Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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TITLE: SEALING ARRANGEMENT FOR A MOVABLE INSERT FOR A
DIE CASTING MOLD HAVING A RETRACTABLE CORE
INVENTOR: CONSTANTIN ELIAT
FIELD OF THE INVENTION
This invention relates to movable inserts for a die-casting mold and more
particularly to such inserts which incorporate a movable core and still more
particularly to sealing between the movable insert and the retractable core.
BACKGROUND OF THE INVENTION
An earlier invention, as described in U.S. Patent No. 5,862,853 which
issued on January 26, 1999, comprises a movable insert for a die-casting mold
having a cavity in which a core is mounted and slidable between a retracted
position in the cavity and an extended position in which the core extends from
the
movable insert.
Figure 1 is a sectional view through a prior art die-casting mold assembly,
generally indicated by reference 10 for casting a part 12 having an opening or
boss
14 extending therethrough which is non-parallel to a "machine direction"
indicated
by arrows 16. The opening 14 is narrower at a point 17 part way along its
length
than it is toward either end.
The mold assembly 10 includes a movable insert 18, a fixed insert 20 and a
slide 22. The mold assembly 10 is generally opened and closed in the machine
direction. The slide 22, as indicated by arrows 24, is inserted and removed
from
the balance of the mold assembly 10 in a direction non-parallel to the machine
direction.
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The slide 22, in combination with a retractable core 26 is used to form an
interior surface which defines the opening 14. The retractable core 26 forms
the
portion of the interior surface of the opening 14 between the movable insert
18 and
the point 17. The slide 22 forms the remainder of interior surface of the
opening
14.
As the part 12 is stripped in the machine direction, obviously it is necessary
to separate and withdraw the retractable core 26 and the slide 22 from the
opening
14 to enable the part to be separated from the movable insert. The slide 22 is
withdrawn to the right as illustrated in the direction of arrows 24. The
retractable
core 26, as its name suggests, is retracted into a cavity 28 in the movable
insert.
Movement of the retractable core 26 is controlled by a locator 62.
Figures 2 and 3 are sectional views illustrating the relationship between the
movable insert 18 and the retractable core 26 in more detail. In Figure 2 the
retractable core is illustrated in a retracted position in which it doesn't
protrude
from the movable insert 18. In Figure 3 the retractable core is illustrated in
an
extended position in which it extends from the movable insert 18. The extended
position corresponds to the molding of the part 12. The retracted position
corresponds to the stripping of the part 12.
It is of course necessary to prevent molten metal from seeping past the
retractable core 26 into the cavity 28 to prevent the retractable core 26 from
becoming "stoned" in metal (i.e., frozen in place). In the prior art
arrangement, as
best illustrated in Figures 2 and 3, sealing was accomplished by the mating of
corresponding tapered surfaces 30 and 32 respectively on the retractable core
26
and the movable insert 18. This arrangement however has some drawbacks. Very
accurate machining is required to match the tapered surfaces 30 and 32 to give
an
effective seal relative to each other. Furthermore the tapered surfaces 30 and
32
must be accurately situated for the surfaces 30 and 32 to abut when the
retractable
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core 26 is in its extended position. Any inaccuracies in the situation of the
tapered
surfaces 30 and 32 will either leave a gap therebetween or prevent the
retractable
core from fully extending. A relatively small degree of wear on the tapered
surfaces 30 and 32 resulting from repeated retraction and extension of the
retractable core 26 will eventually cause the seal between the tapered
surfaces 30
and 32 to lose effectiveness. Once this occurs there is no simple way to
restore the
sealing surfaces as lapping or grinding will give a resultant seal which is
only
effective at a greater degree of extension of the retractable core 26. Further
extending the retractable core 26 is undesirable as it affects the location of
the
portion of the inner surface of the opening 14 which is to be formed thereby.
Finally, there is no "wiping" action upon extension and retraction to prevent
any
solid particles from coming between and interfering with the seal between the
tapered surfaces 30 and 32.
It is therefore an object of the present invention to provide a sealing
arrangement between a retractable core and a movable insert which is not
position
sensitive, which is tolerant of wear between the retractable core and the
movable
insert, which is relatively simple to refurbish and which is tolerant of the
presence
of dirt or other solid particles.
SUMMARY OF THE INVENTION
A movable insert for a die-casting mold, the movable insert having a cavity
with substantially parallel sides extending thereabout and a core slidably
mounted
in the cavity. The core is slidably movable between an extended position in
which
it extends beyond the movable insert and a retracted position in which it does
not
extend from the movable insert. The core has a connector for releasable
attachment to a locator which moves the core between its retracted and its
extended positions. A sealing member extends about the core, between the core
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and the sides of the cavity wall to provide a slidable seal between the core
and the
sides.
The sealing member may be a resilient metal ring which may be received in
a groove extending about the core. The sealing member may be annular and of
cast iron or stainless steel.
DESCRIPTION OF DRAWINGS
Preferred embodiments of the present invention are described below with
reference to the accompanying drawings in which:
Figure 1 is a sectional view through a prior art die-casting mold assembly;
Figure 2 is a sectional view through a prior art movable insert having a
retractable core which is illustrated in a retracted position;
Figure 3 is a sectional view corresponding to Figure 2 but showing the
retractable core in an extended position;
Figure 4 is a sectional view through a movable insert according to the
present invention, showing a retractable core in its retracted position;
Figure 5 is a sectional view corresponding to Figure 4 but showing the
retractable core in an extended position; and
Figure 6 is an isometric view illustrating a retractable core according to the
present invention and a locator.
