U.S. patent application number 09/897154 was filed with the patent office on 2001-11-01 for injection gate insulating and cooling apparatus.
Invention is credited to Nightingale, Richard P., Wright, Paul L..
Application Number | 20010036492 09/897154 |
Document ID | / |
Family ID | 23817146 |
Filed Date | 2001-11-01 |
United States Patent
Application |
20010036492 |
Kind Code |
A1 |
Wright, Paul L. ; et
al. |
November 1, 2001 |
Injection gate insulating and cooling apparatus
Abstract
An injection apparatus comprises a recessed injection gate
allowing cooling ducts to be run proximate thereto and an extended
nozzle configured to extend to the recessed injection gate. The
apparatus also comprises an insulating and sealing insert
positioned adjacent to the injection gate locating it between the
nozzle and the injection cavity during injection to thermally
insulate the injection gate from the nozzle and to prevent melt
material from leaking between the nozzle and the gate. The insert
also accommodates variations in the nozzle sizes to assure a tight
seal at each nozzle.
Inventors: |
Wright, Paul L.; (Aurora,
IL) ; Nightingale, Richard P.; (Woodstock,
IL) |
Correspondence
Address: |
Matthew E. Leno
McDermott, Will & Emery
31st Floor
227 West Monroe Street
Chicago
IL
60606
US
|
Family ID: |
23817146 |
Appl. No.: |
09/897154 |
Filed: |
June 29, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09897154 |
Jun 29, 2001 |
|
|
|
09457547 |
Dec 9, 1999 |
|
|
|
6264460 |
|
|
|
|
Current U.S.
Class: |
425/549 |
Current CPC
Class: |
B29C 2045/2764 20130101;
B29C 2045/2761 20130101; B29C 2045/2767 20130101; B29C 45/27
20130101; B29C 2045/2724 20130101 |
Class at
Publication: |
425/549 |
International
Class: |
B29C 045/20 |
Claims
We claim:
1. An insert for impeding thermal conduction between an injection
nozzle and an injection cavity comprising: an insert nozzle side
for association with a leading face of the injection nozzle; an
insert cavity side for association with the injection cavity; and
an axial bore extending as a through bore from the insert nozzle
side to the insert cavity side; wherein the insert nozzle side is
configured to contact only the leading face of the injection
nozzle.
2. The insert of claim 1 wherein the insert cavity side further
comprises a central flat extending substantially planar from the
axial bore.
3. The insert of claim 2 wherein the central flat is sized to allow
lateral movement of the nozzle across across the insert nozzle
side.
4. The insert of claim 3 wherein the central flat comprises a
diameter at least 0.100 inches larger than the diameter of the
nozzle leading face.
5. The insert of claim 3 wherein the central flat comprises a
diameter of 0.476 inches.
6. The insert of claim 1 wherein the insert cavity side comprises:
an outer land for contacting the injection cavity adjacent to the
injection gate; and a central recess extending from adjacent to the
outer land to the axial bore; wherein the central recess is offset
from the outer land to provide a space between the central recess
and the injection cavity
7. The insert of claim 6 wherein the central recess provides a
flexible portion of the insert for flexing under contact of the
nozzle with the insert.
8. The insert of claim 7 wherein the insert flexible portion
comprises a diameter of 0.50 inches and a thickness of 0.049 inches
from the nozzle side to the cavity side.
9. The insert of claim 8 wherein the insert is comprised of
Vespel.
10. The insert of claim 7 the space between the flexible portion
and the injection cavity is 0.015 inches.
11. The insert of claim 1 wherein the insert is comprised of a low
thermal conductivity.
12. An injection apparatus comprising: an injection nozzle; an
injection cavity having an injection gate; and an insert between
the injection nozzle and the injection cavity wherein the injection
nozzle is free to travel laterally across a central flat of the
insert.
13. The apparatus of claim 12 further defined in that the insert
comprises an insert nozzle side comprising said central flat for
association with a leading face of the injection nozzle and an
insert cavity side for association with the injection cavity,
wherein the insert contacts only the leading face of the injection
nozzle.
