Note: Descriptions are shown in the official language in which they were submitted.
CA 02635475 2008-07-15
1
DIE-CASTING APPARATUS
Background of the Invention
[0001] The present invention relates to die-casting apparatus; and
particularly to apparatus for forming die cast metal parts for various
machines
and products, including motor vehicles.
[0002] Die-casting is being used for the manufacture of larger and larger
articles. Large automotive parts such as internal combustion engine blocks
and the housings for automatic transmissions are now commonly
manufactured with die-casting as the first step in formation of the part. Such
parts have extensive and complex surfaces with close tolerances; and die-
casting permits their formation in high production, eliminating costly
machining
operations and saving metal. Die-casting requires extreme pressures exerted
on the liquid metal and large amounts of heat are released from the molten
metals as they cool and change state. Massive dies are required to maintain
dimensional tolerances within specified limits to make such operations
economically attractive and to provide the strength to withstand the stresses
resulting from high pressures and forces. The die-casting molds for such
large automotive parts as automatic transmission housings are, for example,
frequently seven to eight feet (2.1-2.5 meters) tall, seven to eight fee (2.1-
2.5
meters) wide, and six to seven feet (1.8-2.1 meters) thick when closed. The
die-casting molds must be manufactured from high-grade, high-tensile
strength steel.
[0003] Such dies frequently include one stationary element, one movable
element operated by the die-casting machine to close the mold, and several
slidable elements referred as "slides" that move transversely of the direction
of movement of the die-casting machine to provide a mold cavity, which can
provide intricate and re-entrant surface configurations. The mold slides,
which
slide transversely of the direction of movement of the die-casting machine,
are
generally moved by hydraulic cylinders to their proper positions. These
hydraulic cylinders have typically extended laterally outward from the die-
CA 02635475 2008-07-15
1)
casting machine at right angles by an additional distance at least equal to
the
movement dimension of the slide. By way of example, such outwardly
extending hydraulic cylinders used for movement of such slides can be seen
unnumbered in U.S. Patent 6,761,208, in U.S. Patent 5,865,241 as cylinders
38a and 38b, in U.S. Patent 4,206,799 as cylinders 55, in U.S. Patent
3,596,708 as cylinders 66 and 68, and in U.S. Patent 3,433,292 as cylinders
56, and on one occasion a die was placed in service having a pair of
piston/cylinder units for one of its plurality slides carried within one of
its die
elements.
[0004] The length of a typical hydraulic cylinder used for movement of a
slide in an automatic transmission housing or engine block can be as long as
two feet or longer including its connections with the source of hydraulic
pressure. The hydraulic cylinders used for movement of such slides often
extend laterally outwardly on all four sides of a die, sometimes imposing
limitations in the die casting machines in which a die can be used. The
hydraulic cylinders used for movement of such slides can thus contribute to
the footprint of floor space occupied by a die-casting operation and are
exposed to possible damage by nearby material handling and other industrial
operations.
[0005] In addition, the long piston/cylinder units require heavy supporting
structures extending outwardly from the die to not only carry the heavy
piston/cylinder units but also withstand the stresses imposed on the
supporting structures by the piston/cylinder units and their operations.
[0006] The hydraulic cylinders used for movement of such slides also
require hydraulic couplings leading to flexible hoses typically attached at
both
ends of the hydraulic cylinders to provide for a typical double action of the
pistons within the cylinders to cause both inward and outward motion of the
slides with respect to the cavity in which the die-cast article is to be
formed.
The hoses and couplings are further coupled to valves and controllers that are
located adjacent to the die-casting machine. The exposed hoses and
couplings are thus also exposed to a variety of impacts and abrasions that
CA 02635475 2008-07-15
can easily damage them to the point that any safety margin provided in
prudent design can be exceeded and may result in a hydraulic failure,
damage to the die, injuries to personnel, downtime and contribute to a whole
range of consequences.
