Note: Descriptions are shown in the official language in which they were submitted.
TORCH NOZZLE FOR PLASMA POWDER WELDING
FIELD OF INVENTION
[0001] The present invention relates to a torch nozzle used in plasma powder
welding, more
specifically to a torch nozzle for plasma powder welding having an increased
water quenching
effect achieved by an improved cooling structure while making the size
smaller.
BACKGROUND ART
[0002] Plasma powder welding is a technique for overlay welding on a workpiece
by injecting
powders serving as build-up materials into a plasma arc, melting the powders,
and feeding the melt
to the workpiece. The plasma arc is discharged toward the workpiece from an
arc passing hole
formed at the center of a torch nozzle attached to a tip of a torch head. The
powders are
discharged through powder gas channels formed around the arc passing hole,
together with an inert
gas such as argon gas. A shielding gas comprising an inert gas such as argon
gas is supplied to the
outer circumference of the torch nozzle.
[0003] The
torch nozzle is heated to a very high temperatures by a plasma arc. For this
reason,
the torch nozzle is provided inside thereof with a cooling water passage for
supplying water to cool
the torch nozzle itself. (See, for example, Patent Document 1).
LIST OF PRIOR ART
[0004] Patent Document 1: JP H01-162578 Al
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Date Recue/Date Received 2021-09-09
PROBLEMS TO BE SOLVED BY THE INVENTION
[0005] For the piping made up of small-diameter tubes (for example, an inner
diameter of 80 mm
or less), the torch head and torch nozzle must be made smaller. However,
reducing the size of the
torch nozzle results in an increase in thermal load, which causes an increase
of spatter, an increase
of works of removing the adhered spatter, and a shortened life of the torch
nozzle. Accordingly,
there is a need to improve the cooling effect on the torch nozzle.
[0006] An object of the present invention is to provide a torch nozzle having
a cooling structure
with an enhanced cooling effect.
MEANS OF SOLVING THE PROBLEMS
[0007] In one embodiment of the invention, a torch nozzle has an attachment
surface to be
attached to a tip of a torch head for plasma powder overlay welding, and a
distal end surface facing
a workpiece, the torch nozzle comprising:
an arc passing hole extending through the attachment surface to the distal end
surface and
configured to pass therethrough a plasma arc generated by an electrode rod
inserted from the
attachment surface;
a plurality of powder gas channels arranged at intervals in the
circumferential direction
outside the arc passing hole and each extending through the attachment surface
to the distal end
surface; and
a cooling water passage disposed between the attachment surface and the distal
end
surface to surround the powder gas channels and in communication with a
cooling water inlet and a
cooling water outlet formed in the attachment surface;
wherein the cooling water passage is formed in a meander shape and includes a
first
section extending along an outer periphery of each of the powder gas channels,
and a second section
positioned between each pair of the adjacent powder gas channels and extending
toward the arc
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Date Recue/Date Received 2021-09-09
passing hole.
[0008] With the torch nozzle in the embodiment mentioned above, the cooling
water inlet and the
cooling water outlet are positioned adjacent to each other on a concentric
circle about the arc
passing hole, and the cooling water passage includes an inlet-side bent
portion in communication
with the cooling water inlet and an outlet-side bent portion in communication
with the cooling
water outlet, the inlet-side bent portion and the outlet-side bent portion
being bent to each other in
mutually approaching directions.
[0009] In another embodiment of the invention, a torch nozzle has an
attachment surface to be
attached to a tip of a torch head for plasma powder overlay welding, and a
distal end surface facing
a workpiece, the torch nozzle comprising:
an arc passing hole extending through the attachment surface to the distal end
surface and
configured to pass therethrough a plasma arc generated by an electrode rod
inserted from the
attachment surface;
a plurality of powder gas channels arranged at intervals in the
circumferential direction
outside the arc passing hole and each extending through the attachment surface
to the distal end
surface; and
a cooling water passage disposed between the attachment surface and the distal
end
surface to surround the powder gas channels and in communication with a
cooling water inlet and a
cooling water outlet formed in the attachment surface,
wherein the cooling water inlet and the cooling water outlet are positioned
adjacent to
each other on a concentric circle about the arc passing hole,
the cooling water passage includes an inlet-side bent portion in communication
with the
cooling water inlet and an outlet-side bent portion in communication with the
cooling water outlet,
and the inlet-side bent portion and the outlet-side bent portion are bent to
each other in mutually
approaching directions.
