U.S. patent application number 14/918282 was filed with the patent office on 2016-04-07 for injection nozzle with multi-piece tip portion.
The applicant listed for this patent is Otto Manner Innovation GmbH. Invention is credited to Gheorghe George Olaru, Swen Spuller.
Application Number | 20160096299 14/918282 |
Document ID | / |
Family ID | 51654637 |
Filed Date | 2016-04-07 |
United States Patent
Application |
20160096299 |
Kind Code |
A1 |
Spuller; Swen ; et
al. |
April 7, 2016 |
INJECTION NOZZLE WITH MULTI-PIECE TIP PORTION
Abstract
A hot runner nozzle assembly includes a nozzle heater, a hot
runner nozzle, a nozzle tip, a nozzle tip seal surrounding the
nozzle tip and a connecting element positioned to removably couple
the tip seal to the nozzle tip and to create a first contact seal
between the nozzle tip and the tip seal and a second annular
contact seal between the tip seal and a mold component. The nozzle
tip is made or shaped via a sintering process from a metal matrix
composite (MMC) material having a first coefficient of thermal
expansion. The tip seal is made or shaped from a ceramic based
powder material, having a second coefficient of thermal expansion
that is different from the first coefficient of thermal expansion.
In operation this hot runner nozzle assembly provides an improved
heat profile and a reduced leakage at the tip area under a wider
operating processing window.
Inventors: |
Spuller; Swen; (Forchheim,
DE) ; Olaru; Gheorghe George; (Freiburg, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Otto Manner Innovation GmbH |
Bahlingen |
|
DE |
|
|
Family ID: |
51654637 |
Appl. No.: |
14/918282 |
Filed: |
October 20, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14224058 |
Mar 24, 2014 |
9162384 |
|
|
14918282 |
|
|
|
|
61804602 |
Mar 22, 2013 |
|
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Current U.S.
Class: |
425/549 |
Current CPC
Class: |
B29C 45/20 20130101;
B29C 45/278 20130101; B29C 45/1734 20130101; B29K 2995/0013
20130101; B29C 2045/2787 20130101; B29K 2995/0012 20130101; B29C
45/1735 20130101 |
International
Class: |
B29C 45/20 20060101
B29C045/20 |
Claims
1. A hot runner nozzle comprising: a hot runner nozzle body having
a nozzle melt channel therethrough and having a nozzle body head
portion; a nozzle heater coupled to the hot runner nozzle body; a
nozzle tip having an outer surface and an nozzle tip melt channel,
wherein the nozzle tip is made from a sintered metal matrix
composite (MMC) powder material, the nozzle tip having a first
coefficient of thermal conductivity and a first coefficient of
thermal expansion at an operating temperature window between about
100 degrees C. and about 400 degrees C. provided by the nozzle
heater, and wherein the nozzle tip is removably coupled to the hot
runner nozzle; a tip seal surrounding the nozzle tip and having an
inner surface and an outer surface and is made from a sintered
ceramic-based powder material, the tip seal having a second
coefficient of thermal conductivity lower than the first
coefficient of thermal conductivity and a second coefficient of
thermal expansion that is at least equal lower than the first
coefficient of thermal expansion at an operating temperature window
between about 100 degrees C. and about 400 degrees C. provided by
the heater, and wherein the tip seal is removably coupled to the
nozzle tip, wherein the tip seal is configured to form a seal with
a mold component having a mold gate that adjacent the nozzle tip;
and a seal and connector element made as a unitary component, where
the seal and connector element contacting both the nozzle tip and
the tip seal, and wherein the unitary seal and connector element is
positioned onto the nozzle tip and removably couples the tip seal
to the nozzle tip, and controls a first seal between the nozzle tip
and the tip seal.
2. A hot runner nozzle according to claim 1, wherein the seal and
connector element is threadedly connected to the nozzle tip.
3. A hot runner nozzle according to claim 1, wherein the nozzle tip
is threadedly connected to the nozzle body.
4. A hot runner nozzle according to claim 1, wherein the metal
matrix composite (MMC) powder material is a carbide that includes
tungsten in a proportion exceeding 50%.
