U.S. patent application number 14/091896 was filed with the patent office on 2014-12-04 for gas laser having a heat exchanger.
This patent application is currently assigned to TRUMPF Laser-und Systemtechnik GmbH. The applicant listed for this patent is TRUMPF Laser-und Systemtechnik GmbH. Invention is credited to Matthias Breisacher, Mark Geschwandner.
Application Number | 20140355633 14/091896 |
Document ID | / |
Family ID | 46201610 |
Filed Date | 2014-12-04 |
United States Patent
Application |
20140355633 |
Kind Code |
A9 |
Geschwandner; Mark ; et
al. |
December 4, 2014 |
Gas Laser Having A Heat Exchanger
Abstract
A gas laser includes a fan for producing a flow of a laser gas
and a heat exchanger including multiple heat exchanger pipes. The
heat exchanger further includes two end plates to which the
multiple heat exchanger pipes are secured at the opposing ends
thereof. The two end plates include openings for supplying a heat
exchanger fluid to the multiple heat exchanger pipes. The multiple
heat exchanger pipes extend substantially transversely relative to
a flow direction of the flow of laser gas.
Inventors: |
Geschwandner; Mark;
(Korntal-Muenchingen, DE) ; Breisacher; Matthias;
(Ditzingen, DE) |
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Applicant: |
Name |
City |
State |
Country |
Type |
TRUMPF Laser-und Systemtechnik GmbH |
Ditzingen |
|
DE |
|
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Assignee: |
TRUMPF Laser-und Systemtechnik
GmbH
Ditzingen
DE
|
Prior
Publication: |
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Document Identifier |
Publication Date |
|
US 20140092928 A1 |
April 3, 2014 |
|
|
Family ID: |
46201610 |
Appl. No.: |
14/091896 |
Filed: |
November 27, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP2012/060027 |
May 29, 2012 |
|
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14091896 |
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Current U.S.
Class: |
372/34 |
Current CPC
Class: |
F28F 2280/02 20130101;
F28F 2220/00 20130101; F28F 19/06 20130101; F28F 1/24 20130101;
H01S 3/041 20130101; H01S 3/0971 20130101; H01S 3/0835 20130101;
F28F 21/083 20130101; H01S 3/036 20130101; H01S 3/2232 20130101;
F28F 21/084 20130101; F28D 7/1623 20130101 |
Class at
Publication: |
372/34 |
International
Class: |
H01S 3/041 20060101
H01S003/041 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 1, 2011 |
DE |
102011076871.8 |
Claims
1-14. (canceled)
15. A gas laser, comprising: a fan for producing a flow of laser
gas; and a heat exchanger including a plurality of heat exchanger
pipes and two end plates to which the plurality of heat exchanger
pipes are secured at opposing ends thereof, wherein the two end
plates include openings for supplying a heat exchanger fluid to the
plurality of heat exchanger pipes, and wherein the plurality of
heat exchanger pipes extends substantially transversely relative to
a flow direction of the flow of laser gas.
16. The gas laser according to claim 15, wherein the two end plates
further include channels for fluidly connecting at least two
openings that are associated with different heat exchanger pipes of
the plurality of heat exchanger pipes.
17. The gas laser according to claim 16, wherein at least one
channel is configured to connect two heat exchanger pipes of the
plurality of heat exchanger pipes.
18. The gas laser according to claim 16, wherein the two end plates
include covers for closing the channels in a fluid-tight
manner.
19. The gas laser according to claim 15, wherein the heat exchanger
pipes of the plurality of heat exchanger pipes are orientated
parallel to each other.
20. The gas laser according to claim 15, wherein heat exchanger
pipes of the plurality of heat exchanger pipes are positioned in a
matrix-like arrangement.
21. The gas laser according to claim 20, wherein the heat exchanger
pipes of adjacent rows of the matrix-like arrangement are arranged
offset relative to each other.
22. The gas laser according to claim 15, wherein each heat
exchanger pipe of the plurality of heat exchanger pipes includes an
inner pipe and a plurality of cooling ribs.
23. The gas laser according to claim 22, wherein the inner pipe and
the plurality of cooling ribs are produced from different
materials.
24. The gas laser according to claim 23, wherein the different
materials comprise metals.