[0010] With the torch nozzle in another embodiment, the cooling water passage
extends
annularly around the arc passing hole.
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Date Recue/Date Received 2021-09-09
[0011] With the torch nozzle in the foregoing embodiments, the cooling
water inlet and the
cooling water outlet are positioned between a pair of the adjacent powder gas
channels.
[0012] With the torch nozzle in the foregoing embodiments, the cooling water
passage has an
inner surface provided with an agitation member configured to stir a cooling
water flow.
[0013] A torch head is provided at a tip thereof with the torch nozzle as
mentioned above.
ADVANTAGEOUS EFFECTS OF THE INVENTION
[0014] According to the torch nozzle of the present invention, the cooling
water passage is
formed in a meander shape and includes a section extending toward the arc
passing hole, so that
peripheral edges of the arc passing hole can be effectively cooled even if
heated to high
temperatures.
[0015] In addition, according to the torch nozzle of the present invention,
the cooling water
passage comprises an inlet-side bent portion in communication with the cooling
water inlet and an
outlet-side bent portion in communication with the cooling water outlet,
wherein the inlet-side and
outlet-side bent portions are bent in mutually approaching directions, so that
the portion between
the cooling water inlet and the cooling water outlet can be effectively
cooled.
[0016] With the torch nozzle of the present invention, the cooling water
passage has the shape as
mentioned above. Therefore, the torch nozzle is featured with sufficient
cooling ability even if
made smaller. The torch nozzle of the present invention has advantages in that
an increase in the
thermal load of the torch nozzle is suppressed, the spatter is reduced, the
works of removing the
adhered spatter is alleviated, and the longer life of the torch nozzle is
attained.
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Date Recue/Date Received 2021-09-09
BRIEF DESCRIPTION OF DRAWINGS
[0017] FIG. 1 is a perspective view of a torch nozzle according to one
embodiment of the
invention, when viewed from an attachment surface side.
FIG. 2 is a plan view of the torch nozzle.
FIG. 3 is a front view of the torch nozzle.
FIG. 4 is a bottom view of the torch nozzle.
FIG. 5 shows sectional views of the torch nozzle, wherein 5 (a) to 5 (c) are
views taken
along the lines A-A, B-B, and C-C shown in FIG. 2, respectively.
FIG. 6 shows sectional views of the torch nozzle, wherein 6 (d) and 6 (e) are
views taken
along the lines D-D and E-E shown in FIG. 3, respectively.
FIG. 7 shows sectional views of the torch nozzle, wherein 7 (f) and 7 (g) are
views taken
along the lines F-F and G-G shown in FIG. 2, respectively.
FIG. 8 shows sectional views of the torch nozzle having four agitation members
provided
in the cooling water passage, wherein 8 (c), 8 (d), and 8 (e) are views taken
along the line C-C
shown in FIG. 2, the line D-D shown in FIG. 3, and the line E-E shown in FIG.
3, respectively.
Date Recue/Date Received 2021-09-09
FIG. 9 shows sectional views of the torch nozzle having two agitation members
provided
in the cooling water passage, wherein 9 (c), 9 (d), and 9 (e) are views taken
along the line C-C
shown in FIG. 2, the line D-D shown in FIG. 3, and the line E-E shown in FIG.
3, respectively.
FIG. 10 shows sectional views of the torch nozzle having the cooling water
passage in a
circular shape prepared for the comparison purpose, wherein 10 (c), 10 (d), 10
(e), and 10 (f) are
views taken along the line C-C shown in FIG. 2, the line D-D shown in FIG. 3,
the line E-E shown
in FIG. 3, and the line F-F shown in FIG. 2, respectively.
