Note: Descriptions are shown in the official language in which they were submitted.
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VIBRATORY ME:THOD FOR PACXING FOUNDRY SAND INTO
A PI~TTERN PRIOR TO THE POURING OF MOLTEN METAL
Metal casting operations have long employed
the combination of a pattern set in a mold flask and
with foundry sand compacted therearound to form the
desired shape. In the normal operation, the pattern
is then withdrawn from the sand and molten metal poured
in the place previously occupied by the pattern which
causes the metal to assume the shape of the pattern~
More recently, a modi~ied system is employed
wherein the pattern is made of a material which is
converted to gas when contacted by the molten metal.
With such patterns, it is not necessary to remove the
pattern prior to casting and the result has been the
ability to utilize more complicated patterns, i.e,
patterns with more complex configurations such as
internal passages, cavities, and the like.
In an effort to cause the foundry sand to
fill cavities and the like in patterns, a system has
been used wherein air is in~roduced into the bottom of
the mold flask and flows upwardly through the sand with
the intent being that the force of the moving air will
in effect blow the sand into the cavities. While this
method is effective for relatively simple patterns, it
has not been completely effective where the pattern
contains a number of internal passages, cavities, and
the like.
- In accordance with the present invention, the -
casting process causes the sand to fill a~ ca~ities,
internal passages, etc., in a pattern by utilizing a method
introducing foundry sand into a mold flask containing a
pattern, then subjecting the mold flask to vibratory move-
ment at a frequency and stroke to produce accelerations
on the mold flask and contents thereof in excess of the
acceleration due to gravity to cause the sand to fill all
openings in the pattern. Then the mold flask is subjected
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to vibratory movement at a frequency and stroke to produce
accelerations on the mold flask and contents thereof less
than the acceleration due to gravity to pack the sand in
place.
In a variation of the inventive method, the pattern
in the mold flask is of a material which substantially
entirely vaporizes when contacted by molten metal.
In a further embodiment, the two vibratory move-
ments to which the mold flask is subjected is substantially
vertical.
In a preferred embodiment the first vibratory
movement of the mold flask is at a frequency of the order
of 3600 cycles per minute with a stroke having an amplitude
of the order of 0.007 inches, and the second vibratory
movement is at the same frequency but with an amplitude of
0.0045 inches.
Fig. 1 is a vertical sectional view showing a
mold flask in a pattern suspended therein;
Fig. 2 is a view like Fig. 1 illustrating the
introduction of foundry sand into the mold flask;
Fig. 3 is a side elevational view (partly in
section) showing the mold flask, pattern and sand fixed in
position on a vibratory apparatus;
Fig. 4 is a vertical sectional view illustrating
the operation of pouring molten metal into the mold flask;
and
Fig. 5 is a vertical sectional view showing the
resulting metal cast into the shape of the pattern.
The drawings described above illustrate the
steps of the process which is the subject matter of this
invention. Thus there is shown a mold flask 10 with a
pattern 11 suspended therein by suspension means 12.
Whi~e the pattern may be of any conventional material,
the process of the present invention is particularly
useful when dealing with complex patterns which, by
their very complexity, cannot be removed from the mold
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box and sand prior to pouring the molten metal. Rather,
these comple~ patterns are made of material which gasi-
fies when contacted by the molten metal, such as poly-
urethane foam and Styrofoam.
The complexities of the pattern 11 are
schematically illustrated by the cavities 13 and the
passage 14 which may be a dead-end passage in the
pattern.
With the pattern suspended in place as shown
in Fig. 1, sand is introduced by means of a conveyor 16
to fill the mold flask completely. The filled mold
flask is then placed upon a vibratory apparatus 17 which
includes a base 18, and a bed 19 suspended above the
base by springs 20. Vibration generators 21 in the form
of electric motors 22 having shafts carrying eccentric
weights 23 are suspended from the bottom of the bed 19
in order to produce the vibrations. Preferably, the
vibration generators 21 are of the type shown in my
United States patent No. 3,358,815, where the effective
force of the eccentric weights may be varied from zero
to maximum and thus produce a variation in stroke as
desired.
The mold flask 10 either is clamped to the
bed 19 by clamps 24 or is positioned in an-unclamped
state on the bed 19. The vibration generators are then
energized to produce a vibratory force on the mold flask
and its contents in excess of the acceleration due to
gravity. The acceleration in g's can be calculated by
the formula S x F2 where S is the amplitude of the stroke
70400 ~-
and F is the frequency of the stroke. For example, with
a frequency of 3600 strokes per minute and a stroke
amplitude of .007 inches, there is produced an accelera-
tion of 1.29 g's on the mold box and its contents. This
acceleration causes the sand to flow into and completely
fill the cavities 13 and passage 14 even though those
passages may be dead-ended. If the pattern contains
~ven finer passages, the result is still to fill those
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passages completely. After a few minutes of vibration
at accelerations in excess of gravity, the stroke of
the vibratory apparatus is reduced thereby to reduce
the accelerations to a force less than the accelera-
tion due to gravity. Thus, maintaining the frequencyat 3600 cycles per minute and reducing the amplitude of
the stroke to .0045 inches reduces the force to 0.92 g's.
The effect of the acceleration at less than one g for
several minutes is to compact the sand in place allowing
it to retain its position when the molten metal is
introduced into the mold flask.
In Fig. 4 I have illustrated the introduction
of molten metal into the flask, the molten metal being
given access to the pattern by a short passage, and the
effect of contact of the molten metal with the foam
pattern causes the latter to gasify, i.e., be converted
into gas which escapes and the metal takes on the form
o~ the pattern. The metal then is allowed to cool and,
as illustrated in Fig. 5, completely fills the space
previously occupied by the foam pattern and is formed
with a true reproduction of all the cavities and passages
that were formerly in the pattern.
The process of the present invention is par-
ticularly useful :in the aluminum casting of engine
cylinder blocks. By virtue of the process of this
invention, the patterns for the cylinder blocks can be
formed with coolant passages and other cavities and
passages, and the result of the casting process pro-
duces an engine cylinder block having-formed therein
the configuration just mentioned.
