Note: Descriptions are shown in the official language in which they were submitted.
CA 02495607 2005-02-O1
SELF-CLEANING MOLD VALVE WI'CH AIR INJECTION SYSTEM
BACKGROUND OF TH(E INVENTION
The present invention relates to a mold valve for a molding system and, more
particularly, to a mold valve with a system to assist demolding.
A typical molding system provides for the mixing of at least two materials to
form a mixture that is discharged into a mold cavity to form a finished
article. The
materials are typically fed from a supply by a delivery or feed assembly,
which
communicates with a mixing head. The materi als are mixed by the mixing head
and
discharged into the mold cavity through a mold valve. The mold assembly and
attached
mold valve are heated to cure the molded article.
Once the molded article has cured, the rr olded article must be removed from
the
mold assembly. Typically knock out pins drive the molded article away from the
mold
assembly. Disadvantageously, the molded article may adhere to the mold
assembly to
an extent that the knock out pins may damage the molded article.
Accordingly, it is desirable to provide ;~ mold valve that assists removal of
a
finished article from the mold assembly.
SUMMARY OF THE INVENTION
The present invention provides a mold valve assembly, which generally includes
a mold valve chamber having an output port and an injection chamber in
communication with the mold valve chamber. 7'he mold valve chamber defines a
mold
valve axis and the injection chamber defines an injection chamber axis. The
injection
chamber axis is transverse to the mold valve axi,~. An inlet port in
communication with
the injection chamber defines an inlet axis angled relative the mold valve
axis.
An air injection system communicates with the mold valve assembly. The air
source provides an airflow into the mold assem>~~ly to pressurizes the space
between the
cured molded article and the inner surfaces of the mold cavity to promote
separation of
the cured molded article from within the mold assembly.
The present invention therefore provide; a mold valve that assists removal of
a
finished article from the mold assembly.
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BRIEF DESCRIPTION OF THE DRAWINGS
The various features and advantages of :his invention will become apparent to
those skilled in the art from the following detailed description of the
currently preferred
embodiment. The drawings that accompany the detailed description can be
briefly
described as follows:
Figure 1 is a simplified schematic representation of a multiple material
molding
system having a valve assembly designed according to the present invention;
Figure 2 is an expanded partial sectional view of a mold valve assembly;
Figure 3 is a perspective view of the mold valve assembly of Figure 2;
Figure 4A is an expanded side view of am injection piston;
Figure 4B is an expanded top view of the injection piston of Figure 4A rotated
90 degrees;
Figure SA is an exploded view of a mold valve piston of the mold valve
assembly according to the present invention;
Figure SB is an perspective view of the mold valve piston of Figure SA in an
assembled condition;
Figure 6 is a sectional view of the mold valve piston scraping the injection
piston during operation of the present invention;
Figure 7 is a flow chart illustrating operation of the air injection system of
the
present invention;
Figure 8 is an expanded partial sectional view of a mold valve assembly with
an
air injection system; and
Figure 9 is an expanded partial sectional view of a mold assembly
schematically
illustrating an air pressure to demold a cured melded article.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Figure 1 schematically illustrates a multiple material molding system 10. The
system 10 generally includes a plurality of mate:-ial supplies 12A, 12B and
12C, which
communicate with a feed assembly 14 through r~apective supply conduits 16A-
16C. It
should be understood that the materials include fluids and solids. The feed
assembly 14
drives a desired quantity of material from each material supply 12A-12C
through output
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conduits 18A-18C to a mix head assembly 20. The mix head assembly 20
thoroughly
mixes the material from each material supply 12A-12C and injects the mixture
material
into a mold assembly 22 through a mold valve assembly 24.
The mold assembly 22 preferably includes an A-side base portion 22A and a B-
side upper portion 22B which is removed to acc;ess a mold cavity 25. The mold
valve
assembly 24 is typically removably connected to the B-side upper portion 22B.
