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CENTRIFUGAL CASTING MACHINE AND METHOD OF REPLACING MOLDS
Field of the Invention
The present invention relates to a centrifugal
casting machine for casting a metal tube with a
centrifugal force, and a method of replacing molds.
Background of the Invention
In a known centrifugal casting method, a metal tube
such as a cast iron tube having a bell on one end and a
spigot on the other end is cast with a centrifugal force
by pouring molten metal into a cylindrical mold while
rotating the mold about the axis held in the horizontal
position. In this centrifugal casting method, a metal
tube is cast while being pressed with a centrifugal force,
thereby achieving a fine metal tube containing just a few
inclusions.
As a centrifugal casting machine used for such a
centrifugal casting method, a water-cooled centrifugal
casting machine has been already known which performs
centrifugal casting while cooling a mold with a coolant
from the outside.
Japanese Patent Publication No. 46-27957 (claiming
the priority, April 19, 1968, France, 148643) and so on
disclose centrifugal casting machines of so-called rotary
water box type as simply illustrated in FIG. 14, in which
a cylindrical mold 51 and a sleeve (rotary cylinder) 52
provided around the mold 51 with a clearance are disposed
in a concentric manner, the mold 51 and the sleeve 52 are
integrally supported so as to rotate about the axes of
the mold 51 and the sleeve 52, and a coolant is supplied
into a ring-shaped space 55 between the mold 51 and the
sleeve 52 from the outside. On a part of the perimeter of
the sleeve 52, fixed ring-shaped members 53 are disposed
to rotatably support the sleeve 52 and the mold 51 and

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have internal spaces communicating with the ring-shaped
space 55. The ring-shaped space 55 includes a coolant
passage communicating with the outside of a system. On a
boundary between the rotary cylinder 52 and the fixed
ring-shaped members 53, sealing portions 54 for
preventing water leakage are provided. Reference numeral
56 in FIG. 14 denotes the outer frame of a movable rack
for holding the fixed ring-shaped members 53. In this
centrifugal casting machine, the sleeve 52 and the mold
51 are rotatably supported on the outer frame 56 of the
movable rack via the sealing portions 54 and the fixed
ring-shaped members 53. Reference numeral 57 denotes a
motor acting as a driving source for the rotation of the
sleeve 52 and the mold 51. The driving force of the motor
57 is transmitted to the sleeve 52 through a driving
force transmitting member 58 made up of a belt
penetrating the outer frame 56, so that the driving force
rotates the sleeve 52.
The centrifugal casting machine is configured to cool
the mold 51 with a coolant. Thus it is possible to
shorten a cooling/solidification time after molten metal
is poured, thereby increasing the number of produced
metal tubes.
However, in this centrifugal casting machine of
rotary water box type, the sleeve 52 provided around the
mold 51 rotates with the mold 51. Therefore, it is
necessary to provide the sealing portions 54 for
preventing water leakage between the fixed ring-shaped
members 53 and the sleeve 52 and the mold 51 is rotatably
supported by the fixed ring-shaped members 53 having the
sealing portions 54. Thus the sealing portions 54 having
the rotatably supporting function and the water sealing
function are apt to have seriously complicated
configurations, the cost of equipment increases, and
replacement of the molds 51 requires a long time.

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On the other hand, centrifugal casting machines of
so-called water box type are disclosed in, for example,
Japanese Patent No. 3 73 99 and so on in which a box for
storing a coolant is not rotated but fixed, though a
similar water-cooling centrifugal casting method is used
to perform centrifugal casting while cooling a mold with
the coolant from the outside.
In this centrifugal casting machine, as shown in FIGS.
15 and 16, a mold 64 can be stored in a box 63 including
a lower frame 61 substantially shaped like a box and an
upper cover 62 substantially shaped like a semicircle in
cross section and a pair of support rollers 65 and 66 are
disposed so as to support the lower part of the mold 64
from both sides. One of the support rollers 65 is rotated
by a driving motor 70 in a state in which a coolant 67 is
stored in the box 63, so that the mold 64 can be cooled
by the coolant from the outside. Further, the box 63
includes a coolant inlet pipe 74 for introducing the
coolant 67 and a coolant outlet pipe 75 for discharging
the coolant 67. Reference numeral 71 in FIG. 16 denotes a
driving pulley attached to the end of the support roller
65 protruding from the box 63. The driving pulley 71 is
placed on the opposite side of a driving belt 72 from the
driving motor 70. The driving belt 72 is looped over the
driving pulley 71 and the driving motor 70.
Also in this centrifugal casting machine, the mold 64
is cooled by the coolant 67. Thus it is possible to
shorten a cooling/solidification time of molten metal as
compared with the case where a mold is air-cooled,
thereby increasing the number of produced metal tubes.
Additionally, in this centrifugal casting machine, the
box 63 for storing the coolant 67 does not rotate and
thus a sealing portion having a complicated configuration
is not necessary on a joint (not shown) of the coolant
inlet pipe 74 and the coolant outlet pipe 75. Since a

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sealing portion having a complicated configuration is not
necessary, the cost of equipment can be reduced
accordingly.
However, in this centrifugal casting machine, the
mold 64 is only supported by the pair of support rollers
65 and 66 from the below. Thus when the mold 64 is
rotated at high speed, the mold 64 moves so as to float
upward and vibrates, so that the quality of a metal tube
may deteriorate. For example, a produced metal tube may
have an uneven thickness, fractures, or cracks. Another
problem is that since the mold 64 can be rotated only at
low speed and the pressure of a centrifugal force is
relatively small, it is not possible to fully make use of
the centrifugal casting method for obtaining a fine metal
tube containing just a few inclusions.
In order to address these problems, as shown in FIG.
17, a pressing roller 69 for preventing the mold 64 from
moving upward may be provided in addition to the
configuration of FIG. 15. With this configuration, the
mold 64 does not move upward. Thus even when the mold 64
is rotated at high speed, it is possible to minimize
vibrations in the vertical direction and so on, thereby
preventing problems such as an uneven thickness of the
metal tube. Further, since the mold 64 can be properly
rotated at high speed, the pressure of a centrifugal
force can be increased. Thus it is possible to achieve a
metal tube while fully making use of the advantage of the
centrifugal casting method for producing a fine metal
tube containing just a few inclusions.
In a centrifugal casting machine of FIG. 17, wheels
71 are attached to the lower part of a box 63 and can
move along rails 73 provided on a foundation 72. Moreover,
the centrifugal casting machine can be moved to a
location where molten metal is supplied, a location where
a metal tube is removed, and so on.

