Note: Descriptions are shown in the official language in which they were submitted.
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B~CKGRO~ND OF ~HE I~VE~IT10~
This invention relates to a vertlcal die casting
device which consists of a sleeve connecting the pouring
gate and the cavity gate and of a plunger tip inserted
in the upper portion of -the sleeve Eor injec-ting mol-ten
metal under pressure and a counter tip inserted in the
lower portion of the sleeve for guiding the molten metal
into the cavity gate. More particularly this invention
relates to a vertical die casting device in which the
counter tip is made .o retract at the same time and a-t
the same speed as the plunger tip moves down so that the
molten metal can be poured, without being pressurized,
into cavity.
In the conventional vertical die casting devices,
a plunger tip and counter tip are disposed opposite to each
other in a sleeve that connects the pouring gate and the
cavity gate. When the counter tip is at a position that closes
the cavity gate, molten metal i.s poured from the gate into
the sleeve and then the plunger tip is forced down by a proper
pressure application mechanism to apply pressure to the molten
metal so as to push down the counter tip via the pressurized
molten metal and cause the molten metal to flow into the
cavity through the cavity gate.
This construction, however, has disadvantages:
that is, since the molten metal i.n the sleeve is pressurized
between the plunger tip and the counter tip, the resulting
increase in adhesion between the mol.ten metal and the sleeve
or the tips allows more heat to be transferred to the sleeve and
tips, resulting in reduction in -the temperature of molten
metal. This can prevent a smoo-th flowing of -t.he mo:Lten me-tal
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into the vacity or recluce the life of ~he sleeve and tips.
SUM~RY OF THE~ INVENTION
The primary object of the invention is to provide a
vertical die casting device which overcomes the above-mentioned
drawbacks of the conventional die casting devices by leading
the molten metal poured in the sleeve into the cavity without
pressurizing the molten metal.
Briefly stated, the present invention is a vertical die
casting device comprising: a pouring gate; a cavity gate
located below the pouring gate; a sleeve connecting the pouring
gate and the cavity gate; an injection plunger tip inserted in
the upper portion of the sleeve and a counter tip inserted in
the lower portion of the sleeve with the plunger tip and the
counter tip disposed opposite to each other; a retracting
mechanism linked to the counter tip; a pressure applying mechan-
ism to activate the plunger tip; lowerins speed regulators pro-
vided to the retracting mechanism and the pressure applying
mechanism so as to activate both mechanisms at the same speed;
and a controller to activate the pressure applying mechanism
and the retracting mechanism in synchronism with each other.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is an explanatory drawing showing the conventional
die casting technique; and
Figu;-e 2 is a cross section of the vertical die casting
device embodyin{J the present invention.
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DESCRIPTION OF THE PREFE~RED EMBODIMENT
Designated 7 is a vertical die casting device
which has a cavity 10 formed between the upper die 8
and the lower die 9.
A sleeve 11 is vert:Lcally disposed with the lower
portion comm~micating wi~h the cavity 10 through the
cavity gate 12 and with the upper portion having a slant
pouring gate 13.
The sleeve 11 has an injection plunger tip 14
inserted in the upper porti.on ther~of and a counter tip 15
in the lower portion in such a way that they face each
other. The plunger tip 14 is connected through a rod 16
to a hydraulic cylinder 17 as a pressure applying mechanism,
and the counter tip 15 is conencted through the rod 18
to a hydraulic cylinder 19 as a retracting mechanism.
The hydraulic cylinder 19 is equal in diameter to the
other hydraul:ic cylinder 17.
The hydraulic cylinder 17 has a pis-~on 20 connected
with the rod 16 to form an upper chamber 21 and a lower
chamber 22, both of these chambers being interconnect~d
by an oil pipe 23 with a pump 24 and a solenoid changeover
valve 25 provided on the pipe 23. The pump 24 and the
solenoid changeover valve 25 are connectQd to a controller
26.
