U.S. patent application number 11/269999 was filed with the patent office on 2007-05-10 for thermal management system for high energy laser.
Invention is credited to Jan Vetrovec.
Application Number | 20070104233 11/269999 |
Document ID | / |
Family ID | 37545975 |
Filed Date | 2007-05-10 |
United States Patent
Application |
20070104233 |
Kind Code |
A1 |
Vetrovec; Jan |
May 10, 2007 |
Thermal management system for high energy laser
Abstract
A method and system are disclosed for cooling a laser, such as a
high average power (HAP) solid state laser (SSL). A coolant that
has been heated from previous use can be conditioned by
transferring heat from the coolant to a phase change medium. The
conditioned coolant can then be re-used to cool the laser. In this
manner, a low cost, lightweight, compact cooling system that
generates comparatively quiescent flow at comparatively high flow
rates can be provided.
Inventors: |
Vetrovec; Jan; (Larkspur,
CO) |
Correspondence
Address: |
MACPHERSON KWOK CHEN & HEID, LLP
2033 GATEWAY PLACE
SUITE 400
SAN JOSE
CA
95110
US
|
Family ID: |
37545975 |
Appl. No.: |
11/269999 |
Filed: |
November 9, 2005 |
Current U.S.
Class: |
372/35 ;
257/E23.089 |
Current CPC
Class: |
H01L 2924/0002 20130101;
H01S 3/0407 20130101; H01S 3/042 20130101; H01L 23/4275 20130101;
H01L 2924/0002 20130101; H01L 2924/00 20130101 |
Class at
Publication: |
372/035 |
International
Class: |
H01S 3/04 20060101
H01S003/04 |
Claims
1. A method for cooling a solid state laser, the method comprising:
cooling the solid state laser with a liquid; and using down time
between laser shots to move coolant through a phase change medium
heat exchanger with a blow down system so as to prepare the coolant
for a subsequent round of laser cooling.
2. The method of claim 1, wherein the coolant is stored in a first
tank prior to cooling the laser and is stored in a second tank
subsequent to cooling the laser.
3. The method of claim 1, wherein the coolant is stored in a first
tank prior to cooling the laser, the coolant is communicated to a
second tank subsequent to cooling the laser, the coolant is cooled
by transferring heat therefrom to a phase change medium after being
stored in the second tank, and the coolant is communicated back to
the first tank after being cooled.
4. The method of claim 1, wherein the coolant is stored in a first
tank, the coolant is cooled by transferring heat therefrom to a
phase change medium prior to cooling the laser, the coolant is
communicated to a second tank after cooling the laser, and the
coolant is communicated back to the first tank after being
communicated to the second tank.
5. The method of claim 1, further comprising transferring heat from
a phase change medium of the phase change medium heat
exchanger.
6. The method of claim 1, further comprising transferring heat from
a phase change medium of the phase change medium heat exchanger via
a refrigerator.
7. The method of claim 1, further comprising using pressurized gas
to urge coolant from at least one of a first tank and a second
tank.
8. The method of claim 1, further comprising using pressurized gas
to urge coolant from at least one of a first and a second tank and
preventing mixing of the coolant and the pressurized gas.
9. The method of claim 1, further comprising using pressurized gas
to urge coolant from at least one of a first tank and a second tank
and preventing mixing of the coolant and the pressurized gas via at
least one device selected from the group consisting of a diaphragm
and a bladder.
10. The method of claim 1, further comprising inhibiting sloshing
of the coolant in a tank.
11. The method of claim 1, wherein a phase change medium of the
phase change medium heat exchanger comprises at least one substance
selected from the group consisting of paraffin wax and Glauber
salt.
12. A system for cooling a solid state laser, the system
comprising: a phase change medium heat exchanger to which heat can
be transferred from a coolant after the coolant has cooled the
solid state laser; and a blow down system for moving the coolant
between the solid state laser and the phase change medium heat
exchanger.
13. The system as recited in claim 12, wherein the blow down system
comprises: a first coolant tank within which the coolant is stored
prior to cooling the laser; and a second coolant tank within which
the coolant is stored subsequent to cooling the laser.
14. The system of claim 12, further comprising a refrigerator for
removing heat from a phase change medium of the phase change medium
heat exchanger.