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However, in the configuration of the centrifugal
casting machine shown in FIG. 17, the support positions
of the support rollers 65 and 66 and the pressing roller
69 are fixed on predetermined points. Thus when holding
the molds 64 varied in diameter in response to kinds of
metal tubes having different diameters, it is necessary
to provide a plurality of centrifugal casting machines
having different sizes for the molds 64, considerably
increasing the cost of equipment.
In order to address this problem, the support
positions of the support rollers 65 and 66 may be moved
so as to change dimensions between the support rollers 65
and 66 or the pressing roller 69 may be provided so as to
move up and down. Moreover, it is necessary to provide a
relative height adjusting mechanism according to the
position of a gutter for pouring molten metal. In this
case, as compared with the case where the plurality of
centrifugal casting machines are provided for the
respective metal tubes, only a single centrifugal casting
machine is necessary and thus the cost of equipment can
be reduced. However, when using the centrifugal casting
machine configured thus, every time the mold 64 is
replaced with another mold having a different size, the
positions of the support rollers 65 and 66 and the
pressing roller 69 have to be adjusted by, for example, a
person who enters the box 63. This adjustment requires a
long time and the centrifugal casting machine has to be
stopped during this adjustment. In other words, when
replacing the molds 64, the centrifugal casting machine
has to be stopped for a long time, reducing the operating
rate of the centrifugal casting machine.
Further, in the configuration of the centrifugal
casting machine shown in FIG. 17, when replacing the mold
64 with another mold having a different size according to
the size of a produced tube, a troublesome operation of

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removing the upper cover 62 from the lower frame 61
substantially shaped like a box is necessary and this
operation requires a long time, further reducing the
operating rate of the centrifugal casting machine.
A similar problem arises in the centrifugal casting
machine of rotary water box type shown in FIG. 14. When
replacing the mold 51 with another mold having a
different size, parts of the sealing portions 54 are
removed with the mold 51 and the sleeve 52, and then the
mold 51 and the sleeve 52 have to be removed from the
outer frame 56 along the axial direction. During this
operation, the centrifugal casting machine has to be
stopped and the removal of the parts of the sealing
portions 54 requires a long time. Moreover, the driving
force transmitting member 58 made up of a belt for
transmitting the rotational driving force of the motor 57
to the sleeve 52 is disposed so as to penetrate the outer
frame 56. Thus it is considered that it takes a long time
to remove the driving force transmitting member 58 and
perform a relative height adjustment for aligning the
position of the mold 51 with a position where molten
metal is poured. In other words, the centrifugal casting
machine of rotary water box type shown in FIG. 14 also
has to be stopped for a long time when the mold 51 is
replaced with another, so that the operating rate of the
centrifugal casting machine decreases.
Disclosure of the Invention
The present invention is designed to solve these
problems. An object of the present invention is to
provide a centrifugal casting machine and a method of
replacing molds which can respond to kinds of molds
having different diameters without greatly increasing the
cost of equipment, minimize the operation stop time of
the centrifugal casting machine during the replacement of

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the molds, and improve the operating rate of the
centrifugal casting machine.
In order to solve the problems, a centrifugal casting
machine of the present invention in which a metal tube is
cast using a centrifugal force by pouring molten metal
into a cylindrical mold while rotating the mold about the
axis, and the mold is cooled by a coolant from the
outside during casting, including: an outer frame
disposed on a location where the molten metal is supplied,
a replaceable inner frame inserted into and removed from
the outer frame while rotatably holding the mold about
the axis, a coolant introducing device for introducing
the coolant into a space between the mold and the inner
frame disposed in the outer frame, and a rotational
driving force transmitting device for transmitting a
rotational driving force to the mold held in the inner
frame, and rotating the mold.
With this configuration, when the centrifugal casting
machine is operated, another inner frame different from
the inner frame disposed inside the outer frame of the
centrifugal casting machine can be disposed outside the
outer frame, another mold can be held in the another
inner frame, and positioning and so on of the mold
relative to the inner frame can be completed beforehand.
Therefore, at the completion of a centrifugal casting
operation, the inner frame having held the mold used for
centrifugal casting is moved to the outside from the
outer frame, and the inner frame having held the another
mold is moved into the outer frame instead, so that the
molds can be replaced in a short time after the
completion of the centrifugal casting operation. As a
result, it is possible to minimize the stop time of the
centrifugal casting machine during the replacement of the
molds, thereby increasing the operating rate of the
centrifugal casting machine.