FIG. 11 shows temperature distribution diagrams of the torch nozzles of the
Inventive
Example 3 and the reference example provided in the first embodiment, wherein
11 (a) shows
temperature distributions of a cross section taken along the line A-A shown in
FIG. 2, 11 (f3) shows
temperature distributions of the entire of the distal end surface, and 11(y)
shows enlarged
temperature distributions of an evaluation surface at the center of the distal
end surface.
MODE FOR CARRYING OUT THE INVENTION
[0018] A torch nozzle 10 of one embodiment of the present invention will be
described below
with reference to the drawings.
[0019] The torch nozzle 10 is a device loaded on a torch head (not shown) used
in plasma
powder welding. The torch head has a protruded electrode rod usually made of
tungsten. The
torch head comprises a plurality of powder gas feeding ports, a cooling water
supply port for
supplying the cooling water, a cooling water collection port for collecting
the cooling water, and a
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Date Recue/Date Received 2021-09-09
shielding gas feeder for feeding the shielding gas. The torch head has four
powder-feeding ports
at intervals of 75 to 105 around its circumference, with the electrode rod
at the center, and is
provided between adjacent powder-feeding ports with the cooling water supply
port and the cooling
water collection port. This structure of the torch head will be understood
from the arrangement of
the attachment surface 11 of the torch nozzle 10, which will be described
below. The structure of
the torch head and the positions and number of the feeding ports are not
limited to those described
above.
[0020] FIG. 1 is a perspective view of the torch nozzle 10 when viewed from
the attachment
surface 11 to be loaded on the torch head. FIG. 2 is a plan view of the torch
nozzle 10, with the
attachment surface 11 facing upward. FIG. 3 is a front view of the torch
nozzle 10. FIG. 4 is a
bottom view of the torch nozzle 10 when viewed from a distal end surface 12
facing a workpiece.
FIG. 5 includes sectional views taken along the lines A-A to C-C shown in FIG.
2. FIG. 6
includes sectional views taken along the lines D-D and E-E shown in FIG. 3.
FIG. 7 includes
sectional views taken along the lines F-F and G-G shown in FIG. 2.
[0021] The torch nozzle 10 can be made of a material such as chromium copper
and is formed
into a shape described below using a 3D printer. The material and the
manufacturing method of
the torch nozzle 10 are not limited to them.
[0022] As shown in FIG. 1 and other figures, the torch nozzle 10 may be formed
into a
cylindrical column having a forward end with a slightly tapered shape. An
electrode rod of the
torch head can be inserted into a central portion on the top face of the torch
nozzle, which serves as
an attachment surface 11 to be loaded on the torch head. The attachment
surface 11 is formed
with an arc passing hole 20 in shape tapered toward the distal end surface 12
as shown in FIGS. 5
(a) to 5 (c). As shown in FIG. 4, the arc passing hole 20 extends through the
torch nozzle 10 and is
opened in the distal end surface 12.
[0023] The attachment surface 11 has a flange extending outwardly from the
outer periphery
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Date Recue/Date Received 2021-09-09
thereof and is formed with a plurality of shielding gas paths 30 to flow a
shielding gas. In the
illustrated embodiment, the shielding gas paths 30 are recesses formed in the
flange of the
attachment surface 11. When the torch nozzle 10 is loaded on the torch head,
the shielding gas
flow paths 30 communicate with a shielding gas feeder and supply the shielding
gas. The
shielding gas flow paths 30 may be through-holes.
[0024] As shown in FIGS. 1, 2, and 5 (c), the arc passing hole 20 is formed
therearound with
powder gas channels 40 (individual powder gas channels are indicated by
reference numerals 40a,
40b, 40c, and 40d in the figures) at an interval of 750 to 105 . The powder
gas channels 40a, 40b,
and the powder gas channels 40c, 40d are opened in the bottom of curve-shaped
recesses 41, 41
formed in the attachment surface 11. The recesses 41, 41 are connected to the
powder gas feeding
ports formed in the torch head. Each of the powder gas channel 40 is inclined
toward the central
portion of the arc passing hole 20 from the attachment surface 11 to the
distal end surface 12 and is
opened in the vicinity of the arc passing hole 20 on the side of the distal
end surface 12, as shown in
FIG. 4.
