Note: Descriptions are shown in the official language in which they were submitted.
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Title: Integral Multi-Material Injection Molding Nozzle Seal and Tip
FIELD OF THE INVENTION
This invention relates to injection molding and, in particular, to
an integral multi-material nozzle seal and tip which is removably attachable
to an injection molding nozzle.
BACKGROUND OF THE INVENTION
One piece nozzle seals and gate inserts for insertion in the
front end of a heated nozzle are well known and have various configurations.
U.S. Patent No. 4,043,740 to Gellert shows a nozzle seal which fits into a
matching seat in the front end of the nozzle and has a portion which tapers
inwardly around the gate. U.S. Patent No. 4,981,431 to Schmidt discloses a
nozzle seal having an outer sealing flange which is screwed into place in a
seat in the front end of the heated nozzle. U.S. Patent No. 4,875,848 to
Gellert describes a gate insert which screws into place and has an integral
electrical heating element. U.S. Patent No. 5,028,227 to Gellert et al. shows
a gate insert having a circumferential removal flange to permit it to be pried
from the nozzle seat when removal is desired.
These nozzle seals, however, are unsatisfactory when molding
materials having a narrow temperature window because heat transfer is
slow along the nozzle seal and heat is lost to the surrounding cooled mold.
To combat this problem, U.S. Patent No. 5,299,928 to Gellert discloses the
use of a two-piece nozzle insert, wherein an outer sealing piece is made of
a material having relatively low thermal conductivity, such as titanium, and
wherein an inner tip piece is made of a material having a relatively high
thermal conductivity, such as beryllium copper, or a wear resistant material
like tungsten carbide. This results in good heat transfer in the interior
portion of the part, with an insulative effect being created by the exterior
less
conductive portion. However, because the inner tip piece must be made of
a material such as beryllium copper or tungsten carbide, it cannot be easily
and reliably threaded for attachment to the outer sealing piece of the two-
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piece seal. Consequently the inner tip portion is trapped in place between
the seal and nozzle to hold the inner piece in place while the seal is
installed in the nozzle. Typically, as shown in Gellert 5,299,928, this is
achieved by providing the inner piece with an outwardly extending shoulder
against which the outer piece can bear to securely retain the inner piece
between the outer piece and the nozzle when the outer piece is threaded
onto the nozzle.
This two-piece design, however, presents several problems
not present with the one-piece gate seals. First and foremost among these
is the difficulties which are experienced when the nozzle seal is to be
removed. Periodic removal of the nozzle seal and tip is required for
maintenance, replacement and resin colour changes. In use, however,
heated melt often seeps in and around the junction of the nozzle and the
inner piece of the removable nozzle seal. When cooled, this resin seepage
acts like a glue to stick in the nozzle seal in the nozzle end. When the
connector is unthreaded in single piece devices, the "glue" is broken,
however, because the inner and outer pieces of the nozzle seal are
unattached in two-piece nozzles seals like that of the Gellert '928, when the
outer piece is unscrewed and removed from the nozzle, the inner piece
remains stuck within the nozzle. The inner piece must then be dislodged
from the nozzle by other means, such as by hitting or prying the inner piece
to unstick it from its seat in the nozzle end. Invariably, whatever the
technique for dislodging, additional wear and/or even outright damage to the
inner piece results, shortening the life of the piece.
Other multi-piece designs are also known. United States
Patents Nos. US,545,028 to Hume, 5,658,604 to Gellert and 6,089,468 to
Bouti show various alternatives or improvements to the design of Gellert
'928, but these also suffer from the same drawback, namely that the tip
insert is not fixed to the nozzle seal, but rather trapped between the seal
and
the nozzle. Thus, these devices are still susceptible to having the tip remain
stuck in the nozzle end when the seal is unscrewed and removed from the
nozzle for maintenance, etc.
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Also similar to the Gellert '928 configuration is the removable
nozzle tip and seal insert disclosed in US 5,208,052 to Schmidt. Here a
beryllium copper tip is held in place between the nozzle and a titanium seal
which is threaded to the nozzle. An insulative air space is further provided
between the tip and the sleeve. A zero clearance fit exists between the tip
and the sleeve in the cold condition so that, when the nozzle reaches
operating temperature, the tip longitudinal growth caused by thermal
expansion forces the sleeve outward and downward against the mold.