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Further, according to the centrifugal casting machine
of the present invention, the inner frame can be inserted
into and removed from the outer frame along the axis.
With this configuration, the inner frame can be
inserted into and removed from the outer frame with a
relatively simple configuration.
Moreover, according to the centrifugal casting
machine of the present invention, the inner frame has an
insertion/removal sliding contact mechanism coming into
sliding contact with the outer frame when inserted into
and removed from the outer frame, and the outer frame has
a guide portion provided along the axis such that the
insertion/removal sliding contact mechanism of each inner
frame comes into sliding contact with the guide portion
in a sharing manner.
With this configuration, even when the inner frames
have different sizes, the inner frames can be properly-
inserted into and removed from the common outer frame.
Further, according to the centrifugal casting machine
of the present invention, the mold has an end protruding
from the inner frame and the outer frame in a state in
which the mold is held in the inner frame and the inner
frame is introduced into the outer frame, and the
rotational driving force transmitting device is attached
to the protruding end.
With this configuration, during the replacement of
the molds, a driving force transmitting member such as a
driving belt looped over the rotational driving force
transmitting device can be easily removed in a short time,
so that high working efficiency can be obtained.
A method of replacing molds according to the present
invention is used for a centrifugal casting machine in
which a metal tube is cast using a centrifugal force by
pouring molten metal into a cylindrical mold while
rotating the mold about the axis, and the mold is cooled

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by a coolant from the outside during casting, including
the steps of: replaceably disposing an inner frame such
that the inner frame can be inserted into and removed
from an outer frame disposed on a location of casting,
the inner frame rotatably holding the mold about the axis
and allowing a coolant to be introduced into the inner
frame; and replacing the molds by disposing, outside the
outer frame, another inner frame different from the inner
frame disposed inside the outer frame of the centrifugal
casting machine when the centrifugal casting machine is
operated, holding another mold in the another inner frame,
moving the inner frame having held the mold used for a
centrifugal casting operation to the outside from the
outer frame at the completion of the centrifugal casting
operation, and moving the inner frame having held the
another mold into the outer frame instead.
With this method of replacing the molds, when the
centrifugal casting machine is operated, another mold can
be held in the inner frame disposed outside the outer
frame and positioning and so on of the another mold
relative to the inner frame can be completed beforehand.
Therefore, the molds can be replaced in a short time at
the completion of the centrifugal casting operation. As a
result, it is possible to minimize the stop time of the
centrifugal casting machine during the replacement of the
molds, thereby increasing the operating rate of the
centrifugal casting machine.
According to the centrifugal casting machine and the
method of replacing molds, only a single component is
necessary other than the inner frames having mold guide
mechanisms and outer frame guide mechanisms, thereby
minimizing an increase in the cost of equipment.
As described above, according to the present
invention, the inner frame for rotatably holding the mold
about the axis can be replaceably inserted into and

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removed from the outer frame. Thus when the centrifugal
casting machine is operated, another mold can be held in
another inner frame disposed outside the outer frame, and
positioning and so on of the another mold relative to the
inner frame can be completed beforehand. Therefore, it is
possible to minimize the stop time of the centrifugal
casting machine and increase the working rate. Further,
since only the single outer frame is necessary, it is
possible to minimize an increase in the cost of equipment.
Moreover, the inner frame includes the
insertion/removal sliding contact mechanism coming into
sliding contact with the outer frame when inserted into
and removed from the outer frame, and the outer frame has
the guide portion provided along the axis such that the
insertion/removal sliding contact mechanisms of the inner
frames come into sliding contact with the guide portion
in a sharing manner. Thus even when the inner frames have
different sizes, the inner frames can be quickly inserted
into and removed from the common outer frame in a proper
manner, thereby further increasing the operating rate.
Further, the rotational driving force transmitting
device is provided on a point protruding from an end of
the outer frame in the metal mold. Thus during the
replacement of the molds, the driving force transmitting
member such as the driving belt looped over the
rotational driving portion can be easily removed in a
short time, so that high operating efficiency can be
obtained.
Brief Description of the Drawings
FIG. 1(A) and FIG. 1(B) are partially broken front
views showing an overall centrifugal casting machine
according to an embodiment of the present invention;
FIG. 2(A) and FIG. 2(B) are front sectional views
showing outer frames of the centrifugal casting machine;

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FIG. 3(A) and FIG. 3(B) are partially broken front
views showing (large) inner frames of the centrifugal
casting machine;
FIG. 4(A) and FIG. 4(B) are partially broken front
views showing (small) inner frames of the centrifugal
casting machine;
FIG. 5(A) and FIG. 5(B) are a front sectional view
and a side sectional view showing a state of a coolant
supplied into the centrifugal casting machine;
FIG. 6(A) and FIG. 6(B) are a front sectional view
and a side sectional view showing a state of the coolant
supplied into the outer frame of the centrifugal casting
machine;
FIG. 7 is a front sectional view showing a state of
the coolant supplied into the inner frame of the
centrifugal casting machine;
FIG. 8(A) and FIG. 8(B) are a front sectional view
and a side sectional view showing the outer frame of the
centrifugal casting machine;
FIG. 9 is a partially broken enlarged view showing
the main part of the large inner frame in the centrifugal
casting machine;
FIG. 10(A) and FIG. 10(B) are side sectional views
showing a mold guide mechanism and an outer frame guide
mechanism of the large inner frame in the centrifugal
casting machine;
FIG. 11 is a partially broken enlarged view showing
the main part of the small inner frame in the centrifugal
casting machine;
FIG. 12(A) and FIG. 12(B) are side sectional views
showing a mold guide mechanism and an outer frame guide
mechanism of the small inner frame in the centrifugal
casting machine;

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FIG. 13(A) and FIG. 13(B) are enlarged sectional
views showing a spigot-side portion of the centrifugal
casting machine;
FIG. 14 is a sectional view showing a conventional
centrifugal casting machine;
FIG. 15 is a sectional view showing another
conventional centrifugal casting machine,-
FIG. 16 illustrates the outside shape of the another
conventional centrifugal casting machine; and
FIG. 17 is a sectional view showing still another
conventional centrifugal casting machine.
Description of the Embodiment
A centrifugal casting machine and a centrifugal
casting method according to an embodiment of the present
invention will now be described in accordance with the
accompanying drawings. FIG. 1(A) and FIG. 1(B) are
partially broken front views showing the overall
centrifugal casting machine according to the embodiment
of the present invention. FIG. 2(A) and FIG. 2(B) are
front sectional views showing the outer frames of the
centrifugal casting machine. FIG. 3(A), FIG. 3(B), FIG.
4(A), and FIG. 4(B) are partially broken front views
showing the inner frames of the centrifugal casting
machine. FIG. 1(A), FIG. 2(A), FIG. 3(A), and FIG. 4(A)
show the centrifugal casting machine for a short mold for
casting a metal tube having small longitudinal dimensions
along the axial direction. FIG. 1(B), FIG. 2(B), FIG.
3(B), and FIG. 4(B) show the centrifugal casting machine
for a long mold for casting a long metal tube having
large longitudinal dimensions along the axial direction.
As shown in FIGS. 1(A) to 4(B), the centrifugal
casting machine of the present invention casts a metal
tube 10 such as a cast iron tube with a centrifugal force
by pouring molten metal into a cylindrical mold 1 while