[0025] The
attachment surface 11 of the torch nozzle 10 includes a cooling water inlet 51
and a
cooling water outlet 52 in communication with a cooling water passage 50. In
the embodiments
illustrated in FIGS. 1 and 2, the cooling water inlet 51 and the cooling water
outlet 52 are
respectively formed in the bottom of gasket attachment recesses 51a and 52a of
the attachment
surface 11, and may be connected to the cooling water supply port and the
cooling water collection
port of the torch head, via gaskets mounted on the recesses 51a and 52a.
[0026] The cooling water passage 50 is provided within the torch nozzle 10 to
extend along the
outside the arc passing hole 20 and the powder gas channels 40. The cooling
water is supplied to
the cooling water passage 50 from the cooling water supply port of the torch
head via the cooling
water inlet 51 to cool the torch nozzle 10, and is discharged from the cooling
water outlet 52 to the
cooling water collection port.
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Date Recue/Date Received 2021-09-09
[0027] The cooling water inlet 51 and the cooling water outlet 52 are
preferably provided
adjacent to each other between a pair of the powder gas channels 40a and 40d,
on a concentric
circle thereabout. As the cooling water inlet 51 and the cooling water outlet
52 are provided
between the powder gas channels 40a and 40d, the cooling water inlet 51 and
the cooling water
outlet 52 can be positioned closer to the arc passing hole 20, so that the
cooling effect on the torch
nozzle 10 is increased.
[0028] As shown in FIGS. 6 (d) and 6 (e), in more detail in FIGS. 7 (f) and
7 (g), the inside of the
cooling water inlet 51 has an inlet-side bent portion 53 and the cooling water
outlet 52 has an outlet-
side bent portion 54, and the inlet-side and outlet-side bent portions 53, 54
are bent to each other in
mutually approaching directions. The inlet-side bent portion 53 is a flow path
extending from the
cooling water inlet 51 toward the distal end surface 12, and is bent toward
the outlet-side bent
portion 54 in a substantial dogleg shape, as shown in the illustration.
Likewise, the outlet-side
bent portion 54 is a flow path extending from the cooling water outlet 52
toward the distal end
surface 12, and is bent toward the inlet-side bent portion 53 in a substantial
dogleg shape, as shown
in the illustration. The cooling water inlet 51 and the cooling water outlet
52 are required to have
a distance therebetween to connect to the cooling water supply and cooling
water collection ports of
the torch head, resulting in a decrease of the cooling ability between the
cooling water inlet 51 and
the cooling water outlet 52. According to the present embodiment, the inlet-
side bent portion 53
and the outlet-side bent portion 54 create a flow path of the cooling water
between the cooling
water inlet 51 and the cooling water outlet 52 to provide an increased cooling
ability.
[0029] As described above, the cooling water passage 50 positioned between the
cooling water
inlet 51 and the cooling water outlet 52 extends around the arc passing hole
20 and along the outer
periphery of the powder gas channels 40. In the torch nozzle 10, the arc
passage hole 20 receives
heat generated by an arc and is heated in a region therearound. If the cooling
water passage 50 is
located at a position closer to the arc passing hole 20, the cooling effect on
the torch nozzle 10 can
be increased, accordingly. With the present invention, the cooling water
passage 50 is formed in a
meander shape to extend a position closer to the arc passing hole 20 as shown
in the cross-sectional
views in FIGS. 6 (d) and 6 (e), instead of an annular shape. Specifically, the
cooling water passage
50 may comprise a first section 55 extending along an outer periphery of each
of the powder gas
channels 40, and a second section 56 extending toward the arc passing hole 20,
wherein the first and
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Date Recue/Date Received 2021-09-09
second sections 55, 56 are continued. With reference to the longitudinal
sectional view of the
torch nozzle 10, as seen in FIG. 5 (c), the first section 55 of the cooling
water passage 50 is located
outside the powder gas channel 40 and runs near the circumference of the torch
nozzle 10. As
seen in FIGS. 5 (a) and 5 (b), the second section 56 of the cooling water
passage 50 is located
between powder gas channels 40 and runs in the vicinity of the arc passing
hole 20, i.e., near a
position closer to an inner circumference of the arc passing hole 20.