Preferably, a controller 23 communicates with the feed assembly 14, the mix
head assembly 20, and the mold valve assembly 24 to assure the system 10 is
operating
within predefined parameters. Controls for injection-molding equipment are
known in
the art and detailed description of the algorithrr~s will not be further
detailed herein.
An air injection system 27 includes an air source 29 such as a compressor or
the
like which communicates with the mold valve assembly 24. The air source 29
provides
an airflow into the mold assembly 22 in respon;:e to the controller 23. By
injection air
into the mold assembly 22 after the molded article has cured within the mold
cavity 25,
the air pressurizes the space between the cured molded article and the inner
surfaces of
the mold cavity 25 (Figure 9) to promote separation of the cured molded
article from
within the mold assembly 22. It should be understood that although air is
described in
the illustrated embodiment various gases will also benefit from the invention.
The mix head assembly 20 mixes the multiple of materials components, e.g.,
material matrix, to form a settable mixture, which is then discharged into the
mold
cavity 25 of the mold assembly 22 through the: mold valve assembly 24. The
mold
valve assembly is then located in an oven or the like to cure the mixture to
form an
article defined by the mold cavity 25.
Typically, a single mix head 20 feeds the matrix into a multiple of mold
assemblies that are arranged in an assembly line like environment. The mold
valve
assembly 24 is removably mounted to the mold valve assembly 24 through a
coupling
25 or the like.
Refernng to Figure 2, a schematic view of the mold valve assembly 24
according to the present invention is illustrated. The mold valve assembly 24
generally
includes a mold valve chamber 26 having an out gut port 28 and an injection
chamber 30
in communication with the mold valve chamber 26 (also illustrated in Figure
3). The
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mold valve chamber 26 defines a mold valve axis M. The injection chamber 30
defines an injection chamber axis I. The injection chamber axis I is
transverse to the
mold valve axis M. An inlet port 32 in communication with the injection
chamber 30
defines an inlet axis N. The inlet port 32 receives the mixture material from
the mix
head assembly 20 (Figure 1) through a conduit 34 or the like.
An actuator 36 drives an injection piston 38 (Figure 4A, 4B) along the
injection
chamber axis I within the injection chamber 30 =o drive mixture material from
the inlet
port 32 into the mold valve chamber 26. The actuator 36 is preferably a
pneumatic,
hydraulic or electric ram, however, various other drive assemblies will also
benefit from
the present invention.
An actuator 40 drives a mold valve piston 42 (Figure SA, SB) along the mold
valve axis M within the mold valve chamber 2fi to drive mixture material
through the
output port 28 and into the mold cavity 25 of the; mold assembly 22. The
actuator 40 is
preferably a pneumatic, hydraulic, or electric ram; however, various other
drive
assemblies will also benefit from the present invention. The mold valve piston
42
closely fits within the mold valve chamber 26 and scrapes along an end segment
44 of
the injection piston 38 to clean any mixture material remnants therefrom
(Figure 6).
That is, the mold valve piston 42 scrapes the mixture material off the end
segment 44
and the inner perimeter 46 of the mold valve chamber 26 such that no remnants
remain
within the mold valve chamber 26. The necessity of flushing between injection
cycles
is substantially eliminated as the plunger need only be cycled up and down.
Cycle time
for production and expense of each finished article is thereby decreased.
Referring to Figure 4A, a side view of the end segment 44 of the injection
piston
38 includes an arcuate segment 48 transverse to axis I. A second arcuate
segment 50 is
defined approximately ninety degrees to the fi -st arcuate segment 48 and
defines an
apex toward the mold valve chamber 26 (Figare 6). The configuration of the end
segment 44 completes the inner perimeter 46 of the mold valve chamber 26 when
fully
extended. By completing the inner perimeter 45 of the mold valve chamber 26
where
the injection chamber 30 communicates with the mold valve chamber 26, the mold
valve piston 42 will scrape along the end segment 44 of the injection piston
38 (Figure
6).