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rotating the mold 1 about an axis X. The centrifugal
casting machine includes an outer frame 3 disposed on a
location where molten metal is supplied, and a
replaceable inner frame 2 inserted in and removed from
the outer frame 3 while rotatably holding the mold 1
about the axis X. In this configuration, the inner frames
2 having a plurality of sizes (a plurality of diameters
and lengths) are provided. In this embodiment, one of the
inner frames 2 is selected according to the size of the
mold 1 and can be stored in the outer frame 3. The inner
frame 2 and the outer frame 3 having lengths
corresponding to the short mold 1 are used as common
components. When the mold 1 is long, an auxiliary inner
frame 2' and an auxiliary outer frame 3' are connected to
the inner frame 2 and the outer frame 3 along the
longitudinal direction.
The inner frame 2 includes mold holding mechanisms 4
for rotatably holding the mold 1 about the axis X and
insertion/removal sliding contact mechanisms 5 which come
into sliding contact with the outer frame 3 when the
inner frame 2 is inserted in or removed from the outer
frame 3. The inner frame 2 having held the mold 1 is
disposed, in a removable manner along the axis X, on a
storage position where the inner frame 2 is stored in the
outer frame 3 and a position outside the outer frame 3 in
a state in which the insertion/removal sliding contact
mechanisms 5 are in sliding contact with guide rails 18
provided as guide portions in the outer frame 3.
Reference numeral 9 in FIG. 1(A), FIG. 1(B) and so on
denotes inner frame fixing mechanisms for positioning the
inner frame 2 stored in the outer frame 3 and fixing the
inner frame 2.
Both ends of the mold 1 (ends corresponding to a
spigot 10a and a bell 10b of the produced metal tube 10)
are laterally protruded from the inner frame 2, and a

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rotational driving force transmitting portion 6 is
provided as a rotational driving force transmitting
device on an end lb of the mold 1 on the bell side of the
produced metal tube 10 (hereinafter, will be simply-
referred to as a bell side). A rotational driving force
from a driving motor (not shown) for generating a driving
force for rotating the mold 1 is transmitted to the
rotational driving force transmitting portion 6 through a
driving belt 33 (indicated by virtual lines in FIG. 9 and
FIG. 11) and is transmitted to the mold 1 by the
rotational driving force transmitting portion 6. As shown
in FIGS. 5 to 7, the centrifugal casting machine includes
coolant introducing portions 7 provided as a coolant
introducing device for introducing a coolant W into the
inner frame 2, to be specific, into a space between the
inner frame 2 and the mold 1, and coolant discharging
portions 8 provided as a coolant discharging device for
discharging the coolant W from the inside of the inner
frame 2, to be specific, from the space between the inner
frame 2 and the mold 1. The coolant W is basically
introduced into the inner frame 2 and discharged from the
inner frame 2, and is also introduced into a space
between the outer frame 3 and the inner frame 2 through
openings 2a and so on provided on the inner frame 2.
Although the coolant introducing portions 7 and the
coolant discharging portions 8 are provided on the inner
frame 2 and the outer frame 3 in FIGS. 5 to 7, the
coolant introducing portions 7 and the coolant
discharging portions 8 are omitted in the other drawings.
Each part of the centrifugal casting machine will be
specifically described below.
Since the metal tubes (cast iron tubes) 10 to be cast
have a plurality of diameters and lengths, the molds 1
having a plurality of diameters and lengths are used for
casting according to the diameters of the metal tubes 10.

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Thus in order to properly respond to the kinds of molds 1,
two inner frames 2 having different diameters are
provided (when the mold 1 is long, the auxiliary inner
frame is connected in the longitudinal direction as
necessary) and the auxiliary inner frame 2' is provided.
The auxiliary inner frame 2' is joined, when the mold 1
is long, to the inner frame 2 having the same length as
the short mold 1. In this embodiment, a large inner frame
2A and a small inner frame 2B having two different
diameters are used as the inner frame 2.
As shown in FIGS. 9 to 12 and so on, the inner frame
2 has the mold holding mechanisms 4 provided on a
plurality of points (four points in this embodiment)
spaced in the axial direction. The mold holding mechanism
4 is substantially shaped like a cylinder (circular in
cross section) in this embodiment. The mold holding
mechanism 4 is made up of three rotary rollers 11 making
contact with the mold 1 from the outside. Support shafts
12 for rotatably supporting the rotary rollers 11 are
supported by support pieces 13 which are formed in pairs
protruding from the inner frame 2 to the outside. Further,
on the inner frame 2, positions corresponding to the
rotary rollers 11 are opened and the rotary rollers 11
are placed into the inner frame 2 through openings 2a.
The axes of the rotary rollers 11 are in parallel with
the axis X of the mold 1, and the mold 1 is rotatably
held in the inner frame 2 by the rotary rollers 11 about
the axis X in a state in which the mold 1 and the inner
frame 2 are coaxial about the axis X. In this embodiment,
a point for inserting the support shaft 12 in the support
piece 13 is formed in a long hole 13a extending in the
radial direction of the inner frame 2. The positions of
the support shafts 12 are adjusted in the radial
direction of the inner frame 2, so that the rotary
rollers 11 can properly hold the molds 1 having a