[0007] Furthermore, the hydraulic hoses are made from materials that
expand when exposed to the high hydraulics pressures frequently
encountered in die casting operations. For example, it is a common practice
for operators of die casting dies to suddenly and repeatedly apply high
pressure shocks to the hydraulic cylinders driving the slides to loosen and
dislodge die cast parts that may not release from an open die cavity. The
desired sudden application of high pressure to jar the stuck part from the
mold
cavity is dampened and delayed by the expansion of the hydraulic hoses,
inhibiting the dislodging effect desired by the operator of the die.
[0008] Despite the various features and benefits of the prior die casting
dies, there remains a need for a more compact, lighter and reliable die-
casting
die. There also remains a need for a die-casting die that has inherently
higher
safety margins that will reduce the number and severity of any hydraulic
failures.
Summary of the Invention
[0009] These several needs may be satisfied by providing a die-casting die
having a plurality of laterally movable slides, with a plurality of hydraulic
cylinders located and carried internally within the die and connected with the
plurality of slides to move the slides between cavity-open and cavity-closed
positions.
[0010] A die of the invention for casting a metal part can comprise, for
example, a stationary die element including a cavity-forming surface for
mounting on the stationary platen of a die casting machine; and a movable die
element for mounting on a movable platen of a die casting machine for
movement into cavity-forming engagement with the stationary die element, the
movable die element including a cavity-forming surface portion, and carrying a
plurality of slides including cavity-forming surfaces for movement
substantially
CA 02635475 2010-07-21
71035-51
4
transversely with respect to the movement of the movable platen between
cavity-forming and part-removal positions, and a plurality of hydraulic
piston/cylinder units carried internally within the movable die element to
drive
the plurality of slides substantially transversely with respect to the
movement
of the movable platen between their cavity-forming positions and part-
removable positions. Preferably the movable die element is also formed to
include means for delivering hydraulic fluid from the hydraulic power source
to
the plurality of piston/cylinder units to move them between their cavity-
forming
and part-removable positions. Such a die of the invention can be lighter, have
a substantially smaller profile, and deliver significantly greater forces for
opening the slides and cavity than prior art dies and avoid limitations in the
selection of die casting machines with which the die can be used.
[0011] In one application the invention also permits an inexpensive die for
die casting a V-block for internal combustion engines, which may be operated
by a wide range of die casting machines, including those with inadequate
capacity to operate the heavy prior art dies used for large cast parts, by
providing , in addition to the elements set forth above, at least a pair of
cylinder-forming die core pieces carried by the movable die element for
reciprocation at an acute angle with respect to the movement of the movable
platen between extended positions within the die cavity and retracted
positions removed from the die cavity and with die core locking means
movably carried within the movable die element to a die core piece locking
position. Such a V-block die-casting die is disclosed in U.S. Patent No.
6,761,208.
CA 02635475 2010-07-21
71035-51
4a
In accordance with an aspect of the invention, there is provided a die
for die casting a metal part, comprising: a stationary die element including a
cavity-forming surface for mounting on a stationary platen of a die-casting
machine; and a movable die element for mounting on a movable platen of the
die-casting machine for movement into cavity-forming engagement with said
stationary die element, said movable die element including a cavity-forming
surface portion, and carrying a plurality of slides including cavity-forming
surfaces
for movement substantially transversely with respect to the movement of the
movable platen between cavity-forming positions and part-removal positions,
and
a plurality of hydraulic piston/cylinder units with their cylinders carried
internally
within the movable die element and their pistons extending outwardly from
within
the movable die element, said pistons having, at their extending ends,
interconnecting means, said interconnecting means being connected with and
driving the plurality of slides substantially transversely with respect to the
movement of the movable platen between their cavity-forming positions and
part-removal positions.
