Note: Descriptions are shown in the official language in which they were submitted.
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Title: GAP SEAL BETWEEN A NOZZLE AND A MOLD COMPONENT IN
AN INJECTION MOLDING APPARATUS
FIELD OF THE INVENTION
This invention relates to an injection molding apparatus, and more
particularly to a seal between a nozzle and a mold component in an injection
molding apparatus.
BACKGROUND OF THE INVENTION
A hot runner injection molding apparatus typically includes nozzles that
are heated to maintain melt therein at a controlled temperature. The nozzles
are typically in contact with a mold component that defines one or more mold
cavities. The mold cavities in the mold component are filled with melt that
first
passes through the nozzles. The mold component is then typically cooled in
order to solidify the melt in the mold cavities, thus forming a plurality of
molded parts, which are then ejected from the mold cavities.
Because the nozzles are typically heated, and the mold component is
cooled for at least a portion of an injection molding cycle, it is desirable
to
have a relatively low heat transfer from the nozzles into the mold component.
Many nozzle constructions have been proposed in the past to address this
issue.
An example of such a nozzle construction is shown in US Patent No.
5,554,395, to Hume et al. The '395 patent teaches a multi-piece nozzle tip
assembly including a tip piece, a tip surrounding piece and a resilient
element.
The resilient element is provided between the tip piece and the mold
component, to inhibit melt leakage therepast. However, heat can be lost from
the tip piece through the resilient element and into the mold component. In
particular, the heat losses occur near the downstream end of the tip piece,
where control over the temperature of the melt is particularly important.
Thus, there is a continuing need for new nozzle constructions that have
further improved heat transfer efficiency.
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SUMMARY OF THE INVENTION
In a first aspect, the invention is directed to a nozzle for an injection
molding apparatus, comprising a nozzle body, a heater and a first gap seal
surface. The nozzle body defines a nozzle body melt passage, that is
adapted to be downstream from and in fluid communication with a melt
source, and upstream from and in fluid communication with a gate into a mold
cavity in a mold component. The heater is thermally connected to the nozzle
body for heating melt in the nozzle body melt passage. The first gap seal
surface is positioned on a structure that is connected at least indirectly to
the
nozzle body. The first gap seal surface is adapted to be separated by a gap
with respect to a second gap seal surface on the mold component. The gap
is sized to inhibit the flow of melt between the first gap seal surface and
the
second gap seal surface.
In a second aspect, the invention is directed to an injection molding
apparatus incorporating the nozzle described above.
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, in which:
Figure 1 is a sectional view of a portion of a nozzle in accordance with
a first embodiment of the present invention;
Figure 2 is a magnified view of a sealing portion of the nozzle shown in
Figure 1;
Figure 3a is a sectional view of a portion of a nozzle in accordance with
a second embodiment of the present invention;
Figure 3b is a magnified view of a sealing portion of the nozzle shown
in Figure 2;
Figure 3c is a sectional view of a portion of a nozzle in accordance with
a third embodiment of the present invention;
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Figure 4 is a sectional view of a portion of a nozzle in accordance with
a fourth embodiment of the present invention;
Figure 5 is a sectional view of a portion of a nozzle in accordance with
a fifth embodiment of the present invention;
Figure 6 is a sectional view of a portion of a nozzle in accordance with
a sixth embodiment of the present invention;
Figure 7 is a side view of a nozzle in accordance with a seventh
embodiment of the present invention;
Figure 8 is a sectional view of a portion of the nozzle shown in Figure
7;
Figure 9 is a sectional view of a portion of a nozzle in accordance with
an eighth embodiment of the present invention;
Figure 10 is a sectional view of a portion of a nozzle in accordance with
a ninth embodiment of the present invention;
Figure 11 is a sectional view of a portion of a nozzle in accordance with
a tenth embodiment of the present invention; and
Figure 12 is a sectional view of an injection molding apparatus
incorporating a nozzle in accordance with an eleventh embodiment of the
present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Reference is made to Figure 1, which shows a nozzle 10, in
accordance with a first embodiment of the present invention. Nozzle 10 is for
transferring melt from a runner in a manifold in a hot runner injection
molding
apparatus to a mold cavity 11 in a mold component 12. Mold cavity cooling
channels 13 may optionally be included in mold component 12.