5. A hot runner nozzle according to claim 1, wherein the metal
matrix composite (MMC) powder material has a coefficient of thermal
expansion at 20-1000 C in the range of 4.00-6.00 (.times.10.sup.-6
K.sup.-1).
6. A hot runner nozzle according to claim 1, wherein the metal
matrix composite (MMC) powder material has a coefficient of thermal
conductivity at 20 C in the range of (50-90) W m.sup.-1
K.sup.-1.
7. A hot runner nozzle according to claim 1, wherein the tip seal
is made of a ceramic powder including zirconium oxide in a
proportion in excess of 50%.
8. A hot runner nozzle according to claim 1, wherein the tip seal
is made of a ceramic powder having a coefficient of thermal
conductivity in the range of (12-15) W/m.degree. K.
9. A hot runner nozzle according to claim 1, wherein the tip seal
is made of a ceramic powder having a coefficient of thermal
expansion in the range of (2.5-7) .times.10.sup.-6/.degree. C.
10. A hot runner nozzle according to claim 1, wherein the seal and
connector element drives an annular surface on the tip seal against
an annular surface on the nozzle tip with a selected force to
generate the first seal therebetween.
11. A hot runner nozzle according to claim 1, wherein the tip seal
controls a seal between a radially inner surface of the tip seal
and a radially outer surface of the nozzle tip.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. patent
application Ser. No. 61/804,602, filed Mar. 22, 2013, the contents
of which are incorporated herein by reference in their entirety
FIELD OF THE INVENTION
[0002] The present disclosure relates to an injection molding
apparatus and more particularly to hot runner injection nozzles
made of several cooperating parts.
BACKGROUND OF THE INVENTION
[0003] Hot runner injection nozzles are known. These nozzles are
made of several parts designed to meet injection molding operating
conditions for various materials and for various applications.
These parts are made of various materials that need to be
manufactured with high accuracy, low tolerances and also configured
to be machine-able with available manufacturing equipment. These
hot runner nozzles and the associated parts need to be designed and
made to be easy to assemble and service in the field.
[0004] An area at the end of the nozzle is the nozzle tip area,
which is proximate to the mold gate. In this area the injection
pressure is very high. Nozzle tips are known and they are in many
cases attached to the body of the nozzle in the nozzle tip
area.
[0005] The nozzle tips sometimes have to be made of materials
having conflicting properties or characteristics. If they are made
of highly conductive materials, these materials are in many cases
not very wear resistant. Many of the materials that can be used for
the nozzle tips used in hot runner nozzles and that have good wear
resistance have low thermal conductivity.
[0006] In many hot runner nozzle applications there is a need to
use nozzle tip connectors, nozzle tip seals and nozzle tip
insulators that have to cooperate with the nozzle tips and operate
and perform together as a unit.
[0007] Because the nozzle tips and the tip seals are made of
different materials and because they have a different thermal
conductivity and a different coefficient of thermal expansion at
the injection molding processing temperatures, there is always a
concern with the known tips and seals regarding two types of
leakage caused by the injection pressure of a molten material into
a mold cavity through the nozzle tips. A first leakage, that
sometimes is harder to contain, can appear between an outer surface
of the tip and an inner surface of the tip seal. A second more
common leakage can appear between an outer surface of the tip seal
and a wall of a mold component adjacent the mold gate contacting
the outer surface of the tip seal. Other leakage paths can further
appear between other cooperating surfaces of the nozzle tip and tip
seal that have small gaps caused by manufacturing errors or thermal
expansion.
[0008] There is a need to design and manufacture hot runner nozzles
and hot runner nozzle tips that have improved features and good
thermal and wear resistance properties.
[0009] There is a need to design and manufacture nozzle tips,
nozzle tip connectors, nozzle tip seals and nozzle tip insulators
that have improved features and characteristics to better cooperate
with the nozzle tips and better operate and better perform together
as a unit.
[0010] There is a need to design and manufacture nozzle tips,
nozzle tip connectors, nozzle tip seals and nozzle tip insulators
where the first leakage and the second leakage are contained for
long hours of operation of the hot runner nozzle.
