided on the actuator of
the servomotor.
[0020] According to a further embodiment, the locating bearing
comprises a bearing ball provided at the other end of the adjusting
lever, and a bearing socket provided in the valve housing. In
addition, the locating bearing may comprise spring elements. The
bearing may e.g. be pre-tensioned in one direction via leaf springs
which are attached between the housing and the socket. These
springs make it possible to obtain cushioning when moving against
the limit position as well as to obtain temperature-compensated
length equalisation, thus maintaining shutoff power, as well as
reinforcement or supplementation of the opening movement as a
result of the energy stored in the springs. The locating bearing of
the coaxial valve may comprise spring elements also so as to
compensate for materials shrinkage and tolerances.
[0021] Preferably pressure-equalised retention of the valve sleeve
in the coaxial valve is provided. Due to such pressure-equalisation
of the valve, the pressure of the flow medium has no direct
influence on the hydraulic power of the valve sleeve.
[0022] Furthermore, encapsulation of the valve or the drive may be
provided. This provides protection against explosion in the case of
gaseous media. Material present as a result of leaks due to
improper sealing can be removed from the valve in a controlled way,
with the valve also being suitable for aggressive media such as for
example MMH and N.sub.2O.sub.4 (storable fuels).
[0023] The valve according to the invention has the advantage that
it is "scaleable", i.e. in that the valve can be made in all sizes
without principle changes.
[0024] Advantageously, the coaxial valve according to the invention
is used for temperatures of the flow medium from 3 K (for liquid
helium) to 350 K. Furthermore, the coaxial valve according to the
invention is advantageously used for pressures of the flow medium
of up to 290 bar.
[0025] Regulating and shutting off liquid or gaseous flow media, in
particular cryogenic, i.e. deep-frozen, media for propulsion of
aircraft or spacecraft is a preferred field of application of the
coaxial valve according to the invention. Throughout this
specification, the term "flow media" is intended to cover all
liquid or gaseous media that may selectively flow through or be
shut-off by the present valve.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] In order that the invention may be clearly understood, it
will now be described in connection with example embodiments, with
reference to the accompanying drawings, wherein:
[0027] FIG. 1 is a cross-sectional view of a coaxial valve for
shutting off and regulating a liquid or gaseous flow medium
according to a first embodiment of the invention; and
[0028] FIG. 2 is a cross-sectional view of a coaxial valve for
shutting off and regulating a liquid or gaseous flow medium
according to a second embodiment of the invention.
DETAILED DESCRIPTION OF PREFERRED EXAMPLE EMBODIMENTS AND OF THE
BEST MODE OF THE INVENTION
[0029] FIGS. 1 and 2 show two embodiments of the coaxial valve
according to the invention. The coaxial valve generally comprises a
hydraulic part or valve body 10, an electric linear drive 20, and a
transmission part or mechanism 30.
[0030] The hydraulic part 10 includes a valve sleeve 12 arranged in
a valve housing 11. The valve sleeve 12, in an axial direction, is
arranged and longitudinally slidable between an open position in
which an open flow passage is provided through the valve housing
11, and a closed position closing off the flow passage in relation
to the valve housing 11. The longitudinal slidability and sealing
arrangement of the valve sleeve 12 in relation to the valve housing
11 is achieved by bearing surfaces 14, 15 provided on the exterior
of the valve sleeve 12, cooperating with slide-thrust bearings 16,
17 with slide seals provided in the valve housing 11. At one end of
the valve sleeve 12, a closing body 13 is arranged coaxially to the
valve sleeve 12, with the closing body 13 being contoured at its
side facing the valve sleeve 12, for example cone-shaped, and
comprising a valve seat area 13a interacting with the end of the
valve sleeve 12 so as to provide a seal. The closing body 13 is
fixed in the flow passage within the housing, e.g. by a spider
arrangement.
[0031] The closing body 13 is surrounded by a flow chamber 13b by
way of which the liquid or gaseous flow medium can flow around the
closing body 13 when the valve is open. The valve sleeve 12 and the
closing body 13 are arranged coaxially in a flow path leading from
an inlet E to an outlet A of the coaxial valve. In the closed
position of the coaxial valve, the valve sleeve 12 rests against
the valve seat area 13a of the closing body 13, as shown in FIG. 1.
In the open position of the valve, the valve sleeve 12 is spaced
apart from the closing body 13 while freeing a valve aperture
cross-section V, as shown in FIG. 2.