15. The system of claim 13, wherein the blow down system further
comprises a pressure source for pressurizing the first coolant tank
and the second coolant tank, the pressure source being selected
from the group consisting of a gas bottle, a gas tank, and a
compressor.
16. The system of claim 13, further comprising: a first diaphragm
for separating coolant from pressurized gas in the first coolant
tank; and a second diaphragm for separating coolant from
pressurized gas in the second coolant tank.
17. The system of claim 13, further comprising: a first bladder for
separating coolant from pressurized gas in the first coolant tank;
and a second bladder for separating coolant from pressurized gas in
the second coolant tank.
18. A system for cooling a solid state laser, the system
comprising: means for conditioning a coolant by transferring heat
from the coolant to a phase change medium; means for cooling the
laser with the conditioned coolant; and means for using pressurized
gas to move the coolant between the solid state laser and the phase
change medium.
19. A solid state laser system comprising: a solid state laser; and
a system for cooling the laser, the system comprising a phase
change medium to which heat can be transferred from a coolant after
the coolant has cooled the laser and a blow down system for moving
the coolant between the solid state laser and the phase change
medium.
20. The system as recited in claim 19, wherein the laser comprises
a high average power (HAP) solid state laser (SSL).
Description
TECHNICAL FIELD
[0001] The present invention relates generally to thermodynamics
and, more particularly, to a heat management system, such as for a
high energy solid state laser.
BACKGROUND
[0002] High average power (HAP) solid state laser (SSL) systems are
known. They are becoming increasingly important in both defense and
commercial applications. Much of the recent growth in the
popularity of SSL systems can be attributed to the introduction of
pumping by laser diodes.
[0003] As those skilled in the art will appreciate, diodes are
inherently very efficient in converting electric energy into pump
light. Thus, diodes deposit only a comparatively small amount of
waste heat into the solid state medium. Advantages of diode pumped
SSL systems with respect to gas lasers include all electric
operation, short wavelength, compatibility of optical fibers,
continuous duty, high efficiency, and the prospect of engineering a
high power device having a comparatively small and lightweight
package.
[0004] Emerging military and industrial applications for HAP SLL
systems required the integration of laser systems on mobile
platforms such as trucks, ships, and aircraft. More particularly,
there is a strong need for 100 kW class HAP SSL systems for use in
air defense and precision strike. Air defense applications for HAP
SSL include defense against tactical and strategic missiles. HAP
SSL systems are also used worldwide in industrial applications,
such as in cutting and welding tools for use in the automotive,
aerospace, appliance, and shipbuilding industries.
[0005] Solid-state lasers utilize electrical pumping, such as by
the use of highly efficient semiconductor diodes. Despite the use
of such electrical pumping, the operation of SSL systems still
produces a significant amount of waste heat that must be rejected.
Typically, for each joule of laser energy produced, three to four
joules of heat must be removed from a SSL system and then rejected
to the environment.
[0006] Rejecting waste heat from a SSL system into an environment
that is at the same or higher temperature with respect to the SSL
system inherently necessitates the use of refrigeration in order to
pump the heat from laser components into the environment. A variety
of cooling systems of this type are commercially available and
currently used in many applications. Indeed, closed loop cooling
systems are commonly used with contemporary SSL systems. However,
such closed loop cooling systems tend to be undesirably bulky and
heavy in comparison to the SSL system that they support.
[0007] The size and weight of the refrigeration system is not of
particular concern in fixed laser installations, e.g., factory
installations. However, such closed loop refrigeration systems are
entirely unsuitable for use in large, e.g., multi kW, SSL systems
that are installed upon mobile platforms where size and weight are
paramount.
[0008] Furthermore, producing the very high flow rates (hundreds of
gallons per minute) required to support high energy SSL lasing
requires the use of very large pumps that are typically
electrically operated. These pumps can require 20%-30% of the SSL
system's electric power budget.
[0009] Furthermore, such pumps generate substantial flow vibrations
that can have a wide band spectrum. The wide band spectrum tends to
find resonances in coolant lines and structures. These resonances
tend to undesirably perturb the alignment of laser components.
[0010] Thus, contemporary cooling systems for high average power
solid state laser systems suffer from inherent disadvantages that
tend to detract from their overall desirability and effectiveness.
For example, contemporary cooling systems tend to be undesirably
bulky, heavy, and costly. They also tend to generate excessive flow
vibration, particularly at the high flow rates that are required to
provide effective cooling.
