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Патент USA US3065520

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Nov. 27, 1962
Filed May 27, 1960
2 Sheets-Sheet 1
Nov. 27, 1962
Filed May 27, 1960
2 Sheets-Sheet 2
United States
Patented Nov. 27, 1962
adjacent surface of the cold chamber. The space 30 is
Robert ‘W. Parker, Erie, Pa., ass‘ignor to Parker White
Metal Company, Erie, Pa., a corporation of Pennsyl
Filed May 27, 1960, Ser. No. 32,170
1 Claim. (Cl. 22-73)
conveniently formed by a taper 32 on the end of the
plunger which provides an annular crack between the
extreme outer end 31 of the plunger and the inner surface
of the cold chamber. The width of the crack is such
that the molten metal will not flow by gravity into the
space 30. This is a well-known property of metal. For
the temperatures encountered in die casting, molten metal
will not ?ow into a crack having a width of the order
This invention is a cold chamber vacuum die casting
machine which evacuates air from the cold chamber and 10 of ?fty thousandths of an inch. This is true even if the
space 30 is evacuated so that the molten metal is also
mold cavity without entraining molten metal which would
subjected to atmospheric pressure. Furthermore, since
clog the vacuum lines.
the plunger 11 is cooled, the metal coming into initial
In the drawing, FIG. 1 is a diagrammatic view of a die
contact with the outer end of the plunger is chilled as
casting machine, FIG. 2 is a vertical transverse section
through the pour opening and cold chamber, FIG. 3 15 indicated at 34 and this still further restricts the possibility
of flow of molten metal into the space 30. There may
is a section on line 3—3 of FIG. 1, FIG. 4 is an enlarged
be some slight bowing of the metal into the space 30 as
fragmentary view showing the behavior of the metal dur
indicated at 35, but for all practical purposes the metal
ing evacuation, and FIG. 5 is a similar view at right angles
is eifectively kept out.
to FIG. 4.
While the space 30 is a restricted space so far as the
In the drawing, the conventional elements of the die 20
molten metal is concerned, it is a very large opening so
casting machine are readily identi?ed, 1 being the sta
far as air is concerned and in no way interferes with
tionary platen, 2 the movable platen, 3 and 4 the sta
the evacuation of the cold chamber and mold through the
tionary and movable parts of the mold, 5 the cold cham
suction way 29. If di?iculty is encountered in speed of
ber into which metal 6 is poured through a pouring hole
or opening '7, and 8 the knockout plate carried on rod 9 25 evacuation, the upper part of the cold chamber below
the way 29 may be crowned as indicated by dotted lines 36
and having knockout pins 10' slidable through the mov
in FIGS. 4 and 5 and this will still further enlarge the
able mold 4 to eject the cast parts as the mold is opened.
space through which air may ?ow into the suction way
In the sequence of operations, after the mold is closed
29. The crowning indicated by dotted lines 36 do not in
molten metal is poured into the cold chamber ‘5 through
the opening 7, partially ?lling the chamber, and this metal
any way permit molten metal to enter the space 30. The
is forced by a water cooled pressure piston or shot plunger
11 through sprue opening 12 into the mold cavity 13.
level of molten metal indicated by numeral 37 is well
below the top of the cold chamber and is also well be
After ?lling of the mold cavity, the mold is opened and
during the opening movement the knockout pins 10' eject
low the enlargement produced by the crowning 36. Under
4. No attempt has been made to describe the die open
ing and closing mechanism. The controls and the asso
the suction there is some ?ow of air in the direction of
arrows 38 and 39 but the greater part of the air ?ows in
the direction of the arrows 40 which is in a direction
in which there is little tendency for the air to pick up and
ciated structure are common to die casting machines.
The parts so far described are in common use in the die
entrain droplets of molten metal. Even if particles of
molten metal were picked up by the air, they would not
the ?nished parts and sprue from the movable mold part
casting industry and may differ substantially in appear 40 flow into the narrow crack between the cold chamber and
the outer end 31 of the plunger.
ance from those illustrated.
The mold parts 3 and 4 carry sealing rings 1-4 and 15
providing a sealed chamber surrounding the parting line
This construction eliminates a very troublesome prob
lem in vacuum die casting. Where the vacuum is applied
17 of the mold. The movable mold part 4 is sealed to 45 directly above the surface of molten metal such as would
an annular ring 18 surrounding the back surface of the
be the case if it were applied directly to the pour opening
7, the air picks up and entrains ?ne droplets of molten
mold and providing a chamber 19 between the back sur
face of the mold and the movable platen 2. The knock
metal which follow the air, even as far as the pump.
out plates 8 and pins 10 operate within the chamber 19.