While apparently providing an improved means for sealing the mold gate,
the insert of Schmidt also suffers from the limitations of the prior art
discussed above, in that when the sleeve is removed for maintenance or
replacement, the tip is susceptible to remaining stuck in the nozzle end
because the tip and sleeve are unconnected. Thus, tip damage of the type
already described may still result. A further disadvantage of the Schmidt
design is that the nozzle tip and sleeve require extremely accurate
machining to within tight tolerances to ensure that the zero clearance
sealing mechanism of the invention is effective. Such accurate machining
is time-consuming and expensive.
Another removable tip and gate configuration is provided by
United States Patent No. 5,879,727 to Puri. Puri discloses providing an
intermediate titanium or ceramic insulating element between a copper-alloy
nozzle tip and a steel gate insert to thermally isolate the nozzle tip from
the
gate insert while permit a secure mechanically connection between the two.
The tip itself joins the assembly to the nozzle end, either removably, through
the provision of threads, or integrally. As described above, however, the
threading of the nozzle tip is undesirable where copper-alloy tips are used
and impossible if a tungsten carbide tip insert is desired. Furthermore, the
additional insulating sleeve of Puri is an additional element which must be
accurately machined and maintained, thereby adding to both the initial cost
and the maintenance demands on the operator.
US 4,004,871 to Hardy discloses a bi-material mold gate
conduit for use in injection molding thermosetting resins. The Mold gate
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conduit has an inner tube welded or brazed to an outer sleeve-like body.
The outer sleeve is slidably received within and pinned between co-
operating mold plate members, and an annular chamber for circulating
coolant around the gate is provided between the outer sleeve and the inner
tube. However, because the outer sleeve is only slidably received by the
assembly, there is no secure attachment provided and, further, removal can
be difficult because resin leakage can freeze the conduit to the assembly,
making the unit just as susceptible to damage in removal as in those
devices described above.
Accordingly, there is a need for an improved multi-material
replaceable nozzle tip which is more easily removable and which is less
susceptible to damage than the replace able nozzle tips of the prior art.
Further, there is a need for such tips which are more easily manufacturable
and at a reduced cost.
SUMMARY OF THE INVENTION
In one aspect, the present invention provides a removable
injection molding nozzle tip comprising a tip member formed of a first
material, said tip member having a rear end, a front end communicating
with a mold gate, a central melt duct extending through said tip member
from said rear end to said front end, and an outer surface extending around
said tip member, and a sleeve member formed of a second material
different from said first material, said sleeve member extending around at
least a portion of said tip member, said sleeve member having a front end
adapted to sealingly contact a mold plate around a mold gate, a rear end
adapted for removable attachment to an injection molding nozzle body, and
a inner surface contacting at least a portion of said outer surface of said
tip
member to form an interface between said sleeve member and said tip
member, wherein said sleeve member is threadlessly integrally attached to
said tip member at said interface.
In a second aspect, the present invention provides a
removable injection molding nozzle tip comprising a tip member formed of a
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first material, said tip member having a rear end, a front end adapted to
communicate with a mold gate, a central melt duct extending through said
tip member from said rear end to said front end, and a substantially smooth
outer surface extending around at least a portion of said tip member, and a
sleeve member formed of a second material different from said first
material, said sleeve member extending around at least a portion of said tip
member, said sleeve member having a front end adapted to sealingly
contact a mold plate around a mold gate, a rear end adapted for removable
attachment to an injection molding nozzle body, and a substantially smooth
inner surface contacting at least a portion of said outer surface of said tip
member to form a interface therebetween, said sleeve member being
integrally attached to said tip member at said interface.
