Note: Descriptions are shown in the official language in which they were submitted.
COLD CHAMBER DIE CASTING MACHINE INJECTION SYSTEM
This invention relates to an injection system for
injecting metal into a die in a cold chamber die casting
process.
The injection system includes an upwardly disposed
injection sleeve having an open top which is adapted to be top
filled with molten metal. The volume of the injection sleeve
is varied by adjusting the lower position of the plunger in
the injection sleeve. The injection system is used with a
die casting machine having a fixed die attached to a fixed
platen. The top of the injection sleeve is praximate or on
the part line at which the dies close. The blunaer in t-r,A
injection sleeve is adapted to force the hot metal into the
die cavity after the dies are locked.
An injection sleeve receiver adapted to receive the
injection sleeve is connected to the fixed platen immediately
below the fixed die which is also connected to the fixed
platen. The injection sleeve may be withdrawn from the
injection sleeve receiver for servicing and returned to the
injection sleeve receiver where it remains during casting
operations.
In another embodiment of the invention an aperture in the
fixed die is substituted for an injection sleeve receiver.
In preparation for top filling the injection sleeve with
molten metal, the dies are opened, the top of the injection
sleeve extends into an injection sleeve receiver which is
fastened to the fixed platen below the fixed die so as to
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present an open cylinder adapted to receive hot metal by ladle
or other means. The volume of the injection sleeve is
controlled by controlling the position of the injection
plunger in the injection sleeve. The position of the
injection plunger is controlled so that the size of the metal
shot required for a particular casting will substantially top
up the injection sleeve when the injection sleeve is filled
with molten metal.
The extent of retraction of the injection plunger is
adjusted relative to the volume of molten metal required to
complete the metal casting. For a large metal casting
requiring considerable metal the injection plunger is
retracted deeply into the injection sleeve whereas for a
smaller casting requiring less metal the plunger is retracted
less deeply into the injection sleeve. It is desirable that
the injection sleeve be top filled by ladling or other means
approximately to the top of the injection sleeve to minimize
air inclusion during the casting operation.
After the injection sleeve is filled with metal the
moving platen and moving die are closed on the part line,
clamping pressure is applied to the moving platen and die, the
injection plunger is advanced driving the molten metal thraugh
a runner in the face of the moving die into the cavity. When
the casting is sufficiently solid, the injection plunger is
retracted, the clamping pressure is released and the moving
platen and die are opened. The casting and biscuit are
simultaneously removed with the left hand die. When the dies
are open molten metal may be ladled or otherwise transferred
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into the injection sleeve prior to the next cycle.
The injection system of this invention avoids any ninety
degree turns between the injection sleeve and the dies in
which the casting is effected. The forcing of molten metal
into the dies through a combination of turns may result in
pressure drops causing the metal to cool or in the alternative
introducing the molten metal at a higher temperature to allow
for temperature loss. The instant injection system without
any ninety degree turns between the injection sleeve and the
runner or dies is consistent with maintaining a suitable time
cycle per shot.
One problem in some existing die casting machines is
caused by air entrapment associated with ninety degree turns
between the injection sleeve and the dies in which casting is
effected. Air entrapment is caused by wave fronts created as
the metal approaches and travels around a ninety degree turn
into the runners and cavity. Transferring molten metal around
ninety degree turns also causes unwanted load losses and
turbulence.
Some metals such as liquid aluminum used in cold chamber
die casting are very corrosive. In prior die casting machines
for casting aluminum the aluminum travelled a substantial
distance before reaching the cavities in the mold. Being
highly corrosive the longer the distance the liquid aluminum
,z5 has to travel the greater the wear on the delivery system. Tn
this invention the injection sleeve when in operative position
is immediately adjacent the part line. The aluminum or other
corrosive metal has a very short distance to travel during
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injection.
In the processes of filling the injection sleeve the
liquid metal is ladled, poured or otherwise transferred
directly into the top of the injection sleeve which is open
when the dies of the die casting machine are opened. The
opening at the top of the injection sleeve is closed by the
closing of the moving platen and moving die. The injection
unit is disposed either below the dies or at an angle up to
15° below the horizontal centerline through the dies. The
l0 instant invention has the advantage of easy top ladling or
transfer by robot of molten metal into the top opening of the
injection sleeve. Metal filling of the injection sleeve close
to the top of the injection sleeve results in less entrapped
air in the injection sleeve when the top of the injection
sleeve is closed by the moving die.
