Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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APPARATOB FOR LOCATING AND SEALING
AN INJECTION MOLDING NOZZLE
BACKGROUND OF THE INVENTION
This invention relates generally to injection
molding and more particularly to apparatus for locating and
sealing an injection molding nozzle in an opening in the
mold.
Very accurate location of a heated nozzle in an
opening in a cooled mold has become more and more critical
for successful hot tip gating. As seen in the applicant s
U.S. Patent Number 4,557,685 which issued December 10, 1985
and U. S. Patent Number 4, 768, 945 to Schmidt et al. which
issued September 6, 1988 it is well known for heated
injection molding nozzles used for hot tip gating to have
a rear locating flange and a front seal extending
therearound. Another example of hot tip gating is shown in
U.S. Patent Number 5,658,604 to Gellert et al. which issued
August 19, 1997 in which the front seal is provided by a
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threaded nozzle seal which is screwed into the front end of
the nozzle.
However, the previous apparatus all has the
disadvantage that extremely close tolerances are required
to ensure the front end of the nozzle is accurately aligned
and there is a good seal against melt leakage.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present
invention to at least partially overcome the disadvantages
of the prior art by providing injection molding apparatus
wherein each nozzle has a rear locating flange which
prealigns the nozzle before accurate alignment by a front
locating and sealing ring.
To this end, in one of its aspects, the invention
provides injection molding apparatus having an integral
heated nozzle extending into an opening in a mold. The
opening has a rear end and a surface extending to a gate
leading to a cavity. The integral heated nozzle has an
elongated inner portion, an outer collar portion, and an
electrical heating element. The elongated inner portion
has a rear end, a front end, a melt bore extending
therethrough from the rear end to the front end, and a
generally cylindrical outer surface with a spiral groove
extending therearound The electrical heating element is
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wound into the spiral groove extending around the outer
surface of the inner portion and the outer collar portion
fits around the inner portion adjacent the rear end of the
inner portion. The surface of the opening in the mold is
generally cylindrical with a first locating shoulder
extending inwardly near the rear end and a second locating
shoulder extending inwardly near the gate. The outer
collar portion has a rear locating flange to extend
outwardly into locating contact with the first inwardly
extending locating shoulder of the surface of the opening
in the mold. A front locating and sealing ring is mounted
around the heated nozzle near the front end of the heated
nozzle to provide locating contact the with the second
inwardly extending locating shoulder of the surface of the
opening in the mold. The distance between the first
inwardly extending locating shoulder and the second
inwardly extending locating shoulder being greater than the
distance between the rear locating flange and the front
locating and sealing ring. Thus, during insertion of the
nozzle into the opening in the mold and thermal expansion
of the nozzle, the rear locating flange comes into locating
contact with the first inwardly extending locating shoulder
of the surface of the opening in the mold to prealign the
nozzle before the front locating and sealing ring comes
into locating and sealing contact with the second inwardly
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extending locating shoulder of the surface of the opening
in the mold.
Further objects and advantages of the invention
will appear from the following description taken together
5 with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a sectional view of a portion of a
multi-cavity injection molding apparatus in the operating
l0 position wherein each heated nozzle has a rear locating
flange and a front locating and sealing ring according to
a preferred embodiment of the invention,
Figure 2 is an isometric view of the front end of
the nozzle and the front locating and sealing ring seen in
Figure 1,
Figure 3 is a sectional view similar to Figure 1
showing one of the nozzles being inserted into place,
Figure 4 is a sectional view showing the ribbed
locating and sealing ring contacting the surface of the
mold during insertion,
Figure 5 is a similar view showing the ribbed
locating and sealing ring fully inserted, and
Figure 6 is an isometric view of a locating and
sealing ring according to another embodiment of the
invention.
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DETAILED DESCRIPTION OF THE INVENTION
Reference is first made to Figure 1 which shows
a portion of a multi-cavity hot tip gated injection molding
system or apparatus having a melt passage 10 with branches
12 which extend outwardly in a steel melt distribution
manifold 14 from a central inlet portion 16 to an integral
heated nozzle 18. Each branch 12 of the melt passage 10
extends through a central melt bore 20 in one of the heated
nozzles 18 to a gate 22 leading to a cavity 24. While the
l0 mold 26 can have a greater number of plates depending upon
the application, in this case, only a back plate 28 and a
manifold plate 30 secured together by bolts 32 are shown
for ease of illustration.
The melt distribution manifold 14 has a central
inlet portion 34 surrounded by a locating ring 36 and is
heated by an integral heating element 38. The melt
distribution manifold 14 is mounted between the back plate
28 and the manifold plate 30 by a central manifold locator
40 and a number of pressure discs 42 which provide an
insulative air space 44 between the heated manifold 14 and
the surrounding mold 26 which is cooled by pumping a
cooling fluid such as water through cooling conduits 46,
The melt distribution manifold 14 is accurately aligned in
place by a locating pin 48 extending outward into a cam 50
seated in the manifold plate 30. Each branch 12 of the
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melt passage 10 bends in a steel plug 52 seated in an
opening 54 through the melt distribution manifold 14. The
plug or insert 52 is very accurately aligned in place by a
small prealignment pin 56 and a larger alignment and
retaining pin 58.
As also seen in Figure 3, each of the heated
nozzles 18 has an elongated inner portion 60 with the
central bore 20 extending therethrough and an integral
outer collar portion 62 fitting around its rear end 64.