[0011] In view of the foregoing, it is desirable to provide a
lightweight, compact, low cost thermal management system for a high
energy solid state laser (SSHEL) weapon. It is further desirable to
provide such a thermal management system that has very quiescent
flow of coolant at the flow rates required for effective cooling.
Such a thermal management system would facilitate the construction
of more powerful and more economical high average power solid state
laser systems.
SUMMARY
[0012] Systems and methods are disclosed herein to provide for the
cooling of a laser, such as a high average power (HAP) solid state
laser (SSL). Such lasers are suitable for use in high power
military and industrial applications. According to one embodiment
of the present invention, the down time between laser shots can be
used to condition coolant so that the coolant is prepared for next
round of laser cooling. According to another embodiment of the
present invention, the coolant is conditioned in real time, i.e.,
immediately prior to and/or during use thereof for laser
cooling.
[0013] More particularly, the laser can be cooled using a liquid
coolant. Heat absorbed from the laser by the coolant is
subsequently, e.g., between laser firings and/or immediately prior
to reuse, transferred from the coolant to a phase change medium. In
this manner, the coolant is conditioned for use in the next round
of laser firing and cooling. That is, the conditioned coolant is at
a temperature such that it is ready to once again cool the
laser.
[0014] The coolant can be stored in a first tank prior to cooling
the laser and can be stored in a second tank subsequent to cooling
the laser. Thus, the coolant can flow from the first tank, to the
laser (where it cools the laser), and then to the second tank.
[0015] For example, the coolant can be stored in the first tank
prior to cooling the laser. This is coolant that is at a
temperature suitable for cooling the laser, and thus may have
already been cooled (as would be necessary if it had recently been
used to cool the laser). After cooling the laser, the coolant can
be communicated to the second tank. Then, the coolant can be cooled
by transferring heat therefrom to a phase change medium. Then, the
coolant can be communicated back to the first tank after being
cooled.
[0016] As a further example, the coolant can be stored in a first
tank. This can be coolant that has recently been used to cool the
laser and that has not yet been cooled. The coolant can be cooled
by transferring heat therefrom to a phase change medium prior to
using the coolant to cool the laser. After cooling the laser, the
coolant is communicated to a second tank. In this instance, the
coolant can be communicated back to the first tank after being
communicated to the second tank and is not cooled by communicating
heat therefrom to the phase change medium until after it leaves the
first tank on its way once again to the laser.
[0017] Heat can be transferred from the phase change medium, such
as via the use of a refrigerator. That is, a refrigerator can be
used to cool the coolant after the coolant has cooled the laser.
The phase change medium can comprises paraffin wax, Glauber salt,
or any other suitable substance. Advantage is taken of the phase
change medium's ability to absorb a large amount of heat during its
phase change. For example, paraffin wax absorbs a large amount of
heat as it melts from a solid state to a liquid state.
[0018] Pressurized gas can be used to cause the coolant to flow
between the first tank, the second tank, the laser, and the phase
change medium. Undesirable mixing of the coolant and the
pressurized gas can be prevented via the use of a diaphragm, a
bladder, or the like. The diaphragm, bladder or other structure can
also inhibit sloshing of the coolant and the pressurized gas.
[0019] The scope of the invention is defined by the claims, which
are incorporated into this section by reference. A more complete
understanding of embodiments of the present invention will be
afforded to those skilled in the art, as well as a realization of
additional advantages thereof, by a consideration of the following
detailed description of one or more embodiments. Reference will be
made to the appended sheets of drawings that will first be
described briefly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 shows a block diagram illustrating a system for
cooling a solid state laser in accordance with contemporary
practice;
[0021] FIG. 2 shows a block diagram illustrating a system for
cooling a solid state laser in accordance with an exemplary
embodiment of the present invention;
[0022] FIG. 3 shows a block diagram illustrating a system for
cooling a solid state laser in accordance with another exemplary
embodiment of the present invention;
[0023] FIGS. 4 and 5 show block diagrams illustrating a system for
cooling a solid state laser in accordance with yet another
exemplary embodiment of the present invention; and
[0024] FIG. 6 shows a block diagram illustrating the use of a
refrigerator to remove heat from the phase change medium of the
phase change medium heat exchanger of FIGS. 2-5.