While it is possible to separate from the air a few drop
The chambers 16 and 19 are maintained under vacuum 50 lets of metal by the use of traps and similar separators, if
by a vacuum line 20 connected to a suction pump 21.
more than a few droplets of metal are entrained, the
The parts so far described are disclosed in greater detail
entrainment of molten metal is progressive and very quick
in application Serial No. 745,943, ?led July 1, 1958, now
rly a solid mass of molten metal is drawn into the suction
lines, forcing a machine shut-down. With the present
While there is some evacuation of the mold cavity 55 construction, this is not possible. In the ?rst place, the
through the vacuum maintained in the chambers 16 and
air is sucked out of the chamber over the chilled outer
19, the primary evacuation is in the cold chamber 5
end of the plunger where the molten metal has already
under the control of a slide valve 22 having a way 23
begun to set up. Furthermore, the highest velocity air
connected to a line 24 leading to the Vacuum pump 21.
which would have the greatest tendency to pick up molten
The slide 22 is of circular cross section and is slidably
metal, flows through a crack so restricted that molten
guided in a bore 25 in the cold chamber 5. In the
metal will not ?ow through the crack under atmospheric
position shown in FIG. 2 an opening 27 in the slide reg
pressure. It is accordingly possible to obtain a high
isters with the pouring hole 7 for the cold chamber so
degree of evacuation of the space above the metal in
that molten metal can be poured into the chamber by any
the cold chamber and of the mold cavity without run
suitable means. In this position, the way 23 is sealed 65 ning the risk of metal entrainment. When the evacuation
against the inner surface of the bore 25. When the de
is completed, the shot plunger 11 is advanced and the
sired amount of molten metal has been poured into the
metal in the cold chamber is forced under high pressure
cold chamber 5 (enough to partially ?ll the cold cham
into the mold cavity. Of course, under pressure the metal
ber as shown in FIGS. 1 and 2), the slide 22 is moved
is forced into the space 30 surrounding the end 31 of the
to the left as viewed in FIG. 2, bringing the way 23 into
plunger. However, when the mold is opened at the
end of the cycle, the metal which ?lled the space 30 is
register with a way 29 (FIG. 3) leading to a restricted
part of the sprue and is forcibly separated from the outer
space 30 between the end 31 of the plunger 11 and the
end 31 of the plunger so that at the beginning of the next
cycle the space 39 is open.
charge of molten metal may be poured into the cold
chamber cylinder when the shot plunger is in its retracted
The vacuum can be added to existing die casting ma
position, said charge partially ?lling the cold chamber
chines Without modifying the control. As the slide valve
22 is moved to the pouring position shown in FIG. 2,
a valve 23 in line 24 is opened. When the pouring is
completed, the slide 22 is moved to the vacuum position
connecting the Way 23 with the way 29 and evacuating the
cold chamber and mold cavity. The evacuation takes
cating with the mold cavity, said cylinder having a way
in the upper part opposite the tapered end of the shot
plungerin the retracted position, the tapered end of the
shot plunger providing a crack between it and the part
of the cylinder having said way, said crack having a
cylinder and leaving a space above the metal communi
only a few seconds. A simple timer or other control 10 maximum width of the order of ?fty thousandths of an
set in operation by movement of the slide valve 22 to the
inch so that air will flow freely from the cold chamber
vacuum position can shut the valve 23 when the desired
into the crack but molten metal will not ?ow into the
vacuum is reached and initiate the machine control to
crack under atmospheric pressure and the crack is metal
complete the casting cycle. The closing of the valve
free in back of the molten metal after delivery of metal
28 prevents connection of the vacuum line 24 to the
to the cold chamber, suction means, valve means for
atmosphere when the mold is opened at the end of the
closing said pour opening and for connecting said suction
casting cycle.
What is claimed as new is:
A die casting machine of the cold chamber type in
which the molten metal is ?rst delivered to the cold
chamber and then mechanically transferred to a mold
cavity under pressure comprising, a horizontal cold cham
ber cylinder closed at one end by a shot plunger having
a tapered end and connected at the other end to a mold,
said cylinder having a pour opening in its upper part ad
jacent said one end of the cylinder and in front of the
shot plunger in its retracted position through which a
means to said way to evacuate the cold chamber and the
mold cavity through said crack without entraining molten
References Cited in the ?le of this patent
Pack ________________ __ Nov. 14, 1933
During et al ___________ __ Apr. 10, 1934
Hodler ______________ __ Dec. 18, 1956
Morgenstern __________ __ Oct. 11, 1960
Cornell ______________ __ Feb. 6, 19612
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