25. The gas laser according to claim 24, wherein the cooling ribs
are made of aluminum.
26. The gas laser according to claim 24, wherein the inner pipe is
made of stainless steel.
27. The gas laser according to claim 15, further comprising at
least two connection pieces for supplying and discharging a heat
exchanger fluid.
28. The gas laser according to claim 15, further comprising a
housing defining an opening for receiving the heat exchanger.
29. The gas laser according to claim 28, wherein the opening is
formed as a through-opening.
30. The gas laser according to claim 28, wherein one of the two end
plates protrudes beyond the opening of the housing along a side
edge of the housing.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of and claims priority
under 35 U.S.C. .sctn.120 to PCT Application No. PCT/EP2012/060027
filed on May 29, 2012, which claims priority to German Application
No. 10 2011 076 817.8, filed on Jun. 1, 2011. The contents of both
of these priority applications are hereby incorporated by reference
in their entirety.
TECHNICAL FIELD
[0002] The present disclosure relates to gas lasers that include
fans for producing gas flows and heat exchangers including multiple
heat exchanger pipes.
BACKGROUND
[0003] A heat exchanger can be included in a gas laser to cool gas
that forms a gain medium of the gas laser. Such a heat exchanger
may include multiple heat exchanger pipes which have cooling ribs
which are produced by rolling of a heat radiation pipe, into which
an inner pipe is introduced. A large number of such heat exchanger
pipes can be connected to each other to form a heat exchanger which
serves to cool a laser gas. Some gas lasers have heat exchangers
which have a helical cooling coil and which are arranged in a
discharge housing or a supply housing in order to discharge or
supply the laser gas to a radial fan. However, the efficiency
(e.g., quantified as a cooling power per cm.sup.3) of helical
cooling coils is comparatively low. Use of such cooling coils may
also lead to undesirable fluctuations or pressure jumps of the
laser gas to be cooled.
SUMMARY
[0004] The present disclosure relates togas lasers including heat
exchangers that have a compact structural form and that exhibit
efficient heat exchange.
[0005] In some embodiments of a gas laser, a heat exchanger has two
end plates to which the heat exchanger pipes are secured with the
opposing ends thereof (in a fluid tight manner). In the end plates
are formed openings for supplying a heat exchanger fluid to the
heat exchanger pipes.
[0006] Owing to the fixing of the heat exchanger pipes to the two
end plates, the heat exchanger may be produced in a compact
structural form, with the end plates ensuring a high level of
stability. The distribution or the supply of the heat exchanger
pipes with a heat exchanger fluid (in the applications involved
here, generally water) can be carried out via the openings formed
in the end plates. Such a cartridge-like heat exchanger can be
fitted in a corresponding housing of the gas laser in a simple
manner and also be exchanged if modifications have to be carried
out on the heat exchanger. The end plates may be produced from
metal (for example, from stainless steel).
[0007] The heat exchanger is orientated with respect to the flow
direction of the gas flow of the laser gas in such a manner that
the heat exchanger pipes extend substantially transversely relative
to the flow direction of the gas flow. The fan may be a radial fan
which is arranged at a central location and from which multiple
supply pipes and discharge pipes extend into the region of the
laser resonator, which is typically folded in a square manner.
[0008] In an embodiment, there are formed in the end plates
channels for connecting at least two openings, which are associated
with different heat exchanger pipes. Multiple heat exchanger pipes
can be connected to each other by the channels in the end plates
and, in this manner, the distribution of the heat exchanger fluid
can be directed in an appropriate manner. The flow path of the heat
exchanger fluid may be selected in such a manner that only a single
supply and a single discharge for the heat exchanger fluid may be
provided in the heat exchanger. Alternatively, it is also possible
to carry out the distribution of the heat exchanger fluid in such a
manner that multiple separate heat exchanger circuits are arranged
in the heat exchanger by multiple groups of heat exchanger pipes
which are separated in a fluid-tight manner, with each heat
exchanger circuit being provided with a separate supply and
discharge.
[0009] The channels may be formed by a method involving material
removal, for example, by means of milling, at the end plates which
may, for example, be constructed in an integral manner.
Alternatively, other (e.g., shaping) methods, for example,
so-called hydroforming, may also be used to form the channels.