SUMMARY OF THE INVENTION
[0011] This invention discloses designs and materials to
manufacture hot runner nozzles and hot runner nozzle tips with
improved operation characteristics. These nozzle tips cooperate
with improved nozzle tip connectors, improved nozzle tip seals and
improved nozzle tip insulators.
[0012] In one embodiment of the invention, the nozzle tip is shaped
or is made by sintering metal matrix composite (MMC) materials. In
one embodiment of the invention, the metal matrix composite (MMC)
material for the tip is a cemented carbide. In one embodiment of
the invention, the cemented carbide material for the tip is
Tungsten Carbide (e.g. a carbide that includes tungsten in a
proportion exceeding 50%). In one embodiment of the invention the
cemented carbide material for the tip is Titanium-Carbide. As a
result of the use of the metal matrix composite (MMC) material, the
nozzle tip has a first coefficient of thermal expansion at an
operating temperature provided by a nozzle heater between about 100
degrees C. and about 400 degrees C.
[0013] In another embodiment of the invention the nozzle tip is
coated to increase the lifetime, especially the wear resistance, of
the nozzle tip. In some embodiments the coating for the nozzle tip
is selected for each application. The coatings are selected from
one of these materials: TiN (titanium nitride), TiC (titanium
carbide), Ti(C)N (titanium carbide-nitride), and TiAIN (titanium
aluminum nitride). In other embodiments the coating is made with
DLC (Diamond-like carbon).
[0014] In some of the embodiments the coatings are deposited via
thermal CVD
[0015] (Chemical Vapour Deposition) and, for certain applications,
with the mechanical PVD (Physical Vapour Deposition) method.
[0016] In one embodiment of the invention a nozzle tip seal
surrounding the nozzle tip and having an inner surface and an outer
surface is shaped or made from a ceramic based powder material, the
tip seal having a second coefficient of thermal expansion that is
different from (e.g. less than) the first coefficient of thermal
expansion at an operating temperature provide by the heater between
about 100 degrees C. and about 400 degrees C.
[0017] In one embodiment of the invention a connecting element
contacting the nozzle tip and the nozzle tip seal is positioned to
removably couple the tip seal to the nozzle tip. This connecting
element is also positioned to create a first contact seal (which
may be annular) between the nozzle tip and the tip seal. The
connecting element may also create a second contact seal between
the tip seal and a mold component. In another embodiment of the
invention the connecting element is positioned to create third
annular contact seal between the nozzle tip and the tip seal. The
nozzle tip being adjacent to a mold cavity gate in the mold
component.
[0018] In operation this hot runner nozzle assembly provides an
improved heat profile, reduced wear of the tip, and reduced leakage
at the tip area under a wider operating processing window.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Non-limiting embodiments may be more fully appreciated by
reference to the following detailed description when taken in
conjunction with the accompanying drawings, in which:
[0020] FIG. 1 is a sectional side view of a portion of an injection
molding machine that includes a plurality of hot runner injection
nozzles in accordance with an embodiment of the present
invention;
[0021] FIG. 1a is a magnified view of a portion of the injection
molding machine shown in FIG. 1, showing a mold cavity;
[0022] FIG. 1b is a magnified view of a portion of the injection
molding machine shown in FIG. 1, illustrating heat loss from a
nozzle to a mold component proximate the mold cavity;
[0023] FIG. 2 is a sectional side view of one of the hot runner
injection nozzles shown in FIG. 1;
[0024] FIG. 2a is a sectional side elevation view of a variant of
the hot runner injection nozzle shown in FIG. 1 whereby a tip is
connected to a tip retainer by a brazed connection;
[0025] FIG. 3 is a sectional side view of the hot runner injection
nozzle shown in FIG. 2, with an optional nozzle heater;
[0026] FIG. 4 is a sectional side view of the hot runner injection
nozzle shown in FIG. 2, with an optional valve pin;
[0027] FIG. 5 is a sectional side view of the hot runner injection
nozzle shown in FIG. 2, with an optional nozzle heater and valve
pin; and
[0028] FIG. 6 is a sectional side view of the hot runner injection
nozzle shown in
[0029] FIG. 2, with an optional nozzle heater and valve pin, and a
valve pin alignment member; and
[0030] FIGS. 7-15b are sectional side views of portions of
additional embodiments of the hot runner injection nozzle shown in
FIG. 2.