In accordance with another aspect of the invention, there is provided
a die for die casting a metal part, comprising: a plurality of die elements
and a
plurality of slides, said die elements and slides being operable between
closed
cavity-forming positions and open part-removal positions, said plurality of
slides
being moved between their cavity-forming and part-removal positions by a
plurality
of piston/cylinder units having cylinders and piston-driven rods; each of a
plurality
of slides being moved by an adjacent pair of the plurality of piston/cylinder
units
having their cylinders carried within a die element with their piston-driven
rods
extending from the die element to an extending end; each slide being connected
to the extending rods of the adjacent pair of piston/cylinder units, by an
interconnecting element, each interconnecting element having a pair of pockets
for receipt of the extending ends of the pair of extending rods, each said
pocket
having a bottom opening for each of the piston-driven rods of the adjacent
pair of
piston/cylinder units, said bottom opening providing a clearance space around
the
piston-driven rods, and a pair of fasteners, accessible from outside of the
interconnecting element, connecting the extending rods of the adjacent pair of
piston/cylinder units with the interconnecting element so that removal of the
CA 02635475 2010-07-21
71035-51
4b
fasteners permits the interconnecting element and slide to be removed from the
die without work on the piston/cylinder units.
In accordance with another aspect of the invention, there is provided
in a die for die casting a metal part including a stationary die element, a
movable
die element, and plurality of movable slides forming a cavity for casting the
part,
and a plurality of pairs of hydraulic piston/cylinder units connected to drive
the
movable slides between cavity-forming and part-removal positions, the
improvement wherein the plurality of pairs of hydraulic piston/cylinder units
include
cylinders carried within the movable die element with their pistons extending
outwardly from the movable die element and connected in pairs with the movable
slides, the movable slides being carried by the movable die element between
the
pairs of piston/cylinder units, said slides being connected with the pairs of
pistons
by interconnecting elements, said interconnecting elements providing pockets
for
connection with the pairs of pistons, said pockets having open tops and bottom
openings, the open tops of the pockets being closable by plates fastenable to
the
interconnecting element, said pairs of pistons being engaged at their
extending
ends with couplers within the pockets of the interconnecting element, said
open
tops of the pockets of the interconnecting elements permitting the couplers to
be
engaged with and disengaged from the ends of the pistons, said pockets and
plates providing engagement surfaces for the couplers permitting the slides to
be
driven between their cavity-forming and part-removal positions, removal of the
plates from the interconnecting element permitting removal of the
interconnecting
elements and the slides from the die without disconnecting the piston/cylinder
units.
In accordance with another aspect of the invention, there is provided
a die for die casting a metal part, comprising: a stationary die element
including a
cavity-forming surface for mounting on the stationary platen of a die-casting
machine; and a moveable die element for mounting on the movable platen of a
die-casting machine for movement into cavity-forming engagement with said
stationary die element, said movable die element including a cavity-forming
surface portion, and carrying a plurality of slides including cavity-forming
surfaces
for movement substantially transversely with respect to the movement of the
CA 02635475 2010-07-21
71035-51
4c
movable platen between cavity-forming positions and part-removal positions,
and
a plurality of hydraulic piston/cylinder units with their cylinders carried
internally
within the movable die element and their pistons extending outwardly from
within
the movable die element for connection at their extending ends with the
plurality of
slides, and interconnecting means between the extending ends of the pistons
and
the plurality of sides for driving the slides between their part-forming and
part-
removal positions without imposing bending forces on the hydraulic
piston/cylinder
units.
[0012] Other features of the present invention and the corresponding
advantages of those features will be apparent from the following discussion of
the
preferred embodiments of the present invention, exemplifying the currently
known
best mode of practicing the present invention, which is illustrated in the
accompanying drawings. The components in the drawings are not necessarily to
scale, and the drawings eliminate a showing of many details of an actual die,
which will be apparent to those of ordinary skill, to more clearly
CA 02635475 2008-07-15
J
illustrate the elements of the invention and their operation. In the figures
the
same referenced numerals designate corresponding parts throughout the
different figures.
Brief Description of the Drawings
[0013] FIG. 1 is an illustration, from above, of a die of the invention
mounted on the stationary and movable platens of a die casting machine in its
die-open position, but with the plurality of slides in their die closed
positions;
[0014] FIG. 2 is a partial cross-section through the die element carried on
the movable platen illustrated in FIG. 1 taken at a section indicated by the
line
2-2 in FIG. 1, but with the slide partially open to illustrate how the
internal
piston/cylinder units operate in moving the slides;
[0015] FIG. 2A is a cross-sectional view showing a preferred connection
between the piston/cylinder units and the slides; and
[0016] FIG. 3 is a perspective view of a die element which may be mounted
on the movable platen of a die casting machine showing a plurality of internal
cavities formed for a plurality of piston/cylinder units to be carried within
the
die element.