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plurality of diameters within the storage ranges of the
inner frames 2 (simply illustrated in FIG. 10(A) and FIG.
12(A)). Although the support shaft 12 is fixed on a given
position along the long hole 13a by, e.g., a nut and the
like, the configuration is not particularly limited.
Moreover, on the outer periphery of the inner frame 2,
the insertion/removal sliding contact mechanisms 5 are
attached to the plurality of points (three points in this
embodiment) spaced in the axial direction. As shown in
FIGS. 9 to 12 and so on, the insertion/removal sliding
contact mechanism 5 includes two moving rollers 15 having
rotating shafts rotatably supported by support arms 14
extending diagonally downward from the inner frame 2 to
both sides. The moving rollers 15 can travel in sliding
contact with the guide rails 18 axially extending on two
points of the lower part of the inside of the outer frame
3. Therefore, the inner frame 2 can move along the axial
direction in a state in which the moving rollers 15 are
placed on the guide rails 18.
Further, two pressed arms 17 extending diagonally
upward from the inner frame 2 to both sides are attached
to positions immediately above the insertion/removal
sliding contact mechanisms 5 in the outer frame 3. In a
state in which the inner frame 2 is placed on a
predetermined position in the outer frame 3, the pressed
arms 17 are pressed from the above by a holding member 16
movable up and down in a space 2b provided in the upper
part of the outer frame 3, so that the inner frame 2 is
fixed on the predetermined position (normal position).
The space 2b in which the holding member 16 can move up
and down is formed by a recessed cover 19 fixed on the
upper part of the outer frame 3. The holding member 16 is
positioned by a tap bolt 20 capable of coming in and out
of the recessed cover 19. The inner frame fixing
mechanism 9 is made up of the holding member 16, the

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pressed arms 17, and so on. The pressed arms 17 are
formed so as to extend upward as long as possible and so
as not to come into contact with the upper inner wall
surface of the outer frame 3 when the inner frame 2 moves
into the outer frame 3 along the axial direction. The
upper ends of the pressed arms 17 are equal in height
even on the different kinds of inner frames 2.
In this embodiment, the main body other than a truck
26 (see FIG. 5(B) and FIG. 6(B)) provided on the bottom
of the outer frame 3 is substantially shaped like a
cylinder. The inner frame 2 having held the mold 1 is
positioned in the outer frame 3, so that the mold 1, the
inner frame 2, and the main body of the outer frame 3 are
coaxial to one another. According to the size (diameter)
of the inner frame 2, the pressed arms 17 and the support
arms 14 for supporting the moving rollers 15 are formed
long in the radial direction as the inner frame 2
decreases in diameter. On any one of the inner frames 2,
the moving rollers 15 are properly guided in contact with
the guide rails 18 and the pressed arms 17 are properly
pressed and positioned by the holding member 16.
As simply illustrated in FIG. 13(A) and FIG. 13(B),
on the inner frame 2 or the auxiliary inner frame 2'
connected to the inner frame 2, a spigot-side inner frame
socket 27 is detachably attached by a bolt and the like
to the end of a side where the spigot 10a of the metal
tube 10 is centrifugally cast (hereinafter, will be
simply referred to as a spigot side). The spigot-side
inner frame socket 27 is so shaped as to come into
contact with the outer surface of a spigot-side end la of
the mold 1. On the inner periphery of the spigot-side
inner frame socket 27, a gasket 28 for sealing a coolant
in the inner frame 2 is placed. On a spigot-side end 3a
of the outer frame 3, a spigot-side outer frame socket 29
is detachably attached by a bolt and the like. The

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spigot-side outer frame socket 29 is so shaped as to come
into contact with the outer surface of the spigot side of
the inner frame 2. On the inner periphery of the spigot-
side outer frame socket 29, a gasket 30 for sealing a
coolant in the outer frame 3 is placed. As shown in FIG.
13(A), when the mold 1 is short, a flange plate 36 for
receiving the spigot-side inner frame socket 27 is
attached to the end of the inner frame 2, and the spigot-
side inner frame socket 27 is attached to a spigot-side
end 2f of the inner frame 2 via the flange plate 36. When
the mold 1 is long, as shown in FIG. 13(B), a flange
portion 3 6' is integrally formed on the end of the
auxiliary inner frame 2' connected to the inner frame 2,
and the spigot-side inner frame socket 27 is attached to
the auxiliary inner frame 2' via the flange portion 36'.
In other words, in either case, the common inner frame 2
is used.
As shown in FIG. 9 and FIG. 11, a point near the
bell-side end 2d of the inner frame 2 is expanded like a
brim while being slightly recessed to the spigot side in
the axial direction, and the point 2d is fit into the end
of the outer frame 3 from the inner side. Further, a
ring-shaped portion 22a of a bell-side socket 22 is
provided so as to laterally cover the point 2d near the
end of the inner frame 2, and the outer periphery of the
ring-shaped portion 22a is fixed with a bell-side end 3d
of the outer frame 3 and the bell-side end 2f of the
inner frame 2 by a bolt and the like. On the inner
periphery of the bell-side socket 22, a cylindrical
portion 22b is formed so as to extend laterally from the
inner edge of the ring-shaped portion 22a. The rotational
driving force transmitting portion 6 is rotatably
supported around the cylindrical portion 22b via bearings
23 such as ball bearings. The rotational driving force
transmitting portion 6 is a pulley driven by the driving