14. The apparatus of claim 13 wherein the central flat extends
substantially planar from an insert axial bore and the nozzle
leading face is substantially planar.
15. The apparatus of claim 14 wherein the insert central flat
extends at least approximately 0.050 inches in any direction from a
perimeter of the injection nozzle leading face when the apparatus
is at operating temperature.
16. The apparatus of claim 15 wherein the insert central flat
comprises a diameter of at least 0.476 inches.
17. The apparatus of claim 12 wherein the insert cavity side
comprises an outer land contacting the injection cavity adjacent to
the injection gate and a central recess spaced from the injection
cavity allowing an insert flexible portion to flex toward the
injection cavity under contact of the nozzle with the insert.
18. The apparatus of claim 17 wherein the insert flexible portion
comprises a diameter of 0.50 inches and a thickness of 0.049 inches
from the nozzle side to the cavity side.
19. The apparatus of claim 17 wherein the central recess is spaced
0.015 inches from the injection cavity.
20. The apparatus of claim 12 wherein the injection cavity
comprises a recess and the insert is removably located within the
recess such that an axial bore of the insert is substantially
axially aligned an injection gate of the injection cavity.
21. The apparatus of claim 20 wherein the injection cavity
comprises cooling ducts proximate to the injection gate.
22. The apparatus of claim 12 wherein the nozzle axial bore is in
substantial axial alignment with the insert axial bore when the
apparatus is at operating temperature and the nozzle is in
substantially forced contact with the insert to prevent the leakage
of a melt material from between the nozzle and the insert into the
recess.
23. The apparatus of claim 12 wherein the insert of comprised of a
low thermal conductivity relative to the injection nozzle.
24. An injection apparatus comprising: an injection nozzle; an
injection cavity having an injection gate; and an insert positioned
between the injection nozzle and the injection cavity to prevent
the leakage of a melt material from between the insert and the
injection nozzle and wherein the insert is capable of preventing
leakage from between the insert and the injection nozzle at
temperatures up to 600.degree. F.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates generally to an injection
apparatus; particularly an injection apparatus maintaining the
nozzle and the injection gate at respective desired
temperatures.
[0003] 2. Background of the Invention
[0004] It has long been known that the temperature of a melt
material is important to successful injection. This is particularly
true when the melt material has a high melt temperature. For
example, polyethylene terephthalate ("PET") is typically injected
above 500.degree. F. A drop in the temperature of the melt material
prior to reaching the injection cavity would lower the melt
material temperature below that required for proper melt material
flow causing less than ideal flow characteristics. These flow
characteristics can cause deformed or defectively molded parts;
particularly when injecting multilayer parts comprising very thin
layers. Therefore, it is desirable to maintain the nozzle
temperature at or above the temperature required to assure proper
melt material flow as the melt material leaves the nozzle.
[0005] It is also known to maintain an injection cavity at a
temperature relatively low compared to the temperature of the melt
material to facilitate quick cooling of the melt material upon
reaching the cavity. The colder the cavity temperature at the time
the melt material is injected, the faster the melt material will
solidify and allow removal of the solidified part from the cavity.
Therefore, a relatively lower cavity temperature will decrease the
overall cycle time for injection molding a part. Moreover, it is
known that if the injection gate temperature exceeds the desired
temperature of the melt material, `stringing` of the melt material
will occur in the nozzle and gate area as the injected part is
removed from the cavity after injection is complete. These
`strings` either break off with the injected part and interfere
with further processing of the part (e.g. blowmolding) or stay in
the gate or cavity and cause a physical or aesthetic defect in
subsequently injected parts.