Description of a Preferred Embodiment of the Invention
[0017] FIG. 1 illustrates, from above, a die 20 of the invention mounted
on the stationary platen 11 and a movable platen 12 of a die casting machine
10. The die 20 includes a stationary die element 21 mounted on the
stationary platen 11 and a movable die element 22 mounted on the movable
platen 12 of the die casting machine, which moves the movable die element
22 toward and away from the stationary die element 21. The stationary die
element 21 and movable die element 22 include a pair of cavity-forming
portions 21 a and 22a respectively. The movable die element 22 carries a
plurality of movable slides 23 (shown in FIG. 2), which include cavity-forming
portions (not shown). The movable die element 22 also carries internally a
plurality of hydraulic piston/cylinder units 24 which move the plurality of
slides
between their cavity-forming and cavity-open, or part-removal, positions. In
CA 02635475 2008-07-15
6
FIG.1 the movable die element 22 is illustrated with the cavity-forming slides
23 in their closed cavity-forming positions.
[0018] As illustrated by FIGS. 1 and 2, and as indicated by FIG. 3, the
plurality of hydraulic piston/cylinder units 24 are carried within cylindrical
cavities 25 formed in the movable die element 22. Thus, a die 20 of the
invention can have a substantially reduced weight compared to prior art dies
because of the weight of the steel removed from the movable die element 22
in forming the cavities for the piston/cylinder units 24, and the omission of
the
heavy structures necessary to carry and support piston/cylinder units outside
of the movable die elements of the prior art dies. The reduced weight of a
movable die element 22 of the invention reduces the operating forces
imposed on a die casting machine and guides in opening and closing the die
cavity.
[0019] FIG. 2 is a partial cross-sectional view of the movable die
element 22 illustrated in FIG. 1, taken at a section corresponding to line 2-2
of
FIG. 1, but with the slide 23 having been moved partially to its cavity-open
position. As shown in FIG. 2, a pair of piston/cylinder units 24 is carried
within
the movable die element 22 on opposite sides of the slide 23, with their pair
of
pistons and rods 24a extending therefrom outwardly for movement
substantially transversely to the movement of the movable platen (as
indicated by arrow 27). As also illustrated in FIG. 2, the slide 23 is
attached to
an interconnecting element 26 which is driven by the pair of pistons and rods
24a substantially transversely in the directions illustrated by arrow 27 to
move
the slide 23 between its cavity-open position and its cavity-closed position
where it is held by engagement with the stationary die element 11 in its
cavity-
closed position. As indicated in FIG. 2, the interconnecting element 26 is
connected adjacent its opposite ends to the pistons and rods 24a of a pair of
piston/cylinder units 24, the cylinders 24b of which are carried within the
die
element 22. As described in greater detail below, the pistons and rods 24a
are preferably connected to the interconnecting element 26 by alignment
couplers 29. The pistons and rods 24a are illustrated in FIG. 2 midway
CA 02635475 2008-07-15
7
between the extremities of their cylinders 24b. When the pistons and rods
24a are driven to the bottom of the cylinders 24b, the slide 23 will be in its
cavity-closed position, and when the pistons and rods 24a are driven to the
top of the cylinders 24b, the slide 23 will be at its cavity-open extremity.