- 19 -
motor (not shown) through the driving belt 33. To the
rotational driving force transmitting portion 6, bell
attaching pieces 32A and 32B for holding and fixing the
bell-side end lb of the mold 1 are attached via a
cylindrical turning force transmitting member 31 which is
substantially shaped like a brim extended from the
rotational driving force transmitting portion 6 to the
inside. Therefore, a rotational driving force transmitted
to the rotational driving force transmitting portion 6 is
transmitted to the bell-side end lb of the mold 1 through
the turning force transmitting member 31 and the bell
attaching pieces 32A and 32B, so that the rotational
driving force is applied to the mold 1 rotatably
supported by the mold holding mechanisms 4 and the mold 1
is properly rotated. Moreover, the turning force
transmitting member 31 has an inner cylindrical portion
31a extending near the cylindrical portion 22b of the
bell-side socket 22 so as to face the inner periphery of
the cylindrical portion 22b. A gasket 21 fit into a joint
of the ring-shaped portion 22a and the cylindrical
portion 22b of the bell-side socket 22 comes into contact
with the outer periphery of the end of the inner
cylindrical portion 31a of the turning force transmitting
member 31, achieving sealing for preventing the coolant W
in the inner frame 2 from leaking from the bell side.
Referring to FIGS. 5 to 7, the following will discuss
a configuration for introducing the coolant W into the
inner frame 2 and discharging the coolant W from the
inner frame 2. In this embodiment, outer-frame-side
coolant introducing portions 7a for introducing the
coolant W are attached to two points on the top of the
outer frame 3. The outer-frame-side coolant introducing
portions 7a penetrate these points in a radial direction.
Further, branching/introducing portions 7b are formed on
positions corresponding to the outer-frame-side coolant

- 20 -
introducing portions 7a on the inner frame 2. The coolant
introducing portion 7 for introducing the coolant W into
the inner frame 2 is made up of the outer-frame-side
coolant introducing portion 7a and the
branching/introducing portion 7b. As shown in FIG. 5,
when the inner frame 2 is stored in the outer frame, the
outer-frame-side coolant introducing portions 7a and the
branching/introducing portions 7b are connected to each
other to form the coolant introducing portions 7. When
the inner frame 2 is placed outside the outer frame 3 as
shown in FIGS. 6 and 7, the outer-frame-side coolant
introducing portions 7a and the branching/introducing
portions 7b are separated from each other.
Moreover, in this embodiment, outer-frame-side
coolant discharging portions 8a for discharging the
coolant W are attached to three points on the bottom of
the outer frame 3. The outer-frame-side coolant
discharging portions 8a penetrate these points. Further,
branching/discharging portions 8b are formed on positions
corresponding to the outer-frame-side coolant discharging
portions 8a on the inner frame 2. The coolant discharging
portion 8 for discharging the coolant W from the inside
of the inner frame 2 is made up of the outer-frame-side
coolant discharging portion 8a and the
branching/discharging portion 8b. As shown in FIG. 5,
when the inner frame 2 is stored in the outer frame, the
outer-frame-side coolant discharging portions 8a and the
branching/discharging portions 8b are connected to each
other to form the coolant discharging portions 8. When
the inner frame 2 is placed outside the outer frame 3 as
shown in FIGS. 6 and 7, the outer-frame-side coolant
discharging portions 8a and the branching/discharging
portions 8b are separated from each other.
As described above, the coolant W is basically
introduced into the inner frame 2 from the coolant

- 21 -
introducing portions 7 and then is discharged from the
coolant discharging portions 8. The coolant W is
introduced not only into the inner frame 2 but also into
the outer frame 3 through the openings 2a and so on
provided for placing the rotary rollers 11. Therefore,
the overall internal configuration of the outer frame 3
is waterproofed and thus the coolant W does not leak out
of the outer frame 3.
In this embodiment, wheels 2 5 are attached under the
outer frame 3. Thus the outer frame 3 is shaped like a
truck capable of moving (traveling) on predetermined
rails (not shown). Therefore, the centrifugal casting
machine can be moved to a location where molten metal is
supplied, a location where the metal tube 10 is removed,
and so on.
In this configuration, during centrifugal casting,
the inner frame 2 having held the mold 1 is stored in the
outer frame 3. In this state, the coolant W is introduced
into the inner frame 2 and the outer frame 3. Further, in
this state, molten metal is supplied into the mold 1 by
means of a teeming trough and the like while the mold 1
is rotated through the rotational driving force
transmitting portion 6, and casting is performed using a
centrifugal force while the mold 1 is cooled from the
outside with the coolant W.
With this configuration, the mold 1 is cooled from
the outside by forcibly circulating the coolant W during
casting. Thus as compared with the case where the mold 1
is simply cooled by air, it is possible to shorten the
cooling/solidification time of molten metal in the mold 1
after the molten metal is poured, thereby increasing the
number of produced metal tubes 10.
The following is the replacement of the molds 1 in
this configuration.

- 22 -
First, when the centrifugal casting machine is
operated using the mold 1 before replacement (will be
referred to as a pre-replacement mold), another mold 1 to
be replaced (will be referred to as a post-replacement
mold) is placed in the inner frame 2 disposed on another
location outside the outer frame 3. At this moment, the
inner frame 2 disposed outside is adjusted such that the
mold holding mechanisms 4 rotatably hold the post-
replacement mold 1 in a proper manner on a predetermined
position on the inner frame 2.
Thereafter, at the completion of the centrifugal
casting operation of the pre-replacement mold 1, the
driving belt 33 is removed from the rotational driving
force transmitting portion 6, the coolant W is discharged
from the coolant discharging portions 8, and the tap
bolts 20 of the inner frame fixing mechanisms 9 are
loosened. Further, the spigot-side outer frame socket 29
is removed from the spigot-side end 3a of the outer frame
3 and the bolt for joining the bell-side end 3d of the
outer frame 3, the bell-side end 2d of the inner frame 2,
and the bell-side socket 22 is removed. With this
operation, the inner frame 2 having held the mold 1 comes
into a movable state from the outer frame 3 along the
axis X. Thus the inner frame 2 is moved along the axis X
and removed out of the outer frame 3. In this case, the
inner frame 2 has the insertion/removal sliding contact
mechanisms 5. The inner frame 2 can be moved in a state
in which the moving rollers 15 of the insertion/removal
sliding contact mechanisms 5 are placed on the guide
rails 18, so that the inner frame 2 can be quickly-
removed out of the outer frame 3 with ease and thus high
operating efficiency is obtained.
Next, the another inner frame 2 having held the post-
replacement mold 1 is moved into the outer frame 3 and is
stored in the outer frame 3. Also in this case, the inner

