Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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1 The present invention relates to a method of
and an apparatus for pouring a predetermined amount of
molten non-ferrous metal into a mold.
Conventionally, the pouring of a molten non-
ferrous metal such as zinc into a mold of a linear type
casting machine has been controlled by means of an
electrode rod suitably suspended and located at a height
within the mold. As the surface of the molten zinc
comes up to a predetermined level in the mold, it is
detected by the electrode rod which in turn issues a
signal for controlling the supply of the molten zinc.
~ his conventional technique of controlling
the supply of molten metal has been found, however,
inconvenient in that it often suffers a trouble caused
by a consumption of the electrode rod and unfavorable
spill of the molten metal from the conduit attributable
to a time lag in stopping the pouring. In addition, ;
scums contained by the zinc in the molten sta-te are
allowed to get into the mold. -
In order to overcome these problems, the
present applicant has proposed an improved apparatus -
capable of performing a pouring of molten metal with a
precise quantum control, as disclosed in the specifica- ;
tion of Japanese Patent Appllcation No. 90916/1974.
Although this apparatus disclosed in the
specification of Japanese Patent Application No.
9091~/1974 does pretty well, it inconveniently suffers
a di~ficulty in obtaining a satisfactory synchronization
of the movement of molds and the rotation of a distributing
conduit from which the molten metal is poured into
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successive molds.
In addition, this apparatus relying for its quantum
control upon a gap formed between a needle valve and
associated peripheral edge of an opening often experiences
a change or deterioration in pouring characteristic due to a
deposit of metal containing oxides which clogs and changes the
gap as time elapses.
It is therefore an object of the invention to avoid
the above described drawbacks and shortcomings of the prior art
by providing an improved method and apparatus which ensure a
substantially constant amount of the molten metal in the molds
by changing the rate of supply in accordance with the change in
the amount of the metal received by the molds.
According to one aspect of the present invention there
is provided a method of pouring a predetermined amount of a
molten metal into successive molds and controlling the change in
the amount of said molten metal in said molds by means of a
casting apparatus making use of a needle valve adapted to control
the rate of pouring of said molten metal, said method comprising: ~
pouring said molten metal into a mold by said predeter- ~-
mined amount by means of said casting apparatus,
measuring a distance between the surface of said molten
metal in said mold and a level change detector to obtain electric
signals representative of said distance~
selecting a suitable signal from said signals by means
o~ a hold ampli~ier adapted for cooperating with a limit switch
for delivering a signal for holding,
comparing said signal selected b~ said hold amplifier
~ith a predetermined reference value to obtain an output signal
of a magnitude and tendency for negating the deviations of said
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selected signal from the signal of said reference value, and
actuating a control motor in accordance with said
output signal to cause a displacement of said needle valve there-
by to control the change in said amount of molten metal in said
molds.
According to another aspect of the invention there is
provided in a casting machine having a needle valve adapted to
regulate the rate of pouring of a molten metal into molds, an
apparatus for pouring a predetermined amount of molten metal into
said molds and for controlling the change in the amount of molten
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metal contained by said molds, characterized by comprising a level
change detector adapted to detect the level of the surface of .
said molten metal in said molds, :~
a hold amplifier adapted to select a signal from those :
delivered by said level change detector being assisted by a limit
s~itch capable of contacting said molds,
a controller adapted to compare and calculate a difference .
bet~een a signal delivered from said hold amplifier and a predeter-
mined reference value, and to issue a signal of a magnitude to negate
said difference and .
a control motor adapted to actuate said needle valve in :
accordance with the signal from said controller.
In the accompanying drawings:
Figure 1 is a plan vie~ of a constant-pouring apparatus i
embodying the present invention,
Figure 2 is a side elevational vieu,
Figure 3 i5 a front elevational vie~, .
Figure 4 is a schematic representation of a method in
~accordance uith the present invention, :~
Figure S shous partly in section a front elevation of a
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cooling device incorporated in the apparatus of the invention, and
Figure 6 is a sectional view taken along the line VI-VI
of Figure 5.