Nozzle 10 includes a nozzle body 14, a tip 16, and a heater 17 and
may include a tip surrounding piece 18, an alignment piece 20 and a
thermocouple 26. The nozzle body 14 has a body melt passage 28 that
passes therethrough.
The heater 17 may be any suitable kind of heater, such as a resistive
wire heater, or a sleeve heater, as long as it is thermally connected to the
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nozzle body 14, i.e. the heater 17 is connected such that heat is transferable
from the heater 17 to the nozzle body 14. For example, the heater 17 may
wrap around the nozzle body 14 in a groove on the outer surface of the nozzle
body 14.
The tip 16 may be removably connected to the nozzle body 14. The tip
16 defines a tip melt passage 30 therethrough that is downstream from and in
fluid communication with the body melt passage 28. The tip melt passage 30
may exit from tip 16 into a chamber 32. A gate 34 transfers melt from the
chamber 32 into the mold cavity 11.
Melt passes from a melt source, through one or more runners in a
runner component such as a manifold, through the nozzle body melt passage
28, through the tip melt passage 30, through the chamber 32, through the
gate 34 and finally into the mold cavity 11. The centre of the gate 34 defines
an axis 35, which is parallel to the direction of flow of melt through gate
34,
into the mold cavity 11.
The exit from the tip melt passage into the chamber 32 is shown at 36.
Exit 36 may be concentric with respect to axis 35, as shown in Figure 1.
Because the melt flows through the tip 16, the tip 16 can be used to
transfer heat from the heater 17 to the melt. To facilitate the heat transfer,
the
tip 16 is preferably made from a thermally conductive material, such as
Beryllium-Copper.
Because of the melt flow through tip 16, the tip 16 may be exposed to a
highly abrasive environment, and it may be desirable to make the tip 16 from
a wear resistant material. An example of a material that is both thermally
conductive and wear resistant is Tungsten Carbide. The tip 16 may be made
in accordance with the teachings in US Patent No. 5,658,604 (Gellert et al.),
which is hereby incorporated by reference and which discloses the
construction of a nozzle tip using Tungsten Carbide.
The tip 16 may be positioned within a bore 37 in the nozzle body 14.
Depending on the material selected for the tip 16, a threaded portion can be
relatively difficult to machine. Furthermore, such a threaded portion can be
brittle and subject to premature failure, depending on the material of
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manufacture for the tip 16. Thus, by making the tip 16 threadless, a greater
number of materials are available for its manufacture.
Furthermore, by making the tip 16 threadless, some cost of
manufacture is saved for the tip 16 and correspondingly for the nozzle body
14, relative to a threaded tip.
The tip surrounding piece 18 may retain the tip 16 in place in the
nozzle body 14. The tip surrounding piece 18 may include a jam surface 38
which abuts a shoulder 39 on the tip 16 to retain the tip 16 in place. The jam
surface 38 and the shoulder 39 may cooperate to form a mechanical seal.
The tip surrounding piece 18 may be removably attachable to the
nozzle body 14. For example, the tip surrounding piece 18 may include a tip
surrounding piece threaded portion 40 for mating with a corresponding nozzle
body threaded portion 41 on the nozzle body 14. The threaded portion 40 as
shown in Figure 1 is an external thread, however, it is alternatively possible
for the tip surrounding piece to include an internal thread to mate with an
external thread on the nozzle body 14.
The tip surrounding piece 18 may also include a tool engagement
portion 42, for receiving a tool (not shown), for the installation and removal
of
the tip surrounding piece 18 with respect to the nozzle body 14.
A gap seal 48 may be formed by the tip surrounding piece 18 in
cooperation with the mold component 12, as shown more clearly in Figure 2.