[0030] As described above, the cooling water passage 50 formed in a meander
shape provides a
direct cooling for the region heated to high temperatures in the arc passing
hole 20, thus increasing
the cooling ability to the torch nozzle.
[0031] In a more preferable embodiment, the cooling water passage 50 is formed
such that the
flow path is positioned as close as possible to the arc passing hole 20 and
the wall of the flow path
on the arc passing hole 20 side has a large area while ensuring the strength
required for the torch
nozzle 10. In the illustrated embodiment as shown in FIG. 5 (c), the first
section 55 of the cooling
water passage 50 includes, on the inner circumferential side, an inclined
surface that conforms to
the incline of the powder gas channel 40, and also includes, on the outer
circumferential side, a
surface that is partially recessed on the distal end surface 12 side and
shaped to conform to the
shape of the circumferential face of the torch nozzle 10. The second section
56 includes an
inclined surface that conforms to the shape of the arc passing hole 20, as
shown in FIG. 5 (a). This
feature makes the cross-sectional area of the cooling water passage 50 larger,
makes the flow
resistance of cooling water in the flow path smaller and allows as much
cooling water as possible to
be distributed to increase the cooling ability. The torch nozzle 10 that
includes the cooling water
passage 50 described above may be produced preferably using a 3D printer.
[0032] In the embodiment shown in FIGS. 1 to 7, the cooling water passage 50
is configured to
communicate the inlet-side bent portion 53 and the outlet-side bent portion 54
with the cooling
water inlet 51 and the cooling water outlet 52, respectively, and is formed in
a meander shape
Date Recue/Date Received 2021-09-09
including the first section 55 extending along the outer periphery of the
powder gas channel 40 and
the second section extending toward the arc passing hole 20 at between the
powder gas channels 40.
This is the best mode of the present invention. In another embodiment, the
inlet-side bent portion
53 and the outlet-side bent portion 54 may be connected by a cooling water
passage in an annular
shape, although the cooling ability may slightly drops. Alternatively, the
cooling water passage 50
may be formed in a meander shape with the first section 55 and the second
section 56 free from the
inlet-side bent portion 53 and the outlet-side bent portion 54.
[0033] With the torch nozzle 10 of the present invention, the cooling water
passage 50 formed as
described above can perform heat exchange with cooling water effectively to
increase the cooling
effect on the torch nozzle 10. The torch nozzle 10, even if downsized, has an
improved cooling
ability, prevents an increase in the thermal load between the torch nozzle 10
and the torch head,
reduces spatter, decreases works of removing the adhered spatter, and achieves
a longer life of the
torch nozzle.
[0034] <Variation of Embodiments>
The cooling ability is further increased by stirring the flow of cooling water
flowing
through the cooling water passage 50 to form a flow of cooling water colliding
with the inner
surface of the cooling water passage 50. To implement this flow, one or more
agitation members
60 may be provided in the cooling water passage 50, as shown in FIGS. 8 and 9.
The agitation
members 60 may be in the form of a fin, a baffle plate, or a protrusion.
[0035] FIG. 8 shows an embodiment in which four agitation members 60 are
provided, and FIG.
9 shows an embodiment in which two agitation members 60 are provided. A
plurality of agitation
members 60 causes the water in the cooling water passage 50 to stir unifoimly
to increase the
cooling ability.
[0036] In the case where only one agitation member 60 is provided, the
agitation member 60 is
preferably formed at a position close to the cooling water inlet 51. The
agitation member 60
provided on the upstream side is advantageous in that the stirring effect can
be maintained longer
11
Date Recue/Date Received 2021-09-09
throughout the cooling water passage 50 (even in the midstream and the
downstream side), as
compared with the case where the agitation member 60 is provided in the
midstream or on the
downstream side.