Alternatively, it is also possible to use end plates which have
multiple layers which are arranged one on top of the other, with
the channels being formed as recesses in one or more of the layers.
The channels and the connection thereof to form the heat exchanger
pipes can be configured freely in terms of their arrangement and
consequently allow multi-stage operation, (that is to say, multiple
separate heat circuits which can also be operated at the same
time). In such embodiments, the heat of the laser gas to be
discharged is transferred to different water circuits which are
typically geometrically directly sequential (for example, a hot and
a cold water circuit). This modular structure provides a high level
of flexibility, which enables different variant constructions to be
produced within a short period of time in the event of changed
requirements or ambient conditions.
[0010] In some embodiments, there is formed at least one channel
for connecting precisely two (typically adjacent) heat exchanger
pipes. Owing to the use of such channels, a serial connection may
be produced between multiple heat exchanger pipes. In this manner,
the heat exchanger fluid in a first heat exchanger pipe flows from
the first end plate to the second end plate and, in a second heat
exchanger pipe which is connected to the first heat exchanger pipe
via the channel, flows from the second end plate back to the first
end plate.
[0011] In certain embodiments, the end plates have covers for
closing the channels in a fluid-tight manner. If the end plates and
the covers are formed from a metal material (for example, from
stainless steel), the fluid-tight closing of the channels can be
carried out, for example, by means of welding.
[0012] In some embodiments, the heat exchanger pipes are orientated
parallel to each other and typically extend substantially
perpendicularly to a (main) flow direction of the laser gas. In
this manner, the efficiency of the heat transmission between the
laser gas and the heat exchanger fluid can be increased.
[0013] In certain embodiments, the heat exchanger pipes are
positioned in a matrix-like arrangement (that is to say, in
multiple rows and columns). Owing to the regular arrangement,
pressure peaks and fluctuations of the laser gas can be kept low.
The number of rows of heat exchanger pipes which are used in the
heat exchanger is typically eight or more, and the number of heat
exchanger pipes in a row is generally approximately three or more.
Such an arrangement ensures, even with a comparatively low pressure
of the laser gas (for example, approximately 150 hPa), a
sufficiently large heat exchange.
[0014] In some embodiments, the heat exchanger pipes of adjacent
rows are arranged so as to be offset relative to each other. This
arrangement, in the event of a flow direction of the laser gas
extending substantially perpendicularly relative to the heat
exchanger pipes, may lead to the formation of a turbulent gas flow,
which significantly increases the efficiency of the heat
transmission, without the pressure losses of the laser gas becoming
too great. Such an arrangement consequently provides an optimal
compromise between the efficiency of the heat transmission and the
pressure losses of the laser gas. In particular, in such an
arrangement, a high heat exchange can be achieved even at a low
pressure of the laser gas (for example, approximately 150 hPa).
[0015] The heat exchanger pipes advantageously have an inner pipe
and multiple cooling ribs. The heat exchanger fluid is guided
through the inner pipe. The cooling ribs may be constructed on the
inner pipe, for example, by rolling (that is to say, the inner pipe
is surrounded by an outer pipe, on which the cooling ribs are
formed). During the rolling operation, there is pushed over the
inner pipe an outer pipe which is not yet provided with ribs. Owing
to cutting rollers which run into each other, the cooling ribs are
cut or formed from the smooth outer pipe. The very high shaping
forces during the rolling of the pipes ensure a very secure fit and
consequently very good heat transmission between the two
materials.
[0016] It is advantageous for the inner pipe and the cooling ribs
or the outer pipe to be produced from different materials (e.g.,
metal materials) when the heat exchanger pipe is a bimetal pipe.
For example, the inner pipe may be made of stainless steel in order
to prevent corrosion of the inner pipe by the heat exchanger fluid
which is guided therein. The cooling ribs or the outer pipe may in
contrast be made of another metal material (for example, from
aluminum,) that has a high level of thermal conductivity. Since the
material of the cooling ribs does not come into contact with the
heat exchanger fluid, it is not necessary for the cooling ribs to
have a high level of corrosion resistance.