DESCRIPTION OF PREFERRED EMBODIMENT
A movable insert for a die-casting mold according to the present invention
is generally indicated by reference 50 in Figures 4 and 5. The movable insert
50
includes a cavity 52 having substantially parallel sides 54. In most cases the
cavity
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sides '.>4 will be cylindrically disposed however this is not an absolute
requirement.
A retractable core 56 is slidably mounted in the cavity 52 for movement
between a retracted position, as illustrated in Figure 4, and an extended
position,
as illustrated in Figure 5. In the retracted position, the retractable core 56
is
substantially housed within the movable insert 50 and does not extend
therefrom.
In the extended position the retractable core 56 extends from the movable
insert 50
to present a mold face 58.
A connector 60, described in more detail below, is provided on the
retractable core 56 for releasably connecting the retractable core 56 to a
locator 62
which vmoves the retractable core 56 between its extended and its retracted
positions.
~~ sealing member 64 extends about the retractable core 56 and extends
between the retractable core 56 and the cavity sides 54. The sealing member 64
1 S may be; a resilient metal ring received in a groove 66 extending about the
retractable core 56. The sealing member 64 is preferably of stainless steel or
cast
iron, such as used for piston rings of internal combustion engines. Most
preferably
the seal'.ing member is of cast iron which appears to have better temperature
stability than stainless steel. The sealing member 64 will typically have a
gap 65
along its circumference to allow it to be expanded for mounting over the
retractable core 56. The breadth of the gap should be selected so as to be
substantially closed at operating temperatures to prevent metal seepage
therethrough.
?gin advantage of the arrangement of the present invention is that the
resiliently expansive nature of the sealing member 64 allows it to maintain a
closer
spacing with the walls 54 of the cavity 52 than between the walls 54 of the
cavity
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and the retractable core 56. Furthermore, the resiliently expansive nature of
the
sealing member 64 enables it to accommodate wear along the cavity walls 54.
As the walls 54 of the cavity 52 are substantially parallel and lack the
tapered surfaces 30 and 32 of the prior art, it will be apparent that lateral
positioning of the retractable core 56 does not determine the effectiveness of
the
seal between the retractable core 56 and the cavity 52. Accordingly, unlike
the
earlier arrangement, the present arrangement allows the stroke of the
retractable
core 56 to be adjusted to adjust part accuracy.
Should the parts of the movable insert 50 become overly worn,
refurbishment is a relatively simple matter and includes various options such
as:
boring and sleeving the cavity 52; honing the cavity 52 and fitting an
oversize
sealing member 64; and, boring the cavity 52 and fitting suitably dimensioned
retractable core 56 and sealing member 64.
As in the previous arrangement, the retractable core is moved between its
retracted and extended positions by a locator 62. The interrelationship
between the
locator 62 and the retractable core 56 is best seen in Figure 6. The locator
62 is
coupled and uncoupled from the retractable core 56 by a connector comprising
radially inwardly extending projections 70 surrounding a recess 72 extending
into
the retractable core and corresponding radially outwardly extending
projections 76
on an end of the locator 62. The connector 60 is movable between engaged and
disengaged positions: In the disengaged position, which is shown in Figure 6,
the
outwardly extending projections 76 on the locator 62 and the inwardly
extending
projections 70 on the retractable core 56 are misaligned so that the locator
62 may
be inserted into or removed from the recess 72 in the retractable core 56. In
the
engaged position, which is shown in Figure 5, the outwardly extending
projections
76 are aligned with the inwardly extending projections 70 as to register
therewith
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and enable the locator 62 to withdraw the retractable core 56 from the cavity
52
into its extended position.
Movement of the locator 62 may be controlled by a positioning device such
as described in U.S. Patent No. 5,862,853 referred to above or the improved
device in U.S. Patent No. 5,843,494. The latter is generally depicted by
reference
80 in Figure 6.
Preferably means should be provided to lock the retractable core 56 in its
extended and retracted positions. Failure to lock the retractable core 56 in
its
extended position may result in the pressure of the molten metal being
injected
tending to move the retractable core 56 into the cavity 52. Failure to lock
the
retractable core 56 in its retracted position may result in the retractable
core 56
being at least partially sucked into its extended position by removal of a
slide 78
adjacent thereto.
As illustrated in Figure 5; a wedge shaped abutment member 90 may be
slidably inserted between a rear face 92 of the retractable core 56 and a rear
wall
94 of the cavity 52. Slidable movement of the abutment 90 in a direction shown
by
arrows 96 may be effected by a hydraulic cylinder (not shown) having a rod 98
connected to the abutment member 90.
As illustrated in Figures 4 and 5, to prevent movement of the retractable
core 56 out of its retracted position, a core lack may be provided which
includes a
first component in the form of a recess 100 in an end of the abutment member
90
which registers and may be pressed into engagement with a corresponding
projection 102 formed in the retractable core 56 adjacent its rear face 92.
Movement of the projection 102 into the recess i00 may be effected by action
of
the rod 98. It will be appreciated that this is but one possible configuration
for the
core lock. For example, a projection may be provided on the abutment 90 which
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registers with a corresponding recess in the retractable core 56.
Alternatively both
projection recesses may be provided on each component.
The above description is intended in an illustrative rather than a restrictive
sense. Variations may be apparent to persons skilled in such apparatus without
departing from the spirit and scope of the invention as defined by the claims
set
out below.