Referring to the drawings, a molten metal
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1 which has been transferred by suitable means such as a
-pump from a furnace (not shown) for preserving the metal
in the molten state is at first delivered to one end of
a measuring trough or a ladle which can be tilted to : :
5 assume a position as shown by a two-dots-and-dash line of :. :
~ig. 1 by a cylinder 6.
The conduit or ladle 1 is provided with baffle . : :
plates 5 secured certain gaps between their bottom edges
and the bottom of the trough or ladle 1. The baffle -
plates are intended for preventing a disturbance of the
molten metal due to the change of the level thereof : :~
within the trough or ladle, and to settle the molten metal
to facilitate the removal of the scums including oxides
entrapped by the metal during the metal is held by the
15 furnace, the removal is made through an overflow -
provided at the other end of the conduit or ladle 1.
The conduit or ladle 1 is provided with an
outlet for the molten metal, at its one end. The ou-tlet
11 is preferably cylindrical, to which adapted to fit is
a regulating valve 4. The regulating valve 4 is in the
form of a needle valve and is adapted to closely fitted
to the outlet 11, and is operatively connected to means
for detecting the level of the metal so as to be operated ~:
in accordance with the level, thereby to regulate the
25 metal supply to the molds. Thus, the gap between the .
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regulating valve 4 and the peripheral edge of the outlet -
is adjustable to provide different rates of the metal
supply.
The trough or ladle 1 is adapted to hold only
a predetermined amoun-t of the molten metal. The excessive
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1 metal is overflows the other end of the trough or ladle
1, and returned to the aforementioned furnace through a
returning conduit 9.
The molten metal discharged through the
regulating valve 4 from the outlet 11 is then poured into
molds 12 f through tiltable or rotatable intermediate and
guiding trough 2 and 3.
The intermediate trough 2 is adapted to be
tilted by a cylinder 7, when the pouring must be suspended
10 due to an accidental stopping of the casting machine or -
the like reasons, to the position as shown by two-dots-
and-chain line of Fig. 2, for returning -the molten metal
delivered from the outlet 11 to the aforementioned furnace
through another returning conduit 10.
The guide conduit 3 is disposed in plural on
the casting machine, and is intended for preventing the
dropping of the molten metal between successive molds,
when a leading mold has been supplied with a predetermined
amount of the molten metal by the pouring apparatus of the
invention. ~amely, as one of the successively conveyed
molds has been filled with the molten metal to a prede-
termined level, the guide conduits are rotated by an --
associated cylinder 8 to the position as shown b~ two-
dot and-dash line of ~ig. 2, so as to deliver the metal
to the subsequent or trailing mold.
~he molds having been filled with the molten
metal are then moved by means of, for example, a chain
conveyor, to a position of a non-contacting level change
detector 101.
The level change detector 101 is adapted to
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1 detect the distance between itself and the level of the
surface of the molten metal. To explain in more detail,
the detector 101 incorporates a high-frequency induction
coil adapted to be supplied with a high-frequency current
of 1 M~Iz or so. The inductance of the coil changes as
a metal, i.e. the molten metal in the mold in this case,
approaches the coil. Accordingly, an outpu-t voltage of
0 to 1 v is obtained through a v/v convertor 102, in
accordance with the distance between the level of the
surface of the molten metal and the level change detector
101 . " - .
In the vicinity of the level change detector
101, disposed air cooling means 109 for protecting the
detector 101 against a radiation heat from the molten
metal in the mold. The cooling means 109 are further
adapted to cool the metal in the mold, and consist of a
water spraying pipe 135 and an air jetting device general-
ly designated at 131 and having an inclined surface 136
heneath the water spraying pipe 135. The air jetting
device 131 further has a nozzle port 134 for jetting
the air from an air pipe toward the level change detector
101, as well as to the surface of the molten metal.
The water from a water pipe 133 dropps, through
the water spraying pipe 135, onto the inclined surface
136 and flows along the surface toward the nozzle port
134, to be atomized by the air jetted from the nozzle
port, thereby to increase the cooling effect.