DETAILED DESCRIPTION OF THE INVENTION
[0031] In this specification and in the claims, the use of the
article "a", "an", or "the" in reference to an item is not intended
to exclude the possibility of including a plurality of the item in
some embodiments. It will be apparent to one skilled in the art in
at least some instances in this specification and the attached
claims that it would be possible to include a plurality of the item
in at least some embodiments.
[0032] Reference is made to FIG. 1, which shows a portion of an
injection molding machine 10. The injection molding machine 10
includes, among other things, a hot runner manifold 100 with a
plurality of melt channel network 102 having an inlet 104 and a
plurality of outlets 106. The machine 10 further including a
plurality of injection nozzles 11 each of which receive melt from
one of the outlets 106 and transport the melt to a gate 24 of a
mold cavity 25 (see FIG. 1a) of a mold component 26. Only a portion
of the mold component 26 is shown, however it will be understood
that the mold component 26 includes a plurality of elements that
mate together to define a plurality of mold cavities 25.
[0033] The melt that is transported through the hot runner manifold
100 and through the nozzles 11 is heated so as to improve its flow
characteristics. Referring to FIG. 1a, each mold cavity 25 receives
melt from a nozzle 11 and cools the melt to solidify it and thereby
form a molded product. Cooling channels shown at 27 are provided in
the mold component 26 near the mold cavities 25 to transport
coolant for the purpose of cooling the melt. Referring to FIG. 1b,
the nozzle 11 is located in a space 28 in the mold component 26 and
contacts the mold component 26 via a tip seal 18 to seal off the
area immediately around the gate 24 in order to contain the melt.
Because it is desired to keep the melt hot in the nozzle 11 and to
cool the melt in the mold component 26, there is a temperature
difference between the nozzle 11 and the mold component that
results in some heat loss from the nozzle 11 into the mold
component 26. It is desirable to reduce this heat loss as it is
detrimental to both the flow of melt leaving the nozzle 11 and to
the cooling of the melt in the mold cavities 25.
[0034] Reference is made to FIG. 2, which shows a magnified view of
a portion of one of the injection nozzles 11. The injection nozzle
11 includes a nozzle body 12, which itself includes a nozzle head
portion 13, a nozzle tip 14, a tip retainer 16 and the
aforementioned tip seal 18.
[0035] The nozzle body 12 has a melt channel 20 therethrough that
is positioned to transport melt from one of the hot runner manifold
outlets 106 (FIG. 1) to the nozzle tip 14. The nozzle tip 14 has a
melt channel 22 therethrough that is positioned downstream from the
melt channel 20 so as to transport the melt to the gate 24 for one
of the mold cavities 25 in a mold component 26. The nozzle tip 14
is preferably made from a suitably hard material and has a first,
(preferably high), thermal conductivity and a first coefficient of
thermal expansion in the operating temperature window (i.e.
temperature range) of about 100 degrees C. to about 400 degrees C.
The first coefficient of thermal expansion may be in the range of
4.00-6.00 (.times.10.sup.-6 K.sup.-1) at 20-1000 C. An example of a
material for the nozzle tip 14 is a sintered metal matrix composite
(MMC) powder, such as tungsten carbide in order to resist wear
during use from contact with the melt, particularly when the melt
is a resin that contains a glass filler or other hard fillers. In
some embodiments, such as the embodiments shown in FIGS. 4, 5 and
6, a tungsten carbide tip is also useful in order to resist wear
from friction during movement of a valve pin, as discussed further
below.
[0036] Referring to FIG. 2, the tip retainer 16 is removably
coupled to the nozzle body 12 and has the tip 14 connected thereto,
so that the tip 14 is effectively removable from the nozzle body 12
for service. For example, the tip retainer 16 may have an inner
threaded portion 30 and may be coupled by the inner threaded
portion 30 to an outer threaded portion 32 on the nozzle body
12.