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Referring to Figure SA, the mold valve piston 42 includes a metallic support
assembly 52 and a nonmetallic member 54. The metallic support assembly 52 is
preferably manufactured of 4140 tool steel and the nonmetallic member 54 is
preferably
manufactured of 25 percent glass filled Teflon. The metallic support assembly
52
includes an upper portion 56 and a lower portion 58. The upper and lower
portions 56,
58 are preferably threaded together to retain the cylindrical nonmetallic
portion 54
(Figure SB).
The upper portion 56 defines an upper cylindrical flange 60 and the lower
portion 58 defines a lower cylindrical portion 62. The upper and lower
portions 56, 58
are threaded together through complimentary threads 64a, 64b to retain the
nonmetallic
member 54 therebetween. The upper cylindrical flange 60 and the lower
cylindrical
portion 62 define an outer diameter which provi de a clearance fit with the
mold valve
chamber 26.
Referring to Figure 6, the mixture material is injected into the inlet port 32
of the
mold valve assembly 24. Once a predefined quantity is injected through mold
valve
assembly 24, the actuator 36 is initiated by the controller 23 to drive the
injection piston
38 along the injection chamber axis I toward the mold valve chamber 26. The
injection
piston 38 closes off the inlet port 32 to the injection chamber 30 and
simultaneously
drives the mixture material within the injection chamber 30 into the mold
valve
chamber 26. The end segment 44 of the inj~.ction piston 38 completes the inner
perimeter 46 of the mold valve chamber 26 (Fil;ure 4B).
The actuator 40 is then initiated by the controller 23 to drive the mold valve
piston 42 along the mold valve axis M within the mold valve chamber 26 to
drive
mixture material through the output port 28 an into the mold cavity 25 of the
mold
assembly 22. The mold valve piston 42 closely fits within the mold valve
chamber 26
and scrapes along the end segment 44 of the in ~ection piston 38 to clean any
mixture
material remnants therefrom such that no remnants remain within the mold valve
chamber 26.
Referring to Figure 7, once mixture material injection is completed, the
molded
article is cured within the mold assembly 22. Once the mold article A has
cured, the
mold valve piston 42 is retracted to an ejection position (Figure 8) to expose
an air inlet
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66 to the mold valve chamber 26 and thereby th~~ mold cavity 25. Airflow from
the air
source 29 is communicated through the mold valve chamber 26 and into the mold
cavity
25. The mold assembly 22 is pressurized by the air source 29 to pressurize the
space
between the cured article A and the mold assembly 22 (Figure 9).
The pressurized air between the cured ar:icle and the mold assembly 22
operates
to assist in the separation of the cured molded article from the inner
surfaces of the
mold assembly 22. It should be understood that knock-out pins (not shown) or
the like
may additionally be utilized in combination with the pressurization of the
mold
assembly 22 to further assist separation of the cured molded article from the
mold
assembly 22. That is, the air pressure frees the c ured molded article A from
the B-side
mold portion prior to separating the B-side mold portion from the A-side mold
portion.
Once the cured molded article A is removed from the mold assembly 22, the
mold valve piston 42 is retracted to an injection position (Figure 8) to block
the air inlet
66 in preparation for the next mixture material injection cycle. It should be
understood
that the mold valve piston 42 selectively blocks or opens air inlet 66 to
control air flow
into the mold assembly 22; however, separate control of the air flow may
alternatively
and/or additionally be provided.
The foregoing description is exemplary rather than defined by the limitations
within. Many modifications and variations of the present invention are
possible in light
of the above teachings. The preferred embodiments of this invention have been
disclosed, however, one of ordinary skill in the art would recognize that
certain
modifications would come within the scope oi~ this invention. It is,
therefore, to be
understood that within the scope of the appended claims, the invention may be
practiced
otherwise than as specifically described. For than reason the following claims
should be
studied to determine the true scope and content of this invention.
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