In a third aspect, the present invention provides an injection
molding apparatus for forming a molded article, the apparatus comprising
at least one mold cavity, said at least one mold cavity formed between at
least one pair of mold plates, said at least one mold cavity having a mold
gate for communicating with an interior of said at least one cavity, an
injection molding nozzle having a body, an end, and at least one melt
channel through said body, said injection molding nozzle connectable to a
source of molten material and capable of feeding molten material from said
source to said end through said at least one melt channel, and a nozzle tip
removably mounted to said end of said injection molding nozzle, said nozzle
tip having a tip member formed of a first material, said tip member having a
rear end, a front end communicating with a mold gate, a central melt duct
communicating with said at least one melt channel and extending through
said tip member from said rear end to said front end, and an outer surface
extending around said tip member, and a sleeve member formed of a
second material different from said first material, said sleeve member
extending around at least a portion of said tip member, said sleeve member
having a front end adapted to sealingly contact one of said mold plates
around said mold gate, a rear end adapted for removable attachment to
said injection molding nozzle body, and a inner surface contacting at least a
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portion of said outer surface of said tip member to form an interface
between said sleeve member and said tip member, said sleeve member
being threadlessly integrally attached to said tip member at said interface.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the present invention and to
show more clearly how it may be carried into effect, reference will now be
made by way of example to the accompanying drawings showing articles
made according to a preferred embodiment of the present invention, in
which:
Figure 1 is a sectional view of an injection molding system
incorporating a removable multi-material nozzle tip according to a preferred
embodiment of the present invention;
Figure 2 is an enlarged sectional view of the nozzle tip of
Figure 1;
Figure 3 is an enlarged sectional view of an alternate
embodiment of the nozzle tip of Figure 1, having no internal shoulder;
Figure 4 is an enlarged sectional view of a further alternate
embodiment of the nozzle tip of Figure 1, having a tip of reduced size;
Figure 5 is an enlarged sectional view of a yet further alternate
embodiment of the nozzle tip of Figure 1, having a two-piece seal portion;
Figure 6 is an enlarged sectional view of a still further alternate
embodiment of the nozzle tip of Figure 1, having a two-piece tip portion;
Figure 7a is an enlarged sectional view of another alternate
embodiment of the nozzle tip of Figure 1, having a wear-resistant tip;
Figure 7b is an enlarged sectional view of a second
configuration of the embodiment of Figure 7a;
Figure 8a is an enlarged sectional view of yet another alternate
embodiment of the nozzle tip of Figure 1, having an internal angled portion at
an upper end thereof;
Figure 8b is a much enlarged sectional view of a portion of
Figure 8a;
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Figure 8c is an enlarged sectional view of a second
configuration of the embodiment of Figure 8a, having an internal angled
portion at a lower end thereof;
Figure 8d is a much enlarged sectional view of a portion of
Figure 8c;
Figure 9 is an enlarged sectional view of an alternate
embodiment of the nozzle tip of Figure 1, having a two-channel tip;
Figure 10 is an enlarged sectional view of an alternate
embodiment of the nozzle tip of Figure 1, having alternate attachment
means;
Figure 11 is an enlarged sectional view of an alternate
embodiment of the nozzle tip of Figure 1, having a further alternate
attachment means;
Figure 12 is an enlarged sectional view of a portion of an
injection molding system incorporating a replaceable integral nozzle tip
according a second main embodiment of the present invention;
Figures 13a-13d are enlarged sectional views of alternate
embodiments of the nozzle tip of Figure 12;
Figure 14 is a sectional view of a portion of an injection
molding system incorporating a replaceable integral valve-gated nozzle tip
according to the present invention;
Figure 15 is an enlarged sectional view of the nozzle tip of
Figure 14;
Figure 16 is an enlarged sectional view of an alternate
embodiment of the nozzle tip of Figure 14, having an internal shoulder; and
Figure 17 is an enlarged sectional view of an alternate
embodiment of the nozzle tip of Figure 14, having an integral construction.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A portion of a multi-cavity injection molding system or
apparatus made in accordance with the present invention is shown in the
Figures generally at M. Referring to Figure 1, apparatus M has a melt
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distribution manifold 10 interconnecting several heated nozzles 12 in a mold
14. While mold 14 usually has a greater number of plates depending upon
the application, in this case a nozzle mold platen 15, cavity plate 16, a
support plate 17, a back plate 18 and under cavity platen 19, which are
secured together by bolts 20, are shown for ease of illustration. The melt
distribution manifold 10 is heated by an integral electrical heating element
22 and mold 14 is cooled by pumping cooling water through cooling
conduits 24. Melt distribution manifold 10 is mounted between cavity plate
16 and back plate 18 by a central locating ring 26 and insulative spacer
members 28 which provide an insulative air space 30 between heated
manifold 10 and surrounding mold 14.