The other hydraulic cylinder 19 also has a piston 27
to form an upper chamber 28 and a :I.ower chamber 29, both
of which are interconnected by an oil pipe 30 with a
pump 31 and a solenoid changeover valve 32 installed
on the pipe 30~ The solenoid changeover valve 32, the
limit swi.tch 33 activated by a device fitted to the rod 16,
another limit switch 34 activated by a device fitted -to
the rod 18, and the pump 31 are all connected to the
controller 260 The pump 31 and the solenoid changeover
valve 32 are activated by the controller 26 when the plunger
tip 14 reaches the lower edge of the-pouring ga~e 13 and
the upp~r surface of the counter tip 15 reaches the
lower edge of the cavity gate 12.
The flow regulating valves 35, 36 provided in the
oil pipes 23, 30 serve as speed controllers that cause
the plunger tip 14 and the counter tip 15 to move down
at the same speed, by controlling the oil flows entering
the upper chambers 21 and 28 of the cylinders 17, 18
~o be equal. Designated 37 is a molten metal.
The process of die casting using the vertical
die casting device of the above construction will be
explained with reference to Figure 2. First, the
solenoid changéover valv~ 25 is shifted to the b mode
as shown and the other solenoid changeover valve 32 is
energized to shift to the a mode to lift the plunger
tip 14 and the counter tip 15. The pouring gate 13 is
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then opened and the cavity gate is closed by the side of
the counter tip 15~
As the molten metal 37 is poured from the gate 13
into the sleeve 11, the molten metal 37 will stay in
~he sleeve 11 on the counter tip 15 as shown.
Next, when a command signal is given to the controller
26 to shlft the solenoid valve 2S to the a mode and
operate the pump 24, the pressurized oil is then delivered
into the upper chamber 21 of the cylinder 17 causing the
piston 20 and the plunger tip 14 to move down.
When the plunger tip 14 reaches the lower edge of
the pouring gate 13, iOe., the upper surface o:f the
molten metal 37, a signal from the limit switch 33 shi~ts
the solenoid valve 32 to the _ mode and operates the
pump 31 to deliver the oil pressure to the upper chamber
28 of the cylinder 19 causing the piston 27 and the countPr
tip 15 to move down. The flow rates of pressurized oil
entering the upper chambers of the cylinders 17, 19 are
controlled by the flow regulating valves 35, 36 so that
they are virtually equal. Since the diameters of the
hydraulic cylinders 17, 19 are the same, the plunger
tip 14 and the counter tip 15 move down at the same speed.
Therefore, when the plunger tip 14 and the counter
tip 15 are moving downward, no pressure is applied to
the molten metal 37 held between them, so that heat
transfer from the mol~en metal 37 to the sleeve 11 or
the tips 14, 15 cannot easily occur.
Now, when the upper surface of the counter tip 15
reaches the lower edge of the cavity gate 12, a signal
from the limit switch 34 causes the pump 31 to stop
as well as the counter tip movement.
As a resultl the plunger tip 14 that continues
moving down causes the molten metal 37 -to flow into
the cavity 10 through the cavity gate 12. At this time
becasue the temperature decrease of the molten metal 37
is kept minimum as explained earlier, the molten metal
can smoothly flow into the cavity.
With the above process completed, the upper die 8
and the lower die 9 are separated to take a product out
of the cavity 10.
- The, the upper and lower dies are again clamped
together; the solenoid changeover valve 25 is changed
over to the _ mode and the solenoid valve 32 to the a
mode; and the pumps 24, 31 are operated to return the
plunger tip 14 and the counter tip 15 to their upper
positions, as shown in Figure 2, to repeat the die casting
process described above.
It should be noted that this invention is not
limited to the above embodiment alone and various modifi-
cations are possible. For instance, the mechanism for
lowerlng the plunger tip and counter tip may be replaced with
the combination of motor and gear instead of the hydraulic
cylinders.
As can be seen in the foregoing, since the pressure
~pplying mechanism for the injection plunger tip and th~e
mechanism for lowering the counter tip are activated
in synchronism with each other, the molten metal is not
pressurized in the sleeve by the opposing plunger tip and
counter tip, so that the adhesion between the molten
metal and the sleeve or tips is kept from increasing and
the molten metal temperature maintained, thus assuring
the smooth flow of molten metal into the cavity and
therefore a good cast product.
Furthermore, since khe molten metal is not pressurized,
it will not enter between the sleeve and the tips and
this prevents the sticking of sleeve and tips and elongates
their life.