More specifically, a tip surrounding piece sealing surface 50 on the tip
surrounding piece 18 may cooperate with a mold component sealing surface
52 on the mold component 12 to form the gap seal 48. The tip surrounding
piece sealing surface 50 may be an outer surface on the tip surrounding piece
18, and the mold component sealing surface 52 may be the wall of the nozzle
well, which is shown at 53 The tip surrounding piece sealing surface 50 and
the mold component sealing surface 52 are separated from each other by a
gap G. The tip surrounding piece sealing surface 50 may be referred to as
the first gap seal surface 50, and the mold component sealing surface 52 may
be referred to as the second gap seal surface 52.
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Due to the viscosity of the melt in the chamber 32, the proximity of the
first tip surrounding piece sealing surface 50 and the mold component sealing
surface 52 inhibits melt from flowing between the first tip surrounding piece
sealing surface 50 and the tip sealing surface 52. Thus, the gap G, in
conjunction with the viscosity of the melt, acts as a seal.
The Gap G may be less than approximately .07 mm if it the only seal
and is not combined with a mechanical seal. If the gap seal 48 is used in
combination with a mechanical seal, the gap G may optimally be
approximately .15 mm, or may be less than approximately .25 mm. It will be
noted that the gap G required to inhibit the flow of melt is dependent on the
specific molding application. The rheological properties of the melt at the
injection temperature, such as its viscosity, determine the maximum gap G
that provides the desired seal.
An advantage to including the gap seal 48 is that the manufacturing
tolerances for sealing surfaces 50 and 52 are less demanding, relative to a
typical mechanical sealing portion. A further advantage is that because melt
does not pass through the gap seal 48, an air space 54 is maintained
between the tip surrounding piece 18 and the mold component 12. The air
space 49 provides an insulative layer to reduce heat transfer between the tip
surrounding piece 18, and from the entire nozzle 10 in general, into the mold
component 12.
To further reduce heat losses from the tip surrounding piece 18 and
from the nozzle 10 in general into the mold component 12, the tip surrounding
piece 18 may be made from a material that has a thermal conductivity that is
lower than that of the material for the tip 16, depending on the specific
requirements of the molding application.
The tip surrounding piece 18 may alternatively be made from a material
that has a thermal conductivity that is similar to that of the nozzle tip 16.
Because the tip surrounding piece 18 may be positioned between a portion of
the heater 17 and the tip melt passage 30, as shown in Figure 1, it may be
advantageous to make the tip surrounding piece 18 from a material that has a
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thermal conductivity that is generally equal to that of the tip 16, to improve
heat transfer between the heater 17 and the tip melt passage 30.
Because the melt that contacts the tip surrounding piece 18 is
generally slower moving than the melt flowing through the tip 16, the tip
surrounding piece 18 may be made from a material that is less wear resistant
than that of the tip 16. Accordingly, the tip surrounding piece 18 may be
made from a material that is relatively easily machined with threads.
Referring to Figure 1, the alignment piece 20 may be included to align
the nozzle 10 with respect to the gate 34 in molding applications where such
alignment is important. The alignment piece 20 may be positioned between
the nozzle body 14 and a bore 56 in the mold component 12. The bore 56
includes therein, the nozzle well 53. The alignment piece 20 may be
positioned between the mold component 12 and any other suitable
component of the nozzle 10, instead of the nozzle body 10.
The alignment piece 20 may be made from a material that has a lower
thermal conductivity than that of the nozzle portion with which it is in
contact,
which is in this case, the nozzle body 14. For example, the alignment piece
may be made from tool steel, titanium, H13, or any other suitable material.
It is alternatively possible for the alignment piece 20 to be integrally
formed
20 into the nozzle body 14, or into any other suitable portion of the nozzle
10,
such as the tip surrounding piece 18.
Reference is made to Figure 3a, which shows a nozzle 60 in
accordance with a second embodiment of the present invention, in
combination with a mold component 61.
Nozzle 60 is similar to nozzle 10 (Figure 1 ), and includes the nozzle
body 14, the tip 16, and the heater 17, and may include a tip surrounding
piece 62 and a thermocouple 26. The tip surrounding piece 62 may be similar
to the tip surrounding piece 18 (Figure 1), and may have a jam surface 63
thereon which cooperates with the shoulder 39 on the tip 16 to retain the tip
16 in place in the nozzle body 14.