- 23 -
frame 2 can be moved in a state in which the moving
rollers 15 of the insertion/removal sliding contact
mechanisms 5 attached to the inner frame 2 are placed on
the guide rails 18, so that the inner frame 2 can be
quickly placed into the outer frame 3 with ease and thus
high operating efficiency is obtained. Thereafter, the
spigot-side outer frame socket 29 is attached to the
spigot-side end 3a of the outer frame 3. The bell-side
end 3d of the outer frame 3, the bell-side end 2d of the
inner frame 2, and the bell-side socket 22 are joined by
the bolt. Further, the tap bolts 20 of the inner frame
fixing mechanisms 9 are tightened to fix the inner frame
2 in a positioned state in the outer frame 3. Also in
this state, the mold 1 is rotatably held by the mold
holding mechanisms 4 of the inner frame 2. Thereafter,
the driving belt 33 is looped around the rotational
driving force transmitting portion 6, the driving motor
(not shown) is rotatably driven, the mold 1 is rotated
through the driving belt 33, the rotational driving force
transmitting portion 6, and the turning force
transmitting member 31, and simultaneously the coolant W
is introduced from the coolant introducing portions 7, so
that the subsequent casting operation can be quickly
started.
According to this configuration and method, during
the replacement of the molds 1, when the centrifugal
casting machine operates with the pre-replacement mold 1
(before the completion of the previous casting operation),
another mold 1 to be replaced (post-replacement mold) can
be disposed in the another inner frame 2 disposed outside
the outer frame 3 and positioning of the mold 1 and the
rotary rollers 11 of the mold holding mechanisms 4 can be
completed beforehand. Such a positioning operation has
been troublesome in prior art.

- 24 -
Therefore, at the completion of the centrifugal
casting operation before the replacement of the molds, it
is only necessary to replace the inner frame 2 with the
another inner frame 2 having held the another mold 1 to
be replaced, so that the stop time of the centrifugal
casting machine can be minimized and the operating rate
can be increased.
Moreover, only the single outer frame 3 having the
inner frame fixing mechanisms 9 is necessary, minimizing
an increase in the cost of equipment.
Further, according to the present embodiment, the
inner frame 2 can be inserted into and removed from the
outer frame 3 along the axis X, so that the inner frame 2
can be inserted into and removed from the outer frame 3
with a relatively simple configuration. To be specific,
the outer frame may be divided into, e.g., two in the
vertical or horizontal direction before the inner frame
is inserted into or removed from the outer frame. In this
case, a large-scale divided configuration, connected
configuration, or sealing configuration is necessary. In
contrast, in the present embodiment, the inner frame 2
can be inserted into and removed from the outer frame 3
along the axis X, so that the inner frame 2 can be
properly inserted into and removed from the outer frame 3
and can be stored in the outer frame 3 without the
necessity for a large-scale divided configuration,
connected configuration, or sealing configuration.
Further, according to this configuration, the inner
frame 2 has the insertion/removal sliding contact
mechanisms 5 coming into sliding contact with the outer
frame 3 when inserted into and removed from the outer
frame 3, and the outer frame 3 has, along the axis, the
guide rails 18 with which the insertion/removal sliding
contact mechanisms 5 of the inner frames 2 come into
sliding contact in a sharing manner. Thus even when the

- 25 -
inner frames 2 have different sizes, the inner frames 2
can be properly inserted into and removed from the common
outer frame 3.
Since the inner frames 2 having a plurality of sizes
are provided according to the dimensions of the molds 1,
it is possible to reduce a movement for positioning the
rotary rollers 11 in the case where the molds 1 having
different dimensions are placed in the inner frame 2. The
reduced movement also improves the operating efficiency.
Although the inner frames 2 having two different
diameters are provided in the present embodiment, the
inner frames 2 having three or more different sizes may
be provided. As described above, the inner frame 2 and
the outer frame 3 are provided so as to correspond to the
short mold 1. For the long mold 1, the auxiliary inner
frame 2' and the auxiliary outer frame 3' are connected
to the inner frame 2 and the outer frame 3. With the
shared inner frame 2 and outer frame 3, this
configuration can properly respond to the molds 1 having
different lengths while suppressing an increase in the
cost of equipment.
Moreover, according to this configuration, the inner
frame fixing mechanisms 9 are disposed immediately above
points where the insertion/removal sliding contact
mechanisms 5 are disposed. Thus when the pressed arms 17
are pressed from the above by the holding member 16 of
the inner frame fixing mechanism 9, a load from the
holding member 16 is vertically applied from the moving
rollers 15 on the guide rails 18, so that positioning can
be properly performed and a bend caused by a displacement
load applied to the inner frame 2 can be minimized. In
other words, in the case where the load point of the load
of the inner frame fixing mechanism 9 and the moving
rollers 15 of the insertion/removal sliding contact
mechanism 5 are located on different positions along the