The
slide 23 is driven to its cavity-closed position by a flow of pressurized
hydraulic fluid from connection 30, which is preferably metallic tubing
attached with fittings (not shown) to the ports 24c of hydraulic
piston/cylinder
units 24. As the pistons and rods 24a are forced downwardly by the pressure
and flow of the hydraulic fluid into the ports 24c, hydraulic fluid from the
other
side of the piston 24a is forced from within the cylinders 24b, out of the
other
ports 24d of the hydraulic piston/cylinder units 24 and into passageways 22b
and 22c formed in the movable die element 22. Conversely, when the slide
23 is moved by the hydraulic piston/cylinder units 24 to its cavity-open
position, hydraulic fluid is forced through passageways 22b and 22c formed in
the metallic die element 22 and through the ports 24d of the hydraulic
piston/cylinder units 24, moving the pistons and rods 24a outwardly of the
hydraulic piston/cylinder units 24 and driving the interconnecting element 26
and the attached slide 23 outwardly into its cavity-open position. During its
movement to the cavity-open position, hydraulic fluid is urged from the
cylinders 24b of the hydraulic piston/cylinder units 24 outwardly through the
ports 24c and through the connections 30 to return to the fluid source for the
hydraulic pump. The slide 23 is held in its cavity-open position by the
continued application of pressurized hydraulic fluid through the passageways
22b and 22c and the ports 24d of the hydraulic piston/cylinder units 24 and
into the cylinders 24b below the pistons and rods 24a.
[0020] In the operation of die casting dies there are frequently a holding
forces imposed on the cavity-forming surfaces of the slides to hold them in
their cavity-closed positions after the cast parts have cooled sufficiently to
permit the cavity to be opened. The forces tending to hold the slides in their
cavity-closed positions can result from a number of sources such as the
contraction of the cooling cast part and adhesion between their cavity-forming
CA 02635475 2008-07-15
surfaces and the cast part. With the invention significantly greater slide
opening forces can be generated to overcome such slide holding forces than
in the prior art. As apparent from FIG. 2, hydraulic fluid urged into the
cylinders 24b through ports 24d to move the slide 23 to its cavity-open
position acts on the entire areas of pistons 24e. In prior art dies hydraulic
fluid
was directed to the sides of the cylinders that included the piston rods, and
the area of the pistons which were exposed to the pressure of the hydraulic
fluid was thus less, reducing the force that could be developed on the pistons
and the slides.
[0021] As indicated above, the pistons and rods 24a are preferably
connected with the interconnecting elements 26 and slides 23 by alignment
couplers 29, particularly when the slides 23 extend outwardly from the sides
of
the movable die element 22 where gravity exerts a downward force on the
extended slides that may displace the slides 23 several degrees downwardly
from their designed extended positions perpendicular to the movable die
element 22. In the absence of the alignment couplers 29, the weight of an
interconnecting element 26 and slide 23 would produce a bending force on
the piston and rods 24a. As illustrated in FIG. 2A, the alignment couplers 29
float within pockets 26a formed in the interconnecting element 26 and include
coupler elements 29a with internally threaded shanks 29b that can be
threaded onto the ends of the piston and rods 24a. The threaded shanks 29b
are smaller than bottom openings of the pockets 26a into which they extend,
but the coupler elements 29a have bottom surfaces 29c that are larger than
the bottom openings of the pockets 26a and provide engagement surfaces to
drive the slides 23 inwardly. The pockets 26a are closed at their tops by
plates 26b and threaded fasteners 35. By removing the threaded fasteners 35
and plates 26b, the alignment couplers 29 can be threaded onto the threaded
ends of the pistons and rods 24a. By replacing the plates 26b and threaded
fasteners 35, the connection between the piston/cylinder units 24 and the
interconnecting element 23 is complete. The alignment couplers 29 may also
have arcuate lubricious elements 29d at their upper surfaces that provide
CA 02635475 2008-07-15
9
engagement surfaces to drive the slides 23 outwardly. As apparent from FIG.
2A, except for the engagement of the alignment couplers 29 with the attached
plates 29b at their tops and engagement of the bottom surfaces of the
threaded shanks 29b with the bottom surfaces of pockets 26a, the alignment
couplers are free of any contact with the interconnecting elements 26 that may
result from angular variations between the interconnecting element 26 and the
pistons and rods 24a. Thus, the use of alignment couplers 29 prevents the
imposition of harmful bending forces on the piston/cylinder units 24 that may
result from the extended weight of a slide 23 and interconnecting element 26
and also accommodates any angular displacement of the slides 23 that may
be produced by an unequal application of forces by a driving pair of
piston/cylinder units 24.
