Note: Descriptions are shown in the official language in which they were submitted.
INJECTION MOLDING SYSTEM HAVING
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A THERMAL LOCATING FLANGE
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1 BACKGROUND OF THE INVENTION
This invention relates generally to injection
molding and more particularly to an injection molding
system in which a circumferential locating flange
extends from a heated nozzle or manifold outwardly
aceoss an air space to locate the nozzle in a well in a
cooled cavity plate in which it is received~
Many injection molding systems are known
which have a heated nozzle extending from a heated
1~ manifold into a well in a cooled cavity plate to convey
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1 pressurized melt through a melt passage to a gate
leading to a cavity. In order to mini~ize heat loss
from the heated nozz]e to the cooled cavity plate, an
insulative air space is provided between them.
However, the air space must be bridged by means which
accurately locates the nozzle in the well in the cavity
plate and also takes the machine nozzle pressure.
Usually in order to maintain accurate alignment of the
nozæle in the weIl, sealing and locating means are
provided near the front end of the nozzle and locating
means are provided towards the rear end of the
nozzle. For example, the applicant's U.S~ patent
number 4,579,520 which issued April 1, 1986 shows a
heated nozzle seated on an insulation bushing with a
nose portion extending into an opening in the cavity
plate leading to the cavity. The applicant's U.S.
patents number 4,768r283 which issued September 6, 1988
and number 4,771,534 which issued September 20, 1988,
as well as U.S. patent number 4,588,367 to Schad which
issued May 13, 1986 disclose nozzles having insulating
flanges which extend across the insulative air space
into contact with the surrounding cavity plate.
Other noæzles having insulating rings or
hoops with circu~ferentially extending grooves or ridges
are disclosed in the applicant's U.S. patent number
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1 4,777,348 which issued ~ctober 11, 1988 and Canadian
application serial numb~r 569,756 filecl
June 17, 1988. Another arrangement to provide
additional insulation far a heated nozzle is shown in
the applicant's U~S. patent number 4,795,338 which
issued January 3, 1989~ UOS. patent number 4,705,473
to Schmidt which issued November 10, 1987 shows a valve
pin bushing having a locating flange mounted between
each nozzle and the manifold. Thus, nozzles having
locating flanges are known and are satisfactory for
many applications. However, in systems for molding
materials having a critical temperature window, heat
loss from the heated nozzle and manifold to the cooled
cavity plate through the locating flange has become
increasingly critical to successful operation of the
system.
SUMMARY OF THE INVENTION
Accordingly~ it is an object of the invention
to at least partially overcome the disadvantages of the
prior art by reducing heat loss through the locating
flange to the cooled cavity plate.
To this end, in one of its aspects, the
invention provides a valve gated hot runner injection
molding system having a heated nozzle with a rear face
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1 which is secured against a heated manifold/ the nozzle
being received in a well having an inner surface in a
cooled cavity plate with an insulative air space
extending between the nozzle and the surrounding cavity
plate, the manifold and the nozzle havi:ng a melt
passage extending therethrough to convey pressurized
melt to a gate ].eading to a cavity, the nozzle having
sealing and locating means extending into contact with
the surrounding cavity plate to prevent leakage of melt
from the melt passage into the insulative air space,
one of the heated nozzle and the heated manifold having
an outwardly extending circumferential locating flange
which extends across the insulative air space into
contact with the inner surface of the well in the
surrounding cavity plate in a position wherein the
locating flange is seated against a rearwardly facing
circ~mferential shoulder formed by the inner surface of
the well to locate the nozzle in the well, the
improvement wherein: the outwardly extending locating
flange has a plurality of openings extending
transversely therethrough according to a predetermined
configuration.
Further objects and advantages of the
invention will appear from the following description
taken together with the acco~panying drawings.
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1 BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a sectional view of a portion of
an injection molding system according to one embodiment
of the :inventiont
Figure 2 is a split section vi.ew at a right
angle to Figure 1~ showing the valve member in the open
and closed positions,
Figure 3 i9 an isometric view of the manifold
and a portion of the nozzle seen in Figures 1 and 2,
Figure 4 is a sectional view of an injection
molding system according to another embodiment of the
invention, and
Figure 5 is an isometric view of a portion of
the nozzle seen in Figure 4, showing the locating
flange.