[0037] To increase the cooling ability, the cooling water passage 50 may
include, in addition to
the first section 55 extending around each powder gas channel 40, a cooling
water passage that runs
between the inner circumferential side of the powder gas channel 40 and the
arc passing hole 20.
In the case where the inlet-side bent portion 53 and the outlet-side bent
portion 54 are connected by
an annular-shaped cooling water passage, the cooling water passage 50 may
comprise a single flow
path that runs on the inner circumferential side of the powder gas channels
40.
[0038] The foregoing embodiments are merely to explain the present invention
and should not be
construed to limit the invention defined in the appended claims or narrow the
scope of the present
invention. Also, the structural elements of the present invention are not
limited to those described
in the embodiment given above, and various modifications can be, of course,
made within the
technical scope recited in the appended claims.
[0039] For example, the outer shape of the torch nozzle 10, the shape of
the arc passing hole 20,
the shape of the powder gas channels 40, and the number of powder gas channels
40 are, of course,
not limited to those of the embodiment given above. Also, the sectional shape
of the cooling water
passage 50, the meander shape of the cooling water passage 50, and the like
are not limited to the
embodiments given above. The meander shape of the cooling water passage 50 is
not only formed
in a plane parallel to the attachment surface 11 but also may be formed in an
up-down direction
perpendicular to the attachment surface 11.
EXAMPLES
[0040] Torch nozzles were produced as described below to compare the cooling
effect on the
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Date Recue/Date Received 2021-09-09
torch nozzles. The torch nozzles were produced by a 3D printer using a
chromium copper powder
(with a specific heat at constant pressure of 385 J/kg=K and a thermal
conductivity of 324 W/m=K).
[0041] <First Embodiment>
The Inventive Example 1 is an example of a cooling water passage 50 that
comprises an
inlet-side bent portion 53 and an outlet-side bent portion 54 provided in a
cooling water inlet 51 and
a cooling water outlet 52, respectively. The cooling water passage 50 between
the inlet-side bent
portion 53 and the outlet-side bent portion 54 is an annular shape and runs
outside powder gas
channels 40. This example relates to only the "bent portion."
[0042] Inventive Example 2 is a cooling water passage 50 that is formed in a
meander shape, and
includes a first section 55 extending along an outer periphery of powder gas
channels 40 and a
second section extending toward an arc passing hole 20 at between adjacent
powder gas channels
40. This example relates to only the "meander shape" without the "bent
portion."
[0043] Inventive Example 3 is an example of a cooling water passage 50 that
comprises an inlet-
side bent portion 53 and an outlet-side bent portion 54 provided in a cooling
water inlet 51 and a
cooling water outlet 52, respectively, and is formed in a meander shape and
includes a first section
55 extending along an outer periphery of powder gas channels 40 and a second
section 56 extending
toward an arc passing hole 20 at between adjacent powder gas channels. This
example is shown in
FIGS. 1 to 7 and relates to both "bent portion" and the "meander shape." The
sectional view of the
cooling water passage 50 is shown in FIGS. 5 to 7.
[0044] Reference Example shown in FIG. 10 is provided as an example of a torch
nozzle 70
prepared for the purpose of comparison wherein a cooling water inlet 72 and a
cooling water outlet
73 were connected directly to an annular cooling water passage 71. This
example does not include
both the "bent portion" and the "meander shape." The sectional view of the
cooling water passage
71 is substantially triangle shape, as shown FIG. 10 (c).