[0025] Embodiments of the present invention and their advantages
are best understood by referring to the detailed description that
follows. It should be appreciated that like reference numerals are
used to identify like elements illustrated in one or more of the
figures.
DETAILED DESCRIPTION
[0026] At least one embodiment of the present invention provides a
simple, rugged, efficient, inexpensive, compact, and lightweight
thermal management system for a laser, such as a laser of a high
average power (HAP) solid state laser (SSL) system. Thus, one or
more embodiments of the present invention are suitable for use on
mobile platforms such as trucks, trains, ships, aircraft, missiles,
satellites, and spacecraft.
[0027] According to one aspect, the present invention takes
advantage of the fact that unlike industrial SSL's which operate
continuously, a HAP SSL fires discrete shots. In particular, HAP
SSL shots are typically 5 to 10 seconds long and they are separated
by 10 or more seconds of down time.
[0028] According to one embodiment, the present invention uses the
down-time between shots to condition the coolant and prepare it for
another round of cooling. The subject invention can use two
pressurized coolant tanks together with transfer lines and control
valves to move a coolant from one tank to another with the HAP SSL
therebetween.
[0029] The coolant can be water, such as deionized water. The
coolant can also be a fluid that is resistant to freezing, such as
ethylene glycol or a mixture of water and alcohol. The coolant can
also be any desired combination of water and a freeze resistant
substance. Indeed, as those skilled in the art will appreciate, the
coolant can be a wide variety of substances or combinations of
substances.
[0030] The motive force for transferring the coolant can be
provided by pressure differential between the two tanks. The
pressure differential can be high enough to overcome HAP SSL flow
impedances. The pressure can generated by a gas provided by a
compressor or at least one pressurized gas bottle. Optionally, the
tanks can have diaphragms or bladders to prevent mixing of the
pressurized gas and the liquid coolant and/or to mitigate sloshing
of the liquid coolant when the HAP SSL platform executes maneuvers.
Preventing the gas and the liquid from mixing can be critical to
preventing the gas from coming out of the solution inside cooled
components, e.g., after a pressure drop, and for providing a
consistent cooling action.
[0031] The pressurized gas can comprise nitrogen, helium, carbon
dioxide or air. As those skilled in the art will appreciate, the
pressurized gas can comprise a wide variety of different gases or
combinations of gases.
[0032] To maintain temperature of the coolant at a constant level,
the thermal management system of the present invention utilizes a
phase change medium (PCM) heat exchanger (HEX). Thus, the waste
heat of the HAP SSL is deposited into the phase change medium of
the heat exchanger, where it melts at least a portion of a phase
change medium. Multiple shots of the laser may be required to melt
the entire phase change medium. One example of a suitable phase
change medium heat exchanger is disclosed by Delgado et al. in U.S.
patent publication 20040141539, Ser. No. 731,311, published on Jul.
22, 2004 and entitle Phase-Change Heat Exchanger, the entire
contents of which are expressly incorporated herein by reference.
There are also suitable phase change materials that are available
commercially.
[0033] The phase change medium can comprises paraffin wax, Glauber
salt, or any other suitable substance. Those skilled in the art
will appreciate that various different phase change mediums are
suitable.
[0034] The phase change medium heat exchanger can be further
connected to a refrigerator. Such connection can be accomplished
via a thermally conductive member of a separate cooling loop. The
refrigerator can extract heat from the phase change medium heat
exchanger and thereby restore the phase change medium back to its
solid state. Although the process of restoring the phase change
medium back to its solid state may take a comparatively long time
(as compared to the process of melting the phase change medium), in
many instances it can be done fast enough to condition the phase
change medium for the next shot of the HAP SSL. In any event, the
coolant will be quickly conditioned for the next use of the HAP
SSL. Thus, the time required for reconditioning of the phase change
medium will not inhibit immediate reuse of the HAP SSL.
[0035] It is worthwhile to note that while HAP SSL operation
consists of several (such as about 10-20) shots lasting about 5-10
seconds each, the phase change medium can be conditioned for an
extended period of time (such as about an hour). During this
recovery period, the phase change medium heat exchanger batteries
can be recharged.
[0036] Complete reconditioning of the phase change medium can make
it ready to be used for a plurality of shots of the HAP SSL.