DETAILED DESCRIPTION OF TNE DRAWINGS
: Reference is first made to Figure 1 which
shows a center entry valve gated injection molding
~ system having a valve member 10 which is received in a
central bore 12 in a nozzle 14 which is secured by
bolts 16 to a manifold 18. The steel manifold lB has a
circumferential locating flange 20 which extends
outwardly to seat against a circumferential shoulder 22
formed by the inner surface 23 of a well 24 in the
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1 cavity plate 26. This accurately locates the manifold
18 and the nozzle 14 secured to it in a position in
which the nozzle is centrally received in the well 24
with an insulative air space 28 extending between the
heated nozzle 14 and the surrounding cooled cavity
plate 26. As seen in Figure 3, in this embodiment, the
locating flange 20 has a ring of holes 30 drilled
transversely through it which reduces heat loss through
the locating fIange 20 from the heated manifold 18 and
nozzle 14 to the cooled cavity plate 26. While a
single cavity plate 26 is shown in this embodiment of
the invention, there can be various other plate
arrangements such as a support plate located between
the cavity plate 26 and the back plate 32. The nozzle
14 and manifold 18 are also located laterally by a
forward nose portion 34 of the nozzie 14 being received
in a matching cylindrical opening 36 through the cavity
plate 26 and by the :rear end 38 of the manifold 18
being received and retained in a matching openlng in a
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: 20 locating collar~40. The locating collar 40 is held
: securely in place by bolts 42 which extend through the
back plate 32 into the cavity plate 26.
The central bore 12 through the nozzle 14 has
: a rear portion 44 and a larger diameter forward portion
46 which extends through the nose portion 34 of the
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1 nozzle to form a qate 48 with a forward mouth 50~ The
valve member 10 has a forward portion 52, a central
portion 54 which extends through the rear portion 44 of
the central bore 12, and a rear portion 56 which
extends into a central opening 58 in the mani.fold 18.
As can be seen, the forward portion 52 of the valve
member 10 is smaller in diameter than the surrounding
forward portion 46 of the central nozæle bore 12 which
provides a melt flow space 60 between them, except that
the forward portion 52 of the valve member has an
enlarged forward end 62 which seats in the mouth 50 of
the gate 48 in the retracted closed position. The
enlarged end 62 of the valve member 10 has a flat
forward face 64 which aligns at working temperature
with the same side 66 of the cavity 68 in the closed
position. The central portion 54 of the valve member
lO has a number; of spaced ridges 70 whlch fit in the
: rear portion 44 of the central nozzle bore 12 through
: the nozzle 14 to preven~t leakage of pressurized melt
around the reciprocating valve member 10.
In this embodiment, the nozzle 14 is heated
by plate heaters 72 which are secured in opposite sides
as seen in Fi~ure 2. The manifold 18 is heated by an
elec~rical heating element 74 which is integrally
brazed or cast into it~ The cavity plate 26 is cooled
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1 by pumping cooling w~ter through cooling conduits 76.
In this large volume application with the Eorward face
64 of the valve member extending to the cavity 68, it
i9 desirable to provide controlled cooling to the
enlarged end 62 of the valve memher 10. Thus, a
twisted partition 78 is mounted in the hollow valve
member 10, and a circulation of cooling water is
provided between inlet and outlet pipes 80,82 which
extend laterally from the rear portion 56 of the valve
member 10 through lateral openinys 84,86 in the
manifold 18. Thus, cooling fluid flows into the valve
member 10 through the inlet pipe 80, forward along one
side of the twisted partition 78 to the enlarged end 62
where it crosses over and flows rearwardly along the
1~ other side of the twisted partition and back out
through outlet pipe 82. In an alternate embodiment the
cooling fluid flowing from the inlet pipe 80 to the
outlet pipe 82 through the hollow valve member 10 can
be air rather than water.