[0037] The tip 14 may be coupled to the tip retainer 16 by any
suitable means. For example, the tip retainer 16 may have a second
inner threaded portion 34 and the tip 14 may have an outer surface
35 on which there is an outer threaded portion 36, through which
the tip 14 is coupled to the tip retainer 16. This structure
eliminates the need to provide an inner threaded portion on the tip
14, which can be relatively difficult to manufacture particularly
in embodiments wherein the tip 14 is made from tungsten carbide.
The inner threaded portion 30 (which may, for convenience be
referred to sometimes as the first inner threaded portion 30) and
the second inner threaded portion 34 may be separate, distinct
portions of the tip retainer 16, or alternatively they may join to
form a continuous threaded portion as shown in FIG. 2.
[0038] In another embodiment shown in FIG. 2a, the tip 14 may be
brazed to the tip retainer 16. In FIG. 1a, the brazed joint a shown
at 38. Brazing the tip 14 to the tip retainer 16 provides several
advantages. One advantage is that it eliminates the need to provide
the outer threaded portion 36 on the tip 14, which can be difficult
when the tip 14 is made from a material such as tungsten carbide.
In yet another embodiment, the tip 14 may be connected to the tip
retainer 16 by a press-fit connection.
[0039] The tip 14 may be sealingly engaged with the nozzle body 12
via engagement of tip engagement surface 47 on the nozzle body 12
with a body engagement surface 49 on the tip 14, so as to permit
melt to flow from the nozzle body 12 into the tip 14 without
leaking out of the nozzle 11.
[0040] The tip seal 18 is positioned around the tip 14 and has an
outer surface 37 is positioned to engage a sealing surface 39 on
the mold component 26 to form a seal therewith so as to inhibit the
flow of melt therepast. The tip seal 18 may be made from a material
that has a second thermal conductivity that is preferably lower
than that of the tip 14 so as to inhibit heat transfer from the tip
14 into the mold component 26. The tip seal 18 also has a second
coefficient of thermal expansion in the operating temperature
window of about 100 degrees C. to about 400 degrees C. The second
coefficient of thermal expansion may be lower than that of the tip
14. The tip seal 18 is preferably made from an insulative material.
An example of a suitable insulative material is a sintered ceramic
based powder material. The tip seal 18 further includes a radially
inner surface 41 that faces a portion of the outer surface 35 of
the tip 14. The tip seal 18 further includes a first annular
surface 43 and a second annular surface 45.
[0041] It will be noted that it can be difficult to directly join a
ceramic component to a component made from a metal matrix composite
such as tungsten carbide. To overcome this difficulty, a seal
retainer 40 (which may also be referred to as a seal and connector
element 40) may be used to retain the tip seal 18 on the tip 14.
The seal retainer 40 is a unitary component which contacts both the
tip 14 and the tip seal 18. The seal retainer 40 removably connects
to the tip 14 by any suitable means, so that the seal 18 is held
between a retainer surface 42 on the seal retainer 40 and a
retaining surface 44 on the tip 14, such that first annular surface
43 on the tip seal 18 faces retaining surface 44 and second annular
surface 45 on the tip seal 18 faces retainer surface 42. The seal
retainer 40 may connect to the tip 14 by an inner threaded portion
46 on the seal retainer 40 that engages an outer threaded seal
retainer engagement portion 48 on the tip 14. In other words the
seal retainer 40 may be threaded onto the tip 14 and removably
couples the tip seal 18 to the tip 14.
[0042] Optionally, the seal retainer 40 may be welded to the tip
14, however, in preferred embodiments it is not welded. In yet
another alternative, the seal and/or the seal retainer 40 may be
connected to the tip 14 by an adhesive such as a suitable type of
Loctite (provided by Henkel Corporation of Rocky Hill, Conn., USA).
In yet another alternative, the seal retainer 40 may be shrink fit
(i.e. an interference fit formed by mounting the seal retainer 40
the tip 14 when either the seal retainer 40 is heated to
temporarily expand its inner diameter and/or the tip 14 is cooled
to temporarily reduce its outer diameter, and then to return them
to a temperature where the inner diameter of the seal retainer 40
is smaller than the outer diameter of the tip 14).
[0043] It has been found that, due to the materials used for one or
both of the tip 14 and the tip seal 18 it can be difficult to
manufacture the tip 14 and the tip seal 18 to tight tolerances.