- 26 -
axis X, the inner frame is bent by a bending load between
the positions. The configuration of the present
embodiment does not cause such a problem and achieves
proper positioning.
Moreover, in the configuration of the present
embodiment, as the inner frame fixing mechanism 9, the
pressed arms 17 are formed so as to largely extend upward
from the inner frame 2 to the vicinity of the location of
the holding member 16. Thus the fixation of the inner
frame 2 with the inner frame fixing mechanism 9 can
minimize the moving stroke of the tap bolt 20 for moving
the holding member 16, so that the operating time can be
shortened and high operating efficiency can be obtained.
Further, even on a different inner frame 2, the top ends
of the pressed arms 17 are equal in height. Thus
similarly on all of the inner frames 2, positioning can
be performed and the position of the inner frame 2 can be
reset in a short time. The present embodiment described
the case where the holding member 16 is pressed by the
tap bolt 20. The configuration is not particularly
limited and the holding member 16 may be pressed by a
hydraulic cylinder and the like.
Further, according to this configuration, the coolant
W mainly circulates in the inner frame 2 disposed
relatively closely to the mold 1, that is, the coolant W
mainly circulates in a relatively narrow space. Thus the
temperature of the coolant W can be easily controlled and
the mold 1 can be properly cooled. When the inner frame 2
is not provided and the coolant is simply introduced into
the outer frame 3, the coolant is introduced to a wide
space and thus the temperature of the coolant tends to
greatly fluctuate, so that it is difficult to cool the
mold 1 with the coolant having an even temperature. In
contrast, according to the present invention, the coolant
W is introduced into the inner frame 2 making contact

- 27 -
with the mold 1 and then is discharged. Thus by
controlling the temperature and so on of the coolant W
discharged from the coolant discharging portions 8, the
coolant W at a suitable temperature for casting can be
properly brought into contact with the mold 1 and
centrifugal casting can be properly performed.
Further, in the present embodiment, the inner frame 2
is shaped like a circle coaxial to the mold 1 in cross
section. Thus there is an advantage that the coolant W
can be properly circulated in a space between the inner
frame 2 and the mold 1. The shape of the inner frame 2 is
not limited and may be any shape other than a circle in
cross section. For example, the inner frame 2 may be
rectangular or hexagonal in cross section. Further, the
shape of the outer frame 3 is not limited to a circle in
cross section and may be any shape other than a circle.
For example, the outer frame 3 may be rectangular or
hexagonal in cross section.
Moreover, in this embodiment, the rotational driving
force transmitting portion 6 is provided on a portion
protruding from the end of the outer frame. Thus at the
replacement of the molds 1, the driving belt 33 looped
over the rotational driving force transmitting portion 6
can be easily removed in a short time, so that high
operating efficiency can be obtained.
Further, in this embodiment, the inner frame 2 has
four pairs of the mold holding mechanisms 4, three pairs
of the insertion/removal sliding contact mechanisms 5,
and the three inner frame fixing mechanisms 9. The number
of mechanisms is not particularly limited. Any
configuration may be used as long as at least two pairs
of the mold holding mechanisms 4 and the
insertion/removal sliding contact mechanisms 5 are
provided and at least two inner frame fixing mechanisms 9
are provided.

- 28 -
Moreover, in this embodiment, the plurality of inner
frames 2 are two kinds of inner frames 2 whose bodies
have different diameters. The configuration is not
particularly limited and the plurality of inner frames 2
may be identical in shape. Also in this configuration,
the mold 1 having different dimensions may be placed in
another inner frame 2 before the completion of casting,
thereby shortening the stop time of the centrifugal
casting machine.

- 29 -
What is claimed is:
1. A centrifugal casting machine in which a metal tube
is cast using a centrifugal force by pouring molten metal
into a cylindrical mold while rotating the mold about an
axis, and the mold is cooled by a coolant from outside
during casting, comprising:
an outer frame disposed on a location where the
molten metal is supplied;
a replaceable inner frame inserted into and removed
from the outer frame while rotatably holding the mold
about the axis;
a coolant introducing device for introducing the
coolant into a space between the mold and the inner frame
disposed in the outer frame; and
a rotational driving force transmitting device for
transmitting a rotational driving force to the mold held
in the inner frame, and rotating the mold.
2. The centrifugal casting machine according to claim 1,
wherein the inner frame can be inserted into and removed
from the outer frame along the axis.
3. The centrifugal casting machine according to claim 2,
wherein the inner frame has an insertion/removal sliding
contact mechanism coming into sliding contact with the
outer frame when inserted into and removed from the outer
frame, and the outer frame has a guide portion provided
along the axis such that the insertion/removal sliding
contact mechanism of each inner frame comes into sliding
contact with the guide portion in a sharing manner.
4. The centrifugal casting machine according to one of
claims 1 and 2, wherein the mold has an end protruding
from the inner frame and the outer frame in a state in
which the mold is held in the inner frame and the inner

- 30 -
frame is introduced into the outer frame, and the
rotational driving force transmitting device is attached
to the protruding end.
5. A method of replacing molds for a centrifugal casting
machine in which a metal tube is cast using a centrifugal
force by pouring molten metal into a cylindrical mold
while rotating the mold about an axis, and the mold is
cooled by a coolant from outside during casting,
comprising the steps of:
replaceably disposing an inner frame such that the
inner frame can be inserted into and removed from an
outer frame disposed on a location of casting, the inner
frame rotatably holding the mold about the axis and
allowing a coolant to be introduced into the inner frame;
and
replacing the mold by disposing, outside the outer
frame, another inner frame different from the inner frame
disposed inside the outer frame of the centrifugal
casting machine when the centrifugal casting machine is
operated, holding another mold in the another inner frame,
moving the inner frame having held the mold used for a
centrifugal casting operation to the outside from the
outer frame at completion of the centrifugal casting
operation, and moving the inner frame having held another
mold into the outer frame instead.
Dated this 4th day of DECEMBER 2007

A centrifugal casting machine in which a metal tube
10 is cast by pouring molten metal into a cylindrical
mold 1 while rotating the mold 1 about an axis X, and the
mold 1 is cooled by a coolant from the outside during
casting, including: an outer frame 3, a replaceable inner
frame 2 inserted into and removed from the outer frame 3
while rotatably holding the mold 1 about the axis, a
coolant introducing device for introducing the coolant
into a space between the mold and the inner frame, and a
rotational driving force transmitting portion 6 for
transmitting a rotational driving force to the mold 1,
and rotating the mold 1. With this configuration, when
the centrifugal casting machine is operated, positioning
and so on of the mold 1 relative to the inner frame 2 can
be completed beforehand for the subsequent centrifugal
casting operation.