As seen in Figure 1, a melt passage 88
extends to convey pressurized melt fro~ a central inlet
90 at the rear end 38 of the manifold 18 to the gate
48. The passage 88 splits into two branches 92 which
extend around the opening 58 in the manifold and join
the space 60 around the forward portion 52 of the valve
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1 member 10. While the foeward portion 52 of the valve
member 10 is shown in this embodimen~ as being smaller
in diameter than the central portion 54, this is not
necessaril.y the case. The important thing is that the
forward portion 46 of.the central nozzle bore 12 must
be sufficiently larger than the forward portion 52 o
the valve member 10 to provide the space 60 with a
sufficient cross-sectional area to convey the melt
received through the split branches 92 of the melt
passage 88. When the in~ection pressure of the melt
forces the valve member 10 to the forward open
position, the melt then flows through the gate 48
outwardly around the enlarged head 62 of the valve
member 10 into the cavity 68.
The rear portion 56 of the valve member 10
which extends into the central opening 58 in the
manifold 18 has a smaller diameter neek portion 94
which joins a rearward extending larger diameter
portion 96 at a shoulder 98. The neck portion 94
~ extends between this outwardly extendiny rearward
shoulder 98 and an outwardly extending forward shoulder
100 where it joins the central portion 54 oF the valve
member 10. The valve member 10 is engaged
longitudinally by a split ring 102 which is mounted
around the neck portion 94 of the valve member 10 and
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1 reciprocally received in the central opening 58 in the
manifold 18. The split ring 102 has a notch 104 to
receive the inner end 106 of a pivotal lever member
108. The lever member 108 receives a biasing force
Erom a compression spring 110 which is seated in a
cylindrical opening 112 in the manifold 18.
In use, the system is assembled as shown by
inserting the valve member 10 through the central bore
12 of the nozzle 14 and then mounting the two segments
of the split ring 102 around the neck portion 94. As
can be seen, there is just sufficient clearance to do
this when the valve member 10 is in the retracted
closed position. The spring 110 and lever member 108
are then mounted in position and the nozzle 14 is
bolted to the manifold 18. Electrical power is applied
to the plate heaters 72 and the terminal 114 of the
:; heating element 74 to heat the nozzle 14 and manifold
18 to a predetermined operating temperature.
Pressurized melt from a molding machine (not shown) is
introduced 1nto the melt passage 88 through the central
inlet 90 according to a predetermined cycle. When
injection pressure is applied, the force of the melt on
the enlarged end 62 of the valve member 10 overcomes
the force of the spring 110 and drives the valve member
10 forward to the open position. The melt then flows
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1 through the melt passage 88 and the gate 48 until the
cavity 68 is filled. When the cavity 68 is full, the
combination of the back pressure of the melt in the
cavity 6B against the forward face 64 of the valve
member and the force of the spring 110 drives the valve
member 10 to the retracted closed position in which the
enlarged forward end 62 is seated in the matching mouth
50 of the gate 48. The force from the spring 110 is
applied by the lever ~ember lOB to the split ring 102
which transmits it to the valve member 10 by bearing
against the outwardly extending rearward shoulder 98.
Receipt of the split ring 102 in the central opening 58
in the manifold 18 holds it in place in engagement with
the valve member 10 as it reciprocate between the open
and closed positions. The injection pressure is tnen
released and after a short cooling period, the mold is
opened to eject the molding products. After ejection
the mold is closed and injection pressure is reapplied
which reopens the gate 48. This cycle is repeated
continuously with a frequency dependent upon the size
of the cavity and the type of material being molded.
As can be seen, the travel o the valve member 10 is
relatively short, but large cavities can be filled
quickly because of the large diameter of the enlarged
2~ end 62 of the valve member and the mouth 50 of ~he gate
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1 48. The shape of the enlarged end 62 and the mouth 50
causes the pressurized melt to flare outwardly as it
enters the cavity 68. This produces a radial molecular
orientation of the melt which is advant:ageous in
increasing the strength of products having certain
configurations. When molding certain materia1s it is
critical to successful operation of the system that
minimal heat is lost from the heated manifold 18 and
nozzle 14 to the surrounding cooled cavity plate 26,
but at the same time accurate location of the nozzle 14
in the cavity plate well 24 must be maintained. This
is achieved by the locating flange 20 providing
accurate location (together with the nose portion 34
and the Iocating collar 40), while the ring of holes 30
therethrough limit heat loss by restricting the
effective cross sectional area.