This can be because the manufacturing processes used for both are
inherently difficult to provide tight tolerances. This can also be
because of the different coefficients of thermal expansion between
the tip 14 and the tip seal 18. As a result, it has been found that
there can be a leakage path between the tip 14 and the tip seal 18.
There can also be a leakage path between the tip seal 18 and the
mold component 26, however, it has been found that this is
relatively easier to address and to arrive at a suitable seal
between the outer surface 37 of the tip seal 18 and the sealing
surface 39 of the mold component 26.
[0044] The seal retainer 40 controls a first seal between the tip
seal 18 and the tip 14, which is the seal formed between annular
surface 43 on the tip seal 18 and the associated annular surface 44
on the tip 14. This seal may be referred to as a first "tip
seal-nozzle tip" seal. The seal retainer 40 may control this first
tip seal-nozzle tip seal by, for example, controlling the force
with which the surface 43 on the tip seal 18 engages the surface 44
on the tip 14 (i.e. driving the annular surface 43 into engagement
with the annular surface 44 with a selected force). If a sufficient
force is not used, there will not be an effective seal between the
tip 14 and the tip seal 18. Where the term `seal` is used in the
context of this patent application, it is intended to mean that
substantially no leakage occurs therepast during normal operation
of the associated components. Thus, simple contact between the
surfaces 43 and 44 may not provide a seal. Thus it can be seen that
the seal retainer 40 may do more than just hold the tip seal 18 on
the tip 14. By controlling the first seal between the nozzle tip 14
and the tip seal 18 (in particular by controlling the seal between
annular surfaces 43 and 44) the seal retainer 40 compensates to
some extent for the difference in thermal expansion in operation
between the tip 14 and the seal 18 and more broadly compensates for
the poor seal that may be provided between radially inner and outer
surfaces 41 and 51 and between surfaces 43 and 44, which results
from manufacturing tolerances and differences in amounts of thermal
expansion.
[0045] The seal between surfaces 41 and 51 may be referred to as a
second "tip seal-nozzle tip" seal between the tip seal 18 and the
nozzle tip 14. The seal retainer 40 may also control the second
"tip seal-nozzle tip" seal in one or more of several ways. For
example, a seal may be formed between surfaces 42 and 45 thereby
preventing leakage of melt therepast. A seal may be formed between
the inner surface 46 of the seal retainer 40 and the corresponding
outer surface 48 (which his part of outer surface 35) on the tip
14.
[0046] Referring to FIG. 3, the nozzle 11 may further include a
nozzle heater 50 that may include a heater body 52 and an electric
heating element 54 that is positioned in a groove 56 in the heater
body 52. The nozzle heater 50 is engaged with the nozzle body 12
and is configured for heating melt in the nozzle 11. The nozzle
heater 50 provides an operating temperature window for the nozzle
11 of between about 100 degrees C. and about 400 degrees C.
[0047] Referring to FIG. 4, the nozzle 11 may further include a
valve pin 58, that is movable between a closed position (shown in
FIG. 3) in which the valve pin 58 prevents the flow of melt through
the gate 24, and an open position to permit the flow of melt
through the gate 24. A tip portion 60 of the valve pin 58 is
aligned with the gate 24 by a wall 61 of the nozzle tip 14. Thus
there may be frictional contact between the valve pin 58 and the
nozzle tip 14 during movement of the valve pin 14. Making the
nozzle tip 14 from a hard material such as tungsten carbide reduces
the amount of wear that results from such frictional contact.
[0048] Referring to FIG. 5, the nozzle 11 may further include both
the valve pin 58 and the nozzle heater 50.
[0049] Referring to FIG. 6, the nozzle 11 is shown including both
the valve pin 58 and the nozzle heater 50, and also a valve pin
alignment member 62 that is positioned between the nozzle tip 14
and the nozzle body 12 (and that is held in place by the tip
retainer 16). The valve pin alignment member 62 is configured for
aligning a portion 64 of the valve pin 58 upstream from the tip
portion 60 of the valve pin.