The inner portion 60 has a cylindrical outer surface 66
with a spiral groove 68 into which an electrical heating
element 70 is wound. The electrical heating element 70 has
terminal portions 72 extending outwardly through the outer
collar portion 62. Each heated nozzle 18 has a tip insert
74 integrally brazed into a seat 76 in the front end 78 of
its inner portion 60. The tip insert 74 has a melt bore 80
extending therethrough and a tip 82 which must be very
accurately aligned with the gate 22. As best seen in
Figures 4 and 5, the heated nozzle 18 also has a locating
and sealing ring backer sleeve 84 integrally brazed around
its inner portion 60 adjacent its front end 78. In this
embodiment, the locating and sealing ring backer sleeve 84
has a hole 85 into which a thermocouple element 87 extends
to control the operating temperature. The locating and
sealing ring backing sleeve 84 has an outer surface 86 with
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a forwardly facing outer shoulder 88. A ribbed locating
and sealing ring 90 is heat shrunk around the outer surface
86 of the locating and sealing ring backer sleeve 84 to
abut against the outer shoulder 88. The ribbed locating
and sealing ring 90 is made of a material such as a soft
titanium alloy which is suitably deformable as described
below.
Each heated nozzle i8 extends into an elongated
opening 92 in the mold 26. As can be seen, the elongated
l0 opening 92 has a surface 94 which is generally cylindrical
with a tapered portion 96 extending inwardly to the gate
22. The outer collar portion 62 of the heated nozzle 10
has a forwardly extending locating flange 98 which abuts
against an inwardly extending seat or shoulder 100 on the
surface 94 of the opening 92 in the mold 26. The surface
94 of the opening 92 also has a first locating shoulder 102
which tapered inwardly near its rear end 106 and a second
locating shoulder 104 which tapers inwardly near the gate
2 2 . The first locating shoulder 102 tapers inwardly to f it
around the rear locating flange 98 to accurately locate the
rear end 108 of the heated nozzle 18 in the operating
position shown in Figure 1. The second locating shoulder
104 tapers inwardly to fit around the front locating and
sealing ring 90 to accurately locate the tip 82 of the tip
insert 74 with the gate 22.
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The distance between the first locating shoulder
102 and the second locating shoulder 104 is greater than
the distance between the rear locating flange 98 and the
front locating and sealing ring 90. Thus, as clearly seen
in Figure 3, when each nozzle 10 is inserted into one of
the elongated openings 92 in the mold 26, the rear locating
flange 98 of the outer collar portion 62 contacts the first
locating shoulder 102 before the front locating and sealing
ring 90 contacts the second locating shoulder 104. The
contact between the rear locating flange 98 and the first
locating shoulder 102 when the nozzle 10 is partially
inserted into the opening 92 aligns the nozzle 18 so the
tip 82 of the tip insert 74 is first prealigned with the
gate 22. Then, as the nozzle 18 is further inserted into
the elongated opening 92, the front locating and sealing
ring 90 contacts the second locating shoulder 104 as seen
in Figure 4 which more accurately aligns the tip 82 of the
tip insert 74 with the gate 22.
Finally, when the melt distribution manifold 14
and the nozzles 18 are heated to the operating temperature,
thermal expansion drives the front locating and sealing
ring 90 further forward against the second locating
shoulder 104. As seen in Figure 5, this deforms the ribs
110 sufficiently to very accurately locates the tip 82 of
the tip insert 74 with the gate 22. The deformed locating
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and sealing ring 90 also seals against the second locating
shoulder 104 to prevent melt leakage from the space 112
around the tip insert 74 into the insulative air space 114
around the melt distribution manifold 14. In this final
5 operating position, the locating flange 98 of the outer
collar portion 62 abuts against the seat 100 extending
around the surface 94 of the elongated opening in the mold.
As seen in Figure 6, in another embodiment the
locating and sealing ring 90 which is made of a suitably
l0 deformable material such as a soft titanium alloy can be
made with a cylindrical outer surface 116 rather than with
the ribs 110 seen in the first embodiment.
In use, the system is assembled as shown in
Figure 1. Electrical power is applied to the heating
elements 38, 70 in the melt distribution manifold 14 and
the nozzles 18 to heat them to a predetermined operating
temperature. Pressurized melt is then supplied from a
molding machine (not shown) to a central inlet 118 of the
melt passage 10 according to a predetermined cycle. The
melt flows through the melt distribution manifold 14 and
the heated nozzles 18 into the cavities 24. After the
cavities 24 are filled and a suitable packing and cooling
period has expired, injection pressure is released. The
mold 26 is then opened to eject the molded product. After
ejection, the mold 26 is closed and the cycle is repeated
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continuously every 15 to 30 seconds with a frequency
depending upon the wall thickness and number and size of
the cavities 24 and the exact material being molded.
While the description of the injection molding
apparatus wherein each nozzle is first prealigned by a rear
locating flange and then accurately located by a front
locating and sealing ring has been given with respect to
preferred embodiments, it will be evident that various
other modifications are possible without departing from the
scope of the invention as understood by those skilled in
the art and as defined in the following claims. For
instance, the mold can be shaped to have several gates
around each nozzle and the tip insert 74 can be shaped to
provide multiple hot tip or edge gate molding.
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