The avoidance of any ninety degree angles between the
sleeve of the injection unit and the cavity of the dies
results in less entrapped air.
The injection unit of the instant invention includes an
injection plunger which displaces the molten metal from the
injection sleeve through a short runner directly into the die
cavity. The die filling is less affected by gravity than most
existing machines. The injection system fox a die casting
machine disclosed herein has a metal to air ratio of 80/90%
compared with 30% for some conventional machines.
The injection unit of the instant invention includes a
temperature control system associated with the injection
plunger such that the temperature of the injection plunger may
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be controlled to improve the speed of each cycle and thus the
speed of the machine. In the machine of this invention
removal of the casting and filling of the injection sleeve can
be carried out simultaneously once the dies have opened.
The applicant's earlier Canadian Patent Application
Number 2,045,879-8 entitled Die Casting Machine disclosed an
improved die casting machine which has a frame comprising two
opposed fixed end platens separated by two connecting rods, a
moving platen being mounted on said connecting rods. The
moving platen and the opposed fixed platen have dies mounted
thereon for closing arid clamping prior to casting. The patent
application also discloses a novel and an improved injection
system in which said injection system is disposed in close
proximity to the fixed die so that the injection nozzle may be
inserted in the bottom portion of the fixed die below the
cavity.
The injection unit of this invention differs in important
respects from the invention disclosed in the earlier
application referred to above. In the invention which is the
subject matter of this invention the liquid metal is ladled or
otherwise transferred directly into the opening at the top of
the injectian unit receiver of the injection sleeve. The
volume of the liquid metal which must be injected varies from
casting to casting. To minimize air entrapment the bottom
position of the injection plunger is adjusted so that the
volume of the interior of the injection sleeve is
substantially topped up with molten metal whether the casting
calls for a small volume or larger volume of metal. Other
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differences include temperature control of the injection
plunger and temperature control of the injection sleeve. A
still further difference is the projecting shape of the
injection plunger head which is so shaped as to reduce the
size of the biscuit left cooling in the top of the injection
sleeve when the casting is cooled. The injection plunger is
retracted as soon as the metal has solidified. The biscuit
cooling on the top of the injection sleeve remains attached to
the runner and casting and is removed from the part line with
the withdrawal of the moving platen and moving die. The
biscuit and runner are subsequently trimmed from the casting
during the trimming operation. The fact that the biscuit is
limited in size and is removed with the moving die leaves the
top of the injection sleeve free of debris and ready for
filling for the next shot.
One embodiment of the invention is an injection unit for
a cold chamber die casting machine having a part line on which
the dies meet, the injection unit being comprised of an open
upwardly inclined injection sleeve, an injection plunger,
means to advance and retract the injection plunger and means
to control the extent of retraction of the injection plunger,
the top of the injection sleeve being disposed at or proximate
the part line.
Another embodiment of the invention is an injection unit
for a cold chamber die casting machine having a part line on
which the dies meet, the injection unit being comprised of an
open upwardly inclined injection sleeve, an injection plunger,
means to advance and retract the injection plunger and means
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to control the extent of retraction of the injection plunger,
the top of the open upwardly inclined injection sleeve being
disposed at the part line, the bottom of the stroke of the
injection plunger is within the injection sleeve and is
adjusted to enable the injection sleeve to be substantially
filled to the top with molten metal when the dies are open.
A further embodiment of the invention is an injection
unit fox a cold process die casting machine having a part line
on which the dies meet, an injection unit receiver mounted
below one of the dies on the part line, the injection unit
being comprised of an open upwardly inclined injection sleeve,
an injection plunger, means to advance and retract the
injection plunger and means to control the extent of
retraction of the injection plunger, the injection sleeve is
open and upwardly disposed, an injection unit receiver mounted
below the fixed die on the part line adapted to receive the
upwardly inclined injection sleeve of the injection unit.