The tip surrounding piece 62 may include a tip surrounding piece
threaded portion 64 that cooperates with the threaded portion 41 on the
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nozzle body 14, so that the tip surrounding piece 62 is removably attached to
the nozzle body 14.
The tip surrounding piece 62 cooperates with the mold component 61
to form a multi-portion seal 65 therebetween. The multi-portion seal 65
includes a gap seal 66 and also includes a second seal 68, which may be, for
example, a mechanical seal, that is adjacent the gap seal 66. The gap seal
66 may be similar to the gap seal 48 (Figure 1), and is formed by the
cooperation of a first tip surrounding piece sealing surface 70 on the tip
surrounding piece 62, with a first mold component sealing surface 72 on the
mold component 61. The first tip surrounding piece sealing surface 70 and
the first mold component sealing surface 72 are separated by the gap G, as
shown more clearly in Figure 3b. The first tip surrounding piece sealing
surface 70 and the first mold component sealing surface 72 may be referred
to as the first gap seal surface 70 and the second gap seal surface 72,
respectively.
Because of the presence of the second seal 68, the gap G, in the
embodiment shown in Figure 3a may optimally be approximately .15 mm, and
may be less than approximately .25 mm.
The second seal 68 may also be referred to as a supplementary seal
68, and is formed by the cooperation of a second tip surrounding piece
sealing surface 74 on the tip surrounding piece 62, with a second mold
component sealing surface 76 on the mold component 61. The sealing
surfaces 74 and 76 may contact each other, as shown in Figure 3a. The
second tip surrounding piece sealing surface 74 and a second mold
component sealing surface 76 may be referred to as the first supplementary
seal surface 74 and the second supplementary seal surface 76 respectively.
The second seal 68 may be positioned behind the gap seal 66 with
respect to the chamber 32, so that melt is exposed to the gap seal 66 before
the second seal 68.
Because of the presence of the gap seal 66, the surface area of
contact between the tip surrounding piece 62 and the mold component 61
along the sealing surfaces 74 and 76, is smaller than would be required if the
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second seal 68 acted alone to seal against melt leakage therepast. Thus, the
heat transfer from the tip surrounding piece 62 and from the nozzle 60 in
general, into the mold component 61 is reduced accordingly.
In addition to forming the second seal 68, the second sealing surfaces
74 and 76 may cooperate to align the nozzle 10 with respect to the gate,
which is shown at 78. This applies particularly in the case, as shown in
Figure
3a, where the sealing surfaces 74 and 76 are substantially vertical surfaces.
However, the second sealing surfaces 74 and 76 may be inclined instead of
being vertical, and may still be adapted to align the nozzle 60 with respect
to
the gate 78.
Referring to Figure 3a, the mold component 61 may be similar to the
mold component 12 (Figure 1), and defines a plurality of mold cavities 80,
each of which has at least one gate 78 leading thereto. The mold component
61 may include cooling channels 82 for cooling of melt in the mold cavities
80.
Reference is made to Figure 3c, which shows a variant 60' of the
embodiment shown in Figure 3a. In the nozzle 60', a tip 84 replaces the tip 16
(Figure 3a). The tip 84 may be similar to the tip 16 (Figure 3a) and may
define a tip melt passage 86 therethrough. However, the tip 84 includes a
torpedo portion 87, and the tip melt passage 86 may have an exit 88 that is
off-centre from the axis of the gate 78, which is shown at 90.
It will be noted that the tip 84 may also replace the tip 16 in the
embodiment shown in Figures 1 and 2.