[0006] For these reasons, it has been found desirable to prevent
excessive heat transfer from the injection nozzle to the injection
cavity. The melt material can thus be maintained at its appropriate
temperature in both the nozzle and the cavity. Prior injection
apparatuses were often designed to space a nozzle tip from an
associated injection cavity during injection to leave a gap
therebetween. It was thought that this gap would act as a thermal
break between the nozzle and the cavity and allow the nozzle to
operate at high temperatures while maintaining a relatively cool
cavity. Unfortunately, the thermal break of this configuration
could not be maintained at efficient cycle times. During the
injection process, melt material would deviate from the injection
path and flow into the gap between the nozzle and the cavity. The
thermal break thus became a thermal bridge.
[0007] Other attempts to insulate an injection nozzle from a cavity
have involved the use of nozzle inserts. For example, U.S. Pat. No.
4,279,588 issued to Gellert and entitled "Hot Tip Seal" disclosed a
seal (12) located between the nozzle and the injection gate to
limit heat transfer therebetween. The seal (12) of Gellert resided
substantially within the nozzle and extended outward therefrom to
contact the cavity. Similarly, U.S. Pat. No. 4,521,179 issued to
Gellert and entitled "Injection Molding Core Ring Gate System"
disclosed a nozzle seal (76). The seal (76) of Gellert also resided
substantially within the nozzle and extended outward therefrom to
contact the cavity.
[0008] It has been found that movement of the various parts within
an injection apparatus will result from thermal expansion as
portions of the apparatus are heated from ambient temperature to
the temperature necessary to inject a melt material. Different
injection apparatuses accommodate this thermal expansion in
different ways. It has been found that the thermal expansion of
some injection apparatuses results in movement of the nozzle both
along the longitudinal axis thereof and perpendicular to that
longitudinal axis. In other words, it has been found that the
nozzles of some apparatuses will elongate and shift laterally as
the apparatus is heated. Seals that attached to the nozzle, such as
those of the Gellert patents discussed above, break or deform due
to this lateral nozzle movement. Such seals are therefore
inapplicable to apparatuses experiencing this lateral nozzle
movement.
[0009] It has also been found that many seals cannot withstand the
high temperatures and pressures associated with injection;
especially when the high temperatures are maintained for long
periods of time. Many prior inserts degraded after prolonged
exposure to high temperatures resulting in rupture or deformation
of the inserts which allowed melt material to leak into the area
between the nozzle and the cavity causing in a thermal bridge.
[0010] It has also been known to supply a cooling means to a cavity
to remove the heat transferred from the nozzle or melt material to
the cavity. Cooling ducts circulating coolants such as glycol were
typically employed. However, the distance between the part void and
the injection gate has heretofore limited the proximity of the
cooling ducts to the injection gate.
SUMMARY OF THE INVENTION
[0011] It is one of the principal objectives of the present
invention to provide an injection apparatus which will facilitate
the injection of melt material at the appropriate melt temperature
while allowing the cavity to remain cool to reduce cycle time.
[0012] It is another objective of the present invention to provide
an injection apparatus in which the nozzle is thermally insulated
from the cavity.
[0013] It is another objective of the present invention to provide
an injection apparatus in which the injection flow path is sealed
between the nozzle and cavity.
[0014] It is another objective of the present invention to provide
an injection apparatus susceptible to lateral nozzle movement
wherein the nozzle is thermally insulated from the cavity.
[0015] It is another objective of the present invention to provide
an injection apparatus susceptible to lateral nozzle movement
wherein and the injection flow path between the nozzle and cavity
is sealed to prevent diversion or interruption of the flow
path.
[0016] It is another objective of the present invention to provide
an injection apparatus in which the injected parts cool
quickly.
[0017] It is another objective of the present invention to provide
an injection apparatus having a low cycle time.
[0018] It is another objective of the present invention to provide
an injection apparatus which can maintain a desired melt material
temperature and prevent stringing of the melt material.
[0019] It is still another objective of the present invention to
provide an insert to limit heat transfer from a nozzle susceptible
to lateral movement to an adjacent cavity.
BRIEF DESCRIPTION OF DRAWINGS
[0020] FIG. 1 is a cross sectional view of a single injection
nozzle, an injection cavity and an insert of an injection molding
apparatus according to the present invention.