Optionally, the phase change medium can be used for one or more
shots of the HAP SSL after partial reconditioning (before it is
completely re-solidified).
[0037] Since the recovery period can be a comparatively long time,
the refrigerator used to condition the phase change medium can be a
relatively small unit. Thus, the large, heavy, and costly
refrigerator required for the cooling of contemporary HAP SSL's is
not necessary. Further, the undesirable flow vibration and
consequent misalignment of critical components of the HAP SSL are
substantially mitigated because the smaller refrigerator inherently
has smaller flow rates (and thus less vibration) associated
therewith.
[0038] FIG. 1 shows a contemporary HAP SSL system wherein SSL
system 10 creates a heat load 11. A heat exchanger 12 of a thermal
management system 13 extracts heat from heat load 11. Fluid that is
pumped through heat exchanger 12 by pump 14 is communicated to
refrigerator 16, which removes heat from the fluid and thereby
conditions the fluid for reuse.
[0039] This brute force system requires the use of a comparatively
large refrigerator 16, since refrigerator 16 is directly
responsible for immediately effecting cooling of SSL system 10. By
way of contrast, the present invention can use a substantially
smaller refrigerator, with the consequent advantages discussed
herein, because the refrigerator is not directly responsible for
immediately effecting cooling of the SSL system.
[0040] FIG. 2 shows a first embodiment of the thermal management
system of the present invention. According to the first embodiment,
the thermal management system comprises a delivery or first tank
21, a receiving or second tank 22, and a phase change medium heat
exchanger 25. Coolant can be caused to flow from first tank 21,
through a HAP SSL 23 (also known as a solid state high energy laser
or SSHEL) and then into second tank 22. As the coolant flows
through HAP SSL 23, it effects cooling thereof.
[0041] Heated coolant that has flowed into second tank 22 can then
be conditioned for reuse and transferred back into first tank 21.
The heated coolant is conditioned for reuse by causing it to flow
through phase change medium heat exchanger 25. In phase change
medium heat exchanger 25, the heated coolant melts a phase change
medium 62 (FIG. 6), thereby extracting heat from the coolant and
thus substantially reducing the coolant's temperature. After
passing through phase change medium heat exchanger 25, the coolant
is thus conditioned for reuse and is stored once again in first
tank 21. This process can repeat as desired.
[0042] Pressurized gas, such as nitrogen at approximately 150 psig,
can be used to effect movement of coolant between first tank 21 and
second tank 22 (and consequently through HAP SSL 23 and phase
change medium heat exchanger 25). Check valve 26 facilitates the
flow of pressurized gas into first tank 21 and second tank 22,
while inhibiting the undesirable flow of pressurized gas therefrom
(such as may otherwise occur if the gas source shut down, was
depleted, and/or developed a leak). Pressure regulators 27 and 28
maintain a desired pressure of the gas within first tank 21 and
second tank 22, respectively.
[0043] Flow control valves 31-34 can be configured to control the
flow of fluid from first tank 21 to second tank 22 and vice-versa.
For example, with the pressure of pressurized gas greater in first
tank 21 than in second tank 22, with flow control valves 31 and 34
closed, and with flow control valves 32 and 33 open, fluid will
flow from first tank 21 through HAP SSL 23 to second tank 22.
Similarly, with the pressure of pressurized gas less in first tank
21 than in second tank 22, with flow control valves 31 and 34 open,
and with flow control valves 32 and 33 closed, fluid will flow from
second tank 22 through phase change medium heat exchanger 25 to
first tank 21.
[0044] Thus, during HAP SSL lasing the coolant can be provided by
first tank 21 (which is operating at a comparatively higher
pressure) to HAP SSL 23 and subsequently collected by second tank
22 (which is operating at a comparatively lower pressure). During
the non-lasing time the pressure of first tank 21 can be reduced
and the pressure of second tank 22 can be increased. Valves 31-34
are then configured such that the coolant is transferred back to
first tank 21 through phase change medium heat exchanger 25 (where
the temperature of the coolant is substantially reduced, such as
approximately back to its original temperature).
[0045] This type of fluid transport system (where a pressurized
fluid is used to move another fluid, such as from one tank to
another, can define a blow down system.