Reference is made to Figure 4, which shows another variant 60" of the
embodiment shown in Figure 3a. In the variant shown in Figure 4, the tip 84
replaces the tip 16 (Figure 3a). The items shown in Figure 4 are similar to
those in Figure 3a, except as follows. A gap seal 66" is formed which is
similar to the gap seal 66 (Figure 3a), except that the gap seal 66" is formed
between a first tip surrounding piece sealing surface 70" on a tip surrounding
piece 62", and a first mold component sealing surface 72" on a mold
component 61 ". The first sealing surfaces 70" and 72" may be entirely
inclined surfaces in the embodiment shown in Figure 4, whereas they are
shown as including an inclined portion and a substantially vertical portion in
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the embodiment shown in Figures 3a. The first sealing surfaces 70" and 72"
may also be referred to as the first and second gap seal surfaces 70" and 72"
respectively.
Reference is made to Figure 5, which shows yet another variant 60"' of
the embodiment shown in Figure 3a. In the variant shown in Figure 5, the tip
84 replaces the tip 16 (Figure 3a). The items shown in Figure 5 are similar to
those in Figure 3a, except as follows. A gap seal 66"' is formed which is
similar to the gap seal 66 (Figure 3a), except that the gap seal 66"' is
formed
between a first tip surrounding piece sealing surface 70"' on a tip
surrounding
piece 62"', and a first mold component sealing surface 72"' on a mold
component 61 "'. The first sealing surfaces 70"' and 72"' may be substantially
vertical surfaces in the embodiment shown in Figure 5, whereas they are
shown as including an inclined portion and a substantially vertical portion in
the embodiment shown in Figures 3a. The first sealing surfaces 70"' and 72"'
may also be referred to as the first and second gap seal surfaces 70"' and
72"'
respectively.
Reference is made to Figure 6, in which a nozzle 100 is shown in
accordance with an alternative embodiment of the present invention. The
nozzle 100 may be similar to the nozzle 60 (Figure 3a), and may include a
multi-portion seal 101 between a tip surrounding piece 102 and a mold
component 103.
The multi-portion seal 101 includes a gap seal 104 and a second seal
105. The gap seal 101 is made by a first tip surrounding piece sealing
surface 106 on the tip surrounding piece 102 cooperating with a first mold
component sealing surface 107 on the mold component 103.
In this embodiment, the sealing surfaces 106 and 107 may be
substantially horizontal as shown, and are separated by the gap G. The
sealing surfaces 106 and 107 may also be referred to as the first and second
gap seal surfaces 106 and 107 respectively. In this embodiment, a separate
alignment means (not shown) may be included if desired.
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It will be noted that the nozzle 100 may optionally not include the
second seal 105, and have only the gap seal 101 with the mold component
103.
Reference is made to Figures 7 and 8, which show a nozzle 200.
Nozzle 200 is similar to nozzle 10, but is an edge-gated nozzle. Nozzle 200
includes a nozzle body 201 having a nozzle melt passage 202, which divides
into a plurality of the melt passage portions 204 (Figure 8). Nozzle 200 is
for
feeding melt through a plurality of gates 205 into a plurality of mold
cavities
206, in a mold component 208. Nozzle 200 has an end 210, which may be
positioned in a bore 212 in the mold component 208, for transferring melt into
the mold cavities 206. On the end 210 is mounted a guide piece 214. The
guide piece 214 fits within a guide aperture 215 for aligning the end 210 of
nozzle 200 in the bore 212. The nozzle 200 may include a heater 216 and a
thermocouple 218 (Figure 7).
Referring to Figure 8, each nozzle melt passage portion 204 has
therewith a nozzle tip 220 and a tip surrounding piece 222. The tip 220 and
the tip surrounding piece 222 may mount to the nozzle body 201, in a similar
manner to tip 16 and tip surrounding piece 18 to nozzle body 14 (Figure 1).
The tip 220 includes a tip melt passage 224 is in communication with a nozzle
melt passage portion 204, and has an exit 226. The tip surrounding piece 222
may include a tip surrounding piece sealing surface 228 that surrounds exit
226 and gate 205, and is positioned at a gap G from a mold component
sealing surface 230 on the mold component 208, forming a gap seal 232
therewith. A chamber 234 is defined between the tip 220 and the gate 205.