[0021] FIG. 2 is a cross sectional view of a retrofit nozzle tip
according to the present invention.
[0022] FIG. 3A is a nozzle side elevational view of an insert
according to the present invention.
[0023] FIG. 3B is a cross sectional view of the insert shown in
FIG. 3A taken along line 3B-3B.
DETAILED DESCRIPTION OF THE DRAWINGS
[0024] In one embodiment of the present invention depicted in FIG.
1, the injection apparatus 10 comprises a nozzle 12, associated
with an injection manifold 14 interfaced with an injection cavity
16 having a core 18 located therein to define a part void 20
therebetween into which melt material is injected to form the
desired part. The nozzle may be part of an injection mold system
comprising multiple nozzles 12 and associated injection cavities
(not shown) such as that disclosed in U.S. Pat. No. 4,712,990 which
is incorporated herein by reference in its entirety. An axial bore
22 runs along a longitudinal axis 52 of the nozzle 12 to define a
melt material flow path 24 therein. A gate 26 is located in the
injection cavity 16 and a bore opening 28 located at the end of the
nozzle axial bore 22 is positioned to be substantially in axial
alignment with the gate 26 to direct flow of melt material from the
nozzle 12 through the gate 26 and into the part void 20 within the
injection cavity 16. An insert 30 is located between the nozzle 12
and the injection cavity 16.
[0025] As depicted in FIG. 1, the gate 26 of the present injection
apparatus 10 is located in a recess 32 from an upper surface 34 of
the injection cavity 16. The recess 32 also comprises a diameter 36
and a land 38 against which an outer boss 40 of the injection
manifold 14 may abut. A tip 42 of the nozzle 12 extends outward
beyond the outer boss 40 of the injection manifold 14 to present a
leading face 44 which comprises the bore opening 28 therein. The
nozzle tip 42 is preferably frustoconical in shape such that the
nozzle 12 narrows as it extends outward of the outer boss 40 to the
leading face 44. The leading face 44 of the nozzle 12 therefore
comprises a reduced surface area. Because the leading face 44 is
the only portion of the nozzle 12 which contacts the insert 30, the
heat transfer from the nozzle 12 to the injection cavity 16 is
limited by this reduced surface area of the leading face 44. That
is, because the rate of heat transfer is proportional to the
surface area susceptible to thermal conduction, the allowed rate of
heat transfer from the nozzle 12 to the injection cavity 16 is
lowered by the reduced surface area of the leading face 44. Other
nozzle tip configurations are also contemplated.
[0026] The recess 32 distances the gate 26 from the injection block
upper surface 34 as depicted in FIG. 1 providing the injection
cavity 16 with additional volume therebetween as compared to prior
injection apparatuses in which injection gates were located at or
near the injection block upper surface. This additional volume
allows cooling facilities such as cooling ducts 46 to be located
closer to the injection gate 26 than with those prior injection
apparatuses. Because the part void 20 extends substantially
radially from the axis 52 defined by the nozzle axial bore 22,
sufficient injection cavity volume does not exist between a recess
flat 48 and the part void 20 to locate the cooling ducts 46
immediately adjacent to the injection gate. However, the additional
injection cavity volume provided by the recess 32 of the present
invention allows the cooling ducts 46 to be placed just beyond the
perimeter of the recess 32 facilitating a much closer proximity of
the cooling ducts 46 to the injection gate 26 than obtained in
prior injection apparatuses. The injection cavity volume necessary
to locate cooling ducts proximate to an injection gate did not
exist in those prior injection apparatuses. By way of example, if
the additional injection cavity volume did not exist in the
injection cavity 16 of the present invention, and the flat 48 of
the embodiment of the present invention depicted in FIG. 1 were to
extend across the injection cavity and thus represent an injection
cavity upper surface, the cooling ducts depicted in FIG. 1 would be
opened to the atmosphere and rendered useless. Thus, the additional
injection cavity volume provided by the present invention allows
the cooling ducts 46 to be placed proximate to the gate 26 to
regulate its temperature.