[0017] In certain embodiments, the heat exchanger includes at least
two connection pieces or openings for supplying and discharging a
heat exchanger fluid. The modular heat exchanger allows all the
heat exchanger pipes to be used in a single heat exchanger circuit
or alternatively allows multiple groups of heat exchanger pipes to
be formed, which are each associated with different heat exchanger
circuits. For each of these circuits, there may be provided on the
heat exchanger, more specifically on the end plates, a separate
pair of connection pieces. Of course, the covers of the channels
may optionally be provided with a connection for supplying or
discharging the heat exchanger fluid in order to increase the
flexibility when the heat exchanger is used. Alternatively, the
supply or discharge at an end plate may also be directly connected
to the opening of a heat exchanger pipe.
[0018] In some embodiments, the gas laser additionally includes a
housing for receiving the heat exchanger. The housing may, for
example, be a supply housing or a discharge housing for the laser
gas to or from the laser resonator, respectively. The
cartridge-like heat exchanger may be pushed into such a housing,
which has a recess or an opening for this purpose. The opening may
be constructed in a continuous manner so that the end plates form
the side faces of the housing.
[0019] The cartridge-like heat exchanger received in the housing is
connected to the housing in a gas-tight manner, more specifically
in a vacuum-tight manner, in order to encapsulate the flow of the
laser gas. In particular, all the interfaces of the housing with
the heat exchanger received therein are intended to be constructed
in a helium-tight or vacuum-tight manner. For example, the sealing
at interfaces between the laser gas and the ambient air (for
example, between the cartridge-like heat exchanger insert and the
housing) should have a leakage rate of less than 1.times.10.sup.-8
mbar liter/sec., even with a comparatively low pressure of the
laser gas of (for example, approximately 150 hPa). The sealing at
interfaces between the laser gas and the cooling water at the heat
exchanger should also have a leakage rate of less than
1.times.10.sup.-12 mbar liter/sec. at high pressures of the cooling
fluid of up to 10 bar.
[0020] One of the end plates may protrude from the edge of the
housing beyond the opening in order to fix the heat exchanger which
is inserted into the housing to a peripheral housing edge (that is
to say, this end plate has a larger surface than the second end
plate which is inserted into the opening). The larger end plate is
fixed to the peripheral housing edge in a gas or vacuum-tight
manner and acts at the same time as a seal in order to produce a
compact structure. A vacuum-tight connection may, for example, be
ensured by screwing the end plate to the housing edge. In
particular, a peripheral seal may be fitted between the housing
edge and the end plate, with the peripheral seal preferably being
located further inwards than the securing locations during the
screwing operation. In particular, there may be provided at the
housing edge (or on the end plate) a peripheral recess for
receiving the seal (for example, in the form of an O ring). In
order to produce the sealing effect, the seal may be clamped
between the end plate and the housing edge during the screwing
operation. Alternatively, the end plates may be constructed in a
symmetrical manner (that is to say, the surfaces of the end plates
may be of the same size).
[0021] Other aspects, features, and advantages will be apparent
from the description, the claims, and the drawings. The
above-mentioned features and those set out below may also be used
individually or together in any combination. The embodiments shown
and described are not intended to be a conclusive listing but
instead are of an exemplary nature.
DESCRIPTION OF DRAWINGS
[0022] FIG. 1 is a cross-sectional top view of a CO.sub.2 gas laser
with a folded laser resonator.
[0023] FIG. 2 is a perspective view of the CO.sub.2 gas laser of
FIG. 1.
[0024] FIG. 3 is a perspective view of a heat exchanger cartridge
for the CO.sub.2 gas laser of FIG. 1 and FIG. 2.
[0025] FIG. 4 is a perspective view of the heat exchanger cartridge
of FIG. 3 and an associated housing.
[0026] FIG. 5 is a cross-sectional view of a heat exchanger pipe of
the heat exchanger cartridge of FIG. 3.
DETAILED DESCRIPTION
[0027] The CO.sub.2 gas laser 1 shown in FIG. 1 and FIG. 2 has a
laser resonator 2 which is folded in a square manner. The laser
resonator 2 has four mutually adjacent laser discharge pipes 3
which are connected to each other by corner housings 4, 5. A laser
beam 6 which extends in the direction of the axes of the laser
discharge pipes 3 is illustrated with dot-dash lines. Redirection
mirrors 7 in the corner housings 4 serve to redirect the laser beam
6 by 90.degree. in each case. A rear mirror 8 and a partially
transmissive output coupling mirror 9 are arranged in one of the
corner housings 5. The rear mirror 8 is constructed in a highly
reflective manner and reflects the laser beam 6 by 180.degree. so
that the laser beam passes through the laser discharge pipes 3
again in the opposing direction.