[0046] FIG. 3 shows a second embodiment of the temperature
management system of the present invention. According to the second
embodiment, the thermal management system is similar to the first
embodiment thereof, except that the phase change medium heat
exchanger 25 is configured such that coolant flows therethrough as
the coolant flows from first tank 21 to second tank 22 (instead of
as the coolant flows from second tank 22 to first tank 21, as in
the first embodiment of the present invention). That is, phase
change medium heat exchanger 25 is placed upstream of HAP SSL 23 so
that coolant provided by first tank 21 is conditioned immediately
prior to delivery to HAP SSL 23. During the non-lasing time coolant
can be transferred from second tank 22 back to first tank 21.
[0047] FIGS. 4 and 5 show a third preferred embodiment of the
present invention, wherein either of the two tanks can operate as a
delivery tank while the other tank operates as a receiving tank.
Thus, their functions can be reversed for each coolant flow cycle.
In each instance, valves 31-34 are configured such that phase
change medium heat exchanger 25 is always upstream with respect to
HAP SSL 23, i.e., so that coolant provided by the higher pressure
tank is conditioned prior to delivery to HAP SSL 23. According to
this embodiment of the present invention, it is not necessary to
transfer the coolant during the non-lasing time.
[0048] For example, with the coolant initially in first tank 21,
the coolant can be caused to flow through phase change medium heat
exchanger 25 and HAP SSL 23, as shown in FIG. 4, by opening valves
31 and 33 while keeping valves 32 and 34 shut. The coolant is then
received by second tank 22.
[0049] According to this embodiment of the present invention, there
is no need to transfer the coolant back to the first tank 21 prior
to using the coolant to cool HAP SSL 23 again. Thus, for the next
use of HAP SSL 23, coolant from second tank 22 can be caused to
flow through phase change medium heat exchanger and HAP SSL 23, as
shown in FIG. 5, by opening values 32 and 34 while keeping values
31 and 33 shut. The coolant is then received by first tank 21.
[0050] FIG. 6 shows the use of a refrigerator 61 to condition phase
change medium 62 of phase change medium heat exchanger 25. That is,
refrigerator 61 re-solidifies phase change medium 62 after phase
change medium 62 has melted while conditioning the coolant. In this
manner, phase change medium 62 can be made ready for another
fire/cooling cycle of HAP SSL 23.
[0051] Refrigerator 61 can be substantially smaller than the
refrigerator (such as refrigerator 16 of FIG. 1) used in
contemporary HAP SSL systems, since refrigerator 61 does not
directly and immediately cool HAP SSL 23. Rather, refrigerator 61
can take a comparatively longer time (such as an hour or more) to
re-solidify phase change medium 62 and thereby condition phase
change medium 62 for another use.
[0052] Operation of valves 31-34 for any embodiment of the present
invention can be performed by remote control and/or can be
automatic. Automatic control can be provided by a computer or other
processor. A single valve assembly can incorporate all of valves
31-34, such as to simplify operation (by requiring that only a
single action be performed to change the state of all valves
31-34). Pressure regulators 27 and 28 can be remotely operated by
pneumatic, hydraulic, and/or electric means and can be under
computer control.
[0053] One or more embodiments of the present invention make it
possible to manufacture more powerful and yet more economical HAP
SSL systems. Thus, the present invention is expected to enable new
applications such as rock drilling for oil and gas exploration.
[0054] Although described herein as being used with a solid state
laser, those skilled in the art will appreciate that the thermal
management system of the present invention is suitable for use with
other types of lasers, as well as other types of directed energy
devices. Thus, use of the thermal management system of the present
invention with a solid state laser is by way of example only, and
not by way of limitation.
[0055] In view of the foregoing, at least one embodiment of the
present invention provides a lightweight, compact, low cost thermal
management system for a high energy solid state laser (HAP SSL)
weapon. Because of its size and weight, the thermal management
system facilitates the use of HAP SSL systems on mobile platforms.
At least one embodiment of the present invention further provides a
thermal management system that has very quiescent flow of coolant
at the flow rates required for effective cooling. At least one
embodiment of the present invention has no moving parts other than
the valves and refrigerator, and is thus comparatively easy to
use.
[0056] Embodiments described above illustrate but do not limit the
invention. It should also be understood that numerous modifications
and variations are possible in accordance with the principles of
the present invention. Accordingly, the scope of the invention is
defined only by the following claims.
* * * * *