[0027] To obtain the injection cavity 16 having additional volume
according to the present invention, an entire new injection cavity
may be manufactured according to existing manufacturing techniques
known in the art. Alternatively, the recess 32 may be retrofitted
onto an injection cavity not having such a recess. To accomplish a
retrofitted injection cavity 16, material may be added to an
existing injection cavity by welding or other known methods to
build up the injection cavity around the gate. The recess 32 may
then be bored, or otherwise machined, into the added material.
Cooling ducts may be incorporated into the added material prior to
attachment to the pre-existing injection cavity and configured to
interact with the preexisting cooling ducts of the pre-existing
injection cavity.
[0028] As discussed above, the nozzle tip 42 of the present
invention extends outward beyond the injection manifold outer boss
40 toward the gate 26 in order to extend into the recess 32 and
interface with the insert 30. This entire extended nozzle
configuration may be accomplished by manufacture according to
standard manufacturing techniques. Alternatively, the extended
nozzle configuration may be accomplished by the addition of a
retrofit to a previous nozzle configuration.
[0029] A nozzle retrofit 50 consistent with the present invention
is depicted in FIG. 2. The nozzle retro-fit 50 comprises an outer
shell 54 having a cavity 56 therein configured to accommodate a
pre-existing nozzle and attachment means 58 to facilitate
attachment of the nozzle retro-fit 50 to a pre-existing nozzle or
other portion of a pre-existing injection apparatus. The nozzle
retro-fit 50 further comprises a nozzle retro-fit axial bore 60
configured to align with the axial bore of a pre-existing nozzle
such that a flow of melt material will pass through the nozzle
axial bore to the nozzle retro-fit axial bore 60 and out of the
nozzle retro-fit 50 at a nozzle retro-fit bore opening 62. An inner
wall 64 of the nozzle retrofit 50 defines the nozzle retrofit
cavity 56. The inner wall 64 may be configured to conform exactly
to the outer contours of the pre-existing nozzle to which the
nozzle retrofit will be attached. Alternatively, the inner wall 64
may be configured to have only limited contact with the
pre-existing nozzle to limit heat conduction from the pre-existing
nozzle to the nozzle retro-fit 50. In either configuration, the
inner wall 64 may comprise additional means for attaching the
nozzle retro-fit to the pre-existing nozzle which is exclusive of,
or in addition to, the attachment means 58 depicted. It will be
recognized, however, that the nozzle retrofit 50 should be secure
and relative movement between the pre-existing nozzle and the
nozzle retrofit 50 should be minimized. A seal (not depicted) may
be placed between the pre-existing nozzle and the nozzle retrofit
50 to insure that melt material does not seep therebetween. It will
also be recognized that sufficient heat must be conducted to the
nozzle retrofit axial bore 60 to ensure that the proper melt
material temperature is maintained during injection consistent with
the objectives of the present invention.
[0030] The insert 30 of the present invention is positioned in the
recess 32 interposed between the injection cavity 16 and the nozzle
12 as depicted in FIG. 1. The insert 30 insulates the injection
gate 26 from the relatively high temperatures of the nozzle 12 in
two manners. First, the insert 30 seals the space between the
nozzle 12 and the injection cavity 16 to prevent melt material from
accumulating therebetween and creating the thermal bridge
experienced in the prior art. Second, the insert 30 may be
comprised of a material that is low in thermal conductivity to
minimize heat transfer from the nozzle 12 to the injection gate 26.
In this configuration, heat conducted from the nozzle 12 to the
injection gate 26 is conducted only through the insert 30 and may
thus be regulated by the thermal conductivity of the insert 30. In
this configuration, the present apparatus 10 thus differs from
prior configurations in which the melt material accumulated between
the nozzle and the injection cavity 16 allowing relatively free
conduction of heat therebetween.