[0028] A portion of the laser beam 6 passes out of the laser
resonator 2 through the partially transmissive output coupling
mirror 9, and the other portion remains in the laser resonator 2
and passes through the laser discharge pipes 3 again. The portion
of the laser beam 6 passing out of the laser resonator 2 through
the output coupling mirror 9 is designated 10 in FIG. 1.
[0029] In the center of the folded laser resonator 2, there is
arranged as a pressure source for laser gas a radial fan 11 which
is connected to the corner housings 4, 5 by supply housings 12 for
laser gas. Centrally between the corner housings 4, 5 there are
arranged additional housings 14 of the laser resonator 2 which are
connected to discharge housings 13 which serve to discharge the
laser gas from the laser resonator 2 and return it to the radial
fan 11. The flow direction of the laser gas inside the laser
discharge pipes 3 and in the supply and discharge housings 12, 13
is indicated in FIG. 1 by arrows.
[0030] The excitation of the laser gas is carried out by electrodes
15 which are arranged adjacent to the laser discharge pipes 3 and
which are connected to a high frequency (HF) generator (not shown).
HF generators that may be used include, for example, a pipe
generator having an excitation frequency of 13.56 MHz or 27.12
MHz.
[0031] As shown in FIG. 2, there are introduced both in the supply
housings 12 and in the discharge housings 13 of the gas laser 1 a
cartridge-like heat exchanger 20 which is illustrated in detail in
FIG. 3. The heat exchanger 20 has multiple heat exchanger pipes
21a, 21b which are arranged between two rectangular end plates 22,
23 and which are welded at the opposing ends thereof to the end
plates 22, 23. In the end plates 22, 23 there are formed openings
24a, 24b which enable a heat exchanger fluid to be introduced into
the inner side of each heat exchanger pipe 21a, 21b (e.g., water
being used as the heat exchanger fluid in the present example).
[0032] FIG. 3 also shows cooling channels 25 which in the example
shown each connect two adjacent heat exchanger pipes 21a, 21b to
each other in order to enable a serial flow through of all the heat
exchanger pipes 21a, 21b of the heat exchanger. The channels 25 are
sealed by respective plate-like covers 26 in a fluid-tight manner
with respect to the environment. In the present example, the end
plates 22, 23 are formed of stainless steel (e.g., V4A steel,
1.4571) and the covers 26 are also produced from this material so
that the fluid-tight sealing of the channels 25 can be carried out
by welding. Only a small number of covers 26 are shown in FIG. 2
and FIG. 3. However, during operation of the heat exchanger 20, all
of the channels 25 are typically closed by covers 26.
[0033] In the example shown in FIG. 3, the cooling channels 25 are
milled as recesses in the end plates 22, 23, but the cooling
channels 25 may also be produced in a different manner (for
example, via hydroforming). It is also possible to construct the
end plates 22, 23, not integrally as shown in FIG. 3, but instead
in several layers, with the cooling channels 25 being constructed
as recesses in individual layers.
[0034] Owing to the cooling channels 25, the distribution of the
cooling medium (e.g., water) can be carried out inside the end
plates 22, 23 so that the heat exchanger 20 can be produced in a
compact construction. In the present example, a first connection
piece 27a (see FIG. 4) on the first end plate 22 serves to supply
water to the heat exchanger 20, and a second connection piece 27b
serves to discharge the water heated by the laser gas during the
heat exchange from the heat exchanger 20. The connection pieces
27a, 27b are each directly connected to a respective opening of a
heat exchanger pipe. However, the connection pieces 27a, 27b can
also be fitted in a cover 26 of the end plate 22, which is not
illustrated on the end plate 22 in FIG. 4 for simplicity. This last
arrangement is particularly advantageous when multiple rib pipes
(for example, entire rows of rib pipes) are intended to be supplied
with the cooling medium in parallel.