The tip surrounding piece sealing surface 228 and the mold component
sealing surface 230 may be referred to as the first and second gap seal
surfaces 228 and 230 respectively.
Melt passes through nozzle melt passage 202, melt passage portions
204, tip melt passages 224, out from exits 226 into chambers 234, through
gates 205 and into mold cavities 206. Melt is inhibited from escaping from
chamber 234 by the gap seal 232.
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Nozzle 200 may include an alternative tip 240 and tip surrounding
piece 242 which are integrally joined, forming a single piece, instead of tip
220
and tip surrounding piece 222, or may include some of each type of tip and tip
surrounding piece.
Reference is made to Figure 9, which shows a nozzle 300 in
accordance with another embodiment of the present invention, in combination
with a mold component 301. The nozzle 300 may be similar to nozzle 10
(Figure 1), and includes a nozzle body 302, the heater 17, a tip 304 and may
optionally include the thermocouple 26. The nozzle body 302 defines a
nozzle body melt passage 306 therethrough. The heater 17 may be
positioned on the nozzle body 302 in any suitable way, for heating melt in the
nozzle body melt passage 306.
The tip 304 may be similar to the tip 16 (Figure 1) and defines a tip
melt passage 308 therethrough. The tip 304 may be removably connected to
the nozzle body 302 in any suitable way, so that the tip melt passage 308 is
in
fluid communication with and downstream from the nozzle body melt passage
306. The tip 304 may, for example, have a tip threaded portion 310 for mating
with a nozzle body threaded portion 312 on the nozzle body 302. The tip may
further include a tip tool engagement portion 314 for receiving a tool (not
shown), for the installation and removal of the tip 304 with respect to the
nozzle body 302.
The mold component 301 defines a plurality of melt cavities 316, each
of which has at least one gate 318 leading thereto. A plurality of cooling
channels 320 may be included in the mold component 301 to cool melt in the
mold cavities 316.
A gap seal 322 may be formed by the cooperation of the tip sealing
surface 324 and a mold component sealing surface 326, which are separated
by the gap G. The tip sealing surface 324 and the mold component sealing
surface 326 may also be referred to as the first and second gap seal surfaces
324 and 326 respectively.
The tip can be manufactured by any of the materials that are used for
the tip 16 (Figure 1 ), however, it may be advantageous to use a material
other
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than Tungsten Carbide, due to the existence of the threaded portion 310 on
the tip 304.
Reference is made to Figure 10, which shows a nozzle 400 in
accordance with another embodiment of the present invention, in combination
with the mold component 301. The nozzle 400 may be similar to the nozzle
300 and includes a nozzle body 402, the heater 17, a tip 404, a tip
surrounding piece 406 and may optionally include the thermocouple 26. The
nozzle body 402 may be similar to the nozzle body 302 (Figure 9), and
defines a nozzle body melt passage 408 therethrough. The nozzle body 402
also includes a first nozzle body threaded portion 410 for mating with a tip
threaded portion 412 on the tip 404. The nozzle body 402 also includes a
second nozzle body threaded portion 414 for mating with a tip surrounding
piece threaded portion 416 on the tip surrounding piece 406. The tip 404 may
be similar to the tip 304 and defines a melt passage 418 therethrough. The
tip 404 may also include a tip tool engagement portion 420 for receiving a
tool
(not shown). In the embodiment shown in Figure 10, the tip 404 is removably
connected to the nozzle body 402 by means of the cooperation of threaded
portions 416 and 410.
The tip surrounding piece 406 may be similar to the tip surrounding
piece 18 (Figure 1), except that the threaded portion 414 on the tip
surrounding piece 406 may be an internally threaded portion, instead of an
externally threaded portion, and except that the tip surrounding piece 406
does not retain the tip 404 in place.
The tip surrounding piece 406 may include a tip surrounding piece tool
engagement portion 422 for receiving a tool (not shown).
The tip surrounding piece 406 has a tip surrounding piece sealing
surface 424, which cooperates with the mold component sealing surface 326
to form a gap seal 428 therewith. The sealing surfaces 424 and 326 are
separated by the gap G, which inhibits melt leakage therebetween. The
sealing surfaces 424 and 326 may also be referred to as the first and second
gap seal surfaces 424 and 326 respectively.