Another embodiment of the invention is an injection unit
for a cold chamber die casting machine having a fixed die with°
an upwardly inclined aperture therein and a moving die, the
upwardly inclined aperture in the fixed die is adapted to
receive the upwardly inclined injection sleeve of the
injection unit in the aperture therein
In still a further embodiment of the invention there is
provided an injection chamber for a cold process die casting
machine having a part line on which the dies meet, the
injection unit comprised of an open upwardly inclined
injection sleeve, an injection plunger and means to advance
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and retract the injection plunger, an injection unit receiver
mounted below the fixed die on the part line adapted to
receive the upwardly inclined injection sleeve of the
injection unit, in which the moving die closes on the fixed
die and the injection unit receiver prior to the advance of
the injection plunger of the injection unit.
The invention also relates to a method of injecting
molten metal in a cold chamber die casting machine having a
moving die and a fixed die, the fixed die fastened to a fixed
platen, the fixed die and moving die meeting on the part
line,. an injection sleeve having a retractable plunger
therein disposed at a vertical or inclined angle at or
proximate the part line, the retractable plunger being adapted
to receive or dispel molten metal therefrom, the method
comprising the steps of
(a) opening the moving die sufficiently to fill the
injection sleeve at the part line substantially to the top
with molten metal,
(b) closing the moving die on the fixed die and top of
the injection sleeve,
(c) operating the injection plunger to inject the molten
metal into the dies.
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In the drawings:
Figure 1 is a side elevation view of a cold chamber die
casting machine with an injection unit connected to the end of
the machine to which the fixed platen and fixed die are
connected.
Figure 2 is a perspective view of the injection unit
connected to the machine base at one end of the cold chamber
die casting machine.
Figure 3 is a cross-sectional view along the longitudinal
centerline of the injection unit showing the injection plunger
in open position adapted to receive hot liquid metal.
Figure 4 is a cross-sectional view along the longitudinal
centerline of the top of injection unit showing the
relationship of the injection unit to the closed left and
right hand side dies during the injection step.
Figure 5 is a cross-sectional view along the longitudinal
centerline of the injection unit showing a protruding cooled
nose extending from the face of the left hand side die in
close proximity to an injection plunger with a flat face.
Figure 6 is a perspective view of a 4-tie bar cold
chamber die casting machine with toggles.
Figure 7 is a cross-sectional view through a cold chamber
die casting machine in which the injection unit is disposed in
a bevel sleeve in an aperture in the base of the fixed die.
Referring to Figure 1, there is shown a cold chamber die
casting machine 1 with an injection unit 2 mounted on the
right hand end of the cold chamber die casting machine 1. The
cold chamber die casting machine 1 is comprised of a die
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casting machine base 3. A fixed right hand platen 4 is
mounted towards the right hand end of die casting machine base
3 and a fixed left hand side platen 5 is mounted above the
left hand end of die casting machine base 3. The fixed right
and left hand platens 4, 5 have rods 6,7 mounted therethrough.
A moving platen 8 is mounted on rods 6, 7 for movement towards
the fixed right hand platen 4 or withdrawal from fixed right
hand platen 4. The moving platen 8 is moved towards fixed
left hand side platen 5 or withdrawn from fixed left hand side
platen 5 by hydraulics, toggles or other mechanical means
known in the art represented by number 9. Cooling base 10 and
moving die 11 are mounted on moving platen 8. Fixed platen
cooling base 12 and fixed die 14 are mounted on fixed right
hand side platen 4.
As seen in Figures 1 and 2 injection unit 2 is mounted by
front and rear brackets 20, 21 and injection unit support arms
22, 23 to the right hand end of die casting machine base 3 and
fixed right hand side platen 4 respectively.
The injection unit 2 is comprised of an injection
cylinder 24 having a piston 25 mounted near the base of the
injection cylinder 24 for movement of the injection plunger 28
towards and away from the fixed right hand side platen 4,
cooling base 12 and fixed die 14. A piston rod 26 is
connected at one end to the piston 25 and at the other end to
the piston rod - injection plunger connecting link 27. the
piston rod - injection plunger connecting link 27 is connected
at its upper end to injection plunger 28.
As seen in Figure 1, the moving die 11 is mounted on
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cooling base 10 which in turn is mounted on moving platen 8.
As seen in Figure 4, the face of moving die 11 closes on the
part line immediately prior to injection, during injection and
until the injected metal solidifies sufficiently to withdraw
the moving platen 8, cooling base 10 and moving die 11 away
from the fixed die 14 mounted on fixed platen cooling base 12.