[0035] In the example shown in FIG. 3 and FIG. 4, the cooling
medium passes through all of the heat exchanger pipes 21a, 21b, one
after the other (in series) starting from the first connection
piece 27a. Alternatively, additional pairs of connection pieces may
also be provided on the heat exchanger 20 in order to form multiple
independent heat circuits (for example, a heating circuit and an
independent cooling circuit). To this end, the covers 26 may be
modified in an appropriate manner. For example, the covers 26 may
be provided with connection pieces or individual covers 26 may be
constructed in such a manner that they separate the openings which
belong to a channel 25 and consequently separate the connection of
heat exchanger pipes 21a, 21b which belong to different heat
circuits.
[0036] As shown in FIG. 4, the heat exchanger 20 is inserted into a
supply housing 12 (also shown in FIG. 2). The heat exchanger 20 can
also be inserted into a discharge housing 13 since both housings
12, 13 are substantially of the same construction type. The supply
housing 12 has a through-opening 28 in order to be able to
laterally insert the heat exchanger 20 into the housing 12. A first
end plate 22 is constructed to be larger than the through-opening
28 so that the heat exchanger 20 which is inserted or recessed into
the housing 12 can be fixed to the housing 12 at the peripheral
edge of the end plate 22. The fixing may, for example, be carried
out by screwing fasteners, for example, through the openings shown
in FIG. 4 along the edges of the end plate 22. Between the
peripheral edge of the end plate 22 and the housing 12, a
peripheral seal (not shown) may be provided in order to connect the
heat exchanger 20 to the housing 12 in a gas-tight manner (more
specifically, in a vacuum-tight manner). The seal is preferably
arranged between the through-opening 28 and the openings which are
provided at the edges of the end plate 22 for the screwing
operation. At an end face of the supply housing 12 there is formed
a gas inlet opening 29 through which the laser gas flows from the
radial fan 11 into the heat exchanger 20, with a flow direction 30
of the laser gas indicated by an arrow in FIG. 4 extending parallel
to the end plates 22, 23.
[0037] Since the heat exchanger pipes 21a, 21b are orientated in a
parallel manner and extend at a right angle relative to the end
plates 22, 23, the laser gas strikes the heat exchanger pipes 21a,
21b substantially perpendicularly relative to the longitudinal pipe
direction. As shown in FIG. 3, the heat exchanger pipes 21a, 21b
are arranged in rows which are offset relative to each other, there
being arranged in a row in each case four heat exchanger pipes 21a
and, in an adjacent row, five heat exchanger pipes 21b. The heat
exchanger pipes 21a, 21b are so close to each other that a
turbulent gas flow is produced. In this manner, particularly
effective heat exchange can be achieved between the laser gas and
the water which flows through the heat exchanger pipes 21a, 21b
without an excessively great pressure loss of the laser gas
occurring in this instance. The discharge of the laser gas to the
laser resonator 2 is carried out through an opening (not
illustrated in FIG. 4) at the lower side of the supply housing
12.
[0038] FIG. 5 shows the structure of a heat exchanger pipe 21 a,
which is a bimetal pipe. The heat exchanger pipe 21 a has an inner
pipe 31 of stainless steel and multiple cooling ribs 32 made of
aluminum which are rolled onto the inner pipe 31 (that is to say,
the cooling ribs 32 are formed as an outer pipe). For rolling,
there is pushed over the inner pipe 31 an outer pipe of aluminum
which is not yet provided with ribs. Via cutting rollers which run
into each other, the cooling ribs 32 are cut or shaped from the
smooth outer pipe. The use of an inner pipe 31 of stainless steel
prevents corrosion by the cooling fluid, whilst the cooling ribs 32
of aluminum ensure efficient heat exchange.
[0039] In the manner described above, there may be provided a heat
exchanger 20 which is optimized in terms of flow technology and has
a compact structure. Since individual cooling circuits can be
divided by cooling medium connections being fitted to selected
cooling channels for distribution of the cooling medium at the end
plates, there is further produced a modular construction which can
be adapted in a simple and rapid manner to the respective
requirements during operation of the gas laser 1.
[0040] A number of embodiments of have been described.
Nevertheless, it will be understood that various modifications may
be made without departing from the spirit and scope of the
disclosure. Accordingly, other embodiments are within the scope of
the following claims.
* * * * *