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Date Recue/Date Received 2021-09-09
[0045] The arc passing hole 20 of the torch nozzle 10 in Inventive Examples 1
to 3 and
Reference Example was heated to 1000 C. Cooling water at a temperature of 15 C
was supplied
from the cooling water inlet at a flow rate of 500 liters/h. With regard to
the distal end surface 12,
a circular region surrounding the powder gas channels 40 is identified as an
evaluation surface 13
(See FIG. 11). The average temperature of the evaluation surface and the
temperature of the
cooling water discharged from the cooling water outlet were measured. The
lower the average
temperature of the evaluation surface, the higher the cooling ability, and the
higher the temperature
of the discharged cooling water, the higher the cooling ability, because heat
exchange between the
torch nozzle and cooling water is performed effectively. The results are shown
in Table 1. The
temperature distribution diagrams of Inventive Example 3 and Reference Example
are shown in
FIG. 11, wherein FIG. 11 (a) shows temperature distributions of a cross-
section taken along the line
A-A shown in FIG. 2, FIG. 11 (fl) shows temperature distributions of the
entire distal end surface
12, and FIG. 11(y) shows enlarged temperature distributions of the evaluation
surface 13 at the
center of the distal end surface 12.
[0046]
[Table 1]
Inventive Example 1 Inventive Example 2 Inventive Example 3 Reference Example
With bent portion and Without bent portion
Feature With bent portion With meander shape
meander shape and meander shape
Average temperature of
689 621 596 712
evaluation surface ( C)
Temperature of discharged
33 33.9 34.3 32.8
cooling water ( C)
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Date Recue/Date Received 2021-09-09
[0047] Referring to Table 1, Inventive Example 1 indicates that the average
temperature of the
evaluation surface decreased by 23 C, and the temperature of the discharged
cooling water
increased by 0.2 C, as compared to Reference Example. In Inventive Example 1,
the cooling
water passage includes an inlet-side bent portion and an outlet-side bent
portion in the cooling water
passage. As there is formed the cooling water flow path between the cooling
water inlet and the
cooling water outlet, a non-cooled region is not present therebetween.
[0048] Referring again to Table 1, Inventive Example 2 indicates that the
average temperature of
the evaluation surface decreased by 91 C, and the temperature of the
discharged cooling water
increased by 1.1 C, as compared to Reference Example. In Inventive Example 1,
the cooling
water passage is formed in a meander shape and includes a section extending
toward the arc passing
hole, thus cooling the vicinity of the arc passing hole.
In addition, a comparison of Inventive Examples 1 and 2 indicates that the
meander shape
of the cooling water passage in Example 2 provides a cooling effect more
significant than that of
Inventive Example 1.
[0049] A comparison of Inventive Example 3 with Reference Example is made with
reference to
FIG. 11. In FIG. 11, a dark color portion close to the arc passing hole 20 has
a temperature of
about 750 C to 1000 C, a light color portion in the vicinity of the powder gas
channels 40 has a
temperature of about 400 C to 750 C, and the outer circumferential side of the
evaluation surface
13 has a temperature of about 150 C to 400 C.
With reference to FIG. 11(a), Inventive Example 3 comprising the section 56
extending
toward the arc passing hole 20 shows a decrease of the temperature of the
region in the vicinity of
the arc passing hole 20. Inventive Example 3 comprising the inlet-side bent
portion and the outlet-
side bent portion (not illustrated) shows a decrease of the temperature of the
region opposing the
section 56 across the arc passing hole 20.
Date Recue/Date Received 2021-09-09
FIGS. 11 (P.) and 11 (y) also show that a decrease of the temperature was
achieved in both
the distal end surface 12 and the evaluation surface 13.
[0050] Furthermore, as can be taken from Table 1, Inventive Example 3
exhibited excellent
cooling ability than Reference Example and Inventive Examples 1 and 2. This is
due to the
synergistic effect of providing an inlet-side bent portion and an outlet-side
bent portion and forming
the cooling water passage in a meander shape. Accordingly, it can be said that
the embodiment of
Inventive Example 3 is the best mode of the invention.
[0051] <Second Embodiment>
Torch nozzles having agitation members 60 formed in the cooling water passage
50 of
Inventive Example 3 were prepared as Inventive Examples 4 and 5. The cooling
water passage in
Example 4 is formed with four agitation members 60, as shown in FIG. 8. The
cooling water
passage in Example 5 is formed with two agitation members 60, as shown in FIG.