[0022] A further feature of the invention is the ability to remove a slide
23 without affecting the piston/cylinder units 24. Removal of the threaded
fasteners 35, the plates 26b, and the alignment couplers 29 of a slide 23
permits the interconnecting element 26 and the slide 23 to be removed from
the pistons and rods 24a and from the movable die element 22 without
removal of the conduits for the hydraulic fluid to the cylinders, e.g.
connectors
30, or otherwise affecting the piston/cylinder units 24.
[0023] While FIG. 2 illustrates only one of the plurality of slides 23 and a
pair of driving piston/cylinder units 24, FIG. 2 illustrates the manner in
which
each of the plurality of the slides 23 carried by a movable die element 22 is
operated. As indicated by FIG. 3, a movable die element 22 may be provided
with the plurality of cavities 25, located in pairs on the opposite sides of
each
of the plurality of slides (not shown) to drive each of the plurality slides
in the
same manner as illustrated in described above with respect to FIG. 2. The
cylindrical cavities 25, as illustrated in FIG. 3, are located in the portions
of a
die, such as movable die element 22, where temperature is normally not a
factor in the reliability and life of the hydraulic cylinders although they
are
carried within the movable die element. While not illustrated herein, the
slides of a movable die element may be driven by single piston/cylinder units
CA 02635475 2008-07-15
carried within the die element, but this is not preferred because the offset
location of a single piston/cylinder unit from the slide it drives necessarily
imposes unbalanced forces of the pistons and rods of the piston/cylinder
units.
[0024] As indicated above, in the operation of die casting dies, the
person operating the dies sometimes operates the hydraulic system for the
piston/cylinder units to provide a sudden application of hydraulic pressure to
the piston/cylinder units in an effort to dislodge cast parts that may be
stuck in
the die cavity. As shown in FIG. 2, the hydraulic fluid is preferably
connected
to the plurality of piston/cylinder units 24 by metallic tubing exterior to
the
movable die element 22 (e.g. 30) and by passageways formed within the
movable die element 22 (e.g. 22b, 22c). The invention thus results in an
elimination of a substantial portion of the hydraulic hoses that have been
used
to deliver hydraulic fluid to the hydraulic piston/cylinder units, resulting
in a
reduced possibility in the instance of hydraulic hose failures in operation of
the
die. In addition, the substantial reduction in substantially flexible and
expandable hydraulic hoses can substantially eliminate the absorption by the
hydraulic hoses of the sudden application of pressure by an equipment
operator as a result of the absorption of the imposed pressure energy by the
expansion of the flexible hydraulic lines, and permits the transmission of a
more sudden application of forces to the slides and an increased possibility
that the operator may dislodge cast parts that remain in the die cavity.
[0025] While cracking of the movable die elements is infrequent, placing
a substantial portion of the hydraulic fluid passageways within the movable
die
element increases their exposure to the effects of die cracking and the
possibility of hydraulic fluid leaks and pressure losses. This problem can be
prevented in the invention by lining the hydraulic fluid passageways within
the
movable die element, for example, passageways 22b and 22c in FIG. 2, with
tubing of a compliant material, such as a VITONTM or high temperature
rubber, which will maintain the integrity of the passageways in the event the
movable die element forms a crack that intercepts a passageway.
CA 02635475 2008-07-15
l]
[0026] Thus, the invention provides a die that is lighter and has a
reduced profile than prior art dies and is more easily fit to a larger variety
of
die casting machines and may be more easily and reliably connected with a
hydraulic pump or other source of hydraulic pressure.
[0027] Where this description refers to movements "substantially
transversely" with respect to the movement of the movable platen of a die
casting machine, it means movements proximate to 90 with respect to the
movement of the movable platen, that is, movements within only a few
degrees of 90 with respect to the direction of movement of the movable
platen. And wherein the term "compliant" is used with respect to the
properties of a lining for the passageways formed in the movable die element,
it means a material that remains plastic in this application and will retain
its
integrity if the surrounding metal cracks or becomes dislodged.
[0028] While the figures and descriptions above illustrate and describe
preferred embodiments, other embodiments of the invention will be apparent
to those skilled in the art that come within the spirit of the invention as
defined
by the following claims.