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Reference is made to Figure 11, which shows a nozzle 60"", in
combination with a mold component 61 "", in accordance with a variant of the
nozzle 60"' and mold component 61 "' shown in Figure 5. The nozzle 60""
may be similar to the nozzle 60"' with the exception that a tip surrounding
piece 62"" on the nozzle 60"" includes a seal piece 450 thereon. The seal
piece 450 may be a band that surrounds the outer surface of the tip
surrounding piece 62"", and forms a gap seal 452 with the mold component
61"". The seal piece 450 has a sealing surface before that mates with mold
component sealing surface 72"" to form the gap seal 452. The sealing
surfaces 454 and 72"" are separated by the gap G, which inhibits melt
leakage therepast. The sealing surfaces 454 and 72"" may also referred to as
the first and second gap seal surfaces 454 and 72"" respectively.
The seal piece 450 may be made from a material that has a lower
thermal conductivity than that of the tip surrounding piece 62"". The seal
piece 450 may, for example, be made from titanium, H13, stainless steel,
mold steel or chrome steel. Other alternative materials include ceramics and
plastics. The seal piece 450 may, instead of being a separate piece that is
joined to the tip surrounding piece 62"", be a coating or layer that is
applied to
a portion of the outside surface of the tip surrounding piece 62"".
The tip surrounding piece 62"" may be positioned, at least in part,
between the heater and the tip melt passage 86. It may be advantageous in
the case shown in Figure 11, for the tip surrounding piece 62"" to be made
from a material that is generally equally thermally conductive as the material
of the tip 84. The seal piece 450 reduces the heat transfer between the tip
surrounding piece 62"" and the mold component 61"", by being made from a
material that has a lower thermal conductivity than that of the tip
surrounding
piece 62"".
Reference is made to Figure 12, which shows an injection molding
apparatus 500, that includes a runner component 502, the mold component
12 and a plurality of nozzles 504 in accordance with the present invention.
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The runner component 502 includes a plurality of runners 506 which
transfer melt from a main runner inlet 508 to the nozzles 504. The runner
component 502 may be heated by a heater 510.
The nozzles 504 transfer melt from the runner component 502 to the
mold component 12. The nozzles 504 may be any of the nozzle
embodiments and variants described above and shown in Figures 1-11, and
include a nozzle sealing surface 512 that is separated from a mold component
sealing surface 514 by the gap G to form a gap seal 516 therewith. The
nozzle sealing surface 512 and the mold component sealing surface 514 may
also be referred to as the first and second gap seal surfaces 512 and 514
respectively. The nozzle sealing surface 512 may be positioned on any
suitable portion or component of the nozzle 504.
A particular example of an injection molding apparatus is shown in
Figure 12. It will be appreciated that the injection molding apparatus that
incorporates the gap seal of the present invention may be any suitable type of
injection molding apparatus and is not limited to the example shown.
It will be appreciated that the first and second gap seal surfaces that
make up the gap seal of the present invention, may be surfaces on any
component of the nozzle and mold component respectively, and are not
limited to the examples shown and described herein. For greater certainty,
the first gap seal surface may be positioned on any suitable structure that is
part of the nozzle, and is therefore connected at least indirectly to the
nozzle
body.
Thermal expansion and contraction during a molding cycle must be
considered during the construction of the nozzles described above, so that the
gap G is within the ranges given above when the nozzle feeds melt into the
gate.
It will be appreciated that it may be advantageous to size the gap G so
as to reduce to a desired level, the amount of heat lost from the nozzle.
It will be appreciated that the particular configuration of the gap seal
portion may be selected depending on the specific molding application,
including the rheological properties of the melt, such as its viscosity at the
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injection temperature. It is contemplated that the invention can be applied to
nozzles with types of melt other than those types of melt specifically
disclosed
herein.
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.
SUBSTITUTE SHEET (RULE 26)