[0031] The insert 30 is preferably constructed of a material
retaining a high structural integrity at high temperatures such as,
by way of example only, the 500-550.degree. F. at which PET is
typically injected, such that the insert 30 maintains its shape and
strength. The continued strength and shape of the insert 30 is
important to insure that the seal between the nozzle 12 and the
injection cavity 16 is maintained throughout prolonged operation of
the injection apparatus 10. Distortion, cracking or rupture of the
insert would allow the pressurized melt material to divert from the
melt material flow path 24 and set between the nozzle 12 and the
injection cavity 16, increasing the thermal conduction therebetween
and disrupt the desired flow characteristics. It has been found
that the material sold by DuPont under the name Vespel.RTM.
provides the insert 30 with appropriate structural integrity to
withstand injection of PET at temperatures of 500-550.degree. F.
while limiting thermal conductivity. Other materials including, but
not limited to, titanium and stainless steel are also
contemplated.
[0032] One embodiment of the insert 30 is depicted in FIGS. 3A and
3B. This embodiment of the insert 30 comprises an insert nozzle
side 66, an insert cavity side 68 and an outer perimeter 70. The
outer perimeter 70 of the insert 30 is depicted herein as annular.
However, the outer perimeter 70 could comprise any shape. The
insert nozzle side 66 comprises an outer ridge 72 and a central
flat 74 with a radius 76 therebetween. The cavity side 68 of the
depicted insert 30 comprises an outer land 78 and a central recess
80 with a radius 82 therebetween. An axial bore 84 is located
centrally through the insert 30 to align with the nozzle axial bore
22 and extend the melt material flow path 24 toward the injection
gate 26.
[0033] The insert cavity side 68 is designed to fit into the recess
32 of the injection block 16 so that the outer land 78 abuts the
recessed flat 48 thereof. In one embodiment, the outer perimeter 70
of the insert 30 is designed to provide interference fit into the
injection block recess 32. However, the insert 30 could be secured
into the injection block recess 32 in other manners as will become
evident to one of ordinary skill in the art. In either
configuration, it is desirable that the insert 30 be removable to
facilitate its replacement in the event that deterioration occurs.
It is contemplated, however, that the insert 30 of the present
invention may be employed in an injection apparatus which does not
comprise the recess 32 of the present invention. The recess could
be configured to be only as deep as the insert 30 to allow the
recess 32 to retain the insert 30 within the injection cavity.
Furthermore, the insert 30 of the present invention may be employed
with an injection apparatus having no recess. Indeed, the insert 30
may be employed in any injection apparatus in which the insert may
be sufficiently secured between the nozzle and the injection cavity
to maintain substantial axial alignment of the insert axial bore 84
to the nozzle axial bore 22 and the injection gate 26 during
injection.
[0034] As depicted in FIG. 3B, the insert central recess 80 is
displaced inward of the outer land 78 such that when the outer land
78 abuts against the recessed flat 48, which is preferably
substantially planar, a space 86 will remain between the insert
central recess 80 and the recessed flat 48. This space 86 allows a
flex portion 88 of the insert 30 (defined as the portion extending
inward from the outer land 78) to flex under the force of a nozzle
12 contacting the nozzle side 66 of the insert 30. This
configuration of the insert 30 allows the injection apparatus 10 of
the present invention to accommodate nozzles of varying lengths or
varying thermal expansion properties. In other words, variations in
nozzle length caused by machining, assembly tolerances and
variations in thermal expansion of the nozzles 12 can be absorbed
by the flexible nature of the insert 30 which is afforded by the
space 86.
[0035] The ability to accommodate variations in nozzle lengths is
especially important when employing a multi-cavity injection system
in which multiple nozzles are mounted on a single carriage
operatively associated with a plurality of injection cavities. Such
a system is described in U.S. Pat. No. 4,712,990. Regardless of the
number of nozzles 12 employed by a multi-cavity injection
apparatus, some nozzles 12, as discussed above, will likely
protrude further than others due to tolerances so that upon
approaching the injection cavity 16 (due to thermal expansion
during warm-up of the injection apparatus 10), the longest nozzle
12 will encounter an associated insert 30 before contact occurs
between other nozzles 12 and their associated inserts 30.