A melt passage 32 extends from a central inlet 34 in a
cylindrical inlet portion 36 of manifold 10 and branches outward in manifold
10 to convey heated melt through a central bore 38 in each of heated
nozzles 12. Heated melt then flows through a melt duct 40 in an integral
nozzle seal and tip 42 according to the present invention to a gate 44
extending through cavity plate 16 leading to a cavity 46. Each nozzle 12 has a
rear end 48 which abuts against front face 50 of melt distribution manifold
10 and a front end 52 with a threaded seat 54 extending around central melt
bore 38. An electrical heating element 56 extends in the nozzle 12 integrally
around central melt bore 38 to an external terminal 58 to receive power
through leads 60. Nozzle 12 is seated in a well 62 in cavity plate 16 with an
insulative air space 68 between heated nozzle 12 and cooled mold 14.
Nozzles 12 are securely retained in wells 62 by bolts 74 which extend from
manifold 10 into cavity plate 16.
Referring to Figure 2, integral nozzle seal and tip 42 has a tip
member 76 integrally joined to a sleeve member 78. As will be described
below, sleeve 78 performs a sealing function and a connecting function. Tip
76 has an outer surface 80, a rear end 82, and a front end 84 and melt duct
40 extending from rear end 82 to front end 84. Outer surface 80 has a
substantially smooth (i.e. unthreaded) cylindrical portion 86 extending
between a shoulder 88, which extends outwardly near the rear end 82, and
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a portion 90, which tapers inwardly to the front end 84. Sleeve 78 of integral
nozzle seal and tip 42 has a rear end 92, a front end 94, and an inner
surface 96 with a substantially smooth (i.e. unthreaded) cylindrical portion
98 which fits around the cylindrical portion 86 of the outer surface 80 of the
tip 76. Tip 76 is integrally attached to sleeve 78 at an interface 100 where
portion 86 of outer surface 80 and portion 98 of inner surface 96 contact one
another, as will be described in more detail below. Sleeve 78 also has a
hexagonal nut-shaped portion 102 extending between a rear portion 104
and a cylindrical front seal portion 106. Rear portion 104 is threaded and
adapted to engage mating threads in seat 54 in front end 52 of nozzle 12.
Melt duct 40 through tip 76 of integral nozzle seal and tip 42 is aligned with
central melt bore 38 through nozzle 12 and leads to an outlet 110 at front
end 84 and is aligned with gate 44. The nut-shaped intermediate portion
102 extends outwardly into insulative air space 68 between front end 52 of
the heated nozzle and cooled mold 14 and is engageable by a suitable tool
to tighten integral nozzle seal and tip 42 in place or remove it for cleaning
or
replacement if necessary, as will be described further below. Sleeve 78 of
integral nozzle seal and tip 42 extends forwardly towards gate 44 and seal
portion 106 of sleeve 78 is in sealing contact with cylindrical surface 114 of
opening 112 to prevent pressurized melt escaping into insulative air space
68.
Tip 76 may be made of a corrosion and wear resistant material
such as tungsten carbide or may be a highly thermally conductive material
such as beryllium copper (BeCu) or other copper alloys. Sleeve 78 of
integral nozzle seal and tip 42, which is in contact with both heated nozzle
12
and cooled mold 14, is made of a material which is less thermally
conductive, and preferably much less thermally conductive, than the tip 76.
Materials such as a high speed steel, H13 stainless steel and titanium are
preferred. Tip 76 is integrally attached to sleeve 78, preferably by nickel
alloy
brazing, along an interface 100.