Reference is now made to Figures 4 and 5
which show a valve gated injection molding system
according to another embodiment of the invention. In
this case, there are a number of heated nozzles 120
each seated in a well 122 in a cavity plate 124 to
receive melt from a common elongated manifold 126. A
heated circular manifold 128 is secured between each
nozzle 120 and the elongated manifold 126 by bolts
~5 130. Each nozzle 120 has a circumferential locating
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1 flange 132 which extends outwardly to seat against a
circumferential shoulder 134 which is formed by the
inner surface 136 of the well 122. This accurately
locates the nozzle 120 in the well 122 with an
insulat:ive air space 138 between the nozzle 120 which
is heat:ed by integral electrical heating element 140
and the sureounding cavity plate 124 which is cooled by
pumping cooling water through cooling conduits 142. As
can be seen, in this embodiment of the invention, the
locating flange 132 which is on the nozzle 120 rather
than the circular manifold 128 has two rings of holes
144 drilled transversely through it to reduce heat
loss. It will be appreciated that other configurations
of transverse openings through the locating flange 132
can be utilized to reduce hea~ loss from the heated
nozzle 120 to the cooled cavity plate 124.
~; ~ Each nozzle 120 has a central bore 146 which
receives a hollow valve member 148 similar to that
described above. However, in this embodiment, the
valve member 148 has a tip end 150 which seats in a
tapered gate 152 formed by the nose portion 154 of the
nozzle~ Thus, in this embodiment, the valve member 148
retracts to the open position and is driven forwardly
to the closed position rather than the reverse as
described in regard to the first embodiment. The valve
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1 member 148 is driven forwardly to the closed position
by pivotal actuating mechanism ~not shown~ which
includes a lever member mounted between a pneu~atic
piston and a split ring which engages the valve
member. Cooling water or air flows through the hollow
valve member 148 on opposite sides of a twisted
partition 156 from an inlet pipe to an outlet pipe as
described above~
The elongated manifold 126 is located
securely in place between a back plate 162 and the
cavity plate 124 by a central locating ring 164 and a
titanium pressure pad 166. The elongated manifold 126
is heated by an integral electrical heating element 168
which is cast into it as described in the applicant's
U.S. patent number ~,688,622 which issued
August 25, 1987. The locating ring 164 provides
another insulative air space 170 between the heated
manifold 126 and the cavity plate 124.
A melt passage 172 extends from an inlet 174
and branches in the elongated manifold 126 to each of
the circular manifolds 128 where it splits into two
branches 176 to extend around the valve member
actuating mechanism and join the central bore 146 of
each nozzle 120. As described above, the central bore
146 is sufficiently larger in diameter than the valve
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1 member 148 to convey the melt forwardly to the gate 152
leading to the cavity 1780
In use, the system is assembled as shown and
pressurized melt is injected by a molding machine tnot
shown~ into the melt passage 172 through the central
inlet 174 according to a predeterminecl cycle. The
pressure of the melt causes the valve member 148 to
retract to the open position and the pressurized melt
flows through the melt passage 172 and the gate 152
until the cavity 178 is filled. When the cavity is
full, pneumatic pressure is applied to drive the valve
member 148 forwardly to the closed position in which
the tip end 150 of the valve member 148 is seated in
the gate 152. The injection pressure is then released
and after a short cooling period, the mold is opened
for ejection. After ejection the mold is closed and
in]ection pressure is reapplied which reopens the ~ate
152and the cycle is repeated continuously.
While the description of the injection
molding system with a thermal locating flange has been
given with respect to preferred embodiments, it is not
to be construed in a limiting sense. Variations and
modifications will occur to those skilled in the art.
Reference is made to the appended claims for a
definition of the invention.
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