Additionally, nozzles grouped in a single carriage (or manifold)
will be subjected to different temperatures depending on, for
example, their positioning on the carriage. Variations in nozzle
thermal expansion result consistent with these temperature
differentials. By employing the insert 30 of the present invention
to allow the longest nozzle 12 to flex its associated insert 30 and
to continue travel toward the injection gate 16, each nozzle 12 of
the multi-cavity injection system is able to come into contact with
its associated insert 30 consistent with the objectives of the
present invention. Each nozzle 12 will preferably contact the
associated insert 30 firmly enough to prevent the escape of melt
material from therebetween. Melt material buildup between the
nozzle 12 and the insert 30 is thus prevented and the
above-discussed tolerances may be maintained.
[0036] Although each insert 30 will likely flex a different amount,
the depth of the space 86 (i.e. the distance between the plane
defined by the outer land 78 and the central portion 80) may be
designed to accommodate both the longest and shortest nozzle 12
allowed by tolerance so that all nozzles 12 may firmly contact the
respective insert 30 according to the present invention. That is,
the depth of space 86 could equal the difference between the
longest nozzle 12 allowed by tolerance and the shortest nozzle 12
allowed by tolerance at operating temperatures. In this embodiment,
the depth of the space 86 would be dictated by the system into
which the insert 30 is incorporated. In one embodiment a depth of
0.015 inch was found to provide sufficient depth for the space 86
in a multicavity injection apparatus. Also, a thickness of 0.049
inches for the flex portion 88 when having a diameter of 0.50
inches and the insert 30 is comprised of Vespel.RTM. has been found
to provide flex portion 88 with sufficient flexibility consistent
with the objectives of the present invention.
[0037] While the flex portion 88 of one or more insert 30 in a
multi-cavity injection apparatus may contact the associated
recessed flat 48 of the injection cavity 16 upon flexing, at least
a portion of the space 86 will remain for other inserts. The space
86 may fill with melt material upon injection of melt material from
the nozzle 12. However, thermal conduction from the nozzle 12 to
the injection cavity 16 remains minimized by the relatively low
thermal conductivity of the insert 30 despite the existence of melt
material in the space 86.
[0038] In another embodiment, the diameter of the central flat 74
on the insert nozzle side 66 is configured to be larger than the
diameter of the nozzle tip 44 in order to accommodate the lateral
nozzle movement which occurs due to thermal expansion of the nozzle
12 during warm-up of some injection apparatuses. By configuring the
diameter of the central flat 74 to be substantially larger than the
diameter of the nozzle leading face 44 (as depicted in FIG. 1) the
nozzle 12 is provided the freedom to move laterally across the
central flat 74 without damaging either the nozzle 12 or the insert
30. It has been found that the lateral component of the nozzle 12
expansion may be as great as fifty thousandths of an inch. In one
embodiment, the diameter of the central flat 74 is at least one
hundred thousandths of an inch greater than the diameter of the
nozzle leading face 44. In this embodiment, the nozzle tip 42 is
allowed the requisite fifty thousandths of an inch of lateral
movement in any direction from the central axis without the nozzle
12 contacting the insert outer ridge 72 or radius 76. In another
embodiment, an insert 30 having a central flat diameter of 0.476
inches was found to operate properly, as defined herein, for a
nozzle tip 42 having a 0.375 inch diameter.
[0039] From the foregoing description, it will be apparent that the
injection apparatus of the present invention has a number of
advantages, some of which have been described above and others of
which are inherent in the apparatus of the present invention. Also,
it will be understood that modifications can be made to the
apparatus of the present invention without departing from the
teachings of the invention. Accordingly the scope of the invention
is only to be limited as necessitated by the accompanying
claims.
* * * * *