The face of moving die 11 attached to cooling base 10 attached
to the moving platen 8 includes a runner 30 through which the
molten metal 31 travels to the cavity 32 remaining between
moving die 11 and fixed die 14.
Figure 5 discloses an injection plunger 28 having a flat
face as opposed to the nose of the injection plunger 28 shown
in Figure 4. The left hand die 11 has a protruding cooled
nose 37 which extends across the part line between the left
hand die 11 and right hand die 14 when the dies are closed.
When the dies are opened after the casting has solidified, the
casting, runner and biscuit 35 are withdrawn with the left
hand die 11 which is connected to the left side moving platen
8.
Referring to Figure 4, the fixed die 14 terminates at a
downwardly inclining angle adapted to receive injection unit
receiver 33 which may be fastened to and removed from the
downwardly inclined base of fixed die 14. Injection unit
receiver 33 has a cylindrical opening 34 adapted to receive
injection sleeve 29 forming the outside portion of the
injection unit 2.
Referring to Figure 7, a fixed die is disclosed which has
a cylindrical opening 34 adapted to receive injection sleeve
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29 forming the top part of the injection unit 2. The
injection sleeve 29 shown in Figure 7 extends close to the
face of fixed die 14. The fixed die of Figure 7 differs from
the fixed die of Figure 4 in that the fixed die of Figure 7
does not have a lower downwardly inclined base adapted to
receive an injection unit receiver 33 as shown in Figure 4.
Referring to Figure 4 the injection sleeve 29 may be
withdrawn from the opening 34 in the injection unit receiver
33 if the piston injection sleeve 29, piston 25, piston rod 26
or piston rod-injection plunger connecting link 27 require
adjustment or repair. Likewise the injection sleeve 29 may be
removed from the cylindrical opening 34 in fixed die 14. The
range of movement of piston 25 in injection cylinder 24 is
adjusted with each die so as to reduce air at the top of the
injection sleeve 29 to a minimum during filling of the
injection sleeve 29 with molten metal and secondly to limit
the size of the biscuit 35 remaining above the injection
plunger 28 when the casting 36 cools.
While the injection unit 2 is shown i.n Figures 1 to 3
mounted on the right hand end of the cold chamber die casting
machine 1 in such a manner that the injection unit 2 extends
upwardly at forty-five degrees relative to the right hand end
of the cold chamber die casting machine 1, it will be
appreciated by those skilled in the art that the angle of the
injection unit 2 relative to the dies may extend from
vertical, where the injection power unit 2 would be located
under the part line on which the moving die 11 and the fixed
die 14 meet anywhere up to approximately 20° relative to
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horizontal where the benefits of gravity and control of air
entrapment are greater.
As seen in Figures 1 and 3 the moving platen 8 is
withdrawn from the fixed right hand side platen 4. The top of
the injection sleeve 29 is open at the part line and adapted
to receive molten metal. The injection plunger 28 has been
withdrawn within the injection sleeve to a position such that
when the injection sleeve 29 is filled with molten metal the
injection sleeve 29 will be substantially topped up with metal
decreasing air entrapment during the injection cycle. When
the injection sleeve 29 is filled, the moving left hand side
platen is moved towards the part line until the moving die 11
closes on the fixed die 14 as shown in Figure 4. Following
the closing of the moving die 11 and fixed die 14 the dies are
clamped shut prior to injection of the molten liquid. After
clamping the injection plunger 28 is advanced towards the part
line driving the molten liquid in the injection sleeve 29 into
the runner 30 and cavity 32 between the moving die 11 and the
fixed die 14. When the molten liquid has solidified into a
casting, the left side moving platen 8 is withdrawn from the
part line. The casting, runner and biscuit 35 are withdrawn
with the moving die 11 which is connected to the left side
moving platen 8. The casting, runner and biscuit 35 are
subsequently removed from the moving die 11 and runner 30 by
ejection pins prior to commencement of the next cycle. The
injection plunger 28 is withdrawn within injection sleeve 29
prior to the addition of molten metal to the injection sleeve
29 as part of the next cycle.
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While the injection power unit has been described herein
with respect to a cold chamber die casting machine 1 having a
fixed platen and a moving platen, it will be recognized by
those skilled in the art that the power injection unit of this
invention may be adapted for use with any cold chamber die
casting machines which have been suitably adapted without
departing from the scope of the invention.