[0032] The actuating drive formed by the electric linear drive 20
of the coaxial valve comprises a servomotor 21 which is fixed to
the valve housing 11 via a motor mounting 28, as well as a linear
actuator 22 with a linear movement, whereby a screw with a
recirculating ballnut assembly or a planetary ballnut assembly 23
translates the rotary movement of the servomotor 21 to a
back-and-forth linear movement of the actuator 22. The actuator 22
of the servomotor 21 is movable in the valve housing 11 collinear
or parallel to the direction of the sliding displacement of the
valve sleeve 12, i.e. parallel to the longitudinal direction in
which the valve sleeve 12 moves.
[0033] The transmission part or mechanism 30 is used to transmit
the linear movement of the actuator 22 to the valve sleeve 12. The
transmission part 30 comprises an adjusting lever 31 extending
transversally to the direction of displacement of the valve sleeve
12. The adjusting lever 31 is coupled both to the actuator 22 of
the servomotor 21 and to the valve sleeve 12. The adjusting lever
31 is a rocking lever. At a first end thereof, the adjusting lever
31 comprises a drive bearing 39, coupled to the actuator 22 of the
servomotor 21 so as to be articulated and slidable. At the opposite
second end thereof the adjusting lever 31, in a locating bearing
32, comprises spring elements (not shown). Thereby, the second end
of the adjusting lever 31 is coupled to the valve housing 11 so as
to be articulated. In a middle region of the adjusting lever
between the two opposite ends thereof, the adjusting lever 31 is
coupled to the valve sleeve 12 via an actuator bearing 38, so as to
be articulated thereto.
[0034] When opening and closing the coaxial valve, the adjusting
lever 31, as a result of the linear movement of the actuator 22 of
the servomotor 21, carries out a swivel motion around the locating
bearing 32 between two extreme positions which are both shown in
FIG. 1. One of the positions (shown in dash-dotted lines)
corresponds to the completely open state of the coaxial valve while
the other position (shown in solid lines for parts visible in the
sectional view and dashed lines for hidden parts) of the valve
sleeve 12 shown in FIG. 1 corresponds to the completely closed
position. FIG. 2 shows the open position of the valve.
[0035] The drive bearing 39 establishing the connection to the
actuator 22 of the servomotor 21 comprises a bearing ball 36
provided on the first end of the adjusting lever 31 and a bearing
socket 26 provided on the actuator 22 of the servomotor 21. The
locating bearing 32 establishing the connection to the valve
housing 11 comprises a bearing ball 33 provided on the opposite
second end of the adjusting lever 31 and a bearing socket 34
provided in the valve housing 11.
[0036] In the embodiment shown in FIG. 1, the actuator bearing 38
establishing the connection of the middle section of the adjusting
lever 31 with the valve sleeve 12, comprises an actuator cog or
journal pin 18a provided on the exterior of the valve sleeve 12,
and a bearing bore 38a provided in the adjusting lever 31 and
accommodating the actuator cog 18a. In the region of the actuator
bearing 38, the adjusting lever 31 is shaped so as to surround the
valve sleeve 12. Namely, two arms or legs of the lever 31 form a
yoke around the sleeve 12. Respective bearing bores 38a are
provided in the two arms or legs of the adjusting lever 31 on both
sides of the valve sleeve 12, with one actuator cog or journal pin
18a located on each side of the valve sleeve 12 and respectively
received in the bearing bore 38a in the lever arm on that side of
the sleeve.
[0037] In the embodiment shown in FIG. 2, the actuator bearing 38
connecting the middle region of the adjusting lever 31 with the
valve sleeve 12 comprises a ball surface 18b provided on the
exterior of the valve sleeve 12 (e.g. directly integrally formed on
the exterior of the valve sleeve 12 or non-integrally affixed
thereon), and a socket surface 38b formed on the adjusting lever 31
and accommodating the ball surface 18b therein. The adjusting lever
31 is again formed in the region of the actuator bearing 38 in a
way so as to surround the valve sleeve 12, with the socket surface
38b accommodating the ball surface 18b provided on the exterior of
the valve sleeve 12, in the region of the adjusting lever 31
surrounding the valve sleeve 12.
[0038] The present coaxial valve is advantageous in particular for
shutting off gaseous or liquid flow media at temperatures from 20 K
to 350 K and at pressures up to 290 bar, and is particularly
advantageous for shutting off liquid or gaseous flow media for
propulsion of aircraft and spacecraft, i.e. flying craft.
[0039] Although the invention has been described with reference to
specific example embodiments, it will be appreciated that it is
intended to cover all modifications and equivalents within the
scope of the appended claims. It should also be understood that the
present disclosure includes all possible combinations of any
individual features recited in any of the appended claims.
* * * * *