Referring again to Figure 1, in use electrical power is applied
to heating element 22 in manifold 10 and to heating elements 56 in nozzles
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12 to heat them to an operating temperature. Pressurized melt is provided
from a molding machine (not shown) to central inlet 34 of melt passage 32
according to a predetermined cycle. The melt flows through melt
distribution manifold 10, nozzles 12, integral nozzle seal and tip 42 and gate
44 into cavity 46. After cavity 46 is filled and a suitable packing and
cooling
period has expired, the injection pressure is released and the melt
conveying system is decompressed to avoid stringing through open gates
44. The mold 14 is then opened to eject the molded product. After ejection,
mold 14 is closed and the cycle is repeated continuously with a cycle time
dependent upon the size of cavities 46 and the type of material being
molded. During this repetitious injection cycle, heat is continuously
transferred by integral nozzle seal and tip 42 according to a predetermined
thermodynamic cycle. The proximity of the cooled metal around cavity 46
and the uniform thin insulation provided between it and integral nozzle seal
and tip 42 allows for controlled solidification of the sprue. During
injection,
the highly conductive tip 76 of integral nozzle seal and tip 42 helps to
conduct excess heat which is generated by the friction of the melt flowing
through the constricted area of gate 44 rearwardly to avoid stringing and
drooling of the melt when the mold opens for ejection. After the melt has
stopped flowing, solidification of melt in gate 44 is enhanced by the removal
of excess friction heat through tip 76 of integral nozzle seal and tip 42.
Also, in use, integral nozzle seal and tip 42 is periodically
removed for maintenance, repair or resin colour change. To do so, nozzle
12 is withdrawn from well 62 and hex-nut portion 102 of integral nozzle seal
and tip 42 is engaged by a suitable tool permit integral nozzle seal and tip
42 to be threadingly removed from end 52 of nozzle 12. Since the nozzle
seal of the present invention is integral, the nozzle seal is always removed
in one piece from end 52 of nozzle 12. Unlike the prior art, due to its
integral
nature integral nozzle seal and tip 42 is not susceptible to having tip 76
remain stuck within nozzle 12 after sleeve 78 is removed. The thread-
advancing action in unscrewing integral seal and tip 42 from nozzle 12
ensures that the integral seal and tip does not stick thereto.
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As is known in the art, employing a highly conductive tip 76 with
a sleeve 78 of lesser conductivity provides the combination of good
conductivity along tip 76, to maintain a rapid thermodynamic cycle, and
provides thermal separation via sleeve 78 to reduce heat lost to cooled
mold 14. (A measure of insulation is also provided by a circumferential air
space 120 provided between tip 76 and sleeve 78, which also partially fills
with melt which solidifies to provide additional insulation.)
According to the present invention, however, bonding tip 76 to
sleeve 78 provides an nozzle seal integral unit which results in better
performance and longevity, by reason of facilitating maintenance and tip
change because removal of the threaded connector portion also intrinsically
removes the tip portion as well from the nozzle seat, thereby removing the
possibility that the tip will be independently stuck in the nozzle and thereby
require additional effort to remove. In doing so, the present invention
provides a tip which will not need to be subject to the physical abuse, as it
were, the prior art nozzle tips are subject to in removal from a stuck
condition
in a nozzle. This permits the present invention to provide a nozzle seal unit
with increased longevity and which facilitates easier nozzle seal removal
overall.
Advantageously, the present invention also permits integral
nozzle seal and tip 42 to be fabricated more simply because brazing tip 76
to sleeve 78 permits these components to be made within less strict
tolerances than the prior art. Specifically, because an additional brazing
material is added between tip 76 and sleeve 78 at interface 100, outer
surface 80 and inner surface 96 do not necessarily have to be within the
same strictness of tolerances as with the prior art, which typically requires
a
smooth, face-to-face contact at interface 100. Thus, the present invention
provides a replaceable nozzle tip and seal which may be made more
economically.
Referring to Figures 3-9, alternate embodiments of the nozzle
tip of Figure 1, are shown. As most of the elements are the same as those
described above, common elements are described and illustrated using the
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same reference numerals. Referring to Figure 3, in a first alternate
embodiment, tip 76 and sleeve 78 are of roughly the same length and tip 76
resides completely within sleeve 78.