[0050] Referring to FIG. 7, the tip seal 18 may be retained on the
nozzle tip 14 by a seal retainer 40 (which may be made from steel
for example), however, an insulator member 66 may be provided
between the seal retainer 40 and the tip seal 18 so as to inhibit
heat transfer from the seal retainer 40 into the tip seal 18. The
seal retainer 40 is shown in FIG. 7 as being welded to the nozzle
tip 14, wherein the weld is represented by a circle 68. It will be
noted that the circular shape identified at 68 is provided only to
identify that a weld is there. The weld 68 need not be circular in
cross-section and may have any suitable shape, such as a fillet
weld. It will be further noted that the weld is entirely optional
may be omitted and the seal retainer 40 may be connected to the
nozzle tip 14 any other suitable way.
[0051] Referring to FIG. 8, the tip seal 18 is retained on the
nozzle tip 14 by a seal retainer 40 that is itself also an
insulator member 66a so as to inhibit heat transfer from the nozzle
tip 14 to the tip seal 18 through the seal retainer 40.
Additionally, a second insulator member 66b is provided between the
inner diameter surface (shown at 70) of the tip seal 18 and the
nozzle tip 14 so as to reduce heat transfer from the nozzle tip 14
into the tip seal 18 (and ultimately into the mold component 26
(FIG. 1)). The insulator member 66b also acts as a seal to prevent
leakage of melt therepast where it mates with other elements. In
FIG. 8, the first insulator member and seal retainer 40, 66a is
shown as being welded to the tip seal 18 via weld 68. An optional
weld 68 or some other connecting means such as a threaded
connection, holds the first insulator member and seal retainer 40,
66a, the second insulator member 66b and the tip seal 18 in place
in a groove shown at 71 in the nozzle tip 14.
[0052] Referring to FIG. 9, the tip seal 18 is retained on the
nozzle tip 14 by the seal retainer 40, which may be joined to the
nozzle tip in any suitable way. An insulator member 66 is provided
between the inner diameter surface 70 of the tip seal 18 and the
nozzle tip 14 to inhibit heat transfer from the nozzle tip 14 into
the tip seal 18 through surface 70.
[0053] Referring to FIG. 10, an insulator member 66 is provided
between axial end face 43 of the tip seal 18 and the nozzle tip 14
so as to reduce heat transfer from the nozzle tip 14 into the tip
seal 18 through end face 43. Also shown in FIG. 10, the seal
retainer 40 is threaded onto to the nozzle tip 14.
[0054] The embodiment in FIG. 10a is the same as the embodiment in
FIG. 10, except that there is no insulator member 66; instead the
tip seal 18 abuts the shoulder 44 on the tip 14.
[0055] Referring to FIG. 11, an insulator member 74, which may be,
for example, an o-ring, is provided between the end face 43 of the
tip seal 18 and the retaining surface 44 of the nozzle tip 14. A
groove for the o-ring may be provided in one or both surfaces 43
and 44. The insulator member 74 may also act as a seal member that
prevents the leakage of melt therepast. In a preferred embodiment
the o-ring acts to space the surface 43 from the surface 44,
thereby increasing its effectiveness to inhibit heat transfer into
the tip seal 18. Even if the two surfaces 43 and 44 contact each
other, however, the insulator member 74 preferably still has
sufficient resiliency to act as a seal to prevent melt leakage
therepast. The seal retainer 40 may be welded to the nozzle tip 14
or connected to the nozzle tip 14 by any other suitable means (e.g.
a threaded connection).
[0056] Referring to FIG. 12, a first insulator member 74a (which
may be, for example, an o-ring) is provided between the end face 43
of the tip seal 18 and the retaining surface 44 of the nozzle tip
14, and a second seal member 74b (which may be, for example, an
o-ring) is provided between the inner diameter surface 70 of the
tip seal 18 and the nozzle tip 14. One or both of the insulator
members 74a and 74b may act as seal members to prevent the leakage
of melt therepast. In a preferred embodiment the o-rings act to
space the surface 43 from the surface 44 and the inner diameter
surface 70 from the corresponding surface on the tip seal 18,
thereby increasing their effectiveness to inhibit heat transfer
into the tip seal 18. The seal retainer 40 may be welded to the
nozzle tip 14 or connected to the nozzle tip 14 by any other
suitable means (e.g. a threaded connection). It is possible to have
an embodiment wherein only member 74b is provided and not insulator
member 74a.