The level change detector 101 is rendered
withstandable against the heat of the molten metal in
30 the mold, by the provision of this cooling means. ~
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1 Thc v/v convcrtor connected to the level change
detector 101 in turn is connected by a v/i convertor 103
adapted to transduce the output :Erom the v/v convertor
to a signal of 0 to 20 mA which is then transmitted to
a hold-amplifier 104 connected to the v/i convertor 103.
Since the level change detector 101 continuously
transmits the ultrasonic wave signal to provide a
continuous output, the output therefrom includes a signal
representative of not only the distance between the
detector and the surface of the molten metal, but the
distance between the detector and the upper edge of the
wall of the mold as well. The train of the molds includes,
not only the common or standard mold 12 but also molds
for legged ingots. Since these molds have additional
cavities for legs, the level of the surface of the molten
metal in these molds does not coincide to those of the
standard molds.
The hold amplifier performs to select the
signals necessary for the subsequent control, from the
20 signals provided by the level change detector 101, so as - -
to neglect the unnecessary signals. This selection is
performed by a limit switch 110 connected to the amplifier
and adapted to provide a hold signal to the amplifier.
The limit switch 110 is disposed close to the
-25 path of travel of the molds and is adapted for engaging
a projection 119 formed on each one of the successive
molds. In the arrangement as shown in Fig. 1, the limit
switch 110 delivers a hold signal to the hold amplifier ;~
104, when it gets in contact with the projection 119,
30 i.e. when the projection 119 is within a hold-signal ~
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1 range C, so that the signal from the level change
detector 101 is not adopted.
As the mold advances, the limit switch 110 is
released from the projection 119, and the mold is now
within a detecting range B. The hold amplifier then
takes up the signal delivered from the level change
detector 101 and outputs it to a controller 105 connected
to the amplifier 104. The controller 105 is adapted to
compare the signal from the hold amplifier with a prede- -
termined value representative of a predetermined amount
of the molten metal in the mold, and produces a signal of
4 to 20 mADC to be fed back to negate the difference
between the predetermined reference value and the output
of the hold amplifier 10~.
The signal from the controller 105 is trans-
mitted to a positioner 106 connected to the controller.
The positioner 106 is connected in one hand to a control
motor 107, while, on the other hand, to a twin timer 111.
The positioner 106 is adapted to control the
amount of operation of the control motor 107, in-accord-
ance with the signal delivered from the controller 105.
~ amely, the positioner 106 is adap-ted to compare
a signal from the controller 105 for setting the degree
of opening of the valve with a signal fed back by the
control motor representative of the actual opening degree
of the valve, and to provide the control motor with a
signal to actuate the later -for negating the difference
between the compared signals. ;
The control motor is operatively connected to
the needle valve 4, so that the rotative motion of the
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l control motor which follows the signal given by the
positioner is transmitted to the needle valve 4.
Consequently, the opening degree of the needle valve 4
is controlled in response to the level of the molten
metal, i.e. the amount, in the mold 112.
~ he twin timer lll connected to the positioner
106 is adapted to control the duration of time of opera-
tion of the positioner so as to allow the positioner to
be operated at a predetermined interval. Thus, the
operation of the control motor following the signal from
-the positioner is made intermittently, so as to avoid an
excessive operation of the valve. ~he compensation for
the change in the quantity of the metal in the mold is
therefore made gradually.
An externally operable limit switch 108 is
associated with the control motor 107, so as to allow an
optional operation of the control motor 107 independently
of the positioner.
It will be seen from the foregoing description
20 that the present invention provides a continuous pouring ~
of the molten metal to successive molds avoiding so ~-
called 'iloss time", without causing unfavorable dropping
or leak of the molten metal.
In addition, since the rate of return of the
~; 25 molten metal to the furnace preserving the molten state
of the metal is reduced, a smaller capacity of the pump
for shifting the metal to be poured can be adopted. ~
Furthermore, the fluctuation or change in the -
amount of the molten metal in the mold is considerably
reduced, by an automatic control of the opening degree of
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1 the needle valve in response to the actual change in the
amount of metal poured to the mold, resulting in an ~:
enhanced casting capacity of the equipment.
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