Referring to Figure 4, in an alternate embodiment of the nozzle
tip of Figure 1, tip 76 is shorter than sleeve 78, and terminates at a
shoulder
122. Melt duct 40 has two regions, namely a connector melt duct 40A and a
tip melt duct 40B.
Referring to Figure 5, in a further alternate embodiment of the
nozzle tip of Figure 1, sleeve assembly 130 comprises a seal member 132
and a connector member 134 integrally joined, preferably by brazing, along
an interface 136. Seal member 132 is preferably made of a material having
lower thermal conductivity, such as H13 stainless steel, high speed steel or
titanium, while connector member 134 is more thermal conductive and
made of BeCu or other alloys of copper.
Referring to Figure 6, in a further alternate embodiment of the
nozzle tip of Figure 1, tip assembly 140 comprises a rear member 142 and
a tip member 144 integrally joined, preferably by brazing, along an interface
146.
Referring to Figure 7a, in a further alternate embodiment of the
nozzle tip of Figure 1, tip portion 150 comprises a body member 152 and a
tip point 154 integrally joined, preferably by brazing, along an interface
156.
Body member 152 is preferably made of a material having high thermal
conductivity, such as beryllium copper, and tip point 154 is made of a
corrosion and wear resistant material such as tungsten carbide. Referring
to Figure 7b, in an alternate configuration, a tip insert 154' is used, which
is
integrally joined, preferably by brazing, along an interface 156'. The brazing
is preferably achieved with a brazing material having a substantially lower
melt temperature than the brazing done at interface 100, such that tip insert
154' is removable without compromising the braze at interface 100.
Referring to Figure 8a, in another alternate embodiment nozzle
tip of Figure 1, tip 76 and sleeve 78 have a mating angled section 160, near
rear end 82 of tip 76, at which tip portion is slightly expanded in diameter.
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This construction assists in the assembly of integral nozzle seal and tip 42
prior to the integral joining of tip 76 and sleeve 78. Referring to Figure 8b,
alternately a mating angled section 162 may be provided near front end 94
of sleeve 78, at which tip 76 is slightly reduced in diameter.
Referring to Figure 9, in another alternate embodiment nozzle
tip of Figure 1, tip 76 is a two-channel tip in which melt duct 40 terminates
in
two outlets 110a and 110b.
As one skilled in the art will appreciate, the replaceable
integral nozzle seal and tip of the present invention is not limited to one in
which nozzle seat 54 and seal rear portion 104 are threaded to one another.
Rather, other means of removably connecting integral nozzle seal and tip 42
to nozzle 12 may be employed. For example, rear portion 104 can be brazed
to seat 54 using a second brazing material which has a melting
temperature which is substantially lower than the brazing material used at
interface 100, as disclosed in U.S. Patent No. 6,009,616 to Gellert,
incorporated herein by reference. Referring to Figure 10, in one aspect tip
76 is integrally brazed to sleeve 78 along interface 100 using a first brazing
material, as described above, to make integral nozzle seal and tip 42. The
integral tip insert is then brazed to nozzle 12, along an interface 170, using
a
second brazing material which has a melting temperature preferably
substantially below that of the first brazing material. This approach allows
integral tip to be easily removed for replacement or repair by heating but
does not affect the metallurgical bond at interface 100 during either
installation or removal. Referring to Figure 11, in a second aspect, a
combined attachment means for attaching integral nozzle seal and tip 42 to
nozzle 12 is shown. In this aspect, integral nozzle seal and tip 42 is both
threaded and brazed to nozzle 12. Rear portion 104 has threads for
engaging seat 54, as described for the embodiments above, and is
additionally brazed along interface 172 using a second brazing material
which has a melting temperature preferably substantially below that of the
first brazing material employed at interface 100.