[0057] Referring to FIG. 13, an insulator member 74 which may be an
o-ring is provided in a corner groove 75 between surfaces 43 and
41, and a corner groove 77 between surfaces 51 and 44 on the nozzle
tip 14. Generally speaking, melt may infiltrate between the nozzle
tip 14 and the tip seal 18 until it is stopped by whatever seals
exist between the two surfaces. The melt itself can act as a seal
and furthermore can act as an insulator.
[0058] Referring to FIG. 14, the tip seal 18 may be connected to
the nozzle tip 14 via one or more set screws 78 or dowels 78. The
set screws or dowels 78 may be considered to the seal retainers and
may act to provide the surfaces 43 and 44 by virtue of driving the
tip seal axially into surface 44 when they are in place in both the
apertures shown at 79 and 81 in the tip seal 18 and the tip 14
respectively. The set screws or dowels 78 may also seal against the
tip and tip seal to prevent melt leakage out through the apertures
79. Alternatively they may not seal the apertures 79, however the
seals formed between the outer surface of the tip seal 18 and the
mold component 26 and between the surfaces 43 and 44 will prevent
melt leakage outwards.
[0059] Referring to FIG. 15a, the tip seal 18 may have a groove 80
therein that receives an insulator member 82, which may also be a
seal member, as with the embodiments shown in FIGS. 10-14. The
insulator member 82 may be C-shaped. A corresponding groove 84 is
provided in the nozzle tip 14. As shown in FIGS. 15a and 15b, the
tip seal 18 may slide into place on the nozzle tip 14. As the seal
18 is slid onto the nozzle tip 14, the clearance between the two is
sufficiently small to force the insulator member 82 to compress. As
the seal 18 is slid into place such that the grooves 80 and 84 line
up, the insulator member 82 expands into the groove 84 thereby
providing an insulation function, a seal function providing the
first "tip seal-nozzle tip" seal, and acting as a seal retainer to
retain the tip seal 18 on the nozzle tip 14.
[0060] In FIGS. 15a and 15ab member 82 controls and provides a
first annular sealing. When the tip seal 18 is slid over the member
82, the curvature of the ring 82 becomes flatter and may enter the
corners of the inner grooves 84 and 80. By positioning the outer
groove of the tip 14 closer to the shoulder we need to seal, the
member 82 will apply a sealing force. If resin under pressure
enters the chamber formed by grooves 84 and 80, more pressure will
be applied on the seal ring 82 to generate the first annular
seal.
[0061] In the embodiments shown herein, the tip seal 18 is provided
on the nozzle tip 14 instead of being on the tip retainer 16. This
is advantageous for several reasons. By providing the seal 18 on a
smaller diameter element (i.e. the tip 14 as opposed to the larger
diameter tip retainer 16) the reliability of the seal increases
because there is a generally smaller area being sealed.
Additionally, the overall diameter of the nozzle 11 is kept
relatively smaller by mounting the seal 18 on the tip 14 instead of
being on the tip retainer 16, which permits the pitch between
nozzles 11 to be smaller, thereby permitting a greater number of
articles to be molded on a machine, in some instances where the
nozzle pitch is a limiting factor on the production capacity of the
machine.
[0062] While the element 18 is referred to as a tip seal, it may be
more broadly referred to as a mold component contacting piece.
[0063] In FIG. 1, two nozzles 11 are shown, one with a valve pin
and one without. It will be noted that the two different nozzles
are provided for illustrative purposes only, and that in practice,
an injection molding machine may have all its nozzles including
valve pins, or may have all of its nozzles without valve pins.
[0064] In any embodiments where a weld is provided between the seal
retainer and the tip the weld is optional and may be a continuous
weld or a point weld or a plurality of point welds.
[0065] The above-described embodiments of the invention are
intended to be examples of the present invention and alterations
and modifications may be effected thereto, by those of skill in the
art, without departing from the scope of the invention which is
defined solely by the claims appended hereto.
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