9. Examples 4
and 5 were compared with the torch nozzle of Inventive Example 3 without
agitation members, with
respect to the cooling ability based on the average temperature of the
evaluation surface and the
temperature of the discharged cooling water.
The heating temperature of the torch nozzle and the temperature of the cooling
water
supplied were the same as those of the First Embodiment. The agitation members
60 were formed
in the first section 55 as shown in FIGS. 8 and 9 The results are shown in
Table 2.
[0052]
[Table 2]
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Date Recue/Date Received 2021-09-09
Inventive Example 3 Inventive Example 4 Inventive Example 5
Number of agitation 0 4 2
members
Average temperature of
596 584 589
evaluation surface ( C)
Temperature of discharged
34.3 34.6 34.5
cooling water ( C)
[0053] Table 2 shows that the cooling ability is enhanced by the presence
of the agitation
members disposed in the cooling water passage. The cooling ability of Example
4 having four
agitation members is superior to that of Example 5 having two agitation
members because there is
occurred more collision of the cooling water with the cooling water passage,
which results in more
agitation.
[0054] <Third Embodiment>
Torch nozzles having one single agitation member 60 formed at different
positions in the
cooling water passage 50 of Inventive Example 3 were prepared as Inventive
Examples 6-10. The
agitation member in Example 6 is disposed in the inlet-side bent portion 53.
The agitation
member in Example 7 is disposed on the upstream, i.e., in the section
immediately under the inlet-
side bent portion 53 (indicated as 55a in FIG. 8). The agitation member in
Example 8 is disposed
on the midstream, i.e., in the section immediately under the inlet-side bent
portion 55a (indicated as
55b in FIG. 8). The agitation member in Example 9 is disposed on the
downstream, i.e., in the
section immediately above the outlet-side bent portion 54 (indicated as 55d in
FIG 8). The
agitation member in Example 10 is disposed in the outlet-side bent portion 54.
The cooling ability
of Examples 6-10 was compared based on the average temperature of the
evaluation surface. The
heating temperature of the torch nozzle and the temperature of supplied
cooling water were the
same as those of the First Embodiment. The results are shown in Table 3.
17
Date Recue/Date Received 2021-09-09
[0055]
[Table 3]
Inventive Example 3 Inventive Example 6 Inventive Example 7 Inventive Example
8 Inventive Example 9 Inventive Example 10
Position of agitation
No agitation member In inlet-side bent In outlet-side
bent
Upstream Midstream Downstream
member portion portion
Average temperature of
596 593 592 591 594 595
evaluation surface ( C)
[0056] Table 3 shows that the cooling ability of Examples 6-10 are superior to
that of Example 3
without agitation member. A comparison between Examples 6-10 exhibits that the
highest cooling
ability is achieved by Example 8 wherein the agitation member is disposed in
the midstream of the
cooling water passage.
Example 6 wherein the agitation member was disposed in the inlet-side bent
portion and
Example 7 wherein the agitation member was disposed on the upstream were
inferior to Example 8
with respect to the cooling ability. The reason for this could be due to that
the cooling water
flowing from the torch head enters the torch nozzle while changing the
direction of flow at the inlet-
side bent portion, and the cooling water is stirred, and thus the agitation
effect provided by the
agitation member is small. On the other hand, the agitation member disposed in
the midstream of
the cooling water passage as in Example 8 serves to stir the cooling water
again during passing
through the meander-shaped path, thus improving the cooling ability effect
over the entire of the
cooling water passage.
Example 9 wherein the agitation member was disposed on the downstream and
Example
wherein the agitation member was disposed in the outlet-side bent portion are
observed to have
the cooling effect provided by the presence of the agitation member. However,
these Examples
cannot achieve a higher cooling effect than in Example 8. The agitation
member, if disposed in
the cooling water passage, is preferably in the midstream, in more particular,
at a position 1/4 to 3/4
of the cooling water passage from the upstream side of the cooling water
passage, and more
preferably at a position 1/3 to 2/3 of the cooling water passage from the
upstream side of the
cooling water passage.
18
Date Recue/Date Received 2021-09-09