Referring to Figure 12, in another embodiment of the present
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invention sleeve 78 is connected around and outside front end 52 of nozzle
12. Sleeve 78 has a threaded read end 104 which removably engages
threads in seat 54 of nozzle 12. Tip 76 is integrally brazed to sleeve 78 at
interface 100. Optionally, tip 76 may also be brazed directly to nozzle 12,
along interface 180, using a second brazing material which has a melting
temperature preferably substantially below that of the first brazing material
employed at interface 100, in a process as disclosed in Gellert 6,009,616
and described above. The integral connection between tip 76 and sleeve
78, along interface 100 permits the integral nozzle seal and tip 42 to be
removed as a single unit.
Figures 13a-13d disclose some of the many modifications
possible to the Figure 12 embodiment of the present invention. In Figure
13a, the threaded connection between rear portion 104 and seat 54 is
replaced by a braze along interface 182, this braze being of a second
brazing material which has a melting temperature preferably substantially
below that of the first brazing material employed at interface 100. Referring
to Figure 13b, nozzle 12 may be provided with a band heater either in
place of or conjunction with electrical heating element 56 (not seen in Figure
13b but shown in Figure 1). As shown in Figure 13c, electrical heating
element 56 may extend to front end 52 of nozzle 12 and inside the portion of
nozzle 12 surrounded by rear portion 104 of sleeve 78. Referring to Figure
13d, tip 76 may be a two-channel tip in which melt duct 40 terminates in two
outlets 110a and 110b.
As one skilled in the art will appreciate, the replaceable
integral nozzle seal and tip of the present invention is not limited to a
torpedo style gating as described above. Referring to Figures 14-17, the
present invention is shown in use in several a valve gating embodiments.
As most of the elements are the same as those described above, common
elements are described and illustrated using the same reference numerals.
Referring to Figure 15, a portion of an injection molding nozzle
is shown with a replaceable integral valve-gated nozzle according to the
present invention. As with the embodiments above, integral nozzle seal and
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tip 42 comprises a tip 76 and a sleeve 78. Centrally located within melt
passage 32 and melt duct 40 is a valve pin 190 positionable between an
"open" position (as seen on the left half of Figure 14) and a "closed"
position
(as seen on the right half of Figure 14). During the injection cycle, valve
pin
is withdrawn to its "open" position by suitable means (not shown) to permit
pressurized melt to flow from an injection molding machine (not shown),
through melt passage 32, melt duct 40 and gate 44 into cavity 46. When the
cavity is filled with melt and a suitable packing period has passed, valve pin
190 is moved to the closed position to block and seal gate 44 prior to the
opening of the mold to eject the molded part. The specifics of the operation
of such valve gates are not within the scope of the present invention and are
well-known in the art and, thus, a more detailed description is not required
in this specification.
Tip 76 and a sleeve 78 are again integrally joined, preferably by
nickel alloy brazing, along an interface line 100 between outer surface 80 of
tip 76 and inner surface 96 of sleeve 78. As with the embodiments
described above, tip 76 is preferably made of a highly thermally conductive
material such as beryllium copper (BeCu) while sleeve 78 is preferably
made of a material which is less thermally conductive, and preferably much
less thermally conductive, than the tip 76. Materials such as a high speed
steel, H13 stainless steel and titanium are preferred.
Referring to Figure 16, in an alternate embodiment of the valve
gate of Figure 10 and 11, tip 76 has a shoulder 88 which extends outwardly
near the rear end 82.
It will be understood that, in the descriptions in this
specification, the same reference numerals have been used throughout the
Figures to depict the elements which are common to, or have a common
function within, the embodiments described.
While the above description constitutes the preferred
embodiments, it will be appreciated that the present invention is susceptible
to modification and change without departing from the fair meaning of the
accompanying claims. For example, other brazing materials may be used
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or, rather than brazing, the nozzle tip and seal portions may be integrally
made by thermally bonding, welding, thermally expanding, interference
fitting tip 76 within sleeve 78. As well, one skilled in the art will
appreciate
that the present invention may also be applied to inserts utilizing other
gating methods, such as sprue gates, edge gates, multi-tip gates and
horizontal tip gates, and that the present invention is not limited to the
gating
configurations described herein. Still other modifications will be apparent to
those skilled in the art and thus will be within the proper scope of the
accompanying claims.
